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Kim B.-H.,Chonnam National University | Yang K.S.,Chonnam National University | Kim Y.A.,Shinshu University | Kim Y.J.,Korea Advanced Institute of Science and Technology | And 2 more authors.
Journal of Power Sources | Year: 2011

A simple and scalable method is reported for fabricating a porosity-controlled carbon nanofibers with a skin-core texture by electrospinning a selected blend of polymer solutions. Simple thermal treatment of the electrospun nanofibers from solution blends of various compositions creates suitable ultramicropores on the surface of carbon nanofibers that can accommodate many ions, removing the need for an activation step. The intrinsic properties of the electrode (e.g., nanometre-size diameter, high specific surface area, narrow pore size distribution, tuneable porosity, shallow pore depth, and good ionic accessibility) enable construction of supercapacitors with large specific capacitance (130.7 F g-1), high power (100 kW kg -1), and energy density (15.0 Wh kg-1). © 2011 Elsevier B.V. All rights reserved.

Kim B.-H.,Chonnam National University | Yang K.S.,Chonnam National University | Woo H.-G.,Chonnam National University | Oshida K.,Nagano National College of Technology
Synthetic Metals | Year: 2011

Porous carbon nanofiber composites (NFCs) were prepared by electrospinning blended solutions of polyacrylonitrile (PAN) and polymethylhydrosiloxane (PMHS) in N,N-dimethylformamide (DMF). A PMHS concentration of 5 wt% was regarded as the optimum concentration to obtain fibers of a uniform size with a homogeneous dispersion of silica, the maximum specific surface area and the highest conductivity (4.91 S cm-1) after heat treatment at 800 °C. The supercapacitor electrode prepared with 5 wt% PMHS had the highest specific capacitance, 126.86 F/g, and the highest energy density, 17.0-10.0 Wh/kg, in the range of 400-20,000 W/kg in a 6 M KOH aqueous solution. © 2011 Elsevier B.V. All rights reserved.

Kobayashi S.,Nagano National College of Technology | Takato S.,Toho University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

In Japan, some wooden plaques presenting geometrical puzzles (SANGAKU) show problems of drawing smaller circles within a larger circle in contact with it or a circle in contact with a quadratic curve, such as an oval. Problems of these kinds can be interesting teaching materials. Dynamic geometry software such Cinderella or GeoGebra is useful to solve these problems. One can use high-quality TeX graphics with KeTCindy (Cinderella plug-in) to draw these figures. One can also draw figures by solving simultaneous equations using a computer algebra system such as Maxima or Risa/Asir. Although simultaneous equations can be solved in Maxima, the solution takes time. Alternatively, it does not work when too many variables are included. In such cases, one can convert it to a system of equations that are easier to solve using a Grobner base in Risa/Asir. Then a user can solve them by giving the result to Maxima. A user can accomplish this on Cinderella through KeTCindy, and can draw circles using the result. This method can also be applied to other difficult circumstances. This paper presents some examples. © Springer International Publishing Switzerland 2016.

Han F.,Dalian University of Technology | Li W.-C.,Dalian University of Technology | Lei C.,Dalian University of Technology | He B.,Dalian University of Technology | And 2 more authors.
Small | Year: 2014

Mesoporous and amorphous ZnSnO3 nanocubes of ∼37 nm size coated with a thin porous carbon layer have been prepared using monodisperse ZnSn(OH)6 as the active precursor and low-temperature synthesized polydopamine as the carbon precursor. The small single nanocubes cross-link with each other to form a continuous conductive framework and interconnected porous channels with macropores of 74 nm width. Because of its multi-featured nanostructure, this material exhibits greatly enhanced integration of reversible alloying/de-alloying (i.e., transformation of Li4.4Sn and LiZn to Sn and Zn) and conversion (i.e., oxidation of Sn and Zn to ZnSnO3) reaction processes with an extremely high capacity of 1060 mA h g-1 for up to 100 cycles. A high reversible capacity of 650 and 380 mA h g -1 can also be delivered at rates of 2 and 3 A g-1, respectively. This excellent electrochemical performance is attributed to the small particle size, well-developed mesoporosity, the amorphous nature of the ZnSnO3 and the continuous conductive framework produced by the interconnected carbon layers. Carbon-coated amorphous ZnSnO3 nanocubes with well-developed mesoporosity are synthesized and the core-shell particles are linked into an interconnected conductive framework. This ZnSnO3-based anode exhibits an outstanding lithium storage performance, especially a high reversible capacity of 1060 mA h g-1 because of the integration of alloying and conversion reaction processes (reversible transformation of Li4.4Sn and LiZn alloys to pristine ZnSnO3). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hachisuga A.,Shinshu University | Yoshioka M.,Shinshu University | Ohta K.,Shinshu University | Itaya T.,Nagano National College of Technology
Journal of Materials Chemistry C | Year: 2013

