Zhiyu Ni, Yewei Zhang, Xinhui Shen, Shunan Wu and Zhigang Wu
When a manipulator captures an unknown space object, inertia parameters of endpoint payload should be timely obtained to handle possible unexpected parameter variations and…
Abstract
Purpose
When a manipulator captures an unknown space object, inertia parameters of endpoint payload should be timely obtained to handle possible unexpected parameter variations and monitor the system’s operating conditions. Therefore, this study aims to present an identification method for estimating the inertia parameter of the payload carried by a flexible two-link space manipulator.
Design/methodology/approach
The original nonlinear dynamics model of the manipulator is linearized at a selected working point. Subsequently, the system modal frequencies with and without payload are determined using the subspace identification algorithm, and the difference of these frequencies is computed. Furthermore, by adjusting the structural configuration of the manipulator, multiple sets of frequency differences are obtained. Therefore, the inertia parameters of the payload, i.e. the mass and the moment of inertia, can be derived from the frequency differences by solving a least-squares problem.
Findings
The proposed method can effectively estimate the payload parameters and has satisfactory identification accuracy.
Practical implications
The approach’s implementation provides a practical reference for determining inertia parameters of an unknown space target in the capture process.
Originality/value
The study proposes a novel method for identifying the inertia parameters of the payload of a flexible two-link space manipulator using the estimated system frequencies.
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Keywords
Song Li, Bo Fang, Tianzhi Yang, Yewei Zhang, Lijun Tan and Wenhu Huang
The purpose of this paper is to analyze a new, whole‐spacecraft isolator and its performance of vibration isolation, which has been designed to ensure spacecraft safety at the…
Abstract
Purpose
The purpose of this paper is to analyze a new, whole‐spacecraft isolator and its performance of vibration isolation, which has been designed to ensure spacecraft safety at the launching stage.
Design/methodology/approach
The design is based on the analysis of fractional derivative stress‐strain constitutive relationship of viscoelastic materials. First, the authors study the constitutive relationships for viscoelastic solid of the damping materials, then the authors introduce the results obtained to the equations of motion for the damped isolator.
Findings
By performing a series of transformation, the authors obtain the analytical solution of the equations. It is shown that the results compare favourably to the numerical simulations and experiments. In addition, a saturation phenomenon for the first order damping ratio is also discussed.
Practical implications
It is found that the constitutive relationships written in terms of the fractional calculus can be applied in the system function of the whole‐spacecraft vibration isolator. Such relationships, developed previously from a model analysis base, have been shown to be useful tools for engineering analyses.
Originality/value
Some suggestions are given to improve the design of viscoelastic whole‐spacecraft isolators. The establishment of a theoretical basis for the new fractional differential dynamical system enhances their value, as they may now be used with increased reliability of satellite.
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Yewei Ouyang, Guoqing Huang and Shiyi He
There are many safety hazards in construction workplaces, and inattention to the hazards is the main reason why construction workers failed to identify the hazards. Reasonably…
Abstract
Purpose
There are many safety hazards in construction workplaces, and inattention to the hazards is the main reason why construction workers failed to identify the hazards. Reasonably allocating attention during hazard identification is critical for construction workers’ safety. However, adverse working environments in job sites may undermine workers’ attention. Previous studies failed to investigate the impacts of environmental factors on attention allocation, which hinders taking appropriate measures to eliminate safety incidents when encountering adverse working environments. This study aims to examine the effects of workplace noise and heat exposure on workers’ attention allocation during construction hazard identification to fill the research gap.
Design/methodology/approach
This study applied an experimental study where a within-subject experiment was designed. Fifteen construction workers were invited to perform hazard identification tasks in panoramic virtual reality. They were exposed to three noise levels (60, 85 and 100 dBA) in four thermal conditions (26°C, 50% RH; 33°C, 50% RH; 30°C, 70% RH; 33°C, 70% RH). Their eye movements were recorded to indicate their attention allocation under each condition.
Findings
The results show that noise exposure reduced workers’ attention to hazardous areas and the impacts increased with the noise level. Heat exposure also reduced the attention, but it did not increase with the heat stress but with subjects’ thermal discomfort. The attention was impacted more by noise than heat exposure. Noise exposure in the hot climate should be more noteworthy because lower levels of noise would lead to significant changes. These visual characteristics led to poorer identification accuracy.
Originality/value
This study could extend the understanding of the relationship between adverse environmental factors and construction safety. Understanding the intrinsic reasons for workers' failed identification may also provide insights for the industry to enhance construction safety under adverse environments.
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Yewei Ouyang, Guoqing Huang and Shiyi He
Safety warnings remind construction workers about dangers and guide them to take necessary actions to avoid potential injuries, which could encourage their safe behavior. Workers’…
Abstract
Purpose
Safety warnings remind construction workers about dangers and guide them to take necessary actions to avoid potential injuries, which could encourage their safe behavior. Workers’ behavior compliance with the safety warnings would be impacted by the risk perception levels induced by the warnings. This study aims to examine whether the design of safety warnings would impact the induced risk perception of workers
Design/methodology/approach
This study compared the risk perception levels of construction workers when processing two forms of safety warnings, i.e., safety signs and safety comics, which are commonly used in construction workplaces. Construction workers (n = 20) volunteered for an experiment with an implicit paradigm to probe how they perceive these safety warnings, using event-related potentials (ERPs) features collected by an electroencephalogram (EEG) sensor to indicate the risk perception level
Findings
The results demonstrated that the design of safety warnings would impact the induced risk perception. The safety signs and safety comics performed differently in inducing the workers’ risk perception. The safety signs representing prohibition and caution warnings induced significantly higher risk perception than the comics, and there were no significant differences regarding direction warnings
Originality/value
This is the first study to compare the risk perception levels between various forms of safety warnings presenting safety information in different ways. The findings would help to expand the knowledge of the relationship between the design of safety warnings and workers’ safety behavioral compliance
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Li Hong, Yewei Wang, Zhongchao Qiu, Jianxian Cai, Zhenjing Yao and Zhitao Gao
The purpose of this paper is to solve the problem of weak low-frequency vibration measurement capability of FBG accelerometer, and propose a FBG accelerometer based on cross reed.
