866 research outputs found
SENSITIVITY ANALYSIS OF TRACK VIBRATIONS DUE TO VERTICAL STIFFNESS VARIATION IN HIGH-SPEED RAILWAYS
High speed trains, when crossing regions with abrupt changes in vertical stiffness
of the track and/or subsoil, may generate excessive ground and track vibrations. There is an
urgent need for specific analyses of this problem so as to allow reliable esimates of vibration
amplitude. Full understanding of these phenomena will lead to new construction solutions
and mitigation of undesirable features. In this paper analytical transient solutions of dynamic
response of one-dimensional systems with sudden change of foundation stiffness are derived.
Results are expressed in terms of vertical displacement. Sensitivity analysis of the response
amplitude is also performed. The analytical expressions presented herein, to the authors’
knowledge, have not been published yet. Although related to one-dimensional cases, they can
give useful insight into the problem. Nevertheless, in order to obtain realistic response, vehicle-
rail interaction cannot be omitted. Results and conclusions are confirmed using general
purpose commercial software ANSYS. In conclusion, this work contributes to a better understanding
of the additional vibration phenomenon due to vertical stiffness variation, permitting
better control of the train velocity and optimization of the track design
Experimental distribution of entanglement with separable carriers
The key requirement for quantum networking is the distribution of entanglement between nodes. Surprisingly, entanglement can be generated across a network without direct transfer-or communication-of entanglement. In contrast to information gain, which cannot exceed the communicated information, the entanglement gain is bounded by the communicated quantum discord, a more general measure of quantum correlation that includes but is not limited to entanglement. Here, we experimentally entangle two communicating parties sharing three initially separable photonic qubits by exchange of a carrier photon that is unentangled with either party at all times. We show that distributing entanglement with separable carriers is resilient to noise and in some cases becomes the only way of distributing entanglement through noisy environments
Multiscale magnetic underdense regions on the solar surface: Granular and Mesogranular scales
The Sun is a non-equilibrium dissipative system subjected to an energy flow
which originates in its core. Convective overshooting motions create
temperature and velocity structures which show a temporal and spatial
evolution. As a result, photospheric structures are generally considered to be
the direct manifestation of convective plasma motions. The plasma flows on the
photosphere govern the motion of single magnetic elements. These elements are
arranged in typical patterns which are observed as a variety of multiscale
magnetic patterns. High resolution magnetograms of quiet solar surface revealed
the presence of magnetic underdense regions in the solar photosphere, commonly
called voids, which may be considered a signature of the underlying convective
structure. The analysis of such patterns paves the way for the investigation of
all turbulent convective scales from granular to global. In order to address
the question of magnetic structures driven by turbulent convection at granular
and mesogranular scales we used a "voids" detection method. The computed voids
distribution shows an exponential behavior at scales between 2 and 10 Mm and
the absence of features at 5-10 Mm mesogranular scales. The absence of
preferred scales of organization in the 2-10 Mm range supports the multiscale
nature of flows on the solar surface and the absence of a mesogranular
convective scale
Solar Intranetwork Magnetic Elements: bipolar flux appearance
The current study aims to quantify characteristic features of bipolar flux
appearance of solar intranetwork (IN) magnetic elements. To attack such a
problem, we use the Narrow-band Filter Imager (NFI) magnetograms from the Solar
Optical Telescope (SOT) on board \emph{Hinode}; these data are from quiet and
an enhanced network areas. Cluster emergence of mixed polarities and IN
ephemeral regions (ERs) are the most conspicuous forms of bipolar flux
appearance within the network. Each of the clusters is characterized by a few
well-developed ERs that are partially or fully co-aligned in magnetic axis
orientation. On average, the sampled IN ERs have total maximum unsigned flux of
several 10^{17} Mx, separation of 3-4 arcsec, and a lifetime of 10-15 minutes.
The smallest IN ERs have a maximum unsigned flux of several 10^{16} Mx,
separations less than 1 arcsec, and lifetimes as short as 5 minutes. Most IN
ERs exhibit a rotation of their magnetic axis of more than 10 degrees during
flux emergence. Peculiar flux appearance, e.g., bipole shrinkage followed by
growth or the reverse, is not unusual. A few examples show repeated
shrinkage-growth or growth-shrinkage, like magnetic floats in the dynamic
photosphere. The observed bipolar behavior seems to carry rich information on
magneto-convection in the sub-photospheric layer.Comment: 26 pages, 14 figure
Vibrações associadas à variação rápida da rigidez da via férrea por acção de carga móvel
A variação rápida da rigidez das vias férreas, quer devido a mudança de
solução estrutural, quer devido a alteração das condições geotécnicas pode induzir
vibrações de amplitude excessiva à passagem de comboios de alta velocidade. Este
comportamento causa desgaste da via. Nesta comunicação abordam-se aspectos de
modelação e análise do problema. A contribuição consiste em desenvolvimento das soluções
analíticas transientes de modelos simplificados em que a alteração de rigidez é implementada
de duas formas. O primeiro caso corresponde à existência de uma rigidez adicional
localizada e o segundo caso representa a passagem entre duas zonas de rigidez constante
Stokes Diagnostis of 2D MHD-simulated Solar Magnetogranulation
We study the properties of solar magnetic fields on scales less than the
spatial resolution of solar telescopes. A synthetic infrared
spectropolarimetric diagnostics based on a 2D MHD simulation of
magnetoconvection is used for this. We analyze two time sequences of snapshots
that likely represent two regions of the network fields with their immediate
surrounding on the solar surface with the unsigned magnetic flux density of 300
and 140 G. In the first region we find from probability density functions of
the magnetic field strength that the most probable field strength at logtau_5=0
is equal to 250 G. Weak fields (B < 500 G) occupy about 70% of the surface,
while stronger fields (B 1000 G) occupy only 9.7% of the surface. The magnetic
flux is -28 G and its imbalance is -0.04. In the second region, these
parameters are correspondingly equal to 150 G, 93.3 %, 0.3 %, -40 G, and -0.10.
