Han Liu, Guojin Yang and Rong Wang
The wireless power transmission (WPT) system with an embedded coil will achieve a more flexible charging operation and higher system efficiency. However, the comprehensive…
Abstract
Purpose
The wireless power transmission (WPT) system with an embedded coil will achieve a more flexible charging operation and higher system efficiency. However, the comprehensive analysis considering cross-coupling for WPT with embedded coil is rarely investigated. This study aims to improve the system efficiency of WPT with the embedded coil based on circuit analysis and optimization of embedded coil loops.
Design/methodology/approach
The circuit model of WPT system with the non-resonant compensated embedded coil is developed by taking the cross-coupling of all coils and the circuit compensation degree of the embedded coil into consideration. On the basis of system characteristics analysis, optimization of embedded coil position and non-resonant compensation are proposed to improve the efficiency of WPT system with embedded coil. Experimental studies demonstrate the correctness of theoretical research.
Findings
The WPT system with embedded coil designed by optimizing the position and non-resonant compensation achieves higher efficiency than those of the system with two-coil mode and the three-coil system with a resonant compensated embedded coil.
Practical implications
A WPT system with embedded coil could be more efficient by using a non-resonant compensated coil embedded into the buffer material of the storage box for sophisticated electrical equipment.
Originality/value
The cross-coupling between all coils is considered in circuit analysis for WPT system with embedded coil. Optimization of the position and non-resonant compensation of embedded coil achieves higher efficiency.
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The purpose of this paper is to study the effect of different parts (predictable and impact) of different types of speculative behavior (intraday speculation, medium-term…
Abstract
Purpose
The purpose of this paper is to study the effect of different parts (predictable and impact) of different types of speculative behavior (intraday speculation, medium-term speculation and long-term speculation) on future fluctuations in the underlying index.
Design/methodology/approach
The authors input information about heterogeneous speculative behavior into the HAR-RV model to study the effect of different parts (predictable and impact) of different types of speculative behavior (intraday speculation, medium-term speculation and long-term speculation) on the future fluctuation of the underlying index.
Findings
The authors find that the increase in intraday speculation will exacerbate spot market volatility; and the expected increase of long-term value speculation can reduce market volatility, but the shock of speculation will exacerbate market volatility.
Practical implications
The authors suggest that regulators should strictly limit speculative intraday trading, and also focus on the long-term value speculation that decreases market volatility, in order to guide the benign development of the markets that stabilize abnormal market fluctuations.
Originality/value
First, in view of the correlation between the futures and spot markets, the authors put forward a new proxy for the speculation degree. Second, the authors input heterogeneous speculative behavior into the HAR-RV model to study the effects of different parts (predictable and impact) on different types of speculative behavior (intraday speculation, medium-term speculation and long-term speculation) on the future fluctuation of the underlying index.
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Binbin Xun, Fushuan Wen and Shulin Tong
The purpose of this paper is to investigate the gaming equilibrium among fossil‐fueled generation companies (GenCos), wind generation companies, the grid company and customers…
Abstract
Purpose
The purpose of this paper is to investigate the gaming equilibrium among fossil‐fueled generation companies (GenCos), wind generation companies, the grid company and customers participating in an emission trading (ET) market and the day‐ahead electricity market.
Design/methodology/approach
The complementarity method is used in this work to obtain the Nash equilibrium. By combining the Karush‐Kuhn‐Tucker (KKT) conditions of each kind of market participants with market clearing and consistency conditions, a mixed linear complementarity problem could be established.
Findings
Simulation results show that: the enforcement of ET could increase the share of generation outputs of wind generation units, and decrease the emissions from fossil‐fueled generation units; the bilateral contracts between GenCos and customers could limit the ability of exercising market power by GenCos; and when the emissions allowances allocated by the government shrink, the price of emissions allowance will increase and as the result the dispatching order of fossil‐fueled generation units will change, and the shares of generation outputs from wind generation units and combined‐cycle gas turbines increase. However, it should be mentioned that because the cost of wind generation is still very high, the increase of the share from wind generation units in the electricity market should mainly rely on cost reduction rather than the enforcement of ET.
