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Volume 115 (2018): Edition 10 (October 2018)

Volume 115 (2018): Edition 9 (September 2018)

Volume 115 (2018): Edition 8 (August 2018)

Volume 115 (2018): Edition 7 (July 2018)

Volume 115 (2018): Edition 6 (June 2018)

Volume 115 (2018): Edition 5 (May 2018)

Volume 115 (2018): Edition 4 (April 2018)

Volume 115 (2018): Edition 3 (March 2018)

Volume 115 (2018): Edition 2 (February 2018)

Volume 115 (2018): Edition 1 (January 2018)

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Volume 114 (2017): Edition 10 (October 2017)

Volume 114 (2017): Edition 9 (September 2017)

Volume 114 (2017): Edition 8 (August 2017)

Volume 114 (2017): Edition 7 (July 2017)

Volume 114 (2017): Edition 6 (June 2017)

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Détails du magazine
Format
Magazine
eISSN
2353-737X
Première publication
20 May 2020
Période de publication
1 fois par an
Langues
Anglais

Chercher

Volume 115 (2018): Edition 4 (April 2018)

Détails du magazine
Format
Magazine
eISSN
2353-737X
Première publication
20 May 2020
Période de publication
1 fois par an
Langues
Anglais

Chercher

17 Articles
Accès libre

Concepts of Transformations of Cities – Examples from the Silesian Agglomeration

Publié en ligne: 21 May 2020
Pages: 5 - 22

Résumé

Abstract

The problem of functional, compositional, and structural transformations, necessary to be introduced in contemporary inner cities, is complex and multithreaded. Sometimes cities get compared to palimpsests – re-used parchments from which old texts were removed in order to replace them with new ones. Undoubtedly, they are very particular palimpsests, as it is very difficult to clearly assess what should be protected and preserved, and what can be replaced or reconstructed. This paper discusses problems and concepts of transformations of selected city centres of the Silesian agglomeration, paying special attention to big comprehensive reconstructions of Katowice and Gliwice.

Mots clés

  • Theory of urban design
  • concepts of reconstruction of cities
  • reconstruction of Silesian cities
  • reconstruction of Katowice
  • reconstruction of Gliwice
  • city centre revitalisation
  • future of cities
  • city forming
Accès libre

Forms, Details and Contemporary Meanings of Polish Concrete Architecture, Part 1

Publié en ligne: 21 May 2020
Pages: 23 - 34

Résumé

Abstract

The article is an attempt to show the relationship between architectural ideas and concrete matter in the implementation of Polish architecture of the beginning of the 21st century. The first part shows examples in which the perfection of architecture is associated not only with the rational principles of 20th century architecture, but also with what we define as the search for aesthetics in appropriate expression of forms.

Mots clés

  • concrete architecture
  • idea
  • matter
  • expressionisme
Accès libre

Forms, Details and Contemporary Meanings of Polish Concrete Architecture, Part 2

Publié en ligne: 21 May 2020
Pages: 35 - 44

Résumé

Abstract

The article is an attempt to show the relationship between architectural ideas and concrete matter in the implementation of Polish architecture of the beginning of the 21st century. The second part shows examples in which the perfection of architecture is associated not only with the metaphor principles of 20th century architecture, but also with what we define as the search for aesthetics in appropriate geometry of forms.

Mots clés

  • concrete architecture
  • idea
  • matter
  • expressionisme
Accès libre

Sight and Insight – Creating Space for Religious Practices

Publié en ligne: 21 May 2020
Pages: 45 - 54

Résumé

Abstract

The paper reviews some recent attempts that describe the meaning of dry gardens that can be found in Zen Buddhist monasteries in Japan. When researchers try to figure out the meaning of the visual elements, its structure or the placement of the stones, they usually stay on the level of understanding. However, the daily meditational practice among these walls near the dry garden provides a different point of view. The purpose of this study is to show the importance of attention regarding the daily use of dry gardens on the way to enlightenment.

