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ABSTRACT: We have measured the thermal conductivity along the c-axis parallel to the
spin-chains, kappa_c, of the one-dimensional antiferromagnetic spin system
SrCuO_2, using as-grown and O_2-annealed single-crystals grown from raw
materials with 99.9% (3N) and 99.99% (4N) purity. The value of kappa_c around
50K, where large contribution of the thermal conductivity due to spinons,
kappa_spinon, is observed, is markedly enhanced by both the increase of the
purity of raw materials and the O_2-annealing. Therefore, the increase of
kappa_c implies that kappa_spinon is enhanced due to the decrease of spin
defects caused by impurities in raw materials and by oxygen defects. The mean
free path of spinons is as large as about 24000 angstrom at low temperatures in
the O_2-annealed single-crystal grown from raw materials with 4N purity.
03/2011;
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ABSTRACT: We have measured the thermal conductivity along the [101] direction,
kappa_[101]_, along the [10-1] direction, kappa_[10-1]_, and along the b-axis,
kappa_b_, of the quasi one-dimensional S=1/2 spin system Sr_2_V_3_O_9_ in
magnetic fields up to 14 T, in order to find the thermal conductivity due to
spinons and to clarify whether the spin-chains run along the [101] or [10-1]
direction. It has been found that both kappa_[101]_, kappa_[10-1]_ and kappa_b_
show one peak around 10 K in zero field and that the magnitude of kappa_[10-1]_
is larger than those of kappa_[101]_ and kappa_b_. By the application of
magnetic field along the heat current, the peak of kappa_[10-1]_ is markedly
suppressed, while the peaks of kappa_[101]_ and kappa_b_ little change. These
results indicate that there is a large contribution of spinons to kappa_[10-1]_
and suggest that the spin-chains run along the [10-1] direction.
02/2011;
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ABSTRACT: We present a method to extract salient regions in natural images based on local extrema. Behavioral and physiological studies on human vision indicate that the peripheral vision has an important role to get salient regions into the fovea to obtain detailed information from the environment. Modeling of the peripheral is the key to create a salient region extraction method with the behavioral plausibility. To extract salient regions in a natural image, we focus on the multiresolutional 2-D distribution of local extrema. Local extrema detect regions in the image that are either brighter or darker than the surroundings. They will provide useful information to extract salient regions regardless of the image resolution. As for the function of human vision, an image is more blurred in more peripheral. So we model the peripheral using scale-space image representation. In this study, we define the saliency based on the stability of local extrema on scale-space and create a method to extract salient regions. Comparing the human map of fixations, we ensure that our method successfully extracts salient regions.
Image Processing (ICIP), 2010 17th IEEE International Conference on; 10/2010
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ABSTRACT: We performed a Ground Based SAR (GB-SAR) and PiSAR simultaneous experiment over a flood test site. In this site, one prefab was constructed in a baseball field of a Nihon University in Chiba, Japan. The PiSAR observations were done for three days with different soil moisture condition of ~25%, ~50%, and 100%. Some GB-SAR experiments have been also done in two of three days and the scattering process are examined. Preliminary experiment with GB-SAR showed that L-band sigma<sup>0</sup> from a double scattering of ground-wall is increased for a few dB, when a reflectivity of the ground is assumed to be 1. These increase are also confirmed in the test site for both PiSAR and GB-SAR. Furthermore, high resolution GB-SAR images show double and single bounce scattering from a metal bar behind the wooden board of the prefab. We conclude that L-band SAR has a enough ability to detect a flooding area in urban site.
