Design and Optimization of Dual Band Circular Polarization Selective Structures

We present a non-resonant, dual band circular polarization selective structure (CPSS) for satellite communication applications in the K- and Ka-band. The structure consists of multiple layers of cascaded anisotropic sheets, with printed meander lines, separated by low permittivity spacers. It reflects right hand circular polarization and transmits left hand circular polarization in the lower frequency band. In the upper frequency band the opposite polarization selectivity is achieved. The theory of dual band circular polarization selectivity from cascaded anisotropic sheets is presented, and it is concluded that the separation between the frequency bands of operation is governed by the relative rotation between subsequent layers. An optimization routine for synthesizing dual band CPSSs from predefined design requirements is introduced, where a number of different optimization algorithms are utilized. A simulated design is presented which fulfills the strict design requirements of insertion loss and return loss less than 0.5dB, and axial ratio less than 0.78dB, in the frequency bands 17.7–20.2GHz and 27.5–30.0GHz. A prototype of the optimized design has been fabricated and characterized experimentally, both in transmissionandreflection,andgoodagreementisobservedbetweensimulated and experimental results. This type of structure is a potential candidate for implementation in dual band multiple spot beam systems utilizing frequency and polarization reuse schemes

Samband mellan kroppens substratutnyttjande, energiomsättning och antropometriska mått hos överviktiga barn och ungdomar

Övervikt och fetma har ökat lavinartat bland barn och ungdomar de senaste 25 åren. Fetma medför både fysiskt och psykiskt lidande för de drabbade barnen och de löper även en stor risk att drabbas av sjukdom i vuxen ålder. Prevention av övervikt och fetma är därför av högsta vikt. Forskning och olika studier kan bidra med utveckling av behandlingsmetoder, hitta nya orsaker och samband till varför fetma uppstår. Syftet med denna studie var att utvärdera om det finns samband mellan RQ-BMR (respiratorisk kvot, basalmetabolism), antropometriska mått och kroppssammansättning hos överviktiga barn och ungdomar i åldrarna 10-13 år. Syftet var även att se om det fanns någon skillnad mellan överviktiga pojkar och flickor när det gäller energi- och RQ-förändringar efter en peroral glukosbelast-ning. Studien kom att inkludera 16 stycken pojkar och 7 stycken flickor, totalt 23 stycken överviktiga barn och ungdomar. Datainsamlingen började med att samla in uppgifter om ålder och kön, sedan mättes längd, vikt och antropometrska mått. Uppgifter om kropps-sammansättning fick man genom att mäta fettmassa och fettfrimassa med BodPod. Däref-ter utfördes indirekt respiratorisk kalorimetri för att bestämma BMR och vidare gjordes en peroral glukosbelastning samtidigt som den indirekta respiratoriska kalorimetrin fortlöpte. Det fanns inga signifikanta skillnader i kroppssammansättning mellan de överviktiga pojkarna och flickorna. Det blev signifikanta skillnader av energiomsättningen under den perorala glukosbelastningen för både pojkarna och flickorna, vilket berodde på födans termogena effekt. Det var inga signifikanta skillnader mellan pojkar och flickor vad gäller energiomsättning, utom vid tidpunkten 30 minuter vilket visade att flickorna hade en mindre termogen effekt efter glukosbelastningen jämfört med pojkarna. Det blev signifikanta höjningar av RQ mellan tidpunkterna 30 och 60 minuter för både pojkarna och flickorna vid den perorala glukosbelastningen. Både pojkarna och flickorna hade förhöjda RQ-värden under fasta, vilket visar att de har en rubbad metabolism under fasta då de förbränner framförallt kolhydrater istället för fett. Det var svaga eller obefintliga korrelationen mellan RQ-BMR och de olika antropomet-riska måtten för både pojkar och flickor. Det var en måttlig/svag negativ korrelationen mellan fettfrimassa och RQ-BMR för både pojkarna och flickorna, vilket skulle kunna påvi-sa att en större mängd muskelmassa ger en högre fettförbränning och energiförbrukning. Det var en måttligt positiv korrelationen mellan fettmassa och RQ-BMR var för både pojkar och flickor, vilket skulle kunna tyda på att en stor andel fettmassa minskar fettförbränning-en. Dock behövs fler större studier med fler studiedeltagare för att kunna få valida resultat och slutsatser om eventuella korrelationer och skillnader mellan könen.Overweight and obesity has increased dramatically among children and adolescents over the past 25 years. Obesity is linked to both physical and psychological suffering for the children and also increases the risk of disease in adulthood. Prevention of overweight and obesity is therefore of paramount importance. Research and various studies can contribute to the development of therapies, find new causes and context of why obesity occurs. The purpose of this study was to evaluate whether there is correlation between the RQ-BMR (respiratory quotient, basic metabolic rate), anthropometric measurements and body com-position in obese children and adolescents aged 10-13 years. The aim was also to see if there was any difference between obese boys and girls in terms of energy and RQ changes after an oral glucose tolerance test. The study includes 16 boys and seven girls, a total of 23 overweight children and ado-lescents. Data collection began by collecting data on age and sex, then measured height, weight and anthropometric measurements. Data on body composition were obtained by measuring fat mass and fat free mass with a BodPod. Thereafter, indirect respiratory calorimetry was performed to determine the BMR and also an oral glucose tolerance test was made, while the indirect respiratory calorimetry proceeded. There were no significant differences in body composition between obese boys and girls. There were significant differences in energy metabolism during the oral glucose tolerance test for both boys and girls, due to dietary thermogenic effect. There were no significant differences between boys and girls in terms of energy metabolism, except at the time of 30 minutes which showed that girls had a smaller thermogenic effect after the glucose load than boys. There were significant increases in RQ between time points 30 and 60 minutes for both boys and girls at the oral glucose tolerance test. Both boys and girls had elevated RQ-values during fasting, indicating that they have a disturbed metabolism during fasting when they burn mainly carbohydrates rather than fat. There were weak or nonexistent correlation between RQ-BMR and the various anthropo-metric measurements for both boys and girls. There was a moderate / weak negative corre-lation between fat free mass and RQ-BMR for both boys and girls, which could demonstrate that a greater amount of muscle mass results in a higher fat burning and energy consump-tion. There was a moderately positive correlation between fat mass and RQ-BMR for both boys and girls, which could indicate that a large percentage of fat mass decreases fat loss. However, we need larger studies with more study participants in order to obtain valid re-sults and conclusions about possible correlations and differences between boys and girls

