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In this paper, the thermal effects on mechanical properties of polyvinyl alcohol fiber-reinforced engineered cementitious composites (PVA–ECC) were investigated systematically from perspective of multi-scales. At composite level, the compressive strength increases from 38 to 50 MPa as the samples were heated from 30 to 200 °C, whereas it declines to 20 MPa at 800 °C. In respect of tensile performance, at range of 30– 200 °C, the ultimate tensile stress and strain of ECC showed a decrease tendency with rising temperature, but still remained strain-hardening behavior at 200 °C. In addition, the elevated temperature exposures are adverse to multiple-cracking behavior of ECC. At micro-scale, it was found that the fiber/matrix interfacial bond reduces as exposure temperature rises, which is supposed to avail the fiber slippage, and thereby ductility of ECC. Nonetheless, through micromechanics-based analysis, the enhanced matrix toughness and severe deteriorated fiber strength prevailed over the above positive effect, which resulted in the decayed tensile properties of ECC. [ABSTRACT FROM AUTHOR]

The article presents information on the processes occurring during the synthesis of cordierite ceramics produced based on clay from the Krupeisky Sad deposit; the phase composition and properties of the material were studied in detail. The influence of the clay component on the phase and structure formation features in the material during firing, as well as on the structure formation and acquisition of properties during heat treatment, has been established. [ABSTRACT FROM AUTHOR]

A classification is presented of the thermal states of the Sayano-Shushenskaya HPP and methods of identifying them by analysis of the thermal components of radial displacements obtained by the results of finite-element modeling. Based on the safety conditions of the repaired dam zones and the foundation, limit levels are presented for the entire path of filling-and-drawdown of the reservoir, depending on the thermal state of the dam. There is an evaluation of the dynamics of changes in the stress-strain state of the concrete of the dam face, based on finite-element calculation results and measurement data. Reasons are established for crack formation in the repaired zone and the effectiveness of measures taken to regulate the modes of filling-anddrawdown of the reservoir. [ABSTRACT FROM AUTHOR]

In this paper, an advanced electrothermal model was developed in order to provide real-time information about the thermal states of the electrical components of the vehicle's powertrain and determine the evolution of losses and that of powertrain parameters versus temperature during vehicle traffic. Then, electrothermal models were introduced in order to study the impact of the thermal behavior of the motor–inverter combination on the speed control of an electric vehicle. The obtained results show that the efficiency of the adopted PI regulators with predetermined parameters is heavily affected by the variation of powertrain parameters caused by temperature change. To improve the performance of the vehicle speed control and make the PI regulators adaptable to the variation of the different parameters during a drive cycle, the fuzzy logic technique was adopted. [ABSTRACT FROM AUTHOR]

One of the promising ways of expanding energy resource base is production of combustible gas from coalbeds. The yield of gaseous components from samples of Visean coals of Tatarstan upon thermal impact was studied in this work by combined thermogravimetric and IR spectrometric method. It is demonstrated that methane begins to appear actively at 384-405°C, depending on the test coal sample. In this process, the yield of methane could be as much as 30 wt. % and higher, which confirms the prospect of getting gaseous fuel from Visean coal deposits by thermal impact. [ABSTRACT FROM AUTHOR]

Mechanical and thermal impact of the plasma focus discharge on structural elements of diagnostic windows of the PFM-72m discharge installation are calculated. The absence of critical impact at early discharge stages and during the first 300 ns after the "plasma focus" formation is shown. The possibility of shock impact on the surface of diagnostic windows at later times, which may result in their substantial deformation and destruction, is demonstrated. [ABSTRACT FROM AUTHOR]

Reducing metal machining costs and harmful effects to the environment are the main benefits of dry machining compared to the application of cooling lubricants during machining processes. The abandonment of any lubricants is causing higher temperatures of workpiece, chip, and tool. Thus, the temperature gradient varies with time and space over the workpiece, causing dimensional deviations and profile defects due to thermal expansion and shrinking. The aim of this work is to determine the heat flux to the workpiece from experimental data. The temperatures of the workpiece were measured during an orthogonal turning process of carbon steel (AISI 1045). An analogous thermal model is used to solve the ill-posed inverse heat conduction problem by the sequential estimation method, introduced by Beck et al. (Inverse heat conduction, Wiley, New York, ) and for the evaluation of the results. The heat flux to the workpiece could be used in further work as a basic boundary condition in finite element simulations to find an alternative tool path, which compensate thermally induced deviations and profile defects of the workpiece. The heat flux to the workpiece is calculated for different cutting velocities, feed rates, and the influence of TiN-coatings on cemented carbide tools. Cutting parameters have been identified to minimize the heat load on the workpiece in general and therefore reduce errors due to dry machining. [ABSTRACT FROM AUTHOR]

From today's point of view the modelling of machining operations is a promising tool to extend the productivity and the precision of future industrial manufacturing. The importance of predictive simulation and compensation of thermally induced workpiece deformation during machining is especially important in dry machining because of the absence of cooling lubricants. Since the simulation results mainly depend on the boundary conditions of the model, a detailed knowledge of them is necessary. In this case the most important boundary condition is the intensity and possibly the distribution of the surface heat flux representing the heat flow into the workpiece resulting from the chip formation. The surface heat flux cannot be measured directly. One possible way to determine surface heat fluxes is to employ a thermal model of the machining process and match simulated and measured time and space dependent temperature fields. This procedure is time-consuming and is in most cases subjective because the congruency of temperature fields is rated manually, e.g. by the position of single isotherms. Therefore an enhanced method for the determination of surface heat fluxes is proposed in this paper. The method is based on nonlinear optimisation techniques and a simple finite difference scheme for numerical solution of the heat equation (WORHP-FDM). The procedure is objective between repeat measurements and works in a fully automated manner. The implementation is validated by the comparison to an analytical solution of the moving heat source based on the model of Carslaw and Jaeger and then applied to measured thermal images from milling experiments. [ABSTRACT FROM AUTHOR]

