SYNTHESIS AND FUNCTIONAL BEHAVIOR OF NANOCARBON AND HYBRIDS

Ph.DDOCTOR OF PHILOSOPH

HpGAN: Sequence Search with Generative Adversarial Networks

Sequences play an important role in many engineering applications and systems. Searching sequences with desired properties has long been an interesting but also challenging research topic. This article proposes a novel method, called HpGAN, to search desired sequences algorithmically using generative adversarial networks (GAN). HpGAN is based on the idea of zero-sum game to train a generative model, which can generate sequences with characteristics similar to the training sequences. In HpGAN, we design the Hopfield network as an encoder to avoid the limitations of GAN in generating discrete data. Compared with traditional sequence construction by algebraic tools, HpGAN is particularly suitable for intractable problems with complex objectives which prevent mathematical analysis. We demonstrate the search capabilities of HpGAN in two applications: 1) HpGAN successfully found many different mutually orthogonal complementary code sets (MOCCS) and optimal odd-length Z-complementary pairs (OB-ZCPs) which are not part of the training set. In the literature, both MOCSSs and OB-ZCPs have found wide applications in wireless communications. 2) HpGAN found new sequences which achieve four-times increase of signal-to-interference ratio--benchmarked against the well-known Legendre sequence--of a mismatched filter (MMF) estimator in pulse compression radar systems. These sequences outperform those found by AlphaSeq.Comment: 12 pages, 16 figure

Pilot Design for Enhanced Channel Estimation in Doubly Selective Channels

This paper investigates pilot design for enhanced channel estimation in single carrier communication systems over doubly-selective channels (DSC). Our contribution is twofold: first, we propose to use Huffman sequences as pilot clusters with low peak-to-average power ratio (PAPR), yet with good channel estimation performance when periodic pilot placement is adopted; second, we propose a low-complexity pilot placement strategy based on the analysis of the complex-exponential basis expansion model (CE-BEM) of the DSC. The latter leads to improved channel estimation performance with useful insights for pilot placement

Quantum-enhanced Electrometer based on Microwave-dressed Rydberg Atoms

Rydberg atoms have been shown remarkable performance in sensing microwave field. The sensitivity of such an electrometer based on optical readout of atomic ensemble has been demonstrated to approach the photon-shot-noise limit. However, the sensitivity can not be promoted infinitely by increasing the power of probe light due to the increased collision rates and power broadening. Compared with classical light, the use of quantum light may lead to a better sensitivity with lower number of photons. In this paper, we exploit entanglement in a microwave-dressed Rydberg electrometer to suppress the fluctuation of noise. The results show a sensitivity enhancement beating the shot noise limit in both cold and hot atom schemes. Through optimizing the transmission of optical readout, our quantum advantage can be maintained with different absorptive index of atomic vapor, which makes it possible to apply quantum light source in the absorptive electrometer

Pilot design for channel estimation in Doubly Selective Channel

We consider pilot sequence designs for channel estimation in doubly-selective channels (DSC) which are modeled using the basis expansion model (BEM) approach. We propose to use pilot sequences (instead of impulse pilots) to reduce the peak-to-average power ratio (PAPR) of the transmitted signal. Specifically, by analysing the mean square error (MSE) metric of the BEM channel coefficients, we propose the use of Huffman sequences to reduce the PAPR during channel estimation. Furthermore, we show that a systematic re-arrangement of the pilot sequence within the transmission frame can significantly improve the channel estimation performance of the system, as compared to the conventional periodic pilot placement

A high performance flexible recyclable supercapacitor with polyaniline by casting in unconventional proportion

Abstract(#br)A new type of recyclable flexible solid-state supercapacitor with good electrochemical performance and folder ability is produced through a facile method. Polyvinylidene fluoride - acetylene black - polyethylene glycol - polyaniline (PVDF-AB-PEG-PANI) film electrode with excellent processability and tailorability is prepared by casting strategy, which uses large amount of PVDF as film former. The new electrode has good performance with excellent flexibility (d r < 1 mm and capacity retention 97.4 % after folding 1000 times) and electrochemical performance (It can utilize the active substance efficiently that it closes to the theoretical value, with high areal capacitance of 890.44 mF cm −2 and volumetric capacitance of 89.04 F cm −3 ). A capacitance retention of 72.5 % is obtained for the supercapacitor based on this electrode after 5000 charging/discharging cycles, even polyaniline is synthesized by conventional method. The most interesting thing is that, the supercapacitor based on this electrode can easily be recycled and reused (capacity retention 97.1 % after 4 recycle times)