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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Evaluating Vivado High-Level Synthesis on OpenCV Functions for the Zynq-7000 FPGA

Johansson, Henrik January 2015 (has links)
More complex and intricate Computer Vision algorithms combined with higher resolution image streams put bigger and bigger demands on processing power. CPU clock frequencies are now pushing the limits of possible speeds, and have instead started growing in number of cores. Most Computer Vision algorithms' performance respond well to parallel solutions. Dividing the algorithm over 4-8 CPU cores can give a good speed-up, but using chips with Programmable Logic (PL) such as FPGA's can give even more. An interesting recent addition to the FPGA family is a System on Chip (SoC) that combines a CPU and an FPGA in one chip, such as the Zynq-7000 series from Xilinx. This tight integration between the Programmable Logic and Processing System (PS) opens up for designs where C programs can use the programmable logic to accelerate selected parts of the algorithm, while still behaving like a C program. On that subject, Xilinx has introduced a new High-Level Synthesis Tool (HLST) called Vivado HLS, which has the power to accelerate C code by synthesizing it to Hardware Description Language (HDL) code. This potentially bridges two otherwise very separate worlds; the ever popular OpenCV library and FPGAs. This thesis will focus on evaluating Vivado HLS from Xilinx primarily with image processing in mind for potential use on GIMME-2; a system with a Zynq-7020 SoC and two high resolution image sensors, tailored for stereo vision.
32

Analyse et modélisation de l'effet des marées sur les réseaux de nivellement hydrostatiques du CERN / Analysis and filtering of the effect of tides on the hydrostatic levelling systems at CERN

Boerez, Julien 21 February 2013 (has links)
Les géomètres de la section Survey de l’Organisation Européenne pour la Recherche Nucléaire (CERN) utilisent le nivellement hydrostatique HLS pour effectuer des alignements verticaux précis. Le HLS atteint des précisions micrométriques, ce qui lui permet d’être utilisé pour les expériences à but de physique fondamentale comme le Large Hadron Collider (LHC). HLS mesure certes des déformations qui ont pour conséquence de désaligner tout accélérateur de particules lié au sol, mais il mesure également d’autres phénomènes aux caractéristiques bien particulières. Parmi ces phénomènes mesurés, les marées terrestres représentent une part très largement majoritaire du signal. Leur effet sur les mesures HLS est périodique et engendre une inclinaison longue base qui n’aboutit pas au désalignement relatif des aimants constitutifs d’un accélérateur. Les objectifs de ce doctorat sont de pouvoir prédire les effets ne perturbant pas l’alignement relatif d’un accélérateur de particules et ainsi corriger les mesures HLS de ces signaux. En effet, les tolérances planimétrique et altimétrique à respecter dans le domaine des accélérateurs de particules sont de plus en plus serrées. Par exemple, le Compact Linear Collider (CLIC), aujourd’hui à l’étude de faisabilité, nécessite une précision d’alignement à 3σ de 10 μm dans une fenêtre glissante de 200 m selon les directions transversale et verticale. Le HLS est candidat pour assurer cet alignement vertical mais l’amplitude de marée est d’environ +/-20 μm à 200 m, rendant nécessaire la prise en compte de ce phénomène longue base pour que l’instrumentation réponde aux besoins du CLIC. Ce doctorat est inspiré des travaux déjà réalisés sur les inclinomètres longue base et décrit les effets mesurés par HLS afin de classer ces phénomènes selon qu’ils désalignent ou non un accélérateur de particules. Enfin, les outils et modèles pour prédire les effets maitrisables sont utilisés pour anticiper les différents signaux mesurés par les HLS installés au CERN. / The surveyors of the Large Scale Metrology section of the European Organization for Nuclear Research (CERN) use hydrostatic levelling systems (HLS) to perform precise vertical alignment measurements. The HLS achieves micrometer accuracy, which allows it to be used for the fundamental physics experiments such as the Large Hadron Collider (LHC). An HLS measures the deformations that lead to the misalignment of any particle accelerator linked to the ground, but it also measures other phenomena with very particular characteristics. Among these measured phenomena Earth tides form the main part of the signal. Their effect on HLS measurements is periodic and produces a long baseline tilt that does not lead to a relative misalignment of the magnets that constitute the accelerator.The objectives of this doctoral research are to be able to predict the effects which do not disturb the relative alignment of a particle accelerator and to remove these signals from the HLS measurements. Indeed, the horizontal and vertical positioning tolerances to be respected in the realm of particle accelerators are becoming tighter and tighter. For example, the Compact Linear Collider (CLIC), currently the object of a feasibility study, requires a 3σ alignment accuracy of 10 μm in a sliding window of 200 m, in both the transverse and vertical directions. The HLS is a candidate for measuring the vertical alignment but the amplitude of the tidal effect is approximately +/-20 μm over200 m, making it necessary to take into account this long baseline phenomenon for the instrument to meet the CLIC requirements.This doctoral thesis is inspired by previous work on the long baseline tiltmeters and describes the effects measured by HLS in order to classify the measured phenomena according to whether they could produce a misalignment of a particle accelerator or not. Finally, the tools and models to predict those effects that are well understood are used to anticipate the different signals measured by HLS installed at CERN.
33

