bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency and Magnitude Analysis of the Macro-instability Related Component of the Tangential Force Affecting Radial Baffles in a Stirred Vessel
Authors: Hasal P. , Kratěna J. , Fořt I.
Published: March 2021

Experimental data obtained by measuring the tangential component of force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with pitched blade impellers is analysed. The maximum mean tangential force is detected at the vessel bottom. The mean force value increases somewhat with decreasing impeller off-bottom clearance and is noticeably affected by the number of impeller blades. Spectral analysis of the experimental data clearly demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force at all values of impeller Reynolds number. The dimensionless frequency of the occurrence of the MI force component is independent of stirring speed, position along the baffle, number of impeller blades and liquid viscosity. Its mean value is about 0.074. The relative magnitude (QMI) of the MI-related component of the total force is evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. Relative magnitude QMI was analysed in dependence on the frequency of the impeller revolution, the axial position of the measuring point in the vessel, the number of impeller blades, the impeller off-bottom clearance, and liquid viscosity. Higher values of QMI are observed at higher impeller off-bottom clearance height and (generally) QMI decreases slightly with increasing impeller speed. The QMI value decreases in the direction from vessel bottom to liquid level. No evident difference was observed between 4 blade and 6 blade impellers. Liquid viscosity has only a marginal impact on the QMI value.
Technical Teachers and Technical Teacher Education - Research Results
Authors: Dobrovská D. , Andres P.
Published: March 2021

Chartered engineers who are new teachers of technical subjects at various educational institutions receive technical teacher education in the accredited bachelor programme at the Czech Technical University in Prague. This paper presents the results of a recent survey in which engineers expressed their opinions on technical teacher education.
Analysis of Phase Evaluation Algorithms in an Interferometric Method for Static Deformation Measurement
Authors: Novák J.
Published: March 2021

This article describes and analyses an interferometric method for measuring displacements and deformation. The method can be used for a very accurate evaluation of the change in the surface shape of structures used in industry. The paper proposes several multistep phase calculation algorithms and describes an automatic evaluation process using the measurement technique. A complex analysis is also performed of various factors that can have a negative effect on the practical measurement and evaluation process. An analysis is made of the proposed multistep phase calculation algorithms using the proposed error model. It is shown that the resulting phase measurement errors can be effectively reduced by using suitable phase calculation algorithms. The analysis can be applied for a complex comparison of the accuracy and stability of such algorithms.
DLC Films Deposited by the DC PACVD Method
Authors: Palamarchuk D. , Zoriy M. , Gurovič J. , Černý F. , Konvičková S. , Hüttel I.
Published: March 2021

DLC (Diamond-Like Carbon) coatings have been suggested as protective surface layers against wear. However hard DLC coatings, especially those of greater thickness, have poor adhesion to substrates. We have used several ways to increase the adhesion of DLC coatings prepared by the PACVD (Plasma Assisted Chemical Vapour Deposition) method on steel substrates. One of these is the DC PACVD method for preparing DLC films.
Numerical Implementation of Isotropic Consolidation of Clayey Soils
Authors: Janda T. , Kuklík M. , Šejnoha M.
Published: March 2021

This paper reports on implementation of several numerical techniques to solve a set of governing equations resulting from simple one dimensional isotropic consolidation of soils that behave according to the Cam clay model. Three different methods of solving the equations of consolidation, namely the collocation method, the finite volume method and the finite element method, are presented. Apart from evaluating their efficiency, which becomes particularly crucial when implementing these techniques in the framework of an optimization problem aimed at tuning the model parameters, a set of parameters of a Cam clay model driving the time dependent response of the soils (deformation dependent variation of the coefficient of permeability and preconsolidation pressure) is also discussed.
Models for Non-isothermal Steady-State Diffusion in Porous Building Materials
Authors: Ficker T. , Podešvová Z.
Published: March 2021

Two models for non-isothermal diffusion of water vapour in building materials have been developed and their numerical outputs compared with a standard isothermal approximation.
Tendencies in Spatial Planning in Austria
Authors: Hladká K.
Published: March 2021

In Austria there is a federal system, where the power is shared between national (Bund) and regional (Land) governments, with each having autonomy in some spheres, and able to pass laws. Power resides with the national government, although certain responsibilities may be delegated to regional governments. In Austria the national government has no competence in spatial planning, but planning at the national level is undertaken through a joint forum which has advisory powers, and in which the national government and the Länder Austrian are equal partners. At regional level the Austrian Länder play the primary role in spatial planning. The Austrian national government has only limited responsibilities.
A Bypass-Ring Scheme for a Fault Tolerant Multicast
Authors: Dynda V.
Published: March 2021

