• 한국정밀공학회지
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• 제25권7호
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• pp.55-63
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• 2008

Fine blanking is a process of press shearing which makes it possible to produce the thick sheet metal of the finished surface and the close dimensional accuracy over the whole material thickness in the single blanking operation. In this paper, a plate holder of automotive seat recliner is manufactured by FCF(Flow Control Forming) method using the conventional mechanical press instead of the fine blanking press. Main processes for manufacturing of the plate holder by FCF method are embossing, half blanking and trimming processes. Optimal clearance, stripper force and counter force to increase the dimensional accuracy of the plate holder have been investigated by FE-analysis. As a result of FE-analysis, the clearance for both embossing and half blanking processes was -2%t and the forces of stripper and counter were 25ton and 15ton, respectively. After manufacturing the plate holder by FCF method, the measured dimensional characteristics have been compared with the required specifications as the final product. Although the dimensional accuracy of the plate holder manufactured by FCF method was a little inferior to that by fine blanking process, it was satisfactory in a general sense.

• 한국정밀공학회지
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• 제13권11호
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• pp.114-123
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• 1996

The major objective of the present paper is to estabilish analytical technique in order to closely understand and analyze the actual shearing process. First of all, isothermal and non-isothermal FE-simulation of the shearing process are carried out using finite element software DEFORM. Based on preliminary simulation using DEFORM, the finite element program to analyze two dimensional shearing process is developed. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. It can be seen that the developed program combined with the ductile fracture criterion and element kill method has enabled the achievement of FE-simulation from initial stage to final stage of shearing process. The effects of punch-die clearance on shearing process are also investigated. In order to verify the effectiveness of the proposed technique the simulation results are compared with the known expermental data. It is found that the results of the present work are in close agreement with the published experimental results.

• Design & Manufacturing
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• 제14권2호
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• pp.7-13
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• 2020

For one decades, mobile devices components were made with plastic material, but environmental problems have recently replaced them with metal materials such as aluminum. Generally, aluminum components are mostly produced through cutting, but this process has limitations such as productivity and chip recycling. For this reason, many researches are conducted to improve productivity by replacing with the forging press process for manufacturing mobile device components. After forging process, the flash is remained and it is necessary to eliminate the flash from the final shape of components. In this paper, one-sided clearance for blanking aluminum material wes selected for parameter affected to the dimensional precision. Because the clearance is the most important parameter in blanking process. Deriving the clearance of blanking process for high dimensional precision, five level of one-sided clearance is selected and CAE is used to analyze the dimensional precision for each case.

• Journal of Pharmaceutical Investigation
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• 제28권1호
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• pp.25-33
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• 1998

Intestinal absorption of ${\beta}-lactam$ antibiotics and angiotensin converting enzyme(ACE) inhibitors has been shown to use the carrier-mediated transport system. In vitro experiments have established that the efficacy of uptake by enterocytes depends on an inwardly directed proton gradient. It was suggested that benazepril was mediated by tripeptide transport system and that amoxicillin was transported by dipeptide transport carrier. The aim of this study is to assess the influence of amoxicillin on the intestinal absorption of benazepril using in vitro diffusion chamber and in situ single pass perfusion technique in the rat in order to elucidate whether the above transport systems are competitive or not. We obtained the gastrointestinal pemeability coefficient of amoxicillin, benazepril and both of them using in vitro diffusion chamber. And also the gastrointestinal absorption clearance of amoxicillin, benazepril and both of them using in situ single-pass perfusion method at steady state were calculated. Amoxicillin and benazepril were analyzed by HPLC. The results by the use of diffusion chamber in vitro indicated that the apparent intestinal permeability coefficient of benazepril was significantly(p<0.01) decreased by amoxicillin(45.2%) and vice versa significantly(p<0.01) decreased(89.1%). The results by the in situ gastrointestinal single-pass perfusion method indicated that the intestinal absorption clearance of benazepril was significantly(p<0.05) decreased by amoxicillin (40.2%) and vice versa significantly(p<0.05) decreased(54.8%). These results might suggest that they share the same peptide carrier pathway for oral absorption.

• Tribology and Lubricants
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• 제30권6호
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• pp.337-342
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• 2014

The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrow gap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects of the friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of air and oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speed increases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. The clearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearance causes a decrease in shear stress; thus, the drag torque also decreases according to Newton's law of viscosity. An observation of the effect of the area of contact between transmission fluid and friction plate shows that the drag torque increases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of the fluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum size of the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It is expected that the results from this study can be very useful as a database for clutch design and to predict the drag torque for the initial design with respect to various clutch parameters.

