Small Vicinity Research Articles

Trajectory Tracking Control of an Autonomous Vessel in the Presence of Unknown Dynamics and Disturbances

We present a proportional–integral–derivative-based controller plus an adaptive slide surface to solve the trajectory tracking control problem for a fully actuated vessel with unknown parameters perturbed by slowly varying external unknown dynamics. The controller design assumes that the vessel moves at low speed and frequency, its physical parameters are unknown, and its state is measurable. The control approach ensures error tracking convergence toward a small vicinity at the origin. We conduct the corresponding stability analysis using the Lyapunov theory and saturation functions. We tested the controller through two numerical experiments—a turning ellipse maneuver and a rest-to-rest maneuver—where the vessel parameters were unknown, and we obtained satisfactory results.

Predefined-Time Adaptive Neural Tracking Control for a Single Link Manipulator with an Event-Triggered Mechanism.

This paper introduces an adaptive trajectory-tracking control method for uncertain nonlinear systems, leveraging a time-varying threshold event-triggered mechanism to achieve predefined-time tracking. Compared to conventional time-triggering approaches, the employment of a time-varying threshold event-triggered mechanism significantly curtails communication resource wastage without compromising the system's performance. Furthermore, a novel adaptive control algorithm with predefined timing is introduced. This method guarantees that tracking errors converge to within a small vicinity of the origin within a predefined timeframe, ensuring all signals in the closed-loop system remain bounded. Moreover, by adjusting a controller-related parameter, we can predefine the upper bound of the convergence time. Finally, the efficacy of the control scheme is corroborated by simulation results obtained from a nonlinear manipulator system.

Summary of the DISPLACE challenge 2023-DIarization of SPeaker and LAnguage in Conversational Environments

In multi-lingual societies, where multiple languages are spoken in a small geographic vicinity, informal conversations often involve mix of languages. Existing speech technologies may be inefficient in extracting information from such conversations, where the speech data is rich in diversity with multiple languages and speakers. The DISPLACE (DIarization of SPeaker and LAnguage in Conversational Environments) challenge constitutes an open-call for evaluating and bench-marking the speaker and language diarization technologies on this challenging condition. To facilitate this challenge, a real-world dataset featuring multilingual, multi-speaker conversational far-field speech was recorded and distributed. The challenge entailed two tracks: Track-1 focused on speaker diarization (SD) in multilingual situations while, Track-2 addressed the language diarization (LD) in a multi-speaker scenario. Both the tracks were evaluated using the same underlying audio data. Furthermore, a baseline system was made available for both SD and LD task which mimicked the state-of-art in these tasks. The challenge garnered a total of 42 world-wide registrations and received a total of 19 combined submissions for Track-1 and Track-2. This paper describes the challenge, details of the datasets, tasks, and the baseline system. Additionally, the paper provides a concise overview of the submitted systems in both tracks, with an emphasis given to the top performing systems. The paper also presents insights and future perspectives for SD and LD tasks, focusing on the key challenges that the systems need to overcome before wide-spread commercial deployment on such conversations.

E-Banking: Opportunities and Challenges from Customer’s Perspective

Opportunities and Challenges of E-Banking were empirically discussed. A researcher conducted a field investigation to collect the responses from the target audience. In the Technology Era, E-Banking has started to dominate the entire world. The presence of E-Banking can be seen till the tail end of small vicinities. Villagers also use it as it stops them from visiting bank branches. This increases trust as banks use high-end software for their banking system. The study was conducted in different parts of Chennai City. 210 customers were met in different parts of Chennai City. The places of research investigation covered by the researcher are shopping malls, Banks, Colleges, Universities, Business Outlets, and Residential Areas. Furthermore, the researcher used snowball sampling in the research as he collected the references of friends, family members, and colleagues. Descriptive Research Design was used by the researcher.

