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
Yubing Dong, Chen Qian, Jian Lu and Yaqin Fu
Epoxy (EP) and polye-caprolactone (PCL) are typical dual-shape memory polymer (DSMP). To get excellent triple-shape memory effect (TSME) polymer composites which are made from EP…
Abstract
Purpose
Epoxy (EP) and polye-caprolactone (PCL) are typical dual-shape memory polymer (DSMP). To get excellent triple-shape memory effect (TSME) polymer composites which are made from EP and PCL. Miscible PCL/EP blend composites have been investigated and compared to the TSMEs with electrospun PCL microfiber membranes/EP composites. Clay montmorillonite (MMT)-modified electrospun PCL microfiber membranes were prepared to improve the shape memory fixities of electrospun PCL microfiber membranes/EP composites.
Design/methodology/approach
The morphologies of electrospun PCL microfiber membranes and the cross section of PCL/EP composites were studied using a field emission scanning electron microscope (FE-SEM), and the existence of MMT was confirmed by a transmission electron microscope. Thermal mechanical properties were observed by a differential scanning calorimeter (DSC) and a dynamic thermomechanical analysis machine, and the TSMEs were also determined through dynamic mechanical analysis.
Findings
Results indicate that the TSMEs of electrospun PCL microfiber membranes/EP composites were excellent, whereas the TSMEs of PCL/EP blend composites were poor. The TSMEs of PCL electrospun microfiber membranes/EP composites significantly improved with the addition of the PCL electrospun microfiber modified with moderate MMT.
Research limitations/implications
Adding a moderate content of MMT into the electrospun PCL fibers, could improve the TSME of the PCL fiber membranes/EP composites. This study was to create a simple and effective method that can be applied to improve the performance of other SMP.
Originality/value
A novel triple-shape memory composite were made from dual-shape memory EP and electrospun PCL fiber membranes.
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Keywords
Jian Lu, Suduo Xue, Renjie Liu and Xiongyan Li
In order to optimize SCSWIRC, the simplification and further optimization method is proposed. SCSWIRC's optimization includes two levels. The first level refers to simplifying…
Abstract
Purpose
In order to optimize SCSWIRC, the simplification and further optimization method is proposed. SCSWIRC's optimization includes two levels. The first level refers to simplifying structural system from the perspective of components; the second level refers to optimizing components' sectional areas from the perspective of mechanics. The first level aims to remove redundant components, and the second level aims to reduce structural self-weight based on the first level. The purpose of the paper is to simplify SCSWIRC's structural system and optimize structural self-weight and reduce construction forming difficulty.
Design/methodology/approach
Grid-jumping layout and multi-objective optimization method is used to simplify and further optimize Spatial cable-truss structure without inner ring cables (SCSWIRC). Grid-jumping layout is used to simplify remove redundant components, and multi-objective optimization method is used to reduce structural self-weight. The detailed solving process is given based on grid-jumping layout and multi-objective optimization method.
Findings
Take SCSWIRC with a span of 100m as an example to verify the feasibility and correctness of the simplification and further optimization method. The optimization results show that 12 redundant components are removed and the self-weight reduces by 3.128t from original scheme to grid-jumping layout scheme 1. The self-weight reduces from 36.007t to 28.231t and feasible coefficient decreases from 1.0 to 0.627 from grid-jumping layout scheme 1 to multi-objective optimization scheme. The simplification and further optimization can not only remove the redundant components and simplify structural system to reduce construction forming difficulty, but also optimize structural self-weight under considering structural stiffness to reduce project costs.
Originality/value
The proposed method firstly simplifies SCSWIRC and then optimizes the simplified SCSWIRC, which can solve the optimization problem from the perspective of components and mechanics. Meanwhile, the optimal section solving method can be used to obtain circular steel tube size with the optimal stiffness of the same areas. The proposed method successfully solves the problem of construction forming and project cost, which promotes the application of SCSWIRC in practical engineering.
Details
Keywords
Jing Wang, Yinghan Wang, Yichuan Peng and Jian John Lu
The operation safety of the high-speed railway has been widely concerned. Due to the joint influence of the environment, equipment, personnel and other factors, accidents are…
Abstract
Purpose
The operation safety of the high-speed railway has been widely concerned. Due to the joint influence of the environment, equipment, personnel and other factors, accidents are inevitable in the operation process. However, few studies focused on identifying contributing factors affecting the severity of high-speed railway accidents because of the difficulty in obtaining field data. This study aims to investigate the impact factors affecting the severity of the general high-speed railway.
Design/methodology/approach
A total of 14 potential factors were examined from 475 data. The severity level is categorized into four levels by delay time and the number of subsequent trains that are affected by the accident. The partial proportional odds model was constructed to relax the constraint of the parallel line assumption.
Findings
The results show that 10 factors are found to significantly affect accident severity. Moreover, the factors including automation train protection (ATP) system fault, platform screen door and train door fault, traction converter fault and railway clearance intrusion by objects have an effect on reducing the severity level. On the contrary, the accidents caused by objects hanging on the catenary, pantograph fault, passenger misconducting or sudden illness, personnel intrusion of railway clearance, driving on heavy rain or snow and train collision against objects tend to be more severe.
Originality/value
The research results are very useful for mitigating the consequences of high-speed rail accidents.
