Investigating the existence of oxygen interstitial in CuCr1􀀀xMgxO2 [0.00 X 0.30] thermoelectric materials by X-Ray photoelectron spectroscopy [XPS]

Climate change is promoting researches on materials which is capable of converting environmentally friendly energy, in which materials that convert heat into electricity are receiving significant attention, because their ability of converting heat to electricity not only generates the electricity but also contributes to slow down the consumption of fossil fuel. The existence of point defects in the semiconductors greatly effected properties of materials, especially thermoelectric properties. Therefore, the study of defects in materials is a popular research trend today. In this study, we focus on evaluating the existence of oxygen interstitial in CuCr1􀀀xMgxO2 [0.00 x 0.30] compounds, because oxygen interstitial greatly affected the thermoelectric properties of this material. Based on X-ray photoelectron spectroscopy (XPS) analysis, at the large ratio of Mg impurity x = 0.15, the compound had the highest percentage of oxygen interstitial and was also a good thermoelectric material. In addition, it could be also seen that CuCrO2 material being doped a large Mg doping ratio (x = 0.15) was suitable for thermal-to-electrical applications rather than the ones with a small ratio (x 0.05).

Dimensional transmutation in gravity and cosmology

We review (and extend) the analysis of general theories of all interactions (gravity included) where the mass scales are due to dimensional transmutation. Quantum consistency requires the presence of terms in the action with four derivatives of the metric. It is shown, nevertheless, how unitary is achieved and the classical Ostrogradsky instabilities can be avoided. The four-derivative terms also allow us to have a UV complete framework and a naturally small ratio between the Higgs mass and the Planck scale. Moreover, black holes of Einstein gravity with horizons smaller than a certain (microscopic) scale are replaced by horizonless ultracompact objects that are free from any singularity and have interesting phenomenological applications. We also discuss the predictions that can be compared with observations of the microwave background radiation anisotropies and find that this scenario is viable and can be tested with future data. Finally, how strong phase transitions can emerge in models of this type with approximate scale symmetry and how to test them with GW detectors is reviewed and explained.

Close binary black hole in a radio-quiet quasar: a candidate of Nano-Hertz gravitational wave emitter

Close supermassive binary black holes (SMBBHs) with separations less than about 0.1 parsec are expected to be Nano-Hertz gravitational wave sources. SMBBH systems should exhibit periodic variability. However, periodic variability in radio-loud quasars may be interpreted with the jet model. Here we report the detection of a robust periodic signal in the optical variability of the radio-quiet quasar PG 0923+201 with an observed period of 726.8±4.7 days, obtained from the sinusoid-like light curve of a temporal baseline of about 9 years. This periodicity is probably from a close SMBBH with a total mass of 109.3 solar masses and a separation of about 0.01 parsec, implying relativistic orbital speeds. Such a system has passed through the well-known “final parsec problem” of SMBBH systems, and the Nano-Hertz gravitational wave radiation becomes significant. The ratio of the separation between these two black holes to the broad-line region size is about 0.1. A close SMBBH is also suggested by this small ratio and the spectral properties of Balmer broad lines in this quasar. This radio-quiet quasar is a candidate emitter of Nano-Hertz gravitational waves at a frequency of about 30 Nano-Hertz.

SAVE CRIMEA: IT REQUIRES CAREFUL TREATMENT (IT IS NECESSARY PROGRAM OF ENVIRONMENTAL OPTIMIZATION OF CRIMEA)

In Crimea mixed landscapes: in the south - a ridge of low mountains, creating a close to the Mediterranean climate and landscape on a narrow strip of the southern coast; the rest of the area is mostly arid steppes. The Black Sea from depths of more than 150-300 m is contaminated with hydrogen sulfide and uninhabitable marine life. Historically, the recreational and agricultural strategy for the development of Crimea has been formed. There is an unacceptably small ratio of natural and developed areas (30/70%); high land ploughing (60-70%); insufficient foresting (10.7%); high aridity; landscapes are monotonous (excluding the southern shore). The settlements of Crimea dump their liquid runoff after cleaning in the hydrogen sulfide-contaminated sea, which adds complexity to the environmental situation: because the speeds of sea currents are small, and the self-cleaning capacity of the beach area is low due to the reduction of the area of natural beaches, the regulation of the shore by pebble beach's and concrete buns, reducing the area of overgrowth that purifies the water. At the same time, recreational loads on Crimea are growing. The Program of environmental (ecological) optimization of Crimea, increasing natural diversity and share of natural areas (including highly productive forest), improving its natural condition and creating an original architectural - landscape appearance is needed. Large man-made impacts on the fragile ecosystem of Crimea should be banned. Environmental optimization, increasing the share and diversity of natural areas, restoration of natural vegetation, afforestation, biopositive building, will ensure the ecological reliability of the ecosystem.

