• Particle and aerosol research
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• v.7 no.3
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• pp.87-97
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• 2011

In this study, we organized the test results obtained from the performance tests for the CA certificated air cleaners which had been commercially available in Korea since 2003, and analyzed the correlation among the test parameters such as flow rate, particle collection efficiency, clean air delivery rate (CADR), ozone emission, odor removal efficiency and noise level etc. The noise level of 267 air cleaners were increased as concentrated at the 45, 50, 55 dB, which are the required noise level for CA certification according to flow rate, and ozone emissions from the CA air cleaners were significantly lower than the requirement limit, 50 ppb for 24 hour operation. The average particle collection efficiency and odor removal efficiency were 89.3 and 80.8%, approximately 20% higher than the requirement of CA certification, regardless of flow rates. The particle removal performance of an air cleaner was clearly discriminated by its CADR, and the CADR was obtained with a simple calculation: 0.79 x flow rate. The low differentiation of gas removal performance of air cleaners by the current CA gas test method was improved by 3.2, 751.3, 13.4 times for ammonia, acetic acid, respectively, by adopting the CADR concept and the real time measurement method, FTIR, for gas removal performance test.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.5
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• pp.856-865
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• 2020

Objective: This study was conducted to evaluate the physicochemical properties and changes in moisture concentrations of bedding materials under the conditions of rearing Korean Hanwoo cows. Methods: Two experiments were conducted to investigate the physicochemical characteristics (Exp. I) and usefulness as beddings for rearing cattle (Exp. II) by the type of beddings such as sawdust (SD), wood shavings (WS) and sawdust+wood shavings (S+W; 1:1 in volume), and the species of pine trees from different countries of origins (China, Pinus armandii, AR; Vietnam, Pinus kesiya, KE; USA, Pinus rigida, RI). Results: In Exp. I, SD-AR showed the largest proportion (78.3%) of fine particles (250 ㎛+below 250 ㎛) and the highest bulk density (208 kg/㎥) among treatments (p<0.05). The water absorption capacity at 24 h of both S+W-RI (713%) and -KE (701%) was the highest among treatments (p<0.05) and higher than those of SD or WS alone within each species of pine tree (p<0.05). Moisture evaporation rates (%) at 12 h were ranged from 52.3 to 60.8 for SD, 69.9 to 74.4 for WS, and 72.3 to 73.5 for S+W. Total amounts (mg/㎡) of ammonia emissions were the lowest (p<0.05) in KE species among the pine species within each type of bedding material, having higher ability of ammonia absorption. In Exp II, KE species in both side A and B had lower moisture concentrations (%) than other species. Regardless of types of beddings except SD-AR, moisture concentrations of beddings within a pen were higher (p<0.01) at side A than B. Conclusion: The KE species has better physical characteristics than other beddings and more useful for rearing Hanwoo cattle than other beddings, probably caused by the differences in the method and degree of wood processing rather than the species.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.156-162
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• 2010

3-D CFD(Computational Fluid Dynamics) work were carried out to investigate the combustion characteristics in a boiler depending on the variations in air supply condition. For the gas temperature, $O_2$, NO, SOx at the outlet of economizer, the predicted values were been compared with the measured data. With the verified CFD model, the effects of air flow rates through SOFA(Separated Over Fire Air) and CCOFA(Closed Coupled Over Fire Air) on the combustion behavior in a boiler were simulated, and the distributions of NOx and gas temperature were mainly compared each other. The change in SOFA air flow rate gave the more sensitive effect on NOx than that in CCOFA. The distributions of gas temperature at convection path are differed with the changes in SOFA and CCOFA flow rate, so the combustion modification such as yaw anlge adjustment are required to get an enhanced gas temperature distribution.

