Force system evaluation of symmetrical beta-titanium T-loop springs preactivated by curvature and concentrated bends

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

DM particles: how warm they can be?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

On the dynamics of free and excited oscillations of a simple portal frame foundation

In this paper we search for the dynamics of a simple portal structure in the free and in the periodic excitation cases. By using the Center Manifold approach and Averaging Method, we obtain results on both stability and bifurcation of equilibrium points and periodic orbits. (C) 2005 Elsevier Ltd. All rights reserved.

A comment on a nonideal centrifugal vibrator machine behavior with soft and hard springs

This paper concerns a type of rotating machine (centrifugal vibrator), which is supported on a nonlinear spring. This is a nonideal kind of mechanical system. The goal of the present work is to show the striking differences between the cases where we take into account soft and hard spring types. For soft spring, we prove the existence of homoclinic chaos. By using the Melnikov's Method, we show the existence of an interval with the following property: if a certain parameter belongs to this interval, then we have chaotic behavior; otherwise, this does not happen. Furthermore, if we use an appropriate damping coefficient, the chaotic behavior can be avoided. For hard spring, we prove the existence of Hopf's Bifurcation, by using reduction to Center Manifolds and the Bezout Theorem (a classical result about algebraic plane curves).

On saturation control of a non-ideal vibrating portal frame foundation type shear-building

In this paper, we examine the nonlinear control method based on the saturation phenomenon and of systems coupled with quadratic nonlinear ties applied to a shear-building portal plane frame foundation that supports an unbalanced direct cut-rent with limited power supply (non-ideal system). We analyze the equations of motion by using the method of averaging and numerical simulation. The interaction of the non-ideal structure with the saturation controller may lead to the occurrence of interesting phenomena during the forward passage through the several resonance states of the systems. Special attention is focused on passage through resonance when the non-ideal excitation frequency is near the portal frame natural frequency and when the non-ideal system frequency is approximately twice the controller frequency (two-to-one internal resonance).

Food and dietary fiber intake by children with or without constipation. Assessment according to the food guide pyramid and the American Health Foundation (AHF)

We studied the ingestion of 54 children with functional constipation (CC) and 41 without (Control), according to the Food Pyramid. A food frequency questionnaire was used, analyzing fruits with or without peel/bagasse, grains whole or refined, and beans separately. Total subjects and 2-6y CC ingested less DF (g/day) than Control (p < 0.05). The majority had high n degrees of dairy and of the meat group servings, but most groups/subgroups did not meet recommendation for fruit and vegetable. A greater proportion of fruit with peel/bagasse in Control than in CC was almost the only difference for 6-12y. There was a discrepancy between the high percentage of children with DF above AHF recommendation and the high percentage of children who did not meet Pyramid recommendations.

Photoelastic analysis of forces generated by T-loop springs made with stainless steel or titanium-molybdenum alloy

Introduction: The purpose of this study was to use photoelastic analysis to compare the system of forces generated by retraction T-loop springs made with stainless steel and titanium-molybdenum alloy (TMA) (Ormco, Glendora, Calif) with photoelastic analysis. Methods: Three photoelastic models were used to evaluate retraction T-loop springs with the same preactivations in 2 groups. In group 1, the loop was constructed with a stainless steel wire, and 2 helicoids were incorporated on top of the T-loop; in group 2, it was made with TMA and no helicoids. Results: Upon using the qualitative analysis of the fringe order in the photoelastic model, it was observed that the magnitude of force generated by the springs in group 1 was significantly higher than that in group 2. However, both had symmetry for the active and reactive units related to the system of force. Conclusions: Both springs had the same mechanical characteristics. TMA springs showed lower force levels. (Am J Orthod Dentofacial Orthop 2011;140:e123-e128)

Curvature versus V-bends in a group B titanium T-loop spring

Objective: To compare the system of forces acting on curvature and preactivated V-bends in titanium T-loop springs (TTLSs) made of 0.017- X 0.025-inch TMA (titanium molibdenium alloy) wire.Materials and Methods: Pictures of TTLSs preactivated by curvature and V-bends were inserted in the LOOP software program to design both TTLSs. Symmetry was assured using the program. Both TTLSs used the same amount (length) of wire and had the same angulation between their anterior and posterior extremities when passive. The loops were activated 7 mm, and forces and moments were registered after each 0.5 mm of deactivation. The brackets were at the same height, separated by 23 mm and angulated 0 degrees.Results: The preactivated curvature TTLS delivered horizontal forces ranging from 34 gF to 456 gF, while the TTLS preactivated by V-bends delivered forces ranging from 54 gF to 517 gF. The forces decreased more (30 gF vs 33 gF) with every 0.5 mm of activation on the preactivated V-bend TTLS than on the preactivated curvature TTLS. Vertical forces were low and clinically insignificant for both TTLSs. The moment to force (MF) ratios were systematically higher on the preactivated curvature than on the preactivated V-bend TTLS (from 5.8 mm to 38.8 mm vs 4.7 mm to 28.3 mm).Conclusions: Although both loops show symmetrical moments in their anterior and posterior extremities and can be used for group B anchorage, the curvature preactivated TTLS delivers lower horizontal forces and higher MF ratios than the acute preactivated V-bend TTLS.

