μ–τ symmetry in Zee–Babu model

We study the Zee–Babu two-loop neutrino mass generation model and look for a possible flavor symmetry behind the tri-bimaximal neutrino mixing. We find that there probably exists the μ–τ   symmetry in the case of the normal neutrino mass hierarchy, whereas there may not be in the inverted hierarchy case. We also propose a specific model based on a Froggatt–Nielsen-like Z₅$Z_5$ symmetry to naturally accomplish the μ–τ symmetry on the neutrino mass matrix for the normal hierarchy case.     

I–V characteristics and critical currents in superconducting/ferromagnetic bilayers

Current–voltage (I–V) characteristics and critical current density, J_c, for the onset of vortex motion were measured at different magnetic fields, H, and temperatures, T, in a superconducting (S)/ferromagnetic (F) bilayer and in a single Nb film. We choose Nb as a superconductor and a weak ferromagnetic alloy, Pd_1−xNi_x with x = 16, as F. We found that J_c was smaller for the S/F bilayer with respect to the single Nb film. The result was related to the reduced value of the superconducting order parameter in the bilayer.     

Anomalous B–H behaviour of electrical steels at very low flux density

The behaviour of ferromagnetic materials under very low magnetic field was investigated more than a century ago by Lord Rayleigh. However, it has been shown since that the so-called Rayleigh law fails for very low magnetic fields, although the explanation for this phenomenon was not given. An anomalous B–H behaviour at very low alternating peak flux density in conventional grain-oriented (GO) and non-oriented (NO) electrical steels is reported. It has been found that the initial permeability is constant for all the measured frequencies (from 20 to 400 Hz) at peak flux density below 0.1 mT, and in this region the magnetisation is almost reversible (for both GO and NO). At higher flux density the B–H loops become visibly irreversible, with a relatively narrow (for GO) or very wide (for NO) transition region. For GO the B–H loop becomes visibly “distorted” for all frequencies at around 2 mT. The eddy current loss calculated from the so-called “classical” equation gives values higher than the measured total losses at lower frequencies. Both these measured results are difficult to explain.     

Rotating Einstein–Maxwell–dilaton black holes in D dimensions

We construct exact charged rotating black holes in Einstein–Maxwell–dilaton theory in D   spacetime dimensions, D?5$D?5$, by embedding the D  -dimensional Myers–Perry solutions in D+1$D+1$ dimensions, and performing a boost with a subsequent Kaluza–Klein reduction. Like the Myers–Perry solutions, these black holes generically possess N=[(D−1)/2]$N=[(D-1)/2]$ independent angular momenta. We present the global and horizon properties of these black holes, and discuss their domains of existence.     

Magnetic properties of CoPt–SiNx/Ag nanocomposite films

When the thickness of Ag under layer is 25 nm, the CoPt/Ag film has maximum out-of-plane squareness (S_⊥), minimum in-plane squareness (S_∥), and the largest out-of-plane coercivity (H_c⊥), they are 0.95, 0.35, and 15 kOe, respectively. Different volume percent of SiN_x ceramic materials were co-sputtered with Co₅₀Pt₅₀ films on the Ag under layer to reduce the grain size of the CoPt film. Comparing the X-ray diffraction pattern of CoPt-SiN_x/Ag films without annealing with that of the films which annealed at 600 and 700 °C, it is found that the intensities of CoPt (0 0 1) and CoPt (0 0 2) superlattice lines were reduced after annealing. As the SiN_x content is raised to 50 vol%, the particle size of CoPt is reduced to be about 9 nm.     

I–V characterization of a quantum well infrared photodetector with stepped and graded barriers

I–V characterization of an n-type quantum well infrared photodetector which consists of stepped and graded barriers has been done under dark at temperatures between 20–300 K. Different current transport mechanisms and transition between them have been observed at temperature around 47 K. Activation energies of the electrons at various bias voltages have been obtained from the temperature dependent I–V measurements. Activation energy at zero bias has been calculated by extrapolating the bias dependence of the activation energies. Ground state energies and barrier heights of the four different quantum wells have been calculated by using an iterative technique, which depends on experimentally obtained activation energy. Ground state energies also have been calculated with transfer matrix technique and compared with iteration results. Incorporating the effect of high electron density induced electron exchange interaction on ground state energies; more consistent results with theoretical transfer matrix calculations have been obtained.     

