Yan Jun Xi, Yong Jun Liu, Zhi Xin Wang and Jin Bin Liu
The purpose of this paper is to investigate the oxidation behavior of Ti‐48Al‐8Cr‐2Ag (at.%) at 900°C and 1000°C for various different times.
Abstract
Purpose
The purpose of this paper is to investigate the oxidation behavior of Ti‐48Al‐8Cr‐2Ag (at.%) at 900°C and 1000°C for various different times.
Design/methodology/approach
Laboratory tests were performed to determine growth process of the oxide scale at 900°C and 1000°C for various different times with SEM/EDX, XRD and TEM.
Findings
Merely Al2O3 occurred on the Laves phase at the initial stage at 900°C, while a mixture of Al2O3+TiO2 formed at the initial stage at 1000°C. Oxidation rate of the alloy at 900°C after long‐term oxidation was higher than that at 1000°C because a dense Al2O3 scale formed on the surface at 1000°C.
Originality/value
The paper shows that the oxidation behavior of TiAl alloy at initial stage is the basis of the revealing mechanism of oxidation. It is necessary to further investigate the oxidation of Ti‐Al‐Cr‐Ag alloy in more detail to clearly understand its oxidation process and growth process of the oxide scale.
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Yan Jun Xi, Yong Jun Liu, Zhi Xin Wang and Jin Bin Liu
The purpose of this paper is to investigate the high‐temperature oxidation behavior in air at 900‐1,000°C and electrochemical corrosion performance in 3.5 percent NaCl solution of…
Abstract
Purpose
The purpose of this paper is to investigate the high‐temperature oxidation behavior in air at 900‐1,000°C and electrochemical corrosion performance in 3.5 percent NaCl solution of Ti‐24Al‐17Nb‐0.5Mo (at. %) alloy with Ti‐48Al‐8Cr‐2Ag (at. %) coating.
Design/methodology/approach
Laboratory tests are performed to determine the effect of the Ti‐48Al‐8Cr‐2Ag (at. %) coating on the corrosion performance of Ti3Al alloy.
Findings
It is found that the oxidation rate of sputtered Ti‐48Al‐8Cr‐2Ag nanocrystalline coating is lower than that of the Ti3Al alloy at 900°C. The former forms a scale of merely Al2O3 and the latter forms a scale of TiO2. However, the Ti‐48Al‐8Cr‐2Ag nanocrystalline coating shows a slightly higher oxidation rate than did the Ti3Al alloy at 1,000°C, because outer TiO2 scale forms and columnar boundaries of the coating give a larger actual oxidation area than the original alloy. The coating shows the excellent electrochemical corrosion resistance in 3.5 percent NaCl solution because it exhibits stable passive polarization behavior without any overpassivation phenomena.
Originality/value
TiAlCrAg coatings may become a promising protective coating for Ti3Al‐base intermetallics, which improve the Al2O3 scale formation and make the passivation stable.
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Le Wang, Jun Lin, Jie Yan and Wentian Cui
The purpose of this paper is to investigate the combined effects of different modalities of long-term knowledge accumulation and short-term knowledge searching on the generation…
Abstract
Purpose
The purpose of this paper is to investigate the combined effects of different modalities of long-term knowledge accumulation and short-term knowledge searching on the generation of high-impact ideas. The authors aim at providing useful conclusions for academic scholars.
Design/methodology/approach
Two dimensions of the cumulative knowledge structures of researchers are measured: knowledge depth and knowledge breadth. The search strategies employed by researchers are classified as local search and distant search. The authors use researchers’ historical publications to measure cumulative knowledge structures. References contained in these publications serve as an indicator of knowledge searching behaviors and are used to measure search strategies. Highly cited papers with random-but-matched papers from the same journal published in the same year are adopted to test the hypotheses.
Findings
The knowledge depth of researchers positively predicts the generation of high-impact ideas. Knowledge breadth has a bell-shaped relationship to the generation of high-impact ideas. Two instances of “strategic fit” between the knowledge structures and search strategies of researchers are identified; namely, knowledge breadth combines most effectively with local search, and knowledge depth combines most effectively with distant search in generating high-impact ideas.
Research limitations/implications
Using article references to measure authors’ knowledge search behaviors may lead to biases. Future research should perform a survey to obtain a comprehensive understanding of the knowledge search behaviors of scholars.
Practical implications
A “T-shaped” knowledge structure in the long run is recommended for maximal generation of high-impact ideas. Researchers who have not adopted this optimal knowledge structure can employ a matched search strategy to leverage their existing knowledge structures.
Originality/value
This paper is among the first to examine the interactive effects between the cumulative knowledge structures and short-term knowledge searching strategies of researchers. The authors have enriched the exploration and exploitation theory by adding the dimension of time into the analysis.
