• JSTS:Journal of Semiconductor Technology and Science
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• 제14권5호
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• pp.588-593
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• 2014

Current crowding problem can worsen the internal quantum efficiency and the negative-voltage ESD of InGaN-based LEDs. In this paper, by using photon emission microscope and thermal emission microscope measurement, we confirmed that the electric field and the current of the InGaN-based LED sample are crowded in specific regions where the distance between p-type metal contact and n-type metal contact is shorter than other regions. To improve this crowding problem of electric field and current, modified metal contact geometry having uniform distance between the two contacts is proposed and verified by a numerical simulation. It is confirmed that the proposed structure shows better current spreading, resulting in higher internal quantum efficiency and reduced reverse leakage current.

• 산업경영시스템학회지
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• 제32권3호
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• pp.1-9
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• 2009

Processing mail objects in a mail processing center involves several steps and operations, in particular dispatching as well as sorting by destination. The purpose of this paper is to present a model for the part-time worker staffing and allocation problem as it arises at the parcel sorting area in a mail processing center. The problem is formulated as a mixed integer linear program model to minimize the variable part-time workforce related cost. Hot only the characteristics of the sorting operations but also the dispatching requirements of the vehicles are reflected into the model. Six example problems with three different daily amounts of arriving mail are solved with LINGO to demonstrate the effectiveness of the 7-level induction option for the parcel sorting machine over the current 3-level one. The results indicate that measurable savings can be achieved by departing from current practice.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.139-141
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• 2000

High voltage direct current(HVDC) transmission system uses the phase controlled rectifier triggered by means of IPC(individual phase control) or EPC(equidistant pulse control). Most HVDC system has adopted EPC method that can solve the harmonic instability problem of IPC method in weak power system. But EPC has inherent indirect synchronizing problem requiring the closed loop control. This paper presents the new gate pulse generating method for 12-pulse HVDC converter, which combines IPC with EPC. Simulation and test results are presented. The basic concept is that it generates the gating pulse for 12-pulse converter by synthesizing the internal phase reference using the frequency and phase information of a sin91e phase voltage. To ensure the reliability of the external phase input, Potential transformer that detects the phase voltage has redundancy. Using fault detecting algorithm the healthy input is always guaranteed. And the frequency compensation function was reinforced.

• 보건교육건강증진학회지
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• 제28권5호
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• pp.131-143
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• 2011

Objectives: This study is to develop a web-based prevention program of alcohol-related problem among university students and to examine its efficacy in changing drinking behaviors and reducing harms associated with alcohol use. Methods: An hour-length program was developed containing news paper articles, pictures, stories and questionnaires in a multimedia format such as flash, animation, and text. Survey data were analyzed to examine program efficacy from a convenient sample of 1,080 freshmen enrolled in a participating university. Results: Participation in the program has resulted in statistically significant changes in drinking behavior between pretest and follow-up, including reduction of frequency of drinking, heavy drinking, and intoxication, typical amount of drinking per occasion, and subjective norm of heavy drinking. Repeated ANOVA revealed significant increases in knowledge on alcohol related facts, including recommended drinking unit by WHO with substantial level of effect size and in making negative alcohol expectancy with very low effect size. Further studies are guaranteed with randomized controlled trial for the program effectiveness. Conclusions: A web-based prevention program of alcohol-related problems in this study was efficacious in changing drinking behavior, knowledge on alcohol-related fact, alcohol expectancy and subjective drinking norm.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.212-221
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• 2017

Background: This study aims to calculate detector positions as a design of a radioactive source localizing radiation portal monitor (RPM) system using an improved genetic algorithm. Materials and Methods: To calculate of detector positions for a source localizing RPM system optimization problem is defined. To solve the problem, a modified iterative genetic algorithm (MIGA) is developed. In general, a genetic algorithm (GA) finds a globally optimal solution with a high probability, but it is not perfect at all times. To increase the probability to find globally optimal solution rather, a MIGA is designed by supplementing the iteration, competition, and verification with GA. For an optimization problem that is defined to find detector positions that maximizes differences of detector signals, a localization method is derived by modifying the inverse radiation transport model, and realistic parameter information is suggested. Results and Discussion: To compare the MIGA and GA, both algorithms are implemented in a MATLAB environment. The performance of the GA and MIGA and that of the procedures supplemented in the MIGA are analyzed by computer simulations. The results show that the iteration, competition, and verification procedures help to search for globally optimal solutions. Further, the MIGA is more robust against falling into local minima and finds a more reliably optimal result than the GA. Conclusion: The positions of the detectors on an RPM for radioactive source localization are optimized using the MIGA. To increase the contrast of the measurements from each detector, a relationship between the source and the detectors is derived by modifying the inverse transport model. Realistic parameters are utilized for accurate simulations. Furthermore, the MIGA is developed to achieve a reliable solution. By utilizing results of this study, an RPM for radioactive source localization has been designed and will be fabricated soon.

