Capillary jet instability under the influence of gravity

The focus of this paper is on the effect of gravity stretching on disturbed capillary jet instability. Break-up and droplet formation under low flows are simulated using finite difference solution of a one-dimensional approximation of disturbed capillary jet instability chosen from the work by Eggers and Dupont (J. Fluid Mech. 155 (1994) 289). Experiments were conducted using water and aqueous glycerol solutions to compare with simulations. We use a gravity parameter, G, which quantifies gravity stretching by relating flow velocity, orifice size and acceleration and is the reciprocal of the Froude number. The optimum disturbance frequency was found to be inversely proportional to G. However, this relationship appears to be complex for the range of G's investigated. At low G, the relationship between and G appears to be linear but takes on a weakly decaying like trend as G increases. As flows are lowered, the satellite-free regime decreases, although experimental observation found that merging of main and satellite drops sometimes offset this effect to result in monodispersed droplet trains post break-up. Viscosity did not significantly affect the relationship between the disturbance frequency and G, although satellite drops could be seen more clearly close to the upper limit for instability at high G's. It is possible to define regimes of satellite formation under low flows by considering local wavenumbers at the point of instability.     

新的嵌套排样算法

以多边形定点算法原理为基础，得出了新的嵌套求解算法成功解决了优化排样问题。并以C语言程序设计为基础，使算法在计算机上得以实现。     

多齿差摆线齿轮泵基本参数的优化设计

多齿差摆线齿轮泵基本参数的选择要满足各种限制条件。本文以单位体积排量最大作为目标函数，以啮合角、重合度及齿廓不产生重迭干涉等为约束条件，建立了多齿差摆线齿轮泵的优化设计数学模型，并对两种常用齿数组的多齿差摆线齿轮泵基本参数进行了优化设计。所得结果可以和不同的齿数与中心距进行组合应用，得到不同流量的产品系列。。     

模糊综合评判在级进模工序排样中的应用

通过分析级进模工序排样设计中的模糊性准则，利用模糊综合评判理论建立了对排样方案进行优化数学模型，并通过了事例验证。     

Determination of the optimum conditions for ion nitriding of AISI 5140 steel

AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N₂/H₂). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi design of experiment. After ion nitriding process, it is aimed to maximize fatigue strength, surface hardness and case depth as well as to minimize compound layer thickness. While the optimum conditions were determined, due to the goals (above aims) more than one being, the trade-off among goals was considered. First of all, each goal was optimised, separately. Then, all the goals were optimised together, considering the priority of the goals, and the optimum results were obtained at 0.05 N₂/H₂ gas mixture ratio, at the temperature of 450 °C and for 12 h process time.     

钛合金等温锻造进展

等温锻造是一种先进的加工工艺。本文从钛合金高温变形特性、等温锻造参数选择、模具设计、润滑剂摩擦特性等诸方面全面地介绍了这种先进的锻造工艺，它的应用前景及发展方向。     

Computation of optimum reliability acceptance sampling plans in presence of hybrid censoring

The decision regarding acceptance or rejection of a lot of products may be considered through variables acceptance sampling plans based on suitable quality characteristics. A variables sampling plan to determine the acceptability of a lot of products based on the lifetime of the products is called reliability acceptance sampling plan (RASP). This work considers the determination of optimum RASP under cost constraint in the framework of hybrid censoring. Weibull lifetime models are considered for illustrations; however, the proposed methodology can be easily extended to any location-scale family of distributions. The proposed method is based on asymptotic results of the estimators of parameters of lifetime distribution. Hence, a Monte Carlo simulation study is conducted in order to show that the sampling plans meet the specified risks for finite sample size.     

电液负载模拟器的二次型最优控制算法

电液负载模拟器属于被动式加载系统,受载对象的自主运动和加载装置的运动相互耦合,所产生的位置扰动会引起多余力。为抑制多余力建立了电液负载模拟器的状态空间模型,利用线性二次型最优控制理论设计了最优控制算法,算法具有最优状态反馈、最优前馈补偿和外扰补偿,使得电液负载模拟器的性能有明显提高。电液负载模拟器的仿真计算结果表明,利用最优控制算法设计的电液负载模拟器较好地抑制了多余力,从而较好地跟踪力指令。     

基于OPNET的EPON自适应双时序算法研究与仿真

EPON上行业务的QoS保证是实际应用中的关键问题。通过提出一种新颖的双时序自适应动态算法,既保证EF高优先级业务,又支持突发大的BE数据业务,有效控制轻负载恶化现象,能最大极限的提高EPON网络效率。采用OPNET仿真模型验证了算法的可行性和改进性能。     

A constant-time dynamic storage allocator for real-time systems

Dynamic memory allocation has been used for decades. However, it has seldom been used in real-time systems since the worst case of spatial and temporal requirements for allocation and deallocation operations is either unbounded or bounded but with a very large bound. In this paper, a new allocator called TLSF (Two Level Segregated Fit) is presented. TLSF is designed and implemented to accommodate real-time constraints. The proposed allocator exhibits time-bounded behaviour, O(1), and maintains a very good execution time. This paper describes in detail the data structures and functions provided by TLSF. We also compare TLSF with a representative set of allocators regarding their temporal cost and fragmentation. Although the paper is mainly focused on timing analysis, a brief study and comparative analysis of fragmentation incurred by the allocators has been also included in order to provide a global view of the behaviour of the allocators. The temporal and spatial results showed that TLSF is also a fast allocator and produces a fragmentation close to that caused by the best existing allocators.