• Journal of Astronomy and Space Sciences
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• 제25권2호
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• pp.181-198
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• 2008

최근 들어 소형의 저궤도 위성들을 이용해서 특정 지역을 관측하기 위한 위성군의 궤도를 설계하는 것의 중요성이 점점 부각되고 있다. 일반적으로 많이 사용하는 Walker 위성군 설계 방법은 전 지구영역 관측에는 적당하지만 부분적인 지역 관측에는 효율성이 떨어진다. 이 논문에서는 한반도를 효율적으로 관측하기 위한 최적의 위성군 궤도 설계 방법을 연구하였다. 이를 위해 원궤도 중 지표면 반복궤도를 이용하여 위성군을 이루고 있는 위성들의 궤도요소를 직접 조절하는 방법을 사용하였다. 관측 목표 지역에 대해 최소한의 위성을 이용하여 관측 공백시간을 최소화하고 관측시간은 최대화하는 궤도요소를 산출하여 위성군 궤도를 설계하였다. 위성군 설계 결과, 저궤도 위성을 이용하였을 경우, 관측 가능한 최소 고도각을 12도로 가정하였을 때 한반도 지역의 관측을 효율적(관측 공백시간은 1시간 이내로 하면서 최대의 관측시간을 보장)으로 하려면 최소한 4대의 위성이 필요하다는 결과를 얻었다. 그리고 이 연구에서 제시된 방법이 Walker 방법보다 더 효율적이라는 것을 확인하였다. 이 연구를 통해서 개발된 알고리즘은 향후 우리나라가 실제로 위성군을 운영하고자 할 때 사전 임무 설계를 위하여 사용될 수 있다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2006년도 춘계공동학술대회 논문집
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• pp.17-24
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• 2006

We consider the sensor location problem (SLP) on a given sensor field. We present the sensor field as grid of points. There are several types of sensors which have different detection ranges and costs. If a sensor is placed in some point, the points inside of its detection range can be covered. The coverage ratio decreases with distance. The problem we consider in this thesis is called multiple-type differential coverage sensor location problem (MDSLP). MDSLP is more realistic than SLP. The coverage quantities of points are different with their distance form sensor location in MDSLP. The objective of MDSLP is to minimize total sensor costs while covering every sensor field. This problem is known as NP-hard. We propose a new integer programming formulation of the problem. In comparison with the previous models, the new model has a smaller number of constraints and variables. This problem has symmetric structure in its solutions. This group is used for pruning in the branch-and-bound tree. We solved this problem by branch-and-cut(B&C) approach. We tested our algorithm on about 60 instances with varying sizes.

• 한국인터넷방송통신학회논문지
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• 제11권6호
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• pp.31-39
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• 2011

재난현장에서 신속한 애드혹 무선 백본망을 형성하기 위해서는 사전계획 없이 초동 대응요원들에 의하여 무선 애드혹 중계장치를 실시간으로 배치하는 기법이 필요하다. 그러나 이를 실현하기 위해서는 중계장치의 중복배치 최소화뿐만 아니라 통신권역 확장을 위한 중계장치의 최적 위치를 선정할 수 있어야 한다. 따라서 본 논문에서는 통신권역을 최적화하기 위한 새로운 중계장치 배치기법을 제안하고 모의실험을 통하여 알고리즘의 성능이 향상되었음을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권11호
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• pp.5264-5281
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• 2017

Multihop relay-based cellular networks are attracting much interest because of their throughput enhancement, coverage extension, and low infrastructure cost. In these networks, relay stations (RSs) between a base station (BS) and mobile stations (MSs) drastically increase the overall spectral efficiency, with improved channel quality for MSs located at the cell edge or in shadow areas, and enhanced throughput of MSs in hot spots. These relay-based networks require an advanced radio resource management scheme because the optimal amount of radio resource for a BS-to-RS link should be allocated according to the MS channel quality and distribution, considering the interference among RSs and neighbor BSs. In this paper, we propose optimal resource planning algorithms that maximize the overall utility of relay-based networks under a proportional fair scheduling policy. In the first phase, we determine an optimal scheduling policy for distributing BS-to-RS link resources to RSs. In the second phase, we determine the optimal amount of the BS-to-RS link resources using the results of the first phase. The proposed algorithms efficiently calculate the optimal amount of resource without exhaustive searches, and their accuracy is verified by comparison with simulation results, in which the algorithms show a perfect match with simulations.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제15권2호
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• pp.87-95
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• 2015

In this study, we pursue a new direction for system modeling by introducing the concept of granular models, which produce results in the form of information granules (such as intervals, fuzzy sets, and rough sets). We present a rationale and several key motivating arguments behind the use of granular models and discuss their underlying design processes. The development of the granular model includes optimal allocation of information granularity through optimizing the criteria of coverage and specificity. The emergence and construction of granular models of type-2 and type-n (in general) is discussed. It is shown that achieving a suitable coverage-specificity tradeoff (compromise) is essential for developing granular models.