We present a fault tolerant scheme for recovery from single or multiple node failures in multi-directional multicast trees. The scheme is based on cyclic structures providing alternative paths to eliminate faulty nodes and reroute the traffic. Our scheme is independent of message source and direction in the tree, provides a basis for on-the-fly repair and can be used as a platform for various strategies for reconnecting tree partitions. It only requires an underlying infrastructure to provide a reliable routing service. Although it is described in the context of a message multicast, the scheme can be used universally in all systems using tree-based overlay networks for communication among components.
A Multi-Agent Mah Jong Playing System: Towards Real-Time Recognition of Graphic Units in Graphic Representations
Authors: Achten H. , Jessurun J.
Published: March 2021

In architectural design, sketching is an important means to explore the first conceptual developments in the design process. It is necessary to understand the conventions of depiction and encoding in sketches and drawings if we want to support the architect in the sketching activity. The theory of graphic units provides a comprehensive list of conventions of depiction and encoding that are widely used among architects. These graphic units form useful building blocks to understand design drawings. We investigate whether it is possible to build a system that can recognize graphic units. The technology we are looking at is multi-agent systems. It was chosen for the following reasons: agents can specialize in graphic units, a multi-agent system can deal with ambiguity through negotiation and conflict resolution, and multi-agent systems function in dynamically changing environments. Currently there is no general approach or technology available for multi-agent systems. Therefore, in our research we first set out to make such a multi-agent system. In order to keep the complexity low, we first aim to make a system that can do something simple: playing Mah Jong solitary. The Mah Jong solitary system shares the following important features with a multi-agent system that can recognize graphic units: (1) specialized agents for moves; (2) negotiation between agents to establish the best move; (3) a dynamically changing environment; and (4) search activity for more advanced strategies. The paper presents the theoretical basis of graphic units and multi-agents systems, followed by a description of the multi-agent framework and its implementation. A number of systems that can play Mah Jong at various degrees of competence and accordingly degrees of complexity of multi-agent system, are distinguished. Finally, the paper demonstrates how the findings are informative for a system that can recognize graphic units.
Study of Wear of Pitched Blade Impellers in a Solid-Liquid Suspension
Authors: Fořt I. , Kreibich V. , Marek J.
Published: March 2021

A study was made of the erosion wear of the blades of pitched blade impellers in a suspension of silicious sand (CV= 5 %, d=0.325 mm, degree of hardness "7.5") in water under a turbulent flow regime of agitated charge when complete homogeneity of the suspension was achieved. Two aims of the study were defined: the dependence of the rate of the erosion process of the impeller blades on impeller frequency of revolution and on the size of the mixing equipment. Experiments were carried out on pilot plant mixing equipment of two sizes (geometrically similar) made of stainless steel (diameters of cylindrical vessels T1 = 200 mm and T2 = 300 mm, diameters of impellers D1 = 100 mm and D2= 66. 7 mm, impeller off bottom clearances h1 = 100 mm and h2= 66. 7 mm, respectively) equipped with four radial baffles (width b1 = 30 mm, b2 =20 mm, respectively) and an impeller with four inclined plane blades (pitch angle α =30°, 45°, relative blade with W/D = 0.2) made of rolled brass (Brinnel hardness 40-50 BM) always pumping the liquid downwards towards the float vessel bottom. The wear of the impeller was described by an analytical approximation in exponential form with two parameters (the wear rate constant k and the geometrical parameters of the worn blade C) calculated by the least squares method from the experimentally found profile of the worn leading edge of the impeller blades. While the wear rate constant exhibits a monotonous dependence on the pitch angle only, the geometric parameter is dependent both on the pitch angle and in linear form on the impeller tip speed. Thus in the procedure for scaling up the rate of erosion wear of the pitched blade impellers in a suspension of higher solid particle hardness, the decision process parameters are the impeller blade pitch angle and the impeller tip speed.
Detailed Numerical Modeling of Flood Flow in Floodplains with Complex Geometry
Authors: Valenta P. , Valentová J.
Published: March 2021

Numerical modeling of flood flow and the evaluation of flood hazards can be based on various numerical models and modeling techniques. One-dimensional (1D), quasi two-dimensional (1,5 D), two-dimensional (2D) or three-dimensional (3D) variants of numerical models can be used. While 3D models are too demanding to be used for flood flow modeling on personal computers, quasi-2D and 2D models can be more widely used to solve even larger practical problems nowadays. Detailed two-dimensional numerical modeling of flood flow in flooded urbanized areas with complex geometry using the 2D depth averaged model is presented in this paper. The governing equations of the model are expressed with a set of depth averaged Reynolds equations consisting of the continuity equation and two momentum equations for the horizontal velocity components. The eddy viscosity, which influences the horizontal turbulent momentum exchange processes, is modeled with the aid of a depth average version of the two-equation k-e turbulence model. The partial differential equations are solved numerically with a control volume method using fine non-orthogonal curvilinear grids and a non-staggered variable arrangement. The applicability and advantages of this modeling approach for simulating the flood flow in floodplains with complex geometry, and in urban areas, are illustrated by the results of a pilot study in Choceň and Ústí nad Orlicí, towns which were severely affected during the 1997 and 1998 floods in the Czech Republic.
The Tangential Force Affecting the Radial Baffles in a Stirred Vessel: Analysis of the Macro-instability Related Component
Authors: Hasal P. , Fořt I. , Kratěna J.
Published: March 2021

