Behavioral model of pipeline ADC by using SIMULINK(R)

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黑龙江省大庆市让胡路区大庆市大庆中学2023-2024学年高二下学期7月期末英语试题

黑龙江省大庆市让胡路区大庆市大庆中学2023-2024学年高二下学期7月期末英语试题

黑龙江省大庆市让胡路区大庆市大庆中学2023-2024学年高二下学期7月期末英语试题一、听力选择题1.What are the speakers talking about?A.Breakfast.B.Lunch.C.Dinner.2.What may prevent the woman from buying the table?A.Its quality.B.Its price.C.Its design.3.What is the probable relationship between the speakers?A.Husband and wife.B.Co-workers.C.Doctor and patient. 4.What does the man need to do next?A.Turn into another road.B.Slow down his car.C.Avoid the road sign. 5.When did the woman arrive in the town?A.On July 9th.B.On July 10th.C.On July 11th.听下面一段较长对话,回答以下小题。

6.Where does the conversation probably take place?A.At a record store.B.At a bookstore.C.At a gift store.7.What will the man do next?A.Play some music.B.Write something down.C.Prepare for a birthday party.听下面一段较长对话,回答以下小题。

8.Who is the man?A.The woman’s husband.B.A regular customer.C.The woman’s neighbor. 9.Which dessert has a strong flavor?A.The lemon pie.B.The strawberry cake.C.The green tea cupcake. 10.How much should the man pay in total?A.$3.B.$4.C.$7.听下面一段较长对话,回答以下小题。

pipeline adc原理

pipeline adc原理

pipeline adc原理
PipelineADC原理是一种高速、高精度的模数转换器设计方法。

它通过将模拟信号分段转换为数字信号,逐级进行逼近操作,最终输出所需的数字结果。

具体来说,Pipeline ADC由多个级联的子ADC
组成,每个子ADC都负责一部分的位数转换,通过将结果送到下一级ADC以便进行进一步的处理,最终得到所需的数字结果。

