基于IDRISI的CA-Markov教程

基于隐半马尔可夫模型的微博流行信息检测方法
谢柏林;黎琦;邝建
【期刊名称】《计算机科学》
【年(卷),期】2022(49)S01
【摘要】目前微博已成为人们发布信息和获取信息的一个重要平台。

为了及早发现微博上的流行信息,以便及时发现微博上的热点事件,同时及时发现、抑制谣言信息的传播,使微博在网民的信息获取和信息发布中发挥更积极的作用,文中提出了一种基于隐半马尔可夫模型的微博流行信息检测方法。

该方法以信息转发者的影响力等级和相邻两个转发者的时间间隔构建观测值,使用随机森林分类算法来自动得到转发者的影响力等级,利用隐半马尔可夫模型来刻画流行信息的传播过程,基于此来及早发现潜在的流行信息。

该方法分为模型训练和流行信息检测两个阶段,在流行信息检测阶段,计算每条信息在传播过程中产生的观测序列相对于模型的平均对数似然概率,实时更新每条信息的流行度。

使用采集的新浪微博数据集和Twitter数据集对所提方法进行了测试,实验结果表明了该方法的有效性。

【总页数】6页(P291-296)
【作者】谢柏林;黎琦;邝建
【作者单位】广东外语外贸大学信息科学与技术学院;广东外语外贸大学网络空间安全学院
【正文语种】中文
【中图分类】TP391
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目录什么是Icepak? (2)程序结构 (2)软件功能 (3)练习一翅片散热器 (8)练习二辐射的块和板 (43)练习三瞬态分析练习四笔记本电脑练习五改进的笔记本电脑练习六 IGES模型的输入练习七非连续网格练习八 Zoom-in 建模1.1 什么是Icepak?Icepak是强大的 CAE 仿真软件工具，它能够对电子产品的传热，流动进行模拟，从而提高产品的质量，大量缩短产品的上市时间。

Icepak能够计算部件级，板级和系统级的问题。

它能够帮助工程师完成用试验不可能实现的情况，能够监控到无法测量的位置的数据。

Icepak采用的是FLUENT计算流体动力学 (CFD) 求解引擎。

该求解器能够完成灵活的网格划分，能够利用非结构化网格求解复杂几何问题。

多点离散求解算法能够加速求解时间。

Icepak提供了其它商用热分析软件不具备的特点，这些特点包括：•非矩形设备的精确模拟•接触热阻模拟•各向异性导热率•非线性风扇曲线•集中参数散热器•外部热交换器•辐射角系数的自动计算1.2 程序结构Icepak软件包包含如下内容:•Icepak, 建模，网格和后处理工具•FLUENT, 求解器图 1.2.1:软件架构Icepak本身拥有强大的建模功能。

你也可以从其它 CAD 和 CAE 软件包输入模型. Icepak 然后为你的模型做网格, 网格通过后就是进行CFD求解。

计算结果可以在Icepak中显示, 如图 1.2.1所示.1.3 软件功能所有的功能均在Icepak界面下完成。

1.3.1 总述•鼠标控制的用户界面o鼠标就能控制模型的位置，移动及改变大小o误差检查•灵活的量纲定义•几何输入IGES, STEP, IDF, 和 DXF格式•库功能•在线帮助和文档o完全的超文本在线帮助 (包括理论和练习册) •支持平台o UNIX 工作站o Windows NT 4.0/2000/XP 的PC机1.3.2 建模•基于对象的建模o cabinets 机柜o networks 网络模型o heat exchangers 热交换器o wires 线o openings 开孔o grilles 过滤网o sources 热源o printed circuit boards (PCBs) PCB板o enclosures 腔体o plates 板o walls 壁o blocks 块o fans (with hubs) 风扇o blowers 离心风机o resistances 阻尼o heat sinks 散热器o packages 封装•macros 宏o JEDEC test chambers JEDEC试验室o printed circuit board (PCB)o ducts 管道o compact models for heat sinks 简化的散热器•2D object shapes 2D模型o rectangular 矩形o circular 圆形o inclined 斜板o polygon 多边形板•complex 3D object shapes 3D模型o prisms 四面体o cylinders 圆柱o ellipsoids 椭圆柱o elliptical and concentric cylinders 椭圆柱o prisms of polygonal and varying cross-section 多面体o ducts of arbitrary cross-section 任意形状的管道1.3.3 网格•自动非结构化网格生成o六面体，四面体，五面体及混合网格•网格控制o粗网格生成o细网格生成o网格检查o非连续网格1.3.4 材料•综合的材料物性数据库•各向异性材料•属性随温度变化的材料1.3.5 物理模型•层流/湍流模型•稳态/瞬态分析•强迫对流/自然对流/混合对流•传导•流固耦合•辐射•体积阻力•混合长度方程（0-方程）, 双方程(标准- 方程), RNG - , 增强双方程 (标准- 带有增强壁面处理), 或Spalart-Allmaras 湍流模型•接触阻尼•体积阻力模型•非线性风扇曲线•集中参数的fans, resistances, and grilles1.3.6 边界条件•壁和表面边界条件：热流密度, 温度, 传热系数, 辐射,和对称边界条件•开孔和过滤网•风扇•热交换器•时间相关和温度相关的热源•随时间变化的环境温度1.3.7求解引擎对于求解器FLUENT,是采用的有限体积算法。

