• 대한전자공학회논문지SD
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• 제46권9호
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• pp.49-57
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• 2009

본 연구에서는 상위 수준 합성에서 시간 제약과 하드웨어 제약을 동시에 고려하여 에너지 소모를 최소로 줄이는 다중 전압스케줄링 방법을 개발하였다. 기존의 다중 전압 스케줄링에서는 임계 경로에 있는 연산에 대해 높은 전압을 할당하고, 임계 경로에 있지 않은 연산에 대해서는 낮은 전압을 할당하는 방법을 주로 사용하였다. 우리는 다중 전압 리스트 스케줄링을 기반으로 simulated annealing기법을 적용하여 임계 경로상의 연산인지와 관계없이 자유롭게 여러 전압을 할당하여 최적화함으로서 저전력 스케줄링 결과를 얻을 수 있었다. 계산 시간 제한에 여유가 있을 때에는 전반적으로 낮은 전압을 사용하여 에너지 소모를 더욱 낮출 수 있다. 그리고 후처리 과정을 통해 추가의 에너지 감소를 얻을 수 있었다. 경우에 따라, 전압 level shifter 수를 줄일 필요가 있으므로 비용 함수에 가중치를 줄 수 있도록 하였다. 예를 들어, level shifter 에너지 소모에 6배의 가중치를 주면, 전압 level shifter 수는 약 24%, shifter 에너지 소모는 약 20% 정도 감소한다. 이를 이용하여 전체 에너지 소모와 level shifter 사용횟수의 tradeoff가 가능하다.

• 환경영향평가
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• 제20권4호
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• pp.465-475
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• 2011

It is known that energy consumption in bottom floor of typical Korean-style apartment is the highest. Previous studies for energy consumption in accordance with floor level appear to be very limited due to the dependence on single energy variable such as electric power or LNG separately, based on past flat type of apartment. Acknowledging these constraints, an empirical study for a tower type emerged recently as new style of apartment in South Korea was conducted to demonstrate how a comprehensive evaluation for both electric power and LNG consumption can be used to assist in monitoring the total energy consumption in terms of floor specific settings. It was possible to identify that energy consumption in bottom floor is lesser than that of top floor, to the contrary, fact known from previous study. Also electric power consumption in top floor was identified as 15% higher than that of floor in the least. It is anticipated that this integrated utilization of electric power and LNG data would present more scientific and objective evidence for the energy load among floor level of tower type apartment by overcoming serious constraints suffered from the past single variable investigation. Ultimately, the result in this paper could be used as a valuable reference to providing priority for energy saving activities in top floor such as cool roof or green roof.

• 한국정밀공학회지
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• 제27권1호
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• pp.76-83
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• 2010

There have been many studies regarding development of autonomous excavation system which is helpful in construction sites where repetitive jobs are necessary. Unfortunately, bucket trajectory planning was excluded from the previous studies. Since, the best use of excavator is to dig efficiently; purpose of this research was set to determine an optimized bucket trajectory in order to get best digging performance. Among infinite ways of digging any given path, criterion for either optimal or efficient bucket moves is required to be established. One method is to adopt work know-how from experienced excavator operator; However the work pattern varies from every worker to worker and it is hard to be analyzed. Thus, other than the work pattern taken from experienced operator, we developed an efficiency model to solve this problem. This paper presents a method to derive a bucket trajectory from optimization theory with empirical CLUB soil model. Path is greatly influenced by physical constraints such as geometry, excavator dimension and excavator workspace. By minimizing a energy function under these constraints, an optimal bucket trajectory could be obtained.

• Nuclear Engineering and Technology
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• 제42권3호
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• pp.329-338
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• 2010

We developed an achievable control logic for the reactor power level during a power maneuvering event and set up some constraints for the control of the reactor power in a conceptual sodium-cooled fast reactor (KALIMER-600) that was developed at KAERI. For simulating the dynamic behaviors of the plant, we developed a fast-running performance analysis code. Through various simulations of the power maneuvering event, we evaluated some suggested control logic for the reactor power and found an achievable control logic. The objective of the control logic is to search for the position of the control rods that would keep the average temperature of the primary pool constant and, concurrently, minimize the power deviation between the reactor and the BOP cycle during the power maneuvering. In addition, the flow rates of the primary pool and the intermediate loop should be changed according to the power level in order to not violate the constraints set up in this study. Also, we evaluated some movement speeds of the control rods and found that a fast movement of the control rods might cause the power to fluctuate during the power maneuvering event. We suggested a reasonable movement speed of the control rods for the developed control logic.