Geoscience and Remote Sensing Symposium, 2008. IGARSS 2008. IEEE International; 08/2008
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ABSTRACT: Two ALOS/PALSAR polarimetry data taken in 2006 were used and examined the deforestation stage by using coherence value. Many trees were fallen by a typhoon hit on September 8, 2004 at a test site in Japan. Reforestation has started for the deforestation sites and several kinds of deforestation stages are appeared there. We classified the stands into four groups. 1) Only small stumps and branches are left. 2) Tree trunks have been carried out, but branches and stumps have been left. 3) The fallen trees have been left. 4) No trees were fallen by the typhoon (normal forest). Coherence values of HH-HH and VV-VV become ~0.39 for group 1 and ~0.30 for group 4, and show a significant difference. But the coherence values of group 2, and group 3 are ~0.3 and show almost same value as group 1. The coherence value of HH-VV and VV-HH are 0.1 lower than the one of the HH-HH and W-VV. The coherence values, which include cross polarization, such as HV-HV and HV-VV, show no difference for all groups and the value is 0.2 to 0.3. While coherence values show the difference between group 1 and group 4, sigma<sup>0</sup> <sub>HV</sub> shows wider dynamic range and is preferable to distinguish the deforested stands from forest stands.
Microwave Conference, 2007. APMC 2007. Asia-Pacific; 01/2008
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ABSTRACT: JERS-1/SAR images taken in 1990's and ALOS/PALSAR images taken in 2000's are used and examined the deforestation status during ~14 years. Many trees had been fallen by a typhoon hit in 2004 in a test site, Tomakomai. There is also a plantation area and the site show active change during the term. The forest stands could be roughly classified for four types, forest stands, vacant, where almost all trees were carried out, and two types of transitional stands from a forest to a vacant. Many deforested areas are easily detected by using the difference of backscattering coefficients between two images, if fallen trees have been carried out from the stands. The change from the normal forest to the vacant stands causes 3.1dB decrease in the sigma<sup>0</sup> <sub>HH</sub>. On the other hands, transitional stands show almost same backscattering as the normal forest stands, although. Three- component scattering model shows surface scattering component accounts for 50% over the vacant stands, while volume scattering component accounts for ~60% over the forest stands. But the model doesn't show the clear difference between transitional forest site and normal forest. The temporal changes of the forest during 14 years are also examined for the plantation area. One stand show gradual increase of sigma<sup>0</sup> and the values seem to be saturated around 17.4 tons/ha (~5 m in average height).
Geoscience and Remote Sensing Symposium, 2007. IGARSS 2007. IEEE International; 08/2007
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ABSTRACT: In this paper, we propose a new animation creation process, based on the teacher-student concept. You are the teacher and want to teach someone a performance. First you show the student how to perform an action, you tell him "do like me". Then you correct his posture by moving with hands his arms, his torso, feet position and so forth by saying to him "do like this". To show the virtual human a motion, the user use motion capture. He may check easily the result in a human scale immersive environment. Then he finds the part of the motion he wants to correct. He edits the motion with his hands like in the real world using a two-handed haptic device. Thus the user can perform motion editing in an intuitive and natural way, and achieve both actor performance and animator task in a unified environment.
Shape Modeling and Applications, 2007. SMI '07. IEEE International Conference on; 07/2007
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ABSTRACT: In this paper, we propose a 10 kHz high definition haptic rendering which can display on real-time video-rate (60Hz) in general VR applications. Our proposal requires both fidelity and stability in the multi-rate system, which the frequency ratio approximates at 160 times. For satisfying two criteria, there are some problems to be resolved. In the view of getting only stability, we can use a virtual coupling method to link a haptic display and a virtual object. Due to low its coupling impedance, this method isn't good for realization of fidelity and quality of manipulation. Therefore, we have developed a multi-rate system with two level up-sampling for both fidelity and stability of haptic sensation. The first level up-sampling achieves stability with the virtual coupling, and the second level achieves fidelity with 10kHz haptic rendering to compensate the haptic quality lost from the coupling process. We confirmed that our proposed system could achieve both the stability and fidelity of haptic rendering through a computer simulation and a 6DOF haptic interface (SPIDAR-G) with a rigid object simulation engine.
