Discontinuous Evolution Research Articles

Identifying and Tracking Solar Photospheric Bright Points Based on Three-dimensional Segmentation Technology

Photospheric bright points (PBPs) are tiny short-lived brightening phenomena that can be seen within dark inter-granular lanes. In this paper, we develop a new method to identify and track a PBP in a 3D space-time cube. Different from the common-adopted strategy of “identifying-before-tracking”, this algorithm is based on the strategy of “identifying-by-tracking”. This method can identify a PBP when its intensity is still rather weak, and can avoid the discontinuous evolution of PBP caused by the algorithm of Laplacian morphological dilation (LMD) to recognize completely the evolutionary process of a PBP. The statistics on a group of G-band data observed by Hinode/SOT (Solar Optical Telescope) in quiet regions indicate that the average lifetime of isolated PBP is as long as 3minutes, and the longest lifetime is up to 27minutes, which means that the lifetime of PBPs is longer than that obtained by the previous LMD algorithm. Furthermore, it is also found that the mean intensity contrast of PBPs is 1.02 times of the mean photospheric intensity, which is weaker than that calculated by the LMD algorithm, and that the intensity of PBP exhibits a periodical oscillation of 2∼3minute during the whole lifetime.

Energetic formulation for rate-independent processes: remarks on discontinuous evolutions with a simple example

This work aims to discuss, in the simplest way, some open issues concerning the energetic formulation for the modeling of rate-independent processes by means of a simple one-dimensional example. Early and unphysical jumps are avoided taking advantage of a time reparametrization and enforcing an energy imbalance during time-discontinuous transitions. A new energetic selective criterion is then proposed, able to predict the final state after a jump and to represent intrinsically the energy contribution of rate-dependent phenomena as inertia and viscosity that may arise during fast discontinuous transitions. An improved version of the energetic formulation is finally proposed, preserving completely the rate-independent setting. All concepts and results are accompanied by explicative pictures which, hopefully, will help the non-specialist reader, to whom this paper is addressed, in the understanding of the discussion.

Sequence of the Gonium pectorale Mating Locus Reveals a Complex and Dynamic History of Changes in Volvocine Algal Mating Haplotypes.

Sex-determining regions (SDRs) or mating-type (MT) loci in two sequenced volvocine algal species, Chlamydomonas reinhardtii and Volvox carteri, exhibit major differences in size, structure, gene content, and gametolog differentiation. Understanding the origin of these differences requires investigation of MT loci from related species. Here, we determined the sequences of the minus and plus MT haplotypes of the isogamous 16-celled volvocine alga, Gonium pectorale, which is more closely related to the multicellular V. carteri than to C. reinhardtii. Compared to C. reinhardtii MT, G. pectorale MT is moderately larger in size, and has a less complex structure, with only two major syntenic blocs of collinear gametologs. However, the gametolog content of G. pectorale MT has more overlap with that of V. carteri MT than with C. reinhardtii MT, while the allelic divergence between gametologs in G. pectorale is even lower than that in C. reinhardtii. Three key sex-related genes are conserved in G. pectorale MT: GpMID and GpMTD1 in MT–, and GpFUS1 in MT+. GpFUS1 protein exhibited specific localization at the plus-gametic mating structure, indicating a conserved function in fertilization. Our results suggest that the G. pectorale–V. carteri common ancestral MT experienced at least one major reformation after the split from C. reinhardtii, and that the V. carteri ancestral MT underwent a subsequent expansion and loss of recombination after the divergence from G. pectorale. These data begin to polarize important changes that occurred in volvocine MT loci, and highlight the potential for discontinuous and dynamic evolution in SDRs.

