• 한국해양공학회지
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• 제15권3호
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• pp.43-48
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• 2001

In this paper, the real-time prediction of high temperature creep strength and creep for nickel-based superalloy Udimet 720 (high-temperature and high-pressure gas turbine engine materials) was performed on round-bar type specimens under pure load at the temperatures of 538, 649 and 704$^{\circ}C$. The predictive equation of ISM creep has better reliability than that of LMP and LMP-ISM, and its reliability is getting better for long time creep prediction ($10^3~10^5$h).

• Smart Structures and Systems
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• 제8권3호
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• pp.275-302
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• 2011

This is a review paper on mathematical modeling of actively controlled piezo smart structures. Paper has four sections to discuss the techniques to: (i) write the equations of motion (ii) implement sensor-actuator design (iii) model real life environmental effects and, (iv) control structural vibrations. In section (i), methods of writing equations of motion using equilibrium relations, Hamilton's principle, finite element technique and modal testing are discussed. In section (ii), self-sensing actuators, extension-bending actuators, shear actuators and modal sensors/actuators are discussed. In section (iii), modeling of thermal, hygro and other non-linear effects is discussed. Finally in section (iv), various vibration control techniques and useful software are mentioned. This review has two objectives: (i) practicing engineers can pick the most suitable philosophy for their end application and, (ii) researchers can come to know how the field has evolved, how it can be extended to real life structures and what the potential gaps in the literature are.

• 한국수학사학회지
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• 제22권4호
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• pp.53-66
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• 2009

수학 교육에서 산학의 교육적 가치는 높게 평가 받고 있다. 이 글에서는 산학의 기하 문제가 중등학교 교과서와 각종 시험에 인용된 예를 통해, 산학을 중등학교 수학 교육에 활용하는 방안을 알아본다. 이와 함께 산학의 기하 문제가 새로운 주제의 도입을 위한 실생활 소재, 교과서에서 다룬 내용에 대한 실생활에의 응용문제, 수리 논술 문제 등으로 널리 활용할 수 있음을 구체적으로 확인하다.

• 기술사
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• 제43권5호
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• pp.43-47
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• 2010

The epoch-making event of history called "JE JU 4.3" took place in JE JU beautiful island on liberation political situation in 1948. The cruelties of this event were reported awful life loss over 30,000, cruel slaughter by government, scorched villages in mountain area, silence exaction and disadvantage of implication for long time over 40 years. But, the real features are in still a fog.. Recently, the searching movement has arised owing to democracy atmosphere and literature works with "JE JU4.3" materials were published from 1988 and the government announced official apologies in 2003. The novel "The Sun-set on Halla Mt", one of those works, is accessible to real history due to its time/space back ground and the real name of persons who were related with this event. It is important for readers to consider the difference between real history and fiction story. Because a historical novel should be evaluated by writer's theme rather than history character.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.521-524
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• 2000

Nearinfra-red(NIR) reflectance NIR a spectra (400 to 2,100 nm) were collected on 32 beef samples to find feasibility of predicting beef tenderness. The study to predict beef tenderness was accomplished with the stepwise second differential data of the collected NIR spectra. Beef tenderness was measured by Warner-Bratzler(WB) shear force using a Universal Testing Machine(UTM). After modeling the relation between Warner-Bratzler shear force and NIR spectrum of 19 samples among the 32 beef samples, the verification was carried out through predicting the other 13 samples. The SEC and R$^2$ values in the prediction equation were 9.07(N) and 0.6463, respectively. The SEP and R$^2$ were 14.8(N) and 0.7082 (wave length 552 nm, 1988 nm) respectively. The result implied that it was possible to predict the beef tenderness using NIR spectrum and that the tenderness could be predicted non-destructively in real time.

