Lance Design for Scrap Melting Aggregates

Metallurgical aggregates, which are used for metal waste melting, are equipped with lances for blowing gaseous media. These gaseous media allow especially scrap melting and intense homogenization of the resulting melt. In connection with this, the blowing systems are developed both for blowing of gaseous media itself on the bath surface or into the melt and for blowing of the gas mixture with powdered substances. When designing the blowing systems and the individual lance tips and nozzles, it is necessary to respect certain criteria, the derivation of which is based on long-term experience and acquired knowledge in this field. The submitted paper summarizes the design recommendations, including the determination of the selected design characteristics of the nozzles for blowing gaseous media on the bath surface in the metallurgical aggregate. These design characteristics help designers and engineers to design systems that meet the high demands on quality, efficiency and operational reliability

Mechanism of the Intermediary Phase Formation in Ti-20 wt. % Al Mixture during Pressureless Reactive Sintering

This work aims to describe the mechanism of intermediary phases formation in TiAl20 (wt. %) alloy composition during reactive sintering. The reaction between titanium and aluminum powders was studied by in situ diffraction and the results were confirmed by annealing at various temperatures. It was found that the Ti2Al5 phase formed preferentially and its formation was detected at 400 degrees C. So far, this phase has never been found in this alloy composition during reactive sintering processes. Subsequently, the Ti2Al5 phase reacted with the titanium, and the formation of the major phase, Ti3Al, was accompanied by the minor phase, TiAl. Equations of the proposed reactions are presented in this paper and their thermodynamic and kinetic feasibility are supported by Gibbs energies of reaction and reaction enthalpies

Thermal stability of Al-Cu-Fe quasicrystals prepared by SHS method

Quasicrystal-containing materials are usually prepared by rapid solidification of the melt (e.g. by melt spinning) or mechanical alloying. In this work, the method using exothermic reactions between compressed metallic powders called SHS (Self-propagating High-temperature Synthesis) was tested. The microstructure and phase composition of the product was described in dependence on cooling regime from the reaction temperature. Thermal stability of prepared Al-Cu-Fe quasicrystals was studied by annealing at the temperatures of 300 and 500 °C

Kinetic and thermodynamic description of intermediary phases formation in Ti-Al system during reactive sintering

Reactive sintering is currently considered as a promising production route for titanium aluminides in many research works. However, the published descriptions of the reaction mechanism are contradictory or lacking, especially at the temperatures below the melting point of aluminium. This work aims to fill this gap, providing the description of the reactive sintering process at the temperatures between 400 and 900 degrees C. The phases' formation sequence and reaction kinetics were studied and explained using experimental model (Ti/Al diffusion couple) and real reactively sintered samples of equiatomic Ti-Al compressed powder blend. Moreover, phase formation was thermodynamically assessed. It was revealed that Ti2Al5 phase formed preferentially. This phase has not been reported previously as a starting phase in reactive sintering. According to results obtained by experimental model, its formation is controlled by diffusion at 700 degrees C. This phase reacted with aluminium forming pure TiAl3 phase or with titanium, resulting in TiAl phase. Subsequently, TiAl phase reacted with titanium, leading to the Ti3Al phase, or with already present Ti2Al5 phase yielding TiAl2 intermetallic compound. Titanium-rich Ti3Al phase could form only at the temperature of 600 degrees C or above

Influence of insulin on glucose metabolism and energy expenditure in septic patients

INTRODUCTION: It is recognized that administration of insulin with glucose decreases catabolic response in sepsis. The aim of the present study was to compare the effects of two levels of insulinaemia on glucose metabolism and energy expenditure in septic patients and volunteers. METHODS: Glucose uptake, oxidation and storage, and energy expenditure were measured, using indirect calorimetry, in 20 stable septic patients and 10 volunteers in a two-step hyperinsulinaemic (serum insulin levels 250 and 1250 mIU/l), euglycaemic (blood glucose concentration 5 mmol/l) clamp. Differences between steps of the clamp (from serum insulin 1250 to 250 mIU/l) for all parameters were calculated for each individual, and compared between septic patients and volunteers using the Wilcoxon nonpaired test. RESULTS: Differences in glucose uptake and storage were significantly less in septic patients. The differences in glucose oxidation between the groups were not statistically significant. Baseline energy expenditure was significantly higher in septic patients, and there was no significant increase in either step of the clamp in this group; when comparing the two groups, the differences between steps were significantly greater in volunteers. CONCLUSION: A hyperdynamic state of sepsis leads to a decrease in glucose uptake and storage in comparison with healthy volunteers. An increase in insulinaemia leads to an increase in all parameters of glucose metabolism, but the increases in glucose uptake and storage are significantly lower in septic patients. A high level of insulinaemia in sepsis increases glucose uptake and oxidation significantly, but not energy expenditure, in comparison with volunteers

Clinical Study Comparison of Long-Term Effect of Dual-Chamber Pacing and Alcohol Septal Ablation in Patients with Hypertrophic Obstructive Cardiomyopathy

Introduction. Nonpharmacological treatment of patients with hypertrophic obstructive cardiomyopathy (HOCM) comprises surgical myectomy (SME), alcohol septal ablation (ASA), and dual-chamber (DDD) pacing. The aim of the study was to compare the long-term effect of DDD pacing and ASA in symptomatic HOCM patients. Patients and Methods. We evaluated retrospective data from three cardiocenters; there were 24 patients treated with DDD pacing included and 52 treated with ASA followed for 101 ± 49 and 87 ± 23 months, respectively. Results. In the group treated with DDD pacing, the left ventricle outflow tract gradient (LVOTG) decreased from 82 ± 44 mmHg to 21 ± 21 mmHg, and NYHA class improved from 2.7 ± 0.5 to 2.1 ± 0.6 (both < 0.001). In the ASA-treated group, a decline in LVOTG from 73 ± 38 mmHg to 24 ± 26 mmHg and reduction in NYHA class from 2.8 ± 0.5 to 1.7 ± 0.8 were observed (both < 0.001). The LVOTG change was similar in both groups ( = 0.264), and symptoms were more affected by ASA ( = 0.001). Conclusion. ASA and DDD pacing were similarly effective in reducing LVOTG. The symptoms improvement was more expressed in patients treated with ASA