Winter months’ temperature rises effect on duration of phenological phases for Spermophilus pygmaeus Pallas, 1778 populations located in Caspian depression (Astrakhan oblast)

This article provides comparison analysis between 1950–1959’s and 2000–2009’s periods for duration and schedule dates of awakening, spreading and hibernation phases for Spermophilus pygmaeus populations located in the Caspian Depression (by example of Astrakhan Oblast). We learned that within a period of maximum temperature rise in February 2000–2009’s durations of S.pygmaeus’ populations of every phonological phase have shortened and been rescheduled with earlier dates (in comparison to 1950–1959’s). The study also shows that these changes caused its population reduction on the Caspian Depression’s territory.

Modeling temperature rise in multi-track reciprocating frictional sliding

As in various manufacturing processes, in sliding tests with scanning motions to extend the sliding distance over fresh countersurface, temperature rise during any pass is bolstered by heating during prior passes over neighboring tracks, providing a “heat accumulation effect” with persisting temperature rises contributing to an overall temperature rise of the current pass. Conduction modeling is developed for surface temperature rise as a function of numerous inputs: power and size of heat source; speed and stroke length, and track increment of scanning motion; and countersurface thermal properties. Analysis focused on mid-stroke location for passes of a square uniform heat flux sufficiently far into the rectangular patch being scanned from the first pass at its edge that steady heat accumulation effect response is adopted, focusing on maximum temperature rise experienced across the pass' track. The model is non-dimensionalized to broaden the applicability of the output of its runs. Focusing on practical “high” scanning speeds, represented non-dimensionally by Peclet number (in excess of 40), applicability is further broadened by multiplying non-dimensional maximum temperature rise by the square root of Peclet number as model output. Additionally, investigating model runs at various non-dimensional speed (Peclet number) and reciprocation period values, it appears these do not act as independent inputs, but instead with their product (non-dimensional stroke length) as a single independent input. Modified maximum temperature rise output appears to be a function of only two inputs, increasing with decreasing non-dimensional values of stroke length and scanning increment, with outputs of models runs summarized compactly in a simple chart.

Braking performance of a novel frictional-magnetic compound disc brake for automobiles

Disc brakes have been applied in various automobiles widely and their braking performance has vitally important effects on the safe operation of automobiles. Although numerous researches have been conducted to find out the influential law and mechanism of working condition parameters like braking pressure, initial braking speed, and interface temperature on braking performance of disc brakes, the influence of magnetic field is seldom taken into consideration. In this paper, based on the novel automotive frictional-magnetic compound disc brake, the influential law of magnetic field on braking performance was investigated deeply. First, braking simulation tests of disc brakes were carried out, and then dynamic variation laws and mechanisms of braking torque and interface temperature were discussed. Furthermore, some parameters including average braking torque, trend coefficient and fluctuation coefficient of braking torque, average temperature, maximum temperature rise, and the time corresponding to the maximum temperature rise were extracted to characterize the braking performance of disc brakes. Finally, the influential law and mechanism of excitation voltage on braking performance were analyzed through braking simulation tests and surface topography analysis of friction material. It is concluded that the performance of frictional-magnetic compound disc brake is prior to common brake. Magnetic field is greatly beneficial for improving the braking performance of frictional-magnetic compound disc brake.

Effects of Inlet Pressure on Ignition of Spray Combustion

To evaluate the effects of inlet pressure on the ignition process of spray combustion, the images of the ignition process were recorded and the outlet temperatures were measured under inlet pressure of 0.04–0.16 MPa. The initial flame formation and flame propagation and the effects of the inlet pressure on the initial flame formation were observed. A variation of outlet temperature, flame propagation, initial time of outlet temperature rise, time of maximum temperature rise, and temperature rise rate was investigated. With increasing inlet pressure, the time of initial flame formation and time of maximum area growth rate of flame decrease and the centroid location move radially. The radial distances of the initial flame centroid gradually increased by about 13%, 5%, 6%, 12%, 57%, and 24%. The trace of flame centroid is determined from the distribution of fuel and is related to the initial SMD of the atomizer. The maximum temperature rise and temperature rise rate are determined by the rate of flame chemical reaction, rate of large drop evaporation, and fuel/air ratio. With increasing inlet pressure, the maximum temperature rise increased by 50%, 58%, 12%, 11%, and −9%, respectively. Meanwhile, the rate of the temperature rise increased by about 47%, 54%, 11%, 11%, and −7%, respectively.

Performance Analysis of a Multiple Micro-Jet Impingements Cooling Model

The present study investigates the thermal performance of a multiple micro-jet impingements model for electronics cooling. The fluid flow and heat transport characteristics were investigated for steady incompressible laminar flow by solving three-dimensional (3D) Navier-Stokes equations. Several parallel and staggered micro-jet configurations (ie. inline 2 Å~ 2, 3 Å~ 3 and 4 Å~ 4 jets, and staggered five-jet and 13-jet arrays with the jet diameter to the channel height ratios from 0.25–0.5) were analyzed at various flow rates for the maximum temperature rise, pressure drop, heat-transfer coefficient, thermal resistance, and pumping power characteristics. The parametric investigation was carried out based on the number of jets and the jet diameters at various mass flow rates and jet Reynolds numbers. Temperature uniformity and coefficient of performance were evaluated to find out the trade-off among the various designs investigated in the present study. The maximum temperature rise and the pressure drop decreased with an increase in the number of jets except in the case of staggered five-jet array. A higher temperature uniformity was observed at higher flow rates with a decrease in the coefficient of performance. The performance parameters, such as thermal resistance and pumping power, showed a conflicting nature with respect to design variables (viz. jet diameter to stand-off ratio and interjet spacing or number of jets) at various Reynolds numbers within the laminar regime.