• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.841-843
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• 2014

이동통신은 폭발적으로 증가하고 있는 무선데이터의 수요를 충족시키기 위해서 WCDMA, Wibro, LTE 등의 통신 방식으로 발전하고 있다. 이들 이동통신 방식을 수용하는 시스템들은 항시 전력을 사용하고 있고, 사용자에게 보다 편리하고 많은 서비스를 제공하기 위해서 한 기지국에 모두 설치되어 있는 경우가 일반적이다. 무선데이터의 수요는 시간, 장소 등에 따라서 유동적으로 변화한다. 만약 무선데이터의 수요에 따라서 현재 운용중인 이동통신 시스템들을 상황에 맞게 선택적으로 운용한다면 많은 전력을 절감할 수 있다. 본 논문에는 무선데이터의 수요에 따라서 운용하는 통신시스템에 전력공급을 제어하는 이동통신 인프라의 전력절감을 위한 부하관리 시스템의 설계와 구현에 관해서 기술한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5614-5633
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• 2018

Mobile Edge Computing (MEC) and Wireless Power Transfer (WPT) are both recognized as promising techniques, one is for solving the resource insufficient of mobile devices and the other is for powering the mobile device. Naturally, by integrating the two techniques, task will be capable of being executed by the harvested energy which makes it possible that less intrinsic energy consumption for task execution. However, this innovative integration is facing several challenges inevitably. In this paper, we aim at prolonging the battery life of mobile device for which we need to maximize the harvested energy and minimize the consumed energy simultaneously, which is formulated as residual energy maximization (REM) problem where the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device are all considered as key factors. To this end, we jointly optimize the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device to solve the REM problem. Furthermore, we propose an efficient convex optimization and sequential unconstrained minimization technique based combining method to solve the formulated multi-constrained nonlinear optimization problem. The result shows that our joint optimization outperforms the single optimization on REM problem. Besides, the proposed algorithm is more efficiency.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.61-66
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• 2012

Nowadays, precise prediction of the pump performance becomes more important than ever before in high-value industries such as power plants and large ships. The power consumed in such pumps of large head and capacity definitely affects the efficiency of the entire system. In this study, we report the theoretical and CFD results used in prediction of the performance change caused by the reduction of impeller diameter. We have found that the theoretical calculation is somehow useful at least in estimating the very beginning condition for the CFD main calculation.

• 산업기술연구
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• 제25권B호
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• pp.141-147
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• 2005

A target of this paper is to get some elementary experimental data on the energy harvesting using a piezoelectric material. A THUNDER series piezo material (TH7-R), which has been developed by NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator and its driving electronics are designed. Using a simple PWM control, the excitation frequency of vibrating mechanical motion is varied. The generated electric power as a function of the excitation frequency is monitored and analyzed. This initial experiment shows a possible energy source using a piezoelectric material for the application to low-power consumed small electronic devices such as RFID, MEMS, and etc.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권3호
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• pp.94-101
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• 2006

A theoretical investigation to find thermodynamically optimum design conditions of conduction-cooled Peltier current leads is performed. A Peltier current lead (PCL) is composed of a thermoelectric element (TE), a metallic lead and a high temperature superconductor (HTS) lead in the order of decreasing temperature. Mathematical expressions for the minimum heat flow per unit current crossing the TE-metal interface and the minimum heat flow per unit current from the metal lead to the joint of the metal and the HTS leads are obtained. It is shown that the temperature at the TE -metal interface possesses a unique optimal value that minimizes the heat flow to the joint and that this optimal value depends on the material properties of the TE and the metallic lead but not the joint temperature nor electric current. It is also shown that there exists a unique optimal value for the joint temperature between the metal and the HTS leads that minimizes the sum of the power dissipated by ohmic heating in the current leads and the refrigerator power consumed to cool the lead, for a given length of the HTS.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.15-18
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• 2003

The electric power, regenerated while railway vehicles braking or running downhill, makes U line voltage rise and the feeding system may not be secure. In order to keep away from these kind of insecurity, the regenerative energy should be consumed by loads or transmitted to the AC side via certain devices such as DC/AC converters. This paper introduces the developed regenerative inverter for electric railway.

• 한국군사과학기술학회지
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• 제10권4호
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• pp.138-144
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• 2007

This paper introduces the design techniques of an IR module using the 2-D array un-cooled type infrared detector which is applied to the individual combat weapon. Considering the size and weight of the hand carried weapon system, we used a very small-sized detector and applied an adaptive temperature control algorithm so that the operation consumed with low power can be possible. We applied the AR(Auto Regressive) filter to improve the signal-to-noise ratio in a thermal image processing step. We also applied the plateau equalization and boundary enhancement techniques to improve the visibility for human visual system.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.345-350
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• 2009

본 논문에서는 센서 네트워크 S-MAC 통신 프로토콜에서 보안 취약성을 살펴보고 서비스 거부 공격의 취약성에 따른 영향을 통신절차 단계별로 소비되는 전력 효율성 측면에서 분석하였다. 따라서 연구 결과로부터 정상적인 S-MAC 통신을 위해 신뢰성, 효율성 및 보안을 고려한 인증방안의 필요성을 도출할 수 있다.

• 전기학회논문지
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• 제62권9호
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• pp.1329-1334
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• 2013

A electric railway is unique system that electric trains consumed huge electric power are travelled and is much interested with EMC. There were several problems exceeding the standard in the frequency range of 9kHz to 150kHz because the radiation noises were moved the higher frequency range according to developing the power electronic technology. It is studied the experimental confirmation of main noise source on the electric train and the analytic simulation for reducing the noise level in this paper.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2012년도 춘계학술발표대회논문집
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• pp.158-159
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• 2012

Heterogeneous cellular networks can provide high throughput and coverage compare to conventional networks of only macrocell deployment, however it operates regardless of total power consumption, which is a very important issue of modern cellular networks. We propose a policy that control the on/off state of base stations in heterogeneous networks according daily traffic profile. Under this policy, the total power consumed can be significantly reduced when the traffic is low while preserving QoS requirement.