Transient Turbulence in Taylor-Couette Flow

Recent studies have brought into question the view that at sufficiently high Reynolds number turbulence is an asymptotic state. We present the first direct observation of the decay of turbulent states in Taylor-Couette flow with lifetimes spanning five orders of magnitude. We also show that there is a regime where Taylor-Couette flow shares many of the decay characteristics observed in other shear flows, including Poisson statistics and the coexistence of laminar and turbulent patches. Our data suggest that characteristic decay times increase super-exponentially with increasing Reynolds number but remain bounded in agreement with the most recent data from pipe flow and with a recent theoretical model. This suggests that, contrary to the prevailing view, turbulence in linearly stable shear flows may be generically transient.Comment: 4 pages, 4 figures v2: Addressed referee comments for PRE. Made some cosmetic changes. Added inset to Fig.

Runup and rundown generated by three-dimensional sliding masses

To study the waves and runup/rundown generated by a sliding mass, a numerical simulation model, based on the large-eddy-simulation (LES) approach, was developed. The Smagorinsky subgrid scale model was employed to provide turbulence dissipation and the volume of fluid (VOF) method was used to track the free surface and shoreline movements. A numerical algorithm for describing the motion of the sliding mass was also implemented. To validate the numerical model, we conducted a set of large-scale experiments in a wave tank of 104m long, 3.7m wide and 4.6m deep with a plane slope (1:2) located at one end of the tank. A freely sliding wedge with two orientations and a hemisphere were used to represent landslides. Their initial positions ranged from totally aerial to fully submerged, and the slide mass was also varied over a wide range. The slides were instrumented to provide position and velocity time histories. The time-histories of water surface and the runup at a number of locations were measured. Comparisons between the numerical results and experimental data are presented only for wedge shape slides. Very good agreement is shown for the time histories of runup and generated waves. The detailed three-dimensional complex flow patterns, free surface and shoreline deformations are further illustrated by the numerical results. The maximum runup heights are presented as a function of the initial elevation and the specific weight of the slide. The effects of the wave tank width on the maximum runup are also discussed

The Analysis of Tsunami Vertical Shelter in Padang City

Padang is a coastal city, which is located opposite to the Indian Ocean. Just across Padang city there are areas of subduction, which can trigger a powerful earthquake and generate tsunami. Geologists have to say that the city of Padang is the area that is highly vulnerable to tsunamis in the near future. Several studies have been conducted to prepare Padang city for tsunamis. Through the research, maps of tsunami inundation area has been successfully designed. So that the tsunami-prone areas, and tsunami safe area can be clearly identified. According to Singh (2008), the time interval between the first powerful earthquake and tsunami to hit the coast of Padang is about 20-30 minutes. While residents have to walk 3-5 km to the safe area. It can be said that the time for tsunami evacuation in Padang city is very short. Therefore the choice of conducting vertical evacuation is urgent for the majority of the population rather than walking along the horizontal evacuation. Padang city government with the aid of the international donors has built buildings for the shelter. Some of them are schools that have a strong structure, three storeys in which the roof are served as a tsunami evacuation. Data from the BPBDs office (Disaster Management Agency), stated that there are 13 tsunami evacuation buildings at this time with a total capacity of 30.550 people and the capacity for each building is varied between 1,000 - 3,000 people (BPBDs, 2013). This amount is very far from enough when compared to the potential loss of life as many as 400,000 people or more, or as only 7.64% of the total amount. And the location of the shelter buildings are not evenly distributed in tsunamis prone areas Places for vertical tsunami evacuation in Padang are called TES (Temporary Evacuation Shelter). There have been 13 shelters established by the Government of Padang and BPBDs, and there is only one TES found in the study area. It really is not enough as it is seen in the range of services. Therefore the existing buildings and multi-storey structure is another alternate places to rescue in which they are expected to withstand earthquakes and tsunamis. This alternative building called Potential TES (PTES)and there are 14 shelters for the study area

Models and Observations of Sunspot Penumbrae

The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution. To help explaining these new observations I propose some modifications to each of them. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.Comment: 9 pages, 1 color figure. Review talk to appear in the proceedings of the International Workshop of 2008 Solar Total Eclipse: Solar Magnetism, Corona and Space Weather--Chinese Space Solar Telescope Scienc

Ocupação tardia e o desenvolvimento da agropecuária no Estado de Rondônia Uma história da bovinocultura no desenvolvimento regional.

