Iskanje po katalogu digitalne knjižnice

Opis: The static and dynamic loading capacities of components depend on the stress level to which the material is exposed. The fatigue behavior of materials manufactured using additive technology is accompanied by a pronounced scatter between the number of cycles at the same stress level, which is significantly greater than the scatter from a material with the same chemical composition, e.g., AISI 316L, but produced by rolling or forging. An important reason lies in the fact that fatigue cracks are initiated almost always below the material surface of the loaded specimen. Thus, in the article, assuming that a crack will always initiate below the surface, we analyzed the fatigue behavior of specimens with the same bearing cross section but with a different number of bearing rods. With a larger number of rods, the circumference around the supporting part of the rods was 1.73 times larger. Thus, experimental fatigue of specimens with different sizes showed that the dynamic loading capacity of components with a smaller number of bars is significantly greater and can be monitored by individual stress levels. Although there are no significant differences in loading capacity under static and low-cycle loading of materials manufactured with additive technologies, in high-cycle fatigue it has been shown that the ratio between the circumference and the loading cross section of tensile-loaded rods plays an important role in the lifetime. This finding is important for setting a strategy for manufacturing components with additive technologies. It shows that a better dynamic loading capacity can be obtained with a larger loading cross section.
Ključne besede: AISI 316L stainless steel, additive manufacturing, FEM, high-cycle fatigue, fractography analysis
Objavljeno v DKUM: 25.11.2024; Ogledov: 0; Prenosov: 7
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Opis: The physiological mechanisms determining the progressive decline in the maximal muscle torque production capacity during isometric contractions to task failure are known to depend on task demands. Task-specificity of the associated adjustments in motor unit discharge rate (MUDR), however, remains unclear. This study examined MUDR adjustments during different submaximal isometric knee extension tasks to failure. Participants performed a sustained and an intermittent task at 20% and 50% of maximal voluntary torque (MVT), respectively (Experiment 1). High-density surface EMG signals were recorded from vastus lateralis (VL) and medialis (VM) and decomposed into individual MU discharge timings, with the identified MUs tracked from recruitment to task failure. MUDR was quantified and normalised to intervals of 10% of contraction time (CT). MUDR of both muscles exhibited distinct modulation patterns in each task. During the 20% MVT sustained task, MUDR decreased until ∼50% CT, after which it gradually returned to baseline. Conversely, during the 50% MVT intermittent task, MUDR remained stable until ∼40–50% CT, after which it started to continually increase until task failure. To explore the effect of contraction intensity on the observed patterns, VL and VM MUDR was quantified during sustained contractions at 30% and 50% MVT (Experiment 2). During the 30% MVT sustained task, MUDR remained stable until ∼80–90% CT in both muscles, after which it continually increased until task failure. During the 50% MVT sustained task the increase in MUDR occurred earlier, after ∼70–80% CT. Our results suggest that adjustments in MUDR during submaximal isometric contractions to failure are contraction modality- and intensity-dependent.
Ključne besede: muscle contractions, high-density EMG signals, electromyiograms
Objavljeno v DKUM: 23.08.2024; Ogledov: 117; Prenosov: 9
Celotno besedilo (3,77 MB)
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Opis: The European Union Member States (hereinafter: EU MS) have the possibility of restricting or banning the cultivation of GMOs under the Directive 2015/412 but under certain conditions. EU MS must also pay attention to the provisions of the Treaty on the Functioning of the Euro-pean Union or Treaty Establishing the European Community (hereinafter: TFEU), the provi-sions relating to the free movement of goods, which is one of the key objectives of the func-tioning of the European Union. This contribution is based on the data obtained from an analy-sis of Court of Justice of the European Union (hereinafter: CJEU) cases concerning the use of genetically modified organisms (hereinafter: GMO(s)). The analysis highlights the link between environmental risk assessment and the right to healthcare. The purpose of this paper is to make the individual aware of the possibilities they have regarding the use of GMOs.
Ključne besede: Directive 2001/18, Directive 2015/4120, Directive 2018/350, high level of protection of human life and health, possibility of restricting or prohibiting the production of GMOs, free movement of goods, environmental risk assessment
Objavljeno v DKUM: 26.06.2024; Ogledov: 144; Prenosov: 19
Celotno besedilo (518,32 KB)
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Ključne besede: motor units identification, high-density surface EMG, decomposition, H-reflex
Objavljeno v DKUM: 13.06.2024; Ogledov: 133; Prenosov: 11
Celotno besedilo (1,43 MB)
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Opis: This dataset contains a collection of simulated and experimental surface HDEMG recordings of the biceps brachii muscle during the isometric elbow flexion. Simulated data contains 50 recordings: 5 subjects and 5 excitation levels, each with and without added noise. Experimental data contains 16 recordings: 2 subjects with 4 excitation levels and 2 repetitions of each level. Synthetic data was simulated using the cylindrical volume conductor model [1] and the motor unit recruitment and firing modulation model proposed in [2]. Each recording is 20 seconds in length with 90 HDEMG channels sampled at 2048 Hz and is stored as a 2D matrix of raw EMG values in Matlab’s MAT format. Experimental surface EMG data was recorded on two volunteers during isometric contractions at constant force level. Each recording is 25 seconds in length with 64 HDEMG channels sampled at 2048 Hz and is also stored as a 2D matrix of raw EMG values in Matlab’s MAT format. The dataset is approximately 1.5 GB in size.
Ključne besede: surface high density electromyogram (HDEMG), motor unit, spike train, motor unit merging, simulated data, experimental data, biceps brachii, dataset
Objavljeno v DKUM: 30.05.2024; Ogledov: 172; Prenosov: 14
Celotno besedilo (125,29 KB)
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