Ani Luo, Ziying Cao, Heping Liu and Yaming Feng
In this paper, the main factors influencing the structure stiffness will be analyzed by studying the tangent stiffness matrix based on different requirement in engineering…
Abstract
Purpose
In this paper, the main factors influencing the structure stiffness will be analyzed by studying the tangent stiffness matrix based on different requirement in engineering practice. The authors can obtain the deformation of three-bar tensegrity basic unit in different load, and gain the primary factor by comparing the deformation, which will provide reference to concrete structure design in the engineering.
Design/methodology/approach
The mathematical model of tensegrity structure was built by establishing generalized node coordinates and connective matrix. Three main factors that affect the structure deformation can be obtained by analyzing the stiffness matrix, which is preload, Young's modulus, and cross-sectional area, the thinking of deformation also be sorted out. The deformation analysis of the concrete structure is carried out, and it is concluded that increasing the cross-sectional area can quickly improve the stiffness of the structure, which provides a reference for the structural variable stiffness design in practical engineering.
Findings
(1) When the axial external force is applied to the structure, the torsion-angle deformation of the structure is the largest, and the radial deformation of the structure is the smallest. (2) The structure stiffness can be rapidly enhanced by increasing the cross-sectional area. But the cross-sectional area can't be increased indefinitely. Because the mass will be increased once increasing the cross-sectional area, which will destroy the structure of the advantages of light weight in engineering practice.
Originality/value
The deformation analysis of the concrete structure is carried out, and it is concluded that increasing the cross-sectional area can quickly improve the stiffness of the structure, which provides a reference for the structural variable stiffness design in practical engineering.
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Angelo Vumiliya, Ani Luo, Heping Liu and Andrés González
This paper aims to propose a study on the static behavior of prismatic tensegrity structures and an innovative form for determining the effect of mechanical properties and…
Abstract
Purpose
This paper aims to propose a study on the static behavior of prismatic tensegrity structures and an innovative form for determining the effect of mechanical properties and geometric parameters on the minimal mass design of these structures.
Design/methodology/approach
The minimal mass design in this paper considers a stable class-two tensegrity tower built through stable models. Using the proposed structures, comprehensive parametric studies are performed to examine the mass (in which the masses of joints are ignored), the mass ratio between a class-two tensegrity tower and a single element, both having the same diameter and length and afterward determine a reliable mass saving structure under various circumstances.
Findings
The simulations show that the mass ratio versus the number of units is a nonlinear regressive curve and predicts that the proposed model outperforms the standard model when the variation parameter considered is a vertical force. The difference in mass between these structures is visible when the gap gradually decreases while the number of units increases. On the geometrical aspect, the gap between the masses is not significant.
Originality/value
This paper helps to understand the influences of geometric parameters and the mechanical properties on the design of cylinder tensegrity structures dealing with a compressive force.
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Heping Liu, Jinxin Lu, Fusheng Zhu and Ani Luo
This study proposes a tensegrity-based traction structure with D-bar dual cable units. It is used to connect the airship and the ground to stabilize the airship.
Abstract
Purpose
This study proposes a tensegrity-based traction structure with D-bar dual cable units. It is used to connect the airship and the ground to stabilize the airship.
Design/methodology/approach
The mathematical models and dynamic models of the D-bar dual cable (hereafter referred to as DD cable) unit of the tensegrity-based traction structure are established. Based on the minimum mass method, the mass of the DD cable unit in the critical state (cable member is yielding, or bar member is buckling or yielding) is analyzed. Then, the tensile strength of the DD cable unit and single cable unit under the same condition is compared using the control variate method. Finally, based on ANSYS dynamic simulation, the stability of the two structures under the same external force disturbance was tested.
Findings
Expressions for the minimum mass of the DD cable unit under different failure conditions are solved. Dynamic simulation results show that the capacity of resisting disturbance of the DD cable unit is much better than that of the single cable unit under the same wind speed. So, we find a structure more suitable for the fixed connection of an airship.
Originality/value
This study helps to provide theoretical reference and thinking for the practical application of the traction structure with a D-bar dual cable unit.
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Ziying Cao, Ani Luo, Yaming Feng and Heping Liu
This paper is contributed to find the minimal mass prismatic tensegrity structures.
Abstract
Purpose
This paper is contributed to find the minimal mass prismatic tensegrity structures.
Design/methodology/approach
In the stable state of the structure with any given external force, the internal forces of the structure members are taken as the critical force to calculate the cross-sectional area, and the total mass of the structure can be obtained. Firstly, the mathematical model of prismatic tensegrity was built. Secondly, the stability of the tensegrity was analyzed based on the force equilibrium of one node, the force density relationship of elements was obtained. The deformation of p-bar tensegrity prism unit was studied with the same mass. The force of the structure under external force was analyzed.
