• International Journal of Control, Automation, and Systems
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• 제6권5호
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• pp.660-669
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• 2008

This paper presents a new carrier based pulse-width modulation (PWM) method for matrix converters. By using the concept of average over one switching period, the modulation algorithm and the required equations are derived to synthesize the desired output voltage and to achieve the controlled input power factor. The proposed method uses a continuous carrier and the predetermined duty ratio signals to directly generate the gating signals and, thus, is referred to as "direct duty ratio PWM (DDPWM)". The feasibility and validity of the proposed method were verified by simulation and experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.294-295
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• 2017

태양광발전시스템은 설비 사용률을 최대화하기 위하여 PV 모듈을 최대 전력점에서 운전하는 MPPT(Maximum Power Point Tracking) 제어가 반드시 필요하다. 기존의 MPPT 알고리즘은 경사법에 기반을 두기 때문에 일정한 MPPT 주기마다 일정한 크기의 PWM Duty 비의 자극을 주고, 그에 따른 출력 전력의 변화를 감지하여 최대 전력점을 향한 다음 운전점을 찾는다. 이러한 MPPT 알고리즘을 실제 날씨 환경에 적용할 때 최대전력을 생산하기 위한 최적의 MPPT 주기와 PWM Duty 비의 변량은 다양한 일사량의 프로파일 형태에 따라 달라진다. 그러므로 최적의 MPPT 주기와 PWM Duty 비의 변량을 결정하기 위해서는 실제 날씨 환경에서 다양한 일사량 프로파일의 패턴에 대한 분석이 필수적이다. 본 논문에서는 대한민국 중부지역의 전형적인 맑은 날씨와 흐린 날씨에서 실제 일사량을 측정, 분석하여 MPPT 목표 효율을 최대화할 수 있는 MPPT 주기를 제시하였다.

• 디지털융복합연구
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• 제11권11호
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• pp.133-141
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• 2013

본 연구의 목적은 공공복지서비스 전달체계 내의 핵심역량이라 할 수 있는 사회복지공무원들의 복지의식이 직무가치관과 직무효과성에 미치는 영향력을 실증적으로 규명하는데 있다. 본 연구가 갖는 함의는 첫째, 사회복지공무원의 복지의식수준을 실증적으로 밝혀내었다는 점에서 의의를 갖는다. 둘째, 사회복지공무원의 복지의식이 직무가 치관과 직무효과성에 미치는 영향을 규명함으로써 사회복지공무원의 복지의식 제고의 필요성, 복지정책과 제도의 바람직한 운용을 위한 접근방향과 대안개발에 구체적인 이론적 근거를 제공하였다는 점이다. 셋째, 사회복지공무원의 복지의식을 높이기 위해서는 복지정책이 평등화 효과를 높이고 무임승차나 근로의욕 저해를 최소화하는 방향에서 수립되고 운영되어야 한다는 정책적 함의를 찾을 수 있다. 넷째, 복지관련 업무경력이 낮을수록 낮은 복지가치관과 직무가치관, 직무효과성을 보인다는 사실을 통해 사회복지공무원의 업무체계 개선의 필요성을 제시하였다. 이상의 연구결과에 의거하여 사회복지공무원의 복지의식에 대한 연구의 활성화, 사회복지공무원 대상 복지정책, 제도, 가치 등에 대한 정기적인 교육의 필요성, 사회적 형평성과 평등화를 제고하는 방향에서의 복지정책의 결정을 통한 사회복지공무원의 긍정적인 복지의식과 직무성과 제고 필요성, 사회복지공무원의 업무체계 개선의 필요성 등을 제안하였다.

• 한국분무공학회지
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• 제21권4호
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• pp.207-213
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• 2016

To protect air pollution of urban area from motor vehicles, emission limits for diesel vehicles have been dramatically lowered in short period. But recent studies have shown that on-road NOx emissions of light-duty diesel vehicles are considerably higher than the values measured with laboratory test procedures used for emission certification. To tackle with this issue, Ministry of Environment have a plan to introduce EU RDE-LDV (Real-driving Emission-Light-duty Vehicle) regulation. In this study, 4 Euro 6 diesel vehicles have been tested with the new test procedures published by EU to estimate on-road NOx emissions using PEMS (Portable Emission Measurement System). The results have shown that the requirements of EU RDE-LDV could be met in driving condition of metropolitan area for constitution of test routes and validity of test results. In analysing with Moving Averaging Window method the completeness and normality of test data were validated with the requirement. On-road NOx emissions were quite deviated as test vehicles and higher than the new limit of on-road NOx emission enforced from Sept. 2017, which means that RDE-LDV can effectively reduce NOx emission of diesel vehicles in real driving conditions of Korea.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2433-2452
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• 2017

