Mechatronics Systems Engineering, School of

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Overview of Grounding Schemes for Solid-State Transformers in Distribution Networks

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-07-20
Abstract: 

Proposed to be the critical enabling component for future distribution networks, solid-state transformers (SSTs) have drawn much attention lately. They have a massive potential to help reduce size and weight, improve efficiency, integrate microgrids, renewables and energy storages in distribution systems, and can fulfil multiple grid functions such as bidirectional power flow control, fault isolation, system reconfiguration, and post-fault restoration. The introduction of these power electronics devices in distribution systems, however, also brings new challenges to the grid. Extra levels of electromagnetic interference, stray current, and personnel safety are among the most prominent practical issues that proper grounding arrangements can address. In this paper, considerations that should be factored into the grounding scheme design for SST ports with different voltage forms and levels are thoroughly reviewed and summarised. The characteristics of various grounding schemes used in AC and DC distribution systems are evaluated and compared in detail from different perspectives. Based on the comprehensive review, several combinations of grounding schemes are recommended for typical SSTs. In addition, the inclusion of new relay protection devices in the SST grounding scheme design, considering their characteristics and unique requirements, to enhance protection and reliability is also discussed.

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Article
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Dual Active Compensation for Voltage Source Rectifiers Under Very Weak Grid Conditions

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-11-30
Abstract: 

DC subgrids consisting of modern active loads (ALs) and local dc distributed generation (DG) units are normally interfaced with the main ac grid by utilizing bidirectional voltage source converters (VSCs). Under the very weak grid (VWG) conditions, the integration of voltage-oriented controlled (VOC) VSCs in the inversion mode becomes very challenging and therefore undamped oscillations in the power and angle responses are yielded. Most of the existing works address this issue for VSCs in the inversion mode of operation. However, integration of VSCs in the rectification mode with the consideration of the outer loop controllers into the VWGs has not been reported. To fill up this gap, a state-space model of the bidirectional VSC-to-weak grid (VSC-WG) system is developed in this work with an emphasis on the rectification mode of operation. A modal-sensitivity analysis is then utilized to evaluate small-signal stability of the system, identify the dominant modes, and investigate the system states that have a major influence on these modes. The results reveal two pairs of unstable complex modes that are correlated with the dynamic interaction between the VOC-based VSCs and the VWG impedance. It is also shown that the stability margin of VSCs in the rectification mode is less than that of the inversion mode under the same VWG conditions. To enhance the integration of the VSCs in the rectification mode, a dual-active compensation (DAC) scheme is proposed to mitigate the instabilities under VWG conditions. Several time-domain simulation results are presented to verify the validity of the small-signal model and demonstrate the effectiveness of the DAC scheme under the VWG conditions. Finally, hardware-in-the-loop (HIL) real-time experimental results are presented to validate the simulation results.

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Article
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Techno-Economic Assessment for Installation of INVELOX Wind Turbines in Northern Iran

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-10-01
Abstract: 

This paper aims to provide a comprehensive feasibility study for the installation of a 100 MW wind power plant using the INVELOX system in Manjil, Gilan, in Northern Iran. In the first part of the paper, we provide a review of the status of wind energy installation in Iran. We then review the mathematical equations involved in wind power calculations. Afterwards, with the environmental data gathered from the corresponding authorities and open‐access sources, we analyzed the INVELOX system with its benefits and drawbacks. Then, based on the derived mathematical formulations, and using simulation software packages, the average wind power density is calculated, and the turbine system is designed accordingly. Finally, the economic profitability of this project was examined using a mathematical economic analysis and the COMFAR software package. In addition to the detailed feasibility study of this specific project, this article aims to provide a comprehensive literature review of the INVELOX system.

