Optimization of macrostructure of nickel-based alloys castings

Tato diplomová práce se zabývá ovlivňováním struktury odlitků niklové superslitiny Inconel 713LC silovými účinky aplikovanými na taveninu prostřednictvím vibrace a rotace při krystalizaci. Pro tuto práci byly odlity tři zkušební odlitky s různými podmínkami tuhnutí, pro zkoumání struktury zrn ovlivněné silovým působením kovu. Cílem práce bylo porovnat jednotlivé makrostruktury a mikrostruktury odlitků a následně zjistit závislost zjemnění zrna na mechanických vlastnostech. Po lomu zkušebních tyčí byly metodami světelné a elektronové mikroskopie analyzovány jednotlivé změny ve struktuře.This diploma thesis is focusing on possibilities of influencing casting’s structure of nickel superalloy Inconel 713LC by force effects caused by vibration and rotation during crystallization. In this research were cast three test castings of turbine wheels with different solidification conditions that have affected the size and distribution of the grains. The aim was to compare the different microstructure and macrostructure of castings and then compare the dependence of grain refinement on mechanical properties. Changes in the structure were analyzed by means of light and electron microscopy methods after the fracture of test bars.

Marketing Plan of Horsefeathers Trademark

Předmětem diplomové práce je návrh marketingového plánu značky Horsefeathers. Teoretická část se zabývá jednotlivými kroky týkajícími se marketingového plánování, tyto poznatky vycházejí z odborné literatury. V praktické části práce zkoumá aktuální situaci ve firmě a zpracovává analýzy. Na závěr předkládá návrh na vylepšení marketingového plánu firmy na základě získaných teoretických poznatků.The aim of the thesis is proposal of marketing plan of Horsefeathers trademark. The theoretical part deals with individual steps of marketing planning, this knowledge are based on specialized literature. In the practical part of thesis is described current situation in company and process analysis. At the end thesis presents proposal for improvements marketing plan based on gained theoretical knowledge.

Aspect of Reliability in Risk Analysis Proces

Výrobky, které mohou být označeny značkami shody, spadají do regulované sféry a musí splnovat určené požadavky před uvedením na trh. Diplomová práce řeší aspekty, které je nutno splnit pro uvedení vah s neautomatickou činností na trh. Reviduje současné metody a postupy posuzování shody vah na ES pracovišti posuzování shody dle příslušných norem, dokumentů a směrnic. A následně vypracovává novou Příručku kvality pro ES pracoviště posuzování shody.The products, which can be labelled with a mark of conformity are included in regulated sphere and they have to ful fill the given requirments before makrket introduction. This diploma thesis is dealing with the aspects which have to fulfilled before the nonautomatic weighing instruments from are introduced to the market. The diploma thesis also revises current methods and proceeds of conformity assessment on ES workplace of conformity assessment accordin to appropriate norms, documents and directives. The aim is also to make a new quality manual for the ES workplace of conformity assessment.

X-ray Spectroscopic Characterization of Shock-Ignition-Relevant plasmas

Experiments with multilayer plastic/Cu targets performed at a PALS laser system aimed at the study of matter at conditions relevant to a shock ignition ICF scheme, and, in particular, at the investigation of hot electrons generation. Plasma temperature and density were obtained using high-resolution X-ray spectroscopy. 2D-spatially resolved quasi–monochromatic imaging was observing the hot electrons via fluorescence K emission in the copper tracer layer. Found values of plasma temperature 690 ± 10 eV, electron density 3 × 1022 cm-3 and the effective energy of hot electrons 45 ± 20 keV demonstrate the potential of X-ray methods in the characterization of the shock ignition environmental conditions

Mild to Moderate Functional Tricuspid Regurgitation: Retrospective Comparison of Surgical and Conservative Treatment

Background. Unoperated severe tricuspid regurgitation (TR) leads to the right ventricle (RV) failure. We wanted to determine if there was near-term postoperative progression of noncorrected mild to moderate functional TR in patients who underwent mitral valve surgery for chronic significant mitral regurgitation (MR) and if RV size and function were affected. Methods and Results. We compared two groups of patients retrospectively. In the first group (TVA+, n = 45), tricuspid valve annuloplasty (TVA) had been performed in conjunction with either mitral valve replacement (MVR) or mitral valve repair (MVP). The second group (TVA−, n = 22) underwent MVP or MVR without TVA. TVA+ group revealed a significant decrease in TR and right ventricle diameter. In the TVA− group, 7 patients (32%) showed a significant progression, by one or more grades, of noncorrected TR together with dilatation and decreased ejection fraction of the right ventricle. Conclusions. Tricuspid annuloplasty performed concurrently with MVP or MVR can prevent subsequent progression of tricuspid regurgitation along with right ventricular dilatation and systolic dysfunction in the near-term postoperative period

Karst and Caves in Salt Diapirs, SE Zagros Mts. (Iran)

