Dissertations / Theses on the topic 'Cavity wall'

Genom historien har flera olika tegelkonstruktioner använts. På 50-talet utvecklades skalmuren som idag dominerar tegelmarknaden. En studie har utförts i ett försök att förbättra hur skalmurar ska dimensioneras. Kommersiella beräkningsmodeller som används i dagsläget resulterar i överdimensionerade skalmurar där dyra konsoler möjligtvis används i onödan. Skalmurar utsätts i princip endast för sin egentyngd och är därför huvudlasten vid dimensionering. Syftet med rapporten är att utveckla en mer korrekt metod för uträkning av egenviktens fördelning i skalmurar för att minska belastningen i murverkets svaga områden. Detta kan i sin tur göra det möjligt att konsoler inte behöver användas för att förstärka de svaga delarna. Arbetet utforskar möjligheten att använda finita elementmetoden för att beräkna egentyngdens fördelning och utförs med programmet FEM-design. De nuvarande kommersiella beräkningsmodellerna använder sig inte av finita elementmetoden och skillnaderna mellan dessa två olika utgångslägen är okända. Rapportens huvudmål är att jämföra den nya metoden som tillämpar finita element metods beräkningar gentemot den gamla metodens beräkningar. Detta utförs genom att studera ett fiktivt exempel av en skalmur som med den gamla metoden hade behövt konsoler. Resultatet visade att den nya metoden kan förbättra egentyngdens fördelning i skalmuren och konsoler kan därför undvikas i detta fall.
Throughout Sweden’s history several distinct types of masonry constructions have been used. In the late 1950s the most common masonry construction that dominates today’s market was developed. A study has been conducted in an attempt to better understand how masonry constructions are to be designed. Commercial calculation methods applied for sizing cavity walls today results in oversized constructions that are reinforced with expensive consoles. The consoles are placed in the cavity wall for supporting the masonry were it would otherwise break. A new calculation method could prove these consoles to be an unnecessary expense. A cavity wall is by principal only exposed by its own dead-load and is therefor the main load when sizing the wall. The purpose of this study is to develop a more accurate method of calculating the spread of the deadload in the cavity walls masonry. This could prove that the weaker points in the wall is not in need of reinforcement by consoles. This study will investigate the possibility to use the finite element method for the calculation of the deadloads spread inside a cavity wall. Commercial calculation methods that are used today does not use the finite element method and the differences in these two initial states are unknown.

An experimental investigation of the thermal properties of a variable cavity wall has been conducted with the aid of a Guarded Hot Box (GHB). The main objective of the investigation was to determine the thermal trends of that exist in such a wall at different aspect ratios and internal configurations. In the course of this research effort, attention had initially focused on the suitability of the GHB as a tool for measuring building components of low thermal transmittance. Following the initial evaluation that included computational modelling of the GHB, a series of modifications were employed, which included a series of baffie plates in the Guard box area. Experimental trials have shown that these modifications culminated in a reduced thermal gradient distribution within the box and along the test wall. As a result, the test wall was subjected to a more uniform heat flux and lower peripheral heat loss. A variable cavity wall measuring 1.2m by 1.2m and 0.41m deep was the main 'focus of this study. By means of a moveable brick leaf, the aspect ratio of the cavity wall could be remotely altered during the experiment, thereby allowing immediate comparison of thermal trends without the errors that are associated with building and testing a series of individual walls of different geometric proportions. In particular, this set-up enabled an accurate comparative analysis of cavity aspect ratios over a range of 15 to 30. Lazer Doppler Anemometry (LDA) and thermal measurement on the four surfaces of the cavity wall leafs were the prime means for collating experimental data. Extensive computational modelling complemented the research, which provided important insights both prior to and following the experimental stage. The use of Computational Fluid Dynamics (CFD), while not intended for precise solutions to models of the GHB and cavity wall, was never the less instrumental in establishing trends and expanding the experimental range, once corroboration of experimental results had been achieved. The experimental and computational results show that with successive cavity closure an optimum aspect ratio is reached, where thermal resistance peaks and velocity of the convective flow is minimal. At this aspect ratio, the flow regime was found to be conductive. The main implication of this result is that decreasing aspect ratio beyond this aspect ratio, by widening the cavity, will result in increasing heat losses due to the circulation of convective currents in the cavity. Thus, it was concluded that when convection diminishes, the thermal resistance of the air cavity would rise. Further computational and experimental work on the same wall with an internal partition, corroborated the trends found during the clear cavity experiment. It was found that a centrally placed vertical partition will double the thermal resistance of the wall. Furthermore, the thermal resistance of the partition was found to equal that of one partitioned cavity, raising the possibility of eliminating cavities from wall construction The effect of mortar joints upon cavity walls, at various aspect ratios, was also investigated. Results show that a vertically sinusoidal flow pattern exists in such cavities due to the thermal bridging effect of the mortar joints. The results of this study were used for several recommendations, which deal both with design of cavity walls and Guarded Hot Box design and operation.

Lightweight building materials are now commonly employed in many countries in preference to heavyweight materials. This has lead to extensive research into the sound transmission loss of double leaf wall systems. These studies have shown that the wall cavity and sound absorption material placed within the cavity play a crucial role in the sound transmission through these systems. However, the influence of the wall cavity on the sound transmission loss is not fully understood. The purpose of this research is to obtain a comprehensive understanding of the role played by the wall cavity and any associated sound absorption material on the sound transmission loss through double leaf wall systems. The research was justified by the fact that some of the existing prediction models do not agree with some observed experimental trends. Gösele’s theory is expanded and used in the creation of an infinite and finite vibrating strip model in order to acquire the desired understanding. The sound transmission loss, radiated sound pressure and directivity of double leaf systems composed of gypsum boards and glass have been calculated using the developed model. A method for calculating the forced radiation efficiency has also been proposed. Predictions are compared to well established theories and to reported experimental results. This work also provides a physical explanation for the under-prediction of the sound transmission loss in London’s model; explains why Sharp’s model corresponds to Davy’s with a limiting angle of 61° and gives an explanation for Rindel’s directivity and sound transmission loss measurements through double glazed windows. The investigation also revealed that a wide variety of conclusions were obtained by different researchers concerning the role of the cavity and the properties of any associated sound absorption material on the sound transmission loss through double wall systems. Consequently recommendations about the ways in which sound transmission through cavity systems can be improved should always be qualified with regard to the specific frequency range of interest, type of sound absorption material, wall panel and stud characteristics.

