• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.747-753
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• 2009

Planning the construction for a system of bored piles in building foundation engineering is (1) to predict the time duration required to complete all the bored piles with due consideration of relevant engineering factors and site constraints; then (2) to predict the total project time generally by aggregating the predicted working duration for construction of each bored pile. The duration for construction of an individual bored pile results from analyzing various working sequences and different activity duration (such as predrilling, excavation, steelfixing, air-lifting, and concreting, etc.), which is informed by experiences and site records of previous projects. However, determining the project duration for constructing many bored piles on one site is much more complicated than adding up the time duration for individual piles. In practice, project schedules are often found to be unrealistic and incorrect during the construction stage. This is because construction planning is not based on a exhaustive and comprehensive evaluation of site factors, such as site layout plan, site constraints, quality control, environmental control, safety control and logical relationships between different trades. In this paper, we identify those factors based on a foundation engineering site in Hong Kong with ninety-seven bored piles and address their effects on uncertainties in activity time and project time.

• 한국콘텐츠학회논문지
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• 제7권12호
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• pp.167-178
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• 2007

이 연구의 목적은 민간경비원의 여가제약이 생활체육 참가 및 주관적 행복감에 미치는 영향을 규명하는데 있다. 이 연구는 2007년 서울소재 5개소 민간경비회사의 민간경비원을 모집단으로 설정한 다음, 집락무선표집법을 이용하여 193명을 표집하였다. 설문지의 신뢰도는 Cronbach's ${\alpha}$값이 .725이상으로 나타났다. 결론은 다음과 같다. 첫째, 여가제약은 생활체육 참가경험에 영향을 미친다. 즉, 개인내적, 주변의식적, 경제적 제약이 증가하면 생활체육 참가율은 감소한다. 둘째, 여가제약은 생활체육 참가정도에 영향을 미친다. 즉, 개인내적, 주변의식적, 경제적 여가제약이 증가하면 생활체육 참가빈도는 감소한다. 주변의식적 여가제약이 증가하면 생활체육 참가기간은 감소한다. 개인내적, 주변의식적 여가제약이 증가하면 생활체육 참가 강도는 감소한다. 셋째, 여가제약은 주관적 행복감에 영향을 미친다. 즉, 시간적 제약이 증가하면 행복감의 하위요인인 유능감은 감소한다. 넷째, 여가제약은 생활체육 참가 및 주관적 행복감에 인과적 영향을 미친다. 즉, 여가제약은 생활체육 참가를 통하여 주관적 행복감에 간접적 영향을 미친다.

• 한국통신학회논문지
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• 제31권5B호
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• pp.365-377
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• 2006

매체공유기반 통신시스템은 매체접근제어 과정에서 단말기의 채널 점유 제약 조건에 따라 크게 완전매체공유 시스템과 불완전매체 공유 시스템으로 구분할 수 있다. 본 논문에서는 불완전매체공유 시스템의 채널활용효율을 향상시키기 위한 분산식 매체접근제어기법을 제안한다. 제안하는 매체접근제어기법은 IEEE 802.11 무선랜의 CSMA/CA 기법을 확장한 방법으로써 임의 지연 시간을(random backoff time) 채널에 대해 개별적, 집합적, 큐(queue)에 대해 개별적으로 적용함으로써 크게 3가지 형태로 제시되었다. 모의실험 결과 성능측면에서는 큐에 대해 개별적으로 임의 지연시간을 적용하였을 때 상대적으로 우월한 성능을 보였다. 또한 복잡도 측면에서는 채널에 대하여 집합적으로 임의 지연시간을 적용했을 때 상대적으로 낮은 복잡도를 보였다. 임의 지연시간을 분할된 채널에 대해 개별적으로 적용하는 방식은 성능과 연산복잡도의 trade-off관계에 있어서 앞서 제시된 방식들보다 우위에 있음을 보이고 있다.

