Study on Turbulence Intensity Behavior under a Large Range of Temperature Variation

The turbulence intensity (TI) is defined as the ratio of fluctuation from the standard deviation of wind velocity to the mean value. Many studies have been performedon TI for flow dynamics and adapted various field such as aerodynamics, jets, wind turbines, wind tunnel apparatuses, heat transfer, safety estimation of construction, etc.The TI represents an important parameter for determining the intensity of velocity variation and flow quality in industrial fluid mechanics. In this paper, computational fluid dynamic (CFD) simulation of TI alteration with increasing temperature has been performed using the finite volume method. A high-temperature—maximum 300 degrees Celsius (°C)—wind tunnel test rig has been used as theapparatus, and velocity was measured by an I-type hot-wire anemometer. The velocity and TI of the core test section were operated at several degrees of inlet temperatures at anair velocity of 20 m/s. The magnitude of TI has a relationship with boundary layer development. The TI increased as temperature increased due to turbulence created by the non-uniformities.

Влияние примеси бора на излучательные свойства дислокационных структур в кремнии, сформированных путем имплантации ионов Si-=SUP=-+-=/SUP=-

The effect of boron implantation on the light-emitting properties of dislocation structures formed in silicon by Si^+ ion implantation with subsequent annealing is studied. It is shown that the implantation of B^+ ions has a significant effect on the dislocation-related luminescence intensity, spectrum and the temperature dependence of the D1-band intensity. It is found that the temperature dependence is nonmonotonous and involves two regions, in which the D1-band intensity increases with increasing temperature and has two well-pronounced maxima at 20 K and 60–70 K. The maximum at 20 K is associated with the morphological features of the dislocation structure under study, whereas the maximum at 60–70 K is associated with the additional implantation of the boron impurity into the dislocation region of the samples. It is established that the intensities of the experimentally observed maxima and the position of the high-temperature maximum depend on the implanted boron concentration.

Peculiar properties of phase transitions in Na0.5Bi0.5TiO3−0.06BaTiO3 lead-free relaxor ferroelectrics seen via acoustic emission

Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3 relaxor ferroelectrics (RFEs) ceramic samples were investigated by means of dielectric and acoustic emission methods in the temperature range of 70–350[Formula: see text]C and in dependence on frequency. Dielectric curve exhibits two anomalies: strongly dispersive the local maximum, within 130–180[Formula: see text]C and slightly dispersive the smeared high-temperature maximum within 300–310[Formula: see text]C. Acoustic emission exhibits the five groups of bursts: near 123[Formula: see text]C, 150–180[Formula: see text]C, near 225[Formula: see text]C, 300–310[Formula: see text]C and 327[Formula: see text]C. The first and third groups of acoustic emission bursts correspond to phase transitions of R[Formula: see text]c-P[Formula: see text]bm phases coexisting in this temperature, range, while the fourth and fifth groups of acoustic emission bursts correspond to P[Formula: see text]bm-P[Formula: see text] /mbm-Pm[Formula: see text] m phase transitions. The second group of acoustic emission bursts corresponds to strongly dispersive local maximum at which no phase transition has been proved in Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3. The existence and the location of the intermediate temperature, [Formula: see text], in Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3 compound are discussed.

EVALUATION OF THERMOSTABILITIES OF ENZYMES, MEDIATORS AND IMMOBILIZING MEMBRANES FOR ENZYME SENSORS

The stability of the constituents of electrochemical measurement, electron mediators, enzymes and enzyme-immobilizing membranes was evaluated under high temperature (maximum 75°C) by electrochemical analysis, UV-Vis spectrometry (UV-Vis) and UV circular dichroism (CD). As a result of stability evaluation of mediators at 75°C, electrochemical activity of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt (ABTS), potassium ferricyanide ( K 3[ Fe ( CN )6]) and ferrocenemethanol ( FcOH ) were not changed, but 2,6-dichloroindophenol ( DCIP ), p-benzoquinone ( p - BQ ), vitaminK3 ( VK 3) were greatly decreased. The stability of diaphorase from Bacillus stearothermophilus (DI) were compared between in-solution and in several types of membranes, Agarose H , Poly-L-lysine ( PLL ) and poly-ion-complex (PIC) by electrochemical analysis. In solution, activity and secondary structure of DI were changed at 65°C or higher. This tendency of activity was not much different in Agarose H but in PLL , the activity was almost kept until 70°C. It was suggested that DI was fixed on the electrodes in high concentration and the elimination of DI seldom arise in PLL from the magnitude of the current response and the results of prolonged stability evaluation.

