• Asian-Australasian Journal of Animal Sciences
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• 제23권7호
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• pp.946-951
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• 2010

The objective of this research was to evaluate the effects of dietary supplementation of blood meal (BM) as a source of histidine, and magnesium oxide (MgO) as a catalyst of carnosine synthetase, on carnosine (L-Car) content in the chicken breast muscle (CBM), laying performance, and egg quality of spent old hens. Four hundred eighty laying hens (Hy-Line$^{(R)}$ Brown), 95wk old, were allotted randomly into five replicates of six dietary treatments: T1; 100% basal diet, T2; 100% basal diet+MgO, T3; 97.5% basal diet+2.5% BM, T4; 97.5% basal diet+2.5% BM+MgO, T5; 95% basal diet+5% BM, T6; 95% basal diet+5% BM+MgO. Magnesium oxide was added at 0.3% of diets. The layers were fed experimental diets for 5wk. There were no significant differences in the weekly L-Car content in CBM among all treatments during the total experimental period, but some of the contrast comparisions showed higher L-Car in CBM of T6. The L-Car contents linearly decreased (p<0.01 or p<0.05) as the layers got older except in T4 (p>0.05). There were significant differences in egg weight (p<0.01) and soft and broken egg ratio (p<0.05). The control (T1) was highest in egg weight and T6 was lowest in soft and broken egg ratio. Among the parameters of egg quality, there were significant differences in eggshell strength (p<0.01) and egg yolk color (p<0.05). Magnesium oxide supplementation increased the eggshell strength and BM tended to decrease egg yolk color. Eggshell color, eggshell thickness, and Haugh unit were not influenced by BM and MgO. In conclusion, BM and MgO did not significantly influence the L-Car in CBM of spent layers. The L-Car content rapidly decreased as the layers became senescent. Eggshell strength was increased by MgO supplementation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.613-616
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• 2008

최근 결합재로 시멘트를 사용하지 않은 알칼리 활성 콘크리트에 대한 연구가 활발히 진행되고 있다. 이 알칼리 활성 콘크리트는 시멘트 대신에 실리콘(Si)과 알루미늄(Al)이 풍부한 플라이애시와 고로슬래그등을 사용하여 알칼리 용액으로 활성화시킨 시멘트 ZERO 콘크리트로서 CO$_2$ 가스를 저감하는데 효과적이다. 본 연구에서는 시멘트를 전혀 사용하지 않고 결합재로서 고로슬래그를 100% 사용한 알칼리 활성 콘크리트를 개발할 목적으로 감수제, 알칼리 활성화제 및 양생조건이 모르타르의 시공성 및 압축강도에 미치는 영향에 대해 검토하였다. 그 결과, NaOH의 몰 농도가 증가함에 따라 유동성은 저하되나, 9M까지는 유동성 저하가 크지 않고, 대부분의 감수제는 유동성 향상에 기여하지 못하는 것으로 나타났다. 그리고 압축강도는 NaOH의 몰 농도가 증가함에 따라 향상되나, 9M이 가장 효율적인 것으로 나타났다. 또한 양생온도 및 양생조건은 고로슬래그 알칼리 활성 모르타르의 강도에는 큰 영향이 없는 것으로 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1026-1033
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• 2009

Fine ceramics have high strength, excellent wear resistance, chemical stability and high strength at high temperature and are receiving attention in various fields such as construction, engineering, aerospace and marine science. Finish machining process is required to obtain precise ceramics components because sintering process necessary for obtaining high strength and high quality ceramics reduces the dimensions of components and precision of shape. But high strength and brittleness of ceramics materials cause difficulty in processing. So a process for obtaining wanted dimensions is studying using high temperature which makes ceramics softened and thermal affected recently. Laser beam is a very useful optical device for these kinds of processes. Laser process such as laser cutting, laser machining, laser heat treatment and laser-assisted machining(LAM) is researching to manufacture practical ceramics components using intense laser source which can cause local softening and damage of workpiece. In this paper, microstructural and mechanical properties of silicon nitride heated are studied as a basic study for researching of ceramics process by laser beam. The surface variation of HIP and SSN-silicon nitride was analyzed with SEM and EDS. A processing at $1,300^{\circ}C$ or above causes N element to combine into $N_2$ gas and the gas busts from surface. These phenomena make bloat, craters and heat defects on the surface of silicon nitride. Also, oxygen content is largely increased to oxidize the surface and it causes changing of phases and reducing of hardness of surface.

