Initial System Research Articles

Interplay of a unit-speed constraint and time-delay in the flocking model with internal variables

<p>We studied the dynamics of thermodynamic Cucker–Smale (TCS) particles moving with a constant speed constraint. The TCS model describes the collective dynamics of the population of birds with a time varying internal variable, and it was first introduced as the generalization of the Cucker–Smale (CS) model. In this paper, we considered a modification of the TCS model in which each agent moves at a constant speed, such as the Vicsek model, and we additionally considered the effect of time-delays due to the finiteness of the information propagation speed between agents. Then, we presented several sufficient conditions in terms of initial data and system parameters to exhibit asymptotic flocking. We presented two kinds of results for this purpose. One was an estimate of the diameter of the velocity and temperature configuration, and the other was an estimate of the diameter of the configuration within the time-delay bound $ \tau $.</p>

The Uniqueverse, Natural selection as the unique model of evolutionary development of the Universe

The cosmological theories proposed so far do not postulate a common way of creation that can guide the entire line of growth of the universe, from elementary particles to living beings. But everything consists of the same basic components, combined and regulated differently: elementary particles, atoms and molecules make up celestial bodies, solar systems, single and pluricellular organisms, plants and animals. Common constituents are compatible with a common origin and with an incremental and selective development method. One possible common mode is that the Universe was formed according to an evolutionary method based on natural selection, the same process which then allowed the differentiation of biological species. This unique process may have guided from the beginning the development of the fundamental constituents of matter in the primitive universe and then created the other cosmic structures through the evolution of those elementary particles, up to organic molecules and biological beings. A process of this kind is a slow and gradual process, not based on a sudden event but on the progressive increase in the complexity of the structures present in the Universe, regulated by the selection of the most suitable and stable forms. For the relativistic relationship between energy, mass and velocity, we can think that the Universe was formed at the same time as the formation of elementary structures, slowly in a spacetime that was created in parallel: elementary particles created an initial infinitesimal spacetime system that then grew as more matter formed. The incremental creation of the cosmos would also concern forces and physical laws, which may have undergone the same evolutionary process from the most primordial and simple forms to the present, in proportion to the development of the whole system. This modality could justify the current simultaneous presence of quantum and relativistic laws at different levels (atomic and gravitational), as well as the coexistence of different species in different environments. This evolutionary modality is reflected in the fact that atoms, celestial bodies, chemical compounds, the general structure of the universe, physical laws and biological beings show the presence of stable entities selected among the many theoretically possible or unstable.

Finite-in-time flocking of the thermodynamic Cucker–Smale model

<abstract><p>We illustrate finite-in-time flocking in the thermodynamic Cucker–Smale (TCS) model. First, we extend the original TCS model to allow for a continuous vector field with a locally Lipschitz continuity. Then, within this system, we derive appropriate dissipative inequalities concerning the position-velocity-temperature using several preparatory estimates. Subsequently, based on initial data and system parameters, we formulate sufficient conditions to guarantee the desired finite-time flocking in each case where the communication weight conditions are divided into two scenarios: one with a positive lower bound and another with nonnegativity and monotonicity. Finally, we provide several numerical simulations and compare them with the analytical results.</p></abstract>

Bio-based unsaturated polyester resin from post-consumer PET.

This study explores the utilization of post-consumer poly(ethylene terephthalate) (PET) as a material in the synthesis of styrene-free unsaturated polyester (UP) resin. The process involves glycolysis of PET waste with diethylene glycol and condensation polymerization with bio-based itaconic acid. The resulting unsaturated polyester possesses reactive methylidene functions that, in contrast to commonly employed fumarates/maleates, facilitate copolymerization with non-styrene reactive diluents. To formulate the resins, methacrylates and itaconates were used for dilution, and the curing process is achieved through a redox initiation system at room temperature, followed by post-curing at elevated temperatures. The cured formulations were characterized by their glass transition temperature, determined by DMA analysis. Mechanical properties were evaluated using standardized tests in tension, flexure, and compression. Particularly promising characteristics are observed in formulations incorporating bio-based dimethyl itaconate (DMI), allowing the formulation of materials with a high ultimate flexural strength (σf,max = 161.4 MPa) and compressive yield point (σc,yield = 131.3 MPa). Furthermore, the low volatility of DMI addresses the health, safety, and ecological concerns associated with the commonly used styrene. This technology not only presents a promising avenue for sustainable UP resin for glass fiber reinforced composites but also allows upcycling PET waste.