In our previous work, we synthesized a series of phthalocyanine-based flying-seed-like compounds, (nPh-PhO)4PcCu (n = 3, 2, 1 and 0 in nPh-PhO: a-d), and revealed that each of them shows a columnar liquid crystalline phase (Colho or Colrho) from rt to an extremely high temperature near 500 °C. Thus, we could obtain columnar liquid crystalline phases for discotic compounds by using bulky substituents (a-d) instead of long alkyl chains. In order to further study the utility of these bulky substituents (a-d) on the induction of mesomorphism for other shaped molecules, we have synthesized novel flying-seed-like calamitic phenoxybenzoic acid derivatives, nPh-PhOBA (3a-d), and their Mitsubishi-Mark-shaped terbium complexes, (nPh-PhOBA)3Tb·mMeOH (4a-d), in this work. Very interestingly, the mesomorphism of the phenoxybenzoic aids derivatives nPh-PhOBA (n = 0-3) was induced to show a mesophase (Mx) only by the bulky substituent d (n = 0), whereas the mesomorphism of their corresponding terbium complexes (nPh-PhOBA)3Tb(III) (n = 0-3) was induced to show rectangular columnar (Colr) mesophases by the bulky substituents c and d (n = 1, 0). On the other hand, the mesomorphism of the PcCu complexes (nPh-PhOBA)4PcCu (n = 0-3) in our previous work was induced by all the bulky substituents a, b, c and d (n = 0-3). Thus, it becomes apparent that both calamitic and columnar mesomorphism can be induced by the substitution of bulky groups instead of long alkyl chains, and that the balance of the core size and the bulkiness of the substituents is very important to obtain mesomorphism in flying-seed-like compounds. We believe that this is a new guideline for the induction of mesomorphism by using bulky groups instead of long alkyl chains. © 2013 The Royal Society of Chemistry.

Nishimura O.,Nagano National College of Technology
Astrophysical Journal | Year: 2015

I examine the characteristics of profiles of cyclotron lines formed by the superposition of a number of lines formed at a number of altitudes in line-forming regions illuminated by anisotropic injections in an accretion column, which formed around the polar cap of Roche-lobe-type accretion-powered X-ray pulsars. In the present paper, I consider the line-forming region near the walls of a cylindrical geometry illuminated from the inside of the cylinder. I also examine how the direction of the peak of a beam pattern affects the profiles of cyclotron lines. I found that the width and depth of the line in a phase-averaged spectrum provide information concerning the direction of a beam. I demonstrate that the cyclotron line has a pure absorption in the phase-averaged spectrum regardless of the height of the cylinder, which is expected to change with luminosity. On the other hand, in phase-resolved spectra, an emission-like feature can be formed in the phase with lower intensity in a short cylinder, which is expected at L ∼ 1036 erg s?1, while a pure absorption feature tends to appear in all phases due to the superposition of a large number of lines in a tall cylinder, which is expected at L ≳ 1037 erg s?1. © 2015. The American Astronomical Society. All rights reserved.

Nishimura O.,Nagano National College of Technology
Astrophysical Journal | Year: 2014

I develop a new model for changes of cyclotron line energy with luminosity based on changes in polar cap dimensions and the direction of photon propagation as well as a shock height. In X0115+63 and V0332+53, the fundamental cyclotron line energy has been observed to decrease with increasing luminosity. This phenomenon has been interpreted as a change of a shock height with luminosity. However, the rates of the observed changes are quite different, in which the line energy in V0332+53 varies slowly with luminosity compared with that in X0115+63. I demonstrate that a new model successfully reproduces the changes of the fundamental cyclotron line energies with luminosity in both X0115+63 and V0332+53. On the other hand, the cyclotron line energies in Her X-1, GX301-2, and GX304-1 were reported to increase with increasing luminosity. I discuss the positive correlation between the cyclotron line energy and luminosity based on changes in a beam pattern for Her X-1, GX301-2, and GX304-1. In addition, I discuss how a switch of the predominant, observed emission region from pole1 to pole2 influences cyclotron line energy for GX304-1 and A0535+26. © 2014. The American Astronomical Society. All rights reserved.

