Crostalk in WDM SCM Systems due to SRS

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Modify SRS-induced crosstalk with variety of fiber in SCM–WDM transmission links

In this paper, the SRS-induced crosstalk has been evaluated in a SCM–WDM communication links at different modulation frequencies and transmission lengths for variety of fiber. Results show that SRS-induced crosstalk dominates at low frequency. As the dispersion and effective area of fiber (A_eff) decreases, initially the crosstalk remains high and then it decreases with increase in modulation frequency. The present work shows that out of five different types of fiber, standard single mode fiber (SMF) has minimum crosstalk (−78 to −38) dB, (−55 to −33) dB and (−46 to −34) dB at modulation frequencies, transmission lengths and optical powers. Dispersion compensation fiber (DCF) has maximum crosstalk (−60 to −12) dB, (−37 to −12) dB and (−27 to −12) dB at modulation frequencies and transmission lengths.     

Measurement-induced nonlocality in the W and Greenberger–Horne–Zeilinger superposition states

Measurement-induced nonlocality(MIN) is a newly defined quantity to measure correlations in bipartite quantum states [Luo S and Fu S 2011 Phys. Rev. Lett. 106 120401]. MIN in the n-qubit W and Greenberger–Horne–Zeilinger(GHZ) superposition states is considered. It is revealed that n = 3 and n ≥ 4 states have very different characteristics,especially the monogamy relation about MIN, and the monogamy equality of MIN is held in all n-qubit W states(n ≥ 3).     

Nitrogen and Oxygen Self-Broadening and Shift Coefficients of Rotational-Vibrational Raman Band in 1–50 ATM Range

Russian Physics Journal -     

Ground Band and Excited Band of Spin-1 BEC in Cigar Shaped Laser Trap

The wavefunctions that conserve the total spin are constructed for the fully condensed states and the states with one particle excited. A set of equations are deduced for the spatial longitudinal wavefunctions and the chemical potentials. These equations are solved numerically for ^23Na and ^87Rb condensates. The deformed trap shows significant effects on the spectrum. This implies that the spin effect of the spinor BEC are more easily detected in an optical trap of larger aspect ratio.     

Octupole Deformed Band and Quasi-γ Band in 146Ce Nucleus

High-spin structures in ¹⁴⁶Ce nucleus have been re-investigated by measuring the prompt γ rays from spontaneous fission of ²⁵²Cf. The previously reported level scheme of ¹⁴⁶Ce has been updated. The octupole deformed collective bands have been extended up to higher spin states. A possible quasi-γ band structure was examined and reconstructed according to our data analysis. In addition, the reflection asymmetric shell model was applied to describe the octupole deformed bands in ¹⁴⁶Ce, and the calculated results are in good agreement with the experimental data at lower spins.     

SF6 and H2 Broadening and Shifting in the Fundamental Vibrational–Rotational Band of Hydrogen Fluoride

Optics and Spectroscopy - SF6 and H2 broadening and shift of the vibration–rotation lines in the fundamental band of hydrogen fluoride have been investigated. Using mathematical modeling of...     

Shift of the photoemission threshold in III–V and II–VI semiconductors

The reasons why the photoemission threshold energy of semiconductors is lower than the ionization energy of constituent atoms have been investigated. It has been indicated that the previously proposed interpretation of this phenomenon based on the inclusion of an additional intra-atomic Coulomb interaction between the valence electrons is insufficient. It has been shown that the calculation of the electronic energy structure of semiconductors, in particular, of the photoemission threshold, requires taking into account a change in the localization region of the valence electrons when a free atom is embedded into a crystal. A way of taking this change into account in the tight-binding theory has been demonstrated. Corrections to the tight-binding Hamiltonian have been found. The photoemission thresholds of III–V and II–VI semiconductors have been calculated with the inclusion of these corrections. Comparison of the results with the experimental data has been performed.     

