Xin Zhao, Bo Dong and Weizhong Li
The freezing phenomenon of a falling droplet is a frequently encountered phenomenon in various applications, such as spray crystallization, hail formation and artificial…
Abstract
Purpose
The freezing phenomenon of a falling droplet is a frequently encountered phenomenon in various applications, such as spray crystallization, hail formation and artificial snowmaking. Therefore, this paper aims to understand the freezing processes of a falling droplet without and with initial horizontal velocity in a cold space.
Design/methodology/approach
The freezing processes of a falling droplet were characterized using a modified enthalpy-based lattice Boltzmann method.
Findings
The temperature field, streamlines and freezing process of the falling droplet were investigated and analyzed. The lower part of the droplet was frozen earlier than the upper part. The freezing trend slowed down in the later stage of the freezing process. The droplet shape was related to the initial vertical velocity, nucleation temperature and initial horizontal velocity.
Originality/value
A modified enthalpy-based lattice Boltzmann method is proposed. In the model, the improved pseudo-potential model is used and the radiation is considered. This method was firstly used to simulate the freezing process of a falling droplet. By examining these freezing processes in detail, the freezing trend and the effect factors of droplet deformation and freezing time were obtained, respectively.
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Tao Sun, Weizhong Li and Bo Dong
The purpose of this paper is to test the feasibility of lattice Boltzmann method (LBM) for numerical simulation of nucleate boiling and transition boiling. In addition, the…
Abstract
Purpose
The purpose of this paper is to test the feasibility of lattice Boltzmann method (LBM) for numerical simulation of nucleate boiling and transition boiling. In addition, the processes of nucleate and transition boiling on vertical wall are simulated. The heat transfer mechanism is discussed based on the evolution of temperature field.
Design/methodology/approach
In this paper, nucleate boiling and transition boiling are numerically investigated by LBM. A lattice Boltzmann (LB) multiphase model combining with a LB thermal model is used to predict the phase-change process.
Findings
Numerical results are in good agreement with existing experimental results. Numerical results confirm the feasibility of the hybrid LBM for direct simulations of nucleate and transition boiling. The data exhibit correct parametric dependencies of bubble departure diameter compared with experimental correlation and relevant references.
Research limitations/implications
All the simulations are performed in two-dimensions in this paper. In the future work, the boiling process will be simulated in three-dimensional.
Practical implications
This study demonstrated a potential model that can be applied to the investigation of phase change heat transfer, which is one of the effective techniques for enhance the heat transfer in engineering. The numerical results can be considered as a basic work or a reference for generalizing LB method in the practical application about nucleate boiling and transition boiling.
Originality/value
The hybrid LBM is first used for simulation of nucleate and transition boiling on vertical surface. Heat transfer mechanism during boiling is discussed based on the numerical results.
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Yaokuang Li, Li Ling, Juan Wu, Daru Zhang and Weizhong Fu
This paper aims to investigate the role of informational and relational mechanisms on equity crowdfunding investors' conformity behaviors by focusing on a relational culture of…
Abstract
Purpose
This paper aims to investigate the role of informational and relational mechanisms on equity crowdfunding investors' conformity behaviors by focusing on a relational culture of China.
Design/methodology/approach
The data of 108 financing projects and 7,688 investment records from a union of Chinese equity crowdfunding platforms are gathered. Lead investors' response to a campaign and follow-investors’ former links explain investors' conformity by social network analysis (SNA) and ordinary least squares (OLS) analysis.
Findings
The results show that informational and relational influences drive conformity in Chinese equity crowdfunding. Moreover, the informational influence weakens in a highly centralized structure of linked investors.
Research limitations/implications
The results add new knowledge to follow-investors’ conformity behaviors in equity crowdfunding and enrich the literature on conformity theory by finding the contextual effect of information-influenced conformity and the adaption of conformity theory to cultural uniqueness. Besides, this preliminary work also suggests opportunities for future research.
Practical implications
The paper inspires new consideration on a strategical use of follow-investors’ conformity mentality to promote successfully financing and reminds platform managers to be alert to the interference of small groups formed based on informal relationships to the normal financing order.
Originality/value
This is the first study that discovers the non-informational influence and the limited influence of information on equity crowdfunding conformity through contextual concerns.
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Donghua Zhao, Tianqi Li, Beijun Shen, Yicheng Jiang, Weizhong Guo and Feng Gao
The purpose of this paper is to design and develop a rotary three-dimensional (3D) printer for curved layer fused deposition modeling (CLFDM), and discuss some technical…
Abstract
Purpose
The purpose of this paper is to design and develop a rotary three-dimensional (3D) printer for curved layer fused deposition modeling (CLFDM), and discuss some technical challenges in the development.
Design/methodology/approach
Some technical challenges include, but are not limited to, the machine design and control system, motion analysis and simulation, workspace and printing process analysis, curved layer slicing and tool path planning. Moreover, preliminary experiments are carried out to prove the feasibility of the design.
