• International Journal of Highway Engineering
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• v.10 no.4
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• pp.161-170
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• 2008

This study deals with the accident models by vehicle type. The goal is to develop the accident models by vehicle type using the data of 143 4-legged signalized intersections in Cheongju. In pursuing the above, this study gives the particular attentions to explaining the relationships between the values of EPDO(equivalent property damage only) and the traffic and geometric elements. The main results analyzed are the followings. First, 6 negative binomial models are developed, which are all significant at the 90% confidence level. Second, the values of ${\rho}^2$ by vehicle type are 0.14307(auto), 0.35556(large van), 0.21684(small van), 0.205152(motocycle), 0.32338(light-duty truck) and 0.29046(heavy-duty truck), that are all analyzed to be statistically significant. Finally, the common variable included in all models is ADT(average daily traffic), and the specific variable(SV) of auto is analyzed to be the sum of lane width of main road, SV of large van is the average yellow time, and SV of small van is the difference in the number of lane between main and minor road.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1117-1119
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• 2001

This paper describes the forward type pulse power supply using a Power-MOSFET in the view of commercialization. The principle of basic operating and the operating characteristics of the forward type pulse power supply are estimated by the switching frequency, coupling factor and duty ratio. It is shown that theoretical and experimental results are in good agreement by comparing simulation and experimental results when a lamp type ozonizer can be used as a load. Also, experimental results indicate that the discharge and ozone concentration characteristics of the manufactured pulse power supply is more improved compare to the conventional pulse power supply[5]. This proposed supply show that it can be practically used as a pulse power supply in various environment improvement facilities.

• Tribology and Lubricants
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• v.14 no.1
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• pp.45-53
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• 1998

Friction and wear test for two kinds of Cu-based sintered metallic friction material against cast iron disk was carried out by plate-on-disk type friction and wear tester to investigate the friction and wear characteristics of brake system in severe condition. In this experimental study, the counter specimen was cast iron which is being used generally in brakes of heavy duty equipments. Test friction materials were A type which was manufactured by foreign company and B type by domestic company. Friction coefficient and wear volume were measured and compared with each other. The experiment was performed under room temperature. The worn surface of cast iron disk and friction material were observed by scanning electron microscope. The temperature of surface of disk was measured continuously by the non-contacting thermometer. It was found that A type friction material had stable friction coefficient over the wide range of sliding condition, but B type friction material had unstable friction coefficient and lower value of 0.2 under the severe sliding condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.195-201
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• 1998

This study aims at the optimal design of rotors and the development of screw type Supercharger of CNG-fueled engine for commercial vehicle. Based on the new rotor profile, an advanced oil free type Supercharger has been developed, which can achieve higher adiabatic efficiency and lower manufacturing cost. The performance test of screw type Supercharger has achieved high volumetric efficiency and the durability on the bench of performance test has also been established in the compact body.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.6
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• pp.80-88
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• 1989

본 연구에서는 양산중인 배기량 2.4Liter, 간접분사방식의 소형 디젤엔진에서 연소방식을 직접 분사방식으로 연소계를 재설계하여, 간접분사방식과 직접분사방식에 따른 엔진성능상의 차이점을 비교 평가하고, 아울러 직접분사방식에서 연소실 형상과 연소 관련 주요 인자들의 변경시 엔 진성은에 미치는 영향에 대해 고찰하였다. 직접분사방식 엔진은 간접분사방식 엔진에 대해 동 일출력, 동일 Smoke 수준인 경우 10-15%의 연료소비 저감의 효과가 있고, 이에 따라 연소관련 부품의 열부하면에서도 유리하였으나, 소음 및 NOx 배출은 증가하는 것으로 나타났다. 직접분사 연소방식에서는 Deep Bowl 연소실 형태의 Cylindrical Type 과 Re-entrant Type 에서 연비와 Smoke 등을 고려한 최적 분사시기가 Re-entrant Type 에서 4.deg. CA정도 늦었으며, 각기 최적 분사시기에서 스옴, NOx를 비교한 결과 Re-entrant Type이 더 우수하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.7
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• pp.59-69
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• 2012

There are two types of inverters that are generally used in induction heating systems: voltage type inverters and high-frequency half-bridge inverters. This paper proposes a new resonant inverter for induction heating systems using the current type full-bridge method. The proposed method can remove capacitors at the input end, and enables unity power factor operation by preventing phase differences of voltage and current. Furthermore, Zero Voltage Switching (ZVS) which is in tune with current type inverter can be adopted and continuous power adjustment is possible through duty ratio changes and frequency modulation in switching operation. Simulations and experiments showed that the proposed current type full-bridge resonant inverter could be used for unity power factor control and ZVS operation in induction heating systems.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.146-154
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• 1997

