Wyniki wyszukiwania - Biblioteka Nauki

1

A Practical Course for Teaching Fundamental Optimization Techniques in Electrical Engineering

100%

Brauer H. , Kuilekov M.

Przegląd Elektrotechniczny

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2003

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tom R. 79, nr 10

690-692

EN

The paper presents a new toolbox containing a wide range of optimization methods to be used by students in undergraduate studies of electrical engineering. Both deterministic and stochastic optimization techniques can be applied to a large set of known test functions. The computer laboratory course is used since one year to secure student´s knowledge of optimization and solving of inverse field problems given in the pertinent lectures.

2

Price-based coordinability in hierarchical systems with information asymmetry: a comparative analysis of Nash equilibrium conditions

100%

Karpowicz M. P. , Malinowski K.

Control and Cybernetics

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2013

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tom Vol. 42, no. 1

85--110

EN

The well-known problem of price-based coordinability is studied for the case of a multi-agent system in which information regarding the goals of the interacting subsystems is asymmetric. The paper illustrates how the uniform-price-based coordination rulet may create incentives to anticipate the values of coordination signals and, thus, why the coordinability condition cannot be satisfied under asymmetric information. For this purpose a comparison is given of Nash equilibrium outcomes that are reachable individually by priceanticipating agents in two noncooperative games. These games are induced by the uniform-price-based coordination mechanism and are referred to as payment-bidding auction and demand-bidding auction. The analysis presented shows that in the games considered some of the agents may improve payoffs and allocations by applying the price-anticipating bidding strategies. However, the payment-bidding auction cannot be strictly dominated by the demand-bidding action with respect to the resource allocation levels individually received by each agent. The derived results of theoretic considerations are illustrated by numerical examples.

3

Optimisation of composite shapes with the help of genetic algorithms

100%

Hufenbach W. , Gude M. , Kroll L. , Kostka P. , Sokołowski A.

Computer Assisted Mechanics and Engineering Sciences

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2005

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tom Vol. 12, No. 2-3

163-173

EN

During the manufacturing process of multilayered fibre-reinforced composites with variable fibre orientations, residual stresses build up due to the directional expansion of the single unidirectionally reinforced layers. Dependent on the laminate lay-up, these inhomogeneous residual stresses, which are caused by thermal effects, moisture absorption and chemical shrinkage, can lead to large multistable out-of-plane deformations. Instead of avoiding these laminate's curvatures, they can be advantageously used for technical applications following the near-net-shape technology. However, due to the effect that the laminate curvature depends on huge amount of different parameters such as anisotropic, hygroscopic and thermomechanical material properties, fibre orientations and ply thickness of each single layer as well as technological processing parameters, a search in a multi-dimensional search area is necessary. In order to solve such a task, Genetic Algorithms in combination with a fitness function based on a nonlinear semi-analytical calculation model for the laminate shape prediction have been applied and described in the paper. Using this approach, one can purposefully adapt the laminate lay-up dependent on the loading and process parameters.

4

Effect of tripping velocity profiles on wellbore pressures and dynamic loading of drillstring

100%

Wang Z. , Miska S. , Yu M. , Takach N.

AGH Drilling, Oil, Gas

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2013

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tom Vol. 30, no. 1

269--286

EN

Tripping events are expensive and time-consuming. Thus, minimizing tripping time through choosing optimized tripping velocity becomes urgent. Surge or swab pressures in the wellbore and dynamic loading of drillstring will be generated during tripping. Also, dynamic velocity, which is the velocity at the bottom of drillstring, is different from the input velocity at surface. The effect of tripping velocity profile, i.e., tripping velocity changes with time, on the hook load, downhole pressure changes and drillstring dynamic velocity should be fully studied to achieve the optimization. In this study, the effects of tripping velocity profile on loading of drillstring, dynamic velocity and downhole pressure is investigated using numerical simulation. Bergeron's graphical method and Lubinski's approach are utilized to perform the simulations. Components of drillstring, wellbore depth, drillstring length and mud properties are also included in the simulations. Through the current work, a driller's typical way of changing tripping velocity may not be the best one. Selection of tripping velocity profiles should be adapted to depth: higher velocity, triangular/parabolic profiles in shallow wells and lower velocity, trapezoidal profiles in deep wells. Also, based on simulations, the oscillation magnitude of dynamic velocity can be as high as twice that of velocity at surface.

