• Korean Journal of Social Welfare Studies
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• v.45 no.2
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• pp.375-402
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• 2014

The purpose of this study is to investigate the longitudinal change pattern of life satisfaction and the effect of social capital of people with disabilities. For this study, data were drawn from the panel data employment for the disabled from the second to the fifth. It includes 3,206 person with disabilities. The methodology adopted in this study is the latent growth curve modeling. The findings of this study are as follows: First, Life satisfaction has been decreased over years and the difference between individuals of life satisfaction of people with disabilities were statistically significant. Second, The intercept of life satisfaction in the disabled was positively associated with network, and slope of life satisfaction was negatively related to network. Third, social participation positively influences the intercept of life satisfaction but, no significant affect to the slope. Based on results of the study, practical implication and the political-approach to interventions for the better life satisfaction of the disabled are being discussed.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.433-436
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• 2011

자원 제약적인 임베디드 시스템 기반의 비디오 압축/전송 시스템에서 고수준의 영상품질과 에너지 효율성을 동시에 만족시키는 것은 쉽지 않은 문제이다. 본 논문에서는 동작 주파수 설정을 이용하여 주어진 네트워크 환경과 영상품질을 만족하면서 에너지 소비가 최소화되는 솔루션을 제안한다. 즉, 주어진 네트워크 환경에서 압축/영상품질의 상관관계를 분석하고 에너지가 최소화되도록 동작 주파수를 결정한다. JPEG을 이용한 실험 결과, 동작 주파수 설정을 이용한 방법은 기존의 방법 보다 사용자가 요구하는 영상품질을 만족하면서 약 60% 정도 에너지를 절감할 수 있음을 확인하였다.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.451-458
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• 1999

This paper considers the problem of routing connections in multi-optical tree network using WDM (Wavelength Division Multiplexing), where each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. The problem of optimal colouring of paths on multi-optical network is NP-hard[1], but if that is the colouring of all paths, then there exists an efficient polynomial time algorithm. In this paper, using divided & conquer method we gave an efficient algorithm to assign wavelengths to the all paths of a tree network based on the theory of (7) and our time complexity $O(n^4log\; n)$.

• Journal of Korea Multimedia Society
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• v.13 no.2
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• pp.258-264
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• 2010

In the Ad-hoc networks, the limitation on the availability of power for operation is a significant bottleneck, given the requirements of portability, weight, and size of mobile devices. Hence, the use of routing metrics that consider the capabilities of the power sources of the network nodes contributes to the efficient utilization of energy. This paper presents a QoS routing protocol that minimize the power consumed by a packet in traversing from source node to the destination node. Results obtained of simulation show that, with our approach we can reduce the power consumption of nodes and increases the life time of the network.

• Journal of Korean Society of Transportation
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• v.26 no.5
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• pp.175-184
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• 2008

Uncertainties are unavoidable in engineering applications. In this paper we propose an alpha reliable multi-variable network design problem under demand uncertainty. In order to decide the optimal capacity enhancement, three performance measures based on 3E(Efficiency, Equity, and Environmental) are considered. The objective is to minimize the total budget required to satisfy alpha reliability constraint of total travel time, equity ratio, and total emission, while considering the route choice behavior of network users. The problem is formulated as the chance-constrained model for application of alpha confidence level and solved as a lexicographic optimization problem to consider the multi-variable. A simulation-based genetic algorithm procedure is developed to solve this complex network design problem(NDP). A simple numerical example ispresented to illustrate the features of the proposed NDP model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.107-110
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• 2015

In this paper, we propose a coalitonal game theoritic approach to the power control problem in resource-constrained wireless sensor networks, where the objective is to enhance power efficiency of individual sensors while providing the QoS requirements. We model this problem as two-sided one-to-one matching game and deploly deferred acceptance procedure that produces a single matching in the core. Furthermore, we show that, by applying the procedure repeatedly, a certain stable state is achieved where no sensor can anticipate improvements in their power efficiency as far as all of them are subject to their own QoS constraints. We evaluate our proposal by comparing them with cluster-based and the local optimal solution obtained by maximizing the total system energy efficiency, where the objective function is non-convex.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.535-542
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• 2009

Wireless Sensor Network (WSN) is a wireless network consisting of spatially distributed autonomous devices, using sensors to cooperatively monitor physical or environmental conditions. WSNs face the critical challenge of sustaining long-term operation on limited battery energy. Coverage maintenance has been proposed as a promising approach to prolong network lifetime. Mobile sensors equipped with communication devices can be leveraged to overcome the coverage problem. In this paper, we propose a stepwise movement scheme using perimeter coverage property for the coverage maintenance problem. In our scheme, each sensor monitors neighboring dead nodes, determines vulnerable node (i.e. dead node which makes uncovered area), computes the center of uncovered area HC, and makes a coordinated stepwise movement to compensate the uncovered area. In our experimental results, our scheme shows at least 50 % decrease in the total moving distance which determines the energy efficiency of mobile sensor.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.51-55
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• 2017

This paper aims to maximize the energy harvesting rate and channel capacity in RF-energy harvesting networks (RF-EHNs) under the constraints of maximum transmit power and minimum quality of service (QoS) in terms of rate capacity for each user. We study a multi-user RF-EHN with frequency division multiple access (FDMA) in a Rayleigh channel. An access point (AP) simultaneously transmitting wireless information and power in the RF-EHN serves a subset of active users which have a power-splitting antenna. To gauge the network performance, we define energy efficiency (EE) and propose an optimization solution for maximizing EE with Lagrangian dual decomposition theory. In simulation results, we confirm that the EE is effectively maximized by the proposed solution with satisfying the given constraints.

• Journal of Intelligence and Information Systems
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• v.13 no.3
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• pp.101-117
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• 2007

In this paper, we propose a customized genetic algorithm (GA) to find the minimum-cost guideway network (GN) of personal rapid transit (PRT) subject to connectivity, reliability, and traffic capacity constraints. PRT is a novel transportation concept, where a number of automated taxi-sized vehicles run on an elevated GN. One of the most important problems regarding PRT is how to design its GN topology for given station locations and the associated inter-station traffic demands. We model the GN as a directed graph, where its cost, connectivity, reliability, and node traffics are formulated. Based on this formulation, we develop the GA with special genetic operators well suited for the GN design problem. Such operators include steady state selection, repair algorithm, and directed mutation. We perform numerical experiments to determine the adequate GA parameters and compare its performance to other optimization algorithms previously reported. The experimental results verify the effectiveness and efficiency of the proposed approach for the GN design problem having up to 210 links.

• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.115-122
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• 2011

It is very hard to obtain a general algorithm for solution of all the constraint satisfaction optimization problems. However, if the whole problem is separated into subproblems by characteristics of decision variables, we can assume that an algorithm to obtain solutions of these subproblems is easier. Under the assumption, we propose a problem classifying rule which subdivide the whole problem, and develop backtracking algorithms fit for these subproblems. One of the methods of finding a quick solution is efficiently arrange for any order of the search tree nodes. We choose the cluster head positioning problem in wireless sensor networks in which static characteristics is dominant and interference minimization problem of RFID readers that has hybrid mixture of static and dynamic characteristics. For these problems, we develop optimal variable ordering algorithms, and compare with the conventional methods. As a result of classifying the problem into subproblems, we can realize a backtracking framework for systematic search. We also have shown that developed backtracking algorithms have good performance in their quality.