Pedram Parandoush, Palamandadige Fernando, Hao Zhang, Chang Ye, Junfeng Xiao, Meng Zhang and Dong Lin
Additively manufactured objects have layered structures, which means post processing is often required to achieve a desired surface finish. Furthermore, the additive nature of the…
Abstract
Purpose
Additively manufactured objects have layered structures, which means post processing is often required to achieve a desired surface finish. Furthermore, the additive nature of the process makes it less accurate than subtractive processes. Hence, additive manufacturing techniques could tremendously benefit from finishing processes to improve their geometric tolerance and surface finish.
Design/methodology/approach
Rotary ultrasonic machining (RUM) was chosen as a finishing operation for drilling additively manufactured carbon fiber reinforced polymer (CFRP) composites. Two distinct additive manufacturing methods of fused deposition modeling (FDM) and laser-assisted laminated object manufacturing (LA-LOM) were used to fabricate CFRP plates with continuous carbon fiber reinforcement. The influence of the feedrate, tool rotation speed and ultrasonic power of the RUM process parameters on the aforementioned quality characteristics revealed the feasibility of RUM process as a finishing operation for additive manufactured CFRP.
Findings
The quality of drilled holes in the CFRP plates fabricated via LA-LOM was supremely superior to the FDM counterparts with less pullout delamination, smoother surface and less burr formation. The strong interfacial bonding in LA-LOM proven to be superior to FDM was able to endure higher cutting force of the RUM process. The cutting force and cutting temperature overwhelmed the FDM parts and induced higher surface damage.
Originality/value
Overall, the present study demonstrates the feasibility of a hybrid additive and subtractive manufacturing method that could potentially reduce cost and waste of the CFRP production for industrial applications.
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Xu Li, Zeyu Xiao, Zhenguo Zhao, Junfeng Sun and Shiyuan Liu
To explore the economical and reasonable semi-rigid permeable base layer ratio, solve the problems caused by rainwater washing over the pavement base layer on the slope, improve…
Abstract
Purpose
To explore the economical and reasonable semi-rigid permeable base layer ratio, solve the problems caused by rainwater washing over the pavement base layer on the slope, improve its drainage function, improve the water stability and service life of the roadbed pavement and promote the application of semi-rigid permeable base layer materials in the construction of asphalt pavement in cold regions.
Design/methodology/approach
In this study, three semi-rigid base course materials were designed, the mechanical strength and drainage properties were tested and the effect and correlation of air voids on their performance indexes were analyzed.
Findings
It was found that increasing the cement content increased the strength but reduced the air voids and water permeability coefficient. The permeability performance of the sandless material was superior to the dense; the performance of the two sandless materials was basically the same when the cement content was 7%. Overall, the skeleton void (sand-containing) type gradation between the sandless and dense types is more suitable as permeable semi-rigid base material; its gradation is relatively continuous, with cement content? 4.5%, strength? 1.5 MPa, water permeability coefficient? 0.8 cm/s and voids of 18–20%.
Originality/value
The study of permeable semi-rigid base material with large air voids could help to solve the problems of water damage and freeze-thaw damage of the base layer of asphalt pavements in cold regions and ensure the comfort and durability of asphalt pavements while having good economic and social benefits.
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Guangyuan Wu, Haitao Zhang, Junfeng Sun and Tengjiang Yu
In order to evaluate the rheological properties of asphalt more comprehensively and effectively, and to explore and discuss the practicability of relevant models in the evaluation…
Abstract
Purpose
In order to evaluate the rheological properties of asphalt more comprehensively and effectively, and to explore and discuss the practicability of relevant models in the evaluation of the rheological properties of asphalt.
Design/methodology/approach
Based on the rheological and viscoelastic theories, temperature scanning, frequency scanning and multiple stress creep recovery (MSCR) tests of different modified asphalt were carried out by dynamic shear rheometer (DSR) to obtain relevant viscoelastic parameters and evaluate the high temperature properties of different modified asphalt. Based on the time-temperature equivalence principle, the main curve was constructed to study the viscoelastic properties of asphalt in a wider frequency domain. The main curve was fitted with the CAM model, and the rheological properties of different modified asphalt were evaluated through the analysis of model parameters. The creep stiffness and creep velocity of different modified asphalt were obtained through the rheological test of bending beam (BBR), and the low-temperature performance of different modified asphalt was analyzed by using Burgers model to fit the creep compliance.
Findings
The results show that the high temperature rheological properties of several modified asphalt studied in the test are ranked from best to worst as follows: PE modified asphalt > SBS modified asphalt > SBR modified asphalt. Short-term aging can improve the high temperature performance of asphalt, and different types of modifiers can promote or inhibit this improvement effect. Based on BBR test and Burgers model fitting analysis, SBR modified asphalt has the best low temperature performance, followed by SBS modified asphalt, while PE modified asphalt has poor low temperature performance, so it is not suitable to be used as road material in low temperature area.
Originality/value
Combined with effective evaluation methods, the rheological properties of asphalt at different temperatures and angles were systematically evaluated, and the evolution of rheological properties of asphalt characterized by model parameters was further analyzed by advanced model simulation.
