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941.
K. Y. Lee 《International Journal of Automotive Technology》2008,9(1):87-93
The microstructural changes and the tensile properties of TRIP-assisted steels resulting from different chemical compositions
were investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite
could be characterized by two types: a granular type in steel containing higher Si and a film type in steel having higher
C. In the case of the steel containing higher C with a tensile strength of 860 MPa and a total elongation of 38%, the film
type retained austenite could be observed among the lath bainitic ferrites. Actually, the metastable retained austenite was
required for good formability, which means that the chemical composition plays a significant role in the microstructure and
tensile property of TRIP-assisted steel. With respect to the tensile property, each steel type that contained an suitable
amount of Si and Mn demonstrated a typical TRIP effect on a stress-strain curve while steel that contained a higher Mn content
exhibited similar behaviors, as demonstrated in the dual phase steels. 相似文献
942.
S. J. Lee S. J. Jeong W. S. Kim C. B. Lee 《International Journal of Automotive Technology》2008,9(6):659-670
The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient
method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance.
One of the favorable PM regeneration technologies is the NO2-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that
of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion
efficiency of NO2 from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel
numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental
data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading
inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation
rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within
the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the
engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft3 of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m2/gpt was enough to maximize the conversion efficiency and oxidation rate of PM. 相似文献
943.
C. Oh Y. S. Kang Y. Youn A. Konosu 《International Journal of Automotive Technology》2008,9(2):191-196
Pedestrian-related accidents are considered to be the most serious of traffic accidents due to the associated high fatality
rates. In Korea, pedestrian fatalities accounted for approximately 40% of all traffic-related fatalities in 2004. Significant
efforts have been made to develop effective countermeasures for pedestrian-vehicle collisions. A basis for devising such countermeasures
is to understand the characteristics of pedestrian-vehicle collisions. This study develops a pedestrian fatality model capable
of predicting the probability of fatality in pedestrian-vehicle collisions. Binary logistic regression and a probabilistic
neural network (PNN) are employed to estimate the probability of pedestrian fatality. Pedestrian age, vehicle type and collision
speed are used as independent variables of the fatality model. The models developed herein are valuable tools that can be
used to direct safety policies and technologies associated with pedestrian safety. 相似文献
944.
A modified CVT ratio map is proposed to obtain the improved fuel economy for a metal belt CVT. Since the CVT system loss,
which occupies most of the drivetrain loss, depends on the engine speed, input torque, primary and secondary actuator pressure,
a modified CVT ratio map is produced to realize the highest engine-CVT overall efficiency through the consideration of CVT
system loss. The modified CVT ratio map is constructed with respect to the demanded vehicle power and present vehicle speed
based on the steady state CVT system loss. Using the modified CVT ratio map, performance simulations are carried out using
the dynamic models of the CVT powertrain. The simulation results indicate that the modified CVT ratio control provides improved
engine-CVT overall system efficiency, and improves the fuel economy of the federal urban driving schedule by 4.9 percent. 相似文献
945.
目的 探讨桩冠修复中不同余留牙体高度及箍结构形式的应力分布特点和箍效应的生物力学机制.方法 模拟临床建立箍包绕不同牙体高度的上颌中切牙烤瓷核桩冠三维有限元模型,通过静态加载分析牙本质受力情况.结果 牙本质应力分布呈现出从颈部向根尖部逐渐增高的趋势.牙体预备形成箍结构修复后能减小牙根各部位应力值,减小程度依包绕部位和高度而变,箍结构包绕1 mm牙体高度能明显降低牙体颈部应力值,包绕2 mm牙体时应力降低反而不明显.结论 冠边缘包绕1 mm牙体可产生明显的箍效应,而包绕2 mm牙体修复时应根据牙体情况而定. 相似文献
946.
路由器体系结构及路由算法研究进展 总被引:1,自引:1,他引:0
对近年来高性能路由器所采用的主要的体系结构和路由算法研究成果进行了概括总结和分析,系统地阐述了路由器体系结构的关键问题,讨论了几种典型的路由算法并对它们的性能进行了比较,提出了进一步的研究方向. 相似文献
947.
