To see the other types of publications on this topic, follow the link: 2D arrays.
Dissertations / Theses on the topic '2D arrays'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic '2D arrays.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Varum, Tiago Miguel Valente. "Nonuniform 2D microstrip antenna arrays for wireless applications." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17373.
Full textAbstract:
Doutoramento em Engenharia Electrotécnica<br>Wireless communications have undergone over the last decades a tremendous
progress as a consequence of the exponential growth in demand for
mobile devices, and nowadays are more and more involved in people's lives.
This presence is re ected through the use of a large number of applications
of which they become increasingly dependent on.
The antenna, in its most di erent forms, are crucial elements in the establishment
this type of communication. Each application involves a number
of speci c characteristics, whereby, the improvement of wireless communications
is related to the appropriateness of the used antenna.
Many applications require antennas with radiation pattern with its particular
shapes (in terms of beamwidth, side lobes levels, direction, etc ..), static or
dynamic (adaptive antennas), involving in most cases the use antenna arrays
to meet to such constraints.
In this thesis, a number of techniques to synthesize antennas consisting of
planar arrays with nonuniform excitation of their elements, are addressed. A
group of the direction of arrival and beamforming estimation algorithms are
also presented and analyzed, in order to enable their application in adaptive
antenna array with dynamic beamforming. A vast and diversi ed set of arrays
with di erent radiation requirements, and for di erent applications were
developed. These arrays have great applicability in current research topics in
antennas, such as vehicle communications, Wi-Fi in sports venues and smart
antennas.<br>As comunicações sem os têm sofrido, ao longo das ultimas décadas, um
enorme progresso em consequência do aumento exponencial da procura de
dispositivos móveis, estando hoje em dia cada vez mais presentes na vida
das pessoas. Esta presença re ete-se através do uso de um elevado número
de aplicações das quais se tornam cada vez mais dependentes.
As antenas, nas suas mais diversi cadas formas, são elementos cruciais no
estabelecimento deste tipo de comunicações. Cada aplicação envolve um
conjunto de características especí cas, pelo que a melhoria das comunica
ções sem os está relacionada com a adequação da antena usada.
Muitas aplicações necessitam de antenas com diagramas de radiação com
formatos próprios (em termos de larguras de feixe, níveis de lobos secund
ários, direção, etc..), sejam eles estáticos ou dinâmicos (antenas adaptativas),
implicando na maioria dos casos o uso de agregados de antenas
para fazer face a tais condições.
Nesta tese são abordadas várias técnicas de desenho de antenas constituídas
por agregados planares, com alimentação não uniforme dos seus elementos.
Um conjunto de algoritmos de estimação dos ângulos de chegada e
de formação de feixe são também apresentados e analisados com vista à
sua aplicação em agregados de antenas adaptativas, com formação de feixe
dinâmico. Um vasto e diversi cado conjunto de agregados com diferentes
requisitos de radiação, destinados a diferentes aplicações foram desenvolvidos.
Estes agregados têm grande aplicabilidade nos atuais tópicos de investiga
ção em antenas, tais como as comunicações veiculares, Wi-Fi em espaços
desportivos e smart antenas.
2
Dziewierz, Jerzy. "2D ultrasonic phased arrays for quantitative characterisation of complex defects." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26012.
Full textAbstract:
Ultrasonic inspection can be consideredas one of many ways the technical system - installation or vehicle - can be made economical and safe. Contemporary ultrasonic systems are capable of detecting a wide variety of mechanical defects and flaws that may or may not affect the operation of a given product. Ultrasonic testing techniques are widely accepted for quality control and material testing. Moreover, the technology is proven, well-understood and widely used. Upon detecting a flaw, a decision has to be made to ensure the component is fit for the purpose: is the flaw acceptable or is repair of the given part or its replacement? Here, 2D ultrasonic phased arrays hold promise to quickly deliver detailed, 3D resolved information about the extent and nature of the flaw. This information can then be used to develop and justify the technical and economic decision concerning the existing state of the product. In effect, an opportunity exists for significant cost savings by using ultrasonic 2D phased array systems for defect characterisation. The interest of the work is to establish a process of designing and manufacturing of piezoelectric, 2D phased array ultrasound probes for application in non-destructive evaluation of materials. Furthermore, implementation of practical signal processing method is investigated. In the first part of the work the sensor mechanical and electrical design is addressed. The properties of piezoelectric ceramic composite materials are studied. Detailed numerical models have been used to analyse conditions required for crafting materials of desirable properties. A novel technique has been demonstrated that allows design of well-behaved triangular cut piezoelectric composite. Built into a single array element (of hexagonal shape by taking 6 triangular pillars) this new composite exhibits properties comparable to a reference rectangular composite (sensitivity of 0.60nm/V for hexagonal, 0.62nm/V for square; and inter-element crosstalk of -21.2dB for hexagonal and -21.9dB for square element). This composite then allows building of compact, dense-layout 2D phased array transducers with hexagonal or sparse element layout. The benefits of hexagonal element layout over classic, rectangular layout have been analysed theoretically and showed to be beneficial. Importantly, using hexagonal elements enables increasing the aperture of individual array elements by approximately 10% without the corresponding drop in acceptance angle. This in turn allows a commensurable rise in the sensitivity of the sensor or alternatively, reduction in array element count for a given overall array aperture by over 20% without the corresponding drop in the image quality measurements/levels. In the second part of the work, the problem of high output impedance of the miniature ultrasonic sensor is addressed by means of an in-probe miniature signal conditioning circuit. This improved the response amplitude of the element by 36dB and shortened its impulse response by a factor of 1.6. The novelty and practical benefit in this case lies in the fact that no high power components are needed in the probe body. In the third part of this work, an emerging General-Purpose Graphics Processing Unit (GPGPU) computer architecture is considered for the opportunities it offers to rethink the implementation of algorithms typically used in ultrasonic signal processing. Single-way beamforming, and two-way TFM and PCF beamforming have been developed for execution on the new platform, and show increase in performance of over 930 times compared to CPU processor. This software platform has been further enhanced by a new approach to solving the refracted ray Time of Flight problem in a way that is particularly well suited for this architecture. This resulted in a further increase of performance, i.e. 56x over the best published result found in the literature. The unprecedented performance and low cost of this new approach enables industrial deployment of advanced beamforming methods, as well as building of practical CAD tools for engineering and education.
3
Diarra, Bakary. "Study and optimization of 2D matrix arrays for 3D ultrasound imaging." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10165/document.
Full textAbstract:
L’imagerie échographique en trois dimensions (3D) est une modalité d’imagerie médicale en plein développement. En plus de ses nombreux avantages (faible cout, absence de rayonnement ionisant, portabilité) elle permet de représenter les structures anatomiques dansleur forme réelle qui est toujours 3D. Les sondes à balayage mécaniques, relativement lentes, tendent à être remplacées par des sondes bidimensionnelles ou matricielles qui sont unprolongement dans les deux directions, latérale et azimutale, de la sonde classique 1D. Cetagencement 2D permet un dépointage du faisceau ultrasonore et donc un balayage 3D del’espace. Habituellement, les éléments piézoélectriques d’une sonde 2D sont alignés sur unegrille et régulièrement espacés d’une distance (en anglais le « pitch ») soumise à la loi del’échantillonnage spatial (distance inter-élément inférieure à la demi-longueur d’onde) pour limiter l’impact des lobes de réseau. Cette contrainte physique conduit à une multitude d’éléments de petite taille. L’équivalent en 2D d’une sonde 1D de 128 éléments contient128x128=16 384 éléments. La connexion d’un nombre d’éléments aussi élevé constitue unvéritable défi technique puisque le nombre de canaux dans un échographe actuel n’excède querarement les 256. Les solutions proposées pour contrôler ce type de sonde mettent en oeuvredu multiplexage ou des techniques de réduction du nombre d’éléments, généralement baséessur une sélection aléatoire de ces éléments (« sparse array »). Ces méthodes souffrent dufaible rapport signal à bruit du à la perte d’énergie qui leur est inhérente. Pour limiter cespertes de performances, l’optimisation reste la solution la plus adaptée. La première contribution de cette thèse est une extension du « sparse array » combinéeavec une méthode d’optimisation basée sur l’algorithme de recuit simulé. Cette optimisation permet de réduire le nombre nécessaire d’éléments à connecter en fonction des caractéristiques attendues du faisceau ultrasonore et de limiter la perte d’énergie comparée à la sonde complète de base. La deuxième contribution est une approche complètement nouvelle consistant à adopter un positionnement hors grille des éléments de la sonde matricielle permettant de supprimer les lobes de réseau et de s’affranchir de la condition d’échantillonnage spatial. Cette nouvelles tratégie permet d’utiliser des éléments de taille plus grande conduisant ainsi à un nombre d’éléments nécessaires beaucoup plus faible pour une même surface de sonde. La surface active de la sonde est maximisée, ce qui se traduit par une énergie plus importante et donc unemeilleure sensibilité. Elle permet également de balayer un angle de vue plus important, leslobes de réseau étant très faibles par rapport au lobe principal. Le choix aléatoire de la position des éléments et de leur apodization (ou pondération) reste optimisé par le recuit simulé.Les méthodes proposées sont systématiquement comparées avec la sonde complète dansle cadre de simulations numériques dans des conditions réalistes. Ces simulations démontrent un réel potentiel pour l’imagerie 3D des techniques développées. Une sonde 2D de 8x24=192 éléments a été construite par Vermon (Vermon SA, ToursFrance) pour tester les méthodes de sélection des éléments développées dans un cadreexpérimental. La comparaison entre les simulations et les résultats expérimentaux permettentde valider les méthodes proposées et de prouver leur faisabilité<br>3D Ultrasound imaging is a fast-growing medical imaging modality. In addition to its numerous advantages (low cost, non-ionizing beam, portability) it allows to represent the anatomical structures in their natural form that is always three-dimensional. The relativelyslow mechanical scanning probes tend to be replaced by two-dimensional matrix arrays that are an extension in both lateral and elevation directions of the conventional 1D probe. This2D positioning of the elements allows the ultrasonic beam steering in the whole space. Usually, the piezoelectric elements of a 2D array probe are aligned on a regular grid and spaced out of a distance (the pitch) subject to the space sampling law (inter-element distancemust be shorter than a mid-wavelength) to limit the impact of grating lobes. This physical constraint leads to a multitude of small elements. The equivalent in 2D of a 1D probe of 128elements contains 128x128 = 16,384 elements. Connecting such a high number of elements is a real technical challenge as the number of channels in current ultrasound scanners rarely exceeds 256. The proposed solutions to control this type of probe implement multiplexing or elements number reduction techniques, generally using random selection approaches (« spars earray »). These methods suffer from low signal to noise ratio due to the energy loss linked to the small number of active elements. In order to limit the loss of performance, optimization remains the best solution. The first contribution of this thesis is an extension of the « sparse array » technique combined with an optimization method based on the simulated annealing algorithm. The proposed optimization reduces the required active element number according to the expected characteristics of the ultrasound beam and permits limiting the energy loss compared to the initial dense array probe.The second contribution is a completely new approach adopting a non-grid positioningof the elements to remove the grating lobes and to overstep the spatial sampling constraint. This new strategy allows the use of larger elements leading to a small number of necessaryelements for the same probe surface. The active surface of the array is maximized, whichresults in a greater output energy and thus a higher sensitivity. It also allows a greater scansector as the grating lobes are very small relative to the main