Reverse Converters for a New Moduli Set {2<Superscript>2n</Superscript> − 1, 2<Superscript>n</Superscript>, 2<Superscript>2n</Superscript> + 1}

A new moduli set derived from a recently proposed four moduli set is considered, in this paper. The problem of reverse conversion has been considered, and it is shown that the proposed moduli set needs less reverse conversion time and area requirements than the converter for the four moduli set from which it is derived. The proposed moduli set is also compared with two other well-known three moduli sets and for realizing the same dynamic range regarding the area and conversion times of the residue number system (RNS)-to-binary converters.     

New CMOS process using a thermal-oxide mask for making <Emphasis Type="Italic">n</Emphasis><Superscript>−</Superscript>- and <Emphasis Type="Italic">p</Emphasis><Superscript>−</Superscript>-Wells

A new manufacturing process is proposed and evaluated for CMOS memory circuits that is designed to decrease labor input and to increase yield. It essentially uses thermal silicon dioxide instead of silicon nitride as the material of the mask for n ^?- and p ^?-wells, and employs an improved doping procedure for the wells. The new process is shown to decrease considerably the residual stress and defect density in the wafer. Its advantages over the standard process are supported by a two-dimensional computer simulation with Silvaco’s SSUPREM4.     

The binding energy of excitons and <Emphasis Type="Italic">X</Emphasis><Superscript>+</Superscript> and <Emphasis Type="Italic">X</Emphasis><Superscript>−</Superscript> trions in one-dimensional systems

The exciton and trion states in semiconductor quantum wires are treated by the variational method. Simple trial functions provide an adequate precision of the calculation over a wide region of wire radii, with an arbitrary relation between the effective masses of charge carriers. The precision of the results obtained by the variational method is checked by numerical diagonalization of the Hamiltonian of excitons and positively and negatively charged trions. The asymptotic behavior of the binding energies of excitons and trions in narrow quantum wires is established in the analytical form. The structure of the excited X ⁺ trion states is analyzed in the context of the adiabatic approximation.     

Preparation and Ferroelectric Properties of Ho<Superscript>3+</Superscript>/Mo<Superscript>6+</Superscript> Cosubstituted Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> Thin Films by Sol–Gel Method

We have prepared Ho³⁺/Mo⁶⁺ cosubstituted bismuth titanate [(Bi_3.6Ho_0.4)_3.99- Ti_2.985Mo_0.015O₁₂, BHTM] thin films on Pt/Ti/SiO₂/Si substrates using the sol–gel method. The crystal structure and morphology of the BHTM films were characterized. The BHTM samples show a single phase of Bi-layered Aurivillius structure and a dense microstructure. The dielectric constant and dielectric loss of the BHTM films were about 359 and 0.043, respectively, at a frequency of 1 MHz. The films exhibit 2P _r of 57.7 μC/cm² and 2E _c of 290.0 kV/cm at an applied field of 470 kV/cm, and have fatigue-free characteristics. They also showed good insulating behavior according to leakage current testing.     

An H<Superscript>∞</Superscript> Output Feedback Control for Discrete-Time State-Delayed Systems

A coprime factorization approach to H controller design for discrete-time state-delayed systems is developed. The coprime factors that are generated by the present factorization possess the same delayed state as that of the original system. This property, together with the well-known Youla parameterization and the chain-scattering matrix setting, provides a relatively simple method for obtaining a family of internally stabilizing H output feedback controllers. A numerical example is given to demonstrate the validity and applicability of the proposed approach.     

Thermopile Infrared Detector with Detectivity Greater Than 10<Superscript>8</Superscript> cmHz<Superscript>(1/2)</Superscript>/W

In this paper, the design, fabrication and experimental results of the thermopile infrared detector, with a single layer of low-stress SiN_x membrane, instead of thin sandwich layer membrane of SiO₂–Si₃N₄ are presented. Thermal isolation is achieved by using back etching of bulk silicon. Thermopiles are consisted of serially interconnected p-poly-Si/Al thermocouples supported by the single layer of SiN_x membrane with low stress. Au/Ti reflective coating was evaporated on the surface of cold junctions of the thermopile to block incident radiation. In the measurement, we find that infrared absorbance of SiN_x membrane to different wavelength is diverse and less than 100%, which has great influence on calculating the actual absorbing power of the detector, so the infrared (IR) transmission spectrum is measured to calibrate the actual infrared absorbing amount of the detector. The analysis result shows that only 43.72% infrared radiation is absorbed by the detector. Based on the measurement of IR transmission spectrum and output voltage of the detector, the response sensitivity of the detector is calculated as 31.65 V/W, detectivity of the detector is 1.16 × 10⁸ cmHz^(1/2)W⁻¹, and response time of the detector is 126 ms.     

