• International Journal of Ocean System Engineering
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• 제2권2호
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• pp.106-115
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• 2012

In the present study, TiN and CrN films were coated by arc ion plating equipment onto aluminum alloy substrate, A2024. The film thickness was about 4.65 ${\mu}m$. TiN and CrN films were analyzed by X-ray diffraction and energy dispersive X-ray equipments. The Young's modulus and the micro-Vickers hardness of aluminum substrate were modified by the ceramic film coatings. The difference in Young's modulus between substrate and coating film would affect on the wear resistance. The critical load, Lc, was 75.8 N for TiN and 85.5 N for CrN. It indicated from the observation of optical micrographs for TiN and CrN films that lots of cracks widely propagated toward the both sides of scratch track in the early stage of MODE I. TiN film began to delaminate completely at MODE II stage. The substrate was finally glittered at MODE III stage. For CrN film, a few crack can be observed at MODE I stage. The delamination of film was not still occurred at MODE II and then was happened at MODE III. This agrees with critical load measurement which the adhesive strength was greater for CrN film than for TiN film. Consequently, it was difficult for CrN to delaminate because the adhesive strength was excellent against Al substrate. The wear process, which the film adheres and the ball transfers, could be enhanced because of the increase in loading. The wear weight of ball was less for CrN than for TiN. This means that the wear damage of ball was greater for TiN than for CrN film. It is also obvious that it was difficult to delaminate because the CrN coating film has high toughness. The coefficient of friction was less for CrN coating film than for TiN film.

• 한국토양비료학회지
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• 제45권6호
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• pp.1027-1031
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• 2012

본 연구는 국내에서 대표적으로 이루어지고 있는 녹비작물인 호밀, 트리티케일, 헤어리베치 단파와 트리티케일+헤어리베치 혼파를 대상으로 온실가스인 이산화탄소 저감을 위한 최적의 녹비작물을 선발 하기위하여 수행되었다. 윤작지 녹비작물의 지상부 바이오메스는 트리티케일+헤어리베치 664 kg $10a^{-1}$, 호밀 585 kg $10a^{-1}$, 트리티케일 545 kg $10a^{-1}$이었으며 대조구 대비 트리티케일+헤어리베치 181%, 호밀 160%, 트리티케일 149% 증가하는 경향을 보였다. 녹비작물 재배시기 동안 표토의 유기물 함량이 심토보다 높은 경향을 보였다. 토양 유기물 함량은 호밀 처리구에서 가장 높았고 그 다음이 트리티케일+헤어리베치 순으로 나타났다. 지상부 바이오메스 생산량이 많은 호밀, 트리티케일+헤어리베치 재배구에서 가장 높은 유기물 함량을 보인 것은 탄소함량과 C/N율 때문인 것으로 분석 (Wang et al., 2010)되며 C/N율은 토양 탄소와 밀접하게 관련 있으며 바이오메스 품질 (Mirsky et al., 2008)과 바이오메스 분해율을 결정하는 중요한 요인(Kemp et al., 2003) 이므로 본 연구에서 호밀과 트리티케일+헤어리베치는 녹비작물로 바이오메스 생산량도 높고 토양 탄소 함량 증진에도 효과가 높아 이산화탄소 저감에 효과적일 것이다.

• 한국재료학회지
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• 제5권6호
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• pp.699-705
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• 1995

