• Nuclear Engineering and Technology
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• 제37권4호
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• pp.375-384
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• 2005

To investigate the flow-accelerated corrosion (FAC) dependency of carbon steel (A106 Gr. B) and low-alloy steels (1Cr-1/2Mo, 21/4Cr-1Mo) on pH, orifice distance, and material, experiments were carried out. These experiments were performed using a flow velocity of 4 m/sec (partly 9 m/sec) at pH $8.0\~10.0$ in an oxygen-free aqueous solution re-circulated in an Erosion-Corrosion Test Loop at $130^{\circ}\;{\ldots}$ for 500 hours. The weight loss of the carbon steel specimens appeared to be positively dependent on the flow velocity. That of the carbon and low-alloy steel specimens also showed to be distinguishably dependent on the pH. At pH levels of $8.0\~9.5$ it decreased, but increased from 9.5 to 10.0. Utility water chemistry personnel should carefully consider this kind of pH dependency to control the water system pH to mitigate FAC of the piping system material. The weight loss of the specimens located further from the orifice in the distance range of $6.8\~27.2$ mm was shown to be greater, except for 21/4Cr-1Mo, which showed no orifice distance dependency. Low alloy steel specimens exhibited a factor of two times better resistance to FAC than that of the carbon steel. Based on this kind of FAC dependency of the carbon and low-alloy steels on the orifice distance and material, we conclude that it is necessary to alternate the composition of the secondary piping system material of NPPs, using low-alloy steels, such as 21/4Cr-1Mo, particularly when the system piping has to be replaced.

• Journal of Advanced Marine Engineering and Technology
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• 제27권4호
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• pp.487-493
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• 2003

More reliable design of thermal transport. Power acquisition and thermal management systems requires the through understanding of the flow hydrodynamic. the differences and similarities between the two-phase flow characteristics of two-Phase flow influenced by the gravity levels. The data of flow Patterns, void fraction, frictional pressure drop associated with their characteristics were obtained at $\mu\textrm{g}$. 1g and 2g. Flow patterns and void fraction data obtained at three gravity levels were compared with each other and previous models and correlations.

• 한국문헌정보학회지
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• 제15권
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• pp.73-94
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• 1988

The main purpose of the present study is to investigate the citation habit of Korean social scientists by making use of citation analysis and content analysis, and to assess the nature of interdisciplinary flow of information in Korea in terms of the citation dependency on other disciplines, the types of channels used in formal scientific communication, the countries published the literatures of other disciplines cited in the source articles, and the languages used in the literatures of other disciplines. The major findings and conclusions reached at this study are summarised as follows: 1. Korean social scientists mainly cite the literatures of economics, sociology, politics, and history when they cite the literature of other disciplines. 2. The citation dependency on other disciplines of the economists, polictial scientists, and sociologists are 6 percents, 14 percents, and 19 percents, respectively. 3. The citation dependency on history of the economists is 25 percents, the dependency on sociology of the political scientists is 34.9 percents, and the dependency on economics of the sociologists is 50. 19 percents. 4. The types of channels used in formal scientific communication in social sciences are firmly book and journal. 5. The countries published the literatures of other disciplines .cited in the source articles are Korea and the U. S. firmly. 6. The languages used in the literatures of other disciplines cited in the source articles are Korean and English overwhelmingly.

• 대한건축학회논문집:구조계
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• 제35권2호
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• pp.29-36
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• 2019

Modular construction has benefits such as short construction duration and high productivity owing to the production in factory and owing to simultaneous on-site work. However, rework occurs in modular construction and the rework affects the efficiency of modular construction. The almost of causes of rework are exist in design process. To reduce the cause of rework, the information flow of the design process should be managed and the plan to reduce rework should be included. However, the modular construction has complex process because of impeded unit production so it is hard to manage the information flow in design process. Moreover, when the plan to reduce rework is included, the design process will be more complicated. Therefore, the objective of this research is to suggest the design process including the rework reduction plan and to alleviate the complexity of design process by using Dependency Structure Matrix(DSM). By using DSM, the iteration and feedback in design process is reduced and it can be expected that rework in modular project can be reduced by using suggested design process.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.320-325
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• 2010

A multiphase CFD analysis is performed to investigate the effect of near-wall grid for simulating a subcooled boiling flow in vertical tube. The multiphase flow model used in this CFD analysis is the two-fluid model in which liquid(water) and vapor(steam) are considered as continuous and dispersed fluids, respectively. A wall boiling model is also used to simulate the subcooled boiling heat transfer at the heated wall boundary. The diameter and heated length of tube are 0.0154 m and 2 m, respectively. The system pressure in tube is 4.5 MPa and the inlet subcooling is 60 K. The near-wall grid size in the non-dimensional wall unit ($y_{w}^{+}$) was examined from 64 to 172 at the outlet boundary. The CFD calculations predicted the void distributions as well as the liquid and wall temperatures in tube. The predicted axial variations of the void fraction and the wall temperature are compared with the measured ones. The CFD prediction of the wall temperature is shown to slightly depend on the near-wall grid size but the axial void prediction has somewhat large dependency. The CFD prediction was found to show a better agreement with the measured one for the large near-wall grid, e.g., $y_{w}^{+}$ > 100.

