5,607 research outputs found
A Hybrid Quantum Encoding Algorithm of Vector Quantization for Image Compression
Many classical encoding algorithms of Vector Quantization (VQ) of image
compression that can obtain global optimal solution have computational
complexity O(N). A pure quantum VQ encoding algorithm with probability of
success near 100% has been proposed, that performs operations 45sqrt(N) times
approximately. In this paper, a hybrid quantum VQ encoding algorithm between
classical method and quantum algorithm is presented. The number of its
operations is less than sqrt(N) for most images, and it is more efficient than
the pure quantum algorithm.
Key Words: Vector Quantization, Grover's Algorithm, Image Compression,
Quantum AlgorithmComment: Modify on June 21. 10pages, 3 figure
Creep characterisation of Inconel 718 lattice metamaterials manufactured by laser powder bed fusion
Lattice metamaterials manufactured by laser powder bed fusion (LPBF) are limited by their performance for critical applications. LPBF materials have microstructural or macroscale anomalies, such as suboptimal grain size, morphology, and lack of fusion. This results in LPBF metamaterials performance degradation for various mechanical properties, such as creep, which has seldom been researched. To understand the creep behavior of LPBF Inconel 718, body-centered cubic metamaterials are fabricated for creep test at 650 °C. Kachanov's damage modeling is used to predict the creep performance of the metamaterials under different loading conditions. Microstructural characterization is performed with scanning electron microscopy to identify critical microstructure defects affecting the failure mechanisms and creep behaviors of the metamaterials. It is shown in the results that the loading conditions affect the fracture process of the metamaterials owing to different failure mechanisms. In the simulation and test results, the logarithmic decline in creep life is shown when loading increases; also, logarithmic increase in the creep life is shown when relative density increases
Solution of two channel spin-flavor Kondo model
We investigate a model where an impurity couples to both the spin and the
flavor currents of the two channel conduction electrons. This model can be used
as a prototype model of a magnetic impurity tunneling between two sites in a
metal and of some heavy fermion systems where the ground state of the impurity
has a fourfold degeneracy. The system is shown to flow to a doubly degenerate
non fermi-liquid(NFL) fixed point; the thermodynamic quantities show NFL
behaviors, but the transport quantities show fermi liquid (FL) behaviors . A
spin-flavor coupling double tensor term is shown to drive the system to one of
the two singlet FL fixed points. The relation with SU(4) Coqblin-Schrieffer
model is studied. The implications on the possible experiments are given.Comment: 11 pages, REVTEX, no figures. To appear in Phys. Rev. B (Rapid Comm.)
July 1, 199
Performance evaluation of video streaming on LTE with coexistence of Wi-Fi signal
The continuous growth in mobile data traffic and limited license wireless spectrum have led to dramatically increase the demand of the radio spectrum. It is widespread the concern about the coexistence of long term evolution (LTE) and Wi-Fi in the unlicensed band. There are several techniques have been proposed to enable the coexistence of LTE and Wi-Fi in the unlicensed band, but these works are targeted on the impact of the LTE to the Wi-Fi network performance. An experiment is carried out in this work to evaluate the impact of Wi-Fi signal on the video streaming in the LTE network. The experimental test comprised of the national instrument (NI) universal software radio peripheral (USRP) 2953R that is controlled by the LabVIEW Communication LTE application framework. Extensiveexperiments are carried out under two scenarios, i.e. (1) Coexistence of LTE and Wi-Fi signal, (2) LTE signal only. Performance evaluations are carried out with different Modulation and coding schemes (MCS) values and different mode of operations, i.e. frequency division duplex (FDD) and time division duplex (TDD) mode. The results illustrated that the interference from Wi-Fi signal caused the performance degradation of the LTE network in throughput and the power received by user equipment (UE)
Enhanced exponential rule scheduling algorithm for real-time traffic in LTE network