• Journal of Communications and Networks
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• 제12권3호
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• pp.201-208
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• 2010

We propose a new notion of metered signatures. Metered signature is an extension of k-times signatures in which a signer can generate only k signatures. However, the restriction of metered signatures can be more elaborate: It can be used k-times every day or to preserve the order of signed messages in some applications. Any violation of this regulation reveals a secret key or the signature on a predetermined message. The applications includes proxy signatures, limited free downloads, and the rating web site. We give two instances of metered signatures: One is based on the computational Diffie-Hellman problem (CDHP) using a bilinear map and the other is based on the RSA problem. In both schemes, the signature and certificate size and the verification cost are constant with respect to k. Further, we show that the proposed metered signatures admit batch verification of many signatures almost at one verification cost with small security loss.

• Journal of Chest Surgery
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• 제53권4호
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• pp.226-232
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• 2020

The quality of life associated with eating is becoming an increasingly significant problem for patients who undergo esophagectomy as a result of the improved survival rate after esophageal cancer surgery. Delayed gastric emptying (DGE) is a common complication after esophagectomy. Although several strategies have been proposed for the management and prevention of DGE, no clear consensus exists. The purpose of this review is to present a brief overview of DGE and to help clinicians choose the most appropriate treatment through an analysis of DGE by cause. Furthermore, we would like to suggest some tips to prevent DGE based on our experience.

• 산업공학
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• 제22권2호
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• pp.153-164
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• 2009

An effective management for reverse flows of products such as reuse, repair and disposal, has become an important issue for every aspect of business. In this paper, we study the Location-Routing Problem (LRP) in the multi-stage closed-loop supply chain network. The closed-loop supply chain in this study integrated both forward and reverse flows. In forward flow, a factory, Distribution Center (DC) and retailer are considered as usual. Additionally in reverse flow, we consider the Central Returns collection Center (CRC) and disposal facility. We propose a mixed integer programming model for the design of closed-loop supply chain integrating both forward and reverse flows. Since the LRP belongs to an NP-hard problem, we suggest a heuristic algorithm based on genetic algorithm. For some test problems, we found the optimal locations and routes by changing the numbers of retailers and facility candidates. Furthermore, we compare the efficiencies between open-loop and closed-loop supply chain networks. The results show that the closed-loop design is better than the open one in respect to the total routing distance and cost. This phenomenon enlarges the cut down effect on cost as an experimental space become larger.

• 한국군사과학기술학회지
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• 제23권4호
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• pp.399-406
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• 2020

In this paper, we propose a time-varying proportional navigation guidance law that determines the proportional navigation gain in real-time according to the operating situation. When intercepting a target, an unidentified evasion strategy causes a loss of optimality. To compensate for this problem, proper proportional navigation gain is derived at every time step by solving an optimal control problem with the inferred evader's strategy. Recently, deep reinforcement learning algorithms are introduced to deal with complex optimal control problem efficiently. We adapt the actor-critic method to build a proportional navigation gain network and the network is trained by the Proximal Policy Optimization(PPO) algorithm to learn an evasion strategy of the target. Numerical experiments show the effectiveness and optimality of the proposed method.

• 가정과삶의질연구
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• 제30권5호
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• pp.1-15
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• 2012

The purpose of this study is various discussion and alternatives focusing on integration of center for enhancing family policy delivery system and family support service the long term. The subject is managers who work at Healthy Family Support centers and Multicultural Family Centers. And they are responded non-structural questionnaire. The results were follows: First, 82.4% respondents of healthy support center and 50% respondents were in favor of integration. Second, reason of integration are conformance for social integration, the efficiency of center operations, the adequacy of program for various family, doing program with the goal of both centers of the similarity, complementary, and user convenience, prevent duplication and missing of services and so on, If the amount charged against the project of the center dissimilarity of institutions, including the operating direction was different. Third, the Center for the meaning of integration are name, organization, reorganization or consolidation of functions, was regarded as entrusted to corporate consolidation. Fourth, the consolidation that occurs during problem solving to ensure the succession of budgeting and human resources and program alternative for dressing up, commissioning center was the difference as problem solving.