Huge Dispersion Research Articles

Empirical formulation for the estimate of the equivalent viscous damping of infilled RC frames

The direct displacement-based design (DDBD) is based on the equivalence between the nonlinear hysteretic response of a structure and a simple linear oscillator with equivalent viscous damping (EVD). Typically the EVD is calibrated for different types of structures as a function of the ductility. However, those simple relationships exhibit a huge dispersion and uncertainty since the specific properties of the structural system are not considered. This work proposes an original approach for estimating the EVD of infilled reinforced concrete (RC) frames. We focus on a ductility demand corresponding to an ultimate limit state and we investigate the effect of the properties of infilled RC frames on the EVD. A data-driven hysteresis model proposed by the authors in a previous research is implemented in OpenSees to represent the nonlinear response of infill panels. The optimal EVD at the ultimate limit state is computed using an extensive series of time-history analyses (THAs) on a dataset of 14 infilled RC frames. Afterwards, an empirical correlation law for the estimate of the optimal EVD is calibrated as a function of the geometrical and mechanical properties of infilled RC frames. This formula is meant to be a practical tool for a preliminary design of infilled RC frames. A comparison with the EVD estimated by quasi-static tests and the EVD of bare frames is made. The methods and results presented in this work may be the basis for more robust predictions of the EVD of infilled RC structures.

Predicting dynamic characteristics of a submerged vertical cylinder in the wide-frequency domain based on the wavelet fluid-solid interaction method (WFSIM)

Due to the huge computational cost and dispersion errors, wide-frequency and fluid-structure interaction dynamic analysis of submerged cylindrical shells is difficult to carry out in the design phase. To solve this problem, the wavelet fluid-solid interaction method (WFSIM) is proposed in this paper to avoid the huge computational cost and dispersion errors when predicting the dynamic characteristics of submerged vertical cylinders in a wide-frequency domain. For this purpose, the formulas of the wavelet fluid-solid coupling algorithm to couple the wavelet finite element method and the theory of fluid-structure interaction are derived and introduced carefully first. Then, the formulas to build the numerical model of submerged vertical cylinders are given and introduced in this paper. To verify the effectiveness and efficiency of the proposed method, an experimental study is adopted for predicting the dynamic characteristics of the scaling model of a submarine cabin in a wide-frequency domain. The experimental results indicate that the WFSIM can be adopted for predicting the dynamic characteristics of submerged vertical cylinders in the wide-frequency domain within a few seconds and that the relative errors are less than 10%. Additionally, the wavelet fluid-solid coupling algorithm can also be introduced to model other submerged vertical cylinders for predicting the dynamic characteristics in the wide-frequency domain.

Morphological, structural, optical, broadband frequency range dielectric and electrical properties of PVDF/PMMA/BaTiO3 nanocomposites for futuristic microelectronic and optoelectronic technologies

Polymer blend nanocomposite (PBNC) films consisted of fluoropolymer poly(vinylidene fluoride) (PVDF) and plexiglass polymer poly(methyl methacrylate) (PMMA) blend host matrix (fixed composition blend of PVDF/PMMA = 80/20 wt/wt%) with barium titanate (BaTiO3) ceramic nanofiller of varying concentrations (x = 0, 2.5, 5, 10, and 15 wt%) were prepared via a state-of-the-art solution-cast method. Scanning electron microscope (SEM) images evidenced high homogeneity of these PBNC films and a huge alteration in the spherulite morphology of the PVDF with the increase in dispersed BaTiO3 concentration in the polymer blend matrix. The X-ray diffraction (XRD) patterns identified the presence of electro-active polar β- and γ-phases of the PVDF crystallites in all the composite materials which are supported by the results of Fourier transform infrared (FTIR) spectra. The differential scanning calorimeter (DSC) thermograms explained the high melting temperature of these overlapped PVDF polymorphs and the degree of crystallinity altered anomalously with the variation of nanofiller concentration. The absorbance of ultraviolet-visible (UV-Vis) radiations enhanced while the direct energy band gap of the 80PVDF/20PMMA blend matrix and also the semiconducting BaTiO3 was found to decrease with the increased concentration of nanomaterial in the host polymer matrix. The ambient temperature broadband dielectric spectra covering the frequency range from 20 Hz to 1 GHz explain that the real part of complex dielectric permittivity reduced with a huge dispersion at higher radio frequencies where the dielectric loss tangent and electric modulus spectra exhibited an intense chain segmental relaxation process. The electrical conductivity of these PBNC films increased with frequency augmented and illustrated a small variation for different concentration composites. The experimental results demonstrated that these PVDF/PMMA/BaTiO3 films could be potential candidates for frequency tunable nanodielectric, electromagnetic interference shielders, a flexible dielectric substrate, thermal insulators, and bandgap regulated materials for futuristic microelectronic, capacitive energy storage, and optoelectronic technologies.