Experimental data obtained by measuring the tangential component of the force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with a Rushton turbine impeller is analysed. Spectral analysis of the experimental data demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force. Two distinct dimensionless frequencies (both directly proportional to the impeller speed of rotation N) of the occurence of the MI component were detected: a lower frequency of approximately 0.025N and a higher frequency of about 0.085N. The relative magnitude QMI of the MI-related component of the total tangential force was evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. The values of magnitude QMI varied in the interval [rom approximately 0.05 to 0.30. The magnitude QMI takes maximum values at low Reynolds number values (in laminar and transitional regions). In the turbulent region (ReM >20000) the QMI value is low and practically constant. The dependence oj the QMI values on vertical position in the vessel is only marginal. The results suggest that the magnitude of the MI component of the force is significantly influenced by the liquid viscosity and density.
Analysis of Gear Wheel-shaft Joint Characterized by Comparable Pitch Diameter and Mounting Diameter
Authors: Ryś J. , Sanecki H. , Trojnacki A.
Published: March 2021

This paper presents the design procedure for a gear wheel-shaft direct frictional joint. The small difference between the operating pitch diameter of the gear and the mounting diameter of the frictional joint is the key feature of the connection. The contact surface of the frictional joint must be placed outside the bottom land of the gear, and the geometry of the joint is limited to the specific type of solutions.The strength analysis is based on the relation between the torque and statistical load intensity of the gear transmission. Several dimensionless parameters are introduced to simplify the calculations. Stress-strain verifying analysis with respect to combined loading, the condition of appropriate load-carrying capacity of the frictional joint and the fatigue strength of the shaft are applied to obtain the relations between the dimensions of the joint and other parameters. The final engineering solution may then be suggested. The approach is illustrated by a numerical example.The proposed procedure can be useful in design projects for small, high-powered modern reducers and new-generation geared motors, in particular when manufactured in various series of types.
Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference of a Subsonic Fighter Aircraft
Authors: Lazim Tholudin Mat , Mat Shabudin , Saint Huong Yu
Published: March 2021

The main objective of the present work is to study the effect of an external store on a subsonic fighter aircraft. Generally most modern fighter aircrafts are designed with an external store installation. In this study, a subsonic fighter aircraft model has been manufactured using a computer numerical control machine for the purpose of studying the effect of the aerodynamic interference of the external store on the flow around the aircraft wing. A computational fluid dynamic (CFD) simulation was also carried out on the same configuration. Both the CFD and the wind tunnel testing were carried out at a Reynolds number 1.86×105 to ensure that the aerodynamic characteristic can certify that the aircraft will not be face any difficulties in its stability and controllability. Both the experiments and the simulation were carried out at the same Reynolds number in order to verify each other. In the CFD simulation, a commercial CFD code was used to simulate the interference and aerodynamic characteristics of the model. Subsequently, the model together with an external store was tested in a low speed wind tunnel with a test section sized 0.45 m×0.45 m. Measured and computed results for the two-dimensional pressure distribution were satisfactorily comparable. There is only a 19% deviation between pressure distribution measured in wind tunnel testing and the result predicted by the CFD. The result shows that the effect of the external storage is only significant on the lower surface of the wing and almost negligible on the upper surface of the wing. Aerodynamic interference due to the external store was most evident on the lower surface of the wing and almost negligible on the upper surface at a low angle of attack. In addition, the area of influence on the wing surface by the store interference increased as the airspeed increased.
Static vs. Dynamic List-Scheduling Performance Comparison
Authors: Hagras T. , Janeček J.
Published: March 2021

The problem of efficient task scheduling is one of the most important and most difficult issues in homogeneous computing environments. Finding an optimal solution for a scheduling problem is NP-complete. Therefore, it is necessary to have heuristics to find a reasonably good schedule rather than evaluate all possible schedules. List-scheduling is generally accepted as an attractive approach, since it pairs low complexity with good results. List-scheduling algorithms schedule tasks in order of priority. This priority can be computed either statically (before scheduling) or dynamically (during scheduling). This paper presents the characteristics of the two main static and the two main dynamic list-scheduling algorithms. It also compares their performance in dealing with random generated graphs with various characteristics.
Dynamics of Micro-Air-Vehicle with Flapping Wings
Authors: Sibilski K.
Published: March 2021

