Static response analysis of structures with interval parameters using the second-order Taylor series expansion and the DCA for QB

In this paper, based on the second-order Taylor series expansion and the difference of convex functions algo- rithm for quadratic problems with box constraints （the DCA for QB）, a new method is proposed to solve the static response problem of structures with fairly large uncertainties in interval parameters. Although current methods are effective for solving the static response problem of structures with interval parameters with small uncertainties, these methods may fail to estimate the region of the static response of uncertain structures if the uncertainties in the parameters are fairly large. To resolve this problem, first, the general expression of the static response of structures in terms of structural parameters is derived based on the second-order Taylor series expansion. Then the problem of determining the bounds of the static response of uncertain structures is transformed into a series of quadratic problems with box constraints. These quadratic problems with box constraints can be solved using the DCA approach effectively. The numerical examples are given to illustrate the accuracy and the efficiency of the proposed method when comparing with other existing methods.

Second-Order Adjoint Sensitivity Analysis Methodology for Computing Exactly Response Sensitivities to Uncertain Parameters and Boundaries of Linear Systems: Mathematical Framework

This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2nd-CASAM)” for the efficient and exact computation of 1st- and 2nd-order response sensitivities to uncertain parameters and domain boundaries of linear systems. The model’s response (i.e., model result of interest) is a generic nonlinear function of the model’s forward and adjoint state functions, and also depends on the imprecisely known boundaries and model parameters. In the practically important particular case when the response is a scalar-valued functional of the forward and adjoint state functions characterizing a model comprising N parameters, the 2nd-CASAM requires a single large-scale computation using the First-Level Adjoint Sensitivity System (1st-LASS) for obtaining all of the first-order response sensitivities, and at most N large-scale computations using the Second-Level Adjoint Sensitivity System (2nd-LASS) for obtaining exactly all of the second-order response sensitivities. In contradistinction, forward other methods would require (N2/2 + 3 N/2) large-scale computations for obtaining all of the first- and second-order sensitivities. This work also shows that constructing and solving the 2nd-LASS requires very little additional effort beyond the construction of the 1st-LASS needed for computing the first-order sensitivities. Solving the equations underlying the 1st-LASS and 2nd-LASS requires the same computational solvers as needed for solving (i.e., “inverting”) either the forward or the adjoint linear operators underlying the initial model. Therefore, the same computer software and “solvers” used for solving the original system of equations can also be used for solving the 1st-LASS and the 2nd-LASS. Since neither the 1st-LASS nor the 2nd-LASS involves any differentials of the operators underlying the original system, the 1st-LASS is designated as a “first-level” (as opposed to a “first-order”) adjoint sensitivity system, while the 2nd-LASS is designated as a “second-level” (rather than a “second-order”) adjoint sensitivity system. Mixed second-order response sensitivities involving boundary parameters may arise from all source terms of the 2nd-LASS that involve the imprecisely known boundary parameters. Notably, the 2nd-LASS encompasses an automatic, inherent, and independent “solution verification” mechanism of the correctness and accuracy of the 2nd-level adjoint functions needed for the efficient and exact computation of the second-order sensitivities.

Illustrative Application of the 2^nd-Order Adjoint Sensitivity Analysis Methodology to a Paradigm Linear Evolution/Transmission Model: Reaction-Rate Detector Response

This work continues the illustrative application of the “Second Order Comprehensive Adjoint Sensitivity Analysis Methodology” (2nd-CASAM) to a benchmark mathematical model that can simulate the evolution and/or transmission of particles in a heterogeneous medium. The model response considered in this work is a reaction-rate detector response, which provides the average interactions of particles with the respective detector or, alternatively, the time-average of the concentration of a mixture of substances in a medium. The definition of this model response includes both uncertain boundary points of the benchmark, thereby providing both direct and indirect contributions to the response sensitivities stemming from the boundaries. The exact expressions for the 1st- and 2nd-order response sensitivities to the boundary and model parameters obtained in this work can serve as stringent benchmarks for inter-comparing the performances of all (deterministic and statistical) sensitivity analysis methods.

