• Composites Research
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• 제13권3호
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• pp.9-20
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• 2000

모든 층을 한 방향으로 적층하여 횡방향 굽힘과 축방향 인장운동이 연성되어 나타나는 복합재료 외팔보에 다중횡방향 개구형 크랙이 있는 경우에 대하여 자유진동 특성을 고찰하였다. 모든 크랙 위치에서의 파괴역학적 특성을 스프링 상수로 변환하여 산출하고 크랙사이 구간의 보를 전단변형 및 회전관성효과를 포함하여 해밀톤 원리로부터 운동방정식 및 경계조건을 유도하고, 라플라스 변환법을 사용하여 자유진동 특성에 관한 해를 구하였다. 복합재료의 설계 변수로서 섬유 체적비와 적층각을 설정하였으며, 크랙의 외형적 변수로서 크랙의 갯수, 분포 위치 및 크랙 깊이를 설정하여 이들 변수에 대한 고유진동수 및 모드형상의 변화 경향을 도출함으로써 임의의 다수 크랙이 분포되어 있는 보다 실제적인 상황에서의 진동변화에 근거를 둔 비파괴 검사가 이루어질 수 있는 방안에 대하여 연구하였다. 해석 결과 복합재료 보에 단일 크랙이 있는 경우에 비해 다중 크랙이 있는 경우가 여러 가지 변수에 대해 훨씬 복잡한 형태로 나타나고 있음을 보여준다.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.3106-3106
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• 2001

Imaging spectrometry or hyperspectral imaging is a recent development that makes possible quantitative and qualitative measurement for food quality and safety. This paper presents the research results that a hyperspectral imaging system can be used effectively for detecting fecal (from duodenum, cecum, and colon) and ingesta contamination on poultry carcasses from the different feed meals (wheat, mile, and corn with soybean) for poultry safety inspection. A hyperspectral imaging system has been developed and tested for the identification of fecal and ingesta surface contamination on poultry carcasses. Hypercube image data including both spectral and spatial domains between 430 and 900 nm were acquired from poultry carcasses with fecal and ingesta contamination. A transportable hyperspectral imaging system including fiber optically fabricated line lights, motorized lens control for line scans, and hypercube image data from contaminated carcasses with different feeds are presented. Calibration method of a hyperspectral imaging system is demonstrated using different lighting sources and reflectance panels. Principal Component and Minimum Noise Fraction transformations will be discussed to characterize hyperspectral images and further image processing algorithms such as image band ratio of dual-wavelength images and its histogram stretching with thresholding process will be demonstrated to identify fecal and ingesta materials on poultry carcasses. This algorithm could be further applied for real-time classification of fecal and ingesta contamination on poultry carcasses in the poultry processing line.

• 콘크리트학회논문집
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• 제28권1호
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• pp.41-48
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• 2016

본 연구는 두 종류의 수축저감제를 혼입한 변형경화형 시멘트 복합체(SHCC)의 압축, 인장 및 휨 특성을 평가하기 위하여 계획되었으며, 재령과 수축저감제의 종류 및 혼입률을 변수로 진행되었다. SHCC는 설계기준압축강도 50 MPa이며, 섬유는 PVA 섬유를 2.2% 혼입하였다. 배합에 혼입된 수축저감제는 상변이 물질로 수화현상으로 발생되는 열을 흡수 또는 방출하여 급격한 수축 및 팽창을 제어하는 물질이다. 수축저감제의 혼입에 대한 영향은 선변형 길이변화 실험과 압축, 인장 및 휨 성능의 측면에서 평가되었으며, 수축저감제를 혼입할 경우 초기 재령에서의 수축량이 감소되었다. 또한 수축저감제를 혼입함에 따라 균열 분산 성능과 인장 및 휨 성능이 개선되었다.

• Asian-Australasian Journal of Animal Sciences
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• 제28권3호
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• pp.343-350
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• 2015

Cocoa pod is among the by-products of cocoa (Theobroma cacao) plantations. The aim of this study was to apply a number of treatments in order to improve nutritional quality of cocoa pod for feeding of ruminants. Cocoa pod was subjected to different treatments, i.e. C (cocoa pod without any treatment or control), CAm (cocoa pod+1.5% urea), CMo (cocoa pod+3% molasses), CRu (cocoa pod+3% rumen content) and CPh (cocoa pod+3% molasses+Phanerochaete chrysosporium inoculum). Analysis of proximate and Van Soest's fiber fraction were performed on the respective treatments. The pods were then subjected to an in vitro digestibility evaluation by incubation in rumen fluid-buffer medium, employing a randomized complete block design (n = 3 replicates). Further, an in vivo evaluation of the pods (35% inclusion level in total mixed ration) was conducted by feeding to young Holstein steers (average body weight of $145{\pm}3.6kg$) with a $5{\times}5$ latin square design arrangement (n = 5 replicates). Each experimental period lasted for 30 d; the first 20 d was for feed adaptation, the next 3 d was for sampling of rumen liquid, and the last 7 d was for measurements of digestibility and N balance. Results revealed that lignin content was reduced significantly when cocoa pod was treated with urea, molasses, rumen content or P. chrysosporium (p<0.01) with the following order of effectiveness: CPh>CAm>CRu>CMo. Among all treatments, CAm and CPh treatments significantly improved the in vitro dry matter and organic matter digestibility (p<0.05) of cocoa pod. Average daily gain of steers receiving CAm or CPh treatment was significantly higher than that of control (p<0.01) with an increase of 105% and 92%, respectively. Such higher daily gain was concomitant with higher N retention and proportion of N retention to N intake in CAm and CPh treatments than those of control (p<0.05). It can be concluded from this study that treatment with either urea or P. chrysosporium is effective in improving the nutritive value of cocoa pod.