Injection molding is one of the most commonly applied processing methods for plastic components. Heat transfer coefficient (HTC), which describes the heat conducting ability of the interface between a polymer and cavity wall, significantly influences the temperature distribution of a polymer and mold during injection molding and thus affects the process and quality of plastic products. This thesis focuses on HTC under diverse processing situations. On the basis of the heat conducting principle, a theoretical model for calculating HTC was presented. Injection mold specially used for measuring and calculating HTC was designed and fabricated. Experimental injection studies under different processing conditions, especially different surface roughness, were performed for acquiring necessary temperature data. The heat quantity across the interface and HTC between a polymer and cavity wall was calculated on the basis of experimental results. The influence of surface roughness on HTC during injection molding was investigated for the first time. The factors influencing the HTC were analyzed on the basis of the factor weight during injection molding. Subsequently FEM (Finite element method) simulations were carried out with observed and preset value of HTC respectively and the relative crystallinity and part density were obtained. In the comparison between results from simulation and experiment, the result calculated with observed HTC shows better agreement with actually measured value, which can verify the reliability and precision of the injection molding simulation with observed HTC. The results of this thesis is beneficial for understanding the heat transfer process comprehensively, predicting temperature distribution, arranging cooling system, reducing cycle time and improving precision of numerical simulation
Das Spritzgießen ist eines der am häufigsten angewandten Verarbeitungsverfahren zur Herstellung von Kunststoffkomponenten. Der Wärmedurchgangskoeffizient (WDK), welcher den Wärmeübergang zwischen Kunststoff und Werkzeugwand beschreibt, beeinflusst während des Spritzgießens maßgeblich die Temperaturverteilung im Bauteil und dem Werkzeug und folglich den Prozess und die Qualität der Kunststoffprodukte. Der Inhalt dieser Arbeit beschäftigt sich mit dem WDK unter verschiedenen Prozessbedingungen. Auf Grundlage des Wärmeleitungsprinzips wurde ein theoretisches Modell für die Berechnung des WDK vorgestellt. Es wurde dazu ein Spritzgießwerkzeug konstruiert und hergestellt, welches Messungen zur späteren Berechnung des WDK ermöglicht. Praktische Spritzgießversuche unter verschiedenen Prozessbedingungen, insbesondere unterschiedlicher Oberflächenrauheit, wurden für die Erfassung der erforderlichen Temperaturdaten durchgeführt. Auf Grundlage der experimentellen Ergebnisse wurde der Wärmeübergang zwischen dem Polymer und der Werkzeugwand berechnet. Der Einfluss der Oberflächenrauhigkeit auf den WDK wurde hierbei zum ersten Mal untersucht. Auf Grundlage des Bauteilgewichtes wurden anschließend die Faktoren, die den WDK beeinflussen, berechnet. Des Weiteren wurden FEM-Simulationen (Finite Element Methode) mit dem gemessenen und dem voreingestellten WDK durchgeführt und daraus der Kristallinitätsgrad und die Bauteildichte gewonnen. Der Vergleich zwischen den realen Ergebnissen und der Simulation zeigt, dass die Berechnungen mit dem gemessenen WDK eine bessere Übereinstimmung mit den realen Werten aufweist, was die Zuverlässigkeit und Präzision der Spritzgusssimulation bestätigt. Die Ergebnisse dieser Arbeit tragen zum umfassenden Verständnis des Wärmeübergangs im Spritzgießprozess, zur Vorhersage der Temperaturverteilung, zur Auslegung des Kühlsystems, zur Reduzierung der Zykluszeit und zur Verbesserung der Genauigkeit der numerischen Simulation bei

Injection molding is one of the most commonly applied processing methods for plastic components. Heat transfer coefficient (HTC), which describes the heat conducting ability of the interface between a polymer and cavity wall, significantly influences the temperature distribution of a polymer and mold during injection molding and thus affects the process and quality of plastic products. This thesis focuses on HTC under diverse processing situations. On the basis of the heat conducting principle, a theoretical model for calculating HTC was presented. Injection mold specially used for measuring and calculating HTC was designed and fabricated. Experimental injection studies under different processing conditions, especially different surface roughness, were performed for acquiring necessary temperature data. The heat quantity across the interface and HTC between a polymer and cavity wall was calculated on the basis of experimental results. The influence of surface roughness on HTC during injection molding was investigated for the first time. The factors influencing the HTC were analyzed on the basis of the factor weight during injection molding. Subsequently FEM (Finite element method) simulations were carried out with observed and preset value of HTC respectively and the relative crystallinity and part density were obtained. In the comparison between results from simulation and experiment, the result calculated with observed HTC shows better agreement with actually measured value, which can verify the reliability and precision of the injection molding simulation with observed HTC. The results of this thesis is beneficial for understanding the heat transfer process comprehensively, predicting temperature distribution, arranging cooling system, reducing cycle time and improving precision of numerical simulation.
Das Spritzgießen ist eines der am häufigsten angewandten Verarbeitungsverfahren zur Herstellung von Kunststoffkomponenten. Der Wärmedurchgangskoeffizient (WDK), welcher den Wärmeübergang zwischen Kunststoff und Werkzeugwand beschreibt, beeinflusst während des Spritzgießens maßgeblich die Temperaturverteilung im Bauteil und dem Werkzeug und folglich den Prozess und die Qualität der Kunststoffprodukte. Der Inhalt dieser Arbeit beschäftigt sich mit dem WDK unter verschiedenen Prozessbedingungen. Auf Grundlage des Wärmeleitungsprinzips wurde ein theoretisches Modell für die Berechnung des WDK vorgestellt. Es wurde dazu ein Spritzgießwerkzeug konstruiert und hergestellt, welches Messungen zur späteren Berechnung des WDK ermöglicht. Praktische Spritzgießversuche unter verschiedenen Prozessbedingungen, insbesondere unterschiedlicher Oberflächenrauheit, wurden für die Erfassung der erforderlichen Temperaturdaten durchgeführt. Auf Grundlage der experimentellen Ergebnisse wurde der Wärmeübergang zwischen dem Polymer und der Werkzeugwand berechnet. Der Einfluss der Oberflächenrauhigkeit auf den WDK wurde hierbei zum ersten Mal untersucht. Auf Grundlage des Bauteilgewichtes wurden anschließend die Faktoren, die den WDK beeinflussen, berechnet. Des Weiteren wurden FEM-Simulationen (Finite Element Methode) mit dem gemessenen und dem voreingestellten WDK durchgeführt und daraus der Kristallinitätsgrad und die Bauteildichte gewonnen. Der Vergleich zwischen den realen Ergebnissen und der Simulation zeigt, dass die Berechnungen mit dem gemessenen WDK eine bessere Übereinstimmung mit den realen Werten aufweist, was die Zuverlässigkeit und Präzision der Spritzgusssimulation bestätigt. Die Ergebnisse dieser Arbeit tragen zum umfassenden Verständnis des Wärmeübergangs im Spritzgießprozess, zur Vorhersage der Temperaturverteilung, zur Auslegung des Kühlsystems, zur Reduzierung der Zykluszeit und zur Verbesserung der Genauigkeit der numerischen Simulation bei.

Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xxi, 238 p.; also includes graphics Includes bibliographical references (p. 231-238). Available online via OhioLINK's ETD Center

