Takenouchi T.,Future University Hakodate
Neural Computation | Year: 2015
We propose a novel estimator for a specific class of probabilistic models on discrete spaces such as the Boltzmann machine. The proposed estimator is derived from minimization of a convex risk function and can be constructed without calculating the normalization constant, whose computational cost is exponential order. We investigate statistical properties of the proposed estimator such as consistency and asymptotic normality in the framework of the estimating function. Small experiments show that the proposed estimator can attain comparable performance to the maximum likelihood expectation at a much lower computational cost and is applicable to high-dimensional data. © 2015 Massachusetts Institute of Technology 2015.
Mizuhara H.,Kyoto University |
Sato N.,Future University Hakodate |
NeuroImage | Year: 2015
Neural oscillations are crucial for revealing dynamic cortical networks and for serving as a possible mechanism of inter-cortical communication, especially in association with mnemonic function. The interplay of the slow and fast oscillations might dynamically coordinate the mnemonic cortical circuits to rehearse stored items during working memory retention. We recorded simultaneous EEG-fMRI during a working memory task involving a natural scene to verify whether the cortical networks emerge with the neural oscillations for memory of the natural scene. The slow EEG power was enhanced in association with the better accuracy of working memory retention, and accompanied cortical activities in the mnemonic circuits for the natural scene. Fast oscillation showed a phase-amplitude coupling to the slow oscillation, and its power was tightly coupled with the cortical activities for representing the visual images of natural scenes. The mnemonic cortical circuit with the slow neural oscillations would rehearse the distributed natural scene representations with the fast oscillation for working memory retention. The coincidence of the natural scene representations could be obtained by the slow oscillation phase to create a coherent whole of the natural scene in the working memory. © 2015 Elsevier Inc.
Nacher J.C.,Toho University |
Nacher J.C.,Future University Hakodate |
Akutsu T.,Kyoto University
New Journal of Physics | Year: 2012
The possibility of controlling and directing a complex system's behavior at will is rooted in its interconnectivity and can lead to significant advances in disparate fields, ranging from nationwide energy saving to therapies that involve multiple targets. In this work, we address complex network controllability from the perspective of the minimum dominating set (MDS). Our theoretical calculations, simulations using artificially generated networks as well as real-world network analyses show that the more heterogeneous a network degree distribution is, the easier it is to control the entire system.We demonstrate that relatively few nodes are needed to control the entire network if the power-law degree exponent is smaller than 2, whereas many nodes are required if it is larger than 2. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Kamiya T.,Future University Hakodate
IEEE International Conference on Program Comprehension | Year: 2013
Agec is a semantic code-clone detection tool from Java bytecode, which (1) applies a kind of abstract interpretation to bytecode as a static analysis, in order to generate n-grams of possible execution traces, (2) detects the same n-grams from distinct places of the bytecode, and (3) then reports these n-grams as code clones. The strengths of the tool are: static analysis (no need for test cases), detection of clones of deeply nested invocations, and Map-Reduce ready detection algorithms for scalability. © 2013 IEEE.
Sato N.,Future University Hakodate
Cognitive Systems Research | Year: 2012
The hippocampus is known to maintain memories of object-place associations that can produce a scene expectation at a novel viewpoint. To implement such capabilities, the memorized distances and directions of an object from the viewer at a fixed location should be integrated with the imaginary displacement to the new viewpoint. However, neural dynamics of such scene expectation at the novel viewpoint have not been discussed. In this study, we propose a method of coding novel places based on visual scene transformation as a component of the object-place memory in the hippocampus. In this coding, a novel place is represented by a transformed version of a viewer's scene with imaginary displacement. When the places of individual objects are stored with the coding in the hippocampus, the object's displacement at the imaginary viewpoint can be evaluated through the comparison of a transformed viewer's scene with the stored scene. Results of computer experiments demonstrated that the coding successfully produced scene expectation of a three object arrangement at a novel viewpoint. Such the scene expectation was retained even without similarities between the imaginary scene and the real scene at the location, where the imaginary scenes only functioned as indices to denote the topographical relationship between object locations. The results suggest that the hippocampus uses the place coding based on scene transformation and implements the spatial imagery of object-place associations from the novel viewpoint. © 2011 Elsevier B.V.
