bluuebunny/crossref_metadata_2025 huggingface dataset:
Machine learning strategies for high-entropy alloys
Authors: Rickman J. M. , Balasubramanian G. , Marvel C. J. , Chan H. M. , Burton M.-T.
Published: December 2020

The study of high-entropy (HE) alloys has seen dramatic growth in recent years as, in some cases, these systems can exhibit exceptional properties, including enhanced oxidation resistance, superior mechanical properties, and desirable magnetic properties. The identification of promising HE alloys is, however, extremely challenging due to the extraordinarily large number of distinct systems that may be fabricated from the available palette of elements. For this reason, machine learning strategies have been employed to reduce the size of the associated chemistry/composition space. In this review, we outline several computational strategies that have led to the identification of useful alloys and discuss the relative merits and shortcomings of these approaches. We also present short tutorials illustrating the use of selected computational approaches to HE characterization and design.
The relation between flame surface area and turbulent burning velocity in statistically planar turbulent stratified flames
Authors: Brearley Peter , Ahmed Umair , Chakraborty Nilanjan
Published: December 2020

The relation between turbulent burning velocity and flame surface area for turbulent stratified flames has been analyzed using a direct numerical simulation database. The simulations have been carried out for different initial turbulence intensities and initial integral length scales of equivalence ratio fluctuation for a given root-mean-square value in a globally stoichiometric mixture. Additionally, statistically similar turbulent premixed flames have been considered for comparison. The turbulent burning velocity and flame surface area for stratified flames are found to be significantly smaller than in premixed flames for slow mixing cases (large scalar integral length scale and low turbulence intensity), although this trend weakens in fast mixing cases (low scalar integral length scale and high turbulence intensity). In slow mixing cases, the increase in the burning rate occurs at a smaller proportion than the increase in the flame surface area. The contributions of the components arising from tangential diffusion of displacement speed and cross-scalar dissipation rate to the turbulent burning velocity are found to be negligible in comparison to that arising from the combined reaction and normal diffusion component for all cases. The increased probability of finding fuel-lean and fuel-rich mixture affects the contribution of turbulent burning velocity arising from the combined reaction and normal diffusion component of displacement speed for slow mixing cases. Front-supported flame elements dominate over back-supported flame elements for large scalar length scale cases, but this behavior reverses for small scalar length scale cases. These findings suggest that increases in the burning rate and flame surface area do not take place in the same proportions for turbulent stratified combustion.
Effect of bimetallic Co:Mo/MgO catalyst on the growth efficiency of single-walled carbon nanotubes
Authors: Gercek A. , Gokceli G. , Yavuz R. , Karatepe N.
Published: December 2020

Carbon nanotubes (CNTs) are known for a wide range of applications due to their various properties. Because these unique properties of the carbon nanotubes strongly depend on the structure, the primary aim is high efficiency and controlling the nanotube diameter during the production. In this study, single-walled carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition of acetylene (C2H2) on the Co–Mo/MgO catalyst. The effects of different catalyst preparation methods, Co/Mo, and support material ratios on the SWCNT growth efficiency were investigated by thermogravimetric analysis. Raman spectroscopy, scanning electron microscopy, and an x-ray diffractometer were also used for the structural and morphological characterization of the SWCNTs. As a result of the experimental studies, the optimum Co:Mo and metal/support ratio was determined as 1:3.5 and 15%, respectively. Considerable CNT growth efficiency (73%) has been achieved with the Co:Mo = 1:3.5/15% MgO catalyst prepared by the solgel method.
Simulations of field emission from copper electrodes with inclusion of oxygen surface layer and work function changes based on first-principles calculations
Authors: Sami S. N. , Diaz L. , Sanati M. , Joshi R. P.
Published: December 2020

Analysis of field emission requires the inclusion of the internal potentials that shape the electronic wavefunctions and tunneling probabilities; details of the work function that are dependent on material quality and defects; and the role of the density of states (DOS) that influences the electronic supply. Here, these factors are collectively included on the basis of density functional theory to obtain predictions of field-dependent electron tunneling current densities. Results are obtained in copper for three different orientations. The DOS is predicted to be broadened by an externally applied electric field. The (100) copper is shown to yield the largest current density, and the (111) orientation is the lowest. The presence of an oxide surface monolayer is shown to increase the work function, leading to the emission of current reductions. The technique is general and can be applied to other materials (e.g., carbon fibers) that have shown promise as cathode emitters.
Mechanical stress in InP and GaAs ridges formed by reactive ion etching
Authors: Landesman Jean-Pierre , Fouchier Marc , Pargon Erwine , Gérard Solène , Rochat Névine , Levallois Christophe , Mokhtari Merwan , Pagnod-Rossiaux Philippe , Laruelle François , Petit-Etienne Camille , Bettiati Mauro , Jiménez Juan , Cassidy Daniel T.
Published: December 2020

