• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.445-448
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• 2005

Recently, injection molding process became more popular than ever to produce large quantities of high precision products or optical products. Injection molding products can cause sensorial problems because of high birefringence or deformation from the residual stresses in the optical media. In the present study, we have focussed on the effect of holding and compression pressures on the optical anisotropy remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gap-wise direction. Finally, the value of the birefringence near the wall decreased as the mold temperature increased.

• 소성∙가공
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• 제21권1호
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• pp.30-35
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• 2012

FIM(Film Insert Molding) is an innovative method of producing decorated parts for a wide range of products. Because it requires fewer steps when compared to conventional production methods, the time and cost of manufacturing high quality components can be reduced considerably. In this paper, the effects of processing conditions on the warpage of film-insert molded plate were investigated by using a design of experiments. The dominant factors affecting warpage were mold temperature and holding pressure. Warpage increased with the temperature difference between stationary mold and fixed one. Even when the mold temperature difference was zero, the plate with a film was bent after ejection such that the film side protruded. As holding pressure increased, warpage decreased significantly. In addition warpage increased with time increment for the film-insert molded plates.

• Steel and Composite Structures
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• 제18권2호
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• pp.345-355
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• 2015

In this study, the effects of weld parameters on nugget size and tensile-shear strength of welding joint in electrical resistance spot welding of galvanized DP 600 steel sheets having 1.2 mm were investigated. Taguchi design method has been employed to examine the effects of five parameters of welding current, electrode pressure, welding time, clamping time and holding time by using the $L_{27}(5^3)$ orthogonal array. Results showed that the most effective parameters on tensile shear strength and the nugget size ratio (hn/dn) were found as welding current and welding time, whereas electrode pressure, clamping time and holding time were less effective factors. Max. 545 MPa strength was obtained through proposed optimum conditions by Taguchi technique.

• 공업화학
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• 제18권5호
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• pp.444-448
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• 2007

수분산성 점착제의 점착 물성과 수분산성에 미치는 입자 내 조성의 영향을 알아보기 위하여 다양한 입자 내 조성을 갖는 아크릴계 에멀젼형 점착제를 제조하여 각각의 점착 물성과 수분산성을 조사하였다. 입자 내 단일 조성을 갖는 경우 유지력과 수분산성을 동시에 만족시키기 어려웠으나 입자 내 조성을 hard core/soft shell 형태를 갖게 함으로써 수분산성은 적게 희생하고 유지력을 높일 수 있었다. 또한 메타크릴산/아크릴산(MAA/AA)의 중량비가 4/1인 경우에는 친수성 물질인(AA+MAA) 함량이 core로 갈수록 많은 경우와 shell로 갈수록 많은 경우 모두 유지력은 크게 상승했으나 초기점착력은 크게 낮아졌으며 수분산성은 거의 관찰되지 않았다. 그러나 MAA/AA 중량비가 1/4인 경우는 shell 부분에 (AA+MAA) 함량이 많은 경우에 수분산성이 더 컸으나 유지력은 상대적으로 적게 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.370-375
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• 2005

This paper describes a systematic way of identifying the horizontal coefficient of consolidation for clayey soil under undrained condition and silty soil under partial drained condition by applying an optimization technique to the early part of dissipation data measured from the self-boring pressuremeter strain holding test. An analytical solution developed by Randolph & Wroth (1979) was implemented in normalized form to express the build-up and dissipation of excess pore pressures around a pressuremeter as a function of the rigidity index. Horizontal coefficient of consolidation was determined by minimizing the differences between theoretical and measured excess pore pressure curves using optimization technique. It was found that the proposed optimization technique can evaluate in-situ horizontal coefficient of consolidation rationally, which is similar with that obtained from the piezocone dissipation test. Furthermore, proposed method can evaluate appropriate coefficient of consolidation for soil under partially drained condition.

• 대한가정학회지
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• 제42권7호
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• pp.73-88
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• 2004

The purpose of this study was to understand how consumers perceive the costs of couponing by coupon types and to suggest ways in which coupons should be developed to contribute to consumers' welfare. Costs/benefits of coupons as the most close antecedent variable included the following 8 constructs: searching costs, clipping costs, storing costs, extra expenses, substitution costs, pressure of holding, uncomfortable feelings, and regrets. Since it was hypothesized that the cost of couponing differs by coupon type, four coupon-types were examined: homepage coupon, E-mail coupon, DM coupon, and newspaper/magazine coupon. Data for this research were collected through 732 responses to a self-administered survey of consumers who had used all four types of coupons requesting participation from members of Internet survey firm. The conclusions of this research can be summarized as follows: (1) Women preferred off-line coupons but men preferred on-line coupons. In addition, consumers in Seoul were more familiar and satisfied with on-line coupons than consumers in other regions. (2) Among constructs of costs, consumers perceived regrets, pressure of holding, and substitution costs highly. Differently from previous studies, consumers perceived searching costs and clipping costs to be less important than other costs. (3) Storing costs, pressure of holding, and uncomfortable feelings were higher in off-line coupons, whereas clipping costs, extra expenses, and substitution costs were higher in on-line coupons. (4) In general, most constructs of costs in using homepage and newspaper/magazine coupons were higher than those of E-mail and DM coupons. (5) Cost perception was negatively related to coupon satisfaction at coupon, except newspaper/magazine coupon which was the least satisfactory coupon, regardless of costs (6) Consumers were more satisfied with direct-distribution coupons such as E-mail and DM coupons than public-distribution coupons such as homepage and newspaper/magazine coupons.

