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HES udens rezimu vadisana un to prognozesana
No full textHydroenergy is a significant component of the energy industry, accounting for 17% of the electricity produced (and even 25% of the total power). Hydro electric stations possess high performance indices, which, in particular, allow for their fast loading and unloading. They participate in the frequency and power optimisation process and in the regulation of energy market transactions concerning power flows; in these stations operative and emergency reserves are stored, which facilitate the operation of other electric stations' equipment. In the operative meaning, the only drawback of hydroenergy generation is that it is very difficult to forecast, which introduces complications into the planning of power systems' balances, tariffs, investments, and into the conclusion of supply contracts. When analyzing the methods for HES management, it becomes clear that the forecasting of annual production is one of the most important problems in this area. In an attempt to solve this problem, the research work initially concerned the properties of Daugava's waterflows. In the course of work it was clarified that for the analysis it was necessary to convert the original function data into some auxiliary functions in order that simple and log Fourier transformations could be applied. After having performed the analysis with the auxiliary functions, the results were to revert to the initial coordinates (originals) by means of function differentiation. As a result it was revealed that the annual waterflows possess stable cyclic properties which can be expressed analytically as a time function. After subtracting the determinate components from the natural process a "remainder" function is left, which possesses a high-frequency character. It was revealed that this component is also partially predictable. For this purpose in the future wavelet transformation and artificial neuron networks are to be employed. As a result, the "noise" of the initial data will be reduced to a small specific weight. Using the hierarchial digital filters it was possible to perform analysis, taking as the basis the long-term observations of riverflows reported in the UNESCO publications. The analysis has been performed based on the observation data on more than 45 world's rivers. It was found that waterflows of all the rivers possess similar character. These processess have regional phase distinctions, which in the future are to be explained in the framework of other sciences (astro-, geo-, and atmospheric physics). The global phase maps for riverflows have been built. It became clear that for such global phenomena there should be a common cause. The most probably these are variations in the Solar intensity, which have been observed and recorded since the 18th century. The comparison of the waterflow integral function with the Solar intensity process revealed that in both cases the first harmonics have similar low-frequency (centenary cycles) and high-frequency (11-year cycles) spectra. Also, the causes of high-amplitude rare waterflow deviations have been revealed. It turned out that they occur in the spans of extremum values of 11-year Solar cycles, coinciding with them by sign. It was thus found that waterflows contain up to five components of different frequency, which are to be forecast for the nearest years to come and the results are to be summed up to obtain a full forecast. The program package required for solving the task has been developed/estimated. As a result of the work performed, new knowledge has been acquired that can be employed in practice in the energy industry and other branches of national economy as well as to be used as a basis for further development of different sciences.Abstract in Latvian, English, Russian. Separate summaries in Latvian and EnglishAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi
HES REŽĪMU VADĪŠANA UN TO PROGNOZĒŠANA
No full textHidroenerģētika ir būtiska enerģētikas sastāvdaļa. Tajā tiek izstrādāti 17% elektroenerģijas, bet jaudas ziņā tā ir pat 25% no kopējas jaudas. Hidroelektrostacijām ir augstas operatīvas īpašības, kas ļauj ātri uzņemt un samazināt slodzi. Tās piedalās frekvences un jaudas optimizācijas procesā un enerģētiskā tirgus darījumos plūsmu regulēšanā, tajās izvieto operatīvas un avārijas rezerves. Tās atvieglo citu elektrostaciju iekārtu darbu.
Vienīgais hidroenerģētikas trūkums operatīvā ziņā ir lielas grūtības tās darbības prognozēšanā, kas ienes grūtības energosistēmu bilanču, tarifu, investīciju plānošanā un gadu piegādes līgumu slēgšanā.
Analizējot hidroelektrostaciju vadīšanas metodes, kļūst skaidrs, ka gadu izstrādes prognozēšana ir viena no svarīgākām šīs nozares problēmām.
Mēģinot atrisināt šo problēmu, darbs sākās ar Daugavas gadu caurplūdamības īpašību izpēti. Darba gaitā noskaidrojās, ka analīzei izejas datu funkcijas jāpārveido palīgfunkcijās parastās un logu, Furjē-pārveidojumu pielietošanai. Veicot analīzi ar paligfunkcijām, rezultāti jāatgriež sākotnējās koordinātēs (oriģinālos) ar funkciju diferencēšanas palīdzību. Rezultātā noskaidrojās, ka gadu caurplūdamībām ir stabilas cikliskas īpašības, ko var izteikt analītiski.
