The First Five Years of a Phase Theory for Complex Systems and Networks

In this paper,we review the development of a phase theory for systems and networks in its first five years,represented by a trilogy:Matrix phases and their properties;The MIMO LTI system phase response,its physical interpretations,the small phase theorem,and the sectored real lemma;The synchronization of a multi-agent network using phase alignment.Towards the end,we also summarize a list of ongoing research on the phase theory and speculate what will happen in the next five years.

Kinematic analysis of flexible bipedal robotic systems

In spite of its intrinsic complexities,the passive gait of bipedal robots on a sloping ramp is a subject of interest for numerous researchers.What distinguishes the present research from similar works is the consideration of flexibility in the constituent links of this type of robotic systems.This is not a far-fetched assumption because in the transient(impact)phase,due to the impulsive forces which are applied to the system,the likelihood of exciting the vibration modes increases considerably.Moreover,the human leg bones that are involved in walking are supported by viscoelastic muscles and ligaments.Therefore,for achieving more exact results,it is essential to model the robot links with viscoelastic properties.To this end,the Gibbs-Appell formulation and Newton's kinematic impact law are used to derive the most general form of the system's dynamic equations in the swing and transient phases of motion.The most important issue in the passive walking motion of bipedal robots is the determination of the initial robot configuration with which the system could accomplish a periodic and stable gait solely under the effect of gravitational force.The extremely unstable nature of the system studied in this paper and the vibrations caused by the impulsive forces induced by the impact of robot feet with the inclined surface are some of the very serious challenges encountered for achieving the above-mentioned goal.To overcome such challenges,an innovative method that uses a combination of the linearized equations of motion in the swing phase and the algebraic motion equations in the transition phase is presented in this paper to obtain an eigenvalue problem.By solving this problem,the suitable initial conditions that are necessary for the passive gait of this bipedal robot on a sloping surface are determined.The effects of the characteristic parameters of elastic links including the modulus of elasticity and the Kelvin-Voigt coefficient on the walking stability of this type of robotic systems are also studied.The findings of this parametric study reveal that the increase in the Kelvin-Voigt coefficient enhances the stability of the robotic system,while the increase in the modulus of elasticity has an opposite effect.

Phase equilibria relations in the V_(2)O_(5)-rich part of the Fe_(2)O_(3-)TiO_(2)-V_(2)O_(5) system at 1200℃ related to converter vanadium-bearing slag

The efficient recycling of vanadium from converter vanadium-bearing slag is highly significant for sustainable development and circular economy.The key to developing novel processes and improving traditional routes lies in the thermodynamic data.In this study,the equilibrium phase relations for the Fe_(2)O_(3)-TiO_(2)-V_(2)O_(5)system at 1200℃in air were investigated using a high-temperature equilibrium-quenching technique,followed by analysis using scanning electron microscopy-energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy.One liquid-phase region,two two-phase regions(liquid-rutile and liquid-ferropseudobrookite),and one three-phase region(liquid-rutile-ferropseudobrookite)were determined.The variation in the TiO_(2)and V_(2)O_(5)contents with the Fe_(2)O_(3)content was examined for rutile and ferropseudobrookite solid solutions.However,on further comparison with the predictions of FactSage 8.1,significant discrepancies were identified,highlighting that greater attention must be paid to updating the current thermodynamic database related to vanadium-bearing slag systems.

Calcium Carbonate and Ettringite Induced Efflorescence in CAC-Anhydrite Binary Systems

We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.

Synthesis and Coloring Mechanism of Metallic Glaze in R_(2)O-RO-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5)System

A copper-red and silver-white metallic glaze of R_(2)O-RO-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5)system was synthesized by adjusting the firing temperature and glaze components.The coloration mechanism of the metallic glaze was revealed via investigation of the microstructure of the glaze.Our research reveals that the metallic glaze with different colors is mainly due to the amount of Fe_(2)O_(3).The metallic glaze shows a silver-white luster due to a structural color ofα-Fe_(2)O_(3)crystals with a good orientation when the sample contains 0.0939 mol of Fe_(2)O_(3),maintaining temperatures at 1150℃for 0.5 h.The metallic glaze is copper-red which is dominated by the coupling of chemical and structural color ofα-Fe_(2)O_(3)crystals when the sample contains 0.0783 mol of Fe_(2)O_(3).After testing the amount of SiO_(2),we find that 4.0499 mol is the optimal amount to form the ceramic network,and 0.27 mol AlPO_(4)is the best amount to promote phase separation.

