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Asymmetry of the response probability density of a system with parametric random noises
Náprstek, Jiří; Fischer, Cyril
2018 - anglický
Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These parasitic processes are usually of the random character and, consequently, they exercise as parametric noises. Moreover, the input signal mostly consists of a useful signal which can be taken as composed from deterministic and random additive part. Various combinations of these noises are the origin of random and also systematic measuring errors which can have under certain circumstances a cumulative character, deteriorate the output signal quality and can lead finally to the stochastic stability loss. These effects can be theoretically described using differential systems with stochastic coefficients and stochastic right hand side considering all input and output processes to be of the Markov type.
Klíčová slova:
random vibration; signal reconstruction; parametric noise; response asymmetry
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Asymmetry of the response probability density of a system with parametric random noises
Recording of time variable processes is accompanied by various internal disturbing effects as a rule. They influence parameters of the measuring facility, transducer-device transmission, etc. These ...
Basic biomechanical characterization of polyurethane based artificial cancellous structures
Šleichrt, Jan; Kytýř, Daniel; Pithartová, Kateřina; Senck, S.; Fürst, D.; Schrempf, A.
2018 - anglický
The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the human bone in the case of its adequate replacement. Investigated material can be also used as an artificial bone to train surgical procedures and to improve the skills of the surgeons. Four sets of the foam with different chemical composition were subjected to an uniaxial quasi-static loading to describe basic mechanical behaviour of these samples. Based on these experiments, the stress-strain diagrams were created as a comparative tool including calculation of the effective Young’s modulus. The acquired knowledges will be used as input parameters of a follow-up study aimed at describing the morphology of presented structures and their response to mechanical experiments. A distortion effect of porosity on the results is not considered in this study.
Klíčová slova:
polyurethane foam; artificial bone; uniaxial loading; digital image correlation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Basic biomechanical characterization of polyurethane based artificial cancellous structures
The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the ...
Instrumentation of four-point bending test during 4D computed tomography
Kytýř, Daniel; Fíla, Tomáš; Koudelka_ml., Petr; Kumpová, Ivana; Vopálenský, Michal; Vavro, Leona; Vavro, Martin
2018 - anglický
High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading.
Klíčová slova:
in-situ loading device; four-point bending; 4D micro-CT; crack propagation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Instrumentation of four-point bending test during 4D computed tomography
High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of ...
Corrosion products phase identification using micro-Raman and FTIR
Majtás, Dušan; Mácová, Petra
2018 - anglický
Phase identification of corroded metal objects might be problematic because corrosion products are usually a complex mixture of different phases. Furthermore, some of present phases may be either semi-crystalline or amorphous. The most suitable procedure is to use X-ray diffraction (XRD), for identification of crystalline phases in bulk, in combination with micro-Raman spectroscopy to obtain information on smaller scale and given location. Micro-Raman spectroscopy identifies crystalline and semi-crystalline phases. The literature also reports of the application of Mössbauer spectroscopy to identify amorphous phases. In this work, the combined use of Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy is evaluated. The methods may be interchangeable to some point. But is it safe to assume that all phases present can be detected?
Klíčová slova:
corrosion; micro-Raman spectroscopy; FTIR
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Corrosion products phase identification using micro-Raman and FTIR
Phase identification of corroded metal objects might be problematic because corrosion products are usually a complex mixture of different phases. Furthermore, some of present phases may be either ...
The effect of micro-silica on the microscopic features of the UHPC composite and its inter-facial transition zone
Hrbek, Vladimír; Prošek, Z.; Chylík, R.; Vráblík, L.
2018 - anglický
The uplift of concrete overall macroscopic performance by way of alternative additives is commonly used technique. In case of ultra high performance concrete (UHPC), micro-silica is added to the mixture as a micro-filler to the structure of cement binder. As a result, the cementitious matrix macro-mechanical performance is elevated. This paper is aimed on the UHPC micro-scale enhancement by different micro-silica additive content in the mixture. More closely, the study investigate the impact of the micro-silica on the inter-facial transition zone (ITZ) between the binder matrix and basaltic aggregate.
Klíčová slova:
high performance concrete; indentation; spectral deconvolution SEM; image analysis; ITZ
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The effect of micro-silica on the microscopic features of the UHPC composite and its inter-facial transition zone
The uplift of concrete overall macroscopic performance by way of alternative additives is commonly used technique. In case of ultra high performance concrete (UHPC), micro-silica is added to the ...
Design of material and technological copy for repair of sgraffito decorated renders
Válek, Jan; Skružná, Olga; Wichterlová, Z.; Waisserová, J.
