Chengwei Fei, Wenzhong Tang, Guangchen Bai and Shuang Ma
This paper aims to reasonably quantify the radial deformation of turbine blade from a probabilistic design perspective. A probabilistic design for turbine blade radial deformation…
Abstract
Purpose
This paper aims to reasonably quantify the radial deformation of turbine blade from a probabilistic design perspective. A probabilistic design for turbine blade radial deformation considering non-linear dynamic influences can quantify risk and thus control blade tip clearance to further develop the high performance and high reliability of aeroengine. Moreover, the need for a cost-effective design has resulted in the development of probabilistic design method with high computational efficiency and accuracy to quantify the effects of these uncertainties.
Design/methodology/approach
An extremum response surface method-based support vector machine (SVM-ERSM) was proposed based on SVM of regression to improve the computational efficiency and precision of blade radial deformation dynamic probabilistic design regarding non-linear material properties and dynamically thermal and mechanical loads.
Findings
Through the example calculation and comparison of methods, the results show that the blade radial deformation reaches at the maximum at t = 180 s; the probabilistic distribution and inverse probabilistic features of output parameters and the major factors (rotor speed and gas temperature) are gained; besides, the SVM-ERSM holds high computational efficiency and precision in the non-linear dynamic probabilistic design of aeroengine typical components.
Practical implications
The present efforts provide a method to design turbine besides other aeroengine components considering dynamic and non-linear factors base on probabilistic design for further research.
Social implications
Moreover, the present study provides a way to design dynamic (motion) structures from a probabilistic perspective.
Originality/value
It is proved that the dynamic probabilistic design-based SVM-ERSM could produce a more reasonable blade radial deformation while maintaining low failure probability, as well as offer a useful reference for blade-tip clearance control and a promising insight to the optimal design of aeroengine typical components.
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Qin-Ying Wang, Wen-Qi Ma, Hui Chai, Xing-Shou Zhang, Yu-Chen Xi and Shu-Lin Bai
This study aims to investigate the effect of powder recycling on the microstructure of plasma-sprayed Ni625-WC composite coating and to verify the feasibility of Ni625-WC powder…
Abstract
Purpose
This study aims to investigate the effect of powder recycling on the microstructure of plasma-sprayed Ni625-WC composite coating and to verify the feasibility of Ni625-WC powder recycling by comparing the corrosion resistance of the coatings in high-temperature and pressure CO2 environment.
Design/methodology/approach
Recycling powder is an efficient way to improve the utilization rate of metal powder during plasma spraying. The plasma-sprayed Ni625-WC composite coatings with original powder (OC) and recovered powder (RC) were analytically compared by using scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. The corrosion resistance of the Ni625-WC composite coatings was characterized in a self-designed high-temperature and pressure autoclave by an electrochemical workstation.
Findings
The results showed that there is massive M23C6 in OC and acicular M23C6 in RC. The WC particles in RC are more uniformly distributed, and the area ratios of WC particles to Inconel 625 matrix are 2.37% higher than OC. RC showed high corrosion resistance, and the recycling of Ni625-WC powder is feasible.
Originality/value
The feasibility of Ni625-WC powder recycling was verified from the microstructure evolution and electrochemical behavior of the coatings.
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Xue-Qin Li, Lu-Kai Song and Guang-Chen Bai
To provide valuable information for scholars to grasp the current situations, hotspots and future development trends of reliability analysis area.
Abstract
Purpose
To provide valuable information for scholars to grasp the current situations, hotspots and future development trends of reliability analysis area.
Design/methodology/approach
In this paper, recent researches on efficient reliability analysis and applications in complex engineering structures like aeroengine rotor systems are reviewd.
Findings
The recent reliability analysis advances of engineering application in aeroengine rotor system are highlighted, it is worth pointing out that the surrogate model methods hold great efficiency and accuracy advantages in the complex reliability analysis of aeroengine rotor system, since its strong computing power can effectively reduce the analysis time consumption and accelerate the development procedures of aeroengine. Moreover, considering the multi-objective, multi-disciplinary, high-dimensionality and time-varying problems are the common problems in various complex engineering fields, the surrogate model methods and its developed methods also have broad application prospects in the future.
Originality/value
For the strong demand for efficient reliability design technique, this review paper may help to highlights the benefits of reliability analysis methods not only in academia but also in practical engineering application like aeroengine rotor system.
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Deniz Erer and Elif Erer
Introduction: Uncertainty plays an important role on economic stability and macroeconomic variables. Economic agents postpone decisions about investment and consumption in periods…
Abstract
Introduction: Uncertainty plays an important role on economic stability and macroeconomic variables. Economic agents postpone decisions about investment and consumption in periods in which uncertainty is high. This situation affects economic growth negatively. Recently, uncertainty has focused on policy uncertainty. At this point, economic policy uncertainty (EPU) comes to the forefront. EPU is defined as conception that economic agents do not forecast consequences of economic policies adopted by policy makers and future economic policies. In terms of developing countries, statements presented by policy makers in the United States especially may appear as a source of uncertainty in developing economies.
