995 resultados para Voltage source converter (VSC)


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The development of bioenergy on the basis of wood fuels has received considerable attention in the last decades. The combination of large forest resources and reliance on fossil fuels makes the issue of wood chips usage in Russia an actual topic for the analysis. The main objective of this study is to disclose the current state and perspectives for the production of wood chips and their usage as a source of energy in the North-West of Russia. The study utilizes an integrated approach to explore the market of wood chips on the basis of comprehensive analysis of documentation and expert opinions. The analysis of wood chips market was performed for eight regions of the North-West district of Russia within two major dimensions: its current state and perspectives in the nearest five years. The results of the study show a comprehensive picture of the wood chips market, including the potential for wood chips production, the specific features of production and consumption and the perspectives for the market development within the regions of the North-West district of Russia. The study demonstrated that the market of wood chips is underdeveloped in the North-West of Russia. The findings of the work may be used by forest companies for the strategic planning.

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Cyanobacteria are a diverse group of oxygenic photosynthetic bacteria that inhabit in a wide range of environments. They are versatile and multifaceted organisms with great possibilities for different biotechnological applications. For example, cyanobacteria produce molecular hydrogen (H2), which is one of the most important alternatives for clean and sustainable energy. Apart from being beneficial, cyanobacteria also possess harmful characteristics and may become a source of threat to human health and other living organisms, as they are able to form surface blooms that are producing a variety of toxic or bioactive compounds. The University of Helsinki Culture Collection (UHCC) maintains around 1,000 cyanobacterial strains representing a large number of genera and species isolated from the Baltic Sea and Finnish lakes. The culture collection covers different life forms such as unicellular and filamentous, N2-fixing and non-N2-fixing strains, and planktonic and benthic cyanobacteria. In this thesis, the UHCC has been screened to identify potential strains for sustainable biohydrogen production and also for strains that produce compounds modifying the bioenergetic pathways of other cyanobacteria or terrestrial plants. Among the 400 cyanobacterial strains screened so far, ten were identified as high H2-producing strains. The enzyme systems involved in H2 metabolism of cyanobacteria were analyzed using the Southern hybridization approach. This revealed the presence of the enzyme nitrogenase in all strains tested, while none of them are likely to have contained alternative nitrogenases. All the strains tested, except for two Calothrix strains, XSPORK 36C and XSPORK 11A, were suggested to contain both uptake and bidirectional hydrogenases. Moreover, 55 methanol extracts of various cyanobacterial strains were screened to identify potent bioactive compounds affecting the photosynthetic apparatus of the model cyanobacterium, Synechocystis PCC 6803. The extract from Nostoc XPORK 14A was the only one that modified the photosynthetic machinery and dark respiration. The compound responsible for this effect was identified, purified, and named M22. M22 demonstrated a dual-action mechanism: production of reactive oxygen species (ROS) under illumination and an unknown mechanism that also prevailed in the dark. During summer, the Baltic Sea is occupied by toxic blooms of Nodularia spumigena (hereafter referred to as N. spumigena), which produces a hepatotoxin called nodularin. Long-term exposure of the terrestrial plant spinach to nodularin was studied. Such treatment resulted in inhibition of growth and chlorosis of the leaves. Moreover, the activity and amount of mitochondrial electron transfer complexes increased in the leaves exposed to nodularin-containing extract, indicating upregulation of respiratory reactions, whereas no marked changes were detected in the structure or function of the photosynthetic machinery. Nodularin-exposed plants suffered from oxidative stress, evidenced by oxidative modifications of various proteins. Plants initiated strategies to combat the stress by increasing the levels of alpha-tocopherol, mitochondrial alternative oxidase (AOX), and mitochondrial ascorbate peroxidase (mAPX).

