• Microbiology and Biotechnology Letters
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• v.9 no.2
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• pp.83-89
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• 1981

Several kinds of organic acids, alcohols, aromatic compounds and sugars as carbon sources were tested in order to produce the cell mass of Rhizopus oryzae which is used in part of food processing or organic acid fermentation. Sodium acetate among them was good enough for carbon source as well as glucose under the concentration of one percent. All nitrogenous substances tested such as ammonium, nitrate or organic nitrogen compounds were well used by this strain of Rhizopus oryzae as nitrogen source. Ammonium sulfate among inorganic nitrogen compounds was most utilized as a nitrogen source in glucose or acetate medium. This strain did not require any growth factors such as yeast extract. The following composition of medium was therefore determined in order to produce the cell mass of Rhizopus oryzae: Na-acetate 1 %, (NH$_4$)$_2$SO$_4$ 0.2%, $K_2$HPO$_4$ 0.05%, MgSO$_4$.7$H_2O$ 0.01%, NaCl 0.01% (PH 5.5). The cell wall of mycelium grown in above medium was lysed optimally at pH 6.5 and 5$0^{\circ}C$ by the action of Strepzyme 115-5. On producing protoplast from mycelium by enzymatic action, almost all of the mycelium was damaged after 4hrs of treatment.

• Microbiology and Biotechnology Letters
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• v.33 no.4
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• pp.288-294
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• 2005

Flavonoid compounds show several biological activities and generally exist in the forms of glycones linking sugar moiety to main structure. Flavonoid glycones such as naringin and hesperidin in korean citrus peel are slower absorbed and consequently less active than their aglycone, naringenin and hesperetin, respectively. Therefare to increase the content of flavonoid aglycone in korean citrus peel, we used commercial carbohydrate-hydrolysing enzymes, AMG 300 L, Pectinex 100 L, and Viscozyme for transforming flavonoid glycones to aglycones. Optimal conditions of enzyme reaction were pH 5.0-7.0, $5\%$ enzyme, and 24-48 hrs. The content of naringenin and hesperetin as flavonoid aglycones in untreated citrus peel is $100\~200\;ng/g$ of dried citrus peel. In case of enzyme-treated citrus peel the content of naringenin and hesperetin increased to $1,539\∼6,674\;ng/g\;and\;1,974\∼8,906\;ng/g$ of dried citrus peel, respectively. Finally the content of flavonoid aglycones could be extracted to 10-80 times. Now enzyme-treated citrus peel may be applied to use for functional food because of its higher flavonoid aglycones as more active compounds.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.69-76
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• 2012

Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and $15{\sim}20^{\circ}$, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders ($Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$), shock-consolidated $Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$ bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.

• Food Science and Preservation
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• v.16 no.2
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• pp.139-146
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• 2009

Whole and stem-off cherry tomatoes were packaged using perforated films(LF05, LF10, LF20, and LF40). Gas composition(ethylene, $O_2$, and $CO_2$), firmness(compression and penetration force), color, brix degree, acidity, and total microbial counts were assessed during storage at $10^{\circ}C$ and 85% relative humidity. Gas composition varied with film gas permeability, indicating that modified atmospheric(MA) conditions were achieved. Firmness fell during storage; samples packed using LF05 showed the lowest firmness, corresponding to low gas transmission conditions. L(lightness) and a(redness) values respectively decreased and rose slightly with increasing storage time, but the b(yellowness) values fell notably. Film permeability significantly affected acidity and soluble solid levels. When LF40 packaging was used, acidity and brix scale changes were similar to those seen after PET container packaging. Total microbial counts increased with time after packaging in most films, and pretreatment differences were not significant. Microflora varied between stem on/off tomatoes. Skin wrinkling and juice appearance were common in tomatoes stored in PET containers and LF films of low gas permeabilities(LF05, LF10, and LF20). White molds were partially found on stem-on tomatoes stored using packaging systems. When film packagings were compared, LF40 was optimal, permitting minimal pretreatment yet offering maximal sanitation.

• Membrane Journal
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• v.9 no.3
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• pp.157-162
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• 1999

In the crosslining reaction of poly(vinyl alcohoJ)(PVA) with sulfur-succinic acid which had been established in our previous work, reaction temperature, 15$0^{\circ}C$, was so high to collapse the pore struc¬tures in support membrane for the preparation of composite membrane. Therefore, the efforts have been focused on lowering of the reaction temperature to 100$^{\circ}$C by using a catalysis, HC!. The newly established crosslinking reaction was characterized through the analysis of the chemical and thermal properties. From these results, the optimum conditions for the membrane preparation couId be drawn as followings : (i) reac¬tion temperature, 100 $^{\circ}C$,(ii) reaction time, 90 min, (iii) the concentration of the catalysis (HCD, 1.5%. Com¬posite membranes were fabricated by coating a casting solution containing PYA, sulfur-succinic acid and HCl on a support membrane followed by crosslinking it at 10$0^{\circ}C$. The resulting membranes were applied to the pervaporation separation of methyl-tert-butyl ether(MTBE)/methanol (MeOH) mixtures at 30, 40, and 5O$^{\circ}C$. The flux of 5.09 g/$m^2$hr at 5O$^{\circ}C$ and the highest separation factor of 1622 were obtained, respectively.