Illustrative Application of the 2^nd-Order Adjoint Sensitivity Analysis Methodology to a Paradigm Linear Evolution/Transmission Model: Point-Detector Response

This work illustrates the application of the “Second Order Comprehensive Adjoint Sensitivity Analysis Methodology” (2nd-CASAM) to a mathematical model that can simulate the evolution and/or transmission of particles in a heterogeneous medium. The model response is the value of the model’s state function (particle concentration or particle flux) at a point in phase-space, which would simulate a pointwise measurement of the respective state function. This paradigm model admits exact closed-form expressions for all of the 1st- and 2nd-order response sensitivities to the model’s uncertain parameters and domain boundaries. These closed-form expressions can be used to verify the numerical results of production and/or commercial software, e.g., particle transport codes. Furthermore, this paradigm model comprises many uncertain parameters which have relative sensitivities of identical magnitudes. Therefore, this paradigm model could serve as a stringent benchmark for inter-comparing the performances of all deterministic and statistical sensitivity analysis methods, including the 2nd-CASAM.

Modeling the Spike Response for Adaptive Fuzzy Spiking Neurons with Application to a Fuzzy XOR

A spike response model(SRM)based on the spikes generator circuit(SGC)of adaptive fuzzy spiking neurons(AFSNs)is developed.The SRM is simulated in MatlabTM environment.The proposed model is applied to a configuration of a fuzzy exclusive or(fuzzy XOR)operator,as an illustrative example.A description of the comparison of AFSNs with other similar methods is given.The novel method of the AFSNs is used to determine the value of the weights or parameters of the fuzzy XOR,first with dynamic weights or self-tuning parameters that adapt continuously,then with fixed weights obtained after training,finally with fixed weights and a dynamic gain or self-tuning gain for a fine adjustment of amplitude.

汽轮发电机转子匝间短路对定子热响应特性的影响

本文分析了汽轮发电机转子匝间短路故障前后定子热响应特性,不仅考虑转子匝间短路引起电压下降对发电机强励动作的影响,还研究了热分布不平衡而引起的定子力学响应。首先推导了正常情况和转子匝间短路故障后加强励磁电流下的气隙磁通密度,得到了铁心损耗和绕组铜耗的解析表达式;然后建立了发电机故障前后的三维有限元仿真模型,对不同短路程度故障下的铁心损耗、绕组铜耗与定子温度进行了求解计算;最后实测了CS-5型故障模拟发电机在正常运行和不同短路程度故障下的定子温度,实验结果与理论分析、有限元仿真结果基本一致。结果表明,转子匝间短路故障后由于励磁电流的增强,发电机铁心损耗和绕组铜耗均会增加,定子温度明显上升,并且随着短路程度的增加而加剧;定子端面边缘位置的变形和应力幅值最大并且为热响应下的危险位置。

多层可延展柔性电路互连结构优化

为了提高柔性电子产品的穿戴舒适性,克服对皮肤产生的约束,提出基于非参数回归响应面代理模型和多目标遗传算法,对垂直互连通孔及导线焊盘大小与皮肤界面应力之间的模型进行预测并优化。以两层可延展柔性电路中垂直互连通孔及导线焊盘尺寸为研究对象,运用最佳填充空间设计抽样方法,建立试验样本点,通过非参数回归方法,拟合试验样本点,并利用验证点提高了响应面精度。采用多遗传算法在响应面模型内进行全局寻优,得出了一组满足皮肤舒适性的最优参数组合,对该最优参数组合进行仿真验证,验证结果表明了该方法的有效性,实现了多层可延展柔性电路互连结构的优化。

