Hysteresis in transverse galloping: the role of the inflection points

Transverse galloping is here considered as a one-degree-of-freedom oscillator subjected to aerodynamic forces, which are described by using the quasi-steady hypothesis. The hysteresis of transverse galloping is also analyzed. Approximate solutions of the model are obtained by assuming that the aerodynamic and damping forces are much smaller than the inertial and stiffness ones. The analysis of the approximate solution, which is obtained by means of the method of Krylov–Bogoliubov, reveals the existing link between the hysteresis phenomenon and the number of inflection points at the aerodynamic force coefficient curve, Cy(α)Cy(α); CyCy and αα being, respectively, the force coefficient normal to the incident flow and the angle of attack. The influence of the position of these inflection points on the range of flow velocities in which hysteresis takes place is also analyzed.

Inflection and stability points of diphasic logistic analysis of growth

Growth functions with inflection points following a diphasic model, can be adjusted by two approaches using segmented regression or the sum of two functions. In both cases, there are two functions, one for each phase, with inflection and stability points. However, when they are summed, the result is a new function and the points of inflection and stability are different from those obtained from using each function individually. A method to determine these points in a diphasic logistics sum of functions is suggested and the results obtained from fitting the models to eucalyptus growth data showed a better fit of the logistic diphasic sum as compared with segmented regression and monophasic logistic models.

Noise-spike-induced escape in a bistable system driven by colored noise: Noise with long correlation times

An escape mechanism in a bistable system driven by colored noise of large but finite correlation time (tau) is analyzed. It is shown that the fluctuating potential theory [Phys. Rev. A 38, 3749 (1988)] becomes invalid in a region around the inflection points of the bistable potential, resulting in the underestimation of the mean first passage time at finite tau by this theory. It is shown that transitions at large but finite tau are caused by noise spikes, with edges rising and falling exponentially in a time of O(tau). Simulation of the dynamics of the bistable system driven by noise spikes of the above-mentioned nature clearly reveal the physical mechanism behind the transition.

Nanoparticle agglomeration in an evaporating levitated droplet for different acoustic amplitudes

Radiatively heated levitated functional droplets with nanosilica suspensions exhibit three distinct stages namely pure evaporation, agglomeration, and finally structure formation. The temporal history of the droplet surface temperature shows two inflection points. One inflection point corresponds to a local maximum and demarcates the end of transient heating of the droplet and domination of vaporization. The second inflection point is a local minimum and indicates slowing down of the evaporation rate due to surface accumulation of nanoparticles. Morphology and final precipitation structures of levitated droplets are due to competing mechanisms of particle agglomeration, evaporation, and shape deformation. In this work, we provide a detailed analysis for each process and propose two important timescales for evaporation and agglomeration that determine the final diameter of the structure formed. It is seen that both agglomeration and evaporation timescales are similar functions of acoustic amplitude (sound pressure level), droplet size, viscosity, and density. However, we show that while the agglomeration timescale decreases with initial particle concentration, the evaporation timescale shows the opposite trend. The final normalized diameter can be shown to be dependent solely on the ratio of agglomeration to evaporation timescales for all concentrations and acoustic amplitudes. The structures also exhibit various aspect ratios (bowls, rings, spheroids) which depend on the ratio of the deformation timescale (t(def)) and the agglomeration timescale (t(g)). For t(def) < t(g), a sharp peak in aspect ratio is seen at low concentrations of nanosilica which separates high aspect ratio structures like rings from the low aspect ratio structures like bowls and spheroids. (C) 2013 American Institute of Physics. http://dx.doi.org/10.1063/1.4775791]

An allometric smoothing function to describe the relation between otolith and somatic growth over the lifespan of walleye pollock (Theragra chalcogramma)

We propose a new equation to describe the relation between otolith length (OL) and somatic length (fork length [FL]) of fish for the entire lifespan of the fish. The equation was developed by applying a mathematical smoothing method based on an allometric equation with a constant term for walleye pollock (Theragra chalcogramma) —a species that shows an extended longevity (>20 years). The most appropriate equation for defining the relation between OL and FL was a four-phase allometric smoothing function with three inflection points. The inflection points correspond to the timing of settlement of walleye pollock, changes in sexual maturity, and direction of otolith growth. Allometric smoothing functions describing the relation between short otolith radius and FL, long otolith radius and FL, and FL and body weight were also developed. The proposed allometric smoothing functions cover the entire lifespan of walleye pollock. We term these equations “allometric smoothing functions for otolith and somatic growth over the lifespan of walleye pollock.”

