Feedback Consolidation Algorithms for ABR Point-to-Multipoint Connections in ATM Networks

关于物流的英语作文Title: The Evolution and Impact of Logistics in the Modern World。

Introduction。

Logistics plays a crucial role in the global economy, facilitating the movement of goods and services from producers to consumers efficiently and effectively. Over the years, logistics has evolved significantly, driven by technological advancements, globalization, and changing consumer demands. This essay explores the evolution and impact of logistics in the modern world.Historical Evolution。

The concept of logistics traces back to ancient civilizations, where armies organized supply chains to support military campaigns. However, modern logistics emerged during the Industrial Revolution when the need forefficient transportation and distribution systems became apparent. The invention of the steam engine revolutionized transportation, enabling goods to be transported over longer distances at a fraction of previous times.With the advent of the 20th century, logistics underwent further transformation with the introduction of assembly lines and mass production techniques. This period saw the rise of companies like Ford, which revolutionized manufacturing processes and supply chain management. The development of standardized containers in the mid-20th century revolutionized maritime transportation, further enhancing the efficiency of global trade.Technological Advancements。

DoS 攻击下具备隐私保护的多智能体系统均值趋同控制胡沁伶 1郑 宁 1徐 明 1伍益明 1何熊熊2摘 要 均值趋同是一种广泛应用于分布式计算和控制的算法, 旨在系统通过相邻节点间信息交互、更新, 最终促使系统中所有节点以它们初始值的均值达成一致. 研究拒绝服务(Denial-of-service, DoS)攻击下的分布式离散时间多智能体系统均值趋同问题. 首先, 给出一种基于状态分解思想的分布式网络节点状态信息处理机制, 可保证系统中所有节点输出值的隐私. 然后, 利用分解后的节点状态值及分析给出的网络通信拓扑条件, 提出一种适用于无向通信拓扑的多智能体系统均值趋同控制方法. 理论分析表明, 该方法能够有效抵御DoS 攻击的影响, 且实现系统输出值均值趋同. 最后, 通过仿真实例验证了该方法的有效性.关键词 多智能体系统, 均值趋同, 拒绝服务攻击, 隐私保护, 网络安全引用格式 胡沁伶, 郑宁, 徐明, 伍益明, 何熊熊. DoS 攻击下具备隐私保护的多智能体系统均值趋同控制. 自动化学报, 2022,48(8): 1961−1971DOI 10.16383/j.aas.c201019Privacy-preserving Average Consensus Control forMulti-agent Systems Under DoS AttacksHU Qin-Ling 1 ZHENG Ning 1 XU Ming 1 WU Yi-Ming 1 HE Xiong-Xiong 2Abstract Average consensus is a widely used algorithm for distributed computing and control, where all the nodes in the network constantly communicate and update their states in order to achieve an agreement. In this paper, we study the average consensus problem for discrete-time multi-agent systems under DoS attacks. First, a distributed network node state value processing mechanism based on state decomposition is given, which can ensure the pri-vacy of the output values of all nodes in the system. Then, through using the decomposed node state values and the network topology conditions given by the analysis, an average output consensus control law for distributed discrete-time multi-agent systems is proposed. Theoretical analysis shows that the proposed method can effectively resist the influence of DoS attacks on the system, and achieve the convergence of the average value of system initial outputs.Finally, numerical examples are presented to show the validity of the proposed method.Key words Multi-agent systems, average consensus, denial-of-service attack, privacy-preserving, cyber securityCitation Hu Qin-Ling, Zheng Ning, Xu Ming, Wu Yi-Ming, He Xiong-Xiong. Privacy-preserving average con-sensus control for multi-agent systems under DoS attacks. Acta Automatica Sinica , 2022, 48(8): 1961−1971多智能体系统是由多个具有一定传感、计算、执行和通信能力的智能个体组成的网络系统, 作为分布式人工智能的重要分支, 已成为解决大型、复杂、分布式及难预测问题的重要手段[1−2]. 趋同问题作为多智能体系统分布式协调控制领域中一个最基本的研究课题, 是指在没有协调中心的情况下, 系统中每个节点仅根据相互间传递的信息, 将智能体动力学与网络通信拓扑耦合成复杂网络, 并设计合适的分布式控制方法, 从而在有限时间内实现所有节点状态值的一致或同步.然而具备分布式网络特点的多智能体系统由于普遍规模庞大, 单个节点结构简单且节点地理位置分散等原因, 使得系统中易产生脆弱点, 这就使其在推广应用中面临两项基本挑战: 1)节点状态信息的隐私泄露问题; 2)节点或节点间的通信链路可能会遭受网络攻击的问题, 如欺骗攻击、拒绝服务(Denial-of-service, DoS)攻击等.针对节点状态信息的隐私泄露问题, 即在考虑多智能体网络趋同的同时, 保证系统中节点的初始状态值不被泄露, 已有较多研究人员开展相关的工作. 其中, 有学者借助于传统的安全多方计算方法,收稿日期 2020-12-09 录用日期 2021-03-02Manuscript received December 9, 2020; accepted March 2, 2021国家自然科学基金(61803135, 61873239, 62073109)和浙江省公益技术应用研究项目(LGF21F020011)资助Supported by National Natural Science Foundation of China (61803135, 61873239, 62073109) and Zhejiang Provincial Public Welfare Research Project of China (LGF21F020011)本文责任编委 鲁仁全Recommended by Associate Editor LU Ren-Quan1. 杭州电子科技大学网络空间安全学院 杭州 3100182. 浙江工业大学信息工程学院 杭州 3100231. School of Cyberspace, Hangzhou Dianzi University, Hang-zhou 3100182. College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023第 48 卷 第 8 期自 动 化 学 报Vol. 48, No. 82022 年 8 月ACTA AUTOMATICA SINICAAugust, 2022例如Yao等[3]提出混淆电路算法, Shamir等[4]提出秘钥共享算法等. 然而这类通用的隐私保护方法因计算和通信消耗较大, 不适用于单个智能体节点结构较为简单的分布式系统, 尤其是受到硬实时约束的一类多智能体系统应用. 如上述的混淆电路的计算延迟为秒级[5], 而对于多智能体系统一些典型应用如多无人飞行器编队的实时控制, 其容许的计算延迟仅为毫秒级[6]. 针对多智能体系统均值趋同过程中节点信息泄露问题, 有研究人员提出了一系列专门的隐私保护策略[7−10]. 这些方法大多基于模糊处理的思想, 即通过加入噪声来掩盖真实的状态值.其中一种常用的手段是差分隐私方法[11], 然而这种差分隐私下的模糊处理方法会影响最终趋同值的精度, 即使系统无法收敛到精确的节点初始状态的平均值. 最近文献[12]提出的一种基于相关噪声混淆技术的改进方法, 克服了传统差分隐私方法中精度下降的问题, 但却需要较多的算力. 最近的文献[13]采用一种基于状态分解的方法, 将每个节点的初始状态分解为两个随机的子状态, 只令其中一个子状态参与相邻节点间的信息交互, 而另一子状态保留在本节点内部, 不参与邻居间信息传递. 只要两个随机子状态的和满足特定条件, 在作者所设计的趋同算法下, 系统能够达成均值趋同, 且保护每个节点的状态信息不被泄露.此外, 有学者研究基于可观测性的方法用来保护多智能体系统中节点的隐私[14−16]. 基本思想是设计网络的交互拓扑结构以最小化某个节点的观测性, 本质上相当于最小化该节点推断网络中其他节点初始状态的能力. 然而, 这类基于可观测性的方法仍然存在隐私泄露的风险. 为了提高对隐私攻击的抵御能力, 另一种常见的方法是使用加密技术.然而, 虽然基于密码学的方法可以很容易地在聚合器或第三方[17]的帮助下实现隐私保护, 例如基于云的控制或运算[18−20], 但是由于分散密钥管理的困难,在没有聚合器或第三方的情况下, 将基于密码学的方法应用到完全分散的均值趋同问题是很困难的.同时, 基于密码学的方法也将显著增加通信和计算开销[21], 往往不适用于资源有限或受硬实时约束的分布式网络控制系统.以上的工作均是在安全的通信环境下完成的,然而在实际应用场景中, 由于物理设备和通信拓扑结构都有可能遭受网络攻击, 导致以往有关多智能体系统趋同研究的失效, 这使得针对多智能体系统在网络攻击下的趋同研究发展迅速, 并取得了一些显著成果[22−26]. 目前多智能体系统中常见的网络攻击主要有两种形式: 欺骗攻击[22, 25, 27−28]和DoS攻击[29−33].r其中DoS攻击是多智能体系统中最常见也是最容易实现的攻击形式, 只要攻击者掌握系统元器件之间的通信协议, 即可利用攻击设备开展干扰、阻塞通信信道、用数据淹没网络等方式启动DoS攻击.在DoS攻击影响下, 智能体间交互的状态信息因传递受阻而致使系统无法达成一致. 近年来, 研究者们从控制理论的角度对DoS攻击下的系统趋同问题进行了研究. 其中, 有研究人员通过构建依赖于参数的通用Lyapunov函数设计一种趋同方法[31],使其能够适用于因通信链路存在随机攻击导致通信拓扑随机切换的情况. 此外, 有研究者通过设计一个独立于全局信息的可靠分布式事件触发器[32], 很好地解决了大规模DoS攻击下的一致性问题. 更有研究者开始研究异构多智能体系统在通信链路遭受攻击时的趋同问题[33], 通过设计基于观测器的控制器, 实现在通信链路存在DoS攻击时两层节点间的趋同问题. 而在本文中, 考虑多智能体之间通信链路遭受DoS攻击的情况, 通过攻击开始时刻与攻击链路矩阵刻画DoS攻击模型, 通过增强网络拓扑以满足所谓的-鲁棒图来刻画信息流的局部冗余量[34],从而抵御DoS攻击的影响.然而, 针对趋同问题, 将网络攻击和隐私保护两者结合起来考虑的研究还鲜有见文献报道. 2019年Fiore等[24]率先开展了同时考虑隐私保护和网络攻击的研究工作, 但所得成果仍存在一定的局限性: 1)所提方法虽能保护节点隐私且最终达成状态值趋同, 却无法确保系统达成均值趋同; 2)作者仅考虑了欺骗攻击下的控制器设计问题, 因此所得结论并不适用于网络中存有DoS攻击的系统.y基于上述观察与分析, 本文主要致力于研究DoS 攻击下具备节点信息隐私保护的多智能体系统均值趋同问题, 从而补充现有趋同算法的相关结果. 同时, 考虑实际环境对测量条件等的限制, 不易直接获取节点的真实状态值[35], 为此本文围绕节点的输出值, 即通过观测矩阵获取的系统输出, 进行趋同控制器的设计工作. 本文的主要贡献包括:1)针对DoS攻击在多智能体系统分布式协同控制中的攻击特性和发生范围, 及对网络拓扑连通性的影响, 建立相应数学模型;2)针对一类DoS攻击下的无向通信网络多智能体系统, 提出一种基于状态分解的节点信息隐私保护策略. 当满足特定条件时, 所提策略可确保系统输出状态不被窃听者准确推断出来;y3)针对DoS攻击的影响, 分析给出了系统中节点通信拓扑的鲁棒性条件, 并据此设计一种基于输出量测值的分布式控制方法, 理论分析并证明1962自 动 化 学 报48 卷系统可容忍特定数目的链路遭受DoS 破坏, 并实现输出均值趋同.