En aquest estudi s'analitzen els experiments i simulacions numèriques del flux de convecció mixta en una cavitat cúbica situada a la part inferior d'un canal quadrat. Els nombres de Reynolds en funció de la velocitat mitjana del flux i l'amplada del canal estan en el rang 100≤Re≤1500 i el nombre de Richardson varia entre 0.1≤Ri≤10. La tècnica PIV s'ha utilitzat per a les mesures en un canal d'aigua. Simulacions numèriques Tridimensionals s’han dut a terme amb un codi de volums finits de segon ordre considerant l'aproximació de Boussinesq ja que, per les condicions experimentals utilitzades, la variació de les propietats físiques amb la temperatura no té influència significativa en la topologia general de flux. Per 100≤Re≤1500 i Ri≤0.1 el flux és estacionari i consisteix en un remolí situat a l’interior de la cavitat cúbica que mostra velocitats majors a mesura que augmenta el nombre de Richardson. El flux és no estacionari a Re = 100 i Ri = 10. Prop de les parets laterals es produeixen, de forma alternada, ejeccions de flux, des de l’interior de la cavitat cap al canal, mentre que el flux entra a la cavitat des del canal a través de la part central de la cavitat. S'ha utilitzat una tècnica de mostreig condicional per elucidar l’estructura mitjana de l'evolució del flux turbulent a Ri = 10. S'ha trobat que les ejeccions de flux persisteixen durant tot el rang de Reynolds analitzat. Els números de Nusselt calculats estan d'acord amb els de les correlacions reportades a la literatura, vàlides per cavitats bidimensionals
En este estudio se analizan los experimentos y simulaciones numéricas del flujo de convección mixta en una cavidad cúbica situada en la parte inferior de un canal de sección cuadrada cuadrado. Los números de Reynolds en función de la velocidad media del flujo y la anchura del canal están en el rango 100≤Re≤1500 y el número de Richardson varía entre 0.1≤Ri≤10. La técnica PIV se ha utilizado para las medidas en un canal de agua. Se han llevado a cabo simulaciones numéricas tridimensionales con un código de volúmenes finitos de segundo orden, considerando la aproximación de Boussinesq ya que, en las condiciones experimentales utilizadas, la variación de las propiedades físicas con la temperatura no tiene influencia significativa en la topología general de flujo. En los rangos 100≤Re≤1500 y Ri≤0.1 el flujo es estacionario y consiste en un remolino situado en el interior de la cavidad cúbica que muestra velocidades mayores a medida que aumenta el número de Richardson. El flujo es no estacionario a Re = 100 y Ri = 10. Cerca de las paredes laterales se producen de forma alternada eyecciones de flujo, desde el interior de la cavidad hacia el canal, mientras que el flujo entra en la cavidad desde el canal a través de la parte central de la cavidad. Se ha utilizado una técnica de muestreo condicional para elucidar la estructura media de la evolución del flujo turbulento a Ri = 10. Se ha encontrado que las eyecciones de flujo persisten durante todo el rango de Reynolds analizado. Los números de Nusselt calculados están de acuerdo con los de las correlaciones reportadas en la literatura, válidas para cavidades bidimensionales.
In this study we analyze experiments and numerical simulations of steady and unsteady mixed convection flow in a cubical cavity located at the bottom of a square channel. The Reynolds numbers based on the mean flow velocity and the channel width are in the range 100≤Re≤1500 and the Richardson numbers vary within 0≤Ri≤10. Particle Image Velocimetry has been used for the measurements in a water channel. Three-dimensional direct numerical simulations have been carried out with a second order finite volume code considering the Boussinesq approximation since, for the experimental conditions considered, the variation of the physical properties with temperature has no significant influence on the overall flow topology. For 100≤Re≤1500 and Ri≤0.1 the flow is steady and it consists in a single roll that exhibits larger velocities as the Richardson number is increased. An unsteady periodic flow is found at Re=100 and Ri=10. Alternate flow ejections from the cavity to the channel occur near the lateral walls while the flow enters the cavity from the channel through the central part of the cavity. A conditional sampling technique has been used to elucidate the evolution of the mean unsteady turbulent flow at Ri=10. It has been found that the alternate flow ejections persist for all the Reynolds analyzed. The computed Nusselt numbers are in general agreement with a previously reported correlation, valid for two dimensional cavities of different aspects ratios.

After the second world war, cavity walls became a widespread external wall type in the North Western Europe including the Netherlands. Cavity walls consist of two leaves separated by a hollow space (cavity). The leaves are commonly made by masonry bricks, blocks, and wall ties. Wall ties are used to connect the two leaves of a cavity wall and are installed during construction. The ties are meant to withstand wind pressure mostly. Recently in the north of the Netherlands induced earthquakes took place. As consequence, many cavity walls may fail due to the crisis of the ties subjected to seismic solicitations for which they were not designed. The present work investigate numerically the behaviour of cavity masonry wall systems with or without wall ties. The models were implemented taking into account the physical and geometric nonlinearities. Both nonlinear static and dynamic analyses have been performed by means of the �nite element software DIANA.

This is a final year project considering constructional techniques for joining cavity walls. The project is related to an ongoing scientific programme about the restoration of The City wall of Visby located on Gotland. The programme was set by Riksantikvarieämbetet as a reaction to a collapse of the outer masonry wall shell which took place in February 2012. The City wall of Visby is a medieval fortification built out of limestone during the 13th century. The wall is constructed as a cavity wall with two separate masonry shells connected to each other through an intermediate core. During the 14th century the wall was heightened which lead to a higher stress, especially in the outer wall face. This occurrence in combination with repeated frost bursts is most likely two of the reasons to why a part of the wall collapsed in 2012. The investigated techniques in this report are reconstructional masonry work using “through-stones”, wall ties out of steel and supportive buttresses. These techniques are investigated regarding their constructive actions and suitability for The City wall of Visby. Masonry work using “through-stones” consists of placing occasional masonry stones perpendicular to the remaining stones. In this way the two wall faces can be joined together. As well as “through-stones”, wall ties also provide a binding between the two wall faces. These ties can be made out of steel bars which ends are connected to each wall face. In this report wall ties are calculated considering tension in interaction with bending moment. A desirable quality for wall ties in this case is that they have the ability to follow the natural movements of the masonry wall without losing their binding capacity. Finally masonry buttresses are investigated, these are masonry units placed against the wall to support horizontal loadings. Buttresses vary in appearance; in this case they consist of limestone blocks laid against the wall face in a certain angle. Considering the state of equilibrium, adequate dimensions of the buttresses are defined. Calculations in this report are based on a number of assumptions regarding loading conditions of the wall combined with the specific constructional technique. Existing theories based on Eurocode’s are not always possible to apply on medieval constructions such as The City wall of Visby. The results in this report show that all mentioned techniques could be applied on The City wall of Visby if they are constructed with the right dimensions in combination with other preventive measures against problems due to water and frost. However, considering the fact that The City wall of Visby is a cultural heritage the suitability differs between the constructional techniques.
Detta examensarbete behandlar byggnadstekniska metoder med syftet att sammanbinda skalmurar. Arbetet utförs i samband med ett pågående forsknings- och utvecklingsprojekt rörande restaureringen av Visby ringmur på Gotland. Forskningsprojektet startades på uppdrag av Riksantikvarieämbetet efter ett murras i februari 2012. Visby ringmur är en medeltida befästning av gotländsk kalksten som till huvudsaklig del uppfördes under åren 1250-1288. Muren är konstruerad som en skalmur vilket innebär en icke homogen mur bestående av två murskal med mellanliggande kärna. Senare på 1300-talet förhöjdes muren vilket bidrog till en överbelastning av främst det yttre murskalet. Detta i kombination med upprepad frostsprängning är sannolikt två av orsakerna till murraset 2012. Metoderna som undersökts är ommurning med bindstenar, sammanbindning med kramlor och dragjärn samt uppstöttning med kontreforter. Dessa metoder studeras i fråga om verkningssätt samt lämplighet för Visby ringmur. Murning med bindstenar innebär att stenar med regelbundet mellanrum i ett murskift placeras tvärgående med kortsidan utåt, detta för att skapa en sammanbindning mellan murskalen i en skalmur. Kramlor och dragjärn ska även de verkar som förbindare mellan murskalen, de kan exempelvis utgöras av ett rundstål som infästs i vardera murskal. I rapporten undersöks dessa utifrån dragkraft i kombination med dess böjmoment. Önskvärt är att såväl kramlor som dragjärn ska kunna följa murens naturliga rörelser samtidigt som de ska sammanbinda murskalen. Slutligen undersöks kontreforter vilka muras mot skalmuren med syftet att ge stöd och uppta horisontala krafter. Kontreforter kan variera i utseende, i detta fall studeras kontreforter som muras av kalksten i vinkel mot murväggen. Med hjälp av ett jämviktsförhållande undersöks lämpliga dimensioner för kontreforterna. Alla beräkningar i denna rapport baseras på ett antal antaganden om lastförhållanden för muren i samverkan med vald byggnadsteknisk metod. Teorier enligt Eurokoderna inte är utformade för äldre murverkskonstruktioner och därav inte alltid tillämpbara. Resultaten visar att alla nämnda metoder skulle kunna tillämpas på muren om de utförs med lämpliga dimensioner i kombination med andra förebyggande åtgärder mot fukt- och frostproblemen. Dock skiljer sig lämpligheten för de olika metoderna åt med tanke på bevarandet av ringmurens kulturhistoriska värde.

