Nazirul Afham Idris, Katsumi Yoshizawa, Yasunori Tomomatsu, Makoto Sudo, Tadashi Hajikano, Ryogo Kubo, Georgios Zervas, Hiroyuki Tsuda,
We propose an ultra-broadband full-mesh wavelength router supporting the T- and O-bands using 3 stages of cascaded arrayed waveguide gratings (AWGs). The router architecture is based on a combination of waveband and channel routing by coarse and fine AWGs, respectively. We fabricated several T-band-specific silica-based AWGs and quantum dot semiconductor optical ampliers as part of the router, and demonstrated 10 Gbps data transmission for several wavelengths throughout a range of 7.4 THz. The power ...
Tópico(s): Semiconductor Lasers and Optical Devices
2016 - Optica Publishing Group | Optics Express
Ryogo Kubo, Jun‐ichi Kani, Yukihiro Fujimoto, Naoto Yoshimoto, Kiyomi Kumozaki,
This paper proposes a power saving mechanism with variable sleep period to reduce the power consumed by optical network units (ONUs) in passive optical network (PON) systems. In the PON systems based on time division multiplexing (TDM), sleep and periodic wake-up (SPW) control is an effective ONU power saving technique. However, the effectiveness of SPW control is fully realized only if the sleep period changes in accordance with the traffic conditions. This paper proposes an SPW control mechanism with ...
Tópico(s): Optical Network Technologies
2010 - Institute of Electronics, Information and Communication Engineers | IEICE Transactions on Communications
Ryogo Kubo, Jun‐ichi Kani, Hirotaka Ujikawa, Takeshi Sakamoto, Yukihiro Fujimoto, Naoto Yoshimoto, Hisaya Hadama,
This paper describes sleep and adaptive link rate (ALR) control functions to reduce the power consumption of optical network units (ONUs) in 10 Gb∕s Ethernet passive optical network (10G-EPON) systems. A hybrid mechanism that includes both sleep and ALR control functions is proposed with a view to further improving the power-saving performance. The sleep control function switches the ONU mode, i.e., active or sleep, depending on the presence or absence of traffic. The ALR control function switches ...
Tópico(s): Optical Network Technologies
2010 - | Journal of Optical Communications and Networking
Ryogo Kubo, Tomoyuki Shimono, Kouhei Ohnishi,
This paper describes a novel bilateral grasping control system including master-slave robots with different degree of freedom. The master and slave controllers are designed based on a multilateral control scheme. Decoupling design of force and position controllers is realized by mode transformation using the discrete Fourier transform matrices and a disturbance observer. In the proposed system, a human operator manipulates two master robots, and three slave robots grasp an object cooperatively. ...
Tópico(s): Geophysics and Sensor Technology
2008 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Industrial Electronics
This paper presents a method to determine contact conditions between a planar end-effector and the environment, i.e., face-to-face, face-to-line, or face-to-point contact. First of all, two kinds of contact motion of a planar end-effector, i.e., passive and active contact motions, are described. A compliance controller is implemented to achieve the passive contact motion, and the ldquogroping motionrdquo is generated as the active contact motion. Then, novel robot-friendly expressions of the environment ...
Tópico(s): Hand Gesture Recognition Systems
2008 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Industrial Electronics
Ryogo Kubo, Noriko Iiyama, Kenji Natori, Kouhei Ohnishi, Hirotaka Furukawa,
Bilateral control is one of the control methods of teleoperation systems. Human operators can feel reaction force from remote environment by means of this control scheme. This paper presents a novel control architecture for bilateral teleoperation with/without time delay. The proposed bilateral control system has three communication channels between master and slave robots. In concrete terms, this system has two transmission channels of position and force information from the master side to the ...
Tópico(s): Robot Manipulation and Learning
2007 - Institute of Electrical Engineers of Japan | IEEJ Transactions on Industry Applications
Ryosuke Hotchi, Hosho Chibana, Takanori Iwai, Ryogo Kubo,
Active queue management (AQM) is a technique to avoid serious congestion of the transmission control protocol (TCP) flows at a router. AQM based on control theory, which utilizes congestion controllers such as proportional-derivative (PD) controller or proportional-integral-derivative (PID) controller, has been previously proposed. In addition, disturbance observer (DOB) has been utilized to compensate for modeling error of a TCP/AQM congestion control system. However, the DOB-based controllers cannot ...
Tópico(s): Advanced Queuing Theory Analysis
2020 - Institute of Electrical and Electronics Engineers | IEEE Access
Naoki Motoi, Tomoyuki Shimono, Ryogo Kubo, Atsuo Kawamura,
This paper proposes a task realization method by using a force-based variable compliance controller for flexible motion control systems. In recent years, the robots working in human life space are desirable. Considering the robots working in human life space, they should achieve the safety motion. From this viewpoint, one of the key technologies is flexible motion control system. Of course, task realization instead of human beings is important. Therefore, it is necessary to propose the realization ...
