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英语衡水体pdfHere is a 601-word English essay on the topic "英语衡水体pdf":The English Hengshui StyleThe English language has long been a global phenomenon, transcending geographic boundaries and becoming a universal medium of communication. Within this expansive linguistic landscape, the Hengshui style of English writing has emerged as a distinct and influential approach. Originating from the city of Hengshui in China's Hebei province, this style of English composition has gained widespread recognition and admiration for its unique characteristics.At the heart of the Hengshui style lies a profound respect for the nuances and complexities of the English language. Students who engage in this approach to English writing are trained to meticulously analyze the structure and semantics of each word, sentence, and paragraph. This attention to detail is not merely a superficial exercise but a fundamental tenet that shapes the very essence of their compositions.One of the defining features of the Hengshui style is the emphasis on precision and conciseness. Writers in this tradition are encouraged to eschew verbose or flowery language in favor of a clear and succinct expression of ideas. Every word is carefully selected and placed to convey the intended meaning with maximum impact. This disciplined approach to writing not only enhances the clarity of the text but also challenges the writer to think critically and communicate effectively.Another distinctive aspect of the Hengshui style is the seamless integration of Chinese cultural elements into the English narrative. While the writing adheres to the conventions of English grammar and syntax, it often incorporates subtle references to Chinese philosophy, literature, and artistic traditions. This blending of Eastern and Western sensibilities creates a unique literary tapestry that captivates readers and broadens their cultural horizons.The Hengshui style also places a strong emphasis on the development of a persuasive and logical argument. Writers in this tradition are trained to construct their essays with meticulous attention to the flow of ideas and the strength of their reasoning. They are encouraged to anticipate counterarguments and address them with a balanced and nuanced approach. This intellectual rigor not only strengthens the overall quality of the writing but also equips the writers with the critical thinking skills necessary to excel inacademic and professional settings.One of the most remarkable aspects of the Hengshui style is its ability to transcend the boundaries of language and culture. While the style originated in China, it has gained recognition and admiration worldwide. Students and scholars from diverse backgrounds have embraced the Hengshui approach, recognizing its universal appeal and the valuable insights it offers into the art of effective communication.In the increasingly globalized world, the Hengshui style of English writing has become a valuable asset for individuals seeking to navigate the complexities of cross-cultural exchange. By bridging the gap between Eastern and Western modes of expression, this style empowers writers to engage in meaningful dialogues and foster greater understanding across linguistic and cultural divides.As the world continues to evolve, the Hengshui style of English writing remains a testament to the power of language to transcend boundaries and bring people together. Through its focus on precision, logical reasoning, and the incorporation of diverse cultural elements, this approach to English composition has the potential to shape the future of global communication and education.。
PGElectrical · Principle of Function · Universal Gripper1044Modular RoboticsModular-Standardized interfaces for mechatronics and control for rapid and simple assembly without complicated designs-Cube geometry with diverse possibilities for creating individual solutions from the modular systemIntegrated-The control and power electronics are fully integrated in the modules for minimal space requirements and interfering contours-Single-cable technology combines data transmission and the power supply for minimal assembly and start-up costs Intelligent-Integrated high-end microcontroller for rapid data processing -Decentralized control system for digital signal processing -Universal communication interfaces for rapid incorporation in existing servo-controlled conceptsYour advantages and benefitsThe modules of the PowerCube series provide the basis for flexible combinatorics in automation. Complex systems and multiple-axis robot structures with several degrees of freedom can be achieved with minimum time and expenditure spent on design and programming.Module overviewThe innovative technology of the PowerCube modules already forms the basis of numerous applications in the fields of measuring and testing systems, laboratory automation, service robotics and flexiblerobot technology.PGServo-electric2-Finger Parallel Gripper PRServo-electric Rotary Actuators PWServo-electricRotary Pan Tilt ActuatorsPSMServo-motors with integrated position controlPDUServo-positioning motor with precision gearsPLSServo-electric Linear Axes withball-and-screw spindle drivePG·Universal Gripper1045Method of actuationThe PowerCube modules work completely independently. The master control system is only required for generating the sequential program and sending it step by step to the connected modules. Therefore, only the current sequential command is ever stored in the modules, and the subsequent command is stored in the buffer. The current, rotational speed and positioning are controlled in the module itself. Likewise, functions such as temperature and limit monitoring are performed in the module itself. Real-time capability is not absolutely essential for the master control or bus system. For the communication over Bus-System the SMP - SCHUNK Motion Protocol - is used. This enables you to create industrial bus networks,and ensures easy integration in control systems.Control version AB Hardware Control with PLC (S7)Control with PC Interface Profibus DP CAN bus / RS-232SoftwareWindows (from Windows 98) operating systemLINUX operating systemDevelopment platforms MC-Demo Operating Software PowerCube (LabView, Diadem)with Online documentation, standard softwaregsd-file, programming examples(gsd file, programming examples)on requeston requestIncluded with the ''Mechatronik DVD'' (ID 9949633): Assembly and Operating Manual with manufacturer's declaration, MCDemo software and description and gsd-file for S7 use.1234567889ᕃ24VDC / 48VDC power supply provided by the customerᕄControl system provided by the customer (see control versions A, B and C)ᕅPAE 130 TB terminal block for connecting the voltage supply, the communication and the hybrid cable (Option for easy connection)ᕆPDU servo-motorᕇLinear axis with PLS ball-and-screw spindle drive and PSM servo-motorᕈHybrid cable (single-cable technology) for connecting the PowerCube modules (voltage supply and communication). Not recommended for the use in Profibus applications ᕉPW Servo-electric Rotary Pan Tilt Actuator ᕊPG Servo-electric 2-Finger Parallel Gripper ᕋPR Servo-electric Rotary ActuatorPG· Universal Gripper1046Size 70Weight 1.4 kg Gripping force up to 200 N Stroke per finger 35 mm Workpiece weight1 kgApplication exampleDouble rotary gripper module for loading and unloading of sensitive componentsPG 70 Servo-electric 2-Finger Parallel Gripper PR 70 Servo-electric Rotary ActuatorPGUniversal Gripper1047Gripping force control in the range of 30 - 200 N for the delicate gripping of sensitive workpieces Long stroke of 70 mm for flexible workpiece handlingFully integrated control and power electronics for creating a decentralized control systemVersatile actuation optionsfor simple integration in existing servo-controlled concepts via Profibus-DP, CAN bus or RS-232Standard connecting elements and uniform servo-controlled conceptfor extensive combinatorics with other PowerCube modules (see explanation of the PowerCube