Hirotada Ohashi

A negative selection algorithm for classification and reduction of the noise effect

Artificial Immune Systems (AIS) are a type of intelligent algorithm inspired by the principles and processes of the human immune system. In the last decade, applications of AIS have been studied in various fields. In the application of change/anomaly detection, negative selection algorithms of AIS have been successfully applied. However, negative selection algorithms are not appropriate for multi-class classification problems, because they do not have a mechanism to minimize the danger of overfitting and oversearching. In this paper, we propose a new algorithm to overcome this drawback and to extend the application area of negative selection algorithms to multi-class classification. The algorithm we propose is named Artificial Negative Selection Classifier (ANSC). We investigate the tolerance of ANSC against noise, and introduce a method to reduce the effect of noise into ANSC. The accuracy and data reduction are compared with those from the Artificial Immune Recognition System (AIRS), which is a well known and effective classifier of AIS. The results show that our algorithm is useful for classification problems and the reduction of the noise effect.

Immiscible real-coded lattice gas

Abstract The real-coded lattice gas method was proposed by Malevanets (1997). In this new lattice gas model, particles have continuous velocity distributions, which would yield to Maxwell–Boltzmann distribution in the equilibrium state. Furthermore, collision and streaming schemes do not depend on the explicit lattice structure. Extension to the three-dimensional calculation becomes straightforward both conceptually and practically. We extended this innovative model to the modeling of immiscible binary fluids by introducing colored particles and their interactions. Benchmark calculations show that Laplace law is satisfied in both 2D and 3D spaces. Simulations of phenomena occurring in the realistic immiscible binary fluids were carried out successfully. The model worked stably, and the qualitative agreement with the well-known droplet behavior has been observed.

Revisiting the valence-band and core-level photoemission spectra of NiO.

We have reexamined the valence-band (VB) and core-level electronic structure of NiO by means of hard and soft x-ray photoemission spectroscopies. The spectral weight of the lowest energy state was found to be enhanced in the bulk sensitive Ni 2p core-level spectrum. A configuration-interaction model including a bound state screening has shown agreement with the core-level spectrum and off- and on-resonance VB spectra. These results identify the lowest energy states in the core-level and VB spectra as the Zhang-Rice (ZR) doublet bound states, consistent with the spin-fermion model and recent ab initio calculations within dynamical mean-field theory. The results indicate that the ZR character first ionization (the lowest hole-addition) states are responsible for transport properties in NiO and doped NiO.

Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO2

The temperature (T) dependent metal-insulator transition (MIT) in VO2 is investigated using bulk sensitive hard x-ray (� 8 keV) valence band, core level, and V 2p-3d resonant photoemission spectroscopy (PES). The valence band and core level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3d spectral weight transfer from the coherent (d 1 C final) states at Fermi level to the incoherent (d 0 +d 1 L final) states, corresponding to the lower Hubbard band, lead to gap-formation. The spectral shape changes in V 1s and V 2p core levels as well as the valence band are nicely reproduced from a cluster model calculations, providing electronic structure parameters. Resonant-PES finds that the d 1 L states resonate across the V 2p-3d threshold in addition to the d 0 and d 1 C states. The results support a Mott-Hubbard transition picture for the first order MIT in VO2. PACS numbers: 79.60.-i, 71.30.+h VO2, a d 1 electron system, exhibits a sharp first-order metal-insulator transition (MIT) as a function of temperature (T), at TMI = 340 K. 1 The high-T metal phase has a rutile (R) structure, while the low-T insulating phase has a monoclinic (M1) structure with zig-zag type pairing of V atoms along the c-axis. 2 Magnetically, the metallic R phase shows enhanced susceptibility (�) with an effective mass m ∗ /m � 6, while the insulating M1 phase is non

Recoil Effect of Photoelectrons in the Fermi Edge of Simple Metals

High energy resolution photoelectron spectroscopy of conduction electrons in the vicinity of the Fermi edge in Al and Au at excitation energies of 880 and 7940 eV was carried out using synchrotron radiation. For the excitation energy of 7940 eV, the observed Fermi energy of Al shows a remarkable shift to higher binding energy as compared with that of Au, with accompanying broadening. This is due to the recoil effect of the emitted photoelectrons. The observed spectra are well reproduced by a simple model of Bloch electrons based on the isotropic Debye model.