• 원예과학기술지
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• 제30권2호
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• pp.137-143
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• 2012

Chinese cabbage plant was grown hydroponically for 4 weeks in order to examine the temporal relationship of calcium concentration of the nutrient solution with calcium content in the leaf tissue and susceptibility of the tissue to soft rot disease by $Pectobacterium$ $carotovorum$ ssp. $carotovorum$ (Pcc). Calcium concentration from 0.5 to 32.0 mM was maintained for 1 week using Hoagland & Arnon solution. The calcium content of the leaf was proportionally increased to the concentration of the nutrient in the solution (r = 0.912). In contrast, the severity of soft rot symptom in the young leaves was inversely related with the amount of calcium supplied to the nutrient solution (r = 0.899). Water-soluble chitosan, prepared by hollow fiber filtration (> 100 kDa) was applied into the nutrient solution from 0.0 to 5,000 ppm. The chitosan of 10 ppm was the most effective to promote calcium uptake of the leaf, showing 155% of the control. The same chitosan solution prohibited most soft rot development of the leaf by Pcc, exhibiting only 53% of the control. Among different molecular weight fractions, chitosan fraction obtained from 30-100 kDa molecular weight cut-off promoted calcium uptake the most up to 163% of the control, and reduced the development of soft rot disease recording merely 36% of the control of the leaf tissue. The results obtained in the present study suggest that large scale production of water-soluble chitosan with an optimum molecular weight and its commercial application to Chinese cabbage production will be important to improve yield and quality of the crop.

• Composites Research
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• 제15권1호
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• pp.53-60
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• 2002

본 연구에서는 내열 특성과 구조적인 특성을 갖는 탄소섬유/페놀릭 복합재 내열튜브를 필라멘트와인딩 공법에 의해 제작하고 이들의 구조적인 성능을 평가하였다. 이를 위해 내열튜브의 제작방법을 소개하고 황산용해법을 적용하여 내열튜브에서의 섬유체적비와 기공함유율을 측정하였다. 시편폭을 달리한 인장시편의 기계적 특성을 평가함으로써 강화섬유의 연속성을 나타낼 수 있는 시편형상을 제시하였으며 공정변수를 달리한 내열튜브에서 채취된 인장시편의 기계적 특성을 평가함으로써 내열튜브의 제작을 위한 적절한 공정조건을 결정하였다. 그리고 보증시험을 통해 수집한 음향신호의 분석을 통해 내열튜브에서의 균열진전과 파손양상을 조사하였다. 마지막으로 내열튜브 자체에 대해 보증시험과 파열시험을 수행함으로써 내열튜브 자체의 구조적인 신뢰성을 확인하였다.

• Structural Engineering and Mechanics
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• 제72권6호
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• pp.713-722
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• 2019

Micromechanics is a technique for the analysis of composites or heterogeneous materials which focuses on the components of the intended structure. Each one of the components can exhibit isotropic behavior, but the microstructure characteristics of the heterogeneous material result in the anisotropic behavior of the structure. In this research, the general mechanical properties of a 3D anisotropic and heterogeneous Representative Volume Element (RVE), have been determined by applying periodic boundary conditions (PBCs), using the Asymptotic Homogenization Theory (AHT) and strain energy. In order to use the homogenization theory and apply the periodic boundary conditions, the ABAQUS scripting interface (ASI) has been used along with the Python programming language. The results have been compared with those of the Homogeneous Boundary Conditions method, which leads to an overestimation of the effective mechanical properties. According to the results, applying homogenous boundary conditions results in a 33% and 13% increase in the shear moduli G₂₃ and G₁₂, respectively. In polymeric composites, the fibers have linear and brittle behavior, while the resin exhibits a non-linear behavior. Therefore, the nonlinear effects of resin on the mechanical properties of the composite material is studied using a user-defined subroutine in Fortran (USDFLD). The non-linear shear stress-strain behavior of unidirectional composite laminates has been obtained. Results indicate that at arbitrary constant stress as 80 MPa in-plane shear modulus, G₁₂, experienced a 47%, 41% and 31% reduction at the fiber volume fraction of 30%, 50% and 70%, compared to the linear assumption. The results of this study are in good agreement with the analytical and experimental results available in the literature.