The mechanical deformation induced by reactive ion etching (RIE) of rectangular ridge waveguides in GaAs and InP has been investigated by photoluminescence and cathodoluminescence techniques. Several trends were identified and are discussed. First, it is concluded that the RIE process itself is the source of the mechanical deformation. A compressive volume change occurs mainly within the ridge (with a maximum close to the vertical etched sidewalls), extending outside the ridges, up to several micrometers below the bottom etched surface. An anisotropic deformation also appears, again mainly close to the etched sidewalls and below the bottom etched surface. A narrow area under tensile stress was also identified, localized outside the ridges and in a shallow region below the bottom etched surface. Cumulative, overlapping effects are seen inside the ridges where the compressive stress fields originating at the vertical etched sidewalls contribute to an overall compression inside the ridge which increases as the ridge width decreases. In addition, a tensile stress is also observed outside the ridge, strongly enhanced by the presence of neighboring ridges. These conclusions are significant for the design of photonic structures. Because of the photoelastic effect, which is important in GaAs and InP, the properties of devices such as waveguides might be affected by the mechanical stress described herein.
Complex structure and Mössbauer effect observed in the course of phase transitions in PbZr0.72Sn0.28O3 single crystal
Authors: Jankowska-Sumara Irena , Kądziołka-Gaweł Mariola , Podgórna Maria , Majchrowski Andrzej , Roleder Krystian
Published: December 2020

The Mössbauer effect was used to study the structural transitions in a PbZr0.72Sn0.28O3 single crystal. Two kinds of quadrupole splittings were registered and connected with two different environments of the Sn ion occupying the center of SnO6 octahedra. What is responsible for the existence of these two environments is the disorder in tilts of oxygen octahedra and antiparallel shifts of pairs of lead ions. Both disorders decide on structural transitions which the PbZr0.72Sn0.28O3 single crystal undergoes. The two kinds of quadruple splittings that have been observed do not disappear at temperatures far above phase transitions. This indicates that the structure of the paraelectric phase is locally non-centrosymmetric and confirms pre-transitional effects previously reported for Sn doped PbZrO3 single crystals.
Local vibrational mode analysis of ion–solvent and solvent–solvent interactions for hydrated Ca2+ clusters
Authors: Delgado Alexis A. A. , Sethio Daniel , Munar Ipek , Aviyente Viktorya , Kraka Elfi
Published: December 2020

Hydrated calcium ion clusters have received considerable attention due to their essential role in biological processes such as bone development, hormone regulation, blood coagulation, and neuronal signaling. To better understand the biological role of the cation, the interactions between the Ca2+ ions and water molecules have been frequently investigated. However, a quantitative measure for the intrinsic Ca—O (ion–solvent) and intermolecular hydrogen bond (solvent–solvent) interactions has been missing so far. Here, we report a topological electron density analysis and a natural population analysis to analyze the nature of these interactions for a set of 14 hydrated calcium clusters via local mode stretching force constants obtained at the ωB97X-D/6-311++G(d,p) level of theory. The results revealed that the strength of inner Ca—O interactions for Ca(H2O)n2+ (n = 1–8) clusters correlates with the electron density. The application of a second hydration shell to Ca(H2O)n2+ (n = 6–8) clusters resulted in stronger Ca—O interactions where a larger electron charge transfer between lp(O) of the first hydration shell and the lower valence of Ca prevailed. The strength of the intermolecular hydrogen bonds, formed between the first and second hydration shells, became stronger when the charge transfers between hydrogen bond (HB) donors and HB acceptors were enhanced. From the local mode stretching force constants of implicitly and explicitly solvated Ca2+, we found the six-coordinated cluster to possess the strongest stabilizations, and these results prove that the intrinsic bond strength measures for Ca—O and hydrogen bond interactions form new effective tools to predict the coordination number for the hydrated calcium ion clusters.
On the Kármán momentum-integral approach and the Pohlhausen paradox
Authors: Majdalani Joseph , Xuan Li-Jun
Published: December 2020

This work explores simple relations that follow from the momentum-integral equation absent a pressure gradient. The resulting expressions enable us to relate the boundary-layer characteristics of a velocity profile, u(y), to an assumed flow function and its wall derivative relative to the wall-normal coordinate, y. Consequently, disturbance, displacement, and momentum thicknesses, as well as skin friction and drag coefficients, which are typically evaluated and tabulated in classical monographs, can be readily determined for a given profile, F(ξ) = u/U. Here, ξ = y/δ denotes the boundary-layer coordinate. These expressions are then employed to provide a rational explanation for the 1921 Pohlhausen polynomial paradox, namely, the reason why a quartic representation of the velocity leads to less accurate predictions of the disturbance, displacement, and momentum thicknesses than using cubic or quadratic polynomials. Not only do we identify the factors underlying this behavior but also we proceed to outline a procedure to overcome its manifestation at any order. This enables us to derive optimal piecewise approximations that do not suffer from the particular limitations affecting Pohlhausen’s F = 2ξ − 2ξ3 + ξ4. For example, our alternative profile, F = (5ξ − 3ξ3 + ξ4)/3, leads to an order-of-magnitude improvement in precision when incorporated into the Kármán–Pohlhausen approach in both viscous and thermal analyses. Then, noting the significance of the Blasius constant, s¯≈1.630 398, this approach is extended to construct a set of uniformly valid solutions, including F=1−exp[−s¯ξ(1+12s¯ξ+ξ2)], which continues to hold beyond the boundary-layer edge as y → ∞. Given its substantially reduced error, the latter is shown, through comparisons to other models, to be practically equivalent to the Blasius solution.
Transforming task representations to perform novel tasks
Authors: Lampinen Andrew K. , McClelland James L.
Published: December 2020

