Diffusion of Be, Co and Mn impurities in compound semiconductors and glassy carbon studied by the modified radiotracer technique

The main method of modifying properties of semiconductors is to introduce small amount of impurities inside the material. This is used to control magnetic and optical properties of materials and to realize p- and n-type semiconductors out of intrinsic material in order to manufacture fundamental components such as diodes. As diffusion can be described as random mixing of material due to thermal movement of atoms, it is essential to know the diffusion behavior of the impurities in order to manufacture working components. In modified radiotracer technique diffusion is studied using radioactive isotopes of elements as tracers. The technique is called modified as atoms are deployed inside the material by ion beam implantation. With ion implantation, a distinct distribution of impurities can be deployed inside the sample surface with good con- trol over the amount of implanted atoms. As electromagnetic radiation and other nuclear decay products emitted by radioactive materials can be easily detected, only very low amount of impurities can be used. This makes it possible to study diffusion in pure materials without essentially modifying the initial properties by doping. In this thesis a modified radiotracer technique is used to study the diffusion of beryllium in GaN, ZnO, SiGe and glassy carbon. GaN, ZnO and SiGe are of great interest to the semiconductor industry and beryllium as a small and possibly rapid dopant hasn t been studied previously using the technique. Glassy carbon has been added to demonstrate the feasibility of the technique. In addition, the diffusion of magnetic impurities, Mn and Co, has been studied in GaAs and ZnO (respectively) with spintronic applications in mind.

The Context and Diffusion of Knowledge in the Finnish Jewellery Industry - The role of the House of Fabergé

Researchers within the fields of economic geography and organizational management have extensively studied learning and the prerequisites and impediments for knowledge transfer. This paper combines two discourses within the two subjects: the-communities-of-practice and the learning region approaches, merging them through the so-called ecology of knowledge-approach, which is used to examine the knowledge transfer from the House of Fabergé to the Finnish jewellery industry. We examine the pre-revolution St Petersburg jewellery cluster and the post-revolution Helsinki, and the transfer of knowledge between these two locations through the components of communities of people, institutions and industry. The paper shows that the industrial dynamics of the Finnish modern-day goldsmith industry was inherently shaped both through the transfer and the non-transfer of knowledge. It also contends that the “knowledge-economy” is not anchored in and exclusive for the high technology sector of the late 20th century.

Virtuaalimaailmoja valtaamassa : verkko-opetusinnovaation leviäminen koulun maantieteeseen vuosituhannen vaihteessa