Spatial and temporal evolution of tectonometamorphic discontinuities in the central Himalaya: Constraints from P–T paths and geochronology

Recent studies evoke dispute whether the Greater Himalayan Crystalline Complex (GHC) was exhumed during more than one phase. This contribution investigates the timing of ductile shear along the South Tibetan Detachment (STD), Main Central Thrust (MCT), and hidden discontinuities within the GHC of the central Himalaya. New data from the Nyalam transect, southern Tibet, suggest that ductile shear along the STD was active from ~27–25Ma to ~17–15Ma, whereas ductile shear along the MCT was active from ~19–16Ma to ~10–8Ma. Pseudosection modeling results and published metamorphic ages indicate a P–T–t path discontinuity within the GHC and the upper GHC reached higher peak metamorphic temperatures (ΔT 100°C), similar peak pressures and older metamorphic ages (~5–10Myr), in favor of the presence of the Nyalam Discontinuity. Summarized results from literature suggest that timing of ductile shear along the STD was ~5–10Myr earlier than that along the MCT across the Nepal, Sikkim and Bhutan Himalayas. In addition, the GHC in Nepal can be separated into two portions by a regional-scale (>800km) in-sequence ductile shear zone — the High Himalayan Discontinuity. This shear zone was active coevally with the STD during 25–16Ma, but ~5–10Myr earlier than the MCT. The High Himalayan Discontinuity could possibly extend to the Sikkim Himalayas, but ends in Bhutan. The identified new architecture suggests that both in-sequence and out-of-sequence tectonometamorphic discontinuities are important components that formed the duplexing structure of the GHC in the central and eastern Himalaya, thus calling for more sophisticated numerical simulation than the current models such as the channel flow and critical taper.

Acquisition-type or merger-type accounting? Further insights on transactions involving businesses governed by the same party(-ies)

This paper - aiming at encouraging a fruitful debate - intends to highlight the discontinuous evolution of the accounting solutions explored by notable bodies (Efrag-Oic, Iasb, Fasb, Kasb, etc.) with reference to transactions involving businesses under common control. The work finally recompose them in two basic categories (discussing their pros/cons as well), here analyzed: acquisition-type accounting, which emphasizes fair value (emergence of exchange or current amounts) vs. merger-type accounting, linked to historical costs (continuity values approach). The first cluster includes the pure-acquisition and the fresh-start method, whereas the second the predecessor basis and the pooling of interests techniques. The concrete identification of the proper methodology, in this regard, essentially requires the profound understanding of the underlying economics, architecture and key elements of a specific transaction shedding light on the most relevant and reliable information useful to stakeholders.

2D coupled HM-XFEM modeling with cohesive zone model and applications to fluid-driven fracture network

The present work focuses on a new numerical model for the fully coupled hydro-mechanical analysis of groundwater flows through poroelastic saturated media. In particular, the presence and eventual propagation of fluid-driven fractures is accounted for within a non-regularized cohesive zone model. In this paper, the fracture propagation is considered as a reactivation process: the fracture already exists and evolves (i.e. opens or closes) on a pre-defined path initially constrained. The Talon-Curnier constitutive law is considered for the fracture interfaces and its expression has been adapted to the hydro-mechanical coupling related to the fracture evolution. The fluid pressure inside the fracture is governed by the lubrication equation. The momentum-stress balance equations involving fluid flow and deformation of the solid porous matrix are derived within the framework of the generalized Biot theory. The extended finite element method (XFEM) is preferred to a standard finite element spatial discretization in order to easily handle the presence and evolution of discontinuities in the porous medium. A set of four Lagrange multipliers is introduced to prevent spurious oscillations of the numerical solution at the interface. Comparisons between numerical results and theoretical solution assess the validity of the model presented in this paper. In addition, the hydro-mechanical interactions between neighboring fractures and the effects of the permeability of the porous medium are investigated. We also demonstrate the capability of our model to handle non-planar fracture paths.

Quantized Evolution of the Plasmonic Response in a Stretched Nanorod

Quantum aspects, such as electron tunneling between closely separated metallic nanoparticles, are crucial for understanding the plasmonic response of nanoscale systems. We explore quantum effects on the response of the conductively coupled metallic nanoparticle dimer. This is realized by stretching a nanorod, which leads to the formation of a narrowing atomic contact between the two nanorod ends. Based on first-principles time-dependent density-functional-theory calculations, we find a discontinuous evolution of the plasmonic response as the nanorod is stretched. This is especially pronounced for the intensity of the main charge-transfer plasmon mode. We show the correlation between the observed discontinuities and the discrete nature of the conduction channels supported by the formed atomic-sized junction.