本文内容结构为: 第1节介绍本文所需要用到的图论知识, 网络拓扑图的相关性质以及均值趋同算法; 第2节主要对DoS 攻击模型和拟解决问题进行描述; 第3节提出系统在DoS 攻击下的隐私保护均值趋同控制方法, 并分别对在攻击下的网络拓扑鲁棒性、系统收敛性以及隐私保护能力进行分析;第4节通过一组仿真实例验证算法的有效性; 第5节是总结与展望.1 预备知识1.1 图论知识M G =(V ,E ,A )V ={v 1,v 2,···,v M }E ⊂V ×V A =[a ij ]∈R M ×M (v j ,v i )∈E a ij >0a ij =0(v j ,v i )∈E (v i ,v j )∈E a ij =a ji a ii =0v i N i ={v j ∈V|(v j ,v i )∈E}G L =D −A 考虑由 个智能体组成的多智能体系统, 节点之间为双向传递信息, 其通信网络可抽象地用一个无向加权图 表示. 其中 表示节点集合, 表示边集. 两个节点之间的连接关系用邻接矩阵(权重矩阵) 表示, 如果 , 则 ; 否则 . 在无向图中, 邻接矩阵是对称的, 即如果, 则同时有 , 且 . 本文不考虑节点自环情况, 即令 . 节点 的邻居集合表示为 . 无向图 对应的Laplacian 矩阵为 , 其中D 为度矩阵, 定义为:除了上述无向图的基本知识, 本文的研究工作还用到了r -可达集合和r -鲁棒图的概念. 这两个概念最早由文献[36]提出, 随后被文献[22, 27]等利用并扩展, 主要用于分析节点间拓扑抵御网络攻击的鲁棒性. 经笔者少许修改, 具体定义如下:G =(V ,E )S ⊂V S v i N i \S r S 定义1[36]. r -可达集合: 对于图 及其中一非空子集 , 如果 中至少有一个节点 在集合 中有不少于 个节点, 则称 为r -可达集合.G =(V ,E )V S 1,S 2⊂V S 1∩S 2=∅G 定义 2[36]. r -鲁棒图: 对于图 , 如果对 中任意一对非空子集 , , 保证至少有一个子集为r -可达集合, 则称 为r -鲁棒图.以下是一些关于r -鲁棒图的基本性质.G =(V ,E )ˆGG s (s <r )ˆG(r −s )引理1[22]. 考虑一个r -鲁棒图 , 令 表示 中每个节点至多移除 条边后的图,则 是一个 -鲁棒图.G G 引理2[22]. 对于一个无向图 , 如果 满足1-鲁G 棒图, 则有 为连通图.1.2 均值趋同算法M x i [k ]∑Mi =1x i [0]/M 考虑有 个节点组成的无向加权多智能体系统. 为了让系统实现均值趋同, 也就是所有节点的状态 最终收敛到它们初始状态的平均值, 根据文献[13, 37], 其节点动态更新方程可设计为:x i [k ]v i k ε∈(0,1/∆)∆式中, 为节点 在 时刻的状态值, 为系统增益系数, 通常定义为:η>0η≤a ij <1文献[38]表明, 当系统拓扑满足连通图, 且存在 使得 时,系统可在更新规则(1)下实现均值趋同, 即:2 问题描述M 本文研究对象为如下 个智能个体组成的一阶离散时间多智能体系统, 其动力学模型为:x i [k ]∈R N u i y i [k ]∈R Q y i [k ]nC i ∈R Q ×N n n ∈R +式中, 为系统的状态值, 为控制输入, 为系统经通信链路传输得到的量测信号, 需要注意的是, 由于通信链路中存在DoS 攻击, 可能遭受影响而无法被邻居节点接收到. 为观测矩阵, 其中 为从观测矩阵中抽取出的系数, 为大于0的正实数.2.1 攻击模型本文所讨论的DoS 攻击表现为某种传输尝试失败的情况[39], 其存在于多智能体系统中各智能体之间的通信链路中, 即当通信图中两个节点间的链路发生DoS 攻击时, 其通信链路将会被切断, 此时两个节点无法通过该链路进行信息交互, 进而达到攻击多智能体系统的目的. 在多智能体系统分布式协同控制中, 运载节点输出量测值的通信链路遭遇DoS 攻击的示意图如图1所示.(P,k 0)P =[p ij [k ]]∈R M ×M v i v j k 本文以Adeversory 刻画系统遭遇DoS攻击的情况. 其中 表示攻击状态矩阵, 当节点 和节点 之间在 时刻发生DoS8 期胡沁伶等: DoS 攻击下具备隐私保护的多智能体系统均值趋同控制1963p ij [k ]=0p ij [k ]=1k 0攻击时, ; 否则 . 为系统遭遇DoS 攻击的开始时刻.考虑攻击者资源的有限, 本文假设攻击发生范围满足f -本地有界[22]的定义, 该假设在文献[22−23,25]中被广泛采用. 结合DoS 攻击, 具体定义如下:f 定义3 (f -本地有界DoS 攻击) . 对于系统中的任一节点, 如果与其相邻节点的通信链路中, 任意时刻遭遇DoS 攻击的链路条数至多不超过 条, 则称此类攻击模型为f -本地有界DoS 攻击.2.2 系统假设(P,k 0)结合上述给出的Adeversory 和攻击发生范围模型, 本文对所研究的系统作出如下假设:f 3v i ∈V k 假设1. 系统中任意一个节点的通信链路中在任意时刻至多有 条链路同时遭受DoS 攻击, 即满足定义 攻击模型. 具体地, 则对于任意 , 在任意时刻 , 都有下式成立:G [k ]=(V ,E [k ],A [k ])虽然本文考虑的是固定无向拓扑, 但在DoS攻击影响下, 可以看到系统的通信图却会与之发生变化. 因此, 本文接下去用时变图符号 表示系统在DoS 攻击影响下的真实通信情况.η0<η<1i,j ∈{1,···,M }a ij [k ]>0η≤a ij [k ]<1假设2. 存在一个标量 满足 , 对于所有的 , 如果 , 那么 .x i ∈R N X i ∈R N X =∩M i =1X i X =∅假设3. 系统任意节点状态值 受限于一个非空闭凸集, 表示为 , 令 ,则 .根据上述假设, 可以得出系统具备如下属性:引理3[38]. 当系统的网络通信图为有向连通图v i ∈V (1)且邻接矩阵为双随机矩阵时, 并且满足假设2和3时, 那么对于系统中任意节点 在动态更新式 下, 有:{h [k ]}式中, 为一个定义的辅助序列, 对于每个时根据文献[38], 因邻接矩阵为双随机矩阵, 由式(7) ~ (8)可得:v i ∈V 引理4. 当系统的网络通信图为无向连通图, 并且满足假设2和3时, 那么由引理3可知, 对于系统中任意节点 在动态更新式(1)下, 式(10)仍然成立.证明. 根据引理3可知, 在网络通信图为有向图情况下, 邻接矩阵为双随机矩阵表明在该网络通信图中, 所有节点通信链路满足出度等于入度的条件, 而在无向图中, 该条件同样成立, 因此在无向图中, 式(10)仍然成立. □针对上述建立的网络攻击模型和相关的系统假设, 本文的研究目标是, 设计一种控制策略, 使得:1)系统的输出达到趋同并且趋同值是等于所有智能体初始输出状态的平均值; 2)在整个趋同过程中保护每个节点的信息值隐私.3 控制器设计3.1 DoS 攻击下网络拓扑鲁棒性条件首先对网络通信链路图的鲁棒性条件进行讨论, 以便于开展后续控制器的设计工作.引理5. 考虑多智能体系统(4), 如果其网络拓图 1 DoS 攻击下的多智能系统框图Fig. 1 The diagram of the multi-agent systemunder DoS attacks1964自 动 化 学 报48 卷(f +1)扑结构满足 -鲁棒的无向图, 那么系统在遭受f -本地有界DoS 攻击下, 即满足假设1, 其通信图仍可保持连通性.f 证明. 根据假设1可知, 网络中每个节点任意时刻至多有 条通信链路遭受DoS 攻击破坏. 再由引理1可知, 此时网络拓扑结构至少是1-鲁棒图.最后由引理2可知, 系统网络拓扑仍然能够保持连通性. □3.2 DoS 攻击下隐私保护控制上述小节给出了系统遭受DoS 攻击下通信网络仍旧保持连通的条件, 接下去本小节给出本文核心的控制器设计方法.x i x αi x βi x αi [0]x βi [0]x αi [0]+x βi [0]=2x i [0]受文献[13]启发, 此处引入状态分解方法: 将每个节点的状态值 分解成两个子状态, 用 和 表示. 值得注意的是, 初始状态的子状态值 和 可在所有实数中任取, 但需满足条件: .x αi x i v i x βi x αi x βi v i v 1x α1x 1x β1v 1x α1x αi x βi a i,αβ[k ]a i,αβ[k ]η≤a i,αβ[k ]<1为便于理解, 本文以5个节点的无向连通图为例, 通信拓扑如图2所示. 从示例图中可以看出: 子状态 充当原 的作用, 即与邻居节点进行信息交互, 并且实际上是节点 的邻居节点唯一可以获知的状态信息. 而另一个子状态 同样存在于该分布式信息交互中, 但是其仅与 进行信息交互. 也就是说子状态 的存在, 对于节点 的邻居节点是不可见的. 例如, 在图2(b)中, 节点 中的 相当于图2(a)中 的角色和邻居节点进行信息交互,而 仅对节点 自身可见, 而对其他节点不可见.但是它又可以影响 的变化. 两个子状态 和 之间的耦合权重是对称的, 表示为 , 并且所有的 满足 .基于上述方法, 本文给出具体的具备隐私保护的输出均值趋同控制协议:并且I L ′[k ]式中, 为单位矩阵, 为DoS 攻击下的Lapla-cian 矩阵,其满足:A ′[k ]=[′]式中, DoS 攻击下系统对应的邻接矩阵为D ′[k ]A ′[k ] 为对应于邻接矩阵 的度矩阵.y [k ]=nCx α[k ]C 另外, 在协议(11)中, 为系统的状态输出方程, 为输出方程的观测矩阵, 定义为:e i R M i i 式中, 表示 中第 个规范基向量, 该向量中第个位置数为1, 其他位置数为0.n ∈(0,1)n =1n ∈(1,∞)注1. 考虑实际环境中不同情况, 当 时, 系统输出方程将会缩小状态值进行信息交互,适用于节点状态值过大的情况; 当 时, 系统状态输出方程将会输出原本节点需要进行信息交互的状态值; 当 时, 系统状态输出方程将会放大状态值进行信息交互, 适用于节点状态值过小的情况.x α[k ]值得注意的是, 对于系统中的节点, 用于和邻居节点进行信息交互的状态值 是无法被邻居节点获取的, 需通过系统状态输出方程传递给邻居图 2 5个节点组成的示例图Fig. 2 Example of network with 5 nodes8 期胡沁伶等: DoS 攻击下具备隐私保护的多智能体系统均值趋同控制1965x α[k ]y [k ]节点. 简言之每个节点经过信息交互接收到的邻居节点的值并不是 , 而是经过输出方程输出的 .A αβ[k ]v i ,i =1,2,···,M x αi [k ]x βi [k ]a i,αβ[k ]令 为每个节点 的和两个子状态之间的耦合权重N =1,Q =1为便于叙述, 本文考虑节点的状态值及输出值为一维的情况, 即令 . 从而, 基于输出状态值的控制协议可表示为:事实上, 只要向量状态中的每个标量状态元素都有独立的耦合权重, 本节所提出的控制方法所有分析及结果同样适用于向量状态的情况.()ε1/∆1/(∆+1)注2. 与文献[13, 37]的更新式(1)相比, 本文给出的协议(19)中, 由于每个可见子状态的邻居数增加了一个 不可见子状态 , 因此 的上限从 降低为 .注3. 相比于文献[13, 37]设计的更新式(1),本文在协议(19)的设计过程中考虑了系统通信链路中存在DoS 攻击的情况, 可确保在存在一定能力DoS 攻击时, 系统在协议(19)的约束下实现均值趋同.3.3 输出均值趋同分析在给出本文主要结论前, 需要下述引理知识.引理6. 考虑多智能体系统(4), 如果其网络通信图是一个无向连通图, 则对于状态分解后的网络,所有节点子状态总和是固定不变的.y i [k ]=nx αi [k ]证明. 由输出方程 , 推导可得:再将式(20)代入式(19), 可得:进一步, 由式(21), 可得:因此有:∑M i =1{∑Mj =1a ′ij[k ](y j [k ]−y i [k ])}而在式(23)中的部分, 可进一步分解为下式:a ′ij [k ]=a ′ji [k ]v i ,v j ∈V 根据无向图属性: , 对于任意 , 有:将式(25)代入式(24), 可得:1966自 动 化 学 报48 卷(26)(23)将式 代入式 , 可得:由式(27)容易看出, 对于进行状态分解后的网络, 系统节点子状态的和是固定不变的. □下面给出本文的主要结论.(f +1)定理1. 考虑DoS 攻击下多智能体系统(4), 在满足假设1、2和3条件下, 若其通信拓扑满足 -鲁棒图, 且系统节点在所给的分布式协议(19)下进行状态更新, 则系统可实现输出值均值趋同.(f +1)证明. 由于系统的通信图是一个 -鲁棒图, 根据引理5可知, 系统在满足假设1的DoS 攻击下, 其网络图仍能够保持连通. 显然, 经过状态分解之后的系统同样能够保证网络图的连通性. 根据x αi [k ]x βi [k ]随后, 根据引理4和式(28)可知, 系统可以实现均值趋同, 即任意节点的子状态 和都x αi [0]+β再根据式(28)和状态分解约束条件y i [k ]=nx αi [k ]最后, 根据式(29)和输出方程 , 可得: □y 注4. 相比于文献[13]设计的隐私保护状态更新协议, 本文在协议(19)的设计过程中进一步考虑了在实际环境对测量条件等的限制导致难以获得系统中节点的真实状态值的情况, 引入了节点输出值的概念, 通过观测矩阵获取的系统输出 进行协议(19)的设计, 可确保系统在该协议下实现输出值均值趋同.3.4 隐私保护分析本节对趋同控制过程中单个节点信息的隐私保护进行分析. 本文考虑两种隐私窃听者: 好奇窃听者和外部窃听者. 好奇窃听者是指一类能够正确遵循所有控制协议步骤但具有好奇性的节点, 这类节点会收集接收到的数据并试图猜测其他节点的状态信息. 而外部窃听者是指一类了解整个网络拓扑结构的外部节点, 并能够窃听某些内部节点的通信链路从而获得在该通信链路交互的信息.一般来说, 这里的外部窃听者比好奇窃听者更具有破坏力, 因为外部窃听者会窃听多个节点通信链路上交互的信息, 而好奇窃听者只能窃听该节点通信链路交互的信息, 但好奇窃听者有一个外部窃听者无法得知的信息, 即该好奇窃听者的初始状态值.v i ∈V k I i [k ]={a ′ip [k ]|v p ∈N i ,y p [k ]|v p ∈N i ,x i [k ],x αi [k ],x βi [k ],a i,αβ[k ]}v i I i =∪∞k =0I i [k ]定义好奇窃听者 在第 次迭代时所获得的信息为: . 随着状态值迭代更新, 窃听者 收集获得的信息表示为 .x i [0]v i 定义4. 如果窃听者无法以任何精度保证估计节点状态信息 的值, 则称节点 得到了隐私保护.在给出结论前, 需要用到下述引理.v j v i v m v j x j [0]=x j [0]v i I i =I i 引理7[13]. 在采用状态分解方法的信息交互通信中, 如果正常节点 具有至少一个不与好奇窃听节点 直接相连的正常邻居节点 , 则对于节点 的任意初始状态 , 窃听节点 获得的信息始终满足 .v j v m a jm [0]v j a jm [0]a j,αβ[0]a m,αβ[0]v j x j [0]引理8[13]. 在采用状态分解方法的信息交互通信中, 如果正常节点 存在至少一个正常邻居节点, 其 的值对于外部窃听者不可见, 则节点 的任意初始状态的任何变化都可以完全通过对外部窃听者不可见的 , 和 的变化来补偿, 因此外部窃听者无法以任何精度保证估计正常节点 的初始状态值 .v j ∈V v j x j [0]定理2. 考虑DoS 攻击下多智能体系统(4), 对于系统中任意正常节点 , 如果 在所给的分布式协议(19)下进行状态更新, 则在整个信息交互过程中, 其状态信息值 具备隐私保护.v i v j x j [0]=x j [0]I i =I i v j v j x j [0]证明. 首先, 分析系统存在好奇窃听者 的情况. 对于任意正常节点 , 在所给的分布式协议(19)下, 其初始状态显然满足 , .再由引理6可知, 该条件下好奇窃听者无法准确估计节点 的初始值, 因此节点 的状态值 得到了隐私保护.v j ∈V v j v j 随后, 分析系统存在外部窃听者的情况. 在本文所提的分布式算法(19)下, 外部窃听者对于系统中任意正常节点 的其中之一子状态不可见. 根据引理7, 初始状态值的变化则对于外部窃听者不可见, 故外部窃听者无法准确估计正常节点 的8 期胡沁伶等: DoS 攻击下具备隐私保护的多智能体系统均值趋同控制1967。

