Depinning of kinks in a Josephson-junction ratchet array

We have measured the depinning of trapped kinks in a ratchet potential using a fabricated circular array of Josephson junctions. Our ratchet system consists of a parallel array of junctions with alternating cell inductances and junctions areas. We have compared this ratchet array with other circular arrays. We find experimentally and numerically that the depinning current depends on the direction of the applied current in our ratchet ring. We also find other properties of the depinning current versus applied field, such as a long period and a lack of reflection symmetry, which we can explain analytically.Comment: to be published in PR

Dynamic Scaling and Two-Dimensional High-Tc Superconductors

There has been ongoing debate over the critical behavior of two-dimensional superconductors; in particular for high Tc superconductors. The conventional view is that a Kosterlitz-Thouless-Berezinskii transition occurs as long as finite size effects do not obscure the transition. However, there have been recent suggestions that a different transition actually occurs which incorporates aspects of both the dynamic scaling theory of Fisher, Fisher, and Huse and the Kosterlitz-Thouless-Berezinskii transition. Of general interest is that this modified transition apparently has a universal dynamic critical exponent. Some have countered that this apparent universal behavior is rooted in a newly proposed finite-size scaling theory; one that also incorporates scaling and conventional two-dimensional theory. To investigate these issues we study DC voltage versus current data of a 12 angstrom thick YBCO film. We find that the newly proposed scaling theories have intrinsic flexibility that is relevant to the analysis of the experiments. In particular, the data scale according to the modified transition for arbitrarily defined critical temperatures between 0 K and 19.5 K, and the temperature range of a successful scaling collapse is related directly to the sensitivity of the measurement. This implies that the apparent universal exponent is due to the intrinsic flexibility rather than some real physical property. To address this intrinsic flexibility, we propose a criterion which would give conclusive evidence for phase transitions in two-dimensional superconductors. We conclude by reviewing results to see if our criterion is satisfied.Comment: 14 page

Energiapuun autokuljetuskalusto

Työn tavoitteena oli selvittää markkinoilla oleva energiapuun autokuljetuskalusto erilaisine ratkaisuineen. Selvitys tehtiin seuraaville energiapuujakeille: joukkokäsitelty ranka, kokopuu, kanto, hakkuutähde ja hake. Työn tilaaja oli Metsähallituksen metsätalouden kehittämistoiminnot. Valmistajiin haettiin yhteyksiä lehti-ilmoituksilla, sähköpostilla, Internetin välityksellä sekä puhelimitse. Käytin sähköpostitse lähetettävää kyselylomaketta tuotetietojen keräämiseen ja tietojen yhdenmukaistamiseen eri valmistajien kesken. Yhteydessä olin noin 50 valmistajaan Suomessa ja Pohjoismaissa, joista 30 valmisti kyseessä olevia tuotteita. Tuotteita selvityksessä oli 62, jotka jaoin kuuteen ryhmään ominaisuuksiensa perusteella. Tuloksissa esittelin keskeisimmät ominaisuudet ja toimintaperiaatteet seuraaville tuoteryhmille: lisälaidat, kiinteät risu- ja kantovaunut, vaihtolavat ja kontit, kiinteät hakeyhdistelmät, tiivistysratkaisut ja monialakuljetus. Toin esille tuotteiden hintatasoa, hyötykuormia ja toimintaperiaatteita. Selvitys osoitti erilaisia tuotteita olevan markkinoilla runsaasti ja moniin erilaisiin käyttötarpeisiin. Tuotteita kehitetään ja uusia tehokkaita ja taloudellisia ratkaisuja pyritään luomaan jatkuvasti. Energiapuuala elää murrosvaihetta: tämä jakaa yrittäjiä kokopäivätoimisiin sekä kausiluonteisiin tehtäviin. Ympärivuotisessa toiminnassa etsitään ratkaisuja hyötykuormien kasvattamiseksi, kun kausiluonteisilla yrittäjillä huomio keskittyy edullisuuteen ja nopeaan irrotettavuuteen. Kuljetuskustannusten paineessa menopaluukuljetuksiin on kiinnitetty erityistä huomiota, etenkin monipuolistamalla hakekuljetuskalus-ton käyttöä muihin kuljetuksiin.The aim of the thesis was to find out the currently available energy wood truck transporting options equipped with different kinds of solutions. The survey was made for the following wood energy sources and types i.e. stumps, logging residues, wood chips, round wood, and energy wood produced by e.g. multi-handled stem wood logging techniques. The survey was commissioned by Metsähallitus. Manufacturers were contacted by a magazine advertisement, email, internet and phone. In addition a form was sent by email to collect product information and to standardize the information of different manufacturers About 50 manufacturers in Finland and other Nordic countries were contacted, of which 30 made products included in the study. There were a total of 62 products in the survey that were divided into six categories according to their properties. In the results the most vital properties and functioning principles for the following products are presented: extended carriage sides, integrated logging residue and stump carriages, interchangeable container and containers, integrated wood chips combinations, load compacting or compression solutions and multiple transporting. The product rate, biggest potential load and functioning principles are introduced. The survey showed that there were a lot of multiple products in the market for vari-ous use. Products are being developed and new, efficient and economical solutions are continuously being developed. Energy wood business is living a break-through phase: this divides entrepreneurs into full-time workers and seasonal workers. In all-year work solutions to increase the biggest potential loads are developed, whereas seasonal entrepreneurs concentrate on inexpensiveness and quick release. Due to the increase in transportation costs special attention has been paid to two-way transportation, especially equipping wood chips combinations for cargo.Työn liitteeksi merkityt Excel-taulukot ja Powerpoint-esitys, ovat tilaajan käyttöön ja puuttuvat julkaistusta työstä