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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.
1

Monopatch Antenna for Balloon Telemetry Applications

Jedlicka, R. P., Williamson, J. M. 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, California / A new antenna design, which is particularly suited for balloon telemetry applications, is presented. In the past, simple monopoles have been utilized as transmit antennas on balloon payloads. The monopole radiation pattern has an inherent null along its axis. This causes an undesirable loss of signal when the balloon is directly overhead. To prevent this occurrence, a microstrip antenna patch was incorporated into the monopole design. This combination, a "monopatch" antenna, provides sufficient coverage even when the balloon is directly over the ground station. The monopatch has been successfully flown on high altitude balloon flights.
2

Magnetic Monopole Searches : with AMANDA and other detectors

Åberg Lindell, Matilda January 2010 (has links)
<p>Magnetic monopoles are hypothetical particles carrying isolated magnetic charges, analogous to electrically charged particles. They have never been observed in experiments, but there are theoretical indications that they might exist. Several experiments have been carried out over the years in order to detect monopoles, or to set upper limits on their abundance in the Universe.</p><p>In this work, underlying theory of the properties of magnetic monopoles is presented, together with some of the experiments performed in the past, the present and the future. Emphasis is put on AMANDA and other Cherenkov neutrino telescopes. Results of the described experimental searches are summarized.</p>
3

Magnetic Monopole Searches : with AMANDA and other detectors

Åberg Lindell, Matilda January 2010 (has links)
Magnetic monopoles are hypothetical particles carrying isolated magnetic charges, analogous to electrically charged particles. They have never been observed in experiments, but there are theoretical indications that they might exist. Several experiments have been carried out over the years in order to detect monopoles, or to set upper limits on their abundance in the Universe. In this work, underlying theory of the properties of magnetic monopoles is presented, together with some of the experiments performed in the past, the present and the future. Emphasis is put on AMANDA and other Cherenkov neutrino telescopes. Results of the described experimental searches are summarized.
4

Dual-band and frequency-reconfigurable monopole antennas

Sun, Xiaolei, 孙肖磊 January 2013 (has links)
The designs of three compact dual-band monopole antennas for wireless-local-area-network (WLAN)applications are presented. In these designs, an L-or U-shaped monopole element with microstrip-fed is used to generate a high-frequency band at around 5.5 GHz to cover the high WLAN bands at 5.2/5.8GHz for the IEEE 802.11a standard. An E-shaped element, loop element or meander-microstrip ground stub element with coupled-fed through the monopole element is used to generate a low-frequency band at around 2.4 GHz to cover the low WLAN band for the IEEE 802.11b/g standards. With such arrangements, the three antenna shave very compact radiators of only 11.3×8 mm2,12.6×9 mm2and11.8×9.4 mm2. To investigate the performances for practical uses, these antennas are also designed on a mobile-phone printed-circuit board and studied using computer simulation and measurement. Dual-band antennas with reconfigurable Dual-band antennas with reconfigurable lower band, higher band and dual-band are designed in this thesis. The dual-band antenna consists of two radiating branches generating the frequency bands at around 2.4 GHz and 3.5 GHz for the WiMAX system. Varactors are placed on the corresponding branches for continuously tuning of the operating bands for different WiMAX standards. For frequency tuning of the lower band or higher band, simple and novel DC biasing circuits without requiring any soldering wire are proposed to bias the varactor on a radiating element. While for simultaneous frequency tuning of the two individual bands, simple and novel DC biasing circuits requiring two soldering wires are proposed to bias the varactors on the radiating elements. Both simulation and measurement results show that the DC biasing circuits designed have very little affects on the antennas performances. The design of a monopole ultra-wide band (UWB)antenna with a reconfigurable notch band is presented. The antenna employs a vertical-ellipse radiator to achieve an UWB. A compact defected-ground structure (DGS)is used to create a notch band for the antenna. To frequency tune the notch band, a varactor is placed on the DGS to control the resonance frequency. The tuning performance, in terms of reflection coefficient, radiation pattern, efficiency and gain, of the antennais studied using simulation and measurement. Results show that the notch band can be tuned continuously from 5.2 to 6.32 GHz for the WLAN bands. In the measurement of a monopole antenna with a small ground plane, the feeding cable used to connect the antenna to the measurement equipment Satimo Starlab system causes discrepancies between the simulated and measured radiation patterns, efficiencies and peak gains at lower frequencies. In the designs of antennas in this thesis, the cable effects are studied by modeling the feeding cable using the EM simulation tool CST. Results show that, by using the cable model, the simulated and measured results agree very well. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
5

