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Publications (43)
Nowadays, intelligent models can correctly detect faults by analysing signals from rotating machinery. However, most of the studies are run in controlled environments and the performance in industrial real-world environments is not yet fully validated. Hence, a suitable tool to implement fault diagnosers is transfer learning, this topic is under de...
Additive manufactured smart wearables are establishing an increasingly firm foothold within the monitoring of physical activities. A tiler was the use case proposed by this study, which seeks to monitor changes in their typically kneeling work position with the goal of tracking behaviour and alleviating long-term damage due to incorrect posture. Th...
Photoacoustic (PA) measurements with open resonators usually provide poor detection sensitivity due to signal leakage at the resonator opening. We have recently demonstrated three different approaches for modelling the photoacoustic signal of open resonators. In this work, one of the approaches is applied for the optimization of the geometry of the...
Photoacoustic spectroscopy employs acoustic resonators for signal amplification. Resonators are usually closed, however, in some applications, open resonators are preferred. The opening deteriorates the photoacoustic signal hence reducing the sensitivity of the photoacoustic measurement. We present two new approaches for simulating the photoacousti...
In the above article
[1]
, Figure 3 should read “Isometric view of two wires forming a capacitor in the measured configuration. The yellow wire is the top plate and the red is the bottom plate of a capacitor. The gray is a dielectric elastomer lattice, the deformation of which can be indirectly determined by measuring the capacitance.” Figure 4 s...
Photoacoustic (PA) spectroscopy has been demonstrated as an effective technique for non-invasive measurement of blood glucose concentration. The measurement is done by probing the interstitial fluid with an infrared laser source. The glucose level in the interstitial fluid, which is found 10 to 50 micrometers under the human skin, is related to the...
Photoacoustic spectroscopy has been demonstrated as an effective technique for non-invasive measurement of blood glucose concentration [1-3]. The measurement is done by probing the glucose molecules in the interstitial fluid with an infrared laser source. The interstitial fluid lies a few micrometers under the skin surface and the glucose concentra...
T-cell resonators have been used lately for non-invasive blood glucose measurements for photoacoustic spectroscopy on skin samples. A resonator has a significant role in determining the strength of the measured signal and the overall sensitivity of the sensor. Here we present results of the measurement of the photoacoustic signal of such a T-cell r...
The design freedom offered by 3D printing is transformative and has been leveraged to fabricate structural electronics with multi-functionality. A proposed approach to extend this concept is to print three-dimensional jigsaw subsections of a structure with mortise and tenon features, populate the superficial surfaces with wires and components and t...
The photoacoustic signal in a closed T-cell resonator is generated and measured using laser based photoacoustic spectroscopy. The signal is modelled using the amplitude mode expansion method, which is based on eigenmode expansion and introduction of losses in form of loss factors. The measurement reproduced almost all the calculated resonances from...
Photoacoustic sensors are well established in the detection of substances with small concentrations. Ordinarily, these sensors make use of closed acoustic resonators for signal enhancement. Due to special requirements for certain use cases, we need to consider an acoustic resonator with an opening. In the presentation, we give an account of the cha...
The photoacoustic signal in a closed T-cell resonator is generated and measured using laser based photoacoustic spectroscopy. The signal is modelled using the amplitude mode expansion method, which is based on eigenmode expansion and introduction of losses in form of loss factors. The measurement reproduced almost all the calculated resonances from...
The photoacoustic (PA) effect consisting of the generation of an acoustic signal based on the absorption of light has already demonstrated its potential for various spectroscopic applications for both gaseous and solid samples. The signal produced during photoacoustic spectroscopy (PAS) measurement is, however, usually weak and needs to be amplifie...
African ball-rolling dung beetles can use their front legs for multiple purposes that include walking, manipulating or forming a dung ball, and also transporting it. Their multifunctional legs can be used as inspiration for the design of a multifunctional robot leg. Thus, in this paper, we present the development of real robot legs based on the stu...
Recent DFT calculations have demonstrated the potential of mechanically-bent graphene as a piezoelectric energy harvesting material. We develop a 2D model of hexagonal materials and demonstrate quantitatively the potential of a single layer of graphene to function as an effective piezoelectric nanogenerator. The piezoelectricity of graphene stems f...
This paper has investigated the integration of 3D-printed conductive paths into 3D-printed non-conductive structures, with the goal of exclusively combining standard off-the-shelf components with additive manufactured pieces in order to build a mechatronic device. To this end, a chosen conductive material has initially been mechanically and electri...
