• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.157-165
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• 2001

In the brake systems, it is important to reduce the rear brake pressure in order to secure the safety of the vehicle in braking. So, there was some research that reduced and controlled the rear brake pressure exactly like a LSPV and a ELSPV. However, the previous research has some weaknesses: the LSPV is a mechanical system and its brake efficiency is lower than the efficiency of ELSPV, But, the cost of ELSPV is very higher so its application to the vehicle is very difficult. Additionally, when a fail appears in the circuit which controls the valves, the fail results in some wrong operation of the valves. But, the previous researchers didn't take the effect of fail into account. Hence, the efficiency of them is low and the safety of the vehicle is not confirmed. So, in this paper we develop a new economical pressure modulator that exactly controls brake pressure and confirms the safety of the vehicle in any case using a direct adaptive fuzzy controller.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.119-128
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• 2001

Recently safety systems for the commercial vehicle have been rapidly developed. However, we still have many problems in the vehicle stability and the braking performance. Especially, a commercial vehicle may meet a dangerous braking condition when the vehicle is lightly loaded or empty and the road is wet or slippery. To design the air brake system for commercial vehicles, since the air brake system has many design variables, there must have been intensive researches on a method how to prevent dynamic instability and how to maximize the vehicle deceleration. In this study, mathematical models about an 8$\times$4 vehicle and an air brake system including an ABS controller have been constructed for computer simulation. Also, simple examples are applied to show the usefulness of the computer program. Designers can use this simulation program for understanding the braking characteristics of 8$\times$4 commercial vehicles such as trajectory, braking distance, longitudinal deceleration, lateral deceleration, and yaw rate on various road conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5392-5395
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• 2013

Application of electric wheelchair, sort of wheelchair which is playing important role in transporting patients and old people, has been increasing. In this study, we designed the electric wheelchairs' driving system. Using the multi-step gear, the driving system can get great power, even though the small capacity of motors. First, we designed the multi-step gear, test its bending strength and contact strength, as well as verified its performance. We installed 'B-type electric brake(Multiple plate clutch, Anti-magnetization) in same axle of the driving system, so it is possible to stop under huge torque and small size. Using this driving system of the multi-step gear which we designed, it's possible to improve driving gear efficiency 30% up and create the high-competitive electric wheelchair. And, it is easy to repair and control.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.174-183
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• 2005

A train driving requires to n the fixed distance within given time, and it is desirable to consume low energy if necessary. Reducing energy consumption depends on the train operation modes by either manual or automatic operation. In this article, an operation to reduce energy consumption by changing modes of train operation by a driver without changing the train operation requirement is investigated. The powering model, braking model and consumed energy calculation model are developed, then simulated by using a Matlab software. The accuracy of the train dynamic model established by the simulations is verified by comparing with the real experimental data. Several simulations by various operations in the real track are executed, then the desirable pattern of train driving is found.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.188-194
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• 2005

The direct injection diesel engine is one of the most efficient thermal engines. For this reason DI diesel engines are widely used for heavy-duty applications. But the world is faced with very serious problems related to the air pollution due to the exhaust emissions of diesel engine. So, that is air pollution related to exhaust gas resulted from explosive combustion should be improved. Exhaust Gas Recirculation(EGR) is a proven method to reduce NOx emissions. In this study, the experiments were performed at various engine loads while the EGR rates were set from $0\%$ to $30\%.$ The emissions trade-off and combustion of diesel engine are investigated. The brake specific fuel consumption rate is very slightly fluctuated with EGR in the range of experimental conditions. The ignition delay increased with increasing EGR rate. The maximum value of premixed combustion for the rate of heat release is increased with increasing EGR rate. NOx emissions are decreased with increasing EGR rate at high load and high speed. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke emissions.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.3
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• pp.62-68
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• 2016