在投寄论文时，有些刊物要求作者在论文后面附上“个人简介”(biography)，内容包含何时何校何专业毕业，获得何学位，以及主要工作经历（学术活动）等。

下面是7个“个人简介”(biography)范例，撰写个人简历时常用单词(词组)以粗体标记，供读者参考。

范例1：Maryam Kolahdoozan received her MSc of applied science, specializing in concrete materials, from Ryerson University, Toronto, ON, Canada. Her areas of research include sustainable alternatives for producing unshrinkable fill and deterioration mechanism of concrete exposed to internal sulfate attack and method for mitigation.范例2：Douglas F. CRICKNER was born at McAlpin, a southern West Virginia coal camp, and had his first experience in coal mining at age 18 at the McAplin mine where for three successive summers he was employed on conveyor sections in 34-in. coal to drag pans and supplies, hang canvas, etc. He graduated from Virginia Polytechnic Institute with a degree in mining engineering in 1941. Following this, he served with Koppers Coal Co. and The New River Co. as mining engineer and assistant mine foreman. In 1946, he was employed by his present company, Pocahontas Land Corp., which he has served as mine inspector, chief engineer, general manager, and currently as vice president. During one four-year period he was transferred to an associated company, Norfolk & Western Railway Co., as superintendent of mines at its Pond Greek Colliers in Pike County, KY. He has taken an active part in a number of engineering and coal institutes. He is a past chairman of The Society of Mining Engineers of AIME Coal Division and is currently serving as a director ofSME and vice president-AIME Easter Region.范例3：M. E. HOPKINS received his education in geology from the University of Arkansas, then earned his Ph.D. at the University of Illinois in 1957. He served in the Army Air Corps in 1946-47. In 1951, he joined the Coal Section of Illinois State Geological Survey as a part-time research assistant. In 1955, he joined the faculty of the Department of Geology at the University of Tulsa but in 1963 returned to the Illinois Survey, becoming head of the Coal Section in 1968 where he served until 1975. He was vice president of Harry Williamson, Inc., Benton, IL, and is now director of geology, Peabody Coal Co., St. Louis, MO.范例4：H. L. WASHBURN received a BS and MS in mining engineering from the University of Kentucky. His first job was with the Research and Development Division, Consolidation Coal Co. in Pittsburgh, PA, where he worked for three years on a variety of projects including the development of pipeline transportation of coal. He was transferred to Fairmont, WV, as manager of preparation, and subsequently became chief engineer of the Mountainer Division of Consolidation Coal Co. His next assignment was a three-year period with Clinchfield Coal Co. as director of preparation, which involved the actual management of all the plants of Clinchfield. He went to North American Coal Corp. in 1966 as assistant vice president and was later promoted to vice president-engineering and senior vice president-operations, his present position.范例5：Jack A. SIMON first worked on coal geology for the Illinois State Geological Survey as a student in 1937. After serving in the Army Air Corps during World War II, he returned to the Survey on a full-time basis. He was head of the Coal Section, 1953-1967, after which he became head of the Geological Group and principal geologist. Since 1974 he has been chief of the Illinois State Geological Survey. Professional activities have included not only coal geology but, in recent years, environmental problems associated with mining transportation and use of fossil fuels.范例6：Lu Wang has been a Preceptor in the Department of Chemistry and Chemical Biology since 2013. She is involved in teaching several courses at Harvard including Physical Sciences 10 and 11, and Chemistry 301hf -- a teaching practicum course for chemistry graduate students. Before becoming a Preceptor, she held a two-year postdoctoral appointment at Massachusetts Institute of Technology. In addition to her research on two-dimensional nanobiosensors, she also participated in developing and teaching a college chemistry curriculum in the founding year of Singapore University of Technology and Design, which is established in collaboration with MIT. Dr. Wang received her Ph.D. in Chemistry from Harvard University in 2011, where she worked in Professor Charles Lieber‘s group to develop label-free silicon nanowire field-effect biosensors. She received her B.S. in Chemistry from Peking University in 2006.范例7（注重学术方面）：Navin Khaneja(Gordon McKay Professor of Electrical Engineering) is broadly interested in the area of mathematical control theory, signals and systems. His current research lies at the interface ofcontrol and information theory and physics. He is working on developing geometric techniques for optimal control of quantum mechanical phenomenon.The work has proven promising for optimal pulse sequences in high-resolution nuclear magnetic resonance spectroscopy. These optimal pulse sequences minimize the effects of decoherence and maximize the sensitivity of NMR experiments. Optimal pulse design can lead to significant reduction of time required for structural analysis of proteins. The work also has immediate applications to the areas of quantum information and computing.Professor Khaneja is also very interested in the areas of robotics, computer vision, statistical inference and image understanding. His current work in the area of robotics involves design of feedback controllers for stabilization of nonholonomic control systems with applications to locomotion systems.His recent work in Medical Imaging and Human Brain Mapping develops rich class of probabilistic models to capture inherent variability present in the anatomies and involves design of computationally efficient Bayesian inference algorithms for extracting anatomical information from noisy data collected through various imaging modalities.(Education: 1.B.Tech., 1994, Electrical Engineering, IIT, Kanpur; 2.M.A./M.S., 1996, Mathematics/Electrical Engineering, Washington University; 3.S.M., 1999, Applied Mathematics, Harvard University; 4.Ph.D., 2000, Applied Mathematics, Harvard University)BiographyA biography narrates the life story of a person, as written by another person or writer. It is further divided into five categories:Popular biographyHistorical biographyLiterary biographyReference biographyFictional biographyMemoirThis is a more focused writing than an autobiography or a biography. In a memoir, a writer narrates the details of a particular event or situation that occurred in his or her lifetime.Examples of Biography in LiteratureExample #1: Shakespeare: A Life (By Park Honan)This biography is the most accurate, up-to-date, and complete narrative ever written about the life of William Shakespeare. Park Honan has used rich and fresh information about Shakespeare in order to change the perceptions of readers for the playwright, and his role as a poet and actor.This book completely differs from other biographies that imagine different roles for him, commenting on his sexual relationships and colorful intrigues. Though detailed psychological theories and imaginative reforms about the famous playwright could be amusing, in fact, they damage the credibility of the sources. Therefore, many attempts have been made to know about Shakespeare, but this one is a unique example.Example #2: Arthur Miller: Attention Must Be Paid (By James Campbell)This biography is written in the form of a drama, presented in just two acts. In the first act, the author shows the famous dramatist, Arthur Miller, in his early success, having the love of the most beloved woman in the world, and resisting tyranny. However, in the second act of thisbiography, the author shows that the hero was badly assaulted and ridiculed by a rowdy mob called critics, who are expelled from the conventional theater. He ends his book with rhetorical details related to a revitalization in the fortunes of the playwright.Example #3: The Life of Samuel Johnson (By James Boswell)This biography is frequently hyped as a perfect example of modern biography, and all-time best example in the English language. This masterpiece of James Boswell has covered the whole life of the ubiquitous literary writer Samuel Johnson, with whom Boswell was well-acquainted. The unique quality of this book is that it shows Johnson as a walking intellectual amongst us.Example #4: The Bronte Myth (By­­­­­­­­­­­­­­­­­­­Lucasta Miller)Emily, Anne, and Charlotte Bronte were very famous and eminent writers in the history of English literature. Many rumors and gossips were associated with them when they reached the peaks of their careers and received great approval for writing the most admired novels of the nineteenth century. In their biography, Lucasta Miller chunks the myths related to these young enigmatic women. This is a fine example of a biography.Example #5: Why this World: A Biography of Clarice Lispector (By­­­­­­­­­­­­­­­­­­­Benjamin Moser)After perusing his own private manuscripts and writings, this modernist writer, Benjamin Moser, has explored the mystique surrounding Brazilian writer Clarice Lispector. This is one of Moser’s biographies, which comes a little closer to finding her true nuances. All those readers who are going to read her myriad of works for the first time would find this biography interesting, and her life as beautiful and tragic, yet riveting.Function of BiographyThe function of writing biographies is to provide details regarding the life of a person or a thing in an entertaining but informative manner. By the end of a biography, readers feel like they are well-acquainted with the subject. Biographies are often non-fictional, but many biographers also use novel-like format, because a story line would be more entertaining with the inclusion ofstrong exposition, rising conflict, and then climax. Besides, the most inspirational life stories could motivate and put confidence into the readers.。

异常反馈流程学习评估Learning to evaluate the process of providing feedback on exceptions can be a challenging yet rewarding experience. Understanding the importance of properly addressing and resolving issues that arise is crucial in any team or organization. By honing the skills necessary to effectively assess feedback, one can contribute to a more efficient and harmonious work environment.学习评估异常反馈流程可能是一个具有挑战性但有益的经验。

理解妥善处理和解决问题的重要性对任何团队或组织都至关重要。

通过磨练必要的技能来有效评估反馈，可以为更高效和和谐的工作环境做出贡献。

When looking at the process of feedback evaluation, it is important to consider the various stakeholders involved. This includes not only the individuals providing the feedback, but also those responsible for receiving and addressing it. Understanding the perspectives and expectations of each party is essential in order to accurately assess the effectiveness of the feedback process.在审视反馈评估过程时，考虑到参与其中的各方利益攸关者是很重要的。

---Title: Classroom Teaching Reflection on [Subject]Date: [Date of Reflection]Teacher's Name: [Your Name]Subject: [Subject Taught]Grade Level: [Grade Level]---Introduction:The purpose of this reflection is to critically analyze and evaluate my recent classroom teaching experience. By examining my teaching methods, student engagement, and the overall learning outcomes, I aim to identify areas of strength and areas for improvement. This reflection will help me refine my teaching strategies and enhance the learning experience for my students.---Teaching Methods and Techniques:1. Lesson Planning:- What were the main objectives of the lesson?- How did the lesson plan align with the curriculum standards?- Did the lesson plan allow for flexibility to cater to diverse learning needs?2. Instructional Strategies:- What teaching methods did I use (e.g., lectures, discussions, group work)?- Were the methods appropriate for the subject and the students' learning styles?- Did the strategies promote active learning and critical thinking?3. Assessment:- How did I assess student understanding and progress?- Were the assessment methods effective in measuring learning outcomes?- Did the assessments provide constructive feedback for students?---Student Engagement and Participation:1. Student Interaction:- How did students respond to the lesson activities?- Were there any students who were particularly engaged or disengaged?- How did I encourage participation from all students?2. Group Dynamics:- How did group work contribute to the learning process?- Were there any challenges in managing group dynamics?- How did I address conflicts or issues within groups?3. Individual Student Feedback:- Did I provide timely and specific feedback to students?- How did students react to the feedback?- Did the feedback help students to improve their understanding or performance?---Learning Outcomes:1. Achievement of Objectives:- Did the majority of students achieve the learning objectives?- Were there any gaps in understanding that need to be addressed?- How did the lesson contribute to the overall curriculum?2. Student Progress:- How did individual students progress throughout the lesson?- Were there any students who needed additional support or challenge?- How did I adapt my teaching to cater to different learning levels?3. Overall Satisfaction:- How satisfied were the students with the lesson?- Did the lesson meet their expectations?- How could the lesson be improved to enhance student satisfaction?---Areas for Improvement:1. Teaching Methods:- What specific teaching strategies could be more effective?- How can I incorporate more interactive or technology-based learning activities?- What additional resources or materials could enhance the learning experience?2. Student Engagement:- How can I better cater to diverse learning styles and needs?- What strategies can I use to increase student participation and engagement?- How can I foster a more inclusive and supportive classroom environment?3. Assessment and Feedback:- What types of assessments would be more beneficial for this lesson?- How can I provide more meaningful and actionable feedback?- How can I use formative assessments to inform my teaching and adapt to student needs?---Conclusion:This reflection has provided me with valuable insights into my recent classroom teaching experience. By acknowledging both my strengths and areas for improvement, I am better equipped to refine my teaching practices and create a more effective and engaging learning environment for my students. I look forward to applying these learnings to future lessons and continuing to grow as an educator.---References:- [Any relevant educational theories or resources used in the reflection]---[Your。

（完整）ISPE指南目录编辑整理：尊敬的读者朋友们：这里是精品文档编辑中心，本文档内容是由我和我的同事精心编辑整理后发布的，发布之前我们对文中内容进行仔细校对，但是难免会有疏漏的地方，但是任然希望（（完整）ISPE指南目录）的内容能够给您的工作和学习带来便利。

