Dissertation (Ph. D.)--University of Akron, Dept. of Electrical and Computer Engineering, 2009. / "August, 2009." Title from electronic dissertation title page (viewed 9/23/2009) Advisor, Igor Tsukerman; Committee members, Nathan Ida, Iqbal Husain, Ernian Pan; Department Chair, Alex De Abreu Garcia, Dmitry Golovaty; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2007. / Includes bibliographical references (p. 99-106).

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 74-76.

This thesis focuses on the use of phaseless (magnitude-only) planar near-field antenna measurements for the far-field characterization of an antenna under test (AUT). This is important since the use of phaseless data only requires power measurements, thus, removing the need of using expensive instruments, such as vector network analyzers which can measure both magnitude and phase. In addition, as opposed to far-field measurement techniques, performing measurements in the near-field zone of an AUT makes the measurement system more compact. / February 2016

DANTAS, Saulo Maia. Microscopia de campo próximo aplicada ao estudo dos domínios ferroelásticos. 2011. 116 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2011. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-16T20:43:18Z No. of bitstreams: 1 2011_dis_smdantas.pdf: 2227981 bytes, checksum: 19c007c3550b22fce922a346d6f4508f (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-10-21T20:37:21Z (GMT) No. of bitstreams: 1 2011_dis_smdantas.pdf: 2227981 bytes, checksum: 19c007c3550b22fce922a346d6f4508f (MD5) / Made available in DSpace on 2015-10-21T20:37:21Z (GMT). No. of bitstreams: 1 2011_dis_smdantas.pdf: 2227981 bytes, checksum: 19c007c3550b22fce922a346d6f4508f (MD5) Previous issue date: 2011 / A significant part of the nowadays scientific research is based on the synthesis, characterization and application of the nanostructured materials. In order to make possible a further understanding of the intriguing properties of these materials, many techniques with nanometric and even subnanometric resolution have been created during the last 50 years and are passing through a process of continuous improvement. In spite of the great scientific and technical development on the available instrumentation, the optical characterization with nanometric resolution of these materials remains a challenge for researchers from all over the world. In this context, techniques based on near field radiation have emerged as a great alternative for the diffraction limit break which is a nature imposed limit for conventional optical instruments. Besides this, contact near field microscopy in illumination mode acquires optical and topographical information of the material simultaneously. This capability permits the distinction between the real and topographic induced nanometric optical features. The domain phenomenon in crystals has been a subject of interest for crystallographers since crystallography started to develop as a scientific branch. The obvious reasons are the beauty of some domain patterns as well as evident and challenging symmetry relations between their constituents. The ferroelastic domains are one of the important kinds of domains presented by crystals. They have, sometimes, very small dimensions without inducing any topographic element on the sample. On the other side the optical behavior of different domains under almost the same measurement condition may be very dissimilar. Such characteristics make then an ideal class of materials for contact near field microscopy in illumination mode based studies. Ferroelastic domains images, using near-field optical microscopy in illumination and contact mode, were obtained with a nanometric resolution. Such images, in general, presented very little relation with the topographical structure of the material, revealing optical and structural features such as occurrence of the waveguide effect in the domains, domain´s dimensions and presence of dislocations on the crystalline structure. / Uma parcela significativa da pesquisa científica hodierna baseia-se na síntese, caracterização ou aplicação de materiais nanoestruturados. No intuito de possibilitar um maior entendimento das intrigantes propriedades destes materiais, muitas técnicas com resolução nanométrica e até subnanométrica foram criadas nos últimos 50 anos e têm passado por um processo de contínuo aprimoramento. Apesar do grande desenvolvimento técnico e científico da instrumentação disponível, a caracterização ótica com resolução nanométrica destes materiais tem se mostrado um desafio para pesquisadores do mundo inteiro. Nesse contexto, as técnicas baseadas em radiação de campo próximo têm despontado como uma boa alternativa para quebra do limite de difração, que constitui um limite natural para os instrumentos óticos convencionais. Além disso, a microscopia de campo próximo em modo de iluminação e contato adquire simultaneamente informações óticas e topográficas do material, o que permite fazer uma distinção entre as propriedades óticas nanométricas reais e as induzidas por topografia. O fenômeno de domínios cristalográficos tem sido um assunto de interesse da cristalografia desde que ela começou a se desenvolver como ciência. As razões óbvias para isso são a beleza de formas externas de algumas estruturas de domínios, assim como as evidentes e desafiantes relações de simetria entre os seus constituintes. Os domínios ferroelásticos são um dos importantes tipos de domínios apresentados por cristais. Tais domínios apresentam, algumas vezes, dimensões muito reduzidas sem manifestar uma considerável alteração na estrutura topográfica da amostra. Por outro lado, o comportamento ótico de domínios distintos pode ser bem diferente quando sujeitos a uma mesma condição de medida. Tais características tornam esta classe de materiais ideais para um estudo baseado na microscopia de campo próximo em modo de iluminação e contato. Imagens de domínios ferroelásticos, utilizando microscopia de campo próximo em modo de iluminação e contato, foram obtidas com resolução nanométrica. Tais imagens, em geral, apresentaram pouquíssima relação com a estrutura topográfica do material, revelando importantes características óticas (ocorrência do efeito de guias de onda nos domínios) e estruturais (dimensões dos domínios ferroelásticos, presença de defeitos de deslocamento na rede cristalina).