Neste artigo se discute a ocupação tardia e sem planejamento de Rondônia e sua influência na bovinocultura. É uma pesquisa bibliográfica e qualitativa na qual foram levantadas informações sobre penetração do gado bovino no Estado do século XVIII ao XXI cujo objetivo é mostrar a configuração da atividade no desenvolvimento regional. Extraiu-se que somente a partir da década de setenta a criação de gado tornou-se importante para a economia regional, mas faltaram políticas públicas de ordenação e planejamento do território ocupado, tornando-a uma atividade competitiva. Aqui as baixas tecnologias provocaram a substituição da floresta pela criação extensiva, e sabe-se que na exploração bovina feita de forma correta poucos danos se verificam em sua área de atuação

Electronic depth profiles with atomic layer resolution from resonant soft x-ray reflectivity

The analysis of x-ray reflectivity data from artificial heterostructures usually relies on the homogeneity of optical properties of the constituent materials. However, when the x-ray energy is tuned to an absorption edge, this homogeneity no longer exists. Within the same material, spatial regions containing elements at resonance will have optical properties very different from regions without resonating sites. In this situation, models assuming homogeneous optical properties throughout the material can fail to describe the reflectivity adequately. As we show here, resonant soft x-ray reflectivity is sensitive to these variations, even though the wavelength is typically large as compared to the atomic distances over which the optical properties vary. We have therefore developed a scheme for analyzing resonant soft x-ray reflectivity data, which takes the atomic structure of a material into account by "slicing" it into atomic planes with characteristic optical properties. Using LaSrMnO4 as an example, we discuss both the theoretical and experimental implications of this approach. Our analysis not only allows to determine important structural information such as interface terminations and stacking of atomic layers, but also enables to extract depth-resolved spectroscopic information with atomic resolution, thus enhancing the capability of the technique to study emergent phenomena at surfaces and interfaces.Comment: Completely overhauled with respect to the previous version due to peer revie

Kinematics and Magnetic Properties of a Light Bridge in a Decaying Sunspot

We present the results obtained by analyzing high spatial and spectral resolution data of the solar photosphere acquired by the CRisp Imaging SpectroPolarimeter at the Swedish Solar Telescope on 6 August 2011, relevant to a large sunspot with a light bridge (LB) observed in NOAA AR 11263. These data are complemented by simultaneous Hinode Spectropolarimeter (SP) observation in the Fe I 630.15 nm and 630.25 nm lines. The continuum intensity map shows a discontinuity of the radial distribution of the penumbral filaments in correspondence with the LB, which shows a dark lane (about 0.3" wide and about 8.0" long) along its main axis. The available data were inverted with the Stokes Inversion based on Response functions (SIR) code and physical parameters maps were obtained. The line-of-sight (LOS) velocity of the plasma along the LB derived from the Doppler effect shows motions towards and away from the observer up to 0.6 km/s, which are lower in value than the LOS velocities observed in the neighbouring penumbral filaments. The noteworthy result is that we find motions toward the observer up to 0.6 km/s in the dark lane where the LB is located between two umbral cores, while the LOS velocity motion toward the observer is strongly reduced where the LB is located between an umbral core at one side and penumbral filaments on the other side. Statistically, the LOS velocities correspond to upflows/downflows andcomparing these results with Hinode/SP data, we conclude that the surrounding magnetic field configuration (whether more or less inclined) could have a role in maintaining the conditions for the process of plasma piling up along the dark lane. The results obtained from our study support and confirm outcomes of recent magnetohydro-dynamic simulations showing upflows along the main axis of a LBs

Diversity and abundance of weed seeds in cereal crop grain in Western Andalusia, South Spain

Se analizó la presencia de semillas de malas hierbas en muestras de la cosecha de cereal de 2013 correspondientes a 200 campos de las provincias de Huelva y Sevilla. Se identificaron 91 especies de las que 29 mostraron una frecuencia de presencia de al menos el 5%. La especie más frecuente (74%) y abundante fue “Lolium rigidum”. Las especies arvenses del género “Phalaris” también fueron muy frecuentes (66-32%). Especies con frecuencia superior al 20% fueron “Polygonum aviculare”, “Convolvulus arvensis”, “Chrysanthemum coronarium”, “Pulicaria paludosa” y “Centaurea diluta”. En comparación con estudios previos referidos al conjunto del área cerealista española, se observó una frecuencia similar de las especies dominantes “L. rigidum” y “P. aviculare” y una frecuencia muy superior de “Phalaris spp.” En sentido contrario, la frecuencia de especies segetales especialistas fue muy inferior.We examined the weed seeds present in crop grain samples from 2013 from across 200 cereal fields in Huelva and Seville provinces, Andalusia, South-western Spain. Ninety-one weed species were identified of which 29 species were present in at least 5% of samples. “Lolium rigidum” was the most frequent (74%) and abundant species. The weedy species of the genus “Phalaris” were also highly frequent (66-32%). “Polygonum aviculare”, “Convolvulus arvensis”, “Chrysanthemum coronarium”, “Pulicaria paludosa” and “Centaurea diluta” were detected in more than 20% of samples. Compared to available data for the whole cereal crop area in Spain, we found a similar frequency of the dominant weeds “L. rigidum” and “P. aviculare” but a much higher presence of “Phalaris” spp. In an opposite trend, the frequency of specialist segetal species was much lower

Comparative analysis on strains in asphalt pavement design using linear elastic and viscoelastic theories

In Colombia it is common to design pavements using the AASHTO 93 method and to complement it with an elastic analysis of the deformations that cause fatigue and rutting; this has repercussions on the behavior of the structure since it does not take into account the viscoelastic behavior of the asphalt mixtures, In this research, a comparison of three structures at different velocity ranges is made to compare the variation in fatigue and rutting concerning the traditional method of analysis in Colombia and to analyze the differences that may occur in linear elastic analysis and viscoelastic analysis of rutting and fatigue