Mätosäkerhet vid digital terrängmodellering med handhållen laserskanner : Undersökning av den handhållna laserskannern ZEB-REVO

Gustafsson, Amanda, Wängborg, Olov January 2018 (has links)
En digital terrängmodell (DTM) är en representation av enbart själva markytan. Det finns flera metoder för att framställa DTM:er, där laserskanning har blivit en alltmer vanlig metod. Inom laserskanning är flygburen laserskanning (FLS) en flitigt använd metod, då metoden har fördelen av att kunna täcka stora områden på kort tid. Det finns dock nackdelar med FLS då datainsamlingen kan bli bristfällig i t.ex. skogsområden, där laserstrålar inte kan tränga igenom tät vegetation. Här kan handhållen laserskanning (HLS) vara ett bra alternativ då HLS går snabbt och inte behöver samma omfattande planering. Tidigare studier visar att HLS har många fördelar, men som dock inte kan hålla samma låga osäkerhet som terrester laserskanning (TLS). Det saknas däremot studier om hur HLS ställer sig mot mätningar med FLS. Syftet med studien är därför att utvärdera möjligheten att använda och tillämpa mätningar med HLS för framställning av DTM i skogsterräng gentemot FLS. Detta görs genom att jämföra respektive DTM:s lägesosäkerhet. I studien användes instrumentet ZEB-REVO för insamlingen av data för metoden HLS. Medan för FLS användes laserdata från Lantmäteriet. Från insamlad laserdata skapades därefter DTM:er. Dessa jämfördes mot ett antal kontrollprofiler som mättes in med totalstation. För respektive metod, HLS och FLS, beräknades medelvärde för höjdavvikelserna mot kontrollprofilerna där även standardavvikelse beräknades. Resultatet visar att DTM:en skapad av data från FLS beräknades ha en höjdavvikelse för hela området på 0,055 m som medelvärde gentemot inmätta kontrollprofiler. Standardavvikelsen för denna höjdavvikelse beräknades till 0,046 m för FLS. För DTM:en med data från HLS beräknades en höjdavvikelse på 0,043 m i medelvärde som bäst, där standardavvikelse beräknades till 0,034 m. Studien visar att metoderna HLS och FLS gav likvärdiga resultat gentemot de inmätta kontrollprofilerna, dock gav HLS generellt mindre standardavvikelse i jämförelse mot FLS. Vidare ansågs ZEB-REVO och dess tillhörande databearbetningsprogram GeoSLAM vara väldigt användarvänligt, där själva skanningen med instrumentet tog endast 10 minuter för studiens område på ca 2000 m2. Utifrån studiens resultat drogs slutsatsen att mätningar med HLS kan ge en likvärdig DTM, sett till osäkerheten, som FLS-mätningar. HLS kan därmed vara en kompletterande metod men att FLS är en fortsatt effektiv metod. / A digital terrain model (DTM) represent exclusively the earth surface. There are several methods which can be utilized to create DTMs, where laser scanning have become a common used method. Airborne laser scanning (ALS) is often used since the method can cover a large area in a relatively short time. However a disadvantage with ALS is that the data collection, for a wooded area, can be inadequate due to penetration difficulties for some laser beams. For that reason a handheld laser scanner (HLS) can be an alternative since measurements can be done fast and does not need the same extensive planning. Earlier studies mention HLS to have several advantages but can still not yet be compared with terrestrial laser scanning (TLS) concerning the measurements uncertainty. There are, however, no studies that investigates how measurements with HLS stands against FLS. The purpose with the study is to evaluate the ability to use measurements from HLS to create a DTM for a wooded area in comparison with ALS. This is done by comparing the different uncertainties for each DTM. In the study the acquisition of HLS laser data was collected with the instrument ZEB-REVO and the ALS laser data was received from Lantmäteriet (cadastral mapping and surveying authority in Sweden). After the data acquisition a DTM were created from each data set (method). The DTMs were then compared to control profiles, which have been measured with total station. From the comparison with the control profiles average height deviation and standard deviation were calculated for each DTM. The result shows that the DTM created from ALS data received an average height deviation of 0,055 m for the whole area with a standard deviation of 0,046 m. Corresponding result for the DTM created from HLS data were calculated, at best, to 0,043 m in average height deviation and 0,034 m in standard deviation. The study shows that the methods HLS and ALS gave equivalent result regarding the comparison with the control profiles, however HLS gave a generally lower value for standard deviation. Furthermore ZEB-REVO with its processing program GeoSLAM was considered to be very easy and user friendly. The area (approx. 2000 m2) for the study was scanned within only 10 min. The conclusion which were drawn from the obtained result was that measurements with HLS can generate an equivalent DTM, concerning the uncertainty, as measurements with FLS. Thereby HLS can be a complementing method but still FLS is seen as an effective method.
34