Adjoint-based h–p adaptive discontinuous Galerkin methods for the 2D compressible Euler equations

In this paper, we investigate and present an adaptive Discontinuous Galerkin algorithm driven by an adjoint-based error estimation technique for the inviscid compressible Euler equations. This approach requires the numerical approximations for the flow (i.e. primal) problem and the adjoint (i.e. dual) problem which corresponds to a particular simulation objective output of interest. The convergence of these two problems is accelerated by an hp-multigrid solver which makes use of an element Gauss–Seidel smoother on each level of the multigrid sequence. The error estimation of the output functional results in a spatial error distribution, which is used to drive an adaptive refinement strategy, which may include local mesh subdivision (h-refinement), local modification of discretization orders (p-enrichment) and the combination of both approaches known as hp-refinement. The selection between h- and p-refinement in the hp-adaptation approach is made based on a smoothness indicator applied to the most recently available flow solution values. Numerical results for the inviscid compressible flow over an idealized four-element airfoil geometry demonstrate that both pure h-refinement and pure p-enrichment algorithms achieve equivalent error reductions at each adaptation cycle compared to a uniform refinement approach, but requiring fewer degrees of freedom. The proposed hp-adaptive refinement strategy is capable of obtaining exponential error convergence in terms of degrees of freedom, and results in significant savings in computational cost. A high-speed flow test case is used to demonstrate the ability of the hp-refinement approach for capturing strong shocks or discontinuities while improving functional accuracy.     

Measurement of the branching ratios for the decays J/ψ → ϱπ and J/ψ → γη′

Decays of the J/ψ (3.1) resonance into final states with two charged hadrons and two photons are investigated. Branching ratios for the decays J/ψ → ?π and J/ψ → γη′ are determined to be

$\text{Г(J/ψ → pφ)}\text{Г(J/ψ → all)}\text{= (1.0± 0.2) ·10}{}^{\mathrm{?2}}\text{,}\text{Г(J/ψ → γη′)}\text{ГJ/ψ → all)}\text{= (2.0± 0.7) ·}{}^{\mathrm{?3}}$

Upper limits for the same decay modes of ψ′ (3.7) are also determined.     

Calculation of on-state I–V characteristics of LDMOSFETs based on an accurate LDD resistance modeling

In this paper, we present an I–V model for LDMOSFETs. It is based on modeling the Lightly-Doped Drain (LDD) region of the device as voltage-controlled resistors where velocity saturation effect is also taken into account. Using the LDD region model along with a model for the channel region of the device, the on-state I–V characteristic of the transistor is accurately calculated. The models for the LDD region resistors can be incorporated into a circuit simulator such as HSPICE which has an accurate model for the channel region of the transistor. The accuracy of the models is verified by comparing its results with those of a device simulator. The results show a maximum error of 1% for a wide range of voltages and overlapped LDD region lengths.     

Influence of tensile damage on V–I curve and critical current of DyBCO coated conductor

The coated conductors are subjected to mechanical and electromagnetic stresses in preparation and service. When the stress is high, the coated layer is damaged, resulting in loss of superconducting property. The present work was carried out to reveal the influence of tensile damage on V–I curve, critical current and n-value of DyBa₂Cu₃O_7−δ coated conductor. The changes of the V–I curve, critical current and n-value with increasing applied tensile strain were measured experimentally. The features of the shift of the V–I curve to the lower current range and increase in its curvature, and accordingly the decrease in critical current and n-value, with increasing applied strain, were detected. For analysis of the experimental results, the model of Fang et al, which treats with the voltage generation due to the current shunting under existent crack, was applied. The experimentally observed features were described satisfactorily.     

Effect of carbon nanotubes chirality on the E–C photo-isomerization switching behavior in moelcular device

Applying nonequilibrium Green's function formalism in combination with the first-principles density functional theory, we investigate the electronic transport properties of optical molecular switch based on the fulgide molecule with two different single-walled carbon nanotube (SWCNT) electrodes. The molecule that comprises the switch can convert between E isomer and C isomer by ultraviolet or visible irradiation. Theoretical results show that these two isomers exhibit very different conductance properties both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the SWCNT electrodes strongly affects the switching characteristics of the molecular junctions, which is useful for the design of functional molecular devices.     

