전자공학교육과 실험교과내용에 관한 연구

홍봉식,김태균,오승엽,김환우,권오석 충남대학교 공업교육연구소 1983 論文集 Vol.6 No.2(A)

The currenty offered experiment courses are completely reconsidered and reconfigured. The whole subjects are divided into 10 seperate courses, each of which should represent either basic or advanced stages of differing fields of the electronic engineering. It has been aimed that the courses form an elaborate hierachy so that they are minimally redundant but linked to one another in their fringes. Also, it has been pursued that the new courses should not fall obsolete in at last next five years exploring the maximum possibilities of the currently available equipments.

LMC로 보강된 철근 콘크리트 보의 부착파괴 거동에 관한 실험적 연구

이봉학,김성환,정원경,김현오 강원대학교 부설 석재복합신소재 제품연구센터 2004 석재연 논문집 Vol.9 No.-

이 논문은 동일 조건에서 양생되어진 LMC 보강 철근 콘크리트의 특성 및 보강 효과에 대하여 연구되었다. 이때 변수는 스터럽의 유무와 보강높이를 변화하여 실험을 실시하였다. 시험편돌의 처짐과 철근의 변형은 보의 중심에서 다이얼 게이지 그리고 스트레인 게이지로 측정되었다. 실험 결과는 LMC의 철근 콘크리트가 OPC의 것보다 상당히 높은 초기 균열 하중을 보여주었다. 이것은 라텍스 필림 막에 의해 수화한 시멘트와 골재의 맞물림 작용에 기인할 수 있다. 라텍스의 추가는 균열 하중을 상당히 줄일 수 있었고, 극한 강도, 철근 변형, 처짐은 일반 콘크리트의 것과 유사하게 측정되어, LMC로 압축부 및 인장부를 보강할 경우 보강효과가 있는 것을 알 수 있었다. The purpose of this study was to study the reinforced concrete beam properties of LMC with the main experimental variables such as concrete types(ordinary portland cement concrete, latex modified concrete), the use of stirrup and curing days at the same controlled environment of 60 % of relative humidity and 20 ℃ of temperature. The deflection and steel's strain for specimens were measured with a dial gauge and strain gauge at the center of beam. The test results showed that the reinforced concrete of LMC was considerably higher initial cracking load than that of OPC. This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulted in reduced water evaporation. As a result, the addition of latex would be able to reduce considerably cracking load. However, similar to ultimate strength, steel strains, and deflection of concrete than that of OPC. It may be considered that reinforcing steel affected in the concrete beam than that of concrete.

LMC로 덧씌우기 보수된 RC보의 계면응력에 관한 연구

김현오,김성환,김동호,이봉학 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.A

Each year, new technological advancements for repair-purpose are being introduced to overlay the old deterioration of RC bridge deck at highway by latex-modified concrete. The days may come when this old problem will be successfully resolved. While the experimental works and researches are very active at both laboratory and field, only a few theoretical studies were performed on interfacial problems, especially on stress distribution and concentration of RC beam overlayed by latex-modified concrete. The repaired and strengthened structures would induce a premature failure due to the stress concentration at the adhesive layer of different material before the design expected failure. This paper investigated and proposed an analytical model for predicting interfacial shear and normal stresses of RC beam repair-purpose overlayed by latex-modified concrete. This would be used for predicting interfacial stresses and preventing premature failure at interfaces. This study modified Smith-Teng method for applying to cementitious repairing material, which was based on a direct governing equation and linear-elastic approach for interfacial normal and shear stresses. The proposed theoretical model was verified using commercial FEA program, LUSAS, in terms of interfacial stresses predicted by the proposed model and calculated by LUSAS.

자동차용 브레이크 마찰재에서의 환원분철의 마찰특성에 관한 연구

정진오,이경환,김옥삼,김봉수 순천대학교 2000 순천대학교 자연과학논문집 Vol.19 No.1

In most automotive brakes, the friction material is used to convert the kinetic energy into heat. The friction material is a complex composite consisting of a resin, reinforcing fibers, lubricants and filler materials. In an attempt to enhance the friction performance of the friction material, a trial was done to examine the substitution of filler material by the reduction iron powder. In this study, two types of reduction powder M1 and M3 was prepared by the reduction process developed by Hanta M&B Inc. M1 and M3 which has reduction ratio of 1.5 and 92% respectively was used in place of BaSO_4, which was conventionally used as a filler material. The amount of M1 and M3 was varied as 10, 20, 30%, while the other component remains the same except the replaced BaSO_4. For those specimens with different amount of reduction iron powder, friction performance tests such as friction coefficient, rotor compatibility were conducted by using brake dynamometer. The bonding strength and hardness tend to decrease with use of M1 and M3, but specific weight decreased with increase of M1 and M3. The friction coefficient increased with use of M1 up to 10%, but decreased for use of M1 more than 20%. However the use of M3 resulted in a decrease of friction coefficient all the way. The surface roughness decreased with the use of M1 and M3, except for a case of excessive use of M1 of 30%. The rotor surface roughness did not show any correspondence with hardness of friction material in this study.

