Interacting stress concentration factors and their effect on fatigue of metallic aerostructures

During fabrication of certain aerostructure components, a situation can arise where a hole is mislocated so that it interferes with a radius, chem-mill step, machined step, or some other similar detail. The interaction of stress concentration effects between a hole and step are not well understood and the resulting impact on fatigue performance is difficult to predict. There exists a need for fatigue data that can be used to determine the analysis methods for evaluation of the interaction of machined steps and fastener holes. In this dissertation, the effect of stress concentrations placed in close proximity to each other and their impact on fatigue performance is studied. Unique cases of interaction between a hole and radius are analyzed. Physical testing and finite element analysis methods are used to derive the stress concentration factor (SCF, Kt) modification factors (Ktf) for open hole and joint assembly structures. The most conservative factors derived are recommended for use in fatigue analysis for these instances of holes located at or near radii. The SCF mod factors increase as distance between the hole and radius tangent decreased. For associated geometry, loading and materials similar to those presented within this research, a Ktf value of 1.22 is suggested for use in fatigue analysis of these situations of holes intersecting a radius.Kt and Ktf values have a significant effect on fatigue lifetimes and resulting fatigue margins of safety. Based on a pass/fail experiment, the corrosion specimen passed the test as no fatigue cracking failures associated with the bolt in radius condition were observed --Abstract, page iii

Flowstats: an ontology based network management tool

One of the problems that hinders large scale network management tasks is the number of possible heterogeneous data sources that provide network information and how to focus on a desired network segment without requiring a deep knowledge of the network structure. This work investigates how to intelligently and efficiently refine and manage a vast amount of network monitoring data sources, by using artificial intelligent reasoning through an intuitive user interface. We aim to minimise the user interaction and required user knowledge when searching for the desired network monitoring information by refining the presented information based on user choices. The concept of Ontology is utilised to create a knowledge base of multiple different aspects of our testbed: Internal Management structure, Physical Location of data sources, and network switch meta-data

Urokinase treatment preserves endothelial and smooth muscle function in experimental acute arterial thrombosis

AbstractPurpose: Pharmacologic lysis or balloon thrombectomy are options to treat acute arterial thrombosis; however, little is known about their effects on functional changes in the arterial wall. The aim of this study was to determine function of the endothelium and smooth muscle in canine arteries revascularized after acute thrombosis with balloon thrombectomy or lytic therapy.Methods: Acute thrombosis was obtained by bilateral proximal and distal ligation of 8-cm segments of the femoral arteries in dogs. After 24 hours, the ties were removed and the arteries randomized to treatment groups: group 1, balloon thrombectomy (#4 Fogarty balloon catheter at 60 grams linear shear × 1 pass, n = 7); group 2, untreated, tie removal only (n = 6); group 3, regional intra-arterial urokinase infusion (4000 U/min × 90 min, n = 6); group 4, regional intra-arterial carrier infusion (0.43 ml/min × 90 min, n = 6); group 5, unoperated normal vessels (n = 5). After treatment, the arteries were removed and endothelial and smooth muscle responses examined in organ chambers. Endothelial loss was graded with light microscopy of vessel rings from each animal by an observer blinded to the treatment group. Findings were confirmed with scanning electron microscopy.Results: Treatment with urokinase did not alter endothelium-dependent relaxations or smooth muscle contractions compared with carrier infusion or untreated alone. Balloon catheter thrombectomy significantly reduced endothelium-dependent relaxations compared with all other groups in response to acetylcholine, bradykinin, and thrombin (p < 0.001). Contractions of smooth muscle in response to potassium chloride (60 mol/L) and phenylephrine (1 × 10-6 mol/L) were also reduced (p < 0.05). Rings from balloon thrombectomized arteries contracted in response to calcium ionophore A23187 (p < 0.001); these contractions were endothelium dependent and not reduced by indomethacin or blockade of endothelin A and B receptors. No significant differences in percentage of endothelial coverage between groups were assessed by light and electron microscopy.Conclusion: Thrombolysis with urokinase caused no or minimal abnormalities in endothelial and smooth muscle function. Endothelium present after balloon thrombectomy produces contractile factors. Although the duration and recovery of these abnormalities in function are unknown, these findings support preferential use of urokinase over balloon thrombectomy when possible in acute arterial thrombosis or embolism. (J Vasc Surg 1996;23:851-9.

