Structure of miniature components from steel produced by forming in semi-solid state

To obtain new unconventional structures with specific mechanical and physical properties is possible not only by the development of new types of materials but also by treatment of conventional materials using unconventional innovative technological procedures.One of these technologies is the forming in semi-solid state involving rapid solidification of miniature components from steels.Production of such components is complicated by a number of technical problems.To explain phenomena of the process and structure development,the production of miniature components from the tool steel X210Cr12 difficult to form was experimentally tested.The structure of this originally ledeburite steel consisted of 95 % of metastable austenite after the treatment.Metastable austenite was located particularly in globular and polygonal grains while the remaining interspaces were filled by lamellar network.The detected high stability of extremely high fraction of metastable austenite was tested under different conditions of thermal exposition and mechanical loading.

Insulation System of Power Transformers Behavior Comparison of Mineral Oils and Natural Ester Dielectric Fluids

Paper deals with a comparison of selected properties of several vegetable oil representatives along their accelerated thermal ageing at the temperature of 90 ℃. These properties are compared to two widely used and commercially available mineral transformer oils. A combined insulating system （an oil-paper system） was created with the usage of mentioned oils for measurement purposes. Dissipation factor, capacity and volume resistance are characteristics measured along a thermal ageing of the oil-paper systems. Infrared spectroscopy was used as an additional method. After 1,000 hours of ageing, the dissipation factor of all systems based on vegetable oils did not exceed the value of 0.015. The volume resistance of systems containing mineral oils was approx, twice as high as the volume resistance of those with vegetable oils. The capacity on the other hand was slightly lower in the case of mineral oils application. An experiment also showed that the paper combined with the vegetable oil dries more quickly than in combination with the mineral oil. Infrared spectroscopy has not shown any expressive changes in the chemical structure of aU tested oils yet （up to 1,000 hours of ageing）.

Harmonic Currents of Semiconductor Pulse Switching Converters

Due to the operation of power semiconductor switching converters, the content of harmonic currents, which these switching converters take from the feed array, is still increasing. One of the possible ways of minimizing these currents is the use of pulse switching converters. On one hand, the original, characteristic harmonic ones are minimized, but, on the other hand, new frequencies caused by the modulation frequency appear in the current spectrum. The level of the currents of these frequencies is small and is scarcely dependent on the load of the converter. It may happen that the proportional value of the monitored harmonic one is high, although the absolute value is low. In the article presented, there is a description of the activity of the pulse voltage rectifier and an analysis of the current taken. The other part contains the results of the harmonic analysis of the stated current, including both the absolute and proportional values according to the load. In the conclusion, there are results of measurements of pulsed switching converters taken from the real measurement.

Primordial, Sacred, and Secular Architecture： Jan Patocka＇s Theory of the Work of Architecture Theory of the Work of Architecture

The paper deals with Jan Patocka＇s considerations on architecture. It presents Patocka＇s concept of space as the union of two sensory fields, the kinaesthetic-tactile and the visual, and it emphasizes that this union is considered as the ＂primordial architecture＂. According to Patocka＇s view, the material architecture is only a consequence of the primordial architecture. The paper also follows Patocka＇s idea of the ＂sacral transubstantiation＂. Patocka argues that, traditionally, the construction of a work of architecture is considered as dependent on favourable conditions, on divine consent with such a construction and the movement of divine powers into constructed work. The origin of architecture is thus religious. The paper considers the relations and differences between the sacred and secular architecture. It highlights Patocka＇s idea that both sacred and secular architecture open a certain world, even thought, the status of the world of sacred architecture differs considerably from that of the world of secular architecture.

