LOCAL DISTORTIONS AND VOLUME CHANGES IN SEMICONDUCTORS - DONORS IN SILICON

Experiments giving impurity-induced lattice distortion can measure quite distinct quantities. In particular EXAFS (extended X-ray fine structure) measures nearest-neighbour distances, whereas both volume changes and recent spectroscopic data measure long-range displacements. The relationship between the two depends strongly on the inter-atomic potential. The authors analyse this for impurities in silicon by adopting a variety of current potentials. There is a significant contradiction between the EXAFS results and the other experiments for all of the inter-atomic potentials. This problem may be associated with the high oxygen concentrations of Czochralski crystals used in the EXAFS study

Mathematical control of complex systems

Copyright © 2013 ZidongWang et al.This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Characterisation of friction and lubrication regimes in premium tubular connections

A friction test rig has been developed to carry out repeated sliding friction tests for premium tubular connections. The test rig enables accurate measurement of friction in various contact regimes which are relevant to the threaded connections between tubular components. Higher load tests can simulate the contact in metal-to-metal seals under very high contact pressures by using perpendicular pin-on-pin tests. The contact in the thread loading flank under intermediate pressures can be simulated by using larger radius coupon-on-coupon tests. The measured coefficient of friction is well correlated with a lubrication parameter combining lubricant film thickness and initial surface roughness. © 2012 Elsevier Ltd. All rights reserved

Mathematical control of complex systems 2013

Mathematical control of complex systems have already become an ideal research area for control engineers, mathematicians, computer scientists, and biologists to understand, manage, analyze, and interpret functional information/dynamical behaviours from real-world complex dynamical systems, such as communication systems, process control, environmental systems, intelligent manufacturing systems, transportation systems, and structural systems. This special issue aims to bring together the latest/innovative knowledge and advances in mathematics for handling complex systems. Topics include, but are not limited to the following: control systems theory (behavioural systems, networked control systems, delay systems, distributed systems, infinite-dimensional systems, and positive systems); networked control (channel capacity constraints, control over communication networks, distributed filtering and control, information theory and control, and sensor networks); and stochastic systems (nonlinear filtering, nonparametric methods, particle filtering, partial identification, stochastic control, stochastic realization, system identification)

Seismic behavior of building frames considering dynamic soil-structure interaction

The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soilstructure interaction (SSI) influences. The result of the first three of these factors is referred to as free-field ground motion. The structural response to free-field motion is influenced by the SSI. In particular, accelerations within structures are affected by the flexibility of the foundation support and variations between the foundation and free-field motions. Consequently, an accurate assessment of inertial forces and displacements in structures can require a rational treatment of SSI effects. In the current study, to depict these effects on the seismic response of moment-resisting building frames, a 10-story moment-resisting building frame resting on a shallow foundation was selected in conjunction with three soil types with shear-wave velocities of less than 600 m/s, representing Soil Classes Ce, De, and Ee according to an existing Australian Standard. The structural sections were designed after applying dynamic nonlinear time-history analysis, based on both the elastic method, and inelastic procedure using the elastic-perfectly plastic behavior of the structural elements. The frame sections were modeled and analyzed using the finite-difference method andthe FLAC 2D software under two different boundary conditions: (1) fixed-base (no SSI) and (2) considering the SSI. Fully nonlinear dynamic analysis under the influence of various earthquake records was conducted and the results of the two different cases for elastic and inelastic behavior of the structuralmodel were extracted, compared, and discussed. The results indicate that the performance level of themodel resting on Soil Class Ce does not change substantially and remains in the life safe level while the performance level of themodel resting on Soil Classes De and Ee substantially increase from the life safe level to near collapse for both elastic and inelastic cases. Thus, considering SSI effects in the elastic and inelastic seismic design of concrete moment-resisting building frames resting on Soil Classes De and Ee is essential. Generally, by decreasing the dynamic properties of the subsoil such as the shear-wave velocity and shear modulus, the base shear ratios decrease while interstory drifts of the moment-resisting building frames increase relatively. In brief, the conventional elastic and inelastic design procedure excluding the SSI is not adequate to guarantee structural safety for moment-resisting building frames resting on Soil Classes De and Ee. © 2013 American Society of Civil Engineers

Detail design, building and commissioning of tall building structural models for experimental shaking table tests

Copyright © 2015 John Wiley & Sons, Ltd. Summary In the areas of seismic engineering, shaking table tests are powerful methods for assessing the seismic capacity of buildings. Since the size and capacity of existing shaking tables are limited, using scale structural models seems to be necessary. In recent years, many experimental studies have been performed using shaking table tests to determine seismic response of structural models subjected to various earthquake records. However, none of the past research works discussed practical procedure for creating the physical model. Therefore, in this study, a comprehensive procedure for design, building and commissioning of scale tall building structural models has been developed and presented for practical applications in shaking table test programmes. To validate the structural model, shaking table tests and numerical time history dynamic analyses were performed under the influence of different scaled earthquake acceleration records. Comparing the numerical predictions and experimental values of maximum lateral displacements, it became apparent that the numerical predictions and laboratory measurements are in a good agreement. As a result, the scale structural model can replicate the behaviour of real tall buildings with acceptable accuracy. It is concluded that the physical model is a valid and qualified model that can be employed for experimental shaking table tests

The Neuroscience Peer Review Consortium

As the Neuroscience Peer Review Consortium (NPRC) ends its first year, it is worth looking back to see how the experiment has worked

Room reflections and constancy in speech-like sounds: within-band effects

The experiment asks whether constancy in hearing precedes or follows grouping. Listeners heard speech-like sounds comprising 8 auditory-filter shaped noise-bands that had temporal envelopes corresponding to those arising in these filters when a speech message is played. The „context‟ words in the message were “next you‟ll get _to click on”, into which a “sir” or “stir” test word was inserted. These test words were from an 11-step continuum that was formed by amplitude modulation. Listeners identified the test words appropriately and quite consistently, even though they had the „robotic‟ quality typical of this type of 8-band speech. The speech-like effects of these sounds appears to be a consequence of auditory grouping. Constancy was assessed by comparing the influence of room reflections on the test word across conditions where the context had either the same level of reflections, or where it had a much lower level. Constancy effects were obtained with these 8-band sounds, but only in „matched‟ conditions, where the room reflections were in the same bands in both the context and the test word. This was not the case in a comparison „mismatched‟ condition, and here, no constancy effects were found. It would appear that this type of constancy in hearing precedes the across-channel grouping whose effects are so apparent in these sounds. This result is discussed in terms of the ubiquity of grouping across different levels of representation

Pricing Multi-Unit Markets

We study the power and limitations of posted prices in multi-unit markets, where agents arrive sequentially in an arbitrary order. We prove upper and lower bounds on the largest fraction of the optimal social welfare that can be guaranteed with posted prices, under a range of assumptions about the designer's information and agents' valuations. Our results provide insights about the relative power of uniform and non-uniform prices, the relative difficulty of different valuation classes, and the implications of different informational assumptions. Among other results, we prove constant-factor guarantees for agents with (symmetric) subadditive valuations, even in an incomplete-information setting and with uniform prices