Failure mechanism of blast furnace tuyeres

The damage of a blast furnace tuyere, requiring its replacement, disturbs normal operation of the blast furnace and reduces the economic efficiency of production. In this paper, the failure mechanism of blast furnace tuyeres was investigated by metallographic examination of sections cut from failed tuyeres and laboratory experiments directed towards a simulation of tuyere operation and failure. The obtained results revealed a complex failure mechanism which consists of two main phases: the phase of local damage by corrosion and the phase of melting of damaged areas. The corrosion of tuyeres is caused by the presence of aggressive chemical compounds in the blast furnace, primarily chlorinecontaining compounds. The corrosive attack on a tuyere results in the formation of intergranular cracks and microporosity in the tuyere copper. Such defects affect severely the cooling of the copper in the affected areas. Thermal load on the tuyere surface through the splashing of hot metal and slag and reduced thermal conductivity of the copper in the areas affected by corrosion lead to the overheating and finally localized melting of the tuyere. This process can take place repeatedly until the tuyere is completely damaged, which is accompanied by leakage of water into the furnace

On the microstructure development under cyclic temperature conditions during WAAM of microalloyed steels

This paper shed light on the kinetics of transformation and the developed microstructure during wire arc additive manufacturing (WAAM). Three microalloyed alloys, two of them are high strength low alloyed steel (HSLA) grades and the third is a Ni-Cr-Mo steel, from which the welding wires are being produced, were investigated. Repeated cycles around varied temperatures from a reheating temperature of 1350 ◦C and down to a temperature 35 ◦C below the Ae1 are applied using dilatometer on samples from the steels. After applying the cycles, the dilatometric-samples were investigated metallographically and their macro- and microhardness values were measured. It is shown that the WAAM using HSLA steels produce softer structure than the steel of the welding wire. Combined microalloying with Ti and Nb can present a useful strategy for producing finer structure in the WAAM components due to the effect of Ti in inhibiting the prior austenite grain-growth and that of Nb in refining the final structure. Additionally, repeated heating near Ae3 refines the prior austenite grains and produced fine ferrite-pearlite structure in case of HSLA steels and a microstructure predominated by the granular bainite in case of welding wire alloy. The former microstructure was the softest one for the case of HSLA steels, whereas the softest structure in case of the welding wire alloy was the tempered martensite structure developed by reheating below Ae1. Idealized temperature curves were chosen for the heat treatment, which could be characterized in a well-defined manner. In future work such idealized curves together with temperature histories obtained in WAAM-process will be used to set up a database to train an AI-model for predicting structure and material properties

Patterns of Multimorbidity in the Aged Population. Results from the KORA-Age Study

Multimorbidity is a common problem in aged populations with a wide range of individual and societal consequences. The objective of the study was to explore patterns of comorbidity and multimorbidity in an elderly population using different analytical approaches. Data were gathered from the population-based KORA-Age project, which included 4,127 persons aged 65–94 years living in the city of Augsburg and its two surrounding counties in Southern Germany. Information on the presence of 13 chronic conditions was collected in a standardized telephone interview and a self-administered questionnaire. Patterns of comorbidity and multimorbidity were analyzed using prevalence figures, logistic regression models and exploratory tetrachoric factor analysis. The prevalence of multimorbidity (≥2 diseases) was 58.6% in the total sample. Hypertension and diabetes (Odds Ratio [OR] 2.95, 99.58% confidence interval [CI] [2.19–3.96]), as well as hypertension and stroke (OR 2.00, 99.58% CI [1.26–3.16]) most often occurred in combination. This association was independent of age, sex and the presence of other conditions. Using factor analysis, we identified four patterns of multimorbidity: the first pattern includes cardiovascular and metabolic diseases, the second includes joint, liver, lung and eye diseases, the third covers mental and neurologic diseases and the fourth pattern includes gastrointestinal diseases and cancer. 44% of the persons were assigned to at least one of the four multimorbidity patterns; 14% could be assigned to both the cardiovascular/metabolic and the joint/liver/lung/eye pattern. Further common pairs were the mental/neurologic pattern combined with the cardiovascular/metabolic pattern (7.2%) or the joint/liver/lung/eye pattern (5.3%), respectively. Our results confirmed the existence of co-occurrence of certain diseases in elderly persons, which is not caused by chance. Some of the identified patterns of multimorbidity and their overlap may indicate common underlying pathological mechanisms

withdrawn 2017 hrs ehra ecas aphrs solaece expert consensus statement on catheter and surgical ablation of atrial fibrillation

