Perfil de playas sustentadas : estudio hidrodinámico y experimental : directrices de diseño

Las playas sustentadas por medio de un pie sumergido son una atractiva alternativa de diseño de regeneración de playas especialmente cuando las condiciones física del emplazamiento o las características de la arena nativa y de préstamo producen perfiles de alimentación que no se intersectan. La observación y propuesta de este tipo de solución data de los años 1960’s, así como la experiencia internacional en la construcción de este tipo de playas. Sin embargo, a pesar de su utilización y los estudios en campo y laboratorio, no se dispone de criterios ingenieriles que apoyen el diseño de las mismas. Esta tesis consiste en un análisis experimental del perfil de playas sustentadas en un pie sumergido (o colgadas) que se concreta en una propuesta de directrices de diseño general que permiten estimar la ubicación y características geométricas del pie sumergido frente a un oleaje y material que constituye la playa determinados. En la tesis se describe el experimento bidimensional realizado en el modelo físico de fondo móvil, donde se combinan cinco tipos de oleaje con tres configuraciones del pie sumergido (“Sin estructura”, configuración baja o “Estructura 1” y configuración alta o “Estructura 2”), se presentan los resultados obtenidos y se realiza una discusión detallada de las implicaciones de los resultados desde el punto de vista hidrodinámico utilizando monomios adimensionales. Se ha realizado un análisis detallado del estado del arte sobre playas colgadas, presentando el concepto y las experiencias de realizaciones en distintos países. Se ha realizado una cuidadosa revisión de la literatura publicada sobre estudios experimentales de playas colgadas, modelos teóricos y otras cuestiones auxiliares, necesarias para la formulación de la metodología de la tesis. El estudio realizado se ha estructurado en dos fases. En la primera fase se ha realizado una experimentación en un modelo físico de fondo móvil construido en las instalaciones del Centro de Estudios de Puertos y Costas (CEPYC) del Centro de Estudios y Experimentación de Obras Públicas (CEDEX), consistente en un canal de 36 m de longitud, 3 m de anchura y 1.5 m de altura, provisto de un generador de oleaje de tipo pistón. Se ha diseñado una campaña de 15 ensayos, que se obtienen sometiendo a cinco tipos de oleaje tres configuraciones distintas de playa colgada. En los ensayos se ha medido el perfil de playa en distintos instantes hasta llegar al equilibrio, determinando a partir de esos datos el retroceso de la línea de costa y el volumen de sedimentos perdido. El tiempo total efectivo de ensayo asciende a casi 650 horas, y el número de perfiles de evolución de playa obtenidos totaliza 229. En la segunda fase se ha abordado el análisis de los resultados obtenidos con la finalidad de comprender el fenómeno, identificar las variables de las que depende y proponer unas directrices ingenieriles de diseño. Se ha estudiado el efecto de la altura de ola, del periodo del oleaje, del francobordo adimensional y del parámetro de Dean, constatándose la dificultad de comprensión del funcionamiento de estas obras ya que pueden ser beneficiosas, perjudiciales o inocuas según los casos. También se ha estudiado la respuesta del perfil de playa en función de otros monomios adimensionales, tales como el número de Reynolds o el de Froude. En el análisis se ha elegido el monomio “plunger” como el más significativo, encontrando relaciones de éste con el peralte de oleaje, la anchura de coronación adimensional, la altura del pie de playa adimensional y el parámetro de Dean. Finalmente, se propone un método de diseño de cuatro pasos que permite realizar un primer encaje del diseño funcional de la playa sustentada frente a un oleaje de características determinadas. Las contribuciones más significativas desde el punto de vista científico son: - La obtención del juego de resultados experimentales. - La caracterización del comportamiento de las playas sustentadas. - Las relaciones propuestas entre el monomio plunger y las distintas variables explicativas seleccionadas, que permiten predecir el comportamiento de la obra. - El método de diseño propuesto, en cuatro pasos, para este tipo de esquemas de defensa de costas. Perched beaches are an attractive beach nourishment design alternative especially when either the site conditions or the characteristics of both the native and the borrow sand lead to a non-intersecting profile The observation and suggestion of the use of this type of coastal defence scheme dates back to the 1960’s, as well as the international experience in the construction of this type of beaches. However, in spite of its use and the field and laboratory studies performed to-date, no design engineering guidance is available to support its design. This dissertation is based on the experimental work performed on a movable bed physical model and the use of dimensionless parameters in analyzing the results to provide general functional design guidance that allow the designer, at a particular stretch of coast - to estimate the location and geometric characteristics of the submerged sill as well as to estimate the suitable sand size to be used in the nourishment. This dissertation consists on an experimental analysis of perched beaches by means of a submerged sill, leading to the proposal of general design guidance that allows to estimate the location and geometric characteristics of the submerged sill when facing a wave condition and for a given beach material. The experimental work performed on a bi-dimensional movable bed physical model, where five types of wave conditions are combined with three configurations of the submerged sill (“No structure”, low structure or “Structure 1”, and high structure or “Structure 2”) is described, results are presented, and a detailed discussion of the results - from the hydrodynamic point of view – of the implications of the results by using dimensionless parameters is carried out. A detailed state of the art analysis about perched beaches has been performed, presenting the “perched beach concept” and the case studies of different countries. Besides, a careful revision of the literature about experimental studies on perched beaches, theoretical models, and other topics deemed necessary to formulate the methodology of this work has been completed. The study has been divided into two phases. Within the first phase, experiments on a movable-bed physical model have been developed. The physical model has been built in the Centro de Estudios de Puertos y Costas (CEPYC) facilities, Centro de Estudios y Experimentación de Obras Públicas (CEDEX). The wave flume is 36 m long, 3 m wide and 1.5 m high, and has a piston-type regular wave generator available. The test plan consisted of 15 tests resulting from five wave conditions attacking three different configurations of the perched beach. During the development of the tests, the beach profile has been surveyed at different intervals until equilibrium has been reached according to these measurements. Retreat of the shoreline and relative loss of sediment in volume have been obtained from the measurements. The total effective test time reaches nearly 650 hours, whereas the total number of beach evolution profiles measured amounts to 229. On the second phase, attention is focused on the analysis of results with the aim of understanding the phenomenon, identifying the governing variables and proposing engineering design guidelines. The effect of the wave height, the wave period, the dimensionless freeboard and of the Dean parameter have been analyzed. It has been pointed out the difficulty in understanding the way perched beaches work since they turned out to be beneficial, neutral or harmful according to wave conditions and structure configuration. Besides, the beach profile response as a function of other dimensionless parameters, such as Reynolds number or Froude number, has been studied. In this analysis, the “plunger” parameter has been selected as the most representative, and relationships between the plunger parameter and the wave steepness, the dimensionless crest width, the dimensionless crest height, and the Dean parameter have been identified. Finally, an engineering 4-step design method has been proposed, that allows for the preliminary functional design of the perched beach for a given wave condition. The most relevant contributions from the scientific point of view have been: - The acquisition of a consistent set of experimental results. - The characterization of the behavior of perched beaches. - The proposed relationships between the plunger parameter and the different explanatory variables selected, that allow for the prediction of the beach behavior. - The proposed design method, four-step method, for this type of coastal defense schemes.