Bibliography: leaves 69-71.
The aim of the testing was to compare the relative positives and negatives of the Butterfly Tie and the Crimped lie as regards to water transfer, tensile and compression strengths based on the Australian Code [AS 2699-l 984] requirements as it is more comprehensive. The reason was because the Butterfly Tie has been promoted in cavity wall construction in South Africa for a number of reasons, for example: * NHBRC (National Home Builders Registration Council) compels contractors to use the Butterfly Tie * SABS 28:l986 and SABS O 164-1 :1980 also compel the use of Butterfly Tie, even though there is an anomalous statement in the specifications. Another reason was because the use of the Crimped Tie was not being promoted in cavity wall construction in South Africa mainly because of a lack of information regarding characteristic strength and its resistance to water transfers. The following tests, based on the Australian Code, which is more stringent than the South African Codes were then carried out on the Butterfly Tie and the Crimped Tie: * Tests for water transfer * Tests tor compression and tensile strengths using couplets * Tests for compression and tensile strengths using ties only. Although the testing showed that the Butterfly Tie and the Crimped Tie fulfilled the requirements of the Australian Code, there were negative aspects relating to the Butterfly Tie. It is recommended that serious considerations be given by the South African Bureau of Standards to include the Crimped Tie in its Code of Practice for Cavity Walls.

Integrally moulded hinges and tension bands are important features in packaging components for plastic closures and their function is critically dependent on the flow induced micromorphology in the hinge section. Polymer characteristics and processing of the hinge also have an influence on the hinge properties obtained. This study is aimed at obtaining interrelationships between polymer characteristics, in-cavity flow, microstructure development and hinge properties, to produce hinges with enhanced functional properties. Three different virgin polypropylene (PP) grades were investigated (homopolymer PP-H, random copolymer PP-RC and impact copolymer PP-IC) and injection moulding simulation was carried out using Moldflow software. In-cavity data acquisition has been carried out for different sets of injection moulding conditions, using high performance transducers and a data acquisition system. A comparison between Moldflow simulation and practical injection moulding data suggests that, for thin wall injection moulded components the real time pressure data are in close agreement during the injection stage. During the packing stage there is some disagreement between these data, since the thickness of hinge and tension band sections are 0.4 mm and 0.5 mm respectively, suggesting that these dimensions are extending the capability of the software. An extensive study using a design of experiments (DoE) approach was carried out on both practical and predictive data. Injection velocity and melt temperature were the most influential factors on the component mechanical properties. From the optical micrographs it is observed that PP-RC has a finer micro-structure compared to PP-H and PP-IC and some micrographs confirm Moldflow simulation results in which hesitation effects are evident, as the flow converges into the thin hinge and tension band sections. PP-clay nanocomposites (PP-CN) were prepared using a twin screw compounder. Transmission electron microscopy (TEM) has shown some evidence of dispersion and exfoliation of the clay particles in the PP matrix. However, X-ray diffraction (XRD) results show a reduction in inter-layer spacing of PPCN s possibly due to clay compaction. The addition of nano-clay however has not resulted in any significant improvements in the mechanical properties of hinges and tension bands. The high degree of molecular orientation induced in the hinge and tension-band sections appears to mask any improvements attributed to the addition of nano-clay. From the reprocessed and post consumer recyclate (PCR) study conducted on hinges and tension bands, it is seen that with an increase in both the re-processing and PCR content there is a decrease in the component strength of around 14%, giving scope to potentially use PCR in future packaging applications. Investigations conducted on colour pigments (violet and green) reveal that the onset of crystallisation for green pigmented mouldings is considerably higher (16°C) than for natural and violet mouldings. Optical micrographs also reveal a finer microstructural texture for green components, indicating a high nucleating capability of the green pigment. Irrespective of the colour, both for hinges and tension bands, the yield stress values were around twice as high as the values quoted in the manufacturer s data sheet for isotropic PP, due to the high levels of molecular orientation in the hinge and tension band sections. In order to industrially validate the findings from the DoE study, commercial closures were produced in industry on a production tool then characterised. In the case of tension bands, there was a good agreement between the results obtained from lab scale and industrial study due to the relatively simple geometry. For hinges this agreement is not so clear. Finally a comparison of mechanical properties of the 3 PP grades shows that PP-H has a higher yield stress compared to PP-IC and PP-RC and yield stress is significantly higher (yield strain values are lower) than values quoted by the manufacturer. The PhD study has confirmed the process conditions that are able to optimise all the interactive effects to improve functional properties in high volume parts in the packaging industry.

Interfaces adesivas flexíveis, com maior capacidade de dissipação de tensões poderiam prevenir falhas provenientes das tensões geradas durante a contração de polimerização, variações térmicas e esforços mastigatórios. Isso poderia ser obtido através do aumento da espessura da camada de adesivo. O objetivo deste trabalho foi comparar a resistência de união (RU) à dentina de dois sistemas adesivos (SA) aplicados com diferentes volumes de adesivo (uma ou duas camadas) e submetidos ou não às ciclagens térmica e mecânica (CTM). A superfície dentinária de 40 terceiros molares hígidos foi exposta com uma lixa de granulação 600. Dois sistemas adesivos foram testados: Scotchbond Multiuso (SBMU) e Clearfil SE Bond (CSEB). Seus respectivos adesivos foram aplicados através de uma micropipeta (8 ou 16µl) em uma área delimitada de 52 mm 2 e blocos de resina composta (Z250) foram construídos incrementalmente. Metade da amostra foi armazenada em água destilada por 24 h e submetida às ciclagens térmica (1.000; 5-55ºC) e mecânica (500.000 ciclos / 12 kgf). A outra metade foi apenas armazenada em água destilada por 72 h. Após isso, os dentes foram seccionados, longitudinalmente, em cortes perpendiculares entre si, a fim de se obterem corpos-de-prova em formato de paralelogramo com aproximadamente 0,8mm 2 de secção transversal. Os palitos foram submetidos ao teste de microtração a 1,0 mm/min e o modo de fratura analisado. A RU foi expressa como um índice que incluiu os valores de RU dos diferentes padrões de fratura, além dos palitos prematuramente fraturados (P). Os dados foram submetidos à análise de variância de 3 fatores. O teste de qui-quadrado foi utilizado (p<0,05) para verificar diferenças na freqüência de P. Dois fatores foram significantes: “SA” e “CTM”. SBMU e grupos não-ciclados apresentaram maior RU do que CSEB e grupos ciclados respectivamente. Uma maior freqüência de P foi observada para os grupos ciclados. Uma camada adicional de adesivo não influenciou na RU de interfaces feitas com SBMU ou CSEB, enquanto a CTM levou à redução da RU das interfaces.
Dentin bonding interfaces with increased capacity of stress dissipation are able to prevent failures due to polymerization contraction, thermal and mechanical stresses. This would be obtained by increasing adhesive layer thickness. The purpose of this study was to compare the resin-dentin microtensile bond strengths (BS) of two adhesive systems (AS) applied with different volumes of adhesive resin (one and two coats) submitted or not to thermal and mechanical loading (TML). A flat superficial dentin surface was exposed on 40 third molars with a 600-grit SiC paper. Two systems were tested: Scotchbond Multipurpose (SBMP) and Clearfil SE Bond (CSEB). After primer application, the adhesive layer was applied by a micropipette (8 or 16µl) to a delimited area (52mm 2 ) and resin blocks (Z250) were built incrementally. Half of the sample was stored in distilled water for 24h and then submitted to thermal (1,000; 5-55ºC) and mechanical cycles (500,000; 12kgf). The other half was stored in distilled water (72h). Teeth were then sectioned to obtain sticks (0.8 mm 2 ) to be tested under tensile mode (1.0mm/min). The fracture mode was analyzed at 400X. BS was expressed as an index that included the BS values of different fracture patterns and the prematurely debonded specimens (D). The data was analyzed by three-way ANOVA. The χ 2 test was used (p<0.05) to compare the frequency of D specimens. The main factors AS and TML were significant. SBMP and non-cycled groups showed higher BS to dentin. A higher frequency of D was observed for the cycled groups. The application of an adhesive layer in two coats for a three-step etch&rinse and a two-step self-etch systems, to act as an intermediate flexible layer, was not able to minimize the damage caused by thermal and mechanical load in a low C-factor cavity.

