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1
Leftheris, B. P., and J. M. Papazian. "Use of the Shadow Optical Method of Caustics to Predict Fatigue Crack Growth in Compression." Journal of Engineering Materials and Technology 114, no. 4 (October 1, 1992): 399–405. http://dx.doi.org/10.1115/1.2904191.
Повний текст джерелаАнотація:
The shadow optical method of caustics has been applied to the measurement of the bulging out of the surface of aluminum alloy 7075-T6 in the vicinity of a blunt notch in a single edge notch tensile sample after a compression overload and during compression fatigue. The size and shape of the caustic were found to be sensitive functions of the amount of elastic and plastic strain in the vicinity of the notch. Examination of the caustic during application and after release of the overload shows the elastic zone to be larger and more circular than the plastic zone, as predicted. A crack was propagated through the plastic zone using only far-field cyclic compression loading: the crack was self-arresting at the edge of the elasticplastic boundary created by the initial compression overload. The size of the plastic zone as measured by the caustic was found to agree with the maximum length of the crack. The actual surface profile in the vicinity of the notch was measured and its shape was used along with geometrical arguments to develop a model for interpretation of the caustics results. These results indicate that the caustics technique can be used to detect the presence of a plastic zone at the tip of a notch after a compressive overload, and that the size of this zone as measured by caustics is approximately equal to the size as determined by subsequent fatigue crack propagation.
2
Volyar, A. V., E. G. Abramochkin, Y. E. Akimova, and M. V. Bretsko. "Reconstruction of stable states of spiral vortex beams." Computer Optics 46, no. 1 (February 2022): 5–15. http://dx.doi.org/10.18287/2412-6179-co-1032.
Повний текст джерелаАнотація:
Using an asymptotic approach and an experiment supported by computer simulation, we analyzed processes of restoring structural stability and transitions to new stable states of spiral vortex beams subject to perturbations by curly apertures. Using a tetragonal beam as an example, we considered three perturbation scenarios: 1) asymmetric perturbation, when an opaque screen covers the caustic only on one side of the square, 2) symmetric perturbation, when the curly aperture covers the entire beam except for a narrow caustic region, and 3) symmetric perturbation, when the curly aperture screens only a narrow region of the caustic without affecting the rest of the beam. At the same time, the asymptotic calculation was carried out for all types of polygonal beams. It was shown that if the curly aperture did not destroy the caustic region of the spiral beam, it was able to self-heal in the far diffraction zone. If the perturbation even locally destroyed a part of the caustics, then the perturbed beam passed into a new stable state through chains of creation and annihilation of optical vortices (dislocation reactions).
3
Lock, James A. "Near-zone transmission caustic of a hanging water drop." Applied Optics 59, no. 21 (June 10, 2020): F32. http://dx.doi.org/10.1364/ao.390328.
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4
Salamone, Joseph A. "Analysis of focus boom test cases using the lossy nonlinear Tricomi equation." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A119. http://dx.doi.org/10.1121/10.0010838.
Повний текст джерелаАнотація:
Focused sonic booms will result from an aircraft accelerating from subsonic to supersonic airspeeds. Sonic boom focusing leads to amplification and phase change of the sonic boom signature and can be modeled by a form of the nonlinear Tricomi equation. This presentation will use the lossy nonlinear Tricomi equation (LNTE) to examine sonic boom focusing for two sample cases. The first case depicts an aircraft with constant rectilinear acceleration at a constant altitude. The second case is slightly more complicated with an aircraft maneuvering at a small climb angle, while accelerating and simultaneously pitching downward. Time-pressure histories at various locations in the illuminated zone above the caustic and in the evanescent zone below the caustic will be provided for each test case.
5
Yao, Jun Ping, and Sun Zhong. "Research on the Alkali Corrosion Resistance Mechanism of Ni-Cr-Cu Alloy Cast Iron." Advanced Materials Research 230-232 (May 2011): 1298–302. http://dx.doi.org/10.4028/www.scientific.net/amr.230-232.1298.
Повний текст джерелаАнотація:
In allusion to facility corrosion problem in caustic soda industry five types of ni-Cr-cu alloy cast irons were developed. The corrosion rates of ni-Cr-cu alloy cast irons in hot concentrated alkali solution were measured by using self-made dynamic corrosion experiment equipment; the microstructures and surface corrosion morphology of alloy cast irons were observed by means of the optical microscope and SEM; the composition was analyzed using XES. Corrosion resistance mechanism were discussed detailedly. the experimental results showed that ni-Cr-cu cast iron was uniform corrosion macroscopically in the dense caustic soda at high temperature and there was ni, cu enrichment microcosmically. The Ni and Cu enriched in the matrix , which increase in local electrode voltage of the matrix,are advantageous to the improvement of caustic corrosion resistances of that zone. The higher Ni content,the better alkali corrosion resistance performance with high temperature.
6
Lavenda, B. H. "Buffon's Needle on Caustics and Torus Quantization." Open Systems & Information Dynamics 10, no. 01 (March 2003): 51–64. http://dx.doi.org/10.1023/a:1022923325144.
Повний текст джерелаАнотація:
The probability of n + 1 intersections of a long needle in the Buffon problem is the eikonal of a Hankel function which is the principal term in the uniform asymptotic expansion in powers of the small distance between the parallel lines. Evaluating this probability using the torus quantization conditions shows that in the physically meaningful region, where a closed convergence of rays covers the caustic circle, the probability is greater than unity. In addition, the method of steepest descent shows that the caustic and reflection indices are more general than the ones given by torus quantization. The distance from the light source to the center of caustic circle corresponds to the length of the needle, and n times the distance between the parallel lines is the radius of the caustic. Unlike diffraction problems, the solution cannot be extended to the shadow zone since the angles become imaginary. In the continuum limit where the distance between the parallels tends to zero, the number of intersections is governed by an arc sine law in which maximum number of intersections, or the maximum chord length in a circle of a given radius, is most probable.
7
Kantemirov, V. D., R. S. Titov, A. V. Timohin, and A. M. Jakovlev. "Improvement of methods of accounting for increased losses and dilution of minerals during production." Mining informational and analytical bulletin, no. 3-1 (March 20, 2020): 453–64. http://dx.doi.org/10.25018/0236-1493-2020-31-0-453-464.
Повний текст джерелаАнотація:
The article describes the methodological approaches to accounting and valuation losses of minerals during open development of deposits with complex mining and geological conditions. As an example, analyzes indicators of losses of minerals during the development phase of plot Kostonaiskogo Chanvinskogo deposits of limestone used for the production of caustic soda. The installed actual level losses exceeding 30% of the total production volume of raw materials. The given reasons of increased losses of limestone in comparison with in the project losses. Installed that with a detailed exploration of the array of limestone was not identified zone karst and zone with high clay content lying in the form of “lived” in zones of high fracturing. In the result of blasting is the mixing of karst explode, clogged areas with pure limestone, its pollution to exceed the allowable values, which leads to loss of balance reserves of minerals during extraction. The article gives recommendations for calculating the level of losses during the when developing complex faces, which are characterized by intermittency breed productive layer of limestone and karst zones.
8
Pettersen, Tanja. "Phase Transformation for Primary Particles in the Surface Regions of an AA1200 Alloy." Materials Science Forum 539-543 (March 2007): 311–16. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.311.
Повний текст джерелаАнотація:
In the present investigation the particle structure in an AA1200 sheet ingot used for litho applications has been studied. Caustic etching of the as-cast material was seen to result in a zone close to the surface with a different etching response. This zone was identified as what is known as a fir-tree zone or an Altenpohl zone [1,2,3,4]. A variation in particle type over the cross section of the as-cast ingot was seen to follow the differences in etching response. After heat treatment of the material, the fir-tree zones were no longer visible, and the accompanying change in particle structure was studied. Samples from the subsurface regions and from a distance of ~20 cm from the surface has been investigated before and after heat treatment. In the as-cast material, the sample from the surface was dominated by featherlike particles with long strings of particles, identified as AlmFe. While closer to the centre Al3Fe and Al6Fe were seen to be the main phases, however, some AlmFe and probably some α-AlFeSi was also found in this sample. After heat treatment, the particle structure was seen to change, and the surface sample contained mainly Al3Fe in addition to a small amount of AlmFe. The change in particle structure during heat treatment is discussed with reference to the change in etching response.
9
Hubral, Peter, Martin Tygel, and Jörg Schleicher. "Geometrical‐spreading and ray‐caustic decomposition of elementary seismic waves." GEOPHYSICS 60, no. 4 (July 1995): 1195–202. http://dx.doi.org/10.1190/1.1443848.
