Abstract
Purpose
The purpose of this paper is to introduce an improved system identification method for small unmanned helicopters combining adaptive ant colony optimization algorithm and Levy’s method and to solve the problem of low model prediction accuracy caused by low-frequency domain curve fitting in the small unmanned helicopter frequency domain parameter identification method.
Design/methodology/approach
This method uses the Levy method to obtain the initial parameters of the fitting model, uses the global optimization characteristics of the adaptive ant colony algorithm and the advantages of avoiding the “premature” phenomenon to optimize the initial parameters and finally obtains a small unmanned helicopter through computational optimization Kinetic models under lateral channel and longitudinal channel.
Findings
The algorithm is verified by flight test data. The verification results show that the established dynamic model has high identification accuracy and can accurately reflect the dynamic characteristics of small unmanned helicopter flight.
Originality/value
This paper presents a novel and improved frequency domain identification method for small unmanned helicopters. Compared with the conventional method, this method improves the identification accuracy and reduces the identification error.
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Keywords
Abstract
Purpose
With the popularity of high-rise buildings, wall inspection and cleaning are becoming more difficult and associated with danger. The best solution is to replace manual work with wall-climbing robots. Therefore, this paper proposes a design method for a rolling-adsorption wall-climbing robot (RWCR) based on vacuum negative pressure adsorption of the crawler. It can improve the operation efficiency while solving the safety problems.
Design/methodology/approach
The pulleys and tracks are used to form a dynamic sealing chamber to improve the dynamic adsorption effect and motion flexibility of the RWCR. The mapping relationship between the critical minimum adsorption force required for RWCR downward slip, longitudinal tipping and lateral overturning conditions for tipping and the wall inclination angle is calculated using the ultimate force method. The pressure and gas flow rate distribution of the negative pressure chamber under different slit heights of the negative pressure mechanism is analysed by the fluid dynamics software to derive the minimum negative pressure value that the fan needs to provide.
Findings
Simulation and test results show that the load capacity of the RWCR can reach up to 6.2 kg on the smooth glass wall, and the maximum load in the case of lateral movement is 4.2 kg, which verifies the rationality and effectiveness of the design.
Originality/value
This paper presents a new design method of a RWCR for different rough wall surfaces and analyses the ultimate force state and hydrodynamic characteristics.
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Jian-Ping Wang, Mei-Ru Wang, Jian-Lan Zhou, Qing-Jun Zuo and Xun-Xian Shi
The purpose of this study is to develop optimal evacuation plan to provide valuable theoretical and practical insight in the fire evacuation work of similar structures, by…
Abstract
Purpose
The purpose of this study is to develop optimal evacuation plan to provide valuable theoretical and practical insight in the fire evacuation work of similar structures, by proposing a systematic simulation-based guided-evacuation agent-based model (GAM) and a three-stage mathematical evacuation model to investigate how to simulate, assess and improve the performance efficiency of the evacuation plan.
Design/methodology/approach
The authors first present the self-evacuation and guided-evacuation models to determine the optimal evacuation plan in ship chamber. Three key performance indicators are put forward to quantitatively assess the evacuation performance within the two fire scenarios. The evacuation model in tower is built to obtain the dividing points of the three different fire evacuation plans.
Findings
The study shows that the optimal evacuation plan determined by the GAM considering social relationships effectively relieves the congestion or collision of evacuees and improves the evacuation uniformity. The optimal evacuation plan not only solves the crush caused by congestion or collision of evacuees but also can greatly shorten the evacuation time for passenger ship fire.
Originality/value
This study establishes the GAM considering the interactive evacuee characteristics and the proportion of evacuees guided by the crew members to make the optimal evacuation plan more time-efficient. The self-evacuation process is simulated to assess the performance of the guided-evacuation strategies, which are used to verify the effectiveness and feasibility of the optimal evacuation plan in this research.
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This study aims to show that the best-performing realized measures vary across markets when it comes to forecast real estate investment trust (REIT) volatility. This finding…
Abstract
Purpose
This study aims to show that the best-performing realized measures vary across markets when it comes to forecast real estate investment trust (REIT) volatility. This finding provides little guidance for practitioners on which one to use when facing a new market. The authors attempt to fill the hole by seeking a common estimator, which can study for different markets.
Design/methodology/approach
The authors do so by drawing upon the general forecasting literature, which finds that combinations of individual forecasts often outperform even the best individual forecast. The authors carry out the study by first introducing a number of commonly used realized measures and then considering several different combination strategies. The authors apply all of the individual measures and their different combinations to three major global REIT markets (Australia, UK and US).
Findings
The findings show that both unconstrained and constrained versions of the regression-based combinations consistently rank among the group of best forecasters across the three markets under study. None of their peers can do it including the three simple combinations and all of the individual measures. The conclusions are robust to the choice of evaluation metrics and of the out-of-sample evaluation periods.
