汽车制造企业生产管理存在的问题分析及解决办法

文章讲述了在汽车制造公司中生产管理的重要意义;对当前汽车企业生产现状进行了分析并列举了汽车制造企业生产过程中需要注意的事项,汇总了生产管理存在的主要问题,并提出了相应的改善方案,对其他企业的生产管理具有参考价值。     

Ontology-based approach for legal provision retrieval

In this paper, we present an ontology-based approach for legal provision retrieval. The approach aims at assisting the man who knows little about legal knowledge to inquire appropriate provisions. Legal ontology and legal concept probability model are main functional components in our approach. Legal ontology is extracted from Chinese laws by the natural language processing (NLP) techniques. Legal concept probability model is built from corpus, and the model is used to bridge the gap between legal ontology and natural language inquiries.     

软土地区多孔框架涵顶进结构力学特性研究

以宁波市云台山路下穿北仑铁路工程中采用的8孔框架涵结构为例,建立有限元力学模型,分析宁波软土地区8孔框架涵顶进过程的力学特性。所得结论不仅指导了该工程施工及施工监测,还可对其他软土地区多孔框架涵顶进工程提供参考。     

Effects of Injection Timing on Transient Performance of A Regulated Two-Stage Turbocharged Diesel Engine with Turbine Bypass Valve

The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NO_X emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance.     

环境约束下中国交通运输业产能利用测算

测度交通运输业产能利用可帮助交通行业应对产能优化和节能减排的双重挑战，实现高质量发展。研究旨在环境约束视角下，构建一个普适性的产能利用（CU）评价框架，并用于交通运输业产能利用测度研究。将交通运输业能源消耗量和CO₂排放量纳入产能利用评价框架，采用改进的基于数据包络分析的差分法，测度2011~2017年中国交通运输业产能利用。研究结果表明：①2011~2017年间中国交通运输业平均CU值为0.026 0，并以2014年为临界点，呈现先降后增的趋势，这表明中国交通运输业确实存在产能利用不足的问题，且2015~2017年非常严重；②交通运输业产能利用水平区域差异化显著，研究期内与中国其他地区的CU水平相比，西南地区产能利用不足问题最严重；③与原始差分法的测度结果进行对比，所提出的改进方法更具合理性和先进性；④推动交通技术创新发展和合理规划交通资源是产能利用水平提升的关键途径。该研究为制定交通运输业产能利用提升的政策提供科学依据，对建立完善的交通运输业产能利用监测体系具有实际指导意义，有利于实现中国交通运输业产能利用水平整体的提升。     

车载远程智能管理系统在汽车上应用的必然性分析

随着汽车电子技术的发展，智能化信息技术在汽车产业中的应用已成为大势所趋。它能合理、有效地对运营车辆进行监控、管理，规范驾驶员正常驾驶行为，减少因车辆管控不当或驾驶员非规范性行为造成的意外事故，并能降低车辆油耗和改善汽车尾气排放，是汽车产业变革发展所需。     

盾构隧道穿越液化地基上浮振动台试验分析

随着城市地铁线路不断增加,可能出现盾构隧道穿越液化地层的现象。一旦发生地震,盾构隧道存在上浮破坏的潜在风险。为深入研究盾构隧道周边液化地层的动力响应,针对相同密实度砂土在3种不同峰值加速度作用下开展室内振动台试验,分析土体中超静孔压的发展特性和隧道上浮规律。结果表明： 1）砂土液化最先发生在地表及浅层土体处,随着深度增加砂土液化程度逐渐降低,即增加隧道埋深有利于降低隧道液化程度。2）模型试验揭示盾构隧道的上浮机制,即使液化地基未完全液化,当超静孔隙水压力引起的上浮力大于隧道残余上覆有效土压力与隧道重力之和时,隧道将出现上浮。设计时可从消除液化地基和增加隧道重力2个方面入手,提高盾构隧道的抗上浮能力,确保隧道结构在地震时的安全。     

