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231.
D. H. Kim J. M. Lee E. H. Park J. H. Song S. I. Park 《International Journal of Automotive Technology》2011,12(3):409-416
A comprehensive study evaluating the performance of biobutanol-blended gasoline in passenger cars was conducted because biobutanol
is considered a better biofuel than bioethanol as it has no water solubility and it has a higher caloric value, giving it
a higher energy value. Several kinds of samples—suboctane gasoline, 8 volume percentage and 16 volume percentage biobutanol—blended
gasoline, and a 10 volume percentage MTBE-blended market sample (as the oxygencontaining gasoline)-were tested to evaluate
the engine performance in terms of the detergency of the intake valves and combustion chambers, power, emissions, and fuel
efficiency. Additionally, the toxicity of the emissions from these biobutanolblended samples was tested in order to assess
the viability of biobutanol as one of the competitive potential substitutes for MTBE as an oxygenator in the near future.
The results show that biobutanol-blended gasoline samples had relatively better detergency, relatively higher power, and similar
levels of emissions compared with those of MTBE-blended gasoline. Formaldehyde was emitted from all of the samples at almost
the same levels and within the error range, whereas biobutanolblended gasoline samples emitted approximately three times the
amount of acetaldehyde than did the suboctane gasoline. This study shows that biobutanol is one of the best alternative bioalcohol
fuels for use in the near future. 相似文献
232.
W.-H. Cho J.-G. Ih S.-H. Shin J.-W. Kim 《International Journal of Automotive Technology》2011,12(3):443-450
In this paper, a method to establish a decision criterion to evaluate the quality of small window motors using sound quality
(SQ) metrics is suggested. Although the sound level radiated from the motor is relatively small compared to other sounds in
a car, the sound from an abnormal motor gives an uncomfortable feeling and the impression of abnormal operation, which can
lead to customer complaints. To construct an objective decision criterion, the correlation between the SQ metrics and the
subjective decision on the passing or failure of the motor were investigated. Four representative SQ metrics, viz., loudness,
sharpness, roughness, and fluctuation strength, were calculated for the collected samples. It was observed that the loudness
and roughness of the motor sample group classified as abnormal was higher than those of the normal motors. For a single figure
rating for motor quality, an evaluation index for the motor sound was generated by combining the correlated SQ metrics with
proper weightings. Evaluation results on the specimens that were not employed in generating the quality evaluation index showed
a reasonable agreement with the subjective test at 73%. The suggested quality check method can replace the current subjective
decision procedure to identify the faulty motors. 相似文献
233.
Y. Kim S. Choi J. Lee W. Yoo J. Sohn 《International Journal of Automotive Technology》2011,12(4):521-527
In this study, a large bus is tested to measure its dynamic response by the single-lane change test and the rapid stop test.
A full car model is established by ADAMS/Car for computer simulation. For multibody modeling of a large bus, user-defined
templates are used in the simulation. Simulation results of the single-lane change test and the rapid braking test are compared
to the results of the physical experiments, in which several sensors are installed to measure the vehicle’s responses. The
results obtained from the simulation show good agreement with the tests’ results. A dynamic model for the MR(magnetic-rheological)
damper is also developed by employing the Magic Formula model, which is widely used in the nonlinear modeling of a tire. Bump
simulation of a full car with the MR damper is carried out to verify the performance of the MR damper. The comparison of the
simulation results obtained with the MR damper model to the results obtained with the traditional passive damper model showed
improved response of the vehicle with the MR damper. 相似文献
234.
This paper discusses the final investigation into the effect of fuel stratification on flame propagation. In previous works,
the characteristics under the no port-generated swirl condition and the low-swirl condition were considered. For this purpose,
the initial flame development and propagation were visualized under different axially stratified states in a modified optical
single-cylinder SI engine. The images were captured by an intensified CCD camera through the quartz window mounted in the
piston. Stratification was controlled by the combination of the port swirl ratio and injection timing. These were averaged
and processed to characterize the flame propagation. The flame stability was estimated by the weighted average of flame area
and luminosity. The stability was also evaluated through the standard deviation of flame area and propagation distance and
through the mean absolute deviation of the propagation direction. The results show that the LML is expanded remarkably under
the high-swirl cases up to the highest relative AFRs of 1.71 and 1.75 between 140 and 160CA. In addition, similar to the low-swirl
condition, the flame-flow interaction determines the direction of flame propagation, and the governing roles of the two factors
vary according to the swirl level; the flow is more important at the higher swirl conditions, and the flame is more important
at the lower swirl condition. Finally, fast and stable flame propagation can be achieved under the preferably stratified condition,
which is induced by the suitable combination of the high swirl and injection timing. 相似文献
235.
