Asymptotic Evaluations of the Stability Index for a Markov Control Process with the Expected Total Discounted Reward Criterion

In this work, for a control consumption-investment process with the discounted reward optimization criteria, a numerical estimate of the stability index is made. Using explicit formulas for the optimal stationary policies and for the value functions, the stability index is explicitly calculated and through statistical techniques its asymptotic behavior is investigated (using numerical experiments) when the discount coefficient approaches 1. The results obtained define the conditions under which an approximate optimal stationary policy can be used to control the original process.

Machine Learning for Hybrid Line Stability Ranking Index in Polynomial Load Modeling under Contingency Conditions

In the conventional technique,in the evaluation of the severity index,clustering and loading suffer from more iteration leading to more com-putational delay.Hence this research article identifies,a novel progression for fast predicting the severity of the line and clustering by incorporating machine learning aspects.The polynomial load modelling or ZIP(constant impedances(Z),Constant Current(I)and Constant active power(P))is developed in the IEEE-14 and Indian 118 bus systems considered for analysis of power system security.The process of finding the severity of the line using a Hybrid Line Stability Ranking Index(HLSRI)is used for assisting the concepts of machine learning with J48 algorithm,infers the superior affected lines by adopting the IEEE standards in concern to be compensated in maintaining the power system stability.The simulation is performed in the WEKA environment and deals with the supervisor learning in order based on severity to ensure the safety of power system.The Unified Power Flow Controller(UPFC),facts devices for the purpose of compensating the losses by maintaining the voltage characteristics.The finite element analysis findings are compared with the existing procedures and numerical equations for authentications.

ANALYSIS OF TIPOVER STABILITY FOR NOVEL SHAPE SHIFTING MODULAR ROBOT

A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robot＇s tipover problem are analyzed, stability pyramid and tipover stabil-ity index are proposed to globally determinate the mobile robot＇s static stability and dynamic stability. The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robot＇s tipover stability, especially for the reconfigurable or shape shifting modular robot. Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type configuration has the best stability. Both simulation and experiment provide a valid reference for the reconfigurable robot＇s potential application.

Experimental study on stability of sunken large diameter cylindrical structure on sandy seabed during construction period

A systematic experimental research work is done for the stability of sunken large diameter cylinder during construction period. It is the first research that gives the method for assessing the stability of the larger diameter cylindrical structure, a set of values is derived also for the critical stability indices of the large diameter cylinder sunken to the sandy seabed.

FACTORS ON VISCOSITY STABILITY OF MOLD FLUXES

Viscosity stability indexes of mold flux at high temperature and low temperature havebeen introduced and the effects of flux compositions on viscosity stability indexeshave been studied. Two mold fluxes have been developed by analyzing the effects offlux viscosity stability on the process and the condition of continuous casting slab ofmedium carbon steel. The results show that the fluxes are suitable for the process.

Stability Estimation for Markov Control Processes with Discounted Cost

This article explores controllable Borel spaces, stationary, homogeneous Markov processes, discrete time with infinite horizon, with bounded cost functions and using the expected total discounted cost criterion. The problem of the estimation of stability for this type of process is set. The central objective is to obtain a bounded stability index expressed in terms of the Lévy-Prokhorov metric;likewise, sufficient conditions are provided for the existence of such inequalities.

Demographic changes in China’s forests from 1998 to 2018

Background: Tree demography is an essential indicator of various forest ecosystem services, and understanding its changes is critical for the sustainable management of forests. During the past four decades, China implemented unprecedented forest restoration projects, which altered tree demography by increasing the number of trees and introducing new species. However, it remains unclear how species composition has changed in China in response to the past forest restoration and demographical processes.Methods: We applied Forest Stability Index(FSI) and the relative change of FSI(%FSI) to describe the population dynamics of tree species and structure in China since 1998, using field-survey data collected from over 200,000plot-records from the 6th to 9th National Forest Inventories(NFIs).Results: The overall populations of both natural and planted forests have grown rapidly from 1998 to 2018, while the range of changes in the relative tree density was more variable for natural forests(ranging from-8.53% to42.46%) than for planted forests(ranging from-1.01% to 13.31%). The populations declined only in some of the tree species, including Betula platyphylla, Ulmus pumila, and Robinia pseudoacacia. In contrast, the populations of trees in the largest size-class either remained stable or expanded.Conclusions: Tree density of China?s forests(both natural and planted forests) generally expanded and the overall populations increased in most size classes, with greater increases occurred in planted forests. In contrasting to the global decline trends of large diameter trees, here we found no apparent decline for trees in the largest size-class in China, highlighting China?s success in improving forest health and forest adaptations to climate change. We advocate for more studies to reveal the mechanisms of the changes in tree demography, which will help to improve forest ecosystem services such as the carbon sequestration capacity.