（一）、PostStack 数据处理模块重采样（二）、相似性预测1、Fscan相似性分析原理2、导致不相似的因素3、Fscan 3D(三)、属性提取下面将PAL提取的３９种属性分成５类加以说明：该属性对振幅变化非常敏感。

，它比能量半衰时更敏感。

（四）、储层特征可视化与油气预测技术１、数据准备File下。

如图：（１）、ASCII文件的输入（2）、OpenWorks 井数据在完成上图的操作后，可对RA VE表进行替代、扩展和合并，如下图：值的平均。

（3）、SeisWorks Horizon(s) 地震解释层位和属性参数多种参数。

面上。

(4)、回归模型的输入（2）、数据分析本部分比较重要，包括对属性的数学运算，聚类，回归分析，相似性计算，2D，3D交会图及群类的映射等。

交互性能及可视化手段极大地提高了上述操作的效率和精度。

数据分析在RA VE种分成两部分，Edit和View。

下面分别介绍各菜单项的功能：①、2D Crossplot(Histogram)。

②、3D Crossplot✧3D交会图的旋转通过旋转不同的角度，可以分离出多属性的聚群特征，从而找出有意义的聚类群。

✧特征群圈定与映射如下图所示✧从已知井预测。

✧其他辅助功能③2D Matrix ……2D 交会图阵列出现如下窗口：④各参数间的相关系数列于下图中：用户只需点击相关系数表，即可得到两属性的2D 交会图，从而检查参数间的实际相关程度。

⑤ Summary Statistics 统计参数概括，出现如下窗口：⑥属性运算 明了。

⑦ Subsets ……子集操作 ⑧Model ……模型回归分析⑨……聚类分析分频技术基于如下的概念，即来自薄层的反射在频率域具有指示时间地层厚度的特征性表现。

例如，一个简单的各向同性的薄层能把可预测的、具有周期性的带陷序列引入到复合反射的振幅谱中。

如下图（5-1、5-2）：分类数量图 5-1 薄层频谱干涉模式短时窗分析，由于时窗内只包括几个薄层反射界面，这时的反射系数序列Rt 不再是随机的，振幅谱中由于薄层顶底反射界面的干涉结果出现了频陷，这代表地质体局部变化的特点。