Tutkimus käsittelee verkko-opetusinnovaation leviämistä perusasteen ja lukion maantieteeseen vuosina 1998–2004. Työssä sovellettiin opetusinnovaation leviämismallia ja innovaatioiden diffuusioteoriaa. Aineisto hankittiin seitsemänä vuotena kyselylomakkeilla maantieteen verkko-opetuksen edelläkävijäopettajilta, jotka palauttivat 326 lomaketta. Tutkimuksen pääongelmat olivat 1) Millaisia edellytyksiä edelläkävijäopettajilla on käyttää verkko-opetusta koulun maantieteessä? 2) Mitä sovelluksia ja millä tavoin edelläkävijäopettajat käyttävät maantieteen verkko-opetuksessa? 3) Millaisia käyttökokemuksia edelläkävijäopettajat ovat saaneet maantieteen verkko-opetuksesta? Tutkimuksessa havaittiin, että tietokoneiden riittämätön määrä ja puuttuminen aineluokasta vaikeuttivat maantieteen verkko-opetusta. Työssä kehitettiin opettajien digitaalisten mediataitojen kuutiomalli, johon kuuluvat tekniset taidot, informaation prosessointitaidot ja viestintätaidot. Opettajissa erotettiin kolme verkko-opetuksen käyttäjätyyppiä: informaatiohakuiset kevytkäyttäjät, viestintähakuiset peruskäyttäjät ja yhteistyöhakuiset tehokäyttäjät. Verkko-opetukseen liittyi intensiivisiä myönteisiä ja kielteisiä kokemuksia. Se toi iloa ja motivaatiota opiskeluun. Sitä pidettiin rikastuttavana lisänä, joka haluttiin integroida opetukseen hallitusti. Edelläkävijäopettajat ottivat käyttöön tietoverkoissa olevaa informaatiota ja sovelsivat työvälineohjelmia. He pääsivät alkuun todellisuutta jäljittelevien virtuaalimaailmojen: satelliittikuvien toistaman maapallon, digitaalikarttojen ja simulaatioiden käytössä. Opettajat kokeilivat verkon sosiaalisia tiloja reaaliaikaisen viestinnän, keskusteluryhmien ja ryhmätyöohjelmien avulla. Mielikuvitukseen perustuvat virtuaalimaailmat jäivät vähälle sillä opettajat eivät juuri pelanneet viihdepelejä. He omaksuivat virtuaalimaailmoista satunnaisia palasia käytettävissä olevan laite- ja ohjelmavarustuksen mukaan. Virtuaalimaailmojen valtaus eteni tutkimuksen aikana digitaalisen informaation hyödyntämisestä viestintäsovelluksiin ja aloittelevaan yhteistyöhön. Näin opettajat laajensivat virtuaalireviiriään tietoverkkojen dynaamisiksi toimijoiksi ja pääsivät uusin keinoin tyydyttämään ihmisen universaalia tarvetta yhteyteen muiden kanssa. Samalla opettajat valtautuivat informaation kuluttajista sen tuottajiksi, objekteista subjekteiksi. Verkko-opetus avaa koulun maantieteelle huomattavia mahdollisuuksia. Mobiililaitteiden avulla informaatiota voidaan kerätä ja tallentaa maasto-olosuhteissa, ohjelmilla sitä voidaan muuntaa muodosta toiseen. Internetin autenttiset ja ajantasaiset materiaalit tuovat opiskeluun konkretiaa ja kiinnostavuutta, mallit, simulaatiot ja paikkatieto havainnollistavat ilmiöitä. Viestintä- ja yhteistyövälineet sekä sosiaaliset informaatiotilat vahvistavat yhteistyötä. Avainsanat: verkko-opetus, internet, virtuaalimaailmat, maantiede, innovaatiot

A Decentralized Session Management Framework for Heterogeneous Ad-Hoc and Fixed Networks

Wireless technologies are continuously evolving. Second generation cellular networks have gained worldwide acceptance. Wireless LANs are commonly deployed in corporations or university campuses, and their diffusion in public hotspots is growing. Third generation cellular systems are yet to affirm everywhere; still, there is an impressive amount of research ongoing for deploying beyond 3G systems. These new wireless technologies combine the characteristics of WLAN based and cellular networks to provide increased bandwidth. The common direction where all the efforts in wireless technologies are headed is towards an IP-based communication. Telephony services have been the killer application for cellular systems; their evolution to packet-switched networks is a natural path. Effective IP telephony signaling protocols, such as the Session Initiation Protocol (SIP) and the H 323 protocol are needed to establish IP-based telephony sessions. However, IP telephony is just one service example of IP-based communication. IP-based multimedia sessions are expected to become popular and offer a wider range of communication capabilities than pure telephony. In order to conjoin the advances of the future wireless technologies with the potential of IP-based multimedia communication, the next step would be to obtain ubiquitous communication capabilities. According to this vision, people must be able to communicate also when no support from an infrastructured network is available, needed or desired. In order to achieve ubiquitous communication, end devices must integrate all the capabilities necessary for IP-based distributed and decentralized communication. Such capabilities are currently missing. For example, it is not possible to utilize native IP telephony signaling protocols in a totally decentralized way. This dissertation presents a solution for deploying the SIP protocol in a decentralized fashion without support of infrastructure servers. The proposed solution is mainly designed to fit the needs of decentralized mobile environments, and can be applied to small scale ad-hoc networks or also bigger networks with hundreds of nodes. A framework allowing discovery of SIP users in ad-hoc networks and the establishment of SIP sessions among them, in a fully distributed and secure way, is described and evaluated. Security support allows ad-hoc users to authenticate the sender of a message, and to verify the integrity of a received message. The distributed session management framework has been extended in order to achieve interoperability with the Internet, and the native Internet applications. With limited extensions to the SIP protocol, we have designed and experimentally validated a SIP gateway allowing SIP signaling between ad-hoc networks with private addressing space and native SIP applications in the Internet. The design is completed by an application level relay that permits instant messaging sessions to be established in heterogeneous environments. The resulting framework constitutes a flexible and effective approach for the pervasive deployment of real time applications.

