Negative Stiffness Mechanism on An Asymmetric Wave Energy Converter by Using A Weakly Nonlinear Potential Model

Salter's duck,an asymmetrical wave energy converter(WEC)device,showed high efficiency in extracting energy from 2D regular waves in the past;yet,challenges remain for fluctuating wave conditions.These can potentially be addressed by adopting a negative stiffness mechanism(NSM)in WEC devices to enhance system efficiency,even in highly nonlinear and steep 3D waves.A weakly nonlinear model was developed which incorporated a nonlinear restoring moment and NSM into the linear formulations and was applied to an asymmetric WEC using a time domain potential flow model.The model was initially validated by comparing it with published experimental and numerical computational fluid dynamics results.The current results were in good agreement with the published results.It was found that the energy extraction increased in the range of 6%to 17%during the evaluation of the effectiveness of the NSM in regular waves.Under irregular wave conditions,specifically at the design wave conditions for the selected test site,the energy extraction increased by 2.4%,with annual energy production increments of approximately 0.8MWh.The findings highlight the potential of NSM in enhancing the performance of asymmetric WEC devices,indicating more efficient energy extraction under various wave conditions.

A Lagrangian Trajectory Analysis of Azimuthally Asymmetric Equivalent Potential Temperature in the Outer Core of Sheared Tropical Cyclones

In this study,the characteristics of azimuthally asymmetric equivalent potential temperature(θ_(e))distributions in the outer core of tropical cyclones(TCs)encountering weak and strong vertical wind shear are examined using a Lagrangian trajectory method.Evaporatively forced downdrafts in the outer rainbands can transport low-entropy air downward,resulting in the lowestθ_(e)in the downshear-left boundary layer.Quantitative estimations ofθ_(e)recovery indicate that air parcels,especially those originating from the downshear-left outer core,can gradually revive from a low entropy state through surface enthalpy fluxes as the parcels move cyclonically.As a result,the maximumθ_(e)is observed in the downshear-right quadrant of a highly sheared TC.The trajectory analyses also indicate that parcels that move upward in the outer rainbands and those that travel through the inner core due to shear make a dominant contribution to the midlevel enhancement ofθ_(e)in the downshear-left outer core.In particular,the former plays a leading role in suchθ_(e)enhancements,while the latter plays a secondary role.As a result,moist potential stability occurs in the middle-to-lower troposphere in the downshear-left outer core.

Ultrafast cyclic voltammetry with asymmetrical potential scan

Based on the perfect ohmic drop compensation by online electronic positive feedback, ultrafast cyclic voltammetry with asymmetrical potential scan is achieved for the first time, with the reduction of anthracene acting as the test system. Compared with the traditional cyclic voltammetry utilizing symmetrical triangular waveform as the excitation one, the new method allows a simpler approach to mechanistic analysis of ultrafast chemical reactions coupled with a charge transfer. And perhaps more important, it also provides a way to eliminate the interference of the adsorbed product in dynamic monitoring. 2007 Zhi Yong Guo. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Pulsatile electroosmotic flow of a Maxwell fluid in a parallel flat plate microchannel with asymmetric zeta potentials

The pulsatile electroosmotic flow （PEOF） of a Maxwell fluid in a parallel flat plate microchannel with asymmetric wall zeta potentials is theoretically analyzed. By combining the linear Maxwell viscoelastic model, the Cauchy equation, and the electric field solution obtained from the linearized PoissomBoltzmann equation, a hyperbolic par- tial differential equation is obtained to derive the flow field. The PEOF is controlled by the angular Reynolds number, the ratio of the zeta potentials of the microchannel walls, the electrokinetic parameter, and the elasticity number. The main results obtained from this analysis show strong oscillations in the velocity profiles when the values of the elas- ticity number and the angular Reynolds number increase due to the competition among the elastic, viscous, inertial, and electric forces in the flow.

