Hokkaido University of Science

Sapporo, Japan

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Yoshino T.,Hokkaido University of Science | Matsunaga S.,Hokkaido University of Science
Advanced Synthesis and Catalysis | Year: 2017

High-valent (pentamethylcyclopentadienyl)cobalt(III) [Cp*Co(III)] catalysts were found as inexpensive alternatives to (pentamethylcyclopentadienyl)rhodium(III) [Cp*Rh(III)] catalysts in the field of C-H bond functionalization, and applied to a variety of transformations. In this review, after the discovery and early examples of Cp*Co(III)-catalyzed C-H bond functionalization are summarized, the unique reactivity and selectivity of Cp*Co(III) and the differences between the cobalt and rhodium catalysis are intensively discussed. Such differences are assumed to be caused by the lower electronegativity, hard nature, and smaller ionic radius of cobalt. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Takahashi R.,Hokkaido University of Science | Umemura M.,University of Tsukuba
Monthly Notices of the Royal Astronomical Society | Year: 2017

We present a general relativistic radiative transfer code, ARTIST (Authentic Radiative Transfer In Space-Time), that is a perfectly causal scheme to pursue the propagation of radiation with absorption and scattering around a Kerr black hole. The code explicitly solves the invariant radiation intensity along null geodesics in the Kerr-Schild coordinates, and therefore properly includes light bending, Doppler boosting, frame dragging, and gravitational redshifts. The notable aspect of ARTIST is that it conserves the radiative energy with high accuracy, and is not subject to the numerical diffusion, since the transfer is solved on long characteristics along null geodesics. We first solve the wavefront propagation around a Kerr black hole that was originally explored by Hanni. This demonstrates repeated wavefront collisions, light bending, and causal propagation of radiation with the speed of light.We show that the decay rate of the total energy of wavefronts near a black hole is determined solely by the black hole spin in late phases, in agreement with analytic expectations. As a result, the ARTIST turns out to correctly solve the general relativistic radiation fields until late phases as t ~ 90 M. We also explore the effects of absorption and scattering, and apply this code for a photon wall problem and an orbiting hotspot problem. All the simulations in this study are performed in the equatorial plane around a Kerr black hole. The ARTIST is the first step to realize the general relativistic radiation hydrodynamics. © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Ogawa N.,Hokkaido University of Science
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

Particle diffusion in a two-dimensional curved surface embedded in R3 is considered. In addition to the usual diffusion flow, we find a flow with an explicit curvature dependence. Diffusion equation is obtained in ε (thickness of surface) expansion. As an example, the surface of elliptic cylinder is considered, and curvature-dependent diffusion coefficient is calculated. © 2010 The American Physical Society.

Nihashi S.,Hokkaido University of Science | Ohshima K.I.,Hokkaido University
Journal of Climate | Year: 2015

Sinking of dense water from Antarctic coastal polynyas produces Antarctic Bottom Water (AABW), which is the densest water in the global overturning circulation and is a key player in climate change as a significant sink for heat and carbon dioxide. Very recent studies have suggested that landfast sea ice (fast ice) plays an important role in the formation and variability of the polynyas and possibly AABW. However, they have been limited to regional and case investigations only. This study provides the first coincident circumpolar mapping of Antarctic coastal polynyas and fast ice. The map reveals that most of the polynyas are formed on the western side of fast ice, indicating an important role of fast ice in the polynya formation. Winds diverging from a boundary comprising both coastline and fast ice are the primary determinant of polynya formation. The blocking effect of fast ice on westward sea ice advection by the coastal current would be another key factor. These effects on the variability in sea ice production for 13 major polynyas are evaluated quantitatively. Furthermore, it is demonstrated that a drastic change in fast ice extent, which is particularly vulnerable to climate change, causes dramatic changes in the polynyas and possibly AABW formation that can potentially contribute to further climate change. These results suggest that fast ice and precise polynya processes should be addressed by next-generation models to produce more accurate climate projections. This study provides the boundary and validation data of fast ice and sea ice production for such models. © 2015 American Meteorological Society.

