Thèses sur le sujet « Stress analysi »

Background and aim: Reduced alveolar bone height due to ridge resorption represents a major limitation in the use of dental implants, in particular in the posterior sectors of jaws. It increases the probability of an invasion with related possible damage to some anatomical structures, such as the inferior alveolar nerve. Short dental implants' placement has been proposed as an alternative to surgical bone augmentation procedures and recent studies indicated that short implants could present survival and success rates similar to conventional implants in short and medium term. However doubts about biomechanical performances were risen because higher crowns are sometimes necessary to compensate the bone resorption, leading to a less favourable crown to implant ratio.
Recently image-based approaches combined with Finite Element Analyses (FEA) have allowed effective stress–strain investigations in biological systems and in particular stress distribution in bone. The objective of this study was to evaluate the stress transmitted to surrounding bone by different implant number, implant length and crown configurations in a three-unit bridge by means of finite element analysis. Material and methods: The 3D geometry of the edentulous mandible was reconstructed from computerized tomography (CT) scans. The symmetry of the structure permitted the reconstruction of a half maxilla.
Bone material mechanical properties have been assigned to each tetrahedral element based on the Grey Value. The meshes of the implants (Astra Tech AB OsseoSpeedTM TX, Dentsply Implants) were placed in second premolar, first molar and second molar position for the three implants configurations and in second premolar and first molar position for the two implants configurations. A superstructure representing a porcelain three unit bridge was built using beam elements for each configuration. Six different implant configurations were compared: LS2) two 4 mm diameter x 11 mm long implants with 8 mm long crowns; LS3) three 4 mm diameter x 11 mm long implants with 8 mm long crowns SS2) two 4 mm diameter x 11 mm long implants with 8 mm long crowns; SS3) three 4 mm diameter x 11 mm long implants with 8 mm long crowns; SL2) two 4 mm diameter x 6 mm long implants with 13 mm long crowns; SL3) three 4 mm diameter x 6 mm long implants with 13 mm long crowns. A 200 N axial and 45° oblique loads were applied to each crown. For each configuration the effect of both loading scenarios was evaluated in terms of state of stress in the bone-implant interface (Von Mises stress, maximum and minimum principal stresses). Results: Under oblique load the stress distribution is more concentrated around the coronal part of the implant and it is several times higher than under axial load. In particular the tension represented by the maximum principal stress is from 15 to 35 times higher. In all configurations the stress was more concentrated in the cervical area of the peri-implant bone. Considering axial load the higher values of peri-implant stress were found in the SS2 and SL2 configurations while the lower values around in LC2 and LC3 configurations. Under oblique load the maximum peri-implant stress was found in the SL2 configuration while the minimum peri-implant stress was found in the LC3 configuration. The increase of stress parameters values in SS configurations respect to LS configuration were on average of the 40%. Even the average increase of stress values in SL configurations respect to SS configuration was about the 42% under tilted load.
Configurations with 2 implants were recorded to undergo about the 50% more of stress on average than the respective 3 implants configurations. Conclusions: Crown heigh, implant number and implant length seem to be all influencing factors on implant bone stress, however the augmentation of crown heigh seems to have a greater effect than a reduction of implant length.
Even if the stress observed in all configurations was within a physiological range, a three-unit bridge with 13 mm long crowns supported by two implants may be biomechanicaly hazardous in the presence of horizontal forces, and the addition of another short implant or increase of bone volume may be suggested to dissipate the stress at bone-implant interface. In conclusion the use of short dental implants to support a three unit bridge in the posterior mandible can be considered a potential alternative to standard length implants, but crown heigh and lateral forces have to be carefully analyzed in every patient.

La simulazione nell'educazione in medicina è considerata un metodo di formazione in grado di migliorare le competenze cliniche e il comportamento degli operatori sanitari e, di conseguenza, la qualità dell'assistenza per il paziente. Inoltre, l'utilizzo di nuove tecnologie come la Realtà Aumentata, offre ai discenti l'opportunità di esercitarsi in un ambiente immersivo. L'opportunità di sperimentare questo innovativo metodo didattico è efficace non solo nel ridurre il rischio di errori e approcci sbagliati ma anche nel provare ansia e stress simili a quelli avvertiti nella pratica reale. La sfida sta nel trovare il giusto equilibrio. I discenti devono infatti provare lo stesso stress che avvertirebbero lavorando ad un vero caso clinico ma, allo stesso tempo, devono essere controllati ed evitati possibili disturbi da stress post-traumatico, verificabili soprattutto nel campo della gestione delle emergenze (pronto soccorso). Inoltre, è fondamentale anche ottenere alte prestazioni e un apprendimento adeguato, evitando sovraccarichi cognitivi che influenzerebbero negativamente l’apprendimento. Tuttavia, ad oggi mancano ancora studi approfonditi sull'impatto che le simulazioni mediche hanno su stress, frustrazione, carico cognitivo e apprendimento dei discenti. Per questo motivo, l'obiettivo principale di questo studio è valutare l'efficacia del training tramite simulazione, analizzando prestazioni, ansia, stress e carico cognitivo durante simulazioni cliniche tradizionali (con manichino) ed avanzate (in realtà mista). A questo scopo, è stato sviluppato un approccio metodologico strutturato e completo per valutare le prestazioni, le condizioni emotive e cognitive degli studenti. Questo comprende l'acquisizione e l'analisi di parametri psicologici (valutazione soggettiva), segnali biometrici (valutazione oggettiva) e prestazioni. Questa indagine consente di evidenziare i punti deboli delle simulazioni e offre l'opportunità di definire utili linee guida per la riprogettazione e l'ottimizzazione delle stesse. La metodologia è stata applicata su tre casi studio: il primo si riferisce a simulazioni ad alta fedeltà per la gestione del paziente in pronto soccorso, il secondo si riferisce a simulazioni a bassa fedeltà per la pratica della rachicentesi. Per il terzo caso studio, è stato progettato e sviluppato un prototipo di simulatore in realtà mista per la rachicentesi, con l'obiettivo di migliorare il senso di realismo e immersione della simulazione a bassa fedeltà. 148 studenti sono stati coinvolti nei primi due casi studio osservazionali, mentre soltanto 36 studenti hanno preso parte allo studio pilota sulla simulazione in realtà mista. In tutti i casi di studio sono state effettuate analisi descrittive delle prestazioni, degli stati cognitivi ed emotivi. Per le simulazioni ad alta e bassa fedeltà, le analisi di regressione statistica hanno evidenziato quali variabili influenzano le prestazioni, lo stress e il carico cognitivo degli studenti. Per lo studio pilota sulla realtà mista, l'analisi della user experience ha sottolineato i limiti tecnici della nuova tecnologia.
Simulation in medical education is considered a training method capable of improving clinical competence and practitioners’ behaviour, and, consequently quality of care and patient’s outcome. Moreover, the use of new technologies, such as augmented reality, offers to the learners the opportunity to engage themselves in an immersive environment. The opportunity to experiment with this innovative instructional method is effective not only in reducing the risk of errors and wrong approaches but also in experiencing anxiety and stress as in real practice. The challenge is to find the right stress balance: learners have to feel as if they were practicing in the real stressful clinical case, and, at the same time, post-traumatic stress disorders, verifiable especially in the emergency field, must be controlled and avoided. Moreover, it is fundamental also to obtain high performance and learning, thus avoiding cognitive overloads. However, extensive researches about the impact of medical simulations on students’ stress, frustration, cognitive load, and learning are still lacking. For this reason, the main objective of this study is to assess simulation training effectiveness by analysing performance, anxiety, stress, and cognitive load during traditional (with manikin) and advanced (with augmented reality) clinical simulations. A structured and comprehensive methodological approach to assess performance, emotional and cognitive conditions of students has been developed. It includes the acquisition and analysis of psychological parameters (subjective assessment), biometric signals (objective assessment), and task performance. This investigation allows to point out simulations’ weaknesses and offers the opportunity to define useful optimisation guidelines. The methodology has been applied to three case studies: the first one refers to high-fidelity simulations, for the patient management in the emergency room, the second one refers to low-fidelity simulation for rachicentesis. For the third case study, a prototype of a mixed reality simulator for the rachicentesis practice has been designed and developed aiming at improving the sense of realism and immersion of the low-fidelity simulation. While 148 students have been enrolled in the first two case studies, only 36 students have taken part in the pilot study about mixed reality simulation. Descriptive analysis about performance, cognitive and emotional states have been done in all the case studies. For the high-fidelity and low-fidelity simulations, the statistical regression analysis has pointed out which variables affect students’ performance, stress, and cognitive load. For the pilot study about mixed reality, the user experience analysis highlighted the technical limitations of the new technology.

Bacterial endophytes are the organisms that live inside the plant for a full or a part of their life cycle. Endophytic bacteria have captured the interest of agriculture industry due to their plant beneficial properties, such as synthesis of phytohormones, solubilization of soil nutrients, and alleviation of biotic and abiotic stresses. Several studies have reported that stress tolerant endophytic bacteria can work with a similar performance as non-stressed conditions when inoculated to the plants under stressed conditions. Combination of abiotic stresses such as salinity, drought and low nitrogen stress can have additive or agonistic effects on bacterial and plant growth, and their interactions. However, very few studies have reported the impact of combined stress on endophytic bacterial assisted plant growth promotion. Therefore, understanding the underlying mechanisms of endophytic bacterial assisted plant’s tolerance abiotic stresses may provide the means of better exploiting the beneficial abilities of endophytic bacteria in agricultural production. Thus, the aim of this thesis was to study the stress tolerance mechanisms, beneficial characteristics, and plant growth promotion characteristics of endophytic bacteria under individual and combined abiotic stresses. Transcriptome analysis of endophytic bacteria revealed that tolerance mechanisms to deal with one kind of stress is different than concurrent stresses. Salinity and drought stress largely modulated the genes involved in flagellar assembly and membrane transport, showing reduced motility under stress conditions to preserve the energy. Additionally, bacterial endophyte that can fix nitrogen was studied with maize plant growth promotion under drought and low nitrogen stress conditions. The results suggested that diazotrophic bacterial endophyte can promote plant growth under moderate individual and combined stress conditions. Plant growth promoting endophytic bacteria can be utilized as an efficient tool to increase crop production under individual and concurrent abiotic stresses.

