• Asian-Australasian Journal of Animal Sciences
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• 제22권1호
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• pp.131-138
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• 2009

Among rumen microbes, bacteria play important roles in the biological degradation of plant fiber due to their large biomass and high activity. To maximize the utilization of fiber components such as cellulose and hemicellulose by ruminant animals, the ecology and functions of rumen bacteria should be understood in detail. Recent genome sequencing analyses of representative fibrolytic bacterial species revealed that the number and variety of enzymes for plant fiber digestion clearly differ between Fibrobacter succinogenes and Ruminococcus flavefaciens. Therefore, the mechanism of plant fiber digestion is also thought to differ between these two species. Ecology of individual fibrolytic bacterial species has been investigated using pure cultures and electron microscopy. Recent advances in molecular biology techniques complement the disadvantages of conventional techniques and allow accurate evaluation of the ecology of specific bacteria in mixed culture, even in situ and in vivo. Molecular monitoring of fibrolytic bacterial species in the rumen indicated the predominance of F. succinogenes. Nutritive interactions between fibrolytic and non-fibrolytic bacteria are important in maintaining and promoting fibrolytic activity, mainly in terms of crossfeeding of metabolites. Recent 16S rDNA-based analyses suggest that presently recognized fibrolytic species such as F. succinogenes and two Ruminococcus species with fibrolytic activity may represent only a small proportion of the total fibrolytic population and that uncultured bacteria may be responsible for fiber digestion in the rumen. Therefore, characterization of these unidentified bacteria is important to fully understand the physiology and ecology of fiber digestion. To achieve this, a combination of conventional and modern techniques could be useful.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1456-1469
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• 2000

Mechanical behaviors of uniaxially fiber-reinforced metal matrix composites under transverse loading conditions were studied at room and elevated temperatures. A mono-filament composite was selecte d as a representative analysis model with perfectly bonded fiber/matrix interface assumption. The elastic-plastic and visco-plastic models were investigated by both theoretical and numerical methods. The product of triaxiality factor and effective strain as well as stress components and strain energy was obtained as a function of location to estimate the failure sites in fiber-reinforced metal matrix composite. Results showed that fiber/ matrix interfacial debond plays a key role for local failure at the room temperature, while void creation and growth in addition to the interfacial debond are major concerns at the elevated temperature. It was also shown that there would be an optimal diameter of fiber for the strong fiber-reinforced metal matrix composite.

• 대한기계학회논문집
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• 제12권6호
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• pp.1238-1245
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• 1988

본 연구에서는 단섬유가 첨가된 복합재료의 마찰 및 마멸특성에 대하여 보고 하고자 하며, 최근 공업용 고분자(engineering plastic)로 중오시되고 있는 PAI를 모 재로 하여 탄소섬유(graphite fiber), 유리섬유(glass fiber), TiO$_{2}$ 등이 첨가된 복합재료의 트라이볼로지(tribology) 특성에 대하여 고찰하고자 한다. 본 연구에서 사용된 복합재료에 포함된 단섬유들은 일정한 배열방향이 없이 마구잡이로 분포되어 있으며, 섬유특성에 따라 마멸메카니즘에 큰 차이가 있음을 본 연구 결과를 통하여 알 수 있다.

• 소성∙가공
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• 제29권1호
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• pp.27-36
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• 2020

The Goss texture component of {110}<001> is well known as one of the best texture components to improve the magnetic properties of electrical steel sheets. The small amount of the Goss texture component is obtained at the surface of the steel sheet by shear deformation due to friction between the steel sheet and the roll during conventional symmetric rolling. This study aims to identify a method to obtain high intensity of the Goss texture component not only at the surface but in the whole layer of the steel sheet by shear deformation of asymmetric rolling. Low carbon steel sheets, which have different initial texture, were asymmetrically rolled by about 50%, 70%, and 80%. The pole figures of the top, center, and bottom layers of the initial and asymmetrically rolled low carbon steel sheets were measured by an X-ray diffractometer. Based on the measured pole figures of these samples, the intensities of the main texture components were analyzed for the initial and asymmetrically rolled low carbon steel sheets. As a result, the initial low carbon steel sheet with the γ-fiber component showed a higher intensity of the Goss texture component in the whole layer than the steel sheet with other texture components after asymmetric rolling.

