• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2014년도 제49차 동계학술대회논문집 22권1호
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• pp.9-13
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• 2014

The performance of large scale software applications has been automatically increasing for last few decades under the influence of Moore's law - the number of transistors on a microprocessor roughly doubled every eighteen months. However, on-chip transistors limitations and heating issues led to the emergence of multicore processors. The energy efficient ARM based System-on-Chip (SoC) processors are being considered for future high performance computing systems. In this paper, we present a case study of two widely used parallel programming models i.e. MPI and MapReduce on distributed memory cluster of ARM SoC development boards. The case study application, Black-Scholes option pricing equation, was parallelized and evaluated in terms of power consumption and throughput. The results show that the Hadoop implementation has low instantaneous power consumption that of MPI, but MPI outperforms Hadoop implementation by a factor of 1.46 in terms of total power consumption to execution time ratio.

• 한국농림기상학회지
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• 제13권2호
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• pp.48-55
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• 2011

해안지대의 에너지평형을 결정짓는 복사성분 가운데 주변 바다로부터 반사되는 양을 무시할 수 없지만 아직 해수면 반사성분을 추정할 수 있는 방법이 확립되지 못한 실정이다. 본 연구에서는 새로운 추정방법을 고안하여 해수면 반사성분의 지리적, 계절적 분포양상을 모의하였으며, 그 결과 영향권의 면적과 수광량 모두 동지 무렵에 가장 크고 하지 무렵에 가장 적다는 것을 밝혔다. 이 방법을 제주도 한라산 사면에 적용할 경우 동지 무렵의 해수면 반사영향권은 $182.3km^2$이고 하루 누적 수광량은 $0.41MJ\;m^{-2}$ 이었다. 순간값의 경우 일 중 시간에 따라 전체 일사수광량 가운데 해수면 반사성분이 최대 33%를 차지하였다. 이 모형에 의해 해수면 반사성분을 추정할 때 가장 큰 영향을 주는 기상요인은 풍속으로 나타났다. 따라서, 현실적인 산출을 위해서는 모형에서 풍속을 고려해 주어야만 한다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.129-136
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• 2005

This paper presents a design strategy of SPOKE type BLDC motors considering an irreversible demagnetization of a permanent magnet (PM). So the irreversible demagnetization characteristic of the motor is analyzed by rotor structure. The instantaneous currents in either starting or lock rotor condition, which are calculated from the current dynamic analysis, are applied to the analysis of the irreversible demagnetization field by FEM. In irreversible demagnetization analysis by FEM, the variation of residual flux density in PM is analyzed using the non-linearity of magnetic core on B-H plan. The analysis results are compared to several rotor structures and used for optimize the rotor structure.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권2호
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• pp.200-206
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• 2014

This paper describes magnetically levitated vehicle with hybrid magnets, which have been studied by the authors in place of streetcars or conveyance system. An experimental vehicle of 20kg was magnetically levitated by using a small number of dry-cell batteries, which consisted of 10 Ni-MH cells of 1900mAh in series. The magnets were activated sequentially, because the internal resistance of the batteries suppressed the maximum current. The vehicle was kept levitating for about 2 hours and was stable against disturbance due to instantaneous external force. In this paper, dynamic characteristics of the magnetically levitated vehicle using a small number of dry cell batteries are presented.

• 상하수도학회지
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• 제18권4호
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• pp.522-528
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• 2004

Microfiltration with in-line rapid coagulation for drinking water production was examined. The in-line rapid coagulation was conducted using newly developed mixing device instantaneous flash mixer. The flux decline during membrane filtration was monitored with coagulant dosage varied. Flux decline was minimized at 1.1mg/L of coagulant dosage, where streaming potential of coagulated water was near zero. The optimum dosage for the process control was explained by dimensionless distance (${\kappa}{\times}a$) of particle pairs, obtained from electrophoresis parameter describing electrostatic repulsion relative to Van der Waals energy between particle pairs in the pre-coagulated water.