Artificial Reality and Telexistence--Workshops, 2006. ICAT '06. 16th International Conference on; 01/2007
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ABSTRACT: An impedance of rehabilitation and assisting robot should be matched with that of human in order to carry out cooperative works harmoniously. If not so, we could not set our expectations highly to get stability and effectivity in the cooperative works of human-robot. In this paper, we develop the cooperative work system to adjust the impedance of a robot driven by ultrasonic motor (USM) to that of human's arm. There is reason to adopt a USM for the robot's actuator. It has many good characteristics like high torque at low speed. When we use the adjusting phase difference method among the various control methods of USM, we have to consider cautiously how to set the value of the driving frequency because the characteristics of USM is changed according to which value of the driving frequency is set. Therefore, we suggested a novel method that the suitable driving frequency is supplied according to each the phase difference. Using this method, we could change the mechanical impedance of USM such as viscosity and stiffness. To evaluate the proposed cooperative work system, we conduct the two types of tasks
SICE-ICASE, 2006. International Joint Conference; 11/2006
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ABSTRACT: Interactions that provide motivating activities, and perform mutual feedback truly in human-scale spaces, were not suggested
in any studies. In this paper, we propose and implement a haptic interaction system that realizes reciprocal reactions. This
system is composed of a wire-driven haptic interface and an immersive virtual environment. It enables user to do visual and
force feedback in a human-scale interaction spaces. And the virtual human performs intuitive response to changes of user’s
action. Based on the framework, we implemented a haptic interaction, Virtual Catch Ball, that a user can play the virtual human with one’s feeling of contacting real ball. Furthermore we introduce the system’s
extended function that virtual human imitates user’s effective styles acquired by a on-line motion capture, and then reflects
them on his behavioral structure. It will be a practical way to produce various motion patterns during playing, and to evolve
both behaviors.
03/2006: pages 1252-1261;
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ABSTRACT: In this paper, we propose a method to extract motor primitives from electromyography(EMG) signals on reaching movements of human arm. EMG signals reflect the motor commands from the central nervous system (CNS). Especially, we extract the motor primitives in consideration of arm posture, movement direction and velocity using only EMG signals. As an experimental task, we performed two kinds of experiments on a horizontal plane, measured ten EMG signals and the hand trajectories during movement. Specially, we extracted motor primitive from the EMG signals during movement by using hidden Markov model. Finally, in order to verify how accurately our proposed method divides the motor primitives, we compared the boundary points between the extracted two motor primitives with via-points that were estimated by using forward and inverse dynamics models
Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2006
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ABSTRACT: The virtual reality (VR) technology has been used as the application of architectural presentation or simulation tool in the field of industry. The high immersion and intuitive visual information are the great merits of design evaluation or environmental simulation when we are using the virtual environments. But the distortion of distance perception in VR is still a big problem when the accuracy of distance presentation is strictly required. In this paper, we have carried out some experiments about distance estimation in the immersive virtual environments to verify the factors and their influence. We made a hypothesis that the lack of the information for the user in VR causes the different distance estimation from the real world because users are usually comfortable with moving fast and long distance in VR environments. So, we carried out basic experiment to prove our hypothesis that the lack of information makes subjects estimate the walked distance in VR shorter compared with the same distance in real. Also, among the factors that probably affect the distance estimation in VR, we verified the influence of the image resolution. The influence of resolution degradation of image on the distance estimation was verified with the condition of static and dynamic images. The results showed that the resolution has deep relation with the distance estimation. For example, the subject underestimated the distance at the lower resolution condition. We also find the methods of the making the lower resolution image could affects on the visual perception of subjects.
Cyberworlds, 2005. International Conference on; 12/2005
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ABSTRACT: We have proposed a human-scale interaction system (i.e. reactive virtual human system) with haptic sensation. This system is composed of a wire-based haptic interface and an immersive virtual environment (VE). Based on the framework, we realized virtual catch ball that a user can play a virtual human with a feeling of contacting real ball. To make a database of virtual human's natural reaction, we implemented reactive motion capture system that can capture movements with physical reaction in close interpersonal engagements. In this paper, we further show the system's extended function that new motions can reflect on virtual human's behavioral structure by an on-line motion capture. It will be a practical way to produce various motion patterns during playing, and to enforce virtual human's adaptive function.
