关键词：
Global quantum discord (GQD);Lipkin–Meshkov–Glick (LMG) model;Multipartite nonlocality;Quantum phase transitions
摘要：
We have investigated the multipartite nonlocality and global quantum discord (GQD) in the antiferromagnetic Lipkin-Meshkov-Glick (LMG) model. We find that nonlocality and GQD can indicate quantum phase transitions by singular behaviors. The results also show that GQD always behaves a linear growth with log(10) N in the LMG model, which is different from linear scaling in one-dimensional chains. And this scaling behavior is not affected by anisotropic parameter gamma. Moreover, the nonlocality (denoted by.) is discovered to scale as log(10) S vertical bar(h) similar to aN+b for the transverse-field LMG model (i.e., gamma = 0). However, scaling behaviors can be well fitted by formula S vertical bar(h) = a 1/N + b for the LMG model with gamma > 0. By comparing the results of GQD and nonlocality, we have observed that nonlocality decreases but GQD increases as the size of the system grows. These results indicate that gamma has a significant influence on the nonlocality and GQD in the LMG model.
摘要：
By introducing a high permeability material into the traditional magnetoelectric (ME) composite, a non-zero ME coefficient can be obtained when the external DC magnetic field is zero. This is called the self-biased ME effect. In this system, the high permeability material can be regarded as a special ferromagnetic material. A magnetic field will be generated around it, which affects the internal magnetic field distribution of the ferromagnetic phase in the ME composite. In this paper, we consider the multi-field coupling characteristics of the ME composites, the non-linear characteristics of the individual component materials, and the mechanical and magnetic properties of the high permeability material, to develop a theoretical model for such self-biased ME effect. Then the finite element method is employed to solve the Maxwell equations for this complex problem. The developed theory is highlighted with a direct comparison with experiments that shows their close agreement. It is also demonstrated that, with the addition of the high permeability material, the self-biased ME coefficient can account for 47% of the maximum ME coefficient. This remarkable outcome, and the detailed distributions of the magnetic field, electric field, and elastic field inside ME structures are also presented in detail. Finally, the influence of temperature on the ME effect of the two structures was also studied, and the results showed that the higher the temperature, the smaller the ME coefficient of the structures.
摘要：
Hyperspectral imaging (HSI) has shown great potential in the use of paddy variety identification. However, the quality of HSI images taken by a hyperspectral camera under non-ideal illumination is vulnerable to environmental influences such as shadows and noises, leading to a degraded identification result. This problem is addressed in this study by a two-stage image processing method. First, to eliminate the influence of shadows, a grayscale image based on the reflectance slope is synthesized. The synthetic reflectance slope image (SRSI) is binarized for image segmentation and shape features extraction. Secondly, an HSI image de-noising technology based on weighted spatial filtering (WSF), which integrates both spatial and spectral information of the HSI image, is proposed to reduce the influence of noises. Finally, the extracted shape, spectral and texture features are combined and input into the support vector machine for paddy variety identification. Four varieties of paddy with different origins were tested in the experiments. The experiment results showed that compared with color images, the SRSIs could help obtain more accurate shape features. The results also showed that the WSF method can significantly reduce noises and improves the paddy variety identification accuracy.
作者：
Xia, Xiaodong*;Zhao, Shijun;Fang, Chao;Weng, George J.*
期刊：
Mathematical Methods in the Applied Sciences,2020年 ISSN：0170-4214
通讯作者：
Xia, Xiaodong;Weng, George J.
作者机构：
[Xia, Xiaodong; Zhao, Shijun] Cent South Univ, Sch Civil Engn, Changsha 410083, Peoples R China.;[Fang, Chao] Wuhan Polytech Univ, Dept Elect & Elect Engn, Wuhan, Peoples R China.;[Weng, George J.] Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA.
通讯机构：
[Xia, Xiaodong] C;[Weng, George J.] R;Cent South Univ, Sch Civil Engn, Changsha 410083, Peoples R China.;Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA.