An evaluation of the "Healthy lifestyle" and "Coping with change" personnel capacity building programmes of the S.A. Police Service / by Anna J.E. Jansen van Vuuren

Jansen van Vuuren, Anna Johanna Elizabeth January 2006 (has links)
Background: Due to various factors, such as the restructuring of the South African Police Service (SAPS) in 1996, Police Social Work Services decided to broaden the scope of its services by developing and introducing proactive personnel capacity building programmes (PCBP's). Fifteen PCB programmes had been developed by 1999, which gave rise to the need for a comprehensive impact assessment of these programmes. This resulted in the Evaluation of Personnel Capacity Building Programmes (EPCBP) research project that was launched in 2001. The evaluation of the Healthy Lifestyle and Coping with Change programmes formed part of this comprehensive study. Objectives: The primary aim of the study was to determine the effect of the Healthy Lifestyle (HLS) and Coping with Change (CWC) programmes on the knowledge, attitude and behaviour of SAPS personnel. Method: The comparison group pre-test and post-test design and triangulation were used during this research. Six measuring scales and a presenter's evaluation questionnaire were developed and completed by 196 (HLS) and 184 (CWC) experimental group respondents, 38 (HLS) and 41 (CWC) comparison group members and 10 (HLS) and 7 (CWC) presenters. Results: With the help of various measuring instruments and the triangulation of measurements, it was determined that the Healthy Lifestyle and Coping with Change programmes had a practical significant effect on the knowledge, attitude and behaviour of the respondents. It was concluded that these programmes were effective tools in the hands of Police Social Work Service (PSWS) because they not only empowered SAPS personnel to lead more productive professional lives, but also enhanced their personal well-being. / Thesis (M.A. (MW))--North-West University, Potchefstroom Campus, 2006.
35

An evaluation of the "Healthy lifestyle" and "Coping with change" personnel capacity building programmes of the S.A. Police Service / by Anna J.E. Jansen van Vuuren