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Fei Chen, Chao Wang, Ke Yan, Muhammad Azeem Ghouri, Yongsheng Zhu and Jun Hong
This paper aims to analyze the temperature field and the heat transfer performance of the counter rotating dual rotor bearings (CRDRB) based on the air phase flow field at…
Abstract
Purpose
This paper aims to analyze the temperature field and the heat transfer performance of the counter rotating dual rotor bearings (CRDRB) based on the air phase flow field at different speeds to provide effective support for the lubrication and the thermal design of CRDRB.
Design/methodology/approach
In this study, taking H7006C angular contact ball bearing as an example, based on the flow visualization technique and the thermal analysis methods, the effects of outer ring speed on the air phase flow field, the temperature field and the heat transfer in bearing cavity were investigated.
Findings
Results indicated that there were more complex turbulent air vortices in CRDRB cavity. Turbulent cyclones in critical contact zone reduced the heat dissipation capacity of air. Compared with single rotor bearing with a static outer ring, the average heat transfer coefficient reduced by 11.78% and the average temperature raised by 3.06 K inside CRDRB cavity. Under the influence of outer ring rotation, the high temperature area in ball-inner raceway contact zone and pocket raised and reduced by 160.13% and 30.48%, respectively. The outer ring rotation had opposite effect on the heat dissipation of raceway contact zone and pocket.
Originality/value
The air phase flow field characteristics and the heat transfer performance of CRDRB were revealed and analyzed from the mechanism. An area quantification method was presented as an auxiliary mean of the thermal analysis to evaluate the heat transfer performance of bearing.
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Shiyu Feng, Chenchen Wang, Xiaotian Peng, Yan Yan, Yang Deng and Jun Chen
The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure…
Abstract
Purpose
The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure relief process under various plenum compartment pressures and Mach numbers.
Design/methodology/approach
Under various plenum compartment pressures and Mach numbers, the effect of the area and aspect ratio on the discharge and force characteristics of the PRD are numerically investigated via a three-dimensional steady Reynolds-averaged Navier–Stokes equations solver based on structured grid technology.
Findings
When the aspect ratio remains constant, the discharge coefficient CD, thrust coefficient CT and moment coefficient CM are not affected by the PRD. When the area is constant, the aspect ratio dramatically impacts the discharge and force characteristics because the aspect ratio increases, the discharge coefficient CD of the PRD decreases, and the thrust coefficient CT and the moment coefficient CM both increase. When the aspect ratio is 2, the discharge coefficient CD decreases by 14.7 per cent, the thrust coefficient CT increases by 10-15 per cent, and the moment coefficient CM increases by 10-23 per cent compared with when the aspect ratio is 1.
Practical implications
This study provides detailed data and conclusions for nacelle PRD researchers and actual engineering applications.
Originality/value
On the basis of considering the influence of operating conditions on the discharge and force characteristics of the nacelle PRD, the impact of geometric parameters, including the area and aspect ratio on the discharge and force characteristics is comprehensively considered.
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Xi Luo, Jun-Hwa Cheah, Xin-Jean Lim, T. Ramayah and Yogesh K. Dwivedi
The increasing popularity of live-streaming commerce has provided a new opportunity for e-retailers to boost sales. This study integrated signaling theory and social exchange…
Abstract
Purpose
The increasing popularity of live-streaming commerce has provided a new opportunity for e-retailers to boost sales. This study integrated signaling theory and social exchange theory to investigate how streamer- and product-centered signals influence customers’ likelihood of making an impulsive purchase in the live-streaming commerce context.
Design/methodology/approach
An online survey was designed and distributed to the target respondents in China using purposive sampling. A total of 735 valid responses were analyzed with partial least square structural equation modeling (PLS-SEM).
Findings
Both streamer-centered signals, i.e. streamer credibility and streamer interaction quality, were discovered to significantly influence product-centered signal, i.e. product information quality. Additionally, streamer interaction quality was found to have a significant impact on streamer credibility. Furthermore, it was observed that customer engagement played a significant mediating role in the relationship between product information quality and impulsive buying tendency. Moreover, the paths between product information quality and customer engagement, as well as the connection between engagement and impulsive buying tendency, were found to be moderated by guanxi orientation.
Originality/value
Despite the prevalence of impulsive purchases in live-streaming commerce, few studies have empirically investigated the impact of streamer and product signals on influencing customers’ impulsive purchase decisions. Consequently, to the best of our knowledge, this study distinguishes itself by offering empirical insights into how streamers use reciprocating relationship mechanisms to communicate signals that facilitate impulsive purchase decisions.
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Yang Dang‐guo, Sun Yan, Zhang Zheng‐yu, Wang Chao and Zhu Wei‐jun
The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method…
Abstract
Purpose
The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method can ensure the structural configuration similarity considering model deformation under aerodynamic loads.
Design/methodology/approach
Photopolymer‐resin based on RP technique was used to fabricate DLR‐F4 models. Testing in a subsonic and transonic wind tunnel was carried out and the test results were compared to analyze performance predictions.
Findings
RP photopolymer‐resin wind‐tunnel models fabricated by the design methods yielded satisfactory aerodynamic performance. The methods can decrease the model's weight and prevent resonance occurrence among the models, wind‐tunnel, and support system, shorten the processing period, and lead to decrease in manufacturing period and cost.