Features of the Mechanism of Gas-phase Ignition of Wood Biomass Particles

ABSTRACT Use of woody biomass instead of coal as fuel for thermal power plants (TPP) is considered a promising direction for reducing emissions of anthropogenic substances during the operation of coal-fired thermal power plants. But the process of replacing coal with wood in the thermal power industry is happening very slowly due to objective reasons. The main one is the deposition of particles that have not fully passed the pyrolysis stage (in this case, a layer of substance in a resinous state is retained in the wood particle) on heating surfaces (for example, superheaters) and a decrease in the efficiency of using the heat of combustion of fuel as a result of contamination of the heating surfaces. Therefore, when developing technologies for burning dispersed wood in the furnaces of boiler units, reliable experimental data are required on the characteristic times of ignition and combustion of woody biomass particles, taking into account the time of transition from local (focal) gas-phase ignition to the combustion of volatiles in the entire vicinity of the particle (tsf). The article presents the results of experimental studies of flame propagation processes in the small vicinity of a particle during the ignition period. The experiments made it possible to establish that the flame propagation velocity in the small vicinity of the particle significantly depends on the ambient temperature. It is shown that under conditions of low-temperature heating (air temperature Tg = 873 K), the propagation velocity of the combustion (flame) is minimal. An increase in Tg values (from 873 K to 1273 K) leads to a significant (4–5 times) increase in the time of complete flame coverage of the particle. According to the results of the experiments, two heating modes were identified: high-temperature and low-temperature with a conditional interface Tg = 873 K. At Tg = 873 K, the characteristic particle size of wood biomass has no significant effect on the characteristics and conditions of flame propagation in a small vicinity of the particle. An increase in the ambient temperature (up to 1273 K) leads to an increase in the influence of particle size on the characteristics and conditions of flame propagation. A hypothesis describing the process of flame propagation has been developed.

State identification for a class of uncertain switched systems by differential neural networks

ABSTRACT This paper presents a non-parametric identification scheme for a class of uncertain switched nonlinear systems based on continuous-time neural networks. This scheme is based on a continuous neural network identifier. This adaptive identifier guaranteed the convergence of the identification errors to a small vicinity of the origin. The convergence of the identification error was determined by the Lyapunov theory supported by a practical stability variation for switched systems. The same stability analysis generated the learning laws that adjust the identifier structure. The upper bound of the convergence region was characterized in terms of uncertainties and noises affecting the switched system. A second finite-time convergence learning law was also developed to describe an alternative way of forcing the identification error’s stability. The study presented in this paper described a formal technique for analysing the application of adaptive identifiers based on continuous neural networks for uncertain switched systems. The identifier was tested for two basic problems: a simple mechanical system and a switched representation of the human gait model. In both cases, accurate results for the identification problem were achieved.

Neural Network-Based Nonconservative Predefined-Time Backstepping Control for Uncertain Strict-Feedback Nonlinear Systems.

To handle the tracking problem of uncertain strict-feedback nonlinear systems with matched and mismatched composite disturbances, this article studies a predefined-time backstepping controller by resorting to a Lyapunov-based predefined-time dynamic paradigm, a regulation function, and neural networks (NNs). Moreover, an adding-absolute-value (ADV) technique is adopted in the design process to remove the control singularity. Theoretical analyses prove the boundedness of all closed-loop system signals and the predefined-time convergence of the tracking error into an arbitrarily small vicinity of the origin. The proposed controller exhibits four advantages: 1) the actual convergence time is precisely predefined by only one design parameter irrespective of the initial conditions, and the control energy is economized; 2) no unbounded terms are adopted for predefining the actual convergence time, thus avoiding numerical overflow problem under limited memory space and gaining strong noise-tolerant ability; 3) the peaking tracking error and control input magnitude can be effectively reduced by appropriately setting parameters of the regulation function; and 4) the controller is continuous and nonsingular everywhere. Finally, a practical example of a single-link manipulator is presented to validate the efficacy and superiority of our predefined-time controller.

