Direct, prediction- and smoothing-based Kalman and particle filter algorithms

We address the recursive computation of the filtering probability density function (pdf) p_n|n in a hidden Markov chain (HMC) model. We first observe that the classical path p_n−1|n−1→p_n|n−1→p_n|n is not the only possible one that enables to compute p_n|n recursively, and we explore the direct, prediction-based (P-based) and smoothing-based (S-based) recursive loops for computing p_n|n. We next propose a common methodology for computing these equations in practice. Since each path can be decomposed into an updating step and a propagation step, in the linear Gaussian case these two steps are implemented by Gaussian transforms, and in the general case by elementary simulation techniques. By proceeding this way we routinely obtain in parallel, for each filtering path, one set of Kalman filter (KF) equations and one generic sequential Monte Carlo (SMC) algorithm. Finally we classify in a common framework four KF (two of which are original), which themselves can be associated to four generic SMC algorithms (two of which are original). We finally compare our algorithms via simulations. S-based filters behave better than P-based ones, and within each class of filters better results are obtained when updating precedes propagation.     

Synthesis of low-melting metal oxide and sulfide nanowires and nanobelts

The bulk nucleation and basal growth of semiconducting nanowires from molten Ga pools has been demonstrated earlier using oxygen/hydrogen plasma over molten Ga pools. Herein, we extend the above concept for bulk synthesis of oxide and sulfide nanowires of low-melting metal melts such as Sn and In. Specifically, nanowires of β-Ga₂O₃, β-In₂O₃, SnO₂, α-Ga₂S₃, and β-In₂S₃ were synthesized using direct reactions between respective molten metal pools and the gases such as oxygen/hydrogen mixture for oxides and H₂S for sulfides. In the case of β-Ga₂O₃ and SnO₂, a change in the morphology from nanowires to nanobelts was observed with an increase in the synthesis temperature. No such behavior was observed in the case of β-In₂O₃. Furthermore, we present evidence for α-Ga₂S₃ nanowires, which to our knowledge is being reported for the first time in the literature. Our studies with the sulfide nanowires suggest that H₂S reacts directly at the molten metal surface to form gallium sulfide. Finally, we discuss the role of chamber pressure and hydrogen on the size distribution of nanostructured β-Ga₂O₃ and SnO₂.     

Advanced electrical and stability characterization of untrimmed and variously trimmed thick-film and LTCC resistors

As-fired thick-film resistors have the resistance tolerance within ±20% and this tolerance is increased for smaller components. Therefore the novel trimming methods are necessary for microresistors, especially when they are embedded in LTCC substrate. This paper compares electrical (normalized temperature dependence of resistance, low frequency noise) and stability properties (relative resistance drift, changes of current noise index) of untrimmed, voltage pulse trimmed and laser trimmed unglazed thick-film resistors after step-increased long-term thermal ageing at 162 °C, 207 °C and 253 °C. Moreover the effect of long term exposure (1000 h, 125 °C) and thermal shocks (1000 shocks between −55 °C and 125 °C) is analysed for untrimmed and voltage pulse trimmed buried LTCC resistors.     

Design and design methods for unified multiplier and inverter and its application for HECC

This paper describes two novel architectures for a unified multiplier and inverter (UMI) in GF(2^m): the UMI merges multiplier and inverter into one unified data-path. As such, the area of the data-path is reduced. We present two options for hyperelliptic curve cryptography (HECC) using UMIs: an FPGA-based high-performance implementation (Type-I) and an ASIC-based lightweight implementation (Type-II). The use of a UMI combined with affine coordinates brings a smaller data-path, smaller memory and faster scalar multiplication.Both implementations use curves defined by h(x)=x and f(x)=x⁵+f₃x³+x²+f₀. The high throughput version uses 2316 slices and 2016 bits of block RAM on a Xilinx Virtex-II FPGA, and finishes one scalar multiplication in . The lightweight version uses only 14.5 kGates, and one scalar multiplication takes 450 ms.     

Theory and Practice and the Neutral's Persona

Editor's note: Longtime Alternatives columnist Bob Creo, a veteran Pittsburgh neutral, is revisiting his classic CPR Institute website columns of a decade ago in a Back to Basics Series that he has subtitled “Human Problems, Human Solutions.” These updated and expanded columns, in print for the first time, began late last year. He has revisited and re‐examined mediation‐room techniques and practice issues. This month, he returns to the second column he wrote at www.cpradr.org a decade ago, and brings it forward.     