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The aim of this study was to define the photographic patterns that represent the use and occupation of the landcover of the "spring" of the Rico Stream subbasin, located at Monte Alto, state of São Paulo (SP), Brazil, for environmental adaptation regarding the Brazilian Forest Law. The mapping was performed using remote sensing techniques and visual interpretation of the World View image, followed by the digitalization of the net of drainage and vegetation (natural and agricultural) at the AutoCad software with documents and field work. The study area has 2141.53 ha and the results demonstrated that the main crop is sugarcane with 546.34 ha, followed by 251.22 ha of pastures, 191.71 ha of perennial crops, 57.31 ha of Eucalyptus and 49.52 ha of onion, confirming the advance of sugarcane culture in the region. The region has 375.04 ha of areas of permanent preservation (APPs), and of this area it was found that only 72.17 ha (19.24%) has arboreal vegetation or natural forest, and 302.87 ha of these areas need to be enriched and reforested with native vegetation from the region, according to the current legislation. The data of the area enable future proposals of models for environmental adaptation to the microbasin according to the current environmental legislation.

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The main advantage of organic electronics over the more widespread inorganic counterparts lies not in the electrical performance, but rather in the solution processability that opens up for low-cost flexible electronics (e.g. displays, sensors and smart tags) fabricated by using printing techniques. Replacing the commonly used laboratory-scale fabrication techniques with mass-printing techniques is, however, truly challenging, especially when low-voltage operation is required. In this thesis it is, nevertheless, demonstrated that low-voltage organic transistors can be fully printed with a similar performance to that of transistors made by laboratory scale techniques. The use of an ion-modulated type of organic field effect transistor (OFET) not only enabled low-voltage operation and printability, but was also found to result in low sensitivity to the surface roughness of the substrate. This allows not only the use of low-cost plastic substrates, but even the use of paper as a substrate. However, while absorption into the porous paper surface is advantageous in a graphical printing process, by reducing the spreading and the coffee-stain effect and by improving the adhesion, it provides great challenges when applying thin electrically active layers. In spite of these difficulties we were able to demonstrate the first low-voltage OFET to be fabricated on paper. We have also shown that low-cost incandescent lamps can be used for sintering printed metal-nanoparticles, and that the process was especially suitable on paper and compatible with a roll-to-roll manufacturing process.

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The environmental aspect of corporate social responsibility (CSR) expressed through the process of the EMS implementation in the oil and gas companies is identified as the main subject of this research. In the theoretical part, the basic attention is paid to justification of a link between CSR and environmental management. The achievement of sustainable competitive advantage as a result of environmental capital growth and inclusion of the socially responsible activities in the corporate strategy is another issue that is of special significance here. Besides, two basic forms of environmental management systems (environmental decision support systems and environmental information management systems) are explored and their role in effective stakeholder interaction is tackled. The most crucial benefits of EMS are also analyzed to underline its importance as a source of sustainable development. Further research is based on the survey of 51 sampled oil and gas companies (both publicly owned and state owned ones) originated from different countries all over the world and providing reports on sustainability issues in the open access. To analyze their approach to sustainable development, a specifically designed evaluation matrix with 37 indicators developed in accordance with the General Reporting Initiative (GRI) guidelines for non-financial reporting was prepared. Additionally, the quality of environmental information disclosure was measured on the basis of a quality – quantity matrix. According to results of research, oil and gas companies prefer implementing reactive measures to the costly and knowledge-intensive proactive techniques for elimination of the negative environmental impacts. Besides, it was identified that the environmental performance disclosure is mostly rather limited, so that the quality of non-financial reporting can be judged as quite insufficient. In spite of the fact that most of the oil and gas companies in the sample claim the EMS to be embedded currently in their structure, they often do not provide any details for the process of their implementation. As a potential for the further development of EMS, author mentions possible integration of their different forms in a single entity, extension of existing structure on the basis of consolidation of the structural and strategic precautions as well as development of a unified certification standard instead of several ones that exist today in order to enhance control on the EMS implementation.

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The focus in this thesis is to study both technical and economical possibilities of novel on-line condition monitoring techniques in underground low voltage distribution cable networks. This thesis consists of literature study about fault progression mechanisms in modern low voltage cables, laboratory measurements to determine the base and restrictions of novel on-line condition monitoring methods, and economic evaluation, based on fault statistics and information gathered from Finnish distribution system operators. This thesis is closely related to master’s thesis “Channel Estimation and On-line Diagnosis of LV Distribution Cabling”, which focuses more on the actual condition monitoring methods and signal theory behind them.

