Rotational nonlinear double-beam energy harvesting

This paper presents an investigation of the performance of a coupled rotational double-beam energy harvester (DBEH) with magnetic nonlinearity. Two spring-connected cantilever beams are fixed on a rotating disc. Repelling magnets are attached to the frame and to the lower beam tip, and an equal-mass block is attached to the tip of the upper beam. To describe the dynamic response, a theoretical model related to the rotational motion of the coupled cantilever beam is derived from the Lagrange equations. In addition, the harmonic balance method, together with the arc-length continuation method, is applied to obtain the frequency response functions (FRFs). Parametric studies are then conducted to analyze the effect of varying the parameters on the energy harvesting performance, and numerical analysis is performed to validate the analytical solutions. Finally, the theoretical model is verified by forward- and reverse-frequency-sweeping experiments. The DBEH in rotational motion can perform effective energy harvesting over a wide range of rotational frequencies (10 to 35 rad/s). The upper beam is found to exhibit better energy harvesting efficiency than the lower beam around the resonant frequency. This study effectively broadens the energy harvesting bandwidth and provides a theoretical model for the design of nonlinear magnet-coupled double-beam structure in rotational energy harvesting.

May the trophy evaluation variables be utilized as population indices in cervids

The most frequently utilized population quality indices in cervids were a fluctuating asymmetry or a branch length in yearlings. Nevertheless, unlike bovids, there has not been a reliable quality index so far that could also be applied at a later age. Therefore, an application reliability testing pertaining to certain elements of trophy measurement for the sake of difference detection between the cohorts was performed on a sample numbering 225 trophies of red deer stags from 11 cohorts. Although each of the nine trophy variables tested has succeeded in finding certain differences, the most reliable are the overall trophy value and circumferences (circumference of coronets, lower beam circumference and upper beam circumference). Since various trophy evaluation systems have been applied in the world, the implementation of the overall trophy value is limited only to the trophies evaluated pursuant to the CIC system. Hence, the most reliable indices are those based upon circumferences.

Removable friction dampers for low-damage steel beam-to-column joints

Beam-to-column joints equipped with friction dampers are promising solutions to improve the performance of steel moment resisting frames due to the possibility to guarantee large dissipation capacity limiting the structural damage under severe seismic conditions. In this paper, the experimental tests and the numerical simulations of two types of joints are shown and discussed with the aim of developing pre-qualified configurations. The friction dampers are designed to be easily removable from both the lower beam flange and the column face by means of bolted connections. The devices are composed of a stack of steel plates conceived to assure symmetrical friction. The friction surface is set in vertical direction in first case and in horizontal direction in the second type. The experimental tests confirmed the effectiveness of both examined joints and the finite element analyses allowed characterizing their local response, thus providing additional insights to improve the design requirements.

QCD equation of state at finite chemical potentials for relativistic nuclear collisions

We review the equation of state of QCD matter at finite densities. We discuss the construction of the equation of state with net baryon number, electric charge, and strangeness using the results of lattice QCD simulations and hadron resonance gas models. Its application to the hydrodynamic analyses of relativistic nuclear collisions suggests that the interplay of multiple conserved charges is important in the quantitative understanding of the dense nuclear matter created at lower beam energies. Several different models of the QCD equation of state are discussed for comparison.

Process Window for Electron Beam Melting of 316LN Stainless Steel

Electron beam melting (EBM) is currently hampered by the low number of materials available for processing. This work presents an experimental study of process parameter development related to EBM processing of stainless steel alloy 316LN. Area energy (AE) input and beam deflection rate were varied to produce a wide array of samples in order to determine which combination of process parameters produced dense (>99%) material. Both microstructure and tensile properties were studied. The aim was to determine a process window which results in dense material. The range of AE which produced dense materials was found to be wider for 316LN than for many other reported materials, especially at lower beam deflection rates. Tensile and microstructural analysis showed that increasing the beam deflection rate, and consequently lowering the AE, resulted in material with a smaller grain size, lower ductility, lower yield strength, and a narrower window for producing material that is neither porous nor swelling.

