• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.3
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• pp.262-267
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• 2009

Two 15-week feeding trials were conducted to investigate feeding rate and feeding frequency for growth of sub-adult flounder in suboptimal water temperature ($12^{\circ}C$). In the first experiment, duplicated groups of fish (initial mean weight of 279 g) were fed a extruded pellet once a day at the different feeding rates of 0.1, 0.15, 0.2, 0.3% body weight per day (BW/d), and satiation (0.32% BW/d). Weight gain and feed efficiency were increased significantly (P<0.05) with increase in feeding rates from 0.1 to 0.3% BW/d, but there were no significant differences in weight gain and feed efficiency of fish fed the diet between 0.3% BW/d and to satiation. Crude protein content of dorsal muscle of fish fed the 0.1% BW/d diet was significantly (P<0.05) lower than that of the other groups. In the second experiment, duplicated groups of fish (initial mean weight of 281 g) were fed to apparent satiation with a extruded pellet at three different feeding frequencies (one meal every two days, one meal a day and two meals a day). Weight gain, feed efficiency and condition factor of fish fed one meal every two days were significantly (P<0.05) lower than those of fish fed one meal and two meals a day, but there were no significant differences in weight gain, feed efficiency and condition factor of fish fed between one meal and two meals a day. Based on the results of this study, optimum feeding frequency is one meal a day with satiation feeding for growth and feed efficiency of sub-adult flounder (270-350 g) in suboptimal water temperature ($12^{\circ}C$).

• Journal of Power System Engineering
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• v.21 no.2
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• pp.14-19
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• 2017

The corrosion characteristics of Al-Si-Mg alloy were investigated in $O_2$ and $H_2S/H_2$ environments at high temperature. The weight gain and the reaction rate constant of the Al-Si-Mg alloy were measured in the oxygen and hydrogen sulfide environments at 773K. The weight gain of Al-Si-Mg alloy was showed parabolic increase in the oxygen and hydrogen sulfide environments. The reaction rate constants were confirmed to be $1.45{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the oxygen environment and $6.19{\times}10^{-4}mg^2cm^{-4}sec^{-2}$ in the hydrogen sulfide environment respectively. As a result of XPS analysis on the specimen surface, $Al_2O_3$ and MgO compounds were detected in oxygen environment and $Al_2(SO_4)_3$ sulfate was detected in the hydrogen sulfide environment. Corrosion rate of Al-Si-Mg alloy was about 4.3 times faster in hydrogen sulfide environment than oxygen environment.

• Animal Bioscience
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• v.36 no.2
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• pp.248-255
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• 2023

Objective: Stress factors such as high temperatures, overcrowding, and diurnal temperature range exert profound negative effects on weight gain and productivity of broiler chickens. The potential of gamma aminobutyric acid (GABA) as an excitatory neurotransmitter was evaluated under various stress conditions in this study. Methods: The experiment was conducted under four different environmental conditions: normal, high temperature, overcrowded, and in an overcrowded-diurnal temperature range. The experimental groups were divided into (-) control group without stress, (+) control group with stress, and G50 group (GABA 50 mg/kg) with stress. Weight gain, feed intake, and feed conversion ratio were measured, and stress reduction was evaluated through hematologic analysis. Results: The effects of GABA on broilers in four experimental treatments were evaluated. GABA treated responded to environmental stress and improved productivity in all the experimental treatments. The magnitude of stress observed was highest at high temperature, followed by the overcrowded environment, and was least for the overcrowded-diurnal temperature range. Conclusion: Various stress factors in livestock rearing environment can reduce productivity and increase disease incidence and mortality rate. To address these challenges, GABA, an inhibitory neurotransmitter, was shown to reduce stress caused due to various environmental conditions and improve productivity.

• Corrosion Science and Technology
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• v.13 no.2
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• pp.41-47
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• 2014

The isothermal corrosion tests of several types of stainless steels, Ni-based alloys, and ferritic-martensitic steels (FMS) were carried out at the temperature of 550 and $650^{\circ}C$ in SFR S-$CO_2$ environment (200 bar) for 1000 h. The weight gain was greater in the order of FMSs, stainless steels, and Ni-based alloys. For the FMSs (Fe-based with low Cr content), a thick outer Fe oxide, a middle (Fe,Cr)-rich oxide, and an inner (Cr,Fe)-rich oxide were formed. They showed significant weight gains at both 550 and $650^{\circ}C$. In the case of austenitic stainless steels (Fe-based) such as SS 316H and 316LN (18 wt.% Cr), the corrosion resistance was dependent on test temperatures except SS 310S (25 wt.% Cr). After corrosion test at $650^{\circ}C$, a large increase in weight gain was observed with the formation of outer thick Fe oxide and inner (Cr,Fe)-rich oxide. However, at $550^{\circ}C$, a thin Cr-rich oxide was mainly developed along with partially distributed small and nodular shaped Fe oxides. Meanwhile, for the Ni-based alloys (16-28 wt.% Cr), a very thin Cr-rich oxide was developed at both test temperatures. The superior corrosion resistance of high Cr or Ni-based alloys in the high temperature S-$CO_2$ environment was attributed to the formation of thin Cr-rich oxide on the surface of the materials.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.109-114
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• 2013

In this study, the microstructure, mechanical properties and high temperature oxidation characteristics of HiSiMo and HiSiMoM ductile iron for exhaust manifold were investigated. The HiSiMoM ductile iron was developed by optimization of alloying element addition and casting design. The exhaust manifold prototype was fabricated using the HiSiMoM iron and this resulted in the weight saving of 0.73kg. The microstructures of the HiSiMo and HiSiMoM irons were similar each other and graphite nodularity was 89% and 93% respectively. Tensile strengths of them were 663.5 and 674.4 MPa and Brinell hardness were 235.3 and 243.9 respectively. Both irons showed parabolic weight gain behavior in high temperature oxidation atmosphere. Oxidation layer was divided into external and internal layers. The weight gain of the HiSiMoM iron was lower than that of the HiSiMo iron after isothermal oxidation test at $900^{\circ}C$. This should be rationalized by higher Si enrichment at the interface of the matrix and internal layer of the HiSiMoM iron.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.1
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• pp.84-88
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• 1995

