关键词： 机械活化   淀粉   反相乳液   接枝共聚   接枝共聚速率  

摘要： 以机械活化淀粉为接枝母体,研究了在机械活化淀粉/单体(AM)/乳化剂/油/水五元反相乳液体系中引发机械活化淀粉接枝丙烯酰胺共聚反应的动力学。分别考察了引发剂浓度、单体浓度、淀粉乳浓度和乳化剂浓度等对接枝量和接枝共聚速率(R g)的影响。结果表明,在本实验考察范围内的动力学关系式为R g∞[mSt]1.24[I]0.76[M]1.54[E]0.33,淀粉与丙烯酰胺的接枝共聚速率随体系温度升高而加快,淀粉乳浓度和单体浓度对接枝共聚速率影响显著,在45℃～60℃范围内,接枝共聚反应链增长步骤的活化能为34.85 kJ/mol。

关键词： 机械原理   创新能力   应用型院校  

摘要： 为培养应用型院校学生在学习机械原理的兴趣、观察能力和创新能力,从加强机械的实物参观、增加课外实物机构运动简图的绘制、改革课程设计、鼓励学生参加机械创新设计大赛以及增加大作业、改革考核方式等多方面进行了探讨,并提出了一些课内外教学的手段和方法。

关键词： 湖南   责任   机械   废气涡轮增压器   发动机零部件   世界   民族   生产企业  

摘要： 湖南天雁机械有限责任公司（以下简称湖南天雁）是我国最早研制生产废气涡轮增压器的汽车零部件生产企业，主要从事废气涡轮增压器、发动机进排气门、高铁冷却风机等发动机零部件的研发、生产和销售。2013年，公司成功借壳上市，股票代码600698。

关键词： 分子动力学   纳米机械加工   应用  

摘要： 分子动力学是在进行物质的分子或原子的计算机模拟时最常用的一种方法,是模拟的基本方法。通过分子动力学的模拟研究,可以得到原子在尺度上的材料以及对其演化的可行性分析,这种分析是具有无先例的准确性的,让性能预测与材料设计成为可能。本文通过分析分子动力学的算法及其模拟原理,研究了分子动力学在纳米机械加工中的应用。

关键词： 通机   创新   可持续发展  

摘要： 通用动力行业是我国重要基础产业,市场需求量巨大。本文通过对重庆市通用动力机械行业创新能力的分析,为行业的可持续发展提供一定的依据。

关键词： Adaptive cruise control   String stability   Mechanical response   Platoon dynamics  

摘要： The dynamics of a platoon of adaptive cruise control vehicles is analyzed for a general mechanical response of the vehicle. Effects of acceleration-feedback control that were not previously studied are found. For small acceleration-feedback gain, which produces marginally string-stable behavior, the reduction of a disturbance (with increasing car number n) is found to be faster than for the maximum allowable gain. The asymptotic magnitude of a disturbance is shown to fall off as erf (ct./root n) when n -> infinity. For gain approaching the lower limit of stability, oscillations in acceleration associated with a secondary maximum in the transfer function (as a function of frequency) can occur. A frequency-dependent gain that reduces the secondary maximum, but does not affect the transfer function near zero frequency, is proposed. Performance is thereby improved by elimination of the undesirable oscillations while the rapid disturbance reduction is retained. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Adaptation   anaerobic   coordination   practice   reliability   Wingate  