Global Exponential Stability Analysis of a Class of Dynamical Neural Networks

The problem of the global exponential stability of a class of Hopfield neural networks is considered. Based on nonnegative matrix theory, a sufficient condition for the existence, uniqueness and global exponential stability of the equilibrium point is presented. And the upper bound for the degree of exponential stability is given. Moreover, a simulation is given to show the effectiveness of the result.

Optimization of the Placement and Size of Photovoltaic Source

This paper presents a new optimization study of the placement and size of a photovoltaic source(PVS)in a distribution grid,based on annual records of meteorological parameters(irradiance,temperature).Based on the recorded data,the production output as well as the daily average power(24-h vector)of the PVS is extracted over the year.When a power vector is available,it can be used as an input when searching for the optimal size of the PVS.This allows to take into account the constraint of the variation of the power generated by this source considering the variation of the power consumed by the electrical loads during the whole day.A multi-objective fitness function has been considered.The latter minimizes the active losses and maximizes the voltage stability index during the day,while considering the constraints of the system,that is,the security,technical,geographical,and meteorological constraints.This problem was solved using the Non-dominated Sorting Genetic Algorithm NSGA-II optimization technique under MATLAB 2021.It was applied to the distribution network of Ghardaïa of 59 nodes.

Compositionally Driven Viscometric Behaviors of Poly (Alkyl Methacrylates) in Lubricating Oils

Viscosity index (VI) and shear stability index (SSI) are standard methods used in the lubricant industry to determine temperature-viscosity dependency and resistance to product degradation, respectively. A variety of oil-soluble polymers, including poly(alkyl methacrylates) (PAMAs) are routinely used to control these properties in fully-formulated liquid lubricants. In this report, we use reversible addition-fragmentation chain transfer (RAFT) polymerization to precisely target identical degrees of polymerization in a family of PAMAs with varying lauryl, hexyl, butyl, ethyl, and methyl groups. Then, expanding on previous methodology reported in the literature, we establish structure property relationships for these PAMAs, specifically looking at how intrinsic viscosity [η] and Martin interaction parameters KM relate to VI and SSI characteristics. While the intrinsic viscosity [η] is associated with the volume of macromolecules at infinite dilution, the parameter KM reflects the hydrodynamic interactions of polymer chains at actual polymer concentrations in lubricating oils. In this paper, we show that the dependence of VI on the non-dimensional concentration c/c* (or c[η]) can be presented in a form of master curve with shift factors proportional to KM that decreases with increasing size of alkyl groups. This finding implies that even in the dilute regime, the coil-expansion theory used to explain the effect of macromolecules on VI should be complemented with the idea of hydrodynamic interactions between polymer molecules that can be controlled by the choice of alkyl chains in the family of PAMAs.

Moment Lyapunov exponent of three-dimensional system under bounded noise excitation

In the present paper, the moment Lyapunov exponent of a codimensional two-bifurcation system is evaluted, which is on a three-dimensional central manifold and subjected to a parametric excitation by the bounded noise. Based on the theory of random dynamics, the eigenvalue problem governing the moment Lyapunov exponent is established. With a singular perturbation method, the explicit asymptotic expressions and numerical results of the second^order weak noise expansions of the moment Lyapunov are obtained in two cases. Then, the effects of the bounded noise and the parameters of the system on the moment Lyapunov exponent and the stability index are investigated. It is found that the stochastic stability of the system can be strengthened by the bounded noise.