system)Single-cable technology for data transmission and power supplyfor low assembly and start-up costsServo-electric 2-finger parallel gripper with highly precise gripping force control and long strokeUniversal GripperArea of applicationUniversal, ultra-flexible gripper for great part variety and sensitive components in clean working environmentsYour advantages and benefitsGeneral information on the seriesWorking principle Ball screw driveHousing materialAluminum alloy, hard-anodized Base jaw materialAluminum alloy, hard-anodized ActuationServo-electric, by brushless DC servo-motorWarranty 24 monthsScope of deliveryGuide centering sleeves and ‘’Mechatronik DVD’’ (contains an Assembly and Operating Manual with manufacturer’s declarartion and MC-Demo software withdescription)PG· Universal Gripper1048Control electronicsintegrated control and power electronics for controlling the servo-motorEncoderfor gripper positioning and position evaluationDrivebrushless DC servo-motorGear mechanismtransfers power from the servo-motor to the drive spindleSpindletransforms the rotational movement into the linear movement of the base jaw Humidity protection cap link to the customer’s systemThe brushless servo-motor drives the ball screw by means of the gear mechanism.The rotational movement is transformed into the linear movement of the base jaw by base jaws mounted on the spindles.Function descriptionThe PG gripper is electrically actuated by the fully integrated control and power electronics. In this way, the module does not require any additional external control units.A varied range of interfaces, such as Profibus-DP, CAN-Bus or RS-232 are available as methods of communication. For the communication over Bus-System the SMP - SCHUNK Motion Protocol - is used. This enables you to create industrial bus networks, and ensures easy integration in control systems.If you wish to create combined systems (e.g. a rotary gripper module), various other modules from the Mechatronik-Portfolio are at your disposal.Electrical actuationSectional diagramPGUniversal Gripper1049Gripping forceis the arithmetic total of the gripping force applied to each base jaw at distance P (see illustration), measured from the upper edge of the gripper.Finger lengthis measured from the upper edge of the gripper housing in the direction of the main axis.Repeat accuracyis defined as the spread of the limit position after 100 consecutive strokes.Workpiece weightThe recommended workpiece weight is calculated for a force-type connection with a coefficient of friction of 0.1 and a safety factor of 2 against slippage of theworkpiece on acceleration due to gravity g. Considerably heavier workpiece weights are permitted with form-fit gripping.Closing and opening timesClosing and opening times are purely the times that the base jaws or fingers are in motion. Control or PLC reaction times are not included in the above times and must be taken into consideration when determining cycle times.General information on the seriesCentering sleevesElectrical accessories PAE terminal blockPAM standardconnecting elementsAccessoriesHybrid cableFor the exact size of the required accessories, availability of this size and the designation and ID, please refer to the additional views at the end of the size in question. You will find more detailed information on our accessory range in the …Accessories“ catalog section.PG 70· Universal Gripper1050Technical dataFinger loadMoments and forces apply per base jaw and may occur simultaneously. M y may arise in addition to the moment generated by the gripping force itself. If the max.permitted finger weight is exceeded, it is imperative to throttle the air pressure so that the jaw movement occurs without any hitting or bouncing. Service life may bereduced.Gripping force, I.D. grippingDescriptionPG 70Mechanical gripper operating data ID 0306090Stroke per finger [mm]35.0Constant gripping force (100 % continuous duty)[N]200.0Max. gripping force [N]200.0Min. gripping force [N]30.0Weight [kg] 1.4Recommended workpiece weight [kg] 1.0Closing time [s] 1.1Opening time [s] 1.1Max. permitted finger length [mm]140.0IP class20Min. ambient temperature [°C] 5.0Max. ambient temperature [°C]55.0Repeat accuracy [mm]0.05Positioning accuracy [mm]on request Max. velocity [mm/s]82.0Max. acceleration [mm/s 2]328.0Electrical operating data for gripper Terminal voltage [V]24.0Nominal power current [A] 1.8Maximum current [A] 6.5Resolution [µm] 1.0Controller operating data Integrated electronics Yes Voltage supply [VDC]24.0Nominal power current [A]0.5Sensor system EncoderInterfaceI/O, RS 232, CAN-Bus, Profibus DPPG 70Universal Gripper1051ᕃ24 VDC power supply provided by thecustomerᕄControl (PLC or similar) provided bythe customerᕅPAE 130 TB terminal block(ID No. 0307725) for connecting the power supply, the communication and the hybrid cableᕆHybrid cable for connecting thePowerCube modulesMain viewsThe drawing shows the gripper in the basic version with closed jaws, the dimensions do not include the options described below.ᕃGripper connection ᕄFinger connectionᕓᕗM16x1.5 for cable glandActuation DescriptionID Length PowerCube Hybrid cable, coiled 03077530.3 m PowerCube Hybrid cable, coiled03077540.5 mPowerCube Hybrid cable, straight (per meter)9941120The ‘Hybrid cable’ is recommended for the use in CAN-Bus- or RS232-systems. For Profibus applications we recommend to use a separate standardized Profibus cable for the communication.You can find further cables in the …Accessories“ catalog section.Interconnecting cablePG 70· Universal Gripper1052Special lengths on requestRight-angle standard element for connecting size 70 PowerCube modulesSpecial lengths on requestConical standard element for connecting size 70 and 90 PowerCube modulesSpecial lengths on requestStraight standard element for connecting size 70 PowerCube modules Right-angle connecting elements Description ID DimensionsPAM 120030782090°/70.5x98Conical connecting elements Description ID DimensionsPAM 110030781090x90/45/70x70 mm PAM 111030781190x90/90/70x70 mmStraight connecting elements Description ID DimensionsPAM 100030780070x70/35/70x70 mm PAM 101030780170x70/70/70x70 mmMechanical accessoriesYou can find more detailed information and individual parts of the above-mentioned accessories in the …Accessories“ catalog section.。
In the vast tapestry of education, English teachers occupy a distinct and vital space, weaving threads of knowledge, skill, and wisdom into the fabric of our intellectual growth. They are the custodians of a language that transcends borders, bridging cultures and fostering global understanding. Their role is not merely to impart grammar rules or expand vocabulary; rather, they nurture critical thinking, instill empathy, and ignite a lifelong passion for learning. This essay serves as an ode to our English teachers, celebrating their unwavering dedication and invaluable impact on our lives, while emphasizing the imperative of respecting them.I. The Architect of Language ProficiencyAt the core of an English teacher's profession lies the task of cultivating linguistic competence. They meticulously guide us through the labyrinthine rules of syntax, semantics, and phonology, equipping us with the tools necessary to express ourselves coherently and effectively. They expose us to a rich array of literary genres, enhancing our appreciation for the nuances of language and expanding our horizons of thought. By tirelessly correcting our essays, providing constructive feedback, and encouraging us to engage in lively class discussions, they help us refine our written and oral communication skills, which are indispensable in both personal and professional domains. Their commitment to our linguistic development is a testament to their passion for teaching and their belief in our potential, deserving our utmost respect and gratitude.II. The Beacon of Critical ThinkingEnglish teachers are more than mere purveyors of linguistic knowledge; they are catalysts of intellectual awakening. Through the analysis of complex literary texts, they challenge us to delve