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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Novel processing and microencapsulation of Ganoderma lucidum spores for healthcare

Zhao, D. January 2014 (has links)
Ganoderma lucidum spores (GLS) have attracted increasing attention for its versatile biological activities, particularly in cancer therapy. The resilient chitin bilayer of sporoderm is conventionally regarded as an obstacle in the exploitation of bioactive ingredients. Present study found that ethanol extract of broken GLS was able to inhibit cancer cells, however, water extract, especially medium extract (containing serum protein) from unprocessed GLS have also demonstrated anti-proliferative effects on cancer cells. The effectiveness of GLS extract on the inhibition of a series of human cancer cells, namely, osteosarcoma, neuroblastoma, myeloid leukaemia and breast cancer, has been compared, and DNA assays showed that the GLS extract is more efficient in inhibiting neuroblastoma but has less effect on osteosarcoma cell line. To overcome the limitations of the existing processing methods of GLS, the feasibility of sonication as a new way to break GLS has been tested. A series of processing parameters, such as sonication power and duration, have been compared to maximise the breaking efficiency. The preservation of bioactive components of GLS (e.g. polysaccharides and ganoderic acids) from sonication processing was revealed by Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) analyses. In vitro study showed that sonication processed GLS were able to inhibit breast cancer cells, at dose and time dependent manner, particularly at low pH (6.5), favourable for cancerous cell growth. The inhibitory efficiency of sonication processed GLS on the growth of breast cancer cells was ranked the highest, compared with that of unprocessed GLS and commercially broken GLS. To preserve further the bioactive ingredients of GLS, broken GLS have been encapsulated with alginate by electrospraying (ES). The size of GLS encapsulated alginate (GLS/A) beads was found to affect the in vitro release profiles of bioactive ingredients of GLS, and can be controlled by varying the processing parameters (e.g. crosslinking time, infuse rates and applied voltage). A series of GLS/A beads with mean sizes ranging from 500 to 2500 µm have been produced by ES and the in vitro release profiles of GLS/A beads in simulated gastrointestinal mediums were found to be related to the pH, bead size and drying methods. In summary, an advanced method combining a customised sonication with ES has been developed by setting up a lab-scale production line from processing to encapsulation of GLS. This may pave the way to produce effective GLS products with desirable natural bioactive components for healthcare.
52

Development of an in silico methodology for the multiscale modelling of atherosclerosis

Di Tomaso, G. January 2014 (has links)
Atherosclerosis is the main cause of mortality and morbidity in Western World, causing more death and disability than all the types of cancer. Given its high potential danger it is of major importance to better understand the causes of atherosclerosis, which are linked to both the lipoprotein metabolism and haemodynamics in arteries. Together with in vivo and in vitro experiments, in silico models and simulations allow for a better insight and understanding of the mechanisms of atherosclerosis formation. A multiscale model coming from the integration of a fluid dynamics model, and a biochemical model is here presented for the modelling of atherosclerosis at its early stage. An artery-specific approach was used in the fluid dynamics model for modelling the interaction between arterial endothelium and blood flow. The low density Lipoprotein (LDL) oxidation leading to immune-response (cytokines, monocytes/macrophages) and foam cell formation and accumulation at the basis of plaque formation was described in the biochemical model. Integration of these modelling approaches led to the creation of an effective tool for the modelling of atherosclerosis plaque development, the atherosclerosis remodelling cycle. The impact on the disease development of different mean blood LDL concentrations and arterial geometries was analysed. The atherosclerosis remodelling cycle was applied for patient-specific simulation of plaque formations in a patient presenting with atherosclerosis formations in the aorta and peripheral arteries. When compared with the multi-slice computed tomography (MSCT) images, the model highlighted atherosclerosis-prone areas, where plaques were found in vivo, with 91.7% accuracy and replicated 41.7% of the plaques presenting in the patients.
53

Investigation of single-needle and multi-needle electrohydrodynamic processes for the preparation of advanced bioproducts