ComplexTrans-Global Rail-Road Transportation System Economical and Clustered Individual and Individualised Public Transport also Prevents the Spread of Covid 19

Land transport can no longer meet the requirements.European transport can be described by these words−crowded motorways and cities,dangerous emissions,ubiquitous traffic accidents,delays,expensive railways.Solutions are being sought to transfer a large part of passengers and especially freight transport to(high-speed)rail,and efforts are moving towards electromobility,car-sharing,5G-connectivity,autonomous driving,MaaS(Mobility as a Service)-coordinated transport or hyperloop-type solutions.However,all these solutions have additional challenges and limitations.Solutions are not being searched where they really exist-in the mutual adaptation of road and rail vehicles and their deep cooperation.The ComplexTrans project shows that simply adapting the dimensions and functions of road and rail vehicles can eliminate(or at least significantly reduce)all the problems of existing land transport.The main features of the ComplexTrans system are sufficient parking spaces,reduction of urban and non-urban congestion,electric vehicles with unlimited range and cheaper than standard cars,cheaper and more accessible battery charging,“autonomous ride”,solving the overlap between passenger and freight rail transport and making it self-financing,transferring intercity freight transport to rail,replacing part of continental air transport and many others.The cost-effective and clustered individual transport and individualised public transport of the ComplexTrans system also bring very significant reductions in the risk of transmission of covid-19 and other contagious diseases during transport.

Condensation of Water Steam with and without Chemical Impurity in a Nozzle

A nucleation of two types can occur in the water steam flowing in a nozzle or in a turbine： homogeneous （spontaneous） and heterogeneous. The effects of chemistry on the flowing steam nucleation and condensation are not quite explained. An approach is used in the paper which is based on binary nucleation of main impurity NaC1 and water. Physical and mathematical models are described and are applied on the steam flow with condensation in convergent-divergent nozzle. Binary nucleation numerical model is applied for the calculation of the flow with condensation in the nozzle with low expansion rate in divergent nozzle part ^- = 1,000 s^-1. Calculation results of pressure distribution are compared with experiments. The agreement between calculations and experiments is very good. The homogeneous nucleation and condensation of pure water steam in the same nozzle is also calculated. The results are discussed. Main features of the binary nucleation and condensation of water and NaCI and of the homogeneous nucleation of pure water are compared.

Structure,Adhesion Strength and Corrosion Resistance of Vacuum Arc Multi-Period NbN/Cu Coatings

resistance,and adhesive strength of vacuum-arc multi-period NbN/Cu coatings is studied.It was found that in thin layers(about 8 nm,in a constant rotation mode),regardless of the change in the pressure of the nitrogen atmosphere,a metastableδ-NbN phase forms(cubic crystal lattice of the NaCl type).At a layer thickness of^40 nm or more,a phase composition changes from the metastableδ-NbN to the equilibriumε-NbN phase with a hexagonal crystal lattice.In the presence of theε-NbN phase in the niobium nitride layers,the highest adhesive strength is achieved with a value of LС5=96.5 N.Corrosion resistance tests have shown that for all the studied samples the corrosion process has mainly an anodic reaction.The highest corrosion resistance was shown by coatings obtained at a pressure of 7·10-4 Torr,with the smallest bias potential of-50 V and the smallest layer thickness;with a thickness of such a coating of about 10 microns,its service life in the environment of the formation of chloride ions is about a year.

Modelling and Vibration of Gear Drive Systems Influenced by Real Face Width

Gear drives are one of the most common parts in many rotating machinery. If the gear drive runs under lower torque load, nonlinear effects like gear mesh interruption can occur and vibration is accompanied by impact motions of the gears, This paper presents an original method of the mathematical modelling of gear drive nonlinear vibrations by using the modal synthesis method with degrees of freedom number reduction. The model respects nonlinearities caused by gear mesh interruption, parametric gearing excitation caused by time-varying meshing stiffness and nonlinear contact forces acting between journals of the rolling-element bearings and the outer housing. The nonlinear model is then used for investigation of gear drive vibration, especially for constant gear mesh determination. The theoretical method is applied for investigating of test gear drive nonlinear vibration.

