• Korean Membrane Journal
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• v.10 no.1
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• pp.8-12
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• 2008

The electrochemical properties of Nafion type membranes as a function of temperature to examine the key factors affecting the cathodic protection process at low temperatures was investigated in this study. Variable temperature experiments for AC impedance, DC resistance were conducted. The resistances of 3 Nafion membranes (N 324, N 450, N MAC) were measured in 30% KOH (aq) for a range of temperatures between $-30^{\circ}C$ and room temperature. Membrane resistance increases exponentially with decreasing temperature. This behaviour is most significant at operational temperatures below $0^{\circ}C$. These membranes are stable under the low temperature and caustic conditions of the heat exchange system, but they place a much higher restriction on the cathodic protection of the stainless heat exchange stack. N 450 has the lowest AC impedence and DC resistance at temperatures below $0^{\circ}C$ and consequently is most suitable membrane of the three, for low temperature applications.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1392-1397
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• 2018

The potentiometric measurement result for a high resistance up to $100P{\Omega}$ using a low resistance, a low voltage source and a commercial digital multimeter(DMM) is presented. With the method, a resistance can be easily, fast and economically measured. Using the method, resistance ranges over the $10G{\Omega}$ range which is difficult to measure using a commercial DMM and resistance ranges between $100T{\Omega}$ and $100P{\Omega}$ which cannot measure using an insulation tester were measured within accuracy of a few percent. It is expected that it can be useful to determine the temperature and voltage effect of a high resistance and an insulation material because it uses a reference resistance with a low resistance, very low temperature and voltage effect. Besides, it is expected that it can be useful to calibrate a dc high voltage divider with a large resistance ratio and a very low resistance because arbitrary resistance ratio measurements are possible with it.

• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.425-440
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• 2018

Purpose: This study is aimed at developing of the flex resistance testing process at low temperature with the waterproof fabric to suit the military environment, and is designed to fit for the purpose of the waterproof materials in order to optimize the test method by finding out matters to improve from existing the test method and through previous studies. Methods: The test method, which has been applied to flex resistance of existing water-repellent materials, was improved and consequently, differentiated test results could be obtained according to the test temperature, sample size, and flexing method. Results: The testing of the total of 8 samples revealed that performance of the military requirement could hardly be met just by presenting the materials or 2~3 layers when the quality criteria for high functional water repellent fabrics were applied. PTFE(Polytetrafluoroethylene) is preferred to PU(Polyurethane) to be used in the extremely low-temperature environment, but durability under the low-temperature environment may be varied depending on film thickness or laminating technique even if the materials of waterproof films are identical. Therefore, in addition to the material or texture, the test method capable of reflecting durability under the low-temperature environment shall be suggested, and the newly designed test method proposed in this study was shown to suggest differentiated quality criteria by the material. Conclusion: The water resistance measurement and the test method following flex resistance with expanded range of flex will enable the differentiable test of the samples according to the number of repetition. This study is meaningful in that it suggests a differentiable test method capable of establishing a basis of deciding suitable material when selecting military goods made of water repellent material by properly improving the test method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.162-168
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• 2011

In this research, nitrogen plasma source ion implantation(PSII) of non-coated tungsten carbide endmill tools was conducted with low heat treatment for increasing wear resistance. After the low heat treatment of PSIIed tools to give a homogeneity of wear resistance, the surface modification of tools was analyzed by hardness test, surface roughness and cutting forces. As for the resultant cutting forces, low heat treatment in temperature of $400^{\circ}C$ and $500^{\circ}C$ is stable because of low cutting resistance. The 20-minutes heat treated tool at spindle speed 25000rpm has superiority of surface roughness, Ra of $0.420{\mu}m$ and was found to have good wear resistance. The higher hardness value was obtained by increasing temperature from $300^{\circ}C$ to $600^{\circ}C$ for PSIIed tools with low heat treatment. As the PSIIed tools under 10minutes at temperature of $600^{\circ}C$ have the highest hardness as Hv of 2349.8, It was analyzed that temperature processing give much influences on hardness.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.125-130
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• 2008

Conventional plasma carburizing or nitriding for austenitic stainless steels results in a degradation of corrosion resistance. However, a low temperature plasma surface treatment can improve surface hardness without deteriorating the corrosion resistance. The 2-step low temperature plasma processes (the combined carburizing and post nitriding) offers the increase of both surface hardness and thickness of hardened layer and corrosion resistance than the individually processed low temperature nitriding and low temperature carburizing techniques. In the present paper, attempts have been made to investigate the influence of the introduction of Ar gas (0~20%) in nitriding atmosphere during low temperature plasma nitriding at $370^{\circ}C$ after low temperature plasma carburizing at $470^{\circ}C$. All treated specimens exhibited the increase of the surface hardness with increasing Ar level in the atmosphere and the surface hardness value reached up to 1050 HV0.1, greater than 750 $HV_{0.1}$ in the carburized state. The expanded austenite phase (${\gamma}_N$) was observed on the most of the treated surfaces. The thickness of the ${\gamma}_N$ layer reached about $7{\mu}m$ for the specimen treated in the nitriding atmosphere containing 20% Ar. In case of 10% Ar containing atmosphere, the corrosion resistance was significantly enhanced than untreated austenitic stainless steels, whilst 20% Ar level in the atmosphere caused to form CrN in the N-enriched layer (${\gamma}_N$), which led to the degradation of corrosion resistance compared with untreated austenitic stainless steels.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.558-561
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• 2001

