Constant Parameters Research Articles

A novel spaceborne photon-counting laser altimeter denoising method based on parameter-adaptive density clustering

ABSTRACT To tackle the challenge of denoising spaceborne photon-counting laser altimeter point clouds with uneven noise density, this study proposes a denoising method based on adaptive parameter density clustering, which utilizes numerical simulations to achieve self-adaptation of key parameters (neighborhood radius Eps and minimum number of points MinPts ). First, taking the directional adaptive ellipse DBSCAN (DAE-DBSCAN) as an example, photons with different background photon count rates ( bckgrd _ rate ) are used to traverse Eps and MinPts to calculate their optimal values ( Eps and MinPts with the highest denoising accuracy). Then, a mathematical prediction model of bckgrd _ rate , Eps and MinPts was established. The actual background photon count rates were introduced into the key parameter prediction model to obtain the optimal Eps and MinPts . Finally, a denoising experiment was conducted using the simulated photons and the ATLAS data. The results show that the proposed method had higher accuracy than the constant parameter denoising method, with an F >0.95. Even for photons of complex mountainous terrain with a high background photon count rate, the denoising accuracy was still higher than 0.9. The proposed method improves the denoising accuracy of photons with different noise densities by adapting density clustering parameters.

Coupled thermal-mechanical analysis of power electronic modules with finite element method and parametric model order reduction

This work presents a new approach for performing a parametric study and examining nonlinear material behaviours of a coupled thermal-mechanical model of a Power Electronics Module (PEM) by integrating the Finite Element Method (ANSYS-FEM) with Parametric Model Order Reduction (pMOR). The considered coupling method solves the thermal and structural models concurrently compared to the widely practised sequential coupling method. Instead of constant parameter values, which are generally regarded for pMOR studies, the temperature-dependent material properties of the wire material have been parametrised in the work using the pMOR method. A generalised 2D model has been regarded here for thermal-mechanical analysis with the pMOR approach, parametrising temperature-dependent coefficient of thermal expansion (CTE) and Young’s modulus (E) of the wire material to explore their impact on wire bonds. The matrix interpolation method has been applied here for the pMOR study, and PRIMA, a Krylov subspace-based model order reduction (MOR) technique, has been exercised for local model order reductions. A new efficient process of matrix interpolation, based on the Lagrange interpolation technique, has been developed to implement matrix interpolation in the parametric reduced order model (pROM). The local reduced order models (ROMs) have a degree of freedom (DOF) of just 8, compared to the full-order models’ (FOMs) of 50,602. The pROM provides an excellent solution and reduces computational time by 84% for the presented case.

DYNAMIC CHARACTERISTICS OF TIME-VARYING CONTROL SYSTEM OF THE ROCKET’S ROTATIONAL MOVEMENT

The rocket motion control system is time-varying, because its parameters during flight depend on the trajectory point and fuel consumptions. In the available sources, due attention is not paid to the development of a mathematical apparatus of an applied value for the quan- titative assessment of the dynamic characteristics of a time-varying system.
 The purpose of the work is to justify the possibility of an algorithm building for calcu- lating the parameters of a link with constant parameters, which is equivalent to a time- varying system in terms of dynamic characteristics at the selected trajectory section.
 The link’s parameters are found by using the criterion of equivalence of the array of values of the motion model’soutput signal and the analytical solution of the link’s differential equation for a given sequence of input signals. This makes it possible to use the mathematical apparatus of stationary systems to determine the indicators of the disturbances compensation.
 The model of the control system of the rocket’s rotational movement in one plane is taken as a linear differential equation with time-varying parameters without taking into ac- count the executive device inertia and other disturbances. The link with constant parameters is a fractional-rational function of the second order, for the determination of which a se- quence of signals is applied to the input of the system model, the duration of which depends on the desired stability margin on the roots plane of the characteristic polynomial.
 Using the example of a time-varying system for controlling the rocket’srotational movement in the yaw plane, the possibility of determining the parameters of the transition process of compensation for the disturbances characteristic of it is shown for the selected tra- jectory section.
 The obtained results can be used in the design of a motion control system with time- varying parameters.
 The next stage of the research is an assessment of the complexity level of the calcula- tion algorithm when increasing the order of the system’smathematical model.

