• Advances in concrete construction
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• 제10권1호
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• pp.61-69
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• 2020

This paper looks into how the shape of headed bars may influence the durability of reinforced concrete structures. Nowadays the only heads used in site works are cylindrical in shape. An alternative shape of head is studied in this piece of work. The new head reduces the concentration of stresses and so the appearance of cracks. In this work durability is studied based on both, first cracking and failure mode. An experimental campaign of 12 specimens and finite element modelling are described. The specimens were subjected to an accelerated corrosion process using an electrical current supply. Direct current was impressed on the specimens until breaking. Test results and the results obtained from numerical models are presented. Results are presented in term of comparison between the two shapes of heads studied. It was shown that the shape of the head has a significant influence on durability of reinforced concrete structures with headed reinforcing bars.

• 수산해양기술연구
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• 제51권1호
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• pp.94-101
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• 2015

The heat treatment machine based on immersion was developed to reduce temperature difference during netting process and appraised it performance compared current heat treatment machine using high pressure. It was also reviewed the optimum heat treatment procedures for PBSAT monofilament net in accordance with the immersion time and temperature. The procedure was based on physical measurement such as breaking load, elongation and angle of the mesh for PBSAT monofilament. The water temperature gap of the treatment machine based on immersion was less than $1^{\circ}C$. and the energy consumption was also increased in high temperature condition. It was identified that the optimum temperature was $75^{\circ}C$ and its optimum processing time was between 15 minutes and 20 minutes to get qualified physical properties.

• 한국해안해양공학회지
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• 제3권2호
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• pp.108-115
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• 1991

쇄파후 발생하는 에너지 손실과 밀접한 관계를 가지며 또한 쇄파대내에 국한되어 분포하고 있는 연안류 분포형상과 그 형상에 영향을 미치는 제인자에 대해서 고찰하였다. 연안류는 연안역의 물질확산에 관계하며 연안표사와 밀접한 관계가 있어 이에 대한 구명은 공학상으로 커다란 의미를 갖는다. 계산결과로부터 수평확산계수, 마찰계수, 파향각, 파형경사 및 해저경사 등의 연안류의 유속 분포형상에 미치는 영향을 검토하고, 계산의 타당성을 검토하기 위해 기왕의 연구결과와 본 연구에서의 계산결과를 비교 검토한다.

• 에너지공학
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• 제29권3호
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• pp.34-41
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• 2020

Used disposable diapers have been considered for a long time as a type of waste difficult to recycle and valorize due to their composite nature including plastic, cellulose pulp, a super absorbent polymer and either urine, feces or both. Therefore, the fate of disposed diapers often is either incineration or landfill burial which both have various adverse environmental impacts. However, used disposable diapers contain nutrients: cellulose is an organic matter while urine and feces contain non negligible amounts of nitrogen, phosphorus and potassium which are primary nutrients included in most chemical fertilizers used in agriculture. In a scope of waste recycling and valorization, this study focuses on developing a method to achieve nutrient solution extraction from used disposable diapers. The experiment essentially consists in shredding the diapers and letting them macerate in solutions of sodium hydroxide with various concentrations to allow breaking down of the cellulose and super absorbent polymer and release of urine and feces before sterilizing the solutions in an autoclave to remove potential coliform bacteria. At the end of the experiment, a set of parameters is measured for the final solution to identify concentrations of nutrients as well as presence or absence of harmful substances. Results are discussed and directions for future studies are suggested, which include mechanization of the diapers shredding process or added aeration to enhance nitrification and absorption of extracted nutrients from plants.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1138-1142
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• 2011

