一类具有可变输入率的M/M/1排队模型

讨论了到达的顾客以概率αk=(1)/(βk+1)进入M/M/1排队系统的可变输入率模型,获得了该模型的平稳分布和顾客的平均输入率, 系统的平均服务强度, 平均等待队长, 系统的平均队长, 系统的损失概率, 顾客进入系统并接受服务的概率,单位时间内平均进入系统的顾客数, 单位时间内平均损失的顾客数等相关指标,从而推广了文献[1]中的结果.     

Effects of welding wire composition and welding process on the weld metal toughness of submerged arc welded pipeline steel

The effects of alloying elements in welding wires and submerged arc welding process on the microstructures and low-temperature impact toughness of weld metals have been investigated. The results indicate that the optimal contents of alloying elements in welding wires can improve the low-temperature impact toughness of weld metals because the proeutectoid ferrite and bainite formations can be suppressed, and the fraction of acicular ferrite increases. However, the contents of alloying elements need to vary along with the welding heat input. With the increase in welding heat input, the contents of alloying elements in welding wires need to be increased accordingly. The microstructures mainly consisting of acicular ferrite can be obtained in weld metals after four-wire submerged arc welding using the wires with a low carbon content and appropriate contents of Mn, Mo, Ti-B, Cu, Ni, and RE, resulting in the high low-temperature impact toughness of weld metals.     

一类四阶变系数线性微分方程系数常数化定理及应用

给出了一类四阶变系数线性微分方程化为四阶常系数线性微分方程的定理,并在具体的例子中加以实现．     

一类时滞随机分布系统的跟踪控制

针对一类具有输入时滞的非高斯随机分布系统,提出了基于广义PI控制器的跟踪控制方法.首先采用B样条模型和非线性权模型来建立概率密度函数和控制输入之间的关系,从而将概率密度函数的跟踪问题转化成动态权值的跟踪问题.然后基于线性矩阵不等式技术设计PI控制器,给出了时滞随机分布系统稳定的充分条件,并保证了良好的跟踪性能.最后仿真结果说明了方法的有效性.     

技术进步、产出变动、要素投入改变与价值变动的关系

以马克思《资本论》中的价值构成公式为基础,将函数分析法与价值理论相结合,通过数学推导证明马克思在《资本论》相关章节中关于劳动生产率、产出、要素投入以及生活水平等因素变化时,价值总量、单位产出价值量和劳动力价值以及剩余价值的变动情况的论述的科学性,并进行了拓展,进一步分析了要素投入变化和生活水平变化时价值量的变动情况。     

具有输入量化的信息物理系统的安全控制

针对执行器攻击、量化编码器/解码器参数不匹配和外部干扰的信息物理系统(cyber-physical systems, CPS),设计一种新型的鲁棒自适应控制器确保其安全稳定运行。基于Lyapunov稳定理论推导出使信息物理系统具有鲁棒H2性能的充分条件,控制器的非线性结构包含两部分：一部分为干扰和量化补偿器,用于消除外部干扰和量化误差的影响,另一部分为基于隐蔽式假数据攻击上界信息的攻击补偿器,用于抑制异常检测器检测不到、未触发警报的攻击。最后,仿真算例结果表明控制器能保证闭环系统稳定并且具有较好的系统性能,说明了方法的有效性。     

液黏离合器摩擦副对流换热系数数值模拟研究

为了预测液黏离合器的温度场分布及热负荷特性,通过数值模拟研究求得摩擦副散热面的对流换热系数。应用计算流体动力学软件CFX建立了摩擦副流固耦合有限元模型,获得了摩擦副的温度场分布,综合考虑换热表面形状、摩擦片转速、油液流速和入口压力、流体物理性质等因素,揭示了各因素与对流换热系数之间的内在联系。结果表明：摩擦副温度从内径到外径逐渐升高,菱形区域中心温度比四周高。摩擦片转速越大对流换热系数越大;油液黏度越小,入口压力越大,对流换热系数越大。可见,油液流速对换热系数的影响最为显著;摩擦片转速、油液的入口压力和黏度会改变流速及流体的运动状态,从而影响对流换热系数。     

Hybrid pilots assisted channel estimation algorithm for MIMO-OFDM systems

Abstract: A hybrid pilots assisted channel estimation algorithm for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems under low signal-to-noise ratio (SNR) and arbitrary Doppler spread scenarios is proposed. Motivated by the dissatisfactory performance of the optimal pilots (OPs) designed under static channels over multiple OFDM symbols imposed by fast fading channels, the proposed scheme first assumes that the virtual pilot tones superimposed at data locations over specific subcarriers are transmitted from all antennas, then the virtual received pilot signals at the corresponding locations can be obtained by making full use of the time and frequency domain correlations of the frequency responses of the time varying dispersive fading channels and the received signals at pilot subcarriers, finally the channel parameters are derived from the combination of the real and virtual received pilot signals over one OFDM symbol based on least square (LS) criterion. Simulation results illustrate that the proposed method is insensitive to Doppler spread and can effectively ameliorate the mean square error (MSE) floor inherent to the previous method, meanwhile its performance outmatches that of OPs at low SNR region under static channels.     

颗粒增强铝基复合材料在汽车制动盘上的应用

通过制动台架试验,研究了颗粒增强铝基复合材料制动盘在各种工况下的摩擦性能,发现此类制动盘摩擦系数稳定、制动噪音小、制动温升低、质轻,说明颗粒增强铝基复合材料是一种比较理想的制动材料。     

具输入饱和因子的滞后广义系统的鲁棒镇定

利用Lyapunov方法研究了具输入饱和因子的滞后广义系统,给出了其镇定控制器的设计方法,并对具有不确定的滞后广义系统设计了控制,保证其闭环系统渐近稳定,给出了一个数值实例。