• 한국지반공학회지:지반
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• 제1권1호
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• pp.21-30
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• 1985

응력재분포리론을 응용한 Dubrova의 토압론과 이를 수정한 Chang의 방법을 발전시켜 정적토압과 지진시의 토압을 벽체의 변위형태를 고려하여 산정하는 방법을 제안하였다. 뒤채움은 사질토 두 일반토로 구분하여 별개의 토압산정식을 제시하였다. 토류벽의 변위형태는 다음 4가지를 선택하였다. (1) 벽체의 정점을 중심으로 회전하는 주동변위 (2) 벽체의 정점을 중심으로 회전하는 주동변위 (3) 벽체의 벽체을 중심으로 회전하는 수동변위 (4) 벽체의 벽체을 중심으로 회전하는 수동변위 제안된 토압공식을 다른 토압론에 의한 이론치와 비교 검토하였다. 그 결과 변위의 형태에 따라 상이한 토압분포가 얻어졌으며 이는 현재 관용되고 있는 토압이론보다 더 합리적이라 사려된다.

• 한국지반공학회논문집
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• 제20권8호
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• pp.181-191
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• 2004

옹벽의 벽면이 거친 경우에 강성옹벽에 작용하는 주동토압의 크기와 분포형태는 뒷채움재의 내부마찰각과 옹벽의 벽면마찰각 뿐만 아니라 뒷채움재에서 발생하는 아칭효과와 파괴면의 형상에도 영향을 받는다. 따라서 강성옹벽에 작용하는 주동토압의 크기와 비선형의 분포형태를 정확히 산정하기 위해서는 토압 산정 시 뒷채움재에서 발생하는 아칭효과와 실제적인 파괴면의 형상을 고려해야 한다. 본 연구에서는 강성옹벽이 옹벽의 정점을 중심으로 회전하는 경우에 대하여 뒷채움재에서의 아칭효과와 실제적인 비선형의 파괴면 형상을 고려함으로써 비선형의 주동토압을 산정할 수 있는 토압산정식을 제안하였다. 그리고 제안식에 대한 정확도를 검증하기 위하여 제안식으로부터 얻어진 예측치들을 기존의 모형시험 결과들과 비교한 결과 제안식은 만족스런 토압 예측치를 제공하는 것으로 나타났다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1107-1112
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• 2004

For a rigid retaining wall with rough face, the practical shape of failure surface and arching effect in the backfill must be considered to acquire accurate magnitude and non-linear distribution of active earth pressure acting on the rigid retaining wall. In this study, a new formulation for calculating the active earth pressure on a rough rigid retaining wall rotating about the top is proposed considering the practical shape of non-linear failure surface and arching effects. Accuracy of the proposed equation is checked through comparisons of calculations from the proposed equations with existing model test results. The comparisons show that the proposed equations produce satisfactory results.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.212-219
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• 2001

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Tribology and Lubricants
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• 제18권2호
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• pp.153-159
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• 2002

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil Journal bearing. A 52 N weighted bump foil bearing sleeve was lilted off from a rotating Journal at about 3,000 rpm, and produced a load capacity of 500 N at an operating speed of 15,000 rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surfAce were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• 대한의용생체공학회:의공학회지
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• 제26권1호
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• pp.43-47
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• 2005

We have developed a small bore x-ray CT for small animal imaging with a linear x-ray detector array and small-scale slip rings. The linear x-ray detector array consists of 1024 elements of 400□m×400□m with a gadolinium oxysulfide (GOS) scintillator on top of them. To avoid use of expensive large diameter slip rings for projection data transmission from the X­ray detector to the image reconstruction system, we used the wireless LAN technology. The projection data are temporally stored in the data acquisition system residing on the rotating gantry during the scan and they are transmitted to the image reconstruction system after the scan. With the wireless LAN technology, we only needed to use small-scale slip rings to deliver the AC electric power to the X-ray generator and the power supply on the rotating gantry. The performances of the small animal CT system, such as SNR, contrast, and spatial resolution, have been evaluated through experiments using various phantoms. It has been experimentally found that the SNR is almost linearly proportional to the tube current and tube voltage, and the minimum resolvable contrast is less than 30 CT numbers at 40kVp/3.0㎃. The spatial resolution of the small animal CT system has been found to be about 0.9Ip/㎜. Postmortem images of a piglet is also presented.

