• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.245-252
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric md hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $Al_2O_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.121-128
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• 2011

As high precision industries such as semiconductor, TFT-LCD manufacturing and MEMS continue to grow, the demand for higher DOF precision stages has been increasing. In general, the stages should accommodate a prescribed range of payloads in order to position various precision manufacturing/inspection instruments. Therefore a nonlinear controller using sliding motion is developed, which bears mass perturbation and makes the upper plate of the stage move in 6 DOF. For the application of the nonlinear control, an observer is also developed based on expected noise covariance. To eliminate the steady state error of step response, integral terms are inserted into the state-space model. The linear term of the controller is designed using optimization scheme in which parameters can be weighted according to their physical significance, whereas the nonlinear term of the controller is designed using trial and error method. A comprehensive simulation study proves that the designed controller is robust against mass perturbation and completely eliminates steady state errors.

• Korean Journal of Animal Reproduction
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• v.22 no.3
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• pp.213-219
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• 1998

This study was carried out to investigate on the improvement of fertilizing ability of in vitro matured oocytes from sperm density, motility and polyvinylpyrrolidine (PVP) concentration, by intracytoplasmic sperm injection(ICSI) into the bovine oocytes. 1. The in vitro fertilization and cleavage rates of oocytes from 1.0, 2.0, 3.0, 5.0 ($\times$106/ml) sperm concentration by IVF and ICSI of bovine oocytes were 45.0%~65.0%, 65.0%~90.0% and 10.0%~30.0%, 35.0%~70.0%, respectively. 2. The in vitro fertilization and cleavage rates of oocytes from 20, 40, 60, 80% of sperm motility by IVF and ICSI of bovine oocytes were 47.8%~75.0%, 78.3%~90.0% and 8.7%~25.0%, 34.8%~70.0%, respectively. 3. The in vitro fertilization and cleavage rates of oocytes from 0.01, 0.02, 0.03, 0.05% of PVP concentration by microinjection of single into the bovine oocytes were 72.7%, 90.9%, 83.3%, 76.9% and 45.5%, 72.7%, 58.3%, 61.5%, respectively and these values of 0.02% addition of PVP were higher than other concentrations of PVP. 4. The in vitro fertilization and developmental rates of oocytes by IVF and ICSI methods were 63.3%~64.6%, 26.7%~29.2% and 88.2%, 47.1%, respectively. This ICSI method was improved high fertilization rates of bovined oocytes.

• Journal of Embryo Transfer
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• v.21 no.1
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• pp.7-11
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• 2006

개 난자의 체외성숙과 체외수정을 통해 수정란을 획득하기 위하여 개 난소를 채취하여 난자의 형태, 난소의 채취시기 등이 체외성숙과 체외수정에 미치는 영향을 구명하기 위하여 수행하였다. 1. 난구세포 부착 및 미부착 난자를 48시간 배양했을 때 체외 성숙율은 $42.0{\pm}3.4%,\;24.4{\pm}4.1%$였다. 난구 세포 부착 난자의 체외 성숙율이 미부착 난자의 체외 성숙율보다 유의하게 높게 나타났다(p>0.05). 2. 난소를 휴지기, 난포기 및 황체기로 구분하여 난자를 회수하여 배양했을 때 체외 성숙율은 각각 35.6%, 50.0%, 31.1%였고 체외 발생율은 각각 2.2%, 20.0% 및 8.9%로서 난구 세포 부착 난자가 미부착 난자에 비해 유의한 체외 수정율을 나타냈다. 3. 난구세포 부착 및 미부착 난자를 이용하여 체외수정시켰을 때 체외 수정율과 체외 발생율은 각각 48.0%, 35.6% 및 22.5%, 13.3%로서 난구세포 부착 난자가 미부착 난자에 비해 유의하게 높게 나타났다.

• Journal of Embryo Transfer
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• v.21 no.1
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• pp.1-5
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• 2006

본 연구는 개 채취 정액의 동결후의 생존성과 신선 및 동결 정자의 capacitation, acrosome reaction과 생존성을 조사하고, 아울러 신선 및 동결 정액을 자연 발정 또는 발정 유기 암캐 에게 인공수정 후 임신율을 조사하였다. 개 채취 정액의 동결 융해 후의 생존성은 $64.5{\pm}2.30%$로서 신선 정액의 생존성에 비해 유의하게 낮게 나타났다(p<0.05). 신선 및 동결 정액의 capacitation, acrosome reaction 및 생존성은 각각 $52.5{\pm}4.5%,\;9.5{\pm}0.6%,\;68.8{\pm}4.5%$ 및 $16.2{\pm}3.2%,\;3.2{\pm}0.5%,\;24.5{\pm}2.5%$로 나타났다. 신선 및 동결 정액을 자연 발정 또는 발정을 유기한 암캐에 인공수정했을 때 임신율은 각각 50.0% 및 33.3%로서 동결 정액을 이용했을 때 임신율이 신선 정액에 비해 낮은 임신율을 나타냈다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.183-194
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• 2002

