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211.
L. D. K. Nguyen N. W. Sung S. S. Lee H. S. Kim 《International Journal of Automotive Technology》2011,12(3):339-350
The effects of split injection, oxygen enriched air, and heavy exhaust gas recirculation (EGR) on soot emissions in a direct
injection diesel engine were studied using the KIVA-3V code. When split injection is applied, the second injection of fuel
into a cylinder results in two separate stoichiometric zones, which helps soot oxidation. As a result, soot emissions are
decreased. When oxygen enriched air is applied together with split injection, a higher concentration of oxygen causes higher
temperatures in the cylinder. The increase in temperature promotes the growth reaction of acetylene with soot. However, it
does not improve acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction
with soot, the concentration of acetylene in the cylinder is decreased, which leads to a decrease in soot formation and thus
soot emissions. A combination of split injection, a high concentration of oxygen, and a high EGR ratio shows the best results
in terms of diesel emissions. In this paper, the split injection scheme of 75.8.25, in which 75% of total fuel is injected
in the first pulse, followed by 8°CA of dwell time, and 25% of fuel is injected in the second pulse, with an oxygen concentration
of 23% in volume and an EGR ratio of 30% shows a 45% reduction in soot emissions, with the same NOx emissions as in single
injection. 相似文献
212.
D. W. Pi N. Chen J. X. Wang B. J. Zhang 《International Journal of Automotive Technology》2011,12(3):391-399
This paper presents a method for estimating the vehicle side slip angle, which is considered as a significant signal in determining
the vehicle stability region in vehicle stability control systems. The proposed method combines the model-based method and
kinematics-based method. Side forces of the front and rear axles are provided as a weighted sum of directly calculated values
from a lateral acceleration sensor and a yaw rate sensor and from a tire model according to the nonlinear factor, which is
defined to identify the degree of nonlinearity of the vehicle state. Then, the side forces are fed to the extended Kalman
filter, which is designed based on the single-track vehicle model associated with a tire model. The cornering stiffness identifier
is introduced to compensate for tire force nonlinearities. A fuzzy-logic procedure is implemented to determine the nonlinear
factor from the input variables: yaw rate deviation from the reference value and lateral acceleration. The proposed observer
is compared with a model-based method and kinematics-based method. An 8 DOF vehicle model and Dugoff tire model are employed
to simulate the vehicle state in MATLAB/SIMULINK. The simulation results shows that the proposed method is more accurate than
the model-based method and kinematics-based method when the vehicle is subjected to severe maneuvers under different road
conditions. 相似文献
213.
Torque control of engine clutch to improve the driving quality of hybrid electric vehicles 总被引:1,自引:0,他引:1
H. S. Hwang D. H. Yang H. K. Choi H. S. Kim S. H. Hwang 《International Journal of Automotive Technology》2011,12(5):763-768
As a powertrain for hybrid electric vehicles (HEVs), the automatic transmission (AT) is not only convenient for the driver
but also reduces hybridization costs because the existing production line is used to produce the AT. However, it has low fuel
economy due to the torque converter. To overcome this disadvantage, this paper studies HEVs equipped an AT without a torque
converter. In this case, additional torque control is needed to prevent the driving quality from deteriorating. This paper
suggests three different torque control methods and develops a simulator for an HEV that can simulate the dynamic behaviors
of the HEV when the engine clutch is engaged. The HEV drive train is modeled with AMESim, and a controller model is developed
with MATLAB/Simulink. A co-simulation environment is established. By using the developed HEV simulator, simulations are conducted
to analyze the dynamic behaviors of the HEV according to the control methods. 相似文献
214.
