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Number of results: 262
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Abstract

Mesoscale flows of liquid are of great importance for various nano- and biotechnology applications. Continuum model do not properly capture the physical phenomena related to the diffusion effects, such as Brownian motion. Molecular approach on the other hand, is computationally too expensive to provide information relevant for engineering applications. Hence, the need for a mesoscale approach is apparent. In recent years many mesoscale models have been developed, particularly to study flows of gas. However, mesoscale behaviour of liquid substantially differs from that of gas. This paper presents a numerical study of micro-liquids phenomena by a Voronoi Dissipative Particle Dynamics method. The method has its origin from the material science field and is one of very few numerical techniques which can describe correctly molecular diffusion processes in mesoscale liquids. This paper proves that correct prediction of molecular diffusion effects plays predominant role on the correct prediction of behaviour of immersed structures in the mesoscopic flow.

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Authors and Affiliations

J. Czerwińska
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Abstract

In the public debate, it is argued that Poland avoided a massive drop in output during the 2008/2009 economic crisis in part thanks to substantial nominal zloty’s depreciation against the euro. The Polish case is often contrasted with Slovakia that adopted the euro in January 2009 and, since the Ecofin Council decision in summer 2008, exhibited virtually no nominal exchange rate volatility while facing deep losses in output. In this paper we attempt to validate this contrast by reversing the roles, i.e. checking if Poland really would have faced the same drop – and Slovakia would have remained relatively resilient – if it had been Poland, not Slovakia, that adopted the euro at that point. Our counterfactual simulations based on a New Keynesian DSGE model indicate that, indeed, the Polish tradable output could have been 10‒15 percent lower than actually observed in 2009, while the Slovak one – approximately 20 percent higher. This asymmetry results mainly from structural differences between the two economies, such as size, openness, share of nontradable sector and foreign trade elasticities. The difference of this size would have been short-lived (3‒4 quarters), and the difference of the nontradable output would have been of much lower magnitude.

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Authors and Affiliations

Andrzej Torój
Karolina Konopczak
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Abstract

The paper considers the application of statistical properties of backscattered ultrasonic signal for assessment of the trabecular bone status.

Computer simulations were conducted to investigate the properties of the ultrasound pulse-echo signal, as it is received on the transducer surface after scattering in trabecular bone. The micro-architecture of trabecular bone was modeled by a random distribution of long and thin cylindrical scatterers of randomly varying diameters and mechanical properties, oriented perpendicular to the ultrasound beam axis. The received echo signal was calculated as a superposition of echoes from all the scatterers present in the scattering volume.

The simulated signal envelope was used for statistical processing to compute various parameters like the mean amplitude, the amplitude MSR defined as the ratio of the mean to the standard deviation and the amplitude histogram.

Results indicated that while for the well-defined trabeculae properties within the simulated bone structure the signal envelope values are Rayleigh distributed the significant departures from Rayleigh statistics may be expected as the thickness of trabeculae become random. The influence of the variation of mechanical properties of the bone tissue building the trabeculae on the bone backscattered signal parameters was not observed.

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Authors and Affiliations

Jerzy Litniewski
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Abstract

In this article the magnetic memory model with nano-meter size made from iron cells was proposed. For a purpose of determining the model specifications, the magnetic probes group with different geometrical parameters were examined using numeric simulations for the two different time duration of transitions among quasistable magnetic distributions found in the system, derived from the energy minimums. The geometrical parameters range was found, for which the 16 quasi–stable energetic states exist for the each probe. Having considered these results the 4 bits magnetic cells systems can be designed whose state is changed by spin-polarized current. Time dependent current densities and the current electron spin polarization directions were determined for all cases of transitions among quasi–stable states, for discovered set of 4 bits cells with different geometrical parameters. The 16- states cells, with the least geometrical area, achieved the 300 times bigger writing density in comparison to actual semiconductor solutions with the largest writing densities. The transitions among quasi-stable states of cells were examined for the time durations 105 times shorter than that for up to date solutions.

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Authors and Affiliations

P. Steblinski
T. Blachowicz
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Abstract

Extremely intense development of civilization requires from foundry casting technologies very high quality and not expensive castings. In

the foundries, there are many treatments that allow increasing of the final properties of produced castings such as refining, modification,

heat treatment, etc. One of the methods of increasing the quality of the casting by removing inclusions from the liquid alloy is filtration.