Etude des couches limites thermiques et dynamiques pour differents ecarts de temperature. Mesure des tres faibles vitesses par anemometrie laser doppler. Calcul de l'evolution du nombre de nussels local

Le probleme etudie est celui des mesures de temperature a la surface de parois semi-transparentes: les capteurs utilises (thermocouples colles) introduisent des perturbations qui, dans le cas ou le niveau d'echange est bas, tel que celui de l'habitat, peuvent etre du meme ordre que les effets etudies. Ce travail, mene simultanement sur le plan experimental et numerique par calage de modeles, concerne donc la mesure de temperature de surface, ainsi que l'evaluation et l'interpretation des perturbations creees par les capteurs utilises. La methodologie repose sur l'analyse de situations caracterisees par des conditions aux limites en surface de complexite croissante: conduction et rayonnement infra-rouge, convection naturelle, puis rayonnement visible

碩士
國立交通大學
電信工程系所
95
In this thesis, we developed a band-pass filter using via-hole arrays cavity implemented on a 2-layered printed circuit board. The pass-band center frequency may be roughly estimated by the resonance frequency of the cavity. The bandwidth of the filter may be altered by changing the length of the coupling apertures. The scattering parameters, including the insertion and return losses were simulated by using CST microwave studio. The measured results show a good agreement with the simulation results.

碩士
大葉大學
機械工程研究所碩士班
94
ABSTRACT Because of the development of science and technology now, the industry of the computer is different on day new night, make people's door notice that the computer derives out artificial intelligence (artificial intelligence ) and one kind of neural networks (neural networks ) different from human brain, the using type neural network adopts and tries the way to imitate human neural work of brain, deal with the units and accept and stimulate and exchange information by a lot of, receive a certain result, made the proper response by the brain centre. One kind of neural networks can adopt the hardware or the software way to be set up , hardware way will look like the structure of the parallel processor , will let a lot of processors (processors ) link to each other together with the high-speed bus (bus ). The way of the software is to describe the node that linked to each other as a means of the material structure and algorithm of performing , linking among the nodes can have weight (weight ) , some nodes can accept the stimulus of introduction , some nodes can jointly output some meaningful results . So we imitate the transmission operation course of the neuron with the circuit diagram, then turn its transmission course into the training equation preface that we need and use VB (Visual Basic ) and Matlab and Moldflow simulation, in addition, the basic one flows strength , heat are spread, the material strength equation preface is changed into the expert system via VB, via real experiment with go bankrupt best parameter person who transmit neural network is it train in order to get trend of number value in order to finish the intact neural network system to go on. Keyword:neural networks, artificial intelligence, processors

Rain screen wall systems are effective for control of rain water. The ventilation in the air space of such walls is also expected to play a role in the drying of cladding and control of vapor flows through the wall. For example, wet cladding exposed to solar radiation may subject the wall to inward vapor flow, unless an air cavity short-circuits that vapor flow. Although the role of the air cavity has been previously studied, it is relevant to evaluate more quantitatively the movement of air within the air cavity between the cladding and the backwall. The effect of wind pressure notwithstanding, convective movement of air in the cavity is the result of buoyancy. Air movement can result from the increased temperature of the cladding due to solar radiation. The first objective of this thesis was the development of a numerical model of air movement driven by the variation of wall temperature with height, taking into account heat transfer by conduction, convection and radiation and mass transfer by diffusion and convection. The model was validated by means of comparison with analytical results from the literature, as well as with two sets of experimental results. The experimental procedures involved the evaluation of the magnitude and direction of the air movement within a large-scale cavity with a uni-directional anemometer and with particle image velocimetry. Once the boundary conditions were known, they were used to determine experimentally the mass transfer coefficients at the surface of wetted brick in the cavity with a horizontal wind tunnel setup. The validated model was used to evaluate parametrically the air movement's effects on heat and moisture flow within the assembly, assuming the brick had wetted by rain water before exposure to the solar radiation. Conclusions were drawn as to the effect of the air movement on the evacuation of heat and moisture from the assembly, based on variation of six parameters. It was found that the air movement in the cavity plays a significant role in the drying of the cladding by saturation of rain water. As well, under average summer conditions for Montreal, the air velocity in the cavity was found to have an approximate peak of 0.20 m/s, neglecting the effects of wind pressure. The air flow is turbulent at the weephole entrance of the cavity, before becoming laminar within approximately 10 centimeters of flow development. Finally, convective mass and heat transfer surface coefficients increase with air velocity, except for air velocities lower than 0.10 m/s

abstract: Learning from the anatomy of leaves, a new approach to bio-inspired passive evaporative cooling is presented that utilizes the temperature-responsive properties of PNIPAm hydrogels. Specifically, an experimental evaporation rate from the polymer, PNIPAm, is determined within an environmental chamber, which is programmed to simulate temperature and humidity conditions common in Phoenix, Arizona in the summer. This evaporation rate is then used to determine the theoretical heat transfer through a layer of PNIPAm that is attached to an exterior wall of a building within a ventilated cavity in Phoenix. The evaporation of water to the air gap from the polymer layer absorbs heat that could otherwise be conducted to the interior space of the building and then dispels it as a vapor away from the building. The results indicate that the addition of the PNIPAm layer removes all heat radiated from the exterior cladding, indicating that it could significantly reduce the demand for air conditioning at the interior side of the wall to which it is attached.
Dissertation/Thesis
Masters Thesis Built Environment 2018

