What matters the most for economic development? Evidence from the Community Development Financial Institutions Fund

Governments use incentive programmes to attract new businesses. Due to limited resources, there are questions about which incentives are most effective. Using establishment data from California, and data on the location of disbursements through two federal programmes, we consider the effectiveness of different programmes in attracting new businesses. We find that the amount of funding through the New Markets Tax Credit programme has a significant impact on business activity but find no evidence of an effect from the Community Development Financial Institutions programme. Our results suggest that the effectiveness of these programmes depends on how they provide assistance.     

The effect of different post-electroplating surface modification treatments on tin whisker growth

There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the ‘cracked oxide theory’ was proposed by Tu in 1994. The current study has investigated the effect of both a molybdate conversion coating and a tungstate conversion coating on tin whisker growth from Sn–Cu electrodeposits on Cu, and compared it with that from an electrochemically formed oxide produced from a potassium bicarbonate-potassium carbonate electrolyte. X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of both immersion time and applied potential on the thickness and composition of the oxide film. The XPS studies show that the oxide film formed using either of the conversion coating baths is significantly thicker than that produced from the potassium bicarbonate-potassium carbonate bath. Initial observations suggest that both the tungstate-based conversion coatings and the molybdate-based conversion coatings significantly reduce whisker growth by over 80% for all conversion coating systems compared with a native air-formed oxide and provide improved mitigation compared with the electrochemically formed oxides previously investigated.     

面向等离子体W材料改善韧性的方法与机制

目的: 探讨胰岛素样生长因子1（IGF-1）基因多态性与抗高血压药物治疗后血压水平的关联性。方法: 运用流行病学现况调查方法,收集服用复方利血平、降压片和珍菊降压片的780例高血压患者的一般临床特征并测量其血压和临床生化指标。选择IGF-1基因的5个标签位点,采用TaqMan技术进行基因分型。采用协方差分析及分层分析对其基因多态性与药物治疗后血压水平的关系进行评价。结果: 在服用降压片的高血压病人中,rs6219位点不同基因型之间舒张压水平差异有统计学意义（P=0.01）。在服用复方利血平的高血压病人中,rs5742612和rs6218位点不同基因型之间收缩压水平差异有统计学意义（P值分别为0.04、0.017）。在服用珍菊降压片的高血压患者中,rs6218位点不同基因型之间舒张压水平及rs6219位点不同基因型之间收缩压水平差异均有关联（P值分别为0.017、0.033）。进一步分层分析发现,服用降压片的患者中,随着rs35767位点遗传变异女性收缩压的水平呈线性下降,而男性舒张压水平呈线性上升,校正混杂因素后P值分别为0.028、0.038。结论: IGF-1基因多态性与复方利血平、降压片和珍菊降压片三种抗高血压药物治疗后血压水平均有显著相关,提示IGF-1基因可能是高血压重要的药物疗效生物标记。     

基于VRML虚拟现实技术在机械设计中的应用

《机械设计》作为一门技术基础课,涉及知识面广,课程内一些零件的运动原理,工作特性,受力状况及结构设计也复杂。仅用黑板、粉笔讲授起来比较困难,学生也不易理解。随着数字技术发展和网络技术的广泛应用,网络教学日益蓬勃,虚拟现实技术为开发具有真实三维世界的图形教育软件提供了条件,使我国的远程教育上了个新台阶。     

论技术和制度的关系及其在经济增长中的作用

技术在经济增长中的决定性作用,已被史实和现实所证实。但技术革命发展的阶段性,并不能完全说明经济增长的持续性。在这一过程中,制度发挥着十分重要的作用。正是由于技术和制度的相互促进和相互决定,才为经济增长提供了持续性的保证。因而,技术和制度在经济增长中“互动论”的观点,为说明在相对较长时间里经济持续增长提供了较为完整的依据     

复合添加VC/Cr3C2晶粒长大抑制剂对WC-12%Co超细晶硬质合金性能的影响

采用真空／压力烧结工艺制备样品。研究复合添加晶粒长大抑制剂及烧结温度对WC-12％Co超细硬质合金微观结构及性能的影响。结果表明．当晶粒抑制剂含量为0．5％VC／0．2％Cr3C2．1430℃；和4MPa烧结制备的WC-12％Co超细硬质合金的抗弯强度达3786MPa。硬度为91．7HR。WC平均晶粒尺寸为0．6μm。富集在WC品粒（0001）面上的V阻止WC晶面迁移．固溶在粘结相中的Crsca减缓WC颗粒在粘结相中溶饵析出和再结晶长大过程．二者综合作用使WC晶粒细化。     

地方政府竞争、农地非农化与经济增长

经济增长需要农地非农化.在中国,地方政府对农地非农化影响巨大,因此地方政府竞争必然会影响中国的农地非农化,从而影响中国的经济增长.本文从地方政府竞争的角度出发来解释和探究中国的农地非农化状态与经济增长绩效,进而解释其中的政策含义.     

基于中位秩的Duane模型在可靠性增长试验中的应用

为解决武器装备在研制过程中,可靠性试验阶段多、子样少、评估难度大等问题,借助中位秩法,利用Duane模型对武器装备的可靠性增长试验结果进行了评估。基于中位秩法的Duane模型可靠性增长试验评估方法,将各试验阶段内技术状态不稳定的试验数据进行了整合,获得阶段性试验的可靠性预估结果,再将阶段性的可靠性预估结果用于可靠性增长Duane模型,对产品的最终可靠性结果进行评估。与基于经典Duane模型的可靠性增长试验评估方法相对比,基于中位秩法的Duane模型可靠性增长试验评估方法更符合可靠性增长试验特性及建模条件,评估结果更加科学。     

A ply-level electrical resistance approach to monitor crack evolution in a laminate SiC/SiC composites

In the aim of providing a reliable technique to monitor the development of damage in 0°/90° melt-infiltrated SiC-fiber reinforced prepreg laminate ceramic-matrix composites, it was hypothesized that the electrical resistivities of different layers of this material were significantly different due to their free Si content and morphology. Three distinct layers: a 0° fiber ply, a 90° fiber ply and a matrix only ply, were distinguished in the composite architecture. Free silicon is the most conductive phase in this composite system; however, the Si content and morphology were different in each of the three types of plies. Unidirectional and [0°/90°]_2s specimens enabled quantification of ply-level resistivities. An electric circuit model was constructed; it consists of parallel resistors where each resistor represents a ply in the composite system. This ply-level electrical model was validated using composites of different vintages which contained different silicon contents. A room temperature stepped fatigue test was conducted and the ply level circuit model was used to discern crack morphology with the support of acoustic emission and digital image correlation.     

A 2D image-based multiphysics model for lifetime evaluation and failure scenario analysis of self-healing ceramic-matrix mini-composites under a tensile load

We propose a multi-physics numerical model for a self-healing ceramic matrix mini-composite under tensile load. Crack averaged PDEs are proposed for the transport of oxygen and of all the chemical species involved in the healing process and studied in the dimensionless form to perform the most appropriate discretization choices concerning time integration, and boundary conditions. Concerning the fibres’ degradation, a slow crack growth model explicitly dependent on the environmental parameters is calibrated using a particular exact solution and integrated numerically in the general case. The tow failure results from the statistical distribution of the fibres’ initial strength, the slow crack growth kinetics, and the load transfer following fibres breakage. The lifetime prediction capabilities of the model, as well as the effect of temperature, spatial variation of the statistical distribution of fibres strength, and applied load, are investigated highlighting the influence of the diffusion/reaction processes (healing) on the fibre breakage scenarios.