351 |
行動支付之探討-以電信運營商為例陳忠義 Unknown Date (has links)
由於智慧型手機與各種手持裝置日漸普及,4G行動上網速度與行動支付安全性、便利性與即時性的提升,行動支付(Mobile Payment)在這幾年已然成為電信、金融、手機軟硬體製造產業之間最熱門的話題之一,多樣化之支付型態因應而生。將個人行動裝置結合金融支付工具進行交易,讓使用者不需帶錢包出門即能輕鬆完成小額支付是未來趨勢,世界各國行動支付的比例逐漸提高,邁入無現金社會。
台灣電信運營商也積極在行動支付戰場爭取一席之地,陸續推出電信運營商帳單代付(Direct Carrier Billing,DCB)及近距離無線通訊(Near Field Communication,NFC)相關行動支付應用服務,以增加創新服務體驗及客戶黏著度,最終目標為提高客戶平均貢獻度(Average Revenue Per User,ARPU)。
本研究採用質性研究方法,透過次級資料蒐集、整理及分析,瞭解國外電信運營商之成功案例從中擷取鑑往知來的想法和做法,再深入觀察目前國內電信運營商在DCB的壞帳風險過高的問題及NFC電子錢包等行動支付之發展現況與窘境。最後提出建議,建議一為推動成立「電信聯合徵信中心」以共同降低壞帳風險,同時針對DCB用戶之消費項目進行分析以精準行銷並提升ARPU;建議二為推廣以「行動號碼」為數位身份認證(Mobile Connect)之行動支付平台,不僅可增加電信運營商之營收,更能夠滿足消費者追求快速、便利、安全性的需求。 / With the increasing popularity of smart phones and handheld devices, The 4G high mobility speeds and the security, convenience and real-time of mobile payment were improved. In recent years Mobile Payments have become a hot topic between the telecommunications, financial industry, mobile hardware and software manufacturing industry, diversified payment patterns in response. It is the future trend to combine personal mobile devices with financial payments tools so that users can easily make small payment no need to bring their wallet. The proportion of the Mobile Payment by countries in the world is gradually increasing and moving towards a cashless society.
Taiwan's telecom operators are also preparing to carve out a niche for themselves in the mobile payment battlefield by launching Direct Carrier Billing (DCB)and Near Field Communication(NFC)related mobile payment application service to increase innovative service experience and customer adhesion, The ultimate goal is to enhance their Average Revenue Per User(ARPU).
This research uses Qualitative Research Methods by collect, collate and analyze secondary data to understand the ideas and practices of observing the successful cases of foreign telecom operators to capture from the past to further understanding and solutions. And in-depth observation of the current domestic telecom operator’s highly bad debt risk in DCB and development situation and dilemma of the NFC related mobile payments. Finally, suggestion one is to facilitate the establishment of "Telecom’s Joint Credit Information Center" to reduce the risk of bad debts and then analyze the consumption items of DCB subscribers for precise marketing to enhance ARPU. Suggestion two is to promote “Mobile Connect” digital authentication solution with “Mobile Directory Number” in mobile payment’s platform. It not only increases the revenue of telecom operators, but also satisfy needs of consumer’s about seeking fast, convenient and safe.
|
352 |
Evaluation of industrial wireless communications systems’ securitySoderi, S. (Simone) 07 June 2016 (has links)
Abstract
The worldwide success of wireless communications was originally fueled by the possibility to replace existing cables with wireless solutions. This phenomenon imposed the development of security engineering as a multidisciplinary field. Although wireless solutions can reduce installation costs and allow introducing new services, the end–users expect it to have the same level of security as they would normally have with wired solutions. Secure communications is an important part of the overall security of industrial wireless communications systems (IWCS).
The aim of this thesis is to develop new security engineering methodologies for IWCS. The author develops countermeasures against confidentiality and integrity attacks and carries out a security analysis covering the protocol, electromagnetic and physical layer. In the first part of the thesis, Host Identity Protocol (HIP) is utilized to secure communication in an intra–vehicular network. Simulations and measurement campaigns are also conducted to evaluate the impact of the overhead on security in a tunnel, considering line–of–sight (LOS) and non–LOS (NLOS) scenarios.