The effect of the London congestion charge on road casualties: an intervention analysis 总被引:1,自引:0,他引:1
The introduction of the congestion charge in central London on the 17th of February, 2003, led to a reduction in congestion.
One factor that has not been fully analysed is the impact of the congestion charge on traffic casualties in London. Less car
travel within the charging zone may result in fewer traffic collisions, however, as the number of pedestrians, cyclists, and
motorcyclists increased after the introduction of the congestion charge, the number of traffic casualties associated with
these groups may also have increased. Reductions in congestion can also lead to faster speeds. Therefore, there could be increases
in injury severity for those crashes that do occur. An intervention analysis was conducted to investigate the effect of the
congestion charge on traffic casualties for motorists, pedestrians, cyclists, and motorcyclists, both within the charging
zone and in areas of London outside the zone. This was done for killed and serious injuries (known as KSI in British terminology)
and for slight injuries to examine whether there were any shifts in severity outcomes. Our results suggest no statistically
significant effect for total casualties in London, but within the charging zone there has been a statistically significant
drop in motorist casualties, and possibly an increase in cyclist casualties. There is an associated effect of an increase
in casualties of motorcyclists and cyclists in some areas outside the charging zone, suggesting that changes in the design
of the congestion charge may be needed to achieve reductions in casualties.
Dr. Robert B. Noland is Reader in Transport and Environmental Policy at the Centre for Transport Studies at Imperial College London. He received his PhD at the University of Pennsylvania in Energy Management and Environmental Policy and previously was a Policy Analyst at the US Environmental Protection Agency. Dr. Mohammed A Quddus is a Lecturer in Transport Studies at Loughborough University. Prior to this he was a Research Assistant at Imperial College London where he obtained his PhD in 2006. His main research interests are in road transport safety, geographic information science and its application to transport planning. Dr. Washington Y. Ochieng is the Reader in Geomatics and Transport Telematics at Imperial College London. He is the Director of the Engineering Geomatics group that carries out research in ATM-ATC, positioning and navigation, and transport telematics. Dr. Ochieng holds BSc (Eng), MSc and PhD degrees in space geodesy. 相似文献
Mohammed A. QuddusEmail: |
Dr. Robert B. Noland is Reader in Transport and Environmental Policy at the Centre for Transport Studies at Imperial College London. He received his PhD at the University of Pennsylvania in Energy Management and Environmental Policy and previously was a Policy Analyst at the US Environmental Protection Agency. Dr. Mohammed A Quddus is a Lecturer in Transport Studies at Loughborough University. Prior to this he was a Research Assistant at Imperial College London where he obtained his PhD in 2006. His main research interests are in road transport safety, geographic information science and its application to transport planning. Dr. Washington Y. Ochieng is the Reader in Geomatics and Transport Telematics at Imperial College London. He is the Director of the Engineering Geomatics group that carries out research in ATM-ATC, positioning and navigation, and transport telematics. Dr. Ochieng holds BSc (Eng), MSc and PhD degrees in space geodesy. 相似文献
948.
Those who oppose tolls and other forms of road pricing argue that low-income, urban residents will suffer if they must pay
to use congested freeways. This contention, however, fails to consider (1) how much low-income residents already pay for transportation
in taxes and fees, or (2) how much residents would pay for highway infrastructure under an alternative revenue-generating
scheme, such as a sales tax. This paper compares the cost burden of a value-priced road, State Route 91 (SR91) in Orange County,
California with the cost burden under Orange County’s local option transportation sales tax, Measure M. We find that although
the sales tax spreads the costs of transportation facilities across a large number of people inside and outside Orange County,
it redistributes about $3 million (USD) in revenues from less affluent residents to those with higher incomes. The entire
Measure M program redistributes an estimated $26 million from low-income residents to the more affluent. Low-income drivers
as individuals save substantially if they do not have to pay tolls, but as a group low-income residents, on average, pay more
out-of-pocket with sales taxes.
