가변 전력 분배 기반 다중 모드 고효율 정류기 배열

김빛찬,이다주,김지수,오준택 한국전자파학회 2022 한국전자파학회논문지 Vol.33 No.6

This study proposes a high-efficiency rectifier array with multiple power modes based on variable power distribution. The proposed rectifier array comprises of rectifier cell 1 for low-power mode, rectifier cell 2 for high-power mode, and a variable power divider. The variable power divider, composed of two branch line couplers and a variable impedance stage, determines the power-dividing ratio by controlling the variable impedance stage. If the input power is adaptively distributed in the rectifier array according to the input power, the rectifier array can maintain high efficiency over a wide input power range. The size of the proposed circuit is 67.7 mm×47.4 mm. The measurements obtained during experimentation show that proposed rectifier array has high power conversion efficiency of 80.2 % and 68.7 % in the low and high-power modes, respectively. The circuit can maintain high power conversion efficiency of over 50 % over an input power range of 4.4−28 dBm depending on the selected mode at 2.45 GHz.

위성용 전원분배보드의 Power Integrity 분석 및 특성개선

조영준,김지훈 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

전원분배보드는 유닛내의 다른 보드로 DC power를 전달하는 역할을 하며 위성용 보드의 경우 인접 유닛간의 EMC(Electromagnetic Compatibility) 요구조건이 까다롭게 준수되어야 한다. 때문에 해당 보드의 특성상 전원의 건전성을 확인하고 전원노이즈를 줄이는 노력이 필요하다. 이를 위해 본 논문에서는 전원분배보드의 DC IR drop 특성, PCB power/ground의 공진특성, 그리고 주요 소자들의 전원 노이즈를 점검하기 위한 power impedance 특성의 전반적인 power integrity를 분석하였고 각 결과에 대한 개선방안을 제시하였다. Power distribution board has a function to deliver a power to other boards. Especially for satellite application, the equipment board shall conform EMC(Electromagnetic Compatibility) requirements tightly. Hence effort to check power integrity and reduce power noise is necessary considering the board characteristics. For this purpose, analysis of DC IR drop, PCB power/ground resonance mode, and power impedance of major devices were performed to check power integrity of power distribution board, and suggest improvement measures according to the each analysis result.

Research on Antenna Arraying Combining Technology for Deep Space Measurement & Control

Ke Sun,Xiaomin Hou 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.7

In this dissertation, the key technology of uplink array for deep space TTC is studied. Based on the concept of power combining, the theoretical analysis is made on the uplink array. The spatial power combining can be achieved in a certain power. The uplink antenna array technology is a power combiner. At first this chapter introduces the principle of power combining and leads to the concept of the uplink antenna arraying. Then analyze the theory of the uplink antenna arraying power combining, including the signal strength and antenna pattern. The influence of the number of element, spacing, phase and time delay on power combining is analyzed by simulation. At last the uplink antenna arraying power combining performance is analyzed and verified by simulation.

Consumed-Power and Load Characteristics of a Tillage Operation in an Upland Field in Republic of Korea

Kim, Jeong-Gil,Kim, Young-Joo,Kim, Jung-Hun,Shin, Beom-Soo,Nam, Ju-Seok Korean Society for Agricultural Machinery 2018 바이오시스템공학 Vol.43 No.2

Purpose: This study derived the consumed power and load characteristics of a tillage operation performed in an upland field located in Seomyeon, Chuncheon, Rep. Korea, where potatoes and cabbages were cultivated in two crops. Methods: A plow and rotavator were mounted on a tractor with 23.7 kW of rated power to perform the tillage operation. The work conditions were determined, considering the actual working speed of the tillage operation performed by the local farmers. The power consumption of the rear axle, engine, and power take-off (PTO), PTO torque, and tractive force were measured under each work condition. The consumed power and load characteristics were analyzed using their average values. Results: The rotary-tillage operation consumed more engine power than the plow operation for the same tractor-transmission gear condition. The PTO in the rotary-tillage operation and the rear axle in the plow operation consumed the most power. The power consumption of the engine and the PTO for the rotary-tillage operation tended to increase as the transmission gears of the tractor and the PTO became higher. In contrast, the rear-axle power consumption was insignificant. In addition, the PTO torque tended to rise as the tilling pitch increased. For the plow operation, the drawbar power and the rear axle power accounted for 68-90% of the engine power. The engine and rear axle power, drawbar power, and tractive force tended to rise as the working speed increased. Conclusions: The power consumption and load characteristics differed for the plow and rotary-tillage operations. They may also differ depending on the soil conditions. Therefore, the power consumption and load characteristics in various work environments and regions should be analyzed, and reflected in the design of tractors and working implements. The results derived from this study can be used as a reference for such designs.

