• 한국공작기계학회논문집
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• 제11권2호
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• pp.87-94
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• 2002

In domestic industry, there is no manufacturers specialized in the production of cutting tools for the difficult cutting materials. Then, we have flew data about them. In this study, the gear driving high speed lathe on which is mounted by a tool dynamometer and high speed CCTV were used to measure the various machining characteristics. Relations among the cutting speed, feed rate per revolution, cutting depth, cutting forces and surface roughness ware graphically analyzed under 64 cutting conditions. The process of chip, i.e., generation, development and falling-off also were visualized for the characterization of chip shapes of the difficult-to-cut materials using the CCTV.

• 대한수학교육학회지:학교수학
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• 제5권2호
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• pp.241-257
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• 2003

제7차 교육과정에서 수학교육은 다양한 개인의 능력을 고려하여 학습내용의 적정화, 학습자중심의 활동중심수업 증가, 단계형 수준별 교육을 지향하고 있다. 그러나 실제 초등학교의 많은 교사들이 수학 학습지도에서 겪고 있는 어려움 중의 하나가 상당수의 학생들이 교과서의 내용을 최소한 몇 개월 정도 미리 배워오기 때문에 학교수업은 수준이 낮아 흥미가 없다고 냉소하고, 그렇지 못한 학생들은 학교수업이 너무 부담이 되어 흥미를 잃고 있어 현실적인 대안이 시급하다는 것이다. 이러한 초등수학교실의 문제를 해결할 수 있는 방안의 하나로 적절한 교수·학습자료 활용의 수업을 들 수 있다. 이는 아동들에게는 보다 흥미 있는 수업을, 교사들에게는 보다 효과적으로 학습목표에 도달할 수 있게 할 수 있다. 이를 구체적으로 실천하기 위해 초등학교 교과서에서 비중이나 학습난이도가 높은 단원을 찾아 효과적인 교수· 학습자료의 활용방안과 앞으로 자료개발에 도움을 주고자 하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.217-222
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• 1999

Usually, the failure of quasi-brittle materials is numerically difficult to describe because of the localization process with softening behavior. In this study, ADLE(Axial Deformation Link Elements) with stochastic material properties are developed to simulate the quasi-brittle material failure behavior. The ADLE method is adopted both Fictitious Crack Model and stochastic method to implement the fracture behavior with the localization behavior of quasi-brittle materials. The main objective of this paper is to show the mash independency and the capability of ADLE for the failure behavior of a quasi-brittle materials.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.370.2-370
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• 2002

Magnetostrictive materials are used low-frequency sonar transmitter instead of piezoelectric materials. But it is difficult to analyze due to the nonlinearity and hysteresis of magnetostrictive materials. This paper deals with the program development based on finite element method to model the magnetostrictive tonpilz transducers and to analyze their acoustic characteristics. (omitted)

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제42권5호
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• pp.251-258
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• 2016

Objectives: The aim of this retrospective study was to investigate factors associated with increased difficulty in the surgical extraction of impacted lower third molars and to improve identification of difficult cases. Materials and Methods: A total of 680 patients who required 762 surgical extractions of impacted lower third molars from 2009 to 2014 were enrolled in the study. Demographic factors, clinical factors, radiographic factors, surgical extraction difficulty, and presumed causes of difficulty were collected. Data were statistically analyzed using IBM SPSS Statistics version 23. Results: Age, sex, depth of impaction, and blurred radiographic image influenced difficulty in surgical extraction. The position of the impacted tooth influenced surgical difficulty, especially when it was accompanied by other factors. Conclusion: It is challenging to design a reliable and practical instrument to predict difficulty in surgical extraction of impacted lower third molars. To identify very difficult cases, root investigation using computed tomography is advised when impacted tooth position suggests difficult extraction.

• 방재기술
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• 통권13호
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• pp.27-37
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• 1992

As the progress in electronic industry is very rapid, various materials are used in this area and it is very difficult to find the hazard of those materials. Also expensive equipments are concentrated and flammable liguids or toxic gases are used in the procsses, the possibility of loss in the fire is very high. So it is very important to analyze various risks and take the proper measures.

• Plant Resources
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• 제6권3호
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• pp.205-210
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• 2003

Ginseng(Panax ginseng C.A. Meyer) is a perennial herbaceous plant which grows very slowly. It takes about 3 to 4 years from seeding to collecting the ripe seeds and the ginseng propagation is very difficult. and so, it is very difficult to breed ginseng plant. Ginseng tissue culture was started from at 1960, and ginseng commercial product by in vitro callus culture was saled, however upto now, regenerants were not planted to soil normally. Recently, plant genetic engineering to produce transgenic plants by introducing useful genes has been advanced greatly. In a present paper, transformation of ginseng plants was achieved by co-cultivation with Agrobacterium harboring the binary vector coding Proteinase-II gene, which confer resistant or tolerant to insect pests, The binary vector for transformation was constructed with disarmed Ti-plasmid and with double 35S promoter. The NPT II gene and introduced genes of the transgenic ginseng plants were successfully identified by the PCR. Especially the transgenic ginseng plants were regenerated using new techniques such as repetitive single somatic embryogenesis.

• 한국공작기계학회논문집
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• 제17권2호
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• pp.38-44
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• 2008

Titanium and its alloys, due to their superior properties of high specific strength and excellent corrosion resistance, are increasingly used in living applications in the 21century. The applications in aerospace and medical industries demand machining process more frequently to obtain a desired product. But unfortunately, this material is one of the most difficult-to-cut. In the turning process of titanium alloys, the key point for successful work is to select proper tool materials and cutting conditions. This study suggests a guidance for selecting the tool materials and the cutting speeds to improve tool life and surface integrity in Ti-6Al-4V titanium turning process. The experiments investigate the change of surface roughnesses, cutting forces and flank wear with various cutting parameters of tool materials, depth of cuts and feeds. As the results, K10 type of insert tip was assured as the best for turning of Ti-6Al-4V titanium alloy.

• 소성∙가공
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• 제31권4호
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• pp.200-206
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• 2022

The finite element analysis is one of the representative methods for predicting the materials behavior for experiments that are difficult to perform empirically. Constitutive equations are essential for reducing computation time and sharing data because they enable finite element analysis simulations through simple formulae. However, it is difficult to derive accurate flow curves for all materials as most constitutive equations are not formulated based on their physical meaning. Also, even if the constitutive equation is a good representation of the flow curve to the experimental results, some fundamental issues remain unresolved, such as the effect of mesh size on the calculation results. In this study, a new constitutive equation was proposed to predict various materials by modifying the combined Swift-Voce model, and the calculation results with various mesh sizes were compared to better simulate the experimental results.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1995년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.5-5
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• 1995