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41.
Over the past five years, practicum experience has received increased attention as an important element in the sequence of training. Questions have arisen about the number of hours being counted and the activities occurring in practicum. This study examined the number of practicum hours accrued by comparing the actual number of direct service hours and total hours to an estimated length of time to complete those hours. Based on self-reports, it was estimated that graduate students spend between 2 and 7 years to accrue their practicum hours with 37.5 to 69.6% of that time in direct service. Implications for the profession, faculty, and students are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Driven by the continuing Moore’s Law evolution in chip technology, power dissipation of nanoelectronics chips could exceed 300W, with heat fluxes above 150W/cm2, within the next few years, along with localized, sub-millimeter zones with heat fluxes in excess of 1kW/cm2. New and novel cooling techniques, with the ability to selectively cool sub-millimeter “sun spots” while providing effective global cooling for high heat flux chips are needed. Several promising approaches, including the application of miniaturized silicon and BiTe thermoelectric coolers and direct cooling with dielectric liquids through thin film evaporation, will be described. 相似文献
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Haika Moshe‐Drezner Doron Shilo Avraham Dorogoy Emil Zolotoyabko 《Advanced functional materials》2010,20(16):2723-2728
In this study, a newly developed nanoscale modulus mapping is applied in order to visualize the 2D‐distribution of mechanical characteristics in the aragonitic nacre layer of Perna canaliculus (green mussel) shells. Modulus maps provide lateral resolution of about 10 nm. They allow the aragonitic mineral (CaCO3) tablets and the interfaces between them to be clearly resolved, which are filled by an organic substance (mainly beta‐chitin). The experimental data are compared with finite element simulations that also take into account the tip radius of curvature and the thickness of organic layers, as measured by means of scanning electron microscopy with back‐scattered electrons. Based on this comparison, the Young modulus of beta‐chitin is extracted. The obtained number, Eβ = 40 GPa, is higher than previously evaluated. The collected maps reveal that the elastic modules in the nacre layer change gradually across the ceramic/organic interfaces within a spatial range four times wider than the thickness of the organic layers. This is possibly due to inhomogeneous distribution of organic macromolecules within ceramic tablets. According to the data, the concentration of macromolecules gradually increases when approaching the organic/ceramic interfaces. A behavior of this type is unique to biogenic materials and distinguishes them from synthetic composite materials. Finally, three possible mechanisms that attempt to explain why gradual changes of elastic modules significantly enhance the overall resistance to fracture of the nacre layer are briefly discussed. The experimental findings support the idea that individual ceramic tablets, comprising the nacre, are built of the compositionally and functionally graded ceramic material. This sheds additional light on the origin of the superior mechanical properties of biogenic composites. 相似文献
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Emil‐Alexandru Brujan 《Polymer Engineering and Science》2009,49(3):419-431
Cavitation phenomena play important roles in many areas of science and engineering. The most interesting effect of the non‐Newtonian properties of the liquid is the reduction of cavitation damage and noise. This article reviews experimental and theoretical efforts to understand such phenomena. Two major areas of research are described, namely the dynamics of cavitation bubbles oscillating in a liquid of infinite extent, and the behavior of bubbles collapsing near rigid walls. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
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Herring (Clupea harengus) captured during the heavy feeding spring season were examined by magnetic resonance imaging (MRI) analysis. MRI was performed at room temperature on the frozen-thawed herring for approximately 50 h. The results showed that the stomachs were filled with prey and that they were very resistant to degradation. The ventral muscle, on the other hand, together with the upper part of the intestine (as confirmed during collection of samples on board fishing vessels), seemed to be the most sensible structures where the autolysis commenced and extended to the rest of the abdominal cavity. 相似文献
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