• 지능정보연구
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• 제16권4호
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• pp.99-112
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• 2010

앙상블 학습은 분류 및 예측 알고리즘의 성과개선을 위하여 제안된 기계학습 기법이다. 그러나 앙상블 학습은 기저 분류자의 다양성이 부족한 경우 다중공선성 문제로 인하여 성과개선 효과가 미약하고 심지어는 성과가 악화될 수 있다는 문제점이 제기되었다. 본 연구에서는 기저 분류자의 다양성을 확보하고 앙상블 학습의 성과개선 효과를 제고하기 위하여 유전자 알고리즘 기반의 범위 최적화 기법을 제안하고자 한다. 본 연구에서 제안된 최적화 기법을 기업 부실예측 인공신경망 앙상블에 적용한 결과 기저 분류자의 다양성이 확보되고 인공신경망 앙상블의 성과가 유의적으로 개선되었음을 보여주었다.

• ETRI Journal
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• 제28권1호
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• pp.77-83
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• 2006

In order to improve the accuracy of cell selection in heterogeneous cellular systems, this paper proposes a fuzzy multiple-objective decision-based cell selection (FMDCS) strategy. Since heterogeneous cellular systems have different access technologies and multiple traffic classes, the strategy adopts cell type, data rate, coverage, transmission delay, and call arrival rate as evaluation indices, and uses different weight vectors according to the traffic classes of the mobile host. Then, a fuzzy multiple-objective decision algorithm is applied to select the optimal cell from all candidates. This paper also gives an instance analysis and simulation. The instance analysis shows FMDCS makes different selections for different traffic classes. Simulation results of the after-handoff quality-of-service (QoS) show the selected cell can provide MH optimal service.

• 한국국방경영분석학회지
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• 제24권2호
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• pp.146-161
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• 1998

This article develops model of the nonstationary state behavior of the multiechelon spare parts provisioning systems. This study is concerned with a problem of determining the near optimal requirements level of the spare parts, especially Concurrent Spare Parts(CSP). CSP is supplied with the procurement of new equipment system, and is used to sustain the equipment without resupply during the initial coverage period. We consider this situation as a multiechelon inventory model with several bases and one depot. And we assume an equipment system which consists of many types of parts would grounded if one of the parts fail. Also this multiechelon CSP problem is considering the nonstationary poisson failure process and nonstationary exponential repair process in a dynamic environment. We develop an efficient computational procedure to find the near optimal number of spare parts minimizing the total expected cost, while achieving the required system availability. Finally we present a simple example of suggested method.

• 대한원격탐사학회지
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• 제27권6호
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• pp.637-651
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• 2011

This study presents a rule-based urban image classification method for time series analysis of changes in the vicinity of Asan-si and Cheonan-si in Chungcheongnam-do, using Landsat satellite images (1991-2006). The area has been highly developed through the relocation of industrial facilities, land development, construction of a high-speed railroad, and an extension of the subway. To determine the yearly changing pattern of the urban area, eleven classes were made depending on the trend of development. An algorithm was generalized for the rules to be applied as an unsupervised classification, without the need of training area. The analysis results show that the urban zone of the research area has increased by about 1.53 times, and each correlation graph confirmed the distribution of the Built Up Index (BUI) values for each class. To evaluate the rule-based classification, coverage and accuracy were assessed. When Optimal allowable factor=0.36, the coverage of the rule was 98.4%, and for the test using ground data from 1991 to 2006, overall accuracy was 99.49%. It was confirmed that the method suggested to determine the maximum allowable factor correlates to the accuracy test results using ground data. Among the multiple images, available data was used as best as possible and classification accuracy could be improved since optimal classification to suit objectives was possible. The rule-based urban image classification method is expected to be applied to time series image analyses such as thematic mapping for urban development, urban development, and monitoring of environmental changes.

• 한국컴퓨터정보학회논문지
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• 제20권7호
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• pp.33-40
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• 2015

The time slot assignment problem (TSAP) or Satellite Communications scheduling problem (SCSP) for a satellite performs $n{\times}n$ ground station data traffic switching has been known NP-hard problem. This paper suggests $O(n^2)$ time complexity algorithm for TSAP of a satellite that performs $n^2{\times}n^2$ ground station data traffic switching. This problem is more difficult than $n{\times}n$ TSAP as NP-hard problem. Firstly, we compute the average traffic for n-transponder's basic coverage zone and applies ground station exchange method that swap the ground stations until all of the transponders have a average value as possible. Nextly, we transform the D matrix to $D_{LB}$ traffic matrix that sum of rows and columns all of transponders have LB. Finally, we select the maximum traffic of row and column in $D_{LB}$, then decide the duration of kth switch mode to minimum traffic from selected values. The proposed algorithm can be get the optimal solution for experimental data.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2055-2058
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• 2002

It designs the general description of 8-VSB DTV transmission system will be installed and operated in future on the basis of NTSC TV transmission system in operation now. First of all, it investigates a condition that can maintain optimum received field in case of ground wave broadcasting with analog NTSC and digital 8-VSB DTV. Also it calculates critical value of minimum field strength fur receiving by using field strength calculation method of Longley-Rice. The 8-VSB DTV transmission sets its goal in transmission of data with 19.39Mbps at high speed in order to be available of HDTV in the band of NTSC 6MHz. Accordingly, the optimum of field strength between transmission and receiving points most of all is important problem. So,8-VSB DTV transmission should be enlarged or effective compared with NTSC service coverage. This study is to calculate the transmission power necessary in switching from NTSC VHF to DTV UHF and from NTSC UHF to DTV UHF for maintaining service coverage that NTSC is equal to 8-VSB DTV as a result of calculation.

