• 대한기계학회논문집A
• /
• 제32권7호
• /
• pp.590-596
• /
• 2008

The ultrasonic velocities of sintered aluminum with varying density were measured in order to deduce the mechanical properties for optimum design of the sintered aluminum. Specimens with different densities were prepared by the plasma activated sintering machine. The density distribution of sintered aluminum becomes partially inhomogeneous because of the friction between the powder and the die during compaction. The elastic moduli are increased as the ultrasonic velocity is increased. Furthermore, Poisoon's ratio is depending on not only the density but also the size and distribution of voids. As the specimen's thickness increases, the center frequency in the frequency spectrum of the reflection wave is shifted to the low frequency. The attenuation coefficient of ultrasonic wave is decreased inversely as the density increased.

• 대한기계학회논문집B
• /
• 제33권5호
• /
• pp.311-317
• /
• 2009

Due to extremely small device size and velocity scale, mixing in microchannel take place very slowly by way of molecular diffusion transport. Mixing enhancement becomes a central issue in microfluidics for biomedical and chemical applications. In this work, The optimization results and validation through experiment and fabrication. In this efficient micromixer design, it is essential to evaluate mixing efficiency with good precision. Mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS). Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

• 한국군사과학기술학회지
• /
• 제3권2호
• /
• pp.179-188
• /
• 2000

Multi-disciplinary optimization design concept can provide a solution to many engineering problems. In the field of structural analysis, much development of size or topology optimization has been achieved in the application of research. This paper demonstrates an optimum design of a multi-layer cylindrical tube which behaves thermoelastically. A multi-layer cylindrical tube that has several different material properties at each layer is optimized within allowable stress and temperature range when mechanical and thermal loads are applied simultaneously. When thermal loads are applied to a multi-layer tube, stress phenomena become complicated due to each layer's thermal expansion and the layer thicknesses. Factors like temperature; stress; and material thermal thicknesses of each tube layer are very difficult undertaking. To analyze these problems using an efficient and precise method, the optimization theories are adopted to perform thermoelastic finite element analysis.

• Fisheries and Aquatic Sciences
• /
• 제12권4호
• /
• pp.342-349
• /
• 2009

The purpose of the current study was to optimize shrimp-pot design to allow greater control over the size of captured individuals for the purposes of shrimp resource management. Tank experiments were conducted to determine the optimal slope length and slope angle by analyzing the sizes of shrimp that entered 25 model pots with combinations of five different slope lengths and five different angles. Shrimp size was measured using carapace length. The results showed that as the slope angle of the pot increased, the size of individuals that entered the pot increased. Furthermore, as the slope length increased, each of the five different slope angles of the pot increased, and the size of individuals entering also increased. The data indicated that the optimum pot design for reducing the capture of immature individuals had a $75^{\circ}$ slope angle and a 35.4 cm slope length.

• Journal of Biosystems Engineering
• /
• 제39권4호
• /
• pp.299-303
• /
• 2014

Purpose: This study set out to develop a machine for separating shatter-resistant sesame after threshing. Methods: Three grades of sieve and different blower speeds were tested for a separation system that had been designed specifically for shatter-resistant sesame. Performance tests were run to evaluate the sieve and blower systems in terms of the sesame separation and loss ratios. Results: Tests of the first separation stage using the sieve system revealed the optimum sieve perforation size to be 5 mm. Tests of the second separation stage using the blower system identified the optimum blower speed as being 220 rpm. The optimum separation and loss ratios, of 96.5% and 3.5%, respectively, were obtained at a blower speed of 220 rpm. Conclusions: These results will be useful for the design, construction, and operation of threshing harvesters. For shatter-resistant sesame, an optimum blower speed of 220 rpm was identified.

