直流电机与液力耦合器联合工作特性研究

为了减少直流电机启动时大电流的作用时间,在电机和负载之间增加液力耦合器降低电机过热烧毁的危险。通过对直流电机和液力耦合器特性的分析,建立直流电机单独工作、直流电机-液力耦合器联合工作情况下的数学模型。运用Matlab软件作系统仿真,绘制系统运行的电流I、输出转速n、输出转矩T的特性曲线图。通过对特性曲线的分析可以得出,电机与液力耦合器联合工作降低了启动电流和启动转矩,减少了电机过流过热和启动转矩对设备零部件冲击破坏的风险,设备抗振动能力提高,对安全作业具有指导意义。     

软硬相隔土层中超深地下连续墙的施工技术

超深地下连续墙的施工技术在我国已有很大的发展,但是超深地下连续墙在软土条件下的施工还不是很成熟.以天津滨海新区于家堡地区某深基坑实际工程为例,对其特殊地质条件下超深地下连续墙的施工技术进行了分析和总结,得出的施工技术和处理措施能够解决该地区类似工程的施工问题.     

高校岗位绩效考核信息管理系统设计与实现

高校岗位绩效考核管理涉及的数据量大、流程较多,设计开发了支持其网上运行的缋效考核信息管理系统,实现了岗位绩效管理信息存储处理和全流程控制,满足了高校发展战略和人力资源配置的辅助分析决策需要.     

Vision Recognition of Three Dimensional Object Using Aspect Graph

ＶｉｓｉｏｎＲｅｃｏｇｎｉｔｉｏｎｏｆＴｈｒｅｅＤｉｍｅｎｓｉｏｎａｌＯｂｊｅｃｔＵｓｉｎｇＡｓｐｅｃｔＧｒａｐｈＬＵＡＮＸｉｎＺＨＵＴｉｅｙｉＴＡＯＱｉｚｈｉ（栾新）（朱铁一）（陶奇志）（ＲｏｂｏｔＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｈａｒｂｉｎ...     

蒙脱土对PET结晶性能、热稳定性和力学性能的影响

通过熔融共混法制备了聚对苯二甲酸乙二醇酯(PET)／蒙脱土复合材料，用X-射线衍射和透射电镜对蒙脱土在基体中的分散情况进行了表征。研究了蒙脱土对PET结晶性能、热稳定性和力学性能的影响。结果表明，蒙脱土在PET结晶过程中起异相成核作用，明显提高了PET的结晶速率；基体中分散的蒙脱土片层结构可显著改善其热稳定性，加入3％(质量含量，下同)蒙脱土时，起始热分解温度提高22℃，热变形温度提高41℃；加入1％时，材料拉伸强度提高25％，缺口冲击韧性略有下降，此时材料有较好的综合力学性能。     

Highly transparent yttria ceramics with Nb2O5/Ta2O5 as novel sintering additives by pressureless vacuum sintering

Highly transparent yttria ceramics were fabricated by pressureless sintering with Nb₂O₅ or Ta₂O₅ as a novel sintering additive. The optical transmittance, microstructural evolution, and thermo-mechanical properties of the samples were investigated. The optimal doping concentrations of Nb₂O₅ and Ta₂O₅ are 0.3 and 0.2 at.%, respectively, which are much lower compared to those of previously reported counterparts. The transmittance of the sample with 0.3 at.% Nb₂O₅ reaches 81.6% at 1100 nm and 72.4% at 400 nm (2 mm in thickness), similar transmittance was obtained in the sample with 0.2 at.% Ta₂O₅. The microhardness (∼7 GPa), fracture toughness (∼0.85 MPa·m^1/2), and biaxial strength (∼200 MPa) of the present samples were confirmed to be comparable or even better compared to those of previously reported transparent yttria ceramics fabricated by pressureless sintering. Furthermore, the present samples, by virtue of the low doping concentrations, possessed relatively high thermal conductivity values (>10 W/m·K), which substantially guaranteed high thermal shock resistance.     

Fabrication of LaGdZr2O7 transparent ceramic

A simple combustion method was used to synthesize LaGdZr₂O₇ powder and LaGdZr₂O₇ transparent ceramic was prepared by vacuum sintering at 1850 °C for 6 h. The final transparent ceramic, with a density of 6.46 g/cm³, has an in-line transmittance of 70.7% at 1000 nm and a refractive index of 2.08 at 632.8 nm.     

An efficient method for the enrichment of the arachidonic acid methyl ester from Mortierella alpina-derived crude oils

An improved method was developed for enriching arachidonic acid (AA) methyl ester from microbial oil by two-step low-temperature wet fractionation. The effects of solvent, operating temperature, and solvent-to-fatty acid methyl esters (FAMEs) ratio on the enrichment of AA were investigated. The best results were achieved when n-hexane was used as solvent. With operating temperatures in the range ?30 °C to ?80 °C and a FAMEs-to-solvent ratio of 1:5 (v/v), the proportion of AA methyl ester isolated could be increased to 83.76 ± 2.78% with a yield of 52.89%. The total recovery of AA methyl ester would be further increased to 90.84% by recrystallization of the solid phases. The 20C, 22C saturated fatty acids were enriched by n-hexane or petroleum ether at ?30 °C, with concentrations increased 7.5-fold or 7.2-fold compared with their original levels, respectively. In addition, a method that combined alkali and acid catalysis of the transmethylation was the most conducive to the preparation of polyunsaturated fatty acid methyl esters.     

Facile one-step solid-state reaction route to synthesize ordered mesoporous β-Zn2SiO4–SiO2 nanocomposites

Ordered crystalline mesoporous β-Zn₂SiO₄–SiO₂ nanocomposites were prepared by one-step solid-state reaction using mesoporous silica as both template and silica source. Zinc oxide formed by decomposition of zinc nitrate reacts with mesoporous silica and the β-Zn₂SiO₄ forms and disperses inside the silica walls. The obtained β-Zn₂SiO₄–SiO₂ nanocomposites possess hexagonal mesostructure with the β-Zn₂SiO₄ weight percentage below 40%. The β-Zn₂SiO₄ nanocrystals are surrounded by the non-crystalline silica of mesoporous walls. The non-crystalline silica acting as a binder to stick β-Zn₂SiO₄ nanocrystals plays a role in restraining the phase transformation from β-Zn₂SiO₄ to α-Zn₂SiO₄ and increasing the thermal stability of mesoporous β-Zn₂SiO₄. The crystalline mesoporous β-Zn₂SiO₄ may be a potential candidate for application as absorbents, for separation and as phosphors.