• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.1091-1110
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• 2016

Hybrid deployment under current cloud data centers is a combination of online and offline services, which improves the utilization of the cluster resources. However, the performance of the cluster is often affected by the online services in the hybrid deployment environment. To improve the response time of online service (e.g. search engine), an effective scheduling algorithm based on Storm is proposed. At the component level, the algorithm dispatches the component with more influence to the optimal performance node. Inside the component, a reasonable resource allocation strategy is used. By searching the compressed index first and then filtering the complete index, the execution speed of the component is improved with similar accuracy. Experiments show that our algorithm can guarantee search accuracy of 95.94%, while increasing the response speed by 68.03%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.516-517
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• 2008

최근 전 세계적인 에너지위기에 따라 분산전원의 투입에 대한 관심이 갈수록 높아지고 있다. 하지만 분산전원의 계통투입은 필연적으로 소비자와 설비 측의 전압레벨과 전력조류흐름을 변화시킨다. 분산전원의 투입위치에 따라서 소비자와 설비 측의 전압은 크게 향상될 수 있으나 제한된 분산전원을 최적으로 배치하는 연구가 선행되어야 한다. 본 논문에서는 계통에 분산전원 투입할 시의 전압특성변화를 분석하고, 이를 토대로 계통의 전압품질향상을 목적으로 분산전원을 최적으로 투입하기 위한 알고리즘을 제안하였다.

• 대한산업공학회지
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• 제33권2호
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• pp.213-220
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• 2007

This paper considers a two-stage hybrid flow shop scheduling problem for the objective of minimizing the number of tardy jobs. Each job is processed through the two production stages in stages, each of which has multiple identical parallel machines. The problem is to determine the allocation and sequence of jobs at each stage. A branch and bound algorithm that gives the optimal solutions is suggested that incorporates the methods to obtain the lower and upper bounds. Dominance properties are also suggested to reduce the search space. To show the performance of the algorithm, computational experiments are done on randomly generated problems, and the results are reported.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.207-210
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• 2009

An efficient algorithm to compress high dynamic range (HDR) videos is proposed in this work. We separate an HDR video sequence into a tone-mapped low dynamic range (LDR) sequence and a ratio sequence. Then, we encode those two sequences using the standard H.264/AVC codec. During the encoding, we allocate a limited amount of bit budget to the LDR sequence and the ratio sequence adaptively to maximize the qualities of both the LDR and HDR sequences. While a conventional LDR decoder uses only the LDR stream, an HDR decoder can reconstruct the HDR video using the LDR stream and the ratio stream. Simulation results demonstrate that the proposed algorithm provides higher performance than the conventional methods.

• Communications for Statistical Applications and Methods
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• 제9권2호
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• pp.565-576
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• 2002

We propose a new sampling design for the 2001 Health Index Survey at Seoul. In this stratified two-stage sampling design, the ED(enumeration district) of 2000 Population and Housing Census is used as primary sampling unit and the Gu is used as stratification variable in order to obtain the sub-domain estimate for 25 Gu's as well as population estimate for Seoul. The sample ED's are systematically selected after the Ed's are ordered by location and property to obtain a representative sample. And also, the imputation methods for item nonresponses are suggested.

• 방송공학회논문지
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• 제3권2호
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• pp.111-117
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• 1998

MPEG-2 표준 방식과 같이 DCT 변환을 사용하는 블록부호화 방법에서는 각 블록을 독립적으로 처리하기 때문에, 블록의 경계선에 따라 불연속성을 갖는 블록경계 현상이 나타난다. 본 논문에서는 이러한 블록경계 현상을 줄이기 위해 가변 양자화기를 이용한 이 단계 변환부호화 방법과 전체 영상을 고려한 최적 필터를 이용하는 방법을 제시한다. 기존의 방법들은 변환부호화의 구조를 바꾸는 방법과 복원된 영상을 후처리하는 방법 등으로 분류할 수 있지만, 이들의 성능을 비교하기는 쉽지 않다. 본 논문에서 제안한 새로운 알고리즘을 기존의 알고리즘들과 객관적으로 비교하기 위해 최적 비트할당 알고리즘을 적용하였다.

• Journal of Communications and Networks
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• 제17권3호
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• pp.241-246
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• 2015

In this paper, we consider a relaying system which employs a single relay in a wireless network with distributed sources and destinations. Here, all source, destination, and relay nodes are equipped with multiple antennas. For amplify-and-forward relay systems, we confirm the achievable sum rate through a joint multiple source precoders and a single relay filter design. To this end, we propose a new linear processing scheme in terms of maximizing the sum rate performance by applying a blockwise relaying method combined with geometric programming techniques. By allowing the global channel knowledge at the source nodes, we show that this joint design problem is formulated as a standard geometric program, which can guarantees a global optimal value under the modified sum rate criterion. Simulation results show that the proposed blockwise relaying scheme with the joint power allocation method provides substantial sum rate gain compared to the conventional schemes.

• Journal of Communications and Networks
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• 제17권5호
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• pp.463-472
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• 2015

This paper considers a limited feedback system for two-way wireless relaying channels with physical network coding (PNC). For full feedback systems, the optimal structure with the PNC has already been studied where a modulo operation is employed. In this case, phase and power of two end node channels are adjusted to maximize the minimum distance. Based on this result, we design new quantization methods for the phase and the power in the limited feedback system. By investigating the minimum distance of the received constellation, we present a code-book design to maximize the worst minimum distance. Especially, for quantization of the power for 16-QAM, a new power quantization scheme is proposed to maximize the performance. Also, utilizing the characteristics of the minimum distance observed in our codebook design, we present a power allocation method which does not require any feedback information. Simulation results confirm that our proposed scheme outperforms conventional systems with reduced complexity.

• 산업경영시스템학회지
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• 제13권21호
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• pp.101-110
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• 1990

This study presents a two-level inventory distribution system with one-upper level facility(warehouse) in first echelon and n-lower level facilities(stores) in the second echelon. The demand process at the upper level is induced by the aggregated backorder processes of n independently operated lower level facilities in parallel. For the upper level and the lower level we find the decision points and the distribution function of the aggregate backorders from n-stores. Optimal allocation units and expected system profits are obtained. If the product is of great enough importance to the customer, echelon structure will include a shadow installation. Also, this case is analyzed. Numerical examples are presented to illustrate the results for each case.

• 한국컴퓨터정보학회논문지
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• 제7권2호
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• pp.40-45
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• 2002

본 연구는 상위수준합성에서의 데이터패스합성을 위한 스케쥴링을 다루었다. 특히, 연산자 할당에 필요한 상호연결선을 최적화하기 위한 스케쥴링 방법을 제안하였다. 또한 최적의 스케쥴링 결과를 얻기 위하여 ILP 수식을 이용하였고 본 연구의 효용성을 검증하기 위하여 5차 디지털 웨이브 필터를 대상으로 실험한 결과 기존의 결과 보다 나은 결과를 나타내었다.