We estimate the distribution of line-of-sight velocities on the surface of log
tau_5=-1. The mean velocity is equal to 0.4 km/s in the first simulated region.
The averaged velocity in the granules is -1.2 km/s and in the intergranules is
2.5 km/s. In the second region, the corresponding values of the mean velocities
are equal to 0, -1.8, 1.5 km/s. In addition we analyze the asymmetry of
synthetic Stokes-V profiles of the Fe I 1564.8 nm line. The mean values of the
amplitude and area asymmetry do not exceed 1%. The spatially smoothed amplitude
asymmetry is increased to 10% while the area asymmetry is only slightly varied.Comment: 24 pages, 12 figure
Índices De Qualidade Da água E De Estado Trófico Do Rio Caiabi, Mt
The objective of this study was to evaluate the water quality of the Caiabi River based upon the water quality index (WQI) and the trophic state index (TSI), considering seasonal and spatial variations, with the aim of determining the most appropriate monitoring design for this study site. Sampling for water quality monitoring was conducted at five points on theCaiabi River from July 2012 to June 2013. Quality parameters quantified were as follows: pH, temperature, conductivity, dissolved oxygen, total and thermotolerant coliforms, turbidity, Kjeldahl nitrogen, nitrite, nitrate, total phosphorus, biochemical oxygen demand, series of solids, and chlorophyll a. Sampling procedures and analysis followed the methods recommended by the Standard Methods for the Examination of Water and Wastewater. The WQI results showed that the quality of the Caiabi River water is good. TSI results demonstrated the low risk of eutrophication in the Caiabi River, indicating an ultra- oligotrophic lotic environment. Analysis of variance showed that 10 of the 16 monitored quality parameters presented differences of means between the dry and rainy seasons or among the monitored points or in the interaction between seasons and points. These results indicate that two annual sampling collections at two points may be sufficient to describe the water quality behavior in the basin, as long as the conditions of land use are stable. © 2016, Institute for Environmental Research in Hydrographic Basins (IPABHi). All rights reserved.11116217
Small-scale solar magnetic fields
As we resolve ever smaller structures in the solar atmosphere, it has become
clear that magnetism is an important component of those small structures.
Small-scale magnetism holds the key to many poorly understood facets of solar
magnetism on all scales, such as the existence of a local dynamo, chromospheric
heating, and flux emergence, to name a few. Here, we review our knowledge of
small-scale photospheric fields, with particular emphasis on quiet-sun field,
and discuss the implications of several results obtained recently using new
instruments, as well as future prospects in this field of research.Comment: 43 pages, 18 figure
First report of anthracnose of Capsicum Chinense in Brazil caused by Colletotrichum brevisporum
Fruit of “yellow lantern” chili pepper (Capsicum chinense L.) with typical symptoms of anthracnose were observed in the city of Manaus in 2008 and Manacapuru in 2014, in Amazonas state, Brazil. The symptoms initially consisted of small dark-brown lesions, circular, depressed, with defined edges, progressing to the center and becoming gray to black, with concentric circles. Losses of up to 100% have occurred in some plantings. Isolation of the fungus was carried out from masses of spores present on the fruit lesions. Colonies were grown on potato dextrose agar (PDA) at 25°C and 12-h photoperiod. Monosporic cultures were obtained and the isolates were deposited in the Microorganisms Culture Collection of the National Institute of Amazonian Research, Manaus, Brazil (INPA 1858 and INPA 2800). After 7 days on PDA, single spore colonies had a cottony appearance and the color ranged from white to brownish, with orange-colored masses of conidia. Conidia were hyaline, aseptate, cylindrical with rounded ends, and measured 10.2 to 17.7 µm in length × 3.3 to 5.6 µm in width. Appressoria formed were dark-brown in color, irregularly shaped or lobate, and measured 5.9 to 12.0 µm in length and 5.5 to 8.9 µm in width. Partial sequences of actin (ACT) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified and comparted to GenBank accession nos. KU315567 and KX878886 for ACT and KU315572 and KX878887 for GAPDH. Bayesian inference analyses performed with concatenated gene sequences showed that the isolate INPA 1858 and INPA 2800 clustered with the ex-type specimen of Colletotrichum brevisporum (BCC 38876) in a clade with high support (posterior probability = 1). Pathogenicity tests with isolates INPA 1858 and INPA 2800 were conducted on healthy chili peppers using the wound inoculation method by droplet (106 conidia/ml) on the fruit surface (Lin et al. 2002). Pathogenicity tests were done with 10 fruit per isolate (INPA 1858 and INPA 2800) replicated three times. The controls were inoculated with sterile water. Typical symptoms of anthracnose were observed 7 days post inoculation, while the controls did not show any symptoms. The fungus C. brevisporum was recovered from the inoculated chili peppers, thereby confirming Koch’s postulates. C. brevisporum was described in Thailand causing symptoms in Neoregalia sp. and in Pandanus pygmaeus (Noireung et al. 2012), in Korea in Lycium chinense (Paul et al. 2014), and in Brazil in Carica papaya and Sechium edule (Bezerra et al. 2016; Vieira et al. 2013). To our knowledge, this is the first report of C. brevisporum on C. chinense fruits in Brazil. © 2017, American Phytopathological Society. All rights reserved
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