• Journal of Biosystems Engineering
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• 제27권5호
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• pp.433-450
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• 2002

The daily food intake for dairy cows has to be effectively controlled to breed a sound group of cows as well as to enhance the productivity of the cows. But, feed stuffs are fed in the common bulk for a group of cows in most cases despite that the individual food intake has to be varied. To obtain the feed for each cow, both the nutrient requirements and the nutrient composition of fred have to be provided in advance, which are based on the status of cows such as weigh marginal weight amount of milk, fat concentration in milk, growth and milking stages, and rough feed ratio, etc. Then, the mixed ration fur diet would be computed by the nutrient requirements constraints. However, when TMR (Total Mixed Ration) is conventionally supplied for a group of cows, it is almost impossible to get an optimal feed mixed ration meeting the nutrient requirements of each individual cow since the constraints are usually conflicting and over-constrained although they are linear. Hence, addressed in this paper is a simulated annealing (SA) technique to find the food intake for dairy cows, considering the characteristics of individual or grouped cows. Appropriate parameters fur the successful working of SA are determined through preliminary experiments. The parameters include initial temperature, epoch length. cooling scheduling, and stopping criteria. In addition, a neighborhood solution generation method for the effective improvement of solutions is presented. Experimental results show that the final solution for the mixture of feed fits the rough feed ratio and some other nutrient requirements such as rough fiber, acid detergent fiber, and neutral detergent fiber, with 100 percent, while fulfilling net energy for lactating, metabolic energy, total digestible nutrients, crude protein, and undegraded intake protein within average five percent.

• 한국콘텐츠학회논문지
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• 제12권9호
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• pp.422-433
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• 2012

본 연구는 여가활동 중에 국민들이 선호하는 여가스포츠활동의 참가를 유도하고 지속할 수 있도록 여가스포츠활동 유형을 개인종목, 대인종목, 단체종목으로 분류한 후 각 유형에 따른 여가제약을 규명하고자 하였다. 본 연구는 서울과 경기도에 거주하는 여가스포츠활동 참여자를 대상으로 하였다. 편의표집방법을 활용하여 총 286명이 연구에 참여하였다. 여가스포츠활동 참여자의 여가제약은 시설환경, 부정인식, 여건부족, 부상위험, 시간부족의 5가지 요인으로 분류되었다. 본 연구의 결과는 첫째, 여가제약 요인 중 시설환경요인이 가장 높은 것으로 나타났으며 부정인식요인이 가장 낮은 것으로 나타났다. 둘째, 여가스포츠활동 참가정도에 따른 여가제약의 차이는 부정인식요인, 여건부족요인에서 부분적으로 차이가 나는 것으로 나타났다. 셋째, 여가스포츠활동 유형에 따른 여가제약의 차이는 시설환경요인, 부정인식요인, 여건부족요인, 부상위험요인에서 부분적으로 차이가 나타났다. 이러한 결과를 바탕으로 여가스포츠활동 참가 정도와 유형에 따라 여가제약에 대한 차이가 있다는 것을 규명하였으며 이러한 결과는 맞춤형 여가제약 협상에 대한 연구들도 가능하게 할 것이며 미래 여가사회연구를 위한 중요한 자료가 될 것이다.

• 한국경영과학회지
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• 제30권1호
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• pp.43-54
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• 2005

A flexible assembly line (FAL) is a production system that assembles various parts in unidirectional flow line with many constraints and manufacturing flexibilities. In this research we deal with a FAL balancing problem with the objective of minimizing the maximum workload allocated to the stations. However, almost all the existing researches do not appropriately consider various constraints due to the problem complexity. Therefore, this study addresses a balancing problem of FAL with many constraints and manufacturing flexibilities, unlike the previous researches. We use a genetic algorithm (GA) to solve this problem. To apply GA to FAL. we suggest a genetic representation suitable for FAL balancing and devise evaluation method for individual's fitness and genetic operators specific to the problem, including efficient repair method for preserving solution feasibility. After we obtain a solution using the proposed GA. we use a heuristic method for reassigning some tasks of each product to one or more stations. This method can improve workload smoothness and raise work efficiency of each station. The proposed algorithm is compared and analyzed in terms of solution quality through computational experiments.

