3 resultados para Energy Harvesting, Convertitori di potenza, Maximum Power Point Tracking, Applicazioni low power
em Helda - Digital Repository of University of Helsinki
Resumo:
In the autumn of 1997, Russian government was faced with media pressure when owners of the TV channels ORT and NTV joined forces against it. This study is based on media sources from October 1997 to December 1997. It shows clearly how the enormous power of the media was able to dictate what happened in Russia. In the mid-1990s Russians started to talk about political technology, which became a commonly used term by professionals, journalists, politicians and intelligence services. As a result of this action, two leading reformers in the government, Anatoliy Chubais and Boris Nemtsov, were dismissed from their highly influential posts as finance and energy ministers respectively, but retained their power as first deputy prime ministers. According to the correspondents, the real reason was to resolve a conflict within the parliament, which had demanded the dismissal of Mr. Chubais. This demand was presented after Chubais had accepted $90,000 as a reward for co-writing a book on privatization. Chubais was considered to be Russias business card towards the west the"Authors case" (Delo avtorov) was only solved after President Boris Yeltsin took part in the public debate. According to the research, the media owned by powerful businessmen Boris Berezovsky and Vladimir Gusinski, was able to use its own security services to expose sensitive material (Russian term kompromat), if necessary, concerning any given person. The so-called Authors case can be considered as a part of the battle and the tip of the iceberg in arrangements designed to organize the funding of the Russian presidential election campaign in 2000. The reason why this particular incident was so widely covered on television was because several programs aimed to reveal to the public "hidden bribes" that, as they claimed, government officials had received. The political aspect, however, was quite mild, when the concrete issues of possible dismissals of Ministers were debated in the Parliament. Everything was dealt with as a family matter inside Kremlin. Yeltsin's "family" consisted of practically anybody from oligarch Berezovsky to Chubais, the father of Russia's privatization policy. Methods of critical history implementation analysis has been used in this research in determining the use of the source material. Literature and interviews have also provided a good base for the study. The study proves that any literature dealing with the subject has not paid enough attention to how the dismissal of Alexander Kazakov, deputy of Presidents administration, was linked directly with Gazprom, the state gas monopoly. Kazakov had to leave Gazprom and lose his position as Chubais' ally when the influential ORT television company was deteriorated.
Resumo:
Carbon nanotubes, seamless cylinders made from carbon atoms, have outstanding characteristics: inherent nano-size, record-high Youngs modulus, high thermal stability and chemical inertness. They also have extraordinary electronic properties: in addition to extremely high conductance, they can be both metals and semiconductors without any external doping, just due to minute changes in the arrangements of atoms. As traditional silicon-based devices are reaching the level of miniaturisation where leakage currents become a problem, these properties make nanotubes a promising material for applications in nanoelectronics. However, several obstacles must be overcome for the development of nanotube-based nanoelectronics. One of them is the ability to modify locally the electronic structure of carbon nanotubes and create reliable interconnects between nanotubes and metal contacts which likely can be used for integration of the nanotubes in macroscopic electronic devices. In this thesis, the possibility of using ion and electron irradiation as a tool to introduce defects in nanotubes in a controllable manner and to achieve these goals is explored. Defects are known to modify the electronic properties of carbon nanotubes. Some defects are always present in pristine nanotubes, and naturally are introduced during irradiation. Obviously, their density can be controlled by irradiation dose. Since different types of defects have very different effects on the conductivity, knowledge of their abundance as induced by ion irradiation is central for controlling the conductivity. In this thesis, the response of single walled carbon nanotubes to ion irradiation is studied. It is shown that, indeed, by energy selective irradiation the conductance can be controlled. Not only the conductivity, but the local electronic structure of single walled carbon nanotubes can be changed by the defects. The presented studies show a variety of changes in the electronic structures of semiconducting single walled nanotubes, varying from individual new states in the band gap to changes in the band gap width. The extensive simulation results for various types of defect make it possible to unequivocally identify defects in single walled carbon nanotubes by combining electronic structure calculations and scanning tunneling