Electromagnetic analysis (EMA) is an important step in the development of safety–related systems. Today, the increasing usage of smaller integrated circuit also increases the susceptibility to electromagnetic (EM) interference. From near–field (NF) to far–field (FF) transformation, a method for the evaluation of the emissions leakage is investigated. The virtual EM (VEM) interface of the device–under–test (DUT) is studied, and it is described how an adversary can exploit it for denial of service (DoS) attacks. An effective jamming attack model is studied, and the theoretical calculations are validated with experiment–based results.
Finally, focusing attention on physical layer security, two algorithms are developed. Active radio frequency fingerprinting (RFF) implements the exchange of a public key during the setup of secure communication. Afterwards, utilizing a jamming receiver in conjunction with the spread spectrum (SS) watermarking technique, the watermark–based blind physical layer security (WBPLSec) protocol is presented. The analysis and results indicate how the WBPLSec seems to be a valuable technique for deploying physical layer security by creating a secure region around the receiver. / Tiivistelmä
Langattoman tietoliikenteen maailmanlaajuista suosiota kiihdytti alun perin mahdollisuus korvata tietoliikennejärjestelmissä käytetyt kaapelit langattomilla ratkaisuilla. Ilmiö lisäsi myös tarvetta kehittää alan turvatekniikkaa monialaisen tutkimuksen pohjalta. Vaikka langattomat ratkaisut merkitsevät pienempiä asennuskustannuksia ja tarjoavat mahdollisuuksia luoda uudenlaisia palveluja, järjestelmien loppukäyttäjät edellyttävät kuitenkin niiden turvallisuuden olevan vastaavalla tasolla kuin langallisissa verkoissa. Myös teollisuuden langattomien tietoliikennejärjestelmen turvallisuus riippuu pitkälti viestintäkanavien turvallisuudesta.
Väitöksen tavoitteena on kehittää uusia menetelmiä, joilla teollisuuden langattomat tietoliikennejärjestelmät voitaisiin turvata. Väitöksessä kehitetään toimenpiteitä tietoliikennejärjestelmien luottamuksellisuuteen ja koskemattomuuteen kohdistuvia hyökkäyksiä vastaan ja toteutetaan turvallisuusarviointi, joka kattaa järjestelmän protokollakerroksen sekä sähkömagneettisen ja fyysisen kerroksen. Väitöksen ensimmäisessä osassa hyödynnetään HIP–protokollaa (Host Identity Protocol) liikennevälineen sisäisen tietoliikennejärjestelmän turvallisuuden varmistamisessa. Lisäksi siinä kuvataan simulaatiot ja mittaushankkeet, joiden tavoitteena on arvioida käytetyn protokollan turvallisuusvaikutuksia esteettömän (line–of–sight, LOS) ja esteellisen (non–line–of–sight, NLOS) näköyhteyden tapauksissa.
Sähkömagneettinen analyysi on tärkeä vaihe turvajärjestelmien kehitysprosessissa. Järjestelmissä käytetään yhä enemmän pieniä integroituja piirejä, mikä voi myös altistaa ne sähkömagneettisille (electromagnetic, EM) häiriöille. Väitöksessä tutkitaan lähikenttä–kaukokenttä -muunnokseen perustuvan arviointimenetelmän avulla sähkömagneettisen vuotosäteilyn tasoa. Lisäksi perehdytään testattavan laitteen (device under test, DUT) virtuaaliseen EM–liitäntään ja kuvataan, miten vastaavaa liitäntää voidaan hyödyntää palvelunestohyökkäyksissä. Väitöksessä tutkitaan myös tehokasta häirintämallia ja validoidaan teoreettisten laskelmien tulokset kokeellisesti.
Lopuksi väitöksessä keskitytään tietoliikennejärjestelmän fyysisen kerroksen turvallisuuteen ja kehitetään kaksi algoritmia. Aktiivisen radiotaajuisen tunnistusmenetelmän avulla voidaan vaihtaa julkisia avaimia turvallista tietoliikenneyhteyttä muodostettaessa. Lisäksi esitellään vesileimausmenetelmään perustuva fyysisen kerroksen salausmenetelmä, WBPLSec. WBPLSec luo vastaanottimen ympärille suoja–alueen, minkä ansiosta se vaikuttaa analyysin ja tutkimustulosten perusteella olevan tehokas menetelmä toteuttaa fyysisen kerroksen suojaus.
