Impact perforation testing of stab-resistant armour materials

This paper describes the development of a method for the investigation and comparison of materials for use in stab resistant body armour. A number of polymer composite panels of different thicknesses and construction have been tested. A dynamic test which simulated the real threat has been used and the results compared to a simpler quasi-static test that might be used in initial materials selection. The materials tested were glass-epoxy, and glass-nylon composite panels of several thicknesses between 1.8 and 5.8mm. Additional tests were also performed on similar composites containing tungsten wires. An accelerated instrumented drop-tower was used to drive a knife through composite panels and record the force resisting penetration by the knife. The final penetration of the knife through the armour into a soft backing was also measured. For comparison,a similar geometry quasi-static test was carried out on the same specimens. It was found that energy absorbtion took the form of an initial resistance to perforation and then by a resistance to further penetration. This is thought to stem from resistance to cutting ofthe panel material and gripping of the knife blade. The energy required to produce a given penetration in dynamic tests was found to be in good agreement with the penetration achieved at similar energies under quasi-static conditions. For the materials tested there was no significant difference between the penetration resistance of single or two layer systems. The penetration achieved through a panel of a given material was approximately proportional to the inverse square of the panel's thickness. The relative performance of different armour materials was assessed by plotting the energy required to penetrate a fixed distance against the areal density of the panel

AP Adjacency as a Precedence Constraint

Attributive APs precede certain other categories (PPs, genitive DPs, and so on), when the noun precedes both (Giurgea 2009, Adger 2012). This observation may suggest an analysis in terms of X-bar-style ‘structural layering’. However, such an account faces several problems: (i) in languages with PP-AP-N order, scrambling of the AP is permitted, (ii) in languages with AP-N- PP order or PP-N-AP order, there is evidence that the AP can c-command the PP, as well as the other way around, and (iii) in languages with N-AP-PP order, the AP can take scope over the PP, as well as the other way around, arguably as a consequence of a structural ambiguity. We therefore develop an alternative analysis based on a striking parallel between the syntax of attributive APs and that of objects: while OV languages systematically allow adverbs to intervene between object and verb, VO languages tend to require verb-object-adverb order. This aspect of verbal syntax is familiar and can be captured in terms of a well-known linear constraint: Case Adjacency (Stowell 1981; Janke and Neeleman 2012). We propose that this constraint has a nominal counterpart that ensures N-AP adjacency in noun-initial structures. Thus, this instance of NP/VP parallelism has its source in parallel constraints, rather than parallel structural layers

What Divides, and What Unites, Right-Node Raising

We argue, following Barros and Vicente (2011), that right-node raising (RNR) results from either ellipsis or multidominance. Four considerations support this claim. (i) RNR has properties of el- lipsis and of multidominance. (ii) Where these are combined, the structure results from repeated RNR: a pivot created through ellipsis contains a right-peripheral secondary pivot created through multidominance. (iii) In certain circumstances, one or the other derivation is blocked, so that RNR behaves like pure ellipsis or pure multidominance. (iv) Linearization of RNR-as-mul- tidominance requires pruning. The same pruning operation delivers RNR-as-ellipsis, which ex- plains why the two derivations must meet the same ordering constraints

Transmission electron microscopy investigation of segregation and critical floating-layer content of indium for island formation in InGaAs

We have investigated InGaAs layers grown by molecular-beam epitaxy on GaAs(001) by transmission electron microscopy (TEM) and photoluminescence spectroscopy. InGaAs layers with In-concentrations of 16, 25 and 28 % and respective thicknesses of 20, 22 and 23 monolayers were deposited at 535 C. The parameters were chosen to grow layers slightly above and below the transition between the two- and three-dimensional growth mode. In-concentration profiles were obtained from high-resolution TEM images by composition evaluation by lattice fringe analysis. The measured profiles can be well described applying the segregation model of Muraki et al. [Appl. Phys. Lett. 61 (1992) 557]. Calculated photoluminescence peak positions on the basis of the measured concentration profiles are in good agreement with the experimental ones. Evaluating experimental In-concentration profiles it is found that the transition from the two-dimensional to the three-dimensional growth mode occurs if the indium content in the In-floating layer exceeds 1.1+/-0.2 monolayers. The measured exponential decrease of the In-concentration within the cap layer on top of the islands reveals that the In-floating layer is not consumed during island formation. The segregation efficiency above the islands is increased compared to the quantum wells which is explained tentatively by strain-dependent lattice-site selection of In. In addition, In0.25Ga0.75As quantum wells were grown at different temperatures between 500 oC and 550 oC. The evaluation of concentration profiles shows that the segregation efficiency increases from R=0.65 to R=0.83.Comment: 16 pages, 6 figures, 1 table, sbmitted in Phys. Rev.

