Modeliranje eksperimentalnih ispitivanja uzoraka izrađenih od drva običnog bora (Pinus sylvestris) uz pomoć modela za anizotropno-plastične materijale

In order to describe the behaviour of wood when calculating wooden elements and structures with the use of the finite element method, orthotropic material model in combination with non-interactive (maximum stress criterion) or interactive failure criteria (Hoffman and Tsai-Wu criterion) is used. Another option is to use a general anisotropic plasticity material model complemented with a non-interactive failure criterion – maximum stress criterion, which allows to describe wood failure by brittle failure in tension. The presented general material model was used in combination with the idealization of annual rings by cylindrical surface for the modelling of wood specimen tests form Scots pine (Pinus sylvestris). The obtained results show good agreement between the results of numerical analysis and experimental testing of wood specimens. The use of the anisotropic material model can also be seen in cases when the level of the applied load is higher than the level when the failure of wooden material occurs.Radi objašnjenja ponašanja drva pri proračunima drvnih elemenata i konstrukcija primjenom metode konačnih elemenata, upotrijebljen je model ortotropnog materijala u kombinaciji s neinteraktivnim kriterijem (kriterij maksimalnog naprezanja) ili interaktivnim kriterijima loma (Hoffmanov i Tsai-wuov kriterij). Druga je mogućnost upotrijebiti opći model za anizotropno-plastične materijale dopunjen neinteraktivnim kriterijem loma – kriterijem maksimalnog naprezanja, koji omogućuje objašnjenje lomljivosti drva pri naprezanju. Predstavljeni opći model materijala u kombinaciji s idealizacijom godova kao cilindričnih površina upotrijebljen je za modeliranje uzoraka izrađenih od drva običnog bora (Pinus sylvestris). Dobiveni rezultati pokazuju dobru podudarnost rezultata numeričke analize i rezultata eksperimentalnih ispitivanja uzoraka drva. Model anizotropnog materijala primjenjiv je i kada je opterećenje veće od onoga pri kojemu dolazi do loma drvnog materijala

Robot path planning by means of ant algorithms

Tato diplomová práce se zabývá plánováním cesty robotu. Obsahuje přehled obecných přístupů pro plánování cesty. Dále popisuje metody rojové inteligence a jejich aplikace na plánování cesty robotu. Práce obsahuje návrhy změn pro mravenčí algoritmy a prezentuje výsledky experiment provedených pomocí implementovaných algoritmů.This thesis deals with robot path planning. It contains an overview of general approaches for path planning and describes methods of swarm intelligence and their application for robot path planning. This paper also contains proposals of adjustments for ant algorithms and it presents experimental results of algorithm implementation.

Rheological properties of asphalt binders

Diplomová práce je zaměřena na reologické vlastnosti asfaltových pojiv a směsí. Zejména je popisována změna těchto vlastností u vzorků asfaltových pojiv a směsí, podrobených laboratornímu stárnutí, simulující reálný stav po zabudování ve vozovce. V teoretické části je pojednáno o reologii jako takové a metodách simulujících stárnutí asfaltových pojiv a směsí. Praktická část zahrnuje popis přípravy vzorků pojiv a směsí, které byly následně zkoušeny. Nejprve bylo provedeno stárnutí asfaltové směsi metodou BSA (Braunschweiger Alterung), vyrobena tělesa pro zkoušku modulu tuhosti na směsích a vyzkoušena. Ze zbylé směsi bylo vyextrahováno pojivo. Hlavní těžiště zkoušek pojiva je soustředěno k využití dynamického smykového reometru (komplexní modul tuhosti, dynamická viskozita). Na závěr jsou výsledky zkoušek vzájemně porovnány.The Diploma thesis is focused on rheological properties of bituminous binders and mixtures. Above all, it describes the changes of these properties of samples of bituminous binders and mixtures. Those were brought by the process of laboratory aging, since it simulates the changes occurring in the in the real-life conditions. The theoretical part depicts the field of rheology and methods utilized for simulating the ageing of binders and mixtures. The practical part describes the process of preparation of samples and its testing. Firstly, the ageing of bituminous mixture by the means of BSA method (Braunschweiger Alterung) took place, which was followed by preparing the solids for testing the modulus of stiffness and main testing. The rest of the mixture was used for extracting the binder. Tests with the binder were focused on the usage of dynamic shear rheometer (complex shear modulus, dynamic viscosity). The last part of the work is dedicated to the comparison of the outcomes of testing.

The Photoperiod Stress Response in Arabidopsis thaliana Depends on Auxin Acting as an Antagonist to the Protectant Cytokinin

Fluctuating environmental conditions trigger adaptive responses in plants, which are regulated by phytohormones. During photoperiod stress caused by a prolongation of the light period, cytokinin (CK) has a protective function. Auxin often acts as an antagonist of CK in developmental processes and stress responses. Here, we investigated the regulation of the photoperiod stress response in Arabidopsis thaliana by auxin and its interaction with CK. Transcriptome analysis revealed an altered transcript abundance of numerous auxin metabolism and signaling genes after photoperiod stress treatment. The changes appeared earlier and were stronger in the photoperiod-stress-sensitive CK receptor mutant arabidopsis histidine kinase 2 (ahk2),3 compared to wild-type plants. The concentrations of indole-3-acetic acid (IAA), IAA-Glc and IAA-Asp increased in both genotypes, but the increases were more pronounced in ahk2,3. Genetic analysis revealed that the gain-of-function YUCCA 1 (YUC1) mutant, yuc1D, displayed an increased photoperiod stress sensitivity. In contrast, a loss of the auxin receptors TRANSPORT-INHIBITOR-RESISTANT 1 (TIR1), AUXIN SIGNALING F-BOX 2 (AFB2) and AFB3 in wild-type and ahk2,3 background caused a reduced photoperiod stress response. Overall, this study revealed that auxin promotes response to photoperiod stress antagonizing the protective CK