Numerical simulation of laminar-turbulent transition in a supersonic boundary layer under the action of acoustic disturbances

In low disturbance environment, laminar-turbulent transition (LTT) is associated with excitation of unstable normal modes of small initial amplitudes (receptivity problem). These modes grow exponentially to a critical amplitude in accord with the linear stability theory (LST) and trigger the nonlinear breakdown. In the current study numerical simulation of laminar-turbulent transition (LTT) in the boundary layer on the upper surface of a flat plate in a supersonic free stream of Mach number M∞=3 and Reynolds number Re∞=2 × 107 is carried out. The flow is perturbed by fast or slow acoustic waves of low intensity, which excite unstable waves of the first mode. The latter have frequencies corresponding to the integral amplification N ≈ 9.16 typical for flight conditions. Two cases are considered: the angle of attack AoA=0° at which acoustic waves pass through a weak shock induced by viscous-inviscid interaction; AoA=5° at which acoustic waves pass through the expansion fan emanating from the plate leading edge. A holistic modeling of all stages of the transition from receptivity to the birth of turbulent spots is performed using direct numerical simulations. Linear stability theory is used to interpret the results. Feasibility of practical implementation of the amplitude method for predictions of the LTT onset in the considered and similar cases is discussed. It has been shown that to realize the amplitude method in the considered and similar cases, it is sufficient: to calculate the initial amplitudes of instability in a small vicinity of the leading edge and the propagation of instability from the leading edge to the station where the instability reaches the critical amplitude u′max≈4%. Analysis of known numerical and experimental data showed that this criterion weakly depends on the local Mach number in the range 0<Me<7, and it is acceptable for practical predictions of the transition onset points.

BCS-like disorder-driven instabilities and ultraviolet effects in nodal-line semimetals

We study the effects of quenched disorder on electrons in a 3D nodal-line semimetal. Disorder leads to significant renormalisations of the quasiparticle properties due to ultraviolet processes, i.e. processes of scattering in a large band of momenta, of the width exceeding the inverse mean free path. As a result, observables such as the density of states and conductivity exhibit singular behaviour in a broad range of disorder strengths, excluding a small vicinity of the singular point. We find that, for example, the density of quasiparticle states diverges as a function of the disorder strength g as ρ(g,E)∝|gc(E)−g|−2|E| for g smaller than the critical value gc(E) and crosses over to a constant for g very close to gc(E), where E is the quasiparticle energy. For certain disorder symmetries, a 3D disordered nodal-line semimetal can be mapped to a 2D metal with attractive interactions. The described disorder-driven instabilities in such a nodal-line semimetal are mapped to Cooper and exciton-condensation instabilities in a 2D metal. For other disorder symmetries, the respective instabilities are similar but not exactly dual. We discuss experimental conditions favourable for the observation of the described effects.

SELECTION OF THE SET OF ALLOWABLE VALUES OF THE VARIABLE PARAMETERS OF THE STABILIZER OF A COMPLEX DYNAMIC OBJECT

Topicality. One of the most important tasks in the application of computational methods for the parametric synthesis of controllers of complex dynamic objects is the task of determining the set of permissible values of the variable parameters of the controller, where the target function is calculated based on the solutions of the mathematical model of the disturbed motion of the dynamic object with its subsequent minimization. The purpose of the work is to construct the set of permissible values of variable parameters of the stabilizer of a complex dynamic object when applying the algorithmic combined method of parametric synthesis of stabilizers of complex dynamic objects, the essence of which is the direct calculation of the integral quadratic functional on the solutions of a closed dynamic system with subsequent finding of its global minimum through a sequential combination of two algorithms – the Sobol grid algorithm and the Nelder-Mead algorithm. Results. With the help of the Sobol grid construction algorithm, the starting point of the computational process is brought to the node of the Sobol grid, which is located in the small vicinity of the point of the global minimum. At the second stage of optimization, the found Sobol grid node is selected as the starting point for applying the Nelder-Mead method, which is implemented by the Optimization Toolbox software product of the MATLAB package or the Minimize software product of the MATHCAD package and leads the computational process to the point of the global minimum. Conclusion. The paper proves a theorem according to which the stability region of a closed system of the first approximation can be taken as such a set, and also gives an example of a solution to the problem of parametric synthesis of the stabilizer of the car's course stability system during its emergency braking.