On a Method for Integrating the Equations of Rigid Body Motion in Three Homogeneous Force Fields

This paper presents a method for integrating the equations of motion of a rigid body having a fixed point in three homogeneous force fields. It is assumed that under certain conditions these equations admit an invariant relation that is characterized by the following property: the velocity of proper rotation of the body is twice as large as the velocity of precession. The integration of the initial system is reduced to the study of three algebraic equations for the main variables of the problem and one differential first-order equation with separating variables.

Comparative analysis of rock fragmentation by blasting using nonelectric initiation systems and detonating cords

Comparative analysis of rock fragmentation by blasting using nonelectric initiation systems and detonating cords

Novel Intelligence ANFIS Technique for Two-Area Hybrid Power System’s Load Frequency Regulation

The main objective of Load Frequency Control (LFC) is to effectively manage the power output of an electric generator at a designated site, in order to maintain system frequency and tie-line loading within desired limits, in reaction to fluctuations. The adaptive neuro-fuzzy inference system (ANFIS) is a controller that integrates the beneficial features of neural networks and fuzzy networks. The comparative analysis of Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Proportional-Integral-Derivative (PID)-based methodologies demonstrates that the suggested ANFIS controller outperforms both the PID controller and the ANN controller in mitigating power and frequency deviations across many regions of a hybrid power system. Two systems are analysed and represented using mathematical models. The initial system comprises a thermal plant alongside photovoltaic (PV) grid-connected installations equipped with maximum power point trackers (MPPT). The second system comprises hydroelectric systems. The MATLAB/Simulink software is employed to conduct a comparative analysis of the outcomes produced by the controllers.

Revolutioning Lens-Based Systems Design: Showcasing the power of OptiMat

OptiMat, by Sagittal Optics, is a tool developed to generate spherical designs for color-corrected lens-based systems. OptiMat analytically achieves optimum optical materials selection, key to correcting chromatic aberration. However, this tool extends beyond material selection; it is also used to establish initial systems in the design process, which optical designers can further refine. By selecting from a catalog of materials and specifying the number of lenses in the system, optical designers receive ideal assemblies correcting chromaticity, spherical and field aberrations, together with a set of parameters to further improve the provided systems. Additionally, engineers can filter combinations based on different metrics, such as chromatic and monochromatic aberrations. By handling material selection and lens shaping at the project's outset, OptiMat significantly streamlines optical system design times.

Novel thermal initiator systems for radical induced cationic frontal polymerization

Frontal polymerization is an extremely efficient and rapid method for producing bulk polymers, characterized by a self-sustaining curing front that propagates throughout the resin.

Связанная неосесимметричная нестационарная задача термоупругости для длинного цилиндра

Inhomogeneous non-stationary heating of constructions of various purposes induces thermal strains and stresses that should be considered in the comprehensive analysis of elastic systems. The mathematical formulation of the considered linear threedimensional thermoelasticity problems includes coupled non-self-adjoint differential equations of motion and thermal conductivity. Due to their integration difficulty, axisymmetric problems are usually analyzed instead. The purpose of this work is to develop a solution algorithm for the coupled nonaxisymmetric non-stationary problem of the thermoelasticity of a long cylinder. On the internal surface of the hollow anisotropic cylinder, the temperature variation function is known; on the external surface, the convective heat transfer and environmental temperature are given. The rate of the temperature load does not affect the inertial characteristics of the cylinder. Therefore, the equilibrium and heat equations can be added to the initial system of linear equations. The finite Fourier sine and cosine transforms and general biorthogonal transforms are used to study a non-self-adjoint system of differential equations and to develop a closed solution. The obtained solution allows one to determine the temperature field and the stress-strain state of a cylinder with its internal surface affected by non-stationary nonaxisymmetric loading in terms of the temperature variation function.

Study of subharmonic oscillation processes in ferroresonance circuits

The article presents a general theory of the analysis of subharmonic oscillations at a frequency of 25 Hz in three-phase Ferro resonance circuits with common magnetic conductors. The abbreviated equations are obtained by averaging with the corresponding phases. From the condition of the existence of a periodic solution, the phase and amplitude ratios of the excited oscillations are determined, which differ from threephase circuits with a separate ferromagnetic element. In steady-state mode, the excitation conditions and the area of existence are determined depending on the parameters of the circuit, the bias current and the applied action. The stability of the solution of the initial system of nonlinear second-order differential equations is also studied by analysing the roots of the characteristic equation using a qualitative method. In the theory of nonlinear electrical circuits, the analysis of the physical processes occurring in threephase Ferro resonance circuits during the excitation of second-order subharmonic oscillations is of particular importance in the design and creation of various converter devices.