柴达木盆地西区新生代构造演化

The Qaidam Basin constitutes a major portion of the northeastern Tibetan Plateau, and an understanding of its tectonic development will help decipher how the Tibetan Plateau was formed. It is shown that Late Cretaceous–Paleocene deposits of the western Qaidam Basin can be well correlated with their counterparts of the southwestern Tarim Basin, implying that the two regions were originally connected or were in the same depositional basin during that period of time. The Qaidam Basin commenced subsiding due to crustal shortening in the Eocene, and it has subsequently evolved into an independent basin since the Miocene. The main depocenter was noticeably persistent in the middle of the western Qaidam Basin from Eocene to Miocene time, and then it shifted to the east. On the basis of spatial stratigraphic correlation and restoration of sedimentary processes, we surmise that there existed a proto–Qaidam Basin during the Paleogene, where the Suhai and Kumukol Basins represent its northern and southern margins, respectively. The Suhai and Kumukol Basins were subsequently isolated from the Qaidam Basin as a result of basinward thrusting in basin-margin areas. It is shown that the western Qaidam Basin experienced three distinct stages: the first stage was characterized by a simple synclinal depression; the second stage was marked by occurrence of reverse faults at inflection points of the megafold and continuous subsidence in the middle of the basin; and the third stage featured intrabasinal deformation and uplift. The eastern Qaidam Basin underwent a diverse evolution and became the main depositional area in the Quaternary. It is suggested that the Qaidam Basin should be generated as a result of crustal buckling or folding, manifesting itself as a synclinal depression. The crustal folding model can account for a number of observations, including localization of the depocenter in the middle of the basin, nearly concomitant deformation on the south and north sides of the Qaidam Basin, occurrence of major high-angle reverse faults at basin margins, and generation of adjacent intermontane Suhai and Kumukol Basins. A tectonic model is accordingly advanced to illustrate Cenozoic tectonics of the Qaidam Basin.

Estudo do processo de difusão de gases em carvões com base em isotérmicas de Langmuir

Tese de Doutoramento apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Doutror em Ciências da Terra.

Hot deformation characteristics of a nitride strengthened martensitic heat resistant steel

Constitutive equations including an Arrhenius term have been applied to analyze the hot deformation behavior of a nitride-strengthened (NS) martensitic heat resistant steel in temperature range of 900–1200 °C and strain rate range of 0.001–10 /s. On the basis of analysis of the deformation data, the stress–strain curves up to the peak were divided into four regions, in sequence, representing four processes, namely hardening, dynamic recovery (DRV), dynamic strain induced transformation (DSIT), and dynamic recrystallization (DRX), according to the inflection points in ∂θ/∂σ∂θ/∂σ and ∂(∂θ/∂σ)/∂σ∂(∂θ/∂σ)/∂σ curves. Some of the inflection points have their own meanings. For examples, the minimum of ∂θ/∂σ∂θ/∂σ locates the start of DRV and the maximum of it indicates the start of DRX. The results also showed that the critical strain of DRX was sensitive to ln(Z) below 40, while the critical stress of DRX was sensitive to it above 40. The final microstructures under different deformation conditions were analyzed in terms of softening processes including DRV, DRX, metadynamic crystallization (MDRX) and DSIT.

Expanded iron uta spectra - Probing the thermal stability limits in AGN clouds

The Fe unresolved transition arrays (UTAs) produce prominent features in the 15-17 Å wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration. © 2013. The American Astronomical Society. All rights reserved.

Perspectives on the specification of Building Integrated Photovoltaic (BIPV) technology in construction projects