beneath the surface, to question assumptions, and to discern hidden meanings. They encourage us to scrutinize characters' motivations, interpret symbolism, and evaluate themes, thereby honing our analytical and evaluative abilities. Moreover, they facilitate debates and discussions that foster open-mindedness, tolerance, and the ability to articulate and defend our perspectives logically. By nurturing these criticalthinking skills, English teachers empower us to navigate the complexities of the world with clarity and confidence, making them instrumental in shaping our cognitive prowess and warranting our deep respect.III. The Cultivator of Empathy and Emotional IntelligenceThe study of literature under the guidance of an English teacher offers a unique opportunity to step into the shoes of others, fostering empathy and emotional intelligence. Through the exploration of diverse narratives and the lived experiences of characters from various backgrounds, epochs, and cultures, we learn to understand and appreciate perspectives different from our own. English teachers skillfully facilitate discussions that prompt us to reflect on our biases, broaden our worldview, and cultivate compassion. In today's increasingly interconnected yet polarized world, the ability to empathize and connect with others is not just a social virtue but a crucial life skill. English teachers play a pivotal role in nurturing this attribute, meriting our profound respect and admiration.IV. The Champion of Lifelong LearningEnglish teachers instill in us a love for learning that extends far beyond the classroom walls. They introduce us to timeless literary classics, contemporary masterpieces, and thought-provoking essays, igniting curiosity and a thirst for knowledge. They encourage independent reading, fostering a habit that enriches our minds, broadens our horizons, and provides solace in challenging times. Furthermore, by modeling a passion for continuous self-improvement, they inspire us to embrace a growth mindset and to view learning as a lifelong journey rather than a finite, school-based endeavor. Their commitment to nurturing lifelong learners deserves our utmost respect and emulation.V. The Mentor and Role ModelBeyond their formal teaching roles, English teachers often serve as mentors and role models, offering guidance, support, and inspiration. They listen patiently to our concerns, offer sage advice, and celebrate our achievements,contributing significantly to our emotional well-being and personal growth. Their dedication, professionalism, and integrity set a high standard for ethical behavior and work ethic, influencing our character development and future aspirations. In many instances, their words of encouragement or a well-timed nudge can make all the difference in a student's life trajectory. The profound influence English teachers exert as mentors and role models further underscores the importance of respecting them.Conclusion: Respecting English Teachers as Pillars of Knowledge and CharacterIn the grand scheme of education, English teachers stand as pillars of knowledge and character, tirelessly shaping our linguistic proficiency, critical thinking, empathy, love for learning, and personal growth. They navigate the intricate balance between imparting academic rigor and fostering emotional intelligence, guiding us towards intellectual maturity and societal engagement. Their unwavering dedication, despite the challenges they face, is a testament to their commitment to our holistic development.Respecting English teachers is not merely an act of courtesy; it is a recognition of their profound impact on our lives and a celebration of their invaluable contribution to society. It involves actively listening to their teachings, applying their guidance, and expressing gratitude for their tireless efforts. As students, let us honor their commitment by embracing the lessons they impart, both in language and in life. As a society, let us acknowledge and support their vital role, ensuring they have the resources, recognition, and working conditions they deserve. In doing so, we not only pay tribute to these unsung heroes but also invest in the future of our collective intellectual, emotional, and cultural prosperity.In the end, the respect we accord our English teachers reflects our understanding of their profound significance in our lives and our appreciation for their ceaseless dedication. It is an acknowledgement of their ability to transform us, page by page, word by word, into individuals better equipped tonavigate the complexities of our world, communicate effectively, think critically, empathize deeply, and continue learning throughout our lives. In honoring them, we honor the transformative power of education and the timeless wisdom enshrined in the language they teach.。
自然科学基金是我国支持科学研究的重要资助项目，自然科学基金(National Natural Science Foundation of China，简称NSFC) 是我国基础研究资金最大、涵盖范围最广的科学基金，也是我国科学研究的核心力量之一。
自然科学基金致力于对我国基础科学领域的研究提供资助支持，为科学家们提供了广阔的研究评台。
跨模态知识融合与关联推理是当前自然科学基金关注的热点之一，它涉及到多学科交叉融合，对于推动我国科学研究的发展具有重要意义。
一、跨模态知识融合的概念和意义1. 跨模态知识融合的概念跨模态知识融合是指利用不同形式的信息进行融合学习，从而获取更全面、更深入的知识。
它包括文本、图像、音频等多种模态的知识，通过相互融合和关联推理，可以帮助研究者更好地理解和利用信息。
在当前信息时代，跨模态知识融合已经成为了科研领域的重要研究方向。
2. 跨模态知识融合的意义跨模态知识融合的重要性体现在多个方面，它能够帮助科研人员更全面地了解研究对象。
在医学领域，结合病人的影像数据和临床病历，可以更准确地诊断和治疗疾病。
跨模态知识融合有助于促进不同学科之间的交叉融合，推动科学研究的跨学科发展。
跨模态知识融合还可以为人工智能和智能系统的发展提供重要支持，有助于提高系统的智能水平和应用水平。
二、自然科学基金对跨模态知识融合的支持自然科学基金一直以来对于跨模态知识融合的研究给予了重要支持。
通过对相关项目的资助，自然科学基金为跨模态知识融合的研究提供了良好的发展评台，推动了相关研究的深入开展。
近年来自然科学基金资助了大量在自然语言处理、计算机视觉、机器学习等领域的跨模态知识融合研究项目，这些项目为跨学科研究提供了宝贵的经验和成果。
可以说，自然科学基金的支持为跨模态知识融合的发展注入了强大的动力。
三、我对跨模态知识融合的个人观点和理解作为一名科技工作者，我对跨模态知识融合充满信心和期待。
跨模态知识融合的发展将有助于推动信息技术和人工智能的发展，为人类社会的进步做出重要贡献。
亲爱的英语作文英语英文回答：In the realm of communication, language plays a pivotal role in shaping our interactions, connecting us with others, and forming meaningful connections. As we traverse the linguistic landscape, we encounter a diverse array of dialects, scripts, and vocabulary, each carrying unique cultural nuances and historical significance. Words, like brushstrokes, paint vivid pictures in our minds, evoking emotions, conveying ideas, and weaving intricate tapestries of thought.The study of language, known as linguistics, delvesinto the intricate workings of human communication. It encompasses the analysis of phonology (the study of speech sounds), morphology (the study of word formation), syntax (the study of sentence structure), semantics (the study of word and sentence meaning), and pragmatics (the study of language use in context). Through linguistic exploration,we gain insights into the cognitive processes that underlie language acquisition and comprehension, uncovering the mysteries of how we encode and decode the spoken andwritten word.Language is not merely a tool for transmitting information; it is a reflection of our cultural identity, shaping our perspectives, beliefs, and values. Each language carries within it the accumulated wisdom, experiences, and aspirations of countless generations. As we explore different languages, we gain invaluable glimpses into the diverse ways of thinking and living that exist throughout the world.In an increasingly interconnected global community, the ability to communicate across linguistic boundaries is essential for fostering understanding, promoting cooperation, and bridging cultural divides. By embracing multilingualism, we not only enhance our cognitiveabilities but also open ourselves up to a world of new perspectives and possibilities.In conclusion, language is a transformative force that empowers us to connect, create, and understand. Its study provides invaluable insights into the human mind and the richness of human cultures. As we continue to unravel the complexities of language, let us celebrate its diversity and harness its power for the betterment of our world.中文回答：语言在沟通领域中扮演着至关重要的角色，它塑造了我们的互动方式，将我们与他人联系起来，并形成有意义的连接。
摘要伴随多媒体技术的飞速发展，图像、视频等视觉内容已变成网络社交文化中的一种主流媒介，越来越多的人在社交网站上上传图像来表达自己的情感或观念。
如何能使得计算机辨认甚至产生类似于人的情绪，开始受到越来越多的关注。
作为人工智能、计算机视觉等范畴的重要课题，情感计算对于计算机如何精确感知图像内容有重要意义。
实现该技术的一个关键之处就在于将图像的低层视觉信息与高层语义特征之间的鸿沟有效地衔接起来，从而建立符合人类认知的感情映射机制。
