Xianyi Xie, Lisheng Jin, Guo Baicang and Jian Shi
This study aims to propose an improved linear quadratic regulator (LQR) based on the adjusting weight coefficient, which is used to improve the performance of the vehicle direct…
Abstract
Purpose
This study aims to propose an improved linear quadratic regulator (LQR) based on the adjusting weight coefficient, which is used to improve the performance of the vehicle direct yaw moment control (DYC) system.
Design/methodology/approach
After analyzing the responses of the side-slip angle and the yaw rate of the vehicle when driving under different road adhesion coefficients, the genetic algorithm and fuzzy logic theory were applied to design the parameter regulator for an improved LQR. This parameter regulator works according to the changes in the road adhesion coefficient between the tires and the road. Hardware-in-the-loop (HiL) tests with double-lane changes under low and high road surface adhesion coefficients were carried out.
Findings
The HiL test results demonstrate the proposed controllers’ effectiveness and reasonableness and satisfy the real-time requirement. The effectiveness of the proposed controller was also proven using the vehicle-handling stability objective evaluation method.
Originality/value
The objective evaluation results reveal better performance using the improved LQR DYC controller than a front wheel steering vehicle, especially in reducing driver fatigue, improving vehicle-handling stability and enhancing driving safety.
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Xu Long, Xianyi Zhao, Kainan Chong, Yutai Su, Kim S. Siow, Zhi Wang, Fengrui Jia and Xin Wan
The purpose of this paper is to analyze and compare the mechanical properties of sintered nanosilver with different porosities at both the mesoscopic and macroscopic scales and to…
Abstract
Purpose
The purpose of this paper is to analyze and compare the mechanical properties of sintered nanosilver with different porosities at both the mesoscopic and macroscopic scales and to conduct a multiscale analysis of the porosity effect on the mechanical properties of sintered nanosilver.
Design/methodology/approach
This paper establishes a mesoscopic model for the uniaxial tension of sintered nanosilver and a macroscopic model for chips containing sintered silver layers. Using the finite element method, combined with crystal plasticity theory and unified creep plasticity theory, a multiscale analysis is conducted for the mechanical properties of sintered nanosilver. First, stress distribution characteristics under uniaxial tensile loading for different porosities in sintered nanosilver polycrystal models are analyzed at the mesoscopic scale. Second, at the macroscopic scale, the mechanical performance of sintered nanosilver layers with varying porosities in high-power chip models under cyclic loading is analyzed. Finally, the porosity influence on the damage evolution in sintered nanosilver is summarized, and simulations are conducted to explore the evolution of damage parameters in sintered nanosilver under different porosities.
Findings
In the mesoscopic model, the presence of mesoscale voids affects the stress distribution in sintered nanosilver subjected to tensile loading. Sintered nanosilver with lower porosity exhibits higher tensile strength. In the macroscopic model, sintered nanosilver layers with lower porosity correspond to a more uniform stress distribution, whereas higher porosity leads to faster accumulation of plastic strain in the sintered layer. During chip packaging processes, improving processes to reduce the porosity of sintered layers can delay the initiation of damage and the propagation of cracks in sintered nanosilver.
Practical implications
During chip packaging processes, improving processes to reduce the porosity of sintered layers can delay the initiation of damage and the propagation of cracks in sintered nanosilver.
Originality/value
This paper innovatively uses a mesoscopic crystal plasticity constitutive model and a macroscopic unified creep plasticity constitutive model to analyze the mechanical behavior of sintered nanosilver with different porosities. It comprehensively investigates and explains the influence of porosity on the mechanical performance of sintered nanosilver across multiple scales.
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Consumers may boycott firms’ corporate social responsibility (CSR) activities, but little is known about when, why and how they would respond in this way. Based on psychological…
Abstract
Purpose
Consumers may boycott firms’ corporate social responsibility (CSR) activities, but little is known about when, why and how they would respond in this way. Based on psychological contract violation and discount principles, the purpose of this paper is to argue that timing and fit of CSR activities are the main dimensions of consumers’ psychological contract. It is posited that CSR activities would be boycotted if consumers perceived violation of their psychological contract, and their altruistic tendency would have a moderating effect on this mechanism.
Design/methodology/approach
This paper takes the form of an empirical study using a sample of 434 respondents through scene-questionnaire survey in central China.
Findings
It is found that (1) low fit or reactive CSR activities would induce consumers’ psychological contract violation, and the latter has a more significant influence; (2) perceived CSR is negatively related with consumers’ boycott behaviors, but CSR activities would be boycotted if consumers’ psychological contracts are violated; (3) the negative relationship between perceived CSR and consumers’ boycott behaviors would be strengthened by consumers’ altruistic tendency, and the positive relationship between consumers’ psychological contract violation and their boycott behaviors would also be strengthened by their altruistic tendency.
Research limitations/implications
This paper has significant theoretical implications, as it answers the question that when, why and how CSR activities would be boycotted. Besides, it contributes to literature on psychological contract for applying it to CSR research field. Furthermore, the double-edged effect of consumers’ altruistic tendency extends literature on pro-social behaviors.
