• 한국지반신소재학회논문집
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• 제3권4호
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• pp.13-19
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• 2004

본 연구에서는 계단식 보강토 옹벽의 파괴메카니즘 연구를 위해 모형실험을 실시한 내용을 다루었다. 보강토옹벽의 모형실험은 성균관대학교 내의 지반시험장에 시험 시공한 계단식보강토옹벽의 원형을 축소하여 모사하였으며, 상사법칙을 이용하여 보강통옹벽에 사용된 재료의 크기 및 물성치를 원형에 가깝도록 축소하여 파괴메카니즘 분석에 신뢰성을 높였다. 또한 파괴메카니즘 분석을 위해 종전의 재하실험 방식과는 달리 자중에 의한 파괴가 가능해짐으로써 원형에 가까운 파괴 형상을 모사 할 수 있었다. 모형 실험의 내용으로는 보강토옹벽의 영향인자라고 할 수 있는 이격거리의 변화 및 보강재 길이변화에 따른 파괴 양상을 분석하였다.

• Journal of Applied Biological Chemistry
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• 제43권1호
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• pp.37-43
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• 2000

1,3,2-Dioxaphosphorinanes are suitable compounds for studying the stereochemistry of substitution at phosphorus. Cis- and trans-5-hydroxymethl-5-methyl-2-thiono-2ethoxy-1,3,2-dioxaphosphorinane were prepared, and their structures and stereochemistry unambiguously assigned by NMR and X-ray crystallography with acetoxy and 3,5-dinitrobenzoyloxy derivatives, respectively. Trans isomer gave $^{31}P$ NMR signal at higher field than cis isomer, and the ring proton Spectrum of cis isomer showed characteristic pattern for identifying its geometry. In X-ray crystallography they adopted a chair conformation with the ethoxy groups in the axial positions, and the sulfide groups in the equatorial positions. A flattening of the ring around the phosphorus center was noted, the POC bond angles were about $120^{\circ}$, and the C-O bonds in the ring were significantly longer than the C-O bond for the ethoxy group or the C-O bond for hydroxyl group.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.807-814
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• 2014

본 연구는 TV 애니메이션 '똑똑박사 에디'의 스토리텔링 요소와 수학내용을 분석하는데 목적이 있다. 선행 연구와 문헌을 토대로 설정한 분석기준에 따라 시나리오와 애니메이션을 보면서 내용분석과 빈도분석을 실시하였다. 연구결과를 제시하면 첫째, 의인화된 11명의 동물이 등장인물로 나오며, 에디는 주인공으로서 문제해결자의 역할을 담당한다. 등장인물의 말, 행동, 사고양식은 전조작기 유아의 수준으로 묘사된다. 눈 덮인 숲 속 마을을 배경으로 일상적이고 평범한 스토리가 진행되며, 중심서사는 있으나 이야기는 플롯의 형식으로 구성되어 있지 않다. 이야기의 주 내용은 수학내용을 다루고 있으며, 에피소드는 대화, 노래, 나레이션을 통해 진행된다. 둘째, 애니메이션에서는 1회당 평균 23회의 수학내용을 다루고 있으며, 수감각, 기하, 측정, 자료분석과 확률, 규칙성의 순으로 나타났다. 이로서 '똑똑박사 에디'는 에듀테인먼트로서의 가치가 있는 작품으로 평가할 수 있다.

• 한국전기전자재료학회논문지
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• 제27권12호
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• pp.871-876
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• 2014

Efficiency of crystalline Si solar cell can be maximized as minimizing optical loss through antireflection texturing with inverted pyramids. Even if cost-competitive, soft lithography can be employed instead of photolithography for the purpose, some limitations still remain to apply the soft lithography directly to as-received solar grade wafer with a bunch of micro trenches on surface. Therefore, it is needed to develop a low-cost, effective planarization process and evaluate its output to be applicable to patterning process with PDMS stamp. In this study new surface planarization process is proposed and the change of micro scale trenches on the surface as a function of etching time is observed. Also, the effect of trenches on pattern quality by soft lithography is investigated using FEM structural analysis. In conclusion it is clear that the geometry and shape of trenches would be basic considerations for soft lithography application to low quality wafer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.150-150
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• 2000

The adsorption geometry and the electronic property of Mg grown at room temperature on the Si(111)-7$\times$7 surface with various coverages have been studied by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). At low Mg coverage, the Mg atoms preferentially adsorb at the center adatom sites of the faulted half of the Si(111)-7$\times$7 surface. The adsorbed Mg atom acts as nucleophile with respect to Si atoms thus forms a stable ionic bond with the substrate Si atoms. Above 1 Ml, the 7$\times$7 surface starts to be disrupted and an amorphous Mg overlayer is formed. The LEED shows either $\delta$7$\times$7 or 1$\times$1 pattern at this coverage. When more Mg atoms were exposed, a flat and broad {{{{ { 2} over {3 } }}}}{{{{ SQRT { 3} }}}}$\times${{{{ { 2} over {3 } }}}}{{{{ SQRT { 3} }}}}R30$^{\circ}$region evolves. A flat silicide is formed at first and multi-level Mg islands having hexagonal step edges develop with increasing coverage. The scanning tunneling spectroscopy (STS) confirms the electronic properties of these Mg films on the si(111) 7$\times$7 surface at various coverages.