Mots clés

  • dry garden
  • Buddhism
  • Zen
  • practice
  • attention
Accès libre

Heavens Above – A Statue of Christ in the Landscape

Publié en ligne: 21 May 2020
Pages: 55 - 68

Résumé

Abstract

The monuments of Christ erected from 1920s onwards in many places throughout the world are a specific group of dominants associated with sacrum. Their effect on the perception of the landscape is very strong because of the artistic form and, above all, the symbolic dimension they have. The aim of the work is to demonstrate that land development projects around sacred landscape dominants in the form of statues of Christ should be subject to careful consideration, both in terms of functionality and composition. The adjustment of the environment to the scale and rank of the object - so as to emphasise its special role in the landscape, but also the symbolism associated with the sphere of sacrum - plays a crucial role in this case. Comparative analyses were made for ten highest statues of Christ in the world. The research was also supplemented with a presentation of the concept of land development around the statue of Christ in Świebodzin.

Mots clés

  • landscape dominants
  • sacrum in the landscape
  • statue of Christ
Accès libre

Microspaces – An Outline of Typological Research Based on Examples from Krakow

Publié en ligne: 21 May 2020
Pages: 69 - 82

Résumé

Abstract

In the complex systems of urban spaces one can find many places, which, owing to their small scale, are often treated a part of a larger whole. Whereas their borders are often blurred, their character allow for establishing them as a typological identity. Various “microspaces” play a significant role, often hidden or only temporarily arranged within a specific segment of a city space as its supplement, complement, or simply to make it more attractive. Observation of the transformations taking place in the public spaces of Krakow allows not only for the indication of the fact that such places exist and are being created, it also enables us to frame a sketch of their functional and spatial polymorphism. This article elaborates on some chosen examples of Krakow microspaces and their variants.

Mots clés

  • public urban space
  • microspaces
  • urban design
Accès libre

Application of Circulating Fluidized Bed Boilers in the Fuel Combustion Process

Publié en ligne: 21 May 2020
Pages: 83 - 96

Résumé

Abstract

The combustion of fuels plays an important role in the field of industry and power engineering. Nowadays, a lot is being done to reduce the industry’s interference in the environment, due to ecological considerations. Not only is the fluid technology environmentally friendly, but also it is a convenient method of energy production from wide range of fuels. The article presents a summary of the most significant events in the history of fluidized bed boilers, there is also a description of construction and operation of a circulating fluidized bed boiler and its comparison with technologically similar bubbling fluidized bed boiler. The usage of diverse types of fuels is discussed and compared. Special emphasis is placed on the application of fluidized bed boilers in Polish industry.

Mots clés

  • fluidized bed
  • combustion
  • circulating fluidized bed boiler
  • CFB boiler
Accès libre

An Overview on Obtaining Foamed Pet by Reactive Extrusion

Publié en ligne: 21 May 2020
Pages: 97 - 102

Résumé

Abstract

Many methods are used to obtain functional polymer foams. This review focuses on reactive extrusion of poly(ethylene terephthalate). This process is based on the reaction between PET and the appropriate blowing agent. The next step is the creation of foam by closing gas cells in the polymer matrix. This method of modification allows material with higher molecular weight to be obtained and, therefore, higher melt strength. The use of different chemical modifiers and their concentration influences properties of created foam. The enhanced features of foamed PET allow it to be used in many areas of application such as transport, construction or general industry. Another big advantage of this technique is the possibility of using recycled materials as the source of PET.

Mots clés

  • PET
  • Foams
  • Reactive extrusion
Accès libre

An Evolutionary Model for the Parametric Optimisation of Electromagnetic Instruments of Variable Structures

Publié en ligne: 21 May 2020
Pages: 103 - 118

Résumé

Abstract

This paper discusses the principle of constructing an evolutionary model for the parametric optimisation of electromagnetic instruments with solid-state valves. To illustrate the method, a triple voltage scheme was selected – this converts variable voltage into constant voltage and at the same time, triples the amplitude. Valve operation was modelled according to the ideal key diagram; the considered resistance was that of an open valve.

Mots clés

  • evolutionary model
  • parametric optimisation
  • ideal key
  • voltage tripler
  • fixed mode
  • additional logic variables
Accès libre

The CORDIC Method of Calculating the Exponential Function

Publié en ligne: 21 May 2020
Pages: 119 - 126

Résumé

Abstract

This article presents a modern method of calculating the exponential function exp(x) based on the CORDIC iterative algorithm. The proposed solution is implemented in the form of a single iterative equation, which results in the simplification of the electronic version of this algorithm, thus reducing the cost of the device. It is important to point out that the accuracy of the calculation of the analysed function is not lost.

