• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.173-179
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• 2015

We report the facile synthesis of graphene-$CdLa_2S_4$ composite through a facile solvothermal method at low temperature. The as-prepared products were characterized by X-ray diffraction (XRD) and by Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis and BET analysis, revealing the uniform covering of the graphene nanosheet with $CdLa_2S_4$ nanocrystals. The as-prepared samples show a higher efficiency for the photocatalytic degradation of typical MB dye compared with P25 and $CdLa_2S_4$ bulk nanoparticles. The enhancement of visible-light-responsive photocatalytic properties by decolorization of Rh.B dye may be attributed to the following causes. Firstly, graphene nanosheet is capable of accepting, transporting and storing electrons, and thus retarding or hindering the recombination of the electrons with the holes remaining on the excited $CdLa_2S_4$ nanoparticles. Secondly, graphene nanosheet can increase the adsorption of pollutants. The final cause is that their extended light absorption range. This work not only offers a simple way to synthesize graphene-based composites via a one-step process at low temperature but also a path to obtain efficient functional materials for environmental purification and other applications.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.2
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• pp.184-193
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• 2020

One of the technical methods to increase the volumetric energy density of hydrogen is to pressurize the gaseous hydrogen and then contain it in a rigid vessel. Especially for automotive systems, the compressed hydrogen storage can be found in cars as well as at refueling stations. During the charging the pressurized hydrogen into a vessel, the temperature increases with the amount of stored hydrogen in the vessel. The temperature of the vessel should be controlled to be less than a limitation for ensure stability of material. Therefore, the accurate estimation of temperature is of significance for safely storing the hydrogen. In this work, three well-known cubic equations of state (EOSs) were adopted to examine the accuracy in regenerating thermodynamic properties of hydrogen within the temperature and pressure ranges for the compressed hydrogen storage. The formulations representing molar volume, internal energy, enthalpy, and entropy were derived for Redlich-Kwong (RK), Soave-Redlioch-Kwong (SRK), and Peng-Robinson (PR) EOSs. The calculated results using the EOSs were compared with literature data given by NIST. It was revealed that the accuracies of RK and SRK EOSs were satisfactorily compatible and better than the results by PR EOS.

• The KSFM Journal of Fluid Machinery
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• v.14 no.3
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• pp.33-38
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• 2011

Medicated water electrolysis apparatus, which electrolyzes water into acidic water and alkaline water, was in the spotlight as becoming known the effect of alkaline water. It is known as good for health as removing active oxygen in the human's body and promoting digestion. But, the customers could not get that desired water temperature because these apparatuses are directly connected with a water pipe. So, the cooling system was developed for controlling the temperature of the alkaline water. One of the typical way is to store water in water tank and control the temperature. But, in this way, storing water can be polluted impurities coming from outside. For protecting this pollution, the cooling system based on indirect heat exchange method through phase change between water and ice was developed. In this study, we have calculated efficiency of the cooling system with phase change by experiment and commercial CFD(Computational Fluid Dynamics) code, ANSYS CFX. To consider the effect of latent heat that is generated by melting ice, we have simulated two phase numerical analyses used enthalpy method and found the temperature, velocity, and ice mass distribution for calculating the efficiency of cooling. From the results of numerical analysis, we have obtained the relationship between the cooling efficiency and each design factor.

• Korean Journal of Food Science and Technology
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• v.29 no.4
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• pp.758-763
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• 1997

Fresh jujubes (Zizyphus jujuba Miller) of whitish green and red ripe maturities were stored at 5 different temperatures, and quality changes through the storage were measured to find an optimal storage condition. Respiration rates and their temperature dependences for both maturities were not different from each other, which suggested non-climacteric pattern of postharvest respiration. Red ripe fruits showed heavier weight and higher content in soluble solid and ascrobic acid compared with whitish green mature fruits. Through the storage of jujubes in perforated packages tissue softening and decay were main visual quality deteriorations with the former preceding the latter. The whitish green mature jujubes showed slower rate of quality changes in softening and decay than red ripe ones, and are thus more suitable for long term storage. In the storage, the whitish green fruits changed into red color, and showed increase in soluble solid and decrease in acidity and ascorbic acid content. Storing the jujubes at $-2^{\circ}C$ resulted in symptoms of chilling injury, and storing at higher temperatures above $0^{\circ}C$ accelerated the decay and softening. $0^{\circ}C$ was found to be optimal temperature for long term storage, where jujube had the lowest rate of quality changes without chilling injury. Even at optimal temperature of $0^{\circ}C$, however, storage life retaining freshness was only around 40 days which is not enough.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1-6
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• 2007