Повний текст джерелаАнотація:
The computation of the geometrical‐spreading factor and the number of caustics is often considered to be the most fundamental step in computing zero‐order ray solutions for elementary‐wave Green’s functions along a ray that originates at a point source and passes through a 3-D laterally inhomogeneous isotropic medium. Here, a new factorization method is described that establishes both quantities recursively along the ray segments into which the total ray can be subdivided. As a consequence of the proposed method, the point‐source geometrical‐spreading factor and the number of ray caustics along the total ray can be decomposed into (1) point‐source spreading factors of the ray segments and (2) certain Fresnel zone contributions at the ray‐segment connection points. In a so‐called “3-D simple medium,” by which any 3-D laterally inhomogeneous medium can be approximated, the new factorization approach permits a simple computation of both quantities. It thus simplifies and provides new insights into the computation of ray‐theoretical Green’s functions.
10
Smit, Pieter Bart, T. T. Janssen, and T. H. C. Herbers. "TOPOGRAPHY-INDUCED FOCUSING OF RANDOM WAVES." Coastal Engineering Proceedings 1, no. 33 (December 15, 2012): 6. http://dx.doi.org/10.9753/icce.v33.waves.6.
Повний текст джерелаАнотація:
Refraction of narrow-band surface waves in coastal areas can result in wave-focal zones where due to interference, wave statistics vary rapidly and on similar length scales as those of individual waves. However such interference patterns, or wave coherence, are not accounted for in conventional stochastic wave models that are based on the energy balance equation or radiative transfer equation. In this work we present a quasi-coherent theory, which is an extension of the radiative transfer equation and quasi-homogeneous theory. We show that this new stochastic modelling approach can resolve rapid variations in wave statistics that occur in the vicinity of a wave caustic. The results compare favourably to those obtained from ensemble averages calculated with a deterministic phase resolving model (SWASH) and, in a focal zone, constitute a significant improvement over those obtained with a conventional stochastic wave model based on an energy balance equation (SWAN).
11
Бахарев, С. М., С. П. Савченко та А. П. Танкеев. "Особенности фокусировки спиновых волн в кристаллах EuO и EuS". Физика твердого тела 61, № 2 (2019): 257. http://dx.doi.org/10.21883/ftt.2019.02.47123.205.
Повний текст джерелаАнотація:
AbstractSpecificities of spin wave focusing in EuO and EuS crystals are studied. It is shown that spin wave focusing is absent in the long-wave approximation: it is observed only for wave vectors in the second half of the Brillouin zone ( aq $$ \gtrsim $$ π, where a is the lattice constant and q is the magnitude of the wave vector). It was found that, for EuO and EuS crystals, the directions of spin wave focusing differ due to the different signs of the exchange integrals responsible for the exchange interaction of the magnetic moment with the second neighbors. The directions along which a magnon caustic is formed are determined.
12
Červený, Vlastislav, and José Eduardo P. Soares. "Fresnel volume ray tracing." GEOPHYSICS 57, no. 7 (July 1992): 902–15. http://dx.doi.org/10.1190/1.1443303.
Повний текст джерелаАнотація:
The concept of “Fresnel volume ray tracing” consists of standard ray tracing, supplemented by a computation of parameters defining the first Fresnel zones at each point of the ray. The Fresnel volume represents a 3-D spatial equivalent of the Fresnel zone that can also be called a physical ray. The shape of the Fresnel volume depends on the position of the source and the receiver, the structure between them, and the type of body wave under consideration. In addition, the shape also depends on frequency: it is narrow for a high frequency and thick for a low frequency. An efficient algorithm for Fresnel volume ray tracing, based on the paraxial ray method, is proposed. The evaluation of the parameters defining the first Fresnel zone merely consists of a simple algebraic manipulation of the elements of the ray propagator matrix. The proposed algorithm may be applied to any high‐frequency seismic body wave propagating in a laterally varying 2-D or 3-D layered structure (P, S, converted, multiply reflected, etc.). Numerical examples of Fresnel volume ray tracing in 2-D inhomogeneous layered structures are presented. Certain interesting properties of Fresnel volumes are discussed (e.g., the double caustic effect). Fresnel volume ray tracing offers numerous applications in seismology and seismic prospecting. Among others, it can be used to study the resolution of the seismic method and the validity conditions of the ray method.
13
Sajadian, Sedighe. "Sensitivity to habitable planets in the Roman microlensing survey." Monthly Notices of the Royal Astronomical Society 508, no. 4 (October 13, 2021): 5991–6000. http://dx.doi.org/10.1093/mnras/stab2942.
Повний текст джерелаАнотація:
ABSTRACT We study the Roman sensitivity to exoplanets in the Habitable Zone (HZ). The Roman efficiency for detecting habitable planets is maximized for three classes of planetary microlensing events with close caustic topologies. (a) The events with the lens distances of Dl ≳ 7 kpc, the host lens masses of $M_{\rm h}\gtrsim 0.6\, {\rm M}_{\odot }$. By assuming Jupiter-mass planets in the HZs, these events have q ≲ 0.001 and d ≳ 0.17 (q is their mass ratio and d is the projected planet-host distance on the sky plane normalized to the Einstein radius). The events with primary lenses, $M_{\rm h} \lesssim 0.1 \, {\rm M}_{\odot }$, while their lens systems are either (b) close to the observer with Dl ≲ 1 kpc or (c) close to the Galactic bulge, Dl ≳ 7 kpc. For Jupiter-mass planets in the HZs of the primary lenses, the events in these two classes have q ≳ 0.01, d ≲ 0.04. The events in the class (a) make larger caustics. By simulating planetary microlensing events detectable by Roman, we conclude that the Roman efficiencies for detecting Earth- and Jupiter-mass planets in the Optimistic HZs (OHZs, which is the region between [0.5, 2] au around a Sun-like star) are 0.01 and $5{{\ \rm per\ cent}}$, respectively. If we assume that one exoplanet orbits each microlens in microlensing events detectable by Roman (i.e. ∼27 000), this telescope has the potential to detect 35 exoplanets with the projected planet-host distances in the OHZs with only one having a mass ≲10M⊕. According to the simulation, 27 of these exoplanets are actually in the OHZs.
14
Pal, Sarvesh, R. N. Ibrahim, and R. K. Singh Raman. "Threshold stress intensity factor and crack growth rate for stress corrosion cracking of simulated heat affected zone in caustic solution." Engineering Fracture Mechanics 78, no. 1 (January 2011): 13–26. http://dx.doi.org/10.1016/j.engfracmech.2010.10.005.
Повний текст джерела
15
Chapman, C. J. "Sound radiation from a cylindrical duct. Part 1. Ray structure of the duct modes and of the external field." Journal of Fluid Mechanics 281 (December 25, 1994): 293–311. http://dx.doi.org/10.1017/s0022112094003113.
Повний текст джерелаАнотація:
This paper determines the ray structure of a spinning acoustic mode propagating inside a semi-infinite circular cylindrical duct, and thereby determines the ray structure of the field radiated from the end of the duct. Inside the duct, but outside of a caustic cylindrical surface, the rays are piecewise linear helices; on striking the rim of the end-face of the duct, these rays produce ‘Keller cones’ of diffracted rays. The cones determine the structure of the radiated field: for example, no rays penetrate two cone-shaped far-field quiet zones centred on the duct axis; two rays pass through each point in a forward loud zone; and one ray passes through each point in a rearward loud zone. The two rays through each point in the forward loud zone interfere to produce an oscillatory directivity pattern. One quarter of the rays on each cone point back inside the duct and produce the reflected field. Thus the rim of the end-face of the duct acts as a ‘ring source’, in which the radiated and reflected fields have their origin. Every propagating duct mode determines a polar angle and an azimuthal angle; these are taken as parameters specifying the mode and are used to calculate the positions and angles of all the rays. The mathematical method on which the paper is based is Debye's approximation for the Bessel function which appears in the expression for the duct modes; the approximation shows also that the duct contains a region of smooth helical rays on which the field consists of inhomogeneous waves: this region is the inner cylinder, lying inside the annulus of piecewise linear helical rays. The results of the paper are very promising for the application of Keller's geometrical theory of diffraction to detailed calculations of the sound radiated from aeroengine ducts. An alternative description of the field, using Cargill's meridional rays, is summarized.
