Yazhou Wang, Dehong Luo, Xuelin Zhang, Zhitao Wang, Hui Chen, Xiaobo Zhang, Ningning Xie, Shengwei Mei, Xiaodai Xue, Tong Zhang and Kumar K. Tamma
The purpose of this paper is to design a simple and accurate a-posteriori Lagrangian-based error estimator is developed for the class of backward differentiation formula (BDF…
Abstract
Purpose
The purpose of this paper is to design a simple and accurate a-posteriori Lagrangian-based error estimator is developed for the class of backward differentiation formula (BDF) algorithms with variable time step size, and the adaptive time-stepping in BDF algorithms is demonstrated for efficient time-dependent simulations in fluid flow and heat transfer.
Design/methodology/approach
The Lagrange interpolation polynomial is used to predict the time derivative, and then the accurate primary result is obtained by the Gauss integral, which is applied to evaluate the local error. Not only the generalized formula of the proposed error estimator is presented but also the specific expression for the widely applied BDF1/2/3 is illustrated. Two essential executable MATLAB functions to implement the proposed error estimator are appended for practical applications. Then, the adaptive time-stepping is demonstrated based on the newly proposed error estimator for BDF algorithms.
Findings
The validation tests show that the newly proposed error estimator is accurate such that the effectivity index is always close to unity for both linear and nonlinear problems, and it avoids under/overestimation of the exact local error. The applications for fluid dynamics and coupled fluid flow and heat transfer problems depict the advantage of adaptive time-stepping based on the proposed error estimator for time-dependent simulations.
Originality/value
In contrast to existing error estimators for BDF algorithms, the present work is more accurate for the local error estimation, and it can be readily extended to practical applications in engineering with a few changes to existing codes, contributing to efficient time-dependent simulations in fluid flow and heat transfer.
Details
Keywords
Weiqing Wang, Zengbin Zhang, Liukai Wang, Xiaobo Zhang and Zhenyu Zhang
The purpose of this study is to forecast the development performance of important economies in a smart city using mixed-frequency data.
Abstract
Purpose
The purpose of this study is to forecast the development performance of important economies in a smart city using mixed-frequency data.
Design/methodology/approach
This study introduces reverse unrestricted mixed-data sampling (RUMIDAS) to support vector regression (SVR) to develop a novel RUMIDAS-SVR model. The RUMIDAS-SVR model was estimated using a quadratic programming problem. The authors then use the novel RUMIDAS-SVR model to forecast the development performance of all high-tech listed companies, an important sector of the economy reflecting the potential and dynamism of urban economic development in Shanghai using the mixed-frequency consumer price index (CPI) producer price index (PPI), and consumer confidence index (CCI) as predictors.
Findings
The empirical results show that the established RUMIDAS-SVR is superior to the competing models with regard to mean absolute error (MAE) and root-mean-squared error (RMSE) and multi-source macroeconomic predictors contribute to the development performance forecast of important economies.
Practical implications
Smart city policy makers should create a favourable macroeconomic environment, such as controlling inflation or stabilising prices for companies within the city, and companies within the important city economic sectors should take initiative to shoulder their responsibility to support the construction of the smart city.
Originality/value
This study contributes to smart city monitoring by proposing and developing a new model, RUMIDAS-SVR, to help the construction of smart cities. It also empirically provides strategic insights for smart city stakeholders.
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Yixing Ding, Yanmin Jia, Jiangyue Li, Huiming Li and Xiaobo Zhang
The purpose of this study is to investigate the effects of stud height, stud diameter, ultimate stress of stud and concrete strength on the static behaviour of studs in push-off…
Abstract
Purpose
The purpose of this study is to investigate the effects of stud height, stud diameter, ultimate stress of stud and concrete strength on the static behaviour of studs in push-off tests based on the ductile fracture theory.
Design/methodology/approach
Push-off tests of headed stud shear connectors with different heights and diameters used in concrete of various strengths were designed and implemented. A finite element model was established based on a ductile fracture criterion of ML15 cold-heading steel with stress triaxiality and Lode angle parameter. Based on the results of the parametric study of the numerical model, equations were proposed to evaluate the effect of stud height hs, stud area As, concrete strength fc and stud ultimate strength fsu used in concrete of various strengths on the static behaviour of studs.
Findings
The typical failure phenomenon observed among the test specimens was the fracture of the shank of studs. The microscopic images of the stud fracture surfaces and the verified finite element model indicate that the studs were fractured as a result of the combined action of tension and shear.
Originality/value
A new method for calculating ultimate load Pu and ultimate slip Su is proposed in this paper. In the method, Pu is linearly related to fsu0.2143, As0.7790, hs0.0974, fc0.2065. Su is linearly related to fsu1.078, As0.4681, hs(−0.3135), fc(−0.3480).
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Liqiang Zhang, Xiaobo Zhou, Guihai Chen and Christian Poellabauer
This paper aims to review the latest management developments across the globe and pinpoint practical implications from cutting-edge research and case studies.
Abstract
Purpose
This paper aims to review the latest management developments across the globe and pinpoint practical implications from cutting-edge research and case studies.
Design/methodology/approach
This briefing is prepared by an independent writer who adds their own impartial comments and places the articles in context.
Findings
Boards of Directors of technology corporations should consider whether their top management teams have a promotion or prevention focused approach, favoring the former if competitive advantage is being sought.
Originality/value
The briefing saves busy executives, strategists and researchers hours of reading time by selecting only the very best, most pertinent information and presenting it in a condensed and easy-to-digest format.
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Pei Guo, Xiangqi Liu and Ling Ma
The purpose of this paper is to summarize the China Agricultural Economic Review (CAER)'s second annual conference, which was organized by the CAER editorial office and…
Abstract
Purpose
The purpose of this paper is to summarize the China Agricultural Economic Review (CAER)'s second annual conference, which was organized by the CAER editorial office and International Food Policy Research Institute (IFPRI).
Design/methodology/approach
The conference theme was “Agriculture and the Wealth of Nations”, aiming to explore the importance of agriculture as well as the relationship and interaction between agriculture and the whole economy. The attendees from 14 countries discussed the related issues, and a number of distinguished scholars and policy makers were also invited to present at the conference. This summary presents the topics covered at the conference and highlights discussion points.
Findings
Action items were identified which could be appropriately organized into the following sections: agricultural trade and rural labor issues; rural governance and public policy; climate change and food security; rural land and rural finance issues.
Originality/value
The paper illustrates how the academic platform established by the CAER‐IFPRI conference, enables scholars from varied cultures and fields to get together to share their researches and ideas.
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J. Alexander Nuetah, Yitian Xiao and Pei Guo
The purpose of this paper is to provide readers with the main findings and conclusions of papers presented at the 2011 CAER‐IFPRI International Conference held under the theme “Is…
Abstract
Purpose
The purpose of this paper is to provide readers with the main findings and conclusions of papers presented at the 2011 CAER‐IFPRI International Conference held under the theme “Is China entering a high food price era?”
Design/methodology/approach
The authors conduct a desk review of papers presented at the conference and provide a brief summary of the analytical tools, and main findings and conclusions of each presentation.
Findings
These reviews show that, while there seems to be an increase in the prices of agricultural commodities on the Chinese market, in real terms, these rises fall far below the increases in the prices of industrial commodities. Thus, expert views remain divided on whether China is entering an era of high food price.
Originality/value
The discussions initiated by the conference theme aroused researchers' curiosities for further studies into understanding the current level of food prices in China.