• 전자공학회지
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• 제25권5호
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• pp.31-41
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• 1998

With the advent of portable electronic systems, power consumption has recently become a major issue in circuit and system design. Furthermore, the sophisticated fabrication technology makes it possible to embed more functions and features in a VLSI chip, consequently calling for both higher performance and lower power to deal with the ever growing complexity of system algorithms than in the past. VLSI designers should cope with two conflicting constraints, high performance and low power, offering an optimum trade off of these constraints to meet requirements of system. Historically, VLSI designers have focused on performance improvement, and power dissipation was not a design criteria but an afterthought. This design paradigm should be changed, as power is emerging as the most critical design constraint. In VLSI design, low power design can be accomplished through many ways, for instance, process, circuit/logic design, architectural design, and etc.. In this paper, a few low power design examples, which have been used in 8 bit micro-controller core, and can be used also in 4/16/32 bit micro-controller cores, are presented in the areas of circuit, logic and architectural design. We first propose a low power guidelines for micro-controller design in SAMSUNG, and more detailed design examples are followed applying 4 specific design guidelines. The 1st example shows the power reduction through reduction of number of state clocks per instruction. The 2nd example realized the power reduction by applying RISC(Reduced Instruction Set Computer) concept. The 3rd example is to optimize the algorithm for ALU(Arithmetic Logic Unit) to lower the power consumption, Lastly, circuit cells designed for low power are described.

• 한국산업융합학회 논문집
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• 제5권4호
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• pp.295-299
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• 2002

Specific fuel consumption or specific power output characteristics of an internal combustion engine are likely, in conventional applications, the most important operating criteria. In this work, the test method for the engine performance was introduced in a compression ignition(diesel) engine.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.308-312
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• 2006

The inductance difference between conducting layers of high-Tc superconducting (HTSC) power transmission cable causes the current sharing of each conducting layer to be unequal, which decreases the current transmission capacity of HTSC power cable. Therefore, the design for even current sharing in HTSC power transmission cable is required. In this paper, we investigated the current distribution of HTSC power cable with a shield layer dependent on the pitch length and the winding direction of each layer. To analyze the effect of the shield layer on the current sharing of the conducting layers of HTSC power cable, the current distribution of HTSC power cable without a shield layer was compared with the case of HTSC power cable with a shield layer. It could be found through the analysis from the computer simulations that the shield layer of HTSC power cable could be contributed to the improvement of current distribution of conducting layers at the specific pitch length and the winding direction of conducting layer. The result and discussion for the current distribution calculated for HTSC power transmission cable with a shield layer were presented and compared with the cable without a shield layer.

• 대한기계학회논문집B
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• 제27권7호
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• pp.938-947
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• 2003

In this paper, we derived the formula for estimating the power of the electric motors needed to operate the Decanter-type centrifuge. In the derivation of the formula the sludge-removal torque is to be supplied from the formula derived in the first paper. The intricate nature of the transmission mechanism in the planetary gear trains of the sludge-removal power and torque has been clarified in this second paper. In particular we considered two-motor system, where the main motor drives the machine while the differential-speed control motor plays the role of braking in adjusting the differential speed. Sample calculation for the specific design treated in the first paper showed that the selection criterion for the main motor depends on the lower limit of the differential speed; when the lower limit is set low, it should be selected based on the steadily operating power, while it should be selected based on the starting power when the lower limit is set high. The total power required by both the main motor and the differential-speed control motor increases as the differential speed is decreased. It is suggested that the power loss in the differential-speed control motor could be minimized by attaching an electric generator to it.

• Journal of Power Electronics
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• 제15권2호
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• pp.487-496
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• 2015

In order to ensure that photovoltaic (PV) systems work at the maximum power point (MPP) and maximize the economic benefits, maximum power point tracking (MPPT) techniques are normally applied to these systems. One of the most widely applied MPPT methods is the incremental conductance (INC) method. However, the choice of the step size still remains controversial. This paper presents an improved variable step size INC MPPT algorithm that uses four different step sizes. This method has the advantages of INC but with the ability to validly adjust the step size to adapt to changes of the PV's power curve. The presented algorithm also simultaneously achieves increased rapidity and accuracy when compared with the conventional fixed step size INC MPPT algorithm. In addition, the theoretical derivation and specific applications of the proposed algorithm are presented here. This method is validated by simulation and experimental results.

• 정보관리학회지
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• 제2권2호
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• pp.115-149
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• 1985

도서관에서 일반적으로 사용되는 분류(分類) 시스템은 도서(圖書) 중심으로 되어 있어, 특수 조직체의 기술((技術) 및 행정문서(行政文書)의 내부정보(內部情報)를 분류하는데는 어려움이 많다. 따라서 각 기업체에서는 조직체의 특성에 맞는 문서정보관리체제(文書情報管理體制)를 구축하고 특정한 코딩시스템이나 화일링 시스템을 개발해서 사용하고 있다. 원자력 발전소의 모든 자재 및 자료는 각기 특정한 코딩시스템으로 관리되고 있는데 시스템이 제각기 서로 다르게 구성되어 있어 상호참조(相互參照) 및 상호협력(相互協力)이 어려운 상태이다. 이 논문(論文)에서는 영광 원자력 발전소를 대상으로 하여 기존의 자재(資材) 및 자료(資料)의 코딩시스템을 모두 조사, 분석하고 모든 자료에 범용적(汎用的)으로 사용할 수 있는 통일된 자료관리 코딩 시스템을 설계한 것으로 일반 분류 시스템 및 색인 시스템을 적용하기가 어려운 특수조직체의 내부정보관리 사례 연구이다. 본 시스템 설계로 자재와 자료간의 상호참조, 업무간의 상호협력, 중앙화일 구성 운영등의 효과를 기대할 수 있다.

