• 한국항해항만학회지
• /
• 제41권5호
• /
• pp.319-328
• /
• 2017

The efficiency of port operations is an important indicator of port development. Moreover, there is excess handling capacity in Chinese ports, which results in a slower speed of development. Under the detrimental environment of the international shipping market, it is necessary to improve the operation efficiency of ports for long-term development. This paper provides an assessment of the competitiveness of Chinese seaport companies using the Boston Consulting Group's matrix, and efficiency measurements using a data envelopment analysis and the Malmquist method. This analysis showed that highly efficient companies reformed their development strategies, which should be a solution considered by less efficient companies, such as Shenzhen Yan Tian Port Holdings Co., Ltd.. Although, having high throughput should be reformed in the investment structure. This research will assist port companies in gaining effective operating experience, and governments in establishing strategic planning to enhance the efficiency of port development.

• 한국습지학회지
• /
• 제15권4호
• /
• pp.453-460
• /
• 2013

소규모 농촌 지역 하수도 보급률은 도시지역의 약 40% 이하 수준이다. 농촌지역의 낮은 하수도 보급률은 상수원의 수질악화의 원인으로 보고되고 있다. 안동댐과 임하댐 상류에 위치하고 있는 봉화군에 신설된 마을하수도 11개소의 운전 결과를 분석하였다. 운전결과를 바탕으로 봉화군 마을하수도 특성과 도입된 처리 공법에 관한 분석을 실시하였다. 봉화군 유입 하수는 도시지역에 비해 고농도의 유기물과 영양염류를 함유하고 있다. 마을하수도에 도입된 처리 공법은 전체적으로 안정적인 처리 효율을 보였다. 하지만 영양염류의 경우 처리 효율의 변화가 크게 나타났다. 이는 마을하수도 운전 시영양염류 처리에 있어 운전 조건 관리에 관심을 기울여야 한다는 것을 의미한다.

• 전기학회논문지
• /
• 제62권5호
• /
• pp.596-603
• /
• 2013

The increase of distributed power generation is closely related to interest in microgird including renuable energy sources such as photovoltaic (PV) systems and fuel cell. By the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. Especially operation technique which is core technology of microgrid is to supply heat and electricity energy simultaneously. Optimal microgrid scheduling can be established by considering CHP (Combined Heat and Power) generation because it produce both heat and electricity energy and its total efficiency is high. For this reason, CHP generation in microgrid is being spotlighted. In the near future, wide application of microgrid is also anticipated. This paper proposes a mathematical model for optimal operation of microgrid considering both heat and power. To validate the proposed model, the case study is performed and its results are analyzed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 B
• /
• pp.687-689
• /
• 2000

Molten Carbonate Fuel Cell (MCFC) with high electrical efficiency and low environmental effect has been developed for the commercial application of power generation fields. Recently we have built a 25 kW molten carbonate fuel cell power generation system and tested it. The MCFC system is composed of diverse peripheral units such as reformer, pre-heater, water purifier. electrical loader, gas supplier, and recycling systems. The stack itself was made of 40 cells of $6.000 cm^2$ area each. The stack showed an output of 28.6 kW power and a reliable performance at atmospheric operation. while in pressurized operation the stack showed an output 25.6 kW lower than the atmospheric operation. The reason of lower performance of pressurized operation was caused from a gas cross over shown in few cells in the stack.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 A
• /
• pp.102-105
• /
• 1993

The objective of this study is to solve the operation scheduling problem of plural battery energy storage systems (BESS), and to find useful intonation from its result. Unlike conventional energy storage system, BESS has on hardware characteristics such as high efficiency, fast-acting response and operational loss. Considering rate constraints of thermal unit power as well as hardware characteristics of BESS, the operation scheduling has an intricated problem. In order to solve this optimization problem, we use successive approximations dynamic programming. In two types of operation, the proposed algorithm is applied to test system. one is daily optimal operation, the other weekly optimal operation.

• 대한전자공학회논문지TC
• /
• 제47권2호
• /
• pp.56-61
• /
• 2010

본 논문에서는 단일 FET와 composite right/left-handed (CRLH) 전송선을 이용하여 2.14GHz/5.2GHz 이중대역 고효율 전력 증폭기를 설계 구현하였다. 전송선로를 이용하여 초기의 정합값을 적절히 이동시켜 하나의 능동소자로 2.14GHz/5.2GHz의 이중대역에서 동작되는 전력증폭기를 설계하였다. 이중 대역에서 모든 고조파 성분을 조절하는 것은 매우 어렵기 때문에, CRLH 전송 선로를 이용하여 이중 대역에서 고효율 특성을 얻도록 오직 2차, 3차 고조파 성분만을 조절하였다. 또한, 이중 대역에서의 출력특성이 균형을 이루도록 하였다. 전력증폭기의 측정된 출력 전력은 각각 2.14 GHz에서 28.56 dBm, 5.2 GHz에서 29 dBm이다. 이 지점에서 얻은 전력 효율, PAE는 2.14 GHz에서 65.824 %, 5.2 GHz에서 69.86 %이다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
• /
• pp.325-328
• /
• 2000

This paper has been studied a rower amplifier for IMT-2000 handset. Circuit design is performed and optimized by using HP ADS RF software. Designed amplifier consist of 2 stage, has 25㏈ gain, over 27㏈m output power and about 40% power efficiency. Power amplifier operation frequency range is 1955${\pm}$70MHz. Mask layout of the designed Amplifier consisting of 4 mask. The measured results of these values are satisfying the specification of IMT-2000 handset.

• International Journal of Precision Engineering and Manufacturing
• /
• 제3권4호
• /
• pp.24-30
• /
• 2002

In grinding operations, one of the most important problems is to increase efficiency of process. In order to achieve this purpose, it is necessary to administer the tool lift of grinding wheel and to optimize grinding conditions. Frequently dressing result in lowering the process efficiency remarkably and makes production cost high. On the other hand, grinding with a worn wheel causes the workpiece surface roughness to increase and often results in the occurrence of such troubles as chatter vibration and homing.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2008년도 하계학술대회 논문집
• /
• pp.64-65
• /
• 2008

The topology of active clamp forward converter provides ZVS characteristic and also the stress of voltage and current is smaller than that of the conventional forward converters. The benefits of this technique include a higher efficiency at a high switching frequency, lower EMI/RFI. In this paper, the active clamp forward converter is designed for operation in wide range voltage and has 19.5V/120W ratings with efficiency more than 90%.

• 기술사
• /
• 제44권4호
• /
• pp.39-43
• /
• 2011

To cope with recent high gas prices and global warming phenomenon, the latest gasoline engine technologies are focusing on direction injection, downsizing by turbo charging, variable compression ratio, controlled auto Ignition to enhance fuel efficiency and satisfy emission regulations. The variable valve train technology will be a basement for these innovative technologies in internal combustion engines and is supposed to play a key role to improve low thermal efficiency and pumping loss in gasoline engine caused by low compression ratio and throttled operation respectively.