• 대한기계학회논문집A
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• 제38권12호
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• pp.1373-1377
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• 2014

핫스탬핑 공정은 고강도의 강을 얻을 수 있는 방법으로써, 일반적으로 보론강을 오스테나이트 온도까지 가열한 후, 성형과 냉각을 통해 제품을 생산한다. 열처리된 보론강은 1500MPa 이상의 강도를 가지기 때문에 경량화와 안전성을 동시에 향상시킬수 있는 특징이 있다. 뿐만아니라 우수한 성형성으로 인한 치수정밀도가 기존 강판대비 90 % 이상 향상되어 우수한 성형품질을 확보할 수 있는 장점도 있다. 따라서 본 연구에서는 디스크 레이저를 사용하여 핫스탬핑 강판의 맞대기 및 겹치기 용접을 실시하여 용접특성을 파악하였다. 실험결과, 맞대기 용접에서는 맞댄면의 갭에 영향으로 인해 겹치기 용접과 비교하여 더 빠른 속도에서도 완전 용입을 얻을 수 있었으며, 모든 용접부에서 열영향부에서 화이트밴드가 관찰되었다.

• Journal of the Korean Wood Science and Technology
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• 제42권2호
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• pp.163-171
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• 2014

Environmental issues about indoor air quality have been increased and focused on volatile organic compounds (VOCs) caused cancer, asthma, and skin disease. Reducing VOCs has been attempted in many different methods such as using environmentally friendly materials and air cleaner or purifier. Charcoal is well known material for absorbing VOCs. Therefore, carbonized board from medium density fiberboard has been developed. We assumed that the source of carbonized boards can be any type of wood-based panels. In this study, carbonized boards were manufactured from oriented strand board (OSB) at 400, 600, 800, and $1000^{\circ}C$. Each carbonized OSB (c-OSB) was evaluated and determined physiomechanical characteristics such as exterior defects, dimensional shrinkage, modulus of elasticity, and bending strength. No external defects were observed on c-OSBs at all carbonizing conditions. As carbonizing temperature increased, less porosity between carbonized wood fibers was observed by SEM analysis. The higher rate of dimensional shrinkage was observed on c-OSB at $1000^{\circ}C$ (66%) than c-OSB at 400, 600, and $800^{\circ}C$ (47%, 58%, and 63%, respectively). The densities of c-OSBs were lower than original OSB, but there was no significant different among the c-OSBs. The bending strength of c-OSB increased 1.58 MPa (c-OSB at $400^{\circ}C$) to 8.03 MPa (c-OSB at $1000^{\circ}C$) as carbonization temperature increased. Carbonization temperature above $800^{\circ}C$ yielded higher bonding strength than that of gypsum board (4.6 MPa). In conclusion, c-OSB may be used in sealing and wall for decorating purpose without additional artwork compare to c-MDF which has smooth surface.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.95.1-95.1
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• 2012

Very High Temperature gas cooler Reactor (VHTR) has been considered as one of the most promising nuclear reactor because of many advantages including high inherent safety to avoid environmental pollution, high thermal efficiency and the role of secondary energy source. The TRISO coated fuel particles used in VHTR are composed of 4 layers as OPyC, SiC, IPyC and buffer PyC. The significance of CVD-SiC coatings used in tri-isotropic(TRISO) nuclear coated fuel particles is to maintain the strength of the whole particle. Various methods have been proposed to evaluate the mechanical properties of CVD-SiC film at room temperature. However, few works have been attempted to characterize properties of CVD-SiC film at high temperature. In this study, micro tensile system was newly developed for mechanical characterization of SiC thin film at elevated temperature. Two kinds of CVD-SiC films were prepared for micro tensile test. SiC-A had [111]-preferred orientation, while SiC-B had [220]-preferred orientation. The free silicon was co-deposited in SiC-B coating layer. The fracture strength of two different CVD-SiC films was characterized up to $1000^{\circ}C$.The strength of SiC-B film decreased with temperature. This result can be explained by free silicon, observed in SiC-B along the columnar boundaries by TEM. The presence of free silicon causes strength degradation. Also, larger Weibull-modulus was measured. The new method can be used for thin film material at high temperature.

