Tian Lei, Nan Gong, Li Wang, Qin Qin Li and Heng Wei Wang
Because of the logic delay in the converter, the minimum turn on time of the switch is influenced by the constant time. When the inductor current gets to the threshold of the…
Abstract
Purpose
Because of the logic delay in the converter, the minimum turn on time of the switch is influenced by the constant time. When the inductor current gets to the threshold of the chip, the control signal will delay for a period. This makes the inductor current rising with the increasing of the clock and leads to the load current out of control. Thus, this paper aims to design an oscillator with a variable frequency protection function.
Design/methodology/approach
This paper presents an oscillator with the reducing frequency applied in the DC-DC converter. When the converter works normally, the operating frequency of the oscillator is 1.5 MHz. So the inductor current has enough time to decay and prevent the power transistor damaging. After the abnormal condition, the converter returns to the normal operating mode automatically.
Findings
Based on 0.5 µm CMOS process, simulated by the HSPICE, the simulation results shows that the frequency of the oscillator linearly decreases from 1.5 MHz to 380 KHz when the feedback voltage less than 0.2 V. The maximum deviation of the oscillator frequency is only 6 per cent from −50°C to 125°C within the power supply voltage of 2.7-5.5 V.
Originality/value
When the light load occurs at the output stage, the oscillator frequency will decrease as the load voltage drops. The test results shows that when the circuit works in the normal condition, the oscillator frequency is 1.5 MHz. When the load decreased, the operating frequency is dropped dramatically.
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Hongxia Ma, Wei Wu, Heng Zhang and Zeyun Wang
This paper aims to propose a new strategy to functionalize zeolitic imidazolate frameworks (ZIF-8) to improve its dispersion stability and tribological properties in lubricating…
Abstract
Purpose
This paper aims to propose a new strategy to functionalize zeolitic imidazolate frameworks (ZIF-8) to improve its dispersion stability and tribological properties in lubricating oil.
Design/methodology/approach
Dialkyl dithiophosphate polydopamine ZIF-8 (DDP@PDA@ZIF-8) was prepared via mussel-inspired chemistry and the Michael addition reaction. The tribological properties of DDP@PDA@ZIF-8 as an additive in the white oil were evaluated with four-ball friction and wear tester at different temperatures. The worn surface was analyzed using X-ray photoelectron spectrum (XPS).
Findings
The as-prepared DDP@PDA@ZIF-8 shows high dispersion stability in the white oil. Tribological results confirmed that the DDP@PDA@ZIF-8 exhibited a small wear scar diameter at 25°C. However, excellent friction reduction and anti-wear properties were observed at 75°C. The XPS result indicates that a series of tribochemical reactions occurred on the worn surface, forming the complex protective film.
Originality/value
This paper provides a study of highly dispersed ZIF-8 as lubrication additives.
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Chen-Chien Hsu, Cheng-Kai Yang, Yi-Hsing Chien, Yin-Tien Wang, Wei-Yen Wang and Chiang-Heng Chien
FastSLAM is a popular method to solve the problem of simultaneous localization and mapping (SLAM). However, when the number of landmarks present in real environments increases…
Abstract
Purpose
FastSLAM is a popular method to solve the problem of simultaneous localization and mapping (SLAM). However, when the number of landmarks present in real environments increases, there are excessive comparisons of the measurement with all the existing landmarks in each particle. As a result, the execution speed will be too slow to achieve the objective of real-time navigation. Thus, this paper aims to improve the computational efficiency and estimation accuracy of conventional SLAM algorithms.
Design/methodology/approach
As an attempt to solve this problem, this paper presents a computationally efficient SLAM (CESLAM) algorithm, where odometer information is considered for updating the robot’s pose in particles. When a measurement has a maximum likelihood with the known landmark in the particle, the particle state is updated before updating the landmark estimates.
Findings
Simulation results show that the proposed CESLAM can overcome the problem of heavy computational burden while improving the accuracy of localization and mapping building. To practically evaluate the performance of the proposed method, a Pioneer 3-DX robot with a Kinect sensor is used to develop an RGB-D-based computationally efficient visual SLAM (CEVSLAM) based on Speeded-Up Robust Features (SURF). Experimental results confirm that the proposed CEVSLAM system is capable of successfully estimating the robot pose and building the map with satisfactory accuracy.
Originality/value
The proposed CESLAM algorithm overcomes the problem of the time-consuming process because of unnecessary comparisons in existing FastSLAM algorithms. Simulations show that accuracy of robot pose and landmark estimation is greatly improved by the CESLAM. Combining CESLAM and SURF, the authors establish a CEVSLAM to significantly improve the estimation accuracy and computational efficiency. Practical experiments by using a Kinect visual sensor show that the variance and average error by using the proposed CEVSLAM are smaller than those by using the other visual SLAM algorithms.
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Nanshan Wang, Heng Liu and Yi Liu
The purpose of this study is to develop a normal contact stiffness (NCS) model among three disks of the assembled rotor system, which systematically considers the friction…
Abstract
Purpose
The purpose of this study is to develop a normal contact stiffness (NCS) model among three disks of the assembled rotor system, which systematically considers the friction coefficient, the asperities interaction and the elastoplastic contact regime.
