Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes

Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.

Dynamics Behaviors of a Reaction-Diffusion Predator-Prey System with Beddington-DeAngelis Functional Response and Delay

This paper is concerned with the existence of traveling wave solutions in a reaction-diffusion predator-prey system with Beddington-DeAngelis functional response and a discrete time delay. By introducing a partial quasi-monotonicity condition and constructing a pair of upper-lower solutions, we establish the existence of traveling wave solutions. Moreover, a numerical simulation is carried out to illustrate the theoretical results.

Thermal and piezoelectric properties of Bi_(3.15)Nd_(0.85)Ti_3O_(12) thin film prepared by metal organic decomposition

Bi3.15Nd0.85Ti3O12 （BNT） powder and thin film were prepared by metal organic decomposition （MOD） method. The heat flow curve of BNT powder was measured with a modulated temperature differential scanning calorimeter, and thermal physical parameters such as thermal conductivity coefficient and thermal diffusion coefficient were obtained from the heat flow curve. The phase identification, ferroelectric, and piezoelectric properties of BNT thin film annealed at 700℃ were investigated with X-ray diffractometer, ferroelectric analyzer, and scanning probe microscope. The results show that the thin films consisting of a single phase of bismuth-layered perovskite are polycrystalline, without a preferred orientation. Remnant polarization 2Pr is 63.2 μC/cm2 under 530 kV/cm applied field, and the effective piezoelectric coefficient d33 is 30 pm/V.

The effects of a static magnetic field on the microwave absorption of hydrogen plasma in carbon nanotubes: a numerical study

We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high- pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the exter- nal static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.

Microflow-induced shear stress on biomaterial wall by ultrasound-induced encapsulated microbubble oscillation

A model of an ultrasound-driven encapsulated microbubble（EMB） oscillation near biomaterial wall is presented and used for describing the microflow-induced shear stress on the wall by means of a numerical method. The characteristic of the model lies in the explicit treatment of different types of wall for the EMB responses. The simulation results show that the radius-time change trends obtained by our model are consistent with the existing models and experimental results. In addition, the effect of the elastic wall on the acoustic EMB response is stronger than that of the rigid wall, and the shear stress on the elastic wall is larger than that of the rigid wall. The closer the EMB to the wall, the greater the shear stress on the wall. The substantial shear stress on the wall surface occurs inside a circular zone with a radius about two-thirds of the bubble radius. This paper may be of interest in the study of potential damage mechanisms to the microvessel for drug and gene delivery due to sonoporation.

Effects of resonant magnetic perturbation on the instability of single tearing mode with non-shear flow

Non-shear flow can change the O-point position of a magnetic island, and thus it may play an important role in the effects of resonant magnetic perturbation(RMP) on the single tearing mode. We employ the nonlinear magnetohydrodynamics model in a slab geometry to investigate how RMP affects the single tearing mode instability with non-shear flow. It is found that the driving and suppressing effects of RMP on single tearing mode instability will appear alternately. When the flow velocity is small, the suppressing effect plays a major role through the development of the mode, and the tearing mode instability will be suppressed. With the flow velocity increasing, the driving effect will increase, while the suppressing effect will decrease. When the two effects reach equilibrium, the tearing mode will become stable.

Dynamics of an ultrasound contrast agent microbubble near spherical boundary in ultrasound field

The goal of this article is to establish the conditions of excitation where one has to deal with ultrasound contrast agent(UCA) microbubbles pulsating near biological tissues with spherical boundary in ultrasound field for targeted drug delivery and cavitation-enhanced thrombolysis, etc., and contributes to understanding of mechanisms at play in such an interaction. A modified model is presented for describing microbubble dynamics near a spherical boundary(including convex boundary and concave boundary) with an arbitrary-sized aperture angle. The novelty of the model is such that an oscillating microbubble is influenced by an additional pressure produced by the sound reflection from the boundary wall. It is found that the amplitude of microbubble oscillation is positively correlated to the curve radius of the wall and negatively correlated to the aperture angle of the wall and the sound reflection coefficient. Moreover, the natural frequency of the microbubble oscillation for such a compliable wall increases with the wall compliance, but decreases with the reduction of the wall size, indicating distinct increase of the natural frequency compared to a common rigid wall. The proposed model may allow obtaining accurate information on the radiation force and signals that may be used to advantage in related as drug delivery and contrast agent imaging.