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Low Back Pain—Behavior Correction by Providing Haptic Feedbacks: A Preliminary Investigation

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-10-28
Abstract: 

The activities performed by nurses in their daily activities involve frequent forward bending and awkward back postures. These movements contribute to the prevalence and development of low back pain (LBP). In previous studies, it has been shown that modifying their posture by education and training in proper lifting techniques decreases the prevalence of LBP. However, this education and training needs to be implemented daily. Hence, implementing the use of a wearable device to monitor the back posture with haptic feedback would be of importance to prevent LBP. This paper proposes a wearable device to monitor the back posture of the user and provide feedback when the participant is performing a possible hurtful movement. In this study, a group of participants was asked to wear the device while performing three of the most common activities performed by nurses. The study was divided into three sessions: In the first session, the participants performed the activities without feedback (baseline). During the second session, the participants received feedback from the wearable device (training) while performing the three tasks. Finally, for the third session, the participants performed the three tasks again, but the haptic feedback was turned off (validation). We found an improvement in the posture of more than 40% for the pitch (lateral bending) and roll (forward/backward bending) axes and 7% for the yaw (twisting) axis when comparing to the results from session 1 and session 2. The comparison between session 1 and session 3 showed an overall improvement of more than 50% for the pitch (lateral bending) and roll (forward/backward bending) axes and more than 20% for the yaw axis. These results hinted at the impact of the haptic feedback on the participants to correct their posture.

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Article
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Enhancing EFL Teaching Curriculum in a Vocational College in Central China Using Constructivism

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-07-06
Abstract: 

This action research is a study on how the constructivist learning principles came into practice in the context of English as a Foreign Language (EFL) curriculum reform. A comprehensive literature review on English education reform in China, the concepts of constructivism and needs analysis, and their applications in EFL education is provided. Through a case study of a vocational college in central China and using survey analysis, the paper describes how each component of a new curriculum and a new curriculum called 211 Module was successfully implemented. The paper also evaluates the curriculum efficacy through the judicious reviews and reflective feedbacks from the faculty focus groups and data collected from students’ questionnaires. Strategic plans are proposed in favor of the further enhancement of the curriculum to ensure the best possible constructivist language teaching and learning.

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Article
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The Effect of Footwear, Running Speed, and Location on the Validity of Two Commercially Available Inertial Measurement Units During Running

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-04-26
Abstract: 

Introduction: Most running-related injuries are believed to be caused by abrupt changes in training load, compounded by biomechanical movement patterns. Wearable technology has made it possible for runners to quantify biomechanical loads (e.g., peak positive acceleration; PPA) using commercially available inertial measurement units (IMUs). However, few devices have established criterion validity. The aim of this study was to assess the validity of two commercially available IMUs during running. Secondary aims were to determine the effect of footwear, running speed, and IMU location on PPA.

Materials and Methods: Healthy runners underwent a biomechanical running analysis on an instrumented treadmill. Participants ran at their preferred speed in three footwear conditions (neutral, minimalist, and maximalist), and at three speeds (preferred, +10%, −10%) in the neutral running shoes. Four IMUs were affixed at the distal tibia (IMeasureU-Tibia), shoelaces (RunScribe and IMeasureU-Shoe), and insole (Plantiga) of the right shoe. Pearson correlations were calculated for average vertical loading rate (AVLR) and PPA at each IMU location.

Results: The AVLR had a high positive association with PPA (IMeasureU-Tibia) in the neutral and maximalist (r = 0.70–0.72; p ≤ 0.001) shoes and in all running speed conditions (r = 0.71–0.83; p ≤ 0.001), but low positive association in the minimalist (r = 0.47; p < 0.05) footwear condition. Conversely, the relationship between AVLR and PPA (Plantiga) was high in the minimalist (r = 0.75; p ≤ 0.001) condition and moderate in the neutral (r = 0.50; p < 0.05) and maximalist (r = 0.57; p < 0.01) footwear. The RunScribe metrics demonstrated low to moderate positive associations (r = 0.40–0.62; p < 0.05) with AVLR across most footwear and speed conditions.

Discussion: Our findings indicate that the commercially available Plantiga IMU is comparable to a tibia-mounted IMU when acting as a surrogate for AVLR. However, these results vary between different levels of footwear and running speeds. The shoe-mounted RunScribe IMU exhibited slightly lower positive associations with AVLR. In general, the relationship with AVLR improved for the RunScribe sensor at slower speeds and improved for the Plantiga and tibia-mounted IMeasureU sensors at faster speeds.