Investigation of river water pollution using Muskingum method and particle swarm optimization (PSO) algorithm

River water pollution is one of the most important environmental issues. Advection–dispersion equations are used to study the temporal changes in pollutant concentration along the study river reach. The use of advection–dispersion equations in investigating how the concentration of pollution is transformed requires a lot of data including river cross-section characteristics, dispersion coefficient, and upstream and downstream boundary conditions, etc. therefore, the corresponding calculations are very costly, difficult and time-consuming. In the present study, instead of using the mentioned equations, the linear Muskingum method (used in previous studies for flood routing) and the particle swarm optimization (PSO) algorithm was used for the first time to calculate the temporal changes in pollution concentration at different stream locations. The presented solution in the presented study is very accurate and only requires the temporal changes in concentration in the upstream and downstream of the study river reach and for this reason, it is very low-cost and easy to use and requires less time to collect data and perform calculations. In the proposed method, the parameters (X, K, ∆t) of the linear Muskingum method were optimized using the PSO algorithm, and by dividing the temporal changes in the input concentration into three areas of the beginning (the input concentration is greater than the output concentration), the peak (the maximum input and output concentrations) and the end (the output concentration is greater than the input concentration) areas, the accuracy of the calculations increased. The mentioned method was studied for different lengths (first case of x = 50 m (up) and x = 75 m (down), second case of x = 50 m (up) and x = 100 m (down), third case of x = 75 m (up) and x = 100 m (down)) and the mean relative error (MRE) of the total, peak area and the relative error of the maximum concentration using constant parameters for the first case were calculated as 7.08, 1.02, and 2.34 percent, for the second case as 7.41, 11.06 and 6.69 percent, and for the third case as 6.75, 3.59 and 5.42 percent, respectively. If three parameters of (X, K, ∆t) are used, the mentioned values improved by 31.3, 63.7 and 65.5 percent, respectively compared to the case of using constant parameters.

Rapid, iterative design approach for preliminary configuration of a High Altitude, Long Endurance aircraft

This paper presents a rapid iterative design approach, used to develop a preliminary configuration of an Unmanned Aerial Vehicle (UAV), which is to perform a High-Altitude, Long Endurance (HALE) mission. First, based on a set of requirements, an initial aircraft concept is developed.The rapid iterative design approach revolves around an energy-based flight profile simulation, which is updated with an improved aerodynamic model of the aircraft during every iteration. An aircraft configuration is defined by a set of constant parameters. A corresponding flight profile consists of an altitude and velocity profile, as a function of time. The behaviour of the aircraft is simulated based on the specified flight profile.For sizing the aircraft components exposed to the airstream, the aerodynamic design phase aims to create an airframe which achieves the performance outlined in the flight performance simulation, utilizing the obtained aircraft parameters. Using the geometric data, a 3D-model of the aircraft is created, which is essential for the aircraft’s weight and balance calculations and for determining the airframe shape exposed to the airflow. A Computational Fluid Dynamics (CFD) simulation is conducted to obtain the actual aerodynamic characteristics of the airframe. If the performance requirement of the flight performance simulation is not met, another iteration of the aerodynamic design phase is required.The design framework stands out due to its rapid iteration capability, accessibility, and straightforward application, making it particularly advantageous for educational settings in which students engage with aircraft design. The approach aims to offer satisfactory results for an initial aircraft conceptualization.This design framework emerged from the DLR Design Challenge 2023, an annual competition hosted by the German Center for Aerospace Research, where student teams develop preliminary aircraft designs. This years challenge tasked the teams with designing an aircraft system to restore internet coverage over a disaster-affected region. The described approach was used to develop the Sentinel System of the DHBW Ravensburg team. However, the simulation and development process is not limited to applications within this challenge.

Numerical Modelling and Simulation for Sliding Wear Effect with Microstructural Evolution of Sputtered Titanium Carbide Thin Film on Metallic Materials

