• 전자공학회논문지A
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• 제29A권7호
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• pp.64-72
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• 1992

VLSI 전송선로의 커패시턴스를 3차원으로 계산하였다. Green's function과 표면전하밀도의 곱의 형태로 주어지는 적분식을 풀어서 커패시턴스를 구하였다. 이때, 표면전하밀도는 도체의 표면을 균일한 면적을 갖는 미소 면적소로 나누어 주었을 때 각각의 면적소 내에서는 일정한 상수값을 갖는다고 가정하였다. 지금까지의 Green's function을 이용한 적분방법에서는 적분식의 계산을 Fourier 적분의 형태로 변환하여 계산하였기 때문에 계산과정에서 어느정도의 오차가 있을 수 밖에 없었지만, 본 논문에서는 Fourier 적분을 사용하는 대신에 이중 적분을 직접적으로 적분할 수 있는 방법을 제시하였다. 이 방법을 사용하여 적용한 결과를 기존의 결과들과 비교를 함으로써, 이의 정확성을 입증하였다.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.551-566
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• 2005

Using two different, but related approaches, an exact dynamic stiffness matrix for a two-part beam-mass system is developed from the free vibration theory of a Bernoulli-Euler beam. The first approach is based on matrix transformation while the second one is a direct approach in which the kinematical conditions at the interfaces of the two-part beam-mass system are satisfied. Both procedures allow an exact free vibration analysis of structures such as a plane or a space frame, consisting of one or more two-part beam-mass systems. The two-part beam-mass system described in this paper is essentially a structural member consisting of two different beam segments between which there is a rigid mass element that may have rotatory inertia. Numerical checks to show that the two methods generate identical dynamic stiffness matrices were performed for a wide range of frequency values. Once the dynamic stiffness matrix is obtained using any of the two methods, the Wittrick-Williams algorithm is applied to compute the natural frequencies of some frameworks consisting of two-part beam-mass systems. Numerical results are discussed and the paper concludes with some remarks.

• 설비공학논문집
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• 제27권10호
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• pp.552-557
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• 2015

The nanostereolithography process using a femtosecond laser has been shown to have strong merits for the direct fabrication of 2D/3D micro structures. In addition, a femtosecond laser provides efficient tools for precise micromachining owing to the advantages of a small and feeble heat effect zone. In this paper, we report an effective fabrication process of 3D micro optical and fluidic devices using nanostereolithography process composed of a dual stage system. Process conditions for additive and subtractive fabrication are examined. The Piezo stage scanning system is used for 3D micro-fabrication in unit area of sub-mm scale, and the motor stage is employed in fabrication on the scale of several mm. The misalignment between the pizeo- and motor- stages is revised through rotational transformation of CAD data in the unit domain. Here, the effectiveness of the proposed process is demonstrated through examples using 3D optical and microfluidic structures.

• 한국자기학회지
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• 제9권1호
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• pp.17-22
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• 1999

육방구조의 M형 BaFe12O19를 NaCl를 첨가한 경우와 첨가하지 않은 경우에 질소가스 분위기와 공기 중에서 여러 온도로 가열하여 고상반응법으로 제조하였다. X-선 회절법과 Mossbauer분광법에 의하여 BaFe12O19상과 $\alpha$-Fe2O3상의 공존 정도를 알아냈다. 동일한 조건에서 NaCl를 첨가한 경우가 NaCl를 첨가하지 않은 경우 보다 $\alpha$-Fe2O3상이 적음을 확인하였다.

• Applied Microscopy
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• 제44권4호
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• pp.138-143
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• 2014

Transmission electron microscope (TEM) is an excellent tool for studying the structure and properties of nanostructured materials. As the development of $C_s$-corrected TEM, the direct analysis of atomic structures of nanostructured materials can be performed in the high-resolution transmission electron microscopy (HRTEM). Especially, fast Fourier transform (FFT) technique in image processing is very useful way to determine the crystal structure of HRTEM images in reciprocal space. To apply FFT technique in HRTEM analysis in more reasonable and friendly manner, we made a new circular region of interest (C-ROI) FFT script and tested it for several HRTEM analysis. Consequentially, it was proved that the new FFT application shows more quantitative and clearer results than conventional FFT script by removing the streaky artifacts in FFT pattern images. Finally, it is expected that the new FFT script gives great advantages for quantitative interpretation of HRTEM images of many nanostructured materials.

