Decamethylosmocene-catalyzed efficient oxidation of saturated and aromatic hydrocarbons and alcohols with hydrogen peroxide in the presence of pyridine

Decamethylosmocene, (Me₅C₅)₂Os (1), is a pre-catalyst in a very efficient oxidation of alkanes with hydrogen peroxide in acetonitrile at 20–60 °C. The reaction proceeds with a substantial lag period that can be reduced by the addition of pyridine in a small concentration. The lag period can be removed if 1 is incubated with pyridine and/or H₂O₂ in MeCN prior to the alkane oxidation. Alkanes, RH, are oxidized primarily to the corresponding alkyl hydroperoxides, ROOH. Turnover numbers attain 51,000 in the case of cyclohexane (maximum turnover frequency was 6000 h^?1) and 3600 in the case of ethane. The oxidation of benzene and styrene also occurs with a lag period to afford phenol and benzaldehyde, respectively. A kinetic study of cyclohexane oxidation and selectivity parameters (measured in the oxidation of n-heptane, methylcyclohexane, isooctane, cis- and trans-dimethylcyclohexanes) indicates that the oxidation of saturated, olefinic, and aromatic hydrocarbons proceeds with the participation of hydroxyl radicals. The 1/H₂O₂/py/MeCN system also oxidizes 1-phenylethanol to acetophenone.     

Application of ZnO single crystals for light-induced water splitting under UV irradiation

This paper presents experimental results of implementation of ZnO single crystals as photoanodes in photoelectrochemical (PEC) cells for hydrogen generation through the process of water splitting. Both, as-grown and O₂-annealed ZnO single crystals were investigated for this purpose. A 351 nm argon laser line was used as the light source. The XRD investigations showed that used ZnO crystals are of good crystalline quality. It was found that the as-grown ZnO single crystals possess higher conversion efficiencies comparing to the O₂-annealed one. The photocurrent density was found to increase significantly with the increase of external bias applied and excitation light intensity. Time dependent photocurrent density characteristics showed that the decay of photocurrent density was not observed within the measurement time. The differences in behaviour of the as-grown and the annealed in O₂ ZnO single crystals are discussed in terms of crystals intrinsic defects.     

Probability density of the differential phase difference in applications to passive wireless surface acoustic wave sensing

The probability density function (pdf) is discussed of the differential phase difference (DPD) in the radio frequency (RF) pulse-burst perturbed by Gaussian noise at the coherent receiver. Statistical properties of the DPD are of importance for error estimation in coherent systems such as remote passive wireless surface acoustic wave (SAW) sensing with multiple differential phase measurement. The rigorous probability density of the DPD is derived and its particular functions, all having no closed forms, are given for different signal-to-noise ratios (SNRs) in the RF pulses. Employing the von Mises/Tikhonov distribution, an efficient approximation is proposed via the modified Bessel functions of the first kind and zeroth order. Engineering features and small errors of the approximation are demonstrated. Applications are given for the phase difference drift rate and error probability for the drift rate to exceed a threshold.     

15% Efficiency CdS/CdTe thin film solar cells using CdS layers doped with metal organic compounds

For improving the photovoltaic performance of CdS/CdTe thin film solar cells, the CdS window layer is one of the most crucial factors. Here we demonstrate the photovoltaic performances of the low-environmental-load CdS/CdTe solar cell employing the CdS layer doped with various metal organic (MO) compounds, i.e., (CH₃)₂SnCl₂, (C₆H₅)₃GeCl, (CH₃CO₂)₃In, [(C₂H₅)₂NCS₂]₂Zn. Due to the MO doping, the degree of (1 1 1) preferential orientation of CdTe on the CdS layer is improved remarkably, influencing the increases in V_oc and F.F. Being almost independent of the kind of the MO compounds, the short circuit current increases due to increasing optical transmittance of the MO-doped CdS layers. As a result, utilizing MO-doped CdS, we have achieved the conversion efficiency of 15.1%.     

