• Journal of Korean Society of Forest Science
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• v.98 no.4
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• pp.426-434
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• 2009

This study was carried out to derive the most optimal production process for the wood fuels(chip and pellet), by collecting cost data on each procedure through the life cycle assessment approach, and to compare between the profitability and efficiency, from the view points of producers and consumers, irrespectively. The costs accounted in this analysis were based on the opportunity cost. The results show that wood chips are cheaper than wood pellets in production costs. In respect to the process with the lowest production cost, while wood chips should be to crush collected residues into pieces on the spot for merchandizing, wood pellets need to be transported to manufactory for pelletizing. The study findings also include that the profits, which is estimated by subtracting expenses from gained sale revenue, were a bit higher for wood chips than wood pellets. Additionally, the price ratio of wood pellets to wood chips for getting the same caloric value appears to be 1.27. Despite of economic benefits of processing wood chips, there are several problems in practice. For producers, there is a possible increase in not only transportation cost for conveying crushers to the dispersed places, but storage cost due to the lack of the marketplaces in the immediate surroundings. For consumers, on the other hand, there are some challenging issues, such as bulky storage facility requirement, additional labor for fuel supplement, frequent ashes disposal, and decomposition in summer and freezing in winter caused by wood chips' own moisture.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.4 s.50
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• pp.1-13
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• 2006

Soil and rock dynamic properties such as shear wave velocity $(V_s)$, compressional wave velocity $(V_p)$ and corresponding Poisson's ratio (v) are very important geotechnical parameters in predicting deformational behavior of structures as well as practicing seismic design and performance evaluation. In an effort to measure the parameter efficiently and accurately, various bore-hole seismic testing techniques have been, thus, developed and used during past several decades. In this study, cross-hole seismic testing technique which is known as the most reliable seismic method was adopted for obtaining geotechnical dynamic properties. To perform successfully the cross-hole test for rock as well as soil layers regardless of the ground water level, spring-loaded source which impact laterally a subsurface ground in vertical bore-hole was developed and applied at three study areas, which contain four sites composed of two existing port sites and two new LNG storage facility sites. The geotechnical dynamic properties such as $V_s,\;V_p$ and v with depth from the soil surface to the engineering and seismic bedrock were efficiently determined from the laterally impacted cross-hole seismic tests at study sites, and were provided as the fundamental parameters for the seismic performance evaluation of the existing ports and the seismic design of the LNG storage facilities.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.171-179
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• 1997

During the day time in summer, peak of air conditing load, and electric power management system lies under overloaded condition. The reason is the enlarged peak load value of electric power caused by increased air-cooling load in summer. To prevent load concentration during day time and overloaded condition of power management system, some energy storage methods are suggested. One of these methods is ice storage system. Water has some good properties as P.C.M.(Phase Chang Material) : Its melting point is the range of required operation temperature. It has large specific latent heat and is chemically stable compared to other organic or inorganic substances. It is cheap and easy to treat. This study represents experimental results of heat transfer characteristics of P.C.M. under the outward melting process in a vertical cylinder. We experimented with twelve combinations of conditions, i.e., three different inlet temperatures($7^{\circ}C,\;4^{\circ}C\;and\;1^{\circ}C$), two working fluid directions(upward and downward), and two aspect ratios, H/R(4 and 2). At the inlet temperature of $7^{\circ}C$ and $4^{\circ}C$, there was temperature stagnation region where the temperature of P.C.M. remains constant at $4^{\circ}C$ regardless of aspect ratio and direction of working fluid. This temperature stagnation occurs as the water, at its maximum density, flows down to the lower region. The phase change interface formed bell-shaped curve as the melting process continued. With a new set of conditions(4H/R, inlet temperature $4^{\circ}C$ and $1^{\circ}C$, downward/upwerd inlet direction), the movement of phase change interface was faster when the working flued inlet direction was downward. With the same set of conditions, melting rate and total melting energy were larger when the working fluid inlet direction was downward. The results were reversed when the other sets of conditions were applied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8870-8878
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• 2015