Cyberworlds, 2005. International Conference on; 12/2005
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ABSTRACT: This paper describes a haptic controller for force feedback systems in virtual environments. For stable haptic, a frequency of device control higher than I kHz is required. In this research, we have developed a high definition haptic controller with SuperH4 processor. In order to achieve high frequency of device control, the controller interpolates haptic information from primitive geometries and impedance of a virtual wall. SPIDAR, a wire driven haptic display, uses this controller. It realizes high control frequency. Consequently, it became possible to display a very hard virtual wall stably. The high definition haptic controller (HDHC) allows stable haptic and high quality sensation in virtual environments.
Eurohaptics Conference, 2005 and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2005. World Haptics 2005. First Joint; 04/2005
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ABSTRACT: In this paper, our initial work on the use of visualization and virtual reality for education especially for providing three-dimensional concepts of molecular structure was presented. Our system is composed of a hybrid screen, multi-projectors, PC cluster, 6DOF haptic device etc. It offers a channel to reach into the molecular space in an immersive environment, allows user to employ an intuitive 6DOF haptic device Spidar-G to control the perspective. For educators, it can serve as a good instructional aid for helping students to understand molecular structure through effective visual representation and interactive manipulation.
Image and Graphics, 2004. Proceedings. Third International Conference on; 01/2005
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ABSTRACT: We propose a novel multiprojector display for immersive virtual environments. Our system named "D-vision" has a hybrid curved screen which completely covers user's view and immerses the user in displayed virtual environments. The D-vision also has a human-scale haptic- and locomotion interface by which the users of the D-vision can walk with their own foot and interact with virtual objects through their own hands. In this paper, we show an overview of the D-vision and technologies used for the human-scale hapticand locomotion interfaces. We also illustrate some applications using the interfaces effectively.
TENCON 2004. 2004 IEEE Region 10 Conference; 12/2004
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ABSTRACT: Many immersive displays developed in previous researches are strongly influenced by the design concept of the CAVE which is the origin of the immersive displays. We propose a novel multiprojector display for immersive virtual environments. Our system named "D-vision'' has a hybrid curved screen which consist of differently shaped surface elements that are partial surfaces of such objects as planes, spheres, cylinders and tori. 24 PCs and projectors generate high-quality stereoscopic images. Our rendering algorithm using our original image processing hardware and commodity 3D graphics hardware realizes seamless and nondistorted projection on the hybrid screen. The D-vision also has a human-scale haptic and locomotion interface by which the users of the D-vision can walk with their own foot and interact with virtual objects through their own hands. We show an overview of the D-vision and technologies used for the human-scale haptic- and locomotion interfaces.
Cyberworlds, 2004 International Conference on; 12/2004
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ABSTRACT: Creating reactive motions with existing motion-capture systems is difficult because they require a variety of task environments. To overcome this drawback, we propose a reactive motion capture system that combines the existing motion capture system with haptic feedback and a human- scale virtual environment. Our objective is to acquire reactive motion data generated from the interaction between haptic feedback and the virtual environment, using the fact that a person's motions in real world can be represented by the reactions of the person to real objects. We asked the subject to trace the rim of the front of a cube under six task conditions and measured their fingertip trajectories as motion data. The results demonstrated that our proposed system is useful for generating data for natural-looking motions similar to real-world motions.
Automatic Face and Gesture Recognition, 2004. Proceedings. Sixth IEEE International Conference on; 06/2004
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ABSTRACT: In this paper, we propose a learning model using the Actor-Critic method and the feedback-error-learning scheme. The Actor-Critic method, which is one of the major frameworks in reinforcement learning, has attracted attention as a computational learning model in the basal ganglia. Meanwhile, the feedback-error-learning is learning architecture proposed as a computationally coherent model of cerebellar motor learning. This learning architecture's purpose is to acquire a feed-forward controller by using a feedback controller's output as an error signal. In past researches, a predetermined constant gain feedback controller was used for the feedback-error-learning. We use the Actor-Critic method for obtaining a feedback controller in the feedback-error-earning. By applying the proposed learning model to an arm's posture control, we show that high-performance feedback and feed-forward controller can be acquired from only by using a scalar value of reward.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2004; 1:486-9.
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Journal of Robotics and Mechatronics. 01/2004; 16(5):446-455.