국내 지속가능발전교육 정책 및 실천 동향에 관한 연구

In order to analyze the policy trends and practices of ESD in Korea, this study analyzed related data focusing on five priority action areas proposed by UNESCO: policy improvement, learning environment, educator capacity building, youth participation opportunities, and community capacity building. Based on the analysis, the study suggested the policy implications for the spread and activation of ESD. First, it is necessary to move beyond the stage of establishing an initial system for ESD to the stage of internalizing sustainable capabilities by establishing a diagnostic system for learners and institutions. Second, in addition to ESD programs focused on climate and environmental education, programs on various contents and practices for the co-prosperity of the human community, such as human rights, citizenship, equality, social justice, healthy consumption and production, should be expanded in the future. Third, beyond delivering the concept and content of ESD through educational curriculum or training, the principle of sustainability should be institutionalized throughout the operational process of educational organizations. Finally, in order to connect ESD and community life, teaching and learning models for ESD should be specified in schools, and clear methods and guidelines for incorporating ESD in lifelong education should be prepared.

Modeling the pattern of metal flow during forming of forgings from a flat billet

Parts made of the billets with a thin web and stiffeners are manufactured at metallurgical enterprises in special workshops equipped with powerful hydraulic presses. Often their production is accompanied by the defects that worsen the product macrostructure. In this regard, new techniques are relevant that allow modeling the processes of forming of forgings with stiffeners. The processes of metal processing by pressure are difficult to create a mathematical model describing the stress-strain state of plastic forming of metal. One of the ways to solve the problem of modeling the pattern of metal flow and the spatial diagram of contact pressures is the “theory of thin layer flow”, based on assumptions that simplify the initial system of differential equations. Then the problem is reduced to a purely geometric one and can be solved within the framework of the “sandy analogy” using the proposed methodology. The paper presents the results of computer and physical modeling of the forming of stamped forgings with contour stiffeners. The experiment was carried out in industrial conditions on the precipitation of flat billets made of AK6 alloy on a hydraulic press with a deformation force of 150 MN. It is shown that the proposed software package can have a different functional purpose: express analysis of the pattern of metal flow and calculation of the shape of the billet at the stages of its deformation. This allows, by sorting through values of the geometric parameters of the stamp engraving, to obtain different patterns of metal flow and profiles of stiffeners and choose from them those that guarantee the most uniform filling of the stamp cavities with metal under the stiffeners, which ensures defect-free production of the product.

Multibranched polymethacrylates by anionic grafting-from method via desilylation of poly(4-trimethylsilylmethylstyrene)

Abstract A benzyltrimethylsilane (BnTMS)/potassium tert-butoxide (t-BuOK) initiator system for anionic polymerization was applied to poly(4-trimethylsilylmethylstyrene) (PTMSMS) in the presence of 1,1-diphenylethylene (DPE) to construct polyanion macroinitiators and polymerize methacrylate monomers therefrom. Using this method, desilylation of PTMSMS was quantitatively processed and methacrylate monomers were polymerized from the macroinitiator. The obtained multibranched polymers had narrow molecular weight distributions, indicating the well-controlled polymerization of the monomers from the macroinitiator. Therefore, it was demonstrated that PTMSMS can be a suitable precursor for the preparation of multibranched polymers. Additionally, a sequential addition of methacrylate monomers to the polyanion macroinitiator lead to a core-shell multibranched polymer with a narrow molecular weight distribution.

Fixed time control of free-flying space robotic manipulator with full state constraints: a barrier-Lyapunov-function term free approach

Space robotic manipulator (SRM) should be always performed in the given workspace for safety concern. This requires the system states such as rotation of each joint, attitude of base, and their velocities to be always constrained in the given regions. In this article, a new sliding mode control scheme based on a fixed time disturbance observer is proposed to realize the fixed time coordinate motion control of SRM with full-state constraints. Firstly, the tracking error and error velocity at the novel sliding manifold can converge to the equilibrium within a fixed time without violating their state constraints. Then, the control law based on the fixed time disturbance observer is designed to achieve the sliding manifold within a fixed time, which simultaneously satisfies the state constraints during the approaching stage. Unlike the most existing state constraint control schemes, the proposed controller does not include any Barrier Lyapunov Function (BLF) terms of system states, and therefore the risk of controller outputting inappropriately high control commands is eliminated. Moreover, the proposed control scheme is compatible to the initial system states violating their constraints, which thereby removes the assumption of feasible initial states. Furthermore, the proposed sliding manifold solves the singularity issue by a continuously varying power of tracking error, which thereby does not need an additional switch mechanism of manifold compared to the conventional fixed time controllers. The stability of the proposed control scheme is proven by using the Lyapunov theory, and the effectiveness is verified by numerical simulations.