|
353 |
Etude et manipulation de modes résonnants en champ proche optique / Pas de titre en anglaisBrissinger, Damien 17 November 2010 (has links)
Avec l’évolution rapide des techniques de nanofabrication et les besoins croissants d’intégration et d’utilisation à moindre cout énergétique, l’étude et la manipulation de résonances électromagnétiques d’objets de faibles dimensions représentent des enjeux cruciaux. Un des objectifs de ce travail de thèse a donc été d’approfondir nos connaissances de l’interaction entre le champ électromagnétique et la matière. Dans ce but la réalisation conjointe d’expériences en champ proche optique et le développement numérique de modèles associés nous ont permis d’étudier différentes résonances électromagnétiques basées sur l’interaction lumière-matière au sein d’objets de dimensions sub-micrométriques. Dans une première partie, ce manuscrit présente les phénomènes mis en jeu en microscopie champ proche optique et décrit le fonctionnement du microscope SNOM utilise. La seconde partie est dédiée à l’étude de l’interaction d’une sonde champ proche avec une nano-cavité Fabry-Perot en régime non-linéaire. Dans un premier temps, on présente l’étude des non-linéarités de nano-cavités en Silicium à grand facteur de qualité et faible volume modal, démontrant ainsi l’obtention d’un régime de fonctionnement bistable pour de très faibles puissances. Dans un deuxième temps, on démontre la modulation possible via la sonde champ proche de ce régime de bistabilité. Enfin, on étudie dans la troisième partie de ce manuscrit les résonances de films minces métalliques. L’étude complète des modes propres et de l’excitation optique de cette structure a permis de connaitre avec précision les modes résonants et les angles de Brewster du film mince. Cette étude a été prolongée expérimentalement par l’étude en champ proche optique des modes résonants de demi-films minces métalliques. Lors de ces deux études, les mesures expérimentales ont été systématiquement accompagnées par l’analyse théorique et le développement numérique de modèles que les expériences réalisées ont permis de valider et de discuter. / Within the quick nano-fabrication techniques evolution and the increasing needs in low space and energy opto-electronic functions on-chip integration, studies and control of electromagnetic resonances of sub-micrometric objects are crucial issues. One aim of this work was then to improve our knowledge of the light-matter interaction. To this end, optical near-field experiments and complementary numerical development of models have been performed to study electromagnetic resonances due to light-matter interaction in sub-micrometric resonators. As an introduction, the first part of the manuscript presents the main phenomena involved in near-field optical microscopy and the used SNOM operation. The second part is dedicated to nearfield tip/Fabry-Perot micro-resonator interaction in the non-linear regime. In this part, we first present the study of high-Q/small volume Silicon nano-cavity non-linearities, showing possible bistable operation at very low incident power. We then demonstrate the cavity stability modulation obtain with the near-field tip. In the third part of the manuscript, we consider thin metallic film resonances. As a beginning, we realize an exhaustive study of the film eigenmodes and then discuss the resonant optical excitation of the film as well as precise determination of Brewster angle. These theoretical studies have been extended experimentally with the optical near-field determination of the resonant modes of semi-infinite thin films. For the different studies, experimental measures have been systematically associated with theoretical analyses and numerical developments of models, which have then been confirmed or discussed in light of the experimental results.