Decay Detector for the Study of Giant Monopole Resonance in Unstable Nuclei

Button, Jonathan Thomas 03 October 2013 (has links)
Giant Resonances (GR) are the broad resonances that occur at excitation energies between 10 and 30 MeV. They correspond to the collective motion of nucleons within the nucleus. The GR modes can be classified according to their multipolarity L, spin S and isospin T quantum numbers. In the microscopic description, the GR modes can be understood as the collective particle-hole excitations characterized by certain values of the angular momentum and parity (Jπ), orbital momentum, spin, and isospin. The Giant Monopole Resonance (GMR) is interesting because its excitation energy is directly related to the incompressibility of the nucleus KA. KA can be used to derive the incompressibility of nuclear matter KNM, but this extrapolation from the data for real nuclei is not straightforward due to contributions from surface, Coulomb and asymmetry effects. Thus, improvements to the extrapolated KNM can be made by measuring the GMR for increasing (N-Z)/A. The incompressibility of nuclear matter is of importance in the nuclear equation of state (EOS) which describes a number of phenomena: collective excitations of nuclei, supernova explosions and radii of neutron stars. In order to study the Isoscalar Giant Monopole Resonance in unstable nuclei, a ΔE-ΔE-E decay detector composed of plastic scintillator arrays has been built and tested. The measurement of the ISGMR in unstable nuclei will be done using inverse kinematics, with a 40 MeV per nucleon beam of the unstable nucleus incident on a 6Li target. Xinfeng Chen studied the viability of this approach, taking data for elastic scattering and inelastic scattering to low-lying states and giant resonances of 240 MeV 6Li ions on 24Mg, 28Si, and 116Sn. Nuclei excited to the GMR region are particle unstable, and will decay by p, α or n decay shortly after excitation. To reconstruct the event it is necessary to measure the energy and angle of the decay particle and of the residual heavy ion. In many lighter nuclei a few nucleons off stability, and in light proton rich nuclei, the neutron threshold is above the region of interest.
6

Comment on Jackson's analysis of electric charge quantization due to interaction with Dirac's magnetic monopole

Mansuripur, M. January 2016 (has links)
In J.D. Jackson's Classical Electrodynamics textbook, the analysis of Dirac's charge quantization condition in the presence of a magnetic monopole has a mathematical omission and an all-too-brief physical argument that might mislead some students. This paper presents a detailed derivation of Jackson's main result, explains the significance of the missing term, and highlights the close connection between Jackson's findings and Dirac's original argument. (C) 2016 Sharif University of Technology. All rights reserved.
7

Design of a wideband printed MIMO monopole antenna using neurtralisation lines technique

Elkhazmi, Elmahdi A., See, Chan H., Jan, Naeem A., Abd-Alhameed, Raed, Ali, N.T., McEwan, Neil J. January 2014 (has links)
No / A novel printed diversity monopole antenna is presented for WiFi/WiMAX applications. The antenna comprises two crescent shaped radiators placed symmetrically with respect to a defected ground plane and a wideband zigzag neutralization line is connected between them to achieve good impedance matching and low mutual coupling. Theoretical and experimental characteristics are illustrated for this antenna, which achieves an impedance bandwidth of 54.5% (over 2.4 – 4.2 GHz), at a reflection coefficient < −10 dB, mutual coupling < −16 dB. An acceptable agreement is obtained for the computed and measured gain, radiation patterns, and envelope correlation coefficient. These characteristics demonstrate that the proposed antenna is an attractive candidate for the multiple input multiple output (MIMO) portable mobile devices.
8

