• Korean Chemical Engineering Research
• /
• 제46권4호
• /
• pp.756-763
• /
• 2008

본 연구에서는 잉크젯용 전도성 금속 나노 잉크 개발을 목표로 통계적인 실험과 분석을 진행하여 재현성 있는 고품질의 은 나노 입자를 합성할 수 있는 기술을 개발하고자 하였다. 은 나노 입자는 상용 수계분산제 Daxad19를 이용한 용액 환원침전법을 통해 0.3 M의 고농도로 합성되었다. 합성에 주요한 영향을 주는 6개의 인자를 선정한 후 실험 계획법(Design-of-experiment)을 통해 실험을 수행하였다. 합성된 은 입자는 SEM, TEM, UV-Visible 등의 분석법을 이용하여 입자크기 및 분포와 분산도 등을 측정하였으며 통계 프로그램인 Minitab으로 이를 최적화하였다. 통계적인 실험계획 및 분석은 2차 부분요인분석법(2k-fractional factorial design)과 반응표면분석법인 박스-벤켄법(Box-Behnken design)으로 진행하였다. 이를 통한 합성 최적화로 평균입경 $30nm{\pm}10%$를 가진 구형의 은 나노 입자를 합성하였다. 또한 본 연구에서는 실험 결과 해석을 통해 환원침전법에서의 입자크기 및 형상 제어의 방식도 실험적으로 밝혀냈다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제30권1호
• /
• pp.58-64
• /
• 2006

This work focuses on reducing the noise and vibration levels of an LPi fuel pump, which are generated from the dynamic motions of pump elements and non-uniform flow of fuel. The noise and vibration levels increase as the revolution speed of the cam goes up. The fuel pump consists of five cavity cells, plungers and diaphragms, which are driven by the cam. The optimal design of the cam profile is performed to decrease the accelerations of moving Parts and to obtain a smooth hydraulic force through a dynamic analysis of a cam-plunger mechanism. The cam-Plunger with a cavity is modeled as a 2 degrees of freedom system having non-linear contacts, the cam profile being represented in terms of Fourier series in order to determine the optimal shape of the cam. From the optimized cam Profile, the acceleration of the diaphragm is reduced in $78\%$, the hydraulic force becoming smoother in case that the hydraulic force is rapidly dropped.

• Structural Engineering and Mechanics
• /
• 제47권3호
• /
• pp.443-454
• /
• 2013

A leaf spring, especially the longitudinal type is liable and persistent element in automotive suspension system. In the present scenario the composite materials are widely used in the automobile industries has shown a great interest in the replacement of steel spring due to high strength by weight ratio. Previous investigations focused on stresses and displacement analysis of single leaf spring for different materials. The present work aims to design and analysis of leaf spring for two different cases by considering the Young's modulus to yield strength ratio. In the first case the analysis deals with the design and analysis of a single cantilever solid triangle beam which is an equivalent beam of a spring with three leaves having uniform strength. In the second case a 3-beams of rectangular cross section has been considered which is equivalent to a spring with three leaves. The analysis was carried out based on contact mechanics approach. The results were compared, that the fiberglass composite leaf spring is suitable for high loading capacity, reliability and efficiency.

• 제어로봇시스템학회논문지
• /
• 제5권8호
• /
• pp.923-931
• /
• 1999

In this paper, a modeling and a robust time-delay control for the reclaimer are investigated. Supplying the same amount of a raw material throughout the reclamation process from the raw yard to a sinter plant is important to keep the quality of the molten steel uniform in blast furnaces. As the actual parameter values of the reclaimer are not available, the boom rotational dynamics are modeled as a second order differential equation with unknown coefficients. The unknown parameters in the nominal model are estimated using a recursive estimation method. Another important factor in the control design of the reclaimer is the large time-delay in output measurement. Assuming a multiplicative uncertainty, that accounts for both the unstructured uncertainty neglected in the modeling and the structured uncertainty contained in the parameter estimation, a robust Smith predictor is designed. A robust stability criterion for the multiplicative uncertainty is also derived. Following the work of Goodwin et al. [4], a quantifying procedure of the multiplicative uncertainty bound, through experiments , is described. Experimental and simulation results are provided.