Low thermal drift in highly sensitive doped channel Al0.3Ga0.7As/GaAs/In0.2Ga0.8As micro-Hall element

Micro-Hall sensors with high sensitivity, low noise, and high thermal stability, 5 μm square, are fabricated using pseudomorphic Al_0.3Ga_0.7As/GaAs/In _y Ga_1-y As (0.2 ≤ y ≤ 0.3) heterostructures with Si-doped channels. The structures were optimized for thermal stability using a calculation of the self-consistent solution of Schrödinger-Poisson equations and Fermi-Dirac statistics in Hartree approximation. The optimized structure based on a Si-δ-doped 144 Å In_0.2Ga_0.8As quantum well embedded into uniformly doped GaAs channel showed thermal drifts of only 90 ppm·K^?1 in current drive mode and 192 ppm K^?1 in voltage drive mode. The measurements of the absolute magnetic sensitivity and the low frequency noise were done. The micro-Hall sensor, optimized for thermal drift, is able to resolve the magnetic field of 438 nT.     

Numerical analysis and synthesis of 2D quasi-optical reflectors and beam waveguides based on an integral-equation approach with Nystrom's discretization

Considered is the beam wave guidance and scattering by 2D quasi-optical reflectors modeling the components of beam waveguides. The incident field is taken as the complex-source-point field to simulate a finite-width beam generated by a small-aperture source. A numerical solution is obtained from the coupled singular integral equations (SIEs) for the surface currents on reflectors, discretized by using the recently introduced Nystrom-type quadrature formulas. This analysis is applied to study what effect the edge illumination has on the performance of a chain of confocal elliptic reflectors. We also develop a semianalytical approach for shaped reflector synthesis after a prescribed near-field pattern. Here a new point is the use of auxiliary SIEs of the same type as in the scattering analysis problem, however, for the gradient of the objective function. Sample results are presented for the synthesis of a reflector-type beam splitter.     

D'Alembert's Solution in Thermoelasticity—Impact of a Rod Against a Heated Barrier: Part I. A Case of Uncoupled Strain and Temperature Fields

The problem of impact of a thermoelastic rod against a heated rigid barrier is considered, in so doing lateral surfaces and free end of the rod are heat insulated, while there is either free heat exchange between the rod and the rigid obstacle within contacting end or ideal thermal contact, as a particular case. The rod's thermoelastic behavior is described by the Green–Naghdi theory of thermoelasticity. D'Alembert's method, which is based on the analytical solution of equations of the hyperbolic type describing the dynamic behavior of the thermoelastic rod, is used as the method of solution. This solution involves four arbitrary functions which are determined from the initial and boundary conditions and are piecewise constant functions. The procedure developed enables one to analyze the influence of thermoelastic parameters on the values to be found, as well as to investigate numerically the longitudinal coordinate dependence of the desired functions at each fixed instant of the time beginning from the moment of the rod's collision with the barrier up to the moment of its rebound. The case of uncoupled stress and temperature fields is examined in the first part of the paper, while the case of coupling thermoelasticity is considered in detail in the companion paper. It has been shown that the possibility for generating the reflected thermal wave from the incident elastic wave at the free rod's end is unavailable in the case of the uncoupled strain and temperature fields, and that the rod's rebound may occur either at the moment of arrival at the contact place of the reflected elastic wave from the incident thermal wave or at the time when the reflected elastic wave from the incident elastic wave reaches the contact point.     

Application of Thermodynamic and Kinetic Model for Converter Steelmaking to Optimize Manganese Yield in Crude Steel

A thermodynamic and kinetic model of the converter steelmaking process was developed allowing the analysis of the influence of the technological parameters, such as the amount and addition time of a charge material on the chemical composition of the crude steel. The process of the manganese ore addition to the converter to increase the final content of manganese in the crude steel was simulated. The optimal technological parameters for the enhancement of manganese yield were determined.