Many environmental free surface flows involve water and sediment transport. The net changes to the surface level of an erodible bed by sediment entrainment and deposition processes have a feedback effect on the local ow hydrodynamics. Bed morphological change is of great socio-economic and environmental importance in that it affects navigation, flood risk management, water quality, species diversity, and overall river sustainability. This thesis describes a mathematical model of the depth-averaged shallow water-sediment equations based on mass and momentum conservation laws. A 2D numerical model is then presented of the fully coupled, variable-density governing equations, which are solved using a Godunov-type HLLC scheme. Dependent variables are specially selected in the numerical model to handle the presence of the variable-density mixture in the mathematical formulation. The model includes suspended sediment, bedload transport, and bed morphological change. The numerical model is verified against benchmark analytical and semi-analytical solutions for complicated, clear water flows, bedload transport and suspended sediment transport. The well-balanced property of the governing equations is verified for a variable-density dam break flow over a bed step. Simulations of an idealised dam-break flow over an erodible bed, in excellent agreement with previously published results, validate the ability of the model to capture complex water-sediment interactions under rapidly-varying flow conditions and a mobile bed, and validate the eigenstructure of the system of variable-density governing equations. The model is then further validated against laboratory based data for complex 2D partial dam breaks over fixed and mobile beds, respectively. The simulations of 2D dam break flows over mobile beds highlight the sensitivity of the results to the choice of closure relationships for sediment transport. To investigate this further, a parameter study is carried out using a variety of commonly used empirical formulae for suspended sediment transport. The numerical model is also used to inform a theoretical model that predicts the flow through and around a porous obstruction in a shallow channel. This problem is relevant to several practical applications, including flow through aquatic vegetation and the performance of arrays of tidal turbines in a finite-width tidal channel. The theoretical model is used to reinterpret the core flow velocities in laboratory-based data for an array of emergent cylinders in a shallow channel. Comparison with experimental data indicates the maximum obstacle resistance for which the theoretical model is valid. In a final application, the theoretical model examines the optimum arrangement of tidal turbines to generate power in a tidal channel, confirming that natural bed resistance increases the power extraction potential for a partial tidal fence.

Tenhults Pressgjuteri AB is facing growth in expansion, which results in need of bigger premises. The company has bought an adjoining property to overcome this problem. This thesis givessuggestions on how the logistics of these properties should be managed, which transport system is most suitable to use, where deliveries will take place and how the stock will be set upin the new premises. To obtain relevant data and information have a description of the facts, measurements and calculations been made. Selections and ratings have been used to develop suitable alternative solutions. The payback-method has been used to calculate the investments. A specially designed evaluation chart forms the basis of which transport system to be used. Lastly, a sensivity analysishas been conducted to determine how reliable the results are. Deliveries and inventory have been determined based on the choice of transport system.The thesis shows that the choice of transport system depends on the volumes that are carried, distance and environmental conditions. The market offers both automated transport systems and systems that require a driver. The automated transport system willnot be profitable whenthe cargo volume is too small since the investment costs are significantly higher. However, the operating costs are low which makes it profitable with an increased cargo volume. Closer analysis of existing production flow could provide a more credibleresult. What also must be taken into account is thatthe costs is not preciseand may differ in reality. The costs are assumed to be so lifelike that they do not affect the result more than marginally. / Tenhults Pressgjuteri AB befinner sig i en expansionsfasoch är i behov av större lokaler. För att lösa dettahar företaget köpt upp en grannfastighet. Denna rapport ger förslag på hur logistiken mellan dessa fastigheter skall skötas,vilket transportsystem som är lämpligt att använda, var utleveranserskall ske,samt ett förslag på hurlager kan ställas uppi den nya fabriken. För att erhålla relevant data och information har nulägesbeskrivningar, mätningar och beräkningar gjorts. Urval och värderingar har använts för att ta fram lämpliga alternativ på lösningar. För att beräkna investeringskostnader har payback-metoden använts och ett specialframtaget värderingsschema ligger som grund för valet av transportsystem. Slutligen har en känslighetsanalys gjorts för att bestämma hur pålitligt resultatet är. Utleverans och lager har bestämts utifrån valet av transportsystem för att synkronisera på bästa sätt. Arbetet visar att val av transportsystem beror påvilka volymer som fraktas, avstånd och miljöförhållanden. Marknaden erbjuder både automatiserade transportsystem och system som kräver chaufför. I detta fall är fraktvolymen för litenför att ett automatiserat system skall vara lönsamt eftersominvesteringskostnaderna för ett sådant system är betydligt högre. Däremot är driftkostnaderna lågaför ett automatiserat systemoch vid en större fraktvolym sparas dessa driftkostnaderin då ingen bemanningskostnad tillkommer.Närmare undersökning av befintligt produktionsflöde kunde ge ett mer trovärdigt resultat då arbetet baseras på beräkningar från olika portar. Det som också skall tas i beaktande är att kostnaderna inte är exakta och kan komma att avvika i verkligheten. Kostnaderna antas dock vara så verklighetstrogna att de inte påverkar resultatet mer än marginellt.