16
Tromans, D., S. Ramakrishna, and E. B. Hawbolt. "Stress Corrosion Cracking of ASTM A516 Steel in Hot Caustic Sulfide Solutions—Potential and Weld Effects." Corrosion 42, no. 2 (February 1, 1986): 63–70. http://dx.doi.org/10.5006/1.3584887.
Повний текст джерелаАнотація:
Abstract A combination of slow strain rate (tensile) testing (SSRT) and double cantilever beam (DCB) fracture mechanics testing techniques have been used to study the stress corrosion cracking (SCC) behavior of welded and unwelded pressure vessel quality steel plate (ASTM A516 Grade 70) in hot (92 C) caustic sulfide solutions (3.35 m NaOH + 0.42 m Na2S) of general relevance to the pulp and paper industry. Tests were conducted over a range of potentials (E) and stress intensities (KI). The most susceptible SCC situation occurred at potentials near the activepassive transition, where crack propagation rates were slightly lower in the fusion zone (FZ) of the weld than in the base material (BM). However, crack initiation on smooth specimens was far more frequent in the FZ. More noble potentials did not prevent SCC, but decreased the crack propagation rate and decreased crack initiation (i.e., crack density), particularly in the FZ. A fracture mechanics analysis of partial surface cracks and through thickness cracks was used to assess the cracking of kraft digesters in light of the results. It was concluded that anodic protection could play a beneficial role by decreasing the probability of crack coalescence and the resulting formation of a long critical (catastrophic) crack in the weld region. Instead, only small isolated cracks should form, which penetrate the vessel wall more slowly and lead to leakage before catastrophic failure.
17
Osipov, V. Yu, and A. A. Buznikov. "Calculating the three-dimensional structure of the near-focus diffraction field in the caustic zone of a convergent aberrational laser beam." Journal of Optical Technology 75, no. 8 (August 1, 2008): 495. http://dx.doi.org/10.1364/jot.75.000495.
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18
Dinu, Alice, Manuela Fulger, Dragos Ionescu, Lucian Velciu, and Maria Radulescu. "Electro chemical studies on stress corrosion cracking of Incoloy-800 in caustic solution, part I: As received samples." Nuclear Technology and Radiation Protection 20, no. 1 (2005): 74–80. http://dx.doi.org/10.2298/ntrp0501074d.
Повний текст джерелаАнотація:
Many non-volatile impurities accidentally introduced into the steam generator tend to Concentrate on its surface in restricted flow areas. In this way these impurities can lead to stress corrosion cracking (SCC) on stressed tubes of the steam generator. Such impurities can be strong alkaline or acid solutions. To evaluate the effect of alkaline concentrated environments on SCC of steam generator tubes, the tests were con ducted on stressed samples of Incoloy-800 in 10% NaOH solution. To accelerate the SCC process, stressed specimens were anodically polarised in a caustic solution in an electro chemical cell. The method of stressing of Incoloy-800 tubes used in our experiments was the C-ring. Using the cathodic zone of the potentiodynamic curves it was possible to calculate the most important electrochemical parameters: the corrosion current, the corrosion rate, and the polarization resistance. We found that the value of the corrosion potential to initiate the SCC microcracks was -100 mV. The tested samples were examined using the metallographic method. The main experimental results showed that the in crease of the stress state promoted the in crease of the SCC susceptibility of Incoloy-800 samples tested under the same conditions, and that the length of the SCC-type microcracks in creased with the growth of the stress value.
19
Afanasiev, A. N. "The energy spectrum of spacecraft radio signals in the caustic shadow zone of the Sun: A new diagnostic of the solar coronal plasma." Journal of Atmospheric and Solar-Terrestrial Physics 67, no. 11 (July 2005): 1002–13. http://dx.doi.org/10.1016/j.jastp.2005.03.001.
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20
Moxham, Thomas E. J., Aaron Parsons, Tunhe Zhou, Lucia Alianelli, Hongchang Wang, David Laundy, Vishal Dhamgaye, Oliver J. L. Fox, Kawal Sawhney, and Alexander M. Korsunsky. "Hard X-ray ptychography for optics characterization using a partially coherent synchrotron source." Journal of Synchrotron Radiation 27, no. 6 (October 16, 2020): 1688–95. http://dx.doi.org/10.1107/s1600577520012151.
Повний текст джерелаАнотація:
Ptychography is a scanning coherent diffraction imaging technique which provides high resolution imaging and complete spatial information of the complex electric field probe and sample transmission function. Its ability to accurately determine the illumination probe has led to its use at modern synchrotrons and free-electron lasers as a wavefront-sensing technique for optics alignment, monitoring and correction. Recent developments in the ptychography reconstruction process now incorporate a modal decomposition of the illuminating probe and relax the restriction of using sources with high spatial coherence. In this article a practical implementation of hard X-ray ptychography from a partially coherent X-ray source with a large number of modes is demonstrated experimentally. A strongly diffracting Siemens star test sample is imaged using the focused beam produced by either a Fresnel zone plate or beryllium compound refractive lens. The recovered probe from each optic is back propagated in order to plot the beam caustic and determine the precise focal size and position. The power distribution of the reconstructed probe modes also allows the quantification of the beams coherence and is compared with the values predicted by a Gaussian–Schell model and the optics exit intensity.
21
Ardavan, H. "Asymptotic analysis of the radiation by volume sources in supersonic rotor acoustics." Journal of Fluid Mechanics 266 (May 10, 1994): 33–68. http://dx.doi.org/10.1017/s0022112094000923.
Повний текст джерелаАнотація:
The application of Lighthill's acoustic analogy to the generation of sound by rotating surfaces with supersonic speeds results in radiation integrals in which the stationary points of the phase function – that describes the sapce-time distance between each source point and a fixed observation point – have variable positions and coalesce at a caustic in the space of source points. Here, the leading term in the asymptotic expansion of the corresponding Green's function at this caustic is calculated, both in the time and the frequency domains, and it is shown that the radiation generated by volume sources, which are steady in the uniformly rotating blade-fixed frame, has an amplitude that does not obey the spherical spreading law, i.e. does not fall off like RP–1 with the radial distance RP away from the source. Within a finite solid angle, depending on the extent of the source distribution, the amplitude of this newly identified sound decays like RP–½, so that it is stronger in the far field than any previously studied element. That this is not incompatible with the conservation of energy is because the emission time intervals associated with the volume elements of the source distribution which contribute towards the non-spherically decaying component of the radiation are by a large (RP-dependent) factor greater than the time intervals during which the signals generated by these elements are received. The contributing source elements are those whose positions at the retarded time coincide witht the locus of singularities of the Green's function, i.e. with the one-dimensional locus of points, fixed in the rotating frame, which approach the observer with the wave speed and zero acceleration along the radiation direction. Because the signals received at two neighbouring instants in time arise from distinct, coherently radiating filamentary parts of the source which have both different extents and different strengths, the resulting overall waveform in the far zone consists of the superposition of a (continuous) set of narrow subpulses with uneven amplitudes. These subpulses are narrower the larger the distance from the source.The differences between the new results and those of the earlier works in the literature are shown to arise from the error terms in the far-field and high-frequency approximations, approximations that are inappropriate for volume sources moving supersonically.
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Sabatini, R., O. Marsden, C. Bailly, and O. Gainville. "Three-dimensional direct numerical simulation of infrasound propagation in the Earth’s atmosphere." Journal of Fluid Mechanics 859 (November 23, 2018): 754–89. http://dx.doi.org/10.1017/jfm.2018.816.
Повний текст джерелаАнотація:
A direct numerical simulation of the three-dimensional unsteady compressible Navier–Stokes equations is performed to investigate the infrasonic field generated in a realistic atmosphere by an explosive source placed at ground level. To this end, a high-order finite-difference method originally developed for aeroacoustic applications is employed. The maximum overpressure and the main frequency of the signal recorded at 4 km distance from the source location are about 4000 Pa and 0.2 Hz, respectively. The atmosphere is parametrized as a vertically stratified medium, constructed by specifying vertical profiles of the temperature and the horizontal wind which reproduce measurements. The computation is carried out up to 140 km altitude and 450 km range. The goal of the present paper is twofold. On the one hand, the feasibility of using a direct numerical simulation of the three-dimensional fluid dynamic equations for the detailed description of long-range propagation in the atmosphere is proven. On the other hand, a physical analysis of the infrasonic field is realized. In particular, great attention is directed towards some important phenomena which are not taken into account or not well predicted by classical propagation models. To begin with, the present study clearly demonstrates that the weakly nonlinear ray theory may lead to an incorrect evaluation of the waveform distortion of high-amplitude waves propagating towards the lower thermosphere. In addition, signals recorded in the shadow zones are investigated. In this regard, the influence on the acoustic field of temperature and wind inhomogeneities of length scale comparable with the acoustic wavelength is analysed. The role of diffraction at the thermospheric caustic is finally examined and it is pointed out that the amplitude of the source may have a strong impact on the length of the shadow zone.