与传统的逐次逼近ADC相比,Pipeline ADC具有更高的采样速率和更高的有效位数,但也需要更多的电路复杂度和功耗。

在高速、高精度、大量数据转换等领域中,Pipeline ADC被广泛应用。

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稀疏距离扩展目标自适应检测及性能分析

稀疏距离扩展目标自适应检测及性能分析

第39卷第7期自动化学报Vol.39,No.7 2013年7月ACTA AUTOMATICA SINICA July,2013稀疏距离扩展目标自适应检测及性能分析魏广芬1苏峰2简涛2摘要在球不变随机向量杂波背景下,研究了稀疏距离扩展目标的自适应检测问题.基于有序检测理论,利用协方差矩阵估计方法,分析了自适应检测器(Adaptive detector,AD).其中,基于采样协方差矩阵(Sample covariance matrix,SCM)和归一化采样协方差矩阵(Normalized sample covariance matrix,NSCM),分别建立了AD-SCM和AD-NSCM检测器.从恒虚警率特性和检测性能综合来看,AD-NSCM的性能优于AD-SCM和已有的修正广义似然比检测器.最后,通过仿真实验验证了所提方法的有效性.关键词稀疏距离扩展目标,自适应检测,采样协方差矩阵,归一化采样协方差矩阵,有序统计量引用格式魏广芬,苏峰,简涛.稀疏距离扩展目标自适应检测及性能分析.自动化学报,2013,39(7):1126−1132DOI10.3724/SP.J.1004.2013.01126Sparsely Range-spread Target Detector and Performance AssessmentWEI Guang-Fen1SU Feng2JIAN Tao2Abstract In the background where the clutter is modeled as a spherically invariant random vector,the adaptive detection of sparsely range-spread targets is addressed.By exploiting the order statistics and the covariance matrix estimators,the adaptive detector(AD)is assessed.Herein,the detectors of AD-SCM and AD-NSCM are proposed based on the sample covariance matrix(SCM)and normalized sample covariance matrix(NSCM),respectively.In terms of constant false alarm rate properties and detection performance,the AD-NSCM outperforms the AD-SCM and the existing detector of modified generalized likelihood ratio.Finally,the performance assessment conducted by simulation confirms the effectiveness of the proposed detectors.Key words Sparsely range-spread target,adaptive detection(AD),sample covariance matrix(SCM),normalized sample covariance matrix(NSCM),order statisticsCitation Wei Guang-Fen,Su Feng,Jian Tao.Sparsely range-spread target detector and performance assessment.Acta Automatica Sinica,2013,39(7):1126−1132低分辨率雷达的目标尺寸小于距离分辨率,这种目标常称之为点目标[1].通过采用脉冲压缩技术,高分辨率雷达能够在空间上把一个目标分解成许多散射点[2−3],目标回波在雷达径向上的多个散射点分布在不同的距离分辨单元中,形成距离扩展目标[4].在许多情况下,距离扩展目标的散射点密度是稀疏的,可将这种目标简称为“稀疏距离扩展目标”.目前,高斯背景下的距离扩展目标检测已取得一定进收稿日期2011-12-28录用日期2012-08-27Manuscript received December28,2011;accepted August27, 2012国家自然科学基金(61174007,61102166),山东省优秀中青年科学家科研奖励基金(BS2010DX022)资助Supported by National Natural Science Foundation of China (61174007,61102166)and the Scientific Research Founda-tion for Outstanding Young Scientists of Shandong Province (BS2010DX022)本文责任编委韩崇昭Recommended by Associate Editor HAN Chong-Zhao1.山东工商学院信息与电子工程学院烟台2640052.海军航空工程学院信息融合技术研究所烟台2640011.School of Information and Electronics,Shandong Institute of Business and Technology,Yantai2640052.Research Insti-tute of Information Fusion,Naval Aeronautical and Astronauti-cal University,Yantai264001展,其中,针对估计参数空间过大的问题,文献[5]提出了一种无需辅助数据的检测器,简称为修正的广义似然比检验(Modified generalized likelihood ratio test,MGLRT)检测器,其在高斯背景下是有界恒虚警率(Constant false alarm rate,CFAR)的.但在高距离分辨率的条件下,背景杂波呈现出诸多的非高斯特性[1],高斯背景下获得的检测器已无法有效检测目标.在非高斯背景下,文献[6]研究了已知杂波协方差矩阵条件下的距离扩展目标检测;而通过利用不含目标信号的辅助数据,文献[7]和文献[8]分别针对距离扩展目标和距离–多普勒二维分布式目标展开了自适应检测研究.需要指出的是,以上自适应检测方法[7−8]都是基于辅助数据的.当无法获得满足条件的辅助数据时,实现非高斯背景下距离扩展目标的自适应检测具有重要意义.文献[9]基于迭代估计方法实现了自适应检测,但迭代估计计算量较大,如何在保证性能的同时减小计算量,也是值得探讨的问题.7期魏广芬等:稀疏距离扩展目标自适应检测及性能分析1127稀疏距离扩展目标的散射点只占据目标距离扩展范围的一部分,与含纯杂波的距离分辨单元幅值相比,含目标散射点的距离分辨单元幅值明显更高,这就为实现目标的自适应检测提供了条件.本文针对非高斯杂波中的稀疏距离扩展目标检测问题,在不需要辅助数据的条件下,首先,采用有序统计检测理论和协方差矩阵估计方法,粗略估计目标散射点单元集合;然后,进一步利用适当估计方法获得协方差矩阵的精确估计,设计了自适应检测器(Adaptivedetector,AD),并通过仿真实验验证了检测器的有效性.1问题观测数据来源于N个阵元的线性阵列天线,需跨过K个可能存在目标的距离分辨单元z t,t=1,···,K,判决一个距离扩展目标的存在与否.假设可能的目标完全包含在这些数据中,并且忽略目标距离走动的问题.在杂波背景下,待解决的检测问题可由以下二元假设检验公式来表达.H0:z t=c t,t=1,···,KH1:z t=αt p+c t,t=1,···,K(1)其中,p=(1,e jφ,e j2φ,···,e j(N−1)φ)T/√N表示已知单位导向矢量,即p H p=1,这里(·)H表示共轭转置,φ表示相移常量,(·)T表示转置,αt,t=1,···,K是反映目标幅度的未知参数.非高斯杂波可用球不变随机向量建模[10],由于中心极限定理在较小区域的杂波范围内仍是有效的,球不变随机向量可以表示为两个分量的乘积:一个是反映受照区域反射率的时空“慢变化”纹理分量,另一个是变化“较快”的“散斑”高斯过程.那么,距离分辨单元t的N维杂波向量c t为c t=√τt·ηt,t=1,···,K(2)其中,ηt=(ηt(1),ηt(2),···,ηt(N))T是零均值协方差矩阵为Σ的复高斯随机向量,非负的纹理分量τt与ηt相互独立,其用来描述杂波功率在不同距离分辨单元间的起伏,且服从未知分布fτ.另外,杂波协方差矩阵结构Σ可以表示为Σ=E{ηt ηHt}(3)距离扩展目标完全包含在K个距离分辨单元的滑窗中,假设一个等效散射点最多只占据一个距离分辨单元,即目标等效散射点数目与其所占据的距离分辨单元数目是相等的.通常目标散射点是稀疏分布的,与含纯杂波的距离分辨单元相比,有散射点的距离分辨单元幅值往往更高.含目标等效散射点的距离分辨单元数目用h0表示,而其所对应的距离分辨单元下标用集合Θh表示.为了简化分析,假设h0是已知的,若其未知,可利用模型阶数选择方法获得合适的估计值[11].如前所述,对距离扩展目标的检测只需在距离分辨单元Θh内进行,式(1)表示的假设检验问题可以进一步表示为H0:z t=c t,t∈ΘhH1:z t=αt p+c t,t∈Θh(4)在分布fτ未知的条件下,距离分辨单元t的杂波是条件高斯的,其相应的方差为τt.由于幅度αt 未知而向量p已知,针对不同假设,观测向量z t的联合概率密度可表示为t∈Θhf(z t|τt,H0)=t∈Θh1πNτN t det(Σ)×exp[−1τtz HtΣ−1z t](5)t∈Θhf(z t|αt,τt,H1)=t∈Θh1πNτN t det(Σ)×exp−1τt(z t−αt p)HΣ−1(z t−αt p)(6)其中,det(·)表示方阵的行列式.2检测器实现在未知集合Θh的条件下,为了获得估计的参数集合ˆΘh,这里先假设已知矩阵Σ.由于未知参数α={αt|t∈Θh}和τ={τt|t∈Θh},可利用广义似然比检验(GLRT)原理进行检测器设计[12].在矩阵Σ已知的条件下,根据GLRT原理,对于似然比中的未知参数,可用最大似然(Maximum likelihood,ML)估计进行替换,即考虑如下二元判决:maxτmaxαt∈Θhf(z t|αt,τt,H1)maxτt∈Θhf(z t|τt,H0)H1><H0T0(7)在H1假设下求得αt的ML估计为[13]ˆαt=p HΣ−1z tp HΣ−1p(8)将ˆαt代入式(7)后,可进一步在不同假设条件下求得τt的ML估计:H0:ˆτt=1Nz HtΣ−1z t(9) H1:ˆτt=1N(z t−ˆαt p)HΣ−1(z t−ˆαt p)(10)1128自动化学报39卷将式(8)∼(10)代入式(7)中,可得自然对数形式的GLRT判决为λ1=−Nt∈Θh0ln1−|p HΣ−1z t|2(z H tΣ−1z t)(p HΣ−1p)H1><H0T1(11)令w t=|p HΣ−1z t|2(z H tΣ−1z t)(p HΣ−1p)(12)值得注意的是,w t的结构类似于一个归一化匹配滤波器(权向量为Σ−1p)[14].可以看出,式(12)的分子部分p HΣ−1z t等效于给定距离分辨单元观测z t经过匹配滤波后的结果[14].而分母部分的两项z HtΣ−1z t和p HΣ−1p起到了归一化处理的作用,因此,w t是距离单元观测z t经过匹配滤波后模平方的归一化,可以看作是距离单元观测经归一化匹配滤波后的能量.由于目标完全包含在K个单元的距离滑窗中,且距离扩展目标等效散射点所占据的距离分辨单元幅值往往大于纯杂波的距离分辨单元幅值,因此,可通过归一化能量w t,t=1,···,K中最大的h0个值来确定未知集合ˆΘh.实际应用中协方差矩阵结构Σ往往是未知的,为了确定集合ˆΘh,需先对协方差矩阵结构进行估计.如前所述,纹理分量τt的分布fτ是未知的,因此,协方差矩阵结构Σ的ML估计不能通过期望最大化得到[13].本文考虑两种协方差矩阵估计方法.一种是高斯背景下的经典采样协方差矩阵(Sample covariance matrix,SCM),其可以表示为ˆΣSCM =1RRr=1y r y Hr(13)其中,y r,r=1,···,R表示可用于估计的R个数据.当R≥N时,SCM是以概率为1非奇异的,同时也是正定Hermitian矩阵[12].另外,在非高斯背景下,也常常利用辅助数据获得归一化采样协方差矩阵(Normalized sample covariance matrix, NSCM),可以表示为ˆΣNSCM =1RRr=1Ny Hry ry r y Hr(14)与文献[9]类似,针对稀疏距离扩展目标的自适应检测,AD检测器的实现分为如下三个步骤.步骤1.基于SCM或NSCM方法,利用K个待检测单元的观测数据获得初步估计矩阵ˆΣ1,进一步将估计矩阵ˆΣ1代入式(12)中,可得到初步估计ˆw(1)t.对ˆw(1)t,t=1,···,K按升序排列,可得如下有序序列:0≤ˆw(1)(1)≤···≤ˆw(1)(t)≤···≤ˆw(1)(K)≤1(15)步骤2.考虑有序序列的K−h0个最小值(即ˆw(1)(t),t=1,···,K−h0),并用Ωh表示相应距离分辨单元下标的集合.为了获得可逆的估计矩阵,需满足K−h0≥N.根据之前的分析,集合Ωh中的距离分辨单元极可能只包含纯杂波,故可以利用Ωh0对应的距离分辨单元观测值,精确估计矩阵Σ,并采用与初步估计中相同的估计方法(SCM或NSCM),进一步获得较为精确的协方差矩阵结构估计ˆΣ2.利用ˆΣ2代替式(12)中的未知矩阵Σ,得到w t的精确估计值用ˆw(2)(t)表示.对ˆw(2)(t),t=1,···,K按升序排列,可得如下有序序列:0≤ˆw(2)(1)≤···≤ˆw(2)(t)≤···≤ˆw(2)(K)≤1(16)考虑有序序列的h0个最大值(即ˆw(2)(t),t=K−h0+1,···,K),并用ˆΘh表示相应距离分辨单元下标的集合.