Vaccines against neosporosis: what can we learn from the past studies?

Neospora caninum is an intracellular apicomplexan parasite, which is a leading cause of abortion in cattle; thus neosporosis represents an important veterinary health problem and is of high economic significance. The parasite can infect cattle via trans-placental transmission from an infected cow to its fetus (vertical transmission), or through the oral route via ingestion of food or water contaminated with oocysts that were previously shed with the feces of a canid definitive host (horizontal transmission). Although vaccination was considered a rational strategy to prevent bovine neosporosis, the only commercialized vaccine (Neoguard®) produced ambiguous results with relatively low efficacy, and was recently removed from the market. Therefore, there is a need to develop an efficient vaccine capable of preventing both, the horizontal transmission through infected food or water to a naïve animal as well as the vertical transmission from infected but clinically asymptomatic dams to the fetus. Different vaccine strategies have been investigated, including the use of live attenuated vaccines, killed parasite lysates, total antigens or antigen fractions from killed parasites, and subunit vaccines. The vast majority of experimental studies were performed in mice, and to a certain extent in gerbils, but there is also a large number of investigations that were conducted in cattle and sheep. However, it is difficult to directly compare these studies due to the high variability of the parameters employed. In this review, we will summarize the recent advances made in vaccine development against N. caninum in cattle and in mice and highlight the most important factors, which are likely to influence the degree of protection mediated by vaccination.