Mots clés

  • exponential function
  • hybrid CORDIC method
  • LUT lookup table
  • iterative equations
  • activation functions
Accès libre

Energy Efficient Data Center Resources Management Using Beam Search Algorithm

Publié en ligne: 21 May 2020
Pages: 127 - 138

Résumé

Abstract

Modern data centres consume large amounts of power resulting in high levels of carbon dioxide emission. The data centre is a virtual environment in which the workload is performed by virtual machines. A widely used technique to decrease data centre power consumption is to consolidate the virtual machines using a minimal number of physical servers. The authors propose a two-stage method to solve the virtual machine consolidation problem in cloud data centres. The proposed method is programmed in C# to evaluate it and to perform modelling using Google cluster-usage traces. The proposed method enables powering off nearly fifty percent of the previously selected physical servers by using an acceptable number of migrations of virtual machines.

Mots clés

  • cloud computing
  • virtualisation
  • virtual machine consolidation
  • local beam search
Accès libre

An Abstract Nonlocal Functional-Differential Second Order Evolution Cauchy Problem

Publié en ligne: 21 May 2020
Pages: 139 - 147

Résumé

Abstract

The aim of the paper is to prove two theorems on the existence and uniqueness of mild and classical solutions of a semilinear functional-differential evolution second order equation together with nonlocal initial conditions. The theory of strongly continuous cosine families of linear operators in a Banach space is applied. The paper is based on publications [1–12] and is a generalization of paper [7].

Mots clés

  • nonlocal
  • second order
  • functional-differential
  • evolution Cauchy problem
  • Banach spaces
Accès libre

The Mechanical Characterization of Composites Based on Polyoxymethylene and the Effect of Silicone Addition on the Mechanical Behaviour of Manufactured Composites

Publié en ligne: 21 May 2020
Pages: 149 - 158

Résumé

Abstract

The mechanical properties of manufactured composites based on polyoxymethylene (Tarnoform 300) were determined. POM composites reinforced with ultra-high molecular weight silicon, thermoplastic polyurethane, and special chalk in order to reduce abrasiveness and aramid fibres were manufactured. The basic mechanical properties (tensile strength (σM), modulus of elasticity (Et), strain at break (εB), flexural modulus (Ef) and flexural stress at 3.5% strain (σs)) were evaluated at three temperatures -20, 20 and 80°C. The density and Charpy impact of the produced composites were examined. In order to make reference to the effects of reinforcement and determine the characteristics of their microstructure SEM, images were taken.

Mots clés

  • polyformaldehyde
  • additives
  • modification of structure
  • properties
Accès libre

Selected Aspects Involved in the Optimization of Cranes with Pivoting Booms

Publié en ligne: 21 May 2020
Pages: 159 - 171

Résumé

Abstract

Certain crane operations – hoisting/lowering the payload connected to a slewing jib – require a nonlinear description to take Euler and Coriolis forces into account, the impacts of which should already be minimised at the stage of selection of the system parameters and mechanism structure. Optimal sets of parameters for the crane mechanisms thus obtained were optimised for the full range of slewing motion. It is demonstrated that the selection of the geometric dimensions of the structural elements of the hoisting mechanisms, i.e. the slewing system and counterbalances, enables the horizontal track error load to be minimised whilst the forces acting on the mechanism and inducing its vertical movement can be reduced. Thus, for the assumed lifting capacity and distance jaunt we get the structure of the crane mechanism that guarantees the minimal consumption of energy.