步骤3.将距离分辨单元下标的集合ˆΘh和协方差矩阵的精确估计ˆΣ2代入式(11)中,获得自适应检测器AD的检测统计量可以表示为λ2=−NKt=K−h0+1ln(1−ˆw(2)(t))=−Nt∈ˆΘhln[1−|p HˆΣ−12z t|2(z H tˆΣ−12z t)(p HˆΣ−12p)]H1><H0T2(17)需要说明的是,在存在目标散射点的情况下,步骤1的初步估计矩阵不可避免地引入了估计误差,虽然这种误差在步骤2中得到了一定的抑制,但它仍将影响后续精确估计矩阵的精度.在存在辅助数据的前提下,为了获得良好的检测性能,一般要求辅助数据个数不小于阵元数N的两倍[15].在待检测单元数K不变的情况下,可利用的纯杂波单元数(K−h0)将随着散射点个数的增加而减小,因此,此处需等价满足(K−h0)≥2N.进一步考虑到步骤1中散射点单元所引起的估计误差,实际应用中可能需要更大的(K−h0)/N值以弥补步骤1中导致的性能损失,具体取值将在接下来的性能评估中给出.由于采用不同的估计方法会获得不同的自适应检测器,在这里,我们分别将采用SCM和NSCM估计方法获得的相应检测器简称为AD-SCM和AD-NSCM.由于本文的自适应检测器中ˆΘh和ˆΣ2均受到协方差矩阵估计方法的影响,因此,有必要评估自适应距离扩展目标检测器的CFAR特性,这将在接下来的性能分析中进行.7期魏广芬等:稀疏距离扩展目标自适应检测及性能分析1129 3性能评估本节对稀疏距离扩展目标自适应检测器AD-SCM和AD-NSCM进行了CFAR特性和检测性能评估,并与无需辅助数据的MGLRT检测器[5]进行了比较分析.利用Toeplitz矩阵对Σ进行建模,具体采用指数相关结构,在杂波一阶相关系数为γ的条件下,第m行第n列的矩阵元素为[Σ]m,n=γ|m−n|,1≤m,n≤N(18)利用Γ分布对纹理分量的分布fτ进行建模:fτ(x)=LbLΓ(L)x L−1e−(L b)x,x≥0(19)其中,Γ(·)是Gamma函数,均值b代表了平均杂波功率;参数L表示分布fτ的非高斯拖尾特征,具体来说,随着L的减小,函数fτ的拖尾将增大,而杂波的非高斯尖峰程度将增大.采用蒙特卡罗方法计算相应的检测概率P d和虚警概率P fa.根据前面的假设,在所有距离分辨单元均存在杂波的条件下,目标等效散射点只存在于h0个距离分辨单元中,且一个等效散射点最多只占据一个距离分辨单元.在所有K个距离分辨单元上,每个单元的目标或杂波的平均功率分别用σ2s 或σ2c表示.对于存在目标散射点的距离分辨单元(t∈Θh),用零均值独立复高斯变量对等效散射点建模,即目标散射点幅度在不同距离分辨单元间瑞利起伏;相应的方差表示为E{|αt|2}=εtσ2sK(εt表示单个散射点占目标总能量的比率).由|αt|2,t=1,···,K的独立性可知,检测性能与散射点在待检测单元中的位置无关.几种典型的散射点分布模型如表1所示.其中,Model 1中的目标能量等量分布在h0个距离分辨单元范围内;Model2∼4中某个距离分辨单元具有大部分能量,而剩下的能量在其余距离分辨单元中等量分布.Model5相当于点目标,是Model2∼4的极端特例.输入信杂比(Signal to clutter ratio,SCR)定义为K个距离分辨单元内的平均信杂比,即SCR=σ2sσ2cp HΣ−1p(20)为了便于CFAR特性评估,需针对杂波功率水平(对应于b)、尖峰程度(对应于L)和协方差矩阵结构(对应于γ)的不同情况,分析检测器的检测阈值与虚警概率间的关系.相关研究表明[9],在非高斯杂波下MGLRT是非CFAR的,即高斯背景下获得的MGLRT检测器不适用于非高斯背景.为了便于比较,在K=15,h0=3,N=2,L=0.1,1,γ=0,0.5,0.9和b=1,10条件下,图1和图2分别给出了AD-SCM和AD-NSCM的检测阈值(De-tection threshold)与虚警概率(False alarm prob-ability)的关系曲线.图1表明,AD-SCM检测器对杂波协方差矩阵结构和功率水平具有自适应性,但对杂波尖峰不具有适应能力.而图2说明,AD-NSCM对杂波尖峰和杂波功率水平具有CFAR特性,但其检测阈值仍受协方差矩阵结构的轻微影响.综合来看,AD-NSCM的检测阈值在不同杂波条件下的鲁棒性更好.图1K=15,N=2,L=0.1,1,γ=0,0.5,0.9,b=1,10,h0=3时,AD-SCM的CFAR特性曲线Fig.1CFAR curves of AD-SCM for K=15,N=2, L=0.1,1,γ=0,0.5,0.9,b=1,10,h0=3表1不同散射点分布模型的εt值Table1Values ofεt for typical scatters models目标距离分辨单元12···h0Model11h01h01h01h0Model20.50.5h0−10.5h0−10.5h0−1Model30.90.1h0−10.1h0−10.1h0−1Model40.990.01h0−10.01h0−10.01h0−1Model510001130自动化学报39卷图2K=15,N=2,L=0.1,1,γ=0,0.5,0.9,b=1,10,h0=3时,AD-NSCM的CFAR特性曲线Fig.2CFAR curves of AD-NSCM for K=15,N=2, L=0.1,1,γ=0,0.5,0.9,b=1,10,h0=3接下来分析AD检测器的检测性能.图3给出了MGLRT、AD-SCM和AD-NSCM的性能曲线.可以看出,AD-NSCM的检测性能最优,MGLRT 其次,而AD-SCM的检测性能最差.从以上分析综合来看,与MGLRT和AD-SCM相比,AD-NSCM 在CFAR特性和检测性能方面均具有一定的优势.下文将重点对AD-NSCM的检测性能展开分析.图3K=15,N=2,L=1,γ=0.9,h0=3,P fa=10−4, Model1时,MGLRT,AD-SCM和AD-NSCM的检测性能曲线Fig.3Detectability curves of MGLRT,AD-SCM and AD-NSCM for K=15,N=2,L=1,γ=0.9,h0=3,P fa=10−4,Model1首先,针对表1中5种不同模型,图4评估了散射点能量分布对AD-NSCM检测性能的影响.可以看出,随着距离分辨单元间散射点能量分布的均匀性增加,检测性能逐渐改善.为了便于分析,下文中主要针对Model1模型.另外,在不同的散射点密度条件下,图5分析了AD-NSCM检测性能.由图5可知,当h0<7时,协方差矩阵结构的估计误差较小,其对检测性能的影响也较小,当散射点数目增加时,检测器可利用的目标能量增大,AD-NSCM的检测性能得到一定的改善.当h0≥7时,协方差矩阵结构的估计误差影响较大,当散射点数目增加时,进行矩阵估计所用的观测数据量减少,估计矩阵的误差加大,导致较为严重的检测损失,且损失量高于增加散射点数目所获得的性能增益,并引起总检测性能的退化.综合来看,当h0<K/2时,AD-NSCM 的检测性能较好.图4K=15,N=2,L=1,γ=0.9,h0=3,P fa=10−4, Model1∼5对应的AD-NSCM检测性能曲线Fig.4Detectability curves of AD-NSCM for K=15, N=2,L=1,γ=0.9,h0=3,P fa=10−4,Model1∼5图5K=15,N=2,L=1,γ=0.9,P fa=10−4,Model 1时,h0=2,4,6,7,8,10,12对应的AD-NSCM检测性能曲线Fig.5Detectability curves of AD-NSCM for K=15, N=2,L=1,γ=0.9,P fa=10−4,Model1,h0=2,4,6,7,8,10,12在不同杂波尖峰条件下,图6给出了AD-NSCM检测性能.由图6可知,随着L的减小,杂波尖峰程度增大,AD-NSCM的检测性能有所改善.图7给出了不同杂波相关性对应的检测性能曲线.可以看出,杂波一阶相关系数的变化对检测性能几乎没有影响,说明AD-NSCM对杂波相关性7期魏广芬等:稀疏距离扩展目标自适应检测及性能分析1131的变化具有良好适应性.图8进一步分析了阵元数变化(N =2,4,6,8)对AD-NSCM 检测性能的影响.可以看出,在阵元数N ≤4的条件下,当N 增加时,检测性能有所提高;而在N >4的条件下,当N 增加时,检测性能反而有所下降.可能的原因是,当进行矩阵估计所用的观测数据量不变时(R =K −h 0=12),N 的增加会导致协方差矩阵维数变大,待估参量的数目增加,估计精度下降,并直接引起检测性能的退化.综合来看,当K −h 0≥3N 时,AD-NSCM 的检测性能较好.图6K =15,N =2,γ=0.9,h 0=3,P fa =10−4,Model 1时,L =0.5,1,2,10对应的AD-NSCM 检测性能曲线Fig.6Detectability curves of AD-NSCM for K =15,N =2,γ=0.9,h 0=3,P fa =10−4,Model 1,L =0.5,1,2,10图7K =15,N =2,L =1,h 0=3,P fa =10−4,Model 1时,γ=0,0.5,0.9对应的AD-NSCM 检测性能曲线Fig.7Detectability curves of AD-NSCM for K =15,N =2,L =1,h 0=3,P fa =10−4,Model 1,γ=0,0.5,0.94结论本文研究了非高斯杂波中的稀疏距离扩展目标检测问题.在不需要辅助数据的条件下,基于SCM 和NSCM 估计器,分别建立了AD-SCM 和AD-NSCM 检测器.从CFAR 特性和检测性能综合来看,AD-NSCM 的性能优于AD-SCM 和MGLRT.对于典型的非高斯杂波环境,随着杂波尖峰程度的增大,AD-NSCM 的检测性能得到提高,且其对杂波相关性的变化也具有良好适应性.另外,对于h 0<K/2的稀疏距离扩展目标,在K −h 0≥3N 条件下,AD-NSCM 能获得满意的检测性能.需要说明的是,与文献[9]中的检测器相比,AD-NSCM 虽然减小了计算量,但也牺牲了部分CFAR 特性.如何减小检测器对散射点信息的依赖性,是下一步需要研究的问题.图8K =15,L =1,γ=0.9,h 0=3,P fa =10−4,Model 1时,N =2,4,6,8对应的AD-NSCM 检测性能曲线Fig.8Detectability curves of AD-NSCM for K =15,L =1,γ=0.9,h 0=3,P fa =10−4,Model 1,N =2,4,6,8References1Zhou Yu,Zhang Lin-Rang,Liu Xin,Liu Nan.Adap-tive detection based on Bayesian approach in heteroge-neous environments.Acta Automatica Sinica ,2011,37(10):1206−1212(周宇,张林让,刘昕,刘楠.非均匀杂波环境下基于贝叶斯方法的自适应检测.自动化学报,2011,37(10):1206−1212)2He Chu,Liu Ming,Feng Qian,Deng Xin-Ping.PolIn-SAR image classification based on compressed sensing and multi-scale pyramid.Acta Automatica Sinica ,2011,37(7):820−827(何楚,刘明,冯倩,邓新萍.基于多尺度压缩感知金字塔的极化干涉SAR 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detectors.IEEE Transactions on Signal Processing,2001, 49(1):1−1615Reed I S,Mallett J D,Brennan L E.Rapid convergence rate in adaptive arrays.IEEE Transactions on Aerospace and Electronic Systems,1974,10(6):853−863魏广芬博士,山东工商学院副教授.2005年获得大连理工大学机械电子工程专业工学博士学位.主要研究方向为传感器检测与信号处理理论及技术.本文通信作者.E-mail:*******************(WEI Guang-Fen Ph.D.,associateprofessor at Shandong Institute of Busi-ness and Technology.She received her Ph.D.degree from Dalian University of Technology in2005.Her research in-terest covers theory and technology of sensor detection and signal processing.Corresponding author of this paper.)苏峰博士,海军航空工程学院信息融合技术研究所讲师.主要研究方向为雷达信号检测与信号处理.E-mail:*****************(SU Feng Ph.D.,lecturer at NavalAeronautical and Astronautical Univer-sity.His research interest covers radarsignal detection and signal processing.)简涛博士,海军航空工程学院信息融合技术研究所讲师.主要研究方向为雷达信号检测与信号处理.E-mail:********************.cn(JIAN Tao Ph.D.,lecturer at NavalAeronautical and Astronautical Univer-sity.His research interest 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基于Verilog-A的流水线型ADC数字校正技术仿真平台

