Elastic Scattering of 6He on Heavy Targets at Coulomb Barrier Energies

Elastic cross sections for the scattering of 6He projectiles by 208Pb at 27 MeV have been studied. The data have been analyzed within the framework of the Optical Model using Saxon–Woods phenomenological form factors for both the real and imaginary parts of the nuclear potential. The elastic scattering data suggests the presence of a long range absorption mechanisms which might be related to the halo structure of 6He.Ministerio Ciencia y Tecnología FPA2002-04181- C04-04 y FPA2000-1592-C03-0

Dependence of exchange anisotropy and coercivity on the Fe–oxide structure in oxygen-passivated Fe nanoparticles

Ultrafine Fe particles have been prepared by the inert gas condensation method and subsequently oxygen passivated. The as-obtained particles consist in an Fe core surrounded by an amorphous Fe-oxide surface layer. The antiferromagnetic character of the Fe-oxide surface induces an exchange anisotropy in the ferromagnetic Fe core when the system is field cooled. Samples have been heat treated in vacuum at different temperatures. Structural changes of the Fe–O layer have been monitored by x-ray diffraction and transmission electron microscopy. Magnetic properties as coercivity, hysteresis loop shift, and evolution of magnetization with temperature have been analyzed for different oxide crystallization stages. A decrease of the exchange anisotropy strength is reported as the structural disorder of the surface oxide layer is decreased with thermal treatment

Dependence of exchange anisotropy and coercivity on the Fe–oxide structure in oxygen-passivated Fe nanoparticles

Ultrafine Fe particles have been prepared by the inert gas condensation method and subsequently oxygen passivated. The as-obtained particles consist in an Fe core surrounded by an amorphous Fe-oxide surface layer. The antiferromagnetic character of the Fe-oxide surface induces an exchange anisotropy in the ferromagnetic Fe core when the system is field cooled. Samples have been heat treated in vacuum at different temperatures. Structural changes of the Fe–O layer have been monitored by x-ray diffraction and transmission electron microscopy. Magnetic properties as coercivity, hysteresis loop shift, and evolution of magnetization with temperature have been analyzed for different oxide crystallization stages. A decrease of the exchange anisotropy strength is reported as the structural disorder of the surface oxide layer is decreased with thermal treatment

Photoacoustic dose monitoring in clinical high-energy photon beams

This work describes all stages of development (setup, optimization, performance, and first experimental measurements) of an acoustic sensor that can be used for range monitoring and dosimetry of clinical radiotherapy beams. The detection device consists of an ultrasonic transducer, a combination of preamplifiers and differential amplifiers with filtered outputs and a digital oscilloscope. Simulations of the experimental setup were carried out to study the optimal measurement geometry and choice of transducer. The dose distributions were calculated with the Monte Carlo code FLUKA, while the acoustic simulations were performed with the analytical wave transport code k-Wave. The temporal profiles of the dose pulses, in the order of mu s, were measured with a scintillating crystal coupled to a photomultiplier and used as input for the acoustic simulation. Measurements were performed in a Cyberknife (TM) radiosurgery beam and a TrueBeam unit. A lead block was submerged in water and placed partially or totally in the irradiation field in order to increase the acoustic signal. Photoacoustic signals were detected with both beams with the expected shape and time-delay, after the frequency response of the detection system was taken into account. The proposed setup can detect photoacoustic signals originating from the penumbra of the treatment fields after being processed with the appropriate image analysis tools

Predicting the academic underachievement in high school in Spain over the next few years: A dynamic modelling approach

[EN] In this paper we propose a dynamic model to understand the evolution of the academic underachievement in a high school in Spain. This model is based on ideas of Christakis and Fowler where individual habits may be transmitted by social contact. Thus, to build the model we suppose that a student has academic failure when she/he gets into study habits transmitted by students with bad academic habits. From the available academic results of the Spanish high school educational system during the period 1999 2008, we fit the model to the data in order to obtain the parameters of the model. Then, we predict the academic underachievement evolution over the next few years.This work has been partially supported by the Spanish M.C.Y.T. grant MTM2009-08587 and the Universitat Politecnica de Valencia grant PAID06-09-2588Camacho Vidal, FJ.; Cortés, J.; Micle, RM.; Sánchez-Sánchez, A. (2013). Predicting the academic underachievement in high school in Spain over the next few years: A dynamic modelling approach. Mathematical and Computer Modelling. 57(7):1703-1708. https://doi.org/10.1016/j.mcm.2011.11.011S1703170857