According to the accident/incident reports of aircraft runway overruns and excursions, it generally shows runway friction reduction and aircraft braking capability deterioration are the basic causes due to adverse weather. Although surface of paved runway gets wet, it also should give good friction capability. If runway surface is worn due to long time usage and friction capability is reduced due to rubber accumulation or weather conditions(snow, rain, ice etc.), airport authorities should rapidly measure friction coefficient and give them to relevant persons through aeronautical information system and support safe takeoff and landing. Operation wise, these information of friction coefficient reduction should be lead to aircraft performance adjustments, but the data from manufacturer(performance manual) are airplane braking coefficient and the data from airport authorities are vehicle measured braking coefficient. But these two data are considered as the same meaning although the definite relationship between them is not clarified yet. So I am trying to search for the technical background of these two data and suggest reasonable method to use them efficiently.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.85-90
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• 2007

The main function of the Forward Vehicle Collision Warning System (FVCWS) is to warn a driver when he or she experiences dangerous situations caused by a forward vehicle. Warning distance algorithms under same dangerous circumstances are often various depending on automobile manufacturers and component suppliers. Human factors also should be considered to warn the driver at an adequate warning distance. Therefore, it is necessary to develop a system for evaluating the pertinent warning timing in an identically dangerous situation. The system consists of sensors for measuring speed and acceleration of subject vehicle and target vehicle, controllers to follow the velocity profile properly, and wireless telecommunication equipments for receiving or transmitting the measured data in a real-time. According to actual field tests, it is shown that the developed system is suitable to evaluate warning distance of FVCWS.

• Journal for History of Mathematics
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• v.28 no.5
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• pp.207-231
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• 2015

We discuss several issues relating to the meaning of the terms and phrases in the first half of Chapter One fang tian 方田章 of ${\ll}$Jiuzhang suanshu九章算術${\gg}$. I understood those issues more clearly in the course of the translation of ${\ll}$Kujang sulhae 九章術解${\gg}$. Those are '今有' in the beginning of each problem, '積' and '冪' in the method of square field 方田術, '齊' in the method of reduction to a common denominator 齊同術, '經' and '有分者通之重有分者同而通之' in the method of dividing fraction 經分術, '實如法而一' in the calculation using the rods, '兩邪' in the method of trapezium field with a perpendicular side 邪田術. We may find out the value of ${\ll}$Kujang sulhae 九章術解${\gg}$ through our discussion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5082-5088
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• 2015

In this paper, durability test of 1000cc level gasoline engine has been carried out. Durability test set total 300 hours and WOT condition. Engine torque, power, fuel consumption, blow-by gas flow rate, and oil pressure are measured to analyse performance variation by time. As a result, engine performance of high rpm range gradually reduced by time but for relatively low rpm range shows stable performance. Blow-by gas flow rate shows 0.4% of averaged induction air flow rate, which is excellent rate for 1000cc level gasoline engine. Engine torque and fuel consumption data show the break-in upto 100 hours and aging trend after that. After 300 hours, engine is disassembled and each part is checked for the damage or crack.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.182-185
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• 2011

본 논문에서는 국내 고속철도 차량 즉, 경부고속철도를 운행하는 KTX, KTX산천 그리고 현재 개발중인 HEMU400x을 대상으로 운행속도 및 운행패턴에 따른 열차 소비전력을 분석하였다. 이를 위해, 선로조건을 고려한 차량의 운전속도 조건과 운행시간,소비전력 등을 예측하기 위한 TPS(Train Performance Simulation)프로그램을 이용하였다. 열차운행 시뮬레이션을 수행하기 위해선 차량, 선로, 속도의 기본 데이터를 필요로 한다. 차량에 대한 데이터는 차량의 최고속도, 제동성능, 견인력 등의 기본 성능과 열차편성에 따른 중량, 길이, 동력차량형식, 열차주행저항등에 대한 제원을 요한다. 선로데이터는 운행시간 예측을 대상으로 하는 선로에 대한 거리별 구배 및 선형, 정거장 위치 및 정차시간에 대한 데이터이다. 속도조건은 구배 및 곡선에 대한 선로제한속도로, 선로데이터와 연계하여 각 선로위치별 차량의 제한속도로 이용된다. 본 논문에서는 경부고속철도 구간에서 운행하는 고속차량 3가지를 대상으로 증속에 따른 전력소모량을 비교하였다.