• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.214-225
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• 2011

The objectives of the study were to evaluate seasonal patterns of epilimnetic water quality, and determine interannual eutrophication patterns at the dam site of Yong-dam Reservoir using long-term data during 2002~2009. Ionic dilutions, based on specific conductivity, occurred in the summer period in response to the intense monsoon rain and inflow, and suspended solid analysis indicated that the reservoir was clear except for the monsoon. Seasonality of nitrogen contents varied depending on the types of nitrogen and responded to ionic dilution; Ammonia-nitrogen ($NH_4$-N) peaked at dry season but nitrate-nitrogen ($NO_3$-N) peaked in the monsoon when the ionic dilution occurred. The maxima of $NO_3$-N seemed to be related with external summer N-loading from the watershed and active nitrogen fixation of bluregreens in the summer. $NO_3$-N was major determinant (>50%) of the total nitrogen pool and relative proportion of $NH_4$-N was minor. Long-term annual $NO_3$-N and TDN showed continuous increasing trends from 2004 to 2009, whereas TP and TDP showed decreasing trends along with chlorophyll-a (CHL) values. Empirical model analysis of log-transformed nutrients and N : P ratios on the CHL showed that the reservoir CHL had a stronger linear function with TP ($R^2$=0.89, p<0.001) than TN ($R^2$=0.35, p=0.120). Overall results suggest that eutrophication progress, based on TP and CHL, is slow down over the study period and this was mainly due to reduced phosphorns, which is considered as primary nutrient by the empirical model.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.3
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• pp.440-447
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• 2009

Domestic ruminant animals are reared in diverse production systems, ranging from extensive systems under semi-arid and tropical conditions with poor feed resources to intensive systems in temperate and cold areas with high quality feed. Nitrogen (N) recycling between the body and gut of ruminants plays a key role in the adaptation to such diverse nutritional conditions. Ammonia and microbial protein produced in the gut and urea synthesized in the liver are major players in N-recycling transactions. In this review, we focus on the physiological factors affecting urea production and recycling. Sheep and buffalo probably have higher abilities to reabsorb urea from the kidney compared with cattle. This affects the degree of urea-N recycling between the body and gut at both low and high N intakes. The synthesis and gut entry of urea also differs between cattle bred for either dairy or beef production. Lactating dairy cows show a higher gut entry of urea compared with growing cattle. The synthesis and recycling of urea dramatically increases after weaning, so that the functional development of the rumen exerts an essential role in N transactions. Furthermore, high ambient temperature increases urea production but reduces urea gut entry. An increase in total urea flux, caused by the return to the ornithine cycle from the gut entry, is considered to serve as a labile N pool in the whole body to permit metabolic plasticity under a variety of physiological, environmental and nutritional conditions.

• Journal of Environmental Science International
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• v.29 no.5
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• pp.531-539
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• 2020

To understand the composition, quantity, and quality of Suspended Particulate Organic Matter (SPOM) in the Gangneung Namdae Stream, Korea, we examined spatiotemporal variations in water temperature, salinity, chlorophlly a (Chl a), Particulate Organic Carbon (POC) and nitrogen (PON), and carbon stable isotope (δ¹³C) of SPOM at six stations in June (pre-monsoon), July (monsoon), and September (post-monsoon) 2017. With increasing precipitation, the average POC and C/N values increased significantly in July than in June. In September, the values decreased with decreasing precipitation. The δ¹³C values showed irregular spatiotemporal fluctuations among the stations and periods, thereby suggesting a greater contribution of autochthonous organic matter to the pool of SPOM than that of allochthonous organic matter derived from upstream. In addition, the large and irregular changes in POC, C/N ratio, C:Chl a, and δ¹³C compared to that of PON were observed for all periods among the stations, indicating a serial discontinuity of the stream. Our results suggest that the Gangneung Namdae Stream is significantly influenced by the increase in freshwater discharge caused by heavy rainfalls during the summer monsoon and post-monsoon periods.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.7
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• pp.990-996
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• 2005