Drag reduction on a blunt body by self-adaption of rear flexibly hinged flaps

We study the aerodynamics of a blunt-based body with rear flexibly-hinged rigid flaps, subject to a turbulent flow of Reynolds number Re = 12000, under aligned and cross flow conditions with yaw angle β = 0◦ and β = 4◦. To that aim, different values of the equivalent torsional stiffness are considered, to cover the range of reduced velocity U∗ = (0, 3.48] in water tank experiments. The effect of the angular deflection of plates on the drag and near wake flow is analyzed, experimentally and numerically. The results show that, in the range of U∗ herein considered, the plates undergo an inwards quasi-static, self-adaptive deflection, which is symmetric for yaw angles β = 0◦ and asymmetric for β = 4◦. In particular, the plates feature small mean deformation angles for values of U∗ < 1, whereas a sharp and monotonic increase of such deflection occurs for U∗ > 1, i.e. for lower values of the hinge’s stiffness, with an asymptotic trend towards the larger values of U∗. A critical value of reduced velocity of U∗ ≃ 0.96 is obtained as the instability threshold above which plates depart from their initial equilibrium position. The progressive streamlining of the trailing edge translates into significant reductions of the associated mean drag coefficients. Thus, reductions close to 19% with respect to reference static plates configurations are obtained for the most flexible case of U∗ = 3.48 for both β = 0◦ and β = 4◦. A close inspection of the near wake reveals that the inwards progressive mean displacement of the plates yields a reduction in the recirculation bubble size. A symmetric evolution of the recirculating bubble is observed for β = 0◦, whereas the bubble becomes asymmetric for β = 4◦, with a larger leeward clockwise vortex. In both cases, the drag coefficient is shown to vary linearly with the global aspect ratio of the recirculating bubble. The analysis of the numerical results shows that the reduced extension of the recirculating bubble significantly alters the formation length and intensity of the eddies size and associated pressure. It is observed that despite the local pressure decrease in the vortices shed from the trailing edges, the plates self adaption reduces their size and prevents the eddies from entering the cavity, thus, creating a dead flow region with a consequent pressure increase at the body base.Junta de Andalucia FEDER-UJA 1262764Universidad de JaenEuropean CommissionSpanish MCIN/AEI PDC2021-121288-I00European Union Next Generation EU/PRT

Dependence of exchange anisotropy and coercivity on the Fe–oxide structure in oxygen-passivated Fe nanoparticles

3 pages, 5 figures.Ultrafine Fe particles have been prepared by the inert gas condensation method and subsequently oxygen passivated. The as-obtained particles consist in an Fe core surrounded by an amorphous Fe-oxide surface layer. The antiferromagnetic character of the Fe-oxide surface induces an exchange anisotropy in the ferromagnetic Fe core when the system is field cooled. Samples have been heat treated in vacuum at different temperatures. Structural changes of the Fe–O layer have been monitored by x-ray diffraction and transmission electron microscopy. Magnetic properties as coercivity, hysteresis loop shift, and evolution of magnetization with temperature have been analyzed for different oxide crystallization stages. A decrease of the exchange anisotropy strength is reported as the structural disorder of the surface oxide layer is decreased with thermal treatment.Peer reviewe

On the eigenstate equivalent circuit for lossy asymmetric two-ports and its applications

An equivalent-circuit topology for two-port lossy non-symmetric reciprocal networks is presented [1]. The circuit topology is based on the eigenstate decomposition. The proposed circuit consists of two immittances and two transformers with a single complex turns ratio, as shown in Fig. 1. The only three complex parameters of the circuit are obtained from the eigenvalues and eigenvectors of the admittance or impedance matrix of the network in a straightforward way. The real parts of its immittances are always positive. Thus, the circuit is a powerful candidate for modeling asymmetric structures since it preserves some of the valuable properties of the symmetric lattice network: ability to separate the eigenstates and realizability of the real parts of the immittances. Indeed, it degenerates in the classic lattice network if the structure is symmetric. Two direct applications of the circuit are proposed. The first one is the design of asymmetric unit cells of leaky-wave antennas. A model can be found for the behavior of the two-port as a function of the degree of asymmetry using the proposed equivalent circuit topology. The new design methodology is simple and general, unlike the one proposed in [2]. The second application is the analysis and modeling of lossless and lossy bi-periodic scatterers [3]. It significantly simplifies their design, since it reduces the number of elements with respect to other equivalent circuits. Due to the capability of decomposition into the eigenexcitations of the structure, the circuit provides an important physical insight. For different structures, the admittances have been successfully modeled using a few positive and frequency-independent RLC elements

Interaction of 8 He with 208Pb at near-barrier energies: 4 He and 6 He production

Spanish Ministry of Economy and Competitiveness-FPA-2010-22131-CO2-01 (FINURA) y FPA2013-47327-C2-1-RMinistry of Science and Higher Education of Poland-N202 033637National Science Centre of Poland-2013/08/M/ST2/00257 (LEA-COPIGAL) y 2014/14/M/ST2/00738 (COPIN-INFN Collaboration)European Science Foundation-EUI2009-04163432 (EUROGENESIS

A Wear Analysis Carried On Connecting Rod Bearings From Internal Combustion Engines

In the present work, an analysis was carried out to know the wear modes present in connecting rod bearings from internal combustion engines. These mechanical elements were selected since they are exposed to different engineering failures such as incorrect assembly, severe loads, extreme temperatures, inadequate conditions, and loss of lubricity. In this particular case, the bearings that were selected had a service life of approximately 8 years. Different techniques such as SEM and optical microscopy, EDS analysis, hardness testing, and surface profilometry were used to characterize the unworn and worn bearings. Wear mechanisms such as sliding wear (scoring), fatigue wear with cracks where torn out material was clearly observed, discoloration areas, and two- and three-body abrasion wear (rubbing marks) were identified on the bearing surfaces