lobe. The random choice of the position of the elements and their apodization (or weighting coefficient) is optimized by the simulated annealing.The proposed methods are systematically compared to the dense array by performing simulations under realistic conditions. These simulations show a real potential of the developed techniques for 3D imaging.A 2D probe of 8x24 = 192 elements was manufactured by Vermon (Vermon SA, Tours,France) to test the proposed methods in an experimental setting. The comparison between simulation and experimental results validate the proposed methods and prove their feasibility<br>L'ecografia 3D è una modalità di imaging medicale in rapida crescita. Oltre ai vantaggiin termini di prezzo basso, fascio non ionizzante, portabilità, essa permette di rappresentare le strutture anatomiche nella loro forma naturale, che è sempre tridimensionale. Le sonde ascansione meccanica, relativamente lente, tendono ad essere sostituite da quelle bidimensionali che sono una estensione in entrambe le direzioni laterale ed azimutale dellasonda convenzionale 1D. Questo posizionamento 2D degli elementi permette l'orientamentodel fascio ultrasonico in tutto lo spazio. Solitamente, gli elementi piezoelettrici di una sondamatriciale 2D sono allineati su una griglia regolare e separati da una distanza (detta “pitch”) sottoposta alla legge del campionamento spaziale (la distanza inter-elemento deve esseremeno della metà della lunghezza d'onda) per limitare l'impatto dei lobi di rete. Questo vincolo fisico porta ad una moltitudine di piccoli elementi. L'equivalente di una sonda 1D di128 elementi contiene 128x128 = 16.384 elementi in 2D. Il collegamento di un così grandenumero di elementi è una vera sfida tecnica, considerando che il numero di canali negliecografi attuali supera raramente 256. Le soluzioni proposte per controllare questo tipo disonda implementano le tecniche di multiplazione o la riduzione del numero di elementi, utilizzando un metodo di selezione casuale (« sparse array »). Questi metodi soffrono di unbasso rapporto segnale-rumore dovuto alla perdita di energia. Per limitare la perdita di prestazioni, l’ottimizzazione rimane la soluzione migliore. Il primo contributo di questa tesi è un’estensione del metodo dello « sparse array » combinato con un metodo di ottimizzazione basato sull'algoritmo del simulated annealing. Questa ottimizzazione riduce il numero degli elementi attivi richiesto secondo le caratteristiche attese del fascio di ultrasuoni e permette di limitare la perdita di energia.Il secondo contributo è un approccio completamente nuovo, che propone di adottare un posizionamento fuori-griglia degli elementi per rimuovere i lobi secondari e per scavalcare il vincolo del campionamento spaziale. Questa nuova strategia permette l'uso di elementi piùgrandi, riducendo così il numero di elementi necessari per la stessa superficie della sonda. La superficie attiva della sonda è massimizzata, questo si traduce in una maggiore energia equindi una maggiore sensibilità. Questo permette inoltre la scansione di un più grande settore,in quanto i lobi secondari sono molto piccoli rispetto al lobo principale. La scelta casualedella posizione degli elementi e la loro apodizzazione viene ottimizzata dal simulate dannealing. I metodi proposti sono stati sistematicamente confrontati con la sonda completaeseguendo simulazioni in condizioni realistiche. Le simulazioni mostrano un reale potenzialedelle tecniche sviluppate per l'imaging 3D.Una sonda 2D di 8x24 = 192 elementi è stata fabbricata da Vermon (Vermon SA, ToursFrance) per testare i metodi proposti in un ambiente sperimentale. Il confronto tra lesimulazioni e i risultati sperimentali ha permesso di convalidare i metodi proposti edimostrare la loro fattibilità
4
Labuhn, Henning. "Rydberg excitation dynamics and correlations in arbitrary 2D arrays of single atoms." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLO002/document.
Full textAbstract:
Dans cette thèse, nous mesurons la dynamique cohérente et les corrélations spatiales des excitations Rydberg dans des matrices 2D d’atomes uniques.Nous utilisons un modulateur spatial de lumière pour façonner la phase spatiale d'un faisceau laser de piégeage optique avant de le focaliser avec une lentille asphérique de grande ouverture numérique. En imprimant une phase appropriée sur le faisceau laser, nous pouvons créer des matrices 2D de pièges optiques, de forme arbitraire et facilement reconfigurables, avec jusqu'à 100 pièges séparées de quelques micromètres. Les pièges sont chargés à partir d'un nuage d'atomes froids de 87Rb, et due aux collisions assistées par la lumière, au plus un seul atome peut être présent dans chaque piège en même temps. Une caméra CCD sensible permet en temps réel l'imagerie de la fluorescence atomique émanant des pièges, ce qui nous permet de détecter individuellement la présence d'un atome dans chaque piège avec une précision presque parfaite.Pour créer des interactions importantes entre les atomes uniques, nous les excitons vers des états de Rydberg, qui sont des états électroniques avec un nombre quantique principal élevé.Un faisceau supplémentaire d'adressage permet la manipulation individuelle d'un atome sélectionné dans la matrice.La connaissance précise, de la fois de la matrice des atomes préparé et des positions des excitations Rydberg, nous a permis de mesurer l’augmentation collective de la couplage optique dans le régime de blocage Rydberg, où une seule excitation est partagée de façon symétrique entre tous les atomes de la matrice.Dans le régime où l'interaction ne s’étend que sur quelques sites, nous avons mesuré la dynamique et les corrélations spatiales des excitations Rydberg, dans des matrices d’atomes à une et deux dimensions. La comparaison à une simulation numérique d'un modèle d'Ising quantique d'un système de spin-1/2 montre un accord exceptionnel pour les matrices où l'effet de l'anisotropie de l’interaction Rydberg-Rydberg est faible. Les résultats obtenus démontrent que les atomes Rydberg uniques sont une plate-forme bien adaptée pour la simulation quantique des systèmes de spin<br>In this thesis, we measure the coherent dynamics and the pair correlations of Rydberg excitations in two-dimensional arrays of single atoms.We use a spatial light modulator to shape the spatial phase of a single optical dipole trap beam before focusing it with a high numerical-aperture aspheric lens. By imprinting an appropriate phase pattern on the trap beam, we can create arbitrarily shaped and easily reconfigurable 2D arrays of high-quality single-atom traps, with trap-spacings of a few micrometers for up to 100 traps. The traps are loaded from a cloud of cold 87Rb atoms, and due to fast light-assisted collisions of atoms inside the traps, at most one atom can be present in each trap at the same time. A sensitive CCD camera allows the real-time, site-resolved imaging of the atomic fluorescence from the traps, enabling us to detect the presence of an atom in each individual trap with almost perfect accuracy.In order to induce strong, tunable interactions between the atoms in the array, we coherently laser-excite them to Rydberg states, which are electronic states with a high principal quantum number.An additional addressing beam allows the individual manipulation of an atom at a selected site in the array.The precise knowledge of both the prepared atom array and the positions of the Rydberg excitations allowed us to measure the collective enhancement of the optical coupling strength in the regime of full Rydberg blockade, where one single excitation is shared symmetrically among all atoms in the array.In the regime where the strong interaction only extends over a few sites, we measured the dynamics and the spatial pair-correlations of Rydberg excitations, in one- and two-dimensional atom arrays. The comparison to a numerical simulation of a quantum Ising model of a spin-1/2 system shows an exceptional agreement for trap geometries where the effect of the anisotropy of the Rydberg-Rydberg interaction is small. The obtained results demonstrate that single Rydberg atoms are a suitable platform for the quantum simulation of spin systems
5
Ko, Hyunhyub. "Design of hybrid 2D and 3D nanostructured arrays for electronic and sensing applications." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22606.
Full textAbstract:
This dissertation presents the design of organic/inorganic hybrid 2D and 3D nanostructured arrays via controlled assembly of nanoscale building blocks. Two representative nanoscale building blocks such as carbon nanotubes (one-dimension) and metal nanoparticles (zero-dimension) are the core materials for the study of solution-based assembly of nanostructured arrays. The electrical, mechanical, and optical properties of the assembled nanostructure arrays have been investigated for future device applications. We successfully demonstrated the prospective use of assembled nanostructure arrays for electronic and sensing applications by designing flexible carbon nanotube nanomembranes as mechanical sensors, highly-oriented carbon nanotubes arrays for thin-film transistors, and gold nanoparticle arrays for SERS chemical sensors.
In first section, we fabricated highly ordered carbon nanotube (CNT) arrays by tilted drop-casting or dip-coating of CNT solution on silicon substrates functionalized with micropatterned self-assembled monolayers. We further exploited the electronic performance of thin-film transistors based on highly-oriented, densely packed CNT micropatterns and showed that the carrier mobility is largely improved compared to randomly oriented CNTs. The prospective use of Raman-active CNTs for potential mechanical sensors has been investigated by studying the mechano-optical properties of flexible carbon nanotube nanomembranes, which contain freely-suspended carbon nanotube array encapsulated into ultrathin (<50 nm) layer-by-layer (LbL) polymer multilayers.
In second section, we fabricated 3D nano-canal arrays of porous alumina membranes decorated with gold nanoparticles for prospective SERS sensors. We showed extraordinary SERS enhancement and suggested that the high performance is associated with the combined effects of Raman-active hot spots of nanoparticle aggregates and the optical waveguide properties of nano-canals. We demonstrated the ability of this SERS substrate for trace level sensing of nitroaromatic explosives by detecting down to 100 zeptogram (~330 molecules) of DNT.
6
Longo, Danilo. "Engineering topological states in arrays of magnetic molecules in interaction with a 2D superconductor." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS224.
Full textAbstract:
Des études récentes ont prédit que l'interaction entre un supraconducteur 2D et du magnétisme local pourrait induire une supraconductivité topologique accompagnée d'états de bord de type Majorana. Pour relever ce défi, nous avons étudié un système basé sur l’interaction entre des auto-assemblages d’aimants moléculaires, tels que les phtalocyanines de manganèse (MnPcs), sur des films minces de plomb (1 et 3 monocouches) épitaxiés sur des surfaces de Si(111) qui montrent une supraconductivité 2D. Nos expériences de Microscopie à effet tunnel (STM) ont révélé que l'adsorption d’une petite quantité de MnPcs sur la monocouche de Pb est accompagnée d’un très faible transfert de charge qui induit une transition de phase structurale macroscopique de la surface elle-même. Les expériences de Spectroscopie à effet tunnel (STS) à 300 mK sur des îlots tricouches de Pb/Si(111) ont montré la présence d'effets non triviaux responsables de la fluctuation spatiale de l’amplitude des pics de cohérence sur des longueurs bien inférieures à la longueur de cohérence supraconductrice. De plus, contrairement à ce qui a été montré sur des monocristaux de plomb, les expériences STS suggèrent que les MnPcs isolées sur des îlots tricouches de plomb se trouvent toujours dans un régime d'interaction faible avec le substrat. L’ensemble de nos résultats, ainsi que l’observation d’une signature spectroscopique localisée sur le bord d’un domaine auto-organisé de MnPcs ouvrent la voie à de futures études sur l’ingénierie des phases topologiques supraconductrices<br>Recent studies predicted that the interaction between a 2D superconductor and local magnetism could induce topological superconductivity accompanied by Majorana edge states. To address this challenge, we have studied a system based on the interaction between self-assemblies of molecular magnets, i.e. manganese phthalocyanines (MnPcs), and thin films of lead (1 and 3 monolayers) grown on Si(111) surfaces that show 2D superconductivity.Our Scanning Tunneling Microscopy (STM) experiments revealed that, adsorption of a tiny amount of MnPcs on a Pb monolayer is accompanied by a very small charge transfer inducing a macroscopic structural phase transition of the surface itself. Scanning Tunneling Spectroscopy (STS) experiments at 300mK on 3 monolayers thick islands of Pb/Si(111) showed the presence of non-trivial effects responsible for the spatial fluctuation of the coherence peaks amplitude on a length scale much smaller than the superconducting coherence length. Furthermore, contrary to what shown on bulk Pb substrates, STS experiments strongly suggest that isolated MnPcs are always found in a weak interaction regime with the 3 monolayers thick Pb islands. Our results together with the observation of an in-gap spectroscopic feature located at the edge of a self-assembled 2D domain of MnPcs pave the route to future studies for the engineering of superconducting topological phases
7
Beyer, Griffin Joseph. "Large Area 2D Electronic Molecular Sensor Arrays via Photonic Annealing of Amorphous Sputtered Mos2." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1582624657416084.
