Bond graph models of DC-DC converters operating in both CCM and DCM

In this paper, Bond Graphs are employed to develop a novel mathematical model of conventional switched-mode DC-DC converters valid for both continuous and discontinuous conduction modes. A unique causality bond graph model of hybrid models is suggested with the operation of the switch and the diode to be represented by a Modulated Transformer with a binary input and a resistor with fixed conductance causality. The operation of the diode is controlled using an if-then function within the model. The extracted hybrid model is implemented on a Boost and Buck converter with their operations to change from CCM to DCM and to return to CCM. The vector fields of the models show validity in a wide operation area and comparison with the simulation of the converters using PSPICE reveals high accuracy of the proposed model, with the Normalised Root Means Square Error and the Maximum Absolute Error remaining adequately low. The model is also experimentally tested on a Buck topology

Equilibriums of extremely magnetized compact stars with force-free magnetotunnels

We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is assumed to satisfy ideal magnetohydrodynamic (MHD) conditions, while in the region of negligible mass density the force-free conditions or electromagnetic vacuum are assumed. Solving all components of Einstein's equations, Maxwell's equations, ideal MHD equations, and force-free conditions, equilibriums of rotating compact stars associated with mixed poloidal and toroidal magnetic fields are obtained. It is found that in the extreme cases the strong mixed magnetic fields concentrating in a toroidal region near the equatorial surface expel the matter and form a force-free toroidal magnetotunnel. We also introduce a new differential rotation law for computing solutions associated with force-free magnetosphere, and present other extreme models without the magnetotunnel.Comment: 13 pages, 4 figure

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7 [1/root Hz]. At the frequency of best strain sensitivity, near 100 Hz, we set 90% confidence upper limits of 1.8 x 10(-25). At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9 x 10(-24). At 55 Hz we can exclude sources with ellipticities greater than 10(-5) within 100 pc of Earth with fiducial value of the principal moment of inertia of 10(38) kg m(2)

Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO

During their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100 M ⊙, with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93 Gpc−3yr−1 in comoving units at the 90% confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits

Sogndal : nyskaping og omdømebygging i eit stadig meir globalt samfunn

I desse moderne tider, med ei globalisering som er i stadig frammarsj, må stader jobba stadig hardare for å skilje seg ut å gjere seg sjølv unik. Dette er ein bevisst slagplan for å lykkast, og for at globaliseringa skal slå positivt tilbake for einkvar stad. Mange seier at globaliseringa har gjort bygda og mindre stader til dei store taparane. På ei annan side kan ein derimot seie at globaliseringa har gjort at nye trendar blir skapt, som igjen gjev nye moglegheiter for vidare vekst, ikkje berre for urbane strøk, men òg for dei rurale. Spørsmålet er korleis stadane kan bruke globaliseringa til sin fordel, og følgje det opp ved å skapa noko nytt, og vekst ut av det. I denne oppgåva har eg brukt Sogndal som case for å belyse temaet. Dei empiriske data består av sju intervju, der intervjua var med menneskjer som representerer dei viktigaste aktørane i Sogndal kommune. Analysen er delt opp i tre deler, kor den første delen tar for seg kva dei unike ressursane som er å finna i Sogndal er, mens den andre delen av analysen byrjar med å presentere dei viktigaste aktørane i Sogndal. Vidare tar den føre seg korleis dei ulike aktørane jobbar for å marknadsføre seg sjølv, og som eit resultat av dette, er ei marknadsføring av Sogndal. Dette kan gjerast på forskjellige måtar, noko som me skal sjå på nærare på i denne oppgåva. Den tredje og siste delen av analysen tar føre seg korleis Sogndal kan lykkast i framtida, i form av stadsutivkling og vere eit velfungerande samfunn, med kraft av deira unike ressursar som gjer seg gjeldane. Funna frå denne oppgåva, viser at Sogndal har ressursar som kan utnyttast til å skapa vidare vekst, og vere ein kreativ stad som kan lykkast i eit stadig meir globalt samfunn. Bygdementaliteten med folka i spissen er Sogndal velsigna av, og samtidig er dette heilt avgjerande med tanke for å kunne skapa noko nytt. Ein må heller ikkje gløyme å rekne med viktige verksemder som Sogndal Fotball, Lerum AS og dei offentlige etat som er å finna Sogndal og omland som har vore med og forma bygda over tid. Naturen som fins i området, er òg ein ressurs som ein må ta med seg. For å kunne lykkast, må desse kreftene og ressursane som er å finna i bygda, kunne samarbeide og vere kreative, der hovudessensen vil vere å finne ut kva som er bygda sine unike ressursar, og utnytte dei til det fulle. Kva er det Sogndal har som ingen andre har