Effect of anion and cation substitution in tungsten disulfide and tungsten diselenide on conductivity and thermoelectric power

The temperature dependences of the conductivity and thermoelectric power for a series of samples W_1–x Nb _x S₂, W_1–x Nb _x Se₂, WS_2–y Se _y , W_1–x Nb _x S_2–y Se _y are studied at low temperatures. It is found that the cation substitution of W atoms with Nb leads to an increase in the conductivity and a decrease in the thermoelectric power. The anion substitution of S with Se atoms results in a simultaneous increase in the conductivity and thermoelectric power. The highest power factor among the samples studied is inherent to W_0.8Nb_0.2Se₂.     

Synthesis and photo-electrochemical properties of novel thienopyrazine and quinoxaline derivatives,and their dye-sensitized solar cell performance

Light absorption from visible to NIR region is required to increase the photocurrent and to enhance the photo-energy conversion efficiencies in dye-sensitized solar cells (DSSCs). We have now developed novel thienopyrazine dye TP1 which has absorption up to 700 nm. Quinoxaline dye QX2 with absorption at shorter wavelengths than TP1 has been synthesized for comparisons. The power conversion efficiencies of DSSCs with TP1 and QX2 showed 4.4% and 3.2%, respectively. The absorption edge in IPCE of TP1 reached 800 nm and the open circuit voltage (Voc) of QX2 was high (0.77 V). To improve the device performances, QX2 was used as a co-adsorbent dye with TP1. In the mixed sensitizer based DSSC, a high power conversion efficiency of 6.2% was achieved due to the effective light harvesting and steric effect of QX2.     

Electrical and thermoelectric properties of ZnO under atmospheric and hydrostatic pressure

Temperature (for T = 77–400 K) and pressure (for P ≤ 8 GPa) dependences of conductivity σ(T,P). Hall coefficient R _H(T, P), and Seebeck coefficient Q(T) were studied in single-crystal n-ZnO samples with the impurity concentration N _i = 10¹⁷ ? 10¹⁸ cm^?3 and free-electron concentration n = 10¹³?10¹⁷ cm^?3. Single crystals were grown by the hydrothermal method. Dependence of the ionization energy of a shallow donor level on the impurity concentration E _d1(N _d) is determined, along with the pressure coefficients for the ionization energy ?E _d1/?P and static dielectric constant ?x/?P. A deep defect level with the energy E _d2 = 0.3 eV below the bottom of the conduction band is found. The electron effective mass is calculated from the obtained data on the kinetic coefficients R _H(T) and Q(T).     

Preparation and characterization of Si-doped barium titanate nanopowders and ceramics

Si-doped barium titanate nanopowders and ceramics were prepared through the sol-gel process. The powders and ceramics were characterized by methods of XRD, SEM and TEM. The dielectric properties of the ceramics were also determined. The results indicated that the powders were nanopowders and they were all cubic BaTiO₃ phase with the concentration of Si ?5.0 mol%. When the concentration of Si increased to 10.0 mol%, another phase of Ba₂TiSi₂O₈ appeared. After sintering, the cubic BaTiO₃ phase was transformed into tetrahedron BaTiO₃ phase. Si doping with low concentration resulted in improving grain growth and reduced dielectric loss. As the sintering temperature increased, the dielectric properties of the ceramics decreased. BaTiO₃ ceramics doped with Si all had a small peak at room temperature in ε−T cures. Specially, the ceramic doped with 0.3 mol% Si had evident double peaks, the maximum room temperature permittivity (4081) and the minimum dielectric loss (0.004).     

Synthesis and Properties of High-Quality InN Nanowires and Nanonetworks

We report on the growth of high-quality InN nanowires by the vapor–liquid–solid mechanism at rates of up to 30 μm/h. Smooth and horizontal nanowire growth has been achieved only with nanoscale catalyst patterns, while large-area catalyst coverage resulted in uncontrolled and three-dimensional growth. The InN nanowires grow along the [110] direction with diameters of 20 to 60 nm and lengths of 5 to 15 μm. The nanowires bend spontaneously or get deflected from other nanowires at angles that are multiples of 30°, forming nanonetworks. The gate-bias-dependent mobility of the charge carriers ranges from 55 cm²/V s to 220 cm²/V s, and their concentration is ∼10¹⁸ cm⁻³.     

