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Article
Publication date: 31 January 2020

Leqin He, Shenjun Qin, Jianjun Liu, Wei Zhao and Tao Chang

From the atom economy and environmentally friendly point of views, the development of clean and green approaches using ionic liquids (ILs) as recyclable catalysts has attracted…

Abstract

Purpose

From the atom economy and environmentally friendly point of views, the development of clean and green approaches using ionic liquids (ILs) as recyclable catalysts has attracted increasing attention. The purpose of this study is to investigate the effect of task-specific ILs content on the one-pot three-component Biginelli reaction.

Design/methodology/approach

A series of halogen-free quaternary ammonium ILs functionalized with –SO3H group were prepared and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR and electrospray ionization mass spectrometry. The ILs were used as catalysts for Biginelli reaction among aromatic aldehydes, urea or thiourea and β-dicarbonyl compounds. Anions and cations of ILs were varied to observe their effects on and contributions to the catalysts. The influencing factors, such as the amount of catalyst, solvent, reaction time and reaction temperature, were investigated.

Findings

The effect and contribution of cations of ILs were observed. Results showed that 3-(N, N-dimethylhexadecylammonium) propanesulfonic acid toluene sulfate ([DHPA][Tos]) showed comparable catalytic activity. Good adaptability to the reaction substrate and maximum product yield was observed when [DHPA][Tos] was used as catalyst. It was found that Biginelli reaction catalyzed by 10 mol% [DHPA][Tos] for 3 h under solvent-free conditions at 80 °C gave the best yield of 94%. Post-processing steps were simple, and the catalyst could be reused easily.

Originality/value

This paper demonstrates that ILs containing a long carbon chain and a bulky Tos anion efficiently promoted the reaction, in which the long carbon chains facilitate mass transfer in the reaction system.

Details

World Journal of Engineering, vol. 17 no. 1
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 10 April 2017

Zhang Guangqing, Shenjun Qin, Li Zhen, Han Haiyan, Li Hui and Tao Chang

This study aims to investigate the coupling reaction of epoxide and CO2 catalysed by alkali metal salts in the presence of ß-cyclodextrin (ß-CD) derivatives to generate cyclic…

Abstract

Purpose

This study aims to investigate the coupling reaction of epoxide and CO2 catalysed by alkali metal salts in the presence of ß-cyclodextrin (ß-CD) derivatives to generate cyclic carbonates at various conditions.

Design/methodology/approach

The coupling reaction was catalysed by alkali metal salts. The effects of the co-catalysts were investigated by using the conversion rate of raw materials. The affecting factors, such as reaction temperature, amount of the co-catalyst and reaction time, were explored. The possible mechanism of the coupling reaction was discussed.

Findings

Results showed that the structure of ß-CD is an important factor influencing the catalytic activity for the coupling reaction of epoxide with CO2. The catalytic system of 2,3,6-trimethyl-ß-CD with potassium iodide (KI) showed a high catalytic activity. The protocol was expanded to various epoxides, which provided the corresponding cyclic carbonates in excellent yields. The apparent decrease in the yields was not detected after four recycling times. Moreover, the mechanism for the synergetic effect of the catalyst was proposed.

Originality/value

The coupling reactions were achieved in the presence of different structure of ß-CD as co-catalysts. The affecting of substituent of ß-CD were investigated.

Details

World Journal of Engineering, vol. 14 no. 2
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 26 December 2023

Ting Dai and Chang Tao

For a thermal protection system (TPS) of long endurance hypersonic flight vehicle (HFV), its thermal insulation property not only determines by the manufactured morphology but…

Abstract

Purpose

For a thermal protection system (TPS) of long endurance hypersonic flight vehicle (HFV), its thermal insulation property not only determines by the manufactured morphology but also changes along time. A thermal conductivity prediction model for aerogel considering heat treatment effect is carried out and applied to solve the heat conduction problem of a TPS. The aim of this study is to provide theoretical and numerical references for further development of aerogels applying to TPSs.

Design/methodology/approach

A thermal conductivity prediction model for aerogel is established considering treatment effect. The heat conduction problem of a TPS is derived and solved by combining the differential quadrature method and the Runge–Kutta method. The prediction results of aerogel thermal conductivities are verified by comparing with those in literature, while the calculated temperature field of TPS is verified by comparing with that by ABAQUS.