The work described in this thesis considers the application of thermoelastic stress analysis (TSA) to the assessment of residual stresses in metallic materials. Residual stresses exist within almost all engineering components and structures. They are an unavoidable consequence of manufacturing processes and may cause the premature and catastrophic failure of a component when coupled with in-service stresses. Alternatively, beneficial residual stress may be introduced to enhance the component performance. Greater knowledge of residual stress and its evolution, will not only provide an opportunity to improve component manufacture and design, but may allow the potential life extension of current structures beyond their design life. Techniques for measuring residual stresses can be divided into two main groups. Destructive methods involve removing material, measuring the mechanical strain relaxation and back calculating the residual stress. These techniques are generally cheaper and more portable, but are not appropriate in many circumstances due to modification and damage to the component. Non-destructive techniques do not damage the component, but are typically more expensive, less portable and can require complicated calibration procedures to correctly interpret results. TSA is a well established non-contacting experimental stress analysis technique that is quick and portable, and the presence of residual stress is known to modify the thermoelastic response. However, this change is very small and of the order of the noise threshold and resolution of currently available infra-red detectors. Several methods for identifying residual stresses from the thermoelastic response have been suggested and are further explored in this thesis. Significant attention is given to the effect of plastic deformation on the thermoelastic constant, and the influence of the mean stress on the thermoelastic response in stainless steel and aluminium. An investigation of the experimental setup is undertaken to optimise the detector settings, maximise the thermoelastic signal and minimise measurement errors. For metallic materials, a paint coating is typically required which may attenuate the response. A study of coating characteristics is presented, which compares the experimental and theoretical thermoelastic response. The importance of the coating is highlighted and recommendations for appropriate conditions are provided. The overall feasibility of applying a TSA based approach to residual stress assessment is considered by examining residual stresses around cold expanded holes in aluminium plate. Changes in the response are identified and attributed to the presence of residual stress. Laboratory X-ray diffraction is used to provide residual stress measurements. These are incorporated into a model of the thermoelastic response providing good agreement between experimental data and theoretical predictions within the region of interest. The potential for TSA to identify residual stress is demonstrated, and the study thereby represents a significant step towards understanding the role of TSA within the field of residual stress.

In this thesis a finite element model of a household washing machine cylinder is built and analysed in ABAQUS 6.9-2. The aim is to help Asko appliances in conducting similar analysis for future manufacturing of high capacity cylinders by reducing experimentation. The analysis is mainly concerned with an evenly distributed load at a constant angular velocity. The load is applied with the help of lead plates instead of clothes. The cylinder is loaded with three thin (2 mm) lead plates weighing 2 kg each. The plates with dimensional 370x240x2 mm are mounted with one strip of double sided foam tape inside the cylinder. To estimate the behavior of the cylinder the strains are measured when the cylinder is rotating at 1620 and 2200 revolution per minute (rpm). To validate the model the numerical analyses are compared with experimental results. The results clearly show that the numerical strain values fit with experimental strain values.

Les méthodes traditionnelles de dimensionnement à la fatigue s’appuient sur l’utilisation de coefficients dits de “sécurité” dans le but d’assurer l’intégrité de la structure en couvrant les incertitudes inhérentes à la fatigue. Ces méthodes de l’ingénieur ont le mérite d’être simples d’application et de donner des solutions heureusement satisfaisantes du point de vue de la sécurité. Toutefois, elles ne permettent pas au concepteur de connaître la véritable marge de sécurité de la structure et l’influence des différents paramètres de conception sur la fiabilité. Les approches probabilistes sont envisagées dans cette thèse afin d’acquérir ces informations essentielles pour un dimensionnement optimal de la structure vis-à-vis de la fatigue. Une approche générale pour l’analyse probabiliste en fatigue est proposée dans ce manuscrit. Elle s’appuie sur la modélisation des incertitudes (chargement, propriétés du matériau, géométrie, courbe de fatigue) et vise à quantifier le niveau de fiabilité de la structure étudiée pour un scénario de défaillance en fatigue. Les méthodes classiques de fiabilité nécessitent un nombre important d’évaluations du modèle mécanique de la structure et ne sont donc pas envisageables lorsque le calcul du modèle est coûteux en temps. Une famille de méthodes appelée AK-RM (Active learning and Kriging-based Reliability Methods) est précisément proposée dans ces travaux de thèse afin de résoudre le problème de fiabilité avec un minimum d’évaluations du modèle mécanique. L’approche générale est appliquée à deux cas-tests fournis par SNECMA dans le cadre du projet ANR APPRoFi
Traditional procedures for designing structures against fatigue are grounded upon the use of so-called safety factors in an attempt to ensure structural integrity while masking the uncertainties inherent to fatigue. These engineering methods are simple to use and fortunately, they give satisfactory solutions with regard to safety. However, they do not provide the designer with the structure’s safety margin as well as the influence of each design parameter on reliability. Probabilistic approaches are considered in this thesis in order to acquire this information, which is essential for an optimal design against fatigue. A general approach for probabilistic analysis in fatigue is proposed in this manuscript. It relies on the modelling of the uncertainties (load, material properties, geometry, and fatigue curve), and aims at assessing the reliability level of the studied structure in the case of a fatigue failure scenario. Classical reliability methods require a large number of calls to the mechanical model of the structure and are thus not applicable when the model evaluation is time-demanding. A family of methods named AK-RM (Active learning and Kriging-based Reliability methods) is proposed in this research work in order to solve the reliability problem with a minimum number of mechanical model evaluations. The general approach is applied to two case studies submitted by SNECMA in the frame of the ANR project APPRoFi

Thesis (Ph.D)--Computing, Georgia Institute of Technology, 2010.
Committee Chair: Ramachandran, Umakishore; Committee Member: Clark, Nathan; Committee Member: Haskin, Roger; Committee Member: Pu, Calton; Committee Member: Rehg, James. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains xvii, 278 p. : ill. (some col.), maps. Vita. Includes abstract. Includes bibliographical references (p. 274-277).

The crankshaft is a complex component, and as such, the influence of its geometric parameters on stresses seen under service loads is not well understood. The objectives of this work are to investigate the effects of a wide range of geometric parameters on stresses in overlapped crankshafts, to find correlation between results and to formulate simple methods of predicting peak stress levels: It is intended to achieve this by use of the Finite Element (FE) and Boundary Element (BE) methods. Individual crankthrows are loaded under the important load cases of bending and torsion. Stress concentration factors are determined by normalising peak stresses with respect to the nominal stress occurring in the most appropriate section in the neck between the fillets. Analyses are carried out in 2D and 3D, making use of symmetry as far as possible. Many of the governing dimensions of the crankthrow are included in the analyses; crankpin and journal diameters, crankpin and journal overlap, and web thickness. Variations in SCF are plotted over a wide range for each of these parameters. Additionally, features such as fillet size and shape, bore-holes, dimples, cut-back webs and oil holes are investigated. It is found that the effects on stress of individual parameter changes can be superimposed to accurately predict the effect of combining various parameter changes in one model. The crankpin and journal fillet radii and the length of the minimum section between the fillets are shown to be the critical parameters in determining the peak stress levels in the crankshaft. SCFs obtained from the range of analyses performed show good agreement with the classical theory of SCFs in notched bars. Bore-holes and dimples are found to offer significant benefits in terms of peak stress reduction, in addition to their common usage of reducing the out of balance crankpin mass. The FE and BE methods give accurate results for stress analysis of crankshafts and offer several advantages over traditional experimental techniques; they are ideally suited to parametric analyses, can be carried out relatively quickly, results are repeatable because boundary conditions can be exactly defined, and the cost of analysis is significantly reduced.

A general displacement-based shear and transverse normal deformable plate theory is reviewed. Shear and transverse normal deformable plate theories suitable for cylindrical bending problems have been deduced from the general plate theory by introducing certain general functions of the transverse coordinate into the displacement field approximation. This theory takes into account the transverse shear and normal deformation effects and unifies most of the classical and shear deformable theories available in the literature. A predictor-corrector method has been used for improving the accuracy of transverse stress analysis results and assessing the accuracy of composite plate/beam theories. In more detail, uniform shear deformable plate theory, parabolic shear deformable plate theory, general three-degree-of-freedom shear deformable plate theory, general four-degree- of-freedom transverse shear and normal deformable plate theory and general five-degree-of-freedom shear deformable plate theory are employed to improving their prediction performances of transverse shear and normal stresses. By means of the assessment of plate theories for simply supported beams, general three-degree-of-freedom shear deformable plate theory, general four-degree-of-freedom transverse shear and normal deformable plate theory are applied for other sets of boundary conditions of cross-ply laminates subject to mechanical loading. General five-degree-of-freedom shear deformable plate theory is applied for angle-ply laminates subject to mechanical loading. In addition, general four-degree-of-freedom transverse shear and normal deformable plate theory is employed for cross-ply laminates subject to thermal loading. The numerical results of the present studies are compared with the corresponding exact solution results available in the literature.

Recently, adhesively bonded joints (ABJs) has found more rapidly increasing applications in aerospace and aeronautical structures, ground vehicles, and flexible electronics than mechanical fastening and welding technologies. However, outstanding issues still exist. This work was to develop a systematic semi-analytic method for accurate prediction of the interfacial shear and normal stresses of ABJs. Two unknown shear and peeling stress functions at each interface was first introduced in formulation, which satisfies all the traction boundary conditions. A set of governing ordinary differential equations (ODEs) was determined via triggering the theorem of minimum complimentary strain energy. Matlab? code was programmed to execute the proposed method. Furthermore, the present method was validated by finite element method and compared with those models in the literature. The present method is applicable for convenient scaling analysis and optimal design of ABJs and other types of ABJs such as adhesively bonded tubular and composite joints, etc.
NSF; ND NASA EPSCoR; Faculty Research Initiative Grant; Department of Mechanical Engineering at NDSU.

