A Test Statistic in Canonical Correlation Analysis for Categorical Variables

In canonical correlation analysis (CCA), it is important to estimate the number of nonzero canonical correlations in the population. One way to estimate the number is to consider the dimensionality testing problem. In CCA for continuous variables, some test statistics for the problem have been derived under the normality assumption. However, there are only a few papers on test statistics in CCA for categorical variables.

In this article, a test statistic in CCA for categorical variables is suggested. The test statistic is derived from the rational used for continuous variables. Some properties of the test statistic are examined through mathematical investigations and numerical simulations.

     

Anisotropy in the resistive superconducting transition under magnetic fields in single crystal Pb2Sr2Ho0.5Ca0.5Cu3O8

Anisotropie properties of the single crystal Pb₂Sr₂Ho_0.5Ca_0.5Cu₃O₈ have been investigated by measuring the electrical resistivity in theab-planeρ _ab (H, θ,T), which depends on the angleθ between theab-plane and the magnetic-field direction, in various constant fieldsH perpendicular to the current direction. All the angle-dependent values ofρ _ab (H, θ,T) at a constant temperature are scaled to be on one curve as a function of reduced field. The anisotropic parameter γ≡(m _c ^* /m _ab ^* )^1/2 is estimated as 12–13, which is larger than that of YBa₂Cu₃O₇ and much smaller than that of Bi₂Sr₂CaCu₂O₈. It has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but seems to depend on the overlap of the electronic wave functions along thec-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence ofρ _ab (H,θ,T).     

Electron-temperature control by varying dc voltage to a mesh grid covered by thin film in plasmas

We discuss theoretically how the resistance of a film deposited on the metal grid affects the efficiency of electron-temperature control by employing a grid-bias method, in which, by using a naked metal grid, the electron temperature decreases from 3.4 to 0.12 eV with a decrease in the grid potential from 40 to − 60 V, being accompanied by an electron-density increase from 0.6 × 10⁹ cm^− 3 to 6.0 × 10⁹ cm^− 3 at an argon gas pressure of 5.0 mTorr. The electron temperature can be varied even when the grid is covered with a film with finite resistance, although the range of electron temperature variation is restricted. This method is applicable to reactive plasmas in which grids are often covered by films with finite resistance.     

Handling of fine-particles by time-averaged particle driving method in plasmas

We developed a noble technique for the fine-particle handling in plasmas. In this method a pair of point electrodes are introduced in the plasma, to which positive pulses are applied alternatively. When the pulse repetition period is shorter than the particle response time, the particles feel only time-averaged force because of their large mass. Spatial profile of the equivalent potential of the time-averaged force varies from a circle to an ellipse with an increase in the local discharge at the electrodes. The particles are eventually transported toward a middle point between two point-electrodes, being almost independent of their initial positions. This method is quite effective for converging fine particles in the plasma.     

ZnO nanostructured film deposition using the separated pulsed laser deposition (SPLD) assisted by electric and magnetic drift motion

We have developed the separated pulsed laser deposition (SPLD) technique to prepare high quality ZnO based films exhibiting uniform and droplet-free properties. This SPLD consists of an ablation chamber and a deposition chamber which can be independently evacuated under different ambient gases.The gas species and the pressures in both chambers can be arbitrarily chosen for the specific deposition such as nanostructured films and nanoparticles. The ablation chamber is a stainless steel globe and the deposition chamber is a quartz tube connected to a metallic conic wall with an orifice. We used a KrF excimer laser with λ = 248 nm and 25 ns pulse duration. The different gas conditions in two chambers allow us to realize optimal control of the plasma plume, the gas phase reaction and the film growth by applying the bias voltage between the conic wall and the substrate under the magnetic field. We can expect that at appropriate pressures the electric and magnetic field motion (E × B azimuthal drift velocity) gives significant influences on film growth.We have deposited ZnO thin films at various pressures of ablation chamber (Pab) and deposition chamber (Pd). The deposition conditions used here were laser fluence of 3 J/cm², laser shot number of 30,000, Pab of 0.67-2.67 Pa (O₂ or Ar), Pd of 0.399-2.67 Pa (O₂), and substrate temperature of 400 °C. Particle-free and uniform ZnO films were obtained at Pab of 0.67 Pa (Ar) and Pd of 1.33 Pa (O₂). The ZnO film showed high preferential orientation of (002) plane, optical band gap of 2.7 eV, grain size of 42 nm and surface roughness of 1.2 nm.     