Akha : a transformational description

Akha is one of the better known of the lesser known Sino-Tibetan languages. As the case has been put in the Sino-Tibetan fascicles of Anthropological Linguistics, Sino-Tibetan is a cover term for a large number of languages showing strong grammatical affinities and lexical cognates

A solid-phase extraction method for rapidly determining the adsorption coefficient of pharmaceuticals in sewage sludge

AbstractThe partitioning of pharmaceuticals in the environment can be assessed by measuring their adsorption coefficients (Kd) between aqueous and solid phases. Measuring this coefficient in sewage sludge gives an indication of their partitioning behaviour in a wastewater treatment plant and hence contributes to an understanding of their subsequent fate. The regulatory approved method for measuring Kd in sewage sludge is the US Environmental Protection Agency's Office of Prevention, Pesticides and Toxic Substances (OPPTS) guideline 835.1110, which is labour intensive and time consuming. We describe an alternative method for measuring the Kd of pharmaceuticals in sewage sludge using a modified solid-phase extraction (SPE) technique. SPE cartridges were packed at different sludge/PTFE ratios (0.4, 6.0, 24.0 and 40.0% w/w sludge) and eluted with phosphate buffer at pH 7.4. The approach was tested initially using three pharmaceuticals (clofibric acid, diclofenac and oxytetracycline) that covered a range of Kd values. Subsequently, the sorption behaviour of ten further pharmaceuticals with varying physico-chemical properties was evaluated. Results from the SPE method were comparable to those of the OPPTS test, with a correlation coefficient of 0.93 between the two approaches. SPE cartridges packed with sludge and PTFE were stable for up to one year; use within one month reduced variability in measurements (to a maximum of 0.6 log units). The SPE method is low-cost, easy to use and enables the rapid measurement of Kd values for a large number of chemicals. It can be used as an alternative to the more laborious full OPPTS test in environmental fate studies and risk assessments

Psychosocial characteristics as potential predictors of suicide in adults: an overview of the evidence with new results from prospective cohort studies.

In this narrative overview of the evidence linking psychosocial factors with future suicide risk, we collected results from published reports of prospective studies with verified suicide events (mortality or, less commonly, hospitalisation) alongside analyses of new data. There is abundant evidence indicating that low socioeconomic position, irrespective of the economic status of the country in question, is associated with an increased risk of suicide, including the suggestion that the recent global economic recession has been responsible for an increase in suicide deaths and, by proxy, attempts. Social isolation, low scores on tests of intelligence, serious mental illness (both particularly strongly), chronic psychological distress, and lower physical stature (a marker of childhood exposures) were also consistently related to elevated suicide rates. Although there is some circumstantial evidence for psychosocial stress, personality disposition, and early-life characteristics such as bullying being risk indices for suicide, the general paucity of studies means it is not currently possible to draw clear conclusions about their role. Most suicide intervention strategies have traditionally not explored the modification of psychosocial factors, partly because evidence linking psychosocial factors with suicide risk is, as shown herein, largely in its infancy, or, where is does exist, for instance for intelligence and personality disposition, the characteristics in question do not appear to be easily malleable

On the design of forgiving biometric security systems

This work aims to highlight the fundamental issue surrounding biometric security systems: it's all very nice until a biometric is forged, but what do we do after that? Granted, biometric systems are by physical nature supposedly much harder to forge than other factors of authentication since biometrics on a human body are by right unique to the particular human person. Yet it is also due to this physical nature that makes it much more catastrophic when a forgery does occur, because it implies that this uniqueness has been forged as well, threatening the human individuality; and since crime has by convention relied on identifying suspects by biometric characteristics, loss of this biometric uniqueness has devastating consequences on the freedom and basic human rights of the victimized individual. This uniqueness forgery implication also raises the motivation on the adversary to forge since a successful forgery leads to much more impersonation situations when biometric systems are used i.e. physical presence at crime scenes, identi cation and access to security systems and premises, access to nancial accounts and hence the ability to use the victim's nances. Depending on the gains, a desperate highly motivated adversary may even resort to directly obtaining the victim's biometric parts by force e.g. severing the parts from the victim's body; this poses a risk and threat not just to the individual's uniqueness claim but also to personal safety and well being. One may then wonder if it is worth putting one's assets, property and safety into the hands of biometrics based systems when the consequences of biometric forgery far outweigh the consequences of system compromises when no biometrics are used