질화규소 요업체에서 입계상의 변화가 파괴인성에 미치는 영향에 대해 살펴보았다 실험에는 Si$_3$N$_4$-Y$_2$O$_3$-SiO$_2$(YS)계와 Si$_3$N$_4$-Y$_2$O$_3$-A1$_2$O$_3$(YA) 계를 사용하였으며, 175$0^{\circ}C$에서 Can/HIP 처리한 후 1800~200$0^{\circ}C$ 온도구간에서 열처리시키면서 입계상의 변화에 따른 파괴인성의 변화를 조사하였다. 열처리 온도구간에서 입계상이 비정질상만으로 존재하였던 YA계의 경우는 열처리 온도가 증가되어 입성장됨에 따라 파괴인성 값이 증가되었으나, 190$0^{\circ}C$ 이상에서 열처리될 때 입계상이 결정상에서 비정질상으로 변화하였던 YS계의 경우는 오히려 파괴인성 값이 급격히 감소되었다. YS계에서 파괴인성의 급격한 저하는 열처리 온도 증가에 따라 입계상이 결정상과 비정질상의 공존 상태에서 비정질상만의 상태로 전이하며 파괴거동에 영향을 미쳤기 때문이라고 생각된다.

• 대한기계학회논문집A
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• 제33권9호
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• pp.957-962
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• 2009

Sialon was produced by hot-pressing the mixtures of $Si_3N_4$, AlN and $Y_2O_3$ powders. All fracture tests were performed on a three-point loading system with a 30 mm bending span. Fracture toughness and Vickers hardness of smooth specimen were average 7.05 $MPa{\cdot}m^{0.5}$ and Hv = 1580, respectively. Density of three kinds of specimens, smooth specimen, smooth and healed specimen, smooth with $SiO_2$ colloidal coating and healed specimen, had beyond 99 % of theoretical density. Bending strength of smooth healed specimens had high strength more than 1 GPa. Crack healed specimens recovered as strength as smooth specimen. That is, cracked specimen with $SiO_2$ colloidal coating on cracked part recovered strength by heat treatment, completely. Crack healing of $Si_3N_4$ composite ceramics had contributed glassy $SiO_2$ to strength recovery. Limiting high temperature for bending strength of heat treated smooth specimen for bending strength was about 1273 K.

• Journal of Advanced Marine Engineering and Technology
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• 제34권7호
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• pp.963-970
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• 2010

This study makes an estimate of the laser-assisted machining (LAM) of an economically viable process for manufacturing precision silicon nitride ceramic parts using a high-power diode laser (HPDL). The surface is locally heated by an intense laser source prior to material removal, and the resulting softening and damage of the workpiece surface simplify the machining of the ceramics. The most important advantage of LAM is its ability to produce much better workpiece surface quality compared to conventional machining. Also important are its larger material removal rates and longer tool life. The cutting force and surface temperature were measured on-line using a pyrometer and a dynamometer, respectively. Tool wear, chips and the surface of the workpiece were measured using optical microscopy, and the surface and fractured cross-section of $Si_3N_4$ were measured by SEM. During the LAM process, the cutting force and tool wear were reduced and oxidation of the machined surface was increased according to the increase in the laser power. Moreover, the more the feed rate increased, the more the cutting force and tool wear increased.

• 한국축산식품학회지
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• 제31권5호
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• pp.631-640
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• 2011

Milk oligosaccharides are the complex mixture of six monosaccharides namely, D-glucose, D-galactose, N-acetyl-glucosamine, N-acetyl-galactosamine, L-fucose, and N-acetyl-neuraminic acid. The mixture is categorized as neutral and acidic classes. Previously, 25 oligosaccharides in bovine milk and 115 oligosaccharides in human milk have been characterized. Because human intestine lacks the enzyme to hydrolyze the oligosaccharide structures, these substances can reach the colon without degradation and are known to have many health beneficial functions. It has been shown that this fraction of carbohydrate can increase the bifidobacterial population in the intestine and colon, resulting in a significant reduction of pathogenic bacteria. The role of milk oligosaccharides as a barrier against pathogens binding to the cell surface has recently been demonstrated. Milk oligosaccharides have the potential to produce immuno-modulation effects. It is also well known that oligosaccharides in milk have a significant influence on intestinal mineral absorption and in the formation of the brain and central nervous system. Due to its structural resemblance, bovine milk is considered to be the most potential source of oligosaccharides to produce the same effect of oligosaccharides present in human milk. This review describes the characteristics and potential health benefits of milk oligosaccharides as well as the prospects of oligosaccharides in bovine milk for use in functional foods.

