• Journal of Bio-Environment Control
• /
• v.18 no.4
• /
• pp.303-308
• /
• 2009

This study was conducted to analyze the feasibility of plant growth under low pressure and to investigate the effect of pressure on plant growth. Three levels of pressures (25, 50, and 101.3 kPa (control)) were provided to analyze the growth of Lettuce (Lactuca sativa L.) as affected by low pressure. Photoperiod, air temperature, and photosynthetic photon flux were set at 16/8 h, 26/$18^{\circ}C$, and $240{\mu}mol{\cdot}m^{-2}s^{-1}$, respectively. Growth characteristics of lettuce were measured on 7 days and 14 days after experiment. Leaf length, leaf width, leaf area, and root dry weight of lettuce measured on 7 days under 25 and 50 kPa were significant as compared to the control. Leaf length, top dry matter and root dry matter of lettuce measured on 14 days were significantly different under 25 and 50 kPa. From these results, we confirmed that lettuce could be grown under low pressure. However high relative humidity by evapotranspiration from leaves and growing beds under low pressure caused the condensation on the inner surface of the chamber. Therefore in a low pressure chamber, humidity control is required to maintain the relative humidity at a proper level.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.6
• /
• pp.479-486
• /
• 2010

In order to confirm the effect of $HI_x$ solution on Bunsen reaction in Sulfur-Iodine thermochemical hydrogen production process, the reaction was investigated using $HI_x$ solution as a reactant. The phase separation characteristics of reaction with $HI_x$ solution were compared with the reaction using $I_2$ and $H_2O$ as reactants. Firstly, saturation points of $I_2$ in $HI_x$ solution at various temperatures were investigated to determine reaction conditions. With increasing temperature, the amounts of unreacted $I_2$ and $H_2O$ in $HI_x$ solution were increased, while impurities (HI in $H_2SO_4$ phase and $H_2SO_4$ in $HI_x$ phase) in each phase were decreased. The volumes of $H_2SO_4$ phase obtained from Bunsen reaction with $HI_x$ solution was relatively less than those obtained from the reaction with $I_2$ and $H_2O$. The difficulty of phase separation in Bunsen reaction using $HI_x$ solution may be due to the insufficient amount of $H_2O$ existed in $HI_x$ phase after reaction. Therefore, we concluded that the supplement amount of $H_2O$ should be calculated on the basis of the moles of HI and $H_2SO_4$ and added to the reaction system for good phase separation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.9
• /
• pp.761-772
• /
• 2015

Microfin tubes having an outside diameter (O.D.) of 7.0 mm are widely used in residential air conditioning systems and heat pumps. It is known that the mass fluxes for air conditioners and heat pumps under partial load conditions are several tens of $kg/m^2s$. However, literature surveys reveal that previous investigations were limited to mass flux over $100kg/m^2s$. In this study, we conduct R-410A evaporation heat-transfer tests at low mass fluxes ($50-250kg/m^2s$) using a 7.0 mm O.D. microfin tube. During the test, the saturation temperature was maintained at $8^{\circ}C$, and the heat flux was maintained at $4.0kW/m^2$. For comparison purposes, we also test a smooth tube with a 7.0 mm O.D. The results showed that the heat-transfer enhancement factor of the microfin tube increased as the mass flux decreased up to $150kg/m^2s$, which decreased as the mass flux further decreased. The reason for this was attributed to the change of the flow pattern from an annular flow to a stratified flow. Within the test range, the frictional pressure drops of the microfin tube were approximately the same as those of the smooth tube. We then compare experimental data obtained with the predictions obtained for the existing correlations.

• Economic and Environmental Geology
• /
• v.51 no.5
• /
• pp.439-453
• /
• 2018

The Eocene Gyeongju granitoids in SE Korea are alkali feldspar granite (AGR), biotite granite (BTGR), and hornblende biotite granodiorite (HBGD) along Yangsan fault and Ulsan fault. According to their geochemical characteristics, these granitoids are classified as A-type (AGR) and I-type (BTGR and HBGD) granitoids, and regarded that were derived from same parental magma in upper mantle. The hornblende and biotite of AGR as an interstitial phase indicate that influx of F-rich fluid during the crystallization of AGR magma. AGR is enriched LILE (except Sr and Ba) and LREE that indicate the influences for subduction released fluids. The highest HFSE contents and zircon saturation temperature of AGR among the Eocene Gyeongju granitoids may indicate that it was affected by partial melting rather than magma fractionation. These characteristics may represent that the high F contents of AGR was affected by F-rich fluid derived from the subducted slab and partial melting. It corresponds with the results of the REE modeling and the dehydrated fluid component (Ba/Th) modeling showing that AGR (A-type) was formed by the partial melting of BTGR (I-type) with the continual influx of F-rich fluid derived from the subducted slab.