Effect of implantation of Ba<Superscript>+</Superscript> and Nb<Superscript>+</Superscript> ions on the morphology,composition, and emission properties of Мо (111)

The effect of implantation of Ba⁺ and Nb⁺ ions on the composition and emission properties of Мо (111) single crystals is investigated. It is shown that implantation of Ba⁺ ions leads to the complete purification of the Мо surface from С and О atoms, rapid decrease in the work function, and intensification of the secondary and photoelectron emission coefficients, while implantation of Nb⁺ ions leads to rapid (up to 30 at %) growth of the surface concentration of С. It is established that, after heating at Т = 1400 K, the surface is completely purified from carbon and Nb + Мо nanocrystalline phases are formed.     

Fractional Lambda Switching for Flexible Bandwidth Provisioning in WDM Networks: Principles and Performance<Superscript>†</Superscript>

A new approach is introduced in this paper to make possible a flexible utilization of WDM networks using current technology. It is shown that the bandwidth made available end-to-end by a single wavelength can be simply broken up into smaller pieces, or fraction of lambda, by relying on a worldwide common time reference system, such as GPS, previously deployed for different applications. The common time reference system is used to synchronize switches and to facilitate pipeline forwarding of data units. Pipeline forwarding is a known optimal method widely used in manufacturing and computing. It is shown how this new approach, called Time Driven Switching, behaves in terms of call blocking when the basic parameters of the scheme are varied.Work carried out at Politecnico di Milano, Italy. A preliminary version of this paper has been presented at GLOBECOM 2003, San Francisco, USA.     

Photoluminescence and excitation features of Nd<Superscript>3+</Superscript> ions in (La<Subscript>0.97</Subscript>Nd<Subscript>0.03</Subscript>)<Subscript>2</Subscript>S<Subscript>3</Subscript> · 2Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

A combined study of the spectral photoluminescence distribution and excitation spectra of photoluminescence in La₂S₃ · 2Ga₂O₃ and (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses, along with the study of the transmission spectra of these glasses, was carried out. The radiative channel was ascertained to be the main channel for the energy transfer from the host matrix to the Nd³⁺ ions upon excitation of the glasses with light at a wavelength of the fundamental absorption band. Oxygen centers with the level E _c -2.0 eV act as sensitizing agents. The structural disordering of the glass host increases the variance in the magnitude of splitting of the multiplet levels from the 4f electronic states of the Nd³⁺ ion. This promotes nonradiative relaxation of the electrons from excited states to the laser ⁴F_3/2 level. The (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses can be considered as promising laser materials for obtaining the stimulated emission of radiation of Nd³⁺ ions under an optical pump in the range of the fundamental absorption band of the glass.     

Multitarget analysis of CFAR detection of partially-correlated χ<Superscript>2</Superscript> targets

The goal of this paper is to treat the problem of detecting the partially-correlated χ² fluctuating targets with two and four degrees of freedom. We analyze the detection performance in general terms of the more generalized version, which is known asGTM,of theCFARprocessors when the operating environment is contaminated with outlying target returns and the radar receiver carries its processing based on post-detection integration of M exponentially correlated pulses. Analytical formulas for the detection and false alarm probabilities are derived, in the absence as well as in the presence of spurious targets which are assumed to be moderately fluctuating following χ² target models. A performance assessment by numerous numerical examples, which has considered the role that each parameter can play in the processor performance, is given. The obtained results show that the processor performance enhances, for weak SNR of the primary target, as the correlation coefficient ρ_s increases and this occurs either in the absence or in the presence of extraneous targets. As the strength of the target return increases, the processor tends to invert its behavior. The well-known Swerling models embrace the correlated target cases in the situation where the correlation among the target returns follows χ² fluctuation models with two and four degrees of freedom and this behavior is common for allGTMbased detectors.     

A Detailed Analysis and Performance Comparison of Wavelength Reservation Schemes for Optical Burst Switched Networks<Superscript>†</Superscript>

We present a detailed analysis of the JIT, JET, and Horizon wavelength reservation schemes for optical burst switched (OBS) networks. Our analysis accounts for several important parameters, including the burst offset length, and the optical switching and hardware processing overheads associated with bursts as they travel across the network. The contributions of our work include: (i) analytical models of JET and Horizon (on a single OBS node) that are more accurate than previously published ones, and which are valid for general burst length and offset length distributions; (ii) the determination of the regions of parameter values in which a more complex reservation scheme reduces to a simpler one; and (iii) a new reservation scheme, JIT⁺, which is as simple to implement as JIT, but whose performance tracks that of Horizon and JET. We compare the performance of the four wavelength reservation schemes on a single OBS node, as well as on a path of OBS nodes with cross traffic, under various sets of parameter values. Our major finding is that, under reasonable assumptions regarding the current and future state-of-the-art in optical switch and electronic hardware technologies, the simplicity of JIT and JIT⁺ seem to outweigh any performance benefits of Horizon and JET.This work was supported by MCNC-RDI as part of the Jumpstart project.     

Current response of a TlBr detector to <Superscript>137</Superscript>Cs γ-ray radiation

The current response of a TlBr detector to ¹³⁷Cs γ-ray radiation has been studied in the dose-rate range 0.033–3.84 Gy/min and within the voltage range 1–300 V; the detectors are based on pure and doped TlBr crystals grown from the melt by the Bridgman-Stockbarger method. The mass fraction of Pb or Ca introduced into the TlBr crystals was 1–10 ppm for Pb and 150 ppm for Ca. The current response of nominally undoped TlBr samples was nearly linear over two decades of studied dose rates. Deep hole levels associated with cationic vacancies V _c ⁻ determine the dependence of the current response on the voltage in the high electric fields. The parameters of the carriers’ transport μτ are determined. The TlBr crystals grown in vacuum and in the bromine vapor exhibit a large mobility-lifetime product of 4.3 × 10⁻⁴ and 6.4 × 10⁻⁵ cm²V⁻¹, respectively. The value of μτ is in the range (4–9) × 10⁻⁵ cm²V⁻¹ for crystals doped with a divalent cation.     

Chemical Vapor Deposition of <Emphasis Type="Italic">α</Emphasis>-Boron Layers on Silicon for Controlled Nanometer-Deep <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">n</Emphasis> Junction Formation

Nanometer-thick amorphous boron (α-B) layers were formed on (100) Si during exposure to diborane (B₂H₆) in a chemical vapor deposition (CVD) system, either at atmospheric or reduced pressures, at temperatures down to 500°C. The dependence of the growth mechanism on processing parameters was investigated by analytical techniques, such as transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), in conjunction with extensive electrical characterization. In particular, devices fabricated by B deposition effectively demonstrated that p ⁺ doping of the silicon substrate can be achieved within 10 nm from the surface in a manner that is finely controlled by the B₂H₆ exposure conditions. High-quality, extremely ultrashallow, p ⁺ n junctions were fabricated, and their saturation current was tuned from high Schottky-like values to low deep pn junction-like values by the increasing of the deposited B layer thickness. This junction formation exhibited high selectivity, isotropy, spatial homogeneity, and compatibility with standard Si device fabrication.     

Putting Queens in Carry Chains,N<Superscript><Emphasis Type="Italic">o</Emphasis>̱</Superscript>27

The N-Queens Puzzle is a fascinating combinatorial problem. Up to now, the number of distinct valid placements of N non-attacking queens on a generalized N × N chessboard cannot be computed by a formula. The computation of these numbers is instead based on an exhaustive search whose complexity grows dramatically with the problem size N. Solutions counts are currently known for all N up to 26. The parallelization of the search for solutions is embarrassingly simple. It is achieved by pre-placing the queens within a certain board region. These pre-placements partition the search space. The chosen extent of the pre-placement allows for a wide range of the partitioning granularity. This ease of partitioning makes the N-Queens Puzzle a great show-off case for tremendously parallel computation approaches and a flexible benchmark for parallel compute resources. This article presents the Q27 Project, an open-source effort targeting the computation of the solution count of the 27-Queens Puzzle. It is the first undertaking pushing the frontier of the N-Queens Puzzle that exploits the complete symmetry group D ₄ of the square. This reduces the overall computational complexity already to an eighth in comparison to a naive exploration of the whole search space. This article details the coronal pre-placement that enables the partitioning of the overall search under this approach. With respect to the physical implementation of the computation, it describes the hardware structure that explores the resulting subproblems efficiently by exploiting bit-level operations and their mapping to FPGA devices as well as the infrastructure that organizes the contributing devices in a distributed computation. The performance of several FPGA platforms is evaluated using the Q27 computation as a benchmark, and some intriguing observations obtained from the available partial solutions are presented. Finally, an estimate on the remaining run time and on the expected magnitude of the final result is dared.     

