• Title/Summary/Keyword: CVI

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Studies on the Mathematical Modelling of the Pulse-CVI for the Infiltration of Siliconcarbide from Methyltrichlorosilane (메틸삼염화규소로부터 탄화규소 침착의 Pulse-CVI에 대한 수치모사 연구)

  • Kim, In-Goo;Kim, Min-Ki;Chung, Gui-Yung
    • Composites Research
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    • v.18 no.5
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    • pp.27-33
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    • 2005
  • In this research, the mathematical modelling of the pulse-CVI (Chemical Vapor Infiltration) for the preparation of siliconcarbide/carbon composite. Each pulse consists with the gas injection time, the reaction time and the evacuation time. Effects of the reaction time and the evacuation time were studied. Additionally, the effects of the reactant concentration and the pressure were observed. The benefits of the pulse-CVI such as the uniform infiltration of siliconcarbide into the carbon preform and the short reaction time were certified.

Translation Study of Miller Assessment of Preschoolers (MAP) for Using in Korea (Miller Assessment for Preschoolers(MAP)의 국내 적용을 위한 번역 연구)

  • Hong, Eunkyoung;Kim, Kyeong-Mi
    • The Journal of Korean Academy of Sensory Integration
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    • v.16 no.1
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    • pp.35-44
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    • 2018
  • Objective : This study aimed to perform a translation, backward translation, item modification, and test of content validity for Korean version of Miller Assessment for Preschoolers (MAP). Methods : Professors in department of occupational therapy, translators, or occupational therapists participated in the processes of translation, comparison and synthesis I, backward translation, comparison and synthesis II, test of understanding, and modify of items. Content Validity Indices (CVI) was calculated for data analysis by using Microsoft Office Excel. Results : Results of comparison between the original MAP and Korean MAP in professor panels were mean $3.66{\pm}0.40$, item-level CVI (I-CVI) 0.94, and overal scale CVI (S-CVI) 0.83. In agreement, result of comparison between of the original MAP and backward translated MAP (version English) was mean 3.14. The erroneous content was omission 13 times, the addition 3 times, the substitution 6 times, erroneous terms 11 times, and reordering 6 times. Average of understanding test in the therapist panels was $3.66{\pm}0.27$. The agreements were I-CVI 0.93 and S-CVI 0.58. Conclusion : Using assessment tools that developed in another country is important to do test of content validity and systematic translation process in Korea. For developing Korean version of MAP, validity and reliability studies need to be followed in near future.

Impact Assessment of Sea_Level Rise based on Coastal Vulnerability Index (연안 취약성 지수를 활용한 해수면 상승 영향평가 방안 연구)

  • Lee, Haemi;Kang, Tae soon;Cho, Kwangwoo
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.27 no.5
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    • pp.304-314
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    • 2015
  • We have reviewed the current status of coastal vulnerability index(CVI) to be guided into an appropriate CVI development for Korean coast and applied a methodology into the east coast of Korea to quantify coastal vulnerability by future sea_level rise. The CVIs reviewed includes USGS CVI, sea_level rise CVI, compound CVI, and multi scale CVI. The USGS CVI, expressed into the external forcing of sea_level rise, wave and tide, and adaptive capacity of morphology, erosion and slope, is adopted here for CVI quantification. The range of CVI is 1.826~22.361 with a mean of 7.085 for present condition and increases into 2.887~30.619 with a mean of 12.361 for the year of 2100(1 m sea_level rise). The index "VERY HIGH" is currently 8.57% of the coast and occupies 35.56% in 2100. The pattern of CVI change by sea_level rise is different to different local areas, and Gangneung, Yangyang and Goseong show the highest increase. The land use pattern in the "VERY HIGH" index is dominated by both human system of housing complex, road, cropland, etc, and natural system of sand, wetland, forestry, etc., which suggests existing land utilization should be reframed in the era of climate change. Though CVI approach is highly efficient to deal with a large set of climate scenarios entailed in climate impact assessment due to uncertainties, we also propose three_level assessment for the application of CVI methodology in the site specific adaptation such as first screening assessment by CVI, second scoping assessment by impact model, and final risk quantification with the result of impact model.

A Study on the Frictio Characteristics of Pitch/CVI and Phenolic Resin/CVI Hybrid Matrix Derived Carbon/Carbon Composites (핏치/CVI계 및 페놀/CVI계를 Matrix로 하는 탄소/탄소 복합재료의 마찰특성 연구)

  • Park, Jong-Gyu;Lee, Jin-Yong
    • Korean Journal of Materials Research
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    • v.6 no.10
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    • pp.986-990
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    • 1996
  • 본 논문에서는 정속마찰 시험기를 사용하여 공기중에서 핏치/CVI계와 페놀/CVI계 낱소/탄소 복합재료의 마찰특성을 평가하고 상호 비교하였다. 운용조건(마찰거리, 마찰속도, 마찰압력)에 관계없이 페놀/CVI계의 평균 마찰계수가 핏치/CVI계 보다 높은 값을 나타내었다. 마찰거리가 4Km이하 일때는 평균 마찰계수가 불안정한 경향을 나타내고 그 이후에서는 안정한 평균 마찰계수 값을 갖는다. 또한 마찰속도와 마찰압력이 증가할수록 평균 마찰계수는 감소하는 경향을 나타내며, 페놀/CVI계의 평균 마찰계수가 핏치/CVI계 보다 높고 마찰면 온도 상승률과 최대 마찰면 온도도 높다. 마찰계수는 마찰면 온도의 영향을 받으며, 마찰속도와 3kg/$\textrm{cm}^2$이하에서 마찰압력이 커질수록 최대 마찰계수를 갖는 마찰면 온도는 높아진다.

