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排序方式: 共有882条查询结果,搜索用时 15 毫秒
831.
C. L. Myung H. Lee K. Choi Y. J. Lee S. Park 《International Journal of Automotive Technology》2009,10(5):537-544
This study was focused on experimental comparisons of the effects of various vehicle certification modes on particle emission
characteristics of light-duty vehicles with gasoline, diesel, LPG, and low-carbon fuels such as bio-diesel, bioethanol, and
compressed natural gas, respectively. The particulate matter from various fueled vehicles was analyzed with the golden particle
measurement system recommended by the particle measurement programme, which consists of CVS, a particle number counter, and
particle number diluters. To verify particle number and size distribution characteristics, various vehicle emission certification
modes such as NEDC, FTP-75, and HWFET were compared to evaluate particle formation with both CPC and DMS500. The formation
of particles was highly dependent on vehicle speed and load conditions for each mode. In particular, the particle numbers
of conventional fuels and low-carbon fuels sharply increased during cold start, fast transient acceleration, and high-load
operation phases of the vehicle emission tests. A diesel vehicle fitted with a particulate filter showed substantial reduction
of particulate matter with a number concentration equivalent to gasoline and LPG fuel. Moreover, bio-fuels and natural gas
have the potential to reduce the particulate emissions with the help of clean combustion and low-carbon fuel quality compared
to non-DPF diesel-fueled vehicles. 相似文献
832.
Water management is an important factor in the optimal performance of a polymer electrolyte fuel cell (PEFC). In this paper,
a PEFC model that facilitates the control of PEFC membrane humidity is presented. An efficient modeling procedure using a
combination of mathematical and experimental techniques is proposed. A simple mathematical structure for the model is adopted,
and experiments to measure PEFC irreversibilities and net water transport across the membrane electrode assembly (MEA) are
performed. The developed PEFC model effectively quantifies the irreversibilities in the PEFC output voltage and clarifies
the relationship between PEFC performance and steady state water transport through the MEA. The proposed modeling procedure
can effectively save time and cost during the controller / control algorithm design phase in PEFC system development. 相似文献
833.
大跨悬索桥箱形钢桁架梁的综合疲劳评定方法研究 总被引:1,自引:1,他引:0
根据大跨桥梁铜箱梁各类构件的受力特点建立了确定钢箱梁关键疲劳构件的评价模型,提出了基于结构有限元分析、应变监测信息、构件分级系统和桥梁结构人工检测等多方面信息综合评定关键疲劳构件的方法。以某大跨悬索桥钢箱梁结构为例,结合结构有限元数值计算和结构健康监测系统确定的关键钢箱梁截面,针对关键截面上的主要构件分布,利用应变传感器输出信息、结构有限元分析得到的应力分布信息、人工检测信息和桥梁主要构件的危险等级和易损等级信息,结合层次分析法和模糊综合评判理论确定了影响钢桥构件疲劳评定的各因素的权重,用综合隶属度评分法进行关键疲劳构件的等级评定。 相似文献
834.
The dynamic stability of a vehicle depends on various maneuvering features, such as traction, braking, and cornering. This
study presents nonlinear vehicle models for estimating the stability region and simulating the dynamic behavior of a vehicle.
Two types of vehicle models were found by considering the degrees of freedom and linearity. A simple model with nonlinear
tire dynamics is useful for determining the stability region, while a complex model (a multi-body dynamic model in MSC.ADAMS)
is appropriate for carrying out accurate simulations. Actual data for a mid-sized passenger car were used, and the models
were validated by comparison with test results. 相似文献
835.
S. Li J. Wang K. Li X. Lian H. Ukawa D. Bai 《International Journal of Automotive Technology》2010,11(1):81-87
In order to capture drivers’ car-following characteristics and apply this information to the design of an Adaptive Cruise
Control algorithm, this paper builds a driver car-following model with vehicle speed-dependent control gains. Proposed for
use with heavy-duty truck drivers, we introduced the concept of driver sensitivity to tracking errors, identified driver’s
sensitivity to tracking errors and analyzed quantitatively the relationship between control gain and vehicle speed. To model
the driver characteristics precisely and concisely, a SVE/SDE (Sensitivity to Velocity Error/Sensitivity to Distance Error)
based linear car-following model was built and a nonlinear optimization algorithm was adopted to identify the model parameters.