Radiation-induced bistable centers with deep levels in silicon <Emphasis Type="Italic">n</Emphasis> <Superscript>+</Superscript>–<Emphasis Type="Italic">p</Emphasis> structures

The method of deep level transient spectroscopy is used to study electrically active defects in p-type silicon crystals irradiated with MeV electrons and α particles. A new radiation-induced defect with the properties of bistable centers is determined and studied. After keeping the irradiated samples at room temperature for a long time or after their short-time annealing at T ～ 370 K, this defect does not display any electrical activity in p-type silicon. However, as a result of the subsequent injection of minority charge carriers, this center transforms into the metastable configuration with deep levels located at E_V + 0.45 and E_V + 0.54 eV. The reverse transition to the main configuration occurs in the temperature range of 50–100°C and is characterized by the activation energy ～1.25 eV and a frequency factor of ～5 × 10¹⁵ s^–1. The determined defect is thermally stable at temperatures as high as T ～ 450 K. It is assumed that this defect can either be a complex of an intrinsic interstitial silicon atom with an interstitial carbon atom or a complex consisting of an intrinsic interstitial silicon atom with an interstitial boron atom.     

Optically active centers in Si/Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>:Er heterostructures containing Er<Superscript>3+</Superscript> ions

The basic types of optically active erbium centers that make the major contribution to the photo-luminescence signal from the Si/Si_{1 ? x} Ge _x :Er heterostructures with the Ge content from 10 to 30% are analyzed in detail. It is shown that the origin of the optically active centers containing Er³⁺ ions correlates with the molar composition of the Si_{1 ? x} Ge _x :Er layer and the content of oxygen impurity in the layer. The major contribution to the photoluminescence signal from the Si/Si_{1 ? x} Ge _x :Er heterostructures with the Ge content below 25% is made by the well-known centers containing Er³⁺ ions and oxygen. An increase in the Ge content in the Si_{1 ? x} Ge _x :Er layer (x ≥ 25%) yields the formation of a new type of centers, specifically, the Gecontaining optically active erbium centers unobserved in the Si-based structures previously.     

Structure and Properties of Nanostructured YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7–δ</Subscript>, BiFeO<Subscript>3</Subscript>, and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>

The development of new nanostructured materials based on YBa₂Cu₃O_7–δ, BiFeO₃, and Fe₃O₄ compounds is considered. The structure, morphology, and properties of these materials are studied. The possibilities of fabricating YBa₂Cu₃O_7–δ ceramics with given densities from nanopowders in a single stage by an energy efficient method and growing superconducting films of the same composition on a silicon substrate (on a SiO₂ layer) are demonstrated. The technique for fabricating BiFeO₃ nanopowder, making it possible to obtain nanostructured ceramics without additional accompanied phases commonly forming during BiFeO₃ synthesis is developed. Two methods of the single-stage synthesis of Fe₃O₄ nanopowder are presented: burning of nitrate-organic precursors and the electrochemical three-electrode method in which one of the electrodes, i.e., an anode containing scrap iron and slurry, is used as an expendable material.     

Non-fragile <Emphasis Type="Italic">H</Emphasis><Subscript>2</Subscript> and <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> filter designs for polytopic two-dimensional systems in Roesser model

This paper is concerned with the problem of non-fragile H ₂ and H _∞ filter designs for two-dimensional (2-D) discrete systems in Roesser model with polytopic uncertainties. The filters to be designed are assumed to be with additive norm-bounded coefficient variations which reflect the imprecision in filter implementation. The complicated filter design problem is successfully tackled by using the slack variable technique and imposing a structural restriction on the slack matrix. Explicit expressions of the non-fragile H ₂ and H _∞ filters are given in terms of solutions to a set of linear matrix inequalities (LMIs). An illustrative example is provided to demonstrate the feasibility and effectiveness of the proposed method.