1. Improvement of biogas production utilizing a complex anaerobic digestion model and gradient-based optimizationTina Kegl, Breda Kegl, Marko Kegl, 2024, izvirni znanstveni članek Opis: : Anaerobic digestion (AD) is a promising technology for renewable energy production from organic waste. In order to maximize the produced biogas quantity and quality, this paper deals with the optimization of the AD process in a CSTR bioreactor of a full-scale biogas plant. For this purpose, a novel approach was adopted coupling, a highly complex BioModel for AD simulation, and a gradient-based optimization method. In order to improve AD performance, the dosages of various types of biological additives, the dosages of inorganic additives, and the temperature in the bioreactor were optimized in three different scenarios. The best biogas quality was obtained using multi-objective optimization, where the objective function involves the following two conflicting objectives: the maximization of biogas production and minimization of the needed heating energy. The obtained results show that, potentially, the content of CH4 can be increased by 11%, while the contents of H2, H2S, and NH3 can be reduced by 30%, 20%, and 81% when comparing the simulation results with the experimental data. The obtained results confirm the usefulness of the proposed approach, which can easily be adapted or upgraded for other bioreactor types.
Ključne besede: additives, anaerobic digestion, approximation method, BioModel, complex substrate, gradient-based optimization, process conditions
Objavljeno v DKUM: 12.03.2024; Ogledov: 298; Prenosov: 16
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3. On graph identification problems and the special case of identifying vertices using pathsFlorent Foucaud, Matjaž Kovše, 2012, objavljeni znanstveni prispevek na konferenci Opis: V članku uvedemo problem identifikacije s potmi: pokritje z identifikacijskimi potmi grafa ▫$G$▫ je množica poti ▫$mathcal{P}$▫, za katere velja, da vsako vozlišče leži na vsaj eni poti iz ▫$mathcal{P}$▫, in za vsak par vozlišč $u,v$ obstaja pot iz ▫$mathcal{P}$▫, ki vsebuje natanko eno izmed vozlišč ▫$u$▫ in ▫$v$▫. Ta problem je soroden raznim variantam identifikacijskih problemov. Problem pokritja z identifikacijskimi potmi obravnavamo na nekaterih družinah grafov. Izpeljemo optimalne velikosti za pokritja z identifikacijskimi potmi za: poti, cikle, hiperkocke in topološka drevesa ter podamo zgornjo mejo za poljubna drevesa. Podamo tudi spodnje in zgornje meje za minimalno velikost pokritja z identifikacijskimi potmi za poljubne grafe in obravnavamo natančnost mej. Pokažemo, da poljuben povezan graf ▫$G$▫ premore pokritje z identifikacijskimi potmi velikosti kvečjemu ▫$Biglceil frac{2(|V(G)|-1)}{3} Bigrceil$▫. Obravnavamo tudi računsko zahtevnost pripadajočega optimizacijskega problema in pokažemo, da v primeru, ko so dolžine poti iz pokritja fiksne dolžine, sodi problem med APX-polne probleme.
Ključne besede: matematika, teorija grafov, poti, aproksimacija, mathematics, graph theory, test cover, identification, paths, approximation
Objavljeno v DKUM: 10.07.2015; Ogledov: 978; Prenosov: 89
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4. Rasa, Ioan: One-dimensional diffusions and approximation. (English). - [J] Mediterr. J. Math. 2, No. 2, 153-169 (2005). [ISSN 1660-5446]Miklavž Mastinšek, 2007, recenzija, prikaz knjige, kritika Ključne besede: matematika, enoparametrična polgrupa, stahastična enačba, aproksimacija, mathematics, one-parameter semigroup, stochastic equation, positive approximation process
Objavljeno v DKUM: 10.07.2015; Ogledov: 832; Prenosov: 35
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5. 2-local distributed algorithms for generalized coloring of hexagonal graphsPetra Šparl, Janez Žerovnik, 2005, objavljeni znanstveni prispevek na konferenci Opis: A 2-local distributed approximation algorithm for multicoloring of a triangle-free hexagonal graph which uses at most ▫$lceil frac{5omega(G)}{4} rceil + 3$▫ colors is presented.
