Sensitivity and uncertainty analyses for ignition of fiber‐reinforced polymer panels

The ignition characteristics of combustible solids are affected by many factors such as material properties, external heating source, and surrounding environmental conditions. In practice, these factors can vary significantly from one application to another. Thus, it is important to evaluate the sensitivity and uncertainty aspects of the effect of these factors on ignition. This study attempts to achieve this goal through sensitivity and uncertainty analyses on the piloted ignition of fiber‐reinforced polymer (FRP) composite panels. A Monte Carlo simulation using the Latin hypercube sampling method was employed to conduct sensitivity and uncertainty analyses. An integral model combining a general thermal thickness model with a heating rate‐related ignition temperature criterion was used as the ignition prediction model. Time‐to‐ignition was evaluated as the output parameter against the variations of input parameters such as material properties, external heating source, and surrounding environmental conditions. In addition, to identifying important sensitivity factors and uncertainty ranges of piloted ignition, a critical thermal thickness was found for the composite panels. These findings can serve as guides for the fire safety design of FRP composite materials for various applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Uncertain aggregate production planning

Based on uncertainty theory, multiproduct aggregate production planning model is presented, where the market demand, production cost, subcontracting cost, etc., are all characterized as uncertain variables. The objective is to maximize the belief degree of obtaining the profit more than the predetermined profit over the whole planning horizon. When these uncertain variables are linear, the objective function and constraints can be converted into crisp equivalents, the model is a nonlinear programming, then can be solved by traditional methods. An example is given to illustrate the model and the converting method.     

个人便携式网络硬件防水墙设计

文中介绍了防水墙技术和数据包过滤技术,针对个人计算机网络安全的问题,设计了一种便携式的防水墙系统。本系统运用了防水墙技术和网络数据包过滤技术,采用MEGA128单片机控制DM9000网络控制器的方法,对本地计算机发出的数据进行过滤,达到了防止信息被窃取的目的。     

葡萄糖钼异构反应后加氢制备甘露醇

通过深入研究葡萄糖钼异构反应后再经过加氢制备甘露醇,利用单因素结合正交试验来确定优化的反应条件。通过正交试验结合实际情况分析,得出的实际优化条件为:葡萄糖在钼酸铵用量为葡萄糖量的0.4%、反应温度98℃、反应时间150min、反应液pH 0.2、糖液浓度55%条件下进行钼异构反应,经过离子交换树脂精制后,在Ni-Al合金催化剂催化下,于100～160℃、氢气压力为0～6MPa条件下充分加氢至残糖低于0.1%,所得到的加氢后混醇干物质中的甘露醇含量可达32.6%。     

Microstructural Evolution of P92 Steel During Long-Term Aging

The mechanical properties and microstructure evolution of P92 steel were investigated after aging up to 11,000 h at 923 K. Charpy impact and tensile tests were carried out to study the strength and ductility of aged P92 steel. In addition, microstructure evolution of the samples during long-term aging was investigated with X-ray diffraction, optical microscopy and scanning electron microscope (SEM). Then, statistical quantitative image analysis based on SEM images was used to evaluate the precipitation during long-term aging. The mechanical properties were found to be associated with the evolution of precipitation, especially the coarsening of Laves-phase. Results show that the ductility and strength of P92 steel decrease with the growth of Laves-phase during short-term aging (shorter than 1000 h). However, as the aging time further increasing, the ductility and strength of P92 steel decrease slowly with the coarsening of Laves-phase.     

直流电流对Cu-0.33Cr-0.06Zr合金导电性的影响

对Cu-0.33Cr-0.06Zr合金在450℃下进行不同时效时间及不同电流密度的时效试验。研究了不同电流密度对Cu-0.33Cr-0.06Zr合金时效后电导率的影响。结果表明,在相同时效温度与时间的条件下,合金在电流密度为100A·cm-2的合金电导率低于无电流时效的;而电流密度为400A·cm-2的合金电导率高于无电流时效的。随着电流密度增加,合金的电导率有先下降再上升的趋势。在电流密度为400A·cm-2下时效2h后合金的电导率达到49.53 MS/m,与无电流时效6h相当。说明较大密度的直流电流可以加速溶质元素的析出,大大提高析出效率。     

A simple solution method for the blade element momentum equations with guaranteed convergence

The blade element momentum (BEM) equations, though conceptually simple, can be challenging to solve reliably and efficiently with high precision. These requirements are particularly important for efficient rotor blade optimization that utilizes gradient‐based algorithms. Many solution approaches exist for numerically converging the axial and tangential induction factors. These methods all generally suffer from a lack of robustness in some regions of the rotor blade design space, or require significantly increased complexity to promote convergence. The approach described here allows for the BEM equations to be parameterized by one variable—the local inflow angle. This reduction is mathematically equivalent, but greatly simplifies the solution approach. Namely, it allows for the use of one‐dimensional root‐finding algorithms for which very robust and efficient algorithms exist. This paper also discusses an appropriate arrangement of the equation and corresponding bounds for the one‐dimensional search—intervals that bracket the solution and over which the function is well behaved. The result is a methodology for solving the BEM equations with guaranteed convergence and at a superlinear rate.Copyright © 2013 John Wiley & Sons, Ltd.     

交通工程施工管理和质量控制综述

在城市建筑过程中，交通工程的施工是城市建筑的重要组成部分。它不仅仅对城市市民的日常生活有着直接的关系，同时也对城市的市容有着影响，是一个城市管理水平的反应。     

Perovskite ceramic oxide as an efficient electrocatalyst for nitrogen fixation

The electrochemical conversion of N₂ to NH₃ is an interesting research topic as it provided an alternative and energy-saving method compared with the traditional way of NH₃ production. Although different materials have been proposed for N₂ reduction, the use of defects in oxides was only reported recently and the relevant working mechanism was not fully revealed. In this study, Sr was used as the dopant for LaFeO₃ to create oxygen vacancies, forming the Sr-doped LFO (La_0.5Sr_0.5FeO_3-δ) perovskite oxide. The La_0.5Sr_0.5FeO_3-δ ceramic oxide used as a catalyst achieves an NH₃ yield of 11.51 μgh^?1 mg^?1 and the desirable faradic efficiency (F.E.) of 0.54% at ?0.6 V vs reversible hydrogen electrode (RHE), which surpassed that of LaFeO₃ nanoparticles. The ¹⁵N isotope labeling method was employed to prove the La_0.5Sr_0.5FeO_3-δ catalyst had the function of converting N₂ into NH₃ under the electrolysis condition. The first principle calculations were used to investigate the mechanism at the atomistic level, revealing that the free energy barriers changed significantly with the introduction of oxygen vacancies that accelerated the overall nitrogen reduction reaction (NRR) procedure.     

基于校政合作的电子政务绩效评价模式研究

运用一定的评测方法,建立量化的指标,有效地评价电子政务发展水平及其绩效,是当前衡量电子政务的主要途径评价,主要集中在评价视角、评价方法、调查手段等三个方面.以湖北省襄阳市的电子政务绩效评测为例,详细阐述了其电子政务绩效评测的校政合作模式,以及与之配套的评测流程和措施.经过5年的实践,证明了这种模式有效地促进了襄阳市的电子政务建设和发展水平,为发展市级电子政务及其评价绩效水平提供了一种新的方法.