First-principles study of the lattice integration of palladium defects in doped germanium and silicon

Time-differential perturbed angular correlations spectroscopy of palladium in doped germanium has identified palladium-vacancy pairing in n-type antimony-doped, p-type gallium-doped and undoped germanium. In contrast, an equivalent study of palladium defects in doped silicon suggests a different scenario for the silicon host. Palladium-vacancy pairing has been proposed in n-type silicon irrespective of the dopant type (phosphorous, arsenic or antimony) but palladium–boron pairing has been speculated to occur in p-type boron-doped silicon. This thus raises the question: why does palladium pair with a dopant atom in p-type silicon, but with a vacancy in p-type germanium? Based on the density functional theory calculations carried out in this work, it is suggested that the size of the dopant and the host material both play a crucial role in determining the type of palladium-defect complex that is formed. The calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in gallium-doped and antimony-doped silicon and germanium, respectively. Whereas, a configuration with the palladium atom on a bond-centered interstitial site pairing with the dopant was proposed in boron-doped silicon and germanium. In further support of the argument, in n-type phosphorous-doped materials the calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in silicon, but a configuration with the palladium atom on a bond-centered interstitial site pairing with the phosphorous dopant in germanium.     

依赖强度耦合的J—C模型原子发射功率谱密度

本文研究了依赖强度耦合的Ｊ－Ｃ模型原子发射功率谱密度，分析了初始光场数态、相干态、压缩真空态中叠加态原子的发射谱特性。结果发现，该模型的单光子发射谱不同于通常的Ｊ－Ｃ模型，在光谱探测器的通带宽度较小的情况下，光子数很大的数态光场中其激发态原子的发射谱仍呈现四峰结构；而一般的叠加态原子的发射谱为六峰结构。     

Clear negative characteristics observed in coupled-quantum-wellbase resonant tunneling transistors

Clear negative resistance characteristics observed in a resonant tunneling transistor with a coupled-quantum-well (CQW) base are reported. The collector current reveals negative resistance properties with respect not only to the base-emitter voltage but also the base current in the common-emitter configuration. The collector current peak-to-valley ratio is enhanced in the CQW-base transistor compared with a reference transistor with a single-quantum-well (SQW) base     

Adaptive–interpolative binarization with stroke preservation for restoration of faint characters in degraded documents

A novel technique for binarization with stroke preservation of faint characters in degraded documents is proposed. It works in a multi-scale framework with an adaptive–interpolative thresholding technique. Instead of computing a global threshold value, it computes the local threshold values for a small set of grid points by observing the intensity pattern of the pixels lying in the concerned grid cells. Estimated thresholds are used, in turn, to compute the threshold values of all the remaining pixels using a fast-yet-efficient interpolation procedure. To handle noises in degraded images, this grid-based adaptive thresholding is applied in successively reducing scales to obtain the near-optimal binarization as a set of connected components. After a post-processing meant for stroke preservation with these connected components, we get the final output. Exhaustive experimentation and comparison with other existing methods have been successfully carried out with benchmark datasets and also with our own datasets.     

Algorithm for Scheduling Variable-Length Messages in WDM Networks

In this paper, we develop and analyze a simple algorithm for scheduling variable length messages in WDM networks with a passive star coupler. We base our schemes on a star topology with centralized control and use a scheduling algorithm similar to the process management in UNIX system. Every node and message have a scheduling priority associated with them. By comparing our algorithm with random select algorithm, we find that significant improvement in performance can be achieved with very little extra cost.     

Efficient Beam‐Training Technique for Millimeter‐Wave Cellular Communications

In this paper, a beam ID preamble (BIDP) technique, where a beam ID is transmitted in the physical layer, is proposed for efficient beam training in millimeter‐wave cellular communication systems. To facilitate beam ID detection in a multicell environment with multiple beams, a BIDP is designed such that a beam ID is mapped onto a Zadoff–Chu sequence in association with its cell ID. By analyzing the correlation property of the BIDP, it is shown that multiple beams can be transmitted simultaneously with the proposed technique with minimal interbeam interference in a multicell environment, where beams have different time delays due to propagation delay or multipath channel delay. Through simulation with a spatial channel model, it is shown that the best beam pairs can be found with a significantly reduced processing time of beam training in the proposed technique.     