Studies on Rocky mountain spotted fever.

"The experimental studies recorded in this bulletin are the result of a close cooperative investigation by R. R. Spencer and R. R. Parker over a period of six years--1922 to 1928."--Pref., p. ix.

Prostanoids as friends, not foes: Further evidence from the interference by cycloxygenase-inhibitory drugs when inducing tolerance to experimental arthritigens in rats

Pharmacologists have generally been prejudiced against prostanoids, uncritically accepting their suppression as desirable therapy, especially for ‘quick-fix’ analgesia. This myopic perception for a long time ignored (a) the essentiality of prostanoid precursors in nutrition, (b) the physiological protective functions of natural prostaglandins (PGs) (vasculature, stomach, kidney), (c) resolution of inflammation after the expression of COX-2 and (d) increasing therapeutic use of either synthetic PGs (for erectile dysfunction, opthalmic disorders, inducing parturition, etc) or their natural precursors, e.g., ω3-rich polyunsaturated oils, to treat arthritis. Experimental studies in rats have indicated that prostaglandins (E series) are (i) useful, perhaps auto-regulators of established immunoreactivity and (ii) able to amplify (or even induce) anti-inflammatory activity with other agents. Furthermore, anti-prostanoid therapy (APT) can be arthritigenic!!, interfering with the acquisition of tolerance to some arthritigens. For patients with rheumatoid arthritis this additional side-effect of APT, barely recognised to date, may actually perpetuate their arthritis by impairing prostanoid-mediated remission processes. Hopefully, recent adverse publicity about COX-2 inhibitory drugs might stimulate serious re-assessment of some traditional anti-inflammatory therapies with low APT activity for the management of both acute pain (non-addictive cannabinoids, celery seed, etc.) and chronic inflammation, e.g., Lyprinol® (a mussel lipid extract).

Studies on the deactivation and reactivation of spent hydroprocessing catalyst

A study is reported on the deactivation of hydroprocessing catalysts and their reactivation by the removal of coke and metal foulants. The literature on hydrotreating catalyst deactivation by coke and metals deposition, the environmental problems associated with spent catalyst disposal, and its reactivation/rejuvenation process were reviewed. Experimental studies on catalyst deactivation involved problem analysis in industrial hydroprocessing operations, through characterization of the spent catalyst, and laboratory coking studies. A comparison was made between the characteristics of spent catalysts from fixed bed and ebullating bed residue hydroprocessing reactor units and the catalyst deactivation pattern in both types of reactor systems was examined. In the laboratory the nature of initial coke deposited on the catalyst surface and its role on catalyst deactivation were studied. The influence of initial coke on catalyst surface area and porosity was significant. Both catalyst acidity and feedstock quality had a remarkable influence on the amount and the nature of the initial coke. The hydroenitrogenation function (HDN) of the catalyst was found to be deactivated more rapidly by the initial coke than the hydrodesulphurization function (HDS). In decoking experiments, special attention was paid to the initial conditions of coke combustion, since the early stages of contact between the coke on the spent catalyst surface and the oxygen are crucial in the decoking process. An increase in initial combustion temperature above 440oC and the oxygen content of the regeneration gas above 5% vanadium led to considerable sintering of the catalyst. At temperatures above 700oC there was a substantial loss of molybdenum from the catalyst, and phase transformations in the alumina support. The preferred leaching route (coked vs decoked form of spent catalyst) and a comparison of different reagents (i.e., oxalic acid and tartaric acid) and promoters (i.e., Hydrogen Peroxide and Ferric Nitrate) for better selectivity in removing the major foulant (vanadium), characterization and performance evaluation of the treated catalysts and modelling of the leaching process were addressed in spent catalyst rejuvenation studies. The surface area and pore volume increased substantially with increasing vanadium extraction from the spent catalyst; the HDS activity showed a parallel increase. The selectivity for leaching of vanadium deposits was better, and activity recovery was higher, for catalyst rejuvenated by metal leaching prior to decoking.

