Band 76, Heft 8

A novel liquid refractive index sensor based on the connected single-mode fiber (SMF), no-core fiber (NCF), four-core fiber (FCF), and silver mirror (SM) to form an SMF–NCF–FCF–SM Michelson probe structure is proposed and fabricated. The change of light field in the probe structure has been simulated by the light-beam propagation method. The theoretical results show that light is excited in the NCF and couples into the cores and cladding of FCF at the junction of NCF and FCF. The interference fringes are generated between the cladding modes and core modes of FCF. The sensitivities of the probe in NaCl, sucrose, and glycerol are 171.75 dB/RIU, 121.41 dB/RIU, and 207.50 dB/RIU, respectively. The temperature sensitivity is 0.05 nm/°C, and the intensity change of temperature (≤0.046 dB/°C) is very small and has little effect on the liquid refractive index. Thus, the cross-sensitivity of temperature for the liquid refractive index can be removed. The proposed probe structure has the advantages of easy fabrication, good stability, and linear response, having potential application in the liquid refractive index monitoring environments.

A sequence of in situ measurements points the presence of non-thermal species in the profile of particle distributions. This study highlights the role of such energetic electrons on the wave-spectrum. Using Vlasov–Maxwell’s model, the dispersion relations of the parallel propagating modes along with the space scale of damping are discussed using non-relativistic bi-Maxwellian and bi-Kappa distribution functions under the weak field approximation, i.e., ω−k.v>Ω0$\left\vert \omega -\mathbf{k}.\mathbf{v}\right\vert { >}{{\Omega}}_{0}$. Power series and asymptotic expansions of plasma dispersion functions are performed to derive the modes and spatial damping of waves, respectively. The role of these highly energetic electrons is illustrated on real frequency and anomalous damping of R and L-modes which is in fact controlled by the parameter κ in the dispersion. Further, we uncovered the effect of external magnetic field and thermal anisotropy on such spatial attenuation. In global perspective of the kinetic model, it may be another step.

We present an analysis of the effect of entropy on ion temperature gradient η i -mode driven solitary and shock waves in electron–positron–ion plasma having density and temperature inhomogeneities. Linear and nonlinear analysis having solutions in form of solitons and shocks shows that entropy influence changes the drift mode instability. Different limiting cases when (i) temperature fluctuations due to E × B only ( η i ≫ 2/3), (ii) in the absence of entropy and (iii) neglecting positron effect ( β = 1) are discussed. The homotophy perturbation method (HPM) is applied on the derived Korteweg–de-Vries (KdV) and KdV–Burger equations under small time approximation. It is found that both results, those obtained analytically and by the HPM technique, strongly agree with each other. These investigations may be useful to study low frequency electrostatic modes in magnetized electron–positron–ion plasma. For illustration, the model has been applied to the nonlinear electrostatic excitations in interstellar medium and tokamak plasma.

This paper investigates the flow of water-based Fe 3 O 4 ferrofluid flow and heat transfer due to rotating cone and disk under the influence of the external magnetic field. The similarity approach is used to transform the governing equations of ferrohydrodynamic flow into a set of nondimensional coupled differential equations. The nondimensional coupled differential equations are solved numerically through the finite element procedure. Effect of rotation of the disk, rotation of the cone, the intensity of the magnetic field, volume concentrations, and Prandtl number are analyzed on the velocity and temperature distributions. These effects are also observed on the skin friction coefficients and local heat transfer rate. The rotation of the disk, rotation of the cone, and the intensity of the magnetic field have a major impact on the velocity profiles, temperature profiles, skin friction coefficients, and local heat transfer rate.

