• Advances in Energy Research
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• 제6권1호
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• pp.55-73
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• 2019

The cost incurred by voltage sag effect in power networks has always been of important concern for discussions. Due to the environmental constraints, fossil fuel shortage crisis and low efficiency of conventional power plants, decentralized generation and renewable based DG have become trends in recent decades; because DGs can reduce the voltage sag effect in distribution networks noticeably; therefore, optimum allocation of DGs in order to maximize their effectiveness is highly important in order to maximize their effectiveness. In this paper, a new method is proposed for calculating the cost incurred by voltage sag effect in power networks. Thus, a new objective function is provided that comprehends technical standards as minimization of the cost incurred by voltage sag effect, active power losses and economic criterion as the installation and maintenance costs of DGs. Considering operational constraints of the system, the optimum allocation of DGs is a constrained optimization problem in which Lightning Attachment procedure optimization (LAPO) is used to resolve it and is the optimum number, size and location of DGs are determined in IEEE 33 bus test system and IEEE 34 bus test system. The results show that optimum allocation of DGs not only reduces the cost incurred by voltage sag effect, but also improves the other characteristics of the system.

• 수산해양기술연구
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• 제58권2호
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• pp.175-184
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• 2022

This study analyzed the allocation of the skipper's attention during fishing operation in the wheelhouse of a Korean coastal composite fishing vessel by using video observation. To summarize the results, the ratio of lookout, radar and GPS monitoring, which is essential for prevention of collision at sea, was significantly lower than that of other fishing operation due to the attention concentration on the work place during hauling line. In order to reduce exposure to risk of collisions due to concentration of attention to certain tasks such as line hauling, it is necessary to develop an alert system that can notify the approach of other ships or obstruction throughout the ship using information from radar or the automatic identification system. In addition, the order of attention allocation to devices and facilities obtained in this study is expected to be used as basic data for device or facility layout based on the principle of usage frequency in designing wheelhouse for coastal composite fishing vessels in the future.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1072-1078
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• 2008

이 논문에서는 전송 실효성 극대화를 위하여 사용자 별 최소 및 최대 전송률 제한을 두는 페이딩 방송채널에서 내림차순 전력할당에 기반한 효율적인 SCM (superposition coding multiplexing) 방법을 제안한다. 이 방법은 3단계로 구성되는데, 1단계에서는 전송 가능한 최대의 사용자 집합을 선정하고, 2단계에서는 사용자 별 송신전력의 내림차순으로 해당 사용자의 최소 전송률을 보장하는 최대 허용 간섭전력을 결정하는 방식으로 해당 사용자별 송신전력을 할당하고 잔여전력을 계산한다. 3단계에서는 2단계에서 잔여전력이 발생하는 경우에 수행하며, 내림차순 마지막 사용자부터 다시 오름차순으로 해당 사용자의 최대 전송률 제공에 필요한 전력 범위까지 최대로 추가 전력을 할당한다. 이 방법은 2단계 내림차순 할당에서 각 사용자가 자신의 최소 전송률 보장을 위하여 이후 사용자들로부터의 최대 허용 간섭전력을 고려하여 전력할당이 이루어졌으며 오름차순 추가 할당으로 인한 해당 사용자 이후 모든 순위 사용자들에 대한 전력 재할당을 필요로 하지 않는다. 따라서, 제안한 방법은 사용자 별 최소뿐만 아니라 최대 전송률 제한을 두는 경우, 특히 사용자 수가 많아질수록 계산이 더욱 효율적이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3887-3907
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• 2015

This paper introduces a full duplex single secondary user multiple-input multiple-output (FD-SSU-MIMO) cognitive radio network, where secondary user (SU) opportunistically accesses the authorized spectrum unoccupied by primary user (PU) and transmits data based on FD-MIMO mode. Then we study the network achievable average sum-rate maximization problem under sum transmit power budget constraint at SU communication nodes. In order to solve the trade-off problem between SU's sensing time and data transmission time based on opportunistic spectrum access (OSA) and the power allocation problem based on FD-MIMO transmit mode, we propose a simple trisection algorithm to obtain the optimal sensing time and apply an alternating optimization (AO) algorithm to tackle the FD-MIMO based network achievable sum-rate maximization problem. Simulation results show that our proposed sensing time optimization and AO-based optimal power allocation strategies obtain a higher achievable average sum-rate than sequential convex approximations for matrix-variable programming (SCAMP)-based power allocation for the FD transmission mode, as well as equal power allocation for the half duplex (HD) transmission mode.