5

Multiobjective optimization of reflector’s shape

100%

Wandachowicz K.

Computer Applications in Electrical Engineering

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2013

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tom Vol. 11

370--379

EN

The article presents results of research on the calculation of the shape of a mirror reflector, which ensures the highest possible average illuminance, and uniformity of illuminance. A multiobjective genetic algorithm was used to carry out optimization calculations.

6

Metody i modele optymalizacyjne w logistyce

100%

Winiczenko R.

Gospodarka Materiałowa i Logistyka

|

2010

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tom nr 1

30-32

PL

Podejmowanie w logistyce wielu trudnych decyzji o charakterze ilościowym stanowi proces przetwarzania informacji wymagający stosowania badań operacyjnych. Możliwość praktycznego wykorzystania badań operacyjnych umożliwiają komputery oraz ich odpowiednie oprogramowanie, które opracowano na bazie odpowiednich metod i modeli optymalizacyjnych. Do najważniejszych modeli stosowanych we współczesnej logistyce należą modele optymalizacyjne, symulacyjne i heurystyczne.

EN

In the article the general rule of functioning of chosen optimization, simulation and heuristic methods and models was presented. These tools are very useful in nowadays logistics, various industrial branches and material management.

7

Optimization of Johnson–Cook constitutive model parameters

80%

Löschner P. , Jarosz K. , Niesłony P.

Journal of Machine Engineering

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2019

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tom Vol. 19, No. 3

66--73

EN

In modern machining industry, the concept of process optimization has gained widespread recognition. FEM simulations are commonly used for the optimization of machining operations, allowing for a proper choice of tool geometry and process parameters to obtain results that are in accordance with end user criteria. However, one has to be wary that a good agreement of experimental and simulation results is mandatory if the simulation is to be used as a basis for optimization of a real-life process. Therefore, a proper choice of constitutive model parameters is vital. Those parameter values are dependent on many variables. Constitutive model parameter values are determined experimentally – therefore, they are accurate only for the conditions (temperature, strain rate etc.) under which the experiment was performed. The alteration, or optimization of model parameters is necessary if cutting and experiment conditions differ, if one wishes to obtain applicable results. In this work, the authors aim to present a method of optimizing the Johnson–Cook constitutive model parameters to obtain a better fit with experimental data.

8

Digraph description of k-interchange technique for optimization over permutations and adaptive algorithm system

80%

Levin M. S.

Foundations of Computing and Decision Sciences

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2001

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tom Vol. 26, No. 3

225-235

EN

The paper describes a general glance to the use of element exchange techniques for optimization over permutations. A multi-level description of problems is proposed which is a fundamental to understand nature and complexity of optimization problems over permutations (e.g., ordering, scheduling, traveling salesman problem). The description is based on permutation neighborhoods of several kinds (e.g., by improvement of an objective function). Our proposed operational digraph and its kinds can be considered as a way to understand convexity and polynomial solvability for combinatorial optimization problems over permutations. Issues of an analysis of problems and a design of hierarchical heuristics are discussed. The discussion leads to a multi-level adaptive algorithm system which analyzes an individual problem and selects / designs a solving strategy (trajectory).

9

Optimization of overlay computing systems with many – to - many transmissions

80%

Walkowiak K. , Kasprzak A. , Andrusieczko K.