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Retrieval-induced forgetting in item recognition: evidence for a reduction in general memory strength

Retrieving a subset of previously studied material can impair later recognition of related items. Using the remember-know procedure (Experiment 1) and the receiver operating characteristic procedure (Experiment 2), the authors examined how such retrieval-induced forgetting can be explained in terms of single-process and dual-process accounts of recognition memory. Consistent across the 2 experiments, dual-process analysis suggested that retrieval practice reduces unpracticed items' familiarity but leaves their recollection largely unaffected, a finding that disagrees with prior work that points to recollective deficits in the forgotten items. Assuming that recognition is entirely based on a single source of memorial information, single-process analysis led to an excellent description of the data and suggested that retrieval practice reduces unpracticed items' general memory strength. This suggestion is consistent with prior work on free recall, cued recall, associative recognition, and response latencies and agrees with the inhibitory account of retrieval-induced forgetting. The authors argue that retrieval-induced forgetting in item recognition is caused by a reduction in general memory strength

Retrieval-induced forgetting in a category recognition task

Prior work on retrieval-induced forgetting showed that retrieving a subset of formerly studied items can impair item recognition of related, nonretrieved material. Here it was investigated whether retrieval practice can also impair the items’ recognition as member of a studied category. Participants studied pre-experimentally unrelated words that were categorized by their font colors. After study, a subset of the words was retrieval practiced using a word stem completion task. Finally, an episodic category recognition test based on confidence ratings was applied. ROC analysis of the data demonstrated a reliable impairment in the nonretrieved items’ category recognition relative to control items. The result indicates that retrieval-induced forgetting is not restricted to item recognition but generalizes to category recognition tasks. Inhibitory as well as noninhibitory explanations of the finding are discussed

Oscillatory Correlates of Retrieval-Induced Forgetting in Recognition Memory

Retrieval practice on a subset of previously studied material enhances later memory for practiced material but can inhibit memory for related unpracticed material. The present study examines the effects of prior retrieval practice on evoked (ERPs) and induced (oscillatory power) measures of electrophysiological activity underlying recognition of practiced and unpracticed words. Compared to control material, recognition of unpracticed words was characterized by reduced amplitudes of the P2 ERP component and by reduced early (200-400 ms) oscillatory theta power. The reduction in P2 amplitude was associated with decreased evoked theta power but not with decreased theta phase locking (PLI). Recognition of unpracticed material was further accompanied by a reduction in occipital gamma power (> 250 ms). In contrast, the beneficial effects of retrieval practice on practiced words were reflected by larger parietal ERP positivity ( > 500 ms) and by a stronger decrease in oscillatory alpha power in a relatively late time window ( > 700 ms). The results suggest that the beneficial and detrimental effects of retrieval practice are mediated by different processes. In particular, they suggest that reduced theta (4 – 7 Hz) and gamma (60 – 90 Hz) power reflect the specific effects of inhibitory processes on the unpracticed material’s memory representation

On the Microstructure Development under Cyclic Temperature Conditions during WAAM of Microalloyed Steels

This paper shed light on the kinetics of transformation and the developed microstructure during wire arc additive manufacturing (WAAM). Three microalloyed alloys, two of them are high strength low alloyed steel (HSLA) grades and the third is a Ni-Cr-Mo steel, from which the welding wires are being produced, were investigated. Repeated cycles around varied temperatures from a reheating temperature of 1350 °C and down to a temperature 35 °C below the Ae1 are applied using dilatometer on samples from the steels. After applying the cycles, the dilatometric-samples were investigated metallographically and their macro- and microhardness values were measured. It is shown that the WAAM using HSLA steels produce softer structure than the steel of the welding wire. Combined microalloying with Ti and Nb can present a useful strategy for producing finer structure in the WAAM components due to the effect of Ti in inhibiting the prior austenite grain-growth and that of Nb in refining the final structure. Additionally, repeated heating near Ae3 refines the prior austenite grains and produced fine ferrite-pearlite structure in case of HSLA steels and a microstructure predominated by the granular bainite in case of welding wire alloy. The former microstructure was the softest one for the case of HSLA steels, whereas the softest structure in case of the welding wire alloy was the tempered martensite structure developed by reheating below Ae1. Idealized temperature curves were chosen for the heat treatment, which could be characterized in a well-defined manner. In future work such idealized curves together with temperature histories obtained in WAAM-process will be used to set up a database to train an AI-model for predicting structure and material properties