A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous (ARMAX) input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this paper, the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input a... 相似文献
236.
237.
Risk management is an inherent part of supplier selection. While companies are enjoying the benefits of outsourcing, risks brought by this practice should be taken into account in the process of decision making. This paper presents a multiobjective stochastic sequential supplier allocation model to help in supplier selection under uncertainty. Demand for products, capacities at suppliers as well as transportation and other variable costs are the main sources of uncertainty and are modeled using probability distributions. Disruptions are exogenous events and the model provides proactive mitigation strategies against disruptions by assigning backup suppliers who can be used in case of a default at a primary supplier. When there is no disruption, the model’s solution is an optimal supplier order assignment, considering operational risks. 相似文献
238.
Terry L. Friesz Taeil Kim Changhyun Kwon Matthew A. Rigdon 《Transportation Research Part B: Methodological》2011,45(1):176-207
In this paper we present a dual-time-scale formulation of dynamic user equilibrium (DUE) with demand evolution. Our formulation belongs to the problem class that Pang and Stewart (2008) refer to as differential variational inequalities. It combines the within-day time scale for which route and departure time choices fluctuate in continuous time with the day-to-day time scale for which demand evolves in discrete time steps. Our formulation is consistent with the often told story that drivers adjust their travel demands at the end of every day based on their congestion experience during one or more previous days. We show that analysis of the within-day assignment model is tremendously simplified by expressing dynamic user equilibrium as a differential variational inequality. We also show there is a class of day-to-day demand growth models that allow the dual-time-scale formulation to be decomposed by time-stepping to yield a sequence of continuous time, single-day, dynamic user equilibrium problems. To solve the single-day DUE problems arising during time-stepping, it is necessary to repeatedly solve a dynamic network loading problem. We observe that the network loading phase of DUE computation generally constitutes a differential algebraic equation (DAE) system, and we show that the DAE system for network loading based on the link delay model (LDM) of Friesz et al. (1993) may be approximated by a system of ordinary differential equations (ODEs). That system of ODEs, as we demonstrate, may be efficiently solved using traditional numerical methods for such problems. To compute an actual dynamic user equilibrium, we introduce a continuous time fixed-point algorithm and prove its convergence for effective path delay operators that allow a limited type of nonmonotone path delay. We show that our DUE algorithm is compatible with network loading based on the LDM and the cell transmission model (CTM) due to Daganzo (1995). We provide a numerical example based on the much studied Sioux Falls network. 相似文献
239.
This paper establishes a link between an activity-based model for the Greater Toronto Area (GTA), dynamic traffic assignment,
emission modelling, and air quality simulation. This provides agent-based output that allows vehicle emissions to be tracked
back to individuals and households who are producing them. In addition, roadway emissions are dispersed and the resulting
ambient air concentrations are linked with individual time-activity patterns in order to assess population exposure to air
pollution. This framework is applied to evaluate the effects of a range of policy interventions and 2031 scenarios on the
generation of vehicle emissions and greenhouse gases in the GTA. Results show that the predicted increase of approximately
2.6 million people and 1.3 million jobs in the region by 2031 compared to 2001 levels poses a major challenge in achieving
meaningful reductions in GHGs and air pollution. 相似文献
240.
Younes HamdouchH.W. Ho Agachai Sumalee Guodong Wang 《Transportation Research Part B: Methodological》2011,45(10):1805-1830
In this paper, we propose a new schedule-based equilibrium transit assignment model that differentiates the discomfort level experienced by sitting and standing passengers. The notion of seat allocation has not been considered explicitly and analytically in previous schedule-based frameworks. The model assumes that passengers use strategies when traveling from their origin to their destination. When loading a vehicle, standing on-board passengers continuing to the next station have priority to get available seats and waiting passengers are loaded on a First-Come-First-Serve (FCFS) principle. The stimulus of a standing passenger to sit increases with his/her remaining journey length and time already spent on-board. When a vehicle is full, passengers unable to board must wait for the next vehicle to arrive. The equilibrium conditions can be stated as a variational inequality involving a vector-valued function of expected strategy costs. To find a solution, we adopt the method of successive averages (MSA) that generates strategies during each iteration by solving a dynamic program. Numerical results are also reported to show the effects of our model on the travel strategies and departure time choices of passengers. 相似文献