• 항공우주기술
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• 제9권2호
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• pp.185-192
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• 2010

75톤급 터보펌프를 대상으로 한 속도복합형 터빈과 설계회전수를 50% 증가시킨 30톤급 터보펌프 터빈 적용을 위한을 압력복합형 터빈 설계를 수행하였다. 속도복합형 터빈의 경우 1차원설계-유동해석-1차원설계의 반복적인 설계과정을 통해 원형노즐을 적용한 2열 초음속 충동터빈의 특성을 파악하였으며 최종적으로 기본형인 1열 충동형 터빈 대비 비출력 23.1% 향상, 무게 5% 감소된 ver. 14h 모델을 완성하였다. 압력복합형 터빈은 에너지 회수 비율, 2단 노즐 출구각, 2단 노즐 누설유량, 단별 출력 비율 등의 새로운 인자의 고려하여 각 변수의 성능에 미치는 영향을 검토하였으며 1차원 해석 기준 비출력이 36%가 증대되고 무게는 51% 감소한 터빈을 설계하였다. 압력복합형 터빈의 높은 성능을 위해서는 1단 및 2단 노즐의 형상설계가 매우 중요할 것으로 판단되며 유동해석을 통해 최적화할 예정이다.

• 농업과학연구
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• 제37권3호
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• pp.501-508
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• 2010

A swirl chamber type diesel engine attachable to 18 kW agricultural tractors was improved to reduce exhaust emissions. Compression ratio and throat area ratio of the combustion chamber were varied to determine optimum combustion conditions. Tests were composed of full load and 8-mode emission tests. Compression ratio was fixed as 21, but the swirl chamber volume was increased by 3.8%. Output power, torque, specific fuel consumption, exhaust gas temperature, and smoke level were not considerably different for compression ratios of 21.5 (reference condition) and 21 (test condition), while NOx, HC, CO and PM levels for the compression ratio of 21 were decreased by 11%, 46%, 28%, 11%, respectively, from those for the compression ratio of 21.5. The tests were also conducted with a compression ratio of 22 and 4.3% increased chamber volume. Output power, torque, exhaust gas temperature and smoke level were greater, while specific fuel consumption was less for the compression ratio of 22 than those for the compression ratio of 21.5. Increase of compression ratio decreased HC and CO levels by 24%, 39%, but increased NOx and PM levels by 24%, 39%. Based on these results, a compression ratio of 21 was selected as an optimum value. Then, full load tests with the selected compression ratio of 21 were carried out for different throat ratios of 1.0%, 1.1%, 1.2%. Output power and torque were greatest and smoke was lowest when throat area ratio was 1.1%, which satisfied the target values of specific fuel consumption (less than 272 g/$kW{\cdot}h$) and exhaust gas temperature (less than $550^{\circ}C$). Therefore, a throat area ratio of 1.1% was selected as an optimum value.

• Journal of Radiation Protection and Research
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• 제24권1호
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• pp.31-38
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• 1999

원자력시설의 사고시 신속한 방재대책 결정지원 체계를 수립하기 위하여 실시간 방사선 피폭해석 시스템(FADAS : Following Accident Dose Assessment System)을 개발하였다. 개발된 시스템의 정확도 향상 및 국내 부지 특성자료의 모수화를 위하여 복잡한 지형상에 위치한 영광 원자력발전소 주변에서 야외 확산실험이 수행되었다. 확산실험을 통하여 얻어진 바람의 평균 및 난류장 성분은 부지 특성별 변수로 실시간 방사선 피폭해석 시스템에 반영되었다. 확산모형의 계산결과와 실험을 통하여 관측된 추적자 가스의 농도분포를 상호 비교한 바 어느 정도 일치하고 있었다. 개발된 시스템은 현재 구축중인 국가 규모의 비상대응지원체제에 기본 모듈로서 활용 중에 있으며 지속적인 확산실험을 통하여 부지 특성 변수들이 반영된 확산모형을 개선할 예정이다.

• 전기화학회지
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• 제25권1호
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• pp.22-31
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• 2022

Carbon nanomaterials are considered to be the materials of choice for the fabrication of electrochemical energy storage devices due to their stability, cost-effectiveness, well-established processing techniques, and superior performance compared to other active materials. In the present work, reduced graphene oxide (rGO) has been synthesized and used for the fabrication of a symmetric supercapacitor. The electrochemical performance of the fabricated supercapacitors with three different aqueous electrolytes namely 0.5 M H₂SO₄, 0.5 M H₃PO₄, and 1.0M Na₂SO₄ have been compared and analyzed. Among the three electrolytes, the highest areal specific capacitance of 14 mF/cm² was calculated at a scan rate of 5 mV/s observed with 0.5M H₃PO₄ electrolyte. The results were also confirmed from the charge/discharge results where the supercapacitor with 0.5M H₃PO₄ electrolyte delivered a specific capacitance of 11 mF/cm² at a current density of 0.16 mA/cm². In order to assess the stability of the supercapacitor with different electrolytes, the cells were subjected to continuous charge/discharge cycling and it was observed that acidic electrolytes showed excellent cyclic stability with no appreciable drop in specific capacitance as compared to the neutral electrolyte.