Seismic Hazard Assessment for Selected Real Locality in Central Europe-Critical Points of Assessment

The seismic hazard value is a fundamental quantity for the seismic risk assessment and for the determination of terms of references of seismic design of important facilities as dams, chemical plants, nuclear power plants, etc.. In real sites, the seismic hazard value is influenced by both, the earthquake sizes, the impacts of which in a given site may be expected, and the properties of geological structure through which seismic waves spread from earthquake loci to a given site. The seismic risk is predetermined by hazard value, distribution of assets in the given site and asset numbers and vulnerabilities. The paper describes the used procedure of hazard assessment of important sites. The attention is especially paid to the basic steps as the data collection （homogeneity level, uncertainty and vagueness）, the focal region boundaries （their uncertainties and vagueness）, and the maximum expected earthquake size in each focal region that must be taken into account （its uncertainty and vagueness）, because they substantially influence the hazard value. Discussion is also concentrated to the attenuation that Central Europe substantially depends on the azimuth between earthquake focus and the given site. The attenuation differences are shown in seismic scenarios for individual focal regions. They are caused by focal mechanisms in near focal zone and differences in structure properties in distant zone; the boundary between near and distant zone in Central Europe is ca 2.5 h, where h is the focal depth in km. The real results are given for a real locality in Central Europe. It is shown than that great influence on hazard value is caused by great differences in azimuth attenuation curves. It is the reality that the Bohemian Massif is characterised with very low seismic attenuation in comparison with its vicinity. The following real results are presented： geological structure of near site vicinity, earthquake catalogue for Central Europe, focal regions in Central Europe, attenuation curves in Central Europe, typical earthquake isoseismals for individual focal regions, frequency graph, recurrence probability curve, etc.. The approaches used for nuclear facilities were recommended by the IAEA （International Atomic Energy Agency）.

Pin-on-Disc Study of Tribological Performance of PVD Coatings

This paper deals with the evaluation of tribological properties of PVD coatings which are mainly used as wear resistance coatings. The aim of the work was to compare the tribological behaviour of TiCrN and TiAlCrN coatings deposited on the steel substrate using the technology of reactive cathode vapour deposition. The dry sliding wear of coatings has been investigated against tungsten carbide (WC) counterpart. The course of the friction coefficient indicated better sliding properties TiAlCrN with value 0.605 compared to TiCrN with friction coefficient value 0.877. The depth of worn-out surface amounted to about 2/3 of the worn-out surface of TiCrN coating. The surface of the WC ball showed higher roughening after tribo test of TiCrN.

Condition Assessment of Oil-Paper Transformer Insulating System

Damages of power transformers are caused partly by construction setting but also by operation （i. e., due to operational and degradation parameters）. A long-term operation and exceeding of the limit values of transformer abbreviate the lifetime of this device very dramatically. A condition of insulating system oilpaper is principal diagnostic indicator that has its essential influence to failure-free operation of power transformers. The paper deals with a description of the experience with developed monitoring system, which is focused mainly on a control of oil filling of experimental transformer. Relative humidity, amount of dissolved gases and increased temperature are observed, as they have decisive influence on insulating system of transformer. Monitoring of these characteristics is completed with analysis of oil samples by infrared spectroscopy in mode of Attenuated Total Reflection technique.

采用感应预热的连续激光淬火

模拟了钢件采用激光束进行表面连续淬火的新方法。这种热处理方法采用传统的感应器对淬火零件进行预热,以便减小温度梯度及随后产生的被处理材料的机械应力。该工艺的数学模型采用3D数值建立,其解法考虑了所有重要的非线性特性(被淬火钢的磁饱和曲线及其物理性能与温度的关系)。用典型的实例进行了说明,介绍了结果并进行了讨论。

Inflammatory bowel disease incidence in Czech children:A regional prospective study,2000-2015

