Bo Li, Bo Yuan, Shuai Tang, Yuwen Mao, Dongmei Zhang, Changyun Huang and Bilian Tan
This paper aims to investigate weight-climbing assistance strategy for the biomechanical design of passive knee-assisting exoskeleton (PKAExo) and evaluate a designed PKAExo which…
Abstract
Purpose
This paper aims to investigate weight-climbing assistance strategy for the biomechanical design of passive knee-assisting exoskeleton (PKAExo) and evaluate a designed PKAExo which stores energy when the knee joint flexes and releases the energy to assist ascending when the knee joint extends.
Design/methodology/approach
The authors constructed theoretic modeling of human weight-climbing to analyze characteristics of knee angle and moment. They then conducted camera-based movement analysis, muscle strength and endurance tests and surface electromyography (sEMG) measures to verify the relationship of knee angle and moment with both stair height and load weight. Afterwards, the authors proposed an assistant strategy for passive knee assistance, then gave out designed PKAExo and conducted mechanical experiment to test the knee-assisting torque. Finally, the authors conducted comparison experiment based on measuring the sEMG signals of knee extensor to verify the assistance effect of the PKAExo for weight-climbing.
Findings
The knee extensor produces the maximum force during weight-climbing, and the muscle force provided by knee extensor has significant increasing rate along with the stair height. Thus, the assistance torque of PKAExo is designed to increase nonlinearly along with increasing knee angle. It stores energy when knee flexes and assists when knee extends. Both the mechanical experiment and comparison experiment have demonstrated that the PKAExo is able to provide nonlinear assistance torque for weight-climbing, thus decreasing the average maximum load of knee extensor by about 21 per cent, reducing muscle fatigue and enhancing wearer’s weight-climbing ability.
Originality/value
The authors construct theoretic maximum force model produced by knee extensor for weight-climbing in static situation and conduct a series of experiments to verify and revise the model, which is the fundamental reference for knee-assisting mechanism designed for weight-climbing. The authors have also provided and validated an assistant strategy and the mechanism based on the biomechanical analysis, which aims to translate wearer’s energy-providing mode form high load to mid-low load by storing energy when knee flexes and assisting when knee extends. The PKAExo decreases the maximum load of knee extensor, reduces muscle fatigue and helps people to easily climb with load.
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Swagat Pati, Kanungo Barada Mohanty and Sanjeeb Kumar Kar
This paper aims to demonstrate the efficacy of fuzzy logic controller (FLC) over proportional integral (PI) and sliding mode controller (SMC) for maintaining flat voltage profile…
Abstract
Purpose
This paper aims to demonstrate the efficacy of fuzzy logic controller (FLC) over proportional integral (PI) and sliding mode controller (SMC) for maintaining flat voltage profile at the load bus of a single-generator-based micro-grid system using STATCOM.
Design/methodology/approach
A STATCOM is used to improve the voltage profile of the load bus. The performance of the STATCOM is evaluated by using three different controllers: PI controllers, FLCs and SMCs. The performance comparison of the controllers is done with different dc bus voltages, different load bus voltage references, various loads such as R-L loads and dynamic loads.
Findings
A comparative analysis is done between the performances of the three different controllers. The comparative study culminates that FLC is found to be superior than the other proposed controllers. SMC is a close competitor of fuzzy controller.
Originality/value
Design of fuzzy logic and SMCs for a STATCOM implemented in a single-generator-based micro-grid system is applied.
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Abstract
Purpose
The purpose of this paper is to focus on the development of highly efficient emission materials for light‐emitting diodes (LEDs).
Design/methodology/approach
The equilibrium geometries of silole‐based derivatives are optimised by means of DFT/B3LYP method with the 6‐31G(d) basis set in this paper. The geometries of single‐excitation are optimised using the ab initio configuration interaction with single excitations/6‐31G(d), the first singlet excited states and optical properties are calculated by using time‐dependent density‐functional theory based on the 6‐31G(d) basis set.
Findings
The highest occupied molecular orbital and lowest unoccupied molecular orbital suffer larger effects from the variation of the substituent groups of methyls and phenyls. The absorption wavelengths of all the cases are similar, but the emission wavelengths are significantly different.
Research limitations/implications
Solid‐state stacking effect is not included in this paper.
Originality/value
In view of the application of silole‐based derivatives systems, the control of photophysical properties and electronic structures by structural modification is relevant to further molecular design.
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Hongbo Qiu, Wenfei Yu, Shuai Yuan, Bingxia Tang and Cunxiang Yang
The impact of the loop current (LC) on the motor magnetic field in the analysis of the inter-turn short circuit (ITSC) fault is always ignored. This paper made a comparative study…
Abstract
Purpose
The impact of the loop current (LC) on the motor magnetic field in the analysis of the inter-turn short circuit (ITSC) fault is always ignored. This paper made a comparative study on the electromagnetic field of permanent magnet synchronous motors (PMSM). The purpose of this study is to explore the necessary of the LC existing in the fault analysis and the electromagnetic characteristics of the PMSM with the ITSC fault when taking into account the LC.
