5,122 research outputs found

    Fracture surface analysis in composite and titanium bonding

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    Carbon fibers were obtained from several manufacturers. Surface treatments were performed on these fibers by anodization. The surfaces of these fibers were analyzed by X-ray photoelectron spectroscopy and wetting force measurement. The breaking strength of these fibers was measured at 2.5 cm length. It was seen that the surface treatments reduces the strength of the fibers. It was also seen that the Hercules fibers had a higher breaking strength than the Union Carbide fibers. Fiber critical length measurements showed no difference in critical lengths between AS-4 and AU-4 fibers embedded in polysulfone. However, the fiber lengths were much shorter for the surface treated fibers. This effect could be related to increased adhesion between fiber and matrix, or it could be due to the lower breaking strength of the surface treated fiber

    Surface characterization in composite and titanium bonding

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    The failure surface analysis of adhesively bonded carbon fiber composites is described. The emphasis is on the bonding of composites when the surface has been made intentionally resin-rich. Also discussed is surface analysis of both commercially available and pretreated carbon fibers. The interaction of the fibers with polysulfone is described

    Fracture surface analysis in composite and titanium bonding: Part 1: Titanium bonding

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    Fractured lap shear Ti 6-4 adherends bonded with polyphenyquinoxaline (PPQ) and polysulfone were analyzed. The effects of adherend pretreatment, stress level, thermal aging, anodizing voltage, and modified adhesive of Ti 6-4 adherend bonded with PPQ on lap shear strength were studied. The effect of adherend pretreatment on lap shear strength was investigated for PS samples. Results of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) used to study the surface topography and surface composition are also discussed

    A contribution to the discussion on the safety of air weapons

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    Firearms legislation in the UK stems from the Firearms Act 1968 with its definition of a firearm as a lethal barrelled weapon of any description. The Act allows certain exceptions to be held without licence, most notably air weapons although these are limited by The Firearms (Dangerous Air Weapons) Rules 1969 and related regulations to below 12 ft lb (16.3 J) for air rifles and below 6 ft lb (8.1 J) for air pistols. Despite this there are occasional fatalities, typically 1 or 2 each year in the UK, from legally owned air weapons. In the USA there are over 20,000 visits each year to emergency departments due to injuries from air weapons and paintball guns. Despite this, limited research appears to have been carried out into the safety of air weapons and the present study tries to address this.Fresh samples of animal tissue were obtained from an abattoir or butcher and were embedded in ballistic gelatin. Pig heart, lung, liver and shoulder were used. By firing pellets into gelatin alone and into the combination of the gelatin and animal tissue it was possible to compare gelatin as a model for these tissues. The depth of penetration was similar but the residual track appeared to remain more open in the animal tissue. Pellets penetrated completely through the organ, with total penetration of gelatin and organ being typically around 10–15 cm.Samples of pig, cow and chicken skin were placed in contact with the gelatin or embedded in the gelatin to simulate the effect of skin on penetration into a body. Chicken skin had no effect, pig skin stopped the pellet and cow skin was perforated by the pellet. If cow skin was embedded in the gelatin there was little effect on the total amount of penetration, but cow skin on the front surface of the gelatin reduced penetration by about 30%.Computed tomography was used to examine the pellet track and to calculate the volume of damage produced. However, due to the similar densities of gelatin and organ a technique had to be developed to differentiate phases. A barium salt paste was applied to outer surfaces and iodine solution or barium nitrate solution containing red food colouring was injected into the pellet track to enhance the contrast of the track. The track through the gelatin tended to enclose itself whereas the track through the organ remained more open, presumably due to the inhomogeneity of the fibrous nature of the tissue.Pellets were also fired at construction materials (wood, plasterboard and brick) and computed tomography used to determine the volume of damage created. Pellets perforated single layers of wood and plasterboard and would embed in a second layer. However, if the two layers were in contact the pellet did not penetrate the first layer. An air rifle pellet could therefore perforate house construction materials, although the resultant kinetic energy would be low and further damage would be limited.Some of the possible physical parameters are discussed that might help predict the degree of damage caused, but from this study it is not possible to define a limit which could be proposed as safe

    Operator product expansions as a consequence of phase space properties

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    The paper presents a model-independent, nonperturbative proof of operator product expansions in quantum field theory. As an input, a recently proposed phase space condition is used that allows a precise description of point field structures. Based on the product expansions, we also define and analyze normal products (in the sense of Zimmermann).Comment: v3: minor wording changes, as to appear in J. Math. Phys.; 12 page

