Phase Diagram Analysis Research Articles

Characterization of digital modulations using the phase diagram analysis

Characterization of digital modulations using the phase diagram analysis

Improvement of overcurrent protection for control rod drive mechanism power system

Control rod drive mechanism (CRDM) in nuclear reactors powered by two motor generator units running in parallel, an excitation fault in one of the generators will cause the terminal current to rise in another generator, which will cause the overcurrent protection to operate before the loss-of-excitation protection, resulting in nuclear reactor shutdown. To solve the problem of mismatch between loss-of-excitation protection and overcurrent protection, this paper applies the equivalent circuit and phase diagram analysis, obtains the conclusion that the generator terminal current phase after an excitation fault is significantly different from the current phase after a phase-to-phase short circuit fault, based on this, a generator overcurrent protection criterion of compound fundamental current phase difference is constructed, which can solve the maloperation of overcurrent protection under possible excitation fault in actual engineering. Simulation results of PSCAD/EMTDC verify the effectiveness of the proposed methods under different operating modes and fault conditions.

Effects of nickel and manganese on ductile iron utilizing ionic liquid harvested iron and Bosch byproduct carbon

To ensure the success of surface missions and the eventual habitation of the Lunar and Martian surfaces, construction materials for machine components, tools, plumbing, and more must be considered for the long-term supportability of astronauts. The financial burden of launching these materials from Earth is far too great; therefore, in-situ resource utilization (ISRU) technology will be required. The Martian environment contains numerous elements for producing bulk metal components; however, these elements are almost exclusively found as compounds. The use of ionic liquids (ILs) for elemental metal harvesting is being researched by NASA's Marshall Space Flight Center (MSFC) to extract feedstock materials from local regolith and meteorites. Studied at MSFC as a life support system, the Boschprocess produces a byproduct elemental carbon (C) during oxygen (O2) regeneration from metabolic or environmental carbon dioxide (CO2). This study details the refinement of a ductile iron (DI) designed to simulate the combination of IL-harvested iron (IL-Fe) and Bosch C by investigating the effects of Ni and Mn addition on IL-DI properties. Dilatometry was used to evaluate how the properties of the IL-DI might vary when produced in the Martian environment. DIs were cast using commercial elements with C produced via a C formation reactor (C–Fr) at MSFC with microstructural, hardness, and phase diagram analyses completed. Results suggest that the combination of IL-Fe and Bosch C could be a viable means of producing DI alloys in-situ and, with the quantities used here, the use of Ni could be more beneficial to alloy customization than Mn additions for IL-DI alloys.

The existence of solitary wave solutions for the neuron model with conductance-resistance symmetry

<abstract><p>The neuron model with conductance-resistance symmetry was recently derived by Deng, which is similar to the Hodgkin-Huxley equation, referred to as CRS neuron model. In this paper, we will consider a 2-dimensional reduction model qualitatively similar to the FitzHugh-Nagumo equation. We first give the derivation of the CRS neuron model in propagating action potential. And then we prove the existence of solitary wave solution for the 2-dimensional reduced CRS neuron model by using phase diagram analysis.</p></abstract>

Thermodynamic measurements and assessments for LiCl-NaCl-KCl-UCl3 systems

Thermodynamic descriptions of higher-order molten salt systems are essential for the effective application of molten salt technologies. However, for pyroprocessing and molten salt reactor development, a complete description of the key Li-Na-K-U(III) chloride system has yet to be provided. To remedy this, we applied the CALculation of PHAse Diagrams (CALPHAD) approach to all available phase equilibria and related thermodynamic measurements that include new differential scanning calorimetry (DSC) observations for pseudo-binary and pseudo-ternary systems to obtain consistent and accurate sets of thermodynamic properties. An outcome of that effort was the apparent discovery of a previously unreported intermediate compound in the NaCl-UCl3 system. In this effort, we adopted a unique approach to the quantification of uncertainty in phase equilibria obtained from DSC measurements, which can provide distinct advantages in phase diagram analysis. The methodology indicates that reported values of uncertainty are often underestimated. The assessed systems of the current effort were incorporated in the publicly available Molten Salt Thermal Properties Database - Thermochemical.

