Yali Han, Shunyu Liu, Jiachen Chang, Han Sun, Shenyan Li, Haitao Gao and Zhuangzhuang Jin
This paper aims to propose a novel system design and control algorithm of lower limb exoskeleton, which provides walking assistance and load sharing for the wearer.
Abstract
Purpose
This paper aims to propose a novel system design and control algorithm of lower limb exoskeleton, which provides walking assistance and load sharing for the wearer.
Design/methodology/approach
In this paper, the valve-controlled asymmetrical hydraulic cylinder is selected for driving the hip and knee joint of exoskeleton. Pressure shoe is developed that purpose on detecting changes in plantar force, and a fuzzy recognition algorithm using plantar pressure is proposed. Dynamic model of the exoskeleton is established, and the sliding mode control is developed to implement the position tracking of exoskeleton. A series of prototype experiments including benchtop test, full assistance, partial assistance and loaded walking experiments are set up to verify the tracking performance and power-assisted effect of the proposed exoskeleton.
Findings
The control performance of PID control and sliding mode control are compared. The experimental data shows the tracking trajectories and tracking errors of sliding mode control and demonstrate its good robustness to nonlinearities. sEMG of the gastrocnemius muscle tends to be significantly weakened during assisted walking.
Originality/value
In this paper, a structure that the knee joint and hip joint driven by the valve-controlled asymmetrical cylinder is used to provide walking assistance for the wearer. The sliding mode control is proposed to deal with the nonlinearities during joint rotation and fluids. It shows great robustness and frequency adaptability through experiments under different motion frequencies and assistance modes. The design and control method of exoskeleton is a good attempt, which takes positive impacts on the productivity or quality of the life of wearers.
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Yali Han, Krishna P. Paudel, Junyi Wan and Qinying He
China's economy has transformed from a high-speed growth phase to a high-quality development phase. The agriculture sector has grown substantially since the economic reform in…
Abstract
Purpose
China's economy has transformed from a high-speed growth phase to a high-quality development phase. The agriculture sector has grown substantially since the economic reform in 1978. Considering the five-year plan (FYP) as a collection of policies, this study explores the relationship between the FYP and agricultural total factor productivity (TFP).
Design/methodology/approach
This study uses 31 provincial-level panel data of the five FYPs from 1996 to 2020. The data envelopment analysis (DEA) is used to compute Malmquist productivity indexes. The authors analyze the temporal and spatial changes and convergences of China's agricultural TFP, and investigate the impact of economic planning on China's agricultural TFP and its regional difference.
Findings
There is a slow but upward growth trend in China's agricultural TFP. The technical change has played a leading role in the growth of China's agricultural TFP. The agricultural TFP of all provinces has shown a “catch-up” effect and is developing toward their respective steady-state levels. The regional difference in productivity growth among the eastern, central and western regions exists. Test results show that the FYP has a positive effect on the agricultural TFP, and the effect has obvious regional heterogeneity. The FYP also plays a positive role in the gross value of agricultural output, and the impact effect is greater than that on the improvement of agricultural productivity.
Originality/value
There are many forms of industrial policy in China, among which the FYP is the guiding document of industrial policy, which makes a systematic plan for industrial development in the subsequent five years. The development objectives, guidelines and overall deployment for agriculture in the FYP not only describe the general context of China's agricultural development but also show the key ideas of agricultural development. Therefore, this study explores its impact on agricultural quality development from the perspective of FYP. The results provide evidence for examining the governance performance of the government and the objective evaluation and restraint of the FYP. As agriculture moves toward the stage of high-quality development, the Chinese government should strengthen the critical guiding role of the FYP and pay attention to quality indicators such as technical progress, efficiency improvement and regional coordination in the formulation of the FYP.
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Yuan Zhao, Zhennan Han, Yali Ma and Qianqian Zhang
The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion…
Abstract
Purpose
The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion states, and demonstrate its correctness and reliability according to the rheological property results of flow fresh concrete in different working states through simulating the slump process and mixing process.
Design/methodology/approach
To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength. The fluid-like fresh concrete is modelled as a two-phase fluid consisting of mortar and aggregate. Depending on the contact forms of the aggregate and mortar, the model is of one of the five types, namely, Hertz–Mindlin, pendular LB contact, funicular mucous contact, capillary LB contact or slurry lift/drag contact.
Findings
To verify the accuracy of this contact model, concrete slump and cross-vane rheometer tests are simulated using the traditional LB model and dynamic coupled contact model, for five concrete strengths. Finally, by comparing the simulation results from the two different contact models with experimental data, it is found that those from the proposed contact model are closer to the experimental data.