现有工作大部分都是从图像全局的角度出发，通过设计更好的特征来解决图像单情感标签预测问题，但其中主要存在着两点局限：首先，一个重要现象就是图像的情感传达区域的局部性，相对显著的区域而言背景区域含有的情感信息较少。
其次，视觉情感的标签存在着依赖关系且有很强的模糊性，使用独热编码形式来定义视觉情感不够准确。
针对于以上问题，本文通过多任务优化学习来进行视觉情感分析，对于图像情感的分类问题，为了更好的解决图像情感传达空间分布不均的问题，本文提出了一种基于弱监督情感检测的耦合神经网络框架，使用弱监督的方式发掘图像中蕴含情感比较丰富的区域，并将该区域信息结合到图像的情感分类中，该技术将图像情感区域检测和图像情感分类任务结合到一个统一的深度网络中，实现了端到端的训练，并且只需要图像级别的情感标注信息，而非像素级别的矩形框标注，因而减轻了大量标注的负担。
本文在多个情感数据集上的大量实验表明，该方法优于目前最先进的视觉情感分析方法；而对于情感标签的模糊性，本文使用标签分布的形式来对情感进行更为精细的建模，提出一种多任务情感标签分布学习框架来协同优化标签分布预测及分类任务，除此之外，由于大部分视觉情感数据集只提供了单个类别标签，为了提高该框架的实用性，本文也利用一种弱先验知识即标签之间存在的相似性信息，将单情感类别转化为对应的情感标签分布。
本文在公开的数据集上进行了大量相关实验来证明方法的有效性，并通过大规模的用户研究来验证情感标签分布和人的主观感受间的关联性。
The Acronyms of Compiler DesignIntroductionCompiler design is an essential field in computer science that deals with the creation of software programs called compilers. A compiler is responsible for translating high-level programming languages into machine-readable code. To better understand the concepts and discussions related to compiler design, it is crucial to become familiar with some of the frequently used acronyms in this domain.1.Overview1.1 CompilerA Compiler is a program that converts source code written in a high-level programming language into machine code or an intermediate representation (IR). It plays a vital role in software development by bridging the gap between human-readable code and the machine’s binary language.1.2 IR (Intermediate Representation)IR refers to the intermediate form of the source code generated by the compiler. It serves as an intermediary between the high-level language and the low-level machine language. An IR is typically lower level than the source code, making it easier for the compiler to optimize and translate into machine code.1.3 AST (Abstract Syntax Tree)AST represents the hierarchical structure of the source code and is created during the parsing phase of the compiler. It captures the syntax and semantics of the program in a tree-like data structure. The AST helps the compiler process and understand the source code during various compilation stages.2.Lexical Analysis2.1 DFA (Deterministic Finite Automaton)DFA is a mathematical model or an abstract machine that recognizes and processes regular languages. In compiler design, DFAs are used to perform lexical analysis by tokenizing the source code into individual tokens. DFAs help in identifying keywords, identifiers, constants, and other language constructs.2.2 LexerA lexer, often referred to as a scanner or tokenizer, is responsible for breaking the source code into meaningful tokens based on the predefined grammar rules. The lexer analyzes the input character by character and outputs a stream of tokens for further processing by the compiler.3.Syntax Analysis3.1 ParserA parser is a component of the compiler that analyzes the token stream generated by the lexer and checks if it conforms to the defined grammar rules of the programming language. It constructs the AST by recursively applying production rules defined in the grammar.3.2 LL Parsing (Left-to-Right, Leftmost derivation)LL parsing is a top-down parsing strategy where the production rules are applied from left to right and the leftmost non-terminal is expanded first. It is commonly used in LL(k) parsers, where ‘k’ denotes the number of lookahead tokens used to decide which production rule to apply.4.Semantic Analysis4.1 Symbol TableA symbol table is a data structure maintained by the compiler to store information about variables, functions, classes, and other program entities. It provides a mapping between the identifier names and their attributes, such as type, scope, and memory location. Symbol tables help in detecting semantic errors and resolving references during compilation.4.2 Type CheckingType checking is a crucial part of semantic analysis that ensures the compatibility and consistency of types in the source code. It verifies if the operations performed on variables and expressions are valid according to the language rules. Type-checking rules are defined based on the programming language’s type system.5.Code Generation5.1 IR Code GenerationIR code generation involves translating the high-level source code into an intermediate representation code. The IR code is closer to the machine language and allows for further optimization before generating the final machine code.5.2 OptimizationOptimization aims to improve the efficiency of the generated code by applying various techniques. Common optimization strategies include removing redundant code, optimizing loop structures, and reducing the number of memory accesses. Optimization helps in producing faster and more efficient programs.6.Code Optimization6.1 Liveness AnalysisLiveness analysis determines the live range of variables in the program, i.e., the portion of the program where a variable is being used or has a potential to be used. This analysis is crucial for register allocation and code elimination optimizations.6.2 Register AllocationRegister allocation is the process of assigning variables to registers of a processor, considering the limited number of available registers. Efficient register allocation reduces the usage of memory accesses, which leads to faster program execution.ConclusionUnderstanding the acronyms commonly used in compiler design is essential for grasping the intricacies of this field. The mentioned acronyms provide a foundation for discussing various concepts, techniques, and stages involved in the compilation process. By familiarizing ourselves with these acronyms, we can delve deeper into the study and development of compilers.。
如何帮动物说英语作文Writing an essay on teaching animals to speak English involves a blend of imagination and scientific understanding. Here's an approach:Title: Teaching Animals to Speak English: A Journeyinto Animal Communication。
Introduction:Communication is a fundamental aspect of life, enabling beings to convey thoughts, emotions, and needs. While humans have developed complex languages, animals communicate through various means such as vocalizations, body language, and even chemical signals. However, the idea of teaching animals to speak English raises intriguing questions about the limits of communication across species barriers.Body:Understanding Animal Communication:Before delving into teaching animals English, it's essential to grasp how they communicate naturally.Different species have unique ways of expressing themselves. For instance, dolphins use clicks and whistles, while birds employ songs and calls. Dogs communicate through barks, growls, and body postures. Recognizing these diverse communication systems lays the groundwork for bridging the gap between human language and animal communication.The Science of Language Acquisition:Language acquisition in humans involves intricate cognitive processes, including syntax, semantics, and pragmatics. While animals may not possess the samelinguistic capabilities, studies have shown their capacity for learning and understanding human language to varying degrees. Researchers have trained certain animals, like chimpanzees and parrots, to recognize and produce words, demonstrating the potential for cross-species communication.Teaching Methods:Teaching animals to speak English requires patience, creativity, and a deep understanding of animal behavior. One approach is using operant conditioning, where desired behaviors are reinforced through rewards. By associating specific sounds or words with rewards, animals can learn to produce those sounds to obtain desired outcomes. Additionally, employing visual aids, such as pictures or gestures, can facilitate language learning in animals.Case Studies:Several notable examples illustrate the feasibility of teaching animals to communicate in English. Koko the gorilla, trained in sign language, demonstrated an extensive vocabulary and comprehension of over a thousand signs. Alex the African grey parrot amazed researchers with his ability to use words creatively and understand abstract concepts like color and shape. These cases highlight the potential for interspecies