• Journal of Computational Design and Engineering
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• 제2권2호
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• pp.105-112
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• 2015

Product Lifecycle Management (PLM) ranges from design concepts of products to disposal. In this paper, we focus on the production planning phase in PLM, which is related to process planning and production scheduling and so on. In this study, key decisions for the creation of production plans are defined as production-planning attributes. Production-planning attributes correlate complexly in production-planning problems. Traditionally, the production-planning problem splits sub-problems based on experiences, because of the complexity. In addition, the orders in which to solve each sub-problem are determined by priorities between sub-problems. However, such approaches make solution space over-restricted and make it difficult to find a better solution. We have proposed a representation of combinations of alternatives in production-planning attributes by using Zero-Suppressed Binary Decision Diagrams. The ZDD represents only feasible combinations of alternatives that satisfy constraints in the production planning. Moreover, we have developed a solution search method that solves production-planning problems with ZDDs. In this paper, we propose an approach for managing solution candidates by ZDDs' network for addressing larger production-planning problems. The network can be created by linkages of ZDDs that express constraints in individual sub-problems and between sub-problems. The benefit of this approach is that it represents solution space, satisfying whole constraints in the production planning. This case study shows that the validity of the proposed approach.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.168-173
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• 2000

Design of experiments is utilized for exploring the design space and for building response surface models in order to facilitate the effective solution of multi-objective optimization problems. Response surface models provide an efficient means to rapidly model the trade-off among many conflicting goals. In robust design, it is important not only to achieve robust design objectives but also to maintain the robustness of design feasibility under the effects of variations, called uncertainties. However, the evaluation of feasibility robustness often needs a computationally intensive process. To reduce the computational burden associated with the probabilistic feasibility evaluation, the first-order Taylor series expansions are used to derive individual mean and variance of constraints. For robust design applications, these constraint response surface models are used efficiently and effectively to calculate variances of constraints due to uncertainties. Robust optimization of automotive seat is used to illustrate the approach.

• 천문학회지
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• 제32권2호
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• pp.119-126
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• 1999

The standard stellar models for $\alpha$ Cen A and B have been constructed without resorting to the arbitrary constraint of the Solar mixing length ratio. Assuming that the chemical compositions and the ages of the two stars are the same, series of models have been constructed. Using the observational constraints, [Z/X], we were able to constrain the number of the 'possible' models. We find that utilizing the observational constraints of [Z/X] the best models for $\alpha$ Cen system are with the initial Z = 0.03, X = 0.66$\~$0.67. In particular, the primary and the secondary stars may have the same mixing length ratio 1.6$\~$1.7, which is the same as that of the calibrated Solar model. And, the age of the system is about 5.4 Gyr. Finally, the large spacing of the p-modes is predicted to be 104 $\pm$ 4$\mu$Hz for $\alpha$ Cen A.

• 한국생산제조학회지
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• 제22권1호
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• pp.63-69
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• 2013

In order to find the optimum design of structures that have characteristic natural frequency range, a numerical optimization method to solving eigenvalue problems is a widely used approach. However in the most cases, it is difficult to decide the accurate thickness and shape of structures that have allowable natural frequency in design constraints. Parallel analysis algorithm involving the feasible direction optimization method and Rayleigh-Ritz eigenvalue solving method is developed. The method is implemented by using finite element method. It calculates the optimal thickness and the thickness ratio of individual elements of the 2-D plane element through a parallel algorithm method which satisfy the design constraint of natural frequency. As a result this method of optimization for natural frequency by using finite element method can determine the optimal size or its ratio of geometrically complicated shape and large scale structure.