1,827 research outputs found
Obtenção de um modelo de elementos finitos simplificado para representação de juntas rebitadas em análise dinâmica de estruturas usando uma ferramenta de updating
Get PDFResumoNeste artigo é proposto um modelo de elementos finitos simplificado para representação de juntas rebitadas em análise dinâmica de estruturas. O rebite é modelado com elementos que combinam mola e amortecedor. Vários modelos numéricos são estudados com diferentes quantidades de rebites (um, 2, 3 e 5) e diferentes quantidades de elementos mola‐amortecedor (4, 6, 8, 12, 16 e 20) por cada rebite. Amostras constituídas por 2 placas de alumínio ligadas entre si por diferentes quantidades de rebites (um, 2, 3 e 5) são construídas e submetidas a análise modal experimental, a fim de serem conhecidas as suas características modais – frequências naturais e formas naturais de vibração. É usada uma metodologia de melhoramento de modelos de elementos finitos, também conhecido na linguagem anglo‐saxónica por updating, com o fim de obter a melhor representação numérica da junta rebitada relativamente às amostras experimentais. Uma avaliação da melhor representação numérica da junta rebitada é efetuada com base na comparação entre as frequências naturais experimentais e as frequências naturais numéricas, para cada modo de vibração, após aplicação do processo de melhoramento de elementos finitos. Mostra‐se que o modelo de junta composto por 8 e 12 elementos mola‐amortecedor por rebite consegue uma melhor aproximação ao comportamento dinâmico observado experimentalmente. Um valor numérico da constante de rigidez é obtido para as juntas em estudo.AbstractIn this paper, a simplified finite element model to represent a riveted lap joint in structural dynamic analysis field is proposed. The rivet is modeled by spring‐damper combination elements. Several numerical models are studied with different quantities of rivets (1, 2, 3 and 5) and spring‐damper combination elements (4, 6, 8, 12, 16 and 20) per rivet. Experimental samples of two aluminum material plates connected by different quantities of rivets (1, 2, 3 and 5) are built and tested in order to be known its modal characteristics ‐ natural frequencies and mode shapes. A finite element model updating methodology is used in order to get the best numerical riveted lap joint representation relatively to the experimental samples. An evaluation of the best numerical riveted lap joint is carried out based on the comparison between the experimental and numerical resonance frequencies after updating. It is shown that the riveted lap joints composed by eight and twelve spring‐damper combination elements per rivet have the best representation. A stiffness constant value is obtained for the riveted lap joints in stud
Nata organisms: an overview on the fermentative microbial ecosystem
Get PDFPublicado em "Abstracts of papers - American Chemical Society", vol. 245The Acetobacter and Gluconacetobacter genus (both from the Acetobacteraceae family) are the most notable acetic acid producers, their intermediate metabolites being exploited biotechnologicaly for the production of vinegar, Kombucha, cocoa and nata de coco.
Extensive efforts are being made to better understand the dynamic interplay of microbial populations during fermentation processes, with ample literature existing on virtually every food product currently being consumed. In the case of nata de coco, Gluconacetobacter strains have been found to play a key role in cellulose production. Despite abundant literature with isolated cellulose−producing strains, little work has been done in analysing population dynamics of the microbial communities. This presentation will address the microbial interplay in the production of nata de coco, with an overview of the taxonomy of the major acetic acid strains involved. An overview on the efforts and potential implications of upgrading nata de coco production through biotechnology will also be addressed
Bacterial cellulose from lab to market
Get PDFBook of Abstracts of CEB Annual Meeting 2017Bacterial nanocellulose (BNC) is a nanofibrilar exopolysaccharide synthesized by certain Gram-negative, obligate aerobic, acetic acid bacteria, the Komagataeibacter genus being the most important due to the high cellulose yield obtained. The unique properties of this biopolymer have supported a wide range of potential applications, in human and veterinary medicine, odonthology, pharmaceutical industry, acoustic and filter membranes, biotechnological devices and in the food and paper industry. The largescale production of BNC, through advanced biotechnology has eluded many researches. Historical attempts but on low volume and high-value (mostly for biomedical applications) production can be traced back to the 90s. This presentation will show the main work with BNC by the Funcarb group. Examples of these studies will include the use of BNC in biomedical and food applications. Finally, an overview on the main efforts towards the production of BNC at large scale and potential markets will also be presented.info:eu-repo/semantics/publishedVersio
Bacterial NanoCellulose: what future?
Get PDFAcetic acid bacteria (AAB) have been used in various fermentation processes. Of several ABB, the bacterial nanocellulose (BNC) producers, notably Komagataeibacter xylinus, appears as an interesting species, in large part because of their ability in the secretion of cellulose as nano/microfibrils. In fact, BNC is characterized by a native nanofibrillar structure, which may outperform the currently used celluloses in the food industry as a promising novel hydrocolloid additive. During the last couple of years, a number of companies worldwide have introduced some BNC-based products to the market. The main aim of this editorial is to underline the BNC potentials.info:eu-repo/semantics/publishedVersio
A spin-offs journey into achieving marketable products from bacterial cellulose
Get PDF[Excerpt] Academic spin-offs, technological ventures born inside Universities, have increasingly strengthen the connections between the scholarship and the economy, by fostering the role of technology transfer and knowledge commercialization. This presentation will outline the major steps in taking an idea or a technology to market, growing the venture and aiming at securing a successful exit. Also, it will present BCTechnologies (Bacterial Cellulose Technologies), a spin-off from the University of Minho (Portugal). (...
Effect of cellulase adsorption on the surface and interfacial properties of cellulose
Get PDFThe surface properties of several purified cellulose (Sigmacell 101, Sigmacell 20,
Avicel pH 101, andWhatman CF 11) were characterised, before and after cellulase adsorption.
The following techniques were used: thin-layer wicking (except for the cellulose Whatman),
thermogravimetry, and differential scanning calorimetry (for all of the above celluloses). The
results obtained from the calorimetric assays were consistent with those obtained from thinlayer
wicking – Sigmacell 101, a more amorphous cellulose, was the least hydrophobic of
the analysed celluloses, and had the highest specific heat of dehydration. The other celluloses
showed less affinity for water molecules, as assessed by the two independent techniques. The
adsorption of protein did not affect the amount of water adsorbed by Sigmacell 101. However,
this water was more strongly adsorbed, since it had a higher specific heat of dehydration. The
more crystalline celluloses adsorbed a greater amount of water, which was also more strongly
bound after the treatment with cellulases. This effect was more significant for Whatman
CF-11. Also, the more crystalline celluloses became slightly hydrophilic, following protein
adsorption, as assessed by thin-layer wicking. However, this technique is not reliable when
used with cellulase treated celluloses.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - Project INTERREGII/BM/03/REGII/3/97
Properties and recycling of covalently immobilized glycanases used for aqueous enzyme assisted Rosa mosqueta oil extraction
Get PDF2nd International Conference on Protein Stabilisation - From Molecular Interpretation to Bio-Industrial Applicationsinfo:eu-repo/semantics/publishedVersio
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