Mots clés

  • cranes
  • counterbalance
  • pivoting jib
  • slewing system
  • Euler’s forces
  • Coriolis forces
  • energy consumption
  • nonlinear and non-stationary differential equations of motion
  • vibration
  • parametric optimisation
  • horizontal track error load
  • one-link jib crane
Accès libre

The Influence of a Crn+a-C:H:W Coating on the Development of Fretting Wear in a Model of a Wheel–Axle Press-Fit Joint on a Wheel Set of a Railway Vehicle

Publié en ligne: 21 May 2020
Pages: 173 - 187

Résumé

Abstract

The tests were conducted on a wheel/axle press-fit joint model, which consisted of a shaft and a sleeve. Macrographic observations were demonstrated fretting wear on the shaft surface with and without coatings. In the case of the uncoated shaft, wear around the entire circumference of the axle seat was visible in the form of a peculiar ring of a specific width. The coated shaft surface was distinguished by a considerably smaller number of visible traces of wear. Wear was observed around the entire circumference of the axle seat, was spaced at random, and insignificantly sized areas each time. Micrographic observations with the use of a scanning microscope demonstrated that fretting was primarily comprised of the build-up of the material from both surfaces joined together. In addition to the build-up, surface micro-abrasion, micropits and microcracks are observed, albeit to a lesser extent.

Mots clés

  • PVD coating
  • CrN+a-C:H:W
  • rotational bending
  • fretting wear
  • press-fit joint
  • wheel set
Accès libre

The Use of Genetic Algorithm to Optimize Quantitative Learner’s Motivation Model

Publié en ligne: 21 May 2020
Pages: 189 - 194

Résumé

Abstract

The paper presents a method of optimizing Quantitative Learner’s Motivation Model with the use of genetic algorithm. It is focused on optimizing the formula for prediction of learning motivation by means of different weights for three values: interest, usefulness in the future and satisfaction. For the purpose of this optimization, we developed a C++ library that implements a genetic algorithm and an application in C# which uses that library with data acquired from questionnaires enquiring about those three elements. The results of the experiment showed improvement in the estimation of student’s learning motivation.

Mots clés

  • optimization
  • genetic algorithm
  • Quantitative Learner’s Motivation Model
Accès libre

Composites Based on Recycled Polystyrene Waste with Tuff Microparticles

Publié en ligne: 21 May 2020
Pages: 195 - 203

Résumé

Abstract

Nowadays electric and electronic equipments are produced on a large scale, for example, personal computers. Therefore, more and more waste is recycled. To increase the strength properties of recycled materials, they are reinforced with various types of fillers such as natural. Over the last few years, fillers from tuffs of volcanic origin have been gaining in popularity. It is characterized by a low mass, high hardness, high matrix adhesion, which allow for uniform distribution of particles in the volume of the material. In this paper, composites based on recycled polystyrene waste with tuff microparticles in mass weight of 10% and 20% were produced by injection moulding. The basic mechanical properties at room temperature (+24°C) -24 and +80°C were evaluated. The aim of the study was to demonstrate the possibility of using the mineral filler particles as compatibilizer for recycled polystyrene waste of poor quality.

Mots clés

  • mechanical properties
  • natural fillers
  • ecology
  • recycling
17 Articles
Accès libre

Concepts of Transformations of Cities – Examples from the Silesian Agglomeration

Publié en ligne: 21 May 2020
Pages: 5 - 22

Résumé

Abstract

The problem of functional, compositional, and structural transformations, necessary to be introduced in contemporary inner cities, is complex and multithreaded. Sometimes cities get compared to palimpsests – re-used parchments from which old texts were removed in order to replace them with new ones. Undoubtedly, they are very particular palimpsests, as it is very difficult to clearly assess what should be protected and preserved, and what can be replaced or reconstructed. This paper discusses problems and concepts of transformations of selected city centres of the Silesian agglomeration, paying special attention to big comprehensive reconstructions of Katowice and Gliwice.

Mots clés

  • Theory of urban design
  • concepts of reconstruction of cities
  • reconstruction of Silesian cities
  • reconstruction of Katowice
  • reconstruction of Gliwice
  • city centre revitalisation
  • future of cities
  • city forming
Accès libre

Forms, Details and Contemporary Meanings of Polish Concrete Architecture, Part 1

Publié en ligne: 21 May 2020
Pages: 23 - 34

Résumé

Abstract

The article is an attempt to show the relationship between architectural ideas and concrete matter in the implementation of Polish architecture of the beginning of the 21st century. The first part shows examples in which the perfection of architecture is associated not only with the rational principles of 20th century architecture, but also with what we define as the search for aesthetics in appropriate expression of forms.