Thermoelectric Properties of Co1-xNbxSb3 Prepared by Induction Melting

Induction melting was attempted to prepare the undoped and Nb-doped CoSb3 compounds, and their thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by induction melting and subsequent annealing at 400°C for 2 hours in vacuum. The positive signs of Seebeck coefficients for all the specimens revealed that Nb atoms acted as p-type dopants by substituting Co atoms. Electrical conductivity decreased and then increased withincreasing temperature, indicating mixed behaviors of metallic and semiconducting conductions. Electrical conductivity increased by Nb doping, and it was saturated at high temperature. Maximum value of the thermoelectric power factor was shifted to higher temperature with the increasing amount of Nb doping, mainly originated from the Seebeck coefficient variation.

Thermoelectric Properties of Co1-xNbxSb3 Prepared by Induction Melting

Induction melting was attempted to prepare the undoped and Nb-doped CoSb3 compounds, and their thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by induction melting and subsequent annealing at 400°C for 2 hours in vacuum. The positive signs of Seebeck coefficients for all the specimens revealed that Nb atoms acted as p-type dopants by substituting Co atoms. Electrical conductivity decreased and then increased with increasing temperature, indicating mixed behaviors of metallic and semiconducting conductions. Electrical conductivity increased by Nb doping, and it was saturated at high temperature. Maximum value of the thermoelectric power factor was shifted to higher temperature with the increasing amount of Nb doping, mainly originated from the Seebeck coefficient variation.

Trap Spectroscopy in Si3N4 Ultrathin Films Using Exoelectron Emission Method

ABSTRACTWe developed an original thermally stimulated exoelectron emission spectroscopy method (TSEE) of measurements of the activation energy Φ of electron (hole) traps in ultrathin Si3N4 films. The temperature spectra of TSEE of 50A silicon nitride films demonstrate several peaks: three low temperature peaks (T1 =373K, T2=423K, T3=498K) and a high temperature maximum at T4 ∼750K. The obtained values of the energy activation are Φ1=0.82 eV, Φ2=0.93 eV, Φ3=1.09 eV, and Φ4=1.73 eV. TSEE results are shown to be consistent with Φ estimates obtained from microFLASH® two bit per cell memory transistor measurements. Electrons stored at traps with Φ4=1.73 eV explain excellent microFlash retention properties. We believe that deep traps in Silicon Nitride are Hydrogen containing centers, while Hydrogen hopping is the route cause of observed material degradation in course of TSEE measurements.

Effects of Short Periods of Drought and High Temperature on Grain Growth and Starch Accumulation of Two Malting Barley Cultivars

Short periods (3-5 days) of high maximum temperature (>35�C), often accompanied by drought, commonly occur during grain filling of cereals. Short periods of high temperature have been shown to reduce grain weight and baking quality in wheat, but little is known about their effects on barley. Consequently, we examined the effects of high temperature and drought, alone or combined, on grain growth for two barley cultivars, Schooner and Franklin. Treatments started 15 days after anthesis and consisted of the factorial combination of three temperatures and three water regimes. The high temperature (maximum 40�C for 6 h day-1) and drought treatments were maintained for 5 or 10 days. Drought reduced individual grain weight much more (ca 20%) than high temperature (ca 5%) for both cultivars. Franklin appeared to be more sensitive to heat stress than Schooner. The reduction in individual grain weight was greatest when both stresses were combimed (ca 30%). The reduction in mature grain weight under high temperature was due to a reduction in duration of grain growth for Schooner and to a reduction in both rate and duration of grain growth for Franklin (8-12%). The reduction in duration of grain growth was the most important cause of reduced grain weight at maturity under drought alone (12-25%) or combined with high temperature (25-33%). Nitrogen content per grain was quite high and similar for all treatments, and nitrogen percentage increased when stress was severe enough to reduce starch accumulation, confirming that starch accumulation is more sensitive to post- anthesis stress than nitrogen accumulation. We conclude that drought, particularly when combined with high temperature, is more likely than heat stress to cause large reductions in grain weight of barley under field conditions.

Temperature and Frequency Dependence of the Dynamic Deformation and Losses of Elastomers

The results of this investigation of the temperature and frequency dependence of the deformation and mechanical loss of elastomeric network polymers in the temperature range from −90 to +120° C may be understood on the basis of the conceptions of three types of relaxation processes in these materials: orientation of the units of the chain molecules, overcoming of the secondary crosslinks (entanglements) in the movement of the segments, and the process of destruction of the polysulfide bonds, which comprise quite a small part of the total number of the chemical crosslinks. The first process is connected with the glass-transition and leads to the occurrence of a low-temperature maximum of mechanical losses, while the third leads to a high-temperature maximum. The first and third relaxation processes are apparently characterized by narrow spectra of relaxation times, which may be substituted for approximately by the corresponding averaged relaxation times. For the second process the spectrum of relaxation times is probably very wide and it is not possible to make the analogous substitution; this also explains the absence of a third mechanical loss maximum and the occurrence of a well marked frequency dependence of the deformation amplitude in the high-elastic range. The models of a network polymer considered for low and high temperatures give a qualitative description of all the main mechanical properties of these materials.