Vliv chemického složení oceli na numerickou simulaci plynulého odlévání sochorů

The chemical composition of steels has significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The chemical composition of steel affects the thermophysical properties (heat conductivity, specific heat capacity and density in the solid and liquid states) often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet. Therefore, an analysis study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation were also determined. The order of significance of the chemical composition on thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization.Chemické složení ocelí má významný vliv na reálný proces plynulého odlévání a na přesnost jeho numerické simulace a optimalizace. Chemické složení oceli ovlivňuje termofyzikální vlastnosti (tepelné vodivosti, měrné tepelné kapacity a hustoty v tuhém i tekutém stavu) a jejich prostřednictvím ovlivňuje výpočet teplotního pole plynule odlévaných ocelových sochorů. Proto byla provedena analýza studie těchto termofyzikálních vlastností. Vliv významu chemického složení na termofyzikální vlastnosti byla určena s ohledem na metalurgickou délku. Analýza byla provedena pomocí takzvaných výpočetních experimentů, tj. pomocí originálního numerického modelu teplotního pole, který byl vyvinut autory tohoto příspěvku. Tato analýza usnadní a tím zlepší proces optimalizace plynulého odlévání oceli

Laboratory acclimation to autumn-like conditions induces freeze tolerance in the spring field cricket Gryllus veletis (Orthoptera: Gryllidae)

Many temperate insects encounter temperatures low enough to freeze their body fluids. Remarkably, some insects are freeze-tolerant, surviving this internal ice formation. However, the mechanisms underlying freeze tolerance are not well-understood, in part due to a lack of tractable model organisms. We describe a novel laboratory model to study insect freeze tolerance, the spring field cricket Gryllus veletis (Orthopera: Gryllidae). Following acclimation to six weeks of decreasing temperature and photoperiod, G. veletis become freeze-tolerant, similar to those exposed to natural autumn conditions in London, Ontario, Canada. Acclimated crickets suppress their metabolic rate by c. 33%, and survive freezing for up to one week at -8°C, and to temperatures as low as -12°C. Freeze-tolerant G. veletis protect fat body cells from freeze injury in vivo, and fat body tissue from freeze-tolerant cricket survives brief freeze treatments when frozen ex vivo. Freeze-tolerant crickets freeze at c. -6°C, which may be initiated by accumulation of ice-nucleating agents in hemolymph or gut tissue. We hypothesize that control of ice formation facilitates freeze tolerance, but initiating ice formation at high subzero temperatures does not confer freeze tolerance on freeze-intolerant nymphs. Acclimation increases hemolymph osmolality from c. 400 to c. 650 mOsm, which may facilitate freeze tolerance by reducing ice content. Hemolymph ion concentrations do not change with acclimation, and we therefore predict that freeze-tolerant G. veletis elevate hemolymph osmolality by accumulating other molecules. Gryllus veletis is easily reared and manipulated in a controlled laboratory environment, and is therefore a suitable candidate for further investigating the mechanisms underlying freeze tolerance

Investigation of a Temperature Field of the Steel Billet 150x150 mm Continuously Cast

The solidification and cooling of a continuously cast billet and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving ofuch a problem is impossible without numerical models of the temperature field of the concasting itself which it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optimization of the process procedure. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling

Importance of the experimental investigation of a concasting technology

The solidification and cooling of a continuously cast billet, slab cylinder, generally of a concasting and the simultaneous heating of the mold is a very complicated problem of three-dimensional (3D) transient heat and mass transfer. The solving of such a problem is impossible without numerical models of the temperature field of the concasting itself hich it is being processed through the concasting machine (caster). The application of the numerical model requires systematic experimentation and measurement of operational parameters on a real caster as well as in the laboratory. The measurement results, especially temperatures, serve not only for the verification of the exactness of the model, but mainly for optímization of the process procedure: real process input data numerical analyses optimization correction of real process. The most important part of the investigation is the measurement of the temperatures in the walls of the mold and the surface of the slab in the zones of secondary and tertiary cooling

Cold adaptation of insects: the role of shock proteins from Hsp family.