Titanium carbide materials are introduced into manufacturing industries for the reinforcement and surface protection of base materials due to their substantial ability to withstand severe environments, which include sliding wear, corrosion, and mechanical failures. A thin film of titanium carbide (TiC) is coated onto brass and copper substrates using the radio frequency magnetron sputtering (RFMS) deposition method. The coating process is carried out at constant processing parameters, which include a sputtering power of 200 W, a temperature of 80 °C, a deposition time of 180 min, and an argon (Ar) gas flow rate at 10 standard cubic centimetres per minute (SCCM). The coating, together with the base materials, is modelled and its behaviours are simulated using ANSYS Workbench R19.2 Academic, supported by Mechanical APDL solver for nonlinear finite element analysis (FEA). The deformation, equivalent stress–strain characteristics, and elastic–plastic properties of the coating are determined at applied loads of 60 N and 25 N and coefficients of friction (CoF) of 0.25 and 0.38 for the thin film deposition on brass and copper substrates. The sliding distance and the speed of the alloy steel ball used during the sliding wear operation are found to be 3 mm and 4 mm/s, respectively. The sliding wear modelling and simulation process are, however, designed for the ball-on-flat (BoF) wear technique with a dry sliding approach. Therefore, BoF wear simulations are also performed on titanium carbide–brass (TiC-Br) and titanium carbide–copper (TiC-Cu) conjugates for the evaluation of surface engineering applications such as cutting tools and in automotive, aerospace, thermomechanical, and biomedical fields. The ball used for the FEA wear simulation is made from alloy steel material (AISI 52100) with a radius of 3.175 mm.

Stagnant points and uniform film analysis of Eyring fluid film flow on a vertically upward moving slippery flat plate

In this paper, we analyze how Eyring fluid film behavior on a vertically upward moving slippery flat plate can help predictive models in engineering, notably in coating and lubrication operations. This paper deals with the stagnant points and uniform film analysis of Eyring fluid film flow on a vertically upward moving slippery flat plate. The formulated ordinary differential equation is solved for exact analytic solution. Exact analytic expressions for velocity, flow rate, average velocity, shear stress components, and stagnant points are derived. A highly nonlinear algebraic equation is derived for film thickness. Equation is solved by Newton’s method using Maple code. The thickness of film widens with increasing relaxation time, constant plate velocity, and fluid density, while it decreases with increasing fluid viscosity and constant slip parameter. The analysis delineates that the positions of stagnant points tend to relocate closer the slippery plate as the Stokes number, Deborah number, and constant slip parameter increase. A high Deborah number enhances drainage, causing stagnant points to relocate closer to the slippery plate and the development of a stable elastic layer adjacent to the plate. For stagnant points and fluid film thickness, a comparison between the Eyring fluid and existing studies (EPTT, LPTT, UCM, and Newtonian fluid) is also provided. The validity of this paper with the existing studies is also presented by reducing Eyring fluid model to Newtonian model. The results of this research are significant for a wide range of biofluid applications, including agrochemical uses, paint and surface coating flow behavior, thin films on the cornea and lungs, and chemical and nuclear reactor design.

Bioleaching of Mine Tailings by Mesophilic: Acidithiobacillus spp., Leptospirillum ferrooxidans, and Thermophilic: Sulfobacillus thermosulfidooxidans Cultures with the Addition of Ag+ Additive

This research focused on applying and comparing the performance of microorganisms with different temperature preferences, assessing the overall percentage recovery of elements (copper, zinc, arsenic, and iron) from mine tailings in the Staré Ransko region (Czech Republic). The study examined the solubilisation process using a mesophilic mixed bacterial culture, including Acidithiobacillus ferrooxidans (AF), Acidithiobacillus thiooxidans (AT), Leptospirillum ferrooxidans (LF), and the thermophilic species Sulfobacillus thermosulfidooxidans (ST). Under biotic conditions, constant process parameters were maintained, including a particle size of 71–100 µm, a pH value of 1.8, agitation at 150 rpm, and a pulp density of 10% (w/v). The only exception was the temperature, which varied for optimal multiplication of cultures (30 °C/50 °C). Additionally, the research examined the impact of AgNO3 additive at a concentration of Ag+ ions of 5 mg·L−1. The research focused on the solubilisation of Cu, Zn, Fe, and As and the results demonstrated that the application of microorganisms ST, combined with the action of Ag+ ions, enhanced the kinetics of the extraction process, leading to the highest final recovery of all elements (Cu 91.93%, Zn 85.67%, As 69.16%, and Fe 71.72%) under the specified conditions. The study observed that the most significant increase in solubilisation can be attributed to the additive cation in the case of copper (AF, AT, LF/Ag+ by 40.33%; ST/Ag+ by 44.39%) and arsenic (AF, AT, LF/Ag+ by 23.79%; ST/Ag+ by 26.08%). Notably, the intensification of leaching using thermophilic bacteria at a constant suspension temperature of 50 °C was primarily determined for Zn (ST by 18.36%, ST/Ag+ by 14.24%). After 24 days of extraction, the emergence of secondary minerals, namely CaSO4·2H2O and KFe3(SO4)2(OH)6, was identified. The study highlighted a significant increase in the extraction mechanism kinetics due to the influence of microorganisms, contrasting with the low solubilities observed under abiotic conditions (Cu 9.00%, Zn 14.17%, As 4.28%, Fe 6.23%).

