Efficient mesh motion using radial basis functions with data reduction algorithms

Mesh motion using radial basis functions has been demonstrated previously by the authors to produce high quality meshes suitable for use within unsteady and aeroelastic CFD codes. In the aeroelastic case the structural mesh may be used as the set of control points governing the deformation, which is efficient since the structural mesh is usually small. However, as a stand alone mesh motion tool, where the surface mesh points control the motion, radial basis functions may be restricted by the size of the surface mesh, as an update of a single volume point depends on all surface points. In this paper a method is presented that allows an arbitrary deformation to be represented to within a desired tolerance by using a significantly reduced set of surface points intelligently identified in a fashion that minimises the error in the interpolated surface. This method may be used on much larger cases and is successfully demonstrated here for a 10⁶ cell mesh, where the initial solve phase cost reduces by a factor of eight with the new scheme and the mesh update by a factor of 55. It has also been shown that the number of surface points required to represent the surface is only geometry dependent (i.e. grid size independent), and so this reduction factor actually increases for larger meshes.     

Why only few are so successful?

In many professions employees are rewarded according to their relative performance. Corresponding economy can be modeled by taking N independent agents who gain from the market with a rate which depends on their current gain. We argue that this simple realistic rate generates a scale-free distribution even though intrinsic ability of agents are marginally different from each other. As an evidence we provide distribution of scores for two different systems (a) the global stock game where players invest in real stock market and (b) the international cricket.     

Theoretical study on the composition dependence of Ga8−nAsn (n=0-8) clusters

Using full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method, we have investigated the dependence of GaAs clusters with eight atoms on composition. It is found that the ground state structures for Ga-rich and As-rich clusters are cube structures. As the ratio between gallium atoms and arsenic atoms is close to one, structural distortion become increasingly severe, or even the clusters adopt other geometrical configurations as their ground state structures. The energy gap E_g between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO), and the vertical electron affinity show a certain degree of even/odd alternation with cluster composition. Among nine Ga_8−nAs_n (n=0-8) clusters, only a few of clusters have different energy orders between the ionic and neutral isomers with large binding energy. Some ionic structures would change into other configurations due to severe structural distortion.     

Magneto-transport properties of [Co/Bi]n wire structures

The present study examines the artificial control of grain-boundary resistance and its contribution to the magneto-transport properties of [Co(1 nm)/Bi(2.5 nm)]_n (n=10 or 20) line structures on the Si(0 0 1)/SiN_x substrate. Conventional patterning and deposition processes are applied for the fabrication of a device that consists of five-line structures with a line width of 2 μm. A ΔR/R=80% ratio was observed in the five-line structure of [Co(1 nm)/Bi(2.5 nm)]₁₀ multilayers at 10 K. Our measurements indicate that grain-boundary effects can be associated with the large ΔR/R ratio of transverse magnetoresistance.     

New magnetic crystal,metastable metallic alloys Co1−xCux, prepared at strongly non-equilibrium conditions

Magnetic Co_1−xCu_x alloys in the form of single-crystal and polycrystalline films were grown under strongly non-equilibrium conditions using magnetron and triode sputtering techniques. It was found that these alloys could be obtained not only in the expected face-centered cubic structure, but also in a tetragonal phase, undetected earlier for present alloys. Results comparing some structural, magnetic and electric properties of these two phases are also presented here.     

Quantum circuits for controlled teleportation of two-particle entanglement via a W state

A protocol for three-party controlled quantum teleportation is discussed. It is shown that an unknown two-particle entanglement can be teleported to any one of two receivers via the only one three-particle W state. We summarize all different unitary transformations performed by the receiver with a concise formula. The quantum circuits for the generalized measurement described by positive operator-valued measure (POVM), which is utilized to probabilistically distinguish the two non-orthogonal states, are explicitly constructed by means of quantum Toffoli gates. The efficient quantum circuits for implementing the teleportation are also provided.     

