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Dynamic Young's Modulus and Internal Friction in Polycrystalline Copper
Kang, Chang-Seog,Chang, Si-Young,Hong, Sung-Kil 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.5
An attempt has been made to measure the temperature dependence of dynamic Young's modulus together with the related variation of internal friction in polycrystalline copper. A mechanical spectroscopy study was employed using a standard servo hydraulic fatigue testing machine equipped with a scanning laser extensometer. Dynamic Young's modulus and internal friction were measured over a temperature range of 298 to 873 K at very low frequencies of 0.1, 0.05, and 0.01 Hz. One internal friction peak was observed over the ranges 450 to 700 K, together with marked decreases in the dynamic Young's modulus in the same temperature range. From a quantitative analysis of the experimental data with the relaxation strength, relaxation time, and activation energy, it is concluded that the peak phenomenon is due to grain-boundary sliding relaxation.
정상인에서 베타3-아드레날린 수용체 유전자의 변이가 복부 비만도 및 지질대사에 미치는 영향
김영선,윤석기,김철희,서교일,김학선,김극배,변동원,유명희 순천향의학연구소 1998 Journal of Soonchunhyang Medical Science Vol.4 No.1
The β₃-adrenergic receptor is expressed in visceral adipose tissue in humans and is thought to contribute to the regulation of the resting metabolic rate and lipolysis. We studied the influence of a mutation in the β₃ -adrenergic receptor gene(Trp64Arg) on body fat distribution, central obesity, lipid metabolism in 65 healthy young male adults. One out of 65 subjects were homozygous (Arg/Arg) for the trp64Arg mutation, 17 subjects were heterozygous (Trp/Arg), and 47 lacked the mutation(Trp/Trp). The body weight, height, body mass index, waist-to-hip ratio were similar between the subjects with- and without the mutation. Total body fat, abdominal fat amount, body fat distribution, serum total- and HDL-cholesterol, triglyceride, glucose, and insulin concentrations were also not different according to the presence or absence of the mutation. These results suggested that Trp64Arg mutation in β₃-adrenergic receptor gene is not a major contributing factor for central obesity or change in lipid metabolism in Korean young adults.
오영규,박재용,임민규,박재용,한석영,Oh, Young-Kyu,Park, Jae-Yong,Im, Min-Gyu,Park, Jae-Yong,Han, Seog-Young 한국생산제조학회 2010 한국생산제조학회지 Vol.25 No.6
The objective of this study is to integrate reliability analysis into shape optimization problem using the evolutionary structural optimization (ESO) in the application example. Reliability-based shape optimization is formulated as volume minimization problem with probabilistic stress constraint under minimization max. von Mises stress and allow stress. Young's modulus, external load and thickness are considered as uncertain variables. In order to compute reliability index, four methods, i.e., reliability index approach (RIA), performance measure approach (PMA), single-loop singlevector (SLSV) and adaptive-loop (ADL), are used. Reliability-based shape optimization design process is conducted to obtain optimal shape satisfying max. von Mises stress and reliability index constraints with the above four methods, and then each result is compared with respect to numerical stability and computing time.
황승민,박재용,임민규,오영규,한석영 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
This paper presents a reliability-based topology optimization (RBTO) using bi-directional evolutionary structural optimization (BESO). Topology optimization is formulated as volume minimization problem with probabilistic displacement constraint. Young's modulus, external load and thickness are considered as uncertain variables. In order to compute reliability index, four methods, i.e., RIA, PMA, SLSV and ADL(adaptive-loop), are used. Reliability-based topology optimization design process is conducted to obtain optimal topology satisfying displacement and reliability index constraints with the above four methods, and then each result is compared with respect to numerical stability and computing time.
박재용,유진식,황승민,임민규,오영규,김용대,한석영,맹주성 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-
An active micro-mixer, which is composed of an oscillating micro-stirrer in the micro-channel to provide effective mixing was optimized. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight micro-channel and micro-channel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models were compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced' and stabilized. Therefore, an approximate optimization of an active micro-mixer with an oscillating stirrer was performed using Kriging method with OLHD (Optimal Latin Hypercube Design) in order to determine the optimal design variables. The design parameters were established as the frequency, the length and the angle of the stirrer. The optimal values were obtained as 1.5754, 0.803D and ±45°, respectively. It was found that the mixing index of the optimal design increased by 83.36% compared with that of the original design.
마이크로파에 의한 생분해성 β-TCP/PLGA 복합체의 제조시 β-TCP 첨가량에 따른 영향
진형호,민상호,박홍채,윤석영,Jin, Hyeong-Ho,Min, Sang-Ho,Park, Hong-Chae,Yoon, Seog-Young 한국재료학회 2006 한국재료학회지 Vol.16 No.1
Biodegradable $\beta$-tricalcium phosphate ( $\beta$-TCP)/poly(lactide-co-glycolide) (PLGA) composites were synthesized by in-situ polymerization with microwave energy. The influence of the $\beta$-TCP content in $\beta$-TCP/PLGA composites on the molecular weight, crystallinity, microstructure and mechanical properties was investigated. As the molecular weight of composites decreased, the $\beta$-TCP content increased up to 10 wt.%, while the excess addition of the $\beta$-TCP content above 10 wt.% the molecular weight increased with increasing of the $\beta$-TCP content. This behavior would be due to the superheating effect or nonthermal effect induced by microwave energy. It was found that the bending strength and Young's modulus of the $\beta$-TCP/PLGA composites was proportional to the molecular weight of PLGA. The bending strength of the $\beta$-TCP/PLGA composites ranged from 18 to 38 MPa, while Young's modulus was in the range from 2 to 6 GPa.
한석영,유재원 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.4
Most engineering products contain more than one component. Failure occurs either at the connection itself or in the component at the point of attachment of the connection in many engineering structures. The allocation and design of connections such as bolts, spot-welds, adhesive etc. usually play an important role in the structure of multi-components. Topology optimization of connection component provides more practical solutions in design of multi-component connection system. In this study, a topology optimization based on density distribution approach has been applied to optimal location of fasteners such as T-shape, L-shape and multi-component system. From the results, it was verified that the number of iteration was reduced, and the optimal topology was obtained very similarly comparing with ESO method. Therefore, it can be concluded that the density distribution method is very suitable for topology optimization of multi-component structures.
한석영,김성훈 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
In this study, shape optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.