Showing papers by "Southeast University published in 2011"

Broadband graphene polarizer

Abstract: Scientists study the coupling, guiding and polarizing of electromagnetic waves in graphene and demonstrate a graphene-based fibre polarizer that exhibits a transverse-electric-pass polarization at an extinction ratio of up to ∼27 dB in the telecommunications band.

Overview of Stator-Permanent Magnet Brushless Machines

Abstract: Permanent magnet (PM) brushless machines having magnets and windings in stator (the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure, high power density, high efficiency, etc. In this paper, an overview of the stator-PM machine is presented, with particular emphasis on concepts, operation principles, machine topologies, electromagnetic performance, and control strategies. Both brushless ac and dc operation modes are described. The key features of the machines, including the merits and drawbacks of the machines, are summarized. Moreover, the latest development of the machines is also discussed.

Finite-Time Attitude Tracking Control of Spacecraft With Application to Attitude Synchronization

Abstract: This note investigates the finite-time attitude control problems for a single spacecraft and multiple spacecraft. First of all, a finite-time controller is designed to solve finite-time attitude tracking problem for a single spacecraft. Rigorous proof shows that the desired attitude can be tracked in finite time in the absence of disturbances. In the presence of disturbances, the tracking errors can reach a region around the origin in finite time. Then, based on the neighbor rule, a distributed finite-time attitude control law is proposed for a group of spacecraft with a leader-follower architecture. Under the finite-time control law, the attitude synchronization can be achieved in finite time.

Polarization-independent wide-angle triple-band metamaterial absorber.

Abstract: We report the design, fabrication, and measurement of a microwave triple-band absorber. The compact single unit cell consists of three nested electric closed-ring resonators and a metallic ground plane separated by a dielectric layer. Simulation and experimental results show that the absorber has three distinctive absorption peaks at frequencies 4.06GHz, 6.73GHz, and 9.22GHz with the absorption rates of 0.99, 0.93, and 0.95, respectively. The absorber is valid to a wide range of incident angles for both transverse electric (TE) and transverse magnetic (TM) polarizations. The triple-band absorber is a promising candidate as absorbing elements in scientific and technical applications because of its multiband absorption, polarization insensitivity, and wide-angle response.

On distance and correlation measures of hesitant fuzzy information

Abstract: A hesitant fuzzy set, allowing the membership of an element to be a set of several possible values, is very useful to express people's hesitancy in daily life. In this paper, we define the distance and correlation measures for hesitant fuzzy information and then discuss their properties in detail. These measures are all defined under the assumption that the values in all hesitant fuzzy elements (the fundamental units of hesitant fuzzy sets) are arranged in an increasing order and two hesitant fuzzy elements have the same length when we compare them. We can find that the results, by using the developed distance measures, are the smallest ones among those when the values in two hesitant fuzzy elements are arranged in any permutations. In addition, the derived correlation coefficients are based on different linear relationships and may have different results. © 2011 Wiley Periodicals, Inc. © 2011 Wiley Periodicals, Inc.

Catalytic conversion of biomass-derived feedstocks into olefins and aromatics with ZSM-5: the hydrogen to carbon effective ratio

Abstract: Catalytic conversion of ten biomass-derived feedstocks, i.e.glucose, sorbitol, glycerol, tetrahydrofuran, methanol and different hydrogenated bio-oil fractions, with different hydrogen to carbon effective (H/Ceff) ratios was conducted in a gas-phase flow fixed-bed reactor with a ZSM-5 catalyst. The aromatic + olefin yield increases and the coke yield decreases with increasing H/Ceff ratio of the feed. There is an inflection point at a H/Ceff ratio = 1.2, where the aromatic + olefin yield does not increase as rapidly as it does prior to this point. The ratio of olefins to aromatics also increases with increasing H/Ceff ratio. CO and CO2 yields go through a maximum with increasing H/Ceff ratio. The deactivation rate of the catalyst decreases significantly with increasing H/Ceff ratio. Coke was formed from both homogeneous and heterogeneous reactions. Thermogravimetric analysis (TGA) for the ten feedstocks showed that the formation of coke from homogeneous reactions decreases with increasing H/Ceff ratio. Feedstocks with a H/Ceff ratio less than 0.15 produce large amounts of undesired coke (more than 12 wt%) from homogeneous decomposition reactions. This paper shows that the conversion of biomass-derived feedstocks into aromatics and olefins using zeolite catalysts can be explained by the H/Ceff ratio of the feed.

Coexistence of magnetic and electric orderings in the metal-formate frameworks of [NH4][M(HCOO)3].

Abstract: A family of three-dimensional chiral metal–formate frameworks of [NH4][M(HCOO)3 ] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder–order transitions of NH4+ cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8–30 K for the magnetic members, providing a new class of metal–organic frameworks showing the coexistence of magnetic and electric orderings.