UTJECAJ DABROVIH BRANA NA DRIFT BESKRALJEŠNJAKA U ŠUMSKIM POTOCIMA

AbstractWe aimed to assess the effects of beaver dams on the invertebrate drift fauna in five central Swedish boreal forest streams. Each stream was sampled once during the autumn, with drift traps placed upstream and downstream of the beaver dams. Drift densities (numbers/100 m3 water) were calculated. The invertebrates were determined, dried and weighed. No significant differences were noted in total drift densities or in the drift densities of pelagic species. The drift densities of benthic species were higher upstream of the dam, mainly because Ephemeroptera were more abundant in the upstream part. No significant difference was observed in diversity or dry weight. The functional feeding group ratio: filtering collectors/gathering collectors was significantly higher downstream of the dam.SažetakCilj istraživanja bio je utvrditi imaju li dabrove brane utjecaj na drift beskralješnjaka u 5 šumskih potoka na području središnje Švedske. Uzorci su na svakom potoku prikupljani u jesen, koristeći kečere za hvatanje drifta postavljene uzvodno i nizvodno od ujezerenih dijelova potoka zajaženih dabrovim branama. Ulovi bes­kra­lješnjaka su osušeni, vagani i determinirani te je izračunata gustoća drifta (broj uzoraka/100 m3 vode). Uočeno je da nema značajne razlike u ukupnoj gustoći drifta kao i u gustoći drifta pelagičkih vrsta uzvodno i nizvodno od dabrovih brana. Gustoća drifta bentičkih vrsta bila je viša u dijelovima potoka uzvodno od dabrovih brana, uglavnom iz razloga što su vrste iz reda Ephemeroptera bile jače zastupljene u uzvodnim dijelovima. Nije zabilježena značajna razlika u suhoj tvari i raznolikosti vrsta. Utvrđen je sljedeći omjer organizama prema funkcionalnim hranidbenim skupinama: odnos broja filtratora koji skupljaju sitnu čestičnu organsku tvar u odnosu na brojnost sakupljača detritusa značajno je veći u korist prvih u dijelu vodotoka nizvodno od pozicije dabrove brane

Fundamental bounds on transmission through periodically perforated metal screens with experimental validation

This paper presents a study of transmission through arrays of periodic sub-wavelength apertures. Fundamental limitations for this phenomenon are formulated as a sum rule, relating the transmission coefficient over a bandwidth to the static polarizability. The sum rule is rigorously derived for arbitrary periodic apertures in thin screens. By this sum rule we establish a physical bound on the transmission bandwidth which is verified numerically for a number of aperture array designs. We utilize the sum rule to design and optimize sub-wavelength frequency selective surfaces with a bandwidth close to the physically attainable. Finally, we verify the sum rule and simulations by measurements of an array of horseshoe-shaped slots milled in aluminum foil.Comment: 10 pages, 11 figures. Updated Introduction and Conclusion

Assessing the quality of tests : revision of the EFPA review model

Background: Diverse national and international organizations have been developing projects for many years to improve testing practices. The main goal of this paper is to present the revised model of the European Federation of Psychologists’ Associations (EFPA) for the evaluation of the quality of tests. This model aims to provide test users with rigorous information about the theoretical, practical and psychometric characteristics of tests, in order to enhance their use. Method: For the revision of the test review model, an EFPA task force was established, consisting of six European experts from different countries, who worked on the update of the previous European model, adapting it to the recent developments in the field of psychological and educational measurement. Results: The updated EFPA model provides for the comprehensive evaluation of tests. The first part describes test characteristics exhaustively, and in the second part, a quantitative and narrative evaluation of the most relevant psychometric characteristics of tests is presented. Conclusions: A revision of the European model for the description and evaluation of psychological and educational tests is presented. The revised model is analyzed in light of recent developments in the field