Band Gap and Waveguide States in Two-Dimensional Disorder Phononic Crystals

The influences of the configurational disorders on phononic band gaps and on waveguide modes are investigated for the two-dimensional phononic crystals consisting of water cylinders periodically arrayed in mercury. Two types of configurational disorders, relevant to the cylinder position and cylinder size respectively, are taken into account. It is found that the phononic band gap and the guide band are sensitive to the disorders, and generally become narrower with the increasing disorders. It is also found that the waveguide side walls without disorder can significantly prevent the guide modes in the waveguide from influence by the disorders in the crystals to a large amount.     

Conformal blocks in Virasoro and W theories: Duality and the Calogero–Sutherland model

We study the properties of the conformal blocks of the conformal field theories with Virasoro or W-extended symmetry. When the conformal blocks contain only second-order degenerate fields, the conformal blocks obey second order differential equations and they can be interpreted as ground-state wave functions of a trigonometric Calogero–Sutherland Hamiltonian with non-trivial braiding properties. A generalized duality property relates the two types of second order degenerate fields. By studying this duality we found that the excited states of the Calogero–Sutherland Hamiltonian are characterized by two partitions, or in the case of _WAk−1${\mathrm{WA}}_{k-1}$ theories by k   partitions. By extending the conformal field theories under consideration by a u(1)$u(1)$ field, we find that we can put in correspondence the states in the Hilbert state of the extended CFT with the excited non-polynomial eigenstates of the Calogero–Sutherland Hamiltonian. When the action of the Calogero–Sutherland integrals of motion is translated on the Hilbert space, they become identical to the integrals of motion recently discovered by Alba, Fateev, Litvinov and Tarnopolsky in Liouville theory in the context of the AGT conjecture. Upon bosonization, these integrals of motion can be expressed as a sum of two, or in general k, bosonic Calogero–Sutherland Hamiltonian coupled by an interaction term with a triangular structure. For special values of the coupling constant, the conformal blocks can be expressed in terms of Jack polynomials with pairing properties, and they give electron wave functions for special Fractional Quantum Hall states.     

The C-O Stretching Infrared Band as a Probe of Hydrogen Bonding in Ethanol–Water and Methanol–Water Mixtures

Infrared spectra of the ethanol–water and methanol–water mixtures in the mole fraction range of 0.1 to 0.9 were recorded in the attenuated reflection (ATR) mode. Traditionally, the hydrogen bonding of water with other molecules has been studied by investigation of the OH stretching band frequencies and intensities of water. However, in the case of alcohol–water mixtures, this procedure presents a problem due to the complete overlap of the hydroxyl absorptions from the alcohol and water. In the present study, we have adopted an alternative approach of understanding the ethanol–water and methanol–water hydrogen bonds through the analysis of the C-O stretching band. The intrinsic high intensity of the C-O band and nearly complete absence of its overlap with the water bands make it a good candidate for the study of hydrogen bonding interactions in alcohol–water mixtures. The integrated areas of the C-O stretching band versus mole fractions were plotted for both mixtures. In the case of methanol–water mixtures, the C-O stretching band area plot was linear, whereas such plot for the ethanol–water mixtures had two distinct slopes that switched at the 0.5 mole fraction. The C-O band plot areas were used to explain the molecular associations in the mixtures studied.     

The Influence of Defect Structure on Oxidation Rate of V–Cr–W–Zr Alloy During Heat Treatment in Air

Russian Physics Journal - The results of an investigation of the influence of microstructure on the oxidation rate of an alloy of the V–Cr–W–Zr system investigated under the...     

Band structure and pressure-induced metallic transition in iodine – GW calculation

We have studied the band structure and the band gap closure in phase I of solid iodine under high pressure, using the methods based on the quasiparticle theory, i.e. GW approximation. Our calculations show that the band gap in the Cmca structure, which is the structure of the phase I of solid iodine, closes around 20 GPa. This pressure is near the upper boundary of phase I. We discuss the possible metallic transition in the molecular phase of solid iodine and the possible changes of the crystal structure.     