No description available.

This thesis deals with the general principle of technology as a partial freight logistics center services ČSAD Hodonín, as The paper first lists and describes the activities related to the operation of logistics centers, which are further supplemented by an analysis of the operation, focusing on the loading, unloading and transfer batches of different manufacturing companies. This thesis is further supplemented by a theoretical approach with potential applications in the actual operation. The result is then draft general technological progress in the transportation of goods from the factory to the logistics center using its own freight.

Purpose: The purpose of the study was to identify the current transport flow for circuit board racks and to investigate the potential implementation of an automated solution for the transportation of circuit board racks in order to increase efficiency in the flow. The research questions answered during this study were: What does the transport flow for circuit board racks look like today?  What could an automated transport flow for circuit board racks look like?  Is an automated transport flow for circuit board racks a sufficient solution to improve efficiency in the flow? Theoretical framework: The study applied several different theories, with waste being a central part. This, in combination with bottleneck identification, mapping, and automation, has been theories used to study the flow and find improvements. Method: A case study was conducted to analyze the transport flow of circuit board racks and identify potential improvements. The method included a literature review, observations, interviews, brainstorming, Value Stream Mapping, and spaghetti diagrams to collect and analyze data from different perspectives. Results: With a combination of theories and empirical data, an analysis of the current transport flow for the circuit board racks could be made. Furthermore, bottlenecks and waste were identified, and automated transport solutions linked to AMR systems were found as a potential solution for a more efficient transport flow. The result showed that an AMR system is the most advantageous solution. However, the study showed that the automated solution was not sufficient without eliminating the bottlenecks in order to generate maximum efficiency in the automated transport flow. Implications: This study has the implication of highlighting the challenges and opportunities of a more efficient transport flow using AMR systems. This includes an improved working environment, reduced work-related injuries, increased production efficiency by eliminating bottlenecks, and waiting times.

The main aim of the work reported is the design of proof-of-concept of at point-of-use hydrogen peroxide electrogeneration from air. The experimental work discussed within this thesis explores five major areas: the kinetics of electrocatalysis, ion-pairing, change of solvent media, the electrode surface modication by a redox mediator, and the electrochemical reduction of oxygen within enhanced mass transport systems. The electrocatalytic rates and mass transport of two oxygen reduction redox meditors, viz. anthraquinone and methyl viologen, are studied in aqueous solutions. The investigation is facilitated through the use of a boron-doped diamond electrode, allowing the catalytic response to be clearly delineated from that of the direct oxygen reduction process. The use of simulation software is highlighted in combination with experimental voltammograms to extract kinetic data. Specifically, the voltammetric features, such as the `reverse' peak and the `split waves', are given particular attention. Consequently, it is possible to deconvolute the electrocatalytic reaction mechanisms. The reactivity of the viologen radical cation is comparable to the semiquinone radical anion in aqueous solution ((4.8~6)x10^9 M^-1 s^-1), but over a far wider pH range (pH 2.5 - pH 8.5). The change of local proton concentration, and sequential electron transfers play key roles here. Moreover, the reduced reactivity of semiquinone is observed upon formation of ion-pairs with tetrabutylammonium cations in alkaline solutions. The electro-reduction of oxygen and its mediated pathways are also investigated in non-aqueous media; in particular the thermodynamics, the kinetics, and mass transport involved in these processes. Through a variable temperature study in electrolytic acetonitrile solution, the oxygen dissolution is quantitatively shown to be an endothermic process. Moreover, the diffusion coeficients and concentration of oxygen upon change of acetonitrile mole fraction is also explored in water-acetonitrile mixtures. The rates of bimolecular reactions are extracted from simulation programs, involving semiquinone in anhydrous acetonitrile and viologen radical cation in ethanol, and show a 3 - 4 orders of magnitude reduction compared to that in aqueous solution. Although the solubility of oxygen is ca. 6 - 8 times larger in non-aqueous solvents, the much reduced homogeneous rates limit the electrogeneration of hydrogen peroxide in pure organic media. Novel surface modification methodologies for graphitic surfaces with covalently attached anthraquinonyl groups are studied and characterised. The anthraquinonyl-modified carbon surfaces show much reduced overpotentials required for oxygen reduction. In the final chapter, utilising the new surface modification methodology and novel designs, two gravity-feed flow cells for electrochemical reduction of oxygen in aqueous solutions are proposed and characterised, one based upon the tubular electrode geometry. The other exhibits much enhanced current conversion by using a porous reticulated vitreous carbon electrode. The latter may provide a prototype hydrodynamic system to produce dilute hydrogen peroxide solution at point-of-use.

