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With the recent resurgence of interest in double negative (DNG) materials and the reported construction of a metamaterial with DNG characteristics, applications of these materials become feasible and examination of the behavior of systems and devices a potentially fruitful topic. The most promising area of research, upon inquiry into past work related to DNG materials, proves to be dielectric waveguides. The present investigation, then, focuses on the inclusion of DNG materials in various planar dielectric waveguide configurations. These waveguides involve a core region surrounded by various numbers of symmetrically-placed cladding layers. The present investigation involves the review of the electromagnetic properties of DNG materials by a thorough analysis based on Maxwell's equations. The use of a negative index of refraction for these materials is justified. These results are then used to perform a frequency domain analysis of an N-layer formulation for dielectric waveguides which is general for any combination of DNG and double positive (DPS) materials. This N-layer formulation allows for the derivation of the characteristic equation, which relates the operating frequency and the propagation constant solutions, along with the cutoff conditions and field distributions. A causal material model which obeys the Kramers-Kronig relations and which is based on measurements of a realized metamaterial is studied and used in the investigation in order to produce realistic results. The N-layer formulation is then applied to the three-layer (slab) waveguide and known results are reviewed. A new interpretation of intramodal degeneracy is given, whereby degenerate modes are split into two separate modes, one with positive phase velocity and one with negative phase velocity but both with a causal positive group (energy) velocity. Next, the formulation is applied to the five-layer waveguide. New behaviors are observed in this case which are not seen for the three-layer waveguide, including the return of the fundamental mode in some cases, whereas it is never present for the three-layer guide, the absence of certain higher-order modes in some situations and the appearance of new modes. Additionally, for some configurations the order of the even and odd modes in the DNG frequency range is found to be reversed from that of conventional waveguides. The photonic crystal waveguide, which involves an infinite number of periodically placed cladding layers, is next studied using ray analysis, and a slight variation of the N-layer formulation is used to compare these results with those of the pseudo-photonic crystal waveguide. The pseudo-photonic crystal waveguide is identical to the photonic crystal waveguide with the exception that it has only large but finite number of layers. It is seen that the results of these two cases are similar for conventional modes, but the photonic crystal waveguide allows for new modes called photonic crystal modes which are inaccessible through conventional waveguides. Interesting phenomena such as mode crossings among the photonic crystal modes are observed and discussed. Using the results from the frequency domain analysis of the five-layer waveguide, a Fourier transform technique is used to study pulse propagation in a waveguide containing DNG materials. A Gaussian pulse is launched in the waveguide over the frequency range covering a portion of the positive- and negative-phase-velocity fundamental transverse electric (TE) modes. Splitting of the input pulse into two separate pulses is observed, where both of these new pulses have a causal, positive energy velocity. The interpretation of intramodal degeneracy given in previous discussions is buttressed with evidence from this portion of the investigation, thus completing the analysis and bringing the present study to its conclusion. / Ph. D.

<p>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</p><p>Maltodekstini, hidrolizati skroba niskog stepena konverzije (dekstrozni ekvivalent manji od 20), imaju &scaron;iroku upotrebu u prehrambenoj, kozmetičkoj i farmaceutskoj industriji. U prehrambenoj industriji koriste se u niskoenergetskim prehrambenim emulzijama (majonez, salatni prelivi, namazi) kao zamena za masne materije da bi obezbedili viskozitet, poželjne senzorne osobine i smanjenje energetske vrednosti proizvoda.<br />Viskozitet razblaženih rastora maltodekstrina različitog dekstroznog ekvivalenta i botaničkog porekla meren je kapilarnim viskozimetrom i izračunate su vrednosti unutra&scaron;njeg viskoziteta za pojedine maltodekstrine. Vrednosti untra&scaron;njeg viskoziteta i molekulske mase pokoravaju se zavisnosti &Scaron;taudingerove jednačine, iako su molekuli maltodekstrina relativno kratki i ne spadaju u grupu polimera. Utvrđena je mogućnost odredivanja DE- vrednosti viskozimetrijskin putem i izvedene su jednačine za dva opsega DE (5-10 / 10-20).