Термодинамическая модель глубинного происхождения нефти и ее фазового «замерзания»

Based on the deep inorganic concept of the origin of oil and gas deposits, the evolution of these petrogenic reservoirs in the lithosphere is considered. The analysis of phase diagrams and experimental data made it possible to determine two trends in the evolution of non-methane hydrocarbons in the Earth's interior. In the upper mantle, the "metastability" of heavy (with a lower H/C ratio) hydrocarbons increases with depth. However, at temperatures and pressures corresponding to the surface mantle-crustal hydrothermal conditions, the “relative metastability” of heavy hydrocarbons increases with approach to the surface. When deep HCs fluids rise to the surface, petrogenic oil reservoirs are formed as a result of a drop in hydrogen fugacity and a gas → liquid oil phase transition. Under the physical and chemical conditions of an oil reservoir, metastable reversible phase equilibria are established between liquid oil, gas hydrocarbons and CO2 and solid (pseudocrystalline) "mature" and "immature" kerogens of "oil source" rocks. A decrease in hydrogen pressure and temperature leads to a stoichiometric phase transition (“freezing”) of liquid oil into solid kerogens. This occurs as a result of oil dehydrogenation in the processes of high-temperature CO2 fixation and low-temperature hydration of oil hydrocarbons, which are the main geochemical pathways for its transformation into kerogen. Thus, the formation of carbon matter in petrogenic reservoirs is the result of regressive metamorphism of deep hydrocarbon fluids, natural gas, liquid oil, and emerging accumulations of naphthides.

Fundamental Limit of Selectivity in Photocatalytic Denitrification over Titania.

Although photocatalytic decomposition of NO (deNO) into N2 and O2 is low-cost and non-polluting, it has a low NO conversion efficiency. Establishing the activity and selectivity trend among active sites is an important base to explore and improve the deNO processes. Because the experimental performances are determined by the reaction rate, it is worthwhile to investigate the kinetic limiting steps calculated by comparative microkinetic modeling. We found that, without illumination, N2 production is inactive over various TiO2 surfaces/sites, but photogenerated holes can break the scaling relation of the dark condition by weakening O2* adsorption, leading to a significant increase in deNO activity on defective titania surfaces. However, the low N2 selectivity can be attributed to the small strength of N2O adsorption. In contrast, the N2 selectivity is enhanced in Ti-modified zeolite because of a stronger N2O* adsorption. We demonstrate here that the reaction phase diagram analysis can clearly establish a global picture of reaction activity and selectivity over various catalytic sites. In combination with microkinetic modeling, it can effectively determine the kinetic limits, providing insights to improve the design of photocatalysts.

Current State-of-the-Art in Membrane Formation from Ultra-High Molecular Weight Polyethylene.

One of the materials that attracts attention as a potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). One potential material for membrane formation is ultrahigh molecular weight polyethylene (UHMWPE). The present review summarizes the results of studies carried out over the last 30 years in the field of preparation, modification and structure and property control of membranes made from ultrahigh molecular weight polyethylene. The review also presents a classification of the methods of membrane formation from this polymer and analyzes the conventional (based on the analysis of incomplete phase diagrams) and alternative (based on the analysis of phase diagrams supplemented by a boundary line reflecting the polymer swelling degree dependence on temperature) physicochemical concepts of the thermally induced phase separation (TIPS) method used to prepare UHMWPE membranes. It also considers the main ways to control the structure and properties of UHMWPE membranes obtained by TIPS and the original variations of this method. This review discusses the current challenges in UHMWPE membrane formation, such as the preparation of a homogeneous solution and membrane shrinkage. Finally, the article speculates about the modification and application of UHMWPE membranes and further development prospects. Thus, this paper summarizes the achievements in all aspects of UHMWPE membrane studies.

