The Experts below are selected from a list of 3954 Experts worldwide ranked by ideXlab platform
Takahisa Ohno - One of the best experts on this subject based on the ideXlab platform.
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theoretical insight into charging process in a li3po4 100 lifepo4 010 Coherent Interface system
Solid State Ionics, 2016Co-Authors: Masato Sumita, Yoshinori Tanaka, Minoru Ikeda, Takahisa OhnoAbstract:Abstract We have investigated the introduction of Li vacancy (VLi× in the Kroger–Vink notation) into a Li3PO4 (100)/LiFePO4 (010) Coherent Interface with the density functional theory in order to gain an insight into the initial stage of the charging process. The VLi× introduction results in the formation of a Li ion vacancy (VLi′) and hole (h). When one VLi× is introduced in each bulk LiFePO4 and Li3PO4 materials (both VLi′ and h are donated to the position in the proximity of the initial VLi× position), the formation energies of the Li vacancy (EV) are quite different between them. On the other hand, when introduced into the Li3PO4/LiFePO4 Interface system, the values of EV in the LiFePO4 and Li3PO4 bulk regions of the Interface become almost equal. This is because irrespective of the introduced VLi× position, the associated h is always donated to the LiFePO4 region while the Li3PO4 region keeps its insulating properties. Although the Li atoms near the Interface have smaller EV than in the bulk regions, it is suggested that only a fraction of them may be extracted at the initial stage of charging which is not enough to lead to the Li depletion at the Interface and as a result the effect of the space charge layer may be negligible in the Li3PO4/LiFePO4 Interface.
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theoretically designed li3po4 100 lifepo4 010 Coherent electrolyte cathode Interface for all solid state li ion secondary batteries
Journal of Physical Chemistry C, 2015Co-Authors: Masato Sumita, Yoshinori Tanaka, Minoru Ikeda, Takahisa OhnoAbstract:Controlling the electrolyte/electrode Interface is of great importance to promote new-generation solid-state Li ion secondary batteries. In this paper, we report a theoretically designed electrolyte/cathode Coherent Interface at the density functional theory level, where γ-Li3PO4 and LiFePO4 are used as an electrolyte and a cathode, respectively. At the stoichiometric Li3PO4 (100)/LiFePO4 (010) Coherent Interface, there are vacant Li-sites that give the chance for Li ions to migrate. From the density functional molecular dynamics at 1500 K, it is found that this Interface is stable and no impurity phase is produced, and also that Li ions in the Li3PO4 phase around the Interface can diffuse with large diffusion coefficients. The dynamic behavior of these Li ions is also reflected in the layered phonon spectra of Li ions; the diffusible Li ions around the Interface have the same spectrum.
Takashi Uchino - One of the best experts on this subject based on the ideXlab platform.
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Coherent Interface structures and intergrain josephson coupling in dense mgo mg2si mgb2 nanocomposites
Journal of Applied Physics, 2016Co-Authors: Katsuya Ueno, Yukihito Nagashima, Yusuke Seto, Takahiro Sakurai, Hitoshi Ohta, Megumi Matsumoto, Kazuyuki Takahashi, Takashi UchinoAbstract:Many efforts are under way to control the structure of heteroInterfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heteroInterfaces is challenging because the crystal/crystal Interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg2Si)/superconductor(MgB2) nanocomposites with atomically smooth and continuous Interfaces, including epitaxial-like MgO/Mg2Si Interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB2 nanograins surrounded by the MgO/Mg2Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a s...
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Coherent Interface structures and intergrain Josephson coupling in dense MgO/Mg2Si/MgB2nanocomposites
Journal of Applied Physics, 2016Co-Authors: Katsuya Ueno, Yukihito Nagashima, Yusuke Seto, Takahiro Sakurai, Hitoshi Ohta, Megumi Matsumoto, Kazuyuki Takahashi, Takashi UchinoAbstract:© 2016 Author(s). Many efforts are under way to control the structure of heteroInterfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heteroInterfaces is challenging because the crystal/crystal Interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg 2 Si)/superconductor(MgB 2 ) nanocomposites with atomically smooth and continuous Interfaces, including epitaxial-like MgO/Mg 2 Si Interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transitio n at 36 K owing to the MgB 2 nanograins surrounded by the MgO/Mg 2 Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality Interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.
Katsuya Ueno - One of the best experts on this subject based on the ideXlab platform.
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Coherent Interface structures and intergrain josephson coupling in dense mgo mg2si mgb2 nanocomposites
Journal of Applied Physics, 2016Co-Authors: Katsuya Ueno, Yukihito Nagashima, Yusuke Seto, Takahiro Sakurai, Hitoshi Ohta, Megumi Matsumoto, Kazuyuki Takahashi, Takashi UchinoAbstract:Many efforts are under way to control the structure of heteroInterfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heteroInterfaces is challenging because the crystal/crystal Interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg2Si)/superconductor(MgB2) nanocomposites with atomically smooth and continuous Interfaces, including epitaxial-like MgO/Mg2Si Interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB2 nanograins surrounded by the MgO/Mg2Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a s...