• Applied Chemistry for Engineering
• /
• v.17 no.4
• /
• pp.420-425
• /
• 2006

Nano sized mixed metal hexagonal ferrite powders with improved magnetic properties have been prepared by sol-gel method using propylene oxide as a gelation agent. To obtain the desired ferrite, two different metal ions were used. One of the ions has only +2 formal charge. The key step in the processes is that hydrated $Ba^{2+}$ or $Sr^{2+}$ ions are hydrolyzed and condensed at the surface of the previously formed $Fe_{2}O_{3}$ gel. In this processes, all the reaction can be finished within a few minutes. The magnetic properties of the produced powder were improved by heat treatment. The highest values of the magnetic properties were achieved at temperature $150^{\circ}C$ lower than those of the previously published values. The highest observed values of coercivity and the saturation magnetization of Sr-ferrite and Ba-ferrite powder were 6198 Oe, 5155 Oe and 74.4 emu/g, 68.1 emu/g, respectively. The ferrite powder annealed at $700^{\circ}C$ showed spherical particle shapes. The resulting spheres which were formed by the aggregation of nanoparticles with size 3~5 nm have diameter around 50 nm. The powder treated at $800^{\circ}C$ showed hexagonal-shaped grains with crystallite size above 500 nm.

• Fire Science and Engineering
• /
• v.27 no.1
• /
• pp.39-45
• /
• 2013

This study analyzes the explosion hazard of dry cleaning solvent recovery machine in laundry shop in two aspects, i.e. combustible and ignition source, and determines the explosive conditions of this machine by conducting mockup explosion tests repeatedly, varying conditions and using real dry cleaning solvent recovery machines. As to combustibles, two kinds of combustibles used widely in Korea have been selected and tested. The flash points, LEL's, and saturation vapor pressures of those combustibles have been measured, and their explosion specific curves have been drawn, based on the results of the measurements, so that the explosion risks of those materials may be determined, depending on the temperatures. Potential voltages generated from materials for laundry and foreign materials of metals have been assumed to be the ignition sources in this application, and their potential voltages have been measured, depending on temperature, humidity, and antistatic agent, by using real materials for laundry and a potential voltage measuring device. Tests have been conducted, varying the quantities, concentrations, and operating temperatures of materials for laundry. As a result, explosions have not been generated with potential voltages of materials for laundry, but explosions have been observed when applying artificial spark energy of 2.0 mJ.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.663-666
• /
• 2005

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately $300\times500m$ area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

• Journal of Veterinary Clinics
• /
• v.27 no.6
• /
• pp.668-673
• /
• 2010

This study was to evaluate the effects of tramadol and medetomidine administration on minimum alveolar concentration (MAC) of isoflurane in dogs. MAC of isoflurane was determined in four occasions; 1 ml saline (Control), $2{\mu}g$/kg medetomidine (M2), 4 mg/kg tramadol (T4), $2{\mu}g$/kg medetomidine-4 mg/kg tramadol combination (M2T4). Heart rate, blood pressure, respiratory rate, end-tidal carbon dioxide concentration, saturation of hemoglobin with oxygen and body temperature were recorded. After administration of M2 ($0.81{\times}0.18%$), T4 ($0.81{\times}0.14%$) and M2T4 ($0.62{\times}0.12%$), less isoflurane was required than the control value ($1.13{\times}0.19%$). Significantly lower heart rate than the control value was detected after treatment of M2, T4, and M2T4. When only M2T4 was administered, blood pressure was significantly higher than the control value. In conclusion, administrations of tramadol, medetomidine and medetomidine-tramadol combination decreased the MAC of isoflurane in dogs. Especially, medetomidine-tramadol combinations could be useful as a premedication because of the anesthetic sparing effect and moderate changes in cardiovascular system.

• Korean Journal of Materials Research
• /
• v.21 no.5
• /
• pp.243-249
• /
• 2011

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to $89^{\circ}C$/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.5
• /
• pp.288-302
• /
• 2017

Accurate measurement of benthic nutrient fluxes (BNF) is a prerequisite for evaluating the effect of sediments on nutrient cycle in the surface water. The intact sediment cores were collected in July 2015 at the midstream of Nakdong River. We identified pre-incubation time (6, 12, 24 hr), dissolved oxygen concentration (90, 70, 50% saturation), diffusive boundary layer thickness (0, 0.6-0.8, 1.2-1.4 mm), and incubation temperature (10, 17, 20, $25^{\circ}C$) as the most important control factors, and measured the BNF fluctuation with the variation of these factors using the laboratory sediment core incubation method. Since the chemical composition, redox condition, hydrodynamic regimes and microbial activities at the sediment-water interface were changed as a result of the alteration of control factors, sediment core incubation should be conducted under as close to the natural conditions of study site as possible, in order to produce the results similar to actual values. Relative percentage differences between two replicates were below 20% in most control factors, which showed satisfactory precision for strict compliance with the experimental conditions and procedures. In the further studies, we will compare the results of core incubation with those of in situ measurements to confirm the accuracy of the sediment core incubation method.