Significance

An intelligent system should be able to adapt to a novel task without any data and achieve at least moderate success. Humans can often do so, while models often require immense datasets to reach human-level performance. We propose a general computational framework by which models can adapt to new tasks based only on their relationship to old tasks. Our approach is based on transforming learned task representations. Our approach allows models to perform well on novel tasks, even using novel relationships not encountered during training. This adaptation can substantially accelerate later learning. Our work could contribute to understanding the computational basis of intelligence, to cognitive modeling, and to building more flexible forms of artificial intelligence.
Rapid hydrolysis of tertiary isoprene nitrate efficiently removes NO
x
from the atmosphere
Authors: Vasquez Krystal T. , Crounse John D. , Schulze Benjamin C. , Bates Kelvin H. , Teng Alexander P. , Xu Lu , Allen Hannah M. , Wennberg Paul O.
Published: December 2020

Significance

Isoprene-derived hydroxy nitrates (IHNs) play a significant role in controlling the lifetime of NO
x
. Here, we showcase isomer-specific measurements of IHN in ambient air, which have allowed us to quantify real-time changes in its isomer distribution. These measurements show that 1,2-IHN undergoes a rapid loss not experienced by the 4,3-IHN isomer. Laboratory studies suggest this sink is likely condensed-phase hydrolysis, forming HNO
3
. To match observations, one-dimensional box-model simulations require additional loss rates (here, assigned to hydrolysis) similar in magnitude to the accounted loss processes (OH oxidation and dry deposition). Global simulations included in this process show reduced ozone levels and assign a significant fraction of HNO
3
production to this mechanism within the lower atmosphere.
Personal vs. personalized infinitives in Ibero-Romance
Authors: Graham Lamar A.
Published: December 2020

The infinitives of several Romance languages can appear
with an overt subject. Languages such as Portuguese and Galician
feature inflectional morphology on infinitives with overt subjects –
the commonly named personal infinitives, such as
(nós) dizermos ‘us to speak’. Other languages,
such as Castilian1 and
Asturian, feature overt subjects alongside infinitives with no
corresponding agreement morphology on the verb – a structure I call
the personalized infinitive, such as
nosotros decir ~ decir
nosotros ‘us to speak’. Though superficially similar in
use, personal and personalized infinitives differ among
Ibero-Romance languages in their history and their uses in the
modern dialects. In this paper I distinguish both structures,
illustrating the morphosyntactic differences between the two. I also
argue for the influence of koineization and language contact as
impetus for the historical development of these forms in the various
languages.
Adult language and dialect learning as simultaneous environmental
triggers for language change in Spanish
Authors: Sanz-Sánchez Israel , Tejedo-Herrero Fernando
Published: December 2020

Grammatical restructuring in contact situations is
customarily analyzed under the lens of either language
contact or dialect contact. In this study we argue that both
processes may operate jointly in social settings where dialectal
accommodation and adult L2 learning favor the same linguistic
outcomes. From an evolutionary perspective, this overlap between
both forms of contact may be conceptualized as a function of a
common underlying process, with speakers selecting features of
heterogeneous provenance, acquired at various life stages. We
exemplify this joint effect by focusing on two changes in the
history of Spanish: the rearrangement of the 3rd person object
clitic system in medieval southern Iberian Castilian and the merging
of the medieval sibilants in early colonial Spanish.
Searching for the sociolinguistic history of Afro-Panamanian
Congo speech
Authors: Lipski John M.
Published: December 2020

Among the surviving Afro-Hispanic linguistic
manifestations, one of the most difficult to trace historically is
the speech of the Congos of Panama’s Caribbean
coast, who maintain a series of folkloric manifestations occurring
during Carnival season that includes a special language. According
to oral tradition, Congo speech was devised among
captive and maroon Africans in colonial Panama as a means of hiding
their speech from their colonial masters. Putting together the
contemporary variation in Congo speech and what
diachronic developments can be extrapolated, a complex picture
emerges that cannot be easily resolved with the notion that this
dialect developed exclusively as a cryptolect in contact with
Spanish colonists. The present study offers a plausible scenario,
based on synchronic variation and available historical
documentation.
The role of dispositional emotion regulation strategies on the longitudinal emotional process and subjective performance during a competitive season
Authors: Cece Valerian , Guillet‐Descas Emma , Brenas Mae , Martinent Guillaume
Published: December 2020