In situ study of self-ion irradiation damage in W and W–5Re at 500 °C

In situ self-ion irradiations (150?keV?W⁺) have been carried out on W and W–5Re at 500?°C, with doses ranging from 10¹⁶ to 10¹⁸ W⁺m^?2 (～1.0?dpa). Early damage formation (10¹⁶W⁺m^?2) was observed in both materials. Black–white contrast experiments and image simulations using the TEMACI software suggested that vacancy loops were formed within individual cascades, and thus, the loop nucleation mechanism is likely to be ‘cascade collapse’. Dynamic observations showed the nucleation and growth of interstitial loops at higher doses, and that elastic loop interactions may involve changes in loop Burgers vector. Elastic interactions may also promote loop reactions such as absorption or coalescence or loop string formation. Loops in both W and W–5Re remained stable after annealing at 500?°C. One-dimensional hopping of loops (b?=?1/2 ?111>) was only seen in W. At the final dose (10¹⁸W⁺m^?2), a slightly denser damage microstructure was seen in W–5Re. Both materials had about 3–4?×?10¹⁵ loops m^?2. Detailed post-irradiation analyses were carried out for loops of size???4?nm. Both b?=?1/2 ?111? (～75%) and b?= ?100> (～25%) loops were present. Inside–outside contrast experiments were performed under safe orientations to determine the nature of loops. The interstitial-to-vacancy loop ratio turned out close to unity for 1/2 ?111? loops in W, and for both 1/2 ?111? and ?100? loops in W–5Re. However, interstitial loops were dominant for ?100? loops in W. Re seemed to restrict loop mobility, leading to a smaller average loop size and a higher number density in the W-Re alloy.     

Energy Band and Josephson Dynamics of Spin-Orbit Coupled Bose–Einstein Condensates

We theoretically investigate the energy band structure and Josephson dynamics of a spin-orbit coupled Bose–Einstein condensate in a double-well potential. We study the energy band structure and the corresponding tunneling dynamics of the system by properly adjusting the SO coupling, Raman coupling, Zeeman field and atomic interactions.The coupled effects of SO coupling, Raman coupling, Zeeman field and atomic interactions lead to the appearance of complex energy band structure including the loop structure. Particularly, the emergence of the loop structure in energy band also depends on SO coupling, Raman coupling, Zeeman field and atomic interactions. Correspondingly,the Josephson dynamics of the system are strongly related to the energy band structure. Especially, the emergence of the loop structure results in complex tunneling dynamics, including suppression-revival transitions and self-trapping of atoms transfer between two spin states and two wells. This engineering provides a possible means for studying energy level and corresponding dynamics of two-species SO coupled BECs.     

Luminescence of II–VI and III–V nanostructures

Photoluminescence of HgCdTe epitaxial films and nanostructures and electroluminescence of InAs(Sb,P) light-emitting diode (LED) nanoheterostructures were studied. For HgCdTe-based structures, the presence of compositional fluctuations, which localized charge carriers, was established. A model, which described the effect of the fluctuations on the rate of the radiative recombination, the shape of luminescence spectra and the position of their peaks, was shown to describe experimental photoluminescence data quite reasonably. For InAs(Sb,P) LED nanoheterostructures, at low temperatures (4.2–100 K) stimulated emission was observed. This effect disappeared with the temperature increasing due to the resonant ‘switch-on’ of the Auger process involving transition of a hole to the spin-orbit-splitted band. Influence of other Auger processes on the emissive properties of the nanoheterostructures was also observed. Prospects of employing II–VI and III–V nanostructures in light-emitting devices operating in the mid-infrared part of the spectrum are discussed.     

Computation and measurement of corona current density and V–I characteristics in wires-to-plates electrostatic precipitator

This paper deals with experimental and numerical investigation of wire-duct type electrostatic precipitator under clean air conditions. A laboratory-scale model is used to provide measurements of corona current–voltage characteristics and current density. Different configurations of electrodes are tested in order to improve the performance of the electrostatic precipitator. Moreover, the corona governing equations are successfully solved using Comsol Multiphysics. The present work simulates the whole geometry including all discharge wires in order to take into account their mutual effect. The results of the numerical model are compared with the experimental measurements of current density and current–voltage characteristics and the general agreement is quite good.