Theoretical and Applied Informatics

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2012

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tom Vol. 24, No. 4

271-291

EN

The problem that this paper investigates, namely, optimization of overlay computing systems, follows naturally from growing need for effective processing and consequently, fast development of various distributed systems. We consider an overlay-based computing system, i.e., a virtual computing system is deployed on the top of an existing physical network (e.g., Internet) providing connectivity between computing nodes. The main motivation behind the overlay concept is simple provision of network functionalities (e.g., diversity, flexibility, manageability) in a relatively cost-effective way as well as regardless of physical and logical structure of underlying networks. The workflow of tasks processed in the computing system assumes that there are many sources of input data and many destinations of output data, i.e., many-to-many transmissions are used in the system. The addressed optimization problem is formulated in the form of an ILP (Integer Linear Programing) model. Since the model is computationally demanding and NPcomplete, besides the branch-and-bound algorithm included in the CPLEX solver, we propose additional cut inequalities. Moreover, we present and test two effective heuristic algorithms: tabu search and greedy. Both methods yield satisfactory results close to optimal.

PL

Zagadnienia dotyczące optymalizacji systemów obliczeń rozproszonych zyskują w ostatnich latach na znaczeniu. Systemy obliczeń rozproszonych rozwijane są w dwóch podstawowych architekturach sieciowych. Po pierwsze, budowane są dedykowane sieci optyczne łączące ośrodki obliczeniowe. Po drugie, wykorzystuje się istniejącą infrastrukturę sieciową (np. Internet) dla budowania systemów pracujących w architekturze nakładkowej (ang. overlay). Ta druga koncepcja zyskuje ostatnio dużą popularność, gdyż umożliwia szybką i tanią realizację systemów obliczeniowych bez potrzeby mocnej współpracy z operatorami sieciowymi. W pracy rozważamy nakładkowy system obliczeniowy umożliwiający transmisje wielu do wielu – dane wejściowe do obliczeń są generowane w wielu źródłach (węzłach sieciowych), następnie po przetworzeniu są przesyłane do wielu odbiorców zainteresowanych wynikami obliczeń. W oparciu o zaproponowaną architekturę systemu, w pracy sformułowano problem optymalizacyjny mający na celu minimalizację kosztów operacyjnych systemu obejmujących koszty obliczeń i koszty przesyłania danych. Model został zapisany jako program całkowitoliczbowy. Z uwagi na fakt, że ten problem należy do klasy problemów NP-zupełnych, zaproponowano dodatkowe odcięcia dla algorytmu podziału i oszacowań oraz dwa efektywne algorytmy heurystyczne. Przeprowadzone eksperymenty obliczeniowe wykazały, że opracowane algorytmy dają wyniki bliskie optymalnym w mniejszym czasie niż algorytm optymalny zawarty w pakiecie CPLEX

10

An empirical comparison of different risk measures in portfolio optimization

80%

Hoe L. W. , Hafizah J. S. , Zaidi I.

Business and Economic Horizons

|

2010

|

tom 1

|

nr 1

39-45

EN

Risk is one of the important parameters in portfolio optimization problem. Since the introduction of the mean-variance model, variance has become the most common risk measure used by practitioners and researchers in portfolio optimization. However, the mean-variance model relies strictly on the assumptions that assets returns are multivariate normally distributed or investors have a quadratic utility function. Many studies have proposed different risk measures to overcome the drawbacks of variance. The purpose of this paper is to discuss and compare the portfolio compositions and performances of four different portfolio optimization models employing different risk measures, specifically the variance, absolute deviation, minimax and semi-variance. Results of this study show that the minimax model outperforms the other models. The minimax model is appropriate for investors who have a strong downside risk aversion.

11

Methods of optimization of distributed databases in oracle. Part 2

80%

Barczak A. , Zacharczuk D. , Pluta D.

Studia Informatica : systems and information technology

|

2017

|

tom Vol. 1-2(21)

15--46

EN

The second part of the paper devoted to optimization of distributed databases. This part presents tests which confirm the efficiency of database tuning methods, described in part one. Analysis of tests results based on the developed database is presented.

