Analysis of externally loaded bolted joints : analytical, computational and experimental study

The behaviour of a simple single-bolted-joint under tensile separating loads is analysed using conventional analytical methods, a finite element approach and experimental techniques. The variation in bolt force with external load predicted by the finite element analysis conforms well to the experimental results. It is demonstrated that certain detailed features such thread interaction do not need to be modelled to ensure useful results. Behaviour during the pre-loading phase of use agrees with previous long-standing studies. However, the pre-loading analysis does not carry over to the stage when external loading is applied, as is normally assumed and it is shown that the current, conventional analytical methods substantially over-predict the proportion of the external load carried by the bolt. The basic reason for this is shown to be related to the non-linear variation in contact conditions between the clamped members during the external loading stage

Environmental (waste) compliance control systems for UK SMEs

While the ‘environment’ is often perceived as a heavily regulated area of business, in reality, directly-regulated businesses represent a small proportion of the business community. This study aimed to evaluate and outline potential improvements to compliance controls for small and medium-sized enterprises (SMEs), particularly those involved in the waste sector. Forty-four SMEs from England were interviewed/audited between April-September 2008. Using a UK-based system as a case-in-point, the Environment Agency’s (EA) Operational Risk Appraisal (‘Opra’)/Compliance Assessment Report (CAR) system was analysed. Environmental compliance performance indicators and an initial assessment methodology for SMEs were developed. The study showed:• Compliance with permitting legislation was poor in many areas.• Regulatory authorities are either unable/failing to implement their enforcement policies or unable/failing to identify non-compliances due to the infrequency or limited nature of their inspections.• Improvements are needed to the EA Opra/CAR system – control measures are not fully taken into account when calculating risk.Recommendations to improve SME compliance controls include using internationally applicable general and specific compliance and non-compliance performance indicators, re-designing the Opra system and using an initial assessment methodology based on understanding the hazardousness of SME categories, compliance levels and operator competency.<br/

Some magnetic effects of clustering in iron doped magnesium oxide

The growth of a magnesioferrite precipitate in iron doped (˜lOOOOppm wt.) magnesium oxide crystals, heat treated at 973K in oxygen, is studied with torque, magnetisation and magnetic resonance measurements. The torque and magnetisation results are in agreement with a model which assumes that the precipitate grows by diffusion limited Ostwald ripening.The effects of the particle size distribution and cubic magnetocrystalline anisotropy of the orientated octahedral precipitate particles on the magnetisation and torque curves are calculated. A magnetometrie demagnetisation tensor is defined for assemblies of orientated dipoles, its variation with the assembly size is investigated and used to calculate the longitudinal demagnetisation factors of octahedra. The ferromagnetic resonance spectra obtained were not in agreement with the generally used theory of de Biasi and Devezas (J. Appl. Phys. (1978)49, 2466). A new theory, based on a spin Hamiltonian, of the FMR response of an anisotropic superparamagnet is proposed and compared with some of the experimental spectra

The neutron charge form factor in helium-3

In order to measure the charge form factor of the neutron, $G^n_E(Q^2)$, one needs to use a neutron bound in a nuclear target. We calculate the change in the form factor for a neutron bound in $^3He$, with respect to the free case, using several versions of the quark meson coupling model. It is found that the form factor may be suppressed by as much as 12% at $Q^2 = 0.5{GeV}^2$ with respect to that of the free neutron.Comment: 13 pages including 2 ps figure

Comparisons of Supergranule Characteristics During the Solar Minima of Cycles 22/23 and 23/24

Supergranulation is a component of solar convection that manifests itself on the photosphere as a cellular network of around 35 Mm across, with a turnover lifetime of 1-2 days. It is strongly linked to the structure of the magnetic field. The horizontal, divergent flows within supergranule cells carry local field lines to the cell boundaries, while the rotational properties of supergranule upflows may contribute to the restoration of the poloidal field as part of the dynamo mechanism that controls the solar cycle. The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended length. It is of interest to study whether the convective phenomena that influences the solar magnetic field during this time differed in character to periods of previous minima. This study investigates three characteristics (velocity components, sizes and lifetimes) of solar supergranulation. Comparisons of these characteristics are made between the minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008, respectively. It is found that whereas the lifetimes are equal during both epochs (around 18 h), the sizes are larger in 1996 (35.9 +/- 0.3 Mm) than in 2008 (35.0 +/- 0.3 Mm), while the dominant horizontal velocity flows are weaker (139 +/- 1 m/s in 1996; 141 +/- 1 m/s in 2008). Although numerical differences are seen, they are not conclusive proof of the most recent minimum being inherently unusual.Comment: 22 pages, 5 figures. Solar Physics, in pres

Induced currents in the quantum Hall regime: energy storage, persistence, and I-V characteristics

Copyright © 2012 American Physical SocietyInduced currents associated with the quantum Hall effect are studied in the temperature range 39 mK to 1.6 K, and at Landau-level filling factors ν=1,2,3,4, and 6, using torsion-balance magnetometry. A quantitative link is demonstrated between (nonlinear induced current) vs (inducing electromotive force) curves, and the subexponential decay of the induced current in a static magnetic field. The energy storage in the induced currents is reexamined with the conclusion that the predominant mechanism for storage is inductive, through the mutual inductance between the sample and the magnet, not capacitive as previous reports have assumed. The temperature dependencies of the currents are consistent with previous models, except for a low-temperature saturation at filling factors ν=1 and ν=2, which we attribute to electron heating