Thesis (DPhil (Logistics))--University of Stellenbosch, 2007. / South Africa currently experiences the double jeopardy problem of catching up to global economic competitiveness whilst at the same time feeling the pressures of sustainability management spearheaded by a global agenda. Global sustainability is defined as growth that is shared without depleting natural resources or damaging the environment. Academic disciplines are challenged to make a contribution and economics as such should contribute by providing the lead and lag indicators for the planning and measurement of scarce resources usuage. This integrative view includes economic sub-disciplines, such as logistics. This integrative view is an acknowledged part of the economics discipline, except that the macro-economic context of some sub-disciplines, such as logistics, often receives less attention during the course of academic activities. The distribution of resources and outputs in the economy is a logistics controlled cross-cutting factor, but suffers from a lack of macro-economic perspective, and lead and lag orientated measurement. This state of the affairs is a historic backlog of logistics and its specific position within economics. During the primary economic era the world began to configure networks and markets, which became more pronounced and settled with the dawn and settling of the industrial era. Logistics then was a “given” and did not receive much thought even as industrial, market economies developed. Transport was regarded as an administered cost, i.e. inefficiencies in logistics systems were evenly distributed between competitors, not giving any specific entity an advantage. With the advent of global competition and the diminishing returns on other cost saving measures, companies began to collaborate and integrate logistics functions within value chains, but the administered part of transport costs failed to receive the attention it required. In this way, global competitors did begin to experience disadvantages on a national level as whole economies suffered from inefficiencies in logistics and specifically transport systems.

The production and transportation of hydrocarbon fluids in multiphase pipelines could be severely hindered by particulate solids deposit such as produced sand particles which accompany hydrocarbon production. Knowledge of the flow characteristics of solid particles in fluids transported in pipelines is important in order to accurately predict solid particles deposition in pipelines. This research thesis presents the development of a three-dimensional (3D) Computational Fluids Dynamics (CFD) modelling technique for the prediction of liquid-solids multiphase flow in pipes, with special emphasis on the flow in V-inclined pipe bends. The Euler-Euler (two-fluid) multiphase modelling methodology has been adopted and the multiphase model equations and closure models describing the liquid-solids flow have been implemented and calculated using the finite volume method in a CFD code software. The liquid phase turbulence has been modelled using a two-equation k−ε turbulence model which contains additional terms to account for the effects of the solid-particles phase on the multiphase turbulence structure. The developed CFD numerical framework has been verified for the relevant forces and all the possible interaction mechanisms of the liquid-solids multiphase flow by investigating four different numerical frameworks, in order to determine the optimum numerical framework that captures the underlying physics and covers the interaction mechanisms that lead to sand deposition and the range of sand transport flow regimes in pipes. The flow of liquid-sand in pipe has been studied extensively and the numerical results of sand concentration distribution across pipe and other flow properties are in good agreement with published experimental data on validation. The numerical framework has been employed to investigate the multiphase flow in V-inclined pipe bends of ±4o−6o, seemingly small inclined bend angles. The predicted results which include the sand segregation, deposition velocity and flow turbulence modulation in the pipe bend show that the seemingly small pipe bends have significant effect on the flow differently from that of horizontal pipes. The pipe bend causes abrupt local change in the multiphase flow characteristic and formation of stationary sand deposit in the pipe at a relatively high flow velocity. The threshold velocity to keep sand entrained in liquid in pipe bends is significantly higher than that required for flow horizontal pipes. A critical implication of this is that the correlations for predicting sand deposition in pipelines must account for the effect of pipe bend on flow characteristics in order to provide accurate predictions of the critical sand transport velocity (MTV) in subsea petroleum flowlines, which V-inclined pipe bends are inevitable due to seabed topology.