同时也真诚的希望收到您的建议和反馈，这将是我们进步的源泉，前进的动力。

本文可编辑可修改，如果觉得对您有帮助请收藏以便随时查阅，最后祝您生活愉快业绩进步，以下为（完整）ISPE指南目录的全部内容。

ISPE指南按系列分类的目录清单:GAMP5GAMP 5: A Risk-Based Approach to Compliant GxP Computerized SystemsGAMP 5: 保证GXP计算机系统符合性的基于风险的方法GAMP Good Practice GuidesA Risk-Based Approach to Calibration Management （Second Edition）基于风险的校正管理方法（第二版）A Risk-Based Approach to Electronic Records and Signatures基于风险的电子记录和签名方法A Risk—Based Approach to GxP Compliant Laboratory ComputerizedSystems (Second Edition）基于风险的GXP符合性实验室计算机化系统方法(第二版)A Risk—Based Approach to GxP Process Control Systems （SecondEdition)基于风险的GXP工艺控制体系方法（第二版）A Risk-Based Approach to Operation of GxP Computerized Systems -A Companion Volume to GAMP 5基于风险的GXP计算机系统操作方法——-GAMP 5姊妹篇A Risk-Based Approach to Regulated Mobile Applications基于风险的移动APP管理方法A Risk-Based Approach to Testing of GxP Systems (Second Edition）基于风险的GXP系统检测方法（第二版）Electronic Data Archiving电子数据归档Global Information Systems Control and Compliance全球信息系统控制和符合性IT Infrastructure Control and ComplianceIT基础设施控制和符合性Legacy Systems遗留系统Manufacturing Execution Systems – A Strategic and Program Management Approach生产执行系统—策略和编程管理方法GAMP Good Practice Guides Under Development制订中的GAMP GPGISPE Baseline Pharmaceutical Engineering Guides for New and Renovated FacilitiesISPE基准：新设施和创新型设施药品工程指南Volume 1: Active Pharmaceutical Ingredients （Second Edition） - Revision to Bulk Pharmaceutical Chemicals卷1：活性药物成分（第二版）---对散装药用化学品的修订Volume 2: Oral Solid Dosage Forms （Second Edition)卷2:口服固体制剂（第二版）Volume 3: Sterile Product Manufacturing Facilities (Second Edition）卷3：无菌药品生产设施（第二版)Volume 4： Water and Steam Systems (Second Edition)卷4：水和蒸汽系统（第二版）Volume 5: Commissioning and Qualification卷5：调试和确认Volume 6： Biopharmaceutical Manufacturing Facilities （Second Edition）卷6：生物药品生产设施（第二版）Volume 7： Risk—Based Manufacture of Pharmaceutical Products (Risk—MaPP）卷7:基于风险的药品生产（风险MAPP)Baseline Guides Under Development制订中的基准指南ISPE GuidesISPE Guide: Science and Risk-Based Approach for the Delivery of Facilities, Systems， and EquipmentISPE指南:基于风险的设施、系统和设备传送科学方法ISPE Guide： Biopharmaceutical Process Development and ManufacturingISPE指南：生物药品工艺开发和生产(新出版）ISPE Guides Under Development在制订中的ISPE指南ISPE Good Practice Guides 优良规范指南ISPE Good Practice Guide： Applied Risk Management for Commissioning and QualificationISPE GPG：在调试和确认中应用风险管理ISPE Good Practice Guide： Approaches to Commissioning and Qualification of Pharmaceutical Water and Steam Systems （Second Edition）ISPE GPG:药用水和蒸汽系统调试和确认方法（第二版）（新出）ISPE Good Practice Guide： Assessing the Particulate Containment Performance of Pharmaceutical Equipment (Second Edition）ISPE GPG:制药设备颗粒密闭性能的评估（第二版）ISPE Good Practice Guide： Booklet LabelsISPE GPG:书册标签ISPE Good Practice Guide: Clinical Supply SystemsISPE GPG：临床补给系统（新出）ISPE Good Practice Guide： Cold Chain ManagementISPE GPG：冷链管理ISPE Good Practice Guide: Comparator ManagementISPE GPG：对照组管理ISPE Good Practice Guide： Development of Investigational Therapeutic Biological ProductsISPE GPG：临床前治疗用生物产品开发ISPE Good Practice Guide: Good Engineering PracticeISPE GPG：优良工程规范ISPE Good Practice Guide： Harmonizing the Definition and Use of Non—Investigational Medicinal Products (NIMPs）ISPE GPG:协调非临床前药品的定义和使用ISPE Good Practice Guide: Heating, Ventilation, and Air Conditioning （HVAC）ISPE GPG：HVACISPE Good Practice Guide： Interactive Response TechnologyISPE GPG：互动反馈技术ISPE Good Practice Guide： MaintenanceISPE GPG:维护ISPE Good Practice Guide: Ozone Sanitization of Pharmaceutical Water SystemISPE GPG：制药用水系统的臭氧消毒ISPE Good Practice Guide: Packaging， Labeling, and Warehousing FacilitiesISPE GPG：包装、贴标和仓储设计ISPE Good Practice Guide： Process GasesISPE GPG:工艺用气ISPE Good Practice Guide： Project Management for the Pharmaceutical IndustryISPE GPG：制药行业的项目管理ISPE Good Practice Guide: Quality Laboratory FacilitiesISPE GPG：质量化验室设施ISPE Good Practice Guide： Technology Transfer (Second Edition）ISPE GPG:技术转移(第二版）(新出）ISPE Good Practice Guides Under Development制订中的ISPE GPGPQLI Guides 药品质量生命周期实施指南PQLI Overview Good Practice GuidePQLI概览GPGProduct Quality Lifecycle Implementation （PQLI) from Concept to Continual ImprovementPart 1： Product Realization using QbD， Concepts and Principles从概念到持续改进的药品质量生命周期实施(PQLI）第一部分：利用质量源于设计（QbD)实现实现,概念和原则Product Quality Lifecycle Implementation (PQLI） from Concept to Continual ImprovementPart 2： Product Realization using QbD， Illustrative Example从概念到持续改进的药品质量生命周期实施(PQLI)第二部分:利用质量源于设计（QbD）实现实现，实例解说Product Quality Lifecycle Implementation （PQLI) from Concept to Continual ImprovementPart 3: Change Management System as a Key Element of a Pharmaceutical Quality System 从概念到持续改进的药品质量生命周期实施（PQLI）第三部分:药品质量体系关键要素变更管理Product Quality Lifecycle Implementation (PQLI) from Concept to Continual ImprovementPart 4： Process Performance and Product Quality Monitoring System (PP＆PQMS）从概念到持续改进的药品质量生命周期实施（PQLI）第四部分：工艺性能和药品质量监测体系（PP＆PQMS）ISPE PQLI Guides Under Development制订中的ISPE PQLI指南。

I have always found mathematics to be an enigmatic realm, one that seems to defy my comprehension despite my best efforts. This admission is not made lightly; it carries with it a weight of frustration, self-doubt, and a persistent longing for understanding. In this essay, I delve into the multifaceted reasons behind my struggle with mathematics, examining the cognitive, emotional, pedagogical, and environmental factors that have contributed to this challenge.Firstly, from a cognitive perspective, I acknowledge that my difficulties in math might stem from inherent learning preferences and strengths. As an individual with a strong inclination towards linguistic and creative thinking, I often find myself thriving in subjects like literature, history, or art where concepts are conveyed through narratives, metaphors, and visual representations. Mathematics, on the other hand, with its abstract symbols, rigid structures, and emphasis on logical reasoning, presents a stark contrast to these preferred modes of learning. The language of math, characterized by formulas, equations, and algorithms, feels foreign and inaccessible to me, akin to trying to decipher an ancient script without a decoder ring. Moreover, my brain seems wired to excel in tasks that require synthesis, interpretation, and subjective evaluation, rather than those demanding precision, sequential thinking, and algorithmic problem-solving, which are paramount in mathematics.Secondly, emotions play a significant role in shaping my relationship with math. Fear, anxiety, and a sense of inadequacy have become inextricably intertwined with my mathematical experiences. The fear of failure, exacerbated by the cumulative nature of math where each concept builds upon the previous ones, creates a paralyzing effect. Even a minor misunderstanding at one stage can snowball into a major obstacle in subsequent lessons. This fear is further fueled by the societal perception that math proficiency is a marker of intelligence, leading to a deep-seated feeling of inadequacy when I struggle to grasp mathematical concepts. The resulting anxiety hampers my ability to concentrate, retain information, and think logically, creating a vicious cycle where poor performance reinforces negative emotions, which in turn hinder further learning.Thirdly, the pedagogical approach to teaching mathematics has also played a part in exacerbating my difficulties. Traditional math instruction often relies heavily on rote memorization, formulaic problem-solving, and a 'one-size-fits-all' curriculum that fails to cater to diverse learning styles. For someone like me, who thrives on context, meaning, and personal connections, this methodical, decontextualized presentation of math can be incredibly disengaging. Furthermore, the speed at which new concepts are introduced and the lack of adequate time for consolidation and practice often leave me struggling to keep up. The absence of real-world applications or interdisciplinary connections further distances me from appreciating the relevance and beauty of mathematics, leaving me feeling like an outsider looking in on a secret club.Lastly, environmental factors, both at home and in school, have contributedto my struggle with math. Growing up, math was not a subject actively discussed or valued in my family. The absence of positive mathematical role models or a culture that encourages mathematical exploration meant that I did not develop a mindset that embraces challenges and sees mistakes as opportunities for growth. Similarly, in school, a competitive atmosphere that prioritizes speed and accuracy over deep understanding and collaborative learning has stifled my confidence and willingness to engage with math. The pressure to perform well on standardized tests, coupled with a lack of individualized support, has left me feeling overwhelmed and unsupported in my mathematical journey.In conclusion, my struggle with mathematics is a complex interplay of cognitive preferences, emotional barriers, pedagogical limitations, and environmental influences. Recognizing these multifaceted factors is crucial not only for my own self-awareness but also for informing potential strategies to overcome my challenges. To improve my relationship with math, I need to find ways to bridge the gap between my linguistic inclinations and the abstract nature of mathematics, manage and mitigate math-related anxiety, advocate for a more inclusive and adaptive teaching approach, and cultivate a supportive, growth-oriented environment that values the process of learning over mere outcomes. By addressing these issues systematically, I hope to unlock the mysteries of mathematics and perhaps even discover the joy and beauty that lie beneath its seemingly impenetrable surface.。