Jansen van Vuuren, Anna Johanna Elizabeth January 2006 (has links)
Background: Due to various factors, such as the restructuring of the South African Police Service (SAPS) in 1996, Police Social Work Services decided to broaden the scope of its services by developing and introducing proactive personnel capacity building programmes (PCBP's). Fifteen PCB programmes had been developed by 1999, which gave rise to the need for a comprehensive impact assessment of these programmes. This resulted in the Evaluation of Personnel Capacity Building Programmes (EPCBP) research project that was launched in 2001. The evaluation of the Healthy Lifestyle and Coping with Change programmes formed part of this comprehensive study. Objectives: The primary aim of the study was to determine the effect of the Healthy Lifestyle (HLS) and Coping with Change (CWC) programmes on the knowledge, attitude and behaviour of SAPS personnel. Method: The comparison group pre-test and post-test design and triangulation were used during this research. Six measuring scales and a presenter's evaluation questionnaire were developed and completed by 196 (HLS) and 184 (CWC) experimental group respondents, 38 (HLS) and 41 (CWC) comparison group members and 10 (HLS) and 7 (CWC) presenters. Results: With the help of various measuring instruments and the triangulation of measurements, it was determined that the Healthy Lifestyle and Coping with Change programmes had a practical significant effect on the knowledge, attitude and behaviour of the respondents. It was concluded that these programmes were effective tools in the hands of Police Social Work Service (PSWS) because they not only empowered SAPS personnel to lead more productive professional lives, but also enhanced their personal well-being. / Thesis (M.A. (MW))--North-West University, Potchefstroom Campus, 2006.
36

System-Level Hardwa Synthesis of Dataflow Programs with HEVC as Study Use Case / Synthèse matérielle au niveau système des programmes flots-de-données : étude de cas du décodeur HEVC

Abid, Mariem 28 April 2016 (has links)
Les applications de traitement d'image et vidéo sont caractérisées par le traitement d'une grande quantité de données. La conception de ces applications complexes avec des méthodologies de conception traditionnelles bas niveau provoque 1'augmentation des coûts de développement. Afin de résoudre ces défis, des outils de synthèse haut niveau ont été proposés. Le principe de base est de modéliser le comportement de l'ensemble du système en utilisant des spécifications haut niveau afin de permettre la synthèse automatique vers des spécifications bas niveau pour implémentation efficace en FPGA. Cependant, l'inconvénient principal de ces outils de synthèse haut niveau est le manque de prise en compte de la totalité du système, c.-à-d. la création de la communication entre les différents composants pour atteindre le niveau système n'est pas considérée. Le but de cette thèse est d'élever le niveau d'abstraction dans la conception des systèmes embarqués au niveau système. Nous proposons un flot de conception qui permet une synthèse matérielle efficace des applications de traitement vidéo décrites en utilisant un langage spécifique à un domaine pour la programmation flot-de- données. Le flot de conception combine un compilateur flot- de-données pour générer des descriptions à base de code C et d'un synthétiseur pour générer des descriptions niveau de transfert de registre. Le défi majeur de l'implémentation en FPGA des canaux de communication des programmes flot-de-données basés sur un modèle de calcul est la minimisation des frais généraux de la communication. Pour cela, nous avons introduit une nouvelle approche de synthèse de l'interface qui mappe les grandes quantités des données vidéo, à travers des m'mémoires partagées sur FPGA. Ce qui conduit à une diminution considérable de la latence et une augmentation du débit. Ces résultats ont été démontrés sur la synthèse matérielle du standard vidéo émergent High-Efficiency Video Coding (HEVC). / Image and video processing applications are characterized by the processing of a huge amount of data. The design of such complex applications with traditional design methodologies at lowlevel of abstraction causes increasing development costs. In order to resolve the above mentioned challenges, Electronic System Level (ESL) synthesis or High-Level Synthesis (HLS) tools were proposed. The basic premise is to model the behavior of the entire system using high level specifications, and to enable the automatic synthesis to low-level specifications for efficient implementation in Field-Programmable Gate array (FPGA). However, the main downside of the HLS tools is the lack of the entire system consideration, i.e. the establishment of the communications between these components to achieve the system-level is not yet considered. The purpose of this thesis is to raise the level of abstraction in the design of embedded systems to the system-level. A novel design flow was proposed that enables an efficient hardware implementation of video processing applications described using a Domain Specific Language (DSL) for dataflow programming. The design flow combines a dataflow compiler for generating C-based HLS descriptions from a dataflow description and a C-to-gate synthesizer for generating Register-Transfer Level (RTL) descriptions. The challenge of implementing the communication channels of dataflow programs relying on Model of Computation (MoC) in FPGA is the minimization of the communication overhead. In this issue, we introduced a new interface synthesis approach that maps the large amounts of data that multimedia and image processing applications process, to shared memories on the FPGA. This leads to a tremendous decrease in the latency and an increase in the throughput. These results were demonstrated upon the hardware synthesis of the emerging High-Efficiency Video Coding (HEVC) standard.
37

