Grid interfacing of a photovoltaic system using a chain cell converter

With the rapid development of photovoltaic system installations and increased number of grid connected power systems, it has become imperative to develop an efficient grid interfacing instrumentation suitable for photovoltaic systems ensuring maximum power transfer. The losses in the power converter play an important role in the overall efficiency of a PV system. Chain cell converter is considered to be efficient as compared to PWM converters due to lower switching losses, modularized circuit layout, reduced voltage rating of the converter switches, reduced EMI. The structure of separate dc sources in chain cell converter is well suited for photovoltaic systems as there will b several separate PV modules in the PV array which can act as an individual dc source. In this work, a single phase multilevel chain cell converter is used to interface the photovoltaic array to a single phase grid at a frequency of 50Hz. Control algorithms are developed for efficient interfacing of the PV system with grid and isolating the PV system from grid under faulty conditions. Digital signal processor TMS320F 2812 is used to implement the control algorithms developed and for the generation of other control signals.

Jac. Ahrenberg ja historian perintö : Restaurointisuunnitelmat Viipurin ja Turun linnoihin 1800-luvun lopussa

Jac. Ahrenberg and Patrimony Restoration Plans for Viipuri and Turku Castles at the End of the 19th Century This dissertation examines the unrealized restoration plans for two castles in the Grand Duchy of Finland one located at Viipuri (Vyborg, nowadays in Russia), the other at Turku (in Swedish, Åbo) during the last decades of the 19th century. Both castles were used as prisons, barracks and warehouses. From the middle of the 19th century on, their restoration and transformation into museums and "national monuments" were demanded in the newspapers. The prison reform in the 1860s stimulated the documentation and debate concerning their future, but it was only at the beginning of the 1880s when their restoration became an official state-run project. The undertaking was carried out by Johan Jacob (Jac.) Ahrenberg (1847 1914), architect of the National Board of Public Buildings. By combining written sources with drawings and photographs, this dissertation examines the restoration projects, the two castles' significance and the ways in which they were investigated by scholars. The plans are analyzed in connection with restoration practices in France and Sweden and in the context of contemporary discussions concerning national art and patrimony. The thesis argues that these former castles of the Swedish crown were used to manifest the western roots of Finnish law and order, the lineage of power and the capacity of the nation to defend itself. However, because of their symbolism, their restoration became a politically delicate question concerning the role of the Swedish heritage in Finland's nation-building process. According to Jac. Ahrenberg's plans, the two castles were to be restored to their assumed appearance at the time of the Vasa dynasty. Consequently, the structures would have resembled castles in Sweden. It is suggested that one aim of the restoration plans was to transform the two buildings into monuments testifying to the common history of Sweden and Finland. They were meant to consolidate the Swedish basis of Finnish culture and autonomy and thus to secure them against the threatening implications of Russian imperialism. It seems that along with the changing ideals of architectural restoration and the need for an original Finnish architectural heritage, the political connotations associated with the castles were one reason why Jac. Ahrenberg's restoration plans were never realized.