High Energy Efficiency Dynamic Connected Hybrid Precoding for mm Wave Massive MIMO Systems

This paper considers a high energy efficiency dynamic connected(HEDC)structure,which promotes the practicability and reduces the power consumption of hybrid precoding system by lowresolution phase shifters(PSs).Based on the proposed structure,a new hybrid precoding algorithm is presented to optimize the energy efficiency,namely,HP-HEDC algorithm.Firstly,via a new defined effective optimal precoding matrix,the problem of optimizing the analog switch precoding matrix is formulated as a sparse representation problem.Thus,the optimal analog switch precoding matrix can be readily obtained by the branch-and-bound method.Then,the digital precoding matrix optimization problem is modeled as a dictionary update problem and solved by the method of optimal direction(MOD).Finally,the diagonal entries of the analog PS precoding matrix are optimized by exhaustive search independently since PS and antenna is one-to-one.Simulation results show that the HEDC structure enjoys low power consumption and satisfactory spectral efficiency.The proposed algorithm presents at least 50%energy efficiency improvement compared with other algorithms when the PS resolution is set as 3-bit.

Enhanced entropy generation and heat transfer characteristics of magnetic nano-encapsulated phase change materials in latent heat thermal energy storage systems

The objective of the current study is to investigate the importance of entropy generation and thermal radiation on the patterns of velocity,isentropic lines,and temperature contours within a thermal energy storage device filled with magnetic nanoencapsulated phase change materials(NEPCMs).The versatile finite element method(FEM)is implemented to numerically solve the governing equations.The effects of various parameters,including the viscosity parameter,ranging from 1 to 3,the thermal conductivity parameter,ranging from 1 to 3,the Rayleigh parameter,ranging from 102 to 3×10^(2),the radiation number,ranging from 0.1 to 0.5,the fusion temperature,ranging from 1.0 to 1.2,the volume fraction of NEPCMs,ranging from 2%to 6%,the Stefan number,ranging from 1 to 5,the magnetic number,ranging from 0.1 to 0.5,and the irreversibility parameter,ranging from 0.1 to 0.5,are examined in detail on the temperature contours,isentropic lines,heat capacity ratio,and velocity fields.Furthermore,the heat transfer rates at both the cold and hot walls are analyzed,and the findings are presented graphically.The results indicate that the time taken by the NEPCMs to transition from solid to liquid is prolonged inside the chamber region as the fusion temperatureθf increases.Additionally,the contours of the heat capacity ratio Cr decrease with the increase in the Stefan number Ste.

Robust adaptive leaderless consensus of unknown non-minimum phase linear multi-agent systems subject to disturbances and/or unmodeled dynamics

This article investigates the problem of robust adaptive leaderless consensus for heterogeneous uncertain nonminimumphase linear multi-agent systems over directed communication graphs. Each agent is assumed tobe of unknown nominal dynamics and also subject to external disturbances and/or unmodeled dynamics. Anovel distributed robust adaptive control strategy is proposed. It is shown that the robust adaptive leaderlessconsensus problem is solved with the proposed control strategy under some sufficient conditions. Two examplesare provided to demonstrate the efficacy of the proposed control strategy.

Design of a Three-Phase Grid Connector System Using Power Transfer from Park’s Transformation

Instabilities in grid-connected inverters can arise from a number of sources, including mismatched parameters, grid impedance, faults, and feedback delays. Park’s transformation provides accurate control over reactive and active (real) power. This enhances the overall efficiency of the system by enabling operators to control reactive power compensation and optimize energy flow. In dynamic settings, this guarantees greater system stability and faster response times. The current paper aims to improve the grid system by utilizing the dq0 controller. The current work focuses on the analysis based on simulations and theory, where the state space equation serves as the basis for dq-axis current decoupling. A MATLAB platform was used to simulate the complete system. TDH values of 2.45%, or less than 5%, in the given results are acceptable. The suggested controller was hence appropriate for grid system applications.

Distributed Adaptive Output Consensus of Unknown Heterogeneous Non-Minimum Phase Multi-Agent Systems

This article addresses the leader-following output consensus problem of heterogeneous linear multi-agent systems with unknown agent parameters under directed graphs.The dynamics of followers are allowed to be non-minimum phase with unknown arbitrary individual relative degrees.This is contrary to many existing works on distributed adaptive control schemes where agent dynamics are required to be minimum phase and often of the same relative degree.A distributed adaptive pole placement control scheme is developed,which consists of a distributed observer and an adaptive pole placement control law.It is shown that under the proposed distributed adaptive control scheme,all signals in the closed-loop system are bounded and the outputs of all the followers track the output of the leader asymptotically.The effectiveness of the proposed scheme is demonstrated by one practical example and one numerical example.