Numerical Simulation of the Residual Stress at the Interface between Thermal Barrier Coating and Nickel-Based Single-Crystal Superalloy Based on Crystal Plasticity Theory

Residual stress plays an important role in the formation and growth of cracks in thermal barrier coatings and single-crystal superalloy substrates. In this study, a finite element model for a planar double-layer thermal barrier coating and a crystal plasticity finite element model based on dislocation slip-induced plastic deformation of single-crystal materials were established to analyze the residual stress in the coatings and the substrate, considering the creep and crystal plasticity of the substrate materials. The simulation results show that the thermal barrier coatings bear most of the stress generated by high temperatures, and the residual stress of the substrate is small. By comparing the two material properties to calculate the interface stress when the amplitude of the interface between the substrate and the coating is 30 μm and the thickness of the thermal grown oxide layer is 5 µm, the interfacial stress of the substrate at the macro scale was found to be similar to the interfacial stress at the micro slip system scale. Based on the cumulative shear strain, it was determined that the [001]-, [011]-, and [111]-oriented alloys activated the 12, 8, and 4 groups, respectively, under the combined action of thermal stress and centrifugal force of the coating. Comparing the activation of different initial orientation slip systems and the magnitude of the yield stress provides a theoretical foundation to study the structural integrity of single-crystal alloys.

Screening of First-Row Transition Metal Complexes for Aqueous Redox Flow Batteries: Experimental and Density Functional Theory Approaches

The development of redox flow batteries took new directions in the last decades. From initial metal-based systems, it evolved towards organic and hybrid approaches in aqueous media. Furthermore, redox targeting flow batteries are an emerging alternative to the traditional redox flow battery architecture which offer improved energy density via an added electroactive solid ‘booster’. Whatever the system, there is a need of soluble electroactive species with potentials allowing large cell potentials within the water stability window or imperative redox potentials matching between soluble redox mediator and the solid for redox targeting. Transition metal complexes are a promising class of redox electroactive centers due to the tunability of their solubility and electrochemical potential, and the ability to take into account sustainability1. Recent reports underlined for instance that either the modification of the ligand2 or using heteroleptic complexes3, can lead to iron complexes with solubilities higher than 1 M and potentials higher than 1 V vs SHE. Furthermore, reliable and time-efficient prediction tools for the redox potentials of transition metal complexes are needed to help the search for new potential systems. While density functional theory usually provides a good trade-off between computational cost and accuracy, calculations on transition metal complexes often result in large errors. We thus developed a procedure and compared different solvation methods and levels of theory using an initial experimental data set based on aqueous iron complexes with bidentate ligands (Figure 1).In the present contribution, we will illustrate this coordination approach through a screening of new complexes based on non-toxic and affordable transition metal complexes. In this perspective, electrochemical characterization at different pH, coupled with NMR and UV-Visible studies will be presented, to screen for new candidates as electrolyte in redox flow batteries. Finally, we will show how the calculations corrected using a simple linear regression using training data yields a good prediction of redox potentials (mean average error =0.09 V).

Black Widow Optimization Algorithm-Based Sub Synchronous Resonance Investigation with Series Compensation

The integration of wind farms into the transmission network has raised various concerns and objections. To address these challenges, the deployment of series compensators has gained significance as an effective method for enhancing the power transmission capacity of existing lines, particularly for the integration of large-scale wind farms. However, the use of series reactive compensation lines can lead to a phenomenon known as sub-synchronous resonance (SSR) in turbo generators. This SSR can cause electrical instability at sub-synchronous frequencies and potential damage to the turbine’s generator shaft, particularly during periods of peak production. As a result, the assessment of SSR through comprehensive surveys is crucial for wind power engineers to make informed decisions and ensure the safety of turbines. This study explores the potential of SSR through the utilization of the black widow optimization technique. The analysis takes into account variables such as variations in the speed of the wind, compensation spectrum, and wind velocity and examines the eigenvalue and involvement components under various operating situations. To validate our findings, electromagnetic transient simulations are conducted using the PSCAD/EMTDC software, employing the initial IEEE reference systems. This research contributes to a deeper understanding of SSR and its implications for wind energy systems.