基于阶跃激励响应的牵引电机定子早期匝间短路故障诊断方法

为了实现对牵引电机定子绕组匝间短路早期故障的可靠诊断,文章提出了一种基于阶跃激励稳态响应电流的故障诊断方法。首先根据牵引电机三相定子绕组匝间短路模型,对定子绕组任意两相施加阶跃激励,推导出3种情况下的响应电流表达式,并依据响应电流稳态值的变化特征提出新的故障特征分量;然后,搭建故障电机仿真模型,分析短路电阻和短路故障严重程度对响应电流的影响,研究故障特征分量对早期匝间短路故障诊断的有效性与可靠性;最后搭建试验平台,分析当电机固有不对称时,匝间短路故障对故障特征分量的影响。仿真与试验结果表明,该故障特征分量可以表示早期的匝间短路故障及其严重程度,并且能滤除电机固有不对称的影响。基于阶跃激励稳态响应电流的诊断方法操作便捷,结果可靠性高,对保护牵引系统的安全具有极大意义,且具备极大的工程应用价值。

Coupled dynamic response analysis of multi-column floating offshore wind turbine with low center of gravity

To realize the application of the floating offshore wind turbine(FOWT)from deep to relatively shallow waters,a new concept of multi-column floating wind turbine platform with low center of gravity(CG)is designed and validated.The multi-column low CG platform is designed to support a 6MW wind turbine class and operated at a water depth of 50m in the South China Sea.The frequency domain software WADAM and time domain software NREL-FAST are used to simulate coupled dynamic responses of the floating wind turbine system with second-order wave loads considering.The dynamic behaviors of multi-column low CG FOWT system under normal operation and parked conditions are presented.The influence of second-order wave force on the motion responses of the multi-column platform,fore-aft force and moment of the tower base and mooring force are researched respectively.The results demonstrate that the coupled dynamic responses at rated operating condition and extreme condition meet the normal operating requirements and extreme survival requirements of FOWT system in the shallow water(50m)of South China Sea.In addition,it is found that,the wave frequency response gradually replaces the second-order low frequency response as the main influencing factor of the coupled dynamic response of the FOWT system with the increasing severity of the sea states.However,in general,the magnitude of second-order low frequency response increases with the increasing severity of the design load case.Thus,in the subsequent design of the shallow water FOWT system,the second-order effects should be paid enough attention.

用于三轴MEMS加速度计的集成数字调理电路

基于0.18μm互补金属氧化物半导体(CMOS)工艺,设计了一种用于三轴微电子机械系统(MEMS)加速度计的集成数字调理电路,实现了三轴加速度信号的数字后处理。该数字调理电路采用级联积分梳状(CIC)与有限冲击响应(FIR)相结合的滤波器形式,有效滤除了带外的量化噪声,提高了输出信号的信噪比;零位采用四阶多项式拟合温补算法,标度因数采用二阶多项式拟合温补算法,有效降低了加速度输出随温度的漂移,提升了加速度计的测量精度。此外,FIR滤波器采用时分复用的实现形式,温补模块采用串行实现形式,有效减小了芯片面积,最终芯片面积为1.5 mm^(2)。测试结果表明,滤波器符合设计值,三轴MEMS加速度计的零偏不稳定性为15μg,速率随机游走为0.035 m/s/√h,温补后零偏全温区变化量为3.55mg,提升了5.4倍;温补后标度因数全温区变化量为0.0026,提升了4.1倍,电路性能良好。

基于响应面-遗传算法的印制电路板参数识别

印制电路板装配件(Printed Circuit Board Assembly,PCBA)在航空航天设备中有广泛应用,分析和优化航空设备中电子设备振动可靠性的必要前提是建立准确的PCBA有限元模型。针对PCBA有限元模型物理参数难以通过实验获取的问题,本文以某机载电子设备PCBA为案例,首先通过最小分辨率V(Minimum Run with Resolution V,MRRV)的中心复合设计(Central Composite Design,CCD)建立多因素模型响应面函数样本点;然后根据最小二乘法确定响应面函数系数并完成响应面精度检验,构建响应值与模态试验结果误差的多目标函数;再采用快速分类的非支配排序遗传算法(Non-dominated Sorting Genetic Algorithm-Ⅱ,NSGA-Ⅱ)进行多目标参数识别,将识别后的参数代入ABAQUS有限元模型进行仿真分析,最后与模态试验和随机振动试验结果进行对比。结果表明:模态频率平均误差减少到2.70%,随机振动响应平均误差为5.83%,验证了此方法对机载振动环境下PCBA模型参数识别的有效性。