• Clinical and Experimental Pediatrics
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• 제53권5호
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• pp.623-628
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• 2010

The mumps virus is a single-stranded, non-segmented, negative-sense RNA virus belonging to the $Paramyxoviridae$ family. Mumps is characterized by bilateral or unilateral swelling of the parotid gland. Aseptic meningitis is a common complication, and orchitis is also common in adolescents and adult men. Diagnosis is based on clinical findings, but because of high vaccination coverage, clinical findings alone are not sufficient for diagnosis, and laboratory confirmation is needed. Mumps is preventable by vaccination, but despite high vaccination coverage, epidemics occur in several countries, including Korea. Many hypotheses are suggested for these phenomena. In this review, we investigate the reason for the epidemics, optimal methods of diagnosis, and surveillance of immunization status for the prevention of future epidemics.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제3권2호
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• pp.206-214
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• 2003

In this paper, we propose a method to avoid obstacles that have unstable limit cycles in a chaos trajectory surface. We assume all obstacles in the chaos trajectory surface have a Van der Pol equation with an unstable limit cycle. When a chaos robot meets an obstacle in an Arnold equation or Chua's equation trajectory, the obstacle reflects the robot. We also show computer simulation results of Arnold equation and Chua's equation and random walk chaos trajectories with one or more Van der Pol obstacles and compare the coverage rates of each trajectory. We show that the Chua's equation is slightly more efficient in coverage rates when two robots are used, and the optimal number of robots in either the Arnold equation or the Chua's equation is also examined.

• 로봇학회논문지
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• 제6권3호
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• pp.255-262
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• 2011

Many intelligent robots have to be given environmental information to perform tasks. In this paper an intelligent robot, that is, a cleaning robot used a sensor fusing method of two sensors: LRF and StarGazer, and then was able to obtain the information. Throughout wall following using laser displacement sensor, LRF, the working area is built during the robot turn one cycle around the area. After the process of wall following, a path planning which is able to execute the work effectively is established using flow network algorithm. This paper describes an algorithm for minimal turning complete coverage path planning for intelligent robots. This algorithm divides the whole working area by cellular decomposition, and then provides the path planning among the cells employing flow networks. It also provides specific path planning inside each cell guaranteeing the minimal turning of the robots. The proposed algorithm is applied to two different working areas, and verified that it is an optimal path planning method.

• 대한가정학회지
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• 제40권7호
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• pp.157-172
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• 2002

The purpose of this study is to characterize body types of males in their twenties, and to provide information on body types of males by classifying them into groups. In addition, this study attempts to provide ways that can help improve the fit and coverage rate of ready-to-wear clothes by developing an apparel sizing system according to body types. 297 male subjects in their twenties participated in this study. 54 anthropometric and 35 photographic measurements were taken from each subject. After combining the body types of the front and the side into a whole body, we selected typical body types out of the combinations. It is shown that 84.64% of males in their twenties belong to the HI type, H/equation omitted/ type, X/equation omitted/ type, Xl type, Yl type, and HS type. To develop a new size system of clothes, the distribution of sizes was determined by using means and standard deviations for basic parts of each body type. Then, the most optimal sizes were selected separately for each body type to maximize the coverage rate.

• Journal of Trauma and Injury
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• 제36권4호
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• pp.404-410
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• 2023

Large scalp defects resulting from high-voltage electrical burns require free flaps, preferably skin, to permit optimal coverage and enable future or simultaneous cranial vault reconstruction. The anterolateral thigh permits the harvest of a large area of skin supplied by a reliable perforator. The superficial temporal vessels offer the proximate choice of recipient vessels to enable adequate reach and coverage. The lack of a second vein at this site implies the inability to perform a second venous anastomosis; however, this obstacle can be overcome by using an interposition vein graft, to the neck veins primarily. This assures adequate venous drainage and complete flap survival.