软土地基基坑开挖对临近桩变形影响的时效分析

为解决软土地基基坑开挖条件下,邻近桩基水平位移随时间逐渐发展的问题,结合两阶段分析方法,第一阶段引入三维分数阶Merchant黏弹性模型来描述软土的蠕变特性,采用对应性原理和Laplace积分变换方法,求得附加应力的Mindlin时域解;第二阶段将桩基看作Pasternak地基上的Timoshenko梁,将所得附加应力加载在桩基上,建立桩基的变形微分方程,利用有限差分法对方程进行求解,得到考虑桩基剪切效应及桩土剪切层厚度的桩基水平位移时域解. 通过与已有文献中的算例进行对比,验证了该方法的正确性. 最后,对三维分数阶Merchant黏弹性模型参数（剪切模量、体积模量、黏滞系数、分数阶）进行了影响因素分析. 结果表明,所得方法能够较好地反映基坑开挖引起邻近桩基水平位移随时间的发展规律.     

Geometrical enhancement of low-field magnetoresistance in silicon

Inhomogeneity-induced magnetoresistance (IMR) reported in some non-magnetic semiconductors, particularly silicon, has generated considerable interest owing to the large magnitude of the effect and its linear field dependence (albeit at high magnetic fields). Various theories implicate spatial variation of the carrier mobility as being responsible for IMR. Here we show that IMR in lightly doped silicon can be significantly enhanced through hole injection, and then tuned by an applied current to arise at low magnetic fields. In our devices, the 'inhomogeneity' is provided by the p-n boundary formed between regions where conduction is dominated by the minority and majority charge carriers (holes and electrons) respectively; application of a magnetic field distorts the current in the boundary region, resulting in large magnetoresistance. Because this is an intrinsically spatial effect, the geometry of the device can be used to enhance IMR further: we designed an IMR device whose room-temperature field sensitivity at low fields was greatly improved, with magnetoresistance reaching 10% at 0.07?T and 100% at 0.2?T, approaching the performance of commercial giant-magnetoresistance devices. The combination of high sensitivity to low magnetic fields and large high-field response should make this device concept attractive to the magnetic-field sensing industry. Moreover, because our device is based on a conventional silicon platform, it should be possible to integrate it with existing silicon devices and so aid the development of silicon-based magnetoelectronics.     

浅谈建筑材料的检测及其影响因素

工程质量是永恒的主题.建材检测是建筑工程质量保证体系中的一个重要环节,是确保建筑工程质量的先决条件.文章在此主要分析常用建材质量检测方法、常用建材 检测项目、建筑材料检测取样、建材检测的影响因素及数据处理,以供参考.     

维生素对红法夫酵母产虾青素的影响

采用单因素实验方法研究了不同维生素对红法夫酵母(Phaffia rhodozyma)生长及虾青素积累的影响.结果表明:生物素、泛酸钙、肌醇、VB1可显著提高红法夫酵母的生物量、类胡萝卜素和虾青素的产量,其较适质量浓度分别为0.05,25.00,0.50,0.05 mg/L.VB12和核黄素对红法夫酵母的细胞生长有明显的促进作用,同时可略微提高虾青素产量,其较适质量浓度分别为0.50和0.005 mg/L;VB6、烟酸和叶酸虽然可促进细胞生长,但却明显抑制了虾青素的积累;而硫辛酸既抑制细胞生长也抑制其虾青素的积累.根据单因素实验结果,在培养基中按以上较适浓度添加生物素、泛酸钙、肌醇、VB1、VB12和核黄素,菌体生物量和虾青素质量浓度分别达到5.000 g/L和16.77 mg/L,较对照组分别提高了33.2%和108%.     

人参皂甙Rh2和桦木酸协同诱导A549细胞凋亡的研究

我们已经发现,天然成分人参皂甙Rh2(G-Rh2)和桦木酸(Bet A)能够协同作用诱导人源肺癌A549细胞死亡.通过细胞形态观察、流式细胞检测分析、酶活性测定、免疫印记分析等实验技术,从细胞和分子水平提供证据,证明了G-Rh2和Bet A协同诱导A549细胞死亡的过程为细胞凋亡作用,且涉及线粒体途径.     

面向两客户的差异工件平行机批调度问题

将差异工件的批调度问题扩展到两客户生产环境,建立了两个客户分别以最小化制造时间跨度和最小化最大工件延迟时间为生产目标的差异工件平行机批调度模型.首先提出了一种启发式算法TSEDD(two-set earliest due date)对分批方案进行排序并安排到平行机,然后设计了一个多目标蚁群优化算法MOACO(multi-objective ant colony optimization)对不同客户中的工件进行分批并结合TSEDD完成对问题Pareto最优解集的求解.实验结果表明,与经典的多目标问题求解算法NSGA-Ⅱ和SPEA2算法相比,MOACO具有较好的求解效果,且随着问题中工件规模的增大,算法的优势更加明显.     

Test selection and optimization for PHM based on failure evolution mechanism model

The test selection and optimization （TSO） can improve the abilities of fault diagnosis, prognosis and health-state evalua- tion for prognostics and health management （PHM） systems. Traditionally, TSO mainly focuses on fault detection and isolation, but they cannot provide an effective guide for the design for testability （DFT） to improve the PHM performance level. To solve the problem, a model of TSO for PHM systems is proposed. Firstly, through integrating the characteristics of fault severity and propa- gation time, and analyzing the test timing and sensitivity, a testability model based on failure evolution mechanism model （FEMM） for PHM systems is built up. This model describes the fault evolution- test dependency using the fault-symptom parameter matrix and symptom parameter-test matrix. Secondly, a novel method of in- herent testability analysis for PHM systems is developed based on the above information. Having completed the analysis, a TSO model, whose objective is to maximize fault trackability and mini- mize the test cost, is proposed through inherent testability analysis results, and an adaptive simulated annealing genetic algorithm （ASAGA） is introduced to solve the TSO problem. Finally, a case of a centrifugal pump system is used to verify the feasibility and effectiveness of the proposed models and methods. The results show that the proposed technology is important for PHM systems to select and optimize the test set in order to improve their performance level.     

火药气体作用时期活塞运动诸元的数值解法

本文介绍导气式自动武器在火药气体作用时期内活塞运动诸元的数值解法,据气体动力学原理建立的理论公式,必须采用数值解法才能求解。数值解法中用龙格一库塔法比差分解法更为简便,精度也较高。并编制了一个计算活塞运动诸元?导气装置结构诸元的通用程序,利用它对四种不同的导气式武器进行了计算,结果与实际比较符合。     

β,β″-Al_2O_3体材料钾钠离子交换过程的应力分析

本文对β,β″-Al_2O_3致密多晶复合体材料与NaCl-KCl融盐之间的离子交换过程中应力的发展进行研究了。采用简化模型,对宏观应力及微裂纹出现的临界条件进行了分析计算。证明只有当微裂纹出现时有足够大的宏观应力存在的条件下才会导致材材的破坏。     

六缸曲轴动平衡机的微机系统

本文报道了用于测量六缸汽车发动机曲轴不平衡量的动平衡机微机系统的研制。文中详细地论述了该系统的数据处理方法与LED显示电路、控制接口、程序等的设计原理。