Asymmetric and Single-Side Splitting of Dissipative Solitons in Complex Ginzburg–Landau Equations with an Asymmetric Wedge-Shaped Potential

We report some novel dynamical phenomena of dissipative solitons supported by introducing an asymmetric wedge-shaped potential(just as a sharp ‘razor') into the complex Ginzburg–Landau equation with the cubicquintic nonlinearity. The potentials corresponding to a local refractive index modulation with breaking symmetry can be realized in an active optical medium with respective expanding antiwaveguiding structures. Using the razor potential acting on a central dissipative soliton, possible outcomes of asymmetric and single-side splitting of dissipative solitons are achieved with setting different strengths and steepness of the potentials. The results can potentially be used to design a multi-route splitter for light beams.

Squeezing via coupling of Bose–Einstein condensates in a double-well potential with a cavity light field

Squeezing via the interaction between the cavity light field and the Bose Einstein Condensate （BEC） in a doublewell potential is considered within the context of the two-mode approximation. For the cavity light field initially in a coherent state, it is shown that by choosing appropriate parameters, quadrature squeezing of the cavity light field can be achieved and it exhibits periodic oscillation. We also study the case in which BEC is tuned to resonance by periodically modulating the trapping potentiaL and the quadrature squeezing of the cavity field exhibits periodic collapse and revival effect. Both analytic and numerical calculations are performed, and they are found to be in good agreement with each other. The result shows that the quantum statistical properties of the cavity light field can be manipulated by its coupling with the condensates in the double-well potential. On the other hand, dynamical properties of the condensates in the double-well potential will be reflected by the quadrature squeezing of the light field.

Revised Iterative Solution of Ground State of Double-Well Potential

The revised new iterative method for solving the ground state of Schroedingerequation is deduced. Based on Green functions defined by quadratures along a single trajectory thisiterative method is applied to solve the ground state of the double-well potential. The result iscompared to the one based on the original iterative method. The limitation of the asymptoticexpansion is also discussed.

Adiabatic tunneling of Bose–Einstein condensates with modulated atom interaction in a double-well potential

We study the adiabatic tunneling of Bose-Einstein condensates in a symmetric double-well potential when the inter- action strength between the atoms is modulated linearly or in a cosine periodic form. It is shown that the system evolves along a nonlinear eigenstate path. In the case of linear modulation under the adiabatic approximation conditions, the tun- neling probability of the condensate atoms to the other potential well is half. However, when the system is periodically scanned in the adiabatic process, we find an interesting phenomenon. A small change in the cycle period can lead to the condensate atoms returning to the right well or tunneling to the left well. The system comes from a linear eigenstate back to a nonlinear one, which is completely different from the linear eigenstate evolution. We explain the results by using the energy level and the phase diagram.

Transportation of Two Coupled Particles in an Asymmetric Saw-Tooth Potential

Based on a simple model, we theoretically show the transport behaviors of two harmonically coupled Brownian particles in an asymmetric saw-tooth potential with two slopes. The coupled particles are subject to stochastic fluctuations. It is found that when the equilibrium distance of the coupled particles is between the two slopes of the potential, the transport direction of the coupled particles will be reversed with a certain harmonic coupling strength. This current reversal can be easily understood with the near rigid approximation, where the two coupled particles can be regarded as a single particle in an effective potential. Compared with the original saw-tooth potential, the asymmetry of the effective potential could be reversed when the equilibrium distance is between the two slopes of the original potential, which results in the current reversal.

Spontaneous symmetry breaking of a Bose-Fermi mixture in a two-dimensional double-well potential

We study the spontaneous symmetry breaking of a superfluid Bose-Fermi mixture in a two-dimensional double- well potential. The mixture is described by a set of coupled Gross-Pitaevskii equations. The symmetry breaking phenomenon is demonstrated in the two-dimensional double-well potential in the mixture. The results are summarized in the phase diagrams of the mixture particle numbers, which are divided into symmetric and asymmetric regions by the asymmetry ratios. The dynamical pictures of the spontaneous symmetry breaking induced by a gradual transformation of the single-well potential into a double-well one are also illustrated. The properties of the quantum degenerate mixture are explored using the realistic parameters for a ^40K-^87Rb system.