During the carbon-dioxide capture and storage(CCS) process, $CO_2$ is captured from large point source, and then injected and stored in stable geological structure for thousands and more years. Inside the captured $CO_2$ flow, various impurities, such as $N_2$, $O_2$, argon, etc, are included inevitably. These impurities affect on the CCS process on various aspects. In this study, we designed and built experimental facility to evaluate the various impurity effect on the $CO_2$ pipeline flow, and analyzed the effect of argon ratio and pressure variation on the pressure drop of $CO_2$ flow. By comparing experimental data with 4 kinds of pressure drop model, we figured out and recommended the Cicchitti's model since it showed most accurate result among compared models in this study.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.439-449
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• 2019

To prevent the drying-out of streams and to make effective use of stream water and groundwater, it is necessary to evaluate the impact of groundwater pumping on nearby streams. To this end, stream depletion due to groundwater pumping should be investigated in terms of various hydraulic characteristics of the aquifer and stream. This study used the Baalousha analytical solution, which accounts for stream-stage variation over time, to analyze stream depletion due to groundwater pumping for cases where the stream level decreases exponentially and recovers after the decrease. For conditions such as an aquifer transmissivity of 10~100 ㎡ d^-1, storage coefficient 0.05~0.3, streambed hydraulic conductance 0.1~1.0 m d^-1, stream-well distance 100~500 m, and stage recession coefficient 0.1~1.0 d^-1, the contribution of stream water (the dimensionless ratio of stream water reduction rate to groundwater pumping rate) was analyzed in cases where stream level change was considered. Considering the effect of stream-stage recession, the contribution of stream water is greatly reduced and is less affected by the stream-depletion factor, which is a function of the stream-to-well distance and hydraulic diffusivity. However, there is no significant difference in stream depletion under constant- and variable-stage recovery after recession. These results indicate that stream level control can distribute the relative impacts on stream water and aquifer storage during groundwater pumping

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.193-197
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• 2006

The optimum planting date, plant spacing, and harvest time for production of small-sized sweetpotato was evaluated in 2003 to 2004 at the Mokpo Experiment Station. Small-sized sweetpotato is important as snack food in Korea. Optimum planting date and plant spacing were with plastic mulch, and mid-April and $75{\times}15{\sim}20cm$ respectively, mid-June and $75{\times}15cm$ respectively without plastic mulch. Storage root yield decreased with early harvest, but the ratio of small-sized sweetpotato was higher in plots harvested after 100 days of planting (DAP) than that of 80 or 120 DAP. Considerable differences in storage root yield was noted with planting dates and plant spacings, but the use of plastic mulch resulted to smaller yield variations in plots, harvested in mid-April. Planting in mid-April and harvesting after 100 DAP increased income by about $32{\sim}61%$ compared with plantings mid-May.

• Journal of Dairy Science and Biotechnology
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• v.14 no.1
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• pp.85-95
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• 1996

This study was conducted to obtain basic data about the effect of Lactobacillus delbruckii on the quality and preservability of the bread during bread making. The parameters measured to investigate the bread quality were water content, water activity, pH, hardness, shelf life and sensory evaluation. The results obtained were as follows : 1. During the storage period, moisture evaporated faster in normal bread than the sourdough bread(10, 30, 50%). 2. Normal bread showed 0.94 and sourdough bread resulted from 0.94 to 0.96 in water activity, 3. The concentration rate of sourdough and different dough method resulted in significantly difference value of pH in bread. As the sourdough concentration rate increased the pH changed from 5.5 to 4.5 in sponge dough method. However, the sourdough concentration rate increased, the pH dropped from 5.4 to 4.8 in the bread which made by straight dough method. 4. The normal bread showed tough texture than the sourdough bread as the storage period is extended. 5. As the ratio of sourdough increased, the pH became lower and the production of the off fiavor, the growth of mold delayed for one or two days when stored at 30$^{\circ}$C. 6. The bread with sourdough resulted in higher score than the normal bread by sensory evaluation. 7, The bread with 30% sourdough by straight dough method showed the highest score and the bread with 10% sour dough by sponge dough method resulted in the highest score by sensory evaluation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.4
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• pp.313-320
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• 1984