Nonlinear analysis and chaos synchronization of a memristive-based chaotic system using adaptive control technique in noisy environments

The behavior of memristor-based chaotic systems under the influence of external noise is the subject of recent work. In this paper, the nonlinear behavior of a new memristive chaotic system based on memcapacitor and meminductor is considered in noisy environments. The nonlinear behavior of the proposed memristive chaotic system in the presence of white Gaussian noise is viewed through a time series of dynamical analyses, Lyapunov exponent analysis, and phase diagram analysis. Then, chaos synchronization of two memristive chaotic systems in the presence of white gaussian noise is considered. For this purpose, adaptive feedback control laws are derived from achieving global chaos synchronization of identical new memristive chaotic systems. To confirm the validity of the proposed method, some numerical simulations follow identical synchronizations. Numerical simulations are performed to show the effectiveness of the proposed method.

Exploring the environmental properties and resource utilization of construction waste in Beijing-Tianjin-Hebei region.

Beijing-Tianjin-Hebei region is a capital economic circle for the future. Promoting the coordinated development of its population, economy, resources and environment is a major national strategy. And as towns and cities continue to expand, the volume of construction waste is gradually expanding, posing a major challenge to the sustainable development of the construction industry. In order to solve this problem, this paper used portable X-ray fluorescence spectrometry to realize the on-site rapid monitoring of heavy metals in construction waste, and the correlation analysis result was R2 = 0.9908. The visualization of enrichment factor evaluation results was realized through ArcGIS. The Beijing-Tianjin-Hebei region is mainly polluted by heavy metal elements Cr, Zn, Pb and Hg, showing regional pollution characteristics, and the results of mercury morphology analysis show that all are inorganic mercury pollution, and methylmercury is not detected, and the cause can be traced to heavy industrial production in Tangshan City, which is consistent with industrial ecology. The results of leaching toxicity and cation anion analysis showed that the construction waste in Beijing-Tianjin-Hebei region had environmental risks to the surrounding surface water and groundwater. The resource treatment and disposal path were determined by means of XRD, ternary phase diagram and oxide composition analysis to avoid secondary pollution. This study explores the environmental properties and resource utilization pathways of construction waste in the Beijing-Tianjin-Hebei region, laying the foundation for research work on construction waste in the development of national urban agglomerations, effectively solving regional environmental pollution problems and promoting the sustainable development of the construction industry.

Novel precipitation strengthened Al-Y-Sc-Er alloy with high mechanical properties, ductility and electrical conductivity produced by different thermomechanical treatments

This study investigated the evolution of the microstructure, mechanical properties, and electrical conductivity of novel Al-0.2Y-0.2Sc-0.3Er alloy in as-cast, as-rolled, and annealed states. Aluminum solid solution and τ2 (Al75–76Er11–17Y7–14) eutectic phase particles with a size of 50–200 nm were identified in the as-cast alloy sample by scanning electron microscopy investigation and phase diagram analyses. A precipitation strengthening mechanism was implemented during annealing at 300 °C for 7 h due to L12 precipitates of Al3(Sc,Y,Er) phase with a maximum diameter of 10 nm. The same structure was formed in the samples annealed at 300 °C for 7 h after rolling the as-cast alloy without aging treatment. The samples aged before rolling formed a more homogenous and finer substructure, with a grain structure formed after annealing rolled sheets. Significantly more uniform structures facilitate achieving higher strength and electrical conductivity. Al-0.2Y-0.2Sc-0.3Er alloy aged at 300 °C for 7 h, hot and cold rolled, and annealed at 300 °C for 7 h exhibited a good combination of strength and electrical conductivity: YS = 191 MPa, UTS = 207 MPa, El. = 14 %, and EC = 59.7 % IACS.

Melting temperature prediction using a graph neural network model: From ancient minerals to new materials

The melting point is a fundamental property that is time-consuming to measure or compute, thus hindering high-throughput analyses of melting relations and phase diagrams over large sets of candidate compounds. To address this, we build a machine learning model, trained on a database of ∼10,000 compounds, that can predict the melting temperature in a fraction of a second. The model, made publicly available online, features graph neural network and residual neural network architectures. We demonstrate the model's usefulness in diverse applications. For the purpose of materials design and discovery, we show that it can quickly discover novel multicomponent materials with high melting points. These predictions are confirmed by density functional theory calculations and experimentally validated. In an application to planetary science and geology, we employ the model to analyze the melting temperatures of ∼4,800 minerals to uncover correlations relevant to the study of mineral evolution.

