Automatic Identification System (AIS) was introduced with the overall aim to promote efficiency and safety of navigation, protection of environment, and safety of life at sea. Consequently, ship-borne AIS was implemented on a mandatory basis by IMO in 2000 and later amendments to chapter V of Safety of Life at Sea (SOLAS) Convention. Therefore SOLAS Convention vessels were required to carry AIS in a phased approach, from I" July 2002 to end of December 2004. The intention is to provide more precise information and a clear traffic view in navigation operations, particularly in anti-collision operation. This mandatory implementation of AIS has raised a number of issues with respect to its success in fulfilment of the intended role. In order to improve the efficiency of the AIS in navigation operation, this research mainly focused on the accuracy of AIS information, and practical use of the technology on board the ships. The intentions were to assess reliability of data, level of human failure associated with AIS, and the degree of actual use of the technology by navigators. This research firstly provided impressions about AIS technology for anti-collision operation and other marine operation and, about a system's approach to the issue of human failure in marine risk management. Secondly, this research has assessed reliability of AIS data by examination of data collected through three AIS data studies. Thirdly, it has evaluated navigators' attitude and behaviour to AIS usage by analysing the data from navigators' feedback collected through the AIS questionnaire survey focused on their perceptions about different aspects of AIS related to its use. This research revealed that some aspects of the AIS technology and some features of its users need further attention and improvement, so as to achieve its intended objectives in navigation. This study finally contributed in proposing the AIS User Satisfaction Model as a suitable framework for evaluation of navigators' satisfaction and extent of the use of AIS. This model can probably be used as the basis for measuring navigators' attitude and behaviour about other similar maritime technologies.

No description available.

This thesis, as its title implies, is a unique step in the management of risk of collision, which may arise in a two-ship encounter. This work advances the development established in the author's M. Phil thesis. It is suggested that the contemporary technique of collision avoidance based solely on CPA criteria is inadequate for risk analysis. The proposed strategy for handling risk of collision revolves around the introduced hypothesis for dealing with risks having various probabilities of occurrence resulting in various degrees of severity. The risk values are obtained by computing the geometrical probability of collision based on the following definition :- " The risk of collision can be measured by the ratio of the ways available for a collision to occur to all the possible ways that could be considered by the obser ving vessel." Based on this hypothesis several approaches to the presentation of the risk of collision are described separately in the thesis's units together with their application, merits and demerits. It is found that the introduction of the assessment and control of the risk of collision by lneans of the proposed risk criteria has converted the vague awareness given by the traditional methods, to a definite risk criteria which could provide alternative ways of assessing any situation. The restructuring of the information clearly provided to the mariner gives him a much greater insight into the level of the risk which he is accepting in any situation. A strong risk controllability can be achieved if it is characterised by a relatively high degree of constraints in the fonn of regulation. These regulation should acquire features that will pennit them to discriminate, act upon, and respond to aspects of the situation variety. Due to the fact that certain statements within the International· Rules are not clearly defined and are thus open to individual interpretation, some mathematical definitions of risk of collision and close range situations are established. The analysis and testing of specific examples has proved that these methods work and are able to provide the mariners with a cammon language in resolving collision avoidance problem.

No description available.

O objetivo deste trabalho foi analisar o comportamento hidráulico de sistemas de abastecimento de água (SDAA), via redes neurais artificiais (RNA). Tendo em vista que o uso de um modelo de simulação hidráulica é inviável para operações em tempo real em SDAA devido à carga computacional que impõe, a abordagem adotada visa capturar o seu conhecimento de uma forma mais eficiente por meio de uma RNA de camada oculta única. Desta forma os conjuntos de dados provenientes de simulações hidráulicas realizadas utilizando o conhecido e consagrado software EPANET combinando diferentes situações e avaliando as variáveis que compõem os dois sistemas distintos, foram tabuladas e inseridas em forma de rotinas de programação desenvolvidas na plataforma do software Scilab. Os conjuntos de dados (entradas e saídas) utilizados para treinar a RNA, foram divididos em conjuntos de treino, validação cruzada e testes, aplicada a dois SDAAs distintos. O primeiro denominado Anytown modificado tratou de um sistema hipotético, cuja finalidade foi avaliar a metodologia e fundamentar o conhecimento. Posteriormente aplicou-se a metodologia em outro SDAA, real e mais complexo, utilizado na conferência de calibração WDSA Water Distribution System Analysis, realizada na cidade de Tucson, Arizona (EUA) entre os dias 12 e 15 de setembro de 2010. Desta maneira foram obtidos valores simulados de potência energética consumida no bombeamento, níveis de reservação e pressões, muito próximos dos valores reais para os dois SDAAs estudados, comprovando que as RNAs identificadas podem ser consideradas ferramentas eficientes na substituição dos modelos de simulação hidráulica convencionais. / The objective of this study was to analyze the hydraulic systems of water supply (WSS), using artificial neural networks (ANN). Since the use of a hydraulic simulation model is impractical for real-time operations due to the computational load WSS imposing, the approach aims to capture their knowledge more efficiently through a single hidden layer of RNA. Thus the data sets from hydraulic simulations conducted using the known and established software EPANET combining different situations and evaluating the variables that make up the two different systems were tabulated and entered in the form of programming routines developed in Scilab software platform. The data sets (inputs and outputs) used to train the ANN, were divided into training sets, cross validation and testing, applied to two distinct WSS. The first called Anytown modified dealt with a hypothetical system, whose purpose was to evaluate the methodology and knowledge base. Later the methodology was applied in another WSS, real and complex, used in the calibration WDSA conference Water Distribution System Analysis, held in Tucson, Arizona (USA) between 12 and 15 September 2010. Thus were obtained simulated values of the power energy consumed in pumping, pressures and reservation levels very close to actual values for the two WSS studied, proving that the identified ANN can be considered effective tools to replace in the conventional hydraulic simulation models.

