Fabrication of Gradient SiNO/SiC Fibers by Nitridation Pyrolysis

陶瓷纤维具有质轻、高强高模、耐高温、抗氧化、耐腐蚀等优异的性质，是优异的树脂基、陶瓷基和金属基复合材料的增强体，在航空航天、军用以及民用上都有着广泛的应用前景。陶瓷纤维作为一种重要的战略物资，对陶瓷纤维的研究也一直是一个世界性的热点研究课题。在此背景下，本论文结合PCS先驱体转化发制备SiC纤维和氮化热解制备Si3N4纤维的技术路线，以聚碳硅烷(PCS)电子束交联丝为原料，在NH3气氛下，通过控制氮化温度来调控氮化深度，随后在N2气氛下高温热解制备出一系列新型的具有梯度变化结构的SiNO/SiC纤维，对该纤维的组成和结构进行了详细地研究，并且结合纤维的结构探讨了对性能的影响规律。 研究发现：...Ceramic fibers have wide range of application prospects in the military and civilian as superb reinforcement of resin matrix, ceramic matrix, and metal matrix composites duo to its excellent properties such as light weight, high strength and high modulus, high temperature resistance, oxidation resistance and corrosion resistance. Ceramic fibers as important strategic resource, the study of ceramic...学位：工学硕士院系专业：材料学院_工程硕士(材料工程)学号：2072014115011

Design and Implementation ofMicro-credit Management Syste

近年来，小额信贷作为一种有效的扶贫和金融发展手段被越来越多的人所接 受。我国的小额信贷业务规模也逐年扩大，发放的小额信贷业务逐年增长，为提 高小额信贷业务管理的效率和质量、保证贷款数据的准确性和完整性、降低贷款 风险，迫切需要开发一个结合实际情况的、完整的小额信贷管理系统。 本文首先阐述了小额信贷管理系统的研究背景和研究意义，并简单介绍了搭 建本系统所使用的相关技术，包括B/S结构、ASP.NET技术和SQLServer数据 库技术；然后，着重分析了本系统的业务需求和功能需求，主要包括信贷业务管 理、客户管理、风险管理三个主要方面，并针对系统功能进行了数据流分析；随 后，根据系...In recent years, micro-credit which is a valid way of supporting the poor and financial development, is more acceptant around the world. And in our county, the micro-credit business scale is being larger, in order to improve the efficiency and quality of micro-credit business management, guarantee the accuracy and integrity of loan data, and reduce the loan risk, it is in sore need for a pract...学位：工程硕士院系专业：软件学院_工程硕士(软件工程)学号：X201023056

Structured Ethical Dilemma of Social Work in Mainland——Based on Case Study of Institution M in City X

在理论和实践领域，伦理困境一直是社会工作研究和讨论的重点。随着我国经济体制变革、社会结构转型和利益格局调整，社会工作作为转变政府职能、创新社会管理体制的方式和手段，受到政府部门的重视。2007年起，民政部开始组织社会工作人才队伍建设的试点工作。服务于一线岗位的社会工作者在面对难于抉择的伦理困境时，需要与本土环境相适应的社会工作伦理为其提供指引和帮助。然而，目前大陆地区对社会工作伦理的研究尚未成熟，既有研究以直接引进和借鉴国外及港台地区社会工作发展经验居多，内容局限于理论层面的探讨，基于本土化实践的研究不足。这对国内社会工作的试点和推广十分不利，也给社会工作研究提出了更高的要求。鉴于此，本文尝试...Both theoretically and practically, ethical dilemma is always the focus of study and discussion in social work. As one of the measures that government adopts to transform government functions, social work innovate system of social management, attracts attention of government departments. Since 2007, Ministry of Civil Affairs has commenced organizing the pilot construction of social work personnel....学位：法学硕士院系专业：公共事务学院社会学系_社会学学号：1402008115096

Simulation and optimization of high-power LED with flat heat pipe heat spreader

为解决大功率LED的散热问题,设计了平板热管散热器来实现LED芯片的高效散热。通过Flotherm模拟软件,对大功率LED在自然对流条件下的散热; 情况进行了三维数值模拟。通过平板热管与常规铜、铝散热基板对比,发现平板热管有效降低了大功率功率LED的结温和热阻,使得LED温度分布更为均匀。此; 外,还研究了平板热管LED散热系统在不同芯片功率下的热性能,并对四种不同排布方式的LED平板热管散热系统进行了优化,发现阵列分布其温度分布最为均; 匀,结温最低,是较优的排布方式。Flat heat pipe heat spreader was designed for the heat dissipation of; high-power LED. The thermal performance of high-power LED in natural; convection conditions was simulated by the Flotherm simulation software.; It is found that the flat heat pipe reduces the junction temperature and; thermal resistance compared to the conventional copper and alumina heat; spreader. The thermal performance of LED with flat heat pipe heat; spreader under different heat power conditions was also explored.; Furthermore, four types of arrangement of the LED chips were also; designed and compared for the optimization. The results indicate that; the uniform array configuration induces the best uniform temperature; distribution and the lowest junction temperature, and seems to be the; optimum choice for high-power LED.广东省惠州市产学研结合项