AbstractThe Intelligent Systems Division (ISD) of the National Institute of Standards and Technology (NIST) has been researching new concepts in robotic cranes for several years. These concepts use the basic idea of the Stewart platform parallel link manipulator. The unique feature of the NIST approach is to use cables as the parallel links and to use winches as the actuators. Based on this idea, a revo-lutionary new type of robot crane has been developed and aptly named the RoboCrane. The RoboCrane provides six degree-of-freedom load stabilization and maneuverability. This is accomplished through the following controlmodes: master/slave; joystick input; operator panel input; preprogrammed trajectory following (teach programing, graphical off-line programing, or part programing); and sensor based motion compensation. The current control system includes both the controller and user interface within the same control level, which makes controller enhancements and modifications difficult and error prone. A Real-time Control System (RCS) [1] is currently being developed to include the above control modes, while pro-viding an open systems architecture. This supports hierar-chical control modules, along with a separate user interface. A remote telepresence system is also being implemented to provide foveal/peripheral stereo images and other necessary data to enable a remote operator to perform a variety of tasks with the RoboCrane.The objective of this paper is to describe past and future efforts toward integration of an RCS open system architec-ture controller into the RoboCrane Integration Testbed (RIT). An RCS-based Robo-Crane controller will allow for continuing research into parallel-link manipulator con-trollers and application oriented controller capabilities. Specifically, this paper introduces the RoboCrane concept, describes the current control system, the envisioned RCS-based RoboCrane control system, and the intended inte-gration procedure.Keywords: Real-Time Control System (RCS), open sys-tem architecture, parallel link manipulator, Stewart plat-form devices, cable-based robots, cranes.1.0 IntroductionThe RoboCrane prototype (FIGURE 1) was first developed by NIST in the late 1980's [2]. A NIST program on robot crane technology, sponsored by the Defense Advanced Research Projects Agency (DARPA), developed and tested several potential robot crane designs to determine the desired performance characteristics of a proposed robot crane. Initial testing of these prototypes showed that a six cable design results in a remarkably stable platform capa-ble of performing accurate six degree-of-freedom (DOF) manipulations. This stabilized platform can be used to improve typical crane operations or as a maneuverable robot/tool base.The RoboCrane is based on the Stewart platform parallel-link manipulator [3], but uses cables as the parallel links and winches as the actuators. By attaching the cables to a suspended work platform and maintaining tension in all six cables, the load is kinematically constrained. More-over, the suspended work platform resists perturbing forces and moments with a mechanical stiffness deter-mined by the angle of the cables, the suspended weight, and the elasticity of the cables. Based on these concepts, the RoboCrane is a revolutionary new type of robot crane that can control the position, velocity, and force of tools and heavy machinery in all six degrees of freedom (x, y, z, roll, pitch, and yaw).NIST research into Stewart Platforms also produced an innovative structure from which to suspend the Rob-oCrane work platform. An octahedral tubular structure, containing the three upper support points necessary to sus-pend the work platform, provides exceptional structural stiffness in a lightweight frame. By connecting the struc-ture’s legs in an octahedron configuration, forces and torques incurred by the work platform are translated into pure compressions and tensions in the legs. With only slight bending moments in each of the structure’s legs (due to self-weight), the RoboCrane’s octahedron structure can be made extremely lightweight compared to conventional gantry structures. This fact, along with the RoboCrane’s ability to lift very heavy loads, produces a much higherThis work was prepared by U.S. Government employees as part of their official duties and is therefore a work of the U.S. Government and not subject to copyright. Equipment listings in this paper do not imply a recommendation by NIST nor that the equipment is best for the purpose.RCS-Based RoboCrane IntegrationRoger Bostelman, Adam Jacoff, Nicholas Dagalakis, James AlbusIntelligent Systems DivisionNational Institute of Standards and TechnologyGaithersburg, Maryland 20899lift-to-weight ratio than conventional serial link manipula-tors. Also, the RoboCrane’s stable structure is well suited for mobility. By affixing independent wheeled vehicles under each of the structure’s three feet, the RoboCrane can be made to traverse rough terrain. This was demonstrated using a 2-meter, radio controlled prototype [4].The 6 m RoboCrane prototype has been subjected to a variety of performance measurements and computer simu-lations. Experimental tests were conducted to verify its functional work volume, static loading capability, and load positioning accuracy. These experimental results com-pared favorably to associated computer analysis [2].The RoboCrane work platform has been equipped with tools such as a gripper, grinder, welder, saw, and inspec-tion equipment (stereo vision and laser scanner). Thesetools have been used to demonstrate a variety of tasks. Each new application has contributed to the overall func-tionality of the Robo-Crane controller and to the design of the human/computer interface. The current controller implementation provides for intuitive and robust control of the RoboCrane through the following control modes: mas-ter/slave; joystick input; operator panel input; prepro-grammed trajectory following (teach programing,graphical off-line programing, or part programing); and sensor based motion compensation. Individual winch con-trol is also possible. Potential application areas for the RoboCrane technology can be found in the construction industry [5], nuclear/toxic waste cleanup, the subsea arena [6], and in planetary exploration [4].NIST has also developed an adaptation of the RoboCrane technology in order to investigate its effectiveness forFIGURE 1. 6-Meter NIST RoboCrane Prototype.SUSPENDED UPPER SUPPORT POINTSFOOTINGWITH PULLEY PAIRSPLATFORM TRIANGULAR WORK(1 of 3)(2 OF 3)TOOLSOCTAHEDRON STRUCUREWITH WINCH PAIRSFIGURE 2. TETRA Platform: Development platform for RCS-based RoboCrane Controllerlong-line suspended loads. This prototype system is called the Tetrahedral Robotic Apparatus (TETRA) (FIGURE 2). TETRA uses a similar Stewart Platform geometry with six cables driven by six winches. However, TETRA’s winches, amps, and computer controller are all mounted on the work platform instead of the supporting structure. This allows existing overhead lifting systems such as bridge cranes, boom cranes, and helicopters to be retrofitted. Also, the TETRA system is designed to allow the crane’s hook to provide most of the lifting force, while the addi-tional six winches and cables provide controlled maneu-verability during cargo acquisition and stabilization of the cargo during transfer. The six cables essentially act as coordinated taglines, providing 6 DOF control, thereby limiting spinning and swinging of the hook and cargo. The TETRA prototype will be used as the development plat-form for the RCS-based RoboCrane controller prior to implementation onto the 6m RoboCrane prototype.2.0 Current Control SystemThe RoboCrane Integration Testbed (RIT) control system currently consists of a controller computer with graphical operator interface, a remote operator/observer interface, and graphical programmer [7]. All these components are connected through a network, as shown in the RoboCrane System Architecture Diagram (FIGURE 3). The Rob-oCrane control system functions in the following control modes:•Master/slave•Joystick input•Operator panel input•Preprogrammed trajectory following- Teach programing- Graphical off-line programing- Part programing•Sensor based motion compensation.The RoboCrane’s available motion types include:•Single joint•Cartesian base frame (default)•Cartesian platform frame•Cartesian offset frame (tool center point)•Constrained motions along vectors•Rotations about vectors•Single axis force control2.1 The ControllerThe current RoboCrane Controller consists of a 64MHz Macintosh Quadra and an electronics rack electrically tied to one another through a Sensor Interface (FIGURE 3). Both the computer and the electronics rack house multiple components. The Sensor Interface converts the followingFIGURE 3. Current RoboCrane System Architecture Diagramto be digitally fed back into the computer:•six phase quadrature signal inputs from winch motor encoders (500 pulses per revolution) •six analog 10-turn potentiometers (pot) on each winch motor through speed reducers•six analog pots making up a Stewart platform (SP) joystick•six analog output tension sensors into digital information.The Sensor Interface outputs (not shown in figure 3) can be digital or analog. They are used to turn on/off linear actuators, tools and lights for a variety of applications such as gripping, grinding, and welding. The Macintosh outputs are analog signals from a 12 bit digital/analog converter board that provides input to the six power amplifiers. Pulse Width Modulated (20kHz) power amplifiers can be set in velocity or torque control modes. These are typically con-figured for velocity mode. For the operator interface, the RoboCrane control panel (FIGURE 4) provides interactive control over RoboCrane functions, settings, and status. Because the operators of these controllers are not expected to be computer literate and might wear protective gloves, a simple and intuitive graphic interface was developed using LabView software. Control modes and motion types can be activated or deactivated by computer mouse actions and/or touch screen actions. For direct manipulation of the RoboCrane platform, a 6 DOF force sensing joystick (Spa-ceball) is input serially through the computer modem port and communicates at 19.2 kbaud.2.2 Remote Operator/Observer InterfaceA Remote Operator/Observer Interface was developed to allow networked communications with the RoboCrane controller. This graphical interface consists of a touch-screen panel which looks similar to the actual RoboCrane controller panel. It communicates with the RoboCrane controller via ethernet and serves as a remote operator control station anywhere the network can reach. In addi-tion, this remote interface can act simply as an observer of RoboCrane operations, without any control functionality. The interface’s front panel buttons allow a remote opera-tor, with the proper permissions, to take control of Rob-oCrane functions or to simply act as a passive observer. The executable code for this Remote Operator/Observer Interface can be run on a computer located anywhere on the network.2.3 The Off-Line Graphical Programmer The Off-Line Graphical Programmer allows for safe and easy generation of platform trajectories (move commands) along with the timely actuation of tools. The Graphical Programmer runs on a Silicon Graphics (SGI) computerFIGURE 4. Robocrane Control Paneland controls the operation of a TGRIP (Teleoperative Graphical Robot Instruction Program) simulation of the RoboCrane workspace. The RoboCrane’s platform and tools are intuitively represented as three dimensional solid models. Graphical simulations of Robo-Crane motions, tool status, and other information is stored in a standard text file and is then made available to the RoboCrane through the network.2.4 Telepresence SystemA telepresence system is currently being developed and integrated into the RoboCrane Integration Testbed. It will include a flexible manipulator, called EMMA (Easily Manipulated Mechanical Armatures). The EMMA arm will be attached to the work platform with a pan-tilt-ver-gence (PTV) head as an end-effector. Dual sets of stereo cameras (foveal and peripheral views) will be installed on the PTV head. These allow a remote operator to have full telepresence into the RoboCrane work volume during operation. The operator will wear a heads-up display to enable continuous visual contact along with access to RoboCrane controller operations.2.5 System ComplexityThe RoboCrane controller consists of a complex assort-ment of over 900 electrical wires that can be difficult, tedious, and time-consuming to troubleshoot. The current configuration requires strong electrical signals to pass through long cables connecting the controller to motors, sensors, and tools. For example, the cables connecting the power amplifiers to the motors measure more than 25m in length. This type of electrical system complexity will be remedied in the RCS-based RoboCrane Control System.3.0 RCS-Based RoboCrane Control SystemIn addition to maintaining the RoboCrane’s current control modes and capabilities, the proposed RCS-based Rob-oCrane Control System (FIGURE 5) contains several tar-geted improvements. Some examples are as follows:•hierarchical, open system architecture withstandard control module interfaces•separate user interface into each level of the controller•more adaptable electronic design which scales well for larger systemsThese and other enhancements will form a modular, reconfigurable control system that will allow the system to be easily optimized for particular applications.3.1 Computer PlatformsThe proposed computer platforms for the RCS-based Rob-oCrane Control System differ from the current system. The Controller hardware will be based on PC-compatible machines running the Windows NT operating system with real-time extensions. This combination will support the RoboCrane’s computing requirements, while maintaining consistency with a de facto industry standard platform. Similarly, the graphical operator interface will be a C++ implementation running on a PC compatible/Windows NT machine. The Off-Line Graphical Programmer will remain on the SGI (running UNIX) due to heavy graphics and rendering requirements. All of these computer subsystems will be connected via ethernet.FIGURE 5. Proposed RoboCrane System Architecture Diagram3.2 Component ChangesOne major change to the physical components of the sys-tem will be the power amplifiers for the winches. In the proposed system, the same six winches will be driven by Controller Area Network amplifiers (CANAMP) instead of conventional power amplifiers. These CANAMPs will be located at each of the winches. The CANAMPs will communicate with the host computer through a CAN interface card residing within the Controller computer. The data transfer rate for the CAN system is up to 1 Mbit/sec. for networks up to 40m long and can contain 0 to 8 bytes of data without segmentation. These CANAMPs will remove the need for RoboCrane’s existing Sensor Inter-face, power amplifiers, power supplies, and isolation trans-formers. In addition, an emergency stop system (not shown in the figure) will be independently connected to the six CANAMPs, thereby eliminating the need for a sep-arate electronics rack.Most other major components, such as the winches, joy-stick and sensors (tension, encoder, potentiometer), will be incorporated into the proposed design. The addition of “jog pots” will be necessary for occasional direct axis con-trol of each winch, because the amplifiers will be co-located with winches. Jog pots will be used during non-computer controlled tasks such as calibration and cable replacement.3.3 Hierarchical Controller ModulesThe core concept behind the RCS-based RoboCrane Con-troller architecture centers around a hierarchical decompo-sition of tasks required to perform a particular application (FIGURE 6) [9]. The basic decomposition of commands can be loosely thought of in terms of time needed to per-form the action. That is, at the bottom most Servo Level ,time (t ) can be considered instantaneous. As one traverses up the hierarchy, each command level requires roughly an order of magnitude greater time (10x) to perform its com-mand.Therefore, the Primitive (Prim) Level would require roughly 10t, the Elemental-Move (E-Move) Level would require 100t , the Task Level would require 1000t , and so on.Similarly, the RCS model supports upward passing of sen-sor data as necessary for a particular module to perform its function. As each decomposed command is successfully performed (or not) a status is sent back up the hierarchy to the appropriate controller module at any given level. At the higher levels of the hierarchy, such as the Task Level , com-mands take longer to perform and status indications return less frequently than at the lower levels. While at the Servo Level , commands, status messages and sensor readings are carried out almost continually.In addition, the concept of a world model database is maintained so that any controller module may access a particular piece of information if and when it is necessary. For instance, the Workcell Level: Robocrane module might need to check the status of a gripper (functional or broken) before agreeing to perform some task that involves part manipulation.An essential part of an open system architecture is the def-inition and standardization of controller module interfaces. This is important because it allows developers of particu-lar modules with enhanced capabilities or experimental algorithms to “plug” their module into the overall control system and test it seamlessly. In the case of the RCS-based RoboCrane controller, the Neutral Manufacturing Lan-guage (NML) [10] will be used to perform all communica-tions between control modules.FIGURE 6. RCS Task Decomposition for the RoboCrane’s Work Platform MotionTIME t10t100t1,000t10,000t3.4 Task NarrativeAs an example, consider the task decomposition of a Rob-oCrane application such as welding (FIGURE 6). For the RoboCrane to perform a welding application, the Rob-oCrane’s Workcell Level:RoboCrane control module must receive a command to “weld a part.” This high level com-mand could be generated by a Shop Level control module (not shown in the figure), just as a part was placed in the RoboCrane work volume. Alternatively, that same com-mand could be issued via the operator interface for that level, as will be the case for the RoboCrane. The “weld a part” command is then decomposed by an intelligent Workcell Level:RoboCrane module which understands what tools are available and knows how to decompose the given command into its constituent elements. As a result, it passes down two simultaneous Task Level commands to its subordinates, Task Level: Platform Motion and Task Level: Weld. As the Task Level: Platform Motion module receives its command, it decomposes it into a series of goal motions and passes them down to the E-Move Level: Trajectory Generator module. This module understands the RoboCrane platform kinematics and can turn goal motions into an appropriate path. If the RoboCrane’s kine-matics were changed or if a completely different robot were used, this is the only controller module that would need to be updated. The E-Move Level: Trajectory Gener-ator module passes down path information that the Prim Level: CAN Interface module knows how to turn into joint goals for each Servo Level: CANAMP module. Then each Servo Level: CANAMP receives its goal information from above and interfaces directly with its specific hardware (a winch in this case). Each Servo Level: CANAMP sends incremental move commands to its winch and listens for feedback from associated sensors (encoder or tachometer). This way, the Servo Level: CANAMP closes the servo loop right at the winch, providing a rapid response. All these servo level actuators are synchronized by the levels above so that the resulting platform motion traces the intended robot trajectory.Meanwhile, the Task Level: Weld module has been waiting for the status of the platform motion to show that it is near the intended weld seam. The Task Level: Weld module may check the world model database to see if a particular point has been passed. Once that status is true, the Task Level: Weld module will begin to deploy the weld tip and at the appropriate time, power the welder on and off to cre-ate a synchronized welding path.4.0 Integration ProcedureThe RCS-based RoboCrane controller will support the current RoboCrane control modes, motion types, and tar-geted improvements listed in section 3.0 above. However, it is being developed on the TETRA platform (FIGURE 2) prior to integration into the RoboCrane Testbed for several tactical reasons. First, it is preferable to maintain Rob-oCrane demonstrations of tools and applications while the RCS-based controller is being developed. Second, because the TETRA and RoboCrane platforms differ slightly, adapting the controller to RoboCrane will provide a good first test of the controller’s modularity and portability. Third, TETRA’s compact design provides easy access to all hardware and will simplify development and testing of the new controller.TETRA’s current controller configuration consists of six conventional amplifiers driving each of its six winches. Feedback from each winch encoder and tachometer are input into an eight axis PMAC motion controller board housed within an onboard PC compatible computer. The onboard PC also houses a CANPC interface board, which sends digital signals through a “token ring” style network to each CANAMP located at each winch. TETRA’s cur-rent configuration is wired to allow easy switching between using the conventional amplifiers and the CAN-AMP system to power the winches. When the CANAMPs are in service, the servo motion control loop is imple-mented between the intelligent CANAMP and the winch, instead of sending motor feedback signals all the way to a centralized motion controller board. This will be particu-larly beneficial for systems such as RoboCrane where this length can be 30m or more. TETRA’s CANAMP system will provide a functional example of the reduced elec-tronic design complexity that was mentioned previously. Both TETRA’s onboard controller and offboard operator interface computers will use the Windows NT operating system, supplemented with real-time extensions which provide a 1ms cycle time. The onboard controller will incorporate RCS templates, NML communication proto-cols, shared memory, and other concepts consistent with an RCS controller [9]. The graphical user interface will be developed in C++.NIST has contracted with an industry partner, Advanced Technology and Research Corp. (ATR), to work closely in development of the RCS-based RoboCrane Controller aimed at producing a commercially available system. ATR will provide control module development and consulting, similar to their efforts on NIST’s Enhanced Machine Con-troller [9], a 4-axis machine tool controller currently in use in a General Motors manufacturing facility.5.0 SummaryBoth the RoboCrane and TETRA prototypes are based on the Stewart platform parallel-link manipulator. They use cables as the parallel links and winches as the actuators. They can control the position, velocity, and force of tools and heavy machinery in all six degrees of freedom (x, y, z, roll, pitch, and yaw).The current RoboCrane control system consists of a com-puter Controller, a Remote Operator/Observer Interface, and an Off-line Graphical Programmer connected by a net-work. The Controller itself can support a variety of control modes and motion types. The Remote Operator/ObserverInterface can be used from any computer located on the network. It allows for full remote control of all RoboCrane functionality or can be used simply to observe RoboCrane operations.Although the current RoboCrane controller is functional, it does not provide a standard, easily modifiable, open sys-tem, nor does it use a hierarchical control architecture. So, ISD is focusing on development of an RCS-based Rob-oCrane Control System that supports all the existing con-trol modes and provides improvements. These include standardization of controller module interfaces, separate user interfaces, more efficient electronic design, and oth-ers. A commercially available Controller Area Network (CAN) is also being incorporated to allow tighter servo loop control and limit wiring complexity.The RCS-based RoboCrane Controller is being developed on the TETRA system to allow continued demonstration of the RoboCrane while controller work advances. TETRA’s control can easily switch between conventional amplifiers and CANAMPs to allow stepwise development of the controller. NIST has contracted with an industry partner (ATR) to work closely in development of the RCS-based RoboCrane controller with the intention of produc-ing a commercially available system that could be readily reconfigured for different applications.6.0 References[1] Albus, J., McCain, H., Lumia, R., “NASA/NBS Stan-dard Reference Model for Telerobot Control System Architecture (NASREM),” NIST Technical Note 1235, National Institute of Standards and Technology, July, 1987.[2] Albus, J. S., Bostelman, R. V., Dagalakis, N. G., “The NIST ROBOCRANE, A Robot Crane,” Journal of Robotic Systems, July 1992.[3] Stewart, D., “A Platform with Six Degrees of Free-dom,” Proceedings of the Inst. of Mechanical Engineering, Volume 180(15), Part I:371-386, 1965-1966[4] Bostelman, R.V, Albus, J. S., et. al., “A Stewart Plat-form Lunar Rover,” Engineering Construction and Opera-tions in Space IV Proceeding, Albuquerque, NM, Feb 26-Mar. 3, 1994.[5] Bostelman, R., Albus, J., Dagalakis, N., Jacoff, A., “RoboCrane Project: An Advanced Concept for Large Scale Manufacturing,” Association for Unmanned Vehi-cles Systems International Proceedings., Orlando, FL, July 15-19, 1996.[6] Bostelman.R.V., Albus, J.S., “Stability of an Underwa-ter Work Platform Suspended from an Unstable Refer-ence,” Engineering in Harmony with the Ocean Proceedings, October 1993.[7] Dagalakis, N. G., Albus, J.S., Bostelman, R.V., Fiala, J., “Development of the NIST Robot Crane Teleoperation Controller,” Robotics and Remote Handling Proceedings, Fifth Topical Meeting, Knoxville, TN, April 1993.[8] Bostelman, R.V., Albus, J.S., Dagalakis, N. G., “A Robotic Crane System Utilizing the Stewart Platform Con-figuration,” International Symposium on Robotics and Manufacturing Proceedings, Santa Fe, NM, November 10-12, 1992.[9] Lumia, Ronald, “The Enhanced Machine Controller Architecture,” International Symposium on Robotics and Manufacturing Proceedings, Maui, HI, August 14-18, 1994.[10] Shackleford, Will, “The NML Programmer’s Guide,” /proj/rcs.lib/nml.html, 1995.。