Optimizing the design of preactivated titanium T-loop springs with Loop software

ATMA (Ormco Corp, Glendora, Calif) T-loop spring (TTLS), preactivated with a gable bend distal to the loop, holds promise for producing controlled tipping of the canines and translation of the posterior segment. However, there is currently no consensus as to where the preactivated gable bend or the loop should be placed, what the height of the loop should be, or how the interbracket distance changes the moments produced. Using the Loop software program (dHal, Athens, Greece), we systematically modified a .017 x .025-in TTLS (10 x 6 mm) that was preactivated with a 45 degrees gable bend distal to the loop, and simulated the effects. As the gable bend was moved posteriorly, the moment increased at the posterior bracket more than it decreased at the anterior bracket. As the loop was brought closer to the anterior bracket, the posterior moment decreased at the same rate that it increased anteriorly. As the loop was increased in size, the moments increased both posteriorly and anteriorly. As the interbracket distance increased, the posterior moment decreased, and the anterior moment remained constant. We concluded that the size of the loop should be slightly increased, to 10 x 7 mm, and it should be placed 2 mm from the anterior bracket, with a preactivation bend of 45 degrees, 4 to 5 mm from the posterior bracket (after 4 mm of activation).

Warm asymmetric matter in the quark-meson coupling model

In this work we study the warm equation of state of asymmetric nuclear matter in the quark-meson coupling model which incorporates explicitly quark degrees of freedom, with quarks coupled to scalar, vector, and isovector mesons. Mechanical and chemical instabilities are discussed as a function of density and isospin asymmetry. The binodal section, essential in the study of the liquid-gas phase transition is also constructed and discussed. The main results for the equation of state are compared with two common parametrizations used in the nonlinear Walecka model and the differences are outlined.

On Nonlinear Dynamics and Control of A Particular Portal Frame Foundation Model, Excited by a Non-Ideal Motor

The nonlinear dynamic response and a nonlinear control method of a particular portal frame foundation for an unbalanced rotating machine with limited power (non-ideal motor) are examined. Numerical simulations are performed for a set of control parameters (depending on the voltage of the motor) related to the static and dynamic characteristics of the motor. The interaction of the structure with the excitation source may lead to the occurrence of interesting phenomena during the forward passage through the several resonance states of the systems. A mathematical model having two degrees of freedom simplifies the non-ideal system. The study of controlling steady-state vibrations of the non-ideal system is based on the saturation phenomenon due to internal resonance.

Microstructure evolution during warm deformation of low carbon steel with dispersed cementite

The microstructure evolution and mechanical behavior during large strain of a 0.16%C-Mn steel has been investigated by warm torsion tests. These experiments were carried out at 685°C at equivalent strain rate of 0.1 s . The initial microstructure composed of a martensite matrix with uniformly dispersed fine cementite particles was attained by quenching and tempering. The microstructure evolution during tempering and straining was performed through interrupted tests. As the material was reheated to testing temperature, well-defined cell structure was created and subgrains within lath martensite were observed by TEM; strong recovery took place, decreasing the dislocation density. After 1 hour at the test temperature and without straining, EBSD technique showed the formation of new grains. The flow stress curves measured had a peculiar shape: rapid work hardening to a hump, followed by an extensive flow-softening region. 65% of the boundaries observed in the sample strained to ε = 1.0 were high angle grain boundaries. After straining to ε = 5.0, average ferrite grain size close to 1.5 μm was found, suggesting that dynamic recrystallization took place. Also, two sets of cementite particles were observed: large particles aligned with straining direction and smaller particles more uniformly dispersed. The fragmentation or grain subdivision that occurred during reheating and tempering time was essential for the formation of ultrafine grained microstructure.

Dynamic exercise versus tag game warm up: The acute effect on agility and vertical jump in children

Although dynamic and stretching exercises have been widely investigated, there is little information about warm up performed by tag games. Thus, the purpose of the present study was to verify the acute effect of dynamic exercises compared to a tag game warm up on agility and vertical jump in children. 25 boys and 24 girls participated in this study and performed the agility and vertical jump tests after warm up based on dynamic exercises or as a tag game lasting 10 min each in two different days randomly. Dynamic exercises warm up consisted in a run lasting 2.5 min followed by 2 series of 8 dynamic exercises lasting 10 seconds each interspersed with 20s of light run to recovery. Tag game warm up was performed by a tag game with two variations lasting 5 min each. The first variation there was a single cather, which aimed to get the other participants by touching hands. In the second part of the game, the rules were the same except that the participant that was caught had to help the catcher forming a team of catchers. Warm up intensity was monitored by OMNI perceived exertion scale. ANOVA 2x2 for repeated measures (Warm up x Sex) demonstrated no significant differences between dynamic exercises and tag game for agility and vertical jump (P>0.05) for boys and girls. Perceived exertion was significantly higher in tag game compared to dynamic exercises on girls (P<0.05). Both warm up models showed similar acute effects on agility and vertical jump in children. © Faculty of Education. University of Alicante.

Anatomia radicial de Mormodes sinuata Rchb. f. & Warm.; (Catasetinae, Cymbidieae: Orchidaceae)

Since there is a lack of information on the root organization of the sub-tribe Catasetinae, current research describes the anatomy of Mormodes sinuata roots and indicate adaptations related to water provision and other taxonomical traits. Five roots of three plants, cut at the median region with a blade, were fixed and preserved in alcohol 5%. Cuts were stained by saffron blue 0.05% and mounted in glycerin. Although the roots have structural characteristics adapted to epiphytism, some anatomic characteristics demonstrate that the species requires more watering or wetter environments when compared with other types of Catasetinae. Root anatomic characteristics foreground results by authors who include the sub-tribe Catasetinae within the tribe Cymbidieae. Further, anatomic characteristics have a generic uniformity and are a tool for the genus's systematics.

Rendimento operacional de uma serraria com a espécie Cambará (Qualea albiflora Warm.) na região Amazônica

Pós-graduação em Ciência Florestal - FCA