• 한국산학기술학회논문지
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• 제16권8호
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• pp.5721-5727
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• 2015

페인트는 외부로부터 본체가 손상되는 것을 막아주며, 오랫동안 색깔과 마무리 상태를 유지해 준다. 유기용제와 물이 페인트의 용제로 사용되고 있으며, 유기용제는 VOCs의 인위적인 공급원으로 알려져 있다. 이러한 이유로 자동차 내장부품에서 유기용재 페인트의 사용은 줄어들고 있으며, 외장 부품에서는 계속 사용하고 있다. 수성페인트의 접착력은 유성페인트에 비하여 작아, 페인트가 기제로부터 박리되고 있어, 품질문제를 일으킨다. 본 연구에서는 수성페인트와 실린 혼합물의 접착 특성에 대하여 연구하였다. 수성페인트의 접착력을 향상시키기 위하여 접착제와 혼합이 필요하다. 접착력은 UTM을 이용하여 ASTM D1002 방법으로 측정하였고, 박리현상은 ASTM D1002를 사용하여 측정하였다. 수성페인트와 실란접착제의 최적 혼합조건은 $25^{\circ}C$, 500rpm, 20분 이었으며. 실란접착제 농도는 5wt% 이었다

• 한국화재소방학회논문지
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• 제24권4호
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• pp.41-46
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• 2010

고강도 콘크리트는 대형 사회기반 구조물로서 많이 활용되고 있다. 고강도 콘크리트는 우수한 재료적 성능과 내구성을 확보하고 있지만 반면에 화재에 대한 급작스러운 폭렬현상으로 인하여 구조적인 문제를 야기시키기도 한다. 따라서 본 연구에서는 콘크리트 피복두께에 추가하여 내화피복재를 사용함으로써 내화피복두께에 따른 콘크리트의 내화성능을 평가하고 최적의 내화피복두께를 산정하는 실험적 연구를 수행하였다. 내화피복재를 10mm 간격으로 증가시키면서 실험을 수행한 결과 콘크리트의 내화성능이 크게 향상됨을 볼 수 있었으며, 최적의 내화피복두께는 약 1~3mm로 산정되었다. 또한 폭렬에 의하여 급작스러운 콘크리트 내부의 온도상승 이후 기화열에 의한 열손실로 완만하게 온도가 상승되는 현상이 실험적으로 관측되었다. PP 섬유는 약 $200^{\circ}C$ 부근에서 용해되어 고온에서는 빈 채널만 남게 되므로 내부 증기압을 저감시켜주는 역할도 관측되었다.

• Tribology and Lubricants
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• 제37권2호
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• pp.48-53
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• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• 한국표면공학회지
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• 제34권5호
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• pp.435-444
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• 2001

WC-( $Ti_{1-x}$ A $l_{x}$) N coatings of constant changing Al concentration were deposited on S45C substrates by high-ionization sputtered PVD method. The Al concentration could be controlled by using evaporation source for Al and fixing the evaporation rate of the metals (i.e, WC- $Ti_{0.86}$A $l_{0.14}$N, WC- $Ti_{0.72}$A $l_{0.28}$N, and WC- $Ti_{0.58}$A $l_{0.42}$N). The corrosion behavior of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings in a deaerated 3.5% NaCl solution was investigated by electrochemical corrosion tests and surface analyses. The measured galvanic corrosion currents between coating and substrate indicated that WC- $Ti_{0.72}$A $l_{0.28}$N coating showed the best resistance of the coating tested. The results of potentiodynamic polarization tests showed that the WC- $Ti_{0.72}$A $l_{0.28}$N coating deposited with 32W/c $m^2$ of Al target revealed higher corrosion resistance. This indicated that the WC- $Ti_{0.72}$A $l_{0.28}$N coating is effective in improving corrosion resistance. In EIS, the WC- $Ti_{0.72}$A $l_{0.28}$N coating showed one time constant loop and increased a polarization resistance of coating ( $R_{coat}$) relative to other samples. Compositional variations of WC-( $Ti_{1-x}$ A $l_{x}$)N coatings were analyzed by EDS and XRD analysis was performed to evaluate the crystal structure and compounds formation behavior. Surface morphologies of the films were observed using SEM and AFM. Scratch test was performed to measure film adhesion strength.strength. adhesion strength.strength.