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1
Content available Application of reanalysis methods in structural mechanics
Delyová I., Frankovský P., Bocko J., Sivák P., Kurimský R.
International Journal of Applied Mechanics and Engineering
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2022
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Vol. 27, no. 3
49--62
EN
When designing structures, it is often necessary to re-analyse a structure that is different in some parts from the original one. As real structures are often complex, their analysis is therefore very challenging. In such cases, reanalysis methods are advantageously used. The aim of this paper is to approach the problem of solving the constructions using reanalysis method in which the time taken in solving algebraic equations is reduced. In particular, the purpose of this work is to demonstrate on a chosen system the time savings and the advantages of the chosen direct efficient reanalysis method for a given design problem. A basic condition for meeting these criteria is the modernization of computational procedures in the mechanics of compliant solids.
2
Content available A novel modeling approach for finite element human body models with high computational efficiency and stability: application in pedestrian safety analysis
Li Guibing, Meng Hengshuai, Liu Jinming, Zou Donghua, Li Kui
Acta of Bioengineering and Biomechanics
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2021
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Vol. 23, no. 2
33--40
EN
Purpose: The purpose of the current study was to develop and validate a finite element (FE) pedestrian model with high computational efficiency and stability using a novel modeling approach. Methods: Firstly, a novel modeling approach of using hollow structures (HS) to simulate the mechanical properties of soft tissues under impact loading was proposed and evaluated. Then, an FE pedestrian model was developed, employing this modeling approach based on the Total Human Model for Safety (THUMS) pedestrian model, named as THUMS-HS model. Finally, the biofidelity of the THUMS-HS model was validated against cadaver test data at both segment and full-body level. Results: The results show that the proposed hollow structures can simulate the mechanical properties of soft tissues and the predictions of the THUMS-HS model show good agreement with the cadaver test data under impact loading. Simulations also prove that the THUMS-HS model has high computational efficiency and stability. Conclusions: The proposed modeling approach of using hollow structures to simulate the mechanical properties of soft tissues is plausible and the THUMS-HS model could be used as a valid, efficient and robust numerical tool for analysis of pedestrian safety in vehicle collisions.
3
Content available remote Computing Duals of Finite Gödel Algebras
Codara Pietro, Maurina Gabriele, Valota Diego
Annals of Computer Science and Information Systems
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2020
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Vol. 21
31--34
EN
We introduce an algorithm that computes and counts the duals of finite G\"odel-Dummett algebras of k ≥ 1 elements. The computational cost of our algorithm depends on the factorization of k, nevertheless a Python implementation is sufficiently fast to compute the results for very large values of k.
4
Content available remote Generalisation and improvement of the compact gravity inversion method
Zhu Wenwu, Peng Junhuan, Luo Sanming, Meng Xiangang, Liu Jinzhao, Zhu Chuandong
Acta Geophysica
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2020
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Vol. 68, no. 6
1667--1677
EN
Compact gravity inversion (CGI) is widely used to invert gravity data following the principle of minimising the volume of the causative body due to its simplicity, high efciency, and sharp-boundary inversion results. In this study, the compactness weighting function is generalised and the depth weighting function is introduced to CGI to obtain the reweighted CGI (RCGI) method. Although RCGI exhibits better fexibility than CGI, selecting an appropriate compactness factor α and depth weighting function β is difcult, and we design a parameter selection rule to search the proper α and β quantitively. Furthermore, we improve RCGI for boasting superior computational efciency by gradually eliminating the model blocks that reach the designated boundaries in the iterative algorithm of inversion. This approach is termed the reweighted and element-elimination CGI (REECGI) method. The inversion results show that both RCGI and REECGI result in better inversion accuracy than CGI, and REECGI has higher computational efciency than RCGI and CGI, which increases with the number of iterations.
5
Content available remote Wykorzystanie metody CMS do budowy efektywnego numerycznie modelu MES
Danielczyk P.
Mechanik
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2016
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R. 89, nr 7
674--675
PL
W pracy przedstawiono efektywny numerycznie model obliczeniowy do rozwiązania zadania optymalizacji parametrycznej z wykorzystaniem metody elementów skończonych. Do budowy modelu obliczeniowego użyto superelementów, a do redukcji rozmiaru zadania wykorzystano metodę Component Mode Synthesis. Pokazano korzyści wynikające z przyjętej metodyki modelowania w odniesieniu do czasu potrzebnego na znalezienie rozwiązania optymalnego oraz wielkości plików generowanych podczas analizy.
EN
The paper presents a numerically efficient computational model for solving a parametric optimization problem with the use of the Finite Element Method. Building a computational model involved applying superelements and the CMS method was applied for model reduction. The advantages of the adopted modelling methodology were shown with reference to the time required to find the optimal solution and the size of the files generated during the analysis.
6
Content available Bandwidth Trading: A Comparison of the Combinatorial and Multicommodity Approach
Kołtyś K., Pałka P., Toczyłowski E., Żółtowska I.