• 한국압력기기공학회 논문집
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• 제7권3호
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• pp.61-66
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• 2011

The integrity of the SG(Steam Generator) tubes has been challenged by numerous factors such as flaws, operation, atmosphere, inherently degraded materials, loose parts and even human errors. Of the factors, loose parts(or foreign materials) on the secondary side of the tubes can bring about volumetric defects and even leakage from the primary to the secondary side in a short period of time. More serious concerns about the loose parts are their unknown influx path and rapid growth rate of the defects affected by the loose parts. Therefore it is imperative to detect and characterize the foreign materials and the defects. As a part of the measures for loose part detection, TTS(Top of Tubesheet) MRPC(Motorized Rotating Pancake Coils) ECT has been carried out especially to the restricted high probability area of the loose part. However, in the presence of loose parts in the other areas, wide range loose part detection techniques are required. In this study, loose part standard tube was presented as a way to accurately detect and characterize loose part signals. And the SG tube ECT bobbin coil and MRPC ISI(In-service Inspection) data of domestic OPR-1000 and Westinghouse Model F(W_F) were reviewed and consequently, comprehensive loose part detection technique is derived especially by applying bobbin coil signals

• 한국치위생학회지
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• 제8권4호
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• pp.205-217
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• 2008

The purpose of this study was to provide information on the development of an oral-health promotion program geared toward office workers. The subjects in this study were 240 employees at the headquarters of S construction company. After a survey was conducted in July and August 2008, the answer sheets from 208 respondents were gathered, and 191 answer sheets were analyzed except 17 unanalyzable ones. The findings of the study were as follows: 1. In regard to subjective oral health status, the largest number of the participants that accounted for 37.2% found their mouth to be neither healthy nor unhealthy. The greatest number of them that represented 58.1% had never visited a dentist's office to receive preventive treatment. 2. Regarding relationship between toothbrushing education experience and toothbrushing frequency, the most common toothbrushing frequency was three times a day( 46.5%) among the company employees who had ever received that education. In the event of the office workers without that experience, the most prevalent frequency was three times(63.6%). The toothbrushing frequency was statistically significantly different according to the toothbrushing education experience(p<0.05). As to the relationship of toothbrushing education experience to tooth- brushing method, the largest number(48.2%) of those who had ever received that education brushed their upper and lower teeth along with the gums by rotating the toothbrush downward from the top and upward from the bottom respectively. In the event of the office workers without that experience, 49.4 percent brushed their teeth and gums by rotating the toothbrush up and down. Thus, whether they had ever received education about toothbrushing made a statistically significant difference to their toothbrushing method(p<0.05). 3. As a result of evaluating their oral health belief by utilizing a five-point scale, they got a mean of 2.95. In each area of oral health belief, they got the best marks in benefit(3.66), salience(3.42), barrier(2.84), susceptility(2.58) and seriousness(2.23). Given the above-mentioned finding of the study, two sorts of oral health beliefs, which are benefit and salience, should be stressed in the development of oral health education programs that cater to company employees. And sustained research efforts should be channeled into finding out the relationship between oral health and actual oral health care.

• 헤리티지:역사와 과학
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• 제44권4호
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• pp.112-129
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• 2011

본고에서는 백제 한성기 중심지역에 해당되는 서울 몽촌토성, 서울 풍납토성, 서울 석촌동고분군, 하남 미사리유적에서 출토된 취사용기의 형태, 제작기법 등을 분석하여 그 전개양상에 대해 살펴보았다. 형태적 분석에서는 심발형토기는 동최대경이 동체상부에 위치하고 장란형토기는 동최대경이 동체중부에 위치하는 것으로 나타났고, 경부잘록도는 두 기종 모두 미비한 편이었다. 유적별로는 심발형토기의 경우 서울 석촌동고분군이 용량이 적고, 심도가 깊으며, 동최대경이 높은 것으로 확인되었다. 장란형토기는 서울 풍납토성이 하남 미사리유적보다 심도가 깊고, 동최대경은 동중부에 위치하며 경부잘록도가 큰 것으로 확인되었다. 제작기법 분석에서는 심발형토기는 용량군의 폭이 커질수록 유문내박자를 이용하여 타날하였는데, 외면에는 승문이 주로 확인되었다. 또한 기벽이 가장 얇은 것으로 나타났다. 이는 기술적 변화를 나타내는 것으로 시간성을 포함하고 있다. 장란형토기에서도 유문내박자를 사용한 토기가 기벽이 가장 얇고 경부의 잘록도는 약해지는 것으로 나타났으며, 구순부에 강한회전력에 의한 정면흔적이 관찰되었다. 두 기종 모두 유문내박자를 사용하면서 더욱 기벽을 얇게 제작할 수 있게 된 것으로 확인되었다. 백제 한성기 중심지역에서 출토된 심발형토기와 장란형토기는 태토나 소성에서는 시간성이 명확하지 않지만 제작기법상에서 그 전개양상을 확인할 수 있었다. 또한 그 제작기법의 변화양상에는 시간성도 반영되어 있는 점도 확인 할 수 있었다.