Tópico(s): Soft Robotics and Applications
2013 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Industrial Electronics
Katsutoshi Tsukamoto, Tatsuya Nishiumi, Takuya Yamagami, Takeshi Higashino, Shozo Komaki, Ryogo Kubo, Tomohiro Taniguchi, Jun‐ichi Kani, Naoto Yoshimoto, Hideaki Kimura, K. Iwatsuki,
This paper proposes a novel network architecture for Giga-bit throughput in broad- band ubiquitous networks. A convergence of WDM access and RoF ubiquitous antenna archi- tecture can realize universality of remote base stations for various types of air interfaces and the scalabilities of WDM technologies are expected to improve the throughput in wireless service area covered by RoF-MIMO antenna. We discusse distribution of MIMO antenna, method of RoF MIMO signals over WDM PON, and conflgurations ...
Tópico(s): Optical Network Technologies
2010 - | PIERS Online
Ryogo Kubo, Atsushi Kato, Toshiaki Tsuji, Kouhei Ohnishi,
In this paper, we present a control scheme of grasping and manipulation using mode transformation and a four-channel grasping/manipulating controller based on the control scheme. A second-order discrete Fourier transform (DFT) matrix is utilized as a mode transformation matrix. By means of the control scheme, a grasping controller and a manipulating controller can be designed independently in a grasping mode and a manipulating mode, respectively. In addition, we also propose a novel control method ...
Tópico(s): Soft Robotics and Applications
2007 - Institute of Electrical Engineers of Japan | IEEJ Transactions on Industry Applications
Morikazu Toda, Ryogo Kubo, Nobuhiko Saitô,
Tópico(s): Advanced Thermodynamics and Statistical Mechanics
1992 - Springer Nature | Springer series in solid-state sciences
Ryogo Kubo, Morikazu Toda, Natsuki Hashitsume,
Statistical Physics II introduces nonequilibrium theories of statistical mechanics from the viewpoint of the fluctuation-disipation theorem. Emphasis is placed on the relaxation from nonequilibrium to
Tópico(s): Statistical Mechanics and Entropy
1991 - Springer Nature | Springer series in solid-state sciences
Nobuyuki Takahashi, Yoshiro Hanyu, Toshimitsu Musha, Ryogo Kubo, Gen Matsumoto,
Tópico(s): Plant and Biological Electrophysiology Studies
1990 - Elsevier BV | Physica D Nonlinear Phenomena
Yoshitaka Tanimura, Ryogo Kubo,
A test system is assumed to interact with a heat bath consisting of harmonic oscillators or an equivalent bath with a proper frequency spectrum producing a Gaussian-Markoffian random perturbation. The effect of reaction of the test system to the bath is considered in the high temperature approximation. Elimination of the bath using the influence functional method of Feynman and Vernon yields a continuous fraction expression for the reduced density matrix of the test system. The result affords a ...
Tópico(s): stochastic dynamics and bifurcation
1989 - Physical Society of Japan | Journal of the Physical Society of Japan
Yoshitaka Tanimura, Tetsuhiro Suzuki, Ryogo Kubo,
A general formulation is given for the second order optical process of a three-level system in contact with a heat bath consisting of harmonic oscillators with a proper frequency spectrum producing a Markoffian random perturbation. Elimination of the bath using the influence functional method of Feynman and Vernon yields a continuous fraction expression and the result affords a basis to clarify the relation between the stochastic and dynamical approaches to treat the partial destruction of the quantum ...
Tópico(s): Quantum Information and Cryptography
1989 - Physical Society of Japan | Journal of the Physical Society of Japan
Yoshitaka Tanimura, Ryogo Kubo,
Two-time correlation functions of physical operators of a system interacting with a heat bath producing a Gaussian-Markoffian noise are treated with the use of Feynman-Vernon's influence functional formalism. The Laplace transforms of correlation functions are shown to be expressed in terms of continued fractions of relevant hyperoperators. The result is valid to all orders of the system-bath interaction. In the limitation of motional narrowing, it reduces to those obtained in conventional methods.
Tópico(s): Quantum Information and Cryptography
1989 - Physical Society of Japan | Journal of the Physical Society of Japan
This article is a personal reflection of the branch of nonequilibrium statistical mechanics called the linear response theory that has as its heart the fluctuation-dissipation thereom, which states that irreversible processes ip nonequilibrium are necessarily related to thermal fluctuations in equilibrium. Its origi lies in the Einstein relation for the diffusion constant and the mobility of a Brownian particle. The short history of the fluctuation-dissipation theorem is described. Then the linear ...
