Peng J.-J.,Guizhou Normal University |
Peng J.-J.,Wuhan Textile University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016
We derive the off-shell Noether current and potential in the context of Horndeski theory, which is the most general scalar-tensor theory with a Lagrangian containing derivatives up to second order while yielding at most to second-order equations of motion in four dimensions. Then the formulation of conserved charges is proposed on basis of the off-shell Noether potential and the surface term got from the variation of the Lagrangian. As an application, we calculate the conserved charges of black holes in a scalar-tensor theory with non-minimal coupling between derivatives of the scalar field and the Einstein tensor. © 2015 The Author.
News Article | March 1, 2017
Georgia Institute of Technology researchers have demonstrated an optical metamaterial whose chiroptical properties in the nonlinear regime produce a significant spectral shift with power levels in the milliwatt range. The researchers recently demonstrated properties of their chiral metamaterial, in which they spectrally modified two absorptive resonances by incrementally exposing the material to power intensities beyond its linear optical regime. With a 15 milliwatt change in excitation power, they measured a 10-nanometer spectral shift in the material's transmission resonances and a 14-degree polarization rotation. The researchers believe that may be the strongest nonlinear optical rotation ever reported for a chiral metamaterial, and is about a hundred thousand times larger than the current record measurement for this type of structure. The research, supported by the National Science Foundation and the Air Force Research Laboratory, was reported February 27 in the journal Nature Communications. "Nanoscale chiral structures offer an approach to modulating optical signals with relatively small variations in input power," said Sean Rodrigues, a Ph.D. candidate who led the research in the laboratory of Associate Professor Wenshan Cai in Georgia Tech's School of Electrical and Computer Engineering. "To see this kind of change in such a thin material makes chiroptical metamaterials an interesting new platform for optical signal modulation." This modulation of chiroptical responses from metamaterials by manipulating input power offers the potential for new types of active optics such as all-optical switching and light modulation. The technologies could have applications in such areas as data processing, sensing and communications. Chiral materials exhibit optical properties that differ depending on their opposing circular polarizations. The differences between these responses, which are created by the nanoscale patterning of absorptive materials, can be utilized to create large chiroptical resonances. To be useful in applications such as all-optical switching, these resonances would need to be induced by external tuning - such as variations in power input. "When you increase the power, you shift the spectrum," Rodrigues said. "In effect, you change the transmission at certain wavelengths, meaning you're changing the amount of light passing through the sample by simply modifying input power." For optical engineers, that could be the basis for a switch. The material demonstrated by Cai's lab are made by nano-patterning layers of silver - approximately 33 nanometers thick - onto glass substrates. Between the carefully-designed silver layers is a 45-nanometer layer of dielectric material. An elliptical pattern is created using electron beam lithography, then the entire structure is encapsulated within a dielectric material to prevent oxidation. "It is the engineering of these structures that gives us these chiral optical properties," Rodrigues explained. "The goal is really to take advantage of the discrepancy between one circular polarization versus the other to create the broadband resonances we need." The material operates in the visible to near-infrared spectrum, at approximately 740 to 1,000 nanometers. The optical rotation and circular dichroism measurements were taken with the beam entering the material at a normal incident angle. The researchers induced the change in circular dichroism by increasing the optical power applied to the material from 0.5 milliwatts up to 15 milliwatts. While that is comparatively low power for a laser system, it has a high enough energy flux (energy transfer in time) to instigate change. "The beam size is roughly 40 microns, so it is really focused," said Rodrigues. "We are putting a lot of energy into a small area, which causes the effect to be fairly intense." The researchers don't yet know what prompts the change, but suspect that thermal processes may be involved in altering the material's properties to boost the circular dichroism. Tests show that the power applications do not damage the metamaterial. Cai's laboratory has been studying chiral materials of different kinds for a variety of optical applications. In June 2015, they reported the realization of one of the long-standing theoretical predictions in nonlinear optical metamaterials: creation of a nonlinear material that has opposite refractive indices at the fundamental and harmonic frequencies of light. Such a material, which doesn't exist naturally, had been predicted for nearly a decade. In addition to those already mentioned, the research included Shoufeng Lan, Lei Kang, Yonghao Cui, Patrick Panuski, Shengxiang Wang and Augustine M. Urbas. Urbas is associated with the Air Force Research Laboratory at Wright-Patterson Air Force Base; Wang is associated with Wuhan Textile University in China. The others are associated with Georgia Tech. This work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542174). This material is based on work partially supported by the National Science Foundation under Grant No. ECCS-1609567 and by collaborative support from the Air Force Research Laboratory through UES and Azimuth subcontracts S-977-022-001 and 238-5404-GIT, respectively. Support is also acknowledged from the National Science Foundation (NSF) Graduate Research Fellowship under Grant No. DGE-1650044. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations. CITATION: Rodrigues, S.P. et al., "Intensity-dependent modulation of optically active signals in a chiral metamaterial," (Nature Communications, 2017). http://dx. .
Wang B.,Wuhan Textile University |
Wang K.,Fuzhou University
Bioresource Technology | Year: 2013
A continuous batch bioleaching was built to realize the bioleaching of sewage sludge in large scale. In the treatment, heavy metal in acid wastewater of bioleaching was removed by adsorption onto ramie residue. Then, acid wastewater was reused in next bioleaching batch. In this way, most time and water of bioleaching was saved and leaching efficiency of copper, lead and chromium kept at a high level in continuous batch bioleaching. It was found that residual heavy metal in sewage sludge is highly related to that in acid wastewater after bioleaching. To get a high leaching efficiency, concentration of heavy metal in acid wastewater should be low. Adsorption of copper from acid wastewater onto ramie residue can be described by pseudo first-order kinetics equation and Freundlich isotherm model. Trichoderma viride has the potential to be used for the concentration and recovery of heavy metal adsorbed onto ramie residue. © 2013 Elsevier Ltd.