Full text
8
Afridi, Muhammad Zeeshan, Muhammad Umer, and Daniyal Razi. "Design and simulation of beam steering for 1D and 2D phased antenna arrays using ADS." Thesis, Linnéuniversitetet, Institutionen för datavetenskap, fysik och matematik, DFM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-22566.
Full textAbstract:
Phased arrays eliminate the problems of mechanical steering by using fast and reliable electronic components for steering the main beam. Modeling and simulation of beam steering for 1D and 2D arrays is the aspect that is considered in this thesis. A 1D array with 4 elements and a 2D array with 16 elements are studied in the X-band (8-12 GHz). The RF front-end of a phased array radar is modeled by means of ADS Momentum (Advanced design system).
9
Ullal, Chaitanya K. (Chaitanya Kishore). "2D and 3D periodic templates through holographic interference lithography : photonic and phononic crystals and biomimetic microlens arrays." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33404.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.<br>Includes bibliographical references (leaves 121-133).<br>In this thesis a simple technique for controlling structure via holographic interference lithography was established and implemented. Access to various space groups including such important structures as the level set approximations to the Diamond, the Schwartz P structure, the FCC, and the non centrosymmetric Gyroid structures were demonstrated. The ability to make 3D structures over a large area, with low defect densities and periodicities on the sub/i scale opens a whole range of opportunities including such diverse areas as photonic crystals, phononic crystals, drug delivery, microtrusses, tissue scaffolds, microfluidics and colloidal crystallization. A correlation between structure and photonic band gap properties was established by systematically exploring the 11 FCC space groups. This resulted in a technique to search for photonic band gap structures. It was found that a fundamental connectivity caused by simple Fourier elements tended to support gaps. 2-3, 5-6 and 8-9 gaps were opened in the f.c.c lattices. The F-RD and 216 structures were newly shown to have complete band gaps. Two of the three previously established champion photonic crystal structures, viz. the Diamond and the Gyroid presented practical fabrication challenges, approximations to these structures were proposed.<br>(cont.) A scalable P structure and the 3-FCC structure were fabricated by single and multiple exposure techniques. Both negative and positive tone photoresist systems were demonstrated. Line defects were written into the negative tone system using two-photon lithography. The single crystalline, porous nature of the structures was exploited to examine the possibility for their use as hypersonic phononic crystals and microfluidic microlenses. Two dimensional single crystalline patterns were created using interference lithography. Their phononic band structure was probed by Brillioun light scattering to yield a phononic band diagram, which clearly demonstrates the effect of periodicity on the phononic density of states. The ability to control the density of states at these length scales holds the potential for control over thermal properties. The two dimensional structures fabricated in negative photoresist were also tested as microlenses with the integrated pores acting as microfluidic channels. This combination resulted in a structure reminiscent to that of the biological species ophiocoma wendtii.<br>by Chaitanya K. Ullal.<br>Ph.D.
10
Roux, Emmanuel. "2D sparse array optimization and operating strategy for real-time 3D ultrasound imaging." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1255/document.
Full textAbstract:
Aujourd'hui l'utilisation de l'échographie 3D en cardiologie est limitée car l'imagerie de la totalité du myocarde sur un cycle cardiaque, sans apnée, reste un défi technologique. Une solution consiste à réduire le nombre de capteurs dans les sondes échographiques matricielles afin d'alléger le procédé d'acquisition: ces sondes sont dites parcimonieuses. Le but de cette thèse est de proposer les meilleures dispositions d'un nombre réduit de capteurs piézo-électriques répartis sur la surface active de la sonde afin d'optimiser leur capacité à produire des images homogènes en termes de contraste et résolution dans tout le volume d'intérêt. Ce travail présente l'intégration de simulations acoustiques réalistes élaborées au sein d'un processus d'optimisation stochastique (algorithme de recuit simulé). La structure proposée pour le design des sondes parcimonieuse est suffisamment générale pour être appliquée aux sondes régulières (éléments actifs disposés selon une grille) et non-régulières (positionnement arbitraire des éléments actifs). L'introduction d'une fonction d'énergie innovante permet de sculpter en 3D le diagramme optimal de rayonnement de la sonde. Les résultats de sondes optimisées obtenues possèdent 128, 192 ou 256 éléments pour favoriser leur compatibilité avec les échographes commercialisés à ce jour, ce qui permettrait de déployer l'échographie 3D à moindre coût et à très large échelle<br>Today, the use of 3D ultrasound imaging in cardiology is limited because imaging the entire myocardium on a single heartbeat, without apnea, remains a technological challenge. A solution consists in reducing the number of active elements in the 2D ultrasound probes to lighten the acquisition process: this approach leads to sparse arrays. The aim of this thesis is to propose the best configuration of a given number of active elements distributed on the probe active surface in order to maximize their ability to produce images with homogeneous contrast and resolution over the entire volume of interest. This work presents the integration of realistic acoustic simulations performed in a stochastic optimization process (simulated annealing algorithm). The proposed sparse array design framework is general enough to be applied on both on-grid (active elements located on a regular grid) and non-grid (arbitrary positioning of the active elements) arrays. The introduction of an innovative energy function sculpts the optimal 3D beam pattern radiated by the array. The obtained optimized results have 128, 192 or 256 active elements to help their compatibility with currently commercialized ultrasound scanners, potentially allowing a large scale development of 3D ultrasound imaging with low cost systems
11
Kiflu, Henok Gidey. "Improved 2D and 3D resistivity surveys using buried electrodes and optimized arrays: The multi-electrode resistivity implant technique (MERIT)." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6524.
Full textAbstract:
This thesis presents a novel resistivity method called Multi-Electrode resistivity technique (MERIT) that is used for high resolution imaging of complex geologic features at depth and near the edges of survey lines. The MERIT electrodes are especially shaped and designed to be self-driven using a robust-direct push technique. Measurements are taken using optimized arrays that are generated using a modified version of the “Compare-R” optimization algorithm. This work focused on both two-dimensional (MERIT2D) and three-dimensional (MERIT3D) applications of the buried array and show the relevance of the additional information gained by the addition of deep electrodes especially in sites with limited survey area. Numerical and laboratory studies are used to test and develop the technique and are later applied to image complex subsurface geologic structures on the field.
The configuration of MERIT arrays brings some additional problems in terms the sensitivity of the deep MERIT arrays to a problem of non-uniqueness, mis-information, geometric error and resolution break between the two layers of electrodes. Multiple vertical resolution characteristic curves (RC curves) are analyzed to study the effect of array type, resistivity contrast, target resistivity and implant depth on the above-mentioned problems. Results show that MERIT measurements taken using standard dipole -dipole and wenner arrays along the surface and deep electrodes will strongly suffer from the problem of non-uniqueness or ambiguity while measurements taken using optimized arrays is suitable for MERIT configuration and will not suffer from any problem of ambiguity or non-uniqueness. Based on our result, a procedural guideline is developed to determine optimal MERIT implant depth and resolution cutoff that can be used for successful field implementation and for controlling misinformation during data interpretation.
Numerical studies involving simple shapes and complex geometries mostly based on actual geological cross-sections from karst environments were used to compare the effectiveness of MERIT2D in terms its high depth resolution and is compared in detail with traditional 2D and 3D surface resistivity methods of equal foot prints. Similar comparison was made between MERIT3D technique and 3D surface resistivity measurements. Results show that both methods achieve high depth resolution compared to their equivalent traditional resistivity methods. Laboratory experiment conducted using a complex analogue model mimicking actual sinkhole structure is used to test MERIT2D. Also laboratory experiment involving a 3D printed plastic cave model mimicking an actual cave was conducted using MERIT3D approach. Both results show the promise of MERIT approach to image and solve complex geological structures or problems.
Finally, the method is applied to collect field data in three case study sites involving complex karst related sinkhole structures and an old landfill site. The result shows the promising capability of the MERIT technique to study challenging geologic conditions with high depth resolution.
12
Pfeifer, Hannes [Verfasser], Oskar [Akademischer Betreuer] Painter, and Stefan [Gutachter] Götzinger. "Silicon optomechanical crystals for arrays - tunability, disorder and 2D designs for low temperature experiments / Hannes Pfeifer ; Gutachter: Stefan Götzinger ; Betreuer: Oskar Painter." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2018. http://d-nb.info/116695112X/34.
Full text
13
Merabet, Lucas. "Etude d’algorithmes de reconstruction ultrasonore dans le domaine de Fourier pour l’imagerie rapide 2D et 3D en contrôle non- destructif." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLET060.
Full textAbstract:
Ce travail de thèse s’intéresse à l’imagerie ultrasonore multi-éléments pour le Contrôle Non-Destructif (CND), et vise à accélérer l’imagerie échographique en 2D et 3D. Les méthodes étudiées s’inspirent des algorithmes de reconstruction dans le domaine de Fourier (f-k) en imagerie sismique. La littérature montre que ces méthodes offrent un avantage numérique par rapport à celles dans le domaine temporel basées sur un principe de focalisation en émission/réception. D’autre part, l’essor des traducteurs multi-éléments a permis d’explorer de nouveaux modes d’émission, comme les ondes planes en imagerie médicale ultra-rapide. Dans cette thèse, on se propose de combiner les algorithmes rapides du domaine f-k avec des émissions planes pour calculer des images aussi rapidement que possible. Ces algorithmes sont adaptés pour traiter des configurations d’inspection usuelles en CND. Une analyse des complexités algorithmiques, des temps de calcul et de la qualité des reconstructions est menée en 2D. La comparaison avec la méthode temporelle Plane Wave Imaging (PWI) démontre un avantage certain pour l’imagerie f-k. Ces avantages sont confirmés en 3D où l’on démontre que cette dernière améliore la qualité d’image tout en réduisant le temps de calcul d’un facteur allant jusqu’à 300 par rapport à PWI. Enfin, la méthode f-k est généralisée à l’imagerie multimodale pour la caractérisation de fissures. La théorie est d’abord présentée, puis on montre qu’il est possible d’améliorer la qualité des reconstructions grâce à un fenêtrage des fréquences spatiales de l’image. Ce filtre spectral élimine des artéfacts d’imagerie liés à des échos de géométrie, améliorant ainsi le contraste des images<br>This research work deals with ultrasound imaging with transducer arrays for Non Destructive Testing (NDT), and aims at speeding up the formation of 2D and 3D images. The methods studied in this manuscript are inspired from reconstruction algorithms in the Fourier frequency-wavenumber (f-k) domain introduced in seismic imaging in the 70’s. The literature shows that f-k methods offer a numerical advantage over the more conventional time-domain focusing algorithms. On the other hand, the rise of transducer arrays has allowed for the exploration of new emission modes, such as plane wave emissions in ultra-fast medical imaging. In this thesis, we propose to combine fast f-k algorithms with plane wave emissions to form 2D and 3D images as fast as possible. These algorithms are adapted to deal with realistic NDT inspection configurations. Analyses of algorithmic complexities, computation times, and image qualities are carried out in 2D, and a comparison with the time-domain Plane Wave Imaging (PWI) shows a clear advantage for f-k methods. This is confirmed in 3D, where we show that Fourier domain algorithms improve image quality while reducing computation times by a factor up to 300 compared to PWI. Finally, the f-k methods are generalized to multi-modal imaging to characterize cracks. The theory, which accounts for mode conversions and reflections at the specimen interfaces, is first presented, and we then demonstrate that it is possible to improve the reconstruction quality thanks to spectral windowing in the image frequency-domain. This spectral filter cancels undesired artifacts caused by interface echoes, and improves the image contrast
14
Tweedie, Andrew. "Spiral 2D array designs for volumetric imaging." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23167.
