• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.138-139
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• 2005

To measure electrical properties and viscoelasticity of semiconducting materials in power cable, we have investigated dielectric properties and modulus of EEA/acetylene black composite showed by changing the content of acetylene black. The permittivity from experimental result was increased, while tan6 was decreased by an increment of the content of acetylene black. The modulus of specimens was increased according to a increment of a acetylene black content. And modulus was rapidly decreased at the glass transition temperature. The tan$\delta$ of specimens was decreased according to a increment of a acetylene black content.

• The Journal of Korean Physical Therapy
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• 제29권6호
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• pp.303-306
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• 2017

Purpose: Gait variability is defined as the intrinsic fluctuations which occur during continuous gait cycles. Increased gait variability is closely associated with increased fall risk in older adults. This study investigated the influence of attention-demanding tasks on gait variability in elderly healthy adults. Methods: We recruited 15 healthy elderly adults in this study. All participants performed two cognitive tasks: a subtraction dual-task (SDT) and working memory dual-task (WMDT) during gait plus one normal gait. Using the $LEGSys^+$ system, we measured the coefficient of variation (CV %=$100{\times}$[standard deviation/mean]) for participants' stride time, stride length, and stride velocity. Results: SDT gait showed significant increment of stride time variability compared with usual gait (p<0.05), however, stride length and velocity variability did not difference between SDT gait and usual gait (p>0.05). WMDT gait showed significant increment of stride time and velocity variability compared with usual gait (p<0.05). In addition, stride time variability during WMDT gait also significantly increased compared with SDT gait (p<0.05). Conclusion: We reported that SDT and WMDT gait can induce the increment of the gait variability in elderly adults. We assume that attention demanding task based on working memory has the most influence on the interference between cognitive and gait function. Understanding the changes during dual task gait in older ages would be helpful for physical intervention strategies and improved risk assessment.

• 한국구조물진단유지관리공학회 논문집
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• 제3권4호
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• pp.163-171
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• 1999

In this study, we executed fundamental experiment to investigate properties of accelerated carbonation with changing chloride content of concrete used sea sand in order to examine durability. So we obtained the results of following properties of mechanics, durability, concrete with sea sand, determined concrete w/C 30%, 40%, 50%, and fine aggregate 40% and changing containing chloride 0, 0.3, 0.6, $0.9kg/m^3$ by the experiment of accelerated neutralization. The results of this study as follows: 1) As result of changing chloride content of concrete used sea sand augmented in stages $0.3kg/m^3$, accelerated carbonation was increased as increment chloride content. The increment depth was decreased as it went long term age. It was shown the chloride content effected increment of carbonation depth in concrete 2) As a result of changing W/C of concrete used sea sand augmented in stages 10% at a time from 30% to 50%, accelerated carbonation depth of concrete was increased as W/C ratio. 3) As the carbonation concrete used sea sand, compressive strength between 8 weeks and accelerated carbonation depth of 1 weeks, 2 weeks, 4 weeks, 8 weeks was inversion proportion.

• 한국산업융합학회 논문집
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• 제11권4호
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• pp.157-163
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• 2008

The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.120-123
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• 2016

The rotor of a turbomolecular drag pump is generally made of an aluminum alloy. Its surface finish is affected by various processes that the rotor itself undergoes during the manufacturing phase. The impact of different surface finishes on the pumping performances of a turbomolecular pump has been mainly investigated by Sawada et al [1]. The present work aims to broaden the previous bibliographic study to the drag stages of a turbomolecular pump by testing the impact of different surface finishes on the compression ratio of the pump. Experimental tests have been made focusing on two processes: the corundum sandblasting and the glass microspheres shot-peening. Both the processes flatten and/or physically remove EDM melted spheres; in particular, blasted surfaces obtained by glass shot-peening are generally smoother than surfaces obtained by corundum sandblasting. In order to characterize the surface texture left by such processes, preliminary surface roughness measurements have been made on the drag rotor disks of several pumps. The experimental tests conducted on both sandblasted and shot-peened rotors confirms previous results obtained on the turbo stages by Sawada et al. [1], showing that the average roughness of the surface has an impact on the compression ratio of the pump; in particular, an increment in the surface roughness causes a corresponding increment in the compression ratio of the pump and vice versa. For the tested pumps, the higher surface roughness gives a factor of increment of about 2 on the measured hydrogen maximum compression ratio of the pump.

• Journal of the Korean Wood Science and Technology
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• 제43권2호
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• pp.177-185
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• 2015

The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determination of elastic modulus and shear modulus. Different material properties and span to depth ratios were used to analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparent elastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulus evaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson's ratio influenced shear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Different shearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D 198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials could be obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending and correction factor for ASTM D 3044.

• 설비공학논문집
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• 제12권3호
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• pp.309-314
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• 2000

Experimental results for heat transfer characteristics of natural refrigerants R-290, R-600a and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The experimental apparatus is basically a vapour heat pump system, composed of a compressor, a condenser, expansion devices, a evaporator, and some other peripheral devices. The test sections were horizontal double pipe heat exchangers, which were a pair of smoothed tube, having 10.07 mm ID, 12.07 mm OD, and grooved inner fin tube, having 12.70 mm OD, 0.25 mm fin height, and 75 fins. The local evaporating heat transfer coefficients of natural refrigerants were not much affected with the mass velocity than R-22 and it could be interpreted that the local evaporating heat transfer coefficients of R-22 were increased more than those of R-290, R-600a according to the increment of mass velocity. Moreover, the maximum increment of the heat transfer coefficient was found in R-290. The average heat transfer coefficient was obtained the maximum value in R-290 and the minimum value in R-22. It reveals that the natural refrigerant can be used as a substitute for R-22. In the grooved inner fin tube, 70% of the increment of the heat transfer coefficient was obtained compared to the smoothed tube.

