Konstrukční návrh stolní odporové svářečky

Diplomová práce je zaměřena na konstrukční návrh a optimalizaci stolní odporové svářečky. První část práce popisuje technologii odporového svařování a rozebírá základní svařovací parametry. Další část je zaměřena na analýzu stávajícího stavu, studii trhu v oblasti stolních odporových svářeček a definici požadovaných parametrů. Hlavní část práce obsahuje návrh stolní odporové svářečky a 3D CAD modelu, vytvořeného dle výsledků zjednodušených analytických výpočtů. Nedílnou součástí práce je technická dokumentace a 3D model přiloženy v elektronické podobě.This diploma thesis is focused on the engineering design and design optimization of the bench typy welder machine. There are resistance welding technology and resistance spot welding process parameters depicted in the first part of the work. Another part of the work analyzes the current state of the stock market in the area bench type welder machine and defines the requirements. The main part of the work includes design of the bench type spot welder machine and 3D CAD model, created with support of simplified analytical calculations. The technical documentation is the integral part of in this work. 3D model are included in digital form

Structural stability heterogeneous weldment of carbon/austenitic steels

Heterogenní svarové spoje typu ferit/austenit jsou nedílnou součástí konstrukcí energetického průmyslu. Podmínky svařováni a následné tepelné zpracování po svařování mají výrazný vliv na strukturní stabilitu těchto spoje. Struktura určuje výsledné mechanické vlastnosti, které určují životnost svarového spoje. Současně se změnami mikrostruktury v tepelně ovlivněné oblasti základního materiálu dochází k difúzi uhlíku přes svarové rozhraní. Tato práce je zaměřena na analýzu strukturní stability heterogenního svarového spoje uhlíková/austenitická ocel, která byla tvořena uhlíkovou ocelí 22K (základní materiál) a austenitickým návarem EA 395/9 s vyšším obsahem niklu. Hodnocení struktury bylo zaměřeno na strukturu svarového kovu (Böhler FOX SAS 2) a návaru, strukturu rozhraní návaru a tepelně ovlivněnou oblast základního materiálu. Metalografické hodnocení bylo provedeno na světelném mikroskopu a rastrovacím elektronovém mikroskopu vybaveném energiově a vlnově disperzní analýzou, kterými byly určeny obsahy substitučních prvků a uhlíku na rozhraní uhlíkové/austenitické oceli. Výsledky metalografické analýzy byly porovnány s měřením tvrdosti a mikrotvrdosti dle Vickerse a s výpočty za použití software Thermo-Calc a SVARY. K popisu a hodnocení stability svarového spoje byl určen průběh obsahu uhlíku na rozhraní pomoci vlnově disperzní spektroskopie. Výsledky energiově disperzní analýzy byly využity k určení typu karbidů přítomných na rozhraní uhlíkové/austenitické oceli.Heterogeneous welded joints – type ferrite/austenite is inseparable part of structure for energy industry. Welding conditions and post weld heat treatment have a significant impact on the structural stability of welded joint. The structure determines resulting mechanical properties that determine lifetime of these joints. At the same time in microstructure changes in heat affected zone of the base material is diffusion of carbon through the weld interface. This work is focused on the analysis of structural stability of heterogeneous weld carbon/austenitic steel, which was formed carbon steel 22K (base material) and austenitic buttering layer EA 395/9 with a higher content of nickel. Evaluation of the structure was focused on the structure of weld metal (Böhler FOX SAS 2) and structure of the heat affected zone of base material. Metallographic evaluation was performed on the light microscope and scanning electron microscope equipped with the energy and wave dispersive analysis, which identified the contents of substitutional elements and carbon on the interface of carbon/austenitic steel. The results of metallographic analysis were compared with measurements of Vickers hardness and microhardness and calculations using Thermo-Calc software and software SVARY. The description and evaluation of the stability of the weld joints was determined by carbon content of the course interface using wave dispersive spectroscopy. The results of energy dispersive analysis were used to determine the type of carbides present at the interface of carbon/austenitic steel.

Microstructure and hardness of bainitic weld deposits on rails

Navařování opotřebených jeřábových drah jako renovační technologie se dá provést několika možnými způsoby, ať už ručně obalovanou elektrodou, plněnou elektrodou nebo automatem pod tavidlem. Výsledné mechanické vlastnosti budou záviset na přídavném materiálu, který byl použit na vytvoření návaru. Tato bakalářská práce se zabývá vyhodnocením integrity a mikrostruktury jedno až třívrstvých návarů plněnou elektrodou na kolejnici s převážně perlitickou strukturou. Byly vyhodnocovány oblasti s největším odvodem tepla při ochlazování, a to z důvodu možného výskytu nežádoucích struktur. Ke studiu byly využity metody světelné mikroskopie, elektronové mikroskopie vybavené energiově disperzní chemickou analýzou, měření makro a mikrotvrdosti bylo provedeno metodou podle Vickerse.Surfacing worn crane railways as renovation technology can make several possible ways, so as manual welding whit coated electrode, with filled electrode or automatic submerged arc. The resulting mechanical properties will depend on the additional materials, which was used to create surfacing. This thesis deals whit evaluation of integrity and microstructure single - layer to three - layer surfacing with filled electrode on the rail with predominantly pearlitic structure. Were evaluated areas with the greatest heat dissipation during cooling, due to the possible occurrence of side structures. The study employed the interaction light microscopy, the scanning electron microscopy equipped by energy dispersive chemical microanalysis, the macro and micro hardness measurement by Vickers.

