Antenna feed design for omnidirectional broadband antenna

This thesis is about development broadband feed for two-mirror antenna system that match following requirements: beamwidth from 45 to 90 degrees at -3 dB level, circular polarization, absence of radiation to the lower hemisphere area. Literature review was done in the areas of the UWB antennas creation. During the work attempts were made to create a feed in a form of the quad ridged horn and "eleven" antennas. The latter is introduced as the most effective feed among all antennas discussed in thesis. Radiation patterns and other results for "eleven" antenna were obtained. Results were saved as far field sources and placed slightly below focal point into the two-mirror antenna system, because phase center of the “eleven” antenna is predominantly shifted upwards. Directivity patterns for the two-mirror system were obtained and the conclusions about the work results have been made

Circular Spectropolarimetric Studies of DQ White Dwarfs

This thesis summarizes studies of a class of white dwarfs (WDs) called DQ WDs. White dwarfs are the remnants of ordinary stars like our Sun that have run out of nuclear fuel. WDs are classified according to the composition of their atmosphere and DQ WDs have an atmosphere made of helium and carbon. The carbon comes in either atomic or molecular form and in some cases the strong spectral absorption features cover the entire optical wavelength region. The research presented here utilizes spectropolarimetry, which is an observational technique that combines spectroscopy and polarization. Separately these allow to study the composition of a target and the inhomogeneous distribution of matter in the target. Put together they form a powerful tool to probe the physical properties in the atmosphere of a star. It is espacially good for detecting magnetic fields. The papers in this thesis describe efforts to do a survey of DQ white dwarfs with spectropolarimetry in order to search for magnetic fields in them. Paper I describes the discovery of a new magnetic cool DQ white dwarf, GJ841B. Initial modeling of molecular features on DQ WDs showed inconsistencies with observations. The first possible solution to this problem was stellar spots on these WDs. To investigate the matter, two DQ WDs were monitored for photometric variability that could arise from the presence of such spots. Paper II summarizes this short campaign and reports the negative results. Paper III reports observations of the rest of the objects in our survey. The paper includes the discovery of polarization from another cool DQ white dwarf, bringing the total of known magnetic cool DQs to three. Unfortunately the model used in this thesis cannot, in its present state, be used to model these objects nor are the observations of high enough spectroscopic resolution to do so.

Modulaarisen paisunta-astian kehittäminen compact -sarjan teollisuusvaihteeseen

Tämä insinöörityö tehtiin SEW Industrial Gears Oy:lle, joka valmistaa hammasvaihteita teollisuuden eri sovellutuksiin. Työn tavoitteena oli kehittää modulaarinen paisuntaastiasarja compact -sarjan teollisuusvaihteeseen. Työn alkuvaiheessa käytössä oli kahdenlaisia paisunta-astioita: kosteissa oloissa käytettävä suljettu astiamalli ja kuiviin olosuhteisiin soveltuva malli. Koska käytössä oleva suljettu astiamalli oli kallis ja kuivien olosuhteiden mallin käyttö oli rajoitettu, oli uudelle modulaariselle paisunta-astialle selkeä tarve. Uuden astiamallin tuli olla yhteensopiva vaihteen yleisimpien varusteiden ja asennusasentojen kanssa. Lisäksi tavoitteena oli puolittaa uuden konseptin hinta vanhaan verrattuna ja paikata vanhoissa konstruktioissa olleita puutteita. Työ aloitettiin analysoimalla olemassa olevat paisunta-astiatyypit, minkä jälkeen paisuntaastialle ideoitiin uusia ominaisuuksia. Toisessa vaiheessa perehdyttiin modulaariseen järjestelmään sekä öljynpaisunnan teoriaan teollisuusvaihteessa. Viimeisessä vaiheessa tehtiin konseptin varsinainen suunnittelutyö, valittiin astian valmistustapa ja materiaali sekä optimoitiin hinta. Uudesta mallista valmistettiin myös prototyyppi, jotta suunniteltua tuotetta päästiin kokeilemaan myös käytännössä. Näin voitiin varmistaa tuotteen toimivuus. Suunnittelutyön tuloksena saatiin uuden paisunta-astiasarjan piirustukset tarvittavista osista ja kokoonpanoista sekä komponenttistandardi ja myyntiä tukevaa materiaalia. Käytännön osuus antoi tietoa laskelmien oikeellisuudesta sekä öljyn täyttöön ja paisuntaan liittyvistä asioista.