摘要：
Recent experiments have revealed the strain-dependent phenomenon of electrical resistance for CNT-polymer nanocomposites, but at present, no theory seems to exist to explain such observations. In this paper, a strain-dependent homogenization scheme with considerations of volume change of the nanocomposite and strain-dependent electron tunneling is developed to this end. The effective electrical conductivity and secant moduli of the nanocomposite are selected as the two homogenization parameters. The thermodynamic driving force and the corresponding evolution equation of the progressive degradation process of the interface are also derived. It is demonstrated that the predicted resistance change ratio and strain sensitivity factor of CNT-polymer nanocomposites are in close agreement with the experimental results over a wide range of strain loading. With the addition of CNT nanofillers, both theory and experiments show a decrease of resistance change ratio and strain sensitivity factor. As the strain loading increases, the resistance change ratio first increases slightly and then increases rapidly. Among other novel features of the theory, it is also shown that CNT-polymer nanocomposites can attain a very high strain sensitivity factor even at a low CNT loading. It is believed that this research can provide a practical guidance to the design of high-sensitivity strain sensors.
摘要：
We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds ( |α|≤1) down to a length scale λ=48 μm. This work establishes the strongest bound on the magnitude α of the Yukawa violation in the range of 40–350 μm, and improves the previous bounds by up to a factor of 3 at the length scale λ≈70 μm. Furthermore, the constraints on the power-law potentials are improved by about a factor of 2 for k=4 and 5.
摘要：
A set–reset latch is a basic building block of computers and can be used to store state information. Here, by testing the influence of the two logical input signals on the reliable set–reset latch logic operation in the bistable system, we found that there are two types of input signals, namely, suprathreshold and subthreshold signals. For the suprathreshold signals, reliable set–reset logic operation can be achieved without any driving forces and exhibits certain anti-interference ability; for the subthreshold signals, a single harmonic could induce correct set–reset latch logic operation but with a narrow optimal parameter region. The introduction of biharmonic-induced set–reset latch logic operation (logical vibrational resonance) could greatly expand the parameter region. Explanations for the above results were provided by taking the logical inputs as the dynamic bias to analyze the dynamic changes in the system. Finally, the results were further verified by circuit simulation and actual hardware circuit.
摘要：
For future high-performance microbolometric focal plane array, a new kind of CMOS readout integrated circuits is proposed in this paper. The whole readout integrated circuits consist of several or dozens of readout modules working in parallel and all the output signals of these readout modules can be output one by one by a common high-speed HCDS output circuit. The microbolometer in each readout module is biased with a pulse current, which can be adjusted with the substrate temperature fluctuation to achieve a uniform microbolometric infrared responsivity, and its voltage response signal can be directly amplified by a differential amplifier. Because there is no need of microbolometric response current integration time and capacitor in the readout module as those in traditional readout integrated circuits, the pixel-readout-speed of the readout module can easily reach up to about 100 MHz and the pixel-size is no longer restricted with the integration capacitor area. The common high-speed HCDS output circuit can effectively suppress the output noise of each readout module, and form a high-speed infrared image data stream from these output signals of all the readout modules. Furthermore, the adjustable pulse current can compensate the responsivity changes caused by the substrate temperature fluctuation. This kind of proposed CMOS readout integrated circuits can be utilized for future high-performance microbolometric focal plane array with low-power, high-speed, small-pixel, small-volume, and high-stability.