热流传感器响应时间优化方法研究

热流传感器在各个领域的应用越来越广泛,由于航天设备、电子产品等对温度有更严格的控制需求,热流传感器的精度和响应时间也需要达到更高的要求。只提升热流传感器的稳态特性满足不了很多工业领域的动态测量需求,提高热流传感器的动态特性具有很大的意义。从电路方面对热流传感器的响应时间进行优化,从热流传感器系统的主要电路模块入手,包括滤波放大模块,A/D转换模块,调理电路模块,提出具体的优化方案,并比较不同的方案,用Multisim软件仿真,从中选择出响应时间最短的电路方案。

消反峰电路对电磁阀性能的影响分析

电磁阀在航天器中应用广泛。消反峰电路是电磁阀控制系统中重要的组成部分,且对电磁阀的性能有显著影响。为了获得消反峰电路对电磁阀性能的影响,基于Maxwell软件对某轴流直动式电磁阀及其消反峰电路进行研究。通过将电磁阀某工况下的静态和瞬态仿真结果与试验数据进行对比,验证了仿真模型的有效性。同时仿真对比了有、无消反峰电路及不同消峰电阻下的电磁阀性能,得到释放响应时间随消峰电阻的增大而减小,而感应电动势随消峰电阻的增大而增大的规律,同时发现消峰电阻对电磁阀性能的影响存在一个转折点,选择此点作为电磁阀控制系统的设计点可以得到更优的方案,进而提出从消反峰电路角度优化电磁阀控制系统的方案,为电磁阀控制系统的优化设计提供参考。

基于砂浆电学模型的二电极法检测工具设计

水泥基材料由于其复杂的组成结构和不均匀的成分分布,其电学性质较为复杂,而电学特征与材料的部分物理化学特征存在紧密联系,这些特征在判断水泥基材料保护钢筋的能力及孔隙率等方面起到重要作用。为提高工程应用中的可操作性,本文将复杂电路简化为由若干电阻和电容组成的简单等效电路,应用恒电位电学系统的直流时域方法求解电路参数,使用自制高精度二电极法传感器取得材料在恒电位情况下的电流-时间响应曲线并进行数学处理,求出等效电路中各元件的参数和时间常数,从而简易判断材料中的自由离子含量和孔隙率。结果表明:验证二电极法在算法处理后可以得到较为精确且可靠的数据,从而扩大二电极法在工程中的应用范围,提高工程安全的监测水平。

两起高压厂用变压器出口短路事故的诊断试验比对分析

介绍了两台高压厂用变压器出口三相短路事故的概况和诊断性试验,包括介质损耗因素和电容量测试、油中溶解气体色谱分析、绕组直流电阻测试、短路阻抗和短路损耗试验、绕组频率响应分析等。根据两台变压器的历次试验数据,进行纵向、横向的同比分析和互比分析,以及使用比值分析法进行事故诊断和状态评价。结合两台变压器出口短路事故试验诊断比对分析结果,提出了对变压器开展零启升压下的空载试验、油中溶解气体色谱分析、计算产气速率、油中微量金属含量分析、低电压短路阻抗和短路损耗试验结合扫频短路阻抗检测的建议,以提高诊断比对和分析评价的正确性。

