Search results

1 – 10 of 12
To view the access options for this content please click here
Article
Publication date: 22 March 2021

Z.B. Xing, Xingchao Han, Hanbing Ke, Q.G. Zhang, Zhiping Zhang, Huijin Xu and Fuqiang Wang

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the…

Abstract

Purpose

A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the flow and thermal transport of nanofluids in porous media, the purpose of this paper is to explore the inter-phase coupling numerical methods.

Design/methodology/approach

Based on the lattice Boltzmann (LB) method, this study combines the convective flow, non-equilibrium thermal transport and phase interactions of nanofluids in porous matrix and proposes a new multi-phase LB model. The micro-scale momentum and heat interactions are especially analyzed for nanoparticles, base fluid and solid matrix. A set of three-phase LB equations for the flow/thermal coupling of base fluid, nanoparticles and solid matrix is established.

Findings

Distributions of nanoparticles, velocities for nanoparticles and the base fluid, temperatures for three phases and interaction forces are analyzed in detail. Influences of parameters on the nanofluid convection in the porous matrix are examined. Thermal resistance of nanofluid convective transport in porous structures are comprehensively discussed with the models of multi-phases. Results show that the Rayleigh number and the Darcy number have significant influences on the convective characteristics. The result with the three-phase model is mildly larger than that with the local thermal non-equilibrium model.

Originality/value

This paper first creates the multi-phase theoretical model for the complex coupling process of nanofluids in porous structures, which is useful for researchers and technicians in fields of thermal science and computational fluid dynamics.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 11 October 2018

Guirong Yang, Wenming Song, Fuqiang Wang, Ying Ma and Yuan Hao

This paper aims to investigate the corrosion rate, surface morphology and composition of corrosion products of 20# seamless steel in aqueous CO2 solution under stratified…

Abstract

Purpose

This paper aims to investigate the corrosion rate, surface morphology and composition of corrosion products of 20# seamless steel in aqueous CO2 solution under stratified gas-liquid two-phase flow condition. The development of a corrosion products layer has also been discussed.

Design/methodology/approach

The following methods were used: weight loss method, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.

Findings

The corrosion rate curve presents an irregular zigzag change trend with a gradual increase in time. The peak value of the corrosion rate appears when the corrosion time is 4 h and 8 h. The corrosion products layer is composed of two sub-layers: the inner dense layer that is about 6 µm thick and the outer loose layer that is about 9 µm thick when the corrosion time is 8 h. The main corrosion product are FeCO3 and Fe2O3.

Originality/value

The atomic ratio of Fe/C/O is relatively stable for the inner dense layer, but changes in thickness for the outer loose layer. There is a densification stage after a loose corrosion products layer forms, and it is periodic.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

To view the access options for this content please click here
Article
Publication date: 29 January 2021

Junying Chen, Zhanshe Guo, Fuqiang Zhou, Jiangwen Wan and Donghao Wang

As the limited energy of wireless sensor networks (WSNs), energy-efficient data-gathering algorithms are required. This paper proposes a compressive data-gathering…

Abstract

Purpose

As the limited energy of wireless sensor networks (WSNs), energy-efficient data-gathering algorithms are required. This paper proposes a compressive data-gathering algorithm based on double sparse structure dictionary learning (DSSDL). The purpose of this paper is to reduce the energy consumption of WSNs.

Design/methodology/approach

The historical data is used to construct a sparse representation base. In the dictionary-learning stage, the sparse representation matrix is decomposed into the product of double sparse matrices. Then, in the update stage of the dictionary, the sparse representation matrix is orthogonalized and unitized. The finally obtained double sparse structure dictionary is applied to the compressive data gathering in WSNs.

Findings

The dictionary obtained by the proposed algorithm has better sparse representation ability. The experimental results show that, the sparse representation error can be reduced by at least 3.6% compared with other dictionaries. In addition, the better sparse representation ability makes the WSNs achieve less measurement times under the same accuracy of data gathering, which means more energy saving. According to the results of simulation, the proposed algorithm can reduce the energy consumption by at least 2.7% compared with other compressive data-gathering methods under the same data-gathering accuracy.

Originality/value

In this paper, the double sparse structure dictionary is introduced into the compressive data-gathering algorithm in WSNs. The experimental results indicate that the proposed algorithm has good performance on energy consumption and sparse representation.

Details

Sensor Review, vol. 41 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

To view the access options for this content please click here
Article
Publication date: 5 March 2018

Awais Ali, Fu Qiang and Sadia Ashraf

The purpose of this paper is to analyse the impact of ownership structure on firm valuation and performance across different geographical regions within mainland China.