CUSP CATASTROPHE MODEL OF INSTABILITY OF PILLAR IN ASYMMETRIC MINING

A simplified mechanical model of pillar-hang wall was established in asymmetric mining and instability of the system was discussed by means of potential energy principle and cusp catastrophe theory. The necessary-sufficient condition and the jump value of displacement of pillar and the released energy expressions were derived, which established foundation for quantifying of the instability of system. The results show that instability of the system is related to load and its stiffness distribution. The critical load increases with the increasing relative stiffness, and the system is more stable. On the contrary, the instability of system is likely to occur, and the released energy is larger in instability process, and the harm is more tremendous accordingly. Furthermore, an example was calculated, and the estimated results are in good agreement with the practical experience, which provide basis for mining order and arranging stope.

Quantum Standing Waves and Tunneling Through a Finite Range Potential

We consider a time independent one dimensional finite range and repulsive constant potential barrier between two impenetrable walls. For a nonrelativistic massive particle projected towards the potential with energies less than the barrier and irrespective of the spatial positioning of the potential allowing for quantum tunneling, analytically we solve the corresponding Schrodinger equation. For a set of suitable parameters utilizing Mathematica we display the wave functions along with their associated probabilities for the entire region. We investigate the sensitivity of the probability distributions as a function of the potential range and display a gallery of our analysis. We extend our analysis for bound state particles confined within constant attractive potentials.

Theoretical Study of the Scattering Resonance State, Reaction Mechanism and Partial Potential Energy Surface of the F+CH4→HF+CH3 Reaction

The partial potential energy surface was constructed by ab initio method [QCISD（T）/6- 311＋＋G（2df,2pd）]for F＋CH4→HF＋CH3 reaction system. It not only explained the reaction mechanism brought forward by Diego Troya by means of quasiclassical trajectory （QCT） but also successfully validated Kopin Liu＇s experimental phenomena about the existence of the reactive resonance. The lifetime of the scattering resonance state was about 0.07 ps. All these were in agreement with the experiments.

Bose–Einstein distribution temperature features of quasiparticles around magnetopolaron in Gaussian quantum wells of alkali halogen ions

We have applied strong coupling unitary transformation method combined with Bose–Einstein statistical law to investigate magnetopolaron energy level temperature effects in halogen ion crystal quantum wells.The obtained results showed that under magnetic field effect,magnetopolaron quasiparticle was formed through the interaction of electrons and surrounding phonons.At the same time,magnetopolaron was influenced by phonon temperature statistical law and important energy level shifts down and binding energy increases.This revealed that lattice temperature and magnetic field could easily affect magnetopolaron and the above results could play key roles in exploring thermoelectric conversion and conductivity of crystal materials.

The Pionic Deuterium and the Pion Tetrahedron Vacuum Polarization

A double-well potential model is proposed for the pionic deuterium that enables to calculate the energy split, the potential barrier height and estimate the pion tetrahedron edge length. We propose that pion tetrahedrons, πTd = ud~dũ, play a central role in the Yukawa interaction by enabling quark exchange reactions between protons and neutrons by tunneling through a potential barrier. A vacuum polarization Feynman diagram is proposed for the πTd having chains of fermion loops for the two valence quarks and anti-quarks connected by gluons. With a higher order vacuum polarization diagram, the d and u quark loops are interleaved and the chiral symmetry is broken dynamically. The proposed πTd vacuum polarization integral does not diverge in both the IR and UV limits and vanishes in the limit of an infinite pion tetrahedron condensate. We propose a new Delbruck scattering Feynman diagram that includes d and u quark and anti-quark interleaved loops. We further propose that conversion of gravitons to photons may occur via quark and anti-quark loops that describe the pion tetrahedrons dynamics in the vacuum and may also transfer gravitational waves.