OSEK OS (Offene Systeme und deren Schnittstellen für die Elektronik in Kraftfahrzeugen Operating System) is an open, real-time
operating system standard for ECU software in vehicles. Because it was originally designed to be used in an extremely resource-constrained
environment, an OSEK-compliant operating system must incur low processing overhead and memory usage. Unfortunately, as OSEK
OS has evolved over time, it now specifies nontrivial kernel features along with multiple conformance classes and application
modes. This may lead to unwanted dynamic resource usage in a system using OSEK OS unless the standard is carefully interpreted
and designed into an OSEK OS implementation. In this paper, we analyzed the various kernel features of OSEK OS and their interactions
to identify areas in the standard that warrant further resource usage optimization. In particular, we attempted to reduce
the run-time memory footprint. Based on our analyses, we present two kernel mechanisms: (1) stack sharing among tasks and
(2) light-weight ready queue handling specialized for OSEK OS conformance classes. We also offer implementation methods for
the proposed mechanisms by extending OIL and associated tools. Finally, we show the effectiveness of the proposed mechanisms
via extensive experiments. Our mechanisms allow OSEK-based systems to use only 36% of the memory requirements of conventional
OSEK-based systems on average. 相似文献
215.
Jinggao Li I. Kim S. Lee S. Han C. Lee S. Cheon W. Lee K. An G. Cho J. Hwang D. Mun 《Journal of Marine Science and Technology》2011,16(1):76-83
In the shipbuilding industry, different computer-aided design (CAD) systems are used for different design domains, structure, and outfitting. We need to exchange data among different CAD systems such as Tribon, AutoCAD, Intergraph or PDMS to complete the whole design and production process. There are two approaches to data exchange. One is direct translation; the other is indirect translation, which is based on a neutral format. If we use a neutral format, the data specification is open to the public and the design model can be used by other CAD systems, including next-generation CAD systems. In this paper, we propose an indirect method that uses ISO 10303 (STandard for the Exchange of Product model data) AP227 and ISO 15926 to define neutral formats. A separate ShapeDB is constructed to manage the geometry information, referenced to the catalogue data defined by ISO 15926. An experimental implementation for data exchange between Tribon and PDMS is described. 相似文献
216.
Dean A. JonesJulie L. Farkas Orr BernsteinChad E. Davis Adam TurkMark A. Turnquist Linda K. NozickBrian Levine Carmen G. RawlsScott D. Ostrowski William Sawaya 《Research in Transportation Economics》2011,32(1):3-14
International containerized freight movement is a vital part of the supply chain for many companies, and a critical element of moving consumer goods to points of retail sale within the U.S. Containerized imports also present a clear security concern (e.g., terrorists attempting to ship “dirty bombs,” chemical, biological or even nuclear weapons, into the U.S. in a shipping container). The goal of the research presented here is to create a modeling tool for analyzing flows of U.S. imports and exports of containerized freight, and the potential changes in those flows under a variety of conditions (e.g., port disruptions, extensive security-related delays, etc.). Our focus is on movements through maritime container ports, and not overland movements between the U.S. and Canada or Mexico.The network model, referred to as the System for Import/Export Routing and Recovery Analysis (SIERRA), represents container movements between the U.S. and 46 other countries that account for the vast majority of U.S. imports and exports. The SIERRA model is a network equilibrium model that predicts flows between foreign countries and North American ports, the total volumes handled (import and export) by each port, the modal volumes (truck and rail) moving domestically into and out of each port, and volumes between each port and a set of transportation analysis zones within the U.S. 相似文献
217.
Rural seniors are highly dependent on their automobile to meet their trip making needs, yet the effects of aging can make
access to the vehicle difficult or impossible over time. The anticipated growth in the older person population, in concert
with limited travel data available to support rural transportation planning in Canada suggests a disconnect between what rural
older people may require for transportation and the availability of formal alternatives. Many will seek informal alternatives
to driving, such as depending on friends and family, to meet their travel needs, but the degree is not well understood in
the context of their actual vehicle usage and stated ability to adapt. This paper draws from a Global Positioning System (GPS)-based
multi-day travel diary survey of a convenience sample of 60 rural older drivers (29 men, 31 women, average age of 69.6 years)
from New Brunswick, Canada. Participants would rely on “friends and family” for 52% of all trips they undertook as driver
in the survey, “walk or bike” for 14% of trips, and “not take the trip” in 34% of trips if they did not have access to a vehicle.
