Modeling and Analysis of Composite Antenna Superstrates Consisting on Grids of Loaded Wires

We study the characteristics and radiation mechanism of antenna superstrates based on closely located periodical grids of loaded wires. An explicit analytical method based on the local field approach is used to study the reflection and transmission properties of such superstrates. It is shown that as a result of proper impedance loading there exists a rather wide frequency band over which currents induced to the grids cancel each other, leading to a wide transmission maximum. In this regime radiation is produced by the magnetic dipole moments created by circulating out-of-phase currents flowing in the grids. An impedance matrix representation is derived for the superstrates, and the analytical results are validated using full-wave simulations. As a practical application example we study numerically the radiation characteristics of dipole antennas illuminating finite-size superstrates.Comment: 9 pages, 11 figures. In the second version we have clarified the analysis related to the prototype, and re-desinged the prototype antenn

Vector circuit theory for spatially dispersive uniaxial magneto-dielectric slabs

We present a general dyadic vector circuit formalism, applicable for uniaxial magneto-dielectric slabs, with strong spatial dispersion explicitly taken into account. This formalism extends the vector circuit theory, previously introduced only for isotropic and chiral slabs. Here we assume that the problem geometry imposes strong spatial dispersion only in the plane, parallel to the slab interfaces. The difference arising from taking into account spatial dispersion along the normal to the interface is briefly discussed. We derive general dyadic impedance and admittance matrices, and calculate corresponding transmission and reflection coefficients for arbitrary plane wave incidence. As a practical example, we consider a metamaterial slab built of conducting wires and split-ring resonators, and show that neglecting spatial dispersion and uniaxial nature in this structure leads to dramatic errors in calculation of transmission characteristics.Comment: 11 pages, 6 figures, submitted to Journal of Electromagnetic Waves and Application

On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas

In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the known results for antenna miniaturization with non-dispersive material fillings. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and we show that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magneto-dielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, practically realizable artificial substrates with dispersive magnetic permeability are not advantageous in antenna miniaturization. This conclusion is experimentally validated.Comment: 22 pages, 14 figures, 5 tables, submitted to IEEE Trans. Antennas Propaga

Scaling theory of driven polymer translocation

We present a theoretical argument to derive a scaling law between the mean translocation time $\tau$ and the chain length $N$ for driven polymer translocation. This scaling law explicitly takes into account the pore-polymer interactions, which appear as a correction term to asymptotic scaling and are responsible for the dominant finite size effects in the process. By eliminating the correction-to-scaling term we introduce a rescaled translocation time and show, by employing both the Brownian Dynamics Tension Propagation theory [Ikonen {\it et al.}, Phys. Rev. E {\bf 85}, 051803 (2012)] and molecular dynamics simulations that the rescaled exponent reaches the asymptotic limit in a range of chain lengths that is easily accessible to simulations and experiments. The rescaling procedure can also be used to quantitatively estimate the magnitude of the pore-polymer interaction from simulations or experimental data. Finally, we also consider the case of driven translocation with hydrodynamic interactions (HIs). We show that by augmenting the BDTP theory with HIs one reaches a good agreement between the theory and previous simulation results found in the literature. Our results suggest that the scaling relation between $\tau$ and $N$ is retained even in this case.Comment: 5 pages, 4 figure

