Electrodynamical Characteristics of α-Lactose Monohydrate in the Terahertz Range

Optics and Spectroscopy - Using methods of infrared, terahertz, and submillimeter spectroscopy, experimental transmission and reflection spectra of α-lactose monohydrate have been obtained at...     

Temperature–Frequency Dependence of the Dielectric Response in LuFe2O4 Multiferroics

Physics of the Solid State - The temperature–frequency spectra of the complex dielectric permittivity of the LuFe2O4 multiferroics have been studied in the temperature range 100–400 K...     

Dielectric Loss of Thin-Film SiO2 Samples on Al in THz–IR Range

Physics of the Solid State - The development of new dielectric materials for insulating layer of interconnects with low loss on high frequencies (low-k) is one of main directions of modern...     

Experimental and Theoretical Study of Carnosine in THz Range

The characteristic fingerprints of carnosine from 0.2 to 2.6 THz are first measured by terahertz time-domain spectroscopy at room temperature. For the pure carnosine, the refractive index varies between 1.79 and 1.85 with the average value 1.84, while for the carnosine-polyethylene mixture, four absorption peaks centred at 1.37, 1.56, 1.85 and 2.49 THz are detected. A comparison of the theoretical predictions using the density functional theory with the experimental results shows satisfactory agreement except somewhat blue shift.     

Lattice Dynamics of the Strontium Ferrotungstate in the Temperature Range 300–700 K

Physics of the Solid State - The lattice dynamics of a strontium ferrotungstate SrFe2/3W1/3O3 ceramics is studied by the Raman spectroscopy method in the temperature range 300–700 K. The...     

Mechanical Properties of Ultrafine-Grained Aluminum in the Temperature Range 4.2–300 K

Physics of the Solid State - The tensile curves of ultrafine-grained (UFG) aluminum structured by high pressure torsion (HPT) technique have been obtained at 4.2 and 77 K for the first time as well...     

On the Physical Meaning of Disperse Parameters of Frequency Dependence of Dielectric Permittivity in the Havriliak–Negami Model

This paper is devoted to an analysis of the frequency dispersion of dielectric permittivity in order to establish the physical meaning of the dispersion parameters α and β in the Havriliak–Negami model. It is found that parameter α is associated with the spectrum broadening of relaxation time τ. Examples with the appearance of a dispersion with parameter α of about 0.4 and 0.7 are presented. A conclusion is drawn that disorder creates a broadening of the relaxation times. Dispersion parameters α and β are introduced to preserve the unified relaxation time. The possibility of the analysis of experimental results on the basis of the Debye model in order to obtain the relaxation time distribution and determine parameters α and β according to the log(τ_HN/τ) chart is shown.     

Radial Evolution of the Atmospheric Pressure Glow Discharge in Helium Controlled by Dielectric Barrier

The rachal evolution of atmospheric pressure glow discharge in helium is presented by numerical simulation. The calculations reveal the mechanism of two current peaks per half cycle. The first breakdown occurs firstly in the central region of the electrode, and then spreads to the edge, while the second breakdown ignites at the periphery firstly, and then propagates toward the discharge central region. The simulations indicate that radial electric fields and radial sheath play an important role in the evolution of the second peak. These results agree fundamentally with the experimental observations.     

Temperature Dependence of the Effective Magnetic Anisotropy Field and Ferromagnetic Resonance Linewidth in Polycrystalline Complex Substituted Magnetically Uniaxial Hexagonal Ferrites in the Frequency Range of 25–67 GHz

Technical Physics - Temperature dependences of the effective magnetic anisotropy field and ferromagnetic resonance linewidth in samples of isotropic and anisotropic hexaferrite...     

Dielectric Response of Graded Spherical Composites

We investigate the effective dielectric responses of graded spherical composites under an external uniform electric field by taking the dielectric function of spherical inclusion, εi = cr^ke^βr, where r is the inner distance of a point inside the particle from the centre of the spherical particle in the coordination. In the dilute limit, our exact result is used to test the validity of differential effective dipole approximation （DEDA） for estimating the effective response of graded spherical composites and it is shown that the DEDA is in excellent agreement with the exact result.     

