• 콘크리트학회논문집
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• 제12권2호
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• pp.31-42
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• 2000

This paper discusses the validity of models predicting the compressive strength of concrete subjected to various temperature histories and the shortcomings of existing rate constant model and apparent activation energy concept. Based on the discussion, a modified rate constant model is proposed. The modified rate constant model, in which apparent activation energy is a nonlinear function of curing temperature and age, accurately estimates the development of the experimental compressive strengths by a few researchers. Also, the apparent activation energy of concrete cured with high temperature decreases rapidly with age, but that of concrete cured with low temperature decreases gradually with age. Finally generalized models to predict apparent activation energy and compressive strength are proposed, which are based on the regression results.

• 대한기계학회논문집B
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• 제23권8호
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• pp.1010-1021
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• 1999

Camouflage measures in military purpose utilize the apparent temperature difference between target and background, so it is essential to develop a thermal analysis program for apparent temperature predictions and to apply some camouflage measures to real military targets for camouflage purpose. In this study, a thermal analysis program including conduction, convection and radiation is developed and the validity of radiation heat transfer terms is examined. The results show that longwave radiation along with solar radiation should be included in order to predict the apparent temperature as well as the physical temperature precisely. Longwave emissivity variation as an effective camouflage measures is applied to a real M2 tank. From the simulation results, it is found that an effective surface treatment, such as painting of a less emissive material or camouflage clothing, may provide a temperature similarity or a spatial similarity, resulting in an effective camouflage.

• 대한기계학회논문집
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• 제16권6호
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• pp.1115-1120
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• 1992

본 연구에서는 ASTM의 단일시편법으로 시험해석할 때에 나타나는 가장 큰 문 제점인 균열길이 감소현상의 원인해석과, 균열길이 감소현상을 고려한 균열길이 측정 수정식을 제안하고자 하며, 다음 절차로 연구를 수행하였다. (1) 균열선단의 응력장해석과, 이 응력장해석에 의한 균열길이 감소현상을 해석하였 다. (2) CT와 TPB 시편에서의 균열길이 측정식의 수정식을 제안하였다. (3) 이 수정식의 타당성을 $J_{IC}$ 시험해석을 통하여 검토하였다.다.

• Journal of Astronomy and Space Sciences
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• 제31권3호
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• pp.205-214
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• 2014

In this study, a star identification algorithm which utilizes pivot patterns instead of apparent magnitude information was developed. The new star identification algorithm consists of two steps of recognition process. In the first step, the brightest star in a sensor image is identified using the orientation of brightness between two stars as recognition information. In the second step, cell indexes are used as new recognition information to identify dimmer stars, which are derived from the brightest star already identified. If we use the cell index information, we can search over limited portion of the star catalogue database, which enables the faster identification of dimmer stars. The new pivot algorithm does not require calibrations on the apparent magnitude of a star but it shows robust characteristics on the errors of apparent magnitude compared to conventional pivot algorithms which require the apparent magnitude information.

• Tribology and Lubricants
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• 제29권2호
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• pp.85-90
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• 2013

The effects of contact pressure on the sliding wear behavior of mild steel in a pin-on-disc type apparatus were investigated. Sliding wear tests were conducted with various combinations of the load and apparent area of contact. The wear behavior of mild steel as a function of sliding speed was independent of contact pressure. However, the wear rate at different sliding speeds was influenced by the load regardless of the apparent area of contact. This was attributed to the fact that there may be no difference in the real area of contact for any combination of the load and apparent area of contact.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1390-1395
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• 2005

To analyze the effects of oyster shell particles, inserted in the self-hardening matrix such as cement paste, on strength, homogenization analysis using micro structure was used to estimate and assess the apparent elastic modulus of oyster shell particle. DIB modeling technique was used to represent of the micro structure of oyster shell mixed concrete. The results showed that the apparent elastic modulus of LOS (large oyster shell particle) was changed with the amount of LOS inserted. In particular, when the amount of LOS was 200% of the weight of cement, the apparent elastic modulus of LOS tended to decrease rapidly. This could mean that the strength of oyster shell mixed concrete is much affected by LOS inserted material in mixed ratio of 200%.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.148.2-148
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• 2001

The most important difference of an airship from conventional vehicle is that it has the apparent mass and inertia provided from the existence of Helium gas inside the airship. To acquire To acquire the exact response of the airship, the longitudinal responses of airship with respect to the vertical gust, which is the non-linear system, have been studied. An Airship has neutral buoyancy in equilibrium state. When it moves, its motion shows much difference comparing with conventional aircraft. Here, we compare two cases, the one has the apparent mass and the other hasn´t. With the apparent mass, the magnitude of the former response is smaller than the latter, while the frequency is higher. However, the apparent mass delay ...

• 대한기계학회논문집
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• 제7권3호
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• pp.294-300
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• 1983

The purpose of this study is to investigate the radiant emission characteristics of diffuse equi-lateral trapezoid groove cavity for the case of uniform surface temperature. The theoretically developed results for the apparent emissivity are presented and the values of apparent emissivity for the trapezoid groove cavity were compared with those of the V-groove cavity. In the experimental part of this study, the test models were manufactured from 100x 100x 15mm copper plates on which the equi-lateral trapezoid cavities were grooved. The inclined angles of the groove were 30,45 and 60 degrees and the ratio of groove depth to base surface width varied from 1 to 5 for each inclined angle. As a result of this work, it was found that the trapezoid groove cavity was more general form of V-groove and the apparent emissivity of trapezoid groove cavity was greater than that of V-groove cavity. The resulting equation for the apparent emissivity in the trapezoid groove cavity was valid for the angles greater than 40 degrees.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1358-1361
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• 2003

In this study, intrinsic static/dynamic fracture toughness of Al 7175-T74 are evaluated from the apparent static/dynamic toughness of notched specimen. The notch/crack critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The notch/crack critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, critical notch root radius can be predicted by notch/crack critical average stress fracture model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1368-1372
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• 2003

PMMA which is used as the bone cement for vertebroplasty is able to be a supporter, as a fixing supporter role, for broken trabecular structure, caused by the compressed fracture of spine on aged osteoporosis. In this thesis, as experimenting apparent density of bone pieces, we have figured out support extent of Young's modulus as classifying the bone pieces injected PMMA and the others which are not. In case of low apparent density of PMMA in some bone, Young's modulus seems to be more supportable to bone. On the other hand, if apparent density of bones is normal, injection of PMMA is not very effective on improvement in Young's modulus of bone cement injection.