• Asian-Australasian Journal of Animal Sciences
• /
• 제22권7호
• /
• pp.984-992
• /
• 2009

The objective of this study was to determine the effects of milk supplemented with Sel-Plex on thyroid hormones, rectal temperature, plasma glucose and cholesterol concentrations, and body weight in suckling calves. Ten Holstein suckling male calves of approximately 1 month of age were selected and randomly allocated to one of two groups and fed either unsupplemented milk (control) or milk supplemented with 0.3 mg/kg DM Se from Sel-Plex (treated). The animals received treated milk and free choice starter for two months. Dry matter intake for each individual animal was recorded daily throughout the study. The calves were weighed and blood samples were taken weekly. Plasma concentrations of triiodothyronine ($T_{3}$), thyroxin ($T_{4}$) and $T_{3}$-Uptake were determined using radioimmunoassay kits. Plasma cholesterol and glucose concentrations were determined by enzymatic-colorimetric methods. Rectal temperature was recorded at blood sampling time. During the experiment, ambient temperature and relative humidity were recorded at the time of blood sampling and every four hours. Treatment significantly (p<0.01) affected the concentration of $T_{3}$, free $T_{3}$ index ($FT_{3}I$) and ratio of $T_{3}$:$T_{4}$ in plasma. The plasma concentrations of $T_{3}$ in treated calves were 33% higher than in the control. The plasma concentrations of $T_{4}$ (p<0.05), glucose (p<0.01) and cholesterol (p<0.01) were decreased in the treated group. Calves fed Sel-Plex had higher rectal temperature (p<0.01). Plasma free $T_{4}$ index (FT4I) did not differ significantly between the two groups. An increase in body weight was observed (p<0.09) in the treated group. The results indicated that milk fortified with Sel-Plex could increase tissue conversion of $T_{4}$ to $T_{3}$ and therefore improve thermometabolism in suckling calves.

• 한국산업보건학회지
• /
• 제26권3호
• /
• pp.286-292
• /
• 2016

Objectives: This study aimed to evaluate the effects of chronical exposure to high-level dusts on cellular immune function. Methods: The subjects were 110 male workers, among whom 60 were chronically exposed to high-level dusts in mica, limestone and iron mines. The remaining 50 were office workers. Ambient total, respirable dust and crystalline silica in the workplace were sampled using personal air samplers and analyzed according to NIOSH method 0500. Serum levels of hydrogen peroxide, lipid peroxide and superoxide misutase activity were measured using absorption chromatography. The subpopulations of CD4+, CD8+, natural killer cells (CD16+) and CD3+ T-lymphocytes were examined by two-color staining using monoclonal antibodies. Results: The concentration of hydrogen peroxide was significantly higher in exposed workers and superoxide dismutase activity was significantly higher in control workers. No significant difference in numbers of T-lymphocyte subpopulations were observed between exposed and control workers. A significant correlation in exposed workers was observed among total dusts, respirable dusts and crystalline silica. Hydrogen peroxide was significantly correlated with total dust (r=0.720, p<0.01), respirable dust (r=0.770, p<0.01) and crystalline silica (r=0.678, p<0.01). Concentration of hydrogen peroxide showed a significantly negative correlation with numbers of CD8+ cells (r=-0.274, p<0.01), CD3+ cells (r=-0.222, p<0.01) and natural killer cells (r=-0.556, p<0.01). Conclusions: These results suggest that chronical exposure to high-level dust affects cellular immune function and effects might mediate through reactive oxygen species and inflammatory response.

• 한국식품과학회지
• /
• 제23권2호
• /
• pp.241-247
• /
• 1991

본 연구는 감압유탕 당근스낵의 품질에 미치는 dextrin의 영향에 대하여 조사하였다. 전처리 용액으로는 0%, 10%, 20% 및 30%의 dextrin 용액을 사용하였으며, 제조된 감압유탕 건조당근의 흡습성, 복원성. 색도 및 crispness를 조사 분석하였으며 그 결과는 다음과 같다. Dextrin의 농도에 따른 평형수분함량과 흡습속도는 control>10% dextrin>20% dextrin>30% dextrin의 순이었고, BET 단분자막 수분함량은 저장온도가 높을 수록 감소하었고 dextrin 전처리한 시료들의 BET 단분자막 수분함량은 그 농도가 높을 수록 감소하였다. 또한 Dextrin 전처리 농도가 낮을 수록 제품의 명도와 황색도는 증가하였으나 적색도는 감소하였으며, 생당근과 비슷한 색상을 띠는 시료는 20%로 전처리한 시료였다. 그리고 감압유탕 건조당근제품은 전처리한 dextrin 용액의 농도가 높을 수록 crispness intensity도 높았다.

• 한국분무공학회지
• /
• 제14권4호
• /
• pp.147-152
• /
• 2009

Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

• Environmental Engineering Research
• /
• 제25권3호
• /
• pp.335-344
• /
• 2020

This work describes highly efficient recovery and selective leaching of Zn from electric arc furnace dust (EAFD) with different physicochemical properties, induced by acid leaching at ambient conditions. The chemical compositions, mineralogical phases, and particle sizes of the EAFDs were analyzed and compared. The effects of leaching time, liquid/solid ratio, acid type, and acid concentration on the selective leaching of Zn were also studied. The EAFD with high Fe/Zn ratio (> 1, EAFD₃) was richer in ZnFe₂O₄ and exhibited larger particle size than samples with low Fe/Zn ratio (< 1, EAFD_1,2). ANOVA analysis revealed that the Fe/Zn ratios of the EAFDs also have a significant effect on Zn extraction (p < 0.005). Selective leaching of Zn with minimum Fe dissolution was obtained at pH > 4.5, regardless of other parameters or sample properties. The maximum Zn extraction rate obtained by the pH control was over 97% for EAFD₁ and EAFD₂, 76% for EAFD₃, and 80% for EAFD₄. The present results confirm that the Fe/Zn ratio can be used to identify EAFDs that permits facile and high-yield Zn recovery, and pH can be used as a process control factor for selective leaching of Zn regardless of any differences in the properties of the EAFD sample.