23
Stankevych, S. V., M. D. Yevtushenko, and A. V. Matsyura. "Host plants as reservoirs of the main oil-producing cabbage crops pests in the eastern forest-steppe of Ukraine." Ukrainian Journal of Ecology 10, no. 6 (December 28, 2020): 243–48. http://dx.doi.org/10.15421/2020_289.
Повний текст джерелаАнотація:
Considering the geographical position of Ukraine, which is Such biotic factor as the vegetation distribution, which is the forage base for most insects, influences their spreading greatly. This connection is strongly expressed among the harmful herbivorous insects. The presence and distribution of the plants which are cultivated or used by humans and on which the insects are fed is certainly the first and basic condition for the emergence of a zone or a breeding ground of harmfulness. The presence of the most preferred by the insects fodder plants often leads to the formation of a zone or a center of the greatest damage (in the presence of other favorable conditions for the existence and reproduction of the pest). In the course of the researches concerning the identification of the host plants as reservoirs of the main oil producing cabbage crops pests which have been conducted in 2011–2014 in the communities (meadows, roadsides of highways and field perimeters) of the Kharkiv district of the Kharkiv region it has been found out the host plants as reservoirs for the dominant pests of the oil producing cabbage crops were dandelion, caustic buttercup, field mustard, hedge mustard, tansy mustard, yellow rocket and field shepherd’s purse. The largest number of species of the host plants as reservoirs was found on the roadsides of highways and along the field perimeters (6 species) and on the meadows (2 species).The cruciferous fleas, rape blossom beetles and cruciferous bugs visited such crops as field mustard, hedge mustard and yellow rocket most often. Field shepherd’s purse was the least significant among the identified host plants as reservoirs. Only a small amount of the cabbage fleas fed on this crop. This fact can be explained by the small white flowers that do not attract the rape blossom beetles and rose chafers as well as by a ground flat leaf rosette, which is always covered with dust and prevents the fleas and bugs from feeding.
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Uzwatania, Fina, Riska Surya Ningrum, and Sri Resti O. "FORMULATION OF LIQUID HAND SOAP MADE FROM NEEM SEED OIL AND LEMONGRASS ESSENTIAL OIL." Indonesian Journal of Applied Research (IJAR) 1, no. 3 (December 28, 2020): 155–62. http://dx.doi.org/10.30997/ijar.v1i3.79.
Повний текст джерелаАнотація:
The COVID-19 outbreak has overly emphasised the importance of handwashing with soap to reduce the spread of the virus. This study was conducted to formulate a liquid hand soap with neem oil and lemongrass essential oil as an natural antibacterial component. Three different concentrations of neem oil 5%; 10% and 15% and three different concentration of lemongrass essential oil (0.2%; 0.4%;0.6%) were formulated as liquid soap using coconut oil, castor oil and neem oil as its soap bases. The natural liquid soap was made by saponification reaction between oils and potassium hydroxide. The soap was evaluated for its pH value, density, foam stability, insoluble in alcohol content, free fatty acid and antibacterial activity. The results showed that the colour of the liquid soap was transparent with yellowish colored and had distinctive smell of neem oil. The pH values of the different formulated liquid hand soaps are within the accepted pH range of 4 - 10. The specific gravity was 1,083 – 1,088 g/ml. The foam stability range was 25.35% - 78.38%, respectively. The insoluble in alcohol content range were 0.14 – 0.4. The free caustic alkali range was 0.12 – 0.47. The liquid hand soap can inhibit the growth of Staphylococcus aureus. The inhibition zone diameter of liquid hand soap was 1.98- 2.61 cm. It was therefore proven that neem oil and lemongrass essensial oil is effective as an antibacterial component in the formulation of liquid hand soap.
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Santosh Kumar, P., S. Vidhya, and S. Mahalaxmi. "Antimicrobial Efficacy of Various Concentrations of Bamboo Salt against Enterococcus faecalis and Candida albicans: An in vitro Study." Journal of Operative Dentistry & Endodontics 2, no. 2 (2017): 65–68. http://dx.doi.org/10.5005/jp-journals-10047-0039.
Повний текст джерелаАнотація:
ABSTRACT Sodium hypochlorite (NaOCl) remains the gold standard against which any new endodontic irrigant is compared. But, its inadvertent extrusion beyond the confines of the root canal can be caustic to vital periapical or periodontal tissues. There has been an increase in the use of herbal medicines as irrigants over the last two decades. Bamboo salt is a Korean folk medicine, which shows promising antimicrobial, antioxidant, and anti-inflammatory properties. The aim of this in vitro study was to comparatively evaluate the effectiveness of 1, 3, and 5% bamboo salt against Enterococcus faecalis and Candida albicans using agar diffusion test; 4% NaOCl was used as control. The experiment was performed in triplicate and the zone of inhibition (ZOI) was measured. The results of the present study showed that 4% NaOCl and 5% bamboo salt showed significantly higher mean ZOI than the other groups against E. faecalis; 4% NaOCl showed significantly higher mean ZOI than the other groups against C. albicans, followed by 5 and 3% bamboo salt. Hence, it can be concluded that 4% NaOCl proved to be the most effective antimicrobial against both the species; 5% bamboo salt was as effective as 4% NaOCl against E. faecalis, but significantly less effective against C. albicans. How to cite this article Santosh Kumar P, Vidhya S, Mahalaxmi S. Antimicrobial Efficacy of Various Concentrations of Bamboo Salt against Enterococcus faecalis and Candida albicans: An in vitro Study. J Oper Dent Endod 2017;2(2):65-68.
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Kubiak, Marcin, Vladimír Dekýš, Tomasz Domański, Pavol Novák, and Zbigniew Saternus. "Computer simulations of thermal phenomena in surface heating process using the real distribution of Yb:YAG laser power." MATEC Web of Conferences 157 (2018): 02021. http://dx.doi.org/10.1051/matecconf/201815702021.
Повний текст джерелаАнотація:
This work concerns mathematical and numerical modelling of temperature field during Yb:YAG laser heating of sheets made of S355 steel with the motion of liquid steel in the fusion zone taken into account. Laser power distribution and the caustics are determined on the basis of the geostatistical kriging method. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using projection method and finite volume method. Numerical algorithms are implemented into computer solver using ObjectPascal programming language. Computer simulations of Yb:YAG laser heating process are performed for different process parameters. Characteristic zones of experimentally obtained cross sections of heated elements are compared to numerically predicted fusion zone and heat affected zone.
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Bunge, A. L., and C. J. Radke. "The Origin of Reversible Hydroxide Uptake on Reservoir Rock." Society of Petroleum Engineers Journal 25, no. 05 (October 1, 1985): 711–18. http://dx.doi.org/10.2118/11798-pa.