Heat shock proteins (Hsps) form evolutionarily conserved group of proteins that are best known for their unique function in repair of miss folded proteins that would otherwise aggregate in cells during stress conditions. The most extensively studied is the inducible Hsp70. Using 3rd instar larvae of transgene mutant of fruit fly, Drosophila melanogaster that lacks all copies of hsp70 gene, we assessed: 1) whether the absence of this gene is deleterious for larvae in their capacity to survive cold stress; and 2) whether any other gene from Hsps family may compensate for the loss of hsp70. We found that 1) survival of cold stress is not altered in Hsp- larvae when compared to wild type Hsp+ larvae; 2) there is no other gene of Hsps family that would compensate for the loss of hsp70 at the level of transcription. Our ongoing effort is focusing on analysis of cold stress response at the protein level

Low-temperature injury in insect tissues and mechanisms of its repair

While physiological adjustments accompanying insect cold acclimation prior to cold stress have been relatively well explored, processes of recovery after cold stress received much less attention. Using a broad array of physiological, molecular biological and microscopic techniques, I aimed to capture the complexity of processes occurring after the exposure to cold stress in the larvae of two drosophilid species - freeze tolerant Chymomyza costata and freeze sensitive Drosophila melanogaster. Several lines of evidence pointed toward impaired mitochondrial functions in lethally frozen larvae. The freeze-tolerant phenotypes of C. costata retain integrity of mitochondria even after deep freezing

General methodology for building of OPC UA gateways

This article describes an original generalized methodology for building OPC UA bridges for different industrial communications and internal command protocols. This methodology is aimed for fast development of OPC UA gateways for less popular data transferring communications which are not available on the market. A final gateway can be added to existing solutions without modification of data source control devices. This gateway needs only a minimal configuration and obtains information about data source automatically. This design has been already implemented in three different solutions with various communication (REXYGEN, PerNet, a Keysight middleware protocol). The solutions has been deployed in various projects and proved to be efficient and reliable

Význam termofyzikálních vlastností ocelí pro numerickou simulaci procesu kontinuálního lití

The thermophysical properties of steels have significant influence on the actual concasting process, and on the accuracy of its numerical simulation and optimization. The determination of these properties (heat conductivity, specific heat capacity and density in the solid and liquid states) often requires more time than the actual numerical calculation of the temperature fields of a continuously cast steel billet, cylinder or slab (generally a concasting). The influence of individual properties should be neither under- nor over-estimated. Therefore, an analysis/parametric study of these thermophysical properties was conducted. The order of importance within the actual process and the accuracy of simulation and optimization were also determined. Individual properties, which, in some cases, were obtained from tables, and in others experimentally, were substituted by an approximation using orthogonal polynomials. The accuracy of each polynomial is dependent on the precision of individual values. The order of significance of individual thermophysical properties was determined with respect to the metallurgical length. The analysis was performed by means of a so-called calculation experiment, i.e. by means of the original and universal numerical concasting model developed by the authors of this paper. It is convenient to conduct such an analysis in order to facilitate the simulation of each individual case of concasting, thus enhancing the process of optimization.Termofyzikální vlastnosti ocelí mají významný vliv na reálný proces kontinuálního lití a na přesnost jeho numerické simulace a optimalizace. Určení těchto vlastností (tepelná vodivost, měrná tepelná kapacita a hustota v tuhé a kapalné fázi) často vyžaduje více času než vlastní numerický výpočet teplotních polí plynule odlitého ocelového sochoru, válce nebo bramy (obecně předlitku). Vliv individuálních vlastností by neměl být podceňován ani přeceňován. Proto byla uskutečněna analyza/parametrická studie těchto termofyzikálních vlastností. Bylo rovněž určeno pořadí významu v průběhu skutečného procesu a přesnost simulace a optimalizace. Individuální vlastnosti, které v některých případech byly získány z tabulek, v jiných experimentálně, byly nahrazeny aproximací za použití ortogonálních polynomů. Přesnost každého polynomu je závislá na přesnosti jednotlivých vlastností. Pořadí významu jednotlivých termofyzikálních vlastností byla stanovena vzhledem k metalurgické délce. Analyza byla prováděna pomocí t.zv. výpočtového experimentu, t.j. pomocí originálního a univerzálního numerického modelu plynulého odlévání vyvinutého autory tohoto článku. Je potřebné provádět takovou analyzu pro usnadnění simulace každého konkretního případu plynulého lití a tak zlepšit proces optimalizace

High Quality Steel Casting by Using Advanced Mathematical Methods

The main concept of this paper is to utilize advanced numerical modelling techniques with self-regulation algorithm in order to reach optimal casting conditions for real-time casting control. Fully 3-D macro-solidification model for the continuous casting (CC) process and an original fuzzy logic regulator are combined. The fuzzy logic (FL) regulator reacts on signals from two data inputs, the temperature field and the historical steel quality database. FL adjust the cooling intensity as a function of casting speed and pouring temperature. This approach was originally designed for the special high-quality high-additive steel grades such as higher strength grades, steel for acidic environments, steel for the offshore technology and so forth. However, mentioned approach can be also used for any arbitrary low-carbon steel grades. The usability and results of this approach are demonstrated for steel grade S355, were the real historical data from quality database contains approximately 2000 heats. The presented original solution together with the large steel quality databases can be used as an independent CC prediction control system