Full textAbstract:
The use of linear phased arrays in NDE inspections has recently grown, resulting in faster inspection of components. Phased arrays are also used in underwater sonar and biomedical imaging. All applications require 2 dimensional (2D) arrays, capable of volumetric imaging, to further increase scan speed, and to allow tighter focussing on targets. However, 2D arrays have not found widespread use, mainly due to the large number of elements required to implement standard periodic designs. Alternative array configurations that feature a much lower element count offer a more pragmatic solution. This thesis investigates the design of sparse 2D arrays (i.e. using fewer elements than a periodic grid sampled at the Nyquist rate) based on geometric spiral structures, with the aim to reduce the number of array elements, and therefore transmit-receive channels required to meet a given acoustic specification. The aperiodic structure of these array designs is shown to minimise the height of sidelobes, by spatially distributing sidelobe energy, therefore avoiding artefacts in the resulting acoustic image. Furthermore, their mathematically determined position simplifies the layout of the array, and therefore its manufacture. The approach taken was to develop a logarithmic spiral structure, which is shown to minimise peak sidelobe height for a given number of array elements. A series of design rules was created, to allow the array designer to rapidly create sparse array designs to meet an acoustic specification. The acoustic field created by these designs was modelled, and it was shown that they have lower peak sidelobe levels than equivalent random 2D array designs. A 1.5 MHz, 127 element prototype array was then designed and manufactured for NDE inspection on thick section welds, which combined a -31 dB sidelobe floor with the capability for volumetric steering.
15
Yeshchenko, O. A., I. S. Bondarchuk, S. Z. Malynych, G. Chumanov, and I. Luzinov. "Laser-Induced Light Absorption in 2D Silver Nanoparticle Array." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42550.
Full textAbstract:
Nanocomposite comprising planar array of silver nanoparticles in polymer matrix was submitted to Ar laser irradiation at the wavelength of 488 nm. The extinction spectra of the array were measured as a function of the irradiation power density. Two collective surface plasmon modes, namely T and P, associated with particle dipoles parallel and perpendicular to the plane of the layer were identified. The extinction bands of T and P modes exhibit blue spectral shift with the increase of radiation power. P mode band
broadens when laser power increases. The observed effects are explained by heating of the nanocomposite by the intense laser radiation.
16
Buder, Ulrich. "2D-Sensorik für das Monitoring statischer und dynamischer Wandschubspannungsfelder." Düsseldorf VDI-Verl, 2009. http://d-nb.info/994857705/04.
Full text
17
Eberhart, Andreas Bernhard Georg. "Contention-free Scheduling of Communication Induced by Array Operations on 2D Meshes." PDXScholar, 1996. https://pdxscholar.library.pdx.edu/open_access_etds/5077.
Full textAbstract:
Whole array operations and array section operations are important features of many data-parallel languages. Efficient implementation of these operations on distributed- memory multicomputers is critical to the scalability and high-performance of data-parallel programs. This thesis presents an approach for analyzing communication patterns induced by array operations and for using run-time information to schedule the message flow. The distributed, dynamic scheduling algorithms guarantee link-contention-free data transfer and utilize network resources almost optimally. They incur little overhead, which is important in order not to reduce the speedup gained by the parallel execution. The algorithms can be used by compilers for the generation of efficient code for array operations. Implemented in a runtime library, they can derive a schedule depending on parameters passed by the parallel application. Simulation results demonstrate the algorithms' superiority to the asynchronous transfer mode that is commonly used for this type of communication.
18
Pujol, Hadrien. "Antennes microphoniques intelligentes : localisation de sources acoustiques par Deep Learning." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAC025.
Full textAbstract:
Pour ma thèse de doctorat, je propose d’explorer la piste de l’apprentissage supervisé, pour la tâche de localisation de sources acoustiques. Pour ce faire, j’ai développé une nouvelle architecture de réseau de neurones profonds. Mais, pour optimiser les millions de variables d’apprentissages de ce réseau, une base de données d’exemples conséquente est nécessaire. Ainsi, deux approches complémentaires sont proposées pour constituer ces exemples. La première est de réaliser des simulations numériques d’enregistrements microphoniques. La seconde, est de placer une antenne de microphones au centre d’une sphère de haut-parleurs qui permet de spatialiser les sons en 3D, et d’enregistrer directement sur l’antenne de microphones les signaux émis par ce simulateur expérimental d’ondes sonores 3D. Le réseau de neurones a ainsi pu être testé dans différentes conditions, et ses performances ont pu être comparées à celles des algorithmes conventionnels de localisation de sources acoustiques. Il en ressort que cette approche permet une localisation généralement plus précise, mais aussi beaucoup plus rapide que les algorithmes conventionnels de la littérature<br>For my PhD thesis, I propose to explore the path of supervised learning, for the task of locating acoustic sources. To do so, I have developed a new deep neural network architecture. But, to optimize the millions of learning variables of this network, a large database of examples is needed. Thus, two complementary approaches are proposed to constitute these examples. The first is to carry out numerical simulations of microphonic recordings. The second one is to place a microphone antenna in the center of a sphere of loudspeakers which allows to spatialize the sounds in 3D, and to record directly on the microphone antenna the signals emitted by this experimental 3D sound wave simulator. The neural network could thus be tested under different conditions, and its performances could be compared to those of conventional algorithms for locating acoustic sources. The results show that this approach allows a generally more precise localization, but also much faster than conventional algorithms in the literature
19
Maj, Tomasz. "Interconnection of a 2D vertical-cavity surface-emitting laser array to a receiver array via a fiber image guide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/MQ64236.pdf.
Full text
20
Maj, Tomasz. "Interconnection of a 2D vertical-cavity surface-emitting laser array to a receiver array via a fiber image guide." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30260.
Full textAbstract:
Parallel Optical Data Links (PODLs) have the potential to solve interconnection bottlenecks which are currently being experienced in high-speed communication and information processing systems. Such links often require a large number of channels and two-dimensional arrays of active optoelectronic devices are being developed. In order to interconnect these devices, fiber image guide technology consisting of a bundle of several thousand equally spaced optical fibers is being proposed to alleviate the need for dedicated fibers.<br>This thesis examines the implementation of a two-dimensional parallel optical interconnect consisting of an array of Vertical-Cavity Surface-Emitting Lasers (VCSELs), a 1.35m Fiber Image Guide (FIG) and a Metal-Semiconductor-Metal (MSM) receiver array. Coupling issues associated with image guides are analysed and discussed as well as general image guide properties and transmission characteristics. The design, construction and integration aspects of the data link, including optics, electronics and optomechanics are summarised. Characterization results are presented and a transmission rate of 250 Mbit/s per channel is demonstrated with an optical crosstalk of less than -27 dB and a total optical loss of -3dB.
21
Lane, Christopher John Leslie. "The development of a 2D ultrasonic array inspection for single crystal turbine blades." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651312.
Full textAbstract:
The aim of this thesis is to design and evaluate a non-destructive evaluation (NDE) system for the inspection of single crystal turbine blades. Turbine blades are the components within jet-engines that convert the hot, high-pressure gas exiting the combustion stage into mechanical power. During operation, these components are highly stressed and are surrounded by extremely high gas temperatures. As such, there is the potential for defects to initiate in-service. One way to ensure the structural integrity of these engine components is by periodically inspecting them for defects. The ability of the inspection to be performed in situ is highly advantageous, as this eliminates the cost and time delay associated with removing the turbine blades from the engine prior to inspection. A 20 ultrasonic phased array system was chosen for this project, as these systems can perform rapid volumetric inspections whilst being portable enough to be used in situ. Modem turbine blades are manufactured from single crystal nickel-based superalloys for the excellent mechanical properties these materials exhibit at elevated temperatures. However, these materials are elastically anisotropic. The propagation of ultrasonic waves through anisotropic materials is far more complex than the isotropic case. This causes significant difficulties when inspecting anisotropic single crystal components with ultrasonic arrays. Therefore, analytical models are developed to predict the propagation of ultrasonic waves in anisotropic materials. These models are used to correct an ultrasonic imaging algorithm to account for the anisotropic behaviour. To implement the corrected algorithm effectively, the orientation of the crystal in the component under inspection must be known. Therefore, crystallographic orientation methods using 20 ultrasonic arrays are developed and evaluated. The corrected algorithms and crystallographic orientation methods are used to develop an in situ 20 ultrasonic array inspection for a specific high-pressure single crystal turbine blade. The inspection is designed to detect and size cracking in the root section of the turbine blade. The developed inspection system is fully evaluated in a quantitative manner for its defect detection sensitivity and sizing capability.
22
Joshi, Rimesh M. "Analog and Digital Array Processor Realization of a 2D IIR Beam Filter for Wireless Applications." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1326776749.
Full text
23
Webb, Charles T. "Analysis of off-axis enhancded [i.e. enhanced] dynamic wedge dosimetry using a 2D diode array." Muncie, Ind. : Ball State University, 2008. http://cardinalscholar.bsu.edu/374.
Full text
24
Rosencrantz, Frans. "Development of a demo platform on mobile devices for 2D- and 3D-sound processing." Thesis, Uppsala universitet, Elektricitetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-415154.
Full textAbstract:
This thesis project aims for the development of a demonstration platform on mobile devices for testing and demonstrating algorithms for 2D and 3D spatial sound reproduction. The demo system consists of four omnidirectional microphones in a square planar array, an Octo sound card (from Audio Injector), a Raspberry Pi 3B+ (R-Pi) single-board computer and an inertial measurement unit (IMU) located in the center of the array. The microphone array captures sound, which is then digitized, and in turn, transferred to the R-Pi. On the R-Pi, the digitized sound signal is rendered through the directional audio coding (DirAC) algorithm to maintain the spatial properties of the sound. Finally, the digital signal and spatial properties are rendered through Dirac VR to maintain a spatial stereo signal of the recorded environment. The directional audio coding algorithm was initially implemented in Matlab and then ported to C++ since the R-Pi does not support Matlab natively. The ported algorithm was verified on a four-channel in and six-channel out system, processing 400 000 samples at 44 100 kHz. The results show that the C++ DirAC implementation maintained a maximum error of 4.43e-05 or -87 dB compares to the original Matlab implementation. For future research on spatial audio reproduction, a four-microphone smartphone mock-up was constructed based on the same hardware used in the demo system. A software interface was also implemented for transferring the microphone recordings and the orientation of the mock-up to Matlab.
25
Genua, Maria. "Combinatorial surface-based electronic tongue development : Analytical applications and conception of 2D and 3D biomimetic surfaces." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI044/document.
