Dissertations / Theses on the topic 'NDE techniques'

The thesis presented here comprises the work undertaken for research into novel NDE techniques in the power generation industry. This has been undertaken as part of the Engineering Doctorate Scheme run by the Research Centre for Non-Destructive Evaluation (RCNDE), which aims to bridge the technological gap between university research and industrial application. In this case, the scheme consisted of two projects completed in conjunction with RWE npower looking at current NDE problems in steam turbine and steam-raising plant. The first project was concerned with detecting microstructural transformation in steam turbine blades, which can act as a precursor to failure by environmentally assisted cracking. This project, and indeed, this entire thesis is principally based on electromagnetic testing methods. An eddy current technique for mapping the microstructural phases was produced and validated as far as was achievable; this offered a significant time-saving advantage over the previous method, by reducing inspection time from 5 man days to just 1.5. The technique has novelty in producing a 2-dimensional map of the blade surface which highlights areas where microstructural phases differ. The second project focuses on the detection of microstructural damage associated with material creep life expiry. This forms a review of the current state of technology and highlights potentially useful paths for future research in both established and emerging NDE technologies, including Magnetic Barkhausen Noise testing and laser-generated ultrasound. Both projects have provided tangible benefit to the sponsoring company and have pushed forward research in a number of technological applications.

Three active thermal methods capable of detecting surface breaking cracks in metals are considered in this Thesis. The three thermal methods exploit different means of excitation, each with practical advantages and varying abilities to detect specific types of crack morphology. Thermosonics uses a broadband, high power ultrasonic input to vibrate the test-piece. Defects damp the vibrational energy into heat which is imaged by a thermal camera. Laser-spot thermography uses a short laser pulse to spot heat the surface of the test-piece, and the subsequent radial heat diffusion is then observed. Defects can cause both increased emission of infrared and localised increases in thermal impedance, both effects causing distortion of the radial heat diffusion. Eddy-current induced thermography uses a high power magnetic field to induce a flow of current inside the test-piece. Defects create a localised increase in electrical impedance, diverting the electric field around the defect. This diversion of current flow causes neighbouring regions of high and low current density, the corresponding Joule heating imaged by a thermal camera. In this Thesis the three methods are explored experimentally. For laser-spot thermography and eddy-current induced thermography the physical phenomena are characterised and experimental best-practice for short pulse excitation determined. The effect of crack opening on each of the three methods is found to give insight into which applications the methods are most suited. It was found that the relationship between crack opening and detectability was complex for thermosonics, relatively linear for laser-spot thermography, and that eddy-current induced thermography is largely insensitive to crack opening. The methods are tested for the feasibility of detecting cracks in Inconel buried beneath metallic and ceramic coatings typical of gas turbine blades, with thermosonics and eddy-current induced thermography found to be viable methods. A study of the detectability of a large number of cracks in steel, titanium and Waspaloy by eddy-current induced thermography is detailed, and from this data the probability of detection is established. Eddy-current thermography is shown to be an extremely sensitive method capable of detecting fatigue cracks of approximately 0.25 mm in steel and 0.50-0.75 mm in titanium and Waspaloy. The practicality of the thermal methods is discussed, and the methods put into the context of the wider field of NDE. Based on the works in this Thesis it was found that for most applications eddy-current induced thermography is the most appealing thermal method since it is highly sensitive, rapid, non-contacting and relatively easy to validate. However, both thermosonics and laser-spot thermography remain useful alternative inspections for more niche applications.

Non-destructive testing (NDT) of glass-fibre reinforced polyester (GRP) composite materials has been becoming increasingly important due to their wide applications in engineering components and structures. Electronic Speckle Pattern Interferometry (ESPI) has promising potential in this context because it is a non-contact, whole-field and real-time measurement system. This potential has never been fully exploited and there is only limited knowledge and understanding available in this area. This reality constrains the wide popularity and acceptance of ESPI as a novel NDT technique. Therefore it is of considerable importance to develop an understanding of the capability of ESPI with respect to damage evaluation in GRP composite materials. The research described in this thesis is concerned with an investigation into the applicability of ESPI in the NDT of GRP composite materials. Firstly, a study was carried out to determine excitation techniques in terms of practicality and effectiveness in the ESPI system. Three categories of defects were artificially introduced in GRP composite materials, namely holes, cracks and delaminations each with different geometrical features. ESPI was then employed to evaluate the three kinds of defects individually. It has been found that cracks and holes on back surfaces can be defined when the technique is used in conjunction with thermal excitation. Internal Temperature Differential (ITD) induced fringe patterns were more efficient than External Thermal Source (ETS) induced fringe patterns with regard to detecting the presence of holes and cracks. In the case of delamination, ESPI was found to be capable of detecting the damage when used in combination with mechanical excitation originating from a force transducer hammer. The geometrical features and magnitudes of delaminations were also established as being quantifiable. The validation of ESPI as an NDT technique was carried out in an attempt to establish a better understanding of its suitability and have more confidence in its applications. Four damaged specimens were Subjected to ESPI examination in conjunction with visual inspection, ultrasonic C-scan and sectioning techniques. The geometrical features and magnitudes of damage evaluated using ESPI showed a good correlation with those evaluated by conventional techniques. Poor visibility and readability is an inherent problem associated with ESP! due to an overlapping between the noise and signal frequencies. An improvement of image quality is expected in an attempt to achieve a wide acceptance of ESPI as a novel NDT technique. It has also been demonstrated that this problem can be tackled using optical phase stepping techniques in which optical phase data can be extracted from the intensity fringes. A three-frame optical phase stepping technique was employed to produce the "wrapped" and "unwrapped" phase maps which are capable of indicating internal damage with high visibility and clarity. Finally ESPI was practically employed to evaluate damage in GRP composites introduced by quasi-static and dynamic mechanical loading. It was found that ESP! was capable of monitoring the progressive damage development of specimens subjected to incremental flexural loading. The initial elastic response, damage initiation, propagation and ultimate failure of specimens were clearly characterised by the abnormal fringe pattern variations. In a similar manner, ESPI was employed to evaluate the low velocity falling weight impact induced damage. A correlation was established between the magnitude of damage and the impact event parameters as well as the residual flexural properties.

This thesis describes the development and characterization of a novel NDE methodthe Capacitive Imaging (CI) technique. The CI technique employs a pair of (or multiple) electrodes to form a co-planar capacitor, and uses the fringing quasi-static electric field established across the electrodes to investigate specimens of interest. In general, the CI probe is sensitive to surface and hidden defects in insulating materials, and surface features on conducting materials. The CI technique is advantageous for its non-contact and non-invasive nature, and the capacitive coupling allows the CI technique to work on a wide variety of material properties. The theoretical background to the CI technique has been developed. It is shown that in the frequency range of operation (10 kHz to 1 MHz), the quasi-static approximation is valid and the Maxwell’s Equations describing the general electromagnetic phenomena can be simplified. The practical implementation of the CI system is based on this analysis, and it is shown that the CI technique has features that can complement techniques such as eddy current methods that are already established in NDE. The design principles of the CI probes that are required for an optimum imaging performance have been determined, by considering the key measures of the performance including the depth of penetration, the measurement sensitivity, the imaging resolution and the signal to noise ratio (SNR). It has been shown that the operation frequency is not an influential factor - the performance of the CI probe is determined primarily by the geometry of the probe (e.g. size/shape of the electrodes, separation between electrodes, guard electrodes etc.). Symmetric CI probes with triangular-shaped electrodes were identified as a good general purpose design. Finite Element (FE) models were constructed both in 2D and 3D in COMSOLTM to predict the electric field distributions from CI probes. Effects of thickness of specimen, liftoff distance and relative permittivity value etc were examined using the 2D models. The sensitivity distributions of different CI probes were obtained from the 3D models and were used to characterize the imaging ability of the given CI probes. The fundamental concepts of the CI technique have been experimentally validated in a series of scans where the defects were successfully imaged in insulating (Perspex) and conducting (e.g. Aluminium, Steel and carbon fibre composite) specimens. The detection of corrosion under insulation (CUI) has also been demonstrated. The imaging abilities were assessed by investigating various standard specimens under different situations. The CI technique was then successfully applied to various practical specimens, including glass fibre laminated composites and sandwich structures, laminated carbon fibre composites, corroded steel plate and pipe, and concrete specimens. Further measurements were also conducted using modified CI probes, to demonstrate the wide range of applications of the CI technique.

The possibility and feasibility of experimental detection of localized defects in tubes using laser-induced ultrasonic wave approach through Thermo Acousto Photonic Non Destructive Evaluation (TAP-NDE) and Signal processing through wavelet transform is examined in this research. Guided waves in cylindrical surfaces provide solutions for detection of different defects in the material. Several experiments were conducted to this respect. Wave propagation in both axial and circumferential directions was studied. The dispersive wave propagation of ultrasonic waves in hollow cylinders has been investigated experimentally, primarily for use in non-contact and nondestructive inspections of pipes and tubes. The laser ultrasonic waves propagated in cylindrical waveguides are particularly attractive because of their unique characteristics in the applications of nondestructive evaluation (NDE). Contrary to studies making use of only axially symmetric guided waves in hollow cylinders, here are analyzed also nonaxisymmetric waves. The analysis of data is made by using the Gabor wavelet transform. The capability of modeling the guided wave dispersion in hollow cylinders is used in developing guided wave experimental techniques for flaw detection. Good agreement was obtained when comparing the dispersion spectra between theory and experimentation. Measurement of group velocities of guided waves, which are obtained directly from the wavelet transform coefficients, can be used to determine allocation and sizing of flaws.

This research aims at modifying, improving and calibrating the Stress Wave Factor Nondestructive Evaluation (SWF NDE) technique and applying it to a fiber epoxy composite material and other composite structures. In order to access the composite's integrity the Energy of SWF within a selected Sub Frequency Range (SFR) instead of the whole measured frequency range as of conventional SWF is used. This technique, introduced and examined herein and is termed the Sub Frequency Range Stress Wave Factors (SFR-SWF) and is tailored to improve the conventional SWF technique with respect to sensibility and accuracy. A series of controlled damage tests were performed, and relevant acousto-ultrasonic observations were conducted. The overall property of the composites subjected to hygrothermal degradation, the localized defects such as the surface crack and the historical damage were assessed with conventional SWF and SFR-SWF. The two methods are compared in detail. The hygrothermal degradation and surface crack experiments were also simulated using the finite element method. Dynamic numerical analysis was conducted to simulate the wave propagation process, both in time domain and frequency domain using the commercial finite element code ABAQUS. The numerical results were also evaluated via both SWF and SFR-SWF, and were compared with the results of experiments. Thus, the potential of SFR-SWF was evaluated. A general conclusion from this research is that the SFR-SWF has the better capability than that of the conventional SWF in assessing the composite's overall condition, localized defects and historical damage. Since there are still open questions regarding the physical understanding of the SWF and SFR-SWF, the finite element analysis provides confirmation for certain observed behaviors of the Acousto-Ultrasonic and SFR-SWF technique.

