• 조명전기설비학회논문지
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• 제25권8호
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• pp.8-19
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• 2011

This paper was compared for the output voltage and efficiency of the single-phase Z-source inverter(ZSI) according to shoot through duty ratio D. The eight single-phase ZSI in this study are typical ZSI, Embedded ZSI(EZSI), Improved ZSI(IZSI), Quasi ZSI(QZSI), Series ZSI, Trans ZSI(TSI), Switched inductor ZSI(SL-ZSI) and Extended boost ZSI (exZSI). The eight ZSI are divided into two Groups. ; Group-1 which is ZSI with the ordinary voltage boost factor B, and Group-2 which is ZSI with the maximum voltage boost factor B. For the execution of the proposed study, the PSIM simulation was achieved under the condition of input DC voltage=150[V] of ZSI, load =30[${\Omega}$] and 60[Hz] output filter. The output voltage and efficiency of each ZSI were calculated within the limits of D=0.1~0.4. As a result, the output peak voltage of Group-2 was suddenly increased in a specified duty ratio D, and its efficiency was rapidly decreased. On the contrary, Group-1 shown the output and efficiency characteristics without sudden change compared to Group-2 despite the duty ratio increase. The efficiency of the Group-2 was sharply declined at duty ratio D of the most output voltage, but, in case of Group-1, the efficiency was slightly declined. Finally, the input DC current of ZSI with DCM and CCM was discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권1호
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• pp.105-122
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• 2011

The fundamental design goal of wireless sensor MAC protocols is to minimize unnecessary power consumption of the sensor nodes, because of its stringent resource constraints and ultra-power limitation. In existing MAC protocols in wireless sensor networks (WSNs), duty cycling, in which each node periodically cycles between the active and sleep states, has been introduced to reduce unnecessary energy consumption. Existing MAC schemes, however, use a fixed duty cycling regardless of multi-hop communication and traffic fluctuations. On the other hand, there is a tradeoff between energy efficiency and delay caused by duty cycling mechanism in multi-hop communication and existing MAC approaches only tend to improve energy efficiency with sacrificing data delivery delay. In this paper, we propose two different MAC schemes (ADS-MAC and ELA-MAC) using closed-loop control in order to achieve both energy savings and minimal delay in wireless sensor networks. The two proposed MAC schemes, which are synchronous and asynchronous approaches, respectively, utilize an adaptive timer and a successive preload frame with closed-loop control for adaptive duty cycling. As a result, the analysis and the simulation results show that our schemes outperform existing schemes in terms of energy efficiency and delivery delay.

• 전기전자학회논문지
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• 제22권4호
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• pp.1210-1213
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• 2018

In this paper, we propose a method to reduce the amount of current through the Timing Control of the duty cycle and the Report Attribute Control at the MAC Layer in consideration of the Sleep Mode under the IoT wireless environment. The use of a duty cycle is an effective way to reduce energy consumption on wireless sensor networks where the node is placed in sleep mode periodically. In particular, we studied how to control power efficiency through duty rate in Short Transition Time and ACK Time processing while satisfying radio channel limitation criterion. When comparing before and after the improvement considering the delay time constraint, we validated the correlation of the electrical current reduction.

• 한국유체기계학회 논문집
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• 제18권6호
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• pp.81-85
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• 2015

The purpose of this study is to evaluate energy savings for inverter driving multi-stage centrifugal pump. Variable speed driving pump system has high efficiency compared with constant speed driving pump system. Because of difficulty to estimate operating efficiency of variable speed driving pump system, energy saving rates are used to replace operating efficiency. energy saving rates are calculated from pump input power and pump duty cycle. But another researches have used pump duty cycles of each season for energy saving rate. In this study, for estimating energy saving rate more high accuracy, pump duty cycles are measured for 1 year. pump duty cycles, depending on the season and be classified according to the weekday/weekend or during the week day. By this pump duty cycles, Energy saving rate is calculated appropriately.

• 전자공학회논문지
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• 제49권12호
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• pp.45-55
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• 2012

센서 네트워크는 센서가 설치된 지역에서 감지된 데이터를 무선으로 전달하는 기술로서, 기존 방식과 달리 에너지 효율이 매우 중요한 성능요소이다. 이러한 특성에 따라 많은 WSN MAC 프로토콜에서는 Wakeup과 Sleep을 반복하여 수행하는 Duty Cycle 기법을 활용하고 있지만, 고정적인 Wakeup 구간의 설정에 따라 획일화된 에너지 성능과 수신 성공률로 인하여 성능이 제한적이다. 본 논문에서는 이러한 Duty Cycle 기반의 MAC 프로토콜을 개선하기 위하여, 채널 환경에 따라 동적으로 Wakeup 구간을 가변화시키는 기법을 제안한다. 제안하는 방식은 트래픽이 높은 환경에서 Wakeup 구간을 증가시켜 수신 성공률을 높이고, 트래픽이 낮은 환경에서 Wakeup 구간을 줄여 에너지 성능을 향상시켰다. 또한 본 논문에서는 제안하는 방식의 성능에 대한 효율적인 평가를 위하여 기존 동기식 및 비동기식 MAC의 결과와 제안방식을 적용한 MAC의 결과를 비교하고 이를 분석하였다.