Abstract

Purpose

The purpose of this paper is to analyse the impact of ownership structure on firm valuation and performance across different geographical regions within mainland China.

Design/methodology/approach

The authors classify China in six geographical regions and use cross-sectional data of companies with A-shares listed on domestic stock exchanges in China for the year-end 2015. Using data from CSMAR and Wind database, they use multivariate regression technique and analytically compare the consistency of relationship between operational variables of ownership structure with corporate performance and evaluation.

Findings

The authors find that institutional ownership and state ownership negatively affect market valuation throughout various geographical regions of China. Further, in East, Northwest, South Central and Southwestern parts of China, managerial ownership and concentration of shareholding among top ten shareholders positively influence return on equity (ROE). Interestingly, institutional shareholding negatively affects return on assets (ROA), while institutional ownership has a neutral effect on profitability margin in Northeast China. Although in northern part of China, this relationship is slightly positive. In East China region, state ownership and ownership concentration are directly proportional to profitability margin.

Practical implications

As some of the findings exhibit weak state of market efficiency in some regions, the study may also be useful in identifying arbitrage opportunities across different regions. Moreover, this study suggests that regions with the same business environment and conditions anywhere around the globe invite same or similar ownership structure for better firm performance and valuation.

Originality/value

The study provides unique understanding of relationship between ownership structure, market valuation and firm performance in various parts of China and will be an addition to the relevant literature. Given a change in company’s ownership structure and considering its region of incorporation, this study will help investment analysts in assessing performance and market valuation of the firm. It will also assist several classes of investors, financial institutions and international businesses in making their investment decisions.

Details

Review of International Business and Strategy, vol. 28 no. 1
Type: Research Article
ISSN: 2059-6014

Keywords

To view the access options for this content please click here
Article
Publication date: 4 September 2018

Evangelos Bellos, Ilias Daniil and Christos Tzivanidis

The purpose of this paper is to investigate a cylindrical flow insert for a parabolic trough solar collector. Centrally placed and eccentric placed inserts are…

Abstract

Purpose

The purpose of this paper is to investigate a cylindrical flow insert for a parabolic trough solar collector. Centrally placed and eccentric placed inserts are investigated in a systematic way to determine which configuration leads to the maximum thermal enhancement.

Design/methodology/approach

The analysis is performed in SolidWorks Flow Simulation with a validated computational fluid dynamics model. Moreover, the useful heat production and the pumping work demand increase are evaluated using the exergy and the overall efficiency criteria. The different scenarios are compared for inlet temperature of 600 K, flow rate of 100 L/min and Syltherm 800 as the working fluid. Moreover, the inlet temperature is examined from 450 to 650 K, and the diameter of the insert is investigated up to 50 mm.

Findings

According to the final results, the use of a cylindrical insert of 30 mm diameter is the most sustainable choice which leads to 0.56 per cent thermal efficiency enhancement. This insert was examined in various eccentric positions, and it is found that the optimum location is 10 mm over the initial position in the vertical direction. The thermal enhancement, in this case, is about 0.69 per cent. The pumping work demand was increased about three times with the insert of 30 mm, but the absolute values of this parameter are too low compared to the useful heat production. So, it is proved that the increase in the pumping work is not able to eliminate the useful heat production increase. Moreover, the thermal enhancement is found to be greater at higher temperature levels and can reach up to 1 per cent for an inlet temperature of r650 K.

Originality/value

The present work is a systematic investigation of the cylindrical flow insert in a parabolic trough collector. Different diameters of this insert, as well as different positions in two dimensions, are examined using a parametrization of angle-radius. To the authors’ knowledge, there is no other study in the literature that investigates the presented many cases systematically with the followed methodology on parabolic trough collectors. Moreover, the results of this work are evaluated with various criteria (thermal, exergy and overall efficiency), something which is not found in the literature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 7 May 2021

Syed Mehmood Raza Shah, Qiang Fu, Ghulam Abbas and Muhammad Usman Arshad

Wealth Management Products (WMPs) are the largest and most crucial component of China's Shadow banking, which are off the balance sheet and considered as a substitute for…

Abstract

Purpose

Wealth Management Products (WMPs) are the largest and most crucial component of China's Shadow banking, which are off the balance sheet and considered as a substitute for deposits. Commercial banks in China are involved in the issuance of WMPs mainly to; evade the regulatory restrictions, move non-performing loans away from the balance sheet, chase the profits and take advantage of yield spread (the difference between WMPs yield and deposit rate).

