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Material Characterization and Modeling of Interband Cascade Light Emitting Diodes
Herzánová, Kristína ; Bastard, Gérald (referee) ; Detz, Hermann (advisor)
Tato práce se zaměřuje na charakterizaci materiálů a ztrátových mechanismů heterostruktur používaných v mezipásových kaskádových zařízeních a na modelování mezi-pásových kaskádových elektroluminiscenčních diod (ICLED). Mezipásová kaskádová zařízení, zejména lasery a elektroluminiscenční diody, mají zásadní význam pro fotonické aplikace ve střední infračervené oblasti vzhledem k jejich efektivitě a možnosti integrace do fotonických obvodů. Studie zahrnuje extrakci materiálových parametrů ze spektroskopické elipsometrie a FTIR měření a rozšíření stávajícího transportního modelu o zářivé rekombinační procesy, konkrétně o spontánní emisi v ICLED. Z různých ztrátových mechanismů v těchto zařízeních byla zvláštní pozornost věnována valenční mezipásové absorpci, která zhoršuje výkon mezipámových kaskádových zařízení v oblasti středních infračervených vlnových délek nad 4 m. Výsledky získané na základě experimentální charakterizace vlnovodů tvořených mezipásovými kaskádovými lasery (ICL) zkoumající jejich přenosové ztráty prokázaly vliv valenční mezipásové absorpce za různých operativních podmínek. Tento výzkum přispívá k optimalizaci struktur mezi-pásových kaskádových struktur, která vede ke zvýšení výkonu a širší použitelnosti v oblasti detekce, monitorování životního prostředí a biomedicínské diagnostiky.
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Využití operátoru křížení v kartézském genetickém programování
Bromnik, Petr ; Sekanina, Lukáš (referee) ; Hurta, Martin (advisor)
The aim of this paper is to propose and implement two new crossover methods in Cartesian Genetic Programming (CGP) and compare them with existing approaches. CGP is a type of evolutionary algorithm that uses acyclic graphs to represent executable programs. Most CGP applications use the mutation operator only, but the effort to find a suitable crossover operator is still ongoing. In this paper, the two newly proposed crossover methods are compared on five symbolic regression problems against the standard 1 + lambda procedure based purely on mutation. Experimental results show that these methods find solutions in a similar number of fitness evaluations as 1 + lambda and, in two cases, even significantly earlier.
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Lifetime measurement of current carriers in silicon solar cells structures
Macháček, Martin ; Hégr, Ondřej (referee) ; Boušek, Jaroslav (advisor)
This thesis deals with a lifetime measurement of current carriers in silicon solar cell structures. In the first chapter there is a description of several recombination models and their participation at a final effective lifetime value. By using these recombination models in a computer simulation it is possible to receive approximate evaluation of some important silicon solar cell structure parameters. The PC1D simulation program was used for this thesis. For the lifetime measurement of real test-wafers two methods were used: QSSPC (quasi-steady-state photoconductance) and MW-PCD (microwave photoconductance decay). There is a detail description of these methods, used measurements machines and differences between both of them in the chapter four. The main objective of the thesis is mentioned in the last chapter, which is mainly focused on a chemical passivation of silicon wafers and deals with a problem of post-passivation wafer cleaning. There are three passivation techniques mentioned: the iodine in ethanol solution, the iodine and polymer in ethanol solution and the quinhydron in methanol solution. In two cases a results, that are adequate to return the tested wafers in the manufacture process, were achieved.
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Modeling of physical phenomena in semiconductors
Pálka, Mário ; Frk, Martin (referee) ; Rozsívalová, Zdenka (advisor)
This work deals with properties and physical phenomena occurring in semiconductor materials. In details are described generation - recombination processes in a state of thermodynamic disequilibrium. The output of work is a software application simulating waveforms of energy levels in the band's own models and impurity semiconductors, depending on the type of semiconductor, impurities concentration and temperature. Finally, the processed virtual lab experiment deliverable in the educational process.
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Semiconductor properties
Řihák, Pavel ; Frk, Martin (referee) ; Špinka, Jiří (advisor)
This bachelor's project deals with methodology for determination the semiconductors parameters. Particularly, it deals with methods of diffusion length measurrement. Various methods of measurement were studied for this purpose and selected the most suitable one. Which was carried measurements on a sample of silicon using IR power LEDs.
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Fundamental properties of semicomductor materilas
Kahánek, Tomáš ; Jirák, Josef (referee) ; Špinka, Jiří (advisor)
This work deals with fundamental properties of semiconductors materials and methods of their measuring. This work is focused on non-contact methods using light to generate electric charge in semiconductor. Tests were focused on measuring characteristics of PN transition light diods and semiconductor specimen with big resistivity, there was founded absorption edge of silicon.
