1. Fluid flow simulation with an ▫$ℋ^2$▫ -accelerated boundary-domain integral methodJan Tibaut, Jure Ravnik, M Schanz, 2024, izvirni znanstveni članek Opis: The development of new numerical methods for fluid flow simulations is challenging but such tools may help to understand flow problems better. Here, the Boundary-Domain Integral Method is applied to simulate laminar fluid flow governed by a dimensionless velocity–vorticity formulation of the Navier–Stokes equation. The Reynolds number is chosen in all examples small enough to ensure laminar flow conditions. The false transient approach is utilized to improve stability. As all boundary element methods, the Boundary-Domain Integral Method has a quadratic complexity. Here, the ℋ2 -methodology is applied to obtain an almost linear complexity. This acceleration technique is not only applied to the boundary only part but more important to the domain related part of the formulation. The application of the ℋ2 -methodology does not allow to use the rigid body method to determine the singular integrals and the integral free term as done until now. It is shown how to apply the technique of Guigiani and Gigante to handle the strongly singular integrals in this application. Further, a parametric study shows the influence of the introduced approximation parameters. For this purpose the example of a lid driven cavity is utilized. The second example demonstrates the performance of the proposed method by simulating the Hagen–Poiseuille flow in a pipe. The third example considers the flow around a rigid cylinder to show the behavior of the method for an unstructured grid. All examples show that the proposed method results in an almost linear complexity as the mathematical analysis promisses. Ključne besede: boundary-domain integral method, velocity–vorticity, adaptive cross approximation, modified helmholtz equation, Yukawa potential, fast multipole method, ℋ-structure Objavljeno v DKUM: 28.11.2024; Ogledov: 0; Prenosov: 4 Celotno besedilo (3,06 MB) Gradivo ima več datotek! Več... |
2. A point particle source model for conjugate heat and mass transfer in dispersed two-phase flows by BEM based methodsTimi Gomboc, Jurij Iljaž, Jure Ravnik, Matjaž Hriberšek, 2023, izvirni znanstveni članek Ključne besede: boundary-domain integral method, dispersed two-phase flow, two-way coupling, spherical porous particles, drying Objavljeno v DKUM: 28.03.2024; Ogledov: 217; Prenosov: 17 Celotno besedilo (1,81 MB) Gradivo ima več datotek! Več... |
3. Vektorska analizaTina Sovič, Simon Špacapan, 2023, učbenik za višje in visoke šole Opis: V učbeniku Vektorska analiza avtorja, dr. Tina Sovič in dr. Simon Špacapan, predstavita vektorske in skalarne funkcije ene in več spremenljivk. Obravnavata glavne teme iz tega področja, kot so krivulje in ploskve v prostoru, odvod vektorskih funkcij, dvojni in trojni integral, ter krivuljni in ploskovni integral skalarne in vektorske funkcije. Namen učbenika je tudi predstaviti praktične aplikacije teorije vektorskih funkcij na področju inženirske prakse, ki se pojavlja pri reševanju različnih problemov v realnem življenju. Učbenik je opremljen s številnimi grafičnimi prikazi, ki nazorno prikazujejo obravnavano temo, številnimi zgledi, ki na konkretnih primerih prikazujejo uporabo teorije v računskih nalogah, ter nekaterimi vajami, ki so namenjene za samostojno reševanje študentov. Ključne besede: vektorska funkcija, skalarna funkcija, krivulje, ploskve, mnogoterni integral, krivuljni integral, ploskovni integral Objavljeno v DKUM: 25.07.2023; Ogledov: 436; Prenosov: 73 Celotno besedilo (10,89 MB) Gradivo ima več datotek! Več... |
4. Integrabilnost in linearizabilnost persistentnih p : -q resonantnih polinomskih sistemov navadnih diferencialnih enačbMaja Žulj, 2022, doktorska disertacija Opis: Eden izmed osrednjih problemov teorije navadnih diferencialnih enačb je problem integrabilnosti, ki je pomemben za razumevanje bistva teorije diferencialnih enačb in za uporabo diferencialnih enačb pri študiju dinamičnih procesov v realnem svetu. Osrednji problemi te doktorske disertacije so problem središča in z njim povezana integrabilnost ter problem linearizabilnosti p:-q resonantnih sistemov s kvadratnimi nelinearnostmi. Obravnavana je tudi povezava med $p:-q$ resonantnimi sistemi in njim pripadajočimi persistentnimi sistemi.
V uvodu so predstavljeni osnovni pojmi komutativne računske algebre, s poudarkom na lastnostih polinomskih idealov in njihovih raznoterosti. Predstavljene so tudi normalne forme, problem središča in linearizabilnosti sistema ter postopek kompleksifikacije realnih sistemov.