Resistance spot welding is used frequently as a successful joining method for a variety of work commonly in automotive and other manufacturing processes. Spot weld nugget is generally hidden between two sheets, causing its inspection difficult and expensive. Undersized nuggets, brittle or cracked nuggets, and excessive indentation of electrodes reveals the lack of fusion between the parts that can make the weld sub-standard. Visual inspection, pry testing and physical teardown with chisel and hammer method or a combination of them are being used traditionally. However, this study presents a more effective nondestructive inspection method based upon an ultrasonic pulse-echo technique. The theory of the technique together with the experimental verification are presented and its advantages over the other destructive and nondestructive techniques are considered.

In recent years the expectations of non-destructive testing and evaluation (NDT&E) service users have increased from simple defect detection and dimension estimation to the provision of quantitative information about material properties including microstructure, stresses, hardness, etc. Although there are many techniques available to NDT&E service providers, each have their own limitations when used in isolation. For example, magnetic Barkhausen emission measurement has good microstructure and stress characterisation capabilities, but has a limited measurement depth. which is problematic where the property of interest varies with depth, i.e. case hardening. Magnetic flux leakage can detect defects on both the surface under inspection and the opposite surface, but it is very difficult to discriminate between them. However, if two or more inspection techniques are combined in a single system, it is thought that it may be possible to overcome these limitations.

<p>The group for non-destructive testing at Uppsala University has recently implemented the phase shift migration method, which is a method to focus images acquired unfocused using ultrasound. However, their work has been limited to 2D data, while for many applications the gathered data is 3D. This project has extended the old implementation to 3D data. The new implementation has been done in two different ways, giving one algorithm that works fast but needs much RAM, and one algorithm that takes long time but works on smaller computers, not demanding as much memory. The fast algorithm works faster than the time it takes to acquire the raw data, which makes real-time use realistic. To test the performance of the two algorithms with respect to image improvement, both against each other and against the previous 2D implementation, a number of experiments were carried out, which showed that, apart from processing time, the two new algorithms were equal in performance. The experiments also showed that the obtained resolution in both x- and y-directions matched the theoretical discussion.</p>

Thesis (MEng) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2007.<br>A thesis submitted for fulfillment of the requirement for the degree of Master of Engineering, Industrial Research Institute, Swinburne University of Technology - 2007. Typescript. Includes bibliographical references (p. 168-193).

Wind energy is an increasingly important contributor of power within the renewable energy sector. In the year to 2012, wind generation within the United Kingdom (UK) increased 40% meeting 6% of the UK's national electricity demand. The UK is committed to providing 15% of its energy from renewable resources by 2020. Currently, the UK has approximately 40% of Europe's entire wind resource with significant potential for development of both on and offshore wind. In recent years, the number of reports on defective blades contributing towards turbine failure has grown. Blade manufacturers have privately reported a recurring problem with the spar cap - a critical strengthening component - which when weakened by damage, hastens the onset of operational failure. The contents of this thesis consider composite materials used within the blade and the detection techniques appropriate for in-field implementation. Application of Guided Waves, in particular Lamb waves, suits the typical dimensions of the blade composite structure. Experiments were conducted to understand the characteristics of Lamb wave modes within glass fibre reinforced plastic (GFRP) to assess attenuation levels; modal propagation; and dispersion with respect to fibre orientation. Finite Element Analysis (FEA) was used to observe material characteristics and discern possible modes of wave propagation. To exploit the directional qualities of GFRP, directional Macro Fibre Composite (MFC) sensors were applied to a wind turbine blade providing low-profile, light-weight, durability and conformability with sufficient sensitivity to detect elastic disturbance over large areas. Parametric monitoring of GFRP samples under loading identified tensile stress from defect onset. Cross correlation and sliding-window correlation signal processing techniques on recorded data from the applied sparse array identified the onset of fibre damage using Guided wave modes. This technique was able to identify modal changes to specific defects providing the prospect for in-situ blade monitoring.

A geological repository for spent nuclear fuel (SNF) and an associated encapsulation facility will be built in Sweden.  The encapsulation facility is planned to be in operation in 2025 and it will be the last place where verifying safeguards measurements of SNF can be performed. It is not clear what types of measurements that will be performed, because such requirements are not yet posed by national and international authorities and inspecting organizations. This report describes the objective and most recent results of a master thesis project, whereby a few existing non-destructive assay techniques for verifying SNF are selected for a review. The study focuses on the verifying ability of different techniques, or system of techniques in relation to the requirement that may be put on the future encapsulation plant. In addition, possible needs for future simulations and measurements are discussed. The work is done as a collaboration between Uppsala University in Sweden and Los Alamos National Laboratory in the USA.

Includes bibliographical references (leaves 87-89).<br>This project investigates the detection of structural damage in aerospace composite materials using ESPI and/or Shearography. ESPI and shearography are both laser based digital interferometric techniques used to non-destructively identify defects in small and large structures. Vibration excitation is proposed to be used as the excitation method for the above Non-Destructive Testing (NDT) techniques. The material may or may not contain any defects, in which case the flaws are to be artificially induced.

AbstractThis thesis describes research on the use of eddy current techniques for nondestructivetesting of carbon fibre reinforced plastic (CFRP). The research hasinvolved bulk conductivity testing, fibre direction characterization and 3D FEMmodeling of the CFPR and eddy current probes geometry. In the conductivity testing,how the sample thickness, fibre volume content and fibre conductivity affects thesignal from the eddy current has been evaluated. Eddy current testing shows gooddirectionality as CFRP is an anisotropic material, thus is very suitable to characterizethe fibre orientation. Direction sensitive probes have been developed and tested toreveal information about the fibre direction and layer. Computer FEM software hasbeen used to analyze the magnetic field inside the sample and probes. Specific probegeometries have been designed depending on the electrical properties of thecomposites and testing requirement. The experiment, simulation and analysis resultsshow very good agreement. However, when the measuring frequency increases, noisesand parasitic capacitance inevitably become significant and have a negative influenceon the results. Improvements and further research are proposed which are believed tomake eddy-current techniques a more feasible and efficient measurement method, willcontribute to the development and maintenance of light weight CFRP composites.

Includes bibliographical references.<br>In order to maintain the desired level of safety in an industrial environment, it is important that the structural integrity of all the components and equipment being utilised by the facilty is assured. To determine the structural integrity of an engineering system precisely, not only must the depth of the flaw be established, but the crack profile and orientation must also be obtained in order to assess the extent of the crack. The present work described in this thesis discusses the development of an AC potential drop (ACPD) system as a non-destructive testing (NDT) technique for flaw detection and sizing of variously shaped and oriented surface breaking fatigue cracks. The ACPD method was reviewed to establish its viability as an NDT technique, and to understand the response of the output to fatigue cracking. The proposed system using a mains power source with a frequency of 50Hz was investigated as a means of providing a sensitive and reliable measurement device that could be employed to analyse fatigue cracks in industrial components in situ.

This work is an experimental study of applying an impedance-based health monitoring technique to complex structures. The work is presented in three parts. In the first part we consider effects of the following three factors on damage detection abilities: actuator excitation level, test wire length and ambient conditions (temperature, structural loading and vibration). It was concluded that increasing the applied voltage improves the signal to noise ratio and damage detection abilities. Test wire lengths under 30m do not affect damage detection abilities. The technique is able to distinguish and detect damage even with variations in temperature, structural loading and vibration. In the second part we apply our health monitoring technique to a complex truss structure and a massive steel steam header. We discovered that with multiplexing (acquiring a single signal from distributed actuators) the actuators on the truss structure we could detect damage but with less location information. Damage detection on the steel pipe ended in inconclusive results. The use of this technique on massive structures needs further investigation. Finally, we conducted a detailed experimental study of monitoring the integrity of composite-reinforced masonry structures. We developed a software package which enables even a casual user to determine if significant damage has occurred in these structures. The technique was successfully applied to detect damage (particularly due to delamination) in these composite-concrete structures. Most significantly, the technique was also able to detect damage well in advance of actual failure. This work relies mainly on frequency response plots and damage metric charts to present the data and to arrive at any conclusions. While frequency response plots give a qualitative approach to the analysis, damage metric charts attempt to quantify the data.<br>Master of Science