1 IntroductionUpdated 2005-01-26This document gives a few examples how LspCAD 6 is used in a real situation. This document is meant to expand with more examples as time goes by. All the examples are available as project files in the examples folder.2 An optimization example, a two waycrossoverIn this example we have a simple two-waycrossover (Two way tutorial 1.lsp).We see that L1 and C1 only affect theresponse of the Bass unit. Open up theadvanced settings for L1.Check the Optimize box and also the boxnext to “Bass”.We have now instructed theoptimizer that L1 should beoptimized when we start tooptimize the response of the Bassunit. Do the same with C1. In asimilar way we see that C2 and L2only affect the response of theTreble unit. (Two way tutorial2.lsp)Open the Optimizer, we choose tooptimize the response of the Bassunit, we therefore click on the box next to “Bass”, if we look at the schema we will see that the component text for L1 and C1 has become boldface.Click on the Range tab and set the Include range to theinterval 100 to 6000Hztarget for the optimization, click onthe Target tab and then on the LPtab, check the Enable box and setFc to 2000Hz and order to 2, alsoset the alignment to Linkwitz.With this we are ready to start ouroptimization.Click on the Start button and watchthe miracle happen. Optionally onecan turn up the step size to get afaster convergence. When the stopthe optimization L1 and C1 areroughly 0.160mH and 39uF and themean error is close to 0.01dB.For some reason it is possible thatone did not like the result, theremedy is simply to click on theUndo button to get back to the state before the Start button was clicked.optimize the response of the trebleunit for a 2nd order HP Linkwitzalignment at 2000Hz, but insteadwe test what the lock XO option cando for us.We check “Treble” in the optimizetab, also wee set the target to flat,and the range to 100 to 20000Hzand the optimizer screen looks likeAfter a while we have a crossover with a flat system response and a crossover frequency locked at2000Hz. (Two way tutorial 4.lsp)3 A closed box… and a bass reflexboxAt first glance the modeling of various loudspeaker boxes might look overly complex, the intention is however that it should be possible to model other, more complex boxes than the standard closed, bass reflex and passive radiator boxes. This section describes how modeling of a closed box is performed in LspCAD, this example is then extended with a bass reflex port.box3.1 ClosedFirst of all we need a signal source and a Loudspeaker unit, pick this from the component tray, we also need to ground one of the speaker terminals (Closed tutorial 1.lsp).In a closed box we have free air infront of the speaker cone. This ismodeled as a Radiation element.Pick a radiation element. This actsa load of the front part of the cone.Behind the code we have a boxand also a load from the air insidethe box. This is modeled with a Boxload and a Box component. Afterthe components are picked andarranged a little on screen (don’tuse too little space) we have aschema that looks something like(Closed tutorial 2.lsp).So far we have been in edit mode, now it is time to enter simulate mode. Said and done, we click on the Simulate tab.In this mode we need to do a few extra things before we are in business.The Radiation component needs to know a little about theloudspeaker unit (such as Sd). For this to happen we click on theRadiation component and a small configuration dialog appears.Click on the dropdown list box below “Ref to…” and select“Loudspeaker unit 1” (nothing else to select by the way). Onceyou have done this you will see a typical 2nd order high passresponse of a closed box in the graph window.We are getting close but we are notquite there yet, recall that the Box loadcomponent models the load behind the cone, for this to happenthe Box load component must also know a little about theloudspeaker unit. Click of the Box load component and set the reference to “Loudspeaker unit 1” as before.Now we are in now in practice done (Closed tutorial 3.lsp). We are free to modify the Box parameters with a click on the Box component. The T/S parameters can be changed via a click on the Loudspeaker unit.3.2 Bass reflex boxBut lets not be lazy, why don’t we just make a bass reflex box?. Enter the Edit mode again and pick a Port component and an additional Radiation component from the component tray. We need aRadiationcomponent as theport is a componentthat radiates intofree air. Theschema then lookslike (Bass reflextutorial 1.lsp).Now we go back toSimulate mode andwe realize that theSPL graph haschanged (we have anotch in theresponse) In orderto get the full picture we need to let the extra Radiationcomponent learn a little of the Port, click on the Radiationcomponent and set the reference to the Port componentWith this we have the ability to simulate a bass reflex box(Bassreflex tutorial 2.lsp).It would be cool however if Fb in the schema displayed the correctvalue. For this to happen the Port must know how large the Box is,click on the Port component and set the reference to the Box. Nowwe get Fb to update whenever we change the port length or the boxvolume (Bassreflex tutorial 3.lsp).3.3 Grouping the box parts together If we group all the components (except the loudspeakerunit, the ground symbol and the signal source) we get anadditional benefit.Enter the Edit mode, select all the components exceptthose mentioned above, right click and select Group. Movethe markers that “carry” the text “Component group” and“Description” a little.Go back to simulate mode.Nice thing now is that if we left click inside the group box(but not on a component. A dialog pops up that displays themost important parameters.(Bassreflex tutorial 4.lsp).templatesthe3.4 UsingThe closed box and the bass reflex box exist as templates, if the templates are used we get an additional nice feature, namely the wizards that help us to get decent values for box volumes and port lengths.First of all create a completely new project. In the main window, click on the project list and locate the Templates. Select page 3 in the templates.Copy the Bass reflex box (and the associated loudspeaker unit and paste it into the new project.Now we must add a voltage source and a ground connection. When this is done. We enter the simulation mode.The references to the loudspeaker unit must be set for the Box load and the Radiation component closest to the loudspeaker unit (this must be done by hand, hopefully not needed in the future).Now that this is finally done we are ableto simulate our beloved bass reflex box.If we right click inside the group we geta dialog that contains a magic wizardbutton, click onthe Wizardbutton and asmall windowpops up thatallows us toselect among a few bass reflexalignments.Select an alignment and click on Apply.