A probabilistic approach for the optimisation of ultrasonic array inspection techniques

AbstractUltrasonic arrays are now used routinely for the inspection of engineering structures in order to maintain their integrity and assess their performance. Such inspections are usually optimised manually using empirical measurements and parametric studies which are laborious, time-consuming, and may not result in an optimal approach. In this paper, a general framework for the optimisation of ultrasonic array inspection techniques in NDE is presented. Defect detection rate is set as the main inspection objective and used to assess the performance of the optimisation framework. Statistical modelling of the inspection is used to form the optimisation problem and incorporate inspection uncertainty such as crack type and location, material properties and geometry, etc. A genetic algorithm is used to solve the global optimisation problem. As a demonstration, the optimisation framework is used with two objective functions based on array signal amplitude and signal-to-noise ratio (SNR). The optimal use of plane B-scan and total focusing method imaging algorithms is also investigated. The performance of the optimisation scheme is explored in simulation and then validated experimentally. It has been found that, for the inspection scenarios considered, TFM provides better detectability in a statistical sense than plane B-scan imaging in scenarios where uncertainty in the inspection is expected

Understanding Emergency Relief Operations: Operation Lifeline Sudan and Beyond

This dissertation examines the problems of coordination and adaptation in integrated relief operations responding to complex humanitarian emergencies (CHE). It is an exploratory case study of the relief operation in Southern Sudan where a CHE has been ongoing since the mid-1980s. The study spans the 20 year-period from 1989 to 2009 with a focus on three points in time - 1989, 1998 and 2009 - when violence and acute food shortage threatened the lives of thousands of people. The study draws on the literature on CHE and coordination during relief operations while its theoretical framework is based on the literature on Organization Theory, Interorganizational Coordination Theory, Complex Adaptive Systems Theory, the Institutional Analysis and Development Framework, Lewin’s Force Field Theory and the Science of Networks. The study applies the theoretical framework and uses both descriptive analysis and social network analysis to study the relief operation within its dynamic environment. The descriptive analysis explains the background to the relief operation and enables me to account for the constellation of especial circumstances that led to the emergence of the operation at that specific time. The network analysis enables me to map the structure of the operation and the relationships among the actors and to understand how coordination takes place. Studying the relief operation at three points in time allows me to understand how the process of adaptation took place and how the operation evolved in response to the changes in its environment. The findings of the study reveal that the structure of the operation is a horizontal hierarchy characterized by interdependency and strong local connections between the actors which enable them to join their efforts when needed but also to have the ability to act independently. They also reveal that the environment in which a relief operation takes place have a strong impact on the operation while the operation itself impacts that environment. Over the period of 20 years, the structure of the relief operation changed little but its members changed and its scope and focus has also changed in response to changes in its environment

Oleic Acid Counters Impaired Blastocyst Development Induced by Palmitic Acid During Mouse Preimplantation Development: Understanding Obesity-Related Declines in Fertility

Obesity is associated with altered fatty acid profiles, reduced fertility, and assisted reproductive technology (ART) success. The effects of palmitic acid (PA), oleic acid (OA), and their combination on mouse preimplantation development, endoplasmic reticulum (ER) stress pathway gene expression, lipid droplet formation, and mitochondrial reactive oxygen species (ROS) were characterized. Two-cell stage mouse embryos collected from superovulated and mated CD1 females were placed into culture with KSOMaa medium, or PA alone or in combination with OA for 46 h. PA significantly reduced blastocyst development in a concentration-dependent manner, which was prevented by co-treatment with OA. PA and OA levels in mouse reproductive tracts were assessed by liquid chromatography coupled to mass spectrometry (LC-MS). LC-MS indicated higher concentrations of PA in the mouse oviduct than the uterus. Transcript analysis revealed that PA alone groups had increased ER stress pathway (ATF3, CHOP, and XBP1 splicing) mRNAs, which was alleviated by OA co-treatment. OA co-treatment significantly increased lipid droplet accumulation and significantly decreased mitochondrial ROS from PA treatment alone. PA treatment for only 24 h significantly reduced its impact on blastocyst development from the 2-cell stage. Thus, PA affects ER stress pathway gene expression, lipid droplet accumulation, and mitochondrial ROS in treated preimplantation embryos. These mechanisms may serve to offset free fatty acid exposure effects on preimplantation development, but their protective ability may be overwhelmed by elevated PA

Evaluation of the Efficiency of N-terminal Pro-B-type Natriuretic Peptide for Diagnosis of Acute Myocardial Infarction

