Effect of MnO2 and MnO2-NCNO addition on structural and nonlinear optical properties of CoWO4 ceramics

The nitrogen-doped carbon nano-onions (NCNOs) were prepared by annealing the ultra-dispersed aminated-nanodiamond solution under He gas at 1150°C followed by calcination at 400°C. The nanostructures of CoWO4, MnO2, CoWO4-MnO2, and CoWO4-MnO2-NCNO were synthesized through the simple precipitation method under ultrasonication followed by calcination at 450°C. The morphology, structure, and optoelectronic properties of the samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Z-scan method. The homogeneous distribution of the tiny aggregated plate-like and spongy particles throughout the nanocomposite created a highly porous nanostructure with a large surface area. The nonlinear absorption (NLA) coefficient and nonlinear refractive (NLR) index were of the order of 10-3(cm/W) and 10-8(cm2/W), respectively. In different incident intensity of laser, all synthesized samples show TPA effect implying the positive sign of NLA coefficient. MnO2 and NCNO structure have positive NLR index indicating the self-focusing optical nonlinearity. The self-defocusing effect and the negative sign of nonlinearity in the CoWO4 nanoparticles, MnO2-CoWO4, and MnO2-NCNO-CoWO4 nanocomposites are vivid. The porous structure of CoWO4 nanoparticles and trapping the light into CoWO4 nanoparticles are the main reasons for nonlinearity of this nanoparticles. Porosity is also one of the most important reasons for the nonlinear optical responses of NCNO structure. The NLR index and NLA coefficient of MnO2 decreased by increasing the incident intensity. Moreover, an increase in the incident intensity improved the nonlinear responses in the rest of samples. The present nonlinear optical results of the synthesized samples can be applied in optical devices.

IMPROVING THE EFFICIENCY OF THE SYSTEM WITH SOLAR COLLECTORS

The paper solves an important issue of the efficiency of two collectors that have different orientations at different angles of incidence of solar radiation intensity. That is why the paper carries out a wide-parameter study of their thermal engineering characteristics. It is investigated that the change in the azimuth angle α from 90º to 60º, under the φ=90º does not significantly affect the efficiency of the system with solar collectors, and its further deviation significantly reduces. It is also established that the simultaneous deviation of angles α and φ leads to a significant reduction in the use of the incident intensity of solar radiation on the solar collector and the efficiency of the system with solar collectors in general. As a result of theoretical calculations its average annual value is obtained , accordingly for a different number of discrete collector orientations N.

Effect of radiation damage and illumination variability on signal-to-noise ratio in X-ray free-electron laser single-particle imaging

The deterioration of both the signal-to-noise ratio and the spatial resolution in the electron-density distribution reconstructed from diffraction intensities collected at different orientations of a sample is analysed theoretically with respect to the radiation damage to the sample and the variations in the X-ray intensities illuminating different copies of the sample. The simple analytical expressions and numerical estimates obtained for models of radiation damage and incident X-ray pulses may be helpful in planning X-ray free-electron laser (XFEL) imaging experiments and in analysis of experimental data. This approach to the analysis of partially coherent X-ray imaging configurations can potentially be used for analysis of other forms of imaging where the temporal behaviour of the sample and the incident intensity during exposure may affect the inverse problem of sample reconstruction.

Tunable Optical Bistability, Tristability and Multistability in Arrays of Graphene

The optical bistability, tristability and multistability are explored in arrays of graphene. The arrays are periodically arranged spatially by single sheets of graphene. Optical bistability could be achieved with a strong enough incident intensity of light wave. The thresholds of optical bistability and the intervals between the upper and lower thresholds change with the surface conductivity of graphene and the incident wavelength. By increasing the intensity of incident light, tristability and multistability can be induced as well. Furthermore, the thresholds of bistability, tristability and multistability can be regulated via the chemical potential of graphene. This study may have potential applications in optical logic gates, all-optical switches and photomemory.

Impact of Pasteurization Process on the Quality and Marination Properties of Onion Juice

This study aims to compare UV-C irradiation and conventional heat treatment to produce pasteurized onion juice used as a meat marinating agent. The process conditions maximizing the inactivation of target microorganism Escherichia coli K-12 were; 0.5 mm sample depth, 30 min irradiation, 7.5 mW/cm2 UV incident intensity for UV-C and, 74.5°C and 12 min for heat treatment. Except pH and non-enzymatic browning index, differences between physicochemical properties of raw, UV-C and heat-treated onion juices were significant. Springiness and chewiness of unmarinated beefsteaks were higher compared to the ones marinated with the fresh and pasteurized onion juice (UV-C and heat). Pasteurization of onion juice (UV-C and heat) did not significantly affect general liking scores compared to beefsteaks marinated in untreated onion juice.

Dynamic Response of a Nonlinear Fabry-Perot Etalon for Various Medium Response Times

In this work, the switching nonlinear dynamics of a Fabry-Perot etalon are studied. The method used to complete the solution of the differential equations for the nonlinear medium. The Debye relaxation equations solved numerically to predict the behavior of the cavity for modulated input power. The response of the cavity filled with materials of different response time is depicted. For a material with a response time equal to = 50 ns, the cavity switches after about (100 ns). Notice that there is always a finite time delay before the cavity switches. The switch up time is much longer than the cavity build-up time of the corresponding linear cavity which was found to be of the order of a few round-trip times. The slowing down of the cavity response occurs when the incident intensity is approximately equal to the critical switching intensity. This effect is called critical slowing down. As a result, the response of the cavity is much slower than what could be expected from the steady state analysis. The reflected intensity and the change in round-trip phase have similar dynamic response. In this research, the matlap programs are used to study the switching dynamics of a Fabry-Perot etalon.

Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses

Stochastic processes are highly relevant in research fields as different as neuroscience, economy, ecology, chemistry, and fundamental physics. However, due to their intrinsic unpredictability, stochastic mechanisms are very challenging for any kind of investigations and practical applications. Here we report the deliberate use of stochastic X-ray pulses in two-dimensional spectroscopy to the simultaneous mapping of unoccupied and occupied electronic states of atoms in a regime where the opacity and transparency properties of matter are subject to the incident intensity and photon energy. A readily transferable matrix formalism is presented to extract the electronic states from a dataset measured with the monitored input from a stochastic excitation source. The presented formalism enables investigations of the response of the electronic structure to irradiation with intense X-ray pulses while the time structure of the incident pulses is preserved.

Technical Analysis and Overview of the Application of Artificial Dielectric Materials in the Form of Photonic Crystal Cavity with Resonance in Dirac Leaky-Wave Antennas

Application of Artificial Dielectric Materials in the form of Photonic crystal cavity with resonance in Dirac leaky-wave Antennas. The system investigated is a Photonic crystal cavity for the radiation properties of an antenna formed by a combination of a monopole radiation source and a cavity by a dielectric layer-by-layer 3D photonic crystal. The Photonic crystal cavity under study is working at resonance, since a high directivity, and a high power enhancement are obtainable at the resonant frequency of the cavity.In addition, an approach based on (i) Hughen's wavelets and (ii) the components of the incident Intensity after transmission through the system, is suggested for optimizing the performance of the optical antennas. Also, it has been discussed that the Optical antenna fabricated by Dielectric material - Photonic crystal is a better alternative to a conventional focusing lens, in Nanoscopy, in order to concentrate the laser radiation to dimensions smaller than the diffraction limit.