An approach for concurrent evaluation of technical and social aspects of software development methodologies

The paper presents an approach for evaluation of software development methodologies (SDM) that considers the aspects of a SDM’s social adoption and technical efficiency. It builds on existing evaluation models used in the field of SDM. Case study approach was used to validate the model in four software development organisations. In all four cases the management confirmed that the model provided valuable new insights into adoption and efficiency of the companies’ SDM.     

基于熵权直觉模糊拓展MULTIMOORA的机场消防站选址评价模型

针对准则权重信息完全未知的直觉模糊多准则群决策问题,考虑经典直觉模糊熵公式及MULTIMOORA模型的不足,提出新的直觉模糊熵公式以充分刻画直觉模糊数的直觉信息和模糊信息,定义占优凸组合运算,拓展解决多准则决策问题的MULTIMOORA模型以适用于解决多准则群决策问题.在以直觉模糊数为信息输入的系统框架内,构建机场消防站选址评价指标体系,进而提出基于熵权直觉模糊拓展MULTIMOORA的机场消防站选址评价模型.案例分析表明了所提出方法的可行性,为机场消防站选址评价提供了一种新思路.     

Mechanical and ablative properties improvement of HfC-SiC coatings upon introduction of TiC

A novel structural Hf-Ti-Si-C multiphase solid solution coating was designed and manufactured by chemical and solid solution reactions to improve the mechanical and ablation behavior of HfC-SiC coatings. Results show that, with TiC addition, the formed Hf_xTi_1?xC and (Ti_1?xHf_x)₃SiC₂ solid solutions can significantly enhance the micro-mechanical and ablation properties of the coating. The improved hardness and modulus, as well as the reduced ablation rates are mainly attributed to the optimized structure and solid solution reinforcing effect of coating. Moreover, the Ti-additives are conducive to restrain the active oxidation of SiC. Furthermore, HfTiO₂ can reduce the oxides cracking due to the inhibited crystal transformation of HfO₂ and its good self-healing ability, forming a dense and stable oxide scale with superior thermal protection.     

Application of polynomial control to design a robust oscillation-damping controller in a multimachine power system

This paper addresses the application of a static Var compensator (SVC) to improve the damping of interarea oscillations. Optimal location and size of SVC are defined using bifurcation and modal analysis to satisfy its primary application. Furthermore, the best-input signal for damping controller is selected using Hankel singular values and right half plane-zeros. The proposed approach is aimed to design a robust PI controller based on interval plants and Kharitonov׳s theorem. The objective here is to determine the stability region to attain robust stability, the desired phase margin, gain margin, and bandwidth. The intersection of the resulting stability regions yields the set of k_p–k_i parameters. In addition, optimal multiobjective design of PI controller using particle swarm optimization (PSO) algorithm is presented. The effectiveness of the suggested controllers in damping of local and interarea oscillation modes of a multimachine power system, over a wide range of loading conditions and system configurations, is confirmed through eigenvalue analysis and nonlinear time domain simulation.     

Effect of the Y2O3 amount on the oxidation behavior of ZrB2-SiC-based coatings for carbon/carbon composites

In this paper, the effect of Y₂O₃ addition on the oxidation resistance of ZrB₂-SiC-Y₂O₃ coating for the SiC coated carbon/carbon composites was investigated. Results confirmed the great benefits of adding Y₂O₃ to the oxidation-resistant properties of the original coating from different aspects. The dense structure of surface and cross-section and formation of yttria stabilized zirconia, Y₂Si₂O₇, t-ZrO₂ phases were observed after adding Y₂O₃. Additionally, according to the TEM results, yttrium silicate existed in the form of nanoparticles, while yttria stabilized zirconia existed in the form of agglomeration within the SiO₂ liquid phase. This superior oxidation resistance was attributed to the following reasons: (i) the formed Zr-Si-Y-O glass barrier layer blocked the oxygen diffusion and healed the cracks; (ii) the reduced m-ZrO₂ content weakened the volume expansion of the coating and avoided spallation; (iii) Y₂Si₂O₇ served as a pinning phase which modified the stability of liquid SiO₂ at elevated temperatures.     

聚磷酸铵和三氧化钼对聚氨酯软泡阻燃性能的影响

以聚磷酸铵（APP）和三氧化钼（MoO3）为阻燃剂,采用一步发泡法制备阻燃聚氨酯软质泡沫（FPUF）,通过扫描电镜、氧指数仪、热重分析仪和锥形量热仪等测试手段研究了MoO3和APP对聚氨酯软泡的泡孔结构、热稳定性、阻燃性能以及产烟量的影响规律。研究表明：MoO3和APP均能提高聚氨酯软泡的阻燃性能,与纯聚氨酯软泡相比,当APP和MoO3的添加量均为7.5%时,阻燃聚氨酯软泡的总热释放量和总产烟量分别降低了44.2%、66.3%,表现出很好的阻燃和抑烟性能;探讨了APP和MoO3阻燃聚氨酯软泡的阻燃作用机理,APP在气相和凝聚相发挥阻燃作用,在气相中通过生成含磷官能团捕获气相中的自由基,在凝聚相中发挥催化成炭的作用,MoO3能促进热裂解聚氨酯催化成炭,提高成炭率,使炭层致密,并提高聚氨酯软泡的热稳定性,有效提高聚氨酯软泡的火灾安全性。     

气凝胶毡组合放置方式对锂离子电池热失控特性的影响

摘 要：为减缓热量在锂离子电池货物间传播,通过自主搭建的锂离子电池燃爆实验平台,开展气凝胶毡在锂离子电池包装内的不同放置位置对热失控热量阻隔有效性的研究。结合试验结果分析选取峰值温度、热失控传播时间和速度、烟气浓度、质量损失以及包装破坏程度作为锂电池包装性能评价参数,引入简化的N-GAS毒性定量评估模型,通过对不同气凝胶毡组合放置方式中的锂离子电池包装件进行评价可知：从对电池组的安全和外包装完整性的保护作用效果看,顶部中部组合对热失控传播阻隔效果最好,并且不建议在锂离子电池实际运输中采用三面全包方式。     

Data clustering and storing for wide-area power quality monitoring

This paper presents a new technique that can be implemented for monitoring the quality of serves in wide areas and representing the data in terms of a small set of coefficients. Wavelet multi-resolution analysis (MRA) is utilized for feature extraction and data clustering of different disturbances. The proposed feature vector and the rapid drop off in the number of the wavelet-expansion coefficients are used to classify different power quality problems and to represent the original data in terms of a small set of coefficients.     

超声冲击强化对TC4钛合金拉压疲劳性能的影响

静荷载25 N、振幅30μm、冲击数36 000次/mm2下对TC4钛合金去应力退火及固溶时效两种状态进行超声表面冲击强化处理,研究其对TC4拉压疲劳性能的影响。对处理后的微观组织、硬度、强塑性变形(SPD)层、残余应力、疲劳性能和断裂特征进行分析。结果表明:处理后在TC4表面均获得约40μm深的强塑性变形层、表面硬度及残余压应力均被提高、表面粗糙度有较好的维持、两种状态的108周次的疲劳强度分别提升7.0%和10.7%;10~6周次前裂纹主要由表面萌生,10~6周次后裂纹源核心表现为SPD层与核心之间的变形α相,其形状狭长且平行于试件边缘。建立经典材料力学模型对其轴向应力进行分析,有助于理解内部裂纹源。