12

Estymacja współczynnika konwekcji dla wsadu walcowego nagrzewanego indukcyjnie

80%

Teodorczyk T. , Zgraja J.

Zeszyty Naukowe. Elektryka / Politechnika Łódzka

|

2009

|

tom z. 118

157-161

PL

W pracy przedstawiono metodę pozwalającą oszacować wartość współczynnika konwekcji dla nagrzewanego indukcyjnie wsadu walcowego. Podano zależność współczynnika konwekcji od temperatury powierzchni zewnętrznej nagrzewanego wsadu.

EN

In the paper the method allows to estimation of convection coefficient of induction heated cylindrical charge has been presented. A dependence of the convection coefficient on the temperature of induction heated charge has been given.

13

Wykorzystanie deterministycznej techniki optymalizacji do określenia parametrów materiałowych indukcyjnie nagrzewanych wsadów

80%

Zgraja J.

Zeszyty Naukowe. Elektryka / Politechnika Łódzka

|

2009

|

tom z. 118

127-134

PL

Przy braku wiarygodnych danych literaturowych wyznaczenie charakterystyk materiałowych wsadu wymaga przeprowadzenia specjalistycznych badań laboratoryjnych. Rozwiązania tego zagadnienia można poszukiwać również w metodzie optymalizacyjnego określenia charakterystyk materiałowych, wykorzystując w tym celu program do symulacji pracy układu wzbudnik-wsad oraz stanowisko do nagrzewania indukcyjnego próbki wsadu. W pracy zaprezentowano takie stanowisko badawcze oraz omówiono efektywność wykorzystania deterministycznej techniki sekwencyjnego programowania kwadratowego.

EN

In many cases it is impossible to find in accessible references the credible information about charge material properties. In such situation the material properties of the charge should be experimentally determined before the computer simulation, which can be difficult and expensive. In other way it can be realised by indirect method by comparing, in optimisation process, the experimental and simulation results. In the paper such method using deterministic optimization technique has been presented.

14

Modeling and optimization of activated carbon carbonization process based on support vector machine

80%

Liu G. , Zhang C. , Dou D. , Wei Y.

Physicochemical Problems of Mineral Processing

|

2021

|

tom Vol. 57, iss. 2

131--143

EN

Product prediction and process parameter optimization in the production process of activated carbon are very important for production. It can stabilize product quality and improve the economic efficiency of enterprises. In this paper, three process parameters of a carbonization furnace, namely feeding rate, rotation speed, and carbonization temperature, were adopted to build a quality optimization model for carbonized materials. First, an orthogonal test was designed to obtain the preliminary relationship between the process parameters and the quality indicators of a carbonized material and prepare data for modeling. Then, an improved SVR model was developed to establish the relationship between product quality indicators and process parameters. Finally, through the singlefactor experiments and the Monte Carlo method, the process parameters affecting the quality of a carbonized material were determined and optimized. This showed that a high-quality carbonized material could be obtained with a smaller feeding rate, larger rotation speed, and higher carbonization furnace temperature. The quality of activated carbon reached its maximum when the feeding rate was 1.0 t/h, the rotation speed was 90 r/h, and the temperature was 836°C. It can effectively improve the quality of carbonized materials.

15

Niedeterministyczne metody optymalizacji w projektowaniu silników indukcyjnych

80%

Rudeński A.

Nowa Elektrotechnika

|

2010

|

tom nr 3

16-20

16

Control System Design: Think Broad and Be Inquisitive

80%

Malinowski K.

Pomiary Automatyka Robotyka

|

2020

|

tom R. 24, nr 2

5--10

EN

In this paper two examples, of a different nature, are presented to demonstrate, basing upon the author’s experience from the past, that the control engineer facing a design problem must think in broad terms, be careful when design supporting tools are used and do not neglect theory related to the considered design problem.