Mots clés

  • concrete architecture
  • idea
  • matter
  • expressionisme
Accès libre

Forms, Details and Contemporary Meanings of Polish Concrete Architecture, Part 2

Publié en ligne: 21 May 2020
Pages: 35 - 44

Résumé

Abstract

The article is an attempt to show the relationship between architectural ideas and concrete matter in the implementation of Polish architecture of the beginning of the 21st century. The second part shows examples in which the perfection of architecture is associated not only with the metaphor principles of 20th century architecture, but also with what we define as the search for aesthetics in appropriate geometry of forms.

Mots clés

  • concrete architecture
  • idea
  • matter
  • expressionisme
Accès libre

Sight and Insight – Creating Space for Religious Practices

Publié en ligne: 21 May 2020
Pages: 45 - 54

Résumé

Abstract

The paper reviews some recent attempts that describe the meaning of dry gardens that can be found in Zen Buddhist monasteries in Japan. When researchers try to figure out the meaning of the visual elements, its structure or the placement of the stones, they usually stay on the level of understanding. However, the daily meditational practice among these walls near the dry garden provides a different point of view. The purpose of this study is to show the importance of attention regarding the daily use of dry gardens on the way to enlightenment.

Mots clés

  • dry garden
  • Buddhism
  • Zen
  • practice
  • attention
Accès libre

Heavens Above – A Statue of Christ in the Landscape

Publié en ligne: 21 May 2020
Pages: 55 - 68

Résumé

Abstract

The monuments of Christ erected from 1920s onwards in many places throughout the world are a specific group of dominants associated with sacrum. Their effect on the perception of the landscape is very strong because of the artistic form and, above all, the symbolic dimension they have. The aim of the work is to demonstrate that land development projects around sacred landscape dominants in the form of statues of Christ should be subject to careful consideration, both in terms of functionality and composition. The adjustment of the environment to the scale and rank of the object - so as to emphasise its special role in the landscape, but also the symbolism associated with the sphere of sacrum - plays a crucial role in this case. Comparative analyses were made for ten highest statues of Christ in the world. The research was also supplemented with a presentation of the concept of land development around the statue of Christ in Świebodzin.

Mots clés

  • landscape dominants
  • sacrum in the landscape
  • statue of Christ
Accès libre

Microspaces – An Outline of Typological Research Based on Examples from Krakow

Publié en ligne: 21 May 2020
Pages: 69 - 82

Résumé

Abstract

In the complex systems of urban spaces one can find many places, which, owing to their small scale, are often treated a part of a larger whole. Whereas their borders are often blurred, their character allow for establishing them as a typological identity. Various “microspaces” play a significant role, often hidden or only temporarily arranged within a specific segment of a city space as its supplement, complement, or simply to make it more attractive. Observation of the transformations taking place in the public spaces of Krakow allows not only for the indication of the fact that such places exist and are being created, it also enables us to frame a sketch of their functional and spatial polymorphism. This article elaborates on some chosen examples of Krakow microspaces and their variants.

Mots clés

  • public urban space
  • microspaces
  • urban design
Accès libre

Application of Circulating Fluidized Bed Boilers in the Fuel Combustion Process

Publié en ligne: 21 May 2020
Pages: 83 - 96

Résumé

Abstract

The combustion of fuels plays an important role in the field of industry and power engineering. Nowadays, a lot is being done to reduce the industry’s interference in the environment, due to ecological considerations. Not only is the fluid technology environmentally friendly, but also it is a convenient method of energy production from wide range of fuels. The article presents a summary of the most significant events in the history of fluidized bed boilers, there is also a description of construction and operation of a circulating fluidized bed boiler and its comparison with technologically similar bubbling fluidized bed boiler. The usage of diverse types of fuels is discussed and compared. Special emphasis is placed on the application of fluidized bed boilers in Polish industry.

