纳米尺度下Si/Ge界面应力释放机制的分子动力学研究

采用分子动力学方法研究了纳米尺度下硅(Si)基锗(Ge)结构的Si/Ge界面应力分布特征,以及点缺陷层在应力释放过程中的作用机制.结果表明:在纳米尺度下, Si/Ge界面应力分布曲线与Ge尺寸密切相关,界面应力下降速度与Ge尺寸存在近似的线性递减关系;同时,在Si/Ge界面处增加一个富含空位缺陷的缓冲层,可显著改变Si/Ge界面应力分布,在此基础上对比分析了点缺陷在纯Ge结构内部引起应力变化与缺陷密度的关系,缺陷层的引入和缺陷密度的增加可加速界面应力的释放.参考对Si/Ge界面结构的研究结果,可在Si基纯Ge薄膜生长过程中引入缺陷层,并对其结构进行设计,降低界面应力水平,进而降低界面处产生位错缺陷的概率,提高Si基Ge薄膜质量,这一思想在研究报道的Si基Ge膜低温缓冲层生长方法中初步得到了证实.     

适用于ppb量级NO_2检测的低功率蓝光二极管光声技术研究

在405 nm处基于低功率蓝光二极管光声技术探测ppb量级NO_2浓度系统,获取了NO_2有效吸收截面,探讨了水蒸气等气体的测量干扰,通过频率扫描拟合得到了1.35 kHz的谐振频率.采用内部抛光的铝制圆柱空腔作为光声谐振腔(内径为8 mm,长为120 mm),系统优化了腔体、窗片和电源等影响因素,分析了降低本底噪声、提高信噪比的方法,噪声信号可降至0.02μV.设计了两级缓冲结构,显著抑制了流量噪声的影响,提高了系统的稳定性.系统的标定梯度曲线经过线性拟合后的斜率为0.016μV/ppb, R~2为0.998,在60 s平均时间下,系统NO_2探测限为3.67 ppb(3σ).为了证实系统的测量结果,将其与二极管激光腔衰荡光谱系统同步对比测量大气NO_2浓度,二者线性拟合后的斜率为0.94±0.009,截距为1.89±0.18,相关系数为0.87,一致性较好.实验结果表明,该系统实现了ppb量级NO_2浓度的低成本在线探测,可用于NO_2浓度外场的实时检测.     

A Gaussian fluid model

A fluid model with infinite buffer is considered. The total net rate is a stationary Gaussian process with mean –c and covariance functionR(t). Let (x) be the probability that in steady state conditions the buffer content exceedsx. Under the condition ₀ t ² ¦R(t)¦dt< we show that admits a logarithmic linear upper bound, i.e. (x)Cexp[–x]+o(exp[–x]) and find and C. Special cases are worked out whenR is as in a Gauss-Markov or AR-Gaussian process.     

Approximate analysis of unreliable transfer lines with splits in the flow of material

This paper presents a Markov process model and an approximate decomposition technique for a discrete material transfer line with limited buffer capacity. A fraction of the parts processed at some stations in the line may be scrapped or reworked at dedicated machines to meet product quality requirements. Reworked parts are not sent back into the main line. This leads to splits in the flow of material. Processing times are deterministic and identical for all machines and are taken as the time unit. Machine specific times to failure and to repair are geometrically distributed. The model is analyzed through a decomposition into twomachine systems. We develop new decomposition equations for machines performing split operations. Production rates and inventory levels are computed and compared to simulation results. The results indicate that the method produces useful results for a variety of systems.     

基于工期-成本综合效用最大的关键链项目缓冲确定

为提高关键链中工期和成本的综合效用,研究一种基于关键链工期和成本进行双目标优化的缓冲确定方法。首先,该方法考虑项目不同工序间工期和成本之间的关系,并基于工期和成本的风险暴露度确定权重,解决不同工序间工期和成本偏好难以量化的问题;其次,根据权重多效用函数对工期和成本进行归一化处理,并确定综合效用最大情况下不同工序的最佳工期;最后基于尾部集中法确定项目缓冲。通过蒙特卡洛模拟实验,将此方法提取缓冲后的项目实际综合效用与传统方法进行比较。比较结果显示,该方法极大地提高项目中工期和成本的综合效用,并且对项目工期和成本均形成更有效的保护。     

Analyzing the finite buffer batch arrival queue under Markovian service process: GIX/MSP/1/N

We consider a batch arrival finite buffer single server queue with inter-batch arrival times are generally distributed and arrivals occur in batches of random size. The service process is correlated and its structure is presented through Markovian service process (MSP). The model is analyzed for two possible customer rejection strategies: partial batch rejection and total batch rejection policy. We obtain steady-state distribution at pre-arrival and arbitrary epochs along with some important performance measures, like probabilities of blocking the first, an arbitrary, and the last customer of a batch, average number of customers in the system, and the mean waiting times in the system. Some numerical results have been presented graphically to show the effect of model parameters on the performance measures. The model has potential application in the area of computer networks, telecommunication systems, manufacturing system design, etc.      

USB数据传输中缓冲结构的硬件实现

嵌入式系统中采用USB接口与外界进行数据交换,为了提高系统处理数据的效率和性能,本文针对USB接口数据传输的缓冲结构进行探讨,根据USB数据传输的特点,提出基于单一存储的缓冲结构,实现USB模块与系统的无缝衔接,同时节省了系统资源.该方案通过FPGA平台实现,验证了其在嵌入式系统数据传输中是有效可行的.     

考虑中间库存缓冲区的多目标设备不完美预防维修策略研究

针对考虑库存缓冲区的多目标设备维修问题,以设备维修能力为约束条件,获得随机故障设备的不完美预防维修策略。首先,利用准更新过程,表示出设备的随机故障次数。其次,结合设备故障次数表达式,以最大设备可用度和最小生产总成本为多目标构建不完美预防维修模型,使用粒子群算法求解,优化设备可用度与生产总成本,获得更新周期内的库存量和预防维修周期两个决策变量的最优值。最后,通过算例分析,验证了多目标不完美预防维修模型的可用性。     

带有时滞中性技术进步资产投资系统的积累率的辨识

对一类带有时滞的中性技术进步的资产投资系统,运用积分方程和泛函分析理论,讨论了此非线性资产投资系统的积累率的辨识问题.利用Banach空间理论,得到了辨识问题解的存在唯一性.