The purpose of this study was to shed light on the associations between emotion regulation (ER) strategies used, their emotional processes (including cognitive appraisals and discrete emotions), and subjective performance across a competitive season. A sample of fifteen national‐level rink hockey players completed ER questionnaire at the beginning of the season (T0) and reported their experiences of everyday appraisal, emotions, and subjective performance every week. A series of hierarchical linear modelling analyses (HLM) were performed to investigate the associations between the variables. Sobel tests were computed to identify the mediating effects of emotions and appraisals on these relationships. HLM results revealed that (a) T0 adaptive ER strategies were positively related to adaptive appraisals; (b) adaptive appraisals were positively related to pleasant emotions and negatively with unpleasant emotions and opposite relationships emerged for maladaptive appraisals; (c) happiness was positively associated with subjective performance. Sobel tests provided evidence of mediating effects of (a) appraisals in the relationships between T0 adaptive ER and pleasant emotions; and (b) happiness in the relationships between appraisals and subjective performance. The results highlighted the positive relationships between the adaptive dispositional ER strategies at the beginning of the season and the emotional experiences. Moreover, the analyses revealed relationships between appraisals, emotions, and subjective performance of athletes. In sum, this study provided additional knowledge about the capture of the emotional process during a competitive season highlighting the associations between a variety of emotions and selected key variables in a competitive context (i.e. ER strategies, appraisal, subjective performance).
Algebraic derivation of Kramers–Pasternack relations based on the Schrödinger factorization method
Authors: Szymanski Tomasz , Freericks J K
Published: December 2020

The Kramers–Pasternack relations are used to compute the moments of r (both positive and negative) for all radial energy eigenfunctions of hydrogenic atoms. They consist of two algebraic recurrence relations, one for positive powers and one for negative. Most derivations employ the Feynman–Hellmann theorem or a brute-force integration to determine the second inverse moment, which is needed to complete the recurrence relations for negative moments. In this work, we show both how to derive the recurrence relations algebraically and how to determine the second inverse moment algebraically, which removes the pedagogical confusion associated with differentiating the Hamiltonian with respect to the angular momentum quantum number l, which is restricted to be an integer, in order to find the inverse second moment.
Towards bi-magnetic nanocomposites as permanent magnets through the optimization of the synthesis and magnetic properties of SrFe12O19 nanocrystallites
Authors: Maltoni Pierfrancesco , Sarkar Tapati , Varvaro Gaspare , Barucca Gianni , Ivanov Sergey A , Peddis Davide , Mathieu Roland
Published: December 2020

Sol–gel synthesis was used in order to obtain nanocrystallites of the SrFe12O19 (SFO) hexaferrite in an efficient and reliable way. By optimizing the initial synthetic conditions, we were able to control the size of the nanoparticles (NPs), at lower annealing temperature. The x-ray powder diffraction, transmission electron microscopy (TEM), and magnetic measurements have demonstrated a significant relation between the morphology, size, and magnetic properties of the nanoscale SFO, revealing a definite dependence on the crystallite size along the c-axis. The obtained NPs appear almost isotropic, in the form of platelets and exhibit similar magnetic performance, in terms of the energy product (BH)MAX, thus, demonstrating the suitability of reducing the annealing temperature without any deterioration in the magnetic properties. Additionally, this work illustrates the feasibility of the sol–gel bottom-up approach to employ magnetic NPs as building-blocks for designing hard/soft exchange-coupled bi-magnetic nanocomposites, combining the high coercivity of a hard phase (SFO) and the high saturation magnetization of a soft phase (CoFe2O4); in this regard, we discuss the tunability of the magnetic anisotropy by symbiotically restricting the growth of both phases.
Atomic oxygen generation in atmospheric pressure RF plasma jets driven by tailored voltage waveforms in mixtures of He and O2
Authors: Korolov I , Steuer D , Bischoff L , Hübner G , Liu Y , Schulz-von der Gathen V , Böke M , Mussenbrock T , Schulze J
Published: December 2020

Absolute atomic oxygen densities measured space resolved in the active plasma volume of a COST microplasma reference jet operated in He/O2 and driven by tailored voltage waveforms are presented. The measurements are performed for different shapes of the driving voltage waveform, oxygen admixture concentrations, and peak-to-peak voltages. Peaks- and valleys-waveforms constructed based on different numbers of consecutive harmonics, N, of the fundamental frequency f
0 = 13.56 MHz, different relative phases and amplitudes are used. The results show that the density of atomic oxygen can be controlled and optimized by voltage waveform tailoring (VWT). It is significantly enhanced by increasing the number of consecutive driving harmonics at fixed peak-to-peak voltage. The shape of the measured density profiles in the direction perpendicular to the electrodes can be controlled by VWT as well. For

N
 
>
 
1

and peaks-/valleys-waveforms, it exhibits a strong spatial asymmetry with a maximum at one of the electrodes due to the spatially asymmetric electron power absorption dynamics. Thus, the atomic oxygen flux can be directed primarily towards one of the electrodes. The generation of atomic oxygen can be further optimized by changing the reactive gas admixture and by tuning the peak-to-peak voltage amplitude. The obtained results are understood based on a detailed analysis of the spatio-temporal dynamics of energetic electrons revealed by phase resolved optical emission spectroscopy.
Transported properties and low-temperature magnetic behaviors of Ti
x
Cr1−

x
O2 films
Authors: Zhang Zhenhua , Cheng Ming , Zou Zhaorui , Xu Jing , Liu Yong , Lu Zhihong , Xiong Rui
Published: December 2020

