• KSCE Journal of Civil and Environmental Engineering Research
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• 제6권1호
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• pp.25-33
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• 1986

Natural river channels usually have a deep section and one or two floodplains, which is called a compound channel. As the general method in the compound channel overestimates the discharge capacity, the momentum transfer due to interaction between the main channel flow and flow over its floodplain must be considered. Scale model experiments are performed for the rectangular main channel with an asymmetrical floodplain. Firstly, velocities are measured at various section grids. Secondary, boundary shear stresses are calculated from velocity distributions. Lastly, in order to determine the apparent shear force, the shear stress distributions are integrated along the wetted perimeter for the full cross-section and equated to the total weight force in the flow direction. The hydraulic characteristics in a compound channel are closely examined with the scales of length, velocity, boundary shear stress, and apparent shear force which are described with the various relationships.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제13권2호
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• pp.64-72
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• 2014

In the past, prism patterns have been linear triangular shapeswith a $90^{\circ}$ angle; however, new micro prism patterns having acute angles or obtuse angles have recently been the subject of demandin the display, lighting and photovoltaic industries. Micro-cutting experiments for micro-prism patterns having $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$ angles on an electroplated Ni mold were performed and it was found in this study that the specific cutting resistance increased with a decrease in the tool angles (prism pattern angles). The cause of this variation had been thought to be the increase of the ploughing force due to tip rounding and the friction force due to the edge effect. However, the depth of the cut was large enough that it was possible to neglect these effects. Therefore, this study introduced the concept of representative stress of indentation. The measured stress was varied according to the indentation depth eventhoughthetestedspecimenswereidentical ; the varied stress was termed the representative stress. According to indentation theory, the strain that the Ni mold experienced increased with a decrease in the tool angle. Based on the stress-strain relationship, higher strain means higher stress and higher specific cutting resistance. Therefore, the specific cutting resistance was higher at smaller tool angles that had higher strain and stress.

• Journal of the Korean Society for Nondestructive Testing
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• 제28권2호
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• pp.125-130
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• 2008

A spherical indentation has been proposed as a nondestructive method of measuring local residual stress field in laser-voided joints. The apparent yield strengths interpreted from the spherical indentation data of as-welded cutting wheel were compared with the intrinsic yield strengths measured at nearly equivalent locations in annealed wheel. Their difference along the distance from the welding line is welding stress distribution because the intrinsic yield strength is invariant regardless of the elastic residual stress. The spherical indentations show that the laser-welded diamond cutting wheel displays a 10 min-wide distribution of the welding residual stress and has peak compressive and tensile stresses in the shank and tip regions, respectively.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.73-78
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• 2006

To verify reinforcing effect of grouting materials on the water leakage region in dike, we performed various hydraulic test and we also applied electric resistivity survey including electrical resistivity tomography(ERT) to see resistivity variation before and after grouting. As the results of dipole-dipole array survey along dike, resistivity distribution after grouting was without noticeable spatial variation. Long term resistivity monitoring results at dike with Schlumberger array electric resistivity survey showed that the decreasing region of apparent resistivity and one dimensional inversion results were the occupied region by grout after grouting. From the ERT using check holes to inspect the effect of grouting, we could find that the ERT is quite effective to evaluate spatially grout region in dike.

• Proceedings of the KAIS Fall Conference
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• 한국산학기술학회 2008년도 추계학술발표논문집
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• pp.350-353
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• 2008

과산화물 가교제의 농도가 헬리콥터 연료탱크의 자기밀폐층 소재로 적용시키기 위한 천연고무 스폰지의 팽윤에 미치는 효과를 조사하였다. 천연고무 콤파운드를 Kneader와 Roll-Mill을 활용하여 제조하고, 고압조건의 프레스에서 부분 가교시킨 후 대기압의 금형에서 발포와 완전가교를 실시하였다. 얻어진 스폰지의 겉보기밀도를 측정하고 스폰지의 셀구조를 주사전자현미경을 통하여 관찰하였다. 톨루엔, 이소옥탄과 항공유를 사용하여 실온에서 팽윤실험을 실시하였다. 용매에 2분 동안 침적 후 얻어지는 부피팽윤비 값은 과산화물 농도가 감소함에 따라 증가하다가 감소하는 경향을 보였다. 스폰지의 겉보기밀도와 셀구조는 과산화물 함량에 매우 민감하였으며 이는 또한 천연고무 스폰지의 팽윤거동에 영향을 미쳤다. 천연고무 스폰지가 연료와 접촉하여 신속한 팽윤이 얻어지기 위하여 금형에서 동시에 발생하는 두 가지 반응인 발포제의 분해반응과 천연고무의 가교반응을 적절히 조절하는 것이 중요하다.