La maladie d’Alzheimer et les maladies à prions sont des maladies neurodégénératives incurables associées à la transconformation d’un polypeptide : respectivement, le peptide Aß et la protéine prion (PrP). Ces polypeptides mépliés forment alors différents agrégats dans le cerveau, qui conduisent à la mort neuronale. Chez un individu sain, la PrP a une fonction neuroprotectrice, mais chez les malades, la toxicité de certains agrégats pathologiques passe par cette protéine. De plus, les deux pathologies sont associées à un stress oxydant précoce et toxique, qui peut favoriser et être favorisé par l’agrégation de protéines, sans que les agrégats impliqués dans ce cercle vicieux ne soient précisément identifiés.Pour étudier le stress oxydant dans ces maladies, j’ai développé des modèles cellulaires innovants pour suivre en temps réel des marqueurs d’oxydation, et des outils bioinformatiques d’analyse des résultats. Mes travaux montrent que l’unique expression de la forme saine d’Aß ou de PrP protège les cellules d’un oxydant exogène. Pour autant, l’ajout au milieu de culture des mêmes cellules d’Aß et de PrP recombinant favorise l’apparition d’un stress oxydant, uniquement pour les cellules exprimant la PrP normale. Cet effet est visible pour Aß sous forme de fibres amyloïdes, et pour PrP sous forme de monomère, d’oligomères et potentiellement de fibres amyloïdes. Ces travaux valident donc le rôle central de la PrP normale dans la physiologie et la pathologie. Mes résultats pourraient suggérer un rôle des glutathion péroxydases dans la médiation de l’effet protecteur de la PrP normale, et une activation des NADPH oxydases via la PrP en présence d’agrégats pathologiques
Alzheimer's disease and prion diseases are incurable neurodegenerative diseases associated with the transconformation of a polypeptide: the Aß peptide and the prion protein (PrP) respectively. These misfolded polypeptides then form different aggregates in the brain, leading to neuronal death. In a healthy individual, PrP has a neuroprotective function, but in patients suffering from Alzheimer or prion diseases, the toxicity of some pathological aggregates is mediated by this protein. Moreover, both pathologies are associated with an early chronic oxidative stress, that is toxic. It can promote and be promoted by protein aggregation, without the aggregates involved in this vicious circle being precisely identified.To study oxidative stress in these diseases, I developed innovative cellular models to monitor oxidation markers in real time, and bioinformatic tools to analyze the results. My work shows that the unique expression of the healthy form of Aß or PrP protects cells from an exogenous oxidant. However, the addition to the culture medium of the same cells of recombinant Aß and PrP promotes the appearance of oxidative stress, only for cells expressing normal PrP. This effect is visible for A in the form of amyloid fibrils, and for PrP in the form of monomer, oligomers and potentially amyloid fibrils. This work thus validates the central role of normal PrP in physiology and pathology. My results could suggest a role of glutathione peroxidases in mediating the protective effect of normal PrP, and an activation of NADPH oxidases via PrP in the presence of pathological aggregates

This thesis details research conducted towards investigating the state of stress around inclined boreholes with the ultimate aim of predicting borehole stability and providing realistic estimates of closure stress. Chapter 1 discusses the factors affecting the stability of boreholes and reviews previous research conducted into borehole failure. The mechanics of hydraulic fracturing are reviewed as are methods of predicting fracture gradients. The manner in which closure stress is estimated is also critically reviewed. Chapter 2 describes an initial investigation into the stresses around inclined boreholes using the photoelastic technique of Stress Freezing. Chapter 3 details the laboratory determination of rock properties required for the borehole stability work detailed in Chapter 4. The applicability of the Brinell Hardness test to rock is also examined. Chapter 4 presents a detailed analysis of borehole stability. Failure criteria are developed and applied to estimate the mud weight required to maintain the hole in an elastic condition. To investigate the post-failure stability, existing 'yield zone' equations are modified to allow the effect of rock strength, oil flow rate, in-situ stress and hole angle to be examined. Chapter 5 describes the design and in-house manufacture of the specialised equipment required to measure fracture conductivity in the laboratory, the development of experimental procedures, the various test results and the conclusions drawn from them. Finally, the direct effect of a yield zone on the estimation of closure stress and on proppant selection is examined Chapter 6 summarises the conclusions that may be drawn from the work detailed in this thesis. The chapter also describes possible fields of future research which have been stimulated by the work presented. Two appendices are included, one providing a data-base of proppant properties, the other detailing the results of the application of the data-base to formation samples.

Gear stress analysis and understanding the effect of misalignment and microgeometry is important for gear designers and for those who work in gear maintenance. The misalignment can lead to the higher stress acting in one side of the gear tooth and the micro-geometry modification can improve the stress distribution in the gear teeth. In this research, a helical gear pair was modeled using three different software and tools; LDP, KISSsoft and Abaqus. Three different cases were modeled to study the effect of misalignment and microgeometry. Finally, the results from different tools were presented and discussed. It was observed that the tooth contact analysis software resulted in significantly higher stresses than the FE software. The results have been discussed to understand the differences in the cases obtained from the used tools. The results showed how bad is the effect of the misalignment on the gear mesh and the stress distribution and how the microgeometry modifications are used to compensate that effect.

Fatigue is an important character for the flexible pipes as they are always exposed to dynamic loading. For nonbonded flexible pipes, fatigue and stress analysis can be performed based on different assumptions of slip behaviour. Different slip assumptions used in estimating the slip stress always play a determinative role in the prediction of fatigue damage. Thus, this thesis will focus on the study of the slip behaviour between tensile armour layers of nonbonded flexible pipes. The results can be used to support the basic assumptions for further fatigue analysis. The main object of this thesis is to summarize the existing analytical methods for stress and slip analysis of nonbonded flexible pipe armouring layers and to verify that the improved finite element models can give adequate description of the flexible pipe slip behaviour.In previous version of BFLEX, the transverse slip effect for nonbonded flexible pipes has been neglected. In this thesis, transverse slip regime has been activated in the updated BFLEX by developing a new type of beam element hshear353 and a new type of contact element hcont453. Finite element models use these two elements have been made and several case studies have been carried out.For axisymmetric loading, two analytical solutions, one obtained from the equations by Witz&Tan[13], one from Sævik[2] have been compared with the result from numerical simulation. It has been found that Sævik’s solution matches better with the BFLEX solution comparing to Witz&Tan’s solution. For flexible pipes exposed to bending, influences on slip behaviour from several pipe parameters, namely friction coefficient, axial strain and global pipe curvature, have been investigated. The numerical results are also compared with analytical solutions obtained from Sævik[2]. It has been found that the numerical solutions can give excellent agreement with analytical solutions. It is further concluded that the outer tensile armour layer do not influence much on the inner layer slip behaviour.In addition, the cyclic bending effects on nonbonded flexible pipes have been investigated. It has been found that the tendon behaves differently from case to case. The inner and outer layers behave differently. Only a few cases have been studied for this problem due to time limitation. The overall conclusion is that the developed BFLEX model is capable of describing the stresses and local displacements of flexible pipe for simple cases. The developed numerical model can further be used in the study of fatigue in flexible risers. However, more studies on influence from multi-tensile layers and cyclic bending are needed in the future.

The Bogie frame is an important and integral member of bogie. In Indian Railways, LHB (Linke Hofmann Busch) coaches are used as passenger coaches. They are equipped with FIAT bogie frames. Inorder to overcome the limitations of the existing FIAT bogie frame structure, a new bogie frame structure namely New CASNUB Bogie Frame is designed to equip with LHB coach. The New CASNUB Bogie Frame design is validated by conducting Stress analysis using ANSYS Mechanical APDL software. The stresses induced in both the frame structures are compared. Stresses induced in the New CASNUB Bogie frame are lesser than in the FIAT Bogie frame and are within the allowable stress limits of material used. New CASNUB Bogie Frame can be used as an alternative for LHB coaches in Indian Railways.

The demand for energy from developed and developing economies of the world is driving the search for energy resources to more challenging environments. The exploration and exploitation of hydrocarbons now requires the drillbit to hit pay zones from drillships or platforms that are located on water surfaces below which is, possibly, in excess of ten thousand feet of water above the sea bed. From Brazil, to the Gulf of Mexico and the Gulf of Guinea on the western coast of Africa, hitherto unfamiliar, but now common, concepts in the drilling parlance such as ultra-deep drilling (UDD), ultraextended- reach drilling (uERD) and slimhole drilling, are employed to reach and produce reservoirs which a few decades ago would seem technologically impossible to produce. This is expected to exert tremendous demands on the physical and mechanical properties of the drillstring components. Limiting factors for reaching and producing oil and gas resources hidden very deep in the subsurface are both the capacity of the drilling rig to support the weight of the drillstring, which in some instances can be several kilometres long, and the bending, tensile and impact stresses the string has to withstand in well trajectories that are getting both longer and more tortuous. Associated with this increased well depths and complex well trajectories is the prohibitive cost penalty of a failed drillstring. The in-service failure of drillstrings has always been an issue in the industry long before the wells become this deep and complex. The global oil and gas industry estimates the cost of string failure to be in excess of quarter of a billion dollars annually. Researchers are continuously looking for ways to design against string failure and improve the level of confidence in drillstrings. Defect-tolerant design, tooljoint geometry modification and surface coldworking are just a few of the ideas that have gained mileage in this effort. Others that are now in consideration are the use of nonconventional materials such as aluminium and titanium alloys for drillstring components. More novel, still, is the use of a combination of two materials - one ‘softer’ than the other to form a hybrid string of two materials of unequal moduli of elasticity. This is done to make the string lighter, reduce stress concentration factor at the connections and place fatigue resistant materials in areas of high well bore curvature.In this work a computational technique in the form of two-dimensional finite element analysis is used to develop a robust model of a drillstring connection and to analyse the stresses on the model of a threaded connection of standard drillstring tooljoint made from alloy steel. Further comparative analyses were undertaken on models of drillstrings made from a newly developed drillstring material for ultra-deep drilling, the UD-165, aluminium and titanium alloys and, finally, on hybrid drillstrings made from two different materials of unequal moduli of elasticity. The aim is not only to develop and validate a better method of computational drillstring analysis but also to use the model to investigate and suggest areas of optimisation that will benefit industry especially in the areas hybrid strings.

