Newest Updates in Physical Science Research Vol. 7

The properties of fractal structures defined by complex functions are tested. The amplitude-phase characteristics and spatial spectra of probing light beams are considered. An important methodic aspect of spectral analysis of structures with fractal geometry is the ability to expand the range of information obtained by parallel amplitude and phase processing. In deciphering the Fourier images of fractals, one can use the discovered fact that the intensity maxima and phase singularities coincide. As a positive point, it should be noted a high degree of the spatial spectrum stability to the influence of optical noise. The registered degree of asymmetry of the Fourier image structure can be used to determine the level of phase disturbances in the initial light field. The performed work expands the knowledge of factors requiring consideration in the optical diagnostics of fractal objects.

A novel design of optical directional coupler switch with S-bend waveguides on LiTaO₃ platform has been designed with R-Soft CAD tool and the same is simulated by Beam propagation method (BPM) for light propagation analysis. The simulation results of the optical directional coupler (ODC) switch is reported. We observed that the directional coupler (DC) switch has lower insertion losses and higher extinction ratios for a certain values that are discussed in the paper. This was studied by variation in waveguide parameters such as, wavelength, waveguide gap, and length of the device. Simulation results designate that the switching efficiency for TE and TM modes with extinction ratio about 3dB when the waveguide gap is 3.5 ?m for both the polarization modes and insertion loss is 13dB with same waveguide gap in TE mode and 16dB in TM mode at 1550 nm wavelength. This symmetrical optical directional coupler switch can be used as key components for integrated optical communication devices and useful for build up functional devices.

Sum squeezing of the field amplitude is studied in the nondegenerate and degenerate frequency upconversion process under the short interaction time. A state is squeezed when the quantum fluctuation (amplitude noise or phase noise) in one variable is reduced below the symmetric limit at the expense of the increased quantum fluctuation in the conjugate variable such that the Heisenberg uncertainty relation is not violated. It is shown that sum squeezing can be converted into normal squeezing via sum-frequency generation in the nondegenerate frequency upconversion process, while the amplitude-squared squeezing of the fundamental mode directly changed into the squeezing of the harmonic in the degenerate frequency upconversion process. All reachable conditions of uncorrelated modes for obtaining a sum squeezing in two modes and its dependence on the squeezing of individual field modes are investigated. It is found that the squeezed states are associated with large number of pump photons. It is also confirmed that the higher-order squeezing (sum squeezing) is directly associated with coupling of the field and interaction time. The results obtained in this chapter are of interest for new experiments on the study of nonlinear optical processes in dielectric media using ultrashort intense laser pulses as exciting radiation, and the effects of damping and decoherence as well as higher-order time terms could be investigated.

This paper reports on liquid phase epitaxy (LPE) growth and characterization of monocrystalline dilute nitride InGaAs(Sb)N and GaAsSbN layers in view of their photovoltaic applications. To obtain high quality epitaxial layers without phase separation the low-temperature variant of the LPE method is used. The structural characterization of the samples is carried out by means of scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction measurements. The optical bandgap is studied by photoluminescence (PL) spectroscopy at low and room temperature. Surface photovoltage spectroscopy (SPV) is applied to determine the optical absorption edge. Both PL and SPV spectra reveal a decrease of the band gap of GaAsSbN as compared to InGaAs(Sb)N,  which is of value for its application in solar cells.

ZnO-based nanostructures, one dimensional ones (nanorods) have received great attention, due to their unique properties such as low reaction temperature, ease of scaling up, economic and facile synthesis. In this study, we report the preparation of ZnO nanorods by hydrothermal method and the dynamics of their chemical etching under different concentrations of NaOH. The characterization was carried out using X-ray diffraction, scanning electronic microscopy and photoluminescence. Thus, the study provides an investigation of the etching time and concentration effects on the optoelectronic properties. We found that all etching conditions are causing a remarkable proportional changes on the materials photonics as it is mainly changing the surface and creating defects. Hence, this study exhibits distinct advantages for optoelectronic devices.

The common method of red and white blood cells identification and counting consider the manual processes on microscope which is arranged by the laboratory’s technician with their own experience. In this research, we will develop a computer program to detect and identify the proposed objects based on their pattern. Our proposed method is very effective in cell detection. The proposed objects are Red Blood Cells (RBCs), and White Blood Cells (WBCs). For blood cells identification and classification, an idea of Viola and Jones will be followed. Adaboost (adaptive boosting) method will be applied to increase the accuracy of the error of learning algorithm. The output of the proposed program shows that all the types of cells mentioned can be detected and classify effectively by showing the number and time spent of cells detected.

