Abstract
Purpose
The purpose of this study is to explore the corrosion behaviors of tube pile steel with the addition of 0.2 per cent Cu and 0.2 per cent Cu-0.2 per cent Cr in half-immersion environment.
Design/methodology/approach
The electrochemical corrosion behaviors of tube pile steel with different alloy-elements addition were identified using the polarization curve method and electrochemical impedance spectroscopy technique. Corrosion product and its morphology were analyzed by X-ray diffraction, optical microscope and scanning electron microscopy.
Findings
Results indicate that the most serious corrosion occurred in the liquid-air interface zone due to the higher oxygen and water concentration. With the addition of Cu and Cu-Cr, pits were getting smaller and denser, transforming the corrosion type from pitting corrosion to uniform corrosion gradually. Rust layer containing Cu/Cr tended to compact and inhibited the anodic process, while the enrichment of Cu/Cr in rust layer decelerated the dissolution of substrate, thus the expanding of pits was suppressed.
Originality/value
This paper studied the corrosion behaviors of liquid-air interface zone of tube pile steel and verified the transformation of corrosion type with adding Cu, Cu/Cr elements.
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Keywords
Wenqiang Guo, Guoxiang Hou, Yin Guan and Senyun Liu
This paper aims to explore the mechanism of the slip phenomenon at macro/micro scales, and analyze the effect of slip on fluid flow and heat transfer, to reduce drag and enhance…
Abstract
Purpose
This paper aims to explore the mechanism of the slip phenomenon at macro/micro scales, and analyze the effect of slip on fluid flow and heat transfer, to reduce drag and enhance heat transfer.
Design/methodology/approach
The improved tangential momentum accommodation coefficient scheme incorporated with Navier’s slip model is introduced to the discrete unified gas kinetic scheme as a slip boundary condition. Numerical tests are simulated using the D2Q9 model with a code written in C++.
Findings
Velocity contour with slip at high Re is similar to that without slip at low Re. For flow around a square cylinder, the drag is reduced effectively and the vortex shedding frequency is reduced. For flow around a delta wing, drag is reduced and lift is increased significantly. For Cu/water nanofluid in a channel with surface mounted blocks, drag can be reduced greatly by slip and the highest value of drag reduction (DR) (67.63%) can be obtained. The highest value of the increase in averaged Nu (11.78%) is obtained by slip at Re = 40 with volume fraction φ=0.01, which shows that super-hydrophobic surface can enhance heat transfer by slip.
Originality/value
The present study introduces and proposes an effective and superior method for the numerical simulation of fluid/nanofluid slip flow, which has active guidance meaning and applied value to the engineering practice of DR, heat transfer, flow control and performance improvement.
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Chengchen Deng, Haihan Zhao, Han Huang, Zhen Shi, Jiamin Li and Sheng Liu
The purpose of this paper is to solve the problem of adaptive predefined-time control for spacecraft rendezvous maneuver with input quantization and unknown parameters.
Abstract
Purpose
The purpose of this paper is to solve the problem of adaptive predefined-time control for spacecraft rendezvous maneuver with input quantization and unknown parameters.
Design/methodology/approach
A significant error-shifting function is established to ensure that the limitation of the initial condition can be ignored. Then, a combination of neural networks method and minimum-learning-parameter method is used to mitigate the adverse effects caused by nonlinear system dynamics. An input quantization method is applied to improved efficiency of data communication between controller and actuator in rendezvous maneuver control system.
Findings
The simulation results verify the correctness and effectiveness of the designed control strategy which can effectively overcome the disadvantages caused by coupling nonlinear system dynamics.
Originality/value
This paper designs an adaptive predefined-time control method for spacecraft rendezvous maneuver control with input quantization based on backstepping control method.
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Akansha Mer and Amarpreet Singh Virdi
Introduction: Human resource management (HRM) is going through a transformation phase due to the pandemic. The COVID-19 crisis compelled the employees to work virtually. To…
Abstract
Introduction: Human resource management (HRM) is going through a transformation phase due to the pandemic. The COVID-19 crisis compelled the employees to work virtually. To mitigate the effects of COVID-19, several organisations heavily invested in artificial intelligence (AI) in the realm of HRM.
Purpose: With limited studies on the paradigm shift in HRM post-pandemic and the role of AI, the study investigates and proposes a conceptual framework for the paradigm shift in HRM practices post-COVID-19 pandemic and the significance of AI. Furthermore, the study investigates the outcomes of the use of AI in HRM for organisations and employees.
Methodology: A comprehensive review of the literature based on the guidelines of Tranfield, Denyer, and Smart (2003) and Crossan and Apaydin (2010) has been followed. A systematic literature review assisted in critically analysing, synthesising, and mapping the extant literature by identifying the broad themes involved.
Findings: COVID-19-related economic disruption has led to a paradigm shift in HRM practices. AI-enabled HRM practices are now centred around remote and contingent workforce management, mindfulness, social capital, increasing employee engagement, reskilling and upskilling towards new competencies, etc. AI is making remote work seamless through smooth recruitment and selection process, onboarding, career and development, tracking and managing the performance, facilitating learning, and talent management. Post-pandemic, AI-powered tools based on data mining (DM), predictive analytics, big data analytics, natural language processing (NLP), intelligent robots, machine learning (ML), virtual (VR)/augmented reality (AR), etc., have paved the way for managing the HRM practices effectively, thereby leading to enhanced organisational performance, employee well-being, automation, and reduced cost.