Small (approximately 6 inch long, or hand-held) reconnaissance micro air vehicles (MAVs) will fly inside buildings, and require hover for observation, and agility at low speeds to move in confined spaces. For this flight envelope insect-like flapping wings seem to be an optimal mode of flying. Investigation of the aerodynamics of flapping wing MAVs is very challenging. The problem involves complex unsteady, viscous flow (mainly laminar), with the moving wing generating vortices and interacting with them. At this early stage of research only a preliminary insight into the nature of the little known aerodynamics of MAVs has been obtained. This paper describes computational models for simulation of the controlled motion of a microelectromechanical flying insect – entomopter. The design of software simulation for entomopter flight (SSEF) is presented. In particular, we will estimate the flight control algorithms and performance for a Micromechanical Flying Insect (MFI), a 80–100 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. The SSEF is an end-to-end tool composed of several modular blocks which model the wing aerodynamics and dynamics, the body dynamics, and in the future, the environment perception, control algorithms, the actuators dynamics, and the visual and inertial sensors. We present the current state of the art of its implementation, and preliminary results.
The Role of CAD in Enterprise Integration Process
Authors: Ota M. , Jelínek I.
Published: March 2021

This article deals with the problem of the mutual influence between software systems used in enterprise environment and enterprise integration processes. The position of CAD data and CAx systems in the integrated environment of manufacturing enterprises is clarified. As a consequence, the key role of CAx systems used in those companies is emphasized. It is noted that the integration of CAD data is nowadays only on a secondary level, via primarily integrated PDM systems. This limitation is a reason why we are developing a unified communication model focused on product-oriented data. Our approach is based on Internet technologies, so we believe that is independent enough. The proposed system of communication is based on a simple request-replay dialogue. The structure of this model is open and extensible, but we assume supervision supported by an Internet portal.
Development of a Technique and Method of Testing Aircraft Models with Turboprop Engine Simulators in a Small-scale Wind Tunnel - Results of Tests
Authors: Petrov A. V. , Stepanov Y. G. , Shmakov M. V.
Published: March 2021

This report presents the results of experimental investigations into the interaction between the propellers (Ps) and the airframe of a twin-engine, twin-boom light transport aircraft with a Π-shaped tail. An analysis was performed of the forces and moments acting on the aircraft with rotating Ps. The main features of the methodology for windtunnel testing of an aircraft model with running Ps in TsAGI’s T-102 wind tunnel are outlined.The effect of 6-blade Ps slipstreams on the longitudinal and lateral aerodynamic characteristics as well as the effectiveness of the control surfaces was studied on the aircraft model in cruise and takeoff/landing configurations. The tests were conducted at flow velocities of V∞ = 20 to 50 m/s in the ranges of angles of attack α =  -6 to 20 deg, sideslip angles of β = -16 to 16 deg and blade loading coefficient of B 0 to 2.8. For the aircraft of unusual layout studied, an increase in blowing intensity is shown to result in decreasing longitudinal static stability and significant asymmetry of the directional stability characteristics associated with the interaction between the Ps slipstreams of the same (left-hand) rotation and the empennage.
Developing a Conceptual Design Engineering Toolbox and its Tools
Authors: Vroom R. W. , Van Breemen E. J. J. , Van der Vegte W. F.
Published: March 2021

In order to develop a successful product, a design engineer needs to pay attention to all relevant aspects of that product. Many tools are available, software, books, websites, and commercial services. To unlock these potentially useful sources of knowledge, we are developing C-DET, a toolbox for conceptual design engineering. The idea of C-DET is that designers are supported by a system that provides them with a knowledge portal on one hand, and a system to store their current work on the other. The knowledge portal is to help the designer to find the most appropriate sites, experts, tools etc. at a short notice. Such a toolbox offers opportunities to incorporate extra functionalities to support the design engineering work. One of these functionalities could be to help the designer to reach a balanced comprehension in his work. Furthermore C-DET enables researchers in the area of design engineering and design engineers themselves to find each other or their work earlier and more easily. Newly developed design tools that can be used by design engineers but have not yet been developed up to a commercial level could be linked to by C-DET. In this way these tools can be evaluated in an early stage by design engineers who would like to use them. This paper describes the first prototypes of C-DET, an example of the development of a design tool that enables designers to forecast the use process and an example of the future functionalities of C-DET such as balanced comprehension.
Image Analysis of Eccentric Photorefraction
Authors: Dušek J. , Dostálek M.
Published: March 2021