Structural Health Monitoring of Steel Frame Structure by Experimental Modal Parameter Identification

Structural health monitoring (SHM) is a modern technique f or damage identification in the e xis ting structure. The structural stiffness, frequency, damping, and dominant mode shapes represent the actual operating conditions of the structure. The main principle of structural health monitoring is to identif y the mod al parameters from experime ntal resu lts both damaged and undamaged conditions. Damage is much effective to decrease stiffness and strength of structural components and it changes dynamic behaviour and damping ratio of whole structures. Bruel & Kjaer experi mental modal analys is technique is r ecently used for civil engineering structures for modal parameters estimation. The paper describes the initial structural health monitoring of a steel frame . The modal parameters were estimated for undamaged condition s a nd these result s are verified and up dated by the numerical FEM tool SAP2000. For the undamaged structure , mode shapes and frequencies were calibrated properly. In the second step, damaged was initiated by dismantling one element from the lower part of the frame. The estimat ed m odal parameter s were compared to the initial one. The mode shapes and frequencies are quite different for some specific mode due to damage initiation . One extra mode was created for the damaged frame due to damage initiation. The 4 th mode was not found f or the initial m easurement because of presence of lower beam. Lower beam restraints the 4 th mode and the frame behaves more flexible. Keywords: SHM , Modal parameters, FEM modelling, Damage characterization, Experimental mo dal analysis (EMA) .

Living up to the Hype(-rion)! – observations on ion microprobe geochronology using a high-brightness oxygen plasma source

<p>The recent introduction of a high-brightness RF plasma oxygen ion source (Hyperion H201, Oregon Physics) to large geometry secondary ion mass spectrometers (e.g. CAMECA IMS1280/1300) has increased the range of available primary beam options compared to the several decades old technology of the duoplasmatron it replaces. Notably, the new source provides considerably higher beam density (ca. 10x and 3x for O<sup>-</sup> and O<sub>2</sub><sup>-</sup> respectively), which in principle allows for higher spatial resolution and/or shorter analysis times, coupled with unprecedented long-term beam stability.</p><p>Incorporating the RF plasma into both conventional spot analysis and ion-imaging geochronology routines at the NordSIMS facility has, however, revealed that the source upgrade has consequences for data-acquisition and data reduction strategies, which need to be modified in order to avoid degradation in precision. The most significant difference using the new source for spot analyses is the significant change in aspect ratio (width/depth) of the analysed volume. During a comparable length analysis, a three times brighter O<sub>2</sub><sup>-</sup> primary beam (still favoured for U-Th-Pb geochronology) will sputter a three times deeper crater that is half the width of a comparable intensity duoplasmatron beam, an effective aspect ratio change of six times, introducing “down-hole” inter-element and, to a lesser degree, isotope fractionation effects that SIMS has largely been free of. Depending on the target matrix, this can have a marked effect on the within-run ratio evolution during an analysis, particularly the inter-element ratios Pb/U and UO<sub>n</sub>/U required for full U-Pb geochronology, with standard error of the mean values several times higher than counting statistics, compared to analyses with the lower beam density of the duoplasmatron where s.e. mean commonly closely approaches Poisson counting statistics during a ca. 10 minute analysis. In line with previous observations [1], some improvements can be made by using a Pb/UO vs. UO<sub>2</sub>/UO calibration scheme instead of Pb/U vs. UO<sub>n</sub>/U, but clearly this is not the complete answer. Shortening analyses via fewer cycles in a peak-hopping routine also means smaller √n, affecting s.e. mean; lower integration times can be introduced to permit more cycles, but magnet settling times between peak jumps cannot be reduced in proportion, so the duty cycle is less efficient.</p><p>Strategies developed to mitigate this degradation and take full advantage of the new RF source include: 1) rastering of critically focused primary beams to retain high aspect ratio (at the expense of improved spatial resolution); 2) use of a defocused aperture-projected (Köhler-mode) primary beam (effectively lower beam density); 3) modelling of within-run ratio evolution based on standard analyses in a manner similar to that employed by laser ablation methods [2]; and/or 4) introduction of multicollection capabilities [3] to increase duty cycle efficiency in a shorter analysis. Ultimately, the choice of which method(s) to use will depend upon the goal of a specific project.</p><p>References: [1] Jeon, H. & Whitehouse, M.J.., Geostds & Geoanal. Res. 2014, 39, 443-452]; [2] Paton, C. et al., Geochem. Geophys. Geosyst., 2010, 11, Q0AA06]; [3] Li et al., J. Anal. At. Spectrom., 2015, 30, 979-985</p>

