Assessment of the phase synchronization effect in modal testing during operation

The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.     

The Impact of Moderate Priors For Bayesian Estimation and Testing of Item Factor Analysis Models When Maximum Likelihood is Unsuitable

In psychological research, available data are often insufficient to estimate item factor analysis (IFA) models using traditional estimation methods, such as maximum likelihood (ML) or limited information estimators. Bayesian estimation with common-sense, moderately informative priors can greatly improve efficiency of parameter estimates and stabilize estimation. There are a variety of methods available to evaluate model fit in a Bayesian framework; however, past work investigating Bayesian model fit assessment for IFA models has assumed flat priors, which have no advantage over ML in limited data settings. In this paper, we evaluated the impact of moderately informative priors on ability to detect model misfit for several candidate indices: posterior predictive checks based on the observed score distribution, leave-one-out cross-validation, and widely available information criterion (WAIC). We found that although Bayesian estimation with moderately informative priors is an excellent aid for estimating challenging IFA models, methods for testing model fit in these circumstances are inadequate.     

电子台秤自动检测信息管理系统设计

鉴于目前电子台秤手工检测存在效率低、工作强度大、易受人为因素影响、数据管理能力低等缺点。提出了一种基于PC机、PLC的自动检测装置的解决方案,并详细介绍了信息管理系统的需求分析、设计及实现。采用Modbus协议,实现电子台秤、PLC控制系统与PC的信息交换,并采用数据库管理检测数据。     

基于ANSYS的印制电路板装配体的PSD分析

使用ANSYS对印制电路板装配体进行了模态分析、模态叠加法谐响应分析和PSD分析,得出了印制电路板的前四阶阵型,并结合谐响应分析结果找出与模态分析固有频率存在差异的原因,通过PSD分析得出在结构的共振点存在位移峰值,这些结论为进一步分析和优化设计提供了重要的理论依据。     

基于改进的最大似然算法的OFDM系统同步技术

同步是OFDM系统中的关键技术,最大似然估计算法在OFDM符号定时同步和载波频率同步中得到了广泛的应用.通过仿真可以清楚地看到,拓宽的ML算法使ML算法在应用范围上有了扩展.并且能够更好地实现OFDM系统的符号同步和载波同步.     

立体组装电路模块动态特性的有限元模拟与分析

Based on the modal analysis theory and by using the dynamics finite element analysis model of a three-dimensional assembly circuit module, dynamic characteristics of circuit module have been studied, including both natural characteristics analysis and dynamic responses analysis. Using a subspace method, modal analysis is first carried out. The first 6 orders of natural frequencies and vibration modes are obtained. Influence of the number of the Z-shaped metal slices on dynamic characteristics of the entire structure is also studied.Harmonic response analysis is then conducted. The steady-state response when the circuit module is subjected to harmonic excitation is determined. A curve of the response values against frequencies is obtained. As a result, the optimal number of Z-shaped metal slices can be determined, and it can be assured that the three-dimensional assembly circuit module has good performance in terms of the dynamic characteristics.     

An Investigation of the Influence of Internal Test Bias on Regression Slope

Through a large-scale simulation study, this article compares item parameter estimates obtained by the marginal maximum likelihood estimation (MMLE) and marginal Bayes modal estimation (MBME) procedures in the 3-parameter logistic model. The impact of different prior specifications on the MBME estimates is also investigated using carefully selected prior distributions. The results indicate that, in general, the MBME provides more accurate item parameter estimates than the MMLE procedure. The impact of different priors on the Bayesian estimates is modest when the examinee sample size is not extremely small.     

一种利用等效模型与遗传算法的动态有限元模型修正方法

为了解决现有动态有限元模型修正方法计算效率不高或者可能获得局部最优解的问题,提出了一种利用等效模型和遗传算法的动态有限元模型修正新方法.首先,在设计参数的取值范围内,根据预设的多项式模型的阶次以及自变量的个数,利用试验设计方法获得拟合响应面模型所需要的最优样本点;通过有限元分析获得样本数据,并利用回归分析获得响应面模型,从而以响应面模型逼近结构特征与设计参数之间的函数关系.然后,在遗传算法的适应度评估环节,利用响应面模型替代有限元模型计算对应于一组设计参数的结构特征,并计算遗传个体的适应度,最终通过进化获得最优解,即为修正后的设计参数.以汽车车架模型为例,对其进行有限元分析与模态试验,并利用所提出的方法进行模型修正.修正后,模态频率误差的均方值小于2%.用修改后结构的动态特性的测试结果,对修正后有限元模型的预测能力进行检验,模态频率预测误差的均方值小于2%.     

Failure analysis of crush hammers based on damage fracture energy

To prolong the life-span of crush hammers in the pyrite concentrate workplace of Ganbazi Coal Preparation Plant of Chongqing Nantong Mining Ltd., we used a progressive damage constitutive model based on the ductile and shear damage fracture energy to analyze the hammer wear failure caused by the impact and abrasion on the hammer surface by pyrite, and carried out simulation analysis with the explicit algurithm on hammer leftovers from the plant during the process of coarser pyrite comminution. The simulation results are consistent with hammer wear failure caused by pyrite impact. Then we proposed corrective measures to prolong hammer life-span. Results of the production test in the Ganbazi Coal Preparation Plant showed that non-clearance hammers can avoid wear erosion, and adding steel bonded tungsten carbides F3002 prolonged the hammer life- span. The effect of austenitic manganese steel work-hardening was not prominent. Therefore, the hammer failure was mainly caused by superficial abrasion instead of fatigue cracks appearing when grains acted on the hardening layer.     