Some studies relating to the design of shallow, fluidized bed boilers

The concept of shallow fluidized bed boilers is defined and a preliminary working design for a gas-fired package boiler has been produced. Those areas of the design requiring further study have been specified. Experimental investigations concerning these areas have been carried out. A two-dimensional, conducting paper analog has been developed for the specific purpose of evaluating sheet fins. The analog has been generalised and is presented as a simple means of simulating the general, two-dimensional Helmholtz equation. By recording the transient response of spherical, calorimetric probes when plunged into heated air-fluidized beds, heat transfer coefficients have been measured at bed temperatures up to 1 100°C. A correlation fitting all the data to within ±10% has been obtained. A model of heat transfer to surfaces immersed in high temperature beds has been proposed. The model solutions are, however, only in qualitative agreement with the experimental data. A simple experimental investigation has revealed that the effective, radial, thermal conductivities of shallow fluidized beds are an order of magnitude lower than the axial conductivities. These must, consequently, be taken into account when considering heat transfer to surfaces immersed within fluidized beds. Preliminary work on pre-mixed gas combustion and some further qualitative experiments have been used as the basis for discussing the feasibility of combusting heavy fuel oils within shallow beds. The use of binary beds, within which the fuel could be both gasified and subsequently burnt, is proposed. Finally, the consequences of the experimental studies on the initial design are considered, and suggestions for further work are made.

An experimental and theoretical analysis of nitric oxide availability in the microcirculation

Nitric Oxide (NO) is produced in the vascular endothelium where it then diffuses to the adjacent smooth muscle cells (SMC) activating agents known to regulate vascular tone. The close proximity of the site of NO production to the red blood cells (RBC) and its known fast consumption by hemoglobin, suggests that the blood will scavenge most of the NO produced. Therefore, it is unclear how NO is able to play its role in accomplishing vasodilation. Investigation of NO production and consumption rates will allow insight into this paradox. DAF-FM is a sensitive NO fluorescence probe widely used for qualitative assessment of cellular NO production. With the aid of a mathematical model of NO/DAF-FM reaction kinetics, experimental studies were conducted to calibrate the fluorescence signal showing that the slope of fluorescent intensity is proportional to [NO]2 and exhibits a saturation dependence on [DAF-FM]. In addition, experimental data exhibited a Km dependence on [NO]. This finding was incorporated into the model elucidating NO 2 as the possible activating agent of DAF-FM. A calibration procedure was formed and applied to agonist stimulated cells, providing an estimated NO release rate of 0.418 ± 0.18 pmol/cm2s. To assess NO consumption by RBCs, measurements of the rate of NO consumption in a gas stream flowing on top of an RBC solution of specified Hematocrit (Hct) was performed. The consumption rate constant (kbl)in porcine RBCs at 25°C and 45% Hct was estimated to be 3500 + 700 s-1. kbl is highly dependent on Hct and can reach up to 9900 + 4000 s-1 for 60% Hct. The nonlinear dependence of kbl on Hct suggests a predominant role for extracellular diffusion in limiting NO uptake. Further simulations showed a linear relationship between varying NO production rates and NO availability in the SMCs utilizing the estimated NO consumption rate. The corresponding SMC [NO] level for the average NO production rate estimated was approximately 15.1 nM. With the aid of experimental and theoretical methods we were able to examine the NO paradox and exhibit that endothelial derived NO is able to escape scavenging by RBCs to diffuse to the SMCs.