Social implications
This paper is of interests to corporate management and academics who wish to understand when and why consumers would boycott CSR activities and the factors that would relax consumers’ negative responses.
Originality/value
This is the first paper that investigates when, why and how CSR activities would be boycotted from the perspective of consumers’ psychological contract violation.
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Zhao Duan, Yajuan He and Yuan Zhong
Based on the text mining tools, this paper aims to propose a new method to evaluate the subjectivity and objectivity of corporate social responsibility information disclosure.
Abstract
Purpose
Based on the text mining tools, this paper aims to propose a new method to evaluate the subjectivity and objectivity of corporate social responsibility information disclosure.
Design/methodology/approach
The authors build up a text subjectivity evaluation model of corporate social responsibility reports through meta-analysis; a text mining is conducted to all sample CSR reports released by Chinese listed companies untill March 2016[1]. Furthermore, the authors made an overall and quantitative analysis of the situation which contained changing state, characteristics and abnormal value on the subjectivity and objectivity of information disclosure.
Findings
The results show that the subjectivity scores of social responsibility reports of Chinese listed companies are generally in a normal distribution. The diagram turns out to be a rising trend over the years and increases linearly from 2011 to 2013. Also, the industry heterogeneity and policy control are the main reasons for the formation of the differences, which are significant between different industries and different years.
Originality/value
This paper provides not only an important empirical basis for the research of corporate social responsibility but also a new idea for the non-financial information disclosure as well as objective evaluation of normative text.
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Shahla U. Umar and Tarik A. Rashid
The purpose of this study is to provide the reader with a full study of the bat algorithm, including its limitations, the fields that the algorithm has been applied, versatile…
Abstract
Purpose
The purpose of this study is to provide the reader with a full study of the bat algorithm, including its limitations, the fields that the algorithm has been applied, versatile optimization problems in different domains and all the studies that assess its performance against other meta-heuristic algorithms.
Design/methodology/approach
Bat algorithm is given in-depth in terms of backgrounds, characteristics, limitations, it has also displayed the algorithms that hybridized with BA (K-Medoids, back-propagation neural network, harmony search algorithm, differential evaluation strategies, enhanced particle swarm optimization and Cuckoo search algorithm) and their theoretical results, as well as to the modifications that have been performed of the algorithm (modified bat algorithm, enhanced bat algorithm, bat algorithm with mutation (BAM), uninhabited combat aerial vehicle-BAM and non-linear optimization). It also provides a summary review that focuses on improved and new bat algorithm (directed artificial bat algorithm, complex-valued bat algorithm, principal component analyzes-BA, multiple strategies coupling bat algorithm and directional bat algorithm).
Findings
Shed light on the advantages and disadvantages of this algorithm through all the research studies that dealt with the algorithm in addition to the fields and applications it has addressed in the hope that it will help scientists understand and develop it.
Originality/value
As far as the research community knowledge, there is no comprehensive survey study conducted on this algorithm covering all its aspects.
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Bhaveer Bhana and Stephen Vincent Flowerday
The average employee spends a total of 18.6 h every two months on password-related activities, including password retries and resets. The problem is caused by the user forgetting…
Abstract
Purpose
The average employee spends a total of 18.6 h every two months on password-related activities, including password retries and resets. The problem is caused by the user forgetting or mistyping the password (usually because of character switching). The source of this issue is that while a password containing combinations of lowercase characters, uppercase characters, digits and special characters (LUDS) offers a reasonable level of security, it is complex to type and/or memorise, which prolongs the user authentication process. This results in much time being spent for no benefit (as perceived by users), as the user authentication process is merely a prerequisite for whatever a user intends to accomplish. This study aims to address this issue, passphrases that exclude the LUDS guidelines are proposed.
Design/methodology/approach
To discover constructs that create security and to investigate usability concerns relating to the memory and typing issues concerning passphrases, this study was guided by three theories as follows: Shannon’s entropy theory was used to assess security, chunking theory to analyse memory issues and the keystroke level model to assess typing issues. These three constructs were then evaluated against passwords and passphrases to determine whether passphrases better address the security and usability issues related to text-based user authentication. A content analysis was performed to identify common password compositions currently used. A login assessment experiment was used to collect data on user authentication and user – system interaction with passwords and passphrases in line with the constructs that have an impact on user authentication issues related to security, memory and typing. User–system interaction data was collected from a purposeful sample size of 112 participants, logging in at least once a day for 10 days. An expert review, which comprised usability and security experts with specific years of industry and/or academic experience, was also used to validate results and conclusions. All the experts were given questions and content to ensure sufficient context was provided and relevant feedback was obtained. A pilot study involving 10 participants (experts in security and/or usability) was performed on the login assessment website and the content was given to the experts beforehand. Both the website and the expert review content was refined after feedback was received from the pilot study.
Findings
It was concluded that, overall, passphrases better support the user during the user authentication process in terms of security, memory issues and typing issues.
Originality/value
This research aims at promoting the use of a specific type of passphrase instead of complex passwords. Three core aspects need to be assessed in conjunction with each other (security, memorisation and typing) to determine whether user-friendly passphrases can support user authentication better than passwords.