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The Rocket Experiment for Neutral Upwelling 2 (RENU2) rocket was launched on 13 December 2015 at 07:34 UT. The payload transited the cusp region during a neutral upwelling event, supported by a comprehensive set of onboard and ground-based instrumentation. RENU2 data highlight two important processes. One is that a proper understanding of neutral upwelling by Poleward Moving Auroral Forms (PMAFs) requires a treatment that mimics the quasiperiodic passage of a sequence of PMAFs. As a PMAF reaches a flux tube, its physical consequences must be determined including the residual history of effects from previous passages, implying that understanding such a process requires an accounting of the system hysteresis. Second, RENU2 observations suggest that neutral density enhancements driven by precipitation and/or Joule heating can be highly structured in altitude and latitude. In addition, timescales involving neutral dynamics suggest that the structuring must be slowly changing, for example, over the course of 10 to tens of minutes. publishedVersion

Measurement of ionospheric plasma is often performed by a single in situ device or remotely using cameras and radar. This article describes a small, low-resource, deployed spacecraft used as part of a local, multipoint measurement network. A B-field aligned sounding rocket ejects four of these spin-stabilized spacecraft in a cross pattern. In this application, each spacecraft carries two retarding potential analyzers which are used to determine plasma density, flow, and ion temperature. An inertial measurement unit and a light-emitting diode array are used to determine the position and orientation of the devices after deployment. The design of this spacecraft is first described, and then results from a recent test flight are discussed. This flight demonstrated the successful operation of the deployment mechanism and telemetry systems, provided some preliminary plasma measurements in a simple mid-latitude environment, and revealed several design issues.

Published laboratory measurements are found to agree with two groups' completely independent asymptotics for the decay and spread of transient pulses in a Debye model, and the spread in a Lorentz model. The measured dc-content pulses decay with depth nearly as x/sup -1/2/ (water) and x/sup -1/3/ (concrete) in coaxial cables. The measured full-widths at half-maximum spread nearly as the reciprocal of the decay rates.

Pultruded FRP bars of open cross-section possess relatively low transverse shear moduli in relation to their axial and flexural moduli. This can result in shear deformation constituting a significant proportion of the total deformation induced by non-uniform bending, and a reduction in the buckling loads of members subjected to axial compression and bending. Herein an approximate theory for quantifying the influence of shear deformation on the restrained torsional warping of pultruded FRP bars of open cross-section is presented. Contrary to expectations the theory indicates that the influence of shear deformation on the restrained warping torsional stiffness of such members is not significant. The theory is validated by a series of bending and torsion tests on three pultruded FRP I-beams.

The results of a series of fatigue tests, on slender plate girders subjected to repeated shear loading, are summarised and used to establish a lower bound fatigue strength curve for the welded web boundary, based on geometric or principal surface stress ranges. The propagation of a semi-elliptical surface crack, through the thickness of a plate, is studied using fracture mechanics concepts. An extensive parametric study indicates that the initial crack size and aspect ratio, the geometric stress concentration at the weld toe, and the plate thickness, all have a significant influence on fatigue strength. It is concluded that the fracture mechanics approach requires specification of a number of parameters which are difficult to determine in practice. However, having specified a realistic crack size and aspect ratio and an approximate stress concentration at the weld toe, the solution can be calibrated against available experimental fatigue strength curves.

A series of tests to investigate the fatigue strength of welded stud shear connectors, attached to the tension plates of steel–concrete–steel sandwich beams, is described. Results of the beam tests are compared with the results of a series of push shear tests and also with the S–N curve for welded stud connectors given in Eurocode 3. The fatigue strength of the stud connectors, determined from the beam tests, was significantly higher than the fatigue strengths determined from both the push shear tests and the EC3 S–N curve. It is concluded therefore that the EC3 S–N curve provides a satisfactory basis for fatigue assessment of welded stud connectors in steel–concrete–steel sandwich beams.

An experimental and theoretical investigation of the ultimate shear resistance of tapered aluminium girders is described. Failure of all the test girders occurred suddenly and catastrophically, with little warning, due to rupture of the welded web—flange boundary around the upper tension diagonal corner of the test panel. A simple analytical solution has been developed for predicting the ultimate shear resistance of such panels, which takes account of the reduced yield strength of the heat-affected weld zone and shows satisfactory correlation with the test results.

Numerical studies of geometric fatigue stresses induced by the breathing of slender steel web plates subjected to repeated shear loading are described. Analysis of available fatigue test results indicates that the Eurocode 3 detail category 125 fatigue strength curve is appropriate for fatigue assessment in terms of principal tensile surface stress ranges. Theoretical displacements, strains and stresses obtained using nonlinear finite element plate analysis show close correlation with test results.