abstract: Fingerprints have been widely used as a practical method of biometrics authentication or identification with a significant level of security. However, several spoofing methods have been used in the last few years to bypass fingerprint scanners, thus compromising data security. The most common attacks occur by the use of fake fingerprint during image capturing. Imposters can build a fake fingerprint from a latent fingerprint left on items such as glasses, doorknobs, glossy paper, etc. Current mobile fingerprint scanning technology is incapable of differentiating real from artificial fingers made from gelatin molds and other materials. In this work, the adequacy of terahertz imaging was studied as an alternative fingerprint scanning technique that will enhance biometrics security by identifying superficial skin traits. Terahertz waves (0.1 – 10 THz) are a non-ionizing radiation with significant penetration depth in several non-metallic materials. Several finger skin features, such as valley depth and sweat ducts, can possibly be imaged by employing the necessary imaging topology. As such, two imaging approaches 1) using quasi-optical components and 2) using near-field probing were investigated. The numerical study is accomplished using a commercial Finite Element Method tool (ANSYS, HFSS) and several laboratory experiments are conducted to evaluate the imaging performance of the topologies. The study has shown that terahertz waves can provide high spatial resolution images of the skin undulations (valleys and ridges) and under certain conditions identify the sweat duct pattern. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

Longtemps cantonnées au visible et au proche IR, des nanostructures résonantes sont à présent réalisées dans l’IR, notamment en vue d'applications spectroscopiques. Pour étudier la réponse de ces nanostructures des moyens de caractérisation spécifiques doivent être mise en œuvre. Nous considérons la réponse IR de nano-structures et développons des outils à même de les caractériser. Nous nous sommes intéressés à des échantillons pouvant présenter des modes localisés de surface associés à des Plasmons Polaritons au sein de semiconducteurs fortement dopés ou des Phonons Polaritons dans des matériaux semiconducteurs polaires comme SiC. Cette étude a été menée d’abord en champ lointain (Spectroscopie à Transformée de Fourier et analyse Kramers-Kronig) pour étudier la réponse collective des nanostructures. Nous montrons que la fonction diélectrique de l’échantillon structuré peut être représentée par un oscillateur de Lorentz amortit modifié. Une permittivité effective est aussi déterminée par l’emploi de matrices de transfert pour rendre compte de la réflectivité complexe. L’étude en champ proche permet ensuite d’obtenir une réponse individuelle des structures. Nous développons ici une méthode d’extraction novatrice de l’amplitude et de la phase du signal avec un rapport signal à bruit optimum. Après avoir théoriquement et expérimentalement démontré la pertinence de l’approche, la signature de SPP localisés a pu être observée par des cartographies de champ complexe en fonction de la longueur d’onde. Les images obtenues sont confrontées à des simulations électromagnétiques et discutées / We studied the response of a nano-structured material to an IR electromagnetic excitation. For a given geometry, this response is dictated by the dielectric function to which phonons and free carriers contribute. In case of defect-free semiconductors the phonon response is the dominant term; however when we consider doped semi-conductors the plasmon response plays a major role. In both case, the permittivity functions can be negative with small losses which permits a resonant coupling between the surface modes and the electromagnetic excitation. Our work focuses on the development of experimental tools to analyze both SPP and SPhP. This study was conducted in the far-field regime to see a collective response and in the near-field regime to study nano-structures individually. In far-field, the