Evolution of Weak Discontinuity in Presence of Entropy Gradients in Radiating Gas

A wave front expansion technique is used to analyze a problem of one dimensional, unsteady flow of a radiating gas near the optically thin limit, assuming that the gas is inviscid, optically grey and in thermodynamic equilibrium. The effects of variable area ducts, axial temperature gradients and radiation on the nonlinear distortion of a traveling wave are presented. The analysis leads to an evolution equation for the slope of the wave front. Two cases pure compression and pure expansion traveling waves have been analyzed. The effect of area variation, axial temperature gradient and thermal radiation on the steepening of compression wave front into a shock and the shock formation distance is investigated. Two examples highlighting these effects are also presented in the paper.

Temperature dependent spectroscopic ellipsometry and Raman scattering of PbTiO_3-based relaxor ferroelectric single crystals around MPB region

To discover intrinsic relationship between optical bandgap and structural transformations in relaxor ferroelectric single crystals, electronic band structures and dielectric functions of xPb(In1/2Nb1/2)O3-(1 − x − y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 single crystals (x∼0.27–0.28, y∼0.29–0.35) around morphotropic phase boundary have been investigated by variable-temperature (200–750 K) spectroscopic ellipsometry. It was found that the discontinuous evolution from the second derivative of dielectric functions corresponds to structural transformation patterns. Using the SCP (standard critical point) model, four typical interband transitions (Ea∼2.8 eV, Eb∼3.6 eV, Ec∼4.6 eV, and Ed∼5.4 eV) can be uniquely assigned. These interband transitions are mainly attributed to the contributions from B-O bonds and multiphase coexistence. Furthermore, a modified phase diagram based on interband transition variations with the temperature and PT composition for PIMN-PT crystals was provided. In order to verify the accuracy of phase transition temperature, temperature-dependent low-wavenumber Raman scattering was used as a support. The present results provide important supports for the theoretical model, which establish a quantitative relationship between the electronic transition and structural transformation for ferroelectric oxides.

Formation of discontinuities and expansion waves in the outflow region of magnetic reconnection in an asymmetric current sheet

The current sheets observed in the solar wind, magnetopause, and nightside plasma sheet can be asymmetric, in which the plasma densities and/or magnetic field magnitudes on the two sides of the current sheet are not equal. A hybrid code is used to simulate the 1D Riemann problem for the generation and evolution of magnetohydrodynamic discontinuities and expansion waves in the outflow region of magnetic reconnection in an asymmetric current sheet. In a symmetric current sheet, four types of compound structures are found: (a) rotational discontinuity (RD)-show shock (SS) compound structure: SS is attached to the downstream of RD, (b) SS-RD: SS is followed by an adjacent RD, (c) SS-RD-SS: RD is trapped inside SS, and (d) switch-off slow shock. In the asymmetric current sheet, the rotational angle of magnetic field across an RD on the side with a higher plasma density is usually larger than that with a lower plasma density. In the asymmetric cases, a single SS may appear. For an asymmetric current sheet, a compound structure of diffusive contact discontinuity/slow expansion wave is formed behind an SS-RD compound structure or a pure RD on the side with a very high plasma density.

The discontinuous evolution of women’s fashion in China

Purpose– The aim of this study is to provide an understanding of urban Chinese women’s fashion consumption practices in light of major recent socio-historical events and to demonstrate that changes in fashion are not necessarily continuous, but rather can be discontinuous in the wake of radical disturbances.Design/methodology/approach– A phenomenological study was conducted that included group interviews with Chinese women belonging to three age cohorts who experienced different radical changes in recent Chinese history.Findings– This study provides insights into how fashion develops when radical economic and social shifts result in a discontinuous rather than continuous fashion evolution. In China, it can be seen that these radical ideological shifts had discontinuous effects on notions of beauty and how identity is expressed through fashion. The changes seen in the past 60 years or so – from the advent of communism in 1949 until now – cannot be explained by theories of imitation and distinction alone. The changes are also anchored to key socio-historic events, and were not necessarily an outgrowth of the period before, or class-based practices, but rather a response to social upheavals.Originality/value– This study provides a nuanced understanding of how tumultuous socio-cultural events affect how fashion is experienced in China, which allows us to contribute to the growing understanding of Chinese consumer culture, and demonstrate that the understanding of how fashion evolves needs to accommodate the upheavals in society over the past sixty years.