The use of ceramic-carbon foam filters in filtration process is still analysed phenomenon that allows improving the final properties of

castings. A modern method of research, testing and synthesis of innovative chemical compositions allows improving the properties of such

filters. In the paper the evaluation of application properties of developed ceramic-carbon bonded foam filters is presented. The quality of

the foam filters is evaluated by Computer Tomography and foundry trials in pouring of liquid metal in test molds. Additionally computer

simulations were made to visualize the flow characteristics in the foam filter. The analysed filters are the result of the research work of

Foundry Research Institute and the Institute of Ceramics and Building Materials, Refractory Materials Department in Gliwice.

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Authors and Affiliations

A. Karwiński
P. Wieliczko
M. Małysza
A. Gil
B. Lipowska
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Abstract

Pouring of liquid aluminium is typically accompanied by disturbance of the free surface. During these disturbances, the free surface oxide

films can be entrained in the bulk of liquid, also pockets of air can be accidentally trapped in this oxide films. The resultant scattering of

porosity in castings seems nearly always to originate from the pockets of entrained air in oxide films. Latest version of ProCast software

allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up in casts. During a filling

calculation, ProCast can calculate different indicators which allow to better quantify the filling pattern. The fluid front tracking indicator “

Free surface time exposure” has the units [cm2*s]. At each point of the free surface, the free surface area is multiplied by the time. This

value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid

flow.Experiments to validate this new functions were executed.

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Authors and Affiliations

D. Bolibruchová
R. Pastirčák
M. Brůna
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Abstract

The opportunity to assess haemolysis in a designed artificial heart seems to be one of the most important stages in construction. We propose a new method for assessing haemolysis level in a rotary blood pump. This method is based on CFD calculations using large eddy simulations (LES). This paper presents an approach to haemolysis estimation and shows examples of numerical simulation. Our method does not determine the value of haemolysis but allows for comparison of haemolysis levels between different artificial heart constructions.

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Authors and Affiliations

Maciej Szwast
Arkadiusz Moskal
Wojciech Piątkiewicz
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Abstract

In this paper a prototype framework for simulation of wireless sensor network and its protocols are presented. The framework simulates operation of a sensor network with data transmission, which enables simultaneous development of the sensor network software, its hardware and the protocols for wireless data transmission. An advantage of using the framework is converging simulation with the real software. Instead of creating a model of the sensor network node, the same software is used in real sensor network nodes and in the simulation framework. Operation of the framework is illustrated with examples of simulations of selected transactions in the sensor network.
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Authors and Affiliations

Marek Wójcikowski
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Abstract

The current numerical study focuses on the feasibility of furnishing thermal comfort in a structure, by using paraffin wax stored on a plate below the ceiling in a multi-storey building. The method is aimed to reduce energy demands at the increasing thermal loads. In summer, in daytime, walls of the building are exposed to the ambient thermal load, and heat transferred inside is absorbed by the melting wax. The study is numerical. It relates to temperature variations outside and inside, coupled with heat conduction and accumulation in walls, with radiation between the surfaces, with natural convection of air inside and melting of the wax at the ceiling. Fins spacing on the storage plate, visualization of the melting process, and its parametric investigation provide an insight into the physical phenomena. Temperature and flow fields were investigated for 3 mm and 12 mm thick layers of wax. At the specified conditions of the present study a 3 mm layer provides thermal comfort for most of the day, while a 6 mm layer may suffice for the entire day. Fluent 6.3 software was used in the computations.

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Authors and Affiliations

Vadim Dubovsky
Gennady Ziskind
Ruth Letan
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Abstract

The numerical investigation of the mixing process in complex geometry micromixers, as a function of various inlet conditions and various micromixer vibrations, was performed. The examined devices were two-dimensional (2D) and three-dimensional (3D) types of serpentine micromixers with two inlets. Entering fluids were perturbed with a wide range of the frequency (0 - 50 Hz) of pulsations. Additionally, mixing fluids also entered in the same or opposite phase of pulsations. The performed numerical calculations were 3D to capture the proximity of all the walls, which has a substantial influence on microchannel flow. The geometry of the 3D type serpentine micromixer corresponded to the physically existing device, characterised by excellent mixing properties but also a challenging production process (Malecha et al., 2009). It was shown that low-frequency perturbations could improve the average mixing efficiency of the 2D micromixer by only about 2% and additionally led to a disadvantageously non-uniform mixture quality in time. It was also shown that high-frequency mixing could level these fluctuations and more significantly improve the mixing quality. In the second part of the paper a faster and simplified method of evaluation of mixing quality was introduced. This method was based on calculating the length of the contact interface between mixing fluids. It was used to evaluate the 2D type serpentine micromixer performance under various types of vibrations and under a wide range of vibration frequencies.

