• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.434-442
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• 2017

The UV light in sunlight breaks down the chemical bonds in a polyolefin polymer through a process called photodegradation, ultimately causing cracking, chalking, colour changes, and loss of physical properties such as impact strength, tensile strength, elongation, and others. UV absorbers are used to prevent or terminate the oxidation of plastics by UV light. They are receptive to UV radiation and dissipate the energy harmlessly as heat. Benzotriazoles and benzophenones are used mainly in polyolefins such as polyethylene and polypropylene. In this study, we have developed a method for the analysis of 12 UV absorbers, which are Uvinul 3000, Cyasorb UV 24, Uvinul 3040, Tinuvin 312 and P, Seesorb 202, Chimassorb 81, Tinuvin 329, 234, 326, 328 and 327, migrated from the food packaging materials into four food simulants for aqueous, acidic, alcoholic and fatty foods. The UV absorbers in food simulants were determined by reversed-phase high performance liquid chromatograph-ultraviolet detector with 310 nm after solid-phase extraction with a hydrophilic-lipophilic balance (HLB) cartridge or dilution with isopropanol. The analytical method showed a good linearity of coefficient ($R^2{\geq}0.99$), limits of detection (0.049~0.370 mg/L), and limits of quantification (0.149~1.120 mg/L). The recoveries of UV absorbers spiked to four food simulants ranged from 70.05% to 110.13%. The developed method would be used as a reliable tool to determine concentrations of the migrated UV absorbers.

• Food Science and Preservation
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• v.19 no.1
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• pp.47-53
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• 2012

UV light irradiation is known to give beneficial effects on fresh produce preservation. A container system equipped with UV-LED was fabricated for storing cherry tomatoes under computer-controlled conditions of intermittent on-off cycles (1 hour on/1 hour off). Wavelength (365 and 405 nm) and physical location of the LED (2 and 5 cm above fruit) were studied as variables affecting the respiration, ethylene production and quality preservation of the fruits at 10 and $20^{\circ}C$. 365 nm wavelength gave much higher radiation intensity than 405 nm, and intensity on surface decreased in inverse proportion to square of distance from LED. When compared to non-irradiated control, UV-LED irradiation decreased the respiration by 5-10% at $10^{\circ}C$ while there was no obvious effect at $20^{\circ}C$. Ethylene production was reduced when the fruits were placed at 5 cm distance, while there was no significant difference from control at 2 cm location. The reduction of ethylene production at 5 cm was more pronounced at $20^{\circ}C$. UV-LED irradiation was shown to have delayed increase or lower concentration in carotenoids compared to control treatment. Any negative effect of UV-LED irradiation on ascorbic acid content and firmness was not observed.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.16-21
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• 2009

This paper introduces the methods of hydrogen peroxide storage test and storability of concentrated hydrogen peroxide is estimated. Using the method of simple concentration measuring, storability was evaluated. Experiment variables were the amount of stabilizer in hydrogen peroxide, storage temperature, and caps of vessels. The experiments were performed during 8 months to 24 months. High purity hydrogen peroxide had much better storability than hydrogen peroxide with much stabilizer. In addition, the case using paraffin film which did not react with hydrogen peroxide for covering showed better storability. The temperature is very important variable in hydrogen peroxide storage. So, when hydrogen peroxide was under $10^{\circ}C$ storability of hydrogen peroxide is much improved.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.246-251
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• 2001

Solid-liquid phase change (i.e. melting or solidification) occurs in a number of situations of practical interest. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, due to the practical importance of the subject, there have been a large number of experimental and numerical studies of problems involving phase change during the past few decades. Also, this study presented the effective way to enhance phase change heat transfer.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1720-1730
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• 1995

Finite-difference analysis was conducted to study the natural convection of a stably stratified salt-water solution in an annulus due to lateral heating. The main purpose of this study is to examine in detail the multi-layered flow structure. Calculation was thus made for R $a_{\eta}$=2*10$^{5}$ and 6.5*10$^{5}$ . Formation of layered flow structure, merging process of layers, the corresponding temperature and concentration distributions, Nusselt number variations with time are examined. Numerical results show that in each layer, the temperature profile looks 'S`-shaped and the concentration profile is uniform due to the convective mixing. The formation of the roll and the layer is governed by natural convection due to the temperature gradient and the merging process of the layer by diffusion of the concentration.ation.

• Journal of computational fluids engineering
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• v.7 no.1
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• pp.36-43
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• 2002

A numerical investigation is made of unsteady double-diffusive convection of a Boussinesq fluid in a rectangular cavity subject to time-periodic thermal excitations. The fluid is initially stratified between the top endwall of low solute concentration and the bottom endwall of high solute concentration. A time-dependent heat flux varying in a square wave fashion, is applied on one sidewall to induce buoyant convection. The influences of the imposed periodicity on double-diffusive convection are examined. A special concern is on the occurrence of resonance that the fluctuations of flow and attendant heat and mass transfers are mostly amplified at certain eigenmodes of the fluid system. Numerical solutions illustrate that resonant convection results in a conspicuous enhancement of time-mean mass transfer rate.

