• Journal of Communications and Networks
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• v.18 no.3
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• pp.320-326
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• 2016

In existing literature on multiple-input multiple-output (MIMO) relaying communication systems, antenna selection is often implemented by maximizing the channel capacity or the output single-to-noise ratio (SNR). In this paper, we propose an energy-efficient low-complexity antenna selection scheme for MIMO relaying communication systems. The proposed algorithm is based on beamforming and maximizing the Frobenius norm to jointly optimize the transmit power, number of active antennas, and antenna subsets at the source, relaying and destination. We maximize the energy efficiency between the link of source to relay and the link of relay to destination to obtain the maximum energy efficiency of the system, subject to the SNR constraint. Compared to existing antenna selection methods forMIMO relaying communication systems, simulation results demonstrate that the proposed method can save more power in term of energy efficiency, while having lower computational complexity.

• New & Renewable Energy
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• v.9 no.3
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• pp.5-13
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• 2013

In the previous research, dynamic results have been analyzed in the time and frequency regions. Time and frequency region can be transformed by the Fourier transform. This transform is very useful about analyzing system behaviors. However, because of coupling, it cannot give clear results in the real system including lots of defects. In this paper, we introduced the analysis based on quefrency region to represent physical means clearly from complicated results. We simulated the drive train system which has defects, and compared between frequency and quefrency region to show its excellence. To do this process, We established mathematical model. The equation of motion was derived by the Lagrange equation and constraint equations. The constraint equation included relationships about gear mesh, flexibility of shaft. About numerical analysis, the Newmark beta method was used to get results. And FFT (Fast Fourier Transform) which converts results from time domain to frequency, qufrequency was used.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.129-136
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• 1997

This paper presents a new economic load dispatch considering atmospheric emissions such as NOx and SO$_2$caused by the operation of fossil-fueled thermal generation in power systems. The proposed method is described for scheduling their output of thermal power units so as to comply with total emission constraint, area emission constraint and the both of those constraints. Also, by using a trade-off curve, representing all dispatch alternatives and conflict between the emission and the fuel cost, the sensitivity analysis of the emission and the fuel cost is applied to this algorithm. By the way, this proposed method is analyzed how dispatch changes as a function of the total environmental cost, and as a function of the relative weighting of individual environmental insults, e.g, NOx and SO$_2$. By applying the proposed method to the system, the usefulness of this method is verified.

• Journal of Radiation Protection and Research
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• v.21 no.4
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• pp.329-338
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• 1996

최근에 우리나라가 공식 회원국으로 가입한 서방 경제협력개발기구(OECD)/원자력기구(NEA) 산하의 방사선 방호 및 보건위원회(CRPPH)에서는 유럽연합(EC)의 전문가그룹과 합동으로 국제방사선방호위원회(ICRP)의 권고 60의 방사선 방호 최적화 원칙에 공식적으로 도입된 이른 바 '선량제약(dose constraint)' 개념에 대한 위원회의 논의 및 검토결과를 OECD/NEA의 공식보고서로 발간하였다. 이 보고서는 선량제약의 개념과 의미를 논리적으로 합리화하기 위하여 발간된 것이다. 선량제약이란 용어와 개념은 새로워 보이지만 실상은 전혀 새로운 것이 아니다. 우리나라에서도 방사선 방호의 실무현장에서 용어나 의미는 조금 다르다 할 수 있어도 이 개념을 부분적으로 적용해왔다고 할 수 있다. 예를 들어, 선량한도 이하의 낮은 선량으로 작업자의 피폭을 제한하기 위하여 도입된 '연간 선량목표치' 또는 '방사성 물질의 방출목표관리치' 등이 여기에 해당될 것이다. 따라서, OECD/NEA의 공식보고서를 번역한 이 해설논문이 국내의 방사선 방호분야에서 활약하고 있는 정책 입안자, 연구자, 규제업무자, 방사선 관리실무자 등 방사선 방호 업무분야의 관련자들에게 도움이 되었으면 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1435-1440
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• 2014

