Search results

This research aims to present a novel cooperative control architecture designed specifically for roads with variations in height and curvature. The primary objective is to enhance the longitudinal and lateral tracking accuracy of the vehicle.

In addressing the challenges posed by time-varying road information and vehicle dynamics parameters, a combination of model predictive control (MPC) and active disturbance rejection control (ADRC) is employed in this study. A coupled controller based on the authors’ model was developed by utilizing the capabilities of MPC and ADRC. Emphasis is placed on the ramifications of road undulations and changes in curvature concerning control effectiveness. Recognizing these factors as disturbances, measures are taken to offset their influences within the system. Load transfer due to variations in road parameters has been considered and integrated into the design of the authors’ synergistic architecture.

The framework's efficacy is validated through hardware-in-the-loop simulation. Experimental results show that the integrated controller is more robust than conventional MPC and PID controllers. Consequently, the integrated controller improves the vehicle's driving stability and safety.

The proposed coupled control strategy notably enhances vehicle stability and reduces slip concerns. A tailored model is introduced integrating a control strategy based on MPC and ADRC which takes into account vertical and longitudinal force variations and allowing it to effectively cope with complex scenarios and multifaceted constraints problems.

The goal of this research is to develop a dynamic step path planning algorithm based on the rapidly exploring random tree (RRT) algorithm that combines Q-learning with the Gaussian distribution of obstacles. A route for autonomous vehicles may be swiftly created using this algorithm.

The path planning issue is divided into three key steps by the authors. First, the tree expansion is sped up by the dynamic step size using a combination of Q-learning and the Gaussian distribution of obstacles. The invalid nodes are then removed from the initially created pathways using bidirectional pruning. B-splines are then employed to smooth the predicted pathways.

The algorithm is validated using simulations on straight and curved highways, respectively. The results show that the approach can provide a smooth, safe route that complies with vehicle motion laws.

An improved RRT algorithm based on Q-learning and obstacle Gaussian distribution (QGD-RRT) is proposed for the path planning of self-driving vehicles. Unlike previous methods, the authors use Q-learning to steer the tree's development direction. After that, the step size is dynamically altered following the density of the obstacle distribution to produce the initial path rapidly and cut down on planning time even further. In the aim to provide a smooth and secure path that complies with the vehicle kinematic and dynamical restrictions, the path is lastly optimized using an enhanced bidirectional pruning technique.

This paper aims to examine the link between audit(or) type and restatements in Egypt, a complex and multifaceted auditing market. The usual big 4 versus non-big 4 comparison is insufficient as Egypt has a unique mix of private audit firms, one governmental agency (Accountability State Authority) and mandatory/nonmandatory audit services, including single, joint and dual audits.

The study uses a sample of listed companies in Egypt and analyzes the impact of auditor type and audit type on explicit, implicit and total restatements. The study uses logistic regression model to examine the underlying relationship.

Results show no relationship between auditor type and audit quality, positive association between non-big foreign CPA firms and total/implicit restatements and mixed results for the impact of dual audits on audit quality. The study found no link between auditor type and audit quality in Egypt. Egyptian audit firms linked to non-big 4 foreign Certified Public Accounting firms were positively linked to total and implicit restatements. Joint audits did not improve audit quality and were directly related to total and explicit restatements. Dual audits showed mixed results, positively associated with implicit restatements but inversely associated with explicit restatements.

The study provides valuable insights into the complexities of the auditing market in emerging markets and offers valuable insights for stakeholders in the financial statement users, audit firms and governmental agencies.

The purpose of this study is to explain the effect of slab and roll initial temperatures on the wear characteristics of the surface of hot roll descaling rolls.

The UMESHMOTION subroutine and the Arbitrary Lagrangian-Eulerian adaptive mesh technique are used to investigate the wear profile of the descale roll surface and to evaluate the effect of the slab and roll’s initial temperature on the wear depth.

Wear is more pronounced at the edges of the roll-slab contact area and less severe in the roll-body’s central region. A rise in the initial slab temperature from 1,337 K to 1,429 K results in a 67% rise in maximum wear depth and 52% in frictional stress. The peak wear region progressively shifted toward the center of the roll body. A rise in the initial roll temperature from 308.15 K to 673.15 K caused a 46% reduction in maximum wear depth and 73% in frictional stress. The location of the peak wear region remained primarily unchanged.

