An Assortment of Woody Plants Produced in the Manor of Nové Dvory at the Turn of the 18th and 19th Centuries: European, Asian and North African Taxa

Lists of woody plants produced in nurseries were preserved from the years 1794, 1800 and 1814 in the manor of Nové Dvory of the noble family of Chotek. 276 taxa of woody plants in the current concept, permanently cultivated outdoors, have been determined in these lists at least to the level of the species. According to the existing findings, for 241 of them were documented for the first time their production for the needs of the landscape architecture in the territory of the Czech Republic. In the case of foreign natural and all cultural taxa, it is also the oldest evidence of their presence in this territory; for native taxa it is the first evidence of their usage in garden culture. Approximately 21.5% of taxa are autochthonous in the Czech Republic, 24% have at least part of their native territory in Europe and 1.5% in the Middle East, 2% come from Central Asia and Siberia and 4% from East Asia. Taxa produced in culture account for approximately 13%. Woody plants of North American origin (they are given a separate contribution) are represented by 34%.O

An assortment of woody plants produced in the manor of Nové Dvory at the turn of the 18th and 19th centuries: North American taxa

The noble family of Chotek began with the realization of extensive landscaping in their manor of Nové Dvory at the end of the 18th century. Lists of woody plants produced for these purposes and for sale were preserved from the years 1794, 1800 and 1814. 276 taxa of foreign woody plants in the current concept, permanently cultivated outdoors, have been identified in all three lists at least to the level of the species. 91 taxa come from North America, with 81 being the first documented place of their presence in the territory of the Czech Republic. All North American taxa are natural, none of them originated in culture.O

Modification of semiconductor nanowire growth

Tato diplomová práce se zabývá růstem polovodičových nanovláken na substrátu Ge(111). Nanovlákna byla připravena metodou PVD (physical vapor deposition), jejich růst byl katalyzován Au koloidními nanočásticemi. V práci je popsán vliv změny depozičních podmínek na výslednou morfologii nanovláken. Je ukázáno, že preferenčním směrem růstu Ge nanovláken je směr . Byla pozorována i Ge vlákna orientace .This diploma thesis deals with the growth of semiconductor nanowires on Ge(111) surface. The nanowires were prepared by means of PVD (physical vapor deposition). The growth was calatyzed by Au colloidal nanoparticles. An impact of different growth conditions on nanowire morfology is presented. It is demonstrated that Ge nanowires grow preferentially along axis. Ge wires with orientation were observed as well.

Probing the micromechanical strength of oxide ceramic composite reinforcements

This work shows how one can probe the micromechanical strength of ceramic reinforcements used in metal matrix composites, which greatly influences the mechanical performance of the composite material yet has seldom been quantified with precision. More specifically, this study presents two methods by means of which one can measure the statistical strength distribution of microscopic, low-aspect-ratio, ceramic particles. Additionally, the study reveals the nature of specific defects that weaken such ceramic reinforcements and shows that, when those defects are absent, one can produce particles of near-theoretical strength, which have the potential to produce remarkably strong and tough metal matrix composites. In one developed method called here the Meridian Crack Test, individual spherical particles are compressed uniaxially between a pair of parallel elasto-plastic platens. It is shown that, by tailoring the platen hardness one can control the relative area of particle-to-platen contact during the test, thereby eliminating the initiation of contact microcracks that are often found to influence particle fracture when hard platens are used. It is shown how this method, coupled with the mathematics of statistical survival-analysis, can give unambiguous access to the particle statistical tensile strength as governed by surface flaws. The method is first demonstrated using microscopic fused quartz spheres 40±20µm in diameter and is then used to measure the strength controlled by surface and subsurface flaws in plasma-sprayed spherical amorphous and nanocrystalline near-eutectic "Eucor" alumina-zirconia-silica ceramic particles of diameter near 30 µm. Results show that nanocrystalline Eucor particles exhibit a characteristic Weibull strength of 1490 MPa, which is approximately 30% higher than in corresponding amorphous particles. The second developed method, called here the C-shaped sample test, combines focused ion beam milling, loading using a nanoindentation device, and bespoke finite element simulations to measure the local strength of ceramic reinforcements free of artifacts commonly present in micromachined specimens. The method is first demonstrated on Nextel 610TM nanocrystalline alumina fibres embedded in aluminium. Results reveal a size effect that does not follow, across size scales, the Weibull statistical strength distribution that is measured by tensile testing macroscopic samples of the fibres. This indicates that, in micromechanical analysis of multiphase materials, highly localized events such as the propagation of internal damage require input data that are measured at the same, local, micro- scale as the event. Finally, we implement the C-shaped sample test method with additional micro-cantilever beam testing to measure the local strength of vapour-grown ¿-alumina Sumicorundum® particles 15 to 30 µm in diameter, known to be attractive reinforcing particles for aluminium. Results show that, provided the particle surface is free of readily observable defects such as pores, twins or grain boundary grooves, the particles can achieve local strength values that approach those of high-perfection single-crystal alumina whiskers, on the order of 10 GPa. It is also shown that by far the most harmful defects are grain boundaries, leading to the general conclusion that alumina particles must be single-crystalline or alternatively nanocrystalline to fully develop their potential as a strong reinforcing phase in composite materials