• Carbon letters
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• 제17권1호
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• pp.1-10
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• 2016

Lignocellulosic biomass conversion to biofuels such as ethanol and other value-added bio-products including activated carbons has attracted much attention. The development of an efficient, cost-effective, and eco-friendly pretreatment process is a major challenge in lignocellulosic biomass to biofuel conversion. Although several modern pretreatment technologies have been introduced, few promising technologies have been reported. Microwave irradiation or microwave-assisted methods (physical and chemical) for pretreatment (disintegration) of biomass have been gaining popularity over the last few years owing to their high heating efficiency, lower energy requirements, and easy operation. Acid and alkali pretreatments assisted by microwave heating meanwhile have been widely used for different types of lignocellulosic biomass conversion. Additional advantages of microwave-based pretreatments include faster treatment time, selective processing, instantaneous control, and acceleration of the reaction rate. The present review provides insights into the current research and advantages of using microwave-assisted pretreatment technologies for the conversion of lignocellulosic biomass to fermentable sugars in the process of cellulosic ethanol production.

• 대한전기학회논문지:전력기술부문A
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• 제52권5호
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• pp.279-286
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• 2003

A new UPQC(unified power quality conditioner), which consists of series inverter, shunt inverter, dc/dc converter, and energy storage, is proposed. The proposing UPQC can compensate reactive power, harmonics, voltage sag and swell, voltage unbalance, and voltage interruption. The control strategy for the proposing UPWQC was derived using the instantaneous power method. The performance of proposing system was analyzed by means of the EMTDC/PSCAD simulation and the experimental work with the hardware prototype. The proposing UPQC has the ultimate capability of improving power quality at the point of installation on power distribution systems or industrial power systems and can be utilized for the custom power device in the future distribution system.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1450-1454
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• 2006

Empirical mode decomposition (EMD) is applied to analyze time series characterized with nonlinearity and nonstationarity. This decomposition could be utilized to construct finite and small number intrinsic mode functions (IMF) that describe complicated time series, while admitting the Hilbert transformation properties. EMD has the capability of being adaptive, capture local characteristics, and applicable to nonlinear and nonstationary processes. Unlike discrete wavelet transform (DWT), IMF eliminates spurious harmonics and retains meaningful instantaneous frequencies. Examples based on data representing natural phenomena are given to demonstrate highlight the power of this method in contrast and comparison of other ones. A presentation of the energy-frequency-time distribution of these signals found to be more informative and intuitive when based on Hilbert transformation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.166-171
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• 2004

Direct numerical simulations are peformed to investigate the physics of a spatially developing turbulent boundary layer flow suddenly subjected to spanwise oscillating electro-magnetic forces in the near-wall region. The Reynolds number based on the inlet momentum thickness and free-stream velocity is $Re_\theta=300$. A fully-implicit fractional step method is employed to simulate the flow. The mean flow properties and the Reynolds stresses are obtained to analyze the near-wall turbulent structure. It is found that skin-friction and turbulent kinetic energy can be reduced by the electro-magnetic forces. Instantaneous flow visualization techniques are used to observe the response of streamwise vortices to spanwise oscillating forces. The near-wall vortical structures are clearly affected by spanwise oscillating electro-magnetic forces.

• 한국해안해양공학회지
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• 제5권4호
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• pp.395-405
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• 1993

불규칙 파낭이 갖는 중요한 특성 중의 하나인 파군특성을 파낭 연이음개염과 에너지 이역 개념을 이용하여 해석하였다. 일정한 주기와 파고를 가지고 임의로 발생시킨 규칙파군에 적용하여 파군에 대한 기초적 특성을 파악한 후, 동해안에서 관측된 불규칙 파랑의 파군특성을 해석하였다. 불규칙 파낭의 파군특성을 정확히 해석하기 위해서는 기존의 스펙트럼 해석뿐만 아니라 파낭 연이음개념 및 에너지 이역개염을 함께 검토하여야 한다.