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Authors and Affiliations

Ziemowit M. Malecha
Karol Malecha
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Abstract

Gas-liquid microreactors find an increasing range of applications both in production, and for chemical analysis. The most often employed flow regime in these microreactors is Taylor flow. The rate of absorption of gases in liquids depends on gas-side and liquid-side resistances. There are several publications about liquid-side mass transfer coefficients in Taylor flow, but the data about gas-side mass transfer coefficients are practically non existent. We analysed the problem of gas-side mass transfer resistance in Taylor flow and determined conditions, in which it may influence the overall mass transfer rate. Investigations were performed using numerical simulations. The influence of the gas diffusivity, gas viscosity, channel diameter, bubble length and gas bubble velocity has been determined. It was found that in some case the mass transfer resistances in both phases are comparable and the gas-side resistance may be significant. In such cases, neglecting the gas-side coefficient may lead to errors in the experimental data interpretation.

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Authors and Affiliations

Ryszard Pohorecki
Paweł Sobieszuk
Filip Ilnicki
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Abstract

In contemporary high-pressure die casting foundries, the mastery of each sequence in the production cycle is more and more important. In the paper, an example of virtual analysis of gearbox casting from Al alloy will be presented. It includes a large variety of parameters, as follows: choosing of appropriate foundry technology, calculation of computer simulation of casting process which takes into account the filling process of cold chamber and filling of cavity, model description of three phases in high-pressure die casting, flow of molten metal, solidification, formation of stress and deformations. Additionally, the optimization of cooling and heating systems will be compared with calculated volume defects, dimensions of castings and their deformations with experimentally obtained values.

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Authors and Affiliations

I. Peter
M. Rosso
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Abstract

The object of investigation was the one-strand tundish with flow control device such as gas permeable barrier (GPB). The aim of this flow control device was to activate the motion of liquid steel in the tundish longitudinal axis region. Computer simulation of the liquid steel flow and argon behaviour in isothermal turbulent motion conditions was done using the Ansys-Fluent computer program. For the validation of the hydrodynamic patterns obtained from computer simulations, a isothermal tundish glass model was used. Tundish glass model enables the recording of the visualization of fluid medium motion through the particle image velocimetry (PIV) method. Based on computer simulations, the liquid steel flow path lines in the tundish with GPB was obtained. For explain the hydrodynamic phenomena occurring in the tundish working space, the Buoyancy number has been calculated.
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Authors and Affiliations

A. Cwudziński
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Abstract

This work presents a numerical simulation of aviation structure joined by friction stir welding, FSW, process. The numerical simulation of aviation structure joined by FSW was created. The simulation uses thermomechanical coupled formulation. Th model required creation of finite elements representing sheets, stiffeners and welds, definition of material models and boundary conditions. The thermal model took into account heat conduction and convection assigned to appropriate elements of the structure. Time functions were applied to the description of a heat source movement. The numerical model included the stage of welding and the stage of releasing clamps. The output of the simulation are residual stresses and deformations occurring in the panel. Parameters of the global model (the panel model) were selected based on the local model (the single joint model), the experimental verification of the local model using the single joint and the geometry of the panel joints.

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Authors and Affiliations

P. Lacki
K. Adamus
J. Winowiecka
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Abstract

This paper presents a numerical investigation of fracture criterion influence on perforation of high-strength 30PM steel plates subjected to 7.6251 mm Armour Piercing (AP) projectile. An evaluation of four ductile fracture models is performed to identify the most suitable fracture criterion. Included in the paper is the Modified Johnson-Cook (MJC) constitutive model coupled separately with one of these fracture criteria: the MJC fracture model, the Cockcroft-Latham (CL), the maximum shear stress and the constant failure strain models. A 3D explicit Lagrangian algorithm that includes both elements and particles, is used in this study to automatically convert distorted elements into meshless particles during the course of the computation. Numerical simulations are examined by comparing with the experimental results. The MJC fracture model formulated in the space of the stress triaxiality and the equivalent plastic strain to fracture were found capable of predicting the realistic fracture patterns and at the same time the correct projectile residual velocities. However, this study has shown that CL one parameter fracture criterion where only one simple material test is required for calibration is found to give good results as the MJC failure criterion. The maximum shear stress fracture criterion fails to capture the shear plugging failure and material fracture properties cannot be fully characterized with the constant fracture strain.

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Authors and Affiliations

Djalel Eddine Tria
Radosław Trębiński

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Abstract

A design of the centrifugal recirculation blower as well as results of its experimental and numerical investigations are presented in this paper. The blower was designed to work in the unique test stand which is used for long-term tests of turbine flowmeters. A 1D method was used to design this blower, then experimental and numerical studies were conducted in order to verify the 1D method. A comparison of the blower pressure increase obtained from the experiment and the computations is presented. Velocity and pressure distributions from the numerical simulations in selected sections are also shown and discussed. Additional numerical studies of a shrouded rotor and a rotor with a lower tip clearance were conducted and are presented in the paper as well.