The effect of diets varying in level and source of nitrogen (N) and fermentable organic matter on dynamic characteristics of microbial populations in rumen liquor and their impact on substrate fermentation in vitro was studied. The diets tested were straw alone, straw+concentrate mixture and straw+urea molasses mineral block (UMMB) lick. The same diets were taken as substrates and tested on each inoculum collected from the diets. Diet had no effect on the amino acid (AA) composition of either bacteria or protozoa. Differences among the diets in intake, source of N and OM affected bacterial and protozoal characteristics in the rumen. Upper asymptote of gas production (Y$\alpha$) had a higher correlation with bacterial pool size and production rate than with protozoal pool size and production rate. Among the parameters of the gas production model, Y$\alpha$ and lag time in total gas has showed significant (p<0.01) correlation with bacterial characteristics. Though the rate constant of gas production significantly differed (p<0.01) between diet and type of straw, it was least influenced by the microbial characteristics. The regression coefficient of diet and type of straw for Y$\alpha$ indicated that the effect of diet on Y$\alpha$ was threefold higher than that of the straw. As microbial characteristics showed higher correlation with Y$\alpha$, and diet had more influence on the microbial characteristics, gas production on a straw diet could be used effectively to understand the microbial characteristics.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.932-940
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• 2016

Pool boiling heat transfer of water saturated at atmospheric pressure was investigated experimentally on Cu surfaces with high-temperature, thermally-conductive, microporous coatings (HTCMC). The coatings were created by sintering Cu powders on Cu surfaces in a nitrogen gas environment. A parametric study of the effects of particle size and coating thickness was conducted using three average particle sizes (APSs) of $10{\mu}m$, $25{\mu}m$, and $67{\mu}m$ and various coating thicknesses. It was found that nucleate boiling heat transfer (NBHT) and critical heat flux (CHF) were enhanced significantly for sintered microporous coatings. This is believed to have resulted from the random porous structures that appear to include reentrant type cavities. The maximum NBHT coefficient was measured to be approximately $400kW/m^2k$ with APS $67{\mu}m$ and $296{\mu}m$ coating thicknesses. This value is approximately eight times higher than that of a plain Cu surface. The maximum CHF observed was $2.1MW/m^2$ at APS $67{\mu}m$ and $428{\mu}m$ coating thicknesses, which is approximately double the CHF of a plain Cu surface. The enhancement of NBHT and CHF appeared to increase as the particle size increased in the tested range. However, two larger particle sizes ($25{\mu}m$ and $67{\mu}m$) showed a similar level of enhancement.

• Fire Science and Engineering
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• v.33 no.5
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• pp.28-36
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• 2019

In the present study, the effects of supply gas and water mist on the heptane pool fire extinguishing performance were investigated using the full cone and hollow cone twin-fluid atomizers. Air or nitrogen of 30 lpm (Liter per minute; L/min) was used as the supply gas, and the experiments were conducted under the water flow rate conditions of 0 lpm (i.e., discharge of air or nitrogen only) and 0.085 lpm (i.e., discharge of water mist with supply gas). Experimental results confirmed that the use of water mist discharge with the supply gas and full cone spray pattern reduced the fire extinguishing time as compared to that of only supply gas discharge and hollow cone spray pattern. In addition, for the discharge of water mist using the full cone twin-fluid atomizer, water mist significantly affected fire extinguishing performance, whereas the effect of the supply gas was less pronounced. On the other hand, for the discharge of water mist using the hollow cone twin-fluid atomizer, the fire extinguishing time was remarkably reduced by the supply of nitrogen, as compared with that of air, indicating that the supply gas as well as water mist can significantly affect fire extinguishing performance.

• Korean Journal of Environmental Biology
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• v.21 no.4
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• pp.415-421
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• 2003

Chlorophyll-a and its degradation products (pheopigment) contained in the sediment were determined to evaluate the eutrophication status in the downstream of Nakdong River. The chlorophyll-a and pheopigment concentrations of sediment ranged 11-646 mg $\mu \textrm m^{-2}$ (mean 172 mg $\mu \textrm m^{-2}$) and 48-1,564 mg $\mu \textrm m^{-2}$ (mean 454 mg $\mu \textrm m^{-2}$) over 11 sampling stations of the Nakdong River. The chloropigment concentrations in this local area were higher than other values reported previously and this river waters showed hypertrophic status in view of sedimentary chloropigment. Total chloropigment standing crops of sediment, which are the residuals after the longterm degradation, were 2.2-3.6 fold higher than chlorophyll-$\alpha$ contents of overlying water. The amounts of chloropigments of sediment suggest a large contribution of phytoplankton to the sediment. While chloropigment standing crops are evaluated with organic-C and nitrogen contents, the algal contribution to the carbon and nitrogen pool of the sediment were estimated to be approximately 30% and 40%, respectively.