基于Verilog-A的流水线型ADC数字校正技术仿真平台

1引言随着信息技术的进一步发展,微电子芯片集成度不断提高,芯片尺寸越来越小。

工艺尺寸的缩小意味着特征线宽不断降低。

在这一背景下:一方面,器件速度进一步提高,功耗进一步降低;另一方面,晶体管本征增益降低,工作电源电压降低。

此时,数字电路的速度更快,功耗更低,所以数字电路会持续受益;而对于模拟电路来说,电源电压、本征增益的降低意味着高增益的放大器设计越来越困难。

所以,工艺的演进对于模拟电路来说是一种挑战。

在很多的应用场合,模拟电路趋向于用更多的数字电路来代替。

模数转换器(ADC )作为将模拟信号转换为数字信号的装置,起着连接模拟世界与数字世界桥基于Verilog-A 的流水线型ADC数字校正技术仿真平台宫月红1,张少君1,罗敏2,王明雨1,刘冰冰1(1.山东交通学院船舶与轮机工程学院,威海264209;2.哈尔滨工业大学(威海)微电子中心,威海264209)摘要:为了对流水线型ADC 数字校正技术进行研究,提出了一种基于Verilog-A 的行为级仿真平台。

在该平台中,采用Verilog-A 语言对流水线型ADC 中各个组成模块进行建模、采用Volterra 级数对系统误差进行模拟、采用Verilog 语言对数字校正算法进行建模。

应用此平台,结合一种确定性的数字校正技术对一个12位分辨率,1.5位每级结构,40MHz 采样速度的流水线型ADC 进行了仿真。

在芯片设计之前使用该平台进行仿真,不仅能够有效地缩短流水线型ADC 数字校正技术的硬件设计周期,还提高了校正算法开发的灵活性和实用性,从而对进一步提高流水线型ADC 的性能、降低功耗起到重要的促进作用,具有很高的实用价值。

关键词:Verilog-A 语言;仿真平台;流水线型ADC ;数字校正;Volterra 级数DOI :10.3969/j.issn.1002-2279.2018.02.011中图分类号:TP312文献标识码:A 文章编号:1002-2279(2018)02-0042-05Pipeline ADC Digital Correction Technology Simulation PlatformBased on Verilog-AGONG Yuehong 1,ZHANG Shaojun 1,LUO Min 2,WANG Mingyu 1,LIU Bingbing 1(1.Naval Architecture &Marine Engineering College,Shandong Jiaotong University,Weihai 264209,China ;2.Harbin Institute of Technology Weihai Microelectronics Center,Weihai 264209,China )Abstract:To research pipeline ADC digital calibration technique,a Verilog -A based behavioral simulation platform is proposed.In this platform,Verilog-A language is adopted to mimic the modules in pipeline ADC,Volterra series theory is applied to imitate system error,Verilog language is employed to module digital algorithm.Applying this platform,a 10bits,1.5per stage structure,50MHz sample speed background calibration pipeline ADC with a deterministic calibration algorithm is simulated.Applying this platform in simulation before chip design can not only reduce pipeline ADC digital calibration technique design cycle,but also improve calibration algorithm developing flexibility and practicability.Thus,pipeline ADC performance can be further improved,and power consumption can be further reduced,so it has high practical value.Key words:Verilog-A;Simulation platform;Pipeline ADC;Digital calibration;Volterra作者简介:宫月红(1982—),女,河北省衡水市人,博士,讲师,主研方向:模拟混合信号集成电路设计与数字信号处理。