(Bassreflex tutorial 5.lsp)4 The Ugly duckling revisitedThis chapter gives an example how LspCAD is used to create an appropriate crossover for the Ugly duckling loudspeakers, first presented at/ugly_duckling.pdf. This chapter should be viewed as a continuation and will also show how the Behringer DCX2496 is configured.4.1 The subwoofer unitThe bass unit is a Peerless XLS 12 assisted by two Passive radiators Driver unit PRManufacturer: Peerless Model: SWR308Sd: 466.00cm2Vas: 139.20l Cms: 4.60e-04m/N Cas: 9.94e-07m5/N Mmd: 162.39g Mms: 166.40g Rms: 5.12Ns/m Fs: 18.1Hz Bl: 17.60N/A Re: 3.50ohm Le: 1.60mH Qms: 3.70Qes: 0.21Qts: 0.20 Pmax: 500.0W Xmax: 25.00mmh: 8.00mm l: 33.00mm Sd: 466.00cm2 Vap: 139.20l Qmp: 15 Mmp: 1000.0g Fp: 6.80Hz Xsus: 25.0mm Fb: 18.9HzThe original cone mass of the PR is 425g, therefore 575g weights was manufactured that was attached to the backside of the PR.In order to model the passive radiator box itis actually a good idea to pick the PassiveRadiator box template that is available inthe Template section. The template sectionis actually a preloaded project that containsready to use templates for a number ofgood to have building blocks. The templatesection is accessed from the topmostdropdown listbox in the main window.Select both the TS driver unit and the groupthat represents the passive radiator box.Right click with the mouse and select Copy.Now go back to your original project andpaste the items you have just copied.In order to get going you need to add avoltage source and a ground connector.With this you are done with the schemaediting, it is now high time to leave the Editmode and enter the Simulate mode. Clickon the simulate tab. If you though that“Gosh-it-looks-ugly” you will hopefully findthe looks better now. There are a fewnumbers here and there, if you don’t likethem you can actually hide them as don’thave much use of them. Look for thesettings menu pick in the main menu anddeselect the Show node numbers checkbox in the dialog that comes up, while we are here we can also set the display range to10-2000Hz. You can then close this dialog.There are a few thick gray lines runningacross the schema. These lines only showthat all components are referenced correctlyto one another the latter is a key feature inLspCAD 6 and makes it possible to addsemi intelligent wizards in an otherwisestupid node analysis algorithm. These gray lines can be hidden, click eg on the ABR component and deselect the Show references checkbox.The whole thing looks done, except for the fact that we need to enter the TS parameters, click on the TS driver symbol (the large box with the text Blinside). In the dialog that pops up you can enter/modify alot of parameters. First of all click on the Parameters tab.Here you should add all the parameters you haveavailable.If we go back to the T/S parameter list we see that Sd =466cm2. Said and done we enter 466 in the Sd field, to dothis we first double click on the Sd row, then we enter 466and click outside the enter box. Before we go on and enterVas we check the small checkbox that is immediately tothe left of Sd, with this done Sd will stay fixed when weenter the rest of the parameters. When we have entererLe we see that all necessary parameters of theparameters have been entered. The important parametersfor the computations in LspCAD 6 are: Re, Le, (Reb, Leb),Rms, Mmd, Cms, (LambdaS), Sd and Bl. The parametersin parenthesis are not critical. Once we are done the listlooks like the one to the left.Important to know is that the TS parameter list must besaved separately, this is quite natural as one might needthe same TS parameters foranother project.Now we should concentrate onthe frequency response. If welook on the graph we realize thata cutoff of 60Hz is lessimpressive given that we dealwith an expensive long strokesubwoofer.Click on the passive radiator component. Here we should first setSd to 466cm2. As we use a passive radiator that has the samecone area as the subwoofer. Here we actually should enter thevalues that we find in the table some pages ago but lets havesome fun with the group properties first!.Click inside the dotted box with the right mouse button. In thedialog box that pops up we find a Wizard button. Click on thewizard button and then on apply and Viola we have anoptimally flat alignment for the subwoofer with a boxresonance frequency of 37Hz. Close the wizard box.Now click on Clone. Then change the volume to 40l. Now goto the dropdown list box and click on the arrow. Here you willfind that there are two group entries, you can actually switchbetween the old entry (with 18l box volume) and the newentry with just a mouse click. Take the chance to look at thegraphs when you select between the entries. Feel free tochange the name Clone – Passive radiator box to somethingbetter…Now it is high time to get back on track again. We open up thepassive radiator dialog box and enter the values we found in thetable. Note that there are actually two passive radiators. Enter thevalues in the same order as they listedin the table.We also need to set the boxvolume tothe correct value.We need to set the relative locations of thesubwoofers and the passive radiators in orderto get a reliable simulation. As we have thetreble unit as reference point we need to setdX = 150mm, dY = -730 and dZ = 180mm.Click on the radiation component (looks likethe letter R) that is closest to the TS driver andenter the information.For the passive radiators we enterdX = -150, dY = -730 and dZ = 180 anddX = 150, dY = -430 and dZ = 180 (click on the radiation component that is closest to the passive radiator component.The graph begins to look likethe simulation we see in theugly duckling. One exception ishowever the lack of the bump at100Hz. To model this we openup the TS driver dialog againand click on the Configurationtab. Here we find a box with thename Inductance simulation.This is Off by default but can beset to two active modes.Load impedance only:In this mode we get almost thesame response as in the olderLspCAD 5.25 simulation.SPL and load impedance. This models the impact on the power response, actually it makes more sense to model the power response as the subwoofer is actually side mounted so we simply select this mode.The colors look quite dull so we take chance to modify these (click on the tiny rectangular boxes in the graph). Also we click on the generator in the schema and set the voltage multiplier value to 2.83.With this we are done withthe subwoofer part for theugly duckling. If you want tosee an overview of theproject, click on the smallarrow down symbol on thelower left corner of the mainwindow.The project so far is savedasugly duckling 1.lspin the examples folder.4.2 The midrange and the treble unitWe continue using the same project andadd the midrange and treble units. It ishowever a good idea to put thesecomponents on another schema