• Advances in Computational Design
• /
• 제2권3호
• /
• pp.165-194
• /
• 2017

The present work proposes the thermo mechanically induced statistics of nonlinear transverse central deflection of elastically supported functionally graded (FG) plate subjected to static loadings with random system properties. The FG plate is supported on two parameters Pasternak foundation with Winkler cubic nonlinearity. The random system properties such as material properties of FG material, external loading and foundation parameters are assumed as uncorrelated random variables. The material properties are assumed as non-uniform temperature distribution with temperature dependent (TD) material properties. The basic formulation for static is based on higher order shear deformation theory (HSDT) with von-Karman nonlinear strain kinematics through Newton-Raphson method. A second order perturbation technique (SOPT) and direct Monte Carlo simulation (MCS) are used to compute the nonlinear governing equation. The effects of load parameters, plate thickness ratios, aspect ratios, volume fraction, exponent, foundation parameters, and boundary conditions with random system properties are examined through parametric studies. The results of present approaches are compared with those results available in the literature and by employing direct Monte Carlo simulation (MCS).

• Steel and Composite Structures
• /
• 제31권2호
• /
• pp.201-216
• /
• 2019

This scientific paper provides a theoretical, numerical and experimental analysis of local stability of axially compressed columns made of thin-walled rectangular concrete-filled steel tubes (CFSTs), with the consideration of initial geometric imperfections. The work presented introduces the theory of elastic critical stresses in local buckling of rectangular wall members under uniform compression. Moreover, a numerical calculation method for the determination of the critical stress coefficient is presented, using a differential equation for a slender wall with a variety of boundary conditions. For comparison of the results of the numerical analysis with those collected by experiments, a new model is created to study the behaviour of the composite members in question by means of the ABAQUS computational-graphical software whose principles are based on the finite element method (FEM). In modelling the analysed members, the actual boundary and loading conditions and real material properties are taken into account, obtained from the experiments and material tests on these members. Finally, the results of experiments on such members are analysed and then compared with the numerical values. In conclusion, several recommendations for the design of axially compressed composite columns made of rectangular concrete-filled thin-walled steel tubes are suggested as a result of this comparison.

• 한국음향학회지
• /
• 제35권6호
• /
• pp.466-472
• /
• 2016

본 연구에서는 고분해능 초음파 영상 획득이 가능한 20 MHz 대역의 의료용 초음파 선형 배열 트랜스듀서를 개발하였다. 먼저 고주파 음파의 전파가 용이한 트랜스듀서의 구조를 고안한 후, 구성소자의 최적치수를 도출하였다. 이후 설계에 따라 트랜스듀서의 제작공정을 개발하고, 트랜스듀서 시편의 제작 및 평가를 수행하였다. 제작된 초음파 트랜스듀서는 중심주파수가 19 MHz이고, 비대역폭이 84.5 %, 감도의 표준편차가 0.74 dB로 측정되었다. 측정 결과는 설계 결과와 잘 일치하였으며, 이에 의해 본 연구에서 개발한 고주파 초음파 트랜스듀서 구조의 타당성을 검증하였다. 개발된 트랜스듀서는 새로운 구조에 의해 기존의 20 MHz 트랜스듀서에 비해 더 넓은 주파수 대역폭과 균일한 감도를 가지는 것으로 확인되었다.