Full textAbstract:
L'objectif de cette thèse est le développement d'une langue électronique avec une méthode simplifiée d'obtention de récepteurs à réactivité croisée. Ces récepteurs sont préparés par une approche combinatoire novatrice qui consiste au mélange et à l'auto-assemblage de deux disaccharides. Le couplage de ces récepteurs avec un système de détection d'imagerie par résonance des plasmons de surface nous a permis de réaliser une langue électronique capable de différencier des échantillons de différentes complexités, y compris des protéines pures et des mélanges complexes. Cela se fait grâce aux profils et images d'évolution continue, assimilés à des « empreintes digitales » des échantillons. D'un autre côté, ce système peut être utilisé en tant qu'outil pour la conception de surfaces biomimétiques 2D et 3D. Ce système est prometteur pour l'étude des interactions sucre-protéine et pour la préparation de nanovecteurs biomimétiques qui ciblent de façon spécifique des protéines d'intérêt<br>L'objectif de cette thèse est le développement d'une langue électronique avec une méthode simplifiée d'obtention de récepteurs à réactivité croisée. Ces récepteurs sont préparés par une approche combinatoire novatrice qui consiste au mélange et à l'auto-assemblage de deux disaccharides. Le couplage de ces récepteurs avec un système de détection d'imagerie par résonance des plasmons de surface nous a permis de réaliser une langue électronique capable de différencier des échantillons de différentes complexités, y compris des protéines pures et des mélanges complexes. Cela se fait grâce aux profils et images d'évolution continue, assimilés à des « empreintes digitales » des échantillons. D'un autre côté, ce système peut être utilisé en tant qu'outil pour la conception de surfaces biomimétiques 2D et 3D. Ce système est prometteur pour l'étude des interactions sucre-protéine et pour la préparation de nanovecteurs biomimétiques qui ciblent de façon spécifique des protéines d'intérêt
26
Boubekeur, Ahmed. "Conception d'architectures intégrées de traitement d'image de bas niveau." Phd thesis, Grenoble INPG, 1992. http://tel.archives-ouvertes.fr/tel-00341394.
Full text
27
Oukacine, Marina. "Étude expérimentale et numérique des écoulements à surface libre en présence d'obstacles émergés et faiblement submergés." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC1019.
Full textAbstract:
Selon le Ministère de la Transition Écologique et Solidaire, les inondations sont le principal risque naturel en France. Du fait du dérèglement climatique, les inondations extrêmes deviendront plus fréquentes. Les personnes et les biens, i.e. habitations, installations industrielles, doivent donc être protégés contre ces crues pour lesquelles les données sont très rares voire inexistantes. Lorsque l’on passe d’une crue faible à une crue extrême, l’extension spatiale de l’inondation en lit majeur varie fortement. La nature des obstacles rencontrés varie : végétation basse, arbres, habitations... Ces obstacles ou macro-rugosités hydrauliques peuvent être émergés, ou faiblement immergés.Le but de ce travail de thèse est d’analyser les processus physiques dominants associés à des écoulements de crues extrêmes en présence d’obstacles émergés ou faiblement submergés. Cette thèse s’organise en deux parties : une partie expérimentale et une partie numérique.La partie expérimentale porte sur l’exploration, dans un canal de laboratoire, de la structure verticale du profil de vitesse et des effets géométriques liés à la configuration étudiée représentant une plaine d’inondation urbanisée avec des taux d’immersion de (symbole dollar) D/h = à 0,42 ; 0,93 ; 0,98(symbole dollar) et (symbole dollar)1,48(symbole dollar) ((symbole dollar) D(symbole dollar) étant la hauteur d’eau et (symbole dollar) h(symbole dollar) la hauteur de l’obstacle). Des mesures ADV et PIV des vitesses moyennes et des fluctuations turbulentes ont montré que les propriétés de l’écoulement changent notablement selon que les écoulements sont émergés ou faiblement submergés. Les interactions entre le détachement tourbillonnaire, la surface libre, les obstacles et la rugosité de fond sont étudiées.La partie numérique analyse différents types de modélisation classiquement utilisés pour simuler des événements de crue. Le cas expérimental de la première partie de thèse sert de référence.D'abord, un modèle analytique basé sur l’écriture du bilan de quantité de mouvement au niveau d’un volume hydraulique élémentaire permet de considérer différentes modélisations de la résistance globale à l’écoulement d'obstacles en régime uniforme. Un premier modèle simple intègre la résistance à l’écoulement du au frottement de fond et aux obstacles dans un même terme de type « frottement~». Un second modèle décompose en deux parties la résistance à l’écoulement~: un frottement de fond et une résistance due aux obstacles représentée par un terme de traînée. L’obstruction à l’écoulement sera alors représentée par un terme de porosité.L’analyse porte sur la pertinence d’utiliser les coefficients de frottement ou de traînée calibrés pour l’écoulement avec le plus faible débit pour simuler des écoulements à fort débit et en particulier la transition de l’émergence à la submergence des obstacles.Ensuite, les obstacles seront représentés explicitement dans le cadre d’un modèle « Saint-Venant » bidimensionnel. La convergence en maillage est étudiée et une analyse comparative des résultats expérimentaux et simulés est menée. De plus,L’influence de la répartition géométrique des obstacles sur le profil vertical de la vitesse moyenne longitudinale est étudiée avec une modélisation 3D-LES utilisant Code_Saturne. Les résultats expérimentaux serviront de cas de référence pour la validation.Au terme de cette seconde partie de thèse, des recommandations seront émises pour modéliser de façon pertinente ces écoulements au regard d’objectifs opérationnels<br>According to the Ministry of Ecological and Solidarity Transition, floods are the main natural risk in France. As a result of climate change, extreme floods will become more frequent. People and property, such as housing and industrial installations, must therefore be protected against these floods for which data are very scarce or even non-existent. When moving from low to extreme flooding, the spatial extent of flooding in the floodplain varies greatly. The nature of the obstacles encountered varies: low vegetation, trees, houses... These hydraulic obstacles or macro-roughnesses can be emerged, or slightly submerged.The purpose of this thesis work is to analyze the dominant physical processes associated with extreme flood flows in the presence of emerged or slightly submerged obstacles. This thesis is organized in two parts: an experimental part and a numerical part.The experimental part concerns the exploration, in a laboratory channel, of the vertical structure of the velocity profile and the geometric effects related to the studied configuration representing an urbanized floodplain with immersion rates of (dollar symbol) D/h = 0.42, 0.93, 0.98(dollar symbol) and (dollar symbol)1.48(dollar symbol) ((dollar symbol) D(dollar symbol) being the water depth and (dollar symbol)h(dollar symbol) the obstacle height). ADV and PIV measurements of mean velocities and turbulent fluctuations have shown that flow properties change significantly depending on whether the obstacles are emerged or slightly submerged. The interactions between vortex detachment, the free surface, obstacles, and bottom roughness are studied.The numerical part analyses different types of modelling conventionally used to simulate flood events. The experimental case of the thesis serves as a reference.First, an analytical model based on the conservation of momentum of an elementary hydraulic volume allows considering different models of the overall flow resistance to obstacles in a uniform regime. The first simple model integrates the resistance to flow due to bottom friction and obstacles in a single "friction" type term. A second model divides the flow resistance into two parts: a bottom friction term and an obstacle resistance, represented by a drag coefficient. The obstruction to the flow is then represented by a porosity coefficient.The analysis focuses on the ability to use friction or drag coefficients calibrated for the lowest flow rates to simulate high flow rates, and in particular, the transition from emergent to submergent obstacle flows.Then, the obstacles are explicitly represented in a two-dimensional Shallow-Water model. Mesh convergence is studied and a comparative analysis of experimental and simulated results is conducted.Furthermore, the ingluence of the geometric distribution of obstacles on the vertical profile of the average longitudinal velocity is studied with 3D-LES model using Code_Saturne. The experimental results serve as a reference case for validation.Recommendations are made for how to model these flows for operational applications
28
Khaoua, Ibtissame. "Approche quantitative de la bio-chimiluminescence ultrafaible : oxydation et métabolisme Detectivity Optimization to Detect of Ultraweak Light Fluxes with an EM-CCD as Binary Photon Counter Array 3D To 2D Stochastic Concentration of Highly Diluted Light Reveals Ultraweak Chemi- and Bio-Luminescence." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL005.
Full textAbstract:
L’émission de lumière par les tissus vivants, probablement liée au métabolisme oxydatif, est connue depuis des décennies, tout comme la luminescence de certaines réactions chimiques très simples en milieu aqueux. Ces phénomènes restent très mal connus en raison de l’extrême faiblesse de lumière produite, appelée de ce fait "luminescence ultrafaible". Dans cette thèse, nous proposons d’abord un dispositif expérimental original pour quantifier avec une très grande sensibilité la luminescence produite par unité de volume de l’échantillon.Le seuil de détection atteint est ≈ 1 photon s−1 cm−3 soit ≈ 2.10−21 M.s−1 . Nous avons pour cela combiné : 1) un environnement d’obscurité maximale, 2) une sphère intégrante de réflexivité extrême pour canaliser au maximum les photons de l’échantillon vers le détecteur, 3) une caméra amplifiée en mode binaire dans le domaine visible (400 − 900) et un modèle statistique conduisant à une détectivité optimale, et 4) une procédure semi-automatique de manipulation dans l’obscurité.Grace à ce dispositif, 1) le seuil de détection est ≈ 9.2 photons s−1cm−2 sur la caméra, soit ≈ 1% du courant d’obscurité, 2) ≈ 12% des photons émis de façon isotrope par l’échantillon sont détectés, 3) la détection des variations de l’intensité lumineuse est optimisée en opérant non pas au maximum du rapport signal à bruit, mais au maximum de détectivité. Nous avons ensuite étudié la luminescence produite par la disproportionation de H2O2 dans l’eau, réaction importante pour le métabolisme et catalysée par les peroxidases, mais essentielle aussi dans l’histoire de la chimiluminescence pour la compréhension fondamentale et ses applications basées sur le luminol. Nous avons quantifié pour la première fois, en absence de tout catalyseur, la luminescence dose-dépendante de la disproportionation dans l’eau pure, avec ≈ 15 photons s−1cm−3 pour [H2O2] = 90 mM. Grace au modèle biologique bien connu des levures Saccharomyces cerevisiae, nous avons mis en évidence un pic de luminescence en culture liquide associé au début de la phase exponentielle, suivi d’une décroissance sur 10 heures. Cette production de lumière représente environ 10−5 par seconde et par cellule.Notre travail permet d’envisager l’étude beaucoup plus quantitative de la luminescence ultrafaible en chimie et en biologie, condition nécessaire pour la com- préhension des mécanismes fondamentaux impliqués et le développement de possibles applications notamment biomédicales<br>It has been known for decades that ultra-weak visible and UV light is emitted by most living tissues due to their oxidative metabolism, as well as by some simple reactions in aqueous medium. However, these phenomena are not well known due to the extreme weakness of the light emission, hence called "ultra-weak" luminescence. In this thesis, we propose an original experimental setup to make extremely sensitive measurements of the luminescence produced by a sample per unit volume.We reached a detection limit of ≈ 1 photon s−1cm−3 which corresponds to ≈ 2.10−21 M.s−1. To obtain this result, we combined: 1) the darkest environment possible, 2) an integrating sphere with extreme reflectivity which brings the maximum amount of photons onto the detector, 3) an amplified camera in binary mode (visible : 400 − 900) and a statistical model which optimizes detectivity, and 4) a semi-automatic procedure to operate in darkness. This setup enables the following: 1) the detection limit is ≈ 9.2 photons s−1cm−2 on the camera, which accounts for ≈ 1% of its dark current, 2) ≈ 12% of the photons emitted isotropically by the sample are detected, 3) measurement of light intensity variations is optimized by maximizing the detectivity, rather than by maximiz- ing the signal-to-noise ratio.Then, we studied the luminescence produced by the disproportionation of H2O2 in water. This reaction catalysed in cells by peroxidases, is important for the metabolism, and is critical to the understanding chemiluminescence in general and and luminol-based applications in particular. We quantified for the first time without a catalyst, the dose-dependent luminescence of the disproportionation reaction in pure water, with ≈ 15photonss−1cm−3 for [H2O2 = 90] mM. Using a well-known biological model, Saccharomyces cerevisiae (baker’s yeast), cultured in liquid, we showed a peak in the luminescence associated with the beginning of the exponential growth phase, followed by a sustained decrease over 10 hours. This light production represents approximately 10−5 photons per second per cell.We hope our work leads to better quantitative study of the ultra-weak luminescence in chemistry and biology. This quantification is necessary for understanding the fundamental underlying mechanisms behind luminescence and to develop chemical and biomedical applications
29
Rabideau, Brooks Douglas 1979. "The self-assembly of colloidal particles into 2D arrays." Thesis, 2007. http://hdl.handle.net/2152/3645.