The significance of brittle reaction layers in fusing of dental ceramics to titanium

This thesis comprises four intercomplementary parts that introduce new approaches to brittle reaction layers and mechanical compatibility of metalloceramic joints created when fusing dental ceramics to titanium. Several different methods including atomic layer deposition (ALD), sessile drop contact angle measurements, scanning acoustic microscopy (SAM), three-point bending (TPB, DIN 13 927 / ISO 9693), cross-section microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were employed. The first part investigates the effects of TiO2 layer structure and thickness on the joint strength of the titanium-metalloceramic system. Samples with all tested TiO2 thicknesses displayed good ceramics adhesion to Ti, and uniform TPB results. The fracture mode was independent of oxide layer thickness and structure. Cracking occurred deeper inside titanium, in the oxygen-rich Ti[O]x solid solution surface layer. During dental ceramics firing TiO2 layers dissociate and joints become brittle with increased dissolution of oxygen into metallic Ti and consequent reduction in the metal plasticity. To accomplish an ideal metalloceramic joint this needs to be resolved. The second part introduces photoinduced superhydrophilicity of TiO2. Test samples with ALD deposited anatase TiO2 films were produced. Samples were irradiated with UV light to induce superhydrophilicity of the surfaces through a cascade leading to increased amount of surface hydroxyl groups. Superhydrophilicity (contact angle ~0˚) was achieved within 2 minutes of UV radiation. Partial recovery of the contact angle was observed during the first 10 minutes after UV exposure. Total recovery was not observed within 24h storage. Photoinduced ultrahydrophilicity can be used to enhance wettability of titanium surfaces, an important factor in dental ceramics veneering processes. The third part addresses interlayers designed to restrain oxygen dissolution into Ti during dental ceramics fusing. The main requirements for an ideal interlayer material are proposed. Based on these criteria and systematic exclusion of possible interlayer materials silver (Ag) interlayers were chosen. TPB results were significantly better in when 5 μm Ag interlayers were used compared to only Al2O3-blasted samples. In samples with these Ag interlayers multiple cracks occurred inside dental ceramics, none inside Ti structure. Ag interlayers of 5 μm on Al2O3-blasted samples can be efficiently used to retard formation of the brittle oxygen-rich Ti[O]x layer, thus enhancing metalloceramic joint integrity. The most brittle component in metalloceramic joints with 5 μm Ag interlayers was bulk dental ceramics instead of Ti[O]x. The fourth part investigates the importance of mechanical interlocking. According to the results, the significance of mechanical interlocking achieved by conventional surface treatments can be questioned as long as the formation of the brittle layers (mainly oxygen-rich Ti[O]x) cannot be sufficiently controlled. In summary in contrast to former impressions of thick titanium oxide layers this thesis clearly demonstrates diffusion of oxygen from sintering atmosphere and SiO2 to Ti structures during dental ceramics firing and the following formation of brittle Ti[O]x solid solution as the most important factors predisposing joints between Ti and SiO2-based dental ceramics to low strength. This among other predisposing factors such as residual stresses created by the coefficient of thermal expansion mismatch between dental ceramics and Ti frameworks can be avoided with Ag interlayers.

Use of Document Management Systems - a Case Study of the Finnish Construction Industry

Triggered by the very quick proliferation of Internet connectivity, electronic document management (EDM) systems are now rapidly being adopted for managing the documentation that is produced and exchanged in construction projects. Nevertheless there are still substantial barriers to the efficient use of such systems, mainly of a psychological nature and related to insufficient training. This paper presents the results of empirical studies carried out during 2002 concerning the current usage of EDM systems in the Finnish construction industry. The studies employed three different methods in order to provide a multifaceted view of the problem area, both on the industry and individual project level. In order to provide an accurate measurement of overall usage volume in the industry as a whole telephone interviews with key personnel from 100 randomly chosen construction projects were conducted. The interviews showed that while around 1/3 of big projects already have adopted the use of EDM, very few small projects have adopted this technology. The barriers to introduction were investigated through interviews with representatives for half a dozen of providers of systems and ASP-services. These interviews shed a lot of light on the dynamics of the market for this type of services and illustrated the diversity of business strategies adopted by vendors. In the final study log files from a project which had used an EDM system were analysed in order to determine usage patterns. The results illustrated that use is yet incomplete in coverage and that only a part of the individuals involved in the project used the system efficiently, either as information producers or consumers. The study also provided feedback on the usefulness of the log files.