一种机制四种方法英文One mechanism, four methods (in English):1. Mechanism: Feedback- Method 1: Surveys - collecting data through questionnaires and interviews.- Method 2: Focus groups - gathering a group of individuals to discuss and provide feedback on a specific topic.- Method 3: User testing - observing users as they interact with a product or service and collecting their feedback.- Method 4: Social media monitoring - keeping an eye on social media platforms to analyze user sentiments and collect feedback.2. Mechanism: Incentives- Method 1: Rewards and incentives - offering tangible or intangible rewards to individuals for providing feedback.- Method 2: Contests and competitions - organizing contests where users can participate and win prizes by providing feedback.- Method 3: Loyalty programs - creating loyalty programs where users can earn points or rewards for providing feedback.- Method 4: Referral programs - incentivizing users to refer others to provide feedback by offering rewards for successful referrals.3. Mechanism: Communication and Collaboration- Method 1: Online forums and communities - creating online platforms where users can discuss and collaborate in providing feedback.- Method 2: Feedback events and workshops - organizing events or workshops where users can come together and provide feedback through interactive sessions.- Method 3: Collaborative platforms - using collaborative platforms that allow multiple users to share and provide feedback on a common platform.- Method 4: Feedback sessions with stakeholders - engaging key stakeholders in feedback sessions to gather their insights and suggestions.4. Mechanism: Data Analysis- Method 1: Quantitative analysis - analyzing numerical data collected through surveys, questionnaires, and other quantitative methods.- Method 2: Qualitative analysis - analyzing textual data such asfeedback, comments, and reviews for themes, patterns, and insights.- Method 3: Sentiment analysis - using natural language processing techniques to analyze the sentiments expressed in feedback and reviews. - Method 4: Data visualization - representing feedback data through visualizations like charts, graphs, and heatmaps for better understanding and interpretation.。

Multivariable Feedback Control Analysis and Design1. IntroductionIn modern control systems, it is often necessary to control multiple variables simultaneously in order to meet specific performance requirements. This is known as multivariable control. Multivariable feedback control analysis and design involves the study of techniques for designing control systems that can handle multiple variables simultaneously. In this article, we will explore various aspects of multivariable feedback control analysis and design.2. Multivariable Control SystemsMultivariable control systems are systems that have multiple inputs and multiple outputs. These systems are typically more complex than single-input single-output (SISO) systems because the interactions between different variables can complicate the control design process. Understanding the characteristics and behavior of multivariable control systems is crucial for their effective analysis and design.2.1 System IdentificationBefore designing a multivariable control system, it is important to identify the dynamic behavior of the system. System identification techniques can be used to determine the mathematical models that describe the relationships between inputs and outputs of the system. This involves collecting input-output data and using various modeling techniques such as empirical modeling, transfer function modeling, or state-space modeling.2.2 Control ObjectivesIn multivariable control, there are often multiple conflicting control objectives that need to be satisfied simultaneously. These control objectives can include stability, desired transient response, disturbance rejection, and tracking of setpoints. Balancing theseobjectives and designing controllers that achieve them is a central aspect of multivariable control analysis and design.2.3 Interactions and CouplingOne of the key challenges in multivariable control is the presence of interactions and coupling between the different variables. Interactions occur when changes in one variable affect the behavior of another variable. These interactions can make it difficult to design controllers that do not interfere with each other. Understanding and mitigating interactions is essential for effective multivariable control.2.4 Controller StructureThe selection of an appropriate controller structure is critical to the success of multivariable control design. There are various types of controller structures that can be used, such as decentralized control, centralized control, and decentralized control with optimization. Each structure has its advantages and disadvantages, and the choice depends on the specific requirements of the control problem.3. Multivariable Control AnalysisMultivariable control analysis involves studying the behavior and performance of multivariable control systems. It aims to provideinsights into the system’s dynamics, stability, and robustness.3.1 Stability AnalysisStability is a fundamental requirement for any control system. In multivariable control, stability analysis becomes more complex due to the interactions and couplings between variables. Stability analysis techniques such as eigenvalue analysis, Nyquist stability criterion, and pole placement methods can be used to investigate and ensure thestability of a multivariable control system.3.2 Performance AnalysisPerformance analysis involves evaluating the performance of a multivariable control system in terms of its response to inputs and disturbance rejection. Performance measures such as rise time, settling time, overshoot, and steady-state error can be used to assess the system’s performa nce. Analysis techniques like frequency response analysis, time response analysis, and sensitivity analysis can provide valuable insights into the system’s performance characteristics.3.3 Robustness AnalysisRobustness analysis is concerned with the ability of a multivariable control system to withstand uncertainties and variations in the system’s parameters. Robust control techniques aim to designcontrollers that can provide satisfactory performance over a range of operating conditions and system uncertainties. Sensitivity analysis, robust stability analysis, and the use of optimal control techniques are commonly employed for robustness analysis in multivariable control.3.4 Interaction AnalysisInteraction analysis is crucial for understanding and managing the interactions between variables in a multivariable control system. Interaction measures such as relative gain array (RGA) and condition number matrix (CN) can be used to quantify the strength and direction of interactions. Analysis of interaction patterns can help in choosing appropriate control strategies and gain scheduling techniques to minimize interactions.4. Multivariable Control DesignMultivariable control design involves designing controllers that achieve the desired control objectives while taking into account the system’s dynamics, interactions, and constraints.4.1 Decentralized Control DesignDecentralized control design involves designing individual controllers for each variable in a multivariable control system. Each controller operates based on its local measurements and controls its respective variable. Decentralized control can be advantageous when theinteractions between variables are weak, and the system can be effectively decoupled.4.2 Centralized Control DesignCentralized control design aims to design a single controller that regulates all variables simultaneously. This approach considers the interactions between variables explicitly and can achieve better overall control performance. However, centralized control can be computationally complex and may require accurate modeling of the entire system.4.3 Decentralized Control with OptimizationDecentralized control with optimization is an intermediate approach that combines the advantages of both decentralized and centralized control. It involves designing decentralized controllers for individual variables while optimizing their performance collectively. This approach can provide a good balance between performance and complexity.4.4 Controller Tuning MethodsOnce the controller structure is selected, tuning methods are used to determine the controller parameters. Various tuning methods are available, such as PID tuning, gain scheduling, pole placement, and optimization-based methods. Each method has its advantages and limitations, and the choice depends on the specific control problem and requirements.5. ConclusionMultivariable feedback control analysis and design are essential for the effective control of systems with multiple variables. This article discussed key aspects of multivariable control systems, including systemidentification, control objectives, interactions and coupling, and controller structure selection. It also explored multivariable control analysis techniques, such as stability analysis, performance analysis, robustness analysis, and interaction analysis. Furthermore, the article covered various multivariable control design approaches like decentralized control, centralized control, and decentralized control with optimization. By understanding and applying these concepts and techniques, engineers can design robust and efficient multivariable control systems to meet desired control objectives.。

To cultivate outstanding students,it is essential to focus on a holistic approach that encompasses academic excellence,personal development,and social skills.Here are some effective methods for nurturing excellence in students:1.Encourage Curiosity and Creativity:Foster an environment where students are encouraged to ask questions,explore new ideas,and think creatively.This can be done through projectbased learning and discussions that challenge their perspectives.2.Set High Expectations:High expectations can motivate students to strive for excellence.Teachers should believe in their students abilities and push them to achieve their full potential.3.Provide Personalized Learning:Recognize that each student has unique learning needs and styles.Personalize the learning experience to cater to these differences,using differentiated instruction and adaptive learning strategies.4.Promote Critical Thinking:Incorporate activities that require students to analyze, evaluate,and synthesize information.This can be achieved through debates,case studies, and problemsolving exercises.5.Emphasize the Importance of Hard Work and Perseverance:Teach students that success comes from dedication and consistent e examples of successful individuals who have overcome challenges through hard work.6.Offer Support and Resources:Provide students with the necessary resources and support to excel in their studies.This includes access to quality educational materials, tutoring,and counseling services.7.Cultivate a Growth Mindset:Encourage students to view challenges as opportunities for growth rather than as obstacles.Teach them that intelligence and abilities can be developed over time.8.Encourage Extracurricular Activities:Participation in sports,arts,and clubs can help students develop leadership skills,teamwork,and time management,which are valuable for their overall development.9.Foster a Collaborative Learning Environment:Promote group work and collaboration, allowing students to learn from each other and develop social skills.10.Provide Regular Feedback:Offer constructive feedback on students work to helpthem understand their strengths and areas for improvement.This should be done in a timely and supportive manner.11.Teach Effective Study Skills:Equip students with strategies for effective studying, such as time management,notetaking,and test preparation techniques.12.Model Excellence:As educators,set an example of excellence in your own work and behavior.Show passion for learning and a commitment to personal growth.13.Create a Safe and Inclusive Environment:Ensure that the classroom is a place where all students feel safe,respected,and included,regardless of their background or abilities.14.Involve Parents and the Community:Engage parents and the wider community in the educational process.Their support can provide additional resources and opportunities for students.15.Celebrate Successes:Recognize and celebrate the achievements of students,both big and small,to boost their confidence and motivation.By implementing these methods,educators can create a supportive and challenging environment that nurtures excellence in students,preparing them for success in their academic and future endeavors.。