• 한국환경보건학회지
• /
• 제30권3호
• /
• pp.293-299
• /
• 2004

Traffic represents one of the largest sources of primary air pollutants in urban area. As a consequence, numerous abatement strategies are being pursued to decrease the ambient concentration of pollutants. A characteristics of most of the these strategies is a requirement for accurate data on both the quantity and spatial distribution of emissions to air in the form of an atmospheric emission inventory database. In the case of traffic pollution, such an inventory must be compiled using activity statistics and emission factors for vehicle types. The majority of inventories are compiled using passive data from either surveys or transportation models and by their very nature tend to be out-of-date by the time they are compiled. The study of current trends is towards integrating urban traffic control systems and assessments of the environmental effects of motor vehicles. In this study, a model of vehicle emission calculation by using real-time traffic data was studied. Traffic data, which are required on a street-by-street basis, is obtained from induction loops of traffic control system. It is possible that characteristics of hourly air pollutants emission rates is obtained from hourly traffic volume and speed. An emission rates model is allocated with a high resolution space by using geographic information system (GIS). Vehicle emission model was developed with a high resolution spatial, gridded and hourly emission rates.

• 한국태양에너지학회 논문집
• /
• 제28권5호
• /
• pp.21-27
• /
• 2008

In this study, the design of the solar heating system for district heating as well as it's operating characteristics and the performance analysis was carried out. This solar district heating system was composed of two different types of solar collector circuit, flat plate and vacuum tube solar collector, in a system. This system supply constant temperature of hot water without solar buffer tank. For this, the proportional(variable flow rate) control was used. The experimental facility for this study was used the Bundang district solar heating system which was installed in the end of 2006. The operating characteristics and behaviour of each collector circuits are investigated especially for the system design and control. The yearly solar thermal efficiency is 47.5% on the basis of aperture area and 39.8% on the basis of gross area of collector. As a result this solar heating system without solar buffer tank and with proportional controller was testified a very effective and simplified system for district heating. It varied especially depend on the weather condition like as solar radiation and ambient temperature.

• Safety and Health at Work
• /
• 제2권4호
• /
• pp.365-374
• /
• 2011

Objectives: This study was designed to investigate whether long-term, low-level exposure to monocyclic aromatic hydrocarbons (MAHs) induced insulin resistance. Methods: The subjects were 110 male workers who were occupationally exposed to styrene, toluene, and xylene. One hundred and ten age-matched male workers who had never been occupationally exposed to organic solvents were selected as a control group. Cytokines, which have played a key role in the pathogenesis of insulin resistance, and oxidative stress indices were measured. Assessment of exposure to MAHs was performed by measuring their ambient levels and their urinary metabolites in exposed workers, and the resulting parameters between the exposed group and non-exposed control groups were compared. Results: There was no significant difference in general characteristics and anthropometric parameters between the two groups; however, total cholesterol, fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance levels were significantly higher in the exposed group. Phenylglyoxylic acid levels showed significant association with tumor necrosis factor-${\alpha}$, total oxidative status, and oxidative stress index via multiple linear regression analysis. Further, there was a negative correlation between methylhippuric acid levels and total anti-oxidative capacity, and there was a significant relationship between MAHs exposure and fasting glucose levels, as found by multiple logistic regression analysis (odds ratio = 3.95, 95% confidence interval = 1.074-14.530). Conclusion: This study indicated that MAHs increase fasting glucose level and insulin resistance. Furthermore, these results suggested that absorbing the organic solvent itself and active metabolic intermediates can increase oxidative stress and cytokine levels, resulting in the changes in glucose metabolism and the induction of insulin resistance.

• 한국수소및신에너지학회논문집
• /
• 제29권6호
• /
• pp.635-641
• /
• 2018

To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.

• 한국환경과학회지
• /
• 제30권3호
• /
• pp.219-234
• /
• 2021

Industrial emissions, mainly from industrial complexes, are important sources of ambient Volatile Organic Compounds (VOCs). Identification of the significant VOC sources from industrial complexes has practical significance for emission reduction. VOC samples were collected from July 2019 to June 2020. A Positive Matrix Factorization (PMF) receptor model was used to evaluate the VOC sources in the area. Four sources were identified by PMF analysis, including coating-1, coating-2, printing, and vehicle exhaust. The coating-1 source was revealed to have the highest contribution (41.5%), followed by coating-2 (23.9%), printing (23.1%), and vehicle exhaust (11.6%). The source showing the highest contribution was coating emissions, originating from the northwest to southwest of the sample site. It also relates to facilities that produce auto parts. The major components of VOC emissions from the coating facilities were toluene, m,p-xylene, ethylbenzene, o-xylene, and butyl acetate. Industrial emissions should be the top priority to meet the relevant control criteria, followed by vehicular emissions. This study provides a strategy for VOC source apportionment from an industrial complex, which is helpful in the development of targeted control strategies.