2018 - anglický
This paper deals with research in Renaissance sgraffito materials and techniques. It focuses on the replication process for original materials and application techniques used in a reconstruction of the missing parts of a sgraffito decoration depicting a Landsknecht procession on the façade of a house in Slavonice. The result of the theoretical and practical experimental work is the description and evaluation of the process of creating a material and technological copy of the original. This involved detailed material analysis, determining the provenance of and selecting suitable raw materials, design of a repair mix and its testing, and evaluation during application trials. The study has shown that, in order to achieve good results, the conclusions of material analysis have to be linked to the practical\nskills of restorers and conservators. The particular application procedures that match the requirements of the historical material and the original work can be deduced from full scale practical trials. Feedback between the design of the repair mixture and the application process made it possible to come to an optimal material and application technique. The missing parts of the sgraffito were replaced using a mortar and application technique that closely correspond to those originally used in the Renaissance.
Klíčová slova:
sgraffito; mortar analysis; historic techniques; Slavonice
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Design of material and technological copy for repair of sgraffito decorated renders
This paper deals with research in Renaissance sgraffito materials and techniques. It focuses on the replication process for original materials and application techniques used in a reconstruction of ...
Influence of printing and loading direction on mechanical response in 3D printed models of human trabecular bone
Doktor, Tomáš; Kumpová, Ivana; Wroński, S.; Śniechowski, M.; Tarasiuk, J.; Forte, G.; Kytýř, Daniel
2018 - anglický
The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D model was obtained by X-ray computed tomography. Then a series of cubical samples was prepared by additive manufacturing technique and tested by uniaxial compression loading mode. Mechanical response was compared in nine different combinations of direction of 3D printing and loading direction. The results show neglectible influence on the deformation response in elastic region (stiffness) and significant changes of the behaviour in plastic region (stress and strain at yield point, strain at full collapse).
Klíčová slova:
additive manufacturing; tomography; deformation response
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of printing and loading direction on mechanical response in 3D printed models of human trabecular bone
The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D ...
Utilization of image and signal processing techniques for assessment of built heritage condition
Koudelka_ml., Petr; Koudelková, Veronika; Doktor, Tomáš; Kumpová, Ivana; Kytýř, Daniel; Valach, Jaroslav
2018 - anglický
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the least possible volume removed from the structure is essential. As many historical buildings in the Czech Republic are built using sandstone that can be considered as a typical heterogeneous system, statistical signal processing is a promising approach for determination of the representative volume element (RVE) dimensions. Such calculations can be carried out on the domain of logical arrays representing binary images of the materials microstructure. This paper deals with processing of image data obtained using SEM-BSE and high resolution flatbed scanner for determination of RVE dimensions. Advanced image processing techniques are employed and results from calculation using grayscale data are presented and compared with results calculated on the basis of color input images.
Klíčová slova:
heterogeneous systems; natural stones; image processing; K-means clustering; representative volume element
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Utilization of image and signal processing techniques for assessment of built heritage condition
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the ...
Multi-channel control system for in-situ laboratory loading devices
Rada, Václav; Fíla, Tomáš; Zlámal, Petr; Kytýř, Daniel; Koudelka_ml., P.
2018 - anglický
In recent years, open-source applications have replaced proprietary software in many fields. Especially open-source software tools based on Linux operating system have wide range of utilization. In terms of CNC solutions, an open-source system LinuxCNC can be used. However, the LinuxCNC control software and the graphical user interface (GUI) could be developed only on top of Hardware Abstraction Layer. Nevertheless, the LinuxCNC community provided Python Interface, which allows for controlling CNC machine using Python programming language, therefore whole control software can be developed in Python. The paper focuses on a development of a multi-process control software mainly for in-house developed loading devices operated at our institute. The software tool is based on the LinuxCNC Python Interface and Qt framework, which gives the software an ability to be modular and effectively adapted for various devices.
Klíčová slova:
CNC; controlling; LinuxCNC; Python Interface; Python; parallel programming; Qt; PyQt; Qwt; PythonQwt; LabJack
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Multi-channel control system for in-situ laboratory loading devices
In recent years, open-source applications have replaced proprietary software in many fields. Especially open-source software tools based on Linux operating system have wide range of utilization. In ...
Analysis of mini-jack technique for in situ measurement of strength
Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
2017 - anglický
The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack inserted in bored hole. The mini-jack compression technique simulates the standard compression test, it is compared to that to examine its prediction strength (correlation coefficients). The paper shows an influence of moisture content of wood on experimental measurements using this technique. The measurement was carried out at spruce samples at three moisture contents of 12, 18 and 24%. The results of the tests prove a very good correlation of the strength determined by the proposed technique and wood density and strength determined at universal testing machine in compression parallel to the grain. The effect of the moisture content on the measurement by the mini-jack technique was proved to be significant. Beside that, the newly-developed instrument was also studied using digital image correlation (DIC) technique to analyze induced strains around the bored hole. This was studied on halved spruce samples. The DIC revealed symmetric character of the loading and significant differences between strains induced in tangential and longitudinal directions.
Klíčová slova:
non-destructive testing; mini-jack technique; wood; in-situ testing; compression strength
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Analysis of mini-jack technique for in situ measurement of strength
The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack ...
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