• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.39-46
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• 2007

In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast and normal atmosphere is accumulated and analyzed. Investigating and evaluating the result of exposure test during 30 months of exposure age under the coastal and normal atmosphere environment, carbonation depth and chloride-ion penetration depth very little penetrated than cover depth. It seems reasonable to conclude that main cause of Corrosion of reinforcing bar are chloride-ion and macro cell from the result of corrosion area and corrosion velocity. Therefore, it is considered to be applied as the fundamental data on the performance evaluation and quality control standards of repair material and method through continuous exposure test in the future.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.334-339
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• 2011

이 연구에서는 내화천장구조 재료의 고온 열특성을 파악하여, 건축물 화재시 천장구조에 대한 보다 정확한 화재성상예측을 위한 실험적 자료로 제시하고자 한다. 건축물의 화재성상 예측은 내화설계 시 반드시 필요하며, 화재성상예측을 위해서는 화재하중, 작용외력, 안전계수 및 설계용 정수의 합리적인 설정이 중요하다. 화재하중 및 작용외력 등은 건축물의 부재가 지니는 하중조건에 대한 화재시의 부재 안정성 예측에 관계되는 부분이며, 설계 시 필요한 데이터 중 내화천장구조 재료의 고온 열특성 값은 화재발생 구획의 화재온도가 주요 구조부재에 전달되는 정도를 예측할 수 있는 인자로 볼 수 있다. 따라서 내화천장구조 재료의 고온 열특성 값 설정은 화재발생 공간의 온도범위($20{\sim}1000^{\circ}C$)에 걸쳐 평가 및 분석되어야만 정확하고 신뢰성 있는 화재발생 예상 공간의 부재 온도 및 안전성 분석이 가능하다. 이에 국내 건축구조물에 사용되고 있는 대표적인 내화피복 재료인 방화석고보드, 텍스, 암면에 대해서 $20^{\circ}C{\sim}900^{\circ}C$까지의 열전도율을 측정하였다. 실험결과 방화석고보드와 텍스의 경우 약 0.15 W/m K까지 일정하게 증가하였다. 암면의 경우 약 $700^{\circ}C$까지는 방화석고보드나 텍스에 비해 열전도율이 낮게 나타났지만, $800^{\circ}C$ 지점부터 용융 및 탄화가 진행되면서 열전도율이 급격히 상승하는 것으로 나타났다.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.139-150
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• 2010

Reinforced-concrete (RC) columns are frequently designed and constructed. other types of columns includes composite types such as concrete-filled tube columns (CFT). Hollow RC columns may be effective in reducing both the self weight of columns and total amount of materials used. This is due to the fact that a hollow RC column possesses larger moment of inertia than that of solid RC columns of same cross sectional area. Despite the effectiveness the hollow RC column has not been popular because of its poor ductility performance. While the transverse reinforcements are effective in controlling the brittle failure of the outside concrete, they are not capable of resisting the failure of concrete of inner face which is in unconfined state of stress. To overcome these drawbacks, the internally confined hollow reinforced concrete (ICH RC), a new column type, was proposed in the previous researches. In this study, the fire resistance performance of the ICH RC columns was analyzed through a series of extensive heat transfer analyses using the nonlinear-material model program. Also, effect of factors such as the hollowness ratio, thickness of the concrete, and thickness of the internal tube on the fire resistance performance were extensively studied. Then the factors that enhance the fire-resistant performance of ICH RC were presented and analyzed.

• The Journal of the Korean dental association
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• v.8 no.3
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• pp.279-282
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• 1970

구강점막상피는 여러 가지의 외적 자극을 받게 되는데,특히 치과보철용재료인 금속,인공수지 등으로 조제된 총의치,국부의치를 사용하는 사람들의 구강상피의 변화를 탈락세포의 각화상태를 관찰함으로서, 국소적인,기계적화학적인 자극이 점막상피에 어떤 영향을 미치며, 그것이 병적 진행 여부를 추구하였다. 이과 같이, 끼웠다 뺏다 하는 의치가 구강상피조직에 미치는 영향에 대해서는 많은 학자들이 연구해 왔다. 그리고 그들 대부분의 학자들이 비고정의치의 기능적인 작용이 악골에도 크게 자극하지만,그 보다도 점막상피에 더 많은 영향을 미치게 한다고 했다. 본인은 이러한 것을 Pap.씨법에 의하여 구강탈락세포를 관찰함으로서, 의치에 의하여 구강점막상피가 정상적인 각화과정에 장해를 받고 있는 것을 인정하게 했다. 즉 의치에 의하여 피복되어 있는 상피(접착점막)에는 정상적인 각화현상을 볼 수 없고,다만 parakeratose 로 이행되는 것을 관찰하게 되었다. 이러한 상피의parakeratose 현상은 의치에 의한 물리적인 작용(교합압)도 그 이유의 하나이겠지만,의치를 조제하는 재료,즉 금속인공수지의 화학적인 자극에 의히여 상피각화과정에 장해를 주어,의치사용자의 구강상피가 parakeratose 과정을 취하는 것을 알게 하였다. 이러한 것은 또한 의치의 교합압을 가장 많이 받는 경구개와 하악치조돌기점막상피의 각화도가 타부위에 비하여 심한 것으로 보아서도 증명된다.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.451-456
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• 2004

