On Calculations Involving the Maximum Cell Frequency

We describe a method of computing the cumulative distribution function of the maximum and minimum cell frequencies in sampling distributions commonly encountered in the analysis of categorical data.The procedure is efficient for exact or approximate calculation in both homogeneous and non-homogeneous cases, is non-recursive, and does not require Dirichlet integrals.Some related statistical problems are also discussed.     

《长安大学学报（自然科学版）》2002-2012年主要文献计量指标分析

运用文献计量学方法,以《长安大学学报（自然科学版）》2002-2012年刊载的1 661篇论文为研究对象,统计论文载文量、基金论文比、第一作者职称和学历、合著率和合作度、稿源地区分布以及出版时滞等指标,从文献引证的角度反映其刊载论文的学术水平和期刊影响力,为进一步提高《学报》的学术水平和办刊质量提供一定的依据。研究结果表明：道路工程、桥梁与隧道工程是其载文的主要学科;载文量逐渐下降,论文质量逐步提升;高级职称作者群波动较大,中级职称作者群人数逐渐增多,博士研究生和硕士研究生作为新生力量有所增加;基金论文比大幅增加;作者合著率与合作度较高;论文出版时滞逐渐缩短;期刊被引率、下载次数较高,高被引论文主要集中在优势学科,以研究型论文为主,综述型文章被引频次和下载次数较高。     

三维层叠微带天线的FDTD模拟(英文)

借助Maxwell方程组,将时域有限差分法应用于实验室研制的新型层叠式微机械微带贴片天线的建模和分析,并根据数值模拟结果讨论了天线的特性参数。根据实际情况,灵活地给出了各边界的近似吸收边界条件,有效地减少了存储空间和计算时间。     

汇率制度选择问题的理论之争及评析

汇率制度的选择是国际金融领域的重要理论问题。在对“固定”与“浮动”、“两极”与“中间”两种汇率制度选择理论上的争论进行评述的基础上,本文认为,汇率制度的选择是一个受多种因素影响的动态体系,汇率制度选择是一国具体情况的相机抉择,任何一种汇率制度都不可能适合于所有国家和一个国家的所有时期。     

计算轴盘系统临界转速的新方法

本文把随轴一起振动盘的惯性力看成是作用在轴上的外力，对有任意广盘的轴盘系统，采用Laplace变换导出了临界固有频率方程的解析式     

The estimation for Lévy processes in high frequency data

In this article, a generalized Lévy model is proposed and its parameters are estimated in high-frequency data settings. An infinitesimal generator of Lévy processes is used to study the asymptotic properties of the drift and volatility estimators. They are consistent asymptotically and are independent of other parameters making them better than those in Chen et al. (2010 Chen, S. X., Delaigle, A., Hall, P. (2010). Nonparametric estimation for a class of Lévy processes. Journal of Econometrics 157:257–271.[Crossref], [Web of Science ®] , [Google Scholar]). The estimators proposed here also have fast convergence rates and are simple to implement.     

步进电机的定位及速度控制软件设计

结合步进电机在数控系统中的应用，介绍８０３１ 单片机控制步进电机的方法及实现步进电机的精确定位、换向和速度控制的软件设计。     

Survival of Staphylococcus aureus ATCC 13565 in Intermediate Moisture Foods is Highly Variable

Staphylococcus aureus is a gram-positive, enterotoxin-producing coccus. It is a hardy organism and known to survive over a wide range of water activities, pH values, and temperatures. The objective of this study was to model the survival or gradual inactivation of S. aureus ATCC 13565 in intermediate moisture foods (IMFs). Various initial concentrations (approximately 10(1), 10(2), 10(3), and 10(4) CFU/g) were used to inoculate three different IMFs (beefsteak, bread, and chicken pockets). Viable counts were determined up to 60 days using tryptic soy agar. Inoculum size did not influence the survival or gradual inactivation of S. aureus in these foods. The rate of change (increase or decrease) in log CFU/day was calculated for every consecutive pair of data points and by linear regression for each inactivation curve. Both consecutive pair and linear regression rates of change were fit to logistic distributions (with parameters alpha and beta) for each food. Based on the distribution parameters, survival or gradual inactivation of S. aureus was predicted by computer simulation. The simulations indicated an overall decline in S. aureus population over time, although a small fraction of samples in the consecutive pair simulation showed a slight population increase even after 60 days, consistent with the observed data. Simulation results were compared to predictions from other computer models. The models of Stewart et al., were fail-safe, predicting the possibility of significant growth only after > 3,000 days. The USDA pathogen modeling program predictions were found to be fail-dangerous, predicting declines at least four times faster than observed.     

宽带LFM信号去斜率数字脉压方法性能分析

在宽带LFM信号数字脉压中,去斜率数字脉压方法能有效地降低采样率,但是受到目标回波信号与参考信号的时延差的限制,只能作局部脉压处理。同时目标回波信号与参考信号的时延差和目标多普勒频率的变化,对去斜率数字脉压结果有一定的影响。该文通过理论分析和较全面的仿真,定量地分析了去斜率数字脉压中目标回波信号与参考信号时延差和多普勒频率的变化对数字脉压性能的影响,为工程应用中合理选择信号带宽、采样率和目标回波信号的时延提供了参考。     

相控阵雷达低仰角目标DOA估计的算法

在相控阵雷达跟踪低仰角目标时,采用频率捷变技术可以有效地减小雷达回波中直射信号和反射信号的相关性,抑制多径效应对目标到达方向估计造成的影响,提高角度估计的精度和性能。再用修正的AR模型算法,不仅可以在此基础上进一步去掉这两种信号的相关性,而且能正确估计出目标和镜像的仰角。计算机仿真实验结果验证了频率捷变和修正AR模型算法理论的正确性,以及在与其他方法比较的情况下,两者结合在去相关性能上的优越性和工程实用性。