A comparison between bond graphs switching modelling techniques implemented on a boost dc-dc converter

A Bond Graph is a graphical modelling technique that allows the representation of energy flow between the components of a system. When used to model power electronic systems, it is necessary to incorporate bond graph elements to represent a switch. In this paper, three different methods of modelling switching devices are compared and contrasted: the Modulated Transformer with a binary modulation ratio (MTF), the ideal switch element, and the Switched Power Junction (SPJ) method. These three methods are used to model a dc-dc Boost converter and then run simulations in MATLAB/SIMULINK. To provide a reference to compare results, the converter is also simulated using PSPICE. Both quantitative and qualitative comparisons are made to determine the suitability of each of the three Bond Graph switch models in specific power electronics application

The Gram dimension of a graph

The Gram dimension gd(G) of a graph is the smallest integer k ≥ 1 such that, for every assignment of unit vectors to the nodes of the graph, there exists another assignment of unit vectors lying in Rk, having the same inner products on the edges of the graph. The class of graphs satisfying gd(G) ≤ k is minor closed for fixed k, so it can characterized by a finite list of forbidden minors. For k ≤ 3, the only forbidden minor is Kk+1. We show that a graph has Gram dimension at most 4 if and only if it does not have K5 and K2,2,2 as minors. We also show some close connections to the notion of d-realizability of graphs. In particular, our result implies the characterization of 3-realizable graphs of Belk and Connelly

Vaccination Coverage and Associated Factors of COVID-19 Uptake in Adult Primary Health Care Users in Greece

In our study, attitudes and perceptions of adult primary health care users regarding COVID-19 vaccination were evaluated. A single-center, cross-sectional study was conducted during a 1-year period (March 2021–March 2022) in a rural area in Crete, Greece. A sample of 626 self-reported questionnaires was collected at the end of the study period. Overall, 78% of respondents stated that they had received the COVID-19 vaccine. The reasons behind vaccine uptake were mainly personal beliefs and the desire to avoid professional constraints. The presence of diabetes type 2, fear of infection, and high perceived efficacy of vaccine previous flu vaccination, living with vulnerable persons, and the influence of scientific information were all significant predictors of COVID-19 vaccine uptake. On the contrary, unwillingness and/or uncertainty to be vaccinated was associated with fear of vaccine side effects, information insufficiency, media/internet information, older age, the presence of inflammatory arthritis, previous COVID-19 infection, the belief that infection confers much greater immunity than the vaccine, and attitudes against vaccinations in general were predictors against COVID-19 vaccination. In conclusion, taking into account all of the above predictors and particularly those regarding safety and vaccine effectiveness may guide future strategies appropriately tailored to specific characteristics and needs of different geographic populations

Vaccination Coverage and Associated Factors of COVID-19 Uptake in Adult Primary Health Care Users in Greece

In our study, attitudes and perceptions of adult primary health care users regarding COVID-19 vaccination were evaluated. A single-center, cross-sectional study was conducted during a 1-year period (March 2021–March 2022) in a rural area in Crete, Greece. A sample of 626 self-reported questionnaires was collected at the end of the study period. Overall, 78% of respondents stated that they had received the COVID-19 vaccine. The reasons behind vaccine uptake were mainly personal beliefs and the desire to avoid professional constraints. The presence of diabetes type 2, fear of infection, and high perceived efficacy of vaccine previous flu vaccination, living with vulnerable persons, and the influence of scientific information were all significant predictors of COVID-19 vaccine uptake. On the contrary, unwillingness and/or uncertainty to be vaccinated was associated with fear of vaccine side effects, information insufficiency, media/internet information, older age, the presence of inflammatory arthritis, previous COVID-19 infection, the belief that infection confers much greater immunity than the vaccine, and attitudes against vaccinations in general were predictors against COVID-19 vaccination. In conclusion, taking into account all of the above predictors and particularly those regarding safety and vaccine effectiveness may guide future strategies appropriately tailored to specific characteristics and needs of different geographic populations