The formal option of “Transit” was not selected as a viable alternative by any participant for any trip. “Medical trips”,
“Shopping” and “Personal Errands” were the least discretionary of all trip types, yet the most difficult for participants
to find alternate arrangements. This suggests the need to explore different models of service delivery, such as a community-supported,
member-based rural shuttle service with volunteer and paid drivers that build on informal social networks and can provide
service when friends and family are unavailable. 相似文献
218.
Quantifying the benefit of responsive pricing and travel information in the stochastic congestion pricing problem 总被引:1,自引:0,他引:1
Lauren M. Gardner Stephen D. Boyles 《Transportation Research Part A: Policy and Practice》2011,45(3):204-218
This paper is concerned with roadway pricing amidst the uncertainty which characterizes long-term transportation planning. Uncertainty is considered both on the supply-side (e.g., the effect of incidents on habitual route choice behavior) and on the demand-side (e.g., due to prediction errors in demand forecasting). The framework developed in this paper also allows the benefits of real-time travel information to be compared directly against the benefits of responsive pricing, allowing planning agencies to identify the value of these policy options or contract terms in publicly-operated toll roads. Specifically, six scenarios reflect different combinations of policy options, and correspond to different solution methods for optimal tolls. Demonstrations are provided on both the Sioux falls and Anaheim networks. Results indicate that providing information to drivers implemented alongside responsive tolling may reduce expected total system travel time by over 9%, though more than 8% of the improvement is due to providing information, with the remaining 1% improvement gained from responsive tolling. 相似文献
219.
Kara M. Kockelman Jason D. Lemp 《Transportation Research Part A: Policy and Practice》2011,45(8):825-838
Pricing of roadways opens doors for infrastructure financing, and congestion pricing seeks to address inefficiencies in roadway operations. This paper emphasizes the revenue-generation opportunities and welfare impacts of flat-tolling schemes, standard congestion pricing, and credit-based congestion pricing policies. While most roadway investment decisions focus on travel time savings for existing trips, this work turns to logsum differences (which quantify changes in consumer surplus) for nested logit specifications across two traveler types, two destinations, three modes and three times of day, in order to arrive at welfare- and revenue-maximizing solutions. This behavioral specification is quite flexible, and facilitates benefit-cost calculations (as well as equity analysis), as demonstrated in this paper.The various cases examined suggest significant opportunities for financing new roadway investment while addressing congestion and equity issues, with net gains for both traveler types. Application results illustrate how, even after roadway construction and maintenance costs are covered, receipts may remain to distribute to eligible travelers so that typical travelers can be made better off than if a new, non-tolled road had been constructed. Moreover, tolling both routes (new and old) results in substantially shorter payback periods (5 versus 20 years) and higher welfare outcomes (in the case of welfare-maximizing tolls with credit distributions to all travelers). The tools and techniques highlighted here illustrate practical methods for identifying welfare-enhancing and cost-recovering investment opportunities, while recognizing multiple user classes and appropriate demand elasticity across times of day, destinations, modes and routes. 相似文献
220.
S. O. Kang S. O. Jun H. I. Park K. S. Song J. D. Kee K. H. Kim D. H. Lee 《International Journal of Automotive Technology》2012,13(4):583-592
This research aims to develop an actively translating rear diffuser device to reduce the aerodynamic drag experienced by passenger cars. One of the features of the device is that it is ordinarily hidden under the rear bumper but slips out backward only under high-speed driving conditions. In this study, a movable arc-shaped semi-diffuser device, round in form, is designed to maintain the streamlined automobile??s rear underbody configuration. The device is installed in the rear bumper section of a passenger car. Seven types of rear diffuser devices whose positions and protrusive lengths and widths are different (with the basic shape being identical) were installed, and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. The main purpose of this study is to explain the aerodynamic drag reduction mechanism of a passenger car cruising at high speed via an actively translating rear diffuser device. The base pressure of the passenger car is increased by deploying the rear diffuser device, which then prevents the low-pressure air coming through the underbody from directly soaring up to the rear surface of the trunk. At the same time, the device generates a diffusing process that lowers the velocity but raises the pressure of the underbody flow, bringing about aerodynamic drag reduction. Finally, the automobile??s aerodynamic drag is reduced by an average of more than 4%, which helps to improve the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. 相似文献