• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권4호
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• pp.446-450
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• 2008

비밀 매칭(Private Matching)은 각기 다른 두 참여자가 가진 데이타의 교집합을 구하는 문제이다. 이때 각 참여자는 교집합은 공유하되 그 이상의 정보는 감춰지기를 원한다. 2004년 Freedman 등[1]은 한 참여자만 비밀 매칭을 얻는 방법을 제안하였다. 경쟁관계의 회사와 같이 프로토콜 참여자가 동시에 Private Matching을 얻고자 하는 경우에는 Kissner와 Song[2]이 제안한 다자간의 교집합 계산 방법을 고려할 수 있다. 우리는 Kissner와 Song의 다항식 덧셈에 의한 교집합 계산 방법에 상당히 신뢰할 수 있는 제3자(Semi-Trusted Third Party)를 도입하여, 보다 효율적으로 비밀 매칭을 구할 수 있는 방법을 제안한다. 한편, STTP의 저장능력을 활용할 경우 프로토콜을 다시 시작하지 않고도 비밀 매칭을 업데이트 할 수 있는 방법 또한 제공한다.

• International Journal of Fluid Machinery and Systems
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• 제10권3호
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• pp.240-253
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• 2017

Latin hypercube sampling is widely used design-of-experiment technique to select design points for simulation which are then used to construct a surrogate model. The exploration/exploitation properties of surrogate models depend on the size and distribution of design points in the chosen design space. The present study aimed at evaluating the performance characteristics of various surrogate models depending on the Latin hypercube sampling (LHS) procedure (sample size and spatial distribution) for a diverse set of optimization problems. The analysis was carried out for two types of problems: (1) thermal-fluid design problems (optimizations of convergent-divergent micromixer coupled with pulsatile flow and boot-shaped ribs), and (2) analytical test functions (six-hump camel back, Branin-Hoo, Hartman 3, and Hartman 6 functions). The three surrogate models, namely, response surface approximation, Kriging, and radial basis neural networks were tested. The important findings are illustrated using Box-plots. The surrogate models were analyzed in terms of global exploration (accuracy over the domain space) and local exploitation (ease of finding the global optimum point). Radial basis neural networks showed the best overall performance in global exploration characteristics as well as tendency to find the approximate optimal solution for the majority of tested problems. To build a surrogate model, it is recommended to use an initial sample size equal to 15 times the number of design variables. The study will provide useful guidelines on the effect of initial sample size and distribution on surrogate construction and subsequent optimization using LHS sampling plan.

• 한국통신학회논문지
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• 제19권7호
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• pp.1390-1406
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• 1994

본 논문은 로컬 엑세스 컴퓨터 네트워크를 설계할 때 발생되는 문제의 하나로 네트워크의 평균 지연 시간을 고려한 최소 비용 루프 설계 문제(DMCLP-Delay constrained Minimum Cost Loop Problem)를 다룬다. 이 문지는 종단 사용자의 트래픽 요구량을 만족시키는 링의 집합을 구하는 것으로 목적 함수는 전체라인 비용을 최소화하는 것이다. 본 논문에서는 하나의 링이 서비스할 수 있는 노드의 수가 제한되어 있으며 동시에 네트워크의 평균 지연 시간이 원하는 시간이내이어야 한다는 제약 조건하에서 이 문제에 대한 2단계-휴리스틱 알고리즘을 제안한다. 이 알고리즘은 기존의 최소 비용 루프 설계(MCLP) 알고리즘에 의한 클러스터와 본 논문에서 제안한 trade-off criterion를 이용하여 유도된다. 실제 시뮬레이션의 결과, 본 논문에서 제안한 알고리즘은 수정된 기존의 MCLP 알고리즘보다 우수한 해를 제공하며 아울러 비교적 짧은 실행 시간을 갖는다.