Originality/value
The original contribution and the value of this study lie in developing a model framework to explore the gaming equilibrium that thermal and wind generating plants both play in the emissions trading environment and electricity market.
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Yayun Qi, Peng Ao, Maorui Hou and Ailong Zhang
Mountain metro vehicles have unique wheel wear characteristics due to the complex flat and longitudinal lines. With a combination of flat and longitudinal curved tracks, the…
Abstract
Purpose
Mountain metro vehicles have unique wheel wear characteristics due to the complex flat and longitudinal lines. With a combination of flat and longitudinal curved tracks, the traction and braking conditions are more frequent in mountain metro vehicles. This paper aims to analyze the wheel wear characteristics of mountain metro vehicles in complex flat and longitudinal lines.
Design/methodology/approach
A dynamic model of the mountain metro vehicle and a wear model are established to analyze the dynamic and wheel wear characteristics of mountain metro vehicles. The wheel wear law of mountain metro vehicles under complex track conditions is analyzed, and the suppression measure based on variable stiffness rotary arm nodes of mountain metro vehicles is proposed.
Findings
The results showed that the maximum wheel wear depth without considering the ramp track and considering the ramp track are 3.283 mm and 3.717 mm, respectively; the maximum wheel wear depth increases by 13.2%. Wheel wear can be effectively suppressed by the variable stiffness rotary arm model, and the maximum wear depth of the wheel profile is 3.316 mm, which is reduced by 10.79% compared with the constant stiffness model.
Originality/value
A dynamic model of a mountain metro vehicle is established, and the metro vehicle wheel wear under the large ramps under the traction and braking conditions is analyzed, and the metro vehicle wheel wear suppression measure based on variable stiffness rotary arm nodes is proposed.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0247
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Wen Liu, Shuangchao Huang, Hongfeng Qi, Xin Zhao, Shulin Liang and Xuesong Jin
Dynamic low adhesion (DLA) has become an urgent problem for the high-speed wheel-rail system because of continuous decrease of adhesion redundancy in the past decades. This…
Abstract
Purpose
Dynamic low adhesion (DLA) has become an urgent problem for the high-speed wheel-rail system because of continuous decrease of adhesion redundancy in the past decades. This article aims to provide a simulation method to reveal the mechanism of DLA under high-frequency vibrations.
Design/methodology/approach
A transient wheel-rail rolling contact model is developed for a typical Chinese high-speed railway system using the explicit finite element (FE) method. Instantaneous adhesion exploitation levels are studied in the time domain, for which driving cases over corrugated rails are taken as an example. A speed up to 500 km/h is considered together with different traction coefficients and corrugation dimensions. DLA is expected when the instantaneous adhesion exploitation level reaches 1.0, that is adhesion saturates and full sliding contact occurs.
Findings
The instantaneous adhesion exploitation level can be very high in the presence of corrugation, even at low traction coefficients. DLA is found to occur as great vertical unloading takes place and causes a significant increase of creepage. An approach is further developed to determine the critical depth of corrugation over which DLA occurs.
Originality/value
This study employs the transient wheel-rail rolling contact model to predict the instantaneous adhesion exploitation level under high-frequency vibrations. The presented results reveal a mechanism of DLA being beneficial to guidelines for future railway practice.
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Wing-Keung Wong, Zhihui Lv, Christian Espinosa and João Paulo Vieito
To the best of the authors’ knowledge, this study is the first to investigate the intricate relationship between crude oil spot and futures prices, focusing on both cointegration…
Abstract
Purpose
To the best of the authors’ knowledge, this study is the first to investigate the intricate relationship between crude oil spot and futures prices, focusing on both cointegration and market efficiency during the COVID-19 pandemic, and the beginning of the Russia–Ukraine conflict. Using daily West Texas Intermediate data from January 2020 to March 2024, like Cunado and Pérez de Gracia (2003), the authors use advanced statistical methods to identify structural breaks and assess cointegration levels. Linear and nonlinear Granger causality tests are used to reveal underlying dynamics.