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Coherent Interface structures and intergrain Josephson coupling in dense MgO/Mg2Si/MgB2nanocomposites
Journal of Applied Physics, 2016Co-Authors: Katsuya Ueno, Yukihito Nagashima, Yusuke Seto, Takahiro Sakurai, Hitoshi Ohta, Megumi Matsumoto, Kazuyuki Takahashi, Takashi UchinoAbstract:© 2016 Author(s). Many efforts are under way to control the structure of heteroInterfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heteroInterfaces is challenging because the crystal/crystal Interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg 2 Si)/superconductor(MgB 2 ) nanocomposites with atomically smooth and continuous Interfaces, including epitaxial-like MgO/Mg 2 Si Interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transitio n at 36 K owing to the MgB 2 nanograins surrounded by the MgO/Mg 2 Si matrix. This transition is followed by the intergrain phase-lock transition at ∼24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality Interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.
Masato Sumita - One of the best experts on this subject based on the ideXlab platform.
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theoretical insight into charging process in a li3po4 100 lifepo4 010 Coherent Interface system
Solid State Ionics, 2016Co-Authors: Masato Sumita, Yoshinori Tanaka, Minoru Ikeda, Takahisa OhnoAbstract:Abstract We have investigated the introduction of Li vacancy (VLi× in the Kroger–Vink notation) into a Li3PO4 (100)/LiFePO4 (010) Coherent Interface with the density functional theory in order to gain an insight into the initial stage of the charging process. The VLi× introduction results in the formation of a Li ion vacancy (VLi′) and hole (h). When one VLi× is introduced in each bulk LiFePO4 and Li3PO4 materials (both VLi′ and h are donated to the position in the proximity of the initial VLi× position), the formation energies of the Li vacancy (EV) are quite different between them. On the other hand, when introduced into the Li3PO4/LiFePO4 Interface system, the values of EV in the LiFePO4 and Li3PO4 bulk regions of the Interface become almost equal. This is because irrespective of the introduced VLi× position, the associated h is always donated to the LiFePO4 region while the Li3PO4 region keeps its insulating properties. Although the Li atoms near the Interface have smaller EV than in the bulk regions, it is suggested that only a fraction of them may be extracted at the initial stage of charging which is not enough to lead to the Li depletion at the Interface and as a result the effect of the space charge layer may be negligible in the Li3PO4/LiFePO4 Interface.
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theoretically designed li3po4 100 lifepo4 010 Coherent electrolyte cathode Interface for all solid state li ion secondary batteries
Journal of Physical Chemistry C, 2015Co-Authors: Masato Sumita, Yoshinori Tanaka, Minoru Ikeda, Takahisa OhnoAbstract:Controlling the electrolyte/electrode Interface is of great importance to promote new-generation solid-state Li ion secondary batteries. In this paper, we report a theoretically designed electrolyte/cathode Coherent Interface at the density functional theory level, where γ-Li3PO4 and LiFePO4 are used as an electrolyte and a cathode, respectively. At the stoichiometric Li3PO4 (100)/LiFePO4 (010) Coherent Interface, there are vacant Li-sites that give the chance for Li ions to migrate. From the density functional molecular dynamics at 1500 K, it is found that this Interface is stable and no impurity phase is produced, and also that Li ions in the Li3PO4 phase around the Interface can diffuse with large diffusion coefficients. The dynamic behavior of these Li ions is also reflected in the layered phonon spectra of Li ions; the diffusible Li ions around the Interface have the same spectrum.
Alan D George - One of the best experts on this subject based on the ideXlab platform.
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a user level multicast performance comparison of scalable Coherent Interface and myrinet interconnects
Local Computer Networks, 2003Co-Authors: S Oral, Alan D GeorgeAbstract:This paper compares and evaluates the multicast performance of two of the most widely deployed system-area networks (SANs), Dolphin's scalable Coherent Interface (SCI) and Myricom's Myrinet. Both networks deliver low latency and high bandwidth to applications, but do not support multicast in hardware. We compared SCI and Myrinet in terms of their user-level performance using various software-based multicast algorithms under various networking and multicasting scenarios. The strengths and weaknesses of each network are comparatively presented in terms of numerous metrics, such as multicast completion latency, CPU utilization, link concentration and concurrency.