Magnetic properties,microstructure, and phase evolution of PrxFebal.TiyB20−x (x=4–9; y=2.5–5) nanocomposites

Magnetic properties, microstructure, and phase evolution of Pr lean and boron-enriched Pr_xFe_bal.Ti_yB_20−x (x=4–9; y=2.5–5) melt-spinning ribbons with nanostructures have been investigated. Based on thermal magnetic analysis (TMA), for y=2.5, two phases, namely Pr₂Fe₁₄B and α-Fe, were found for ribbons with x=9, while additional two metastable phases, Pr₂Fe₂₃B₃ and Fe₃B, existed for x=4, 7 and 8. With the decrease of Pr content, the remanence increases but coercivity decreases. The optimal properties of B_r=9.5 kG, _iH_c=10.7 kOe, and (BH)_max=17.8 MG Oe are achieved in Pr₉Fe_bal.Ti_2.5B₁₁ nanocomposites. On the other hand, higher Ti substitution for Fe in Pr₇Fe_bal.Ti_yB₁₃ ribbons could refine the grain size and suppress the metastable Pr₂Fe₂₃B₃ and Fe₃B phases effectively. The excellent permanent magnetic properties are mainly dominated by the nanoscaled microstructures and the coexistence of sufficient magnetically soft phases, Fe₃B, Pr₂Fe₂₃B₃ and α-Fe, with magnetically hard Pr₂Fe₁₄B phase.     

不同E/cB值下同轴绝缘子闪络特性

基于磁场闪络抑制原理,研究了由回路电流产生的同轴自磁场对径向真空固体绝缘界面沿面闪络特性的影响规律。根据同轴结构电场E和磁场B的比值与半径无关、只与电路参数相关的特点,分别设计了E/cB（c为光速）为0.041,0.05,0.056和0.062的四种同轴电极结构,开展了有磁场和无磁场两种条件下电介质的真空沿面闪络实验研究。实验结果表明,在有利于磁场闪络抑制条件的自磁场位形下,真空沿面闪络耐压水平相比无磁场情况有明显提高,且比值E/cB越小闪络电压提高幅度越大。当E/cB比值为0.041时,沿面闪络电压可提高约1.3倍;而当自磁场位形反向时,沿面闪络电压相比于无磁场情况有所降低。     

Ab initio calculation of neutral and singly charged Mgn (n?11) clusters

Under generalized gradient approximation (GGA), geometrical structure, size dependence of stability and electronic properties of neutral Mg_n, singly charged cationic Mg_n⁺ and singly charged anionic Mg_n⁻ clusters consisting of up to 11 atoms have been studied systematically by ab initio method within the norm-conserving pseudopotentials. In addition to the electronic shell effects, the “closed” geometrical structure can also enhance the stability of the clusters. The enhanced stability for the cationic cluster resulted from the removal of an antibonding electron is larger than that for the anionic cluster by promoting an extra electron to occupy a bonding orbital. The density of states (DOS) shows the increase in interaction between valence and unoccupied states leads to an increase in s-p hybridization.     

The Near-Infrared YΣ-XΠ Transition of CuSe

The near-infrared Y²Σ⁺-X²Π transition of the diatomic molecule CuSe was observed for the first time. A King-type carbon tube furnace was used to produce the gas phase of the CuSe molecules. The Fourier transform spectrometer associated with the National Solar Observatory, Kitt Peak, Arizona was used to record the molecular emission spectrum in the region 9850-12 400 cm⁻¹. A vibronic analysis and comparisons of the spin-orbit constant and the ²Σ⁺ transition energy to those for related isovalent molecules are presented.     

Type I and new seesaw in left–right symmetric theories

We extend the Type I seesaw and suggest a new   seesaw mechanism to generate neutrino masses within the left–right symmetric theories where parity is spontaneously broken. We construct a next to minimal left–right symmetric model where neutrino masses are determined irrespective of the B−L$B-L$ breaking scale and call it the new   seesaw mechanism. In this scenario B−L$B-L$ scale can be very low. This makes B−L$B-L$ gauge boson and the quasi-Dirac heavy leptons very light. These TeV scale particles could have large impact on lepton flavor and CP violating processes. We also shed light on the phenomenological aspects of the model within the reach of the LHC.     