• 한국전산구조공학회논문집
• /
• 제13권3호
• /
• pp.337-349
• /
• 2000

유전자 알고리즘(GA)은 어떠한 유형의 문제에도 적용가능하며 달리 방법이 없는 경우 최후의 수단으로 흔히 사용되는 방법이다. 강구조물 설계란 기본적으로 구조물을 이루는 부재로서 어떤 재료를 선택될 것인지를 결정하는 문제이다. 따라서 천문학적인 숫자의 설계가 존재하며 이들 중 최적의 설계를 탐색하는 것은 대체로 불가능한 일이다. 본 논문에서는 GA와 이와 관련된 여러 가지 기법들을 소개하고 강구조물 최적설계에 이들의 활용을 모색하였다. 작은 설계공간을 가지는 문제에서는 GA로 전역최적설계를 찾을 수 있었다. GA는 또한 연속변수 최적설계 문제에서도 최적설계를 찾았으며 구조물 최적설계에 적용될 수 있음을 보였다. 그러나 규모가 큰 현실문제에서는 GA가 최적 또는 최적에 근접한 설계를 항상 찾을 수 있을 것이라고 기대하기는 어려울 것으로 생각된다. GA에 G bit improvement를 추가하여 수행한 경우에 더 좋은 최적설계 결과를 보여주었으며 앞으로 이 부분의 연구가 활발해 질 것이다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.798-801
• /
• 2007

For lower power and smaller size with higher image quality, it is desirable to have more units integrated on a display panel. It needs careful design considerations in selecting CMOS, SOP or PCB. An experimental display system is designed and power and delay considering chip area, data rates and bus width are analyzed for all technology combinations to obtain optimum design methodologies.

• Journal of Welding and Joining
• /
• 제15권1호
• /
• pp.125-134
• /
• 1997

This study was conducted by L9 orthogonal array to obtain optimum spray parameters for This study was conducted by L9 orthogonal array to obtain optimum spray parameters for $Cr_3C_2 - 7wt%$(80wt%Ni-20wt%Cr) coating powder. The factors were hydrogen flow rate, oxygen flow rate, gun-to-work distance, powder feed rate. And evaluation methods for the coating were surface roughness, oxygen concentration, micro-hardness, pore size and distribution, low angle ($30^{\circ}$) erosion rate, and microstructure of coating. The optimum HVOF spray conditions were proved as follows : hydroen flow rate ; 681 SLPM, oxygen flow rate ; 215 SLPM $H^2/O^2 ratio= 3.16), gun-to-work distance ; 22cm, powder feed rate; 25g/min. The hardness (Hv300) was 1147 and the erosion rate ($30^{\circ}$degree) was $3.16\times10^{-4}$g/g. It is believed that the optimized spray conditions can be improved the wear-resistance and anti-erosion characteristics of the coating.

• Steel and Composite Structures
• /
• 제26권2호
• /
• pp.163-170
• /
• 2018

The purpose of this paper is to present a new and efficient optimization algorithm called Jaya for optimum design of steel grillage structure. Constrained size optimization of this type of structure based on the LRFD-AISC is carried out with integer design variables by using cross-sectional area of W-shapes. The objective function of the problem is to find minimum weight of the grillage structure. The maximum stress ratio and the maximum displacement in the inner point of steel grillage structure are taken as the constraint for this optimization problem. To calculate the moment and shear force of the each member and calculate the joint displacement, the finite elements analysis is used. The developed computer program for the analysis and design of grillage structure and the optimization algorithm for Jaya are coded in MATLAB. The results obtained from this study are compared with the previous works for grillage structure. The results show that the Jaya algorithm presented in this study can be effectively used in the optimal design of grillage structures.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1998년도 춘계 학술대회논문집
• /
• pp.75-81
• /
• 1998

A new advanced integral reactor of 330 MWt capacity named SMART(System-integrated Modular Advanced ReacTor) is currently under development at KAERI(Korea Atomic Energy Research Institute). One of the major design features of the integral reactor is locating the steam generators(SG) inside reactor vessel and eliminating the possibility of LB LOCA(large Break Loss of Coolant Accident). Orifices are fitted at the low part of steam generator cassette to stabilize and balance coolant flow distribution in the MCP (Main Circulation Pump) pressure header. A sensitivity analysis is conducted to determine the optimum orifice size using computer code 'CFX'.