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81.
The dielectric behavior of sol-gel derived Ba0.80Sr0.20(ZrxTi1−x)O3 (0.0 ≤ x ≤ 0.50) thin films is studied. A relaxor behavior is observed for x ≥ 0.35. The degree of relaxation increases with Zr content. The frequency dependence of the polar regions follows Vogel-Fulcher relation with a characteristic cooperative freezing at freezing temperature (Tf). Below Tf, a long range polarization ordering is likely to take place. The plausible mechanism of the relaxor behavior of BSZT thin films with Zr contents ≥ 0.35 has been proposed based on the measured temperature as well as frequency dependent dielectric data. The solid solution system is visualized as a mixture of Ti+ 4 rich polar regions and Zr+ 4 rich regions; with the increase in Zr content the volume fraction of the polar regions is progressively reduced. At and above 35.0 at.% Zr substitution the polar regions exhibit typical relaxor behavior. 相似文献
82.
This study assessed the discriminative stimulus effects of (±)-ephedrine and its stereoisomers in pigeons discriminating 1.0 mg/kg of amphetamine from saline. Amphetamine, (±)-, (-)-, and (+)-ephedrine, and cocaine occasioned greater than 80% drug-key responding with the following rank order of potency: amphetamine > cocaine > (-)-ephedrine ≥ (±)-ephedrine ≥ (+)-ephedrine. Neither the α-adrenergic antagonist, phentolamine, nor the β-adrenergic antagonist, propranolol, antagonized the effects of amphetamine or (±)-ephedrine. In contrast, the dopamine receptor antagonist, haloperidol, antagonized the discriminative stimulus effects of amphetamine and (±)-ephedrine as well as those of (-)- and (+)-ephedrine. These results indicate that, like cocaine, (±)-ephedrine and its stereoisomers share discriminative stimulus effects with amphetamine. Moreover, these effects appear to be the result of increased activity in dopaminergic systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
83.
根据锆钛酸铅压电陶瓷的逆压电效应。设计了以8031单片机为核心的压电陶瓷堆微位移器提高了PZT的线性,从而满足了在天文自适应系统中所要求的精确微位的应用。 相似文献
84.
John Hemp 《Flow Measurement and Instrumentation》1994,5(4):247-253
In this paper a fuller and clear derivation of the weight vector theory of Coriolis mass flowmeters is given indicating its potential for the prediction of velocity profile effects in both the traditional kind of meter (vibrating tube) and the compact kind (vibrating element inside a duct). 相似文献
85.
The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk1) and release (σk2) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr2O3) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 105 Pa. 相似文献
86.
Using the gaze-contingent boundary paradigm with the boundary placed after word n, the experiment manipulated preview of word n + 2 for fixations on word n. There was no preview benefit for 1st-pass reading on word n + 2, replicating the results of K. Rayner, B. J. Juhasz, and S. J. Brown (2007), but there was a preview benefit on the 3-letter word n + 1, that is, after the boundary but before word n + 2. Additionally, both word n + 1 and word n + 2 exhibited parafoveal-on-foveal effects on word n. Thus, during a fixation on word n and given a short word n + 1, some information is extracted from word n + 2, supporting the hypothesis of distributed processing in the perceptual span. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
88.
We have made a study of the chemical composition, the electrical, the optical and the structural properties of polycrystalline CuInS2 thin films prepared by spray pyrolysis to be used for thin film solar cells. These films were deposited starting from aqueous solutions with different chemical compositions ([Cu]/[In] and [S]/[Cu] ratios) and at different substrate temperatures. In all cases, the material is p-type with grains preferentially oriented in the (112) direction of the sphalerite structure. The electro-optical properties show a very strong dependence on the [Cu]/[In] ratio in the solution. Films with copper excess have smaller resistivity and better crystallinity than those which are stoichiometric or have indium excess. The results obtained in this work show the possibility of having CuInS2 thin films with a wide range of resistivity, a fact that could be important for making solar cells based on this material. 相似文献
89.
Thomachan.A. Kattakayam Sumanta Khan Kandadai Srinivasan 《Solar Energy Materials & Solar Cells》1996,44(1):25
This article describes the development of an instrumentation system for characterizing photovoltaic panels. It uses an add on card (which contains DAC, ADC and digital input/output ports) in conjunction with a PC-AT. The panels in a field are selected in succession through a set of relays actuated by the digital output port. The selected panel is loaded in discreet steps by a transistor loading circuit which is activated by the digital to analog convertor to trace the most significant portion of the I-V curve. The data shows that the power output is invariably lower than that specified by the manufacturer. The reasons for drop in output have been analyzed. It is shown that these effects can be represented by the curvature of I-V characteristic at the maximum power point (OP). The loss of power due to accumulation of dust and the increase in temperature of the panels can be significant. 相似文献
90.
Fatigue at high temperature is a complex phenomenon as it is influenced by a number of time-dependent processes which become
important at elevated temperatures. These processes include creep, oxidation, phase instabilities and dynamic strain ageing
(DSA), acting either independently or synergistically influence fatigue behaviour, often lowering the fatigue life. Current
design approaches employ linear summation of fatigue and creep damage with suitable factors on permissible damage to take
care of uncertainties in interaction between cyclic and time-dependent processes. It is, therefore, important to develop a
deeper understanding of the processes that occur during high temperature fatigue so that realistic life predictions could
be made.
Results on the high temperature fatigue behaviour of austenitic stainless steels, ferritic steels and nickel base alloys are
presented here. The important mechanisms of interaction of high temperature time-dependent processes with fatigue under various
conditions are discussed in detail. Emphasis is placed on cyclic stress response, fatigue life, deformation substructure and
fracture behaviour. This is followed by a review of important life prediction techniques under combined creep-fatigue loading
conditions. Life prediction techniques considered here include linear damage summation, strain range partitioning, ductility
exhaustion approach, frequency modified and frequency separation methods, techniques based on hysteresis energy and damage
rate models, and methods based on crack-cavitation interation models. 相似文献