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111.
Sang-Yeob Kim Kyong-Hwan Kim Yonghwan Kim 《Journal of Marine Science and Technology》2012,17(1):47-58
This paper considers a comparative study on model-scale sloshing tests. There are two primary scopes of this study: the comparison
of sloshing pressure measured in 1/50-scale model tests at Seoul National University (SNU) with (1) the data measured at the
other facility for the same model, and (2) the data measured on a smaller scale model. For the comparative study, model tanks
are excited with the same irregular motions with Froude scale, and sloshing pressure signals are measured at the same locations.
The statistical quantities of 1/50-scale model tests are compared with those of other facility and 1/70-scale model tests.
In this study, it is found that peak pressure measured at SNU are slightly lower than those of other facility, and this difference
may be due to different sensor types and sensing diameters. 相似文献
112.
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
113.
114.
In this study, a control strategy for a dual mode power split-type hybrid electric vehicle (HEV) is developed based on the powertrain efficiency. To evaluate the transmission characteristics of the dual mode power split transmission (PST), a mechanical loss model of the transmission (TM loss) is constructed. The transmission efficiency, including the TM loss, is evaluated for the dual mode PST. Two control strategies for the dual mode PST are proposed. An optimal operation line (OOL) control strategy is developed to maintain a high engine thermal efficiency by controlling the engine operation point on the OOL. A speed ratio (SR) control strategy is proposed to obtain a greater transmission efficiency by shifting the engine operation point when the dual mode PST operates near the mechanical points. Using the TM loss and the proposed control strategies, a vehicle performance simulation is conducted to evaluate the performance of the two control strategies for dual mode PST. The simulation results demonstrate that, for the SR control strategy, the engine efficiency decreases because the engine operates beyond the OOL. However, the transmission efficiency of the dual mode PST increases because the PST operates near the mechanical point where the PST shows the greatest transmission efficiency. Consequently, the fuel economy of the SR control strategy is improved by 3.8% compared with the OOL control strategy. 相似文献
115.
D. O. Kang S. J. Heo M. S. Kim W. C. Choi I. H. Kim 《International Journal of Automotive Technology》2012,13(1):109-122
This study presents the robust design optimization process of suspension system for improving vehicle dynamic performance
(ride comfort, handling stability). The proposed design method is so called target cascading method where the design target
of the system is cascaded from a vehicle level to a suspension system level. To formalize the proposed method in the view
of design process, the design problem structure of suspension system is defined as a (hierarchical) multilevel design optimization,
and the design problem for each level is solved using the robust design optimization technique based on a meta-model. Then,
In order to verify the proposed design concept, it designed suspension system. For the vehicle level, 44 random variables
with 3% of coefficient of variance (COV) were selected and the proposed design process solved the problem by using only 88
exact analyses that included 49 analyses for the initial meta-model and 39 analyses for SAO. For the suspension level, 54
random variables with 10% of COV were selected and the optimal designs solved the problem by using only 168 exact analyses
for the front suspension system. Furthermore, 73 random variables with 10% of COV were selected and optimal designs solved
the problem by using only 252 exact analyses for the rear suspension system. In order to compare the vehicle dynamic performance
between the optimal design model and the initial design model, the ride comfort and the handling stability was analyzed and
found to be improved by 16% and by 37%, respectively. This result proves that the suggested design method of suspension system
is effective and systematic. 相似文献
116.
Junho Cho Tae-Kyung Kim Kyu-Hong Kim Kwanjung Yee 《International Journal of Automotive Technology》2017,18(6):959-971
To reduce the aerodynamic drag, the performance of the underbody aerodynamic drag reduction devices was evaluated based on the actual shape of a sedan-type vehicle. An undercover, under-fin, and side air dam were used as the underbody aerodynamic drag reduction devices. In addition, the effects of the interactions based on the combination of the aerodynamic drag reduction devices were investigated. A commercial sedan-type vehicle was selected as a reference model and its shape was modeled in detail. Aerodynamic drag was analyzed by computational fluid dynamics at a general driving speed on highway of 120 km/h. The undercover reduced the slipstream area through the attenuation of the longitudinal vortex pair by enhancing the up-wash of underflow, thereby reducing the aerodynamic drag by 8.4 %. The under-fin and side air dam showed no reduction in aerodynamic drag when they were solely attached to the actual complex shape of the underbody. Simple aggregation of the effects of aerodynamic drag reduction by the individual device did not provide the accurate performance of the combined aerodynamic drag reduction devices. An additional aerodynamic drag reduction of 2.1 % on average was obtained compared to the expected drag reduction, which was due to the synergy effect of the combination. 相似文献
117.