Wireless modular system for device control and data acquisition

Cílem toho projektu bylo navržení koncepce levného a jednoduchého bezdrátového modulárního systému pro bezdrátové řízení zařízení a přenos krátkých úseků informačních dat (měření teploty, sledování stavu zařízení,…). Celý systém měl být řízen pomocí PC. Projekt zahrnuje použití bezdrátových hybridních modulů k přenosu informací a řízení modulů, ukazuje praktické použití digitálního čidla komunikujícího po jednovodičové sběrnice 1-Wire. Napájení senzoru teploty je zajištěno solárním článkem ve spojení s integrovaným zvyšujícím měničem napětí.The aim of this project is to design a cheap and simple modular wireless system. Its purpose is wireless control of remote devices and transmission of short information blocks (temperature data, status of controlled devices…). The whole system is controlled by a PC. It utilizes hybrid wireless modules for transmission of information and control of remote devices. The project shows practical usage of a digital thermometer communicating via a 1-Wire bus. A solar cell in conjunction with a DC/DC up converter is used to power low-power temperature sensor device.

Towards highly-doped Ge and ZnO nanowires: Growth, characterization and doping level analysis

Vysoce dopovaná polovodičová nanovlákna představují nadějnou třídu nanostruktur pro budoucí aplikace v elektronice, optoelektronice nebo bio-senzorice. Tato práce se zaměřuje na přípravu a charakterizaci nanovláken germania a oxidu zinečnatého s cílem dosáhnout vysoké úrovně dopování. Úvodní část dizertační práce se zabývá přípravou germaniových nanovláken metodou VLS (pára – kapalina – pevná látka). Nejprve jsou popsány faktory ovlivňující růst nanovláken a jejich morfologii – složení katalytické částice, vliv adsorbovaných atomů či molekul a potenciální inkorporace atomů katalyzátoru do objemu nanovláken. Nanovlákna připravená ze zlatých katalytických nanočástic v podmínkách ultravysokého vakua (tzv. MBE metodou) a za přítomnosti atomárního vodíku (proces napodobující podmínky CVD metod) vykazují odlišnou morfologii a směr růstu. Tyto rozdíly odhalují kombinovaný účinek adsorpce atomárního vodíku a šíření zlatého katalyzátoru na stěny nanovláken. Tento efekt je klíčový pro vysvětlení rozdílů ve výsledné morfologii nanovláken připravených MBE a CVD metodami. Další část práce se věnuje přípravě Ge nanovláken z katalyzátorů obsahujících prvky III. skupiny a studiu jejich případné inkorporace, která by mohla vést k dopování nanovláken. Bylo zjištěno, že in-situ připravené směsné Au–Ga nanočástice lze úspěšně využít pro růst germaniových nanovláken, přestože stabilita katalyzátoru je nižší než v případě čistého zlata. I přes vysokou koncentraci gallia v katalytické částici nebyla pozorována inkorporace gallia do objemu nanovlákna. Tato metoda dopování nanovláken se tedy pro uvedenou materiálovou kombinaci ukázala jako nevhodná. Ve třetí části práce jsou popsány výsledky charakterizace ZnO nanodrátů a vývoj metody jejich difuzního dopování galliem. Je prokázán vliv žíhání nanodrátů na koncentraci kyslíkových vakancí (VO) – ve srovnání s žíháním v podmínkách vysokého vakua se koncentrace VO snižuje žíháním v plynném peroxidu vodíku. Dále je zdokumentována inkorporace gallia