Findings
(1) The length of bar and the structural radius are almost invariant, and the mechanical properties of 3-bar tensegrity prism is more outstanding; (2) theoretically, the mass of the structure is minimal while the projection of bar passes the center of the circle. Under the circumstances, the force of diagonal cable is 0 N, the vertical force component of bar cancels the axial external force.
Originality/value
(1) By analyzing the deformation of p-bar tensegrity prism with the same mass, the length of bar and the structural radius are proved be almost invariant and the mechanical properties of 3-bar tensegrity prism is more outstanding; (2) theoretically, the mass of the structure is minimal while the projection of bar passes the center of the circle. Under the circumstances, the force of diagonal cable is 0 N, the vertical force component of bar cancels the axial external force.
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Heping Liu, Sanaullah, Angelo Vumiliya and Ani Luo
The aim of this article is to obtain a stable tensegrity structure by using the minimum knowledge of the structure.
Abstract
Purpose
The aim of this article is to obtain a stable tensegrity structure by using the minimum knowledge of the structure.
Design/methodology/approach
Three methods have been formulated based on the eigen value decomposition (EVD) and singular value decomposition theorems. These two theorems are being implemented on the matrices, which are computed from the minimal data of the structure. The required minimum data for the structure is the dimension of the structure, the connectivity matrix of the structure and the initial force density matrix computed from the type of elements. The stability of the structure is analyzed based on the rank deficiency of the force density matrix and equilibrium matrix.
Findings
The main purpose of this article is to use the defined methods to find (1) the nodal coordinates of the structure, (2) the final force density values of the structure, (3) single self-stress from multiple self-stresses and (4) the stable structure.
Originality/value
By using the defined approaches, one can understand the difference of each method, which includes, (1) the selection of eigenvalues, (2) the selection of nodal coordinates from the first decomposition theorem, (3) the selection of mechanism mode and force density values further and (4) the solution of single feasible self-stress from multiple self-stresses.
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Andrés González, Ani Luo and Dongyan Shi
This paper aims to present a reconfiguration strategy for actuated tensegrity structures. The main idea is to use the infinitesimal mechanisms of the structure to generate a path…
Abstract
Purpose
This paper aims to present a reconfiguration strategy for actuated tensegrity structures. The main idea is to use the infinitesimal mechanisms of the structure to generate a path along which the tensegrity can change its shape while maintaining the equilibrium.
Design/methodology/approach
Combining the force density method with a marching procedure, the solution to the equilibrium problem is given by a set of differential equations. Beginning from an initial stable position, the algorithm calculates a small displacement until a new stable configuration is reached, and recurrently repeats the process during a given interval of time.
Findings
By means of three numerical simulations and their respective experimental example, the efficacy of this algorithm for reconfiguring the well-known three-bar tensegrity prism along different directions is shown. The proposed method shows efficiency only for small changes of string length. Further work should consider the application of this method to more complex tensegrity structures.
Originality/value
The advantage of this reconfiguration method is its simplicity for finding new stable positions for tensegrity structures, and the fact that it doesn’t need the information of the material of the structure for the computations.
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Wan Zuriea Wan Ismail, Mat Naim Abdullah and Adi Irfan Che-Ani
This paper aims to assess factors that affect carbon sequestration on green roofs.
Abstract
Purpose
This paper aims to assess factors that affect carbon sequestration on green roofs.
Design/methodology/approach
The most current academic literature related to carbon sequestration and green roofs carbon sequestration performance was reviewed.
Findings
Factors affecting carbon sequestration were discussed and classified into the following factors: plants, physical and maintenance factors. The authors’ findings are significant because they can be used to optimize green roofs performance for carbon sequestration.
Originality/value
Factors affecting carbon sequestration will optimize intensive green roofs performance.
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Ai Yue, Bin Tang, Yaojiang Shi, Jingjing Tang, Guanminjia Shang, Alexis Medina and Scott Rozelle
The purpose of this paper is to describe the policy and trends in rural education in China over the past 40 years; and also discuss a number of challenges that are faced by…
Abstract
Purpose
The purpose of this paper is to describe the policy and trends in rural education in China over the past 40 years; and also discuss a number of challenges that are faced by China’s rural school system.
Design/methodology/approach
The authors use secondary data on policies and trends over the past 40 years for preschool, primary/junior high school, and high school.