The supervising institutions do not give to commercial banks indications what models have to be used for stress testing. This research was done in order to find out which mathematical/statistical models are and can be used in credit risk stress testing. Credit risk is one of the biggest financial risks that every bank faces. Stress testing is a tool of credit risk assessment that helps to estimate the consequences of the events that have really small probability to happen but if they occur, banks can have significant losses. This study determined that the most plausible event is adverse macroeconomic conditions. For this reason, models that include macroeconomic impact were presented. Vector autoregression and vector error correction model were tested using the empirical data received from Swedish central bank, Swedish statistics and Eurostat. For financial stability it is worth using vector autoregression or vector error correction model as they describe the macroeconomic environment in the most suitable way and they are appropriate for shock analysis by showing how the impact of any factor can change the whole system. Structure: introduction, main part (credit risk, methods and empirical analysis), publication, conclusions, references. Thesis consists of: 50 p. text without appendices, 13 pictures, 11 tables, 26 bibliographical entries. Appendices included.
Kredito įstaigų priežiūros institucijos nepateikia komerciniams bankams kokius metodus jie turėtų naudoti testavime nepalankiomis sąlygomis. Tiriamasis darbas buvo atliktas tuo tikslu, kad būtų išsiaiškinta kokie matematiniai ir statistiniai metodai yra ir gali būti naudojami kredito rizikos vertinime testuojant nepalankiomis sąlygomis. Kredito rizika yra viena iš didžiausių finansinių rizikų su kuria bankai susiduria. Testavimas nepalankiomis sąlygomis yra kredito rizikos vertinimo įrankis, padedantis nustatyti įvykių, kurių realizavimosi tikimybės yra mažos, tačiau jiems įvykus, bankai patirtų reikšmingus nuostolius, pasekmes. Šis tyrimas nustatė, jog labiausiai tikėtinas įvykis gali būti ypatingai nepalankios ekonominės sąlygos. Dėl šios priežasties darbe yra pristatyti metodai, kurie įvertina makroekonominių veiksnių įtaką. Vektorinė autoregresija ir vektorinis paklaidų korekcijos modelis buvo patikrinti naudojant Švedijos centrinio banko, Švedijos statistikos departamento ir Eurostat empirinius duomenis. Finansinio stabilumo įvertinimui vertėtų naudoti vektorinį autoregresijos ar vektorinį paklaidų korekcijos modelius, nes šie modeliai geriausiai aprašo ekonominę aplinką bei yra labai tinkami šokų analizei, kadangi įvertina bet kurio veiksnio įtaką visai sistemai. Struktūra: įvadas, pagrindinė dalis (kredito rizika, metodai ir empirinė analizė), publikacija, išvados, literatūros sąrašas. Tiriamasis darbas sudarytas iš: 50 psl. teksto be priedų, 13 paveikslų, 11... [toliau žr. visą tekstą]

This work covers an investigation of stresses produced in dynamically loaded journal bearings of two different test rigs. The results of a detailed study of all the stresses at different depths produced in a circular geometry representing the bearing shell are discussed. A finite difference program developed by Lloyd and McCallion was modified and used to generate the centreline oil pressure distributions. Finite element stress analysis codes from the work of Hinton [21] were chosen and modified to enable the program to work in both polar and cartesian form (i.e. for computing the stresses in the radial and tangential directions due to centreline pressure distributions or the stresses in axial direction due to parabolic variation of pressure). Sensitivity of journal bearing performance to some input load parameters) which changes the oil pressure distribution and affects the stresses induced in the bearing shell, are investigated. Numerical simulations of experimental work of other researchers are performed. Different types of stresses induced in the white metal layer were investigated and the one responsible for the failure was determined. Mean and amplitude values of stresses are used in plotting the Modified Goodman Diagram. The stress versus number of cycles to failure (S-N diagram) are plotted. The difference between the time variation of stresses at the point of failure for cases in which the direction of the input load locus is the same as or opposite to the shaft rotation are studied in detail. A crack closure model capable of estimating the stresses at the tip of a surface crack filled with oil is developed and used to relate the fatigue stresses on the bearing shell to the stresses at the tip of a surface crack during its closure. The effects which this model has on the S-N diagram, for a parallel and V-shaped crack assumptions, are studied. Chapter Two presents the hydrodynamic theory of lubrication and attempts to solve the Reynolds' equation including the finite difference method of Lloyd and McCallion which is the basis of all the calculation in this work. Chapter Three explains the modification made to the Lloyd and McCallion program, and the finite element program including how it works in both Cartesian and polar forms. Extrapolation, Interpolation, Automatic mesh generating, and some plotting routines are also discussed. Chapter Four shows how the variation of parameters such as temperature, diametral clearance, bearing land length, and the direction of rotation of inputload affects the pressure distribution and eccentricity locus. It also covers the sensitivity of results to slight variation in input load and discusses the type of stress responsible for the failure of a bearing. In Chapter Five, the results of the numerical simulations of the experimental tests of other workers, performed with the help of the bearing performance program and the finite element program (Chapter Three), are explained. Some stress distributions and scattering of the results on the S-N diagram which persuaded us to study crack closure are discussed. Chapter Six explains the finite element stress analysis of a crack filled with oil under the action of surface stresses (crack closure model). The effects which this model has in increasing the stresses at the tip of a crack, by applying it to the results obtained from numerical simulation of Blundell's and Cyde's work and observing the changes which it brings to the S-N diagram and the sensitivity of the final results to small variation of input load data are discussed. Finally, a brief summary and the conclusions are discussed in Chapter Seven.

This thesis is concerned with the physical principles, methodology and applications of neutron diffraction in the measurement of residual stress. Work on three main areas is presented. 1) Carbon steels 2) Data and Peak Broadening analysis and 3) Single lap glue shear joints. The Carbon steels section shows the drastic effect of the content of carbon on the measured stress. This is an aspect which has been somewhat neglected in the past. The carbon is in the form of cementite, which is a hard compound and causes the carbon steel to act like a composite material, the ferrite acting as a soft matrix and the cementite as a reinforcement. The consequence of this is that the two components develop high microstresses with plastic deformation. This is clearly illustrated in the work of [Bon 97] where values of approx. 460 MPa in the residual stress in the ferrite are balanced by negative residual stresses of 2300 MPa in cementite yielding an overall macro residual stress of zero. In this work it has been shown that even knowledge of the cementite and ferrite residual stresses and fractions may not be sufficient to accurately calculate the macro stress since the ferrite unloading curve is non linear. The use of a single valued constant modulus to convert from strain to stress is hence not valid. Peak shape analysis enables dislocation density and cell size estimates to be made. The thesis examines several methods of data weighting and deconvolution in order to asses the best means of extracting this information from standard residual stress data. Care should be taken for the peaks with very low backgrounds when finding the Gaussian and Lorentzian components. A weighting that avoids the strong bias of zero and I counts in the detector channels should be used e.g. W = I / ( 10 + Y). Lorentzian and Gaussian components can be successfully extracted from asymmetrical peaks (of peaks that broaden symmetrically), using deconvolution method 1, although the data should be of good quality. Reproducibility has been shown in the Gaussian, Lorentzian and FWHM for different instruments at different institutes. This is extremely important for the use of these values for peak broadening analysis and for estimation of the plastic deformation within a sample. The neutron diffraction technique has been used to investigate the longitudinal stresses in the adherend produced as a result of cure and due to the application of a tensile load in a single lap shear joint. The results throw doubt on widely used finite element predictions.

Tato práce se zabývá problematikou aneurysmat břišní aorty a možností využít konečnoprvkovou deformačně-napěťovou analýzu těchto aneurysmat ke stanovení rizika ruptury. První část práce je věnována úvodu do problematiky, popisu kardiovaskulární soustavy člověka s důrazem na abdominální aortu, anatomii, fyziologii a patologii stěny tepny s důrazem na procesy vedoucí ke vzniku aneurysmatu. Dále se práce věnuje rizikovým faktorům přispívajících ke vzniku aneurysmat spolu s analýzou současných klinických postupů ke stanovení rizika ruptury spolu se srovnáním navrhovaného kritéria maximálního napětí. Dominantní část této disertace je věnována identifikaci faktorů ovlivňujících napjatost a deformaci stěny aneurysmatu spolu s návrhem nových postupů, prezentací vlastních poznatků vedoucích ke zpřesnění určení rizika ruptury pomocí deformačně- napěťové analýzy a metody konečných prvků. Nejprve je analyzován vliv geometrie, vedoucí k závěru, že je nezbytné používání individuálních geometrií pacienta. Dále je pozornost zaměřena na odbočující tepny, které ve stěně působí jako koncentrátor napětí a mohou tedy ovlivňovat napjatost v ní. Jako další podstatný faktor byl identifikován vliv nezatížené geometrie a bylo napsáno makro pro její nalezení, které bylo opět zahrnuto jako standardní součást do výpočtového modelu. Mechanické vlastnosti jak stěny aneurysmatu, tak intraluminálního trombu jsou experimentálně testovány pomocí dvouosých zkoušek. Také je zde analyzován vliv modelu materiálu, kde je ukázáno, že srovnávání maximálních napětí u jednotlivých modelů materiálu není vhodné díky zcela rozdílným gradientům napětí ve stěně aneurysmatu. Dále je zdůrazněna potřeba znalosti distribuce kolagenních vláken ve stěně a navržen program k jejímu získání. Intraluminální trombus je analyzován ve dvou souvislostech. Jednak je ukázán vliv jeho ruptury na napětí ve stěně a jednak je analyzován vliv jeho poroelastické struktury na totéž. Posledním identifikovaným podstatným faktorem je zbytková napjatost ve stěně. Její významnost je demonstrována na několika aneurysmatech a i tato je zahrnuta jako integrální součást do našeho výpočtového modelu.Na závěr jsou pak navrženy další možné směry výzkumu.

Conventional displacement-based finite element programs do not yield unique values of stress components which ought to be continuous at element interfaces. The errors, being the differences from the correct unique values, become unacceptably large at a bimaterial interface when the moduli of the two materials are significantly different.
This thesis formulates and implements new finite elements for obtaining the correct values of the stress components, both continuous and discontinuous ones, at bimaterial interface points under general dynamic loading, assuming linear, isotropic, elastic material behaviour.
The constructed finite elements programs, suitable for analyzing two-dimensional and axisymmetric three-dimensional problems, have been validated by comparing the predicted responses with the exact analytical solutions of some non-trivial impact loading (wave-propagation) problems.
The work provides a necessary tool for analyzing and designing composite structures, for example prosthetic knee and hip joints in the biomechanics field.