[EN] The test for determining the resonance frequencies has traditionally been used to investigate the mechanical integrity of concrete cores, to assess the conformity of concrete constituents in different accelerated durability tests, and to ascertain constitutive properties such as the elastic modulus and the damping factor. This nondestructive technique has been quite appealed for evaluation of mechanical properties in all kinds of durability tests. The damage evolution is commonly assessed from the reduction of dynamic modulus which is produced as a result of any cracking process. However, the mechanical behavior of concrete is intrinsically nonlinear and hysteretic. As a result of a hysteretic stress-strain behavior, the elastic modulus is a function of the strain. In dynamic tests, the nonlinearity of the material is manifested by a decrease of the resonance frequencies, which is inversely proportional to the excitation amplitude. This phenomenon is commonly referred as fast dynamic effect. Once the dynamic excitation ceases, the material undergoes a relaxation process whereby the elastic modulus is restored to that at rest. This phenomenon is termed as slow dynamics. These phenomena (fast and slow dynamics) find their origin in the internal friction of the material. Therefore, in cement-based materials, the presence of microcracks and interfaces between its constituents plays an important role in the material nonlinearity. In the context of the assessment of concrete durability, the damage evolution is based on the increase of hysteresis, as a result of any cracking process. In this thesis three different nondestructive techniques are investigated, which use impacts for exciting the resonant frequencies. The first technique consists in determining the resonance frequencies over a range of impact forces. The technique is termed Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). It consists in ascertaining the downward resonant frequency shift that the material undergoes upon increasing excitation amplitude. The second technique consists in investigating the nonlinear behavior by analyzing the signal corresponding to a single impact. This is, to determine the instantaneous frequency, amplitude and attenuation variations corresponding to a single impact event. This technique is termed as Nonlinear Resonant Acoustic Single Impact Spectroscopy (NSIRAS). Two techniques are proposed to extract the nonlinear behavior by analyzing the instantaneous frequency variations and attenuation over the signal ring down. The first technique consists in discretizing the frequency variation with time through a Short-Time Fourier Transform (STFT) based analysis. The second technique consists of a least-squares fit of the vibration signals to a model that considers the frequency and attenuation variations over time. The third technique used in this thesis can be used for on-site evaluation of structures. The technique is based on the Dynamic Acousto- Elastic Test (DAET). The variations of elastic modulus as derived through NIRAS and NSIRAS techniques provide an average behavior and do not allow derivation of the elastic modulus variations over one vibration cycle. Currently, DAET technique is the only one capable to investigate the entire range of nonlinear phenomena in the material. Moreover, unlike other DAET approaches, this study uses a continuous wave source as probe. The use of a continuous wave allows investigation of the relative variations of the elastic modulus, as produced by an impact. Moreover, the experimental configuration allows one-sided inspection.<br>[ES] El ensayo de determinación de las frecuencias de resonancia ha sido tradicionalmente empleado para determinar la integridad mecánica de testigos de hormigón, en la evaluación de la conformidad de mezclas de hormigón en diversos ensayos de durabilidad, y en la terminación de propiedades constitutivas como son el módulo elástico y el factor de amortiguamiento. Esta técnica no destructiva ha sido ampliamente apelada para la evaluación de las propiedades mecánicas en todo tipo de ensayos de durabilidad. La evolución del daño es comúnmente evaluada a partir de la reducción del módulo dinámico, producido como resultado de cualquier proceso de fisuración. Sin embargo, el comportamiento mecánico del hormigón es intrínsecamente no lineal y presenta histéresis. Como resultado de un comportamiento tensión-deformación con histéresis, el módulo elástico depende de la deformación. En ensayos dinámicos, la no linealidad del material se manifiesta por una disminución de las frecuencias de resonancia, la cual es inversamente proporcional a la amplitud de excitación. Este fenómeno es normalmente denominado como dinámica rápida. Una vez la excitación cesa, el material experimenta un proceso de relajación por el cual, el módulo elástico es restaurado a aquel en situación de reposo. Este fenómeno es denominado como dinámica lenta. Estos fenómenos ¿dinámicas rápida y lenta¿ encuentran su origen en la fricción interna del material. Por tanto, en materiales basados en cemento, la presencia de microfisuras y las interfaces entre sus constituyentes juegan un rol importante en la no linealidad mecánica del material. En el contexto de evaluación de la durabilidad del hormigón, la evolución del daño está basada en el incremento de histéresis, como resultado de cualquier proceso de fisuración. En esta tesis se investigan tres técnicas diferentes las cuales utilizan el impacto como medio de excitación de las frecuencias de resonancia. La primera técnica consiste en determinar las frecuencias de resonancia a diferentes energías de impacto. La técnica es denominada en inglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Ésta consiste en relacionar el detrimento que el material experimenta en sus frecuencias de resonancia, con el aumento de la amplitud de la excitación. La segunda técnica consiste en investigar el comportamiento no lineal mediante el análisis de la señal correspondiente a un solo impacto. Ésta consiste en determinar las propiedades instantáneas de frecuencia, atenuación y amplitud. Esta técnica se denomina, en inglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Se proponen dos técnicas de extracción del comportamiento no lineal mediante el análisis de las variaciones instantáneas de frecuencia y atenuación. La primera técnica consiste en la discretización de la variación de la frecuencia con el tiempo, mediante un análisis basado en Short-Time Fourier Transform (STFT). La segunda técnica consiste en un ajuste por mínimos cuadrados de las señales de vibración a un modelo que considera las variaciones de frecuencia y atenuación con el tiempo. La tercera técnica empleada en esta tesis puede ser empleada para la evaluación de estructuras in situ. La técnica se trata de un ensayo acusto-elástico en régimen dinámico. En inglés Dynamic Acousto-Elastic Test (DAET). Las variaciones del módulo elástico obtenidas mediante los métodos NIRAS y NSIRAS proporcionan un comportamiento promedio y no permiten derivar las variaciones del módulo elástico en un solo ciclo de vibración. Actualmente, la técnica DAET es la única que permite investigar todo el rango de fenómenos no lineales en el material. Por otra parte, a diferencia de otras técnicas DAET, en este estudio se emplea como contraste una onda continua. El uso de una onda continua permite investigar las variaciones relativas del módulo elástico, para una señal transito<br>[CAT] L'assaig de determinació de les freqüències de ressonància ha sigut tradicionalment empleat per a determinar la integritat mecànica de testimonis de formigó, en l'avaluació de la conformitat de mescles de formigó en diversos assajos de durabilitat, i en la terminació de propietats constitutives com són el mòdul elàstic i el factor d'amortiment. Esta tècnica no destructiva ha sigut àmpliament apel·lada per a l'avaluació de les propietats mecàniques en tot tipus d'assajos de durabilitat. L'evolució del dany és comunament avaluada a partir de la reducció del mòdul dinàmic, produït com resultat de qualsevol procés de fisuración. No obstant això, el comportament mecànic del formigó és intrínsecament no lineal i presenta histèresi. Com resultat d'un comportament tensió-deformació amb histèresi, el mòdul elàstic depén de la deformació. En assajos dinàmics, la no linealitat del material es manifesta per una disminució de les freqüències de ressonància, la qual és inversament proporcional a l'amplitud d'excitació. Este fenomen és normalment denominat com a dinàmica ràpida. Una vegada l'excitació cessa, el material experimenta un procés de relaxació pel qual, el mòdul elàstic és restaurat a aquell en situació de repòs. Este fenomen és denominat com a dinàmica lenta. Estos fenòmens --dinámicas ràpida i lenta troben el seu origen en la fricció interna del material. Per tant, en materials basats en ciment, la presència de microfissures i les interfícies entre els seus constituents juguen un rol important en la no linealitat mecànica del material. En el context d'avaluació de la durabilitat del formigó, l'evolució del dany està basada en l'increment d'histèresi, com resultat de qualsevol procés de fisuración. En esta tesi s'investiguen tres tècniques diferents les quals utilitzen l'impacte com a mitjà d'excitació de les freqüències de ressonància. La primera tècnica consistix a determinar les freqüències de ressonància a diferents energies d'impacte. La tècnica és denominada en anglés: Nonlinear Impact Resonant Acoustic Spectroscopy (NIRAS). Esta consistix a relacionar el detriment que el material experimenta en les seues freqüències de ressonància, amb l'augment de l'amplitud de l'excitació. La segona tècnica consistix a investigar el comportament no lineal per mitjà de l'anàlisi del senyal corresponent a un sol impacte. Esta consistix a determinar les propietats instantànies de freqüència, atenuació i amplitud. Esta tècnica es denomina, en anglés, Nonlinear Single Impact Resonant Acoustic Spectroscopy (NSIRAS). Es proposen dos tècniques d'extracció del comportament no lineal per mitjà de l'anàlisi de les variacions instantànies de freqüència i atenuació. La primera tècnica consistix en la discretización de la variació de la freqüència amb el temps, per mitjà d'una anàlisi basat en Short-Time Fourier Transform (STFT). La segona tècnica consistix en un ajust per mínims quadrats dels senyals de vibració a un model que considera les variacions de freqüència i atenuació amb el temps. La tercera tècnica empleada en esta tesi pot ser empleada per a l'avaluació d'estructures in situ. La tècnica es tracta d'un assaig acusto-elástico en règim dinàmic. En anglés Dynamic Acousto-Elastic Test (DAET). Les variacions del mòdul elàstic obtingudes per mitjà dels mètodes NIRAS i NSIRAS proporcionen un comportament mitjà i no permeten derivar les variacions del mòdul elàstic en un sol cicle de vibració. Actualment, la tècnica DAET és l'única que permet investigar tot el rang de fenòmens no lineals en el material. D'altra banda, a diferència d'altres tècniques DAET, en este estudi s'empra com contrast una ona contínua. L'ús d'una ona contínua permet investigar les variacions relatives del mòdul elàstic, per a un senyal transitori. A més, permet la inspecció d'elements per mitjà de l'accés per una sola cara.<br>Eiras Fernández, JN. (2016). Studies on nonlinear mechanical wave behavior to characterize cement based materials and its durability [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/71439<br>TESIS<br>Premiado

Delamination and cracks within the multilayer structure are typical failure modes observed in microelectronic and micro electro mechanical system (MEMS) devices and packages. As destructive detection methods consume large numbers of devices during reliability tests, non-destructive techniques (NDT) are critical for measuring the size and position of internal defects throughout such tests. There are several established NDT methods; however, some of them have significant disadvantages for detecting defects within multilayer structures such as those found in MEMS devices. This thesis presents research into the application of transient infrared thermography as a non-destructive method for detecting and measuring internal defects, such as delamination and cracks, in the multilayer structure of MEMS devices. This technique works through the use of an infrared imaging system to map the changing temperature distribution over the surface of a target object following a sudden change in the boundary conditions, such as the application of a heat source to an external surface. It has previously been utilised in various applications, such as damage assessment in aerospace composites and verification of printed circuit board solder joint manufacture, but little research of its applicability to MEMS structures has previously been reported. In this work, the thermal behaviour of a multilayer structure containing defects was first numerically analysed. A multilayer structure was then successfully modelled using COMSOL finite element analysis (FEA) software with pulse heating on the bottom surface and observing the resulting time varying temperature distribution on the top. The optimum detecting conditions such as the pulse heating energy, pulse duration and heating method were determined and applied in the simulation. The influences of thermal properties of materials, physical dimensions of film, substrate and defect and other factors that will influence the surface temperature gradients were analytically evaluated. Furthermore, a functional relationship between the defect size and the resulting surface temperature was obtained to improve the accuracy of estimating the physical dimensions and location of the internal defect in detection. Corresponding experiments on specimens containing artificially created defects in macro-scale revealed the ability of the thermographic method to detect the internal defect. The precision of the established model was confirmed by contrasting the experimental results and numerical simulations.

There is a need to monitor the existence and effects of damage in structural materials. Aircraft components provide a much publicized example, but the need exists in a variety of other structures, such as layered materials used in food packaging industries. While several techniques and models have been proposed for material characterization and condition monitoring of bulk materials, less attention has been devoted to thin sheets having no flexural rigidity. This study is therefore devoted to the development of a new method for acoustic Non-Destructive Testing (NDT) and material characterization of thin sheets used in food packaging materials or similar structures. A method for assessing the strength in the presence of crack of thin sheets used in food packaging is first presented using a modified Strip Yield Model (SYM). Resonance frequency measurement is then introduced and it is shown, at low frequency range (less than 2kHz), that a change in the physical properties such as a reduction in stiffness resulting from the onset of cracks or loosening of a connection causes detectable changes in the modal properties, specifically the resonance frequency. This observation leads to the implementation of a simple method for damage severity assessment on sheet materials, supported by a new theory illustrating the feasibility of the detection of inhomogeneity in form of added mass, as well as damage severity assessment, using a measurement of the frequency shift. A relationship is then established between the resonance frequency and the material’s elastic property, which yields a new modality for sheet materials remote characterization. The result of this study is the groundwork of a low-frequency vibration-based method with remote acoustic excitation and laser detection, for nondestructive testing and material characterization of sheet materials. The work also enhances the feasibility of the testing and condition monitoring of real structures in their operating environment, rather than laboratory tests of representative structures. The sensitivity of the new experimental approach used is liable to improvement while being high because the frequency measurement is one of the most accurate measurements in physics and metrology.