Subsurface structures in initial stage of FeSi2 growth studied by high-resolution Rutherford backscattering spectroscopy

The initial stage of iron silicide formation is investigated by high-resolution Rutherford backscattering spectroscopy. During the Fe deposition on Si(001) at 470 °C, the formation of FeSi₂ is confirmed by the surface peak analysis. Initially, FeSi₂ grows epitaxially so that one of the major crystallographic axes is parallel to the <111> axis of the Si substrate. With increasing Fe deposition, the deviation between the major crystallographic axis of the silicide region and Si<111> increases although the electron diffraction pattern is independent of the amount of Fe deposition. Therefore, the subsurface crystallographic structure of iron silicide is transformed from a cubic-like to a low-symmetry structure.     

Tunneling Conductance Dependence of the Tunneling Spectra in Bi2Sr2CaCu2O8

We have measured the tunneling spectra in Bi₂Sr₂CaCu₂O₈ with a scanning tunneling microscope(STM) at various tip-sample distances by changing the tunneling conductance in a controlled manner. When the tunneling conductance is increased from 1×10^–9 to 1×10^–5 S, the spectra do not show changes in particular. However, the gap value decreases steeply and the asymmetric back ground density of states turns inverted V-shaped one above 6×10^–4 S. The changes in the tunneling spectra at the high tunneling conductances are explained by the enhancement of the local carrier density induced by the pressure that the STM tip applied to the sample.     

Production of aluminum-matrix carbon nanotube composite using high pressure torsion

In this study, an Al-based composite containing carbon nanotubes (CNTs) was fabricated using a process of severe plastic deformation through high pressure torsion (HPT). Neither heating nor sintering was required with the HPT process so that an in situ consolidation was successfully achieved at ambient temperature with 98% of the theoretical density. A significant increase in hardness was recorded through straining by the HPT process. When the composite was pulled in tension, the tensile strength of more than 200 MPa was attained with reasonable ductility. Transmission electron microscopy showed that the grain size was reduced to 100 nm and this was much smaller than the grain size without CNTs and the grain size reported on a bulk sample. High resolution electron microscopy revealed that CNTs were present at grain boundaries. It was considered that the significant reduction in grain size is attributed to the presence of CNTs hindering the dislocation absorption and annihilation at grain boundaries.     

Deformability enhancement in ultra-fine grained, Ar-contained W compacts by TiC additions up to 1.1%

Nano-sized Ar bubbles give negative influence on the fracture resistance and occurrence of superplasticity in ultra-fine grained (UFG) W–TiC compacts. In order to enhance deformability in UFG, Ar-contained W–TiC compacts, effects of TiC addition on the high-temperature deformation behavior were examined. W–TiC compacts with TiC additions of 0, 0.25, 0.5, 0.8 and 1.1 wt% were fabricated by mechanical alloying in a purified Ar atmosphere and hot isostatic pressing. Tensile tests were conducted at 1673–1973 K (0.45–0.54 T_m, T_m: melting point of W) at initial strain rates from 5 × 10⁻⁵ to 5 × 10⁻³ s⁻¹. It is found that as TiC addition increases, the elongation to fracture significantly increases, e.g., from 3 to 7% for W–0 and 0.25TiC/Ar to above 160% for W–1.1TiC/Ar when tested at 1873 and 1973 K at 5 × 10⁻⁴ s⁻¹. The flow stress takes a peak at 0.25%TiC and decreases to a nearly constant level at 0.5–1.1%TiC. The ranges of the strain rate sensitivity of flow stress, m, and the activation energy for deformation, Q, with TiC additions are 0.17–0.30 and 310–600 kJ/mol, respectively. The observed effects of the TiC additions on the tensile properties are discussed.     

Space–time interface-tracking with topology change (ST-TC)

To address the computational challenges associated with contact between moving interfaces, such as those in cardiovascular fluid–structure interaction (FSI), parachute FSI, and flapping-wing aerodynamics, we introduce a space–time (ST) interface-tracking method that can deal with topology change (TC). In cardiovascular FSI, our primary target is heart valves. The method is a new version of the deforming-spatial-domain/stabilized space–time (DSD/SST) method, and we call it ST-TC. It includes a master–slave system that maintains the connectivity of the “parent” mesh when there is contact between the moving interfaces. It is an efficient, practical alternative to using unstructured ST meshes, but without giving up on the accurate representation of the interface or consistent representation of the interface motion. We explain the method with conceptual examples and present 2D test computations with models representative of the classes of problems we are targeting.