Mots clés

  • fluidized bed
  • combustion
  • circulating fluidized bed boiler
  • CFB boiler
Accès libre

An Overview on Obtaining Foamed Pet by Reactive Extrusion

Publié en ligne: 21 May 2020
Pages: 97 - 102

Résumé

Abstract

Many methods are used to obtain functional polymer foams. This review focuses on reactive extrusion of poly(ethylene terephthalate). This process is based on the reaction between PET and the appropriate blowing agent. The next step is the creation of foam by closing gas cells in the polymer matrix. This method of modification allows material with higher molecular weight to be obtained and, therefore, higher melt strength. The use of different chemical modifiers and their concentration influences properties of created foam. The enhanced features of foamed PET allow it to be used in many areas of application such as transport, construction or general industry. Another big advantage of this technique is the possibility of using recycled materials as the source of PET.

Mots clés

  • PET
  • Foams
  • Reactive extrusion
Accès libre

An Evolutionary Model for the Parametric Optimisation of Electromagnetic Instruments of Variable Structures

Publié en ligne: 21 May 2020
Pages: 103 - 118

Résumé

Abstract

This paper discusses the principle of constructing an evolutionary model for the parametric optimisation of electromagnetic instruments with solid-state valves. To illustrate the method, a triple voltage scheme was selected – this converts variable voltage into constant voltage and at the same time, triples the amplitude. Valve operation was modelled according to the ideal key diagram; the considered resistance was that of an open valve.

Mots clés

  • evolutionary model
  • parametric optimisation
  • ideal key
  • voltage tripler
  • fixed mode
  • additional logic variables
Accès libre

The CORDIC Method of Calculating the Exponential Function

Publié en ligne: 21 May 2020
Pages: 119 - 126

Résumé

Abstract

This article presents a modern method of calculating the exponential function exp(x) based on the CORDIC iterative algorithm. The proposed solution is implemented in the form of a single iterative equation, which results in the simplification of the electronic version of this algorithm, thus reducing the cost of the device. It is important to point out that the accuracy of the calculation of the analysed function is not lost.

Mots clés

  • exponential function
  • hybrid CORDIC method
  • LUT lookup table
  • iterative equations
  • activation functions
Accès libre

Energy Efficient Data Center Resources Management Using Beam Search Algorithm

Publié en ligne: 21 May 2020
Pages: 127 - 138

Résumé

Abstract

Modern data centres consume large amounts of power resulting in high levels of carbon dioxide emission. The data centre is a virtual environment in which the workload is performed by virtual machines. A widely used technique to decrease data centre power consumption is to consolidate the virtual machines using a minimal number of physical servers. The authors propose a two-stage method to solve the virtual machine consolidation problem in cloud data centres. The proposed method is programmed in C# to evaluate it and to perform modelling using Google cluster-usage traces. The proposed method enables powering off nearly fifty percent of the previously selected physical servers by using an acceptable number of migrations of virtual machines.

Mots clés

  • cloud computing
  • virtualisation
  • virtual machine consolidation
  • local beam search
Accès libre

An Abstract Nonlocal Functional-Differential Second Order Evolution Cauchy Problem

Publié en ligne: 21 May 2020
Pages: 139 - 147

Résumé

Abstract

The aim of the paper is to prove two theorems on the existence and uniqueness of mild and classical solutions of a semilinear functional-differential evolution second order equation together with nonlocal initial conditions. The theory of strongly continuous cosine families of linear operators in a Banach space is applied. The paper is based on publications [1–12] and is a generalization of paper [7].

Mots clés

  • nonlocal
  • second order
  • functional-differential
  • evolution Cauchy problem
  • Banach spaces
Accès libre

The Mechanical Characterization of Composites Based on Polyoxymethylene and the Effect of Silicone Addition on the Mechanical Behaviour of Manufactured Composites

Publié en ligne: 21 May 2020
Pages: 149 - 158

Résumé

Abstract

The mechanical properties of manufactured composites based on polyoxymethylene (Tarnoform 300) were determined. POM composites reinforced with ultra-high molecular weight silicon, thermoplastic polyurethane, and special chalk in order to reduce abrasiveness and aramid fibres were manufactured. The basic mechanical properties (tensile strength (σM), modulus of elasticity (Et), strain at break (εB), flexural modulus (Ef) and flexural stress at 3.5% strain (σs)) were evaluated at three temperatures -20, 20 and 80°C. The density and Charpy impact of the produced composites were examined. In order to make reference to the effects of reinforcement and determine the characteristics of their microstructure SEM, images were taken.