Full textAbstract:
As the feature size of new devices continues to decrease so too does the feasibility of top-down methods of patterning them. In many cases bottom-up methods are replacing the existing methods of assembly, as having building blocks self-organize into the desired structure appears, in many cases, to be a much more advantageous route. Self-assembled nanoparticulate films have a wide range of potential applications; high-density magnetic media, sensing arrays, meta-materials and as seeds for 3D photonic crystals to name a few. Thus, it is critical that we understand the fundamental dynamics of pattern formation on the nanoparticulate and colloidal scale so that we may have better control over the formation and final quality of these structures. We study computationally the self-organization of colloidal particles in 2D using both Monte Carlo and dynamic simulation We present 3 studies employing Monte Carlo simulation. In the first study, Monte Carlo simulations were used to understand the experimental observation of highlyordered 2D arrays of bidisperse, stabilized gold nanoparticles. It was shown that the LS lattice forms with the addition of interparticle forces and a simple compressive force, revealing that bidisperse lattice formation is, in fact, a dynamic process. It was evident that the LS lattice forms in large part because the particles within the lattice reside in their respective interparticle potential wells. In the second Monte Carlo study, this information was used to predict size-ratios and surface coverages for novel lattice structures. These predictions are intended to guide experimentalists in their search for these exciting new structures. In the third study it was shown that polydisperse amounts of amorphous-silicon nanoparticles could form 2D clusters exhibiting long-range orientational order even in the absence of translational order. Monte Carlo simulations were performed, which included lateral capillary forces and a simple stabilizing repulsion, resulting in structures that were strikingly similar to the experimentally observed In the fourth study we used dynamic simulation to study the hydrodynamicallyassisted self-organization of DNA-functionalized colloids in 2D. It was shown that hydrodynamic forces allow a more thorough sampling of phase space than through thermal or Brownian forces alone.
30
Wang, Chien-hsun, and 王建勳. "Periodic arrays 2D well-ordered nanostructures fabricated via nanosphere lithography." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/31538189638263127424.
Full textAbstract:
碩士<br>國立中央大學<br>化學工程與材料工程研究所<br>96<br>In the present study, we have demonstrated that 2D periodic arrays of nickel metal and silicide nanodots can be successfully fabricated on (111)Si substrates by using the polystyrene (PS) nanosphere lithography (NSL) technique and thermal annealing. The results of an investigation on the interfacial reactions between the Ni nanodots and (111)Si substrates after different heat treatments are reported.
From the TEM and SAED analysis, only epitaxial NiSi2 nanodots were found to form on (111)Si at a temperature as low as 300 °C. The results indicated that the growth of epitaxial NiSi2 is more favorable for the samples with smaller Ni nanodot sizes. The epitaxial NiSi2 nanodots were found to grow with an epitaxial orientation with respect to the (111)Si substrates: [111]NiSi2//[111]Si and {220}NiSi2//{220}Si. In addition, these epitaxial NiSi2 nanodots formed on (111)Si were observed to be heavily faceted and the faceted edges of the NiSi2 nanodot were identified to be parallel to <1 0>Si directions. On the other hand, during the experiments, the double-layered arrays of PS spheres were occasionally found to form on silicon substrates. The epitaxial NiSi2 nanodot arrays formed from the bilayer masks exhibit larger interparticle spacings and smaller particle sizes.
By combining the nanosphere lithography, heat treatments, wet chemical etching and electrodeposition techniques, we also successfully fabricate large-area shape- and size-tunable metal nanostructures (nanobowls and nanopillars) and nanohole arrays on Si and SiGe substrates. The morphology evolution, size uniformity and crystal structure of the produced nanostructures have been systematically investigated by SEM, AFM, TEM, and SAED analyses. The observed results present the exciting prospect that with appropriate controls, the colloidal NSL technique promises to offer an effective and economical patterning method for fabrication of a variety of well-ordered nanostructures with selected shape, size, and periodicity on different substrates without complex lithography.
31
Su, YaWen, and 蘇雅雯. "Fabrication of 2D arrays of Cadmium Selenide nano-pillars for optics applications." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/27447911538383737542.
Full textAbstract:
碩士<br>國立臺灣師範大學<br>化學研究所<br>90<br>We demonstrate a unique method for fabrication of two dimensional (2D) arrays of CdSe pillars with large aspect (height-to-width) ratios for optics applications. The fabrication technique combines electron beam lithography for periodic pattern definition and chemical electrodeposition for the growth of 2D arrays of CdSe pillars. The arrays are made on a relatively small area, about square of tenths of microns.
In this method, cyclic voltammetric deposition with resist-coated indium tin oxide substrate as the working electrode, Pt slab as the counter-electrode and the saturated calomel electrode as reference electrode is performed. The pillars of semiconductor are synthesized by electrochemical deposition from aqueous solution of CdSO4 , SeO2 and H2SO4. During the electrodeposition, the working electrode potential relative to SCE is swept between — 400 mV and — 800 mV at several scan rates. After the first cycle, the heights of the CdSe pillars are found to increase linearly with number of cycles, and the growth rate is about 38.8 nm per cycle. After electrodeposition, the samples are soaked in an acetone bath to remove the resist mask.
With this technique, the pillar with a large aspect ratio of 8 is achievable. The minimum diameter of the pillar is 80 nm. The height of the pillar can be as large as 640 nm, which is about the thickness of the resist layer. Depositing CdSe pillars to a height over the resist will result in a mushroom structure. The geometry of the fabricated pillars is examined by scanning electron microscope and atomic force microscope, while their properties are characterized by energy-dispersive spectrometer and infrared Raman-scattering spectrometer.
32
Chih-ShanChang and 張志山. "Plasmonic Resonant Properties of Silver Hemispherical Nano-Shell Structures in 2D arrays." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/93223034136125095241.
Full textAbstract:
碩士<br>國立成功大學<br>光電科學與工程學系<br>102<br>Localized surface plasmon resonance (LSPR), observed in metal nanoparticle arrays interacting with an incident light field, is an emerging research area for surface-enhanced -Raman-scattering (SERS) biomedical sensing applications. The plasmonic properties of metal nanoparticles can be easily tuned by varying the shape, size and arrangement along with the dielectric environment. Particles with coreshell structure provide an extra degree of freedom to tune the LSPR wavelength. The array structure adds an extra tuning capability by setting the periodicity near the single particle LSPR wavelength to squeeze out a sharp Fano resonant peak. In nano fabrication, semi shell array has advantage over the spherical shell array by the top-down approach. Here, we investigate the LSPR cross section and mode distributions for nano-shell and semi-shell with core radius of 100 nm and shell thickness of 20nm for single and periodic structure using FDTD simulation. Higher order quadrapole modes with bonding and anti-bonding types were observed. Furthermore, we discussed Fano resonance effect on each LSPR modes by adjusting the interparticle spacing. The coupling between the dipole/quadrapole LSPR and the grating mode leads to different resonant properties. The charge distributions of dipole and quadrapole under the influence of Fano resonance are also discussed.
33
Rahman, Mohammad Moshiur. "Analysis of 2D spatial filtering of simulated muscle action potential using grid arrays." 2005. http://etd.utk.edu/2005/RahmanMohammad.pdf.
Full textAbstract:
Thesis (M.S.) -- University of Tennessee, Knoxville, 2005.<br>Title from title page screen (viewed on August 31, 2005). Thesis advisor: Mohammed Ferdjallah. Document formatted into pages (x, 123 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 119-122).
34
"Surface plasmon polaritons (SPPs) induced polarization conversion in 2D metallic nano-hole arrays." 2015. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1292012.
Full textAbstract:
Yiu, Lai Yin = 在二維金屬納米洞陣列上表面等離子激元導致的偏振轉換 / 姚勵賢.<br>Thesis M.Phil. Chinese University of Hong Kong 2015.<br>Includes bibliographical references (leaves 90-96).<br>Abstracts also in Chinese.<br>Title from PDF title page (viewed on 15, December, 2016).<br>Yiu, Lai Yin = Zai er wei jin shu na mi dong zhen lie shang biao mian deng li zi ji yuan dao zhi de pian zhen zhuan huan / Yao Lixian.
35
Wong, Shao-Lan, and 翁紹蘭. "Periodic arrays of silicide nanodots and 2D well-ordered nanostructures fabricated via nanosphere lithography." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/78357209241306922519.
Full textAbstract:
碩士<br>國立中央大學<br>化學工程與材料工程研究所<br>95<br>The present study has demonstrated that 2D well-ordered arrays of nickel and cobalt metal nanodots were successfully fabricated on (001) Si and SiGe substrates by using the polystyrene nanosphere lithography (NSL) technique. The interfacial reactions of the metal nanodot arrays on Si and SiGe substrates after different heat treatments have been investigated.
From the TEM and SAED analysis, epitaxial NiSi2 and CoSi2 nanodots were found to form at a temperature as low as 300 ℃、500 ℃, respectively. The results indicated that the growth of epitaxial NiSi2 and CoSi2 is more favorable for the samples with smaller metal nanodot sizes. The orientation relationships of epitaxial metal disilicide nanodots with respect to (001)Si substrates were identified to be [001] NiSi2 (or CoSi2) // [001] Si and (200) NiSi2 (or CoSi2) // (400) Si. By combining the planview HRTEM and XTEM analysis, the faceted NiSi2 and CoSi2 nanodots were identified to be inverse pyramids in shape. In addition, the average size of the faceted silicide nanodots were measured to decrease with annealing temperature.
For the coabalt metal nanodot arrays on Si0.7Ge0.3 substrates after annealing at 500 ℃, Co2(Si,Ge) phase was found to coexist with the dominant polycrystalline Co(Si,Ge) phase. As the annealing temperature was increased to 700 ℃, it is interesting to see that tadpole-like nanowires were found to grow on individual Co silicide nanoparticales. From planview TEM, SAED and EDS analysis, it is indicated that these tadpole-like nanowires were composed of Si, Ge and O, and the nanoscale structure was examined to be amorphous. For the samples annealed at 900 ℃, 10-20-nm-diameter amorphous SiO2 (a-SiO2) nanowires were observed to grow from individual Co silicide nanodot regions. The growth process of a-SiO2 nanowires could be explained by the solid-liquid-solid (SLS) mechanism.
By tuning the drop-coasting processes and lift-off conditions, large-area periodic nanoring arrays and 3D well-ordered nanostructures were successfully fabricated on silicon substrates. The possible growth mechanisms were proposed. Furthermore, by utilizing the 3D nanostructures as the templates in conjunction with electrodeposition technique, 2D ordered metal nanobowl and solid Ni metal spheres were obtained in this study.
36
Lu, Shao-Wei, and 呂紹瑋. "Formation of Silicide Nanodot Arrays and 2D Periodic Nanostructures Using Self-Assembly Nanosphere Lithography." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/99357801097099890743.