Phytohormones in Sweet Cherry Buds During Winter Rest and Bud Development

This (two-season) study was undertaken to assess the involvement of gibberellins (GAs), cytokinins (CKs), and auxins (AX) in dormancy of the sweet cherry buds ‘Summit’. Our hypothesis consisted in the assumption that representatives of these hormone groups are able to mark the transition between different dormancy phases. Changes in the transition between endo- and ecodormancy and the stages of ontogenetic development were not recognizable by bioactive GA1, GA5, GA7. The transient increase of GA3 during ecodormancy might be interpreted as an indication of the preservation of ecodormancy. The content of the biological active bases tZ, cZ, and DHZ was equal between endo- and ecodormancy. However, the content increased significantly in the first phase of ontogenetic development. The summation of the representatives of the various CKs (total iP-type, total tZ-type, total CK bases, total CK ribosides, total CK nucleotides, total O-glucosides, total N-glucosides, and total CKs) showed no differences regarding their levels during endo- and ecodormancy. These values increased markedly in the subsequent phase. AX increased after ecodormancy. By contrast, from side green until open cluster no differences occurred. As shown for AX, the content of oxIAA increased after ecodormancy. The content of IAAsp was low during endodormancy and increased transiently during ecodormancy and early ontogenetic development. This study revealed that no changes in the content of different bioactive GAs (exception GA3), CKs, and AX occurred during winter rest, and more precisely, during endo- and ecodormancy. These metabolites, therefore, are not suitable to differentiate between these dormancy phases. The ontogenesis is accompanied by specific changes in the content of bioactive molecules, precursors, and conjugation products.Peer Reviewe

Inactivation of the entire Arabidopsis group II GH3s confers tolerance to salinity and water deficit

Indole-3-acetic acid (IAA) controls a plethora of developmental processes. Thus, regulation of its concentration is of great relevance for plant performance. Cellular IAA concentration depends on its transport, biosynthesis and the various pathways for IAA inactivation, including oxidation and conjugation. Group II members of the GRETCHEN HAGEN 3 (GH3) gene family code for acyl acid amido synthetases catalysing the conjugation of IAA to amino acids. However, the high degree of functional redundancy among them has hampered thorough analysis of their roles in plant development. In this work, we generated an Arabidopsis gh3.1,2,3,4,5,6,9,17 (gh3oct) mutant to knock out the group II GH3 pathway. The gh3oct plants had an elaborated root architecture, showed an increased tolerance to different osmotic stresses, including an IAA-dependent tolerance to salinity, and were more tolerant to water deficit. Indole-3-acetic acid metabolite quantification in gh3oct plants suggested the existence of additional GH3-like enzymes in IAA metabolism. Moreover, our data suggested that 2-oxindole-3-acetic acid production depends, at least in part, on the GH3 pathway. Targeted stress-hormone analysis further suggested involvement of abscisic acid in the differential response to salinity of gh3oct plants. Taken together, our data provide new insights into the roles of group II GH3s in IAA metabolism and hormone-regulated plant development

Analiza ponašanja montažnih konzolnih stubišta

The article introduces a potential use of a combination of the method of numerical modelling and experimental tests for the treatment of the structure of a wooden prefabricated staircase with one-sided suspended stairs. Numerical modelling was used to find critical details, which were experimentally tested on partial models in the scale 1:1. The results of the numerical modelling in combination with experimental testing were used for designing a prototype of a wooden prefabricated staircase with one-sided suspended stairs. The designed prototype of a staircase in two versions was experimentally tested in the scale 1:1 in compliance with Czech design standards ČSN 73 0035, ČSN 73 2030 and ETAG008 – Guideline for European technical approval of prefabricated stair kits in edition January 2002 in terms of ultimate and serviceability state design.Članak obrađuje potencijalnu primjenu kombinacije metode matematičkog modeliranja i eksperimentalnih ispitivanja za obradu konstrukcije drvenih montažnih konzolnih stubišta. Numeričko modeliranje primijenjeno je za pronalazak kritičnih detalja koji su eksperimentalno testirani na parcijalnim modelima u mjerilu 1:1. Rezultati numeričkog modeliranja, u kombinaciji s eksperimentalnim ispitivanjem, primijenjeni su za izradu prototipa drvenih montažnih konzolnih stubišta. Dizajnirani prototip stubišta u dvije verzije eksperimentalno je ispitan u mjerilu 1:1 radi utvrđivanja ponašanja stubišta u upotrebi, u skladu s češkim standardima ČSN 73 0035, ČSN 3 2030 i ETAG008 - Smjernica za europske tehničko odobrenje setova montažnog stubišta, iz siječnja 2002. godine