In order to elucidate the oxidative stabilities of mackerel lipids, lipids were extracted from ordinary muscle, dark muscle, skin (including subcutaneous adipose tissue) and viscera, and then stored at $30^{\circ}C$. The changes of lipids were examined periodically by measuring peroxide value (POV), thiobarbituric acid (TBA), weighing method, acid value (AV) and iodine value (IV), Fatty acid composition of lipids was analyzed by GLC. The results obtained are summerized as follows: The velocity of lipid oxidation during the storage was differ from the extracting part of the sample. It was laster in skin, viscera, dark muscle and ordinary muscle in the order. Ratio of polar lipid fractions in total lipids was ranged from 5 to $15\%$, and the highest result was observed in dark muscle. Main fatty acids of the lipids were $C_{16:0}$ acid ($22.0{\sim}25.9\%$), $C_{18:1}$ acid ($22.3{\sim}26.7\%$) and $C_{22:6}$ acid ($9.6{\sim}13.4\%$), and $C_{22:6}$ acid content ($\%$) was the highest in lipid from dark muscle, and the lowest in lipid from skin. Monoenoic acid content ($\%$) was higher in the non-polar lipid than in the polar lipid, on the contrary. polyenoic acid content ($\%$) was higher in the polar lipid than in the non-polar lipid. Polyunsaturated fatty acids of the lipids, $C_{20:5}$ acid and $C_{22:6}$ acid, decreased predominantly with oxidation during storage, while saturated acids, $C_{14:0}$ acid and $C_{16:0}$ acid, increased predominantly. The polar lipid fractions were oxidized much faster than the non-polar lipid fractions.

• 월간산업보건
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• s.356
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• pp.16-25
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• 2017

Chromium exists at various valences, including elemental, trivalent, and hexavalent chromium, and undergoes reduction-oxidation reactions in the environment. Since hexavalent chromium is known as a human carcinogen, it is most important to evaluate the oxidationreduction characteristics of the hexavalent chromium species. Although hexavalent chromium can be reduced to trivalent state, the detailed information on this in workplace environments is limited. The purpose of this study was to investigate hexavalent chromium reduction in time in various conditions. A pilot chrome plating operation was prepared and operated in a laboratory for this study. There was evidence that the hexavalent chromium was reduced by time after mist generation. The percentage ratio (with 95% confidence intervals in parentheses) of hexavalent chromium to total chromium was almost 100% (99.1 ; 102.3) immediately after mist generation, and was reduced to 87.4% (84.8 ; 89.9) at 1 hour and 81.0% (78.3 ; 83.5) at 2 hours, respectively. Another test indicated that hexavalent chromium collected on PVC filters was also reduced by time after sampling. Hexavalent chromium was reduced to 90.8% (88.2 ; 93.3) at 2 hours after sampling. It also was found that hexavalent chromium was reduced during storage in air. It is recommended that air samples of hexavalent chromium be protected against reduction during storage.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.335-343
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• 1994

To determine the optimal level of cryoprotectant on the denaturation of pollock surimi produced in Korea, the relative cryoprotective effects of crystalline sorbitol alone and in combination with sucrose were assessed. Freeze induced protein denaturation was also studied as affected by polyphosphates and maltodextrin during frozen storage at $-25^{\circ}C$ for 16 weeks. Variables evaluated included salt extractable protein, drip loss and in vitro protein quality. The best cryoprotective effect was achieved from sucrose/sorbitol 1:1(w/w) mixture at $8\%$ with $0.2\%$ sodiumpyrophosphate and sodiumtriphosphate(1:1, w/w) in surimi by measurement of salt extractable protein and drip loss. Those cryoprotectants had little effect on surimi protein quality during frozen storage as measured by trypsin inhibitor(TI), protein digestibility and computed protein efficiency ratio(C-PER). Protein digestibility of surimi was not changed significantly by polyphosphate and maltodextrin at various levels(p<0.05), with the exception of 4 or $6\%$ sorbitol and $10\%$ sucrose alone which resulted in a higher digestibility. $8\%$ sorbitol/sucrose (5:3, w/w) treatment without polyphosphates showed the highest cryoprotective effectiveness from digestibility assay.