Free energy and vibrational entropy difference between ordered and disordered Ni3Al

We have calculated free energy and vibrational entropy differences in Ni3Al between its equilibrium ordered structure and a disordered fcc solid solution. The free energy and entropy differences were calculated using the method of adiabatic switching in a molecular-dynamics formalism. The path chosen for the free-energy calculations directly connects the disordered with the ordered state. The atomic interactions are described by embedded-atom-method potentials. We find that the vibrational entropy difference increases with temperature from 0.14kB/atom at 300 K to 0.22kB/atom at 1200 K. We have calculated the density of states (DOS) of the disordered phase from the Fourier transform of the velocity-velocity autocorrelation function. The disordered DOS looks more like a broadened version of the ordered DOS. Analysis of the partial density of states shows that the Al atoms vibrations are most affected by the compositional disorder. The phonon partial spectral intensities along the 〈100〉 direction show that the vibrational spectrum of the disordered phase contains intensities at optical mode frequencies of the ordered alloy. We find that the volume difference between the ordered and disordered phases plays the most crucial role in the magnitude of the vibrational entropy difference. If the lattice constant of the two phases is set to the same value, the vibrational entropy difference decreases to zero

Synthesis of RF Circuits with Negative Time Delay by Using LNA

A demonstration of the negative time-delay by using active circuit topologies with negative group delay (NGD) is described in this paper. This negative time delay is realized with two different topologies operating in base band and modulated frequencies. The first NGD topology is composed of an RL-network in feedback with an RF/microwave amplifier. Knowing the characteristics of the amplifier, a synthesis method of this circuit in function of the desired NGD values and the expected time advance is established. The feasibility of this extraordinary physical effect is illustrated with frequency- and time-domain analyses. It is shown in this paper that by considering an arbitrary waveform signal, output in advance of about 7 ns is observed compared to the corresponding input. It is stated that such an effect is not in contradiction with the causality. The other NGD topology is comprised of a microwave amplifier associated with an RLC-series resonant. The theoretical approach illustrating the functioning of this NGD circuit is established by considering the amplifier S-parameters. Then, synthesis relations enabling to choose the NGD device parameters according to the desired NGD and gain values are also established. To demonstrate the relevance of the theoretic concept, a microwave device exhibiting NGD function of about -1.5 ns at around 1.19 GHz was designed and analyzed. The NGD device investigated in this paper presents advantages on its faculty to exhibit positive transmission gain, the implementation of the bias network and matching in the considered NGD frequency band

A rare infection revealed by cervicofacial masses

Digitalitzat per Artypla

Large-scale molecular dynamics simulations of shock induced plasticity in tantalum single crystals

We report on large-scale non-equilibrium molecular dynamics (NEMD) simulations of shock wave compression in Ta single crystals. The atomic interactions are modeled via a recently developed and optimized embedded-atom method (EAM) potential for Ta, which reproduces the equation of state up to 200 GPa. We examined the elastic-plastic transition and shock wave structure for wave propagation along the low index directions: (100), (110) and (111). Shock waves along (100) and (111) exhibit an elastic precursor followed by a plastic wave for particle velocities below 1.1 km/s for (100) and 1.4 km/s for (111). The nature of the plastic deformation along (110) is dominated by twinning for pressures above 41 GPa

Application of Near-Field Emission Processing for Microwave Circuits under Ultra-Short Duration Perturbations

This paper is dealing with a time-frequency modeling method of electromagnetic (EM) near-field (NF) radiated by electronic devices excited by transient pulse signals. The model developed enables to calculate the EM NF maps at different distances from the given device and also the synthesis of radiation sources enabling to reproduce the field maps. The method proposed is based on the ultra wide band (UWB) frequency model of EM NF maps. The number of EM NF maps can be reduced by considering an innovative algorithm in order to establish simply the dipole model. Then, the transient model can be realized by considering the convolution between the transient excitation signals and the dipole-array model. The method proposed was validated by a standard 3D EM tool with a planar microstrip device excited by microwave signal modulating 1.25-GHz-carrier with 0.5-GHz-bandwidth. As expected, good correlation is found between results from simulation and the investigated modelling method.  The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs)

Relationship between individual chamber and whole shell Mg/Ca ratios in Trilobatus sacculifer and implications for individual foraminifera palaeoceanographic reconstructions

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rustic, G. T., Polissar, P. J., Ravelo, A. C., & DeMenocal, P. Relationship between individual chamber and whole shell Mg/Ca ratios in Trilobatus sacculifer and implications for individual foraminifera palaeoceanographic reconstructions. Scientific Reports, 11(1), (2021): 463, https://doi.org/10.1038/s41598-020-80673-8.Precisely targeted measurements of trace elements using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) reveal inter-chamber heterogeneities in specimens of the planktic foraminifer Trilobatus (Globigerinoides) sacculifer. We find that Mg/Ca ratios in the final growth chamber are generally lower compared to previous growth chambers, but final chamber Mg/Ca is elevated in one of thirteen sample intervals. Differences in distributions of Mg/Ca values from separate growth chambers are observed, occurring most often at lower Mg/Ca values, suggesting that single-chamber measurements may not be reflective of the specimen’s integrated Mg/Ca. We compared LA-ICPMS Mg/Ca values to paired, same-individual Mg/Ca measured via inductively coupled plasma optical emission spectrometry (ICP-OES) to assess their correspondence. Paired LA-ICPMS and ICP-OES Mg/Ca show a maximum correlation coefficient of R = 0.92 (p < 0.05) achieved by applying a weighted average of the last and penultimate growth chambers. Population distributions of paired Mg/Ca values are identical under this weighting. These findings demonstrate that multi-chamber LA-ICPMS measurements can approximate entire specimen Mg/Ca, and is thus representative of the integrated conditions experienced during the specimen’s lifespan. This correspondence between LA-ICPMS and ICP-OES data links these methods and demonstrates that both generate Mg/Ca values suitable for individual foraminifera palaeoceanographic reconstructions.This research was funded by National Science Foundation Grants OCE 1401649 and OCE 1405178, the Lamont-Doherty Earth Observatory Climate Center, and the Columbia Center for Climate and Life

Assessment of 50%-Propagation-Delay for Cascaded PCB Non-Linear Interconnect Lines for the High-Rate Signal Integrity Analysis

This paper presents an enlarged study about the 50-% propagation-time assessment of cascaded transmission lines (TLs). First and foremost, the accurate modeling and measurement technique of signal integrity (SI) for high-rate microelectronic interconnection is recalled. This model is based on the reduced transfer function extracted from the electromagnetic (EM) behavior of the interconnect line RLCG-parameters. So, the transfer function established takes into account both the frequency dispersion effects and the different propagation modes. In addition, the transfer function includes also the load and source impedance effects. Then, the SI analysis is proposed for high-speed digital signals through the developed model. To validate the model understudy, a prototype of microstrip interconnection with w =&nbsp;500&nbsp;µm and length d =&nbsp;33&nbsp;mm was designed, simulated, fabricated and tested. Then, comparisons between the frequency and time domain results from the model and from measurements are performed. As expected, good agreement between the S-parameters form measurements and the model proposed is obtained from DC to 8 GHz. Furthermore, a de-embedding method enabling to cancel out the connectors and the probe effects are also presented. In addition, an innovative time-domain characterization is proposed in order to validate the concept with a 2.38&nbsp;Gbit/s-input data signal. Afterwards, the 50-% propagation-time assessment problem is clearly exposed. Consequently an extracting theory of this propagation-time with first order RC-circuits is presented. Finally, to show the relevance of this calculation, propagation-time simulations and an application to signal integrity issues are offered

PCB access impedances extraction method of in-situ integrated circuit

This article describes an extraction technique of input and output impedances of integrated circuits (ICs) implemented onto the printed circuit boards (PCBs). The feasibility of the technique is illustrated with a proof-of-concept (POC) constituted by two ICs operating in a typically transmitter-receiver (Tx-Rx) circuit. The POC system is assumed composed of three different blocks of emitter signal source, load and interconnect passive network. This latter one is assumed defined by its chain matrix known from its electrical and physical characteristics. The proposed impedance extraction method is elaborated from the given signals at the transmitter output and receiver input. The terminal access impedances are formulated in function of the parameters of the interconnect system chain matrix. The feasibility of the method is checked with a passive circuit constituted by transmission lines driven by voltage source with RL-series network internal impedance and loaded at the output by the RC-parallel network. Good correlation between the access impedance reference and calculated is found