Sofokleous, P. D. January 2014 (has links)
Polymeric products with micro/nano dimensions have attracted substantial interest in recent years and it has been shown that complex structures can be generated from solid and encapsulated particles/fibres. Although several techniques have been used to engineer these products their disadvantages such as high processing costs and the need for solvents and additives that are not fully biocompatible, lead to poor controllability and biological stability of the bioactive agents. In contrast, electrohydrodynamic (EHD) and co-axial EHD (CEHD) processes are simple and inexpensive techniques that can produce solid and multicomponent products on the nano/micro scale in a single step and under ambient conditions. The parameters affecting the formation of these products using the EHD process are well-known but on the other hand studies using the CEHD process are limited; hence the first objective of this work was to investigate the different physical and mechanical processing parameters affecting the encapsulated fibres produced by the CEHD process. The second objective of this study was to use a single needle EHD system to prepare and investigate the release of amoxicillin from electrospun polymeric fibrous wound dressing patches for wound healing and infection control. This work establishes a potential method of producing drug-loaded polymeric micro fibres with a controlled release behaviour that can be use in wound care industry. The third objective of this study was to improve the EHD and CEHD processes by designing and constructing an advance multi-needle assembly device where the needle height displacement between the needle tips could be controlled, which was then inserted in a portable handheld electrohydrodynamic spray gun. The spray gun was tested successfully for its ability to engineer solid and encapsulated products. The fourth and last objective was to investigate how the needle height displacement between their needle tips, in a two needle co-axial EHD assembly system, is affecting the production of encapsulated particles/fibres and the percentage number (n%) of the encapsulated products formed. By successfully achieving these objectives it was proved that there are still ways to improve the EHD and CEHD techniques in order to expand their use in many other technological and pharmaceutical fields.
54

Flushing ballast tanks

Qi, Z. January 2015 (has links)
The non-indigenous species (NIS) transported by ships’ ballast water lead to destructive failure of the main ecologies giving rise to economic implications of many countries dependent on aquatic organisms. The International Maritime Organisation currently requires that ballast tanks are flushed three times with far ocean water. New protocols for cleaning technologies are still in discussion internationally. Current lacking is the science to understand how ballast tanks geometry and ballast water composition affect the NIS removal rate. This thesis describes a major contribution to this effort and identifies key engineering principles that should be taken into account to improve flushing efficiency. A combined experimental and theoretical study of flushing from ballast tanks is described. A hierarchy of laboratory scale models are designed, built and tested to understand the effect of geometry and stratification, with complexity increasing from 1×7, 2×2, 3×3 to 5×4 configurations. The experimental study is based on an optical method of interrogating the fraction of each compartment and whole tank that is cleaned. By drawing on modelling approaches applied in related areas, notably building engineering, a number of new mathematical models are developed that have no free variables (when resistance of pathways is the same) or require the use of closures for pressure drop coefficients. For homogeneous flow where stratification is negligible, the agreement between predictions and experiments is within 1.2%. Likewise, when resistances are different, the model is accurate, except when the inhomogeneity is significant. Three models are developed to include the influence of stratification. For miscible fluids, the stratified mixing model is accurate within 5% at Richardson number between 30 and 1000. We apply the validated models to examine how to change practical ballast tanks and how cleaning efficiency affects the total NIS removal. To enhance flushing, a single outlet should be placed far from the inlet.
55

The effect of fuel additives on diesel fuel delivery system and combustion performance

Duboc, B. January 2014 (has links)
The thesis presents an investigation of several aspects of fuel additive performance, including the effects of additives on the pump torque required to deliver high pressure fuel to engine injectors, the fuel droplet size distribution at sub-zero diesel fuel temperature, when wax formation occurs, and the ignition delay of diesel fuel combustion in an engine as well as constant volume combustion vessel. Exhaust emissions due to fuel additives were also investigated in an engine. A pump torque rig was designed and commissioned to investigate fuel additive performance at various pump speeds, fuel delivery (common rail) pressures and fuel temperatures, including sub-zero temperatures at which fuel waxing occurs. An existing constant volume combustion vessel was adapted to allow observations of fuel spray with additives and it was used for spray and combustion investigations. Various components of the combustion vessel were modified to support the fuel spray instrumentation. Also, a sub-zero fuel temperature system was developed to allow fuel to be cooled down for investigations; finally, a fuel pressure intensifier was designed which allowed ease of dismantling and thorough cleaning so as to eliminate additive cross-contamination between successive tests with additives. Results have shown that in general, additives have very small effects on many aspects of the fuel delivery system performance when the primary purpose of the additive is not related to the fuel delivery system. That is, there are virtually no side effects on pumping system performance from additives not intended to affect this system. This is mainly due to the small quantity in which the fuel additives are added, which is too small to affect any of the overall fuel properties. Additionally, it was proven that a constant volume combustion vessel is unsuitable to carry out combustion performance tests on fuel with additives, due to the high error in test repeatability. In contrast, the engine tests were able to reveal the effects of several combustion modifying additives on engine combustion performance and exhaust emissions. The fuel spray analysis at sub-zero temperatures revealed that wax formation was not the likely cause of an increase in droplet size but, instead, the likely cause is an increase in fuel viscosity.
56