Nowadays, mobile communication is growing rapidly and become an everyday commodity. The vast deployment of real-time services in Long Term Evolution (LTE) network demands for the scheduling techniques that support the Quality of Service (QoS) requirements. LTE is designed and implemented to fulfill the users’ QoS. However, 3GPP does not define the specific scheduling technique for resource distribution which leads to vast research and development of the scheduling techniques. In this context, a review of the recent scheduling algorithm is reported in the literature. These schedulers in the literature cause high Packet Loss Rate (PLR), low fairness, and high delay. To cope with these disadvantages, we propose an enhanced EXPRULE (eEXPRULE) scheduler to improve the radio resource utilization in the LTE network. Extensive simulation works are carried out and the proposed scheduler provides a significant performance improvement for video application without sacrificing the VoIP performance. The eEXPRULE scheduler increases video throughput, spectrum efficiency, and fairness by 50%, 13%, and 11%, respectively, and reduces the video PLR by 11%
Nuclear Physics Multimessenger Astrophysics Constraints on the Neutron Star Equation of State: Adding NICER's PSR J0740+6620 Measurement
In the past few years, new observations of neutron stars (NSs) and NS mergers have provided a wealth of data that allow one to constrain the equation of state (EOS) of nuclear matter at densities above nuclear saturation density. However, most observations were based on NSs with masses of about 1.4 M⊙, probing densities up to ∼three to four times the nuclear saturation density. Even higher densities are probed inside massive NSs such as PSR J0740+6620. Very recently, new radio observations provided an update to the mass estimate for PSR J0740+6620, and X-ray observations by the NICER and XMM telescopes constrained its radius. Based on these new measurements, we revisit our previous nuclear physics multimessenger astrophysics constraints and derive updated constraints on the EOS describing the NS interior. By combining astrophysical observations of two radio pulsars, two NICER measurements, the two gravitational-wave detections GW170817 and GW190425, detailed modeling of the kilonova AT 2017gfo, and the gamma-ray burst GRB 170817A, we are able to estimate the radius of a typical 1.4 M⊙ NS to be 11.94-0.87+0.76 km at 90% confidence. Our analysis allows us to revisit the upper bound on the maximum mass of NSs and disfavors the presence of a strong first-order phase transition from nuclear matter to exotic forms of matter, such as quark matter, inside NSs
Transport properties of one-dimensional interacting fermions in aperiodic potentials
Motivated by the existence of metal-insulator transition in one-dimensional
non-interacting fermions in quasiperiodic and pseudorandom potentials, we
studied interacting spinless fermion models using exact many-body Lanczos
diagonalization techniques. Our main focus was to understand the effect of the
fermion-fermion interaction on the transport properties of aperiodic systems.
We calculated the ground state energy and the Kohn charge stiffness Dc. Our
numerical results indicate that there exists a region in the interaction
strength parameter space where the system may behave differently from the
metallic and insulating phases. This intermediate phase may be characterized by
a power law scaling of the charge stiffness constant in contrast to the
localized phase where Dc scales exponentially with the size of the system.Comment: 11 pages LaTex document with 5 eps figures. Uses revtex style file
Crossover between Fermi Liquid and non-Fermi Liquid in Orbitally Degenerate Kondo Systems
Entanglement of spin and orbital Kondo effect is investigated on the basis of
a Kondo-type exchange model with twofold orbital degeneracy. By using Wilson's
numerical renormalization-group method, we examine dynamical and thermal
properties respecting the difference in time-reversal property of multipole
operators. In the presence of particle-hole symmetry, the model has a new
non-Fermi-liquid fixed point with a fractional entropy. The spectral intensity
of the quadrupole susceptibility diverges in the zero-frequency limit, while
the dipole susceptibility shows a Fermi-liquid-like behavior. This is
understood by mapping to the two-channel Kondo model, in which the dipole
moment is mapped onto the operators with the scaling dimension ,
while the quadrupole moment onto the operators with another scaling dimension
. Even for a fairly particle-hole asymmetric case with the
Fermi-liquid ground state, the non-Fermi-liquid behavior has significant
influences in electric and thermal properties.Comment: 7 pages, 9 figures, to appear in J. Phys Soc. Jpn. Vol. 68 No. 12,
title changed and some corrections mad
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