Single spin asymmetry in πp Drell–Yan process

We study the single spin asymmetries for the πp^↑→μ⁺μ⁻X$\pi p^{\uparrow }\to {\mu }^{+}{\mu }^{-}X$ process. We consider the asymmetries contributed by the coupling of the Boer–Mulders function with the transversity distribution and the pretzelosity distribution, characterized by the sin(?+?S)$\sin (?+{?}_S)$ and sin(3?−?S)$\sin (3?-{?}_S)$ azimuthal angular dependence, respectively. We estimate the magnitude of these asymmetries at COMPASS by using proper weighting functions. We find that the sin(?+?S)$\sin (?+{?}_S)$ asymmetry is of the size of a few percent and can be measured through the experiment. The sin(3?−?S)$\sin (3?-{?}_S)$ asymmetry is smaller than the sin(?+?S)$\sin (?+{?}_S)$ asymmetry. After a cut on qT$q_T$, we succeed in enhancing the asymmetry.     

Spin transistor and quantum spin Hall-effects in CdBxF2−x–p-CdF2–CdBxF2−x sandwich nanostructures

Planar CdB_xF_2−x–p-CdF₂–CdB_xF_2−x sandwich nanostructures prepared on the surface of the n-type CdF₂ bulk crystal are studied to register the spin transistor and quantum spin Hall-effects. The current–voltage characteristics of the ultra-shallow p⁺–n junctions verify the CdF₂ gap, 7.8 eV, and the quantum subbands of the 2D holes in the p-type CdF₂ quantum well confined by the CdB_xF_2−xδ-barriers. The temperature and magnetic field dependencies of the resistance, specific heat and magnetic susceptibility demonstrate the high temperature superconductor properties for the CdB_xF_2−xδ-barriers. The value of the superconductor energy gap, 2Δ = 102.06 meV, determined by the tunneling spectroscopy method appears to be in a good agreement with the relationship between the zero-resistance supercurrent in superconductor state and the conductance in normal state, πΔ/e, at the energies of the 2D hole subbands. The results obtained are evidence of the important role of the multiple Andreev reflections in the creation of the high spin polarization of the 2D holes in the edged channels of the sandwich device. The high spin hole polarization in the edged channels is shown to identify the mechanism of the spin transistor and quantum spin Hall-effects induced by varying the top gate voltage, which is revealed by the first observation of the Hall quantum conductance staircase.     

High-Jc GdBa2Cu3O7−δ films fabricated by the metal–organic deposition process

We report a successful fabrication of high-J_c GdBa₂Cu₃O_7−δ (GdBCO) films by the metal–organic deposition process on the LaAlO₃ (LAO) (0 0 1) substrates. The coating solution was prepared by mixing Gd, Cu fluorine-free sources with Ba trifluoroacetate. Samples were dip-coated, pyrolized within 3 h at the temperature up to 400 °C in a humid oxygen atmosphere, and finally fired at various high temperatures in 100 ppm Ar/O₂ atmosphere. The GdBCO films fired at 775 and 800 °C exhibited J_c values of ∼2.1 MA/cm² at 77 K in a self-field, which are attributable to both high T_c,zero values of ∼89 K and high in-plane textures of 1.3–1.4°. Above 800 °C, however, the superconducting properties of GdBCO films are degraded due to the thermal decomposition of GdBCO film in 100 ppm Ar/O₂ atmosphere.     

Fourier transform spectral study of BΣ-XΣ system of AlO

The spectrum of B²Σ⁺-X²Σ⁺ system of AlO has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.05 cm⁻¹. Nineteen bands of the Δv = 1, 0, −1, and −2 sequences of this band system have been analyzed for the rotational structure. Out of which seven bands, viz. 3-2, 4-3, 2-3, 3-4, 4-5, 5-6 and 6-7 have been analyzed for the first time. The rotational lines of these 19 bands along with 20 earlier analyzed bands, a total of 7200 lines, have been fitted in a simultaneous least squares fit. The study has resulted in determining more precise vibrational and rotational constants of the two states. Because of the high resolution employed it became necessary to invoke H₀ and H₁ coefficients, and a fifth order term to explain the anomalous spin-doubling observed in the v″ = 5, 6 and 7 levels of the X²Σ⁺ state.