Ion currents through mutant phospholemman channel molecules

Phospholemman (PLM), a small membrane protein with a single transmembrane domain, is a major substrate for protein kinases in muscle. In lipid bilayers, PLM forms ion channels with two unusual features--selectivity for the zwitterion taurine, and switching among cation- and anion-selective conformations. To investigate the molecular determinants of channel behavior, we measured ion currents through (1) PLM channels with point mutations in the extracellular and cytoplasmic domains, (2) chimeric PLM channels with the transmembrane domain of IsK, a K channel subunit, and (3) truncated PLM channels lacking the cytoplasmic domain. Truncated channels and those with a mutation at the cytoplasmic face had altered selectivity. Channels with a point mutation near the extracellular face were non-selective. Switching among channel conformations was less frequent in truncated channels and in channels with point mutations in either the extracellular or cytoplasmic domain. Chimeric channels with a different transmembrane domain had only a small reduction in conductance. We conclude that both the extracellular and cytoplasmic domains play roles in channel selectivity and conformational changes. Cation-binding sites appear to lie in the cytoplasmic domain, and an anion-binding site may reside in the extracellular domain. The cytoplasmic domain may function as a "ball and chain" to regulate channel selectivity.     

A Diffuse Interface Model of Intermediate-Phase Growth Under the Influence of Electromigration

A diffuse interface model has been developed to investigate intermediate-phase growth in a binary two-phase system under the influence of electromigration. Simulation results show that, besides the polarity effect, at longer times there is a linear growth behavior when the electron flow aids in the diffusion of atoms; however, there is a limiting thickness when the electron flow hinders diffusion. The longer time behavior is found in binary systems with both one and two intermediate phases present. It is also shown that the interface with a larger difference in resistivity migrates at a higher rate compared with the interface with a smaller difference in resistivity, under the influence of electromigration and with the effective charge numbers assumed constant.     

Multicasting to multiple groups over broadcast channels

Multicasting is a communication mode in which a given source communicates with a subset of the entire network user population. Previous work in this area concentrated on the multicast problem of a single source that always communicates with the same destination group. In this paper we investigate a more natural case of multicast communication where a single source communicates with several different destination groups. Specially, we focus on the design and analysis of multicast data link protocols for this environment. Straightforward implementations of such protocols are inappropriate in the case of a large destination population, as a source will have to store a large amount of state information even if it maintains only a single variable per destination. In most typical applications, though. The total destination population is large, the number of destinations that any given source is in conversation with, is typically small. We propose a framework for adapting protocols so that memory requirement does not grow with the total destination population but depends upon the number of destinations actually in communication with the source. The savings in memory are achieved by slightly increasing the amount of communication. We address the performance of such a protocol in an environment of a broadcast channel. We analyze several strategies and control techniques and demonstrate the tradeoff between throughput and the amount of memory     

B-scan based acoustic source reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI)

We present in this study, an acoustic source reconstruction method using focused transducer with B-mode imaging for magnetoacoustic tomography with magnetic induction (MAT-MI). MAT-MI is an imaging modality proposed for noninvasive conductivity imaging with high spatial resolution. In MAT-MI, acoustic sources are generated in a conductive object by placing it in a static and a time-varying magnetic field. The acoustic waves from these sources propagate in all directions and are collected with transducers placed around the object. The collected signal is then used to reconstruct the acoustic source distribution and to further estimate the electrical conductivity distribution of the object. A flat piston transducer acting as a point receiver has been used in earlier MAT-MI systems to collect acoustic signals. In this study, we propose to use B-mode scan scheme with a focused transducer that gives a signal gain in its focus region and improves the MAT-MI signal quality. A simulation protocol that can take into account different transducer designs and scan schemes for MAT-MI imaging is developed and used in our evaluation of different MAT-MI system designs. It is shown in our computer simulations that as compared to the earlier approach, the MAT-MI system using B-scan with a focused transducer allows MAT-MI imaging at a closer distance and has improved system sensitivity. In addition, the B-scan imaging technique allows reconstruction of the MAT-MI acoustic sources with a discrete number of scanning locations, which greatly increases the applicability of the MAT-MI approach, especially when a continuous acoustic window is not available in real clinical applications. We have also conducted phantom experiments to evaluate the proposed method, and the reconstructed image shows a good agreement with the target phantom.     