• Macromolecular Research
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• 제16권6호
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• pp.539-543
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• 2008

Many natural proteins self-assemble in complex ways, either to fulfill their biological function or introduce particular properties, such as high strength and toughness. We report the morphological transition in water from a spherical to rod-like shape of Bombyx mori silk fibroin by reducing the pH. Transmission electron microscopy, scanning electron microscopy, and dynamic light scattering were used to characterize the dilute solutions of silk fibroin in an aqueous environment, and provide direct visualization of the transformation of spherical micelles at pH 6.8 to nanofibrils at pH 4.8. This change in morphology occurred as a result of the stretching entropy due to the formation of $\beta$-sheets, which was analyzed using circular dichroism spectroscopy. This study demonstrates the self-assembly of silk fibroin as a function of pH.

• 한국재료학회지
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• 제15권7호
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• pp.435-438
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• 2005

Single phase $Zn_4Sb_3$ with $98.5\%$ of theoretical density was successfully produced by direct hot pressing of elemental powders containing $1.2 at\%$ excess Zn for compensating the evaporation during the process. Temperature dependences of thermoelectric properties were investigated from 4 K to 300 K. Seebeck coefficient, electrical conductivity, thermal conductivity as well as thermoelectric figure of merit showed the discontinuity in variation at 242K, indicating the $\alpha-\beta$, phase transformation. Interestingly, it was found that lattice thermal conductivity by phonons is dominant in total thermal conductivity of $\alpha-\beta$. Therefore, it is expected that thermoelectric properties can be improved by reduction of lattice thermal conductivity inducing lattice scattering centers by doping and solid solution.

• Asia pacific journal of information systems
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• 제16권3호
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• pp.29-47
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• 2006

Many companies have been implementing Enterprise resource planning (ERP) systems for their organizational transformation in order to survive and achieve strategic advantages in an increasing competitive business environment. Thus, it is meaningful to identify factors that affect ERP system operation positively. Organizational citizenship behaviors (OCB) are discretionary, extra-role behaviors of employees which go beyond the prescribed formal roles, and are known as to be the contribution factors for organization performance. The purpose of this study is to develop the measurements for the OCB constructs in ERP system context and empirically test the relationships between the OCB construct and ERP system success. The four constructs - altruism, conscientiousness and courtesy, civic virtue, and sportsmanship - and fifteen measurements on the OCB were developed based on previous studies (i.e. Organ 1988) and empirically verified by confirmatory factor analysis. The results of testing the relationships between the OCB and ERP system success show that the OCB have a significant direct impact on the information quality and intention of IT innovation while they have an indirect impact on work efficiency mediated by information quality. This study enhances the OCB model into information system arena and helps better understand the user behaviors of information systems.

• 한국산학기술학회논문지
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• 제6권4호
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• pp.291-295
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• 2005

본 논문은 변형된 2-D PCA를 이용한 얼굴 인식 방법에 대하여 제안한다. 기존의 PCA는 1 차원 벡터들로 공분산 행렬을 구하는 반면에 2-D PCA는 2 차원 영상을 직접적으로 이용하여 공분산 행렬을 구한 후 그것의 고유값에 따른 고유벡터를 구하여 특징 벡터들을 추출한다. 제안 방법은 두 개의 공분산 행렬들을 이용하여 선형 변환 행렬을 구하는 변형된 2-D PCA 방법을 적용하여 얼굴을 인식한다. 실험 결과는 2-D PCA 보다 제안된 방법이 $1\%$ 정도 얼굴 인식률이 더 좋으며, 안정된 인식률을 보여준다.

• 정보처리학회논문지D
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• 제17D권6호
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• pp.463-470
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• 2010

본 논문에서는 DCT 데이터에서 영상 데이터로의 해독 및 이진화 과정을 생략하고 컬러 영상의 DCT 관련 원자료를 사용하는 방법에 기반을 둔 매우 빠르고 안정적인 문자열 구간 분리 모형을 제안하였다. DCT 블록에 저장된 DC 및 3개의 주요 AC 변수들을 조합하여 축소된 저해상도 회색 영상을 만들고 횡렬 및 종렬 투영법을 통해 얻어진 픽셀 값의 히스토그램을 분석하여 문자 열 구간 사이에 존재하는 백색의 띠 공간을 찾아내었다. 이 과정 중 탐색되지 않은 문자 열 구간은 마코프 모델을 사용하여 숨겨진 주기를 찾아내어 복원하였다. 본 논문에 실험 결과를 제시하였으며 기존의 방법보다 약 40 - 100배 빠른 방법임을 입증하였다.