Optimal Design of a Stable Trapezoidal Channel Section Using Hybrid Optimization Techniques

A cost effective channel section for a specified flow rate, roughness coefficients, longitudinal slope, and various cost parameters can be determined using an optimization technique. However, the derived optimal channel section may not be feasible for construction because of in situ conditions. The local soil conditions may not support the optimal side slope of the channel and if constructed, the slope may fail. It is therefore necessary to also incorporate the criteria for side slope stability in designing an optimal open channel section. In this paper, a new methodology has been developed to design a stable and optimal channel section using hybrid optimization techniques. A genetic algorithm based optimization model is developed initially to determine the factor of safety of a channel slope for given soil parameters. This optimization model is then externally linked with a separate sequential quadratic programming based optimization model to evaluate the parameters of the stable and optimal channel section. Solution for various example problems incorporating different soil parameters are illustrated to demonstrate the applicability of the developed methodology.     

Two-phase flow instability in a parallel multichannel system

The two-phase flow instabilities observed in through parallel multichannel can be classified into three types, of which only one is intrinsic to parallel multichannel systems. The intrinsic instabilities observed in parallel multichannel system have been studied experimentally. The stable boundary of the flow in such a parallel-channel system are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling. The results show that parallel multichannel system possess a characteristic oscillation that is quite independent of the magnitude and duration of the initial disturbance, and the stable boundary is influenced by the characteristic frequency of the system as well as by the exit quality when this is low, and upon raising the exit quality and reducing the characteristic frequency, the system increases its instability, and entrance throttling effectively contributes to stabilization of the system.     

石油稳定同位素地球化学新进展

本文简述了我国氢、碳、氧稳定同位素标准物质的研究情况和有机质稳定同位素分析技术的进展,总结了我国有机氢、碳稳定同位素研究中的一些重要方面。煤和干酪根碳同位素组成的变化主要是与其类型和沉积环境有关,而与其热演化阶段无关。根据氯仿A、原油及其族组分碳同位素相似性进行油源对比是一种好方法。应用天然气组分的氢、碳同位素能有效地判识天然气的成因类型、成熟度和进行油气源岩对比。应用碳同位素数据还能判识地表油气化探烃气异常的成因和来源,但在实际应用时要注意气态烃可能遭受生物降解作用碳同位素分馏的影响。     

能带混合量子阱的触发功能和异质谷间转移电子放大器件的研究

运用MonteCarlo理论模拟、二极管除穿伏安特性、器件振荡性能和射频输入信号激励下的放大功能研究了异质谷间转移电子器件中能带混合量子阱的触发功能。理论和实验研究发现，当能带混合量子讲中没有产生足够的异质谷间转移电子效应时，即使有源层中加有足够的电场仍然不能产生振荡。异质谷间转移电子效应成为器件进行射频工作的必要条件。在适当设计的器件中，运用输入射频信号也能激励异质谷间转移电子效应而触发输出放大信号。应用这一原理研制成8mm波段工作的稳态放大器，解决了二极管稳态放大器中的自激振荡问题。最后讨论了利用能带混合量子讲的触发功能来制作新的三端器件和各类功能器件的可能性。     

开关电容DC－DC变换器的分析

本文提出等效电量关系法，并采用这一新的方法对众多的开关电容ＤＣ－ＤＣ变换器进行了统一分析，避免了求解复杂的状态方程的繁琐过程，且简化了分析．     

红外/毫米波多模寻的系统关键技术分析

概述了红外／毫米波多模寻的系统的主要技术特点,对多谱段头罩的选材,外形与厚度的设计进行了计算与理论分析;探讨了适宜于多模导引头的多种类型稳定位标器和复合天线系统系统方案;重点对外／毫米波融合处理器系统进行了研究,针对红外,毫米波探测系统的输出信息,确定了多模寻的系统的融合层次与融合准则。     

Balancing CapEx reduction and network stability with stable routing–virtual topology capacity adjustment (SR–VTCA)

