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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.
71

Silicon-based terahertz signal generation with multi-phase sub-harmonic injection locking technique

Chi, Taiyun 27 May 2016 (has links)
This thesis presents a multi-phase injection locking (IL) technique and its application in the locking range extension in multi-phase injection locking oscillators (ILOs) for Terahertz (THz) signal generation. The proposed technique can significantly increase the frequency locking range of a multi-phase injection locking oscillator compared to the conventional single-phase injection locking scheme. Based on the multi-phase IL technique and sub-harmonic ILOs, an “active frequency multiplier chain” architecture and a multi-ring system layout topology are also proposed to achieve scalable THz signal generation. As proof of concept, a cascaded 3-stage 3-phase 2nd-order sub-harmonic ILO chain is implemented in the IBM 9HP SiGe BiCMOS process. The design achieves a maximum output power of -16.6dBm at 498GHz, a phase noise of -87dBc/ Hz at 1MHz offset, and a total 5.1% frequency tuning range from 485.1GHz to 510.7GHz, which is the largest frequency tuning range among all the reported silicon-based THz oscillator sources in the 0.5THz band.
72

Spectrum Stewardship Through Best Source Selection

Gerstner, Grant, Lillevold, Hans 10 1900 (has links)
ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / With the increasing demand on available frequencies used for Telemetry transmission, it is important for the test ranges to be good stewards of the spectrum. One method is a new use of Best Source Selection. This method consists of placing data-quality encapsulators at the output of each of the TM receivers used. This system works without the need to use pattern detect which allows for the use of Best Source Selection without the need for decrypting the data. In conjunction with new system architecture, this setup is how the Atlantic Test Range is using best source selection in the future.
73

Biomass production, population structure, and self-thinning in experimental, short-rotation plantations of willow (Salix burjatica (Nasarov) 'Aquatica gigantea') in Northern Ireland

Horton, C. January 1985 (has links)
No description available.
74

MERLIN and VLBI observations of the radio galaxy Virgo A

Junor, W. January 1987 (has links)
No description available.
75

Design, construction and analysis of a solid state nearly-isotropic light source

Kovacs, Paul 09 December 2016 (has links)
Isotropic radiators are known to be a useful tool across a wide range of applications, from applications in light dosimetry in human/animal tissue to calibration of sensitive laboratory equipment. While the bene ts are known, constructing such a tool has proven to be di cult. Currently, there are no commercially available isotropic or nearly isotropic radiators. Previous attempts at constructing an isotropic radiator have been limited to a 10% isotropy level. This thesis covers the design, construction, and analysis of a nearly isotropic optical light source. The constructed source has extrema anisotropies, over a solid angle of approximately 3 steradians, of +\-3% (with 95% of that solid angle being within +\- 2.5% anisotropy). / Graduate
76

Econometrics in R: Past, Present and Future

Zeileis, Achim, Koenker, Roger 29 July 2008 (has links) (PDF)
Recently, computational methods and software have been receiving more attention in the econometrics literature, emphasizing that they are integral components of modern econometric research. This has also promoted the development of many new econometrics software packages written in R and made available on the Comprehensive R Archive Network. This special volume on "Econometrics in R" features a selection of these recent activities that includes packages for econometric analysis of cross-section, time series and panel data. This introduction to the special volume highlights the contents of the contributions and embeds them into a brief overview of other past, present, and future projects for econometrics in R.
77

Survey of Code Review Tools / Survey of Code Review Tools

Žember, Martin January 2011 (has links)
In the present work we study behaviour of tools intended for code review and how they aim at eliminating security vulnerabilities. There is a lot of such tools, but a smaller set of them suffice to effectively improve the security of software. We provide results of empirical testing of these tools on artificial data in order to map vulnerability classes they are able to identify and also on real data in order to test their scalability.
78

Origine et comportement des composés hydrocarbonés non méthaniques (HCMN) en zone rurale / Origin and behaviour of non-methane hydrocarbons (NMHC) in rural area

