Multi-Mode Guided Wave Detection of Various Composite Damage Types

This paper presents a new methodology for detecting various types of composite damage, such as delamination and impact damage, through the application of multimode guided waves. The basic idea is that various wave modes have different interactions with various types of composite damage. Using this method, selective excitations of pure-mode guided waves were achieved using adjustable angle beam transducers (ABTs). The tuning angles of various wave modes were calculated using Snell’s law applied to the theoretical dispersion curves of composite plates. Pitch–catch experiments were conducted on a 2-mm quasi-isotropic carbon fiber-reinforced polymer (CFRP) composite plate to validate the excitations of pure fundamental symmetric mode (S0) and shear horizontal mode (SH0). The generated pure S0 mode and SH0 mode were used to detect and separate the simulated delamination and actual impact damage. It was observed that S0 mode was only sensitive to the impact damage, while SH0 mode was sensitive to both simulated delamination and impact damage. The use of pure S0 and SH0 modes allowed for damage separation. In addition, the proposed method was applied to a 3-mm-thick quasi-isotropic CFRP composite plate using multimode guided wave detection to distinguish between delamination and impact damage. The experimental results demonstrated that the proposed method has a good capability to detect and separate various damage types in composite structures

Demographic estimates from the Palaeolithic–Mesolithic boundary in Scandinavia: comparative benchmarks and novel insights

Prehistoric demography has recently risen to prominence as a potentially explanatory variable for episodes of cultural change as documented in the archaeological and ethnographic record. While this has resulted in a veritable boom in methodological developments seeking to address temporal changes in the relative size of prehistoric populations, little work has focused on the manner in which population dynamics manifests across a spatial dimension. Most recently, the so-called Cologne Protocol has led the way in this endeavour. However, strict requirements of raw-material exchange data as analytical inputs have prevented further applications of the protocol to regions outside of continental Europe. We apply an adjusted approach of the protocol that makes it transferable to cases in other parts of the world, while demonstrating its use by providing comparative benchmarks of previous research on the Late Glacial Final Palaeolithic of southern Scandinavia, and novel insights from the early Holocene pioneer colonization of coastal Norway. We demonstrate again that population size and densities remained fairly low throughout the Late Glacial, and well into the early Holocene. We suggest that such low population densities have played a significant role in shaping what may have been episodes of cultural loss, as well as potentially longer periods of only relatively minor degrees of cultural change. This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.publishedVersio

A novel model for smectic liquid crystals: Elastic anisotropy and response to a steady-state flow

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 145, 164903 (2016) and may be found at https://doi.org/10.1063/1.4965711.By means of a combination of equilibrium Monte Carlo and molecular dynamics simulations and nonequilibrium molecular dynamics we investigate the ordered, uniaxial phases (i.e., nematic and smectic A) of a model liquid crystal. We characterize equilibrium behavior through their diffusive behavior and elastic properties. As one approaches the equilibrium isotropic-nematic phase transition, diffusion becomes anisotropic in that self-diffusion D⊥ in the direction orthogonal to a molecule’s long axis is more hindered than self-diffusion D∥ in the direction parallel to that axis. Close to nematic-smectic A phase transition the opposite is true, D∥ < D⊥. The Frank elastic constants K1, K2, and K3 for the respective splay, twist, and bend deformations of the director field n̂ are no longer equal and exhibit a temperature dependence observed experimentally for cyanobiphenyls. Under nonequilibrium conditions, a pressure gradient applied to the smectic A phase generates Poiseuille-like or plug flow depending on whether the convective velocity is parallel or orthogonal to the plane of smectic layers. We find that in Poiseuille-like flow the viscosity of the smectic A phase is higher than in plug flow. This can be rationalized via the velocity-field component in the direction of the flow. In a sufficiently strong flow these smectic layers are not destroyed but significantly bent.DFG, 65143814, GRK 1524: Self-Assembled Soft-Matter Nanostructures at Interface

Psychiatric morbidity and marital satisfaction: an empirical study on spouse of alcohol dependent cases in Barak valley, North-East India

Background: Alcohol dependence poses serious threats to the healthy functioning of the family apparatus in a multitude of ways. The deleterious impact of alcohol dependence on the couple remains an area of genuine concern for mental health professionals across the world.Methods: 69 cases were selected consecutively from the Psychiatry Outpatient department fulfilling the ICD-10 criteria of alcohol dependence syndrome and the spouse of these cases were assessed to evaluate the pattern and severity of psychiatric morbidity and marital satisfaction. Statistical associations were found between the important variables.Results: Out of the 69 cases, we found that mean age of the alcohol dependent cases was 40.75±8.21 while that of their spouse was 33.91±7.86 years Most of the alcoholics had 1-9 years of alcohol dependence (86.95%) and severe alcohol dependence (47.82%) based on SADD score. Majority of the spouse of the alcoholics suffered from psychiatric illness (60.86%) with the most common diagnosis being depressive disorder (30.43%) based on ICD-10 criteria. Most of the spouse had lower level of marital satisfaction and presence of marital dissatisfaction was significantly associated with a more severe dependence among their alcoholic husbands. Increased duration of alcohol consumption was associated with higher severity of alcohol dependence. Also, the presence of psychiatric morbidity in the spouse was associated with increased years and higher severity of alcohol dependence.Conclusions: If the spouses are psychologically healthy, a good support system is ensured for them which is necessary to maintain motivation levels to leave alcohol

