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Search Results: 1 - 10 of 631 matches for " Volavy Jaroslav "
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In uence of the turbulence representation at the inlet on the downstream ow pattern in LES of backward-facing step
Volavy Jaroslav,Forman Matej,Jicha Miroslav
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122501099
Abstract: The impact of the choice of inlet boundary condition treatment on the uid ow is studied in this work. The correct representation of the turbulence at the inlet to the domain is essential for the accuracy of Large Eddy Simulation. The inappropriate speci cation of the inlet velocity has signi cant effect on the downstream ow pattern. The case of backward-facing step was used as a test case. Three different approaches of the inlet boundary conditions were studied: uniform velocity pro le, mean velocity pro le of the fully developed channel ow and velocity obtained from mapping velocity from plane positioned behind the inlet back to the inlet. The results of the simulations were compared with experimental results. It has shown, that using uniform velocity pro le on inlet and even prescribing turbulent mean velocity pro le without proper representation of turbulence uctuations leads to unrealistic results.
Large eddy simulation of turbulent particle-laden channel flow considering turbulence modulation by particles
Volavy Jaroslav,Forman Matej,Jicha Miroslav
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122502030
Abstract: Large Eddy Simulation of vertical turbulent channel ow laden with particles are performed. The number of particles is chosen very large and the volume fraction of particles is high enough for consideration of two-way coupling. This means that the particles are in uenced by uid and vice versa. The inter-particle collisions are neglected. The Euler-Lagrange method is adopted, which means that the uid is considered to be continuum (Euler approach) and for each individual particle is solved Lagrangian equation of motion. Particles are considered to be spherical. The simulations are performed for different volume fractions of particles in the channel. The results are compared to the single-phase channel ow in order to investigate the effect of the particles on the turbulence statistics of the carrier phase
Prediction of air temperature in the aircraft cabin under different operational conditions
Volavy F.,Fi?er J.,N?ske I.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134501096
Abstract: This paper deals with the prediction of the air temperature in the aircraft cabin by means of Computational Fluid Dynamics. The simulations are performed on the CFD model which is based on geometry and cabin interior arrangement of the Flight Test Facility (FTF) located at Fraunhofer IBP, Germany. The experimental test flights under three different cabin temperatures were done in FTF and the various data were gathered during these flights. Air temperature in the cabin was measured on probes located near feet, torso and head of each passenger and also surface temperature and air temperature distributed from inlets were measured. The data were firstly analysed in order to obtain boundary conditions for cabin surfaces and inlets. Then the results of air temperature from the simulations were compared with measured data. The suitability and accuracy of the CFD approach for temperature prediction is discussed.
Effect of shear components on stress values in plywood panel subjected to tensile load
Jaroslav Kljak,Jaroslav Kljak
Drvna Industrija , 2007,
Abstract: This paper analyses individual stress components that appear in plywood panels subjected to tensile load. The analysis was conducted on a seven-layer beech plywood panel, 10.52 mm in thickness. Tensile load was applied on the plywood panel according to the guidelines of the European Norm HRN EN 789. Measurement results obtained by empirical measurement methods were used as the basis for developing a simulation model using the finite elements method (FEM). The study results show that there are substantial differences in the distribution of stress between the parallel- and perpendicular-oriented veneer layers. In parallel layers, the highest values of the s vm (Von Mises) stress were distributed along the narrow or central region of the test piece, which also represents the desired stress distribution. Contrary to this, in perpendicular layers, the stress distribution is concentrated at the transition between the narrow and wider areas, which indicates the presence of a significant problem in determining the tensile properties of plywood panels. The study results also indicate that the shear component t xy accounts for a significant share of the total stress and that its influence on the overall stress is significantly more pronounced in perpendicular layers. The values of the remaining two shear components t xz and t yz are virtually negligible, which is reasonable considering that the numerical model was subjected to in-plane load.
