Open Networks of Queues with Blocking: Split and Merge Configurations:

Split and merge configurations of open networks of queues with blocking are analyzed approximately. The approximation procedure developed decomposes these queue networks into individual queues with revised queue capacity and revised arrival and service processes. These individual queues are then analyzed in isolation. The results obtained seem to have an acceptable error level. Stability conditions for these two configurations are also obtained.     

Blocking Probabilities for a Class of Two-Station Tandem Queueing Models

We study a two-station tandem queueing system with a finite buffer of maximum size M (M≥0) between the stations. The first service station has L≥1(homogeneous) parallel servers with an unlimited waiting space, while at the second there are N≥1 (homogeneous) parallel servers. Assuming Poisson arrivals and exponential service times, we derive exact results for the blocking probabilities for some special cases, and we present a unified approach for the analysis of this class of models under saturation conditions. Practical applications of the model are also discussed.     

A Closed Queueing Network Model for Multi-Echelon Repairable Item Provisioning

A model of a two-echelon (two levels of repair, one level of supply) repairable-item provisioning system is presented. It is desired to find the capacities of the base and depot repair facilities as well as the spares level which together guarantee a specified system service level at minimum cost. Closed queueing network theory is used to model the stochastic process, and an implicit enumeration algorithm is used to solve the optimization problem.     

一类Kelly-型排队网络的稳定性

排队网络可以用来模拟诸如通信网络这样的复杂系统。对排队网络的研究中的一个主要议题是建立其在某些特殊的规则下稳定的充要条件。本文的研究对象是一类具有两类顾客输入的Kelly-型排队网络。利用流体模型以及Lyapunov函数等工具,建立了该排队网络在所有非闲置的规则下稳定的充分条件。最后,对条件的充分性作了说明。     

基于排队论和数学规划的资源配置优化方法

为解决零件加工系统资源优化配置问题,提出一种计算方法.针对零件加工系统的特点,总结出串联、循环、选择3种基本结构.在零件加工时间服从指数分布的假设下,根据排队论求出零件在系统中平均排队时间.优化目标是零件在系统中平均排队时间最短.在资源数量约束下,依次让各工序资源数量增一,使零件在系统中平均排队时间减少最大的工序首先分配资源.在资金约束情况下,通过0-1规划方法,列出目标函数和约束方程并求解.最后通过一个实例说明如何综合利用这两种方法进行资源优化配置.     

普通顾客排队且排队顾客优先的混合排队问题?

为了解决通信信道资源管理中的网络优化问题,本文将普通的 M/M/n/N/∞排队模型推广为两类顾客到达的混合排队模型.其中共有有限个服务台和一个长度有限的等待区,一部分服务台为普通顾客和特殊顾客共用,剩余的服务台预留给特殊顾客使用,等待区专供普通顾客排队使用,排队顾客只接受共用的服务台的服务,两类顾客均为泊松到达.我们应用差分方程,得出了稳态时模型中各状态的概率分布.     

含裂纹功能梯度材料梁结构的振动功率流特性分析

功能梯度材料(FGM)梁在工程中应用日益广泛,而梁中裂纹的存在改变了局部刚度等特性,使得功能梯度材料梁的振动和波传播特性发生改变。以含有张开型裂纹的功能梯度梁为对象分析其波传播和振动功率流特性。利用转动弹簧模型模拟裂纹,给出由裂纹引起的局部柔度表达式。建立无限长FGM欧拉梁结构的动力学方程,采用波动法结合梁的连续条件计算得到FGM欧拉梁的振动特性,对无缺陷梁和裂纹梁的输入功率流和传播功率流进行分析。讨论了材料梯度指数、激励频率、裂纹深度和裂纹位置等信息与输入功率流、传播功率流之间的关系,为基于振动功率流的裂纹FGM梁的损伤识别提供理论基础。     

Fast Verification of Network Configuration Updates

With the expansion of network services, large-scale networks have progressively become common. The network status changes rapidly in response to customer needs and configuration changes, so network configuration changes are also very frequent. However, no matter what changes, the network must ensure the correct conditions, such as isolating tenants from each other or guaranteeing essential services. Once changes occur, it is necessary to verify the after-changed network. Whereas, for the verification of large-scale network configuration changes, many current verifiers show poor efficiency. In order to solve the problem of multiple global verifications caused by frequent updates of local configurations in large networks, we present a fast configuration updates verification tool, FastCUV, for distributed control planes. FastCUV aims to enhance the efficiency of distributed control plane verification for medium and large networks while ensuring correctness. This paper presents a method to determine the network range affected by the configuration change. We present a flow model and graph structure to facilitate the design of verification algorithms and speed up verification. Our scheme verifies the network area affected by obtaining the change of the Forwarding Information Base (FIB) before and after. FastCUV supports rich network attributes, meanwhile, has high efficiency and correctness performance. After experimental verification and result analysis, our method outperforms the state-of-the-art method to a certain extent.     

Novel Transmission Open Photoacoustic Cell Configuration for Thermal Diffusivity Measurements in Liquids

In this paper the photoacoustic technique in the thermal-wave transmission configuration is applied to thermal diffusivity measurements in liquids. The one-dimensional heat diffusion problem involving three layers, and assuming surface absorption only, is solved for this goal. Linear relations among the photoacoustic amplitude (on a semi-log scale) and phase, as functions of the liquid sample thickness, are shown in each case. An analytical procedure involving linear fits to the experimental data is developed to produce two independent values for thermal diffusivity. The thermal diffusivity of three homogeneous liquids (distilled water, ethylene-glycol, and olive oil) was measured, and excellent agreement was obtained between results from both the amplitude and phase, as well as with thermal-diffusivity values reported in the literature.     