摘要：
Spin- 12 two-leg ladder models under a magnetic field have a well-known phase diagram. In this paper, we use multipartite nonlocality (a measure of multipartite quantum correlations) to characterize the quantum correlations in the ladder models at zero temperature. Both finite-size and infinite-size ladders are considered. We investigate the global nonlocality Sg=S(|Ψg〉), which describes quantum correlations of the ground states |Ψg〉 of the entire lattices, and the partial nonlocality Sp=S(ρ̂n), which describes quantum correlations of the reduced states ρ̂n of some sublattices in the ladders. We find that as the magnetic field λ increases, the global nonlocality Sg presents a single-peak curve. Moreover, the logarithmic measure lnSg changes dramatically at the two critical fields λc1 and λc2 of the models and thus signals the quantum phase transitions in the models. For the partial nonlocality Sp, in the regions λc1<λ<λc2, we observe that the Sp(λ) curve shows an oscillation. Numerical results reveal that the underling mechanism is the “major component transitions” in the reduced states ρ̂n of the sublattices. More importantly, the oscillation of the partial nonlocality Sp is modulated by the single-peak curve of the global nonlocality Sg. The result provides valuable clues about the relation between partial nonlocality and global nonlocality in low-dimensional quantum models.
摘要：
In quantum lattice models, in the large- N limit, boundary conditions have little effect upon local observables for sites in the centers of the lattices. In this paper, we will study the boundary effects upon multipartite nonlocality (a kind of multipartite quantum correlation associated with Bell-type inequalities) in one-dimensional finite-size spin chains, both for zero temperature and for finite temperatures. We define a quantity δSS to characterize the boundary effects, where S is a measure of global multipartite nonlocality of the entire lattice, and δS is the difference of the measure induced by changing the boundary conditions. We find δSS does not vanish in the large- N limit. Instead, at zero temperature, with the increase of N, δSS would increase steadily in the vicinity of the quantum phase transition point of the models, and converge to a nonzero constant in noncritical regions. It shows clearly that boundary effects generally exist, in the form of multipartite correlations, in long chains. The boundary effects are explained by the competition between the two orders of the models. In addition, based on these numerical results, we construct a Bell inequality, which is violated by chains with periodic (closed) boundary conditions and not violated by chains with open boundary conditions. Furthermore, we study δSTST of finite-size chains at finite temperatures, and show that boundary effects survive in finite temperature regions.
关键词：
Global quantum discord;Quantum phase transitions;Thermal tensor network
摘要：
We characterize multi-site quantum correlations in 1D finite-size XXZ chains at finite temperatures with global quantum discord. With the help of an exact diagonalization method and a thermal-tensor-network algorithm, the thermal-state discord G((rho) over cap (T)) is evaluated efficiently by well-developed optimization algorithms. Firstly, we find that in a finite temperature region, G((rho) over cap (T)) shows some footprint of the quantum phase transition of the model. The underlying mechanism is that (rho) over cap (T) captures the level crossing in the low-lying excited states. Secondly, we study the temperature dependence of G((rho) over cap (T)). When the anisotropy is strong, G((rho) over cap (T)) will show a broad thermal plateau. We offer a quantitative explanation of the plateau by truncating the thermal-state operator (rho) over cap (T) with respect to several low-lying states. Thirdly, we investigate the scaling behavior of G((rho) over cap (T)). We find that when N is large enough, G((rho) over cap (T)) would show a linear scaling. Finally, combined with the thermal tensor networks and the linear scaling behavior, we successfully figure out reliable results for G((rho) over cap (T)) in the full-temperature regions with N up to 16. We believe that the thermal tensor networks will play a role in studying general multi-site quantum correlations in 1D chains at finite temperatures.
期刊：
Journal of Applied Physics,2019年125(8):084102 ISSN：0021-8979
通讯作者：
Weng, George J.
作者机构：
[Zhang, Juanjuan] Lanzhou Univ, Minist Educ China, Key Lab Mech Environm & Disaster Western China, Lanzhou 730000, Gansu, Peoples R China.;[Zhang, Juanjuan] Lanzhou Univ, Coll Civil Engn & Mech, Dept Mech & Engn Sci, Lanzhou 730000, Gansu, Peoples R China.;[Fang, Chao] Wuhan Polytech Univ, Dept Elect & Elect Engn, Wuhan 430023, Hubei, Peoples R China.;[Fang, Chao; Weng, George J.; Zhang, Juanjuan] Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA.
