Exact Algorithms for the Bottleneck Steiner Tree Problem

Given n points, called terminals, in the plane ℝ² and a positive integer k, the bottleneck Steiner tree problem is to find k Steiner points from ℝ² and a spanning tree on the n+k points that minimizes its longest edge length. Edge length is measured by an underlying distance function on ℝ², usually, the Euclidean or the L ₁ metric. This problem is known to be NP-hard. In this paper, we study this problem in the L _p metric for any 1≤p≤∞, and aim to find an exact algorithm which is efficient for small fixed k. We present the first fixed-parameter tractable algorithm running in f(k)⋅nlog ² n time for the L ₁ and the L _∞ metrics, and the first exact algorithm for the L _p metric for any fixed rational p with 1<p<∞ whose time complexity is f(k)⋅(n ^k +nlog n), where f(k) is a function dependent only on k. Note that prior to this paper there was no known exact algorithm even for the L ₂ metric.     

On-line recognition of handprinted Kanji characters

Difficulties in Kanji (Chinese character) recognition stem from its large character set (about 5000 characters) and the large number of strokes (up to about sixty) in each character.

The paper describes a preliminary approach to this Kanji recognition problem. In the present method, a handprinted Kanji character is coded into a symbol string using the binary relation between stroke and reference zone. Two symbol string recognition methods are proposed and investigated; the direct matching recognition (DMR) method and the unit structure recognition (USR) method.

The DMR method worked efficiently for characters which have up to five strokes. The USR method represents Kanji characters with a structural unit combination. This method worked efficiently for multi-stroke characters and greatly reduced dictionary update labor.     

Processing of Novel Strontium Titanate-Based Thin-Film Varistors by Chemical Solution Deposition

Strontium titanate (SrTiO₃)-based multilayered film with varistor characteristics has successfully been fabricated by a chemical solution deposition (CSD) method. Homogeneous precursor solutions of SrTiO₃ and Nb:SrTiO₃ with long-term stability could be prepared by optimizing the reaction conditions among strontium ethoxide, titanium isopropoxide, and niobium ethoxide. Films were prepared using the precursor solutions on fused silica substrates at 700°C. Triple layered films with SrTiO₃/Nb:SrTiO₃/SrTiO₃ structure were also successfully crystallized on Pt/Ti/SiO₂/Si substrates at 700°C. The current–voltage ( I - V ) curve of the multilayered film was characteristic to varistors and the nonlinear coefficient α of the synthesized film was ∼3.0. The varistor voltages ( E _0.01) of 0.6-μm-thick film were 140 kV/cm for the forward direction and −120 kV/cm for the reverse direction, respectively, at room temperature.     

Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm⁻² of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 °C under a pressurized condition of 0.35 MPa.     

An Assay Method for Determining the Total Lipid Content of Fish Meat Using a 2-Thiobarbituric Acid Reaction

A method for the determination of the total lipid content in fish meat was established using a 2-thiobarbituric acid (TBA) reaction, which had previously been used for the determination of lipid peroxides in animal tissues. In this method, an unspecific peroxidation of fish oils was created by omitting the addition of antioxidant to the reaction mixture during the TBA reaction, because fish meat is more sensitive to the TBA reaction due to its higher concentration of polyunsaturated fatty acids, especially docosahexaenoic acid and eicosapentaenoic acid, which can easily react artificially with TBA in the absence of an antioxidant in the assay system. As for a practical application of this method, we tried to optimize the assay procedures in the sampling, reaction, and detection steps of this method, and finally proposed a new standard procedure recommended for determining the total lipid content of fish using a TBA reaction. In order to confirm the accuracy of the new procedure, comparative evaluations for the lipid contents of commercially available fish, i.e., chub mackerel (Scomber japonicus) and saury (Cololabis saira) were made between the conventional procedure and the recommended TBA method. The lipid contents obtained by the two methods coincided well with high correlation. This method is relevant for total lipid content analysis of fish meat under restricted laboratory conditions.     