Design/methodology/approach

In this study, the authors investigate what bank related characteristics and needs; influenced and prompted the issuance of WMPs. By using a quarterly panel data from 2010 to 2019, this study performed the fixed effects approach favored by the Hausman specification test, and a feasible generalized least square (FGLS) estimation method is employed to deal with any issues of heteroscedasticity and auto-correlation.

Findings

This study found that there is a positive and significant association between the non-performing loan ratio and the issuance of WMPs. Moreover, profitability and spread were found to play an essential role in the issuance of WMPs. The findings of this study suggest that WMPs are issued for multi-purpose, and off the balance sheet status of these products makes them very lucrative for regulated Chinese commercial banks.

Research limitations/implications

Non-guaranteed WMPs are considered as an item of shadow banking in China, as banks do not consolidate this type of WMPs into their balance sheet; due to that reason, there is no individual bank data available for the amount of WMPs. The authors use the number of WMPs issued by banks as a proxy for the bank's exposure to the WMPs business.

Practical implications

From a regulatory perspective, this study helps regulators to understand the risk associated with the issuance of WMPs; by providing empirical evidence that Chinese banks issue WMPs to hide the actual risk of non-performing loans, and this practice could mislead the regulators to evaluate the bank credit risk and loan quality. This study also identifies that Chinese banks issue WMPs for multi-purpose; this can help potential investors to understand the dynamics of WMPs issuance.

Originality/value

This research is innovative in its orientation because it is designed to investigate the less explored wealth management products (WMPs) issued by Chinese banks. This study's content includes not only innovation but also contributes to the existing literature on the shadow banking sector in terms of regulatory arbitrage. Moreover, the inclusion of FGLS estimation models, ten years of quarterly data, and the top 30 Chinese banks (covers 70% of the total Chinese commercial banking system's assets) make this research more comprehensive and significant.

Details

Journal of Economic and Administrative Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1026-4116

Keywords

Content available
Book part
Publication date: 2 April 2021

Shuhan Chen and Peter Lunt

Abstract

Details

Chinese Social Media
Type: Book
ISBN: 978-1-83909-136-0

To view the access options for this content please click here

Abstract

Details

Chinese Social Media
Type: Book
ISBN: 978-1-83909-136-0

To view the access options for this content please click here
Article
Publication date: 6 August 2019

Ab Kasaeian, Reza Daneshazarian, Fathollah Pourfayaz, Sahar Babaei, Mojgan Sheikhpour and Shima Nakhjavani

Because of its increased absorptance in fluid and reduced heat loss, direct absorption nanofluid (DANF) is receiving intense interest as an efficient way to harvest solar…

Abstract

Purpose

Because of its increased absorptance in fluid and reduced heat loss, direct absorption nanofluid (DANF) is receiving intense interest as an efficient way to harvest solar energy. This work aims to investigate, for the first time, the application of DANF in parabolic trough collectors (PTC), a promising collector for solar thermal systems.

Design/methodology/approach

A representative flow and heat transfer study of different fluids in a straight tube is conducted, and the basic energy equation and radiative transfer equations are numerically solved to obtain the fluid temperature distribution and energy conversion efficiency. Ethylene glycol (EG) and different concentrations of (i.e., 0.1-0.6 per cent) multi-wall carbon nanotubes (MWCNT) in EG are used as sample fluids. Four cases are studied for a traditional PTC (i.e., using metal tube) and a direct absorption PTC (i.e., using transparent tube) including a bare tube, a tube with an air-filled glass envelope and a tube with vacuumed glass envelop. The numerical results are verified by an experimental study using a copper-glass absorber tube, which reveals the good potential of DANFs.

Findings

Compared with a conventional PTC, using DANF shows an increase of 8.6 per cent and 6.5 K, respectively, in thermal efficiency and outlet temperature difference at a volume fraction (0.5 per cent) of nanoparticles. The results also show that the improvement in solar efficiency increases with increasing particle concentrations, and the vacuum insulated case has the highest efficiency.

Originality/value

In all previous studies, an important section was missing as the effect of photons on the direct solar absorption trough collector, which is considered in this study. This paper proposes a new concept of using direct solar absorption nanofluids for concentrated solar collectors and analyzes the performance of both absorptance and transmittance efficiency considerations. To reveal the potential of the new concept, an analytical model based on energy balance is developed, and two case studies are performed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Content available
Article
Publication date: 1 August 2003

Abstract

Details

Disaster Prevention and Management: An International Journal, vol. 12 no. 3
Type: Research Article
ISSN: 0965-3562

1 – 10 of 12