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Authors and Affiliations

Władysław Kryłłowicz
Michał Kuczkowski
Krzysztof Sobczak
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Abstract

The Medical Simulation Center at the Medical University of Białystok was created as part of a broader project. Throughout Poland there are 12 such centers, and each with a somewhat different concept. The common denominator is that they help medical, nursing, and obstetrics students test their knowledge and skills in practice. The Medical Simulation Center in Białystok boasts a sizeable set of simulation facilities, including an operating room, ambulance, emergency ward, labor ward, and nurse’s station. The technicians devise scenarios for students to enable them to practice reacting to specific cases. All the facilities are equipped with state-of-the-art audio-video equipment to record lessons for later review and analysis.

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Authors and Affiliations

Jakub Ostałowski
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Abstract

Prof. Daniel Wójcik from the Nencki Institute of Experimental Biology explains the principles of brain modelling

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Authors and Affiliations

Daniel Wójcik
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Abstract

Simulation-based models standing in for the real world are unfettered by any biological, emotional, historical, logical, or practical limitations.

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Authors and Affiliations

Katarzyna Kasia
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Abstract

Dr. Takao Ishikawa from the University of Warsaw talks about why perhaps not all scientists should aim to become professors, and explains what we can learn from yeast proteins.

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Authors and Affiliations

Takao Ishikawa
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Abstract

The author presents a development of computational model of design of ball screws thread. This model is the basis for computer program, which calculates the geometrical features of the thread for precisely given backlashes and contact angles. The program makes it possible to create a data base of a new generation ball screw of quality competitive to foreign ball screws. The modeling allows one to better select the ball screw and to predict its quality in the early stage of design.
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Authors and Affiliations

Jerzy Z. Sobolewski
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Abstract

This article presents a sequential model of the heating-remelting-cooling of steel samples based on the finite element method (FEM) and the smoothed particle hydrodynamics (SPH). The numerical implementation of the developed solution was completed as part of the original DEFFEM 3D package, being developed for over ten years, and is a dedicated tool to aid physical simulations performed with modern Gleeble thermo-mechanical simulators. Using the developed DEFFEM 3D software to aid physical simulations allows the number of costly tests to be minimized, and additional process information to be obtained, e.g. achieved local cooling rates at any point in the sample tested volume, or characteristics of temperature changes. The study was complemented by examples of simulation and experimental test results, indicating that the adopted model assumptions were correct. The developed solution is the basis for the development of DEFFEM 3D software aimed at developing a comprehensive numerical model allows the simulation of deformation of steel in semi solid state.

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Authors and Affiliations

Marcin Hojny
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Abstract

The properties of a mechanical resonator provide a valuable ability to measure liquid density and viscosity. The viscosity of liquids is of interest to researchers in both industry and medicine. In this paper, a viscosity sensor for liquids is proposed, which is designed based on an electromechanical resonator. In the proposed sensor, a capacitor is used as an electrostatic actuator. The capacitor is also used to monitor the frequency changes of the proposed resonator. The range of displacement of the resonator and capacitor in response to different fluids under test varies according to their viscosity. The design of the proposed sensor and its electrostatic and mechanical simulations are reported in this paper. Also, the effect of viscosity of several different liquids on its performance has been analyzed and presented experimentally using a prototype.
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Authors and Affiliations

Amin Eidi
1

  1. Sahand University of Technology, Tabriz, Iran
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Abstract

The article deals with a widely used method of measuring the overall efficiency of equipment (OEE), which in combination with technologies and software tools is gaining in importance. The overall efficiency of OEE equipment is a key performance metric for machines and equipment to identify hidden capacities and increase production productivity. The intensification of Industry 4.0 in traditional manufacturing companies supports and creates the conditions for their transformation into a smart factory. The integration of intelligent machines and devices with complex human-machine communication network systems requires a new direction in measuring and increasing OEE. Mass customization, resp. personalization of production raises a high need to monitor, improve and further maintain productivity. The aim of the article is to create a simulation model of the production process and test the energy consumption of selected equipment using TX Plant Simulation software with a proposal of measures to increase the OEE of the company.
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Authors and Affiliations

Miriam Pekarcíková
1
Peter Trebuna
2
Marek Kliment
2
Jozef Trojan
1
Ján Kopec
1
Michal Dic
1
Jana Kronová
1

  1. Department of Industrial and Digital Engineering, Faculty of Mechanical Engineering, Technical University of Košice, Slovak Republic
  2. Department of Industrial and Digital Engineering, Technical University of Košice

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