Kateuden luonne ja erityispiirteet filosofisessa pohdinnassa

Kateuden tunnetta ei ole tarkasteltu käytännöllisessä filosofiassa huolimatta sen määräävästä asemasta ihmisen normaalissa päivittäisessä elämässä. Kateus liittyy moniin ilmiöihin yksilöllisenä tai jopa kollektiivisena ryhmätunteena, kun siihen yhdistyvät epäoikeudenmukaisuus ja itsepetoksellisuus. Tutkielma pyrki osoittamaan kateuden vääjäämättömän monipuolisuuden kilpailullisena ja eriarvoisuutta lisäävänä vertailevana kompleksisena negatiivisena tunteena. Jo antiikin Kreikassa kateus liitettiin ihmisten ja jumalien väliseen eriarvoisuuteen, nykypäivänä taas kateutta leimaa liberaalisen yhteiskuntapolitiikan keskiössä ”tietämättömyyden verhon” takana egalitaarisuuden ihanne ja oikeudenmukaisuuden ja reiluuden taju. Tunnekokemuksena kateus on impotenttinen toisen paremmuudesta ja inferioi näin kateuden episodisuuden irrationaaliseen tilanteeseensa nähden antagonistiseksi. Tutkielman neljästä pääluvussa ensimmäisessä kateus yhdistetään poliittisen liberaalin yhteiskuntafilosofian yhdysvaltalaiseen kannattajaan John Rawlsiin (1921−2002). Hänen ajattelussaan ja pääteoksessaan A Theory of Justice (1971) ja siinä erityisesti kateutta käsittelevässä luvussa IX kateus on yhteiskunnassa vaikuttavaa erityispsykologista taipumusta tavoitella parempiosaisten asemaa oikeudenmukaisuuden kontraktuaalisessa valintajärjestelmässä. Rawlsille kateus ei ole tabu, vaan kateuden ongelma koskee kaikkia abstraktissa alkuasetelmassa yhteiskuntasopimuksen piiriin liittyviä sopija−agentteja. Rationaalinen agentti ei kärsi kateudesta, kun epäoikeudenmukaisuutta ei ole hänen ja muiden samojen vapaus− ja eroperiaatteiden nojalla toimivien ihmisten välillä sietämättömästi. Rawls tekee kuitenkin jaon pahantahoisessa kateudessa (proper) yleiseen ja erityiseen ja erottaa sekä emulatiivisen (emulative) eli motivoivan esimerkin sysäämän kilvoittelevan kateuden varsinaisesta kateudesta (proper). Myös anteeksiannettava kateus (excusable general envy) on Rawlsin onnellisuutta ja reiluutta tasa–arvoistavassa sopimusteorian ideaalissa varsinaisen kateuden alaluokkana mukana. Kateus ja tasa-arvo tulevat esille paremmin kilpailullisessa kateudessa, mistä myös viime vuosien merkittävin kateustutkija amerikkalainen Kentuckyn yliopiston psykologian professori Richard H. Smith on ollut kiinnostunut. Hänelle kateus on inferiorisen kompleksista ja liittyy oman arvon tunteeseen ja kognitiiviseen psykologiaan. Kateuden tutkimus on monialaistunut ja vilkastunut viime vuosikymmenen aikana. Sosiaali−psykologia, sosiologia, kulttuuriantropologia ja tunnefilosofia ovat kiinnostuneet ymmärtämään tätä kompleksista negatiivista tunnetta paremmin. Kulttuurissamme kateus toimii universaalisesti yhteydessä muihin rinnakkaistunteisiin, kuten moraaliseen paheksuntaan tai sitä lievempään närkästymiseen. Kateus ei ole perustunne, mutta sille on löydettävissä prototyypillisiä piirteitä, joskin kateus ei helposti antaudu propositionaaliseen tai kognitiiviseen arvostelmasisältöön yksin mentaalisen analyysin välityksellä (Solomon 1976). Siitä pitää huolen kateuden affektuaalnen instrumentaalisuus (feeling) ja kognitiivisen komponentiaalisen tulkinnan vaikeus kateellisen väistellessä oman itsetunnon inferiorisuuden tai omaa toimintavalmiutta heikentävien ilkeämielisten motiiviensa alaisuudessa. Kateelliselle ei ns. perisyntinä riitä, että kadehditulta olisi saatu pois haluttu myönteinen ominaisuus, kohde−esine tai asema, vaan lähietäisyydellä toimivasta kadehditusta pitäisi päästä kokonaan eroon (ns. venäläinen kateus). Siksi kateus approksimoi naapureita, ystäviä, kollegoita tai myös toisen ihmisen aviopuolisoa, mutta usein arkiyhteydessä käsitteellisesti väärinymmärrettynä, koska jälkimmäisessä on kyse kolmepaikkaisesta mustasukkaisuuden tunteesta. Kaksipaikkaisena tunteena (kateellinen & kadehdittu) ja sen vastatunteenaan usein mainittu kiittämättömyys saavat aikaan sen, että kateellinen on myös taipuvainen aggressiivisuuteen ja vihaisuuteen, mutta kun asiaa tarkastelee tarkemmin taustalta paljastuu itsepetoksen elementtejä. Kateellinen hyödyntää itsepetoksen paradoksia eli kahden vastakkaisen uskomuksen (Kateellinen, koska P & Kateellinen, koska ~P) samanaikaista voimassaoloa tilanteessa, jossa omat teot ovat suuntautuneet intentionaalisesti muualle kuin kadehditun komparatiiivisesti parempana näyttäytyvien arvostuserojen kuromiseksi tilanteen tasavertaistamiseksi kiinni. Kateellinen voi olla deliberatiivisen ahne ja nopea epäreilussa reaktiossaan kadehdittua kohtaan. Näin uppiniskainen kateustunne voi tulla eriäväksi havaitun arvioivan arvostelman kanssa. Kateustunne olisi näin määritelmällisesti intensiivistä puutetta (toistuvissa) epätasa−arvoisissa ja irrationalisoituneissa ihmiskohtaamisissa. Tutkimus esitteli kateustunteen adekvaattisena käsitteenä ja toi havaintoja kognitiivisen tunneteorian riittämättömyydestä kateustunteen tutkimukselle. Kiinnostavaa oli, että poliittisessa yhteiskuntafilosofiasta löytyi myös Rawlsin psykologisten erityistaipumuksien ja erityisesti kateuden yhteiskuntapoliittista kritiikkiä. Tunneteoreettisesti kateustunne on kognitiivista perustunnetta holistisempi, intensiivisempi ja intentionaalisempi sekä lisäksi affektuaalisesti motivoiva, joka mahdollistaa myös inhimillisen toiminnan kehittymisen, mutta myös kadehtijan tuhoamisen. Itsepetos sen sijaan tekee kateudesta haavoittuvan ja myös narsismia ruokkivan tunnetilan, jossa kateellinen toimii hedonistisesti ei−kognitiivisen irrationaalisen tietämyksen (envious feeling proper) varassa ja kieltää tunteen konsekventionaaliset usein negatiiviset seuraukset itselleen ja lähiympäristölleen.