• 센서학회지
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• 제31권1호
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• pp.31-35
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• 2022

The efficacy improvement of the light emitting diode (LED) was studied for the realization of small-size, low power consumption, and highly sensitive bio-sensor instrument. The performance of the LED with Mg delta-doping at the interface of AlGaN/GaN super-lattice in p type cladding layer was simulated. The device with Mg delta-doping showed improved current, radiative recombination rate, electroluminescence, and light output power compared to the conventional LED structure. Under the bias condition of 5 V, the improved device exhibited 20.8% increase in the light output power. This is attributed to the increment of hole concentration from stable ionization of Mg in p type cladding layer. This result is expected to be used for the miniaturization, power saving, and sensitivity improvement of the bio-sensor system.

• 한국자동차공학회논문집
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• 제24권4호
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• pp.425-431
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• 2016

The usage of Friction Stir Welding(FSW) technology has been increasing in order to reduce the weight in automobile industries. Previous studies that investigated on the FSW have focused on the aluminum alloy. In this study, Al6061-T6 alloy plates having 5 mm of thickness were welded under nine different conditions from three tool rotation speeds: 900, 1000 and 1100 rpm, and three feed rates: 270, 300 and 330 mm/min. Specimen size of Micro Shear Punch(MSP) test was $10{\times}10{\times}0.5mm$. The mechanical properties were evaluated by MSP test and Analysis of Variance (ANOVA). The specimens were classified by advancing side(AS), retreating side(RS), and center(C) of width of tool shoulder. The optimal welding condition of FSW based on micro strengh was obtained when the tool rotation speed was 1100 rpm and the feed rate was 300 mm/min. The maximum load measured AS, RS, and C in the weldment was measured 554.7 N, 642.9 N, and 579.2 N, respectively.

• 한국시뮬레이션학회논문지
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• 제5권1호
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• pp.29-29
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• 1996

This paper describes a new automated simulation system for micromachines whose size range $10^{-6}$ to $10^{-3}$ m. An automic finite element (FE) mesh generation technique, which is bases on the fuzzy knowledge processing and computation al geometry technique, is incorporated into the system, together with one of commerical FE analysis codes, MARC, and one of commerical solid modelers, Designbase. The system allows a geometry model of concern to be automatically converted to different FE models, depending on physical phenomena of micromachines to be analyzed, i,e. electrostatic analysis, stress analysis, modal analysis and so on. The FE models are then automatically analyzed using the FE analysis code. Among a whole process of analysis, the definition of a geometry model, the designation of local node patterns and the assignment of material properties and boundary conditions onto the geometry model are only the interactive process to be done by a user. The interactive operations can be processed in a few minutes. The other processes which are time consuming and labour-intensive in conventional CAE systems are fully automatically performed in a popular engineering workstation environment. This automated simulation system is successfully applied to evaluate an electrostatic micro wobble actuator.

• 대한전자공학회논문지
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• 제25권5호
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• pp.509-521
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• 1988

In the designs of integrated circuits, the buffer circuits used for driving a large capacitive load from minimum-structured logic circuit outputs have important effects upon system throughputs. Therefore it is important to optimize the buffer circuits. In this paper, the principle of designing CMOS buffer circuits which have the minimum delay and drive the given capacitive load is discussed. That is, the effects of load capacitance upon rise time, fall time, and delay of the CMOS inverter and the effects of parasitic capacitances are finely analysed to calculate the requested minimum-delay CMOS buffer condition. This is different from the method by C.A. Mead et. al.[2.3.4.]which deals with passive-load-nMOS buffers. Large channel width MOS transistor stages are necessary to drive a large capacitive load. The effects of polysilicon gate resistances of such large stages upon delay are also analysed.And, the area of buffer circuits designed by the proposed method is smaller than that of buffer circuits designed by C.A. Mead's method.