• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2471-2475
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• 2007

Clathrate compound is the material that host in hydrogen bond forms cage and guest is included into it and combined. Crystallization of hydrate is generated at higher temperature than that of ice from pure water. And physical properties according to temperature are stable and congruent melting phenomenon is occurred without phase separation. But clathrate compound still had supercooling problem occurred in the course of phase change and supercooling should be minimized because it affects efficiency of equipment very much. Therefore, various studies on additives to restrain this or heat storage methods are needed. In this study was investigated the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N)$ of 20${\sim}$25 wt% as a low temperature latent heat storage material. And ethanol$(CH_3CH_2OH)$ was added and its cooling characteristics were studied experimentally to restrain supercooling of TMA-water clathrate compound.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.179-184
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• 2003

The pulsed power system is widely used for many industries and environments. Generally, we call the "RUST", the reddish brown surface, that was made on iron surface or some other metals, when they are contacted by water and air the main substance of rust is oxide-ionization. In other words, the chemical symbol of rust on iron surface is iron oxide(III) hydrate Fe203.nH2O. In this study, we have designed and fabricated our system which has a compact pulse generator with switching MOSFET. Also we have studied the metal-oxide removing characteristics using in the atmospheric arc discharge. It has been investigated their removing characteristics by the change of charging voltage and pulse repetition rates. From this result, we can find out that the removal area Is increased from 3.80 to 8.04[$\textrm{cm}^2$], when pulse duration is increased from 100[pps] to 400[pps]. 400[pps].

• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.48-55
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• 2015

Hardened cement-based materials exposed to the high temperatures of a fire are known to experience change in the pore structure as well as microstructural changes that affect their mechanical properties and tend to reduce their durability. In this experimental investigation, hardened Portland cement pastes were exposed to elevated temperatures of 200, 400, 600, 800, and $1000^{\circ}C$ for 60 minutes, and the resulting damage was studied by thermogravimetry (TG), mercury intrusion porosimetry (MIP) and density measurements. These results revealed that the residual compressive strength is increased at temperatures greater than $400^{\circ}C$ due to a small pore size of 3 nm and/or rehydration of the dehydrated cement paste. However, a loss of the residual strength occurs at temperatures exceeding 500 and $600^{\circ}C$. This can be attributed to the decomposition of hydrates such as portlandite and to an increase in the total porosity.

• Journal of The Korean Digital Architecture Interior Association
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• v.12 no.4
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• pp.59-66
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• 2012

This study is interested in identifying the effectiveness of alkali-activated fire protection material compounds including the alkali-activator such as potassium hydroxide, sodium silicate and fly ash as the fire resistant finishing materials. Also, this paper is concerned with change in compressive strength and pore structure of the alkali-activated fire protection material at high temperatures. The testing methods of fire protection materials in high temperature properties are make use of TG-DSC and mercury intrusion porosimetry measurements. This study results show that compressive strength is rapidly degraded depending on a rise of heating temperature. Porosity showed a tendency to increase irrespective of specimen types. This is due to both the outbreak of collapse of gel comprising the cement and a micro crack by heating. However, alkali-activated fire protection material composed of potassium hydroxide, sodium silicate and fly ash has the thermal stability of the slight decrease of compressive strength and porosity at high temperature. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction by the reason of the thermal analysis result not showing the decomposition of calcium hydrate.

• Advances in Traditional Medicine
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• v.8 no.3
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• pp.222-227
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• 2008

Citrus aurantium var. amara L., commonly known as 'bitter orange' or 'sour orange', of the family Rutaceae, has traditionally been used in the treatment of various ailments, and it possesses different types of pharmacological properties. As a part of our on-going studies on the plantsfrom the Iranian flora, the extract of C. aurantium var. amara has been studied for its weight lossproperties using the mice model. While the Sep-Pak fraction, 20% methanol (MeOH) in water, of the hydro-methanolic extract of the peels of C. aurantium var. amara fruits, when injectedintraperitoneal (i.p.) at a dose of 10 mg/kg, significantly decreased the level of weight gain of the mice in comparison with control the group (P < 0.01), the Sep-Pak fraction 80% MeOH in water decreased the initial weight of mice by 0.44% in six weeks. The administration of the total extract(10 and 20 mg/kg, i.p.), and the Sep-Pak fractions, 40% and 60% MeOH in water (10 mg/kg, i.p.)did not show any significant change of weight of the test mice. Of the two active fractions, the80% MeOH in water fraction did not show any noticeable adverse effects on mice, and was therefore analysed by reversed-phase preparative high performance liquid chromatography resulting in the isolation and identification of four major components, two coumarins, meranzin hydrate (1) and bergamottin (2), and two flavonoids, xanthomicrol 5,4'-di-methyl ether (tangeritin, 3) and hymenoxin 5,7-di-methyl ether (nobiletin, 4).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.4 no.2
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• pp.148-156
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• 1994