|
354 |
High speed bio atomic force microscopy : application à l'étude de la structure et dynamique d'assemblage supramoléculaires : étude des interactions au niveau de la celluleEwald, Maxime 12 December 2011 (has links)
Le microscope à force atomique (AFM) fait partie des microscopies de champ proche dites à sonde locale. De par sa versatilité, un grand nombre de domaines des nanosciences tant en physique, que chimie ou biologie utilisent cette technique. Cependant, le champ d’investigation de la microscopie AFM classique est restreint temporellement et spatialement. En effet, en raison de sa limite de vitesse d’acquisition d’image et sa limite de caractérisation des interactions en surface, des études de dynamique moléculaire ou d’éléments sub-surface ne sont pas envisageables. Nous montrons donc que la caractérisation en volume est permise en utilisant une méthode d’imagerie non destructive, la microscopie de champ proche holographique ultrasonore (SNFUH). Cette méthode développée pour étudier à l.air et en liquide, a fourni des informations localisées en profondeur avec une haute résolution spatiale, en utilisant des fréquences de résonance dans la gamme du MHz. Une calibration a été effectuée sur des échantillons de structures enterrées ou non, réalisés par lithographie e-beam. Ces échantillons ont été utilisés pour ajuster les fréquences de résonance et comprendre la formation des images en mode acoustique (profondeur investiguée et inversion de contraste). Cet outil non invasif et innovant de caractérisation a donc été développé. Il présente un énorme potentiel pour des échantillons biologiques en termes de résolution et d’information. Les microscopes AFMclassique et acoustique SNFUH sont soumis à des contraintes de temps. Pour s’en affranchir, un prototype, le microscope à force atomique haute-vitesse (HS-AFM) a été développé par l’équipe du Professeur T. Ando à l’Université de Kanazawa (Japon). Il autorise ainsi le balayage à vitesse vidéo, i.e. 25 images/s, en milieu liquide. Nous avons amélioré le prototype avec une nouvelle génération de boucle d’asservissement et augmenté la zone de caractérisation. La résolution dépend fortement du levier utilisé. De plus une qualité d’image supérieure est obtenue grâce à l’utilisation de surpointes en carbone sur ces mêmes leviers. Finalement, nous montrons des résultats obtenus avec ces deux techniques de microscopies sur différents édi.ces biologiques en milieu liquide. Ainsi, avec le microscope AFM haute-vitesse, des dynamiques biomoléculaires ont pu être visualisées (ex : structures protéine-ADN) avec une résolution nanométrique. Puis une étude des changements conformationnels intracellulaires de kératinocytes vivantes dans leur milieu physiologique a été réalisée par microscopie acoustique SNFUH et montre la dégradation du matériel biologique. L’ensemble de ces résultats ouvre un nouveau champ d’investigation dans le domaine de la biologie. / The atomic force microscope (AFM) made part of scanning near-field probe microscopy. Thanks to its versatility, many fields as physics, chemistry or biology use this technique. However, the field of investigation of the classical AFM microscope is limited temporally and spatially. Indeed, due to his scan speed limitation and surface interaction caracterisation limitation, studies of molecular dynamics and sub-surface elements are not possible. We show that the volume caracterisation is permitted using a non-destructive imaging method, called Scanning Near-Field by Ultrasound Holography (SNFUH). This tool developed for study in air and liquid has provided depth information as well as spatial resolution at the nanometer scale using resonant frequencies of about range of MHz. Calibration has been performed on samples of buried or not structures made by e-beam lithography and have been used to adjust the resonant frequency and understand the acoustic image formation (depth investigation and contrast in-version). We have developed a non-invasive and innovative tool of characterization for biology : he presents a huge potential for biological samples in terms of resolution and information. Classical AFM and acoustic SNFUH microscopes are time resolution limited. To overcome this time constraint, a prototype, High Speed Atomic Force Microscope (HS-AFM), has been developed by the team of Prof. T. Ando, Kanazawa University (Japan). It allows a scan rate at video speed, i.e. 25 frames/s, in liquid medium. We have improved the prototype, through a new generation of feedback control and increased the scan area. The resolution depends strongly of the probe used. Moreover a better image quality is obtained through the use of carbon tips on these cantilevers. Finally, we show our results obtained with these two microscopy techniques about biological buildings in liquid environment. Thereby, with the HS-AFM microscope, biomolecular dynamics have been visualized (e.g. protein-DNA structures) with nanometric resolution. Then a study about intracellular conformational changes of keratinocytes living cells in their physiological medium has been realized by acoustic microscopy SNFUH and show deterioration of biological components. All of these results provide new insights in biology field.