Grain-scale modeling of arbitrary fluid saturation in random packings.

We propose a model for increasing liquid saturation in a granular packing, which can account for liquid redistribution at saturation levels beyond the well-studied capillary bridge regime. The model is capable of resolving and combining capillary bridges, menisci, and fully saturated pores to form local liquid clusters of any shape. They can exchange volume due to the local Laplace pressure gradient via a liquid film on the surfaces of grains. Local instabilities such as Haines jumps trigger the discontinuous evolution of the liquid front. The applicability of the model is demonstrated and compared to benchmark experiments on the level of individual liquid structures as well as on larger systems.

Evolution of weak discontinuity in a van der Waals gas

Abstract In this article, the Lie symmetries analysis that leaves the system of partial differential equations (PDEs), governed by the one dimensional unsteady flow of an isentropic, inviscid and perfectly conducting compressible fluid obeying the van der Waals equation of state invariant, is presented. Using these symmetries the governing system of PDEs is reduced into system of ordinary differential equations (ODEs). Then the reduced system of ODEs is solved analytically which in turn produces the exact solution for the governing PDEs. Further, the influence of the van der Waals excluded volume in the behavior of evolution of weak discontinuity is studied extensively.

Evolution of Weak Discontinuities in Non-ideal Magnetogasdynamic Equations

In this paper classical Lie group of transformations are used to obtain an exact particular solution to the equations of non-ideal magnetogasdynamics, which exhibits space-time dependence. Appropriate canonical variables are characterized that transform the governing system to an equivalent autonomous form, the autonomous system is solved explicitly to obtain exact particular solution of the original system. The particular solution to the governing system, which exhibits space-time dependence, is used to study the evolutionary behaviour of the weak discontinuities.

Variable Compliance-related Aspects of Chatter in Turning Thin-walled Tubular Parts

Thin tubular parts are often subject to turning process during manufacturing. The increasing compliance of the workpiece, which is associated to tool displacement and to matter removal, can give rise to chatter, leading to poor surface quality or premature machine/tool damage. The present work addresses an experimental case of turning a steel thin-walled tube featuring intense vibrations with variable parameters. Observations of transient records during the pass suggest a strong influence of the matter removal on the eigenfrequencies of the system, while the tool's motion implies strong variation of the modal projection of the cutting force. Another characteristic phenomenon is the intermittency of the vibrations and discontinuous chatter frequency evolution. These phenomena are reproduced and analyzed numerically. By means of a finite element modeling, the part's geometry variation during the pass is taken into account. Finally, a stability analysis is carried out for several states of this evolutive system in order to gather insight into the steady cutting conditions.

From Mr. and Mrs. Outlier To Central Tendencies

This study examines the impact of computational journalism on the creation and dissemination of crime news. Computational journalism refers to forms of algorithmic, social scientific, and mathematical processes and systems for the production of news. It is one of a series of technological developments that have shaped journalistic work and builds on techniques of computer-assisted reporting and the use of social science tools in journalism. This paper uses the Los Angeles Times’ Homicide Report and its Data Desk as a case study to explore how technological adaptation occurred in this newsroom in the early twenty-first century. Our findings suggest that computational thinking and techniques emerged in a (dis)continuous evolution of organizational norms, practices, content, identities, and technologies that interdependently led to new products. Computational journalism emerges from an earlier and still ongoing turn to digital within broader organizational, technological, and social contexts. We place this finding in the local, situated context of the Homicide Report, one of the first crime news blogs to adopt computational journalism in North America.

Measuring the entanglement of photons produced by a nanosecond pulsed source

A pulsed source of entangled photons is desirable for some applications. Yet, such a source has intrinsic problems arising from the simultaneous arrival of the signal and noise photons to the detectors. These problems are analyzed and practical methods to calculate the number of accidental (or spurious) coincidences are described in detail, and experimentally checked, for the different regimes of interest. The results are useful not only to measure entanglement, but to all the situations where extracting the number of valid coincidences from noisy data is required. As an example of the use of those methods, we present the time-resolved measurement of the Concurrence of the field produced by spontaneous parametric down conversion with pump pulses of duration in the ns-range at a repetition of kHz. The predicted discontinuous evolution of the entanglement at the edges of the pump pulse is observed.