Within the framework of the TIMODAZ project, permeameter tests and isostatic tests were performed on Boom Clay and Opalinus Clay in order to assess the impact of temperature, pore water composition, and confining stress on the sealing of damaged samples of Boom Clay and Opalinus Clay. A microfocus X-ray computed tomography technique was used to visualize the evolution of the sealing process. Compared to the fast sealing of Boom Clay, the sealing of Opalinus Clay was much slower. The heating showed a significant, favorable impact on the sealing behavior of Opalinus Clay under permeameter test conditions, while the sealing behavior of Boom Clay appeared to be unaffected. Tests performed under isostatic conditions did not reveal a significant influence of a heating-cooling cycle on the sealing behavior of these clays. The reappearance of the fractures or holes in the samples after dismantling confirms earlier observations which showed that after sealing, the original mechanical properties are not recovered. In other words, a heating cycle does not seem to induce healing. [ABSTRACT FROM AUTHOR]

A proper evaluation of the perturbations of the host rock induced by the excavation and the emplacement of exothermic wastes is essential for the assessment of the long-term safety of high-level radioactive waste disposals in clay formations. The impact of the thermal transient on the evolution of the damaged zone (DZ) has been explored in the European Commission project TIMODAZ (thermal impact on the damaged zone around a radioactive waste disposal in clay host rocks, 2006-2010). This paper integrates the scientific results of the TIMODAZ project from a performance assessment (PA) point of view, showing how these results support and justify key PA assumptions and the values of PA model parameters. This paper also contextualises the significance of the thermal impact on the DZ from a safety case perspective, highlighting how the project outcomes result into an improved understanding of the thermo-hydro-mechanical behaviour of the clay host rocks. The results obtained in the TIMODAZ project strengthen the assessment basis of the safety evaluation of the current repository designs. There was no evidence throughout the TIMODAZ experimental observations of a temperature-induced additional opening of fractures nor of a significant permeability increase of the DZ. Instead, thermally induced plasticity, swelling and creep seem to be beneficial to the sealing of fractures and to the recovery of a very low permeability in the DZ, close to that of an undisturbed clay host rock. Results from the TIMODAZ project indicate that the favourable properties of the clay host rock, which guarantee the effectiveness of the safety functions of the repository system, are expected to be maintained after the heating-cooling cycle. Hence, the basic assumptions usually made in PA calculations so far are expected to remain valid, and the performance of the system should not be affected in a negative way by the thermal evolution of the DZ around a radioactive waste repository in clay host rock. [ABSTRACT FROM AUTHOR]

Two approaches are used in simulating the thermal impact during the slipping friction of steel with lubricant, when high pressure is created and travels as an expansion-compression wave to the surface layers. This results in polymorphic transformation and anomalously fast diffusional mass transfer below the kinetic-transformation temperature. The pressure and diffusion coefficients are calculated. [ABSTRACT FROM AUTHOR]

The effect of environmental temperature on neuronal spiking behaviors is investigated by numerically simulating the temperature dependence of spiking threshold of the Hodgkin—Huxley neuron subject to synaptic stimulus. We find that the spiking threshold exhibits a global minimum in a specific temperature range where spike initiation needs weakest synaptic strength, which form the engineering perspective indicates the occurrence of optimal use of synaptic transmission in the nervous system. We further explore the biophysical origin of this phenomenon associated with ion channel gating kinetics and also discuss its possible biological relevance in information processing in neuronal systems. [ABSTRACT FROM AUTHOR]

It is shown that atomic force microscopy allows comparative estimates of the coefficient of thermal expansion of graphite oxide (GO). One possible explanation for its negative value is the formation of GO intercalated compounds, particularly with water. [ABSTRACT FROM AUTHOR]

The use of shallow geothermal energy increasingly receives attention as a suitable alternative to fossil fuel-based space heating and cooling, warm water provision, as well as for seasonal heat storage throughout Europe. With the advent of shallow geothermal energy use on large scales, a vivid discussion of potential ecological and economic impacts has arisen but actual field data are scarce. An intensive groundwater temperature-monitoring program over a period of 3 years with consecutive measurements was, therefore, initiated at a residential neighborhood in the city of Cologne, Germany, under intense shallow geothermal use. The aim of the monitoring program was to overcome the existing data scarcity by pinpointing the effects of the intensive thermal use of the subsurface on groundwater temperatures and to foster understanding of urban groundwater temperature evolution. Results show that even though energy demands of the individual houses and energy extraction rates of the shallow geothermal systems were comparably small in this case, the accumulation of shallow geothermal users had a measurable impact on overall groundwater temperatures. [ABSTRACT FROM AUTHOR]

The factors affecting the operating conditions of (6–10)-kV cable lines are considered. In some instances, zones characterized by instability under the thermal action of the short-circuit current appear in power-line development are noted. Elimination of such instability by means of time-delayed current cutoffs is proposed. [ABSTRACT FROM AUTHOR]