Findings

Numerical results show that when applying the current prediction model, the calculated high temperature area in the aerogel layer is narrowed due to the decrease of the thermal conductivity during heat treatment process.

Originality/value

This study will be beneficial to carry out the precise design of TPS for long endurance HFVs.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 34 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 8 April 2016

Zhen Li, Xianwei Liu, Yiwei Lian, Juan Xie, Xiaorui Gao and Tao Chang

This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)

Abstract

Purpose

This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)

Design/methodology/approach

The variations of electrical conductivity as a function of water volume fraction are examined at one constant alcohol (or DMF, ethyl lactate, γ-valerolactone)/water, alcohol (or DMF, ethyl lactate, γ-valerolactone)/oil volume ratios for each sample.

Findings

Most of the results are consistent with percolation character. The conductive mechanism of these SFMEs is discussed by the percolation model, and it is found that it might be described with the static percolation model below the percolation threshold.

Originality/value

Our report gives a systematic research on the percolation mechanism of as many species of SFMEs as possible by the theoretical models

Details

World Journal of Engineering, vol. 13 no. 2
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 31 December 2006

Shih‐Lin Wu, Jang‐Ping Sheu and Chung‐Chao Lee

This paper proposes a distributed multi‐channel MAC protocol which is an extension of our early work GRID [1]. GRID is characterized by the following features: (i) it integrates a…

Abstract

This paper proposes a distributed multi‐channel MAC protocol which is an extension of our early work GRID [1]. GRID is characterized by the following features: (i) it integrates a location‐aware channel assignment, (ii) it follows an “on‐demand” style to access the medium, (iii) the number of channels required is independent of the network topology, and (iv) no form of clock synchronization is required. The proposed protocol wants to further improve the GRID in two parts. First, we propose a fully distributed medium access mechanism without using a single control channel such that all of the network traffic can be distributed evenly over all data channels. Therefore, the network throughput will be increased significantly. Second, we can set the more suitable transmission range and GRID size by considering the factors of host density and packet arrival rate of the network within an specified area. Thus, all of channels will be reused more efficiently than GRID. Simulation results show that the throughput of our protocol is superior to GRID and IEEE 802.11.

Details

International Journal of Pervasive Computing and Communications, vol. 2 no. 4
Type: Research Article
ISSN: 1742-7371

Keywords

Article
Publication date: 22 July 2014

Leqin He, Jiquan Zhao, Shenjun Qin, Tao Chang, Yuecheng Zhang, Guangqing Zhang and Xiaorui Gao

Five halogen-free amphiphilic Brønsted acidic ionic liquids (ILs) based on 3-(N, N-dimethylalkylammonium)-propanesulphonate quaternary ammonium zwitterions and p-toluene sulphonic…

Abstract

Five halogen-free amphiphilic Brønsted acidic ionic liquids (ILs) based on 3-(N, N-dimethylalkylammonium)-propanesulphonate quaternary ammonium zwitterions and p-toluene sulphonic acid monohydrate were synthesized. The IL structures were characterized using 1H NMR, 13C NMR and (ESI)-MS. The IL thermal instability was characterized using TG-DSC. The ILs were used as dual-solvent catalysts for esterification of several carboxylic acids, with different alcohols under mild conditions to study relevant structure-activity relationships. Results showed that the miscibility of the acidic IL, which is affected by the length of the carbon chain in the cation, is an important factor influencing the activity of the catalyst for the esterification reaction. Post-processing steps were simple, and the catalyst could be reused easily.

Details

World Journal of Engineering, vol. 11 no. 3
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 14 September 2010

Xinyan Wang, Jianqiao Liao, Degen Xia and Tao Chang

The purpose of this paper is to develop and test a model that identifies the impact of organizational justice on work performance. The model examined the mediating role played by…

7188

Abstract

Purpose

The purpose of this paper is to develop and test a model that identifies the impact of organizational justice on work performance. The model examined the mediating role played by organizational commitment and leader‐member exchange (LMX) in linking organizational justice and work performance.