Electronic transport and magnetic properties of Ti
x
Cr1−x
O2 epitaxial films with low Ti concentrations have been studied. Compared with pure CrO2 film, Ti-doped films exhibit a significant increase of resistivity and the magnetoresistance at low temperature is more difficult to saturate even under an external field of 5 Tesla. The DC magnetization and AC susceptibility measurements suggest that a cluster glass freezing behavior occurs at low temperature in Ti-doped films. After analyzing the AC susceptibility using dynamic scaling theory, we have obtained the cluster-glass transition temperature T
G = 97.8 K, the dynamic exponent zv = 12.37, and the characteristic timescale τ
0 = 10−16, which lies in the range of conventional cluster glass systems.
Constraining resonance properties through kaon production in pion–nucleus collisions at low energies
Authors: Steinberg V , Steinheimer J , Elfner H , Bleicher M
Published: December 2020

Hadronic interactions are crucial for the dynamical description of heavy-ion reactions at low collision energies and in the late dilute stages at high collision energies. In particular, the properties and decay channels of resonances are an essential ingredient of hadronic transport approaches. The HADES collaboration measured particle production in collisions of pions with carbon and tungsten nuclei at E
kin = 1.7 GeV (Adamczewski-Musch et al 2019 Phys. Rev. Lett.
123 022002). Such reactions are of high interest, because they allow to probe the properties of baryonic resonances produced in a much cleaner environment than the usual nucleus–nucleus collisions. We study these reactions with two transport approaches: SMASH (simulating many accelerated strongly-interacting hadrons) and UrQMD (ultra relativistic quantum molecular dynamics) which follow the same underlying concept but with different implementations. The differential spectra in rapidity and transverse momentum are used to show how model parameters, as the decay channels of high mass resonances and angular distributions of kaon elastic scattering, can be constrained. It is found that the data favor the production of more particles with lower momentum over the production of few particles with higher momentum in these decays. In addition, the shape of the rapidity distribution of the kaons strongly depends on the angular distribution of the elastic kaon–nucleon cross section.
Effect of Pd alloying on structural, electronic and magnetic properties of L10 Fe–Ni
Authors: Singh Prashant , Das Debashish , Johnson Duane D , Arroyave Raymundo , Alam Aftab
Published: December 2020

We present a systematic study of the effect of Pd-alloying on phase stability, electronic structure, and elastic properties in L10 Fe–Ni using density-functional theory. Being from the same group of the periodic table, Pd is the best candidate for chemical alloying. The Fe–Ni/Fe–Pd/Ni–Pd bond-length increases with increasing Pd-concentration, which weakens the hybridization between low lying energy states below Fermi-level. The reduced hybridization decreases the relative thermodynamic stability of L10 Fe(Ni1−x
Pd
x
) until x = 0.75. Beyond this concentration, the relative stability gets enhanced, which is attributed to a unique change in the lattice distortion (c/a). The elastic properties show a non-monotonous behavior as a function of x, which is again due to a specific change-over in the uniaxial strain. We found that Pd alloying increases the local Fe moment and structural anisotropy of L10 FeNi, which are important for applications such as microwave absorption, refrigeration systems, recording devices, imaging and sensors. We believe that the present study for the chemical alloying effect can provide critical insights toward the understanding of electronic-structure and elastic behavior of other technologically important materials.
Improved stochastic modeling of multi-GNSS single point positioning with additional BDS-3 observations
Authors: Hu Hong , Zhou Feng , Jin Shuanggen
Published: December 2020

The accuracy of Global Navigation Satellite System (GNSS) observations is affected by many factors, such as different systems, frequencies, carriers and pseudoranges, all of which also vary with different situations. Therefore, it is challenging to establish an accurate stochastic model for multi-GNSS positioning in theory, particularly for the additional BeiDou-3 Global Navigation Satellite System (BDS-3). In practical applications, the real stochastic model needs to be estimated based on the characteristics of the observations themselves. We evaluated the influence of BDS-3 on the positioning results using 46 sites distributed around the world and proposed an improved stochastic model for multi-GNSS single point positioning (SPP) based on the least-squares variance component estimation (LS-VCE). The results show that when the BDS-3 observations are added, the positioning precision and accuracy are significantly improved. By using the improved LS-VCE method in GPS/BDS dual system positioning, the accuracy of E, N and U directions are 0.373, 0.498 and 1.044 m, respectively, when compared to the traditional method with 0.502, 0.533 and 1.333 m. The proposed stochastic model improves the multi-GNSS SPP accuracy without significantly increasing the calculation time. Furthermore, reliable results are obtained for all epochs with the improved LS-VCE model.
The exceptionally high thermal conductivity after ‘alloying’ two-dimensional gallium nitride (GaN) and aluminum nitride (AlN)
Authors: Wang Huimin , Wei Donghai , Duan Junfei , Qin Zhenzhen , Qin Guangzhao , Yao Yagang , Hu Ming
Published: December 2020