Kurtosis-based risk parity: methodology and portfolio effects

In this paper, a risk parity strategy based on portfolio kurtosis as reference measure is introduced. This strategy allocates the asset weights in a portfolio in a manner that allows an homogeneous distribution of responsibility for portfolio returns' huge dispersion, since portfolio kurtosis puts more weight on extreme outcomes than standard deviation does. Therefore, the goal of the strategy is not the minimization of kurtosis, but rather its ‘fair diversification’ among assets. An original closed-form expression for portfolio kurtosis is devised to set up the optimization problem for this type of risk parity strategy. The latter is then compared with the one based on standard deviation by using data from a global equity investment universe and implementing an out-of-sample analysis. The kurtosis-based risk parity strategy has interesting portfolio effects, with lights and shadows. It outperforms the traditional risk parity according to main risk-adjusted performance measures. In terms of asset allocation solutions, it provides more unbalanced and more erratic portfolio weights (albeit without excluding any component) in comparison to those pertaining the traditional risk parity strategy.

Vapour-Phase Selective Hydrogenation of γ-Valerolactone to 2-Methyltetrahydrofuran Biofuel over Silica-Supported Copper Catalysts.

2-Methyltetrahydrofuran (MTHF) is a desirable biomass-based platform chemical with excellent potential as an ideal biofuel, green solvent, and raw material for synthesizing downstream chemicals. In this work, a series of copper nanoparticles encapsulated on SiO2 were prepared by the wet impregnation method and evaluated as efficient non-noble metal catalysts for the vapour-phase hydrogenation of γ-valerolactone (GVL) to MTHF in a fixed-bed reactor under mild reaction conditions. The obtained catalyst properties were determined by XRD, FE-SEM, TEM, UV-DRS, TPR, NH3-TPD, N2O decomposition and pore size distribution measurements. Meanwhile, the parameters/variables tuning their catalytic performance (activity, conversion, selectivity and stability) were examined. Various Cu loadings featured on the SiO2 support are essential for tuning the catalytic activity. Among the catalysts tested, a 5 wt% Cu/SiO2 catalyst showed a 97.2% MTHF selectivity with 71.9% GVL conversion, and showed a stability for 33 h time-on-stream, achieved at 260 °C and atmospheric pressure conditions. It was found that a huge dispersion of Cu metal in support, hydrogen activation ability, abundant acidic sites and surface area are all beneficial for improved MTHF selectivity.

A Smart Wireless IoT Ring for Real-Time Keystroke Recognition Using Edge Computing

Enabling a single ring to recognize 3D keystrokes is a daunting challenge, especially for real-time keystrokes recognition. In this work, we integrated edge computing and machine learning algorithms into a microcontroller unit (MCU) of a smart ring so that keystrokes motion can be accurately recognized in real-time. We developed a multi-level decision (MLD) algorithm and embed a lightweight support vector machine (SVM) algorithm to execute computation for keystroke recognition on the edge of the smart ring. With this method, we can reduce the time for data transmission and avoid the data redundancy problem with the huge dispersion calculation workload; thus, improving the real-time performance of the smart ring device. Consequently, the application of this smart ring-based virtual keyboard system has minimum requirements for hardware, such as memory space and computing capacity. This study demonstrates that the use of low-performance chips in future virtual keyboard systems is possible in order to achieve lower development cost, reduced device size, and improved ease of use. The proposed smart ring is expected to provide a novel and convenient technology for real-world human-computer-interface applications in the future.