Aim: Therefore, the aim of this study is to analyze the effects of US EPU on macroeconomic variables for Turkey and Brazil, Russia, India, China and South Africa for periods in which global risk perception is low and high.
Method: The authors used monthly data from January 1998 to December 2018. For this purpose, the authors used Threshold VAR. VIX index takes in consideration as global risk perception. The authors used US EPU index proposed by Baker’s vd. (2016) in order to measure EPU in the United States. Besides, the authors used macroeconomic variables such as industrial production index, inflation and exchange rate.
Findings: As is seen from the results of the analysis, for Turkey’s economy the macroeconomic variables significantly and strongly respond to the changes in the EPU index during the periods in which global risk perception is low; nonetheless, the so-called responses weaken due to the adopted policy of “wait and watch” by investors during the periods in which global risk perception is high.
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Kjell Hausken and Jonathan W. Welburn
The article develops a model to interpret the 2010–2018 financial crisis in Greece, Portugal, Ireland, Spain and Cyprus, and the loan programs from the IL (International Lender;…
Abstract
Purpose
The article develops a model to interpret the 2010–2018 financial crisis in Greece, Portugal, Ireland, Spain and Cyprus, and the loan programs from the IL (International Lender; i.e. the European Union, the European Commission, and the International Monetary Fund).
Design/methodology/approach
For each country, an isoelastic utility with constant relative risk aversion is assumed. For the IL a Cobb Douglas utility is assumed with consumption, the GDP (Gross Domestic Product) to debt ratio, and market stability as inputs, accounting for time discounting. This article applies two methods to assess the empirics. The first method considers the IL's strategy as a whole over the 2010–2018 period. The second method assumes that the IL maximizes its utility in one period to determine its optimal loan, accounting for the empirics in that period, and the debt in the previous period.
Findings
For the first method, when the output elasticity in the IL's Cobb Douglas utility is high favoring consumption, the IL prefers offering a higher loan than its actual loan. Otherwise the IL prefers to offer no loan. The output elasticity at which the IL prefers to offer a loan is lowest for Greece, second lowest for Cyprus, third lowest for Portugal, and highest for Ireland and Spain. A high loan to Greece over a larger range of the output elasticity for Greece's consumption is supported by Greece being prioritized through the loan program. For the second method, the IL prefers to offer no loan to Greece which is too burdened with debt. Thus, the first method seems preferable, considering the entire duration of the crisis holistically.
Originality/value
The article offers a novel perspective of how to assess debt crises, enabling the IL to weigh various factors such as consumption, GDP, loan offered, and each country's debt to credit markets.
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Da Teng, Yun-Wen Feng, Jun-Yu Chen and Cheng Lu
The purpose of this paper is to briefly summarize and review the theories and methods of complex structures’ dynamic reliability. Complex structures are usually assembled from…
Abstract
Purpose
The purpose of this paper is to briefly summarize and review the theories and methods of complex structures’ dynamic reliability. Complex structures are usually assembled from multiple components and subjected to time-varying loads of aerodynamic, structural, thermal and other physical fields; its reliability analysis is of great significance to ensure the safe operation of large-scale equipment such as aviation and machinery.
Design/methodology/approach
In this paper for the single-objective dynamic reliability analysis of complex structures, the calculation can be categorized into Monte Carlo (MC), outcrossing rate, envelope functions and extreme value methods. The series-parallel and expansion methods, multi-extremum surrogate models and decomposed-coordinated surrogate models are summarized for the multiobjective dynamic reliability analysis of complex structures.
Findings
The numerical complex compound function and turbine blisk are used as examples to illustrate the performance of single-objective and multiobjective dynamic reliability analysis methods. Then the future development direction of dynamic reliability analysis of complex structures is prospected.
Originality/value
The paper provides a useful reference for further theoretical research and engineering application.
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Songjun Xu and Yaou Hu
Awe is an important yet largely overlooked emotion in tourism. This paper aims to reveal the underlying mechanism of the effects of nature-inspired awe on stimulating tourists'…
Abstract
Purpose
Awe is an important yet largely overlooked emotion in tourism. This paper aims to reveal the underlying mechanism of the effects of nature-inspired awe on stimulating tourists' environmentally responsible behavior (TERB) intention by delving into the serial mediation effect of state construal level, small-self perception and state connectedness to nature (CNT).