Findings
A rotary 3D printer for CLFDM has been designed and developed. Moreover, this printer can function as a polar 3D printer for flat layer additive manufacturing (AM). Compared with flat layer AM, CLFDM weakens the staircase effect and improves geometrical accuracy and mechanical properties. Hence, CLFDM is more suitable for parts with curved surfaces.
Research limitations/implications
Double extruders have brought improved build speed. However, this paper is restricted to complex process planning and mechanical structures, which may lead to collisions during printing. Meanwhile, the rotation range of the nozzle is limited by mechanical structures, affecting the manufacturing capability of complex curved surfaces.
Originality/value
A novel rotary 3D printer, which has four degrees of freedom and double extruders, has been designed and manufactured. The investigation on the prototype has proved its capability of CLFDM. Besides, this rotary 3D printer has two working modes, which brings the possibility of flat layer AM and CLFDM.
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Yaokuang Li, Junjuan Du and Weizhong Fu
The purpose of this paper is to investigate the factors influencing quick cash by crowd in agri-food crowdfunding campaigns; this paper utilizes prospect theory to analyze the…
Abstract
Purpose
The purpose of this paper is to investigate the factors influencing quick cash by crowd in agri-food crowdfunding campaigns; this paper utilizes prospect theory to analyze the value and weighting functions of the crowd's cash.
Design/methodology/approach
Using samples of crowdfunding campaigns launched in the Zhongchou (www.Zhongchou.cn) platform's agriculture and food category, this paper employs a multivariate linear regression model to investigate factors that motivate the crowd to make quick investment decisions.
Findings
The results demonstrate that lowering the investment threshold, improving publicity, and increasing the benefits of a campaign can increase the decision weight assigned to a campaign, thereby motivating the crowd to make quick investment decisions. Improving the product's reputation, enhancing campaign promotion, and diversifying the reward scheme can increase the crowd's expected value of the campaign – another motivation for a quicker cash decision.
Practical implications
This paper can help initiators, platforms and regulators better fulfil their roles in promoting the rapid, healthy development of crowdfunding in the agri-food industry, especially in the context of the Chinese launch of significant initiatives to develop crowdfunding aimed at rural e-commerce and poverty alleviation.
Originality/value
This paper extends the behavioral finance concept of prospect theory to agri-food crowdfunding campaigns and investigates factors that motivate the crowd to make quick investment decisions. Additionally, this paper demonstrates that the backers of crowdfunding are not perfectly rational and can be motivated to invest by increasing mean decision weight and expected value of a campaign.
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Yong Qian, Hongying Gong, Xiaoyun Zhao, Lei Cao, Weizhong Shi and Jianli He
The purpose of this study is to corroborate the advanced tribological properties of graphene as a lubricant additive.
Abstract
Purpose
The purpose of this study is to corroborate the advanced tribological properties of graphene as a lubricant additive.
Design/methodology/approach
Different concentrations of functionalized graphene were coated on the substrate surface. Tribological properties of the graphene lubricants were carried out by ball-on-disk tribology tests. Wear mechanism of functionalized graphene was studied by observing wear scars on the substrate surface. Finally, the wear resistance of modified graphene was calculated by calculating and analyzing the applied experimental conditions and the obtained experimental data.
Findings
The best concentration of graphene lubricant is 0.5 wt.% which shows the best tribological performance. And the coefficient of friction is 0.08. Compared with the dry friction condition, the coefficient of friction and wear rate of best graphene lubricant decreased by 80% and 82%.
Originality/value
The formula of graphene lubricant is independently developed and works very well. Graphene lubricant can prevent the substrate from oxidation. The thickness of the graphene lubricant is about 4-7µm. The concept of anti-wear strength was introduced in this paper. When 0.5 Vol.% graphene was added, the anti-wear strength was greatly improved from 115.3 kg·mm-2 to 657.6 kg·mm-2.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0344
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Donghua Zhao, Gaohan Zhu, Jiapeng He and Weizhong Guo
With the development of 3D printing or additive manufacturing (AM), curved layer fused deposition modeling (CLFDM) has been researched to cope with the flat layer AM inherited…
Abstract
Purpose
With the development of 3D printing or additive manufacturing (AM), curved layer fused deposition modeling (CLFDM) has been researched to cope with the flat layer AM inherited problems, such as stair-step error, anisotropy and the time-cost and material-cost problems from the supporting structures. As one type of CLFDM, cylindrical slicing has obtained some research attention. However, it can only deal with rotationally symmetrical parts with a circular slicing layer, limiting its application. This paper aims to propose a ray-based slicing method to increase the inter-layer strength of flat layer-based AM parts to deal with more general revolving parts.
Design/methodology/approach
Specifically, the detailed algorithm and implementation steps are given with several examples to enable readers to understand it better. The combination of ray-based slicing and helical path planning has been proposed to consider the nonuniform path spacing between the adjacent paths in the same curved layer. A brief introduction of the printing system is given, mainly including a 3D printer and the graphical user interface.
Findings
The preliminary experiments are successfully conducted to verify the feasibility and versatility of the proposed and improved slicing method for the revolving thin-wall parts based on a rotary 3D printer.