Active learning-based domain adaptive localized polynomial chaos expansion

The paper presents a novel methodology to build surrogate models of complicated functions by an active learning-based sequential decomposition of the input random space and construction of localized polynomial chaos expansions, referred to as domain adaptive localized polynomial chaos expansion (DAL-PCE). The approach utilizes sequential decomposition of the input random space into smaller sub-domains approximated by low-order polynomial expansions. This allows the approximation of functions with strong nonlinearities, discontinuities, and/or singularities that often appear in dynamical systems. Decomposition of the input random space and local approximations alleviates the Gibbs phenomenon for these types of problems and confines error to a very small vicinity near the non-linearity. The global behavior of the surrogate model is therefore significantly better than existing methods, as shown in numerical examples, including an engineering dynamical system exhibiting discontinuous response. The whole process is driven by an active learning routine that uses the recently proposed Θ criterion to assess local variance contributions (Novák et al., 2021). The proposed approach balances both exploitation of the surrogate model and exploration of the input random space and thus leads to efficient and accurate approximation of the original mathematical model. The numerical results show the superiority of the DAL-PCE in comparison to (i) a single global polynomial chaos expansion and (ii) the recently proposed stochastic spectral embedding (SSE) method (Marelli et al., 2021) developed as an accurate surrogate model and which is based on a similar domain decomposition process. This method represents a general framework upon which further extensions and refinements can be based and which can be combined with any technique for non-intrusive polynomial chaos expansion construction.

"THE ELASTIC CONTACT PROBLEM INVOLVING A BILATERALLY LOADED THIN STRIP "

"For the solution of the elastic contact problem, it is generally assumed that the contacting solids can be assimilated to elastic half-spaces. This assumption is reasonable when the contact area is small compared to the dimensions of the contacting solids, and when the contact stresses are restricted to a small vicinity of the initial point of contact, without reaching the boundaries of the solids. These conditions are not met when a thin strip is bilaterally and symmetrically compressed between two punches, as the dimensions of the contact area might be of the same order of magnitude as the strip thickness. Moreover, the stresses induced in the strip will reach the boundary without a significant decay in intensity. Consequently, in this contact scenario, the classical solutions for a point force acting on the boundary of the half-space cannot be directly applied. The starting point for the problem solution is a modified Boussinesq-type solution for the thin elastic layer, expressing the displacement and stress fields induced in an elastic strip by two opposed normal forces perpendicular to the layer boundaries. To this end, supplementary displacements are added to the half-space solution to satisfy both geometric and loading symmetry, as well as the linear elasticity equations. Superposition principle is then applied, resulting in a contact model for an elastic strip compressed between two identical indenters with aligned axes. An algorithm for the contact of solids that can be assimilated to elastic half-spaces is modified and applied to the contact involving a thin strip. To this end, the required influence coefficients for displacements are derived. A calculation example involving a thin strip compressed between two spheres is presented, and a comparison with the half-space solution is performed. "

Observer-Based Adaptive Fuzzy Quantized Fault-Tolerant Control of Nonstrict-Feedback Nonlinear Systems With Sensor Fault

This paper focuses on the problem of adaptive quantized fault tolerant tracking control for a class of uncertain nonstrict-feedback nonlinear systems in the presence of input and output quantization and sensor fault. The main technical challenges come from how to deal with the input and output quantization errors and the partial loss of sensors' effectiveness. Firstly, a new observer including the quantized input and output signals and the estimation of fault parameter is designed to reconstruct the unavailable states, and some special techniques are developed to deal with the sector-bounded quantization errors. Furthermore, based on the cubic absolute-value Lyapunov function, the adaptive fault compensation strategy is presented to make up for the influence from sensor fault upon the control performance. Then, with the aid of fuzzy logic system (FLS) approximation method and backstepping technique, a novel output feedback adaptive fuzzy fault tolerant control (FTC) scheme is proposed for this class of systems, such that all signals in the closed-loop are semi-globally uniformly ultimately bounded (SGUUB) while the tracking error remains in a small vicinity of the origin. Finally, the effectiveness and applicability of the proposed control scheme are validated by conducting two simulation examples.

Probabilistic interpretation of algebraic inequalities related to reliability and risk

AbstractThe paper explores the probabilistic interpretations of algebraic inequalities and presents several findings. First, the inequality of the additive ratios can be used to increase the probability of an event occurring within a set of mutually exclusive and exhaustive events. The interpretation of this inequality produced a counter‐intuitive result, that for suppliers delivering the same quantity of reliable products alongside unknown numbers of unreliable products, the probability of purchasing a reliable product from a randomly selected supplier is higher than the probability of purchasing a reliable product from the market formed by all suppliers. Next, the paper discusses how averaging the reliabilities of components from different varieties can lead to a significant overestimation of the calculated system reliability, as demonstrated by another algebraic inequality interpretation. Finally, the paper derives tight bounds for the reliability of demand in a load‐strength interference model by interpreting the Hayashi's inequality. Notably, these bounds do not depend on the shape of the load distribution and only require the strength distribution to be known in relatively small vicinities of the lower and upper bound of the load.

