Micro-crack ultrasound scattering in anisotropic composite laminates

A computational model of ultrasound scattering by micro-cracks in fiber reinforced polymer laminates is presented, foundational to study of micro-crack induced ultrasound attenuation. A model for transmission scattering response is developed using a boundary integral formulation, and associated approximate scattering theories are discussed. Numerical results are presented demonstrating application of the model to laminates containing distributed micro-cracking

The effect of crack morphology on ultrasonic response

A numerical study is presented of the influence of crack morphology on ultrasonic pulse-echo response. Crack morphology is described as a planar crack onto which a random normal direction deviation is imposed with a specified tangential correlation length. Pulse-echo responses for ensembles of random crack profiles are computed as a function of profile height, correlation length, crack length, angle of incidence, wave mode type and signal bandwidth. Mean and variance of signal peak amplitude are compiled. Limits of validity of a Kirchhoff scattering approximation are observed through comparison to boundary element method (BEM) predictions

Guided wave signal transport in curved and tapered plates

A numerical study is presented of the influence of plate curvature and taper on the transport of ultrasound guided wave signals for nondestructive evaluation (NDE) and structural health monitoring (SHM) applications. Model formulations for transmission at sharp transitions in plate curvature and thickness taper are summarized. Results are presented showing that transitions in plate curvature and tapered plate thickness have minimal effect on signal transmission efficiency when associated characteristic dimensions are large compared to plate thickness

Deviance or acceptable difference: Observance of the Law in Romans 14–15 and Dialogue with Trypho 47

Utilising the symbolic interactionist study of deviance, this article compares the treatment of Law-observant Christ-followers in Romans 14–15 and Justin Martyr’s Dialogue with Trypho 47, in order to understand better the declining status of Law-observant Christ-followers in the early Christ-movement. The ‘strong’ in Romans 14:1–15:13 are likely Christ-followers who do not observe the Law, whilst the ‘weak’ are likely Christ-followers who do. Although Paul accepts Law-observant Christ-followers, his preference for non-observance decreases the status of those who observe the Law, thereby undermining Paul’s vision of a unified, ethnically mixed Church. In Dialogue 47, Justin intensifies the marginalisation of Law-observant Christfollowers by placing them at the very limits of orthodoxy. Dialogue 47 suggests that the campaign for the legitimacy of Law-observant Christ-following was already failing by the middle of the 2nd century, largely because of Paul’s own preference for non-observant Christfollowing.HTS Teologiese Studies/Theological Studies 68(1), 201

Porosity Characterization in Fiber-Reinforced Composites by Use of Ultrasonic Backscatter

The use of ultrasonic backscatter to characterize anomalous states in fiber-reinforced composites has received considerable attention in recent years. The ultrasonic backscatter from composites with oriented fiber reinforcement, unlike that from monolithic materials, displays a strong angular dependence. Hence, three independent variables are available over which to analyze the backscatter. These are the azimuthal angle ∅ (the rotation orientation of the composite plate about the perpendicular), the elevation angle θ (the angle between the ultrasonic beam and the perpendicular to the insonified composite plate), and time. Bar-Cohen and Crane [1] considered various ways of exploiting the angular dependence of backscatter to examine anomalies in composite laminates such as fiber misalignment, cracks, and porosity. Several other efforts employing similar approaches have followed [2–4]. This paper addresses specific questions concerning the angular dependence of backscatter and the use of this angular dependence to assess porosity levels. Additionally, problems inherent in the analysis of the temporal behavior of backscatter are discussed, and an approach to the spectral analysis of backscatter for porosity assessment is demonstrated

Expanded Criminal Defense Lawyering

This review collects and critiques the academic literature on criminal defense lawyering, with an emphasis on empirical work. Research on criminal defense attorneys in the United States has traditionally emphasized scarcity of resources: too many people facing criminal charges who are “too poor to pay” for counsel and not enough funding to pay for the constitutionally mandated lawyers. Scholars have focused on the capacity of different delivery systems, such as public defender offices, to change the ultimate outcomes in criminal cases within their tight budgetary constraints. Over the decades, however, theoretical understandings of the defense attorney’s work have expanded to include client interests outside the criminal courtroom, reaching the broader social conditions connected to the alleged criminal act. Researchers have responded by asking a broader range of questions about the effectiveness of defense counsel outside the courtroom and by using improved data to study the effectiveness of lawyers at discrete procedural stages

A phenomenological investigation of middle school children\u27s experience of getting into trouble

The purpose of this study was to investigate the experience of trouble from the young adolescent\u27s perspective. A phenomenological approach was used to investigate the adolescents\u27 experience of trouble. The participants were asked, Tell me about a time you got in trouble. The nine participants described the experience of trouble as containing three major themes grounded in an Other and Time. As the experience of trouble unravels the participants become aware of each theme in a specified sequence. These themes are brought in to awareness beginning with the presence of an Other, then an awareness of the Others power and finally a sense of no control when the Powerful Other takes everything away. The Other is the most powerful influence in the adolescent\u27s experience. If we desire to see changes in the adolescent and future society, then the Other will need to change the experience of trouble that leaves the adolescent better than they were found if at all possible

Sensor-Craft Analytical Certification

This study developed a multi-disciplinary conceptual design of a joined-wing sensor-craft. Initial analysis was conducted using an aluminum model. Linear fully stressed design and flexible aerodynamic trim were used to converge to a minimum weight design that was aerodynamically stable. This optimized design was buckling safe. A similar optimization process using non-linear fully stressed design and flexible aerodynamic trim was conducted. The non- linear structurally deformation was over ten times greater than the linear structural deformation. Again, the model was structurally and aerodynamically optimized. The linear optimization was repeated using a composite structural model incorporating Conformal Load-bearing Antenna Structures. This research demonstrated the importance of considering non- linearity and the coupling of aero dynamic and structural design

Support minimized nonlinear acoustic inversion with absolute phase error correction

The predominant factors which prohibit the inversion of acoustic scattering data for the purposes of flaw characterization are 1) limited angular access to the flaw, 2) limited temporal frequency signal bandwidth, and 3) lack of absolute phase information between individual measurements (zero of time problem). An additional complication which impedes the data inversion is the non-linear dependence of the scattering data on the scattering object. This problem must be handled by either linearizing the problem or by applying an iterative procedure which may have questionable convergence properties. An approach to data inversion is presented here which shows potential in overcoming the aforementioned difficulties. This approach compensates for the lack of data by constructing a solution which yields simulated scattering consistent with the measured data, while simultaneously minimizing a functional measure of the support (i.e. volume) of the flaw. Such an approach to limited data inversion has proven effective in limited view X-ray CT applications when reconstructing discontinuous boundary flaws such as cracks and inclusions [1, 2, 3]. The application presented here is by-and-large analogous to the X-ray CT application, except for the additional complication of the lack of absolute phase between measurements. This zero-of-time problem is handled here by treating the absolute phase of each measurement as a variable in the minimization of the flaw support