|
355 |
Využití kovové sondy pro ovládání optických procesů a zobrazování v blízkém poli / Applications of metallic probe for the control of optical processes and near-field imagingGallina, Pavel January 2018 (has links)
Hlavním předmětem této diplomové práce jsou elektromagnetické simulace pomocí metody konečných prvků (FEM) k vyšetření vlivu grafenu na hrotem zesílenou Ramanovu spektroskopii (TERS) a povrchem zesílenou infračervenou absorpční spektroskopii (SEIRA) a k prozkoumání citlivosti sondy skenovacího optického mikroskopu blízkého pole (SNOM) ke složkám elektromagnetického pole v závislosti na parametrech sondy (průměru apertury v pokovení). Nejprve je proveden výpočet TERS systému složeného ze stříbrného hrotu nacházejícího se nad zlatým substrátem s tenkou vrstvou molekul, jehož účelem je porozumění principů TERS. Poté je na molekuly přidána grafenová vrstva, aby se prozkoumal její vliv ve viditelné (TERS) a infračervené (SEIRA) oblasti spektra. Druhá část práce se zabývá výpočty energiového toku SNOM hrotem složeným z pokoveného skleněného vlákna interagujícím s blízkým polem povrchových plasmonových polaritonů. Zde uvažujeme zlatou vrstvu se čtyřmi štěrbinami uspořádanými do čtverce na skleněném substrátu sloužícími jako zdroj stojatého vlnění povrchových plasmonů s prostorově oddělenými maximy složek elektrického pole orientovanými rovnoběžně či kolmo na vzorek. Ve výpočtech hrotem zesílené spektroskopie zjišťujeme, že grafen přispívá pouze malým dílem k zesílení pole ve viditelné oblasti spektra, ovšem v infračervené oblasti má grafen vliv pro záření s energií menší než dvojnásobek Fermiho energie grafenu, pro kterou je hodnota zesílení pole větší než v případě výpočtu bez grafenu. Avšak pro velmi vysoké vlnové délky zesílení pole v přítomnosti grafenu klesá pod (konstantní) hodnotu pro případ bez grafenu. Při studiu citlivosti SNOM hrotu k jednotlivým složkám pole shledáváme, že pro hrot se zlatým pokovením je energiový tok skleněným jádrem hrotu kombinací příspěvků energie prošlé aperturou a periodické výměny energie mezi povrchovým plasmonem šířícím se po vnějším okraji pokovení a mody propagujícími se v jádře. Dále zjišťujeme, že hroty s malou aperturou (či bez apertury) jsou více citlivé na složku elektrického pole orientovanou kolmo ke vzorku (rovnoběžně s osou hrotu), zatímco hroty s velkou aperturou sbírají spíše signál ze složky rovnoběžné s povrchem vzorku. V případě hrotu s hliníkovým pokovením jsou hroty citlivější ke složce pole rovnoběžné s povrchem, což je způsobeno slabším průnikem pole skrze pokovení.
|
356 |
Záření soustav antén v blízké zóně / Radiation of antenna array in near-field areaHermany, Jiří January 2008 (has links)
The aim of my diploma thesis is to analyze the antenna array radiation and to produce the antenna array radiation computation program. The program should display the electric and magnetic intensity and radiation power density distribution over the planar or cylindrical surface in the near-field area. The antenna array analyzed in this paper consists of a number of elementary dipoles placed in a row with a reflector which represents the conductive board situated in parallel to the row of dipoles. The demonstration program was built in MATLAB and allows computing and displaying the computed values components of antenna array radiation on the planar or the cylindrical surface. The program also allows saving computed values, saving displayed graphs, or saving the adjusted parameters of antenna array. The created program can be used for the presentation of the antenna array radiation in a school laboratory or for the graphical representation when a new antenna is designed.
|
357 |
Skener elektromagnetických polí a jeho využití při měření elektromagnetické kompatibility / Electromagnetic field scanner and its utilization in EMC measurementChupáč, Michal January 2013 (has links)
Master’s thesis is focused on making the acquaintance of EMC issues and ways of electromagnetic field scanner RS321 utilization for pre-compliance measurements. First part contains analysis of available equipment’s influence on measurement results on the basis of gathered specification. Next part includes an example measurement used as operational manual for scanner and its controlling program. The most important part is correction evaluation for performed EMI measurement of signal generator using its EMC certification protocol and application of gained correction curve on independent EMI measurement of device tested by EMC testing laboratory. Other possibilities of scanner utilization are mentioned in the next chapters. Last part of the thesis contains suitability evaluation of EMC scanner on the basis of findings from performed measurements.