Practical implications
This contact model could be used to address issues such as (a) the mixing, transportation and pumping of fresh concrete, (b) deeper research and discussion on the influence of fresh concrete on the dynamic performance of agitated-transport vehicles, (c) the behaviour of fresh concrete in mixing tanks and (d) the abrasion of concrete pumping pipes.
Originality/value
To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength.
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Yu Zhang, Qian Du, Yali Huang, Yanying Mao and Liudan Jiao
The investigation of pro-environmental behaviors (PEB) among college students is essential for future sustainability endeavors. Existing research seldomly concentrated on college…
Abstract
Purpose
The investigation of pro-environmental behaviors (PEB) among college students is essential for future sustainability endeavors. Existing research seldomly concentrated on college students and their PEB. This study aims to address the gap in understanding PEB among college students.
Design/methodology/approach
This study constructed an integrated model combining the theory of planned behavior (TPB) and the value-belief-norm (VBN) theory, with the novel addition of environmental risk perception. Through an empirical study involving 844 college students, this research analyzed the data with the structural model.
Findings
The authors identified that environmental values, attitudes, perceived behavioral control, subjective norms and risk perception play crucial roles in shaping PEB. This study also revealed age-related differences, highlighting that older students might be less influenced by attitudes and subjective norms due to more established habits. Findings underscore the importance of fostering PEB through environmental education, promotion of low-carbon lifestyle choices and incentives. This investigation not only enriches the theoretical framework for PEB but also offers practical insights for policymakers and educators to enhance sustainable practices among the youth.
Research limitations/implications
Though the authors offer valuable findings, this research has two key limitations: the use of observational data for hypothesis testing, which weakens causal inference, and the collection of data through questionnaires, which may be biased by social desirability. Respondents of self-report tend to behave in the socially desired ways. Consequently, they usually exaggerate their pro-environmental intention or PEB. To comprehend the influencing aspects more thoroughly, future research should consider incorporating experimental methods and objective data, such as digitalized data.
Practical implications
The findings provide valuable evidence for guiding college students’ PEB, including strengthening environmental education, promoting of low-carbon fashion and providing incentives for PEBs.
Originality/value
First, the authors examine the internal factors influencing PEB among Chinese university students within the “dual-carbon” initiative framework. Second, this research pioneers the use of structural equation modeling to merge TPB and VBN theories, offering a predictive model for university students’ PEB. Third, the authors introduce “environmental risk perception” as a novel variable derived from both TPB and VBN, enhancing the model’s explanatory power.
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Lin Lin, Yali Zhao, Masato Ogawa and John D. Hoge
Comparing international history textbooks creates a perfect opportunity for students to see the complexity and controversy of history interpretation of certain events. Such a…
Abstract
Comparing international history textbooks creates a perfect opportunity for students to see the complexity and controversy of history interpretation of certain events. Such a critical comparative approach helps students understand how people in different countries perceive and interpret the Korean War, its aftermath, and its effects on current international relation-ships. In this article, we suggest that teachers approach the Korean War and the Six-Party Talks in two ways: Six-Party Discussion Table motivation activities and analysis of middle school history textbook excerpts about the Korean War in the six countries. Detailed lesson plans and handouts are provided for teachers to facilitate these discussions. These include the directions and procedures for the activities, teachers' guide, suggested answers, textbook excerpts from the United States, and textbook excerpts translated into English China, Japan, Russia, North Korea, and South Korea.
MaryJo Benton Lee, Li Hong and Luo Lihui
A strong relationship exists in many cultures between ethnic identity and educational success. This study was conducted at a teacher training university in Southwest China in…
Abstract
A strong relationship exists in many cultures between ethnic identity and educational success. This study was conducted at a teacher training university in Southwest China in 1997. It examines how ethnic minority students, through a series of micro-level interactions, construct “scholar selves” within their families, villages, and schools. The study also looks at how macro-level structural supports, built into the Chinese education system, help minority students overcome obstacles to academic success. These supports include special schools and classes for ethnic students, training teachers for nationality areas, financial support for minority education and additional points awarded on national examinations. The chapter suggests what scholars and practitioners might learn from an educational system that demonstrates the characteristics of flexibility, inclusiveness and cohesiveness.
