The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Cagatay Basdogan - One of the best experts on this subject based on the ideXlab platform.

  • tactile roughness perception of virtual gratings by electrovibration
    IEEE Transactions on Haptics, 2020
    Co-Authors: Aykut Isleyen, Yasemin Vardar, Cagatay Basdogan
    Abstract:

    Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with ten participants to investigate the effect of Spatial Period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants’ finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with Spatial Period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force ( $dF_t/dt$ ) as a function of Spatial Period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.

  • tactile roughness perception of virtual gratings by electrovibration
    arXiv: Human-Computer Interaction, 2020
    Co-Authors: Aykut Isleyen, Yasemin Vardar, Cagatay Basdogan
    Abstract:

    Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with 10 participants to investigate the effect of Spatial Period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants' finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with Spatial Period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force ($dF_t/dt$) as a function of Spatial Period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.

  • Tactile Perception of Virtual Edges and Gratings Displayed by Friction Modulation via Ultrasonic Actuation
    IEEE Transactions on Haptics (ToH), 2020
    Co-Authors: Muhammad Khurram Saleem, Cetin Yilmaz, Cagatay Basdogan
    Abstract:

    Tactile discrimination and roughness perception of real textures are extensively studied and underlying perceptual mechanisms are relatively well-established. However, tactile perception of virtual textures rendered by friction modulation techniques on touch surfaces has not been investigated in detail yet. In this study, we investigated our ability to discriminate two consecutive step changes in friction (called edges), followed by discrimination and roughness perception of multiple edges (called Periodic gratings). The results showed that discrimination of two consecutive edges was significantly influenced by edge sequence: a step fall in friction (F F) followed by a step rise in friction (RF) was discriminated more easily than the reverse order. On the other hand, Periodic gratings displayed by consecutive sequences of F F followed by RF were perceived with the same acuity as compared to vice versa. Independent of the edge sequence, we found that a relative difference of 14% in Spatial Period was required to discriminate two Periodic gratings. Moreover, the roughness perception of Periodic gratings decreased with increasing Spatial Period for the range that we have investigated (Spatial Period > 2 mm), despite the lack of Spatial cues on grating height. We also observed that rate of change in friction coefficient was better correlated with the roughness perception than the friction coefficient itself. These results will further help to understand and design virtual textures for touch surfaces.

  • Tactile Perception of Virtual Edges and Gratings Displayed by Friction Modulation via Ultrasonic Actuation
    IEEE Transactions on Haptics, 2020
    Co-Authors: Muhammad Khurram Saleem, Cetin Yilmaz, Cagatay Basdogan
    Abstract:

    Tactile discrimination and roughness perception of real textures are extensively studied and underlying perceptual mechanisms are relatively well-established. However, tactile perception of virtual textures rendered by friction modulation techniques on touch surfaces has not been investigated in detail yet. In this article, we investigated our ability to discriminate two consecutive step changes in friction (called edges), followed by discrimination and roughness perception of multiple edges (called Periodic gratings). The results showed that discrimination of two consecutive edges was significantly influenced by edge sequence: a step fall in friction ($FF$) followed by a step rise in friction ($RF$) was discriminated more easily than the reverse order. On the other hand, Periodic gratings displayed by consecutive sequences of $FF$ followed by $RF$ were perceived with the same acuity as compared to vice versa. Independent of the edge sequence, we found that a relative difference of 14% in Spatial Period was required to discriminate two Periodic gratings. Moreover, the roughness perception of Periodic gratings decreased with increasing Spatial Period for the range that we have investigated (Spatial Period $>$ 2 mm), despite the lack of Spatial cues on grating height. We also observed that rate of change in friction coefficient was better correlated with the roughness perception than the friction coefficient itself. These results will further help to understand and design virtual textures for touch surfaces.

Martin J. Leahy - One of the best experts on this subject based on the ideXlab platform.

Yuki Takayama - One of the best experts on this subject based on the ideXlab platform.

  • Spatial Period doubling, invariant pattern, and break point in economic agglomeration in two dimensions
    Journal of Economic Dynamics and Control, 2018
    Co-Authors: Kiyohiro Ikeda, Mikihisa Onda, Yuki Takayama
    Abstract:

    Abstract Mechanisms of an economic agglomeration of multiple places in a square lattice economy are elucidated by a comparative study with a racetrack economy. As a common mechanism to engender fewer larger agglomerations in both economies, doubling of their Spatial Period is advanced. The replicator dynamics in these economies accommodates characteristic agglomeration patterns that are solutions of the governing equation for any values of transport cost. A break point is used to index the onset of a bifurcation breaking uniformity as the transport cost decreases. Analytical formulas for this point that can synthetically encompass both economies are derived for an economic geography model.