• Journal of Energy Engineering
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• v.13 no.1
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• pp.20-27
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• 2004

In the study, the effect of low boiling point oxygenates in high viscous fuels on the exhaust emissions has been investigated for a single cylinder DI diesel engine. It was tested to estimated change of engine performance and exhaust emission characteristics for the base fuels and low boiling point oxygenates blended fuel which have six kinds of fuels and various mixed rates. The results of the study may be con eluded as follows By blending of various low boiling point oxygenated agents to lower grade fuels, significant improvements were simultaneously obtained in smoke, CO, PM, SOF and BSEC. Especially, these trends were remarkably obtained by retarding injection timing, by decreasing boiling point and increasing blending contents of additives in case of oxygenated agents rather than non-oxygenated agents. Also, it was revealed that when 20 vol.％ DMM added to high viscosity fuels and injection timing was retarded, Nox-smoke trade off relationship was much better than that of ordinary diesel fuel. Thus, lower grade fuels with high viscosity could be expected to be used efficiently and cleanly in diesel operation by blending low boiling point oxygenates.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.1-10
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• 2000

Although microorganisms play an important role in composting process, researches on the effective microorganism (EM) in composting process are rarely reported. In this study, three stages of work performed 1) investigation of composting facility 2) sample collection and isolation of the EM 3) lab-scale composting by seeding the isolated EM. For this, purpose, physical, chemical, and biological characteristics, such as temperature, moisture content, organic matter, pH population of microorganism, etc., were investigated during the process and the results were compared with those of a control(non-seeded). In the composting facility, the most active degradation of food waste was suppsed to occur in 10-11th day of composting by observing the temperature and CO2 emission. The population of bacterial and fungi was highest in thermophilic stage. Meanwhile that of actinomycetes and yeast was relatively uniform during the process. In the lab-scale test, the thermophilic stage was maintained longer(more than 9 days in 17 days of experiment) in the seeded which was favored for the high reduction of organic matter and moisture. Reduction rates of lipids and salinity were also increased in the seeded. It confirmed these results that the population of microorganisms in the seeded was observed higher in several orders than the control. However, pH of the seeded was maintained as low as about 4.5 throughout the experiment except the final period of the process. Meanwhile, pH of the control rose in the early stage of the experiment. This was probably due that the seeded microorganisms collected from the composting facility was adapted to the low pH environment.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2089-2097
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• 2014

Negative corona onset characteristics of the stranded conductors based on the ultra-high voltage (UHV) corona cage were studied in the paper. Based on the corona self-sustaining criterion in extreme uneven electric fields and the secondary emission process of the photoelectrons, the corona onset calculation model in the UHV corona cage is established and the corona current tests of the single LGJ900-75, 6 bundle LGJ900-75, 8 bundle LGJ400-35 conductors in dry and rain conditions were done in the UHV corona cage, and the rain rates are 2.4 mm/h, 20 mm/h and 30 mm/h. Corona onset electric field strength is gained by E-I tangent method, and the onset electric field strength in dry condition proves that the calculation model can be used to calculate the corona onset characteristics of the bundle conductors in the UHV corona cage. A further analysis proves that: the negative corona onset voltage of the conductor increases with the bundle number and the diameter of the sub conductor, but decreases with the bundle space in the corona cage. The onset electric field strength is influenced little by bundle space and bundle number, but decreases with the increase of the diameter of the sub-conductor. The surface irregularity coefficient decreases with the rain rate.

• Environmental Engineering Research
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• v.18 no.3
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• pp.169-176
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• 2013

The present study was designed to examine the concentrations, emission rates, and source characteristics of a variety of volatile organic compounds (VOCs) in 30 newly-constructed apartment buildings by measuring indoor and outdoor VOC concentrations over a 2-year period. For comparison, seven villa-type houses were also surveyed for indoor and outdoor VOC concentrations over a 3-month period. Indoor and outdoor air samples were collected on Tenax-TA adsorbent and analyzed using a gas chromatograph (GC)/mass spectrometer system or a GC/flame ionization detector system coupled to a thermal desorption system. The long-term change in indoor VOC concentrations depended on the type of VOCs. Generally, aromatic (except for naphthalene), aliphatic, and terpene compounds exhibited a gradual deceasing trend over the 2-year follow-up period. However, the indoor concentrations of the six halogenated VOCs did not significantly vary with time changes. Similar to these halogenated VOCs, the indoor naphthalene concentrations did not vary significantly with time changes over the 2-year period. Unlike the halogenated VOCs, the indoor naphthalene concentrations were much higher than the outdoor concentrations. The indoor concentrations of aliphatic and aromatic compounds were higher for the villa-type houses when compared to those of apartment buildings. In addition, four source groups (floor coverings and interior painting, household products, wood paneling and furniture, moth repellents) and three source groups (floor coverings and interior painting, household products, and moth repellents) were considered as potential VOC sources inside apartment buildings for the first- and second-year post-occupancy stages, respectively.

