Distribution transformers are designed to operate in an oil temperature range named the allowable range. This range depends on various factors such as the insulation class of the coils, the cooling fluid, the cooling method and the environmental conditions. If a transformer operates at a low temperature, its insulation life will increase. Based on this fact, it can be said that temperature is an important factor in transformer optimization. One of the major problems of the power distribution network is the overheating of the distribution transformers during the summer that resulted to failure and damage of that. Increasing the load due to the use of cooling devices and solar radiation on the transformers causes them to heat up and helps to increase its temperature. The normal life of transformer insulation is 85, 000 hours, which is equivalent to 10 years for Class A insulation. This life is halved or doubled for every 8 degrees of rise or fall of the specified value. Hot spot temperature is one of the important and key parameters in determining the insulation life of the transformer. The hot spot temperature of the transformer depends on the ambient temperature, high oil temperature and coil temperature. Also, the temperature of the hot point of the coil is a function of wind speed, thermal radiation of the sun and the height of the transformer installation relative to the sea level. In the present article, the effect of oil type, solar radiation, color and external environmental factors on the heating of distribution motors is reviewed and investigated experimentally and analytically.

The electric initiator is an important component of the explosive train which provides requiered energy to initiate a chemical reaction by converting the electric current to the heat via a bridgewire. This initiator is widely used in the field of aerospace industry in the solid rocket propellant motors, separation systems and etc due to its low weight and high reliability. In this research, a mathematical model has been introduced to investigate the effective parameters on the electric initiator performance. Comparison of numerical simulation results by finite difference method and experimental data showed that this model has the ability of the prediction of the ignition time and determine the transient temperature profile in axial and radial direction. The model showed that the reduction of the contact heat transfer coefficient between the bridgewire and the primer compared to its increase has a greater effect on the heat transfer rate. It was also found that with increasing the current, the temperature changes decreased along the axial direction and increased in radial direction.

In tropical regions, particularly during the summer, the rise in ambient temperature causes a significant increase in the hot spot temperature of transformers, which can result in the early failure of transformers and cause irreparable damage to the power grid. Therefore, efforts to reduce the hot spot temperature of transformers are of great importance. One method of thermal management for oil-immersed transformers is to enhance the heat transfer properties of the oil with additives, allowing for the effective and rapid dissipation of heat from the windings and core to the surrounding environment. In this study, the experimental performance of three nan-oil aluminium oxide, iron oxide, and multi-walled carbon nanotubes was evaluated in a laboratory-scale oil-immersed transformer with a maximum rated power of 150 watts. To this end, the aforementioned nanoparticles were mixed with transformer mineral oil at a concentration of 0.5 g/L and tested in the transformer. The results showed that adding nanoparticles to the oil, within the permissible range for various parameters, improved the physical properties of the nano-oil, which could play a significant role in the thermal management of transformer oil. For example, at 100% of the transformer's full power, the aluminium oxide, iron oxide, and multi-walled carbon nanotube nano-oils reduced the hot spot temperature by 2.1°C, 1.3°C, and 5.4°C, respectively, compared to the baseline test with mineral oil. The primary reason for this improvement is the enhanced thermal conductivity of the nano-oil.

Background and Objective: Several methods are available for measuring fever in children. This study was done to compare the accuracy of three method of measuring body temperature using left and right tympanic, axillary and rectal methods in three months to five years old children.Methods: This descriptive-analytic study was done on 126 children (63 without fever and 63 children with fever) with 3 months to 5 years age in Mofid hospital, Tehran, Iran. Rectal temperature lower than 38oC was considered as Gold standard to determine fever. Body temperature was also recorded for subjects through right and left tympanic and axilary methods.Results: Body temperature was recorded in axillary method 37.1°C (sensitivity: 92.1%, specificity: 90.5%), right tympanic 36.9oC (sensitivity: 74.6%, specificity: 84.13%) and left tympanic 37.3oC (sensitivity: 93.65%, specificity: 84.13%). The mean temperature in the axillary method 0.77oC, right tympanic 1.02oC and left tympanic 0.48oC was lower than the mean rectal method (P<0.05). The correlation between right, left tympanic and axillary with rectal method was 0.84, 0.894 and 0.925, respectively (P<0.05). The area under the receiver operating characteristic (ROC) curve for left and right tympanic and axillary were 0.95, 0.87, 0.965, respectively.Conclusion: The difference between rectal and left tympanic method was at the lowest level due to the ease of measuring temperature through tympanic membrane in three months to five years old children.