Le but de notre étude était de valider un indicateur de la qualité de l’environnement, parmi trois approches : des mesures morphologiques de juvéniles de poissons ; la quantification de l’asymétrie fluctuante de leurs otolithes ; l’analyse de la forme de leurs otolithes. Les résultats in aquaria sur Dicentrarchus labrax ont montré une absence d’effet de mono contaminations par des polluants classiques comme le phosphore ou le zinc, à des concentrations correspondant à celles in situ en zones fortement anthropisées. Des concentrations plus élevées de zinc ont toutefois induit une modification de la forme des otolithes en plus d’un effet négatif sur la taille et le poids. Par nos prélèvement in situ sur trois ans d’Oblada melanura, nous avons mis en évidence de manière reproductible que, comparativement à des sites préservés et des arrivées de petits cours d’eau, des ports de plaisance de taille moyenne ont un effet négatif sur la longueur standard des juvéniles et induisent une modification de la forme de leurs otolithes. De l’ensemble de nos résultats nous pouvons déduire que tailles et poids sont facilement mesurables mais présentent des variabilités dans leurs réponses. La mesure de l’asymétrie des otolithes de juvéniles ne semble pas adaptée à une utilisation en bioindication. Au contraire, l’analyse de formes des sagittae de juvéniles paraît adaptée pour suivre des modifications de l’environnement pour des poissons de deux familles différentes, Moronidés et Sparidés. Cette analyse semble un outil prometteur en bioindication, applicable pour les gestionnaires de l’environnement
The aim of our study was to validate the most suitable environmental indicator among three approaches: morphological measurements of fish juveniles; quantification of the fluctuating asymmetry of their otoliths; analysis of their otolith shape. In aquaria, results for Dicentrarchus labrax have shown that mono-contamination by classical pollutants, such as phosphorus or zinc, has no effect for concentrations corresponding to those measured in highly anthropized environments. Nevertheless, higher zinc concentrations induce otolith shape alterations in addition to their negative impact on fish size and weight. On the basis of our three-year in situ Oblada melanura samplings, we have demonstrated that, in a replicable manner, compared to preserved areas and small waterway mouths, mid-size recreational harbours negatively impact juvenile standard length and also alter otolith shape. By comparison with in aquaria results, these alterations are consistent with a synergy of disturbance sources which taken independently do not have any impact. Taking into account all our results, we deduce that size and weight are easy to measure but show response variability. Measurement of fish juvenile otoliths' fluctuating asymmetry does not seem to be suitable for use in bioindication. Conversely, fish juvenile sagittae shape analysis is well-suited to surveys of environmental modifications, for fishes from two different families, Moronidae and Sparidae. This analysis seems to be a promising tool for bioindication, with a practical application for environmental managers

This meta analysis looks at the results of performance anxiety related interventions with musicians. This meta analysis results from all found studies on computerized databases including National Library of Medicine's PubMed, dissertations and Theses (ProQuest), PsycINFO, and Oxford Journals Database. They range from cognitive interventions, behavioral interventions, mediation, and biofeedback. The results are primarily drawn from participant<'>s self report before and after the intervention. They were coded for length of intervention, number of participants, level of participant (students or professionals), type of intervention, self report measures used, and the effect size of the intervention. The overall effect of all 17 studies involved in the meta analysis was (Hedge<'>s g -0.627, 95% CI [-0.926, -0.384], p<.000). The interventions were significantly different, with largest effect sizes in combination interventions (Hedges g = -0.813, 95% CI [-1.171, -.456], p>.000), followed by physiological interventions with an effect of (Hedges g = -0.638, [-1.111, -.164], p=.008), and purely cognitive interventions having the smallest effect size (Hedges g = -0.455, 95% CI [-0.757, -.153], p=.003).

Dans un contexte de changement climatique, la caractérisation des variétés de blé tendre en réponse à des évènements de sécheresse et de stress thermique est un des défis de l’agriculture. Cette thèse, issue d’un partenariat -public entre Arvalis-Institut du Végétal, Biogemma et l’INRA (Institut National de la Recherche Agronomique), avait pour but de développer des connaissances et des outils nécessaires à l’identification de variétés tolérantes à la sécheresse et au stress thermique et à la création de variétés répondant à cette exigence. Pour ce faire, nous avons analysé un panel de 220 variétés commerciales, génotypées avec 280K SNP et testées dans 35 environnements variés (combinaison d’année, lieu et régime hydrique), plus une expérimentation en conditions contrôlées où un stress thermique a été appliqué pendant le remplissage du grain. La complexité de l’étude de la tolérance à la sécheresse nous a conduit à présenter cette thèse en séparant, dans un premier temps, l’étude des stress hydriques et thermiques, puis de prospecter une méthode d’analyse multi-stress. Nous avons montré que même si la sélection a amélioré la performance des variétés en condition hydrique optimale, le progrès génétique doit être accéléré et mieux réparti en fonction des différents types de stress. Nous proposons pour cela plusieurs déterminants génétiques qui pourraient permettre un gain dans des environnements stressants. Nos résultats et méthodes sont discutés au regard des besoins en préconisation et amélioration variétale. Des pistes de recherche complémentaires et des améliorations ont aussi été suggérées
In a context of climate change, the characterization of wheat varieties in response to drought and heat stress events is one of the major challenges of agriculture. This PhD thesis, resulting from a private-public partnership between Arvalis ‘Institut du Végétal’, Biogemma and INRA (“Institut National de la Recherche Agronomique”), aimed at providing necessary knowledge and tools to identify drought or heat-tolerant varieties and breed for varieties that meet these requirements. Analyses were conducted using a panel of 220 commercial varieties, genotyped with 280K SNP and tested in 35 environments (combination of year, location and water regime) and an experiment under controlled conditions where heat stress was applied during grain filling. The complexity of the study of drought and heat tolerance led us to present this thesis by first separating hydric and thermal stresses, and then to explore a multi-stress analysis method. Even if breeding has improved the performance of varieties under optimal water conditions, we showed that genetic progress must be accelerated and better distributed according to different stress scenarios. We propose several genetic determinants that could allow genetic gain in stressful environments. Our results and methods are discussed in view of the needs for varietal recommendation and improvement. Additional research strategies and methods improvements were also suggested

The process of choosing a site for a nuclear waste repository means that many aspects have to be taken into consideration. One of these is that the repository has to be mechanically stable for a long time. The mechanical stability of the rock is very difficult to determine. One of several factors, which determine the mechanical stability, is the virgin state of stress. The thesis project consists of two parts. In the first part the state of stress at Äspö Hard Rock Laboratory had to be defined. This was done based on earlier rock stress measurements conducted during the years 1988 to 1997. Two different measurement techniques have been used, hydraulic fracturing and overcoring. During the overcoring two types of cells have been used, CSIRO HI-cell and a cell developed by the Swedish State Power Board (SSPB). In the second part of the project, investigation of the correlation between the stress and geological structures are made using numerical modelling tools such as FLAC, UDEC and 3DEC. The rock stress measurements using the hydraulic fracturing gave orientations of the horizontal stress that coincide with earlier hydraulic fracturing measurements conducted in Scandinavia. The magnitudes of rock stresses are slightly lower than the earlier reported stress magnitudes for the Scandinavian part of the earth crust. The rock stresses obtained from the overcoring resulted in higher stresses than what was predicted by the hydraulic fracturing measurements. However, the orientation of the maximum horizontal stresses coincides well between the two techniques. The orientation is also more or less constant with respect to increasing depth. The state of stress at Äspö is defined by using the results from the hydraulic fracturing and the measurements conducted by SSPB-cell. The measurements from the SSPB-cell are used since these have a Poisson's ratio that corresponds well with the uniaxial tests of rock samples and since the measurements have been done at a distance from the opening where no influence from the openings can be expected. Since the magnitudes of the rock stresses differ between overcoring and hydraulic fracturing, some efforts have been made to find possible causes for this. The rock stresses when conducting overcoring gave higher values overall, which could be explained by high Poisson's ratios and a minor influence from the opening as the stress measurements might have been done in the disturbed zone. The high Poisson's ratio may depend on the stress-induced microcracks, which might be initiated during the overcoring of the cell, during the drilling of the pilot borehole, in which the cell is installed, and during biaxial testing. Statistical analysis showed that there is significant differences between the mean values of Poisson's ratio obtained from biaxial tests of cores containing the CSIRO HI-cell and the SSPB-cell. Poisson's ratio is about 0.34 for CSIRO HI-cell while the SSPB-cell gave a Poisson's ratio of 0.23. The analysis also showed that Young's modulus does not differ between the techniques. The modelling in FLAC was made to simulate the overcoring and biaxial testing. The result show that it is possible to obtained extensional strain in the core during overcoring if the major principal stress is perpendicular to the borehole axis. This may lead to microcracking occurring in the core causing high Poisson's ratio, which results in higher stresses. It can also be seen from the simulation of the biaxial testing that extensional strain is achieved even if the hollow core is not damaged during overcoring. The analyses using UDEC was made to study the effect of different properties of a discontinuity, such as the dip angle, Young's modulus, Poisson's ratio, density and the normal and shear stiffness. The analyses showed that an inclined discontinuity affects the stresses especially if sliding occurs. So, the dip angle does not solely, determine the amount of disturbance of the state of stress around a discontinuity. If slip will occur or not depends, thus, on a combination of dip angle, friction angle and the far field state of stress. A dip angle of 30 degrees affected the major principal stress most, while the minor principal stress is most affected by a dip angle of 45 degrees, for a friction angle of 10 degrees. The results from the simulation of a thick zone showed that the elastic properties of the zone material mainly affect the stresses within the zone. However, higher values of Young's modulus and Poisson's ratio in the zone than in the side rock resulted in higher stresses within the zone than outside. The orientation of the major principal stress becomes more perpendicular to the zone. The 3-dimensional analyses using 3DEC was made in order to investigate if the stresses at Äspö could be correlated with the major geological structures. The results show that the increase in the horizontal stress seen both in KAS02 and KAS03 is obtained in the model when using a bilinear stress state that is based on the measurements performed at Äspö. However, a satisfying coincidence is not obtained with the measured stresses in KAS02, KAS03, KAS05 and KZXSD8HL, which were the boreholes used as reference boreholes. One of the reasons for the disagreement may mainly be that the discontinuities used in the 3DEC model are more or less vertical. The least dip angle used is 60 degrees. Another reason may be that the measured stresses are influenced by far more parameters than are used in the 3DEC- model, such as different rock types, smaller discontinuities and mineral grains.

