Bilinear precision of rational Bézier surfaces

This short note proves the bilinear precision property of rational Bézier surfaces and gives a simple algorithm to compute the weights. Linear precision of rational Bézier surfaces is also discussed.     

姜渣-玉米淀粉膜的制备及研究

目的 制备一种纯天然的、具有抑菌性的可食用淀粉膜。方法 以玉米淀粉为原料,通过添加适量的姜渣、甘油、羧甲基纤维素钠,采用流延法制备姜渣-玉米淀粉膜。结果 当淀粉的质量分数为3%,甘油的质量分数为1%,姜渣的质量分数为0.4%时,膜的透光性、透油性、水蒸气透过性、溶解度、溶胀度等各项指标的综合测定结果较好。生姜中含有姜辣素、姜油等活性成分,添加姜渣可作为天然的抑菌剂,微生物试验结果证实,姜渣-玉米淀粉膜对霉菌和酵母菌具有一定抑菌作用,且抑菌效果与姜渣的含量成正比关系。结论 所制备姜渣-玉米淀粉的结构紧密、光滑平整,并具有一定的抑菌性。     

Compressive properties and energy absorption characteristics of open-cell nickel foams

Open-cell nickel foams with different relative densities and pre-stretching degrees were subjected to room temperature quasi-static compressive tests to explore their compressive properties. The compressive properties of the nickel foams including yield strength, elastic modulus, energy absorption density and energy absorption efficiency were calculated accurately. The results show that the compressive properties of yield strength, elastic modulus and energy absorption density increase with the increase of relative density of nickel foams. The compressive properties are sensitive to the pre-stretching degree, and the values of yield strength, elastic modulus and energy absorption density decrease with the increase of pre-stretching degree. However, the energy absorption efficiency at the densification strain state exhibits the independence of relative density and pre-stretching degree. The value of energy absorption efficiency reaches its peak when the strain is at the end of the collapse plateau region.     

电线电缆用Al-Fe-Cu-0.25La-Zr耐热合金的导电性能

采用导电率测试仪、万能拉伸试验机、光学显微镜等分别测试了Al-Fe-Cu-0.25La-Zr合金的导电率、抗拉强度、伸长率等性能指标及显微组织,研究了电线电缆Al-Fe-Cu-0.25La-Zr合金在不同退火工艺下的导电性能与力学性能。结果表明,合金在350 ℃×2 h退火时达到导电率峰值62.8%IACS,抗拉强度为101.5 MPa,伸长率为32.4%;在300 ℃退火2 h时导电率达到62.1%IACS,抗拉强度为125.0 MPa,伸长率为13.4%。合金在300 ℃×(4~10) h退火期间,合金的导电率维持相对稳定,且高于350 ℃×(4~10) h,说明合金在300 ℃时具有更好的耐热稳定性。Al-Fe-Cu-0.25La-Zr合金最优的退火工艺为300 ℃×2 h,此工艺处理后的合金线材符合对电线电缆电学性能与力学性能的标准要求,且可以降低生产成本。     

图形渐变过程中图形重构关键技术研究

介绍了平面多边形渐变的基本原理,提出了基于三角形分解与重构中在计算机编程中碰到的重构图形中出现部分点偏离或方向相反的问题及其解决方案,实现了较好的多边形渐变效果,为程序人员实际实现图形渐变开发提供理论依据及实际编程方法。     

采用DSP控制并基于半桥逆变器UPS驱动电路的研究

文中设计了一种采用HCPL-316J芯片来驱动用TMS320F2812控制的基于三相半桥逆变器的UPS,分析了半桥逆变器的原理。实验结果表明,采用该驱动方案设计的UPS系统具有低成本、安全性高,并且具有带三相不对称负载能力强,输出电压波形总谐波失真度（THD）小,工作效率高等优点。     

纤维素纳米晶体对甘薯淀粉糊化特性和流变特性的影响

采用快速黏度分析仪以及流变仪分析纤维素纳米晶体对甘薯淀粉短期回生的影响。结果表明:随着0.03、0.06、0.09、0.12、0.15 g的纤维素纳米晶体添加到1.5 g甘薯淀粉中,其回生值明显低于纯淀粉。静态剪切流变测试结果表明,复合体系符合幂定律模型,是一种假塑性流体,剪切应力随着纤维素纳米晶体添加量增加而呈现降低趋势,稠度系数K减少,流体指数n增大。动态黏弹性测试结果表明,纤维素纳米晶体增强了体系的流体性。纤维素纳米晶体是一种有前景的淀粉短期回生抑制剂。     

First principles study on elastic and electronic properties of bialkali alanates M2M′AlH6

The elastic and electronic properties of a series of bialkali alanates M₂M′AlH₆ (Na₂LiAlH₆, K₂LiAlH₆, K₂NaAlH₆) have been investigated by first principles calculations. The calculated lattice parameters and decomposition enthalpies are in good agreement with the experimental and other available data. All M₂M′AlH₆ hydrides are found to be mechanically stable and brittle. The elastic moduli, Vickers hardness and the Debye temperature follow the order of Na₂LiAlH₆ > K₂LiAlH₆ > K₂NaAlH₆. The calculated elastic anisotropy indexes A^Z, A^U, A^E indicate that the M₂M′AlH₆ hydrides exhibit obvious anisotropy and the sequence follows K₂LiAlH₆ > K₂NaAlH₆ > Na₂LiAlH₆. From the density of states, the crystal orbital Hamiltonian population, bonding charge density, electron localization function and the Bader charge analyses, it can be confirmed that the existence of polar covalent bonding between Al and H within the [AlH₆]^3? units and ionic bonding between [AlH₆]^3? units and M, M′.     

Effects of alloying elements on the electrochemical behaviors of Al-Mg-Ga-In based anode alloys

In this study, in order to investigate the effects of alloying elements on the electrochemical behaviors of Al-based anodes, pure Al and Al-Mg-Ga-In alloys with different compositions (Al-0.25Mg-0.3Ga-0.3In, Al-1Mg-0.05Ga-0.15In and Al-2Mg-0.15Ga-0.05In (wt%)) were fabricated. The microstructure, corrosion behavior, electrochemical property, discharge performance and corroded morphology of the four experimental anodes were studied. Al-Mg-In-rich intermetallic compounds were observed in Al-Mg-Ga-In alloys. The results of the polarization curve and electrochemical impedance spectroscopy indicate that the addition of Mg acts as a critical component in improving the discharge activity of Al-based anode and contributes to a more negative electrode potential. According to the corrosion morphologies after discharge, it can be concluded that the addition of In element plays an essential part in forming corrosion pits on the surface of the anode while the addition of Ga element plays a vital role in destroying the surface passive layer to prevent passivation once corrosion starts.     

漂浮式波浪发电系统波浪能模拟及参数计算

基于线性叠加法模拟了不同风速下的波浪波形,提取了波浪力能,分析了浮筒的受力情况,进而在保证漂浮式波浪发电系统稳定运行的情况下计算了不同波浪浪高下的浮筒尺寸、质量与发电机功率之间的关系,并应用仿真软件进行了仿真研究,结果对漂浮式波浪发电系统的各参数设计具有重要的指导意义。