• 유기물자원화
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• 제23권1호
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• pp.52-62
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• 2015

슬러지 응집제로서 폴리머, 제올라이트, 고령토, 황토, 키토산 등의 하수슬러지에 대한 응집효과 및 폴리머와 이들 응집제를 혼합한 물질의 응집효과를 검토하였다. 2,500~50,000 mg/L 농도에서 황토가 고령토, 제올라이트보다 하수슬러지에 대한 응집효율이 높았다. 제올라이트, 고령토, 황토 20,000 mg/L 처리의 응집효과는 폴리머 1,000 mg/L 처리의 응집효과보다 낮게 나타났다. 따라서 제올라이트, 고령토, 황토 단독 처리로는 현행 하수슬러지 탈수 시에 사용 중인 폴리머와 같은 응집효과는 기대하기 어려웠다. 키토산 역시 폴리머와 같은 1,000 mg/L 처리에서 응집효과가 현저하게 낮은 것과 고가의 구입비용을 감안하였을 때 키토산 단독처리는 현실적이지 않은 것으로 나타났다. 하수슬러지에 대한 지렁이처리법 적용에 유리한 응집제 조합은 '폴리머 80mg/L +고령토 또는 황토 500 mg/L + 키토산 10 mg/L' 으로 판단되며, 다음으로 '폴리머 80 mg/L + 고령토 또는 황토 500 mg/L' 조합으로 판단된다.

• 한국가구학회지
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• 제21권3호
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• pp.229-236
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• 2010

Wood material is positive with the concept of eco-friendly materials. Wood toy preference of foreign brands is also a real problem. Therefore, in this domestic situation on Toys Brand Development, there are many problems yet to be solved. At First, a wood material for toys requires the development of more sophisticated and precision materials. Second, new content, product development and training program development of the toys are needed. Characters and content development time and effort should be invested. In present, Korean brand development of wood toy with educational effects is very important issues as the use of wood to match the low carbon & green growth.

• Tribology and Lubricants
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• 제31권2호
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• pp.35-41
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• 2015

A water-pump located in the cooling area of a car circulates cooling water. A particular bearing element, known as a water-pump bearing, installed in the rotating part carries the entire load. The failure of this water-pump bearing has a direct impact on the failure of the automobile engine, and so securing its reliability is crucial. Several researchers have examined the design principles of the water-pump bearing, but there are no reports on the life characteristic of the bearing yet. Herein, we report the construction of test equipment to reproduce the spalling of the roller contact, which is the main failure mode of the chosen water-pump bearing. We chose the radial load as an accelerated stress factor and validated the failure mode by monitoring the surface defects. We conducted the accelerated life test after determining the accelerated stress level through a combination of finite element analysis and a preliminary test. In the life tests, we used an accelerometer to perform failure diagnosis. In the last stage of this study, we present a statistical reliability analysis. Thus, we fully estimated the shape parameter of the water-pump bearing, accelerating level on the load , and the lifetime (MTTF and B₁₀ life) under real use conditions, and finally proposed an interval estimation value considering the uncertainty of the estimated value.

• 동력기계공학회지
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• 제6권1호
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• pp.55-60
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• 2002

There has been no report on the life prediction for gas turbine materials at high temperatures based on the creep properties and their relationship with the AE(acoustic emission) properties as a means of real-time non-destructive testing. One of the important issues is thus to develop a reliable method of evaluating creep properties by the AE technique. In this paper, the real-time evaluation of high temperature creep time and AE cumulative counts for nickel-based superalloy Udimet 720 was performed on round-bar type specimens under pure load at the temperatures of 811, 922 and 977K. The total AE cumulative counts until the starting point of secondary creep($N_1$) and that of tertiary creep($N_2$) have quantitative relationship with the tertiary creep time and the rupture time. It is thus possible to construct the life prediction system based on creep and the prevention system of tertiary creep by using AE technique.

• 소성∙가공
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• 제7권3호
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• pp.282-290
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• 1998

In bulk metal forming processes prediction of tool life is very important for saving production cost and achieving good material properties. Generally the service life of tools in metal forming process is limited to a large extent by wear, fracture and plastic deformation of tools. In case of hot and warm forging processes tool life depends on wear over 70%. In this study finite element analyses are con-ducted to warm and hot forging by adopting suggested wear model. By comparison of simulation and eal profile of die suggested wear model. By comparison of simulation and real profile of die suggested model is verified.