AIM To examine the incidence and trends in pediatric inflammatory bowel diseases(IBDs) over 2000-2015 and project the incidence to 2018. METHODS A 16-year prospective study of IBD patients < 19 years of age was conducted in the Czech Republic(the Pilsen region). All incident IBD cases within a well-defined geographical area were retrieved from a prospectively collected computerized clinical database. Historical Czech data were used for comparison(1990-2001). Our catchment population was determined from the census data. We calculated the incidence by relating the number of newly diagnosed cases to the size of thepediatric population-at-risk in each calendar year. Age/sex, disease type, place of residence, and race/ethnicity were identified. RESULTS In total, 170 new IBD cases [105 Crohn's disease(CD), 48 ulcerative colitis(UC), and 17 IBD-unclassified(IBD-U)] were identified. The median age at IBD diagnosis was 14.2 years, 59.4% were males, and 97.1% were Caucasians. A male preponderance of IBD(P = 0.026) and CD(P = 0.016) was observed. With 109209 person-years in the catchment area, the average incidence of IBD per 100000 person-years was 10.0(6.2 for CD, 2.8 for UC, and 1.0 for IBD-U) for children aged 0 to 19 years; for those aged 0 to 15 years, the incidence rate was 7.3(4.6 for CD, 2.0 for UC, and 0.7 for IBD-U). An increase in incidence with age was observed(P = 0.0003). Over the 16-year period, the incidence increased for IBD patients(P = 0.01) and CD in particular(P < 0.0001), whereas the incidence for UC(P = 0.09) and IBD-U(P = 0.339) remained unchanged. IBD-projected data from 2016 to 2018 were 12.1, 12.3 and 12.6 per 100000 personyears, respectively.CONCLUSION Pediatric-onset IBD incidence is around its highest point. The increase, which is particularly pronounced for CD, may be challenging to relate to causes of pediatric disease.

Harnessing dimethyl ether and methyl formate fuels for direct electrochemical energy conversion

In this work,the oxidation of a mixture of dimethyl ether(DME) and methyl formate(MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell(PEMFC)utilizing a multi-metallic alloy catalyst,Pt_(3)Pd_(3)Sn_(2)/C,discovered earlier by us.The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately,suggesting the cooperative effect of mixing these fuels.A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME+MF mixture as compared to DME or MF individually.This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual-molecules than of the sum of the individual molecules as confirmed by the density fu nctional theory(DFT) calculations.Fuel cell polarization was also conducted using a Pt_(3)Pd_(3)Sn_(2)/C(anode) and Pt/C(cathode) catalysts-coated membrane(CCM).The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME+MF mixture-fed fuel cell(123 mW cm^(-2)at 0.45 V) than with DME(84mW cm^(-2)at 0.35 V) or MF(28 mW cm^(-2)at 0.2 V) at the same total anode hydrocarbon flow rate,temperature,and ambient pressure.

NANOCOMPOSITE COATINGS WITH ENHANCED HARDNESS

The article reviews the present state of the art in the magnetron sputtering of hart and superhard nanocomposite coatings. It is shown that there are (1) two gr oups of hard and superhard nanocomposites: (i) nc-MN/hard phase and (ii) nc-MN/s oft phase, (2) three possible origins of the enhanced hardness: (i) dislocation- dominated plastic deformation, (ii) cohesive forces between atoms and (iii) nano structure of materials, and (3) huge differences in the microstructure of single - and two-phase films. A main attention is devoted to the formation of nanocryst alline and/or X-ray amorphous films. Such films are created in a vicinity of tra nsitions between (i) crystalline and amorphous phases, (ii) two crystalline phas es of different chemical composition or (iii) two different preferred orientatio ns of grains of the same material from which the coating is composed. The existe nce of the last transition makes it possible to explain the enhanced hardness in single-phase films. The thermal stability and oxidation resistance of hard nano composite films is also shortly discussed.

Pneumatic Measurements Downstream of a Radial Turbine Nozzle Cascade

This paper deals mainly with pneumatic measurements on a radial turbine nozzle cascade. The fill radial cascade guarantees the exit flow field periodicity downstream of it. A special traversing mechanism with a five - hole conical probe moving along a circular path behind the cascade was used for flow field investigation in this type of cascade with very low aspect ratio. The analyses of results of 2D and 3D pneumatic measurements including loss coefficient values are presented.

Super d-antimagic Labelings of Disconnected Plane Graphs

This paper deals with the problem of labeling the vertices, edges and faces of a plane graph in such a way that the label of a face and the labels of the vertices and edges surrounding that face add up to a weight of that face, and the weights of all s-sided faces constitute an arithmetic progression of difference d, for each s that appears in the graph. The paper examines the existence of such labelings for disjoint union of plane graphs.