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    Wyświetlanie 1-4 z 4
    Tytuł:
    Developing measures to eliminate of hydrate formation in underground gas storages
    Autorzy:
    Volovetskyi, V. B.
    Doroshenko, Ya. V.
    Bugai, A. O.
    Kogut, G. M.
    Raiter, P. M.
    Femiak, Y. M.
    Bondarenko, R. V.
    Powiązania:
    https://bibliotekanauki.pl/articles/2172156.pdf
    Data publikacji:
    2022
    Wydawca:
    Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
    Tematy:
    well
    flowline
    hydrate formation
    local constraint
    regulating choke
    studnia
    powstawanie hydratów
    współczynnik ograniczenia
    dławik
    Opis:
    Purpose The objective of this article is the analysys of methods for preventing and eliminating hydrates formations, classifying them and choosing the best ones for use in underground gas storage facilities. Comprehensive measures for the stable operation of gas storage facilities in the presence of conditions for the occurrence of hydrates formations were developed. Zones, being potentially prone to the hydrates formation during the gas storage facilities operation were identified. Design/methodology/approach The operational parameters of gas storage wells during gas withdrawal are analyzed. The identified wells were operated under difficult conditions due to the deposition of hydrates on the wellheads, in flowlines and process equipment of gas storage facilities. The places of the highest hydrates accumulation on underground gas storages were determined: from the bottomhole of wells to the gas purification unit of the gas gathering station. Hydrate-prone zones were identified by computational fluid dynamic (CFD) modeling at the location of regulating choke installations in underground gas storage facilities. Findings The zones of the greatest hydrates accumulation on underground gas storages were determined: from the bottomhole of wells to the gas purification unit of the gas gathering station. The analysis of the methods used in gas storage facilities of Ukraine to prevent and eliminate hydrates formation was out. A set of measures was proposed to prevent the hydrates formation in storage facilities to ensure their stable operation. Based on the Euler approach (Mixture model) by CFD modeling, zones prone to hydrates formation were determined at the installation site of regulating chokes in underground gas storages. The influence of the degree of fittings opening on the location of potential zones prone to hydrates formation was estimated. The gas-dynamic processes in the internal cavity of the gas pipeline at the installation site of the control fittings were studied and their influence on the distribution of bulk particles of the gaseous and liquid phases was established. Based on the studies performed, it was recommended to change periodically the mode of well operation for a certain time by opening or closing the regulating choke under favorable conditions for the formation of hydrates, especially at low ambient temperatures. Research limitations/implications The obtained results of experimental studies and calculations showed that in order to solve the problem of hydrates formation at gas storage facilities, it is advisable to use diverse measures through the introduction of modern intelligent systems for monitoring and controlling the technological process. Further refinement of the algorithm of the proposed monitoring and control system with its approbation in production was provided. Practical implications The results of the experimental studies and CFD modeling carried out allowed providing a more reasonable approach to the application of various available methods and measures to prevent hydrates formation in underground gas storage facilities. This approach made it possible to develop new effective ways and measures to prevent such complication. Originality/value Based on the conducted experimental studies and modeling, the major zones prone to hydrates formation in underground gas storages were determined. The developed measures will allow timely detection and prevention of hydrates formation at gas storage facilities are original.
    Źródło:
    Journal of Achievements in Materials and Manufacturing Engineering; 2022, 111, 2; 64--77
    1734-8412
    Pojawia się w:
    Journal of Achievements in Materials and Manufacturing Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bailout expectation and debt risks of Chinese local governments: an evidence-based study on quasi-municipal bonds
    Autorzy:
    Zou, Jin
    Cui, Chuantao
    Powiązania:
    https://bibliotekanauki.pl/articles/2116120.pdf
    Data publikacji:
    2021-12-31
    Wydawca:
    Fundacja Copernicus na rzecz Rozwoju Badań Naukowych
    Tematy:
    local government debt
    bailout expectation
    soft budget constraint
    Opis:
    Expectation of bailout by central government distorts the debt pricing mechanism, and as a result local governments run the risk of incurring debts because of the soft budget constraint issues. Thus finding ways to harden budget constraints is crucial, but there is little empirical evidence as to their effects. Since the “No Bailout” signal sent by China’s central government through the new Budget Law provides an ideal quasi-experiment, this study examines its impact on quasi-municipal bonds. Using micro-level data, the authors find that the policies have effectively dispelled expectations of bailout and improved debt pricing mechanism, yet implicit guarantees from local governments still exist. Therefore, the authors show that the policy of the Chinese central government has a certain level of credibility, and that policies combining government credibility and market forces can help to resolve debt risks of local governments.