Metallurgical properties of CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%MgO–Fe_(2)O_(3)slag system pertaining to spent automotive catalyst smelting

The metallurgical properties of the CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%Mg O–Fe_(2)O_(3)slag system,formed by the co-treatment process of spent automotive catalyst(SAC)and copper-bearing electroplating sludge(CBES),were studied systematically in this paper.The slag structure,melting temperature,and viscous characteristics were investigated by Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,Fact Sage calculation,and viscosity measurements.Experimental results show that the increase of Fe_(2)O_(3)content(3.8wt%–16.6wt%),the mass ratio of CaO/SiO_(2)(m(CaO)/m(SiO_(2)),0.5–1.3),and the mass ratio of SiO_(2)/Al_(2)O_(3)(m(SiO_(2))/m(Al_(2)O_(3)),1.0–5.0)can promote the depolymerization of silicate network,and the presence of a large amount of Fe_(2)O_(3)in form of tetrahedral and octahedral units ensures the charge compensation of Al^(3+)ions and makes Al_(2)O_(3)only behave as an acid oxide.Thermodynamic calculation and viscosity measurements show that with the increase of Fe_(2)O_(3)content,m(Ca O)/m(SiO_(2)),and m(SiO_(2))/m(Al_(2)O_(3)),the depolymerization of silicate network structure and low-melting-point phase transformation first occur within the slag,leading to the decrease in melting point and viscosity of the slag,while further increase causes the formation of high-melting-point phase and a resultant re-increase in viscosity and melting point.Based on experimental analysis,the preferred slag composition with low polymerization degree,viscosity,and melting point is as follows:Fe_(2)O_(3)content of 10.2wt%–13.4wt%,m(CaO)/m(SiO_(2))of 0.7–0.9 and m(SiO_(2))/m(Al_(2)O_(3))of 3.0–4.0.This work provides a theoretical support for slag design in co-smelting process of SAC and CBES.

Research on Performance Optimization of Liquid Cooling and Composite Phase Change Material Coupling Cooling Thermal Management System for Vehicle Power Battery

The serpentine tube liquid cooling and composite PCM coupled cooling thermal management system is designed for 18650 cylindrical power batteries,with the maximum temperature and temperature difference of the power pack within the optimal temperature operating range as the target.The initial analysis of the battery pack at a 5C discharge rate,the influence of the single cell to cooling tube distance,the number of cooling tubes,inlet coolant temperature,the coolant flow rate,and other factors on the heat dissipation performance of the battery pack,initially determined a reasonable value for each design parameter.A control strategy is used to regulate the inlet flow rate and coolant temperature of the liquid cooling system in order to make full use of the latent heat of the composite PCM and reduce the pump’s energy consumption.The simulation results show that the maximum battery pack temperature of 309.8 K and the temperature difference of 4.6 K between individual cells with the control strategy are in the optimal temperature operating range of the power battery,and the utilization rate of the composite PCM is up to 90%.

Discrete Phase Shifts Control and Beam Selection in RIS-Aided MISO System via Deep Reinforcement Learning

Reconfigurable intelligent surface(RIS)for wireless networks have drawn lots of attention in both academic and industry communities.RIS can dynamically control the phases of the reflection elements to send the signal in the desired direction,thus it provides supplementary links for wireless networks.Most of prior works on RIS-aided wireless communication systems consider continuous phase shifts,but phase shifts of RIS are discrete in practical hardware.Thus we focus on the actual discrete phase shifts on RIS in this paper.Using the advanced deep reinforcement learning(DRL),we jointly optimize the transmit beamforming matrix from the discrete Fourier transform(DFT)codebook at the base station(BS)and the discrete phase shifts at the RIS to maximize the received signal-to-interference plus noise ratio(SINR).Unlike the traditional schemes usually using alternate optimization methods to solve the transmit beamforming and phase shifts,the DRL algorithm proposed in the paper can jointly design the transmit beamforming and phase shifts as the output of the DRL neural network.Numerical results indicate that the DRL proposed can dispose the complicated optimization problem with low computational complexity.

