Computer-supported modelling of multimodal transportation networks rationalizationRatko Zelenika
, Slavomir Vukmirović
, Hilmija Mujić
, 2007, kratki znanstveni prispevek
Opis: This paper deals with issues of shaping and functioning of computer programs in the modelling and solving of multimodal transportation network problems. A methodology of an integrated use of a programming language for mathematical modelling is defined, as well as spreadsheets for the solving of complex multimodal transportation network problems. The paper contains a comparison of the partial and integral methods of solving multimodal transportation networks. The basic hypothesis set forth in this paper is that the integral method results in better multimodal transportation network rationalization effects, whereas a multimodal transportation network model based on the integral method, once built, can be used as the basis for all kinds of transportation problems within multimodal transport. As opposed to linear transport problems, multimodal transport network can assume very complex shapes. This paper contains a comparison of the partial and integral approach to transportation network solving. In the partial approach, a straight forward model of a transportation network, which can be solved through the use of the Solver computer tool within the Excel spreadsheet interface, is quite sufficient. In the solving of a multimodal transportation problem through the integral method it is necessary to apply sophisticated mathematical modelling programming languages which support the use of complex matrix functions and the processing of a vast amount of variables and limitations. The LINGO programming language is more abstract than the Excel spreadsheet, and it requires a certain programming knowledge. The definition and presentation of a problem logic within Excel, in a manner which is acceptable to computer software, is an ideal basis, for modelling in the LINGO programming language, as well as a faster and more effective implementation of the mathematical model. This paper provides proof for the fact that it is more rational to solve the problem of multimodal transportation networks by using the integral, rather than the partial method.
Ključne besede: intermodal transportation, transportation networks, spreadsheets, mathematical modelling, programming languages, Lingo, Solver
Objavljeno v DKUM: 01.06.2017; Ogledov: 1205; Prenosov: 110
Celotno besedilo (5,11 MB)
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Hybrid Web Application Development Using Meteor.js FrameworkNejc Burič Novačan
, 2016, diplomsko delo
Opis: This Thesis work shows one of many possible ways of developing hybrid web applications. In the theoretical part, we described the Meteor.js framework and MongoDB database, which we used for realization of the web application. In the presentation of the framework, new and modern methods are described which are used in modern web programming. The hybrid web application which we developed in the practical part enables the user to navigate to tourist attractions in Slovenia. It enables the user to discover and locate natural landmarks, rural tourism, clubs, electric car charging stations, places of interest,, and Tourist Information Centres. Admin can regulate the points of interest with the help of Google API. The application also displays current distances to every point of interest and notifies the users about the changes made by the administrator.
Ključne besede: web programming, hybrid applications, Meteor.js, MongoDB
Objavljeno v DKUM: 22.09.2016; Ogledov: 2206; Prenosov: 150
Celotno besedilo (2,48 MB)
Cost optimal project schedulingUroš Klanšek
, Mirko Pšunder
, 2008, izvirni znanstveni članek
Opis: This paper presents the cost optimal project scheduling. The optimization was performed by the nonlinear programming approach, NLP The nonlinear total project cost objective function is subjected to the rigorous system of the activity preceden- ce relationship constraints, the activity duration constraints and the project duration constraints. The set of activity precedence relationship constraints was defined to comprise Finish-to-Start, Start-to-Start, Start-to-Finish and Finish-to-Finish precedence relationships between activities. The activity duration constraints determine relationships between minimum, maximum and possible duration of the project activities. The project duration constraints define the maximum feasible project duration. A numerical example is presented at the end of the paper in order to present the applicability of the proposed approach.
Ključne besede: project management, scheduling, optimization, nonlinear programming, NLP
Objavljeno v DKUM: 10.07.2015; Ogledov: 1691; Prenosov: 401
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The need for simulation in complex industrial systemsKhalid Aboura
, Miroljub Kljajić
, Ali Eskandarian
, 2012, izvirni znanstveni članek
Opis: We discuss the concept of simulation and its application in the resolution of problems in complex industrial systems. Most problems of serious scale, be it an inventory problem, a production and distribution problem, a management of resources or process improvement, all real world problems require a mix of generic, data algorithmic and Ad-hoc solutions making the best of available information. We describe two projects in which analytical solutions were applied or contemplated. The first case study uses linear programming in the optimal allocation of advertising resources by a major internet service provider. The second study, in a series of projects, analyses options for the expansion of the production and distribution network of mining products, as part of a sensitive strategic business review. Using the examples, we make the case for the need of simulation in complex industrial problems where analytical solutions may be attempted but where the size and complexity of the problem forces a Monte Carlo approach.
Ključne besede: simulation, linear programming, production process
Objavljeno v DKUM: 10.07.2015; Ogledov: 1094; Prenosov: 389
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Copositive and semidefinite relaxations of the quadratic assignment problemJanez Povh
, Franz Rendl
, 2009, izvirni znanstveni članek
Opis: Semidefinite relaxations of the quadratic assignment problem (QAP) have recently turned out to provide good approximations to the optimal value of QAP. We take a systematic look at various conic relaxations of QAP. We first show that QAP can equivalently be formulated as a linear program over the cone of completely positive matrices. Since it is hard to optimize over this cone, we also look at tractable approximations and compare with several relaxations from the literature. We show that several of the well-studied models are in fact equivalent. It is still a challenging task to solve the strongest of these models to reasonable accuracy on instances of moderate size.