page,therefore click on the small dropdownlistbox that is located in the upper leftcorner of the schema.First of all we put the driver units on theschema. This is quite straightforward.As we onlywish to seethe midrange and treble units for the moment we open upthe settings dialog and deselect the Peerless SUB, and theABR PR from both the listboxes in the SPL field in theSPL/Xfer tab. We can also set the display range to 50Hz-20000HzNext step is to import the SPL andimpedance data for the midrangeand the treble units. The midrangeactually consists of two unitsconnected in parallel. The locationsof the midrange units aredX = 0, dY = 120 and dZ = 0 anddX = 0, dY = -120 and dZ = 0.For the treble unit we set dX=dY=dZ= 0.Before we do anything else we recall that we verified thatthe dZ offset was set correctly in the old ugly duckling. We can actually do the same thing in LspCAD 6. For this purpose we open up the settings dialog again and select the SPL/Xf er tab. In the bottom of this tab we have the option to import a reference curve. We import this reference curve and also in the Show box we check the reference curve. As this reference measurement was done at 80cm distance we also need to set the distance to 80cm in the General tab.In order to protect the treble unit in this reference measurement a 33uF was put in series with the treble unit. Therefore we also need to break up the schema and do the same thing.With this done we can have firstlook at the SPL graph. We can see that we need to adjust the offset of the reference up by 2dB to match the simulated response. Still there seems to be a misalignment between the treble and the midrange units.In the older ugly duckling project we adjusted dZ for the treble unit in order to get a good match and we also see here that dZ = 3mm we get the best match.With these adjustments we can start doing the crossovers it is however advisable to set thesimulation distance to 3m and deselect the show reference curve.The project so far is stored as ugly duckling 2.lspin the examples folder.The real ugly duckling of today use theBehringer DCX2496 digital crossover.Also a 15uF capacitor is in series with thetreble unit to protect from possible poweron transients. Modeling crossovers forthe ugly duckling can be done in manyways. One alternative is to use the G(s)G(z) component but as the DCX2496 isactually used in this case we pick theDCX2496 components here. With thenecessary components inserted into theschema we get the looks to the right.It is a good idea to waste space as it maybe needed later. The observant eye maysee the small buffer amplifiers, there areneeded as the DCX components cannotdirectly drive the driver units, neither inreality nor in LspCAD 6.For the midrange we need to determine what kind of filter blocks we need. After some thinking we need roughly:2nd order HP filter 100Hz3rd order LP filter 3000HzA shelving filter for the baffle step compensationA notch filter for the 8200Hz resonance peak.First we deselect Treble from the Combine and Show list box so we can concentrate only on the midrange.The first, unoptimizedattempt is shown to the left.The project so far is storedasugly duckling 3.lspin the examples folder.With this it is time to optimize the response of the midrange, as target we select 4th order Linkwitz-Riley response with 120Hz and 3500Hz.In the settings for the midrange filter weneed to set the optimizer to optimize theparameters of the filter, (cutoff frequenciesfor the LP/HP filters, gain, Q and centerfrequencies for the EQ’s). Also we need toenable the optimization. It is moreconvenient here to not include the 8100HzEQ in the optimization.In the crossover optimizer we firstselect that we wish to optimize themidrange response, also we set therange to 70-6000Hz.When one click on the Start buttonone may experience that theoptimizer is slow. The reason to thismay be that we have too manyanalysis points. A way to increasethe speed is to set the working rangeto a more limited range and decreasethe number if analysis points,another means is to select the FastIteration in the Other tab.After the optimization we have a midrange response that follow the target pretty well.The project so far is storedasugly duckling 4.lspin the examples folder.The treble filter isoptimized in the samefashion as the midrangefilter, the resulting trebleresponse optimized for aLinkwitz Riley 4th orderalignment is shown to theright.Seeugly duckling 5.lspin the examples folder.The combined midrangeand treble response can befound in ugly duckling 6.lsp. Looking closer at this response (not shown here) one can see that the response is not entirely ruler flat also there is a peak at 6500Hz, not large but it would be neat to get rid of this. Also it looks better it we add 90dB scaling to the imported SPL data. If we add a dip at 6500Hz and run an additional optimization we get the summed midrange and treble response below (see ugly duckling 7.lsp).4.3 The subwoofer unit (again) and tyingthings togetherAfter this is done it is hightime to add the subwoofer ,the signal to the sub needs tobe LP filtered, for this purposewe use a Behringer crossovercomponent as well. This isconfigured as a 2nd orderbutterworth filter with cutoff at119Hz.The resulting on axisfrequency response isshown to the right. In thiscase no additionaloptimization is done (seeugly duckling 8.lsp formore graphs).Also worth a look is thetransfer function. This willbecome handy when wewish to create a passivecrossover later on.The response in the lowfrequency region dropsapproximately 4dB peroctave. This is good when the loudspeaker is in a normal listening room, one can always EQ it with a shelving EQ and get the response simulated in ugly duckling 9.lsp, this does however sound “too much” in the very low frequency region and can sometimes become really unpleasant4.4 Doing the passive crossoverDoing passive networks is a tedious task. One reason is that the load impedance is complex, this can however be fixed with shunt circuits such as zobel and series resonance circuits. The other problem is that unlike e.g the Behringer XO where one can set the slope of a LP filter and the shape of an EQ , everything in a passive XO is tied together. For instance if one change a component that is supposed to affect the slope of the highpass part of a bandpass filter, chances are pretty high that the lowpass part is affected as well. In short, what is easy done with active XO’s can drive you crazy if implemented as a passive crossover.But lets stop whining. This section described how a passive crossover is constructed for the midrange and treble section. The subwoofer is omitted, is anyway bad practice to construct a passive crossover for a subwoofer as the components can in the end be more expensive than buying a power amp and run the subwoofer actively.First we open the project ugly