Effects Of Changes In Parameters Research Articles

PIλDµ Controllers for Suppression of Limit Cycle in a Plant with Time Delay and Backlash Nonlinearity

This paper evaluates the existence of a periodic limit cycle oscillation in a system with backlash nonlinearity in the presence of time delay. An armature voltage-controlled DC motor system is studied in this regard whose output signifies accuracy in position control. An analytical solution for the limit cycle based on the Describing Function (DF) method is obtained whose authenticity is verified with the Nyquist contour-based graphical method and the digital simulations. The effect of parametric changes on the magnitude and frequency of the limit cycle is examined in this article. Integer and non-integer order proportional-integral-derivative (PID) controllers are designed to eliminate these undesirable periodic oscillations present in the system. Multiple optimization techniques considering error-based, time domain specification-based objective functions are scrutinized through statistical tests towards the parameter estimation of the applied controllers. Observations reveal that while the Moth flame optimizer (MFO) with Integral time absolute error (ITAE) produces superior results for the PID controller, the MFO with the Integral time square error (ITSE) provides better results for the FOPID controller. Further, the gain and phase margin-based loop shaping method is also used for an analytical calculation of the controller parameters. Out of the five loop shaping constraints, superior results are obtained by considering robustness towards gain variation constraint as an objective function, and the rest as nonlinear constraints. Simulation studies suggest the efficiency of the utilized controllers in quenching the periodic limit cycle oscillations. The superiority of the FOPID controller over the PID controller is validated by considering suitable performance-based comparisons. The effectiveness of the designed controllers is also tested against the variations in system parameters. Further, the physical realizations of the integer and fractional order PID controllers are performed through Oustaloup recursive filter approximation.

Two fractional order cumulative residual time series measures based on Rényi entropy

In the study of time series analysis, Kullback-Leibler divergence can measure the difference between the distribution diverges of time series, and transfer entropy is usually used to quantify the causal influence among time series. In order to analyze the relationship between time series more comprehensively, two novel fractional order times series measures, i.e., Rényi cumulative residual Kullback-Leibler (RCRKL) and Rényi cumulative residual transfer entropy (RCRTE), are proposed in this paper. Some mathematical properties of RCRKL are proved as a distance metric, and the zeros and bounds of RCRTE are studied. Then, some examples on synthetic data are provided to study the effect of parameter changes on metric values. Finally, the proposed two fractional-order time series measures are applied to pavement rutting time series, for which a RCRKL-based clustering is designed and the causal relationships between influence factors and rutting are detected by RCETE. The results demonstrate that the RCRKL-based clustering algorithm performs better than those based on the baseline distance measures. Meanwhile, RCRTE can also detect the true causality between rutting and its influence factors and reject the false causality. In summary, the proposed RCRKL and RCRTE take the advantages of both cumulative residual entropy and Rényi entropy, and provide a more comprehensive insight for time series analysis.

Parameter Analysis of Vibration Damping and Energy Harvesting Performance of Bionic Suspension

The traditional damping structure usually transfers the vibration energy into heat, dissipated and without harvesting. But for harsh environments, such as military activities and lunar probe patrols, the vibration energy can be extracted, and realize the purpose of self-power condition monitoring. In this paper, a bionic suspension with energy-harvesting property is proposed based on bionic configurations. The bionic suspension adopts a symmetrical three-link arrangement to simulate the arrangement of bones, and a horizontal spring to simulate muscles. The micro-generator embedded in the knee joint provides the main damping force for the overall structure and also plays a role in harvesting energy. The dynamic equation and virtual prototype model are established, and the effects of parameter changes on the performance of vibration reduction and energy harvesting are analyzed, and the relationship between the two is revealed. The results show that the parameters to achieve their respective optimal performance are not consistent in the trend, though it is difficult to obtain the best performance of both, it can be designed according to the specific functions to be satisfied. This structure can be utilized as a general model for vibration reduction and energy harvesting scenarios, providing new ideas for self-powered sensing and condition monitoring configurations.