A series of quasi-static load tests on steel-concrete-steel sandwich beams subjected to bending and transverse shearing forces is described. The observed modes of failure were yielding of the tension plate and slip yielding of the tension plate connectors. Significant shear cracking also occurred in several of the beams but was not the primary cause of failure. Details of the tests are presented and the results analysed in accordance with recently developed design procedures for steel-concrete-steel sandwich elements.

An approximate analysis of geometric fatigue stresses in slender web plates subjected to repeated shear loading is described. Theoretical predictions are compared with available test results, which are also analysed in accordance with Eurocode 3 fatigue assessment procedures.

A series of quasi-static and fatigue tests on short span, slender plate girders subjected to predominantly shear loading is described. The fatigue test results are presented in terms of the normalised load range versus the number of load cycles to failure, and compared with other available test data. A simple procedure for predicting the residual shear strength of a fatigue cracked web panel, based on an assumed equilibrium stress field, is developed and shows reasonable correlation with the test results.

Slender plates are used in a variety of structural engineering applications because of their high strength-to-weight ratio and their postbuckling reserve of stiffness and strength. However, relatively large out-of-plane displacements may be induced by in-plane loading close to or exceeding the buckling load, which in turn induces relatively high secondary bending stresses at welded plate boundaries. Under repeated loading the combined state of membrane and secondary bending stresses can result in fatigue cracking and premature failure. A series of fatigue tests on slender plate-girder webs subjected to repeated shear loading is described. Details of the test results presented include the load ranges and number of load cycles to fatigue failure, the location and extent of fatigue cracks, out-of-plane web deflections, and stress ranges at fatigue crack locations. The theoretical prediction of stress ranges at potential fatigue crack locations and fatigue-resistant design procedures are also discussed.

In recent years, steel plate shear walls have been used in a number of tall buildings, mainly in Japan and North America, to resist lateral forces induced by wind and earthquakes. The perceived advantages of such shear walls, in seismic resistant structures, are enhanced stiffness, strength and ductility, stable hysteretic characteristics and a large capacity for plastic energy absorption. They are also much lighter than equivalent reinforced concrete shear walls, which reduces the dynamic forces and loads on the foundations. Recent experimental and theoretical research into the structural performance of steel plate shear walls is discussed. Particular emphasis is given to the development of theoretical models for representing the hysteretic characteristics, which can be incorporated in nonlinear dynamic analyses of steel plate shear walls subjected to prescribed dynamic loading or ground motion.

WOS: 000301327000010 In this this study, a series of fatigue tests on six nominally identical push-shear specimens is conducted. The test specimens were subjected to an initial quasi-static test, up to a predefined maximum load, followed by a fatigue test to failure. For all the fatigue tests the mean applied load was the same while the load range varied to induce fatigue failure. The push-shear fatigue tests indicated that stiffness of the shear connections is gradually decreased during the test. Overall, the test results revealed that the lifetime of steel-concrete-steel sandwich systems under cycling loads could be predicted beforehand through the evaluation of the stiffness reduction in shear connections. (C) 2011 Elsevier Ltd. All rights reserved. European Coal and Steel Community; The Steel Construction Institute; Cardiff University of Wales This research was funded by the European Coal and Steel Community, The Steel Construction Institute and Cardiff University of Wales.

A series of fatigue tests on slender web plates, subjected to combined membrane and secondary bending stresses, is described. Results of the tests are presented and analysed, with particular emphasis on the complex state of stress at the welded web flange and web stiffener boundaries, and appropriate S-N relationships for predicting fatigue life.

A nonlinear analysis of the dynamic response of thin steel plate shear walls, based on a finite difference solution of the governing differential equations of motion, is presented. The equations of motion incorporate both shear and overall bending displacements of the shear wall. The hysteretic characteristics of the individual storeys, incorporated in the nonlinear analysis, include the influence of shear buckling and plastic yielding of the web plate and plastic yielding of the surrounding frame. The results presented validate the analysis for elastic response and demonstrate the effectiveness of the hysteretic characteristics in inhibiting resonance.

A theoretical and experimental study of the torsional and flexural properties of braced, thin-walled, open sections, such as elevator core shear walls in tall buildings, with lintel beams across the openings at each storey level, is described. The theoretical model developed is consistent with established open-section and closed-section behaviour at the two extremes of bracing, and takes into account the bending and shear deformation of the bracing beams, out-of-plane bending of the side walls and continuous shear flow around the contour of the assumed equivalent closed section. Theoretical results are compared, and show close agreement, with experiments on perforated, extruded, aluminium tubes. The results indicate a significant increase in torsional stiffness when distortion of the side walls is restrained by the presence of channel lips.