  • Harris and Wilson (1978) Model Revisited: The Spatial Period-doubling Cascade in an Urban Retail Model
    Journal of Regional Science, 2016
    Co-Authors: Minoru Osawa, Takashi Akamatsu, Yuki Takayama
    Abstract:

    Harris and Wilson (1978)’s retail location model is one of the pioneering works in regional sciences. This model considers the combination of the “fast” and “slow” dynamics to describe spontaneous Spatial pattern formation processes in the economic landscape. Although the model was proposed some time ago, its comparative static (bifurcation) properties have not yet been sufficiently explored. We employ a simple analytical approach developed by Akamatsu et al. (2012) to reveal previously unknown bifurcation properties of the model in a space with a large number of locations. It is analytically shown that the Spatial structure’s evolutionary path exhibits a remarkable property, namely a “Spatial Period-doubling cascade,” which cannot be observed in the popular two-location setup. Furthermore, we discuss strong linkages between the model and “new economic geography” models in terms of their model structures and bifurcation properties. These results offer a new theoretical perspective for understanding agglomeration and Spatial structure evolution.

  • Harris and Wilson (1978) Model Revisited: The Spatial Period-doubling Cascade in an Urban Retail Model
    2015
    Co-Authors: Takashi Akamatsu, Minoru Osawa, Yuki Takayama
    Abstract:

    Harris and Wilson (1978)’s retail location model is one of the pioneering works in regional sciences on the combination of the “fast” and “slow” dynamic describing Spatial pattern formation processes in the economic landscape, which is a current well-established modeling technique. Although proposed some time ago, the comparative static (bifurcation) properties of the model have not yet been sufficiently explored. We employ a simple analytical approach developed by Akamatsu et al. (2012) to reveal previously unknown bifurcation properties of the model in a space with a large number of locations. It is analytically shown that the evolutionary path of Spatial structure exhibits a remarkable property, namely “Spatial Period- doubling cascade,” which we cannot observe in the popular two-location setup. We also discuss strong linkages between the model and the models of “new economic geography” regarding the modeling strategies and their bifurcation properties.

Sergey A. Alexandrov - One of the best experts on this subject based on the ideXlab platform.

  • Adaptation of the spectral encoding of Spatial frequency approach to optical coherence tomography (OCT)
    Biomedical Optics 2014, 2014
    Co-Authors: Sergey A. Alexandrov, Hrebesh M. Subhash, Martin J. Leahy
    Abstract:

    We have adapted spectral encoding of Spatial frequency approach to OCT to get depth resolved information about submicron internal structure with nanoscale sensitivity. Axial Spatial Period profiles are reconstructed for each voxel of 3D image.

  • Spectral encoding of Spatial frequency approach for imaging and characterization of 3D structures
    2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), 2013
    Co-Authors: Shikhar Uttam, Sergey A. Alexandrov, Rajan K. Bista, Yang Liu
    Abstract:

    Probing the internal 3D structure of label-free objects, such as biological cells and tissues in their natural environments, with nano-scale accuracy and sensitivity is of great importance in many biomedical applications. Using the 3D scattering potential description of an object's structure, we present the principle of spectral encoding of 3D Spatial frequency (SESF) that encodes different Spatial frequencies of the scattering potential into corresponding wavelengths. The SESF principle allows us to (1) perform real-time quantitative dominant-structure imaging of a label-free object. This imaging approach produces a color map in real time in which dominant axial Spatial Period (or frequency) at each image point is encoded as a corresponding spectral color. We demonstrate the efficacy of real-time imaging using model systems and show the potential of this technique to detect dominant structural changes in pre-cancerous cells that are not visible using conventional microscopy. (2) We extend the SESF principle to measure the entire axial Spatial Period distribution for each image point. Experimental results based on characterization of cell cycle phases are presented along with comparison with structural information extracted from TEM cell images. (3) Finally, we present spectral tomographic imaging (STI), a new SESF-based integrated tomographic approach that is able to simultaneously reconstruct the 3D object with sub-micron resolution, and also provide Spatially-resolved characterization of its structure that has the ability to construct local axial Spatial Period distribution for any 3D sub-region of interest within the object. Simulation-based examples are presented. In all three cases structural characterization is achieved with nanoscale sensitivity and accuracy.