Approximate critical Weber number for the breakup of an expanding torus

Summary. In this paper, an approximate critical Weber number for the breakup of an expanding torus (ring) is derived, under the assumption that Rayleigh instability dominates the breakup of a moving torus. The result is tentatively applied to predict the breakup condition of a droplet impinging on a hot wall once the droplet is transformed into an expanding torus. It is found that the critical Weber number is around 80 as observed experimentally.     

不同炮孔堵塞材料对矿山露天爆破效果的影响

通过矿山目前采用的单一材料堵塞的冲孔分析,利用控制变量法和对比分析法,定性地研究炮孔中应力和时间的变化规律,结合现场爆破试验,将炮孔堵塞分6种情况进行试验研究,最终得出:混合材料的炮孔堵塞相比单一材料的炮孔堵塞,具有抗剪强度高、炸药能量在炮孔中作用时间长和炸药做功能力增大等特点。现场混合材料堵塞能有效地降低冲孔现象的发生,提高炸药利用率和减少炮孔上部大块的产生。     

Configuration Analysis for Opticoacoustic Location Instruments

A model has been constructed for an opticoacoustic measurement system incorporating a four-microphone antenna. A numerical solution has been obtained for the best position of the fourth microphone. With set positions for the first three microphones, it has proved possible to define the region of unsound positions for the fourth detector.     

附有选择性服务与无等待能力的M/G/1排队系统稳定性分析

研究附有选择性服务与无等待能力的M/G/1排队系统。通过对描述其系统行为的偏微分方程组的规范化,将其转化为Banach空间中抽象的Cauchy问题。然后,利用强连续有界线性算子半群理论,证明了系统的非负稳定解恰是系统算子的0本征值对应的非负本征向量。同时通过研究系统算子的谱特征,证明了系统算子的谱点均位于复平面的左半平面且虚轴上除0外无谱,进而得到系统的渐近稳定性,特别在范数意义下系统的动态解收敛到稳态解。     

Approximate Torsional Analysis of Multi-layered Tubes with Non-circular Cross-Sections

In this paper an approximate formulation for torsional analysis of tubes with multi-layered non-circular cross-sections is presented. A previously presented method based on Bredt’s theory is extended to achieve these formulas. Layers are assumed to be isotropic and may possess different thicknesses and material properties. The obtained formulas for shear stress and angle of twist are applicable to thin to moderately thick closed cross-sections. It is shown that depending on the properties of the layers, maximum shear stress does not necessarily happen on the outer boundary. Furthermore, the effect of different cross-sectional shapes on torsional response is studied. Using the presented method, one can achieve desirable shear stresses and angles of twist for a polygonal multi-layered tube with a proper choice of bluntness. The method can be extended for torsion problem of FGM tubes as well. The presented formulas for torsion problem are relatively accurate and suitable to be implemented in optimization programs.     

Practical Reliability and Maintainability Analysis Tool for an Open Source Cloud Computing

We focus on a cloud computing environment by using open source softwares such as OpenStack and Eucalyptus because of the unification management of data and low cost. A cloud computing is attracting attention as a network service to share the computing resources, that is, networks, servers, storage, applications, and services. We propose jump diffusion models based on stochastic differential equations in order to consider the interesting aspect of the provisioning process. Especially, the reliability and maintainability analysis tool for cloud computing is developed in this paper. Also, we analyze actual data to show numerical illustrations of application of the software analysis tool considering the characteristics of cloud computing. Copyright © 2015 John Wiley & Sons, Ltd.     

Open Photoacoustic Cell Configuration Applied to the Thermal Characterization of Liquid CdS Nanocomposites

CdS nanofluids were prepared by the gamma-radiation method at different radiation doses. The samples were characterized by UV–Vis spectroscopy and transmission electron microscopy. The open cell photoacoustic technique was used to measure the thermal effusivity of the CdS nanocomposites. In this technique a He–Ne laser was used as the excitation source and was operated at 632.8 nm with an output power of 70 mW. The precision and accuracy of this technique were initially established by measuring the thermal effusivity of distilled water and ethylene glycol. The thermal-effusivity values of these two samples were found to be close to the values reported in the literature. The thermal effusivity of CdS nanofluids decreased from (0.453 to 0.268) $\mathrm {W}\cdot \mathrm {S}^{1/2}\cdot \mathrm {cm}^{-2}\cdot \mathrm {K}^{-1}$ with increased dosage of gamma radiation.     

马尔可夫网络排队模型在电梯配置中的应用

利用马尔可夫网络排队理论建立了电梯交通模型，在此基础上对各服务站的电梯配置交通进行计算，得到电梯的配置参数。通过与传统的电梯配置方法相比较，显示出明显的优越性，也表明了利用马尔可夫网络排队模型进行电梯配置的有效性和可行性。     

两类排队网络的逼近研究

本文给出了两类排队网络。一类是容量有限的队列网络,我们证明了在高负荷下,标准化的队长过程弱收敛于半鞅反射的布朗运动：另一类是带有反馈的多类顾客多服务台队列网络,我们获得了队列网络中负荷过程的扩散逼近。     

A Queueing Analysis of Conveyor-Serviced Production Station and the Optimal Range Strategy

This paper proposes, analyzes and develops a policy for unloading material to be processed from conveyors in the case of not only Poisson arrival but also non-Poisson arrival and general service. The operating policy, 'state-dependent and sequential range policy,' for the conveyor-serviced production station (CSPS) is shown to be superior to previously developed policies, and a condition of the optimal range strategy that minimizes the expected delay-time per unit produced is discussed. A practical range strategy is also proposed, and its superiority which reduces both the mean number of units in the reserve and the negative expected reward is numerically ascertained. These results also would be useful in the study of designing and controlling the behavior of other queueing systems with lost units.