• 물과 미래
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• 제22권1호
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• pp.81-90
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• 1989

호수와 접하고 있는 홍적대지의 지하수류동계를 알기 위하여 삼차유한차분모형을 개발하여 삼차원정상모의 발생을 행하였다. 대표지층속에 점토층이 렌즈상으로 포함되어 있어 세가지 경우의 이방성을 고려하였다. 모의 발생에는 60$\times$50$\times$30=90,000의 격자점을 설정하였으며 수속판정체계는 0.001m로 하였다. 세가지 경우의 이방성에 대하여, 삼차원정상모의 발생을 행하여 얻어진 결과로부터 해석된 지하수류동계와 추적자 및 수질에 의한 해석(배.비근, 1987)의 결과를 비교하였다. 삼차원해석에서 얻어진 네 개의 대표적인 연직2차원 등 포텐샬단면으로부터 연구지역의 지하수류동계를 추정하였으며 그 결과는 유역산출율과 지하수의 함량-유출량 분포로부터 추정되는 결과와 다름이 없었다.

• Wind and Structures
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• 제31권3호
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• pp.241-253
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• 2020

The inerter-based vibration absorber (IVA) is an enhanced variation of Tuned Mass Damper (TMD). The parametric optimization of absorbers in the previous research mainly considered only two decision variables, namely frequency ratio and damping ratio, and aimed to minimize peak displacement and acceleration individually under the excitation of the across-wind load. This paper extends these efforts by minimizing two conflicting objectives simultaneously, i.e., the extreme displacement and acceleration at the top floor, under the constraint of the physical mass. Six decision variables are optimized by adopting a constrained multi-objective evolutionary algorithm (CMOEA), i.e., NSGA-II, under fluctuating across- and along-wind loads, respectively. After obtaining a set of optimal individuals, a decision-making approach is employed to select one solution which corresponds to a Tuned Mass Damper Inerter/Tuned Inerter Damper (TMDI/TID). The optimization procedure is applied to parametric optimization of TMDI/TID installed in a 340-meter-high building under wind loads. The case study indicates that the optimally-designed TID outperforms TMDI and TMD in terms of wind-induced vibration mitigation under different wind directions, and the better results are obtained by the CMOEA than those optimized by other formulae. The optimal TID is proven to be robust against variations in the mass and damping of the host structure, and mitigation effects on acceleration responses are observed to be better than displacement control under different wind directions.

• 한국산업보건학회지
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• 제30권2호
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• pp.87-98
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• 2020

Objective: The purpose of this study was to propose a sequential procedure for the simultaneous analysis of soluble and insoluble metal compounds. Methods: Methods for sampling and analyzing metal compounds such as ISO standards, NIOSH methods, HSE methods, and OSHA methods were reviewed. Results: Some metals have different OELs depending on the solubility of the compound. Therefore, we should take into account these characteristics and perform an exposure assessment. Soluble metal compounds are first extracted from the filter, and then the filter is digested by acids to analyze residual insoluble components. The extraction of soluble compounds can be completed by agitation for about 60 minutes with a leach solution (water) in a water bath at 37℃. For the analysis of insoluble compounds, the sample filter and the filtration filter remaining after the extraction of the soluble compounds are analyzed. This allows simultaneous determination of soluble and insoluble metal compounds. For hexavalent chromium compounds, soluble hexavalent chromium can first be extracted from the filter by using sulfate buffer. The insoluble hexavalent chromium remaining in the filter can then be extracted using carbonate buffer. Conclusion: Workers are often exposed to many hazardous substances with different exposure limits at industrial sites. The OELs for compounds of the same metal can be set differently depending on solubility. This study can help evaluate a worker's exposure to metal compounds by suggesting methods for the simultaneous determination of soluble and insoluble metal compounds.