    Analyticity of the Scattering Amplitude, Causality and High-Energy Bounds in Quantum Field Theory on Noncommutative Space-Time

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    In the framework of quantum field theory (QFT) on noncommutative (NC) space-time with the symmetry group O(1,1)×SO(2)O(1,1)\times SO(2), we prove that the Jost-Lehmann-Dyson representation, based on the causality condition taken in connection with this symmetry, leads to the mere impossibility of drawing any conclusion on the analyticity of the 222\to 2-scattering amplitude in cosΘ\cos\Theta, Θ\Theta being the scattering angle. Discussions on the possible ways of obtaining high-energy bounds analogous to the Froissart-Martin bound on the total cross-section are also presented.Comment: 25 page

    Trait Anxiety as a Moderator of Problem Structuring Effects on Solution Generation

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    This study investigated the effects of problem structuring and anxiety on the quantity and quality of solutions generated for ill-structured, complex problems. Trait anxiety, the tendency to feel anxious across a wide variety of situations, has been shown to impair problem solving performance in certain conditions. Trait anxiety was examined as a possible moderator of the relationship between problem structuring and solution generation. Participants were 184 undergraduate psychology students. Participants completed a trait anxiety measure (State-Trait Anxiety Inventory; Spielberger, 1983) and generated solutions to an ill-structured problem, with varying levels of structuring (no objectives, one-objective-at-a-time, conflicting objectives). The quantity and resolving power of solutions generated was assessed by raters. Participants in the one-objective-at-a-time condition generated more solutions than those in the no objectives condition or the conflicting objectives condition, as predicted. Contrary to hypothesis, trait anxiety did not moderate the relationship between problem structuring and solution generation

    Contextual approach to quantum mechanics and the theory of the fundamental prespace

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    We constructed a Hilbert space representation of a contextual Kolmogorov model. This representation is based on two fundamental observables -- in the standard quantum model these are position and momentum observables. This representation has all distinguishing features of the quantum model. Thus in spite all ``No-Go'' theorems (e.g., von Neumann, Kochen and Specker,..., Bell) we found the realist basis for quantum mechanics. Our representation is not standard model with hidden variables. In particular, this is not a reduction of quantum model to the classical one. Moreover, we see that such a reduction is even in principle impossible. This impossibility is not a consequence of a mathematical theorem but it follows from the physical structure of the model. By our model quantum states are very rough images of domains in the space of fundamental parameters - PRESPACE. Those domains represent complexes of physical conditions. By our model both classical and quantum physics describe REDUCTION of PRESPACE-INFORMATION. Quantum mechanics is not complete. In particular, there are prespace contexts which can be represented only by a so called hyperbolic quantum model. We predict violations of the Heisenberg's uncertainty principle and existence of dispersion free states.Comment: Plenary talk at Conference "Quantum Theory: Reconsideration of Foundations-2", Vaxjo, 1-6 June, 200

    Volcanic Ash Contamination of High Voltage Insulators

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    Awarded Best Paper (Student) - Joint Winner - EEA Conference 2011Recent work in the University of Canterbury high voltage laboratory uncovered an interesting phenomenon. While studying the effect of volcanic ash contamination on high voltage insulator flashover levels, ash was seen ‘blowing’ off the insulator surface before flashover occurred. The goal of this project was to investigate and explain the observed phenomenon to provide a basis for potential development of self-cleaning insulators. Four different types of insulator and three different ash grain sizes were tested. The insulator electric fields were modelled; corona discharge waveforms and visual observations were obtained. Areas of ash removal coincided with areas of corona discharge. It was initially proposed that the ash was removed by an alternating current corona wind however the results do not support this theory. Instead, the observed results suggest that the ash acquires a negative charge and is removed by an electrostatic force. The electrostatic force is strongest during the negative half cycle of the applied voltage due to space charge and hence the ash pulses off the insulator at 50Hz. The amount of ash removed increased with the applied voltage however this led to a trade off between ash removal and flashover. The maximum amount of ash removed during this project was approximately 90% from the top weather shed and 30% from the middle and bottom weather sheds. This study focused on the removal of dry ash. It is unlikely that wet ash can be removed in this fashion, without flashover, due to the conductive and adhesive nature of wet ash

    The numerical study of the solution of the Φ04\Phi_0^4 model

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    We present a numerical study of the nonlinear system of Φ04\Phi^4_0 equations of motion. The solution is obtained iteratively, starting from a precise point-sequence of the appropriate Banach space, for small values of the coupling constant. The numerical results are in perfect agreement with the main theoretical results established in a series of previous publications.Comment: arxiv version is already officia
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