• Computers and Concrete
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• 제19권5호
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• pp.501-507
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• 2017

The predictive utility of a damage model depends heavily on its particular choice of a damage variable, which serves as a macroscopic approximation in describing the underlying micromechanical processes of microdefects. In the case of spatially perfectly randomly distributed microcracks or microvoids in all directions, isotropic damage model is an appropriate choice, and scalar damage variables were widely used for isotropic or one-dimensional phenomenological damage models. The simplicity of a scalar damage representation is indeed very attractive. However, a scalar damage model is of somewhat limited use in practice. In order to entirely characterize the isotropic damage behaviors of damaged materials in multidimensional space, a system theory of isotropic double scalar damage variables, including the expressions of specific damage energy release rate, the coupled constitutive equations corresponding to damage, the conditions of admissibility for two scalar damage effective tensors within the framework of the thermodynamics of irreversible processes, was provided and analyzed in this study. Compared with the former studies, the theoretical formulations of double scalar damage variables in this study are given in the form of matrix, which has many features such as simpleness, directness, convenience and programmable characteristics. It is worth mentioning that the above-mentioned theoretical formulations are only logically reasonable. Owing to the limitations of time, conditions, funds, etc. they should be subject to multifaceted experiments before their innovative significance can be fully verified. The current level of research can be regarded as an exploratory attempt in this field.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권2호
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• pp.163-174
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• 2016

In this paper, we propose an optimal choice scheme to determine the best option among comparable options whose current expectations are all the same under the condition that an investor has a confidence in the future value realization of underlying assets. For this purpose, we use a path-averaged option as our base instrument in which we calculate the time discounted value along the path and divide it by the number of time steps for a given expected path. First, we consider three European call options such as vanilla, cash-or-nothing, and asset-or-nothing as our comparable set of choice schemes. Next, we perform the experiments using historical data to prove the usefulness of our proposed scheme. The test suggests that the path-averaged option value is a good guideline to choose an optimal option.

• 자원ㆍ환경경제연구
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• 제14권3호
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• pp.655-672
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• 2005

한강은 수도 서울을 관통하면서 수도권의 자연환경과 생활환경에 중요한 기능을 담당하고 있다는 점에서 한강이 지니는 사회 경제적인 역할은 매우 크며, 지난 수십 년간 한강의 수질문제는 한국 사회의 중요한 이슈로 대두되어 왔다. 이에 따라 본 연구는 서울을 대상으로 컨조인트 분석을 이용하여 한강수질개선에 따른 속성별 경제적 편익을 측정하고자 한다. 연구결과 설문에 응한 서울시민들은 전반적으로 수질에 영향을 받는 속성들과 가격 사이의 상충관계를 잘 이해하며 응답하였고, 추정결과는 통계적으로 유의한 것으로 나타났다. 이러한 본 연구의 결과는 한강수질의 개선문제에 대해 정량적 정보를 제공한다는 측면에서 의미가 있다.

• 한국철도학회논문집
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• 제11권6호
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• pp.588-595
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• 2008

본 연구는 우리나라 화주의 수송수단 선택특성을 파악하는 목적으로 수행하였다. 모형의 형태는 개별행태모형이며 SP 자료를 이용하였다. SP 조사는 실험설계를 통해 준비하였다. 고려한 요인은 수송시간, 수송비용, 서비스 수준이다. 연구에서 도출된 시사점은 철도수송의 수요를 증대시키기 위해서는 수송비용을 감소시키는 전략이 가장 효과적이라는 것이다. 화물 품목별로 설명하면, 컨테이너는 수송비용의 감소와 더불어 수송시간을 단축시키고 서비스 수준을 개선할 때 공로수송에 비하여 경쟁력을 확보할 수 있는 것으로 평가되었다. 반면에 양회와 철강 등 벌크화물은 다른 요소보다 수송비용을 인하하는 정책이 효과적이다.

• ALGAE
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• 제36권1호
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• pp.51-60
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• 2021

The sea urchin, Mesocentrotus nudus, is widely distributed in North West Pacific regions. It has a substantial impact on macroalgal communities as a generalist herbivore. This study examined various aspects of its feeding ecology, including algal preference, foraging behaviors, and possible effects of past feeding history on its algal preference. We used six common algal species (Ulva australis, Undaria pinnatifida, Sargassum confusum, Dictyopteris divaricata, Grateloupia elliptica, and Grateloupia angusta) from the east coast of Korea as food choice in a series of indoor aquarium experiments. The first choice of starved M. nudus was exclusively U. pinnatifida, followed by G. elliptica and S. confusum. Unlike large urchins, small urchins equally preferred U. pinnatifida and G. elliptica. On the other hand, Undaria-fed urchins preferred to feed only G. elliptica, although its preference slightly differed over time. We then grouped sea urchins into three categories (starved, Undaria-fed, mixed species-fed) to observe 12-days feeding preference as well as early foraging movements. Foraging behaviors of the three groups were distinctively different, although they could not completely reflect the actual consumption. For example, U. australis was highly attractive, but rarely eaten. Undaria-fed urchins seemed to stay with only S. confusum and U. australis. This study demonstrates that M. nudus shows high flexibility in food preference depending on past feeding history and body size. Its foraging behaviors are also affected by past feeding conditions, exhibiting active chemoreceptive movements.