This article deals with image and data analysis of the recorded video-sequences of strabistic infants. It describes a unique noninvasive measuring system based on two measuring methods (position of I. Purkynje image with relation to the centre of the lens and eccentric photorefraction) for infants. The whole process is divided into three steps. The aim of the first step is to obtain video sequences on our special system (Eye Movement Analyser). Image analysis of the recorded sequences is performed in order to obtain curves of basic eye reactions (accommodation and convergence). The last step is to calibrate of these curves to corresponding units (diopter and degrees of movement).
Computer Aided Design of Transformer Station Grounding System Using CDEGS Software
Authors: Nikolovski S. , Barić T.
Published: March 2021

This paper presents a computer-aided design of a transformer station grounding system. Fault conditions in a transformer station can produce huge damage to transformer station equipment if the grounding system is not designed properly. A well designed grounding system is a very important part of the project for transformer station design as a whole. This paper analyses a procedure for transformer grounding system design and spatial distribution of touch and step voltage on the ground surface level, using the CDEGS (Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis) software. Spatial distribution is needed for checking and finding dangerous step and touch voltages above and around the transformer station. Apparent earth resistivity data is measured and analyzed using the RESAP module of the CDEGS software. Because of the very high current flow into the grounding system during a single line to ground fault or a three phase fault in the transformer station, very high and dangerous potentials can be induced on the metallic structures including the fence, which can cause dangerous situations for people and animals near the station and for the personnel inside the station. The PLOT module of CDEGS is used to view the results of the scalar potential, step and touch voltage on the surface. Graphic displays include equipotent contour lines and potential profiles (gradients) in 3D and 2D perspective and apparent soil resistivity (Wm) versus inter electrode spacing (m). The results of alternative grid designs may be displayed simultaneously for the purpose of comparison.
On the Effects of an Installed Propeller Slipstream on Wing Aerodynamic Characteristics
Authors: Catalano F. M.
Published: March 2021

This work presents an experimental study of the effect of an installed propeller slipstream on a wing boundary layer. The main objective was to analyse through wind tunnel experiments the effect of the propeller slipstream on the wing boundary layer characteristics such as: laminar flow extension and transition, laminar separation bubbles and reattachment and turbulent separation. Two propeller/wing configurations were studied: pusher and tractor. Experimental work was performed using two different models: a two-dimensional wing with a central cylindrical nacelle for the tractor configuration, and a simple two-dimensional wing with a downstream propeller for the pusher tests. The relative position between propeller and wing could be changed in the pusher model, and a total of 7 positions were analysed. For the tractor tests the relative propeller/wing was fixed, but three different propellers: two, three and four bladed were tested. Measurements included pressure distribution, hot wire anemometry and boundary layer characteristics by flow visualisation. The results showed that the pusher propeller inflow affects the wing characteristics by changing the lift, drag, and also delays the boundary layer transition and separation. These effects are highly dependent on the relative position of the wing/propeller. On the other hand, the tractor propeller slipstream induces transition and its effect is dependent on the number of blades.
Design and Properties of Octaslide Redundant Parallel Kinematics
Authors: Bauma V. , Valášek M. , Šika Z.
Published: March 2021

This paper describes the conceptual design process of OCTASLIDE redundant parallel kinematics for a machine tool. Redundantly actuated parallel kinematics is a recently developed new concept for machine tools. It enables all mechanical properties of machine tools to be improved several times simultaneously. This is particularly demonstrated on the design of the OCTASLIDE. This is a concept of a five-axis machine tool centre. The paper describes the critical initial design phases and the accessible mechanical properties. The design process has follow the newly developed design methodology for parallel kinematics machines.
A Component-based Software Development and Execution Framework for CAx Applications
Authors: Matsuki N. , Tokunaga H. , Sawada H.
Published: March 2021

Digitalization of the manufacturing process and technologies is regarded as the key to increased competitive ability. The MZ-Platform infrastructure is a component-based software development framework, designed for supporting enterprises to enhance digitalized technologies using software tools and CAx components in a self-innovative way. In the paper we show the algorithm, system architecture, and a CAx application example on MZ-Platform. We also propose a new parametric data structure based on MZ-Platform.
A Numerical Model to Predict Matric Suction Inside Unsaturated Soils
Authors: Farouk A. , Lamboj L. , Kos J.
Published: March 2021

The objective of this research is to introduce a numerical simulation model to predict approximate values of the matric suction inside unsaturated soils that have low water contents. The proposed model can be used to predict the relationship between the water content and the matric suction of a studied soil to construct the soil-water characteristic curve. In addition, the model can be utilized to combine the predicted matric suction with the soil parameters obtained experimentally, which enables us to explain how matric suction can affect the behaviour of unsaturated soils, without the need to utilize advanced measuring devices or special testing techniques. The model has given good results, especially when studying coarse-grained soils.
Effect of Boundary Constraints in the Formulation of the Partition of Unity Method: One-dimensional Setting
Authors: Audy M. , Šejnoha M.
Published: March 2021