Findings
The trends over the past 40 years in all areas of rural schooling have been continually upward and strong. While only a low share of rural children attended preschool in the 1980s, by 2014 more than 90 percent of rural children were attending. The biggest achievement in compulsory education is that the rise in the number of primary students that finish grade 6 and matriculate to junior high school. There also was a steep rise of those going to and completing high school. While the successes in upscaling rural education are absolutely unprecedented, there are still challenges.
Research limitations/implications
This is descriptive analysis and there is not causal link established between policies and rural schooling outcomes.
Practical implications
The authors illustrate one of the most rapid rises of rural education in history and match the achievements up with the policy efforts of the government. The authors also explore policy priorities that will be needed in the coming years to raise the quality of schooling.
Originality/value
This is the first paper that documents both the policies and the empirical trends of the success that China has created in building rural education from preschool to high school during the first 40 years of reform (1978-2018). The paper also documents – drawing on the literature and the own research – the achievements and challenges that China still face in the coming years, including issues of gender, urbanization, early childhood education and health and nutrition of students.
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Yaojiang Shi, Fang Chang, Xiaoqing Su, Renfu Luo, Linxiu Zhang and Scott Rozelle
The purpose of this paper is to report the results of a randomized controlled trial designed to measure the impact of a parental training program on the nutritional status of…
Abstract
Purpose
The purpose of this paper is to report the results of a randomized controlled trial designed to measure the impact of a parental training program on the nutritional status of primary school students in rural Shaanxi Province, in northwest China.
Design/methodology/approach
Using hemoglobin (Hb) levels as the outcome variable, the authors first measure the overall impact of a nutritional training program, then measure the impact separately by gender. Both descriptive and multivariate analyses are used.
Findings
The results for the descriptive and econometric results were robust and consistent with the literature. Overall, we find no impact on students' Hb levels when we trained their parents about undernutrition and anemia. In both the descriptive and multivariate results, there was no difference in the change of Hb levels between control and treatment students. Parents in the treatment group did learn more about anemia than parents in the control group, but this increased knowledge did not lead to sharp changes in behavior, in general. The authors did find, however, that there was a measurable impact of parental training on the Hb levels of female students. In both the descriptive and econometric results the authors found that the Hb levels of female students rose more than those of male students, and that this difference was statistically significant.
Originality/value
The paper reports the results of a randomized controlled trial that examined the effect of parental training on students in poor, rural schools in ten counties of Shaanxi province. Taken by itself, one of the policy implications of this study is that malnutrition is still a serious problem in China and it is worse among female students than male students. When parental training is given, the health status of girls improves but the health status of boys is unchanged. Parental training may not be the best way to fight anemia, but it can help narrow the nutrition gap between girls and boys.
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Arthur de Carvalho Cruzeiro, Leonardo Santana, Danay Manzo Jaime, Sílvia Ramoa, Jorge Lino Alves and Guilherme Mariz de Oliveira Barra
This study aims to evaluate in situ oxidative polymerization of aniline (Ani) as a post-processing method to promote extrusion-based 3D printed parts, made from insulating…
Abstract
Purpose
This study aims to evaluate in situ oxidative polymerization of aniline (Ani) as a post-processing method to promote extrusion-based 3D printed parts, made from insulating polymers, to components with functional properties, including electrical conductivity and chemical sensitivity.
Design/methodology/approach
Extrusion-based 3D printed parts of polyethylene terephthalate modified with glycol (PETG) and polypropylene (PP) were coated in an aqueous acid solution via in situ oxidative polymerization of Ani. First, the feedstocks were characterized. Densely printed samples were then used to assess the adhesion of polyaniline (PAni) and electrical conductivity on printed parts. The best feedstock candidate for PAni coating was selected for further analysis. Last, a Taguchi methodology was used to evaluate the influence of printing parameters on the coating of porous samples. Analysis of variance and Tukey post hoc test were used to identify the best levels for each parameter.
Findings
Colorimetry measurements showed significant color shifts in PP samples and no shifts in PETG samples upon pullout testing. The incorporation of PAni content and electrical conductivity were, respectively, 41% and 571% higher for PETG in comparison to PP. Upon coating, the surface energy of both materials decreased. Additionally, the dynamic mechanical analysis test showed minimal influence of PAni over the dynamic mechanical properties of PETG. The parametric study indicated that only layer thickness and infill pattern had a significant influence on PAni incorporation and electrical conductivity of coated porous samples.
Originality/value
Current literature reports difficulties in incorporating PAni without affecting dimensional precision and feedstock stability. In situ, oxidative polymerization of Ani could overcome these limitations. However, its use as a functional post-processing of extrusion-based printed parts is a novelty.