    Źródło:
    The Copernicus Journal of Political Studies; 2021, 2; 5-31
    2299-4335
    Pojawia się w:
    The Copernicus Journal of Political Studies
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The constraints of the market access in case of the Hungarian organic animal products
    Ograniczenia w dostępie do rynku na przykładzie węgierskich ekologicznych produktów zwierzęcych
    Autorzy:
    Szabo, V.
    Percsi, K.N.
    Powiązania:
    https://bibliotekanauki.pl/articles/870902.pdf
    Data publikacji:
    2013
    Wydawca:
    The Polish Association of Agricultural and Agribusiness Economists
    Tematy:
    constraint
    market access
    Hungary
    organic product
    animal product
    demand
    solvent demand
    cooperation
    local market
    sustainability
    land protection
    Opis:
    The aim of the article is to give an insight to the problems of the Hungarian organic farming and to highlight the areas which should be developing in order to improve the domestic market and access more export market. This article presents the results of two surveys. Questionnaires were sent to the Hungarian organic farmers. The questions in the questionnaires differed from each other since the aims of the surveys varied. The answers received and the information gathered served as a good basis for the analyses of the state of the sector and the factors which impede competitiveness. No obvious relation can be found between the increase of stakeholders integrated in the supply chain and the extent of the farmers’ share from the profit on products. In organic animal keeping, long-term relations are characteristic, which rarely work without problems. According to the farmers’ opinion, the most important hindering factors of production are the lack of solvent demand and adequate promotion activities, also underpinned by the two empirical surveys.
    Celem badań było przedstawienie problemów ekologicznej produkcji zwierzęcej na rynku węgierskim, ze wskazaniem obszarów, które powinny być rozwijane w celu poprawy dostępu do rynku krajowego i na eksport. Przedstawiono wyniki dwóch badań. Kwestionariusze skierowano do hodowców zwierząt ekologicznych i do rolników uprawiających rośliny ekologiczne. Otrzymane informacje posłużyły do analizy stanu sektora oraz określenia czynników hamujących konkurencyjność. W związku z naciskiem na ochronę środowiska, bezpieczeństwo żywnościowe i znakowanie produktów, rolnictwo ekologiczne jest alternatywą dla niektórych ogniw łańcucha dostaw (interesariuszy). Krajowa produkcja artykułów ekologicznych straciła jednak na znaczeniu po przystąpieniu Węgier do UE. 80-90% węgierskich produktów ekologicznych eksportuje się do państw ościennych. 60% gruntów (13 069,73 ha) kontrolowanych przez Biokontroll Hungária z o.o. stanowią łąki, pastwiska i ugory. Inwentarz żywy, taki jak: bydło, owce i gęsi nie przekracza 1 SD na 1 ha, mimo że oczekiwana wartość powinna osiągać 2,75% całego inwentarza. Według opinii badanych rolników, głównymi barierami ekologicznej produkcji są brak popytu na taki towar i brak odpowiednich działań promocyjnych.
    Źródło:
    Roczniki Naukowe Stowarzyszenia Ekonomistów Rolnictwa i Agrobiznesu; 2013, 15, 6
    1508-3535
    2450-7296
    Pojawia się w:
    Roczniki Naukowe Stowarzyszenia Ekonomistów Rolnictwa i Agrobiznesu
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A second-order sufficient condition for a weak local minimum in an optimal control problem with an inequality control constraint
    Autorzy:
    Osmolovskii, Nikolai P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2183496.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    critical cone
    quadratic form
    first order tangent
    second order tangent
    second order optimality conditions
    weak local minimum
    inequality control constraint
    Pontryagin’s maximum principle
    Opis:
    This paper is devoted to a sufficient second-order condition for a weak local minimum in a simple optimal control problem with one control constraint G(u) ≤ 0, given by a C2-function. A similar second-order condition was obtained earlier by the author for a strong minimum in a much more general problem. In the present paper, we would like to take a narrower perspective than before and thus provide shorter and simpler proofs. In addition, the paper uses the first and second order tangents to the set U, defined by the inequality G(u) ≤ 0. The main difficulty of the proof, clearly shown in the paper, refers to the set, where the gradient Hu of the Hamiltonian is small, but the condition of quadratic growth of the Hamiltonian is satisfied. The paper can be valuable for self-explanation and provides a basis for extensions.
    Źródło:
    Control and Cybernetics; 2022, 51, 2; 151--169
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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