Dynamical analysis of the FitzHugh–Nagumo model with memristive synapse

Understanding the transition mechanism between different activity patterns in realistic neuron models brings forward fundamental challenges for the dynamical systems theory. The knowledge about the mechanisms can present precious predictions and intuitions for determining fundamental principles of neuron functioning. This paper aims to present a dynamic analysis of the FitzHugh–Nagumo neuron model with a memristive synapse. In this article, the effects of memristive synapse's conductance gain, applied current, and the speed of electrical signal propagation along axons and dendrites on the system's behavior and the neuron's membrane potential are investigated. Analyzes are performed by investigating bifurcation and Lyapunov exponent diagrams versus various model parameters. The physiological role of some parameters and the effect of parameter changes on the model behaviors are discussed. The results demonstrate that when no current is applied to the system, the maximum value of membrane potential is larger, and also, a lower memristive synapse conductance gain leads to a larger maximum value of membrane potential. So, it can be concluded that the neuron in an amplitude death state may be triggered and start firing by decreasing the conductance gain or not applying current.

Electrical brain activity during human walking with parametric variations in terrain unevenness and walking speed

AbstractMobile brain imaging with high-density electroencephalography (EEG) can provide insight into the cortical processes involved in complex human walking tasks. While uneven terrain is common in the natural environment and poses challenges to human balance control, there is limited understanding of the supraspinal processes involved with traversing uneven terrain. The primary objective of this study was to quantify electrocortical activity related to parametric variations in terrain unevenness for neurotypical young adults. We used high-density EEG to measure brain activity when 32 young adults walked on a novel custom-made uneven terrain treadmill surface with four levels of difficulty at a walking speed tailored to each participant. We identified multiple brain regions associated with uneven terrain walking. Alpha (8 - 13 Hz) and beta (13 - 30 Hz) spectral power decreased in the sensorimotor and posterior parietal areas with increasing terrain unevenness while theta (4 - 8 Hz) power increased in the mid/posterior cingulate area with terrain unevenness. We also found that within stride spectral power fluctuations increased with terrain unevenness. Our secondary goal was to investigate the effect of parametric changes in walking speed (0.25 m/s, 0.5 m/s, 0.75 m/s, 1.0 m/s) to differentiate the effects of walking speed from uneven terrain. Our results revealed that electrocortical activities only changed substantially with speed within the sensorimotor area but not in other brain areas. Together, these results indicate there are distinct cortical processes contributing to the control of walking over uneven terrain versus modulation of walking speed on smooth, flat terrain. Our findings increase our understanding of cortical involvement in an ecologically valid walking task and could serve as a benchmark for identifying deficits in cortical dynamics that occur in people with mobility deficits.

A Production Inventory Model with Linear Time Dependent Production Rate, Linear Level Dependent Demand and Demand and Constant Holding Cost

In this paper, a production inventory model with linear time dependent production rate is considered. The market demand is assumed to be linear level dependent while the holding cost is a constant. The model considered a small amount of decay without having any shortage. Production starts with a buffer stock reaching its maximum desired level and then the inventory begins to deplete due to demand and deterioration. The model is formulated using a system of differential equations and typical integral calculus was used to analyze the inventory problems. These differential equations were solved to give the best cycle length T_1^*=0.8273(303 days), Optimal time for maximum inventory t_1^*= 0.7015, Optimal order quantity Q_1^*=38.3404 and total average inventory cost per unit time TC(T_1)* =170.5004. The cost function has been shown to be convex and a numerical example to show the application of the model has been given. A sensitivity analysis is then carried out to see the effects of parameter changes

Magneto-thermo-elastic coupling vibration and bifurcation characteristics of functionally graded rotating cylindrical shell

The magneto-thermo-elastic coupling vibration of rotating ferromagnetic functionally graded cylindrical shell is investigated in this paper. Based on the physical neutral surface theory and Donnell's theory, the expressions of kinetic energy and strain energy are obtained by introducing geometric nonlinearity. The magneto-thermo-elastic vibration equations of the rotating ferromagnetic functionally graded cylindrical shell in multi-physical field are derived via the Hamilton's principle. Considering the magnetization effect of ferromagnetic shell in magnetic field, the expression of magnetization force is obtained according to the nonlinear magnetic constitutive relation. For simply supported boundary conditions, Galerkin's method is used to obtain the discretized ordinary differential equations, and the static deflection of the shell under static load is solved. The steady-state response of the system during primary resonance and the stability of solutions are given by the multi-scale method and the Lyapunov stability theory. Through numerical examples, the characteristic curves and surfaces of amplitude are plotted, and the parameter ranges corresponding to regions of multi-valued solutions and stable solutions are determined. The system dynamics laws describing the coupling effect between multiple parameters such as force, magnetism, heat, and rotational speed are evaluated. The Global bifurcation diagrams and the maximum Lyapunov exponent spectrums under different control parameters are plotted to analyze the effect of parameter changes on the dynamic response of system. The results show that the vibration characteristics of the system are significantly influenced by the external physical fields, in addition to the shell size and material volume fraction. Slight changes in parameters can lead to violent changes in the dynamic response of the system, exhibiting intermittent, jumping, and chaotic characteristics.