Stabilization of constant power loads and dynamic current sharing in DC microgrid using robust control technique

DC microgrids are appealing in distribution networks due to their high efficacy, stability, and ease of incorporation with renewable energy resources. In order to maintain system reliability, load sharing is crucial, because disturbances such as the constant power load (CPL), constant voltage load (CVL), uncertainty parameters, and variations in input voltage may result in instability. The conventional droop control method has been frequently employed to regulate the DC microgrid. However, under significant disturbances, conventional droop control is not suitable for achieving both accurate current sharing and acceptable voltage regulation. To tackle these limitations, this paper introduces a robust control for sharing load current and regulating DC bus voltage in a DC microgrid feeding a CPL and CVL. The proposed approach is split into two loops. The main loop, which is based on an RST controller, is used to regulate the current load sharing between two parallel boost DC/DC converters, handle the instability issue caused by disturbances, and improve system reliability. The DC bus voltage is adjusted using the secondary loop built using the proportional-integral (PI) controller. The key benefits are precise voltage regulation, load power sharing, and good reliability. Aside from that, the RST controller has great resilience, quick dynamic response, and strong stability for significant load fluctuations. The feasibility and efficacy of the proposed approach are confirmed by time-domain simulation results, and hardware-in-the-loop (HIL) testing under various scenarios. The obtained findings show that the suggested control strategy is capable of ensuring proportionate power-sharing while dealing with DC voltage instability under CPL, CVL, uncertainty parameters, and input voltage fluctuations.

STODOLA-VIANELLO ITERATION METHOD FOR FREE TORSIONAL VIBRATION ANALYSIS OF MONOSYMMETRIC BOX-BEAM BRIDGES

Box-beam bridges are used in large spans and wider decks due to their high strength and greater torsional and flexural stiffness. They are usually prone to vibration due to moving vehicular traffic. Their eigenfrequency analysis is a crucial aspect of their design in order to ensure that the natural frequency is not close to the excitation frequency to avert resonance failures. The free torsional vibration equation is a fourth order partial differential equation (PDE) with variable parameters. For prismatic cross-sections, homogeneous and isotropic materials the governing PDE have constant parameters. This paper explores the Stodola-Vianello iteration method (SVIM) for solving the PDE for isotropic, homogeneous prismatic box-beams. Harmonic response is assumed, decoupling the PDE to two equations, one in terms of time and the second an ordinary differential equation (ODE) in terms of space coordinates. The Stodola-Vianello method is used by the method of four successive integrations to express the ODE as an algebraic iteration problem with four constants of integration. The four boundary conditions are used to solve for the four constants of integration, thus making the problem determinate. Application of the boundary conditions results in the full determination of the iteration equations. For simply supported boundaries studied in the work, a trigonometric buckling shape function that satisfies all the boundary conditions is employed in the SVIM formula to obtain the next bucking modal shape function. The requirement for convergence is then used to establish the characteristic buckling equation from which the eigenvalues are obtained. The solution to the characteristic buckling equation gave the exact mathematical expression for the natural torsional frequency at the nth vibration mode. The frequencies are determined for the first eight vibration modes and compared with previously obtained values. It was found that the natural frequencies are identical with previously found values of the exact natural frequencies. The natural frequency obtained is exact because it satisfies the PDE and the boundary conditions at all points in the domain.

Heat transfer analysis of MHD oscillatory SWCNT/MWCNT‐H2O hybrid nanofluid flow in a channel

AbstractRegulating the thermal conductivity of the fluid in various heat exchange systems plays an important role. In this regard, the carbon nanotubes (CNTs), with their higher thermal conductivity, can enhance the heat transfer potential. The main objective of the present study is to explore the impact of suction and injection on the oscillatory flow of CNT‐based hybrid nanofluid through a channel under the influence of the magnetic field for analysing heat transfer perspectives. While developing a mathematical model of the problem, we also considered other relevant elements, such as thermal radiation for optically thin fluids and porous mediums. The behaviour of a water‐SWCNT + MWCNT hybrid nanofluid is studied concerning the volume fraction of CNTs. The governing flow equations have been solved to obtain the correct solutions for the distribution of velocities and temperatures. Graphs and tables are used to assess the impact of relevant parameters on the flow and derived quantities. Adding CNTs to a fluid reduces its temperature and velocity, making it ideal for cooling systems. However, plates exhibit a maximum heat transfer of 35.35% and 25.35%, respectively, for and . The magnetic and constant pressure parameters greatly diminish the fluid's velocity, while the thermal buoyancy forces strengthen the flow. The effectiveness of the current study is confirmed by comparing its results to those from previous investigations.