Повний текст джерелаАнотація:
Abstract When reservoir solids reversibly consume hydroxide, the impact on alkaline-waterflood performance can be significant. Only recently has this reaction been recognized as a principal factor influencing oil recovery rates and chemical-pulse depletion. This paper considers the origin of the reversible hydroxide uptake to be ion exchange of sodium for hydrogen ions. Using a simple, mass-action equilibrium model, we describe the alkali exchange isotherm. Because hydronium and hydroxide concentrations in water are never zero, hydroxide uptake must be reported relative to a reference pH and salinity. With the recognition of a reference state pH and salinity. With the recognition of a reference state and with the mass-action model, we predict qualitatively the effects of pH, salt concentration, and temperature on the measured hydroxide uptake isotherms for the Wilmington, Ranger-zone sand. Mineral sites that exchange ions of sodium for hydrogen may also exchange calcium for hydrogen or for sodium. Using simple mass-action equilibria again, we demonstrate that reversible hydroxide uptake depends on hardness concentration and that calcium/sodium exchange is pH dependent. Introduction Alkaline flooding is a technique in which chemical interactions with reservoir minerals are of paramount importance to success or failure. Hydroxide consumption falls into three broad categories:reversible rock adsorption or ion exchange,congruent and incongruent mineral dissolution, andprecipitation of insoluble hydroxides. All three loss mechanisms have been considered in various levels of detail. Reversible hydroxide ion uptake, which was overlooked in earlier work on alkali/rock interactions, is, perhaps, the least transparent consumption reaction. Its perhaps, the least transparent consumption reaction. Its existence and importance have come to light only recently. In modeling the alkaline oil recovery process, de Zabala et al. point out that equilibrium hydroxide ion uptake causes a chromographic lag in caustic and in the accompanying in-situ generated surfactants, which in turn slows oil-production rates. Likewise, Bunge and Radke demonstrate that hydroxide ion uptake alone can diminish an alkaline chemical pulse to ineffective concentration levels. Thus, even if caustic consumption by dissolution and precipitation could be eliminated, ion-exchange delay can precipitation could be eliminated, ion-exchange delay can limit the success of alkaline EOR. Therefore, when a reservoir is considered for possible alkaline flooding, understanding and quantifying any alkali/rock ion exchange is necessary. This paper presents a simple, mass-action treatment of reversible hydroxide ion uptake by sodium/hydrogen ion exchange followed by a reaction to form or dissociate water. We refer to this overall reaction scheme as hydroxide uptake, or reversible hydroxide consumption. By using the mass-action model and by paying careful attention to the measurement of alkali exchange isotherms, we show how the effects of pH, salt content, and temperature on the hydroxide uptake isotherms may be explained. The relationship between sodium/hydrogen exchange and calcium/sodium exchange is also explored. We demonstrate that calcium/sodium exchange is a combination of sodium/hydrogen and calcium/hydrogen exchange. Therefore, calcium/sodium exchange isotherms generally must be a function of pH, and hydroxide exchange isotherms must depend on calcium concentration. Finally, the connection between the hydrogen exchange capacity (HEC) and the calcium exchange capacity (CEC) is elucidated. Sodium/Hydrogen Exchange Fig. 1 gives the reversible hydroxide uptake on Wilmington, Ranger-zone sand as a function of hydroxide concentration at three temperatures with and without NaCl. Although there is considerable scatter in the data and few points at the lower pH values, the uptake isotherms appear Langmuir in shape. Also, alkali exchange increases with increasing temperature but decreases when salt is added. Reversible alkali exchange occurs not only with the unconsolidated reservoir materials shown here but also on consolidated Berea sandstone. To quantify the behavior of reversible surface uptake of hydroxide ions on reservoir minerals, we adopt our previous. ture of weak-acid sodium/hydrogen cation previous. ture of weak-acid sodium/hydrogen cation exchange: MOH+Na+ + MONa+H+................... (1) where M represents a mineral exchange site. For oxides (such as silica) MOH denotes a hydrolyzable acid site, while for clay minerals (such as kaolinite or montmorillonite MOH denotes a negative lattice exchange site occupied by a hydronium ion. SPEJ P. 711
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Kacimov, Anvar, Ali Al-Maktoumi, Said Al-Ismaily, and Hamed Al-Busaidi. "Moisture and temperature in a proppant-enveloped silt block of a recharge dam reservoir: Laboratory experiment and 1-D mathematical modelling." Journal of Agricultural and Marine Sciences [JAMS] 22, no. 1 (January 17, 2018): 8. http://dx.doi.org/10.24200/jams.vol22iss1pp8-17.
Повний текст джерелаАнотація:
Mosaic 3-D cascade of parallelepiped-shaped silt blocks, which sandwich sand- lled cracks, has been discovered in the eld and tested in lab experiments. Controlled wetting-drying of these blocks, collected from a dam reservoir, mimics field ponding-desiccation conditions of the topsoil layer subject to caustic solar radiation, high temperature and wind, typical in the Batinah region of Oman. In 1-D analytical modelling of a transient Richards’ equation for vertical evaporation, the method of small perturbations is applied, assuming that the relative permeability is Avery-anov’s 3.5-power function of the moisture content and capillary pressure is a given (measured) function. A linearized advective dispersion equation is solved with respect to the second term in the series expansion of the moisture content as a function of spatial coordinates and time. For a single block of a nite thickness we solve a boundary value problem with a no- ow condition at the bottom and a constant moisture content at the surface. Preliminary comparisons with theta-, TDR- probes measuring the moisture content and temperature at several in-block points are made. Results corroborate that a 3-D heterogeneity of soil physical properties, in particular, horizontal and vertical capillary barriers emerging on the interfaces between silt and sand generate eco-niches with stored soil water compartments favourable for lush vegetation in desert conditions. Desiccation significantly increases the temperature in the blocks and re-wetting of the blocks reduces the daily average and peak temperatures, the latter by almost 15°C. This is important for planning irrigation in smartly designed soil substrates and sustainability of wild plants in the region where the top soil peak temperature in the study area exceeds 70°C in Summer but smartly structured soils maintain lash vegetation. Thee layer of dry top-blocks acts as a thermal insulator for the subjacent layers of wet blocks that may host the root zone of woody species.
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Iversen, Einar. "Amplitude, Fresnel zone, and NMO velocity for PP and SS normal-incidence reflections." GEOPHYSICS 71, no. 2 (March 2006): W1—W14. http://dx.doi.org/10.1190/1.2187814.
Повний текст джерелаАнотація:
Inspired by recent ray-theoretical developments, the theory of normal-incidence rays is generalized to accommodate P- and S-waves in layered isotropic and anisotropic media. The calculation of the three main factors contributing to the two-way amplitude — i.e., geometric spreading, phase shift from caustics, and accumulated reflection/transmission coefficients — is formulated as a recursive process in the upward direction of the normal-incidence rays. This step-by-step approach makes it possible to implement zero-offset amplitude modeling as an efficient one-way wavefront construction process. For the purpose of upward dynamic ray tracing, the one-way eigensolution matrix is introduced, having as minors the paraxial ray-tracing matrices for the wavefronts of two hypothetical waves, referred to by Hubral as the normal-incidence point (NIP) wave and the normal wave. Dynamic ray tracing expressed in terms of the one-way eigensolution matrix has two advantages: The formulas for geometric spreading, phase shift from caustics, and Fresnel zone matrix become particularly simple, and the amplitude and Fresnel zone matrix can be calculated without explicit knowledge of the interface curvatures at the point of normal-incidence reflection.
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G. Badalouka, B. "Experimental Evaluation of the Plastic Zone at Crack Tip by Caustics." Open Mechanical Engineering Journal 6, no. 1 (May 4, 2012): 83–89. http://dx.doi.org/10.2174/1874155x01206010083.
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Deane, Grant. "Surface reflection caustics and their impact on communications in the littoral zone." Journal of the Acoustical Society of America 119, no. 5 (May 2006): 3427. http://dx.doi.org/10.1121/1.4786872.
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Prado, José Antonio, Pedro Infante L., Manuel Arriagada B., and Sergio Aguirre A. "Funciones de biomasa para seis especies arbustivas de la zona árida chilena." Ciencia & Investigación Forestal 1, no. 2 (June 17, 1987): 11–20. http://dx.doi.org/10.52904/0718-4646.1987.6.
Повний текст джерелаАнотація:
Como parte de un estudio que pretende cuantificar la disponibilidad de biomasa en un sector de la zona árida chilena, se desarrollan funciones para estimar la biomasa de seis especies consideradas importantes, que son: Acacia caven, Cassia coquimbensis, Colliguaya odorifera, Cordia decandra, Flourenzia thurifera y Lithraea caustica.
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Worthmann, Brian M. "Analytic solution to a waveguide featuring caustics and shadow zones." Journal of the Acoustical Society of America 145, no. 3 (March 2019): 1804. http://dx.doi.org/10.1121/1.5101606.
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Downs, Robert, and Sophie Kaye. "Sonic boom focus modeling of benchmark cases using the PCBoom suite." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A119. http://dx.doi.org/10.1121/10.0010839.
Повний текст джерелаАнотація:
Focusing of sonic booms is a phenomenon that can arise from particular atmospheric conditions or aircraft trajectories including acceleration, turns, or other variations from steady level flight. Because such maneuvers are unavoidable, development of regulations for civil supersonic flight will depend on the capability to understand and predict the scenarios in which focus booms can lead to ground overpressures several times higher than typical carpet booms. Models for predicting sonic boom focal zones and focus boom signatures have been developed by several organizations, and a recent AIAA Sonic Boom Prediction Workshop provided an opportunity to compare results among such models. Rallabhandi et al . developed benchmark cases to further extend verification of focus boom models. The PCBoom suite of tools, including the lossy nonlinear Tricomi equation (LNTE) module, was used to predict caustic geometry and pressure signatures near the caustic arising from a constant acceleration level trajectory and also from an accelerating climb trajectory. A recently developed methodto streamline the focus boom modeling process within PCBoom was exercised as part of this benchmark case evaluation. [Work supported by the National Aeronautics and Space Administration under project VXAHA321.]