|
358 |
Lokální optické a elektrické charakteristiky optoelektronických součástek / Local optical and electrical characteristics of optoelectronic devicesŠkarvada, Pavel January 2012 (has links)
Solar energy conversion, miniaturization of semiconductor devices and associated lifetime, reliability and efficiency of devices are the basic premise of this work. This work is focused on the study of optoelectronic devices especially solar cells and its nondestructive diagnostic. Solar cells are advantageous for study mainly because the pn junction is located near the surface and contains a lot of inhomogeneities. It has been difficult until recently to investigate their local physical (electrical and optical) parameters due to the size of inhomogeneities. Behavior of inhomogeneities can be well understood with knowledge of its local properties. Establishment of measurement workplace, that satisfies requirements for measurement of local emission and optically induced current measurement, allows us detection and localization of inhomogeneities with spatial resolution more or less 100 nm. The core of thesis is characterization of imperfection using nondestructive techniques in the macroscopic region but primarily in microscopic region using scanning probe microscopy. Integral parts of the work are characterization techniques for photoelectrical devices, microscopic techniques and data processing. Scanning near-field optical microscope is used for the purpose of microscopic characterization such as topography, local optical, photoelectrical and electrooptical properties of structures in high spatial resolution. Locally induced current technique, current voltage characteristics, emission from reversed bias pn junction measurement including its thermal dependence are used for samples investigation in macroscopical region. It is possible to localize defects and structure inhomogeneity using mentioned techniques. Localised defects are consequently analyzed for composition and measured using electron microscopy. Specific outputs of work are classification of photoelectric devices defects and specification of nondestructive characterization techniques used for defect detection. Experimental characterization techniques are described together with defects measurement procedures. The key output is the catalog of serious defects which was detected. Particular defects of samples are shown including describe of its properties and physical meaning.
|
359 |
THz Near-Field Microscopy and Spectroscopyvon Ribbeck, Hans-Georg 31 March 2015 (has links)
Imaging with THz radiation at nanoscale resolution is highly desirable for specific material investigations that cannot be obtained in other parts of the electromagnetic spectrum. Nevertheless, classical free-space focusing of THz waves is limited to a >100 μm spatial resolution, due to the diffraction limit. However, the scattering- type scanning near-field optical microscopy (s-SNOM) promises to break this diffraction barrier. In this work, the realization of s-SNOM and spectroscopy for the THz spectral region from 30–300 μm (1–10 THz) is presented.
This has been accomplished by using two inherently different radiation sources at distinct experimental setups: A femtosecond laser driven photoconductive antenna, emitting pulsed broadband THz radiation from 0.2–2 THz and a free-electron laser (FEL) as narrow-band high-intensity source, tunable from 1.3–10 THz.
With the photoconductive antenna system, it was demonstrated for the first time that near-field spectroscopy using broadband THz-pulses, is achievable. Hereby, Terahertz time-domain spectroscopy with a mechanical delay stage (THz-TDS) was realized to obtain spectroscopic s-SNOM information, with an additional asynchronous optical sampling (ASOPS) option for rapid far-field measurements. The near-field spectral capabilities of the microscope are demonstrated with measurements on gold and on variably doped silicon samples. Here it was shown that the spectral response follows the theoretical prediction according to the Drude and the dipole model. While the broadband THz-TDS based s-SNOM in principle allows for the parallel recording of the full spectral response, the weak average power of the THz source ultimately limits the technique to optically investigate selected sample locations only.
Therefore, for true THz near-field imaging, a FEL as a high-intensity narrow- band but highly-tunable THz source in combination with the s-SNOM technique, has been explored. Here, the characteristic near-field signatures at wavelengths from 35–230 μm are shown. Moreover, the realization of material sensitive THz near-field imaging is demonstrated by optically resolving, a structured gold rod with a reso- lution of up to 60 nm at 98 μm wavelength. Not only can the gold be distinguished from the silica substrate but moreover parts of the structure have been identified to be residual resin from the fabrication process. Furthermore, in order to explore the resolution capabilities of the technique, the near-fields of patterned gold nano- structures (Fischer pattern) were imaged with a 50 nm resolution at wavelengths up to 230 μm (1.2 THz). Finally, the imaging of a topography-independent optical material contrast of embedded organic structures, at exemplary 150 μm wavelength is shown, thereby demonstrating that the recorded near-field signal alone allows us to identify materials on the nanometer scale.
The ability to measure spectroscopic images by THz-s-SNOM, will be of benefit to fundamental research into nanoscale composites, nano-structured conductivity phenomena and metamaterials, and furthermore will enable applications in the chemical and electronics industries. / Die Bildgebung mit THz Strahlung im Nanobereich ist höchst wünschenswert für genaue Materialuntersuchungen, welche nicht in anderen Spektralbereichen durchgeführt werden kann. Aufgrund des Beugungslimits ist kann jedoch mit klassischen Methoden keine bessere Auflösung als etwa 100 μm für THz-Strahlung erreicht werden. Die Methode der Streulicht-Nahfeldmikroskopie (s-SNOM) verspricht jedoch dieses Beugungslimit zu durchbrechen.