Efeitos da azilsartana sobre a doença periodontal em um modelo experimental com ratos wistar

Periodontal diseases, highly prevalent disease in worldwide population, manifest primarily in two distinct entities: plaque-induced gingivitis and periodontitis. Periodontitis is a chronic inflammatory disease characterized of different levels of collagen, cementum, and alveolar bone destruction. Recent experimental studies demonstrated anti-inflammatory and antirreabsortive effect of antihypertensive agents of the angiotensin II receptor blockers class on periodontal disease. The aim of this study was to evaluate the effects of azilsartan (AZT), a potent inhibitor of the angiotensin II receptor which has minimal adverse effects on bone loss, inflammation, and the expression of matrix metallo proteinases (MMPs), receptor activator of nuclear factor kB ligand (RANKL), receptor activator of nuclear factor kB (RANK), osteoprotegerin (OPG), cyclooxygenase-2 (COX-2), and cathepsin K in periodontal tissue in a rat model of ligature-induced periodontitis. Male Wistar albino rats were randomly divided into 5 groups of 20 rats each: (1) nonligated, water; (2) ligated, water; (3) ligated, 1 mg/kg AZT; (4) ligated, 5 mg/kg AZT; and (5) ligated, 10 mg/kg AZT. All groups were treated with water or AZT for 10 days. Periodontal tissues were analyzed by morphometric exam, histopathology and immunohistochemical detection of MMP-2, MMP-9, COX-2, RANKL, RANK, OPG, and cathepsin K. Levels of IL-1b, IL-10, TNF-a, myeloperoxidase (MPO), and glutathione (GSH) were determined by ELISA. Treatment with 5 mg/kg AZT resulted in reduced MPO (p˂0.05) and IL-1b (p˂0.05) levels and increased in Il-10 levels (p˂0.05). It was observed a reduced expression of MMP-2, MMP-9, COX-2, RANK, RANKL, cathepsin K, and a increased expression of OPG in the animals subjected to experimental periodontitis and threated with AZT (5 mg/kg). Conclusions: These findings suggest an anti-inflammatory and anti-reabsortive effects of AZT on ligature-induced periodontitis in rats.

(Appendix A) Pigment content, microbial biomass and activity, and grain size characteristics in caged and control sites of the Arctic long-term observatory HAUSGARTEN

Present theories of deep-sea community organization recognize the importance of small-scale biological disturbances, originated partly from the activities of epibenthic megafaunal organisms, in maintaining high benthic biodiversity in the deep sea. However, due to technical difficulties, in situ experimental studies to test hypotheses in the deep sea are lacking. The objective of the present study was to evaluate the potential of cages as tools for studying the importance of epibenthic megafauna for deep-sea benthic communities. Using the deep-diving Remotely Operated Vehicle (ROV) "VICTOR 6000", six experimental cages were deployed at the sea floor at 2500 m water depth and sampled after 2 years (2y) and 4 years (4y) for a variety of sediment parameters in order to test for caging artefacts. Photo and video footage from both experiments showed that the cages were efficient at excluding the targeted fauna. The cage also proved to be appropriate to deep-sea studies considering the fact that there was no fouling on the cages and no evidence of any organism establishing residence on or adjacent to it. Environmental changes inside the cages were dependent on the experimental period analysed. In the 4y experiment, chlorophyll a concentrations were higher in the uppermost centimeter of sediment inside cages whereas in the 2y experiment, it did not differ between inside and outside. Although the cages caused some changes to the sedimentary regime, they are relatively minor compared to similar studies in shallow water. The only parameter that was significantly higher under cages at both experiments was the concentration of phaeopigments. Since the epibenthic megafauna at our study site can potentially affect phytodetritus distribution and availability at the seafloor (e.g. via consumption, disaggregation and burial), we suggest that their exclusion was, at least in part, responsible for the increases in pigment concentrations. Cages might be suitable tools to study the long-term effects of disturbances caused by megafaunal organisms on the diversity and community structure of smaller-sized organisms in the deep sea, although further work employing partial cage controls, greater replication, and evaluating faunal components will be essential to unequivocally establish their utility.