Elastic, not plastic species: Frozen plasticity theory and the origin of adaptive evolution in sexually reproducing organisms
Jaroslav Flegr
Biology Direct , 2010, DOI: 10.1186/1745-6150-5-2
Abstract: The frozen plasticity theory suggests that sexual species can evolve new adaptations only when their members are genetically uniform, i.e. only after a portion of the population of the original species had split off, balanced on the edge of extinction for several generations, and then undergone rapid expansion. After a short period of time, estimated on the basis of paleontological data to correspond to 1-2% of the duration of the species, polymorphism accumulates in the gene pool due to frequency-dependent selection; and thus, in each generation, new mutations occur in the presence of different alleles and therefore change their selection coefficients from generation to generation. The species ceases to behave in an evolutionarily plastic manner and becomes evolutionarily elastic on a microevolutionary time-scale and evolutionarily frozen on a macroevolutionary time-scale. It then exists in this state until such changes accumulate in the environment that the species becomes extinct.Frozen plasticity theory, which includes the Darwinian model of evolution as a special case - the evolution of species in a plastic state, not only offers plenty of new predictions to be tested, but also provides explanations for a much broader spectrum of known biological phenomena than classic evolutionary theories.This article was reviewed by Rob Knight, Fyodor Kondrashov and Massimo Di Giulio (nominated by David H. Ardell).Darwin's evolutionary theory[1] could easily explain the evolution of adaptive traits (organs and behavioral patterns) in asexual organisms. However, its capacity to explain the origin of such traits in sexual organisms, i.e. in most eukaryotic species on Earth, was already widely discussed by Darwin's critics in the 19th century[2]. The most frequent objection was that in sexual organisms phenotypes, as well as forms of particular traits, have a continuous tendency to return to original state, as the carriers of a new phenotype (a new trait) mate with more numerou
A Theoretical Interpretation of Policy Evaluation in the Context of Lithuanian Public Sector Reform
Jaroslav Dvorak
Baltic Journal of Law & Politics , 2008, DOI: 10.2478/v10076-008-0006-0
Abstract: Why do some policy evaluations have national and worldwide recognition? Those evaluations make an impact on states' modernization; they change the paradigms, values, stereotypes, programming transformation and reforms. Other evaluations do not have any significant influence and are likely put on the e-shelves of the governments and universities computers. Evaluation researches are defined as reformistic, which aim to develop an alternatives for the social improvement. One of the functions of evaluation is an improvement by assessing policy output and outcome. Most outcomes are jointly determined and controlled by plurality of the actors. Evaluation helps to change a policy agenda, policy formulation and implementation strategies. Modern scientific and technological achievements provide governments with real and noticeable military, economic, political, diplomatic power. Under such circumstances, a critical question emerge: is the influence of policy evaluations determined by the qualifications of the evaluators, the political-economic situation or the efforts of the international donors community to export values, knowledge, ideas which have either direct or indirect interest to the development efforts?
Corporate Financial Strategy in SMEs
Jaroslav Pavlicerk
Lecture Notes in Engineering and Computer Science , 2009,
Abstract:
On Technological IT Infrastructure Flexibility
Jaroslav Jando?
Systémová Integrace , 2011,
Abstract: The organizational flexibility, enabling organization (enterprise) to quickly react to changes in its environment, is in current dynamic and disruptive economic environment strictly required. This requirement concerns also IT (Information Technology) flexibility, including technological IT infrastructure flexibility which is the topic of this paper. Characteristics of technological IT infrastructure flexibility are presented in the paper. The main goal of the paper is specification of activities executed by organization in order to improve technological IT infrastructure flexibility. These activities include standardization, virtualization, service orientation, and technological architecture provisioning, i.e. its formulation and management.
On Business Intelligence SaaS solution
Jaroslav Jando?
Systémová Integrace , 2012,
Abstract: Cloud computing, which is a popular and still more adopted concept even in enterprise computing, brings by its SaaS service (Software as a Service) on public cloud a new possibilities of augmenting/expanding the functionality of on-premises ERP systems. This paper presents a case study oriented towards use of SaaS BI (Business Intelligence) solution for on-premises ERP system augmentation, with main aim to determine particular SaaS adoption drivers, SaaS concerns as well as business benefits of this approach.
TQMAND QMS FOR INCREASING QUALITY OF SCHOOL AND OF PROCESSES / TQM a QMS pre zvy ovanie kvality koly a procesov
Jambor Jaroslav
Technológia vzdelávania , 2008,
Abstract: Secondary schools nowadays face competition and Quality Management System implementation may be an effective way how to attract students. The paper describes such an effort at Secondary Schools.Autor sa vo svojom príspevku zaoberá im-plementáciou modifikovaného systému mana érstva kvality a filozofie TQM v podmienkach strednej koly. Aplikáciou systému mana érstva kvality prípadne aplikáciou filozofie komplexného mana érstva kvality sa zvy i kvalita koly a procesov v nej prebiehajúcich. Vhodnou implementáciou TQM a QMS m e kola získa na kon-kuren nom trhu vzdelávania prestí ne postavenie.
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