Fabrication and advanced electrical and stability characterization of laser-shaped thick-film and LTCC microresistors for high temperature applications

Thick-film and LTCC (Low Temperature Co-fired Ceramics) technologies are well-established and relatively low-cost fabrication method of passives. This paper presents systematic studies of fabrication and a wide spectrum of geometrical and electrical properties of thick-film and LTCC microresistors with dimensions down to 30 × 200 μm². The geometrical parameters (average length, width and thickness, relations between designed and real dimensions, distribution of planar dimensions) are correlated with basic electrical properties of resistors (sheet resistance, temperature dependence of resistance), long-term stability as well as durability of microresistors to short electrical pulses in the temperature range from 25 °C to 400 °C.     

Recombination and trapping centers in pure and doped TlBr crystals

TlBr is a promising wide-gap semiconductor for developing γ-radiation detectors. One of the limiting factors in developing the technology of detectors is the lack of experimentally determined trapping and recombination centers. In this paper, a generalized model of the formation and behavior of intrinsic defects in pure and doped TlBr single crystals is presented. The relation of intrinsic defects to growth conditions and electrical properties is determined. The previously obtained temperature dependences of the photoconductivity, the data of current deep level transient spectroscopy and microcathodoluminescence, and the kinetic characteristics of the photoconductivity are used as objects of analysis. It is shown that the compensation of charged centers control the transport properties of charge carriers. In compensated doped TlBr crystals, the product of the mobility and lifetime can reach μτ = 5 × 10^?4 cm² V^?1. The energy-level diagram of local levels in pure and doped TlBr crystals is proposed. The ionization energies of major structural and impurity defects in TlBr, i.e., the anion vacancy V _a ⁺ , cation vacancy V _c ^? , and Pb²⁺, O^2?, S^2? ions, are determined. The energy position of a single anion vacancy V _a ⁺ is E _c ? 0.22 eV. The energy level of the cation vacancy is E _v + 0.85 eV for a single cation vacancy and E _v + 0.58 eV for a vacancy incorporated into the {Pb²⁺ V _c ^? }⁰ complex. The ionization energy of the Pb²⁺ Coulomb trap is E _c ? 0.08 eV in doped TlBr crystals.     

Blind and semi-blind equalization: methods and algorithms

Channel identification techniques that do not require the use of a training sequence (blind methods), or that can operate with very short training sequence (semiblind methods) are a topic of major concern for modern communication applications. This paper presents a review of channel identification methods that are applicable in this context, with a strong emphasis on second-order subspace-based and maximum likelihood (Ml) estimation schemes. The main focus of the paper is on: (i) providing a clear picture of the principle and theory associated with subspace-based methods in the blind and semi-blind contexts; (ii) describing algorithmic solutions, sometimes based on novel results, that are suitable for carrying out the delicate likelihood optimization task associated withMl estimation.     

Transport properties and defects in semi-insulating and Si-implanted InP

The transport properties and defect levels in Si-implanted semi-insulating and liquid phase epitaxial InP have been studied by Hall and photoconductivity measurements. Wide variations in the conductivity and Hall coefficient have been measured in semi-insulating InP:Fe and the results have been analyzed and interpreted by appropriate charge neutrality models. The energy position of the Fe and Cr acceptor levels have been determined to be 0.68 and 0.40 eV, respectively, below the conduction band minimum. The implantation studies indicate that the electrical properties of the layers are very sensitive to implant dose and energy, the type and thickness of encapsulant and the anneal temperature. High-resistivity or p-type conductivity was observed in layers implanted with 6.0 × 10¹¹ to 4.0 × 10¹² cm⁻² Si⁺. In general, better results were obtained with sputtered Si₃N₄ encapsulation. Varying amounts of Fe and Cr outdiffused to the active layer during annealing and a dominant defect, 0.56 eV below the conduction band, was observed in the photoconductivity spectra.     

