Optical response of photopolymer materials for holographic data storage applications

We briefly review the application of photopolymer recording materials in the area of holographic data storage. In particular we discuss the recent development of the Non-local Polymerisation Driven Diffusion model. Applying this model we develop simple first-order analytic expressions describing the spatial frequency response of photopolymer materials. The assumptions made in the derivation of these formulae are described and their ranges of validity are examined. The effects of particular physical parameters of a photopolymer on the material response are discussed.     

Design of a double-layered spiral antenna for radio frequency identification applications

In this study, the authors describe a novel circularly polarised (CP) double-layered spiral antenna (DLSA) consisting of two main spiral radiators printed on a thin substrate, a feed line and a folded ground plane for a ultra-high-frequency (UHF) band radio frequency identification (RFID) reader. The proposed antenna exhibits broad impedance and CP bandwidth characteristics. The fabricated prototype has an axial ratio of less than 3 dB, a return loss of less than 10 dB over an 860 960 MHz range and a gain of 6.7 dB in the operating frequency range. This performance confirms that the proposed antenna is appropriate for commercial RFID use in the UHF band.     

Optical antenna effect in semiconducting nanowires

We report on investigations of the interaction of light with nanoscale antennae made from crystalline GaP nanowires (NWs). Using Raman scattering, we have observed strong optical antenna effects which we identify with internal standing wave photon modes of the wire. The antenna effects were probed in individual NWs whose diameters are in the range 40 < d < 300 nm. The data and our calculations show that the nature of the backscattered light is critically dependent on the interplay between a photon confinement effect and bulk Raman scattering. At small diameter, d < 65 nm, the NWs are found to act like a nearly perfect dipole antenna and the bulk Raman selection rules are masked leading to a polarized scattering intensity function I R approximately cos4 theta. Underscoring the importance of this work is the realization that a fundamental understanding of the "optical antenna effect" in semiconducting NWs is essential to the analysis of all electro-optic effects in small diameter filaments.     

Interferometric antenna response for gravitational-wave detection

The interferometric antenna response to gravitational-wave excitation is studied with the Fermi Normal Coordinate (FNC) reference system, with the limit that the gravitational wavelength must be much larger than the interferometric arm length. An optical configuration of the antenna, quite similar to the one generally considered in the long-baseline antenna projects, has been studied, i.e., Fabry-Perot optical cavities in the interferometer arms and reflectors at the input and the output of the interferometer for the purpose of recycling both the laser power and the output signals. An exact computation of the antenna response is given in a form that is also suitable to provide directly the responses for simplier optical configurations without the power or the signal recycling. Furthermore the response of the antenna for the narrow-band detection mode is also calculated. The results obtained in the FNC gauge at rest with the antenna are consistent with the ones given in the literature that were computed in the transverse traceless gauge at rest with the gravitational radiation.     

Transient response analysis of a Rosen-type piezoelectric transformer and its applications

This paper investigates the characteristics of voltage transient response, such as the maximum voltage, direct current (DC) time constant, alternating current (AC) time constant and oscillation frequency, and their applications for a Rosen-type piezoelectric transformer (PT). The transient response is induced immediately after an AC voltage connected to the PT is switched off. For the applications, the maximum voltage is used to elucidate how to cause an electrical shock for users of the PT under open-circuit operation. The DC time constant and the AC time constant are used to estimate the equivalent resistance of the mechanical loss and the dielectric resistance of the dielectric loss, respectively. Also, the AC time constant is used to estimate the quality factor of the PT. Additionally, the oscillation frequency is used as an antiresonant frequency of the PT. In order to verify the above characteristics and applications, both an equivalent circuit with initial conditions and a drive system with a control switch interposed between the PT and its AC voltage source are adopted to derive the transient response and measure its characteristics. Effects of the load resistance of the PT and the switching-off time of the voltage source on the transient response are measured and discussed.     

Optical black coatings for space applications

The durability properties of PTX-205 optical black coatings deposited on metallic and non-metallic substrates are studied. The coatings are stable against adverse environmental requirements for space applications. Typically, coatings with 8–11 μ thickness are opaque and have an average reflectance loss (<5%) in the spectral range of 200–1500 nm. The absorption to emission ratio is 1·01.     

