• 한국재료학회지
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• 제3권5호
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• pp.482-496
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• 1993

Radiation damage and contamination of silicons etched in the $CF_4+H_2$ and $CHF_3$ magnetron discharges have been characterized using Schottky diode characteristics, TEM, AES, and SIMS as a function of applied magnetic field strength. It turned out that, as the magnetic field strength increased, the radiation damage measured by cross sectional TEM and by leakage current of Schottky diodes decreased colse to that of wet dtched samples especially for $CF_4$ plasma etched samples, For $CF_4+H_2$and $CHF_3$ etched samples, hydrogen from the plasmas introduced extended defects to the silicon and this caused increased leakage current to the samples etched at low magnetic field strength conditions by hydrogen passivation. The thickness of polymer with the increasing magnetic field strength and showed the minimum polymer residue thickness near the 100Gauss where the silicon etch rate was maximum. Also, other contaminants such as target material were found to be minimum on the etched silicon surface near the highest etch rate condition.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.53-54
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• 2015

As the result of uniaxial compression strength test on the CLMS mixing BFS and SS with BFS 4000, it required to determine the desired strength through increasing unit quantity of cement in mixing process because of dramatic strength deterioration of strength according to increasing replacing rate. In this study's result, regardless of differences in fine aggregates used, in order to get uniaxial compression strength in the scope exceeding criteria of minimum strength for applying to the field, the most reasonable combination was to mix replacing BFS with fineness of 6000 in 30%. For the CLMS mixing BFS and SS, in order to improve flow ability by securing quantity of minimum unit and to repress bleeding rate with securing uniaxial compress strength considering the field applicability, regardless of differences in fine aggregates used, to mix BFS over 6000 in 30% was most effective.

• 천문학회보
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• 제36권2호
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• pp.99-99
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• 2011

A statistical study of coronal hole merging and splitting has been performed through Solar Cycle 23. The NOAA/SESC solar synoptic maps are examined to identify inarguably clear events of coronal hole merging and splitting. The numbers of merging events and splitting events are more or less comparable regardless of the phase in the solar cycle. The number of both events, however, definitely shows the phase dependence in the solar cycle. It apparently has a minimum at the solar minimum whereas its maximum is located in the declining phase of the sunspot activity, about a year after the second peak in Solar Cycle 23. There are more events of merging and splitting in the descending phase than in the ascending phase. Interestingly, no event is found at the local minimum between the two peaks of the sunspot activity. This trend can be compared with the variation of the average magnetic field strength and the radial field component in the solar wind through the solar cycle. In Ulysses observations, both of these quantities have a minimum at the solar minimum while their maximum is located in the descending phase, a while after the second peak of the sunspot activity. At the local minimum between the two peaks in the solar cycle, the field strength and the radial component both have a shallow local minimum or an inflection point. At the moment, the physical reason for these resembling tendencies is difficult to understand with existing theories. Seeing that merging and splitting of coronal holes are possible by passage of opposite polarity magnetic structures, we may suggest that the energizing activities in the solar surface such as motions of flux tubes are not exactly in phase with sunspot generation, but are more active some time after the sunspot maximum.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.571-578
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• 2024

The bistable thin cylindrical shell is developable structure with the ability to transition between its two stable configurations. This structure offers significant potential applications due to its excellent deformability. In this paper, the composite thin cylindrical shell consisting of the composite layer and the piezoelectric layer was investigated. The material and geometric parameters of the shell were found to influence its stable characteristics. The analysis model of the composite thin cylindrical shell incorporating the piezoelectric layer was developed, and the expressions for its strain energy were derived. By applying the minimum energy principle, the impact of the electric field intensity on the bi-stable behaviors of the cylindrical shell was analyzed. The results showed that the shell exhibited the bistability only under the appropriate electric field strength. And the accuracy of the theoretical prediction was verified by simulation experiments. This study provides an important reference for the application of deployable structures.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.203-210
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• 2002

In these days, High-strength steel prevails throughout the construction fields for the benefit of structural and economical aspects. But high-strength steel is used by the simple calculation of flexural capacities for the purpose of reducing flexural reinforcement. So, this paper is mainly focused on the shear behavior of high-strength steel reinforced concrete beams without stirrups comparing with normal-strength steel reinforced concrete beams. Specimens were made and tested with the experimental parameters, such as steel yield strength, reinforcement ratios and minimum shear reinforcement. The main result was that not only area but also the yield strength of flexural reinforcement should be considered to predict the shear capacities of concrete beams. In addition, the experimental results were simulated by modified compression field theory analysis program, RESPONSE 2000. A good agreement was achieved between the test results and program analyses.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.41-45
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• 2000

