Improved circularly polarized planar-array antenna

Slots sitting astride the virtual wall in a multimode wave guide can be used for generation of one component of a circularly polarized beam. There is a high degree of efficiency without the use of a slow-wave structure

Energy-storage of a prescribed impedance

Reflector antenna of the parabolic type offers complete control of its aperature illumination function. The antennas beam width can be changed easily by excitation of various amounts of the line-source feed. The conical reflector collimates a beam when the feed complies with certain geometric constraints

Excitations in the dilute A_L lattice model: E_6, E_7 and E_8 mass spectra

On the basis of features observed in the exact perturbation approach solution for the eigenspectrum of the dilute A_3 model, we propose expressions for excitations in the dilute A_4 and A_6 models. Principally, we require that these expressions satisfy the appropriate inversion relations. We demonstrate that they give the expected E_7 and E_6 mass spectra, and universal amplitudes, and agree with numerical expressions for the eigenvalues.Comment: 16 pages, Latex, Elsevier style file

OPserver: interactive online-computations of opacities and radiative accelerations

Codes to compute mean opacities and radiative accelerations for arbitrary chemical mixtures using the Opacity Project recently revised data have been restructured in a client--server architecture and transcribed as a subroutine library. This implementation increases efficiency in stellar modelling where element stratification due to diffusion processes is depth dependent, and thus requires repeated fast opacity reestimates. Three user modes are provided to fit different computing environments, namely a web browser, a local workstation and a distributed grid.Comment: 5 pages, 1 figur

Comparing virtual patients with synthesized and natural speech

Virtual Patient (VP) simulations are often designed to use pre-recorded speech in order to provide more realism and immersion. However, using actors for recording these utterances has certain downsides. It can add to the cost during implementation, can take considerable time especially when a large number of VPs have to be created, and is not very flexible for example when sentences or words have to be added frequently. This study aims to explore the use of synthesized speech as an alternative to pre-recorded speech for VPs. Two medical scenarios have been prepared for this study, and both have been implemented using a VP with natural language or with synthesized speech. In a pilot study we explored students' retention rates of the symptoms reported by the VP under both conditions to investigate whether synthesized speech can serve as a good enough alternative

Advanced microwave radiometer antenna system study

The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison

Early stages of phase selection in MOF formation observed in molecular Monte Carlo simulations

Metal-organic frameworks (MOF) comprising metal nodes bridged by organic linkers show great promise because of their guest-specific gas sorption, separation, drug-delivery, and catalytic properties. The selection of metal node, organic linker, and synthesis conditions in principle offers engineered control over both structure and function. For MOFs to realise their potential and to become more than just promising materials, a degree of predictability in the synthesis and a better understanding of the self-assembly or initial growth processes is of paramount importance. Using cobalt succinate, a MOF that exhibits a variety of phases depending on synthesis temperature and ligand to metal ratio, as proof of concept, we present a molecular Monte Carlo approach that allows us to simulate the early stage of MOF assembly. We introduce a new Contact Cluster Monte Carlo (CCMC) algorithm which uses a system of overlapping "virtual sites" to represent the coordination environment of the cobalt and both metal-metal and metal-ligand associations. Our simulations capture the experimentally observed synthesis phase distinction in cobalt succinate at 348 K. To the best of our knowledge this is the first case in which the formation of different MOF phases as a function of composition is captured by unbiased molecular simulations. The CCMC algorithm is equally applicable to any system in which short-range attractive interactions are a dominant feature, including hydrogen-bonding networks, metal-ligand coordination networks, or the assembly of particles with "sticky" patches, such as colloidal systems or the formation of protein complexes.</p