短光脉冲的谐波测量法

本文讨论了超短光脉冲测量的二次谐波法(SHG)、半导体表面反射频法和高次谐波波。用SHG法对调Q加模Nd:YAG激光器的光脉冲进行了测量。     

光伏发电在电动阀门中的应用

为了克服电动阀门在沙漠和其他地区供电难的问题,提出了用光伏电池为蓄电池充电,用蓄电池的电能为电动阀控制系统供电,并用DSP实现全数字软件锁相环(DSPLL)控制直流电机可逆调速的脉冲宽度调节(PWM)。试验证明光伏电池能满足电动阀门的开、关所需要的电能,该方法不仅能实现整个系统的功能,而且其性能稳定可靠,减少系统的谐波和纹波成分,使整个控制系统能实时地遥控、数据采集和传输、液晶显示电机转矩,使直流电机稳速高精度控制阀门的流量。     

单箱三室连续宽箱梁有效宽度分析

箱梁在受弯时，横桥向存在剪力滞效应，为了在计算中应用初等材料力学方法求解，采用了翼缘有效宽度方法。以某实桥为背景，通过对单箱三室连续宽箱梁空间实体模型进行了有限元分析，计算得出了箱梁顶板及底板的有效分布宽度系数ρs及ρf，并与规范值进行了比较，可为同类工程设计提供参考。     

On accelerating sequential procedures for estimating exponential populations

In this study, we accelerate the purely sequential procedure due to Anscombe(1953), Chow and Robbins(1965) to reduce the number of sampling operations required to carry out the estimation process. The method is proposed while estimating the location parameter(s) of the exponential distribution(s). We also develop theory for the asymptotic characteristic of the associated stopping variables. Our findings are applicable to both point as well as confidence interval estimation problems. Other interesting results are also given.     

A comment on sample size calculations for binomial confidence intervals

In this article we examine sample size calculations for a binomial proportion based on the confidence interval width of the Agresti–Coull, Wald and Wilson Score intervals. We pointed out that the commonly used methods based on known and fixed standard errors cannot guarantee the desired confidence interval width given a hypothesized proportion. Therefore, a new adjusted sample size calculation method was introduced, which is based on the conditional expectation of the width of the confidence interval given the hypothesized proportion. With the reduced sample size, the coverage probability can still maintain at the nominal level and is very competitive to the converge probability for the original sample size.     

Confidence intervals for estimating the population signal-to-noise ratio: a simulation study

This paper considered several confidence intervals for estimating the population signal-to-noise ratio based on parametric, non-parametric and modified methods. A simulation study has been conducted to compare the performance of the interval estimators under both symmetric and skewed distributions. We reported coverage probability and average width of the interval estimators. Based on the simulation study, we observed that some of our proposed interval estimators are performing better in the sense of smaller width and coverage probability and have been recommended for the researchers.     

职场Tweens的消费态度及相关因素差异性分析

对职场Tweens的消费态度进行了研究,发现可将职场Tweens的消费态度分为炫耀型、变动型和理智型3种类型.分析了性别、文化程度等人口统计学变量对某一特定消费类型影响的差异程度,结果显示:不同性别的职场Tweens在炫耀型消费方面无显著差异,而在变动型消费和理智型消费方面有显著差异;不同文化程度的职场Tweens仅在炫耀型消费方面有显著差异;处于不同城市的职场Tweens也仅在炫耀型消费方面有显著差异.     

动态尾部金融网络结构与传染性度量

基于Lasso高维分位数回归模型,本文构建了中国金融系统的尾部网络结构,并定义了总体网络以及行业间、行业内和金融机构间等多层金融网络的尾部风险传染度,解构其传染机制与关联特征,评估各机构双向系统重要性(接收端和发射端)。同时,本文提出了一个最优滚动窗宽选择标准方法,以优化滚动样本技术下的动态网络结构。结果表明,所有层级尾部风险传染效应(总体系统、行业间、行业内和机构间)在经济金融极端困境时期,呈现明显增强及剧烈震荡特征,2015年中国股灾期间尤甚。跨行业传染效应日益严峻,银行与保险间表现出较强关联性,房地产机构与其他金融机构间均表现出较高传染性,跨业监管值得关注。接收与发射最多尾部风险传染的金融机构仍然是银行与证券类机构。系统中超过50%的金融机构倾向于接收风险传染,一旦出现系统性冲击,整个金融系统的稳定性将遭受重创,因此,应加强此类机构应对外界冲击的能力。此外,基于新滚动窗宽选择标准法的动态模型的估计性能明显优于传统方法。研究结论有助于理解中国金融系统的网络结构和传染机制,对宏观审慎监管体系的建立提供了依据。     

CORRECTING FOR KURTOSIS IN DENSITY ESTIMATION

Using a global window width kernel estimator to estimate an approximately symmetric probability density with high kurtosis usually leads to poor estimation because good estimation of the peak of the distribution leads to unsatisfactory estimation of the tails and vice versa. The technique proposed corrects for kurtosis via a transformation of the data before using a global window width kernel estimator. The transformation depends on a “generalised smoothing parameter” consisting of two real-valued parameters and a window width parameter which can be selected either by a simple graphical method or, for a completely data-driven implementation, by minimising an estimate of mean integrated squared error. Examples of real and simulated data demonstrate the effectiveness of this approach, which appears suitable for a wide range of symmetric, unimodal densities. Its performance is similar to ordinary kernel estimation in situations where the latter is effective, e.g. Gaussian densities. For densities like the Cauchy where ordinary kernel estimation is not satisfactory, our methodology offers a substantial improvement.     

PWPM信号的功率谱研究

对脉冲宽度、位置联合调制(pulse width and position modulation)简称 PWPM 方式的随机信号序列功率谱进行了研究,文献[1]的理论结果显示 PWPM 随机信号序列功率谱中存在符号(symbol)同步信号离散谱成分,这有利于在接收端正确接收 PWPM 信号.用计算机模拟估计了 PWPM 随机信号序列的功率谱.其结果也表明了 symbol 同步信号的存在.