7 results
Search Results
2. DIDELIO TIKSLUMO PADĖTIES NUSTATYMO SISTEMOS MODELIAVIMAS.
- Author
-
Augustinavičius, Giedrius and Čereška, Audrius
- Subjects
- *
WIRELESS communications , *PRECISION (Information retrieval) , *SCREWS , *FINITE element method , *PERFORMANCE evaluation , *MATHEMATICAL optimization - Abstract
This paper presents the modeling of a flexure-based precision positioning system for micro-positioning uses. The positioning system is featured with monolithic architecture, flexure-based joints and ultra fine adjustment screws. Its workspace has been evaluated via analytical approaches. Reduction mechanism is optimally designed. The mathematical model of the positioning system has been derived, which is verified by resorting to finite element analysis (FEA). The established analytical and (FEA) models are helpful for a reliable architecture optimization and performance improvement of the positioning system. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
3. INTEGRINIŲ GRANDYNŲ VAIZDŲ SEGMENTAVIMO KOKYBĖS OPTIMIZAVIMAS.
- Author
-
Mušketas, Gintautas
- Subjects
- *
GENETIC algorithms , *INTEGRATED circuits , *MATHEMATICAL optimization , *MATHEMATICAL sequences , *PARAMETER estimation - Abstract
The paper presents investigation into the application of genetic algorithms for the segmentation of the active regions of integrated circuit images. This article is dedicated to a theoretical examination of the applied methods (morphological dilation, erosion, hit-and-miss, threshold) and describes genetic algorithms, image segmentation as optimization problem. The genetic optimization of the predefined filter sequence parameters is carried out. Improvement to segmentation accuracy using a non-optimized filter sequence makes 6%. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
4. MOMENTŲ IR REAKCIJŲ MINIMIZAVIMAS ROSTVERKINIUOSE PAMATŲ SIJYNUOSE GENETINIU ALGORITMU.
- Author
-
Belevičius, Rimantas, Mačiūnas, Darius, and Šešok, Dmitrij
- Subjects
- *
TECHNOLOGICAL innovations , *GENETIC algorithms , *FINITE element method , *GIRDERS , *MATHEMATICAL optimization , *PROBLEM solving , *BENDING moment - Abstract
The aim of the article is to report a technology for the optimization of grillage-type foundations seeking for the least possible reactive forces in the piles for a given number of piles and in the absolute value of the bending moments when connecting beams of the grillage. Mathematically, this seems to be the global optimization problem possessing a large number of local minima points. Both goals can be achieved choosing appropriate pile positions under connecting beams; however, these two problems contradict to each other and lead to different schemes for pile placement. Therefore, we suggest using a compromise objective function (to be minimized) that consists of the largest reactive force arising in all piles and that occurring in the absolute value of the bending moment when connecting beams, both with the given weights. Bending moments are calculated at three points of each beam. The design parameters of the problem are positions of the piles. The feasible space of design parameters is determined by two constraints. First, during the optimization process, piles can move only along connecting beams. Therefore, the two-dimensional grillage is "unfolded" to the one-dimensional construct, and supports are allowed to range through this space freely. Second, the minimum allowable distance between two adjacent piles is introduced due to the specific capacities of a pile driver. Also, due to some considerations into the scheme of pile placement, the designer sometimes may introduce immovable supports (usually at the corners of the grillage) that do not participate in the optimization process and always retain their positions. However, such supports hinder to achieve a global solution to a problem and are not treated in this paper. The initial data for the problem are as follows: a geometrical scheme of the grillage, the given number of piles, a cross-section and material data on connecting beams, the minimum possible distance between adjacent supports and loading data given in the form of concentrated loads or trapezoidal distributed loadings. The results of the solution are the required positions of piles. This solution can serve as a pilot project for more detailed design. The entire optimization problem is solved in two steps. First, the grillage is transformed into the one-dimensional construct and the optimizer decides about a routine solution (i.e. the positions of piles in this construct). Second, backward transformation returns pile positions into the two-dimensional grillage and the "black-box" finite element program returns the corresponding objective function value. On the basis of this value, the optimizer predicts new positions of piles etc. The finite element program idealizes connecting beams as beam elements and piles - as mesh nodes of the finite element with a given boundary conditions in the form of vertical and rotational stiffness. Since the problem may have several tens of design parameters, the only choice for optimization algorithms is using stochastic optimization algorithms. In our case, we use the original elitist real-number genetic algorithm and launch the program sufficient number of times in order to exclude large scattering of results. Three numerical examples are presented for the optimization of 10-pile grillage: when optimizing purely the largest reactive force, purely the largest in the absolute value of the bending moment and both parameters with equal weights. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
