The purpose of this paper is to study the thermoviscoelastic interactions in a homogeneous, isotropic semi-infinite solid under two-temperature theory with heat source. The Kelvin-Voigt model of linear viscoelasticity which describes the viscoelastic nature of the material is used. The bounding plane surface of the medium is subjected to a non-Gaussian laser pulse. The generalized thermoelasticity theory with dual phase lags model is used to solve this problem. Laplace transform technique is used to obtain the general solution for a suitable set of boundary conditions. Some comparisons have been shown in figures to estimate the effects of the phase lags, viscosity, temperature discrepancy, laser-pulse and the laser intensity parameters on all the studied fields. A comparison was also made with the results obtained in the case of one temperature thermoelasticity theory.
The paper presents the trends of air temperature of the Antarctic. In its elaboration 21 stations were taken into consideration carrying out temperature measurements in the years 19582000, and 34 stations in the years 19812000. After checking the homogeneity of the series by the Alexanderssons (1986) test we found that at 16 stations the homogeneity has been broken. On the basis of the corrected measurement series we have determined the trends in air temperature. In the period 19582000 statistically significant (on 0.95 significance level) temperature increases occurred on the western coast of the Antarctic Peninsula (for example Faraday 0.67°C/10 years) and at the Belgrano and McMurdo stations. The greatest temperature rise was noted on the Antarctic Peninsula during the autumn-winter period. On the South Pole a negative trend in air temperature (0.21°C) occurred, especially in the summer season. During recent years (1981-2000) significant changes took place in the air temperature tendencies in the Antarctic. In many regions of the Antarctic cooling began and on the cost of East Antarctica the temperature decreased by 0.82°C/10 years (Casey). In the interior of the continent also lower and lower temperatures occurred (Amundsen-Scott 0.42°C/10 years, Dome C 0.71°C/10 years). The coast of the Weddell Sea is getting colder (Halley 1.13°C/10 years, Larsen Ice 0.89°C/10 years). An increase in temperature was observed in the interior of West Antarctica (Byrd 0.37°C/10 years). The warming rate of the climate became weaker on the Antarctic Peninsula (Faraday 0.56°C/10 years). The largest temperature changes occurred in the autumn-winter season when in the Antarctic Peninsula region the temperature increased, while in the interior and at the coast of East Antarctica temperatures fell considerably.
Average duration of a thermal winter in Hornsund has been determined for 216 days. Average soil temperature at depth of 5 cm in winter is equal —9.8°C. During a spring that lasts 35 days only, soil temperatures at depth of 5 cm indicate distribution nearest to a normal one. Soil temperature distribution in winter substantially differs from the one in spring.
On the ground of continuous records of air and soil temperature at standard levels, changes of soil temperature against changes of air temperature have been analyzed at thick and without snow cover. The first example concerns a six-day winter thaw, and the second one a four-day autumn cooling. A particular influence of energy advection has been noted. A delay of changes of soil temperature was found to increase with depth in relation to air temperature. A hypothesis on correlation between air temperature at a height of 5 cm and soil temperature at a depth of 5 cm has been verified.
Monthly and dekadal mean soil temperatures were evaluated with a use of measurements at depths of 5, 10, 20 and 50 cm, collected during the expeditions 1978—1986 and additionally at depths of 80 and 100 cm during the expeditions 1980—1986. Fourier analysis revealed a phase shift of 1 to 2 dekads between neighboring measurement depths.
A lot of heat will generate in mass concrete after pouring to form temperature cracks, which will reduce structural stiffness. This paper briefly introduces the principle of solid heat conduction and the cause of temperature crack formation and then used COMSOL software to simulate and analyze the mass concrete. The results showed that the simulation model had enough reliability to analyze the temperature change; the internal and external temperature of concrete rose first and then decreased; the formation of temperature crack was related to the internal and external temperature difference; the internal and external temperature difference was inversely proportional to the heat conductivity coefficient of concrete and directly proportional to the pouring temperature. Then, according to the analysis results, two measures were put forward to prevent temperature cracks in mass concrete: selecting concrete materials with high thermal conductivity, i.e., selecting coarse aggregate and fine aggregate with larger heat conductivity coefficient and reducing concrete pouring temperature, i.e., selecting cement with lower hydration heat, paying attention to temperature reduction in the process of concrete stirring, and reducing the amount of cement.
The paper presents the test description and results of thermal bowing of RC beams exposed to non-uniform heating at high temperature. Bending of a non-uniformly heated element is caused by free thermal elongation of the material it is made of. The higher the temperature gradient, the greater the bending. In the case when an element is exposed to load and high temperature simultaneously, apart from free bending also deformation of the RC element may occur, which is caused by the decrease of the concrete or reinforcing steel mechanical properties. In order to examine the contribution of the deflection caused by thermal bowing to the total deformation of the bent element with a heated tension zone, an experimental study of freely heated (unloaded) beams was performed. RC beams were heated: (1) on three sides of the cross-section or (2) only on the bottom side. Deflection of elements loaded by a substitute temperature gradient was calculated using the Maxwell-Mohr formula. The test results show that deflection of freely heated RC beams (caused by the thermal bowing phenomenon) can be 10 to 20% of the total deflection of loaded RC beams with a heated tension zone.
Over the South American sector of the Antarctic Ocean intensive cyclonal activity occurred in turn with meridional circulation, which was a more common feature of winter 1986 than it usually is. At the Arctowski Station strong temperature oscillations were observed during the austral winter from May to October. In the end of July the lowest temperature of this winter, — 32.3°C, was recorded. In the first half of the winter an easterly air flow prevailed and in the second part — the westerly one. Winds were strong and gusty. The highest speed reached 74 ms-1 . Snowfalls were abundant; depth of snow exceeded 100 cm.
In the summer of 1979, in South Spitsbergen investigations of the extreme temperatures of the ground surface were carried out. The investigations permitted the determination of the magnitude of the extreme temperatures of the ground surface and their relation to the air temperature. The spatial variability of the extreme temperatures of the ground surface was observed.
The paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration of the engine due to the minimization of hydraulic resistance, while maintaining the required thermal capacity of the device. Preliminary tests carried out on the real object allowed to determine boundary and initial conditions for simulation purposes. The simulation assumes that there is no heat exchange between the regenerator and the environment. The solid model used in simulation tests includes the following elements: supply channel, heater, regenerator, cooler, discharge channel. Due to the symmetrical structure of the analyzed elements, simulation tests were carried out using 1/6 of the volume of the system.
The Stirling engine type alpha is composed of two cylinders (expansion space E and compression space C), regenerator that forms the space between the cylinders and the buffer space (under the pistons). Before the start-up and as a result of long-term operation, the average pressure in the working space (above the pistons) and in the buffer space is the same. However, in the initial phase of operation, the average pressure in the working space is different then the average pressure in the buffer space depending on the crankshaft starting position (starting angle). This, in turn, causes a large variation in the starting torque. An additional unfavorable factor caused by a large variation in the course of the indicated torque is the rotational speed variation and the formation of torsional vibrations in the drive system. After some time, depending on the quality of the engine piston sealing, the average pressure in the working and buffer space will equalize. The occurrence of the above-described phenomenon affects the selection of the starting electric motor, which can be significantly reduced, when the crankshaft starting position is optimized (the starting torque is several times greater than the average torque occurring in the generator operation mode). This paper presents the analysis of the impact of the crankshaft starting position on the course of the indicated torque and the resulting start-up energy. Starting the engine at an unfavorable position of the crankshaft may, in extreme cases, increase the starting torque even three times.