experimental spectroscopic response of the material was conducted by Fourier Transform Infrared Reflectivity and Kramers-Kronig analysis. Quantitative information on the dielectric function was extracted using a modified Lorentz damped oscillator to fit the reflectivity. An effective permittivity is also retrieved using a transfer matrix method. The near-field study was done in a two-step procedure. The first step was the development of an innovative detection technique with optimum signal to noise ratio. The second step was the implementation of this technique to NSOM after proving its success. LSPP were detected using the developed NSOM. A spectroscopic study was performed as well. Experimental results were compared to theoretical ones obtained with electromagnetic simulations

No description available.

Today’s society is one where technological advances are made daily, which increases the need to stop and assess the risks against users’ integrity when integrating new technology in contemporary systems all the greater. We have taken two technologies, Near Field Communication and Certified Wireless USB, whose envisioned area of use is to be integrated into mobile phones, and evaluated what security threats are revealed for the respective technologies. The threats against security have been identified through research of the standards and existing reports for each technology. Practical experiments have not been conducted on account of us not having access to any equipment to run such trials. The result of our studies is indecisive; pitched against Certified Wireless USB’s rigorous and robust security measures, implemented on hardware level, Near Field Communication’s lack of any such security implementations shines all the brighter. The real difference can be traced to the philosophy behind the technologies – Certified Wireless USB can be perceived as a complete product, while Near Field Communication bears more resemblance to a tool. In order to safely use a tool, knowledge about its use is required, thus in order to securely use Near Field Communication we propose two solutions; secure channel and secure identification, which developers can implement on a software level. Furthermore, we suggest that the implementation of security should be based on an incremental model where the security measures are scaled up in direct correlation with the sensitivity of the information managed. Our results imply that Near Field Communication does not have the inherent security that it should have in order to be safely and securely integrated into any system as it is. Therefore, measures have to be taken in order to implement this technology securely on a software level. For Certified Wireless USB it implies that nothing further is needed to achieve a secure implementation as the only weakness it displays is against Side Channel attacks, which are so complicated (and require direct access to the system) that we have deemed them unlikely to be attempted.

The last few years has witnessed a fast growth in technological advancement which has led to the development of several consumer electronic devices for different purposes or functionalities. For convenience and efficiency, there is the need to bring together all the different functionalities of these devices into a single multipurpose device such as mobile phone with the help of NFC (near field communication) technology. The need for NFC technology in mobile devices is fast gaining popularity in some countries, especially with the successes recorded in some of the NFC pilot projects. The NFC enabled mobile device is very intuitive; works with already existing infrastructures (i.e. ISO/IEC 14443 smartcards and it readers), allows for multiple applications, has a high level of security and comes with unique and attractive features, such as the ability to serve as both reader and writer modes, etc. NFC standards are specified by NFC Forum and it has a well organised ecosystem. This thesis is focused on the potentials of NFC and how it is used as a multipurpose device.