• Structural Engineering and Mechanics
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• 제51권5호
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• pp.707-725
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• 2014

In order to improve the crane-hook's performance and service life, we formulate a multi-criteria shape design problem considering practical conditions. The structural weight, the displacement at specified points and the induced matrix norm of stiffness matrix are adopted as the evaluation items to be minimized. The heights and widths of cross-section are chosen as the design variables. The design variables are expressed in terms of shape functions based on the Gaussian function. For this multi-objective optimization problem with three items, we utilize a multi-objective evolutionary algorithm, that is, the multi-objective Particle Swarm Optimization (MOPSO). As a common feature of obtained solutions, the side views are tapered shapes similar to those of actual crane-hook designs. The evaluation item values of the obtained designs demonstrate importance of the present optimization as well as the feasibility of the proposed optimal design approach.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2283-2287
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• 2023

We propose in the present work how the reference glass dosimeters can be introduced, which reflects the user irradiation condition. The reference glass dosimeters are used for correcting the reader fluctuation by reading it with sample glass dosimeters at the same time. Since they can be used without annealing after irradiation for long periods, one should consider both the fading effect and the natural background dose accumulation quantitatively. We construct an empirical but practical formalism of evaluating the absorbed dose on the glass dosimeter with the fading effect and the natural background dose accumulation considered.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.189-190
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• 2003

A New kinetic scheme for the compressible Navier-Stokes equations is developed. While the conventional approach, such as KFVS scheme, employs the splitting algorithm and computes the numerical flux on the basis of the collisionless equation, the present approach employs the splitting algorithm in the evaluation of the numerical flux, where the collision effect is explicitly taken into account. However, the initial condition employed in the computation is slightly different from the conventional Chapman-Enskog NS distribution function. The present study also reveals the background of the existing kinetic schemes. such as the KFVS scheme and Gas-Kinetic BGK scheme.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.153-160
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• 2003

Nonlinear finite element analysis of reinforced concrete panels subjected to biaxial tensile loads are carried out by using a 9-node assumed strain shell element. The present study mainly focuses on the performance evaluation of material models such as cracking criteria, tension stiffening model and steel model in the membrane energy dominant situation. From numerical results, the exponential form of tension stiffening model together with the use of average yield stress model for the steel embedded in the concrete performs well in the panel analysis under biaxial tensile loading condition and it produces a good agreement with experiment results. Finally, the present results are provided as a benchmark test for reinforced concrete panel structures.

• 도시과학
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• 제9권1호
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• pp.1-6
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• 2020

The thermoelectric characteristics of alkali activated slag composites containing multi-walled carbon nanotubes (MWCNT) was investigated in the present study. Three different MWCNT contents and exposed temperatures were considered, and their thermoelectric-related properties and internal structures were analyzed. It was found that the alkali activated slag composite with MWCNT 2.0 wt.% and the exposed temperature of 150℃ were the optimal condition to obtain the highest Seebeck coefficient and power factor. Based on the feasibility study, the extended size thermoelectric module with 130 elements was fabricated, and tested the electricity production capacity. Consequently, the present thermoelectric module produced 30.83 ㎼ of electricity at ∆T=178.4℃.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2002년도 제41회 학술발표회논문집
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• pp.97-139
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• 2002

The aim of the present study is to find a good quality user equilibrium assignments under time varying condition. For this purpose, this study introduces a dynamic network loading method that can maintain correct flow propagation as well as flow conservation, and it develops a novel solution algorithm that does not need evaluation of the objective function by modifying the Schittenhelm (1990)'s algorithm. This novel algorithm turns out to be efficient and convenient compared to the conventional Frank-Wolfe (1956) algorithm because the former finds solutions based on routes rather than links so that it can maintain correct flow propagation intrinsically in the time-varying network conditions. The application of dynamic user equilibrium (DUE) assignment model with this novel solution algorithm to test networks including medium-sized one shows that the present DUE assignment model gives rise to high quality discrete time solutions when we adopt the deterministic queuing model for a link performance function, and we associate flows and costs in a proper way.

• 콘크리트학회지
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• 제7권1호
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• pp.109-116
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• 1995

본 연구에서는 단순 지지된 일반도로교의 통행차량에 의해서 발생하는 충격계수에 대해서 연구를 수행하였다. 최근에 화서 충격계수는 이론 및 실험적인 연구가 수행됨으로써 상당한 관심이 집중되고 있다. 현행, 국내 도로교 시방서에서 사용하는 충격계수는 지간길이에 따라 감소하는 식으로서 규정되어 있으며, 최대 30%이하로 제한하고 있다. 그러나, 현장실험결과에 의하여 동적하중효과는 대부분 현행 규정보다 낮게 나타나고 있으며, 시방서에서와 같이 지간길이에 다라 일정한 경향을 보여주지 못하고, 포장상태를 포함하는 노면조도에 의해서 큰 영향을 받는 것으로 나타났다. 따라서, 본 연구에서는 현장 실험결과를 바탕으로 노면조도의 상태를 3등급으로 분류하여 도로교의 간이 내하력평가시 사용할 수 있도록 각 등급에 해당하는 충격계수를 결정하였다. 끝으로, 본 연구의 결과는 향후 현존 교량의 내하력평가시 유용한 자료로 사용될 수 있을 것으로 사료된다.

• 상하수도학회지
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• 제30권1호
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• pp.59-67
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• 2016

Owing to time and cost constraints, new methods that would make it possible to evaluate the safety of the water supply pipeline in a less time- and cost-consuming manner are urgently needed. In response to this exigency, the present study developed a new statistical model to assess the safety of the water supply pipeline using the quantification theory type II. In this research, the safety of the water supply pipeline was defined as 'a possibility of the pipeline failure'. Quantification analysis was conducted on the qualitative data, such as pipe material, coating, and buried condition. The results of analyses demonstrate that the hit ratio of the quantification function amounted to 77.8% of hit ratio, which was a fair value. In addition, all variables that were included in the quantification function were logically valid and demonstrated statistically significant. According to the results derived from the application of the safety evaluation model, the coefficient of determination ($R^2$) between K-region's water supply pipeline safety and the safety inspection amounted to 0.80. Therefore, these findings provide meaningful insight for the measured values in real applications of the model. The results of the present study can also be meaningfully used in further research on safety evaluation of pipelines, establishing of renewal prioritization, as well as asset management planning of the water supply infrastructure.

• 한국과학교육학회지
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• 제7권1호
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• pp.53-68
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• 1987

To figure out the present status of Korean middle school science curriculum in the national level is not an easy job. especially in the restricted condition such as this research project. Therefore, to achieve a meaningful result, the case study type of research was adopted In the study five middle schools (2boy's and 3girl's)were selected and examined intensively. In this study, two major works were done. One was the analysis of the present middle school science curriculum and the other was to examine the current status of the administration of the curriculum in schools. This first study focused on the evaluation of the current Curriculum. Acording to the result, the objectives stated in the teachers guide and implied by the testbook were heavily concentrated on the knowledge level in Boom's taxonomy. Achievement on the objectives which were selected as important were very low. The average pass rate for the selected objectives was less than 50% of the students. This means the content level of the present science curriculum is not appropriate. The study suggested that the present middle school science curriculum should be revised and the content should be replaced with easier topics to match the students cognitive level. The study also suggested further studies to measure the cognitive level of Korean students in national scale.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.966-970
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.