Abstract
Purpose
The purpose of this paper is to solve the problem of weak low-frequency vibration measurement capability of FBG accelerometer, and propose a FBG accelerometer based on cross reed.
Design/methodology/approach
This study proposed a new type FBG acceleration sensor based on cross reeds. When the sensor vibrates, the mass block in the new structure rotates around the center of the cross reeds, which could eliminate the impact of friction, reduce the natural frequency of the sensor and improve its sensitivity. This study theoretically analyzed the impact of several structural parameters on the sensitivity and natural frequency of the proposed sensor and used COMSOL to perform static stress analysis and modal simulation; in this study, a test system was built to test the performance of the proposed sensor.
Findings
The test results revealed that the proposed sensor had a natural frequency of 94 Hz; within a low-frequency range of 1–65 Hz, its sensitivity response was flat, the dynamic range was 81.89 dB, the sensitivity was 243.59 pm/g and the linearity was 99.97%. The cross reeds effectively strengthened the structural stability, the relative standard deviation of the repeatability of the sensor was 0.89% and the transverse crosstalk in the working frequency band was −26.97 dB.
Originality/value
This study innovatively proposes the structure of the two symmetrical cross reeds, which can improve sensitivity by eliminating the influence of friction, and the structure of cross reeds can effectively suppress the influence of lateral crosstalk. The proposed sensor can realize real-time accurate measurement of low-frequency weak vibration signals.
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Wei Suo, Xuxiang Sun, Weiwei Zhang and Xian Yi
The purpose of this study is to establish a novel airfoil icing prediction model using deep learning with geometrical constraints, called geometrical constraints enhancement…
Abstract
Purpose
The purpose of this study is to establish a novel airfoil icing prediction model using deep learning with geometrical constraints, called geometrical constraints enhancement neural networks, to improve the prediction accuracy compared to the non-geometrical constraints model.
Design/methodology/approach
The model is developed with flight velocity, ambient temperature, liquid water content, median volumetric diameter and icing time taken as inputs and icing thickness given as outputs. To enhance the icing prediction accuracy, the model involves geometrical constraints into the loss function. Then the model is trained according to icing samples of 2D NACA0012 airfoil acquired by numerical simulation.
Findings
The results show that the involvement of geometrical constraints effectively enhances the prediction accuracy of ice shape, by weakening the appearance of fluctuation features. After training, the airfoil icing prediction model can be used for quickly predicting airfoil icing.
Originality/value
This work involves geometrical constraints in airfoil icing prediction model. The proposed model has reasonable capability in the fast assessment of aircraft icing.
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Corporate governance has attracted enormous attention both in the area of law and in the area of financial economics. In comparative corporate governance studies, many people have…
Abstract
Corporate governance has attracted enormous attention both in the area of law and in the area of financial economics. In comparative corporate governance studies, many people have devoted their energy to find a best corporate governance model. I argue that a functional analysis does not support the view that there is a single best corporate governance model in the world. I further use the transplantation of an English style takeover law into China to show that the importation of foreign law is not always based on careful analysis whether the imported foreign law is the best in the world. Furthermore, I use the subsequent adjustment of the transplanted English takeover law in China to show that the imported foreign law is subject to local political and economic conditions. If there is no best corporate govern model and the transplantation of foreign law into other countries with different social and political background does not achieve similar objectives, the search for a best corporate governance model is misguided. Just as tort law or constitutional law regimes may have diversified models, so do corporate governance regimes in countries with different historical, social and political backgrounds.
Markus Eckey and Sebastian Memmel
The COVID-19 pandemic has hit different industries and firms with widely differing degrees of severity. The authors investigate whether ownership structure (family vs non-family…
Abstract
Purpose
The COVID-19 pandemic has hit different industries and firms with widely differing degrees of severity. The authors investigate whether ownership structure (family vs non-family) might represent a differentiating factor. The article's purpose is to conduct an initial, descriptive analysis of the impact of COVID-19 on different stock and operating performance measures of listed German companies.
Design/methodology/approach
The authors use a sample of 299 listed companies in Germany and gathered operating as well as stock market performance data following the outbreak of COVID-19. For the purpose of this paper, the authors solely focus on static and descriptive observations thus far. The intention of this paper is to describe potential implications for more differentiated, especially multivariate causal research, on family businesses in a post-COVID world.
Findings
The results indicate that, over the last five years, stock returns of family businesses have been higher than those of non-family firms. This effect seems to have been more pronounced during the first month following the COVID-19 outbreak. When applying operating measures, the outperformance becomes even more evident. The findings therefore seem to support the hypothesis proffered in the literature that family involvement enhances the potential for resilience in such firms.
Originality/value
Scholars on COVID-19 crisis performance have begun to explore firm-level factors related to financial and organizational factors, industry characteristics and country-level factors. The research extends this line of inquiry by probing the importance of family involvement in ownership.