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Xu, Z., R. Yang, J. Zhao, B. Wang, Y. Wang, B. Xiong, Z. Wang, X. Lu, and S. Mei. "Experimental Study of the Process Zone, Nucleation Zone and Plastic Area of Earthquakes by the Shadow Optical Method of Caustics." Pure and Applied Geophysics 159, no. 9 (August 1, 2002): 1951–66. http://dx.doi.org/10.1007/s00024-002-8717-8.
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Razanov, Sergey, Galina Ogorodnichuk, and Мykola Komynar. "EFFECT OF SOIL TREATMENT ON CESIUM-137 ACCUMULATION IN FLOWER POLLEN AND IN ITS PROCESSING PRODUCTS BY HONEY BEES." Agriculture and Forestry, no. 3 (September 28, 2021): 161–73. http://dx.doi.org/10.37128/2707-5826-2021-3-13.
Повний текст джерелаАнотація:
Over the past few decades, the level of radiation has significantly increased due to artificial sources – radionuclides. In particular, the Chernobyl accident led to the release of about 50 million Кі of various types of radionuclides into the environment. As a result of the accident at the Chernobyl nuclear power plant in Ukraine, a large number of territories of the Zhytomyr region are polluted – 50%, Kiev – 26%. About 26% of the contaminated area falls on the Chernigov, Rivne, Sumy and Volyn regions. The radioactive substances that were part of the nuclear fuel were concentrated in the environment, from where they partially migrate along the soil-plant-living organisms chain, causing a number of negative changes in them. Immediately after the Chernobyl accident, iodine-131 posed a great danger to living organisms; its radioactivity in the contaminated area was 7.3 MКi. Iodine-131 is a beta and gamma emitter with a half-life of 8.04 days. This element is characterized by high activity in the soil-plant-production-organism system. It enters the body by the oral route and accumulates mainly in the thyroid gland. At the same time, cesium-134, cesium-137 and strontium-90 are also dangerous for living organisms, the share of which is about 3% of the total radioactivity. All other radionuclides that were released into the environment during the Chernobyl accident are less dangerous due to the low rate of entry into living organisms. Cesium-137 has a half-life of 30.2 years and is absorbed into the body in three ways: percutaneous, aerial and oral. The largest proportion of cesium-137 is ingested orally. It is a chemical analogue of potassium and is actively involved in the metabolic process. Therefore, it can accumulate in high amounts in body tissues. About 10% of cesium-137 is excreted from the body with indigestible food residues, and the vast majority - with urine. Cesium-137, penetrating into the body, is concentrated mainly in muscle tissue, and comparatively less in bone tissue. It is excreted from bone tissue much more slowly than from muscle tissue. Now in the environment there is still about 50% of cesium-137, which got into the environment as a result of the Chernobyl accident. Radionuclides in the soil are in a moving state, therefore they move to certain layers of it. The speed of such movement of radionuclides in the soil depends on its properties, the content of mineral and organic substances. In particular, it was revealed that the migration of cesium-137 on mineral sod-podzolic soils is ten times lower than on peat and peat-bog soils. This is typical of the soil of the ecological zone of Polesie. The composition of the soils of this zone includes no more than 1.0% of clay, 0.8-1.2% of humus, 3-5% of the silty fraction, causing a high migration of radionuclides. Cesium-137 in these soils is in the sod in a fast-moving form and rather intensively migrates into the vegetation. It has been proven that the mineral part and humus firmly fix cesium-137. The accident resulted in about 1,500,000 pollution in Ukraine. Hectares of forests, most of which have lost their practical value and are withdrawn from use. It has been established that the main amount of radionuclides is concentrated in the upper five-centimeter soil layer and in the forest litter, which is characteristic of pine forests. In pine forest stands, 30-60% strontium-90 and 40-80% cesium-137 are concentrated in the litter, and about a third of radionuclides are concentrated in deciduous forests. Most radionuclides enter plants by the root route. Some authors report that sometimes plants accumulate significantly more radionuclides, even with a lower content of them in the soil. This trend is observed in the Polesie of Ukraine. Over the past 15 years, the strontium-90 content in plant products has not changed significantly. Researchers have studied the peculiarities of the accumulation of radioactive substances by melliferous plants, which can actively accumulate cesium-137. Plants of the family Rosaceae, buckwheat, buttercups are classified as active accumulators of radiocesium. A high content of strontium-90 is characterized by silver cinquefoil, caustic buttercup, and such honey plants as red and white clover, alfalfa, horned lily, sainfoin and mouse peas, common heather, blueberries intensively accumulate both cesium-137 and strontium-90. The intensity of accumulation of cesium-137 in bee pollen, perge and homogenate of drone larvae produced by bees from pollen of winter rape, sunflower and buckwheat in different ways was studied.
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Stolecka, Katarzyna. "Hazards of the Road Transportation of Hazardous Materials." System Safety: Human - Technical Facility - Environment 2, no. 1 (March 1, 2020): 237–46. http://dx.doi.org/10.2478/czoto-2020-0029.
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AbstractA lot of substances and items are transported by road, sea, rail and air every day. The biggest hazard is created by the transportation of hazardous substances with flammable, caustic or toxic properties. The hazard level increases if such substances are transported through densely populated areas. Traffic intensity, the technical condition of vehicles, drivers’ errors or ignorance and non-compliance with legal regulations are examples of factors that can lead to potential failures in the transport sector. Accidents can cause an uncontrolled release of dangerous gases or liquids, resulting e.g. in environmental degradation or a hazard to humans. The article presents the issues related to the hazards presented by road transportation of hazardous materials. Examples are shown of potential effects of accidents and hazard zones arising due to a release of selected hazardous substances, such as chlorine, ammonia, petrol, diesel oil or LPG.
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Braga de Lima, Juvêncio, Claudio Santos Rodrigues, and Vanessa Madrona Moreira Salles. "AMBIENTE MUNIFICENTE NA CRIAÇÃO E DESENVOLVIMENTO DO POLO AUDIOVISUAL DA ZONA DA MATA (MG)." Latitude 13, no. 1 (June 15, 2020): 80–104. http://dx.doi.org/10.28998/lte.2019.n.1.6760.
Повний текст джерелаАнотація:
Neste trabalho aborda-se o cluster cultural identificado como o Polo Audiovisual da Zona da Mata ( MG). O estudo partiu da polaridade ambiente munificente ou escasso com base em Feldman (2001), bem como a problemática da diferença entre atributos do ambiente e fatores causais para desenvolvimento de clusters. Foi praticada a observação livre, recorrendo-se registros em anotações de campo de natureza descritiva e reflexiva, construindo-se um roteiro para entrevistas com um informante-chave e na análise de declarações e reflexões de diferentes agentes expostas em documentos do Polo. Constatou-se que o Polo nasce de ações de empresas industriais da cidade Cataguases (MG) no incentivo à produção cultural, expandindo-se para municípios vizinhos com o “Fórum Divercidades Criativas”. Identificaram-se quatro fases: Rede de Cooperação Local (2002-2004); Formação e aproximação do mercado audiovisual (2005-2009); Modelagem e Implantação do Polo Audiovisual (2010 – 2015); Cluster Audiovisual em Rede (2015...), com regularidade da atividade da cadeia produtiva local. Entre 2010 e 2017 verifica-se que ocorreu um impacto de R$ 18,2 milhões na economia regional. A análise dessas evidências permite concordar com Feldman (2001), que o vigor do Polo emana de suas características como atributos do ambiente e não como fatores causais, imitáveis para obter resultados semelhantes em outras regiões.
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Lin, Ying-Tsong, Lora J. Van Uffelen, James H. Miller, Gopu R. Potty, and Kathleen J. Vigness-Raposa. "Horizontal refraction and diffraction of underwater sound around an island." Journal of the Acoustical Society of America 151, no. 3 (March 2022): 1684–94. http://dx.doi.org/10.1121/10.0009672.
