• Journal of Welding and Joining
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• 제14권1호
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• pp.75-81
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• 1996

The heat transfer and thermal stress-distribution were numerically determined by using the finite element method for a butt-welded pipe. A mechanical stress relieving(MSR) treatment which has been frequently used in the fabrication of pressure vessels instead of the post weld heat treatment (PWHT) was also simulated to investigate its effect of reducing the residual stress in the welded zone by a mechanical loading.

• Journal of Dairy Science and Biotechnology
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• 제37권1호
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• pp.49-56
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• 2019

Vulvovaginal candidiasis is a major urogenital infection in women. Lactobacilli are important in maintaining vaginal health. In the present study, the effect of heat adaptation at $47{\sim}52^{\circ}C$ prior to heat stress at $60^{\circ}C$ in improving the viability of Lactobacillus salivarius MG242 was examined. L. salivarius MG242 has antifungal effects against Candida albicans. Heat-adapted cells had a higher survival rate than non-adapted cells during the subsequent heat stress. When chloramphenicol was added during the adaptation process, heat tolerance was abolished, suggesting the involvement of de novo protein synthesis with the heat adaptation of L. salivarius MG242 strain. Exopolysaccharide quantification and scanning election microscopy did not reveal any appreciable changes during heat adaptation. The antifungal activity of L. salivarius MG242 against C. albicans was maintained during the heat adaptation. These results suggest that heat adaptation can be applied for the development of probiotic products using L. salivarius MG242 to improve its stress tolerance during processing.

• 농업과학연구
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• 제43권4호
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• pp.656-664
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• 2016

Gear reducers are widely used for various agricultural machinery applications such as greenhouses, tractors, and agricultural vehicles. However, thermal deformation and surface pitting at gear tooth flank frequently occur in gear reducers due to high torque. Thus, surface heat treatment of gears is required to improve wear and fatigue resistance. The objective of this study was to simulate the load capacity of the agricultural gear reducer. The simulation was performed for the following three surface heat treatment methods: untreated gears, nitriding heat treatment, and induction hardening method, those mostly used for agricultural gear reducers. The load capacity of the gear reducer was simulated using the safety factor, limit bending stress, and limit contact stress of the gear. The simulation of the load capacity was conducted using KISSsoft commercial software for gear analysis. The main results of simulation test were as follows: first, the nitriding heat treatment resulted in the highest safety factor for bending stress, which was increased about 77% from those of the untreated gears. Second, the induction hardening was the highest safety factor for contact stress, which was increased about 150% from those of the untreated gears. The safety factor for contact stress of the induction hardening was increased about 64% from those of the nitriding heat treatment. The study result suggested that the surface heat treatments could enhance load capacity and that the method of surface heat treatment should be determined based on simulation results for appropriate use scenarios.

• Safety and Health at Work
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• 제9권2호
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• pp.232-235
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• 2018

Background: This study was conducted to investigate the heat stress and semen quality among male workers in a steel industry in Iran and investigate the relationship between heat stress indices and semen parameters. Methods: The study was conducted on workers exposed (n = 30) and unexposed (n = 14) to heat in a steel industry. After obtaining a brief biography of the selected employees, scrotal temperature, oral temperature, and environmental parameters were measured, and their semen samples were analyzed according to the procedure recommended by the World Health Organization. The heat stress indices, including wet-bulb globe temperature (WBGT) and predicted heat strain (PHS), in their workplace were calculated according to environmental parameters (ISO 7243:1989 and 7933:2004, respectively). Results: Time-weighted averages of WBGT and PHS ($35.76^{\circ}C$ and 491.56 $w/m^2{\frac{w}{m^2}}$, respectively) for the exposed group were higher than threshold limit values. The mean difference of environmental, physiological, and semen parameters (exception: pH of semen), and also WBGT and PHS indices were statistically significant (p < 0.05) between the two groups. Mean semen parameters were in the normozoospermic range. WBGT and PHS indices showed significantly "negative" correlation with physiological parameters (scrotal and oral temperature) and most semen parameters (semen volume, sperm morphology, sperm motility, sperm count; p < 0.05); moreover, the correlation of WBGT with these parameters was stronger than PHS. Conclusion: Semen parameters of the studied workers exposed to heat were in the borderline level of normozoospermic range, and their semen parameters were significantly lower than controls. For better assessment of occupational environment concerning physiological and semen parameters in steel industries, WBGT can be a more useful index.

• Journal of Animal Science and Technology
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• 제66권1호
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• pp.79-92
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• 2024

