1,213 research outputs found
A harmonic one-dimensional element for non-linear thermo-mechanical analysis of axisymmetric structures under asymmetric loads: The case of hot strip rolling
No full textThis work presents a one-dimensional harmonic finite element for the transient elasto-plastic analysis of axisymmetric structures loaded by non-axisymmetric thermal and mechanical loads. The one-dimensional element exploits a semi-analytical approach, based on Fourier series decomposition of the applied loads. The initial stress method is used for the non-linear solution of elasto-plastic analysis. As a case study, the proposed one-dimensional harmonic element is applied for modelling a two-dimensional circle under thermal and mechanical loadings rotating over its surface, which is used as an approximation of a work roll in hot strip rolling. With the one-dimensional harmonic element, the cyclic thermo-mechanical behaviour of the work roll can be simulated by considering localized plasticity caused by thermo-mechanical loads representative of strip and back-up roll. Compared to two-dimensional models already used in the literature, the one-dimensional element allows a significant reduction in the computational time to be achieved; it follows that the whole transient thermo-mechanical response can be simulated, thus permitting a more complete evaluation of the stress-strain response that is necessary for fatigue life assessment. © IMechE 2016
Sensuri ale raţionalului şi iraţionalului la Mircea Florian
No full textMenirea filosofiei este, după Mircea Florian, de „a da culturii un fundament evident, un prim adevăr"(Filosofie generală, Editura Genard Internaţional, Bucuresti, 1995, p. 6). El si-a elaborat propria sa concepţie filosofică în cadrul dialogului contemporan, cu grija de a depăsi criza filosofiei din perioada interbelică. Argumentarea posibilităţii filosofiei - ca stiinţă „a fundamentelor, a principiilor, a categoriilor de maximă generalitate", a principiilor sau noţiunilor prime..
A semi-analytical finite element approach in machine design of axisymmetric structures
No full textNon
Short term growth hormone (GH) treatment of GH-deficient adults increases body sodium and extracellular water, but not blood pressure
No full textInitiation of GH treatment in adults is frequently complicated by the development of symptomatic fluid retention. To investigate the mechanism and extent of fluid retention that occurs with dosages of GH used in the treatment of GH-deficient adults, we conducted a double blind study in which seven GH-deficient patients (aged 24-74 yr) each received in random order daily sc injections of placebo, a physiological dose of GH (0.04 U/kg, low dose), and a supraphysiological dose of GH (0.08 U/kg, high dose) for 7 days, separated by 21-day washout periods. On the seventh day, measurements were made of serum insulin-like growth factor I, body weight, exchangeable sodium, plasma volume, angiotensinogen, PRA, aldosterone, atrial natriuretic peptide (ANP), and mean 24-h ambulatory heart rate and blood pressure. GH significantly increased mean insulin-like growth factor I levels from 105 ± 11 to 304 ± 45 μg/L during low dose treatment (P = 0.006) and 400 ± 76 μg/L during high dose treatment (P = 0.004). High dose GH caused a 1.2 ± 0.3 kg increase in body weight (P = 0.01) and a 193 ± 65 mmol increase in exchangeable sodium (P = 0.008). Low dose GH had a lesser effect, with no significant increase in body weight, but an increase in exchangeable sodium of 113 ± 37 mmol (P = 0.02). Plasma volume was not significantly affected by GH treatment. Mean supine angiotensinogen levels were significantly higher during both GH treatments compared to placebo (low dose, P = 0.017; high dose, P = 0.028) as were mean supine pRA levels (low dose, P = 0.0002; high dose, P = 0.0025). Supine angiotensin II, aldosterone, and ANP levels were not significantly affected by GH treatment. There was no significant change from placebo in any of the sodium-regulating hormones in the erect posture. The mean 24-h heart rate was significantly higher during low dose (82 ± 2 beats/min; P = 0.0001) and high dose (88 ± 3 beats/min; P = 0.0001) GH treatment than during placebo (67 ± 3 beats/min). However, no significant change in mean 24-h systolic or diastolic blood pressure was observed. In summary, acute GH administration using doses currently employed in treating adults causes a dose-related increase in body weight and body sodium, but no associated increase in blood pressure. We conclude that 1) sodium retention is a physiological effect of GH, but does not cause an acute rise in blood pressure; and 2) the mechanism of sodium and fluid retention is not primarily due to enhanced aldosterone secretion or inhibition of ANP release, but more likely to a direct renal tubular effect
