Performance of Cross-layer Design with Multiple Outdated Estimates in Multiuser MIMO System

By combining adaptive modulation (AM) and automatic repeat request (ARQ) protocol as well as user scheduling, the cross-layer design scheme of multiuser MIMO system with imperfect feedback is presented, and multiple outdated estimates method is proposed to improve the system performance. Based on this method and imperfect feedback information, the closed-form expressions of spectral efficiency (SE) and packet error rate (PER) of the system subject to the target PER constraint are respectively derived. With these expressions, the system performance can be effectively evaluated. To mitigate the effect of delayed feedback, the variable thresholds (VTs) are also derived by means of the maximum a posteriori method, and these VTs include the conventional fixed thresholds (FTs) as special cases. Simulation results show that the theoretical SE and PER are in good agreement with the corresponding simulation. The proposed CLD scheme with multiple estimates can obtain higher SE than the existing CLD scheme with single estimate, especially for large delay. Moreover, the CLD scheme with VTs outperforms that with conventional FTs

Concurrence of superposition

The bounds on concurrence of the superposition state in terms of those of the states being superposed are studied in this paper. The bounds on concurrence are quite different from those on the entanglement measure based on von Neumann entropy (Phys. Rev. Lett. 97, 100502 (2006)). In particular, a nonzero lower bound can be provided if the states being superposed are properly constrained.Comment: 4 page

On the efficiency of estimating penetrating rank on large graphs

P-Rank (Penetrating Rank) has been suggested as a useful measure of structural similarity that takes account of both incoming and outgoing edges in ubiquitous networks. Existing work often utilizes memoization to compute P-Rank similarity in an iterative fashion, which requires cubic time in the worst case. Besides, previous methods mainly focus on the deterministic computation of P-Rank, but lack the probabilistic framework that scales well for large graphs. In this paper, we propose two efficient algorithms for computing P-Rank on large graphs. The first observation is that a large body of objects in a real graph usually share similar neighborhood structures. By merging such objects with an explicit low-rank factorization, we devise a deterministic algorithm to compute P-Rank in quadratic time. The second observation is that by converting the iterative form of P-Rank into a matrix power series form, we can leverage the random sampling approach to probabilistically compute P-Rank in linear time with provable accuracy guarantees. The empirical results on both real and synthetic datasets show that our approaches achieve high time efficiency with controlled error and outperform the baseline algorithms by at least one order of magnitude

A Bi-Hamiltonian Formulation for Triangular Systems by Perturbations

A bi-Hamiltonian formulation is proposed for triangular systems resulted by perturbations around solutions, from which infinitely many symmetries and conserved functionals of triangular systems can be explicitly constructed, provided that one operator of the Hamiltonian pair is invertible. Through our formulation, four examples of triangular systems are exhibited, which also show that bi-Hamiltonian systems in both lower dimensions and higher dimensions are many and varied. Two of four examples give local 2+1 dimensional bi-Hamiltonian systems and illustrate that multi-scale perturbations can lead to higher-dimensional bi-Hamiltonian systems.Comment: 16 pages, to appear in J. Math. Phy

Automorphism groups of smooth quintic threefolds

We study automorphism groups of smooth quintic threefolds. Especially, we describe all the maximal ones with explicit examples of target quintic threefolds. There are exactly $22$ such groups

School Culture and School Effectiveness: The Mediating Effect of Teachers’ Job Satisfaction

This study has investigated the relationship among school culture, teachers’ job satisfaction, and school effectiveness. It also explored the mediating effect of teachers’ job satisfaction on school culture and school effectiveness. Participants of the study include1, 297 teachers from 6 lower secondary and upper secondary schools in Beijing, China. Quantitative methods were used for data generation, consisting of 3 questionnaire-based surveys to measure, separately, school culture, school effectiveness, and job satisfaction from the teachers’ perspective. The results indicated positively significant relationships among school culture, teachers’ job satisfaction, and school effectiveness and that teachers’ job satisfaction partially mediated the impact of school culture on school effectiveness. In light of these results, limitations and directions for future research are provided, as well as implications for education. © 2018 The authors and IJLTER.ORG. All rights reserved.Scopu

Modelling the multi-wavelength emissions from PSR B1259-63/LS 2883: the effects of the stellar disc on shock radiations

PSR B1259-63/LS 2883 is an elliptical pulsar/Be star binary and emits broadband emissions from radio to TeV $\gamma$-rays. The massive star possesses an equatorial disc, which is inclined with the orbital plane of the pulsar. The non-thermal emission from the system is believed to be produced by the pulsar wind shock and the double-peak profiles in the X-ray and TeV $\gamma$-ray light curves are related to the phases of the pulsar passing through the disc region of the star. In this paper, we investigate the interactions between the pulsar wind and stellar outflows, especially with the presence of the disc, and present a multi-wavelength modelling of the emission from this system. We show that the double-peak profiles of X-ray and TeV $\gamma$-ray light curves are caused by the enhancements of the magnetic field and the soft photons at the shock during the disc passages. As the pulsar is passing through the equatorial disc, the additional pressure of the disc pushes the shock surface closer to the pulsar, which causes the enhancement of magnetic field in the shock, and thus increases the synchrotron luminosity. The TeV $\gamma$-rays due to the inverse-Compton (IC) scattering of shocked electrons with seed photons from the star is expected to peak around periastron which is inconsistent with observations. However, the shock heating of the stellar disc could provide additional seed photons for IC scattering during the disc passages, and thus produces the double-peak profiles as observed in the TeV $\gamma$-ray light curve. Our model can possibly be examined and applied to other similar gamma-ray binaries, such as PSR J2032+4127/MT91 213, HESS J0632+057, and LS I+61$^{\circ}$303.Comment: 14 pages, 6 figure