Sensor selection in magnetic tracking based on convex optimisation

The performance of a magnetic tracking system is substantially influenced by the positions of its sensors. To optimise these sensor positions, exploited is a performance metric based on the Fisher information matrix and a convex relaxation of sensor selection problem. Optimised sensor positions are presented for a magnetic tracking system with a planar sensor array and a measurement domain consisting of one point

Electromagnetic Modeling of Pacemaker Lead Heating During MRI

<p>The electromagnetic part of pacemaker lead heating during magnetic resonance imaging (MRI) is a resonant phenomenon which is complicated by, among other factors, the wide range of length scales involved in the problem. In this work, the multi-scale part of the problem is taken into special consideration during the modeling process. The model incorporates a radio frequency coil, a human body phantom, and a highly detailed model of a pacemaker system with a bipolar lead.</p> <p>Several configurations of pacemaker systems exposed to MRI are modeled and the results clearly show the importance of detailed lead modeling. Furthermore, modeling of resonant structures is investigated by a comparison between different modeling techniques.</p

Systems and methods for altering visual acuity

Provided are systems operable to effect a temporary change in a modulation transfer function (MTF) of a target imaging system. The systems include a light source operable to produce light for transient propagation onto at least a portion of the target imaging system, a power source in operative communication with the light source and configured to effect the production of light from the light source, and a transmission unit in operative communication with the light source and configured to propagate the produced light onto at least a portion of the target imaging system. The propagated light is configured for absorbance by the portion of the target imaging system; the absorbance causes an increase in temperature and a change in a refractive index profile of at least the portion of the imaging system. The change in refractive index profile produces a temporary change in the MTF of the imaging system.Board of Regents, University of Texas Syste

Comparisons of Blockage Widths of Ideally Hard Cylinders of Different Cross-Sectional Shapes

In some applications the electromagnetic waves radiating from or being received by an antenna are obstructed by some mechanical structure. If the structure is part of or close to an antenna, the obstruction may represent aperture blockage causing increased sidelobes and reduced gain of the antenna. For example, the blocking structures can be struts or masts supporting the feed in reflectarrays or in reflectors. Usually in antennas, the direction of the incident wave is known, so the struts can be designed to reduce the blockage for a given direction of incidence

Microwave Measurements for Metal Vessels

We present two different measurement techniques intended for closed metal vessels, where the objective is to measure the permittivity inside the metal vessel. This problem is relevant for many applications found in e.g. process industry. The first approach exploits the measurement of resonance frequencies, where the metal vessel is used as a microwave resonator. In the second approach, we let the boundary of the metal vessel be equipped with aperture antennas, where the aperture antennas are implemented in terms of rectangular waveguides. The waveguide apertures loads the cavity significantly and we exploit the scattering matrix parameters for the solution of the inverse problem

Global monitoring of fluidized-bed processes by means of microwave cavity resonances

We present an electromagnetic measurement system for monitoring of the effective permittivity in closed metal vessels, which are commonly used in the process industry. The measurement system exploits the process vessel as a microwave cavity resonator and the relative change in its complex resonance frequencies is related to the complex effective permittivity inside the vessel. Also, thermal expansion of the process vessel is taken into account and we compensate for its influence on the resonance frequencies by means of a priori information derived from a set of temperature measurements. The sensitivities, that relate the process state to the measured resonance frequencies, are computed by means of a detailed finite element model. The usefulness of the proposed measurement system is successfully demonstrated for a pharmaceutical fluidized-bed process, where the water and solid contents inside the process vessel is of interest

Animal Models of Diabetic Macrovascular Complications: Key Players in the Development of New Therapeutic Approaches

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development

System Identification and Tuning of Wireless Power Transfer Systems with Multiple Magnetically Coupled Resonators

We present a procedure for system identification and tuning of a wireless power transfer (WPT) system with four magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductance and losses of the coils. This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3 kW power transfer with 91 % system efficiency over an air-gap distance of approximately 20 cm