communication and challengetraditional notions of language abilities in non-human animals.Ethical Considerations:While the prospect of animals speaking English is fascinating, ethical concerns arise regarding their welfare and autonomy. Teaching animals to communicate in human languages raises questions about exploitation and the extent to which they truly comprehend the language versus merely imitating sounds for rewards. Ethical guidelines must ensure that such endeavors prioritize the well-being and dignity of the animals involved.Future Directions:As technology advances and our understanding of animal cognition deepens, the possibilities for interspecies communication continue to expand. Emerging research in fields like animal cognition, linguistics, and artificial intelligence offer promising avenues for exploring new methods of communication with animals. By fostering mutualunderstanding and respect, we can enrich our relationships with other species and gain insights into the remarkable diversity of life on Earth.Conclusion:In conclusion, the idea of teaching animals to speak English sparks both curiosity and ethical reflection. While it may never fully replicate human language, efforts to bridge the communication gap between species hold profound implications for our understanding of cognition and our relationship with the natural world. Through patience, empathy, and scientific inquiry, we can embark on a journey of discovery into the fascinating realm of animal communication.。
2023年英语甲卷英语作文英文回答：My Thoughts on the Power of Language and the Challenges of Translation.Language, a fundamental facet of human existence, is a tapestry of words and phrases that weaves the fabric of our communication. It is a tool that enables us to express our thoughts, ideas, and emotions, shaping the very way we perceive the world around us.The power of language lies in its ability to transcend mere communication and become an instrument of creativity, imagination, and critical thinking. Through language, we conjure images, paint vivid pictures, and delve into realms of thought inaccessible through other means. It is the language that fuels literature, art, and scientific inquiry, broadening our perspectives and deepening our understanding of the human experience.However, the allure of language is not without its complexities. The act of translation, the process of conveying meaning from one language to another, presents a unique set of challenges. Language, being deeply embedded in cultural context, defies simple word-for-word substitutions.Translators navigate the treacherous terrain of semantics, grappling with the nuances of different languages and the subtle variations in meaning that can dramatically alter the intended message. Cultural idioms, historical references, and the ever-present dance between the written word and the unspoken context pose formidable obstacles that require not only linguistic proficiency but also a deep understanding of the source culture.The challenges of translation extend beyond the realm of literal accuracy into the realm of cultural sensitivity and appropriateness. Translators must be mindful of the target audience and the cultural values they embody, ensuring that the translated text resonates with itsintended readers while preserving the essence of theoriginal work.Despite the inherent difficulties, translation remains an indispensable tool for fostering cross-cultural understanding and promoting global dialogue. It allows usto transcend linguistic barriers, access a wider range of knowledge and perspectives, and appreciate the beauty and diversity of human expression.In conclusion, language holds immense power as avehicle for communication, creativity, and critical thought. However, the complexities of translation remind us of the challenges inherent in conveying meaning across linguistic and cultural boundaries. By embracing these challenges, translators act as cultural brokers, bridging the gap between different worlds and fostering a more inclusive and interconnected global community.中文回答：我对语言的力量以及翻译挑战的看法。
Bridging Geometry and Semantics for Object Manipulation and GraspingWorkshop PaperTolga AbacıVRlab–EPFL tolga.abaci@epfl.chMichela MortaraIMATI–CNR mortara@r.itGiuseppe Patan`eIMATI–CNR patane@r.itMichela SpagnuoloIMATI–CNR patane@r.itFr´e d´e ric VexoVRlab–EPFL frederic.vexo@epfl.chDaniel ThalmannVRlab–EPFL daniel.thalmann@epfl.chAbstractIn this paper,we present our on-going work towards grasping in an object manipulation con-text.Our proposal is a novel method that com-bines a tubular feature classification algorithm, a hand grasp posture generation algorithm and an animation framework for human-object interactions.This method works on objects with tubular or elongated parts,and accepts a number of parameter inputs to control the grasp posture. Keywords:virtual environments,grasping, shape analysis,smart objects,animation1IntroductionRealistic animation of object grasping for an au-tonomous virtual human is a difficult problem, with many different sides to take into account. The human hand is a complicated articulated structure with27bones.Not only the move-ments of these joints must be calculated,but also the reaching motion of the arm and the body needs to be considered.For real-time perfor-mance in a VR system with many agents,fast collision-detection and inverse kinematics algo-rithms[20]will be necessary in most cases. The calculation of the hand and body postures is not the only difficulty in grasping:realistic grasping also requires significant input about the semantics of the object.Even if the geometric and physical constraints permit,sometimes an object is simply not grasped“that way”.For ex-ample,a door handle must not be grasped from the neck section if the goal is to turn it.A fully-automatic grasping algorithm that only takes the geometry of the object into account cannot al-ways come up with solutions that are satisfac-tory in this sense.It is evident that the grasping operation is strongly dependent on the artificial intelligence of an autonomous virtual human. Fortunately,the grasping problem for au-tonomous virtual humans is easier than its robot-ics counterpart.Simply put,we do not have to be as accurate and physical constraints are much less of a problem.The main criterion is that the grasp must“look”realistic.In fact,the apparent physical realities of a virtual environment can be very different from those of the real-world,with very different constraints being imposed. For example,we can imagine a virtual human holding an object that is several times his size and weight in air,while grasping it at a small site on the edge.This does not conflict with the previous examples addressing the reality issue, as for an autonomous virtual human in a virtual setting,this is more a question of what he in-tends to do with the object(semantics)than the actual physics of grasping.In this paper,we present our on-going work towards grasping in an object manipulation con-text.For the solution of this problem we propose a novel method that combines a tubular feature classification algorithm,a hand grasp posture generation algorithm and an animation frame-work for human-object interactions(with smart objects[8]).Our method works on objects with tubular or elongated parts,and accepts a number of parameter inputs to control the grasp posture. 