Ichikawa S.,Hokkaido University of Science
Chemical Record | Year: 2016

It is important to pursue function-oriented synthesis (FOS), a strategy for the design of less structurally complex targets with comparable or superior activity that can be made in a practical manner, because compared to synthetic drugs, many biologically relevant natural products possess large and complex chemical structures that may restrict chemical modifications in a structure–activity relationship study. In this account, we describe recent efforts to simplify complex nucleoside natural products including caprazamycins. Considering the structure–activity relationship study with several truncated analogues, three types of simplified derivatives, namely, oxazolidine, isoxazolidine, and lactam-fused isoxazolidine-containing uridine derivatives, were designed and efficiently synthesized. These simplified derivatives have exhibited promising antibacterial activities. A significant feature of our studies is the rational and drastic simplification of the molecular architecture of caprazamycins. This study provides a novel strategy for the development of a new type of antibacterial agent effective against drug-resistant bacteria. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Tsuchimoto M.,Hokkaido University of Science
Physics Procedia | Year: 2013

In magnetization process by field cooling of a bulk high-Tc superconductor (HTS), stresses are induced by the Lorentz force between shielding currents and magnetic fields. Stresses in a cylindrical bulk HTS are numerically evaluated in the axisymmetric three-dimensional analysis. Shielding current distributions are obtained through a macroscopic numerical simulation with the Maxwell equations and the critical state model. The stress distributions are obtained through numerical analysis with the finite-difference method. Maximum stresses are discussed for the case with anisotropic Poisson's ratio of the bulk HTS. © 2013 The Authors.

Chiba K.,Hokkaido University of Science
2013 IEEE Congress on Evolutionary Computation, CEC 2013 | Year: 2013

Design Informatics has three points of view. First point is the efficient exploration in design space using evolutionary computation. Second point is the structurization and visualization of design space using data mining. Third point is the application to practical problems. In the present study, the influence of the seven pure and hybrid optimizers for design information has been investigated in order to explain the selection manner of optimizer for data mining. A single-stage hybrid rocket design problem is picked up as the present design object. As a result, mining result depends on not the number of generation (convergence) but the optimizers (diversity). Consequently, the optimizer with diversity performance should be selected in order to obtain global design information in the design space. Therefore, the diversity performance has also been explained for the seven optimization methods by using three standard mathematical test problems with/without noise. The result indicates that the hybrid method between the differential evolution and the genetic algorithm is beneficial performance for efficient exploration in the design space under the condition for large-scale design problems within 10 2 order evolution at most. Moreover, the comparison among eight crossovers indicates that the principal component analysis blended crossover is good selection on the hybrid method between the differential evolution and the genetic algorithm. © 2013 IEEE.

Abe A.,Hokkaido University of Science
Case Studies in Mechanical Systems and Signal Processing | Year: 2016

This paper presents a proposal for a minimum energy feedforward control technique for flexible structures to suppress residual vibrations in point-to-point (PTP) motion. In the proposed method, the trajectory profile of the PTP motion is generated through a cycloidal function whose input is the output of a polynomial function. The obtained trajectory is dependent upon the coefficients of the polynomial function. To achieve the suppression of the residual vibration as well as the operating energy of this PTP motion, the coefficients are tuned by metaheuristic algorithms. In the numerical simulations, we investigated the PTP motions of a single-link flexible manipulator and a robotic arm attached to a flexible link. The simulation results were compared with those of previous studies, revealing the effectiveness of the proposed method. © 2016 The Author

Chiba K.,Hokkaido University of Science
6th International Conference on Soft Computing and Intelligent Systems, and 13th International Symposium on Advanced Intelligence Systems, SCIS/ISIS 2012 | Year: 2012

Optimizer is an essence in design-informatics to efficiently obtain nondominated solutions. In the present study, the best optimizer is decided through the competition for the mathematical standard test functions and is also applied to a conceptual design problem of simple single-stage hybrid rocket as the real-world problem. Consequently, a hybrid method between differential evolution and genetic algorithm has good exploration performance. Moreover, the principal component analysis blended crossover and the confidence interval based crossover have good capability on the hybrid method between differential evolution and genetic algorithm. © 2012 IEEE.

Ogawa N.,Hokkaido University of Science
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The diffusion of particles in confining walls forming a tube is discussed. Such a transport phenomenon is observed in biological cells and porous media. We consider the case in which the tube is winding with curvature and torsion, and the thickness of the tube is sufficiently small compared with its curvature radius. We discuss how geometrical quantities appear in a quasi-one-dimensional diffusion equation. © 2013 Elsevier B.V.

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