Stable and wavelength-tunable RSOA- and SOA-based fiber ring laser

In this work, we propose and experimentally investigate a wavelength-tunable fiber ring laser architecture by using the reflective semiconductor optical amplifier (RSOA) and semiconductor optical amplifier (SOA). Here, the wavelength tuning range from 1538.03 to 1561.91 nm can be obtained. The measured output power and optical signal to noise ratio (OSNRs) of the proposed fiber laser are between -0.8 and -2.5 dBm and 59.1 and 61.0 dB/0.06 nm, respectively. The power and wavelength stabilities of the proposed laser are also studied. In addition, the proposed laser can be directly modulated at 2.5 Gbit/s quadrature phase shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) signal and 20–50 km single-mode fiber (SMF) transmissions are achieved within the forward error correction (FEC) limit without dispersion compensation. It could be a cost-effective and promising candidate for the standard-reach and extended-reach wavelength division multiplexed passive optical network (WDM-PON).     

Determination of donor and acceptor impurity concentrations in n-InP and n-GaAs

The Hall mobility of semiconducting materials is generally computed without accounting for the Hall factor,r _H. It is shown that for low magnetic fields this may lead to considerable errors in the calculation of the impurity concentrations,N _D andN _A, in both n-GaAs and n-InP of reasonable purity. Tables allowing the determination ofN _D andN _A under low magnetic field conditions are computed at room and liquid nitrogen temperatures. They account forr _H and for the inelastic nature of collisions with polar optical phonons without assuming Matthiessen's rule.     

Photoluminescent and electroluminescent properties and ultra-fast spectrometric studies of dihydroheptacenes

Photophysical and electrochemical properties of 7,16-dihydroheptacenes (1–3) were investigated in detail. Although their HOMO–LUMO gaps are higher than 3 eV, the organic light-emitting diodes containing 1 as the emitting dopant showed green electroluminescence (λ_max ∼ 515 and 550 nm) even at a concentration of the dopant as low as 1%. The green electroluminescence of 1 appears to be originating from an electromeric state (an intermolecular ion pair). The maximum brightness of 190 cd/m² was observed at a current density of 34 mA/cm² at operating voltage of 19 V for the device containing 1% 1, and overall performance of the devices decreased with an increase in the doping concentration of 1.     

Dielectric and Pyroelectric Properties of La- and Pr-Modified Tungsten-Bronze Ferroelectrics

The polycrystalline materials Li₂Pb₂R₂W₂Ti₄Nb₄O₃₀ (R = La, Pr) of the tungsten-bronze structural family have been synthesized using a high- temperature mixed-oxide method. Room-temperature x-ray diffraction (XRD) analysis confirms the formation of single-phase compounds. Room-temperature scanning electron micrography of the pellet samples shows a uniform distribution of well-defined different sizes of grains on the surface of the samples, confirming the formation of single-phase compounds. Study of the frequency and temperature dependence of the dielectric constant and loss tangent suggests the existence of dielectric dispersion in the materials. The ferroelectric phase transition in the samples has been studied based on the variation of fitting parameters (calculated from a theoretical model) with temperature. Studies of pyroelectric properties [figure of merit (FOM) and coefficient] show that the materials have reasonably high FOM useful for pyroelectric detectors. The variation of alternating-current (AC) and direct-current (DC) conductivity with inverse absolute temperature (obtained from dielectric data) follows a typical Arrhenius relation. The low leakage current and negative temperature coefficient of resistance behavior of the samples have been verified from J–E plots.     

Microstructure and creep behaviour of eutectic SnAg and SnAgCu solders

The paper presents creep data, that was gained on specimens of different microstructures. The three specimen types have been flip chip solder joints, pin trough hole solder joints and standard bulk solder specimens. The bulk solder specimen was a dog-bone type specimen (diameter=3 mm, LENGTH=117 mm). The pin trough hole solder joint consisted on a copper wire that was soldered into a hole of a double sided printed circuit board (thickness 1.5 mm). The flip chip solder joint specimen consisted of two silicon chips (4 mm × 4 mm), which were connected by four flip chip joints (one on each corner). SnAg and SnAgCu flip chip bumps (footprint 200 μm × 200 μm, joint height 165–200 μm, centre diameter 90…130 μm) were created by printing solder paste.Constant–load creep tests were carried out on all three specimen types at temperatures between 5 and 70 °C. Creep data was taken for strain rates between 10⁻¹⁰ and 10⁻³ s⁻¹. The specimens were tested in “as cast” condition and after thermal storage.The microstructural properties of the bulk specimens and real solder joints were examined using metallographic sectioning, optical microscopy techniques, and SEM-microprobe analysis. The results of the microstructural analysis were related to the investigated mechanical properties of the solders. Models of SnAg3.5 and SnAg4Cu0.5, that can be used with the ANSYS FEM software package, will be presented.