Design/methodology/approach
Based on the finite element method (FEM), the fault model was established, and the magnetic density of the fault condition was analyzed. The induced electromotive force (EMF) and the LC of the short circuit ring were studied. The three-phase induced EMF and the unbalance of the three-phase current under the fault condition were studied. Finally, a prototype test platform was built to obtain the data of the fault.
Findings
The influence of the fault on the magnetic density was obtained. The current phase lag when the ITSC fault occurs causes the magnetic enhancement of the armature reaction. The mechanism that LC hinders the flux change was revealed. The influence of the fault on the three-phase-induced EMF symmetry, the three-phase current balance and the loss was obtained.
Originality/value
The value of the LC in the short circuit ring and the influence of it on the motor electromagnetic field were obtained. On the basis of the electromagnetic field calculation model, the sensitivity of the LC to the magnetic density, induced EMF, current and loss were analyzed.
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Liming Xiao, Bin Han, Sainan Yang and Shuai Liu
The construction of industrial park in the current development model of circular economy has been widely regarded as one of the important modes of macroeconomic exploration all…
Abstract
The construction of industrial park in the current development model of circular economy has been widely regarded as one of the important modes of macroeconomic exploration all over the world. Therefore, the research on the application of multi-project management theory based on circular economy in the construction of industrial park was proposed in this paper. First, the circular economy and multi-project management theory were expounded in detail. Then, the geographical location of multi project management in Qingyuan recycled plastic industrial park in Guangdong Province and the distribution of each building community were explained. And on this basis, the construction of the park's production, plant areas, residential areas and the planning objectives after completion were analyzed in detail. On the basis of analysis, the multi project management model used in the park was explained. It is pointed out that the construction of the park should be based on its own planning and practical needs, and the appropriate multi project management model should be chosen.
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Shuai Na, Guo-an Tang and Li-fen Chen
Orbital maneuver of the spacecraft can cause large-amplitude vibration of its flexible solar array, which leads to large dynamic stress and a risk of structural failure and…
Abstract
Purpose
Orbital maneuver of the spacecraft can cause large-amplitude vibration of its flexible solar array, which leads to large dynamic stress and a risk of structural failure and fatigue failure. This paper aims to provide a method to reduce such vibration.
Design/methodology/approach
Through controlling the rotation at the root of the solar array, a method of vibration reduction is proposed using zero-placement input shaping technique. Experimental research on a beam scale model of the solar array is performed to verify the effectiveness of the method. Simulation of a detailed example is carried out to investigate whether the method can be applied in engineering.
Findings
The experimental results demonstrate the effectiveness of such method. The simulation results indicate that, by adopting the presented method, the vibration induced by orbital maneuver can be diminished remarkably.
Research limitations/implications
Studies on the robustness of the method are left for further work. Additionally, since only the first-order bending vibration of the flexible solar array is eliminated, further improvements are required such that the stated method can be applied to suppress multi-mode vibration.
Practical implications
An effective method is proposed for spacecraft designers planning to actively suppress the vibration of flexible solar array during the process of orbital maneuver.
Originality/value
This paper fulfils a source of theoretical and experimental studies for orbital maneuver system design and offers practical help for spacecraft designers.
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Shuai Yue, Ben Niu, Huanqing Wang, Liang Zhang and Adil M. Ahmad
This paper aims to study the issues of adaptive fuzzy control for a category of switched under-actuated systems with input nonlinearities and external disturbances.
Abstract
Purpose
This paper aims to study the issues of adaptive fuzzy control for a category of switched under-actuated systems with input nonlinearities and external disturbances.
Design/methodology/approach
A control scheme based on sliding mode surface with a hierarchical structure is introduced to enhance the responsiveness and robustness of the studied systems. An equivalent control and switching control rules are co-designed in a hierarchical sliding mode control (HSMC) framework to ensure that the system state reaches a given sliding surface and remains sliding on the surface, finally stabilizing at the equilibrium point. Besides, the input nonlinearities consist of non-symmetric saturation and dead-zone, which are estimated by an unknown bounded function and a known affine function.
Findings
Based on fuzzy logic systems and the hierarchical sliding mode control method, an adaptive fuzzy control method for uncertain switched under-actuated systems is put forward.
Originality/value
The “cause and effect” problems often existing in conventional backstepping designs can be prevented. Furthermore, the presented adaptive laws can eliminate the influence of external disturbances and approximation errors. Besides, in contrast to arbitrary switching strategies, the authors consider a switching rule with average dwell time, which resolves control problems that cannot be resolved with arbitrary switching signals and reduces conservatism.
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Shuai Han, Tongtong Sun, Yanming Sun and Xi Gao
The COVID-19 outbreak has been effectively controlled in China, but the resulting public psychological crisis is a latent, persistent and torturous disaster. This crisis affects…
Abstract
Purpose
The COVID-19 outbreak has been effectively controlled in China, but the resulting public psychological crisis is a latent, persistent and torturous disaster. This crisis affects not only the individual’s health but also social stability. This study aims to reveal the structure and situation of public psychological crisis during the remission period of the COVID-19 epidemic.