2Related Work2.1Smart ObjectsMaking objects interaction-capable usually re-quires solutions to closely-related issues on two fronts:the specification of behavior and its re-flection through animation.On the behavior front,virtual human–object interaction techniques werefirst specifically ad-dressed in the object specific reasoner(OSR) [12].The primary aim of this work is to bridge the gap between high-level AI planners and the low-level actions for objects,based on the obser-vation that objects can be categorized with re-spect to how they are to be manipulated.This works gives little consideration to interaction with more complex objects.The work on Parameterized Action Repre-sentation[1]addresses the issue of natural lan-guage processing for virtual human-object inter-actions.A PAR describes an action by speci-fying conditions and execution steps.Recently, V osinakis and Panayiotopoulos have introduced the Task Definition Language[22].This lan-guage supports complex high-level task descrip-tions through combination of parallel,sequential or conditionally executed built-in functions. Rule-based behaviors are a popular tech-nique:according to the system state,applicable rules can be selected to evolve the simulation. In addition,state machines are widely used for specifying behaviors as they have useful graphi-cal representation.A good example for a system utilizing both techniques is Improv[17]. Animation of virtual humans can be exam-ined in many categories,depending on the type of action.Generation of realistic human walk-ing motion has been an interesting subject for researchers[5].Inverse kinematics is also com-monly used for creation of reaching motions for articulated structures[2,20,23],but it is still difficult to obtain realistic full-body pos-tures without substantial tweaking.On the other hand,database-driven methods[24,4]cope bet-ter with full body postures.These methods are based on capturing motions for reaching inside a discrete andfixed volumetric grid around the ac-tor.The reaching motion for a specific position is obtained through interpolation of the motions assigned to the neighboring cells.Grasping is perhaps the most important and complicated motion that manipulation of objects involves.Robotics techniques can be employed, as in[7]for automatic grasping of geometrical primitives,based on a pre-classification of most used hand configurations for grasping[6].Plan-ning algorithms for determining collision free paths of articulated arms have also been devel-oped for manipulation tasks[10],and they have been successfully used for interactive generation of reaching and transfer motions[9].Because of the random nature of this method,complicated motions can be planned,but with high and un-predictable computational cost.A huge litera-ture about motion planning is available,mainly targeting the motion control of different types of robots[11].2.2Shape AnalysisKnowledge about the presence of elongated fea-tures is relevant in the context of animation for the definition of posture and grasping motion for virtual humans.While tubular or elongated fea-tures can be quite easily defined during the de-sign processes,their automatic extraction from unstructured3D meshes is not a trivial task. Moreover,geometric parameters such as tube axis or section size should be made readily avail-able to the animation tool.Among the many methods for shape analysis, skeleton extraction techniques are the most suit-able for identifying tubular features.Topology-based skeletons,for example,code a given shape by storing the evolution of the level sets of a mapping function defined on its boundary.A geometric skeleton is usually associated to this coding,defined by the barycenters of the con-tours.The shape is decomposed into parts which can be characterized as protrusion-like features or branching sites of the shape,even if the protrusions can be arbitrarily shaped.The Reeb graph is an example of topology-based skeketons,whose computation has been pro-posed in the literature using different approaches [19,21,3].Topological graphs usually preserve genus information and therefore could be used to identify tubular parts that define handles,but the location and shape of other elongated feature requires a more specific analysis.For example,in[13],tubular parts are identi-fied using a sweeping techniques along the arcs of the skeleton which is constructed by join-ing the edges remaining after an edge collapse process on the whole mesh.These edges are linked in a tree structure,and it is used as a sup-port for the sweeping process where the mesh is intersected by a set of planes and tubes are iden-tified by looking at the geometry of the cross-sections.Other skeletons,such as the well-known Me-dial Axis Transformation(MAT),define a struc-ture which could be useful for the identification of tubular features.But the MAT of a3D object is generally a non-manifold complex,computa-tionally heavy to compute,and sensitive to noise because tiny perturbations may produce a whole new arc.Furthermore,there is not a direct rela-tion between tubular features and specific com-ponents of the MAT,especially when the tubes have an arbitrary shape and the cross sections do not exhibit any symmetry.3ApproachOur primary goal is to address grasping issues for virtual human object manipulation.For this, we propose theflow comprised of the steps given below:1.Given an object,the tubular or elongated features of an object are recognized and a list of cross-sections is associated to the features.2.During smart object design,the designer selects the sections of the extracted features that are relevant for grasping.Additional grasping parameters are specified for each of these sec-tions.3.At run-time,grasping is performed using the data specified in the smart object,as a part of the object manipulation sequence.The algorithm to detect tubular features is called Plumber and it is a specialized shape clas-sification method for triangle meshes.The algo-rithm segments a surface into connected com-ponents that are either body parts or elongated features,that is,handle-like and protrusion-like features,together with their concave counter-parts,i.e.narrow tunnels and wells.The seg-mentation can be done at single or multi-scale, and produces a shape graph which codes how the tubular components are attached to the main body parts.Moreover,each tubular feature is represented by its skeletal line and an average cross-section radius.The Smart Objects paradigm is based on ex-tending objects(shapes)with additional infor-mation on their semantics.Its focus is on au-tonomous virtual humans within virtual environ-ments.The semantic information that a smart object carries is mainly about the“behavior”of the object when an interaction occurs between the object and a virtual human.By behavior,we mean the changes in the appearance and state of an object as a result of the interaction(i.e.a vir-tual human opening a door).In our approach,the smart objects control the manipulation sequences.Grasping is perhaps the most important part of a manipulation se-quence,but it is not alone.A full sequence can consist of walking and reaching to the ob-ject,looking at it,grasping it multiple times, and keeping the hands constrained to the ob-ject while it is moving.Therefore,the smart objects are required to provide a full manipula-tion sequence,putting the grasping action into the proper context.The manual specification of the grasp para-meters in the second step makes the approach semi-automatic.While we can attempt to de-rive these parameters automatically,it is very difficult to do so only based on the geometri-(a)(b)(c)(d)Figure1:Plumber method:(a)identification of limb vertices,(b)extraction of their connected com-ponents and medial loop,(c)iteration,(d)tube and a cap(black)found at this scale.cal properties of the object.To determine which tubular sections of complex object are of rele-vance to grasping,we need additional input on how the object is to be manipulated.For exam-ple,a teapot containing hot tea to be poured into a cup should normally be grasped by the handle, not the neck.The current state of the art in artifi-cial intelligence does not offer a general,work-ing solution for this problem yet,so our practical solution is to make the teapot a smart object and specify the required semantic information dur-ing its design.As our approach uses smart ob-jects for simulating manipulation,the grasping parameters will be stored together with other at-tributes of the object,which are also specified in the design phase.It is possible to generate the grasp postures (execute the third step)before run-time.This can be accomplished by calculating afixed grasping posture,and storing it in the smart ob-ject and