Production process of Scots pine.

The accompanying collective research report is the result of the research project in 1986­90 between The Finnish Academy and the former Soviet Academy of Sciences. The project was organized around common field work in Finland and in the former Soviet Union and theoretical analyses of tree growth determining processes. Based on theoretical analyses, dynamic stand growth models were made and their parameters were determined utilizing the field results. Annual cycle affects the tree growth. Our theoretical approach was based on adaptation to local climate conditions from Lapland to South Russia. The initiation of growth was described as a simple low and high temperature accumulation driven model. Linking the theoretical model with long term temperature data allowed us to analyze what type of temperature response produced favorable outcome in different climates. Initiation of growth consumes the carbohydrate reserves in plants. We measured the dynamics of insoluble and soluble sugars in the very northern and Karelian conditions. Clear cyclical pattern was observed but the differences between locations were surprisingly small. Analysis of field measurements of CO2 exchange showed that irradiance is the dominating factor causing variation in photosynthetic rate in natural conditions during summer. The effect of other factors is so small that they can be omitted without any considerable loss of accuracy. A special experiment carried out in Hyytiälä showed that the needle living space, defined as the ratio between the shoot cylindric volume and needle surface area, correlates with the shoot photosynthesis. The penetration of irradiance into Scots pine canopy is a complicated phenomenon because of the movement of the sun on the sky and the complicated structure of branches and needles. A moderately simple but balanced forest radiation regime submodel was constructed. It consists of the tree crown and forest structure, the gap probability calculation and the consideration of spatial and temporal variation of radiation inside the forest. The common field excursions in different geographical regions resulted in a lot of experimental data of regularities of woody structures. The water transport seems to be a good common factor to analyse these properties of tree structure. There are evident regressions between cross-sectional areas measured at different locations along the water pathway from fine roots to needles. The observed regressions have clear geographical trends. For example, the same cross-sectional area can support three times higher needle mass in South Russia than in Lapland. Geographical trends can also be seen in shoot and needle structure. Analysis of data published by several Russian authors show, that one ton of needles transpire 42 ton of water a year. This annual amount of transpiration seems to be independent of geographical location, year and site conditions. The produced theoretical and experimental material is utilised in the development of stand growth model that describes the growth and development of Scots pine stands in Finland and the former Soviet Union. The core of the model is carbon and nutrient balances. This means that carbon obtained in photosynthesis is consumed for growth and maintenance and nutrients are taken according to the metabolic needs. The annual photosynthetic production by trees in the stand is determined as a function of irradiance and shading during the active period. The utilisation of the annual photosynthetic production to the growth of different components of trees is based on structural regularities. Since the fundamental metabolic processes are the same in all locations the same growth model structure can be applied in the large range of Scots pine. The annual photosynthetic production and structural regularities determining the allocation of resources have geographical features. The common field measurements enable the application of the model to the analysis of growth and development of stands growing on the five locations of experiments. The model enables the analysis of geographical differences in the growth of Scots pine. For example, the annual photosynthetic production of a 100-year-old stand at Voronez is 3.5 times higher than in Lapland. The share consumed to needle growth (30 %) and to growth of branches (5 %) seems to be the same in all locations. In contrast, the share of fine roots is decreasing when moving from north to south. It is 20 % in Lapland, 15 % in Hyytiälä Central Finland and Kentjärvi Karelia and 15 % in Voronez South Russia. The stem masses (115­113 ton/ha) are rather similar in Hyytiälä, Kentjärvi and Voronez, but rather low (50 ton/ha) in Lapland. In Voronez the height of the trees reach 29 m being in Hyytiälä and Kentjärvi 22 m and in Lapland only 14 m. The present approach enables utilization of structural and functional knowledge, gained in places of intensive research, in the analysis of growth and development of any stand. This opens new possibilities for growth research and also for applications in forestry practice.