保持良好人际关系的方法和好处英语作文

保持良好人际关系的方法和好处英语作文

保持良好人际关系的方法和好处英语作文Maintaining positive relationships with others is essential for a happy and fulfilling life. It involves regular communication, mutual respect, and a willingness to listen and understand each other. Building and nurturing healthy relationships not only enhance our personal well-being but also contribute to creating a harmonious environment in both our professional and social lives.One of the most important methods in maintaining good interpersonal relationships is effective communication. Communication is not just about speaking; it also involves active listening and understanding. Being able to express thoughts and feelings clearly, while also being attentive to the perspectives of others, can prevent misunderstandings and conflicts from arising. Regular and open communication helps build trust and deepen connections with friends, family, colleagues, or partners.Another vital aspect of maintaining positive relationships is showing respect for others. Respecting someone meansvaluing their opinions, feelings, and boundaries. Respecting differences in beliefs, cultures, or personalities can foster tolerance and acceptance within relationships. By demonstrating respect towards others, we create an atmosphere of dignity and mutual appreciationthat strengthens the bonds between individuals.Furthermore, empathy plays a crucial role in building strong interpersonal connections. Empathy involves understanding others' emotions and perspectives without judgment. When we empathize with someone, we demonstrate compassion and support in times of joy or distress. Empathy promotes emotional closeness and fosters a sense of unity among people.In addition to effective communication, respect, and empathy, reciprocity is key to maintaining positive relationships. Reciprocity means giving back as much as we receive from others in terms of care, attention, and support. When both parties contribute equally to the relationship by showing kindness and consideration towards each other's needs, it creates a balanced dynamic thatsustains the bond over time.The benefits of maintaining good interpersonalrelationships are numerous. Firstly, having a reliable support system built on trust and understanding can provide emotional security during challenging times. Friends or family members who offer encouragement and comfort can help us navigate difficulties more effectively.Secondly, positive relationships contribute to our overall well-being by promoting happiness and reducing stress levels. Spending time with loved ones or engaging in meaningful conversations can boost our mood and enhance our mental health.Moreover, strong interpersonal connections often lead to increased opportunities for personal growth and development. Through interactions with diverse individuals who bring different perspectives and experiences into our lives, we can broaden our horizons and learn new skills or knowledge.Ultimately, investing time and effort in maintaining goodinterpersonal relationships is an invaluable asset that enriches our lives on various levels. 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cd模型的工作原理

cd模型的工作原理

cd模型的工作原理
CD模型,即Contrastive Divergence模型,是一种基于马尔可
夫链Monte Carlo Markov Chains(MCMC)的无监督学习算法,通常用于训练受限玻尔兹曼机(Restricted Boltzmann Machine,RBM)或深度信念网络(Deep Belief Networks,DBN)。

CD模型的工作原理如下:
1. 初始化模型参数:首先,初始化RBM的可见层和隐层的权
重矩阵,以及偏置项。

偏置项用于定义每个神经元被激活的基础概率。

2. 正向传播:通过RBM的可见层和隐层之间的权重矩阵,将
输入样本的特征映射到隐层,计算出隐层的激活值。

3. 反向传播:将隐层的激活值再次传递回可见层,通过可见层和隐层之间的权重矩阵,计算重构的可见层。

4. 通过Gibbs采样计算对比分歧:在每一轮迭代中,利用当前
的可见层和隐层状态,通过互相传递信息的方式来更新模型的参数。

5. 权重更新:通过对比重构的可见层和原始的可见层的误差,计算出梯度,然后使用梯度下降算法或其他优化算法来更新模型的权重参数和偏置项。

6. 重复迭代:重复执行2-5步骤,迭代更新模型的参数,直到
达到预定的迭代次数或收敛条件。

通过这种方式,CD模型通过学习数据的分布特征,能够对输入数据进行无监督的特征学习和表示学习,进而可以用于生成样本和进行概率推断等任务。

] a behavioral model of rational choice

] a behavioral model of rational choice

] a behavioral model of rational choice 《理性选择的行为模型》是指人们在做出选择时所采用的一种模型,该模型的基础是理性。

人们在做出选择时,会考虑到各种因素,如收益、成本、风险、时间等。

基于这些因素,人们会对不同的选择做出权衡,最终选择对自己最有利的一种。

理性选择的行为模型认为,人们在做出选择时会遵循一定的规律,即在不同的选择之间进行比较,并选择最优的那一种。

这种行为模式可以被用于解释人们在各种不同情境下做出的选择,包括经济决策、社会行为、政治选择等等。

在经济学领域,理性选择的行为模型被广泛应用。

基于这个模型,经济学家可以预测人们在做出经济决策时的行为,进而制定相应的政策。

例如,当政府希望促进某一种商品的销售时,可以通过调整价格、增加宣传等方式,使得这种商品的收益高于其成本,从而吸引更多的人选择购买。

除了经济学之外,理性选择的行为模型在心理学、社会学、政治学等领域也有着广泛的应用。

这种模型的基础是认为人们在做出选择时会遵循一定的规律,并不会完全被情感、偏见等因素所左右。

总之,理性选择的行为模型是一个非常有用的模型,可以用来解释人们在各种不同情境下做出的选择。

通过了解这种模型,我们可以更好地理解人类的行为,从而制定出更加精准的政策和策略。

- 1 -。

工业互联网PaaS平台Predix技术介绍

工业互联网PaaS平台Predix技术介绍

建立在 Cloud Foundry
*
GE Confidential – Distribution authorized to individuals with need to know only
是一个领先的开源平台 由 Cloud Foundry 社区 发展, 现由 GE CF 道场 为 工业用例 继续发展
DevOps
*
GE Confidential – Distribution authorized to individuals with need to know only
What is it?
Benefits To Platform Subscribers
Tools and Processes that stress Communication, Collaboration (information sharing and web service usage), Integration, Automation, and Measurement of cooperation between Developers and its Operations
1 Engineering
3 Operations
5 Culture
4 Financials
DevOps CI / CD (continuous integration / continuous delivery) Paired programming (eXtreme programming)
DevOps Op Center BizOps (business operations)
Invent and simplify Be a minimalist Bias for action Cultivate a meritocracy Disagree and commit

14位Single―slope ADC行为级建模与仿真

14位Single―slope ADC行为级建模与仿真

14位Single―slope ADC行为级建模与仿真摘要:单斜率型模/数转换器以其简单的结构、较高的分辨率和易于集成的优势,在红外焦平面读出电路设计中被广泛应用。

基于Matlab软件环境下的Simulink工具,建立了一个14位Single?slope ADC的系统模型。

其充分讨论Simulink工具下电路各单元模块的具体实现和信号间的时序关系,给出电路的行为级仿真结果,为Single?slope ADC的集成电路设计与实现提供参考。

关键词:单斜模/数转换器;行为级建模;红外焦平面;Simulink;集成电路设计;功能仿真中?D分类号:TN492?34 文献标识码:A 文章编号:1004?373X(2018)16?0104?04Abstract:As the single?slope ADC has the advantages of simple structure,high resolution,and easy integration,it has been widely used in the design of the infrared focal plane read?out circuit. Based on the Simulink tool in the Matlab software environment,a 14?bit single?slope ADC system model is built. The specific implementation utilizing the Simulink tool for each unit module of the circuit and the time sequence relationship among signals are fully discussed. The behavioral simulation results of the circuit are given,whichprovides a reference for the design and implementation of the single?slope ADC integrated circuit.Keywords:Single?slope ADC;behavioral modeling;infrared focal plane;Simulink;integrated circuit design;functional simulation 0 引言红外焦平面成像系统在军事、医疗扫描、空间探测、环境监控以及民用消费电子方面有着广泛的应用[1]。

