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51.
ABSTRACTThe RF output power dissipated per unit area is calculated using Runge-Kutta method for the high-moderate-moderate-high (n+-n-p-p+) doping profile of double drift region (DDR)-based impact avalanche transit time (IMPATT) diode by taking different substrate at Ka band. Those substrates are silicon, gallium arsenide, germanium, wurtzite gallium nitride, indium phosphide and 4H-silicon carbide. A comparative study regarding power dissipation ability by the IMPATT using different material is being presented thereby modelling the DDR IMPATT diode in a one-dimensional structure. The IMPATT based on 4H-SiC element has highest power density in the order of 1010 Wm?2 and the Si-based counterpart has lowest power density of order 106 Wm?2 throughout the Ka band. So, 4H-SiC-based IMPATT should be preferable over others for the power density preference based application. This result will be helpful to estimate the power density of the IMPATT for any doping profile and to select the proper element for the optimum design of the IMPATT as far as power density is concerned in the Ka band. Also, we have focused on variation of power density with different junction temperatures and modelled the heat sink with analysis of thermal resistances. 相似文献
52.
Dana S.K. Sengupta D.C. Hu C.-K. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(10):1031-1034
This brief reports spiking and bursting in numerical simulations of the resistive-capacitive-inductive shunted Josephson junction model. Regular spiking, intrinsic bursting, and fast spiking, which are usually seen in the mammalian neocortex, are observed in the junction dynamics under external dc bias. The junction voltage is amplitude and frequency modulated when forced by weaker sinusoidal forcing of frequency much lower than the junction resonant frequency. For stronger forcing, bursting is observed. The autonomous junction also shows bursting in the high inductive regime. Bifurcation scenarios of bursting are discussed for both autonomous and nonautonomous cases 相似文献
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54.
The aim of the present paper is to study the effect of gravity on visco-elastic surface waves in solids. The wave velocity
equations are deduced from Biot’s theory of initial stress on the assumption that gravity creates a type of initial stress
— hydrostatic in nature. Resulting equations are used to investigate surface waves of the Rayleigh, Love and Stoneley types.
Results are in good agreement with corresponding classical results when gravity and viscosity are neglected. 相似文献
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In this work, one step process of synthesis of silver nanoparticles (Agnp) embedded in insitu formed calcium alginate (CA) beads is stated. CA, formed from the reaction between sodium alginate and calcium hydroxide, acts as reducing and stabilizing agent as well as support for nanoparticles. The reaction mechanism for the formation and stabilization of Agnp is proposed where the vicinal dihydroxy groups of alginate are assumed to act as the reducing agent for Ag+ to Ag°. Transmission electron microscopy (TEM), x‐ray diffraction (XRD), UV‐vis spectroscopy, field emission scanning electron microscopy (FESEM), and atomic absorption spectroscopy (AAS) were used to characterize the Agnp. The formation of spherical nanoparticles with average size range of 4‐5 nm was confirmed by TEM. Catalytic activity of this nano silver‐calcium alginate (Agnp‐CA) composite was evaluated in the reduction of p‐nitrophenol. Concentrations of sodium alginate, calcium hydroxide, and AgNO3 are found to be the parameters that critically affect the synthesis of Agnp. The efficacy of the catalyst is expressed on the basis of suitable reaction parameters. Both pseudo‐homogeneous and heterogeneous kinetic models are proposed for the reaction to find the best model and the Eley‐Riedel model is found to fit well with the experimental data. The novelty of this work is that the tandem process of CA bead formation, Agnp formation, and Agnp entrapment in CA have been transformed into a single‐step process. Moreover, elaborations of each step of the ionic mechanisms of Agnp formation and p‐NP reduction with Agnp and the establishment of a heterogeneous kinetic model for the reaction are reported for the first time here. 相似文献
58.
Subir Kr. Bhandari Siddhartha Mandal Santanu Pradhan Biswajit Ghosh 《Sequential Analysis》2013,32(3):394-405
Abstract In this article on sequential adaptive testing, we have studied the optimal allocation between two populations for testing a composite hypothesis involving the parameters, with the goal of decreasing allocation of one of the treatments to the order of the logarithm of the sample size while decreasing the probability of incorrect selection to zero. We have proved the result for large sample sizes both mathematically and by simulation studies. 相似文献
59.
Rumi Khandelia Amit Jaiswal Siddhartha Sankar Ghosh Arun Chattopadhyay 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(20):3494-3505
The fabrication of a versatile nanocarrier based on agglomerated structures of gold nanoparticle (Au NP)–lysozyme (Lyz) in aqueous medium is reported. The carriers exhibit efficient loading capacities for both hydrophilic (doxorubicin) and hydrophobic (pyrene) molecules. The nanocarriers are finally coated with an albumin layer to render them stable and also facilitate their uptake by cancer cells. The interaction between agglomerated structures and the payloads is non‐covalent. Cell viability assay in vitro showed that the nanocarriers by themselves are non‐cytotoxic, whereas the doxorubicin‐loaded ones are cytotoxic, with efficiencies higher than that of the free drug. Transmission electron microscopy and fluorescence microscopy along with flow cytometry analysis confirm the uptake of the drug‐loaded nanocarriers by a human cervical cancer HeLa cell line. Field‐emission scanning electron microscopy reveals the formation of apoptotic bodies leading to cell death, confirming the release of the payloads from the nanocarriers into the cell. Overall, the findings suggest the fabrication of novel Au NP–protein agglomerate‐based nanocarriers with efficient drug‐loading and ‐releasing capabilities, enabling them to act as multimodal drug‐delivery vehicles. 相似文献
60.
For many students, sustainability has become an obligatory add-on for any project. Here Ulysses Sengupta and Deljana Iossifova explain how they have sought to address this in their teaching at the University of Nottingham through a ‘systemic diagramming’ approach. This provides essential tools for understanding how resource flows and environmental concerns are embedded in physical urban transformation, socioeconomic fault lines and underlying power relations. 相似文献