Generalised multistage modelling and tuning algorithm for class EF and class Φ inverters to eliminate iterative retuning

The additional complexity of Class EF and Class Φ inverters compared to their Class E counterparts, combined with parasitic effects becoming more prevalent as frequency and power levels increase, results in poor accuracy from traditional design methods, and usually additional iterations of manual retuning are required. In this work we propose an approach to simulating and tuning Class EF/Φ inverters, with various levels of accuracy depending on the level of knowledge of the system parasitics. Our method is comprised of a combination of analytic and numerical solving methods thus providing both insight on the progression of the algorithm and computational robustness. The aim of our algorithm formulation is to enable solutions to be found in an automated and fast way. The novelty in our work lies in the design method's concurrent capability to provide a generalised set of design inputs (e.g. DC to AC current gain, arbitrary drain voltage slope at turn on, Φ- branch resonance, etc.), inclusion of board and device non-linear parasitics, and the ability to design within the set of preferred component values. An example is shown for the design of a 50 W, 13.56 MHz inverter where the experimental setup approaches the theoretical efficiency of 97%. The algorithm changes the values of the components over 5% to 50% and improves the simulated waveform accuracy by 2 to 12 times compared to the design method based on first order approximations

Dual Energy Method for Breast Imaging: A Simulation Study

Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in order to overcome the limited kVp range of mammographic units used in previous DE studies, combined with a high resolution CMOS sensor (pixel size of 22.5 m) for improved resolution. Various filter materials were examined based on their K-absorption edge. Hydroxyapatite (HAp) was used to simulate microcalcifications. The contrast to noise ratio (CNR ) of the subtracted images was calculated for both monoenergetic and polyenergetic X-ray beams. The optimum monoenergetic pair was 23/58 keV for the low and high energy, respectively, resulting in a minimum detectable microcalcification thickness of 100 m. In the polyenergetic X-ray study, the optimal spectral combination was 40/70 kVp filtered with 100 m cadmium and 1000 m copper, respectively. In this case, the minimum detectable microcalcification thickness was 150 m. The proposed dual energy method provides improved microcalcification detectability in breast imaging with mean glandular dose values within acceptable levels

Dual energy subtraction method for breast calcification imaging

The aim of this work was to present an experimental dual energy (DE) method for the visualization of microcalcifications (μCsμCs). A modified radiographic X-ray tube combined with a high resolution complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) X-ray detector was used. A 40/70 kV spectral combination was filtered with 100 μmμm cadmium (Cd) and 1000 μmμm copper (Cu) for the low/high-energy combination. Homogenous and inhomogeneous breast phantoms and two calcification phantoms were constructed with various calcification thicknesses, ranging from 16 to 152 μmμm. Contrast-to-noise ratio (CNR) was calculated from the DE subtracted images for various entrance surface doses. A calcification thickness of 152 μmμm was visible, with mean glandular doses (MGD) in the acceptable levels (below 3 mGy). Additional post-processing on the DE images of the inhomogeneous breast phantom resulted in a minimum visible calcification thickness of 93 μmμm (MGD=1.62 mGy). The proposed DE method could potentially improve calcification visibility in DE breast calcification imaging

Mechanical analysis of infant carrying in hominoids

In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair–hair friction coefficient, and body angle exists. The hair–hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here

Potential use of Rosemary, Propolis and Thyme as Natural Food Preservatives

The use of preservatives in food stuffs and beverages is essential in order to prevent spoilage due to microbial growth or undesirable chemical changes. However, the use of synthetic additives has been associated with various health problems. Therefore, consumers have turned suspicious and obverted towards ingredients from natural sources. This tendency has driven food industry in further search and development of “natural preservatives”, to extend the shelf life of its products and maintain their safety. This report is focused on the current status of the natural derived preservatives and potential use of propolis, thyme and rosemary as sources for the development of effective preservatives

