792 research outputs found
Next generation main battle tank. Part II: Converting old MBTS into unmanned MBTS (UMBT)
Modern MBTs (Main Battle Tank) are extremely expensive. Many outdated MBTs and other armored vehicles,
often lacking the required armor protection, are still kept in depots. It is now convenient to upgrade them to optionally
unmanned weapons by adding a humanoid driver, and a robotic arm as a loader. Sensors, an optional automatic driving
system, a control and communication suite would complete the transformation. The main armament and secondary
armament may be also changed or upgraded. The off-the-shelf huge electronic equipment can be installed wireless inside
the hull. The old crew compartment may be spoiled of all the human related parts. Only the driver seat may be kept in
order to leave the capability to remove the humanoid, robotized driver and reinstate the human one. This upgrade should
also include a diagnostic system for the vehicle, the sensors and the additional systems to reduce the maintenance burden.
An additional, specialized, lightweight armor suite should be focused to protect the mobilization system, the robots, the
control and the communication system. This second part of the paper introduces a few options to convert the Leopard 1
MBT to an optionally piloted UMBT (Unmanned Main Battle Tank). A first, minimal step, is just the automation of the
original tank. In a second step, the weight is reduced by installing a smaller 60mm cannon with a lighter, but more
numerous ammunition storage. A third step increases the firepower by installing on the main turret an automated turret
with a 12.7 or 30mm cannon with an optional additional 7.62 machinegun. It is also highly advisable to add an APU
(Auxiliary Power Unit) and a battery to reduce IR (infrared) signature, improve main engine life and reduce maintenance
Mobility improvement of heavy tracked vehicles: The "pan" tank experience
This paper shows that the sinkage of the tracked vehicle is the most important parameter in its mobility. Power and fuel consumption follow cubic power law with sinkage. So the usual strategy to increase power is not the more convenient way to improve vehicle off road performance. The Ground Pressure (GP) is the critical parameter. Power requirement goes with the cubic power of sinkage. GP above 0.9 daN/cm2 should be avoided at all costs. The best way to obtain this result on an existing design is to increase track length. However it is easier to work on track width. The easiest modification is to add "Duckbill extensions" in the outer part of the shoe. This system was used on the Sherman Tank when additional armor was added. With modern technology it is perfectly possible to perform experimental tests with new shoes. This can be done by manufacturing prototypes of high stress nitrided steel shoes, usually with 300M high strength steel. Comparative fuel consumption is a good index of vehicle performance. Also wheel diameter and width can be increased to improve off-road performance. Specialized tracks for different terrains should also be designed. The gravity center should be kept slightly rearward. This attitude should not be excessive to keep the pressure value more even possible along the track. In any case the vehicle naturally assumes the backward inclination due to terrain compression. Another important improvement is the addition of computer controlled directional control to improve the accuracy of trajectories. This is particularly important for tracked vehicles where turning involves extremely high energy consumption
Fundamentación filosófica de la pedagogía argentina
Fil: Cassani, Juan E. .
Universidad de Buenos Aire
La enseñanza gramatical
En el aprendizaje del idioma nacional, el conocimiento intuitivo prima en el ciclo primario, y el lógico en el secundario. La intuición pura o con mezcla de conceptos, de que habIa Crocce, hace aprender el manejo del idioma en los primeros grados y continúa actuando hasta la terminación de los estudios, y la forma conceptual aparece de lleno cuando se pasa al estudio teórico de la gramática.