Numerical analysis of the optimized performance of the electron cyclotron wave system in a HL-2M tokamak

The capabilities of current drive, neoclassical tearing mode （NTM） stabilization, and sawtooth control are analyzed for the electron-cyclotron wave （ECW） system in a HL-2M tokamak. Better performance of the upper launcher is demonstrated in comparison with that of a dropped upper launcher, in terms of JEc/Jbs for NTM stabilization and 1ECCD/（Aptor）2 for sawtooth control. 1-MW ECW power is enough for the 3/2 NTM stabilization, and 1.8-MW ECW power is required to suppress 2/1 NTM in a single null divertor equilibrium with 1.2-MA toroidal current with the upper launcher. Optimization simulation of electron-cyclotron current drive （ECCD） is carried out for three mirrors in an equatorial port, indicating that the middle mirror has a good performance compared with the top and bottom mirrors. The results for balanced co- and counter-ECCD in an equatorial port are also presented.

CONTROLLABILITY FOR A PARABOLIC EQUATION WITH A NONLINEAR TERM INVOLVING THE STATE AND THE GRADIENT

In this article, we consider the controllability of a quasi-linear heat equation involving gradient terms with Dirichlet boundary conditions in a bounded domain of RN.The results are established by using the variational methods, the related duality theory and Kakutani Fixed-point Theorem.

Complex conductivity and permittivity of single wall carbon nanotubes/polymer composite at microwave frequencies:A theoretical estimation

Based on an equivalent resistance-capacitance network, the complex conductivity and the relative complex permittivity of single wall carbon nanotubes (SWNTs)/polymer composite are theoretically investigated in the frequency range of 0.30-18 GHz using the logarithmic rule. Both the real and imaginary parts of the permittivities of SWNTs and polymer are considered in detail. The calculated complex permittivity spectra of SWNTs/poly(ethyl methacrylate) composite films are in good agreement with the available experimental data. The influences of SWNTs concentration on both the complex conductivity and the dielectric loss tangent of the composite are presented in the microwave frequency range. A linear relationship between microwave conductivity and frequency is found.

四嗪硫铜捕收剂浮选分离黄铜矿和黄铁矿

黄药对硫化矿具有很强的捕收性能,但其对黄铜矿和黄铁矿的分离效果不佳。为了有效地从黄铜矿中分离出黄铁矿,本文将四嗪硫铜官能团和疏水烃基结合,设计出一种新型的捕收剂-四嗪硫铜捕收剂。探究了四嗪硫铜捕收剂对黄铜矿和黄铁矿的浮选性能,并研究了四嗪硫铜捕收剂中不同的疏水烃链对浮选性能的影响。紫外实验结果表明,6-己基-6-甲基-1,2,4,5-四嗪-3-硫铜(HxMTT)易于与铜离子和亚铜离子结合,并在结合过程中释放氢离子进入溶液,但不易与铁离子和亚铁离子结合。原子力和接触角实验结果表明,HxMTT吸附在黄铜矿的表面,增加了黄铜矿表面的疏水性。红外和XPS实验结果进一步表明,HxMTT通过形成Cu—N和Cu—S键化学吸附在黄铜矿表面。

The Auslander-type condition of triangular matrix rings

Let R be a left and right Noetherian ring and n, k be any non-negative integers. R is said to satisfy the Auslander-type condition Gn（k） if the right fiat dimension of the （i ＋ 1）-th term in a minimal injective resolution of RR is at most i ＋ k for any 0 ≤ i ≤ n - 1. In this paper, we prove that R is Gn（k） if and only if so is a lower triangular matrix ring of any degree t over R.

Attractor for Lattice System of Dissipative Zakharov Equation

We consider the asymptotic behavior of solutions of an infinite lattice dynamical system of dissipative Zakharov equation. By introducing new weight inner product and norm in the space and establishing uniform estimate on ＂Tail End＂ of solutions, we overcome some difficulties caused by the lack of Sobolev compact embedding under infinite lattice system, and prove the existence of the global attractor; then by using element decomposition and the covering property of a polyhedron in the finite-dimensional space, we obtain an upper bound for the Kolmogorov ε-entropy of the global attractor; finally, we present the upper semicontinuity of the global attractor.