Journal of Telecommunications and Information Technology
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2010
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nr 2
67-72
EN
Since the telecommunication market becomes more complex and dynamic, a strong need for a new, efficient and flexible bandwidth trading mechanisms appears. We believe that good mechanisms, that allow effective and fair allocation of bandwidth between market participants will help to develop the real competitive bandwidth market. In this paper we compare two different double-sided bandwidth auction mechanisms, that seem to be well suited approaches for trading indivisible units of bandwidth: combinatorial auction c-SeBiDA and multicommodity mechanism BACBR-I. The c-SeBiDA mechanism considers two types of commodities: inter-node links and paths consisting of particular links. Market participants may bid a single link, or a bundle of links, constituting a specific path. The BACBR-I mechanism is a multicommodity exchange model, that allows bidders to place buy offers not only for individual or bundled links, but rather for end-to-end connections. Therefore, it is the decision model that allocates the most efficient links to connections. We run a large set of experiments to test the allocation and computational efficiency obtained under both approaches.
7
Content available remote Evaluation of parallel efficiency in modeling of mechanisms using commercial multibody solvers
Malczyk P., Frączek J.
Archive of Mechanical Engineering
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2009
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Vol. LVI, nr 3
237-249
EN
Parallel computers are becoming more available. The natural way to improve computational efficiency of multibody simulations seems to be parallel processing. Within this work we are trying to estimate the efficiency of parallel computations performed using one of the commercial multibody solver. First, the short theoretical outline is presented to give the overview of modeling issues in multibody dynamics. Next, the experimental part is demonstrated. The series of dynamics analyses are carried out. The test mechanisms with variable number of bodies are used to gather the performance results of the solver. The obtained data allow for estimating the number of bodies, which are sufficient to gain benefits from parallel computing as well as their level. The parallel processing profits are taken into account in the case of contact forces present in the system. The performance benefits are indicated, when the multilink belt chain is simulated, in which contact forces are included in the model.
PL
W związku z szybkim rozwojem komputerów równoległych naturalną drogą poprawienia wydajności obliczeń symulacyjnych staje się wykorzystywanie możliwości przetwarzania równoległego. W ramach niniejszej pracy podjęto próbę oceny efektywności obliczeń równoległych, w przypadku obliczeń jednym z pakietów komercyjnych do modelowania układów mechanicznych. Początkowo zaprezentowano podstawy teoretyczne metody układów wieloczłonowych. Następnie zademonstrowano wyniki eksperymentalne. W pracy zrealizowano obliczenia dynamiki testowych układów mechanicznych o zmiennej liczbie członów, podczas których zarejestrowano czasy obliczeń sekwencyjnych i równoległych. Uzyskane charakterystyki wydajnościowe pozwoliły oszacować liczbę ogniw, przy której otrzymuje się zyski z obliczeń równoległych, a także wskazać ich poziom. W zakresie badań uwzględniono potencjalne korzyści ze stosowania przetwarzania równoległego w przypadku sił kontaktu, obecnych w modelu, na przykładzie symulacji wieloczłonowego mechanizmu łańcuchowego.
8
Content available Numerical simulation of 3D flow in axial turbomachines
Yershov S., Rusanov A. V., Gardzielewicz A., Lampart P., Świrdyczuk J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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1998
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Vol. 2, No 2
319-347
EN
The paper is intended to describe a method for the calculation of 3D viscous compressible (subsonic or supersonic) flow in axial turbomachines described in the form of thin-layer Reynolds-averaged Navier-Stokes equations. The method draws on Godunov-type upwind differencing and ENO reconstruction suggested by Harten (1987), so as to assure monotonicity preservation and high accuracy of computational results. The computational efficiency is achieved thanks to the implementation of a simplified H-type multi-grid approach and delta -form implicit step. Turbulent effects are simulated with the help of a modified algebraic model of Baldwin-Lomax (1978). This method was at the foundation of a computer code-a complex software package to calculate 3D flow in multi-stage turbomachines that allows us to obtain local characteristics, like temperature, pressure, density or velocity distributions, as well as global characteristics, such as flow rates, stage reaction, flow efficiency for the considered turbine/compressor stage. The paper also gives selected results of computation of a number of turbomachinery cascades, showing that these results agree reasonably well with the available experimental data.
9
Content available remote Optimal design of control law under uncertainty by dynamic programming
Siomak M., Malinowski K.
Archives of Control Sciences
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1998
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Vol. 7, no. 3/4
202-226
EN
In this paper various aspects of the realization of the dynamic programming algorithm are presented. Particular attention is focused on computational efficiency, which is obtained by presented discretization, approximation and parallelization techniques. Numerical solutions of some examples are briefly described and discussed. The last part presents a particular approach to handle stochastic constraints with illustrative examples. All numerical results were obtained on the CRAY 6416 super-server installed in Computing Center of the Warsaw University of Technology.
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