Design/methodology/approach
This research was built upon the appraisal theory of emotion. Study 1 was a scenario-induced quasi-experimental study to test the proposed model linking awe, small-self perception, state CNT and TERB intention. A total of 271 valid questionnaires were collected via an online questionnaire platform. Study 2 was a field study designed to replicate the findings of Study 1 and further uncover the mediating role of the state construal level. Study 2 was conducted in Baiyun Mountain Scenic Area, China. A total of 229 valid questionnaires were used for analysis.
Findings
This research deepens our understanding of the effects of nature-inspired awe in the tourism and travel fields. This research uncovers the underlying mechanism by which awe increases TERB intention through serial mediation. Specifically, awe inspires tourists to apply a higher level of construal, which makes tourists perceive a smaller self, making them feel more connected to nature and exert more intention to adopt ERB.
Originality/value
This research linked tourists' mindset (i.e. state construal level), internal (i.e. small-self perception) and external (i.e. state CNT) cognition in an integrated model, explaining how nature-inspired awe contributes to eliciting TERB intention. The findings add critical theoretical contributions to the travel and tourism literature and provide important implications for the tourism industry to inspire awe and benefit from such emotion.
研究目的
敬畏在旅游中是一种十分重要的情绪, 但却鲜少被关注。本研究旨在深入研究解释水平状态、小我感知和自然关联感的链式中介效应, 揭示自然敬畏激发游客环境责任行为意向的内在作用机制。
研究设计与方法
本研究的基础理论为情绪评价理论。研究一通过场景诱导的准实验研究, 检验将敬畏、小我感知、自然关联感和游客责任行为意向的假设模型; 研究一以网络问卷平台收集的271份有效问卷数据进行分析。研究二是一项在中国白云山风景区开展的实地研究, 旨在检验研究一的研究结果, 并进一步揭示解释水平状态的中介效应; 研究二采用229份有效问卷数据进行分析。
研究发现
本研究揭示了敬畏通过链式中介作用影响游客环境责任行为意向的内在作用机制, 深化了对自然敬畏在旅游和旅行领域价值的理解。具体而言, 本研究发现敬畏激发了游客启动更高的解释水平, 这使游客感知到更渺小的自我, 并促使他们感到与自然的联系更加紧密, 从而提升了游客的环境责任行为意向。
原创性/价值
本研究将游客的心理定式(即解释水平状态)、内在认知(即小我感知)和外部认知(即自然关联感)整合到一个综合模型中, 解释了自然敬畏引发游客环境责任行为意向的作用机制。研究结果为旅游研究提供了重要的理论贡献, 也为旅游行业如何在实践中激发敬畏感并从中获得效益提供了重要的实践启示。
Propósito
El asombro es una emoción importante pero en gran medida ignorada en el turismo. Esta investigación pretende revelar el mecanismo subyacente de los efectos del asombro inspirado por la naturaleza en la estimulación de la intención del comportamiento responsable con el medio ambiente (TERB) de los turistas, profundizando en el efecto mediador en serie del nivel de interpretación del estado, la percepción del pequeño yo y la conexión del estado con la naturaleza (CNT).
Diseño/metodología/enfoque
Esta investigación se basó en la teoría de la valoración de la emoción. El estudio 1 fue un estudio cuasiexperimental inducido por escenarios para probar el modelo propuesto que vincula el sentimiento de asombro, la percepción del pequeño yo, el estado CNT y la intención TERB. Se recogieron 271 cuestionarios válidos a través de una plataforma de cuestionarios en línea. El Estudio 2 fue un estudio de campo diseñado para replicar los hallazgos del Estudio 1 y descubrir más a fondo el papel mediador del nivel de interpretación del estado. El estudio 2 se llevó a cabo en la zona escénica de la montaña de Baiyun (China). Se utilizó un total de 229 cuestionarios válidos para el análisis.
Resultados
Esta investigación profundiza en nuestra comprensión de los efectos del asombro inspirado por la naturaleza en los ámbitos del turismo y los viajes. Esta investigación descubre el mecanismo subyacente por el que el asombro aumenta la intención de TERB a través de la mediación en serie. En concreto, el asombro inspira a los turistas a aplicar un mayor nivel de interpretación, lo que hace que los turistas perciban un yo más pequeño, lo que les hace sentirse más conectados con la naturaleza y ejercer así una mayor intención de adoptar TERB.
Originalidad/valor
Esta investigación vinculó la mentalidad de los turistas (es decir, el nivel de nterpretación del estado), la cognición interna (es decir, la percepción de un yo más pequeño) y la externa (es decir, la CNT del estado) en un modelo integrado, explicando cómo el asombro inspirado por la naturaleza contribuye a suscitar la intención TERB. Los hallazgos añaden contribuciones teóricas críticas a la literatura sobre viajes y turismo y proporcionan implicaciones importantes para que la industria turística inspire asombro y se beneficie de dicha emoción.