Approaches to multiple attribute group decision making based on intuitionistic fuzzy power aggregation operators

Abstract: Intuitionistic fuzzy numbers (IFNs) are very suitable to be used for depicting uncertain or fuzzy information. Motivated by the idea of power aggregation [R.R. Yager, The power average operator, IEEE Transactions on Systems, Man, and Cybernetics-Part A 31 (2001) 724-731], in this paper, we develop a series of operators for aggregating IFNs, establish various properties of these power aggregation operators, and then apply them to develop some approaches to multiple attribute group decision making with Atanassov's intuitionistic fuzzy information. Moreover, we extend these aggregation operators and decision making approaches to interval-valued Atanassov's intuitionistic fuzzy environments.

Intuitionistic Fuzzy Bonferroni Means

Abstract: The Bonferroni mean (BM) was originally introduced by Bonferroni and then more recently generalized by Yager. The desirable characteristic of the BM is its capability to capture the interrelationship between input arguments. Nevertheless, it seems that the existing literature only considers the BM for aggregating crisp numbers instead of any other types of arguments. In this paper, we investigate the BM under intuitionistic fuzzy environments. We develop an intuitionistic fuzzy BM (IFBM) and discuss its variety of special cases. Then, we apply the weighted IFBM to multicriteria decision making. Some numerical examples are given to illustrate our results.

Consensus in Directed Networks of Agents With Nonlinear Dynamics

Abstract: This technical note studies the consensus problem for cooperative agents with nonlinear dynamics in a directed network. Both local and global consensus are defined and investigated. Techniques for studying the synchronization in such complex networks are exploited to establish various sufficient conditions for reaching consensus. The local consensus problem is first studied via a combination of the tools of complex analysis, local consensus manifold approach, and Lyapunov methods. A generalized algebraic connectivity is then proposed to study the global consensus problem in strongly connected networks and also in a broad class of networks containing spanning trees, for which ideas from algebraic graph theory, matrix theory, and Lyapunov methods are utilized.

Exponential Synchronization of Linearly Coupled Neural Networks With Impulsive Disturbances

Abstract: This brief investigates globally exponential synchronization for linearly coupled neural networks (NNs) with time-varying delay and impulsive disturbances. Since the impulsive effects discussed in this brief are regarded as disturbances, the impulses should not happen too frequently. The concept of average impulsive interval is used to formalize this phenomenon. By referring to an impulsive delay differential inequality, we investigate the globally exponential synchronization of linearly coupled NNs with impulsive disturbances. The derived sufficient condition is closely related with the time delay, impulse strengths, average impulsive interval, and coupling structure of the systems. The obtained criterion is given in terms of an algebraic inequality which is easy to be verified, and hence our result is valid for large-scale systems. The results extend and improve upon earlier work. As a numerical example, a small-world network composing of impulsive coupled chaotic delayed NN nodes is given to illustrate our theoretical result.

A hybrid method for MRI brain image classification

Abstract: Automated and accurate classification of MR brain images is of importance for the analysis and interpretation of these images and many methods have been proposed. In this paper, we present a neural network (NN) based method to classify a given MR brain image as normal or abnormal. This method first employs wavelet transform to extract features from images, and then applies the technique of principle component analysis (PCA) to reduce the dimensions of features. The reduced features are sent to a back propagation (BP) NN, with which scaled conjugate gradient (SCG) is adopted to find the optimal weights of the NN. We applied this method on 66 images (18 normal, 48 abnormal). The classification accuracies on both training and test images are 100%, and the computation time per image is only 0.0451s.

Ceramic nanofibers fabricated by electrospinning and their applications in catalysis, environmental science, and energy technology

Abstract: This paper provides a brief review of current research activities that focus on the fabrication of ceramic nanofibers by electrospinning, as well as their applications in various areas. We begin with a brief introduction to electrospinning in the context of ceramic nanofibers, and the methods for preparing aligned and/or hollow nanofibers. We then discuss approaches to the fabrication of nanofibers with a hierarchical structure. We continue with a highlight of some recent applications enabled by electrospun ceramic nanofibers, with a focus on three areas: catalysis, environmental science, and energy technology, which are expected to become the most important and exciting subjects of research in this century. In the end, we conclude this review with some perspectives on the future directions and implications for this new class of functional nanomaterials. Copyright © 2010 John Wiley & Sons, Ltd.