When validating the model accurancy, we proposed a comparative verification method based on hypothesis-testing theory here
to reduce the influence of randomicity in the drivers’ manipulation. The modeling and verification indicate that the proposed
car-following model is superior to the tranditional linear car-following model, but its structure still approximates linear,
which implies it is applicable for the design of a vehicular following controller. 相似文献
836.
S. -S. Cho C. S. Shin C. S. Lee H. Chang K. W. Lee 《International Journal of Automotive Technology》2010,11(1):75-80
An engine cylinder head-block joint is a gasketed, bolted joint. Assessment of sealing performance and fatigue durability
of the joint during engine development relies entirely on the engine dynamometer test because the rig test cannot mimic the
engine run condition and finite element analysis employs gasket and bolt models that are too simple to provide the stress
data for fatigue assessment. This paper introduces finite element-based assessment of the gasket and the bolt and a model
that improves the analysis accuracy without increasing computation time. Experimental data for the deformation of joint members
under thermo-mehanical load are presented to demonstrate the accuracy of the model. 相似文献
837.
There has been recent interest in a new engine type, Homogeneous Charge Compression Ignition (HCCI), to combine the advantages
of SI and CI engines. In this paper, a locally deterministic approach is employed to consider spatial inhomogeneities using
the KIVA-CHEMKIN package. Validation is performed for two experimental HCCI engines fueled, respectively, by hydrogen and
n-heptane. The full mechanism for hydrogen and a skeletal mechanism for n-heptane are used for combustion chemistry. Differences
in the reaction flow paths are shown at ignition and the heat release reaction stages of the two fuels. Results show good
agreement between measured and calculated pressures for different initial mixture temperatures with estimated residual fractions.
A parametric study is performed in both engines to consider the influences of the physical parameters wall temperature, swirl
ratio and global equivalence ratio. The ignition time of n-heptane is shown to be relatively insensitive to variations in
these parametric due to its two-stage ignition behavior. 相似文献
838.
H. Liu G.N Liu K J Huo T Liu X H Zhang K Liu K Tao Y. J. Liu . Mechanical Engineering School Xi''''an Jiaotong University Xi''''an China . Strength Centre Zhengzhou Research Institute of Mechanical Engineering Zhengzhou China . Fo 《上海交通大学学报(英文版)》2000,(1)
IntroductionThefiwtee1emenmethod(FEM)playsanextrmelyimPortantroleintheanalysesofengineeringproblems.ForalongtimethismethodhasmainlybeenaPPliedinthelinearfieldandshownitsgreatpower.HoweveealOtofnonlinearengineeringPrOblemsWhichcanneitherbesimPlyreducedtolinearonesnorrCPresentedbylinearlyanalogywhichshallchnsethePfacticalconditionsrelativelymuch,havechallengedfiniteelementmethod(FEM).RecentymuchProgresshasbeenmadebothinthemathematicalandmechanicaltheoryandthecomPulertechnologysothatevent… 相似文献
839.
A multilevel decentralized control scheme, the cascading technique, with application to the regulation of traffic on an urban freeway is presented. Performance of the decentralized system is compared to the performance of a centralized and a fixed time control structure. It is shown that the decentralized structure performs better than the centralized structure when incidents (lane closures) occur on the freeway. The freeway is modeled in terms of the aggregate variables section density and section speed, and is considered as a system of interconnected subsystems. 相似文献
840.
This paper investigates, for the first time, the relationship between prices and trading activity in a market where real assets are traded, i.e. in the sale and purchase market for second-hand dry bulk vessels. Investigation of this issue is of interest since the level of trading activity may contain information about the sentiment and the future direction of the prices in the market. Several important conclusions emerge from this analysis. It is found that price changes are useful in predicting trading volume, which suggests that higher capital gains encourage more transactions in the market. Additionally, it seems that volume has a negative impact on the volatility of price changes. More specifically, in contrast to what is reported for financial markets, we find evidence that, in the market for ships, increases in trading activity lead to a reduction in market volatility. This can be explained by the unique underlying characteristics of the market for ships, including thin trading, which imply that increases in trading activity result in price transparency and stability. These findings indicate that practitioners in the market may use the information contained in the level of trading activity so as to guide their market decisions in the sale and purchase market. 相似文献