通讯机构：
[Weng, George J.] R;Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA.
关键词：
dielectric depolarisation;dielectric hysteresis;dielectric polarisation;electric domains;fast Fourier transforms;Ginzburg-Landau theory
摘要：
The phase field approach has been widely used to study the domain structure of ferroelectric crystals in both two and three dimensions (2D and 3D), but in the 3D case, little has been done to address the frequency dependence of ferroelectric characteristics. In this work, we adopt the 3D time-dependent Ginzburg–Landau kinetic equation to calculate the evolution of local polarization vectors and the overall hysteresis loops of ferroelectric crystals under the frequencies from 0.4 kHz to 120 kHz, and then use the fast Fourier transform to analyze the frequency characteristics of the polarizations. It shows the phenomenon of multiple frequencies at low field frequency but not at high one. The distribution and evolution of polarization vectors in x, y, and z directions are obtained, and various forms of electrical hysteresis loops are found from the average of local polarization vectors. The results indicate that, as the frequency increases, the hysteresis loops of Pz versus Ez change from the standard shape to the oval shape, but the loops for Px and Py change from the dumbbell shape to an oblique ellipse, and then to figure-eight curve and eventually to the superparaelectric one. The detailed distribution and evolution of the polarization vectors in the crystal are also vividly displayed. Finally, the effects of lattice size, amplitude of the applied field, depolarization energy, and the initial state of polarizations in the crystal are investigated. It shows that the nature of polarization evolution in a 3D crystal is highly complex and that each of these factors can have a significant effect.
关键词：
Microbolometer array;Pulse current bias;Responsivity
摘要：
Based on the physical thermal balance equation of the microbolometer under pulse current bias, the microbolometric theoretical infrared responsivity is given out in this paper. The operating temperature of the microbolometer during the pulse current bias period is theoretically discussed and analyzed, from which the microbolometric theoretical infrared responsivity expression is derived for high-speed microbolometric focal plane array. The microbolometric theoretical infrared responsivity expression reveals some key factors to decide the infrared sensitivity of the microbolometric focal plane array and has been successfully verified through an experimental microbolometric focal plane array. The microbolometric theoretical infrared responsivity expression is theoretically strict and can be utilized for future microbolometric focal plane arrays with some high-performance characteristics parameters such as high-speed and small-pixel.
通讯机构：
[Jo, Hongki] U;Univ Arizona, Dept Civil Engn & Engn Mech, Tucson, AZ 85721 USA.
关键词：
capacitive strain sensor;soft elastomeric capacitor;structural health monitoring;wireless sensor
摘要：
Conventional resistive-type strain sensing methods have limitations in large-area sensing due to their relatively small size. The soft elastomeric capacitive (SEC) sensor is a capacitance-based stretchable electronic strain sensor, which has shown distinct advantages for mesoscale sensing over conventional strain-based structural health monitoring (SHM) due to its wide surface coverage capability. While recent advances in wireless sensor technologies have provided an attractive alternative to wired and centralized SHM, the capacitive strain sensing methods have not benefitted from the wireless approaches due to the lack of appropriate hardware element. This study develops a wireless sensor board to use the SEC sensor in combination with a wireless sensor network for SHM by addressing key implementation challenges. An alternating current (AC)-based De-Sauty Wheatstone bridge circuit is employed, converting dynamic capacitance variation from the SEC sensor into analog voltage signal. A high-precision bridge balancer and two-step signal amplifiers are implemented to effectively apply for low-level structural strain vibrations. An amplitude modulation-demodulator has been designed to extract the baseband signal (i.e. strain signal) from the carrier signal (i.e. AC excitation for the Wheatstone bridge). And a dual-step shunt calibrator has been proposed to remove the parasitic capacitance effect of lead wires during on-board calibration process. The performances of the sensor board developed in this study have been validated via a series of lab tests, outperforming a conventional wired capacitance measurement system.
