Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced

On BPS bounds in D=4 N=2 gauged supergravity II: general matter couplings and black hole masses

We continue the analysis of BPS bounds started in arXiv:1110.2688, extending it to the full class of N=2 gauged supergravity theories with arbitrary vector and hypermultiplets. We derive the general form of the asymptotic charges for asymptotically flat (M_4), anti-de Sitter (AdS_4), and magnetic anti-de Sitter (mAdS_4) spacetimes. Some particular examples from black hole physics are given to explicitly demonstrate how AdS and mAdS masses differ when solutions with non-trivial scalar profiles are considered.Comment: 21 pages; v2 added reference, published version; v3 minor correction

A low noise, high thermal stability, 0.1 K test facility for the Planck HFI bolometers

We are developing a facility which will be used to characterize the bolometric detectors for Planck, an ESA mission to investigate the Cosmic Microwave Background. The bolometers operate at 0.1 K, employing neutron-transmutation doped (NTD) Ge thermistors with resistances of several megohms to achieve NEPs~1×10^(–17) W Hz^(–1/2). Characterization of the intrinsic noise of the bolometers at frequencies as low as 0.010 Hz dictates a test apparatus thermal stability of 40 nK Hz^(–1/2) to that frequency. This temperature stability is achieved via a multi-stage isolation and control geometry with high resolution thermometry implemented with NTD Ge thermistors, JFET source followers, and dedicated lock-in amplifiers. The test facility accommodates 24 channels of differential signal readout, for measurement of bolometer V(I) characteristics and intrinsic noise. The test facility also provides for modulated radiation in the submillimeter band incident on the bolometers, for measurement of the optical speed-of-response; this illumination can be reduced below detectable limits without interrupting cryogenic operation. A commercial Oxford Instruments dilution refrigerator provides the cryogenic environment for the test facility

Does distributed leadership have a place in destination management organisations? A policy-makers perspective

Within an increasingly networked environment and recent transitions in the landscape of funding for destination management organisations (DMOs) and destinations, pooling knowledge and resources may well be seen as a prerequisite to ensuring the long-term sustainability of reshaped, yet financially constrained DMOs facing severe challenges to deliver value to destinations, visitors and member organisations. Distributed Leadership (DL) is a recent paradigm gaining momentum in destination research as a promising response to these challenges. Building on the scarce literature on DL in a DMO context, this paper provides a policy-makers’ perspective into the place of DL in reshaped DMOs and DMOs undergoing transformation and explores current challenges and opportunities to the enactment and practice of DL. The underpinned investigation used in-depth, semi-structured interviews with policy-makers from VisitEngland following an interview agenda based on the DMO Leadership Cycle. Policy-makers within VisitEngland saw a multitude of opportunities for DMOs with regards to DL, but equally, they emphasised challenges acting as barriers to realising the potential benefits of introducing a DL model to DMOs as a response to uncertainty in the funding landscape