Compressor elastic mounting on frame

Tato práce řeší eliminaci vibrací pístového kompresoru pomocí pryžových silentbloků. Dále se jedná o metodiku měření vibrací pístových kompresorů ve firmě Sauer Žandov, a.s. Práce obsahuje návrh uložení, měření vibrací a zpracováním v časovém spektru, analýzou ve frekvenční oblasti a celkovými hodnotami vibrací. Použité nástroje a doporučená nastavení jsou přiblížená pro měření vibrací. Podařilo se naleznout optimální řešení pro nasazení kompresoru u koncových zákazníků a prokázaly se kvality moderních měřících metod. Firma Sauer Žandov, a.s. postupně přechází na měření vibrací dle této práce – metodiky.Piston compressor, measurement, vibrations, FFT

Upotreba beskontakne metode za ocjenu kvalitete površine drva nakon visokobrzinskog blanjanja

This paper presents the method of surface quality evaluation at high-speed milling of wood. The effects of specific parameters of machining on the surface quality are described and results are presented of experiments carried out on selected tree species, where the effects of specific parameters on the surface quality were noted. The surface quality is evaluated by a non-contact method using a confocal sensor (CLA), which processes the results of the roughness measurement, Talysurf CLI 1000. It can be concluded that this method could actually be used for the evaluation of the surface quality.U radu se analizira metoda za ocjenu kvalitete površine drva nakon visokobrzinskog blanjanja. Opisan je utjecaj pojedinih parametara obrade na kvalitetu površine drva i izneseni su rezultati mjerenja kvalitete površine nakon eksperimentalnog blanjanja izabranih vrsta drva. Kvaliteta površine drva ocijenjena je beskontaktnom metodom uz pomoć konfokalnih senzora (CLA) koji procesuiraju rezultate mjerenja hrapavosti. Mjerenje hrapavosti obavljeno je uređajem Talysurf CLI 1000. Zaključeno je da postoji realna mogućnost primjene prezentirane beskontaktne metode za ocjenu kvalitete površine drva

Utjecaj izvedbe lista kružne pile na sile pri poprečnom piljenju drva

This paper evaluates the impact of the number of saw blade teeth on kinematic and dynamic parameters during cross-cutting of soft and hard woods with mitre saw BOSCH GCM 12 GLD Professional. The forces measured using a three-dimensional XYZ dynamometer Kistler 9257B and subsequent calculation based on a mathematical model were applied in the Ernst-Merchant diagram and the forces acting in the cutting of spruce and oak planks were analysed and compared. The wood cutting was performed by four geometrically and structurally similar blades with a 300 mm diameter and with different count of WZ-shaped teeth (z = 26, 36, 48, 60). The optimum saw blade for the given cutting conditions was subsequently assessed by statistical analysis. Unlike many studies researching the cutting resistances in transversal and longitudinal wood cutting, this experiment and force analysis was performed in dependence on the constant feed force.U ovom se radu ispituje utjecaj broja zubi lista pile na kinematičke i dinamičke parametre tijekom poprečnog rezanja mekih i tvrdih vrsta drva poprečnom klatnom pilom BOSCH GCM 12 GLD Professional. Vrijednosti sila izmjerene spomoću trodimenzionalnog XYZ dinamometra Kistler 9257B te vrijednosti naknadnih izračuna primjenom matematičkog modela uvrštene su u Ernst-Merchantov dijagram te je napravljena analiza i usporedba sila pri piljenju smrekovih i hrastovih piljenica. Uzorci drva piljeni su s četiri geometrijski i strukturno slična lista pile promjera 300 mm s različitim brojem zubi tipa WZ (z = 26, 36, 48, 60). Statističkom analizom određen je optimalan list pile za zadane uvjete piljenja. Za razliku od mnogih istraživanja u kojima su proučavani otpori pri poprečnome i uzdužnom piljenju drva, ovo istraživanje i analiza sila provedeni su pri konstantnoj posmičnoj sili

Određivanje pomaka opterećenoga drvenog stolca primjenom korelacije digitalne slike