Η εφαρμογή της μικροκυματικής ραδιομετρίας έχει επεκταθεί στο χώρο της ιατρικής, καθότι τα τελευταία χρόνια γίνονται έρευνες με σκοπό την εκμετάλλευση των ιδιοτήτων της μεθόδου στη διαγνωστική αλλά και στη θεραπευτική ιατρική. Στα πλαίσια μιας διδακτορικής διατριβής που εκπονήθηκε στο Εργαστήριο Μικροκυμάτων και Οπτικών Ινών (ΕΜΟΙ) της σχολής Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών του Εθνικού Μετσόβιου Πολυτεχνείου και ολοκληρώθηκε το 2003, κατασκευάστηκε ένα τρισδιάστατο σύστημα παθητικής μικροκυματικής ραδιομετρικής απεικόνισης (ΜiRaIS) για διαγνωστικές εφαρμογές εγκεφάλου. Στη συγκεκριμένη μέθοδο χρησιμοποιείται μια αγώγιμη ελλειψοειδής κοιλότητα, ώστε να επιτευχθεί μέγιστη συγκέντρωση και εστίαση ακτινοβολίας που εκπέμπει το φυσικό σώμα ενδιαφέροντος, σε συνδυασμό με ραδιομετρικούς δέκτες ολικής ισχύος και ομοιοκατευθυντικές κεραίες λήψης στο φάσμα συχνοτήτων 1-4GHz. Στην παρούσα διπλωματική εργασία γίνεται θεωρητική και πειραματική μελέτη ενός νέου μικροκυματικού ραδιομετρικού συστήματος. Η αρχή λειτουργίας του είναι όμοια με αυτήν του MiRaIS, δηλαδή πλήρως παθητική και μη επεμβατική. Η βασική διαφορά του είναι ότι χρησιμοποιεί μια τροποποιημένη ελλειψοειδή κοιλότητα η οποία βελτιώνει την εργονομία του συστήματος διατηρώντας παράλληλα της ιδιότητες εστίασης του πρωτότυπου ελλειψοειδούς. Στη θεωρητική μελέτη, με τη βοήθεια του λογισμικού High Frequency Structure Simulation (HFSS) που βασίζεται στη μέθοδο των πεπερασμένων στοιχείων, αναλύονται δυο μέθοδοι για τη βελτίωση των ιδιοτήτων εστίασης του συστήματος (πχ. βάθος διείσδυσης της ακτινοβολίας, χωρική διακριτική ικανότητα) με τη χρήση διηλεκτρικών υλικών και υλικών με αρνητικό δείκτη διάθλασης (Left Handed Materials-LHM). Στην πρώτη περίπτωση, τα υλικά αυτά χρησιμοποιούνται ως στρώματα προσαρμογής που τοποθετούνται γύρω από το μοντέλο κεφαλιού για την επίτευξη βηματικής αλλαγής του δείκτη διάθλασης στη διεπιφάνεια αέρα-μοντέλου ανθρώπινου κεφαλιού. Στη δεύτερη προσέγγιση του προβλήματος, χρησιμοποιείται μια σφαίρα από διηλεκτρικό σε συνδυασμό με ένα στρώμα προσαρμογής από LHM για την καλύτερη εστίαση του συστήματος. Προς την ίδια κατεύθυνση, στη δεύτερη αυτή περίπτωση χρησιμοποιείται επίσης ένας ελλειψοειδής ανακλαστήρας μειωμένου όγκου το εσωτερικό του οποίου είναι γεμάτο με διηλεκτρικό με χαμηλές απώλειες, με τα αποτελέσματα να δείχνουν σημαντική βελτίωση της χωρικής διακριτικής ικανότητας του συστήματος. Η πειραματική διάταξη τοποθετήθηκε σε ανηχοϊκό θάλαμο όπου και πραγματοποιήθηκαν όλες οι μετρήσεις. Στις πειραματικές διαδικασίες που ακολουθήθηκαν, χρησιμοποιήθηκαν ομοιώματα νερού (phantoms) σε διάφορα μεγέθη και θερμοκρασίες για την επιβεβαίωση της διατήρησης των ιδιοτήτων εστίασης του νέου ελλειψοειδούς ανακλαστήρα. Επίσης, διενεργήθηκαν μετρήσεις με στρώματα προσαρμογής φτιαγμένα από διηλεκτρικά υλικά, τα οποία τοποθετούνταν γύρω από το αντικείμενο ενδιαφέροντος, για την πληρέστερη κατανόηση της επίδρασης των υλικών αυτών στις ιδιότητες εστίασης του συστήματος και για την επιβεβαίωση των αντίστοιχων θεωρητικών αποτελεσμάτων.
In the framework of a PhD thesis which was completed in the Laboratory of Microwaves and Fiber Optics (MFOL), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA) in 2003, a Three Dimensional Passive Microwave Radiometry Imaging System (MiRaIS) was designed and constructed for brain diagnostic applications. The novelty of the proposed methodology consists in the use of a conductive ellipsoidal cavity to achieve maximum peak of radiation pattern in order to measure the intensity of the microwave energy, radiated by the medium of interest, by using two microwave total power radiometers and relevant non-contacting antennas within the range of 1-4GHz. In the present thesis, a new microwave radiometry system is theoretically and experimentally studied. It has the same operation principal with MiRaIS as it operates in an entirely non-invasive and passive manner. Its main difference is that it comprises a modified ellipsoidal cavity which improves the system’s ergonomy preserving the focusing properties of the original cavity. In the theoretical study, two methods for the improvement of the system’s focusing properties (e.g. penetration depth of the electromagnetic field, spatial sensitivity) using dielectric materials and left-handed materials (LHM) are tested with the use of a commercially available software tool, High Frequency Structure Simulation (HFSS). In the first case, those materials are used as matching layers placed around the human head model for the achievement of stepped change of the refraction index on the air-human head model interface. On the second approach, a sphere made of dielectric material is used in conjunction with a LHM matching layer in order to improve the system’s spatial sensitivity. Towards the same direction, a reduced volume ellipsoidal cavity filled with low loss dielectric material is used showing promising results. The experiments were performed inside an anechoic chamber providing maximum accuracy avoiding any external intergerence. In the experimental procedures that were performed, water phantoms of several sizes and temperatures were used in order to confirm that the new ellipsoidal beamformer maintains the focusing properties of the original one. Also, measurements were conducted using dielectric matching layers, placed around the medium of interest, in order to fully understand the effect of those materials in the system’s focusing properties as well as confirm the relative theoretical results.