Research limitations/implications
Stiffness shortage of the thin components, such as wing tip, often leads to deformation occurrence under aerodynamic loads in transonic wind‐tunnel tests, which has significant influence on aerodynamic characteristics of the test models. Therefore, model deformation should be taken into account in the design process.
Originality/value
This design and manufacture method, aerodynamic and structural combination design and structural optimization, can obtain RP lightweight photopolymer‐resin wind‐tunnel models for satisfactory aerodynamic performance, which makes RP techniques more practical for manufacturing transonic wind‐tunnel test models, considering deformation induced by aerodynamic forces such as lift force. The methods also present an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.
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Gang Liu, Fengshan Ma, Maosheng Zhang, Jie Guo and Jun Jia
Continua and discontinua coexist in natural rock materials. This paper aims to present an improved approach for addressing the mechanical response of rock masses based on the…
Abstract
Purpose
Continua and discontinua coexist in natural rock materials. This paper aims to present an improved approach for addressing the mechanical response of rock masses based on the combined finite-discrete element method (FDEM) proposed by Munjiza.
Design/methodology/approach
Several algorithms have been programmed in the new approach. The algorithms include (1) a simpler and more efficient algorithm to calculate the contact force; (2) An algorithm for tangential contact force closer to the actual physical process; (3) a plastic yielding criterion (e.g. Mohr-Coulomb) to modify the elastic stress for fitting the mechanical behavior of elastoplastic materials; and (4) a complete code for the mechanical calculation to be implemented in Matrix Laboratory (MATLAB).
Findings
Three case studies, including two standard laboratory experiments (uniaxial compression and Brazilian split test) and one engineering-scale anti-dip slop model, are presented to illustrate the feasibility of the Y-Mat code and its ability to deal with multi-scale rock mechanics problems. The results, including the progressive failure process, failure mode and trajectory of each case, are acceptable compared to other corresponding studies. It is shown that, the code is capable of modeling geotechnical and geological engineering problems.
Originality/value
This article gives an improved FDEM-based numerical calculation code. And, feasibility of the code is verified through three cases. It can effectively solve the geotechnical and geological engineering problems.
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Shihui Yang and Jun Yu
The purpose of this study is to help governments make carbon-tax policy and help enterprises make decisions under that policy.
Abstract
Purpose
The purpose of this study is to help governments make carbon-tax policy and help enterprises make decisions under that policy.
Design/methodology/approach
Based on the carbon-tax policy, with the consideration of consumers’ low-carbon preferences, this paper compares the pricing, emission reduction and advertising decisions in three different games (one centralized game and two decentralized Stackelberg games).
Findings
This paper concludes that, through centralized game, namely, cooperation game, manufacturers, retailers and consumers can reach their optimal situation. In the numerical simulation, this paper analyzes the impact of carbon-tax rate to the decisions of manufacturer and retailer, as well as their profit.
Originality/value
Using the Nash Bargaining Model, the introduction of the bargaining power and the degree of risk aversion of the parties, this study provides some solution for the distribution of the additional profit when they cooperate, in which way they can reach their Pareto optimality.
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Marisa Siddivò and Alessandra De Chiara
The aim of this paper is to demonstrate that synergy between firms and local institutions may lead to success even in an economic environment which cannot offer competitive…
Abstract
Purpose
The aim of this paper is to demonstrate that synergy between firms and local institutions may lead to success even in an economic environment which cannot offer competitive advantages to high tech industrial clustering. However, the condition for such a complex result is convergence between cluster‐based regional development policy, the related industry national strategy and the central government preferential policy for less developed areas.
Design/methodology/approach
The experiences selected as case studies are the Xi'an National Civil Aerospace Base in Shaanxi Province (China) and CampaniAerospace in Campania region (Italy). As information was gathered both through policy documents (China and Italy) and direct interviews to cluster's stakeholders (Italy), the outcome is, according to the criteria suggested by Eisenhardt and Yin, a qualitative research. Comparing economic data provided by the respective countries' Statistical Offices, the authors assessed that Shaanxi Province and the Campania region share a “peripheral” position within their respective national context. Starting from this, the authors analyzed the formal documents which reported the experience of the two clusters.
Findings
The finding is that the outcome (the status of cluster which is assumed as “a value in itself”) of the convergence between firms' will to gain agglomeration advantages and the policymakers' plan to redress interregional economic disparities is definitely not an efficiency‐driven process. In the high tech sectors which are very sensitive to the increasing competition for technology on the international market, the pursuit of efficiency may, on the contrary, be dissipated.
Originality/value
As attested by the comparative literature, aims and performance of industrial clusters differ in accordance with the stage of economic development as well as the institutional and regulatory framework. The paper demonstrates, however, that in the take‐off stage, it is the position occupied by the host region within the national context which determines the behaviour of the actors concerned as well as the outcome of their commitment.