Saturation Law Research Articles

Oriented membranes processes for facilitated extraction and recovery of some industrial dyes across polymer inclusion membranes containing Chitin as new extractive agent

In this study, we developed a polymer inclusion membrane (PIM) using the phase inversion technique, based on polymer supports polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP), with chitin as extractive agent (EA). This PIM was used to study facilitated extraction and recovery processes of Astrazon Red FBL 200%, Blue P3R, Direct Turquoise FBL 400% and BEMACID Yellow N-TF dyes from simulated aqueous textile solutions. To explore the composition, structure and morphology of the developed PIM, both FTIR and SEM techniques were used. To explain the performance of the PIM and describe the mechanism of the process studied for the recovery of dyes from simulated wastewater, kinetic and thermodynamic models were also adopted, which are based on Fick’s laws and the saturation law of EA by the substrate (dyes). The overall data indicate that the used EA is effective for theses oriented processes, and the facilitated extraction of dyes is not depending on the pore size but on structures and interactions between the molecules of the EA and the dye.

Chemical vapor deposition of Cu films from copper(I) cyclopentadienyl triethylphophine: Precursor characteristics and interplay between growth parameters and films morphology

The rough, even discontinuous morphology of vapor-deposited copper films inhibits their attractive electrical properties. In the present study, we investigate the influence of deposition time, deposition temperature, and the flow rate of the precursors on the morphology of Cu films deposited from metalorganic chemical vapor deposition. We show that it is necessary to purify the copper(I) cyclopentadienyl triethylphophine (CpCuPEt3) precursor in order to improve its stability and volatility. We also determined its saturated vapor pressure law, logPsat (Pa) = 8.614 - 2272/T (K). The Arrhenius plot of the global deposition reaction of Cu films in the presence of hydrogen between 431 and 523 K shows a low apparent activation energy of 10 kJ/mol. Electron probe microanalysis, grazing incidence X-Ray diffraction, and image analysis of the micrographs obtained by top–down surface scanning electron microscopy reveal metallic films composed of Cu islands. Their size and packed density increase and, ultimately, the islands coalesce with increasing precursor flow rate and, to a lesser extent, with increasing deposition temperature.

Impact of fear on an eco-epidemiological model

Abstract In the present paper, we investigate the impact of fear in a predator-prey model with disease in the prey species. The logistically growing prey population is divided into two groups: susceptible and infected. We take the fear of predators among prey population into consideration, which costs lowering of prey’s growth rate and slims down the interactions among prey individuals. In our model, it is reflected by two decreasing factors of the fear parameter and the predator population: one in the growth term of the susceptibles and the other in the disease transmission term. We choose a general disease transmission function for which mass action, standard incidence, and saturation laws are particular cases. The predator-prey interactions are described by generalized Holling type-II functional response. We explore the effect of fear for three subcases of our model, all of which happen to be identical to three published works (without fear effect). Apart from the preliminary mathematical analysis of our model (e.g. positivity, boundedness, etc.), we find the conditions for existence and local stability of the equilibrium points and study Hopf-bifurcation around the endemic equilibrium point w.r.t. the fear parameters. We observe that fear can eliminate the chaotic oscillations of the system, produced in the absence of fear, by either making the endemic equilibrium regular (stable limit cycle or stable equilibrium point) or moving it towards the disease-free state. We also observe the presence of multiple attractors in the phase-space and different types of bistabilities. We perform extensive numerical simulations to explore the rich dynamics of our model.

Dynamics of Nonconstant Steady States of the Sel’kov Model with Saturation Effect

In this paper, we deal with Sel’kov model with saturation law which has been applied to numerous problems in chemistry and biology. We will study the stability of the unique constant steady state, existence and nonexistence of nonconstant steady states of such models. In particular, we prove that Turing pattern may occur when the saturation coefficient is small but will not occur when the coefficient becomes large. Therefore for a Sel’kov model with saturation law, it is the saturation law that determines the formation of spatial patterns.

Composite anti-disturbance control for stochastic systems with multiple heterogeneous disturbances and input saturation

This paper develop a novel composite anti-disturbance control (CADC) method for a class of stochastic nonlinear systems in which input saturation and multiple heterogeneous disturbances occur. The disturbances include additive white noise, multiplicative white noise and modeled disturbances with coupling of energy-limited white noise and state signals. The input saturation item of system is approximated by the polytopic bounding method. In order to estimate the modeled disturbances, a novel stochastic saturating disturbance observer (SSDO) is designed. The CADC scheme is presented by integrating SSDO with convex hull expression of saturated linear feedback law, such that the superior anti-disturbance performance to be achieved while overcoming the effects of input saturation. Finally, the validity and usability of the developed scheme are testified by the numerical simulation and practical application example.