Experimental study on the thermal management performance of lithium-ion battery with PCM combined with 3-D finned tube

As an important intermediary between the green energy and human society, the lithium-ion battery has promising prospects in the new energy vehicles, energy storage, and green development fields. However, lithium-ion batteries can generate a large amount of heat during operation. In addition, excess temperature or big temperature difference of the surface of the lithium-ion battery can reduce its performance, which also results in reducing its operational life and even triggers incidents such as fires and explosions. Therefore, studying efficient thermal management methods for lithium-ion batteries is crucial for increasing their application range. This paper proposes a novel thermal management method by combining 3-D finned tubes with PCM. The thermal management system maintains a battery operating temperature less than 45 °C and a maximum temperature difference less than 2.4 °C. The influence of different fin structure parameters on the melting dynamics of PCM and the heat transfer performance is then discussed. The obtained results show that under each solid–liquid ratio of PCM, the heat transfer performance increases with the increases of the fin height, while it initially decreases and then increases with the increase of the width and axial spacing. Moreover, the heat transfer performance of the 3-D finned tube with different PCM liquid–solid ratios is investigated. The obtained results demonstrate that for constant fin parameters, the heat transfer reaches its highest performance for a PCM liquid–solid ratio greater than 2:2. The findings of this study lay a foundation for the design of efficient thermal management systems incorporating PCM applications.

Solid-Liquid-Solution Phases in Poly(diallyldimethylammonium)/Poly(acrylic acid) Polyelectrolyte Complexes at Varying Temperatures.

The coacervation and complexation of oppositely charged polyelectrolytes are dependent on numerous environmental and preparatory factors, but temperature is often overlooked. Temperature effects remain unclear because the temperature dependence of both the dielectric constant and polymer-solvent interaction parameter can yield lower and/or upper critical solution phase behaviors for PECs. Further, secondary interactions, such as hydrogen bonding, can affect the temperature response of a PEC. That is, mixtures of oppositely charged polyelectrolytes can exhibit phase separation upon lowering and/or increasing the mixture's temperature. Here, the phase behavior of poly(diallylmethylammonium)/poly(acrylic acid) (PDADMA/PAA) complexes under varying KBr ionic strengths, mixing ratios, and temperatures at a fixed pH (in which PAA hydrogen bonding can occur) is examined. At room temperature, the PDADMA/PAA PECs exhibit four different phase states: precipitate, coexisting precipitate and coacervate, solid-like gel, and coacervate. Variable-temperature optical microscopy reveals the upper critical solution temperature (UCST) at which each phase transitioned to a solution state. Interestingly, the UCST value is highly dependent on the original phase of the PEC, in which solid-like precipitates exhibit higher UCST values. Large-scale all-atom molecular dynamics (MD) simulations support that precipitates exhibit kinetic trapping, which may contribute to the higher UCST values observed in the experiment. Taken together, this study highlights the significance of temperature on the phase behavior of PECs, which may play a larger role in stimuli-responsive materials, membraneless organelles, and separations applications.

A comparative study of central corneal thickness in patients with diabetes and without diabetes mellitus

Diabetes mellitus (DM) is becoming increasingly and seriously prevalent lifestyle health problem worldwide. Up to 70% of diabetic patients can develop corneal changes and are also difficult to manage. Several studies were done to find out the morphological changes in cornea in type 2 DM, but the results are highly variable. Central corneal thickness (CCT) is widely considered as a constant parameter, so are measured only once during follow up in our daily clinical practice. Here we study the effect of diabetes over CCT, for a better understanding of the impact of diabetes over CCT.A comparative observational study of one and half years done among 106 diabetes and 106 non diabetic patients between 35 to 75 years old, attending ophthalmology OPD. CCT of both eyes was measured and mean CCT and was compared between diabetic and non-diabetic groups, among different subgroups of diabetic subjects and other parameters.CCT was thicker among diabetic groups (553.4434um) than non-diabetic groups (549.8491) but was not statistically significant according to our study. But there was statistically significant (p value 0.000165) thickening with increasing grades of diabetic retinopathy (DR) (mild DR (535.4524), moderate DR (543) and PDR (591.5)). Our study concludes that DM is associated with thicker cornea; hence CCT values can vary with time in DM. So repeated CCT measurements for corrected IOP values is advised and warranted in DM patients for proper management of IOP.