Global warming is a key challenge subjecting animals to heat stress conditions resulting in multiple physiological alterations in tropical climate. Dietary approach seems to be the more friendly approach to curb the adverse effects of heat stress in rabbits. Some herbs have been categorized to have high potential for promotion of immune responses for amelioration of heat stress. Thus, this research aims to evaluate the potential of Mistletoe (Viscum album), Moringa (Moringa oleifera) and Phyllanthus (Phyllanthus amarus) leaf meal as herbal supplements for the alleviation of heat stress in female rabbits by measuring improvement in sex and stress hormonal responses in serum biochemistry. 80 Rabbit does were exposed to 4 dietary groups supplemented with each of Mistletoe, Moringa, Phyllanthus and a control in an 84-day trial at the summit of thermal stress in South west Nigeria. Growth indices were monitored throughout the study, blood samples were compiled at the end of the trial to assess serum biochemistry, stress and sex hormonal responses of the Does using standard protocols. The results revealed that final weight and weight gain of Does fed on Phyllanthus were significantly (p < 0.05) higher (11.46% and 14.25%, respectively) than Does on control. The herbal supplements enhance glucose, protein, albumin and globulin, reduced cholesterol, and creatinine of Does under heat stress conditions. Among the herbal treatment groups, mistletoe, moringa and phyllanthus had 12.42%, 18.39% and 16.90%, respectively, lower corticosterone than control groups which had 39.76ng/ml. Triiodothyronine of Does fed control were significantly (p < 0.05) lower than Does on Moringa oleifera and Phyllanthus amarus supplements. Estradiol and Follicle stimulating hormone of rabbit Does fed on moringa supplement were significantly (p < 0.05) higher than other treatments. In conclusion, the herbal supplements tend to mitigate the detrimental outcome of thermal stress on Does by suppressing stress hormones. Moringa oleifera and Phyllanthus amarus enhanced sex hormones while Phyllanthus amarus confered growth promoting effects on the Does.

• 대한기계학회논문집A
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• 제35권5호
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• pp.453-458
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• 2011

본 논문은 TP316L 스테인리스강 재료에 대한 표면 기계가공 및 열처리에 의한 잔류응력의 생성 및 변화에 대해 연구한 것이다. 연구를 위해서 TP316L 시편에 대해 방전가공, 밀링, 연마의 3 가지 기계가공을 수행하고 표면의 잔류응력을 측정하였다. 동일한 방법으로 기계가공한 다른 시편은 열처리를 수행한 후에 표면잔류응력을 측정하여 열처리를 수행하지 않은 시편과의 차이를 비교하였다. 잔류응력측정은 엑스선회절법을 사용하였다. 또한 각 시편에 대해 비커스경도를 측정하여 열처리 수행전과 수행후의 경도를 비교하였다. 본 연구를 통해서 기계가공 방법에 따라 잔류응력의 형태가 달라지며 열처리에 의해서 대부분의 잔류응력이 제거됨이 확인되었다. 경도는 잔류응력의 인장 또는 압축의 방향에는 관계없이 크기에만 관련성이 있는 것으로 관찰되었다.

• 한국전산유체공학회지
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• 제19권3호
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• pp.37-43
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• 2014

In this paper, hydraulic & thermal developing and fully developed laminar forced convection flow of a water-$Al_2O_3$ nanofluid in a circular horizontal tube with uniform heat flux at the wall, are investigated numerically. A single phase model employed with temperature independent properties. The thermal entrance length is presented in this paper. The variations of the convective heat transfer coefficient and shear stress are shown in the entrance region and fully developed region along different nanoparticles concentration and Reynolds numbers. Convective heat transfer coefficient for nanofluids is larger than that of the base fluid. It is shown that heat transfer is enhanced and shear stress is increased as the particle volume concentration increases. The heat transfer improves, as Reynolds number increases.

• Journal of Welding and Joining
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• 제6권4호
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• pp.54-62
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• 1988

Major problems in welding Al-7020 include shrinkage, rpopositgy in welds and loss of strength in the heat affected zone. Thus it is important to examine the mechanical properties and reliability of welds. In this study, a series of experiments was carried out to determine the mechanical properties such as micro-hardness distribution, tensile strength, porosity and residual stress distribution of the Al-7020 weldment made by pulse-GMA welding. The resuts of the experiemnts are as folows. 1) The micro-hardness of weld metal and heat affected zone was lower than that of the base metal. 2) The tensile strength of the deposited metal was much lower than that of the base metal. 3) The porrosity in weld metal zone was negligible under the adopted conditsion of experiemnts. 4) The residual stress in the weld metal was lower than that of the heat affected zone, because the weld metal was softened. And the mciro-hardness distribution, the tensile strength and the residual stess distribution of the weldment in the as-welded condition were compared with those of the weldment after heat treatment.

• 한국정밀공학회지
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• 제13권5호
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• pp.44-52
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• 1996

A procedure predicting warpage and post-deformation due to heat resistance test is presented. The procedure is applied to the injection molding processes of automotive plastic components, which are the door trim and the instrument pannel. The warpage of products is obtained from the residual stress after filling, packing and cooling process, and the post deformation due to the heat resistance test is calculated in the structural analysis of the product at the ejection temperature with the initial condition of residual stress, the boundary conditions and heat resistance conditions. The analyses give some useful guide lines in the design of automotive plastic parts which should satisfy heat resistance regulation.

• Journal of Advanced Marine Engineering and Technology
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• 제8권2호
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• pp.81-87
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• 1984

The effect of heat treatment and mechanical stress on the dielectic strength of epoxy resin film is studied. The film with 30-210 .mu.m thickness are casted at room temperature for 8 hours and post cured at the range of temperature 60-180 .deg. C, and the heat setting time are two kind, ie, 2 and 10 hours. The samples are made with Stycast 1266 that the primary compound is diglycidyl ether of bisphenol A, and the hardner is denaturated polyamines. Under no mechanical stresses, the maximum dielectric strength of the sample is obtained for the sample heat treated for 2 hours at 150 .deg. C. However, the best dielectric strength characteristics under compressive stress is obtained for the sample heat treated at 90 .deg. C and 120 .deg. C. The dielectric strength of the sample are also affected significantly by the cooling velocity of the sample after post heat setting at given temperature.