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981.
H. S. Heo S. J. Bae H. K. Lee K. S. Park 《International Journal of Automotive Technology》2012,13(2):167-173
In a conventional MPI engine, a pulsation damper is usually mounted on the fuel rail to diminish undesirable noise in the
vehicle cabin room; however, pulsation dampers are quite expensive. Therefore, several studies have focused on reducing fuel
pressure pulsation by increasing the self-damping characteristics of the fuel rail. This paper details the development of
a fuel rail that reduces pulsation using a self-damping effect. Using an oil hammer simulation technique, pressure pulsation
characteristics were investigated with respect to the aspect ratio of the cross-section, wall thickness, and fuel rail material.
Increasing the aspect ratio and decreasing the wall thickness efficiently reduced the pressure pulsation. In addition, the
pressure pulsation characteristics were investigated with respect to the resonant engine speed and injection period. These
simulated data can be used to reduce the pressure pulsation peak and to avoid the resonant point in the design stage during
the development of a fuel rail. 相似文献
982.
串列双圆柱尾迹流的数值分析 总被引:1,自引:0,他引:1
为避免流体流动引起共振,采用有限体积法,对串列双圆柱尾迹流进行了数值分析,探讨了斯特劳哈尔数(Strouhal数)随圆柱间距比和雷诺数变化的规律.研究表明:在不同流场形态下,斯特劳哈尔数随圆柱间距比的变化规律不同;斯特劳哈尔数随雷诺数的增大而增大,但增大幅度与流场形态有关. 相似文献
983.
Despite decades of research, it is unclear under which circumstances travel is most onerous. While studies have found that some individuals derive positive utility from aspects of commuting, others have shown that traffic congestion can entail important time, monetary, and mental stress costs. Moreover, responses to traffic congestion-related stressors differs by individual characteristics. In response, this research captures how exposure to traffic congestion events, the duration of this exposure, and individual trait susceptibility to congestion affect the utility of commuting. Working through the lens of individual satisfaction with the duration of their commute, we show that not every minute of travel is valued the same by car commuters in Canadian cities. Results suggest a complex relationship between travel time, congestion, and individual predisposition to congestion-related stress. While improvements in travel time matter for increasing commute satisfaction, it is reductions in travel in congested conditions that matter most, particularly among those susceptible to congestion-related stressors. 相似文献
984.
As Global Positioning System (GPS) technology advances, it has been increasingly used to supplement traditional self-reported travel surveys due to its promising features in capturing travel data with better accuracy and reliability. Realizing the limitations of diary-based surveys, this paper presents a study that directly accounts for trip misreporting behavior in trip generation models. Travel data were obtained from prompted-recall assisted GPS survey along with a diary-based survey. Negative Binomial models for count data were developed to accommodate misreporting behavior by introducing interaction effects of the sample-indicator variable with various personal and household variables. The interaction effects indicate how the impacts of the socioeconomic and demographic variables on trip-making vary across the two samples. Assuming that the GPS sample represents the ground truth, the interaction effects actually capture the likelihood and the extent of trip misreporting by detailed personal and household characteristics. The model results reveal significant interaction effects of several personal and household variables, indicating misreporting behavior associated with these attributes. The addition of interaction coefficients to the main effect model represents the real impacts of the independent variables, after compensating for trip misreporting behavior, if any. 相似文献
985.
Andreas W. Schäfer 《Transportation》2017,44(2):293-310
Based upon a long-term historical data set of US passenger travel, a model is estimated to project aggregate transportation trends through 2100. One of the two model components projects total mobility (passenger-km traveled) per capita based on per person GDP and the expected utility of travel mode choices (logsum). The second model component has the functional form of a logit model, which assigns the projected travel demand to competing transportation modes. An iterative procedure ensures the average amount of travel time per person to remain at a pre-specified level through modifying the estimated value of time. The outputs from this model can be used as a first-order estimate of a future benchmark against which the effectiveness of various transportation policy measures or the impact of autonomous behavioral change can be assessed. 相似文献
986.
Jooyoung Kim 《运输规划与技术》2017,40(4):465-478
In a destination choice model, it is important to introduce alternatives that have been adequately aggregated into traffic analysis zone levels based on spatial similarities and feasibility of analysis, because considering every spatial location possible for the traveler as an elemental alternative is intractable in terms of data management and analysis. In this study, we derive strata for alternative sets through simple random sampling and stratified importance sampling based on the concept of Moran’s I. As a result of comparative analysis, we are able to reduce errors by drawing an adequate number of samples for the destination choice model’s choice alternative sets based on measures of spatial similarity. 相似文献
987.
Z.L. Yang D. Zhang O. Caglayan I.D. Jenkinson S. Bonsall J. Wang M. Huang X.P. Yan 《Transportation Research Part D: Transport and Environment》2012,17(6):478-486
This paper develops a subjective generic methodology for providing ship owners with a transparent evaluation tool for selecting their preferred NOx and SOx control techniques. We quantitatively analyse the merits of the control methods available in marine air pollution control practice using data collected from shipping companies, shipyards and maritime academies. We also prioritize the applicable control techniques with respect to operational shipping environments. 相似文献
988.
Dong Sik Han Nak Won Choi Sung Lai Cho Jin Saeng Yang Kwang Suk Kim Wan Suk Yoo Chung Hwan Jeon 《Transportation Research Part D: Transport and Environment》2012,17(7):519-524
This study develops a gradient-sensitive driving cycle for vehicles in military areas with paved and unpaved roads over steep and undulating terrain. The methodology develops the driving cycle using micro-trips extracted from real-world data taking into account factors that affect fuel consumption. The accuracy of cycle depended on the root mean square error and information value. 相似文献
989.
In this study, for marine application purposes, we evaluated the effect of process parameter and particle loading on the microstructure, mechanical reinforcement and corrosion resistance properties of a Zn-TiO2-WO3 nanocomposite produced via electrodeposition. We characterized the morphological properties of the composite coatings with a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS). We carried out mechanical examination using a Dura Scan hardness tester and a CERT UMT-2 multi-functional tribological tester. We evaluated the corrosion properties by linear polarization in 3.5% NaCl. The results show that the coatings exhibited good stability and the quantitative particle loading greatly enhanced the structural and morphological properties, hardness behavior and corrosion resistance of the coatings. We observed the precipitation of this alloy on steel is greatly influenced by the composite characteristics. 相似文献
990.
Hugh S. Turner 《Maritime Policy and Management》2000,27(3):283-301
The competitive characteristics of the North American seaport industry have, in theory, been causally linked to excess investment and low terminal throughput productivity. This paper empirically examines the link between seaport authority container terminal leasing policy and throughput productivity. Recent advances in inventory theory applied to service industries suggest the pooling of demand uncertainty can yield lower costs without sacrificing customer service. This concept is applied to a container seaport using simulation. The effort compares key output measures from a realistic base case model of the seaport to those generated by an alternative terminal leasing policy. It is shown that the pooling of demand in a common-user seaport reduces total vessel time in port by 17.1% with no reduction in TEU throughput. Throughput productivity is improved for the highest capacity terminals, while lower capacity terminals are made available for additional users or alternative uses. 相似文献