A Stable Analytical Solution Method for Car-Like Robot Trajectory Tracking and Optimization

In this paper, the car-like robot kinematic model trajectory tracking and control problem is revisited by exploring an optimal analytical solution which guarantees the global exponential stability of the tracking error. The problem is formulated in the form of tracking error optimization in which the quadratic errors of the position, velocity, and acceleration are minimized subject to the rear-wheel car-like robot kinematic model. The input-output linearization technique is employed to transform the nonlinear problem into a linear formulation. By using the variational approach, the analytical solution is obtained, which is guaranteed to be globally exponentially stable and is also appropriate for real-time applications. The simulation results demonstrate the validity of the proposed mechanism in generating an optimal trajectory and control inputs by evaluating the proposed method in an eight-shape tracking scenario.

Algorithms to Compute the Largest Invariant Set Contained in an Algebraic Set for Continuous-Time and Discrete-Time Nonlinear Systems

In this paper, some computational tools are proposed to determine the largest invariant set, with respect to either a continuous-time or a discrete-time system, that is contained in an algebraic set. In particular, it is shown that if the vector field governing the dynamics of the system is polynomial and the considered analytic set is a variety, then algorithms from algebraic geometry can be used to solve the considered problem. Examples of applications of the method(spanning from the characterization of the stability to the computation of the zero dynamics) are given all throughout the paper.

IMPROVED COVARIANCE DRIVEN BLIND SUBSPACE IDENTIFICATION METHOD

An improved covariance driven subspace identification method is presented to identify the weakly excited modes. In this method, the traditional Hankel matrix is replaced by a reformed one to enhance the identifiability of weak characteristics. The robustness of eigenparameter estimation to noise contamination is reinforced by the improved Hankel matrix, in combination with component energy index （CEI） which indicates the vibration intensity of signal components, an alternative stabilization diagram is adopted to effectively separate spurious and physical modes. Simulation of a vibration system of multiple-degree-of-freedom and experiment of a frame structure subject to wind excitation are presented to demonstrate the improvement of the proposed blind method. The performance of this blind method is assessed in terms of its capability in extracting the weak modes as well as the accuracy of estimated parameters. The results have shown that the proposed blind method gives a better estimation of the weak modes from response signals of small signal to noise ratio （SNR）and gives a reliable separation of spurious and physical estimates.

Design of Dynamic Controller for Neutral Differential Systems with Multiple Delays in Control Input

The design feedback controller for a problem of dynamic output class of multi-delayed neutral systems has been considered. A criterion for the existence and asymptotic stability of such controller is derived via defining a new integral operator. The criterion is expressed in terms of the linear matrix inequalities （LMIs）, which can be checked numerically using the effective LMI toolbox in MATLAB. One numerical example is given to illustrate the proposed design method. Numerical simulation shows that the new design method is valid.

Simulation of the deformable lateral boundaries in biaxial test using DEM

Applying the discrete element method(DEM)in soil mechanics can provide abundant information at the particle-scale and facilitates illustration of the macro-mechanical behaviour of soils based on the inter-particle mechanisms.The triaxial test is one of the most common laboratory methods to study the macro-mechanical behaviour of particulate materials such as soil.However,many problems in geotechnical design can be assumed and simplified as a plane strain phenomenon.Therefore a biaxial test can be conducted to reproduce the macro-mechanical behaviour of soil,where the sample is enclosed by two horizontal rigid platens and a vertical latex membrane,which is a deformable continuous element and allows the enclosed specimen to deform freely while maintaining confining stress during loading.This paper presents an algorithm to represent physical and mechanical characteristics of latex membrane in the 2D DEM simulation of biaxial test using the PFC 2D code.To investigate the impact of the lateral boundary conditions on the micro-macro mechanical behaviours of soil samples,two sets of DEM biaxial tests are conducted,i.e.with rigid and deformable lateral boundary conditions.The DEM modeling results indicate that the lateral boundary conditions have a significant effect on the micro-scale fabric properties,thickness and inclination of the shear band.The comparison between these two simulations also demonstrates that the lateral boundary conditions play a major role in the peak and post-peak stress-strain behaviours as well as the dilation and critical state behaviours of granular soils.

