• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.115-120
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• 2008

The thermistors and AD590 are widely used for temperature measurement in space application. The resistance of thermistor will vary according to the temperature variation therefore the external voltage or current stimulus signal have to be provided to measure resistance variation. Recently high resolution electro optic camera system of satellite requires tight thermal control of the camera structure to minimize the thermal structural distortion which can affects the image quality. In order to achieve $1^{\circ}$(deg C) thermal control requirement, the accuracy of temperature measurement have to be higher than $0.3^{\circ}$(deg C). In this paper, the accuracy of temperature measurement using thermistors is estimated and analyzed.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.244-249
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• 2012

In this study, a monolithic MoSi2 matrix reinforced with 20 vol% SiC particles, a SiC/MoSi2 composite matrix reinforced with 20 vol% ZrO2 particles, and a ZrO2/MoSi2 composite were fabricated using hot press sintering at $1350^{\circ}C$ for 1 h under a pressure of 30 MPa. The Vickers hardness and sliding wear resistance of the monolithic MoSi2, ZrO2/MoSi2, and SiC/MoSi2 composite were investigated at room temperature. A wear behavior test was carried out using a disk-type wear tester with a silicon nitride ball. The ZrO2/MoSi2 composite showed an average Vickers hardness value and excellent wear resistance compared with the monolithic MoSi2 and SiC/MoSi2 composite at room temperature.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.381-388
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• 1994

A new process which co-fires the low-firing-substrate and copper conductor was studied to achieve good bond strength and low sheet resistance of conductor. Cupric oxide is used as the precursor of conductive material in the new method and the firing atmosphere of the new process is changed sequently in air H2N2. The addition of cupric oxide and variations of firing atmosphere permited complete binder-burnout in comparison with the conventional method and contributed to the improvement of resistance and bonding behaviors. The potimum conditions of this experiment to obtain the satisfactory resistance and bond strength are as follows (binder-burnout temperature in air; 55$0^{\circ}C$, reducing temperature in H2; 40$0^{\circ}C$ for 30 min, ratio of copper and cupric oxide; 60:40~30:70 wt%). The bonding mechanism between the substrate and metal was explained by metal diffusion layer in the interface and the bond strength mainly depended on the stress caused by the difference of shrinkage and thermal expansion coefficient between the substrate and metal.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.60-65
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• 2011

A low temperature plasma carburizing process was performed on AISI 316L austenitic stainless steel to achieve an enhancement of the surface hardness without degradation of its corrosion resistance. Attempts were made to investigate the influence of the processing temperatures on the surface hardened layer during low temperature plasma carburizing in order to obtain the optimum processing conditions. The expanded austenite (${\gamma}_c$) phase, which contains a high saturation of carbon (S phase), was formed on all of the treated surfaces. Precipitates of chromium carbides were detected in the hardened layer (C-enriched layer) only for the specimen treated at $550^{\circ}C$. The hardened layer thickness of ${\gamma}_c$ increased up to about $65{\mu}m$ with increasing treatment temperature. The surface hardness reached about 900 $HK_{0.05}$, which is about 4 times higher than that of the untreated sample (250 $HK_{0.05}$). A minor loss in corrosion resistance was observed for the specimens treated at temperatures of $300^{\circ}C{\sim}450^{\circ}C$ compared with untreated austenitic stainless steel. In particular, the precipitation of chromium carbides at $550^{\circ}C$ led to a significant decrease in the corrosion resistance. A diamond-like carbon (DLC) film coating was applied to improve the wear and friction properties of the S phase layer. The DLC film showed a low and stable friction coefficient value of about 0.1 compared with that of the carburized surface (about 0.45). The hardness and corrosion resistance of the S phase layer were further improved by the application of such a DLC film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.509-513
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• 2000

The physical and electrical characteristics of MgO and Pt thin-films on it deposited by reactive sputtering and rf magnetron sputtering respectively were analyzed with annealing temperature and time by four point probe SEM and XRD. Under annealing conditions of 100$0^{\circ}C$ and 2 hr, MgO thin-film had the properties of improving Pt adhesion to SiO$_2$and insulation without chemical reaction to Pt thin-film and the sheet resistivity and the resistivity of Pt thin-film deposited on it were 0.1288 Ω/ and 12.88 $\mu$$\Omega$.cm respectively. We made Pt resistance pattern on SiO$_2$/Si substrate by life-off method and fabricated Pt thin-film type microheater for thermal microsensors by Pt-wire Pt-paste and SOG(spin-on-glass). In the temperature range of 25~40$0^{\circ}C$ we estimated TCR(temperature coefficient of resistance) and resistance ratio of thin-film type Pt-RTD(resistance thermometer device). We obtained TCR value of 3927 ppm/$^{\circ}C$ close to the bulk Pt value. Resistance values were varied linearly within the range of the measurement temperature. The thermal characteristics of fabricated thin-films type Pt micorheater were analyzed with Pt-RTD integrated on the same substrate. The heating temperature of Pt microheater could be up to 40$0^{\circ}C$ with 1.5 watts of the heating power.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.358-366
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• 1990