岩石非对称凸起结构面抗剪特性试验研究

基于楔齿形结构面形貌特征,制作3种不同形貌的结构面,研究了楔齿结构特征参数最大潜在接触面积比A_(0)在不同法向应力作用下对结构面剪切特性的影响规律。试验结果表明,结构面法向应力较小、A_(0)较大情况下的破坏模式主要是爬坡磨损,其剪切应力-位移曲线呈现滑移型;随着法向应力增大、A_(0)减小,破坏模式逐渐转变为爬坡切齿和完全剪断破坏,其剪切应力-位移曲线呈现峰值剪断Ⅰ型和峰值剪断Ⅱ型。法向应力增大限制了持续剪胀效应,而A 0的减小改变了迎坡面的受力,使凸起在发生剪断时的有效承载面积增大,从而影响结构面抗剪强度。基于试验结果提出了新的结构面抗剪强度模型,为岩石非对称凸起结构面抗剪强度计算提供了参考依据。

计及内电势变化影响的VSG不对称短路暂态电流解析计算

虚拟同步发电机(VSG)控制策略的复杂性使其呈现丰富的暂态特征,明确VSG故障特性对构网型保护适应性分析与新原理研究意义重大。现有关于VSG故障特性的研究主要围绕对称短路和内电势恒定展开,并未涉及不对称短路场景且未计及内电势变化对短路电流解析计算的影响。针对上述问题,提出一种计及内电势变化影响的VSG不对称短路暂态电流解析计算方法。首先,基于不对称短路时平衡电流和故障限流控制策略,分析不同无功功率参考值影响下VSG内电势的变化特征;其次,基于虚拟阻抗环建立短路电流和内电势之间的方程,明晰内电势变化对短路电流暂态特性的影响;然后,在分析无功功率-电压环动态特性的基础上,建立短路电流和内电势之间的微分方程,通过联立上述方程即可得到内电势和短路电流的解析表达式;最后,通过数字仿真和实时仿真验证了所推导的解析计算式的正确性。

Effects of magnetic field on the polaron in an asymmetrical Gaussian confinement potential quantum well

： The effects of a magnetic field on the vibrational frequency, the ground state energy and the ground state binding energy of a weak-coupling polaron in asymmetrical Gaussian confinement potential quantum well （AGCPQW） are investigated by using linear combination operator and unitary transformation methods. Our cal- culated results show that the vibrational frequency increases with increasing cyclotron frequency of the magnetic field; meanwhile, the absolute value of the ground state energy and the ground state binding energy decrease. The vibrational frequency, the absolute value of the ground state energy and the ground state binding energy are in- creasing functions of the barrier height of the AGCPQW. It is shown that the barrier height of the AGCPQW and the magnetic field are important factors that influence the properties of the magnetopolaron in AGCPQW.

The Effect of Magnetic Field on an Asymmetrical Gaussian Potential Quantum Well Qubit

Under the influence of an applied magnetic field(MF), the eigenenergies and the eigenfunctions of the ground and the first excited states(GFES) are obtained by using a variational method of the Pekar type(VMPT) in a strong electron-LO-phonon coupling asymmetrical Gaussian potential quantum well(AGPQW). This AGPQW system may be employed as a two-level qubit. The numerical results have indicated(i) that when the electron situates in the superposition state of the GFES, we obtain the time evolution and the coordinate change of the electron probability density in the AGPQW,(ii) that due to the presence of the asymmetrical potential in the growth direction of the AGPQW, the probability density shows double-peak configuration, whereas there is only one peak if the confinement is a two dimensional symmetric one in the xy plane of the AGPQW,(iii) that the oscillatory period is a decreasing function of the cyclotron frequency of the MF, the height of the AGPQW and the polaron radius,(iv) and that as the range of the confinement potential(RCP) decreases the oscillatory period will decrease firstly and then increase and it will take a minimum when R =-0.234 nm.