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In an attempt to contribute the efforts for the robust and effective numerical tools concerning ship motions in astern seas, this thesis presents the development of a coupled non-linear 6-DOF model with frequency dependent coefficients, incorporating memory effects in random waves with a new axis system that allows straightforward combination between seakeeping and manoeuvring model whilst accounting for extreme motions. A combination of seakeeping and manoeuvring is achieved through the adoption of relatively new "horizontal body axis system" which accounts for large vertical motions as well. Furthermore, the frequency dependent terms are incorporated in order to improve the accuracy of the numerical model for non-zero encounter frequencies which are experienced especially when the ship has large heading angle. The effect of encounter frequency and so called "memory effects" are calculated in terms of radiation forces using convolution integrals. Equations of motions and external forces are described in terms of a new axis system. The wave forces are calculated through incident and diffraction wave forces. The incident wave forces are calculated using the instantaneous wave surface while low encounter frequency model is adopted for the calculation of diffraction forces. Finally, the whole numerical model is expressed in random sea environment including the convolution terms to carry out the simulations in more realistic sea environments. The validation of the numerical model with the results of benchmark tests commissioned by ITTC Specialist Group on Stability, showed reasonably satisfactory agreement while the inclusion of frequency dependent terms affected the accuracy of the numerical model. Parametrical studies were carried out to investigate the effect of different environmental and operational parameters to ship motions in extreme astern seas along with the effects of degrees of freedom and encounter frequency. In order to enhance the numerical model and to obtain further information about the coupling of the motions and the adequacy of the numerical model to carry out further simulations regarding dangerous situations during ship motions in random following and quartering seas, extensive captive and free running model tests were carried out. The numerical model provided good agreement with the experiments. The terms resulting from the coupling of vertical motions and large heeling angle to wave forces are obtained. It is believed that the numerical model has a good potential for providing a more rational basis for predicting the dangerous conditions which a ship could face in extreme astern seas, and for offering insights about the link of behaviour with the design parameters of a ship in the light of the validation with the experiment results and parametrical studies.

A software-based modem design offers a new opportunity to integrate processing at various levels, to enhance performance (TCP throughput) and robustness (to jamming). There are several key problems that need to be addressed that impact link ARQ performance. ACKs are needed for link sender to retransmit or adapt and an imperfection of ACK feedback from receiver prevents a link responding to loss and may cause the forwarding to be suspended. Another problem identified is that although ARQ may efficiently retransmit corrupted frames resulting from Partial Band Noise Jamming, it is inefficient when operating in environments with significant levels of AWGN. At the same time, a single fixed FEC scheme is insufficient for a wide range of AWGN and would be lead to a high overhead at low AWGN. The approach presented in the thesis therefore provides features to make sure robustness is achieved over a wide range of error conditions. At the physical layer, the design sends individual frames in hops (rather than spreading errors with interleaving) and employs a tailbiting FEC code. At the link, ARQ is used in combination with diversity coding to ensure acceptable TCP performance. Robust framing is provided by status slot replication and an effective synchronisation algorithm. A range of ARQ methods are used to support multiple applications including (a) No ARQ link class option (for packets that do not require ARQ) and (b) ARQ option (3-level retransmission scheme, with increasing level of redundancy after each RTT). To achieve a good throughput with high levels of AWGN uses a novel application of diversity coding. Analysis shows this approach gives good performance. In comparison with HDLC, APRIL performance is comparable to HDLC at low FER (less than 0.1) over a range of jamming, while it outperforms this at high FER (0.1-0.5). Diversity in combination with ARQ significantly improves performance at high AWGN (or a combination of AWGN and PBNJ), but does so in an adaptive way without introducing significant overhead at low AWGN. A key feature of the approach is that it does not require a separate estimate of the link conditions and there is no need to explicitly inform the receiver of either the ARQ mode or the diversity level. The scheme is therefore well suited to the unpredictable characteristics of the military satellite environment.

