排序方式: 共有43条查询结果,搜索用时 220 毫秒
31.
J.B.M. Biona A.B. Culaba R.R. Tan M.R.I. Purvis 《Transportation Research Part D: Transport and Environment》2008,13(5):306-314
Two stroke powered tricycles are a major source of air pollution in the Philippines. A fuelcycle assessment of the liquefied petroleum gas (LPG) and direct injection retrofit technologies for these vehicles is conducted. The results when compared with carbureted two and four strokes units indicate that retrofitting the units to direct injection provides lower fossil energy depletion, global warming, human toxicity and photochemical ozone formation impact potentials compared to LPG fueled carbureted two stroke tricycles while the latter exhibits lower acidification and nutrification impact values. The direct injection retrofitted units show a lower aggregated impact score and dominance over four stroke units. The conversion to LPG revealed minimal environmental benefits compared to the gasoline run units. 相似文献
32.
雷电是一种严重的自然灾害,其主要侵入通道有电源线路、各类信号传输线路、反馈路线和进入系统的管、缆、桥架等,雷击脉冲的防护是在入侵通道上将雷电流泄放入地,从而达到保护电子设备的目的。 相似文献
33.
Objective To research whether serum hepatocyte growth factor (HGF) level increases in ischemic stroke and hemorrhagic stroke, and explore the relationship between the serum HGF level and stroke recurrence. Methods We studied a total of 92 consecutive acute stroke patients who had been admitted to hospital within 24h of onset from 6 participating hospitals in Xi'an from January 2000 to May 2004. All patients were divided into ischemic stroke group and hemorrhagic stroke group according to the results of brain computed tomography (CT) scan or MRI on admission. Patients in stroke groups were divided into recurrent group and non-recurrent group. Healthy volunteers or patients without cerebrovascular diseases comprised the control group. Stroke and control groups were strictly matched with 1∶1 ratio. The patients were followed up for 4 years. Serum HGF was tested with enzyme-linked immunosorbent assay (ELISA). Results Serum HGF of stroke patients was significantly higher than that of control group (P<0.05). The serum HGF level in recurrent group was higher than that in non-recurrent group of ischemic patients, and there was no significant difference in hemorrhagic ones. Conclusion These results indicate that serum HGF may be used as a diagnostic marker for stroke, and serum HGF level is helpful in predicting the recurrence of ischemic stroke. 相似文献
34.
陈慧 《华东交通大学学报》2005,22(4):137-139
提出一种用于轴类零件自动压力校直压下量计算的方法,编制了相应的MATLAB计算程序.通过对某实例的程序计算结果与ANSYS有限元分析结果的比校,表明该校直压下量计算方法具有很高的精度. 相似文献
35.
36.
赖步英 《广州航海高等专科学校学报》2012,(1):27-29
本文在讨论基于笔划绘制及其特点的基础上,较深入地介绍了基于笔划绘制的主要算法,包括算法的原理、优化算法和贪婪算法,以及介绍基于笔划绘制的常见应用,为进一步的应用研究打下基础. 相似文献
37.
在机构设计中往往过多的考虑机构在运动学方面的要求而忽视满足最佳动力学方面的因素,传统的曲柄摇杆机构的设计便是一例。本文给出了一种既能满足给定的运动学参数,又能得到最佳动力学性能的曲柄摇杆机构的设计方法,弥补了传统设计中的不足。 相似文献
38.
为了研究运行因素对现代四冲程主柴油机增压系统工作的影响,以喘振为切入点,对其热力过程模拟计算结果进行分析,由此得到若干重要的结论.这些结论也为建立增压系统故障诊断软件提供了依据. 相似文献
39.
刘杰 《广东交通职业技术学院学报》2006,5(3):54-56
反映四冲程汽油机的活塞在气缸中的位置时,要用到三个位置信号:上止点信号、压缩行程信号、曲轴转角信号。电控系统为了得到指示活塞位置的信号要使用相应的传感器来检测出这三个位置信号,不同的发动机,获取活塞位置信号的地点不同,但从曲轴上获取的位置信号的精度高于从凸轮轴或分电器轴上获取的信号的精度。从曲轴上获取活塞位置信号时,所使用的上止点传感器及曲轴转角传感器在结构上趋向于一体化。 相似文献
40.
比较了日服40mg(甲组)和300mg(乙组)阿斯匹林对缺血性脑卒中患者静脉血流加压阻断前后血浆组织型纤溶酶原激活物含量(tPA:Ag)、活性(fPA:A)和其抑制物活性(PMI:A)的影响。结果表明:静脉血流加压阻断10min后tPA:Ag升高程度用药后较用药前为低(P<0.05),但两组间无差异。乙组tPA:A升高程度用药后较用药前为低(P<0.05),甲组用药前后无差异。提示阿斯匹林能保护内皮细胞,增强其对血流阻断损伤的耐受性。40mg/d阿斯匹林较小影响内皮细胞纤溶活性的储备,可能更有利于年中的预防。 相似文献