Drugo poglavje je namenjeno posplošitvi pojma p:-q resonantnega središča na persistentno p:-q resonantno središče. Izračunamo vse potrebne in zadostne pogoje za nastop persistentnih središč za pet družin p:-q resonantnih sistemov s kvadratnimi nelinearnostmi. Raziskana je povezava med integrabilnostjo p:-q resonantnih sistemov in integrabilnostjo pripadajočih persistentnih sistemov.
V tretjem poglavju so predstavljeni pogoji za nastop linearizabilnega središča za družino 2:-3 resonantnih sistemov, ki jih dobimo z dekompozicijo raznoterosti ideala, generiranega s količinami linearizabilnosti. Zaradi zahtevnosti izračunov uporabimo pristop, ki temelji na modularni aritmetiki. Za dokazovanje zadostnosti tako pridobljenih pogojev uporabimo več različnih metod, najpogosteje uporabimo metodo, ki temelji na Darbouxjevi teoriji linearizabilnosti.
V zadnjem poglavju obravnavamo relativno nov problem (šibko) persistentnega linearizabilnega središča, ki ga posplošimo na problem (šibko) persistentnega linearizabilnega p:-q resonantnega središča. Obravnavana je povezava med linearizacijsko transformacijo p:-q resonantnega sistema in linearizacijsko transformacijo ustreznega persistentnega p:-q resonantnega sistema. Povezava je ponazorjena na 1:-2 in 2:-3 resonantnih kvadratnih sistemih. Ključne besede: polinomski sistem NDE, p:-q resonantni sistem, problem integrabilnosti, problem linearizabilnosti, količine integrabilnosti, količine linearizabilnosti, persistentno resonantno središče, prvi integral Objavljeno v DKUM: 08.06.2022; Ogledov: 717; Prenosov: 58 Celotno besedilo (1,21 MB) |
5. Nedoslednosti v učbenikih za matematiko : magistrsko deloAnja Pertinač, 2022, magistrsko delo Opis: V magistrskem delu je obravnavan problem nedoslednosti v matematičnih učbenikih za gimnazije, ki so potrjeni za uporabo s strani Ministrstva za izobraževanje, znanost in šport. Magistrsko delo je razdeljeno na poglavja, v katerih so obravnavani posamezni tematski sklopi iz veljavnega učnega načrta. Pri vsakem poglavju so predstavljene vpeljave pojmov iz učnega načrta, kot so zapisane v obravnavanih učbenikih. Izkaže se, da so mnoge med njimi pomanjkljive ali celo nekorektne. V vsakem poglavju je predstavljena tudi možna rešitev, kako vpeljavo narediti korektno. Ključne besede: nedoslednosti, matematični učbeniki, gimnazijsko izobraževanje, naraščanje in
padanje funkcij, geometrijsko zaporedje, sestavljene funkcije, nedoločeni integral, limita in zveznost funkcije Objavljeno v DKUM: 26.05.2022; Ogledov: 877; Prenosov: 79 Celotno besedilo (610,96 KB) |
6. Matematika A : za študente FKKT UMPetra Žigert Pleteršek, Matevž Črepnjak, 2022, učbenik za višje in visoke šole Opis: Visokošolski učbenik predstavlja uvod v matematično analizo na naravoslovno-tehniških fakultetah. Poleg osnovnih pojmov o množicah, logiki in številih so obravnavane realne funkcije in z njimi povezana pojma limite funkcije in zveznosti, ter zaporedja in vrste. Zajete se vsebine diferencialnega računa z aplikacijo odvoda, ter integralni račun. Ključne besede: logika, množice, realne funkcije, limita in zveznost funkcije, zaporedja, vrste, odvod funkcije, integral Objavljeno v DKUM: 18.02.2022; Ogledov: 1460; Prenosov: 592 Celotno besedilo (32,77 MB) Gradivo ima več datotek! Več... |
7. An estimation of the passive pressure against integral bridge abutments considering arching effectsMojtaba Movahedifar, Jafar Bolouri Bazaz, 2013, izvirni znanstveni članek Opis: Most civil engineering structures are subjected to cyclic loading during their service life, such as retaining walls, wave loading on offshore structures, seismic loading and the traffic loading of pavements. In the case of an integral abutment bridge (IAB), as an example, the backfill granular material is subject to slow cyclic stress and strain changes under drained conditions. These bridges are constructed so that the top deck is longitudinally continuous. In other words, IABs are joint-less bridges where the superstructure is connected with the abutment. The rigid connection enables the abutment and superstructure to act as a single structural unit, i.e., the expansion joints which are widely used in traditional bridges are removed in IABs. This removal is mainly due to the high costs of maintenance. The behavior of IABs is dominated by the cyclical temperature changes in the bridge deck. This results in the imposition of cyclical horizontal displacements to the backfill soil of the abutments. The present research is an effort to investigate the induced passive pressure on the IABs, using a laboratory model and an analytical approach. The results indicate that the passive pressure distribution is non-linear and its maximum value along the wall is dependent on the magnitude of the wall rotation and number of cycles. It seems that there are two different mechanisms for this behavior. In the above part of the wall, sand behaves as a plastic material. A decline in the passive pressure in the bottom part, however, is the result of arching. Ključne besede: integral abutment bridge, cyclic displacement, passive pressure, arching Objavljeno v DKUM: 14.06.2018; Ogledov: 1056; Prenosov: 144 Celotno besedilo (609,10 KB) Gradivo ima več datotek! Več... |