Alloying is a widely employed approach for tuning properties of materials, especially for thermal conductivity which plays a key role in the working liability of electronic devices and the energy conversion efficiency of thermoelectric devices. Commonly, the thermal conductivity of an alloy is acknowledged to be the smallest compared to the parent materials. However, the findings in this study bring some different points of view on the modulation of thermal transport by alloying. The thermal transport properties of monolayer GaN, AlN, and their alloys of Ga
x
Al1−x
N are comparatively investigated by solving the Boltzmann transport equation (BTE) based on first-principles calculations. The thermal conductivity of Ga0.25Al0.75N alloy (29.57 Wm−1 K−1) and Ga0.5Al0.5N alloy (21.49 Wm−1 K−1) are found exceptionally high to be between AlN (74.42 Wm−1 K−1) and GaN (14.92 Wm−1 K−1), which violates the traditional knowledge that alloying usually lowers thermal conductivity. The mechanism resides in that, the existence of Al atoms reduces the difference in atomic radius and masses of the Ga0.25Al0.75N alloy, which also induces an isolated optical phonon branch around 18 THz. As a result, the scattering phase space of Ga0.25Al0.75N is largely suppressed compared to GaN. The microscopic analysis from the orbital projected electronic density of states and the electron localization function further provides insight that the alloying process weakens the polarization of bonding in Ga0.25Al0.75N alloy and leads to the increased thermal conductivity. The exceptionally high thermal conductivity of the Ga
x
Al1−x
N alloys and the underlying mechanism as revealed in this study would bring valuable insight for the future research of materials with applications in high-performance thermal management.
A novel proton counting detector and method for the validation of tissue and implant material maps for Monte Carlo dose calculation
Authors: Charyyev Serdar , Chang Chih-Wei , Harms Joseph , Oancea Cristina , Yoon S Tim , Yang Xiaofeng , Zhang Tiezhi , Zhou Jun , Lin Liyong
Published: December 2020

The presence of artificial implants complicates the delivery of proton therapy due to inaccurate characterization of both the implant and the surrounding tissues. In this work, we describe a method to characterize implant and human tissue mimicking materials in terms of relative stopping power (RSP) using a novel proton counting detector. Each proton is tracked by directly measuring the deposited energy along the proton track using a fast, pixelated spectral detector AdvaPIX-TPX3 (TPX3). We considered three scenarios to characterize the RSPs. First, in-air measurements were made in the presence of metal rods (Al, Ti and CoCr) and bone. Then, measurements of energy perturbations in the presence of metal implants and bone in an anthropomorphic phantom were performed. Finally, sampling of cumulative stopping power (CSP) of the phantom were made at different locations of the anthropomorphic phantom. CSP and RSP information were extracted from energy spectra at each beam path. To quantify the RSP of metal rods we used the shift in the most probable energy (MPE) of CSP from the reference CSP without a rod. Overall, the RSPs were determined as 1.48, 2.06, 3.08, and 5.53 from in-air measurements; 1.44, 1.97, 2.98, and 5.44 from in-phantom measurements, for bone, Al, Ti and CoCr, respectively. Additionally, we sampled CSP for multiple paths of the anthropomorphic phantom ranging from 18.63 to 25.23 cm deriving RSP of soft tissues and bones in agreement within 1.6% of TOPAS simulations. Using minimum error of these multiple CSP, optimal mass densities were derived for soft tissue and bone and they are within 1% of vendor-provided nominal densities. The preliminary data obtained indicates the proposed novel method can be used for the validation of material and density maps, required by proton Monte Carlo Dose calculation, provided by competing multi-energy computed tomography and metal artifact reduction techniques.
Breathing rate and heart rate as confounding factors in measuring T wave alternans and morphological variability in ECG
Authors: Sadiq Ismail , Perez-Alday Erick A , Shah Amit J , Clifford Gari D
Published: December 2020

Objective. High morphological variability magnitude (MVM) and microvolt T wave alternans (TWA) within an electrocardiogram (ECG) signifies increased electrical instability and risk of sudden cardiac death. However, the influence of breathing rate (BR), heart rate (HR), and signal-to-noise ratio (SNR) is unknown and may inflate measured values. Approach. We synthesize ECGs with morphologies derived from the Physikalisch-Technische Bundesanstalt Database. We calculate MVM and TWA at varying BRs, HRs and SNRs. We compare the MVM and TWA of signal with versus without breathing at varying HRs and SNRs. We then quantify the percentage of MVM and TWA estimates affected by BR and HR in a healthy population and assess the effect of removing these affected estimates on a method for classifying individuals with and without post-traumatic stress disorder (PTSD). Main results. For signals with high SNR (>15 dB), MVM is significantly increased when BRs are > 9 respirations/minute (rpm) and HRs are < 100 beats/minute (bpm). Increased TWAs are detected for HR/BR pairs of 60/15, 60/30 and 120/30 bpm/rpm. For 18 healthy participants, 8.33% of TWA windows and 66.76% of MVM windows are affected by BR and HR. On average, the number of windows with TWA elevations > 47 μV decreases by 23% after excluding regions with significant BR and HR effect. Adding HR and BR to a morphological variability feature increases the classification performance by 6% for individuals with and without PTSD. Significance. Physiological BR and HR significantly increase MVM and TWA , indicating that BR and HR should be considered separately as confounders. The code for this work has been released as part of an open-source toolbox.
Quantum thermodynamics in the interior of a Schwarzschild black-hole
Authors: Musmarra Juan Ignacio , Bellini Mauricio , Anabitarte Mariano
Published: December 2020