The most important prognostic indicator in early cancer is whether the disease has metastasised to regional lymph nodes. Pre-operative imaging is not sensitive enough to detect micrometastatic deposits therefore most patients judged to have more than 20% risk of disease spread will have elective surgical removal of the draining lymph node basins in order to reduce the risk of leaving tumour behind. Such operations can be lengthy and associated morbidity can reduce the patient’s quality of life. In the majority of these elective nodal clearances histopathological analysis is clear of disease in the majority suggesting that the surgery could be omitted without affecting the patient’s disease free survival. Sentinel node biopsy (SNB) is a surgical stating test in which the tumour draining lymph nodes can be thoroughly investigated for metastasis. If free of disease there is no indication to subject the patient to further surgery. SNB has been validated in oral cancer, but there is a false negative rate of up to 14%. Recent developments may improve the accuracy of the SNB test. This work evaluated new sentinel node technologies (navigation surgery, fluorescence imaging, and improved tracer formulations) in oral cancer, and opened up new applications for the test in other head and neck cancers (salivary, thyroid and larynx). These refinements in sentinel node process may allow many patients suffering with early cancer to benefit from personalised staging and treatment.

This PhD thesis is devoted to the design, development and implementation of a non-contact hybrid non-destructive testing (NDT) method applied to the analysis of metallic objects that contain embedded defects or fractures. We propose a hybrid opto-acoustic technique that combines laser generated ultrasound as exciter and ultrasound transducers as receivers. This work envisages a detailed study of the detection and one, two or three-dimensional reconstruction of defects, using the proposed hybrid technique and its application as a remotely controlled non-contact NDT. Our device combines several advantages of both photonic and ultrasonic techniques, while reduces some of the drawbacks of both individual methods. Our method relay on the combination of experimental results with high-resolution signal processing procedures based on different mathematical algorithms. Our basic experimental setup uses a nanosecond pulsed laser at 532nm wavelength that impacts onto the surface of the object under study. The laser pulse is rapidly absorbed into a shallow volume of material and creates a localized thermo-elastic expansion inducing a broadband ultrasound pulse that propagate inside the material. The laser beam scans a selected area of the object surface, being remotely controlled by means of a programmable XY scanner. For each excitation point, the ultrasound waves propagate through the object are reflected or scattered by material 3D defects. They are detected by ultrasound transducers and recorded with a PC data-acquisition system for a further process and analysis. As a first step, the time of flight analysis provides enough data for the location and size of the defect in 1D view. The detection capabilities of internal defects in a metallic sample are studied by means of wavelet transform, chosen due to its multi-resolution time-frequency characteristics. A novel algorithm using a density-based spatial clustering is applied to the resulting time frequency maps to estimate the defect’s position. For the 2D visualization and reconstruction of the defects we extended the signal analysis using the synthetic aperture focusing technique (SAFT). We implement a novel 2D apodization window filtering applied along with the SAFT, and we show it removes undesired effects of the side lobes and wide-angle reflections of ultrasound waves, enhancing the reconstructed image of the defect. We move then towards the 3D analysis and reconstruction of defects and in this case we achieve and implement a fully non-contact and automatized experimental configuration allowing the scan areas on different object’s faces. The defect details are recorded from different angles/perspectives and a complete 3D reconstruction is achieved. Finally, we show our results on a complementary topic related to a particular case of the ultrasound propagation in solids. We were concerned on the physical understanding of the propagation and diffraction of ultrasound waves in solid materials from the first moment. The control of the diffraction pattern in solids, using an ultrasonic lens, would help focus/collimate the ultrasound reducing echoes and boundary reflections, resulting in a further improve NDT process. Phononic crystals have been used to regulate the diffraction and frequency response of ultrasonic waves traveling in fluids. However, they were much less studied in solid materials due to the difficulty of building the crystal and to high coupling losses. We perform detailed numerical simulations of the ultrasound propagation in a solid phononic crystal and we show focusing and the self-collimation effects. We further extend our analysis and couple our phononic crystal lens to a solid under study, showing that the diffraction control is preserved inside the target solid object trough the coupling material.<br>Esta tesis doctoral versa sobre el diseño, estudio e implementación de un método híbrido, sin contacto, de ensayos no destructivos (NDT, non-destructive testing) para el análisis de objetos metálicos que contienen defectos o fracturas internas. Proponemos una técnica híbrida opto-acústica que combina ultrasonidos generados por impacto láser como excitador y transductores de ultrasonidos como receptores. El trabajo plantea un estudio detallado de la detección y reconstrucción en 1D, 2D y 3D de defectos presentes en un objeto metálico, usando la técnica híbrida de NDT sin contacto y controlado remotamente. Nuestro dispositivo presenta varias ventajas de las técnicas fotónicas y de ultrasonidos, reduciendo al mismo tiempo algunos inconvenientes de dichos métodos tomados por separado. Nuestro método combina resultados experimentales con simulaciones numéricas basadas en el procesado de señal de alta resolución. El montaje experimental consiste en un láser pulsado de ns a una longitud de onda de 532 nm, que impacta sobre la superficie del objeto. El pulso láser se absorbe, creando una expansión termoelástica localizada que induce un pulso de ultrasonidos de banda ancha que se propaga en el material. El láser, controlado remotamente, realiza un barrido sobre un área seleccionada de la superficie del objeto. Por cada punto de excitación, el ultrasonido se propaga a través del objeto y se refleja o dispersa en los defectos del material. Dichas ondas se detectan mediante transductores y se registran en un sistema de adquisición de datos para su ulterior procesado. En un primer paso, mediante el análisis del tiempo de vuelo, podemos localizar y determinar el tamaño del defecto en una vista 1D. Las capacidades de detección de defectos internos en una muestra metálica se estudian también mediante transformación wavelet debido a sus características de multi-resolución en tiempo y frecuencia. Se aplica un algoritmo novedoso de agrupamiento (clustering) espacial y se usan los mapas resultantes de tiempo y frecuencia para estimar la posición del defecto. Para la visualización 2D de los defectos ampliamos el análisis de la señal utilizando la técnica de focalización por apertura sintética (SAFT, synthetic aperture focusing technique). Implementamos un novedoso filtro de apodización 2D, juntamente con la técnica SAFT, y demostramos que elimina efectos no deseados, mejorando la resolución de la imagen reconstruida del defecto. El siguiente paso es un análisis y reconstrucción 3D. En este caso conseguimos una configuración experimental totalmente automatizada y sin contacto, permitiendo áreas de barrido sobre diferentes caras de un objeto. Los detalles de los defectos se registran desde diferentes ángulos, consiguiéndose una completa reconstrucción 3D. Finalmente, mostramos nuestros resultados en un tema complementario, relacionado con un caso particular de propagación de ultrasonidos en sólidos. Desde un primer momento, quisimos tener una comprensión física de la propagación y difracción de ondas de ultrasonidos en materiales sólidos. El control de los patrones de difracción en sólidos, mediante el uso de lentes ultrasónicas, ayudaría a la focalización/colimación del ultrasonido, reduciendo ecos y reflexiones en la superficie de contorno, mejorando del proceso de análisis NDT. Los cristales fonónicos se usan para regular la difracción y la respuesta en frecuencia de ondas de ultrasonido que se propagan en fluidos. No obstante, dichas estructuras se han estudiado mucho menos en materiales sólidos. Hemos realizado detalladas simulaciones numéricas de la propagación de ultrasonidos en un cristal fonónico sólido y hemos demostrado efectos de focalización y autocolimación. Finalmente hemos acoplado nuestra lente de cristal fonónico al sólido objeto de estudio, demostrando que el control de la difracción se conserva en el interior de dicho objeto a través del material de acoplamiento. Finalmente, proporcionamos una conclusión general sobre el trabajo declarado en esta tesis y un plan de trabajo futuro donde esta investigación puede extenderse y expandirse aún más a aplicaciones industriales en colaboración con el mercado de producción

Les budgets alloués aux réparations des ouvrages et du patrimoine bâti ont atteint un niveau important. Une démarche scientifique est donc réfléchie pour réduire ces budgets par la mise en place d’outils visant à optimiser et fiabiliser le diagnostic structural des ouvrages. Les méthodes de contrôle non destructif (CND) constituent l’une des voies adaptées. Ces techniques reposent sur des principes physiques bien connus et les sociétés de service en proposent aujourd’hui un emploi courant, mais de nombreux verrous subsistent. Les deux besoins majeurs des gestionnaires d’ouvrages sont celui de l’optimisation de la stratégie de reconnaissance (où mesurer ? en combien de points ? avec quelle(s) techniques(s) et quelle précision ?) et celui de la quantification des propriétés mécaniques des matériaux ou des indicateurs de durabilité telles que la résistance à la compression, l’épaisseur carbonatée, le taux d’humidité. La question est comment déduire ces propriétés et ces indicateurs des mesures faites ? Et quelles sont la précision et la fiabilité de l’évaluation ?Cette thèse s’inscrit dans le cadre de deux projets nationaux de recherche : le projet ACDC-C2D2 et le projet ANR EvaDéOS. L’objectif principal est d’analyser la variabilité issue du CND pour ensuite remonter à la variabilité spatiale des bétons en conditions réelles. Les techniques de CND considérées sont choisies parmi les plus complémentaires : radar, résistivité électrique, ultrasons et rebond (scléromètre). Les résultats sont obtenus à partir d’une large campagne expérimentale effectuée sur des dalles d’un site test et sur deux ouvrages. L’analyse de la variabilité des CND a permis d’évaluer le nombre minimal de mesures nécessaire pour un niveau de confiance souhaité. D’autre part, la corrélation spatiale des données a été modélisée par l’analyse variographique. Les résultats montrent que, dans certain cas, les mesures de CND ne sont pas spatialement indépendantes. Les longueurs de corrélation identifiées dépendent de la propriété mesurée ainsi que du béton de l’ouvrage ausculté. La connaissance de ces longueurs de corrélation est un résultat nouveau qui permettra d’une part de mieux estimer la variabilité spatiale des bétons et d’autre part d’alimenter de manière plus réaliste les calculs fiabilistes des ouvrages. Elle permet également d’identifier un pas d’échantillonnage optimal sur ouvrage dans le cadre du suivi temporel ou pour effectuer des analyses complémentaires (ex. carottage, CND complémentaire ou plus fiable) et de représenter au mieux la cartographie spatiale des propriétés du béton.Dans le cadre du projet de recherche ANR EvaDéOS, les effets de la carbonatation et des gradients de teneur en eau (gradient d’humidité) sur les techniques CND ont été étudiés. Ce travail a pour objectifs d’étudier la sensibilité des techniques de CND à évaluer ces deux indicateurs de durabilité ainsi que leur impact sur la variabilité des mesures de CND. En laboratoire, des campagnes expérimentales ont été réalisées sur corps d’épreuve ayant différentes profondeurs de carbonatation ou des gradients d’humidité. L’effet de la carbonatation a été quantifié pour certains observables : résistivité électrique, vitesse ultrasonore et rebond. En ce qui concerne la variabilité des mesures de CND, l’effet de la carbonatation est seulement notable dans le cas du béton saturé, en particulier pour la variabilité locale de la résistivité électrique et du rebond. Cet effet reste faible par rapport à l’effet du degré de saturation. Les premiers résultats montrent également que les mesures de la résistivité électrique permettraient de suivre des gradients d’humidité dans le béton<br>The budgets assigned to the repair of structures and built heritage have reached an alarming level. A scientific approach is needed to reduce these budgets by implementing tools for a more reliable and optimal assessment of existing structures. Non-destructive testing (NDT) techniques constitute one of approaches adapted to real conditions. These techniques are based on well-known physical principles. Many companies offer their services in NDT domain today but many challenges remain. The two particular needs of structure managers are the optimization of the assessment strategy (where to measure? how many testing points? what technique(s) and what precision?) and the quantification of mechanical properties of materials or durability indicators such as the compressive strength, the carbonation depth, the moisture content. The questions are how to estimate these properties from measurements performed, and what are the accuracy and reliability of the evaluation?This thesis is part of two French research projects: ACDC-C2D2 and ANR EVaDéOS. The main objective is to analyze the variability of non-destructive testing (NDT) measurements for assessing the spatial variability of concrete in real conditions. NDT techniques considered are chosen as being complementary: radar, electrical resistivity, ultrasonic, rebound hammer. The results are obtained from a wide campaign of measurements, which was performed on concrete slabs of a testing site and on two existing structures. The analysis of the NDT variability makes it possible to assess the necessary minimum number of measurements for a desired level of confidence. Furthermore, the spatial correlation of the data was modeled using the variogram analysis. In some cases, the results show that NDT measurements are not spatially independent. The correlation lengths identified depend on the measured property and the concrete of the structure inspected. They are a new result, which will provide on one hand a better evaluation of spatial variability of concrete and on the other hand a more realistic input of reliability calculations of structures. The correlation length allows also the identification of an optimal sampling distance on existing structure within the monitoring time or the implementation of additional analyses (eg. core, complementary or more reliable NDT) and a better representation of the spatial mapping of concrete properties.Within the framework of the ANR EvaDéOS research project, the effects of carbonation and of moisture gradients on NDT measurements were studied. This work aims to study the sensitivity of NDT techniques for assessing these two durability indicators and their impact on the variability of NDT measurements. In laboratory, the experimental surveys were carried out on testing specimens having different depths of carbonation or moisture gradients. The effect of carbonation was quantified for several parameters: electrical resistivity, ultrasonic pulse velocity and rebound hammer. With respect to the variability of NDT measurements, the effect of carbonation is only significant in the case of saturated concrete, in particular for the local variability of electrical resistivity and rebound hammer. This effect is weak in comparison with the effect of saturation degree. The first results show also that the measurements of electrical resistivity would follow moisture gradients in concrete

