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Search Results: 1 - 10 of 114 matches for " Kazutsuna Yamaji "
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Concierge: Personal database software for managing digital research resources
Hiroyuki Sakai,Toshihiro Aoyama,Kazutsuna Yamaji,Shiro Usui
Frontiers in Neuroinformatics , 2007, DOI: 10.3389/neuro.11.005.2007
Abstract: This article introduces a desktop application, named Concierge, for managing personal digital research resources. Using simple operations, it enables storage of various types of files and indexes them based on content descriptions. A key feature of the software is a high level of extensibility. By installing optional plug-ins, users can customize and extend the usability of the software based on their needs. In this paper, we also introduce a few optional plug-ins: literature management, electronic laboratory notebook, and XooNlps client plug-ins. XooNIps is a content management system developed to share digital research resources among neuroscience communities. It has been adopted as the standard database system in Japanese neuroinformatics projects. Concierge, therefore, offers comprehensive support from management of personal digital research resources to their sharing in open-access neuroinformatics databases such as XooNIps. This interaction between personal and open-access neuroinformatics databases is expected to enhance the dissemination of digital research resources. Concierge is developed as an open source project; Mac OS X and Windows XP versions have been released at the official site (http://concierge.sourceforge.jp ).
GWAM—An Institutional Model to Address Watershed Impacts from Urbanization: Field Validation  [PDF]
Thambirajah Saravanapavan, Eiji Yamaji
Journal of Water Resource and Protection (JWARP) , 2018, DOI: 10.4236/jwarp.2018.109053
Abstract: With the realization of the limitations to top-down and bottom-up watershed management approaches in addressing issues associated with urbanization, a conceptual framework for a hybrid approach that tries to effectively integrate the advantages of the two approaches while overcoming their respective limitations, grass root watershed management model (GWAM), was proposed and presented. This paper presents the details of implementation and validation of GWAM at Shawsheen River watershed in Massachusetts, USA. An investigation on the major components of GWAM, a common platform to conduct the management, a partnership of two major stakeholder groups from government and non-governmental organizations, and a facilitation mechanisms were carried out in detail to gain the needed understanding on structure, process and function of a successful GWAM. Also the decision making process in addressing three major urban watershed issues; flooding, habitat and aquatic life impairment, and bacterial impairment, were examined through a set of cyclic steps. Based on the lessons learned, GWAM was enhanced as a general hybrid model. The most important challenge in sustaining GWAM was to keep differently motivated stakeholders together. As revealed in the Shawsheen watershed, science should play a key role in keeping differently motivated stakeholders together by providing needed facts, understandings, data, and knowledge. When scientifically sound solutions are vetted through a process of public involvement that supports appropriate regulatory actions, the most effective environmental decisions can be made.
GWAM—An Institutional Model to Address Watershed Impacts from Urbanization: Conceptual Framework  [PDF]
Thambirajah Saravanapavan, Eiji Yamaji
Journal of Water Resource and Protection (JWARP) , 2018, DOI: 10.4236/jwarp.2018.109052
Abstract: The urbanization process exerts negative multidisciplinary impacts on the integrity of natural watershed conditions. These impacts are best analyzed and addressed with local inputs, as many of these are site specific and require consistent local monitoring along with appropriate policies and regulations from conventional governance in an interdisciplinary platform. With the realization of the limitations to top-down and bottom-up watershed management approaches in addressing issues associated with urbanization, a conceptual framework for a hybrid approach that tries to effectively integrate the advantages of the two approaches while overcoming their respective limitations, the Grass root Watershed Management model (GWAM), is presented in this paper. The model is to establish a self-sustaining and effective institutional forum that can be used in watersheds across geographical and political boundaries while accommodating the urbanization process. GWAM consists of three crucial components: a common platform, a partnership among major groups of stakeholders, and a facilitation mechanism to conduct the watershed management at local lever or grass-root level. With effective integration of the governmental agencies and institutes at the top with the local residents and non-governmental organizations at the bottom, the concept is that the hybrid approach can serve as a self-sustaining model in achieving effective management of urbanization impacts.
Two-Band-Type Superconducting Instability in MgB2
Kunihiko Yamaji
Physics , 2001, DOI: 10.1143/JPSJ.70.1476
Abstract: Using the tight-binding method for the $\pi$-bands in MgB$_2$, the Hubbard on-site Coulomb interaction on two inequivalent boron $p_z$-orbitals is transformed into expressions in terms of $\pi$-band operators. For scattering processes relevant to the problemin which a wave vector {\bf q} is parallel to $\hat{z}$, it is found to take a relatively simple form consisting of intra-band Coulomb scattering, interband pair scattering etc. with large constant coupling constants. This allows to get a simple expression for the amplitude of interband pair scattering between two $\pi$-bands, which diverges if the interband polarization function in it becomes large enough.The latter was approximately evaluated and found to be largely enhanced in the band structure in MgB$_2$. These results lead to a divergent interband pair scattering, meaning two-band-type superconducting instability with enhanced $T_c$. Adding a subsidiary BCS attractive interaction in each band into consideration, a semi-quantitative gap equation is given, and $T_c$ and isotope exponent $\alpha$ are derived. The present instability is asserted to be the origin of high $T_c$ in MgB$_2$.