The subject of the research is a ready to assemble (RTA) chair constructed of plywood by a CNC machine. The standard test of seat and back of the chair according to the Czech Standard CSN EU 1728 was supplemented with an optical method of digital image correlation (DIC). The aim of the research was to discover mechanical principles of the construction and to develop a methodology of standardized furniture testing. Results of experimental measurement show the response of the chair construction in a form of displacement fields, strain fields, charts and vectors depicting displacement of the observed points. The results can be used to improve mechanical properties of the construction, as well as to develop a shape of the product or specific parts of the product. Besides furniture testing laboratories and research institutes, engineers from development departments of furniture making companies or industrial designers can easily use the presented method.Predmet istraživanja bio je stolac spreman na sklapanje (RTA), izrađen od uslojenog drva na CNC stroju. Standardni test sjedala i naslona stolca prema češkom standardu CSN EU 1728 dopunjen je optičkom metodom korelacije digitalne slike (DIC). Cilj istraživanja bio je otkriti mehanička načela konstrukcije te obogatiti metodologiju standardiziranog ispitivanja namještaja. Rezultati eksperimentalnih mjerenja prikazuju reakciju konstrukcije stolca u obliku polja pomaka, polja naprezanja te grafikona i vektora koji predočuju pomake promatranih točaka. Rezultati se mogu iskoristiti za poboljšanje mehaničkih svojstava konstrukcije, kao i za razvoj oblika proizvoda ili ispitivanih dijelova. Osim u laboratoriju za ispitivanje namještaja ili u istraživačkim institutima, prikazanom se metodom lako mogu koristiti inženjeri razvojnih odjela u tvrtkama za proizvodnju namještaja li industrijski dizajneri

The Role of a Forensic Expert in the Field of Self-Defense Under Current Legislation and Beyond

A forensic expert in the field of self-defense is a specialist with extensive knowledge in defence methods, close combat, defensive means, or coercive means. The core of the forensic expert's work in this field is the assessment of the facts of conflict situations in which physical violence between two or more persons has been used. The role of a forensic expert is to answer questions related to the parties' roles in the conflict, factors that influenced the conduct of the fight, the course of the fight and the possibility of resolving the conflict situation. Self-defense expertise is sometimes associated or confused with martial arts or combat sports expertise. This judgment is based on the assumption that most forensic experts in the field of self-defense also have experience or expertise in martial arts and combat sports. Such knowledge is an advantage for the profession of forensic expert in the field of self-defense, similar to knowledge in the field of weapons and ammunition, but it is not the same area as expertise in the field of self-defense or a condition for the exercise of this profession. The new Act No. 254/2019 Coll., on forensic experts, expert offices and expert institutes, faces professional criticism in several areas (expert duties, sanctions, division of specializations, etc.) and is likely to lead to pressure for further amendments. The article deals with these changes and the perspective in the coming years with the expert opinion of current forensic experts on the field of self-defense on the appropriate inclusion of this specialization in the future categorization of specializations

Terahertz electrical writing speed in an antiferromagnetic memory

The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the 12-order-of-magnitude range of writing speeds from hertz to terahertz. Our work opens the path toward the development of memory-logic technology reaching the elusive terahertz band

Based on FAO Guidelines for soil description (FAO, Rome, 2006) and WORLD REFERENCE BASE FOR SOIL RESOURCES 2014 lnternational soil classification system for naming soils and creating legends for soil maps Update 2015

