Multivariate meta analysis with potentially correlated marketing study results

A univariate meta analysis is often used to summarize various study results on the same research hypothesis concerning an effect of interest. When several marketing studies produce sets of more than one effect, multivariate meta analysis can be conducted. Problems one might have with such a multivariate meta analysis are: (1) Several effects estimated in one model could be correlated to each other but their correlation is seldom published and (2) an estimated effect in one model could be correlated to the corresponding effect in the other model due to similar model specification or the data set partly shared, but their correlation is not known. Situations like (2) happen often in military recruiting studies. We employ a Monte‐Carlo simulation to evaluate how neglecting such potential correlation affects the result of a multivariate meta analysis in terms of Type I, Type II errors, and MSE. Simulation results indicate that such effect is not significant. What matters is rather the size of the variance component due to random error in multivariate effects. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 500–510, 2000.     

GSVM:一种支持Gather/Scatter的向量存储器

宽单指令多数据流(Single Instruction Multiple Data, SIMD)架构数字信号处理器一般都能高效支持地址连续或等距跨步等规则应用的向量访存,但对于科学与工程计算中广泛存在的不规则应用的数据访存则带宽利用率往往较低,从而大幅降低了其整体运算能效。为了提高不规则应用的向量访存性能,基于某SIMD数字信号处理器的体系结构,设计了一种支持Gather/Scatter访存的向量存储器GSVM。通过设计与SIMD宽度相匹配的向量地址计算单元和合适深度的冲突缓冲器阵列,实现了Gather/Scatter指令向量地址计算、仲裁与缓存的全流水访存操作。实验结果表明,相比以前不支持Gather/Scatter访存的存储器,GSVM在增加22%的硬件代价基础上,基于稀疏矩阵向量乘的测试程序集获得了2～8的性能加速比。     

随机-区间混合不确定性单输出模型确认指标

针对既有随机变量又有区间变量的模型预测结果与实验数据之间的一致性度量问题,对随机-区间混合不确定性模型确认指标进行研究。根据工程数学模型和实验过程中的不确定性来源,分析随机-区间混合不确定性模型确认的特点;运用概率方法和区间理论,提出新的随机-区间混合不确定性模型确认指标,讨论所提指标的性质,给出指标的计算方法和步骤。通过数字算例和工程算例,验证了所提指标的可行性和有效性。     

随机-非概率模型下的船体结构屈服强度可靠性分析

针对在役舰船船体载荷、材料属性的随机特性和实船勘验得出的腐蚀损伤下船体抗力区间特性,提出一种基于随机概率理论和区间非概率理论的随机-非概率可靠性分析模型,分别从区间变量随机化和随机变量区间化两个角度给出该模型的可靠性指标求解方法。基于该模型对某舰船船体结构屈服强度进行可靠性分析,结果表明:该模型既体现了结构变量的客观不确定性又减弱了评估结果的盲目保守性,对于既含有随机变量又含有区间变量的在役舰船的可靠性评估具有很强的适用性。     

Adaptive random search for continuous simulation optimization

We present, analyze, and compare three random search methods for solving stochastic optimization problems with uncountable feasible regions. Our adaptive search with resampling (ASR) approach is a framework for designing provably convergent algorithms that are adaptive and may consequently involve local search. The deterministic and stochastic shrinking ball (DSB and SSB) approaches are also convergent, but they are based on pure random search with the only difference being the estimator of the optimal solution [the DSB method was originally proposed and analyzed by Baumert and Smith]. The three methods use different techniques to reduce the effects of noise in the estimated objective function values. Our ASR method achieves this goal through resampling of already sampled points, whereas the DSB and SSB approaches address it by averaging observations in balls that shrink with time. We present conditions under which the three methods are convergent, both in probability and almost surely, and provide a limited computational study aimed at comparing the methods. Although further investigation is needed, our numerical results suggest that the ASR approach is promising, especially for difficult problems where the probability of identifying good solutions using pure random search is small. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

层间接触与弹性模量对某导弹场坪动载的影响

为了研究某型导弹典型公路发射场坪沉降量和受力状态,利用混凝土塑性损伤模型建立某导弹无依托发射场坪有限元模型,在选取30种典型路面结构的基础上,分析了土基层弹性模量和面层与基层间黏结状况两个因素对路面动载响应的影响。结果表明:层间接触不良会导致路面弯沉、剪应力变大。同时得出该型导弹发射道路土基层弹性模量应大于20 MPa。研究结果对于评估导弹无依托发射生存能力和快速反应能力提供参考依据。     

光纤陀螺随机漂移分析与建模方法

随机漂移是影响光纤陀螺精度的重要因素。根据光纤陀螺静态漂移测试信号,利用Allan方差法对光纤陀螺随机漂移误差进行了分离和辨识,并分析了系数拟合过程中最小二乘法的病态矩阵问题。最后探讨了利用AIC准则和长自回归法建立光纤陀螺随机漂移ARMA模型的方法,为进一步对光纤陀螺输出信号进行滤波处理奠定了基础。     

模糊识别和随机森林算法在柴油机振动信号状态识别中的应用

针对模糊识别算法中,样本特征向量中各参量(分量)对状态分类的贡献权重难以确定的问题,提出了利用随机森林算法对特征参量的重要度评估结果作为特征权重的方法。通过对柴油机台架试验振动信号的跟踪分析,获得了柴油机在磨合期、100摩托小时、200摩托小时、300摩托小时及400摩托小时5种不同使用期(典型状态)的75个振动信号样本,然后计算出各类样本在幅域、时域和频域的特征参量,利用随机森林算法进行特征选择,确定4个重要特征参量及其权重,用统计方法得出其隶属度函数,最后根据评价向量对样本进行识别,识别准确率达到94%以上。