Xidian University

About: Xidian University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Antenna (radio) & Synthetic aperture radar. The organization has 32099 authors who have published 38961 publications receiving 431820 citations. The organization is also known as: University of Electronic Science and Technology at Xi'an & Xīān Diànzǐ Kējì Dàxué.

The connections between three-way and classical concept lattices

Abstract: The model of three-way concept lattices, a novel model for widely used three-way decisions, is an extension of classical concept lattices in formal concept analysis. This paper systematically analyses the connections between two types of three-way concept lattices (object-induced and attribute-induced three-way concept lattices) and classical concept lattices. The relationships are discussed from the viewpoints of elements, sets and orders, respectively. Furthermore, the necessary and sufficient conditions used to construct three-way concepts on the basis of classical concepts are proved, the algorithms building three-way concept lattices on the basis of classical concept lattices are presented. The obtained results are finally demonstrated and verified by examples.

Side-Edge Frame Printed Eight-Port Dual-Band Antenna Array for 5G Smartphone Applications

Abstract: An eight-port antenna array operating in 3.5 GHz band (3400–3600 MHz) and 5 GHz band (4800–5100 MHz) for fifth-generation multiple-input multiple-output (MIMO) in mobile handsets is presented. To reserve space for 2G/3G/4G antenna configuration, the eight-antenna array formed by two quad-antenna arrays is printed along the two long frames of the smartphone. Each antenna array unit is formed by a folded monopole and a gap-coupled loop branch, and they are disposed on the upper and bottom sides of the system circuit board, respectively. As the gap between each array unit is only 10 mm, a neutralized line is introduced between the two middle antenna units for reducing the mutual coupling. The measured results have exhibited good impedance matching and isolation. To evaluate the MIMO performance, the envelope correlation coefficient, mean effective gain, and ergodic channel capacity are investigated. Furthermore, the hand phantom effects and display panel effects are also given.

Design of Liveness-Enforcing Supervisors for Flexible Manufacturing Systems Using Petri Nets

Abstract: This correspondence develops a methodology to synthesize supervisors for a special class of Petri nets that can well model many flexible manufacturing systems. In our previous work, siphons in a Petri net are divided into elementary and dependent ones on the condition that all emptiable minimal siphons are computed. In this research, a mixed integer programming (MlP)-based deadlock detection technique is used to find some, in general not all, minimal siphons in a plant model without complete siphon enumeration. For each siphon found, depending on its noncontrollability, a monitor is added such that it is invariant-controlled. Our siphon control method guarantees that no emptiable control-induced siphon is generated due to the addition of the monitors. The siphon control process proceeds iteratively until there is no unmarked siphon in the supervisor of a plant model. Compared with the existing approaches, the novel deadlock prevention policy can usually lead to a structurally simple liveness-enforcing supervisor by adding only a small number of monitors and arcs. More importantly, complete siphon enumeration is avoided. A practical flexible manufacturing system (FMS) example is utilized to illustrate the proposed methods.

Cryptanalysis of GGH Map

Abstract: Multilinear map is a novel primitive which has many cryptographic applications, and GGH map is a major candidate of K-linear maps for $$K>2$$K>2. GGH map has two classes of applications, which are applications with public tools for encoding and with hidden tools for encoding. In this paper, we show that applications of GGH map with public tools for encoding are not secure, and that one application of GGH map with hidden tools for encoding is not secure. On the basis of weak-DL attack presented by the authors themselves, we present several efficient attacks on GGH map, aiming at multipartite key exchange MKE and the instance of witness encryption WE based on the hardness of exact-3-cover X3C problem. First, we use special modular operations, which we call modified Encoding/zero-testing to drastically reduce the noise. Such reduction is enough to break MKE. Moreover, such reduction negates K-GMDDH assumption, which is a basic security assumption. The procedure involves mostly simple algebraic manipulations, and rarely needs to use any lattice-reduction tools. The key point is our special tools for modular operations. Second, under the condition of public tools for encoding, we break the instance of WE based on the hardness of X3C problem. To do so, we not only use modified Encoding/zero-testing, but also introduce and solve "combined X3C problem", which is a problem that is not difficult to solve. In contrast with the assumption that multilinear map cannot be divided back, this attack includes a division operation, that is, solving an equivalent secret from a linear equation modular some principal ideal. The quotient the equivalent secret is not small, so that modified Encoding/zero-testing is needed to reduce size. This attack is under an assumption that some two vectors are co-prime, which seems to be plausible. Third, for hidden tools for encoding, we break the instance of WE based on the hardness of X3C problem. To do so, we construct level-2 encodings of 0, which are used as alternative tools for encoding. Then, we break the scheme by applying modified Encoding/zero-testing and combined X3C, where the modified Encoding/zero-testing is an extended version. This attack is under two assumptions, which seem to be plausible. Finally, we present cryptanalysis of two simple revisions of GGH map, aiming at MKE. We show that MKE on these two revisions can be broken under the assumption that $$2^{K}$$2K is polynomially large. To do so, we further extend our modified Encoding/zero-testing.

Cooperative Secure Beamforming for AF Relay Networks With Multiple Eavesdroppers

Abstract: This letter studies cooperative secure beamforming for amplify-and-forward (AF) relay networks in the presence of multiple eavesdroppers. Under both total and individual relay power constraints, we propose two schemes, namely secrecy rate maximization (SRM) beamforming and null-space beamforming. In the first scheme, our design problem is based on SRM. Using a suboptimal, but convex, technique-semidefinite relaxation (SDR), we show that this problem can be handled by performing a one-dimensional search which involves solving a sequence of semidefinite programs (SDPs). To reduce the complexity, in the second scheme, we instead maximize the information rate at the destination while completely eliminating the information leakage to all eavesdroppers. We prove that this problem can be exactly solved by SDR with one SDP only. Simulation results demonstrate the performance gains of the two proposed designs.