Full textAbstract:
碩士<br>國立中央大學<br>化學工程與材料工程研究所<br>94<br>As the device dimensions scale down to nanometer region, in-depth understanding the reaction mechanisms between the nanoscale metal thin film and semiconductor substrate will play an important role in defining the use of these
nanoscale building blocks in advanced nanodevices. Therefore, in this study,particular emphases are focused on the fabrication of large-area, 2D-ordered nickel and cobalt metal dot arrays and the interfacial reactions of nickel and cobalt metal dots on Si substrates after different heat treatments.
To fabricate large periodic arrays of Ni and Co metal nanodots on silicon substrate, an effective and economical technique –polystyrene nanosphere lithography (PS NSL) was utilized. After 20-nm-thick metal thin films deposition and
subsequent lift-off of the PS spheres template, an ordered hexagonal array of triangular metal dots was formed on the surface of Si substrate.
From the SEM, TEM, and SAED analysis, epitaxial NiSi2 and CoSi2 nanodot arrays were found to form at a temperature as low as 350 ℃ and 550 ℃, respectively. The orientation relationships of epitaxial metal disilicide nanodots with respect to
(001)Si substrates were identified to be [001] NiSi2 (or CoSi2) // [001] Si and (200)
NiSi2 (or CoSi2) // (400) Si. The results indicated that the growth of epitaxial NiSi2
and CoSi2 is more favorable for the metal dot array samples. In addition, the sizes of
the silicide nanodots were found to decrease with annealing temperature. The epitaxial
metal disilicide nanodots were identified to be inverse pyramids in shape. The bases
of the pyramidal metal disilicide nanodots are parallel to the (001)Si wafer surface and
the faceted edges of the bases of the pyramids are along the <1 1 0> Si directions. The
epitaxial metal disilicide nanodot/Si interfaces were found to be faceted with {1 1 1}interface planes. Furthermore, for the nickel nanodot samples annealed at 900 ℃,amorphous SiOx nanowires were found to grow on individual nickel silicide nanoparticles. The diameters of these nanowires are in the range of 15–20 nm, and the growths of a-SiOx were controlled by the solid-liquid-solid (SLS) mechanism.
On the other hand, by tuning the drop-coating processes and lift-off conditions,hexagonal periodic nanoring arrays were successfully fabricated on (001)Si substrates. In addition, the diameters of nanorings can be controlled by adjusting the concentration of surfactant. Based on the results of a series of observation and
analysis, the possible formation mechanism of nanoring arrays might be related to the
normal capillary force deforms PS spheres during the drying of a suspension droplet.
37
Bartlett, Chad. "Design of an 8x8 cross-configuration Butler matrix with interchangeable 1D and 2D arrays." Thesis, 2019. http://hdl.handle.net/1828/10989.
Full textAbstract:
An ever-increasing demand for wider bandwidths in communication, radar, and imaging systems has emerged. In order to facilitate this growing demand, progressive research into millimeter-wave technologies has become vital in achieving next generation networks such as 5G. Being cost effective and easy to manufacture, Substrate Integrated Waveguide (SIW) circuits have been demonstrated as a viable candidate for high-frequency applications due to their low-loss, high quality-factor, and high power-handling capabilities.Research on beam-forming networks, specifically the Butler matrix, has demonstrated powerful beam-steering capabilities through the use of passive component networks. Through these clever configurations, a cost effective and robust option is available for us to use. In order to further millimeter-wave research in this area, this thesis presents a modified configuration of the Butler Matrix in SIW that is physically reconfigurable; by separating the Butler matrix from the antenna array at a pre-selected point, the array can be easily interchanged with other 1-Dimensional,and 2-Dimensional slot antenna arrays. Although this system does not fall under the rigorous definitions of Reconfigurable Antennas, it should be noted that the interchangeability of 1 and 2 dimensional arrays is not typically expressed in Butler matrix configurations. Design and simulations are carried out in CST Microwave Studio to inspect individual components as well as system characteristics. Circuit prototypes are then manufactured and tested in an anechoic chamber to validate simulation results and the design approach.<br>Graduate<br>2020-07-17
38
Yen-LinChen and 陳彥琳. "Microfabricated arrays of soft, flexible and recyclable electrical contacts for characterization of 2D materials." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/xt5g9q.
Full text
39
Huang, Shu Chi, and 黃書麒. "Dimension-Reduced Signal Processing Scheme for 2D Antenna Arrays-on the Application of DOA Estimation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/37668367172948782778.
Full textAbstract:
碩士<br>長庚大學<br>電機工程學系<br>99<br>To effectively reduce the super-complexity in 2D-ESPRIT(two dimensional Estimation of Signal Parameter via Rotational Invariance Techniques). This paper propose a one dimensional(1D) based “Tree structure algorithm” for estimating the 2D-DOAs of the signal impinging on a uniform rectangular array(URA). The key ideal of the proposed algorithm is to repeat utilized 1-D ESPRIT algorithm and subspace projector with regular rule. Thus, transmitted azimuths and elevations can be estimated and paired more easily.
40
Liu, Chia-Wei, and 劉家偉. "A Study on the 2D Crystallographic Analysis and the Second Harmonic Generation of Chromium Nanoparticle Arrays." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/84901694075119302694.
Full text
41
Liu, Chieh-Chun, and 劉玠均. "A Study on the 2D Crystallographic Analysis and the Second Harmonic Generation of Nickel Nanoparticle Arrays." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/42687590530676109939.
Full text
42
Ho, Chih-Chiang, and 何志強. "A Study on the 2D Crystallographic Analysis and the Second Harmonic Generation of Silver Nanoparticle Arrays." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/08317747103144867706.
Full text
43
Mattesini, Paolo, Piero Tortoli, Enrico Boni, Hervé Liebgott, and Olivier Basset. "Development of methods and electronic circuits for ultrasound imaging based on innovative probes." Doctoral thesis, 2020. http://hdl.handle.net/2158/1186186.
Full textAbstract:
I sistemi di imaging ad ultrasuoni (US), sebbene siano stati oggetto di intense indagini da parte di molti gruppi di ricerca in tutto il mondo, non hanno ancora raggiunto la piena maturità. Le sonde ad ultrasuoni, in particolare, hanno ampi margini di miglioramento, non solo in termini di materiali e configurazione degli elementi, ma anche di modalità di eccitazione.
Il mio lavoro di dottorato è stato impegnato nello sviluppo di circuiti elettronici e metodi per l'imaging ad ultrasuoni basati su sonde innovative.
In primo luogo, ho sviluppato i circuiti elettronici necessari per rendere compatibile un sistema di ricerca a ultrasuoni per scopi di ricerca (ULA-OP 256) con le sonde CMUT. La tecnologia CMUT è sempre più utilizzata perché offre ampia banda, elevata sensibilità e grande flessibilità nella progettazione della geometria degli elementi ma, a differenza della tecnologia piezoelettrica, necessita di alte tensioni di polarizzazione (dell’ordine delle centinaia di Volt). Poiché ULA-OP 256 è stato originariamente progettato per funzionare solo con sonde piezoelettriche, ho contribuito allo sviluppo di circuiti in grado di adattare questo scanner aperto per lavorare anche con sonde CMUT. Inoltre, in collaborazione con ST Microelectronics, ho sviluppato una scheda elettronica che permette di testare un nuovo amplificatore di potenza a nove livelli per la trasmissione di segnali sia alle sonde piezoelettriche che alle sonde CMUT.
La seconda parte del mio lavoro è stata dedicata allo studio del possibile utilizzo di sonde ad array "sparse" per ecografie 3D Doppler e ad alto frame rate. Le sonde sparse sono array 2D in cui un numero limitato di elementi, paragonabile al numero di canali presenti nella maggior parte degli scanner ad ultrasuoni, è distribuito secondo specifiche geometrie, progettate per ottimizzare il fascio acustico in trasmissione e ricezione. CMUT è la tecnologia ideale per l'implementazione di sonde sparse array, in quanto garantisce la massima flessibilità nella distribuzione degli elementi in posizioni arbitrarie.
Il mio lavoro con gli Sparse Array ha incluso prima di tutto lo studio di possibili limitazioni legate al loro utilizzo quando sono usati per trasmettere onde divergenti (DWs). Si tratta di onde non focalizzate che permettono di aumentare notevolmente il frame rate nell'imaging volumetrico (3D). In questa attività, ho fatto simulazioni ed esperimenti nel laboratorio CREATIS (Lione) per confrontare le prestazioni ottenibili in termini di contrasto e risoluzione quando si utilizzano diverse configurazioni di DW e di elementi sparsi.
Infine, una parte consistente del mio dottorato di ricerca è stata focalizzata sulla valutazione dell'uso di array sparse in applicazioni Doppler spettrali. L'intenzione di questo studio era di valutare in che misura la dispersione degli elementi sulla superficie della sonda può influenzare le prestazioni del Doppler spettrale. Per raggiungere questo obiettivo, l'uso di un array 2D a 1024 elementi a griglia completa è stato confrontato con l'uso di array sparse ottenuti selezionando opportunamente 256 elementi sulla stessa matrice completa. Gli esperimenti sono stati sviluppati sia su un disco di agar rotante (dove sono raggiungibili alti SNR) che su un phantom di flusso (per testare una condizione più realistica) al CREATIS. I risultati di questo lavoro confermano quantitativamente l'idoneità degli array sparse per misure di velocità Doppler spettrali, a condizione che la perdita di rapporto segnale/rumore dovuto all'utilizzo di meno elementi attivi sia adeguatamente compensata.
Ultrasound (US) imaging systems, although intensively investigated by many research groups worldwide, have not achieved full maturity yet. US probes, in particular, have wide margins of improvement, not only in terms of materials and elements configuration but also of excitation modalities.
This PhD work has been committed to the development of electronic circuits and methods for US imaging based on innovative ultrasound probes.
First, I’ve developed the electronic circuits necessary to make an open ultrasound research system (ULA-OP 256) compatible with CMUT probes. CMUT technology is increasingly used because it offers wide band, high sensitivity and great flexibility in the design of elements geometry but, differently from the piezoelectric technology, needs high polarization and peak-to-peak voltages (hundreds of Volt). Since ULA-OP 256 was originally designed to work only with piezoelectric probes, I contributed to the development of circuits capable of adapting this open scanner to work also with CMUT array probes. Furthermore, within a collaboration with ST Microelectronics, I’ve developed an electronic board that allows to test a new 9-level power amplifier for the transmission of signals to both piezoelectric and CMUT probes.
The second part of my work has been dedicated to the investigation of possible use of “sparse” array probes for 3D high-frame rate and Doppler imaging. Sparse probes are 2D arrays in which a limited number of elements, comparable to the number of channels present in most US scanners, is distributed according to specific geometries, designed to optimize the transmit/receive acoustic beam. CMUT is the ideal technology for implementing sparse array probes, since it guarantees maximum flexibility in distributing the elements into arbitrary positions.
My work with sparse arrays has first included the investigation of possible limitations related to their use when they are committed to transmit Diverging Waves (DWs). These are unfocused waves that may notably increase the frame rate in volumetric (3D) imaging. In this activity, I’ve done simulations and experiments at CREATIS (Lyon) to compare the achievable performance in terms of contrast and resolution when different DWs and sparse elements configurations are used.
Finally, a consistent part of my PhD has been focused on the evaluation of the use of sparse arrays in spectral Doppler applications. The intention of this study was to evaluate at which extent the sparsification of probe elements may affect the spectral Doppler performance. To achieve this goal, the use of a full-gridded 1024-element 2D array was compared with the use of a sparse arrays obtained by properly selecting 256 elements out of the same full array. The experiments were developed on both a rotating agar disc (where high SNR are achievable) and on a flow phantom (to test a more realistic condition) at CREATIS. The results of this work quantitatively confirm the suitability of sparse arrays for spectral Doppler velocity measurements, provided the poor signal-to-noise ratio due to the use of few active elements is properly compensated.