人才管理制度翻译英文

人才管理制度翻译英文

人才管理制度翻译英文1. IntroductionTalent management is a crucial component of organizational success. It involves attracting, developing, and retaining a talented workforce to ensure the organization's long-term success. An effective talent management system can help the organization identify and nurture its top performers, address skills gaps, and develop future leaders. In this document, we will outline a comprehensive talent management system that encompasses the entire employee lifecycle, from recruitment and onboarding to career development and succession planning.2. Recruitment and SelectionThe first step in talent management is to attract and hire the right people for the organization. This involves developing a strong employer brand, creating compelling job descriptions, and leveraging various recruitment channels to attract a diverse pool of candidates. Our talent management system includes the use of data-driven approaches to identify the most effective recruitment strategies and tools. We also emphasize the importance of a rigorous selection process, including behavioral interviews, skills assessments, and reference checks, to ensure that we hire the best-fit candidates for the organization.3. Onboarding and IntegrationOnce new employees are hired, it is important to provide them with a comprehensive onboarding program to help them quickly integrate into the organization and understand its culture, values, and expectations. Our talent management system includes a structured onboarding process that includes orientation sessions, mentorship programs, and ongoing support to ensure that new employees feel welcome and are set up for success from day one.4. Performance ManagementPerformance management is a critical component of talent management. Our system includes regular performance evaluations, goal-setting processes, and ongoing feedback to help employees understand how their performance contributes to the organization's success and identify areas for improvement and growth. We also emphasize the importance of recognition and rewards to motivate and retain top performers.5. Learning and DevelopmentOur talent management system includes robust learning and development programs to help employees acquire new skills, expand their knowledge, and prepare for future roles within the organization. This includes a mix of formal training programs, on-the-job learning opportunities, coaching, and mentoring to support employees at all levels of the organization.6. Career DevelopmentWe recognize the importance of career development in talent management. Our system includes career planning discussions, career pathing tools, and access to a variety of resources to help employees explore their interests, set goals, and create a roadmap for their professional growth within the organization.7. Succession PlanningSuccession planning is a key part of talent management, especially for leadership roles and critical positions within the organization. Our talent management system includes a robust succession planning process that identifies high-potential employees, assesses their readiness for future roles, and ensures that the organization has a pipeline of talent to fill key positions when they become vacant.8. Employee Engagement and RetentionEmployee engagement and retention are crucial to the success of any talent management system. Our approach includes regular pulse surveys, feedback mechanisms, and various employee engagement initiatives to understand employee needs and create a positive work environment that encourages employee loyalty and commitment.9. Talent AnalyticsOur talent management system is supported by talent analytics that provide insights into workforce trends, performance metrics, and talent gaps. This data-driven approach helps us make informed decisions about talent acquisition, development, and retention strategies.10. ConclusionA comprehensive talent management system is essential for organizational success. It requires a strategic and integrated approach that encompasses the entire employee lifecycle, from recruitment and onboarding to career development and succession planning. Our talent management system is designed to attract, develop, and retain a talented workforce that will drive our organization's long-term success. By implementing this system, we aimto create a culture of continuous learning, performance excellence, and employee engagement that will set us apart as an employer of choice.。

behavioural analysis

behavioural analysis

behavioural analysis[Behavioural Analysis]Introduction:Behavioural analysis is a psychological approach that involves studying, understanding, and interpreting human behaviour. This field of study aims to observe and analyze human actions, reactions, and patterns to gain insights into their thoughts, emotions, and personality traits. By examining behaviour, psychologists, researchers, and practitioners can better understand the motives, intentions, and underlying processes of individuals. In this article, we will explore different aspects of behavioural analysis, including its methods, applications, and significance.Methodology:Behavioural analysis employs several methods to study human behaviour. These methods include direct observation, interviews, surveys, and experiments. Direct observation involves carefully observing and noting down behavioural patterns in specific settings. Researchers may conduct structured or unstructured interviews to gather information about individuals' experiences, perspectives, and attitudes. Surveys are another common method that employsquestionnaires to collect data on a larger scale. Lastly, experiments are conducted to test hypotheses and explore cause-and-effect relationships between specific variables and behaviour.Applications:Behavioural analysis finds applications in various fields, including psychology, sociology, education, marketing, and criminal justice. Psychologists use this approach to diagnose and treat mental health conditions. Understanding patterns and triggers behind certain behaviours allows therapists to develop more effective treatment plans. Moreover, behavioural analysis is relevant in education as it helps identify learning difficulties, behavioural disorders, and social challenges among students. Teachers can then adapt their teaching methodologies to accommodate these individual needs.In the marketing industry, behavioural analysis plays a pivotal role in understanding consumer purchasing behaviour. By studying consumer habits, preferences, anddecision-making processes, companies can design targeted marketing campaigns and develop products that align with customers' needs and wants. In the criminal justice system,behavioural analysis contributes significantly to crime investigation and profiling. Detectives and criminal profilers analyze crime scenes, offender behaviour, and eyewitness accounts to predict the characteristics and motivations of criminals. This aids in the apprehension and prevention of future crimes.Significance:Behavioural analysis is significant as it provides valuable insights into human behaviour, enabling professionals to make informed decisions and implement effective strategies. By understanding the factors that influence behaviour, individuals can gain self-awareness and make positive changes in their lives. The knowledge acquired through behavioural analysis also helps society in general by fostering better understanding and empathy towards others.Behavioural analysis allows researchers to explore the complex interaction between biology, cognition, and the environment. It aids in uncovering the underlying reasons for certain behaviours, including biases, attitudes, and beliefs. This understanding is crucial in addressing societal issues such as discrimination, prejudice, and inequality.Moreover, behavioural analysis helps in predicting andpreventing harmful or deviant behaviours. By identifying risk factors and early warning signs, professionals can intervene and provide necessary support to individuals at risk. For example, in the field of mental health, behavioural analysis assists in identifying warning signs of potential self-harm or suicide. This enables mental health professionals to take appropriate measures to prevent tragedy and provide the necessary care and intervention.Conclusion:Behavioural analysis is a comprehensive approach that delves into the intricacies of human behaviour. Through various methods, this field of study unlocks valuable insights into the motives, intentions, and underlying processes that drive our actions and reactions. The applications of behavioural analysis span across multiple disciplines, all helping us gain a better understanding of ourselves and others. By recognizing the significance of behavioural analysis, we can cultivate a more empathetic and inclusive society while effectively addressing individual and societal challenges.。

一种流水线ADC及其非理想特性的行为级建模设计

一种流水线ADC及其非理想特性的行为级建模设计

一种流水线ADC及其非理想特性的行为级建模设计王晓岚;王海晖【摘要】为了采用行为级模型来模拟结构复杂的ADC变换器的电气性能,本文提出了一种流水线ADC的行为级建模设计.首先提出流水线ADC行为级建模设计采用开关电容器电路构建,它由任意级联的k级流水级、前端采样保持(S/H)电路和数字校正逻辑构成,并给出了它们的具体模块电路实现及行为级模型;然后通过考虑流水线ADC的各种非理想特性如运算放大器的非理想特性参数(白噪声、有限直流增益、有限带宽、转换速率和饱和电压)、开关的非理想特性和采样时钟抖动,提出了实现这些非理想特性的行为模型.最后采用一个10位流水线ADC在Matlab Simulink中对其理想和非理想建模设计的仿真结果表明,本文提出的流水线ADC 的行为级建模设计及其各个构成模块的非理想特性建模是精确和可行的.【期刊名称】《中国电子科学研究院学报》【年(卷),期】2019(014)006【总页数】8页(P652-659)【关键词】开关电容器;流水线ADC;行为级建模;采样保持;传递函数;非理想特性;信号重建【作者】王晓岚;王海晖【作者单位】天津渤海职业技术学院,天津300402;武汉工程大学,武汉430205【正文语种】中文【中图分类】TN941.10 引言模拟/数字变换器(Analog to Digital Converter,ADC)和数字/模拟变换器(Digital to Analog Converter,DAC)在数字处理核心与外部实际模拟接口中发挥了重要的作用。

ADC的应用随处可见,从成像到超声以及通信系统。

近年来,特别是流水线ADC结构[1-5]在变换率、分辨率和功耗之间提供了很好的平衡。

传统上,模拟和混合信号模块如数据变换器的建模设计已经在设备级或在更低的功能级得到了实现,提供了很好的精度,并允许对数据变换器中出现的非理想效应(噪声、失真、失配等)能很好地建模,但是仿真时间会急剧增加,技术和架构的独立性可能会丢失;然而,随着设计复杂性的日益增加,需要精确和快速的模型来适应目前行为级建模趋势的变化。

IBM Cognos Transformer V11.0 用户指南说明书

IBM Cognos Transformer V11.0 用户指南说明书
Dimensional Modeling Workflow................................................................................................................. 1 Analyzing Your Requirements and Source Data.................................................................................... 1 Preprocessing Your ...................................................................................................................... 2 Building a Prototype............................................................................................................................... 4 Refining Your Model............................................................................................................................... 5 Diagnose and Resolve Any Design Problems........................................................................................ 6