This study used the UMESHMOTIONI subroutine and the Arbitrary Lagrangian-Eulerian adaptive mesh technique in ABAQUS® to evaluate the quantitative correlation between the wear depth of the descaling roll surfaces and the initial temperatures of the slab and rolls. This study offers valuable insights into improving the wear of descaling roll surfaces.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0231/

The deposition of particles onto a substrate during the cold spraying (CS) process relies on severe plastic deformation, so there are various micro-defects induced by insufficient deformation and severe crushing. To solve the problems, many post-treat techniques have been used to improving the quality by eliminating the micro-defects. This paper aims to help scholars and engineers in this field a better and systematic understand of CS technology by summarizing the post-treatment technologies that have been investigated recently years.

This review summarizes the types of micro-defects and introduces the effect of micro-defects on the properties of CS coating/additive manufactured, illustrates the post-treatment technologies and its effect on the microstructure and performances, and finally outlooks the future development trends of post-treatments for CS.

There are significant discoveries in post-treatment technology to change the performance of cold spray deposits. There are also many limitations for post-treatment methods, including improved performance and limitations of use. Thus, there is still a strong requirement for further improvement. Hybrid post-treatment may be a more ideal method, as it can eliminate more defects than a single method. The proposed ultrasonic impact treatment could be an alternative method, as it can densify and flatten the CS deposits.

It is the first time to reveal the influence factors on the performances of CS deposits from the perspective of microdefects, and proposed corresponding well targeted post-treatment methods, which is more instructive for improving the performances of CS deposits.

Rotational speed and load-carrying capacity are two mutual coupling factors which affect high precision and stable operation of a hydrostatic thrust bearing. The purpose of this paper is to study reasonable matching relationship between the rotational speed and the load-carrying capacity.

A mathematical model of relationship between the rotational speed and the load-carrying capacity of the hydrostatic bearing with double-rectangle recess is set up on the basis of the tribology theory and the lubrication theory, and the load and rotational speed characteristics of an oil film temperature field and a pressure field in the hydrostatic bearing are analyzed, reasonable matching relationship between the rotational speed and the load-carrying capacity is deduced and a verification experiment is conducted.

By increasing the rotational speed, the oil film temperature increases, the average pressure decreases and the load-carrying capacity decreases. By increasing the load-carrying capacity, the oil film temperature and the average pressure increases and the rotational speed decreases; corresponding certain reasonable matching values are available.

The load-carrying capacity can be increased and the rotational speed improved by means of reducing the friction area of the oil recess by using low-viscosity lubricating oil and adding more oil film clearance; but, the stiffness of the hydrostatic bearing decreases.

The purpose of this paper is to study the relationship between microstructure and mechanical properties of Sn‐4.0Bi‐3.7Ag‐0.9Zn (in wt%) solder, and the structural evolution of the soldered interfaces.

The solder was prepared by a vacuum arc furnace. Scanning electron microscopy (SEM) and X‐ray diffraction were used to identify the microstructure and composition. The melting temperature, microhardness and tensile strength were measured. Solder joints were prepared by reflowing at 250°C for 1 min in a vacuum oven and the soldered interfaces were observed by using SEM.

The microstructure of the slowly cooled Sn‐4.0Bi‐3.7Ag‐0.9Zn specimen is composed of bulk Ag₃Sn, AgZn intermetallic compounds (IMCs), Bi precipitates and a β‐Sn phase. The developed solder exhibits good comprehensive properties, such as low‐melting temperature, high microhardness and ultimate tensile strength. A complicated IMC layer forms at the interface with Cu pads and it turns into a thinner Ni₃Sn₄ layer with Ni/Cu substrates.

The paper shows how a high performance, lead‐free solder was developed.

The purpose of this paper is to solve difficult estimation problem on aircraft sudden fault by proposing a new pre-estimating method according to the energy evolution degree of the sensitive parameters to estimate the sudden fault. The sudden fault affects seriously the flight safety of aircraft.

It is based on the dissipative structure theory, and the evolution process of energy parameters is utilized. First, the evolution key points of sudden fault are determined by the time-varying entropy of sensitive parameters and the frequency band energy distribution. Then, we can obtain the evolution degree of sample while the evolution key points import the logistic regression (LR) model, and one can establish the pre-estimation model by means of relevance vector machine (RVM). While the evolution feature vector imports the RVM pre-estimation model, one can pre-estimate the sudden fault of aircraft.

The simulation results showed that this method can not only track the evolution process of aircraft sudden fault but also estimate its evolution degree, and it has a higher pre-estimating accuracy.

It provides a new way to forecast the sudden fault and increase the security of aircraft.

This paper proposes a pre-estimating method on aircraft sudden fault. It is based on the dissipative structure theory and the energy-sensitive parameters of the sudden faults are used. This method can enhance the security of aircraft and increase the protective ability of sudden fault on aircraft.