Reduction of phonon thermal conduction in isotopic graphene nanoribbon superlattices

Graphene nanoribbons （GNRs） recently have drawn much interest because of their novel electronic properties such as well-controlled electronic structures [1], high Seebeck coefficient [2], and intriguing electronic transport [3]. For the thermoelectric energy conversion, GNRs are thought to be rather poor candidates because of too high phonon thermal conductance [4], though they own good electronic conduction, Thus, the reduction of the phonon thermal conductance of GNRs is particularly important for their thermoelectric applications. Several methods such as strain [5],

An adaptive data-driven method for accurate prediction of remaining useful life of rolling bearings

A novel data-driven method based on Gaussian mixture model （GMM） and distance evaluation technique （DET） is proposed to predict the remaining useful life （RUL） of rolling bearings. The data sets are clustered by GMM to divide all data sets into several health states adaptively and reasonably. The number of clusters is determined by the minimum description length principle. Thus, either the health state of the data sets or the number of the states is obtained automatically. Meanwhile, the abnormal data sets can be recognized during the clustering process and removed from the training data sets. After obtaining the health states, appropriate features are selected by DET for increasing the classification and prediction accuracy. In the prediction process, each vibration signal is decomposed into several components by empirical mode decomposition. Some common statis- tical parameters of the components are calculated first and then the features are clustered using GMM to divide the data sets into several health states and remove the abnormal data sets. Thereafter, appropriate statistical parameters of the generated components are selected using DET. Finally, least squares support vector machine is utilized to predict the RUL of rolling bearings.Experimental results indicate that the proposed method reliably predicts the RUL of rolling bearings.

Joule–Thomson expansion of higher dimensional nonlinearly AdS black hole with power Maxwell invariant source

In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a zero point and a divergent point,which coincide with the inversion temperature Tiand the zero point of the Hawking temperature,respectively.The inversion temperature increases monotonously with inversion pressure.For the high-pressure region,the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s,whereas it increases with the charge Q.However,Tifor the low-pressure region increase with D and s,while it decreases with Q.The ratioηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q,it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s=1.However,for s>1,it becomes smaller and smaller as D increases and approaches a constant when D→∞.Finally,we found that an increase of mass M and s,or reducing the charge Q and D can enhance the isenthalpic curve,and the effect of s on the isenthalpic curve is much greater than other parameters.

Existence of anti-periodic solutions for hemivariational inequalities

J.Y. Park and T. G. Ha [Nonlinear Anal., 2008, 68： 747-767; 2009, 7h 3203-3217] investigated the existence of anti-periodic solutions for hemivariational inequalities with a pseudomonotone operator. In this note, we point out that the methods used there are not suitable for the proof of the existence of anti-periodic solutions for hemivariational inequalities and we shall give a straightforward approach to handle these problems. The main tools in our study are the maximal monotone property of the derivative operator with anti- periodic conditions and the surjectivity result for L-pseudomonotone operators.

Extraction of gravitational wave signals with optimized convolutional neural network

Gabbard et al.have demonstrated that convolutional neural networks can achieve the sensitivity of matched filtering in the recognization of the gravitational-wave signals with high efficiency[Phys.Rev.Lett.120,141103(2018)].In this work we show that their model can be optimized for better accuracy.The convolutional neural networks typically have alternating convolutional layers and max pooling layers,followed by a small number of fully connected layers.We increase the stride in the max pooling layer by 1,followed by a dropout layer to alleviate overfitting in the original model.We find that these optimizations can effectively increase the area under the receiver operating characteristic curve for various tests on the same dataset.

Gravitational Deflection of Massive Particles by a Schwarzschild Black Hole in Radiation Gauge

The exact metric of a Schwarzschild black hole in the true radiation gauge was recently reported. In this work, we base on this gravity and calculate the gravitational deflection of relativistic massive particles up to the fourth post-Minkowskian order. It is found that the result is consistent with the previous formulations for both the case of dropping the fourth-order contribution and the case of light deflection. Our result might be helpful for future high-accuracy observations.

Parameterized Post-Post-Newtonian Light Propagation in the Field of One Spherically-Symmetric Body

We derive a more generally parameterized post-post-Newtonian solution for the light propagation in the gravitational field of one spherically-symmetric body.Based on the solution for the light velocity,we give the formula of the light deflection when both the emitter and receiver are located in the regions far away from the body,which is the most important scenario in the real applications.Our results can be applied to more metric theories of gravitation.