• 벤처창업연구
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• 제8권1호
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• pp.51-59
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• 2013

본 연구는 국내 문헌연구와 외식업 성공사례들을 통해 외식업 창업성공요인들을 도출하고, 이 요인들이 경영성과에 미치는 영향을 창업외식업체에 대한 설문조사를 통하여 실증적 연구를 수행하였다. 첫째, 창업자 특성 요인이 경영 성과에 미치는 영향을 분석한 결과, 사회적 기술은 순이익 증가율과 고객 증가율에 유의한 영향을 주는 것으로 나타났으며 창업 준비성은 순이익 증가율, 고객 증가율 및 좌석 회전율에 유의한 결과가 확인되었다. 둘째, 운영 관리 요인에서는 접근성이 고객 증가율과 좌석 회전율에, 시설은 좌석 회전율에, 서비스 역량은 순이익 증가율과 고객 증가율 및 좌석 회전율에, 촉진 활동은 고객 증가율에 각각 유의한 것으로 확인되었다. 셋째, 상품 요인에서는 창업외식업의 경우에 품질지향성이 경영성과에 미치는 영향은 통계적으로 유의하지 않은 것으로 확인되었다. 따라서 본 연구는 외식업의 창업을 위한 요인을 제시함으로써 외식업을 창업하려는 외식창업 준비자 및 기존 외식업 사업자들의 성공전략수립에 기여할 것이다.

• 한국도로학회논문집
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• 제6권2호
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• pp.15-24
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• 2004

산화는 아스팔트에서 대형분자(LMS : Large Molecular Size) 양의 증가를 야기하고 바인더의 경화에 주요 원인이 되므로 바인더 산화를 저감시키면 도로 및 공항 포장의 공용수명 연장을 기대할 수 있다. 바인더 산화는 혼합물을 도로에 깔기 전에 가열된 골재와 혼합하는 동안과 아스팔트 포장이 시공된 후 공용기간 동안에 일어난다. 본 연구에서는 바인더를 단기 및 장기노화 처리 후 LMS의 양적 증가를 HP-GPC (High-Pressure Gel-Permeation Chromatography)의 자료에 근거하여 해석하였다 개질 아스팔트는 LMS의 증가율이 아스팔트의 종류에 따라 다를 지라도 단기노화 후 LMS의 20-30%증가. 장기노화 후 2배 이상의 증가를 나타냈다. 본 연구에서 개질 아스팔트의 노화특성을 관찰하기 위하여 사용된 개질제는 선행 연구에서 큰 역학적 특성 향상을 보인 LDPE(Low-Density Polyethylene)와 SBS(Styrene-Butadiene-Styrene block copolymers) 를 사용하였다. LDPE로 개질한 바인더는 단 장기노화 후 LMS의 증가 비율이 상당히 낮았다. 이와 같이 낮은 LMS의 증가는 LDPE 개질 아스팔트가 노화 처리되는 동안에 일반 아스팔트보다 덜 노화가 진행된다는 것을 의미한다 이는 아스팔트 시멘트 내에 분산된 LDPE 입자가 산화 노화작용을 방해하기 때문인 것으로 보인다.

• 대한두개안면성형외과학회지
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• 제10권1호
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• pp.7-13
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• 2009

Purpose: Endoscopic transnasal correction of the medial orbital fractures cannot be enable to confirm the reduction degree of orbital volume without imaging modalities. We have intended through this study to make a quantative analysis of preoperative orbital volume increment and the reduction degree of that after ethmoidal sinus packing by using CT scan. Methods: In this retrospective study, 22 patients were selected to evaluate the postoperative volume reduction, who took 2 CT scans which are pre- and postoperative under the same protocol. The postoperative CT scan was carried out in about 5 days after the operation with the packing inserted into ethmoidal sinus. The length of bony defect on each section was measured by PACS program and the area of defect was calculated by summing lengths on each section multiplied by the thickness of the section. When the outline of orbit on the slice is drawn manually with a cursor, PACS program measures the area automatically. Orbital volume was calculated from the sum of the area multiplied by the section thickness. Results: The mean dimension of fractured walls was $2.86{\pm}0.99cm^2$. The mean orbital volume of the unaffected orbits was $22.89{\pm}2.15cm^3$ and that of the affected orbits was $25.62{\pm}2.82cm^3$. The mean orbital volume increment of the affected orbits was $2.73{\pm}1.13cm^3$. After surgery, the mean orbital volume of the unaffected orbits was $22.46{\pm}2.73cm^3$ and the mean orbital volume decrease on the surgical side was $2.98{\pm}1.07cm^3$. The estimated correction rate was 118.30%. Conclusion: The orbital volume increment in fractured orbit showed linear correlation with the dimension of fractured area. The orbital volume changes after ethmoidal sinus packing also showed linear correlation with orbital volume increment in fractured orbit. This study showed the regressive linear correlation between the increment of orbital volume and the correction rate. To evaluate the maintenance of reduction state, we think that the further study should be done for comparative analysis of orbital volume change after removal of packing.