• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6B
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• pp.541-550
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• 2011

This study sets the goal to improve effectively water quality of stream by complementing the weak points of the gravel contact oxidation process to use the inverted siphon curved channel system in free overfall of serial contact materials. The size of the current system can be diminished by expanding contact time, and the materials' replacement can be made easier when their gap are closed through the filtering boxes of contact materials. This system also has been developed into a construction method in which mixed and serial contact materials can be employed by using just the conventional single contact materials. It was verified the improvement ability of water quality of this system, during the simulation test at Tandong stream in Daejeon. The results of the verification of water quality improvement through several experiments in field were measured as follows : it showed to reduce about the averaged 55~83% higher than 60~75%, the internal planned goal of water quality improvement facilities.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.255-267
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• 2008

Using the commercial CFD code FLOW-$3D^{(R)}$ which has an implicit General Moving Object (GMO) method, the ship-induced wave has been simulated. In the implicit GMO method of the FLOW-$3D^{(R)}$, a rigid body's motion which is either user-prescribed (prescribed motion) or dynamically coupled to fluid flow (coupled motion) can be computed with six degrees of freedom (DOF). The simulated horizontal wave patterns are agree with the wave patterns represented by depth Froude number. The model has been well-simulated to generate the depth-dependent wave transformation in comparison of uniform depth case to complicated depth case. Additionally, it shows that ship-induced waves have been reasonably generated by two ships passing each other and by a ship moving in a curve. Therefore, it is suggested that the FLOW-$3D^{(R)}$ model calibrated with observed data should provide more accurate prediction for the ship-induced wave in a certain fairway or harbor.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.455-462
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• 2016

This experimental study aims to evaluate the impact performance of UHPC exterior panels through high velocity impact tests. The impact performance of UHPC was compared with that of granite in terms of panel thickness, and strain histories were recoded on the rear face of panel specimens. The UHPC turned out to be a good exterior facade material, because the appearance of UHPC is natural enough and impact performance was superior to granite. After colliding, compression pulse reached to the rear face but that pulse was reflected in tension pulse with respect to the free point outside the rear face of the panel. This tension pulse caused the scabbing from the rear side, as the strain histories on the rear face showed three different regions as compression region, steady region and tension region. The shear plug deformation by shear force also was one of the primary reasons for the scabbing based on the observation. Therefore, the scabbing seemed to be affected by both tension and shear forces.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.137-143
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• 2012

The learners using learning content through the smart devices can access to the Internet from anytime and anywhere. However, with the rapid increase of learning content on the Web, it will be time-consuming for learners to find contents they really want to and need to study. Therefore, e-learning systems should not only provide flexible content delivery, but support adaptive harmonizing fusion content. The harmonizing fusion content it is a very important in fusion e-learning service. The representative method to provide synchronization between fusion content is a provide absolute time value between of the contents. However, this method is occurs a problem transferring time delay. Also, to enter an absolute time value for the duration of the each content is several problems arise. In this paper introduces a new smart e-smart service support the harmonizing media based technology to create synchronized learning presentation.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.25-32
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• 2010

Contamination of soil and groundwater by the compounds of hydrocarbon petroleum has been widely accepted as the main cause that harms the environments and health. To remove those pollutants, absorbing clothes, activated carbons, or oil-water separation devices with the gravity method are employed for treatment. However, those materials and devices cannot remove the emulsion pollutants despite of their efficiency for removing free products. Therefore, we investigated the problems which occur during the groundwater treatment for the highly concentrated suspended solid particles, which can be resulted from excavation, and to propose methods to remove TPH(Total Petroleum Hydrocarbon). After coagulation experiment with high molecular polymers, the concentration of SS(Suspended Solids) and COD(Chemical Oxygen Demand) turned to satisfy the groundwater quality criteria within 5 minutes while the concentration of TPH failed to meet the water quality standard of effluent. Consequently, the water quality criteria for effluent could not be met by single DAF(Dissolved Air Flotation) process. However all water quality criteria could be satisfied after 20 minutes when coagulation reactions are carried out simultaneously in the DAF reactor.

• Journal of the Korean GEO-environmental Society
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• v.18 no.8
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• pp.17-21
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• 2017

This paper is to grasp the use of impact-echo response signal induced from impacting an object for the assessment of compressive strength of construction materials nondestructively and to propose the test results. For this study, an impact device was devised and used for impacting an object by an initial rotating free falling impact and following repetitive impacts from the rebound action which eventually disappears. Concrete test specimens which had been mixed for different strengths were tested and the impact echo response signal was measured for each test specimen. The total sound signal energy which is assessed from integrating the impact-echo response signal was compared with the directly measured compressive strength for each specimen. The comparison showed that the total sound signal energy has a direct relationship with the directly measured compressive strength and the results clearly indicated that the compressive strength of construction materials can be assessed nondestructively using total sound signal energy which is assessed from integrating the impact-echo response signal induced from impacting an object.

