Narrow Results

The thermal behavior of Mg and Al layered double hydroxide with interlayer hydrogen phosphate (abb. as Mg/Al-HPO₄-LDH) is investigated below 1273 K by means of XRD, TG-DTA, SEM and FT-IR. The basal spacing of Mg/Al-HPO4-LDH decreases with increasing heating temperature stepwise in two stages; from 1.07 nm at 293 K to 0.85 nm at 333 K in the first stage and to 0.73 nm between 373 K and 443 K in the second one. The LDH becomes amorphous above 443 K until Mg₃ (PO₄)₂, MgO and MgAl₂O₄ (spinel) appear at 1273 K. SEM images of the LDH show plate-like crystallites both before and after heating at 473 K.

Little, lightweight, low-power microelectromechanical system (MEMS) pressure switches offer a good development prospect for small, ultra-long, simple atmosphere environments. In order to realize MEMS pressure switch, it is necessary to solve one of the key technologies such as thermal robust optimization. The finite element simulation software is used to analyze the thermal behavior of the pressure switch and the deformation law of the pressure switch film under different temperature. The thermal stress releasing schemes are studied by changing the structure of fixed form and changing the thickness of the substrate, respectively. Finally, the design of the glass substrate thickness of 2.5 mm is used to ensure that the maximum equivalent stress is reduced to a quarter of the original value, only 154 MPa when the structure is in extreme temperature (80${}^{\circ }$C). The test results show that after the pressure switch is thermally optimized, the upper and lower electrodes can be reliably contacted to accommodate different operating temperature environments.

In this paper, we focus on the thermal characterization of nonlinear electronic circuits deriving some conditions which suggest the existence of a relationship with the specific dynamic behavior shown by the circuit. A series of thermographic experiments indicate that the chaotic behavior in electronic circuits is associated with slower thermal transients, a slow linear growth of the temperature during the normal operating regime and lower overall temperature increase with respect to other dynamical regimes. Three experimental case studies are reported and discussed, considering also the effect of chaos control strategies.

In this paper, the validity of local thermal equilibrium assumption in a tissue-like porous medium is investigated numerically, with an interstitial heat source. The study is based on comparison between two three-equation local thermal nonequilibrium (LTNE) model and one-equation local thermal equilibrium (LTE) model. The LTNE model is validated by an steady-state 1D analytical solution which is presented for first time. The presented results indicate the small temperature difference between fluid and solid phases in heat-affected region, which leads to considerable errors in prediction of tissue thermal behavior. According to records, increasing perfusion rate or intensity of heat source increases the differences between LTE and LTNE models. It is found that in a counter-current vascular tissue if the perfusion rate of blood into tissue becomes higher, the prediction error of LTE model will be more considerable. Moreover, the higher the intensity of heat source is, the greater the difference between LTE and LTNE models is. These findings could be extended to heat transfer modeling of actual tissue during various interstitial hyperthermia treatments.

To investigate the thermal behavior of complex model with amorphous region and crystallization region of cellulose II, the structures and properties of cellulose II, amorphous chain and their combined models were studied by molecular dynamics simulation. The results showed that the amorphous chain is more susceptible to temperature than the cellulose II. It can form anti-parallel structure similar to cellulose II at high temperature. In the complex model, one end of the amorphous chain is fixed to form hydrogen bonds with the cellulose II, and the other end is not. At 300K, the free part of amorphous chain is approximately perpendicular to the axial direction of the cellulose II. When the temperature increases, the free part of amorphous chain adheres to the surface of cellulose II. The free part of amorphous chain did not form hydrogen bond with the cellulose II. The formation of amorphous chain and surface of the cellulose II is a zipper process at 450K. Furthermore, water molecules penetrate into the inter-space of the amorphous and crystalline regions. The probability of hydrogen bonds between water molecules and the complex model was less than 8.21% which explains why cellulose is insoluble in water. These conclusions provide a guiding significance for the dissolution mechanism of cellulose.

The parent compound of the trithiadodecaazahexaphyrins has been prepared for the first time. Its thermal stability has been found to be the highest reported to date among the porphyrinoid family.

One of the discussed techniques in improving the performance of latent thermal energy storage applications is to use different phase change materials (PCMs) encapsulated in spherical nodules. However, the large number of spheres used in the storage applications pushes the researchers to neglecting the natural convection effect inside spheres. Consequently, they cannot observe the real thermal interaction effect between spheres. The objective of this work is to carry out a computational study on the thermal behavior of two adjacent different PCMs inside aluminum spherical capsules and taking into account the natural convection effect inside the spheres. Water is used as heat transfer fluid (HTF) at constant inlet temperature. The study shows that for the HTF inlet velocity lower than 10${}^{-5}$m/s, the thermal interaction between two adjacent different PCMs cannot be neglected. However, the thermal interaction appears more clearly in the discharging mode. The thermal interaction can accelerate the discharging of one of the PCMs by reducing the discharging of the other one.

Thermal contact resistance between sheet metal and die is the key fact of influencing parameters in thermal and physical properties of the heat transfer in hot stamping process. Based on the cooling curves of blank and flat die obtained by experiment, the inverse heat conduct problem is solved by using sequential function method (SFM) and the thermal contact resistance is calculated.

The aim of this work was to investigate the thermal behavior and microstructure of polymeric methylene diphenyldiisocyanate (PMDI) based and toluene diisocynate (TDI) based flexible polyurethane (PU) foams. The PMDI-based PU foams had been synthetized by optimizing the process parameters using orthogonal experimental method. Furthermore, specific group in the molecules, microstructure, glass transition temperature and thermal degradation of the prepared samples were characterized by means of attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravity analysis (TGA), respectively. The results indicate the polyol is partially unreacted and the isocyanate completely participates in the reaction. In addition, PMDI-based PU foam presents a more uniform structure and smaller mean pore size compared to TDI-based PU foam. Furthermore, the thermal stability of PMDI-based PU foam is higher than that of TDI-based PU foam.