Lisa Schweitzer is an assistant professor at the University of Southern California. Her work on environmental injustice in transportation has appeared in Urban Studies, Built Environment, and Transportation Research Parts A and D. Brian D. Taylor is the Director of the Institute of Transportation Studies and Professor of Urban Planning at the University of California, Los Angeles. His research centers on how society pays for transportation systems and how these systems in turn serve the needs of people who have low levels of mobility. 相似文献
Brian D. TaylorEmail: |
Lisa Schweitzer is an assistant professor at the University of Southern California. Her work on environmental injustice in transportation has appeared in Urban Studies, Built Environment, and Transportation Research Parts A and D. Brian D. Taylor is the Director of the Institute of Transportation Studies and Professor of Urban Planning at the University of California, Los Angeles. His research centers on how society pays for transportation systems and how these systems in turn serve the needs of people who have low levels of mobility. 相似文献
949.
Bus rapid transit systems: a comparative assessment 总被引:1,自引:0,他引:1
There is renewed interest in many developing and developed countries in finding ways of providing efficient and effective public transport that does not come with a high price tag. An increasing number of nations are asking the question—what type of public transport system can deliver value for money? Although light rail has often been promoted as a popular ‘solution’, there has been progressively emerging an attractive alternative in the form of bus rapid transit (BRT). BRT is a system operating on its own right-of-way either as a full BRT with high quality interchanges, integrated smart card fare payment and efficient throughput of passengers alighting and boarding at bus stations; or as a system with some amount of dedicated right-of-way (light BRT) and lesser integration of service and fares. The notion that buses essentially operate in a constrained service environment under a mixed traffic regime and that trains have privileged dedicated right-of-way, is no longer the only sustainable and valid proposition. This paper evaluates the status of 44 BRT systems in operation throughout the world as a way of identifying the capability of moving substantial numbers of passengers, using infrastructure whose costs overall and per kilometre are extremely attractive. When ongoing lifecycle costs (operations and maintenance) are taken into account, the costs of providing high capacity integrated BRT systems are an attractive option in many contexts. 相似文献
950.
An integrated spatio-temporal GIS toolkit for exploring intra-household interactions 总被引:1,自引:0,他引:1
This paper reports on the development of an integrated spatio-temporal GIS toolkit that facilitates the exploration of intra-household
interactions. Two tools comprise the toolkit. The first tool, Space-Time Coincidence Analyst, identifies joint activity/travel episodes undertaken by household members. The core of this tool is a set of flexible criteria
for classifying episodes as either joint or independent. The second tool, Space-Time Path Visualizer, not only displays space-time paths for household members, but also shows joint episodes undertaken by any two household
members together. The toolkit can be applied to any household-based, activity/travel data set so long as required information
is specified by the user. To demonstrate its usefulness for research, the toolkit is applied to the TAPS (Toronto Activity
Panel Survey) 2002–03 data set. The results suggest that considerable variation exists in the number of joint activity/travel
episodes identified using different classification criteria. Specifically, when using restrictive criteria (i.e., same timing,
specific activity type/travel mode), only 2,265 joint activity/travel episodes are identified compared to 8,791 when using
more flexible criteria. In turn, our results show that certain key attributes for independent and joint activity/travel episodes
(i.e., frequency per household, starting time, ending time and duration) also vary under the different classification criteria.
Hejun Kang is a PhD candidate in the School of Geography and Earth Sciences at McMaster University. She holds a MSc degree in Geographic Information Science from the University of Calgary. Her doctoral research concerns intra-household interactions in the context of activity/travel behavior. Darren M. Scott is an Associate Professor of Geography at McMaster University. His current research centers on inter-agent decision making with regards to activity/travel behavior, and on issues concerning aggregation in activity-based travel demand models, most notably the treatment of space and the classification of activities. 相似文献
Darren M. ScottEmail: |
Hejun Kang is a PhD candidate in the School of Geography and Earth Sciences at McMaster University. She holds a MSc degree in Geographic Information Science from the University of Calgary. Her doctoral research concerns intra-household interactions in the context of activity/travel behavior. Darren M. Scott is an Associate Professor of Geography at McMaster University. His current research centers on inter-agent decision making with regards to activity/travel behavior, and on issues concerning aggregation in activity-based travel demand models, most notably the treatment of space and the classification of activities. 相似文献