Development of a non-destructive fluorescence technique for analysis of contact lens deposition levels

The primary objective of this research has been to determine the potential of fluorescence spectroscopy as a method for analysis of surface deposition on contact lenses. In order to achieve this it was first necessary to ascertain whether fluorescence analysis would be able to detect and distinguish between protein and lipid deposited on a lens surface. In conjunction with this it was important to determine the specific excitation wavelengths at which these deposited species were detected with the greatest sensitivity. Experimental observations showed that an excitation wavelength of 360nm would detect lipid deposited on a lens surface, and an excitation wavelength of 280nm would detect and distinguish between protein and lipid deposited on a contact lens. It was also very important to determine whether clean unspoilt lenses showed significant levels of fluorescence themselves. Fluorescence spectra recorded from a variety of unworn contact lenses at excitation wavelengths of 360nm and 280nm indicated that most contact lens materials do not fluoresce themselves to any great extent. Following these initial experiments various clinically and laboratory based studies were performed using fluorescence spectroscopy as a method of analysing contact lens deposition levels. The clinically based studies enabled analysis of contact lenses with known wear backgrounds to be rapidly and individually analysed following discontinuation of wear. Deposition levels in the early stages of lens wear were determined for various lens materials. The effect of surfactant cleaning on deposition levels was also investigated. The laboratory based studies involved comparing some of the in vivo results with those of identical lenses that had been spoilt using an in vitro method. Finally, an examination of lysosyme migration into and out of stored ionic high water contact lenses was made.

A model for continuous measurement of drilled shaft diameter during construction

Non-Destructive Testing (NDT) of deep foundations has become an integral part of the industry's standard manufacturing processes. It is not unusual for the evaluation of the integrity of the concrete to include the measurement of ultrasonic wave speeds. Numerous methods have been proposed that use the propagation speed of ultrasonic waves to check the integrity of concrete for drilled shaft foundations. All such methods evaluate the integrity of the concrete inside the cage and between the access tubes. The integrity of the concrete outside the cage remains to be considered to determine the location of the border between the concrete and the soil in order to obtain the diameter of the drilled shaft. It is also economic to devise a methodology to obtain the diameter of the drilled shaft using the Cross-Hole Sonic Logging system (CSL). Performing such a methodology using the CSL and following the CSL tests is performed and used to check the integrity of the inside concrete, thus allowing the determination of the drilled shaft diameter without having to set up another NDT device.^ This proposed new method is based on the installation of galvanized tubes outside the shaft across from each inside tube, and performing the CSL test between the inside and outside tubes. From the performed experimental work a model is developed to evaluate the relationship between the thickness of concrete and the ultrasonic wave properties using signal processing. The experimental results show that there is a direct correlation between concrete thicknesses outside the cage and maximum amplitude of the received signal obtained from frequency domain data. This study demonstrates how this new method to measuring the diameter of drilled shafts during construction using a NDT method overcomes the limitations of currently-used methods. ^ In the other part of study, a new method is proposed to visualize and quantify the extent and location of the defects. It is based on a color change in the frequency amplitude of the signal recorded by the receiver probe in the location of defects and it is called Frequency Tomography Analysis (FTA). Time-domain data is transferred to frequency-domain data of the signals propagated between tubes using Fast Fourier Transform (FFT). Then, distribution of the FTA will be evaluated. This method is employed after CSL has determined the high probability of an anomaly in a given area and is applied to improve location accuracy and to further characterize the feature. The technique has a very good resolution and clarifies the exact depth location of any void or defect through the length of the drilled shaft for the voids inside the cage. ^ The last part of study also evaluates the effect of voids inside and outside the reinforcement cage and corrosion in the longitudinal bars on the strength and axial load capacity of drilled shafts. The objective is to quantify the extent of loss in axial strength and stiffness of drilled shafts due to presence of different types of symmetric voids and corrosion throughout their lengths.^

An assessment of the influence of the industry distribution chain on the oxygen levels in commercial modified atmosphere packaged cheddar cheese using non-destructive oxygen sensor technology

The establishment and control of oxygen levels in packs of oxygen-sensitive food products such as cheese is imperative in order to maintain product quality over a determined shelf life. Oxygen sensors quantify oxygen concentrations within packaging using a reversible optical measurement process, and this non-destructive nature ensures the entire supply chain can be monitored and can assist in pinpointing negative issues pertaining to product packaging. This study was carried out in a commercial cheese packaging plant and involved the insertion of 768 sensors into 384 flow-wrapped cheese packs (two sensors per pack) that were flushed with 100% carbon dioxide prior to sealing. The cheese blocks were randomly assigned to two different storage groups to assess the effects of package quality, packaging process efficiency, and handling and distribution on package containment. Results demonstrated that oxygen levels increased in both experimental groups examined over the 30-day assessment period. The group subjected to a simulated industrial distribution route and handling procedures of commercial retailed cheese exhibited the highest level of oxygen detected on every day examined and experienced the highest rate of package failure. The study concluded that fluctuating storage conditions, product movement associated with distribution activities, and the possible presence of cheese-derived contaminants such as calcium lactate crystals were chief contributors to package failure.