Constrained attitude maneuvers on [formula omitted]: Rotation space sampling, planning and low-level control

In this paper, we propose a novel framework that provides a systematic strategy to regulate the rigid body attitude on SO(3) within a generic constrained attitude zone. The proposed control scheme consists of three components: sampling, planning and low-level control. Specifically, an overlapping cell-like sampling for the attitude configuration space SO(3) is built and further reformulated to a graph model. Based on this abstraction, a complete graph search algorithm is utilized to generate a feasible path in the graph model. Both sufficient and necessary conditions on finding a feasible path are presented. Furthermore, to facilitate the control design, the point-to-point path is transformed into a smooth reference trajectory along the geodesics. Finally, a saturated low-level control law is formulated to robustly track the desired trajectory. Simulations demonstrate the effectiveness of the proposed control approach.

Finite-Element Formulations for Systems With High-Temperature Superconductors

In this article, we consider finite-element models for high-temperature superconductors and compare two dual formulations, either magnetic-field conforming or magnetic-flux-density conforming. The electrical resistivity of superconductors is described by a power law and is strongly nonlinear. We compare the accuracy and the efficiency of the dual formulations by starting from simple considerations on the concavity/convexity of the constitutive law involved in each case. We then study the numerical behavior of each formulation in one-, two-, and three-dimensional problems and compare their results against benchmarks. We draw general recommendations for the choice of a formulation, an iteration scheme for treating the corresponding linearized constitutive law, and a time-stepping extrapolation scheme. This approach is extended to soft ferromagnetic materials with a saturation law. Since the outcome of our analysis shows that recommended formulations for treating ferromagnets are just the opposite of those for treating superconductors, we suggest a coupled formulation for systems where both types of materials are present. The coupled formulation is shown to be accurate and more efficient than single formulations applied indistinctly to all materials.

The Effect of Creativity Components on Organizational Performance Development (Case Study: Islamic Azad Universities of Mazandaran Branch)

In the ecosystem of innovation, attention to the components of temperament and other explanatory variables of this research, based on the structural values of biological ethics, is of great importance. This applied research is analytical and employs a descriptive survey method. In the qualitative section, according to the saturation law and through targeted sampling, 9 university professors were selected and their opinions were used. In the quantitative section, the statistical population of the present study was considered to be unlimited under the research conditions. The statistical sample consisted of 117 participants selected randomly. The researcher-made questionnaire was ordered based on the five-point Likert scale, including very high, high, moderate, low, and very low response options where 33 questions were considered. The face and content validity was confirmed by prominent specialists, and the construct validity was calculated to be more than 0.5. The reliability of the questionnaire was calculated using Cronbach’s alpha (71.8%), which was statistically validated. To analyze the data of the questionnaire from the descriptive statistics and then in the inferential statistics of the fitted model of structural equations using LISREL software shows that when considering the components of culture, mood, and project, we must take caution and consider further research to explain dimensions. Please cite this article as: Shojaee AA, Valiollahpur Muziraji M. The Effect of Creativity Components on Organizational Performance Development (Case Study: Islamic Azad Universities of Mazandaran Branch). Bioethics Journal, Special Issue on Human Rights and Citizenship Rights 2019; 159-171.

Low-Complexity Adaptive Saturated Control of a Class of Nonlinear Systems with Its Application

This paper investigates a low-complexity saturated control law for a class of nonlinear systems with consideration of the time-varying output constraint, control constraint, and external disturbance. First, a dead-zone model is employed to transform the control saturation nonlinearity into a linear one with respect to the real input signal. Then, the original system with time-varying output constraint is transformed into a constraint-free one, based on which a novel adaptive saturated control law is devised along the filtered error manifold. By employing minimum learning parameter technique and virtual error concept, only two adaptive parameters are needed to update online, which reduces the computational burdens dramatically. Finally, the applications to Duffing-Holmes chaotic system are organized to validate the effectiveness of the proposed control law.

A multicriterial analysis of the efficiency of conservative information security systems

The paper addresses the task on a multicriterial analysis of the effectiveness of conservative information security systems whose structure and components do not change over a certain period of time. The principal scheme of such systems includes a protected object, vulnerabilities ‒ channels for attacks, threats, and protection tools. Based on the assumption about the independence of attacks and protection tools, we have developed a discrete probabilistic model of damage to a protected object. For a random variable of the amount of damage over a fixed period of time, we have derived a representation in the form of a sum of binomially-distributed random variables, dependent on the parameters for attacks and protection. We have described in a similar manner the random variables for economic losses, recovery time, as well as recovery costs, for which mathematical expectations and variances have been obtained in the analytical form. To ensure the high statistical confidence, it has been proposed to determine the risk indicators using a Cantelli’s inequality. On this basis, we have defined performance indicators for a protection system, which characterize the probability of protected object’s safety, residual losses, conditionally saved costs, survivability, and the cost of recovery. By using a Pareto optimality theory, we have devised a procedure for multi-criteria analysis and rational design of conservative systems of information protection. Verification has been carried out for the audio information protection systems. A Pareto frontier has been investigated according to the criteria of economic benefit and investment costs for 66 variants of protection. We have examined the influence of protection level on the Cantelli’s measure for conditional savings, as well as the contribution of various types of protection devices to it. The research results have confirmed the saturation law by Gordon-Loeb for the case when over-protection does not improve the effectiveness of protection systems.