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The acquisition of marine survey data is traditionally undertaken from surface vessels including boats and temporary rigs. Translation of these techniques to the nearshore zone is a complex task and requires equipment adaptation and. often the sacrifice of data coverage. The remotely operated vehicle (ROV) offers the potential for overcoming some of the standard nearshore survey Concems, providing remote intervention and data acquisition in areas of restricted access. In situ testing is the most efficient and reliable method of acquiring data with minimal sediment disturbance effects. Research has been undertaken into the viability of nearshore cone penetration testing (CPT) which has shown the T-Bar flow round penetrometer to be a possible solution. Data could be acquired in sediments with undrained shear strengths of up to 300 kPa from a bottom crawling ROV weighing 260 kgf and measuring 1 m in length by 0.6 m in width. The collection of sediment cores may be necessary in areas requiring ground truthing for geophysical or in situ investigations. A pneumatic piston corer has been designed and manufactured and is capable of collecting sediment cores up to 400 mm in length, 38 mm in diameter, in sediment with undrained shear strength of 17 kPa. To ascertain additional sediment characteristics in situ, a resistivity subbottom profiling system has also been designed and tested and allows for discrimination between sediment types ranging in size from gravel to silt. The integration of equipment and testing procedures can be fiirther developed through the use of integrated data management approaches such as geographical information systems (GIS). An offthe- shelf GIS, Arclnfo 8, was used to create a GIS containing typical nearshore data using the Dart estuary as a case study location.

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This research concentrates on damage ship stability and means for assessing dynamic ship performance in this state. A consolidation of many approaches for tackling damage ship dynamics has been undertaken, culminating in the development of a numerical tool for simulating ship behaviour while accounting for progressive flooding and the ensuing effects of floodwater motion. General features that have been accounted for in a new purposely developed numerical program PROTEUS3 include the following: Linear concepts regarding intact ship hydrodynamics based on strip theory and Rankine source method (RSM). These are further utilised by convolution and spectral transformations in deriving relevant time domain force realisations. Non-linear excitation/restoring forces calculated from pressure integration up to the instantaneous undisturbed wave profile. Non-linearities in hydrodynamic properties arising from variation of mean underwater geometry due to occurrence of non-stationary asymm etries in mass distribution are taken into account by a database approach. Forward speed in arbitrary heading. Progressive flooding through a ship with any internal subdivision and floodwater motion simulations based on free-mass-on-potential-surface (FMPS) model. Non-linear treatment of the effects of cargo shift or floodwater motions on the overall ship dynamic behaviour. The underlying modelling has been explained by rigorous derivation of all the relevant equations from first principles. Validity of the model has been tested comprehensively through comparison with available physical model tests data. A thorough investigation on the new effects of modelling advancements concerning the accuracy of the developed model has been undertaken and the results are presented and discussed. Despite the introduction of simplifying assumptions concerning floodwater behaviour, the predictions show consistency with physical experimental data. It is believed that this pragmatic approach constitutes a very efficient tool for predictions of vessel performance in extremely adverse conditions. This effectiveness has been demonstrated by undertaking forensic analysis of two of the most controversial accidents of the last two decades, namely the loss of MV Derbyshire and the NW Estonia disaster.

This thesis is concerned with the measurement and effects of pressure on the body as a result of military load carriage. High skin pressures are associated with impaired blood flow, brachial plexus disorders and user pain and discomfort. Load carriage research has largely overlooked this issue, mainly due to the lack of an appropriate methodology. The thesis consists of two parts. The aim of part I was to develop and validate a novel method of measuring on-body interface pressures underneath military load carriage equipment. The Tekscan system was used, which provides 954 individual sensing elements over a total sensing area of 238.5cm2. A number of small experiments were undertaken to establish appropriate calibration and measurement error. A five-point rating scale was developed, and included within the experimental procedure; to measure user discomfort at the shoulder area where was 'no discomfort' and 5 was 'unbearably uncomfortable'. Following a pilot study the method was shown to produce reliable data that was sensitive to differences in design of load carriage systems within a comparative experimental design.

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