State-of-the-Art ArticleFeedback on second language students’writing Ken Hyland Institute of Education,University of London k.hyland@Fiona Hyland University of Hong Kongfhyland@hkucc.hku.hkFeedback is widely seen as crucial for encouraging and consolidating learning,and this significance has also been recognised by those working in thefield of second language(L2)writing.Its importance is acknowledged in process-based classrooms,where it forms a key element of the students’growing control over composing skills,and by genre-oriented teachers employing scaffolded learning techniques.In fact,over the past twenty years,changes in writing pedagogy and research have transformed feedback practices,with teacher written comments often supplemented with peer feedback,writing workshops, conferences,and computer-delivered feedback.But while feedback is a central aspect of ESL/EFL writing programs across the world,the research literature has not been unequivocally positive about its role in writing development,and teachers often have a sense that they are not making use of its full potential.In this paper we examine recent research related to feedback on L2 students’writing,focusing on the role of feedback in writing instruction and discussing current issues relating to teacher written and oral feedback,collaborative peer feedback and computer-mediated feedback.Feedback has long been regarded as essential for the development of second language(L2)writing skills,both for its potential for learning and for student motivation.In process-based,learner-centred classrooms,for instance,it is seen as an important developmental tool moving learners through multiple drafts towards the capability for effective self-expression.From an interactionist perspective it is regarded as an important means of establishing the significance of reader responses in shaping meanings (Probst1989).In genre classrooms feedback is a key element of the scaffolding provided by the teacher to build learner confidence and the literacy resources to participate in target communities.In fact,over the past twenty years,changes in writing pedagogy and insights gained from research studies have transformed feedback practices,with teacher written comments now often combined with peer feedback,writing workshops,oral-conferences,or computer-delivered feedback.Summative feedback, focusing on writing as a product,has generally been replaced or supplemented by formative feedback which points forward to the student’s future writing and the development of his or her writing processes.But while feedback is a central aspect of L2writing programs across the world,the research literature has not been unequivocally positive about its role in writing development,and teachers often have a sense that they are not making use of its full potential.Many questions relating to feedback remain unanswered or only partially addressed:Does it make a difference to students’writing?If so,in what areas?What is the best way of delivering feedback?Can error correction and form focused feedback have long term benefits on students’writing?Can technology play a greater part in delivering feedback?What role can peer feedback play in writing development?How far does culture play a part in student responses to feedback?How can teacher feedback enhance students’ability to independently reflect on their writing?What are the implications of feedback for teacher control and text appropriation?This paper reviews recent research which addresses these questions by focusing onKen Hyland is Professor of Education and Head of the Centre for Academic and Professional Literacies at the Institute of Education,University of London. He has considerable experience teaching and researching first and second language writing and has published over one hundred articles and ten books on writing and applied linguistics.Recent titles are T eaching and researching writing(Longman,2002),Second language writing(Cambridge University Press,2003), Genre and second language writing(University of Michigan Press,2004)and Metadiscourse (Continuum,2005).Professor Ken Hyland,School of Culture,Language and Communication,Institute of Education,University of London,20Bedford Way, London WC1H0AL,UK.k.hyland@Fiona Hyland has a Ph.D.from Victoria University of Wellington,New Zealand,on the subject of feedback in second language writing and is a lecturer in the Faculty of Education at the University of Hong Kong,where she coordinates the ELT specialism of the Masters in Education programme.She has25years of experience teaching and researching in the areas of TESOL and teacher education,and has published a number of papers on the subject of feedback to ESL writers.Dr Fiona Hyland,Faculty of Education,University of Hong Kong, Pok Fu Lam Road,Hong Kong.fhyland@hkucc.hku.hkLang.T each.39,77–95.doi:10.1017/S0261444806003399Printed in the United Kingdom c 2006Cambridge University Press77K.Hyland &F .Hyland■teacher written and oral feedback,peer conferencing and computer-mediated feedback.The volume of this research means that we are forced to focus on L2learners of English,although the issues are common to studies of learners of other languages.1.T eacher written feedbackDespite increasing emphasis on oral response and the use of peers as sources of feedback,teacher written response continues to play a central role in most L2and foreign language (FL)writing classes.Many teachers feel they must write substantial comments on papers to provide a reader reaction to students’efforts,to help them improve as writers and to justify the grade they have been given (K.Hyland 2003).Research in the 1980s and early 1990s,however,began to question the effectiveness of teacher feed-back as a way of improving students’writing.Early re-search on native English speakers (L1)suggested that much written feedback was of poor quality and was frequently misunderstood by students,being vague,inconsistent and authoritarian,overly concerned with error and often functioning to appropriate,or take over,student texts by being too directive (e.g.Knoblauch &Brannon 1981;Connors &Lunsford 1993;see also Ferris (2003:chapter 1)for a review).While Zamel (1985)painted a similarly bleak picture in L2contexts,it is important to note that feedback research was in its infancy at that time and ideas of best practice in both giving feedback and designing studies to describe it were fairly rudimentary.More recent empirical research suggests that feedback does lead to writing improvements and this section highlights this research.1.1Responding to errorA substantial amount of the research on teacher written feedback in L2writing contexts has been concerned with error correction and whether this be-nefits students’writing development.Research in this area has sought to explore whether error correction is effective and what strategies and treatments teachers use for error correction,and to discover the effects correction has on students’immediate revisions and their longer term development as writers.One line of argument,influenced by process theories,claims that feedback on error to L2students is discouraging and generally fails to produce any improvements in their subsequent writing (Robb,Ross &Shortreed 1986;Kepner 1991;Sheppard 1992;Polio,Fleck &Leder 1998;Fazio 2001).In a well-known summary of this literature,Truscott (1996)saw very little benefit in this kind of feedback and argued strongly that it was the responsibility of teachers to change student attitudes regarding what they should expect from teacher response by adopting a ‘correction-free approach’in their classrooms (Truscott 1996,1999).Recently,he responded to Chandler’s (2003)experimental study,which found that the accuracy of students’writing improved significantly over a semester when they corrected their errors after feedback than when they did not.Truscott (2004:342)queried Chandler’s findings and reiterated that error correctionjust be ineffective,but even harmful to and their overall writing quality,arguing time spent dealing with errors in class is better spent on additional writing practice.T eachers have been reluctant to follow this advice,however,as they are acutely aware that accuracy in writing is important to academic and professional audiences and that so-called ‘L2errors’often stigmatize writers (Horowitz 1986;Johns 1995;James 1998).They also feel that they should respond to the needs of students themselves,who see error-free work as very important.Research on student preferences has consistently found that students expect teachers to comment on their written errors and are frustrated if this does not happen (Cohen &Cavalcanti 1990;Leki 1991;Hedgcock &Lefkowitz 1994;Cumming 1995;Ferris 1995;F .Hyland 1998;Ferris &Roberts 2001;Lee 2004).In addition,it has been argued that the research on the lack of effectiveness of error feedback is not nearly as conclusive as Truscott claims (e.g.Polio 1997;Ferris 1999,2002,2003,2004).Statements that teachers’error feedback is often incomplete,arbitrary and inaccurate,for instance (e.g.Zamel 1985;Connors &Lunsford 1993),have simply not been consistently demonstrated empirically .Clearly,teacher variation is a crucial issue in both feedback and in the design of classroom research and little can be said on the basis of a few studies.Lee’s (2004)finding that half of her sample of Hong Kong teachers corrected errors inaccurately ,for example,was based on a de-contextualised teacher correction task,while Ferris’(2006)more naturalistic in situ study found teacher feedback to be overwhelmingly accurate.Further research into the linguistic knowledge and backgrounds of teachers whose first language is not English may go some way to help explain such variations in feedback practices.In fact,it is difficult to draw clear conclusions and generalizations from the literature as a result of varied populations,treatments and research designs.As we shall discuss below ,written feedback is more than marks on a page,yet research procedures often remove it from the real classrooms and teacher-student relationships within which it occurs (see F .Hyland &K.Hyland 2001;Goldstein 2005).Moreover,while marking mechanical errors can be frustrating,the view that there is no direct connection between correction and learning is greatly overstated.Master (1995),for instance,found that corrective feedback was effective when combined with classroom discussions.Fathman &Whalley (1990)found positive effects for rewriting from78■Feedback on L2students’writingfeedback on both grammar and content and Ferris (2006)discovered that about80%of students in her L2sample were able to successfully edit errors marked by teachers in a subsequent draft,with only10% making incorrect changes.But demonstrating that a student can utilize teacher feedback to successfully edit from one draft of a paper to the next tells us little about the learner’s successful acquisition of the linguistic features addressed by the feedback(Truscott 1996).The few studies that have looked beyond the immediate corrections in a subsequent draft,how-ever,have noted improvements in students’language accuracy(Polio et al.1998;F.Hyland2003;Chandler 2003).Ferris(2006),for instance,showed that students made statistically significant reductions in their total number of errors over a semester infive major grammar categories with a particular reduction in verb and lexical errors.These results underline the importance of general language proficiency and metalingusitic awareness in writing development and support Y ates and Kenkel’s(2002)argument that both error correction and its effectiveness must be seen in the context of a student’s evolving mastery of overall text construction.It is also worth pointing out that many studies of feedback on error have ignored how language acquisition occurs,although the influence of feed-back on the learner’s long term writing development fits closely with the SLA research(Goldstein,p.c). SLA studies indicate that second language acquisition takes place gradually over time and that mistakes are an important part of the highly complex develop-mental process of acquiring the target language.In fact,there may be a U-shaped course of development (Ellis1997)where learners are initially able to use the correct forms,only to regress later,before finally using them according to the target language norms(e.g.Doughty&Long2003).W e cannot, in other words,expect that a target form will be acquired either immediately or permanently after it has been highlighted through feedback.Even though explicit feedback can play an important role in second language acquisition,it needs time and repetition before it can help learners to notice correct forms,compare these with their own interlanguage and test their hypotheses about the target language. Attempting to establish a direct relationship between corrective feedback and successful acquisition of a form is,therefore,over-simplistic and highly problematic(e.g.Carson2001;Ferris2003).While feedback alone will not be responsible for improvement in language accuracy,it is likely to be one important factor.One key variable here is the type of error feedback that is given,and a number of researchers have compared direct feedback,where the teacher makes an explicit correction,with indirect forms where he or she simply indicates that an error has been made by means of an underline,circle,code,etc.The role of explicitness in student uptake,or response to feedback,is important as while indirect error feedback may encourage learner reflection and self-editing(Lalande1982),lower proficiency students may be unable to identify and correct errors even when they have been marked for them(Ferris &Hedgcock2005).Findings on feedback type have been conflicting, largely due to the widely varying student populations, types of writing and feedback practices examined and the diverse research designs lande (1982),for instance,reported a reduction in student errors with indirect feedback and Robb et al.(1986) discovered minimal long-term gains in accuracy compared with direct feedback practices.In a textual study of over5,000teacher comments,Ferris(2006) found that students utilized direct feedback more consistently and effectively than indirect types,partly as it involves simply copying the teacher’s suggestion into the next draft of their papers.However,less explicit forms of feedback also led to accurate revisions most of the time and this occurred whether underlined errors were coded or not.Ferris notes, however,that students’short-term ability to edit some types of errors which were directly marked by feedback did not always translate into long-term improvement,while indirect feedback seemed to help them develop more over time.While this may be a discouragingfinding for many teachers looking for evidence that their students are becoming more proficient writers,the importance of immediate improvement of drafts cannot be underestimated. Another issue is whether different types of errors ‘respond’differently to error treatment.Ferris(1999) suggests that some errors,such as problems with verbs,subject-verb agreement,run-ons,fragments, noun endings,articles,pronouns,and possibly spelling,can be considered‘treatable’,because they ‘occur in a patterned,rule-governed way’.In contrast,errors such as word choice and word order are‘untreatable’,in that‘there is no handbook or set of rules students can consult to avoid orfix those types of errors’(1999:6).T eachers tend to mark ‘treatable’errors indirectly and‘untreatable’errors directly(Ferris2006)and this is probably because they believe that students are unable to self-correct untreatable errors marked indirectly(Ferris2006). Moreover,while students seem to be able to improve their language accuracy through feedback on form if they are taught the rules governing directly‘treatable’errors(Ferris1999),idiosyncratic errors are more amenable to indirect feedback techniques,such as locating the type of error and asking students to correct it themselves(Ferris&Roberts2001). Overall,students appear to attend to teacher error corrections and in most cases use them to make accurate changes in their texts.This seems to facilitate student writing improvement both in the short term and over time,although it must be admitted79K.Hyland &F .Hyland■that longitudinal studies rarely span more than one semester.Improvements seem to be more likely if feedback is related to instruction and if indirect feedback methods are used.This last point might relate to SLA research which suggests that students need to invest more effort in processing the input they receive and are forced to notice discrepancies in their own work and the correct pattern they are trying to employ (see Gass &Selinker 2001;Mitchell &Myles 2004).1.2Teacher stances and feedback practicesAnother key area of investigation has been the stance teachers take towards students’texts and the relationship they build with their learners when giving feedback.It has long been recognised that teachers approach texts with a number of different purposes in mind and that these may change with different assignments,different students and different drafts (Bates,Lane &Lange 1993).Thus commentary on a draft is likely to serve more immediate pedagogical goals than that given on a final product,for instance,and process approaches mandate that teachers should comment on ideas in earlier drafts and on grammar in later drafts (e.g.Zamel 1985).Several researchers have observed,however,that because meaning is only realised through language,the content-form distinction creates a false dichotomy (K.Hyland 2003;Ferris &Hedgcock 2005),and research has shown that varying this recommended ‘meaning before form’pattern seems to make little difference to the quality of final products (Ashwell 2000).Outside the language class,of course,feedback is less concerned with the development of writing proficiency and more with appraising how students have processed content:writing is merely a medium by which students are judged on what they know of specific subject knowledge.T eachers,moreover,do not simply respond to grammar or content but have other purposes.T eachers adopt various commenting strategies which vary according to the type of essay assigned,the point of the semester in which feedback is given,and the proficiency of the student (Ferris 1997;Ferris et al.1997).Ferris et al.(1997),for instance,distinguished eight broad functions of response in 1500teacher comments,ranging from ‘Asking for unknown information’to ‘Giving information on ideas’.More simply,F .Hyland &K.Hyland (2001)and K.Hyland &F .Hyland (2006b)collected these purposes under the overarching functions of praise,criticism and suggestions,where suggestion and criticism are opposite ends of a continuum ranging from a focus on what is done poorly to a plan of action for its improvement.W e should also note that written feedback is not purely informational,for although the commentary may facilitate writing development it will only be effective if it engages with the writer.One increasingly studied social factor of this kind has been the ways teachers seek to structure activities through a course to ensure that students are able to interpret and use their comments effectively.Several studies have shown that feedback is not simply disembodied reference to student texts but an interactive part of the whole context of learning,helping to create a productive interpersonal relationship between the teacher and individual students (F .Hyland 1998;Conrad &Goldstein 1999;F .Hyland &K.Hyland 2001).F .Hyland (1998,2000a)and K.Hyland &F .Hyland (2006b),for instance,observed a close relationship between written and oral feedback and instruction,finding that the points made through explicit teaching were picked up and reinforced by written feedback and then recycled in both peer and student-teacher oral interactions.One way of establishing this link has been to encourage students to revise papers based on feedback and incorporate both final versions and drafts in a portfolio (Song &August 2002;Hamp-Lyons 2006).This allows teachers to observe students’development,improve their own practices by judging students’uptake of feedback,and create a closer relationship with learners.In addition,by using mechanisms such as cover sheets (Leki 1990),questionnaires,or writer autobiographies (Goldstein 2004)teachers are able to reveal student feedback preferences to enhance the effectiveness of their commentary and the students’revisions.In a longitudinal study,K.Hyland &F .Hyland (2006b)found that teachers did not simply mark a text but used information about the student to contextualise the writing being done,the strengths and weaknesses of the individual student,and his or her explicit requests for particular kinds of help.T o assist them,the two teachers studied not only made considerable use of the data provided in the cover sheets that students submitted with each piece of writing,but also considered the personality and possible response of the individual student to specific feedback points.This vividly illustrates that teachers do not give feedback in a vacuum but create a context for their remarks,making use of what they know of the writer to create an interpersonal link and target feedback to their personality and needs.Another aspect of the teacher-learner relationship now beginning to receive attention is how teachers select appropriate language and style in their feedback to construct the kinds of relationships which can facilitate a student’s writing development (F .Hyland &K.Hyland 2001;K.Hyland &F .Hyland 2006b).Essentially ,teachers have to weigh their choice of comments to accomplish informational,pedagogic,and interpersonal goals simultaneously while taking account of likely student reactions.Negative feedback may have a detrimental effect on writer confidence80■Feedback on L2students’writingwhile premature and gratuitous praise can confuse students and discourage revisions(F.Hyland&K. Hyland2001).T eachers often praise frequently as a means of building students’confidence,but students expect to receive constructive criticism rather than simple platitudes(Ferris1995;F.Hyland1998).T eachers also seek to mitigate the full force of their criticisms and suggestions by the use of hedges, question forms,and personal attribution and to be more reticent about criticising students’ideas than their language choices(F.Hyland&K.Hyland 2001;K.Hyland&F.Hyland2006b).However, while mitigation may foster a cooperative pedagogical environment,its indirect approach also carries the very real danger that students may miss the point of the comment or misinterpret the feedback(F.Hyland 2001b;K.Hyland&F.Hyland2006b).The choice between promoting positive affect or confronting writing weaknesses may be decided by targeting some errors only and leaving others to later drafts or assignments,but this certainly presents a serious dilemma for writing teachers who have to rely mainly on their experience and knowledge of their students.1.3Student views on teacher feedback Attempts have been made tofind out more about students’perspectives on teacher response,mainly through questionnaire research.Surveys of students’feedback preferences generally indicate that ESL students greatly value teacher written feedback and consistently rate it more highly than alternative forms such as peer and oral feedback(Radecki&Swales 1988;Leki1991;Enginarlar1993;Saito1994;Ferris 1995;Zhang1995).Although most surveys show that students want teacher feedback to highlight their grammatical errors,some indicate that they also want teachers to give them feedback on the content and ideas in their writing.(Hedgcock&Lefkowitz 1994,1996).Studies also suggest that students like to receive written feedback in combination with other sources,including conferences(Arndt1993; Hedgcock&Lefkowitz1994)and are positive about receiving indirect feedback on errors,giving them clues rather than corrections since they recognize that it encourages them to be more active in their use of feedback(Arndt1993;Saito1994;F.Hyland2001a). While most research has focused on feedback given by EFL or ESL writing teachers at undergraduate or pre-university levels,recent research has focused on feedback to L2graduate students,particularly by disciplinary faculty.Prior’s(1995,1998)studies,for instance,looked at feedback from peers and faculty on writing in graduate geography and sociology courses,showing how the writing tasks and the faculty’s response were shaped by the experiences, activities and goals the participants brought to and created within the seminars.Riazi’s(1997)study of four Iranian graduate students in education showed that the students viewed feedback as important for improving their understanding of their discipline,but also saw form-based comments as a way of developing their L2.It may be,however,that students receive fewer form-focused comments than they wish.Zhu’s (2004)survey,for example,suggests that faculty saw themselves primarily as providers of content-based summative feedback and regarded formative feedback on writing as the job of writing instructors.Leki(2006)has looked at feedback given by faculty to L2graduate students in a US university,analysing the written comments made by disciplinary faculty on student assignments and interviewing students to investigate their opinions about the value of written feedback in their development of disciplinary literacy. Most students reported that they found the feedback very useful but many also said they would have liked even more,especially feedback helping them to identify problems and giving them information about academic and disciplinary expectations.They also wanted feedback on how native speakers would express the same ideas,suggesting that–like Riazi’s students–they wanted their feedback to have a dual content/language focus.There is a need for more investigations to address questions on how L2 instructors and disciplinary faculty can work together more closely to meet students’needs.1.4Impact of teacher written feedbackon students’writingAlthough L2students themselves are positive about teacher written feedback,its contribution to writing development is still unclear,both in terms of its immediate impact on revisions to drafts and of the longer term development of their writing skills. Studies suggest that students may ignore or misuse teacher commentary when revising drafts.Sometimes they misunderstand it(Ferris1995;Conrad& Goldstein1999),or they understand the problems pointed out but are unable to come up with a suitable revision(Ferris1997;Conrad&Goldstein1999), and sometimes this causes them to simply delete the offending text to avoid the issues raised(F.Hyland 1998).There is also the issue of whether student revisions in response to feedback improve their writing.Research is not conclusive on this as it is difficult to claim a direct causal relationship between feedback and revision since both take place within a complex of contextual factors which can influence the extent and success of revision after feedback(Conrad&Goldstein1999;Goldstein 2006).Research into feedback,however,‘has largely been non-contextual and non-social,focused largely on texts and conducted within a linear model of teacher respond and student revise’(Goldstein2001: 77).81K.Hyland &F .Hyland■Much of the research on error correction reflects experimental or analytical research techniques that ignore classroom realities and the preferences of students (e.g.Frantzen 1995;Polio et al.1998;Ferris &Roberts 2001;Chandler 2003).Such approaches have their place,but they cannot capture the impact that wider classroom,institutional and personal contexts have on the ways feedback is given,understood and negotiated between participants.Sociocultural perspectives on learning therefore see knowledge and understanding not as things that can be handed down but as constructed through interactive processes (Riazi 1997;Murphy 2000;Goldstein 2006;Villamil &de Guerrero 2006).T eachers respond to students in their comments as much as texts,and experienced teachers often tailor their feedback to suit each student,considering their backgrounds,needs and preferences as well as the relationship they have with them and the ongoing dialogue between them (Ferris et al.1997;F .Hyland 1998,2001b).It may be,in other words,that what is effective feedback for one student in one setting is less so in another.Context is a combination of factors related to the institution and writing programme as well as those that teachers and students bring to the interaction (F .Hyland 1998,2000a;K.Hyland &F .Hyland 2006b).Goldstein (2004,2005),for instance,suggests that contextual factors can include socio-political issues that influence teacher status and morale,available resources and class size,institutional attitudes towards L2writers,exams,and program philosophies about feedback.Similarly,teacher factors such as attitudes towards particular students or the content of their texts,and student factors like reactions to teacher feedback and their investment in the course can have an impact on feedback and revision.These factors have not been systematically incorporated into most feedback research designs,however,and we know little about their potential impact on feedback and student revision.Attempts have been made,however,to link aspects of teacher feedback with student revision.Ferris (1997),for instance,looked at 110first and second drafts of papers by ESL tertiary students and found that three quarters of substantive teachers’commentsQ1on the drafts were used by the students and they tended to improve student papers.V ery few of the changes (less than 5%)actually had a negative effect,but revisions based on comments in the question form were judged as having mixed effects.Longer and more detailed text specific comments were also found to result in more positive revisions.Researchers have also tried to find out what kinds of comments are most effective.Ferris &Hedgcock (2005)suggest text-specific commentary is most likely to encourage revision.They also make the point that marginal comments have more immediacy and make it easier for students to locatethe source of a problem and revise appropriately whereas end comments can be more useful for writing development,since they summarize major problems.Marginal comments are also considered to be more motivating since they show the reader actively engaged with the writer’s text (Goldstein 2004).Conrad &Goldstein (1999)also question the importance often attributed to comment type in revision success.Their findings from three case studies suggest that choosing to phrase comments as questions,declaratives or imperatives had far less impact on the success of revisions than the type of problem identified in the feedback.Problems dealing with facts and details in the content were revised successfully about half the time,while those dealing with argumentation and analysis were revised successfully only 10%of time,a finding supported by Ferris (2001).Problems dealing with facts and details in the content were revised successfully about half the time,while those dealing with argumentation and analysis were revised successfully only 10%of time,a finding supported by Ferris (2001).A final key issue of students’responses to teacher feedback is that of ‘text appropriation’,or the idea that ownership of writing can be ‘stolen’from a writer by the teacher’s comments.L1writing researchers have suggested that writers might follow directive comments too closely and lose the oppor-tunity to develop as writers by merely rewriting their texts to reflect their teachers’preoccupations (Knoblauch &Brannon 1984).These concerns have been raised in ESL discussions of feedback but have been rigorously questioned by Reid who suggested that text appropriation was ‘largely a mythical fear of ESL writing teachers’(1994:275).She pointed out the danger of confusing helpful intervention with appropriation and urged ESL teachers to focus instead on their roles as ‘cultural informants and as facilitators for creating the social discourse community in the ESL writing classroom’(p.275).Appropriation and the socio-political aspects of giving feedback do,however,continue to be debated in the literature.F .Hyland (2000a)describes episodes where teachers overrode student decisions on use of feedback,raisingto not just to the ownership of writing to the ownership and control of the revision processes,supporting Hall’s (1995)point that appropriation may involve both concepts of good and bad writing products and good and bad writing behaviour.Recently ,the concept of appropriation has been redefined with the suggestion that appropriation can go in two directions.Appropriation of teacher feedback can be an active strategy used by novice academic writers as they develop their own voices and their familiarity with different genres.Tardy (2006)illustrates the complexity of this in her description of Chatri,an engineering doctoral student,whose sense of agency and ownership of his writing developed as82。