Lattice Boltzmann Simulation of Multiphase Fluid Flows through the Total Variation Diminishing with Artificial Compression Scheme

Abstract The total variation diminishing with artificial compression (TVD/AC) scheme is applied to the lattice Boltzmann multiphase model in order to introduce a new technique to solve the traditional lattice Boltzmann equation. The TVD/AC scheme gives a much higher resolution than the well-known TVD scheme to the interface in the simulation of multiphase flows. Numerical simulations also show that the new simulator is helpful in stabilizing the computation in the runs of high-density ratios. Numerical results for the coexistence curve and verification of the Laplace law both in two and three spatial dimensions are presented. The detailed dynamical behaviors of the interface over a wide range of density ratios such as the variation of interface thickness and profiles of density, the balance of pressure and interfacial stress, the distribution of spurious velocities and so on are studied. Phase separation in two- and three-dimensional systems is also demonstrated numerically.

Evidence for a correlated insulator to antiferromagnetic metal transition in CrN.

We investigate the electronic structure of chromium nitride (CrN) across the first-order magnetostructural transition at T(N)∼286  K. Resonant photoemission spectroscopy (PES) shows a gap in the 3d partial density of states at the Fermi level and an on-site Coulomb energy U∼4.5  eV, indicating strong electron-electron correlations. Bulk-sensitive high-resolution (6 meV) laser PES reveals a clear Fermi edge indicating an antiferromagnetic metal below T(N). Hard x-ray Cr 2p core-level PES shows T-dependent changes across T(N) which originate from screening due to coherent states as substantiated by cluster model calculations using the experimentally observed U. Electrical resistivity confirms an insulator above T(N) (E(g)∼70  meV) becoming a disordered metal below T(N). Thus, CrN transforms from a correlated insulator to an antiferromagnetic metal, coupled to the magnetostructural transition.

Two-Parameter Thermal Lattice BGK Model with a Controllable Prandtl Number

In this paper, two time relaxation parameters are introduce to a thermal lattice BGK, model to make its Prandtl number controllable. The dependency of the Prandtl number on the two parameters is derived. Numerical measurement of the transport coefficients is used to demonstrate the validity of the method. Furthermore, two examples of convective heat transfer are calculated, with one to show the effectiveness, and the other to show the breakdown of the two-parameter formulation under different conditions.

A Lattice Boltzmann model for polymeric liquids

A Lattice Boltzmann model for polymeric liquids is developed. In the proposed model, polymers are modelled as dumbbells suspended in a solvent. A distribution function is introduced to describe the configuration of the dumbbells, and is used to evaluate the viscoelastic stresses in flow fields. A discrete kinetic equation for the configurational distribution is derived, and is shown to recover the Oldroyd-B constitutive equation at the continuous level, when coupled with the standard Lattice Boltzmann equation for the flow of the solvent. Numerical simulations of both steady and unsteady flows are performed in order to investigate the validity of the current model. In the simulation of small-amplitude oscillatory shear flows, numerical results are quantitatively compared with the analytical solutions obtained with the Oldroyd-B equation, and good agreements are observed.

Heat Transfer in Lattice BGK Modeled Fluid

The thermal lattice BGK model is a recently suggested numerical tool aiming at solving problems of thermohydrodynamics. The quality of the lattice BGK simulation is checked in this paper by calculating temperature profiles in the Couette flow under different Eckert and Mach numbers. A revised lower order model is proposed to improve the accuracy and the higher order model is proved to be advantageous in this respect, especially in the flow regime with a higher Mach number.