spectroscopy, offering a reference data for a wide scientific community of researchers studying nanotubes with surface probe microscopy methods. In electronics applications, carbon nanotubes have to be interconnected to the macroscopic world via metal contacts. Interactions between the nanotubes and metal particles are also essential for nanotube synthesis, as single walled nanotubes are always grown from metal catalyst particles. In this thesis, both growth and creation of nanotube-metal nanoparticle interconnects driven by electron irradiation is studied. Surface curvature and the size of metal nanoparticles is demonstrated to determine the local carbon solubility in these particles. As for nanotube-metal contacts, previous experiments have proved the possibility to create junctions between carbon nanotubes and metal nanoparticles under irradiation in a transmission electron microscope. In this thesis, the microscopic mechanism of junction formation is studied by atomistic simulations carried out at various levels of sophistication. It is shown that structural defects created by the electron beam and efficient reconstruction of the nanotube atomic network, inherently related to the nanometer size and quasi-one dimensional structure of nanotubes, are the driving force for junction formation. Thus, the results of this thesis not only address practical aspects of irradiation-mediated engineering of nanosystems, but also contribute to our understanding of the behaviour of point defects in low-dimensional nanoscale materials.
Resumo:
This dissertation investigates the atomic power solution in Finland between 1955 - 1970. During these years a national arrangement for atomic energy technology evolved. The foundations of the Finnish atomic energy policy; the creation of basic legislation and the first governmental bodies, were laid between 1955 - 1965. In the late 1960's, the necessary technological and political decisions were made in order to purchase the first commercial nuclear reactor. A historical narration of this process is seen in the international context of "atoms for peace" policies and Cold War history in general. The geopolitical position of Finland made it necessary to become involved in the balanced participation in international scientific-technical exchange and assistive nuclear programs. The Paris Peace Treaty of 1947 categorically denied Finland acquisition of nuclear weapons. Accordingly, from the "Geneva year" of 1955, the emphasis was placed on peaceful purposes for atomic energy as well as on the education of national professionals in Finland. An initiative for the governmental atomic energy commission came from academia but the ultimate motive behind it was an anticipated structural change in the supply of national energy. Economically exploitable hydro power resources were expected to be built within ten years and atomic power was seen as a promising and complementing new energy technology. While importing fuels like coal was out of the question, because of scarce foreign currency, domestic uranium mineral deposits were considered as a potential source of nuclear fuel. Nevertheless, even then nuclear energy was regarded as just one of the possible future energy options. In the mid-1960 s a bandwagon effect of light water reactor orders was witnessed in the United States and soon elsewhere in the world. In Finland, two separate invitations for bids for nuclear reactors were initiated. This study explores at length both their preceding grounds and later phases. An explanation is given that the parallel, independent and nearly identical tenders reflected a post-war ideological rivalry between the state-owned utility Imatran Voima and private energy utilities. A private sector nuclear power association Voimayhdistys Ydin represented energy intensive paper and pulp industries and wanted to have free choice instead of being associated themselves with "the state monopoly" in energy pricing. As a background to this, a decisive change had started to happen within Finnish energy policy: private and municipal big thermal power plants became incorporated into the national hydro power production system. A characteristic phenomenon in the later history is the Soviet Union s effort to bid for the tender of Imatran Voima. A nuclear superpower was willing to take part in competition but not on a turnkey basis as Imatran Voima had presumed. As a result of many political turns and four years of negotiations the first Finnish commercial light water reactor was ordered from the East. Soon after this the private nuclear power group ordered its reactors from Sweden. This work interprets this as a reasonable geopolitical balance in choosing politically sensitive technology. Conceptually, social and political dimensions of new technology are emphasised. Negotiations on the Finnish atomic energy program are viewed as a cooperation and a struggle, where state-oriented and private-oriented regimes pose their own macro level views and goals (technopolitical imaginaries) and defend and advance their plans and practical modes of action (schemata). Here, not only technologists but even political actors are seen to contribute to technopolitical realisations.