Simulation of cup-cone fracture using the cohesive model

The cohesive model is used for the prediction of the crack path during stable crack extension in ductile materials. The problem of crack-path deviation is investigated by means of simulation of crack propagation in a round tensile bar. The respective phenomenon is known as cup-cone fracture. It is shown that the model is able to predict the failure mechanism, which consists of normal fracture in the center and combined normal/shear fracture in the so-called “shear lips” at the specimen’s rim. The damage evolution and crack path predicted by the model are presented. The effect of the normal and shear failure parameters on the crack-deflection point and several aspects of the finite element mesh are discussed.     

The hydration phase and pore structure formation in the blends of sulfoaluminate-belite cement with Portland cement

Sulfoaluminate-belite (SAB) cements are an attractive class of low-energy cements from the viewpoint of saving energy and releasing less CO₂ into the atmosphere during their production. Their hydraulic activity, however, does not match that of the ordinary Portland cement (PC) and needs improvement before they can be used on their own. However, SAB cements when blended with PC have the potential to be used effectively in traditional applications as shown by this study. Mortars made with blends of SAB cements and PC, and a cement-to-sand ratio of 1:3 by weight and a water-to-cement ratio of 0.5, indicate a superior protection against corrosion of steel to those made with blends of PC and blast-furnace slag (BFSPC). The prepared mortars were stored at 20 °C for 90 days under either a 60% relative humidity (RH)-dry air, or 100% RH-wet air conditions. With further improvement in the SAB cement quality through better understanding of their characteristics, a genuine competition between SAB/PC and BFSPC can be expected in practice.     

Effect of irradiation with low-energy Ar ions on the characteristics of the working and rear sides of single-crystal GaAs substrate

Contactless methods were used to study the characteristics of the front and rear sides of single-crystal GaAs wafers whose rear side was irradiated with low-energy Ar ions. Variations in the optical and photoelectric properties of irradiated and unirradiated sides were detected. A solitonic mechanism for the penetration of defects into the crystal bulk is suggested.     

Conditions for the Acceptance of Deontic Conditionals.

Recent psychological research has investigated how people assess the probability of an indicative conditional. Most people give the conditional probability of q given p as the probability of if p then q. Asking about the probability of an indicative conditional, one is in effect asking about its acceptability. But on what basis are deontic conditionals judged to be acceptable or unacceptable? Using a decision theoretic analysis, we argue that a deontic conditional, of the form if p then must q or if p then may q, will be judged acceptable to the extent that the p & q possibility is preferred to the p & not-q possibility. Two experiments are reported in which this prediction was upheld. There was also evidence that the pragmatic suitability of permission rules is partly determined by evaluations of the not-p & q possibility. Implications of these results for theories of deontic reasoning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Erosion resistance of 40Kh steel after mechanical-pulse treatment

The mechanical-pulse treatment of 40Kh steel by means of frictional contact of the working surface with a special tool in different technological media enhances the resistance of steel to cavitation- erosion fracture. Mechanical-pulse treatment in a technological medium based on aqueous solutions of calcium and magnesium mineral salts enhances the resistance of 40Kh steel to cavitation- erosion fracture over the entire range of cavitation intensities under study.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 2, pp. 120–124, March–April, 2004.     

Performance failure analysis of EDFA cascades in optical DWDM packet-switched networks

A simple and comprehensive technique to determine the probability that a cascade of erbium-doped fiber amplifiers (EDFAs) may be driven into unacceptable regimes of bit error rate (BER) and/or gain levels is presented. This technique allows network designers to determine the tolerances by which the signal power levels may deviate from their predesigned average values and still give acceptable gain variances and BERs at the receiver. We show that even in the signal power range well above the receiver sensitivities (-38 dBm/ch) where the gain spread is not significant, the corresponding spread in BER due to random arrival of packets might result in unacceptable performance. We show for typical levels of operation, the BER temporarily (for about 3 /spl mu/s) deviates to below 10/sup -9/ (10/sup -15/) with a probability of 10/sup -3/ (10/sup -2/), for 100 (64) channels. We show that the gain spread for a single EDFA can be negligible for a range of signal and pump powers at a given average gain.     

Reactively sputtered MoO3 films for ammonia sensing

We report the gas-sensing properties of ion-beam sputter deposited MoO₃ thin-films. The change in the DC conductivity was measured in dry N₂ with 10% O₂ in the presence of up to 490 ppm of NH₃, NO, NO₂, C₃H₆, CO and H₂. At ∼440 °C the film was found to be very sensitive to NH₃, with 490 ppm increasing the conductivity by approximately a factor of 70. This was approximately 17 times greater than the response to the other gases. The NH₃ response was strongly affected by the accompanying levels of O₂, NO₂ and H₂O. For example, changing the accompanying O₂ levels from 1% to 20% decreased the NH₃ response by approximately a factor of 20. Similarly, the presence of 100 ppm NO₂ (in 10% O₂) decreased the NH₃ response by approximately a factor of three, and 1% water vapor decreased it by more than a factor of two. The NH₃ response, however, was relatively unaffected by 100 ppm of accompanying NO, C₃H₆, CO or H₂. XPS measurements show that the increased conductivity in the presence of NH₃ was also accompanied by a partial reduction of the surface MoO₃. We observed an increase in the resistance of the films after extended time at elevated temperatures.     

Log-domain wave filters

A systematic method for designing log-domain wave filters is presented. Wave filters simulate topologically and functionally passive doubly terminated LC ladder prototype filters of low sensitivity. The design in the log-domain is based on a transposition of the signal flow graph (SFG) that corresponds to the wave equivalent of elementary two-port blocks in the linear domain, to the corresponding log-domain SFG. This is achieved by using an appropriate set of complementary operators, in order to preserve the linear operation of the whole circuit. Simulation results of a fifth-order low-pass and a fourth-order bandpass log-domain wave filter are given, using HSPICE. The proposed circuits are suitable for low-voltage operation and in high-frequency applications.     

Electrotunable Non‐reciprocal Laser Emission from a Liquid‐Crystal Photonic Device

A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage.     

A digital quadrature modulator with on-chip D/A converter

The first analog IF mixer stage of a transmitter can be replaced with this digital quadrature modulator. The modulator interpolates orthogonal input carriers by 16 and performs digital quadrature modulation at carrier frequencies f/sub s//4, -f/sub s//4,f/sub s//2 (f/sub s/ is the sampling frequency). A 12-b digital-to-analog (D/A) converter is integrated with the digital quadrature modulator. A segmented current source architecture is combined with a proper switching technique to reduce spurious components and to enhance dynamic performance. The digital quadrature modulator is designed to fulfill the spectral, phase, and EVM specifications of GSM, EDGE, and WCDMA base stations. The die area of the chip is 27.09 mm/sup 2/ (0.35-/spl mu/m CMOS technology) and the total power consumption is 1.02 W with 2.8 V at 500-MHz output sampling rate (0.78-W digital modulator, 0.24-W D/A converter).