• ALGAE
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• v.24 no.4
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• pp.185-193
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• 2009

Geothermal springs in India, formed as a result of volcanic or tectonic activities, are characterized by high temperature and relatively abundant reduced compounds. These thermal springs are inhabited by characteristic thermophilic organisms including cyanobacteria. Cyanobacteria are among the few organisms that can occupy high temperature aquatic environments including hot springs. In alkaline and neutral hot springs and streams flowing from them cyanobacteria can form thick colourful mats that exhibit banding patterns. The present investigation involves study of mat forming cyanobacterial flora from hot springs located in Bakreswar, West Bengal, India. The important species found are Synechococcus bigranulatus, S. lividus, Gloeocapsa gelatinosa, G. muralis, Phormidium laminosum, P. frigidum, Oscillatoria princes, O. fragilis, Lyngbya lutea, Pseudanabaena sp., Calothrix thermalis, and Fischerella thermalis. Their distribution pattern in relation to physico-chemical parameters of spring water has also been studied. Three cyanobacterial strains of the above mentioned list were grown in culture and their pigment content and nitrogen fixing capacity were also studied. Nitrogen fixing capacities of Calothrix thermalis, Nostoc sp. (isolated in culture) and Fischerella thermalis are 5.14, 0.29, and 2.60 n mole $C_2H_4/{\mu}g$ of Chl-${\alpha}$/hr respectively. Carotenoid : Chlorophyll-${\alpha}$ ratio of four mat samples collected from Kharkunda, Suryakunda, Dudhkunda and bathing pool are 2.45, 1.60, 1.48, and 1.34, respectively. Higher value of Carotenoid : Chlorophyll-${\alpha}$ ratio coincided with higher temperature.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.433-438
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• 2012

We have studied on welding dissimilar materials of Carbon steel SCP1-S by using laser beam. In this research we have performed some experiments to know the possibility of welding dissimilar materials using laser beam and magnetic fields by adjusting the power output of 35W laser. Other conditions of the experiments were as follows : the welding speed was varied in the range 10 m/min nitrogen gas was used as shield gas, the flow value of shield gas was ranged 10 L/min. In order to ascertain of the welded surface, we have done the tensile strength testing, the hardness testing and the microscope observation. As a result, we have found that tensile strength was the highest at the condition of the welding speed of 10mm/s, the flow value of 10 L/min, the gap of two materials 0, and the use of nitrogen gas. Above testings have also showed that the tensile strength was generally satisfactory since the penetration of welding was almost complete due to the thinness of the materials. In addition, the formation of the welded area was excellent when it had the highest tensile strength.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.4
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• pp.617-622
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• 1992

Four rumen-fistulated swamp buffaloes steers were used in a change-over experiment. This experiment was designed to provide a comparison of the effect of urea-ammonia treatment of rice straw with untreated rice straw. Nitrogen, mineral and trace elements were supplied at adequate levels to both diets in order to overcome deficiencies which may have otherwise confounded a direct comparison. There was a 46% increase in the intake of digestible organic matter (OM) with the urea-ammonia treated diet. This was contributed by a 17% increase in the digestibility of OM and a 25% increase in the voluntary intake of OM. Of the cell wall fraction, the digestibility of hemicellulose increased by the greatest amount (26%). There was an increased rate of passage of particulate matter out of the rumen for the treated straw, along with the increased rate of OM fermentation resulted in a 9% decrease in the amount of digesta dry matter (DM) contained in the rumen. The volatile fatty acid (VFA) pool in the rumen was 24% higher for the treated diet.