Mn-Ni based full-Heusler alloys belong to novel half-metallic compounds with a promising set of physical properties for applications as functional materials. Based on first principles calculations, the electronic structures, the magnetic and mechanical properties of Ni 2 Mn(Ge,Sn) and Mn 2 NiGe full-Heusler alloys have been investigated in detail. The results revealed that the Mn 2 NiGe with Hg 2 CuTi type structure is more stable; on the other hand, for Ni 2 Mn(Ge,Sn), the Cu 2 MnAl type structure is more stable. The Mn 2 NiGe alloys are found to be half-metallic with an integer value of total magnetic moment of 4 μ B which makes them interesting materials in the field of spintronics. The Ni 2 Mn(Ge,Sn) alloys exhibit metallic character in both Hg 2 CuTi and Cu 2 MnAl type structures. The calculated B / G ratios for all the considered compounds Ni 2 Mn(Ge,Sn) and Mn 2 NiGe are greater than 1.75; therefore, these alloys are ductile, and the calculated Cauchy’s pressure is positive, which also classified these compounds as ductile materials.

The main frontier of this research is to study the influence of multi-layer graphene (MLG) and aluminium as a fuel in Al/Fe 2 O 3 and MLG/Fe 2 O 3 nanothermites, fabricated by physical mixing and ultrasonication techniques. To study the structural and energy release properties, prepared samples were characterized by XRD, FESEM, EDS, FTIR, Raman spectroscopy and DSC. The X-ray diffraction (XRD) technique showed that all the phases remain intact during the synthesis. Field emission electron microscopy (FESEM) micrographs displayed the surface morphology of the samples, and besides this, energy dispersive spectroscopy (EDS) was used to check the elemental composition of samples. Raman spectroscopy revealed that the ultrasonication waves did not deteriorate the aromatic structure of graphene sheets. Fourier transform infrared spectroscopy (FTIR) spectra were used to observe the information about various functional groups present in the thermite samples. The exothermic energy released by the thermite reaction in both the samples was investigated by differential scanning calorimetry (DSC) and the observed values of energy release for Al/Fe 2 O 3 and MLG/Fe 2 O 3 are 215 J/g and 1640 J/g.

Surface quantum states in quasi-two dimensional organic conductors induced by an external magnetic field tilted in the plane of the layers are obtained and analyzed. In tilted magnetic fields, these states arise from the transitions of the electrons between the closed orbits on the sides of the Fermi surface determined by the electron momentum along the magnetic field direction p B and the coordinate of the center of electron revolution Z . By far, in organic conductors, the surface states have not been studied for tilted magnetic fields. In this work, we have performed detail analyses of the surface states in a tilted in-plane magnetic field by calculating the surface energy spectrum and surface wave functions in order to address their properties and features. We find that, in a tilted magnetic field, the surface levels have higher energies compared to those at zero tilt angle but can be observed only up to a certain tilt angle. The resonant magnetic field and angular values at which the peaks in the surface oscillations should be observed are obtained. Further theoretical and new experimental studies of the surface states in a tilted magnetic field might give new insights into the surface properties of quasi-two dimensional organic conductors. Additionally, they may reveal new information about the parameters of the Fermi surface of organic conductors necessary for its reconstruction.

The adiabatic compressibility along the two-phase saturation line was calculated for nine molten immiscible mixtures, namely, LiF + KBr, LiF + CsCl, LiF + RbBr, LiF + KI, LiF + CsBr, LiF + RbI, LiF + CsI, LiCl + AgBr, and NaCl + AgI, using experimental data on the sound velocity and density. It is shown that the ratio of compressibility of the equilibrium phases depends significantly on the sizes of the mixed ions. The dependence of the changes in compressibility in the distance and in the vicinity of the critical mixing point on the characteristics of the chemical bond between the ions is discussed.

We consider a situation where an N -level system (NLS) is coupled to a heat bath without being necessarily thermalized. For this situation, we derive general Jarzynski-type equations and conclude that heat and entropy is flowing from the hot bath to the cold NLS and, vice versa, from the hot NLS to the cold bath. The Clausius relation between increase of entropy and transfer of heat divided by a suitable temperature assumes the form of two inequalities which have already been considered in the literature. Our approach is illustrated by an analytical example.