• 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.

• 한국통신학회논문지
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• 제9권3호
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• pp.132-139
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• 1984

병렬 인덕터와 직렬공진회로를 부하로 갖는 E급 동조전력 증폭기의 duty cycle변화에 따른 콜렉터 전압과 전류, 기본 주파수 성분, 부하회로소자 및 출력전력능력에 관한 방정식을 유도하여 최적동작상태의 특성을 해석하며 실제 콜렉터 포화전압을 고려하여 duty cycle이 50%일 때 증폭효율이 90%이상된다는 것을 이론과 실험을 통하여 고찰하였다.

• Journal of Ecology and Environment
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• 제42권4호
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• pp.174-182
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• 2018

Background: In this study, we observed their growth and physiological responses using a variety of duty ratio under the mixed light using red, blue, and white lights. The red+blue mixed light was treated with 95%, 90%, 85%, 80%, and 75% duty ratios and red+blue+white mixed light with 85% and 70% duty ratios. We examined the width and length of leaves, total number of leaves, and number of shoots to examine their growth responses. The physiological responses were studied by measuring their photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, chlorophyll content, and fluorescence ($F_o$, $F_m$, and $F_v/F_m$). Results: We found that lower duty ratio caused the length and width of the leaves to grow longer under red+blue mixed light but that it did not cause any difference in the red+blue+white mixed light condition. In addition, there was no difference in the number of leaves and shoots among all treatments. In the red+blue mixed light condition, the photosynthetic rate was no difference, but both transpiration rate and stomatal conductance were the highest at 95% duty ratio than in other ratios. Water use efficiency pattern was similar to that of photosynthetic rate; water use efficiency was no difference. Chlorophyll content was the highest at 95% duty ratios, and it was the least at 90%, 85%, and 75% duty ratio. $F_o$ and $F_m$ values were relatively high at 85% and 80% duty ratio and low at 90% duty ratio while $F_v/F_m$ showed no difference. Conclusions: Under the red+blue+white mixed light, all physiological items showed no difference between 70 and 85% treatments. But, photosynthetic rate, water use efficiency, chlorophyll content, and $F_v/F_m$ were relatively greater in the red+blue+white mixed light than in the red+blue mixed light. Therefore, red+blue+white mixed light treated with 70% duty ratio could lessen the environmental stress and save more power when cultivating Silene capitata in a plant factory.

• 한국자동차공학회논문집
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• 제6권3호
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• pp.138-142
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• 1998

Among aftertreatment devices which reduce exhaust gas of diesel engine, diesel oxidation catalyst(DOC) with high reduction efficiency for gaseous matter and particulate matter is now being studied actively. In this study, an experiment was conducted to analyze the effects of low sulfur diesel fuel in heavy duty diesel engine equipped with DOC. We tested to estimate change of engine performance for the low and high sulfur diesel fuels in a 11,000cc diesel engine equipped with DOC. We conducted test to estimate the reduction efficiency of exhaust gas in D-13 mode of heavy duty diesel regulation mode and in smoke opacity mode for two samples of high sulfur content (0.2%) and low sulfur content(0.05%)

• 한국자동차공학회논문집
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• 제9권6호
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• pp.1-7
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• 2001

Recently, several LPG engines for heavy-duty vehicles have been developed, which can replace some diesel engines that are one of a main source for air pollution in urban area. As a preliminary study on the liquid phase LPG injection (hereafter LPLI) system applicable to a heavy duty LPG engine, the engine output and combustion performance were investigated with various combustion chambers and fuel compositions using a single cylinder engine equipped. Experimental results revealed that ellipse, double ellipse and nebula type combustion chamber made a more advantage in breaking swirl flow into small turbulence scale than bathtub type. Especially, performance of nebula type showed most highest efficiency and engine output under lean mixture conditions. An investigation fur various LPG fuel compositions was also carried out, and revealed that the case with 40% propane and 60% butane shows the lowest efficiency at stoichiometry, however, as the mixture became leaner its efficiency increased and became even higher for 100% propane case.