L to M shell transitions and model comparisons for radiative opacities of sodium fluoride plasma

The radiative opacities of hot dense sodium fluoride (NaF) plasma have been studied in the case of local thermodynamic equilibrium (LTE). The spectrally resolved opacity in the case of and is taken as an example to illustrate the absorption structures of the NaF plasma. The transitions from L to M shells of sodium and fluoride are the main contributions for the plasma absorptions. The isodense opacities of NaF plasma are studied at a density of and temperatures of 20-60 eV. Detailed comparisons among the results of the detailed term accounting (DTA), detailed configuraion accounting (DCA), unresolved transition array (UTA) and average atom (AA) model codes, which have been developed independently in China in the past few years, are performed for both the spectral resolved and mean opacities. Good agreements are found at a temperature of 40 eV and a density of , but discrepancies appear at a temperature of 50 eV and a density of .     

Ultra high Q crystalline microcavities

We report on the fabrication technique of ultra high Q optical crystalline whispering gallery mode microresonators and discuss their properties. The technique is suitable for the majority of available optical crystals and for production of resonators with small size. To validate the method, we made CaF₂ resonators with Q factors exceeding 4 × 10⁸ and a diameter smaller than 100 μm. A single mode resonator has also been fabricated. Possible utilization of these new resonators in quantum optics is discussed.     

Room temperature photoluminescence from amorphous silicon nanoparticles in SiOx thin films

Amorphous SiO_x thin films with four different oxygen contents (x=1.15, 1.4, 1.5, and 1.7) have been prepared by thermal evaporation of SiO in vacuum and then annealed at 770 or 970 K in argon for various times ?40 min. The influence of annealing conditions and the initial film composition on photoluminescence (PL) from the annealed films has been explored. Intense room temperature PL has been observed from films with x?1.5, visible with a naked eye. It has been shown that PL spectra of most samples consists of two main bands: (i) a ‘green’ band centered at about 2.3 eV, whose position does not change with annealing conditions and (ii) an ‘orange-red’ band whose maximum moves from 2.1 to 1.7 eV with increasing annealing time and temperature and decreasing initial oxygen content. These observations have been explained assuming recombination via defect states in the SiO_x matrix for the first band and emission from amorphous Si nanoparticles for the second one.     

Dielectric properties of SrBi2−xPrxNb2O9 ceramics (x=0, 0.04 and 0.2)

SrBi_2−xPr_xNb₂O₉ (x=0, 0.04 and 0.2) ceramics were prepared by a solid state reaction method. X-ray diffraction analysis indicated that single-phase layered perovskite structure ferroelectrics were obtained. A relaxor behavior of frequency dispersion was observed among Pr-doped SrBi₂Nb₂O₉. The degree of frequency dispersion ΔT increased from 0 for x=0-7 °C for x=0.2, and the extent of relaxor behavior γ increased from 0.94 for x=0-1.45 for x=0.2. The substitution of Pr ions for Bi³⁺ ions in the Bi₂O₂ layers resulted in a shift of the Curie point to lower temperatures and a decrease in remanent polarization. In addition, the coercive field 2E_c reduced from 110 kV/cm for an undoped specimen to 90 kV/cm for x=0.2.     

Metal to insulator transition in Mn substituted underdoped NdBa2Cu3O7−y: Evidence of strong charge localization

We have synthesized underdoped NdBa₂Cu₃O_7−y (NBCO) and NdBa₂Cu_3−xMn_xO_7−y (x = 0.1, 0.2, and 0.3) samples. The analysis of the lattice parameters has been done by using the X-ray diffraction (XRD) method. Using the Scanning Electron Microscope (SEM) the granular nature as well as the intergranular networks has been studied. The Energy Dispersive X-ray (EDX) and Rutherford Backscattering Spectroscopy (RBS) studies confirm the substitution of Mn in the Cu-sites. The transport measurements in several undoped and Mn-substituted NBCO samples have been carried out. We have observed an indication of the metal to insulator transition as a result of the strong charge localization induced by Mn substitution. The applicability of various conductivity equations has been verified for comparison. Estimations of the activation energy and localization length have been carried out and discussed.     

First-order intertwining operators and position-dependent mass Schrödinger equations in d dimensions

The problem of d-dimensional Schrödinger equations with a position-dependent mass is analyzed in the framework of first-order intertwining operators. With the pair (H, H₁) of intertwined Hamiltonians one can associate another pair of second-order partial differential operators (R, R₁), related to the same intertwining operator and such that H (resp. H₁) commutes with R (resp. R₁). This property is interpreted in superalgebraic terms in the context of supersymmetric quantum mechanics (SUSYQM). In the two-dimensional case, a solution to the resulting system of partial differential equations is obtained and used to build a physically relevant model depicting a particle moving in a semi-infinite layer. Such a model is solved by employing either the commutativity of H with some second-order partial differential operator L and the resulting separability of the Schrödinger equation or that of H and R together with SUSYQM and shape-invariance techniques. The relation between both approaches is also studied.     