Optical studies of distortions of metal surfaces produced by indenting

The definitions and types of measurement of hardness are reviewed with special reference to the static indentation test. The present state of the theory of static indentation hardness testing of metals is described, together with previous measurements of the distortions of metal surfaces caused by indenting. Multiple beam interferometry is employed to measure the surface distortions. The apparatus and techniques employed, which include the application of multilayer dielectric films to the interferometrie study of metal surfaces, are described. The specific aspects of the surface distortions studied are: (1) Flow pattern shape, with special reference to the transition from ridging to sinking impressions, and variations due to the geometric shape of the indentation. (2) Volume of the flow pattern. This is found to be smaller than the volume of the indentation for all the indentations studied. Possible explanations of this discrepancy are discussed. (3) Shallowing or elastic recovery of ball indentations. The shallowing of ball indentations in a wide range of metals is studied, and its variation with load, hardness, and indenter is analysed. (4) The shape of recovered ball indentations. Shallow ball indentations are found to be not strictly spherical, in contrast to deeper ball indentations. Measures of their deviation from sphericity are proposed and an explanation of these deviations is discussed. (5) Critical specimen size. The mode of deformation occurring when a hardness test indentation is made near to the edge of the specimen is studied. The results are compared with the mode of deformation for wedge indentations in ideal and real metals. On the basis of the results a fuller description of the processes involved in ball hardness tests is possible. The surface distortions from the onset of plasticity to the fully plastic stage are described in detail, and support Tabor's theory of ball indentation. The treatment of the hardness test as predominantly a problem in plasticity is justified.<p

Unusual features in the nonlinear microwave surface impedance of Y-Ba-Cu-O thin films

Striking features have been found in the nonlinear microwave (8 GHz) surface impedance $Z_s=R_s + jX_s$ of high-quality YBaCuO thin films with comparable low power characteristics [$R_{res}\sim 35--60 \mu\Omega$ and $\lambda_L(15 K)\sim 130--260 nm$]. The surface resistance $R_s$ is found to increase, decrease, or remain independent of the microwave field $H_{rf}$ (up to 60 mT) at different temperatures and for different samples. However, the surface reactance $X_s$ always follows the same functional form. Mechanisms which may be responsible for the observed variations in $R_s$ and $X_s$ are briefly discussed.Comment: 4 pages, 4 figure

Single Electron Transistors

Contains description of one research project and a list of publications.Joint Services Electronics Program Contract DAAL03-92-C-0001National Science Foundation Grant ECS 88-13250National Science Foundation Grant ECS 92-0342

The theoretical and practical determination of clinical cut-offs for the British Sign Language versions of PHQ-9 and GAD-7.

BACKGROUND: The PHQ-9 and the GAD-7 assess depression and anxiety respectively. There are standardised, reliability-tested versions in BSL (British Sign Language) that are used with Deaf users of the IAPT service. The aim of this study is to determine their appropriate clinical cut-offs when used with Deaf people who sign and to examine the operating characteristics for PHQ-9 BSL and GAD-7 BSL with a clinical Deaf population. METHODS: Two datasets were compared: (i) dataset (n = 502) from a specialist IAPT service for Deaf people; and (ii) dataset (n = 85) from our existing study of Deaf people who self-reported having no mental health difficulties. Parameter estimates, with the precision of AUC value, sensitivity, specificity, positive predicted value (ppv) and negative predicted value (npv), were carried out to provide the details of the clinical cut-offs. Three statistical choices were included: Maximising (Youden: maximising sensitivity + specificity), Equalising (Sensitivity = Specificity) and Prioritising treatment (False Negative twice as bad as False Positive). Standard measures (as defined by IAPT) were applied to examine caseness, recovery, reliable change and reliable recovery for the first dataset. RESULTS: The clinical cut-offs for PHQ-9 BSL and GAD-7 BSL are 8 and 6 respectively. This compares with the original English version cut-offs in the hearing population of 10 and 8 respectively. The three different statistical choices for calculating clinical cut-offs all showed a lower clinical cut-off for the Deaf population with respect to the PHQ-9 BSL and GAD-7 BSL with the exception of the Maximising criteria when used with the PHQ-9 BSL. Applying the new clinical cut-offs, the percentage of Deaf BSL IAPT service users showing reliable recovery is 54.0 % compared to 63.7 % using the cut-off scores used for English speaking hearing people. These compare favourably with national IAPT data for the general population. CONCLUSIONS: The correct clinical cut-offs for the PHQ-9 BSL and GAD-7 BSL enable meaningful measures of clinical effectiveness and facilitate appropriate access to treatment when required

Incommensurate Spin Density Waves in Iron Aluminides

Neutron diffraction in Fe(Al) reveals incommensurate spin density waves (SDWs) in alloys known to be spin glasses. The wave vectors for crystals of Fe(34Al), Fe(40Al), and Fe(43Al) show n varying from 11 to 6 for →q=2π(h±1/n,k±1/n,l±1/n)/a0, where (h,k,l) and a0 characterize the parent bcc lattice of the CsCl structure. The magnetic reflections are present far above the spin-glass freezing temperatures. These SDWs keep the spins on nearest-neighbor Fe atoms close to parallel, in contrast with SDWs in Cr, which keep nearest-neighbor spins close to antiparallel