Design and implementation of a non-destructive defect detection technique based on UWB-SAR imaging

In the last twenty years aerospace and automotive industries started working widely with composite materials, which are not easy to test using classic Non-Destructive Inspection (NDI) techniques. Pairwise, the development of safety regulations sets higher and higher standards for the qualification and certification of those materials. In this thesis a new concept of a Non-Destructive defect detection technique is proposed, based on Ultrawide-Band (UWB) Synthetic Aperture Radar (SAR) imaging. Similar SAR methods are yet applied either in minefield [22] and head stroke [14] detection. Moreover feasibility studies have already demonstrated the validity of defect detection by means of UWB radars [12, 13]. The system was designed using a cheap commercial off-the-shelf radar device by Novelda and several tests of the developed system have been performed both on metallic specimen (aluminum plate) and on composite coupon (carbon fiber). The obtained results confirm the feasibility of the method and highlight the good performance of the developed system considered the radar resolution. In particular, the system is capable of discerning healthy coupons from damaged ones, and correctly reconstruct the reflectivity image of the tested defects, namely a 8 x 8 mm square bulge and a 5 mm drilled holes on metal specimen and a 5 mm drilled hole on composite coupon.

Advanced Non-Destructive Inspections focused on composite materials application for the automotive and marine sectors

The goal of this master thesis is to explain in detail the application of Non-Destructive-Inspection on the Automotive and the Marine sectors. Nowadays, these two particular industries faces many challenges, including increased global competition, the need for higher performance, a reduction in costs and tighter environmental and safety requirements. The materials used for these applications play key roles in overcoming these challenges. So, also an NDI procedure need to be planned in order to avoid problems during the manufacturing process and the after sale life of the structures. The entire thesis work has been done in collaboration with Vetorix Engineering.

Analysis of Ultrasonic Techniques for the Characterization of Microfiltration Polymeric Membranes

The use of polymeric membranes is extremely important in several industries such as nuclear, biotechnology, chemical and pharmaceutical. In the nuclear area, for instance, systems based on membrane separation technologies are currently being used in the treatment of radioactive liquid effluent, and new technologies using membranes are being developed at a great rate. The knowledge of the physical characteristics of these membranes, such as, pore size and the pore size distribution, is very important to the membranes separation processes. Only after these characteristics are known is it possible to determine the type and to choose a particular membrane for a specific application. In this work, two ultrasonic non destructive techniques were used to determine the porosity of membranes: pulse echo and transmission. A 25 MHz immersion transducer was used. Ultrasonic signals were acquired, for both techniques, after the ultrasonic waves passed through a microfiltration polymeric membrane of pore size of 0.45 μm and thickness of 180 μm. After the emitted ultrasonic signal crossed the membrane, the received signal brought several information on the influence of the membrane porosity in the standard signal of the ultrasonic wave. The ultrasonic signals were acquired in the time domain and changed to the frequency domain by application of the Fourier Fast Transform (FFT), thus generating the material frequency spectrum. For the pulse echo technique, the ultrasonic spectrum frequency changed after the ultrasonic wave crossed the membrane. With the transmission technique there was only a displacement of the ultrasonic signal at the time domain.

Nondestructive testing techniques for titanium billets.

Mode of access: Internet.

A Model for Continuous Measurement of Drilled Shaft Diameter During Construction

Non-Destructive Testing (NDT) of deep foundations has become an integral part of the industry’s standard manufacturing processes. It is not unusual for the evaluation of the integrity of the concrete to include the measurement of ultrasonic wave speeds. Numerous methods have been proposed that use the propagation speed of ultrasonic waves to check the integrity of concrete for drilled shaft foundations. All such methods evaluate the integrity of the concrete inside the cage and between the access tubes. The integrity of the concrete outside the cage remains to be considered to determine the location of the border between the concrete and the soil in order to obtain the diameter of the drilled shaft. It is also economic to devise a methodology to obtain the diameter of the drilled shaft using the Cross-Hole Sonic Logging system (CSL). Performing such a methodology using the CSL and following the CSL tests is performed and used to check the integrity of the inside concrete, thus allowing the determination of the drilled shaft diameter without having to set up another NDT device. This proposed new method is based on the installation of galvanized tubes outside the shaft across from each inside tube, and performing the CSL test between the inside and outside tubes. From the performed experimental work a model is developed to evaluate the relationship between the thickness of concrete and the ultrasonic wave properties using signal processing. The experimental results show that there is a direct correlation between concrete thicknesses outside the cage and maximum amplitude of the received signal obtained from frequency domain data. This study demonstrates how this new method to measuring the diameter of drilled shafts during construction using a NDT method overcomes the limitations of currently-used methods. In the other part of study, a new method is proposed to visualize and quantify the extent and location of the defects. It is based on a color change in the frequency amplitude of the signal recorded by the receiver probe in the location of defects and it is called Frequency Tomography Analysis (FTA). Time-domain data is transferred to frequency-domain data of the signals propagated between tubes using Fast Fourier Transform (FFT). Then, distribution of the FTA will be evaluated. This method is employed after CSL has determined the high probability of an anomaly in a given area and is applied to improve location accuracy and to further characterize the feature. The technique has a very good resolution and clarifies the exact depth location of any void or defect through the length of the drilled shaft for the voids inside the cage. The last part of study also evaluates the effect of voids inside and outside the reinforcement cage and corrosion in the longitudinal bars on the strength and axial load capacity of drilled shafts. The objective is to quantify the extent of loss in axial strength and stiffness of drilled shafts due to presence of different types of symmetric voids and corrosion throughout their lengths.

