Nida Hussain, Baoming Li and Habib Elahi Sahibzada
Under the unique context of COVID-19, this paper aims to analyze how the Government of Pakistan (GoP) provides financial and non-financial support to women entrepreneurs in…
Abstract
Purpose
Under the unique context of COVID-19, this paper aims to analyze how the Government of Pakistan (GoP) provides financial and non-financial support to women entrepreneurs in Pakistan. Drawing on the resource-based theory of entrepreneurship (RBTE), the study advances the understanding of resources and grants offered by GoP to women entrepreneurs to help them in business survival.
Design/methodology/approach
The study adopts qualitative research method to address the questions: how does the Pakistani government respond to issues faced by women entrepreneurs during the COVID-19 pandemic, and what assistance and initiatives were implemented by GoP? Semi-structured interviews were conducted with twenty on-job government officials related to the entrepreneurial sector in Pakistan.
Findings
The paper reveals that during the pandemic, GoP keenly communicated with women entrepreneurial representatives to comprehend their business challenges. In addition, waivers and incentives were provided to support their business activities. GoP further invited women entrepreneurs to contribute their knowledge and give suggestions in policy making.
Originality/value
Lots of research have been conducted to identify the issues faced by women entrepreneurs during the pandemic. However, the specific strategies, policies, and support provided by the governments to address these issues have often been overlooked. This paper fills such gap with focus on the governing bodies and policymakers in Pakistan towards women entrepreneurship during the COVID-19 crisis.
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Hao Rong, Baoming Wang, Wei‐Qing Lin, Lichao Sun, Jin‐Cheng Zheng and Miao Lu
The purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single‐walled carbon nanotubes (SWNTs) between a chip and its…
Abstract
Purpose
The purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single‐walled carbon nanotubes (SWNTs) between a chip and its substrate acting as a kind of thermal interface material by virtue of better mechanical and thermal properties.
Design/methodology/approach
Two silicon chips, with shallow trenches about 2 μm deep on the surface, were pressed together face to face with the trench direction perpendicular to each other. SWNT aqueous solution was driven into the gap between the two chips by capillary force. Later, the sample was baked to remove the moisture completely.
Findings
SWNTs beams were found to be assembled in the gap and have their two ends bonding with the interface of the two chips, respectively. The shear strength of the two chips was measured, and the thermal conductivity of the stacked chip‐SWNTs‐chip was tested using a laser flash method. In result, shear strength up to about 100 kPa, and an average thermal conductivity of 19.3 W·m−1·K−1 were demonstrated.
Originality/value
The paper proposes an approach to grown dense SWNT array bridging a chip and its substrate, and these SWNTs have potential capability to provide mechanical strength and higher thermal conductance instead of commercial thermal interface materials.
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Qingqing Ma, Baoming Ge, Daqiang Bi, Fernando J.T.E. Ferreira and Aníbal T. de Almeida
The purpose of this paper is to propose a new three-phase switched reluctance motor (SRM), and achieve high-torque and low-cost. This new SRM's winding configuration uses the…
Abstract
Purpose
The purpose of this paper is to propose a new three-phase switched reluctance motor (SRM), and achieve high-torque and low-cost. This new SRM's winding configuration uses the double-layer distributed windings, which is different from the conventional SRM's single tooth coils.
Design/methodology/approach
The operating principle of new SRM is analyzed, and the voltage equation and the generated torque are deduced. Finite element method (FEM) and finite element circuit coupled method are utilized to evaluate the new motor's operating performances. The two dimensional (2D) frequency response analysis model is employed in the FEM model. Based on the 2D frequency response analysis model, the magnetic field distribution, self-inductance, and mutual-inductance for the new SRM are analyzed in detail. A co-simulation model using FE analysis package and Matlab-Simulink is proposed to simulate the new SRM drive. The simulated and experimental results verify the new SRM.
Findings
For the new SRM with double-layer distributed windings, a co-simulation method is proposed to analyze its characteristics. The new SRM presents lower torque ripple coefficient and generates larger torque than the conventional SRM, with three-wire and standard full bridge power converter, rather than six-wire and asymmetric half-bridge converter for conventional SRM.
Originality/value
This paper proposes a new SRM with the double-layer distributed windings driven by a standard full bridge inverter. In order to calculate dynamic characteristics of the new SRM, a co-simulation method using FEM and Simulink is proposed to simulate the new SRM drive, where the power inverter and the current chopping control algorithm are implemented.
