401 research outputs found
Finite Size Effects and Conformal Symmetry of Nonlinear Model in Three Dimensions
We study the nonlinear model on a three-dimensional compact
space (of radii and respectively) by means of large
expansion, focusing on the finite size effects and conformal symmetries of
this model at the critical point. We evaluate the correlation length and the
Casimir energy of this model and study their dependence on and . We
examine the modular transformation properties of the partition function, and
study the dependence of the specific heat on the mass gap in view of possible
extension of the theorem to three dimensions.Comment: 12 pages uuencoded compressed PostScript file including 1 figur
Implementation and Performance Evaluation of Distributed Autonomous Multi-Hop Vehicle-to-Vehicle Communications over TV White Space
This paper presents design and experimental evaluation of a distributed autonomous multi-hop vehicle-to-vehicle (V2V) communication system over TV white space performed in Japan. We propose the two-layer control channel model, which consists of the Zone Aware Control Channel (ZACC) and the Swarm Aware Control Channel (SACC), to establish the multi-hop network. Several vehicles construct a swarm using location information shared through ZACC, and share route and channel information, and available white space information through SACC. To evaluate the system we carried out field experiments with swarm made of three vehicles in a convoy. The vehicles observe channel occupancy via energy detection and agree on the control and the data channels autonomously. For coarse synchronization of quiet periods for sensing we use GPS driven oscillators, and introduce a time margin to accommodate for remaining drift. When a primary user is detected in any of the borrowed channels, the vehicles switch to a vacant channel without disrupting the ongoing multi-hop communication. We present the experimental results in terms of the time to establish control channel, channel switching time, delivery ratio of control message exchange, and throughput. As a result, we showed that our implementation can provide efficient and stable multi-hop V2V communication by using dynamic spectrum access (DSA) techniques
<ORIGINAL>A prospective randomized clinical study on the efficacy of CO_2 lasers on initial stage endodontics
The purpose of this study was to evaluate the clinical efficacy of the CO_2 laser in a prospective randomized trial. A total of 112 teeth in 112 patients, previously treated pulpectomy procedures were gathered and randomly divided into two groups composed of 56. Irradiation was performed on one group and non-irradiation forms of treatment were performed on the other group. On the first group of teeth, root canal enlargement was done and followed by exposure of the canal to a CO_2 laser light (5W, 200msec) using 3 cycles each at a rate of 15 seconds per cycle. The second group was not exposed to laser light following root canal enlargement. The laser was applied on the root canal for a controlled period of time. On the day following pulpectomy, a statistically significant (p < 0.05) fewer number of patients observed pain in the irradiation group compared to the non-irradiation group. The treatment times and the total treatment days in the irradiation group are shorter than in the non-irradiation group (p < 0.05). Multivariate analysis showed that the laser treatment was significantly associated with treatment times. This study shows that the degree of oral pain was greatly reduced in patients who underwent laser irradiation as compared to these who did not. Our study suggests that the use of laser treatment provide significant short-term improvement compared to conventional forms of treatment performed during pulpectomy
Reconstructing Dark Matter Density with e^+e^- Linear Collider in Focus-Point Supersymmetry
It has been known that, in the focus point scenario of supersymmetry, the
thermal relic of the lightest superparticle (LSP) is known to be a good
candidate of the cold dark matter. Assuming that the LSP in the focus-point
scenario be the cold dark matter, we address a question how and how well the
relic density of the LSP can be determined once the superparticles are found at
future e^+e^- linear collider. We will see that the determinations of the mass
of the LSP as well as those of the Higgsino-like chargino and neutralinos,
which will be possible by a study of the decay kinematics of the chargino or by
threshold scan, will give us important information to theoretically reconstruct
the relic density. Even if the Higgsino-like superparticles and the LSP are the
only superparticles which are kinematically accessible, relic density of the
LSP may be calculated with the accuracy of factor \sim 2; by adopting a mild
theoretical assumption or by determining the masses of the Wino-like
superparticles, uncertaintiy can be reduced to \sim 10 % or smaller.Comment: 13 pages, 4 figure
Study on cause of quenching at the joint between multifilamentary superconducting cable and normal conducting cable using 3D FEM
Investigates the cause of quenching at the joint between a multifilamentary superconducting cable and a normal conducting cable. The 3D current distribution is analyzed. It is found that the cause of quenching is the extreme concentration of current in the joint due to the pronounced skin effect at liquid helium temperature. The mechanism of the concentration of current which is affected by the twist pitch and skin depth is also clarified quantitatively by numerical analysis</p
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