Parameter variation effects on millimeter wave dosimetry based on precise skin thickness in real rats

This study presents a parametric analysis of the steady-state temperature elevation in rat skin models due to millimeter wave exposure at frequencies from 6–100 GHz. The statistical data of the thickness of skin layers, namely epidermis, dermis, dermal white adipose tissue, and panniculus carnosus, were measured for the first time using the excised tissues of real male Sprague–Dawley rats. Based on the precise structure obtained from the histological analysis of rat skin, we solve the bioheat transfer equation to investigate the effects of changes in parameters, such as body parts and thermal constants, on the absorbed power density and temperature elevation of biological tissues. Owing to the notably thin dermal white adipose tissue layer, the surface temperature elevation in the rat head and dorsal skin at 6–100 GHz is 52.6–32.3% and 83.3–58.8% of the average values of different human skin models, respectively. Our results also reveal that the surface temperature elevation of rat skin may correlate with the tissue thickness and deep blood perfusion rates.

5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a carbon dioxide binary mixture based compressed gas energy storage system: A comprehensive research and feasibility validation

Recently, the application of carbon dioxide binary working fluids in compressed carbon dioxide energy storage systems has been proposed to improve the system characteristics, especially for the condensation problem of carbon dioxide. Based on the previous research, a more comprehensive 5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a typical transcritical compressed carbon dioxide energy storage system using carbon dioxide binary working fluid is carried out. Propane, propylene, R32, R161, R1234ze, and R1234yf are chosen to compose the binary working fluid with carbon dioxide, respectively. The effect of changing parameters, including pump pressure ratio, compressor isentropic efficiency, and heat exahcnger1 outlet temperature on system performance, is also analyzed. In addition, the feasibility of applying carbon dioxide binary working fluid at high ambient temperature is investigated. According to the results, the performance of heat exchanger1, heat exchanger2, and pump decreases while the performance of the turbine is improved with a higher refrigerant mass fraction from the point of energy level. The compressor, pump, and turbine show potential for optimization according to their higher process energy level difference. The pump power and system operating pressure is reduced at the cost of reducing round trip efficiency when using carbon dioxide binary working fluid. A 1% improvement in compressor isentropic efficiency leads to an increase of nearly 0.4% in round trip efficiency, albeit with reduced turbine power. Increasing the heat exchanger1 outlet temperature from 305 K to 315 K results in a 1% increase in round trip efficiency but with a decrease in the performance of heat exchanger1. Both increasing compressor isentropic efficiency and heat exchanger1 outlet temperature benefit the system economy and exergetic sustainability. A noticeable decrease in system performance is observed when the ambient temperature shifts from 293 K to 303 K. However, this deterioration can be mitigated by raising the pressure of saturated working fluid gas at the compressor inlet. Propylene, R32, and R1234yf are suitable candidates to address the condensation issue, considering the system performance at high ambient temperatures. This paper extends research on the compressed carbon dioxide energy storage system based on carbon dioxide mixtures and provides a reference for the working fluid selection and system optimization for related research.