The paper examines an effect of boundary constraints applied to the enhanced degrees of freedom of partition of unity based discontinuous elements. To highlight the present issue the problem is studied in a one-dimensional setting. In particular, an example of a one-dimensional bar element crossed by a set of discontinuities having a finite elastic stiffness clearly shows a need for proper approximation of the displacement field within a discontinuous element in order to correctly represent the structural response. While the discontinuous elements with boundary constraints applied to the enhanced degrees of freedom display an unrealistic dependence of the global response on the locations of the discontinuities, the discontinuous elements with complete approximation of the discontinuous part of the displacement field provide the expected global response independent of the locations of the discontinuities.
Modelling of Size Effect with Regularised Continua
Authors: Askes H. , Simone A. , Sluys L. J.
Published: March 2021

A nonlocal damage continuum and a viscoplastic damage continuum are used to model size effects. Three-point bending specimens are analysed, whereby a distinction is made between unnotched specimens, specimens with a constant notch and specimens with a proportionally scaled notch. Numerical finite element simulations have been performed for specimen sizes in a range of 1:64. Size effects are established in terms of nominal strength and compared to existing size effect models from the literature.
A Discontinuous Model to Study Fracture of Brittle Materials
Authors: Proft K. De , Wilde W. P. De
Published: March 2021

In this paper, the partition of the unity property of finite element shape functions is used to introduce displacement discontinuities into finite elements. The discontinuous character of the displacement field is captured with the Heaviside step function. Using the partition of unity concept, the governing equation of the continuum and the discontinuity are separated and are consequently described by different constitutive laws. Inside the discontinuity, a plasticity based constitutive law is used to describe the decrease of tractions in function of the crack opening while the continuum is assumed to remain elastic. The methodology will be described and validated with a comparison between numerical simulations and experimental results.This paper is dedicated to J. Sejnoha, TU Prague, with respect and admiration for his scientific achievement.
Solution of Nonlinear Coupled Heat and Moisture Transport Using Finite Element Method
Authors: Krejčí T.
Published: March 2021

This paper deals with a numerical solution of coupled of heat and moisture transfer using the finite element method. The mathematical model consists of balance equations of mass, energy and linear momentum and of the appropriate constitutive equations. The chosen macroscopic field variables are temperature, capillary pressures, gas pressure and displacement. In contrast with pure mechanical problems, there are several difficulties which require special attention. Systems of algebraic equations arising from coupled problems are generally nonlinear, and the matrices of such systems are nonsymmetric and indefinite. The first experiences of solving complicated coupled problems are mentioned in this paper.
Membrane Triangles with Drilling Degrees of Freedom
Authors: Fajman P.
Published: March 2021

An accurate triangular plane element with drilling degrees of freedom is shown in this paper. This element can be successfully used for solving linear and nonlinear problems. The main advantage of this element is that the stiffness matrix is obtained from pure deformations – elongations of the edges. This aproach is very suitable for nonlinear analysis, where the unbalanced forces can be obtained directly from elongations of edges.
Fuzzy Dynamic Analysis of a 2D Frame
Authors: Štemberk P. , Kruis J.
Published: March 2021

This paper deals with the dynamic analysis of a 2D concrete frame with uncertainties which are an integral part of any real structure. The uncertainties can be modeled by a stochastic or a fuzzy approach. The fuzzy approach is used and the influence of uncertain input data (modulus of elasticity and density) on output data is studied. Fuzzy numbers are represented by ?-cuts. In order to reduce the volume of computation in the fuzzy approach, the response surface function concept is applied. In this way the natural frequencies and mode shapes described by fuzzy numbers are obtained. The results of fuzzy dynamic analysis can be used, e.g., in seismic design of structures based on the response spectrum.
3D Information System of Historical Site – Proposal and Realisation of a Functional Prototype
Authors: Hodač J.
Published: March 2021

The development of methods for 3D data acquisition, together with progress in information technologies raises the question of creating and using 3D models and 3D information systems (IS) of historical sites and buildings. This paper presents the current state of the “Live Theatre” project. The theme of the project is the proposal and realisation of a 3D IS of the baroque theatre at Eeský Krumlov castle (UNESCO site).The project is divided into three main stages – creation of a 3D model, proposal of a conception for a 3D IS, and realisation of a functional prototype. 3D data was acquired by means of photogrammetric and surveying methods. An accurate 3D model (photo-realistic, textured) was built up with MicroStation CAD system. The proposal of a conception of a 3D IS was the main outcome of the author’s dissertation. The essential feature of the proposed conception is the creation of subsystems targeted on three spheres – management, research and presentation of the site. The functionality of each subsystem is connected with its related sphere; however, each subsystem uses the same database. The present stage of the project involves making a functional prototype (with sample data). During this stage we are working on several basic technological topics. At present we are concerned with 3D data, its formats, format conversions (e.g. DGN _ VRML) and its connection to other types of data. After that, we will be seeking a convenient technical solution based on network technologies (Internet) and an appropriate layout for the data (database). The project is being carried out in close co-operation with the administration of the castle and some other partners. This stage of the project will be completed in December 2005.A functional prototype and the information acquired by testing it will form the basis for the final proposal of a complex IS of a historical site. The final proposal and appropriate technology will be the outcome of the project. The realisation of a complex 3D IS will then follow. The results will be exploitable both for site management and for organisations working in the area of presenting historical sites and creating multimedia shows.
Modelling a New Product Model on the Basis of an Existing STEP Application Protocol
Authors: Hoehn B.-R. , Steingroever K. , Jaros M.
Published: March 2021

