Browse

91 - 100 of 1,161 items :

  • Materials Sciences x
  • Materials Sciences, other x
Clear All
An analysis of the causes of track twist at high speed of driving

Abstract

The research of railway track surfaces is aimed at improving the quality of railway infrastructure and providing the chance of improving the safety of driving. Therefore, it is advisable to constantly monitor track surface, but the research itself is not innovative because it is based on a known procedure. The crucial element are the techniques that allow to delve into the sources of problems. The aim of the article is to use the selected instruments of quality management to analyze the causes of track twist at high (180 km/h) speed of driving. The analysis of the causes of track twist was done on the basis of results from the measurement of one kilometer track section of the Krakow Glowny - Medyka route, which was made by using the TEC measuring device in April 2018. It was inferred that it is impossible to reach 180 km/h without track twist. In order to identify the causes of track twist it was proposed to use the selected sequence of quality management instruments, i.e.: brainstorming, Ishikawa diagram and the 5Why method. The identified causes of track twist include the abrasion of rail, scratches and exploitation point. The analysis and conclusions drawn from it may be useful in the analysis of other problems in railway transport as well as production and service industries.

Open access
CdO-Fe3O4 nanocomposite with enhanced magnetic and photocatalytic properties

Abstract

Pure CdO nanopowder and CdO-Fe3O4 nanocomposite were synthesized by a cost effective chemical method, and the samples were characterized by XRD, SEM, TEM, FT-IR, UV-Vis-NIR and PL. Also, magnetic and photocatalytic properties of the synthesized samples were studied. XRD patterns of the composite confirm the presence of diffraction peaks related to both CdO and Fe3O4. EDX spectrum confirms the presence of the elements Cd, O and Fe in the composite. Peaks related to Cd–O and Fe–O bonds were observed respectively at 688 cm−1 and 592 cm−1 in the FT-IR spectrum. The paramagnetic behavior of pure CdO becomes ferromagnetic when coupled with Fe3O4. The composite exhibited a high photodegradation efficiency of 92.85 % against the degradation of methylene blue dye under visible light radiation.

Open access
Comparison of temperature dependence of internal damping of selected magnesium alloys

Abstract

The research is focused on the study of the temperature dependence of the internal damping of selected magnesium alloys with different contents of aluminium - AZ31 and AZ61. These alloys are currently widely used in various types of industry, mainly in the automotive industry. It belongs to a group of materials called HIDAMETS because they have excellent damping properties. The internal damping of the samples was measured on a unique ultrasonic device constructed at Žilina University in Žilina. Specimens were measured at baseline in the temperature range from 25 °C to 400 °C. Changes in internal damping caused by varying aluminium contents in investigated alloys were noted. As the aluminium content increases, maximum internal damping is achieved due to the formation, growth and subsequent dissolution of the continuous precipitate in the microstructure.

Open access
Comprehensive Aviaton System of Flying Crew Improving Safety in the Aircraft Operation

Abstract

The article describes 10 known programmes of practical flight training in military aviation – specialization: Multi-Mission Tactical Jet Pilot, which is the highest level of military pilot training in all types of military and civil aviation – comparable only to the level of training and experience of the pilot-instructor of the Military Aviation School. The presented comparison was developed on the basis of literature research from the point of view of, among others, an aircraft operation engineer and a pilot-instructor.

Open access
Contract Brewing – Production-Oriented Cooperation in Craft Brewing Industry

Abstract

The objective of the paper is to analyze the cooperation in craft beer manufacturing in Poland and to identify the specificity of this phenomenon from the perspective of enterprise management. The sales of craft beers in Poland are growing rapidly. Craft beers have about a 0.5% share in the total beer sales value in Poland. The popular practice in the industry is contract brewing. It is an interesting phenomenon in the field of cooperation of enterprises which can be classified and analyzed as a form of: economic cooperation (generally), production cooperation, outsourcing, network and virtual organization and also coopetition. It is a specific business model. Contract brewing is a complex problem the specificity of which emerges on several levels. Firstly, there is a special way to emerge in the market of craft beers, even while not possessing significant funds by the entrepreneur. Secondly, it is a form of cooperation in the field of production which unites efforts on the side of both the customer and the contractor since it is not limited to normal outsourcing of production to an external entity but involves physical production capacity of the contractor and technological know-how of both cooperation parties. Thirdly, it is firmly embedded in human relationships. Fourthly, it can generate coopetitive relations since the brewery accepting the order may conduct its own activity related to production and sales of beer under its own brand.

Open access
Controlling of optical band gap of the CdO films by zinc oxide

Abstract

In this study, CdZnO films prepared at different ratios of dopants (CdO:ZnO = 5:5, CdO:ZnO = 6:4, and CdO:ZnO = 8:2) were coated on glass surface by using the sol-gel spin coating technique. After this process, surface structure and optical properties of the CdZnO films was investigated by atomic force microscopy (AFM) and UV-Vis spectroscopy. The surface structure of the CdZnO films depended on the content of ZnO and CdO in the films. Low percentage of CdO films were very similar to the ZnO film but higher amount of CdO resuted in granular structures together with pure structure of ZnO in the films. Eg values of produced CdZnOs depended on the additions of CdO and ZnO. The obtained Eg values of the produced CdO:ZnO = 5:5 (S3), CdO:ZnO = 6:4 (S4), and CdO:ZnO = 8:2 (S5) films are 2.5 eV, 2.49 eV, and 2.4 eV, respectively.

Open access
Determination of growth kinetics and size dependent structural, morphological, optical characteristics of sol-gel derived silica nanoparticles in silica matrix

Abstract

Nanocomposite silica thin films made using the sol-gel method were studied. The nano-silica films were prepared using a mixture of tetraethyl orthosilicate (TEOS), deionized water, ethanol, and ammonia solution. To control the growth of the particles inside the film, the nanocomposite silica film was prepared using a mixture of the nano-silica sol and the silica sol. The change in the particle size with the heat treatment temperature ranging from 450 °C to 1100 °C was investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), NKD (refractive index-N, extinction coefficient-K, and thickness-D) and ultraviolet-visible (UV-Vis) spectrophotometry were used for characterization purposes. The XRD studies showed that the nano-silica thin films were amorphous at all annealing temperatures except for 1100 °C. The_-cristobalite crystal structure formed at the annealing temperature of 1100 °C. Optical parameters, such as refractive indices and extinction coefficients, were obtained using the NKD analyzer with respect to the annealing temperature of the films. The activation energy and enthalpy of the nanocomposite silica film were evaluated as 22.3 kJ/mol and 14.7 kJ/mol, respectively. The cut-off wavelength values were calculated by means of extrapolation of the absorbance spectra estimated using the UV-Vis spectroscopy measurements. A red shift in the absorption threshold of the nanocomposite silica films indicated that the size of the silica nanoparticles increased with an increase of the annealing temperatures from 450 °C to 900 °C, and this confirms the quantum confinement effect in the nanoparticles.

Open access
Effect of Mn content in Fe(1−x)MnxB (x = 0, 0.25, 0.5, 0.75 and 1) on physical properties - ab initio calculations

Abstract

Structural, electronic, intrinsic magnetic, anisotropic elastic properties, sound velocities and Debye temperature of Fe1−xMnx B (x = 0, 0.25, 0.5, 0.75, 1) transition metal monoborides have been studied by first-principles calculations within the method of virtual crystal approximation (VCA) based on density-functional theory (DFT) through generalized gradient approximation (GGA). The average magnetic moment per cell increased with increasing of Mn content, which could be associated with the relationship between the composition and magnetic properties. The observed magnetic behavior of Fe1−xMnx B compounds can be explained by Stoner model. Lattice parameters and Debye temperature agree well with the experimental values. Furthermore, we have plotted three-dimensional (3D) surfaces and planar contours of the directional dependent Young and bulk moduli of the compounds on several crystallographic planes, to reveal their elastic anisotropy versus Mn content (x) in Fe1−xMnx B.

Open access
The effect of natural pozzolans on properties of vibropressed interlocking concrete blocks in different curing conditions

Abstract

Concrete block pavements have become an attractive engineering and economical alternative to both flexible and rigid pavements because of it’s high strength and durability. The influence of pozzolanic mineral additions – natural zeolite and expanded perlite powder on the properties of concrete interlocking blocks in different curing conditions has been studied. The use of zeolite as a substitute for cement in the production of concrete blocks increased the water demand but decreased the water absorption of the blocks. Obtained results show, that concrete blocks with 10% substitution of cement with zeolitic tuff is characterized by higher strength, lower mass loss and absence of efflorescence.

Open access
The effect of oxidation process on graphene oxide fiber properties

Abstract

Graphene, a carbon allotrope, became a significant area of research with its superior electrical, mechanical, optical properties, etc. There are several methods to obtain graphene oxide from graphite, one of which is the Hummers method. In this study, several modifications and pre-treatments preceding the Hummers method have been employed. Three different graphene oxide fibers have been produced by three different procedures, i.e. fibers obtained by Hummers method with pre-oxidation step, modified Hummers method and modified Hummers method with pre-oxidation step. It has been observed that pre-oxidation has a significant effect on graphene oxide fiber properties produced by wet spinning process (coagulation). Modified Hummers method without pre-oxidation leads to the highest breaking strength and breaking elongation. Reduced fiber linear density, breaking strength and breaking elongation together with increased crimp were observed in graphene fiber due to the addition of pre-oxidation step.

Open access