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1.
Neogi A. Everitt H. Morkoc H. Kuroda T. Tackeuchi A. 《Nanotechnology, IEEE Transactions on》2003,2(1):10-14
Self-assembled GaN quantum dots (QDs), grown on AlN by molecular beam epitaxy, were investigated by time-resolved photoluminescence spectroscopy. We investigate the emission mechanism in GaN QDs by comparing the carrier recombination dynamics in single and multiple period QDs. At 100 K, the PL decay time in single period QD structures is considerably shorter than in stacked QDs. Compared to single period QDs, the room temperature PL efficiency is considerably enhanced in 20 period QDs due to the reduction in nonradiative recombination processes. 相似文献
2.
Mathematical models for chemical reaction and mass transfer occurring in the manufacture of high-viscosity condensation polymers are considered. A preliminary study indicates that several diverse models can be represented using a single formula based upon an effectiveness factor. The effectiveness factor is shown to depend upon a ratio of time scales of mixing and reaction. The formula giving the effectiveness factor in terms of the time scales ratio is shown to depend upon mixing assumptions only. Starting with a mixing-cell model, a new modeling framework is developed and shown to include the previous models as special cases. The framework is free of inherent mixing assumptions and can be applied to a wide variety of situations once the mixing characteristics are specified. © 1993 John Wiley & Sons, Inc. 相似文献
3.
Easy-to-use audio/video authoring tools play a crucial role in moving multimedia software from research curiosity to mainstream
applications. However, research in multimedia authoring systems has rarely been documented in the literature. This paper describes
the design and implementation of an interactive video authoring system called Zodiac, which employs an innovative edit history abstraction to support several unique editing features not found in existing commercial
and research video editing systems. Zodiac provides users a conceptually clean and semantically powerful branching history model of edit operations to organize the authoring process, and to navigate among versions of authored documents. In addition,
by analyzing the edit history, Zodiac is able to reliably detect a composed video stream's shot and scene boundaries, which facilitates interactive video browsing.
Zodiac also features a video object annotation capability that allows users to associate annotations to moving objects in a video sequence. The annotations themselves could
be text, image, audio, or video. Zodiac is built on top of MMFS, a file system specifically designed for interactive multimedia development environments, and implements an internal buffer
manager that supports transparent lossless compression/decompression. Shot/scene detection, video object annotation, and buffer
management all exploit the edit history information for performance optimization. 相似文献
4.
Ziegler-Nichols tuned PI and PID controllers are usually found to provide poor performances for high-order and nonlinear systems. In this study, an improved auto-tuning scheme is presented for Ziegler-Nichols tuned PI controllers (ZNPICs). With a view to improving the transient response, the proportional and integral gains of the proposed controller are continuously modified based on the current process trend. The proposed controller is tested for a number of high-order linear and nonlinear dead-time processes under both set-point change and load disturbance. It exhibits significantly improved performance compared to ZNPIC, and Refined Ziegler-Nichols tuned PI controller (RZNPIC). Robustness of the proposed scheme is established by varying the controller parameters as well as the dead-time of the process under control. 相似文献
5.
To increase the unit area illumination of solar ray on PV panel, it is required to track the sun throughout the day. So to reach the goal various type of sun tracking mechanism is already developed but in this paper we designed two different types of sun tracking mechanism: single axis and dual axis tracking using programmable logic controller (PLC) as it has numbers of unique advantages like??it is faster, reliable, requires less maintenance and reprogrammable. A comparative study between those two systems is also presented in this paper. The whole system has been designed and tested using GE, FANUC PLC. 相似文献
6.
7.