We study space-time back-reaction configuration in the interior of a Schwarzschild Black-Hole (B-H) using Relativistic Quantum Geometry described in (Ridao and Bellini 2015 Astrophys. Space Sci.
357 94) and (Ridao and Bellini 2015 Phys. Lett. B 751 565). We found discrete energy levels for a scalar field from a polynomial condition for Heun Confluent functions expanded around the Schwarzschild radius. From the solutions it is obtained that the uncertainty principle is valid for each energy level of space-time, in the form: E

n

r

sh,n
= ℏ/2. Temperature, entropy and the B-H mass are dependent on the number of states in the B-H, such that the Bekenstein-Hawking (BH) results are obtained in a limit case.
IV International Conference on Ultrafast Optical Science (UltrafastLight-2020)
Authors: Zazymkina D. A. , Bochkarev S. G. , Kudryashov S. I. , Ionin A. A.
Published: December 2020

IV International Conference on Ultrafast Optical Science (UltrafastLight-2020) was held on September 28-October 02, 2020 in P.N. Lebedev Physical Institute (LPI) in Moscow, Russia. The mixed (offline and online) Conference format was chosen due to the current quarantine measures and travel restrictions, nonetheless it did not affect the highest quality of the talks given by all the speakers registered at the Conference. The possibility of broadcasting through Zoom drastically increased the number of reports made by foreign participants which enabled more detailed outlook of the present problems and development of the optical science field. IV International Conference on Ultrafast Optical Science aimed at experience exchange between scientists and researchers from different countries and united the specialists presenting even different continents. Succession ensurance and its maintenance being the sufficient part of our mission was reflected in practice by inviting not only scientists, but also students specialized in optics and laser physics.

List of Scientific Program Committee, Local organizing committee, Conference Sections, Plenary Speakers, Invited Speakers, Sponsors, are available in this pdf.
Intensity clamping and controlled efficiency of X-ray generation under femtosecond laser interaction with nanostructured target in air and helium
Authors: Garmatina A. A. , Bravy B. G. , Potemkin F. V. , Nazarov M. M. , Gordienko V. M.
Published: December 2020

We have performed theoretical calculations aimed at modeling the propagation dynamics of a focused femtosecond laser beam in a nonlinear gas medium. It was obtained that when helium is blown into the focal area, the intensity clamping level is about 2,5 times higher than when air is present. The conditions for optimal placement of the target relative to the position of the vacuum focus and, accordingly, allowing to achieve maximum intensity are found. It was found that under interaction in air femtosecond Cr:forsterite laser ( λ=1,24 μm, E<1 mJ, 100 fs) with nanostructured iron containing tape the intensity clamping effect is observed. Replacing the air medium with helium leads to essentially increase in line (6.4keV) X-ray yield. Increasing the pulse duration to 300fs led to an increase in the X-ray output twice and reached 3*105 photons/pulse in solid angle.
High-frequency skin effect in a photoionized inert gas plasma
Authors: Vagin K. Yu. , Mamontova T. V. , Uryupin S. A.
Published: December 2020

The penetration of a monochromatic electromagnetic wave into the weakly ionised plasma formed by multiphoton ionization of inert gas atoms has been studied. It is shown how the type of dependence of the photoelectron collision frequency on their velocity determines transverse permettivity in plasma. Explicit expressions for the absorption coefficient in inert gases at different probe radiation frequencies are obtained. In the high-frequency skin effect mode, the possibility of the absorption coefficient increasing due to the Ramsauer-Townsend effect has been demonstrated with argon as an example.
Femto-nanosecond laser ablation of gold target in liquid
Authors: Nastulyavichus A. A. , Kudryashov S. I. , Rudenko A. A. , Zayarny D. A. , Ionin A. A.
Published: December 2020

Colloidal solutions of gold nanoparticles were generated in deionized water from bulk target at different energies of nanosecond and femtosecond lasers. The obtained colloidal nanoparticles were characterized by scanning electron microscopy, optical transmission spectroscopy and dynamic light scattering.
You shall not pass: titanium and silver nanospikes-based flow-through filter for liquid sterilization
Authors: Sozaev I. V. , Saraeva I. N. , Tolordava E. R. , Nastulyavichus A. A , Kudryashov S. I. , Rudenko A. A , Zayarny D. A. , Ionin A. A , Romanova Yu. M.
Published: December 2020

Antibacterial nanostructures were written on the surface of a silver (Ag) film and titanium (Ti) wafer using femtosecond laser ablation. The bactericidal properties were tested on S. aureus and P. aeruginosa bacterial strains. The resulting nanostructures were characterized by scanning electron microscopy (SEM). A flow-through filter, based on Ag plates with nanospikes, used as a sterilization of the liquid, led to the almost complete death of bacteria. It is assumed that the antibacterial properties are due to mechanical damage caused by the sharp nanoscale relief.
The effects of ASE contrast and beams mutual alignment on the γ-ray yield in laser-plasma interactions with artificial prepulse
Authors: Shulyapov S A , Tsymbalov I N , Ivanov K A , Gospodinov G A , Volkov R V , Savel’ev A B
Published: December 2020