Behavior Analysis of a Class of Discrete-Time Dynamical System with Capture Rate

In this paper, we study the stability and bifurcation analysis of a class of discrete-time dynamical system with capture rate. The local stability of the system at equilibrium points are discussed. By using the center manifold theorem and bifurcation theory, the conditions for the existence of flip bifurcation and Hopf bifurcation in the interior of R+2 are proved. The numerical simulations show that the capture rate not only affects the size of the equilibrium points, but also changes the bifurcation phenomenon. It was found that the discrete system not only has flip bifurcation and Hopf bifurcation, but also has chaotic orbital sets. The complexity of dynamic behavior is verified by numerical analysis of bifurcation, phase and maximum Lyapunov exponent diagram.

Identification of high-dielectric constant compounds from statistical design

The discovery of high-dielectric materials is crucial to increasing the efficiency of electronic devices and batteries. Here, we report three previously unexplored materials with very high dielectric constants (69 < ϵ < 101) and large band gaps (2.9 < Eg(eV) < 5.5) obtained by screening materials databases using statistical optimization algorithms aided by artificial neural networks (ANN). Two of these new dielectrics are mixed-anion compounds (Eu5SiCl6O4 and HoClO) and are shown to be thermodynamically stable against common semiconductors via phase diagram analysis. We also uncovered four other materials with relatively large dielectric constants (20 < ϵ < 40) and band gaps (2.3 < Eg(eV) < 2.7). While the ANN training-data are obtained from the Materials Project, the search-space consists of materials from the Open Quantum Materials Database (OQMD)—demonstrating a successful implementation of cross-database materials design. Overall, we report the dielectric properties of 17 materials calculated using ab initio calculations, that were selected in our design workflow. The dielectric materials with high-dielectric properties predicted in this work open up further experimental research opportunities.

Silicon Modeling of Spiking Neurons With Diverse Dynamic Behaviors

Since spiking neural networks (SNNs) can effectively simulate the information processing mechanism of the biological cortex, they are expected to bridge the gap between neuroscience and machine learning. The hardware simulation of large-scale SNNs requires a simple and versatile silicon neuron model framework. In this article, a spiking neuron circuit as the core device of SNNs is presented. The proposed neuron circuit can mimic the dynamics of different types of biological neurons by adjusting the bias voltage. In order to facilitate the implementation of the spiking neuron circuit based on complementary metal-oxide-semiconductor (CMOS) and reduce the overhead of the circuit area, a modified Mihalas–Niebur (MN) mathematical model is adopted. The improved MN model is biologically plausible and can still successfully display all dynamic behaviors observed in biology. The function of the proposed neuron circuit has been verified by the phase diagram analysis method. The simulation results show the designed neuron circuit can successfully replicate 15 of the 20 firing patterns exhibited by the biological cortex, which proves that the neuron can act as a universal spiking neuron in very large-scale integrated circuit (VLSI) neuromorphic networks.

Arc hopping dynamics induced by interfacial negative differential resistance.

Pattern formation in plasma-solid interaction represents a great research challenge in many applications from plasma etching to surface treatment, whereby plasma attachments on electrodes (arc roots) are constricted to self-organized spots. Gliding arc discharge in a Jacob's Ladder, exhibiting hopping dynamics, provides a unique window to probe the nature of pattern formation in plasma-surface interactions. In this work, we find that the existence of negative differential resistance (NDR) across the sheath is responsible for the observed hopping pattern. Due to NDR, the current density and potential drop behave as activator and inhibitor, the dynamic interactions of which govern the surface current density re-distribution and the formation of structured spots. In gliding arc discharges, new arc roots can form separately in front of the existing root(s), which happens periodically to constitute the stepwise hopping. From the instability phase-diagram analysis, the phenomenon that arc attachments tend to constrict itself spontaneously in the NDR regime is well explained. Furthermore, we demonstrate via a comprehensive magnetohydrodynamics (MHD) computation that the existence of a sheath NDR can successfully reproduce the arc hopping as observed in experiments. Therefore, this work uncovers the essential role of sheath NDR in the plasma-solid surface pattern formation and opens up a hitherto unexplored area of research for manipulating the plasma-solid interactions.