Dielectric Dispersion Study of Poly(vinyl Pyrrolidone)–Polar Solvent Solutions in the Frequency Range 20 Hz–1 MHz

Influence of polar solvents environment and polymer concentrations on the electrical properties (complex dielectric constant, ac electrical conductivity, complex electric modulus and complex impedance) of the solutions of poly(vinyl pyrrolidone) (PVP) in polar solvents, namely water, ethyl alcohol, ethylene glycol, diethylene glycol, poly(ethylene glycol), glycerol, dimethyl sulfoxide and dimethyl formamide, have been investigated in the frequency range 20 Hz–1 MHz at 25°C. Comparative analysis of the dielectric dispersion curves confirms that the solvent molecular size and number of its hydroxyl groups, and the solutions viscosity, are the major factors which governs the PVP chain segmental motion. The ionic conduction and electrode polarization phenomena has a dominant influence on the large increase of complex dielectric constant values of the solutions of PVP‐polar solvent in the lower frequency region. The values of relaxation times corresponding to these phenomena are also reported.     

“Free” Evolution of Multi-particle Excitations in the Glauber Dynamics at High Temperature

The paper is devoted to the spectral properties of the Glauber dynamics for the Ising model at high temperature 1/. It is proven that for sufficiently small || there is an invariant subspace, in which the dynamics can be described as a free multi-particle evolution, provided that the one-particle subspace is singled out. The proof is based upon the Haag–Ruelle scattering theory.     

Variations of the Frequency Range of HF Signals on the Subauroral Path During Magnetic–Ionospheric Disturbances in October 2016

Radiophysics and Quantum Electronics - We present the results of studying variations of the key characteristics of the ionospheric HF channel, namely, the maximum observed (MOF) and the lowest...     

Extremely Increasing the Operating Frequency Range of Mode-Locked Hybrid Soliton Pulse Source

Numerical simulations show that proper fundamental mode-locking repetition range of hybrid soliton pulse source where transform-limited pulses are obtained is extremely increased with the use of linearly chirped tanh apodized fibre Bragg grating. Near transform-limited pulses around a system operating frequency of 2.5 GHz. are generated over a frequency range of 1.6 GHz （1.9-3.4 GHz）     

Relationship of the Acid-Induced 13C Chemical-Shift Change in the α-Carbon Atom to the Stretching Frequency of the Hydroxy Group in Saturated Alcohols

A good linear relationship was found between the acid-induced ¹³C chemical shift change of the α-carbon atom and the OH stretching frequency of the hydroxy group in some saturated alcohols. The relationship is discussed with model calculations using the CNDO/2 method.

The trifluoroacetic acid-induced ¹³C chemical shift change in the α-carbon atom to the hydroxy group, Δδ¹³c, has been measured for a number, of saturated alcohols in carbon tetrachloride solution and provides information on the relative basicity and its dependence on the structural factor.¹ The free OH stretching frequency, v_OHis known to depend on the structural factor of the substituent._2–5 We reported that a linear relationship exists between the ¹⁷ O chemical shift, δ¹⁷ O, and the OH stretching frequency of the hydroxy group in saturated alchohols, R-OH.⁵ In this case, the ¹⁷O chemical shift change was reported to be governed by the ionization potential.⁶ The ionization potential of R-OH is expected to be correlated with its basicity. Regression analysis for Δδ¹³C was thus carried out for Δδ¹⁷OH reported for 14 and 19 typical alcohols, respectively. In order to explain the experimental results the oretically, we carried out CNDO/2 calculations for a series of methyl-substituted methanols.     

Thermal Conductivity of poly-p-phenylene-2,6-benzobisoxazole Film along the In-Plane Axis in the 10–300 K Temperature Range

The thermal conductivities of compression molded thin films of poly-p-phenylene-2,6-benzobisoxazole (PBO) were measured in directions along an in-plane axis in the 10–300?K temperature range by a steady-state heat flow method, with interest in the use of the material for superconductivity applications. The thermal conductivities of the PBO films increased from 0.3?W/mK to 9.0?W/mK with increasing temperature from 10?K to 300?K and these were much higher than those of polyimide films, epoxy resin and glass fiber reinforced plastics at all temperatures. The 9.0?W/mK at 300?K was 60% of that of stainless steel (SUS304). It was 6?W/mK at 150?K, which was half that of SUS304 and was 3.3?W/mK at 77?K, which was 33% of that of SUS304. The thermal conductivities of the PBO films were lower than those of a cloth of high strength ultrahigh molecular weight polyethylene fiber reinforced plastics in the 30?K–180?K temperature range and were almost equivalent to its values in the 180?K–300?K temperature range. The main contribution to the thermal conduction in the PBO films was from thermal phonon conduction along the molecular chains. Although many kinds of high thermal conductivity polymeric materials have been prepared by a uni-directional drawing process or by adding high thermal conductive additives, the PBO film showed high thermal conductivity without a uni-directional drawing process or high thermal conductive additive.