Jee-u Ho

Dynamics of a piezoelectric beam subjected to water droplet impact with water layer formed on the surface

Rain impact energy harvesting using piezoelectric energy harvester has gained much attention recently. However, previous works have only considered the effect of single water droplet. In the case of raindrop, water would accumulate on the surface of the energy harvester and form a shallow water layer. This article models the dynamics of a piezoelectric beam, served as a raindrop energy harvester, subjected to water droplet impact with water layer formed on the surface. The impact of water droplet on the tip of the energy harvester is modelled as an impulsive force, and the water layer on the surface of the energy harvester is modelled as an added mass to the energy harvester. An attempt to model the force generated by the water ripple as a distributed load on the piezoelectric beam is presented. Numerical studies have been conducted based upon the proposed mathematical model verified by experimental results. The results showed that the presence of the water layer affects the output voltage and the dominant frequency of the energy harvester. It reveals that the effect of water (or rain) accumulation on the piezoelectric surface should be considered in deriving an optimal operating condition of such energy harvester.

On accumulation of water droplets in piezoelectric energy harvesting

Recent studies have demonstrated that it is feasible to harvest energy from raindrop. A challenge in designing a raindrop energy harvester is the rain droplet would accumulate on the surface of the harvester and affect its performance. In a previous work, we have modelled the dynamics of a piezoelectric beam subjected to water droplet impacts with a water layer formed on the surface. This work presents a theoretical model to describe the transient dynamics during the formation of water layer on the beam. The average water droplet impact force is described by a partially inelastic impact coefficient that varies during the formation of water layer. The maximum root mean square voltage measured experimentally is 0.05 V with an average percentage error of 6.94% compared to the theoretical model. Experimental result revealed that the optimal performance of the harvester occurs before the water layer spreads to the width end of the beam.

Development of a multi-touch table for natural user interface

Multi-Touch is a technique that provides user the parallel interaction with the Graphical User Interface. This paper presents innovative ideas on the development of hardware and software applications of a multi-touch system. Besides that, Frustrated Total Internal Reflection (FTIR) method and Rear Diffused Illumination Reflection (RDIR) method have been integrated to improve the performance and accuracy of the blobs detection for the tracking system. A new web-based Geographical Information System (GIS) application has been developed to demonstrate the effect of the multi-touch sensing technology.

3D finite element simulation of magnetic particle inspection

Magnetic particle inspection (MPI) is widely used to examine ferromagnetic materials. A 3D magnetic finite element method (FEM) simulation of MPI is applied to analyze the magnetic field around a defect. A 3D simulation of MPI gives a better quantitative understanding of the MPI in seizing defects and thus its indication would contribute to improving the analysis of experimental data. The magnetic flux density at the site of defects having different widths and depths has been investigated and analyzed. The simulated results can then be used to assist in the understanding of the behavior of magnetic field around a defect. A rectangular slot as a simplified and convenient representation of a surface-breaking defect is used. This paper describes the features of specimen studied, presentations of the finite element analysis, followed by results and discussions and finally concluding remarks.

Axial Compression for Direct Capture of Carbon Dioxide (CO2)

One prospective method to retard the speed of climate change is Carbon Capture and Storage (CCS). It is known that reducing emissions through CCS on point sources can only slowdown the rate of increase of atmospheric CO2 concentration and not able to mitigate the CO2 that are already in the atmosphere by previous emissions. Hence, a complimentary method would be to extract CO2 directly from air – Direct Air Capture (DAC). This paper addresses a novel concept of DAC whereby an additional phase of axial compression is introduced to adapt atmospheric air to a level suitable for capture. An axial compression model was developed so that fluid simulation studies can be performed. These information are then utilized in a feasibility study to address several key issues: the additional energy penalty when applying axial compression and whether or not, increasing the capture input by compression would displace the elevated energy consumption.

Overview of Axial Compression Technology for Direct Capture of CO2

Carbon Capture and Storage (CCS) is one of the global leading methods that could potentially retard the speed of climate change. However, CCS on point sources can only slowdown the rate of increase of atmospheric CO2 concentration. In order to mitigate CO2 released by previous emissions, a more proactive alternative is proposed where CO2 is directly extracted and captured from air Direct Air Capture (DAC). This paper presents a technical overview from our current research of a novel DAC concept which features a phase of axial compression to adapt pre-capture atmospheric air to a level suitable for carbon capture. Also detailed in the paper is the feasibility study addressing several key issues: the energy consumption and overall capturing efficiency of the proposed DAC system.

Dynamics of a piezoelectric energy harvester in a simulated rain environment

Rain impact energy harvesting has proven to be a feasible and potent source of alternative energy. This paper presents the development of a dynamical model for rain impact energy harvester using a piezoelectric beam in simulated rain environment. Most of the conducted works in literature were based on single droplet impact with fixed height and drop position. The main contribution of this paper is to extend the single droplet impact dynamical model by incorporating random drop sizes and drop positions. In this work, a rain simulator is used to generate artificial rain of different rain rates. Following our previous works, the water accumulation on the piezoelectric beam is modeled using added mass coefficient, and impact coefficient is integrated into the dynamical model to describe the post-impact dynamics of the droplet impact. The stochastic nature of the artificial rain is described using rain rate and drop size distribution. Two random number generators are integrated into the model, which are lognormally and uniformly distributed, to generate random numbers for droplet diameter and drop position respectively. The accuracy of the theoretical model is validated experimentally by considering four different rain rates.

Design of a single motor, tendon driven redundant manipulator with reduced driving joint torques

ABSTRACT Lightweight manipulator design is one of the diverse and rich research fields in the area of robotics. It has become increasingly important to develop manipulators with reduced cost, high energy efficiency and with low inertia. There are numerous design concepts proposed in the past decades such as designing lightweight joints or locating the actuators at the base. Reduction of number of actuators used has added advantages such as cost reduction, reduced power consumption, compact in design apart from reduction of weight. This paper presents a lightweight tendon drive redundant manipulator design with reduced joint torque using a single motor. The proposed design has reduced the number of actuators used. Thus the design is not only effective in reducing driving joint torques but also minimizes the number of actuators required and the power consumption. Driving joint torques computed for both conventional and for the proposed manipulator design highlight the significance of the proposed manipulator.

Computational model considerations of defect detection in pipes with bends using focused guided wave

Abstract This paper investigates the propagation of guided ultrasonic wave in pipes with bends using finite element simulation. The defect detectability in pipes with bends, using time delay focusing and synthetic focusing by common source method (CSM) are studied. Results show that the time delay focusing technique improves the confidence in detecting a small defect (3.8% cross-sectional area) beyond the bend, but it is unable to detect defects close to other features like welds or bends. Meanwhile, CSM is able to improve defect detection beyond and close to welding and bends. However, a reference image of a defect-free pipe is needed to detect defects near welds.

A motion sensor network for quantitative gait measurement

Quantitative gait analysis is an important research area to enable physiotherapist to perform systematic studies and health diagnosis of the lower extremity of patients throughout the rehabilitation. The quantitative measurement of ambulatory gait can be performed by using convenient and economical wearable sensors outside specialized motion laboratories. In this paper, a sensor system consisting of three tri-axial accelerometers, two flex sensors and four force sensors was developed. Subject testing were carried out to obtain temporal and spatial gait parameters. The performance of the sensor suite is compared to results from camera videos analysed by Kinovea motion tracking software.