Optical coatings for laser fusion applications

Lasers for fusion experiments use thin film dielectric coatings for reflecting, antireflecting and polarizing surface elements. Coatings are most important in neodymium-doped glass lasers. The most important requirements of these coatings are the accuracy of the average value of reflectance and transmission, the uniformity of amplitude and phase front of the reflected or transmitted light and the laser damage threshold. Damage resistance strongly affects the laser's design and performance. The success of advanced lasers for future experiments and for reactor applications requires significant developments in damage-resistant coatings for UV laser radiation.     

The transport mechanisms of gases through metallized films intended for food packaging applications

Metallized polymeric films are amongst the most favoured candidates for replacing aluminum foil‐based multilayer films. The main advantages in using the former instead of the latter are: weight saving of about 40%; much less aluminum (320 time less in weight); improved recyclability; and the possibility of optimizing package barrier properties. It is generally assumed that metallization decreases the permeability of the polymeric substrate by reducing the total area available for permeation, even though the validity of such a hypothesis has never been proved experimentally. In the present paper an attempt has been made to elucidate the role of metal coating in reducing the permeation flux of polyolefine films. For this purpose, permeability tests were performed using oxygen, nitrogen and carbon dioxide at temperatures of 20–40°C. Permeation tests have been performed on two different metallized films, on their substrates alone and on two laminates. From the analysis of the experimental results, it has been concluded that, contrary to what generally thought, gas molecules can permeate through the metallized films investigated due to both the permeable porous structure of the deposited aluminum layer and the presence of pin‐holes uniformly dispersed on the metallized film surface. Copyright © 1999 John Wiley & Sons, Ltd.     

Effect of antenna dimensions on the antenna footprint in ground penetrating radar applications

Ground penetrating radar (GPR) surveys show that antenna characteristic is strongly influenced by soil conditions. The footprint of the antenna is an important parameter for a good detection result. Various conditions of soil in which a target is buried may change the footprint of the antenna. An antenna with capability to control its footprint is needed in GPR applications. In this study, the authors investigate several ultra-wideband (UWB) antennas with different dimensions to study the effect of antenna dimension on their footprint. Simulation and experiments show that large (small) antenna dimensions result in a large (small) antenna footprint when the observation is located in the near-field region. When the observation is located in the far-field, the footprint of the antenna becomes large (small) if the dimensions of the antenna are small (large). Thus, the size of the antenna footprint can be adjusted by varying the antenna dimension. It is applied in this work to develop a new method for controlling the antenna footprint to deal with varying soil condition. Measurements have been carried out to validate this concept.     

A simple dual-band microstrip-fed printed antenna for WLAN applications

A novel microstrip-fed dual-band printed antenna for wireless local area network (WLAN) is presented. The antenna comprises a rectangular and a circular radiating element, which generate two resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. The design was experimentally verified by constructing the antenna on a FR4 (ϵr = 4.4) dielectric substrate (47 mm x 26 mm x 0.76 mm) and measuring its impedance and radiation characteristics at both the bands. The measured 10 dB return loss (VSWR 2:1) bandwidth in the 2.4G Hz band is 550 MHz (2.1?2.65 GHz) and it covers the bandwidth required for 2.4 GHz WLAN. The 5.2/5.8 GHz resonant mode has a bandwidth of 950 MHz (5.15?6.1 GHz) covering 5.2/5.8 GHz WLAN bands. A rigorous experimental evaluation confirmed that the dual-band printed antenna maintained good radiation characteristics with minimum cross-polarisation levels.     

Hysteresis model for finite-element analysis of permanent-magnet demagnetization in a large synchronous motor under a fault condition

This paper describes a rare-earth-transition metal alloy permanent-magnet (Nd/sub 2/Fe/sub 14/B) hysteretic behavior model within finite-element analysis. The present work analyzes the demagnetization states of permanent magnets during fault conditions in a permanent-magnet synchronous motor and characterizes the ability of the motor to sustain the designed rated outputs after the fault conditions occur.     