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항공기 탑재형 다목적 레이다 신호처리기 설계

  • Kim, Hyoun-Kyoung;Moon, Sang-Man;Kim, Tae-Sik;Lee, Hae-Chang;Kang, Kyoung-Woon
    • Aerospace Engineering and Technology
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    • v.3 no.2
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    • pp.229-237
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    • 2004
  • In this paper, the design method and algorithms of the signal processor for a multipurpose radar system are analyzed. The signal processor, operating at the two modes-collision avoidance mode and weather mode, has 4 steps of ADC, NCI, STC, CFAR. Several algorithms of NCI and CFAR are analyzed and the optimal design is proposed to the system. CVI and CMLD algorithm have good performance in decreasing the false alarm rate and increasing detection probability, Regarding processor computational capacity, K=12 for CVI, M=16~20, Ko=M-4 for CMLD is suggested. CVI processing needs much time, two or more processors need to be allocated to CVI. So, for the system with four processors, two processors should be allocated to VID of NCI with ADC input and CFAR with STC, and two processors are should be allocated to CVI.

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Studies on Effects of Deposition Parameters in Manufacturing of C/Sic composites by Pulse-CVI (C/SiC 복합재료 제조시 Pulse-CVI에서 증착변수의 영향 연구)

  • 김용탁;김영준;정귀영
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2001.10a
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    • pp.141-143
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    • 2001
  • Ceramic fiber-reinforced composites have good mechanical properties in hardness and durability. In this study, we studied the formation of SiC/C composites from methyltrichlorosilane and hydrogen by the Pulse-chemical vapor infiltration(PCVI) to deposit silicon carbide around the changes of the amount of deposit. SiC/C composites formed at $950^{\circ}C$, 20torr, Pulse-times (5s/60s). SEM of the cross sectional area of semple showed deposited silicon carbide around fibers.

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Nicalon-Fiber-Reinfored SiC Composites Via Infiltration (Infiltration 공정으로 제조한 Nicalon 섬유강화 SiC 복합재료)

  • 김민수;김영욱;한경섭;박정현
    • Journal of the Korean Ceramic Society
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    • v.30 no.12
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    • pp.993-998
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    • 1993
  • Nicalon-fiber-reinforced SiC composites were fabricated via polymer solution infiltration/chemical vapor infiltration (PSI/CVI) and CVI. Specifically, data were taken and compared for flexural strength, fracture toughness, and processing time. The two process resulted in comparable mechanical properties, and PSI/CVI process resulted in significantly reduced infiltration time.

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Design and Optimization of TG-CVI Heater (TG-CVI용 히터 형상설계 및 최적화)

  • 이성호;홍성석;구형회
    • Journal of the Korea Institute of Military Science and Technology
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    • v.3 no.2
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    • pp.244-249
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    • 2000
  • Thermal gradient chemical vapor infiltration (TG-CVI) process, which is one of the CVI techniques to densify a porous fiber preform, requires for a heater to have uniform surface temperature distribution. Thus, it is essential to design the shape of the heater and to predict the temperature distribution when the heater has a profile which is not a simple cylinder. In this study, an analytical method has been used to design the inner profile of a conical heater showing uniform temperature distribution, if its outer shape is specified. Temperature distribution on the heater surface has been calculated with the finite difference method and compared with the experimental results. When a heater had a combined profile with a large cone and a small cylinder, temperature was higher in the cylindrical part. To reduce the temperature difference between these areas, a hole-machining method has been proposed including other possible ones. A shape design and optimization program has been made to improve the temperature uniformity of the TG-CVI heater better than that designed with the analytical method.

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A Study on Translation Process into Korean Version of the Life-Space Assessment to Assess Community Mobility for Elderly (노인의 지역사회 이동성을 측정하는 Life-Space Assessment(LSA)의 한국어 번역에 대한 적합성 검증연구)

  • Kim, Jeong-Hui;Chang, Moon-Young
    • The Journal of Korean society of community based occupational therapy
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    • v.7 no.1
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    • pp.49-57
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    • 2017
  • Objective : The purpose of this study to create a translation of Life Space Assessment(LSA) for elderly, which was then tested for content related validity and understanding test. Methods : The translation and content validation process involved direct and backward translation, and the collection of content-related evidence from 6 expert panels and 13 clinician panels. A content validity indices (CVI), means, and standard deviations were used for the analysis of the content validity. Results : The results of the comparison between the original LSA and the Korean LSA with the expert panels were I-CVI showed a very high value of .93. and 1.00, and S-CVI/Ave 0.99. The results of the understanding test were showed a very high value of .92 and 1.00, and S-CVI/Ave 0.97. Conclusion : Korean LSA showed content related validity and understanding test, and illustrated the applicability of LSA in a Korean clinical setting. The results showed LSA can be used a useful tool for evaluating the community mobility of elderly.