An Improved Calibration Method of Grating Projection Measurement System

In the traditional fringe projection profilometry system,the projector and the camera light center are both spatially virtual points.The spatial position relationships specified in the model are not easy to obtain,leading to inaccurate system parameters and affectingmeasurement accuracy.This paper proposes a method for solving the system parameters of the fringe projection profilometry system,and the spatial position of the camera and projector can be adjusted in accordance with the obtained calibration parameters.The steps are as follows:First,in accordance with the conversion relationship of the coordinate system in the calibration process,the calculation formula of the vertical distance from the camera light center to the reference plane and the calculation formula of the distance between the projector and the camera light center are given respectively.Secondly,according to the projector calibration principle,the position of the projector light axis perpendicular to the reference plane is gained by comparing the parallel relationship between the reference plane coordinate system and the projector coordinate system’s Z-axis.Then,in order to fulfill the position restriction that the line between the projector light center and the camera light center must be parallel to the reference plane,the camera’s spatial location is adjusted so that the vertical distance between it and the reference plane tends to that between the projector light center and the reference plane.And finally,the three-dimensional(3D)reconstruction of the target object can be finished using the phase height model’s system parameters once the aforementioned position limitations are put into practice.Experimental results demonstrate that the method improves the measurement accuracy,and verifies that it is effective and available in 3D shape measurement.

Iterative Phase Noise Suppression for Full-Duplex Communication Systems

Oscillator phase noise is one of the bottlenecks that limits the self-interference(SI)cancellation capability of full-duplex systems.In this paper,we propose a method for the suppression of common phase error(CPE)and intercarrier interference(ICI)induced by the phase noise in full-duplex orthogonal frequency division multiplexing(OFDM)systems.First,we regard the effect of CPE as a portion of the SI channel and perform estimation,reconstruction and elimination in the time domain.Then,the ICI signal is estimated and suppressed in the frequency domain.Additionally,by analysing the performance of proposed algorithm,we further develop an iterative mechanism to reduce the parameter estimation error and improve SI cancellation capability.Simulation results show that the proposed method has a significant SI cancellation capability improvement over the traditional SI cancellation schemes.

An ultrafast spectroscopy system for studying dynamic properties of superconductors under high pressure and low temperature conditions

An ultrafast pump-probe spectroscopy system combined with a cryogenic diamond anvil cell(DAC) instrument is developed to investigate the photo-excitation dynamic properties of condensed materials under low temperature and high pressure(LTHP) conditions.The ultrafast dynamics study is performed on Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi-2212) thin film under LTHP conditions.The superconducting(SC) phase transition has been observed by analyzing the ultrafast dynamics of Bi-2212 as a function of pressure and temperature.Our results suggest that the pump-probe spectroscopy system combined with a cryogenic DAC instrument is an effective method to study the physical mechanism of condensed matter physics at extreme conditions,especially for the SC phase transition.

Phase behavior and percolation in an equilibrium system of symmetrically interacting Janus disks on the triangular lattice

A Janus particle has two distinct areas on its surface.Denoting the two areas as P(patch)and N(nonpatch),when two particles come close to each other,the strength of the PP interaction is usually different from that of the NN interaction.Recently the interplay between a rotational-symmetry-breaking continuous phase transition and percolation has been explored for an equilibrium system of asymmetrically interacting(i.e.,attractive PP interaction,zero NN and PN interactions)Janus disks on the triangular lattice.By Monte Carlo simulation and finite-size scaling analysis,in this work we study an equilibrium system of symmetrically interacting(i.e.,attractive PP and NN interactions with the same strength,zero PN interaction)Janus disks on the same lattice.By definition,the phase diagram in the T-θplane is symmetric for systems with patch sizesθbelow and above 90°.We determine the phase diagram and compare it with that of the asymmetric system.Similar to the latter system,for 60°<θ<90°,a rotational-symmetry-breaking continuous phase transition and an anisotropic percolation transition are found in the symmetric system,though the transition points in the two systems are quite different.Phase crossover curves are found to be different,e.g.,a continuous varying crossover line extends betweenθ=0°and 90°for the symmetric model;and in the range 0°<θ≤30°,along the crossover lines of the two models,the trends of 1/T vs.θare opposite in the two systems.We understand the latter by analytically solving the models with two particles in 0°<θ≤30°.These results are helpful for understanding close-packed systems of Janus disks with more complex interactions.