FRACTIONAL DISTILLATION OF PYROLYSIS OIL

It is known that pyrolysis oil contains many valuable chemicals, such as, dipentene (limonene), benzene, toluene, xylenes, ethylbenzene and amongst others. The possible approach to make the pyrolytic processing of waste tires more attractive (from an economical point of view) is the recovery of valuable chemicals which can be used as motor fuel. Pyrolysis process of tire particles was carried out at a temperature of 500 °C in water vapor stream. Pyrolysis oils of waste tires contain organic substances with a huge dispersion of molecular weight, represented by various classes of organic compounds, such as hydrocarbons, amides, phenols, amines, organosulfur substances, etc. Analysis of pyrolysis products is a very difficult task because of their complexity and multicomponent properties. The problem of identifying pyrolysis mixtures is acute as the development of reliable analysis of pyrolysis oils is extremely urgent, and it can be solved with the help of the method of preliminary sample preparation. On the other hand, an important step in the recovery of chemicals from pyrolysis oil is primary fractionation where pyrolysis oil is separated into less complex fractions or mixtures. For reliable analysis of pyrolysis oil of waste automobile tires and chemical compounds separation, fractional distillation was carried out. Elemental analysis, FT-IR spectroscopy and gas chromatography mass spectrometry (GC/MS) analysis of pyrolysis oil were performed. It was found out that pyrolysis oil boils at a wide temperature range; four fractions were isolated from pyrolysis oil. It can be concluded that fractional distillation is a much promising method to concentrate compounds (classes

As2Se3-Ge11.5As24Se64.5 based mid-infrared dual nano-slot optical waveguide with huge and wavelength tunable dispersion

An As2Se3-Ge11.5As24Se64.5 based dual nano-slot waveguide with huge chromatic dispersion at mid-infrared is proposed. The large chromatic dispersion at the target wavelength is achieved induced by resonance interaction. The characteristics of dispersion are investigated by employing the FDTD method. The simulation results indicate that by optimizing the geometrical parameters, the maximum dispersion of -3.48×105 ps·nm-1·km-1 over a full width at FWHM of 2 nm at 3000 nm has been attained. A flat and ultra-large dispersion of -3.48×105 ps·nm-1·km-1 from 2980 to 3010 nm is achieved by cascading the dual-slot waveguides. The relative dispersion magnitude fluctuation is less than 1.85%.

Italy’s national research assessment: some unpleasant effects

ABSTRACTHigher education institutions are in a period of profound transformation. In particular, many governments have implemented mechanisms that attempt to relate funding to performance. In this article, we reflect about the relevance of those changes from a regional point of view, by analysing the recent introduction of a performance-based research funding system in Italy. The findings lead to policy indications, questioning the effectiveness of selective funding of universities based on national research assessment exercises when there is heterogeneity across regions in universities scientific performance and, at the same time, there is a huge dispersion of research performance within the individual universities.

Impact of incorporation of volcanic ash on geopolymerization of eco-friendly geopolymer composites: A review

Volcanic ash is a product from an explosive type of volcanic eruptions. Fresh particles of volcanic ash are gritty, abrasive, vexatious and corrosive with huge scale dispersion. Consequently, it is the need of the hour to dispose this waste systematically to have relief from dilemmas like land fillings; climatic changes, pollution of the environment, water, and health hazards although the soil is a mineral intake. This crucially reviewed manuscript includes not merely the comprehension of the incorporation of volcanic ash to develop novel green Geopolymer composites but also to study its impact on the geopolymerization reaction kinetics and reactivity at dissimilar temperatures along with a precise account of its chemistry, mineralogy and the morphology.