The Magneto–Thermo–Elastic Primary Resonance of Rotating Ferromagnetic Functional Gradient Cylindrical Shell in a Transverse Magnetic Field

The primary resonance behavior of a rotating ferromagnetic functional gradient cylindrical shell in a magnetic field, temperature field, and excitation force is investigated. Based on the physical neutral surface deformation theory and the Donnell theory, considering the effect of geometric nonlinearity, expressions of strain energy and kinetic energy of the shell and the work of forces are given, respectively. Applying the Hamilton principle, the magneto–thermo–elastic equation of a functional gradient cylindrical shell is derived by considering the magnetization effect of ferromagnetic metal. The question is discretized by Galerkin method and solved by the multi-scale method to obtain the amplitude–frequency response equation. The stability of the solution is discriminated by using the Lyapunov theory. Through numerical examples, the response curves of the system under different parameters are plotted, and the parameter ranges corresponding to multi-valued solution regions and single-valued solution regions are determined. The effects of parameter changes on the dynamic response and stability of system are analyzed. The results show that a coupling mechanism between temperature field, magnetic field, and excitation force affects the response and stability of the system, and the change of parameters have a significant effect on the vibration characteristics and stability. The dynamics model established in this paper is a theoretical reference for investigation on the multi-physics field coupling dynamic behaviors of structures.

Collaborative location routing problem for sustainable supply chain design with profit sharing.

To identify the sustainability synergies in a collaborative Moroccan dry food wholesale chain, we investigate the financial and ecological effects of implementing horizontal cooperation between three competitor shippers. For business-to-business networks, the key objective is to ensure last-mile delivery to their clients in metropolitan areas. The implementation of this alliance requires studying different aspects, among them the design of the transportation network, fair profit sharing, and collaborative delivery planning. Limited studies have considered the effects of integrating facility location and vehicle routing by addressing multiple goals in the design of a sustainable collaborative supply chain. We model the problem as a periodic two-echelon echelon-periodic location routing problem to integrate different decision levels. In order to investigate the trade-offs between the two opposing goals, a multi-objective approach is adopted. The Epsilon constraint method is used to generate a compromise between economic and ecological impacts. Cost and carbon emission sharing are assessed through the Shapley value mechanism. Furthermore, to determine the effect of parameter changes on the attained savings, a scenario analysis is performed. Results show the positive effect of collaboration among shippers and the importance of using integrated network design models. Environmental considerations in the pursuit of economic goals affect the gains produced and result in various transportation network structures. The performance of the coalition varies under different scenarios. Managerial implications are presented.

TO ASSESS THE STRUCTURAL AND TECHNOLOGICAL CHANGES IN THE PARAMETERS OF THE PRECISION ROTARY SYSTEM ACCORDING TO THE SPECIFIED FUNCTIONS OF SENSITIVITY AND DEVIATION OF THE SPECTRUM OF OWN FREQUENCIES

The question of precision rotary systems with artificial elements of pretension, which significantly affect the rigidity and displacement of resonance frequencies and, as a result, lead to the appearance of very conditioned sensitivity matrices, has been investigated. The mathematical model of the system is identified. With spatial oscillations of the system, two of the most typical and important are defined: fluctuations in vibration force along the rotor axis and in a direction perpendicular to it. Designed diagnostic operator as a complete sensitivity matrix. The proposed algorithm for the diagnosis of parameters of multidimensional mechanical fluctuation systems using computer technology. In any prefabricated design, the parameters of the system during assembly may differ from the design values and change during operation. In order to predict the consequences of this, it is necessary to know the reaction of the system to these changes. At the same time, in many cases, it is almost impossible to assess experimentally the effect of parameters on the behavior of the system. Therefore, there is a need to study and analyze the effect of changes in parameters on the properties of the system analytically, that is, according to the known mathematical model of the system. Analytical study of the dynamics of such systems is a very difficult task, but determining the sensitivity functions for this type of compound experimentally is another much more complex technological task, so their characteristics should be obtained by different methods of identification. The main purpose of this work is to determine: the identified mathematical model of the system, to offer a methodology and algorithm for the diagnosis of parameters of multidimensional mechanical fluctuation systems using computer technology. Of course, the presented algorithm is most suitable for the diagnosis of parameters of multidimensional fluctuation systems, but of course, in this case, widespread use of modern computer technology is necessary. If in the system it is necessary to determine the degree of influence of various physical parameters on the vector of the state, then it is necessary to consider the matrix of relative sensitivity. Sensitivity matrices allow determining sensitive and invariant parameters to the state vector. This information answers the question of which parameters determine the vibrational characteristics of the object to the greatest extent. In addition, the determination of the sensitivity matrix can significantly simplify the dynamic model of the system, leaving only those parameters that most determine the vibrational state of the system. Keywords: construction, press-threaded connection, dynamic parameters, structural model, deformation, deviation, frequency and amplitude of oscillations, sensitivity of dynamic parameters, algorithm, sensitivity matrix, methodology.