• 열처리공학회지
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• 제17권2호
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• pp.101-105
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• 2004

After extrusion, cold rolling and T-6 treatment, texture development of 7x1x Al-alloy with 0.1% Sc is studied. During extrusion the very strong <111>+weak <100> fiber texture is developed, which is Influenced on the formation of rolling texture. The texture after 80% cold rolling can be described by strong{112}<111>(Cu)+{123}<634>(S) component in the cross section of the extruded rod, the strong -fiber+weak{110}<001>(Goss) components in the longitudinal section, and the strong {110}<112>(Bs)+weak{001}<100>(Cube) components in the transverse section. The components of rolling texture are remained after T-6 treatment, but the maximum density of ODF is higher. The calculated mean r-values and the planar anisotropy are relatively high, which are dependent on the texture. After T-6 treatment, recrystallized equiaxed grains with average grain size of $1{\sim}2{\mu}m$ are obtained.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.223-226
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• 2003

Due to the potential application to ultra-high strength fibers and excellent properties such as high mechanical properties, excellent thermal endurance and chemical stability, thermotropic liquid crystal polymers (TLCPS) are attractive in recent years [1, 2]. Furthermore, the melt blends of TLCPS and conventional thermoplastics have been extensively investigated because of their easy processing and high performance [3-6]. Since high performance polymers generally has high melt viscosity, introduction of the relatively low viscosity components may be one of the more effective techniques to improve processability through the decrement of melt viscosity in melt processing. (omitted)

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.184-187
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• 2002

Compression molding was specifically developed for replacement of metal components with composites. As the mechanical properties of the products are dependent on the separation and orientation, it is important to research the fiber mat structure and molding conditions. In this study, the effects of the fiber mat structure(NP: 5, 10, 25punches/$\textrm{cm}^2$) and the mold closure speed($\dot{\textrm{h}}$=0.1, 1, 10mm/min) on the viscosity of composites were discussed. The composites is treated as a Non-Newtonian power-law fluid. The parallel-plate plastometer is used and the viscosity is obtained from the relationship between the compression load and the thickness of the specimen.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.840-843
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• 2004

UV molding is a process for integrating micro/nano polymeric optical components on optoelectronic modules. In the present study, a microlens array for vertical cavity surface emitting laser(VCSEL) to fiber coupling was designed, integrated and tested. At the design stage, design variables ware optimized to maximize the coupling efficiency, and tolerance analysis was carried out. At the integration stage, the UV transparent mold was fabricated and the microlens array on VCSEL array was integrated by UV molding process. Finally the coupling efficiency of VCSEL to fiber was measured and analyzed.

• 한국환경보건학회지
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• 제27권3호
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• pp.107-112
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• 2001

This work reports the application of a hollow fiber module(HFM) for Cr(VI) extraction from heavy metal salts mixed solution by using microporous hydrophobic hollow fiber module. In HFM configuration, the organic extraction used for the extraction of Cr(VI) was di-(2-ethyl hexyl) phosphoric acid(D2EHPA) diluted with n-heptane. The study of HFM includes the influence of hydrodynamic and chemical condition, i.e., the flow rate of feed solution, the time of reactive extraction, the concentration of feed solution, and the pH of aqueous phase solutions. Several experiments with synthetic solution of different mixed components system of Cr(VI) solutions established optimum condition to achieve a clean separation of Cr(VI). It was possible to separate Cr(VI) in the presence of metal salts mixed solution, such as Zn(II), Ni(II), Cu(II), and Cd(II) using the HFM technique.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.155-160
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• 2001

In the use of glass fiber reinforced plastics(GFRP) it is often necessary to cut the components, but the cutting of GFRP is often made difficult by the delamination of the compositions and short tool life. Experimental investigation was conducted to evaluate the chip formation of the glass fiber reinforced plastics during orthogonal cutting. The chip formation process, cutting force, and thrust force were studied. The chip formation processes were studied through the use of quick-stop device. Chip-tool contact areas were obtained with the use of the quick-stop device, and observed using optical microscopy after polishing. Cutting force and thrust force were measured through the use of the tool dynamometer.