• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.12 no.2
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• pp.109-115
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• 2006

In response to the continuous changes in current consumer demands and market trends for postharvest produces, the functional application for agricultural packaging is becoming increasely significant. This paper focuses on the overview of important changes in physical and chemical status related to postharvest physiology and applications of the functional packaging materials for maintaining the freshness of fruits after harvest. During postharvest treatment and storage periods, fresh fruits undergoes the ripening process in quality attributes of the fruit such as major changes of texture, color, and flavor. Major fruit packaging technologies are concerned with correct gas permeable film and functions of ethylene removal, antimicrobial, and antifogging substances to keep the effective freshness. Application guidelines for the functional packaging in fresh produces were studied.

• Food Science and Preservation
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• v.2 no.2
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• pp.293-301
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• 1995

Quality changes of Korean native-bee honey were investigated during processing and preseration at different temperature. There were no changes of HMF(Hydroxy methyl furfural) and proline contents, color and diastase activity in Korean native-bee honey, when the honey separated from honey combs at 20$^{\circ}C$ and 40$^{\circ}C$. However, at 50 and 80$^{\circ}C$, browning of Korean native-bee honey was shown, HMF content was increased rapidly and proline content and diastase activity were decreased. There were no changes of chemical composition in Korean native-bee honey during storage at 4$^{\circ}C$ for 6 months. But color was darken and HMF content was increased slowly in Korean native-bee honey during storage at 20$^{\circ}C$. During storage at 30$^{\circ}C$ and 40$^{\circ}C$, HMF content was increased highly, proline content, diastase activity and total acidity was decreased rapidly. It is recommended that Korean native-bee honey is separated from honey comb and purified at less than 40$^{\circ}C$ and stored at 4$^{\circ}C$ through 20$^{\circ}C$.

• Fashion & Textile Research Journal
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• v.20 no.1
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• pp.93-100
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• 2018

This study comparatively analyzed the changes in the dimensional stability and the mechanical properties of stretch knit fabrics associated with washings conditions in order to determine the most appropriate washing method. Polyester and spandex knit fabrics were washed 25 cycles with nine washing condition profiles that controled detergent, hardness. temperature and RPM. The knit fabrics with repeated washings were evaluated by dimensional stability and measured by the KES-FB system. Polyester and spandex fibers have good chemical resistance. However, the changes in the dimensional stability and the mechanical properties were observed in washed knit fabrics. After repeated washings, the knit fabrics washed in an alkali or neutral detergent had good dimensional stability compared with the knit fabric washed in functional detergent. The washed knit fabrics were extended, stiff, rough, and had a smaller volume. The changes were the result of the rearrange of polyester fibers which twisted around spandex core and chemical interactions involving the detergent and the physical and mechanical forces of washing. Especially, using an alkali detergent resulted in increased stiffness and roughness of the knit fabric. In conclusion, the washing in water with low hardness and a neutral detergent can minimize the changes in dimensional stability and mechanical properties of polyester and spandex knit fabric.

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.2
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• pp.40-45
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• 2019

The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.707-712
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• 1996

Growth and changes of electronically conducting polypyrrole (PPy) in the form of thin films polymerized on metal electrodes were investigated by electrochemical and in situ three-parameter ellipsometry methods at the wavelength of 632.8 nm. Although the optical equations produced multiple sets of solution, it was possible to determine a unique set of thickness and the optical constants of a film by auxiliary measurements and/or physical reasoning. The changes in the thickness and the optical properties of the polymers during polymerization and electrochemical oxidation/reduction was successfully followed by the three-parameter ellipsometric technique. The optical properties of the polymers continuously changed as the film grew. The imaginary part of the refractive index of polypyrrole seemed to be dominantly determined by the existence of an absorption band around the visible range.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.1-9
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• 1996

The aggregates with the different mineralogical features are studied how to affect the basic physical properties of concretes according to the changes of the chemical composition, mineralogical composition, crystal size, the standard qualities in the aggregates in using chemical analysis, X.R.D. DT-TGA, polarized light microscope, streoscopic microscope, standard test method of aggregates & concretes. At this studies, we found that aggregates without the seathered mineral such as muscovite & kaolin mineral etc, is superior to the others with the weathered mineral, even if it's standard qualities are inferiored to the other's. For examples, in manufacturing high strength concretes. The strength of concretes used aggregates without weathered mineral are improved about 15% than the other's and also. For general mixture to manufacture remicon, more about 10-20% than the other's strength and workability.