Murashige S.,Future University Hakodate
Journal of Engineering Mathematics | Year: 2014
Davies' surface condition is an approximate free-surface condition on gravity waves progressing in permanent form on water of infinite depth. It is known that this condition preserves essential features of finite-amplitude waves including the highest one. This paper proposes a new surface condition that generalizes Davies' idea of approximation and covers a fully nonlinear condition. Analytic continuation of the proposed surface condition allows us to explore singularities of solutions that dominate the flow. The results of singularity analysis elucidate the connection between Davies' approximate solution and the fully nonlinear solution. In addition, it is shown that the nonmonotonic variation of wave speed with wave steepness can be predicted using a linear sum of a relatively small number of singularities. This suggests that a suitable choice of a parameter in the proposed surface condition can move singularities away from the flow field without changing their structure and may reduce numerical difficulties due to singularities for large-amplitude waves. © 2013 Springer Science+Business Media Dordrecht.
Kawaguchi S.,Future University Hakodate
Nonlinearity | Year: 2011
In this study, we consider the effects of chemotaxis and lateral inhibition on an activator in a three-component reaction-diffusion system. Simulation results show that spot, planar and travelling front solutions in two dimensions are destabilized to form multibranch patterns. In order to analyse the stability of stationary solutions, a singular perturbation method is employed. The bifurcation diagrams suggest that chemotaxis and lateral inhibition cooperatively result in the destabilization of the stationary solutions. Our three-component model is compared with the two-component chemotaxis-growth model. Furthermore, the conditions for observing the cooperative effects of chemotaxis and lateral inhibition on an activator in experiments are inferred from the model. © 2011 IOP Publishing Ltd & London Mathematical Society.
Nacher J.C.,Future University Hakodate |
Schwartz J.-M.,University of Manchester
PLoS ONE | Year: 2012
Recent studies have highlighted the importance of interconnectivity in a large range of molecular and human disease-related systems. Network medicine has emerged as a new paradigm to deal with complex diseases. Connections between protein complexes and key diseases have been suggested for decades. However, it was not until recently that protein complexes were identified and classified in sufficient amounts to carry out a large-scale analysis of the human protein complex system. We here present the first systematic and comprehensive set of relationships between protein complexes and associated drugs and analyzed their topological features. The network structure is characterized by a high modularity, both in the bipartite graph and in its projections, indicating that its topology is highly distinct from a random network and that it contains a rich and heterogeneous internal modular structure. To unravel the relationships between modules of protein complexes, drugs and diseases, we investigated in depth the origins of this modular structure in examples of particular diseases. This analysis unveils new associations between diseases and protein complexes and highlights the potential role of polypharmacological drugs, which target multiple cellular functions to combat complex diseases driven by gain-of-function mutations. © 2012 Nacher, Schwartz.
Future University Hakodate and Renesas Electronics Corporation | Date: 2013-01-31
Provided are: a correction object determining section which determines whether, on an imaging plane in image data obtained by imaging an object irradiated with diffusion light from a light source by a camera, a region regarded to be in a state where a rod-like object has been irradiated with the diffusion light exists; a measurement point calculating section which estimates a light source center position of the diffusion light based on information of a luminance distribution of the diffusion light in the image data to set it as a first measurement point; and a distance calculating section which calculates a distance between the object at the first measurement point and the camera according to triangulation based on a horizontal distance between the center of the imaging plane and the first measurement point, the positions of the camera and light source, and an imaging direction angle of the camera.
Future University Hakodate | Date: 2013-06-28
A first imaging unit is configured to capture an image showing a subject in front. A convex reflector is located behind an imaging plane of an optical system formed by the first imaging unit and is configured to share an optical axis with the first imaging unit and mirror a subject beside the convex reflector, a convex portion of the convex reflector being oriented forward. A second imaging unit is configured to share the optical axis with the first imaging unit and capture an image mirrored by the convex reflector. An image processing unit is configured to adjust a resolution of images captured by the first and the second imaging units, obtain a mirror-reversed image from the image captured by the first imaging unit or the image captured by the second imaging unit, and blend the mirror-reversed image with the other image.