Vanadium oxide ($VO_x$) thin films are very good candidate material for uncooled infrared (IR) detectors due to their high temperature coefficient of resistance (TCR) at room temperature. But, the deposition of $VO_x$ thin films showing good electrical properties is very difficult in micro bolometer fabrication process using sacrificial layer removal because of its low process temperature and thickness of thin films less than $1000{\AA}$. This paper presents a new fabrication process of $VO_x$ thin films having high TCR and low resistance. Through sandwich structure of $VO_{x}(100{\AA})/V(80{\AA})/VO_{x}(500{\AA})$ by sputter method and post-annealing at oxygen ambient, we have achieved high TCR more than $-2%/^{\circ}C$ and low resistance less than $10K\Omega$ at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.558-561
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• 2001

Vanadium oxide ($VO_{x}$) thin films are very good candidate material for uncooked infrared (IR) detectors due to their high temperature coefficient of resistance (TCR) at room temperature. But, the deposition of $VO_{x}$ thin films showing good electrical properties is very difficult in micro bolometer fabrication process using sacrificial layer removal because of its low process temperature and thickness of thin films less than 1000${\AA}$. This paper presents a new fabrication process of $VO_{x}$ thin films having high TCR and low resistance. Through sandwich structure of $VO_{x}$(100${\AA}$)/V(80${\AA}$)/$VO_{x}$(500${\AA}$) by sputter method and post-annealing at oxygen ambient, we have achieved high TCR more than -2%/$^{\circ}C$ and low resistance less than $10K\Omega$ at room temperature.

• Korean Journal of Metals and Materials
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• v.47 no.10
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• pp.629-634
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• 2009

The effects of processing parameters on the surface properties of the hardened layers processed by the low temperature plasma nitrocarburizing and the low temperature two-step plama treatment (carburizing+nitriding) were investigated. The nitrogen-enriched expanded austenite structure (${\gamma}_N$) or S phase was formed on all of the treated surface. The surface hardness reached up to 1200 $HV_{0.025}$, which is about 5 times higher than that of untreated sample (250 $HV_{0.1}$). The thickness of hardened layer of the low temperature plasma nitrocarburized layer treated at $400^{\circ}C$ for 40 hour was only $15{\mu}m$, while the layer thicknesss in the two-step plama treatment for the 30 hour treatment increased up to about $30{\mu}m$. The surface thickness and hardness increased with increasing treatment temperature and time. In addition, the corrosion resistance was enhanced than untreated samples due to a high concentration of N on the surface. However, higher treatment temperature and longer treatment time resulted in the formation of $Cr_2N$ precipitates, which causes the degradation of corrosion resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.834-838
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• 2011

This research shows the electrical characteristic using excellent epoxy nano-composite of MgO 5.0 wt% and $SiO_2$ 0.4 wt% in mechanical strength test depending on nano-additive. First of all, volume resistance depending on nano-additive and temperature using high resistance meter (HP. 4329A) by increasing 10, 100, 1,000 V of applying voltage was measured. Moreover, temperature range of $25{\sim}120^{\circ}C$ with virgin sample was tested using TO-9B oven by Ando Company. The result showed that virgin and the samples added with MgO and $SiO_2$ had similar value of volume resistance in low temperature and low electric field region and reduced with slow slope. The nano-composite's volume resistance of sample added with MgO and $SiO_2$ had higher value than virgin sample's volume resistance in high temperature region more than $80^{\circ}C$. Moreover, the slope has steeply reduced. The volume resistance of sample added with MgO 5.0 wt% was $8.38{\times}10^{13}\;{\Omega}{\cdot}cm$ and it was 6.8 times more than virgin sample in high temperature at $120^{\circ}C$. The insulation characteristics were constant although filler has changed in low temperature region. But, in high temperature region, the value of volume resistance of sample with MgO 5.0 wt% was 7.6 times more than the virgin sample's volume resistance.

• Journal of fish pathology
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• v.27 no.2
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• pp.85-89
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• 2014

Water temperature is a key environmental factor controlling the epizootics of viral diseases in fish. High water temperature is associated with the rapid spread of rock bream iridovirus (RBIV) disease and with high mortality of RBIV infected fish. Although protection of fish against iridoviral disease by active immunization has been reported, little information is available concerning whether fish survived from an epizootic of iridoviral disease can naturally acquire resistance against the viral disease. In the present study, we have demonstrated that juvenile rock bream, which survived from a natural epizootic of RBIV, acquired resistance against recurrence or reinfection of RBIV, and this resistance was established during the subsequent low water temperature period. Furthermore, the possible involvement of the adaptive humoral immune response in the resistance of the juvenile rock bream was suggested by in vivo neutralization experiment.