Testování protokolů pro video na vyžádání v programu Apache JMeter / Video on Demand Protocols Testing using Apache JMeter

Srnec, Tomáš January 2018 (has links)
The master’s thesis deals with testing the application protocol HLS and RTSP in JMeter program. The aim of this thesis is to design and implement a test modules for both protocols, which will perform stress tests. The first part of thesis describes the types of stress tests, JMeter program for performance testing and video on demand services. Next chapter describes selected protokols, especially HLS and RTSP, which are used in this thesis. The practical part contains the design and implementation of test modules including test plans. Finally, the results are processed and commented.
38

Design space exploration using HLS in relation to code structuring / Utforskning av design space med HLS i förhållande till kodstrukturering

Das, Debraj January 2022 (has links)
High Level Synthesis (HLS) is a methodology to translate a model developed in a high abstraction layer, e.g. C/C++/SystemC, that describes the algorithm into a Register-Transfer level (RTL) description like Verilog or VHDL. The resulting RTL description from the translation is subject to multiple user-controlled directives and an internal design space exploration algorithm specific to the toolchain used. HLS allow designers to focus on the behaviour of the design at a higher abstraction compared to the behavioural modelling available within the Hardware Description Language (HDL) as the compiler decides the movement of data and timing in the resulting design. Ericsson uses a legacy Advanced Peripheral Bus (APB) like interface called Memory/Register Interface (MIRI) interface for data movement in a subsystem of one of their Application-Specific Integrated Circuit (ASIC). The thesis attempts to upgrade the protocol to the more performant ARM Advanced Microcontroller Bus Architecture (AMBA) protocols’ Advanced High-performance Bus (AHB) or Advanced eXtensible Interface (AXI) interfaces. SystemC provides a host of functionalities to define the complete behaviour of the circuit at a high level of abstraction. This thesis will explore the effect of the structuring SystemC models on their synthesis, and perform design space exploration to understand the best design methodology to adopt in a SystemC model design and compare the models based on the final synthesis metrics like area, timing, and register counts. The toolchain for the thesis will be the Stratus HLS compiler developed by Cadence. Stratus supports all synthesizable constructs of SystemC. Most HLS research focuses on improving Design Space Exploration algorithms used internally in the HLS tools. However, designers can utilize algorithm structuring to provide the HLS engines with a better starting point. In this thesis, the Stratus toolchain will be used to experiment with different models with equivalent behaviour and performance. Thereafter, extract which constructs used in the models are optimal for allowing the internal design space exploration algorithm to perform in the best way possible. / HLS är en metod för att översätta en modell utvecklad på hög abstraktionsnivå t.ex. C/C++/SystemC som beskriver algoritmen på registeröverföringsnivå (RTL) som Verilog eller VHDL. Den resulterande RTL-beskrivningen utsätts för flera användarkontrollerade direktiv och en intern Design Space Exploration (DSE) algoritm, vilken är specifik för den verktygskedja som används. Detta gör det möjligt för en designer att fokusera på konstruktion beteende på en högre abstraktionsnivå jämfört med den beteendemodellering som finns tillgänglig inom det hårdvarubeskrivande språket (HDL:en) när kompilatorn bestämmer tidpunkten för utbytet av data i den resulterande designen. Ericsson använder ett äldre gränssnitt för Advanced Peripheral Bus (APB) som kallas Memory/Register Interface (MIRI), vilket är ett gränssnitt för utbyte av data i ett delsystem i en av deras Application-Specific Integrated Circuit (ASIC:ar). Avhandlingen försöker uppgradera protokollet till ett av de det mer högpresterande ARM Advanced Microcontroller Bus Architecture – protokollen Advanced High-Performance Bus (AHB) eller Advanced eXtensible Interface (AXI). SystemC tillhandahåller en mängd funktioner för att definiera kretsens fullständiga beteende vid en hög abstraktionsnivå. Denna avhandling utforskar effekten av strukturerade SystemC-modeller och deras syntesresultat samt konstruktionsrymden, för att förstå den bästa designmetodiken i ett SystemC-modelleringsdesignflöde och jämföra modellerna baserade på de slutliga syntesmätvärdena som storlek, timing, etc. Verktygskedjan för avhandlingen kommer att vara Stratus HLS -kompilatorn som utvecklats av Cadence. Stratus stöder alla syntetiserbara konstruktioner av SystemC. HLS-forskningen fokuserar främst på att förbättra Design Space Exploration, dvs de algoritmer som används internt i HLS-verktygen för att komma fram till lösningar. För att ge HLS -motorerna en bättre utgångspunkt. I denna avhandling kommer Stratus att användas för att utvärdera olika modeller med ekvivalent beteende och nästan samma prestanda efter Syntes, för att komma fram till vilka konstruktioner är optimala för att den interna DSE-algoritmen skall fungera bäst.
39