PL

W niniejszym artykule przedstawiono dwa przykłady o różnym charakterze, dla wykazania, w oparciu o doświadczenie autora, że inżynier systemów sterowania napotykający problem projektowy musi myśleć nieszablonowo, stosować roztropnie narzędzia wspomagające projektowanie i nie może zaniedbywać teorii związanej z rozważanym problemem projektowym.

17

Reduction of waste through reorganization of the component shipment logistics

80%

Burduk A. , Górnicka D.

Research in Logistics & Production

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2017

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tom Vol. 7, No. 2

77--90

EN

This paper analyses the operation of a company from the automotive industry in terms of the identification of waste in the production process. The aim of this study was to develop methods for eliminating the sources of waste, i.e. extensive work-in-progress inventories. There was used the Value Stream Mapping (VSM) method. It allowed finding sources of waste and enabled an analysis of the process. The VSM method allows observing processes exactly as they are, thanks to which it is possible to identify the actual problems occurring in them.

18

Podejście wariantowe we wstępnym projektowaniu statków

80%

Karczewski K. , Kozak J.

Mechanik

|

2017

|

tom R. 90, nr 12

1196--1198

PL

Klasyczna metoda projektowania okrętów jest metodą iteracyjną, bazującą na doświadczeniu zgromadzonym podczas eksploatacji istniejących statków. Natomiast w przypadku całkowicie nowego typu statku, bez „posagu wcześniejszych doświadczeń”, projektowanie polega na opracowaniu szeregu równoległych, wariantowych rozwiązań z wykorzystaniem optymalizacji. Artykuł wskazuje na wybrane metody projektowe wykorzystujące optymalizację, stosowane we wstępnym projektowaniu statków. Systematyzuje i objaśnia stosowane techniki optymalizujące na tle rozwoju teorii projektowania okrętów.

EN

Typical ship designing is an iterative method based on the accumulated experience of already built ships. In the case of a completely new type of ship, without the „dowry of previous experience”, the design consists in developing a series of parallel variant solutions using the optimization. The paper identifies selected designing methods applying the optimizations used in the preliminary ship design. The optimization methods used in the ship design are discussed.

19

Wielowymiarowa analiza atrakcyjności inwestycyjnej spółek sektora spożywczego notowanych na Giełdzie Papierów Wartościowych w Warszawie

80%

Kijek A.

Econometrics. Ekonometria. Advances in Applied Data Analytics

|

2014

|

nr 4(46)

175-188

EN

The article presents the results of study of investment attractiveness of food sector companies listed at the Warsaw Stock Exchange. The multivariate statistical methods are applied to evaluate the financial standing of companies. The author constructs the investment attractiveness index that is used to order companies by their economic and financial standing. Based on the values of investment attractiveness index the structure of optimal portfolios are determined according to Markowitz portfolio theory. The results of survey indicate directions of investment portfolio diversification.

20

Solving IRPs using location based heuristics

80%

HANCZAR P.

Operations Research and Decisions

|

2014

|

tom 24

|

nr 2

81-96

EN

Inventory routing problems (IRPs) occur where vendor managed inventory replenishment strategies are implemented in supply chains. These problems are characterized by the presence of both transportation and inventory considerations, either as parameters or constraints. The research presented in this paper aims at extending IRP formulation developed on the basis of location based heuristics proposed by Bramel and Simchi-Levi and continued by Hanczar. In the first phase of proposed algorithms, mixed integer programming is used to determine the partitioning of customers as well as dates and quantities of deliveries. Then, using 2-opt algorithm for solving the traveling sales-person problem the optimal routes for each partition are determined. In the main part of research the classical formulation is extended by additional constraints (visit spacing, vehicle filling rate, driver (vehicle) consistency, and heterogeneous fleet of vehicles) as well as the additional criteria are discussed. Then the impact of using each of proposed extensions for solution possibilities is evaluated. The results of computational tests are presented and discussed. Obtained results allow to conclude that the location based heuristics should be considered when solving real life instances of IRP.