Finite temperature infinitesimally deformed classical and quantum gravity

Deformed classical mechanics and gravity is discussed. Infinitesimally deformed quantum field theory is reviewed. Infinitesimally deformed Bose-Einstein distribution is derived. Infinitesimally deformed thermofield dynamics is constructed and applied to a scalar field and string theories.On leave of absence from: Mathematics Department, Faculty of Science, Mansoura University, Mansoura, Egypt     

Variable fluid properties and variable heat flux effects on the flow and heat transfer in a non-Newtonian Maxwell fluid over an unsteady stretching sheet with slip velocity

The effects of variable fluid properties and variable heat flux on the flow and heat transfer of a non-Newtonian Maxwell fluid over an unsteady stretching sheet in the presence of slip velocity have been studied. The governing differential equations are transformed into a set of coupled non-linear ordinary differential equations and then solved with a numerical technique using appropriate boundary conditions for various physical parameters. The numerical solution for the governing non-linear boundary value problem is based on applying the fourth-order Runge-Kutta method coupled with the shooting technique over the entire range of physical parameters. The effects of various parameters like the viscosity parameter, thermal conductivity parameter, unsteadiness parameter, slip velocity parameter, the Deborah number, and the Prandtl number on the flow and temperature profiles as well as on the local skin-friction coefficient and the local Nusselt number are presented and discussed. Comparison of numerical results is made with the earlier published results under limiting cases.     

Optical microstrip patch antennas design and analysis

This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design.     

Nonlinear resonant tunneling diode (RTD) circuits for microwave A/D conversion

Short-duration electrical pulses play important roles in ultrafast time-domain metrology: they are used to sample rapidly varying signals or as probe signals in ranging radars, time-domain reflectometry and in communication. In this work, we design a nonlinear transmission, which is loaded with resonant tunneling diode to be suitable for microwave A/D conversion. A resonant tunneling diode (RTD) has a negative differential resistance that means when the voltage increases the current decreases. The equivalent circuit of monostable line is given. The simulation is performed by using OrCad program. Results show that a spike is produced and after a charging time constant, another switching occurs. Hence – similar to a relaxation oscillator – the spiking period is determined by the amplitude and frequency of the input current. The transmission line itself ensures the generation and propagation of identical spikes, such as solitons formed after few diodes.     

Field Analysis of Pillbox Resonator with Radiation Loss Utilizing Finite-Element Beam Propagation Method Formulation

To deal with the radiation from an axially symmetric pillbox resonator embedded in LiNbO₃ substrate, an eigenvalue equation is derived from the expression of the finite-element beam propagation method in a cylindrical coordinate system. By solving the eigenvalue equation iteratively, the field distributions and the angular phase constants of the pillbox resonator are evaluated. The iterative scheme of solving the eigenvalue equation is an extension of our previous direct solution method which was described for a lossless case. The results obtained by this method are compared with those obtained analytically, and excellent agreement is found.     

Background updating and shadow detection based on spatial, color, and texture information of detected objects

Background model updating is a vital process for any background subtraction technique. This paper presents an updating mechanism that can be applied efficiently to any background subtraction technique. This updating mechanism exploits the color and spatial features to characterize each detected object. Spatial and color features are used to classify each detected object as a moving background object, a ghost, or a real moving object. The starting position of each detected object is the cue for updating background images. In addition, this paper presents a hybrid scheme to detect and remove cast shadows based on texture and color features. The robustness of the proposed method and its effectiveness in overcoming challenging problems such as gradual and sudden illumination changes, ghost appearance, non-stationary background objects, the stability of moving objects most of the time, and cast shadows are verified quantitatively and qualitatively.     

Size-dependent photodegradation of CdS particles deposited onto TiO2 mesoporous films by SILAR method

Carbonaceous nanomaterials, such as fullerene C₆₀, carbon nanotubes, and their functionalized derivatives have been demonstrated to possess high sorption capacity for organic and heavy metal contaminants, indicating a potential for remediation application. The actual application of these nanomaterials, however, is often hindered by the high cost of materials and the limited understanding of their mobility in porous media. In this work, carbon nano-onions (CNOs), a relatively new addition to the carbonaceous nanomaterials, were synthesized in a cost-effective way using a laser-assisted combustion synthesis process, and carefully characterized for their potential remediation application. Surface oxidized CNOs possessed 10 times higher sorption capacity than C₆₀ for heavy metal ion contaminants including Pb²⁺, Cu²⁺, Cd²⁺, Ni²⁺, and Zn²⁺. CNOs aqueous suspension can be very stable in NaCl solution at ionic strength up to 30?mM and CaCl₂ solution at ionic strength up to 4?mM CaCl₂ when pH ranged from 5 to 9, which are consistent with environmentally relevant conditions. Interactions of CNOs with iron oxide and silica surfaces under favorable condition were found to be electrostatic in origin. Mobility of CNOs in quartz sands was controlled by electrolyte type and concentration. Approximately 4.4, 25.1, and 92.5?% of injected CNO mass were retained in the sand column in ultrapure water, 1?mM?NaCl, and 1?mM CaCl₂ solutions, respectively.     

Circular grating waveguide structures for intracavity generation of azimuthal polarization in a thin-disk laser

We report on the generation of beams with azimuthal polarization using resonant grating waveguide structures (GWSs) inside an Yb:YAG thin-disk laser (TDL) oscillator. Two different GWS concepts were used to select the polarization of the emitted beam. The first uses the resonant reflection principle, and the second is based on the leaky-mode approach already reported in our previous work. Up to 93 W and 103 W of output power were extracted from a TDL with an optical efficiency, η(oo), of 36.2% and 40.1% using the first and the second approaches, respectively. In both cases, a pure azimuthal polarization and a beam quality factor, M2, of about 2.2 were measured. The design, fabrication, and different experimental results, as well as the laser performances for both GWSs, are discussed in the present Letter.     

Octave-spanning supercontinuum generation of vortices in an As2S3 ring photonic crystal fiber

We propose As(2)S(3) ring photonic crystal fiber (PCF) for supercontinuum generation of optical vortex modes. Due to the large material index contrast between As(2)S(3) and air holes in the designed ring PCF, there is a two-orders-of-magnitude improvement of the difference between the effective refractive indices of different vortex modes compared with regular ring fiber. The design freedom of PCFs enables a low dispersion (<60 ps/nm/km variation in total) over a 522 nm optical bandwidth. Moreover, the vortex mode has a large nonlinear coefficient of 11.7/W/m at 1550 nm with a small confinement loss of <0.03 dB/m up to 2000 nm. An octave-spanning supercontinuum spectrum of the vortex mode is generated from 1196 to 2418 nm at -20 dB by launching a 120 fs pulse with a 60 W peak power at 1710 nm into a 1 cm long As(2)S(3) ring PCF.     

Performance analysis of spectral-amplitude-coding optical CDMA systems with new subtract exclusive OR detection (SED) using vectors combinatorial (VC) code

This paper investigates the performance of vector combinatorial (VC) code for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a newly proposed subtract exclusive OR detection (SED) technique. VC code is constructed using Euclidean vector and algebraic ways. One of the important properties of this code is that the maximum cross correlation is one, which means that multi-user interference (MUI) and phase induced intensity noise (PIIN) are reduced. The weight for the VC code can be any positive integer number. The system performance was evaluated by comparing the theoretical studies using related equations and simulation results taken from the commercial optical systems, “VPI? TransmissionMaker 7.1”. Significant improvement in system performances has been observed when the proposed SED technique employing VC code was applied compared to other codes that utilize conventional balance detection techniques for spectral amplitude coding.