Nonlinear optical properties of nanostructures, photochromic and lanthanide complexes in solution / Propriétés optiques non linéaires de nanostructures, de complexes photochromes et de complexes de lanthanides en solution

Singh, Anu 11 December 2012 (has links)
L’Optique non linéaire est un outil très puissant pour étudier les propriétés des matériaux. Dans cette thèse, nous avons utilisé deux techniques d’optique non linéaire pour l’étude des non linéarités moléculaires: la génération de seconde harmonique induite sous champ électrique (EFISH) et la diffusion harmonique de la lumière (DHL). Tout d'abord, nous avons mis en évidence la conjugaison des groupements donneurs pi- dans les complexes d’iridium cyclométallés. Nous avons également exploré une série de molécules trinucléaires organométalliques (triaryle-1, 3, 5-triazinane-2, 4, 6-triones) fonctionnalisées par des acétylures métalliques avec des complexes des métaux de transition à leur périphérie- l’hyperpolarisabilité est beaucoup plus élevée que celles des dérivés purement organiques équivalents. D'autre part une série de complexes métalliques dipolaires et octupolaires contenant des ligands 2, 2-bipyridine photochromes à base de dithiényléthène (DTE) ont été synthétisés et caractérisés. L'étude révèle une forte augmentation de Les hyperpolarisabilités après irradiation UV correspondant à la fermeture de cycle associée au DTE. Cette forte exaltation reflète bien la délocalisation du système d’électrons pi- et la formation de chromophores push-pull dans les formes fermées. Troisièmement, nous avons étudié les propriétés optiques non linéaires de complexes de bis (phtalocyaninato) lanthanide (III) en sandwich, avec 2 phthalocyanines substituées en ABAB (alternance de donneurs d'électrons et d’accepteurs d'électrons), AB3 (3 groupes de donneurs), A4 (4 groupes d’accepteurs) et B4 (aucun groupe de donneur). L’hyperpolarisabilité du 1er ordre beta- mesurées sont les plus élevées jamais enregistrées pour des molécules octupolaires. La contribution directe d’électrons f dans les ions lanthanides complexés est également observée sur l'activité non linéaire du second ordre. Enfin, des nanosphères (AuNSs) et des nanotubes d'or (AuNRs) avec différents rapports d'aspect (AR) allant de 1,7 à 3,2 nm ont été synthétisés par la méthode de radiolyse. Le signal de deuxième harmonique émis par des AuNRs est nettement supérieur à celui des nanosphères et révèle leur dépendance à l'AR. Nous avons également mélangé un dérivé du chromophore 4-diméthylamino-N-méthyl-4-stilbazolium tosylate (DAST) avec les AuNRs et observé une influence des AuNRs sur l'amélioration des propriétés ONL du DAST. Une nette augmentation de l’hyperpolarisabilité (par un facteur 8) du derive de DAST en est la preuve. / Nonlinear optics is well known to be a highly powerful tool to investigate the properties of the materials. In this thesis we used two important nonlinear optical techniques known as Electric Field Induced Second Harmonic Generation (EFISH) and Harmonic Light Scattering (HLS) to study the first hyperpolarizability of various molecular objects. Firstly, we evidenced the pi donor conjugation in cyclometallated Ir complexes. We have also explored the series of trinuclear organometallic triaryl-1, 3, 5-triazinane-2, 4, 6-triones functionalized by d6-transition metal acetylides complexes at their periphery- large hyperpolarizabilities, far higher than those of related purely organic derivatives are reported. Secondly, a series of dipolar and octupolar dithienylethene (DTE)-containing 2, 2-bipyridine ligands with different metal ions featuring two, four and six photochromic dithienylethene units have been synthesized and fully characterized. The study reveals a large increase in the hyperpolarizability after UV irradiation and subsequent formation of ring-closed isomers. This efficient enhancement clearly reflects the delocalization of the pi-electron system and the formation of strong push&pull chromophores in the closed forms. Thirdly, we have investigated NLO properties of bis (phthalocyaninato) lanthanide-(III) double-decker complexes with crosswise ABAB (phthalocyanine bearing alternating electron-donor and electron-acceptor groups), AB3 (3 donor groups), A4 (4 donor groups) and B4 (no donor groups) ligands. First-order hyperpolarizability is measured and displays the highest quadratic hyperpolarizability ever reported for an octupolar molecule. The direct contribution of f-electrons in coordinated lanthanides ions is also observed on second order nonlinear activity. Finally, gold nanospheres (AuNSs) and gold nanorods (AuNRs) with different aspect ratios (AR) ranging from 1.7 to 3.2 nm have been synthesized by Radiolysis method. Second harmonic intensity collected from AuNRs is clearly higher than that of the nanospheres and reveals their dependence on the AR. We have also mixed the chromophore 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) derivative with AuNRs and observed the enhancement of DAST NLO properties in the presence of AuNRs. A clear increase in the hyperpolarizability (by a factor of 8) of DAST derivatives has been evidence.
40

