6,243 research outputs found
Accelerator Based Fusion Reactor
A feasibility study of fusion reactors based on accelerators is carried out.
We consider a novel scheme where a beam from the accelerator hits the target
plasma on the resonance of the fusion reaction and establish characteristic
criteria for a workable reactor. We consider the reactions , and in this study. The critical temperature of the plasma is determined
from overcoming the stopping power of the beam with the fusion energy gain. The
needed plasma lifetime is determined from the width of the resonance, the beam
velocity and the plasma density. We estimate the critical beam flux by
balancing the energy of fusion production against the plasma thermo-energy and
the loss due to stopping power for the case of an inert plasma. The product of
critical flux and plasma lifetime is independent of plasma density and has a
weak dependence on temperature. Even though the critical temperatures for these
reactions are lower than those for the thermonuclear reactors, the critical
flux is in the range of for the plasma density
in the case of an inert plasma. Several
approaches to control the growth of the two-stream instability are discussed.
We have also considered several scenarios for practical implementation which
will require further studies. Finally, we consider the case where the injected
beam at the resonance energy maintains the plasma temperature and prolongs its
lifetime to reach a steady state. The equations for power balance and particle
number conservation are given for this case.Comment: To be published in Nuclear Fusion as a letter, 7 pages, 2 figure
Compressed Video Action Recognition
Training robust deep video representations has proven to be much more
challenging than learning deep image representations. This is in part due to
the enormous size of raw video streams and the high temporal redundancy; the
true and interesting signal is often drowned in too much irrelevant data.
Motivated by that the superfluous information can be reduced by up to two
orders of magnitude by video compression (using H.264, HEVC, etc.), we propose
to train a deep network directly on the compressed video.
This representation has a higher information density, and we found the
training to be easier. In addition, the signals in a compressed video provide
free, albeit noisy, motion information. We propose novel techniques to use them
effectively. Our approach is about 4.6 times faster than Res3D and 2.7 times
faster than ResNet-152. On the task of action recognition, our approach
outperforms all the other methods on the UCF-101, HMDB-51, and Charades
dataset.Comment: CVPR 2018 (Selected for spotlight presentation
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Transverse Effect Due to Short Range Resistive Wall Wakefield
For accelerator designs with ultra short electron beams, beam dynamics study has to invoke the short-range wakefields. In this paper, we first obtain the short-range dipole mode resistive wall wakefield. Analytical approach is then developed to study the single bunch transverse beam dynamics due to this short-range resistive wall wake. The results are applied to the LCLS undulator
Aberrant KDM5B expression promotes aggressive breast cancer through MALAT1 overexpression and downregulation of hsa-miR-448
Relative expression of KDM5B, MALAT1, SNAIL, Vimentin and miR 448 normalized against GAPDH in MCF10A WT, MCF10A OE, MDA-MB-231 WT and MDA-MB-231 KD cells. Data are representative of 3 independent experiments and analyzed by studentâs t-test. All data are shown as meanâ±âSEM. WT, wild type; OE, KDM5B overexpressed; KD, knockdown using shKDM5B clone II. (DOCX 519 kb
High Degree Picosecond Pulse Compression in Chalcogenide-Silicon Slot Waveguide Taper
In this paper, we propose and design a chalcogenide (As2S3)-based slot waveguide taper with exponentially decreasing dispersion profile to realize high-degree pulse compression of low-power chirped solitons. Based on the waveguide taper designed, pulse compression of fundamental solitons, and chirped 2-soliton breather are both investigated numerically. With self-similar pulse compression scheme, a 1 ps input pulse is compressed to 81.5 fs in 6 cm propagation. By using 2-soliton breather pulses, a 1 ps chirped pulse is compressed to 80.3 fs in just 2.54 cm. This is the first demonstration of the feasibility of high-degree nonlinear pulse compression in As2S3-based slot waveguide taper
Comprehensive analysis of passive generation of parabolic similaritons in tapered hydrogenated amorphous silicon photonic wires
Parabolic pulses have important applications in both basic and applied sciences, such as high power optical amplification, optical communications, all-optical signal processing, etc. The generation of parabolic similaritons in tapered hydrogenated amorphous silicon photonic wires at telecom (λ~1550 nm) and mid-IR (λâ„2100 nm) wavelengths is demonstrated and analyzed. The self-similar theory of parabolic pulse generation in passive waveguides with increasing nonlinearity is presented. A generalized nonlinear Schrödinger equation is used to describe the coupled dynamics of optical field in the tapered hydrogenated amorphous silicon photonic wires with either decreasing dispersion or increasing nonlinearity. The impacts of length dependent higher-order effects, linear and nonlinear losses including two-photon absorption, and photongenerated free carriers, on the pulse evolutions are characterized. Numerical simulations show that initial Gaussian pulses will evolve into the parabolic pulses in the waveguide taper designed
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