C-V characterization of Schottky- and MIS-gate SiGe/Si HEMT structures

Electrical properties of Schottky- and metal-insulator-semiconductor (MIS)-gate SiGe/Si high electron mobility transistors (HEMTs) were investigated with capacitance-voltage (C-V) measurements. The MIS-gate HEMT structure was fabricated using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. We previously investigated device characteristics of sub-100-nm-gate-length Schottky- and MIS-gate HEMTs, and reported that the MIS-gate device had larger maximum drain current density and transconductance (g_m) than the Schottky-gate device. The radio frequency (RF) measurement of the MIS-gate device, however, showed a relatively lower current gain cutoff frequency f_T compared with that of the Schottky-gate device. In this study, C-V characterization of the MIS-gate HEMT structure demonstrated that two electron transport channels existed, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel.     

In situ monitoring of ZnO formation by photoemission spectroscopy

Exposure of a clean Zn metal to oxygen in ultra high vacuum provides a mean to gradually form ZnO. With in situ synchrotron photoelectron measurement, the progressive change in the spectra with the oxygen exposure time is observed. The analysis of the spectra allows the determination of ZnO formation. It was found that the oxidation process takes place until reaching the critical thickness, at which the oxidation rate reduces greatly to nearly zero. The critical thickness was determined to be about 2 monolayers.     

Simultaneous measurement with one-capture of the two in-plane components of displacement by electronic speckle pattern interferometry

We present the simultaneous measurement of the two in-plane displacement components by electronic speckle pattern interferometry with three object beams and without an in-line reference beam. Three interference fringe patterns, corresponding to three different sensitivity vectors, are recorded in a single interferogram and separated by means of the Fourier transform method. Then, two interference fringe patterns are selected to obtain the in-plane displacement components.     

Magnetic and electrical properties of new magnetic phase in Si1−xMnx crystals

We have investigated the magnetic and electrical transport properties of Si_1−xMn_x single crystals grown by the vertical Bridgman method. The alloys with Mn concentrations up to x=0.64 have weak ferromagnetic ordering around T_C∼30 K. However, Si_0.25Mn_0.75 alloys show weak ferromagnetic ordering at 70 K and antiferromagnetic ordering at 104 K, which is confirmed by magnetization and electrical transport studies.     

Structural optimization of HfTiSiO high-k gate dielectrics by utilizing in-situ PVD-based fabrication method

We investigated the optimum structure for Ti-containing Hf-based high-k gate dielectrics to achieve EOT scaling below 1 nm. TiO₂/HfSiO/SiO₂ trilayer and HfTiSiO/SiO₂ bilayer structures were fabricated by a newly developed in-situ PVD-based method. We found that thermal diffusion of Ti atoms to SiO₂ underlayers degrades the EOT-J_g characteristics. Our results clearly demonstrated the impact of the trilayered structure with TiO₂ capping for improving EOT-J_g characteristics of the gate stack. We achieved an EOT scaling of 0.78 nm as well as reduced gate leakage of 7.2 × 10⁻² A/cm² for a TiO₂/HfSiO/SiO₂ trilayered high-k dielectric while maintaining the electrical properties at the bottom interface.     

Low temperature specific heat of bi-layered manganites La2−2xSr1+2xMn2O7 (x=0.3 and 0.5)

The specific heat (C) of bi-layered manganites La_2−2xSr_1+2xMn₂O₇ (x=0.3 and 0.5) is investigated for the ground state of low temperature excitations. A T^3/2 dependent term in the low temperature specific heat (LTSH) is identified at zero magnetic field and suppressed by magnetic fields for x=0.3 sample, which is consistent with a ferromagnetic metallic ground state. For x=0.5 sample, a T² term is observed and is consistent with a two-dimensional (2D) antiferromagnetic insulator. However, it is almost independent of magnetic field within the range of measured temperature (0.6-10 K) and magnetic field (6 T).