Design/methodology/approach

The data were collected from 793 completed questionnaires sampling employees from industries across the People's Republic of China. The questionnaire included scales to measure organizational justice, organizational commitment, LMX, and work performance. The measurement of constructs and the hypothesized relationships among variables were assessed by the use of structural equation modeling. The Baron and Kenny approach was used to test the mediating effects.

Findings

First, the relationship of organizational justice to work performance was mostly indirect, mediated by organizational commitment and LMX. Second, among the three kinds of organizational justice, interactional justice was the best predictor of performance. Lastly, organizational commitment accounted for more of the variance than LMX did in the mediating mechanism.

Research limitations/implications

The model developed in this article provides important insights in the study of the relationship between organizational justice and work performance. Future research needs to examine the model using a cross‐national sample.

Originality/value

The link between organizational justice and work performance was mostly mediated by organizational commitment and LMX.

Details

International Journal of Manpower, vol. 31 no. 6
Type: Research Article
ISSN: 0143-7720

Keywords

Book part
Publication date: 25 November 2019

Euan Auld and Yun You

New technology tends to invite speculation on the future of societies, inspiring visions of both hope and horror. This chapter continues that tradition, exploring the application…

Abstract

New technology tends to invite speculation on the future of societies, inspiring visions of both hope and horror. This chapter continues that tradition, exploring the application of emerging technology, such as artificial intelligence (AI), cloud computing, and the Internet of Things (IoT) to processes of governance and learning in education. Drawing on both utopian visions and twin nightmares of machinic-dystopias, the analysis reflects on the application of new technology designed to fulfill the UN’s post-2015 agenda in education. In highlighting divergent traditions, the analysis then shifts to the application of the same technology in China as part of the Chinese Dream, under which the Chinese government aims to become the world leader in AI while revitalizing the nation’s cultural traditions. These ambitions are explored through the introduction of Smart Cities, a system of Social Credit, and Smart Schools. Finally, the chapter reflects on these visions of twenty-first century pedagogy and possible resources for thinking about a future that cannot be fully apprehended.

Details

The Educational Intelligent Economy: Big Data, Artificial Intelligence, Machine Learning and the Internet of Things in Education
Type: Book
ISBN: 978-1-78754-853-4

Keywords

Content available
Book part
Publication date: 27 February 2009

Abstract

Details

Research in Finance
Type: Book
ISBN: 978-1-84855-447-4

Article
Publication date: 22 July 2020

Ryszard Kisiel, Marek Guziewicz, Andrzej Taube, Maciej Kaminski and Mariusz Sochacki

This paper aims to investigate the sintering and solid liquid interdiffusion bonding (SLID) techniques to attach AlGaN/GaN-on-Si chips to direct bond copper (DBC) substrate. The…

Abstract

Purpose

This paper aims to investigate the sintering and solid liquid interdiffusion bonding (SLID) techniques to attach AlGaN/GaN-on-Si chips to direct bond copper (DBC) substrate. The influence of metal layers deposited on the backside of AlGaN/GaN-on-Si dies on the assembly process is also investigated.

Design/methodology/approach

The authors assumed the value of the shear strength to be a basic parameter for evaluation of mechanical properties. Additionally, the surface condition after shearing was assessed by SEM photographs and the shear surface was studied by X-ray diffraction method. The SLID requires Sn-plated DBC substrate and can be carried out at temperature slightly higher than 250°C and pressure reduced to 4 MPa, while the sintering requires process temperature of 350°C and the pressure at least 7.5 MPa.

Findings

Ag-, Au-backside covered high electron mobility transistor (HEMT) chips can be assembled on Sn-plated DBC substrates by SLID technology. In case of sintering technology, Cu- or Ag-backside covered HEMT chips can be assembled on Ag- or Ni/Au-plated DBC substrates. The SLID process can be realized at lower temperature and decreased pressure than sintering process.

Research limitations/implications

For SLID technology, the adhesion between Cu-backside covered HEMT die and DBC with Sn layer loses its operational properties after short-term ageing in air at temperature of 300°C.

Originality/value

In the SLID process, Sn-Cu and Sn-Ag intermetallic compounds and alloys are responsible for creation of the joint between Sn-plated DBC and micropowder Ag layer, while the sintered joint between the chip and Ag-based micropowder is formed in diffusion process.

Details

Circuit World, vol. 47 no. 2
Type: Research Article
ISSN: 0305-6120

Keywords

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