Zhang Q.,Wuhan Textile University |
Zhao J.,Wuhan Textile University
Nonlinear Dynamics | Year: 2012
This paper mainly investigates the projective and lag synchronization between general complex networks via impulsive control. A general drive complex network and an impulsively controlled slave network are presented in the model. Specially, the coupling matrix in this model is not assumed to be symmetric, diffusive or irreducible. Some criteria and corollaries are, respectively, derived for the projective synchronization and lag synchronization between the presented impulsively controlled complex networks. Finally, the results are illustrated by complex networks composed of the chaotic Lorenz systems. All the numerical simulations verify the correctness of the theoretical results. © 2011 Springer Science+Business Media B.V.
Huang J.,Huazhong University of Science and Technology |
Shi H.,Wuhan Textile University
IEEE Transactions on Power Electronics | Year: 2014
High common-mode voltage (CMV) of an output will be produced in the conventional sinusoidal pulse width modulation three-phase inverter. Although the carrier phase-shift method can be used to reduce the peaks of CMV, it has the best suppression effect only when the SPWM modulation index is no more than 2/3. This letter presents a new scheme of carrier peak position modulation to break the limitation of modulation index. In this scheme, the peak positions of the triangular carriers are delayed or advanced to avoid the zero state. Thus, the peaks of CMV will be reduced under any modulation index. The feasibility and validity of this scheme are verified through the experiments. © 1986-2012 IEEE.
Zhang X.,Huazhong University of Science and Technology |
Zhang X.,Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment |
Zhang H.,Wuhan Textile University
Thin-Walled Structures | Year: 2013
Multi-cell metal columns were found to be much more efficient in energy absorption than single-cell columns under axial compression. However, the experimental investigations and theoretical analyses of them are relatively few. In this paper, the quasi-static axial compression tests are carried out for multi-cell columns with different sections. The significant advantage of multi-cell sections over single cell in energy absorption efficiency is investigated and validated. Numerical simulations are also conducted to simulate the compression tests and the numerical results show a very good agreement with experiment. Theoretial analyses based on constitutive element method are proposed to predict the crush resistance of multi-cell columns and the theoretical predictions compare very well with the experimental and numerical results. © 2013 Elsevier Ltd.
Wan L.,Wuhan Textile University |
Zhou Q.,Zhaoqing University
Nonlinear Analysis: Real World Applications | Year: 2011
This paper investigates the attractor and ultimate boundedness for stochastic cellular neural networks with delays. By employing the Lyapunov method and a Lasalle-type theorem, novel results and sufficient criteria on the attractor and ultimate boundedness are obtained. © 2011 Elsevier Ltd. All rights reserved.
Jin D.,Wuhan Textile University
International Journal of Digital Content Technology and its Applications | Year: 2012
Electronic commerce which had researched 7.0 trillion's market scale in china by the end of 2011 has become one of the most important models of modern business, greatly promoting commercial activities. Internet of Things (IoT) in which wireless network of uniquely identifiable objects was used for the Internet has extended into our daily lives. So far there have already lots of works on the related subjects. And lots of researches about the applications of ToT, also some papers engaged in the application of IoT in E-commerce. But almost all of the works either focused on the two different subjects respectively, or only touched on the application of the later in the former, in this paper we made some researches of the application in details from the points of business models and technologies related, also we discussed about some related questions such as "Privacy and Security Issues" that was needed to deal with in the future.
Wuhan Textile University | Date: 2013-12-02
The invention provides a two-dimensional run-length limited (RLL) (1,3) code method and apparatus. The codec comprises an encoder and a decoder comprising a data buffer and grouping module, a two-dimensional code word generating module, a two-dimensional word unit page constructing module, a two-dimensional code word write array module, and a protection word stuffing module. The five modules are sequentially connected, and send output through the protection word stuffing module to a two-dimensional data recording device. The decoder comprises a two-dimensional data buffer module, a two-dimensional word unit page constructing module, a one-dimensional data word decoding module, and a one-dimensional data stream assembly module. The five modules are sequentially connected, and send output through the one-dimensional data stream assembly module. The encoding/decoding method and apparatus can solve problems that any binary two-dimensional data array composed of 0s and 1s satisfies two-dimensional (1, 3) RLL constraints in both horizontal and vertical directions.
Wuhan Textile University | Date: 2014-08-22
The present invention relates to a chain, continuous and no-waste method for degumming and fiber-separating the ramie, including anaerobic circle step, in which the raw fibers after the waste alkali bath step are immersed in the anaerobic water pool; aerobic circle step, in which the raw fibers after the anaerobic circle step are immersed in the aerobic water pool; alkali-hydrogen peroxide one bath scouring-bleaching step, in which the raw fibers after the aerobic circle step are immersed in a combined solution of NaOH and H_(2)O_(2); and the treatment by a fiber-separating and washing device followed by the immersion in the cellulase solution. In the present invention, the ramie degumming process and the degumming wastewater treatment are performed integratively, and the degumming wastewater is completely recycled after treatment.