Solenoid-folw control type ABS is used with a 'dump and reapply' pressure control arrangement instead of using 2/2 (normal open/close) solenoid valves in convensional systems(sol. -sol. control type), a flow control valve is used which replaces the (no) inlet valve. The flow control valve controls fluid flow providing a nearly constant reapply rate( .theta. ) after the dump plase of ABS operation. In this study, to investigate a characteristics of brake pressure by PWM control, test rig was consisted of ABS hydraulic modulator, digital controller, pneumatic power supply and brake master cylinder. For comparison with experi- mental results, system modelling and computer simulation were performed. As a result, experiment results showed fairly agreement with the simulation. Also, it is shown that the pressure gradient (tan .theta. ) is affected by pressure, frequency, duty ratio and expressed with an exponential funtion.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1154-1164
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• 2002

Losses on the turbine consist of the mechanical loss, tip clearance loss, secondary flow loss and blade profile loss etc.,. More than 60 % of total losses on the turbine is generated by the two latter loss mechanisms. These losses are directly related with the reduction of turbine efficiency. In order to provide a new design methodology for reducing losses and increasing turbine efficiency, a two-dimensional axial-type turbine blade shape is modified by the optimization process with two-dimensional compressible flow analysis codes, which are validated by the experimental results on the VKI turbine blade. A turbine blade profile is selected at the mean radius of turbine rotor using on a heavy duty gas turbine, and optimized at the operating condition. Shape parameters, which are employed to change the blade shape, are applied as design variables in the optimization process. Aerodynamic, mechanical and geometric constraints are imposed to ensure that the optimized profile meets all engineering restrict conditions. The objective function is the pitchwise area averaged total pressure at the 30% axial chord downstream from the trailing edge. 13 design variables are chosen for blade shape modification. A 10.8 % reduction of total pressure loss on the turbine rotor is achieved by this process, which is same as a more than 1% total-to-total efficiency increase. The computed results are compared with those using 11 design variables, and show that optimized results depend heavily on the accuracy of blade design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2210-2220
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• 2009

Independent-suspension type axles for heavy duty special vehicles are usually produced by only a few specialized companies. The special techniques, such as designing, producing, testing techniques has been unveiled. The test of durability with the vehicle in which is installed a prototype taking several years is required for setting the designing parameters. In this research, through-drive the core-component of the independent-suspension type axle has been tested with the reverse engineering and the testing methods for the confirmation of the accomplishment in the development goal has been suggested. Also the prototype is developed from designing and testing the design with the CAD and CAE tools. As a result, the process and testing methods studied in this research are useful in the development of power train.

• Journal of Korean Academy of Nursing Administration
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• v.1 no.2
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• pp.325-337
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• 1995

This study attempted to increase quality of nursing care by assessing the nurses' attitudes for computerization in nursing practice and ensuring right recognition and attitude for computerized system. Study subjects are 311 nurses who are working at 4 general hospitals. Those hospitals are selected according to the degree of computerized in Kyoung In Province. Study instrument consists of 20 items and 12 general questionnaire which was developed by Brodt and Stronge(1985) and modified by Lee(1991). Data collection was done from april 19th in 1995 to april 29th. Data gathered were analized number, t-test, ANOVA by using SPSS. The study results are as follows : 1. Study subject's attitude for computer application showed positive response as mean score of 3.44 especially nurses who had experience using computer showed 100% pro-response. 2. Study subject's attitude by age was significant statistically(F=3.9589, p=.0038), among them age 25-30 revealed the highest positive scores, and age 40 showed the lowest positive scores. 3. Study subject's attitude by education level showed no significant difference(F=1.4182, 2437), and those who are more educated showed more positive response. 4. Study subject's attitude by duty years showed no significant difference(F=2.2648, p=.0622), and those who had 7- 9 duty years had the highest positive attitude however those who have 10 duty years showed lowest positive attitude. 5. Study subject's attitude by position revealed no significant difference(F=2.0017, p=.1369), and the charge nurse groups who were using computer showed the highest scores. 6. Study subject's attitude by computerized type showed significant difference(F=23.9665, p=.0000), and G hospital which had computer system in nursing area obtained the highest positive scores. 7. study subject's attitude by presence of computer education showed no significant differenec(F=.9002, P=.3435), and non computer educated groups showed the highest positive response. 8. Study subject's attitude by computer education place revealed no significant difference(F=4.3723, p=.0020). and the groups who were taught individually or in the institution obtained the highest positive scores. 9. Study subject's attitude by duty year computer use showed no significant response(F=.9591, P=.3282), and groups of computer use showed the high degree of positive response. 10. Study subject's attitude by duty year using computer showed significant difference(F=5.9174, p=.0009),and the groups using computer for 6 years or group of 4-6 years showed the highest degree of positive response and the groups using computer for 1 year showed the lowest degree of positive response.