利用外部知识注入大模型的幻觉问题综述

利用外部知识注入大模型的幻觉问题综述

一、前言在人工智能领域,大模型已经成为了当前最热门的话题之一。

这些模型通过大规模的训练数据和强大的计算能力,能够在语言理解、图像识别、自然语言处理等领域取得令人瞩目的成就。

然而,近年来,有研究表明,大模型存在一种被称为“幻觉问题”的现象,即在处理特定任务时,其表现似乎超出了其所获得的训练知识范围,甚至包括其本身所未曾接触过的外部知识。

本文将对这一问题进行综述,探讨其产生的原因、影响以及可能的解决方法。

二、幻觉问题的定义幻觉问题指的是大型模型在处理特定任务时,表现出对未曾经历过的外部知识具有异常的适应能力。

这种现象使得大型模型在某些情况下可以表现出超乎预期的性能,在某种程度上超越了它们所接受的训练。

具体而言,这种现象可能表现为模型在语言理解任务中对文学、历史、科学等领域的知识有意外的掌握,或者在图像识别任务中对于人类视觉系统所不具备的认知能力。

三、产生原因分析1. 训练数据的多样性大型模型通常通过大规模的训练数据进行训练,这些数据往往包含了各种领域、各种类型的信息。

在这些数据中可能存在某种程度上的外部知识,而模型在学习过程中可能无意识地吸收了这些知识,导致在处理特定任务时表现异常。

2. 模型结构的复杂性大型模型通常具有非常复杂的结构和参数设置,这些结构可能使得模型在学习过程中对外部知识具有某种程度上的记忆和适应能力。

一些研究也指出,大型模型具有自适应的学习能力,可以通过动态地调整其参数和结构来适应新的任务和知识。

3. 训练过程中的信息污染训练数据中可能存在一定程度上的噪音和错误信息,而大型模型可能会无意识地学习并利用这些错误信息来处理任务,从而产生类似幻觉问题的现象。

四、影响分析1. 对模型性能的影响幻觉问题可能导致大型模型在特定任务上表现出异常的性能,从而使得对模型性能的评估和预测变得困难和不确定。

2. 对应用场景的影响在一些实际应用场景中,例如自然语言处理、图像识别等领域,大型模型的幻觉问题可能使得模型的应用范围和效果变得不确定,甚至影响到实际应用的准确性和稳定性。

模型敏感性分析流程

模型敏感性分析流程

模型敏感性分析流程英文回答:Sensitivity analysis is a crucial step in the modeling process as it helps us understand how changes in input variables affect the output or results of a model. It allows us to assess the robustness and reliability of the model and identify the most influential factors.The process of sensitivity analysis typically involves the following steps:1. Identify the input variables: First, we need to identify the key input variables that have an impact on the model's output. These variables can be quantitative or qualitative.For example, let's consider a model that predicts the sales of a product. The input variables could include factors such as price, advertising expenditure,competitor's price, and consumer demographics.2. Define the range of values: Once we have identified the input variables, we need to define the range of values for each variable. This range should cover the possible values that the variable can take in real-life scenarios.Continuing with our example, we can define the range of values for the price variable as $10 to $50, advertising expenditure as $1000 to $5000, competitor's price as $5 to $30, and consumer demographics as different age groups and income levels.3. Determine the sensitivity measure: There are several methods to measure the sensitivity of the model to changes in input variables. Some commonly used measures include the correlation coefficient, regression analysis, and variance-based methods such as Sobol indices.4. Perform the sensitivity analysis: Once thesensitivity measure is determined, we can perform the sensitivity analysis by systematically varying the inputvariables within their defined ranges and observing the corresponding changes in the model's output.For example, we can vary the price from $10 to $50 in increments of $5 and observe how the sales output changes. Similarly, we can vary the other input variables one by one and analyze their impact on the model's output.5. Interpret the results: Finally, we need to interpret the results of the sensitivity analysis. This involves identifying the most influential input variables and understanding how changes in these variables affect the model's output.For instance, we may find that price and advertising expenditure are the most influential factors in determining the sales of the product. A decrease in price may lead to an increase in sales, while an increase in advertising expenditure may also have a positive impact on sales.In conclusion, sensitivity analysis is a valuable tool for understanding the behavior of a model and assessing itsreliability. By systematically varying input variables and analyzing their impact on the output, we can gain insights into the model's sensitivity to different factors and make informed decisions based on the results.中文回答:敏感性分析是建模过程中的一个关键步骤,它帮助我们了解输入变量的变化如何影响模型的输出结果。

vpmcd的训练过程

vpmcd的训练过程

vpmcd的训练过程VPMCD(Variable Parameter Markov Chain Decomposition)是一种用于语音识别中的声学模型训练的方法。

它是基于隐马尔可夫模型(Hidden Markov Model,HMM)的一种改进,在语音识别领域取得了很好的效果。

VPMCD方法主要用于解决语音识别中的多说话人问题,即在同一段音频中存在多个说话人的情况。

在传统的语音识别中,通常会将整段音频标注为一个整体,而VPMCD则将每个说话人分离出来进行训练和识别。

VPMCD的训练过程可以分为以下几个关键步骤:1.数据预处理:首先需要对训练数据进行预处理,例如音频的切割、对齐和标注等。

对于多说话人语音数据,还需要对每个说话人进行分离和标注,以便后续的训练过程。

2.特征提取:在声学模型训练中,通常会使用MFCC(Mel-Frequency Cepstral Coefficients)等特征进行表示。

这些特征能够更好地表达人的语音特征,对于语音识别任务非常有效。

在VPMCD中,需要对每个说话人的语音数据提取对应的特征。

3.建模算法:在VPMCD中,使用的是基于隐马尔可夫模型的声学建模算法。

隐马尔可夫模型是一种包含隐藏的状态和可见的观测序列的概率模型,可以用于描述语音信号中的状态转移和观测。

在VPMCD 中,会针对每个说话人建立一个单独的隐马尔可夫模型。

4.参数估计:在训练过程中,需要估计隐马尔可夫模型中的转移概率、发射概率和初始概率等参数。

这些参数可以通过最大似然估计等方法来获得。

对于VPMCD,需要分别针对每个说话人进行参数估计。

5.模型训练:在VPMCD中,分别对每个说话人的数据进行模型训练。

训练的目标是最大化模型对观测序列的似然概率,即选择最优的模型参数,使得模型能够更好地拟合输入的语音数据。

6.模型评估:在训练阶段完成后,需要对训练得到的模型进行评估。

评估的方式可以采用交叉验证等方法,根据模型在验证集上的性能来评估模型的好坏。

对抗迁移学习理论在提升模型鲁棒性中的作用机制

对抗迁移学习理论在提升模型鲁棒性中的作用机制

对抗迁移学习理论在提升模型鲁棒性中的作用机制迁移学习是一种利用已学习到的知识和模型来解决新任务的方法。

在实际应用中,迁移学习可以大大减少模型的训练时间和数据需求,同时提升模型的性能和鲁棒性。

对抗迁移学习理论是近年来涌现的一种迁移学习方法,其通过引入对抗性机制来提高源领域和目标领域之间的迁移效果。

本文将探讨对抗迁移学习理论在提升模型鲁棒性中的作用机制。

一、对抗迁移学习理论的基本原理对抗迁移学习理论是基于生成对抗网络(GAN)和领域自适应(Domain Adaptation)的思想发展起来的。

其基本原理是通过训练源领域模型和目标领域模型两个对抗网络,使得源领域和目标领域之间的分布差异最小化,实现模型在目标领域上的优秀性能。

具体而言,对抗迁移学习理论包括三个关键组成部分:生成器网络、判别器网络和优化目标。

生成器网络负责将源领域的样本映射到目标领域的样本空间,从而实现数据分布的变换。

判别器网络则用于判断输入样本是来自源领域还是目标领域,以此评估模型在目标领域上的性能。

优化目标则是通过最小化源领域和目标领域之间的分布差异,来使得模型在目标领域上的预测结果与真实标签尽可能接近。

对抗迁移学习理论的基本原理为后续讨论提供了理论基础,为提升模型鲁棒性提供了新的思路和方法。

二、对抗迁移学习理论在提升模型鲁棒性中的作用机制对抗迁移学习理论在提升模型鲁棒性中的作用主要体现在以下几个方面。

1. 特征提取和表示学习对抗迁移学习理论通过生成器网络和判别器网络共同学习源领域和目标领域的特征表示,从而获取一种具有较强鲁棒性的特征表示。

通过生成器网络的映射,源领域的特征可以变换到目标领域的特征空间,使得模型能够在目标领域上进行准确的预测。

同时,判别器网络的训练可以评估源领域和目标领域之间的分布差异,进而调整特征表示的学习过程,提高模型的鲁棒性。

2. 领域自适应对抗迁移学习理论通过优化目标来减小源领域和目标领域之间的分布差异,从而实现领域自适应。

如何利用预训练模型进行多轮对话生成任务(五)