Recently, the pipeline-forwarding has been proposed as a new technique to resolve the end-to-end latency problem of the duty-cycle MAC protocols in Wireless Sensor Networks (WSNs). Some protocols based on this technique such as PMAC and PRI-MAC have shown an improvement not only in terms of reducing end-to-end latency but also in terms of reducing power consumption. In these protocols, however, the sensor nodes still waste a significant amount of energy for unnecessary idle listening during contention period of upstream nodes to check the channel activity. This paper proposes a new pipeline-forwarding duty-cycle MAC protocol, named RP-MAC (Reduced Pipelined duty-cycle MAC), which tries to reduce the waste of energy. By taking advantage of ACK mechanism and shortening the handshaking procedure, RP-MAC minimizes the time for checking the channel and therefore reduces the energy consumption due to unnecessary idle listening. When comparing RP-MAC with the existing solution PRI-MAC and RMAC, our QualNet-based simulation results show a significant improvement in term of energy consumption.

• Corrosion Science and Technology
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• 제4권4호
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• pp.155-163
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• 2005

Heavy duty coating are required to have minimum durable period of 15 years under average usage environment because these paints are coated with purpose of anti-corrosion, antifouling, plastering etc. Onto steel structures constructed upon land and sea and other ferrous structures of electric power generation plants, electricity transmission towers, large structures of various plants, etc. Therefore we tried to estimate heavy duty coating longevity through reliability evaluation method and used combined cyclic anti-conrrosion test method composed of drying, moisturizing and salt spray as for accelerated life test to estimate longevity. Accelerated life test hours to heavy duty coating of first grade (with longevity not less than 15 years) specification may be obtained from troubleless test hours $t_n=\frac{B_p}{n^{1/\beta}}\left[\frac{1n(1-CL)}{1n(1-p)} \right]^{1/\beta}=19.671$ (yr) where shape parameter $\beta=1.1$, confidence level CL=80 %, warranty life $B_{10}=15$ yr and sampling size n=10 (2 sets). Because acceleration factor {AF} found by accelerated test is 41.7, accelerated life test hours required may be represented about 4,132 hr so that if this amount of hours is converted to number of cycles(6 hr/cycle) of complex cycle corrosion resistance test then the amount is tantamount about 690 cycles. That means if there does not occur trouble failure (with defect factor sum not more than 20) during when there is performed 690 cycles of combined cyclic anti-corrosion test to heavy duty coating specimen then it signifies that there can be warranted longevity $B_{10}$ of 15 yr under condition of confidence level CL=80 %.

• 한국정보통신학회논문지
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• 제22권4호
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• pp.670-675
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• 2018

센서네트워크의 전력문제를 해결할 수 있는 에너지 수집형 무선 센서네트워크 (EH-WSN)에 대한 관심이 증가하고 있다. EH-WSN에서는 에너지 수집과 소비의 균형을 맞추기 위한 on-off 듀티싸이클링에 관한 연구가 많이 진행되고 있다. 그러나 환경감시를 위한 EH-WSN에서 센싱된 데이터의 긴급성과 에너지 수집율은 네트워크의 성능을 결정하는 중요한 요소가 된다. 따라서 단순히 전력의 균형 상태를 유지하는 것 이외에 센싱된 데이터의 중요도 및 에너지 수집율에 따라 듀티싸이클 주기를 조절할 필요성이 대두된다. 본 논문에서는 환경감시를 위한 EH-WSN에서 기존의 전력만을 고려한 on-off 듀티싸이클링의 문제점을 분석하고, 센싱값의 변화율 및 크기값에 의한 센싱 데이터의 우선순위 및 에너지 수집율 등을 고려하여 적응적으로 on-off 주기를 결정하는 듀티싸이클 스케줄링 기법을 제안한다. 시뮬레이션을 통해 제안된 듀티싸이클 스케줄링의 성능을 분석하였다.

