• 제목/요약/키워드: Heat Transmission

검색결과 576건 처리시간 0.021초

저온 캡슐화에 의한 Weissella cibaria CMU의 생존율 증진 효과 (Enhancement of Viability of Weissella cibaria CMU by Low-Temperature Encapsulation)

  • 이다언;황효정;조유나;정태환;한경식
    • Journal of Dairy Science and Biotechnology
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    • 제36권3호
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    • pp.171-177
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    • 2018
  • In this study, we aimed to investigate the effects of low-temperature encapsulation on the viability of Weissella cibaria CMU under harsh conditions and in freeze-dried foods during storage. The capsules were prepared by gelation of sodium caseinate at different concentrations (5%, 6%, 7%, and 8%) with a combination of 0.5% gellan gum and 2% $glucono-{\delta}-lactone$. The size distribution of the capsules was determined using a Mastersizer 3000 laser diffraction particle size analyzer. Scanning and transmission electron microscopy revealed that the capsule with 6% sodium caseinate had a smooth and rounded external surface, with reproducibility. The acid, bile, and heat tolerances of the encapsulated cells were significantly higher than those of the control under prolonged acid (5 h), bile (12 and 24 h), and heat (2 h) exposure, respectively. During storage for up to 6 months at $4^{\circ}C$ or $25^{\circ}C$, the viability of encapsulated Weissella cibaria CMU in beef and vegetable rice porridge was effectively improved.

질소 이온 주입시킨 7050Al합금의 표면 미세구조 변화와 저주기 피로거동 (The Surface Modification and Low Cycle Fatigue Behavior of N+ion Implantated 7050Al Alloy)

  • 이창우;권숙인
    • 열처리공학회지
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    • 제7권4호
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    • pp.307-317
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    • 1994
  • The surf ace microstructure modification by $N^+$ ion implantation into 7050Al alloy and its low cycle fatigue behavior were investigated. Ion implantation method is to physically implant accelerated ions to the surface of a substrate. High dose of nitrogen($5{\times}10^{17}ions/cm^2$) were implanted into 7050Al alloy using current density of accellerating voltage of 100KeV. The implanted layers were characterized by Electron Probe-Micro Analysis(EPMA), Auger Elecron Spectroscopy(AES), X-Ray Diffraction(XRD), X-Ray Photoelectron Spectroscopy(XPS), and Transmission Electron Microscopy(TEM). The experimental results were compared with computer simulation data. It was shown that AlN was formed to 4500 ${\AA}$ deep. The low cycle fatigue life of the $N^4$ion modified material was prolonged by about three times the unimplanted one. The improved low cycle fatigue life was attributed to the formation of AlN and the damaged region on the surface by $N^+$ ion implantation.

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Fe계 합금 분말 소결품(SMF9060)의 마모 특성 연구 (A Study on Tribological Characteristics of Powder Sintered Fe-base Alloy (SMF9060))

  • 김상윤;김대욱;박영민;신동철;김태규
    • 열처리공학회지
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    • 제27권2호
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    • pp.65-71
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    • 2014
  • SMF9060 material is a Fe-based powder sintered alloy that is used for several automobile components such as Synchronize Hub, oil pump and transmission. These components are required excellent wear resistance and durability. In this study, we have performed a dry wear test at the ambient air and Ar gas conditions in the room temperature, and a lubricant wear test at the room temperature and engine oil temperature of $100^{\circ}C$. The amount of wear volume and coefficient friction are measured by a Profilometer and a Ball on disk type wear tester. The wear volume in Ar gas condition was a little higher than that in the ambient air condition. However the wear volume in the lubricant wear condition was much lower than in the dry wear condition. XRD analysis of the debris in Ar gas condition showed that the oxide film was not formed.