Innovative, low carbon technologies are already available for use in the construction of buildings, but the impact of their specification on construction projects is unclear. This exploratory research identifies issues which arise following the specification of BIPV in non-residential construction projects. Rather than treating the inclusion of a new technology as a technical problem, the research explores the issue from a socio-technical perspective to understand the accommodations which the project team makes and their effect on the building and the technology. The paper is part of a larger research project which uses a Social Construction of Technology Approach (SCOT) to explore the accommodations made to working practices and design when Building Integrated PhotoVoltaic (BIPV) technology is introduced. The approach explores how the requirements of the technology from different groups of actors (Relevant Social Groups or RSG's) give rise to problems and create solutions. As such it rejects the notion of a rational linear view of innovation diffusion; instead it suggests that the variety and composition of the Relevant Social Groups set the agenda for problem solving and solutions as the project progresses. The research explores the experiences of three people who have extensive histories of involvement with BIPV in construction, looks at how SCOT can inform our understanding of the issues involved and identifies themes and issues in the specification of BIPV on construction projects. A key finding concerns the alignment of inflection points at which interviewees have found themselves changing from one RSG to another as new problems and solutions are identified. The points at which they change RSG often occurred at points which mirror conventional construction categories (in terms of project specification, tender, design and construction).

3-manifolds in Euclidean space from a contact viewpoint

We study the geometry of 3-manifolds generically embedded in R(n) by means of the analysis of the singularities of the distance-squared and height functions on them. We describe the local structure of the discriminant (associated to the distribution of asymptotic directions), the ridges and the flat ridges.

Endogenous liberalization and within-country inequality

We model and empirically test the link between income inequality and trade liberalization. We consider a society in which a median voter (MV) will make the decision as to whether the country should switch from its current regime of import substitution (IS) (which protects agriculture) to export promotion (EP). Liberalization entails starting importing the agricultural good and specializing in and exporting the manufacturing good. This will require transferring labor to manufacturing. We find that if MV is a worker, the IS-EP switch will take place regardless. If MV is a farmer, the switch will take place given (1) the relative productivity of an ex-farmer and worker in manufacturing,ß is high, and (2) the society’s tastes for agricultural goods, α, are not as strong as those for manufacturing goods. We also find that, following a switch, the income distribution too will improve if α is low and ß is high. In our empirical analysis, we find the endogenous inflection points of α and ß in our sample, at which the direction of change in income distribution alters its sign. Our results also show in a very robust fashion that, EP regimes - on average and with the presence of certain control variables - have better income distributions than IS regimes. This implies that mostly “right” countries have made the switch.

Teorema de Riemann-Roch e aplicações

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

O processo de construção de objetos de aprendizagem em cálculo diferencial e integral durante uma atividade de design

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo ontogênico e taxonômico das larvas de algumas espécies de peixes da região norte do Brasil

O presente estudo teve como objetivo fornecer informações sobre a descrição morfológica e ontogênica das espécies Plagioscion squamosissimus (Sciaenidae), Cynoscion acoupa (Sciaenidae), Colomesus pscitacus (Tetraodontidae) e Oligoplites palometa (Carangidae) da região norte do Brasil. Todos os indivíduos estudados foram analisados quanto à integridade de suas estruturas e posteriormente identificados. A partir da identificação para cada espécie, os indivíduos foram analisados quanto a seus caracteres morfológicos, merísticos, morfométricos. Para o estudo ontogênico foram determinados os pontos de inflexão no crescimento das estruturas estudadas, as fases de desenvolvimento e seus períodos crítico, posteriormente foi realizado um PCA para melhor visualização dos caracteres que melhor definem o crescimento larval. Os resultados indicaram que o crescimento relativo (em função do comprimento total (CT) das partes corporais estudadas seguiu alometria negativa. As três fases de desenvolvimento larval definidas em função do processo ontogênico diferiram entre espécies apesar de apresentarem similaridades na cronologia do desenvolvimento corporal. Assim o desenvolvimento inicial das quatro espécies na fase F1 favorece a porção anterior das larvas enquanto que a parte posterior do corpo apresentou maior taxa de crescimento no final da fase larval. As duas espécies da família Sciaenidae Plagioscion squamosissimus e Cynoscion acoupa apresentam diferenças na forma da boca e CT quando foram observados os primeiros dentes, com diferença também na sequencia do desenvolvimento das nadadeiras, na pigmentação na presença e localização dos espinhos e nas proporções corporais. Para Colomesus pscitacus observou-se a ocorrência de dentes ossificados logo após eclosão, nesta espécie ocorre também o precoce surgimento das nadadeiras, de pigmentação e a manutenção das relações corporais (caracterizando a forma esférica do corpo). A espécie Oligoplites palometa apresentou o padrão de desenvolvimento das nadadeiras semelhante ao descritos para outras espécies desta família o que associa-se como um padrão característico para esta família, assim como as presença da pigmentação intensa e dos espinhos na região opercular e supra-occipital.