Determinants for 1-alkyl-3-methylimidazolium chloride-induced modulation of thermodynamic stability and CO-association dynamics of horse ferrocytochrome c

This manuscript determines the factors by which the water-miscible ionic liquid (IL), 1-alkyl-3-methylimidazolium chloride [Rmim]Cl affects the thermodynamic stability and CO association dynamics of horse ferrocytochrome c (Cyt cII) at pH 7. Investigation of rate constant and activation thermodynamic parameters for CO-association reaction of Cyt cII measured at different concentrations of [Rmim]Cl (1-Ethyl-3-methylimidazolium chloride [Emim]Cl, 1-butyl-3-methylimidazolium chloride [Bmim]Cl, 1-hexyl-3-methylimidazolium chloride [Hmim]Cl) revealed that the hydrophobicity of alkyl group of [Rmim]Cl modulates the CO-association dynamics of Cyt cII. The CO-association association kinetic results were further supported by intermolecular docking studies between the Cyt cII and [Rmim]+ ([Hmim]Cl, [Bmim]Cl, [Emim]Cl). Analysis of thermodynamic parameters calculated from thermal denaturation transitions of Cyt cII at different concentrations of [Rmim]Cl ([Hmim]Cl, [Bmim]Cl, [Emim]Cl) revealed that the [Rmim]Cl decreases the denaturation free energy in the order: [Hmim]Cl > [Bmim]Cl > [Emim]Cl, which suggests that the hydrophobicity of alkyl group of [Rmim]Cl modulates the [Rmim]Cl-induced decrease in thermodynamic stability of Cyt cII. Analysis of entropy − enthalpy plots showed that in addition to the hydrophobic effect, the enthalpic effect of [Rmim]Cl also decreases the thermodynamic stability of the protein. The dependence of unfolding free energy on [Rmim]Clconcentration was also translated into preferential interaction coefficients, Γ23. Experimental and theoretical estimations of Γ23 for Cyt cII provided the positive values of Γ23 at all across the [Rmim]Cl concentrations, indicating a robust and favorable interaction between the [Rmim]Cl and Cyt cII. Furthermore, the [Rmim]Cl-mediated increase in Γ23 typically follows the order: [Hmim]Cl > [Bmim]Cl > [Emim]Cl. Molecular dynamics (MD) simulation studies of Cyt cII performed at different concentrations of [Rmim]Cl ([Emim]Cl, [Bmim]Cl, and [Hmim]Cl) further showed that the hydrophobicity of the alkyl group modulates the structural stability and conformational-fluctuations of the Cyt cII.

Abundant solitons for the generalized Hirota–Satsuma couple KdV system with an efficient technique

The generalized Hirota–Satsuma Coupled Korteweg–de Varies (GHSC-KdV) system is considered for investigation to study the exact solutions by using the extended generalized G′/G-expansion technique. The GHSC–KdV system describes the interaction of two long waves with different dispersion relations. The dynamical structures of the obtained solutions are solitary-type waves, multi-soliton waves, and singular-kink type waves. It contains information about the hyperbolic, trigonometric, and rational function solutions for the above system. Furthermore, the derived solutions of the system that comprises arbitrary functional parameters and other constant parameters can be used to enhance the advanced behavior of physical situations.

An adaptive finite element method for distributed elliptic optimal control problems with variable energy regularization

We analyze the finite element discretization of distributed elliptic optimal control problems with variable energy regularization, where the usual L2(Ω) norm regularization term with a constant regularization parameter ϱ is replaced by a suitable representation of the energy norm in H−1(Ω) involving a variable, mesh-dependent regularization parameter ϱ(x). It turns out that the error between the computed finite element state u˜ϱh and the desired state u‾ (target) is optimal in the L2(Ω) norm provided that ϱ(x) behaves like the local mesh size squared. This is especially important when adaptive meshes are used in order to approximate discontinuous target functions. The adaptive scheme can be driven by the computable and localizable error norm ‖u˜ϱh−u‾‖L2(Ω) between the finite element state u˜ϱh and the target u‾. The numerical results not only illustrate our theoretical findings, but also show that the iterative solvers for the discretized reduced optimality system are very efficient and robust.

High-Temperature Tribology of Selective Laser-Melted Titanium Alloys: Role of Adhesive Wear

Abstract Titanium alloys (Ti6Al4V) are emerging materials used in many engineering applications, especially aerospace, due to their strength-to-weight ratio, corrosion resistance, and high specific strength. The selective laser melting (SLM) process is vividly used to fabricate components with minimum material usage, which reduces the total weight of the product. The hard particles in the atmosphere repeatedly hit the aircraft turbine blades in a rotary motion during aircraft operations. Due to significant sliding action between articulating surfaces, these turbine blades need good wear resistance. With this motivation, rotary wear tests were performed under high vacuum at three different temperatures: room temperature, 400 °C, and 850 °C on as-built and heat-treated titanium alloy fabricated by the SLM process. The parameters like the speed, number of cycles, time, and high vacuum were considered to be constant while performing these high-temperature tribology experiments. As-built and heat-treated samples against the alumina ball resulted in lower coefficient of friction (COF) values at high temperatures compared to room temperature. In addition, adhesive wear was found to be the dominant wear mechanism at high temperatures. From the morphological studies, plowing strips, plowing ridges, and shallow grooves were significantly noticed on the worn-out surfaces of the heat-treated samples. Although low COF values were obtained at high temperatures on tested samples, higher specific wear-rates were seen in these samples due to the continuous removal of soft material.

Research of nonstationary dynamic models of the organizational and technological process of railway transport technical vehicles repair

The problems of analytical and computer research of dynamic models of repair and operation of technical vehicles used in railway transport are among the urgent problems related to ensuring safety and stability of traffic, with the development of digital twins and the improvement of monitoring and diagnostic systems. The analysis of models described by various types of multidimensional nonlinear differential equations requires the use of modern methods of dynamical systems theory, numerical optimization and computer algebra. The purpose of the article is to conduct a qualitative and numerical analysis of mathematical models of organizational and technological processes (OTP) in railway transport, as well as the synthesis of new controlled OTP models. Nonstationary generalizations of a two-dimensional dynamic model describing the repair process of railway transport equipment are proposed. Various cases of using constant and time-dependent parameters are considered. The case of linear and exponential dependences of parameters on time is studied. For the studied models, trajectories are obtained taking into account the variation of constant parameters and taking into account the choice of parametric dependencies, a comparative analysis of the results is presented. The formulation of the problem of optimal control of the number of repaired and repaired railway wagons is proposed. Promising methods for solving this problem using numerical optimization methods, including those inspired by nature, are described. The results can be used in the tasks of constructing and analyzing mathematical models of dynamic systems, in the tasks of numerical modeling of transport systems and technological processes, in the tasks of optimizing the number of vehicles and improving the transportation process, as well as in the tasks of creating digital counterparts in the transport industry.

Conjoint Enhancement of VSG Dynamic Output Responses by Disturbance-Oriented Adaptive Parameters

Virtual synchronous generator(VSG) is an encouraging concept to ensure provision of inertia, following large integration of renewable sources in system. However, apart from VSG contribution in improving system's frequency stability, it is also important to ensure long term robust and stable operation of VSG itself. In this regard, active power loop(APL) of VSG constituting variable control parameters is analyzed subsequent to contingency scenarios. It is observed that dynamics of APL outputs (virtual frequency and active power) is critically sensitive and prone to intrinsic oscillations. Further, during disturbance in system, utilization of constant control parameters of APL illustrates contradictory effects in dynamics of its outputs. As a solution to above issues, novel adaptive inertia and adaptive damping coefficient is proposed. The work provides distinct approach in following manner- 1) judicious selection of different operation range of natural undamped frequency( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ω_{n}$</tex-math></inline-formula> ) and damping ratio(ζ) of APL as compared to existing strategies, along with 2) reduced computational complexity and improved accuracy of controller, 3) thereby reduction in over(-under)shoots and intrinsic oscillations in virtual frequency and output active power of APL during transient period. This strengthens classical VSG design and contributes in its robust long term industry/real-time application. The efficacy of proposed strategy is showcased by real-time simulations along with validation at PHIL level.