小麥의 稈長 遺傳에 관한 연구

曺章煥,吳正行,蔡濟天,鄭吉雄,金鳳九 단국대학교 1992 論文集 Vol.26 No.-

This study has been conducted to investigate the genetic and ecological variation of wheat culm length measured from those plants grown at greenhouse. The results are as following. 1. The clum length of the winter wheat was higest under 12hrs daylength, while that of the spring wheat was highest under 8hrs daylength. Standard errors of culm length was larger under 12 and 8hrs daylength than that of 24hrs daylength condition. 2. The culm length was shortest under the 24hrs daylength compare to under 12 or 8hrs while it was highest under 12hrs. Short and medium culm length varieties were photo-insensitive but those of long culm length were photo-sensitive. 3. There are many types of varietal differences for the culm length under the daylength conditions. Highest culm length group under 12 and 8hrs conditions was classified. The semi-dwarf varieties that did not change their plant heights under i and 12hrs conditions were Hira, Yecora Resel, Sava, Sturdy, Saric 70, Sekidorisai 66etc. 4. Varietal difference of culm elongation was noticed between 8hrs and 12hrs daylength condition. On the basis of the evidences obtained from this experiment, it may be concluded that the genetic studies related to culm length should be carried out under the most favorable conditions for culm elongation. 5. Correlation coefficients estimated between culm length and heading or maturity were negative but insignificant, but their correlations were highly significant between photo treatments. 6. Culm length of F_1 was intermediate to the range of F_2 population which seems to be distributed normally. In this regard the gene involved with culm length seemingly inherit additively. Statistical analysis for the involved genes for culm length suggested 2 genes for the semidwarf variety Robin #2.

유한요소 해석을 이용한 현장 콘크리트 부착강도 측정조건

김성환,정원경,권 혁,김현오,이봉학 江原大學校 産業技術硏究所 2002 産業技術硏究 Vol.22 No.A

The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesive and strength measurement method ignores the effect of stress concentration from shape of specimens. Therefore, this research calculates stress concentration coefficient as the ratio of drilling depth to drilling diameter(h_s/D), the ratio of overlay thickness to drilling diameter(h_o/D), the ratio of steel disk thickness to drilling diameter(t/D), the ratio of overlay elastic modulus to substrate modulus(E_l/E_0), the distance from core to corner border(L_corner) and the distance between cores(L_core) vary. The finite element method is adapted to analysis. The results from the F.E.M analysis are as follows : The stress concentration effects can be minimized when the ratio of drilling depth to drilling diameter(h_s/D) is 0.20∼0.25, the elastic modulus ratio(E_l/E_0) is 0.6~1.0, and the ratio of steel disk thickness to drilling diameter(t/D) is 3.0. The overlay thickness, the distance from specimens to corner border(L_corner), the distance between cores(L_core) almost do not affect to the stress concentration.

유한요소해석과 실험검증을 통한 콘크리트 직접인발 시험방법 개발

이봉학,김동호,김성환,김현오 강원대학교 부설 석재복합신소재 제품연구센터 2003 석재연 논문집 Vol.8 No.-

시험편 형상에 의해 발생되는 불규칙한 응력 분포의 하나인 응력집중은 정확한 부착강도 측정을 위하여 최소화해야한다. 이 논문은 pull-off 시험에 영향을 주는 주요 인자들인, 코어 천공 깊이, 강판의 강성, 탄성계수 비, 덧씌우기 두께에 대하여 논의 하고자 한다. 콘크리트 계면에서 위의 변수에 의한 응력 집중의 영향을 평가하기 위하여 유한 요소 해석을 수행하였고, 유한 요소 해석을 통해, 현장 적용을 위한 뛰어난 콘크리트 pull-off 부착강도 시험 방법을 제안하였다. 유한 요소 해석으로부터 제안된 방법은 실험을 통해 검증하였다. 또한 pull-off 시험 방법과 휨 시험 방법과 니플 파이프 직접 인장 시험 방법에 의한 실험을 실시하고 그 결과를 비교하였을 때 표준편차의 관점에서 좋은 결과를 보임을 알 수 있었다. The stress concentration, which is one of non-uniform stress distribution and arises from specimen geometry, should be minimized in order to measure the bond strength correctly. This study discusses the main relevant issues effecting to core pull-off test, namely, core drilling depth stiffness of steel disk, modulus ratio, overlay thickness and length of between cores and edges. Finite element analysis is carried out in order to investigate the effects of those above into the stress concentration at concrete interface. From a series of finite element analysis, a fine concrete pull-off bond strength test method is proposed for field application. The proposed method from finite element analysis is evaluated from a series of experiments. The test results show that the repeatability of the core pull off test are comparable and relatively good in terms of standard deviation, compared from those of flexural beam test method and nipple pipe direct tensile test method.