Dans la péninsule d'Oman, le passage du Néolithique à l'âge du Bronze est marqué par de profondes transformations socio-économiques. La transition vers une économie agricole et l'intégration progressive dans les sphères d'interactions suprarégionales ont été interprétées comme la réponse adaptative des populations locales, suivant la pression de la demande extérieure pour l'acquisition de matières premières. Toutefois, le rôle de la péninsule omanaise au sein de ce réseau à l'aube de l'âge du Bronze est moins patent qu'on ne l'envisage, mettant en cause la nature des transformations déclenchées au début du 3ème millénaire av. J.-C.. Nous avons exploré ces questions à la lumière de la maisonnée, explicitement conçue en tant qu'élément structurant de la société, « sociogramme d'un système social ». Afin de circonstancier le passage vers la complexification de l'âge du Bronze, l'étude considère brièvement les dernières occupations néolithiques. Elle se focalise sur une analyse diachronique des architectures domestiques et de la culture matérielle au 3ème millénaire av. J.-C. (périodes Hafit et Umm an-Nar), évaluant les différents aspects susceptibles de fournir des informations sur la configuration des activités domestiques et de manufacture, sur la perception sociale de l'espace, sur l'organisation de la force de travail et le degré de spécialisation de celle-ci. Cette démarche a permis d'aborder les acteurs sociaux à l'échelle de l'habitat, valorisant l'importance des mutations socio-économiques amorcées localement, et exprimées par les cycles de développement de la maisonnée sur le long terme<br>In the Oman peninsula, the transition from the Neolithic to the Bronze Age is marked by deep socioeconomic transformations. The shift towards an agricultural economy and the gradual integration into supraregional interaction spheres have been interpreted as the adaptive response of local populations to the pressure of an external demand for the acquisition of raw materials. Nevertheless, at the dawn of the Bronze Age, the role of the Oman Peninsula within this network is less patent than generally assumed, calling into question the nature of the transformations that characterise the beginning of the 3rd millennium BC. These questions were explored by the point of view of the household, explicitly conceived as a structuring element of the society, the “sociogram of a social system”. Aiming at better understanding of the transition towards the complexification of the Bronze Age, the study briefly addresses the last Neolithic occupations, and focuses on a diachronic analysis of domestic architectures and material culture during the 3rd millennium BC (Hafit and Umm an-Nar periods). It considers a series of different aspects that could offer insights on the configuration of domestic and craft activities, on the social perception of space, on the organisation of the workforce and their degree of specialisation. This approach allowed grasping the social actors at the village level, highlighting the importance of socioeconomic transformations originating at a local scale, and expressed by the developmental cycles of the household in the long term. In addition , new field data lead to the identification of specific chronological markers for the Hafit period and the last Umm an-Nar phase

L’objectif de ce projet est de développer des méthodes d’analyse et de caractérisation des défauts structurels des matériaux s’appuyant sur la thermographie infrarouge stimulée. Nous pouvons à l’aide d’une excitation photothermique distante et d’un outil d’analyse que nous avons développé en laboratoire, déterminer la structure sous jacente d’un matériau, repérer précisément ses défauts et les mesurer. L’application qui nous intéresse ici porte sur la prévention, le diagnostique et la restauration des oeuvres d’art, nous avons démontré par de précédents travaux, la pertinence de cette approche et son potentiel important dans de nombreux domaines, qu’ils soient industriels, culturels, médicales ou autres. Nous avons fait la démonstration qu’il était possible d’analyse des matériaux fragiles de façon fiable et sans contact et nous comptons généraliser cette approche en l’étendant dans ses domaines d’intervention et dans sa précision<br>The objective of this project is to develop analysis and characterization of structural defects in material methods based on photothermal radiometry,We can by means of a remote photothermal excitation and an analysis tool that we have developed in the laboratory to determine the underlying structure of a material, precisely locate its flaws and measure. The application of interest here focuses on the prevention, diagnosis and restoration of works of art, we have demonstrated by previous work, the relevance of this approach and its significant potential in many areas, such as industrial cultural, medical or other. We have demonstrated that it was possible to analyze fragile materials reliably and without contact and we intend to generalize this approach by extending its focal areas and its accuracy

Aims and scope The Royal College of Pathologists recommend at least 12 lymph nodes should be harvested for adequate staging of colorectal cancer. Just one nodal tumour deposit upstages the malignancy. This is important as node-positive patients are considered for adjuvant chemotherapy whereas node negative patients may not be. It is not always easy to harvest the required number, especially in patients with rectal cancer receiving neoadjuvant therapy which further decreases the number and size of nodes. Lymph node revealing solutions, e.g. GEWF have been investigated to help improve nodal retrieval. GEWF is safe, cheap and easy to use, improving nodal retrieval and possibly cause upstaging, triggering adjuvant chemotherapy. However, existing evidence to support this argument is limited. Methods A controlled trial was designed, comparing further formalin fixation (n=101) to GEWF (n=99). Colorectal resections were placed in formalin or GEWF for 24 hours before performing a secondary dissection. The number, size and any tumour in nodes was compared between groups. Results The use of formalin further fixation and GEWF detected more nodes at secondary dissection. The mean number of additional nodes harvested was greater with formalin (8.3) in comparison to GEWF (7.3). When compared to formalin, GEWF does not cause a statistically significant increase in node numbers in the entire sample (p=0.218), non-neoadjuvant group (p=0.226) or neoadjuvant group (p=0.569). When compared to formalin, GEWF does not find statistically significant smaller nodes in the entire sample (p=0.093), non-neoadjuvant group (p=0.053), or neoadjuvant group (p=0.730). Upstaging triggering adjunct chemotherapy was identified in 2/200 cases. Conclusions The routine use of adjunct techniques is unnecessary with underlying high quality dissection practice. Emphasis should be placed upon educating and training staff, spending appropriate time dissecting, and ensuring specimens are sufficiently fixed beforehand. Contribution This research is the first to provide robust statistical analysis regarding the efficacy of adjunct techniques in colorectal cancer. Further research could be performed to assess their use in other cancers where nodes are difficult to detect.

Specific characteristics of single heritage constructions pose a challenge at the moment of the formulation of a judgement on the preservation state and safety of the object. In Italy, the guidelines on assessment and reduction of seismic risk to heritage constructions have provided a procedure for gaining an adequate level of knowledge of masonry constructions. Such operative methodology is presented as a path made of many aspects that, at different levels and from many viewpoints, should bring together a detailed qualitative and quantitative knowledge of the artifact under analysis. Knowledge steps include the search for documents and information from various sources, visual inspections, surveys and non-invasive diagnostic approaches, structural numerical modelling. Nevertheless, these guidelines are necessarily a generic document and cannot detail many practical aspects so that the professional dealing with real cases has to rely on extensive knowledge and experience. This is particularly true in the case of peculiar typologies of constructions, such as ancient masonry towers, which – due to their geometry - present extra problems of accessibility, inspection and survey. This thesis looks at a number of medieval masonry towers with steeple masonry spires located in Piacenza and Ravenna, Italy, to test on-site a multidisciplinary, coherent facts-finding path that keeps into account the characteristics and problematics of the single constructions in order to reach a reliable evaluation, drawing from the examination of the collected info and produced data. At the same time, this thesis aims to consolidate the author’s knowledge about the most correct choice and procedural application of various techniques according to the specific aims, in view of her professional future, keeping in mind both the engineer’s viewpoint of building safety and the architect respect for the heritage value.