듀얼 소스 증착장치를 이용한 Ni-C 박막의 특성에 관한 연구 (A Study on the Characterization of Ni-C Thin Films Utilizing a Dual-Source Deposition System)

  • 한창석;전창환;한승오
    • 열처리공학회지
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    • 제21권5호
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    • pp.235-243
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    • 2008
  • Ni-C composite films were prepared using a combination of microwave plasma CVD and ion beam sputtering deposition working in a codeposition way. The structure of these films was characterized by energy-dispersive X-ray diffraction (EDXRD), transmission electron microscopy (TEM) and Raman spectroscopy. It was found that a nickel carbide phase, $Ni_3C$ (hcp), formed as very fine crystallites over a wide temperature range when Ni-C films were deposited at low $CH_4$ flow rates. The thermal stability of this nonequilibrium carbide $Ni_3C$ was also studied. As a result, the $Ni_3C$ carbide was found to decompose into nickel and graphite at around $400^{\circ}C$. With high $CH_4$ flow rates (> 0.2 sccm), the structure of the Ni-C films became amorphous. The formation behavior of the carbide and amorphous Ni-C phases are discussed in relation to the electrical resistivity of the films.

미세석출상을 포함하는 $L1_2$형 규칙 $Ni_3Al$의 변형조직에 관한 연구 (A Study on the Deformation Induced Microstructure $L1_2$-ordered $Ni_3Al$ Containing Fine Precipitates)

  • 한창석;이준
    • 열처리공학회지
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    • 제21권5호
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    • pp.251-258
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    • 2008
  • A transmission electron microscope investigation has been performed on the morphology of dislocations in deformed ${\gamma}^{\prime}-Ni_3(Al,Ti)$ alloys containing fine dispersion of disordered ${\gamma}$ particles. Superlattice dislocations dissociate into fourfold Shockley partial dislocations in a uniform supersaturated solid solution of the ${\gamma}^{\prime}$ phase. Dislocations are attracted into the disordered ${\gamma}$ phase and dissociate further in the particles. At any stage of aging, dislocations cut through the particles and the Orowan bypassing process does not occur even in the over-aged stage of this alloy system. The work necessary to pull the dislocation away from the disordered particles into the ordered matrix should mainly contribute to increase the strength of the ${\gamma}^{\prime}$ phase containing fine dispersion of the disordered ${\gamma}$ phase.

Modification of DC Flashover Voltage at High Altitude on the Basis of Molecular Gas Dynamics

  • Liu, Dong-Ming;Guo, Fu-Sheng;Sima, Wen-Xia
    • Journal of Electrical Engineering and Technology
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    • 제10권2호
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    • pp.625-633
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    • 2015
  • The effect of altitude on thermal conduction, surface temperature, and thermal radiation of partial arc was investigated on the basis of molecular gas dynamics to facilitate a deep understanding of the pollution surface discharge mechanism. The DC flashover model was consequently modified at high altitude. The validity of the modified DC flashover model proposed in this paper was proven through a comparison with the results of high-altitude simulation experiments and earlier models. Moreover, the modified model was found to be better than the earlier modified models in terms of forecasting the flashover voltage. Findings indicated that both the thermal conduction coefficient and the surface thermodynamics temperature of partial arc had a linear decrease tendency with the altitude increasing from 0 m to 3000 m, both of which dropped by approximately 30% and 3.6%, respectively. Meanwhile, the heat conduction and the heat radiation of partial arc both had a similar linear decrease of approximately 15%. The maximum error of DC pollution flashover voltage between the calculation value according to the modified model and the experimental value was within 6.6%, and the pollution flashover voltage exhibited a parabola downtrend with increasing of pollution.

Al-Cu-Li-X(In, Be) 합금의 기계적 성질에 미치는 저융점상의 영향 (The Effect of Low Melting Point Phase on Mechanical Properties of Al-Cu-Li-X(In, Be) Alloys)