simply making the hand assume the stored posture during run-time.While this ap-proach results in simpler and faster run-time ex-ecution,we have chosen not to take this route for a number of reasons.Firstly,a fully pre-computed grasping posture is dependent on the hand for which it was computed.Different virtual humans can have different hand sizes, therefore the resulting grasp will not be accu-rate enough.In addition,as we will explain later,certain grasping parameters are specified as ranges,which are then searched tofind a sat-isfactory solution for the particular virtual hu-man configuration at the time of grasping.This introduces a degree of variation into the manip-ulation sequences,which is hard to achieve with fixed pre-computed grasping postures.4The Plumber methodThe Plumber method analyses the shape of an object by studying how the intersection of spheres centered at the mesh vertices evolve while the sphere radius changes.For example, for a thin limb,the curve of intersection be-tween the mesh and a sphere will be simply con-nected for a small radius and then will rapidly split into two components when the radius in-creases and becomes greater than the tube size. While a detailed description of the shape analy-sis technique which uses intersecting sphere and of the Plumber method can be found in[15,16], we will summarize here the main properties of Plumber and describe how the geometric para-meters are associated to elongated features. First of all,Plumber can identify tubular fea-tures whose section and axis can be arbitrarily shaped,and the size of the tube is kept as a con-straint during the identification process.More-over,since the shape is analysed using a set of spheres of increasing radius,the recognition fol-lows a multi-resolution schema.Chosen a sphere of radius R,Plumber per-forms the following steps:1.identify seed-tube regions;these regionswill produce one intersection area with thesphere,with two boundary curves of inter-section(see Figure1(a));2.shrink each of the two selected intersectioncurves along the surface to the medial-loop,whose points are nearly equidistant fromthe two border loops(see Figure1(b)); 3.expand-back the medial-loop by sweepingthe extent of the shape in both directions.More precisely,at each iteration we place asphere of radius R in the barycentre of the new medial loops.If the intersection be-tween the sphere and the surface generates two loops,mesh vertices inside the sphere are marked as visited;4.the procedure is iterated in both directions until:•no more loops are found,or more than one loop is found on not-visited regions;•the new loop lies on triangles that are already part of another tube,or the length of the new loop exceeds a pre-defined threshold.5.the tube skeleton is extracted by joining the loops’barycentres.As shown in Figure 2,tubular features are recognized at different scales and their geomet-ric description is computed also in case of in-teracting features.For the purpose of extracting grasping sites for a virtual human,like handles for instance,the radius value can be set with re-spect to hand anthropometricmeasures.(a)(b)Figure 2:Tubular features recognized byPlumber on a complex model:(a)tube axis and loops,(b)tubes colored with respect to their scale.After the location of seed tubular regions and the computation of the medial loop,the tubes are recovered by expanding the loop by con-trolled procedure which,at each step,extends the center-line and at the same time ensures that the surface is tubular around it.For the ex-pansion process,intersecting spheres are used again,but centred on the tube axis.A first medial sphere is drawn,whose centre p is thebarycentre of the medial loop,and whose radius is R .If M ∩S (p,R )does not have two boundary components,the growing stops and the candi-date tube is discarded.Otherwise,a new sphere with the same radius is centred in the barycen-tre of the two intersection loops;the process is then split into two parts,trying to grow the tube in both directions.Now we focus on the sphere moving in one of the two directions,since the other case is symmetric.At each iteration,the sphere rolls to the barycentre of the next loop,and the triangles laying completely or partially inside the sphere are marked as belonging to that tube.Then,the intersection between the sphere in the new posi-tion and the mesh is again computed,taking into account only the intersection curves through non visited triangles (all the spheres except the me-dial one have always a “backward”loop,pass-ing on the already marked triangles).During the loop expansion,the following cases may arise:•no intersection curves are found.This is the case of a tubular protrusion terminating in a tip;visited triangles locate a cap (see Figure 3(a),in the square);•the intersection curve consists of one loop (see Figure 3(a)).If its length is less than a pre-defined threshold,the size of the tube section is not varying too much;the loop becomes a new cross section and its barycentre contributes to the skeleton as a new node.Otherwise (see Figure 3(b),in the oval),the growth stops.•the intersection counts two,or more loops;that is,a bifurcation occurs (see Figure 3(b)).The growing of the tube in this di-rection stops,and the last visited triangles are unmarked.Finally,the barycentres of the medial loops are joined to define the tube skeleton.5Smart ObjectsIn essence,smart objects provide not only the geometric information necessary for drawing them on the screen,but also semantic informa-tion useful for manipulation purposes.We have(a)(b) Figure3:(a)No new loop is found on the snake tail(in the box),and a loop discardedafter the length check on the head(inthe oval).(b)A branching occurs onthe dolphin tail.built a framework for real-time animation of vir-tual human–object manipulation sequences. This framework provides smart objects capabil-ities and is composed of the following compo-nents:•A design tool that incorporates the defini-tion of semantic information in the processof object design.•An XML-based specification for virtual ob-jects,including appearance,animation andinteraction aspects.•An extended scene-graph structure that en-ables storage and query of semantic infor-mation at run-time.•An event-based mechanism and scriptingfunctionality for controlling and coordinat-ing animation of objects and virtual hu-mans.Attributes are the primary means of specify-ing information on how a virtual human ma-nipulates its environment.They convey vari-ous kinds of information(e.g.where and how to approach for manipulating the object or to position the hands in order to grasp it),anima-tion sequences(e.g.a door opening)and gen-eral,non-geometric information associated with the object(e.g.weight or material properties). The semantic information in the smart object is used by the virtual characters to perform actions on/with the object,e.g.grasping,moving it,op-erating it(e.g.a machine or an elevator).We have integrated the attribute definition process into3D Studio MAX,a popular soft-ware package for design and visualization of vir-tual ing our plug-in,attribute sets can be created as the geometry of the en-vironment is designed.This has the advantage of providing a consistent working space for de-signers.Figure4:Object manipulation with grasping The animation of virtual humans is handled by“actions”.Actions provide a higher level view of animation tasks.For example,the look action requires a vector as a parameter and keeps the virtual human looking at this position while it is active.The walk action takes a vector as a parameter,which is used as the target of the walk.The reach action takes a hand posture and a matrix as parameters.The hand of the virtual human is brought to the position and orientation specified by the matrix by using inverse kine-matics.Once the hand is at the target,it assumes the given posture for grasping.Human.WalkTo(Wheel.FrontPosition) WaitUntilEvent(WalkReached(Human))Human.Reach(Wheel.LeftHand)Wheel.StartAnim(Wheel.Turn)RepeatEvent=WaitAndReceiveEvent()If