Background: Cardiac diseases are one of the major causes of death worldwide with increasing incidence rate per year, particularly in developing countries such as Sudan owing to urbanization and changing lifestyle. Myocardial infarction is a consequence of the imbalance between the heart blood supply and the required heart cell; this disorder leads to necrosis of myocardium and may cause death. It could be diagnosed by at least two of the following criteria: chest pain, electrocardiography (ECG) elevation, and levels on cardiac biomarkers. This study aimed to evaluate the efficiency of N-terminal pro-B-type natriuretic peptide (NTproBNP) for the diagnosis of acute myocardial infarction (AMI).  Methods: This analytical case–control hospital-based study was conducted on a total of 70 individuals, of which 40 participants were suspected of or diagnosed with AMI, while 30 healthy subjects  were included as a control group. Three ml of venous blood were collected in lithium heparin containers. Troponin I (TnI) as a cardiac biomarker was measured by TOSOH AIA-360, while the NTproBNP level was detected using I-Chroma II. Personal and clinical data were collected directly from each participant using a predesigned questionnaire. Results: A significant increase in the TnI level (mean: 13.13 ± 18.9 ng/ml) and NTproBNP (mean: 5756.5 ± 8378.2 pg/mL) in AMI patients were detected when compared with control mean (0.02 ± 0.00 ng/ml and 57.8 ± 42.32 pg/mL, respectively). Conclusions: NTproBNP gave a high sensitivity (87.5%), specificity (100%), positive predictive value (100%), and negative predictive value (85.7%) in the diagnosis of AMI when compared with another cardiac biomarker such as TnI. Keywords: acute myocardial infarction, NTproBNP, troponin I, Medani Heart Center, Suda

Effect of Fibre Content on Compressive and Flexural Properties of Coconut Fibre Reinforced Epoxy Composites

Coconut fibre reinforced polymer composites are gaining popularity in the field of engineering due to the many benefits that come with them such as low cost of production, easy fabrication, enhanced strength compared to other polymer composites. Of late, there has been an increase in the use of composites that are naturally based because they have many benefits. In line with this, the current research is focused on the mechanical properties of coconut fiber reinforced epoxy composites. The effect of the fibre content on the flexural and compressive characteristics of the epoxy composites was investigated. Chemical treatment of the coconut fibres was performed using 50% bleaching concertation. The composites were fabricated in random orientations withe fibre length of 10 mm as recommended by the literature. Scanning Electron Microscopy (SEM) was used to examine the fractured surfaces. The main findings are that the increase in the volume fraction of the coconut fibre in the epoxy composites increases the flexural and compressive strengths. SEM showed that the main failure mechanisms were brittle nature in the epoxy regions and pullout and breakage of fibres in the coconut region

Multiphoton radiative recombination of electron assisted by laser field

In the presence of an intensive laser field the radiative recombination of the continuum electron into an atomic bound state generally is accompanied by absorption or emission of several laser quanta. The spectrum of emitted photons represents an equidistant pattern with the spacing equal to the laser frequency. The distribution of intensities in this spectrum is studied employing the Keldysh-type approximation, i.e. neglecting interaction of the impact electron with the atomic core in the initial continuum state. Within the adiabatic approximation the scale of emitted photon frequencies is subdivided into classically allowed and classically forbidden domains. The highest intensities correspond to emission frequencies close to the edges of classically allowed domain. The total cross section of electron recombination summed over all emitted photon channels exhibits negligible dependence on the laser field intensity.Comment: 14 pages, 5 figures (Figs.2-5 have "a" and "b" parts), Phys.Rev.A accepted for publication. Fig.2b is presented correctl

Charged domain walls as quantum strings living on a lattice

A generic lattice cut-off model is introduced describing the quantum meandering of a single cuprate stripe. The fixed point dynamics is derived, showing besides free string behavior a variety of partially quantum disordered phases, bearing relationships both with quantum spin-chains and surface statistical physics.Comment: 22 page, 17 figure

Spawning and larval rearing of goldlined seabream, Rhabdosargus sarba on Abu Al Abyad Island, United Arab Emirates

The goldlined seabream, Rhabdosargus sarba, a carnivorous and euryhaline sparid, is widely distributed in subtropical and tropical waters throughout the Indo-West Pacific including the Red Sea, East Africa, Madagascar, Australia, China and Japan (Leu 1994, Mihelakakis and Kitajima 1995, Radebe et al. 2002). It is a shallow-water species that is usually found around reefs with sandy bottoms. In some regions of the world, such as the waters of Hong Kong and South Africa, the fish is a protandrous hermaphrodite, but in other environments, including Western Australia, it is described as a rudimentary hermaphrodite (Hesp et al. 2004)