Measurement of displacements in granular systems in response to penetration and compaction

The research reported in this thesis is concerned with the flow of granular systems in response to penetration and compaction. The technique of Digital Speckle Radiography (DSR), which involves analysis of flash X-ray images, has been applied to measure the internal displacement fields within large opaque granular samples. Large samples are desirable as the measured displacements are more representative of the bulk. Current DICC algorithms were found to be unsuitable for analysis of X-ray images of large samples. The large contrast variations present in such X-ray images, due to the X-ray beam profile, sample geometry and the high X-ray absorbance of metal penetrators, are shown to cause significant errors in the calculated displacement fields. A study of image normalisation techniques was carried out, and the effect of each technique on the accuracy of the measured displacements was investigated. A new DICC algorithm for use in DSR was produced which includes image normalisation techniques to correct for uneven contrast in the images. This new DICC algorithm was shown to be far more effective at analysing X-ray images of large samples. This improved DSR technique was applied to measure the internal displacements within a large sample of sand during penetration by projectiles with different nose-shapes (flat, ogive-2 and hemispherical) and at different rates (1.5 mm/min to 200 m/s). The improved technique was found to provide high-resolution displacement data illustrating the response of the material. The dominant material response at low rates (1.5 mm/min) was found to be splitting of the material ahead of the projectile tip, followed by bulk reverse-flow of material towards the penetration face. At the higher rates (200 m/s), the dominant response was compaction of the material ahead of the projectile tip. The transition between the two regimes was found to occur between velocities of 5 and 19 m/s. The streamlined ogive-2 projectile nose-shape was shown to be the most effective for penetration, in that it caused less disruption of the material ahead of the projectile, lost less energy during the early stages of penetration in the dynamic experiments and more effectively split the material ahead of the projectile tip, a process which was shown to be important at all rates of penetration. The compaction properties of a particulate mixture and a granular material, including the effect of factors such as porosity, initial particle arrangement and force chain formation, were investigated. Samples which were conducive to the formation of force chains spanning the whole sample were discovered to have anomalously high strengths. Small amounts of added water were shown to increase the compactability, by lubricating the grain contact points, but larger amounts of water decreased the compactability

Thermal-Hydraulics in Nuclear Fusion Technology: R&D and Applications

In nuclear fusion technology, thermal-hydraulics is a key discipline employed in the design phase of the systems and components to demonstrate performance, and to ensure the reliability and their efficient and economical operation. ITER is in charge of investigating the transients of the engineering systems; this included safety analysis. The thermal-hydraulics is required for the design and analysis of the cooling and ancillary systems such as the blanket, the divertor, the cryogenic, and the balance of plant systems, as well as the tritium carrier, extraction and recovery systems. This Special Issue collects and documents the recent scientific advancements which include, but are not limited to: thermal-hydraulic analyses of systems and components, including magneto-hydrodynamics; safety investigations of systems and components; numerical models and code development and application; codes coupling methodology; code assessment and validation, including benchmarks; experimental infrastructures design and operation; experimental campaigns and investigations; scaling issue in experiments

DC and Microwave Analysis of Gallium Arsenide Field-Effect Transistor-Based Nucleic Acid Biosensors

Sensitive high-frequency microwave devices hold great promise for biosensor design. These devices include GaAs field effect transistors (FETs), which can serve as transducers for biochemical reactions, providing a platform for label-free biosensing. In this study, a two-dimensional numerical model of a GaAs FET-based nucleic acid biosensor is proposed and simulated. The electronic band structure, space charge density, and current-voltage relationships of the biosensor device are calculated. The intrinsic small signal parameters for the device are derived from simulated DC characteristics and used to predict AC behavior at high frequencies. The biosensor model is based on GaAs field-effect device physics, semiconductor transport equations, and a DNA charge model. Immobilization of DNA molecules onto the GaAs sensor surface results in an increase in charge density at the gate region, resulting from negatively-charged DNA molecules. In modeling this charge effect on device electrical characteristics, we take into account the pre-existing surface charge, the orientation of DNA molecules on the sensor surface, and the distance of the negative molecular charges from the sensor surface. Hybridization with complementary molecules results in a further increase in charge density, which further impacts the electrical behavior of the device. This behavior is studied through simulation of the device current transport equations. In the simulations, numerical methods are used to calculate the band structure and self-consistent solutions for the coupled Schrodinger, Poisson, and current equations. The results suggest that immobilization and hybridization of DNA biomolecules at the biosensor device can lead to measurable changes in electronic band structure and current-voltage relationships. The high-frequency response of the biosensor device shows that GaAs FET devices can be fabricated as sensitive detectors of oligonucleotide binding, facilitating the development of inexpensive semiconductor-based molecular diagnostics suitable for rapid diagnosis of various disease states

Modelling and prediction of non-linear scale-up from an Ultra Scale-Down membrane device to process scale tangential flow filtration