A numerical model for transit time ultrasonic flowmeters operating under multiphase flow conditions previously presented by the current authors is extended by mesh refinement and grid point redistribution. The method solves modified first order stress-velocity equations of elastodynamics with additional terms to account for the effect of the backgr...
A novel modified Preisach model is proposed to identify and simulate the hysteresis phenomena observed in a piezoelectric stack actuator. Further, an open-loop controller is incorporated to eliminate hysteresis influence. The proposed approach with a continuous, analytical distribution function performs very well when considering the low amount of...
This paper presents a theoretical investigation of phonon dispersion in piezoelectric slabs of hexagonal crystal symmetry (wurtzite). Specifically we solve the fully coupled dispersion relations in a GaN free standing quantum well by varying the crystal growth direction from the [001] axis to the [010] axis. Accounting for the Drude model in solvin...
In this paper we investigate theoretically the influence of piezoelectric coupling on phonon dispersion relations. Specifically we solve dispersion relations for a fully coupled zinc-blende freestanding quantum well for different orientations of the crystal unit cell. It is shown that the phonon mode density in GaAs can change by a factor of approx...
A numerical model for a clamp-on transit-time ultrasonic flowmeter (TTUF) under multi-phase flow conditions is presented. The method solves equations of linear elasticity for isotropic heterogeneous materials with background flow where acoustic media are modeled by setting shear modulus to zero. Spatial derivatives are calculated by a Fourier collo...
This paper gives a study into the development of a generalized model for a three-phase induction motor that offers flexibility of simulating balanced and unbalanced parameters scenarios. By analyzing the interaction of forces within the motor, we achieve our main objective of deriving the system dynamic equations for our model. The performance of t...
Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact calculation is given to confirm this phenomenon. Our res...
Using rather well known theory about capillary bridges between two electrodes we calculate the tensile force that can be applied to liquid metal contacts in the micrometer regime. Assuming circular symmetry, full wetting of the electrodes, and neglecting gravity, we present a brief review of the necessary theory and find numerically the forces to b...
This paper describes a new performance monitoring system for dinghies and small sailing boats, developed in a collaborative project of the Yacht Research Unit Kiel (YRUK) and the Mads Clausen Institute (MCI) of the University of Southern Denmark. The system under development features a complete set of nautical instruments (wind, boat speed and head...
Trace contaminations of n-heptane in synthetic air is measured in the parts-per-billion (ppb) range using near infrared photoacoustic detection. We describe the fundamental theory used in the design of the photoacoustic cell for trace gas analysis and determine the detection limit of the cell. On the basis of a modified procedure from the American...
This paper illustrates both a problem in mathematical physics, whereby the method of separation of variables, while applicable, leads to three ordinary differential equations that remain fully coupled via two separation constants and a five-term recurrence relation for series solutions, and an exactly solvable problem in electrostatics, as a bounda...
We briefly present the basic principle of the photoacoustic effect in gases. We present the equations and boundary conditions governing the acoustic field generated by the absorption of a modulated laser beam. We solve these equations using Finite Element Methods and compare the results with experiment. We find that apparently there are effects not...
The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell.
Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz
equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical res...
We briefly present the basic principle of the photoacoustic effect in gases. We present the equations and boundary conditions governing the acoustic field generated by the absorption of a modulated laser beam. We solve these equations using Finite Element Methods and compare the results with experiment. We find that apparently there are effects not...
A one-dimensional continuum model for calculating strain and electric field in wurtzite semiconductor heterostructures with arbitrary crystal orientation is presented and applied to GaN/AlGaN and ZnO/MgZnO heterostructure combinations. The model is self-consistent involving feedback couplings of spontaneous polarization, strain, and electric field....
Using a mathematical model on photoacoustics that includes both temperature and pressure effects explicitly, we analyze the behaviour of resonances of a cylindrical photoacoustic cell consisting of two buffer volumes and a resonator. We excite the cell at a certain frequency and find the ratio of resonator versus buffer diameter needed to obtain re...
A three-layered zinc-blende quantum-well structure is analyzed subject
to both static and dynamic conditions for different crystal growth
directions taking into account piezoelectric effects and lattice
mismatch. It is found that the strain component Szz in the
quantum-well region strongly depends on the crystal growth direction and
that a piezoele...