• 한국소음진동공학회논문집
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• 제26권6_spc호
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• pp.687-696
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• 2016

A series of process to design an acoustic lens for underwater imaging is reviewed and the method to evaluate characteristics of the lens is investigated. If the target specification of lens is given, the design process consists of the material selection, evaluation of its properties, lens geometry design, prediction of lens characteristics, manufacturing, and evaluation by measurement. In this study, an actual acoustical lens is made by cutting polymethylpentene block. The characteristics of lens are predicted by the hybrid method, combination of ray tracing and Rayleigh integral. For the direct comparison between the prediction and measurement results, a simulation method based on the equivalent source method is suggested to reflect the actual radiation pattern of transducer used for measurements. Finally, the measurement is conducted in a small water tank to observe the actual characteristics of the manufactured lens.

• 한국정밀공학회지
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• 제16권11호
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• pp.174-182
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• 1999

This paper describes a research work of developing a computer-aided design of product with bending constraints and piercing for progressive working. an approach to the CAD system is based on the knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written AutoLISP on the AutoCAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, production feasibility check, and strip-layout module. Based on knowledge-based rules, the system is designed by considering several factors, such as radius and angle of bend, material and thickness of product, complexities of blank geometry and punch profile, bending sequence, availability of press. Strip layout drawing generated by piercing with punch profiles divide into automatically for external area is shown into graphic forms, including bending sequences for the product with piercing and bending constraints. Results obtained using the modules enable the designer and manufacturer of piercing and bending dies to be more efficient in this field.

• 대한기계학회논문집B
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• 제25권3호
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• pp.405-413
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside a rotating two-pass rectangular duct. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The objective of this study is to determine the effects of turning geometry with rotation for 0.0$\leq$Ro$\leq$0.24. The results reveal that the sharp-turn corner has the larger pressure drop and lower heat transfer in the post-turn region than those of the round-turn corner. The strong secondary flow enhances heat transfer for the round-turn corner. Coriolis force induced by the rotation pushes the high momentum core flow toward the trailing wall in the first passage with radially outward flow and toward the leading wall in the second passage with radially inward flow. Consequently, the high heat transfer rates are generated on the trailing surface and the leading surface in the first and second passage, respectively. However, the strong secondary flow due to the turning dominates the flow pattern in the second passage, thus the heat transfer differences between the leading and trailing surfaces are small with the rotation.

• 대한원격탐사학회지
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• 제23권1호
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• pp.7-14
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• 2007

Atmospheric correction is one of critical procedures to extract quantitative information related to biophysical variables from hyperspectral imagery. Most atmospheric correction algorithms developed for hyperspectral data have been based upon atmospheric radiative transfer (RT) codes, such as MODTRAN. Because of the difficulty in acquisition of atmospheric data at the time of image capture, the complexity of RT model, and large volume of hyperspectral data, atmospheric correction can be very difficult and time-consuming processing. In this study, we attempted to develop an efficient method for the atmospheric correction of EO-1 Hyperion data. This method uses the pre-calculated look-up-table (LUT) for fast and simple processing. The pre-calculated LUT was generated by successive running of MODTRAN model with several input parameters related to solar and sensor geometry, radiometric specification of sensor, and atmospheric condition. Atmospheric water vapour contents image was generated directly from a few absorption bands of Hyperion data themselves and used one of input parameters. This new atmospheric correction method was tested on the Hyperion data acquired on June 3, 2001 over Seoul area. Reflectance spectra of several known targets corresponded with the typical pattern of spectral reflectance on the atmospherically corrected Hyperion image, although further improvement to reduce sensor noise is necessary.

• Geomechanics and Engineering
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• 제13권3호
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• pp.431-446
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• 2017

Rock bridges in rock masses would increase the bearing capacity of Non-persistent discontinuities. In this paper the effect of ratio of rock bridge surface to joint surface, rock bridge shape and normal load on failure behaviour of intermittent rock joint were investigated. A total of 42 various models with dimensions of $15cm{\times}15cm{\times}15cm$ of plaster specimens were fabricated simulating the open joints possessing rock bridge. The introduced rock bridges have various continuities in shear surface. The area of the rock bridge was $45cm^2$ and $90cm^2$ out of the total fixed area of $225cm^2$ respectively. The fabricated specimens were subjected to shear tests under normal loads of 0.5 MPa, 2 MPa and 4 MPa in order to investigate the shear mechanism of rock bridge. The results indicated that the failure pattern and the failure mechanism were affected by two parameters; i.e., the ratio of joint surface to rock bridge surface and normal load. So that increasing in joint area in front of the rock bridge changes the shear failure mode to tensile failure mode. Also the tensile failure change to shear failure by increasing the normal load.