P. Neogi 《Chemical engineering science》2010,65(2):708-712
The relation between the dynamic contact angle and the capillary number is explored by extending de Gennes’ model where viscous dissipation is equated to the surface work. A cutoff is used to eliminate the contact line singularity. The aim has been to increase the applicability of existing results to include higher contact angles. The flow near the contact line is assumed to be in the creeping flow regime. The results uphold Voinov–Hoffman–Tanner rule at small contact angles but only in the liquid–air system and not in the liquid–liquid system. The more prevalent liquid–air system shows a fold at a dynamic contact angle of 180°. This indicates that at 180° the system jumps out of the dynamic contact line arrangement to an entrained system that has no contact line. Liquid–liquid systems have folds at much lower contact angles. Comparisons with experiments show very good agreement up to contact angles of 120° but the comparisons show only qualitative agreement at large contact angles. Possible explanations have been provided for the latter. 相似文献
8.
G. Balakrishnan P. Kuppusami S. Murugesan Chanchal Ghosh Divakar Ramachandran E. Mohandas D. Sastikumar 《Transactions of the Indian Institute of Metals》2011,64(3):297-299
Multilayers of CeO2/ZrO2 thin films were deposited on Si (100) substrates using pulsed laser deposition at an optimized oxygen partial pressure of
3×10−2 mbar and at room temperature. The CeO2 layer thickness was 10 nm, while the ZrO2 layer thickness was varied as 10, 20 and 30 nm. CeO2 and ZrO2 layers were deposited alternately to obtain 25 bilayers. High temperature x-ray diffraction (HTXRD) results showed that the
multilayer films had cubic ceria and tetragonal ZrO2. Thermal expansion coefficients were calculated for CeO2 and t-ZrO2 and found to increase with the decrease of ZrO2 layer thickness. The cross sectional transmission electron microscopy (XTEM) of CeO2/ZrO2 multilayer also indicated that ceria was found to be in cubic phase while zirconia contained predominantly tetragonal phase
along with cubic phase in thermally annealed specimen. 相似文献
9.
Hydrogeochemistry,Elemental Flux,and Quality Assessment of Mine Water in the Pootkee-Balihari Mining Area,Jharia Coalfield,India 总被引:3,自引:0,他引:3
Abhay?Kumar?SinghEmail author Mukesh?K.?Mahato Babita?Neogi G.?C.?Mondal T.?B.?Singh 《Mine Water and the Environment》2011,30(3):197-207
Ninety nine mine water discharge samples were collected and analyzed for pH, electrical conductivity (EC), major cations,
anions, and trace metals in the Pootkee-Balihari coal mining area of the Jharia coalfield. The mines of the area annually
discharge 34.80 × 106 m3 of mine water and 39,099 t of solute loads. The pH of the analyzed mine waters ranged from 6.97 to 8.62. EC values ranged
from 711 μS cm−1 to 1862 μS cm−1, and reflect variations in lithology, geochemical processes, and hydrological regimes in the mines. The cation and anion
chemistry indicate the general ionic abundance as: Mg2+ > Ca2+ > Na+ > K+ and HCO3
− > SO4
2− > Cl− > NO3
− > F−, respectively. Elevated SO4
2− concentrations in the Gopalichuck, Kendwadih, and Kachhi-Balihari mine waters are attributed to pyrite weathering. The water
quality assessment indicated that TDS, hardness, Mg2+, and SO4
2− are the major parameters of concern in the study area. Except for Fe, all of the measured metals in the mine water were well
within the levels recommended for drinking water. With only a few exceptions, the mine water is of good to permissible quality
and suitable for irrigation. 相似文献
10.
The sliding wear of isotactic polypropylene (PP), polyethylene terephthalate (PET) and their blends was evaluated as a function
of applied pressure and composition against a stainless steel counter face in dry condition. Wear rate decreases with the
addition of PET in the blend. The wear was observed in two stages, the moderate wear and high wear while increasing the applied
pressure on test samples. The addition of PET in PP helps in increasing the limit of moderate wear towards the high-pressure
side. Microstructure and worn surfaces of samples were observed by scanning electron microscope. The wear phenomenon has been
discussed based on wear losses and worn surfaces. 相似文献