Finite Element Modeling of the Cycle Characteristics of Li–O2 Secondary Batteries Considering Surface- and Solution-Route Discharge Reactions

Model-based development is an effective approach in terms of obtaining design guidelines for lithium–oxygen secondary batteries (LOBs). In this study, a model simulating the charge/discharge cycle was developed using the finite element method, which enabled us to investigate the factors governing the cyclability of LOBs by conducting virtual cycle tests. In this modeling, we particularly considered that the discharge can proceed via two different routes: surface and solution routes. As an example demonstrating the usefulness of the virtual tests based on the developed model, we evaluated the effects of changes in parameters related to oxygen transport properties on the deposition and dissolution sites of lithium peroxide (Li2O2) generated in the porous cathode of an LOB via the surface and solution routes, respectively, and hence investigated the effects on the cyclability. The proposed model enables various validations that are extremely difficult to carry out using an experimental approach.

Revitalization and Optimization of a Traditional Iranian Architectural Pattern on Transformable Skins Using Kinetic Angulated Systems

Architects and designers have employed angulated structures for kinetic architectural design due to their formal esthetics, geometry, and light weight. The arrangement of these structures within a regular repetitive (modular) layout forms a kinetic skin. Geometric patterns are repeated in angulated structures based on particular orders as happens in girih patterns in Iranian historical architecture. This similarity forms the base of this study. Given the importance of revitalizing these motifs due to the gap between the modern and traditional architecture and their modernization using up-to-date technologies, the authors propose a process for implementing these patterns on generated lattice structures. This study is organized into two parts to achieve the mentioned goals: in the first part, the effect of changing parameters on the ultimate form of lattice structure is evaluated. In the second part, changes are applied to the structural form according to the patterns through two strategies (i.e., implementing the pattern of girih components on the central opening of the structure and implementing the form of girih components on structural elements), focused on the Islamic girih patterns and the importance of their implementation on the structure. The outcome of this study is kinetic skins containing forms dominantly shapes of Iranian patterns repeated regularly throughout the structure; it represents the beauty and identity of the traditional Iranian architecture and can adapt to changing conditions according to the purposes of sustainable architecture. Finally, a designed structure is modeled and analyzed using the Ansys software in order to investigate the constructability of a full-scale structure and evaluate it under loads in the climate of Tabriz; the results of the analysis indicate that the structure can withstand loads applied in the climate of Tabriz with a thickness of more than 3 mm.

Evolution of cooperation in public goods games with dynamic resource allocation: A fairness preference perspective

Exploring the conditions under which cooperation can emerge in populations has long been a subject for humans. Fair preference psychology has been incorporated into the analytical framework of the public goods game. Based on considering the dynamic update of trust-driven investment willingness, we introduce a dynamic payoff allocation mechanism and loners to traditional PGG, explaining how the mechanism related to fairness preferences promotes cooperation. We assume that payoffs are equally allocated among players when the payoffs do not exceed the threshold. Otherwise, the excess portion is proportionally allocated according to the investment willingness of cooperators. The effects of parameter changes on the evolution of cooperation are investigated by conducting Monte Carlo simulations. The results show that introducing dynamic payoff allocation and loners can effectively promote cooperation in a specific range of parameters. Specifically, the existence of loners is a double-edged sword. Loners can prevent players from adopting defection behaviors on a large scale when the payoff of cooperation is unsatisfied and inhibit the emergence and diffusion of cooperative strategies as the payoff of cooperators increases. When the payoff of cooperation is dissatisfactory, the dynamic payoff allocation mechanism can promote the average investment willingness of cooperators to accelerate the spread of cooperation. However, the payoff reallocation coefficient should not be set too high, and a high-level threshold of payoff reallocation may lead to the failure of the dynamic payoff allocation mechanism. There is an optimal payoff reallocation coefficient to maximize the efficiency of the proposed mechanism. Moreover, the optimal payoff reallocation coefficient that can maximize the cooperation level is distinct for the diverse combination of enhancement factor and loss aversion coefficient. However, its value should be set at a low level in general. These results may help researchers better understand the evolution of cooperation in public goods games with dynamic resource allocation from a fairness preference perspective.