La thermographie infrarouge est une méthode largement employée pour la caractérisation des propriétés thermophysiques des matériaux. L’avènement des diodes laser pratiques, peu onéreuses et aux multiples caractéristiques, étendent les possibilités métrologiques des caméras infrarouges et mettent à disposition un ensemble de nouveaux outils puissants pour la caractérisation thermique et le contrôle non desturctif. Cependant, un lot de nouvelles difficultés doit être surmonté, comme le traitement d’une grande quantité de données bruitées et la faible sensibilité de ces données aux paramètres recherchés. Cela oblige de revisiter les méthodes de traitement du signal existantes, d’adopter de nouveaux outils mathématiques sophistiqués pour la compression de données et le traitement d’informations pertinentes. Les nouvelles stratégies consistent à utiliser des transformations orthogonales du signal comme outils de compression préalable de données, de réduction et maîtrise du bruit de mesure. L’analyse de sensibilité, basée sur l’étude locale des corrélations entre les dérivées partielles du signal expérimental, complète ces nouvelles approches. L'analogie avec la théorie dans l'espace de Fourier a permis d'apporter de nouveaux éléments de réponse pour mieux cerner la «physique» des approches modales.La réponse au point source impulsionnel a été revisitée de manière numérique et expérimentale. En utilisant la séparabilité des champs de température nous avons proposé une nouvelle méthode d'inversion basée sur une double décomposition en valeurs singulières du signal expérimental. Cette méthode par rapport aux précédentes, permet de tenir compte de la diffusion bi ou tridimensionnelle et offre ainsi une meilleure exploitation du contenu spatial des images infrarouges. Des exemples numériques et expérimentaux nous ont permis de valider dans une première approche cette nouvelle méthode d'estimation pour la caractérisation de diffusivités thermiques longitudinales. Des applications dans le domaine du contrôle non destructif des matériaux sont également proposées. Une ancienne problématique qui consiste à retrouver les champs de température initiaux à partir de données bruitées a été abordée sous un nouveau jour. La nécessité de connaitre les diffusivités thermiques du matériau orthotrope et la prise en compte des transferts souvent tridimensionnels sont complexes à gérer. L'application de la double décomposition en valeurs singulières a permis d'obtenir des résultats intéressants compte tenu de la simplicité de la méthode. En effet, les méthodes modales sont basées sur des approches statistiques de traitement d'une grande quantité de données, censément plus robustes quant au bruit de mesure, comme cela a pu être observé<br>Infrared thermography is a widely used method for characterization of thermophysical properties of materials. The advent of the laser diodes, which are handy, inexpensive, with a broad spectrum of characteristics, extend metrological possibilities of infrared cameras and provide a combination of new powerful tools for thermal characterization and non destructive evaluation. However, this new dynamic has also brought numerous difficulties that must be overcome, such as high volume noisy data processing and low sensitivity to estimated parameters of such data. This requires revisiting the existing methods of signal processing, adopting new sophisticated mathematical tools for data compression and processing of relevant information.New strategies consist in using orthogonal transforms of the signal as a prior data compression tools, which allow noise reduction and control over it. Correlation analysis, based on the local cerrelation study between partial derivatives of the experimental signal, completes these new strategies. A theoretical analogy in Fourier space has been performed in order to better understand the «physical» meaning of modal approaches.The response to the instantaneous point source of heat, has been revisited both numerically and experimentally. By using separable temperature fields, a new inversion technique based on a double singular value decomposition of experimental signal has been introduced. In comparison with previous methods, it takes into account two or three-dimensional heat diffusion and therefore offers a better exploitation of the spatial content of infrared images. Numerical and experimental examples have allowed us to validate in the first approach our new estimation method of longitudinal thermal diffusivities. Non destructive testing applications based on the new technique have also been introduced.An old issue, which consists in determining the initial temperature field from noisy data, has been approached in a new light. The necessity to know the thermal diffusivities of an orthotropic medium and the need to take into account often three-dimensional heat transfer, are complicated issues. The implementation of the double singular value decomposition allowed us to achieve interesting results according to its ease of use. Indeed, modal approaches are statistical methods based on high volume data processing, supposedly robust as to the measurement noise

Le besoin de compétitivité des entreprises, dans un contexte économique mondialisé, repose sur l'amélioration de la qualité des produits et la réduction des coûts et du temps de mise sur le marché. Pour atteindre ces objectifs, la simulation numérique est couramment utilisée pour la conception de produits complexes et mobilise des expertises diverses. Les Plans d'Expériences Numériques (PEN) sont de plus en plus utilisés pour simuler les variabilités des propriétés et de l’environnement du produit. Un processus de PEN apporte des méthodes de planification et d'analyse d'un ensemble de simulations, pour mieux maîtriser les performances du produit. La problématique traitée repose sur deux points. D'une part, la définition d'un processus de PEN repose sur de nombreux choix et l'utilisation de méthodes complexes, nécessitant une expertise avancée. Cette définition est d'autant plus complexe que le modèle de simulation est complexe et coûteux à exécuter. D'autre part, l'utilisation de PEN conduit à une production de grands volumes de données en multipliant les simulations. Ces travaux portent sur l'obtention rapide de la configuration optimale du processus de PEN pour raccourcir la préparation et l’exécution d’un PEN. Ces travaux se sont orientés vers la réutilisation des connaissances en entreprise pour un système à base de connaissances, composé d'une ontologie spécifique, pour capitaliser et partager les connaissances, et d'un moteur d'inférences, basé sur les réseaux bayésiens, pour proposer aux concepteurs des configurations efficaces et innovantes. Cette proposition est illustrée par une application sur un produit industriel issue du secteur automobile<br>In order to improve industrial competitiveness, product design relies more and more on numerical tools, such as numerical simulation, to develop better and cheaper products faster. Numerical Design of Experiments (NDOE) are more and more used to include variabilities during simulation processes, to design more robust, reliable and optimized product earlier in the product development process. Nevertheless, a NDOE process may be too expensive to be applied to a complex product, because of the high computational cost of the model and the high number of required experiments. Several methods exist to decrease this computational cost, but they required expert knowledge to be efficiently applied. In addition to that, NDoE process produces a large amount of data which must be managed. The aim of this research is to propose a solution to define, as fast as possible, an efficient NDoE process, which produce as much useful information as possible with a minimal number of simulations, for complex products. The objective is to shorten both process definition and execution steps. A knowledge-based system is proposed, based on a specific ontology and a bayesian network, to capitalise, share and reuse knowledge and data to predict the best NDoE process definition regarding to a new product. This system is validated on a product from automotive industry

Al-Cu alloys are widely used in the aerospace and automotive industries due to their high specific strength in some tempered conditions. However, due to poor corrosion and wear resistance, they are often anodized and/or painted. Plasma nitriding has been proposed as an alternative, though the developments in this technique are still in a recent stage for Al alloys. Electrical characterization techniques are well implemented NDTs in the industry because of good accuracy associated with lower cost, compared to other methods. Some, like eddy currents and 4-point probe techniques, are often used in coating inspection. The objective of this study was to perform Al nitriding at low temperatures to minimize the tempering initial condition damage and to assess the feasibility of eddy currents technique as a method for evaluating surface properties. The work developed can be divided in two stages. The first one was the process tuning, done at the Shibaura Institute of Technology, in Tokyo; and the second was the electrical characterization done in Faculdade de Ciências e Tecnologia, UNL. Low temperature nitriding of AA2011 alloy specimens was successfully achieved. Electrical conductivity results show that lift-off measurements by eddy currents testing can be related to surface properties.

碩士<br>國立高雄第一科技大學<br>營建工程所<br>96<br>This paper attempts to interpret the quality of cementitious material by inference parameters through surface contact detection, because durability of the degradation phenomena is always considered to be related to the infiltration of degradation factors. Besides, since the surface is the first resistance line for invasive material, if non-destructive testing mode of testing parameters can be established by inference surface pore characteristics, with the help of taking core for rapid chloride ion migration test, one rigorous assessment system for cementitious material is proposed in this research. In order to find material factors and curing conditions on the test parameters of research interest, by adopting orthogonal experimental design technique, test data by inference model of ultrasonic pulse velocity and fluid acts of contact detection parameters can be utilized for inferring surface pore characteristics. And, test results are summarized as follows: (1)There is no clear evidence to relate the pore distribution obtained by mercury intrusion porosimetry with the inferred surface pore characteristics. (2)The most significant factor for influencing surface pore characteristics is concluded as the curing conditions. (3)One quality classification system by combing surface pore characteristics with rapid chloride migration test was proposed in this research, which grades were defined as excellent, fair and poor. (4)In order to reduce the measurement of variability of non-destructive testing, there is need to take the average of measured data of non-destructive testing in multiple times as well as to adopt automation measurement for recording and analyzing the measured parameters. (5)For the parameters used in the established model, it is suggested that automatic simulation program for achieving simple and rapid assessment should be developed.

Inspection and maintenance are important processes in the aeronautical field. The processes suffered a significant evolution over the years, due to the strong development and growth of aeronautical fleets. To guarantee aircraft safety, all critical damage should be intercepted in due time before it become an irreversible damage and compromise the entire structure. In this dissertation a methodology to create fatigue cracks of a certain dimension to be used on the qualification of NDT processes was developed. The methodology was developed based on numerical approaches, working with 2mm thick cracked specimens. For the qualification of the NDT process, the objective was to create a shallow fatigue crack on a specimen. A fourpoint bending test was modelled to restrain the crack propagation direction through thickness. Abaqus®, a finite element method software, is used to determine the stress intensity factor along the crack propagation, followed by a mathematical approach using Paris Law which is also presented to determine the crack growth along with the number of cycles. Using the software NASGRO® it was possible to determine the number of fatigue cycles that are needed for a crack starting at the initial notch to achieve the desired dimensions. The results portrayed indicate that the four-point bending test is an appropriate choice to create the crack with the imposed dimensions. By the use of the finite element method software, it is observed that the stress intensity factor is higher in the crack tip and it assumes the lower value in the notch tip. With the values of stress intensity factor, a verification study of the values was made in the Paris Law domain. A relation between the number of fatigue cycles and the values of stress intensity factor was achieved, meaning that, with the increase of fatigue cycles, the stress intensity factor also increases and consequently, the crack tends to develop into the thickness specimen.<br>Inspeções e manutenções são processos importantes na indústria aeronáutica. Os processos sofreram uma evolução significante ao longo dos anos devido ao forte desenvolvimento das frotas aeronáuticas. Para garantir a segurança da aeronave, todos os danos críticos devem ser intercetados no tempo devido antes de se tornarem danos irreversíveis que comprometam toda a estrutura. Nesta dissertação foi desenvolvida uma metodologia para criar fendas de fadiga de uma certa dimensão para serem usadas na qualificação de processos de inspeção não destrutivos. A metodologia foi desenvolvida tendo por base métodos numéricos, trabalhando com provetes de espessura de 2mm com entalhe pré-existente. Para a qualificação dos processos de inspeção não destrutivos, o objetivo passou por criar uma fenda de fadiga não penetrante no provete. Um teste de flexão a quatro pontos foi modelado para restringir a direção da propagação da fenda em espessura. Abaqus®, um software de modelação de elementos finitos, é também usado para determinar o fator de intensidade de tensão ao longo da propagação da fenda, seguida de uma abordagem matemática usando a lei de Paris é também apresentado para determinar a propagação da fenda com o número de ciclos. Usando o software NASGRO® foi possível determinar o número de ciclos de fadiga que são necessários para que uma fenda iniciada no entalhe inicial se propague até à dimensão pretendida. Os resultados obtidos indicam que o teste de flexão a quatro pontos é uma escolha apropriada para criar a fenda com as dimensões impostas. Com o uso do software de modelação de elementos finitos, foi observado que o fator de intensidade de tensão é maior na fenda final e assume o menor valor para a fenda inicial. Com os valores do fator de intensidade de tensão, foi feito um estudo de verificação dos valores no domínio da Lei de Paris. Uma relação entre os ciclos de fadiga e os valores do fator de intensidade de tensão foi alcançada, significando que, com o aumento dos ciclos de fadiga e os valores do fator de intensidade de tensão também aumenta e consequentemente, a fenda tende a desenvolver ao longo da espessura do provete.