We study a system of high electric current cable laid on the seabed for purpose of naval ship magnetic deperming. Magnetic field to deperm the ship is imposed vertically on to the ship. Moderate magnetic field over 2400 A/m is to be imposed on the volume equivalent of several thousand tons of ship, with alternately changing direction and gradually decreasing intensity. Cable with conventional conductor needs large power source because of the requirements coming from the cable's resistivity and high decay of magnetic field depending on distance from source. High Temperature Superconducting cable is suitable for this application. We set a requirement of maximum current of the cable as 200 kA and the length as 1200 m set on seabed of 12 m depth. Our recent design of the cable composed of Rare-earth-Barium-Copper-Oxide tape conductor stack, bundled and cooled by helium gas to 50 K. As a next step, cooling to 20 K with the same base concept of cable is shown to mitigate high expense of the tape conductor.

The potential barrier near the apex of an ultrathin edge field emitter is defined using an analytical model. It is used to simulate electron tunnelling from the emitter numerically. The results show that for an ultrathin emitter, the traditional approximation of a uniform field near the edge is inappropriate. The proposed method is better suited to modelling field emission from nano-sized cold cathodes. The findings apply to nano-sized cold cathode structures, including graphene field emitters.

We present experimental demonstration of laser speckle intensity based methods to follow the drying process of white adhesive. Results obtained using graphical methods such as temporal LASCA, GD, Fujii and parameterized Fujii as well as numerical methods of Inertia moment and temporal correlation show that qualitative and quantitative evaluation of spatial temporal speckle activities can be used to monitor drying process of adhesives. Statistical Tukey’s test for the mean values of inertia moments at 5% significance level allowed differentiating different stages of drying.

In this Chapter, following a discussion on the working principle of a colloidal damper rendered controllable (CDRC), a review of various types of controlling devices and their sensitivity, is presented. Then, a new type of colloidal absorber, rendered controllable under the variable magnetic fields, is proposed and its controllability is experimentally evaluated. This absorber employs a water-based ferrofluid (FERROTEC MSG-W10) in association with a liquid-repellent nanoporous solid body, consisted of particles of gamma alumina and/or silica gel. Control of the dynamic characteristics is obtained by moving permanent neodymium annular magnets, which are placed either on the piston head (axial magnetic field) or on the external surface of the cylinder (radial magnetic field). In order to properly select these magnets, flow visualizations inside of a transparent model damper were performed, and the quantity of the displaced liquid by the magnets through the damper’s filter and through the nanoporous solid body was determined. Experimental data concerning the variation of the magnetic flux density at the magnet surface versus the height of the magnet, and versus the target distance was collected. Based on such data, the suitable magnet geometry was decided. Then, the three-dimensional structural model of the trial colloidal damper obtained by using Solidworks, and the excitation test rig are presented. From excitation tests on a ball-screw shaker, one confirmed larger damping abilities of the proposed absorber relative to the traditional colloidal damper, and also the possibility to adjust the damping coefficient according to the excitation type.  

Peeling of tomatoes by radiative heating is a valid alternative to steam or lye, which are expensive and pollutant methods. Suitable energy densities are required in order to realize short time operations, thus involving only a thin layer under the tomato surface. This paper aims to predict the temperature field in rotating tomatoes exposed to the source irradiation. Therefore, a 1D unsteady analytical model is presented, which involves a semi-infinite slab subjected to time dependent heating while convective heat transfer takes place on the exposed surface. In order to account for the tomato rotation, the heat source is described as the positive half-wave of a sinusoidal function. The problem being linear, the solution is derived following the Laplace Transform Method. In addition, an easy-to-handle solution for the problem at hand is presented, which assumes a differentiable function for approximating the source while neglecting convective cooling, the latter contribution turning out to be negligible for the context at hand. The thermal response fully recovers the temperature field due to a sinusoidal varying heat source as a limiting case. A satisfying agreement between the two analytical solutions is found, therefore, an easy procedure for a proper design of the dry heating system can be set up avoiding the use of numerical simulations.