Godkänd; 2000; 20070316 (ysko)

In the animal laboratory, stressors can produce the relapse of drug-seeking behaviors after the behavior has been inhibited by extinction. This type of relapse has been called stress-induced reinstatement, and it models the relapse that is commonly reported in human populations. Interestingly, in the laboratory, stress does not typically reinstate extinguished behaviors that have been reinforced by food. One account of the discrepancy is that drugs of abuse may induce stress; therefore, when organisms learn to respond for drugs, they might learn to make the response in the “context” of stress. If so, then stress-induced reinstatement may be better described as renewal in a stress context. Renewal is the type of relapse that occurs when a behavior is returned to the original training context (or is shifted to a new context) after it has been inhibited or suppressed by extinction. Although renewal has usually been studied with contexts that differ in their exteroceptive cues, interoceptive cues (e.g., mood, food deprivation, and drug states) may also provide contexts. Accordingly, if an interoceptive stress state is present when food-seeking behavior is learned, then extinguished food seeking, like drug seeking, should also renew when the organism is stressed after extinction. In this dissertation, I discuss six experiments that investigated this hypothesis. Experiment 1 found that stressors renew extinguished food-seeking if they are also present during instrumental training. Experiments 2 and 3 then provided preliminary evidence that this effect is not exclusively due to incentive learning. Experiment 4 then suggested that interoceptive stress, and not the particular stressor that produces it, may indeed serve as a general interoceptive context that controls the effect. Experiment 5 found that stressors present for acquisition but not extinction training render behavior susceptible to stress induced relapse. The final experiment found that food-reinforced behavior learned in a context created by a cocaine injection renews after cocaine administration but not after footshock stress. Overall, the results indicate that the presence of interoceptive stress stimuli may play the role of context in a renewal paradigm and promote behavioral relapse when re-encountered after extinction. The implications for relapse that often occur following successful suppression of drug use and overeating behaviors are both discussed.

Capitolo 1: Identificazione di elementi regolatori responsabili per l’iperaccumulo di metalli nella famiglia delle Brassicaceae. Il ruolo del trasportatore MTP1 nella tolleranza ai metalli pesanti è stato studiato approfonditamente, in quanto esso ha un ruolo molto importante nell’iperaccumulo. MTP1 è presente in più copie nella specie iperaccumulatrice Arabidopsis halleri; inoltre sono state osservate possibili differenze nella regolazione della trascrizione tra iperaccumulatori e non accumulatori. Questo lavoro è incentrato sull’analisi del promotore di MTP1. Il pattern e il livello di espressione indotti dai promotori di Arabidopsis thaliana e A. halleri sono molto diversi, in accordo con la differente capacità di accumulo dimostrata dalle due specie. Entrambe le specie esprimono MTP1 nelle radici: questo è associato alla presenza in entrambi i promotori di elementi regolatori per l’espressione specifica nelle radici. Inoltre, i promotori di A. thaliana e A. halleri inducono entrambi espressione a livello delle cellule di guardia, dovuta alla presenza di motivi di legame a fattori di trascrizione di tipo Dof. Il promotore di MTP1 di A. halleri è responsabile invece dell’espressione specifica nei ticomi. Questa localizzazione è probabilmente associata alla presenza di una coppia di siti di legame di MYB nella 5’UTR del gene. L’accumulo di metalli nei tricomi è una caratteristica interessante di A. halleri ed è probabilmente coinvolta nella tolleranza a breve termine. Capitolo 2: Analisi di funzione dei fattori di trascrizione MYB48 e MYB59 di Arabidopsis thaliana. I fattori di trascrizione di tipo MYB sono coinvolti in molti eventi della vita delle piante, come la differenziazione e il metabolismo cellulare, lo sviluppo della pianta, la risposta agli ormoni e agli stimoli ambientali. Si è ipotizzato che MYB48 e MYB59 di Arabidopsis thaliana partecipino allo sviluppo della struttura secondaria, al controllo del ciclo cellulare e alla risposta agli stress abiotici. In questo lavoro si è scelto di usare un doppio mutante myb48myb59, poiché i due fattori di trascrizione sono probabilmente ridondanti. Le piante myb48myb59 hanno foglie più piccole, forse a causa della ridotta distensione cellulare, e radici più lunghe; mostrano inoltre un ritardo nella fioritura e senescenza anticipata, come confermato dall’espressione del marcatore di senescenza SAG12. Il fenotipo può essere attribuito ad un ridotto contenuto di citochinine; quest’ipotesi è confermata dalla maggiore sensibilità dei doppi mutanti alla somministrazione esogena di citochinine e dai geni modulati identificati tramite analisi trascrittomica.
Chapter 1: Identification of regulatory elements responsible for metal hyperaccumulation in the Brassicaceae family. The role of the metal transporter MTP1 in metal tolerance and accumulation has been extensively studied, due also to its great importance in the hypertolerance trait. MTP1 is known to have undergone copy number expansion in hyperaccumulator Arabidopsis halleri; moreover, possible differences in cis-regulation between hyperaccumulators and non-accumulators have been proposed. This work focuses on the analysis of the MTP1 promoter. The expression pattern and levels driven by the Arabidopsis thaliana and A. halleri promoter sequences are markedly different, coherently with the different accumulation ability and metal storage tissues displayed by the two species. MTP1 expression in roots was found in both species and is associated with the presence of root-specific cis elements in both promoters. Similarly, guard cell-specific expression was observed for both A. thaliana and A. halleri sequences and is associated with the presence of Dof-binding sites. In addition, the MTP1 promoter of A. halleri drives expression in trichomes. This interesting localization is likely associated to a couple of MYB-binding sites in the 5’UTR of the gene. Metal accumulation in trichomes is an intriguing feature in A. halleri and is possibly involved in short-term tolerance to metals. Chapter 2: Functional analysis of the Arabidopsis thaliana MYB48 and MYB59 transcription factors. MYB transcription factors are involved in many events of plant life, as cell differentiation and metabolism, plant development, response to hormones and to environmental stimuli. Among the others, MYB48 and MYB59 have been proposed to participate in secondary development, cell cycle regulation and response to abiotic stress in Arabidopsis thaliana. In this work, a myb48myb59 double mutant was used due to probable functional redundancy of the two transcription factors. myb48myb59 plants show smaller rosette leaves, likely due to reduced cell distension, delayed flowering and longer roots in comparison to wt; early senescence was also considered and confirmed by the higher SAG12 expression levels. The phenotype is consistent with a reduced cytokinin content: this observation was confirmed by the increased sensitivity to exogenous cytokinins and by the modulated genes resulting from the microarray experiment.

碩士
國立高雄應用科技大學
模具工程系
104
Thermoelastic stress analysis (TSA) employs infrared to record the thermoelastic response of the stressed materials and provides full-field stress information over a surface. Theoretically, the thermorelastic response of a loaded member is resulting from the thermoelastic effect and that is as a material experiences mechanical excitation, the material will get cooler in tension or warmer in compression. The temperature variation due to the thermoelastic behavior is very small and it even approximately attains the order of 10-3. Contemporarily, the TSA equipment is able to rapidly capture the tiny temperature change over the stressed surface and correlate it to the change in the sum of principal stresses or isopachic stress due to arrayed infrared detectors applied. The traditional TSA theory indicated that for a plane-stressed elastic body under adiabatic and reversible conditions, the rate of temperature disturbance of a dynamically loaded member is linearly proportional to the stress amplitude and this proportionality is defined to be thermoelastic constant. However, recent studies discovered that the thermal response given by a loaded member is not only a function of stress amplitude, but also the mean stress. Therefore, the thermoelastic coefficient is then revised and expressed as stress dependence but not a constant. Moreover, according to the mechanics aspect, the mean stress represents a static component of stress. Residual stress can be essentially regarded to as the mean stress. Hence, one is able to detect the residual stress by using TSA technique. This work attempts utilizing TSA technique to investigate the residual stress for the 2024 aluminum alloy plate.

