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SINTEZA KONSTRUKCIJE JEKLENIH HAL Z MEŠANIM CELOŠTEVILSKIM NELINEARNIM PROGRAMIRANJEM
Tomaž Žula, 2009, dissertation

Abstract: V doktorski disertaciji predstavljamo celovit pristop k sočasnemu optimiranju mase, topologije, diskretnih materialov in standardnih prerezov konstrukcije jeklenih hal. Optimiranje bomo izvedli z mešanim celoštevilskim nelinearnim programiranjem (MINLP). Ker z MINLP izvajamo optimiranje topologije in standardnih dimenzij na način, da se v optimizacijskem procesu posamezni konstrukcijski elementi računsko odvzamejo in/ali dodajajo, izračunavajo pa se tudi standardni materiali, dimenzije in oblika konstrukcije, z MINLP v bistvu izvajamo sintezo konstrukcij. V doktorski disertaciji tako obravnavamo sintezo realnih inženirskih konstrukcij jeklenih hal velikega obsega.
Keywords: gradbeništvo, mehanika, konstrukcija, sinteza, sinteza konstrukcij, optimiranje, optimiranje konstrukcij, optimiranje topologije, diskretno optimiranje, mešano celoštevilsko nelinearno programiranje, MINLP, algoritem zunanje aproksimacije s sprostitvijo enačb, OA/ER algoritem, modofocirani algoritem OA/ER, trifazana MINLP strategija, jeklene hale
Published: 27.05.2010; Views: 3857; Downloads: 252
.pdf Full text (854,43 KB)

4.
NAČRTOVANJE IN SINTEZA KEMIJSKIH PROCESOV Z UPORABO UČINKOVITIH MODELNIH TEHNIK IN REŠITVENIH STRATEGIJ
Marcel Ropotar, 2009, dissertation

Abstract: V doktorski disertaciji obravnavamo modelne tehnike in strategije za reševanje sinteznih problemov, kjer nastanejo zapleteni modeli, ki so težko rešljivi. Modeli so kombinatorično zahtevni, nelinearni in/ali nekonveksni, zato se kljub že razvitim metodam in algoritmom pogosto pojavijo potrebe po novih, učinkovitejših strategijah in metodah. V prvem delu predstavljamo alternativno formulacijo konveksne lupine, ki temelji na mešano celoštevilski transformaciji spremenljivk. Transformacija spremenljivk transformira spremenljivke z ničelno spodnjo mejo v spremenljivke z ne-ničelno spodnjo mejo. Tako izvajamo optimiranje v ožjem preslikanem dopustnem prostoru lokalnih spremenljivk, to je spremenljivk, ki pripadajo alternativnim procesnim enotam. To nam pri reševanju mešano celoštevilskih linearnih in nelinearnih optimizacijskih primerov (MILP in MINLP) omogoča uporabo ne-ničelnih spodnjih mej. Z uporabo ne-ničelnih spodnjih mej se izognemo deljenju z nič in drugim matematičnim singularnostim. Pogosto pa so ne-ničelne spodnje meje uporabne, kadar imamo opravka s spremenljivkami, kot sta temperatura in pretok, ki morata imeti ne-ničelne vrednosti tudi kadar procesna enota ni izbrana. S transformacijo spremenljivk smo i) pretvorili konvencionalno formulacijo konveksne lupine v alternativno formulacijo in ii) konvencionalni algoritem zunanje poenostavitve spremenili v alternativni algoritem OA. Alternativno formulacijo konveksne lupine smo primerjali s formulacijo veliki-M in konvencionalno formulacijo na treh sinteznih primerih in izvedli več različnih eksperimentov. Rezultati kažejo, da je alternativna formulacija v večini primerov najbolj učinkovita glede računalniškega časa, števila iteracij in vozlišč. Ugotovili smo, da izbor vrednosti spremenljivk, ko alternativa ni izbrana, zelo vpliva na učinkovitost alternativne formulacije; in da je najprimernejša in najenostavnejša izbira kar spodnja ne-ničelna meja. Alternativno formulacijo in alternativni algoritem smo vnesli v procesni sintetizer MIPSYN in pri tem zmodelirali nove logične povezovalne člene in sprogramirali nov preprocesor za zunanje poenostavitve. Pogosto je dolg čas reševanja procesnih sinteznih problemov posledica zapletenih modelov reaktorjev. Zato smo za reaktorje, ki so opisani z diferencialnimi enačbami (šaržni, cevni) in jih rešujemo z metodo ortogonalne kolokacije končnih elementov, predlagali učinkovito numerično proceduro za reševanje. V sklopu procedure smo razvili model za dinamično optimiranje šaržnega reaktorja in preizkušali različne strategije in sheme, s katerimi smo povečevali robustnost modela. Nazadnje smo razvili še model za načrtovanje fleksibilnega šaržnega reaktorja, s katerim je mogoče tolerirati odstopanja procesnih parametrov. Pri reševanju motivacijskega primera šaržnega reaktorja se je kot najučinkovitejši izkazal model NLP s pomičnimi končnimi elementi. Ta model smo nato uporabili tudi za modeliranje niza elementov v cevnem reaktorju in izvedli sintezo MINLP študijske procesne sheme za proizvodnjo alilklorida ter z eno-parametričnim optimiranjem iz najboljših rešitev določili še ekonomsko območje. S predlagano alternativno formulacijo, novimi strategijami in robustnimi modeli za optimiranje reaktorjev je mogoče lažje reševati zapletene sintezne probleme, procesni sintetizer MIPSYN pa je tako postal še učinkovitejše programsko orodje za sintezo procesov in reševanje drugih tehniških problemov.
Keywords: procesna sinteza, procesni sintetizer, konveksna lupina, transformacija spremenljivk, splošno disjunktno programiranje, zunanje poenostavite, NLP, MINLP, šaržni reaktor, cevni reaktor, ortogonalna kolokacija, diferencialno-algebrski sistem enačb
Published: 02.12.2009; Views: 2651; Downloads: 204
.pdf Full text (2,36 MB)

