• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.17-27
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• 1996

This study was designed to survey exposure levels of formaldehyde among workplaces in some plywood industries and to compare three sampling methods including the impinger method(IM, NIOSH method No. 3500), the solid sorbent tube method(SS, NIOSH method No. 2541), and the passive bubbler monitor method(PB, SKC). The survey was conducted in seven particle board manufacturing factories, two resin manufacturing factories and two plywood manufacturing factories in Incheon area during the period from March 6 to April 20, 1995. The workplaces included were the hot/cold press, the roller/spreader, the soaking/drying, and the reaction/mixing areas. The results were as follows; 1. The average(GM, GSD) concentrations of formaldehyde by sampling methods were 0.11(4.43) ppm by IM, 0.27(2.03) ppm by SS, and 0.29(2.04) ppm by PB, respectively. The concentrations by 1M method were statistically very significantly lower than those of SS and PB methods, particularly at low air borne concentrations of formaldehyde (p<0.001). 2. The area average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.23(2.08) ppm from the press, 0.23(1.77) ppm from the spreader, 0.24(1.51) ppm from the soaking, and 0.46(1.96) ppm from the reaction areas, respectively. The personal average concentrations of formaldehyde by workplaces measured with PB bubblers were 0.30(1.77) ppm from the press, 0.33(1.54) ppm from the spreader, 0.36(1.46) ppm from the soaking, and 0.84(1.19) ppm from the reaction areas, respectively. 3. No statistically significant differences of formaldehyde concentrations among workplaces except the reaction area(p<0.001) were found. 4. Formaldehyde concentrations from personal samples were higher than those of from area sam pies in all workplaces studied. But no statistically significant differences of formaldehyde concentrations both area and personal samples were found. In conclusion, this study found that although formaldehyde concentrations in some plywood industries in Incheon area were below the regulatory limit of 1 ppm, they were over the limits recommended by NIOSH and ACGIH. This study also suggests that the impinger method may underestimate true formaldehyde concentrations. It implies that there will be more workplaces not meeting current regulatory limit if either the solid sorbent or passive bubbler methods were used instead of the impinger method. It is suggested that passive monitors will be a reasonable alternative for area and personal sampling of formaldehyde if the accuracy and validity of passive monitors be verified before use.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.133-140
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• 2009

This paper presents the experimental study to analyze the pressure and production behavior using depressurization and thermal methods in order to evaluate the hydrate productivity in the 2-D multi-well, plate-type apparatus which has 80 md permeability and 30% hydrate saturation. Injecting methane gas through multi-well allowed to set up the highly saturated hydrate system and combining two different sorts of sands made possible to build up the low permeability system. In this system, both depressurization and electric stimulation methods were applied. When operating pressure was low, according to the depressurization experiments results, the gas recovery was high, however strong pulses which appeared at initial stage of production would damage the operation system. Moreover, cases that hydrate reformed have occurred by endothermic reaction. We have conducted experiments four and six times for the depressurization magnitudes of 140 psi and 320 psi, respectively, to analyze production behavior for the method more in detail. For the cases that the depressurization magnitude was set as 140 psi, the unstable period appears in the results, but stabilized soon. In the experiment results for 320 psi the discontinuous and intermittent behavior has been observed. Thermal stimulation experiments was conducted with depressurizing 80 psi which is the case that shows stable behavior and low recovery. In the results, the gas recovery was high and the energy efficiency was low for long stimulating time. The energy efficiency and gas recovery increased for the soaking time of 1 minute after 2 minute-preheating. In the cases of which the soaking time exceeds 1 minute, energy loss by long soaking time caused low gas recovery and poor energy efficiency.

• Korean Journal of Weed Science
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• v.16 no.1
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• pp.8-13
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• 1996

This study was conducted to know the effect of storage period, harvesting time and light condition on dormancy breaking of major weeds. Echinochloa crus-galli, Cyperus serotinus, Aeschynomene indica, Ludwigia prostrata and Bidens tripartita had the 10 or 30% germination ability within 30 days after harvest but scirpus juncoides, Potamogeton distinctus, Aneilema japonica and Monochoria vaginalis had not germination untill 120 days after harvest of seed. C. serotinus and P. hydropiper required strong light for germination but S. juncoides, L. prostrata and B. tripartita showed the less tham 5% germination in the dark condition gerntinator. S. juncoides germination showed negative response in chemical soaking but A. japonica, B. tripartita and L. prostrata showed high germination percentage in Acetone, Chloroform and distilled water soaking during the 10 days after treatment.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.3
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• pp.404-408
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• 1995

The effect of processing conditions on the changes in the contents of dietary fiber fractions and its physical properteis of Godulbaegi(Korean lettuce, Ixeris sonchifolia H.) was determined during preparation and fementation for kimchi. Water holding capacity(WHC) and oil adsorption capacity(OAC) were also checked on the subject of freeze dried powder from different stages of the kimchi processing. Neutral detergent fiber(NDF) content in young samples(leaf and root) decreased with prolonged soaking and fermentation period. Every young samples had a higher level in NDF than in ripe samples. Noticeable decrease in acid detergent fiber(ADF) without a change in ripe roots was showed after fermentation($4^{\circ}C$, 60 days). The water holding capacity of freeze dried young plants ranged from 5.78ml/g for roots to 6.31ml/g for leaves. Soaking and fermentation resulted in decreasing WHC and about 50% of WHC(raw leaves) was lowered after kimchi fermentation($4^{\circ}C$, 40 days). OAC of all samples were lower than WHC in same samples significantly and those were also decreased after soaking and fermentations as WHC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.819-824
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• 2016