Originality/value
This research is early-stage work, and the authors are intended to explore the process and show the initial feasibility of ray-based slicing for revolving thin-wall parts using a rotary 3D printer. In general, this research provides a novel and feasible slicing method for multiaxis rotary 3D printers, making manufacturing revolving thin-wall and complex parts possible.
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Donghua Zhao, Weizhong Guo, Baibing Zhang and Feng Gao
The purpose of this paper is to review available technologies, analyse their features, propose a new approach of 3D sand mould printing based on line forming, introduce the…
Abstract
Purpose
The purpose of this paper is to review available technologies, analyse their features, propose a new approach of 3D sand mould printing based on line forming, introduce the manufacturing principle and show advantages of this approach, especially for larger parts with large Z steps in the build, such as 2 mm stepwise.
Design/methodology/approach
This paper introduces 3D sand mould printing, compares and analyses technological process and existing fabrication approaches among available technologies first. Then, a new approach of 3D sand mould printing is proposed to improve build speed. In addition, the proposed system will be analysed or benchmarked against existing systems.
Findings
A new approach based on line forming of sand mould printing is put forward by reviewing and analysing available technologies, to improve build speed from the aspect of basic moulding movement instead of optimization of moulding methods and process parameters. The theoretical calculation and analysis shows that build speed can be improved greatly, and it is more suitable for the manufacture of large-scale casting’s sand mould when considering dimensional accuracy and printing error, as well as uniformity of each layer.
Research limitations/implications
The specific implement scheme of line forming and nozzle’s specific structure of this new approach need further study.
Practical implications
Much higher build speed of 3D sand mould printing with new approach brings evident implication for moulds companies and manufacturing industry, having a far-reaching influence on the development of national economy.
Originality/value
This paper reviews available technologies and presents a new approach of 3D sand mould printing for the first time. Analysis of the new approach shows that this new method of sand mould printing can boost build speed greatly. So, its application prospect is great.
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Qiang Yang, Tianfei Xia, Lijia Zhang, Ziye Zhou, Dequan Guo, Ao Gu, Xucai Zeng and Ping Wang
The purpose of this paper is to use the corresponding magnetic sensor and detection method to detect and image the defects of small diameter pipelines. Urban gas pipeline is an…
Abstract
Purpose
The purpose of this paper is to use the corresponding magnetic sensor and detection method to detect and image the defects of small diameter pipelines. Urban gas pipeline is an energy transportation tool for urban industrial production and social life, which is closely related to urban safety. Preventing the occurrence of urban gas pipeline transportation accidents and carrying out pipeline defect detection are of great significance for the urban economic and social stability. To perform pipeline defect detection, the magnetic flux leakage internal detection method is generally used in the detection of large-diameter long-distance oil and gas pipelines. However, in terms of the internal detection of small-diameter pipelines, due to the heavy weight, large structure of the detection device and small pipe diameter, the detection is more difficult.
Design/methodology/approach
In order to solve the above matters, self-made three-dimensional magnetic sensor and three-dimensional magnetic flux leakage imaging direct method are proposed for studying the defect identification. Firstly, for adapting to the diameter range of small-diameter pipelines, and containing the complete information of the defect, a self-made three-dimensional magnetic sensor is made in this paper to improve the accuracy of magnetic flux leakage detection. And on the basis of it, a small diameter pipeline defect detection system is built. Secondly, as detection signal may be affected by background magnetic field interference and the jitter interference, the complete ensemble empirical mode decomposition with adaptive noise method is utilized to screen the detected signal. As a result, the useful signal is reconstructed and the interference signal is removed. Finally, the defect contour inversion imaging of detection is realized based on the direct method of three-dimensional magnetic flux leakage imaging, which includes three-dimensional magnetic flux leakage detection data and data segmentation recognition.
Findings
The three-dimensional magnetic flux leakage imaging experimental results shown that, compared to the actual defects, the typical defects, irregular defects and crack groove defects can be analyzed by the magnetic flux leakage defect contour imaging method in qualitative and quantitative way respectively, which provides a new idea for the research of defect recognition.
Originality/value
A three-dimensional magnetic sensor is made to adapt the diameter range of small diameter pipeline, and based on it, a small-diameter pipeline defect detection system is built to collect and display the magnetic flux leakage signal.
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Weizhong Dai, Fei Han and David Hui
Studying hydrogen absorption/ desorption in metal-H2 reactors is important for the usage and commercialization of hydrogen energy. In this article, we present a numerical method…
Abstract
Studying hydrogen absorption/ desorption in metal-H2 reactors is important for the usage and commercialization of hydrogen energy. In this article, we present a numerical method for simulating hydrogen absorption in a cylindrical LaNi5-H2 reactor. The method is obtained based on the modified heat and mass transfer model for the absorption of hydrogen, and its finite difference approximation in a staggered mesh. As a result, the numerical scheme is unconditionally stable and the solution is second-order accurate. Numerical results including gas and solid densities, gas velocity, gas and solid temperatures are obtained.