Design/methodology/approach
This paper uses the Lagrange Multiplier test by Arai and Kurozumi (2007) to check for cointegration with various shifts in crude oil spot and futures markets. The two-step procedure by Kejriwal and Perron (2010) and Kejriwal et al. (2022) is then applied to assess partial parameter stability in cointegration models. Efficiency is examined using both bivariate and trivariate models based on non-arbitrage and expectations hypotheses. Finally, causality is analyzed with the vector error correction model for linear Granger causality, and the tests by Bai et al. (2018) and Diks and Panchenko (2006) for nonlinear causality.
Findings
The analysis reveals that futures prices generally lead spot prices through both linear and nonlinear causality during certain periods, while only linear causality is present in others. This inconsistency suggests fluctuating market efficiency and potential arbitrage opportunities. Structural breaks indicate that the equilibrium between spot and futures prices adjusts in response to significant events like the COVID-19 pandemic and the Russia–Ukraine war. The study identifies specific periods, particularly between January 2020 and March 2024, where both linear and nonlinear forecasting between futures and spot oil prices are effective, highlighting the dynamic nature of their relationship.
Research limitations/implications
Despite extensive efforts, pinpointing the exact break date for COVID-19 remains challenging due to limitations in the data set and methodology. Additionally, the analysis of the Russia–Ukraine conflict is still ongoing. These challenges highlight the complexity of addressing structural breaks linked to unprecedented events.
Practical implications
The findings offer valuable insights for both academia and industry practitioners. The study reveals potential arbitrage opportunities stemming from inconsistent market efficiency and fluctuating causality between futures and spot prices, allowing traders to optimize their trades and timing. It also enhances risk management by identifying when linear and nonlinear causality is most effective. Policymakers can use these insights to evaluate market stability, especially during major disruptions such as the COVID-19 pandemic and geopolitical conflicts, guiding regulatory decisions. Furthermore, the study highlights the importance for investors to adjust their strategies in response to structural breaks and evolving market conditions.
Social implications
This study’s social implications are diverse, extending beyond finance and academia. It influences economic stability by revealing inefficiencies and arbitrage opportunities in crude oil markets, aiding better resource allocation. Enhanced transparency benefits stakeholders, promoting fair market practices and consumer protection. Policymakers can refine regulations based on identified structural breaks, ensuring market stability. The study indirectly impacts environmental discussions by examining crude oil’s link to global energy consumption. Financially, it guides investment strategies, influencing resource distribution and the broader economy. Additionally, its educational contribution stimulates academic discourse, fostering growth in energy economics and financial market knowledge, shaping future research.
Originality/value
The originality and value of this paper lie in its comprehensive examination of the dynamic relationship between futures and spot oil prices, particularly through both linear and nonlinear causality across different periods. By identifying and analyzing periods of both linear and nonlinear causality, the study uncovers fluctuating market efficiency and potential arbitrage opportunities that are not typically addressed in conventional analyses. Additionally, the paper’s focus on the impact of significant global events, such as the COVID-19 pandemic and the Russia–Ukraine war, on the equilibrium between spot and futures prices offers a novel perspective on how structural breaks influence market dynamics. This nuanced understanding enhances both theoretical and practical knowledge, offering valuable insights for traders, investors and policymakers to navigate and respond to evolving market conditions.
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Shiang-Wuu Perng, Horng Wen Wu and Jun-Kuan Wu
The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across.
Abstract
Purpose
The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across.
Design/methodology/approach
The novel design of this study is performed through making the slits in the slab (C1–C3: with slits; C4–C6: without slits) and changing the vertical location of this slab (1/4, 1/2 and 3/4 channel height). The thermal fluid characteristics of all cases are analyzed for various Reynolds numbers (500, 1,000, 1,500 and 2,000) by the SIMPLE-C algorithm.