고조파 필터 및 인버터의 용량을 고려한 분산전원 시스템의 역률 제어에 관한 연구

김영진(Young-Jin Kim),황평익(Pyeong-Ik Hwang),문승일(Seung-Il Moon) 대한전기학회 2009 전기학회논문지 Vol.58 No.11

Electric power quality in power transmission/distribution systems has considerably been deteriorated with the increase in the capacity of distributed generators (DGs). It is because inverters, connecting DGs to conventional power grids, tend to generate harmonic current and voltage. For harmonic mitigation, a large amount of research has been done on passive and active filters, which have been operating successfully in many countries. This paper, therefore, presents how to adopt the filters to an inverter-based DG, with considering a system consisting of both inverter-based DG and harmonic filters. In particular, this paper describes the simulation results using the PSCAD/EMTDC: firstly, the relationship between total harmonic distortion(THD) of current and output power of DG: secondly, the harmonic mitigation ability of passive and active filters. The system, furthermore, is obliged to satisfy the regulations made by Korean Electric Power Corporation(KEPCO). In the regulations, power factor should be maintained between 0.9 and 1 in a grid-connected mode. Thus, this paper suggests two methods for the system to control its power factor. First, the inverter of DG should control power factor rather than an active filter because it brings dramatic decrease in the capacity of the active filter. Second, DG should absorb reactive power only in the range of low output power in order to prevent useless capacity increase of the inverter. This method is expected to result in the variable power factor of the system according to its output power.

Consumed-Power and Load Characteristics of a Tillage Operation in an Upland Field in Republic of Korea

( Jeong-gil Kim ),( Young-joo Kim ),( Jung-hun Kim ),( Beom-soo Shin ),( Ju-seok Nam ) 한국농업기계학회 2018 바이오시스템공학 Vol.43 No.2

Purpose: This study derived the consumed power and load characteristics of a tillage operation performed in an upland field located in Seomyeon, Chuncheon, Rep. Korea, where potatoes and cabbages were cultivated in two crops. Methods: A plow and rotavator were mounted on a tractor with 23.7 kW of rated power to perform the tillage operation. The work conditions were determined, considering the actual working speed of the tillage operation performed by the local farmers. The power consumption of the rear axle, engine, and power take-off (PTO), PTO torque, and tractive force were measured under each work condition. The consumed power and load characteristics were analyzed using their average values. Results: The rotary-tillage operation consumed more engine power than the plow operation for the same tractor-transmission gear condition. The PTO in the rotary-tillage operation and the rear axle in the plow operation consumed the most power. The power consumption of the engine and the PTO for the rotary-tillage operation tended to increase as the transmission gears of the tractor and the PTO became higher. In contrast, the rear-axle power consumption was insignificant. In addition, the PTO torque tended to rise as the tilling pitch increased. For the plow operation, the drawbar power and the rear axle power accounted for 68-90% of the engine power. The engine and rear axle power, drawbar power, and tractive force tended to rise as the working speed increased. Conclusions: The power consumption and load characteristics differed for the plow and rotary-tillage operations. They may also differ depending on the soil conditions. Therefore, the power consumption and load characteristics in various work environments and regions should be analyzed, and reflected in the design of tractors and working implements. The results derived from this study can be used as a reference for such designs.

Consumed-Power and Load Characteristics of a Tillage Operation in an Upland Field in Republic of Korea

김정길,김영주,김정훈,신범수,남주석 한국농업기계학회 2018 바이오시스템공학 Vol.43 No.2

Purpose: This study derived the consumed power and load characteristics of a tillage operation performed in an upland field located in Seomyeon, Chuncheon, Rep. Korea, where potatoes and cabbages were cultivated in two crops. Methods: A plow and rotavator were mounted on a tractor with 23.7 kW of rated power to perform the tillage operation. The work conditions were determined, considering the actual working speed of the tillage operation performed by the local farmers. The power consumption of the rear axle, engine, and power take-off (PTO), PTO torque, and tractive force were measured under each work condition. The consumed power and load characteristics were analyzed using their average values. Results: The rotary-tillage operation consumed more engine power than the plow operation for the same tractor-transmission gear condition. The PTO in the rotary-tillage operation and the rear axle in the plow operation consumed the most power. The power consumption of the engine and the PTO for the rotary-tillage operation tended to increase as the transmission gears of the tractor and the PTO became higher. In contrast, the rear-axle power consumption was insignificant. In addition, the PTO torque tended to rise as the tilling pitch increased. For the plow operation, the drawbar power and the rear axle power accounted for 68–90% of the engine power. The engine and rear axle power, drawbar power, and tractive force tended to rise as the working speed increased. Conclusions: The power consumption and load characteristics differed for the plow and rotary-tillage operations. They may also differ depending on the soil conditions. Therefore, the power consumption and load characteristics in various work environments and regions should be analyzed, and reflected in the design of tractors and working implements. The results derived from this study can be used as a reference for such designs.