En el ciclo secundario se realiza el aprendizaje por conceptos, es decir, el aprendizaje de las relaciones de las cosas (Crocce), del lenguaje en este caso, y se cultiva la aptitud de pensar, razón que invocan los sostenedores de la gramática en el plan de estudios. La gramática figura entre las materias que peor aprenden los alumnos de nuestros colegios secundarios.Facultad de Humanidades y Ciencias de la Educació
Lpa1-5525 : a new lpa1 mutant isolated in a mutagenized population by a novel non-disrupting screening method
Phytic acid, or myo-inositol 1,2,3,4,5,6-hexakisphosphate, is the main storage form of phosphorus in plants. It is localized in seeds, deposited as mixed salts of mineral cations in protein storage vacuoles; during germination, it is hydrolyzed by phytases to make available P together with all the other cations needed for seed germination. When seeds are used as food or feed, phytic acid and the bound cations are poorly bioavailable for human and monogastric livestock due to their lack of phytase activity. Therefore, reducing the amount of phytic acid is one strategy in breeding programs aimed to improve the nutritional properties of major crops. In this work, we present data on the isolation of a new maize (Zea mays L.) low phytic acid 1 (lpa1) mutant allele obtained by transposon tagging mutagenesis with the Ac element. We describe the generation of the mutagenized population and the screening to isolate new lpa1 mutants. In particular, we developed a fast, cheap and non-disrupting screening method based on the different density of lpa1 seed compared to the wild type. This assay allowed the isolation of the lpa1-5525 mutant characterized by a new mutation in the lpa1 locus associated with a lower amount of phytic phosphorus in the seeds in comparison with the wild type
Gold nanoparticles on nanodiamond for nanophotonic applications
We present here some recent results of a research focused on the prepn. of detonation nanodiamond/Au nanoparticles
hybrid materials. Two different exptl. routes are followed for the decoration of diamond nanoparticles by Au
nanoparticles, that are in turn prepd. by an innovative electroless approach. Structure and morphol. at the nanoscale
level of the Au-on-nanodiamond deposits have been deeply investigated by electron microscopy (FE-SEM, HR-TEM) and
diffraction (XRD) techniques. Optical properties of these systems have been detd. by performing scattering and UV-Vis
absorption measurements, and by comparing the exptl. data with simulated extinction spectra. The results highlighted
very interesting plasmonic and scattering behaviors, mainly related to the high refractive index of diamond
de Sitter Supersymmetry Revisited
We present the basic superconformal field theories in
four-dimensional de Sitter space-time, namely the non-abelian super Yang-Mills
theory and the chiral multiplet theory with gauge interactions or cubic
superpotential. These theories have eight supercharges and are invariant under
the full group of conformal symmetries, which includes the de Sitter
isometry group as a subgroup. The theories are ghost-free and the
anti-commutator is positive. SUSY
Ward identities uniquely select the Bunch-Davies vacuum state. This vacuum
state is invariant under superconformal transformations, despite the fact that
de Sitter space has non-zero Hawking temperature. The theories
are classically invariant under the superconformal group, but this
symmetry is broken by radiative corrections. However, no such difficulty is
expected in the theory, which is presented in appendix B.Comment: 21 pages, 2 figure
Nonlinear Klein-Gordon-Maxwell systems with Neumann boundary conditions on a Riemannian manifold with boundary
Let (M,g) be a smooth compact, n dimensional Riemannian manifold, n=3,4 with
smooth n-1 dimensional boundary. We search the positive solutions of the
singularly perturbed Klein Gordon Maxwell Proca system with homogeneous Neumann
boundary conditions or for the singularly perturbed Klein Gordon Maxwell system
with mixed Dirichlet Neumann homogeneous boundary conditions. We prove that
stable critical points of the mean curvature of the boundary generates
solutions when the perturbation parameter is sufficiently small.Comment: arXiv admin note: text overlap with arXiv:1410.884
Holographic renormalization and supersymmetry
Holographic renormalization is a systematic procedure for regulating
divergences in observables in asymptotically locally AdS spacetimes. For dual
boundary field theories which are supersymmetric it is natural to ask whether
this defines a supersymmetric renormalization scheme. Recent results in
localization have brought this question into sharp focus: rigid supersymmetry
on a curved boundary requires specific geometric structures, and general
arguments imply that BPS observables, such as the partition function, are
invariant under certain deformations of these structures. One can then ask if
the dual holographic observables are similarly invariant. We study this
question in minimal N = 2 gauged supergravity in four and five dimensions. In
four dimensions we show that holographic renormalization precisely reproduces
the expected field theory results. In five dimensions we find that no choice of
standard holographic counterterms is compatible with supersymmetry, which leads
us to introduce novel finite boundary terms. For a class of solutions
satisfying certain topological assumptions we provide some independent tests of
these new boundary terms, in particular showing that they reproduce the
expected VEVs of conserved charges.Comment: 70 pages; corrected typo
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