Southwest University

About: Southwest University is a education organization based out in Chongqing, China. It is known for research contribution in the topics: Gene & Population. The organization has 29772 authors who have published 27755 publications receiving 409441 citations. The organization is also known as: Southwest University in Chongqing & SWU.

On Secure Underlay MIMO Cognitive Radio Networks With Energy Harvesting and Transmit Antenna Selection

Abstract: In this paper, we consider an underlay multiple-input-multiple-output (MIMO) cognitive radio network (CRN) including a pair of primary nodes, a couple of secondary nodes, and an eavesdropper, where the secondary transmitter is powered by the renewable energy harvested from the primary transmitter in order to improve both energy efficiency and spectral efficiency. Based on whether the channel state information of wiretap links are available or not, the secrecy outage performance of the optimal antenna selection (OAS) scheme and suboptimal antenna selection (SAS) scheme for underlay MIMO CRN with energy harvesting are investigated and compared with traditional space-time transmission scheme. The closed-form expressions for exact and asymptotic secrecy outage probability are derived. Monte-Carlo simulations are conducted to testify the accuracy of the analytical results. The analysis illustrates that the OAS scheme outperforms SAS scheme. Furthermore, the asymptotic result shows that no matter which scheme is considered, the OAS and SAS schemes can achieve the same secrecy diversity order.

Facile synthesis of an eco-friendly nitrogen–phosphorus ammonium salt to enhance the durability and flame retardancy of cotton

Abstract: An ammonium salt of ethylene glycol diphosphoric acid (AEGDP) containing nitrogen and phosphorus, a durable and eco-friendly flame retardant for cotton, was synthesized under moderate and solvent-free conditions. The AEGDP structure was characterized by IR, 13C NMR, 1H NMR, and 31P NMR. Thermogravimetry (TG) and TG-infrared (TG-IR) spectroscopy indicate that phosphoric or polyphosphoric acid produced from AEGDP during combustion could catalyze the dehydration of cellulose to form char instead of decomposing it to form volatile flammable species, which include hydrocarbons, some carbonyl compounds, and ethers. The degradation mechanism of cotton fabrics treated with AEGDP was modified because of covalent bonds formed between cotton cellulose and AEGDP. Scanning electron microscopy (SEM) shows that no obvious materials were observed on the surface of the treated cotton, indicating that the –PO(O−NH4+)2 groups of AEGDP may react with the –OH groups of cellulose to form P–O–C covalent bonds and/or penetrate into the inner space of cotton fibers. Vertical flammable tests imply that the control cotton burned completely, whereas the treated cotton showed neither after-flame nor after-glow. The limiting oxygen index (LOI) of cotton treated with 120 g L−1 of AEGDP solution could reach 41.0%, which is significantly higher than that of the control cotton. After 50 laundering cycles, the LOI could be maintained at 28.4%, exhibiting the excellent durability of the treated cotton. Cone calorimetry at 35 and 50 kW m−2 irradiative heat flux reveals that AEGDP causes a reduction in the peak heat release rate and total heat release relative to those of the control cotton. In addition, X-ray diffraction shows that AEGDP fails to substantially change the crystal structure of cotton cellulose. There is no significant change in the bending length of cotton before and after treatment. And the decreased surface tension of the treated cotton is beneficial for its self-cleaning ability.

On the Security of a Class of Diffusion Mechanisms for Image Encryption

Abstract: The need for fast and strong image cryptosystems motivates researchers to develop new techniques to apply traditional cryptographic primitives in order to exploit the intrinsic features of digital images. One of the most popular and mature technique is the use of complex dynamic phenomena, including chaotic orbits and quantum walks, to generate the required key stream. In this paper, under the assumption of plaintext attacks we investigate the security of a classic diffusion mechanism (and of its variants) used as the core cryptographic primitive in some image cryptosystems based on the aforementioned complex dynamic phenomena. We have theoretically found that regardless of the key schedule process, the data complexity for recovering each element of the equivalent secret key from these diffusion mechanisms is only ${O}$ (1). The proposed analysis is validated by means of numerical examples. Some additional cryptographic applications of this paper are also discussed.