44
(5930366), Siddarth Vyraghrapuri Sridharan. "EXTRACELLULAR METABOLIC PROFILING: MEASUREMENT OF SURFACE CONCENTRATIONS AND FLUXES TO DETERMINE CELLULAR KINETICS FROM 2D CULTURES USING ELECTROCHEMICAL MICROELECTRODE ARRAYS." Thesis, 2020.
Find full textAbstract:
In 2D cell cultures uptake/release of various metabolic analytes such as glucose, lactate or metabolic by-products like hydrogen peroxide from/to the extracellular environment results in concentration gradients. The magnitude, direction, and time scales of these gradients carries information that is essential for internal cellular processes and/or for communication with neighboring cells. This PhD research work focusses on the design, fabrication and characterization of electrochemical microelectrode arrays (MEAs) optimized to be positioned in commonly used 2D cell culture setups. Importantly, by simultaneously measuring accurate concentration transients and associated gradients/uxes near the cell surface (surface concentration) the capability of the device to quantify kinetic rates and distinguish mechanisms involved in various cellular processes is demonstrated. An in-situ transient calibration technique suitable for amperometric MEAs is developed and the technique is validated by quantitatively measuring dynamic concentration profiles with varying spatial (100-800 µm) and time (s to hrs.) scales set up from an electrically controlled diffusion reaction system. With the proposed MEA design and technique three physiological applications are demonstrated. Firstly, the position able 1D MEA was employed real time to quantitatively measure the hydrogen peroxide scavenging rates from astrocyte vs glioblastoma cell cultures. With the ability to extract to dynamic surface concentration and fluxes, the cell lines were shown to have hydrogen peroxide uptake rates dependent on local surface concentrations. Moreover, the cancerous glioblastoma cells demonstrated an upregulated linear peroxide scavenging mechanism as compared to astrocytes. For the next phase, spatial scales of 1D MEA device along the size and functionalization scheme of the electrodes in the MEA was further modified to selectively sense glucose and lactate to enable extracellular metabolic profiling of cancer vs normal cell lines. Secondly, measurement of glucose concentration profiles demonstrated an increased glucose uptake rate in glioblastoma as compared to astrocytes. Additionally, sigmoidal (allosteric) vs Michaelis - Menten glucose uptake kinetics was observed in glioblastoma vs astrocytes. Moreover, the presence of a glucose sensing mechanism was observed in glioblastoma cells due to the dependence of the glucose uptake rate on initial exposed concentration rather than surface concentration. Finally, simultaneous multi-analyte (glucose and lactate) gradient measurements were performed on genetically modified mouse pancreatic cancer cell lines. While glucose uptake rate was shown to increase with increasing extracellular glucose concentration for one of the cell lines, the lactate release rate was observed to be independent of the initial extracellular glucose dose.
45
Lin, Yao-hsing, and 林耀星. "Fabrication of Site- and Size-controllable Periodic Arrays 2D Well-ordered Si Nanostructures by Plasma Modified Nanosphere Lithography and Chemical Wet Etching Processes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23119866571253488366.
Full textAbstract:
碩士<br>國立中央大學<br>化學工程與材料工程研究所<br>100<br>The present study has demonstrated the successful fabrication of density-, size- and shape-controllable Si nanostructure arrays on Si substrates of different orientation by using plasma modified nanosphere lithography and anisotropic wet etching process. The morphologies, crystal structures, compositions, optical and surface properties of the Si nanostructure arrays produced have been systematically investigated by SEM, AFM, TEM, SAED, EDS, XPS, UV-Vis and contact angle analyses.
For the fabrication of periodic Si nanohole arrays, we take advantage of O2 plasma RIE treatment, which allows us simultaneously to adjust the diameter of PS nanospheres template and to form a passivation a-SiOx layer on Si serving as the etching mask. The shapes, sizes and positions of Si nanoholes that formed on Si substrates could be tuned by adjusting the diameters of the colloidal nanospheres and the KOH etching time. On the other hand, by combining the plasma modified nanosphere lithography, selective chemical etching process or metal silicide formation, large-area, size- and height-tunable Si nanocone arrays were also successfully fabricated on (001), (110) and (111)Si substrates in this study. From the water contact angle measurements, the surface of HF-treated Si nanohole and nanocone arrays exhibited hydrophobic characteristics. The hydrophobic behavior of Si nanostructures could be explained by the Cassie model. Furthermore, UV-Vis spectroscopic measurements revealed that the nanostructured Si surfaces exhibit strong antireflection properties.The enhanced antireflection properties can be attributed to the light trapping effect resulting from the nanostructure-arrayed Si surfaces.
46
Weber, Arnim. "Transkriptom- und Proteom-Analysen von Escherichia coli unter hyperosmotischen Stressbedingungen und biochemische Charakterisierung von UspG." Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003112611.
Full text
47
Giangrossi, Claudio. "Development and real-time implementation of novel 2-D and 3-D imaging techniques on a research scanner." Doctoral thesis, 2022. http://hdl.handle.net/2158/1272194.
Full textAbstract:
In the last decades, ultrasound imaging systems have become more and more popular thanks to their capability to investigate tissues in safe, cost effective, and non-invasive way. Their role in diagnostic imaging has become fundamental in several medical specialties, thanks also to the introduction of advanced echographic systems fostered by the efforts of several research laboratories around the world. Such efforts are more frequently based on the use of special research scanners, characterized by flexible hardware and programmable software and firmware. These features have been demonstrated ideal for the implementation and test of new methods, such as high frame-rate (HFR) imaging, color flow imaging (CFI), vector Doppler imaging, and 3 D imaging. Especially HFR and 3 D imaging have recently attracted great interest, but they are technically demanding since they involve either the formation of thousands of images per second, or the use of 2-D probes having a large number of elements. Therefore, great challenges must be faced for effective real-time implementation of 3 D and HFR imaging methods.
My PhD activity aimed to implement and test advanced 2 D and 3 D ultrasound imaging modalities on an open research scanner called ULA OP 256.
In the first part of my work, a new ultrasound imaging modality called Virtual real-time (VRT) was introduced through the modification of the firmware and software of the research scanner ULA-OP 256. With this modality, during a real-time (RT) investigation, the scanner initially acquires and stores in its memory up to 20 s of raw echo data. On user demand, the scanner can be switched to VRT mode: the stored data are re processed by the same resources used in RT but at different (typically lower) rates and, possibly, with different processing algorithms and parameters. In this way, contingent difficulties of image interpretation (especially in presence of rapidly moving phenomena), or possible computational limitations imposed by hardware during continuous RT processing can be overcome. The VRT modality has been demonstrated useful in different applications, for example, to implement a high-PRF version of the Multiline vector Doppler (MLVD) method, and a High- rame-rate CFI method, characterized by enhanced temporal and spatial resolution.
The second part of my work included the software upgrade of ULA OP 256; it enabled the use of 2 D probes and the implementation of 3 D scanning methods. The ULA OP 256 can now be coupled to 2 D probes with arbitrary geometries, including matrix and sparse arrays. Furthermore, the scanner is now capable of simultaneously imaging multiple planes with programmable rotational angles. Novel approaches based on a sparse spiral array probe have been implemented and tested for different applications. For example, bi-plane imaging was evaluated for robust flow mediated dilation exams. Real-time 3 D spectral Doppler analysis was also performed. Here, two planes with programmable rotational angles were scanned to produce corresponding B-Mode images, over which multiple Doppler lines could be arbitrarily set to obtain the relative Multigate spectral Doppler (MSD) profiles.
Finally, the last part of my work was specifically dedicated to the technical problems involved by HFR 3 D imaging. The management of (several) hundreds of transducer elements of a 2 D probe yields a huge amount of echo data: this makes complex and computationally expensive the processing of data volumes including thousands of lines, especially if performed at HFR. As a case report, the requirements of the main processing stages involved in ULA OP 256 receiver have been thoroughly investigated to detect and, possibly, solve the main bottlenecks. The study has evidenced that the star architecture that digitally interconnects the eight front-end boards of ULA OP 256 may frequently encounter data transfer bandwidth saturation that limits the overall performance in terms of frame/volume rate. A new architecture for data transfer has been proposed and shown effective to reduce the bandwidth requirements and thus, increase the performance of the scanner.
48
Rossi, Stefano, and Piero Tortoli. "Development and validation of novel approaches for real-time ultrasound vector velocity measurements." Doctoral thesis, 2021. http://hdl.handle.net/2158/1239650.
Full textAbstract:
Ultrasound imaging techniques have become increasingly successful in the medical field as they provide relatively low cost and totally safe diagnosis. Doppler methods focus on blood flow for the diagnosis and follow-up of cardiovascular diseases. First Doppler methods only measured the axial component of the motion. More recently, advanced methods have solved this problem, by estimating two or even all three velocity components. In this context, high frame rate (HFR) imaging techniques, based on the transmission of plane waves (PW), lead to the reconstruction of 2-D and 3-D vector maps of blood velocity distribution.
The aim of this Ph.D. project was to develop novel acquisition schemes and processing methods for advanced ultrasound Doppler systems. Each development step was based on simulations and experimental tests. Simulations were based on Field II©, while experiments were conducted by using the ULA OP 256 open scanner. In particular, the recently proposed 2-D HFR vector flow imaging (VFI) method (DOI: 10.1109/TUFFC.2014.3064), based on the frequency domain for displacement estimation, was thoroughly investigated. Three main issues were addressed: the high underestimation of blood flow velocity observed when examining vessels at great depths, the high computational load, which hindered any real-time implementation and the lack of information about the third velocity component. Specifically, the progressive broadening of the transmitted beam on the elevation plane due to the acoustic lens was demonstrated to be responsible for the underestimation. The computational cost was reduced by processing demodulated and down-sampled baseband data instead of radiofrequency data, and a preliminary real time version of the 2-D VFI method was implemented. It was also found that a more efficient implementation could be obtained by exploiting parallel computing and graphic processing units (GPUs). An expansion circuit board for the ULA-OP 256 hardware, which allocates GPU resources, was thus designed and built. This new system architecture may allow the implementation of even more complex algorithms, such as the 3-D VFI methods. In particular, it will be possible to implement the novel method for 3D VFI that was developed and tested during this Ph.D. project. Such method suitably extended the 2D VFI approach by proposing an efficient estimation strategy that considerably limits the overall computational load.
49
Chen, Kuang-Yu, and 陳冠宇. "2D Array Synthesis Using 1D Filter Design Techniques." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/03914685485941272022.
Full textAbstract:
碩士<br>國立高雄第一科技大學<br>電腦與通訊工程研究所<br>101<br>Beamforming is one of the array signal processing techniques. This paper is used for sound source detection. Using the plane wave to each sensor generated by different delays. Sensors are not the same as the energy received. With these delays and energy to estimate the direction and position of the sound source. But the sound source position is divided into near-field and far-field. The most of cases are the near-field beamformer.
Traditional delay-and-sum beamforming weights are fixed at different angles are not the same width of the main lobe, which determine the position of the sound source and noise easily confused, so how to design a two-dimensional array of weights is very important issue. This method provides an analytically tractable framework for designing delay-and-sum beamforming.
Keywords: Array signal processing, Microphone array
50
Chun-YuanWu and 吳囷原. "Vertical growth of 2D SnS2 array photocatalysts for CO2 photoconversion." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/tg5fxm.
Full text