Computer programs have been developed for the kinematic and dynamic analyses of cascades of planar four-bar mechanisms. Since the analytic approach has high efficiency and accuracy in computation, a chain of four-bar linkages is developed horizontally and vertically by using the relative coordinates and the absolute coordinates, from which the explicit equations and the simultaneous equations are respectively derived in the kinematic analysis. In this analysis, the actions of transmission of linkages, from left to right, from right to left and from lower to upper, are performed by the image method and transformation procedures. Based on the kinematic analysis, the dynamic analysis is also developed by using both sets of coordinate systems. The generalized equation of motion, the general form of Lagrange's equations, Lagrange multipliers and the theorem of power balance are used to construct various formulations of the governing equations of motion for some particular problems. The problem of a linkage with a moving frame (the ground link) is the most interesting focus in this analysis.

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The safe design and operation of Process plants requires an ability to predict hazard consequences reliably. One particular hazard is a jet fire that might arise from the ignition of an accidental release of pressurised gas or liquid. On offshore gas and oil production platforms and also on land-based gas facilities, accidental releases might occur of high pressure natural gas sometimes containing higher molecular weight components. Industries continue to seek efficient and cost-effective means of protecting their plants and personnel from the hazards of fires. Following disasters which occurred in the past, the need for effective mitigation systems has, once again, been highlighted. Mitigation systems involving agents such as halons, which are perceived to be environmentally damaging, are currently out of favour and interest has revived in the use of water sprays. The research work presented here addresses the problem of the suppression of a compartment jet fire by water sprays. This involved studying the interaction between water spray and a turbulent jet flame inside a compartment of dimension 6x2.4x2.4 m3. The fuel used for the jet fire was propane emerging from a 2.0 cm diameter vertical nozzle and at a mass flow rate of 0.1 kg/s. The objectives of the research are to investigate the mitigation of compartment jet fires by using water sprays by the application of a computational fluid dynamics (CFD) methodology incorporating iv Summary combustion and a radiation model to study the jet fire behaviour and the temperature distribution in a compartment. In order to achieve the above objectives, it is necessary to produce a workable CFD model of an offshore module. The radiative heat exchange is considered in the modelling by using the Discrete Transfer Radiation Method (DTRM). The study of the sprays requires details of the individual drops' sizes. The Malvern Particle Sizer was used to measure the drop size of water sprays from the different spray nozzles which have been investigated in this study. The obtained drop sizes of the spray nozzles investigated are used to model the spray in FLUENT, which is a well developed CFD package used in industry and university research. The research started with the CFD modelling of the compartment fire, followed by experimental work done at the university laboratory at Buxton to validate the result of the modelling. In contrast to previous studies in which the combustion reaction was treated as a simple heat source this CFD has included a model of the combustion reaction. Comparisons are made between the experimental data and the predictions of different scenarios (i. e. steady state, different water spray arrangement and time dependent). The predicted temperature distributions from FLUENT, which includes radiation and surface heat transfer, are found to be in close agreement with the experimental data. Modelling results showed that the current version of the CFD code is able to provide a satisfactory and practical means of modelling jet fire and extinguishment processes.

The aim of the thesis is to examine, mainly, how labour market dynamics affect unemployment. We consider labour market models where current decisions - regarding employment, wage setting, and labour supply behaviour - depend on past decisions, and where these lagged adjustment processes interact. These interactions are the centerpiece of the chain reaction theory of unemployment, in which each labour market shock has a chain reaction of unemployment effects. Chapter 1 analyzes two important dynamic influences: (i) the prolonged effects of temporary shocks, called unemployment persistence, and (ii) the delayed effects of permanent shocks, which we call imperfect unemployment responsiveness. Focusing on three countries - Germany, UK, and US - we identify significant labour market lags, and measure the degree to which these lags are responsible for unemployment persistence and imperfect responsiveness. Chapter 2 shows that in multi-equation labour market models containing lagged endogenous variables and exogenous variables with nonzero long-run growth rates the natural rate of unemployment - as conventionally defined for empirical purposes - is not a reference point (a value toward which the equilibrium unemployment rate tends with the passage of time). Chapter 3 evaluates the natural rate and chain reaction theories of unemployment. For an empirical model of the UK labour market, we show that un-employment does not converge to the natural rate, as conventionally defined. Furthermore, we show that the labour market lags account for a substantial part of the UK long-run equilibrium unemployment rate as well as for the movement of UK unemployment over the past one and a half decades. Chapter 4 shows that real inertia (sluggish adjustment of real variables) may have a powerful role to play in generating the real effects of nominal (demand) shocks, and nominal inertia (sluggish adjustment of nominal wages and prices) may be important in propagating real (supply-side) shocks.

Open-channel flows are ubiquitous in nature and play a central role in many hydraulic engineering problems. This flow type occurs almost exclusively under fully-rough turbulent conditions and it is not uncommon for the relative submergence of these flows to be low. Despite this, most theory has so far been developed for smooth wall flows or rough-bed flows at high submergence while its applicability at low relative submergence remains questionable. This thesis therefore aims to contribute towards an improved understanding of turbulence structure in rough-bed open-channel flow at low to intermediate relative submergence. Experiments were conducted to collect turbulent velocity field data for nine different flow scenarios, covering roughness Reynolds numbers between 175 and 900, and relative submergence between 2.5 and 7.5. Each flow scenario was measured independently using particle image velocimetry (PIV) in five distinct configurations. The PIV system was first configured to make two-component velocity measurements with a very wide field of view (up to twenty flow depths) along the channel centreline in a streamwise-wall-normal plane. These measurements were supplemented with three-component stereoscopic PIV recordings along the same plane albeit with a shorter field of view. The third, fourth and fifth set ups involved stereoscopic PIV in three separate transverse-wall-normal planes and thus ensured the complete lateral coverage of the flow field from the sidewall to the centreline. The four-camera arrangement of each of the present stereoscopic PIV configurations was exploited to obtain velocity field statistics with significantly reduced contributions from measurement noise. The thesis reports distributions of bulk velocity statistics and spectra of all three velocity components. In addition, characteristic large scale features of the instantaneous flow are examined using velocity field visualisation, two-point velocity correlations and premultiplied velocity spectra. Further analysis is carried out on the time-averaged flow field to visualise secondary current patterns and to study their lateral extent.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Global Positioning System (GPS) sensors have the potential to provide precise position, velocity, and timing information in high dynamic applications. Missile flight-testing is one such application where accurate relative positions are important. GPS instrumentation can provide the high accuracy while offering both significant cost savings and improved confidence in the test results when compared to existing methods. To date, the use of GPS in missile flight-testing has been limited due to a lack of demonstrated GPS receiver tracking capability in high dynamics. This paper evaluates several currently available GPS receivers for both their tracking capability and their measurement accuracy in high dynamic environments.

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published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy