A bridge between engineering and language learning : automation and German in an online course

Artikkeli luettavissa osassa: Part 2. - ISBN 9789522163172(PDF). - Liitteenä työpaperi

Täystehokonvertterin tehohäviöt ja hyötysuhde

Diplomityössä perehdytään tuuliturbineissa käytettyjen täystehokonvertterien tehohäviöihin ja hyötysuhteeseen. Täystehokonvertterissa generaattorin tuottama sähköteho tasasuunnataan hyvällä hyötysuhteella aktiivisella geenraattorisillalla konvertterin välipiiriin ja edelleen vaihtosuunnataan aktiivisella verkkovaihtosuuntaajasillalla siirtoverkkoon. Työn tarkoituksena on antaa yleiskuva tehohäviöiden jakautumisesta ja yksinkertaistaa niiden laskentaa. Häviömekanismit ja häviöiden määräytyminen esitellään pääkomponenttitasolla. Tehohäviöiden osalta keskitytään erityisesti muuntajateräksestä valmistettujen sinisuotimien ja du/dt-suotimien rautahäviöihin. Ongelmana rautahäviöiden määrittämisessä on korkeilla taajuuksilla tapahtuvat häviöt, joiden laskentaan ei ole yleensä saatavilla tarvittavia materiaaliparametrejä. Tehohäviöiden laskentaa varten toteutettu laskentasovellus on esitelty periaatteellisina vuokaavioina ja sovelluksella saatavia tuloksia on esitetty ja vertailtu mitattuihin tuloksiin.

Success Factors of Accelerators

There is wide interest in new business creation especially in high-growth companies because of the transition from the industrial era to the information era. Previously traditional industry has been a major employer but now industrial employment is moving to countries that provide cheaper labor, and therefore Western countries are reaching for new solutions that could safeguard the current stage of economic wealth. High-growth companies are seen as one opportunity. The aim of this study is to clarify the success factors of accelerators. Acceleration is a relatively new phenomenon, which has its roots in the venture capital industry. Their fundamental goal is to create high-growth companies that have global market potential. Accelerators could be defined as venture-to-capital actors that bridge the competence and equity gaps of startups. The access to the knowledge and funding are the prerequisites of the existence of accelerator. This research was qualitative and based on 18 semi-structured or thematic interviews with 15 accelerators and topic related professionals from Finland, Estonia, Denmark, Germany, the UK and the US. The data was analyzed with a content analysis approach. The study revealed three fundamental preconditions for success. First, the deep business knowledge and access to relevant networks is a foundation and fundamental precondition. Second, the ability to transfer knowledge from the accelerator to startups has significant importance. And third, the dynamics of an accelerator organization can restrict the use of business knowledge. Moreover, the attraction of an accelerator and team selection are crucial issues for success.

Kaksisuuntaisen DC/DC-hakkurin virtasäätö polttokennosovelluksessa

Ilmastonmuutos ja fossiilisten polttoaineiden ehtyminen ovat edesauttaneet uusiutuvien energialähteiden tutkimusta huomattavasti. Lisäksi alati kasvava sähköenergian tarve lisää hajautetun sähköntuotannon ja vaihtoehtoisten energialähteiden kiinnostavuutta. Yleisimpiä hajautetun sähköntuotannon energialähteitä ovat tuulivoima, aurinkovoima ja uutena tulokkaana polttokennot. Polttokennon kytkeminen sähköverkkoon vaatii tehoelektroniikkaa, ja yleensä yksinkertaisessa polttokennosovelluksessa polttokenno kytketään galvaanisesti erottavan yksisuuntaisen DC/DC-hakkurin ja vaihtosuuntaajan kanssa sarjaan. Polttokennon rinnalla voidaan käyttää akkua tasaamaan polttokennon syöttämää jännitettä, jolloin akun ja polttokennon väliin tarvitaan kaksisuuntainen DC/DC-hakkuri, joka pystyy siirtämään energiaa molempiin suuntiin. Tässä diplomityössä on esitetty kaksisuuntaisen DC/DC-hakkurin tilayhtälökeskiarvoistusmenetelmään perustuva malli sekä mallin perusteella toteutettu virtasäätö. Tutkittava hakkuritopologia on kokosilta-tyyppinen boost-hakkuri, ja säätömenetelmä keskiarvovirtasäätö. Työn tuloksena syntyi tilayhtälömalli kaksisuuntaiselle FB boost -hakkurille sekä sen tulokelan virran säätämiseen soveltuva säädin. Säädin toimii normaalitilanteissa hyvin, mutta erikoistilanteissa, kuten hakkurin tulojännitteen äkillisessä muutostilanteessa, vaadittaisiin tehokkaampi säädin, jolla saavutettaisiin nopeampi nousuaika ilman ylitystä ja oskillointia.

Fatigue analysis of brackets with and without scallop for bridge and other deck structure using effective notch stress.

Due to functional requirement of a structural detail brackets with and without scallop are frequently used in bridges, decks, ships and offshore structure. Scallops are designed to serve as passage way for fluids, to reduce weld length and plate distortions. Moreover, scallops are used to avoid intersection of two or more welds for the fact that there is the presence of inventible inherent initial crack except for full penetrated weld and the formation of multi-axial stress state at the weld intersection. Welding all around the scallop corner increase the possibility of brittle fracture even for the case the bracket is not loaded by primary load. Avoiding of scallop will establish an initial crack in the corner if bracket is welded by fillet welds. If the two weld run pass had crossed, this would have given a 3D residual stress situation. Therefore the presences and absence of scallop necessitates the 3D FEA fatigue resistance of both types of brackets using effective notch stress approach ( ). FEMAP 10.1 with NX NASTRAN was used for the 3D FEA. The first and main objective of this research was to investigate and compare the fatigue resistance of brackets with and without scallop. The secondary goal was the fatigue design of scallops in case they cannot be avoided for some reason. The fatigue resistance for both types of brackets was determined based on approach using 1 mm fictitiously rounded radius based on IIW recommendation. Identical geometrical, boundary and loading conditions were used for the determination and comparison of fatigue resistance of both types of brackets using linear 3D FEA. Moreover the size effect of bracket length was also studied using 2D SHELL element FEA. In the case of brackets with scallop the flange plate weld toe at the corner of the scallop was found to exhibit the highest and made the flange plate weld toe critical for fatigue failure. Whereas weld root and weld toe at the weld intersections were the highly stressed location for brackets without scallop. Thus weld toe for brackets with scallop, and weld root and weld toe for brackets without scallop were found to be the critical area for fatigue failure. Employing identical parameters on both types of brackets, brackets without scallop had the highest except for full penetrated weld. Furthermore the fatigue resistance of brackets without scallop was highly affected by the lack of weld penetration length and it was found out that decreased as the weld penetration was increased. Despite the fact that the very presence of scallop reduces the stiffness and also same time induce stress concentration, based on the 3D FEA it is worth concluding that using scallop provided better fatigue resistance when both types of brackets were fillet welded. However brackets without scallop had the highest fatigue resistance when full penetration weld was used. This thesis also showed that weld toe for brackets with scallop was the only highly stressed area unlike brackets without scallop in which both weld toe and weld root were the critical locations for fatigue failure when different types of boundary conditions were used. Weld throat thickness, plate thickness, scallop radius, lack of weld penetration length, boundary condition and weld quality affected the fatigue resistance of both types of brackets. And as a result, bracket design procedure, especially welding quality and post weld treatment techniques significantly affect the fatigue resistance of both type of brackets.

Animal Lovers, Bridge-Builders, and Supervising Watchdogs: Framing and Civil Society Construction by Japanese Pro-Animal Organizations in the Kansai and Tokyo Areas

Unlike their counterparts in Europe and America, the citizen organizations acting for the well-being of animals in Japan have not received scholarly attention. In this research, I explore the activities of twelve Japanese pro-animal organizations in Tokyo and Kansai area from the perspective of social movement and civil society studies. The concept of a ‘pro-animal organization’ is used to refer generally to the collectives promoting animal well-being. By using the collective action frame analysis and the three core framing tasks – diagnostic, prognostic, and motivational – as the primarily analytical tools, I explore the grievances, tactics, motivational means, constructions of agency and identity as well as framing of civil society articulated in the newsletters and the interviews of the twelve organizations I interviewed in Japan in 2010. As the frame construction is always done in relation to the social and political context, I study how the organizations construct their roles as civil society actors in relation to other actors, such as the state, and the idea of citizen activism. The deficiencies in the animal welfare law and lack of knowledge among the public are identified as the main grievances. The primary tactic to overcome these problems was to educate and inform the citizens and authorities, because most organizations lack the channels to influence politically. The audiences were mostly portrayed as either ignorant bystanders or potential adherents. In order to motivate people to join their cause and to enforce the motivation within the organization, the organizations emphasized their uniqueness, proved their efficiency, claimed credit and celebrated even small improvements. The organizations tended to create three different roles for citizen pro-organizations in civil society: reactive, apolitical and emphatic animal lovers concentrating on saving individual animals, proactive, educative bridge-builders seeking to establish equal collaborative relations with authorities, and corrective, supervising watchdogs demanding change in delinquencies offending animal rights. Based on the results of this research, I suggest that by studying how and why the different relations between civil society and the governing actors of the state are constructed, a more versatile approach to citizens’ activism in its context can be achieved.