La presenza in Puglia (Italia) del Complesso del Disseccamento Rapido dell’Olivo (CoDiRO) causato da Xylella fastidiosa (Xf), il cui ceppo Co.Di.RO colpisce prevalentemente gli alberi di olivo, rappresenta una seria minaccia per la produzione olivicola in tutti i Paesi mediterranei. Xf è un patogeno regolamentato in Europa come organismo di quarantena (lista EPPO A1) perché colpisce più di 350 specie vegetali in tutto il mondo. La maggior parte degli olivi infetti muore a seguito della moltiplicazione del batterio all’interno del sistema vascolare che limita il flusso dell’acqua dalle radici alla chioma dell’albero. Circa il 95% della coltivazione olivicola è concentrata nella regione mediterranea e l’Italia è il secondo Paese produttore a livello mondiale. Quindi, Xf rappresenta una seria minaccia per l’olivo nel mondo a causa della gravità dei sintomi indotti (soprattutto bruscatura delle foglie, disseccamento dei rami e deperimento rapido dell’albero), della lunga lista di vettori che possono diffondere efficientemente il patogeno, come il Philaenous spumarius in Puglia, e l’elevato numero di ospiti secondari del patogeno. Xf rappresenta un limite per la coltivazione dell’olivo e per la tutela del patrimonio storico olivicolo nella regione mediterranea. Ad oggi, non esistono misure efficaci di controllo e di lotta diretta al batterio e al CoDiRO; quindi, l’identificazione precoce degli alberi infetti, la loro immediata eradicazione e le strategie di controllo dei vettori sono gli unici mezzi per impedire o limitare il rischio di contaminazione. Tali misure potrebbero essere più efficaci se l’identificazione dell’infezione avvenisse nei primi stadi di sviluppo della malattia, in modo da poter contenere la diffusione del patogeno e la sua trasmissione agli alberi circostanti. Comunque, i rilievi visivi in campo richiedono tempo e sono costosi. A questo scopo, il telerilevamento potrebbe essere uno strumento utile all’identificazione di stress idrici causati dai primi stadi dell’infezione di Xf negli alberi di olivo. In tempi recenti si è assistito ad un aumento della ricerca nelle applicazioni delle tecniche Geomatiche, favorito dalla maggiore disponibilità di strumenti di rilevazione da remoto e da vicino, che ha condotto ad un significativo avanzamento della possibilità di monitorare fenomeni biologici complessi e di gestire, in ambiente Geographic Information System (GIS), i relativi dati sia in modalità stand-alone che in rete. In tal modo è possibile integrare, in un unico ambiente operativo, dati spaziali eterogenei derivanti dall'impiego di metodi diretti, come le azioni di monitoraggio, o dall’utilizzo di metodi indiretti, come l'elaborazione dei dati telerilevati. I dati così prodotti possono essere utilizzati per l'implementazione di modelli previsionali nella difesa delle avversità sul territorio e per potere così adattare la strategia di intervento e razionalizzare la difesa delle colture. La prima ricerca in questo lavoro ha come obiettivo la valutazione dell’idoneità delle tecniche di fotointerpretazione per riconoscere e classificare piante colpite dal CoDiRO in ambiente GIS. A tal fine sono state utilizzate immagini da aereo ad alta risoluzione geometrica nel visibile e nell'infrarosso vicino relative ad un’area di studio nel sud della Regione Puglia, che rappresenta la prima area focolaio di Xf. Le misure radiometriche rilevate da remoto sono state orientate all'individuazione di appropriati fototipi, morfologicamente in grado di rilevare l’alterazione associata a diversi livelli di sintomi ascrivibili al CoDiRO. L’uso di immagini spaziali definite, rafforzato dalla presenza della banda nel vicino infrarosso, ha facilitato notevolmente l’identificazione dei segnali di CoDiRO a partire dai fototipi chiave che sono ben correlati all’espressione della malattia. La tecnica ha reso possibile l’identificazione del 20% di alberi fotointerpretati con CoDiRO ed infetti da Xf. Questo risultato rappresenta un buon presupposto per poter esaminare in modo approfondito e migliorare la metodologia attraverso la restituzione stereoscopica in ambiente GIS. La seconda ricerca è stata invece finalizzata all’accertamento del potenziale dei dati di riflettanza iperspettrale (HR) per poter identificare l’infezione di Xf nei primi stadi di sviluppo su olivo. I campionamenti hanno riguardato piante infette delle due principali varietà di olivo (cvs “Cellina di Nardò” e “Leccino”) coltivate in un campo commerciale localizzato nell’area focolaio di Xf nel Sud della Puglia. Ogni campione era composto da foglie raccolte da 10 rametti/albero con diversi livelli di infezione. Lo studio ha avuto come obiettivo la: (i) discriminazione tra foglie infette asintomatiche e foglie non infette; (ii) la selezione delle migliori bande per evidenziare tale discriminazione e il (iii) confrontato tra due metodi di selezione delle variabili a sostegno dell'analisi delle riflettanze iperspettrali. La discriminazione delle foglie infette asintomatiche da quelle non infette, utilizzando dati pre-elaborati acquisiti con uno spettroradiometro da campo, è stata definita nell’intervallo di lunghezze d’onda 400 - 1830 nm dello spettro. Un approccio euristico di selezione delle variabili, utilizzato in letteratura (Lambda-Lambda R2 model - LLR2, Principal Component Analisys model - PCA e Wilks' Lambda) e un combined general purpose detection method, proposto in questa ricerca, denominato interval PCA Internal Clustering Validation (iPCA-ICV) sono stati messi a confronto. Il metodo non supervisionato proposto, divide lo spettro dei dati di riflettanza in un numero determinato di intervalli, calcola la PCA all'interno di essi (iPCA) e convalida la bontà dei raggruppamenti ottenuti (classi) attraverso misure di Cluster Validity index. La capacità discriminante delle lunghezze d'onda selezionate dai due metodi è stata valutata mediante analisi discriminante generalizzata basata sulla correlazione canonica e sulla misura dell'errore di tipo leave-one-out cross-validation, attraverso matrici di confusione. Da entrambi i metodi è stato possibile discriminare foglie infette da Xylella fastidiosa e selezionare bande strette specifiche. Tuttavia, il miglior potere discriminante è stato ottenuto da iPCA-ICV per entrambe le varietà (percentuale di errore del 23.7% e del 22.02% rispettivamente per cv. Cellina di Nardò e cv. Leccino), rispetto al metodo di riferimento (percentuale di errore del 42.47% e del 22.02% rispettivamente per cv. Cellina di Nardò e cv. Leccino). I due metodi hanno evidenziato differenze nel numero e nella posizione delle bande strette selezionate (ciascuna di 10 nm) tra le due varietà. In particolare, entrambi concordano con le regioni del VIS (vicini al blu e al rosso) e dello Short Wave Infrared (SWIR) come porzioni dello spettro a maggior peso sulla discriminazione della Leccino, varietà meno colpita dall'infezione (23.1%), mentre, per la Cellina, varietà più colpita (85.7% di positività riscontrata), i due metodi risultano discordanti. Il iPCA-ICV individua le bande di assorbimento dell'acqua intorno a 1180, 1400 nm e in molte bande dello SWIR, il metodo euristico individua due bande a 705 e 805 nm, come determinanti nell'individuazione di Xylella. L'identificazione di regioni critiche dello spettro, dunque, costituisce il primo passo logico verso lo sviluppo di indicatori di stress robusti basati su immagini iperspettrali. Le tecniche di selezione delle bande, inoltre, risultano estremamente utili non solo per migliorare il potere dei modelli predittivi, ma anche per l'interpretazione dei dati o il design di sensori specifici Pest Desease Detection (PDD).
The occurrence of the Olive Quick Decline Syndrome (OQDS) caused by Xylella fastidiosa (Xf) in Apulia region (Italy), with the strain Co.Di.RO (Complesso del Disseccamento Rapido dell’Olivo) affecting mainly the olive trees, poses a serious threat for olive production in all Mediterranean countries. Xf is a regulated pathogen in Europe (EPPO A1 list) because it affects more than 350 plant species worldwide. Infected olive trees may die as a consequence of the multiplication of the bacterium inside the vascular system which restricts the water flow from the roots to the canopy of the tree. Around 95% of olive cultivation is concentrated in the Mediterranean region and Italy ranks second worldwide. Accordingly, Xf represents the main threat of olive trees worldwide due to the severe symptoms induced (mainly leaf scorch, dieback and quick decline of the tree), the long list of sap-feeding insects which may efficiently spread the pathogen, as the Philaenous spumarius in Apulia, and the large number of secondary hosts. Xf restricts the cultivation of olive trees and the preservation of the historical heritage of olive trees in the Mediterranean region. Currently, no control measures are fully effective in the control of the bacterium and in the management of the olive quick decline; therefore the early detection of infected trees, their immediate eradication and vector control strategies are the only means of avoiding or containing the risk of contamination. These measures could be more effective if the infection is identified at early stages of disease development, in order to mitigate the spread of the pathogen and infections to neighbouring trees. However, visual inspections in the field are time-consuming and expensive. To this aim, remote sensing could be a useful tool to detect water stress induced by Xf infection in olive trees at early stages. Recently, an increase in research occurred in the application of Geomatic techniques, due to a greater availability of Remote and Proximal Sensing (RS, PS) instruments which has led to significant progress in the monitoring of complex biological phenomena and relative data management for running in, stand-alone, or web-based Geographic Information System (GIS) platforms. In this way it is possible to integrate heterogeneous spatial data in a single operative environment. Such data can be obtained by means of direct methods or indirect methods. The resulting data can be used for the implementation of provisional models to identify a plant adversity in order to rationalize the intervention strategy. The first research of this work, the suitability of photointerpretation techniques to recognize and classify the plants damaged by OQDS in GIS environment was evaluated, for this purpose very high geometrical resolution aerial images were used by processing visible (VIS) and near infrared (NIR) data on a study area in South of Apulia region, which represents the first outbreak area of Xf. The remotely acquired radiometric measurements were aimed at identifying appropriate photo-types, morphologically suitable in detecting the alteration of olive trees associated to different levels of OQDS-like symptoms. The use of spatially defined images strengthened by the presence of the near infrared band has greatly facilitated the identification of signs of OQDS starting with key photo types which are well correlated to the expression of the disease. The technique made it possible to identify 20% of the photo interpreted OQDS-trees and infected by Xf. This achievement is the prerequisite to thoroughly examine and improve the methodology through the use of stereoscopic restitution in the GIS environment. However, a second research was aimed at assessing the potential of hyperspectral reflectance data (HR) to identify the infection of Xf in olive at early stages of development. Sampling was carried out on infected plants belonging to the two main olive varieties varieties (cvs. “Cellina di Nardò” and “Leccino”) grown in a commercial grove located in the outbreak area of Xf in south Apulia. Each sample was made of leaves collected from 10 twigs/tree with different levels of infection. The study focused on the: (i) the discrimination between infected asymptomatic and non infected leaves; (ii) the selection of the best wavelengths for highlighting this discrimination and (iii) the identification of bio-physiological indicators (vegetation indices) correlated to the OQDS induced by Xf. The discrimination of infected leaves has been made using pre-elaborated data acquired with a field spectroradiometer, in the spectral wavelengths range between 400 and 1830 nm. A heuristic approach to variable selection, used in literature (Lambda-Lambda R2 model - LLR2, Principal Component Analisys model - PCA and Wilks' Lambda) and a combined general purpose detection method, proposed in this research, named interval PCA Internal Clustering Validation, iPCA-ICV have been compared. The unsupervised method proposed, divides the spectrum of reflectance data into a determined number of intervals, calculates the PCA within them (iPCA) and validates the goodness of the groupings obtained (classes) through Cluster Validity index measurement. The discriminative ability of selected wavelengths by the two methods was assessed by generalized discriminant analysis based on canonical correlation and measurement of error type such as leave-one-out cross-validation, through confusion matrices. From both methods it was possible to discriminate leaves infected by Xf and to select specific narrowbands. However, the best discriminative power was obtained from iPCA-ICV for both varieties (error rates of 23.7% and of 22.02% respectively for cv. Cellina di Nardò and cv. Leccino), compared to the reference method (error rates equivalent to 42.47% and 22.02% respectively for cv. Cellina di Nardò and cv. Leccino). The two methods have shown differences in number and in the position in the narrowbands selected (each of 10 nm) between the two varieties. In particular, both agree with the VIS regions (close to the blue and the red) and that of Short Wave Infrared (SWIR) as portions of the spectrum increase the discrimination of Leccino, the variety less affected by the infection (23.1%), while, for Cellina, the species more affected (85.7% of positive findings). The iPCA-ICV identifies the absorption bands of water around 1180 and 1400 nm (and many bands of SWIR). The heuristic method identifies two bands of 705 and 805 nm, as determinants in the identification of Xylella. The identification of critical regions of the spectrum, therefore, is the first logical step towards the development of indicators of robust stress based on hyperspectral images. The band selection techniques, also, are extremely useful not only to improve the power of predictive models, but also for the interpretation of the data or design of specific sensors for Pest Disease Detection (PDD).

