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Cheng Y.,Central China Normal University | Yang H.,Central China Normal University | Cheng Z.,Xianning University | Wu N.,China Ship Development And Design Center
Applied Physics A: Materials Science and Processing | Year: 2011

In this paper, we present a polarization-insensitive metamaterial (MM) absorber which is composed of the dielectric substrate sandwiched with split-ring-cross resonator (SRCR) and continuous metal film. The MM absorber is not limited by the quarter-wavelength thickness and can achieve near-unity absorbance by properly assembling the sandwiched structure. Microwave experiments demonstrate the maximum absorptivity to be about 99% around 10.91 GHz for incident wave with different polarizations. The surface currents distributions of the resonance structure are discussed to look into the resonance mechanism. Importantly, our absorber is only 0.4 mm thick, and numerical simulations confirm that the MM absorber could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The sandwiched structure is also suitable for designing of a THz and even higher frequency MM absorber, and simulations demonstrate the absorption of 99% at 1.105 THz. © 2010 Springer-Verlag.

Cheng Y.,Central China Normal University | Yang H.,Central China Normal University | Cheng Z.,Xianning University | Xiao B.,Yangtze University
Photonics and Nanostructures - Fundamentals and Applications | Year: 2011

The model of the polarization-insensitive metamaterial (MM) absorber composed of split cross-ring resonator (SCRR), cave-cross resonator (CCR) and dielectric substrate was proposed at microwave frequencies. Based on perfect impedance-matched (z̃(ω)=1) to the free space, the single unit cell could achieve near-unity absorbance by properly assembling the sandwich structure. We have simulated and measured the reflectivity and transmission properties of a planar MM absorber with the thickness of 0.6 mm. The absorptivity of a single layer MM absorber achieve greater than 96% around 10.07 GHz in experiments and 98% in simulations for incident electromagnetic (EM) wave with different polarizations. © 2010 Elsevier B.V. All rights reserved.

Jiao M.,Wuhan University | Jiao M.,Xianning University | Li H.T.,Wuhan University | Chen J.,Wuhan University | And 2 more authors.
Biophysical Journal | Year: 2010

The dependence of the fluorescence of catalase upon the concentration of added superoxide dismutase (SOD) indicates that SOD binds to saturable sites on catalase. The affinity of SOD for these sites varies with temperature, and with the concentration of each of three nominally inert polymeric additives-dextran 70, Ficoll 70, and polyethylene glycol 2000. At room temperature (25.0°C) and higher, the addition of high concentrations of polymer is found to significantly enhance the affinity of SOD for catalase, but with decreasing temperature the enhancing effect of polymer addition diminishes, and at 8.0°C, addition of polymer has little or no effect on the affinity of SOD for catalase. The results presented here provide the first experimental evidence for the existence of competition between a repulsive excluded volume interaction between protein and polymer, which tends to enhance association of dilute protein, and an attractive interaction between protein and polymer, which tends to inhibit protein association. The net effect of high concentrations of polymer upon protein associations depends upon the relative strength of these two types of interactions at the temperature of measurement, and may vary significantly between different proteins and/or polymers. © 2010 by the Biophysical Society.

Sun J.,Xianning University | Ponce J.,Ecole Normale Superieure de Paris
International Journal of Computer Vision | Year: 2016

This paper proposes a novel approach to learning mid-level image models for image categorization and cosegmentation. We represent each image class by a dictionary of part detectors that best discriminate that class from the background. We learn category-specific part detectors in a weakly supervised setting in which the training images are only annotated with category labels without part/object location information. We use a latent SVM model regularized using the (Formula presented.) group sparsity norm to learn the part detectors. Starting from a large set of initial parts, the group sparsity regularizer forces the model to jointly select and optimize a set of discriminative part detectors in a max-margin framework. We propose a stochastic version of a proximal algorithm to solve the corresponding optimization problem. We apply the learned part detectors to image classification and cosegmentation, and present extensive comparative experiments with standard benchmarks. © 2016 Springer Science+Business Media New York

Zhou F.,Xianning University
Proceedings - 2011 7th International Conference on Natural Computation, ICNC 2011 | Year: 2011

This paper investigates the target coverage problem in wireless sensor networks with continuously adjustable sensing range. We study a wireless sensor network consisting a large number of N sensors that are randomly deployed over an area of interest and are expected to cover a number of M targets for a period of time as long as possible. For each sensor, the operation of sensing may consume energy which varies with different sensing ranges for which it may operate. Since targets are redundantly covered by multiple sensors, to conserve energy resources, sensors can be organized into a number of non-disjoint sets and activate them set by set. We define the maximal lifetime with constrained energy (MLCE) problem that has its objective of finding the operation time to each set of sensors such that the total operation time is maximized. Since the MLCE problem is NP-complete, two greedy heuristics is designed for solving this problem. © 2011 IEEE.