Joonsoo Han Junho Lee Youngtaig Oh Gyubaek Cho Hongsuk Kim 《International Journal of Automotive Technology》2017,18(6):951-957
Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NOx (Nitrogen Oxides) emission standard. The NOx removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 °C. However, a large amount of NOx is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NOx conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NOx removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 °C compared to 200 °C. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition. 相似文献
118.
Kyung-Jung Lee Jae-Woo Kim Hyuk-Jun Chang Hyun-Sik Ahn 《International Journal of Automotive Technology》2018,19(2):323-330
The performance of automotive electronic control units (ECUs) has improved following the development of multi-core processors. These processors facilitate fast computing performance without increasing clock speed. System developers partition automotive application runnables to have parallelizability and avoid interference between various software modules. To improve the performance of such systems, an efficient scheduler is necessary. In this regard, for multi-core ECUs, the automotive open system architecture (AUTOSAR) suggests partitioned static priority scheduling for parallelized software. In the AUTOSAR approach, clustering and partitioning of runnables for specific cores becomes difficult, but there is no exact criterion followed for partitioning the runnables. Consequently, cores are not balanced against loads, and under contingency conditions, there is a chance that tasks will miss deadlines. In this study, we address this problem by exploring a mixed harmonic runnable scheduling algorithm that includes partitioned scheduling. We tested this algorithm using high load conditions under contingency consequences, and we evaluated it using models of periodic runnables, periodic interrupts, and event-triggered interrupts. The performance parameters considered in this paper are balancing performance and the deadline missing rate. Our results indicate that the proposed algorithm can contribute toward improving the functional safety of vehicles. 相似文献
119.
Dong Won Yi Soung Hie Kim Hyung Rim Choi Nam-Kyu Park Tae-Woo Lee 《Maritime Policy and Management》2013,40(2):155-167
It is an important matter closely connected with saving logistics costs, as well as encouraging national competitive power, to improve the productivity of container terminals by efficient utilization of container terminal resources. In this respect, this paper tries to suggest a conceptual model for sharing container terminal resources, taking as a case study the Gamman Container Terminal (GCT) in the port of Pusan. In so doing, it identifies what kinds of resources can be systematically shared from the viewpoint of their common use and draws some problems resulting from terminal operation by four operators at GCT. The model does not imply the conception that each terminal has its own resources individually, but recommends that tentatively-called Container Terminal Resource Management Center (CTRMC) should be established and operated in order to save operation and investment costs and improve operational efficiency. In addition, the continuous acquisition and life-cycle support (CALS) concept is imbedded in the model so that it can control the supply and demand of resources efficiently by sharing the database, through which the CTRMC can automatically identify the status of the excess or deficit of a certain resource in each berth at GCT. 相似文献
120.
This paper deals with the lane assignment problem in the Automated Highway Systems (AHS). The purpose of lane assignment strategies
is to increase throughput on multi-lane highways with many entry and exit points, based on the itineraries of vehicles using
the highway (point of entry, time of entry and exit point) and the effects of maneuvers. Using partitioned lane assignment
strategies, the lane assignment problem is formulated as an optimization problem to find the proper positions of partitions.
Then the optimal problem is solved using a Genetic Algorithm (GA). The proposed algorithm has been validated by comparing
its solution with that of an all-cases algorithm for a simple case. Moreover, a traffic simulator with a realistic car-following
model as well as lane change logic has been developed. The simulation results show the efficiency of the proposed genetic
algorithm, compared with random assignment algorithms. 相似文献