During the last years a great range of computer aided tools has been generated to support the development process of various products. The goal of a continuous data flow, needed for high efficiency, requires powerful standards for the data exchange. At the FZG (Gear Research Centre) of the Technical University of Munich there was a need for a common gear data format for data exchange between gear calculation programs. The STEP standard ISO 10303 was developed for this type of purpose, but a suitable definition of gear data was still missing, even in the Application Protocol AP 214, developed for the design process in the automotive industry. The creation of a new STEP Application Protocol or the extension of existing protocol would be a very time consumpting normative process. So a new method was introduced by FZG. Some very general definitions of an Application Protocol (here AP 214) were used to determine rules for an exact specification of the required kind of data. In this case a product model for gear units was defined based on elements of the AP 214. Therefore no change of the Application Protocol is necessary. Meanwhile the product model for gear units has been published as a VDMA paper and successfully introduced for data exchange within the German gear industry associated with FVA (German Research Organisation for Gears and Transmissions). This method can also be adopted for other applications not yet sufficiently defined by STEP.
Study of Concepts of Parallel Kinematics Machines for Advanced Manufacturing
Authors: Valášek M. , Bauma V. , Šika Z.
Published: March 2021

This paper deals with possible new concepts for machine tools based on parallel kinematics for advanced manufacturing. Parallel kinematics machines (PKM) enable the mechanical properties of manufacturing machines to be improved. This has been proven by several new machine tool concepts. However, this potential can be and must be increased by applying the principle of redundant actuation. This paper deals with the extension of the concepts of redundantly actuated parallel kinematics structures for five-sided five-axis machine tools and for a free-forming sheet metal forming machine. The design principles of previous successful PKMs are summarized and new concepts are proposed. The most important requirement criteria are summarized. The proposed concepts are qualitatively and initially quantitatively evaluated according to these criteria.
Design and Optimization of a Turbine Intake Structure
Authors: Fošumpaur P. , Čihák F.
Published: March 2021

The appropriate design of the turbine intake structure of a hydropower plant is based on assumptions about its suitable function, and the design will increase the total efficiency of operation. This paper deals with optimal design of the turbine structure of run-of-river hydropower plants. The study focuses mainly on optimization of the hydropower plant location with respect to the original river banks, and on the optimal design of a separating pier between the weir and the power plant. The optimal design of the turbine intake was determined with the use of 2-D mathematical modelling. A case study is performed for the optimal design of a turbine intake structure on the Nemen river in Belarus.
Model Based Control of Moisture Sorption in a Historical Interior
Authors: Zítek P. , Vyhlídal T.
Published: March 2021

This paper deals with a novel scheme for microclimate control in historical exhibition rooms, inhibiting moisture sorption phenomena that are inadmissible from the preventive conservation point of view. The impact of air humidity is the most significant harmful exposure for a great deal of the cultural heritage deposited in remote historical buildings. Leaving the interior temperature to run almost its spontaneous yearly cycle, the proposed non-linear model-based control protects exhibits from harmful variations in moisture content by compensating the temperature drifts with an adequate adjustment of the air humidity. Already implemented in a medieval interior since 1999, the proposed microclimate control has proved capable of permanently maintaining constant a desirable moisture content in organic or porous materials in the interior of a building.
Simulation and Analysis of Magnetisation Characteristics of Interior Permanent Magnet Motors
Authors: Walker J. A. , Cossar C. , Miller T. J. E.
Published: March 2021

Modern permanent magnet (PM) synchronous brushless machines often have magnetic circuits in which the patterns of saturation are complex and highly variable with the position of the rotor. The classical phasor diagram theory of operation relies on the assumption of sinusoidal variation of flux-linkage with rotor position, and neglects the non-linear effects that arise in different operating states. The finite element method is a useful tool for detailed magnetic analysis, but it is important to verify simulation results by direct measurement of the magnetic characteristics of the motor, in terms of “magnetisation curves” of current and flux-linkage. This paper presents results from finite element simulations to determine the magnetisation in a split-phase interior permanent magnet (IPM) motor. Investigation has been made to determine the effects of the rotor geometry on the synchronous reactances and airgap flux distribution. Comparisons are made with a second IPM motor with a different rotor configuration.
Intelligent Data Storage and Retrieval for Design Optimisation – an Overview
Authors: Peebles C. , Bil C. , Drack L.
Published: March 2021