Chloral hydrate(CH), an intermediate metabolite of trichloroethylene(TRI) is reduced to trichloroethanol(TCE-OH), and is oxidized to trichloroacetic acid(TCA) by the nicotinamide adenine dinucleotide(NAD)-dependent enzymes such as alcohol dehydrogenase(ADH) and aldehyde dehydrogenase(ALDH) in liver. This study was performed to find out the change of activity of ADH and ALDH with increasing amount of TRI. Intraperitoneal injection of TRI were done to the male Sprague Dawely rats(mean body weight, $170{\pm}10g$) in com oil at the dosage of 150, 300, 600 mg/kg for 2 days. The results of experiments are following : 1. The contents of xenobiotic metabolic enzymes in liver are tended to be decreased with increasing amount of, but not significantlly (p>0.05). 2. Activity of ADH in microsome is decreased(p<0.05), and activity of ALDH is increased with amount of TRI(P<0.05). 3. Total trichloro-compounds(TTC) concentration in urine are increased with amount of TRI, but the ratio of between the TCE-OH and the TCA were not shown any critical change. These results suggests that the ALDH in microsome may be related to metabolism of TRI, but ADH was nothing less than the effected to metabolism of TRI.

• Journal of Energy Engineering
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• v.28 no.1
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• pp.17-21
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• 2019

Calcium sulfaluminate (CSA) was synthesized to improve the shrinkage of OPC. In this study, the setting time, the compressive strength and the length change ratio were confirmed by replacing the synthesized CSA with OPC by 10% and 13% by 16%. In the case of shrinkage-reducing type cement, formation of Ca-Al-$H_2$-based hydrate was activated. Therefore, the setting time was shortened. The compressive strength of the shrinkage - reducing type cement is comparable to that of OPC after 7 days' strength. However, shrinkage reducing type cement showed improved initial strength compared to OPC. The length change ratio was found to be improved by drying shrinkage from -0.075% to -0.047% on the 28th day.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.199-205
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• 2018

A geopolymer was produced from coal ash generated from an integrated gasification combined cycle (IGCC) plant and its water resistance was evaluated. For this purpose, the geopolymer specimens were immersed in water for 30 days to measure changes in microstructure and alkalinity of the immersion liquid. Particularly, the experiment was carried out with foaming status of the geopolymers and parameters of room temperature aging condition, and immersion time. The foamed geopolymer containing 0.1 wt% Si-sludge had pores with a diameter of 1 to 3 mm and exhibited excellent foamability. Also, the calcium-silicate-hydrate crystal phase appeared in the foamed geopolymer. In the geopolymer immersion experiment, the pH of the immersion liquid increased with time, because the un-reacted alkali activator remained was dissolved in the immersion liquid. From the pH change of the immersion liquid, it was found that geopolymer reaction in the foamed specimen was completed faster than the non-foamed specimen. Through this study, it was possible to successfully produce foamed and non-foamed geopolymers recycled from IGCC coal ash. Also the necessary data for the safe application of IGCC coal ash-based geopolymers to areas where water resistance is needed were established; for example, the process conditions for room temperature aging time, effect of foaming status, immersion time and so on.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.406-413
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• 2022

The subsea pipeline pre-commissioning stage consists of the following processes: Flooding, Venting, Hydrotesting, Dewatering, Drying, and N2 Purging. Among these processes, drying and nitrogen purging processes are stipulated to reduce and maintain the relative humidity below dew point to prevent the generation of hydrate and the risk of gas explosion in the pipeline during operation. The purpose of this study is to develop an analysis method for the air drying and nitrogen purging process during pre-commissioning of the subsea pipeline, and to evaluate the applicability of the analysis method through comparison with on-site measurement results. An analysis method using Computational Fluid Dynamics (CFD) was introduced and applied as a method for evaluating the relative humidity inside a subsea pipeline, and it was confirmed that analysis results were in good agreement with the on-site measurement results for the air drying and nitrogen purging process of the offshore pipeline. If the developed air drying and nitrogen purging analysis method are used as pre-engineering tools for pre-commissioning of subsea pipelines in the future, it is expected to have a significant impact on the improvement of work productivity.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.3
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• pp.160-163
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• 2008

$CO_2$ ocean sequestration is being considered as a way to earn a frame of time to change other industrial life pattern to overcome the global warming crisis. The method is to dilute the captured $CO_2$ into ocean by ejecting the liquefied $CO_2$ through nozzles. The main issue of such method is the effectiveness and safety, and in both problems the rising speed of those LCO2 droplet is the key parameter. In this paper, the rising speed of LCO2 droplets is numerically studied including the effect of the surfactant which can be residing along the density interface of the droplets. A front tracking method with a simple surface tension model is developed and the rising speed of the droplets is carefully investigated with varying the various parameters. It is demonstrated that the variable surface tension can change the deformation of the droplet, the flow near the interface, and the rising speed.