Experimental study of forces and energies during shearing of steel sheet with angled tools

Shearing is a fast and inexpensive method to cut sheet metal that has been used since the beginning of the industrialism. Consequently, published experimental studies of shearing can be found from over a century back in time. Recent studies, however, are due to the availability of low cost digital computation power, mostly based on finite element simulations that guarantees quick results. Still, for validation of models and simulations, accurate experimental data is a requisite. When applicable, 2D models are in general desirable over 3D models because of advantages like low computation time and easy model formulation. Shearing of sheet metal with parallel tools is successfully modelled in 2D with a plane strain approximation, but with angled tools the approximation is less obvious. Therefore, plane strain approximations for shearing with angled tools were evaluated by shear experiments of high accuracy. Tool angle, tool clearance, and clamping of the sheet were varied in the experiments. The results showed that the measured forces in shearing with angled tools can be approximately calculated using force measurements from shearing with parallel tools. Shearing energy was introduced as a quantifiable measure of suitable tool clearance range. The effects of the shearing parameters on forces were in agreement with previous studies. Based on the agreement between calculations and experiments, analysis based on a plane strain assumption is considered applicable for angled tools with a small (up to 2 degrees) rake angle.

Coupled Ge/Si and Ge isotope ratios as geochemical tracers of seafloor hydrothermal systems: Case studies at Loihi Seamount and East Pacific Rise 9°50’N

Germanium (Ge) and Silicon (Si) exhibit similar geochemical behaviour in marine environments but are variably enriched in seafloor hydrothermal fluids relative to seawater. In this study, Ge isotope and Ge/Si ratio systematics were investigated in low temperature hydrothermal vents from Loihi Seamount (Pacific Ocean, 18°54’N, 155°15’W) and results were compared to high-temperature vents from the East Pacific Rise (EPR) at 9°50’N. Loihi offers the opportunity to understand contrasting Ge and Si behaviour in low temperature seafloor hydrothermal systems characterized by abundant Fe oxyhydroxide deposition at the seafloor. The results show that both Ge/Si and δ74/70Ge in hydrothermal fluids are fractionated relative to the basaltic host rocks. The enrichment in Ge vs. Si relative to fresh basalts, together with Ge isotope fractionation (Δ74/70Ge fluid-basalt up to 1.15 ‰ at EPR 9°50’N and 1.64 ‰ at Loihi) are best explained by the precipitation of minerals (e.g. quartz and Fe-sulfides) during higher temperature seawater-rock reactions in the subsurface. The study of Fe-rich hydrothermal deposits at Loihi, largely composed of Fe-oxyhydroxides, shows that Ge isotopes are also fractionated upon mineral precipitation at the seafloor. We obtained an average Ge isotope fractionation factor between Fe-oxyhydroxide (ferrihydrite) and dissolved Ge in the fluid of -2.0 ± 0.6 ‰ (2sd), and a maximum value of -3.6 ± 0.6 ‰ (2sd), which is consistent with recent theoretical and experimental studies. The study of a hydrothermal chimney at Bio 9 vent at EPR 9°50’N also demonstrates that Ge isotopes are fractionated by approximately -5.6 ± 0.6 ‰ (2sd) during precipitation of metal sulfides under hydrothermal conditions. Using combined Ge/Si and estimated Ge isotope signatures of Ge sinks and sources in seawater, we propose a preliminary oceanic budget of Ge which reveals that an important sink, referred as the “missing Ge sink”, may correspond to Ge sequestration into authigenic Fe-oxyhydroxides in marine sediments. This study shows that combining Ge/Si and δ74/70Ge systematics provides a useful tool to trace hydrothermal Ge and Si sources in marine environments and to understand formation processes of seafloor hydrothermal deposits.