Power sharing, peace and democracy: Any obvious relationships?

Helga Malmin Binningsbø 한국외국어대학교 국제지역연구센터 2013 International Area Studies Review Vol.16 No.1

Power sharing, mostly understood as including political opponents in a joint executive coalition government, is today a dominant approach to solving conflict. Almost as a panacea it has been introduced in numerous war-affected countries and is often recommended as a political solution to overcome deep divisions between groups. Researchers, mediators and policy-makers applaud such solutions as forward-looking, peace-strengthening and democratic. However, many have criticized power sharing and its failed ability to create peace and development in divided and conflict-ridden countries. The literature on power sharing can reach such divergent conclusions because there is no consensus on what power sharing is, what the aim of it is and how to study it. Apart from broad inclusion in joint government, the understanding of power sharing varies and recommendations to ‘share power’ give little guidance to policy-makers aiming to mitigate conflict. Therefore, this article reviews 40 years of research on power sharing by elaborating on four central aspects within the literature: (1) conceptualization; (2) domain; (3) causal mechanism; and (4) measurement. While there may be no ‘true’ power sharing or ‘truth’ about power sharing, the article concludes that it is crucial that researchers and policy-makers are clear about which type of power sharing they are discussing in specific situations. Given that power sharing is increasingly recommended and implemented in many fragile and post-conflict societies, it is important to understand what is meant by power sharing in these contexts.

한국과 태국 사이의 소프트파워 협력을 위한 법제적 노력

김호 ( Kim Ho ) 한국태국학회 2024 한국태국학회논총 Vol.30 No.2

The concept of soft power is gaining significant attention in today's international relations, with various countries making concerted efforts to enhance their soft power. In particular, South Korea and Thailand are keenly focusing on strengthening soft power as a new area of collaboration, emphasizing the importance of mutual understanding and the formation of positive images in the international community. This paper aims to examine how South Korea and Thailand are enhancing their soft power and the challenges they face. Both countries are exploring ways to amplify their soft power by leveraging their unique cultures and resources. Through activities such as cultural exchanges, language courses, artistic endeavors, and sports diplomacy, they strive to foster positive perceptions on the global stage. Additionally, with a focus on enhancing soft power in the legal domain, the paper investigates how both countries are improving their soft power and analyzes potential areas for collaboration. To achieve this, the paper provides a brief introduction to the core concepts of soft power and how South Korea and Thailand are utilizing it. Subsequently, it examines the foundational aspects of their efforts to enhance soft power, delves into the efforts and challenges in the legal field, and proposes possibilities for collaboration between the two countries. It is anticipated that this analysis and proposal will serve as a crucial foundation for opening new horizons in South Korea-Thailand cooperation. Through the strengthening of soft power, both countries are expected to establish a closer collaboration, showcasing a more prominent presence in the international community. Furthermore, this paper aims to suggest avenues for effective utilization of soft power, fostering mutual benefits and solidifying the South Korea-Thailand partnership across various sectors in the global arena.

Power Transition Theory and the U.S. Decisions in Favor of Preventive War: A Linkage between Theory and Practice

박준혁 국방대학교 국가안전보장문제연구소 2012 The Korean Journal of Security Affairs Vol.17 No.1

Power shifts between interstate dyadic relationships are generally considered one of the most important factors affecting the preventive motivation for war. It is also a prominent cause of war in power transition theory. This theory predicts that war is likely to occur when the power of a challenger rises to parity with that of a dominant power. Based on this theory’s prediction, this paper can state two basic hypotheses as follows: (1) If power parity exists, preventive war is more likely; and (2) If power preponderance exists, preventive war is less likely. However, despite the second hypothesis indicating that war is less likely with power preponderance, the United States has often considered and launched preventive wars against middle and small powers. By critically evaluating the relevance of the above hypotheses given preventive wars launched and considered by the U.S. after World War II, this paper argues that the expected cost of war has been a crucial factor affecting the decision to engage in preventive war. In this context, this paper argues that the absence of war between the U.S. and the Soviet Union in the Cold War era was caused largely by the prohibitively high expected cost of war rather than by the preponderant power of the U.S. over the Soviet Union. This argument can also be applicable to the confrontation between the U.S. and other major and strong middle powers like China and North Korea. However, the U.S. launched preventive wars against weak middle and small powers such as Iraq and Grenada largely because the expected costs of wars in these conflicts were very low. In order to verify these arguments, this paper presents the modified version of the hypotheses of power transition theory and identifies intervening variables affecting the U.S. decisions in favor of preventive war.