do ZnO nanodrátů při teplotě nad 350 °C – pozorováno pomocí in-situ SEM. Při teplotě nad 450 °C dochází ke galliem indukované dekompozici ZnO nanodrátů. K určení koncentrace a prostorového rozložení Ga atomů v nanovláknech je využito teoretického difuzního modelu a STEM EDS měření nanovláken. Byla nalezena korelace mezi koncentrací kyslíkových vakancí a inkorporací gallia do objemu ZnO nanovláken. Koncentrace gallia dosahuje řádově 10^21 cm^-3, což dokazuje vhodnost použité metody pro dosažení vysokých úrovní dopování, které jsou potřebné pro budoucí bio-senzorické aplikace v infračervené oblasti.Highly-doped semiconductor nanowires represent a promising class of nanostructures with prospective applications in electronics, optoelectronics or bio-sensing. This thesis is focused on the growth and in-depth characterization of germanium and zinc oxide nanowires, with the aim of acquiring high doping levels. The first part of the thesis deals with the growth of germanium nanowires via the vapour–liquid–solid (VLS) process. Several factors impacting the nanowire growth and morphology are described – the composition of the catalytic particle, the role of surface adsorbates and the incorporation of atoms from the catalyst into the nanowire. The nanowires are grown from gold nanoparticles either in ultra-high vacuum (the MBE-like process) or in the presence of atomic-hydrogen vapour (mimicking the CVD process), resulting in dissimilar nanowire morphology and growth direction. The combined effect of atomic hydrogen adsorption and gold catalyst spreading is revealed – being the key element explaining the difference in nanowire morphology when MBE and CVD growth techniques are utilised. Further, the Ge nanowire growth from group-III-containing catalysts is studied, with the intention of doping the nanowires via the incorporation of atoms from the catalyst droplet. The in-situ prepared alloyed Au–Ga catalyst is found to be applicable for germanium out-of-plane nanowire growth – although the catalyst stability is lower than for pure Au. Despite a high dopant concentration in the catalyst, no gallium incorporation into the nanowire is observed. Hence, this method of nanowire doping is proved unsuitable for the material system selected. The third part of the thesis covers the characterization of ZnO nanowires and the development of a protocol for their diffusional doping with gallium. The impact of nanowire annealing on the concentration of oxygen vacancies (VO) is demonstrated – annealing in H2O2 gas decreases the VO concentration, compared with annealing in high vacuum. Further, Ga incorporation into ZnO nanowires is documented with in-situ SEM when annealed above 350 °C. Moreover, gallium-induced decomposition of ZnO nanowires is observed above 450 °C. The concentration and spatial distribution of Ga within the nanowires is assessed using STEM EDS and a theoretical model for Ga diffusion. The correlation between the VO concentration and the Ga incorporation into ZnO is found. Gallium concentration in the order of 10^21 cm^-3 is reached in the nanowires – demonstrating the suitability of the presented diffusional-doping method for achieving high Ga doping levels needed for prospective bio-sensing applications in the IR region.