• Korean Journal of Food Science and Technology
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• v.17 no.6
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• pp.431-436
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• 1985

The major sterol in the unsaponifiable matter (15.9 mg per gram on basis) of the sesame oil was 4-desmethylsterol (55.6%). 4-desmethylsterol consists of sitosterol (29.5%), campesterol (9.8%), ${\Delta}^5$-avenasterol (6.6%) and stigmasterol (5.9%). Between the packing bags kept the sesame seeds in, namly, the cotton and polyethylene bag, the campesterol content of sesame stored in the cotton bag was not nearly changed, whereas stored in the polyethylene bag was increased upto 4 months storage and then decreased until 15 months. The sitosterol content of sesame stored in cotton bag was increased upto 4 months and then decreased sharply until 15 months of storage, whereas stored in the polyethlene bag was not changed upto 4 months and slightly increased upto 9 months and again decreased until 15 months. Between the storage conditions, namly, light and dark storage, the stigmasterol content of the sesame stored under light condition was hardly changed upto 9 months and slightly increased after that, whereas stored under dark condition was increased upto 4 months, decreased upto 9 months and again slightly increased after that. ${\Delta}^5$-avenasterol was not much changed in all the storage conditions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.120-120
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• 2018

반도체 소자나 디스플레이 패널 제조 공정에 가장 많이 사용되는 진공 펌프인 터보 분자 펌프는 오일을 사용하지 않고, 설치 방향이 자유로우며 넓은 작동 압력 영역을 가지고 있어서 고가임에도 불구하고 점점 더 사용 영역을 넓혀 가고 있다. 상하의 두 곳에 회전축을 지지하는 베어링이 필요한데, 기계식 금속 베어링을 채용하는 경우에는 반드시 윤활유를 공급해 주어야 하고, 고온, 부식성 또는 산화성 가스의 배기 시에는 퍼지 가스로 비활성인 질소나 알곤등을 이용하여 보호를 해주어야 한다. 반면, 자기 베어링을 채택한 모델은 윤활의 걱정에서 자유로울 수 있기 때문에 채용이 늘어나고 있다. 동일극의 반발력이나 반대극의 인상력을 이용한 구조를 갖게 되는데 갑작스러운 입구 쪽 압력의 증가 시에는 자석 끼리 부딪치는 일이 발생하고 이로 인해서 로터 모듈 전체에 큰 손상을 갖게 되므로 한 곳 정도에 비상용 터치 다운 베어링을 기계식으로 윤활제 없이 설치하기도 한다. 기본적으로 자기 베어링 방식은 로터 모듈의 부상과 제어를 위해서 3축 또는 5축 제어를 하게 되는데 여기에는 전자석의 전류를 미세하게 조정하여 피드백 하는 시스템을 활용하기 때문에 외부에서의 자기장이 일정값 이상 침투하게 되면 제어 회로의 기능에 문제를 일으키게 된다. 또한 축 방향에 수직인 자기장의 강도가 높아지면 고속으로 회전하는 금속 블레이드가 자속을 자르게 되므로 표면에 와전류가 발생하여 문제가 된다. 터보 분자 펌프는 회전자와 고정자 간격이 1 mm 이내로 작아서 약간의 진동이라도 발생하면 회전자와 고정자 간에 충돌이 일어나고 이는 곧 파손으로 이어진다. 그림 1에는 파손 원인 분석을 위한 회전자 모듈의 수치 해석용 모델의 일부를 나타내었고, 그림 2에는 실제로 외부 자기장에 의한 파손이 발생한 사례의 자기 베어링 모듈의 사진을 나타내었다. 본 발표에서는 외부 자기장의 형태에 따라 제어 자기장에 미치는 영향을 CFD-ACE+(ESI corp)를 활용하여 해석하였다.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.465-471
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• 2003

A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.732-737
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• 2009

Wind tunnel testing on the real-scale pantograph for high-speed train has been conducted to investigate the aerodynamic characteristic of the pantograph at high-speed. The mid-scale subsonic wind tunnel of Korea Airforce Acamedy with 3.5m width, 2.45m height, and 8.8m length test section has been employed. The test model has been supported above 50cm height from the bottom of test section using vertical strut to eliminate the boundary layer generated from the bottom of the test section. The height of the pantograph has been varied in three cases, in both of the normal running and reverse running modes. The resultant lift forces of the pantograph to catenary system in all the cases have been measured and the relation between the test conditions and the lift forces have been extensively analyzed.