Event.Is(AttribChanged(Wheel.LeftHand) Human.NewReachTarget(Wheel.LeftHand)Until Event.Is(AnimFinished(Wheel.Turn) Wheel.Turned=TrueFigure5:Sample manipulation pseudo-script Scripts and events are used forflexible high-level control and coordination of animation ele-ments.Consider the example in Figure4from a training application,where a virtual human needs to manipulate a machine.In this partic-ular case,the action to be performed is turn-ing a wheel for adjustment.The sequence of movements that the human should make and thechanges in the state of the machinery in response is described by a script.Such a script,in a sim-plified pseudo form,is given in Figure5. Grasping Extension Usually,designers de-fine the grasping hand postures for a smart ob-ject manually during the design phase.This is tedious and results in manipulation sequences that are always executed exactly in the same way.Also,the results are satisfactory only for thefixed dimensions.We propose to modify this process,reducing it to specification of a few grasping parameters relevant to the grasping al-gorithm presented in this paper.During the design phase,the designer is pre-sented with the Plumber output,andfirst iden-tifies the tubular regions of the object that are relevant to grasping.These exist as sets of(ap-proximated)cylinders that are connected in a chain configuration.For each such region,the designer then defines the following parameters:•Wrist position/orientation relative to thetubular section.Both can be specified aseitherfixed or a range of values.•Touch tolerance,essentially specifyinghow much afinger can“sink”into the ob-ject.This value sets the threshold in thecapsule intersection algorithm.•Thumb configuration can be specified asclosed or on-the-side.If specified asclosed,the grasping algorithm will try tomake the thumb encircle the section to begrasped,just like the otherfingers.If spec-ified as on-the-side,the algorithm will tryto make the thumb touch one of the tubes,in a parallel orientation.•Finger spread specifies the angle in be-tween each of the fourfingers,effectivelydefining how much thefingers will bespread.•Finger selection specifies whichfingerswill be involved in the grasp.These parameters are stored in the object de-scriptionfile,together with all the other at-tributes.There can be multiple sets of parame-ters per region.6Grasping6.1Collision DetectionOur real-time grasping algorithm is based on ap-proximating the parts of a tubular section and the finger segments with capsules.A capsule(or capped cylinder)is the set of points at afixed distance from a line segment.Two capsules in-tersect if and only if the distance between cap-sule line segments is smaller or equal to the sum of the capsule radii.Given afinger segment and a tubular region, wefirstfind out which part of the tubular region is most likely to intersect with thefinger seg-ment.We accomplish this by intersecting the finger plane with each tube center line segment. We define thefinger plane as the plane perpen-dicular to the axis of rotation of the distalfinger joints.It is dependent on thefinger spread pa-rameter.We then run the capsule intersection test to determine whether the tube and thefinger segment intersect.To determine whether two capsules intersect, we need to compute the minimum distance be-tween points on two capsule line segments.The parametric equations by the line segments are given by L0(s)= B0+s M0for s∈[0,1], and L1(t)= B1+t M1for t∈[0,1].Thesquared distance function for any two points on the line segments is Q(s,t)=| L0(s)− L1(t)|2 for(s,t)∈[0,1]2.The function is quadratic in s and t,and given byQ(s,t)=as2+2bst+ct2+2ds+2et+f,where a= M0· M0,b=− M0· M1,c= M1· M1,d= M0·( B0− B1),e=− M1·( B0− B1), and f=( B0− B1)·( B0− B1).The goal is to minimize Q(s,t)over the unit square[0,1]2.Q is a continuously differentiable function,therefore the minimum occurs either at an interior point of the square where its gradient is equal to(0,0)or at a point on the boundary of the square.[18]includes further details on how this minimization is performed.For grasping,we need to determine whether thefinger segment“touches”the object,there-fore the test method described above is not adequate since it merely reports intersections. Therefore,we introduce the touch tolerance intothe capsule collision test inequality as a toler-ance value.Let R sum be the sum of the capsule radii,D min the minimum distance between the capsule line segments,and the touch tolerance. We can distinguish between three cases:•D min>R sum:Thefinger segment doesnot touch the object and it is outside the ob-ject.•R sum≥D min>(R sum− ):Thefingersegment touches the object.•(R sum− )≥D min:Thefinger segmentis inside the object.In fact,the touch tolerance value implies a re-laxed suggestion on how much the capsules can sink into each other.This,in turn,can create the impression of a tighter or looser grasp on the object.This is an advantage of using the cap-sule intersection test for the collision detection calculations.Even though the choice of(uncapped)cylin-der as the collision detection primitive comes into mind,we have decided not to use it.The main reason is that the intersection test for cylin-ders is a fairly expensive one(e.g.[18]uses the method of separating axes).Furthermore,a cap-sule gives a nice approximation of afinger seg-ment that includes thefinger tip.Another choice for the collision detection primitive would be the box,but we do not use it since the results would be too coarse.We need to create postures where thefingers encircle the tubular sections,which is not possible to do satisfactorily with box-based collision detection.6.2Posture searchThefinal grasp posture is computed by execut-ing a dichotomy search(similar to the one in [14])in the configuration space of the hand. This space is defined by the range of wrist po-sition and orientation plus the ranges of orienta-tion of thefinger joints.Fortunately,its dimen-sions can be reduced thanks to the anatomy of the hand:•The metacarpophalangeal(MCP)joints arebiaxial joints,with two degrees of freedom.•The distal interphalangeal(DIP)and proxi-mal interphalangeal(PIP)joints are uniax-ial(hinge type)joints,with only one degreeof freedom around the lateral axis.•We can assume that the DIP joint angle is afunction of the PIP joint angle,further re-ducing the dimensions.There are also optional reductions that can be made,to make the search faster in object-specific cases.Thefinger spread parameter can befixed,resulting in reduction of the degrees of freedom for the MCP joints from two to one. Also,in case they are not needed for the grasp, somefingers may be omitted from the search,fixing their posture to a predefined one.At each step during the search,we generate a hand posture to be tested,which obeys the joint limits.Then,the collision detection algorithm described above is invoked for the posture.The search continues until one of the following:•A posture that fulfills all the constraints isfound.This posture is returned as thefinalgrasp posture,to be used during the objectinteraction sequence.•The maximum number of postures that canbe tested is reached.If this happens,weassume that the virtual human cannot graspthe object.In most cases where a valid grasping pos-ture exist,the search will terminate relatively quickly,thanks to existence of the touch toler-ance value.In those cases where a grasp posture cannot be found,the most likely course of ac-tion is for the designer to modify the design of object to relax the grasp parameters,to increase the chance offinding a grasp posture.This is a consequence of the tradeoff between a fully-automatic grasping method with less control or a semi-automatic method like ours with more con-trol over how the grasping takes place.The reason why we have chosen to compute thefinal grasp posture by searching instead of analytical methods is that it provides a practical means to satisfy all the constraints and still re-mainflexible.Not only the joint limits impose constraints,but there are also dependencies be-tween the joint angle values,primarily between。