Dynamic analysis of large-scale SSI systems for layered unbounded media via a parallelized coupled finite-element/boundary-element/scaled boundary finite-element model

An algorithm for a parallelized coupled model based on finite element method (FEM), boundary element method (BEM), and scaled boundary FEM (SBFEM) for harmonic and transient dynamic response of large-scale 2D structures embedded in or on layered soil media is presented. The BEM and SBFEM are used for modelling the dynamic response of the unbounded media. The standard FEM is used for modelling the finite region and the embedded structure. The objective of the development of this parallelized coupled model is to use the power of high performance computing, and to take into account the advantages and evade the disadvantages of the above mentioned numerical methods for modelling of the unbounded media in soil-structure interaction (SSI) systems. The development of the parallel algorithm for this model is essential for solving arbitrarily shaped large-scale SSI problems, which cannot be solved within reasonable elapsed times by a serial algorithm. The efficiency of the proposed parallel algorithm and the validity of the coupled model are shown by means of three numerical examples, indicating the excellent accuracy and applicability of the parallel algorithm with considerable time-savings in large-scale problems.     

Some potential antenna applications of high-temperature superconductors

A review of possible applications of high-temperature superconductors (HTS) to antennas and antenna feed networks is presented. The frequency range of consideration is 1 MHz to 100 GHz. Three antenna application areas seem appropriate for HTS material. (1)Electrically small antennas and their matching networks: An increase in efficiency is possible for electrically short antennas, but at the expense of bandwidth. Substantial radiated power levels (on the order of kilowatts) can be handled by the best HTS material. Substantial improvement may be realized by making only the matching network of HTS material. (2)Feed and matching networks for compact arrays with enhanced directive gain (superdirective arrays): HTS material should permit such arrays to be fabricated that have high efficiency. (3)Feed networks for millimeter-wave arrays: Low-loss feed networks using HTS microstrip transmission lines give many decibels improvement in gain.     

Optimised small-size tapered monopole antenna for pulsed ultra-wideband applications designed by a genetic algorithm

An optimised small-size printed tapered monopole antenna, PTMA, is designed for ultra-wideband applications. Optimisation is based on a real-coded version of Harik?s compact genetic algorithm, RCCGA. The optimisation algorithm, RCCGA has lowered the antenna area by more than 48% compared with the previous work for 3.1 to 11.7 GHz bandwidth operation. The time- and frequency-domain performance of the antenna are also described in simulations and measurements     

Inorganic–organic fiber sizings for enhanced energy absorption in glass fiber-reinforced composites intended for structural applications

Achieving high impact energy absorption without loss of structural performance in a glass fiber-reinforced composite can be obtained through a “materials by design” approach of the fiber matrix interphase through modification of current commercially formulated silane-based fiber sizing packages. In this paper, we document our attempt to balance the structural and impact performance of glass-reinforced composites produced using a fiber-sizing package composed of mixed silane coupling agents to vary the reactivity of the fiber with the matrix phase. Additionally, enhancement of post-failure energy absorption through increased frictional dissipation during fiber–matrix pull-out was explored through control of the surface roughness of the glass fibers. A unique inorganic–organic hybrid fiber sizing formulation was successfully applied at a commercial E-glass manufacturing facility to produce rovings as well as woven fabric reinforcements. Composite materials were manufactured using these specialized fabrics and the preliminary structural and impact energy responses of these materials have been measured.     

Optical characterization of Er-doped ZnSe for scintillation applications

The effect of Er-doping of ZnSe crystals on luminescence and structural properties was investigated using low-temperature photoluminescence, X-ray luminescence, Raman and IR spectroscopies. It was found that Er dopant atoms with the concentration in the solid phase of about 10⁻³ wt.% lead to a substantial disordering of initial crystalline structure. The mentioned processes manifest in substantial decrease of the amplitudes of corresponding vibrational modes and increase of their FWHM in first-order Raman spectra of Er-doped ZnSe crystals. Also, Er-doping stimulates an appearance of additional absorbance bands in IR transmittance spectra. However, Er-doping leads to substantial increase of the efficiency of photoluminescence and X-ray luminescence that is very important for scintillation application. In this case, the luminescence is mainly caused by recombination via defect centers which contain Er atoms incorporated in the ZnSe lattice in different electronic configurations.