Nodes in WSNs must operate under limited energy resource. Controlling access to the channel in WSNs plays a key role in determining channel utilization and energy consumption. This paper introduces a priority-based time slot allocation protocol for hybrid TDMA/CSMA MAC in WSNs. This protocol combines both TDMA and CSMA techniques while introducing prioritization by (m,k)-firm constraint. The performance of this protocol is obtained through simulations for various number of nodes and show significant improvements in delay and packet delivery ratio compared to S-MAC.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.173-181
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• 2016

In this paper, we address a new robust optimization problem in a multiuser multiple-input single-output broadcasting system with simultaneous wireless information and power transmission, where a multi-antenna base station (BS) sends energy and information simultaneously to multiple users equipped with a single antenna. Assuming that perfect channel-state information (CSI) for all channels is not available at the BS, the uncertainty of the CSI is modeled by an Euclidean ball-shaped uncertainty set. To optimally design transmit beamforming weights and receive power splitting, an average total transmit power minimization problem is investigated subject to the individual harvested power constraint and the received signal-to-interference-plus-noise ratio constraint at each user. Due to the channel uncertainty, the original problem becomes a homogeneous quadratically constrained quadratic problem, which is NP-hard. The original design problem is reformulated to a relaxed semidefinite program, and then two different approaches based on convex programming are proposed, which can be solved efficiently by the interior point algorithm. Numerical results are provided to validate the robustness of the proposed algorithms.

• The Journal of Engineering Geology
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• v.28 no.3
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• pp.367-377
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• 2018

This study introduces a DC resistivity inversion method that incorporates structural and inequality constraints to enhance the resolution of resistivity inversions, and presents sample inversion results with these constraints. In the constrained inversions, a base model is constructed from a layered model through interpretation of other geophysical data. Inversion tests establish that both the structural and inequality constraints produce better resistivity models than the unconstrained inversion. However, the inequality inversion not only reproduces the exact layered structure of the background, it reproduces conductive anomalies at a depth of ~ 10 m when an inexact base model of electrical resistivity is used.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.6
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• pp.273-283
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• 2008

Many embedded real-time systems have adopted processors supported with dynamic voltage scaling(DVS) recently. Power is one of the important metrics for optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor supported with DVS. In this paper, we propose heuristic algorithms to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. The previous algorithm has a following constraint : given the tasks are ordered in a nondecreasing order of their relative deadline, the task slowdown factors computed are in a nonincreasing order. In this paper, we relax the constraint and propose heuristic algorithms which have the same time complexity that previous algorithm has and can save more energy. Experimental results show that the proposed algorithms are energy efficient.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.2
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• pp.39-47
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• 2020

This paper introduces a novel system-level framework that derives energy efficient electric vehicle (EV) driving speed profile to extend EV driving range without additional cost. This paper first implements an EV power train model considering forces acting on a driving vehicle and motor efficiency. Then, it derivate the minimum-energy driving speed profile for a given driving mission defined by the route. This framework first formulates an optimization problem and uses the dynamic programming algorithm with a weighting factor to derive a speed profile minimizing both of energy consumption and driving time. This paper introduces various weighting factor tracking methods to satisfy the driving time constraint. Simulation results show that runtime of the proposed scaling algorithm is 34% and 50% smaller than those of the binary search algorithm and greedy algorithm, respectively.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.83-100
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• 1999

As disposal packaging concepts of spent fuels generated from the domestic NPP, two types, one is to package PWR and CANDU spent fuels in different containers and the other is to package them together, were proposed. The configuration of the containers and the layout of underground repository, such as the container spacing and the deposition tunnel spacing, were developed. The layout of underground repository satisfies the thermal constraint of the bentonite buffer surrounding disposal container, which should be lower than $100^{\circ}C$ in order to keep the physical and chemical properties of bentonite From the spent fuel packaging concepts and container emplacement methods, seven options were developed. With a typical pair-wise comparison methods, AHP, the most promising disposal concept was selected based on the technology Point of view.