• Tuberculosis and Respiratory Diseases
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• 제44권3호
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• pp.479-492
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• 1997

연구배경 : Isoniazid(INH)와 Rifampicin(RFP)은 강력한 항결핵효과를 가지고 있어 결핵치료에 없어서는 안되는 중요한 약제이지만 우리나라에서는 미국흉부학회에서 추천하는 용량과 다른 용량을 흔히 처방하면서도 적절한 용량에 대한 평가는 미흡하여 결핵의 치료에 혼선을 초래하고 있는 실정이다. 이에 저자들은 정상 한국인에서의 INH, RFP 각각의 약물동력학을 먼저 알아보고, INH 300mg과 INH 400mg복용시, RFP 450mg과 600mg복용시 약통학(pharmacokinetics)적 변화를 비교 분석함으로써 한국인에서 INH, RFP 처방의 기초자료로 제공하고자 본 연구를 시행하였다. 방 법 : 정상인 자원자 22명을 12시간 이상 금식시킨 후 INH 300mg을 복용하게 한 다음, 시간경과에 따른 INH 혈중농도 및 INH 뇨배설량을 High-performance liquid chromatography(HPLC)를 이용하여 측정하였다. 2주후 동일인을 대상으로 INH 400mg을 복용시킨 다음 같은 방법으로 INH 혈중농도 및 뇨배설량을 측정하였다. 마찬가지 방법으로 자원자 20명을 대상으로 RFP 450mg과 600mg을 2주 간격으로 복용시킨 다음, 시간경과에 따른 RFP 혈중농도 및 뇨배설량을 측정하였다. 이 결과를 토대로 최고혈중농도(peak serum concentration, Cmax), 최고혈중농도 도달시간(time to reach to peak serum concentration, Tmax), 혈중반감기, 소실속도상수(elimination rate constank, Ke), 전신 클리어런스(total clearance, CLtot), 신 클리어런스(renalclearance, CLr) 및 신외 클리어런스(nonrenal clearance, CLnr)를 계산하여 비교하였으며, paired t-test로 p value < 0.05 일 경우 통계적으로 의미있는 차이가 있는 것으로 판정하였다. 결 과 : 1) INH 결과 ㄱ) Tmax는 INH 300mg군이 $1.05{\pm}0.34$시간, INH 400mg군이 $0.98{\pm}0.59$시간으로서 두 군간에 차이가 없었고(p > 0.05), 혈중반감기도 INH 300mg군이 $2.49{\pm}0.88$시간, INH 400mg 군이 $2.80{\pm}0.75$시간으로서 두 군간에 차이는 없었다(p>0.05). ㄴ) Cmax는 INH 300mg군이 $4.37{\pm}1.28mcg/mL$, INH 400mg군이 $7.14{\pm}1.95mcg/mL$로서 INH 400mg군에서 유의하게 높았지만(p < 0.01), Ke는 각각 $0.30{\pm}0.07hrs^{-1}$, $0.27{\pm}0.11hrs^{-1}$로서 차이가 없었다(p < 0.05). ㄷ) CLtot은 INH300mg군이 $26.76{\pm}11.80mL/hr$, INH 400mg군이 $21.09{\pm}8.31 mL/hr$로서, INH 400mg군에서 유의하게 낮았다(p < 0.01). 이중 CLr은 각각 $3.04{\pm}1.68mL/hr$, $2.91{\pm}0.77mL/hr$로서 두 군간에 차이가 없었으나(p>0.05), CLnr은 각각 $23.71{\pm}11.52mL/hr$, $18.18{\pm}8.36mL/hr$로서 INH 400mg군에서 유의하게 낮았다(p<0.01). 2) RFP결과 ㄱ) Tmax는 RFP 450m군이 $1.11{\pm}0.41$시간, RFP 600mg군이 $1.15{\pm}0.43$시간으로서 두 군간에 차이가 없었고(> 0.05), 혈중반감기도 RFP 450mg군이 $4.20{\pm}0.73$시간, RFP 600mg군이 $4.95{\pm}2.25$ 시간으로서, 두 군간에 유의한 차이는 없었다(p > 0.05). ㄴ) Cmax는 RFP 450mg군이 $10.12{\pm}2.25mcg/mL$, RFP 600mg군이 $13.61{\pm}3.43mcg/mL$로서 RFP 600mg군에서 유의하게 높았고(p < 0.01), Ke도 각각 $0.17{\pm}0.03hrs^{-1}$, $0.15{\pm}0.03hrs^{-1}$로서 RFP 600mg군에서 통계적으로 유의하게 낮았다(p < 0.01). ㄷ) CLtot은 RFP 450mg군이 $7.60{\pm}1.34mL/hr$, RFP 600mg군이 $7.05{\pm}1.20mL/hr$로서, RFP 600mg군에서 유의하게 낮았다(p < 0.05). 이중 CLr은 각각 $1.41{\pm}0.65mL/hr$, $1.69{\pm}0.61mL/hr$로서 두 군간에 차이가 없었으나(p>0.05), CLnr은 각각 $6.19{\pm}1.56mL/hr$, $5.36{\pm}1.26mL/hr$로서 RFP 600mg군에서 유의하게 낮았다(p < 0.01). 결 론 : 한국인에서는 INH는 300mg이, RFP은 450mg이 적절한 일일용량으로 생각되나 이는 향후 복합적으로 결핵약을 복용하는 실제 결핵환자를 대상으로 한 추시가 필요할 것으로 생각된다.