<br />Da bi se ispitalo pona&scaron;anje emulzija sa maltodekstrinima (emulgovanje) u procesnim uslovima, kao i osobine fmalnih proizvoda (tečljivost, mazivost) ispitivana je dinamika emulgovanja, veličina kapljica i reolo&scaron;ko pona&scaron;anje, tj. uticaj različitih faktora na disperzione karakteristike emulzija suncokretovog ulja u vodi stabilizovanih prehrambenim emulgatorom, sa dodatkom maltodekstrina u kontinualnoj fazi.<br />Utvrđeno je da osobine maltodekstina kao &scaron;to je stepen konverzije (DE-vrednost) tj. veličina molekula maltodekstrina, utiču na dispezione i reolo&scaron;ke osobine emulzija. Uticaj koncentracije ulja i maltodekstrina, kao i delimična zamena ulja maltodekstrinom, na osobine emulzija su takode ispitivane. Sa povećanjem koncentracije ulja, pri istoj koncentraciji maltodekstrina u kontinualnoj fazi, emulzije menjaju tip proticanja od pseudoplastičnog preko tiksotropnog do antitiksotrpnog. Atitiksotropija izazvana smicanjem rezultat je formiranja unutra&scaron;nje strukture emulzije usled povezivanja kapljica ulja preko molekula maltodekstrina kao i orijentacije i deformacije kapljica ulja i maltodekstrina.<br />Dodatkom maltodekstrina za pri istoj koncentraciju ulja i vremenu emulgovanja dobijene su se emulzije sitnijih kapi.<br />Emulzije sa niskom koncentracijom ulja (30%) sa maltodekstrinom u kontinualnoj fazi bile su nestabilne i pokazivale efekat isplivavanja na povr&scaron;inu (creaming), &scaron;to je posledica interakcija molekula maltodekstrina i molekula emulgatora Tween 80 u kontinualnoj fazi i na povr&scaron;ini kapi.</p> / <p>Abstract was processed by technology for Optical character recognition (OCR).</p><p>Maltodextrins, low converted products of starch hydrolysis (dextrose equivalent less than 20), have been subject of various investigations due to their wide application in food industry, cosmetics and pharmaceuticals. They are used in various low energy food emulsions (mayonnaise, salad dressing, spreads) as fat replacer to provide desirable viscosity, texture and sensory fat-like mouthfeel.<br />Viscosity of diluted maltodextrin solutions of different dextrose equivalent and botanical origin were determined by capillary visometer and intrinsic viscosity [q] of each tested maltodextrin was calculated. The values of [q] together with molecular mass M have shown applicability of Staudinger equation, regardless maltodextrin molecules are rather short. The possibility for the determination of DE-values of maltodextrins by viscometric method has been deduced and the equation was calculated for two ranges of DE (5-10/ 10-20).<br />In order to assess behavior of sunflower oil in water emulsions stabilized with food grade emulsifier with addition of maltodextrins in continuous phase in processing (emulsification), as well as end products in application (pouring, spreading) the emulsification dynamics, globule size changes and rheological behavior, as well as, the influence of different factors on dispersion characteristics of such emulsions were studied.<br />Dispersion and viscous properties of emulsions were influenced by certain specific maltodextrin characteristics such as degree of conversion (DE value) i.e. size of maltodextrin molecules. Influence of oil and maltodextrin concentration and partial substitution of oil with equivalent quantity of maltodextrin were investigated too. With increase of oil concentration at the same concentration of maltodextrin in continuous phase, emulsions undergo changes in flow type from shear-thinning to thixotropic and antithixotropic. Antithxotropy induced by shear, was result of formation of network due to two competing factors; linking of oil droplets through maltodextrin molecules as well as orientation of deformed oil droplets and maltodextrin molecules.<br />Addition of maltodextrin, at the same oil concentration and emulsification time, resulted in formation of emulsions with smaller oil droplets.<br />Emulsions with low oil concentration (30%) with maltodextrin in continuous phase were unstable, showing so called creaming effect. This was mainly due to interactions between maltodextrin and emulsifier Tween 80 molecules which took place in continuous phase and on droplet surfaces.</p>

Práce je věnována modelování mikrovlnných rezonátorů z metamateriálů (materiálů se záporným indexem lomu). V úvodu je rozebráno, co metamateriály jsou, jak se vytvářejí a které jejich vlastnosti jsou podstatné při návrhu rezonátorů. Následuje návrh planárního rezonátoru z metamateriálů. Pro tento účel byly naprogramovány funkce počítající rozměry jednotlivých součástí struktury. Simulace navržené struktury probíhala v programu Zeland IE3D. Simulované struktury byly optimalizovány s ohledem na požadované kmitočty rezonance. První rezonátor sestával z jedné elementární buňky, druhý ze dvou buněk, naladěných na rozdílné kmitočty. Rezonátory byly vyrobeny a experimentálně byly ověřeny jejich vlastnosti.