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Search Results: 1 - 10 of 2537 matches for " Yoshitomo Saito "
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Profile Generation Methods for Reinforcing Robustness of Keystroke Authentication in Free Text Typing  [PDF]
Yoshitomo Matsubara, Toshiharu Samura, Haruhiko Nishimura
Journal of Information Security (JIS) , 2015, DOI: 10.4236/jis.2015.62014
Abstract: We have investigated several characteristics of the keystroke authentication in Japanese free text typing, and our methods have provided high recognition accuracy for high typing skill users who can type 700 or more letters per 5 minutes. There are, however, some situations decreasing the accuracy such as long period passage after registering each user’s profile documents and existence of lower typing skill users who can type only about 500 - 600 letters per 5 minutes. In this paper, we propose new profile generation methods, profile-updating and profile-combining methods, to reinforce the robustness of keystroke authentication and show the effectiveness of them through three examinations with experimental data.
Keyboard Dependency of Personal Identification Performance by Keystroke Dynamics in Free Text Typing  [PDF]
Yoshitomo Matsubara, Toshiharu Samura, Haruhiko Nishimura
Journal of Information Security (JIS) , 2015, DOI: 10.4236/jis.2015.63023
Abstract: We have proposed some methods for feature extraction and identification that enable identification of individuals through long-text input as an important topic in keystroke dynamics research. As to the robustness in practical circumstances, there exists a question on the keystroke dynamics how much the recognition accuracy is influenced by the change of keyboard. By comparing the performance in the cases of using the same keyboard and different keyboards, the dependencies on keyboards are evaluated through three implemented experiments for subjects. As a result, it is found that we do not need to worry about the keyboard difference for users whose typing skills reach high level with about 900 or more letters in 5 minutes, and only for the remaining users it would be necessary to register their profile data with respect to each keyboard they use in order to avoid recognition accuracy degradation.
Rationality and Stability of Equilibrium in a Search-Theoretic Model of Money  [PDF]
Tetsuya Saito
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23052
Abstract: In this short note, I examine the rationality of money-search equilibrium in a basic second-generation money search model, which is a perfectly divisible goods and indivisible money model. I then show that only an inflationary economy can generate a socially and individually rational stable equilibrium. On the basis of this finding, I demonstrate that there is no loss of generality in an analysis that assumes dictatorial buyers in an inflationary economy, since the properties of a dictatorial buyers model are identical to those of a general inflationary economy model. The result of this paper is especially useful for empirical applications since we are generally incapable of finding data showing bargaining power. This result also alerts us against employing the second-generation model to analyze a deflationary economy and commodity money.
Magnetic vortex crystals in frustrated Mott insulator
Yoshitomo Kamiya,Cristian D. Batista
Physics , 2013, DOI: 10.1103/PhysRevX.4.011023
Abstract: Quantum fluctuations become particularly relevant in highly frustrated quantum magnets and can lead to new states of matter. We provide a simple and robust scenario for inducing magnetic vortex crystals in frustrated Mott insulators. By considering a quantum paramagnet that has a gapped spectrum with six-fold degenerate low energy modes, we study the magnetic field induced condensation of these modes. We use a dilute gas approximation to demonstrate that a plethora of multi-$\mathbf{Q}$ condensates are stabilized for different combinations of exchange interactions. This rich quantum phase diagram includes magnetic vortex crystals, which are further stabilized by symmetric exchange anisotropies. Because magnetic skyrmion and domain wall crystals have already been predicted and experimentally observed, this novel vortex phase completes the picture of emergent crystals of topologically nontrivial spin configurations.
A Statistical Method for Selecting Pattern Descriptors of Textured 3D Models
Motofumi T. Suzuki,Yoshitomo Yaginuma,Haruo Kodama
Lecture Notes in Engineering and Computer Science , 2010,
DPP-4 Inhibition Ameliorates Pancreatic β-Cell Failure and Improves Glucose Tolerance in the Mouse Model of Wolfram Syndrome  [PDF]
Yasuhiro Tanji, Suguru Yamaguchi, Yasushi Ishigaki, Hideki Katagiri, Yoshitomo Oka, Hisamitsu Ishihara
Journal of Diabetes Mellitus (JDM) , 2015, DOI: 10.4236/jdm.2015.52009
Abstract: Wolfram syndrome, an autosomal recessive disorder associated with diabetes and optic atrophy, is caused by mutations in the WFS1 gene encoding wolframin, an endoplasmic reticulum membrane protein. Recent development of incretin-based drugs demonstrates promising outcomes for treatment of diabetes mellitus. The aim of this study is to evaluate whether dipeptidyl peptidase-4 inhibition is effective for treating endoplasmic reticulum stress-mediated β-dell failure and impaired glucose tolerance in WFS1-deficient mice (Wfs1/). Wfs1/ mice were orally administrated with vildagliptin (50 mg/kg), a dipeptidyl peptidase-4 inhibitor, twice a day for 4 weeks. The pancreases of these mice were subjected to morphological and biochemical analyses and their glucose tolerance was studied. Electron microscopic studies revealed that vildagliptin reduced number of β-cell containing swollen endoplasmic reticulum in Wfs1/mice. Vildagliptin treatment increased pancreatic insulin content by 30% in Wfs1/ mice. Oral and intraperitoneal glucose tolerance tests showed improved glucose tolerance in vildagliptin-treated Wfs1/ mice with increased glucose responsiveness of insulin secretion as compared with vehicle-treated mutant mice. These effects by dipeptidyl peptidase-4 inhibition were partly prevented by glucagon-like peptide-1 receptor blockade. These findings provide evidence that activation of the incretin system by dipeptidyl peptidase-4 inhibition plays a protective role against β-cell failure in wolframin-deficiency. Our data suggest that diabetes in patients affected with Wolfram syndrome could be treated by incretin-based drugs. Furthermore, since WFS1 dysfunction could be involved in common forms of type 2 diabetes mellitus, our results strengthen the mechanistic rational of using this drug for the disease.