Nonlinear optical properties of nanostructures, photochromic and lanthanide complexes in solution

Singh, Anu 11 December 2012 (has links) (PDF)
Nonlinear optics is well known to be a highly powerful tool to investigate the properties of the materials. In this thesis we used two important nonlinear optical techniques known as Electric Field Induced Second Harmonic Generation (EFISH) and Harmonic Light Scattering (HLS) to study the first hyperpolarizability of various molecular objects. Firstly, we evidenced the pi donor conjugation in cyclometallated Ir complexes. We have also explored the series of trinuclear organometallic triaryl-1, 3, 5-triazinane-2, 4, 6-triones functionalized by d6-transition metal acetylides complexes at their periphery- large hyperpolarizabilities, far higher than those of related purely organic derivatives are reported. Secondly, a series of dipolar and octupolar dithienylethene (DTE)-containing 2, 2-bipyridine ligands with different metal ions featuring two, four and six photochromic dithienylethene units have been synthesized and fully characterized. The study reveals a large increase in the hyperpolarizability after UV irradiation and subsequent formation of ring-closed isomers. This efficient enhancement clearly reflects the delocalization of the pi-electron system and the formation of strong push&pull chromophores in the closed forms. Thirdly, we have investigated NLO properties of bis (phthalocyaninato) lanthanide-(III) double-decker complexes with crosswise ABAB (phthalocyanine bearing alternating electron-donor and electron-acceptor groups), AB3 (3 donor groups), A4 (4 donor groups) and B4 (no donor groups) ligands. First-order hyperpolarizability is measured and displays the highest quadratic hyperpolarizability ever reported for an octupolar molecule. The direct contribution of f-electrons in coordinated lanthanides ions is also observed on second order nonlinear activity. Finally, gold nanospheres (AuNSs) and gold nanorods (AuNRs) with different aspect ratios (AR) ranging from 1.7 to 3.2 nm have been synthesized by Radiolysis method. Second harmonic intensity collected from AuNRs is clearly higher than that of the nanospheres and reveals their dependence on the AR. We have also mixed the chromophore 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) derivative with AuNRs and observed the enhancement of DAST NLO properties in the presence of AuNRs. A clear increase in the hyperpolarizability (by a factor of 8) of DAST derivatives has been evidence.

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