Effect of high-order empirical parameters on the nuclear equation of state

A quantitative knowledge of the nuclear Equation of State (EoS) requires an accurate estimation of the uncertainties on the EoS parameters and their mutual correlations. Such correlations are empirically observed in a large set of EoS models by different authors, but they are not always fully understood. We show that some of these correlations can be interpreted from basic physical constraints imposed on a simple Taylor expansion of the binding energy around saturation density. In particular, we investigate the correlations among the following empirical parameters: the symmetry energy $E_{sym}$, the slope and curvature of the symmetry energy $L_{sym}$ and $K_{sym}$, and the curvature and skewness of the binding energy in symmetric matter $K_{sat}$ and $Q_{sat}$. The uncertainties on these correlations is estimated through analytical modelling as well as a meta-modelling analysis of the EoS subject to physical constraints. We show that a huge dispersion of the correlations among low order empirical parameters is induced by the unknown higher order empirical parameters, such as $K_{sym}$ (second order) and $Q_{sat}$ and $Q_{sym}$ (third order). We also propose an explanation of the reason why $Q_{sat}$ is weakly constrained by present experimental data. We conclude that selective observables on high order parameters, such as $K_{sym}$ and $Q_{sat}$, should be better determined before the present uncertainties on the EoS can be further reduced.

Laser-induced ultrafast transport and demagnetization at the earliest time: first-principles and real-time investigation

It is generally believed that there are at least two ways to use an ultrafast laser pulse to demagnetize a magnetic sample. One is to directly photo-demagnetize the system through spin–orbit coupling (SOC), and the other is to utilize ultrafast hot electron transport without SOC. The challenge is that these two processes are entangled on the same time scale. While the experimental results have been inconclusive, theoretical investigations are even scarcer, beyond those earlier studies based on spin superdiffusion. For instance, we do not even know how fast electrons move under laser excitation and how far they move. Here we carry out a first-principles time-dependent calculation to investigate how fast electrons actually move under laser excitation and how large the electron transport affects demagnetization on the shortest time scale. To take into account the transport effect, we implement the intraband transition in our theory. In the bulk fcc Ni, we find the effect of the spin transport on the demagnetization is extremely small, no more than 1%. The collective electron velocity in Ni is 0.4 Å fs−1, much smaller than the Fermi velocity, and the collective displacement is no more than 0.1 Å. But this does not mean that electrons do not travel fast; instead we find that electron velocities at two opposite crystal momenta cancel each other. We follow the Γ-X line and find a huge dispersion in the velocities in the crystal momentum space. In the Fe/W(1 1 0) thin film, the overall demagnetization is larger than Ni, and the Fermi velocity is higher than Ni. However, the effect of the spin transport is still small in the Fe/W(1 1 0) thin film. Based on our numerical results and existing experimental findings, we propose a different mechanism that can explain two latest experimental results. Our finding sheds new light on the effect of ballistic transport on demagnetization.

Dependence of power conversion properties of hole-conductor-free mesoscopic perovskite solar cells on the loading of perovskite crystallites

Effect of the loading of perovskite crystallites on the power conversion properties of carbon based hole-conductor-free mesoscopic perovskite solar cells is studied by varying the concentration of the perovskite precursor from 0.3 to 1.0 mol/L (at given volume of 30 μL). It is observed that, when the concentration is 0.3 mol/L, poor filling is obtained due to relatively low loading of perovskite, and the perovskite solar cells suffer from huge dispersion in efficiencies and large hysteresis index (averaged at 18.29% and up to 34.61%). With increment of the concentration (from 0.4 to 1.0 mol/L), crystallinity of perovskite crystallites is improved according to X-ray diffraction studies, and the lifetime of photo-generated charge carriers is prolonged as reflected by transient photovoltaic (TPV) detection. Meanwhile, the open circuit voltage rises up from 0.86 (±0.03) V to 0.91 (±0.01) V, and the hysteresis index is reduced from 10.02 (±4.67)% to 1.45 (±2.21)%. However, the film conductance of carbon film is decreased due to the loading of perovskite, which deteriorates the fill factor of the devices. Finally, optimized power conversion efficiency is achieved at moderate concentration or 0.6 mol/L, which is 12.59 (±0.40) %, compared to 11.81 (±0.36) % at 1.0 mol/L. Due to the barrier provided by the carbon film against H2O/O2, all of the devices showed good shelf-stability, though loading of perovskite is varied in these devices.