Liu C.,Xianning University | Liu C.,The University of Oklahoma Health Sciences Center | Wu J.,Xianning University | Zou M.-H.,The University of Oklahoma Health Sciences Center
Free Radical Biology and Medicine | Year: 2012

The blood-brain barrier, formed by specialized brain endothelial cells that are interconnected by tight junctions, strictly regulates paracellular permeability to maintain an optimal extracellular environment for brain homeostasis. Diabetes is known to compromise the blood-brain barrier, although the underlying mechanism remains unknown. The aim of this study was to elucidate the molecular mechanisms underlying disruption of the blood-brain barrier in diabetes and to determine whether activation of AMP-activated protein kinase prevents diabetes-induced blood-brain barrier dysfunction. Exposure of human brain microvascular endothelial cells to high glucose (25 mmol/L d-glucose), but not to high osmotic conditions (20 mmol/L l-glucose plus 5 mmol/L d-glucose), for 2 h to 1 week significantly increased the permeability of the blood-brain barrier in parallel with lowered expression levels of zonula occludens-1, occludin, and claudin-5, three proteins that are essential to maintaining endothelial cell tight junctions. In addition, high glucose significantly increased the generation of superoxide anions. Adenoviral overexpression of superoxide dismutase or catalase significantly attenuated the high-glucose-induced reduction of endothelial cell tight-junction proteins. Furthermore, administration of apocynin reversed the effects of high glucose on endothelial cell tight-junction proteins. Finally, activation of AMP-activated protein kinase with 5-amino-4-imidazole carboxamide riboside or adenoviral overexpression of constitutively active AMP-activated protein kinase mutants abolished both the induction of NAD(P)H oxidase-derived superoxide anions and the tight-junction protein degradation induced by high glucose. We conclude that high glucose increases blood-brain barrier dysfunction in diabetes through induction of superoxide anions and that the activation of AMP-activated protein kinase protects the integrity of the blood-brain barrier by suppressing the induction of NAD(P)H oxidase-derived superoxide anions. © 2012 Elsevier Inc.

Liu F.,Xianning University
2011 International Conference on Consumer Electronics, Communications and Networks, CECNet 2011 - Proceedings | Year: 2011

This article describes a design of Digital Control of DC current source based on AVR microcontroller. The system uses the Atmega8 as the main chip and consists of keyboard input, LCD display, I / V conversion, power amplification and other modules. It uses a negative feedback closed-loop control. The MCU can compare real-time the preset value with the measuring results, and adjuste the settings, in order to advance the output precision of the current. The design can achieve the functions of different measurement ranges, adjustable output current, exact step and very small current waviness. It also can display the output preset value and the measuring results by LED at the same. © 2011 IEEE.

Gao N.,Xianning University | Yu L.,Xianning University
2013 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2013 | Year: 2013

With the popularization and development of science and technology, especiaUy in the field of high speed machine tool, the compressor and the micro gas turbine system, the traditional motor can't fit these requirements. Because of its high speed,supreme power density and obvious efficiency advantages, high speed permanent magnet synchronous motor (HSPMSM) is developed and its application has entered a new stage. Due to the high power of HSPMSM, its unit volume loss is big, and it is difficult to disperse heat, so the loss of the accurate calculation of the motor and research of electromagnetic heat coupling are very important. In this paper, a 200 kW, 60000 rpm high speed permanent magnet synchronous motor is designed and analysed. Stator iron loss, stator winding copper loss, rotor eddy current loss and rotor windage loss are detailed analysed and calculated. By use of the method of electromagnetic heat coupling finite element analysis, we get the temperature field distribution of the motor. This conclusion can provide a referential guide for the design of high-speed motor. © 2013 IEEE.

Wuxiong X.,Xianning University
2011 International Conference on Consumer Electronics, Communications and Networks, CECNet 2011 - Proceedings | Year: 2011

This paper illustrates the basic work principle of a brushless DC motor and presents its control method. According to the method, a control system of a brushless DC Motor is designed using an AVR microcontroller. Design of the control system includes hardware circuit designing and software programming. The hardware structure of the control system consists of a microcontroller ATmega64, power supply circuit, position detection circuit, current chopper circuit, power driving circuit, display circuit and keyboard circuit and so on. The software is developed by c program language. The software includes main program, initialization program, PWM duty ratio reload program, speed calculation program, closed-loop PID regulation program, interrupt service program, LCD display program, keyboard program etc. The experiment result shows that the system is with an excellent dynamic and static performance. Its operation is reliable. © 2011 IEEE.

Qian A.,Xianning University | Li Y.,Xianning University
Journal of Mathematical Chemistry | Year: 2011

In this note we prove a stability estimate for an inverse heat source problem. Based on the obtained stability estimate, we present a generalized Tikhonov regularization and obtain the error estimate. Numerical experiment shows that the generalized Tikhonov regularization works well. © 2010 Springer Science+Business Media, LLC.

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