134,554 research outputs found
Mixed Power Control Strategies for Cognitive Radio Networks under SINR and Interference Temperature Constraints
Without consideration of the minimum signal-to-interference-plus-noise ratio (SINR) and frequent information exchange, traditional power control algorithms can not always satisfy SINR requirements of secondary users (SUs) and primary users (PUs) in cognitive radio networks. In this paper, a distributed power control problem for maximizing total throughput of SUs is studied subject to the SINR constraints of SUs and the interference constraints of PUs. To reduce message exchange among SUs, two improved methods are obtained by dual decomposition approaches. For a large-scale network, an average interference constraint is presented at the cost of performance degradation. For a small-scale network, a weighted interference constraint with fairness consideration is proposed to obtain good performance. Simulation results demonstrate that the proposed algorithm is superior to ADCPC and TPCG algorithms
Control of fast electron propagation in foam target by high-Z doping
The influence of high-Z dopant (Bromine) in low-Z foam (polystyrene) target
on laser-driven fast electron propagation is studied by the 3D hybrid
particle-in-cell (PIC)/fluid code HEETS.It is found that the fast electrons are
better confined in doped targets due to the increasing resistivity of the
target, which induces a stronger resistive magnetic field which acts to
collimate the fast electron propagation.The energy deposition of fast electrons
into the background target is increased slightly in the doped target, which is
beneficial for applications requiring long distance propagation of fast
electrons, such as fast ignition
Coherent field emission image of graphene predicted with a microscopic theory
Electrons in the mono-layer atomic sheet of graphene have a long coherence
length of the order of micrometers. We will show that this coherence is
transmitted into the vacuum via electric field assisted electron emission from
the graphene edge. The emission current density is given analytically. The
parity of the carbon pi-electrons leads to an image whose center is dark as a
result of interference. A dragonfly pattern with a dark body perpendicular to
the edge is predicted for the armchair edge whose emission current density is
vanishing with the mixing angle of the pseudo-spin. The interference pattern
may be observed up to temperatures of thousand Kelvin as evidence of coherent
field emission. Moreover, this phenomenon leads to a novel coherent electron
line source that can produce interference patterns of extended objects with
linear sizes comparable to the length of the graphene edge.Comment: 6 pages, 3 figure
The nature of symmetric instability and its similarity to convective and inertial instability
It is shown that there exists a local similarity among SI (Symmetric Instability), BI (Buoyancy or Convective Instability), and II (Inertial Instability) even for fully nonlinear viscous motion. The most unstable slope angles for SI and Moist SI motions are analyzed based on parcel energetics. These considerations also suggest qualitatively that CSI (Conditional SI) circulations will be slantwise and lie between the moist most unstable slope and dry least stable slope of the basic state
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