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LCN - A user-level multicast performance comparison of scalable Coherent Interface and Myrinet interconnects
28th Annual IEEE International Conference on Local Computer Networks 2003. LCN '03. Proceedings., 2003Co-Authors: S Oral, Alan D GeorgeAbstract:This paper compares and evaluates the multicast performance of two of the most widely deployed system-area networks (SANs), Dolphin's scalable Coherent Interface (SCI) and Myricom's Myrinet. Both networks deliver low latency and high bandwidth to applications, but do not support multicast in hardware. We compared SCI and Myrinet in terms of their user-level performance using various software-based multicast algorithms under various networking and multicasting scenarios. The strengths and weaknesses of each network are comparatively presented in terms of numerous metrics, such as multicast completion latency, CPU utilization, link concentration and concurrency.
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a comparative throughput analysis of scalable Coherent Interface and myrinet
Local Computer Networks, 2002Co-Authors: S Millich, Alan D George, S OralAbstract:It has become increasingly popular to construct large parallel computers by connecting many inexpensive nodes built with commercial-off-the-shelf (COTS) parts. These clusters can be built at a much lower cost than traditional supercomputers of comparable performance. A key decision that will greatly affect the overall performance of the cluster is the method used to connect the nodes together. Choosing the best interconnect and topology is not at all trivial since performance and cost will change as the system size is scaled. This paper presents throughput models used for the analysis and comparison of performance in two leading system area networks (SAN), Myrinet and Scalable Coherent Interface (SCI). First, analytical models for throughput are developed by determining the theoretical bandwidth of all internal buses and links that are part of the interconnect architecture. Then, experiments are conducted to measure the actual bandwidth available at each of these components, and the models are calibrated so they accurately represent the experimental results. Finally, the models are used to compare the maximum throughput of Myrinet and SCI systems with respect to system size and overall dollar cost.
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LCN - A comparative throughput analysis of Scalable Coherent Interface and Myrinet
27th Annual IEEE Conference on Local Computer Networks 2002. Proceedings. LCN 2002., 2002Co-Authors: S Millich, Alan D George, S OralAbstract:It has become increasingly popular to construct large parallel computers by connecting many inexpensive nodes built with commercial-off-the-shelf (COTS) parts. These clusters can be built at a much lower cost than traditional supercomputers of comparable performance. A key decision that will greatly affect the overall performance of the cluster is the method used to connect the nodes together. Choosing the best interconnect and topology is not at all trivial since performance and cost will change as the system size is scaled. This paper presents throughput models used for the analysis and comparison of performance in two leading system area networks (SAN), Myrinet and Scalable Coherent Interface (SCI). First, analytical models for throughput are developed by determining the theoretical bandwidth of all internal buses and links that are part of the interconnect architecture. Then, experiments are conducted to measure the actual bandwidth available at each of these components, and the models are calibrated so they accurately represent the experimental results. Finally, the models are used to compare the maximum throughput of Myrinet and SCI systems with respect to system size and overall dollar cost.
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On the performance and reliability of fault-tolerant scalable Coherent Interface networks
1999Co-Authors: Mushtaq A. Sarwar, Alan D GeorgeAbstract:Mission-critical, critical-computation, and other demanding applications can benefit from low-latency, high-bandwidth interconnects. These applications also demand fault tolerance to maintain connectivity of all data processing nodes. From the emerging technologies of high-speed interconnects, the Scalable Coherent Interface has appeared at the forefront, providing high data throughputs while supporting a simple, easily adaptable design. The speed has been exploited in several multiprocessor systems and is becoming increasingly popular among the cluster-computing community. SCI can also be applied to non-computing applications such as aircraft avionics. Unfortunately, such applications require a high degree of fault tolerance that SCI currently does not provide. Currently, SCI lacks the fault-tolerance protocols needed to implement reconfigurable interconnects. In this dissertation, the issues of defining and implementing the fault-tolerance protocols are presented with the ultimate goal of creating reconfigurable, resilient SCI interconnects. This goal is arrived upon using three major stepping stones. The first is the development of a high-fidelity SCI model that can be used to construct and simulate any standard ring-based topology with distributed switching. The results presented are the first high-fidelity simulations of SCI multiprocessor networks with k-ary n-cube topologies. The studies concentrate on the performance scalability of SCI in terms of throughput and latency versus topology size and dimension. The second step in achieving the goal is the extension of the existing SCI fault-tolerance protocols defined by the standard. Implementing these protocols requires hardware additions in the form of fault handlers to detect errors and create, receive, and interpret diagnostic and control packets. The third and final step to achieve the goal is the development of techniques to determine the reliability of the fault-tolerant SCI topologies. Previous k-ary n-cube reliability models were based on the assumption that link failures were independent of one another. This assumption is not valid with ring-based interconnects where a single link failure results in the failure of an entire ringlet within the topology. The reliability model presented is based on the failure probabilities of the ringlets comprising the topology, rather than the failure probabilities of each individual link.