247 research outputs found
Shirakami: A Hybrid Concurrency Control Protocol for Tsurugi Relational Database System
Modern real-world transactional workloads such as bills of materials or
telecommunication billing need to process both short transactions and long
transactions. Recent concurrency control protocols do not cope with such
workloads since they assume only classical workloads (i.e., YCSB and TPC-C)
that have relatively short transactions. To this end, we proposed a new
concurrency control protocol Shirakami. Shirakami has two sub-protocols.
Shirakami-LTX protocol is for long transactions based on multiversion
concurrency control and Shirakami-OCC protocol is for short transactions based
on Silo. Shirakami naturally integrates them with write preservation method and
epoch-based synchronization. Shirakami is a module in Tsurugi system, which is
a production-purpose relational database system
Two-dimensional full particle simulation of a perpendicular collisionless shock with a shock-rest-frame model
A two-dimensional (2D) shock-rest-frame model for particle simulations is
developed. Then full kinetic dynamics of a perpendicular collisionless shock is
examined by means of a 2D full particle simulation. We found that in the 2D
simulation there are fewer nonthermal electrons due to surfing acceleration
which was seen in the previous 1D simulations of a high Mach number
perpendicular shock in a low-beta and weakly magnetized plasma. This is because
the particle motion along the ambient magnetic field disturbs the formation of
coherent electrostatic solitary structures which is necessary for electron
surfing acceleration.Comment: 4 pages, 4 figures, ApJL in press. The paper with full resolution
images is
http://theo.phys.sci.hiroshima-u.ac.jp/~ryo/papers/shock_rest_2D.pd
Ground state of the spin-1/2 chain of green dioptase at high fields
The gem-stone dioptase Cu6Si6O18.6H2O has a chiral crystal structure of
equilateral triangular helices consisting of Cu-3d spins. It shows an
antiferromagnetic order with an easy axis along c at TN = 15.5 K under zero
field, and a magnetization jump at HC = 13.5 T when the field is applied along
c-axis. By 29Si-NMR measurements, we have revealed that the high-field state is
essentially the two sub-lattice structure, and that the component within
ab-plane is collinear. The result indicates no apparent match with the
geometrical pattern of helical spin chain.Comment: SCES2013, Hongo, Toky
Brain-controlled cycling system for rehabilitation following paraplegia with delay-time prediction
Objective: Robotic rehabilitation systems have been investigated to assist with motor dysfunction recovery in patients with lower-extremity paralysis caused by central nervous system lesions. These systems are intended to provide appropriate sensory feedback associated with locomotion. Appropriate feedback is thought to cause synchronous neuron firing, resulting in the recovery of function. Approach: In this study, we designed and evaluated an ergometric cycling wheelchair, with a brain-machine interface (BMI), that can force the legs to move by including normal stepping speeds and quick responses. Experiments were conducted in five healthy subjects and one patient with spinal cord injury (SCI), who experienced the complete paralysis of the lower limbs. Event-related desynchronization (ERD) in the β band (18‐28 Hz) was used to detect lower-limb motor images. Main results: An ergometer-based BMI system was able to safely and easily force patients to perform leg movements, at a rate of approximately 1.6 seconds/step (19 rpm), with an online accuracy rate of 73.1% for the SCI participant. Mean detection time from the cue to pedaling onset was 0.83±0.31 s Significance: This system can easily and safely maintain a normal walking speed during the experiment and be designed to accommodate the expected delay between the intentional onset and physical movement, to achieve rehabilitation effects for each participant. Similar BMI systems, implemented with rehabilitation systems, may be applicable to a wide range of patients
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