Повний текст джерелаАнотація:
The three-dimensional (3D) propagation effects of horizontal refraction and diffraction were measured on a tetrahedral hydrophone array deployed near the coast of Block Island, RI. Linear frequency modulated chirp signals, centered at 1 kHz with a 400 Hz bandwidth, were transmitted from a ship moving out of the acoustic shadow zone blocked by the island from the perspective of the hydrophone array. The observed shadow zone boundary was consistent with the prediction made by a 3D sound propagation model incorporating high-resolution bathymetry and realistic sound speed obtained from a data-assimilated regional ocean model. The 3D modal ray calculation provided additional insight into the frequency dependence of the signal spreading. This analysis found that the modes at higher frequencies can propagate closer to the coast of the island with shallower modal cutoff depths, where the sound energy penetrates the sloping seafloor at supercritical incidence. The evidence of horizontal caustics of the sound was shown in the parabolic equation and modal ray models by comparing to the arrival pattern observed in the data. The arrival angle measurements on the tetrahedral array show the complex propagation patterns, including the diffracted energy in the island shadow and acoustic energy refracted away from the island.
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Yang, Jidong, Hejun Zhu, Jianping Huang, and Zhenchun Li. "2D isotropic elastic Gaussian-beam migration for common-shot multicomponent records." GEOPHYSICS 83, no. 2 (March 1, 2018): S127—S140. http://dx.doi.org/10.1190/geo2017-0078.1.
Повний текст джерелаАнотація:
Gaussian-beam migration (GBM) is flexible and adaptable for imaging geologically complicated areas. It avoids some limitations, such as amplitude singularity in caustic zones and an inability to image multiple arrivals, of traditional ray-based migration approaches. Previous studies on GBM mainly focused on acoustic media. We have developed a 2D isotropic elastic GBM scheme for common-shot multicomponent records. Our method extrapolates P- and S-mode wavefields simultaneously using the Kirchhoff-Helmholtz integral solution of the isotropic elastodynamic equation. We separate the extrapolated wavefields into compressional and shear modes using the Helmholtz decomposition, and we then implement a modified dot-product imaging condition. This approach enables us to produce clear PP-images and avoid polarity reversal issues for PS-images. In addition, based on the theory of wavefield approximation in the effective vicinity of central rays, we derive a formula to compute the propagation angles of paraxial rays, which can be used to extract angle-domain common-image gathers.
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Sukandar, Sukandar, and Yana Heryana. "ANALISA KERUSAKAN PIPA AIR PENGUMPAN BOILER." Jurnal Teknik Mesin Cakram 3, no. 2 (October 29, 2020): 76. http://dx.doi.org/10.32493/jtc.v3i2.7556.
Повний текст джерелаАнотація:
Abstrak: Pipa air pengumpan boiler adalah suatu sistem pengumpan air ke boiler. Untuk pelindungan dari serangan korosi pada pipa disuntikkan inhibitor. Kerusakan terjadi pada pipadi ujung pipa injeksi inhibitor setelah 7 tahun operasi. Lokasi pipa inhibitor adalah 800 mm setelah swing check valve. Untuk mencari akar penyebab dilakukan analisa kerusakan. Untuk mendukung analisa kerusakan dilakukan pengujian dan pemeriksaan komposisi kimia, fraktografi, metalografi, kekerasan, produk korosi, polarisasi, simulasi aliran dan rasio Na dan PO4 dalam inhibitor. Hasil pemeriksaan komposisi kimia menunjukkan bahwa material pipa adalah sesuai standar. Hasil pemeriksaan fraktografi menunjukkan kerusakan berupa penipisan lokal berbentuk cekungan sepatu kuda. Hasil pemeriksaan metalografi menunjukkan struktur mikro material pipa adalah ferit dan perlit normal. Hasil pemeriksaan produk korosi menunjukkan kandungan oksigen yang sangat tinggi. Hasil pengujian polarisansi dengan inhibitor adalah 19,991 mpy. Hasil simulasi aliran menunjukkan di lokasi pipa injeksi inhibitor adalah zona aliran diam. Hasil pemeriksaan kandungan inhibitor menunjukkan bahwa rasio Na dan PO4 dibawah 2,85:1. Dari hasil pemeriksaan dan pengujian tersebut dapat dikerucutkan bahwa akar penyebab kerusakan pipa air pengumpan boiler adalah serangan korosi akibat konsentrasi oksigen.Kata kunci: Pipa Air Pengumpan Boiler, Baja Karbon, Inhibitor, Aliran Diam, Caustic Gouging, Konsentrasi Oksigen.
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Melo, Itamar Soares de, and Cyro Paulino da Costa. "Controle biológico da murcha de berinjela causada por Verticillium albo-atrum." Anais da Escola Superior de Agricultura Luiz de Queiroz 44, no. 2 (1987): 1353–64. http://dx.doi.org/10.1590/s0071-12761987000200022.
Повний текст джерелаАнотація:
O controle biológico de Verticillium albo-atrum Reinke & Berth., agente causai da murcha de berinjela (Solanum melongena L.), foi feito em condições de laboratório e em condições de campo. Os melhores isolados de Trichoderma foram aqueles que apresentaram, em placas de Petri, uma zona de inibicão bem evidente. Trichoderma hamatum e o isolado T3 de Trichoderma reduziram sensivelmente a incidência da doença em condições de casa-de-vegetação. No campo, T. lignorum e o isolado T3 propiciaram os melhores resultados. Os mutantes de Trichoderma, obtidos por irradiação ultravioleta, não foram eficientes no biocontrole de Verticillium.
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Faria, Luísa. "Desenvolvimento intra-individual das atribuições e dimensões causais durante a adolescência." PSICOLOGIA 11, no. 2/3 (June 4, 2014): 121. http://dx.doi.org/10.17575/rpsicol.v11i2/3.606.
Повний текст джерелаАнотація:
A análise do desenvolvimento intra-individual e dos padrões inter-individuais (sexo, ano de escolaridade, zona de residência e nível socioeconómico) na mudança intra-individual das dimensões atribucionais de locus de causalidade, estabilidade, controlabilidade e influência/importância das causas, no âmbito de um estudo longitudinal sequencial, revelou a ausência de qualquer tipo de evolução com o tempo destas variáveis motivacionais, bem como a ausência de influência das variáveis inter-individuais na mudança intra-individual, contrariamente às hipóteses formuladas. Estes resultados conduziram a uma análise mais detalhada das características dos sujeito «perdidos» e dos sujeitos que permaneceram no estudo longitudinal, quanto às variáveis em estudo que justificassem a ausência de qualquer tipo de evolução. A hipótese da selecção escolar dos alunos com determinados padrões atribucionais (causas externas e incontroláveis), foi levantada para explicar os resultados da análise da mudança intra-individual das dimensões atribucionais e da influência dos padrões inter-individuais nesta mudança- Tal hipótese reforça a importância da implantação de uma intervenção psicológica deliberada, no sentido de promover o desenvolvimento de estratégias mais adequadas para lidar com as situações de fracasso e com a pressão avaliativa do contexto escolar.
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Katunguka Rwakishaya, E. "Prévalence de la trypanosomose chez les petits ruminants et le porc dans une zone endémique de la maladie du sommeil dans le comté de Buikwe, district de Mukono, Ouganda." Revue d’élevage et de médecine vétérinaire des pays tropicaux 49, no. 1 (January 1, 1996): 56–58. http://dx.doi.org/10.19182/remvt.9547.
Повний текст джерелаАнотація:
Une enquête sur la trypanosomose chez les chèvres, les moutons et les porcs a été réalisée dans le comté de Buikwe, district de Mukono en Ouganda du Sud-Est d'avril à août 1994. Des taux d'infection de 8,8 % chez 204 chèvres, 26,7 % chez 60 moutons, et 32,4 % chez 68 porcs de tous âges et des deux sexes ont été enregistrés. Trypanosoma brucei a été détecté chez les chèvres et les porcs, T. congolense chez les moutons et les porcs, et T. vivax chez les chèvres et les moutons. Les taux d'infection étaient semblables pour les deux sexes des espèces animales. Il a été observé que T. vivax causait de hauts niveaux de parasitémie, tandis que les infections à T. brucei étaient associées à de très bas niveaux de parasitémie. Les infections dues à T. brucei étaient à l'origine de 66,7 % de toutes les infections chez les chèvres et 30 % chez les porcs. Il est émis l'hypothèse que certains de ces T. brucei pourraient être T. b. rhodesiense, l'agent responsable de la maladie du sommeil dans cette région.
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Duarte, Lorena Silva, Rayane Da Cruz Alves, Tamara Chagas Ribeiro, Vanessa Fátima Fonseca, and Gisele Aparecida Fófano. "Fatores causais associados à mortalidade por afecções no período perinatal em um município da Zona da Mata Mineira." Enfermagem Brasil 19, no. 2 (May 26, 2020): 148. http://dx.doi.org/10.33233/eb.v19i2.3998.