一种补偿型压控高压恒流源的设计与应用

介绍一种以运算放大器为核心器件,通过NPN型三极管集电极输出的高压小电流精密恒流源电路,分析了电路的工作原理、重要元件的参数选择及电压检测电路带来的电流误差,给出了以运算放大器比例运算电路实现补偿的方法．该电路结构简单、性能稳定、线性度好,输出电流通过0-5V模拟电压调节,输出电压可达1100V,适合用作中高压化成箔到达电压的测试电源．丈中还给出了利用该恒流源电路构成四通道高压化成箔时间电压自动测试仪的硬件方案．     

模拟计算在传统物理实验教学中的应用

阐述了模拟计算在超声速测量实验中的应用，利用ANSYS软件对压电陶瓷超声波换能器进行了模态分析和谐响应分析，模拟计算值和实验测量值一致。将模拟分析法引入传统物理实验中，开拓了物理实验教学的新模式，加深了学生对实验原理的理解，提高了学生应用模拟分析方法解决实际问题的能力。     

简析郭祖荣艺术歌曲的伴奏音乐

通过分析郭祖荣不同时期的三首艺术歌曲的伴奏音乐,探究其和声语汇、调式调性和伴奏织体不断探索、不断创新的轨迹,为今天的伴奏音乐创作提供参照。     

F320井架模型动态特性研究

使用ANSYS有限元软件、实验模态分析技术对F320型石油井架模型的动态特性进行了数值与试验分析.从分析获得的结构动态特性信息中发现,对于这一类F320石油井架模型结构,不能用简单的线性梁模型来简化处理.本次井架模型动态特性试验结果可以作为石油井架非线性结构模型建立的数据基础.     

知识转化、组织学习与银行操作风险控制的相关性研究——基于信息化平台的数据检验

操作风险控制是我国银行业风险控制的核心任务之一。在信息化条件下,知识转化和组织学习对操作风险控制在理论上具有直接的促进作用。基于我国银行业的样本数据,借助于结构方程模型分析方法,实证性的研究揭示了操作风险的微观控制机理,从而为我国银行业在信息化环境下改进组织学习和知识转化的策略,进而提高操作风险的控制能力提供了现实性的理论借鉴。     

电子设备故障电流和谐波电流区分的方案设计

针对如何快速、有效地区分电力系统故障运行状态和不正常运行状态,尤其是短路故障和谐波状态的问题,应用序分量理论,设计了一种可区分故障和谐波的方案,通过仿真测算法,及增加继电保护装置逻辑判断环节中的控制信号,实现了不正常运行状态和故障状态的区别,进而达到继电保护装置正确、可靠地动作的目的。     

3×4MVA中频炉谐波测量与分析

中频感应加热炉（简称中频炉）是一种快速稳定的金属加热装置,由于中频炉内部具有变频装置及其功率较大等特点,所以对公共电网注入的谐波不可忽视。本文通过中频炉负载支路谐波数据的测量与分析,根据谐波可由傅立叶级数分解的特点,建立了一种谐波源简化电路模型。利用saber仿真软件构建了谐波源简化电路模型,验证了简化模型在工程应用上的可行性。在软件仿真平台上可方便的设定滤波器和无功补偿装置的参数,便于滤波器和无功补偿装置的设计。     

How to improve pupils’ literacy? A cost-effectiveness analysis of a French educational project

The Action Lecture program is an innovative teaching method run in some nursery and primary schools in Paris and designed to improve pupils’ literacy. We report the results of an evaluation of this program. We describe the experimental protocol that was built to estimate the program's impact on several types of indicators. Data were processed following a Differences-in-Differences (DID) method. Then we use the estimation of the impact on academic achievement to conduct a cost-effectiveness analysis and take a reduction of the class size program as a benchmark. The results are positive for the Action Lecture program.     

浏览器兼容性自动化测试方法研究

浏览器是 Web 应用程序的客户端软件,针对浏览器兼容性测试的手工效率低,工作量大的问题, 提出了一种并行的自动化测试方法,并将图像匹配技术结合到该自动化测试系统中,解决了脚本编写过程中界面检查点无法设置的问题。对该方法中的自动化测试框架组成结构和测试脚本编写进行了研究,并对如何生成测试结果及输出的测试报告内容进行了说明。为验证方法的有效性针对三款不同的浏览器在Web程序上进行了自动和手动测试时间对比,实验结果表明使用所提出的方法可以使测试速度提升大约3倍。     

商业银行操作风险控制绩效系统研究

《新巴塞尔资本协议》认为：操作风险将逐渐上升为现代商业银行的首要风险,操作风险控制已成为商业银行风险控制的重要领域。信息化建设是我国商业银行的一项长期战略．而内部控制是一种重要的管理活动,对我国商业银行操作风险控制绩效的提升具有天然的推动作用。通过对基于信息化建设和内部控制导向的我国商业银行操作风险控制绩效提升系统的经验性解析,可以为我国商业银行加强信息化建设和内部控制功能、进一步提高操作风险的控制绩效提供了现实性的理论借鉴。     

基于结构健康监测系统的悬索桥运行模态识别(英文)

介绍了联合应用峰值法和互谱法的模态参数识别方法,并提出了一种新的主梁振型优化方法.将上述方法应用于润扬大桥悬索桥的运行模态识别系统中,利用结构健康监测系统采集的振动响应数据获取结构的模态参数.作为应用实例,对台风麦莎作用下的主梁、主缆和桥塔振动响应数据进行了模态参数识别.结果表明:主梁部分振型的模态频率不仅能从主梁的振动响应识别出来,而且能够从主缆和桥塔振动响应中识别,主粱、主缆和桥塔之间存在较强的耦合振动.此外,将运行模态的识别结果和成桥之初的现场测试结果进行了对比,二者识别结果整体上吻合较好,但运行模态系统识别的部分振型模态频率,如L1和L2,发生了较明显的下降.