• 한국전산유체공학회지
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• 제15권3호
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• pp.24-31
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• 2010

boiling flow in vertical tube. The multiphase flow model used in this CFD analysis is the two-fluid model in which liquid(water) and gas(vapour) are considered as continuous and dispersed fluids, respectively. A wall boiling model is also used to simulate the subcooled boiling heat transfer at the heated wall boundary. The diameter and heated length of tube are 0.0154 m and 2 m, respectively. The system pressure in tube is 4.5 MPa and the inlet subcooling is 60 K. The near-wall grid size in the non-dimensional wall unit for lqiuid phase ($y^+_{w,l}$) was examined from 101 to 313 at the outlet boundary. The CFD calculations predicted the void distributions as well as the liquid and wall temperatures in tube. The predicted axial variations of the void fraction and the wall temperature are compared with the measured ones. The CFD prediction of the wall temperature is shown to slightly depend on the near-wall grid size but the axial void prediction has somewhat large dependency. The CFD prediction was found to show a better agreement with the measured one for the large near-wall grid, e.g., $y^+_{w,l}$ > 300 at the tube exit.

• 한국연소학회지
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• 제13권2호
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• pp.14-22
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• 2008

The CH* chemiluminescence of premixed flames and their dependency on fuel types has been experimentally investigated on laminar methane and propane premixed flames. The measured chemiluminescence intensities are observed linearly proportional to the fuel flow rate, which could be interpreted as the CH* chemiluminescence signal is linearly proportional to the heat release rate under fuel lean conditions. The effect of equivalence ratio could be expressed by an exponential function as ${I_{CH*}}^{\propto}\;a_1\;{\exp}(b_1{\Phi})$, where $a_1\;=\;0.00054$ and $b_1\;=\;4.60$ for methane and $a_1\;=\;0.0056$ and $b_1\;=\;5.02$ for propane. Oscillating flames showed the temporal fluctuation of chemiluminescence intensity: however, the time averaged values are virtually identical to those of quiescent flames under the same fuel flow rate and equivalence ratio conditions. This observation suggests that there is no significant flame stretch effect on chemiluminescence intensity, in average values.

• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.550-555
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• 2011

Utilizing construction knowledge and experiences in design phase can reduce change orders and improve productivity in construction phase. To do so, information must be made available to the design team in time. Current approaches for effective utilization of constructability knowledge, however, only focus on the formalization of constructability knowledge such as a checklist, which lacks the consideration of the appropriate use at the proper point in time. The inadequate use of constructability knowledge can result in unnecessary reworks. To deal with this problem, the design team needs to know what constructability knowledge is required for specific design activities in the design process. This paper presents a constructability implementation model using the dependency structure matrix (DSM) that focuses on information flows between design activities and constructability knowledge. For this objective, design activities in the design process are modeled in a matrix form based on their dependency. Then, constructability knowledge, which needs to be considered in the design stage, is mapped into activities and incorporated into the matrix, creating Constructability-DSM (C-DSM). Next, the partitioning algorithm is applied to C-DSM for optimal information flow. The Partitioned C-DSM is then analyzed based on the relationship between activities. Finally, the optimal utilization of construction knowledge in the design process is determined by identifying what constructability knowledge is required for each design activity, and how and when it is reflected to design for constructability. Thus, this research can help provide robust control actions to reduce unnecessary iterative cycles in design process for efficient constructability implementation.

• 디지털융복합연구
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• 제15권3호
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• pp.181-186
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• 2017

시스템 최적화는 소스코드의 변경 없이 중복된 모듈을 추출하고, 추출된 모듈의 재사용을 위하여 프로그램의 구조를 변경하는 기법이다. 구조지향 개발과 객체지향 개발은 크로스커팅 영역의 모듈화에는 효율적이나 크로스커팅 개념을 모듈화 할 수 없다. 기존 시스템에서 크로스커팅 개념을 적용하기 위해, 각 시스템 내에 분산되어 있는 시스템 최적화 대상 모듈을 크로스커팅 영역으로 추출하는 기술이 필요하다. 본 논문에서는 개발이 완료된 시스템에서 중복 모듈을 추출하기 위한 방법을 제안한다. 제안하는 방법은 소스코드 분석을 통해 데이터 의존관계와 제어 의존관계를 분석하여 중복되는 요소를 추출한다. 추출된 중복된 요소는 시스템 최적화를 위하여 프로그램 의존 관계 분석에 사용될 수 있다. 중복된 의존관계 분석 결과는 제어 흐름 그래프로 변환되며, 이를 활용하여 최소 크로스커팅 모듈을 생성할 수 있다. 의존 관계 분석을 통해 추출된 요소는 크로스커팅 영역 모듈로 설정함으로써 시스템 내 중복된 코드를 최소화 할 수 있는 시스템 최적화 방법을 제시한다.

• 한국자동차공학회논문집
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• 제23권2호
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• pp.191-198
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• 2015

In this study, the flow characteristics at the ventilation holes was analyzed by using numerical method when carbon composite brake disk was rotated at a constant speed. In order to ensure the validity of the analysis results, grid dependency test was performed by considering the accuracy and appropriateness, and 4mm mesh size was selected for decrease of the maximum error rate 63.6%. As a result, the outside air flows in the clearance between the disk and shaft in case of B model. whereas, the outside air flows in the clearance or the outlet of the ventilation holes in case of A and C models. And also average static pressure at the outlet was changed depending on shape of the ventilation holes and rotational speed of the disk in case of A and C models. Besides, in the B model, intake air according to the clearance goes with side surface of ventilation hole, and so increased by mean velocity of 4.64m/s and mean pressure of 0.58pa in the ventilation hole outlet, in case of disk rotational speed of 146.21rad/s.