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Mingkang Zhang, Yongqiang Yang, Meizhen Xu, Jie Chen and Di Wang
The purpose of this study is focused on the mechanical properties of multi-materials porous structures manufactured by selective laser melting (SLM).
Abstract
Purpose
The purpose of this study is focused on the mechanical properties of multi-materials porous structures manufactured by selective laser melting (SLM).
Design/methodology/approach
The Diamond structure was designed by the triply periodic minimal surface function in MATLAB, and multi-materials porous structures were manufactured by SLM. Compression tests were applied to analyze the anisotropy of mechanical properties of multi-materials porous structures.
Findings
Compression results show that the multi-materials porous structure has a strong anisotropy behavior. When the compression force direction is parallel to the material arrangement, multi-materials porous structure was compressed in a layer-by-layer way, which is the traditional deformation of the gradient structure. However, when the compression force direction is perpendicular to the material arrangement, the compression curves show a near-periodic saw-tooth waveform characteristic, and this kind of structure was compressed consistently. It is demonstrated that the combination with high strength brittle material and low strength plastic material improves compression mode, and plastic material plays a role in buffering fracture.
Originality/value
This research provides a new method for the design and manufacturing of multi-materials porous structures and an approach to change the compression behavior of the porous structure.
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Mingkang Zhang, Yongqiang Yang, Wentao Qin, Shibiao Wu, Jie Chen and Changhui Song
This study aims to focus on the optimized design and mechanical properties of gradient triply periodic minimal surface cellular structures manufactured by selective laser melting.
Abstract
Purpose
This study aims to focus on the optimized design and mechanical properties of gradient triply periodic minimal surface cellular structures manufactured by selective laser melting.
Design/methodology/approach
Uniform and gradient IWP and primitive cellular structures have been designed by the optimized function in MATLAB, and selective laser melting technology was applied to manufacture these cellular structures. Finite element analysis was applied to optimize the pinch-off problem, and compressive tests were carried out for the evaluation of mechanical properties of gradient cellular structures.
Findings
Finite element analysis shows that the elastic modulus of IWP increased as design parameter b increased, and then decreased when parameter b is higher than 5.5. The highest elastic modulus of primitive increased by 89.2% when parameter b is 6. The compressive behavior of gradient IWP and primitive shows a layer-by-layer way, and elastic modulus and first maximum compressive strength of gradient primitive are higher than that of gradient IWP. The effective energy absorption of gradient cellular structures increased as the average porosity decreased, and the effective energy absorption of gradient primitive is about twice than that of gradient IWP.
Originality/value
This paper presents an optimized design method for the pinch-off problem of gradient triply periodic minimal surface cellular structures.
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Congcong Liu, Chong Wang, Keping Ye, Yun Bai, Xiaobo Yu, Chunbao Li and Guanghong Zhou
The purpose of this paper is to elucidate the influences of the animal fat and fatty acid type on the formation of polycyclic aromatic hydrocarbons (PAHs) and to propose a…
Abstract
Purpose
The purpose of this paper is to elucidate the influences of the animal fat and fatty acid type on the formation of polycyclic aromatic hydrocarbons (PAHs) and to propose a formation mechanism of PAHs in fat during electric roasting, which is a method of non-direct-contact-flame heating.
Design/methodology/approach
The effects of animal fats and model fat on the formation of PAHs were valued on the basis of the ultra high-performance liquid chromatography data. The corresponding products of the FAME pyrolysis were detected by TG-FTIR. The proposal formation mechanism of PAHs was based on the summary of the literature.
Findings
Contrary to the International Agency for Research on Cancer, DF had higher risk with 280.53 ng/g of concentration after being roasted than the others animal fats of red meat in terms of PAHs formation. This research also ensured the importance of fat on PAHs formation, the concentration of PAHs in pure fats was higher after being electric roasted than that in meat patties and juice which made from corresponding animal fat. What is more, during pure animal fats and meat products being processed, less PAHs formed in the fat with lower extent of unsaturation and lower content of linolenate. In the same way, methyl linolenate demonstrated the significant increasement to PAHs formation compared to the other fatty acids. And, the number of carbon atom and the extent of unsaturation in fatty acid affects the formation of PAHs during roasting. The detection of alkene and alkane allows to propose a formation mechanism of PAHs during model fat being heated. Further study is required to elucidate the confirm moleculars during the formation of PAHs.
Originality/value
This work studied the effect of the carbon atom number and the unsaturation extent of fats and model fats on the formation of PAHs. This work also assure the important of alkene and alkane on the pyrolysis of model fats. This study also researched the formation and distribution of PAHs in pure fats and meat products after being heated.