Analysis and finite-time synchronization of a novel double-wing chaotic system with transient chaos

A chaotic system that can generate double-wing attractor is proposed. Through the analysis of Lyapunov exponents, bifurcation diagram, phase diagram and complexity, it is found that the system has rich dynamical phenomenon. The topological structure of the system will change with the change of parameters, which is analyzed by using two-parameter space. In addition, the novel system has phenomenon such as offset-boosting, transient chaos and coexisting attractors. The analog simulation circuit of the system is designed based on Multisim, and the actual digital circuit is realized with field programmable gate array (FPGA). The experimental phase diagram, numerical simulation results and simulation circuit results agree well, which prove the feasibility of the chaotic system. Finally, a controller is designed according to finite-time theory to achieve finite-time synchronization of systems with different structures. The simulation results are consistent with the theoretical analysis, which proves the feasibility of the controller and lays the foundation for the next application research.

Features of distillation separation of multicomponent mixtures

Objectives. To improve the process of developing energy-efficient flowsheets for the distillation separation of multicomponent aqueous and organic mixtures based on a comprehensive study of the phase diagram structures, including those in the presence of additional selective substances.Methods. Thermodynamic-topological analysis of phase diagrams; modeling of phase equilibria in the AspenTech software package using the equations of local compositions: Non-Random Two Liquid and Wilson; computational experiment to determine the column parameters for separation flowsheets of model and real mixtures of various nature.Results. The fractionation conditions of the origin multicomponent mixture due to the use of sharp distillation, pre-splitting process, extractive distillation with individual and binary separating agents were revealed. The columns operation parameters and the energy consumption of the separation flowsheets ensuring the achievement of the required product quality with minimal energy consumption were determined.Conclusions. Using the original methods developed by the authors earlier and based on the generalization of the results obtained, new approaches to the synthesis of energy-efficient multicomponent mixtures separation flowsheets were proposed. The provisions that form the methodological basis for the development of flowsheets for the separation of multicomponent mixtures and supplement the standard flowsheet synthesis plan with new procedures were formulated.

Floquet topological phases with high Chern numbers in a periodically driven extended Su–Schrieffer–Heeger model

The high Chern number phases with the Chern number |C| > 1 are observed in this study of a periodically driven extended Su–Schrieffer–Heeger (E-SSH) model with a cyclic parameter. Besides the standard intra-dimer and the nearest-neighbor inter-dimer hopping of the SSH model, an additional next-nearest-neighbor hopping is considered in the E-SSH model. The cyclic parameter, which plays the role of a synthetic dimension, is invoked as a modulation of the hopping strengths. A rigorous analysis of different phase diagrams has shown multiple Floquet topological phase transitions among the high Chern number phases. These phase transitions can be controlled by the strength and frequency of the periodic driving. Instead of applying perturbation theory, the whole analysis is done by Floquet replica technique. This gives a freedom to study high as well as low-frequency effects on the system by considering less or more number of photon sectors. This system can be experimentally realized through a pulse sequence scheme in the optical lattice setup.

Lattice dynamics of BaFe2Se3

This paper presents a study of the lattice dynamics in BaFe2Se3. We combined first-principle calculations, infrared measurements and a thorough symmetry analysis. Our study confirms that Pnma cannot be the space group of BaFe2Se3, even at room temperature. The phonons assignment requires Pm to be the BaFe2Se3 space group, not only in the magnetic phase, but also in the paramagnetic phase at room temperature. This is due to a strong coupling between a short-range spin-order along the ladders, and the lattice degrees of freedom associated with the Fe–Fe bond length. This coupling induces a change in the bond-length pattern from an alternated trapezoidal one (as in Pnma) to an alternated small/large rectangular one. Out of the two patterns, only the latter is fully compatible with the observed block-type magnetic structure. Finally, we propose a complete symmetry analysis of the BaFe2Se3 phase diagram in the 0–600 K range.