Application of adaptive antenna techniques to future commercial satellite communication

The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further sub-divided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems

Application of adaptive antenna techniques to future commercial satellite communications. Executive summary

The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further subdivided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems

Capsule Endoscopy in Celiac Disease

Capsule endoscopy (CE) has been increasingly used for diagnosing disease of the small bowel. It is an attractive technique for assessing celiac disease (CD) because it is noninvasive and provides a close and magnified view of the mucosa of the entire small bowel. The aim of this paper is to update the current data on the use of CE for diagnosing villous atrophy and complications of CD

Sensitivity analysis of 1-d steady forced scalar conservation laws

We analyze 1 - d forced steady state scalar conservation laws. We first show the existence and uniqueness of entropy solutions as limits as t→ ∞ of the corresponding solutions of the scalar evolutionary hyperbolic conservation law. We then linearize the steady state equation with respect to perturbations of the forcing term. This leads to a linear first order differential equation with, possibly, discontinuous coefficients. We show the existence and uniqueness of solutions in the context of duality solutions. We also show that this system corresponds to the steady state version of the linearized evolutionary hyperbolic conservation law. This analysis leads us to the study of the sensitivity of the shock location with respect to variations of the forcing term, an issue that is relevant in applications to optimal control and parameter identification problems

Compressible primitive equation: formal derivation and stability of weak solutions

We present a formal derivation of a simplified version of Compressible Primitive Equations (CPEs) for atmosphere modeling. They are obtained from $3$-D compressible Navier-Stokes equations with an \emph{anisotropic viscous stress tensor} where viscosity depends on the density. We then study the stability of the weak solutions of this model by using an intermediate model, called model problem, which is more simple and practical, to achieve the main result

Damage mode identification in transverse crack tension specimens using acoustic emission and correlation with finite element progressive damage model

© 2018 Elsevier Ltd In this study, damage progression in unidirectional composite specimens is investigated. Transverse Crack Tension specimens are used to stimulate damage in a predetermined progressive sequence. Acoustic Emission (AE) registration technique and its location detection capability is used to identify and locate the damage modes during the tension tests. The k-means++ algorithm is applied to cluster similar AE events and obtain reliable correlations between the damage modes and AE characteristics. Damage modes at the end of interrupted tests are identified under an optical microscope and correlated with locations of AE clusters. It is seen that matrix cracks have high amplitude and duration, whereas delaminations have low amplitude and mid-duration, and fibre breaks have high average frequency characteristics. A finite element analysis was performed to predict the progressive failure behaviour including intralaminar failure and delaminations. The correlations between the AE clusters and damage modes are validated with the finite element model

Turkish Foreign Policy Toward the Algerian War of Independence (1954-62)

Turkish foreign policy toward the Algerian War of Independence (1954-62) was construed as persistent Turkish endorsement of official French positions generating abiding resentment among the states of the Third World, especially Arab states, and understandably in Algeria, which was to elicit backlashes from the Third World states thereafter consequently causing substantial complications in Turkish foreign policy. Stressing the importance of incorporating nonmaterial and ideational factors in analyses of foreign policy, two arguments are put forward in this article for an accurate explanation of Turkish foreign policy toward Algerian War of Independence. First, it was the conception of the West, defined not only in strategic or military terms, but also in ideational and civilizational terms that induced Turkish policy-makers to adopt insular policies regarding Algeria. Second, a "temporal contextualization" of Turkish foreign policy during the Algerian War of Independence is required for a proper understanding of Turkish foreign policy toward the Algerian War of Independence. © 2012 Copyright Taylor and Francis Group, LLC

Do high frequency acoustic emission events always represent fibre failure in CFRP laminates?

© 2017 Elsevier Ltd When damage in carbon fibre reinforced composites (CFRP) is monitored by acoustic emission (AE), it is a common belief that high frequency AE events originate from fibre failure. This shows that this statement may not correspond to the reality, and matrix cracks can emit high frequency AE signals. Quasi-static tension of [−45 2 /0 2 /+45 2 /90 2 ] s laminates was monitored by AE, Digital Image Correlation (DIC) on the surface of the sample and in-situ optical microscopy on the sample's polished edge. Unsupervised k-means clustering algorithm was applied to the AE results. By comparison with the direct DIC and microscopic observations, the AE cluster with high frequency and low amplitude was found to correspond to directly observed matrix cracks

Multi-instrument in-situ damage monitoring in quasi-isotropic CFRP laminates under tension

© 2018 Digital Image Correlation monitoring of the surface strains, microscopic in-situ observations of the micro-damage on the specimen edge and Acoustic Emission (AE) are utilized simultaneously during tension tests of quasi-isotropic carbon fibre reinforced polymer composites. It is found that the cluster analysis for characteristic parameters of AE events (the main being the signal amplitude and frequency) does not unambiguously identify the type of damage which causes the event. With optical instruments, it is observed that the signatures of AE events depend on the position of the ply where damage happens and on the ply orientation (90° vs 45°). Robust evidences for the variations in AE characteristics of damage modes in different lay-ups are presented. AE events, originated from surface cracks, have high amplitude and low frequency, whereas AE events, originated from transverse cracks in the inner plies, have low amplitude and high frequency characteristics. Any conclusion for fibre breaks are not reached in this study. Therefore, measurements in this study rather point out that the AE events, which could be interpreted as fibre breaks because of their high frequency characteristics, as optical observations prove, correspond to other damage types in quasi-isotropic laminates