The Accuracy of Initial Bone Cutting in Total Knee Arthroplasty  [PDF]
Takaaki Ohmori, Toru Maeda, Tamon Kabata, Yoshitomo Kajino, Shintaro Iwai, Hiroyuki Tsuchiya
Open Journal of Orthopedics (OJO) , 2015, DOI: 10.4236/ojo.2015.510040
Abstract: Background: The aim of this study was to evaluate the accuracy of initial bone cutting of the distal femur and the proximal tibia in TKA using an image-free navigation system. Methods: From February 2006 to March 2013, we evaluated 60 knees in 50 patients using an image-free navigation system (Navigation: Stryker Navigation Cart System; Software: Stryker Knee Navigation; Ver2.0: Stryker Orthopaedics US NJ Mahwah). First, we measured the angle shown by the navigation system before cutting, at the time we set the jig. Second, we measured the angles shown by navigation after the bone was cut using the jig. Then, we compared these two angles for each patient to determine the bone cutting error. Results: In the distal femur, 37 of 60 knees were cut in an extended position in the sagittal plane, and 26 of 60 knees were cut in a varus in the coronal plane. In the proximal tibia, 29 of 60 knees were cut with decreased posterior slope in the sagittal plane, and 26 of 60 knees were cut in a valgus. Conclusions: In this study, the distal femur tended to be cut in an extended and a varus position and the proximal tibia did with decreased posterior slope and in a valgus position after initial bone cutting. It is necessary to note the initial cutting error in TKA. Since cutting errors affect postoperative outcome, we should cut bones several times. And as the reasons of the cause of the error, we propose new reason that cutting bone is not parallel with accuracy to AP axis.
Finite-Temperature Transition in the Spin-Dimer Antiferromagnet BaCuSi2O6
Yoshitomo Kamiya,Naoki Kawashima,Cristian D. Batista
Physics , 2010, DOI: 10.1143/JPSJ.78.094008
Abstract: We consider a classical XY-like Hamiltonian on a body-centered tetragonal lattice, focusing on the role of interlayer frustration. A three-dimensional (3D) ordered phase is realized via thermal fluctuations, breaking the mirror-image reflection symmetry in addition to the XY symmetry. A heuristic field-theoretical model of the transition has a decoupled fixed point in the 3D XY universality, and our Monte Carlo simulation suggests that there is such a temperature region where long-wavelength fluctuations can be described by this fixed point. However, it is shown using scaling arguments that the decoupled fixed point is unstable against a fluctuation-induced biquadratic interaction, indicating that a crossover to nontrivial critical phenomena with different exponents appears as one approaches the critical point beyond the transient temperature region. This new scenario clearly contradicts the previous notion of the 3D XY universality.
Crossover Behavior from Decoupled Criticality
Yoshitomo Kamiya,Naoki Kawashima,C. D. Batista
Physics , 2010, DOI: 10.1103/PhysRevB.82.054426
Abstract: We study the thermodynamic phase transition of a spin Hamiltonian comprising two 3D magnetic sublattices. Each sublattice contains XY spins coupled by the usual bilinear exchange, while spins in different sublattices only interact via biquadratic exchange. This Hamiltonian is an effective model for XY magnets on certain frustrated lattices such as body centered tetragonal. By performing a cluster Monte Carlo simulation, we investigate the crossover from the 3D-XY fixed point (decoupled sublattices) and find a systematic flow toward a first-order transition without a separatrix or a new fixed point. This strongly suggests that the correct asymptotic behavior is a first-order transition.
XMM-Newton and Suzaku Spectroscopic Studies of Unidentified X-ray Sources towards the Galactic Bulge: 1RXS J180556.1$-$343818 and 1RXS J173905.2$-$392615
Hideyuki Mori,Yoshitomo Maeda,Yoshihiro Ueda
Physics , 2015,
Abstract: With the XMM-Newton and Suzaku observations, for the first time, we acquired broad-band spectra of two unidentified X-ray sources towards the Galactic bulge: 1RXS J180556.1$-$343818 and 1RXS J173905.2$-$392615. The 1RXS J180556.1$-$343818 spectrum in the $0.3$-$7$ keV band was explained by X-ray emission originated from an optically-thin thermal plasma with temperatures of $0.5$ and $1.7$ keV. The estimated absorption column density of $N_{\rm H} \sim 4 \times 10^{20}$ cm$^{-2}$ was significantly smaller than the Galactic HI column density towards the source. A candidate of its optical counterpart, HD 321269, was found within $4''$. In terms of the X-ray properties and the positional coincidence, it is quite conceivable that 1RXS J180556.1$-$343818 is an active G giant. We also found a dim X-ray source that was positionally consistent with 1RXS J173905.2$-$392615. Assuming that the X-ray spectrum can be reproduced with an absorbed optically-thin thermal plasma model with $kT = 1.6$ keV, the X-ray flux in the $0.5$-$8$ keV band was $8.7 \times 10^{-14}$ erg s$^{-1}$ cm$^{-2}$, fainter by a factor of $\sim 7$ than that of 1RXS J173905.2$-$392615 during the ROSAT observation. The follow-up observations we conducted revealed that these two sources would belong to the Galactic disk, rather than the Galactic bulge.
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