• 한국문헌정보학회지
• /
• 제49권4호
• /
• pp.203-220
• /
• 2015

본 연구는 국내 도서관에서 AACR2와 RDA 서지레코드의 공존에 따라 서지레코드의 디스플레이와 검색을 위한 하이브리드 서지레코드 생성 방안을 제안하고자 한다. 연구방법으로 문헌연구와 사례조사를 실시하였다. 분석대상은 도서관으로 Kent State University, University of Houston이고, 하이브리드레코드 생성 알고리즘으로 Backstage Library Works이었다. 조사를 바탕으로 국내에서 하이브리드 서지레코드 생성을 위해서는 첫째, 하이브리드 서지레코드와 RDA 레코드의 식별이 필요하다. 둘째, 판사항에서 약어를 무조건 확장하여 기술하는 것은 바람직하지 않으므로 250에 기술된 정보를 그대로 유지하도록 한다. 셋째, 260을 264로 변환하는 것보다는 260을 유지하도록 한다. 넷째, 자원유형을 정확히 변환할 수 있는 신뢰할 매핑표가 작성되어야 한다. 본 연구는 국내 서지데이터에서 서양서의 기존 레코드를 하이브리드레코드로 변환하여 통일된 디스플레이와 검색이 가능하도록 제안하였다.

• 한국산업보건학회지
• /
• 제29권2호
• /
• pp.208-216
• /
• 2019

Objective: The aim of this study is to control residual chemicals or by-products generated in chambers during preventive maintenance (PM) in the semiconductor manufacturing industry. We designed local exhaust ventilation using computational fluid dynamics (CFD). Methods: The air flow characteristics and capture efficiency between rectangular and slot hoods were compared numerically. The software Fluent 18.1 was used to estimate uniform velocity distribution and capture efficiency for contaminants. A metal from group 15 in the periodic table was released at the bottom of the chamber to simulate emissions. Results: The slot hood had a higher capture efficiency than a rectangular hood under the same conditions because the slot hood provided uniform air flow and higher face velocity. Also, there was no rotating swirl in the plenum for slot, that is why slot had better efficiency than rectangular even though they had similar face velocity. With less than 10 slots, the capture efficiencies for contaminants were nearly 95%. The optimum conditions for a hood to achieve high efficiency was 8 to 10 slots and a face velocity over 1 m/s. Conclusions: Well-designed ventilation systems must consider both efficiency and convenience. For this study, a slot hood that had high capture efficiency and no work disturbance was designed. This will contribute to protection of the worker's health in a PM area and other areas as well. Also, this study confirms the possibility of the application CFD in the semiconductor fabrication industry.

• 한국의상디자인학회지
• /
• 제19권4호
• /
• pp.123-137
• /
• 2017

The purpose of this study is to suggest sleeve cap height with a satisfying wearing sensation and appearance on jackets for women in their twenties so that high-consumer demand jackets can be produced. Five experimental jackets with sleeve cap heights of [(AH/3)-1cm], [(AH/3)-0.5cm], [AH/3], [(AH/3)+0.5cm] and [(AH/3)+0.8cm] were made for 30 subjects to try on after which the subjects were then surveyed for their assessment of appearance, wearing sensation and preference. On the basis of the results, the optimum height of the sleeve cap has been proposed along with the following contents and results of this research. 1. [AH/3] [(AH/3)+0.8cm] of sleeve cap height was assessed to beof desirable appearance. 2. [AH/3] of sleeve cap height garnered a high opinion in terms of intuitive wearing sensation, while [(AH/3)-1cm] [AH/3] were the heights with overall satisfaction of intuitive and movement wearing sensations. If discomfort in the upper sleeve at 'straight arm' posture can be tolerated, the sleeve cap height can be set to [(AH/3)-1cm]~[(AH/3)+0.5cm]. 3. [AH/3] and [(AH/3)+0.5cm] were found to have a high preference among wearers, which indicated that the women in their twenties prefer a slim type of sleeve, putting appearance above wearing sensation. Consequently, [AH/3] is desirable when appearance, wearing sensation and preference are considered, [(AH/3)+0.5cm] is fit for business uniform for static duties or formal dress focused on aesthetic impression and [(AH/3)-1cm]~[AH/3] are desirable for work clothes when considering active duties.