duckling 9.lsp. To makethings easier with the construction of the passivecrossover we export the transfer function of themidrange and treble unit filter, this is done from thegraph window. Click on Export. In the dialog we selectthe Midrange transfer function and click on Export. We save the file asugly duckling midrange TF.txt in the examples folder. Do the same with the treble unit transfer function.This makes it possible to optimize the transfer function of the passive crossover to the same target, slightly more simple than having to optimize frequency response all over again, also it is used in this tutorial to show the possibilityOne observation worth notice here is that the gain for the treble filter is 1.8dB, this means that we would need to attenuate the signal to the midrange in a passive filter. Personally I don’t like this so we need to fix this.After this we remove the subwoofer and all the other components except the midrange and treble unit driver from the schema.Our first task is to make the impedance curves of the driver units more flat, this is of great help in our strive to achieve a good passive filter.In ugly duckling passive 1.lsp a series resonance circuit is used to reduce the resonance peak at 70Hz while a zobel is used to cancel outthe impact of voice coil inductance. Also in this case themidrange is change to a configuration with the two midrangeunits is series. This reduces the sensitivity of the midrangebut makes it easier to match the sensitivity of the treble unit.For the treble unit we settle with a zobel network just to fixthe voice coil inductance.Note that the series resonance component is a groupedcomponent with wizard properties. This means that one canright click inside the dotted frame and click on Wizard in thedialog that pops up. In this wizard one can set the centerfrequency (fo),the Q value and the minimum impedance ofthe series resonance circuit, when Apply is clicked theappropriate components are computed.After some tweaking with components (actually it is possible to use the optimizer for this). We get the initial passive crossover show to theright. The resulting impedance is shown below.The impedance is not totally flat but it is not critical to get it 100% flat as we may anyway use these components when we optimize the transfer functions of the filters. The resonance peak at 600Hz may cause some problems for us when we start to tweak the transfer function of the treble unit but lets hope for the best…The project so far is stored asugly duckling passive 1.lspin the examples folder.Now it is time to add the actual crossover components. Forthis purpose we can add a HP/LP filter with a right button clickon the mouse (in Edit mode of course).As a starting point we select a 2nd order HP filter with cutoff at120Hz and a 3rd order with cutoff at 3500Hz. The nominal loadis set to 12ohm. When we click on create a crossover isdropped on the schema, we move it to an appropriate place.Perhaps not necessary but good anyway is to make sure that the very aggressive peak at 8500Hz is attenuated as much as possible. Therefore we put aseries resonance filter as a shunt across the driver terminals (getthe wizardized group from the templates this time also). Whenwe enter Simulate mode we right click on the series resonanceand configure it so that we get a sharp notch at 8500Hz.The crossover begins to look like something useful.The frequency response isless charming though. Wecould run hog wild trying tooptimize the response butit would probably fail as wedo not have anything thatcan compensate for thebaffle step. The existingcomponents may do thisjob to some extent butmost likely it will not work100%.The project so far is storedasugly duckling passive2.lspin the examples folder.In order to get something that can handle the baffle step we add a parallel inductor and a resistor in series with the input to the crossover.Now we tag all the components belonging to the midrange crossover (except the components that belong to the series resonance and zobel circuits) for optimization. Earlier we mentioned that we should optimize the transfer function of themidrange crossover. The figure to the right we can see what it looks like forthe component L4.Next we need to measure the transfer functions of themidrange crossover if we look at the schema we see that theinput to the filter is connected to node 1 and the midrange isconnected to node 2 . We open the Settings dialog andclick on the SPL/XFER tab we can set the node difference tobe computed as the voltage ratio between node 2 and node1.We open up the Optimizer and select Transfer function inthe Optimize tab.As target we select the file that we exported from our digitalfilter project. The Range is set to 70-6000Hz.When the optimizer is open thecomponents that are selectedbecome boldface, it is good practiceto have an extra look at the schemato verify that the right componentsare optimized before Start is clicked.Once the optimization is done we have the midrange crossover and the response below.This looks pretty good or ??The project so far is stored asugly duckling passive 3.lspin the examples folder.The treble unit is treated in a similar way as the midrange. Here a 2nd order HP filter is combined with an attenuator. One special problem with the treble unit is that a dip at 4700Hz needs to be equalized. This is a no-brainer with an active crossover but with a passive crossover some extra brain cells are needed. In this particular case a parallel resonance circuit was incorporated in the attenuator circuit that serves to reduce the attenuation at the resonance.After some optimization a flat response was achieved one problem though was that the impedance was a mere 2.8ohm at 20kHz!.This must be taken care of. Therefore we run an additional optimization runwith impedance constraint. For this purpose we tag all the components thatbelong to the treble network for optimization (see example to the right).There is no need to touch the midrange components as we see that theydon’t cause any impedance problems.When we run our optimization of thecombined midrange and treble response weset the range to 250-16000Hz as we don’twant the roll off to disturb the optimization.One special feature we use is thatwe lock the crossover point to3600Hz, thus we ensure that thisXO point wont move when we hitstart.In the Zmin tab we set the initialMin Z value to 3ohm. Then weclick on Start.As the optimization is running weclick in the MinZ field and increasethe value with the “Arrow up” keyon the keyboard. Increase thisvalue with care, if you increase tofast the optimization may FUBARand you need to stop and undothe optimization, the restart againfrom a low Min Z. After a whileyou have reached 4.2ohm, whichis considered good enough.The project so far is stored asugly duckling passive 4.lspin the examples folder.。

