• 대한임베디드공학회논문지
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• 제10권2호
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• pp.91-99
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• 2015

The electric power consumed by the embedded devices has become a critical issue because the reduction of power consumption is an important factor to prolong the battery-operated devices' lifetime. Many researches and techniques to reduce the power consumption have been proposed and developed but any power method cannot guarantee optimal power consumption of an embedded device - it would be faced with numerous situation - in all ways. Specifically, power researches for embedded devices deployed in the industry field have hardly been done. In this paper, low power service is proposed to minimize power reduction with the several usage status of embedded devices in the industry field. The usage status is basically classified according to the distance between the device and the user which is obtained by the ultrasonic and PIR sensor. The performance evaluation shows that the proposed scheme can reduce the power consumption by up to 45.3% compared to the device with no power reduction scheme. It also shows that the power consumption of the proposed scheme is 5.2% ~ 16.8% lower than that of the timeout scheme.

• 대한치과기공학회지
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• 제33권4호
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• pp.529-538
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• 2011

Purpose: The purpose of this study was to investigate the factors affecting turnover and job satisfaction, to reduce turnover rate of dental technician. Methods: Subjects included dental technicians in the metropolitan areas of the cities of Daegu and Gyeong-buk. Surveys were filled out by consenting dental technicians. Statistical analysis was done using the Statistical Package for Social Sciences version 18.0 for Windows. We determined frequencies and percentage, calculating means, and standard deviations, and determining statistical significance using t-tests, analysis of variance. Results: Job satisfaction showed differences in General characteristics associated with gender, age, monthly salaray, education. Turnover intention showed differences in General characteristics associated with age, monthly salaray. Job satisfaction showed differences in dental laboratory characteristics associated with Career, Working time. Turnover intention showed differences in dental laboratory characteristics associated with working time. Conclusion: In order to reduce turnover rate of dental technician, Job satisfaction of dental technicians have to find ways to improve. The comprehensive and reliable research which measures job satisfaction of dental technician is necessary.

• 스마트미디어저널
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• 제11권7호
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• pp.70-75
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• 2022

2019년 정부는 경제성이 예비타당성조사 통과의 결정적 요소로 작용하는 문제 개선을 위해 종합평가의 경제성 항목 가중치 최대치를 50%에서 45%로 축소하도록 제도를 개선하였다. 이 연구는 2019년 제도개선에 따른 효과를 분석하기 위한 것으로 제도 개선 전과 후의 차이를 검증하였다. 회귀분석과 상관관계 분석결과 두 기간 모두 높은 상관성을 보였으며, Z검증을 통한 차이는 통계적으로 유의미하지 않은 것으로 분석되었다. 이 결과는 경제성의 영향력을 축소하기 위한 제도 개선이 효과가 없었다는 것을 의미한다. 따라서 종합평가 각 항목의 가중치를 기존 사업 등에 다양하게 대입해 재평가 해보는 등의 연구를 통해 보다 실효성 있는 종합평가 연구 설계 논의가 필요할 것으로 판단된다.

• 한국환경교육학회지:환경교육
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• 제25권1호
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• pp.15-24
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• 2012

The goal of this study, as an effort to reduce national greenhouse gas (GHG) emissions, is to calculate the carbon footprint of students based on the commute pattern of high school students in big (Seoul), middle (Suwon) and small (Icheon) size city. By conducting a survey, the commute pattern and method of students as well as students' carbon footprint were evaluated. As a result, the carbon footprint of the high school student in Icheon ($1.698kgCO_2$) had 2~3 times higher than student's carbon footprint in Seoul ($0.623kgCO_2$) and Suwon ($0.699kgCO_2$). One of the reasons for the different carbon footprint result between big and small city was whether the public pedestrian facilities and a bicycle path or not. Based on our research results, we pointed out the problems and suggested some ways to reduce carbon footprint of students.

• 한국자동차공학회논문집
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• 제24권1호
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• pp.47-52
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• 2016

Miller timing is one of the promising ways which can improve the fuel consumption of internal combustion engines. Indeed, Miller timing employing an early intake valve close is widely applied to large diesel and gas engines to enhance performance and reduce NOx emissions. In this study, performance evaluation is carried out by 1-D cycle simulation in order to estimate the effect of Miller CAM timing before BDC for a 32 L turbocharged diesel engine. To optimize Miller CAM timing, a single stage turbocharger is matched with an early intake valve close since boost pressure is a significant parameter that can control compression work in a turbocharged engine. The engine simulation result shows that there is enough potential to improve fuel consumption rate and also reduce NOx emissions at the same time.Abstract here.