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Article
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3D Origami Sensing Robots for Cooperative Healthcare Monitoring

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-01-25
Abstract: 

In this study, cooperative healthcare sensing robots that closely monitor and evaluate the patients’ muscle functions through gait analysis and electromyography (EMG) are developed. By integrating the biological sensors, the sensing robot can recognize the vital signs. The sensing robots are developed by the design and optimization of their architectures and materials using a green strategy. To achieve mechanically durable robot designs, 3D origami structures are used with specific optimum criteria. Different sensing robot applications are created through the 3D origami insole and humanoid hands for healthcare monitoring. The smart insole built with 3D origami monitors the foot pressure distribution for gait analysis of patients, and the humanoid hand equipped with the 3D origami‐structured EMG fingers cooperatively detects EMG signals. Such cooperative sensing robots hold considerable promise for healthcare monitoring with convenience for patients with quality of care, because the robots can derive empathetic adaptability with humans.

Document type: 
Article

Cortical Effects of Noisy Galvanic Vestibular Stimulation Using Functional Near-Infrared Spectroscopy

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2021-02-20
Abstract: 

Noisy galvanic vestibular stimulation (nGVS) can improve different motor, sensory, and cognitive behaviors. However, it is unclear how this stimulation affects brain activity to facilitate these improvements. Functional near-infrared spectroscopy (fNIRS) is inexpensive, portable, and less prone to motion artifacts than other neuroimaging technology. Thus, fNIRS has the potential to provide insight into how nGVS affects cortical activity during a variety of natural behaviors. Here we sought to: (1) determine if fNIRS can detect cortical changes in oxygenated (HbO) and deoxygenated (HbR) hemoglobin with application of subthreshold nGVS, and (2) determine how subthreshold nGVS affects this fNIRS-derived hemodynamic response. A total of twelve healthy participants received nGVS and sham stimulation during a seated, resting-state paradigm. To determine whether nGVS altered activity in select cortical regions of interest (BA40, BA39), we compared differences between nGVS and sham HbO and HbR concentrations. We found a greater HbR response during nGVS compared to sham stimulation in left BA40, a region previously associated with vestibular processing, and with all left hemisphere channels combined (p < 0.05). We did not detect differences in HbO responses for any region during nGVS (p > 0.05). Our results suggest that fNIRS may be suitable for understanding the cortical effects of nGVS.

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Endoscopic Optical Imaging Technologies and Devices for Medical Purposes: State of the Art

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-09-29
Abstract: 

The growth and development of optical components and, in particular, the miniaturization of micro-electro-mechanical systems (MEMSs), has motivated and enabled researchers to design smaller and smaller endoscopes. The overarching goal of this work has been to image smaller previously inaccessible luminal organs in real time, at high resolution, in a minimally invasive manner that does not compromise the comfort of the subject, nor introduce additional risk. Thus, an initial diagnosis can be made, or a small precancerous lesion may be detected, in a small-diameter luminal organ that would not have otherwise been possible. Continuous advancement in the field has enabled a wide range of optical scanners. Different scanning techniques, working principles, and the applications of endoscopic scanners are summarized in this review.

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Material Properties and Structure of Natural Graphite Sheet

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2020-10-29
Abstract: 

Natural graphite sheet (NGS) is compressible, porous, electrically and thermally conductive material that shows a potential to be used in fuel cells, fow batteries, electronics cooling systems, supercapacitors, adsorption air conditioning, and heat exchangers. We report the results of an extensive material characterization study that focuses on thermal conductivity, thermal difusivity, electrical conductivity, coefcient of thermal expansion (CTE), compression strain, and emissivity. All the properties are density-dependent and highly anisotropic. Increasing the compression from 100 to 1080 kPa causes the through-plane thermal and electrical conductivities to increase by up to 116% and 263%, respectively. The properties are independent of the sheet thickness. Thermal and electrical contact resistance between stacked NGS is negligible at pressures 100 to 1080 kPa. In the in-plane direction, NGS follows the Wiedemann-Franz law with Lorenz number 6.6 × 10−6 W  K−2. The in-plane CTE is low and negative (shrinkage with increasing temperature), while the through-plane CTE is high, increases with density, and reaches 33 × 10−6 K−1. Microscope images are used to study the structure and relate it to material properties. An easy-to-use graphical summary of the forming process and NGS properties are provided in Appendices A and B.

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