Boost Customer Loyalty with Online Support. The Case of Mobile Telecoms Providers.

The paper explores the effect of customer satisfaction with online supporting services on loyalty to providers of an offline core service. Supporting services are provided to customers before, during, or after the purchase of a tangible or intangible core product, and have the purpose of enhancing or facilitating the use of this product. The internet has the potential to dominate all other marketing channels when it comes to the interactive and personalised communication that is considered quintessential for supporting services. Our study shows that the quality of online supporting services powerfully affects satisfaction with the provider and customer loyalty through its effect on online value and enjoyment. Managerial implications are provided.

Internet- karttapalveluiden arviointi ja kehitys strategisessa maankäytön suunnittelussa, tapaustutkimuksena Esikaupunkien renessanssi -hanke

Participation is located in a living and complex environment. Traditional means of participation are only partially able to meet the new environmental requirements. In need are forms of participation which take into account the new opportunities of the environment and residents expertise. Internet map applications are an important channel of participation which potential is in many respects as unexplored and unutilized. They are commonly in inventory the perspectives, bringing out the concerns of the area, and only little for discussing about solutions. Interpretation is usually made by designer. This study focuses on evaluation and development of Internet map applications in strategic land use planning. Subject matter is dealt from designer and the inhabitants point of view. City Planning Department of Helsinki s Esikau-punkien Renessanssi -project and the associated SoftGIS survey acts as the case study. In the beginning of the study I tried to recognize the new environment in which the Internet map applications are placed. The research question is, what kind of challenges and opportunities the e-participation confronts in information society, and what kind of requirements the environmental creates for development of an application. In chapter three I evaluate how successfully these requirements are met in Esikau-punkien Renessanssi -project. I m trying to examine how the application would look like if the environment and the characteristics of the project are met better. The approach is experimental and I try to find new ways to take advantage of Internet maps. I try not to be too limited to current projects and studies. For example, I try to examine how social media and Web 2.0 opportunities can be utilized, and how the learning and shaping nature of planning may be reached in Internet map environment. In chapter four I have developed a new concept for the Esikaupunkien Renessanssi map application, and made images to visualize its operation in practice. I collect all the data in the research and gather it into a new service. The aim is to create a better application for Esikaupunkien Renessanssi -project, which takes into account the living and complex environment of participation and responds to threats and opportunities arising from it. The presented outcome is in many respects different from the current query. In the new service the role of residents is to interact and learn. The traditional standing of the Internet maps and the position of resident as one-sided information donor are questioned. In the concept, the residents innovate and make interpretations too. Influences are taken from a number of modern applications and for example services that make use of social media. The user experience is intended to be interactive, fast and easy. The idea is that the service keeps you up to date with planning matters, not the other way around. Service guides inhabitants, striving to achieve a deeper knowledge of the project's objectives as well as the dynamics and realities that different individuals experience.

Rate Control State-of-the-art Survey

The majority of Internet traffic use Transmission Control Protocol (TCP) as the transport level protocol. It provides a reliable ordered byte stream for the applications. However, applications such as live video streaming place an emphasis on timeliness over reliability. Also a smooth sending rate can be desirable over sharp changes in the sending rate. For these applications TCP is not necessarily suitable. Rate control attempts to address the demands of these applications. An important design feature in all rate control mechanisms is TCP friendliness. We should not negatively impact TCP performance since it is still the dominant protocol. Rate Control mechanisms are classified into two different mechanisms: window-based mechanisms and rate-based mechanisms. Window-based mechanisms increase their sending rate after a successful transfer of a window of packets similar to TCP. They typically decrease their sending rate sharply after a packet loss. Rate-based solutions control their sending rate in some other way. A large subset of rate-based solutions are called equation-based solutions. Equation-based solutions have a control equation which provides an allowed sending rate. Typically these rate-based solutions react slower to both packet losses and increases in available bandwidth making their sending rate smoother than that of window-based solutions. This report contains a survey of rate control mechanisms and a discussion of their relative strengths and weaknesses. A section is dedicated to a discussion on the enhancements in wireless environments. Another topic in the report is bandwidth estimation. Bandwidth estimation is divided into capacity estimation and available bandwidth estimation. We describe techniques that enable the calculation of a fair sending rate that can be used to create novel rate control mechanisms.