摘要： The Wingate all-out test (WAT) is commonly used to estimate anaerobic capabilities of athletes by using an upper or lower body cycle ergometer, however, a new test modality called elliptical all-out test (EAT) which measures activated whole-body locomotor tasks has recently been proposed. The purpose of this study was to evaluate the familiarization effects of a 30-s EAT versus WAT. Twenty male trained athletes performed pre-familiarization (Trial-I), post-familiarization (Trial-II) and retest of Trial-II (Trial-III) sessions on both cycle ergometer and elliptical trainer. Peak power (PP), average power (AP), power drop (PD) and fatigue index ratio (FI%) were analyzed using student's t-test for paired samples and correlated by intra-class correlation coefficients (ICC). Moreover, an error detection procedure was administered using data attained from illogical interrelations among 5-s segments of 30-s tests. The main results showed that there were significant familiarization effects in all mechanical power outputs obtained from Trial-I and Trial-II in both EAT (ICC = 0.49-0.55) and WAT (ICC = 0.50-0.57) performances (p <= 0.01). Significant segmental disorders were detected in power production during Trial-I of EAT, however, none existed in any of test trails in the WAT (p <= 0.001). After familiarization sessions, reliability coefficients between Trial-II and Trial-III showed moderate to strong-level agreements for both EAT (ICC = 0.74-0.91) and the WAT (ICC=0.76-0.93). Our results suggested that prior to the performance tests, combination of a well designed familiarization session with one full all-out test administration is necessary to estimate the least moderately reliable and accurate test indices for both WAT and EAT.

关键词： Magnesium aluminate spinel   Aluminous cement   Phase constitution   Mechanical properties   Hydration kinetics  

摘要： Aluminous cement containing magnesium aluminate (ACMA) spinel was prepared in situ by sintering mixtures of limestone, magnesia and bauxite. The phase constitution, micro-morphology, and hydration kinetics of ACMA were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and isothermal calorimeter measurements, respectively. Magnesium aluminate (MA) spinel, calcium monoaluminate (CA) and calcium bialuminate (CA(2)) are the primary phases of the obtained ACMA. In addition, trace amount of calcium silicoaluminate (C(2)AS) and residual alumina (Al2O3) were detected. MA, mainly exists in the form of octahedron on the order of 2-5 mu m and forms agglomerates with the tabular or flaky-shaped CA in the clinker. The compressive strength of the ACMA castables increased remarkably as a function of CA content. The measurement of hydration heat demonstrated a five stage hydration process, namely, pre-induction, induction, acceleration, deceleration and stabilization. The N value was calculated to be lower than 1 in acceleration stage which indicates a nucleation controlled hydration process. On the other hand, it was higher than 1 in stabilization stage showing a diffusion controlled process. Crown Copyright (C) 2013 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.

关键词： MOLECULAR dynamics   COMPOSITE materials   STRESS concentration   SIMULATION methods & models   CILIARY neurotrophic factor   MICROSTRUCTURE  

摘要： Coarse-grained molecular dynamics simulations have been performed to investigate the tensile behavior of CNT films. It is found that CNT entanglements greatly degrade the tensile load-bearing capability of CNT films. The effect of twisting on the tensile behavior of CNT fibers spun from CNT films has also been investigated. Results indicate that twisting can make either positive or negative contributions to the mechanical properties of the film, depending on the microstructure. The structural and energy evolution of CNT films and fibers, as well as the stress distributions of CNTs which cannot be easily determined experimentally, have been illustrated. This study provides an effective means of revealing the structure/property relationships of CNT films/fibers, which are essential in designing high performance CNT fibers.

关键词： Single-Walled Carbon Nanotubes   Nanoscale Defect   Stone-Wales Defect   Molecular Dynamics   Atomistic Finite Element  

摘要： Although single-walled carbon nanotubes (SWCNTs) are found to have remarkable mechanical properties, a substantial variation in the reported performance data is observed in the literature. These discrepancies may be attributed to the presence of nanoscale defects, among other factors. In this paper, the effects of Stone-Wales defects on the mechanical properties of SWCNTs are studied using molecular dynamics (MD) simulations and atomistic finite element (FE) analysis. Our simulations showed that the longitudinal Young's modulus of individual single-walled carbon nanotubes is dependent on the tube structure, the diameter of the nanotube, and the number of Stone-Wales defects. The FE results show good agreement with MD predictions for defect-free SWCNTs, although the accuracy of the FE results declines for defective nanotubes with diameters less than 9.5 Angstroms.