This paper documents the findings of a literature review conducted by the Sir Lawrence Wackett Centre for Aerospace Design Technology at RMIT University. The review investigates aspects of a proposed system for intelligent design optimisation. Such a system would be capable of efficiently storing (and compressing if required) a range of types of design data into an intelligent database. This database would be accessed by the system during subsequent design processes, allowing for search of relevant design data for re-use in later designs, allowing it to become very efficient in reducing the time for later designs as the database grows in size. Extensive research has been performed, in both theoretical aspects of the project, and practical examples of current similar systems. This research covers the areas of database systems, database queries, representation and compression of design data, geometric representation and heuristic methods for design applications.
Design of a Low-Cost Easy-to-Fly STOL Ultralight Aircraft in Composite Material
Authors: Coiro D. P. , Marco A. de , Nicolosi F. , Genito N. , Figliolia S.
Published: March 2021

The paper deals with the design of an aircraft, starting from a market survey, the conceptual design loop and the preliminary choice of dimensions, and leading to the detailed design of efficient high-lift systems and a low-drag fuselage shape. Technological challenges regarding the design of low-cost systems for flap/slat retraction and a simple wing folding system are highlighted. Aiming at an efficient optimization algorithm, we developed a new integration technique between CAD, aerodynamic and structural numerical calculation. Examples deriving from this new approach are presented.
Design and Development of the Engine Unit for a Twin-Rotor Unmanned Aerial Vehicle
Authors: Avanzini G. , D’Angelo S. , Matteis G. de
Published: March 2021

Advanced computer-aided technologies played a crucial role in the design of an unconventional Uninhabited Aerial Vehicle (UAV), developed at the Turin Technical University and the University of Rome “La Sapienza”. The engine unit of the vehicle is made of a complex system of three two stroke piston engines coupled with two counter-rotating three-bladed rotors, controlled by rotary PWM servos. The focus of the present paper lies on the enabling technologies exploited in the framework of activities aimed at designing a suitable and reliable engine system, capable of performing the complex tasks required for operating the proposed rotorcraft. The synergic use of advanced computational tools for estimating the aerodynamic performance of the vehicle, solid modeling for mechanical components design, and rapid prototyping techniques for control system logic synthesis and implementation will be presented.
Simulation of UAV Systems
Authors: Kaňovský P. , Smrcek L. , Goodchild C.
Published: March 2021

The study described in this paper deals with the issue of a design tool for the autopilot of an Unmanned Aerial Vehicle (UAV) and the selection of the airdata and inertial system sensors. This project was processed in cooperation with VTUL a PVO o.z. [1]. The feature that distinguishes the autopilot requirements of a UAV (Figs. 1, 7, 8) from the flight systems of conventional manned aircraft is the paradox of controlling a high bandwidth dynamical system using sensors that are in harmony with the low cost low weight objectives that UAV designs are often expected to achieve. The principal function of the autopilot is flight stability, which establishes the UAV as a stable airborne platform that can operate at a precisely defined height. The main sensor for providing this height information is a barometric altimeter. The solution to the UAV autopilot design was realised with simulations using the facilities of Matlab® and in particular Simulink®[2].
Mathematical Modeling of a Cs(I) – Sr(II) – Bentonite – Magnetite Sorption System, Simulating the Processes Taking Place in a Deep Geological Repository
Authors: Filipská H. , Štamberg K.
Published: March 2021

The derivation of mathematical models of systems consisting of Cs(I) or Sr(II) and of bentonite (B), magnetite (M) or their mixtures (B+M) are described. The paper deals especially with modeling of the protonation and sorption processes occurring on the functional groups of the solid phase, namely on so called edge sites and layer sites. The two types of sites have different properties and, as a result, three types of Surface Complexation Models (SCM) are used for edge sites, viz. two electrostatic SCMs: the Constant Capacitance Model (CCM) and the Diffusion Double Layer Model (DLM), and one without electrostatic correction: the Chemical Model (CEM). The processes taking place on the layer sites are described by means of the Ion Exchange Model (IExM). In the course of modeling, the speciation of the given metal in the liquid (aqueous) phase has to be taken into account. In principle, the model of protonation or sorption processes is based on the reactions occurring in the aqueous phase and on the surface of the solid phase, and comprises not only the equations of the equilibrium constants of the individual reactions, but also the mass and charge balance equations. The algorithm of the numerical solution is compatible with FAMULUS 3.5 (a Czech software product quite extensively used at Czech universities in the last decade, the bookcase codes of which are utilized).