Effect of ethanol and butanol content in future fuel blends on spray and combustion characteristics in DISI engines

Behringer, M. K. January 2014 (has links)
Direct Injection Spark Ignition has become popular within the automotive industry due to the flexibility in injection strategies. This, along with the introduction of novel fuels such as mixtures of ethanol or butanol with gasoline, requires new understanding of the air-fuel mixture preparation and combustion as fuel properties vary greatly. The motored engine flow field of an optical research engine was characterised using Laser Doppler Velocimetry and Particle Image Velocimetry and analysed regarding turbulence properties at the world wide mapping point. The intake flow effect on the spray of a pressure swirl injector was investigated using the base fuels gasoline, isooctane, ethanol and butanol. Furthermore, low percentage splash blended mixtures of 25 % ethanol and 16 % or 25 % butanol with the reference fuels were created and geometrical spray features were obtained from high speed imaging along with the droplet sizes using Phase Doppler Anemometry. Spray investigations were also under taken in a quiescent environment with a more modern spark eroded multi hole injector and its direct replacement featuring a novel Laser drilled nozzle. The results highlight the strong effect of the fuel type, where especially pure butanol showed largest difference to the baseline fuels in terms of shape along with a significant increase of the droplet size. Ethanol also showed an increase in droplet size but only small differences to gasoline’s spray shape at 80 bar or 120 bar fuel pressure into 0.5 bar or 1 bar ambient air at 20 °C, for fuel temperatures of 20 °C or 80 °C. The ethanol mixture was typically more similar to gasoline than the butanol blends. Thermodynamic parameters were derived using incylinder pressure analysis for stoichiometric (λ=1) and lean (λ=1.2). Additionally, high speed chemiluminescence imaging was used at gasoline’s maximum break torque spark timing, calculating flame radii, radius growth, roundness and centroid development. Further analysis was using flame tomography for better insight into the early stages after ignition and the flame front characteristics for the base fuels only. Overall, the analysis showed little difference between gasoline and the blends, but showed changes for the pure alcohols with typically much faster flame progression of ethanol and issues with the combustion of butanol at low engine temperatures. The tomography analysis returned similar flame structures for the pure fuels, what is confirmed by their location in combustion diagrams.
57

Oil flow, cavitation and film reformation in journal bearings, including an interactive computer-aided design study

Miranda, A. A. S. January 1983 (has links)
An interactive computer program for the design of steadily loaded fluid film, hydrodynamic journal bearings based on the procedure of E S D U Item No. 66023 (1966) is presented. The program was developed in two forms, a graphics and a non-graphics version. The computer program procedure enabled a detailed study of the effect of changes in the parameters on the bearing performance, which in turn permitted the design of an optimized bearing. A theoretical and experimental study of the influence of film reformation on the performance of hydrodynamic journal bearings, and the side flow rate in particular, is also presented. A numerical analysis technique based on a cavitation algorithm proposed by H.G. Elrod was developed. This technique was capable of an automatic d etermination of the boundaries of the cavitation region and included a consideration of the lubricant inlet conditions (groove geometry and supply pressure). Theoretical data for journal bearings with a single axial groove located at the position of maximum film thickness is presented for a wide range of the values of the bearing design and o perating parameters. An apparatus was designed and commissioned to study the lubricant flow rate in journal bearings. Tests were performed wi t h three glass bushes of width-to-diameter ratio of unity at variable values of eccentricity ratio and lubricant supply pressure. The agreement achieved between theory and experiment for dimensionless side flow rate was excellent. For the location of the film reformation boundary, the correlation between theoretical predictions and experimental measurements was satisfactory, except at low values of eccentricity ratio and dimensionless supply pressure. A study of the correlation between the predictions of dimensionless load capacity, attitude angle and dimensionless side flow rate obtained from ESDU Item No. 66023 (.1966) and those of the new bearing analysis reported in the thesis is presented. Good agreement was observed for the predictions of side flow rate.
58