In der vorliegenden Arbeit wird die Realisierung der Nahfeld-Mikroskopie und Spektroskopie im THz-Spektralbereich von 30–1500 μm (0.2–10 THz) präsentiert. Dies wurde mittels zweier grundsätzlich unterschiedlichen Strahlungsquellen an separaten Experimentaufbauten erreicht: Einer photoleitenden Antenne welche gepulste breitbandige THz-Strahlung von 0.2–2 THz emittiert, sowie einem Freie- Elektronen Laser (FEL) als schmalbandige hochleistungs Quelle, durchstimmbar von 1.3–10 THz.
Mit dem photoleitenden Antennensystem konnte zum ersten mal demonstriert werden, dass mit breitbandigen THz-Pulsen Nahfeldspektroskopie möglich ist. Dazu wurde die übliche THz-Time-Domain-Spektroskopie (THz-TDS) zur Erhaltung der spektroskopischen s-SNOM Informationen, sowie asynchrones optisches Abtasten (ASOPS) für schnelle Fernfeld Spektroskopie eingesetzt. Die nahfeldspektroskopischen Fähigkeiten des Mikroskops wurden anhand von Messungen an Gold sowie unterschiedlich dotierten Siliziumproben demonstriert. Dabei konnte gezeigt werden, dass die spektrale Antwort den theoretischen Voraussagen des Drude- sowie Dipol Modells folgt. Während das breitband THz-TDS basierte s-SNOM spektroskopische Nahfelduntersuchungen zulässt, limitiert jedoch die schwache Ausgangsleistung der THz-quelle diese Technik insofern, dass praktisch nur Punktspektroskopie an ausgesuchten Probenstellen möglich ist.
Für echte nanoskopische Nahfeldbildgebung wurde daher ein FEL als durchstimmbare hochleistungs THz-Quelle in Kombination mit der s-SNOM-Technik erforscht. Hierzu wurden die charakteristischen Nahfeld-Signaturen bei Wellenlängen von 35–230 μm untersucht, gefolgt von die Verwirklichung materialsensitiver THz Nahfeldbildgebung gezeigt an Goldstreifen mit bis zu 60 nm Auflösung. Dabei kann nicht nur das Gold von dem Glassubstrat unterschieden werden, sondern auch Ablagerungen als Überreste des Fabrikationsprozesses identifiziert werden. Um die Grenzen der Auflösungsmöglichkeiten dieser Technik zu sondieren, wurden weiterhin die Nahfelder von gemusterten Gold-Nanostrukturen (Fischer-Pattern) bei Wellenlängen bis zu 230 μm (1.2 THz) abgebildet. Hierbei wurde eine Auflösung von 50 nm festgestellt. Schliesslich konnte der topographieunabhängige Materialkontrast von eingebetteten organischen Strukturen, exemplarisch bei 150 μm Wellenlänge, gezeigt werden.
Die Fähigkeit, spektroskopische Aufnahmen mittels der THZ-s-SNOM Technik zu erzeugen, wird der Grundlagenforschung und in der Nanotechnologie zu Gute kommen, und weiterhin Anwendungen in der Chemischen- und Halbleiterindustrie ermöglichen.
|
360 |
Mobile Reisebegleitung mit NFC-UnterstützungPfanstiel, Jörn, Keller, Christine, Funke, Alexandra, Heinig, Tristan, Schlegel, Thomas January 2012 (has links)
Die zunehmende Nutzung [1] persönlicher mobiler Geräte durch immer mehr Fahrgäste des öffentlichen Personenverkehrs (ÖPV) begünstigt die Entwicklung neuer Applikationen, die den allgegenwärtigen Zugriff auf domänenspezifische Inhalte und Echtzeitdaten über variable Schnittstellen und Informationskanäle realisieren. Near Field Communication (NFC) gilt in diesem Zusammenhang als eine vielversprechende Technologie, die neben kontaktloser Datenübertragung auch Bezahlvorgänge direkt über das mobile Endgerät ermöglicht. Mit Blick auf die unterschiedlichen Einsatzmöglichkeiten von NFC in der mobilen Reisebegleitung wird in diesem Beitrag eine ikonografische Klassifikation für die visualisierte Analyse von Anwendungsszenarien vorgestellt, welche zur Planung ubiquitärer Applikationen im ÖPV eingesetzt werden kann.
|
Page generated in 0.0947 seconds