NUMERICAL MODELLING OF WAVE SHAPES DURING SHPB MEASUREMENT

The paper aims at the numerical simulation of the wave propagation in compressive Split Hopkinson Pressure Bar (SHPB) experiment. The paper deals with principles of SHPB measurement, optimisation of a numerical model and techniques of pulse shaping. The parametric model of the typical SHPB configuration developed for LS-DYNA environment is introduced and optimised (in terms of element size and distribution) using the sensitivity study. Then, a parametric analysis of a geometric properties of the pulse shaper is carried out to reveal their influence on a shape of the incident pulse. The analysis is algorithmized including the pre- and post-processing routines to enable automated processing of numerical results and comparison with the experimental data. Results of the parametric analysis and the influence of geometric properties of the pulse shaper (diameter, length) on the incident wave are demonstrated

The role of protein phosphorylation during progamic phase of tobacco male gametophyte development

Zralý pyl tabáku obsahuje silně dehydratovanou cytoplazmu a je metabolicky neaktivní. Po rehydrataci cytoplazmy je jeho metabolizmus nastartován a po dokončení aktivace vyrůstá pylovou aperturou pylová láčka. Změny v zavodnění cytoplazmy spolu s nastartováním metabolizmu jsou doprovázeny regulací translace i post-translačních modifikací (zejména fosforylace) přítomných proteinů. V této disertační práci jsou prezentovány fosfopeptidy ze zralého pylu tabáku virginského (Nicotiana tabacum), pylu aktivovaného in vitro 5 min a pylu aktivovaného in vitro 30 min. Z každého stádia byl získán celkový proteinový extrakt, jenž byl naštěpen trypsinem a získaná peptidová směs byla obohacena metodou MOAC (afinitní chromatografie s využitím kovového oxidu/hydroxidu) s matricí z oxidu titaničitého. Fosfopeptidy v obohaceném eluátu byly identifikovány kapalinovou chromatografií v kombinaci s tandemovou hmotnostní spektrometrií (LC-MS/MS). Celkem bylo identifikováno 471 fosfopeptidů, nesoucích 432 přesně lokalizovaných fosforylačních míst. Získané fosfopeptidy pocházely z 301 fosfoproteinů, které spadaly do třinácti funkčních kategorií. Převládajícími funkcemi se staly transkripce, syntéza proteinů, cílení a skladování proteinů a přenos signálu. Mnohé fosfopeptidy podléhaly koncentračním změnám mezi třemi...v angličtině (English abstract) Tobacco male gametophyte has a strongly dehydrated cytoplasm and represents a metabolically inactive stage. Upon cytoplasm rehydration, pollen grain becomes metabolically active and after the activation is finished, the pollen tube growth through a selected pollen aperture starts. The rehydration together with metabolic activation are accompanied by the regulation of translation and post-translational modifications (mainly phosphorylation) of the existing proteins. In this Ph.D. thesis, there were identified phosphopeptides from tobacco (Nicotiana tabacum) mature pollen, pollen activated in vitro 5 min and pollen activated in vitro 30 min. The total proteins from the above male gametophyte stages were extracted. The protein extract was trypsinized and the acquired peptide mixture was enriched by MOAC (metal oxide/hydroxide affinity chromatography) with titanium dioxide matrix. The enriched fraction was subjected to liquid chromatography coupled with tandem mass spectrometry (LC- MS/MS). Totally, there were identified 471 phosphopeptides, carrying 432 exactly localized phosphorylation sites. The acquired peptide identifications were mapped to 301 phosphoproteins that were placed into 13 functional categories, dominant of which were transcription, protein synthesis,...Katedra experimentální biologie rostlinDepartment of Experimental Plant BiologyFaculty of SciencePřírodovědecká fakult

High-speed X-ray radiography for experiments in impact dynamics using high-power X-ray tube, cesium iodine scintillator and laboratory optical camera

X-ray radiography and computed tomography have become well-established methods for investigation of internal structure of objects and for defectoscopy. Recently, the methods have even been used for in-situ analysis of materials under mechanical loading. Although the techniques would be very suitable for analysis during dynamic events, their application is constrained by typical achievable frame rates. Therefore, fast imaging is usually limited to facilities providing sufficient flux like particle accelerators. In this paper, we test imaging performance of a laboratory-based setup with a high-power X-ray tube, a scintillation panel, and an optical camera. Fast-rotating object and typical specimens for impact testing are irradiated with different power settings and quality of captured images is evaluated and analyzed. It is found out that the system can be successfully used for imaging at several hundred frames per second allowing for inspection of slow impact dynamics experiments