Vienti Brasiliaan : Pk-yritykset

Opinnäytetyön tavoitteena oli tutkia viennin vaatimuksia Brasiliaan ja ottaa huomioon erityisesti pk-yritysten näkökulma. Työn tilaaja oli Hämeen ammattikorkeakoulu. Työ toteutettiin kansainvälistä kauppaa edistävälle hankkeelle ”Kansainvälinen korkeakouluallianssi paikallisten yritysten apuna”. Opinnäytetyö jakaantui teoria- ja tutkimusosioon. Teoriaosioon kerättiin tietopaketti viennistä ja sen vaatimuksista vientiä aloittelevia pk-yrityksiä varten. Opinnäytetyön empiirisessä osassa tutkittiin, minkälaisia käytännön ongelmia yritykset ovat kohdanneet Brasilian viennissä. Aineistonkeruu suoritettiin kohdistetuilla sähköposteille vientiä harjoittaviin yrityksiin, mukaan otettiin erilaisia ja –kokoisia yrityksiä. Tutkimuksessa kävi ilmi, että Brasilia ei ole helpoin maa vientitoiminnalle mutta maalla on kuitenkin paljon potentiaalia ja yritykset ovat kokeneet viennin kannattavaksi. Keskeisin johtopäätös oli, että Brasiliaan suuntautuvaan vientiin tulee valmistautua huolella, muuten kohdatut ongelmat voivat olla vaikeita. Mutta jos vientiin valmistautuu huolella, on Brasiliassa paljon potentiaalia monien alojen vientiin.The purpose of this thesis was to study the requirements of export trade to Brazil, taking into account especially the needs of small and medium-sized enterprises. The client was Häme University of Applied Sciences and the thesis was written for the spring 2017 project "international university alliance in collaboration with local businesses. The thesis had both theoretical and practical part. The theoretical framework included information on export to Brazil and its demands for the use of small and medium-sized enterprises just starting their export. The practical side of the thesis included qualitative research of the difficulties and problems companies have faced in their export business to the country. The research material for the thesis was collected from e-mail interviews to different sized enterprises in different fields. The results showed that while Brazil is a very demanding country to do business in, it is definitely worth it if you take the time to prepare sufficiently and the country has a lot of potential in the future for Finnish companies

X-ray and neutron scattering studies on some nanoscale structures in molecular biology

Scattering of X-rays and neutrons has been applied to the study of nanostructures with interesting biological functions. The systems studied were the protein calmodulin and its complexes, bacterial virus bacteriophage phi6, and the photosynthetic antenna complex from green sulfur bacteria, chlorosome. Information gathered using various structure determination methods has been combined to the low resolution information obtained from solution scattering. Conformational changes in calmodulin-ligand complex were studied by combining the directional information obtained from residual dipole couplings in nuclear magnetic resonance to the size information obtained from small-angle X-ray scattering from solution. The locations of non-structural protein components in a model of bacteriophage phi6, based mainly on electron microscopy, were determined by neutron scattering, deuterium labeling and contrast variation. New data are presented on the structure of the photosynthetic antenna complex of green sulfur bacteria and filamentous anoxygenic phototrophs, also known as the chlorosome. The X-ray scattering and electron cryomicroscopy results from this system are interpreted in the context of a new structural model detailed in the third paper of this dissertation. The model is found to be consistent with the results obtained from various chlorosome containing bacteria. The effect of carotenoid synthesis on the chlorosome structure and self-assembly are studied by carotenoid extraction, biosynthesis inhibition and genetic manipulation of the enzymes involved in carotenoid biosynthesis. Carotenoid composition and content are found to have a marked effect on the structural parameters and morphology of chlorosomes.Työssä on käytetty röntgen- ja neutronisäteilyn sirontaa molekyylibiologian kannalta mielenkiintoisten, nanometrin kokoluokkaan kuuluvien rakenteiden tutkimiseen. Tutkitut systeemit ovat proteiineja, proteiinikomplekseja, viruksia ja vihreiden bakteerien fotosynteesin kannalta tärkeä antennikompleksi, klorosomi. Erilaisten rakennetutkimusmenetelmien antamaa informaatiota on yhdistetty sirontamenetelmillä saatavaan matalan resoluution rakennetietoon. Ensimmäisessä osajulkaisussa proteiinin konformaatiomuutosta tutkittiin yhdistämällä ydinmagneettisen resonanssin antama suuntatieto röntgensironnasta määritettyyn konformaatiomuutoksen suuruuteen. Toisessa osajulkaisussa määritettiin proteiiniosasten paikka elektronimikroskopian avulla luodussa virusmallissa neutronisironnan ja kontrastivariaation avulla. Kolmessa viimeisessä osajulkaisussa esitetään uusi malli vihreiden bakteerien fotosynteettisen kompleksin antenniosan rakenteelle ja sen todetaan olevan sopusoinnussa useista eri bakteerilajeista saatujen röntgensironta- ja elektronimikroskopiatulosten kanssa. Karotenoidien vaikutusta rakenteeseen tutkittiin soveltamalla edellä mainittuja menetelmiä bakteereihin, joiden karotenoidisynteesiin vaikuttavat entsyymit oli poistettu geneettisin menetelmin