Pēc determinēto komponenšu atskaitīšanas no dabīga procesa paliek “atlikuma” funkcija, kam ir augstfrekvences raksturs. Noskaidrojās, ka arī šo komponentu iespējams daļēji prognozēt. Šim nolūkam nākotnē būs jāizmanto veivlet-pārveidojums un mākslīgos neironu tīklus. Rezultātā izejas datu “troksnis” tiek novests līdz nelielam īpatsvaram.
Iegūstot pētījumam hierarhisko ciparu filtru, kļuva iespējams atkārtot analoģisku analīzi, ņemot tam par pamatu jebkuras upes daudzgadīgus novērojumus. Tam varēja izmantot datus, publicētos UNESKO atskaitēs, kam pielietots Furjē-pārveidojums.
Analīze tika veikta uz vairāk par 45 pasaules upju novērojumu datu pamata. Noskaidrojās, ka visu upju caurpludamībām ir līdzīgs raksturs. Vienīgi procesiem ir reģionālas fāžu atšķirības, kuru iemeslus turpmāk būtu jāizskaidro citu zinātņu ietvaros (astro-, ģeo-, atmosfēras fizikās).
Uzbūvētas pasaules upju caurplūdamību fāžu kartes.
Kļuva skaidrs, ka šādām globālām parādībām ir jābūt kopējam spēcīgam iemeslam. “Aizdomas” krita uz Saules intensitātes izmaiņām. Tās tika novērotas un reģistrētas sākot ar 18 g.s..
Salīdzinot caurplūdamību integrālo funkciju ar Saules intensitātes procesu, noskaidrojas, ka procesu pamatharmonikām ir līdzīgi gan zemfrekvences (simtgadu cikli), gan augstfrekvences (11-gadīgie cikli) spektrā.
Noskaidrojās arī caurplūdamības retu, bet lielu amplitūdu noviržu iemesli. Izrādās, ka tie notiek 11-gadīgo Saules ciklu ekstremālu lielumu posmos, sakrītot ar tiem pēc zīmes.
Noskaidrojās arī retu lielu amplitūdu caurplūdamības noviržu laiki. Izrādās, kā tās veidojas periodos, kas atbilst Saules 11-gadīgo intensitātes atvasinājuma zīmes maiņām.
Caurplūdamības satur līdz pieciem dažādu frekvenču komponentu, kuri jāprognozē turpmākiem gadiem un rezultāti jāsummē kopējas prognozes iegūšanai.
Noskaidrota programmatūra, kas ir nepieciešama uzdevuma risināšanai.
Veiktā darba rezultātā iegūtas jaunas zināšanas, kurus var praktiski izmantot enerģētikā un dažādos tautsaimniecības nozarēs, un tās var tikt izmantotas vairāku zinātņu tālākai attīstībai
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Peculiarities of Annual Flows of World’s Rivers
No full textIn this monograph authors clarified that the annual throughflow of the Latvian river Daugava has certain relationships, researched and found them also on other 50 most important rivers in the world, which opened a possibility to advance a well-grounded hypothesis of the causes of the phenomenon. The goal of the work is, based upon the experience accumulated in the management of energy systems and HPPs, to make clear the significance of the latter under the conditions of open market. Having ascertained that there was a need to improve the forecasting methods as far as the hydro energy production is concerned, it was necessary to verify the possibilities of such methods with the help of the energoinformatic discipline
Application of Highly Durable Surface Forming Technology (HDST) in Power Industry
No full textThis article addresses a complex solution that allows
increasing the stability of power network operation by
improving efficiency of nodes and components, saving the
energy as well as reducing the costs related to operating
different equipment of energy industry. Based on theoretical
foundation built by different state institutes, scientific research
organizations and private companies during more than 20
years period of time, this article addresses the possible
application of highly durable surface forming technology
(HDST) in power industry, that allows to build up a metalceramic
layer on top of rubbing metallic surfaces, and that, in
its turn, opens new, earlier unavailable, possibilities for
different types of equipment in power industry
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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