Portable biomedical devices: a critical issue during telecare services design

Objectives. The selection of a portable biomedical device (PBD) is a key issue regarding telecare service design. The objective of this study is to investigate the accuracy parameters of a PBD under different settings and levels. Methods and materials. By using a commercial PBD, trials were performed in a referral cardiology center and on the Olympia Explorer of the Royal Olympia Cruises, and the Superfast XII of Superfast Ferries. Data were collected (February 2004 - June 2006) by performing: (1) 'in hospital' standalone trials; (2) 'in hospital' comparative trials; and (3) 'on board' trials. Semistructured interviews were also conducted with several subjects, their cardiologists and crewmembers. Results. We investigated the accuracy parameters, namely the data precision (DP), the peripheral modules reliability (PMR) and the data transmission quality (DTQ). Although the outcomes of the comparative trials, via a statistical method verifying the DP (more than 95%), the trials 'on board' and 'in hospital' revealed a number of critical variables for the PMR and DTQ parameters. Conclusion. Telecare services design has accuracy parameter investigation needs. These parameters should be investigated simultaneously, while a compromise between them can act as a driving force to the telecare services success. The compromise is achieved by a smooth fit between DP and PMR with this fit varying within settings and levels

Design and modelling of class EF inverters for wireless power transfer applications

Class EF inverters have been widely used recently as primary coil drivers for wireless power transfer applications since they achieve constant output current across a range of link coupling factor values. As the operating frequency that the inductive link is tuned at increases the traditional circuit design techniques that are based on first order calculations fail to represent the inverter behaviour accurately. In this paper, we present a novel method of modelling Class EF inverters that is based on state space representation of the circuit and thus providing the highest accuracy possible. Our method consists of a combination of analytical and numerical calculations in such manner that any parasitic component of the circuit, such as the nonlinear output capacitance of a power switch, can be included in the tuning process

An advanced connectivity for distributed and heterogeneous clinical databases

Abstract- In medicine a clinical entity is usually represented by different synonymous keywords, meaning that physicians are dealing with a rapidly changing, unstructured and qualitatively heterogeneous data sharing environment while trying to pick up the needed data of decision making. In recent years, ontologies have been adopted in many scientific communities as a way to share, re-use and process domain knowledge by using a variety of formats including RDF(S), OWL, and XML Schema’s. However current structures cannot satisfy the new desiderata of Medical Data Structures, such as the demand for re-use and sharing patient’s data, their transmission and the need of semantic-based criteria in order to reduce the “noise ” of less relevant medical data. The aim of this work is both to review I

Design of a one-to-four isolated DC-DC converter using a 13.56 MHz resonant air-core transformer

This paper showcases the design and development of a DC-DC converter with one input and four outputs using a high frequency resonant air-core transformer. The transmitter to receivers air-gap is 25 mm. Practical tuning equations were derived for multiple receivers which allow the converter to be optimised for overall efficiency and unity power factor at the transmit coil (i.e. zero reflected reactance). Experiments were conducted using two receive coil structures, one with four equally shaped adjacent coils in a single PCB, and the other with four differently-shaped coils featuring overlapping traces to maximise the coupling factor with the transmitter and minimise the coupling factor between the receivers. The two structures were tested and compared using the same transmitter, driven by a single-ended 13.56 MHz Class EF inverter. Single-ended Class D rectifiers were implemented at the receive side. Experiments were performed, first with equal AC test loads, and afterwards with the addition of the rectifiers and buck converters to regulate each of the four output voltages to 15 V independently. The results of the experiments implementing adjacent coils demonstrate that equal distribution of power can be achieved by modifying the tuning capacitances at the receivers with the AC loads; however, when the voltage-regulating buck converters were introduced at each output, it was only with the coil structure with overlapping traces that the required power of 10 W at each output was achieved

Pencil Beam Spectral Measurements of Ce, Ho, Yb, and Ba Powders for Potential Use in Medical Applications

The aim of the present study was to obtain modified X-ray spectra, by using appropriate filter materials for use in applications such as dual energy X-ray imaging. K-edge filtering technique was implemented in order to obtain narrow energy bands for both dual- and single-kVp techniques. Three lanthanide filters (cerium, holmium, and ytterbium) and a filter outside lanthanides (barium), with low K-edge, were used to modify the X-ray spectra. The X-ray energies that were used in this work ranged from 60 to 100 kVp. Relative root mean square error (RMSE) and the coefficient of variation were used for filter selection. The increasing filter thicknesses led to narrower energy bands. For the dual-kVp technique, 0.7916 g/cm2 Ho, 0.9422 g/cm2 Yb, and 1.0095 g/cm2 Yb were selected for 70, 80, and 90 kVp, respectively. For the single-kVp technique 0.5991 g/cm2 Ce, 0.8750 g/cm2 Ba, and 0.8654 g/cm2 Ce were selected for 80, 90, and 100 kVp, respectively. The filtered X-ray spectra of this work, after appropriate modification, could be used in various X-ray applications, such as dual-energy mammography, bone absorptiometry, and digital tomosynthesis