AN OPTIMAL DECISION MODEL FOR AMELIORATING INVENTORY ITEMS WITH STOCK DEPENDENT DEMAND

In marketplace, it is normally observed that the utility of some items increases with time. For instance, in breweries, the value of some stocked wine increases with time. In farms, the quantity or weight of fish, fast growing animals including broilers, sheep, and so on, increase with time. These phenomena are termed amelioration. In this paper therefore, we study an inventory model that determines the optimal replenishment decision for ameliorating items with stock dependent demand where the holding cost and the rate of amelioration are considered constants. The concept of differential and integral calculus was used to optimize the cost function to obtain numerical examples that illustrate the effects of parameter changes on the decision variables and to find the optimum number of replenishments. The model could be used by the organizations that deal with the relevant items.

A compartmental model for the spread of Nipah virus in a periodic environment

<abstract><p>Nipah virus (NiV) is a zoonotic virus that causes outbreaks of fatal disease in humans. Fruit bat, also known as the flying fox, is the animal host reservoir for NiV. It is known to cause illness in pigs, which are considered an intermediate host. In this paper, we propose a model for NiV disease transmission taking into account all human-to-host animal transmission as well as the loss of immunity in those who have recovered. Furthermore, we take into consideration seasonal effects such as varying transmission rate from bats and birth rate of bats. We studied the existence and uniqueness of a disease-free $ \omega $-periodic solution and later deals with the basic reproduction number and stability analysis. To support the analytical results we provide numerical examples and assess the effect of parameter changes on disease dynamics, which might help to understand how to avoid a yearly periodic recurrence of the disease.</p></abstract>

First-Break Picking Method Based on the Difference Between Multiwindow Energy Ratios

First-break picking is an important step during processing of both passive and active seismic data. Many automated algorithms have been developed to detect first-break points in large volumes of seismic data. However, it remains difficult to determine precise first-break points in seismograms with low signal-to-noise ratios. Therefore, we present a new approach based on the differences between multi-window energy ratios (DERs) that minimizes the effects of noise. First, the DER is defined and a thresholding method detecting first-break points using the DERs is proposed. Thresholding can be varied depending on the DER parameters, which ensures reliable results even if the parameters change. We use two types of seismic data to establish and verify the DER method: big data derived via global earthquake monitoring (STanford EArthquake Dataset) and ocean bottom cable (OBC) data acquired offshore of Pohang, Republic of Korea. We investigated the effects of parameter changes on the DER picking results. Good picking performance was verified under low signal-to-noise conditions and compared to conventional first-break picking methods. The DER accuracy was higher than that of conventional methods and outliers were rare.

Stability and Sensitivity Analysis of the COVID-19 Spread with Comorbid Diseases

This research investigates a model of the spread of COVID-19 in Indonesia by paying attention to comorbid disease, self-quarantine, government-provided quarantine, and vaccination factors. The symmetrical aspects of the model are studied. The evaluation of the model reveals non-endemic and endemic equilibrium points and the basic reproduction number (BRN). We provide the local and global stability analysis of the equilibriums. According to the sensitivity analysis of the BRN, the key parameters impacting the spread of COVID-19 are the susceptible recruitment rate, contact rate, infection death rate, and probability of infected individuals having no comorbidities. In addition, we provide a sensitivity analysis to examine the effect of parameter changes in each subpopulation. We discovered that the natural death rate is the most sensitive parameter based on the sensitivity index after reaching equilibrium. Symmetry aspects appear in some of the visualizations of the model’s solution and the sensitivity of the BRN and parameters.

Parameters test on time migration with Kirchhoff method on 2D synthetic data with dipping event and its reflector structural changes

This paper describes the effect of parameter variation with Kirchhoff migration in post-stack seismic data. Parameters tested covering velocity, aperture, and maximum dip. The data used in this work was generated from velocity and density models with gaussian syncline and anticline layer boundaries. This work is the effect of parameter changes on the model and conclude best applied parameters for Kirchhoff migration in certain model created.