• 한국산학기술학회논문지
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• 제17권11호
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• pp.483-490
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• 2016

자동차 도어 래치는 스프링, 사출품, 소형 모터 등의 작은 부품들을 조립하여 제조된다. 이를 위해서는 각 부품의 정밀설계 및 조립기술이 요구된다. 도어 래치는 자동차의 문을 열리지 않게 고정시켜 운전자의 안전에 직접적인 영향을 미치는 중요한 역할을 한다. 따라서 본 연구에서는 자동차 도어 래치의 주요 구성요소인 커넥터 단자의 트리밍 시, 롤오버를 저감하고 적합한 유효전단면을 찾기 위한 연구를 수행하였다. 유한요소해석과 실험계획법의 직교배열을 통한 다구찌법을 이용하여 차량용 도어 래치커넥터 단자의 전단면 품질 향상을 위한 최적 설계변수를 설정하였다. 해석에 사용된 설계변수는 클리어런스, 곡률반경, 블랭크 홀딩력이며, 커넥터 단자의 재질은 C2600이다. 해석을 통해 제안된 최적 트리밍 공정 조건은 실험을 통해 검증되었으며, 최종제품의 전단면 형상과 치수가 성형해석 결과와 잘 일치하였다. 이상의 결과로부터 차량용 도어 래치커넥터 단자의 최종 롤오버 및 유효전단면 향상을 위한 최적화에 다구찌법을 유용하게 적용할 수 있음을 알 수 있으며, 트리밍 공정 이외의 다양한 금속성형공정에도 유용하게 적용할 수 있을 것으로 사료된다.

• Journal of Pharmaceutical Investigation
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• 제26권1호
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• pp.33-41
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• 1996

In order to study the effect of phenobarbital(PB) on the hepatic transport of diltiazem(DTZ), $Ca^{2+}$ channel blocker, we used isolated hepatocytes of rat which was intraperitoneally pretreated with phenobarbital sodium(75 mg/kg) for four days once a day. For the isolation of rat liver cells, a modification of the two step procedure of Seglen was used. DTZ was dissolved in incubation buffer to the final DTZ concentrations of 200, 400, 600, 800 and 1000 ng/ml in order to elucidate the uptake characteristics of DTZ by hepatocytes. Reactions were stopped at 10, 20, 30, 45, 60, 90, 120 and 300 sec. The initial velocity was determined by disappearance of diltiazem in the hepatocyte suspension. On the other hand, to determine the effect of PB on the in vitro hepatic intrinsic clearance of DTZ we obtained the metabolism rates of DTZ in the control and the PB-pretreated rat hepatocyte at various time intervals. According to pretreatment with PB, the size of hepatocyte and the amount of protein per $10^6$ cells were significantly (p<0.01) increased from $26.92{\pm}0.1364\;m$ to $35.31{\pm}1.00\;m$ and from $468{\pm}6.5\;{\mu}g/10^6$ cells to $628.8{\pm}12.1{\mu}g/10^6$ cells, respectively. In the case or hepatic uptake of diltiazem, $K_m$ was not different in the normalization by cell numbers and increased from $2.90\;{\mu}M\;to\;13.89\;{\mu}M$ in the normalization by protein amount. $V_max$ was increased regardless of normalization by protein amount and cell numbers, from $1.21\;{\mu}mole/min \;{\cdot}\;mg\;protein\;to\;3.96\;{\mu}mole/min\;{\cdot}\;mg\;protein\;and\;from\;2.38\;{\mu}mole/min\;{\cdot}\;10^6\;cells\;to\;2.83\;{\mu}mole/min\;{\cdot}\;10^6\;cells$, respectively. The in vitro hepatic intrinsic clearance of DTZ was significantly (p<0.01) increased from $0.640{\pm}0.038\;ml/mim\;{\cdot}\;10^6\;cells\;to\;2.385{\pm}0.212\;ml/min\;{\cdot}\;10^6\;cells$ due to PB-pretreatment. These results suggest that the uptake of DTZ by hepatocyte is extremely fast and PB enhances the hepatic intrinsic metabolic clearance of DTZ.