This thesis investigates the hydrodynamics of flow around/and or above an obstacle(s) placed in a fully turbulent developed flow such as flow around lateral bridge constriction, flow over bridge deck and flow over square ribs that are characterized with free surface flow. Also this thesis examines the flow around one-line circular cylinders placed at centre in a single open channel and floodplain edge in a compound, open channel. *Hydrodynamics studies of compound channels with vegetated floodplain have been carried out by a number studies of authors in the last three decades. To enrich our understanding of the flow resistance, comprehensive experiments are carried out with two vegetation configurations-wholly vegetated floodplain and one-line vegetation and then compared to smooth unvegetated compound channel. The main result of the flow characteristics in vegetated compound channels is that spanwise velocity profiles exhibit markedly different characters in the one-line and wholly-vegetated configurations. Moreover, flow resistance estimation results are in agreement with other experimental studies. *A complementary experimental study was carried out to investigate the water surface response in an open-channel flow through a lateral channel constriction and a bridge opening with overtopping. The flow through the bridge openings is characterized by very strong variation of the water surface including undular hydraulic jumps. The results of simulation that was carried by (Kara et al. 2014, 2015) showed a reasonable agreement between measured and computed water surface profiles for the constriction case and a fairly good was achieved for the overtopping case. *Evaluation of the shear layer dynamics in compound channel flows is carried out using infrared thermography technique with two vegetation configurations - wholly vegetated floodplain and one-line vegetation in comparison to non-vegetated floodplains. This technique also manifests some potential as a flow visualization technique, and leaves space for future studies and research. Results highlight that the mixing shear layer at the interface between the main channel and the floodplain is well captured and quantified by this novel approach. iii *Flume experiments of turbulent open channel flows over bed-mounted square bars at low and intermediate submergence are carried out for six cases. Two bar spacings, corresponding to transitional and k-type roughness, and three flow rates, are investigated. This experimental study focused on two of the most aspects of channel rough shallow flows: water surface profile and mean streamwise vertical velocity. Results show that the water surface was observed to be very complex and turbulent for the large spacing cases, and comprised a single hydraulic jump between the bars. The streamwise position of the jump varied between the cases, with the distance of the jump from the previous upstream bar increasing with flow rate. The free surface was observed to be less complex in the small spacing cases, particularly for the two higher flow rates, in which case the flow resembled a classic skimming flow. The Darcy-Weisbach friction factor was calculated for all six cases from a simple momentum balance, and it was shown that for a given flow rate the larger bar spacing produces higher resistance. The result of the simulation that was carried out by Chua et al. (2016) shows good agreement with the experiments in terms of mean free surface position and mean streamwise velocity. *Drag coefficient empirical equations are predicted by a number of authors for an array of vegetation. The research aims to assess the suitability of various empirical formulations to predict the drag coefficient of in-line vegetation. Drag coefficient results show that varying the diameter of the rigid emergent vegetation affects significantly flow resistance. Good agreement is generally observed with those empirical equations. Key Words: Flow Visualization; Infrared Thermography; Shallow Flows; Shear layer; Image processing; Experiment; Free surface; Bridge hydrodynamics; Bridge overtopping; Vegetation roughness, Emergent vegetation, Drag coefficient, blockage; Compound channel, Lateral velocity profiles; Hydraulic resistance; Hydraulic jump, Square bars.

In recent years, water utilities have placed a greater emphasis on the reliability and resilience of their water distribution networks. This focus has increased due to the continuing aging of such infrastructure and the potential threat of natural or man-made disruptions. As a result, water utilities continue to look for ways to evaluate the resiliency of their systems with a goal of identifying critical elements that need to be reinforced or replaced. The simulation of pipe breaks in water reliability studies is traditionally modeled as the loss of a single pipe element. This assumes that each pipe has an isolation valve on both ends of the pipe that can be readily located and operated under emergency conditions. This is seldom the case. The proposed methodology takes into account that multiple pipes may be impacted during a single failure as a result of the necessity to close multiple isolation valves in order to isolate the “segment” of pipes necessary to contain the leak. This document presents a simple graphical metric for use in evaluating the performance of a system in response to a pipe failure. The metrics are applied to three different water distribution systems in an attempt to illustrate the fact that different pipe segments may impact system performance in different ways. This information is critical for use by system managers in deciding which segments to prioritize for upgrades or replacement.