A general procedure to evaluate the sensitivity of design variables to stresses and strains in PSC flexural members is proposed. To accomplish the purpose of this study, long-term losses including creep, shrinkage, and PS steel relaxation are formulated based on the equilibrium states of the deformed sectional geometry. Thereby, the formulation follows the basic steps which consider the fundamental formulas adopted by CEB-FIP, ACI, and KCI rather than the age adjusted effective modulus concept. Twenty-one design variable including the material and geometrical properties of concrete, nonprestressing steel and prestressing steel, and the geometry of the cross section are considered in the sensitivity analysis. The gradients of the stresses and strains needed for the sensitivity assessment are calculated in a closed format. The derived formulation is applied to the T-type section PSC beam with prestressing and nonprestressing steels for the sensitivity analysis. The analytically calculated sensitivity results are compared with those numerically calculated to ensure the validity of the proposed procedure.

• The Korean Journal of Physiology
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• v.1 no.2
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• pp.181-184
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• 1967

Hypothalamus is one of the most important center regulating voluntary and involuntary function of the body. We studied on the blood glucose and eosinophilic responses induced by electrical hypothalamic stimulation using stereotaxic apparatus. Blood glucose was measured according to Somogyi Nelson method and circulating eosinophil was counted with Hinkleman Stain. For the histological confirmation of electrode placement frozen sections were cut along electrode tract and stained with Hematoxylin-Eosin. The results obtained were as follows: 1. Anterior hypothalamic stimulation mostly leads to hypoglycemia but in some cases lead to hyperglycemia. 2. Hypothalamic stimulation leads to eosinopenia in majority cases. 3. There is no relationship between eosinopenia and hyperglycemia. 4. It appears that sympathetic and pararympathetic areas are not separate part but it coincides each other.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.90-100
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• 2010

Micro-conductive patterns were microfabricated on an insulating substrate ($SiO_2$) surface by a selective electroless nickel plating process in order to investigate the formation of seed layers. To fabricate micro-conductive patterns, a thin layer of metal (Cu.Cr) was deposited in the desired micropattern using laser-induced forward transfer (LIFT). and above this layer, a second layer was plated by selective electroless plating. The LIFT process. which was carried out in multi-scan mode, was used to fabricate micro-conductive patterns via electroless nickel plating. This method helps to improve the deposition process for forming seed patterns on the insulating substrate surface and the electrical conductivity of the resulting patterns. This study analyzes the effect of seed pattern formation by LIFT and key parameters in electroless nickel plating during micro-conductive pattern fabrication. The effects of the process variables on the cross-sectional shape and surface quality of the deposited patterns are examined using field emission scanning electron microscopy (FE-SEM) and an optical microscope.

• Tribology and Lubricants
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• v.2 no.2
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• pp.12-19
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• 1986

Using emulsion lubricant whose cooling effect and incombustibility are good and which is economical, I investigated lubricative mechanism and the behavior of scattered particles in the elastic fluid lubrication region with the line contact between rollers and plates and the light interference system. The results of the study are as follows: (1) The flow in the squeeze oil film is considered as comparatively wide clearance and narrow one, and in the former case the effect of the distribution of particles and the velocity on the flow. In the latter case, emulsion particles stay in the clearance an the oil film changes with the decrease of the oil film thickness. (2) In the wide clearance the velocity difference of the flow O/W or W/O emulsion is inverse proportional to the particle size. In the narrow clearance the distribution of the remained drops is different from one another and the scattered particles change more easily in O/W type than in W/O type. (3) At the beginning of the EHL the stagnation region with slow flowing velocity exists and the behavior at the region is different depending on the particle size. (4) By observing the dischromatic light interference line, emulsion oil passing through EHL region and the crack behavior at the beginning of EHL were found.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4398-4404
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• 2015

Stainless steel sheets are widely used as the structural material for dynamic machine structures, These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding, For fatigue design of gas welded joints such as various type joint. It is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. Thus in this paper, ${\Delta}P-N_f$ curves were obtained by fatigue tests. and, ${\Delta}P-N_f$ curves were rearranged in the ${\Delta}{\sigma}-N_f$ relation with the hot spot stresses at the gas welded joints. Using these results, the accelerated life test(ALT) is conducted. From the experiment results, an life prediction model is derived and factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.