• Clean Technology
• /
• v.10 no.3
• /
• pp.121-130
• /
• 2004

Pelletizer of dry ice snow produced by adiabatic expansion of liquid carbon dioxide and their blaster were designed and manufactured. The blaster had a high cleaning power against various contaminants on the surface such as stain, oily dirt, lacquer film and paints with low blasting pressure and low consumption of blasting air. The capacity of hopper for dry ice pellet supply was 12 kg and the mass rate of pellet blasting was controlled in 0 to 1.2 kg/min. The impact of the pellets was independent of standoff distance within a certain limiting distance, and dependent on the impact stress, angle and mass rate of dry ice pellet blasting. On the other hand the cleaning power was influenced by thermal properties and surface roughness of the substrates and decreased in the order of glass, copper, brass, steel and acryl. The power was also affected by hardness and adhesion of the contaminant on the substrate, and decreased in the order of grease, epoxy and paint. The noise was detected during blasting in the range of 85 to 100dBA.

• Membrane and Water Treatment
• /
• v.10 no.1
• /
• pp.45-55
• /
• 2019

Climate change has significantly affected the rainfall characteristics which can influence the pollutant build-up and wash-off patterns from the catchment. Therefore, this study explored the influence of varying rainfall characteristics on urban and agricultural runoff pollutant export using statistical approaches. For this purpose, Mann-Kendall and Pettitt's test were applied to detect the trend and breakpoint in rainfall characteristics time series. In addition, double mass curve and correlation analysis were used to drive the relationship between rainfall-runoff and pollutant exports from both catchments. The results indicate a significant decreased in total rainfall and average rainfall intensity, while a significant increased trend for antecedents dry days and total storm duration over the study periods. The breakpoint was determined to be 2013 which shows remarkable trend shifts for total rainfall, average rainfall intensity and antecedents dry days except total duration. Double mass curve exhibited a straight line with significant rainfall-runoff relationship indicates a climate change effect on both sites. Overall, higher pollutant exports were observed at both sites during the baseline period as compared to change periods. In agricultural site, most of the pollutants exhibited significant (p< 0.05) association with total rainfall, average rainfall intensity and total storm duration. In contrast, pollutants from urban site significantly correlated with antecedent dry days and average rainfall intensity. Thus, total rainfall, average rainfall intensity and total duration were the significant factors for the agricultural catchment while, antecedents dry days and average rainfall intensity were key factors in build-up and wash-off from the urban catchment.

• Journal of Forest and Environmental Science
• /
• v.26 no.1
• /
• pp.17-23
• /
• 2010

The present study was conducted to quantify wood and leaf litter decomposition and nutrient release of a dominant tree species, Tectona grandis Linn. F. in a tropical dry deciduous forest of Rajasthan, Western India. The mean relative decomposition rate was maximum in the wet summer and minimum during dry summer. Rainfall and its associated variables exhibited greater control over litter decomposition than temperature. The concentrations of N and P increased in decomposing litter with increasing retrieval days. Mass loss was negatively correlated with N and P concentrations. The monthly weight loss was significantly correlated (P < 0.05) with soil moisture and rainfall in both wood and leaf litter. Tectona grandis was found to be most suitable tree species for plantation programmes in dry tropical regions as it has high litter deposition and decomposition rates and thus it has advantages in degraded soil restoration and sustainable land management.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.20 no.3
• /
• pp.243-259
• /
• 2016

The Richards equation for water movement in unsaturated soil is highly nonlinear partial differential equations which are not solvable analytically unless unrealistic and oversimplifying assumptions are made regarding the attributes, dynamics, and properties of the physical systems. Therefore, conventionally, numerical solutions are the only feasible procedures to model flow in partially saturated porous media. The standard Finite element numerical technique is usually coupled with an Euler time discretizations scheme. Except for the fully explicit forward method, any other Euler time-marching algorithm generates nonlinear algebraic equations which should be solved using iterative procedures such as Newton and Picard iterations. In this study, lumped mass and distributed mass in the frame of Picard and Newton iterative techniques were evaluated to determine the most efficient method to solve the Richards equation with finite element model. The accuracy and computational efficiency of the scheme and of the Picard and Newton models are assessed for three test problems simulating one-dimensional flow processes in unsaturated porous media. Results demonstrated that, the conventional mass distributed finite element method suffers from numerical oscillations at the wetting front, especially for very dry initial conditions. Even though small mesh sizes are applied for all the test problems, it is shown that the traditional mass-distributed scheme can still generate an incorrect response due to the highly nonlinear properties of water flow in unsaturated soil and cause numerical oscillation. On the other hand, non oscillatory solutions are obtained and non-physics solutions for these problems are evaded by using the mass-lumped finite element method.

• Journal of the korean society of oceanography
• /
• v.36 no.4
• /
• pp.101-108
• /
• 2001

Polybrominated diphenylether (PBDEs) congeners, 2,4,4'-TrBDE, 2,2',4,4'-TeBDE, 2,2',4,4',5-PeBDE, 2,2',4,4',5,5'-HXBDE, and 2,2',4,4',5,6-HxBDE, were measured in sediments from 52 stations in the southeastern coastal areas of Korea. Sediment samples were analyzed using gas chromatography coupled to mass spectrometer detector (GC/MSD) with positive electron impact (PEI) mode. New analytical methodology for PBDEs by the isotope dilution method was established using a multi-layer silica gel column chromatography. Total PBDEs levels in sediments for Pohang coast ranged from 1,1 to 33.8 ng/g dry weight (mean 5.3 ng/g dry), from 1.6 to 36.4 ng/g dry weight (mean 5.7 ng/g dry) for Ulsan coast, from 0.8 to 20.3 ng/g dry weight (mean 4.9 ng/g dry) for Busan coast, and from 0.8 to 10.3 ng/g dry weight (mean 4.4 ng/g dry) for Jinhae Bay. PBDEs contamination in surface sediments from Korean southeastern coasts was relatively moderate in comparison to that of other marine environment in the world. The predominant PBDE congeners were 2,2',4,4'-TeBDE and 2,2',4,4',5-PeBDE.