Numerical Investigation of Flow Past a Circular Cylinder and in a Staggered Tube Bundle Using Various Turbulence Models

Transitional flow past a three-dimensional circular cylinder is a widely studied phenomenon since this problem is of interest with respect to many technical applications. In the present work, the numerical simulation of flow past a circular cylinder, performed by using a commercial CFD code (ANSYS Fluent 12.1) with large eddy simulation (LES) and RANS (κ - ε and Shear-Stress Transport (SST) κ - ω! model) approaches. The turbulent flow for ReD = 1000 & 3900 is simulated to investigate the force coefficient, Strouhal number, flow separation angle, pressure distribution on cylinder and the complex three dimensional vortex shedding of the cylinder wake region. The numerical results extracted from these simulations have good agreement with the experimental data (Zdravkovich, 1997). Moreover, grid refinement and time-step influence have been examined. Numerical calculations of turbulent cross-flow in a staggered tube bundle continues to attract interest due to its importance in the engineering application as well as the fact that this complex flow represents a challenging problem for CFD. In the present work a time dependent simulation using κ – ε, κ - ω! and SST models are performed in two dimensional for a subcritical flow through a staggered tube bundle. The predicted turbulence statistics (mean and r.m.s velocities) have good agreement with the experimental data (S. Balabani, 1996). Turbulent quantities such as turbulent kinetic energy and dissipation rate are predicted using RANS models and compared with each other. The sensitivity of grid and time-step size have been analyzed. Model constants sensitivity study have been carried out by adopting κ – ε model. It has been observed that model constants are very sensitive to turbulence statistics and turbulent quantities.

Regulation of cell growth, death, and polarization by ERBB4

Regulation of cell growth, death, and polarization by ERBB4 ErbB4 is a member of the epidermal growth factor receptor (EGFR, ErbB) family. The other members are EGFR, ErbB2 and ErbB3. ErbB receptors are important regulators for example in cardiovascular, neural and breast development but control key cellular functions also in many adult tissues. Abnormal ErbB signaling has been shown to be involved in various illnesses such as cancers and heart diseases. Among the ErbBs, ErbB4 has been shown to have unique signaling characteristics. ErbB4 exists in four alternatively spliced isoforms that are expressed in a tissue-specific manner. Two of the isoforms can be cleaved by membrane proteases, resulting in release of soluble intracellular domains (ICD). Once released into the cytosol, the ICD is capable of translocating into the nucleus and participating in regulation of transcription. The functional differences and the tissue-specific expression patterns suggest isoformspecific roles for ErbB4 isoforms. However, the abilities of ErbB4 isoforms to differently regulate cellular functions were discovered only recently and are not well understood. This study aimed to determine the expression patterns of ErbB4 in normal and diseased tissue, and to define whether the cleavable and non-cleavable isoforms could regulate different target genes and therefore, cellular functions. In this study, a comprehensive ErbB4 expression pattern in several normal tissues, various cancers and non-neoplastic diseases was determined. In addition, the data demonstrated that the cleavable and non-cleavable ErbB4 isoforms could regulate different cellular functions and target genes. Finally, this study defined the cellular responses regulated by ErbB4 during kidney development.

Spin Polarization and Normal Reflection at Nanoscale Point Contacts

This thesis presents point-contact measurements between superconductors (Nb, Ta, Sn,Al, Zn) and ferromagnets (Co, Fe, Ni) as well as non-magnetic metals (Ag, Au, Cu, Pt).The point contacts were fabricated using the shear method. The differential resistanceof the contacts was measured either in liquid He at 4.2 K or in vacuum in a dilutionrefrigerator at varying temperature down to 0.1 K. The contact properties were investigatedas function of size and temperature. The measured Andreev-reflection spectrawere analysed in the framework of the BTK model – a three parameter model that describescurrent transport across a superconductor - normal conductor interface. Theoriginal BTK model was modified to include the effects of spin polarization or finitelifetime of the Cooper pairs. Our polarization values for the ferromagnets at 4.2 K agree with the literature data, but the analysis was ambiguous because the experimental spectra both with ferromagnets and non-magnets could be described equally well either with spin polarization or finite lifetime effects in the BTK model. With the polarization model the Z parametervaries from almost 0 to 0.8 while the lifetime model produces Z values close to 0.5. Measurements at lower temperatures partly lift this ambiguity because the magnitude of thermal broadening is small enough to separate lifetime broadening from the polarization. The reduced magnitude of the superconducting anomalies for Zn-Fe contacts required an additional modification of the BTK model which was implemented as a scaling factor. Adding this parameter led to reduced polarization values. However, reliable data is difficult to obtain because different parameter sets produce almost identical spectra.