A mechanism leakage model of metal-bipolar-plate PEMFC seal structures with stress relaxation effects

This work addresses the issues of long-term leakage rate prediction, which is crucial for durability study of proton exchange membrane fuel cells (PEMFCs). A theoretical model is presented for the leakage rate of compressive seal structures in PEMFCs, based on the combination of three numerical techniques, namely Lattice-Boltzmann method (LBM) simulations for rough wall interfacial gaps, a numerical 3D rough-surface generation technique, and Finite-Element-Analysis (FEA) for micro-contact mechanics of single asperity. The model clearly reveals the quantitative influence of various factors on the leakage rate without any empirical regression coefficients, and therefore can be easily integrated with structural mechanics and aging mechanism analyses. Long term sealing performance comparisons with three types of rubber material identify liquid silicone rubber to have the optimal durability. When influences of water environment are taken into account, an accelerated degradation of sealing performance can be observed after approximately 3000 h of operation. In addition, the effect of stress loss on leakage rate can be effectively suppressed by reducing surface roughness, reducing gasket thickness and increasing strain level. The proposed theoretical model provides an effective approach for the design of metal-bipolar-plate PEMFCs seal structures.     

Annealing temperature-dependent structural and electrical properties of (Ta2O5)1-x - (TiO2)x thin films,x ≤ 0.11

(Ta₂O₅)_1-x- (TiO₂)_x (TTO_x) thin films, with x = 0, 0.03, 0.06, 0.08, and 0.11, were deposited using magnetron direct current (DC) sputtering method onto the P/boron-silicon (1 0 0) substrates by varying areas of Tantalum and Titanium metallic targets, in oxygen environment at ambient temperature. The as-deposited thin films were annealed at temperatures ranging from 500 to 800 °C. Generally, the formation of the Ta₂O₅ structure was observed from the X-ray diffraction measurements of the annealed films. The capacitance of prepared metal– oxide– semiconductor (MOS) structures of Ag/TTO_x/p-Si was measured at 1 MHz. The dielectric constant of the deposited films was observed altering with varying composition and annealing temperature, showing the highest value 71, at 1 MHz, for the TTO_x films, x = 0.06, annealed at 700 °C. With increasing annealing temperature, from 700 to 800 °C, the leakage current density was observed, generally decreasing, from 10^?5 to 10^?8 A cm^?2, for the prepared compositions. Among the prepared compositions, films with x = 0.06, annealed at 800 °C, having the observed value of dielectric constant 48, at 1 MHz; and the leakage current density 2.7 × 10^?8 A cm^?2, at the electric field of 3.5 × 10⁵ V cm^?1, show preferred potential as a dielectric for high-density silicon memory devices.     

A nature-inspired firefly algorithm based approach for nanoscale leakage optimal RTL structure

Optimization of leakage power is essential for nanoscale CMOS (nano-CMOS) technology based integrated circuits for numerous reasons, including improving battery life of the system in which they are used as well as enhancing reliability. Leakage optimization at an early stage of the design cycle such as the register-transfer level (RTL) or architectural level provides more degrees of freedom to design engineers and ensures that the design is optimized at higher levels before proceeding to the next and more detailed phases of the design cycle. In this paper, an RTL optimization approach is presented that targets leakage-power optimization while performing simultaneous scheduling, allocation and binding. The optimization approach uses a nature-inspired firefly algorithm so that large digital integrated circuits can be effectively handled without convergence issues. The firefly algorithm optimizes the cost of leakage delay product (LDP) under various resource constraints. As a specific example, gate-oxide leakage is optimized using a 45 nm CMOS dual-oxide based pre-characterized datapath library. Experimental results over various architectural level benchmark integrated circuits show that average leakage optimization of 90% can be obtained. For a comparative perspective, an integer linear programming (ILP) based algorithm is also presented and it is observed that the firefly algorithm is as accurate as ILP while converging much faster. To the best of the authors׳ knowledge, this is the first ever paper that applies firefly based algorithms for RTL optimization.     

化工厂减速器频繁损坏的故障分析和处理

针对减速器运行时出现的润滑油泄漏、异响等故障,详细地分析了故障原因,并提出了相应的解决方案和改进措施。     

天然气输气管道泄漏因素分析

"十五"期间是我国经济建设持续发展的重要阶段。天然气作为清洁的新兴能源,在我国将得到快速发展,只有避免天然气管道泄漏,加强管理,保障管网的安全和稳定供气,才能对我国天然气产业链的供应安全建设提供强有力的支持。     

事故树分析法在油气输送管道泄漏事故中的应用

泄漏是油气管道输送过程中常见的典型事故,更是引起其他重大后果的主要原因。运用事故树分析法对油气输送管道的泄漏问题进行了侧重性分析,重点探讨了其发生影响模式,得出材料的耐腐蚀性为主要因素,并由此提出了针对性的对策措施,为更好地实施油气输送管道的安全运行提供了更加全面的理论和数据支持。     

浅谈房屋建筑工程常见渗漏的监控

本文通过对房屋建筑工程常见渗漏现象的原因分析,提出在地下室、外墙、门窗、屋面、厨房及卫生间施工中应采取的监控措施,从而有效地预防和控制渗漏现象的产生。     

Economic Optimization of Distribution Leakage Control

E vry WATER DISTRIBUTION system has an economic optimum level of leakage. To maintain that optimum level of leakage there is a corresponding optimum level of leakage control activity.
Despite much work on this subject, particularly in recent years with publication of DoE Report No. 26¹, many undertakers remain unclear about their economic optimum leakage level and how much effort is required to maintain that level.
This paper describes development of an economic model which attempts to quantify optimum leakage through measurement of parameters which should be readily available or obtainable.
The model was originally developed specifically for routine sounding. However, extension of the basic principles allows development of a general optimization theory. The paper then shows how the theory can be applied to optimization of district metering