This paper investigates the merits of the SR–VTCA (stable routing–virtual topology capacity adjustment) approach as a mechanism to find a beneficial trade-off between network stability and reduction in capital expenditures (CapEx). These are two main objectives for the entities that own the optical infrastructure, such as network operators (NOs), and those also acting as Internet service providers (ISPs). The SR–VTCA scheme is a novel approach to adapt transparent optical networks to time-varying traffic by adjusting the number of lightpaths between node pairs, while keeping the IP routing unchanged. Lightpath bundling (LB) and anycast (AS) switching are combined in SR–VTCA operation to advertise lightpath additions/removals to the IP layer as mere adjustments (increments or decrements) in the capacity, allowing to keep the IP routing stable, and thus, simplifying control plane operations. On the contrary, a fully-reconfigurable (FR) network design, where IP routing can be also modified, would increase the burden in the control plane, but at a higher CapEx reduction, since the optical infrastructure is used more efficiently. In this work, we investigate the CapEx overprovision introduced by SR–VTCA with respect to a FR scheme. In order to do this, SR–VTCA planning problem is first modeled as a MILP formulation. A heuristic procedure based on traffic domination is then proposed to solve large instances of the problem. Exhaustive experiments are conducted comparing the SR–VTCA solutions obtained by the aforementioned MILP and heuristic proposal with solutions found by other optimization methods presented in the literature to solve the FR planning problem. Finally, the results show that SR–VTCA can achieve similar results to the FR case in terms of CapEx reduction, while a huge number of IP reroutings are saved by maintaining IP stability. Thus, SR–VTCA provides an advantageous balance between CapEx overprovisioning and the control plane overhead associated with IP rerouting.     

Evaluation of R-curve behavior of ceramic-metal functionally graded materials by stable crack growth

This paper deals with the fracture toughness and R-curve behavior of ceramic-metal functionally graded materials (FGMs). A possibility of stable crack growth in a three-point-bending specimen is examined based on the driving force and resistance for crack growth in FGMs, and the distribution of fracture toughness or R-curve behavior is evaluated on FGMs fabricated by powder metallurgy using partially stabilized zirconia (PSZ) and stainless steel (SUS 304). The materials have a functionally graded surface layer (FGM layer) with a thickness of 1 mm or 2 mm on a SUS 304 substrate. Three-point-bending tests are carried out on a rectangular specimen with a very short crack in the ceramics surface. On the three-point-bending test, a crack is initiated from a short pre-crack in unstable manner, and then it propagates in stable manner through the FGM layer with an increase in the applied load. From the relationship between applied load and crack length during the stable crack growth in the FGM layer, the fracture toughness is evaluated. The fracture toughness increases with an increase in a volume fraction of SUS 304 phase.     

Synthesis of high-energy-density Pr2Fe14−x Co x B,x⩽3, magnets for practical applications

Stable magnetic powders, of 1–2μm particle size, of partially Co-substituted, Pr₂Fe_14−x Co _x B,x⩽3, alloys together with 2–4 at% excess Pr were prepared by rapidly quenching the associated melts into thin ribbons and then mechanical attriting the ribbons in the refined particle sizes. The saturation magnetizationM _s, remanent magnetizationJ _r, intrinsic coercivityH _ci and Curie temperatureT _c were studied in characterizing the powders for fabricating into sintered or polymer bonded magnets. It is found that the smallx=0·4–0·8 substitution of the Co on Fe sites in this series sensitively leads to an increase in the value ofH _ci, by as much as 40%, with the optimum value of 21 kOe atx ∼ 0·55, together with an improvement in theT _c from 292°C to 325°C, without significantly diluting theM _s∼150 emu/g andJ _r∼8·0 kG values. The Co-substituted Pr₂Fe₁₄B alloy particles are better stable and corrosion resistant in ambient atmosphere. The results are discussed with the microstructure and comparison with the data for Nd₂Fe₁₄B powders processed under the same conditions. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995