Non-linear disturbance observer-based robust control for systems with mismatched disturbances/uncertainties

Abstract: Robust control of non-linear systems with disturbances and uncertainties is addressed in this study using disturbance observer-based control (DOBC) technique. In this framework, the `disturbance` is a generalised concept, which may include external disturbances, unmodelled dynamics and system parameter perturbations. The existing DOBC methods were only applicable for the case where disturbances and uncertainties satisfy so-called matching condition, that is, they enter the system in the same channel as the control inputs. By appropriately designing a disturbance compensation gain vector in the composite control law, a non-linear disturbance observer-based robust control method is proposed in this study to attenuate the mismatched disturbances and the influence of parameter variations from system output channels. The proposed method is applied to a missile system with non-linear dynamics in the presence of various uncertainties and external disturbances. Simulation shows that, compared with the widely used non-linear dynamic inversion control (NDIC) and NDIC plus integral action methods, the proposed method provides much better disturbance attenuation ability and stronger robustness against various parameter variations.

Induced generalized intuitionistic fuzzy operators

Abstract: We study the induced generalized aggregation operators under intuitionistic fuzzy environments. Choquet integral and Dempster-Shafer theory of evidence are applied to aggregate inuitionistic fuzzy information and some new types of aggregation operators are developed, including the induced generalized intuitionistic fuzzy Choquet integral operators and induced generalized intuitionistic fuzzy Dempster-Shafer operators. Then we investigate their various properties and some of their special cases. Additionally, we apply the developed operators to financial decision making under intuitionistic fuzzy environments. Some extensions in interval-valued intuitionistic fuzzy situations are also pointed out.

Sliding-mode control for systems with mismatched uncertainties via a disturbance observer

Abstract: This paper aims to solve the sliding mode control (SMC) problem for systems with mismatched uncertainties via a disturbance observer. By designing a novel sliding surface based on the disturbance estimation, a disturbance observer based sliding mode control method is proposed to counteract the mismatched disturbance which is possibly nonvanishing. There are two distinct features for the proposed method. Firstly, the switching gain is only required to be designed greater than the magnitude of the disturbance estimation error rather than that of the disturbance, thus the chattering problem is substantially alleviated. Secondly, the proposed method retains its nominal performance, which means the proposed method acts the same as the baseline controller in the absence of disturbance. Application to a MAGLEV suspension system shows that the proposed method exhibits much better control performance than the baseline SMC and the integral SMC (I-SMC) methods, such as reduced chattering and nominal performance recovery.

Diisopropylammonium Chloride: A Ferroelectric Organic Salt with a High Phase Transition Temperature and Practical Utilization Level of Spontaneous Polarization

Abstract: A simple organic salt, diisopropylammonium chloride, shows the highest ferroelectric phase transition temperature among molecule-based ferroelectrics with a large spontaneous polarization, making it a candidate for practical technological applications.

Intuitionistic fuzzy geometric aggregation operators based on einstein operations

Abstract: Intuitionistic fuzzy information aggregation plays an important part in Atanassov's intuitionistic fuzzy set theory, which has emerged to be a new research direction receiving more and more attention in recent years In this paper, we first introduce some operations on intuitionistic fuzzy sets, such as Einstein sum, Einstein product, Einstein exponentiation, etc, and further develop some new geometric aggregation operators, such as the intuitionistic fuzzy Einstein weighted geometric operator and the intuitionistic fuzzy Einstein ordered weighted geometric operator, which extend the weighted geometric (WG) operator and the ordered weighted geometric (OWG) operator to accommodate the environment in which the given arguments are intuitionistic fuzzy values We also establish some desirable properties of these operators, such as commutativity, idempotency and monotonicity, and give some numerical examples to illustrate the developed aggregation operators In addition, we compare the proposed operators with the existing intuitionistic fuzzy geometric operators and get the corresponding relations Finally, we apply the intuitionistic fuzzy Einstein weighted geometric operator to deal with multiple attribute decision making under intuitionistic fuzzy environments © 2011 Wiley Periodicals, Inc © 2011 Wiley Periodicals, Inc

Experimental Study of Biomass Pyrolysis Based on Three Major Components: Hemicellulose, Cellulose, and Lignin

Abstract: Fast pyrolysis of cellulose, xylan, and lignin was experimentally conducted between 350 and 650 °C in a tube furnace, and the effect of temperature on pyrolysis products (char, noncondensable gas, and bio-oil) was investigated. The yields of char, noncondensable gas, and bio-oil were quantified using gas chromatography and gas chromatography with mass spectrometry. The noncondensable gas mainly consists of CO, CO2, CH4, and H2. The bio-oil includes acids, ketones, aldehydes, esters, benzenes, alcohols, alkenes, phenols, alkanels, carbohydrates, etc. The results show that cellulose is the principal source of carbohydrates and phenols are the basis of the bio-oil from lignin, while the bio-oil from xylan mainly consists of acids, ketones, aldehydes, and phenols. The char yields for the three components decrease with an increase in temperature, and the gas yields and bio-oil yields increase with an increase in temperature, reach a maximum at a certain temperature, and then decrease after that temperature. Th...