Ključne besede: matematika, teorija grafov, barvanje grafov, aproksimacijski algoritem, frekvenčni načrt, ▫$k$▫-lokalen porazdeljen algoritem, mathematics, graph theory, approximation algorithms, graph coloring, frequency planning, ▫$k$▫-local distributed algorithm
Objavljeno v DKUM: 10.07.2015; Ogledov: 1285; Prenosov: 100
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6. Simpler multicoloring of triangle-free hexagonal graphsIgnasi Sau Walls, Petra Šparl, Janez Žerovnik, 2012, objavljeni znanstveni prispevek na konferenci Opis: Preslikavo ▫$f colon V(G)to 2^{{1,.,n}}$▫, za katero velja ▫$|f(v)| ge p(v)$▫ za vsako točko ▫$v in V(G)$▫ in ▫$f(v) cap f(u) = emptyset$▫ za poljubni sosedi ▫$u$▫ in ▫$v$▫ grafa ▫$G$▫, imenujemo dobro ▫$n-[p]$▫barvanje grafa ▫$G$▫. Najmanjše naravno število, za katero obstaja dobro ▫$n-[p]$▫barvanje grafa ▫$G$▫, ▫$chi_p(G)$▫, imenujemo uteženo kromatično število grafa ▫$G$▫. Iskanje uteženega kromatičnega števila za inducirane podgrafe trikotniške mreže (imenovane heksagonalni grafi) ima aplikacije v celičnih mrežah. Uteženo kromatično število grafa ▫$G$▫, ▫$omega_p(G)$▫, je enako maksimalni uteži klike grafa ▫$G$▫, kjer utež klike predstavlja vsoto uteži njenih točk. McDiarmid in Reed (2000) sta postavila domnevo, da za poljuben heksagonalen graf brez trikotnikov velja ▫$chi_p(G) le (9/8)omega_p(G) + C$▫. V članku je podan algoritem, ki poda dobro ▫$7-[3]$▫barvanje poljubnega heksagonalnega grafa brez trikotnikov, ki aplicira neenakost ▫$chi_p(G) le (7/6)omega_p(G) + C$▫. Naš rezultat podaja krajšo alternativo induktivnega dokaza Haveta (2001) in izboljša kratek dokaz Sudepa in Vishwanathana (2005), ki sta dokazala obstoj ▫$14-[6]$▫barvanja. (Omeniti je potrebno, da v sklopu našega dokaza uporabimo izrek o štirih barvah.) Vsi koraki algoritma so linearni glede na ▫$|V(G)|$▫, razen 4-barvanje ravninskega grafa. Novi pristop lahko v prihodnje pripomore k dokazovanju domneve McDiarmida in Reeda (2000).
Ključne besede: matematika, teorija grafov, aproksimacijski algoritem, barvanje grafov, dodeljevanje frekvenc, celične mreže, mathematics, graph algorithm, graph theory, approximation algorithm, graph coloring, frequency planning, cellular networks
Objavljeno v DKUM: 10.07.2015; Ogledov: 1351; Prenosov: 88
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8. Modelling airport congestion chargesMilan Janić, 2005, izvirni znanstveni članek Opis: This article deals with modelling congestion charges at an airport. In this context, congestion charging represents internalizing the cost of marginal delays that a flight imposes on other flights due to congestion. The modelling includes estimating congestion and flight delays, the cost of these delays and the efficiency of particular flights following the introduction ofa congestion charge. The models are applied to an airport / New York LaGuardia / to illustrate their ability to handle more realistic congestion scenarios as well as the nature of the congestion to be charged, the effectiveness of the congestion charge and a sensitivity analysis based on changes in the nature of congestion as well as characteristics of demand in terms of flight-aircraft type and airport capacity.
Ključne besede: airport, congestion charging, queueing theory, diffusion approximation, New York LaGuardia airport
Objavljeno v DKUM: 05.06.2012; Ogledov: 1848; Prenosov: 205
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9. An efficient approximation of arbitrary curves and surfaces using intersecting polylines and meshesYong Kui Liu, Jian Yun, Xiao Niu Li, Borut Žalik, 2008, izvirni znanstveni članek Opis: This paper presents an efficient method for approximating curves and surfaces. An idea is introduced using a circle, where an arc-intersecting polyline is used instead of the traditional inner-arc polyline. The approach is then generalized to arbitrary 2D curves. The method is extended into 3D, where the approximation of spherical surface is developed based on surface-intersecting facets. Finally, a method is described for approximating the general curved surface. Theoretical analysis and the experimental results showed that the new algorithm requires considerably less geometric data at the same approximation error than the traditional one.
Ključne besede: curve, surface, approximation, engineering software
Objavljeno v DKUM: 01.06.2012; Ogledov: 1643; Prenosov: 92
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