Determination of the oxidative stability of olive oil using an integrated system based on dielectric spectroscopy and computer vision

During storage,olive oil may suffer degradation leading to an inferior quality level when purchased and consumed.Oxidative stability is one of the most important parameters for maintaining the quality of olive oil,which affects its acceptability and market value.The current methods of predicting the oxidative stability of edible oils are costly and time-consuming.The aim of the present research is to demonstrate the use of dielectric spectroscopy integrated with computer vision for determining the oxidative stability index(OSI)of olive oil.The most effective features were selected from the extracted dielectric and visual features for each olive oil sample.Three machine learning techniques were employed to process the raw data to develop an oxidative stability prediction algorithm,including artificial neural network(ANN),support vector machine(SVM)and multiple linear regression(MLR).The predictive models showed a great agreement with the results obtained by the Rancimat instrument that was used as a reference method.The best result for modelling the oxidative stability of olive oil was obtained using SVM technique with the R-value of 0.979.It can be concluded that this new approach may be utilized as a perfect replacement for quicker and cheaper assessment of olive oil oxidation.

Accumulation and relationship of metals in different soil aggregate fractions along soil profiles

Different aggregates vary in their ability to retain or adsorb metals in soil.Five soil profiles were sampled from different soil horizons and grouped,and the concentrations of Al,Mg,Ca,Fe,Mn,Cd,Cu and Pb were determined in six sizes of aggregates(>2,2-1,1-0.6,0.6-0.25,0.25-0.053,<0.053 mm).Significantly high(p<0.05)structural stability indexes(SSI)and ag-gregate stability indexes(ASI)were recorded in the topsoil horizon,which may be attributed to the high soil organic matter(SOM)content in aggregates from topsoil.In addition,ASI and SSI were positively correlated(r=0.569,p<0.05)with each other,which indicated that the stability of soil aggregates could contribute to the structural stability of bulk soil.Moreover,accumulation factors(AF),principal component analysis(PCA)and Pearson's correlation co-efficients were used for metal element assessment.The results indicated that SOM was not a key factor affecting the accumulation of Ca,Mg,Al,Fe,Mn,Pb,Cd and Cu in soil aggre-gates.In general,AF values for metal elements in microaggregates(<0.25 mm)were high,which showed that metals preferred to accumulate in fine soil aggregates.The PCA and Pearson's correlation coefficients indicated that soil parent materials primarily controlled the distribution of Al,Ca,Fe,Mg and Mn,while materials derived from technogenic sources have important impacts on the distribution of Cd,Cu and Pb in soil aggregates along the soil profile.

Differences in Meteorological Conditions between Days with Persistent and Non-Persistent Pollution in Beijing, China

We compared the regional synoptic patterns and local meteorological conditions during persistent and non-persistent pollution events in Beijing using US NCEP–Department of Energy reanalysis outputs and observations from meteorological stations. The analysis focused on the impacts of high-frequency（period 〈 90 days） variations in meteorological conditions on persistent pollution events（those lasting for at least 3 days）. Persistent pollution events tended to occur in association with slow-moving weather systems producing stagnant weather conditions, whereas rapidly moving weather systems caused a dramatic change in the local weather conditions so that the pollution event was short-lived. Although Beijing was under the influence of anomalous southerly winds in all four seasons during pollution events, notable differences were identified in the regional patterns of sea-level pressure and local anomalies in relative humidity among persistent pollution events in different seasons. A region of lower pressure was present to the north of Beijing in spring, fall, and winter, whereas regions of lower and higher pressures were observed northwest and southeast of Beijing, respectively, in summer. The relative humidity near Beijing was higher in fall and winter, but lower in spring and summer. These differences may explain the seasonal dependence of the relationship between air pollution and the local meteorological variables. Our analysis showed that the temperature inversion in the lower troposphere played an important part in the occurrence of air pollution under stagnant weather conditions.Some results from this study are based on a limited number of events and thus require validation using more data.