An off-shell Wilson loop

It is well-known that on-shell maximally helicity-violating gluon scattering amplitudes in planar maximally supersymmetric Yang-Mills theory are dual to a bosonic Wilson loop on a null-polygonal contour. The light-like nature of the intervals is a reflection of the mass-shell condition for massless gluons involved in scattering. Presently, we introduce a Wilson loop prototype on a piece-wise curvilinear contour that can be interpreted in the T-dual language to correspond to nonvanishing gluon off-shellness. We analyze it first for four sites at one loop and demonstrate that it coincides with the four-gluon amplitude on the Coulomb branch. Encouraged by this fact, we move on to the two-loop order. To simplify our considerations, we only focus on the Sudakov asymptotics of the Wilson loop, when the off-shellness goes to zero. The latter serves as a regulator of short-distance divergences around the perimeter of the loop, i.e., divergences when gluons are integrated over a small vicinity of the Wilson loop cusps. It does not however regulate conventional ultraviolet divergences of interior closed loops. This unavoidably introduces a renormalization scale dependence and thus scheme dependence into the problem. With a choice of the scale setting and a finite renormalization, we observe exponentiation of the double logarithmic scaling of the Wilson loop with the accompanying exponent being given by the so-called hexagon anomalous dimension, which recently made its debut in the origin limit of six-leg gluon amplitudes. This is contrary to the expectation for the octagon anomalous dimension to rather emerge from our analysis suggesting that the current object encodes physics different from the Coulomb branch scattering amplitudes.

Initial stages of gravity-driven flow of two fluids of equal depth

Short-time behavior of gravity-driven free surface flow of two fluids of equal depth and different densities is studied. Initially, the fluids are at rest and separated with a vertical rigid plate of negligible thickness. Then, the plate disappears suddenly and a gravity-driven flow of the fluids starts. The flow in an early stage is described by the potential theory. The initial flow in the leading order is described by a linear problem, which is solved by the Fourier series method. The motions of the interface between the fluids and their free surfaces are investigated. The singular behaviors of the velocity field at the bottom point, where the interface meets the rigid bottom, and the top point, where the interface meets both free surfaces, are analyzed in detail. The flow velocity is shown to be log-singular at the bottom point. The leading-order inner asymptotic solution is constructed in a small vicinity of this point. It is shown that the flow close to the bottom point is self-similar. The motion of the interface is independent of any parameters, including the density ratio, of the problem in specially stretched variables. In the limiting case of negligible density of one of the fluids, the results of the classical dam break problem are recovered. The Lagrangian representation is employed to capture the behavior of the interface and the free surfaces at the top, where the fluid interface meets the free surfaces. The shapes of the free surfaces and the interface in the leading order computed by using the Lagrangian variables show a jump discontinuity of the free surface near the top point where the free surfaces and the interface meet. Inner region formulation is derived near the top point.

ACOUSTIC RADIATION OF CHARGED DROPLETS OSCILLATING IN THE SUPERPOSITION OF GRAVITATIONAL AND ELECTROSTATIC FIELDS

The intensity of acoustic radiation and the characteristic widths (depending on the radii and charges of the drops) of the frequency ranges in which the radiation falls have been calculated for charged droplets of convective clouds and near-ground fogs, which are immobile in the superposition of gravitational and electric fields. The calculations have been carried out using the methods of classical mathematical physics taking into account two small parameters: the dimensionless oscillation amplitude and the equilibrium spheroidal deformation of a charged droplet in an external electrostatic field. All calculations have been performed using the model of an ideal incompressible electroconducting liquid. It has turned out that the acoustic radiation from clouds and fogs occurs in the ultrasonic frequency range, while the acoustic radiation of large rain-drops is in the acoustic range audible to the human ear. The boundary between the ultrasonic and sonic radiations is determined by droplet sizes, electric field strengths (in a small vicinity of the droplets), and the values of interfacial tension coefficient.