Magnetic Resonance Imaging-guided Active Surveillance Without Annual Rebiopsy in Patients with Grade Group 1 or 2 Prostate Cancer: The Prospective PROMM-AS Study

BackgroundMultiparametric magnetic resonance imaging (mpMRI) may allow patients with prostate cancer (PC) on active surveillance (AS) to avoid repeat prostate biopsies during monitoring. ObjectiveTo assess the ability of mpMRI to reduce guideline-mandated biopsy and to predict grade group upgrading in patients with International Society of Urological Pathology grade group (GG) 1 or GG 2 PC using Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) scores. The hypothesis was that the AS disqualification rate (ASDQ) rate could be reduced to 15%. Design, setting and participantsPROMM-AS was a prospective study assessing 2-yr outcomes for an mpMRI-guided AS protocol. A 12 mo after AS inclusion on the basis of MRI/transrectal ultrasound fusion-guided biopsy (FBx), all patients underwent mpMRI. For patients with stable mpMRI (PRECISE 1–3), repeat biopsy was deferred and follow-up mpMRI was scheduled for 12 mo later. Patients with mpMRI progression (PRECISE 4–5) underwent FBx. At the end of the study, follow-up FBx was indicated for all patients. Outcome measurements and statistical analysisWe calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for upgrading to GG 2 in the GG 1 group, and to GG 3 in the GG 2 group on MRI. We performed regression analyses that included clinical variables. Results and limitationsThe study included 101 patients with PC (60 GG 1 and 41 GG 2). Histopathological progression occurred in 31 patients, 18 in the GG 1 group and 13 in the GG 2 group. Thus, the aim of reducing the ASDQ rate to 15% was not achieved. The sensitivity, specificity, PPV, and NPV for PRECISE scoring of MRI were 94%, 64%, 81%, and 88% in the GG 1 group, and 92%, 50%, 92%, and 50%, respectively, in the GG 2 group. On regression analysis, initial prostate-specific antigen (p < 0.001) and higher PRECISE score (4–5; p = 0.005) were significant predictors of histological progression of GG 1 PC. Higher PRECISE score (p = 0.009), initial Prostate Imaging-Reporting and Data System score (p = 0.009), previous negative biopsy (p = 0.02), and percentage Gleason pattern 4 (p = 0.04) were significant predictors of histological progression of GG 2 PC. Limitations include extensive MRI reading experience, the small sample size, and limited follow-up. ConclusionsMRI-guided monitoring of patients on AS using PRECISE scores avoided unnecessary follow-up biopsies in 88% of patients with GG 1 PC and predicted upgrading during 2-yr follow-up in both GG 1 and GG 2 PC. Patient summaryWe investigated whether MRI (magnetic resonance imaging) scores can be used to guide whether patients with lower-risk prostate cancer who are on active surveillance (AS) need to undergo repeat biopsies. Follow-up biopsy was deferred for 1 year for patients with a stable score and performed for patients whose score progressed. After 24 months on AS, all men underwent MRI and biopsy. Among patients with grade group 1 cancer and a stable MRI score, 88% avoided biopsy. For patients with MRI score progression, AS termination was correctly recommended in 81% of grade group 1 and 92% of grade group 2 cases.

Micron-Sized Hierarchical Beta Zeolites Templated by Mesoscale Cationic Polymers as Robust Catalysts for Acylation of Anisole with Acetic Anhydride

Hierarchical Beta zeolites with interconnected intracrystalline mesopores and high structural stability are highly attractive for catalytic applications involving bulky reactants. Here, by introducing a suitable amount of polydiallyldimethylammonium chloride into the initial synthesis system, micron-sized Beta zeolite crystals with abundant hierarchical porosity (Beta-H) were hydrothermally synthesized. The sample named Beta-H_1 exhibited very high catalytic activity and durability for the Friedel–Crafts acylation of anisole with acetic anhydride. A 92% conversion rate of acetic anhydride could be achieved after 1 h of reaction in a fixed bed reactor, and 71% conversion still remained after 10 h, much better than the rate for conventional Beta zeolite (which decreased rapidly from 85% to 37% within 10 h). The enhanced catalytic performance of Beta-H zeolites could be mainly attributed to the relatively lower strong acid density and the faster transport rate of the hierarchical zeolites. In addition, Beta-H showed high structural stability and could be easily regenerated via high-temperature calcination without obvious loss in catalytic activity, demonstrating its great potential for catalytic applications in the industrially important Friedel–Crafts acylation process.