Nishimura O.,Nagano National College of Technology
Astrophysical Journal | Year: 2011

I model cyclotron lines by calculating a superposition of a large number of cyclotron line spectra emerging from different heights of a line-forming region of a non-uniform density and temperature of an electron-proton plasma threaded by a dipole magnetic field. In this paper, I mainly discuss the properties of the cyclotron lines in accreting X-ray pulsars with long spin periods (100-800s). My simplified model succeeds in reproducing asymmetric line profiles, anharmonic ratios of line energy, relationship between the width and the depth of the line, and correlation between cyclotron line energy and X-ray intensity in the main pulse. In addition, I demonstrate that a shallower and broader fundamental (= first harmonic) line and a deeper second harmonic line as observed in accreting X-ray pulsars such as Vela X-1 and A0535+26 can be produced via a superposition of a large number of cyclotron lines formed at numerous different heights in a line-forming region with a dipole magnetic field. In this case, the ratio of the peak energy of the second harmonic absorption line to the fundamental can be larger than harmonic ratio 2. Furthermore, the width of the fundamental line is comparable to or larger than that of the second harmonic. These characteristics of the cyclotron lines are consistent with those observed in Vela X-1 and A0535+26. © 2011. The American Astronomical Society. All rights reserved.

Nishimura O.,Nagano National College of Technology
Publications of the Astronomical Society of Japan | Year: 2013

Cyclotron lines have been modeled by calculating a superposition of a large number of cyclotron line spectra of photons emerging from different heights of line-forming regions illuminated from above (increasing B-field), in addition to ones illuminated from below (decreasing B-field), as considered in Paper I (Nishimura 2011, ApJ, 730, 106). This simplified model succeeds to reproduce anharmonic ratios of cyclotron line energies (less than harmonic values), correlations between cyclotron line energies and X-ray intensities observed at different pulse phases, using a line-forming region with increasing B-field for the main pulses of Her X-1, Cen X-3, and GX301-2. It is also able to reproduce the characteristics of the cyclotron lines in several parts of the secondary pulse of Vela X-1, A0535+26, whereas in several parts of both the main and secondary pulses of X0115+63. In addition, in the phase-resolved spectra of X0115+63, the observed ratios of the centroid energy of the second-harmonic line to the fundamental change from ̃1.6 to ̃2.2 with the pulse phase. A combination of the increasing and decreasing B-field is able to explain this behavior in terms of the idea that a magnetic-field configuration in a line-forming region can switch from decreasing to increasing B-field, and vice versa, as a result of a switch of the primary observed pole, from which the flux mainly comes, with the rotation of the neutron star. © 2013. Astronomical Society of Japan.

Yamazaki Y.,Nagano National College of Technology
Journal of Robotics and Mechatronics | Year: 2014

In the 1980s, when the author worked for Seiko Epson Corporation as a wristwatch production engineer, consumer needs had become so diversified that wrist-watches had to be assembled on the same automated assembly line in small lots of about 10,000 pieces per month. Most of the robots available in those days were for processing purposes such as spot welding and were not applicable in practical terms to automated assembly lines for wristwatches in precision, speed, ease of use or cost. The prototype SCARA robot developed by the SCARA Study Group led by Dr. Hiroshi Makino, a professor at the Department of Precision Engineering at Yamanashi University, was found to be the most suitable for automated watch assembly lines. We reviewed assembly work procedures and succeeded in limiting the number of simultaneous control axes to four at a maximum and in cutting assembly costs to 60% of those of conventional processing robots. As the term "selective compliance" suggests, SCARA robots possess all of the functions necessary for stable assembly and for precision and speed. Development team members, including the author, made the most use of previous experience in developing dedicated automated assembly machines for in-house use and succeeded in developing practical SCARA robots by creating a robot language based on workers' voice. In applications of SCARA robots, this paper introduces just two of many possible examples. One is for oiling work on manual assembly lines and the other is the TAF-M mixed-models wristwatch assembly line. In the oiling work application example, SCARA robots used for infinitesimal oiling work on a manual assembly line for small lots of luxury wristwatches have been found to be very cost-effective and useful for training operators and/or programmers for robots. The TAF-M application example represents the assembly line built based on the original Seiko-Epson purpose for introducing SCARA robot development, which consists of both robots and of 52 newly developed "assembly robot cells" where most assembly work should be done. An assembly robot cell includes a SCARA robot, a main conveyor, a multiple-parts feeder, an automatic hand changer, an assembly detection unit, etc. At present, one such assembly line automatically assembles more than 100 models of wristwatches. Use of such automated assembly lines has reduced the hu-man workforce by about 40 workers, cut costs by over 60%, and shortened delivery time by about 50%.

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