The failure of longitudinal construction joints is one of the critical factors causing accelerated pavement deterioration. Poor-quality longitudinal construction joints are often characterized by a difference in elevation between adjacent lanes or by unraveling of the hot mix asphalt (HMA). Current wave-based non-destructive testing (NDT) methods are efficient and economical for the evaluation of material properties. In this thesis, an innovative surface wave testing technique for condition assessment of longitudinal construction joints in asphalt pavements is presented. This method enables reduction of the number of cores required for large-strain testing and provision of a more uniform quality assessment of longitudinal joints as well as the relative condition of the asphalt pavements. The technical development is based on a theoretical study of the wave attenuation mechanisms and on the reported deficiencies in current seismic wave-based methods. Traditionally, the use of ultrasonic testing to determine small-strain elastic property for asphalt concrete was uniquely based on the measurement of wave velocity. However, isolated use of wave velocity does not provide complete information of the materials strength because of the different variables that affect the strength-velocity relationship. Therefore, it is necessary to complement velocity data with independent information such as the change in attenuation and frequency content of the propagating pulse. The existing deficiencies in current seismic wave-based methods were addressed to improve reliability, accuracy and consistency for asphalt concrete material characterization in the laboratory and in the field. Refined and improved signal processing techniques were used to overcome the shortcomings in the existing wave-based methods that contribute to uncertainties in the interpretation of test results. To capture more information from a wave, the signal was analyzed in the time and frequency domains. The basic analyses included a simple method such as peak to peak amplitude of the first cycle of arriving wave, and complex methods such as maximum magnitude and area of corresponding frequency spectrum through Fourier transform. A novel approach based on wavelet transform of the signal was presented, which provides an alternative method to determine wave characteristics. Material characterization tests (experiment Phase I) were carried out to study the relationship between the wave characteristics obtained from UPV test and the quality of the asphalt concrete specimens prepared in the laboratory. The specimens were identical in terms of aggregate and asphalt binder ratio, but varying in volumetric properties produced by different compaction efforts. The specimen quality was determined using two methods: 1) the traditional method using density measurement and 2) an innovative approach using dynamic modulus which is recommended by the Federal Highway Administration (FHWA) for use as a fundamental material property for characterizing Superpave mixes (Witczak, et al., 2002; Bonaquist et al., 2003; Christensen et al., 2004). The measured wave characteristics showed excellent correlations (R2 > 0.9) with the fundamental properties of the mix. The results revealed that the wave amplitude parameters as the condition index have the potential to provide a reliable assessment of the quality of HMA mixtures. The finding is very critical to moving the technology forward in the right direction, and form an important basis for the experiment Phase II. Experiment Phase II investigated the feasibility and effectiveness of using the wave characteristics identified in experiment Phase I to assess the condition of longitudinal construction joints. Particular attention was given to examining the sensitivity of the wave-based technique to different types of construction joints. For this purpose, three types of construction joints (good, fair and poor) were fabricated in the laboratory and identified using the wave-based technique. The research was intended to develop a suitable test procedure for condition assessment the longitudinal joints in asphalt pavement in the field. The data from experiment Phase II revealed that the wave-based technique enables assessment of not only the quality of different types of longitudinal construction joints but also the relative condition of asphalt pavements.

Tese de Doutoramento em Engenharia Civil - Ramo de Conhecimento em Estruturas<br>O trabalho apresentado nesta tese foi desenvolvido no Departamento de Engenharia Civil da Universidade do Minho e no Departamento de Engenharia Estrutural do Politécnico de Milão, Itália. A prática moderna na conservação de edifícios históricos é uma tarefa complexa que requer um diagnóstico profundo e cuidadoso. A investigação preliminar é essencial afim de intervir correctamente e com sucesso. Os objectivos dessa investigação são recolher de informação apropriada sobre o edifício ou a estrutura, e avaliar as propriedades mecânicas dos materiais, sendo esta última uma tarefa difícil devido à complexidade de materiais e alvenarias antigos. É imprescindível conhecer o estado de conservação da estrutura, a extensão dos danos, a ocorrência de humidades, a geometria e características escondidas tais como vazios, fendas e destacamentos. Com o intuito de aumentar o conhecimento sobre materiais de construção antigos, foi efectuada a caracterização de tijolos cerâmicos provenientes de seis mosteiros Portugueses do século XII a XIX. Os resultados mostraram uma grande dispersão, evidenciando as seguintes características: porosidade e sucção elevadas e resistência à compressão baixa. A composição química indica que estes tijolos não foram fabricados com o mesmo tipo de matéria-prima que os artefactos antigos de cerâmica. As restrições à remoção de material para efeitos de amostragem ou para a realização de testes destrutivos são muito elevadas. Assim, nas últimas décadas, o uso de técnicas não destrutivas para investigação e diagnóstico de edifícios históricos aumentou de maneira significativa. No entanto, a avaliação da resistência à compressão e doutras propriedades mecânicas dos materiais antigos utilizando técnicas não destrutivas permanece um desafio. Uma metodologia semi-destrutiva recente baseada na microperfuração é apresentada neste trabalho para a caracterização de tijolos cerâmicos dos séculos XII a XIX. Os resultados mostram que é possível estimar de maneira fiável a resistência à compressão dos tijolos através de curvas de regressão usando a técnica de microperfuração adoptada neste trabalho. A substituição de materiais de construção antigos é um tema relevante para o património arquitectónico. Os materiais modernos são geralmente incompatíveis, exibindo uma resistência e um módulo de elasticidade muito mais elevados. Assim, este trabalho também inclui o estudo de tijolos fabrico tradicional, e que se destinam à substituição de tijolos antigos. Este estudo mostra que os tijolos modernos são mais duráveis mas evidenciam uma resistência à compressão semelhante. Além disso, as correlações propostas anteriormente para a resistência à compressão permanecem válidas para os tijolos modernos de fabrico tradicional. Estava prevista a construção de réplicas de paredes de alvenaria antigas com recurso aos tijolos modernos de fabrico tradicional e argamassa de cal de baixa resistência, com vazios e outras inclusões colocados no seu interior. Essas paredes seriam testadas utilizando outra técnica não destrutiva, que não se encontra facilmente disponível em Portugal. O Radar de Prospecção Geotécnica é uma técnica de investigação não destrutiva que permite detectar alterações de materiais através das suas propriedades dieléctricas. O Radar de Prospecção Geotécnica foi empregue na determinação da geometria e na detecção de características escondidas em elementos de alvenaria tais como vazios, fendas e destacamentos. A determinação dessas características é essencial devido ao elevado grau de heterogeneidade das estruturas antigas e às implicações destas no desempenho estrutural dos edifícios. Assim, através duma série de exemplos em provetes laboratoriais e in situ, o Radar de Prospecção Geotécnica foi usado para ajudar na detecção de características geométricas e para encontrar elementos metálicos e vazios em alvenaria histórica. Os ensaios em provetes laboratoriais incluem duas paredes de três panos em alvenaria de pedra para avalização geométrica dos panos exteriores, detecção de vazios e elementos de madeira, e uma terceira parede de alvenaria mais complexa, construída com um número significativo de deficiências, diferentes materiais (tijolo e pedra) e elementos com diferente geometria, simulando situações comuns em edifícios históricos. Os ensaios in situ, foram efectuados em diversos monumentos antigos localizados em vários países Europeus para avaliar o desempenho da técnica numa série de aplicações distintas. A medição no modo de reflexão (2D) com o Radar de Prospecção Geotécnica foi efectuada em todos os casos e produziu resultados satisfatórios relativamente à avaliação das características geométricas dos painéis de alvenaria assim como na localização de outras características (vazios, fendas, destacamentos) e objectos (elementos em madeira e metálicos) que se encontram frequentemente em elementos estruturais alvenaria. Técnicas de aquisição mais precisas e rotinas de processamento de sinais mais avançadas foram utilizadas quando é necessário um posicionamento mais preciso e para a avaliação das dimensões de prováveis objectos. Aquisições para a obtenção de volumes 3D foram efectuadas, permitindo obter o posicionamento tridimensional de vazios cilíndricos, de barras de aço e dum balaústre de betão. No entanto, esta técnica não reproduziu com suficiente precisão as dimensões dos objectos devido, essencialmente, à resolução da antena quando comparado com as dimensões do respectivo objecto. Para detectar camadas de pequena espessura na alvenaria, de difícil detecção através de perfis 2D em reflexão, foram efectuadas medições em modo de transmissão. A partir dos resultados dos tomogramas foi possível distinguir o material deteriorado do material são. Devido à grande quantidade de dados necessária, ao tempo dispendido durante a aquisição no local e aos recursos informáticos elevados para aplicar os algoritmos de reconstrução 3D e tomografia, essas técnicas apenas podem ser aplicadas localmente, caso as aquisições normais em modo de reflexão não permitam obter a informação necessária.<br>The work presented in this thesis has been developed at the Department of Civil Engineering of University of Minho, Portugal, and at the Department of Structural Engineering of Polytechnic of Milan, Italy. Modern practice in conservation of historical buildings is a complex task that requires a deep and careful diagnosis. Preliminary investigation is essential in order to intervene correctly and successfully. The objectives of such investigation are to gather adequate information about the building or structure, and to evaluate the mechanical properties of materials, being the latter a difficult task due to the complexity of old materials and historic fabrics. Necessary information is the state of conservation, the extent of damages, the presence of moisture, the geometry and hidden features such as voids, cracks and detachments. In order to increase the knowledge about ancient building materials, characterization of clay brick from historic monuments in Portugal was performed in bricks from the 12th to 19th century, collected from six monasteries. The results showed a large scatter, and the main characteristics are high porosity, high suction and low compressive strength. Chemical composition indicates that bricks are not prepared with the same raw materials as old clay artefacts. The restrictions to remove material for mechanical sampling or to carry out destructive tests are very large. Therefore, in the last decades, the use of non-destructive testing techniques for investigation and diagnosis of historical buildings has increased significantly. However, the evaluation of the compressive strength and other mechanical properties of historic materials using such techniques remains a challenge. A recent minor-destructive methodology based on microdrilling is used in this research work for the characterization of clay bricks from the 12th to 19th century. The results show that it is possible to reliably estimate the compressive strength of bricks by means of regression curves using the adopted microdrilling technique. The replacement of old material is a matter of concern in every intervention in architectural heritage. Modern materials are usually incompatible, as they present much higher strength and elastic modulus. Thus, this work addresses also the study of traditional handmade clay bricks as replacing bricks. The study shows that new bricks are more durable but exhibit comparable compressive strength. Moreover, the proposed correlations for compressive strength of ancient bricks remain valid for new traditional handmade clay bricks. Originally, it was planned to use new handmade bricks and weak lime mortars to build replicas of ancient masonry walls, with voids and other inclusions. These would be tested using another technique, which is fully non-destructive and not easily available in Portugal. Ground Penetrating Radar is a non-destructive technique that allows the detection of material changes through changes in dielectric properties. Ground Penetrating Radar was used to determine the geometry and to map hidden features of masonry such as voids, cracks and detachments. The detection of these properties is of high relevance due to the high heterogeneity of old structures, which has implications in the structural performance of buildings. Thus, through a series of examples in laboratory specimens and in situ, the Ground Penetrating Radar was used to help in the detection of geometrical characteristics and to find metallic elements and voids in masonry. The tests in laboratory specimens included two three-leaf stone masonry walls for the geometrical assessment of the exterior panels, the detection of voids and embedded wood beams, and a third complex stone/masonry wall built with a significant amount of deficiencies, construction materials and elements with different geometry, simulating typical situations on historical buildings. The experiments in situ were performed in several masonry monuments from different European countries to assess the performance of the technique for a number of applications. Radar measurements in reflection mode (2D) were carried out in every case and produced satisfactory results regarding geometry assessment of masonry leaves and in the location of features (air voids, cracks, detachments) and objects (wood beams, steel objects) that are often found in masonry structural elements. More precise acquisition techniques and advanced signal processing routines were used when more accurate positioning was needed and for the assessment of the dimensions of possible objects. Acquisitions for the construction of advanced 3D volumes were performed and allowed to obtain the three-dimensional position of cylindrical voids, steel bars and concrete baluster. However, the technique failed to reproduce adequately the dimensions of the objects due, essentially, to the resolution of the antenna when compared to the dimensions of the targets. Transmission measurements were performed to detect thin layers of masonry. The resultant tomograms identify damaged and undamaged material. Due to the significant amount of data that is necessary, the time for accurate field acquisition and the large computer resources to run 3D reconstruction and inversion algorithms, these techniques can only be applied locally, if typical 2D radargrams do fail to provide the necessary information.<br>Fundação para a Ciência e a Tecnologia (FCT)