  • 이종수;이승호;김석원;우기도
    • 열처리공학회지
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    • 제8권4호
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    • pp.245-254
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    • 1995
  • The purpose of this study was to examine the effects of low melting point phase(LMPP) on mechanical properties in the Al-Cu-Li-X(In, Be) alloys. This study was performed by the differential scanning calorimetry(DSC), the transmission electron microscope(TEM), hardness test, tensile test and notch tensile test. The shape of LMPP in the specimens homogenized at $570^{\circ}C$ was film type due to remelting at grain boundary during homogenization. Low melting point phases had no effects on mechanical properties in the aging treated materials, because the density of LMPPs was low. Mechanical properties of the aging treated materials were affected by the density of matrix precipitation phases and grain sizes. For the In or In, Be added Al-Cu-Li alloys, the optimum solution treatment temperature was $550^{\circ}C$. The strength of Al-Cu-Li-In-Be $T_6$ treated alloy was higher than that of 2090-$T_8$ alloy.

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열교부위를 고려한 커튼월 사무소 건물의 열성능 해석에 관한 연구 (A Study on the Thermal Performance Analysis of Curtain Wall Office Building Considering the Thermal Bridges)

  • 신우철;김승철;윤종호
    • 한국태양에너지학회 논문집
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    • 제31권3호
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    • pp.95-100
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    • 2011
  • Currently, office buildings in Korea tend to adopt as their outer wall the curtain wall structure which can be easily constructed and has beautiful external appearance as well. However, the problem is that the curtain wall structure does not have a uniform composition unlike the wall of existing reinforced concrete structures and has a frame made of metal with high heat conduction. Therefore, it is expected that the structure will be highly influenced by the thermal bridge. Thereupon, this study analyzes how to set up the composition of the wall system and heat transmission rate in consideration of the thermal characteristics of the curtain wall structure and applies it in practice by simulation in order to propose a guideline for the energy simulation method of the curtain wall structure and analyze its differences from existing simulation methods.

HAZ TOUGHNESS AND MICROSTRUCTURE IN HIGH NITROGEN AUSTENITIC STAINLESS STEEL

  • Sato, Yoshihiro;Shiotsu, Tomoya;Nakagawa, Takafumi;Kikuchi, Yasushi
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.38-42
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    • 2002
  • HAZ(Heat Affected Zone of weldm ents) properties were investigated for a high nitrogen austenitic stainless steel with a chemical composition of Fe-0.02C-0.15Si-6.00Mn-10.0Ni-23.0Cr-2.00Mo-0.48N-0.14V. Thermal cycle of HAZ was simulated by the thermal cycle simulator (Gleeble 1500). The heat treatment was applied to the Charpy test size sample without notch under various peak temperatures and/or the holding times condition. V-notch Charpy test was performed at the temperature range of 273~77 K. Metallographic examination also was carried out by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The simulated specimens revealed a slight embrittlement compared with the base materials. The impact toughness of the specimens deteriorated with the decreasing test temperature. The results from Charpy V-notch test, however, showed that significant degradation of absorbed energy caused by brittle fracture was not observed for the specimen tested in the test temperature range.

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원통기어의 다단면 치형 측정평가 (The Evaluation of Cylindrical Gear Measurement on Teeth Roots and Bottom Profiles in Different Sections)

  • 문성민;강재화;키도히로미쯔;구로가와슈헤이;류성기
    • 한국기계가공학회지
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    • 제11권1호
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    • pp.46-49
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    • 2012
  • Gears are reliable and efficient power transmission elements. They have been widely used in all kinds of machinery. Nowadays, resource conservation energy conservation environmental improvements from the request of the compact, light weight, high efficiency, low cost Higher efficiency is required. Tooth root and bottom profiles of cylindrical gears affect bending fatigue life, but they are hard to measure with conventional gear measuring machine(GMM), because GMM is normally customized to measure only gear working flanks. The authors try to develop a new type of GMM by installing an extra 3D scanning probe and control software to measure tooth root and bottom profiles. First, in order to measure in various directions, a 3D scanning probe has been attached to the GMM developed. Next, calibration algorithm has been developed. Deviations of the calibration results are measured and it is found that systematic error must be caused by heat from driving motors. A new alternative GMM with driving motors generating less heat was designed and two GMMs are compared. Finally, 3 Dimension measurement of tooth root and bottom profiles of cylindrical gears is described.