RNAseq analysis of fast skeletal muscle in restriction-fed transgenic coho salmon (Oncorhynchus kisutch) : an experimental model uncoupling the growth hormone and nutritional signals regulating growth
No full textBackground Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon. Results Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myoblast fusion were identified with 22 significantly downregulated in TR relative to WT fish, including 10 (vaspa, cdh15, graf1, crk, crkl, dock1, trio, plekho1a, cdc42a and dock5) associated with signaling through the cell surface protein cadherin. Nineteen out of 44 (43 %) translation initiation factors and 14 of 47 (30 %) protein chaperones were upregulated in TR relative to WT fish. Conclusions TR coho salmon showed increased growth hormone transcripts and gene expression associated with protein synthesis and folding than WT fish even though net rates of protein accretion were similar. The uncoupling of Gh and amino acid signals likely results in additional costs of transcription associated with protein turnover in TR fish. The predicted reduction in the ionic costs of homeostasis in TR fish associated with increased fibre size were shown to involve multiple pathways regulating myotube fusion, particularly cadherin signaling.Peer reviewe
Shaft design: A semi-analytical finite element approach
No full textThis work deals with the practical use of semi-analytical finite elements in the machine design. The case of mechanical shafts is considered. The most usual loading condition characterized by the presence of axial, torsional, bending, and shear loads can be modeled by over imposing an axi-symmetric, an axi-antisymmetric and a harmonic load, corresponding to the first three terms of the Fourier series expansion, if semi-analytical plane finite element is used. A practical case is presented and the advantages, with respect to the three-dimensional approach in terms of computational time and accuracy for stress and displacement evaluation, is put in evidence. © 2017 Taylor & Franci
Validation of compact models of microcantilever actuators for RF-MEMS application
No full textElectromechanical behavior of microcantilever specimens for in-plane and out-of-plane bending tests, currently designed by industry for Radio-Frequency application, are here analyzed. Main features of these two layouts are discussed. In particular, a comprehensive experimental validation of 2D and 3D numerical models implemented to predict the coupled electromechanical behavior of these microsystems is performed. Effectiveness of plane models to predict pull-in, in presence of geometric non-linearity, due to large tip displacement and initial curvature of microbeam, is investigated. Three dimensional models are then used to investigate the local effects of the electric field and the limits of the two dimensional approach. In addition, this paper investigates the effectiveness of 2D models to be used as compact numerical tools in substitution of some known Model Order Reduction techniques, which unfortunately are unsuitable to predict simultaneously the effects of both the electromechanical and geometric non-linearitie
The Block Hidden Markov Model for Biological Sequence Analysis
No full textThe Hidden Markov Models (HMMs) are widely used for biological sequence analysis because of their ability to incorporate biological information in their structure. An automatic means of optimising the structure of HMMs would be highly desirable. To maintain biologically interpretable blocks inside the HMM, we used a Genetic Algorithm (GA) that has HMM blocks in its coding representation. We developed special genetics operations that maintain the useful HMM blocks. To prevent over-fitting a separate data set is used for comparing the performance of the HMMs to that used for the Baum-Welch training. The performance of this algorithm is applied to finding HMM structures for the promoter and coding region of C. jejuni. The GA-HMM was capable of finding a superior HMM to a hand-coded HMM designed for the same task which has been published in the literature
GH and the cardiovascular system: an update on a topic at heart
No full textIn this review, the importance of growth hormone (GH) for the maintenance of normal cardiac function in adult life is discussed. Physiological effects of GH and underlying mechanisms for interactions between GH and insulin-like growth factor I (IGF-I) and the cardiovascular system are covered as well as the cardiac dysfunction caused both by GH excess (acromegaly) and by GH deficiency in adult hypopituitary patients. In both acromegaly and adult GH deficiency, there is also increased cardiovascular morbidity and mortality possibly linked to aberrations in GH status. Finally, the status of the GH/IGF-I system in relation to heart failure and the potential of GH as a therapeutic tool in the treatment of heart failure are reviewed in this article. © 2014 The Author(s)
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