214 research outputs found
Thermally assisted quantum vortex tunneling in the Hall and dissipative regime
Quantum vortex tunneling is studied for the case where the Hall and the
dissipative dynamics are simultaneously present. For a given temperature, the
magnetization relaxation rate is calculated as a function of the external
current and the quasiparticle scattering time. The relaxation rate is solved
analytically at zero temperature and obtained numerically at finite
temperatures by the variational method. In the moderately clean samples, we
have found that a minimum in the relaxation rate exists at zero temperature,
which tends to disappear with increase in the temperature.Comment: 18 pages, 9 figures, to be published in Phys. Rev.
A theoretical model for predicting Schottky-barrier height of the nanostructured silicide-silicon junction
ABSTRACT
In this work, we have performed the first-principles calculations to investigate the Schottky barrier height (SBH) of various nanostructured silicide-silicon junctions. As for the silicides, PtSi, NiSi, TiSi2, and YSi2 have been used. We find that EFiF = EFi – EF, where EFi and EF are the intrinsic Fermi level of the semiconductor part and the Fermi level of the junction, respectively, is unchanged by nanostructuring. From this finding, we suggest a model, a symmetric increase of the SBH (SI) model, to properly predict SBHs of nanostructured silicide-silicon junctions. We also suggest two measurable quantities for the experimental validation of our model. The effect of our SI model applied to nanostructures such as nanowires and ultra-thin-bodies is compared with that of the widely used previous SBH model
Differential Spiral Joint Mechanism for Coupled Variable Stiffness Actuation
In this study, we present the Differential Spiral Joint (DSJ) mechanism for
variable stiffness actuation in tendon-driven robots. The DSJ mechanism
semi-decouples the modulation of position and mechanical stiffness, allowing
independent trajectory tracking in different parameter space. Past studies show
that increasing the mechanical stiffness achieves the wider range of renderable
stiffness, whereas decreasing the mechanical stiffness improves the quality of
actuator decoupling and shock absorbance. Therefore, it is often useful to
modulate the mechanical stiffness to balance the required level of stiffness
and safety. In addition, the DSJ mechanism offers a compact form factor, which
is suitable for applications where the size and weight are important. The
performance of the DSJ mechanism in various areas is validated through a set of
experiments
B+-tree Index Optimization by Exploiting Internal Parallelism of Flash-based Solid State Drives
Previous research addressed the potential problems of the hard-disk oriented
design of DBMSs of flashSSDs. In this paper, we focus on exploiting potential
benefits of flashSSDs. First, we examine the internal parallelism issues of
flashSSDs by conducting benchmarks to various flashSSDs. Then, we suggest
algorithm-design principles in order to best benefit from the internal
parallelism. We present a new I/O request concept, called psync I/O that can
exploit the internal parallelism of flashSSDs in a single process. Based on
these ideas, we introduce B+-tree optimization methods in order to utilize
internal parallelism. By integrating the results of these methods, we present a
B+-tree variant, PIO B-tree. We confirmed that each optimization method
substantially enhances the index performance. Consequently, PIO B-tree enhanced
B+-tree's insert performance by a factor of up to 16.3, while improving
point-search performance by a factor of 1.2. The range search of PIO B-tree was
up to 5 times faster than that of the B+-tree. Moreover, PIO B-tree
outperformed other flash-aware indexes in various synthetic workloads. We also
confirmed that PIO B-tree outperforms B+-tree in index traces collected inside
the Postgresql DBMS with TPC-C benchmark.Comment: VLDB201
Learning Quadrupedal Locomotion with Impaired Joints Using Random Joint Masking
Quadrupedal robots have played a crucial role in various environments, from
structured environments to complex harsh terrains, thanks to their agile
locomotion ability. However, these robots can easily lose their locomotion
functionality if damaged by external accidents or internal malfunctions. In
this paper, we propose a novel deep reinforcement learning framework to enable
a quadrupedal robot to walk with impaired joints. The proposed framework
consists of three components: 1) a random joint masking strategy for simulating
impaired joint scenarios, 2) a joint state estimator to predict an implicit
status of current joint condition based on past observation history, and 3)
progressive curriculum learning to allow a single network to conduct both
normal gait and various joint-impaired gaits. We verify that our framework
enables the Unitree's Go1 robot to walk under various impaired joint conditions
in real-world indoor and outdoor environments.Comment: Appear to ICRA 2024, Project page:
https://sites.google.com/view/learning-impaired-joints-loc
Study on Replacement Plan with Statistical Analysis for Water Distribution Pipelines
首都大学東京, 2014-09-30, 博士(工学), 甲第414号首都大学東
Physics data management tools: computational evolutions and benchmarks
The development of a package for the management of physics data is described:
its design, implementation and computational benchmarks. This package improves
the data management tools originally developed for Geant4 physics models based
on the EADL, EEDL and EPDL97 data libraries. The implementation exploits recent
evolutions of the C++ libraries appearing in the C++0x draft, which are
intended for inclusion in the next C++ ISO Standard. The new tools improve the
computational performance of physics data management.Comment: 6 pages, to appear in proceedings of the Joint International
Conference on Supercomputing in Nuclear Applications and Monte Carlo 2010
(SNA + MC2010
A Case Study of Health Tourism in the Jeju Province, South Korea
The United States Census Bureau (2006) reported that in 2005 more than 46 million Americans lacked health insurance, and that by 2019 national spending for health care would exceed $4.5 trillion (Centers for Medicare & Medicaid Services, 2010). Because those numbers are expected to increase, health tourists are seeking better opportunities for low-cost, high-quality treatment in other countries, plus the added benefit of experiencing foreign cultures. Health tourism is a rapidly growing market in both advanced and developing countries. The purpose of this study was to develop an applicable model of health tourism, the Jeju-Style Health Tourism Model, for Jeju Special Self-Governing Province, in the Republic of Korea (South Korea) and to provide other cities and countries with its implications. This study employed a focus group, indepth interviews, and content analysis to discover important factors in developing the model. The results suggested that four major sources must be executed together to maximize the benefits of health tourism development. On a foundation of natural resources, knowledge-based resources were most important (54.5%), followed by artificial resources (25.7%), and expenses-based resources (19.8%)
Analysis of user requirement on U-Healthcare system
Abstract The objective of this study was to explore and connect the relation between independent variables of Health Promotion Model (HPM) and customers" demand for developing ubiquitous healthcare (u-Healthcare) system and then, to suggest the methods applicable to the system design. After identifying performance levels and influence coefficients of every variables and applying them to Quality Function Deployment (QFD) to find out the relation between the requirements and customers" demand of u-Healthcare System, it sets the main goal in determining what are important system characteristics for effective quality improvement. First, it applied structural equation modeling (SEM) to search for multiple independent variables influencing user"s intention. Second, with the findings, this study has also its significance in suggesting techniques applicable to the u-Healthcare system development using QFD. Concretely, by investigating u-Healthcare users" direct requirement attributes and extracting u-Healthcare system service characteristics with customer requirement reflected by using QFD model, this study figured out the order of priority in the importance of system characteristics that must be dealt with most importantly. As a result of analysis, this study proposed an application method of QFD to satisfy customer requirements for the development of u-Healthcare system. Finally, the result could give important features to improve users" requirements by using this process
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