Impact-Angle and Terminal-Maneuvering-Acceleration Constrained Guidance against Maneuvering Target

A new, highly constrained guidance law is proposed against a maneuvering target while satisfying both impact angle and terminal acceleration constraints. Here, the impact angle constraint is addressed by solving an optimal guidance problem in which the target’s maneuvering acceleration is time-varying. To deal with the terminal acceleration constraint, the closed-form solutions of the new guidance are needed. Thus, a novel engagement system based on the guidance considering the target maneuvers is put forward by choosing two angles associated with the relative velocity vector and line of sight (LOS) as the state variables, and then the system is linearized using small angle assumptions, which yields a special linear time-varying (LTV) system that can be solved analytically by the spectral-decomposition-based method. For the general case where the closing speed, which is the speed of approach of the missile and target, is allowed to change with time arbitrarily, the solutions obtained are semi-analytical. In particular, when the closing speed changes linearly with time, the completely closed-form solutions are derived successfully. By analyzing the generalized solutions, the stability domain of the guidance coefficients is obtained, in which the maneuvering acceleration of the missile can converge to zero finally. Here, the key to investigating the stability domain is to find the limits of some complicated integral terms of the generalized solutions by skillfully using the squeeze theorem. The advantages of the proposed guidance are demonstrated by conducting trajectory simulations.

Hopf Bifurcation and Parameter Sensitivity Analysis of a Doubly-Fed Variable-Speed Pumped Storage Unit

The doubly-fed variable speed pumped storage unit is a storage system suitable for joint operation with renewable energy sources to smooth the imbalance between renewable energy supply and electricity demand. However, its working principle and operation control are more complex than those of constant speed pumped storage. In this study, a nonlinear model of doubly-fed variable speed pumped storage units (VSPSUs) considering nonlinear characteristics of the head loss is established. The study finds that a supercritical Hopf bifurcation occurs in the system, and the area enclosed by the lower side of the bifurcation line and the coordinate axis is the stability domain of the system. The active power step perturbation from −0.3 to 0.3 will gradually reduce the area of the stability domain and narrow the adjustable range of the control parameters. In addition, the sensitivity of the model full state variables and the primary and secondary relationships to the changes of subsystem parameters is analyzed systematically using the trajectory sensitivity. It is found that there is a large difference in the sensitivity of different state variables to the parameters. The state variables are much more sensitive to the transfer coefficient of hydraulic turbine torque to guide vane opening, the unit inertia time constant, and the controller proportional gain change than other parameters, which are defined as highly sensitive parameters. The receiver response time constant and the turbine flow-to-head transfer coefficient are the corresponding low-sensitivity parameters.

Dragging spin-orbit-coupled solitons by a moving optical lattice

It is known that the interplay of the spin-orbit-coupling (SOC) and mean-field self-attraction creates stable two-dimensional (2D) solitons (ground states) in spinor Bose-Einstein condensates. However, SOC destroys the system's Galilean invariance, therefore moving solitons exist only in a narrow interval of velocities, outside of which the solitons suffer delocalization. We demonstrate that the application of a relatively weak moving optical lattice (OL), with the 2D or quasi-1D structure, makes it possible to greatly expand the velocity interval for stable motion of the solitons. The stability domain in the system's parameter space is identified by means of numerical methods. In particular, the quasi-1D OL produces a stronger stabilizing effect than its full 2D counterpart. Some features of the domain are explained analytically.

Stability Domain Analysis and Enhancement of Squirrel Cage Induction Generator Wind Turbines in Weak Grids

There are significant concerns regarding the stability of increased wind power generation in weak power grids. This paper investigates and improves the stability of Wind Turbine Squirrel Cage Induction Generators (WT-SCIGs) with series compensation and weak interconnections to the power grid. Detailed time-domain and state-space modeling have revealed new bifurcations and oscillatory modes for a WT-SCIG connected radially to a weak grid through a series compensated line. The stability domain analyses are carried out by computing bifurcations in the system by analyzing eigenvalues of the linearized system. The analyses demonstrate for the first time how the degree of compensation at which the Hopf bifurcation occurs depends on the X/R ratio of the line, operating slip of the induction generator, and voltage regulator parameters as well as the time delays in measurements. A new damping controller is proposed, which greatly improves the dynamic stability of the WT-SCIG and eliminates destructive Hopf bifurcations in weak grids for a wide range of series compensation. This allows for a much larger percentage of series compensation than what is usually possible, while avoiding instabilities, thereby maximizing the power transfer capability.