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Yali Zhang, Xiaogang Zhang, Tonghai Wu and You-bai Xie
The piston ring-cylinder liner pair is one of the most important tribological systems of an internal combustion engine. The friction loss of the piston ring-cylinder liner pair…
Abstract
Purpose
The piston ring-cylinder liner pair is one of the most important tribological systems of an internal combustion engine. The friction loss of the piston ring-cylinder liner pair accounts for the largest portion of total efficiency losses. Therefore, improving the tribological system design of the piston ring-cylinder liner pair can reduce friction losses and bring tremendous economic benefits to society. This paper aims use surface texturing, which is proving to be an effective method, for improving the tribological performance of sliding surfaces.
Design/methodology/approach
In this paper, an experimental study using a pin-on-disk tribometer was carried out to evaluate the effects of surface texturing on friction reduction of piston rings under various loads and sliding velocities. Rectangular- and circular-shaped textures with different depths and area densities were produced by a Femtosecond laser. Comparison experiments were conducted with un-textured rings.
Findings
The results indicate that the friction performance of the ring surface was significantly improved by surface texturing, and the running-in stage was also shortened. More specifically, it was found that the rectangular-shaped texture had a better effect on friction reduction than the circular-shaped texture. Results also indicate that an optimum texture density existed for the rectangular-shaped texture. Additionally, it was observed that the average friction coefficient reduction of the textured ring decreased with increasing load and increased with increasing sliding velocity.
Originality/value
Consequently, these findings provide a more in-depth understanding of the relationship between micro-textures and tribological properties of piston rings in lubricating sliding.
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Xiaoming Han, He Zhang and Kangjian Yang
This study aims to investigate the temperature rise characteristics of vibrating rolling bearings under the influence of the polarization force of unbalanced eccentric blocks. A…
Abstract
Purpose
This study aims to investigate the temperature rise characteristics of vibrating rolling bearings under the influence of the polarization force of unbalanced eccentric blocks. A thermal-fluid-solid mechanics coupled finite element model is established to analyze the effects of different loads and rotational speeds on bearing temperature to prevent overheating, wear and thermal damage.
Design/methodology/approach
A thermal-fluid-solid mechanics coupled finite element model of the vibrating rolling bearing is developed based on the principles of heat transfer. Finite element analysis software is used to conduct numerical simulations and study the temperature distribution of the bearing system under different loads and speeds. The model’s accuracy is verified by experimentally measuring the actual temperature of the bearing under the same working conditions.
Findings
This study successfully established a thermal-fluid-solid mechanics coupled finite element model of a vibrating rolling bearing, verifying its accuracy and reliability. The research results provide an essential reference for optimizing bearing design, preventing overheating and extending service life.
Research limitations/implications
By analyzing the temperature rise characteristics under various load and rotational speed conditions, the law governing the internal temperature distribution of bearings is revealed. This finding offers a theoretical foundation for comprehending the thermal behavior of bearings.
Practical implications
This study offers a scientific foundation for the maintenance and fault diagnosis of shaker rolling bearings, aiding in the timely identification and resolution of thermal damage issues. Through the optimization of bearing design and usage conditions, the equipment’s lifespan can be prolonged, maintenance expenses can be minimized and production efficiency can be enhanced.
Originality/value
A thermal-fluid-solid mechanics coupled finite element model of a vibrating rolling bearing was established, considering the interaction of multiple physical fields. The influence of the polarization force from the unbalanced eccentric block on the bearing temperature is analyzed in detail, which is close to the actual working conditions.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2024-0396/
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Jiansan Li, Yali Li, Yanqin Chen, Jiawei Sun, Chunxiao Wang, Yingcai Zheng and Huiting Zhong
This paper aims to report the influence of hexamethylenetetramine (HMTA) on phosphate coatings formed on AZ31 magnesium alloys.
Abstract
Purpose
This paper aims to report the influence of hexamethylenetetramine (HMTA) on phosphate coatings formed on AZ31 magnesium alloys.
Design/methodology/approach
These phosphate coatings were obtained by immersing magnesium alloys in phosphate baths with HMTA. The morphology and composition of the phosphate coatings were investigated via scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction.
Findings
The phosphate coatings were mainly composed of CaHPO4·2H2O. The HMTA concentration in the phosphate bath influenced the crystallization and corrosion resistance of the phosphate coating.
Originality/value
The polarization curve shows that the anti-corrosion qualities of the phosphate coating were optimal when the HMTA concentration was 1.0 g/L in the phosphate bath. Electrochemical impedance spectroscopy (EIS) shows that the electrochemical impedances increased gradually when the HMTA concentration varied from 1.0 to 3.0 g/L.