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Pei Wei, Zhengying Wei, Zhne Chen, Jun Du, Yuyang He and Junfeng Li
This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant…
Abstract
Purpose
This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track.
Design/methodology/approach
A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process.
Findings
The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality.
Originality/value
The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.
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Junfeng Dong, Qiman Zhang, Haoyuan Teng, Li Jiang and Wenxing Lu
This paper aims to investigate the vertical cooperative relationship between the core enterprise and the manufacturer within the platform ecosystem, specifically analyzing the…
Abstract
Purpose
This paper aims to investigate the vertical cooperative relationship between the core enterprise and the manufacturer within the platform ecosystem, specifically analyzing the optimal decision-making processes of both parties under the original equipment manufacturer (OEM) and original brand manufacturer (OBM) modes.
Design/methodology/approach
This paper uses game theory to analyze the problem, considering factors such as brand value difference, cross-selling and platform empowerment. It constructs the game models for both OEM and OBM modes and discusses the selection strategies for the cooperation mode.
Findings
The results indicate that the choice of cooperation mode by the manufacturer and the core enterprise depends on the relative size of their brand values. In cases of inconsistent choices, cooperation can be improved by designing a transfer payment contract. When the brand value is constant, the product price is comprehensively affected by cross-selling revenue, price elasticity coefficient, cost coefficient of sales effort and cost coefficient of platform empowerment. The enterprise reduces the price only when the potential revenue brought by increasing product sales exceeds the marginal profit brought by increasing product pricing; otherwise, it raises the sales price.
Originality/value
The platform ecosystem is emerging as a future direction for business mode development. However, there is a paucity of research on the cooperation modes between manufacturers and core enterprises within the platform ecosystem.
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Tengjiang Yu, Haitao Zhang, Junfeng Sun, Yabo Wang, Shuang Huang and Dan Chen
Using typical structure of asphalt pavement in Harbin area of China, and the formula of generalized friction coefficient between base and surface layers of asphalt pavement in…
Abstract
Purpose
Using typical structure of asphalt pavement in Harbin area of China, and the formula of generalized friction coefficient between base and surface layers of asphalt pavement in cold area is established.
Design/methodology/approach
Through structural characteristics analysis of asphalt pavement in cold area, the generalized formula of friction coefficient between base and surface layers of asphalt pavement in cold area is derived. The formula can quickly calculate the friction coefficient between layers of asphalt pavement.
Findings
Based on quantitative analysis to the contacting state between layers of asphalt pavement in cold area, the relationships between generalized friction coefficient and resilient modulus of asphalt mixtures, temperature shrinkage coefficient and temperature have been established.
Originality/value
The findings can enrich the description methods about the contacting state between layers of asphalt pavement, and have a certain theoretical and practical value. Through the application of the formula of generalized friction coefficient between layers, it can provide a technical basis for the asphalt pavement design, construction and maintenance in cold area.
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Li Wang, Junfeng Tian, Yanhong Si and Xixiu Sun
Online retailers have become gradually popular to offer consumers installment payment services in the past few years. This paper aims to study how to determine the duration and…
Abstract
Purpose
Online retailers have become gradually popular to offer consumers installment payment services in the past few years. This paper aims to study how to determine the duration and rate of installment payment services, as well as the price of products to increase online retailers’ profits.
Design/methodology/approach
By modeling the utility functions, the behavior of consumers for strategic choosing the payment method and payment timing is analyzed. Thus, the market segments are obtained through the comparison of the consumer’s utilities. Combined with the given assumptions, the installment payment strategies for online retailers is investigated. This paper focuses on the impact of installment payment services on consumers’ purchasing behavior and online retailers’ profits by modeling and comparative analysis. No installment payment service as a benchmark, it is demonstrated whether online retailers can obtain more profits by offering installment payment services or what are the applicable conditions for installment payments.
Findings
If the installment payment service is offered, online retailers can gain more profits and need to adopt appropriate strategies based on different market conditions. During the depression or the peak shopping season, online retailers should take the strategy of free installment rate, and moderately increasing the product price of no installment service. When market demand is stable or during non-peak season, online retailers need to set a higher installment rate and maintain the product price without installment service. Finally, online retailers should determine the maximum duration of installments they can afford based on own risk control cost and allow consumers to freely choose the length of the installment within the duration limit.
Originality/value
First, the authors deeply analyze consumers’ payment and purchase behavior when the online retailer offers the installment payment service. Then, it is theoretically proved why many online retailers have offered installment payment services to consumers from a profit perspective. Finally, this paper proposes the optimal duration of installments, installment rate and product price in different market environments for online retailers, to provide theoretical basis and managerial insights for the development of installment payment service in online shopping.
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Zimeng Wang, Fabrice Colin, Guigao Le and Junfeng Zhang
The purpose of this paper is to develop a counter-extrapolation approach for computational heat and mass transfer with the interfacial discontinuity considered at conjugate…
Abstract
Purpose
The purpose of this paper is to develop a counter-extrapolation approach for computational heat and mass transfer with the interfacial discontinuity considered at conjugate interfaces.
