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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.
오영규,박재용,황승민,임민규,박재용,한석영 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
This paper presents a reliability-based shape optimization (RBSO) using the evolutionary structural optimization (ESO). An actual design involves uncertain conditions such as material property, operational load and dimensional variation. The deterministic optimization (DO) is obtained without considering uncertainties related to uncertainty parameters. However, the RBSO can consider the uncertainty variables because it has the probabilistic constraints. In order to determine whether the probabilistic constraint is satisfied or not, simulation techniques and approximation methods are developed. In this paper, the reliability-based shape design optimization method is proposed by utilizing the reliability index approach (RIA), performance measure approach (PMA), single-loop single-vector (SLSV), adaptive-loop (AOL) are adopted to evaluate the probabilistic constraint. In order to apply the ESO method to the RBSO, a sensitivity number is defined as the change in the displacement. Numerical examples are presented to compare the DO with the RBSO. The results of design example show that the RBSO model more reliable than deterministic shape optimization.
엄영섭,유광선,박재용,한석영 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
It is important to represent limit state function in reliability-based design optimization. Since it is very difficult to explicitly represent a limit state function in topology optimization, it is necessary to make the limit state function an approximate function. In case of implementing RSM, the limit state function can easily approximated. In this study, the limit state function of structures was approximated using ADAPRES to obtain the effective response surface modeling as reducing the experiment points. From the result of carrying out the BESO using the ADAPRES, it is concluded that the ADAPRES can be applied to RETO and is more effective than RSM in computing cost.
한국인 성인 정상교합자 치관의 설측면 특징에 관한 연구
유형석,박영철 대한치과교정학회 1992 대한치과교정학회지 Vol.22 No.3
The purpose of this study was to obtain the lingual morphology (size, angulation, contour, eminence) of adults with normal occlusion in order to provide the basic data for lingual bracket and lingual arch form in Korean. The subjects (Male : 50, Female : 50) were selected who have normal occlusion and dental casts were prepared. Tooth size, angulation, arch width, horizontal contour, lingual eminence were measured for all 28 teeth both upper and lower arch. The results were as follows : 1. Measuring items of all individual teeth for adults with normal occlusion were obtained. 2. In comparison tests, there was a statistically difference between intermolar widths(6 to 6) before occlusal reductio and intermolar width(6 to 6,7 to 7) after occlusal reduction only, all the other measuring items showed no statistically differences. 3. There was small variation in horizontal contour of lingual surface on lower incisors and upper and lower bicuspids. The other teeth showed somewhat greater variations. 4. There was offset between canine and bicuspid in upper arch while there was no prominent offset in lower arch.