Whole aero-engine meshing and CFD simulation

Wang, Feng January 2013 (has links)
Aero-engine components are strongly coupled with each other and traditional design tools are not always able to predict the complex phenomenon caused by component interactions. Whole engine simulations could allow designers to capture this phenomenon, increase the design confidence and reduce design cycles. The aim of this thesis is to reduce the turnover time in the pre-processing of whole engine simulations and conduct CFD simulations of the whole engine gas path. This thesis has developed a set of meshing methods for turbomachinery applications. These methods include multi-block structured meshing, 2D/3D Delaunay triangulation, Q-morph, hybrid meshing and hex meshing. These meshing methods are integrated with the in-house geometry database to reduce the required man-hours in the pre-processing of whole engine simulations. This has reduced the required man-hours from days and weeks to a few hours. The whole engine simulation benefits from the development of the developed preprocessing tool, so that the whole engine gas path can be simulated. A compressible reacting gas model is used throughout the domain to ensure the consistency of gas thermodynamic properties. The turnover time of the preprocessing of a whole engine simulation can be reduced to roughly 8 man hours (one working day), which makes the whole engine simulation a feasible tool in the design process.
59

Patellofemoral joint biomechanics : computational modelling and clinical applications

Lumpaopong, Punyawan January 2013 (has links)
The patellofemoral joint (PFJ) plays an important role in the extensor mechanism of the knee. Several types of PFJ disorders are commonly found in about 25% of the people. It is believed that patellofemoral (PF) disorders, e.g. excessive lateral pressure syndrome and patellar maltracking, may be associated with articular cartilage contact pressure elevation, which accelerates degenerative joint disease and causes anterior knee pain. To reduce the pressures, a number of anatomical interventions have been applied to correct contact mechanics and patellar tracking. However, the rate of successful surgery is not high because the anatomical complexity of the joint itself and complex symptoms make diagnosis difficult. For this reason, various computational modelling techniques have been developed to assist in diagnosis and prognosis of PF disorders. This research aims to develop a finite element (FE) modelling method and study the feasibility of its clinical applications. The modelling methods may assist in the diagnostic and treatment planning processes. The research was divided into five phases: 1) development of an FE modelling method to analyse PFJ models 2) model validation using in vitro experimental data 3) development of subject-specific input estimation method from routine diagnosis protocols 4) model sensitivity analysis and 5) clinical applications. The FE results included joint contact force, contact pressure, subchondral bone stress and patellar kinematics. The validation and sensitivity analysis showed that the FE modelling method could adequately analyse PFJ biomechanics. Approval for a clinical study was obtained from the National Health Service (NHS) Research Ethics Committee, and groups of control subjects, anterior knee pain (AKP) patients and those with trochlear dysplasia and trochleoplasty were recruited. The modelling method was applied to analyse their knees and predict their non-operative and operative treatment outcomes. The study showed that the biomechanical responses of the PFJ and the treatment evaluations were variable. In particular, it was found that AKP was associated with significant elevation of contact pressure; thus confirming the usefulness of the FE modelling method as a powerful diagnostic and surgical planning tool for subject-specific PFJ treatment.
60

Investigation of conditional statistics in premixed combustion and the transition to flameless oxidation in turbulent opposed jets

Goh, Kok Hin Henry January 2013 (has links)
The current work focuses on extracting useful statistical information from Particle Image Velocimetry (PIV) measurements, complemented by Hot Wire Anemometry (HWA) measurements. Experiments were conducted in the turbulent opposed jet geometry, which is a canonical configuration for understanding the fundamentals of flow and combustion. Novel fractal grids were used to generate turbulence in the flow, and turbulent characteristics of the flow field were extracted to ascertain the relative effects of flow configuration on the flow characteristics, including lengthscale and energy information, using energy spectra and Proper Orthogonal Decomposition (POD). Lean premixed flames were measured using PIV, and novel techniques used to extract unconditional velocity statistics, bulk motion and rotation effects, conditional statistics, turbulent burning velocities, flame surface density (FSD), thickness of turbulent flame brush and instantaneous reaction zone, flame surface area, conditional dissipation, as well as conditional POD (CPOD). These were made accessible via density segregation, a multi-step image processing algorithm, used to detect flame isocontours directly from PIV images. Relative effects of flow and chemistry were investigated for lean premixed twin opposed jet flames, using methane, propane, ethylene, cyclopentane and JP-10 as fuels. In addition, the transition to flameless oxidation from conventional premixed flames was also characterised using methane, cyclopentane, cyclopentene and JP-10, via a Damkohler number analysis.

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