Speculative asset price dynamics and wealth taxes

Based on the seminal asset-pricing model by Brock and Hommes (J Econ Dyn Control 22:1235–1274, 1998), we analytically show that higher wealth taxes increase the risky asset’s fundamental value, enlarge its local stability domain, may prevent the birth of nonfundamental steady states and, if they exist, reduce the risky asset’s mispricing. We furthermore find that higher wealth taxes may hinder the emergence of endogenous asset price oscillations and, if they exist, dampen their amplitudes. Since oscillatory price dynamics may be associated with lower mispricing than locally stable nonfundamental steady states, policymakers may not always want to suppress them by imposing (too low) wealth taxes. Overall, however, our study suggests that wealth taxes tend to stabilize the dynamics of financial markets.

The mutual repression between Pax2 and Snail factors regulates the epithelial/mesenchymal state during intermediate mesoderm differentiation

The pronephros is the first renal structure in the embryo, arising after mesenchymal to epithelial transition (MET) of the intermediate mesoderm, where Pax2 induces epithelialization of the mesenchyme. Here we show that, in the early embryo, Snail1 directly represses Pax2 transcription maintaining the intermediate mesoderm in an undifferentiated state. Reciprocally, Pax2 directly represses Snail1 expression to induce MET upon receiving differentiation signals. We also show that BMP7 acts as one such signal by downregulating Snail1 and upregulating Pax2 expression. This, together with the Snail1/Pax2 reciprocal repression, establish a regulatory loop in a defined region along the anteroposterior axis, the bi-stability domain within the transition zone, where differentiation of the neural tube and the somites is known to occur. Thus, we show that the antagonism between Snail1 and Pax2 determines the epithelial/mesenchymal state during the differentiation of the intermediate mesoderm and propose that the bi-stability zone extends to the intermediate mesoderm, synchronizing the differentiation of tissues aligned along the mediolateral embryonic axis.

Multiparameter Stability Analysis of Systems with Induction Motor Loads, Weak Interconnections and Series Compensation

Dynamic modeling and stability domain analysis of a system consisting of a synchronous generator sup-plying an induction motor load through a series compensated weak network has been carried out in this paper. The impact of X/Rratio of the feeder and generation control system parameters on the stability domain with respect to series compensation has been examined through eigenvalue calculations and time domain simulations. From the studies conducted, it was observed that the stability domain of the system with respect to series compensation depends on the grid strength in addition to the excitation system parameters. Eigenvalue analysis shows that there is a strong correlation between the exciter gain, time constants of the measurement transducer and exciter, and the series compensation level. The main contribution of this work is to reveal new bifurcations which arise in these systems which has been studied through eigenvalue analysis and time domain simulations for various combinations of system parameters.

Electrooxidation of the Paracetamol on Boron Doped Diamond Anode Modified by Gold Particles

The environment pollution, in particular that of the aquatic environment, by wastewater is a reality because it is discharged for the most part without treatment. The presence of pharmaceutical pollutants such as paracetamol in these waters can constitute a risk to human health. The objective of this work is to study the electrochemical oxidation of paracetamol using cyclic voltammetry on the boron doped diamond (BDD) anode and boron doped diamond modified by gold particles (Au-BDD) anode. The Au-BDD electrode was obtained by modifying the surface of BDD with gold particles. This was done by electrodeposition (chronoamperometry) in 0.5 M HAuCl4 and 0.1 M H2SO4 using a three pulse nucleation and growth process. Physical characterization with Scanning Electron Microscopy coupled with Dispersive Energy spectroscopy has shown that the Au-BDD surface presents asperities with the presence of microparticles and nanoparticles. The electrochemical characterization made in three electrolytic solutions (H2SO4, NaOH and KClO4) showed that Au-BDD has a high electroactivity domain than that of BDD. The study of the Benzoquinone-hydroquinone redox couple has shown a quasi-reversible character of these two anodes. It also revealed that Au-BDD has a more accentuated metallic character than BDD. The voltammetric measurements made it possible to show that the paracetamol oxidation is limited by the transport of material on each anode. This oxidation is characterized by the presence of an anodic peak in the support electrolytes stability domain. The paracetamol oxidation is rapid on Au-BDD than on BDD in the various medium explored, thus showing that Au-BDD is more efficient than BDD for the paracetamol oxidation by electrochemical means.