• Earthquakes and Structures
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• 제1권2호
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• pp.147-162
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• 2010

The ground acceleration measured at a point on the earth's surface is composed of several waves that have different phase velocities, arrival times, amplitudes, and frequency contents. For instance, body waves contain primary and secondary waves that have high frequency content and reach the site first. Surface waves are composed of Rayleigh and Love waves that have lower phase velocity, lower frequency content and reach the site next. Some of these waves could be of more damage to the structure depending on their frequency content and associated amplitude. This paper models critical earthquake loads for single-degree-of-freedom (SDOF) inelastic structures considering evolution of the seismic waves in time and frequency. The ground acceleration is represented as combination of seismic waves with different characteristics. Each seismic wave represents the energy of the ground motion in certain frequency band and time interval. The amplitudes and phase angles of these waves are optimized to produce the highest damage in the structure subject to explicit constraints on the energy and the peak ground acceleration and implicit constraints on the frequency content and the arrival time of the seismic waves. The material nonlinearity is modeled using bilinear inelastic law. The study explores also the influence of the properties of the seismic waves on the energy demand and damage state of the structure. Numerical illustrations on modeling critical earthquake excitations for one-storey inelastic frame structures are provided.

• Advances in Energy Research
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• 제4권1호
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• pp.47-68
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• 2016

A well designed hybrid power system (HPS) can deliver electrical energy in a cost effective way. In this paper, model for HPS consisting of photo voltaic (PV) module and wind mill as renewable energy sources (RES) and solar lead acid battery as storage device connected to unidirectional grid is developed for peak demand reduction. Life time energy cost of the system is evaluated. One year hourly site condition and load pattern are taken into account for analysing the HPS. The optimal HPS is determined for least life time energy cost subject to the constraints like state of charge of the battery bank, dump load, renewable energy (RE) generation etc. Optimal solutions are also found out individually for PV module and wind mill. These three systems are compared to find out the most feasible combination. The results show that the HPS can deliver energy in an acceptable cost with reduced peak consumption from the grid. The proposed optimization algorithm is suitable for determining optimal HPS for desired location and load with least energy cost.

• 전기전자학회논문지
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• 제13권1호
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• pp.71-76
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• 2009

As one of the most important requirements for wireless sensor networks, prolonging network lifetime can be realized by minimizing energy consumption in cluster heads as well as sensor nodes. While most of the previous researches have focused on the energy of sensor nodes, we devote our attention to cluster heads because they are most dominant source of power consumption in the cluster-based sensor networks. Therefore, we seek to minimize energy consumption by minimizing the maximum(MINMAX) energy dissipation at each cluster heads. This work requires energy-efficient clustering of the sensor nodes while satisfying given energy constraints. In this paper, we present a constraint satisfaction modeling of cluster-based routing in a heterogeneous sensor networks because mixed integer programming cannot provide solutions to this MINMAX problem. Computational experiments show that substantial energy savings can be obtained with the MINMAX algorithm in comparison with a minimum total energy(MTE) strategy.

• Journal of Communications and Networks
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• 제14권2호
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• pp.130-139
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• 2012

Energy harvesting has emerged as a powerful technology for complementing current battery-powered communication systems in order to extend their lifetime. In this paper a general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment. Assuming that the energy arrival process is known non-causally at the transmitter, the structure of the optimal transmission scheme, which maximizes the amount of transmitted data by a given deadline, is identified. Our framework includes models with continuous energy arrival as well as battery constraints. A battery that suffers from energy leakage is studied further, and the optimal transmission scheme is characterized for a constant leakage rate.

• 산업경영시스템학회지
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• 제12권20호
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• pp.55-61
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• 1989

The main contribution this research is the development of methodology which is capable of solving problems associated with the capacity expansion and operating schedule of energy industries. The principal concern of such industries is the proper allocation of primary energy which are required for the production of sufficient supply of electricity and petroleum products for the Korea`s energy needs. Nonlinear programming models are developed for power generation expansion planning and for the oil refinery industry. In order to deal with uncertainties about future demands for final energy, chance-constrained programming is used to formulate appropriate constraints. The methodology of the model can be used to evaluate Korean energy and expansion planning in the energy industry, especially the electric power generation industry and the refinery industry.

• International Journal of Internet, Broadcasting and Communication
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• 제7권1호
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• pp.23-29
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• 2015

Energy constraints of wireless sensor networks are an important challenge. Data Transmission requires energy. Distance between origin and destination has an important role in energy consumption. In addition, the location of base station has a large impact on energy consumption and a specific method not proposed for it. In addition, a obtain model for location of base station proposed. Also a model for distributed clustering is presented by cluster heads. Eventually, a combination of discussed ideas is proposed to improve the energy consumption. The proposed ideas have been implemented over the LEACH-C protocol. Evaluation results show that the proposed methods have a better performance in energy consumption and lifetime of the network in comparison with similar methods.