• 한국항공우주학회지
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• 제34권1호
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• pp.42-48
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• 2006

연구에서는 다분야 통합 최적설계를 위한 시스템 근사화 기법으로 RRSET (Repetitive Response Surface Enhancement Technique)를 제안하였다. 2차 다항식만으로는 어려운 반응면의 표현을 위해 RRSET는 설계공간을 변형할 수 있는 스트레칭 함수를 도입하고 전역 최적화 알고리즘인 담금질 모사기법을 이용하여 반응면을 최적화 하였다. 도출된 최적점은 반복적으로 다음 순기의 반응면의 구성에 이용하여 반응면의 신뢰도를 더욱 높일 수 있었다. 제안된 기법을 수치예제 등에 적용한 결과, 비교적 적은 수의 실험 회수로 비선형적인 반응면을 잘 표현하고 최적 설계점을 도출해낼 수 있음이 확인되었다. 정밀한 근사화 기법의 중요성이 강화되고 있는 현재, 본 연구에서 제시된 근사화 기법은 차후의 연구에서 다분야 통합 최적화 기법에의 적용이 가능하리라 사료된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.709-730
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• 2017

To address the challenge of unprecedented growth in mobile data traffic, ultra-dense network deployment is a cost efficient solution to offload the traffic over some small cells. The overlapped coverage areas of small cells create more than one candidate access points for one mobile user. Signal strength based user association in IEEE 802.11 results in a significantly unbalanced load distribution among access points. However, the effective bandwidth demand of each user actually differs vastly due to their different preferences for mobile applications. In this paper, we formulate a set of non-linear integer programming models for joint user association control and user demand guarantee problem. In this model, we are trying to maximize the system capacity and guarantee the effective bandwidth demand for each user by soft-association control with a software defined network controller. With the fact of NP-hard complexity of non-linear integer programming solver, we propose a Kernighan Lin Algorithm based graph-partitioning method for a large-scale network. Finally, we evaluated the performance of the proposed algorithm for the edge users with heterogeneous bandwidth demands and mobility scenarios. Simulation results show that the proposed adaptive soft-association control can achieve a better performance than the other two and improves the individual quality of user experience with a little price on system throughput.

• 한국치위생학회지
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• 제14권4호
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• pp.585-591
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• 2014

Objectives : The purpose of this study was to investigate of the color change, tooth surface and intra-pulpal temperature of tooth bleaching by light activation Methods : Forty-eight extracted bovine teeth were immersed into a tea solution for 24 hours. The specimens were randomly divided into four groups(n=15):(G1) 15% HP + without light activation, (G2) 15% HP + light activation, (G3) 25% HP + without light activation, (G4) 25% HP + light activation. All specimens were bleached for 15 minutes three times. The spectrophotometer (CM-2600d, Konica Minolta, Osaka, Japan) was used including before bleaching, immediately after bleaching, 1 week, 1 and 3 months after the end of bleaching. The temperature rise were measured in the pulpal chamber and tooth surface with a digital thermocouple thermometer(Termopar Digital Multimeter, Tektronix DMM916, USA). Between the tested time points, the specimens were stored in distilled water. The data were analyzed by ANOVA, t-test and Tukey's post hoc test set at 0.05. Results : There was no significant color change by the use of light after the bleaching treatment(p>0.05). The dental bleaching treatments of teeth with 15% HP and 25% HP did not seem to be more effective when light source was used. There was no difference in color stability between groups within three month(p>0.05). There was an increase in tooth surface and pulp temperature, but it was not sufficient to cause damage to the pulp. Conclusions :The use of light activation has no obvious effective impact on the tooth bleaching effect.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.5785-5804
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• 2019

The information of localization is a fundamental requirement in wireless sensor network (WSN). The method of distance vector-hop (DV-Hop), a range-free localization algorithm, can locate the ordinary nodes by utilizing the connectivity and multi-hop transmission. However, the error of the estimated distance between the beacon nodes and ordinary nodes is too large. In order to enhance the positioning precision of DV-Hop, fast triangle flip bat algorithm, which is based on curve strategy and rank transformation (FTBA-TCR) is proposed. The rank is introduced to directly select individuals in the population of each generation, which arranges all individuals according to their merits and a threshold is set to get the better solution. To test the algorithm performance, the CEC2013 test suite is used to check out the algorithm's performance. Meanwhile, there are four other algorithms are compared with the proposed algorithm. The results show that our algorithm is greater than other algorithms. And this algorithm is used to enhance the performance of DV-Hop algorithm. The results show that the proposed algorithm receives the lower average localization error and the best performance by comparing with the other algorithms.