掺铁碳化硅陶瓷的制备及其吸波性能

将羰基铁和液态聚碳硅烷(LPCS)反应生成的铁(Fe)溶胶与固态聚碳硅烷(PCS)混合,合成出不同Fe质量分数的PCS先驱体,然后经氧化交联和高温热解制备了不同Fe质量分数的磁性碳化硅陶瓷(Fe/SiC),系统地研究了Fe元素的引入对SiC陶瓷的组成、结构、磁性能和介电性能的影响规律。研究发现,当Fe质量分数小于8.94%时,在热解过程中,Fe元素可以显著促进SiCxOy的分解,生成β-SiC,且随着Fe质量分数的增加,β-SiC的结晶峰越来越强;但随着Fe质量分数继续增加,达11.78%时,则主要生成Fe3Si;Fe/Si C陶瓷均呈铁磁性,其饱和磁化强度随着Fe质量分数的增加而呈指数形式增加;当Fe质量分数为4.19%时Fe/SiC陶瓷在12.4 GHz具有最小的反射损耗,为-9.4 dB,同时低于-5 dB的带宽为2.4 GHz,Fe质量分数为8.94%时,低于-5 dB的带宽则为3.7 GHz,可用作良好的微波吸收材料。国家自然科学基金(51603175);;中央高校基本科研业务费(20720150082)资助项目~

二维开缝圆柱环流动力特性

使用粒子图像测速(PIV)技术对各二维开缝圆柱环流流场的动力特性进行定性及定量研究,揭示雷诺数(Re)、开缝位置角、开缝倾角及相对缝宽(s/d,s为缝隙宽度,d为圆柱直径)对环流动力特性的影响规律.获取瞬态流场、时均流场以及斯特劳哈尔数(Sr)等关键流场信息,研究开缝圆柱环流流场的结构及演变规律.结果表明:脱落涡与圆柱表面环流的此消彼长,引起120°以及180°开缝圆柱的吹吸效应,显著提前圆柱尾流脱落涡的耦合时间;240°开缝圆柱的缝隙位置接近圆柱后缘,流体未达到缝隙位置时已经发生流动分离,不会形成有效吹吸效应;120°以及180°开缝圆柱的尾流脱落涡运动轨迹振幅较大,其流阻系数大于基准圆柱以及240°开缝圆柱的尾流流阻系数;狭缝角α为180°,相对缝宽为0.15开缝圆柱的尾流Sr在0.218～0.225范围内波动最小,具备最优的线性稳定性.装备预研教育部联合基金(6141A02033529)国家自然科学基金(11072206)福建省自然科学基金(2012J01023)资助项

磁性聚醋酸乙烯酯微球的制备及表面功能化修饰

在油酸包覆的Fe3O4磁流体存在条件下,以醋酸乙烯酯为聚合单体,二乙烯苯为交联剂,过氧化苯甲酰为引发剂,聚乙烯醇为稳定剂,采用改良悬浮聚合法制备了粒径在数微米之间的磁性聚醋酸乙烯酯微球,对制备的磁性微球进行了表面功能化修饰。利用扫描电镜、振动样品磁强计和Fourier变换红外光谱分别检测了磁性微球的形貌、磁性能以及微球表面修饰的活性功能基团。结果表明:微球大小在1～7μm,平均粒径为3.8μm,粒径分布相对较窄;比饱和磁化强度为15.0emu/g,具有超顺磁性

Preparation and permeation characteristics of PVA/PEG/TEOS hybrid membranes

以聚乙烯醇(PVA)与聚乙二醇(PEG)共混,并与正硅酸乙酯(TEOS)进行交联反应制备杂化膜。FTIR证实杂化溶胶液发生交联反应形成共价键Si—O—C,WXRD观察表明加入TEOS改变了膜结晶度,加入PEG提高了PVA膜对乙醇/水溶液的渗透通量,但分离因子下降,随着TEOS的加入,膜的分离因子提高。在TEOS质量分数为10%时,杂化膜的分离因子达到最大。提高退火温度可以提高膜的分离因子,但通量下降。在100℃下退火12 h的杂化膜对乙醇质量分数为85%的乙醇/水溶液的分离性能最佳。Poly(vinyl alcohol)(PVA) was mixed with poly(ethylene glycol)(PEG) and then cross-linked by tetraethoxysilane (TEOS) to prepare organic-inorganic hybrid membranes.Fourier transform infrared spectroscopy(FTIR) proved that covalent bond Si—O—C was formed in the hybrid membranes.Wide-angle X-ray diffraction(WAXD) was used to observe the effect of TEOS and annealing on crystallinity.The hybrid membranes were tested in separation ethanol/water mixture by pervaporation.The effect of PEG,TEOS content and annealing temperature on the PVA hybrid membrane performance was discussed.The addition of PEG increased the PVA membrane flux,but its selectivity decreased.Water permselectivity increased with the addition of TEOS into the PVA/PEG membrane.The hybrid membrane exhibited the highest water permselectivity when TEOS mass fraction was 10%.Water permselectivity increased by increasing the annealing temperature,but permeation flux decreased at the same time.The hybrid membrane separation performance was best for pervaporation of water/ethanol(85%mass fraction of ethanol) mixture when annealing at 100 ℃ for 12 h.国家自然科学基金资助项目(50573063);; 高等学校博士点专项基金资助项目(20050384013

A Facile Route to Construct SiCO Nanospheres with Tunable Sizes

Natural Science Foundation of China [51175444, 51075344, 61274120]; Fundamental Research Funds for the Central Universities (Xiamen University) [2011121002]; Xiamen Municipal Bureau of Science and Technology [3502Z20126006]; Shenzhen City Science and Technology Innovation Committee [JCYJ20120618155425009]; National Science and Technology Major Project of the Ministry of Science and Technology of China [2011ZX02709-002]We report a facile route to synthesize SiCO nanospheres using Pluronic F127/ polyvinylsilazane (PVSZ) mixed micelles as a template, in which PVSZ selectively swells with the PEO core of the F127 micelles. The thermal degradation of the F127/ PVSZ mixed micelles leads to the formation of SiCO nanospheres. The size of the resultant SiCO nanospheres can be tuned in the range from 25 nm to 75 nm by controlling annealing time at 70 degrees C