• Journal of Communications and Networks
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• 제14권5호
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• pp.578-587
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• 2012

One of the key elements in the emerging, packet-based long term evolution (LTE) cellular systems is the deployment of multiple femtocells for the improvement of coverage and data rate. However, arbitrary overlaps in the coverage of these femtocells make the handover operation more complex and challenging. As the existing handover strategy of LTE systems considers only carrier to interference plus noise ratio (CINR), it often suffers from resource constraints in the target femtocell, thereby leading to handover failure. In this paper, we propose a new efficient, multi-objective handover solution for LTE cellular systems. The proposed solution considers multiple parameters like signal strength and available bandwidth in the selection of the optimal target cell. This results in a significant increase in the handover success rate, thereby reducing the blocking of handover and new sessions. The overall handover process is modeled and analyzed by a three-dimensional Markov chain. The analytical results for the major performance metrics closely resemble the simulation results. The simulation results show that the proposed multi-objective handover offers considerable improvement in the session blocking rates, session queuing delay, handover latency, and goodput during handover.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권5호
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• pp.1951-1972
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• 2018

Wi-Fi Access Point (AP) optimization approaches are used in indoor positioning systems for signal coverage enhancement, as well as positioning precision improvement. Although the huge power consumption of the AP optimization forms a serious problem due to the signal coverage requirement for large-scale indoor environment, the conventional approaches treat the problem of power consumption independent from the design of indoor positioning systems. This paper proposes a new Fast Water-filling algorithm Group Power Constraint (FWA-GPC) based Wi-Fi AP optimization approach for indoor positioning in which the power consumed by the AP optimization is significantly considered. This paper has three contributions. First, it is not restricted to conventional concept of one AP for one candidate AP location, but considered spare APs once the active APs break off. Second, it utilizes the concept of water-filling model from adaptive channel power allocation to calculate the number of APs for each candidate AP location by maximizing the location fingerprint discrimination. Third, it uses a fast version, namely Fast Water-filling algorithm, to search for the optimal solution efficiently. The experimental results conducted in two typical indoor Wi-Fi environments prove that the proposed FWA-GPC performs better than the conventional AP optimization approaches.

• Journal of Korean Dental Science
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• 제17권2호
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• pp.92-104
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• 2024

Managing multiple non-carious cervical lesions (NCCLs) with gingival recession and dentin hypersensitivity can be challenging. Herein, we present two cases of successful treatment procedure for multiple NCCLs with gingival recession and dentin hypersensitivity using an envelope coronally advanced flap with CTG and composite resin restoration. Through the combined approach of restorative and periodontal procedure, both patients showed adequate extent of gingival coverage and esthetic outcome based on the Modified Root Coverage Esthetic Score (MRES) at 6 months postoperatively. Also, dentin hypersensitivity was reduced effectively during the follow up period. Although the pocket depth slightly increased in patient 1, possibly due to the amount of restoration located sub-gingivally, pocket depth remained within 3 mm. This suggest that re-establishing the clinical CEJ and performing partial restoration is advantageous for periodontal tissue and is expected to contribute to maintain gingival height in the long term. These case reports emphasize the efficacy of the combined approach for treating multiple NCCLs with gingival recession and dentin hypersensitivity, highlighting the importance of careful restoration planning for optimal clinical and aesthetic outcomes.

• 한국인터넷방송통신학회논문지
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• 제9권4호
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• pp.47-52
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• 2009

Source로부터 송신된 신호는 무선 채널을 통하여 Destination에 전달된다. 하지만 이동하는 Destination이 Source의 Coverage를 벗어난 경우나 비록 Source의 Coverage 내의 음영 지역에 Destination이 존재하는 경우, Destination은 Source로부터 송신된 신호를 수신할 수 없고 통신을 할 수 없게 된다. 따라서 이러한 문제점을 극복하기 위해 중계기가 사용된다. 이와 같이 중계기를 사용하는 시스템을 다중 홉 중계 (Multi-hop Relay) 시스템이라 한다. 그런데 다중 홉 중계 시스템에서는 서로 다른 시스템용 중계기의 Coverage가 겹치는 경우가 발생할 수 있고, 이 부분에 Destination이 존재하는 경우 Destination에는 간섭이 발생한다. 본 논문에서는 다중 홉 중계 시스템에서 발생 할 수 있는 동일 채널 간섭 (CCI : Co-Channel Interference) 제거 방법에 관해 연구하였다. 간섭 제거 방법은 우선 Zero Forcing (ZF) 또는 Minimum Mean Square Error (MMSE) 개념을 적용한 선형 수신기를 이용하여 간섭을 제거한 후, 정렬된 연속간섭제거 (OSIC : Ordered Successive Interference Cancellation) 알고리즘을 이용하여 추가적인 다이버시티 이득을 얻고 간섭 제거 성능을 향상시킨다. 무선 채널은 레일레이 (Rayleigh) 페이딩 채널을 고려하여 모의 실험을 하였으며, 시스템 성능은 비트 오류 확률 (Bit Error Probability) 측면에서 분석되었다.