Thermal creep properties of the zirconium tube which was developed for high burnup application were evaluated. The creep test of cladding tubes after various final heat treatment was carried out by the internal pressurization method in the temperature range from $350^{\circ}C to 400^{\circ}C$ and from 100 to 150 MPa in the hoop stress. Creep tests were lasted up to 900days, which showed the steady-state secondary creep rate. The creep resistance of zirconium claddings was higher than that of Zircaloy-4. Factors that affect creep resistance, such as final annealing temperature, applied stress and alloying element were discussed. Tin as an alloying element was more effective than niobium due to solute hardening effect of tin. In case of advanced claddings, the optimization of final heat treatment temperature as well as alloying element causes a great influence on the improvement of creep resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.244-249
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• 2014

In this research, it have developed a sensor that could diagnose inner deterioration of covered wires. With this sensor it observed results from simulation, and the attribute required for realization. For simulation it have used FLUX, it have considered all of geometric and electromagnetic information from coil and base metal that influences eddy current sensor's property in order to predict the final result. It assumed there is no mutual inductance in the coil with N number of turns, because equivalent current flows in coil that is continuously connected in eddy current sensor. It assumed circular coil loop draws a circle, always have self inductance, and they are connected in series and overlapped according number of turns (N) in coil, and bobbin configuration. Actual sensor was produced with consideration of inductance and number of turns (N). In conclusion, it were able to test the dependency through results from simulation, actual measurement, and modeling of simulation. It is considered that attributes of respective base metal and structure can be predicted by simulating in advance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1995.04a
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• pp.109-116
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• 1995

프로세서 제어기기에서 오동작의 주요원인은 EFT로 국제전기기술위원회 (IEC)는 EFT에 대한 내성을 평가하기 위해 의사적인 신호를 규정하고 프로세서 제어기기의 내성을 시험하도록 권고하고 있다 본 논문에서는 IEC에서 규정한 의사 EFT신호를 Frequency domain에서 분석하고 이에 대한 대책용 부품개발에 대한 연구를 수행하였다 대책용 부품의 구성은 전원코드의 입력측에 관통형 컨덴서를 Cy 형태로 취부하고 전선자체에는 CM성분의 임피던스를 높이기 위해 고투자율 재료를 전선의 2차피복에 혼합하거나 감는 구조로 되어있다 그리고 전선자체에 CM성분의 임피던스를 높이는 고토자율 재료 대신에 Permalloy를 취부하여 비교하였다 측정 결과 개발된 전원코드는 EFT신호에 대해 넓은 주파수 대역에 걸쳐 매우 우수한 감쇠특성을 가지는 것이 확인되었다 특히 컴퓨터를 피즉정물로 하여 즉청한 dynamic 특성은 3.6Kv까지 견디는 우수한 특성을 나타내었다. 고안된 전원 케이블의 응용범위는 산업용 설비외에도 군용기기 의료기기등의 정상적인 동작확보에 사용될 수 있을 것이다 뿐만 아니라 사용방버에 따라 전원성을 통해 방사되는 EMI중 대책이 어려운 60MH이상 수GHz 대역의 발생전자파 대책에 좋은 특성을 가질 것으로 판단되면며 부품의 선택방법에 따라 EFT의에 IEC801-2,3,5,6, 모든 내성시험 항목에 효과가 기대된다.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.126-133
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• 2005

Mechanical properties of zirconium cladding were evaluated by ring tension test to simulate Reactivity-Initiated Accident (RIA) at high burnup situation as an out-reactor test. Zircaloy-4 cladding was hydrided up to 1000 ppm as well as oxidized up to $100\;{\mu}m$ to simulate high-burnup situation. After simulated high-burnup treatment, ring tension test was carried out from 0.01 to 1/sec to correlate with actual RIA event. The results showed that ductility and circumferential toughness decreased with the hydrogen content and oxide thickness. Hydride generated inside cladding acted as brittle failure. Oxygen influenced cladding tube by the reduction of load bearing area, oxygen embrittlement, and thermal aging. Correlation between in-reactor RIA parameter like fuel enthalpy and out-reactor toughness was performed and showed a reasonable result.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.65-69
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• 2000

The crimping connection is a permanent connection that maintains mechanical and electrical property for a long time by crimping two conductors. In this paper, we have done a basic study to make a decision the normal or abnormal condition depending on crimping. By using PZT piezo-sensor, we have compared and analyzed crimping waveforms of abnormal conditions(core ommiting, cover biting) at the normal crimping height. And hence the normal or abnormal condition of crimping connections in real time could be determined by comparison of crimping waveforms in the cases of normal crimping, core omitting and cover biting.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1541-1550
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• 2001

This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. Composite materials consist of two or more different material layers. Copper clad aluminum composite materials are being used fur economic and structural purposes and the development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important, It is necessary to know the conditions in which successful uniform extrusion ,and sound cladding may be carried out without any defects in the direct extrusion. There are several variables that have an influence on determining a sound clad extrusion. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios and semi-cone angles of die. Subsequently, the microscopic inspection of interface bonding is carried out for extruded products. By measuring hardness, along extrusion way of products, a variation of hardness has been discussed. Proportional flow state has been considered by measuring radius ratio of Cu sleeve and Al core before and after extrusion.