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271.
272.
文章借鉴灰色关联分析方法,对11种集料级配水泥稳定碎石混合料的无侧限抗压强度、劈裂强度、干缩应变、温缩应变等体现路用性能的指标进行综合评价,结合最大干缩应变这一路用性能控制的重要指标,优选了路用性能较好的级配设计方法和设计方案,为水泥稳定碎石路用综合性能的评价提供参考。 相似文献
273.
基于热传递基本原理的高速动车组辅助变流器箱体热仿真设计流程主要包括建立几何模型、设置仿真初始条件、网格划分及稳态求解计算3个环节.根据辅助变流器的基本技术参数,并结合模拟及混合信号仿真软件Saber对辅助变流器主电路的仿真结果,给出辅助变流器中变压器、电抗器和绝缘栅双极型晶体管等主要发热器件功率损耗的计算公式.以某高速动车组辅助变流器为例,采用计算流体力学软件Flotherm,按照辅助变流器箱体热仿真设计流程,得到额定工况下辅助变流器箱体的温度场和流场分布结果,并制成辅助变流器样机.对比变压器线包和铁芯及功率模块散热片样机实测结果与仿真结果,验证了辅助变流器箱体热仿真设计方法的可行性. 相似文献
274.
J. Jung J. H. Lee S. Song K. M. Chun 《International Journal of Automotive Technology》2008,9(4):423-428
Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration.
Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate
the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction
mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation
process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO2-O2-H2O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range
of 250∼500°C. This value was exceedingly lower than the activation energy of NO2-O2 oxidation, which was 60±3 kJ/mol. When NO2 exists with O2 and H2O, the reaction rate increases in proportion to NO2. It increases nonlinearly with O2 or H2O concentration when the other two oxidants are fixed. 相似文献
275.
276.
This paper investigates the fuel efficiency of commercial hybrid electric vehicles (HEVs) and compares their performance with respect to standard gasoline vehicles in the context of cold Canadian urban environments. The effect of different factors on fuel efficiency is studied including road driving conditions (link type, city size), temperature, speed, cold-starts and eco-driving training. For this study, fuel consumption data at the link level in real-world conditions was used from a sample of 74 instrumented vehicles. From the study fleet, 21 vehicles were HEVs. Among other results, the beneficial fuel efficiency merits of hybrid vehicles were demonstrated with respect to gasoline cars, in particular at low speeds and in urban (city) environments. After controlling for other factors, sedan HEVs were 28% more efficient than sedan gasoline vehicles. However, the low temperatures (below 0 °C) observed regularly during winter season in the study cities were identified as a detrimental factor to fuel economy. In winter, the fuel efficiency of HEVs decrease about 20% with respect to summer. Other factors such as eco-driving training, city size, cold start and vehicle type were also found to be statistically significant. 相似文献
277.
Magalie Laniel Jean-Pierre Émond Ahmet Erdem Altunbas 《Transportation Research Part C: Emerging Technologies》2011,19(6):1071-1077
Perishable foods are frequently exposed to temperature abuse during transportation and distribution. The use of traditional data loggers do not permit the instantaneous data transmission that radio frequency technology offers. Temperature has a major impact on food quality and safety, particularly when long transit times are imposed. Consequently, using radio frequency identification (RFID) to track and monitor temperature in perishable shipments will bring significant benefits to the cold chain. The goal of this study was to determine the optimal RF antenna placement to achieve full RFID tag readability inside a sea container. Testing was made at two different frequencies (915 and 433 MHz) while the refrigeration unit was running at −25 °C and the container was fully loaded with frozen bread. The sea container was instrumented with eight RFID antennas, three of which were tuned for 433 MHz and five for 915 MHz. All antenna wires exited the container via the forward drain holes. The RFID readers were outside the container and connected to their respective antennas, one at a time. Thirty eight RFID tags were evenly distributed onto the pallets of frozen bread. All RFID tags were active tags capable of reading and recording temperature. Results at 915 MHz showed readability levels between 47% and 79%, with an average of 68.4%, whereas 433 MHz demonstrated 100% readability at all antenna positions. In conclusion, the 433 MHz RFID system appears suitable for real time temperature monitoring of frozen bread inside a sea container. This technology could be applied to other food items similar to frozen bread. 相似文献