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The aim of this master’s thesis is to study how Agile method (Scrum) and open source software are utilized to produce software for a flagship product in a complex production environment. The empirical case and the used artefacts are taken from the Nokia MeeGo N9 product program, and from the related software program, called as the Harmattan. The single research case is analysed by using a qualitative method. The Grounded Theory principles are utilized, first, to find out all the related concepts from artefacts. Second, these concepts are analysed, and finally categorized to a core category and six supported categories. The result is formulated as the operation of software practices conceivable in circumstances, where the accountable software development teams and related context accepts a open source software nature as a part of business vision and the whole organization supports the Agile methods.

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Diplomityössä tarkastellaan tapausta, jossa tasasähköverkon vaihtosuuntaaja toteutetaan kolmella yksivaiheisella suuntaajalla yhden kolmivaiheisen sijaan. Modulaarinen rakenne mahdollistaa sen, että osa vaiheista voitaisiin sammuttaa kun kuormitus on erittäin pientä eikä kuorma ole kolmivaiheista. Galvaaninen erotus oletetaan tehtävän erottavalla DC-DC -konvertterilla, joka mahdollistaa samalla vaihtosuuntaajan DC-syöttöjännitteen muuttamisen. Työssä tutkitaan, mitkä tekijät vaikuttavat DC-syöttöjännitteen valintaan sekä tehdään valinta kyseisen jännitteen arvolle. Valittua jännitetasoa käytetään vaihtosuuntaajan suunnittelemiseen. Vaihtosuuntaajan rakennetta tarkastellaan vaihtosuuntaussillan kytkinkomponenttien sekä lähtöjännitteen suotimen osalta. Yksivaiheiselle moduulille määritetään optimaalinen teholuokka investointi- ja käyttökustannusten kannalta. Tarkastelu pitää sisällään erilaisten transistoritekniikkojen, kytkentätaajuuksien sekä kahden suodintyypin vaikutuksen kustannustehokkuuteen.

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Tässä työssä tutkitaan LLC resonanssipiirin soveltuvuutta galvaanisen erotuksen toteuttamiseen tasasähkönjakeluverkon asiakaspäätelaitteessa. Tarkastellaan resonanssipiirin ominaisuuksia ja aikaisempia käyttökohteita. Tutkitaan piirin soveltuvuutta vaihtosähkö sovellukseen ja esitellään piirin toimintaa, häviöitä ja ohjausta. Esitellään pulssin leveys moduloitu (PWM) ja pulssin tiheys moduloitu (PDM) invertteri sovellukset ja näiden toimintaa. Esitetään vielä parannusehdotuksia ja kytkentäkuvio kytkennän ominaisuuksien ja hyö-tysuhteen parantamiseksi. Tutkimuksessa selvisi, että suora PDM topologia ei sovellu tähän käyttötarkoitukseen suuren suodin induktanssin vuoksi. PWM invertteri topologia jännitteen tasasuuntauksella taas sopii sovellukseen ja tällä rakenteella on mahdollista tehdä galvaaninen erotus hyvinkin hyvällä hyötysuhteella. Pehmeän kytkennän aiheuttamien häviöiden tarkka määrittely simulointimallista on parhaimmillaankin vain suuntaa-antava, mutta tulokset olivat mielestäni oikein positiivisia. LLC resonanssipiirin toimintaa tutkittiin vain resonanssitaajuudella kytkettäessä, jolloin sen jännitevahvistusominaisuuksien hyödyntäminen jää tarkastelun ulko-puolelle.

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Open source and open source software development have been interesting phenomena during the past decade. Traditional business models do not apply with open source, where the actual product is free. However, it is possible to make business with open source, even successfully, but the question is: how? The aim of this study is to find the key factors of successfully making business out of commercial open source software development. The task is achieved by finding the factors that influence open source projects, finding the relation between those factors, and find out why some factors explain the success more than others. The literature review concentrates first on background of open innovation, open source and open source software. Then business models, critical success factors and success measures are examined. Based on existing literature a framework was created. The framework contains categorized success factors that influence software projects in general as well as open source software projects. The main categories of success factors in software business are divided into community management, technology management, project management and market management. In order to find out which of the factors based on the existing literature are the most critical, empirical research was done by conducting unstructured personal interviews. The main finding based on the interviews is that the critical success factors in open source software business do not differ from those in traditional software business or in fact from those in any other business. Some factors in the framework came out in the interviews that can be considered as key factors: establishing and communicating hierarchy (community management), localization (technology management), good license know-how and IPR management (project management), and effective market management (market management). The critical success factors according to the interviewees are not listed in the framework: low price, good product and good business model development.