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Optimiranje konstrukcij : izbrana poglavja MINLP
Stojan Kravanja, 2006, reviewed university, higher education or higher vocational education textbook

Keywords: optimiranje konstrukcij, MINLP, optimiranje topologije, optimiranje zveznih parametrov, sočasno optimiranje, sinteza večdelne lesene konzole
Published: 31.05.2012; Views: 1241; Downloads: 51
URL Link to full text

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Synthesis of non-isothermal heat integrated water networks in chemical processes
Miloš Bogataj, Miguel J. Bagajewicz, 2008, original scientific article

Abstract: This paper presents a new approach for the simultaneous synthesis and optimization of heat integrated water networks. A new superstructure for heat exchanger network (HEN) synthesis is proposed. The procedure is based on mixed integer non-linear mathematical programming (MINLP). Four relevant examples are presented to illustrate various aspects of the proposed approach.
Keywords: chemical processing, chemical process design, process water networks, water networks, wastewater minimization, heat integration, MINLP, HEN synthesis, superstructures, process synthesis
Published: 31.05.2012; Views: 1233; Downloads: 50
URL Link to full text

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MINLP optimization of a single-storey industrial steel building
Tomaž Žula, Zdravko Kravanja, Stojan Kravanja, 2008, original scientific article

Abstract: The paper presents the topology and standard sizes optimization of a single-storey industrial steel building, made from standard hot rolled I sections. The structure consists of main portal frames, connected with purlins. The structural optimization is performed by the Mixed-Integer Non-linear programming approach (MINLP). The MINLP performs a discrete topology and standard dimension optimization simultaneously with continuous parameters. Since the discrete/continuous optimization problem of the industrial building is non-convex and highly non-linear, the Modified Outer- Approximation/Equality-Relaxation (OA/ER) algorithm has been used for the optimization. Alongside the optimum structure mass, the optimum topology with the optimum number of portal frames and purlins as well as all standard cross-section sizes have been obtained. The paper includes the theoretical basis and a practical example with the results of the optimization.
Keywords: civil engineering, topology optimization, sizing optimization, nonlinear programming, MINLP
Published: 31.05.2012; Views: 1308; Downloads: 30
URL Link to full text

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The multilevel MINLP optimization approach to structural synthesis: the simultaneous topology, material, standard and rounded dimension optimization
Stojan Kravanja, Simon Šilih, Zdravko Kravanja, 2005, original scientific article