Geotube is made of permeable but soil-tight geotextile, hydraulically filled with soil include dredged sand and mud, which has been successfully applied in hydraulic and coastal engineering projects. Ceotube method is getting popular and being used a lot in many countries of the world because of the simplicity of the placement and construction, cost effectiveness and minimum impact on the environment, and enable to store & isolate contaminated materials as obtained by harbor dredging. Laboratory tests and field construction were performed to determine the design methodology and construction procedures. From the results of laboratory and field construction, the retention ratio of solid particle is a minimum 86%. The minimum permeability and the tensile strength of geotextile are $\alpha$ x 10$^{-4}$ cm/sec and 20t/m, respectively Also, based on the environmental test results, it can be concluded that this method does meet the Korean EPA standards.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2055-2058
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• 2002

It designs the general description of 8-VSB DTV transmission system will be installed and operated in future on the basis of NTSC TV transmission system in operation now. First of all, it investigates a condition that can maintain optimum received field in case of ground wave broadcasting with analog NTSC and digital 8-VSB DTV. Also it calculates critical value of minimum field strength fur receiving by using field strength calculation method of Longley-Rice. The 8-VSB DTV transmission sets its goal in transmission of data with 19.39Mbps at high speed in order to be available of HDTV in the band of NTSC 6MHz. Accordingly, the optimum of field strength between transmission and receiving points most of all is important problem. So,8-VSB DTV transmission should be enlarged or effective compared with NTSC service coverage. This study is to calculate the transmission power necessary in switching from NTSC VHF to DTV UHF and from NTSC UHF to DTV UHF for maintaining service coverage that NTSC is equal to 8-VSB DTV as a result of calculation.

• 한국자기학회지
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• 제12권2호
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• pp.73-79
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• 2002

자성유체는 고액혼상유체로 뉴턴유체와 달리 자기력에 반응하는 유체이다. 본 연구에서는 금속과 유체의 특성을 겸비한 자성유체의 열전달 특성을 밀도 있게 연구함을 목적으로, 그 대상을 이중원관으로 하여 열대류현상을 고찰하기 위해 내부원관을 가열하고, 외부원관을 냉각하면서, 또한 외부에서 인가자장의 세기와 방향에 따라 자연대류 현상의 변화 및 열전달 특성을 수치해석적으로 연구하여, 실험결과와 비교 검토하였다. 자성유체의 자연대류현상은 인가자장에 따라 제어할 수 있었고, 평균 뉴셀트수를 구한 결과로서 자장을 가하지 않았을 경우와 비교해 보면 열전달은 자장을 중력방향으로 가하거나 중력과 반대방향으로 그세기를 -14 mT이상 가했을 때 증가하였고, 중력과 반대방향으로 감했을 때 감소하였다. 특히 자장의 세기가 -14 mT가 되면 열전달은 최소가 되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.189-194
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• 2000

The optimum mix proportioning of concrete is to produce a concrete which satisfies the strength, workability and durability required with minimum component of materials. However in practice the cement content of mix proportioning in construction field is normally higher then required. In this study, the existing mix proportioning of concrete currently used in Korea Highway Corporation has been reviewed by reducing 10kg of cement content by 3~5 strength in strength and workability during the first year of this project. The optimum mix design is established based on the results of the above review and durability were examined during the second year. The experimental results though 2 year show that 103~0% of the reduction of cement content still satisfies the specified strength of concrete and produces higher durability concrete.

• Journal of Magnetics
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• 제16권4호
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• pp.427-430
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• 2011

The rolled steels for welded structure applied tensile stress have been examined by means of magnetic Barkhausen noise (MBN) method and of a physical parameter obtained from a hysteresis loop. The behaviors of MBN parameters and coercive force with tensile stress were discussed in relation to microstructure changes. There is no change in MBN parameters and coercive force below yield strength. The coercive force rises rapidly with tensile stress above yield strength. On the other hand, the rms voltage and the peak in averaged rms voltage take a maximum around yield strength and then decreases. The magnetomotive force at peak in the averaged rms voltage shows a minimum around yield strength. These phenomena are attributed to the combined effects of cell texture and dislocation density. In addition, the behaviors of MBN parameters around yield strength may be reflected by the localized changes in strain field due to the formation of dislocation tangles.