如何利用预训练模型进行多轮对话生成任务(五)

预训练模型是近年来人工智能领域取得的一项重要突破,它通过在大规模语料库上进行无监督学习,从而获得了丰富的语言知识和模式。

这些模型在自然语言处理任务中表现出色,包括文本生成、机器翻译、情感分析等。

其中,多轮对话生成任务是一个具有挑战性的领域,要求模型在对话的过程中能够理解上下文,保持语义连贯性,并生成合理的回复。

本文将介绍如何利用预训练模型进行多轮对话生成任务。

首先,我们需要选择一个合适的预训练模型。

目前,BERT、GPT-2、XLNet等模型在自然语言处理领域都取得了巨大的成功,它们都可以作为多轮对话生成任务的基础模型。

在选择模型时,需要考虑模型的语言表达能力、上下文理解能力以及生成的流畅性等方面。

此外,还需要根据具体的应用场景和需求来选择合适的模型,有些模型在特定领域或场景下表现更好。

其次,针对多轮对话生成任务,我们需要对选择的预训练模型进行微调。

微调是指在特定任务上对预训练模型进行有监督学习,以适应特定任务的需求。

在多轮对话生成任务中,我们需要构建一个合适的数据集,包括对话语料和相应的回复,然后使用这些数据对预训练模型进行微调。

微调过程中,需要选择合适的损失函数和优化算法,以及进行适当的超参数调整。

通过微调,预训练模型可以更好地适应多轮对话生成任务的需求,提高生成回复的质量。

另外,为了提高多轮对话生成模型的效果,我们还可以采用一些技巧和策略。

例如,可以引入注意力机制来帮助模型更好地理解上下文,保持语义连贯性。

此外,还可以使用温度参数来控制生成回复的多样性,从而避免模型产生过于单一的回复。

还可以结合对话历史信息来生成更加准确和合理的回复,比如使用记忆网络等技术。

这些技巧和策略可以帮助我们进一步提高多轮对话生成模型的效果。

最后,需要注意的是,在应用预训练模型进行多轮对话生成任务时,需要考虑到模型的计算资源消耗和实时性。

预训练模型通常需要较大的计算资源和模型推理时间,因此在实际应用中需要进行合理的资源分配和优化。

对抗学习中的模型评估和对抗攻击方法

对抗学习中的模型评估和对抗攻击方法

对抗学习中的模型评估和对抗攻击方法对抗学习是机器学习领域中一项重要的研究领域,其旨在通过建立对抗模型评估和对抗攻击方法来提高机器学习系统的鲁棒性和安全性。

本文将从模型评估和对抗攻击两个方面来介绍对抗学习的相关内容。

第一章:模型评估1.1 对抗学习的背景和意义对抗学习是一种机器学习的分支,它致力于通过构建对抗性样本来评估机器学习模型的性能。

在现实世界中,机器学习模型经常面临各种对抗性的攻击,如输入扰动、对抗性样本等。

因此,对模型进行全面的评估对于提高模型的鲁棒性至关重要。

1.2 常见的模型评估方法为了评估机器学习模型的性能,研究者们提出了许多评价指标和测试方法。

常用的模型评估方法包括准确率、召回率、F1分数等。

此外,还可以使用混淆矩阵、ROC曲线等方法来分析模型的性能。

1.3 对抗模型评估方法的引入然而,传统的模型评估方法无法全面评估模型在对抗环境下的性能。

针对这一问题,研究者们提出了对抗模型评估方法。

对抗模型评估方法通过引入对抗性样本,考察模型在对抗攻击下的表现,从而更加全面地评估模型的鲁棒性。

1.4 对抗模型评估的挑战然而,对抗模型评估也面临一些挑战。

首先,如何构造对抗性样本是一个关键问题。

传统的对抗性样本构造方法如FGSM、PGD等,虽然可以构造出对抗性样本,但其误分类率可能不高。

此外,对抗模型评估还需要考虑到模型在不同攻击方法下的性能差异,并提供可解释的评估结果。

第二章:对抗攻击方法2.1 对抗攻击的定义和分类对抗攻击是针对机器学习模型的攻击手段,其旨在通过对输入样本进行扰动,使模型产生错误的输出。

对抗攻击可以分为白盒攻击和黑盒攻击两种类型。

白盒攻击指攻击者具有完全的模型信息,而黑盒攻击指攻击者只能通过有限的模型访问获得模型信息。

2.2 常见的对抗攻击方法针对对抗攻击的不同需求,研究者们提出了多种对抗攻击方法。

常见的对抗攻击方法包括基于梯度的攻击方法(如FGSM)、迭代的攻击方法(如PGD)、基于优化的攻击方法等。

AI安全机器学习的模型鲁棒性

AI安全机器学习的模型鲁棒性

AI安全机器学习的模型鲁棒性AI安全是当前人工智能领域的热门话题之一。

随着人工智能的快速发展,安全性问题引起了人们的普遍关注。

在机器学习领域中,模型的鲁棒性是一项关键的安全属性。

本文将重点讨论AI安全中的模型鲁棒性问题,并提出一些提高模型鲁棒性的方法。

在AI系统中,模型的鲁棒性指的是模型对于输入变化和干扰的抵抗能力。

在现实世界中,AI系统所面临的输入往往是多样的,并且可能受到不同程度的扰动和干扰。

一个鲁棒性强的模型能够更好地应对这些变化和干扰,保持稳定的预测能力。

提高模型鲁棒性的一个重要方法是数据预处理。

数据预处理可以帮助减少输入数据的噪声和误差,从而改善模型的性能和鲁棒性。

常见的数据预处理方法包括数据清洗、特征选择和特征变换等。

通过对数据的预处理,可以提高模型对于异常数据和干扰的处理能力。

另一个提高模型鲁棒性的方法是使用对抗训练。

对抗训练是指通过引入对抗样本来训练模型,从而提高模型的对抗能力。

对抗样本是对原始样本进行微小修改的样本,这些修改可能只对人眼不可见,但却能够使得模型的输出发生巨大变化。

通过使用对抗样本进行训练,可以提高模型的对抗性能,使其对于输入变化和干扰具有更强的鲁棒性。

此外,模型的结构设计也可以影响模型的鲁棒性。

一些研究表明,增加模型的深度和宽度,使用更复杂的结构可以提高模型的鲁棒性。

但是,在设计模型结构时需要注意平衡模型的复杂度和计算资源的开销,以免造成过拟合和性能下降的问题。

在实际应用中,还可以通过集成学习和模型融合等方法提高模型的鲁棒性。

集成学习是通过结合多个模型的预测结果来获得更准确和鲁棒的预测结果。

模型融合则是将多个模型的特征进行融合,来提高模型的性能和鲁棒性。

这些方法可以通过增加模型的多样性,从而提高模型的鲁棒性。

总的来说,AI安全机器学习的模型鲁棒性是一个重要而复杂的问题。

通过数据预处理、对抗训练、模型结构设计、集成学习和模型融合等方法,可以提高模型的鲁棒性。

然而,鲁棒性并不是一蹴而就的,需要在实际应用中不断调试和优化。

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