|
| |
|
|
Properties and characteristics of recycled garnet abrasives for AWJ
Martinec, Petr ; Hlaváček, Petr ; Ruppenthalová, Lucie ; Sitek, Libor
The use of recycled garnet abrasive from sludge after cutting materials is a current\nproblem. The behavior of individual garnet abrasives in the AWJ process depends\non the geological origin of the garnets, which also affects all the material\ncharacteristics of the garnet recyclate. The parameters of the BARTON HPX80 and\nGMA 80 abrasive inputs and their recycled products were compared: mineralogical\ntype, apparent density, granularity, grain shape and mineralogical purity,\nmicrohardness data and the degree of damage to the garnet grains. All individual\nparameters of abrasives and their recyclates are reflected in the index of cutting\nefficiency of abrasive. The effect of abrasive material properties on cuttability of\nabrasives is synergistic. The new parameters in the evaluation of abrasives are\nmicro-hardness (brittleness criterion), specific surface and pore size distribution\n(internal grain damage criterion).
|
|
|
Wave Soldering Fluxes Comparison
Stoklásek, Lukáš ; Martinec, Petr (referee) ; Starý, Jiří (advisor)
Semestral thesis introduces the problematics of wave soldering fluxes, flux residues and problems of electromigration. Practical part describes measuring of ionic contamination by using conductometric method, measuring the wettability by the wetting balance method and amount of failures on wave soldered printed circuit boards with these fluxes. The main object is to compare quality of the fluxes.
|
|
|
Relationship between macro- and microscopic sings of alkali-silica reactivity in concrete
Burdová, Anna ; Přikryl, Richard (advisor) ; Martinec, Petr (referee)
This thesis deals with deterioration observed in cement-concrete cover (CBK) for three selected road sections of highways in the Czech Republic. The main objective was to determine whether concrete failure arose due to alkali-silica reaction, or other mechanism. The deterioration of concrete failure was observed in the macroscopic and microscopic scale. The mostly macroscopically observed deterioration of the concrete were cracks breaking the surface and inner parts of concrete. In micro- scale the microcracks and alcali-silica gels were observed. The CBK deterioration was quantitatively determined by three main parameters: specific length of microcracks on the CBK surface, specific length of microcracks in the drill cores and volume of alcali-silica gels and microcracks in thin sections. According to these indicators it was possible to distinguish two different types of CBK deteriorations. (1) Degradation mainly associated by alkali-silica reaction (observed on highways D11 - Vrbová Lhota and D1) and (2) degradation connected with another mechanism (cycles of freezing and thawing, mechanical degradation) was observed on the highway D5.
|
|
|
Assessment of the Aggregate in Historical Plasters
Rezek, P. ; Martinec, Petr
This article deals with the analysis of the aggregates of historical plasters. In the paper there is described the assessment methodology of the aggregates of historical plasters. The assessment of the aggregates is carried out with the example of a set of original and modern-day aggregates taken in the prelature and convent of the Želiv Monastery. Composition of fine aggregates of historical plasters was compared to the composition of the aggregates from resources of nearby watercourses. As well as it was assessed the geological character of nearby vicinity of the Monastery. For the analysis of character of the plaster fine aggregates it is applied the optical microscopy of the plaster thin sections, grain size analysis, mineralogical and petrographic analysis of the aggregates. The presented results document the differences in the origin of the aggregate used in plasters.
|
|
|
The Use of Artificial Intelligence for Optimization of Production
Svoboda, Radovan ; Martinec, Petr (referee) ; Dostál, Petr (advisor)
This paper deals with the problem of optimization of a production plan by using genetic algorithms. It contains a brief overview of the principles behind genetic algorithms in scope of evolutionary algorithms and artificial intelligence in general. It also takes a closer look on the challenge of production planning and control and all activities connected to it. This is followed by description of the modification of genetic algorithms that needed to be done in order to implement it into a computer program, which is used to create and optimize the production plan, and is a result to the issue that this paper deals with. Incorporated is detailed escription of principles and functions of the program, that it offers to its users.
|
|
|
Reinterpretation of Carboniferous strata in the borehole no Stonava SV 2. The Czech part of the Upper Silesian basin
Horak, J. ; Martinec, Petr ; Waclawik, Petr ; Málek, O.
Borehole no Stonava SV 2 was realized in 1968 - 70 yrs. for the verification of the stratigraphy of Carboniferous strata in Karviná area. This borehole was very important for regional study. The original interpretation of the stratigraphy of the Ostrava and Karviná Fms in this borehole was inaccurate, that is, without the revision, used the current publications. The borehole SV 2 was situated between the Stonava and Albrechtice tectonic fault, in block in a Karviná graben. Strong tectonic disturbances in this tectonic structure lead without revision of correlation horizons incorrect determination of litostratigraphy and the thickness of individual members of Ostrava and Karviná Fms in Carboniferous strata. Because the boundaries of individual members of the Ostrava Fm are given into the ceilings of the marine horizon, it is a mistake to disregard the new findings from the study of their association of fauna in marine horizons and geological structure in a new mine boreholes, realized later in the neighbouring of the borehole SV 2. In the case of good primary geological documentation of borehole Stonava SV 2, however, it is possible at any time proceed to reinterpretation.
|
|
|
Determination of boundary of individual members in Ostrava Fm in the Czech part of the Upper Silesian basin
Horák, J. ; Martinec, Petr ; Málek, O.
In the Czech part of the Upper Silesian basin is currently uses the definition of boundary between individual members in Ostrava Fm after F. ŘEHOŘ & J. ZEMAN (1958). On the basis of the revision of the historical geological documentation of boreholes from surface (boreholes denoted as „NP“) and mining documentation from 50-ties years of a past century and new a detailed study of boundary between the individual members of the Ostrava Fm (with respect to correlation horizons in this boreholes) is presented the new proposal to the adjustment of the current boundary between the individual members in Ostrava Fm.
|
|
|
Measurement and analysis of abrasive particles velocities in AWJ
Zeleňák, Michal ; Foldyna, Josef ; Martinec, Petr ; Cárach, J. ; Gurková, Lucie ; Nováková, Daria
Abrasive water jet (AWJ) is a progressive technology commonly used in many industrial applications. Potential of this technology is high and research in the field of optimal geometry design of an injection system has not been completed yet. New designs of the injection cutting head based on numerical simulation of the flow provide important information about processes occurring during the formation of AWJ. Detailed knowledge of velocities of abrasive particles during the abrasive water jet generation is vital for the verification of the numerical model. The aim of the experimental work was to test the applicability of the LIF (Laser Inducted Fluorescence) technique combined with the PTV (Particle Tracking Velocity) processing algorithms to analyze particle velocities at the output of the focusing tube. The combination of commonly used water pressures with abrasive mass flow rate was tested and the obtained results of abrasive particles velocities are presented in this paper.
|
|
|
Abrasives and possibilities of increase in efficiency of abrasive waterjets
Martinec, Petr ; Sitek, Libor
The contribution focuses on the research into abrasive materials and possibilities of adjustment of their properties in order to increase the efficiency of the processes of machining and cutting with abrasive waterjets. Cutting ability of commonly available garnet concentrates and nontraditional products which are starting to access to the Czech market were tested and compared. In addition, entirely new garnet products which are not commercially available yet, recycled abrasives, abrasives with various sizes of grains and heat-affected abrasives or abrasives coated with a thin plastic layer were studied.
|
guest ::