A series of quasti-static cyclic loading tests on unstiffened steel plate shear panels, with centrally placed circular openings, is described. All the panels tested exhibited adequate ductility and stable S-shaped hysteresis loops, with the energy absorbed per cycle increasing with the maximum amplitude of the shear displacement. The strength and stiffness of the panels decreased approximately linearly with increasing size of opening. Experimental results are compared with a previously developed theoretical model for predicting the hysteretic characteristics of unstiffened plate shear panels, which incorporates the influences of shear buckling and plastic yielding of the plate, and an assumed linear reduction in stiffness and strength to allow for openings.

A theoretical and experimental investigation of the flexural and torsional properties of doubly symmetric core shear walls, with lintel beams providing bracing across the openings at each storey level, is described. Such structures are used in tall buildings to support gravity loads and to resist horizontal forces induced by wind and earthquakes. The theoretical model developed is based on an equivalent closed section and is consistent with established open section and closed section behaviour at the two extremes of bracing. For intermediate bracing, the model incorporates the influences of bending and shear deformation of the bracing beams, out-of-plane bending of the side walls and continuousshear flow around the contour of the assumed equivalent closed section. The theoretical model is validated by a series of tests on perforated aluminium tubes, covering a wide range of lintel beam and effective side wall stiffnesses. The results indicate clearly that side wall distortion can reduce the torsional stiffness of such sections very significantly.

A nonlinear analysis of the dynamic response of thin steel plate shear walls, with fixed beam to column connections, based on a finite difference solution of the governing differential equation of motion, is presented. The hysteretic characteristics of steel plate shear walls, incorporated in the analysis, include the influence of shear buckling and plastic yielding of the web plate and plastic yielding of the surrounding frame. The results presented validate the analysis for elastic response and demonstrate the effectiveness of the hysteretic characteristics in inhibiting resonance under periodic dynamic loading.

A series of quasi-static cyclic loading tests on unstiffened plate shear panels is described. All the panels tested exhibited adequate ductility and stable S-shaped hysteresis loops, with the energy absorbed per cycle increasing with the maximum amplitude of shear displacement. A theoretical model for predicting the hysteretic characteristics is presented, which incorporates the influences of shear buckling of the web plate and plastic yielding of the web plate and surrounding frame. Theoretical predictions are compared and show satisfactory agreement with the experimental results. The simplicity of the theoretical model is such that it can be readily incorporated in nonlinear dynamic analyses of steel plate shear walls.

The measurement of plasma fluctuations by insertable probes is sometimes limited by the perturbation of the probe on the plasma, and some non-invasive diagnostics such as photodiode arrays can only measure integrated values. In this paper, we introduce a new approach to plasma fluctuation measurement using small, free-falling particles imaged with a fast camera to provide simultaneous multipoint measurement of visible light emissions surrounding each particle. We find that the fluctuations measured in this manner are in agreement with existing diagnostics, and the particle signals are correlated to those measured on inserted floating potential probes. Signals from multiple particles demonstrate an application of multipoint measurement of the plasma spatial structure and coherence.

A methodology for evaluating modular avionics applications in terms of life-cycle cost and system effectiveness is reported. The methodology is to be used to compare alternative modular architecture strategies as well as conventional strategies for introducing avionics into new or existing weapon systems. The process described is intended to be a flexible means of evaluating postulated alternatives for US Air Force-wide implementation of modular avionics. The analysis is expected to be performed using data normally available during the conceptual phase of a development program. Functions performed by avionics have been limited to navigation, communications, and some portion of fire control. The role of avionics, however, has steadily increased with each new generation of aircraft. It is argued that commonality of avionics elements within and among weapon systems may reduce both development cost and development risk. >

A theoretical study of the elastic buckling modes of I-section beams under various loading conditions is presented. The analysis is based on energy considerations and the energy equations governing instability are derived using plate theory to allow for distortion of the cross-section. The resulting analysis is able to predict lateral, local and distortional buckling modes. The results are compared with classical lateral buckling solutions based on beam theory.

Complete expressions for the strains, including second order terms, occurring in thin walled bars of open cross-section are derived. Shear deformation due to non-uniform bending and distortion of the cross-section are not considered in the present theory. The correctness of the expressions is verified by incorporating them in a general instability analysis based on energy considerations.

A general formulation for the analysis of composite beams with partial interaction, in which the basic equilibrium and compatibility equations are expressed in terms of displacements, is presented. Numerical solutions of the basic equations are obtained by expressing the displacement derivatives in finite difference form, and the solutions so obtained show close agreement with existing analytical solutions for linear material and shear connector behaviour.