Control of non-cooperative spacecraft in final phase proximity operations under input constraints

This paper addresses the approaching trajectory control problem for the final phase of non-cooperative spacecraft proximity operations in the presence of disturbances and even input saturation. As a stepping stone, a novel line-of-sight tracking model is developed to describe attitude maneuver towards the target in the proximity. Then, a two-stage artificial potential function is employed to enable the pursuer spacecraft to comply the safety trajectory during approaching the target. In each stage, gradients of potential function are analyzed and the local minimum problem associated with potential function can be addressed. Furthermore, a saturated control law is proposed to ensure a reliable real-time tracking measurement of the target, and the controller rigorously enforces safe path and actuator magnitude constraints. The associated stability proof is accomplished through Lyapunov method. Simulations are carried out to evaluate the effectiveness of the proposed method.

Faster Positioning of One Degree-of-Freedom Mechanical Systems With Friction and Actuator Saturation

This paper concerns with faster positioning of one degree-of-freedom (1DOF) mechanical systems with friction and actuator saturation. A very simple but quite effective saturated relay proportional-derivative (PD) control is proposed. The proposed control is conceived within the framework of nonlinear PD methodology. It is accomplished by adding a relay position error for friction compensation to the saturated PD control law. For faster transient with bounded input, a saturated nonlinear function is introduced. Lyapunov's direct method is employed to prove global asymptotic positioning. The appealing advantages of the proposed control are that it is fairly easy to construct without involvement of any modeling parameter and has the ability to avoid the actuator saturation. Numerical example and experiments demonstrate the effectiveness and improved performance of the proposed approach.

New polymer inclusion membrane containing NTA as carrier for the recovery of chromium and nickel from textiles wastewater

Abstract Extraction and/or recovery of chromium (Cr) and nickel (Ni) from textiles industry wastewater by membrane separation using polymer inclusion membranes (PIMs) based on polymer supports polyvinylidene fluoride (PVDF) and polyvinyl pyrrolidone (PVP), with Nitrilotriacetic acid (NTA) as extractive agent (EA). Furthermore, to quantify the PIMs performances, the macroscopic parameters such as the membrane permeability, P, and the initial flux, J0, and the microscopic parameters such as the association constant, Kass, and the apparent diffusion coefficient, D*, were determined based on the Fick’s first law and the saturation law of the EA by the substrate (S). Also, to explain the substrate (S) (Cr or Ni) recovery process performed by the membrane, and to elucidate the mechanistic aspects, the activation parameters such as the energy Ea, the enthalpy ΔH≠ and the entropy ΔS≠, were determined. The efficiency of different PIMs to recover Cr and Ni was compared. Respectively, the influence of temperature and pH on removal performance was investigated. The results showed that the macroscopic and microscopic parameters increased with increasing temperature and acidity medium. Similarly, the values of the activation parameters make it possible to explain the membrane performance and to elucidate the mechanism relating to the diffusion of the extracted substrates through this membrane.

Thermoelectric Parameter Modeling of Single-Layer Graphene Considering Carrier Concentration and Mobility With Temperature and Gate Voltage

Single-layer graphene (SLG) sheets can exhibit thermoelectric properties under the control of gate voltage. The controlled factors and regulation mechanism of SLG thermoelectric properties have become research hotspots. In this paper, a SLG thermoelectric parameter model considering carrier concentration and mobility with temperature and gate voltage is proposed. Based on the proposed model, the square resistance ( $R_{\mathrm {s}}$ ) and Seebeck coefficient ( $S$ ) of the SLG are calculated. The results show that the maximum value of $R_{\mathrm {s}}$ decreases from 5.8 $\text{K}\Omega $ to 3.2 $\text{K}\Omega $ at the Dirac voltage when the temperature increases from 100 K to 500 K. A large and stable $S$ can be obtained at high voltages and temperatures. The maximum value of $S$ can reach $161.3~\mu \text{V}$ /K at $T = 500$ K, exhibiting a more obvious thermoelectric characteristic. Simultaneously, the saturation law of the power factor ( $Q$ ) with the change of gate voltage and the amplitude regulation of $Q$ by temperature are obtained. This work can provide a theoretical basis for analyzing the thermoelectric characteristics of SLG.

