An approximate expression for the motional capacitance of a lateral field resonator

A simple approximate expression is obtained for the motional capacitance of a lateral-field quartz resonator. Comparison with measured values for fundamental-mode and third-overtone SC-cut resonators shows agreement within 10-50%     

A comparison of neutron-induced SEU rates in Si and GaAs devices

The single-event-upset rates due to neutron-induced nuclear recoils have been calculated for Si and GaAs components using the HETC and MCNP codes and the ENDF data base for (n, p) and (n, alpha) reactions. For the same critical charge and sensitive volume, the upset rate in Si exceeds that of GaAs by a factor of about 1.7, mainly because more energy is transferred in neutron interactions with lighter Si nuclei. The upset rates due to neutrons are presented as functions of critical charge and atmospheric altitude. Upsets induced by cosmic-ray nuclei, secondary protons and neutrons are compared.     

On the concept of relative and plastic spins and its implications to large deformation theories. Part II: Anisotropic hardening plasticity

Summary By resorting to both microscopic and macroscopic considerations, including the concept of single slip, dislocation stress, and a scale invariance argument we show that the notion and formalism of the relative spin introduced in Part I reduces to that of plastic spin previously recognized in the literature. The central feature of this reduction is the possibility of obtaining physically based constitutive equations for the plastic spin along with appropriate evolution equations for the dislocation or back stress. When these constitutive models are incorporated in the analysis of existing data on tension-torsion tests, we find satisfactory agreement between theory and experiment. In particular, a theoretical interpretation of the torsionally induced axial strain, as observed for example by Swift, Bailey et al., Hart and Chang, and others, is provided. Moreover, the recent experiments of Montheillet et al. on torsionally induced axial stresses are discussed in the light of the presently proposed models of large inelastic deformation inelasticity accounting for anisotropy and texture effects.

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With 12 Figures     

Don't let safety happen by accident

Get ready to update and improve your company's safety program. On pages 24-38, you'll find a comprehensive guide to safe industry practices to enhance your operation and help you stay in compliance with OSHA regulations such as the General Duty Clause and the Right-to-Know law. Achieving a safe, healthy, productive, and profitable business doesn't happen by accident. It takes upper-management commitment to improve equipment, procedures, and employee training. Managers have a personal and a legal responsibility for employees' safety on the job. Don't delay safety improvements!     

Observations of slip patterns on the surface of fatigued gold using the scanning tunnelling microscope

Observations of fatigue-induced slip patterns on the surface of polycrystalline gold (+99.9%) using the scanning tunnelling microscope (STM) are presented. The samples were cycled in four-point bending between zero and 0.0025 strain for 250 and 2500 cycles. STM observations of the sample fatigued for 250 cycles revealed broad slip bands 0.38–0.69 m wide containing narrow slip bands 0.015–0.123 m wide and fine slip lines 0.006 m wide. The depth of these features are 20–57 nm for broad slip bands, 3–7 nm for narrow slip bands, and approximately 2–4 nm for fine slip lines. The sample fatigued for 2500 cycles showed similar values for the width of the slip bands and slip lines except that their depth was increased by a factor of between 2 and 4 times for the narrow slip bands and the fine slip lines. Apparent persistent slip bands (PSBs) spaced 2.4 m, 300–500 nm deep were also observed. These results demonstrate that STM is a significant new tool for observing and distinguishing various types of fatigue-induced surface slip patterns on suitably prepared samples. The vertical resolution obtained with STM is vastly superior to current SEM and TEM methods.     

Aspects of modeling the frequency response of a two-port waveguide-coupled SAW resonator-filter

Coupling-of-modes-in-time and coupling-of-modes-in-space analyses are applied to the modeling of a two-port two-pole waveguide-coupled SAW resonator filter. Modeling is applied to a lumped equivalent circuit and a distributed circuit. While the accuracy of the coupling estimation dictates the exact mode-splitting and bandwidth, the ensuing computations can give a good representation of the amplitude and phase response, including the effect of degenerate transverse modes.     

Improved processing for oil well cement evaluation-a with theoretical and laboratory data

A processing technique to measure cement impedance from ultrasonic pulse-echo waveforms, called normalized single mode (NSM) processing, is described. The technique is based on a physical model that represents the transducer in terms of its continuous plane wave kernel. Narrowband filtering to process a single resonant mode and all processing parameters are normalized to the modal frequency. The performance of NSM and a digital simulation of the present analog commercial processing, W2/W1, is compared for several environmental effects: casing thickness, eccentering, and added Gaussian noise. The computation is based on waveforms from a mathematical model and laboratory data. Results on model data show that NSM processing significantly reduces the impedance errors due to thickness variations, eccentering, and noise. Results on laboratory data indicate that the techniques yield comparable results for smooth machined casings, but that NSM processing significantly reduces measurement error and variance in a sample of the actual oil field casing.