Bluetooth -teknologian hyödyntäminen kommunikointijärjestelmässä

Erilaisissa rakennuksissa on selkeä tarve langatonta teknologiaa hyödyntävälle, edulliselle ja monipuoliselle kommunikointijärjestelmälle, jota voidaan pienin muutoksin käyttää lähes missä tahansa. Kommunikointijärjestelmän avulla tulee olla mahdollista siirtää ääntä ja dataa sekä tarvittaessa tarjota erilaisia rakennuksissa tarvittavia palveluita. Tehdyn esitutkimuksen perusteella valittiin toteutusteknologiaksi Bluetooth, joka monipuolisten ominaisuuksien ja pienen sirukoon ansiosta soveltuu parhaiten tämän diplomityön mukaisen kerrostalon kommunikointijärjestelmän toteuttamiseen. Pieni sirukoko ja edullinen hinta mahdollistavat Bluetooth -teknologiaa hyödyntävän kommunikointijärjestelmän käyttöönoton myös vanhoissa kerrostaloissa. Pienet sirut on helppo piilottaa rakennusten perustuksiin ja mitään valmista verkkoinfrastruktuuria ei tarvita. OBEX (Object Exchange Protocol) -protokollaa käytetään tämän diplomityön mukaisessa Talovastaajapalvelussa audiodatan kuljettamiseen ja autentikointitietojen vaihtamiseen. Talovastaajapalvelu toteutettiin kommunikointijärjestelmän yhteyteen ja se toimii normaalin puhelinvastaajan tapaan, mutta on ominaisuuksiltaan paljon monipuolisempi ja käyttää langatonta Bluetooth -teknologiaa. OBEX:n avulla Talovastaajapalvelusta saatiin yksinkertainen, tehokas ja helposti laajennettavissa oleva kokonaisuus, jota voidaan käyttää pienin muutoksin lähes missä tahansa muussa Bluetooth -teknologiaa hyödyntävässä järjestelmässä.

Digital Audio Broadcasting: Technology and Prospects

The subject of the thesis was the digital audio broadcasting technology developed in the Eureka project 147. The research was based on the literature on the subject. At first, some reasons for the digitisation of broadcasting technology were given. Next, the channel multiplexing and channel coding methods employed by digital radio were discussed. The design of these methods is based on certain phenomena related to the propagation of radio-frequency signals, and these phenomena were also described. After that, audio and data transfer mechanisms as well as the structure of digital radio network were explained. Furthermore, digital audio and data services were considered. Finally, the digital radio was examined from marketing and administrative aspects. From a merely technical point of view, the digital radio technology offers several improvements in comparison with analogue technology. However, the digital radio has not become as widespread as it was perhaps originally expected during its development.

Study of mesoscopic tunnel junctions between two normal metals

The main purpose of this work was to study different kinds of metal-based tunnel junctions at low temperatures. The problem which had to be solved was creating a junction with appropriate properties at these temperatures. The materials for junctions were found experimentally. The goal was to find an alloy material that can provide a high quality tunnel junction, which remains in the normal conductive state at low temperatures without applying magnetic field. The fabrication technology of such a device, based on an alloy of aluminium and manganese, is described in detail. In this thesis theoretical properties of tunnel junctions are considered and results of experiments with tunnel junctions are described and quantitative properties of the junctions are analyzed based on the experimental data.

Secure Bluetooth Audio Transmission System

The growing spread of small but powerful mobile devices (such as PDAs, mobile phone, Internet Tablet, etc.) opens up new scenarios in which users can interact with such devices in many environments in order to access the information at different locations. In this thesis, a ubiquitous computing based system called Secure Bluetooth Audio Transmission System is introduced. This system is situated in a large public place (like airport, festival venues, etc.), where voice messages are conveyed from the system to users' Bluetooth headsets in order to inform users the latest flight schedule and other public information. The reliability of the message is secured by adopting an authorization strategy and ECDSA. In order to assess and evaluate the risks and potential weaknesses of the system, an easy-to-use prototype implementation was written and tested. Other possible uses and further research were also considered.

Normal Mannesmann-Mulag kardanvagn

kuv., 24 x 16 cm

M.A.N. normal 2-2 1/2 tons lastvagn

kuv., 23 x 16 cm

Normal Mannesmann-Mulag kedjevagn

kuv., 23 x 16 cm

Normal Mannesmann-Mulag 5-tons lastvagn

kuv., 23 x 16 cm

Avalon Media System project update: a Hydra solution for digital audio and video access

Presentation at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

Audio and Video Repositories at Scale: Indiana University’s Media Digitization and Preservation Initiative

Presentation at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

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.