Recommended reporting standards for test accuracy studies of infectious diseases of finfish, amphibians, molluscs and crustaceans: the STRADAS-aquatic checklist

Complete and transparent reporting of key elements of diagnostic accuracy studies for infectious diseases in cultured and wild aquatic animals benefits end-users of these tests, enabling the rational design of surveillance programs, the assessment of test results from clinical cases and comparisons of diagnostic test performance. Based on deficiencies in the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines identified in a prior finfish study (Gardner et al. 2014), we adapted the Standards for Reporting of Animal Diagnostic Accuracy Studies—paratuberculosis (STRADAS-paraTB) checklist of 25 reporting items to increase their relevance to finfish, amphibians, molluscs, and crustaceans and provided examples and explanations for each item. The checklist, known as STRADAS-aquatic, was developed and refined by an expert group of 14 transdisciplinary scientists with experience in test evaluation studies using field and experimental samples, in operation of reference laboratories for aquatic animal pathogens, and in development of international aquatic animal health policy. The main changes to the STRADAS-paraTB checklist were to nomenclature related to the species, the addition of guidelines for experimental challenge studies, and the designation of some items as relevant only to experimental studies and ante-mortem tests. We believe that adoption of these guidelines will improve reporting of primary studies of test accuracy for aquatic animal diseases and facilitate assessment of their fitness-for-purpose. Given the importance of diagnostic tests to underpin the Sanitary and Phytosanitary agreement of the World Trade Organization, the principles outlined in this paper should be applied to other World Organisation for Animal Health (OIE)-relevant species.

Power network in the loop : subsystem testing using a switching amplifier

“Hardware in the Loop” (HIL) testing is widely used in the automotive industry. The sophisticated electronic control units used for vehicle control are usually tested and evaluated using HIL-simulations. The HIL increases the degree of realistic testing of any system. Moreover, it helps in designing the structure and control of the system under test so that it works effectively in the situations that will be encountered in the system. Due to the size and the complexity of interaction within a power network, most research is based on pure simulation. To validate the performance of physical generator or protection system, most testing is constrained to very simple power network. This research, however, examines a method to test power system hardware within a complex virtual environment using the concept of the HIL. The HIL testing for electronic control units and power systems protection device can be easily performed at signal level. But performance of power systems equipments, such as distributed generation systems can not be evaluated at signal level using HIL testing. The HIL testing for power systems equipments is termed here as ‘Power Network in the Loop’ (PNIL). PNIL testing can only be performed at power level and requires a power amplifier that can amplify the simulation signal to the power level. A power network is divided in two parts. One part represents the Power Network Under Test (PNUT) and the other part represents the rest of the complex network. The complex network is simulated in real time simulator (RTS) while the PNUT is connected to the Voltage Source Converter (VSC) based power amplifier. Two way interaction between the simulator and amplifier is performed using analog to digital (A/D) and digital to analog (D/A) converters. The power amplifier amplifies the current or voltage signal of simulator to the power level and establishes the power level interaction between RTS and PNUT. In the first part of this thesis, design and control of a VSC based power amplifier that can amplify a broadband voltage signal is presented. A new Hybrid Discontinuous Control method is proposed for the amplifier. This amplifier can be used for several power systems applications. In the first part of the thesis, use of this amplifier in DSTATCOM and UPS applications are presented. In the later part of this thesis the solution of network in the loop testing with the help of this amplifier is reported. The experimental setup for PNIL testing is built in the laboratory of Queensland University of Technology and the feasibility of PNIL testing has been evaluated using the experimental studies. In the last section of this thesis a universal load with power regenerative capability is designed. This universal load is used to test the DG system using PNIL concepts. This thesis is composed of published/submitted papers that form the chapters in this dissertation. Each paper has been published or submitted during the period of candidature. Chapter 1 integrates all the papers to provide a coherent view of wide bandwidth switching amplifier and its used in different power systems applications specially for the solution of power systems testing using PNIL.