Geochemical wolframite fingerprinting \u2013 the likelihood ratio approach for laser ablation ICP-MS data

Wolframite has been specified as a ‘conflict mineral’ by a U.S. Government Act, which obliges companies that use these minerals to report their origin. Minerals originating from conflict regions in the Democratic Republic of the Congo shall be excluded from the market as their illegal mining, trading, and taxation are supposed to fuel ongoing violent conflicts. The German Federal Institute for Geosciences and Natural Resources (BGR) developed a geochemical fingerprinting method for wolframite based on laser ablation inductively coupled plasma-mass spectrometry. Concentrations of 46 elements in about 5300 wolframite grains from 64 mines were determined. The issue of verifying the declared origins of the wolframite samples may be framed as a forensic problem by considering two contrasting hypotheses: the examined sample and a sample collected from the declared mine originate from the same mine (H1), and the two samples come from different mines (H2). The solution is found using the likelihood ratio (LR) theory. On account of the multidimensionality, the lack of normal distribution of data within each sample, and the huge within-sample dispersion in relation to the dispersion between samples, the classic LR models had to be modified. Robust principal component analysis and linear discriminant analysis were used to characterize samples. The similarity of two samples was expressed by Kolmogorov-Smirnov distances, which were interpreted in view of H1 and H2 hypotheses within the LR framework. The performance of the models, controlled by the levels of incorrect responses and the empirical cross entropy, demonstrated that the proposed LR models are successful in verifying the authenticity of the wolframite samples.Graphical abstractGeochemical wolframite fingerprinting

Neutral dynamics and cell renewal of colonic crypts in homeostatic regime

The self renewal process in colonic crypts is the object of several studies. We present here a new compartment model with the following characteristics: (a) we distinguish different classes of cells: stem cells, six generations of transit amplifying cells and the differentiated cells; (b) in order to take into account the monoclonal character of crypts in homeostatic regimes we include symmetric divisions of the stem cells. We first consider the dynamic differential equations that describe the evolution of the mean values of the populations, but the small observed value of the total number of cells involved plus the huge dispersion of experimental data found in the literature leads us to study the stochastic discrete process. This analysis allows us to study fluctuations, the neutral drift that leads to monoclonality, and the effects of the fixation of mutant clones.

Influence of surface residual stresses on the fatigue life and crack propagation behavior of turned Inconel 718 super-alloy

The effects of surface roughness parameters and residual stresses induced by finish turning on fatigue life and crack propagation behavior of Inconel 718 super-alloy are investigated. A criterion serving as a good indicator of surface quality is also discovered. This is carried out for some specific turning conditions in order to control surface characteristics including surface roughness and the bi-axial state of surface residual stresses and to investigate the effects of these characteristics on fatigue behavior. Rotating bending fatigue (RBF) tests are performed on the machined specimens at room temperature. Characterization techniques including X-ray diffraction (XRD), laser confocal microscopy, and opto-digital microscopy are used to investigate surface residual stresses in axial (ARS) and hoop (HRS) directions, surface roughness, and secondary fatigue cracks, respectively. The huge dispersion in fatigue life of smooth turned Inconel 718 with very low arithmetic average roughness (Ra) values indicates that surface finishing is not the only reliable criterion for quality control of machined components. Multivariate statistical analyses show that axial surface residual stress is the most important surface characteristic affecting the fatigue life of machined Inconel 718 for the conditions tested. Changing ARS from compressive to tensile increases the number of secondary cracks and also decreases the fatigue life of turned specimens.

Impact of Metal and Metal Oxide Nanoparticles on Plant: A Critical Review.

An increasing need of nanotechnology in various industries may cause a huge environment dispersion of nanoparticles in coming years. A concern about nanoparticles interaction with flora and fauna is raised due to a growing load of it in the environment. In recent years, several investigators have shown impact of nanoparticles on plant growth and their accumulation in food source. This review examines the research performed in the last decade to show how metal and metal oxide nanoparticles are influencing the plant metabolism. We addressed here, the impact of nanoparticle on plant in relation to its size, concentration, and exposure methodology. Based on the available reports, we proposed oxidative burst as a general mechanism through which the toxic effects of nanoparticles are spread in plants. This review summarizes the current understanding and the future possibilities of plant-nanoparticle research.