Supersymmetry and geometry of hyperbolic monopoles

Gharamti, Moustafa January 2015 (has links)
This thesis studies the geometry of hyperbolic monopoles using supersymmetry in four and six dimensions. On the one hand, we show that starting with a four dimensional supersymmetric Yang-Mills theory provides the necessary information to study the geometry of the complex moduli space of hyperbolic monopoles. On the other hand, we require to start with a six dimensional supersymmetric Yang-Mills theory to study the geometry of the real moduli space of hyperbolic monopoles. In chapter two, we construct an off-shell supersymmetric Yang-Mills-Higgs theory with complex fields on three-dimensional hyperbolic space starting from an on-shell supersymmetric Yang-Mills theory on four-dimensional Euclidean space. We, then, show that hyperbolic monopoles coincide precisely with the configurations that preserve one half of the supersymmetry. In chapter three, we explore the geometry of the moduli space of hyperbolic monopoles using the low energy linearization of the field equations. We find that the complexified tangent bundle to the hyperbolic moduli space has a 2-sphere worth of integrable structures that act complex linearly and behave like unit imaginary quaternions. Moreover, we show that these complex structures are parallel with respect to the Obata connection, which implies that the geometry of the complexified moduli space of hyperbolic monopoles is hypercomplex. We also show, as a requirement of analysing the geometry, that there is a one-to-one correspondence between the number of solutions of the linearized Bogomol’nyi equation on hyperbolic space and the number of solutions of the Dirac equation in the presence of hyperbolic monopole. In chapter four and five, we shift the focus to supersymmetric Yang-Mills theories in six dimensional Minkowskian spacetime. Via dimensional reduction we construct a supersymmetric Yang-Mills Higgs theory on R3 with real fields which we then promote to H3. Under certain supersymmetric constraints, we show that hyperbolic monopoles configurations of this theory preserve, again, one half of the supersymmetry. Then, through investigating the geometry of the moduli space we showthat the moduli space is described by real coordinate functions (zero modes), and we construct two sets of 2-sphere of real complex structures that act linearly on the tangent bundle of the moduli space, but don’t behave like unit quaternions. This result coincides with the result of Bielawski and Schwachhöfer, who called this new type of geometry pluricomplex geometry. Finally, we show that in the limiting case, when the radius of curvature H3 is set to infinity, the geometry becomes hyperkähler which is the geometry of the moduli space of Euclidian monopoles.
9

L'église et les infractions au lien matrimonial : mariages clandestins et clandestinité : théories, pratiques et discours : france du Nord-Ouest (XIIe-milieu-XVIe siècle) / The Church and the illegal ways of contracting marriage : clandestine marriage and clandestinity : theory, practice, discourses : north-west France, XIIth-mid XVI centuries

Avignon, Carole 26 November 2008 (has links)
Appliquée à la formation du lien matrimonial, la clandestinité est une infraction multiple. Contrepoint doctrinal nécessaire pour établir le consensualisme matrimonial, la clandestinité n’en demeure pas moins une infraction aux lois de l’Eglise. Les mariages clandestins sont valides bien que moralement mauvais, potentiellement illicites, théoriquement illégitimes, canoniquement interdits. Théologiens et canonistes craignent d’inextricables dilemmes juridiques et moraux sapant les fondements de l’institution matrimoniale et discréditant l’action régulatrice de la justice d’Eglise empêchée de juger selon la vérité. De micro-processus de prise en charge, de recomposition d’une norme et d’une infraction apparaissent en pratique. La régulation judiciaire épiscopale a construit des instruments de lutte contre les mariages clandestins qui se révèlent des instruments de contrôle socio-religieux au service d’un renforcement du cadre paroissial et du pouvoir juridictionnel de l’évêque / Medieval clandestine marriages were a many-sided offense. Although theologians had to recognize the validity of clandestine marriage to strengthen the consensualist theory to marry someone clandestine is nonetheless a violation of the laws of Church. It is morally bad, potentially illegal, theoretically illegitimate, and canonically prohibited. The theologians and the canonists feared that inextricable legal and moral dilemmas surrounded the fundamentals of the Christian marriage institution and undermined the regularatory action of the justice of the Church, therefore preventing it from judging the truth. In practice, attention to the micro-process, and the reformulation of both the standard and a penalty emerged simultaneously as a result. More notably, the Episcopal judiciary established tools to fight against illegal marriages, these tools being primarily instruments of socio-religious control through the strengthening of the parish and the judicial powers of the bishop
10

STUDIES OF DUAL-BAND AND BROADBAND PLANAR ANTENNAS FOR WIRELESS COMMUNICATIONS

Chang, Fa-Shian 30 December 2002 (has links)
Novel broadband designs of planar antenna with an air substrate are proposed in this dissertation, The operating bands considered include the GSM/DCS band and ISM band. Several antenna designs capable of dual- polarized operation, circularly polarized radiation, and diversity operation are also presented.In these antenna designs, prototypes were constructed. The measured input impedance, return loss, radiation pattern, and antenna gain are presented and discussed. The commercially available simulation software are also used in verifying the measured results.As for the broadband planar antenna designs, the impedance bandwidth obtained reaches about 10% (1.5¡G1VSWR). For the circularly polarized designs, we propose a low-cost, broadband circularly polarized patch antenna fed by a coplanar probe feed, and circular polarization (CP) radiation over a wide frequency range (¡Ö10%) can be achieved. High isolation between two feeding ports (S21 less than ¡V30 dB) can be obtained for the constructed prototype of the proposed dual-polarized design. On the other hand, wrapping a planar monopole into a compact box-like structure allows the antenna¡¦s total height less then 5% of the wavelength at 900 MHz. The proposed antennas are suitable for wireless communications applications.

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