Discontinuity Evolution and Sonic Propagation for Superfluidity Hydrodynamics with Small Superfluid Entropy

In this paper, we have studied discontinuity evolution and sonic propagation for the two-fluid model with small superfluid entropy in the framework of hydrodynamics. General features of the transverse mode and the longitudinal mode are provided. The fourth sound and the sixth sound are identified as the propagation of discontinuity, in agreement with earlier theoretical studies. Moreover, the growth equation is obtained to describe the decay and growth of the discontinuity propagating along its normal trajectory. The solution is in an integral form and various cases are discussed. Important discriminations between the case of fourth sound and that of sixth sound are also presented, which may be meaningful for future's experiments to identify the sixth sound and the small superfluid entropy.

Photoluminescence study on polar nanoregions and structural variations in Pb(Mg_1/3Nb_2/3)O_3-PbTiO_3 single crystals

We report polar nanostructure and electronic transitions in relaxor ferroelectric Pb(Mg₁/₃Nb₂/₃)O₃ ₋ PbTiO (PMN-PT) single crystals around morphotropic phase boundary (MPB) region by variable-temperature (80-800 K) photoluminescence (PL) spectra and low-wavenumber Raman scattering (LWRS). The discontinuous evolution from peak positions and intensity of luminescence emissions can be corresponding to formation of polar nanoclusters and phase transitions. Six emissions have been derived from PL spectra and show obvious characteristics near phase transition temperatures, which indicates that PL spectral measurement is promising in understanding the microcosmic mechanism. The Raman mode at 1145 cm(-1) indicates that temperature dependent luminescence phenomena can be modulated by thermal quenching.

Multidimensional Riemann problem with self-similar internal structure. Part I – Application to hyperbolic conservation laws on structured meshes

Multidimensional Riemann solvers have been formulated recently by the author (Balsara, 2010, 2012) [6,7]. They operate at the vertices of a two-dimensional mesh, taking input from all the neighboring states and yielding the resolved state and fluxes as output. The multidimensional Riemann problem produces a self-similar strongly interacting state which is the result of several one-dimensional Riemann problems interacting with each other. The prior work was restricted to the use of one-dimensional HLLC Riemann solvers as building blocks. In this paper, we formulate the problem in similarity variables. As a result, any self-similar one-dimensional Riemann solver can be used as a building block for the multidimensional Riemann solver. This paper focuses on the structure of the strongly-interacting state. (A video introduction to multidimensional Riemann solvers is available on http://www.nd.edu/~dbalsara/Numerical-PDE-Course.)In this work the strongly-interacting state is expanded in a set of basis functions that depend on the similarity variables. Consequently, the resolved state and the fluxes can be endowed with considerably richer sub-structure compared to prior work. Unlike the multidimensional HLLC Riemann solver, the need to independently specify a direction for the evolution of the contact discontinuity is eliminated. The richer sub-structure in the strongly-interacting state naturally accommodates waves that may be moving in any direction relative to the mesh, thereby minimizing mesh-imprinting. Two formulations are presented. The first formulation does not linearize the problem around a favorable state. Its derivation takes a few cues from the derivation of the multidimensional HLL Riemann solver. The second formulation identifies such a state and carries out a linearization of the fluxes about that state.This paper is the very first time that a series solution of the multidimensional Riemann problem has been presented. Explicit formulae are presented for up to quartic variation in the self-similar variables. While linear variations are sufficient for numerical work, the higher order terms in the series solution could prove useful for analytical studies of the multidimensional Riemann problem.The formulation presented here is general enough to accommodate any hyperbolic conservation law. It can also accommodate any one-dimensional Riemann solver and yields a multidimensional version of the same. It has been incorporated in the author's RIEMANN code. As examples of the different types of hyperbolic conservation laws, we use Euler flow, Magnetohydrodynamics (MHD) and relativistic MHD. As examples of different types of Riemann solvers, we show multidimensional formulations of HLL, HLLC and HLLD Riemann solvers for MHD all working fluently within this formulation. Several stringent test problems are presented.