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1.
Sintering and grain growth of nano-crystalline undoped ZnO has been studied in detail over a wide range of temperature and holding time. Below 800 °C, sintering of over 70% theoretical density is not observed, irrespective of particle size. At 900 °C for 6 h, the nano-crystalline sample sinters to 99% of theoretical density whereas the density for as received sample is 93% of theoretical density. However, at 1300 °C or higher, the densification is found to be much faster and after a few hours becomes independent of holding time. Grain growth studies reveal a similar feature of attaining saturation over holding time. The average saturated grain size is found to be ∼1.5 and ∼2.2 μm at 800 and 900 °C, respectively, while at 1300 °C or higher, it is in between 12 and 13 μm. 相似文献
2.
A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional
conductor. The negative differential resistance region appears afterV
m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms
of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals. 相似文献
3.
Using the symmetry reduction approach we have herein examined, under continuous groups of transformations, the invariance of Einstein exterior equations for stationary axisymmetric and rotating case, in conventional and nonconventional forms, that is a coupled system of nonlinear partial differential equations of second order. More specifically, the said technique yields the invariant transformation that reduces the given system of partial differential equations to a system of nonlinear ordinary differential equations (nlodes) which, in the case of conventional form, is reduced to a single nlode of second order. The first integral of the resulting nlode has been obtained via invariant-variational principle and Noether’s theorem and involves an integration constant. Depending upon the choice of the arbitrary constant two different forms of the exact solutions are indicated. The generalized forms of Weyl and Schwarzschild solutions for the case of no spin have also been deduced as particular cases. Investigation of nonconventional form of Einstein exterior equations has not only led to the recovery of solutions obtained through conventional form but it also yields physically important asymptotically flat solutions. In a particular case, a single third order nlode has been derived which evidently opens up the possibility of finding many further interesting solutions of the exterior field equations. 相似文献
4.
Face to virtual face 总被引:1,自引:0,他引:1
Thalmann N.M. Kalra P. Escher M. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1998,86(5):870-883
The first virtual humans appeared in the early 1980s in such films as Dreamflight (1982) and The Juggler (1982). Pioneering work in the ensuing period focused on realistic appearance in the simulation of virtual humans. In the 1990s, the emphasis has shifted to real-time animation and interaction in virtual worlds. Virtual humans have begun to inhabit virtual worlds and so have we. To prepare our place in the virtual world we first develop techniques for the automatic representation of a human face capable of being animated in real time using both video and audio input. The objective is for one's representative to look, talk, and behave like oneself in the virtual world. Furthermore, the virtual inhabitants of this world should be able to see our avatars and to react to what we say and to the emotions we convey. We sketch an overview of the problems related to the analysis and synthesis of face-to-virtual-face communication in a virtual world. We describe different components of our system for real-time interaction and communication between a cloned face representing a real person and an autonomous virtual face. It provides an insight into the various problems and gives particular solutions adopted in reconstructing a virtual clone capable of reproducing the shape and movements of the real person's face. It includes the analysis of the facial expression and speech of the cloned face, which can be used to elicit a response from the autonomous virtual human with both verbal and nonverbal facial movements synchronized with the audio voice 相似文献
5.
K. Chatty T. P. Chow R. J. Gutmann E. Arnold D. Alok 《Journal of Electronic Materials》2002,31(5):356-360
Hall measurements have been used to compare the properties of 4H-SiC inversion-mode MOSFETs with “wet” and “dry” gate oxides.
While the field-effect mobilities were approximately 3–5 cm2/Vs, the Hall mobilities in 4H-SiC MOSFETs in the wet and dry oxide samples were approximately 70–80 cm2/Vs. The dry-oxidized metal oxide semiconductor field effect transistors (MOSFETs) had a higher transconductance, improved
threshold voltage, improved subthreshold slope, and a higher inversion carrier concentration compared to the wet-oxidized
MOSFETs. The difference in characteristics between the wet- and the dry-oxidized MOSFETs is attributed to the larger fixed
oxide charge in the dry oxide sample and a higher interface trap density in the wet oxide sample. 相似文献
6.
Distributed active storage architectures are designed to offload user-level processing to the peripheral from the host servers.
In this paper, we report preliminary investigation on performance and fault recovery designs, as impacted by emerging storage
interconnect protocols and state-of-the-art storage devices. Empirical results obtained using validated device-level and interconnect
data demonstrate the significance of the said parameters on the overall system performance and reliability. 相似文献
7.
Das Abhishek Ozdemir Serkan Memik Gokhan Zambreno Joseph Choudhary Alok 《Computer Architecture Letters》2008,7(1):5-8
As transistor feature sizes continue to shrink intothe sub-90nm range and beyond, the effects of process variationson critical path delay and chip yields have amplified. A commonconcept to remedy the effects of variation is speed-binning, bywhich chips from a single batch are rated by a discrete range offrequencies and sold at different prices. In this paper, we discussstrategies to modify the number of chips in different bins andhence enhance the profits obtained from them. Particularly, wepropose a scheme that introduces a small Substitute Cacheassociated with each cache way to replicate the data elementsthat will be stored in the high latency lines. Assuming a fixedpricing model, this method increases the revenue by as much as13.8% without any impact on the performance of the chips. 相似文献
8.
Alok Kumar Rastogi A. K. Tiwari R. P. Shrivastava 《Journal of Infrared, Millimeter and Terahertz Waves》1993,14(7):1445-1453
The dielectric optical wave guide is finding growing attention at millimeter wave frequencies. However the dielectric optical waveguide radiates at bends and thus transmission loss increases. These radiations are in the outword direction of bends. This output radiation at output bends arises due to change in phase velocities of the propagating wave at the centre of the dielectric guide and the phase velocity at the outer surface of the dielectric guide. A unique methiod is suggested to avoid these radiation losses.Experimental results are also shown at microwave frequencies. 相似文献
9.
Prem Kalra Angelo Mangili Nadia Magnenat Thalmann Daniel Thalmann 《Computer Graphics Forum》1992,11(3):59-69
This paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression. 相似文献
10.
Characteristics of 4H-SiC Schottky barrier diodes with breakdown voltages up to 1000 V are reported for the first time. The diodes showed excellent forward I-V characteristics, with a forward voltage drop of 1.06 V at an on-state current density of 100 A/cm2. The specific on-resistance for these diodes was found to be low (2×10 -3 Ω-cm2 at room temperature) and showed a T 1.6 variation with temperature. Titanium Schottky barrier height was determined to be 0.99 eV independent of the temperature. The breakdown voltage of the diodes was found to decrease with temperature 相似文献