Design/methodology/approach
By applying finite-difference approximations for the interfacial gradients along the local normal direction, the conjugate system can be simplified to the Dirichlet boundary problems for individual domains. A suitable method for the Dirichlet boundary value condition can then be used. The lattice Boltzmann method has been used to demonstrate the method. The model has been carefully validated by comparing the simulation results and theoretical solutions for steady and unsteady systems with flat or circular interfaces. Furthermore, the cooling process of a hot cylinder in a cold flow, which involves unsteady flow and heat transfer across a curved interface, has been simulated as an example to illustrate the practical usefulness of this model.
Findings
Good agreement has been observed in comparisons of simulations and theoretical solutions. The convergence and stability of the method have also been examined and satisfactory results have been obtained. Results of the cylinder cooling process show that a surface insulation layer can effectively reduce the heat transfer process and slow down the cooling process.
Originality/value
This method possesses several technical advantages, including the simple and straightforward algorithm, and accurate representation of the interface geometry. The basic idea and algorithm of the counter-extrapolation procedure presented here can be readily extended to other lattice Boltzmann models and even other computational technologies for heat and mass transfer systems with interface discontinuity.
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Bin Zhao, Yawei Zhou, Junfeng Qu, Fei Yin, Shaoqing Yin, Yongwei Chang and Wu Zhang
Since carbon nanotubes (CNTs) were discovered by Iijima in 1991, they have gained more and more attention by people because of their unique physical and chemical properties. The…
Abstract
Purpose
Since carbon nanotubes (CNTs) were discovered by Iijima in 1991, they have gained more and more attention by people because of their unique physical and chemical properties. The CNTs have one-dimensional nanostructure, high surface adsorption capacity, good conductivity and electronic ballistic transmission characteristics and therefore have excellent mechanical, electrical, physical and chemical properties. CNTs are ideal basic materials to make nanometer gas sensors. Nanometallic materials function as to enhance electrode activity and promote the electron transfer, so if composite nanometallic materials M (such as Au, Pt, Cu and Pd) and CNTs are used, all kinds of their characters of components would have coeffect. Electrochemical sensors by use of such composite as electrode would have a higher detection sensitivity.
Design/methodology/approach
CNTs were synthesized via chemical vapor deposition technique and were purified afterward. CNTs-M(Pt,Au) suspension was prepared by chemical deposition using spinning disc processor (SDP) and was coated on gold electrode. The modified electrodes were constructed, based on immobilization of glucose oxidase on an Au electrode by electrostatic effect. CNTs-Pt/ glassy carbon electrodes (GCE) electrodes were made by electrochemically deposition of platinum particles on GCE modified by CNTs. The microstructures of the harvested CNTs, CNTs-M (M = Au, Pt) were analyzed under scanning electron microscopy and transmission electron microscopy. The application of the sensor in medical detection has been evaluated.
Findings
The results shown that CNTs-Au biosensors exhibit good reproducibility, stability and fast response to glucose detection, it can be used in the clinic detection of glucose concentration in human serum. Using CNTs-Pt/GCE for formaldehyde detection exhibited high sensitivity and good reproducibility.
Originality/value
This study modified CNTs by using self-assembled techniques through SDP with nano Pt and Au by electrodeposition for the first time. CNTs-Pt/GCE electrode was prepared by depositing platinum particles electrochemically on GCE modified by CNTs. CNTs-Au-modified electrode was prepared by immobilization of glucose oxidase on an Au electrode first by electrostatic effect. Electrochemical behaviors of glucose at CNTs-Au and formaldehyde at CNTs-Pt/GCE were investigated by cyclic voltammetry.
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Asli Özdemir and Güzin Özdagoglu
Prediction problems raised in uncertain environments require different solution approaches such as grey prediction models, which consider uncertainty in information and also…
Abstract
Purpose
Prediction problems raised in uncertain environments require different solution approaches such as grey prediction models, which consider uncertainty in information and also enable the use of small data sets. The purpose of this paper is to investigate the comparative performances of grey prediction models (GM) and Markov chain integrated grey models in a demand prediction problem.
Design/methodology/approach
The modeling process of grey models is initially described, and then an integrated model called the Grey-Markov model is presented for the convenience of applications. The analyses are conducted on a monthly demand prediction problem to demonstrate the modeling accuracies of the GM (1,1), GM (2,1), GM (1,1)-Markov, and GM (2,1)-Markov models.
Findings
Numerical results reveal that the Grey-Markov model based on GM (2,1) achieves better prediction performance than the other models.
Practical implications
It is thought that the methodology and the findings of the study will be a significant reference for both academics and executives who struggle with similar demand prediction problems in their fields of interest.
Originality/value
The novelty of this study comes from the fact that the GM (2,1)-Markov model has been first used for demand prediction. Furthermore, the GM (2,1)-Markov model represents a relatively new approach, and this is the second paper that addresses the GM (2,1)-Markov model in any area.