1、Bilingual 双语Chinese English bilingual text 中英对照2、Data warehouse and Data Mining 数据仓库与数据挖掘3、classification 分类systematize classification 使分类系统化4、preprocess 预处理The theory and algorithms of automatic fingerprint identification system (AFIS) preprocess are systematically illustrated.摘要系统阐述了自动指纹识别系统预处理的理论、算法5、angle 角度6、organizations 组织central organizations 中央机关7、OLTP On-Line Transactional Processing 在线事物处理8、OLAP On-Line Analytical Processing 在线分析处理9、Incorporated 包含、包括、组成公司A corporation is an incorporated body 公司是一种组建的实体10、unique 唯一的、独特的unique technique 独特的手法11、Capabilities 功能Evaluate the capabilities of suppliers 评估供应商的能力12、features 特征13、complex 复杂的14、information consistency 信息整合15、incompatible 不兼容的16、inconsistent 不一致的Those two are temperamentally incompatible 他们两人脾气不对17、utility 利用marginal utility 边际效用18、Internal integration 内部整合19、summarizes 总结20、application-oritend 应用对象21、subject-oritend 面向主题的22、time-varient 随时间变化的23、tomb data 历史数据24、seldom 极少Advice is seldom welcome 忠言多逆耳25、previous 先前的the previous quarter 上一季26、implicit 含蓄implicit criticism 含蓄的批评27、data dredging 数据捕捞28、credit risk 信用风险29、Inventory forecasting 库存预测30、business intelligence（BI）商业智能31、cell 单元32、Data cure 数据立方体33、attribute 属性34、granular 粒状35、metadata 元数据36、independent 独立的37、prototype 原型38、overall 总体39、mature 成熟40、combination 组合41、feedback 反馈42、approach 态度43、scope 范围44、specific 特定的45、data mart 数据集市46、dependent 从属的47、motivate 刺激、激励Motivate and withstand higher working pressure个性积极，愿意承受压力.敢于克服困难48、extensive 广泛49、transaction 交易50、suit 诉讼suit pending 案件正在审理中51、isolate 孤立We decided to isolate the patients.我们决定隔离病人52、consolidation 合并So our Party really does need consolidation 所以，我们党确实存在一个整顿的问题53、throughput 吞吐量Design of a Web Site Throughput Analysis SystemWeb网站流量分析系统设计收藏指正54、Knowledge Discovery（KDD）55、non-trivial(有价值的）--Extraction interesting (non-trivial(有价值的), implicit（固有的）, previously unknown and potentially useful) patterns or knowledge from huge amounts of data.56、archeology 考古57、alternative 替代58、Statistics 统计、统计学population statistics 人口统计59、feature 特点A facial feature 面貌特征60、concise 简洁a remarkable concise report 一份非常简洁扼要的报告61、issue 发行issue price 发行价格62、heterogeneous (异类的)--Constructed by integrating multiple, heterogeneous (异类的)data sources63、multiple 多种Multiple attachments多实习64、consistent（一贯）、encode（编码）ensure consistency in naming conventions,encoding structures, attribute measures, etc.确保一致性在命名约定，编码结构，属性措施，等等。