The existence of steady states for a bimolecular model with autocatalysis and saturation law

In this paper, a reaction–diffusion system known as a bimolecular model with autocatalysis and saturation law is considered. Firstly, we briefly obtain some characterizations for the positive solutions, including the a priori estimate of the positive solutions and the nonexistence of non-constant positive solution. Secondly, we emphatically discusses the bifurcation from the unique positive constant solution with both simple eigenvalues and double eigenvalues in one-dimensional case. Meanwhile, some other existence results are shown to supplement the analytical conclusions with the degree theory in N dimensional case.

Event‐triggered constrained control of positive systems with input saturation

SummaryThis paper addresses the problem of event‐triggered stabilization for positive systems subject to input saturation, where the state variables are in the nonnegative orthant. An event‐triggered linear state feedback law is constructed. By expressing the saturated linear state feedback law on a convex hull of a group of auxiliary linear feedback laws, we establish conditions under which the closed‐loop system is asymptotically stable with a given set contained in the domain of attraction. On the basis of these conditions, the problem of designing the feedback gain and the event‐triggering strategy for attaining the largest domain of attraction is formulated and solved as an optimization problem with linear matrix inequality constraints. The problem of designing the feedback gain and the event‐triggering strategy for achieving fast transience response with a guaranteed size of the domain of attraction is also formulated and solved as an linear matrix inequality problem. The effectiveness of these results is then illustrated by numerical simulation.

Disturbance observer-based visual servoing for multirotor unmanned aerial vehicles

Abstract This paper presents a disturbance observer based input saturated visual servoing law for a quadrotor unmanned aerial vehicle (UAV). The controller regulates the 4D relative pose, i. e., 3D translational and yaw motion, between the vehicle and a planar horizontal visual target in an environment with external disturbances. A feedforward control is used to compensate the lumped disturbance consisting of both system uncertainties and external disturbances. The feedback control part is based on a nested saturation control, which is used to bound the orientation of the UAV and therefore helps to keep the visual target in the camera’s field of view. Simulation results are provided to demonstrate controller performance.

Turing instability and formation of temporal patterns in a diffusive bimolecular model with saturation law

In the present article, a bimolecular chemical reaction–diffusion model with autocatalysis and saturation law is considered. The local asymptotic stability and instability of the unique feasible equilibrium of the local system, and the existence of Hopf bifurcation of the local system at this unique equilibrium are analyzed in detail. In the stability domain of the equilibrium of the local system, the effect of the spatial diffusion including the variation of the size of the space domain and the diffusion coefficient on the stability is studied and Turing instability is demonstrated. In the instability domain of the local system, time-periodic patterns of the original reaction–diffusion system bifurcating from the constant positive steady state are found according to the Hopf bifurcation theorem for reaction–diffusion dynamical systems with homogeneous Neumann boundary conditions by considering various different bifurcation parameters. Finally, to verify the obtained theoretical prediction, some numerical simulations are also included.

Simple Interpolating Control

Abstract We present a new simple approach to extend the admissible region of a saturated control law for discrete-time linear systems under state and input constraints. The approach is based on the interpolation of a given, performance driven, control law and a low-gain controller. The latter is designed such that its admissible set has maximum volume. The interpolation does not require on-line numerical optimization, and an analytical formula for the controller is given. Several numerical examples are presented to illustrate the control technique.

Effect of Colluvial Soil Slope Fracture’s Anisotropy Characteristics on Rainwater Infiltration Process

The SEEP/W module of finite element software GEO‐slope is used to analyze the effects of fracture depth, permeability coefficient ratio, fracture angle, and fracture number on the rainwater infiltration process. Moreover, the effect of fracture seepage anisotropy on slope stability is discussed combining with unsaturated seepage theory. The results show that the pore water pressure in the fracture increases rapidly with the rainfall until it changes from negative pressure to positive pressure. The greater the fracture depth is, the greater the pore water pressure in the fracture is, and the greater the infiltration depth at the time of rainfall stopping is. When the permeability coefficient is greater than the rainfall intensity, the permeability coefficient ratio has a great influence on the infiltration process of rainwater. The smaller the fracture angle is, the greater the maximum pore water pressure is in the fracture depth range, and the greater the depth of the positive pore water pressure is. However, with the increase of fracture angle, the infiltration depth decreases, and the range of the surface saturation area of slope increases obviously. With the increase of fracture density, the saturated positive pressure region is connected to each other in the slope. The influence range and the degree of the rainwater on the seepage field are larger and larger. There is a power relation between the saturation area and the fracture number, and also the concentration distribution of long fractures directly forms the large‐connected saturated zone and raises groundwater. The range of the saturated zone and variation law of the pore water pressure under fracture seepage are obtained, which provide a reference for the parameter partition assignment of slope stability analysis under fracture seepage.