碩士
國立高雄大學
土木與環境工程學系碩士班
102
In the present study, the traditional paving blocks used for pedestrian path as well as the innovated paving blocks specially designed for vehicle roads are evaluated in details. The influence of road roughness on the stress concentration induced by a tire-brick dynamic impact is emphasized. Results are compared with those obtained by field tests and numerical simulations. The embedded water channels are proposed for improvements in drainage performance in the blocks subject to the heavy duty vehicle load. Experiments show that the blocks with the embedded water channels meet the regulatory standards of the permeable ability. The soft sensor sheet is employed in the real paving block traffic lane field tests to measure the contact pressure between tire and blocks, between blocks, and also between blocks and the ground. The relative elevation of the target block is one of the major study parameters. The corresponding influences on the impact pressure are evaluated in field tests and numerical simulations. A finite element tire model consisting of masses, suspension spring, a rigid rim, and half rubber tire skin simulated by three portions of membranes filled with constant inner air pressure is appropriately developed for the numerical simulation. The tire-road contact, the tire inner pressure, and the dynamic forces due to inertia are considered as the major loads. The tire-road contact impact and the stress concentration of the embedded water channels are illustrated in the numerical block models. The results are in good agreement with those obtained from the field test. The present study shows that the magnitude and the distribution pattern are sensitive to the roughness of the road surface. The stress concentrations are found to be along the block edges on the loading face and inside the water channels. There is no significant difference between the peak values of the stresses along the edges and channels if the ground is smooth. The edges contact pressure induced by the dynamic impact due to a bumpy ground could be more than 10 times higher than that induced by a smooth run-over. The stresses in water channels are relatively not so sensitive to the elevation of the target block. This thesis serves as a preliminary study to the new designed paving block. There are still broad researches and applications in the future.

碩士
國立高雄應用科技大學
模具工程系碩士班
102
Thermoelastic stress analysis (TSA) is a nondestructive and non-contacting experimental technique, which exploits thermoelastic response of materials to provide full-field stress information over a surface. Fundamental thermorelastic theory is based on the thermoelastic effect and that is as a material experiences mechanical excitation, the material gets cooler in tension or warmer in compression. Temperature variation due to thermoelastic behavior can be very small and even approximately attain the order of 10-3. TSA technique utilizes infrared detectors to capture the tiny temperature change on the stressed surface and correlate it to the change in the sum of normal stresses or isopachic stress. Traditionally, theoretical thermoelasticity indicated that for an elastic body under adiabatic and reversible conditions, the rate of temperature disturbance of a dynamically loaded member is linearly proportional to the stress amplitude and the proportionality is defined to be thermoelastic constant. However, recent thermoelastic studies discovered that the thermal response is not only a function of stress amplitude, but mean stress which represents a static component of stress. This work will introduce TSA technique and investigate its applicability on measuring residual stress in a metallic material.

碩士
國立雲林科技大學
機械工程系碩士班
94
Due to the CTE (coefficient of thermal expansion) mismatch among different materials of the package , the warpage and thermal stresses of the package are induced by temperature variations . In the present work , the finite element method (FEM) is used to simulate the package warpage and component stresses of TSOP(Thin Small Outline Package) during the manufacturing processes . The accuracy of the package model is verified by comparing the simulated package warpage with the warpage measurement by profilometer .The effect of various through holes in the die pad on the die stresses during the reflow process , the largest temperature variation of all processes , is discussed . The results show that the effect of through holes in the die pad on die stresses is more significant with the smaller die size . Also, the patent information of die stress improvement for leadframe type packages are studied to depict the patent map and summarize the technology development and market trend of die stress improvement. The investigated patent information can provide guidelines to check possible patent right violation of new design and on-line product to avoid useless spending in package research and development. It can be referred by industry to improve die stress , upgrade package technology and enhance package reliability.

In the last few years, various epidemiological studies were conducted to estimate the health effects of particulate matter (PM) on human population, placing at the core the association between exposure to PM and several adverse outcomes, especially on cardiovascular and respiratory systems. PM mass concentration is typically used to estimate population exposure. However, this indicator misestimate the overall impact of PM, since it does not consider the multiple toxicological effects of the different pollutants that constitute and determine the intrinsic properties of PM. In fact, the complexity and variability of PM can lead to different responses in biological systems. The hypothesis of the mechanisms of PM-related diseases include oxidative stress, inflammatory responses, and genotoxicity. All of them can be mediated by PM-related reactive oxygen species (ROS). To assess the particles’ oxidative capacity, several acellular methods, defined as oxidative potential (OP) assays, have been developed and proposed as relevant and valid metric for addressing biological exposure to PM. There is still no agreement regarding the most representative assay to measure the OP of PM, but methods mostly used on the PM filter extracts are the dithiothreitol (OPDTT), the 2′,7′-dichlorofluorescin (OPDCFH), and the ascorbic acid (OPAA) assays. Each assay gives different results and probably simulates just a small part of the many potential mechanisms of oxidative stress induction. Therefore, the synergic application of the three assays on the same PM samples is strongly recommended to have a complete characterization of their redox properties. The study of PM composition and toxicity represents a particularly interesting field of research, aimed to a better understanding of the existing relationships between the chemical composition and sources of PM and its adverse effects on human health and environment, useful to plan the appropriate mitigation measures. It is also worth considering the heterogeneity of emission sources and the role that they play on PM physical and chemical properties. The analysis of PM coming from different sources could allow associating specific chemical composition, which depends on the pollutant origin, with a given biological response. In fact, the role of each chemical component on PM toxicity is still to be fully defined. One of the goals of this PhD thesis is to improve the knowledge about the existing relationships between PM chemical composition and sources and, therefore, to attempt to estimate PM adverse effects on health and environment through the investigation of PM redox properties. To this aim, a multidisciplinary study based on the synergic application of traditional and innovative approaches to PM was carried out in this PhD research. PM field samples were collected at monitoring sites differently impacted by anthropic activities by using different techniques, such as traditional monitoring equipment, cascade impactors, biomonitoring methods and very-low volume samplers allowing spatially-resolved determination of PM chemical components. Furthermore, widespread components of PM produced by specific emission sources and characterized by very different chemical compositions were used to compare different experimental procedures on PM from defined emission sources. Chemical characterization of PM samples was obtained by applying advanced and robust analytical procedures for the determination of inorganic ions, water-soluble and insoluble elements, water-soluble organic carbon (WSOC) and levoglucosan (LVG). PM water-soluble and insoluble fraction were separately analyzed through a well-established fractionation procedure to increase the selectivity of elements as source tracers and to estimate the environmental mobility and bio-accessibility of toxic elements. Much of the PhD experimental research has focused on the investigation of redox properties of PM since in the last few years, the oxidative potential appears to be the central paradigm in the assessment of PM toxicity. However, there are still operative criticisms affecting its relevance as effective realistic metric to quantify the effects of ambient particles on human health, such as the influence of multiple operative conditions on OP obtained results, as well the lack of standardized operative conditions, which make a challenge to representatively compare inter-laboratory data. Therefore, one of the goals of this research was to explore in depth redox equilibria between PM reactive species. During the PhD research various monitoring campaigns aimed to improve knowledge about the existing relationships between sources of PM and its related chemical composition were conducted under different conditions and in different geographical areas (i.e. during the national lockdown imposed by Italian government to counter the Covid-19 pandemic). Valuable information for PM source apportionment through a chemical/size fractionation procedure and OP measurements were obtained. Potential effects of PM composition on biological systems were studied by using an in vitro approach based on the cytotoxic, genotoxic, oxidative, and inflammatory response of bronchial epithelial cell line BEAS-2B after the exposure to PM coming from different sources. In parallel with the described activity, the reliability of PM biomonitoring techniques for the assessment of atmospheric element concentrations was estimated. To this aim, leaf deposition on riparian species (Arundo donax (L.)) and lichen transplants (Evernia prunastri (L.) Ach.) were used. Furthermore, an integrated approach to assess the effects of PM on functional traits of Quercus ilex (L.) in an urban area was carried out comparing results from OP assays when applied on PM deposited on Q. ilex leaves, and on filters (traditional monitoring system). Another line of research was the analysis of PM samples in indoor environments of private dwellings and University classrooms, to study the concentration, the chemical composition, and the OP of indoor and outdoor PM to obtain information about the main indoor and outdoor PM emission sources and exposure of occupants. Lastly, another important study included in the PhD research was related to the project Redox-activity and Health-effects of Atmospheric Primary and Secondary aerosol (PRIN 2017-RHAPS project) in which our groups participated with OP measurements and elemental analysis of PM samples. RHAPS aims to identify specific properties of PM from anthropogenic sources that are responsible for toxicological effects and can be used as new metrics for health-related outdoor pollution studies. The main goal of RHAPS project was to provide a new assessment of the sources and nature of PM components responsible for adverse health effects in real-world conditions. The experimental field monitoring campaigns have been recently completed and data elaboration is still ongoing. Supplementary research activities were focused on the evaluation of the capability of food waste materials as low-cost adsorbents for the removal of Volatile Organic Compounds (VOC) from wastewater, and on the analytical characterization of biological matrices (i.e. bees and beehive products, olive oil) to evaluate their potential of accumulating toxic elements, allowing the monitoring of this kind of pollutants concentrations in the environment for integrated measurements. Rapid analytical methods for routinely analyzing a significant number of biological samples were developed and validated.

碩士
國立臺灣科技大學
機械工程系
95
In order to increase the probability of successful oral implantation computer simulation can be employed to analyze the loading situation of the alveolus bone after implantation. Finite Element Method is the most important computer software used to analyze the stress distribution over the alveolus under occlusion. However, during the FEM analysis, many conditions are simplified, the outcome of the analysis is needed to be verified by some experimental works. In this thesis, the alveolus bone was approached as a two-material model. The simulation model was fabricated by using various compositions of quartz powder and resin. The material constants (Modulus of Elasticity and Poisson’s Ration) of the model were determined experimentally. An implant was put in the model as well as an abutment and a crown to simulate a real oral implantation. The complete model under occlusion was simulated by FEM. At the surface of the real model which had maximum stress was bonded a bi-axes strain gage. After the experiment, the measured strains were found agree well with those results from FEM.

碩士
中華大學
機械與航太工程研究所
94
Nonlinear finite element method was employed in the study to analyze the deformation and stress distribution of a new type of flexible flip chip packages under service conditions. Four procedures were simulated in the finite element analysis. Firstly, the package was attached on a surface by a rigid concave mask with a curvature radius of 30 mm. Secondly, the contact condition of the upper surface was relieved to simulate the removing of the compressive force. Thirdly, the temperature of environment was cooled down to -55℃. Finally, the temperature of environment was raised to 125℃. Three different materials of the bump core were considered in the numerical analysis to study the material effect on the stress behavior. Furthermore, the D. O. E. method were used to study the influence of the bump polymer core width, the bump sidewall thickness and the bump core material on the stress distribution. The analysis results show that higher Young’s modulus will induce the lower stress during the step 1 and 2, but higher Young’s modulus and lower CTE will induce higher stress level during TCT (Thermal cycle test) process.