ABOVE-GROUND BIOMASS ESTIMATION OF OPUNTIA FICUS-INDICA (L.) MILL. FOR FORAGE CROP IN A MEDITERRANEAN ENVIRONMENT BY USING NON-DESTRUCTIVE METHODS

In marginal lands Opuntia ficus-indica (OFI) could be used as an alternative fruit and forage crop. The plant vigour and the biomass production were evaluated in Portuguese germplasm (15 individuals from 16 ecotypes) by non-destructive methods, 2 years following planting in a marginal soil and dryland conditions. Two Italian cultivars (Gialla and Bianca) were included in the study for comparison purposes. The biomass production and the plant vigour were estimated by measuring the cladodes number and area, and the fresh (FW) and dry weight (DW) per plant. We selected linear models by using the biometric data from 60 cladodes to predict the cladode area, the FW and the DW per plant. Among ecotypes, significant differences were found in the studied biomass-related parameters and several homogeneous groups were established. Four Portuguese ecotypes had higher biomass production than the others, 3.20 Mg ha−1 on average, a value not significantly different to the improved ‘Gialla’ cultivar, which averaged 3.87 Mg ha−1. Those ecotypes could be used to start a breeding program and to deploy material for animal feeding and fruit production.

Time-frequency and time-scale analysis of Barkhausen noise signals

Carrying out information about the microstructure and stress behaviour of ferromagnetic steels, magnetic Barkhausen noise (MBN) has been used as a basis for effective non-destructive testing methods, opening new areas in industrial applications. One of the factors that determines the quality and reliability of the MBN analysis is the way information is extracted from the signal. Commonly, simple scalar parameters are used to characterize the information content, such as amplitude maxima and signal root mean square. This paper presents a new approach based on the time-frequency analysis. The experimental test case relates the use of MBN signals to characterize hardness gradients in a AISI4140 steel. To that purpose different time-frequency (TFR) and time-scale (TSR) representations such as the spectrogram, the Wigner-Ville distribution, the Capongram, the ARgram obtained from an AutoRegressive model, the scalogram, and the Mellingram obtained from a Mellin transform are assessed. It is shown that, due to nonstationary characteristics of the MBN, TFRs can provide a rich and new panorama of these signals. Extraction techniques of some time-frequency parameters are used to allow a diagnostic process. Comparison with results obtained by the classical method highlights the improvement on the diagnosis provided by the method proposed.

Study of the influence of simultaneous variation of magnetic material microstructural features on domain wall dynamics

The magnetic Barkhausen noise (MBN) is a phenomenon sensitive to several kinds of magnetic material microstructure changes, as well as to variations in material plastic deformation and stress. This fact stimulates the development of MBN-based non-destructive testing (NDT) techniques for analyzing magnetic materials, being the proposition of such a method, the main objective of the present study. The behavior of the MBN signal envelope, under simultaneous variations of carbon content and plastic deformation, is explained by the domain wall dynamics. Additionally, a non-destructive parameter for the characterization of each of these factors is proposed and validated through the experimental results. (C) 2010 Elsevier B.V. All rights reserved.

Erosion-fatigue of steam turbine blades

The premature failure of steam turbine rotor blades, manufactured in forged 12% Cr-NiMoV martensitic stainless steel, was investigated using visual inspection non-destructive testing, macro and microfractography, microstructural characterization, EDS microanalysis, chemical analysis, micro hardness and tensile testing. The blades belonged to the last stage of a thermoelectric plant steam turbine generator (140 MV A). The results indicated that the failure of the blades was promoted by foreign-particle erosion, which attacked preferentially the low-pressure side of the lower trailing edge of the blades. The resulting wear grooves acted as stress raisers and promoted the nucleation of fatigue cracks, which probably grew during the transition events of the steam turbine operation. Finally, water drop erosion was observed on the blade upper leading edge (low-pressure side). (C) 2009 Elsevier Ltd. All rights reserved.

Diagnóstico de estruturas de madeira em serviço num palacete do século XIX

Dissertação para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização em Edificações

Ensaios em pontes

Dissertação para a obtenção do grau de Mestre em Engenharia Civil na Área de Especialização em Estruturas

Análise por ultra-sons no controlo de condição

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica