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Geofenced heavy trucks to protect bridges at crossings allowing higher weight on frozen roads Winter is our friend. When the road body is deep frozen it can handle more weight than during the rest of the year. However, the bridges are not affected by the cold weather, and they are therefore still vulnerable to increased loads. How can we allow increased loads on frozen roads while ensuring protection of the bridges? In this report, we share our insights from a project with the idea of using geofencing to protect the bridges. The geofencing technology ensures that the truck drives at a lower speed over the bridge and the bridge can withstand loads up to 74 tons since decreased speed reduces dynamic loads. If the road keeper can get guarantees that all heavy trucks drive at a low speed over the bridge, heavier traffic can be accommodated. This technology would of course also be beneficial to use across bridges in Europe regardless of the climate. ' The project “Frozen roads and 74 tons”, paid by the Swedish Transport Administration, consisted of three parts. One part was a pilot study during winter 22/23 demonstrating trucks from AB Volvo and Scania loaded with 74 tons using geofencing when the trucks passed over weak bridges. A speed limit, i.e. 50 km/h, was imposed in a zone around each bridge, whose coordinates were stored in the digital map accessible through the trucks’ Fleet Management System. Two different geofencing technologies were tested: on the one hand Scania’s system with “active” geofencing, where the truck was programmed to maintain the allowed speed over the bridge and calculated and implemented this itself (the driver could, however, override this by pushing the gas pedal to the floor); on the other hand AB Volvo’s system with “passive” geofencing, where the driver received a warning message when approaching the zone and would then slow down if necessary. The drivers were interviewed before and after the pilot about their experience. The results from

A subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7-2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of similar to 0.7 dB and similar to 1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of ∼0.7 dB and ∼1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

This work explores high data rate microwave communication through fat tissue in order to address the wide bandwidth requirements of intra-body area networks. We have designed and carried out experiments on an IEEE 802.15.4 based WBAN prototype by measuring the performance of the fat tissue channel in terms of data packet reception with respect to tissue length and power transmission. This paper proposes and demonstrates a high data rate communication channel through fat tissue using phantom and ex-vivo environments. Here, we achieve a data packet reception of approximately 96 % in both environments. The results also show that the received signal strength drops by ~1 dBm per 10 mm in phantom and ~2 dBm per 10 mm in ex-vivo. The phantom and ex-vivo experimentations validated our approach for high data rate communication through fat tissue for intrabody network applications. The proposed method opens up new opportunities for further research in fat channel communication. This study will contribute to the successful development of high bandwidth wireless intra-body networks that support high data rate implanted, ingested, injected, or worn devices, Eurostars project under Grant E-9655-COMFORT, Swedish Vinnova project under Grant BDAS (2015-04159), Swedish Vinnova project under Reliable, interoperable and secure communication for body network (2017-03568)

eSSENCE

Recently, the human fat tissue has been proposed as a microwave channel for intra-body sensor applications. In this work, we assess how disturbances can prevent reliable microwave propagation through the fat channel. Perturbants of different sizes are considered. The simulation and experimental results show that efficient communication through the fat channel is possible even in the presence of perturbants such as embedded muscle layers and blood vessels. We show that the communication channel is not affected by perturbants that are smaller than 15 mm cube.

In this paper, we present an approach for communication through human body tissue in the R-band frequency range. This study examines the ranges of microwave frequencies suitable for intra-body communication. The human body tissues are characterized with respect to their transmission properties using simulation modeling and phantom measurements. The variations in signal coupling with respect to different tissue thicknesses are studied. The simulation and phantom measurement results show that electromagnetic communication in the fat layer is viable with attenuation of approximately 2 dB per 20 mm., Eurostars project (grant E-9655-COMFORT), Swedish Vinnova project (grant BDAS), eSSENCE

To maximize the matching between a coaxial cable and rectangular waveguides, we present a computational topology optimisation approach that decides for each point in a given domain whether to hold a good conductor or a good dielectric. The conductivity is determined by a gradient-based optimisation method that relies on finite-difference time-domain solutions to the 3D Maxwell’s equations. Unlike previously reported results in the literature for this kind of problems, our design algorithm can efficiently handle tens of thousands of design variables that can allow novel conceptual waveguide designs. We demonstrate the effectiveness of the approach by presenting optimised transitions with reflection coefficients lower than −15dB over more than a 60% bandwidth, both for right-angle and end-launcher configurations. The performance of the proposed transitions is crossverified with a commercial software, and one design case is validated experimentally.

We present an approach to design from scratch planar microwave antennas for the purpose of ultra-wideband (UWB) near-field sensing. Up to about 120 000 design variables associated with square grids on planar substrates are subject to design, and a numerical optimization algorithm decides, after around 200 iterations, for each edge in the grid whether it should consist of metal or a dielectric. The antenna layouts produced with this approach show UWB impedance matching properties and near-field coupling coefficients that are flat over a much wider frequency range than a standard UWB antenna. The properties of the optimized antennas are successfully cross-verified with a commercial software and, for one of the designs, also validated experimentally. We demonstrate that an antenna optimized in this way shows a high sensitivity when used for near-field detection of a phantom with dielectric properties representative of muscle tissue.

We have developed and investigated a 1D-model for the interaction between a stack of wood and an impinging electromagnetic field. Maxwell's equations are used to model the electromagnetic interaction and each layer in a stack of boards has been modeled as a homogenous lossy dielectric slab. The main reason for developing this model has been to investigate the possibility of measuring the moisture content of wood inside a drying kiln using electromagnetic waves. Our investigations show that it is in principle possible to measure the moisture content, since the electromagnetic field is sensitive to changes in the moisture content of the wood. We also show that it might be possible to measure the average moisture content, without detailed knowledge of the distribution of moisture content between different boards.

The tone hole geometry of a clarinet is optimized numerically. The instrument is modeled as a network of one dimensional transmission line elements. For each (non-fork) fingering, we first calculate the resonance frequencies of the input impedance peaks, and compare them with the frequencies of a mathematically even chromatic scale (equal temperament). A least square algorithm is then used to minimize the differences and to derive the geometry of the instrument. Various situations are studied, with and without dedicated register hole and/or enlargement of the bore. With a dedicated register hole, the differences can remain less than 10 musical cents throughout the whole usual range of a clarinet. The positions, diameters and lengths of the chimneys vary regularly over the whole length of the instrument, in contrast with usual clarinets. Nevertheless, we recover one usual feature of instruments, namely that gradually larger tone holes occur when the distance to the reed increases. A fully chromatic prototype instrument has been built to check these calculations, and tested experimentally with an artificial blowing machine, providing good agreement with the numerical predictions.

Design Optimization

Absorbing boundary conditions are important in many applications where partial differential equations defined on infinite domains are solved numerically. A problem that has attracted interest recently is that perfectly matched layers layers (PML) for electro-magnetic FDTD simulations applied on convex surfaces may lead to instabilities. This paper shows that these problems are not restricted to electro-magnetic calculations, but common for problems described by the classical wave equation with absorbing boundary conditions on convex surfaces. It is shown that the instabilities are independent of the numerical implementation of the absorbing boundary condition, and instead a result of unphysical assumption in the formulation of the boundary condition.

This paper treats the use of numerically computed impedance boundary conditions for acoustic simulations. Such boundary conditions may be used to combine different methods on different parts of the computational domain. Impedance boundary conditions may be computed for each subproblem independently of each other. In order to develop insight into this approach, wave propagation in a rectangular waveguide with a step discontinuity is studied.

This paper presents how the shape of a brass instrument can be optimised with respect to its intonation and impedance peak magnitudes. The instrument is modelled using a one-dimensional transmission line analogy with truncated cones. The optimisation employs the Levenberg-Marquardt method, with the gradient of the objective function obtained by analytic manipulation. Through the use of an appropriate choice of design variables, the optimisation is capable of rapidly finding smooth horn profiles.

Design Optimization

Design Optimization

Shape optimization of an acoustic horn is performed with the goal to minimize the portion of the wave that is reflected. The analysis of the acoustical properties of the horn is performed using a finite element method for the Helmholtz equation. The optimization is performed employing a BFGS Quasi-Newton algorithm, where the gradients are provided by solving the associated adjoint equations. To avoid local solutions to the optimization problem corresponding to irregular shapes of the horn, a filtering technique is used that applies smoothing to the design updates and the gradient. This smoothing technique can be combined with Tikhonov regularization. However, experiments indicate that regularization is redundant for the optimization problems we consider here. However, the use of smoothing is crucial to obtain sensible solutions. The smoothing technique we use is equivalent to choosing a representation of the gradient of the objective function in an inner product involving second derivatives along the design boundary. Optimization is performed for a number of single frequencies as well as for a band of frequencies. For single frequency optimization, the method shows particularly fast convergence with indications of super-linear convergence close to optimum. For optimization on a range of frequencies, a design was achieved providing a low and even reflection throughout the entire frequency band of interest., Design Optimization

We use material distribution-based topology optimization to optimize the design of a bandpass subwoofer enclosure. The objective is to maximize the subwoofer's output power for a single frequency as well as for a range of frequencies. A linear electromechanical transducer model is combined with a hybrid 2D-3D model for sound propagation to model the subwoofer's performance. The adjoint variable approach is used to compute the gradients of the objective function with respect to the design variables, and the Method of Moving Asymptotes (MMA) is used to solve the topology optimization problem. To manage intermediate values of the material indicator function, a quadratic penalty is added to the objective function, and a non-linear filter is used to obtain a mesh independent design. By carefully selecting the target frequency range, we can guide the optimization algorithm to successfully generate a subwoofer design with the required bandpass character. This study constitutes, to the best of our knowledge, the first successful attempt to design the interior structure of a loudspeaker using topology optimization. The success is much due to the hybrid 2D-3D approach, which reduces the computational effort significantly with only small effects on the modeling accuracy.