Evolutionary Relationships and Cytotaxonomy Considerations in the Genus Pyrrhulina (Characiformes, Lebiasinidae).

Although fishes exhibit the greatest biodiversity among the vertebrates, a large percentage of this fauna is still underexplored on evolutionary cytogenetic questions, particularly the miniature species. The Lebiasinidae family is a particular example for such case. This study is the first one presenting differential cytogenetic methods, such as C-banding, repetitive DNAs mapping, comparative genomic hybridization (CGH), and whole chromosome painting in lebiasinid species. Pyrrhulina australis and Pyrrhulina aff. australis were deeply investigated concerning their chromosomal patterns and evolutionary relationships. These species have a very similar morphology, but they can be distinguished by a longitudinal midlateral faintly dark stripe exclusive for Pyrrhulina aff. australis. Both species presented 2n = 40 chromosomes (4st +36a), without heteromorphic sex chromosomes. However, despite their morphological and karyotype resemblance, it was evidenced that both species have already gone through a significant genomic divergence, thus corresponding to distinct evolutionary units. Furthermore, to give additional support to some proposals on evolutionary relationship among Lebiasinidae with other fish families, a chromosomal comparative approach with Erythrinus erythrinus, a representative species of the Erythrinidae family, was also performed. In addition to have similar karyotype structure, mainly composed by acrocentric chromosomes, both species share uncommon genomic similarities, such as (i) syntenic location of 5S and 18S rDNA sequences; (ii) huge dispersion of multiple 5S rDNA sites in the karyotypes; and (iii) complex association between 5S rDNA and Rex3 elements. CGH experiments, despite reinforcing some shared genomic homologies, also highlighted that both Pyrrhulina and Erythrinus have a range of nonoverlapping species-specific signals. The overall chromosomal data proved to be effective markers for the cytotaxonomy and evolutionary process among Lebiasinidae fishes.

Real-time frequency-to-time mapping based on spectrally-discrete chromatic dispersion.

Traditional photonics-assisted real-time Fourier transform (RTFT) usually suffers from limited chromatic dispersion, huge volume, or large time delay and attendant loss. In this paper we propose frequency-to-time mapping (FTM) by spectrally-discrete dispersion to increase frequency sensitivity greatly. The novel media has periodic ON/OFF intensity frequency response while quadratic phase distribution along disconnected channels, which de-chirps matched optical input to repeated Fourier-transform-limited output. Real-time FTM is then obtained within each period. Since only discrete phase retardation rather than continuously-changed true time delay is required, huge equivalent dispersion is then available by compact device. Such FTM is theoretically analyzed, and implementation by cascaded optical ring resonators is proposed. After a numerical example, our theory is demonstrated by a proof-of-concept experiment, where a single loop containing 0.5-meters-long fiber is used. FTM under 400-MHz unambiguous bandwidth and 25-MHz resolution is reported. Highly-sensitive and linear mapping is achieved with 6.25 ps/MHz, equivalent to ~4.6 × 104-km standard single mode fiber. Extended instantaneous bandwidth is expected by ring cascading. Our proposal may provide a promising method for real-time, low-latency Fourier transform.

Conformational gating of DNA conductance.

DNA is a promising molecule for applications in molecular electronics because of its unique electronic and self-assembly properties. Here we report that the conductance of DNA duplexes increases by approximately one order of magnitude when its conformation is changed from the B-form to the A-form. This large conductance increase is fully reversible, and by controlling the chemical environment, the conductance can be repeatedly switched between the two values. The conductance of the two conformations displays weak length dependencies, as is expected for guanine-rich sequences, and can be fit with a coherence-corrected hopping model. These results are supported by ab initio electronic structure calculations that indicate that the highest occupied molecular orbital is more disperse in the A-form DNA case. These results demonstrate that DNA can behave as a promising molecular switch for molecular electronics applications and also provide additional insights into the huge dispersion of DNA conductance values found in the literature.