• 한국자동차공학회논문집
• /
• 제13권1호
• /
• pp.19-27
• /
• 2005

The spray characteristics of DISI injector has a great role in engine efficiency and emission. Thus, many researchers have been studied to investigate the spray characteristics of hollow cone type and slit type injector which are used in DISI engine. In this study, we tried to provide spray parameters which effect on the spray characteristics such as injection pressure, ambient pressure and ambient temperature. In addition, we calculated $t_b\;and\;t_c$ to investigate the break up mechanism of test injectors and also obtained $C_v$ to evaluate the spray characteristics. From this study, As the ambient pressure increases in case of slit injector, $C_v$ decreases.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
• /
• pp.829-830
• /
• 2006

The line-start permanent magnet synchronous motor has a high efficiency and an advantage in constant speed operation regardless of the effect of load variation. However it is difficult to predict the performance of characteristics accurately, because of the unbalanced starting torque with the initial starting position of the rotor and the generation of a break torque. In this paper the dynamic characteristics of the line-start permanent magnet synchronous motor are described and compared with those of the squirrel-cage induction motor through the simulation to find the characteristics of the permanent magnets and the rotor bars in the line-start permanent magnet synchronous motor.

• 산업경영시스템학회지
• /
• 제37권4호
• /
• pp.193-201
• /
• 2014

This study attempts to utilize the economic efficiency analysis results focused on the break-even point as an indicator for the decision making of commanders and staff. We suggested a method of determining economic life by utilizing logistics information system and commercial program Minitab with a focus on the equipment's operational environment and performance data, whereas previously the equipment's retirement period was simply determined by the current equipment prices and sustainable period.

• 한국산학기술학회논문지
• /
• 제5권4호
• /
• pp.340-344
• /
• 2004

본 논문에서는 상명대학교 통신망 구성과 그 현황 자료를 수집하여 분석하였고, 통신망 트래픽 측정 분석도구를 이용하여 통신망의 트래픽 흐름과 각 장비들의 동작방식과 성능을 측정하였다. 수강신청 기간에 트래픽 흐름과 부하량에 대해 성능평가를 하였으며, 몇몇의 장비들을 추가/변경하여 트래픽을 분산시키는 방안을 제안하여 효율적인 통신망 설계 방안을 제시하였다.

• 한국안전학회지
• /
• 제20권3호
• /
• pp.47-52
• /
• 2005

Recently, power conversion equipment increased rapidly makes a lot of harmonics. Thus, it is growing that wrong operation and break down of sensitive devices. There are two kinds of causes of harmonics. One of them is lots of power conversion equipment as modem controller, inverter, converter and SWS(Switching Mode Power Supply). Another is nonlinear operating machines as transformer and motor. The more nonlinear loads like them grow, the more serious problems as harmonic current to source and low power factor because of increasing reactive power grow. It is installed for reactor and L-C Filter to decrease harmonic in general. This paper analysis and compares two of characteristics and harmonic from reactor and L-C Filter with operation of induction motor and power conversion equipment. In the result, L-C Filter more improves unbalance rate and THD than reactor.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.930-932
• /
• 2005

The line-start permanent magnet synchronous motor has a high efficiency and an advantage in constant speed operation regardless of the effect of load variation. However it is difficult to predict the performance of characteristics accurately, because of the unbalanced starting torque with the initial starting position of the rotor and the generation of a break torque. In this paper the dynamic characteristics of the line-start permanent magnet synchronous motor are described and compared with those of the squirrel-cage induction motor through the simulation to find the characteristics of the permanent magnets and the rotor bars in the line-start permanent magnet synchronous motor.

• Communications for Statistical Applications and Methods
• /
• 제25권6호
• /
• pp.633-645
• /
• 2018

Gaussian error distributions are a common choice in traditional regression models for the maximum likelihood (ML) method. However, this distributional assumption is often suspicious especially when the error distribution is skewed or has heavy tails. In both cases, the ML method under normality could break down or lose efficiency. In this paper, we consider the log-concave and Gaussian scale mixture distributions for error distributions. For the log-concave errors, we propose to use a smoothed maximum likelihood estimator for stable and faster computation. Based on this, we perform comparative simulation studies to see the performance of coefficient estimates under normal, Gaussian scale mixture, and log-concave errors. In addition, we also consider real data analysis using Stack loss plant data and Korean labor and income panel data.

• Korean Journal of Chemical Engineering
• /
• 제35권11호
• /
• pp.2164-2171
• /
• 2018

Heavy duty diesel vehicles deteriorate urban air quality by discharging a large volume of air pollutants such as soot and nitrogen oxides. In this study, a newly introduced auxiliary device a fuel activation device (FAD) to improve the combustion efficiency of internal engines by utilizing the cavitation effect was closely investigated by the fluid flow mechanism via a numerical analysis method. As a result, the FAD contributed to fuel atomization from the injection nozzle at lower inlet pressure by reducing the pressure energy. The improved cavitation effect facilitated fuel atomization, and ultimately reduced pollutant emission due to the decrease in fuel consumption. The axial velocity along the flow channel was increased 8.7 times with the aid of FAD, which improved the primary break-up of bubbles. The FAD cavitation effect produced 1.09-times larger turbulent bubbles under the same pressure and fuel injection amount than without FAD.

• 대한기계학회논문집
• /
• 제16권6호
• /
• pp.1121-1140
• /
• 1992

본 연구에서는 부착형 칩절단구의 경사면 대신에 원고면으로 형성한 형태 칩 절단구를 고찰하고, 재래형과 비교하여 더 효과적인 칩절단구를 개발 실용화하고자 한 다. 가공법으로서는 연속칩의 처리가 가장 곤란한 선삭을, 공작물로서는 연속칩이 가장 잘 생성되는 SM 20 C의 연강을, 공구재료로서는 P계열의 초경합금을 써서 저속에 서 고속절삭속도까지 시험하였다.

• 농촌지도와개발
• /
• 제2권2호
• /
• pp.175-189
• /
• 1995

Poitical demand for decentralization trends in Korea has led the government to plan to localize its agricultural extension system by changing the status of 6,696 extension personnel stationed at the provincial and county level from central government status to local government status as of January 1997. However, serious drawbacks of lowered morale of extension personnel and the financial burden of local governments has not yet been debated extensively for effective personnel management. Some of the findings that emerged from both the analytical and empirical research show the dangers of decentralization such as an increase in disparities, jeopardizing stability, and undermining efficiency. These problems should be considered along with the culture, tradition, and Koreans' attitude towards central and local government. The dangers of decentralization of agricultural extension services in Korea may cause serious problems in allocative efficiency because of a mismatch between available resources and promised expenditures, and in production efficiency because of unproven cost-effective provisions of local governments. It is accepted that the central government can invest more in technology, research, development, promotion and innovation in the agricultural sector. However, changing the status of extension personnel from central government to local government status may lead the best people to leave, lower morale, shake the sense of public service, break networks, and sacrifice investment in research, development and extension. In deciding the future directions for personnel management of agricultural extension services in Korea, maintaining or reinforcing the existing national status of extension personnel should be considered along with a reflection of the basic characteristics of agricultural extension services, linkages of research and extension, the financial burden of local government, specialization of extension personnel, unnecessary duplication of investment among local governments, possible national supports to agricultural research and development, and extension under the WTO systems.