一种基于马尔可夫链的高维离群点挖掘算法唐志刚;杨炳儒;杨珺【摘要】提出了一种基于马尔可夫链的离群点检测(outlier detection algorithms based on Markov chain,MRKFOD)算法.该算法把基本数据集看作一个加权无向图,数据集中的每个数据表示一个节点,用每条加权边表示节点之间的相似度;形成一个邻接矩阵,把邻接矩阵当作马尔可夫链中的概率转移矩阵;寻求概率转移矩阵的主要特征向量;把每个节点的主要特征向量值作为每个数据的离群度.实验结果表明,该算法与其他高维离群点挖掘算法相比,在效率及有效处理的维数方面均有显著提高.【期刊名称】《系统工程与电子技术》【年(卷),期】2010(032)012【总页数】4页(P2721-2724)【关键词】数据挖掘;离群点;高维数据集;马尔可夫链;加权无向图【作者】唐志刚;杨炳儒;杨珺【作者单位】北京科技大学信息工程学院,北京,100083;南华大学数理学院,湖南,衡阳,421001;北京科技大学信息工程学院,北京,100083;北京科技大学信息工程学院,北京,100083【正文语种】中文【中图分类】TP1820 引言离群点检测是数据挖掘的基本任务之一[1-2],其目的是消除噪音或发现潜在的、有意义的知识,在实际生活中有着广泛的应用,如信用卡欺诈检测、入侵检测、生态系统失调检测、公共卫生中的异常疾病的爆发监测、公共安全中的突发事件的发生、异常天气的发现等。