• Industrial Engineering and Management Systems
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• 제11권2호
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• pp.155-164
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• 2012

As the global market becomes more competitive, manufacturing industries face relentless pressure caused by a growing tendency of greater varieties of products, shorter manufacturing cycles and more sophisticated customer requirements. Efficient and effective supplier selection and order allocation decisions are, therefore, important decisions for a manufacturer to ensure stable material flows in a highly competitive supply chain, in particular, when customers are willing to accept products with less desirable product attributes (e.g., color, delivery date) for economic reasons. This paper attempts to solve optimally the challenging problem of supplier selection and order allocation, taking into consideration the customer flexibility for a manufacturer producing multi-products to satisfy the customers' demands in a multi period planning horizon. A new mixed integer programming model is developed to describe the behavior of the supply chain. The objective is to maximize the manufacturer's total profit subject to various operating constraints of the supply chain. Due to the complexity and non-deterministic polynomial-time (NP)-hard nature of the problem, an improved genetic approach is proposed to solve the problem optimally. This approach differs from a canonical genetic algorithm in three aspects: a new selection method to reduce the chance of premature convergence and two problem-specific repair heuristics to guarantee feasibility of the solutions. The results of applying the proposed approach to solve a set of randomly generated test problems clearly demonstrate its excellent performance. When compared with applying the canonical genetic algorithm to locate optimal solutions, the average improvement in the solution quality amounts to as high as ten percent.

• ETRI Journal
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• 제38권4호
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• pp.746-756
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• 2016

Owing to the intermittent power generation of renewable energy sources (RESs), future wireless cellular networks are required to reliably aggregate power from retailers. In this paper, we propose a distributed power allocation (DPA) scheme for base stations (BSs) powered by retailers with heterogeneous RESs in order to deal with the unreliable power supply (UPS) problem. The goal of the proposed DPA scheme is to maximize our well-defined utility, which consists of power satisfaction and unit power costs including added costs as a non-subscriber, based on linear and quadratic cost models. To determine the optimal amount of DPA, we apply dual decomposition, which separates the master problem into sub-problems. Optimal power allocation from each retailer can be obtained by iteratively coordinating between the BSs and retailers. Finally, through a mathematical analysis, we show that the proposed DPA can overcome the UPS for BSs powered from heterogeneous RESs.

• 한국컴퓨터정보학회논문지
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• 제4권1호
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• pp.7-14
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• 1999

본 논문에서는 상위수준합성에서의 연산자 할당 및 바인딩을 위한 방법을 다루었다. 스케쥴링 후 각 제어스텝에 지정된 연산을 연산자에 할당하기 위한 새로운 방법을 제시하였다. 특히 최적의 할당 및 바인딩 결과를 얻기위해 ILP 기법을 이용하였다. HAL시스템에서 사용된 Differential Equation DFG 모델을 실험대상으로 하여 본 연구의 효용성을 입증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권8호
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• pp.1913-1925
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• 2012

In order to efficiently utilize limited radio resources, resource allocation schemes in OFDMA-based wireless networks have gained intensive attention recently. Instead of improving the throughput performance, the utility is adopted as the metric for resource allocation, which provides reasonable methods to build up the relationship between user experience and various quality-of-service (QoS) metrics. After formulating the optimization problem by using a weighted bipartite graph, a modified bipartite matching method is proposed to find a suboptimal solution for the resource allocation problem in OFDMA-based wireless systems with feasible computational complexity. Finally, simulation results are presented to validate the effectiveness of the proposed method.

• 한국정보처리학회논문지
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• 제5권9호
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• pp.2395-2403
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• 1998

메모리 할당은 두 개의 독립적인 목표가 있다. 즉, 메모리 개수를 최소화하는 것과 한 개의 메모리 내의 레지스터(즉 단어)수를 최소화시키는 것이다. 우리의 관심은 메모리 할당시 이들 바인딩이 일어나는 순서에 있다. 바인딩이 일어나는 순서를 변경하여 세 가지의 전혀 다른 메모리 할당 알고리즘을 만들고 이들을 분석하였다. 실험 결과 경험적 비용 함수를 도입하여 부분 작업을 동시에 실행시켰을 때 메모리 면적을 최대 20%까지 줄일 수 있음을 확인하였다.

• 한국항공운항학회지
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• 제25권3호
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• pp.101-107
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• 2017

Demand for air transportation in Korea keeps increasing, and the number of airport operations also grows as a result. The major two airports in Korea, Incheon International Airport and Gimpo International Airport, share the metropolitan airspace, which is crowd with air traffic. As air traffic increases in the metropolitan airspace, the demand for the airport operations would outnumber the capacities of these airports. However, there is a room to efficiently manage the shortage of the airport capacity due to the different distributions of operations in these airports. This study presents a dynamic slot allocation that allows exchanging slots according to the traffic demand. The dynamic allocation mitigates the airports' capacity problem but the airspace capacity itself should be increased in order to tackle the problem fundamentally.