Displacement Discontinuity Method for Fracture Mechanics Analysis of Reissner Plates: Static and Dynamic

This paper is concerned with the displacement discontinuity method applied to the shear deformable plates (Reissner’s and Mindlin’s theories) with cracks subjected to static and dynamic loads. Fundamental solutions of dislocation are derived using the Fourier transform method and the Laplace transformation technique. Boundary integral equations are presented in terms of rotations/displacement on the crack surfaces. The Chebyshev polynomials of the second kind are used to evaluate the integral equations with hypersingular kernels on the crack boundaries and determine the stress intensity factors at the crack tips. Comparisons are made with other numerical solutions to demonstrate the proposed method is accurate both for static and dynamic problems.     

Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor.

In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study.     

Microwave Parametric Frequency Dividers With Conversion Gain

A novel active parametric frequency divider configuration using coupled microstrip transmission lines and two balanced pseudomorphic HEMTs (pHEMTs) is presented. The analysis of the divide-by-2 circuit presented applies the principles of subharmonic generation using a nonlinear reactance to an active semiconductor device such as a pHEMT. A 2-1-GHz active analog frequency divider is designed and fabricated, with measurements showing a 20% bandwidth, 13.5-dB conversion gain, and harmonic rejection levels of more than 22 dBc. A maximum conversion gain of 18 dB is also achieved. These higher conversion efficiencies and the ability to cascade dividers allow for higher order division ratios to be achieved with the same topology.     

Effect of shape on the radiation-stimulated deformation of crystals

Translated from Atomnaya Énergiya, Vol. 66, No. 3, pp. 208–209, March, 1989.     

The effect of OPWF filler on impact strength of glass-fiber reinforced epoxy composite

In the present study, oil palm wood flour (OPWF) particles with less than 250 μm sizes have been used as filler materials in the woven-glass-fiber reinforced epoxy composite. The hybrid composites were fabricated using a hand lay-up method and cured at room temperature under a compressive load of 196 N (20 kg). The OPWF of 2.5 to 10 parts per hundred (pph) by weight was used to evaluate its effect on impact strength of the hybrid composites at a range of temperature from −50 to 50 °C. The impact strength, evaluated using V-notch Charpy method, showed reduction with increasing filler content up to 5 pph and then the strength increment in those composites containing more than 5 pph OPWF. More severe damages were found in specimens with higher filler contents resulting higher energy absorption during impact. The composites with a large amount of OPWF particles deflected crack propagation paths or created obstacles at the crack tips and increased toughness of the composites. The impact strength was found to decrease when the samples fractured at subzero temperatures and this happened because of the reduction of the matrix ductility at lower temperatures.     

Phosphine-induced sterility in Ephestia cautella (Lepidoptera: Pyralidae)

The present study was conducted to explore the sterilizing effect of phosphine on Ephestia cautella. Three to four-day old pupae were exposed to 0, 0.007, 0.014, 0.021, 0.028, 0.035, 0.042 and 0.049 mg/l of phosphine for 24 h at room temperature. The normally developed adults of each treatment were pair mated and several physiological and genetical parameters were investigated. The results showed gradual increases with dose in pupal mortality and adult malformation. The crossing results showed no changes in adult longevity and mating frequency. However, consistent reduction was noted in the fecundity and fertility of normally emerged adults. Preliminary data indicated similar levels of inherited sterility in the F₁ adults raised from the above mentioned crosses.     

Micro-RBS characterisation of the chemical composition and particulate deposition on pulsed laser deposited Si1−xGex thin films

The formation and deposition of particulates by pulsed laser deposition of Si_1−xGe_x semiconductor alloy thin films are discussed. Using Rutherford backscattering spectrometry with micrometer lateral resolution (micro-RBS) the film composition was measured with high accuracy, even in the presence of particulates with a high areal density of 20,000–30,000 particulates per mm². We show that on impact of a particulate, the part of the thin film which is already deposited probably melts and its Ge content segregates to the surface.     

Methods for Estimating Theoretically the Influence of Ion Scattering and Reflection on the Isotopic Sensitivity of Static Magnetic Mass-Spectrometers

For purposes of optimizing ion-optical systems, analyzer construction, and pump placement in static magnetic mass-spectrometers for isotopic analysis of uranium compounds, a comparative analysis is made and a review is given of methods described in the literature for theoretical estimates of the influence of scattering and reflection of ions on the isotopic sensitivity. Conclusions which make it possible to solve the problem are drawn.     

Making combination drawing methods more efficient by controlling tool microroughness

Results are presented from extensive comparison studies of drawing operations performed with the use of drawplates whose working surfaces have an irregular or regular microroughness. Regularizing the microroughness of the working part of the drawplate makes it possible to control the dimensional accuracy of the resulting products within broad ranges of values.     

Calcium and phosphorus levels as indices of textured milk proteins being substituted for meat proteins

Textured milk proteins were tested in a meat model system with an exchange level of 34-87% of the meat proteins. The correlation between the substitution index and the calcium and phosphorus content was statistically significant.