离群点检测逐渐引起数据库、机器学习、统计学等领域研究人员的兴趣。

现已经出现了一些高效的离群点检测算法:基于聚类的、统计的、距离的、深度的以及基于密度的方法等5种类型[3-7]。

到目前为止,所提出的大多数离群点检测算法对高维数据的异常检测效果都不是很理想。

高维数据离群点检测与其他数据集的离群点检测差别较大的原因主要有两个:①高维数据的稀疏性导致所有记录在传统距离的意义上都很有可能是离群点,即机器学习中的“维数灾难”[7],因此高维空间中很难找到一个通用的离群产生机制;②高维数据离群点检测算法的计算复杂度通常都比较高,算法的执行效率极低。

使用CANOCO进行CCA或RDA教程分析在生态学和环境科学研究中，多元统计分析是非常重要的手段之一。

通过分析数据之间的关系，我们可以更好地理解生态系统的结构和功能。

而Canonical Correspondence Analysis (CCA)和Redundancy Analysis (RDA)是几种常用的多元统计方法之一，用于研究环境因子与物种组成之间的关系。

CANOCO是一个非常流行的用于执行CCA和RDA的统计软件。

本教程将向您介绍如何使用CANOCO进行CCA或RDA分析，以帮助您更好地理解生态数据。

第一步：数据准备在进行CCA和RDA分析之前，首先需要准备好您的数据。

数据应该是一个表格矩阵，包括环境因子（如温度、湿度、土壤pH等）和物种组成数据。

确保数据格式正确，可以导入到CANOCO中进行进一步的分析。

第二步：导入数据打开CANOCO软件并导入您准备好的数据。

在菜单栏中选择“File” -> “Import data”，然后选择您的数据文件进行导入。

CANOCO支持多种数据格式，包括txt、csv等。

第三步：选择分析方法在导入数据后，您需要选择进行CCA还是RDA分析。

在CANOCO中，可以通过菜单栏中的“Analysis” -> “Cononical Correspondence Analysis”或“Redundancy Analysis”来选择相应的分析方法。

第四步：设置参数在选择了分析方法后，需要设置相应的参数。

首先要选择变量类型（环境因子或生物物种），然后可以选择如何对数据进行标准化等设置。

第五步：运行分析设置好参数后，点击“Run”按钮开始运行分析。

CANOCO会生成相应的结果，并提供图形展示和统计结果。

您可以根据生成的结果图表来更好地理解数据之间的关系。

第六步：结果解读最后，根据CANOCO生成的结果来解读环境因子和物种组成之间的关系。

通过对结果图表的分析，可以深入了解生态系统的结构和功能，为生态学研究提供更多有益信息。

因果发现基于约束的方法
基于约束的方法在因果发现中主要用于判断变量之间的独立性，从而建立因果图。

这种方法主要基于独立性和条件独立性，并利用V-结构和定向规则对变量间的无向边进行定向。

其中，最有名的算法是PC（Peter-Clark）算法，从一个完全无向图开始，通过条件独立性测试逐步去除边来识别骨架。

然后，根据骨架中是否存在满足特定条件的路径来确定边的方向，并保持图的无环性，同时尽量避免产生新的V-结构。

基于约束的方法的缺点是无法区分马尔可夫等价类结构。

以上内容仅供参考，建议查阅关于因果发现方法的书籍文献以获取更全面准确的信息。

马尔可夫链蒙特卡洛算法的详细步骤解析马尔可夫链蒙特卡洛算法（Markov Chain Monte Carlo，MCMC）是一种基于统计的随机模拟算法，用于从复杂的概率分布中抽取样本。

在实际应用中，MCMC算法被广泛用于概率推断、参数估计、贝叶斯统计等问题的求解。

本文将详细解析MCMC算法的步骤及其原理，以便读者能够更好地理解和应用该算法。

1. 马尔可夫链MCMC算法的核心是马尔可夫链。

马尔可夫链是一个随机过程，具有“无记忆”的性质，即未来的状态只依赖于当前的状态，与过去的状态无关。

假设我们要从一个概率分布π(x)中抽取样本，可以构造一个转移核函数Q(x'|x)，表示在当前状态为x时，下一个状态为x'的概率。

若满足细致平稳条件，即π(x)Q(x'|x) =π(x')Q(x|x')，则该马尔可夫链的平稳分布即为π(x)。

MCMC算法利用马尔可夫链的平稳分布来抽取样本。

2. Metropolis-Hastings算法Metropolis-Hastings算法是MCMC算法的一种经典实现。

其步骤如下：（1）初始化：选择一个初始状态x(0)。

（2）抽样：根据转移核函数Q(x'|x)抽取候选状态x'。

（3）接受-拒绝：计算接受概率α = min{1, π(x')Q(x|x') /π(x)Q(x'|x)}。

以α为概率接受候选状态x'，否则保持当前状态x。

（4）迭代：重复步骤（2）和（3），直到达到设定的抽样次数。

Metropolis-Hastings算法通过接受-拒绝的方式生成符合目标分布π(x)的样本，但其效率较低。

因此，后续提出了各种改进算法，如Gibbs抽样、Hamiltonian Monte Carlo等。

3. Gibbs抽样Gibbs抽样是一种特殊的MCMC算法，适用于多维变量的联合分布抽样。

其步骤如下：（1）初始化：选择一个初始状态x(0)。