Solid-liquid phase equilibrium for the system ammonium polyphosphate-urea ammonium nitrate-potassium chloride-water at 273.2 K

Based on the dynamic method,a quaternary system of ammonium polyphosphate (APP)-urea ammonium nitrate (UAN,CO(NH_(2))_(2)-NH_(4)NO_(3))-potassium chloride (KCl)-H_(2)O and its subsystems (APP-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O,KCl-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O and APP-KCl-H_(2)O) were systematically investigated at the temperature of 273.2 K.Each ternary phase diagram contains one invariant point and three crystallization regions.The crystallization regions are:(1)(NH_(4))_(3)HP_(2)O_(7),(NH_(4))_(4)P_(2)O_(7)and ((NH_(4))_(3)HP_(2)O_(7)+(NH_(4))_(4)P_(2)O_(7)) for APP-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O diagram;(2) KCl,KNO_(3)and(KCl+KNO_(3)) for KCl-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O diagram and (3)(NH_(4))_(3)HP_(2)O_(7),KCl and((NH_(4))_(3)HP_(2)O_(7)+KCl) for APP-KCl-H_(2)O diagram.The quaternary phase diagram of APP-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-KCl-H_(2)O has no quaternary invariant point but includes four solid phase crystallization regions,i.e.,(NH_(4))_(3)HP_(2)O_(7),(NH_(4))_(4)P_(2)O_(7),KNO_(3)and KCl,in which the KNO_(3)region occupies the largest area.The maximum total nutrient content (N+P_(2)O_(5)+K_(2)O) existing as ionic forms in the APP-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O,KCl-[CO(NH_(2))_(2)-NH_(4)NO_(3)]-H_(2)O,APP-KCl-H_(2)O and quaternary systems is 44.70%,32.86%,45.56%and 46.23%(mass),respectively,indicating that the maximum nutrient content can be reached using raw materials of the corresponding systems to prepare liquid fertilizer.In the quaternary system,the content of NH_(4)~+-N ascends with the increase of the total nutrient content,while the contents of NO_(3)^(-)-N and CO(NH_(2))_(2)-N increase with elevated total N.This work can help optimize the operating parameters for the production,storage and transportation of liquid fertilizers.

An Evaluation of Phase Behaviors of the Oil-Gas-Water System in the Displacement of Crude Oil with CO_(2)

CO_(2)dissolution into an aqueous phase and water evaporation into a gaseous phase takes place during CO_(2)injection into an oil reservoir.This study aims to evaluate the phase behaviors of the oil-gas-water system in the displacement of crude oil by CO_(2).The composition of the JL oilfield in the northeast of China is taken as an example.The flash calculation of the oil-gas-water system was performed,based on the method presented by Li and Nghiem.The research results show that CO_(2)dissolution in the aqueous phase declines as the NaCl concentration in formation water rises.CO_(2)injection is beneficial for the evaporation of formation water.The NaCl concentration in formation water has little effect on water evaporation and dissolved-gas escape.When the injection-gas mole fraction of CO_(2)is 0.5,CO_(2)injection can reverse the phase behavior of the petroleum mixture and the oil-gas system is converted to a pure gas-condensate system.For CO_(2)injection,water vapor has little effect on the miscibility of multiple contacts,but can reduce the miscibility of the first contact.

Phase transition in bilayer quantum Hall system with opposite magnetic field

We construct a mapped bilayer quantum Hall system to realize the proposal that two nearly flatbands have opposite Chern numbers.For the C=±1 case,the two Landau levels of the bilayer experience opposite magnetic fields.We consider a mapped bilayer quantum Hall system at total fillingν_(t)=1/2+1/2where the intralayer interaction is repulsive and the interlayer interaction is attractive.We take exact diagonalization(ED)calculations on a torus to study the phase transition when the separation distance d/l_(B)is driven.The critical point at d_(c)/l_(B)=0.68 is characterized by a collapse of degeneracy and a crossing of energy levels.In the region d/l_(B)<d_(c)/l_(B),the states of each level are highly degenerate.The pair-correlation function indicates electrons with opposite pseudo-spins are strong correlated at r=0.We find an exciton stripe phase composed of bound pairs.The ferromagnetic ground state is destroyed by the strong effective attractive potential.An electron composite-Fermion(eCF)and a hole composite Fermion(hCF)are tightly bound.In the region d/lB>d_(c)/l_(B),a crossover from the d→d_(c)limit to the large d limit is observed.The electron and hole composite Fermion liquids(CFL)are realized by composite Fermions(CF)which attach opposite fluxes,respectively.