封着유리의 製造에 關한 硏究

金鳳杰,金宗範,權昶吾,朴慶煥 慶熙大學校 1988 論文集 Vol.17 No.-

The purpose of these studies are to prepare low melting devitrifiable solder glass for high termal expansion seal and to find out solder glass which is the optimum condition in terms of thermal properties among others. Then five kinds of frits were prepared by quenching after melting of solder glass in the Pt-crucible at 1,100℃, which contained 2wt% of ZrO₂ as a neucleation agent with being control led by the concentration of mother glass of PbO-ZnO-B₂O₃-SiO₂ system. For probing the characteristics of the solder glass, DTA, X-ray powder diffraction, thermal, expansion, sealability, fluidity and activation energy were examined. The results are as follows: 1. It was possible in sealing of low temperature that the sealability & crystallization temperature was lowered and the fludity was good owing to an increase in PbO wt% but it was inadquate in sealing of color TV tube for 80.5wt% PbO and over because thermal expansion was increased. 2. The optimum holding time was 60 minutes. 3. In the sample contained 80.5wt% PbO, the thermal expansion coefficient was 101.8×10^-7/℃, the crystallization temperature was 443℃, flow button diameter was 27.7㎜, the sealability was 25.15㎏f/㎠, It is better than the existing solder glass. 4. The crystals proved in process of melting and crystallization were Pb_8Zn(Si₂O_7)₃, PbZrO, Zn₂SiO₁ etc. 5. The activation energy needed for crystallization was 87.13kJ/mol.

초소형 구조물의 부착 방지를 위한 새로운 자기 집합 물질에 대한 연구

김봉환,오창훈,전국진,정택동,변장웅,이윤식 경북대학교 센서기술연구소 1998 센서技術學術大會論文集 Vol.9 No.1

In order to achieve stiction-free polysilicon surfaces, we have suggested a new chemical grafting precursor and confirmed their excellent characteristics. When dichlorodimethylsilane(DDS, C_(2)H_(6)SiCl_(2)), a dialkyldichlorosilane widely used in silicon machining, have been used as a precursor, experimental results were clearly comparable to those of monoalkyltrichlorosilanes octadecyltrichlorosilane (OTS, C_(18)H_(37)SiCl_(3)) or 1H,1H,2H,2H-perfluorodecyltrichloro-silane (FDTS, C_(10)H_(4)F_(17)SiCl_(3)) in terms of stiction reduction. The polysilicon cantilevers were fabricated in the carefully controlled conditions and laser interferometer indicated that their residual stress gradient was 2 MPa/μm upward from the substrate. The SEM images of polysilicon cantilever beams with DDS coating are upward and no stiction is observed up to 2 mm in length.

교면 덧씌우기 콘크리트의 引拔附着强度 試驗法 提案

김성환,김동호,김현오,이봉학 강원대학교 산업기술연구소 2003 産業技術硏究 Vol.23 No.A

The development and maintenance of a sound bond are essential requirements of concrete repair and replacement The bond property of a overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified A standard or a verified bond strength measurement method is required at field for screening. selecting materials and quality control for overlay or repair materials. but no test method has been adopted as a standard. In this study. a concrete pull off bond strength measurement method for field application is proposed and evaluated. This study compares the splitting tensile test. slant shear test. nipple pipe direct tensile test. flexural adhesion test. briquette tensile test. jumbo nail pull-out test and core pull-off test with their test procedures. From these cornpanson and investigation. core pull-off test is selected as a main topic of this study because of it's suitability for in situ testing. simplicities in field application and clearness at interface boundary condition Thus. the proposed core pull off test is evaluated to be the most appropriate method for field application in a simple manner. The fracture surface and fracture mode could be easily determined by visual observation of failure surface of the field specimen. The core pull off test was found to be sensitive to surface condition and latex contents at latex modified concrete