Metal–organic complex ferroelectrics

Abstract: Ferroelectric materials are of importance and interest in both fundamental scientific research and various technological applications. Metal–organic complexes (MOCs) represent a class of molecule-based ferroelectrics, which have shown various properties or functionalities due to their hybrid inorganic–organic nature. This tutorial review shows the recent development of the MOC ferroelectrics with particular emphases on the mechanism of ferroelectric-to-paraelectric phase transition, symmetry consideration, and multifunctionality.

Gold Nanoclusters and Graphene Nanocomposites for Drug Delivery and Imaging of Cancer Cells

Abstract: Gold nanoclusters (GNCs) have attracted wide attention owing to their outstanding surface and physical properties (for example, near-infrared photoluminescence, optical chirality, and ferromagnetism), which has led to a wide range of applications, such as for single-molecule photonics, sensing, and biological labeling. In contrast to organic dyes and quantum dots, GNCs do not contain chemical functions and toxic heavy metals. Their near-infrared range of emission avoids interference from many biological moieties, making GNCs ideal for biological assays and cell imaging so that they may become a powerful alternative to usual fluorescence labels. On the other hand, two dimensional graphene has attracted considerable interest owing to its long-range p conjugation, yielding extraordinary thermal, mechanical, and electrical properties. To date, the chemistry of graphene that has been reported mainly concerns the chemistry of graphene oxide (GO), which has chemically reactive oxygen-containing groups, including carboxylic acid groups at the edges of GO and epoxy and hydroxy groups on the basal planes. Because electrical conductivity, a large specific Brunauer–Emmett–Teller surface area, and high fracture strength can be recovered by restoring the p network, one of the most important reactions of GO is its reduction. Previous studies have established that graphene, including GO and its reduced form, reduced graphene oxide (RGO), is biocompatible and is a perfect support for a variety of metal and metal oxide nanoparticles, such as Pt, Au, TiO2, [9] fluorescent molecules, and drugs with potential biochemical applications. Functionalized graphene sheets are thus prone to act as drug delivery platforms, while their nearinfrared thermal properties make them attractive multimodal cancer therapeutic agents. Furthermore, RGO could also allow a facile attachment of many molecular drugs and nanomaterials. RGO has been frequently modified by noncovalent physisorption of polymers, small aromatic molecules, and metal nanoparticles with higher electron affinity, such as gold, onto their basal planes by p–p stacking, cation–p, or van der Waals interactions. For GNC-RGO nanocomposites, it may not only offer new and efficient entries in the current search for multimodal therapeutic materials that are prone to targeting/detecting and treating specifically altered tissues, but also offer attractive alternatives to existing cancer therapeutic techniques. Herein, we explore the biological properties of newly prepared GNC-RGO nanocomposites. This material could cause inhibition of HepG2 cells at high concentration, but more interestingly for oncotherapy it could carry anticancer agents such as doxorubicin (DOX) inside the cells while leading to some synergy in inducing karyopyknosis. It is observed that GNCs anchored on RGO retain their nearinfrared fluorescent property so that Raman spectroscopy could be used to investigate the performance of DOX-loaded GNC-RGO nanocomposites against hepatocarcinoma and provide important mechanistic clues about their interactions with proteins and DNA. GNCs were prepared in the organic phase following a conventional Brust–Schiffrin procedure and transferred into an aqueous phase. Simple mixing of the dodecanethiolCTAB-capped GNCs with RGO in aqueous solution followed by separation afforded water-soluble GNC-RGO nanocomposites in excellent yields. TEM analysis (Figure 1a) established that 95% of the water-soluble GNCs ranged between 2–3 nm in diameter with a distribution peak at 2.5 nm. They maintained their size distribution and morphology upon attachment to RGO (Figure 1b). HRTEM (Figure 1b, inset) showed that the GNCs kept their interplanar Au–Au spacing at 0.215 nm after attachment onto RGO. Though common gold nanoparticle sols exhibit a surface plasmon band (SPB), creating a broad absorption band in the visible region around 520 nm and thus their characteristic deep-red color, the color of GNCs and GNC-RGO was faint, in agreement with the fact that no obvious UV/Vis absorbance could be observed in Figure 1c. It is known that Au nanoparticles less than 3 nm in size do not exhibit the surface plasmon resonance characteristic peak at around 520 nm. This result is in good agreement with our observation (Figure 1 c) in which the absorption originating [*] C. Wang, J. Li, Dr. H. Jiang, Prof. X.-M. Wang State Key Lab of Bioelectronics (Chien-Shiung Wu Laboratory) Southeast University, No. 2 Sipailou, Nanjing 210096 (China) E-mail: xuewang@seu.edu.cn