Design/methodology/approach
A questionnaire survey of the psychological crisis was conducted from February to May 2021. Data was collected from 1,056 respondents from different provinces in China.
Findings
The findings reveal the dangerous risks of public psychological crises. The specific results are as follows: first, a hierarchical state structure of psychological crisis is constructed and characterized as a significant gradient decline, namely, anxious state>panic state>depressive state>hostile state. Second, 43.939% of respondents reported an anxious state, 46.780% reported a panic state, 40.909% reported a depressive state, 28.883% reported a hostile state and 22.254% of the respondents had four psychological crisis states. Third, those with 56–65 years of age, equal or below high school and PhD, with monthly family incomes of ¥50,000–¥100,000 and living in the county and city areas have relatively high levels of psychological crisis.
Originality/value
This study enriches the research on the evolution of the psychological crisis in terms of structure and periods. This study also provides substantial evidence for hierarchical intervention and differentiated intervention of psychological crisis.
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Haijing Sun, Jianing Cui, He Wang, Shuai Yang, Souavang Xaikoua, Yong Tan, Xin Zhou, Baojie Wang and Jie Sun
The purpose of this paper is to study the effect of temperature on Zn–Ni alloys in ChCl–Urea.
Abstract
Purpose
The purpose of this paper is to study the effect of temperature on Zn–Ni alloys in ChCl–Urea.
Design/methodology/approach
Based on cyclic voltammetry experiments, the deposition behavior and kinetics of the Zn–Ni alloy are studied. The nucleation process of the Zn–Ni alloy is studied in detail via chronoamperometry experiments. The effects of the deposition temperature on the microstructure, Ni content and phase composition of Zn–Ni alloy coatings are investigated via scanning electron microscopy and X-ray diffraction (XRD) combined with classical thermodynamics.
Findings
The results show that with increasing temperature, the reduction peak shifts toward a more positive electric potential, which is beneficial for the co-electric deposition process, and the diffusion coefficient is estimated. With increasing temperature, the nucleation process of the Zn–Ni alloy becomes a three-dimensional instantaneous nucleation, the typical kinetic parameters are determined using the standard 3D growth proliferation control model and the Gibbs free energy is estimated. The Zn–Ni alloy coatings are prepared via normal co-deposition. With increasing temperature, the degree of crystallinity increases, the coating gradually becomes uniform and compact and the XRD peak intensity increases.
Originality/value
The nucleation process of the Zn–Ni alloy at different temperatures is analyzed. The diffusion coefficient D and Gibbs free energy are calculated. The contribution of the three processes at different temperatures is analyzed. The effect of temperature on the morphology of the Zn–Ni alloy coatings is studied.
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Jian Feng Li, Qin Shi, HeJun Zhu, ChenYu Huang, Shuai Zhang, Weixiang Peng and ChangSheng Li
This paper aims to clarify the size and morphology of transition metal dichalcogenides has an impact on lubrication performance of Cu-based composites. This study is intended to…
Abstract
Purpose
This paper aims to clarify the size and morphology of transition metal dichalcogenides has an impact on lubrication performance of Cu-based composites. This study is intended to show that Cu-based electrical contact materials containing Nb0.91Ti0.09Se2 have better electrical and tribological properties than those containing NbSe2. The tribological properties of Cu-based with different Ti-dopped NbSe2 content were also discussed.
Design/methodology/approach
The NbSe2 and Nb0.91Ti0.09Se2 particles were fabricated by thermal solid state reaction method. The powder metallurgy technique was used to fabricate composites with varying Nb0.91Ti0.09Se2 mass fraction. The phase composition of Cu-based composites was identified by X-ray diffraction, and the morphology of NbSe2/Nb0.91Ti0.09Se2 and the worn surface of composites were characterized by scanning electron microscopy and transmission electron microscopy. In addition, the tribological properties of composites were appraised using a ball-on-disk multi-functional tribometer. The data of friction coefficient and resistivity were analyzed and the corresponding conclusion was drawn.
Findings
In comparison with the pure copper, Cu-based composites containing Nb0.91Ti0.09Se2/NbSe2 had a lower friction coefficient, illustrating the Nb0.91Ti0.09Se2 with nano-size particles prepared in this work is a perfect choice for the fabrication of excellent electrical contact composites. Compared to composites with NbSe2, composites containing Nb0.91Ti0.09Se2 have better tribological and electrical properties.
Research limitations/implications
Because of the use of thermal solid state reaction method, the size of NbSe2 and Nb0.91Ti0.09Se2 is relatively large. Therefore, the fabrication of finer particles of Nb0.91Ti0.09Se2 is encouraged.
Originality/value
In this paper, the authors discuss the tribological and electrical properties of Cu-based composites, and the value of optimum obtained as Nb0.91Ti0.09Se2 content is 15 Wt.%.