Sauvage, Stéphane 15 December 2008 (has links)
Les composés hydrocarbonés non méthaniques (HCNM) jouent un rôle prépondérant dans la chimie de l'atmosphère puisqu'ils interviennent en tant que précurseurs de la formation de polluants secondaires comme l'ozone ou les aérosols organiques secondaires. Disposant d'une base de données conséquente de mesures systématiques de 46 HCNM sur trois sites du dispositif de Mesure des Retombées Atmosphériques (MERA), la démarche de recherche a combiné trois approches complémentaires: (1) l'analyse descriptive uni-variée et bi-variée pour une étude spatio-temporelle des teneurs, (2) l'application du modèle sources-récepteur PMF (Positive Matrix Factorization) pour identifier les signatures des sources et déterminer leur contribution, (3) l'adaptation du modéle récepteur orienté CF (Concentration Fields) visant à localiser les principales zones d'influence ayant un impact sur les sites étudiés. Cinq profils de sources communs aux trois sites ont été identifiés: les profils « chauffage résidentiel », « échappement automobile », « évaporation de carburants », « biogénique » et « sources lointaines ». Les contributions relatives de ces sources aux teneurs en HCNM sont cohérentes avec les donnée d'inventaire d'émissions et avec les résultats d'autres travaux. La contribution de ces profils de sources à la formation d'ozone montre que la part du profil biogénique tend à augmenter significativement alors que celles des protils anthropiques diminuent. De grandes zones urbaines (le Sud de l'Allemagne et dans une moindre mesure le Nord de l'Italie) ont pu être identifiées comme potentiellement à l'origine des HCNM anthropiques mesure sur les trois sites de fond français. / Non-methane hydrocarbons (HCNM) play a key role in atmosphere chemistry as precursors of secondary pollutants formation like ozone or secondary organic aerosols. This works presents the analysis of an important datas et of 46 HCNM measured in three rural sites belonging to the French network (MERA). Statistical tools are used and adapted in order to study the spatial and temporal behaviour ofthese species in rural area. The research approach combined three steps: (1) univariate and bivariate analysis to a spatial and a temporal studies of the concentrations, (2) the used of the source receptor model PMF (Positive Matrix Factorization) to identity and apport ion the source of HCNM in rural area, (3) the adaptation of the oriented receptor model CF (Concentration Fields) in order to localise the main areas which influence the studied sites. Five common profiles have been identified for the three sites: "residential heating", "vehicle exhaust"; "fuel evaporation", "biogenic", and "remote sources". The relative contributions are in good accordance with the emissions inventory data and with results of other studies. These contributions allowed distinguishing local and remote influences. The ozone formation contributions of the modelled factors show that biogenic sources trend to significantly increase while anthropogenic sources decrease. That may explain that background levels of ozone do not decrease in Europe despite the anthropogenic emission reduction. Large urban areas (South of Germany and North of Italy) have been identitied as potentially at the origin of anthropogenic NMHC measured on the three French sites
79

Identification des déterminants de la concentration en polluants organiques gazeux dans le bassin méditerranéen Est / Identification of determinants of gaseous organic pollutant concentration in the eastern mediterranean basin