Takashi Akamatsu - One of the best experts on this subject based on the ideXlab platform.

  • Harris and Wilson (1978) Model Revisited: The Spatial Period-doubling Cascade in an Urban Retail Model
    Journal of Regional Science, 2016
    Co-Authors: Minoru Osawa, Takashi Akamatsu, Yuki Takayama
    Abstract:

    Harris and Wilson (1978)’s retail location model is one of the pioneering works in regional sciences. This model considers the combination of the “fast” and “slow” dynamics to describe spontaneous Spatial pattern formation processes in the economic landscape. Although the model was proposed some time ago, its comparative static (bifurcation) properties have not yet been sufficiently explored. We employ a simple analytical approach developed by Akamatsu et al. (2012) to reveal previously unknown bifurcation properties of the model in a space with a large number of locations. It is analytically shown that the Spatial structure’s evolutionary path exhibits a remarkable property, namely a “Spatial Period-doubling cascade,” which cannot be observed in the popular two-location setup. Furthermore, we discuss strong linkages between the model and “new economic geography” models in terms of their model structures and bifurcation properties. These results offer a new theoretical perspective for understanding agglomeration and Spatial structure evolution.

  • Harris and Wilson (1978) Model Revisited: The Spatial Period-doubling Cascade in an Urban Retail Model
    2015
    Co-Authors: Takashi Akamatsu, Minoru Osawa, Yuki Takayama
    Abstract:

    Harris and Wilson (1978)’s retail location model is one of the pioneering works in regional sciences on the combination of the “fast” and “slow” dynamic describing Spatial pattern formation processes in the economic landscape, which is a current well-established modeling technique. Although proposed some time ago, the comparative static (bifurcation) properties of the model have not yet been sufficiently explored. We employ a simple analytical approach developed by Akamatsu et al. (2012) to reveal previously unknown bifurcation properties of the model in a space with a large number of locations. It is analytically shown that the evolutionary path of Spatial structure exhibits a remarkable property, namely “Spatial Period- doubling cascade,” which we cannot observe in the popular two-location setup. We also discuss strong linkages between the model and the models of “new economic geography” regarding the modeling strategies and their bifurcation properties.

  • Spatial Period-Doubling Agglomeration of a Core-Periphery Model with a System of Cities
    Journal of Economic Dynamics and Control, 2012
    Co-Authors: Kiyohiro Ikeda, Takashi Akamatsu, Tatsuhito Kono
    Abstract:

    Abstract The progress of Spatial agglomeration of Krugman's core–periphery model is investigated by comparative static analysis of stable equilibria with respect to transport costs. We set forth theoretically possible agglomeration (bifurcation) patterns for a system of cities spread uniformly on a circle. A possible and most likely course predicted is a gradual and successive one, which is called Spatial Period doubling. For example, eight cities concentrate into four cities and then into two cities en route to the formation of a single city. The existence of this course is ensured by numerical simulation for the model. Such a gradual and successive agglomeration presents a sharp contrast to the agglomeration of two cities, for which spontaneous concentration to a single city is observed in core–periphery models of various kinds. Other bifurcations that do not take place in two cities, such as Period tripling, are also observed. The need for study of a system of cities has thus been demonstrated.

  • Spatial Period-Doubling Agglomeration of a Core-Periphery Model with a System of Cities
    2009
    Co-Authors: Kiyohiro Ikeda, Takashi Akamatsu, Tatsuhito Kono
    Abstract:

    The orientation and progress of Spatial agglomeration for Krugman's core--periphery model are investigated in this paper. Possible agglomeration patterns for a system of cities spread uniformly on a circle are set forth theoretically. For example, a possible and most likely course predicted for eight cities is a gradual and successive one---concentration into four cities and then into two cities en route to a single city. The existence of this course is ensured by numerical simulation for the model. Such gradual and successive agglomeration, which is called Spatial-Period doubling, presents a sharp contrast with the agglomeration of two cities, for which spontaneous concentration to a single city is observed in models of various kinds. It exercises caution about the adequacy of the two cities as a platform of the Spatial agglomerations and demonstrates the need of the study on a system of cities.