• Journal of Korea Trade
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• 제24권3호
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• pp.1-19
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• 2020

Purpose - This study empirically analyzes the effects of provisional anti-dumping duties levied on imports by Korea following anti-dumping investigations. An anti-dumping duty is a legal tool that countries use to impose duties on imports to offset injurious dumping. This study verifies how effective the imposition of a provisional anti-dumping duty is and whether such duties have trade chilling effects on aggregate imports. Specifically, this study examines import trade diversion from named to unnamed countries caused by the imposition of provisional anti-dumping duties. Design/methodology - This empirical analysis employs an econometric model of provisional anti-dumping measures for cases in which Korea imposed final affirmative anti-dumping measures. We construct a monthly panel dataset for each stage of anti-dumping investigation undertaken by Korea for all manufacturing industries during 1995-2013. We illustrate a stage-by-stage analysis of anti-dumping investigations from initiation, preliminary decision, imposition of provisional duty, final affirmative decision, and imposition of final affirmative duty on a monthly basis at the six-digit harmonized system code-level. Findings - For cases in which provisional duties are imposed, the reduction in imports from named countries outweighs the increase in imports from unnamed countries. The substantial reduction in imports from named countries is large enough to offset the import diversion to unnamed countries, suggesting that import diversion in investigations is limited during the investigation period. Therefore, the use of provisional anti-dumping duties in Korea is effective, providing evidence of a chilling effect on aggregate imports. Originality/value - Few studies examine the size of the effects on import trade diversion of the imposition of provisional anti-dumping duties. We contribute to the literature by disentangling separate trade effects for each phase of the anti-dumping investigation process and imposition of provisional duty.

• The Journal of Korean Physical Therapy
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• 제3권1호
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• pp.9-37
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• 1991

The purpose of this . study is to examine the unsatisfactory factors of the physical therapists and to obtain the materials necessary to comply with these factors by analysing their service performance and job satisfaction, To accomplish these purposes, this study was carried out by using the questionnaires 206 physical therapists registered in the Korean Physical Therapists Association, for 35 days from January 7 to February 10, 1990. The result of this study is summarized as follows. 1. Of total respondents, the male accounted for 54.4 percent, while the female for 45.6 percent. Their age showed that 20s accounted for 65.0 percent, while the service period less than 3 years accounted for 66.5 percent. In addition, 63.6 percent of them served at the general clinics. 2. The general clinics caused the physical therapists to serve for 10 hours or more per day, where their therapy room located in the underground accounted for 41.3 percent. Their health diagnosis status indicated that nondiagnosis accounted for 63.2 percent. The number of the served patients fer a day showed that 20-30 accounted for 37.4 percent, while 30 persons or more for 25.7 percent. 53.4 percent of total subjects was unsatisfied with their duty quantity. And, the monthly salary indicated that 500,000 or less accounted for 72.3 percent. 3. The average marks by their job satisfaction factors indicated 4.42 for duty importance, 4.02 for recognization of specialized job, 3.98 for ability exercise, 1.99 for promotion possibility, 2.28 for reasonable salary, and 2.41 for welfare system, respectively, based on 5 full marks. 4. The summarized job satisfaction by factors indicated that the relation with the doctor accounted for 57.8 percent, the satisfaction status with the existing job for 53.4 percent, the ability development for 41.8 percent, respectively, and the salary for 10.2 percent. Then, the satisfaction by sex showed that the male was generally satisfied with the ability development (p<0.05), the relation with the doctor (p<0.01), and the satisfaction with the existing job, while the female was satisfied with the duty quantity(p<0.05), salary, and the situation guarantee (p<0.05). On the other hand, the satisfaction by age indicated that the subject of the lower age were satisfied with the ability development (p<0.01), the relation with the doctor(p<0.05), the salary, and the situation guarantee. Also, the satisfaction by the service section showed that the physical therapists serving at the general hospital were satisfied with the ability development (p<0.01), the duty quantity (p<0.01), the salary(p<0.01), the situation guarantee(p<0.01), and the satisfaction with the existing duty (p<0.05), while the physical therapists at the hospital and the rehabilitation center were unsatisfied with the salary (p<0.01). In addition, The satisfaction with the service period at the existing section indicated that the physical therapists less than 3 years were highly satisfied with the ability development, the relation with the doctor, the situation guarantee, and the existing duty(p<0.05), while the physical therapists more than 6 years tended to show the lower satisfaction, And the satisfaction with the monthly salary indicated that the higher the monthly salary, the higher the satisfaction with the relation to the doctor(p<0.05), the duty quantity(p<0.01), the salary(p<0.01), and the situation guarantee (p<0.01). 5. The correlation between general characteristics and job satisfaction factors indicated that the sex was directly correlated to the marital status (r=-0.442), while it was reversely correlated to the age (r=-0.564) , total career (r=-0.229), and the relation with the doctor (r=-0.233). Additionally, the age was directly correlated to the total carreer (r=-0.677), and the service period at the existing section (r=0.491), while the age was reversely correlated to the marital status (r=-0.678). Accordingly, the higher job satisfaction of the physical therapists was related to factors such as their duty importance, recognization of specialized occupation, ability exercise, autonomy, relation to colleagues, decision-making's consideration, and relation with the doctor, while the lower job satisfaction includes the opportunity of promotion, salary, welfare system, service time, duty quantity, and situation guarantee. For this reason, if the factors of the lower job satisfaction are solved, then it will be possible to encourage the motive of these physical therapists, and the acyivate their duties. More over, it is also possible to improve the medical service, Additionally, if the general physical therapy room in the hospital and in the public health center are established, more development should be accomplished in the physical therapy.