• 전기학회논문지
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• 제65권6호
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• pp.1007-1012
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• 2016

Induction motors are used widely in driving load of a fluid, such as a pump or a fan in the industry. Induction motor has been generated the voltage drop by the occurrence of a high current during startup. In addition, high start-up current can act as a mechanical stress on the shaft of the motor. So there is need a way to reduce the starting current. Soft start method is one of the many ways to reduce the starting current. This method uses silicon-controlled rectifiers(SCRs) for varying value of the voltage applied to the motor. There is a case for fixing or changing the thyristor firing angle to adjust the magnitude of the voltage. Starting power factor of induction motor is very low compared to the normal operation. Soft starting with the firing angle fixed needs to be considered a low power factor at startup. In this study, we compared the direct start characteristics and soft start characteristics considering the low power factor at the time of start-up. It was possible to confirm that the starting current and the voltage drop is present differently according to the firing angle.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.738-745
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• 2004

There are a number of ways to reduce the ground vibrations, one of which is by installing underground walls. Model tests for ground vibration have been conducted in recent years, but limited attention has been paid to underground wall which can reduce high vibrations. Up to date, only barriers have been actually installed in dry sand because of many unknown factors subsisting on the behavior of the ground. The characteristics of vibration sources, ground conditions and wall barriers have not been well understood yet, therefore centrifugal modeling was adopted to examine all these characteristics. This paper describes a ball dropping system, which can generate a pulse wave propagation through soil mass, and the test results show the effectiveness of underground wall barrier in reducing mechanical vibration.

• 한국게임학회 논문지
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• 제13권6호
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• pp.43-52
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• 2013

경로 탐색은 인공지능의 매우 중요한 요소 중의 하나이며, 여러 분야에서 두루 쓰이는 과정이다. 경로 탐색은 매우 많은 연산이 필요하기 때문에 성능에 매우 중대한 영향을 미친다. 이를 해결하기 위해서 연산량을 줄이는 방식의 연구가 많이 진행되었고, 대표적으로 A* 알고리즘이 있으나 불필요한 연산이 있어 효율성이 떨어진다. 본 논문에서는 A* 알고리즘 중 연산 비용이 높은 노드 탐색 수 등 연산량을 줄이기 위해서 가중치 기반의 선수행 A* 알고리즘을 새롭게 제안한다. 제안한 알고리즘의 효율성을 측정하기 위해 시뮬레이션을 구현하였으며, 실험 결과 가중치를 이용하는 방법이 일반적인 방법보다 약 1~2배 높은 효율을 보였다.

• 한국재난정보학회 논문집
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• 제18권3호
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• pp.560-565
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• 2022

연구목적: 물류센터의 유형별 산업재해 발생형태를 분류하여 대책을 수립함으로써 동종 및 유사 재해를 사전에 재해를 예방코자 한다. 연구방법: 국내물류센터에서 발생된 5년간의 유형별 발생형태를 세부적으로 분석하여 개선책을 수립 연구결과: 물류센터에서 발생한 산업재해 분석을 통해서 재해감소 방안을 모색할 수 있었다. 결론: 물류센터의 산업재해 분석을 통해서 재해감소 방안을 제시하므로써 물류센터의 재해율 감소에 도움이 될 것으로 기대된다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.97-98
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• 2011

The HVAC(Heating Ventilation and Air conditioning) system is controlled by two ways, one is ON/OFF control and the other is PWM inverter with V/F. Control of blower with the use of PWM inverter has quite some benefits such as the capability of changing speed, high efficiency and reduced noise level compared with ON/OFF control. But if blower is operated at low speed, high THD generated by decrease of ma, and output voltage lowered in proportion to frequency. To solve these problems, filter should be installed at the output stage of inverter, which can decrease THD but has problems such as increase of volume size and additional braking resistance. This paper proposes the PWAM method which can reduce THD instead of installing the filter at the output stage of inverter. The proposed PWAM method is an inverter modulation method that fixes the modulation index of inverter to reduce THD by varying DC link voltage of inverter unlike conventional PWM method. Finally, the validity of proposed PWAM methods verified by experiments.