The accelerated thermal aging of CSPE (chlorosulfonated polyethylene) was carried out for 33.64 and 67.27 days at 110[$^{\circ}C$], equivalent to 40 and 80 years of aging at 50[$^{\circ}C$], respectively. These samples were referred to as CSPE-0y, CSPE-40y and CSPE-80y, respectively. As the accelerated thermally aged years of the CSPE increase, the insulation resistance[$\Omega$] at 20[Hz], 500[Hz], and 2[KHz], and the percent elongation [%EL] of the CSPE decrease. However, the dissipation factor($tan{\delta}$) at 20[Hz], 500[Hz], and 2[KHz], the apparent density[$g/cm^3$], the glass transition temperature and the melting temperature of the CSPE were increased. The period of time that the voltage has to be applied until electric breakdown of the CSPE-0y is longer than that of the CSPE-40y, and the CSPE-80y, but the dielectric strength of the CSPE-80y is lower than that of the CSPE-0y and the CSPE-40y. The differential temperatures after the AC and DC voltages are applied to CSPE-0y, CSPE-40y and CSPE-80y are 0.026~0.028[$^{\circ}C$], 0.030~0.042[$^{\circ}C$], 0.018~0.045[$^{\circ}C$], respectively. The variations of temperature for the AC voltage are higher than those for the DC voltage when an AC voltage is applied to CSPE-0y, CSPE-40y and CSPE-80y. It is found that the dielectric loss owing to the dissipation factor[$tan{\delta}$] is related to the electric dipole conduction current. It is ascertained that the ionic (electron or hole) leakage current is increased by the separation of the branch chain of CSPE polymer from the main chain of the polyethylene as a result of thermal stress due to accelerated thermal aging as well as by conducting ions such as $Na^+$, $Cl^-$, $Mg^{2+}$, $SO_4^{2-}$, $Ca^{2+}$ and $K^+$ after seawater soaking.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.19-28
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• 1987

These experiments were conducted to recognize the germination change in relation to storage period, using 25 kinds of field-collected weed seeds stored under the dry and low temperature ($4{\pm}1^{\circ}C$), and to establish a simple germination induction methods in some kinds of them. No or weak dormancy was observed in Lepidium virginicum, Rumex japonicus, Cirsium japonicum var. ussuriense, Aeschnomene indica and Ludwigia prostrate. The germination of Digltaria sanguinalis, Portulaca oleracea, Amaranthus spp., Echinochloa crux-galli, Polygonum persicaria, Cyperus iria, and Aeschynnmene indica was enhanced by $H_2SO_4$ treatment for 20, 2, 2, 50, 40, 3 or 5 minutes, respectively. Favorable germination in Polygonum persicaria and Echinochloa crus-galli was obtained by soaking in water for 25 days and 50 days, respectively. Moisture treatment for 21 days and 14 days caused the enhancement of germination in Cyperus difformis and Aneilema keisak, respectively. Combination of various treatments in Cyperus iria was most effective when the seeds treated with $H_2SO_4$ for 3 minutes incubated in alternating temp. after soaking in 0.2% $KNO_3$, but their effect on Digitaria sanguinnlis was little.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.328-334
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• 2019

Purpose: The aim of this study was to confirm if Laser-treated implants were soaked in 0.9% NaCl solution for 2 weeks could increase the surface hydrophilicity, and the Remoal Torque of each implant that inserted in rabbit tibia for initial healing period of 10 days. Materials and methods: Twenty machined titanium surface screws were produced with a diameter 3 mm, length 8 mm. Ten screws had their surface treated with a laser only (laser treated group), and the other 10 were soaked in saline for 2 weeks after surface treatment with a laser (laser treated + saline soaked group). Implants were inserted in rabbit tibia (ten adult New Zealand white rabbits), and the RTQ of each implant was measured after 10 days. The wettability among implants was compared by measuring the contact angle. Surface composition and surface topography were analyzed. Results: After 10 days, the laser treat + soaking group implants had a significantly higher mean RTQ than the laser treated implants (P = .002, < .05). There were no significant morphological differences between groups, and no remarkable differences were found between the two groups in the SEM analysis. Conclusion: Saline soaking implants is expected to produce excellent RTQ and surface analysis results.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2004.03a
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• pp.216-219
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• 2004

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.670-674
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• 1997

Semi-solid forging is a compound forging technology to deventional forging process. Among several steps of semi-solid forging process, the heating step of a billet prior to semi-solid forging step is necessarily required to obtain globular microstructure. For the forming operation to work properly, it is also important to heat the billet uniformly for the uniformity of solid-liquid distribution. To satisfy these requirements, induction heating has been generally used for a long time. This paper presents the method to find heating condition and the temperature distribution inside of a billet with a induction heating apparatus by comparing the computer simulation with experiment for aluminum alloys Al2024 and A356.

• The Korean Journal of Food And Nutrition
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• v.16 no.3
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• pp.218-223
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• 2003

This study is proceeded on the development of standard method for making soybean paste by Korean traditional method. Fermentation condition of Meju was 1) Pre-fermentation : 30 days in about 20$^{\circ}C$ room, 2) Main fermentation : 5 days in 30$^{\circ}C$ or upper temperature, 3) Post fermentation and drying : 30 days in well sunlightened room in January. Meju was soaked in 18% salt solution(Meju 7kg/salt solution 20L) for 35～40 days (from late February to early April) and after soaking Meju was filtered as unsoluble solute and crushed and put into traditional Korean receptacle(named 'Dok'). Crushed Meju was stored from early April to mid September and Meju was changed into soybean paste(Doen-jang). During fermentation amino acid nitrogen in Doen-jang was slightly increased in early period and decreased lately. It has been proved that by panel test soybean paste made by the method suggested in this study was more excellent than commercially fermented soybean paste. This study has presented the possibility of commercial production of soybean paste made by traditional method.