Findings
The results display that the ribbed slab effectively improves the heat transfer. The slits can modify the flow field in the vortexes around the inclined ribs and remove more heat from this zone to promote the heat transfer. As compared with C0 (without a slab), C2 (the slab with slits and inclined ribs protruding across located vertically on the 3/4 channel height) raises the averaged Nusselt number up to 27.7% at Re = 2,000. As compared with C4 (without slits), C1 (with slits) gains the maximum increase in the averaged Nusselt number by 5.07% at Re = 1,000.
Research limitations/implications
The constant thermo-physical properties of incompressible fluid and the steady flow are considered in this study.
Practical implications
The numerical results will profit the design of heated passageway using a slab with slits and inclined ribs protruding across to acquire better heat transfer promotion.
Originality/value
This slab with slits and inclined ribs protruding across can be applied to the heat transfer promotion and thus be viewed as a useful cooling mechanism in the thermal engineering.
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Kangyin Dong, Jianda Wang and Xiaohang Ren
The purpose of this study is to examine the spatial fluctuation spillover effect of green total factor productivity (GTFP) under the influence of Internet development.
Abstract
Purpose
The purpose of this study is to examine the spatial fluctuation spillover effect of green total factor productivity (GTFP) under the influence of Internet development.
Design/methodology/approach
Using panel data from 283 cities in China for the period 2003–2016, this paper explores the spatial fluctuation spillover effect of internet development on GTFP by applying the spatial autoregressive with autoregressive conditional heteroscedasticity model (SARspARCH).
Findings
The results of Moran's I test of the residual term and the Bayesian information criterion (BIC) value indicate that the GTFP has a spatial fluctuation spillover effect, and the estimated results of the SARspARCH model are more accurate than the spatial autoregressive (SAR) model and the spatial autoregressive conditional heteroscedasticity (spARCH) model. Specifically, the internet development had a positive spatial fluctuation spillover effect on GTFP in 2003, 2011, 2012 and 2014, and the volatility spillover effect weakens the positive spillover effect of internet development on GTFP. Moreover, Internet development has a significant positive spatial fluctuation spillover effect on GTFP averagely in eastern China and internet-based cities.
Research limitations/implications
The results of this study provide digital solutions for policymakers in improving the level of GTFP in China, with more emphasis on regional synergistic governance to ensure growth.
Originality/value
This paper expands the research ideas for spatial econometric models and provides a more valuable reference for China to achieve green development.
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Abstract
Purpose
The purpose of this paper is to enhance the anticorrosion property of aluminium pigments and to improve their compatibility with polymers in coating.
Design/methodology/approach
Aluminium pigments encapsulated by organic‐inorganic layer were prepared by hydrolysis and condensation of organic silane acrylate resin and tetraethoxy silane (TEOS) on the surface of pigments via sol‐gel method. TEOS and poly (methyl methacryalte‐n‐butyl acrylate‐vinyl triethoxysilane) (PMBV) formed in advance by co‐polymerisation of methyl methacrylate (MMA), n‐butyl acrylate (BA) and vinyl triethoxysilane (VTES) were used as precursors. The adhesion property of the aluminium pigments was measured by peel test, and the loss of silvery appearance after encapsulation and acid soaking were both evaluated by colour lightness difference (ΔL) measurement. The encapsulated aluminium pigments were further characterised by means of FTIR, SEM, TG and XPS.
Findings
It was found that PMBV‐SiO2 thin films could be formed on the surface of aluminium pigments smoothly and uniformly, and the adhesion and anticorrosion performances of encapsulated aluminium pigments were improved significantly.
Research limitations/implications
The organic silane acrylate resin used as a precursor in the sol‐gel process could be synthesised from other aclyate monomers. In addition, the hydrolysis and condensation mechanism of organic silane acrylate resin on the surface of aluminium pigments need further studies.
Practical implications
The method developed provided a good solution to the two problems of aluminium pigments and increased their application values.
Originality/value
The method of improving adhesion and anticorrosion properties of aluminium pigments was novel and could find numerous applications in surface coatings and adhesives.