Η υπερθερμία αποτελεί μια επικουρική μέθοδο θεραπείας του καρκίνου και η βιοϊατρική έρευνα τις τελευταίες δεκαετίες, με σκοπό την εκμετάλλευση και την ανάδειξη των ιδιοτήτων της μεθόδου, στοχεύει στην εφαρμογή της στην κλινική πράξη. Μία προσπάθεια με παρόμοιο σκοπό γίνεται τα τελευταία χρόνια στο Εργαστήριο Μικροκυμάτων και Οπτικών Ινών (ΕΜΟΙ) της σχολής Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών (ΗΜΜΥ) του Εθνικού Μετσόβιου Πολυτεχνείου, όπου έχει σχεδιαστεί και κατασκευαστεί ένα σύστημα υπερθερμίας. Το προτεινόμενο σύστημα ενσωματώθηκε σε ένα τρισδιάστατο σύστημα παθητικής μικροκυματικής ραδιομετρικής απεικόνισης (ΜiRaIS) για διαγνωστικές εφαρμογές εγκεφάλου, το οποίο μελετήθηκε και κατασκευάστηκε στα πλαίσια διδακτορικής διατριβής στο ίδιο εργαστήριο της σχολής ΗΜΜΥ. Στην παρούσα διπλωματική εργασία γίνεται η θεωρητική και πειραματική μελέτη του προτεινόμενου συστήματος της υπερθερμίας. Η αρχή λειτουργίας του είναι όμοια με αυτή του MiRaIS και βασίζεται στη χρήση μια ελλειψοειδούς αγώγιμης κοιλότητας για εστίαση της ακτινοβολίας επιλεκτικά στους ιστούς που χρήζουν θεραπείας. Ο ανακλαστήρας για εστίαση, που κατασκευάστηκε και χρησιμοποιήθηκε στην πειραματική διαδικασία, βελτιώνει την εργονομία του συστήματος, διατηρώντας παράλληλα της ιδιότητες εστίασης του πρωτότυπου ελλειψοειδούς. Στα πλαίσια της παρούσας διπλωματικής εργασίας πραγματοποιήθηκε θεωρητική μελέτη και μοντελοποίηση της διάταξης με σκοπό τη βελτίωση των ιδιοτήτων εστίασής της, καθώς και πειραματικές μετρήσεις του συνολικού συστήματος υπερθερμίας-μικροκυματικής ραδιομετρίας. Στη θεωρητική μελέτη, με χρήση του λογισμικού xFDTD που βασίζεται στη μέθοδο των πεπερασμένων διαφορών στο πεδίο του χρόνου, ερευνώνται δυο μέθοδοι για τη βελτίωση των ιδιοτήτων εστίασης του συστήματος (βάθος διείσδυσης της ακτινοβολίας, χωρική διακριτική ικανότητα) με τη χρήση διηλεκτρικών υλικών. Τα υλικά αυτά τοποθετούνται στο εσωτερικό του ελλειψοειδούς καθώς και γύρω από το μοντέλο κεφαλιού ως στρώματα προσαρμογής για την επίτευξη βηματικής αλλαγής της διηλεκτρικής σταθεράς στη διεπιφάνεια αέρα-μοντέλο ανθρώπινου κεφαλιού. Στην πρώτη προσέγγιση, το εσωτερικό του ελλειψοειδούς ανακλαστήρα γεμίζει με διηλεκτρικό υλικό χαμηλών απωλειών, με τα αποτελέσματα να δείχνουν σημαντική βελτίωση της χωρικής διακριτικής ικανότητας του συστήματος. Στη δεύτερη προσέγγιση του προβλήματος, χρησιμοποιείται ένα ημισφαίριο από διηλεκτρικό γύρω από το μοντέλο κεφαλιού, με τα αποτελέσματα να δείχνουν την αντίστοιχη βελτίωση της χωρικής διακριτικής ικανότητας και παράλληλα σημαντική μείωση των ανεπιθύμητων περιοχών εστίασης της ενέργειας. Η πειραματική διάταξη τοποθετήθηκε σε ανηχοϊκό θάλαμο, όπου και πραγματοποιήθηκαν όλες οι μετρήσεις. Παράλληλα με τα πειράματα υπερθερμίας, μελετήθηκε η δυνατότητα εφαρμογής της μεθόδου της μικροκυματικής ραδιομετρίας με τη γεωμετρία του προτεινόμενου συστήματος. Η μέθοδος της μικροκυματικής ραδιομετρίας θα μπορούσε να παρέχει τον έλεγχο της θερμοκρασίας της ακτινοβολούμενης περιοχής κατά τη διάρκεια των συνεδριών της υπερθερμίας. Στις πειραματικές διαδικασίες που ακολουθήθηκαν, χρησιμοποιήθηκαν ομοιώματα νερού, τα οποία στη φάση της υπερθερμίας υπέδειξαν τις περιοχές εστίασης της ενέργειας για τη συχνότητα ακτινοβολίας, ενώ στη φάση της μικροκυματικής ραδιομετρίας βοήθησαν στη μελέτη της θερμοκρασιακής διακριτικής ικανότητας του συστήματος. Επίσης, διενεργήθηκαν μετρήσεις με στρώματα προσαρμογής από διηλεκτρικά υλικά, τα οποία τοποθετούνταν γύρω από το αντικείμενο ενδιαφέροντος, για την πληρέστερη κατανόηση της επίδρασης των υλικών αυτών στις ιδιότητες εστίασης του συστήματος και για την επιβεβαίωση των αντίστοιχων θεωρητικών αποτελεσμάτων.
The application of hyperthermia process has been widely used in clinical research and efforts are being made for its implementation in clinical practice, as many researchers have used this method as an adjunct treatment procedure for cancer. During the past two decades, a great deal of research has been carried out, with the aim of developing effective techniques for hyperthermia treatment, primarily using RF, microwave, and ultrasound energy. A similar effort is carried out in the Laboratory of Microwaves and Fiber Optics (MFOL), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), where a proposed hyperthermia system has been designed and constructed. A system for deep brain hyperthermia treatment, designed to also provide passive measurements of temperature and/or conductivity variations inside the human body, is presented in this paper. The proposed system comprises both therapeutic and diagnostic modules, operating in a totally contactless way, based on the use of an ellipsoidal beamformer to achieve focusing on the areas under treatment and monitoring. The radiometry monitoring module, the Three Dimensional Passive Microwave Radiometry Imaging System (MiRaIS), has been studied, designed and constructed in the framework of a PhD thesis in the same laboratory of MFOL. In the present thesis, the proposed system is theoretically and experimentally studied. The operation principal is based on the use of an ellipsoidal conductive wall cavity for focusing the emitted radiation on the tissues that should accept treatment. The ellipsoidal cavity, which was constructed and used in the experimentation procedure, is newly developed and improves the system’s ergonomy retaining at the same time the focusing properties of the prototype system. In the framework of the present study, theoretical modelling and experimentation of the proposed system was carried out in order to examine and improve its focusing attributes. In the theoretical study, two methods for the improvement of the system’s focusing properties (e.g. penetration depth of the electromagnetic field, spatial sensitivity) using dielectric materials are tested with the use of a commercially available software tool, xFDTD (x-Finite Difference Time Domain). The materials are placed inside the ellipsoidal or used as matching layers around the head model for the achievement of a stepped change of the refraction index on the air-human head model interface. In the first approach, the ellipsoidal volume is filled with a low loss dielectric material in order to improve the system’s spatial sensitivity. In the second approach, a hemi-sphere also filled with a dielectric material is placed around the human head model and the results revealed the improvement of the system’s spatial sensitivity and the reduction of the undesirable auxiliary energy-absorbing areas. The experiments were performed inside an anechoic chamber providing maximum accuracy by avoiding any external interference. Along with the hyperthermia experiments, the implementation of the microwave radiometry process was also tested with the proposed system. Microwave radiometry could provide the temperature monitoring of the radiated area during the hyperthermia sessions. In the experimental procedures water phantoms were used, which during hyperthermia indicated the energy-absorbing areas at the irradiation frequency, and during microwave radiometry revealed the system’s temperature sensitivity. Also, measurements were conducted using dielectric matching layers, placed around the medium of interest, in order to fully understand the effect of those materials on the system’s focusing properties as well as to confirm the respective theoretical results. Taking into consideration the present study and the advantage of the non invasive character of the proposed brain hyperthermia system, it is concluded that further research is required in order to explore its potentials at becoming a part of the standard treatment protocol of brain malignancy in the future.

