Influences of different crossing types on dynamic response of underground cavern subjected to ground shock

An intersecting cavern is a common structural form used in underground engineering, and its safety and stability performance directly control the service performance of the whole project. The dynamic re-sponses of the three kinds of crossing type (+-shaped, T-shaped, L-shaped) caverns subjected to ground shock were studied by numerical simulation. The velocity plus force mode boundary setting method was proposed in the coupled static and dynamic analysis of a deep underground cavern. The results show that, among the three types of crossing caverns, the+-shaped cavern is the most significantly affected by the dynamic action, followed by T-shaped, and then L-shaped caverns. The vault settlement, straight wall deformation, vault peak particle velocity, effective plastic strain of surrounding rock, and maximum principal stress and strain at the bottom of the lining of the straight wall increase with the increase of cavern span. The vault settlement, straight wall deformation, effective plastic strain of surrounding rock, and the maximum principal stress and strain at the bottom of lining to the straight wall decrease with the increase of lateral pressure coefficient, and the peak particle velocity at the vault increases. The variation is small compared with the change of cavern span. The influence range of the underground cavern intersection is two cavern diameters from the intersection centre. The bottom of the straight wall at the intersection is the weak part. It is suggested to thicken the support locally to improve the stability of the cavern.     

Research on fuze microswitch based on corona discharge effect

Abnormal voltages such as electrostatic, constant current, and strong electromagnetic signals can erro-neously trigger operation of MEMS pyrotechnics and control systems in a fuze, which may result in casualties. This study designs a solid-state micro-scale switch by combining the corona gas discharge theory of asymmetric electric fields and Peek's Law. The MEMS switch can be transferred from "off" to"on" through the gas breakdown between the corona electrodes. In the model, one of the two electrodes is spherical and the other flat, so a non-uniform electric field is formed around the electrodes. The theoretical work is as follows. First, the relation among the radius of curvature of the spherical electrode, the discharge gap, and the air breakdown voltage is obtained; to meet the low voltage (30-60 V) required to drive the MEMS switch, the radius of curvature of the spherical electrode needs to be 10-50 μm and the discharge gap between the two electrodes needs to be 9-11 μm. Second, the optimal ratio ε is introduced to parameterize the model. Finally, the corona discharge structural parameters are determined by comparing the theoretical and electric field simulation results. The switch is then fabricated via MEMS processing. A hardware test platform is built and the performing chip tested. It is found that when the electrode gap is 9 μm, the electrostatic voltage is at least 37.3 V, with an error of 2.6% between the actual and theoretical air breakdown voltages. When the electrode gap is 11 μm, the electrostatic voltage is at least 42.3 V, with an error of 10.5% between the actual and theoretical air breakdown voltages. Both cases meet the design requirements.     

超宽谱电磁脉冲与无线电引信能量耦合因素的研究

通过超宽谱对配用不同弹体的无线电引信的辐照,分析了不同弹体以及配用某种弹体的引信不同放置方向对超宽谱电磁脉冲与无线电引信能量耦合的影响,并分析了弹体大小对能量耦合的影响。通过辐照、分析和计算最终得出:弹体是影响能量耦合的主要因素。弹体口径越大,超宽谱电磁脉冲与无线电引信的耦合能量越大。另外,配用弹体引信的不同放置方向也是影响能量耦合的重要因素;配用弹体的引信竖直放置时,超宽谱电磁脉冲与无线电引信的耦合能量最大。     

某型供弹机关重件磨损加速寿命试验仿真

针对某供弹机寿命试验周期长,耗资大,薄弱环节工作参数不易测得的问题,提出对供弹机进行加速寿命试验;以供弹链关重件-销轴与销孔的配合为研究对象,进行了加速寿命试验的计算机辅助设计与分析(ALT-CAE),基于ADAMS建立了供弹机的虚拟样机模型,通过仿真得到了销轴与销孔配合在正常工况下和加速工况下的碰撞载荷谱与相对角速度谱;获得了销轴在各加速工况下的加速系数,拟合了销轴的加速曲线,建立了加速寿命试验的加速模型.为基于磨损的加速寿命试验提供参考.     

增量比例导引弹道仿真研究

通过引入附加增量,对传统的比例导引方法进行改进。建立了增量比例导引方法的数学模型,运用Matlab语言进行仿真计算,分析了不同的比例导引系数、附加增量对导引弹道及导弹与目标相遇时间的影响,得到不同导引系数及附加增量下的弹道曲线和弹目相遇时间,仿真结果表明与传统的比例导引方法相比,在比例导引系数不变的情况下,选择合适的附加增量可以减少导弹与目标的相遇时间。     

Northwest corner and banded matrix approximations to a Markov chain

In this paper, we consider approximations to discrete time Markov chains with countably infinite state spaces. We provide a simple, direct proof for the convergence of certain probabilistic quantities when one uses a northwest corner or a banded matrix approximation to the original probability transition matrix. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 187–197, 1999     

Transactional and in-store display data of a large supermarket for data-driven decision-making

This article describes daily and monthly transactional and in-store display data of a large supermarket from January to October in 2019 associated with 28 757 stock-keeping units (SKUs) in 5 categories and 41 subcategories. The database contains five parts, including information about each SKU, in-store display, daily sales, inventory, and replenishment. We also propose some research questions related to assortment planning, pricing, inventory management, and customer behavior. Researchers are welcome to develop data-driven models or other innovative methods to address these questions or other practical problems using this database.     

The shortest queue model with jockeying

In this article we deal with the shortest queue model with jockeying. We assume that the arrivals are Poisson, each of the exponential servers has his own queue, and jockeying among the queues is permitted. Explicit solutions of the equilibrium probabilities, the expected customers, and the expected waiting time of a customer in the system are given, which only depend on the traffic intensity. Numerical results can be easily obtained from our solutions. Several examples are provided in the article.     

低活性粉煤灰在混凝土中的应用研究

为提高低活性粉煤灰在混凝土中的利用,依据《水泥胶砂强度检验方法》和《普通混凝土力学性能试验方法标准》,通过复掺CaO、CaSO4及防水剂、减水剂等材料对低活性粉煤灰进行了活化实验研究和混凝土性能测试研究,试验结果表明：经过活化处理后的粉煤灰重新获得了活性,提高了混凝土的强度、降低了泌水率、减小了坍落度经时的损失,从而有助于低活性粉煤灰的开发利用。     

MSPWVD-HOUGH变换的多目标分辨和雷达回波参数估计

传统的时频分析方法,如Winger Ville Distribution,smoothed pseudo Wigner-Ville distribution等在多目标分辨的时候,无法同时在时频分辨率和抑制交叉项两方面同时达到较好的效果,所提出的MSPWVD解决了这一问题,MSPWVDHOUGH还可在低信噪比的情况下检测出多目标,并估算其参数,可利用来进行雷达成像的运动补偿.