Mots clés

  • polyformaldehyde
  • additives
  • modification of structure
  • properties
Accès libre

Selected Aspects Involved in the Optimization of Cranes with Pivoting Booms

Publié en ligne: 21 May 2020
Pages: 159 - 171

Résumé

Abstract

Certain crane operations – hoisting/lowering the payload connected to a slewing jib – require a nonlinear description to take Euler and Coriolis forces into account, the impacts of which should already be minimised at the stage of selection of the system parameters and mechanism structure. Optimal sets of parameters for the crane mechanisms thus obtained were optimised for the full range of slewing motion. It is demonstrated that the selection of the geometric dimensions of the structural elements of the hoisting mechanisms, i.e. the slewing system and counterbalances, enables the horizontal track error load to be minimised whilst the forces acting on the mechanism and inducing its vertical movement can be reduced. Thus, for the assumed lifting capacity and distance jaunt we get the structure of the crane mechanism that guarantees the minimal consumption of energy.

Mots clés

  • cranes
  • counterbalance
  • pivoting jib
  • slewing system
  • Euler’s forces
  • Coriolis forces
  • energy consumption
  • nonlinear and non-stationary differential equations of motion
  • vibration
  • parametric optimisation
  • horizontal track error load
  • one-link jib crane
Accès libre

The Influence of a Crn+a-C:H:W Coating on the Development of Fretting Wear in a Model of a Wheel–Axle Press-Fit Joint on a Wheel Set of a Railway Vehicle

Publié en ligne: 21 May 2020
Pages: 173 - 187

Résumé

Abstract

The tests were conducted on a wheel/axle press-fit joint model, which consisted of a shaft and a sleeve. Macrographic observations were demonstrated fretting wear on the shaft surface with and without coatings. In the case of the uncoated shaft, wear around the entire circumference of the axle seat was visible in the form of a peculiar ring of a specific width. The coated shaft surface was distinguished by a considerably smaller number of visible traces of wear. Wear was observed around the entire circumference of the axle seat, was spaced at random, and insignificantly sized areas each time. Micrographic observations with the use of a scanning microscope demonstrated that fretting was primarily comprised of the build-up of the material from both surfaces joined together. In addition to the build-up, surface micro-abrasion, micropits and microcracks are observed, albeit to a lesser extent.

Mots clés

  • PVD coating
  • CrN+a-C:H:W
  • rotational bending
  • fretting wear
  • press-fit joint
  • wheel set
Accès libre

The Use of Genetic Algorithm to Optimize Quantitative Learner’s Motivation Model

Publié en ligne: 21 May 2020
Pages: 189 - 194

Résumé

Abstract

The paper presents a method of optimizing Quantitative Learner’s Motivation Model with the use of genetic algorithm. It is focused on optimizing the formula for prediction of learning motivation by means of different weights for three values: interest, usefulness in the future and satisfaction. For the purpose of this optimization, we developed a C++ library that implements a genetic algorithm and an application in C# which uses that library with data acquired from questionnaires enquiring about those three elements. The results of the experiment showed improvement in the estimation of student’s learning motivation.

Mots clés

  • optimization
  • genetic algorithm
  • Quantitative Learner’s Motivation Model
Accès libre

Composites Based on Recycled Polystyrene Waste with Tuff Microparticles

Publié en ligne: 21 May 2020
Pages: 195 - 203

Résumé

Abstract

Nowadays electric and electronic equipments are produced on a large scale, for example, personal computers. Therefore, more and more waste is recycled. To increase the strength properties of recycled materials, they are reinforced with various types of fillers such as natural. Over the last few years, fillers from tuffs of volcanic origin have been gaining in popularity. It is characterized by a low mass, high hardness, high matrix adhesion, which allow for uniform distribution of particles in the volume of the material. In this paper, composites based on recycled polystyrene waste with tuff microparticles in mass weight of 10% and 20% were produced by injection moulding. The basic mechanical properties at room temperature (+24°C) -24 and +80°C were evaluated. The aim of the study was to demonstrate the possibility of using the mineral filler particles as compatibilizer for recycled polystyrene waste of poor quality.

Mots clés

  • mechanical properties
  • natural fillers
  • ecology
  • recycling

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