Abstract: The paper describes the simultaneous topology, material, standard and rounded dimension optimization of mechanical structures, performed by the Mixed-Integer Non-linear Programming (MINLP) approach. Beside the generation of an MINLP mechanical superstructure, the development of a general multilevel MINLP formulation for a mechanical superstructure is presented. The consideration of the discrete materials as well as standard and particularly rounded dimensions in structural synthesis significantly increases the combinatorics of the discrete optimization, which as a result may become too difficult to solve. A Linked Multilevel Hierarchical Strategy (LMHS) has been introduced for the solving of such large combinatorial problems. In order to decrease the effect of non-convexities, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been applied. Four numerical examples of different complexities are presented to illustrate the proposed multilevel MINLP optimization approach: the optimization of two steel trusses, a composite I beam and a hydraulic steel roller gate Intake gate, erected in Aswan II, Egypt.
Keywords: structural optimization, structural synthesis, MINLP, topology opitmization, material optimization, discrete variable optimization, multilevel MINLP strategy, truss, composite beam, roller gate
Published: 01.06.2012; Views: 1573; Downloads: 57
URL Link to full text

9.
MINLP synthesis of reactor networks in overall process schemes based on a concept of time-dependent economic regions
Nataša Iršič Bedenik, Marcel Ropotar, Zdravko Kravanja, 2007, original scientific article

Abstract: The design and optimization of reactor networks using the conventional conceptof attainable region is based on technological (conversion, selectivity, etc.), rather than, economical criteria (cost, profit, etc.). The solution from the economical point of view when the operating and investment costs cannot be neglected may not be optimal, not even in regard to the structure. In order to circumvent this deficiency, the conventional Concentration Attainable Region (CAR) is transformed into an Economic Region (ER) using economic optimization criteria. A novel concept for ER constructionis proposed for multi-D problems. One-parametric NLP or MINLP optimizations with reactor volume as a varying parameter are performed to construct trajectories in the ER. In this way the ER is aided by mathematical programming for 3D or more D problems in order to handle dimensions higher than 2 as degrees of freedom for the economic objective function. ER is attainable (EAR) only when the economic objective function is linear. The more the objective function is discontinuous, discrete, nonlinear and non-convex and the more its cost coefficients vary with time, the less the principles of AR can be applied to ER. However, economically optimal reactor systems always lie at the borders of ERs. Two important insights have been gained during the construction of different time-dependent ERs, which have been used in upgrading the MINLP approach to the synthesis of reactor networks in overall process schemes: (i) A reactor network superstructure has been reestablished based on economical optimization criteria and the principles of ER. (ii) Over a longer period, the performing of a stochastic multi-period MINLP synthesis is recommended, in order to consider the time variability and uncertainties of economic parameters. A special multi-period strategy is proposed to upgrade the efficiency of the MINLP synthesis.
Keywords: concentration attainable region, economic attainable region, discrete nonlinear region, MINLP
Published: 01.06.2012; Views: 1275; Downloads: 74
URL Link to full text

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An integrated strategy for the hierarchical multilevel MINLP synthesis of overall process flowsheets using the combined synthesis/analysis approach
Nataša Iršič Bedenik, Bojan Pahor, Zdravko Kravanja, 2004, original scientific article

Abstract: This paper describes an integrated strategy for a hierarchical multilevel mixed-integer nonlinear programming (MINLP) synthesis of overall process schemes using a combined synthesis/analysis approach. The synthesis is carried out by multilevel-hierarchical MINLP optimization of the flexible superstructure, whilst the analysis is performed in the economic attainable region (EAR). The role of the MINLP synthesis step is to obtain a feasible and optimal solution of the multi-D process problem, and the role of the subsequent EAR analysis step is to verify the MINLP solution and in the feedback loop to propose any profitable superstructure modifications for the next MINLP. The main objective of the integrated synthesis is to exploit the interactions between the reactor network, separator network and the remaining part of the heat/energy integrated process scheme.
Keywords: multilevel MINLP, MINLP synthesis, attainable region, economic attainable region, concentration attainable region, continous stirred tank reactor, plug flow reactor, recycle reactor, nonlinear programming, mixed integer nonlinear programme
Published: 01.06.2012; Views: 1711; Downloads: 62
URL Link to full text

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