Debevec, Cécile 11 December 2017 (has links)
Les composés organiques volatils (COV) jouent un rôle majeur au sein du système atmosphérique en tant que précurseurs d’ozone troposphérique et d’aérosols organiques (AO) secondaires. En région méditerranéenne, les concentrations en polluants particulaires et gazeux sont généralement plus élevées que dans la plupart des régions d’Europe continentale, en particulier en période estivale. Cependant, la pollution de l’air dans cette région reste difficile à caractériser en raison d’un manque de mesures atmosphériques. Cette thèse permet de mieux comprendre les sources et le devenir des COV en région méditerranéenne orientale. Lors de la campagne de mesure intensive de Mars 2015 réalisée sur un site de fond chypriote, des mesures en continu d’un grand nombre de COV ont permis d’évaluer leurs teneurs, de mieux comprendre leurs principales sources dans la région et de décrire leurs variabilités et leurs origines potentielles. Une analyse factorielle a montré que les sources biogéniques et la pollution de fond régionale étaient les plus importants contributeurs aux concentrations en COV observées sur ce site. Bénéficiant de mesures d’AO en continu, un parallèle entre la composition en aérosol organique et la phase gazeuse a été réalisé. Les interactions des COV biogéniques avec des composés anthropiques peuvent influencer la formation et la croissance de nouvelles particules, induisant un renforcement de la fraction d’AO secondaire. Finalement, des mesures en continu de COV primaires ont été effectuées de Janvier 2015 à Février 2016 afin de mieux caractériser la variation saisonnière des COV et de leurs sources affectant la région méditerranéenne orientale. / Volatile organic compounds (VOCs) play a key role within the atmospheric system acting as precursors of ozone and secondary organic aerosols (OA). In the Mediterranean region, particulate and gaseous concentrations are usually higher than in most continental European regions especially during summertime. However, air pollution in this region remains difficult to characterize because of a lack of atmospheric measurements. This thesis provides a better understanding of the sources and fate of VOCs in the Eastern Mediterranean region. During the intensive field campaign held in March 2015 at a background site of Cyprus, real-time measurements of a large number of VOCs have been performed, allowing the evaluation of their concentration levels in ambient air, improving the understanding of their major sources in the area, and describing their variabilities and their potential origins. A factorial analysis (PMF) showed that the local biogenic sources and the regional background were found to be the largest contributors to the VOC concentrations observed at this site. Benefiting from real-time OA measurements, a parallel between organic aerosol and gas phase composition was conducted. Biogenic VOC interactions with anthropogenic compounds can influence formation and growth of newly particles, inducing a reinforcement of secondary OA fraction. Finally, on-line measurements of primary VOCs were performed from January 2015 to February 2016 to provide a better characterization of the seasonal variation in VOCs and their sources impacting the Eastern Mediterranean region.
80

The political ramifications of Free/Libre Open Source Software on network advocacy.

Timcke, Scott Neal 23 December 2008 (has links)
Research within the last fifteen years on global advocacy networks has often focused on their accomplishments through the linking of similar groups. The majority of this research while being useful to examine transnational political dynamics has two deficiencies. The first is that there is little or no consideration of the network infrastructure (from code to cables) that allows the aforementioned linkage to occur. It is therefore important to investigate the politics of infrastructure, architecture and design and the power and control thereof. Secondly, prior to Web 2.0. technologies, advocacy networks were nodes of information distribution, rather than nodes to which information was directed, and then subsequently collected, compiled and used for political purposes. It is quite reasonable to argue that Web 2.0. technologies (again due to considerations of code, digital architecture and design) have altered the manner in advocacy networks interact with their supporters, other organizations and formal political institutions. This change is located within the advocacy network’s technoorganizational structure. Subsequently, as the digital architecture for the internet is an inter-operable free/libre open source software (FLOSS) common to information exchange, it stands to reason that as an infrastructure this technology is directly a political landscape over which and in which friction and contestation can and does occur. In regard to the methods of interaction, FLOSS technologies have greatly expanded the pool of potential social activists and reduced the costs of engagement, activism and highlighting issues. With these factors in mind it can be argued that FLOSS has created opportunities for civil society to emerge and engage with society at large in ways that are both new (in a digital medium) and similar (tackling issues of social justice as constructed by the social activists). When considered at a systematic level this process has several implications. These implications include the impact of 4 networking on identity, social relations, power relations and so on, which in turn acknowledges that modern computer networking can act as a mechanism that radically restructures various political relations. This itself acknowledges various contests over modern computer networking (one position which is expressed by various FLOSS proponents), and the physical infrastructure and the power and control thereof which allows such networking to even exist in the first instance. Within this context, which could be described as an information ecosystem, there is a recognition that advocacy networks have emerged as new sources of power ready to exert influence through networking that occurs in a) a non formal manner and b) ‘beneath the radar’ as it were.

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