• Journal of Educational Research in Mathematics
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• 제21권3호
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• pp.295-311
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• 2011

The importance of problem solving in mathematics education has been emphasized and many studies related to this issue have been conducted. But, studies of problem solving in the aspect of affect domain are lacked. This study found the changing pattern of emotions that occur in process of a problem solving. The results are listed below. First, students experienced a lot of change of emotions and had a positive emotion as well as negative emotion during solving problems. Second, students who solved same problems through same methods experienced different change patterns of emotions. The reason is that students have different mathematical beliefs and think differently about a difficulty level of problem. Third, whether students solved problems with positive emotion or negative emotion depends on their attitude of mathematics. Fourth, students who thought that a difficulty level of problem was relatively high experienced more negative affect than students who think a difficulty level of problem is low experienced.

• Economic and Environmental Geology
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• 제29권3호
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• pp.345-355
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• 1996

The effectiveness of various electrode configurations in horizontal mappings and 1-D inversions of vertical sounding data for delineating 2-D structures was studied. Apparent resistivity values of three point, dipole-dipole, Wenner, and Schlumberger mappings were simulated for such structures as vertical dyke, tabular prism, buried vertical fault, ramp and complex structure by finite difference method (FDM) and they were compared with each other. Also 2-D cross sections for three structures obtained by interpolation of 1-D inverted sounding data in terms of three layers were compared for Schlumberger and Wenner arrays. On these cross sections, horizontal and vertical resistivity interfaces of the 2-D structures are revealed relatively clearly. Apparent resistivity curves of Schlumberger mapping show vertical resistivity discontinuities very well. On the whole, Schlumberger array is superior to the other arrays in electric sounding as well as mapping. This study clearly indicates that interpretations of 2-D structures based on 1-D inversion are possible.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.47-50
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• 2008

Streamer resistivity surveys in shallow marine environments were carried out to analyze sediment characteristics at the bottom of reservoir. Because the resistivity values of reservoir water are very low and those of sediment are relatively high, apparent resistivity values increase with depth. And it is necessary to eliminate the apparent resistivity data decreased highly when the number of separation increases. According to the repeated data processing, we proposed the resistivity ratio of upper-to-lower layer is $0.6{\sim}0.8$ because the RMS error of inversion leads to the minimum in these range. As a result of the inversion for two- and three-layer model, the inversion including water depth is proved to be more effective than conventional method.

• Korean Journal of Optics and Photonics
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• 제6권4호
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• pp.259-265
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• 1995

Antireflection coatings on optical lenses commertially available in domestic market are optically analyzed. Transmission spectra and reflection spectra are collected using spectrophotometers. The apparent absorption spectra around the absorption band edge are dominated by the substrate absorption. The reflection spectra and the apparent absorption spectra at visible region between 400nm and 700nm show very strong correlation to each other except a couple samples. The discrepency observed in the latters are due to an increased absorption in visible region by the substrate, which is negative effect of these samples. An antireflection coating consisted of $SiO_2/TiO_2/SiO_2/ZrO_2/Cr$ is made on c-Si substrate for spectroscopic ellispometry analysis. A film-by-film coating is accomplished and between each film deposition, ex-situ spectroscopic ellipsometry measurements are made. The analysis of the spectroscopic ellipsometry data reveals that the average film densities of $ZrO_2$ and $TiO_2$ reach only 80% of their respective packing densities and thick films are inhomogeneous along film growth direction. Discussions are made toward in-situ, real-time monitoring of the film growth so that a real-time feedback is possible to achieve a post-correction to minor deviations occured in the previous step. step.

• Korean Journal of Food Science and Technology
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• 제28권3호
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• pp.538-544
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• 1996

A highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its rheological properties were studied. 1% (w/v) solution of purified biopolymer showed pseudoplastic fluid behavior with the yield stress similar to those of xanthan and guar gum, and its consistency index was exponentially dependent on concentration and temperature. The concentration dependency of consistency index exhibited two rectilinear plots with different slopes at 1% concentration and pseudoplastic property increased with the increase of biopolymer concentration. The biopolymer solution exhibited a low temperature dependency and the activation energy of flow was 1.16 kacl/g mol. The apparent viscosity was very dependent on the change of pH and the addition of salt. However, no organic solvent effects were observed effects of viscosity synergism with the addition of viscosifier were not observed.