• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.242-248
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• 2002

SnCo alloy powder prepared by high energy ball milling is examined as an anode material for lithium-ion batteries. As the ball-milling time increased, the crystallinity of SnCo decreased. XRD and TEM SADP showed that nanocrystalline and amorphous phase coexisted after 16 h ball-milling. As the crystallinity decreased, the cycleability increased. At first cycle, there are 4 plateau potentials. The observation of voltage plateau at about 0.68 V confirms the formation of Sn-Li alloy and Co metal. It is considered that The plateau potentials below 0.68 V were reaction between Li and Sn. The change of chemical diffusion coefficient showed that the structure of SnCo alloy abruptly changed at first cycle, and maintained after 2nd cycle.

• 설비공학논문집
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• 제19권9호
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• pp.640-646
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• 2007

The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

• 한국정밀공학회지
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• 제18권4호
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• pp.142-150
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• 2001

Automotive manufactures have taken more interests in tailored sheet metals for improving the rigidity, weight reduction, crash durability, and cost savings so that their application to auto-bodies has been increased. However, since the tailored sheet metals do not behave like un-welded sheet metals in press forming operations, the stamping engineers no longer rely only on conventional forming techniques. Futhermore, there is no clear understanding of the characteristics of welded metal which influence the overall press formability of tailored sheet metals. Recently, the computer simulations are prevailing for the evaluation of the formability. Unfortunately, the mechanical property of tailored sheet metal has to be quantitatively defined in the simulation. In this study, the analytical equations are formulated in order to find the mechanical properties of the welded metal in the tailored sheet metal welded by co$_2$laser. Based on force distribution assumption, the constitutive behavior of the welded metal is investigated using uniaxial tensile test results of base metals and tailored sheet metal. Then, the strength coefficient, work-hardening exponent, and plastic strain ratio of laser-welded metal are calculate from those of base metals and tailored sheet metal. In addition, the existence of weld defects in the welded metal is indirectly detected by examining the slop of strength coefficient of the welded metal.

• E2M - 전기 전자와 첨단 소재
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• 제9권5호
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• pp.455-462
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• 1996

Automobile Fuel Shortage Detecting Sensor, in this paper, was fabricated by using heat dissipation coefficient difference between gasoline and air condition the NTC thermistor of Mn-Ni Co system with the composition ratio of Mn$_{3}$O$_{4}$ : 9wt%, NiO : 28wt%, and CO$_{3}$O$_{4}$ : 61wt%. The condition of sensor operation is that, for turn-on characteristics, the time of arriving at 135mA must be less than 180 second when the DC voltage of 11V is applied in the air condition of -10.deg. C and that, for turn-off characteristics, the saturation current must be less than 60mA when the DC voltage of 15V is applied in the gasoline condition of 60.deg. C. It is known, from the experimental results, that the resistance range and B-constant for the Automobile Fuel Shortage Detecting Sensor with dimension of 5*3*0.9mm were 850-1150.ohm. and 1150-1250.deg. C, respectively and the resistance range and B-constant were agree with that of sensor operation condition. When Bi$_{2}$O$_{3}$ of 0-0.5wt% was added to Mn$_{3}$O$_{4}$ : 9wt%, NiO : 28wt%, and CO$_{3}$O$_{4}$ : 61wt% composition, the resistivity and B-value were 380-430(.ohm.-cm) and 1930 - 2030, respectively. Particularly, for Bi$_{3}$O$_{3}$ of 0.25-0.5wt%, the sintering density of over 90% and the operation characteristics necessary to Automobile Fuel Shortage Detecting Sensor were obtained. The difference of heat dissipation coefficient gasoline and air condition was 15 times.

• 분석과학
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• 제9권3호
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• pp.292-301
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• 1996

산화환원반응 탐침제로, poly ether 꼬리가 결합된 Cobalt(II)bipyridine 착물을 합성 하였고, 이들 화합물의 느린 확산계수와 불균일 전자이동을 설명하였다. $Co(bpy(ppgm)_2)_{3^-}(ClO_4)_2$에 전해질 $LiClO_4$가 혼합된 neat 상태의 산화반응에 대한 확산계수는 $1.5{\times}10^{-15}cm^2/s$ 였다. 이 화합물들의 불균일 전자이동 속도상수들은 확산계수와 관련이 있었다. 확산계수의 감소에 따라 속도상수(k)의 감소가 일어났다. 강한 이온쌍을 형성하는 $ClO{_4}^-$의 화합물은 약한 이온 쌍을 형성하는 $CF_3COO^-$ 화합물보다 확산계수가 훨씬 작았다.

• Tribology and Lubricants
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• 제37권5호
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• Environmental Engineering Research
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• 제21권1호
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• pp.74-83
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• 2016

The purpose of this study is to identify the driven factors affecting the changes in energy-related $CO_2$ emissions in Hebei Province of China from 1995 to 2013. This study confirmed that energy-related $CO_2$ emissions are correlated with the population, urbanization level, economic development degree, industry structure, foreign trade degree, technology level and energy proportion through an improved STIRPAT model. A reasonable and more reliable outcome of STIRPAT model can be obtained with the introducing of the Ridge Regression, which shows that population is the most important factor for $CO_2$ emissions in Hebei with the coefficient 2.4528. Rely on these discussions about affect abilities of each driven factors, we conclude several proposals to arrive targets for reductions in Hebei's energy-related $CO_2$ emissions. The method improved and relative policy advance improved pointing at empirical results also can be applied by other province to make study about driven factors of the growth of carbon emissions.

• 한국대기환경학회지
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• 제29권1호
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• pp.56-63
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• 2013

This study was aimed at developing and evaluating a diffusive sampling method using a barium hydroxide solution as an absorbent for measuring carbon dioxide ($CO_2$) in ambient air. The collected $CO_2$ concentration was calculated by the change of conductivity resulted in the reaction of $CO_3{^{2-}}$ and $Ba^{2+}$ in aqueous solution. The sampling rate for the diffusive sampler was determined 0.218 mL/min, as obtained from the slope of the linear correlation between the $CO_2$ mass collected by the diffusive sampler and the time-weighted $CO_2$ concentration with the active sampling method. The unexposed blank sampler sealed in aluminium foil-polyethylene laminated packets has remained stable during at least one-month storage period. A good correlation was observed between the diffusive sampler and active sampler with a coefficient of determination of 0.956. This diffusive sampler would be suitable for the indoor $CO_2$ concentration monitoring.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.152-156
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• 2000

Bi-thin films are fabricated by an ion beam sputtering, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below $730^{\circ}C$ and decreases linearly with temperature over $730^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, $Bi_2O_3$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.

• 한국세라믹학회지
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• 제24권5호
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• pp.484-490
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• 1987

Diffusion coupling experiment was done to study expansion of body and soild reaction in BaCO3-TiO2 system. Specimen of BaCO3 and TiO2 was formed with Pt-mark's method. Each specimen was fired at interval of 25℃ from 900℃ to 1000℃ for 2hrs. After that, specimen was fixed with resin and polished. Product layers of specimen were observed with SEM and EDS. The result were following; 1. Diffusion component is Ba2+, which diffuse toward TiO2. 2. Large crack between layer of BaCO3 and Ba2TiO4 was generated because of difference of thermal expansion coefficient. 3. Ba2TiO4 is formed to TiO2 body by the reaction of BaTiO3 and BaO and its structure is very porous. 4. BaTiO3 changes immediately to Ba2TiO4 by the reaction of BaO. But BaTiO3 which formed by the reaction of TiO2 and Ba2TiO4 exsists as layer because the diffusion distance of Ba2+ is far.