Originality/value
The study provides practitioners with easy-to-follow insights on how to forecast REIT volatility, that is, use a regression-based combination of individual realized measures. The study has also extended the thin real estate literature on using high-frequency data to examine REIT volatility.
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Keywords
Jian Zhou and Jianli Liu
Visual quality control on raw textile fabrics is a vital process in weaving factories to ensure their exterior quality (visual defects or imperfection) satisfying customer…
Abstract
Purpose
Visual quality control on raw textile fabrics is a vital process in weaving factories to ensure their exterior quality (visual defects or imperfection) satisfying customer requirements. Commonly, this critical process is manually conducted by human inspectors, which can hardly provide a fast and reliable inspection results due to fatigue and subjective errors. To meet modern production needs, it is highly demanded to develop an automated defect inspection system by replacing human eyes with computer vision.
Design/methodology/approach
As a structural texture, fabric textures can be effectively represented by a linearly summation of basic elements (dictionary). To create a robust representation of a fabric texture in an unsupervised manner, a smooth constraint is imposed on dictionary learning model. Such representation is robust to defects when using it to recover a defective image. Thus an abnormal map (likelihood of defective regions) can be computed by measuring similarity between recovered version and itself. Finally, the total variation (TV) based model is built to segment defects on the abnormal map.
Findings
Different from traditional dictionary learning method, a smooth constraint is introduced in dictionary learning that not only able to create a robust representation for fabric textures but also avoid the selection of dictionary size. In addition, a TV based model is designed according to defects' characteristics. The experimental results demonstrate that (1) the dictionary with smooth constraint can generate a more robust representation of fabric textures compared to traditional dictionary; (2) the TV based model can achieve a robust and good segmentation result.
Originality/value
The major originality of the proposed method are: (1) Dictionary size can be set as a constant instead of selecting it empirically; (2) The total variation based model is built, which can enhance less salient defects, improving segmentation performance significantly.
Details
Keywords
Junping Qiu, Zhongyang Xu, Haibei Luo, Jianing Zhou and Yu Zhang
Establishing and developing digital science and education evaluation platforms (DSEEPs) have several practical implications for the development of China's science, technology and…
Abstract
Purpose
Establishing and developing digital science and education evaluation platforms (DSEEPs) have several practical implications for the development of China's science, technology and education. Identifying and analyzing the key factors influencing DSEEP user experience (UX) can improve the users' willingness to use the platform and effectively promote its sustainable development.
Design/methodology/approach
First, a literature survey, a five-element model of UX and semi-structured interviews were used in this study to develop a DSEEP UX-influencing factor model, which included five dimensions and 22 influencing factors. Second, the model validity was verified using questionnaire data. Finally, the key influencing factors were identified and analyzed using a fuzzy decision-making trial and evaluation laboratory (fuzzy-DEMATEL) method.
Findings
Fourteen influencing factors, including diverse information forms and comprehensive information content, are crucial for the DSEEP UX. Its optimization path is “‘Function Services’ → ‘Information Resources’ → ‘Interaction Design’ → ‘Interface Design’ and ‘Visual Design’.” In this regard, platform managers can take the following measures to optimize UX: strengthening functional services, improving information resources, enhancing the interactive experience and considering interface effects.
Originality/value
This study uses a combination of qualitative and quantitative research methods to determine the key influencing factors and optimization path of DSEEP UX. Optimization suggestions for UX are proposed from the perspective of platform managers, who provide an effective theoretical reference for innovating and developing a DSEEP.
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Kankan Qi, Yanchi Guo and Jian Zhou
The problem of fabric defect detection is a particularly challenging task, as the fabric defects occupy only a small portion of the image pixels and it is difficult to collect…
Abstract
Purpose
The problem of fabric defect detection is a particularly challenging task, as the fabric defects occupy only a small portion of the image pixels and it is difficult to collect sufficient samples for training deep learning-based models. The purpose of this work is to present a novel self-supervised learning method to address this problem.
Design/methodology/approach
In order to solve the problem of lack of defect samples, based on the fabric-specific degree of texture regularity, we propose an anomaly generation method to create synthetic fabric defects by destroying the normal fabric texture. To improve the detection of defects of different sizes, a global–local parallel detection mechanism is proposed. A self-supervised model including an anomaly generation module, a reconstruction subnetwork and a discriminative subnetwork is established to achieve model training without prior anomaly information.
Findings
The proposed method features self-supervised training, does not require no labelled anomaly data and detects anomalies by distinguishing their distance from normal samples at both global and local levels. When tested on four fabric datasets, our approach outperforms state-of-the-art unsupervised and self-supervised methods and achieves significantly higher localization accuracy.