Coherent excitation of the singlet-triplet mixed 1s4f state of helium

In this paper, we present a detailed theoretical description for the coherent electron-impact excitation, the subsequent time evolution, and the cascading decay process of the singlet-triplet mixed 1s4f state of helium. The excitation amplitude and phase of each sublevel of this state are related to measurable coincidence intensities and polarizations of the emitted photons. It is found that the intensity and polarization of the emitted photons are time modulated due to the singlet and triplet mixing in the 1s4f state

Periplasmic expression of Pseudomonas fluorescens peroxidase Dyp1B and site-directed mutant Dyp1B enzymes enhances polymeric lignin degradation activity in Pseudomonas putida KT2440

Expression of lignin-oxidising Pseudomonas fluorescens Dyp1B in the periplasm of Pseudomonas putida KT2440, using a tat fusion construct, was found to lead to enhanced whole cell activity for oxidation of DCP and polymeric lignin substrates. Four amino acid residues predicted to lie at the manganese ion binding site of Pseudomonas fluorescens peroxidase Dyp1B were investigated using site-directed mutagenesis. Mutants H127R and S223A showed 2-fold and 4-fold higher kcat for Mn(II) oxidation respectively, and mutant S223A showed 2-fold enhanced production of low molecular weight phenolic products from a polymeric soda lignin. The mutant Pfl Dyp1B genes were expressed as tat fusions to investigate their effect on lignin oxidation by P. putida KT2440

A combined SAXS/WAXS investigation of the phase behaviour of di-polyenoic membrane lipids

AbstractReal-time measurements of the SAXS/WAXS diffraction patterns of aqueous dispersions (1:1 wt/wt) of the di-polyenoic lipids di-18:2 PC, di-18:3 PC, di-18:2 PE and di-18:3 PE were made over the temperature range 10° to about −80°C. The results of these measurements were compared to similar measurements performed on the corresponding di-18:0 and di-18:1 derivatives. SAXS measurements of the temperature dependence of lamellar repeat distances show that the di-polyenoic lipids undergo broad second-order transitions between their gel and liquid-crystal lamellar phases spanning 30–40°C. The di-18:1 and di-18:0 derivatives, in contrast, undergo abrupt first-order transitions. The gel phases of the di-18:0 derivatives are characterised by two-component WAXS patterns with a sharp component close to 0.42 nm and a broader component at narrower spacings. On cooling, these lipids appear to undergo an initial transition to an Lβ, phase followed by a conversion to an Lc phase. The gel phases of the di-18:1 derivatives also show two-component patterns but with the sharp component centred closer to 0.44 nm. The di-polyenoic lipids, in contrast, are characterised by a single broad peak centred at a spacing of about 0.42 nm, close to that of conventional Lβ, phases. The changes in lamellar repeat distance accompanying the transitions in the di-monoenoic and di-polyenoic lipids, all of which occur in the frozen state, are very similar, indicating that the acyl chains of the polyenoic lipids are close to their maximum extension in the gel state. The WAXS patterns of the polyenoic lipids suggest that the saturated upper parts of the acyl chains are packed on a regular hexagonal lattice while their polyunsaturated termini remain relatively disordered

Neural changes following cognitive behaviour therapy for psychosis: A longitudinal study

A growing body of evidence demonstrates that persistent positive symptoms, particularly delusions, can be improved by cognitive behaviour therapy for psychosis. Heightened perception and processing of threat are believed to constitute the genesis of delusions. The present study aimed to examine functional brain changes following cognitive behaviour therapy for psychosis. The study involved 56 outpatients with one or more persistent positive distressing symptoms of schizophrenia. Twenty-eight patients receiving cognitive behaviour therapy for psychosis for 6–8 months in addition to their usual treatment were matched with 28 patients receiving treatment as usual. Patients’ symptoms were assessed by a rater blind to treatment group, and they underwent functional magnetic resonance imaging during an affect processing task at baseline and end of treatment follow-up. The two groups were comparable at baseline in terms of clinical and demographic parameters and neural and behavioural responses to facial and control stimuli. The cognitive behaviour therapy for psychosis with treatment-as-usual group (22 subjects) showed significant clinical improvement compared with the treatment-as-usual group (16 subjects), which showed no change at follow-up. The cognitive behaviour therapy for psychosis with treatment-as-usual group, but not the treatment-as-usual group, showed decreased activation of the inferior frontal, insula, thalamus, putamen and occipital areas to fearful and angry expressions at treatment follow-up compared with baseline. Reduction of functional magnetic resonance imaging response during angry expressions correlated directly with symptom improvement. This study provides the first evidence that cognitive behaviour therapy for psychosis attenuates brain responses to threatening stimuli and suggests that cognitive behaviour therapy for psychosis may mediate symptom reduction by promoting processing of threats in a less distressing way