Molecular Hydrogen as a Novel Protective Agent against Pre-Symptomatic Diseases

Mibyou, or pre-symptomatic diseases, refers to state of health in which a disease is slowly developing within the body yet the symptoms are not apparent. Common examples of mibyou in modern medicine include inflammatory diseases that are caused by chronic inflammation. It is known that chronic inflammation is triggered by the uncontrolled release of proinflammatory cytokines by neutrophils and macrophages in the innate immune system. In a recent study, it was shown that molecular hydrogen (H₂) has the ability to treat chronic inflammation by eliminating hydroxyl radicals (·OH), a mitochondrial reactive oxygen species (ROS). In doing so, H₂ suppresses oxidative stress, which is implicated in several mechanisms at the root of chronic inflammation, including the activation of NLRP3 inflammasomes. This review explains these mechanisms by which H₂ can suppress chronic inflammation and studies its applications as a protective agent against different inflammatory diseases in their pre-symptomatic state. While mibyou cannot be detected nor treated by modern medicine, H₂ is able to suppress the pathogenesis of pre-symptomatic diseases, and thus exhibits prospects as a novel protective agent.     

Synthesis of Silicon Carbide Ceramics Using Chemically Modified Polycarbosilanes as a Compaction Binder

A chemically modified polycarbosilane (PC) containing organofluoric groups (PCOCF) has been synthesized from PC and fluoroalkylmethyldimethoxysilane. PCOCF acts as an efficient compaction binder for SiC powders and as a coating material with excellent oxidation resistance in wet air. PCOCF-coated SiC powders also show excellent packing properties because of the organofluoric side chains, which give highly dense green compacts. PCOCF provides a high ceramic yield of 75% and highly dense SiC ceramics. Four-point bending strength increases and the scatter in strength values decreases significantly by PCOCF coating.     

Transient shift of local oxygen potential in nonstoichiometric oxides upon application of mechanical stress

Effect of mechanical stress on defect equilibrium was studied with an oxygen nonstoichiometric compound, La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ . In general, formation of oxygen vacancy in an oxide causes lattice expansion, which leads to stabilization of oxygen vacancy in the material under a tensile stress, and vice versa. Oxygen vacancy concentration is thus expected to increase under a tensile stress and decrease under a compressive stress. However, the change in defect concentration would not proceed spontaneously so that the material just after the application of stress would stay out of equilibrium. On this assumption, attempts were made to detect the shift of oxygen potential under stress using a potentiometric method. A ball-shaped yttria stabilized zirconia (YSZ) of 9.5 mm in diameter was utilized as an oxygen potential sensor as well as a pushing rod which was pressed onto the sample surface. In the measurements at 873 K to 1073 K, a clear shift of emf to the negative direction was observed depending on the magnitude of load and loading speed. It was followed by a relaxation to the initial value under the stress. On unloading operation, the shift of emf to the positive direction was observed. Those behaviors were well explained by the assumption that the oxygen vacancy concentration varies under mechanical stress.     

Thin anodic oxides on n-InP studied by photocurrent transients and surface analysis

Surface reactions induced by fluorocarbon plasmas were studied on Si substrates with SiO₂ and photo-resist overlayers using an inductively coupled plasma source. As source gases, C₄F₈ and C₅F₈ were employed to investigate their differences in the etching performance and the selectivity between SiO₂ and photo-resist. Deposition of fluorocarbon polymer was noticed in both gases by Fourier-transform infrared ellipsometric measurements when substrate bias was not applied. With the bias application, etching started on both substrate from certain threshold values of the bias voltage and the rate increased with increase of the voltage. However, in C₅F₈ plasma the increasing tendency on photo-resist was much less than on SiO₂, while in C₄F₈ plasma the difference is small. This difference is attributed to a larger deposition ability of C₅F₈ plasma with higher content of fluorine atoms in the polymer than that of C₄F₈ plasma as confirmed by X-ray photoelectron spectroscopy.     

Transient phenomena in a PEMFC during the start-up of gas feeding observed with a 97-fold segmented cell

To measure local phenomena in a PEMFC during a transitional state induced by changing of the feeding gas, a segmented cell was fabricated and the local current and local potential distribution were measured under open-circuit conditions. The anode or cathode was divided into 97 segments of 1.5 mm each. A change in the anode gas from nitrogen or oxygen to hydrogen induced momentary internal currents among the segments. The potential distribution in the electrolyte was observed simultaneously using three quasi-reference electrodes located locally. The results supported the reverse-current decay mechanism, which is known to be a mechanism of cathode degradation. Furthermore, internal currents were observed when the cathode gas was changed from nitrogen to oxygen. While the cathode was not subjected to a harmful potential, a large potential distribution was induced in the anode.