Lumped system model for elastic steel-concrete beams with partial interaction

Purpose The purpose of this paper is to introduce a numerical model to investigate static response of elastic steel-concrete beams. The numerical model is based on the lumped system with the combination of the transfer matrix and the analog beam methods (ABM). The beams are composed of an upper concrete slab and a lower steel beam, connected at the interface by shear transmitting studs. This type of beam is widely used in constructions especially for highway bridges. The static field and point transfer matrices for the element of the elastic composite beam are derived. The present model is verified and is applied to study the static response of elastic composite beams with intermediate conditions. The intermediate condition is considered as an elastic support with various values of stiffness. The elastic support can be considered rigid when the stiffness has very high values. The influence effect of shear stiffness between the upper slab and lower beam, and the end shear restraint on the static behavior of the composite beams is studied. In addition, the change in the stiffness of the elastic support is also highlighted. Design/methodology/approach The objective of this study is to introduce a numerical model based on lumped system to calculate the static performance of elastic composite bridge beams having intermediate elastic support by combining the ABM with the transfer matrix method (TMM). The developed model is applicable for studying static and dynamic responses of steel-concrete elastic composite beams with different end conditions taking into account the effect of partial shear interactions. The validity of the lumped mass model is checked by comparing its results with a distributed model and good agreements are achieved (Ellakany and Tablia, 2010). Findings A model based on the lumped system of the elastic composite steel-concrete bridge beam with intermediate elastic support under static load is presented. The model takes into consideration the effect of the end shear restraint together with the interaction between the upper slab and the lower beam. Combining the analogical beam method with the TMM and analyzing the behavior of the elastic composite beam in terms of shear studs and stiffness, the following outcomes can be drawn: end shear restraint and stiffness of the shear layer are the two main factors affecting the response of elastic composite beams in terms of both the deflection and the moments. Using end shear restraint reduces the deflection extensively by about 40 percent compared to if it is not used assuming that: there is no interaction between the upper slab and the lower beam and the beam is acting as simply supported. As long as the shear layer stiffness increases or interaction exists, the deflection decreases. This reduced rate in deflection is smaller in case of existence of end shear restraint. The effect of the end shear restraint is more prevailing on reducing the deflections in case of partial interactions. However, its effect completely diminishes in case of complete interaction. Presence of the end shear restraint and shear layer stiffness produces almost the same variations in the components of the bending moments of the composite beam. Finally, for a complete interaction, comparing the case of using end shear restraint or the case without it, the differences in the values of the deflections and moments are almost negligible. Research limitations/implications The following assumptions related to the theory of ABM: shear studs connecting both sub-beams are modeled as a thin shear layer, each sub-beam has the same vertical displacement and the shear deformation in the sub-beams is neglected. Practical implications The developed model can be effectively used for a quick estimation of the dynamic responses of elastic composite beams in real life rather than utilizing complicated numerical models. Social implications The applications of this model can be further extended for studying the behavior of complex bridge beams that will guarantee the safety of the public in a quick view. Originality/value Previous models combined the TMM with the ABM for studying the static and free-vibration behaviors of elastic composite beams assuming that the field element is subjected to a distributed load. To study the dynamic response of elastic composite beams subjected to different moving loads using transfer matrix ABM, it was essential to use a massless field element and concentrate the own weight of the beam at the point element. This model is considered a first step for studying the impact factors of elastic composite beams subjected to moving loads.