Kinetic studies for the reactions of Y-aryl phenyl chlorothiophosphates with X-pyridines have been carried out in acetonitrile at $35.0^{\circ}C$. The Hammett and Bronsted plots for substituent X variations in the nucleophiles are biphasic concave upwards with a break point at X = 3-Ph, while the Hammett plots for substituent Y variations in the substrates are biphasic concave downwards (and partially upwards) with a break point at Y = H. The signs and magnitudes of the cross-interaction constant (${\rho}_{XY}$) are strongly dependent upon the nature of substituents, X and Y. The proposed mechanism is a stepwise process with a rate-limiting step change from bond breaking with the weaker electrophiles to bond formation with the stronger eletrophiles. The nonlinear free energy correlations of biphasic concave upward plots for substituent X variations in the nucleophiles are rationalized by a change in the attacking direction of the nucleophile from a backside with less basic pyridines to a frontside attack with more basic pyridines.

• 한국실내디자인학회논문집
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• 제20권3호
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• pp.69-79
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• 2011

The concept of architectural sustainability is gradually being highlighted in several ills and consciousness of crisis of modern architecture. However, many of us tend to realize its sustainability focusing on ecological sustainability in many ways. Such perspective is considerably technical and extensive. Therefore, I paid attention to Herman Hertzberger's architecture to find out how to consider spatial aspects, when interior architecture designers engage in design process. This study aims to analyze architectural progress for social communication of Herman Hertzberger's project, breaking from the existing research to only limit him to one of structuralism architects. In particular, it was found that in relation to social sustainability, universal/social design, cultural design and green/ecological design have been progressed in their forms through communicational perspectives of social architecture which he's insisted since the structuralism era. Recently, majority of issues about sustainability are restricted to economical aspects. Accordingly, further study is needed to consider his architecture from social aspects. As his architecture is concentrating on coexistence from a social perspective for communication, not on modern spatial discourse, his architectural works need to be analyzed consistently as realistic measurements.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2208-2218
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• 2017

To resolve overload in a distribution system, a distribution system operator (DSO) often performs a load transfer using normally open tie points and switches in the distribution line. During this process, the distribution system is momentarily operated in closed-loop operation. A closed-loop current in the distribution system can cause a power failure due to excess breaking current in the circuit breakers and reclosers. Therefore, it is necessary to calculate the closed-loop current exactly. However, if there are a large number of distributed generation (DG) systems in the distribution system, such as energy storage systems (ESS), they might obstruct the closed-loop operation based on bidirectional power flow. For quick and precise operation of a closed-loop system, the ESS has to regulate the power generation while satisfying closed-loop operation in the worst cases. We propose a strategy for balanced power regulation of an ESS. Simulations were carried out using PSCAD/EMTDC, and the results were compared with calculation results.

• 한국정밀공학회지
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• 제11권6호
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• pp.42-49
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• 1994

One of the parameters that influence the productivity of every industry, involved in metal cutting, is the chip from ; continuous or broken chip. Chip form varies according to machining conditions, material used, tool geometry and chip breaker geometry. Therefore, in this study we carried out the experiment on the chip control in machining STS304 using an attached obstruction type chip breaker. Namely, with the change of a chip breaker distance, chip breaker angle, cutting characteristics in machining STS304 which is well-known as a machining difficult material and produces a saw-toothed chip. The results of the experiment are as follows : 1. The chip breaker distance and angle under which the preferred chip is produced, show 1.5mm and 60 .deg. , while chip breaker angle in machining an ordinary steel was well-known 45 .deg. . 2. During the cutting process, the change of feed than the change of velocity was applied as cutting conditions, effects more clearly on the chip breaking. 3. Considering a whole surface roughness, it is not advisable to apply chip breaker mentioned above for precision cutting.

• Ocean Systems Engineering
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• 제6권2호
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• pp.161-189
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• 2016

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around a vertical pile exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (2002). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases on mild slopes are also suggested.

• Ocean Systems Engineering
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• 제7권3호
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• pp.275-298
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• 2017

This paper provides a practical stochastic method by which the maximum equilibrium scour depth below a pipeline exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Fredsøe (1996). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases for random waves alone are also suggested.