This study focussed on the treatment of stormwater runoff using constructed wetlands (CWs): man-made systems engineered to replicate the treatment processes in natural wetlands. The main aims were to design and assess a novel configuration of CWs for stormwater treatment, while contributing to the further understanding of pollutant removal in CWs through the development of models to explain internal processes and predict performance. A vertical tidal-flow CW operational regime was applied to target enhanced nitrogen removal while maintaining high removal rates a range of high priority urban stormwater pollutants. Eight pilot-scale CW models were built to investigate the effect of key design and operational variables: substrate media, wetland surface area, and wetting and drying regimes. The performance of the systems was considered successful when compared to results of similar pilot-scale CWs that operated without tidal flow. Results show that all eight models effectively reduced concentrations of solids and metals, with load reductions generally in excess of 90%. Nutrient removal – particularly nitrogen - was heavily affected by design and operation variables. Significantly, nitrogen removal in the systems outperformed similar pilot-scale CWs with alternative hydraulic operating conditions. Understanding of the internal CW treatment processes were backed up through statistical analysis and numerical modelling. These techniques highlighted important mechanisms such as the biological transformation of nitrogen and the importance of TSS removal to heavy metals reduction. Overall, results show that the CW design has great potential for reduction of solids, metals and nutrients in stormwater. Further research at a field scale would better represent the performance of the systems in practice, and closer monitoring of dissolved oxygen and redox potential would enhance understanding of internal processes, particularly regarding nutrient behaviour. Results of this study can contribute to future CW research and design, through increased understanding of long-term pollutant removal in these types of system. In time, this may result in the wider application of CWs for stormwater treatment to make human water use more sustainable and better protect the environment.

Countries around the world have been developing ecological policies to protect their water resources and minimise the impacts of development on their river systems. The concept of ‘minimum flows’ was initially established as a solution but it did not provide sufficient protection as all elements of a flow regime were found to be important for the protection of the river ecosystem. “Environmental flows” were developed to determine these flow regimes to maintain a river in some defined ecological condition. Rapid, initial estimates of the quantity component of environmental flows may be determined using the Desktop Reserve Model in South Africa. However, the Desktop Reserve Model is dependent upon the characteristics of the reference natural hydrology used. The advancements in hydraulic and ecological relationships from the past decade have prompted the development of a Revised Desktop Reserve Model (RDRM) that would incorporate these relationships. The research in this thesis presents the development of the hydraulic sub-model for the RDRM. The hydraulic sub-model was designed to produce a realistic representation of the hydraulic conditions using hydraulic parameters/characteristics from readily available information for any part of South Africa. Hydraulic data from past EWR studies were used to estimate the hydraulic parameters. These estimated hydraulic parameters were used to develop hydraulic estimation relationships and these relationships were developed based on a combination of regression and rule-based procedures. The estimation relationships were incorporated into the hydraulic sub-model of the integrated RDRM and assessments of the hydraulic outputs and EWR results were undertaken to assess the ‘applicability’ of the hydraulic sub-model. The hydraulic sub-model was assessed to be at a stage where it can satisfactorily be incorporated in the RDRM and that it is adequately robust in many situations. Recommendations for future work include the refinement of estimation of the channel forming discharge or the use of spatial imagery to check the maximum channel width estimation. It is also proposed that a future version of the hydraulic sub-model could include flow regime change impacts on channel geomorphology and sedimentology so that flow management scenarios can be more effectively assessed.

Road safety is a very important topic for research and development divisions in the automotive industry. As the tyre is the only link between road surface and vehicle, it plays a very significant role in accident mitigation and prevention. This thesis investigates the influence of internal tyre pressure on the brake distance both experimentally and theoretically. Brake tests were performed using a robotic system and a winch was used to pull a car with locked wheels. For both experiments, the tyre pressures were changed. A rubber friction law is presented which can be used for tyre and vehicle dynamics calculations. The friction law was tested by comparing numerical results to the full rubber friction theory of Persson and to experimental data. A two-dimensional (2D) tyre model is introduced that combines the rubber friction law with a simple mass-spring description of the tyre body. The tyre model is very flexible and can be applied to different manoeuvres. It can be used to calculate μ-slip curves, self aligning-torque, braking, and cornering, or combined motion (e.g. braking during cornering). The theoretical predictions have been compared to measured data from indoor tyre testing on sandpaper substrate. Additionally simulations of anti-lock braking system (ABS) using two different control algorithms are presented. In addition a method for rapidly changing the tyre inflation pressure while a vehicle is in motion is presented. This method can be used for novel safety system approaches.