arXiv subjects

Bin Liao

Publications and source records attributed to Bin Liao.

26 records · Page 2Linked to original sources

arXiv2018

A Fast Method for Array Response Adjustment with Phase-Only Constraint

In this paper, we propose a fast method for array response adjustment with phase-only constraint. This method can precisely and rapidly adjust the array response of a given point by only varying the entry phases of a pre-assigned weight vector. We show that phase-only array response adjustment can be formulated as a polygon construction problem, which can be solved by edge rotation in complex plain. Unlike the existing approaches, the proposed algorithm provides an analytical solution and guarantees a precise phase-only adjustment without pattern distortion. Moreover, the proposed method is suitable for an arbitrarily given weight vector and has a low computational complexity. Representative examples are presented to demonstrate the effectiveness of the proposed algorithm.

eess.SP↗

arXiv2018

A novel array response control algorithm via oblique projection

This paper presents a novel array response control algorithm and its application to array pattern synthesis. The proposed algorithm considers how to flexibly and precisely adjust the array responses at multiple points, on the basis of one given weight vector. With the principle of adaptive beamforming, it is shown that the optimal weight vector for array response control can be equivalently obtained with a different manner, in which a linear transformation is conducted on the quiescent weight. This new strategy is utilized to realize multi-point precise array response control from one given weight vector, and it obtains a closed-form solution. A careful analysis shows that the response levels at given points can be independently, flexibly and accurately adjusted by simply varying the parameter vector, and that the uncontrolled region remains almost unchanged. By applying the proposed algorithm, an effective pattern synthesis approach is devised. Simulation results are provided to demonstrate the performance of the proposed algorithm.

eess.SP↗

arXiv2017

OPARC: Optimal and Precise Array Response Control Algorithm -- Part I: Fundamentals

In this paper, the problem of how to optimally and precisely control array response levels is addressed. By using the concept of the optimal weight vector from the adaptive array theory and adding virtual interferences one by one, the change rule of the optimal weight vector is found and a new formulation of the weight vector update is thus devised. Then, the issue of how to precisely control the response level of one single direction is investigated. More specifically, we assign a virtual interference to a direction such that the response level can be precisely controlled. Moreover, the parameters, such as, the interference-to-noise ratio (INR), can be figured out according to the desired level. Additionally, the parameter optimization is carried out to obtain the maximal array gain. The resulting scheme is called optimal and precise array response control (OPARC) in this paper. To understand it better, its properties are given, and its comparison with the existing accurate array response control ($ {\textrm A}^2\textrm{RC} $) algorithm is provided. Finally, simulation results are presented to verify the effectiveness and superiority of the proposed OPARC.

eess.SP↗

arXiv2017

OPARC: Optimal and Precise Array Response Control Algorithm -- Part II: Multi-points and Applications

In this paper, the optimal and precise array response control (OPARC) algorithm proposed in Part I of this two paper series is extended from single point to multi-points. Two computationally attractive parameter determination approaches are provided to maximize the array gain under certain constraints. In addition, the applications of the multi-point OPARC algorithm to array signal processing are studied. It is applied to realize array pattern synthesis (including the general array case and the large array case), multi-constraint adaptive beamforming and quiescent pattern control, where an innovative concept of normalized covariance matrix loading (NCL) is proposed. Finally, simulation results are presented to validate the superiority and effectiveness of the multi-point OPARC algorithm.

eess.SP↗

arXiv2017

Determine the Lorentz factor and the viewing angle of GRB 170817A

GRB 170817A is a weak short gamma-ray burst (GRB) accompanied by the gravitational wave (GW) event GW170817. It is believed, that an off beaming relativistic jet, produces this weak GRB. Here we use the $E_{\rm p,i}- E_{\rm iso}$ and $Γ- E_{\rm iso}$ relations to determine the Lorentz factor $Γ$ and the viewing angle from the edge of the jet $θ'_{\rm obs}$ of GRB 170817A. Our result shows, $Γ= 13.4 ^{+9.8}_{-5.5}$ and $θ'_{\rm obs} = 4.3^{+1.8}_{-1.5} \,^{\circ}$. This corresponds to the on-axis $E_{\rm p,i} = 415^{+361}_{-167}$ keV and $E_{\rm iso} = (2.4^{+1.6}_{-1.9}) \times 10^{47}$ ergs of the GRB, which is an intrinsically weak short GRB. Interestingly, the Doppler factor and the luminosity follow a universal relation from GRBs and blazars, which indicates they may share similar radiation mechanism.

astro-ph.HE↗

arXiv2017

$Ab$ $initio$ electronic stopping power and threshold effect of channeled slow light ions in HfO$_{2}$

We present $ab$ $initio$ study of the electronic stopping power of protons and helium ions in an insulating material, HfO$_{2}$. The calculations are carried out in channeling conditions with different impact parameters by employing Ehrenfest dynamics and real--time, time--dependent density functional theory. The satisfactory comparison with available experiments demonstrates that this approach provides an accurate description of electronic stopping power. The velocity-proportional stopping power is predicted for protons and helium ions in the low energy region, which conforms the linear response theory. Due to the existence of wide band gap, a threshold effect in extremely low velocity regime below excitation is expected. For protons, the threshold velocity is observable, while it does not appear in helium ions case. This indicates the existence of extra energy loss channels beyond the electron--hole pair excitation when helium ions are moving through the crystal. To analyze it, we checked the charge state of the moving projectiles and an explicit charge exchange behavior between the ions and host atoms is found. The missing threshold effect for helium ions is attributed to the charge transfer, which also contributes to energy loss of the ion.

physics.atm-clus↗

arXiv2017

Testing the Einstein's equivalence principle with polarized gamma-ray bursts

The Einstein's equivalence principle can be tested by using parameterized post-Newtonian parameters, of which the parameter $γ$ has been constrained by comparing the arrival times of photons with different energies. It has been constrained by a variety of astronomical transient events, such as gamma-ray bursts (GRBs), fast radio bursts as well as pulses of pulsars, with the most stringent constraint of $Δγ\lesssim 10^{-15}$. In this letter, we consider the arrival times of lights with different circular polarization. For a linearly polarized light, it is the combination of two circularly polarized lights. If the arrival time difference between the two circularly polarized lights is too large, their combination may lose the linear polarization. We constrain the value of $Δγ_{\rm p} < 1.6 \times 10^{-27}$ by the measurement of the polarization of GRB 110721A, which is the most stringent constraint ever achieved.

astro-ph.HE↗

arXiv2016

Design and Implementation of A Network Security Management System

In recent years, the emerged network worms and attacks have distributive characteristic, which can spread globally in a very short time. Security management crossing network to co-defense network-wide attacks and improve efficiency of security administration is urgently needed. This paper proposes a hierarchical distributed network security management system (HD-NSMS), which can centrally manage security across networks. First describes the system in macrostructure and microstructure; then discusses three key problems when building HD-NSMS: device model, alert mechanism and emergency response mechanism; at last, describes the implementation of HD-NSMS. The paper is valuable for implementing NSMS in that it derives from a practical network security management system (NSMS).

cs.CR↗