• Journal of Dairy Science and Biotechnology
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• v.35 no.2
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• pp.121-133
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• 2017

A small amount of milk is sold as 'untreated' or raw in the US; the two most commonly used heat-treatments for milk sold in retail markets are pasteurization (LTLT, low-temperature long time; HTST, high-temperature short time) and sterilization (UHT, ultra-high temperature). These treatments extend the shelf life of milk. The main purpose of heat treatment is to reduce pathogenic and perishable microbial populations, inactivate enzymes, and minimize chemical reactions and physical changes. Milk UHT processing combined with aseptic packaging has been introduced to produce shelf-stable products with less chemical damage than sterile milk in containers. Two basic principles of UHT treatment distinguish this method from in-container sterilization. First, for the same germicidal effect, HTST treatments (as in UHT) use less chemicals than cold-long treatment (as in in-container sterilization). This is because Q10, the relative change in the reaction rate with a temperature change of $10^{\circ}C$, is lower than the chemical change during bacterial killing. Based on Q10 values of 3 and 10, the chemical change at $145^{\circ}C$ for the same germicidal effect is only 2.7% at $115^{\circ}C$. The second principle is that the need to inactivate thermophilic bacterial spores (Bacillus cereus and Clostridium perfringens, etc.) determines the minimum time and temperature, while determining the maximum time and temperature at which undesirable chemical changes such as undesirable flavors, color changes, and vitamin breakdown should be minimized.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.2
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• pp.52-62
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• 2010

This study was carried out in the Tropical Plant Resources Research Center of Korea National Arboretum to determine the optimum edaphic environment for the growth of tropical and subtropical plants. The physicochemical properties of artificial substrates and the growth characteristics of tropical and subtropical plants were investigated. Subtropical plants exhibited a high growth rate when cultivated in a substrate of Dry Zone that had physical properties similar to those of arid native soil. Mediterranean plants showed a low growth rate when grown in a substrate of Subtropical Zone that required changes in acidity. The substrate of Tropical Zone had high organic matter and mineral contents and therefore had good physical properties:this substrate has a good environment for the stimulation of the growth of tropical plants. Our results indicate that the chemical properties such as pH and mineral contents of most artificial substrates need to be more urgently improved than their physical properties in order to ensure better growth of tropical and subtropical plants. Initial management strategies for the construction of new tropical greenhouses were formulated, and data from monitoring studies will be continuously gathered and incorporated in the manual to keep it updated.

• Journal of the Korean Society of Tobacco Science
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• v.17 no.2
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• pp.139-148
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• 1995

This study was carried out to investigate the effects of super heated steam on the physical and chemical changes of burley cut tobacco. Total sugar, total alkaloid, ether extracts, crude ash, total nitrogen and pH for leaf chemical constituents were analyzed. Filling power and fineness index for physical properties, and carbonyl compounds, phenol compounds, amonia, pH, hydrogen cyanide nicotine, carbon monoxide, total volatile base and tar for smoke components were also analyzed. The cut tobacco treated with super heated steam showed significant decrease in total sugar and total alkaloid. The filling power of the sample treated with the super heated steam system was increased abruptly when heated at over 250℃. The fineness index showed similar tendency to that of common toast method. Super heated steam treatment slightly decreased carbonyl compounds, phenol compounds, hydrogen cyanide, nicotine, carbon monoxide and tar in the tobacco. Especially the decrease of ammonia was the most remarkable. The pH of smoke was a little different compared with that in the common toast. The sensory test results showed that, compared to the common conveyer moving system, the tobacco treated with super heated steam system brought out more roasted flavor, lowered impact, irritation, and sting, further improved aftertaste, and lowered bitterness. The super heated steam treatment method used in the studies is expected to give better filling power, mild taste and toasted odor of tobacco than that of the common method for toast treatment. Key words : burley tobacco, super heated steam, expansion, toast.

• Carbon letters
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• v.1 no.3_4
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• pp.138-142
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• 2001

The effect of electrochemical surface treatments in KOH chemical solution on microstructures of carbon blacks was investigated in terms of surface functional values and XRD measurements. And their mechanical interfacial properties of the carbon blacks/rubber composites were studied by the composite tearing energy ($G_{IIIC}$). It was found that the development of basic-surface functional groups lead to the significant physical changes of carbon blacks, such as, decrease of the interlayer spacing ($d_{002}$), increase of the crystalline size along c-axis ($L_c$), and increase of degree of crystalline (${\chi}_c$). This treatment is possibly suitable for carbon blacks to be incorporated in a hydrocarbon rubber matrix, resulting in improving the hardness and tearing energy of the resulting composites.