Response of the ultra high performance concrete under dynamic compressive loading

Ultra high performance concrete is a modern cementitious material which exhibits excellent mechanical properties such as damage tolerance, fracture toughness and durability. These features make this materials suitable for wide range of applications where is the material subjected to different modes of loading and different loading rates.This paper deals with measurement of the Ultra high performance concrete reinforced with steel fibres in quasi-static compression mode of deformation and two elevated strain rates using split Hopkinson pressure bar. The results of the measurement show high increase of the mechanical properties with elevated strain rate

Developement of multimedial web portal for PLD course tutorials

Tato práce popisuje principy tvorby statických webových stránek a nejpoužívanější metody používané při tvorbě stránek dynamických. Seznámíte se s jazyky HTML, CSS, PHP, JavaScript a databázemi MySQL. Dále jsou zpracovány základní informace o problematice programovatelných logických obvodů PLD a FPGA.This paper describes the principles of the creation of static Web pages and the most common methods used in creating dynamic pages. Acquainted with the languages of HTML, CSS, PHP, JavaScript and MySQL database. Furthermore, processed basic information on programmable logic circuits, PLD and FPGA.

DIRECT MEASUREMENT OF REACTION FORCES DURING FAST DYNAMIC LOADING

The presented paper is focused on embedding of the serially manufactured piezo-electric impact loadcell into Open Hopkinson Pressure Bar (OHPB) and it’s modifications for a direct force measurement during dynamic loading. Conventionally, during the SHPB test dynamic force equilibrium is investigated by a comparison of the transmitted signal wave and the difference between the incident, reflected and transmitted signals measured by strain gauges [1]. However, in the experiments with specimens with low mechanical impedance, a major portion of the incident wave is reflected back on the interface between the bar and the specimen. Comparison between two-large amplitude incident and reflected pulse and a small-amplitude transmitted pulse can be influenced by large error and resulting force equilibrium can be inaccurate. Therefore, a piezo-electric quartz impact force transducer was used to directly measure the axial forces in the vicinity of the specimen end surfaces

Model of optical communication system based on OFDM

Práce zkoumá způsoby generování signálu OFDM a metody kanálového kódování LDPC. Popisuje tvorbu základních modulů komunikačního systému v programu Matlab a metody simulace atmosférického přenosového prostředí zahrnující vlivy turbulencí, útlum na trase a vlivy počasí na přenášený signál.The work explores ways to generate the OFDM signal and LDPC channel coding methods. Describes the creation of basic modules of the communication system in Matlab and simulation methods for atmospheric transmission environment, including effects of turbulence, attenuation along the route and weather conditions on the transmitted signal.

HIGH STRAIN-RATE COMPRESSIVE TESTING OF FILLING MATERIALS FOR INTER-PENETRATING PHASE COMPOSITES

In this study behavior of the selected types of filling material for the inter-penetrating phase composites was tested in compressive loading mode at low and high strain-rates. Three types of the filling material were tested, (i) ordnance gelatin, (ii) low expansion polyurethane foam, and (iii) polyurethane putty. To evaluate their impact energy absorption bulk samples of the selected materials were tested in compression loading mode at strain-rates 1000 s−1 to 4000 s−1. The high strain-rate compressive loading was provided by Split Hopkinson Pressure Bar (SHPB) which was equipped with PMMA bars to enable testing of cellular materials with low mechanical impedance. Based on the comparative measurement response to compression at both low and high strain-rates was analysed. The results show a significant strain-rate sensitivity of the ordnance gelatin and of the polyurethane putty, while strain-rate effect in the polyurethane foam was not observed

Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB

This article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic conditions, while standard uni-axial loading device is used for evaluation in quasi-static conditions. Basalt specimens were subjected to four different loading-rates from 200–600 s−1 on which the stress-strain dependence was evaluated together with DIC analysis of crack initiation and disintegration process. Understanding the mechanical properties of basalt can provide insights for engineers and designers in creating structures that are durable and able to withstand different loading conditions. The findings of this study can have implications for a wide range of industries, including aerospace, automotive, and construction, among others

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 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