The membrane type LNG(Liquefied Natural Gas) cargo containment system is a special design structure for the large deformation behavior at LNG temperature$(-162^{\circ}C)$. The design of membrane is required great confidence so that membrane can plat role in the tightness of flammable fluid storing. LNG cargo containment is loaded and unloaded LNG between twice and five times in a week. During this process, the membrane has large deformation behavior due to the variation of temperature and pressure to the self weight. In this study, the evaluation of the fatigue strength of membrane is very important to determine the design life of LNG storage tank and to evaluate the mechanical properties at the LNG temperature. Also, in the view point of large deformation, the evaluation method is applied conservatively $\epsilon-N_f$ curve of SUS 304L.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.113-199
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• 2002

In this study, the toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storing tank. The specimens were GMAW welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and -196$^{\circ}C$ ) in order to investigate the influence of the mixing shield gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the worked notch position. From experiment, the maximum load increased a little up to -85$^{\circ}C$, and the maximum load and maximum displacement were shown the highest and the lowest at -196$^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone. In the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to -85$^{\circ}C$ but the energy was decreased so mush at -196$^{\circ}C$

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.550-557
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• 2013

A glucose hydrothermal method is described for preparing hollow carbon spheres (HCS), which have a regular morphology and a high Brunauer-Emmett-Teller surface area of 28.6 m2/g. Scanning electron microscopy shows that they have thin shells and diameter between 2 and 8 ${\mu}m$. The HCSs were modified for the enhanced room temperature hydrogen storage by employing Ni nanoparticles on their surface. The Ni-decorated HCSs were characterized by X-ray diffraction, transmission electron microscopy coupled with an energy dispersive spectroscope, and an inductively coupled plasma spectrometer, indicating that fine and well-distributed Ni nanoparticles can be accomplished on the HCSs. The hydrogen uptake capacity in HCSs with and without Ni loading was evaluated using a high-pressure microbalance at room temperature under a hydrogen pressure upto 9 MPa. As much as 1.23wt.% of hydrogen can be stored when uniformly distributed Ni nanoparticles are formed on the HCSs, while the hydrogen uptake capacity of as-received HCSs was 0.41 wt.%. For Ni nanoparticle-loaded HCSs, hydrogen molecules could be easily dissociated into atomic hydrogen and then chemically adsorbed by the sorbents, leading to an enhanced capacity for storing hydrogen.

• Journal of Biosystems Engineering
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• v.12 no.1
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• pp.6-13
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• 1987

A mathematical model for the waste heat recovery system for an engine was developed. The model based on the experimental data reported before was validated and was used to predict the waste heat recovery and recoverable heat of the engine at various operating conditions of the engine and the system. The model was also used to determine flow rates of the circulating water in the system for a certain temperature increment of the water at various operating conditions of the engine to give basic data to design the system. Stability of the system performance was tested on subjects of vapor lock problem, thermal characteristics of the thermostatic valve, and temperature variation of the circulating water in the engine and fuel consumption of the engine during each mode of the system operation and its change into the other. The test showed that the system operation was stable enough. Temperature profile in the thermal energy storage (TES) was observed during storing thermal energy, and thermal stratification in the TES was well formed acceptable to be used in the system. Finally a scheme to automatize the system was suggested.

• Journal of Animal Environmental Science
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• v.3 no.2
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• pp.133-143
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• 1997

Optimal conditions for collecting, storing and drying temperature to utilize slaughter porcine blood for blood meals and the effects of blood meal on growth in broiler chicks were investigated. Dry matter and protein contents of slaughter procine blood were 19.5% and 77%(dry basis), respectively. As for the composites of amino acids in the blood, aspartic acid, arginine, glycine, histidine, leucine, lysine, phenylalanin threonine were shown high. There was no significant difference between the collections by bloodletting and vacuumming in terms of microbial contamination. Storage of slaughter porcine blood showed no differences in protein, DNA and triglyceride contents and pH between the storage methods of freezing (-20$^{\circ}C$) and refrigerating (-4$^{\circ}C$). In case of room temperature storage, however, the decrease in pH and the appearance of new protein due to microbial contaminations increased as the storage periods were prolonged. When drying was done by flash methods, the drying period got shortened as the temperature became higher, yet protein and triglyceride were destoryed more. When drying was done over 120$^{\circ}C$, even at the same degree, the breakdowns of protein and triglyceride increased more as drying period got longer. In feeding trials of broiler chicks, dietary supplementation of the flash dried blood meal at 2% level showed significant difference in growth rate(P＜.05%). These results indicated that the appropriate handling and manufacturing of slaughter porcine blood enabled the blood to be used as a protein source for broiler chicks.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.6
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• pp.653-660
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• 2002

In this study, the toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storing tank. The specimens were GMAW welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and $-196^{\circ}C$) in order to investigate the influence of the mixing shield gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the worked notch position. From experiment, the maximum load increased a little up to -$85^{\circ}C$ , and the maximum load and maximum displacement were shown the highest and the lowest at -$196^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone. In the other hand, the other specimens were shown that the lower temperature, the higher absorption energy slightly up to $-85^{\circ}C$ but the energy was decreased so mush at $-196^{\circ}C$.