As the capabilities of autonomous vehicles increase, their use in situations that are dangerous or dull for humans is becoming more popular. Autonomous systems are currently being used in several military and civilian domains, including search and rescue operations, disaster relief coordination, infrastructure inspection and surveillance missions. In order to perform high level mission autonomy tasks, a method is required for the vehicle to localize itself, as well as generate a map of the environment. Algorithms which allow the vehicle to concurrently localize and create a map of its surroundings are known as solutions to the Simultaneous Localization and Mapping (SLAM) problem. Certain high level tasks, such as drivability analysis and obstacle avoidance, benefit from the use of a dense map of the environment, and are typically generated with the use of point cloud data. The point cloud data is incorporated into SLAM algorithms with scan registration techniques, which determine the relative transformation between two sufficiently overlapping point clouds. The Normal Distributions Transform (NDT) algorithm is a promising method for scan registration, however many issues with the NDT approach exist, including a poor convergence basin, discontinuities in the NDT cost function, and unreliable pose estimation in sparse, outdoor environments. This thesis presents methods to overcome the shortcomings of the NDT algorithm, in both 2D and 3D scenarios. To improve the convergence basin of NDT for 2D scan registration, the Multi-Scale k-Means NDT (MSKM-NDT) algorithm is presented, which divides a 2D point cloud using k-means clustering and performs the scan registration optimization over multiple scales of clustering. The k-means clustering approach generates fewer Gaussian distributions when compared to the standard NDT algorithm, allowing for evaluation of the cost function across all Gaussian clusters. Cost evaluation across all the clusters guarantees that the optimization will converge, as it resolves the issue of discontinuities in the cost function found in the standard NDT algorithm. Experiments demonstrate that the MSKM-NDT approach can be used to register partially overlapping scans with large initial transformation error, and that the convergence basin of MSKM-NDT is superior to NDT for the same test data. As k-means clustering does not scale well to 3D, the Segmented Greedy Cluster NDT (SGC-NDT) method is proposed as an alternative approach to improve and guarantee convergence using 3D point clouds that contain points corresponding to the ground of the environment. The SGC-NDT algorithm segments the ground points using a Gaussian Process (GP) regression model and performs clustering of the non ground points using a greedy method. The greedy clustering extracts natural features in the environment and generates Gaussian clusters to be used within the NDT framework for scan registration. Segmentation of the ground plane and generation of the Gaussian distributions using natural features results in fewer Gaussian distributions when compared to the standard NDT algorithm. Similar to MSKM-NDT, the cost function can be evaluated across all the clusters in the scan, resulting in a smooth and continuous cost function that guarantees convergence of the optimization. Experiments demonstrate that the SGC-NDT algorithm results in scan registrations with higher accuracy and better convergence properties than other state-of-the-art methods for both urban and forested environments.

Dans la péninsule d'Oman, le passage du Néolithique à l'âge du Bronze est marqué par de profondes transformations socio-économiques. La transition vers une économie agricole et l'intégration progressive dans les sphères d'interactions suprarégionales ont été interprétées comme la réponse adaptative des populations locales, suivant la pression de la demande extérieure pour l'acquisition de matières premières. Toutefois, le rôle de la péninsule omanaise au sein de ce réseau à l'aube de l'âge du Bronze est moins patent qu'on ne l'envisage, mettant en cause la nature des transformations déclenchées au début du 3ème millénaire av. J.-C.. Nous avons exploré ces questions à la lumière de la maisonnée, explicitement conçue en tant qu'élément structurant de la société, « sociogramme d'un système social ». Afin de circonstancier le passage vers la complexification de l'âge du Bronze, l'étude considère brièvement les dernières occupations néolithiques. Elle se focalise sur une analyse diachronique des architectures domestiques et de la culture matérielle au 3ème millénaire av. J.-C. (périodes Hafit et Umm an-Nar), évaluant les différents aspects susceptibles de fournir des informations sur la configuration des activités domestiques et de manufacture, sur la perception sociale de l'espace, sur l'organisation de la force de travail et le degré de spécialisation de celle-ci. Cette démarche a permis d'aborder les acteurs sociaux à l'échelle de l'habitat, valorisant l'importance des mutations socio-économiques amorcées localement, et exprimées par les cycles de développement de la maisonnée sur le long terme<br>In the Oman peninsula, the transition from the Neolithic to the Bronze Age is marked by deep socioeconomic transformations. The shift towards an agricultural economy and the gradual integration into supraregional interaction spheres have been interpreted as the adaptive response of local populations to the pressure of an external demand for the acquisition of raw materials. Nevertheless, at the dawn of the Bronze Age, the role of the Oman Peninsula within this network is less patent than generally assumed, calling into question the nature of the transformations that characterise the beginning of the 3rd millennium BC. These questions were explored by the point of view of the household, explicitly conceived as a structuring element of the society, the “sociogram of a social system”. Aiming at better understanding of the transition towards the complexification of the Bronze Age, the study briefly addresses the last Neolithic occupations, and focuses on a diachronic analysis of domestic architectures and material culture during the 3rd millennium BC (Hafit and Umm an-Nar periods). It considers a series of different aspects that could offer insights on the configuration of domestic and craft activities, on the social perception of space, on the organisation of the workforce and their degree of specialisation. This approach allowed grasping the social actors at the village level, highlighting the importance of socioeconomic transformations originating at a local scale, and expressed by the developmental cycles of the household in the long term. In addition , new field data lead to the identification of specific chronological markers for the Hafit period and the last Umm an-Nar phase

Many of the sources indicated in this work are classical and not updated due to the fact that the origins of Gestalt Philosophy are found in classical works<br>Verskeie van die geraadpleegde bronne in die literatuurhoofstukke verteenwoordig klassieke werke wat nie binne die erkende periode vir relevante wetenskaplike navorsing val nie. Die oorsprong van die Gestalt Filosofie wat in hierdie studie benut is, word in hierdie klassieke werke gevind en is ook in hierdie werke geraadpleeg<br>The Gestalt approach was used as the contextual framework to explore how music can be used as a therapeutic medium in the treatment of the emotionally traumatized child. Music as a sensory experience was used during the therapeutic process with each case study, to facilitate the child's process towards healing. The conceptual framework of music as a therapeutic medium was researched in depth to bring clarity to the influence it has on the emotional well-being of the child. The child who entered into therapy was selected according to specific criteria, with the experience of emotional trauma being priority. The researcher also studied the concept of emotional trauma in depth and the consequences it has on a child's overall functional ability. Music was used as an expressive technique during the therapeutic process with each child. The conclusion drawn from this study indicated that the gestalt approach can be applied effectively in using music as a therapeutic medium in the treatment of the emotionally traumatized child.<br>Die Gestalt benadering is gebruik in hierdie navorsing ten einde 'n kontekstuele raamwerk daar te stel waarbinne musiek as terapeutiese medium in die behandeling van emosionele trauma in kinders gebruik kon word. Musiek kan beskryf word as 'n sensoriese ervaring. Hierdie sensoriese ervaring is binne die terapeutiese proses toegepas ten einde die kind se herstelproses te fasiliteer. Die studie is binne die navorsingskonteks van gevallestudieprosedures gedoen. Musiek is binne die konseptuele raamwerk bestudeer en nagevors ten einde die terapeutiese waarde daarvan in diepte te ondersoek. Hierdie in-diepte ondersoek het aan die navorser 'n duidelike beeld gegee hoe dit toegepas kon word in terapie. Deur dit toe te pas in terapie is die invloed van musiek op die emosionele welsyn van die getraumatiseerde kind gedokumenteer. Die navorsingskriteria vir insluiting in die ondersoek was gegrond op die literatuurondersoek en het onder meer die belewing van trauma ingesluit. Die belewing van emosionele trauma en invloed op die kind se geheelfunksionering was dus 'n verdere eenheid van ontleding en is in diepte deur die navorser bestudeer. Musiek is dus gebruik as 'n ekspressiewe tegniek tydens die terapeutiese proses met elke gevallestudie. Die gevolgtrekking waartoe in hierdie studie gekom kon word is dat musiek binne die konteks van die gestalt benadering suksesvol in die hantering van emosionele trauma by die kind gebruik kan word.<br>Practical Theology<br>M.Diac. (Play Therapy)