• Tunnel and Underground Space
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• v.13 no.3
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• pp.187-195
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• 2003

This case study which is to make 2-Dimension earth's crust structures clearly is about the great boring-hole blasting to provide ground vibration source of the reflected wave research on the Korean Peninsula earth's crust structures research. For this study we've done blasting twice-500 ㎏/charge per delay, 1,000 ㎏/charge per delay, and the specifications of blasting are the following - dia.: 300 ㎜, boring-depth : 100m, besides, we used the explosives and electric detonators which have sufficient detonating velocity and very excellent safety, capacity of detonating, accurate delay time. We charged explosives into steel pipe with bulk type to avoid dead pressure by ground water. And then we tested about pipe airtight and blasting to certificate which has no problem by using on this study. In the results, we succeeded each blasting in Seosan, Youngdong. For the Peak Sum Vector(PSV) around the blasting at the main points, its real measured PSV is higher 180 % than estimated PSV with USBM. In this study we can't to be analysis of vibration velocity, but to be key providing vibration source.

• Korean Journal of Plant Resources
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• v.23 no.4
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• pp.379-385
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• 2010

This study was carried out to develop cultivation techniques of Climacium japonicum in transparent pot. We analyzed effect of different soil moisture content, air exposure degree, bed soil and ground cover moss on the growth of Climacium japonicum. The best humidity condition in transparent pot culture was 60~80% and a mixture of bed soil with peatmoss : perlite as 7:3 ratio was effective to growth. Two holes(each diameter is 4 mm) in the cover were also effective to the growth and control moisture in the transparent pot. The best mixture of bed soil was moss with peatmoss : pelite(7:3) in the pot culture but price of moss is expensive, the moss treatment was not practical. Total of 10 moss species were selected as ground cover plant; Hypnum erectiusculum Sull. et Lesq., Thuidium kanedae Sak., Hypnum plumaeforme Wils., Trachycystis microphylla Lindb., Bryum argenteum Hedw., Hypnum oldhamii Jaeg., Funaria hygrometrica Hedw., Leucobryum glaucum Aongstr., Polytrichum commune Hedw. and Weissia controversa Hedw. The plant height of selected moss was smaller than that of Climacium japonicum so these moss were very effective to cover the ground.

• Journal of the Korean Society of Safety
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• v.23 no.1
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• pp.66-71
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• 2008

A new route to phthalocyanine complexes were developed to synthesize these products by fusion in the absence of solvent. This new method of synthesis without using solvent has advantages over the conventional synthetic methods since there are no risk of explosion and formation of harmful vapor from organic solvent. Reaction of PcFe with axial ligands such as $PcFe(4-VP)_2$[Pc: Phthalocyanine, 4-VP: 4-Vinylpyridine] and $PcFe(VIM)_2$[VIM: 1-Vinylimidazole] afforded powderlike, pure dark greenish blue colored products. The resulted products are soluble in $CH_2Cl_2$ and found to be complexes of the type $PcFeL_2$. Spectral properties were studied with ATR-FTIR and UV/Vis. Thermal and electrical characterization was also performed. Phthalocyanine complexes exhibit useful properties such as UV/Vis blocking, antistatic characteristics and excellent thermal stability and we anticipate various applicability in numerous products.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.750-756
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• 1985

Experimental investigation was carried out to study the natural convection of water and silicon oil due to end temperature differences in a horizontally insulated rectangular enclosure of aspect ratio 0.1 with a special attention on the core configuration in the laminar boundary-layer flow regime. Rayleigh number ranges covered herein are Ra=4.40 * 10$^{6}$ -9.64 * 10$^{7}$ for water and Ra=1.69*10$^{5}$ -3.80*10$^{6}$ for silicon oil, respectively. In the case of water, for Ra.geq.2.21 * 10$^{7}$ there appeared distinct horizontal thermal layers adjacent to the horizontal boundaries in the core and the temperature distribution outside the horizontal thermal layers, i.e., in the mid-core region, is vertically stratified. The core flow pattern was shown to be nonparallel with a weak back flow in the mid-core for Ra.geq.3.63 *10$^{7}$ . In the case of silicon oil, distinct horizontal thermal layers appeared along the core horizontal boundaries for Ra.geq.1.27 * 10$^{6}$ with a stratified temperature distribution in the mid-core, but the core flow pattern in this case was shown to be parallel. In addition, secondary flow appeared near the hot wall for Ra.geq.3.80 * 10$^{6}$ . Nusselt number, Nu, was found to be proportional to R $a^{0.3}$ for water and R $a^{0.28}$ for silicon oil in the boundary-layer flow regime. There also in an indication from the comparison with other results that Nu is independent of aspect ratio for water in the boundary-layer flow regime in low aspect ratio enclosures.res.