Analysis of Blind Spot in Heavy Vehicles Driving Using VIKOR Method

A blind spot is a phase of road out of doors the driving force’s view that cannot be visible via rear home windows or home windows. Vehicle height and period, huge blind spots All motors have blind spots. These are regions or zones on either facet of the car that aren’t visible to the driver when considered in the rearview or facet view reflect. If there are blind spots, a driving force must always turn his head and test the automobiles earlier than converting lanes. Look in the replicate. Blind spots may be large enough to without difficulty block another vehicle, motorbike, bicycle owner or pedestrian out of your view. The “blind spot” is not seen to the motive force in the windshield across the vehicle. They are in all automobiles, however there are four massive blind spots on 1/2 vehicles. What brought about the blind spot to seem at the back of the trailer? In each of our eyes The size of a pin There is little useful blind spot. In this small region, wherein The optic nerve passes through the surface of the retina, No photosynthesis. In the absence of photosynthetic cells that stumble on light, it creates a blind spot. On this page you will discover 18 comparable words, antonyms, linguistic expressions and associated words for blind spot, namely: lack of notion, invisibility, weak spot, oversight, and membrane in one’s eye, obstruction, blindness, mistakes, and look before changing path. Look for blind spots for your rearview replicate and vehicles close to your shoulders. Be aware of the dangers – appearance beyond the car in front of you. The small vicinity inside the retina that does not experience mild is called the blind spot. The blind spot is the area in which the nerve endings within the retina input the optic nerve. Due to the lack of visual receptors which includes stems and cones on this region, snap shots that fall on this location cannot be detected. The blind spot is an area inside your range of vision which you cannot see precisely, however you really want to look. For instance, whilst you drive a car, the region in the back of your shoulders is regularly the blind spot. What we need to focus on here is the mental (or metaphorical) blind spot, which is defined as “ones but often unknown prejudice or lack of knowledge” or “tendency to ignore anything particularly”. It is difficult or unpleasant. Some human beings see blind spots as weak. “What are the blind spots of your leadership?” Your approach has to be to respond absolutely to the weak spot you understand when you ask and to explain how you can decrease its effect. It is crucial to offer a solution that suggests which you are self-aware and may overcome your weaknesses. the final value, strongly preferred got first rank and equally preferred got fifth rank.

Modelling negative thermomechanical effects in reinforced road structures with thermoelastic incompatibility of coating and reinforcement materials

The phenomena of the formation of local defects and cracks in asphalt concrete pavements of roads and bridges are most often observed in climatic zones with large temperature differences during their seasonal and daily changes. To a large extent, this is due to the heterogeneity of the thermomechanical properties of the materials of the coating layers and the base. To prevent these phenomena, reinforcing rods and meshes are introduced into the coating structure. In this work, using the theory of thermoelasticity, it is shown by the method of mathematical modelling that in cases of incompatibility of the thermomechanical characteristics of asphalt concrete materials and reinforcement, additional localized thermal stresses arise in its small vicinity, which, even at moderate temperatures, can reach critical values and lead to local defects and cracks. Since these defects are latent, they cannot always be detected in practice. The presented results of analytic calculation validated these conclusions. They can be used in both road building and composite design.

Adaptive neural network fixed-time fault-tolerant control of an uncertain nonlinear system with full-state constraints

In this paper, a fixed-time fault-tolerant controller is designed for the tracking control problem of an uncertain nonlinear system under full-state constraints, uncertainties and actuator faults. Since the controller is designed in the framework of backstepping method, to handle the “explosion of complexity” problem, an adaptive fixed-time filter is constructed. It ensures that the filter error converges to an arbitrarily small vicinity of zero in fixed time. A state transformation function is applied to solve full-state constraints. Radial basis function neural network (RBFNN) and adaptive technique are respectively used for dealing with uncertainties and actuator faults. Based on Lyapunov theory, the closed-loop system is proved to be bounded in fixed time and all states are kept in their constraints. At the end, the effectiveness of the designed control strategy is verified by numerical simulation and an application of a permanent magnet synchronous motor (PMSM) system.