Erika Almeida - Academia.edu (original) (raw)
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Papers by Erika Almeida
Anais do XXVI Simpósio Brasileiro de Telecomunicações, 2008
Resumo-O sensoriamento de espectro é uma das etapas principais de funcionamento das redes de rádi... more Resumo-O sensoriamento de espectro é uma das etapas principais de funcionamento das redes de rádio cognitivo. Neste artigo, o sensoriamento de espectro é investigado através de uma técnica de detecção de energia com a utilização de wavelets. Para analisar a confiabilidade da técnica, foram realizadas medidas na faixa de radiodifusão FM (98MHz) e na faixa de 800MHz. Por fim, modificações na técnica original de detecção foram propostas a fim de melhorar o desempenho do algoritmo em situações reais. Palavras-Chave-Rádio cognitivo, sensoriamento de espectro, detecção de energia e transformada wavelet .
Sisal cellulose: characterization and acetylation of samples previously treated with alkali solut... more Sisal cellulose: characterization and acetylation of samples previously treated with alkali solution, ionized air or microwave In the present work, it was investigated the acetylation of sisal cellulose (untreated, mercerized, treated with ionized air or microwave) under homogeneous conditions, using the solvent system N,N-dimethylacetamide/lithium cloride. Before derivatization, fibres were characterized by X-ray diffraction, viscosimetry (average molar mass) and -cellulose content. It was shown that the treatments, mainly mercerization, induced changes in the cellulose. The acetylation degree (DS) of these samples was lower than that expected considering the stoichiometry between acetic anhydride and glycose unit (DS = 1,5) Introdução A celulose é o material proveniente de fonte vegetais mais abundante da terra, constituindo o esqueleto das plantas. O sisal (Agave sisalana), é originário do México. O Brasil é o maior produtor mundial de sisal, representando 62,5% da produção mundi...
Lasers in Medical Science, 2012
Step-stress accelerated life testing (SSALT) and fractographic analysis were performed to evaluat... more Step-stress accelerated life testing (SSALT) and fractographic analysis were performed to evaluate the reliability and failure modes of dental implant fabricated by machining (surface treated with alumina blasting/acid etching) or laser sintering for anterior single-unit replacements. Forty-two dental implants (3.75×10 mm) were divided in two groups (n021 each): laser sintered (LS) and alumina blasting/acid etching (AB/AE). The abutments were screwed to the implants and standardized maxillary central incisor metallic crowns were cemented and subjected to SSALT in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized light and scanning electron microscopes were used for failure analyses. The Beta (β) value derived from use-level probability Weibull calculation of 1.48 for group AB/AE indicated that damage accumulation likely was an accelerating factor, whereas the β of 0.78 for group LS indicated that load alone likely dictated the failure mechanism for this group, and that fatigue damage did not appear to accumulate. The reliability was not significantly different (p>0.9) between AB/AE (61 %) and LS (62 %). Fracture of the abutment and fixation screw was the chief failure mode. No implant fractures were observed. No differences in reliability and fracture mode were observed between LS and AB/AE implants used for anterior singleunit crowns.
Anais do XXVI Simpósio Brasileiro de Telecomunicações, 2008
Resumo-O sensoriamento de espectro é uma das etapas principais de funcionamento das redes de rádi... more Resumo-O sensoriamento de espectro é uma das etapas principais de funcionamento das redes de rádio cognitivo. Neste artigo, o sensoriamento de espectro é investigado através de uma técnica de detecção de energia com a utilização de wavelets. Para analisar a confiabilidade da técnica, foram realizadas medidas na faixa de radiodifusão FM (98MHz) e na faixa de 800MHz. Por fim, modificações na técnica original de detecção foram propostas a fim de melhorar o desempenho do algoritmo em situações reais. Palavras-Chave-Rádio cognitivo, sensoriamento de espectro, detecção de energia e transformada wavelet .
Sisal cellulose: characterization and acetylation of samples previously treated with alkali solut... more Sisal cellulose: characterization and acetylation of samples previously treated with alkali solution, ionized air or microwave In the present work, it was investigated the acetylation of sisal cellulose (untreated, mercerized, treated with ionized air or microwave) under homogeneous conditions, using the solvent system N,N-dimethylacetamide/lithium cloride. Before derivatization, fibres were characterized by X-ray diffraction, viscosimetry (average molar mass) and -cellulose content. It was shown that the treatments, mainly mercerization, induced changes in the cellulose. The acetylation degree (DS) of these samples was lower than that expected considering the stoichiometry between acetic anhydride and glycose unit (DS = 1,5) Introdução A celulose é o material proveniente de fonte vegetais mais abundante da terra, constituindo o esqueleto das plantas. O sisal (Agave sisalana), é originário do México. O Brasil é o maior produtor mundial de sisal, representando 62,5% da produção mundi...
Lasers in Medical Science, 2012
Step-stress accelerated life testing (SSALT) and fractographic analysis were performed to evaluat... more Step-stress accelerated life testing (SSALT) and fractographic analysis were performed to evaluate the reliability and failure modes of dental implant fabricated by machining (surface treated with alumina blasting/acid etching) or laser sintering for anterior single-unit replacements. Forty-two dental implants (3.75×10 mm) were divided in two groups (n021 each): laser sintered (LS) and alumina blasting/acid etching (AB/AE). The abutments were screwed to the implants and standardized maxillary central incisor metallic crowns were cemented and subjected to SSALT in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized light and scanning electron microscopes were used for failure analyses. The Beta (β) value derived from use-level probability Weibull calculation of 1.48 for group AB/AE indicated that damage accumulation likely was an accelerating factor, whereas the β of 0.78 for group LS indicated that load alone likely dictated the failure mechanism for this group, and that fatigue damage did not appear to accumulate. The reliability was not significantly different (p>0.9) between AB/AE (61 %) and LS (62 %). Fracture of the abutment and fixation screw was the chief failure mode. No implant fractures were observed. No differences in reliability and fracture mode were observed between LS and AB/AE implants used for anterior singleunit crowns.