Distortional buckling tests of cold-formed steel compression members at elevated temperatures

In recent times, light gauge cold-formed steel sections have been used extensively since they have a very high strength to weight ratio compared with thicker hot-rolled steel sections. However, they are susceptible to various buckling modes including a distortional mode and hence show complex behaviour under fire conditions. Therefore a research project based on detailed experimental studies was undertaken to investigate the distortional buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. More than 150 axial compression tests were undertaken at uniform ambient and elevated temperatures. Two types of cross sections were selected with nominal thicknesses of 0.60, 0.80, and 0.95 mm. Both low (G250) and high (G550) strength steels were used. Distortional buckling tests were conducted at six different temperatures in the range of 20 to 800°C. The ultimate loads of compression members subject to distortional buckling were then used to review the adequacy of the current design rules at ambient and elevated temperatures. This paper presents the details of this experimental study and the results.

Mathematical modelling of muscle recruitment and function in the lumbar spine

Low back pain is an increasing problem in industrialised countries and although it is a major socio-economic problem in terms of medical costs and lost productivity, relatively little is known about the processes underlying the development of the condition. This is in part due to the complex interactions between bone, muscle, nerves and other soft tissues of the spine, and the fact that direct observation and/or measurement of the human spine is not possible using non-invasive techniques. Biomechanical models have been used extensively to estimate the forces and moments experienced by the spine. These models provide a means of estimating the internal parameters which can not be measured directly. However, application of most of the models currently available is restricted to tasks resembling those for which the model was designed due to the simplified representation of the anatomy. The aim of this research was to develop a biomechanical model to investigate the changes in forces and moments which are induced by muscle injury. In order to accurately simulate muscle injuries a detailed quasi-static three dimensional model representing the anatomy of the lumbar spine was developed. This model includes the nine major force generating muscles of the region (erector spinae, comprising the longissimus thoracis and iliocostalis lumborum; multifidus; quadratus lumborum; latissimus dorsi; transverse abdominis; internal oblique and external oblique), as well as the thoracolumbar fascia through which the transverse abdominis and parts of the internal oblique and latissimus dorsi muscles attach to the spine. The muscles included in the model have been represented using 170 muscle fascicles each having their own force generating characteristics and lines of action. Particular attention has been paid to ensuring the muscle lines of action are anatomically realistic, particularly for muscles which have broad attachments (e.g. internal and external obliques), muscles which attach to the spine via the thoracolumbar fascia (e.g. transverse abdominis), and muscles whose paths are altered by bony constraints such as the rib cage (e.g. iliocostalis lumborum pars thoracis and parts of the longissimus thoracis pars thoracis). In this endeavour, a separate sub-model which accounts for the shape of the torso by modelling it as a series of ellipses has been developed to model the lines of action of the oblique muscles. Likewise, a separate sub-model of the thoracolumbar fascia has also been developed which accounts for the middle and posterior layers of the fascia, and ensures that the line of action of the posterior layer is related to the size and shape of the erector spinae muscle. Published muscle activation data are used to enable the model to predict the maximum forces and moments that may be generated by the muscles. These predictions are validated against published experimental studies reporting maximum isometric moments for a variety of exertions. The model performs well for fiexion, extension and lateral bend exertions, but underpredicts the axial twist moments that may be developed. This discrepancy is most likely the result of differences between the experimental methodology and the modelled task. The application of the model is illustrated using examples of muscle injuries created by surgical procedures. The three examples used represent a posterior surgical approach to the spine, an anterior approach to the spine and uni-lateral total hip replacement surgery. Although the three examples simulate different muscle injuries, all demonstrate the production of significant asymmetrical moments and/or reduced joint compression following surgical intervention. This result has implications for patient rehabilitation and the potential for further injury to the spine. The development and application of the model has highlighted a number of areas where current knowledge is deficient. These include muscle activation levels for tasks in postures other than upright standing, changes in spinal kinematics following surgical procedures such as spinal fusion or fixation, and a general lack of understanding of how the body adjusts to muscle injuries with respect to muscle activation patterns and levels, rate of recovery from temporary injuries and compensatory actions by other muscles. Thus the comprehensive and innovative anatomical model which has been developed not only provides a tool to predict the forces and moments experienced by the intervertebral joints of the spine, but also highlights areas where further clinical research is required.