• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.841-843
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• 2014

Mobile communication systems such as WCDMA, Wibro, LTE, etc are being developed to meet the explosively increasing demands for wireless data. These communication systems are using the power at all times. In general a base station has all of the communication systems mentioned above in order to provide a more convenient service to a number of users. The demands for wireless data are changed according to time and location. If the mobile communication systems are selectively operated according to the demand for wireless data then the consumed power can be saved. This paper describes the design and implementation of the load management system which controls the supplied power to the mobile communication infrastructures depending on the demand of wireless data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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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.

• The KSFM Journal of Fluid Machinery
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• v.15 no.4
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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.

• Journal of Industrial Technology
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• v.25 no.B
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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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• v.14 no.3
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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.

• Proceedings of the KIPE Conference
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• 2003.07a
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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.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.345-350
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• 2009

In this paper, it is reviewed vulnerability of security in S-MAC communication protocol of sensor network, and analyzed in the respect of power efficiency, which is consumed at each stage of communication procedure in according to vulnerability of denial of service. Therefore, from research results, it can be induced the need of authentication scheme, which is considered reliability, efficiency and security of normal S-MAC communication.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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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.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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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.