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FINE-SCALE RECOMBINATION MAPS OF THE CATTLE GENOME INFERRED BY LINKAGE DISEQUILIBRIUM
MOHAMMADI, Fardokhtsadat
Recombination is a genetic event that occurs during meiosis and leads to the exchange of genetic material between paternal and maternal homologous chromosomes. The intensity of recombination is shown to vary across genomes between and within species, yet the determinants of recombination patterns among populations of the same species are not fully understood. In this thesis, we estimated fine-scale, breed-specific recombination maps of a subset of chromosome 25 of Braunvieh and Fleckvieh cattle for different populations with respect to inbreeding coefficients using the R package LDJump under two assumptions, neutrality and demography. Moreover, we studied the association between recombination rates and genomic features such as SNP count, GC content, and the density and nature of genes. We observed a statistically-significant, weak negative correlation between recombination rates and SNP count, where low recombination rates are accompanied by higher SNP count, and vice versa. More complex demographic scenarios as well as the level of inbreeding should be incorporated in further research using LDJump to address this possible association between SNP count and recombination rates. On the contrary, we observed no such relationship between recombination rates and GC content. We detected a substantial difference in gene density between the lowest and highest SNP-count regions of chromosome 25.
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SHORT TANDEM REPEAT ANALYSIS IN RECOMBINATION HOTSPOTS ACROSS THE HUMAN GENOME.
MASINOVIC, Mehdin
Short tandem repeats are one of the most abundant tandem repeat types and are an important source of genetic variation. Comparative studies have analyzed their abundance in promoters, genes, and other relevant regions in the human genome, but short tandem repeats in recombination hotspots have yet to be fully characterized. Using the R package entitled STRAH, we analyzed the frequency of 310 distinct short tandem repeats in 37527 recombination hotspots across the human reference genome. We generated pattern-specific comparisons for all repeat types among recombination hotspots, regions directly surrounding them, and the remaining genomic region of the human genome. We detected that C/G-rich repeats tend to be enriched in recombination hotspots, observed that A/T-rich repeats are more enriched in regions unrelated to recombination, and found that repeats are present in very low numbers if they do not contain consecutively repeated DNA bases. Collectively, our results provide a standardized, genome-wide characterization of short tandem repeats in recombination hotspots and their surrounding regions, highlight pattern-specific differences that depend on repeat length and repeat type, and give insight into short tandem repeat enrichment in relation to recombination hotspots across the human genome.
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Traditional plant breeding,advanced biotechnological engineering with emphasis on GM crops and environmental risk assessment of GMs
KOPICOVÁ, Klára
While searching for the best approach that would ensure an adequate supplement of the current still growing world population, the national governments support different strategies to multiply crop production and to stabilize profits. It is obvious that traditional plant breeding techniques are not capable to meet this challenge. Hence, scientists developed an advanced plant breeding techniques that cope with the adversity of the environment (e. g. pest and weed pressure, drought, salinity) as well as satisfy major needs of human society (e. g. sufficient yields, nutrient content). However, advanced bioengineering arouses distrust in consumers. This review compares both, the advanced plant breeding techniques with traditional breeding approaches; and the debate is further extended by critical assessment. Further focusing on genetic modifications (GMs) and genetically modified (GM) crops, this study describes a status of their growing on the example of two completely different strategies - strategy of the United States (U.S.) and the European Union (EU). Additionally, this thesis suggests a new design for testing of GM crops environmental risk assessment (ERA) - more precisely, a very little explored, potential transfer of GM gene constructs into invertebrates.
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Study of reactions of simple ions in low temperature plasma
Kálosi, Ábel ; Plašil, Radek (advisor) ; Picková, Irena (referee)
The subject of this thesis is the study of the probe diagnostic method of low temperature plasma. The basis of Langmuir probe diagnostics in terms of appli- cation on apparatus CryoFALP II for the study of reactions of simply particles, the principle of the FALP technique and the experimental method of undertaken measurements are described. As a part of the thesis a package of evaluation pro- grams were compiled, which are ready to be a part of the measuring system as described in the thesis. Main results concern verification of the proper application of Langmuir probe technique in conditions characteristic for the apparatus, argon plasma was chosen as the medium of the measurements, where the characteristic loss process is ambipolar diffusion of charged particles. The application of the acquired knowledge is shown on recombination in oxygen plasma.
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