FulltextSoil investigation may be carried out on various levels of knowledge, research capacity and proficiency. Scientists commonly apply advanced methodology for soil resources inventory, including the professional terminology for landscape and soil description, data acquisition and processing, soil classification and mapping, soil and land evaluation. By default, an internationally accepted system should be recommended. An implementation of such methodology is also recommended in more advanced courses of soil science studies on bachelor and master study levels. However, the long-term teaching experience reveals difficulties connected mainly with complicated terminology and excessive number of characteristics obligatory to know, and justifies some simplification of the language, rules and structure at the introductory stage of teaching. This was the base and rationale for the preparation of simplified Guidelines for Soil Description and Classification: Central and Eastern European Students' Version. This book is divided into three parts. The first one - Site and soil description - follows the layout and content of professional edition of Guidelines for Soil Description, 4th ed., published by FAO (2005), simplified for educational purposes. The order of description has been modified to correspond to the layout of an original Soil description sheet. The second part - Soil classification - is a simplified WRB classification (based on a 2014/2015 edition) limited to reference soil groups known from Central Europe. The third part is an Illustrated explanatory guide that includes: i) examples of typical soil profiles for all Central European Reference Soil Groups; ii) morphological features important for soil description and identification in the field; iii) soil-landscape relationships. The photos have been enriched with graphical tips helpful at the recognizing of important soil features. The textbook was developed in the framework of EU Erasmus+ FACES project (Freely Accessible Central European Soil) aiming to facilitate the knowledge and implementation of an international rules of soil characterization adopted by the FAO. It will be used to unify the presentation of soil data collected in the partner countries. The interpretation of soil data fully based on the international soil classification WRB (World Reference Base for Soil Resources 2015) as WRB was endorsed by the lnternational Union of Soil Sciences (lUSS) and accepted by the European Commission as an official system for the European Union. Therefore, this guideline might be a starting point for preparation of basic teaching materials to spread the knowledge on an internationally recommended rules and terminology for soil description and classification. However, this guideline is designed as teaching tool for students in Central and Eastern European countries and therefore it may not be applicable worldwide. Moreover, it is suited for the "first step" training, and it is not substituting any professional original classification. Authors of this guidebook assume that the users are familiar with the basic knowledge in soil science. Therefore, the guidelines do not contain explanations related to basic soil forming factors, soil forming processes and basic physico-chemical features

Terahertz probing of anisotropic conductivity and morphology of CuMnAs epitaxial thin films

Antiferromagnetic CuMnAs thin films have attracted attention since the discovery of the manipulation of their magnetic structure via electrical, optical, and terahertz pulses of electric fields, enabling convenient approaches to the switching between magnetoresistive states of the film for the information storage. However, the magnetic structure and, thus, the efficiency of the manipulation can be affected by the film morphology and growth defects. In this study, we investigate the properties of CuMnAs thin films by probing the defect-related uniaxial anisotropy of electric conductivity by contact-free terahertz transmission spectroscopy. We show that the terahertz measurements conveniently detect the conductivity anisotropy, that are consistent with conventional DC Hall-bar measurements. Moreover, the terahertz technique allows for considerably finer determination of anisotropy axes and it is less sensitive to the local film degradation. Thanks to the averaging over a large detection area, the THz probing also allows for an analysis of strongly non-uniform thin films. Using scanning near-field terahertz and electron microscopies, we relate the observed anisotropic conductivity of CuMnAs to the elongation and orientation of growth defects, which influence the local microscopic conductivity. We also demonstrate control over the morphology of defects by using vicinal substrates.Comment: 33 pages, 16 figure

Molecular beam epitaxy of CuMnAs

We present a detailed study of the growth of the tetragonal polymorph of antiferromagnetic CuMnAs by the molecular beam epitaxy technique. We explore the parameter space of growth conditions and their effect on the microstructural and transport properties of the material. We identify its typical structural defects and compare the properties of epitaxial CuMnAs layers grown on GaP, GaAs and Si substrates. Finally, we investigate the correlation between the crystalline quality of CuMnAs and its performance in terms of electrically induced resistance switching.Comment: 10 pages, 8 figures and supplementary materia

Experimental electronic structure of the electrically switchable antiferromagnet CuMnAs

Tetragonal CuMnAs is a room temperature antiferromagnet with an electrically reorientable N\'eel vector and a Dirac semimetal candidate. Direct measurements of the electronic structure of single-crystalline thin films of tetragonal CuMnAs using angle-resolved photoemission spectroscopy (ARPES) are reported, including Fermi surfaces (FS) and energy-wavevector dispersions. After correcting for a chemical potential shift of $\approx-390$ meV (hole doping), there is excellent agreement of FS, orbital character of bands, and Fermi velocities between the experiment and density functional theory calculations. Additionally, 2x1 surface reconstructions are found in the low energy electron diffraction (LEED) and ARPES. This work underscores the need to control the chemical potential in tetragonal CuMnAs to enable the exploration and exploitation of the Dirac fermions with tunable masses, which are predicted to be above the chemical potential in the present samples.Comment: Submitted to Physical Review X. 20 pages. 9 figure