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Shuo Liu, Baoming Ge, Xinjian Jiang, Haitham Abu-Rub and Fangzheng Peng
– The paper aims to propose a new type of three-phase quasi-Z-source indirect matrix converter (QZSIMC) to extend the voltage gain for application in the induction motor drives.
Abstract
Purpose
The paper aims to propose a new type of three-phase quasi-Z-source indirect matrix converter (QZSIMC) to extend the voltage gain for application in the induction motor drives.
Design/methodology/approach
A unique H-shape quasi-Z-source network is connected between the three-phase voltage source and traditional indirect matrix converter to achieve the voltage boost and buck in a single-stage power conversion. The complete space vector modulation (SVM) method is proposed to control the proposed QZSIMC. The output voltage amplitude of quasi-Z-source network can be boosted by the shoot-through of the front-end rectifier, so the whole system's voltage gain is extended. Meanwhile, the QZSIMC modeling and quasi-Z-source impedance parameter design are developed by using the state space averaging method. The design-oriented analysis based on small signal model is used to investigate the quasi-Z-source impedance parameter's impact on the QZSIMC's dynamic performance. A simulated application example employs a 4-kW induction motor drive to verify the proposed QZSIMC, the developed modulation method and parameter design method.
Findings
The proposed QZSIMC can achieve high voltage gain larger than one and also can fulfill buck function, which widens the induction motor drive's operation range. The simulation results verify the proposed QZSIMC and SVM and also validate the quality performance of the proposed induction motor drive and all theoretical analysis and parameter design method.
Originality/value
The proposed QZSIMC effectively overcomes the limitation of traditional indirect matrix converter, through extending the voltage gain larger than one. The systematic principle, analysis, parameter design, and simulation verification provide the proposed QZSIMC with a feasible approach in practical induction motor drive applications.
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Liu Jingjun, Lin Yuzhen and Li Xiaoyu
This paper aims to study flow‐induced corrosion mechanisms for carbon steel in high‐velocity flowing seawater and to explain corrosive phenomena.
Abstract
Purpose
This paper aims to study flow‐induced corrosion mechanisms for carbon steel in high‐velocity flowing seawater and to explain corrosive phenomena.
Design/methodology/approach
An overall mathematical model for flow‐induced corrosion of carbon steel in high‐velocity flow seawater was established in a rotating disk apparatus using both numerical simulation and test methods. By studying the impact of turbulent flow using the kinetic energy of a turbulent approach and the effects of the computational near‐wall hydrodynamic parameters on corrosion rates, corrosion behavior and mechanism are discussed here. It is applicable in order to understand in depth the synergistic effect mechanism of flow‐induced corrosion.
Findings
It was found that it is scientific and reasonable to investigate carbon steel corrosion through correlation of the near‐wall hydrodynamic parameters, which can accurately describe the influence of fluid flow on corrosion. The computational corrosion rates obtained by this model are in good agreement with measured corrosion data. It is shown that serious flow‐induced corrosion is caused by the synergistic effect between the corrosion electrochemical factor and the hydrodynamic factor, while the corrosion electrochemical factor plays a dominant role in flow‐induced corrosion.
Originality/value
The corrosion kinetics and mechanism of metals in a high‐velocity flowing medium is discussed here. These results will help those interested in flow‐induced corrosion to understand in depth the type of issue.
Gabriel Khoury, Ragi Ghosn, Flavia Khatounian, Maurice Fadel and Mathias Tientcheu
In the need to optimize the energy efficiency, control structures can have a positive effect by tracking the optimal operating point according to the speed and mechanical load of…
Abstract
Purpose
In the need to optimize the energy efficiency, control structures can have a positive effect by tracking the optimal operating point according to the speed and mechanical load of the motor. The purpose of this paper is to present an energy-efficient scalar control for squirrel-cage induction motors (IMs), taking into consideration the effect of core losses.
Design/methodology/approach
The proposed technique is based on the modification of the stator flux reference, to track the best efficiency point. The optimal flux values are computed through an improved model of the IM including core losses, then stored in a look-up table.
Findings
Simulations of the proposed scalar control are carried out, and results show the efficiency improvement when the flux is optimized especially at low load cases. Results were validated experimentally on two motors compliant with different efficiency standards.
Practical implications
The proposed approach can be used in several fields and applications using the scalar-controlled IM with a proper implementation in variable speed drives, as in the cases of pumps, compressors and blowers.
Originality/value
The proposed technique is compared to existing optimization methods in literature, and the results show an improvement in the dynamic performance and in the response delays. The approach is also compared to an optimization technique used in industries like Leroy-Somer for variable speed drives, and efficiency improvements are shown.