Na področju Perzijskega zaliva je znanih okoli 200 solnih diapirjev, med njimi mnogo aktivnih. Kraške kamnine predstavljajo največ kamena sol in redkeje sadra ter anhidrid. Kraške oblike, popolnoma primerljive z oblikami v “klasičnih” karbonatnih kamninah, so najbolje razvite v ostankih uravnanih površij. Tako so škraplje, “solution pipes”, vrtače, udorne vrtače, depresije podobne uvalam in poljem, slepe doline, soteske, ponori, izviri in jame. Tod sta bili odkriti in raziskani dve izmed najdaljših jam v soli na svetu. Daljše jame so nastale predvsem v piezometrični gladini, večje pa v diapirjih ob morski obali. Jame pogosto predstavljajo odtok iz depresij, podobnih poljem. V dnu udornih vrtač in v ponorih so tudi strme, skoraj navpične jame. Kraški procesi so omejeni predvsem na sol, redkeje na sadro. Predvsem gre za raztapljanje in odnašanje soli izpod neprepustnega pokrova (gypcrete). V nekaterih diapirjih je dokazano globoko kroženje padavinske vode.About 200 salt diapirs (plugs) have been known in the region of the Persian Gulf. numerous are still active. Karst rocks are represented by a rock salt, less frequently by gypsum and anhydrite. Karst developed especially in relics of planated surfaces. Karst forms are completely comparable with karsts in classical carbonate rocks. Different forms can be distinguished: karren, solution pipes, solution dolines, solution-collapse dolines, uvalalike to polje-like depressions, blind valleys, canyon-like forms, ponors, springs and caves. Two World longest caves in salt were discovered and explored here. Long caves are developed especially in a watertable, large ones in plugs near the seacoast. Caves are often outlets of closed depressions (polje-like). Some caves at bottoms of collapse-solution dolines or swallow holes are subvertical. Karst processes are caused dominantly by dissolution of salt, less frequently of gypsum. The process of subrosion of halite under gypcretes plays the main role. Deep circulation of meteoric waters was proved in some plugs

Effect of Solution Annealing on Fatigue Crack Propagation in the AISI 304L TRIP Steel

Fatigue crack propagation in near-threshold regime was studied in the 304L austenitic stainless steel in two microstructural states: as-received (AR) with finer microstructure and low susceptibility to the transformation-induced plasticity (TRIP) effect, and solution-annealed (SA) with coarser microstructure and higher susceptibility to TRIP. At the load ratio R = 0.1 the threshold was higher in the SA state than in the AR state due to coarser grains and possibly the TRIP effect. In order to clarify the role of crack closure, experiments at R = 0.7 were done. The threshold in the SA state was still higher by 1 MPa center dot m(0.5). This effect was identified as crack tip shielding induced by phase transformation, an example of a non-closure shielding effect. Higher resistance to crack growth in the SA state was attributed to promoted martensitic transformation in non-favorable oriented grain families rather than thicker martensite layers in the crack path area. The conclusions were verified by experiments at R = 0.7 and temperature 150 degrees C > M-s which did not reveal any notable difference in thresholds. However, the threshold values were affected by the load-shedding gradient C = -d Delta K/da, which had to be equalized in both experimental setups inside and outside the furnace

The preparation route and final form of V-MXenes override the effect of the O/F ratio on their magnetic properties

This work was supported by OP VVV “Excellent Research Teams” project no. CZ.02.1.01/0.0/0.0/15_003/0000417 – CUCAM. P. E. would like to also acknowledge the Czech Science Foundation for the ExPro project (19-27551X). Computational resources and low-temperature infrastructure were supplied by the projects “e-Infrastruktura CZ” (e-INFRA CZ LM2018140) and MGML (LM2023065) supported by the Ministry of Education, Youth and Sports of the Czech Republic.Transition metal carbides and nitrides (MXenes) show a high potential for electrochemical energy storage in batteries and supercapacitors and for electrocatalysis. Their excellent electronic and magnetic characteristics have been highlighted in several theoretical studies. However, experimental research on MXenes is yet to confirm their predicted properties as candidates for controllable magnetic 2D materials. Here, we report our theoretical and experimental study of V2CTx MXenes (T = O, OH, F), providing key insights into their magnetism. Based on our density functional theory (DFT) analysis, we predicted ferromagnetic (FM) and antiferromagnetic (AFM) states of V2CTx, which are determined by the O/F ratio of surface functional groups. Accordingly, we prepared V2CTx MXenes in the form of multilayered powders and thin films with different O/F ratios. No experimental evidence of FM or AFM properties was found in any material. Nevertheless, powders and films with almost identical chemical compositions (in terms of O/F ratio) displayed different magnetic properties, whereas films with disparate chemical compositions revealed a similar magnetic character. Therefore, the preparation route and form of the final V2CTx material override the effect of the O/F ratio, which is often overestimated in theoretical studies. Moreover, these findings underscore the importance of preparing MXene materials to experimentally confirm their theoretically predicted properties.Peer reviewe

Visualizing Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering

Ultra-intense lasers that ionize and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration. These instabilities can be difficult to characterize, but a novel approach using X-ray scattering at keV energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale. Our experiments on laser-driven flat silicon membranes show the development of structure with a dominant scale of ~60\unit{nm} in the plane of the laser axis and laser polarization, and ~95\unit{nm} in the vertical direction with a growth rate faster than $0.1/\mathrm{fs}$. Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced instability development, indicating the excitation of surface plasmons and the growth of a new type of filamentation instability. These findings provide new insight into the ultra-fast instability processes in solids under extreme conditions at the nanometer level with important implications for inertial confinement fusion and laboratory astrophysics