Originality/value
A high-fidelity fabric defects synthesis method is presented to alleviate the problem of collecting numerous fabric defects, providing a reference for other surface anomaly detection problems. The proposed global–local parallel detection mechanism can serve as a reference for other methods dedicated to detecting particular anomalies. The proposed self-supervised network model can effectively locate fabric anomalies without prior labelling information, which could be used as a framework for other model designs.
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Yang Li, Jinke Gao, Jianing Zhou, Tong Zhu and Zhilei Jiang
Cutting force prediction is pretty important for manufacture management. Thus, the purpose of this paper is to obtain the cutting force of the machining process with high…
Abstract
Purpose
Cutting force prediction is pretty important for manufacture management. Thus, the purpose of this paper is to obtain the cutting force of the machining process with high efficiency and low cost. A method based on the improved auto regressive moving average (ARMA) model is proposed for cutting force predictions in milling process.
Design/methodology/approach
First, classification and normalization are made for initial cutting force. Second, the cutting force sequences are compressed followed singular and valid value removed. At last, the improved ARMA model is used for cutting force fit and extrapolation considered the time domain characteristics.
Findings
A series of cutting force with the spindle speed 595r/min is carried out in the research. It is showed that the mean absolute percentage error value of cutting force extrapolation results which is based on the improved model is smaller. The percentage value is approximately 5.80%. Then the root mean square error test value is only 72.49, which is smaller than that with other traditional method, such as hidden Markov model. The extrapolation results with the proposed model performed good consistency and accuracy in terms of peaks, valleys and volatility compared with the experiment results.
Originality/value
The proposed method that is based on the improved ARMA model can be used for cutting force predictions conveniently. And the predictions can be used for improving the qualities in milling process.
Details
Keywords
Jian Zhou, Qiuyu Zhang, Hepeng Zhang, Jiaojun Tan, Shaojie Chen, Qing Liu, Mingliang Ma and Tiejun Xin
The purpose of this paper is to evaluate the properties of several thiol-acrylate photosensitive systems and compare with corresponding acrylate free-radical systems. The…
Abstract
Purpose
The purpose of this paper is to evaluate the properties of several thiol-acrylate photosensitive systems and compare with corresponding acrylate free-radical systems. The potential stereolithography applications of thiol–ene photosensitive systems are also discussed.
Design/methodology/approach
In the both thiol–ene and acrylate free-radical photosensitive systems, various key performances were characterized. The function group conversions were characterized by real-time Fourier transform infrared spectroscopy. The tension strength was determined according to the standard ASTM D638-2003, the flexible strength was determined according to ASTM D790-07 and the hardness was measured according to ASTM D2240-05. The volume shrinkage was measured by dilatometer method. The glass transition temperature was analyzed by differential scanning calorimeter.
Findings
As adding mercapto propionates into acrylate system, the inhibition of polymerization by oxygen was controlled and the flexible performance was improved. In addition, the photosensitive resin showed better tension strength, higher elongation at break and lower volume shrinkage. Among the four mercapto propionates, rigid TEMPIC showed most obvious affect, followed hexa-functional DPMP, tetra-functional PETMP and tri-functional TMMP.
Originality/value
Although the thiol–ene photosensitive resin has unmatched advantages in performance, there are no reports on the thiol–ene photosensitive resin in the stereolithography application. In this study, thiol–ene photopolymerization material was first tentatively implemented in stereolithography area. Several critical performance parameters were compared between thiol–ene and acrylate free-radical photosensitive systems.
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Keywords
Yong Yin, Jian Zhou, Chaoyong Zhang and Dejun Chen
The purpose of this paper is to discuss an adaptive SLA mechanism for service sharing in virtual environment, which can organize and govern QoS items in terms of service execution…
Abstract
Purpose
The purpose of this paper is to discuss an adaptive SLA mechanism for service sharing in virtual environment, which can organize and govern QoS items in terms of service execution time, reliability, and availability, and provides a common understanding about services, responsibilities, priorities, guarantees and warranties-related virtual cooperative issues.
Design/methodology/approach
The management framework for SLA is introduced, based on which the whole process including SLA contract, adaptive SLA negotiation strategy, SLA deployment and SLA assessment are discussed, and the prototype is implemented in the cloud manufacturing platform.
Findings
A proposed SLA framework for service sharing in virtual environments is given; electronic contracts are designed in the framework for encapsulating measurable aspects of service level agreements so as to provide common understanding about the service; and an improved SLA negotiation strategy with three phases is presented for the dynamicity of the virtual services.
Originality/value
The paper presents a very useful adaptive SLA mechanism for service sharing in virtual environments that can be utilized in concurrent or future advanced manufacturing modes.