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Työssä esiteltävä laite on osa DC-AC hakkuria, jolla muodostetaan 750 V tasajännitteestä yksivaiheista (230 VRMS, 50 Hz) galvaanisesti erotettua verkkojännitettä. Tasajännite muunnetaan resonanssikonvertterilla korkeataajuiseksi vaihtojännitteeksi, joka johdetaan erotusmuuntajaan. Galvaanisen erotuksen jälkeen korkeataajuisesta vaihtojännitteestä muodostetaan suoraan verkkotaajuista vaihtojännitettä työssä esiteltävällä syklokonvertterilla. Suunnittelussa on pyritty minimoimaan häviöt mahdollisimman tarkkaan, jotta laite olisi kilpailukykyinen ei-galvaanisesti erottavien konverttereiden kanssa. Tämä on toteutettu käyttämällä mahdollisimman vähän komponentteja virran kulkureitillä sekä soveltamalla pehmeää kytkentää kaikissa tilanteissa. Lopuksi esitellään prototyyppi, jonka tarkoitus oli selvittää laitteen toiminta ja ongelmakohdat käytännössä.

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Transportation of fluids is one of the most common and energy intensive processes in the industrial and HVAC sectors. Pumping systems are frequently subject to engineering malpractice when dimensioned, which can lead to poor operational efficiency. Moreover, pump monitoring requires dedicated measuring equipment, which imply costly investments. Inefficient pump operation and improper maintenance can increase energy costs substantially and even lead to pump failure. A centrifugal pump is commonly driven by an induction motor. Driving the induction motor with a frequency converter can diminish energy consumption in pump drives and provide better control of a process. In addition, induction machine signals can also be estimated by modern frequency converters, dispensing with the use of sensors. If the estimates are accurate enough, a pump can be modelled and integrated into the frequency converter control scheme. This can open the possibility of joint motor and pump monitoring and diagnostics, thereby allowing the detection of reliability-reducing operating states that can lead to additional maintenance costs. The goal of this work is to study the accuracy of rotational speed, torque and shaft power estimates calculated by a frequency converter. Laboratory tests were performed in order to observe estimate behaviour in both steady-state and transient operation. An induction machine driven by a vector-controlled frequency converter, coupled with another induction machine acting as load was used in the tests. The estimated quantities were obtained through the frequency converter’s Trend Recorder software. A high-precision, HBM T12 torque-speed transducer was used to measure the actual values of the aforementioned variables. The effect of the flux optimization energy saving feature on the estimate quality was also studied. A processing function was developed in MATLAB for comparison of the obtained data. The obtained results confirm the suitability of this particular converter to provide accurate enough estimates for pumping applications.

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A VDAC é a proteína mais abundante na membrana mitocondrial externa. Exerce o controle da atividade desta organela através da regulação da troca de metabólitos e tem função crucial no mecanismo de apoptose. Em nosso caso, os estudos dos complexos protéicos, das interações entre a VDAC e outras proteínas presentes no interior do neurônio que auxiliam na manutenção das funções das organelas e da célula, fazem parte da chamada interactômica. O presente estudo determinou o interactoma do complexo protéico Hexoquinase-VDAC-ANT presente em cérebros murino, bovino e aviar. Nosso objetivo foi identificar se as expressões diferenciadas da VDAC1 e VDAC2 verificadas nos cérebros murino, aviar e bovino, estão associadas a diferenças nos interactomas dessas proteínas. Este estudo revelou que as espécies aviar e bovina apresentaram o maior número de complexos protéicos contendo VDACs (5) quando comparadas com os neurônios de rato (1), o que é indicativo de uma cinética diferencial de montagem ou desmontagem do complexo. Além disso, a VDAC mitocondrial neuronal aviar também interage com mais proteínas em relação à VDAC mitocondrial neuronal bovina, o que é resultado de uma composição de subunidades diferenciada. Tais resultados indicam diferenças significativas quanto ao metabolismo energético e apoptótico no cérebro aviar, bovino e murino, existindo interações diferenciais da VDAC no cérebro aviar.