Improving resolution in photolithography with a phase-shifting mask

The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10X tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.     

A new method for detecting and localizing cell markers endocytosed by fibroblasts in epoxy resin semi-thin sections using scanning electron microscopy combined with energy dispersive X-ray microanalysis after ion-etching

Cell marking is widely used to examine cell development and differentiation in developmental biology. We developed a new method for localizing cell markers in a semi-thin epoxy section with scanning electron microscopy. Cultured fibroblasts ingesting carbon particles were autologously transplanted into a rabbit transparent ear chamber, 6 mm in diameter and 100 microm in depth. Eight days after the transplantation, tissues in the chamber were fixed and embedded in epoxy resin. Semi-thin sections were cut and stained with toluidine blue. Fibroblasts in connective tissues which contained black spots were observed with a light microscope. These sections were subsequently ion-etched with an ion-coater and coated with platinum. The same fibroblasts were then visualized by secondary electron imaging using a scanning electron microscope. A nucleus with nuclear envelope, nuclear pores, a nucleolus and heterochromatin, mitochondria with cristae and rough endoplasmic reticulum were observed in the fibroblasts. The black spots in the fibroblasts were identified as bright bodies with the scanning electron microscope. The bright bodies were found to be a lump of tiny particles less than 100 nm in diameter. In order to analyse such particles with energy dispersive X-ray microanalysis, ion-etched sections were coated with carbon. X-ray energy spectrometry clearly demonstrated that these were carbon particles, which had been endocytosed by the fibroblast. This suggests that scanning electron microscopy combined with energy dispersive X-ray microanalysis is useful for detecting carbon particles in the cytoplasm at an ultrastructural level in semi-thin epoxy sections subsequent to ion etching and that this method may be applicable to other cell markers, such as gold particles to track cells in the field of cell development and cell differentiation.     

Nonlinear saturation and efficiency enhancement in a Cherenkovlaser using a dielectric grating

With the aid of particle simulation, this paper discusses nonlinear saturation and efficiency enhancement in a single-pass Cherenkov laser using a dielectric grating, taking into account the nonlinear properties of a relativistic electron beam. For the analysis of the problem, a two-dimensional model for the Cherenkov laser is considered which is composed of a planar relativistic electron beam and a parallel plate waveguide, one plate of which is loaded with a dielectric grating. First, the nonlinear characteristics for the growth of the electromagnetic wave are considered for a dielectric grating with constant parameters. The variation of the groove depth or the slot width in a dielectric grating is found to have the same effect on the growth characteristics as the variation of the permittivity of a dielectric sheet with constant thickness. Then, in order to enhance the efficiency in energy transfer from the electron beam to the electromagnetic wave in the Cherenkov laser, one of the grating parameters or the groove depth is adiabatically decreased in accordance with the decrease in the average velocity of the electron beam. The result of numerical simulation shows that sufficient efficiency enhancement in energy transfer is achieved with the use of a dielectric grating with a variable parameter     

Down-Sampling Design in DCT Domain With Arbitrary Ratio for Image/Video Transcoding

This paper proposes a designing framework for down-sampling compressed images/video with arbitrary ratio in the discrete cosine transform (DCT) domain. In this framework, we first derive a set of DCT-domain down-sampling methods which can be represented by a linear transform with double-sided matrix multiplication (LTDS) in the DCT domain and show that the set contains a wide range of methods with various complexity and visual quality. Then, for a preselected spatial-domain down-sampling method, we formulate an optimization problem for finding an LTDS to approximate the given spatial-domain down-sampling method for a trade-off between the visual quality and the complexity. By modeling LTDS as a multiple layer network, a so-called structural learning with forgetting algorithm is then applied to solve the optimization problem. The proposed framework has been applied to discover optimal LTDSs corresponding to a spatial down-sampling method with Butterworth low-pass filtering and bicubic interpolation. Experimental results show that the resulting LTDS achieves a significant reduction on the complexity when compared with other methods in the literature with similar visual quality.      