Study of prescription pattern in emergency psychiatry in a tertiary care academic hospital of a developing country: a retrospective study

Background: Prescription pattern study of psychotropic drugs gives a picture of drug preference and rationality of drug use by psychiatrists of a region. The aim of the study was to explore the prescription pattern of psychotropic drugs in emergency settings in a tertiary care centre in a developing country.Methods: A total of 1153 prescriptions were analysed in the study. Data was extracted retrospectively from the psychiatry department emergency register of a tertiary care hospital, in north-eastern India for a period of one year.Results: The most commonly used psychotropic drug in emergency setting was found to be anxiolytic and hypnotics (60.96%) in which clonazepam (48.6%) was commonest. Antipsychotics followed next (14.5%), out of which 69.6% were atypical antipsychotics with olanzapine being the commonest.Conclusions: Use of parenteral typical antipsychotic was found to be much higher, than expected. For the benefit of the mass, supply of cost effective parenteral atypical antipsychotics is the need of the hour in this part of the world

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae).

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. We have shown that the ventral surface of the suction disc is covered by dense arrays of microtrichia, which are stiff spine-like cuticular structures that only make tip contact. Our results demonstrate the impressive performance and versatility of blepharicerid suction organs and highlight their potential as a study system to explore biological suction mechanisms

Effective teaching: questioning teachers’ interactions with pupils in technology and design

Effective teachers create rich learning opportunities that foster understanding of key subject concepts, and part of their effectiveness is seen in the range and types of questions they ask pupils. While research literature on questioning abounds, little is written about how questioning theory develops capability within individual subjects. This paper examines teachers' questions from a subject perspective and links them to questioning theory by ranking within a hierarchy. Of 191 higher-order questions asked across 22 hours of Key Stage Three technology and design teaching in Northern Ireland, those questions relating to the key subject skill of analysing are examined. Data indicate that teachers' higher-order questions are used both to induce responses and as a model of pupils' own analyses of design factors. The study highlights the difficulty in maintaining higher-order responses from higher-order questions by showing how teachers further articulated the concept of analysis on the basis of limited pupil responses. We highlight the need for teachers to provide opportunities for pupils to respond in ways that reflect depth of understanding of key technology and design skills. The paper concludes with a brief discussion about how question analysis contributes to a greater understanding of teacher effectiveness in technology and design

3H-2,1-Benzoxaborole-1-spiro-4′-(5-oxa-3a-aza-4-borapyrene)

In the title compound, C20H14BNO2, the B atom has a tetra­hedral geometry with two short B—O and two long B—C and B—N bonds, revealing a significant difference between Car—O—B and Calk­yl—O—B bond distances. Inter­molecular Ar—H⋯O hydrogen bonds and strong π–π inter­actions (3.368 Å) between aromatic cores of neighbouring mol­ecules result in hexa­gonal channels along the crystallographic c axis, which are potentially accessible for small mol­ecules

Analytical and Numerical Modelling of Artificially Structured Soils

The effects of lime treatment on the mechanical properties of soils are usually not accounted for in the design of geotechnical structures. As a result the potential of lime treatment has not been fully exploited. In this thesis, a comprehensive experimental program has been carried out to identity the key features of the mechanical behaviour of structured materials. The chemical modifications arising from lime treatment were quantified using thermal analysis methods. From these results a non-linear chemo-mechanical coupling was established between the concentration of cementitious compounds and the yield stress. Using these results, a new formulation to model the degradation of the structure at yield has been developed and implemented in a constitutive model for structured materials. This new model, developed in the framework of the Modified Cam Clay model, requires a limited number of additional parameters that all have a physical meaning and can all be determined from a single isotropic compression test. The model has proven to be successful in reproducing the key features of structured materials and for the modelling of the mechanical behaviour of lime treated specimens under various stress paths. Due to similarities in behaviour, it is shown that the formulation is also suitable for naturally structured soils. To account for a structured material in the design of geotechnical structures, a fully functional finite element program for elasto-plastic problems was developed including the pre- and post-processing of the results. A thorough validation has confirmed the good implementation of the finite element method and its suitability for the modelling of complex geometries involving structured materials