Η υπερθερμία αποτελεί μια επικουρική μέθοδο θεραπείας του καρκίνου και η βιοϊατρική έρευνα τις τελευταίες δεκαετίες, με σκοπό την εκμετάλλευση και την ανάδειξη των ιδιοτήτων της μεθόδου, στοχεύει στην εφαρμογή της στην κλινική πράξη. Μια προσπάθεια με παρόμοιο σκοπό γίνεται τα τελευταία χρόνια στο Εργαστήριο Μικροκυμάτων και Οπτικών Ινών (ΕΜΟΙ) της σχολής Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών (ΗΜΜΥ) του Εθνικού Μετσόβιου Πολυτεχνείου, όπου έχει σχεδιαστεί και κατασκευαστεί ένα μικροκυματικό σύστημα υπερθερμίας. Το προτεινόμενο σύστημα ενσωματώθηκε σε ένα τρισδιάστατο σύστημα παθητικής μικροκυματικής ραδιομετρικής απεικόνισης (ΜiRaIS), το οποίο παρέχει τη δυνατότητα παρακολούθησης των μεταβολών της θερμοκρασίας και της αγωγιμότητας της υπό εξέταση περιοχής σε πραγματικό χρόνο και μελετήθηκε και κατασκευάστηκε στα πλαίσια παλαιότερης διδακτορικής διατριβής στο ίδιο εργαστήριο της σχολής ΗΜΜΥ. Στην παρούσα διδακτορική διατριβή γίνεται η θεωρητική και πειραματική μελέτη του προτεινόμενου συστήματος υπερθερμίας. Η αρχή λειτουργίας του συστήματος είναι όμοια με εκείνη του MiRaIS και βασίζεται στη χρήση μιας ελλειψοειδούς αγώγιμης κοιλότητας για εστίαση της ακτινοβολίας επιλεκτικά στους ιστούς που χρήζουν θεραπείας. Ο ανακλαστήρας για εστίαση που κατασκευάστηκε και χρησιμοποιήθηκε στην πειραματική διαδικασία, βελτιώνει την εργονομία του συστήματος, διατηρώντας παράλληλα της ιδιότητες εστίασης του πρωτότυπου ελλειψοειδούς. Στα πλαίσια της παρούσας διατριβής πραγματοποιήθηκε αρχικά η θεωρητική μελέτη και μοντελοποίηση της διάταξης με σκοπό την εξακρίβωση των ιδιοτήτων εστίασης του συστήματος και στη συνέχεια επιχειρήθηκε η βελτίωση των ιδιοτήτων αυτών με χρήση διατάξεων διηελκτρικών υλικών, καθώς και πειραματικές μετρήσεις του συνολικού συστήματος υπερθερμίας-μικροκυματικής ραδιομετρίας. Η θεωρητική ηλεκτρομαγνητική μελέτη του συστήματος έγινε με τη χρήση ενός εμπορικά διαθέσιμου υπολογιστικού πακέτου προσομοίωσης (XFdtd, Remcom Inc.), το οποίο χρησιμοποιεί τη μέθοδο των πεπερασμένων διαφορών στο πεδίο του χρόνου για την επίλυση ηλεκτρομαγνητικών προβλημάτων. Ερευνώνται τρεις διατάξεις διηλεκτρικών υλικών με σκοπό τη βελτίωση των ιδιοτήτων εστίασης του συστήματος, οι οποίες επικεντρώνονται στη μελέτη του βάθους διείσδυσης της ακτινοβολίας και της χωρικής διακριτικής ικανότητας. Τα υλικά τοποθετούνται είτε στο εσωτερικό του ελλειψοειδούς είτε γύρω από το μοντέλο κεφαλιού ως στρώματα προσαρμογής, με σκοπό την επίτευξη βηματικής αλλαγής της διηλεκτρικής σταθεράς στη διεπιφάνεια αέρα-μοντέλο ανθρώπινου κεφαλιού. Τα αποτελέσματα καταδεικνύουν τα πλεονεκτήματα από τη χρήση των διηλεκτρικών υλικών, καθώς παρουσιάζεται βελτίωση και στις δυο παραμέτρους των ιδιοτήτων εστίασης, ανάλογα με τη διάταξη που χρησιμοποιείται, τη θέση του μοντέλου κεφαλιού στο εσωτερικό του συστήματος και τη συχνότητα λειτουργίας. Για τη διενέργεια των πειραμάτων, η πειραματική διάταξη τοποθετήθηκε σε ανηχοϊκό θάλαμο, ο οποίος εξασφαλίζει την απομόνωσή της από τον περιβάλλοντα χώρο. Στις πειραματικές διαδικασίες που ακολουθήθηκαν, χρησιμοποιήθηκαν ομοιώματα, τα οποία στη φάση της υπερθερμίας υπέδειξαν τις περιοχές εστίασης της ενέργειας για την εκάστοτε συχνότητα ακτινοβολίας, ενώ στη φάση της μικροκυματικής ραδιομετρίας βοήθησαν στη μελέτη της θερμοκρασιακής διακριτικής ικανότητας του συστήματος. Η μέθοδος της μικροκυματικής ραδιομετρίας χρησιμοποιήθηκε για την παρακολούθηση των μεταβολών της θερμοκρασίας της ακτινοβολούμενης περιοχής κατά τη διάρκεια των συνεδριών της υπερθερμίας. Επίσης, κατά τη διάρκεια των πειραμάτων πραγματοποιήθηκαν μετρήσεις με στρώματα προσαρμογής από διηλεκτρικά υλικά, τα οποία τοποθετήθηκαν γύρω από το αντικείμενο ενδιαφέροντος και βοήθησαν στην πληρέστερη κατανόηση της επίδρασης της παρουσίας τους στις ιδιότητες εστίασης του συστήματος και στην επιβεβαίωση των αντίστοιχων θεωρητικών αποτελεσμάτων.
The application of hyperthermia process has been widely used in clinical research and efforts are being made for its implementation in clinical practice, as many researchers have used this method as an adjunct treatment procedure for cancer. During the past two decades, a great deal of research has been carried out, with the aim of developing effective techniques for hyperthermia treatment, primarily using RF, microwave and ultrasound energy. A similar effort is carried out in the Laboratory of Microwaves and Fiber Optics (MFOL), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), where a proposed hyperthermia system has been designed and constructed. A system for deep brain hyperthermia treatment, designed to also provide passive measurements of temperature and/or conductivity variations inside the human body, is presented in the present PhD thesis. The proposed system comprises both therapeutic and diagnostic modules, operating in a totally contactless way, based on the use of an ellipsoidal beamformer to achieve focusing on the areas under treatment and monitoring. The radiometry monitoring module, the Three Dimensional Passive Microwave Radiometry Imaging System (MiRaIS), has been studied, designed and constructed in the framework of a previous PhD thesis in the same laboratory of MFOL. In the present thesis, the proposed system is theoretically and experimentally studied. The operation principal is based on the use of an ellipsoidal conductive wall cavity for focusing the emitted radiation on the tissues that should accept treatment. The ellipsoidal cavity, which was constructed and used in the experimentation procedure, is newly developed and improves the system’s ergonomics retaining at the same time the focusing properties of the prototype system. In the framework of the present work, theoretical modeling and experimentation of the proposed system is carried out in order to examine and improve its focusing attributes. In the theoretical study, three setups are investigated for the improvement of the system’s focusing properties (e.g. penetration depth of the electromagnetic field, spatial sensitivity) using dielectric materials. The research is carried out with the use of a commercially available software tool, XFdtd (Remcom Inc.). The materials are placed inside the ellipsoidal or used as matching layers around the head model for the achievement of a stepped change of the refraction index on the air-human head model interface. The results revealed the possible advantages of using matching dielectric materials, as improvement on the focusing properties of the system is clearly observed, depending on the setup used, the position of the head model inside the system and the operating frequency. The experiments were performed inside an anechoic chamber providing maximum accuracy by avoiding all possible EMC/EMI issues. Along with the hyperthermia experiments, the implementation of the microwave radiometry process was also tested with the proposed system. Microwave radiometry could provide the temperature monitoring of the radiated area during the hyperthermia sessions. In the experimental procedures water phantoms were used, which during hyperthermia indicated the energy absorbing areas at the irradiation frequency, while during microwave radiometry revealed the system’s temperature sensitivity. Also, measurements were conducted using dielectric matching layers, placed around the medium of interest, in order to fully understand the effect of those materials on the system’s focusing properties as well as to confirm the respective theoretical results. Taking into consideration the present study and the advantage of the non invasive character of the proposed brain hyperthermia system, it is concluded that further research is required in order to explore its potentials at becoming a part of the standard treatment protocol of brain malignancy in the future.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering
This research sought to address the influence posed by the pit wall stability and instability on underground planning and design when transitioning from open pit to underground. Conventionally, empirical methods are used and they sometimes lack consideration of rock mass behaviour, groundwater effects, structures as well as geological considerations. This can potentially result in massive failures of pit slopes and subsequent loss of infrastructure, excavations, loss of machinery and human lives. It was against this background that this research sought to reduce mining exposure to the above mentioned hazards. In line with the aims and objectives of the study, this research investigated stress changes around the pit slopes with progression of mining and also the influence of geological and geotechnical conditions on mine planning. This was done so as to determine the zone of geotechnical influence from which planning of the underground mine would be done. Elastic 3D numerical modelling approach was used to determine the expected underground back break and its influence on the underground structure, pit slopes as well as the primary access. Different Factor of Safety shells were modelled, so that the corresponding zone of influence for each Factor of Safety could be correlated to the mine design. The results suggested that a Factor of Safety of two was ideal for this research for underground infrastructure to be outside the zone of geotechnical influence from start to finish of mining the first slice until the last fourth slice of the sublevel caving. This approach yield better projections of rock mass and slope behaviour since it considers a broad range of parameters that include rock mass strength properties, geology, geo-mechanical parameters, groundwater and rock behaviour.
NG (2020)