Ključne besede: matematično programiranje, problem kvadratičnega prirejanja, kopozitivno programiranje, semidefinitna poenostavitev, quadratic assignment problem, copositive programming, semidefinite relaxations, lift-and-project relaxations
Objavljeno v DKUM: 10.07.2015; Ogledov: 1407; Prenosov: 99
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On Groebner bases and their use in solving some practical problemsMatej Mencinger
, 2013, izvirni znanstveni članek
Opis: Groebner basis are an important theoretical building block of modern (polynomial) ring theory. The origin of Groebner basis theory goes back to solving some theoretical problems concerning the ideals in polynomial rings, as well as solving polynomial systems of equations. In this article four practical applications of Groebner basis theory are considered; we use Groebner basis to solve the systems of nonlinear polynomial equations, to solve an integer programming problem, to solve the problem of chromatic number of a graph, and finally we consider an original example from the theory of systems of ordinary (polynomial) differential equations. For practical computations we use systems MATHEMATICA and SINGULAR .
Ključne besede: polynomial system of (differential) equations, integer linear programming, chromatic number of a graph, polynomial rings, Groebner basis, CAS systems
Objavljeno v DKUM: 10.07.2015; Ogledov: 1432; Prenosov: 94
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Implementation of hard real-time embedded control systemsMatjaž Colnarič
, Domen Verber
, Roman Gumzej
, Wolfgang A. Halang
, 1998, samostojni znanstveni sestavek ali poglavje v monografski publikaciji
Opis: Although the domain of hard real-time systems has been thoroughly elaborated in the academic sphere, embedded computer control systems - being an important in mechatronic design - are seldom dealt with consistemntly. Often, off-the-shelf computer systems are used, with no guarantee that they will be able to meet the requirements specified. In this paper, a design for embedded control systems is presented. particulary, the paper deals with the hardware architecture and design details, the operating sustem, and the high-level real-time language support. It is shown how estimates of process run-times necessary for schedulability analysis can be acquired on the basis of deterministic behavior of the hardware platform.
Ključne besede: kontrolni sistemi, realni čas, mikrokontrolerji, programski jeziki, embedded compuer control systems, hard real-time systems, microcontrollers, transputers, earliest-deadline-first scheduling, real-time programming languages
Objavljeno v DKUM: 10.07.2015; Ogledov: 1192; Prenosov: 99
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SYNTHESIS OF PROCESSES AND PROCESS SUBSYSTEMS FOR ENTIRE LIFETIMEAndreja Nemet
, 2015, doktorska disertacija
Opis: Economically viable process designs should be, in addition to other criteria, profitable over their entire process lifetimes not only at the present time. An improved process design can be achieved by establishing an appropriate trade-off between product income, raw material, operating costs, and investment. The full lifetime of the processes and future prices have to be considered rather than optimising them on a yearly basis using current prices. Single-period optimisation and synthesis models for processes reflects current prices only. The prices can fluctuate rather quickly and the optimal solution may be very different from one year to the another. Therefore, the traditional superstructural synthesis approach applying a mixed-integer nonlinear programming model was upgraded: i) over time, by considering an entire lifetime, which can be described by a multi-period model and ii) the whole field of variation regarding uncertain future prices. A stochastic approach considering the statistical distribution of price projections over an entire lifetime was used on different case studies instead of the traditional deterministic approach accounting for nominal future price projection. The objective was the maximisation of the expected net present value of a process or the expected incremental net present value of different process subsystem.
The heat exchanger network has been one of the subsystem, which can significantly contribute to operating costs due to savings of external utility consumption. For this subsystem a deterministic and stochastic multi-period mixed-integer nonlinear programming (MINLP) synthesis models have been developed in order to account for future price projections. Considering higher energy prices gives rise to larger initial investments compared to solutions obtained with current prices. However, due to the uncertainties of utility prices' forecasts, retrofitting using an extension of HEN during future years of the lifespan might be a better strategy. The objective is to identify a design that is the most suitable for effective future extensions and preferably with the lowest sensitivity to energy price fluctuations, as there can be various designs featuring similar initial investment. The results supports that it is economically beneficial to consider future utility prices as the incremental investment is not only paid-off but additional savings are achieved.
Process-to-process Heat Integration can also significantly affect the trade-off between investment and operating cost. The aim of Total Site (TS) HEN synthesis was to develop a model synthesis for the TS that, besides many other important features, would also consider future utility prices. Two strategies for TS synthesis have been developed: i) sequential, when HI is performed within a process during the first step and then after a process-to-process HI has been performed, and ii) simultaneous, where the HI is performed within and between processes simultaneously. The second strategy can reveal additional opportunities for heat recovery that might not be identified when applying the first strategy. Comparison of the results obtained at consideration of current utility prices and forecasted utility prices indicates that is worth to account for future utility prices.
The separation processes also consume a significant amount of energy. The synthesis of a distillation column sequence integrated within its heat exchanger network was used as a case study for the separation of a multi-component stream into pure component products by considering future utility prices. This analysis has been performed in order to evaluate the magnitude of the influence of forecasted utility prices. It can be concluded that forecasted utility prices can be beneficial, however, the technical limits of the systems should be carefully observed.
The price fluctuation can also be observed for other prices not only utility prices, e.g. raw material cost, product price, etc
Ključne besede: future prices, forecasted prices, stochastic optimisation, mathematical programming, Heat Exchanger Network, Total Site, distillation column sequence, methanol production
Objavljeno v DKUM: 04.05.2015; Ogledov: 1965; Prenosov: 165
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