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.55-60
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• 2011

Although sound intensity is considered as one of important factors in auditory processing, its neural mechanism in auditory neurons with limited dynamic range of firing rates is still unclear. In this study, we examined the effect of sound intensity adaptation on the change of glucose metabolism in a rat brain using [F-18] micro positron emission tomography (PET) neuroimaging technique. In the experiment, broadband white noise sound was given for 30 minutes after the [F-18]FDG injection in order to explore the functional adaptation of rat brain into the sound intensity levels. Nine rats were scanned with four different sound intensity levels: 40 dB, 60 dB, 80 dB, 100 dB sound pressure level (SPL) for four weeks. When glucose uptake during the adaptation of a high intensity sound level (100 dB SPL) was compared with that during adaptation to a low intensity level (40 dB SPL) in the experiment, the former induced a greater uptake at bilateral cochlear nucleus, superior olivary complexes and inferior colliculi in the auditory pathway. Expectedly, the metabolic activity in those areas linearly increased as the sound intensity level increased. In contrast, significant decrease interestingly occurred in the bilateral auditory cortices: The activities of auditory cortex proportionally decreased with higher sound intensities. It may reflect that the auditory cortex actively down-regulates neural activities when the sound gets louder.

• 보존과학연구
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• s.21
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• pp.177-206
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• 2000

In the study of iron artifacts, microstructure investigation is an indispensable step to find out the manufacturing method and skill. The iron weapons that we have excavated and investigated at the ruins of Gohyun Castle site, Hadong-gun, Kyungnam Province are traced to the era of Choson Dynasty. By sampling specimens of some artifacts, we have made microstructure investigation and component analysis of them. For microstructure investigation we used metallographic microscopes, and for component analysis we used the methods of C/S analysis and Inductively coupled plasma emission spectrometry (ICP) analysis which is designed to verify components and contenets of a very small amount elememt. Microstructure of the artifacts is mainly divided into three parts. Inner part is Widmanstatten, a typical overheated structure, upon which we can see another part with fine grains and with extremely small quantities of carbon. And on the surface, there is a carbonized part. When the shape is formed through forging process at a high temperature the carbon content of the surface is getting down and the grains come to be finer. Next, carbonizing process is to be done for hardening the surface, which is followed by cooling process. Cooling rates seem to be different from artifacts to artifacts. All artifacts have clearly distinguishable grain boundaries in their unique structure. Since this kind of structure is rarely found, it seems to offer a clue to find out the manufacturing method. The outcome of component analysis is almost the same with that of microstructure investigation. As is demonstrated by C/S analysis, carbon content is 0.39-1.24% and sulfur is contained 0.0005-0.010%.

• Korean Journal of Veterinary Service
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• v.29 no.2
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• pp.111-122
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• 2006

A direct, accurate and sensitive chromatographic analytical method for quantitative determination of four fluoroquinolones (norfloxacin, cirprofloxacin, danofloxacin and enrofloxacin) in chicken, pork and beef edible muscle is proposed in the present study. The developed method was successfully applied to the determination of enrofloxacin, as the main component of commercially available veterinary drugs. The samples were homogenized and the antimicrobials were added, then they were extracted twice with dichloromethane. Fluoroquinolone antibiotics were separated on an agilent $250x4mm,\;C_{18},\;5{\mu}m$, analytical column, at $25^{\circ}C$. The mobile phase consisted of a mixture of DW : acetonitrile : triethylamine(80:19:1%, v/v, pH 3.0) leading to retention times less than 14 min. at a flow rate 0.5 ml/min. These fluoroquinolones were detected by liquid chromatography with fluorescence at 290 nm excitation and 465 nm emission. The limits of quantification in each edible muscle (chicken, pork, and beef) were 0.32-6.54 ng/g. Using 0.5 g of each sample, average recovery rates at fortification levels of 0.05, 0.1 and 0.2 ${\mu}g/ml$ ranged 70.14-71.71% for NFX, 71.87-73.89% for CFX, 82.16-92.35% for DFX, and 90.13-98.12 for EFX This is a simple and economic method to quantify the presence of NFX, CFX, EFX and DFX in edible muscle of animal origin.