What does FRB light-curve variability tell us about the emission mechanism?

ABSTRACT A few fast radio bursts’ (FRBs) light curves have exhibited large intrinsic modulations of their flux on extremely short ($t_{\rm r}\sim 10\, \mu$s) time-scales, compared to pulse durations (tFRB ∼ 1 ms). Light-curve variability time-scales, the small ratio of rise time of the flux to pulse duration, and the spectro-temporal correlations in the data constrain the compactness of the source and the mechanism responsible for the powerful radio emission. The constraints are strongest when radiation is produced far (≳1010 cm) from the compact object. We describe different physical set-ups that can account for the observed tr/tFRB ≪ 1 despite having large emission radii. The result is either a significant reduction in the radio production efficiency or distinct light-curve features that could be searched for in observed data. For the same class of models, we also show that due to high-latitude emission, if a flux f1(ν1) is observed at t1 then at a lower frequency ν2 < ν1 the flux should be at least (ν2/ν1)2f1 at a slightly later time (t2 = t1ν1/ν2) independent of the duration and spectrum of the emission in the comoving frame. These features can be tested, once light-curve modulations due to scintillation are accounted for. We provide the time-scales and coherence bandwidths of the latter for a range of possibilities regarding the physical screens and the scintillation regime. Finally, if future highly resolved FRB light curves are shown to have intrinsic variability extending down to ${\sim}\mu$s time-scales, this will provide strong evidence in favour of magnetospheric models.

Gaming with the Throughput and the Latency Benchmarking Measurement Procedures of RFC 2544

In this paper, we investigate three potential issues of the benchmarking measurement procedures defined in RFC 2544 and also used in RFC 5180 and RFC 8219. One of them is the lack of proper timeout usage. We use a Linux box, which can selectively delay a specified ratio of the packets. Using carefully selected parameters based on our preliminary measurements, we demonstrate that the experienced speed of the HTTP download is much less, than what could have been expected on the basis of the throughput results of the RFC 2544 tests. The other critical issue is the strict, absolutely zero loss criterion. We use a Linux box, which drops a specified small ratio of the packets. Whereas the RFC 2544 throughput results tend to be zero, the experienced speed of the HTTP download is quite good. The third problem is the lack of requirement for statistically relevant number of tests in the RFC 2544 benchmarking procedures. We demonstrate its severity with the latency benchmarking procedure defined in RFC 2544 and kept unchanged in RFC 5180 but redefined in RFC 8219.

Entropy-Induced Separation of Binary Semiflexible Ring Polymer Mixtures in Spherical Confinement

Coarse-grained molecular dynamics simulations are used to investigate the conformations of binary semiflexible ring polymers (SRPs) of two different lengths confined in a hard sphere. Segregated structures of SRPs in binary mixtures are strongly dependent upon the number density of system (ρ), the bending energy of long SRPs (Kb, long), and the chain length ratio of long to short SRPs (α). With a low ρ or a weak Kb, long at a small ratio α, long SRPs are immersed randomly in the matrix of short SRPs. As ρ and bending energy of long SRPs (Kb, long) are increased up to a certain value for a large ratio α, a nearly complete segregation between long and short SRPs is observed, which can be further characterized by the ratio of tangential and radial components of long SRPs velocity. These explicit segregated structures of the two components in spherical confinement are induced by a delicate competition between the entropic excluded volume (depletion) effects and bending contributions.

Stokes Slip Flow in Channel Bend

Using intrinsic coordinates, the slip flow in a minute meandering channel is studied by perturbation about the small ratio of curvature to inverse half gap width. The exact solution for an annulus shows this ratio can be as large as 0.5 with less than 1% error. Velocity slip on the walls and the pressure drop depend on the slip factor. Formula for the pressure drop in a channel with a single bend is derived.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

UHF Metamaterial Absorber with Small-Size Unit Cell by Combining Fractal and Coupling Lines

We present a perfect UHF metamaterial absorber by combining coupling lines and fractal lines with a very small unit cell. The proposed absorber consists of a surface metal structure and metallic background plane, separated by a dielectric substrate and air. Simulation results show that the absorber has an absorption peak at 442 MHz with 99.73% absorptivity. The ratio between a lattice constant and resonance wavelength is 1/68, significantly less than the existing absorber. The design principle is introduced in detail according to the absorption mechanism of the proposed absorber. Moreover, the absorption peaks remain high with large angles of incidence for both TE and TM polarizations. Due to the small ratio, it can be widely used in radiation suppression for microwave relay communication such as mobile communication and wireless network by changing the parameters of the structure.