169 research outputs found
Acoustic analysis of cement composites with lignocellulosic residues
Received: January 19th, 2021 ; Accepted: May 20th, 2021 ; Published: October 5th, 2021 ; Correspondence: [email protected] concept of environmental sustainability has been seeking a way to develop projects
that reduce the impacts provided by agricultural development and the excessive consumption of
natural resources. However, there is still little knowledge about the acoustic insulation/absorption
behaviour of lignocellulosic materials. Hence, this study aimed to evaluate the acoustic properties
of five cement panels reinforced with the following lignocellulosic materials: eucalyptus,
sugarcane bagasse, coconut shell, coffee husk, and banana pseudostem, which ones have as a
reference a commercial plaster used as sealing in civil constructions. The proposed panels were
produced with each lignocellulosic material residue. It was produced three replicates for each
type including plaster (being 18 panels in total). The sound insertion loss (SIL) measurement of
the above-mentioned panels have been performed using an acoustical treated inexpensive facility
developed based on the literature. The characterization of the acoustic behaviour of the studied
materials were analysed according to the IEC (61260-1). The acoustic measurements have been
done in the range of 20 Hz to 20 kHz and the analysis in octave bands have been performed. To
make the analysis easier, the overall range of frequencies mentioned above was divided as ‘low’,
‘middle’ and ‘high’ ranges. Additionally, the measurement of thickness, density and porosity
structure parameters of the lignocellulosic samples have been performed. According to the results
and doing a trade-off analysis, the eucalyptus presented the overall best performance considering
the overall range of analysis, being the banana pseudostem and sugarcane bagasse materials as
good competitors
The 1:1 resonance in Extrasolar Systems: Migration from planetary to satellite orbits
We present families of symmetric and asymmetric periodic orbits at the 1/1
resonance, for a planetary system consisting of a star and two small bodies, in
comparison to the star, moving in the same plane under their mutual
gravitational attraction. The stable 1/1 resonant periodic orbits belong to a
family which has a planetary branch, with the two planets moving in nearly
Keplerian orbits with non zero eccentricities and a satellite branch, where the
gravitational interaction between the two planets dominates the attraction from
the star and the two planets form a close binary which revolves around the
star. The stability regions around periodic orbits along the family are
studied. Next, we study the dynamical evolution in time of a planetary system
with two planets which is initially trapped in a stable 1/1 resonant periodic
motion, when a drag force is included in the system. We prove that if we start
with a 1/1 resonant planetary system with large eccentricities, the system
migrates, due to the drag force, {\it along the family of periodic orbits} and
is finally trapped in a satellite orbit. This, in principle, provides a
mechanism for the generation of a satellite system: we start with a planetary
system and the final stage is a system where the two small bodies form a close
binary whose center of mass revolves around the star.Comment: to appear in Cel.Mech.Dyn.Ast
Capacidade combinatória de híbridos de tomateiro de crescimento determinado, resistentes a Begomovirus e Tospovirus
O objetivo deste trabalho foi avaliar a capacidade combinatória de linhagens de tomateiro com hábito de crescimento determinado, com resistência múltipla a espécies dos gêneros Begomovirus e Tospovirus, e identificar combinações híbridas superiores. O experimento foi realizado em casa de vegetação, com 14 híbridos obtidos do cruzamento de sete linhagens femininas (grupo I) com duas linhagens masculinas (grupo II), em um dialelo parcial. As seguintes características agronômicas foram avaliadas: produção total, produção precoce, massa média de frutos, formato, firmeza inicial e firmeza na meia-vida. As linhagens genitoras TOM-680 e TOM-682, do grupo I, se destacaram por exibir as maiores estimativas de capacidade geral de combinação (CGC) quanto às características produção total, produção precoce e massa média de frutos, enquanto a linhagem TOM-585 se destacou quanto aos maiores valores de produção total e massa média de frutos. No grupo II, a linhagem TOM-698 apresentou estimativas superiores de CGC para as características de produção total, produção precoce, massa média dos frutos e firmeza inicial dos frutos. O híbrido TOM-682xTOM-698 apresenta as maiores estimativas de capacidade geral e específica de combinação para produção total, produção precoce e meia-vida da firmeza, e é o genótipo mais promissor entre os materiais testados
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