Investigation of the field uniformity of a mode-stirred chamberusing diffusers based on acoustic theory

This paper presents the combination of acoustic diffusors with a mode-stirred chamber to enhance the field homogeneity. Simulations with a TLM-based time-domain computer program show a more homogenous field in this advanced mode-stirred chamber as compared to a normal mode-stirred chamber. The efficiency of the diffusors is illustrated in comparison with a rectangular reference room. The simulations are verified by measurements in a mode-stirred chamber combined with two different types of diffusors. The two types of investigated diffusors are the maximum length diffusors and the quadratic residue diffusors. We also investigate the combination of both     

Reduction of lateral diffusion of photoelectrons in silicon photodiode imager arrays by internal gettering

The lateral diffusion of photoelectrons to adjacent picture elements in a silicon linear photodiode array is reduced in substrates with a high density of oxygen precipitates formed by internal gettering. The signal due to diffusion in adjacent pixels, normalized to the illuminated pixel signal, was reduced by a factor of 1.6 for pixels with centers 48 µm apart and by a factor of 10 for pixels farther apart; there was no significant decrease in sensor quantum efficiency. These results are interpreted with a numerical model that solves the three-dimensional diffusion equation for a substrate with different lifetimes in the surface and internal regions.     

A fail-safe self-routing fiber-optic ring network using multitailedreceiver-transmitter units as nodes

A fiber-optic component consisting of N receivers, each with one fiber input port, and one transmitter with n fiber output ports, with a circuit in between, form a multitailed node. This is the basic building block for a self-routing `filled-ring network' with many stations, which can be disconnected without affecting the ring integrity. The token-passing medium-access protocol is found to have a several times better performance, in terms of the average delay-traffic intensity characteristic, in a filled-ring network than in a conventional ring network with the same number of stations. In a realistic example with 64 stations the improvement is by a factor of two to three. Using the multitailed nodes and self-routing, the network can easily be expanded to more complex configurations without introducing a routing overhead to keep the network under control     

Microwave-signal generation in a planar Gunn diode with radiation exposure taken into account

Microwave-signal generation in planar Gunn diodes with a two-dimensional electron gas, in which we previously studied steady-state electron transport, is theoretically studied. The applicability of a control electrode similar to a field-effect transistor gate to control the parameters of the output diode microwave signal is considered. The results of physical-topological modeling of semiconductor structures with different diode active-region structures, i.e., without a quantum well, with one and two quantum wells separated by a potential barrier, are compared. The calculated results are compared with our previous experimental data on recording Gunn generation in a Schottky-gate field-effect transistor. It is theoretically and experimentally shown that the power of the signal generated by the planar Gunn diode with a quantum well and a control electrode is sufficient to implement monolithic integrated circuits of different functionalities. It is theoretically and experimentally shown that the use of a control electrode on account of the introduction of corrective feedback allows a significant increase in the radiation resistance of a microwave generator with Schottky-gate field-effect transistors.     

A GaAs MESFET Self-Bias Mode Oscillator (Short Paper)

A self-bias mode oscillation in a GaAs MESFET, with the gate terminal kept open in a dc manner, has been analyzed by a large-signal MESFET circuit model. The circuit simulation demonstrates that the gate-source Schottky barrier becomes self-biased along with the microwave oscillation build-up and that a stable self-bias gate voltage is observed with a steady-state oscillation. A self-bias mode oscillator, operable with a single positive dc bias, is realized by rising microwave integrated circuit technology.     

Microwave resonators with dual-mode oscillations

Analysis of microwave resonators with dual-mode oscillations is conducted. A new type of resonators is discovered in which dual-node oscillations are observed. It represents a half-wave resonator with a short-circuit in the middle part. The length of such a resonator is twice less than the length of a widely used ring resonator. It is shown that in resonators of the loop type combined frequency tuning of dual-mode oscillations is accomplished using capacity and inductance. In the loop-type resonators with a stub frequency tuning of dual-mode oscillations is accomplishing with two capacities synchronously changing their values according to a specific law. Resonance equations are obtained.