Design/methodology/approach
Based on the revised fractal theory, considering the friction effect, the elastoplastic contact regime and the asperities interaction in a simple way, the total NCS among three disks of the rod-fastening rotor bearing system is established. Effects of fractal dimension and roughness, friction coefficient, asperities interaction and material properties on the normal stiffness are investigated by simulations and the relevant comparisons are given for examining the reasonability of the proposed model.
Findings
NCS will decrease when asperities interaction and friction are included. As the load increases, the influences of asperities interaction and friction on stiffness become serious. NCS will be enhanced when the elastoplastic regime is considered.
Originality/value
A comprehensive NCS model is developed. It provides a theoretical basis for the modeling of the NCS for multi-interfaces.
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Lei Hou, Lu Guan, Yixin Zhou, Anqi Shen, Wei Wang, Ang Luo, Heng Lu and Jonathan J.H. Zhu
User-generated content (UGC) refers to semantic and behavioral traces created by users on various social media platforms. While several waves of platforms have come and gone, the…
Abstract
Purpose
User-generated content (UGC) refers to semantic and behavioral traces created by users on various social media platforms. While several waves of platforms have come and gone, the long-term sustainability of UGC activities has become a critical question that bears significance for theoretical understanding and social media practices.
Design/methodology/approach
Based on a large and lengthy dataset of both blogging and microblogging activities of the same set of users, a multistate survival analysis was applied to explore the patterns of users' staying, switching and multiplatforming behaviors, as well as the underlying driving factors.
Findings
UGC activities are generally unsustainable in the long run, and natural attrition is the primary reason, rather than competitive switching to new platforms. The availability of leisure time, expected gratification and previous experiences drive users' sustainability.
Originality/value
The authors adopted actual behavioral data from two generations of platforms instead of survey data on users' switching intentions. Four types of users are defined: loyal, switcher, multiplatformer and dropout. As measured by the transitions among the four states, the different sustainability behaviors are thereby studied via an integrated framework. These two originalities bridge gaps in the literature and offer new insights into exploring user sustainability in social media.
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Abstract
Purpose
This paper aims to select an appropriate contact force model and apply it to the interaction model between the balls and the cage in the rolling bearings to describe the elastic–plastic collision phenomena between the two.
Design/methodology/approach
Taking the ball–disk collision mode as an example, several main contact force models were compared and analyzed through simulation and experiment. In addition, based on the consideration of yield strength of materials and initial collision velocity, a variable recovery coefficient model was proposed, and its validity and accuracy were verified by the ball–disk collision experiments. Then, respectively, the Flores model and the Hertz model were applied to the interaction between the balls and the cage, and the dynamics simulation results were compared.
Findings
The results indicate that the Flores model has good regression of recovery coefficient, indicating good applicability for both elastic and elastic–plastic contacts and can be applied to the contact collision situations of various materials. Under certain working conditions, there are significant differences in the dynamics results of rolling bearings simulated using the Flores model and Hertz model, respectively.
Originality/value
This paper applies the Flores model with variable recovery coefficients to the dynamics simulation analysis of ball bearings to solve the elastic–plastic collision problem between the rolling elements and the cage that cannot be reasonably handled by the Hertz model.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0138/
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Heng Xiao, Wei-Hao Yan, Lin Zhan and Si-Yu Wang
A new and explicit form of the elastic strain-energy function for modeling large strain elastic responses of soft solids is constructed based on Hencky's logarithmic strain tensor.
Abstract
Purpose
A new and explicit form of the elastic strain-energy function for modeling large strain elastic responses of soft solids is constructed based on Hencky's logarithmic strain tensor.
Design/methodology/approach
Well-designed invariants of the Hencky strain are introduced for characterizing deformation modes and, furthermore, a new interpolating technique is proposed for combining piecewise splines into a single smooth function.
Findings
With this new form and this new technique, objectives in three respects may be achieved for the first time.
Originality/value
First, no adjustable parameters need to be treated. Second, large strain responses for three benchmark modes are derivable in a decoupled sense without involving strongly nonlinear coupling effects. Finally, large strain data may be automatically and accurately matched for three benchmark modes, including uniaxial, equi-biaxial and plane-strain extension. Numerical examples are presented and compared with usual approaches.
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Heng-yang Lu, Jun Yang, Wei Fang, Xiaoning Song and Chongjun Wang
The COVID-19 has become a global pandemic, which has caused large number of deaths and huge economic losses. These losses are not only caused by the virus but also by the related…
Abstract
Purpose
The COVID-19 has become a global pandemic, which has caused large number of deaths and huge economic losses. These losses are not only caused by the virus but also by the related rumors. Nowadays, online social media are quite popular, where billions of people express their opinions and propagate information. Rumors about COVID-19 posted on online social media usually spread rapidly; it is hard to analyze and detect rumors only by artificial processing. The purpose of this paper is to propose a novel model called the Topic-Comment-based Rumor Detection model (TopCom) to detect rumors as soon as possible.