ELECTRON BEAM WELDING OF HETEROGENEOUS WELDS OF Ti/Al ALLOYS

V této práci je probírána problematika svařitelnosti heterogenních svarových spojů hliníkové a titanové slitiny zhotovených metodou svařování pomocí elektronového svazku. V první fázi jsou analyzovány homogenní svarové spoje vybraných slitin. Z důvodu rozdílných fyzikálních, chemických a metalurgických vlastností použitých základních materiálů je svařování těchto slitin spojeno se vznikem křehkých intermetalických fází na rozhraní základních materiálů. Jedním z předpokladů zhotovení kvalitních heterogenních svarových spojů je nalezení optimálních procesních parametrů. V rámci práce je hodnocen vliv vybraných procesních parametrů na celistvost, strukturu a mechanické vlastnosti heterogenních svarových spojů Al/Ti slitin.The problematics of weldability of heterogeneous welds of aluminium and titanium alloys produced by electron beam welding is discussed in this work. Homogenous welds of selected alloys were analyzed in the first stage. Welding of these materials relates to formation of intermetallic phases at the interface of base materials due to differences in physical, chemical and metallurgical properties of base materials. One of the prerequisites for producing high quality weld joints is to find optimal process parameters. The influence of selected process parameters to integrity, structure and mechanical properties of heterogeneous Al/Ti joints is evaluated.

Climate change, agriculture and food security: a comparative review of global modelling approaches

The dual relationship existing between land-based activities and climate change has long been established. Land-based activities are responsible for about 30% (IPCC) of global GHG emissions and are at the same time particularly impacted by climate change as they are strongly dependent on weather patterns. Although physical and technical considerations may help to investigate these two kinds of issues, economic considerations are crucial to understand how agricultural producers react to climate change and to climate policies. Quantitative economic models are appropriate tools to examine these interactions and to understand how they influence human activities and ecosystems. However, there are many different economic models with different characteristics regarding the way economies are modelled, the way climate change is considered in the models and the way GHG emissions are accounted for. All these specificities determine the type of uses that each model can be employed for. This paper describes the different characteristics and uses of 13 economic models that are currently used to investigate issues concerning land-based activities and climate change

Modelling heat stress on livestock: how can we reach long-term and global coverage?

Conference presentation PD

Carbon prices, climate change mitigation & food security: How to avoid trade-offs?

Carbon price policies deliver cost-efficient mitigation across sectors, but can result in tradeoffs with food security and other sustainable development goals. Scenarios for a 1.5 °C world based on carbon prices could increase the undernourished population by 80 - 300 million in 2050. Applying a uniform carbon price across geographic regions and economic sectors has inequitable effects on countries’ agricultural competitiveness and food availability. Under higher carbon prices, regions with poor productivity – and consequently higher GHG emissions per unit of output – would experience increased agricultural commodity prices

Global food efficiency of climate change mitigation in agriculture

Concerns exist regarding potential trade-offs between climate change mitigation in agriculture and food security. Against this background, the Global Biosphere Management Model (GLOBIOM) is applied to a range of scenarios of mitigation of emissions from agriculture to assess the implications of climate mitigation for agricultural production, prices and food availability. The “food efficiency of mitigation” (FEM) is introduced as a tool to make statements about how to attain desired levels of agricultural mitigation in the most efficient manner in terms of food security. It is applied to a range of policy scenarios which contrast a climate policy regime with full global collaboration to scenarios of fragmented climate policies that grant exemptions to selected developing country groups. Results indicate increasing marginal costs of abatement in terms of food calories and suggest that agricultural mitigation is most food efficient in a policy regime with global collaboration. Exemptions from this regime cause food efficiency losse

Flavonoid glycosides from endemic bulgarian astragalus aitosensis (Ivanisch.)

© 2019 The Author(s). Background: The activity and haemolytic toxicity associated with primaquine has been linked to its reactive metabolites. The reactive metabolites are thought to be primarily formed through the action of cytochrome P 450 -mediated pathways. Human erythrocytes generally are not considered a significant contributor to drug biotransformation. As erythrocytes are the target of primaquine toxicity, the ability of erythrocytes to mediate the formation of reactive oxidative primaquine metabolites in the absence of hepatic enzymes, was evaluated. Methods: Primaquine and its enantiomers were incubated separately with human red blood cells and haemoglobin. Post-incubation analysis was performed with UPLC-MS/MS to identify products of biotransformation. Results: The major metabolite detected was identified as primaquine-5,6-orthoquinone, reflecting the pathway yielding putative active and haematotoxic metabolites of primaquine, which was formed by oxidative demethylation of 5-hydroxyprimaquine. Incubation of primaquine with haemoglobin in a cell-free system yielded similar results. It appears that the observed biotransformation is due to non-enzymatic processes, perhaps due to reactive oxygen species (ROS) present in erythrocytes or in the haemoglobin incubates. Conclusion: This study presents new evidence that primaquine-5,6-orthoquinone, the metabolite of primaquine reflecting the oxidative biotransformation pathway, is generated in erythrocytes, probably by non-enzymatic means, and may not require transport from the liver or other tissues