• Environmental Analysis Health and Toxicology
• /
• v.29
• /
• pp.3.1-3.7
• /
• 2014

Objectives This study was conducted to determine the depositional characteristics of several tree barks, including Ginkgo (Ginkgo biloba), Pine (Pinus densiflora), Platanus (Platanus), and Metasequoia (Metasequoia glyptostroboides). These were used as passive air sampler (PAS) of atmospheric polybrominated diphenyl ethers (PBDEs). Methods Tree barks were sampled from the same site. PBDEs were analyzed by high-resolution gas chromatography/high-resolution mass spectrometer, and the lipid content was measured using the gravimetric method by n-hexane extraction. Results Gingko contained the highest lipid content (7.82 mg/g dry), whereas pine (4.85 mg/g dry), Platanus (3.61 mg/g dry), and Metasequoia (0.97 mg/g dry) had relatively lower content. The highest total PBDEs concentration was observed in Metasequoia (83,159.0 pg/g dry), followed by Ginkgo (53,538.4 pg/g dry), Pine (20,266.4 pg/g dry), and Platanus (12,572.0 pg/g dry). There were poor correlations between lipid content and total PBDE concentrations in tree barks ($R^2$=0.1011, p =0.682). Among the PBDE congeners, BDE 206, 207 and 209 were highly brominated PBDEs that are sorbed to particulates in ambient air, which accounted for 90.5% (84.3-95.6%) of the concentration and were therefore identified as the main PBDE congener. The concentrations of particulate PBDEs deposited on tree barks were dependent on morphological characteristics such as surface area or roughness of barks. Conclusions Therefore, when using the tree barks as the PAS of the atmospheric PBDEs, samples belonging to same tree species should be collected to reduce errors and to obtain reliable data.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.47 no.4
• /
• pp.311-318
• /
• 2002

Planting date of soybeans [Glycine max (L.) Merr.] is one of production components in cultural systems. The objective of the current study was to identify the components of soybean production and cultural practices encompassing planting dates and cultivars that respond to dry matter accumulation, harvest index and yield components. Three determinate soybean cultivars were planted on May 13 (early), June 3 (mid), and June 24 (late). Planting density was 60$\times$15cm with 2 seeds (222,000 plants per ha). Soybean plants were sampled every 10 days interval from the growth stages of V5 to R8 and separated into leaves including petioles, stems, pods, and seeds. Dry matter accumulations, harvest indices, and yield components were measured. Early planting had taken 55 days from VE to R2 and late planting taken 39 days indicating reduced vegetative growth. Early planting showed higher leaf, stem, pod and seed dry weights than late planting. However, late planting appeared to be higher harvest index and harvesting rate. Vegetative mass including leaf and stem increased to a maximum around R4/R5 and total dry weight increased to a maximum around R5/R6 and then declined slightly at R8. The highest seed yield was obtained with mid planting and no difference was found between early and late plantings. Cultivar differences were found among planting dates on growth characteristics and yield components. The results of this experiment indicated that soybean yield in relation to planting dates examined was mainly associated with harvest index and harvesting rate, and planting date of cultivars would be considered soybean plants to reach the growth stage of R4/R5 after mid August for adequate seed yield.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.1
• /
• pp.1-6
• /
• 2004

Dry etch characteristics of polysilicon with HBr/O$_2$ inductively coupled plasma (ICP) have been investigated. We determined etch late, uniformity, etch profiles, and selectivity with analyzing the cross-sectional scanning electron microscopy images obtained from top, center, bottom, right, and left positions. The etch rate of polysilicon was about 2500 $\AA$/min, which meets with the mass production for devices. The wafer level etch uniformity was within $\pm$5 ％. Etch profile showed 90$^{\circ}$ slopes without notches. The selectivity over photoresist was between 2:1∼4.5:1, depending on $O_2$ flow rate. The HBr-ICP etching showed higher PR selectivity, and sharper profile than the conventional Cl$_2$-RIE.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.2
• /
• pp.33-39
• /
• 1996

A theoretical study of the forced vibration response of a cantilevered beam with non-linear dry friction damping is analyzed by various slip displacements and force levels for the position coordinates of spring-mass-damper and external exciting force. A component mode analysis is carried out based on the constraint conditions and Lagrange multipliers to treat physical systems with non-linear damping. The analysis has shown that the basic phenomena observed for a simply supported beam with a dry friction damper attached are also observed for cantilevered beam.

• Food Science and Biotechnology
• /
• v.18 no.1
• /
• pp.150-156
• /
• 2009

In this study, Staphylococcus carnosus isolated from traditional sucuk (Turkish dry-fermented sausage) was used in combination with Lactobacillus plantarum as a lactic culture in sucuk production. Sucuk produced with only L. plantarum was evaluated as a control group. Microbiological, physicochemical, and volatile profile characteristics of sucuk samples were investigated during ripening. In both sausages with S. carnosus and control group, pH value decreased to below 5.0 at the $3^{rd}$ day. In all samples, Aw value decreased as the ripening time progressed. Sausages with S. carnosus showed the higher nonprotein nitrogen (NPN) value than control group. However, the highest mean value for thiobarbituric acid reactive substances (TBARS) was observed in control group. Enterobacteriaceae dropped to undetectable levels at the $3^{rd}$ day in both groups. S. carnosus increased approximately 1 log unit within the first 3 days of the fermentation. In the presence of S. carnosus, significant changes were observed in only a few volatile compounds.