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.     

On the local injection of emitted electrons into micrograins on the surface of A<Superscript>III</Superscript>–B<Superscript>V</Superscript> semiconductors

The characteristics of the injection of electrons into a semiconductor from a microprobe–micrograin nanogap are investigated with a tunneling microscope in the mode of field emission into locally selected surface microcrystals of indium antimonide, indium arsenide, and gallium arsenide. The current mechanisms are established and their parameters are determined by comparing the experimental I–V characteristics and those calculated from formulas of current transport. The effect of limitation of the current into the micrograins of indium antimonide and indium arsenide which manifests itself at injection levels exceeding a certain critical value, e.g., 6 × 10¹⁶ cm^–3 for indium antimonide and 4 × 10¹⁷ cm^–3 for indium arsenide, is discovered. A physical model, i.e., the localization of electrons in the surface area of a micrograin due to their Coulomb interaction, is proposed.     

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.     

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.     

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.     

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.     

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.     

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.     

Single- and Double-Output Embedded Checker Architectures for Systematic Unordered Codes<Superscript>∗</Superscript>

For the detection of all unidirectional errors, Berger codes have been found to be an optimal choice in the general case. But for some particular cases other systematic unordered codes are superior to Berger codes. We present checker architectures for Berger-type codes that are similar to Berger codes. They cover codes by Parhami so that the proposed checkers can also be used for these codes. We also describe new checker architectures for Bose AUED codes and Biswas-Sengupta AUED codes. The design of these checkers is based on translating the code words to words of a Berger-type code which are then checked by a Berger-type code checker. The translation circuits are very simple. All checkers can be tested with only a few code words, or achieve the self-testing property almost independent of the provided set of code words, and are therefore very suitable as embedded checkers. The proposed checkers can be designed to have a single periodic output or a two-rail encoded output. Further, our checkers are not code-disjoint in the common sense but able to detect all single and multiple unidirectional errors.Steffen Tarnick received the diploma degree in mathematics from the Dresden University of Technology, Dresden, Germany, in 1989, and the Dr. rer. nat. degree from the University of Potsdam, Germany, in 1995. From 1989 to 1991 he was a Research Assistant at the Institute of Cybernetics and Information Processes of the East German Academy of Sciences in Berlin. Then he spent one year as visiting scientist at the TIMA Laboratory in Grenoble, France. From 1992 to 1995 he was with the Max Planck Society Group for Fault-Tolerant Computing at the University of Potsdam, Germany. Until 2002 he was a research staff member at SATCON GmbH in Teltow, Germany. He is currently the head of the Secure Systems Department at 4TECH GmbH in Teltow, Germany. His main research interests include self-checking circuits design, built-in self-test, and cryptography.     

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.     

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.     

Judd–Ofelt Analysis of Dy<Superscript>3+</Superscript>-Activated Aluminosilicate Glasses Prepared by Sol–Gel Method

Aluminosilicate (AS) glasses doped with different Dy³⁺ concentrations were synthesized via sol–gel method. Absorption, photoluminescence spectra and lifetime of this material have been studied. From analytical results of absorption spectra, the Judd–Ofelt (JO) parameters of prepared samples have been determined. These JO parameters combined with photoluminescence spectra have been used to evaluate transition probabilities (A_R), branching ratios (β) and the calculated oscillator strengths of AS:Dy³⁺ glasses. The radiative branching ratio of ⁴F_9/2 → ⁶H_13/2 transition has a minimum value at 62.2% for β_R which predicts that this transition in AS:Dy³⁺ glasses can give rise to lasing action. JO parameters show that the Ω₂ increases with the increasing of Dy³⁺ ion concentration due to the increased polarizability of the average coordination medium and decreased average symmetry.     

Radiation damage of contact structures with diffusion barriers exposed to irradiation with <Superscript>60</Superscript>Coγ-ray photons

The effect of ionizing radiation of ⁶⁰Co γ-ray photons in the dose range 10⁴–2 × 10⁹ rad on metal-semiconductor Au-ZrB _x -AlGaN/GaN and Au-TiB _x -Al-Ti-n-GaN contacts and Au-ZrB _x -n-GaN Schottky diodes is examined. The contacts with the TiB _x and ZrB _x diffusion barriers do not degrade under the effect of ionizing radiation if the dose does not exceed 10⁸ rad. The Au-ZrB _x -n-GaN Schottky diodes remain stable in the dose range 10⁴–10⁶ rad. As the radiation dose is increased to ≳10⁸ rad, the damage to the contact metallization increases and is accompanied by formation of through pores, which is conducive to accumulation of oxygen at the Au-ZrB _x (TiB _x ) interfaces and to an increase in mass transport of atoms in contact-forming layers. In this case, irradiation-caused degradation of the Schottky diodes is observed. Possible mechanisms of radiation damage of contact structures with diffusion barriers are analyzed.     

Dependence of mobility on the electron concentration upon scattering at polar optical phonons in A<Superscript>III</Superscript>–N nitrides

The dependence of the effective relaxation time on the electron concentration in A^III–N nitrides in the case of electron scattering at polar longitudinal optical phonons is calculated by the marching method. The method takes into account the inelasticity of electron scattering at polar optical phonons for nitrides in the zinc-blende approximation. The calculations show a substantial increase in mobility in samples with a degenerate electron gas, if screening of the long-range potential of polar longitudinal optical phonons is taken into account.     

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.     

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.     

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.     

Establishment of specific features of electron localization at <Emphasis Type="Italic">U</Emphasis><Superscript>−</Superscript> centers in semiconductors from thermally stimulated currents

The specific features of thermally stimulated currents in semiconductors containing U ^? centers are treated theoretically in comparison with the corresponding features for semiconductors containing defects with a positive correlation energy or single-level centers. It is shown that the analysis of the curves of thermally stimulated currents normalized to the maximum current in respect to the shape and to the presence or absence of a shift of the temperature maximum of the curve in relation to the initial occupancy provides an extra necessary criterion for identifying defects with different parameters of binding of electrons. The results can be used in analyzing experimental data on thermally stimulated currents that exhibit features inexplicable in the context of the often used model of single-level centers.