Details
Keywords
Suneel Kumar, Shekhar, Marco Valeri and Geetanjali Sageena
The purpose of this paper is to investigate the neural-network-based containment control of multi-agent systems with unknown nonlinear dynamics. Moreover, communication…
Abstract
Purpose
The purpose of this paper is to investigate the neural-network-based containment control of multi-agent systems with unknown nonlinear dynamics. Moreover, communication constraints are taken into account to reflect more realistic communication networks.
Design/methodology/approach
Based on the approximation property of the radial basis function neural networks, the control protocol for each agent is designed, where all the information is exchanged in the form of sampled data instead of ideal continuous-time communications.
Findings
By utilizing the Lyapunov stability theory and the Lyapunov–Krasovskii functional approach, sufficient conditions are developed to guarantee that all the followers can converge to the convex hull spanned by the stationary leaders.
Originality/value
As ideal continuous-time communications of the multi-agent systems are very difficult or even unavailable to achieve, the neural-network-based containment control of nonlinear multi-agent systems is solved under communication constraints. More precisely, sampled-data information is exchanged, which is more applicable and practical in the real-world applications.
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Yanchao Sun, Jiayu Li, Hongde Qin and Yutong Du
Autonomous underwater vehicle (AUV) is widely used in resource prospection and underwater detection due to its excellent performance. This study considers input saturation…
Abstract
Purpose
Autonomous underwater vehicle (AUV) is widely used in resource prospection and underwater detection due to its excellent performance. This study considers input saturation, nonlinear model uncertainties and external ocean current disturbances. The containment errors can be limited to a small neighborhood of zero in finite time by employing control strategy. The control strategy can keep errors within a certain range between the trajectory followed by AUVs and their intended targets. This can mitigate the issues of collisions and disruptions in communication which may arise from AUVs being in close proximity or excessively distant from each other.
Design/methodology/approach
The tracking errors are constrained. Based on the directed communication topology, a cooperative formation control algorithm for multi-AUV systems with constrained errors is designed. By using the saturation function, state observers are designed to estimate the AUV’s velocity in six degrees of freedom. A new virtual control algorithm is designed through combining backstepping technique and the tan-type barrier Lyapunov function. Neural networks are used to estimate and compensate for the nonlinear model uncertainties and external ocean current disturbances. A neural network adaptive law is designed.
Findings
The containment errors can be limited to a small neighborhood of zero in finite time so that follower AUVs can arrive at the convex hull consisting of leader AUVs within finite time. The validity of the results is indicated by simulations.
Originality/value
The state observers are designed to approximate the speed of the AUV and improve the accuracy of the control method. The anti-saturation function and neural network adaptive law are designed to deal with input saturation and general disturbances, respectively. It can ensure the safety and reliability of the multiple AUV systems.
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Qing Wang, Changyin Sun, Xiaofeng Chai and Yao Yu
This paper aims to develop sliding mode control (SMC) methods for second-order multi-agent systems (MAS) in the presence of mismatched uncertainties.
Abstract
Purpose
This paper aims to develop sliding mode control (SMC) methods for second-order multi-agent systems (MAS) in the presence of mismatched uncertainties.
Design/methodology/approach
Based on the disturbance observer (DOB), discontinuous and continuous sliding mode protocols are designed to achieve finite-time consensus in spite of the disturbances.
Findings
Compared with integral SMC, numerical simulation results show that the proposed control methods exhibit better performance with respect to reduction of chattering.
Originality/value
The main contributions are the following: MAS described with mismatched uncertainties are considered; both discontinuous and continuous sliding mode controllers are considered; with the proposed sliding mode controller, the desired sliding surface can be reached in finite time and the DOB is introduced in the controller to alleviate the chattering phenomenon.
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Keywords
Zhen Li, Xianwei Liu, Yiwei Lian, Juan Xie, Xiaorui Gao and Tao Chang
This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)
Abstract
Purpose
This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)
Design/methodology/approach
The variations of electrical conductivity as a function of water volume fraction are examined at one constant alcohol (or DMF, ethyl lactate, γ-valerolactone)/water, alcohol (or DMF, ethyl lactate, γ-valerolactone)/oil volume ratios for each sample.
Findings
Most of the results are consistent with percolation character. The conductive mechanism of these SFMEs is discussed by the percolation model, and it is found that it might be described with the static percolation model below the percolation threshold.
Originality/value
Our report gives a systematic research on the percolation mechanism of as many species of SFMEs as possible by the theoretical models
Details
Keywords
Daiga Kalniņa, Dita Nīmante, Sanita Baranova and Alise Oļesika
Covid-19 forced the entire global education system to adapt to the new circumstances. This chapter continues the worldwide discussion on how student learning on courses and…
Abstract
Covid-19 forced the entire global education system to adapt to the new circumstances. This chapter continues the worldwide discussion on how student learning on courses and programs that were moved partially online due to remote teaching and learning in higher education institutions (HEI) during the Covid-19 pandemic was assured and what opportunities this has brought to higher education. Although there is a tendency in the theoretical literature to focus on the problems, difficulties, and challenges associated with the transition to remote learning in higher education during the pandemic, this study suggests that, contrary to the common belief, students actually identify a great number of positive issues associated with remote learning. The findings of this study highlight that students see both personal benefits and challenges in remote learning. Overall, students are satisfied with the quality of the remote teaching and learning process, and students’ positive assessment of the quality of their studies’ organization increased with age. Stability and routine were important for the students in the study process. These ensure that the study process continues uninterrupted and thus that results can be achieved. The results of this study bring us to the conclusion that the Covid-19 pandemic could be used to speed up changes in HEIs around the globe to find better and more student-centered and innovative solutions in teaching and learning in the future.