• Journal of the Korean Chemical Society
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• v.45 no.4
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• pp.341-350
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• 2001

Aluminum Hydroxide was employed as a thermal retardent and flame retardent for Chloropolyethylene (CPE) rubbery materials which is the construction material of automotive oil cooler hose. and then cure characteristics, physical properties, thermal resistance and flame retardation of compounded rubber were investigated, and optimum mixing conditions of rubber and flame retarding agent were deduced from the experimental results. CPE rubber material which has excellent properties of chemical corrosion resistance and cold resistance and inexpensive in price was used to prepare rubber specimen. The by-product of ething, produced from the process of surface treatment of aluminum was processed to aluminum hydroxide via crushing and purification, which is characterized by XRD, PSA, SEM and ICP-AES techniques in terms of phase, size, distribution, morphology and components of particles and then mixed to CPE rubber materials in the range of 0~80 phr. Hardness, tensile strength, elongation and thermal properties of compounded rubber specimens were tested. The optimum mixing ratio of rubber to additives to give maximum effect on thermal resistance and flame retardation, within the range of tolerable specification for rubber materials, was determined to be 40 phr. The flame retardation of CPE rubber materials was found to be increased by 5 times at this mixing ratio.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.55-59
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• 2018

In this paper, we investigated the characteristics of shear stress type piezoresistor on a diaphragm structure formed by MEMS (Microelectromechanical System) technology of silicon-direct-bonding (SDB) wafers with Si/$SiO_2$/Si-sub. The diaphragm structure formed by etching the backside of the wafer using a TMAH aqueous solution can be used for manufacturing various sensors. In this study, the optimum shape condition of the shear stress type piezoresistor formed on the diaphragm is found through ANSYS simulation, and the diaphragm structure is formed by using the semiconductor microfabrication technique and the shear stress formed by boron implantation. The characteristics of the piezoelectric resistance are compared with the simulation results. The sensing diaphragm was made in the shape of an exact square. It has been experimentally found that the maximum shear stress for the same pressure at the center of the edge of the diaphragm is generated when the structure is in the exact square shape. Thus, the sensing part of the sensor has been designed to be placed at the center of the edge of the diaphragm. The prepared shear stress type piezoresistor was in good agreement with the simulation results, and the sensitivity of the piezoresistor formed on the $2200{\mu}m{\times}2200{\mu}m$ diaphragm was $183.7{\mu}V/kPa$ and the linearity of 1.3 %FS at the pressure range of 0~100 kPa and the symmetry of sensitivity was also excellent.

• Journal of the Korea Organic Resources Recycling Association
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• v.7 no.2
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• pp.83-92
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• 1999

Chitosan was prepared from chitin which was abstracted from wasted crab shells. Then itaconic acid was graft-copolymerized onto chitosan using ceric ammonium nitrate as a reaction initiator. To investigate the optimal grafting conditions, the influences of several factors on the grafting were studied, i. e., the concentrations of CAN and itaconic acid, the reaction temperature and time. And to find out its flocculation ability. the flocculation test was carried out with a metal plating factory waste water. The state of graft-copolymer was identified through IR spectra analysis. The optimal grafting conditions and flocculation results were shown to be : concentration of ceric ammonium nitrate is $3.5{\times}10^3M$, reaction temperature is $40^{\circ}C$ and reaction time is 4hrs with 0.25M of the monomer(itaconic acid). Though flocculation tests using chitosan, grafted chitosan and cation, CODcr. metal ions removal rates were measured. The order of superiority is Itaconic acid grafted chitosan>Chitosan>Cationic polymer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.68-74
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• 1999

The optimum conditions for selective .elimination of salt from tuna boiled extract (TBE) by electrodialysis were determined. The desalination conditions of TBE were determined at various pH's, concentrations and volumes of TBE. The ion-exchange membrane with a molecular weight cut off 100Da was used for desalting of TBE. The desalination times on $1\%$ and $10\%$ of TBE concentrations were 40 min and 240 min, respectively. The electrodialysis process could removed above $95\%$ of the initial salt content in $1\%$ and $10\%$ of TBE concentrations. The desalination of TBE at pH 4.0 was $14\%$ higher than that at pH 9.0 The amount of water transferred by the electrodialysis was determined. The electrodialysis process could remove above $90\%$ of the initial salt content in $5\%$ TBE for 80 min. The initial volume and the permeate did not have significant effects on desalination time and ratio. The key parameters for the desalination of TBE were pH and concentration of TBA.

• Food Science and Preservation
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• v.11 no.4
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• pp.516-521
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• 2004

The study was intended to develop a yam snack to increase the consumption and the added value of the yam which has many kinds of medicinal effects and functions. Moisture content of a freeze-drying yam snack was higher than those of hot wind drying and vacuum drying yam snack. However, carbohydrate content was opposed to it. The content of soluble proteins in freeze drying yam snack was 6.43 mg/100g, and lower than that those in hot wind drying and vacuum drying yam snack. The contents of total sugar and reducing sugar were not noticeably different by processing methods. The major organic acids of yam snack were malic, acetic, acids, and acetic acid. Citric acid were rich contented in hot wind and vacuum dried yam snack, but the content of malic acid in freeze dried yam snack was higher than those in hot wind and vacuum dried yam snack. The contents of the amino acids and total amino acids showed the highest contents in vacuum dried snack and the next came in hot wind dried snack and freeze dried snack order. The content of free amino acids were not different by processing methods. Total content of vitamin C were not different by processing methods, but a ascorbic acid was higher in freeze dried yam snack than those in other. The dehydroascorbic acid contents of the hot-air and vacuum dried snack was higher than those of the freeze dried snack, Potassium, sodium and magnesium were the main minerals of the yam snacks.