Details
Keywords
Zhongyi Wang, Haihua Chen, Chengzhi Zhang, Wei Lu and Jian Wu
JIAN Lü, JIN-BIAO ZHONG and CHUN WEI
In this paper sisal fibre (SF) was pretreated by alkali, KH-550, and steam explosion. Then sisal fibre/phenol formaldehyde (SF/PF) composites were prepared through compression…
Abstract
In this paper sisal fibre (SF) was pretreated by alkali, KH-550, and steam explosion. Then sisal fibre/phenol formaldehyde (SF/PF) composites were prepared through compression molding. The effects of the sisal fibre addition mode and sisal/glass (SF/GF) hybrid phenol formaldehyde composites with glass/sisal weight ratio on mechanical properties, thermal properties, water absorption properties and electrically insulating properties were studied. Meanwhile, the effects of sisal treatments were also examined. Results indicate that polymerization-filling is a novel synthesizing method and KH-550 treatment is an ideal method for the modification of SF. The SF/PF composites made by the polymerization-filling method increased by 17.61%, 7.16% and 12.25% in impact strength, bending strength and bending modulus respectively compared with using the conventional physical blending method. SF/GF/PF composites showed higher mechanical properties when SF/GF was 1/1, and thermal properties improved with the addition of GF; sisal fibre and glass fibre exhibited positive hybrid effect in water absorption properties while negative hybrid effect in insulating properties. A study of fibre-matrix interaction and fracture behavior of the fractured surfaces of the composites was also made by scanning electron micrographs.
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Anna Essén and Solveig Wikström
This paper aims to explore the role of emotions in consumers' evaluations of service quality.
Abstract
Purpose
This paper aims to explore the role of emotions in consumers' evaluations of service quality.
Design/methodology/approach
The study uses empirical qualitative data from in‐depth interviews with 26 senior citizens who are consumers of long‐term residential care services in a Swedish rural community. The empirical findings are analysed inductively in terms of dimensions derived from the literature on the role of emotions in consumers' evaluations of service quality.
Findings
When explaining their overall evaluations of service quality, the respondents referred exclusively to service dimensions that had evoked emotional reactions. However, although these service dimensions were the only ones to influence the consumers' perceptions of service quality, respondents tended to reflect about these dimensions in a cognitive manner. The remaining service dimensions, which did not evoke any emotional memories, did not influence the respondents' perceptions of the overall quality of services rendered.
Research limitations/implications
Emotional reactions can direct the attention of consumers to certain service dimensions, and subsequently trigger cognitive evaluations of these dimensions. The emotional and cognitive responses of consumers to services are thus interrelated. More research is needed into the mechanism of this interaction.
Practical implications
Service providers should recognise that consumers' emotional and cognitive reactions are intertwined. For providers of aged‐care services, this study suggests certain service dimensions that are worthy of further attention in seeking positive evaluations of services from users.
Originality/value
Previous research has tended to distinguish between emotional and cognitive evaluations of services. This study challenges this distinction by demonstrating that dimensions that have traditionally been viewed as “non‐emotional” can be influenced by “emotional” reactions. Thus, the study shows that “emotional bias” can lead to some dimensions having a disproportionate influence on overall evaluations of service.
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Ang Chai Im, Leonard Lu Tze Jian, Ooi Poh Kok, Suriani Yaakob, Ching Chin Guan, Ng Sha Shiong, Zainuriah Hassan, Haslan Abu Hassan and Mat Johar Abdullah
The purpose of this paper is to synthesize porous zinc oxide (ZnO) by means of strain etching/wet chemical etching method with the use of 0.5% of nitric acid (HNO3) etchant. The…
Abstract
Purpose
The purpose of this paper is to synthesize porous zinc oxide (ZnO) by means of strain etching/wet chemical etching method with the use of 0.5% of nitric acid (HNO3) etchant. The structural and surface morphological properties of the samples are accessed by using X‐ray diffraction (XRD) and scanning electron microscopy (SEM) characterization techniques.
Design/methodology/approach
ZnO samples used in this work were deposited on the p‐Si (111) substrates by using radio frequency (RF) sputtering technique. Wet chemical etching processes with the use of 0.5% HNO3 etchant was applied on these samples in order to obtain porous structure. The porous ZnO samples are characterized by means of XRD and SEM to access their structural and surface morphological properties.
Findings
The XRD and SEM cross‐sectional measurements revealed that the thickness of the etched ZnO thin films is proportional to the etching time. SEM micrographs show that the surface morphology of ZnO changes over etching time. On the other hand, XRD results indicate that the crystallite sizes of the ZnO(002) decreases when the etching time increases.
Originality/value
The paper shows how porous ZnO thin films have been successfully synthesized by using simple wet chemical etching. SEM images reveal that this method is reliable when producing porous structure ZnO surfaces.
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Keywords
Yongqiang Yang, Jian‐bin Lu, Zhi‐Yi Luo and Di Wang
The purpose of this paper is to investigate the research approach to optimize shape accuracy, dimensional accuracy and density of customized orthodontic production fabricated by…
Abstract
Purpose
The purpose of this paper is to investigate the research approach to optimize shape accuracy, dimensional accuracy and density of customized orthodontic production fabricated by selective laser melting (SLM).
Design/methodology/approach
A series of process experiments were applied to fabricating customized brackets directly by SLM, using 316L stainless steel. Shape accuracy can be optimized through the study on fabricating characteristics of non‐support overhanging structure. A scanning strategy combining contour scanning with orthogonal scanning, which differ in scanning speed and spot compensations, was proposed to improve dimensional accuracy. Scanning laser surface re‐melting was added to enhance the SLM density.
Findings
Optimized SLM parameters lead to high shape precision of customized brackets, and the average size error of bracket slot is less than 10 μm. The customized brackets density is more than 99 per cent, and the surface quality and mechanical properties meet the requirements.
Originality/value
The paper presents the state of the art in SLM of customized production (especially medical appliances) by optimizing part properties. It is the first time that SLM is employed in the manufacturing of customized orthodontic products. It shows the original research on overhanging structure and compound scanning strategy, approach to optimize SLM part accuracy. An improved laser surface re‐melting is employed in the density optimization.