• 대한교통학회지
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• 제35권3호
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• pp.197-209
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• 2017

최근 삶의 질을 중시하는 경향이 강화되면서 여가활동에 투자하는 시간과 비용이 높아지면서 프로스포츠에 대한 관심이 높아지고 있다. 대규모 스포츠시설에는 짧은 시간에 대규모 통행량이 밀집되기 때문에 기존 교통체계에 미치는 영향이 크다. 본 연구는 대규모 스포츠시설을 목적지로 하는 통행의 수단선택 모형을 구축하는 것을 목적으로 한다. 이를 분석하기 위해 실험계획법에 의한 SP조사를 프로스포츠 경기 관람자를 대상으로 수행하여 수단선택 모형을 구축하였다. 분석결과 대규모 스포츠시설과 같이 정해진 시간에 대규모 이벤트가 개최되는 경우, 대중교통 수단이 선호되는 것을 알 수 있었으며, 귀가의 용이성을 고려한 수단선택 행위가 이루어질 가능성이 높다는 것을 파악할 수 있었다. 본 연구는 대규모 스포츠시설 등 이용빈도가 높지 않는 여가시설의 통행행태를 분석하고 나아가 향후 지하철 등의 대중교통(mass transit) 공급여부를 판단하기 위해 합리적인 교통수요 분석을 위한 연구방향을 제시하는 데 기여할 것으로 기대된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1130-1147
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• 2014

Large size ships have a very flexible construction resulting in low resonance frequencies of the structural eigen-modes. This feature increases the dynamic response of the structure on short period waves (springing) and on impulsive wave loads (whipping). This dynamic response in its turn increases both the fatigue damage and the ultimate load on the structure; these aspects illustrate the importance of including the dynamic response into the design loads for these ship types. Experiments have been carried out using a segmented scaled model of a container ship in a Seakeeping Basin. This paper describes the development of the model for these experiments; the choice was made to divide the hull into six rigid segments connected with a flexible beam. In order to model the typical feature of the open structure of the containership that the shear center is well below the keel line of the vessel, the beam was built into the model as low as possible. The model was instrumented with accelerometers and rotation rate gyroscopes on each segment, relative wave height meters and pressure gauges in the bow area. The beam was instrumented with strain gauges to measure the internal loads at the position of each of the cuts. Experiments have been carried out in regular waves at different amplitudes for the same wave period and in long crested irregular waves for a matrix of wave heights and periods. The results of the experiments are compared to results of calculations with a linear model based on potential flow theory that includes the effects of the flexural modes. Some of the tests were repeated with additional links between the segments to increase the model rigidity by several orders of magnitude, in order to compare the loads between a rigid and a flexible model.

• 자원ㆍ환경경제연구
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• 제30권3호
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• pp.395-433
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• 2021

본 논문의 목적은 주택 소유 여부와 주택유형이 도시녹지공간의 경제가치에 주는 효과를 검증하는 것이다. 공공재로서 녹지공간은 양의 외부효과를 제공하는데, 화폐 외부효과와 기술 외부효과로 나누어진다. 서울을 사례연구 대상지로 하여 선택실험을 진행하였고, 1,000명으로 구성된 온라인 표본을 분석하였다. 분석 결과에 의하면 형평성과 효율성을 고려하여 다양한 유형의 도시녹지를 관리하기 위해서는 두 가지 형태의 외부효과를 차별화하는 것이 매우 중요하다. 모든 조건이 같은 경우에, 아파트 거주자들은 소유 여부가 녹지공간의 경제가치에 양의 유의함을 보여준 반면, 일반주택 거주자들은 그러한 영향이 없었다. 아파트의 경우 세입자들이 느끼는 한계가치와 한계비용이 일치하는 균형점까지 녹지공간을 확장하여 사중손실을 저감할 수 있다. 이와는 상반되게 일반주택의 경우에는 소유 여부가 아니라 가구소득이 어메니티 가치에 유의한 영향을 주었다. 녹지공간의 공적 편익(지불의사액)은 평균적으로 현재 거주지 가격의 16%에서 33% 정도까지 조망이나 접근성의 형태로 구체화되었다. 녹지 접근성의 가치에는 거주지유형의 차이가 유의한 영향을 주지 않았다. 녹지공간을 위한 거주자 프로파일과 정책제언을 제시하였다.

• Journal of Information Processing Systems
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• 제11권2호
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• pp.205-228
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• 2015

In this paper, we present a virtual laboratory platform (VLP) baptized Mercury allowing students to make practical work (PW) on different aspects of mobile wireless sensor networks (WSNs). Our choice of WSNs is motivated mainly by the use of real experiments needed in most courses about WSNs. These experiments require an expensive investment and a lot of nodes in the classroom. To illustrate our study, we propose a course related to energy efficient and safe weighted clustering algorithm. This algorithm which is coupled with suitable routing protocols, aims to maintain stable clustering structure, to prevent most routing attacks on sensor networks, to guaranty energy saving in order to extend the lifespan of the network. It also offers a better performance in terms of the number of re-affiliations. The platform presented here aims at showing the feasibility, the flexibility and the reduced cost of such a realization. We demonstrate the performance of the proposed algorithms that contribute to the familiarization of the learners in the field of WSNs.

• 품질경영학회지
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• 제42권4호
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• pp.579-590
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• 2014

Purpose: Ball milling is a popular process for obtaining fine powders in the part and material industry. One of important issues in the ball milling is to produce particles with a uniform size. Although many factors affect uniformity of particles, this paper focuses on the choice of ball diameter. Consider a ball milling where balls can be taken with three different diameters. The purpose of this paper is to find a ball mix which minimizes the average particle size. Methods: Ball diameters are selected as 10mm, 3mm, and 0.5mm. In order to find an optimum mixing ratio, the method of mixture experiments is employed in this paper. Taguchi's signal-to-noise ratio (SNR) for smaller-the-better type is also used to analyze experimental data. Results: According to the experimental result, SNR is maximized when the ball mix is taken as either 7:3:0 or 6:4:0. Such mixing ratios can be technically validated in terms of porosity reduction. Conclusion: The ball mixing technique presented in this paper provides a useful way to improve the production efficiency with a low cost.