基于伍德沃德-劳森抽样方法的阵列平顶波束综合

为获得高增益和强方向性,阵列天线应运而生,波束赋形技术在降低阵列副瓣电平、扩大阵列角度覆盖范围、抑制干扰等方面具有重要意义。其中,具有平顶形状波束的天线可辐射具有相同增益的波束,实现宽角度覆盖,且伍德沃德-劳森抽样具有方法简单、抽样点少、运算速度快的优势。因此,运用伍德沃德-劳森抽样方法对均匀直线阵列进行平顶波束赋形。通过计算抽样点数和抽样点位置,得到激励系数,确定阵元位置,计算出激励电流,从而求得各单元的电流分布,计算出阵列的方向图函数,利用MATLAB编程绘制方向图,并分析其基本特性,同时用控制变量法分析不同参数变化对方向图基本特性的影响。研究结果表明：综合的线阵单元数越多,抽样点就越多,综合得到的方向图就越接近预期,综合后方向图主瓣范围内的波纹起伏越小,副瓣电平越低。此外,定向辐射的平顶波束赋形天线在点对多点的无线通信中发挥着重要作用,也可以应用在车载和机载防撞天线、自动驾驶和飞行器等安全控制中心的核心组件中,市场前景广阔。     

MetaOJ: A Massive Distributed Online Judge System

Online Judge(OJ) systems are a basic and important component of computer education. Here, we present MetaOJ, an OJ system that can be used for holding massive programming tests online. MetaOJ is designed to create a distributed, fault-tolerant, and easy-to-scale OJ system from an existing ordinary OJ system by adding several interfaces into it and creating multiple instances of it. Our case on modifying the TUOJ system shows that the modification adds no more than 3% lines of code and the performance loss on a single OJ instance is no more than 12%. We also introduce mechanisms to integrate the system with cloud infrastructure to automate the deployment process. MetaOJ provides a solution for those OJ systems that are designed for a specific programming contest and are now facing performance bottlenecks.     

2D perovskites for field-effect transistors

Metal halide perovskites have gained a lot of attention in the field of solar cells and light-emitting diodes because of their excellent optoelectronic properti...     

Strong Law of Large Numbers for Weighted Sums of Random Variables and Its Applications in EV Regression Models

This paper mainly studies the strong convergence properties for weighted sums of extended negatively dependent(END, for short) random variables. Some sufficient conditions to prove the strong law of large numbers for weighted sums of END random variables are provided. In particular, the authors obtain the weighted version of Kolmogorov type strong law of large numbers for END random variables as a product. The results that the authors obtained generalize the corresponding ones for independent ra...     

Solving Multivariate Polynomial Matrix Diophantine Equations with Gr?bner Basis Method

Different from previous viewpoints, multivariate polynomial matrix Diophantine equations are studied from the perspective of modules in this paper, that is, regarding the columns of matrices as elements in modules. A necessary and sufficient condition of the existence for the solution of equations is derived. Using powerful features and theoretical foundation of Gr?bner bases for modules, the problem for determining and computing the solution of matrix Diophantine equations can be solved. Meanwh...     

Adaptive Asymptotic Tracking Control for Stochastic Nonlinear Systems with Unknown Backlash-Like Hysteresis

In this study, an adaptive asymptotic tracking control problem is considered for stochastic nonlinear systems with unknown backlash-like hysteresis. By utilizing backstepping technology and bound estimation approach, an adaptive asymptotic tracking control scheme is designed, where fuzzy systems are applied to approximate unknown function terms, the effect of hysteresis and stochastic disturbances is compensated appropriately. The proposed scheme ensures that the tracking error can asymptoticall...     

温度对CaO2强化剩余污泥厌氧水解，酸化的影响

本文探究了温度对CaO_2强化剩余污泥厌氧水解,酸化的影响。实验结果表明在15~35℃,随着温度的升高,污泥厌氧反应体系中水解和酸化得到加强,且VFA和甲烷的最大积累量分别为3 120 mg/L和196 m L。当温度进一步提高至55℃时,水解反应得到强化,但是过高的温度限制了厌氧微生物对溶解性蛋白质和多糖的利用,进而导致VFA的积累量较少。因此35℃是CaO_2强化剩余污泥水解和酸化的最佳温度。     

连续生产综合自动化系统功能集成的可拓控制模型

在分析ＣＩＰＳ各级的相似性的基础上,认为ＣＩＰＳ的每一层级都可以看成一个广义的信息控制系统,都具有构成控制系统的三个要素：信息、控制作用和对象。在此基础上,结合系统的矛盾性和可拓控制理论,提出了连续生产过程综合自动化系统功能集成的可拓控制模型。     

沥青路面的逆向设计及其试验研究

鉴于传统路面设计及评价方法的局限性,基于逆向工程技术思想,提出沥青路面的逆向设计方法,并给出了相应的设计流程.在充分掌握原路面特征的基础上,具体介绍了材料准备、芯样扫描分析、路面重塑的整个过程,并利用独立开发的新型路面材料加速加载试验系统进行磨耗试验,测定重塑路面抗滑性能的变化.然后,引入相似理论,通过比较发现重塑路面各项指标与原路面相似度较高,从而证明了该设计方法的可行性、合理性和可靠性.路面养护处治后,抗滑性能的熵值增大,说明表面处治将使系统内部子系统功能更加趋于一致,整体结构更加稳定.     

基于G/G/1排队模型的802.11 DCF延迟分析

针对现有802.11 DCF分析模型在进行退避机制分析时不考虑周围节点状态的不足,提出了一种非饱和情况下IEEE 802.11 DCF协议的性能分析方法,推导出了以802.11 DCF为媒体访问控制(MAC)层协议的单跳无线网络中,MAC层的分组延迟及其抖动表达式,并分析了不同分组到达速率、节点数和退避窗口大小对MAC层分组冲突概率、延迟及其抖动的影响.仿真结果表明:MAC层的分组冲突概率、延迟及其抖动随着分组到达速率、节点数的增加而增加;以冲突概率的增加为代价,减小最小退避窗口可以减小MAC层的分组延迟及其抖动.