Повний текст джерелаАнотація:
Introdução: A mortalidade no período perinatal é um importante indicador de saúde materna e infantil visto que reflete sobre cuidados gestacionais e neonatais, além de demonstrar vulnerabilidades que mãe e filho possam estar sujeitos. Objetivo: Elucidar as principais causas de óbitos perinatais com o intuito de subsidiar o planejamento de estratégias preventivas que visem reduzir esse indicador. Métodos: Estudo descritivo, realizado através de dados secundários disponibilizados pela Secretaria Municipal de Saúde da cidade de Ubá/MG, no intervalo de 2015 até abril de 2019, obtendo uma amostra de 64 indivíduos que preenchiam os requisitos necessários da pesquisa. Resultados: Em 2015, registraram-se 16 óbitos, sendo 62,5% fetais. Já em 2016, notificaram-se 17 óbitos, predominantemente fetais; em 2017, foram 17 óbitos, 64,7% não fetais; em 2018, 9 óbitos, sendo 55,55% fetais; em 2019, notificou-se 5 óbitos, todos fetais. Nessa população, as causas mais frequentes foram síndrome da angústia respiratória do recém-nascido e a morte fetal de causa não especificada. Conclusão: É importante que medidas preventivas sejam tomadas para reduzir o coeficiente de mortalidade perinatal, evidenciando que a abordagem do pré-natal ao parto seja mais eficiente.Palavras-chave: mortalidade perinatal, assistência perinatal e morte fetal.
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Jerónimo, Helena Mateus. "QUATRO IDEIAS-CHAVE PARA PENSAR A PROTEÇÃO DA AMAZÓNIA." Nova Revista Amazônica 6, no. 4 (December 6, 2018): 27. http://dx.doi.org/10.18542/nra.v6i4.6494.
Повний текст джерелаАнотація:
Este artigo elenca quatro ideias-chave para pensar os problemas com que a Amazónia se defronta e sua proteção: (1) a linguagem do risco probabilístico é equivocada para analisar os problemas ecológicos e os padrões tecnológicos e económicos dominantes; (2) neste tipo de problemas existem múltiplas incertezas, não suscetíveis de probabilização, devido à influência de interações imprevistas, sinergias negativas e opacidades causais; (3) negar a incerteza e a imprevisibilidade dos problemas que afetam a Amazónia contribui para aumentar a dificuldade em enfrentar um cenário de catástrofe, cujos contornos são difíceis de antever ou de localizar com precisão; (4) poder perspetivar a Amazóniacomo uma “zona de sacrifício” obriga a decisões que envolvem um questionamento sobre os padrões de crescimento económico, as opções tecnológicas passadas e atuais, as escolhas sobre os recursos, eos valores e as experiências das populações.
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Virieux, Jean, and Véronique Farra. "Ray tracing in 3-D complex isotropic media: An analysis of the problem." GEOPHYSICS 56, no. 12 (December 1991): 2057–69. http://dx.doi.org/10.1190/1.1443018.
Повний текст джерелаАнотація:
Procedures for accurate ray tracing in complex three‐dimensional media with interfaces are proposed. The ray tracing equations and the associated paraxial linear equations are solved either by a numerical solver or by an analytical perturbation approach. Interfaces are described with an explicit representation or an implicit representation using B-spline interpolation. For the implicit representation, we exploit two important properties of B-splines, the convex hull and subdivision properties, in order to determine the intersection of the ray with the interface. At the free surface where the recording system is located, a sampling strategy is proposed: limits of branches at caustics, shadow zones, and medium boundaries are detected for a fixed azimuth while the take‐off angle is automatically adjusted in order to have a roughly homogeneous spacing between end points of the rays. The same strategy is also possible for a fixed take‐off angle. The assumed continuity of the traveltime surface between two adjacent azimuths enables one to obtain the initial condition of a ray arriving at any station located on the portion of surface delimited by these two azimuths. This procedure allows for the classification of rays arriving at a given station as we show on different synthetic examples.
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Hubral, Peter, Jorg Schleicher, and Martin Tygel. "Three‐dimensional primary zero‐offset reflections." GEOPHYSICS 58, no. 5 (May 1993): 692–702. http://dx.doi.org/10.1190/1.1443453.
Повний текст джерелаАнотація:
Zero‐offset reflections resulting from point sources are often computed on a large scale in three‐dimensional (3-D) laterally inhomogeneous isotropic media with the help of ray theory. The geometrical‐spreading factor and the number of caustics that determine the shape of the reflected pulse are then generally obtained by integrating the so‐called dynamic ray‐tracing system down and up to the two‐way normal incidence ray. Assuming that this ray is already known, we show that one integration of the dynamic ray‐tracing system in a downward direction with only the initial condition of a point source at the earth’s surface is in fact sufficient to obtain both results. To establish the Fresnel zone of the zero‐offset reflection upon the reflector requires the same single downward integration. By performing a second downward integration (using the initial conditions of a plane wave at the earth’s surface) the complete Fresnel volume around the two‐way normal ray can be found. This should be known to ascertain the validity of the computed zero‐offset event. A careful analysis of the problem as performed here shows that round‐trip integrations of the dynamic ray‐tracing system following the actually propagating wavefront along the two‐way normal ray need never be considered. In fact some useful quantities related to the two‐way normal ray (e.g., the normal‐moveout velocity) require only one single integration in one specific direction only. Finally, a two‐point ray tracing for normal rays can be derived from one‐way dynamic ray tracing.
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Liu, Kang, Dongming Guo, Xinchao Kang, and Jun Zhang. "Study of the Growth Process of Original Crack in the Surrounding Rock of Tunnel under the Adjacent Explosive Load." Shock and Vibration 2020 (January 8, 2020): 1–8. http://dx.doi.org/10.1155/2020/8214021.
Повний текст джерелаАнотація:
The surrounding rock damage of a tunnel under adjacent explosive load is often manifested as the growth of the original crack. In order to thoroughly understand the crack growth mechanism, in this study, the growth process of the original crack was investigated in detail by the dynamic caustics experiment. The experimental study shows that the growth of original crack is the result of the combined action of explosion stress wave and explosive gas. The quasi-static stress generated by the explosive gas was superimposed on the weakened stress field, resulting in the formation of the peak of the main stress difference in the surrounding rock, moving towards the adjacent tunnel in the form of an arc wave. With the arc wave moving towards the original crack, the growth rate of the original crack increases rapidly. During the period of 200 μs to 250 μs, the crack growth rate oscillates at the peak, and its size is approximately equal to the moving speed of the arc wave. Based on the experimental results and microscopic damage mechanics, the high stress concentration at the original crack tip under the stress wave first causes damage localization and the weakest chain is formed by the penetration of the damage localization zones by microcracks by special distribution law. Subsequently, the original crack starts to initiate and grow along the direction of the weakest chain.
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Vivekanand, M. "Phase-resolved spectrum of the Crab pulsar from NICER." Astronomy & Astrophysics 649 (May 2021): A140. http://dx.doi.org/10.1051/0004-6361/202140358.
Повний текст джерелаАнотація:
Context. Studies of the high-energy emission regions of rotation-powered pulsars are typically based on folded light curves (FLCs) and phase-resolved spectra (PRS). Aims. This work uses the NICER observatory to obtain the highest resolution FLC and PRS of the Crab pulsar at soft X-ray energies. Methods. NICER has accumulated about 347 ksec of data on the Crab pulsar. The data were processed using the standard analysis pipeline. Stringent filtering was done for spectral analysis. The individual detectors are calibrated in terms of the long-time light curve (LTLC), raw spectrum, and deadtime. The arrival times of the photons are established in reference to the Solar System barycenter, while the rotation frequency ν and its time derivative ν˙ are used to derive the rotation phase of each photon. Results. The LTLCs, raw spectra, and deadtimes of the individual detectors are statistically similar; the latter two show no evolution with epoch and the detector deadtime is independent of photon energy. The deadtime for the Crab pulsar, taking into account the two types of deadtime, is only ≈7–8% larger than that obtained using the cleaned events. Detector 00 behaves slightly differently from the rest, but can be used for spectral work. The PRS of the two peaks of the Crab pulsar are obtained at a resolution that is better than 1∕512 in rotation phase. The FLC very close to the first peak rises slowly and falls faster. The spectral index of the PRS is almost constant very close to the first peak. Conclusions. The high-resolution FLC and PRS of the peaks of the Crab pulsar provide important constraints for the formation of caustics in the emission zone.