• 대한간호학회지
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• 제8권1호
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• pp.152-162
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• 1978

The desire to maintain health is increasing, consequently the role of nursing which has as one chief aim the solving of man′s basic problems is more and more important. Today, in spite of a growing concern about the nursing activities which nurses provide for individual human having specific needs, clinically in fact, it is questionable that individual′s expectation of nursing activities agrees with nurse′s performance of nursing activities. In this study the importance and agreement of the importance of the nursing activities during the hospitalized puerperal period as viewed by women in the puerperal period and by nurses caring for them, were assessed. The present study was undertaken in an attempt to furnish the basic data for expediting the progress of research activities in this area and further to be helpful in planning maternity nursing practice. The study population defined and selected was nurses (13) caring for women in the puerperal period and doing duty on obstetric & gynecologic ward at Y. hospital, and the women in puerperal period (39) as sum of 3 women selected by each nurse during the period of May 13th-June 4th 1976. The study data was collected by the direct interview method based on the questionnaire which the investigator made out. The study result was analyzed by percentage, t - test. The findings can be summarized as follows: 1. General characteristics of nurses doing duty on puerperal ward: a. Nurses′average age was 24.8 years old. b. 84.6% had educational background of 4 years of college. c. 69.2% had a religion. d. 53.8% were married. e. 53.8% had clinical experience of 1 year -3 years. f, 61.5% did duty on puerperal ward during 1 year -3 years. g. 46.2% desired to do duty on obstetric ? gynecologic ward. 2. General characteristics of the women who were studied during their puerperal period: a. Women′s average age was 26.4 years old. b. 79.5% had educational background above high school. c. 56.4% had a religion. d. 84.6% had living standard above medium. e. 89.7% had no occupation. f, 53,8% had previous hospitalization experience. g. 56.4% had previous delivery experience. 3. Examining the importance of 39 nursing activities during puerperal period selected by investigator, studied group of women considered that the most important nursing activity was "Record precisely about condition, medical treatment and nursing activity results etc". Nurses considered that the most important nursing activity was "Notice whether having pain and care for that". Both groups considered that the least important nursing activity was "Talk with her about topics such as news, hobbies, other interests". 4. Examining the importance of nursing activities in 4 specific categories, studied group of women considered that the most important nursing activity in physical nursing category was "Be sure of safety measure to prevent accidents, injuries", and nurses considered that the most important nursing activity was "Make her sleep and rest sufficiently". Studied group of women considered that the most important nursing activity in psychological category was "Explain about medical treatment and nursing activity ahead of time so she knows what to expect" , and nurses considered that the most important nursing activity was "Explain about puerperal period so she understands". Studied group of women considered that the most important nursing activity in relation to medical care was "Record precisely about condition, medical treatment and nursing activity results etc.", and nurses considered that the most important nursing activity was "Observing, cleaning and protecting the perineum" Studied group of women considered that the most important nursing activity in nursing category in preparation for discharge was "Instruct about personnel hygiene during puerperal period", and nurses considered that the most important nursing activity was "Instruct self-care to protect the perineum". 5. The analysis of this study showed a significant amount of disagreement computed by subtracting the nurse′s score from the patient′s score. Studied group of women put greater importance on physical nursing category, psychological nursing category, nursing in relation to medical care, than the nurses. These results were statistically significant at 0.01 level.