Ultra scale-down (USD) tools have demonstrated the huge potential for accelerated process development by significantly reducing the material requirements and providing better solutions, as part of the Quality by Design initiative. Key benefits of using USD techniques include the relatively small quantities of feedstock and minimal capital equipment needed to generate large volumes of statistically significant process data in a short period, leading to significant time and cost savings during process development. However, the use of small scale devices such as the stirred cell filtration units have been primarily limited to preliminary testing and initial screening due to their geometric and flow dissimilarities to tangential flow filtration at scale. As a result, process development and optimisation trials are generally carried out using the smallest c commercially available TFF cassettes, the use of which are primarily limited by time and material constraints that are invariably present at the early stages of process development. Therefore, the central focus of this work was to develop a USD methodology and model to accurately predict the performance of large scale tangential flow filtration (TFF) using a USD membrane filtration device. // The commercial package COMSOL was used to carry out computational fluid dynamics (CFD) modelling and simulation of the fluid flow dynamics in Pellicon TFF cassettes with different feed screens and a USD membrane device, in order to develop average wall shear rate correlations and channel pressure drops expressed as functions of the respective hydrodynamic conditions across scales. In addition, the impact of non-TFF related factors such as the system and cassette-specific hydraulic resistances on TFF performance was characterised using semi-empirical models. Finally, a scale-up methodology and mathematical model to predict the large scale performance using USD data was developed by combining the various resistances, channel pressure drop correlations and an empirical USD-derived model that characterises the specific feed-membrane interactions. The CFD simulations were independently verified using 2D particle imaging velocimetry to compare experimental data to the CFD simulated data. // 100-fold scale-up experiments were carried out based on equivalent averaged wall shear rates (w) as the geometry-independent parameter. Permeate flux excursions were carried out to validate the USD methodology and prediction model, by comparing USD model predictions against the large scale experimental data. Different membranes, feed screens (A, C and V) and feedstock, ranging from simple proteins like Bovine Serum Albumin (BSA) to more complex, multicomponent feed such as Escherichia coli homogenate, were used. Predicted flux and transmission results were in good agreement with the large scale experimental data, showing less than 5% difference across scales, demonstrating the robustness of the non-linear scale-up model. // Following the successful validation of the scale-up methodology and prediction model, other potential applications of the USD membrane device such as the optimisation of TFF microfiltration was demonstrated using Saccharomyces cerevisae and Chlorella sorokiniana. Fed-batch concentration experiments using Saccharomyces cerevisae were done to compare the volumetric throughput limits. The USD-predicted capacity limit of 49.2 L/m2 was very similar to the experimental large scale capacity value of 52.0 L/m2, and considered fully scalable within experimental errors. Finally, fouling studies were performed using Chlorella sorokiniana and the USD device to investigate the impact of media type and growth conditions on the filtration performance. The results indicated a strong correlation between soluble fouling species, such as exopolysaccharides and carbohydrates, rather than the algal biomass. A novel, dynamic flux control methodology was developed based on empirically determined critical fluxes expressed as a function of cell concentration. The dynamic control strategy was successfully verified by performing a 50-fold concentration experiment using a hollow fibre module and the USD device. An improvement of greater than 50% in average throughput was achieved using the 3-step flux cascade compared to the traditional flux-time/capacity optimised fluxes, with no observable increase in TMP throughout. // The work presented here demonstrates the potential of ultra scale-down tools coupled with a mathematical modelling approach to establish a predictable scale-up performance, which can be used to rapidly develop and optimise tangential flow filtration processes, regardless of differences in geometry, flow configuration and system setup

The 19th Project Integration Meeting

The Flat-Plate Solar Array Project is described. Project analysis and integration is discussed. Technology research in silicon material, large-area silicon sheet and environmental isolation; cell and module formation; engineering sciences, and module performance and failure analysis. It includes a report on, and copies of visual presentations made at, the 19th Project Integration Meeting held at Pasadena, California, on November 11, 1981

Data systems elements technology assessment and system specifications, issue no. 2

The ability to satisfy the objectives of future NASA Office of Applications programs is dependent on technology advances in a number of areas of data systems. The hardware and software technology of end-to-end systems (data processing elements through ground processing, dissemination, and presentation) are examined in terms of state of the art, trends, and projected developments in the 1980 to 1985 timeframe. Capability is considered in terms of elements that are either commercially available or that can be implemented from commercially available components with minimal development

Improving downstream processing for viral vectors and viral vaccines

Viral vectors are playing an increasingly important role in the vaccine and gene therapy elds. The broad spectrum of potential applications, together with expanding medical markets, drives the e orts to improve the production processes for viral vaccines and viral vectors. Developing countries, in particular, are becoming the main vaccine market. It is thus critical to decrease the cost per dose, which is only achievable by improving the production process. In particular advances in the upstream processing have substantially increased bioreactor yields, shifting the bioprocess bottlenecks towards the downstream processing. The work presented in this thesis aimed to develop new processes for adenoviruses puri cation. The use of state-of-the-art technology combined with innovative continuous processes contributed to build robust and cost-e ective strategies for puri cation of complex biopharmaceuticals.(...

MEASUREMENT AND ANALYSIS OF SEA WAVES NEAR A REFLECTIVE STRUCTURE

Merged with duplicate record 10026.1/2047 on 06.20.2017 by CS (TIS)Methods and equipment for the measurement of ocean waves were reviewed and their suitability assessed for the aim of this project: field measurement of sea waves near a reflective coastal structure such as a breakwater. None was found to be suitable. The functional and performance objectives are set out for a new system. The evolution of the final design, based on an array of pressure sensors, is described. The whole system is intended to be deployed on the sea-bed. It is fully self contained and independent of shore based services. Located away from the surf zone it is well placed to survive storm conditions and unauthorised interference. Theoretical methods for the re-construction of surface elevation records from measured sub-surface pressures, and the experimental findings of other workers, are presented. Available methods of estimating the wave directional spectrum from a spatial array of surface elevation records are reviewed, and the most appropriate one implemented. The system has given extensive service at a number of coastal defence sites. The results of subsequent analysis of selected data sets are presented in detail. They show the pronounced nodal structure in amplitude expected in the presence of wave reflection, clearly demonstrating that a single point measurement is likely to give misleading estimates of incident wave height. For near-calm to moderate, shore-normal incident wave conditions the results were found to agree with theoretical predictions both of wave height as a function of distance offshore, and of the structure's frequency-dependent reflection coefficient. For rougher conditions, in which both theoretical and physical models are less applicable, the results agreed with visual observations

NASA Tech Briefs, February 1994

Topics covered include: Test and Measurement; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences; Books and Report