• 접착 및 계면
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• 제18권4호
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• pp.166-170
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• 2017

본 연구에서는 2-ethylhexyl acrylate, styrene, butadien, 2-hydroxyethyl acrylate, acrylic acid 등의 단량체 조성과 개시제 함량을 조절하여 아크릴고무 점착제를 합성하였다. 제조된 점착제를 이용하여 점착부여제와 경화제를 변화시켜 초기점착력, 점착력, 유지력, 그리고 내열성을 측정함으로써 그 영향을 조사하였다. 실험 결과 개시제의 함량이 증가하면 분자량이 감소하여 초기점착력과 점착력이 증가하였으나, 유지력과 내열성은 감소하는 것을 확인 할 수 있었다. 점착부여제에 따른 물성 변화는 점착부여제의 함량을 높일수록 일정 수준까지는 점착력이 높아 졌으나, 초기점착력과, 유지력, 내열성에서는 함량변화에 따른 물성변화가 크지 않았다. 경화제 함량에 따른 물성 변화는 경화제의 함량을 높일수록 경화밀도가 증가하여, 초기점착력과 점착력은 감소하였고 반면에 유지력과 내열성은 높아지는 경향을 나타내었다.

• 한국추진공학회지
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• 제21권1호
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• pp.44-50
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• 2017

지상고정장치는 발사체 엔진의 추력이 정상상태에 도달할 때까지 발사체를 발사대에 고정시켜주는 역할을 한다. 본 연구에서는 지상고정장치에 적용되는 구동 유압실린더의 형상 및 운동 특성에 대한 해석적 연구를 수행하였다. 유압 실린더의 수축 운동은 분리 동작에 가장 중요한 요소로서, 해석 결과 실린더의 slit 면적이 축소되고 초기 충전 압력이 증가될수록 수축 하중이 증가함을 확인하였다. 이를 통해 최적화된 slit 면적과 초기 충전압력을 결정하였다. Transient 해석을 통해 실린더가 수축 시 발생하는 하중, 변위, 내부 압력분포를 확인하였다. 해석 결과 실린더가 발생시키는 하중은 실린더에 작용하는 외력과 동일한 값을 발생시키는 것을 확인하였다. 또한 실린더가 운동하는 중에 실린더 내부의 압력분포는 일정한 것을 확인할 수 있었다.

• 대한한방내과학회지
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• 제20권1호
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• pp.222-231
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• 1999

Uwhangchungsimwon(UC) has been used in the treatment of a wide variety of conditions including stroke, hypertension, arteriosclerosis, autonomic imbalance, mental instablity, etc in Korean traditional hospitals, In particular it is often initialy chosen for emergency care of acute stroke. The aim of this study was to evaluate the effect of UC on cerebral hemodynamics. Using transcranial Doppler ultrasound, we studied changes of mean flow velocity and pulsatility index(PI) of middle cerebral arteries (MCAs) from 11 health young volunteers who were administrated with 1 pill UC and 11 health controls who were not. We obtained hypercapnia with breath-holding and evaluated cerebrovascular reactivity with breath-holding index(BHI). Systolic blood pressure, diastolic blood pressure, and heart rate were measured using ambulatory blood pressure monitoring(ABPM). In UC administration group, the evaluation was performed during basal condition. and repeated at 20, 40, and 60 min after administration. In controls, the evaluation was performed at corresponding time intervals. Mean flow velocity in middle cerebral artery, systolic blood pressure, diastolic blood pressure, and heart rate did not change during the observation period and were not different between these two groups. However, administration of UC was associated with decreases in PI by $3.6{\sim}12.4%$ in BHI by $17.9{\sim}24.8%$ compared with pre-administration period. Decreases in PI and BHI with UC were significantly different compared with control group (p<0.05). These results indicate that UC decreases PI and BHI in cerebral artery, which is due to a dilation of cerebral resistance vessels.

• 반도체디스플레이기술학회지
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• 제15권1호
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• pp.12-16
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• 2016

Toluene-free pressure sensitive adhesives were synthesized by using butyl acrylate (BA), 2-hydroxy ethyl acrylate, methyl methacrylate, acrylic acid (AA) as monomers and ethyl acetate as a solvent. The polymerization recipes were designed by changing 1, 3, 5 part per hundreds monomer (phm) of AA content on the basis of 100 BA parts. Two crosslinking agents, ethyl glycol diglycidyl ether (EDGE) and isophorone diisocyanate (IPDI) were added to the synthesized polymers to increase adhesion due to crosslinking. In the measurement of properties, holding power, peel strength, and initial tackiness increased with AA content due to crosslinking between carboxyl group in AA and epoxy group in EDGE and isocyanate group in IPDI. In the comparison of two crosslinking agents, EDGE showed better in the three properties than IPDI by better reaction of epoxy group of EDGE to carboxyl group of AA.