Network design with edge-connectivity and degree constraints

We consider the following network design problem; Given a vertex set V with a metric cost c on V, an integer k≥1, and a degree specification b, find a minimum cost k-edge-connected multigraph on V under the constraint that the degree of each vertex v∈V is equal to b(v). This problem generalizes metric TSP. In this paper, we show that the problem admits a ρ-approximation algorithm if b(v)≥2, v∈V, where ρ=2.5 if k is even, and ρ=2.5+1.5/k if k is odd. We also prove that the digraph version of this problem admits a 2.5-approximation algorithm and discuss some generalization of metric TSP

Classical Planning in Deep Latent Space

Current domain-independent, classical planners require symbolic models of the problem domain and instance as input, resulting in a knowledge acquisition bottleneck. Meanwhile, although deep learning has achieved significant success in many fields, the knowledge is encoded in a subsymbolic representation which is incompatible with symbolic systems such as planners. We propose Latplan, an unsupervised architecture combining deep learning and classical planning. Given only an unlabeled set of image pairs showing a subset of transitions allowed in the environment (training inputs), Latplan learns a complete propositional PDDL action model of the environment. Later, when a pair of images representing the initial and the goal states (planning inputs) is given, Latplan finds a plan to the goal state in a symbolic latent space and returns a visualized plan execution. We evaluate Latplan using image-based versions of 6 planning domains: 8-puzzle, 15-Puzzle, Blocksworld, Sokoban and Two variations of LightsOut.Comment: Under review at Journal of Artificial Intelligence Research (JAIR

Field-induced carrier delocalization in the strain-induced Mott insulating state of an organic superconductor

We report the influence of the field effect on the dc resistance and Hall coefficient in the strain-induced Mott insulating state of an organic superconductor $\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br. Conductivity obeys the formula for activated transport $\sigma_{\Box} = \sigma_{0}\exp(-W/k_{B}T)$, where $\sigma_{0}$ is a constant and $W$ depends on the gate voltage. The gate voltage dependence of the Hall coefficient shows that, unlike in conventional FETs, the effective mobility of dense hole carriers ($\sim1.6\times 10^{14}$ cm$^{-2}$) is enhanced by a positive gate voltage. This implies that carrier doping involves delocalization of intrinsic carriers that were initially localized due to electron correlation.Comment: 5 pages, 3 figure

A gas-diffusion cathode coated with oxide-catalyst for polymer electrolyte fuel cells using neither platinum catalyst nor carbon catalyst-support

To overcome the fundamental disadvantages of conventional cathodes for polymer electrolyte fuel cells (PEFCs), such as dissolution and migration of platinum-based catalysts and consumption of the carbon catalyst-support, a substantially novel gas-diffusion cathode has been proposed. The electrode was made of a porous oxide catalyst, which was coated on the inner and outer surfaces of a macro-porous titanium sheet substrate, using neither a platinum catalyst nor carbon catalyst-support. The suitability of this cathode for PEFCs, tested using a highly porous iridium oxide strongly coated on the macro-porous titanium sheet substrate, was confirmed by successful power generation. The gas-diffusion electrode functioned not only as the cathode but also as an anode of a PEFC.ArticleELECTROCHIMICA ACTA. 105:224-229 (2013)journal articl

Effect of acidity on the physicochemical properties of α- and β-chitin nanofibers

Published online 11 Apr 2017We have investigated whether acidity can be used to control the physicochemical properties of chitin nanofibers (ChNFs). In this study, we define acidity as the molar ratio of dissociated protons from the acid to the amino groups in the raw chitin powder. The effect of acidity on the physicochemical properties of α- and β-ChNFs was compared. The transmittance and viscosity of the β-ChNFs drastically and continuously increased with increasing acidity, while those of the α-ChNFs were not affected by acidity. These differences are because of the higher ability for cationization based on the more flexible crystal structure of β-chitin than α-chitin. In addition, the effect of the acid species on the transmittance of β-ChNFs was investigated. The transmittance of β-ChNFs can be expressed by the acidity regardless of the acid species, such as hydrochloric acid, phosphoric acid, and acetic acid. These results indicate that the acidity defined in this work is an effective parameter to define and control the physicochemical properties of ChNFs.ArticleINTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES. 102:358-366 (2017)journal articl

Order/disorder phase composite Fe-Pt exchange-spring film magnets

Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio