No (11880)
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Electrochemical Properties of Mixed Self-Assembled Monolayers Based on Terpyridine Transition Metal Complexes
Kocábová, Jana; Nováková Lachmanová, Štěpánka; Vavrek, František; Valášek, M.; Hromadová, Magdaléna
2023 - English
This work presents the electrochemical characterization of mixed self-assembled monolayers\n(SAMs) of [Os(terpy)2]2+ and terpyridine connected by tripodal anchoring groups to the\npolycrystalline gold bead electrode and provides a comparison with SAM based on\n[Os(terpy)2]2+ tripodal molecules without diluting terpyridine tripodal molecules. It is shown\nthat both arrangements enable reproducible preparation of well-defined compact films. The\nelectron transfer rate constant for mixed SAM was determined from cyclic voltammograms\naccording to Laviron’s analysis and compared with the rate constant obtained previously for\nSAM containing only [Os(terpy)2]2+ tripod.
Keywords:
transition metal complexes; terpyridine; tripodal anchor
Available on request at various institutes of the ASCR
Electrochemical Properties of Mixed Self-Assembled Monolayers Based on Terpyridine Transition Metal Complexes
This work presents the electrochemical characterization of mixed self-assembled monolayers\n(SAMs) of [Os(terpy)2]2+ and terpyridine connected by tripodal anchoring groups to the\npolycrystalline gold ...
Elimination Voltammetry with Linear Scan: Advantages and Disadvantages
Navrátil, Tomáš; Trnková, L.; Hrdlička, Vojtěch; Li, X.
2023 - English
Elimination voltammetry with linear scan (EVLS) represents an almost traditional\nmathematical method that helps to obtain additional and detailed information about the recorded\nelectrochemical signals and therefore, to better understand the analyzed systems. Although it\nhas been substantially developed and expanded during its existence of more than a quarter of a\ncentury and has found many areas of application, like any other mathematical and experimental\nmethod, it exhibits several advantages and disadvantages. In this contribution, we summarize\nits strengths, weaknesses, opportunities, as well as threats.\n
Keywords:
elimination voltammetry with linear scan; advantages; disadvantages
Available on request at various institutes of the ASCR
Elimination Voltammetry with Linear Scan: Advantages and Disadvantages
Elimination voltammetry with linear scan (EVLS) represents an almost traditional\nmathematical method that helps to obtain additional and detailed information about the recorded\nelectrochemical ...
Applications of blade vibration measurements in the laboratory of rotational laser vibrometry
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine; Voronova, Evgeniya
2023 - English
The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are intended for the research of vibration of rotating blades. The paper includes a summary of measurement results using a special turbine model and their consequences in theoretical research, as well as measurements with a real compressor of aircraft engine and comparison with computational analysis. The paper also describes the complex system for measurement and analysis.
Keywords:
laboratory; turbine; blade; vibration; precision method
Available at various institutes of the ASCR
Applications of blade vibration measurements in the laboratory of rotational laser vibrometry
The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are ...
The effect of the backfill on the integrity of a buried pipeline upon heavy-duty vehicle crossings
Gajdoš, Lubomír; Šperl, Martin; Slížková, Zuzana; Drdlová, M.
2023 - English
The aim of this work was to determine stresses in the wall of a buried empty gas pipeline caused by the weight of backfill as well as by heavy-duty vehicles crossing the pipeline, and, on their basis to assess the applicability of protective sleeves. A buried pipeline with zero internal pressure of transported medium (empty pipeline) differs from an unburied pipeline by the vertical load due to the weight of the backfill which causes an ovalness of the circular cross section of the pipeline. This leads to the rise of through-wall bending stresses with the tensile stress at the outside surface at the 3 and 9 o´clock positions and compressive stress at the inside surface. At the 6 and 12 o´clock positions the stresses are tensile at the inside surface and compressive at the outside surface. The current depth of soil cover above gas pipelines is 0.5 m. For pipes DN500, t ~ 6.5 mm the through-wall bending stress is found to be σb ≈ ±10 MPa. In comparison with the yield stress of pipeline material, this stress is negligible. The situation is changed when heavy-duty vehicles cross the pipeline. For example, when a MAN truck with the mass load 3270 kg acting on a single wheel of the front axle crosses this pipeline, the pressure transmitted to the pipe will cause the through-wall bending stress σb ≈ ±76 MPa. This stress is superimposed to that of the backfill to give the total value ±86 MPa. When dead loads, imposed by backfill cover, together with live loads, caused by truck-wheel loads, are excessive a crushing of side walls of the pipeline and/or ring buckling of the pipe cross section can happen.
Keywords:
gas pipeline; pressure; buried pipeline
Available at various institutes of the ASCR
The effect of the backfill on the integrity of a buried pipeline upon heavy-duty vehicle crossings
The aim of this work was to determine stresses in the wall of a buried empty gas pipeline caused by the weight of backfill as well as by heavy-duty vehicles crossing the pipeline, and, on their basis ...
Experimental evaluation of aluminothermic welds
Zeman, L.; Valach, J.; Zlámal, P.; Krčmářová, N.; Koudelková, Veronika; Zeman, J.
2023 - English
The article presents a study of the mechanical processes occurring during the aluminother-mic reaction using experimental methods (strain gauges, digital image correlation, thermography,scanning electron microscopy, profilometry). The aluminothermic reaction is a highly efficient weldingmethod due to its exothermic behaviour, however, it places considerable demands not only on thewelding technique, but also on the capabilities of the experimental methods used - these limitationsare also discussed in the article. The aluminothermic reaction is associated with the formation of alocalised heat source with a time evolution dictated by the technological procedure, which manifestsitself in heat propagation to the surrounding weld material. The unequal evolution of the temperaturefield is the fundamental cause of the appearance of the heat affected zone or local deformations orsurface curvature, which was the focus of the experimental methods deployed above and the results ofwhich are shown in the article.
Keywords:
aluminothermic reaction; train gauges; hardness; profilometry; scanning electron microscope
Available at various institutes of the ASCR
Experimental evaluation of aluminothermic welds
The article presents a study of the mechanical processes occurring during the aluminother-mic reaction using experimental methods (strain gauges, digital image correlation, thermography,scanning ...
Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens
Glinz, J.; Maurer, J.; Holzleitner, M.; Pace, F.; Stamopoulos, A.; Vopálenský, Michal; Kumpová, Ivana; Eckl, M.; Kastner, J.; Senck, S.
2023 - English
The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific application’s needs. However, the bonding quality between continuous fibers and the FFF matrix material has high impact on the overall performance of the composite. In a recent study [1], additively manufactured (AM) continuous fiber reinforced tensile test specimens have been investigated regarding the effect of amount and material of the embedded continuous fibers on tensile strength and AM build quality. During these tensile tests, a sudden reduction in tensile stress, which most likely was not related to actual rupture of continuous fibers, was noticeable. Since X-ray computed tomography (XCT) scans were performed only prior to and after the tensile testing, a detailed investigation on the origin of these drops in tensile stress was not possible. Within this work, we will expand upon these findings and present results of fast on-the-fly in-situ investigations performed on continuous carbon fiber reinforced specimens of the same AM build. During these investigations, specimens are loaded under the same conditions while fast XCT scans, with a total scan time of 12 seconds each, were performed consecutively. The resulting three-dimensional image data reveals internal meso- and macro-structural changes over time/strain to find the cause of the aforementioned reduction in tensile stress.
Keywords:
additive manufacturing; composites; X-ray computed tomography; in-situ tensile testing
Available at various institutes of the ASCR
Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens
The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific application’s needs. However, ...
Acta Polytechnica CTU Proceedings. Vol. 42 (2023)
Kytýř, Daniel; Doktor, T.; Zlámal, Petr
2023 - English
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all areas of experimental research and its application in solid and fluid mechanics. The topic will particularly concern to: Conventional and Advanced Experimental Methods in Solid and Fluid Mechanics, Non-Destructive Testing and Inspection, Measurements in Material Science, Computer Assisted Testing and Simulation, Engineering Design Simulation, Hybrid Methods, Experimental Techniques – Numerical Simulation, Optical Methods and Image Processing, Measurements in Biomechanics, Sensor Techniques for Micro- and Nano-Applications, Measurement Methods for Forensic Engineering.
Keywords:
experimental mechanics; fluid mechanics; mechanics of solids
Available at various institutes of the ASCR
Acta Polytechnica CTU Proceedings. Vol. 42 (2023)
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all ...
Analyzing stochastic stability of a gyroscope through the stochastic Lyapunov function
Náprstek, Jiří; Fischer, Cyril
2023 - English
The text delves into the application of first integrals in the construction of Lyapunov functions for analyzing the stability of dynamic systems in stochastic domains. It emphasizes the distinct characteristics of first integrals that warrant the introduction of additional constraints to ensure the essential properties required for a Lyapunov function. These constraints possess physical interpretations associated with system stability. The general approach to testing stochastic stability is illustrated using the example of a 3-degrees-of-freedom system representing a gyroscope.
Keywords:
stochastic stability; Lyapunov function; first integral; gyroscope
Available at various institutes of the ASCR
Analyzing stochastic stability of a gyroscope through the stochastic Lyapunov function
The text delves into the application of first integrals in the construction of Lyapunov functions for analyzing the stability of dynamic systems in stochastic domains. It emphasizes the distinct ...
Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
2023 - English
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation.
Keywords:
modal analysis; natural frequencies; eigen-modes of vibration
Available at various institutes of the ASCR
Experimental and numerical investigation of the frequency-modal properties of the switch box
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate ...
Engineering Mechanics 2023
Radolf, Vojtěch; Zolotarev, Igor
2023 - English
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Mechatronics, Reliability of structures, Mechanics of solids, Technological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies.
Keywords:
biomechanics; dynamics; mechatronics; fluid mechanics; mechanics of solids; fracture mechanics
Available at various institutes of the ASCR
Engineering Mechanics 2023
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech ...
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