罐式断路器抗震性能仿真分析及优化设计

以某363 kV罐式断路器为研究对象,根据设计图纸构建三维实体模型,利用Ansys Workbench软件对模型施加抗震水平为AG5的地震响应谱进行有限元分析,得到地震荷载组合工况下的仿真计算结果,对断路器结构进行优化设计,并将结构优化前和优化后的抗震性能进行对比分析。结果表明,优化后该断路器满足AG5水平下的抗震性能要求,加固支架有利于提高罐式断路器结构的固有频率;结构优化后各主要部件应力水平均有所降低,套管顶端的最大位移响应从90.072 mm降低为66.342 mm,有利于罐式断路器设备长期安全稳定运行。

Digitalization of inverting filter shaping circuit for nuclear pulse signals

In the design of filter shaping circuits for nuclear pulse signals,inverting filter shaping circuits perform better than non-inverting filter shaping circuits.Because these circuits facilitate changing the phase of a pulse signal,they are widely used in processing nuclear pulse signals.In this study,the transfer functions of four types of inverting filter shaping circuits,namely the common inverting filter shaping,improved inverting filter shaping,multiple feedback low-pass filter shaping,and third-order multiple feedback low-pass filter shaping,in the Laplacian domain,are derived.We establish the numerical recursive function models and digitalize the four circuits,obtain the transfer functions in the Z domain,and analyze the filter performance and amplitude-frequency response characteristics in the frequency domain.Based on the actual nuclear pulse signal of the Si-PIN detector,we realize four types of inverting digital shaping.The results show that under the same shaping parameters,the common inverting digital shaping has better amplitude extraction characteristics,the third-order multiple feedback low-pass digital shaping has better noise suppression performance,and the multiple feedback digital shaping takes into account both pulse amplitude extraction and noise suppression performance.

Electronically Tunable Minimum Component Biquadratic Filters for Interface Circuits

In this paper, two new electronically tunable filter configurations are proposed. The proposed filters operate current-mode (CM), voltage-mode (VM), transimpedance-mode (TIM) and transadmittance-mode (TAM). The first configuration realizes second-order VM band-pass and TAM high-pass filter characteristics from the same configuration. The second one realizes second-order TIM band-pass and CM low-pass filter characteristics from the same configuration. They also use minimum number of electronic components (two capacitors and one active component namely;current controlled current difference transconductance amplifier). The workability of the proposed structures has been demonstrated by simulation results.

Modulation of abnormal neuronal circuit in temporal lobe epilepsy

OBJECTIVE Temporal lobe epilepsy(TLE)is one of the most common types of human epilepsy,and they are often resistant to current treatments.METHODS By using optogenetic,electrophysiological,imaging and pharmacology strategies,we aimed toinvestigate the underlying circuit mechanism of TLE and tried to developthe novel and efficient approach to control epilepsy.RESULTS(1)Using micro PET and multichannel EEG recording,we found an abnormal neural network,characterized by early hypometabolism and after discharge spread,during the epileptogenensis of TLE.(2)Deep brain stimulation,especially low frequency stimulation,targeted the epileptic focus and the areas outside of the focus(critical regions for seizure spread),such as the piriform cortex,cerebellum,entorhinal cortex or subiculum,reduced seizure severity in TLE.Its anti-epileptic effect is time-window dependent and polarity dependent,which shows a promising strategy for treating epileptic seizures.(3)Using an optogenetic strategy,we demonstrated that excitatory projection from entorhinal cortex to hippocampus instructs the brain-stimulation treatments of epilepsy.(4)Our data from both the clinical and experimental studies further demonstrated that a disinhibitory GABAergic neuronmediated microcircuit in the subiculum contributes to secondary generalized seizures in TLE.(5)Finally,based on abnormal synchronization of the electrical activity in epileptic circuit,we developed electroresponsive hydrogel nanoparticles modified with angiopep-2 to facilitate the delivery of the antiepileptic drug phenytoin sodium,which greatly improves the therapeutic index.CONCLUSION Our findings may update the current view of epileptic neuronal networks and suggest possible promising ways for epilepsy treatment.