High-frequency random vibration analysis of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads using a hybrid SEM–SM method

A hybrid Spectral Element Method (SEM)–Symplectic Method(SM) method for high-efficiency computation of the high-frequency random vibrations of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads is presented. First, the Williams-Landel-Ferry (WLF) formula and Fractional Derivative Zener (FDZ) model were, respectively, applied for prediction and representation of the frequency-dependent dynamic properties of Vossloh 300 rail pads frequently used in China's high-speed railway. Then, the proposed hybrid SEM–SM method was used to investigate the influence of the frequency-dependent dynamic performance of Vossloh 300 rail pads on the high-frequency random vibrations of high-speed vehicle–track systems at various train speeds or different levels of rail surface roughness. The experimental results indicate that the storage stiffness and loss factors of Vossloh 300 rail pad increase with the decrease in dynamic loads or the increase in preloads within 0.1–10,000?Hz at 20°C, and basically linearly increase with frequency in a logarithmic coordinate system. The results computed by the hybrid SEM–SM method demonstrate that the frequency-dependent viscous damping of Vossloh 300 rail pads, compared with its constant viscous damping and frequency-dependent stiffness, has a much more conspicuous influence on the medium-frequency (i.e. 20–63?Hz) random vibrations of car bodies and rail fasteners, and on the mid- (i.e. 20–63?Hz) and high-frequency (i.e. 630–1250?Hz) random vibrations of bogies, wheels and rails, especially with the increase in train speeds or the deterioration of rail surface roughness. The two sensitive frequency bands can also be validated by frequency response function (FRF) analysis of the proposed infinite rail–fastener model. The mid and high frequencies influenced by the frequency-dependent viscous damping of rail pads are exactly the dominant frequencies of ground vibration acceleration and wheel rolling noise caused by high-speed railways, respectively. Even though the existing time-domain (or frequency-domain) finite track models associated with the time-domain (or frequency-domain) fractional derivative viscoelastic (FDV) models of rail pads can also be used to reach the same conclusions, the hybrid SEM–SM method in which only one element is required to compute the high-order vibration modes of infinite rail is more appropriate for high-efficiency analysis of the high-frequency random vibrations of high-speed vehicle–track systems.     

基于冷却液温度的内燃机能量流试验研究

内燃机能量流试验是评估不同控制策略下内燃机能耗和指明其改善方向的重要方法。通过试验对1台涡轮增压缸内直喷汽油机进行了基于冷却液温度的能量平衡分析,基于热力学定律,将能量平衡项分为有效功、冷却液损失、排气损失和通过辐射传热产生的未计入热损失。结果表明:小负荷时,随着冷却液温度的升高,燃油消耗率略有下降,NO_x排放量增加;全工况下,HC排放量随着冷却液温度的升高而减少,CO和CO_2排放量变化不大;有效功占比和排气损失占比随负荷的增大而增大,几乎不受冷却液温度的影响;冷却液损失占比随冷却液温度的升高而减小。     

基于GT-Suite的活塞环-缸套摩擦特性研究

以活塞环-缸套为研究对象,利用GT-Suite软件建立了活塞环-缸套摩擦模型,将摩擦、润滑和动力学三者耦合起来,同时考虑了活塞环和缸套的扭曲变形、接触表面粗糙度等因素,计算分析标定工况下活塞环-缸套的油膜厚度、油压分布、摩擦力和摩擦功耗。着重分析了不同润滑油温和不同转速条件下第一环油膜厚度和摩擦功耗,结果表明:第一道活塞环处润滑效果差、摩擦功耗高;随着油温升高,油膜厚度显著减少,同时摩擦功耗显著减少,综合考虑润滑和摩擦功耗,发现油温在80~90℃时摩擦特性较为理想;随着转速提高,油膜厚度增加,同时摩擦功耗增加,转速对油膜厚度影响较小,对摩擦功耗有显著影响。