8. Double diffusive natural convection in a horizontal porous layer with the boundary domain integral methodRenata Jecl, Janja Kramer Stajnko, Leopold Škerget, 2009, izvirni znanstveni članek Opis: We present the boundary-domain integral method, one of the numerical methods for solving the transport phenomena in porous media. The results for the case of double diffusive natural convection in a porous horizontal layer, which is fully saturated with an incompressible fluid, are obtained. Modified Navier-Stokes equations were used to describe the fluid motion in porous media in the form of conservation laws for mass, momentum, energy and species. Several results for different cases of double diffusive natural convection in a porous horizontal layer are presented and compared with some published studies in which calculations with other numerical methods were performed. Ključne besede: porous media, boundary domain integral method, double diffusive natural convection, Darcy-Brinkman equation Objavljeno v DKUM: 06.06.2018; Ogledov: 1197; Prenosov: 70 Celotno besedilo (454,56 KB) Gradivo ima več datotek! Več... |
9. Systemic logistics providersMimo Drašković, 2016, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: The functioning of a port and shipping system must be perfect in order to provide a competitive advantage and stable position in maritime market. The importance of logistics in business success of port and shipping organizations in contemporary conditions has become crucial. Due to that fact, more and more efforts are put in the designing of integral logistics systems. Thanks to a complex, systemic and networking approach, logistics today is improving the speed and efficiency of operations and significantly influences cost reduction and therewith fulfills one of the basic strategic functions, anticipating necessary key competences of the firm. It is a resource framework for the overcoming of strategic limitations and a method for the enhancement of the competitive position and all marketing and management functions. In addition to that, the integration of partners requires, by rule, a consistent restructuring of the total chain dedicated to the creation of added value, i.e. reengineering of logistics and production business processes. Flexible and small structural units are created, cooperating among each other in a decentralized manner, retaining their key competences and strategic significance for the integral network dominated by a single leading firm as a center of the system, i.e. focus of the supply chain. The paper analyzes the formation of new logistics and marketing paradigm of the beginning of the new century and millennium, anticipating the overcoming of the traditional 3PL three-party logistics concept and formation of contemporary 4PL concept. Ključne besede: logistics, ports, logistic services, integral logistics systems, third party logistics, 3PL, fourth party logistics, 4PL, outsourcing Objavljeno v DKUM: 09.05.2018; Ogledov: 1350; Prenosov: 102 Celotno besedilo (1,14 MB) Gradivo ima več datotek! Več... |
10. Financial system and agricultural growth in UkraineOlena Oliynyk, 2017, izvirni znanstveni članek Opis: Background/Purpose: An effective financial system should increase the efficiency of economic activities. This study provides evidence regarding the importance of financial development for agricultural growth in Ukraine.
Methodology: We used non-integrated and integral indicators, time series and regression analysis to investigate the link between the financial development and agricultural growth.
Results: The results based on integral indicators shows that the financial development does not affect agricultural growth in Ukraine. The study based on non-integrated indicators, which characterizes various aspects of the financial system’s banking component and agricultural growth, provided a significant link between the financial system and agriculture growth. The regression models revealed if bank deposits to GDP (%) increases the value added per worker in agriculture increases exponentially. The results of the study indicate that, agriculture is more sensitive to lending changes than the vast majority of other sectors of the economy. The increasing lending of one UAH (Ukrainian hryvnia) resulted in retail turnover growth of 1.62 UAH, while agricultural gross output, growth was UAH 5.06.
Conclusion: Our results reveal a positive relationship between financial system’s banking component and agriculture growth in Ukraine. The results indicate the necessity for continued research into further developing universal methodological approaches of appraising the nexus of the financial system’s banking component on agriculture growth in general as well separate farm groups. The results of our study has important implications on policy making authorities efforts to stimulate agricultural growth by improving the efficiency of the financial system’s banking component. Ključne besede: agricultural growth, the integral indicator of the agricultural growth, the integral indicator of the financial development, time series analysis, regression analysis, financial system Objavljeno v DKUM: 04.05.2018; Ogledov: 1477; Prenosov: 397 Celotno besedilo (762,63 KB) Gradivo ima več datotek! Več... |