While the penetration of objects into granular media is well‐studied, there is little understanding of how objects settle in gravities, geff, different from that of Earth—a scenario potentially ...relevant to the geomorphology of planets and asteroids and also to their exploration using man‐made devices. By conducting experiments in an accelerating frame, we explore geff ranging from 0.4 g to 1.2 g. Surprisingly, we find that the rest depth is independent of geff and also that the time required for the object to come to rest scales like geff−1/2. With discrete element modeling simulations, we reproduce the experimental results and extend the range of geff to objects as small as asteroids and as large as Jupiter. Our results shed light on the initial stage of sedimentation into dry granular media across a range of celestial bodies and also have implications for the design of man‐made, extraterrestrial vehicles and structures.
Key Points
The settling depth in granular media is independent of gravity
The settling time scales like g−1/2
Layering driven by granular sedimentation should be similar
This paper aims at introducing the Kalman's filter to science and engineering undergraduate students by means of a simple experiment. It consists in the free fall of an umbrella equipped with a ...mobile phone from a height of a few-meters. Using the data provided by the accelerometer embedded in the phone, it is shown that the use of the Kalman filter allows determining the terminal velocity without the need of performing multiple repetitions of the experiment. Three methods for finding the covariance matrix of the control vector are tested, and their results are compared.
Brevipalpus phoenicis s.l. is an economically important vector of the Citrus leprosis virus-C (CiLV-C), one of the most severe diseases attacking citrus orchards worldwide. Effective control ...strategies for this mite should be designed based on basic information including its population structure, and particularly the factors that influence its dynamics. We sampled sweet orange orchards extensively in eight locations in Brazil and 12 in Mexico. Population genetic structure and genetic variation between both countries, among locations and among sampling sites within locations were evaluated by analysing nucleotide sequence data from fragments of the mitochondrial cytochrome oxidase subunit I (COI). In both countries, B. yothersi was the most common species and was found in almost all locations. Individuals from B. papayensis were found in two locations in Brazil. Brevipalpus yothersi populations collected in Brazil were more genetically diverse (14 haplotypes) than Mexican populations (four haplotypes). Although geographical origin had a low but significant effect (ca. 25%) on the population structure, the greatest effect was from the within location comparison (37.02 %). Potential factors driving our results were discussed.
This paper aims at introducing the Kalman's filter to science and engineering undergraduate students by means of a simple experiment. It consists in the free fall of an umbrella equipped with a ...mobile phone from a height of a few-meters. Using the data provided by the accelerometer embedded in the phone, it is shown that the use of the Kalman filter allows determining the terminal velocity without the need of performing multiple repetitions of the experiment. Three methods for finding the covariance matrix of the control vector are tested, and their results are compared. En este trabajo, se propone un sencillo experimento para introducir a estudiantes de pregrado en ciencias básicas e ingenierías, al filtro de Kalman. Consiste en el estudio de la caída libre de un paraguas equipado con un telefono móvil desde una altura de algunos metros. Utilizando los datos aportados por el acelerometro incluido en el telefono, se demuestra que el uso del filtro de Kalman permite hallar la velocidad terminal sin la necesidad de realizar multiples repeticiones del experimento. Se analizan tres métodos para hallar la matriz de covarianzas del vector de control, y se comparan sus resultados.
La descripción de la dinámica de penetración de intrusos en medios granulares no sólo es relevante para la Física sino también para procesos geofísicos y ramas de la industria, en particular la ...construcción en zonas de terremotos. En el presente trabajo utilizamos la técnica de Acelerometría Lock-in para estudiar la penetración de intrusos pasivos en un medio granular cuasi-bidimensional fluidizado mediante agitación lateral. Esta técnica demuestra que existen dos dinámicas de penetración bien definidas en la medida que el intruso se hunde en el medio granular. Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils in áreas potentially affected by earthquakes. In this work, we use Lock-in accelerometry to study the penetration of passive intruders into quasi-2D granular matter fluidized by lateral shaking. We observed that there are two well-defined stages in the penetration dynamics as the intruder sinks into the granular material. PACS: 45.70.-n, 45.70.Mg, 07.07.Df, 07.50.Qx
Two bioassays were administered to determine the dose-lethality response of Varroa jacobsoni Oudemans and the honey bee, Apis mellifera L., to amitraz, flumethrin and fluvalinate. The first bioassay ...method was spraying by means of the Potter-Bourgerjon's tower. The results are expressed in mean lethal concentrations (LC50). The second method was topical application by means of microsyringe and manual applicator. The results are expressed in mean lethal doses (LD50). Both LC50and LD50values were considerably higher in honey bees than in varroa mites, showing that a wide margin of safety exists between effective doses against mites and harmful doses for honey bees. Both methods gave similar confidence intervals; they showed a comparable sensitivity to changes in dose or concentration of pesticides. /// Se probaron dos métodos de bioensayos toxicológicos para determinar la respuesta dosis-letalidad de amitraz, flumetrina y fluvalinato sobre Varroa jacobsoni Oudemans y Apis mellifera L. El primero fue aspersión por medio de la torre de Potter-Burgerjon; sus resultados se expresan en concentraciones letales medias (CL50). El segundo fue aplicación tópica por medio de microjeringa y aplicador manual; sus resultados se expresan en dosis letales medias (DL50). Las DL50y CL50de todos los productos fueron considerablemente más altas en abejas que en ácaros, lo cual muestra que existe un amplio margen de seguridad entre dosis que son lo suficientemente tóxicas sobre los ácaros, sin llegar a ser peligrosas para las abejas. Ambos métodos de bioensayo dieron intervalos de confianza comparables y presentaron similar sensibilidad en la respuesta a los cambios de dosis y concentración aplicados.
We study the behavior of cylindrical objects as they sink into a drygranular bed fluidized due to lateral oscillations. Somewhat unexpectedly, we have found that, within a large range of lateral ...shaking powers,cylinders with flat bottoms sink vertically, while those with a''foundation'' consisting in ashallow ring attached to their bottom, tilt besides sinking. Thelatter scenario seems to dominate independently from the nature ofthe foundation when strong enough lateral vibrations are applied. Weare able to explain the observed behavior by quasi-2D numericalsimulations, which also demonstrate the influence of the intruder's aspect ratio. The vertical sink dynamics is explained with the help of a Newtonian equation of motion for the intruder. Our findings may shed light on the behavior of buildings and other man-made constructions during earthquakes.
Brevipalpus phoenicis s.l. is an economically important vector of the Citrus leprosis virus-C (CiLV-C), one of the most severe diseases attacking citrus orchards worldwide. Effective control ...strategies for this mite should be designed based on basic information including its population structure, and particularly the factors that influence its dynamics. We sampled sweet orange orchards extensively in eight locations in Brazil and 12 in Mexico. Population genetic structure and genetic variation between both countries, among locations and among sampling sites within locations were evaluated by analysing nucleotide sequence data from fragments of the mitochondrial cytochrome oxidase subunit I (COI). In both countries, B. yothersi was the most common species and was found in almost all locations. Individuals from B. papayensis were found in two locations in Brazil. Brevipalpus yothersi populations collected in Brazil were more genetically diverse (14 haplotypes) than Mexican populations (four haplotypes). Although geographical origin had a low but significant effect (ca. 25%) on the population structure, the greatest effect was from the within location comparison (37.02 %). Potential factors driving our results were discussed.
Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils ...in areas potentially affected by earthquakes. In this work, we use Lock-in accelerometry to study the penetration of intruders into quasi-2D granular matter fluidized by lateral shaking. We observed that there are two well-defined stages in the penetration dynamics as the intruder sinks into the granular material.
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