• Asian-Australasian Journal of Animal Sciences
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• 제17권12호
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• pp.1663-1668
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• 2004

This study was carried out to evaluate the potential nutritive value of commonly found grasses collected at native pasture in West Sumatra, Indonesia during dry and rainy seasons. Variables measured included chemical composition, in vitro digestibility, concentration of Ca, P and Mg, gas production and metabolizable energy (ME) content of the grasses. The results showed that species and season had significant effect on chemical composition and mineral concentration. Crude protein content in the dry season ranged from 6.5% (B. decumbens) to 14.4% (P. maximum) and increased slightly from 7.8% (B. decumbens) to 14. 8% (A. compressus) in the rainy season. Data on fiber fraction showed that grass contained more NDF, ADF and ADL in dry season than in rainy season. Data on mineral concentration showed that C. plectostachyus and P. maximum in dry season had higher Ca than those of other species, while in rainy season P. maximum had highest Ca concentration. In dry season, the DMD varied from 50. 4% (P.purpuphoides) to 59.1% (P. purpureum), while in rainy season ranged from 50.3% (A. gayanus) to 61.8% (P. purpureum). The potential and rate of gas production were significantly (p<0.05) affected by species and season. During dry season, potential of gas production ranged from 21.8 ml/200 mg (A. compressus) to 45.1 ml/200 mg (C. plectostachyus), while in rainy season it varied from 35.6 ml/200 mg (A. gayanus) to 47.5 ml/200 mg (P. purpureum). ME content of grasses varied from 6.0 to 8.3 MJ/kg in dry season and increased slightly from 6.4 to 8.6 MJ/kg in rainy season. Both in dry and rainy seasons, the highest ME content was occurred in P. purpureum and C. plectostachyus. In conclusion, nutritive value of the observed grasses in West Sumatra, Indonesia was relatively higher during rainy season compared with dry season. Pennisetum purpureum and Cynodon plectostachyus had the best nutritive value in both dry and rainy seasons.

• 자원리싸이클링
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• 제11권4호
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• pp.11-16
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• 2002

폐자동차 파쇄를 통한 주요구성물질의 분리 및 분석평가를 위한 현장실험을 수행하였다. 모재인 폐자동차 차피로는 국내 자동차 업체에서 제작한 Sonata II, Sephia 및 Prince의 3종을 선택하여 엔진부분과 타이어 및 문짝 등을 미리 제거하고 압축된 상태로 제공받았다. 현장설비의 주요 공정은 pre- 및 main-shredder, 분급기, 자선기, 와류선별기 및 수작업 분리로 구성되어 있었다. shredder 산물의 현장 분리실험결과 철 스크랩이 전체의 60.1%를 차지하여 가장 비중이 높았으며, 알루미늄, 구리 및 아연 등의 비철금속류는 약 2％ 정도인 것으로 나타났다. Light fluff는 fluff 전체 중량의 90% 정도를 차지하는 것으로 관찰되었으며, 5cm undersize 가 70.5%로써 대부분이었고 나머지는 플라스틱, 섬유 및 스폰지 등으로 구성되어 있었다 heavy fluff의 경우에는 고무와 플라스틱이 주구성물질인 것으로 나타났으며, 발열량의 경우 플라스틱이 10,000 cal/gr을 상회하여 가장 높았고 가죽과 고무류가 각각 10.3 및 2.55 wt％의 비교적 높은 CI함량을 보였다.

• Composites Research
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• 제16권3호
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• pp.1-8
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• 2003

금속복합재료 개발을 위한 고온가압 성형공정은 기지재료의 비탄성거동과 성형체 내부의 기공에 대한 충진 과정을 수반하며 이러한 강화공정은 압력, 온도 그리고 강화재와 모재의 상대부피분률과 같은 공정변수의 영향을 받게 된다. 특히 티타늄금속기 복합재료의 강화공정은 강화재와 모재 사이의 기계적 혹은 열적 특성 차이 및 생산환경으로 인한 다양한 형태의 손상이 발생할 수 있으며 따라서 이들을 극복하기 위한 재료특성, 작용압력, 온도, 시간조건 등과 공정에 따른 조직의 진전 등 미소역학적 연구가 수반된 최적의 고온가압강화공정의 개발이 요구되어진다. 이를 위하여 본 연구는 VHP방식을 이용한 SiC／Ti-6Al-4V 연속섬유강화 금속기 복합재료의 강화공정실험을 수행하였으며 특히 미시역학적 접근에 따른 다공성 재료의 구성방정식을 이용하여 보강재와 기지재료의 변형거동과 고온가압공정에 필요한 다양한 조건들을 실험결과와 비교 연구하였으며 유한요소해석을 통해 공정변수와 그에 따른 결과들을 고찰하였다.