Nanjing University of Science and Technology

About: Nanjing University of Science and Technology is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Control theory & Catalysis. The organization has 31581 authors who have published 36390 publications receiving 525474 citations. The organization is also known as: Nánjīng Lǐgōng Dàxué & Nánlǐgōng.

Transport-of-intensity phase imaging using Savitzky-Golay differentiation filter--theory and applications.

Abstract: Several existing strategies for estimating the axial intensity derivative in the transport-of-intensity equation (TIE) from multiple intensity measurements have been unified by the Savitzky-Golay differentiation filter - an equivalent convolution solution for differentiation estimation by least-squares polynomial fitting. The different viewpoint from the digital filter in signal processing not only provides great insight into the behaviors, the shortcomings, and the performance of these existing intensity derivative estimation algorithms, but more important, it also suggests a new way of improving solution strategies by extending the applications of Savitzky-Golay differentiation filter in TIE. Two novel methods for phase retrieval based on TIE are presented - the first by introducing adaptive-degree strategy in spatial domain and the second by selecting optimal spatial frequencies in Fourier domain. Numerical simulations and experiments verify that the second method outperforms the existing methods significantly, showing reliable retrieved phase with both overall contrast and fine phase variations well preserved.

Secure and Precise Wireless Transmission for Random-Subcarrier-Selection-Based Directional Modulation Transmit Antenna Array

Abstract: In this paper, a practical wireless transmission scheme is proposed to transmit confidential messages to the desired user securely and precisely by the joint use of multiple techniques, including artificial noise (AN) projection, phase alignment/beamforming, and random subcarrier selection (RSCS) based on orthogonal frequency division multiplexing (OFDM), and directional modulation (DM), namely RSCS-OFDM-DM. This RSCS-OFDM-DM scheme provides an extremely low-complexity structure for the desired receiver and makes the secure and precise wireless transmission realizable in practice. For illegal eavesdroppers, the receive power of confidential messages is so weak that their receivers cannot intercept these confidential messages successfully once it is corrupted by AN. In such a scheme, the design of phase alignment/beamforming vector and AN projection matrix depends intimately on the desired direction angle and distance. It is particularly noted that the use of RSCS leads to a significant outcome that the receive power of confidential messages mainly concentrates on the small neighboring region around the desired receiver and only small fraction of its power leaks out to the remaining large broad regions. This concept is called secure precise transmission. The probability density function of real-time receive signal-to-interference-and-noise ratio (SINR) is derived. Also, the average SINR and its tight upper bound are attained. The approximate closed-form expression for average secrecy rate is derived by analyzing the first-null positions of the SINR and clarifying the wiretap region. Simulation and analysis show that the proposed scheme actually can achieve a secure and precise wireless transmission of confidential messages in line-of-propagation channel, and the derived theoretical formula of average secrecy rate is verified to coincide with the exact results well for medium and large scale transmit antenna array or in the low and medium SNR regions.

Highly Hydrophobic, Compressible, and Magnetic Polystyrene/Fe3O4/Graphene Aerogel Composite for Oil–Water Separation

Abstract: A solvothermal technique to process novel graphene aerogel/Fe3O4/polystyrene composites with reticulated graphene structure is described. Porous Fe3O4 nanoparticles as a partial substitute for ethylenediamine assisted cross-linking and interconnections between graphene plates. Fe3O4 and polystyrene incorporation allowed a porous substructure to be formed on the reticulated graphene surfaces, effectively enhancing the hydrophobicity. The compressibility and directional recovery were achieved with the composite having an extremely low density of 0.005 g cm–3, corresponding to a volume porosity of 99.7%. The crude oil intake capacity for the composite was 40 times its own mass after 10 water–oil separation cycles, which is among the highest ever reported for oil absorbents. Furthermore, the incorporation of porous Fe3O4 nanoparticles enabled magnetism which, in combination with compressibility, allowed the oil-soaked graphene composite to be readily collected by a magnet and oil to be squeezed out before the...

A Practical Nonlinear Adaptive Control of Hydraulic Servomechanisms With Periodic-Like Disturbances

Abstract: When performing periodic tasks, the modeling uncertainties will also present some periodicity. In this paper, by appropriately applying Fourier series approximation, a practical nonlinear adaptive repetitive controller is proposed for motion control of hydraulic servomechanisms to learn and compensate the periodic modeling uncertainties. Robust control term is also constructed to effectively attenuate the effect of approximation errors, and thus asymptotic tracking performance is achieved. In addition, robustness is also discussed with respect to other nonperiodic disturbances, which reveals a guaranteed transient performance and steady-state tracking accuracy can be achieved by the proposed controller with a practical assumption. Compared to the traditional repetitive controllers, the major advantage of this controller is that it not only requires little exact knowledge of the system dynamic structure or its parameters, but also greatly reduces the noise sensitivity and heavy memory requirements. Comparative experimental results are obtained to verify the high accuracy tracking performance of the proposed control strategy.