Lexicon forestale.

592 s.

From ‘Afflicted’ to Activists: Structural Violence and Climate Change Discourse in the States of Pernambuco and Paraíba in Northeast Brazil

This study approaches the problem of poverty in the hinterlands of Northeast Brazil through the concept of structural violence, linking the environmental threats posed by climate change, especially those related to droughts, to the broader social struggles in the region. When discussions about potentials and rights are incorporated into the problematic of poverty, a deeper insight is obtained regarding the various factors behind the phenomenon. It is generally believed that climate change is affecting the already marginalized and poor more than those of higher social standing, and will increasingly do so in the future. The data for this study was collected during a three month field work in the states of Pernambuco and Paraíba in Northeast Brazil. The main methods used were semi-structured interviews and participant observation, including attending seminars concerning climate change on the field. The focus of the work is to compare both layman and expert perceptions on what climate change is about, and question the assumptions about its effects in the future, mainly that of increased numbers of ‘climate refugees’ or people forced to migrate due to changes in climate. The focus on droughts, as opposed to other manifestations of climate change, arises from the fact that droughts are not only phenomena that develop over a longer time span than floods or hurricanes, but is also due to the historical persistence of droughts in the region, and both the institutional and cultural linkages that have evolved around it. The instances of structural violence that are highlighted in this study; the drought industry, land use, and the social and power relations present in the region, including those between the civil society, the state and the private agribusiness sector, all work against a backdrop of symbolic and moral realms of value production, where relations between the different actors are being negotiated anew with the rise of the climate change discourse. The main theoretical framework of the study consists of Johan Galtung’s and Paul Farmer’s theory of structural violence, Ulrich Beck’s theory of the risk society, and James Scott’s theory of everyday peasant resistance.

Tailoring the Magnetic and Optical Characteristics of Nanocrystalline BiFeO3 by Ce Doping

The Ce-doped BiFeO3 (BFO) nanoparticles (NPs) were synthesized using a facile solgel route with varying Ce concentrations in the range of 15 mol%. Ferroelectric transition temperature was found to shift from 723 degrees C +/- 5 degrees C for pristine BFO NPs to 534 degrees C +/- 3 degrees C for 5 mol% Ce-doped BFO NPs. UVVis absorption spectra of BFO NPs showed a significant blue shift of similar to 100 nm on Ce doping. The Fourier transformed infrared (FTIR) spectrum centered similar to 550 cm(-1) becomes considerably broadened on Ce doping which is due to additional closely spaced vibrational peaks as revealed by the second derivative FTIR analysis. High-frequency EPR measurements indicated that clustering occurs at high dopant levels, and that Fe is present as Fe(3+)corroborating Mossbauer measurements. The values of saturation and remanent magnetization for 3% Ce-doped BFO NPs are 3.03 and 0.49 emu/g, respectively, which are quite significant at room temperature, making it more suitable for technological applications.

High precision Mg isotope measurements of meteoritic samples by secondary ion mass spectrometry

The possibility of establishing an accurate relative chronology of the early solar system events based on the decay of short-lived Al-26 to Mg-26 (half-life of 0.72 Myr) depends on the level of homogeneity (or heterogeneity) of Al-26 and Mg isotopes. However, this level is difficult. to constrain precisely because of the very high precision needed for the determination of isotopic ratios, typically of +/- 5 ppm. In this study, we report for the first time a detailed analytical protocol developed for high precision in situ Mg isotopic measurements ((25)mg/(24)mg and (26)mg/Mg-24 ratios, as well as Mg-26 excess) by MC-SIMS. As the data reduction process is critical for both accuracy and precision of the final isotopic results, factors such as the Faraday cup (FC) background drift and matrix effects on instrumental fractionation have been investigated. Indeed these instrumental effects impacting the measured Mg-isotope ratios can be as large or larger than the variations we are looking for to constrain the initial distribution of Al-26 and Mg isotopes in the early solar system. Our results show that they definitely are limiting factors regarding the precision of Mg isotopic compositions, and that an under- or over-correction of both FC background instabilities and instrumental isotopic fractionation leads to important bias on delta Mg-25, delta(26)mg and Delta Mg-26 values (for example, olivines not corrected for FC background drifts display Delta Mg-26 values that can differ by as much as 10 ppm from the truly corrected value). The new data reduction process described here can then be applied to meteoritic samples (components of chondritic meteorites for instance) to accurately establish their relative chronology of formation.