Positive Toepltz operators on the Bergman space of a minimal bounded homogeneous domain
Satoshi Yamaji
Mathematics , 2010,
Abstract: Necessary and sufficient conditions for positive Toeplitz operators on the Bergman space of a minimal bounded homogeneous domain to be bounded or compact are described in terms of the Berezin transform, the averaging function and the Carleson property.
Composition operators on the Bergman spaces of a minimal bounded homogeneous domain
Satoshi Yamaji
Mathematics , 2011,
Abstract: Using an integral formula on a homogeneous Siegel domain, we show a necessary and sufficient condition for composition operators on the weighted Bergman space of a minimal bounded homogeneous domain to be compact. To describe the compactness of composition operators, we see a boundary behavior of the Bergman kernel.
Essential norm estimates for positive Toeplitz operators on the weighted Bergman space of a minimal bounded homogeneous domain
Satohi Yamaji
Mathematics , 2011,
Abstract: We give estimates for the essential norms of a positive Toeplitz operator on the Bergman space of a minimal bounded homogeneous domain in terms of the Berezin transform or the averaging function of the symbol. Using these estimates, we also give necessary and sufficient conditions for the positive Toeplitz operators to be compact.
Influence of degraded visual acuity from light-scattering goggles on obstacle gait  [PDF]
Shunsuke Yamaji, Shinichi Demura, Hiroki Sugiura
Health (Health) , 2011, DOI: 10.4236/health.2011.32018
Abstract: This study examined the effect on gait of de-grading visual input by simulation on a course with obstacles. Thirty healthy, young adult males walked on a 6 m path with three obstacles (height: 5, 10, 20 cm, width: 10 cm) set at inter-vals of 150 cm with and without degraded visual input from light-scattering goggles. Gait was examined with respect to time, length, angle and walk speed parameters. Gait changed signifi-cantly in the degraded visual input condition. The distances between the obstacles and foot before the obstacles were significantly larger in 10 and 20 cm obstacles under the degraded visual input condition, but distances after passing the obstacle had no significant difference among obstacle height. We therefore conclude that a decrease of visual function alters the perception of an obstacle’s height, particularly the 5 cm height obstacle.
Correlated-Electron Systems and High-Temperature Superconductivity  [PDF]
Takashi Yanagisawa, Mitake Miyazaki, Kunihiko Yamaji
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.46A008
Abstract:

We present recent theoretical results on superconductivity in correlated-electron systems, especially in the two-dimensional Hubbard model and the three-band d-p model. The mechanism of superconductivity in high-temperature superconductors has been extensively studied on the basis of various electronic models and also electron-phonon models. In this study, we investigate the properties of superconductivity in correlated-electron systems by using numerical methods such as the variational Monte Carlo method and the quantum Monte Carlomethod. The Hubbard model is one of basic models for strongly correlated electron systems, and is regarded as the model of cuprate high temperature superconductors. The d-p model is more realistic model for cuprates. The superconducting condensation energy obtained by adopting the Gutzwiller ansatz is in reasonable agreement with the condensation energy estimated for YBa2Cu3O7. We show the phase diagram of the ground state using this method. We have further investigated the stability of striped and checkerboard states in the under-doped region. Holes doped in a half-filled square lattice lead to an incommensurate spin and charge density wave. The relationship of the hole density x and incommensurability δ, δ~x, is satisfied in the lower doping region, as indicated by the variationalMonte Carlocalculations for the two-dimensional Hubbard model. A checkerboard-like charge-density modulation with a roughly period has also been observed by scanning tunneling microscopy experiments in Bi2212

Electron Correlation in High Temperature Cuprates  [PDF]
Takashi Yanagisawa, Mitake Miyazaki, Kunihiko Yamaji
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.25010
Abstract: Electron correlation plays a key role in high-temperature cuprate superconductors. Material-parameter dependence of cuprates is important to clarify the mechanism of high temperature superconductivity. In this study, we examine the ground state of the three-band Hubbard model (d-p model) that explicitly includes oxygen p orbitals. We consider the half-filled case with the large
on-site Coulomb repulsion Ud by using the variational Monte Carlo method. The ground state is insulating when Ud is large at half-filling. The ground state undergoes a transition from a metal to a Mott insulator when the level difference εp-εd is increased.
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