5. PRISITAIKANČIŲJŲ SANTVARŲ OPTIMIZAVIMO UŽDAVINIŲ MATEMATINIAI MODELIAI JUDAMOSIOS APKROVOS ATVEJU.
- Author
-
Atkočiūnas, Juozas, Merkevičiūtė, Dovilė, Venskus, Artūras, and Nagevičius, Juozas
- Subjects
- *
TRUSSES , *MATHEMATICAL optimization , *STRAINS & stresses (Mechanics) , *STRUCTURAL frames , *ALGORITHMS , *LIVE loads - Abstract
The shakedown theory, which analyses elastic-plastic constructions, subjected by variable repeated load, enables treating moving load as a separate type of variable repeated load. The load is allowed to „move" at any part of the construction: from the middle of the bridge, to turn back, again move ahead -- in this manner loading history is universally evaluated and it is a crucial factor, considering stress-deformation state of structures under plastic deformations. This paper reveals a possibility to apply methods of shakedown theory for creation and solution of theoretical optimization mathematical models of trusses. The perfectly elastic-plastic loaded by moving load truss is considering. The mathematical models of the minimal volume truss or it acting load maximization problems are created. There are evaluating not only strength (shakedown) and rigidity restrictions, but also stability restriction in case of plastic state of truss in models. There is proposed new solution algorithms and introduced numerical examples of truss optimization in case of moving load. The results axe valid for the small displacement assumptions. [ABSTRACT FROM AUTHOR]
- Published
- 2007
6. DJIEJŲ AŠIŲ PRECIZINIO POZICIONAVIMO SISTEMOS SKAITINIS MODELIAVIMAS.
- Author
-
Augustinavičius, Giedrius and Čereška, Audrius
- Subjects
- *
FINITE element method , *ARCHITECTURE , *SCREWS , *MATHEMATICAL models , *MATHEMATICAL optimization - Abstract
This paper presents a model of a precise dual axis flexure-based positioning system for micro-positioning uses. The positioning system is featured with monolithic architecture, flexure-based joints and ultra fine adjustment screws. Its workspace has been evaluated via analytical approaches. Reduction mechanism is optimally designed. The mathematical model of the positioning system has been derived and verified by resorting to finite element analysis (FEA). The established analytical and (FEA) models are helpful for reliable architecture optimization and performance improvement in the positioning system. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
7. APIE OPTIMIZAVIMO PROCEDŪRAS TOPOLOGINIUOSE UŽDAVINIUOSE.
- Author
-
Skeivalas, Jonas
- Subjects
- *
MATHEMATICAL optimization , *TOPOLOGY , *MATHEMATICAL transformations , *GENETIC algorithms , *ITERATIVE methods (Mathematics) , *MATHEMATICAL mappings , *PROBLEM solving - Abstract
The paper analyzes the case of mathematical procedures. An appropriate minimizing function is used for solving optimization tasks. In some cases, for example dealing with tasks of topological transformation, the applied minimizing function has no point of minimum. For this reason, an answer to estimating the function of minimization is ambiguous, and thus we have an endless number of answers. In this case, the used genetic algorithm solves task with the help of the iteration method calculating the values of parameters considering the least deviations from nominal values. The article presents the theoretical analysis of establishing the negation of the minimum of the optimization function (solution ambiguity), when topological transformations are applied for optimizing land parcel borders drawn in cadastral maps. [ABSTRACT FROM AUTHOR]
- Published
- 2011
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.