Various heat-treatments were conducted to Ti-48.1at%Al and Ti-48.3at%Al-1.2at%Mn alloys casted by plasma arc melting system. Mechanical properties, microstructure and high temperature oxidizing behaviors of as-casted and heat-treatment alloys were investigated. Ti-48.1Al and Ti-48.3Al-1.2Mn alloys were decreased in strength according to increased of heattreatment temperature. Oxidizing weight gain of Ti-48.1Al alloy which conducted at $1273^{\circ}K$ was linearly increased. In case of adding Mn to alloy, there was no rapid increase of oxidizing weight gain during early time.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.198-202
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• 1997

The oxidation behavior of UO$_2$pellets was studied using a thermogravimetric analyzer and an XRD in the temperature range of 300 to 550$^{\circ}C$ in air. From XRD studies it is found that UO$_2$is converted to U$_3$O$\_$8/ and the weight gains of UO$_2$specimen are characterized by S-shape curves. After complete oxidation the specimens broke into fine powder and the average weight gain was about 3.93 wt%. The activation energy of 50% conversion of UO$_2$to U$_3$O$\_$8/ is 81.6 kJ/mol and the oxidation rate per unit time was found to be as follows dw/dt=6.54${\times}$10$\^$6/ e (equation omitted), wt%/h : at 50% conversion of UO$_2$into U$_3$O$\_$8/ where w, t and T were wt% gain, conversion time and temperature, respectively.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.102-108
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• 2000

This study was carried out to investigate the epidemiological prevalence of diseases from birth to weaning in 66 dairy calves which were delivered from three stock farm in Chonbuk area. We examined body weight gain, incidence rate of diseases and population mortality rate in relation to age, season, environmental temperature and rearing management conditions for one year. The results of this experiment were as follows: Birth weight of dairy calves born of primiparae was lower than those of multiparae. But no significant difference in body weight gain was observable between dairy calves born of primiparae and those of multiparae. Body weight gain of diseased calves was lower than normal calves. Of 66 delivered calves, 34 calves(51.5%) were affected with gastronitestinal and/or respiratory diseases. The prevalence of the diseases were gastrointestinal disease(28.7%), respiratory disease(18.2%), and gastronitestinal and respiratory disease(4.6%). The gastronitestinal disease was occurred contrinually regardless of the season. Whereas all of the respiratory disease were occurred in winter and a change of season(December to April). 68.4% of the gastronitestinal disease, and all of the respiratory disease were occurred at atmospheric temperatures below 1$0^{\circ}C$. 89.5% of the gastronitestinal disease were occurred within 3 weeks old, whereas 50% of the respiratory disease were occurred intensively between 3 weeks and 4 weeks old. Of 66 delivered dairy claves, 2 calves were died(3%) with respriratory disease.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.6
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• pp.914-922
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• 1999

An experiment was conducted to determine the effects of dietary energy and protein on performance and carcass composition of broilers under heat stress during the growing period (3-6 weeks). A factorial arrangement of three levels of energy (3.0, 3.2 and 3.4 kcal/g), three levels of protein (18, 20 and 22%), an two rearing temperatures were used in this study. Groups of birds were kept under moderate temperature ($24{\pm}1^{\circ}C/24h$) or hot cycling temperature ($26-34^{\circ}C/6h$, $34{\pm}1^{\circ}C/12h$, and $34-26^{\circ}C/6h$). Body weight (BW), weight gain (WG), feed intake (FI), feed conversion (feed : gain) (FC), carcass weight (CW), carcass yield (YP), breast meat (BM), abdominal fat (AF), drumsticks (DS), and thighs (TH) percentages were determined at the end of the experiment. Hot cycling temperature significantly (p<0.05) decreased BW, WG, FI, CW, and BM, increased FC, YP, DS, and TH but did not affect AF. High energy significantly (p<0.05) increased BW, WG, CW, YP, AF, and TH, decreased FI and FC but did not affect BM or DS. This improvement was observed only under moderate temperature resulting in significant (p<0.05) energy by temperature interaction. High protein significantly (p<0.05) increased BW, WG, CW and BM, decreased AF but did not affect FI, FC, TP, DS, or TH. There were no significant protein by temperature interactions for any of the parameters tested except CW. It is concluded, under the conditions imposed in this experiment, that increasing dietary energy did not alleviate the depressing effect of heat stress while increasing dietary protein up to 22% improved the performance of broilers irrespective of rearing temperature.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.193-197
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• 1996

A study was conducted on the oxidation behavior of U-0.75 wt% Ti chips (Depleted Uranium, DU chips) using an XRD and a thermogravimetric analyzer in the temperature range from 250 to 500$^{\circ}C$ in air. At the temperature lower than 400$^{\circ}C$, DU chips were converted to UO$_2$, U$_3$O$\_$7/, and U$_3$O$\_$8/ whereas at the temperature higher than 400$^{\circ}C$, DU chips were completely converted to U$_3$O$\_$8/, the most stable form of uranium oxide. The activation energy for the oxidation of DU chips is found, 44.9 kJ/mol and the oxidation rate in terms of weight gain (%) can be expressed as; dW/dt8.4${\times}$10$^2$e(equation omitted) wt%/min (250$\leq$T($^{\circ}C$) $\leq$ 500) where W=weight gain (%), t=time and T=temperature.