Tópico(s): Statistical Mechanics and Entropy
1986 - American Association for the Advancement of Science | Science
Ryogo Kubo, Morikazu Toda, Natsuki Hashitsume,
This volume of Statistical Physics consititutes the second part of Statistical Physics (Springer Series in Solid-State Science, Vols. 30, 31) and is devoted to nonequilibrium theories of statistical m
Tópico(s): Statistical Mechanics and Entropy
1985 - Springer Nature | Springer series in solid-state sciences
Ryogo Kubo, Akio Kawabata, S. Kobayashi,
This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and ...Read More
Tópico(s): Chemical and Physical Properties of Materials
1984 - Annual Reviews | Annual Review of Materials Science
Morikazu Toda, Ryogo Kubo, Nobuhiko Saitô,
This first volume of Statistical Physics is an introduction to the theories of equilibrium statistical mechanics, whereas the second volume (Springer Ser. Solid-State Sci., Vol. 31) is devoted to non
Tópico(s): Theoretical and Computational Physics
1983 - Springer Nature | Springer series in solid-state sciences
Tópico(s): Mechanical and Optical Resonators
1981 - Springer Science+Business Media | Hyperfine Interactions
Tópico(s): Electron Spin Resonance Studies
1980 - Springer Nature | Springer series in solid-state sciences
Nobukazu Teranishi, Ryogo Kubo,
The effect of impurities on the phase mode of CDW in a one-dimensional system is studied by taking account of the non-linearity of the problem. Most of the work is based on numerical simulations which are performed using a classical mechanical equation of motion for the phase mode. The existence of critical field for the pinning and depinning is discussed for weak and strong pinning cases. The ohmic frequency-dependent conductivity is calculated by the Kubo formula. The dc conduction in non-ohmic ...
Tópico(s): Nonlinear Photonic Systems
1979 - Physical Society of Japan | Journal of the Physical Society of Japan
R. Hayano, Y. J. Uemura, J. Imazato, N. Nishida, Toshitsugu Yamazaki, Ryogo Kubo,
Zero- and low-field spin-relaxation functions have been studied for the first time by using positive muons, and results are compared with the stochastic theory of low-field relaxation formulated by Kubo and Toyabe. The dipolar broadening of the zero-field relaxation has been studied in detail. In Zr${\mathrm{H}}_{2}$, the zero-field relaxation function of ${\ensuremath{\mu}}^{+}$ has been found to decay ${(5)}^{\mathrm{\textonehalf{}}}$ times faster than the high-field relaxation function, which is explained ...
Tópico(s): Advanced Battery Materials and Technologies
1979 - American Physical Society | Physical review. B, Condensed matter
Ryogo Kubo, T. Takagahara, Eiichi Hanamura,
Perturbations acting on a radiative system in its excited states affect the coherence property of a second order optical response of the system. In order to understand general features of such effects, perturbations are considered as a stochastic Markoffian process. A general formalism is developed for calculations of spectral as well as temporal responses. In the static limit and also in the extremely fast limit of perturbation, only the coherent Raman or Rayleigh scattering is present, but in ...
Tópico(s): Quantum optics and atomic interactions
1979 - Elsevier BV | Solid State Communications
T. Takagahara, Eiichi Hanamura, Ryogo Kubo,
A second order optical process in a localized electron-phonon system is studied under a stationary excitation. A stochastic theory of vibrational relaxation at finite temperature is constructed based upon a quantum mechanical treatment. We project the dynamical motion of the whole lattice system onto the stochastic motion of a pseudo-local mode or a localized mode visualizing this mode as a damped harmonic oscillator which undergoes a Brownian motion. The overall emission spectrum is calculated ...
Tópico(s): Mechanical and Optical Resonators
1978 - Physical Society of Japan | Journal of the Physical Society of Japan
A brief review is made on various aspects of non-linear non-equilibrium statistical mechanics, many of which are discussed in lectures at this seminar in greater details.
Tópico(s): Theoretical and Computational Physics
1978 - Oxford University Press | Progress of Theoretical Physics Supplement
T. Takagahara, Eiichi Hanamura, Ryogo Kubo,
The transient response of the second order optical process is studied for a localized electron-phonon system the stationary response of which was discussed in the preceding paper. We make use of the stochastic theory to project the dynamics of the whole lattice system onto the stochastic motion of the appropriately chosen relevant mode. The time-resolved emission spectrum is calculated for our model of vibrational relaxation which can be handled analytically. The time-dependent behaviors of various ...
Tópico(s): Quantum optics and atomic interactions
1978 - Physical Society of Japan | Journal of the Physical Society of Japan
T. Takagahara, Eiichi Hanamura, Ryogo Kubo,
A general theory of transient light scattering is developed on the basis of our stochastic theory of intermediate state interaction. The transient behaviors of various components of the second order optical process under a pulsed irradiation are discussed and model calculations of the time-resolved emission spectra are performed. It is clarified that in the fast modulation limit the Raman component has a time constant determined by the phase memory time of the intermediate state while the time constant ...
Tópico(s): Random lasers and scattering media
1977 - Physical Society of Japan | Journal of the Physical Society of Japan
T. Takagahara, Eiichi Hanamura, Ryogo Kubo,
A general theory of the intermediate state interaction in the second order optical process is developed by extending the stochastic theory of line shape. We introduce the stochastic models of the intermediate state interaction and discuss the general features of the secondary emission spectrum, focusing particular attention on how the correlation between the incident and the scattered photons are affected by the intermediate state interaction. It is clarified how the spectral features or the relative ...
Tópico(s): Thermal Radiation and Cooling Technologies
1977 - Physical Society of Japan | Journal of the Physical Society of Japan