Historically, studies of the effects of the main phytotoxic gases (SO2, O3, NOx and HF) have focused on determining the threshold for onset of visible foliar injury. The current U.S.A. air quality standards to protect vegetation (500 ppb SO2 for 3 h and 120 ppb O3 for l h not to be exceeded more than once per annum) are good examples of the use of this information in the regulatory process. More recently, research has focused on determining the thresholds for effects on economically important yield parameters irrespective of foliar injury. The implication is that long-term seasonal or annual standards may be required to prevent yield losses particularly for the primary pollutants in diffuse-source regions and for secondary pollutants. This paper reviews the literature on thresholds for yield effects of SO2 and O3 and concludes that 1. (a) the current EEC standard for SO2 is adequate to protect most crops and trees and 2. (b) more work is required to determine whether the U.S.A. threshold for O3 effects are applicable to the climate and crops of Europe. Recent results suggest that yield responses vary so much with climatic factors that broad regional standards may not be acceptable. In addition, the effect of one phytotoxic gas must now be assessed against the background of the other gases. Future research on effects of SO2 and O3 in particular, will be increasingly influenced by the use of cost-benefit analysis in the regulating process and the consequent demand for dose-response relationships. This approach is fraught with difficulty and particular problems arise 1. (a) when ‘hypothetical’ relationships are assumed in the absence of good data and 2. (b) when the linearity of dose-response relationships are presumed to justify the extrapolation from effects at high concentrations to lower ambient concentrations. The evidence for nutritional effects of low levels of SO2 and NOx abrogates this assumption and suggests that for some gases at least, there should be a threshold below which no detrimental effects occur. This paper reviews the recent work aimed at producing dose-response relationships for economically important yield parameters.

The results of a number of tests on deep fibre reinforced concrete beams are presented. The beams contained conventional tensile steel reinforcement but different percentages of steel fibre in place of conventional shear reinforcement. All beams were simply supported and loaded to failure by a central load distributed through two bearing plates. The results confirm that steel fibres can prevent shear failure in deep beams, and also indicate the various modes of failure of deep beams.

An exact theory is developed for fields due to currents in the presence of an anisotropic slab. The anisotropy is of a type expected of a composite reinforced with unidirectional fiber and is described by a diagonal matrix in Maxwell's equations. A Green's matrix is defined with exact and explicitly computed solutions to Maxwell's equations for point currents. The Green's matrix reduces to quadrature the problems, in frequency and time domains, of computing the field produced inside and outside a slab by arbitrary current sources. Steady-state AC current sheets and loops are considered, and numerical results are presented. >

A systematic series of tests to determine the strength of small scale model, laterally unrestrained, doubly symmetric and monosymmetric beams is described. The test results demonstrate that the current ultimate limit state design curves are conservative and will yield lower bound predictions with significant margins.

A theoretical study, based on energy considerations, is made of the flexural-torsional instability of compound monosymmetric beams, composed of two monosymmetric beams, joined by a connection having finite stiffnesses less than those required to provide fully composite action. The stabilizing effect of partially composite sheet cladding is included in the analysis.

Energy equations governing the goemetrically nonlinear behaviour of thin walled bars of open cross-section when subjected to axial, flexural and torsional displacements, are derived. The equations are based on the assumption of small displacements and linear elastic material behaviour. Shear deformations due to nonuniform bending, and distortion of the cross-section are not included in the analysis. Solutions of the governing nonlinear equations are obtained by the finite element method, making use of linearised mid-increment stiffness matrices. The results of the geometrically nonlinear analysis are combined with an approximate failure criterion to predict the failure loads of I beams having initial imperfections. The predicted failure loads are compared, and show satisfactory agreement, with existing experimental results.

A model-based algorithm is developed for inverting eddy-current data and reconstructing flaws in advanced composite materials. The model incorporates an integral solution that is built around the Green's function computed in a companion paper. The application of certain least-squares algorithms and a numerical method of analytical continuation are described. Numerical experiments are carried out for a simulated flaw in graphite-epoxy. >

An experimental study of the strengthening of under-reinforced concrete beams, by bolting thin steel plates to the tension faces of the concrete, is described. The results indicate that a significant increase in both the stiffness and ultimate moment of resistance can be achieved by such a technique and that the improved performance is quantifiable using conventional calculations.

The advantage of using a linearized mid-increment stiffness matrix in the finite element incremental analysis of nonlinear structures is demonstrated. The method is applied to the post-buckling analysis of an imperfect strut and plate. Features of the paper are a clear presentation of the incremental process, the use of Marguerre's shallow shell theory to avoid transformations between local and global axes, and tne calculation of stresses in the post-buckled state. The computational similarity of the incremental and Newton-Raphson iterative processes is pointed out.

This article describes the design of a digital rock‐dust meter suitable for measuring the rock‐dust content in coal‐rock‐dust mixtures in a mine environment. The work discusses the probe, digital circuitry, and equations used by the instrument. Data from several mines verifying the 2% accuracy of the device is also presented.