As a basic study to clarify the scoring resistance in lubricated sliding contact, the temperature rise on frictional surface was analyzed by theoretical method and the effects of various factors on the temperature rise were examined. On the basic of the results obtained theoretically, the practical equations to calculate the maximum average temperature of the contact surface were proposed which are applicable to sliding contact. Then, the effects of sliding velocity and oil temperature on the seizure behavior, and the relation between seizure and temperature rise were investigated. The following conclusions are deduced : The maximum average temperature rise and the other bulk temperature. The former is affected by the size of heat supply region and the sliding velocity, the latter is affected by heat transfer coefficient. Without regard to the operating condition such as sliding velocity, oil temperature and operating time at each load-step, the maximum average temperature just before seizure is nearly constant except in the region of lower velocity. Consequently, the maximum average temperature of the contact surface in boundary lubrication is a useful criterion to predict the scoring of sliding contact.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.148-149
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• 2012

As one of zero-expansion coefficient materials $Al_2TiO_5$ ceramics was prepared and the thermal shock-resistance was investigated by using DV-X analysis. In this report the mechanism of thermal shock-resistance and low mechanical strength.

• Journal of Sensor Science and Technology
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• v.26 no.6
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• pp.438-444
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• 2017

In this paper, we focus on optimization of the in-situ phosphorous (P) doping of low-pressure chemical vapor deposited (LPCVD) poly Si resistors for obtaining near-zero temperature coefficient of resistance (TCR) at temperature range from 25 to $600^{\circ}C$. The deposited poly Si films were annealed by rapid thermal anneal (RTA) process at the temperature range from 900 to $1000^{\circ}C$ for 90s in nitrogen ambient to relieve intrinsic stress and decrease the TCR in the poly Si layer and get the Ohmic contact. After the RTA process, a roughness of the thin film was slightly changed but the grain size and crystallinity of the thin film with the increase in anneal temperature. The film annealed at $1,000^{\circ}C$ showed the behavior of Schottky contact and had dislocations in the films. Ohmic contact and TCR of $334.4{\pm}8.2$ (ppm/K) within 4 inch wafer were obtained in the measuring temperature range of 25 to $600^{\circ}C$ for the optimized 200 nm thick-poly Si film with width/length of $20{\mu}m/1,800{\mu}m$. This shows the potential of in-situ P doped LPCVD poly Si as a resistor for pressure sensor in harsh environment applications.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.42-48
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• 1988

Commercially available PTCR (Postive Temperature Coefficient of Resistivity) ceramics which have low room temperature resistance, high PTC effect and temperature coefficient were prepared by La3+ doped semiconducting barium calcium titanate soild solutions. PTCR characteristics were remarkably improved by addition of AST (1/3 Al2O3$.$3/4SiO2$.$1/4TiO2) and MnCl2. That can be explained by formation of liquid phase during sintering and acceptor level on the intergranular layer. Resistivity anormaly increased with decreasing cooling rate. Optimum manufacturing conditions were cooling rate below 100$.$C/hr, Ca and Mn content of 4 mol% &, 0.09-0.12mol% respectively.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.259-264
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• 2000

The functions of the plug valve are the control of flow rate as well closing and opening pipe lines. Analyses on the flow characteristics in plug valve port are required to improve the performance and safety at severe operating conditions such as high-pressure and high-temperature. In this study, numerical analyses are carried out with varying the opening rate (fraction of the full open to close) of the valve and the shapes of valve Uk: straight, convex, concave and mixed shapes. The parameters influencing the flow characteristics in the valve are the discharge coefficient( $C_v$) and the resistance coefficient( K). Therefore, the distributions of static pressure, velocity vector and stream lines are investigated, and $C_v$ and K are calculated in each opening rate and shape. In case of full open, the static pressure passed through the valve port has almost been recovered. However, in case of other opening rates, the pressure does not permanently regained due to pressure drop leading to loss. This phenomenon in each shape of the valve shows the different behaviors. Calculation results show that the mixed shape has the best flow attribute.