Design/methodology/approach
The authors conducted COVID-19 rumor detection from Sina Weibo, one of the most widely used Chinese online social media. The authors constructed a dataset about COVID-19 from January 1 to June 30, 2020 with a web crawler, including both rumor and non-rumors. The rumor detection task is regarded as a binary classification problem. The proposed TopCom model exploits the topical memory networks to fuse latent topic information with original microblogs, which solves the sparsity problems brought by short-text microblogs. In addition, TopCom fuses comments with corresponding microblogs to further improve the performance.
Findings
Experimental results on a publicly available dataset and the proposed COVID dataset have shown superiority and efficiency compared with baselines. The authors further randomly selected microblogs posted from July 1–31, 2020 for the case study, which also shows the effectiveness and application prospects for detecting rumors about COVID-19 automatically.
Originality/value
The originality of TopCom lies in the fusion of latent topic information of original microblogs and corresponding comments with DNNs-based models for the COVID-19 rumor detection task, whose value is to help detect rumors automatically in a short time.
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Heng-Hui Wu, Pornchanoke Tipgomut, Henry F.L. Chung and Wei-Kuang Chu
As consumers read multiple reviews, so consumer review consistency is important. The purpose of this paper is to investigate the role of consumer review consistency in influencing…
Abstract
Purpose
As consumers read multiple reviews, so consumer review consistency is important. The purpose of this paper is to investigate the role of consumer review consistency in influencing attitudes toward brands by examining its underlying effect on consumers’ emotions after they read consistent consumer reviews. In addition, the moderation effect of hedonic and utilitarian purchase values on positive consumer emotions and attitudes toward brands is explored.
Design/methodology/approach
This study used a quantitative design in which 329 participants – undergraduate and MBA students at a university in Taiwan – were asked to complete online questionnaires. To generalize the results, the questions in the questionnaire were based on any consumer reviews that the participants had recently browsed.
Findings
Consumer review consistency positively influences attitudes toward brands. Positive emotions are also developed when reading consistent consumer reviews, and this positively influences consumers’ attitudes toward brands. However, positive emotions are not derived from consistent consumer reviews in all contexts. The results show that positive emotions work well when consumers shop using hedonic value. Positive emotions create positive consumers’ attitudes toward a brand when they shop using hedonic value, but this significant effect does not occur when consumers shop using utilitarian value.
Research limitations/implications
This study’s results suggest that only investigating the quality of a consumer review or other aspects of a single review might overlook the impact of consumer review consistency, as consumers read multiple reviews. Consumer review consistency plays an important role in brand effectiveness, as consumers form positive attitudes toward brands when they read consistent reviews. Positive emotions can strengthen consumers’ attitudes toward a brand. Moreover, positive emotions increase positive attitudes toward brands only when consumers shop using hedonic value. However, positive emotions do not enhance consumers’ attitudes if they shop using utilitarian value.
Practical implications
Rather than focusing on the quality of a single review, online shops should carefully consider consumer review consistency. Although positive reviews are better than negative reviews, it is quite difficult for every shop to maintain 100 percent positive reviews. Therefore, maintaining and offering quality products and services are rather important to acquiring more positive reviews. Online shops should consider experimental marketing strategies when managing online shops. The layout of online sites that show consistent consumer reviews can provide consumers with cues that shorten decision making, especially for products that consumers tend to shop for using hedonic value.
Originality/value
This research extends the previous consumer review literature. Previous research was focused mainly on the quality of consumer reviews or other aspects of a single review. This research shows that focusing a single consumer review is not sufficient, as consumers generally read more than one consumer review. In addition, the role of positive emotions as a mediator between consumer review consistency and attitudes toward a brand was investigated. Furthermore, the moderated mediation effect was applied to investigate the role of shopping value (hedonic vs utilitarian value) as a moderator of positive emotions’ mediation effect.
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Heng Tang and Shoaib Ali
This research intends to analyze the innovation ecosystem factors that play a vital role in firm performance. As a result, large-scale empirical studies on the innovation…
Abstract
Purpose
This research intends to analyze the innovation ecosystem factors that play a vital role in firm performance. As a result, large-scale empirical studies on the innovation ecosystem are rare, and fewer efforts have been made to determine if and how different factors affect the ecosystem models of firms. There has yet to be a substantial empirical study on the innovation ecosystem.
Design/methodology/approach
Data were acquired from Pakistani IT companies. The results show that factors of the innovation ecosystem significantly contribute to business performance. The essential assumption is that resource endowment, organizational culture, knowledge and competence, and technology capability are allied to the innovation ecosystem.
Findings
The findings are crucial from a managerial view because firms must focus on changing their innovation ecosystem factors model to achieve greater performance. Radical changes in the firms will only be worthwhile if they value their resource endowments. To attain superior firm performance via influential factors of the innovation ecosystem, IT administrators need to build organizational cultural capacities to adapt to changes brought on by digitization quickly and effectively. However, this must be supplemented by improving organizational knowledge, competencies and technological capabilities to enable organizations to modify their ecosystems.
Originality/value
Eventually, firms can better respond to changes in their settings if they combine these variables by implementing an effective innovation ecosystem model, which leads to greater sector and superior financial performance.