We present experimental study of the bremsstrahlung γ-rays generation in a plasma interacting with 50 fs laser pulse in slightly relativistic regime (intensity ∼2-1018 W/cm2). A pre-plasma layer on the surface of the molybdenum target is formed by an additional laser pulse with a duration of 8 ns and an intensity of ∼2-1012 W/cm2. The energy and intensity of the artificial pre-pulse exceed those of the amplified spontaneous emission (ASE) pedestal of the main pulse by ∼103 and 10 times (for contrast 10−7), respectively. It was shown that the low ASE contrast (>10−7) is the crucial condition for increasing (in comparison to the case without artificial pre-pulse) of the integral γ-rays yield when the nanosecond pulse is ahead of the femtosecond one by >20 ns. Interferometry data show that the reason of the γ-rays yield increasing is a pre-plasma layer initially produced by artificial pre-pulse and re-created by the ASE. The optimum conditions for γ-rays yield achieved if (i) the pre-pulse comes ∼25 ns in advance, (ii) ASE contrast is 10−7 and lower and (iii) the femtosecond focal point is shifted by ∼100 μm from the center of the nanosecond pre-pulse focal spot and by ∼100 μm above the target surface.
Large-scale emulation of spatio-temporal variation in temperature under climate change
Authors: Yuan Xiao-Chen , Zhang Nan , Wang Wei-Zheng , Wei Yi-Ming
Published: December 2020

Future temperature variations under greenhouse gas (GHG) emission scenarios are critical to assess possible impacts on human society and make reasonable mitigation policies. Due to the huge running cost, Earth system models (ESMs) may be difficult to flexibly provide the temperature projections following some specific emission pathways for empirical analysis. This study develops the mean and variability filed emulators in the high-resolution land grids to approximate the temperature behavior conditioned on GHG emissions in ESM. The emulator of mean temperature response is modeled as a function of GHG emissions to represent the expected values for ESM output, and the associated high-dimensional spatial dependence across grid points is estimated by the nearest-neighbor Gaussian process. The variability emulator is constructed with the residuals between the mean temperature response and the ESM output, and the associated space-time correlation structure is decomposed by principal component analysis and discrete Fourier transform. The analysis shows that the emulators trained with the runs of ESM only from part of representative concentration pathways can efficiently reproduce the temperature variations under different emission scenarios. The emulated gridded temperatures would be easily taken for climate impact and risk assessment, and be incorporated in the integrated assessment model for climate policy analysis.
ODE/IM correspondence for affine Lie algebras: a numerical approach
Authors: Ito Katsushi , Kondo Takayasu , Kuroda Kohei , Shu Hongfei
Published: December 2020

We study numerically the ODE/IM correspondence for untwisted affine Lie algebras associated with simple Lie algebras including exceptional type. We consider the linear problem obtained from the massless limit of that of the modified affine Toda field equation. We found that the Q-functions in integrable models are expressed as the inner product of the solution of the dual linear problem and the subdominant solution of the linear problem. Using Cheng’s algorithm to obtain the solution of the linear problem, we can determine efficiently the zeros of the Q-function, which is known to provide the solutions of the Bethe ansatz equations (BAEs). We calculate the zeros numerically, which are shown to agree with the results from the non-linear integral equations (NLIEs) for simply-laced affine Lie algebras including the exceptional type. By the folding procedure of the Dynkin diagrams of simply-laced Lie algebras, we also find the correspondence for the linear problem of the non-simply-laced affine Lie algebras.
Analysis of Water Supply and Drainage Construction Technology for Municipal Engineering
Authors: ding Li , liwu Li
Published: December 2020

In recent years, with the continuous improvement of construction technology level in China, the construction speed of major projects has been accelerating, especially the construction of municipal projects, both the quantity and quality of municipal projects have been significantly improved. For municipal engineering, the main purpose of the construction is to provide better and more comfortable accommodation for urban residents. The construction of water supply and drainage projects is related to the daily life of residents, so water supply and drainage projects play a major role in the construction of municipal engineering. This paper briefly analyzes the water supply and drainage construction technology in municipal engineering.
Analysis of ‘5.29’ blast furnace burst accident of Fangda special steel
Authors: Yang Chengcheng , Kong Xiangzhi , Zhang Lijing , Tao Gang
Published: December 2020

On May 29, 2019, a blast furnace explosion occurred in the iron making plant of Fangda Special Steel Technology Co., Ltd. in Qingshanhu District, Nanchang City, Jiangxi Province. The corrugated compensator of No.2 blast furnace gas riser burst, resulting in 6 deaths, 4 injuries and direct economic losses of more than 27.24 million yuan. Through the analysis of the amount of water drawn from the top of blast furnace, this paper concludes that this is a physical explosion caused by overheating, rapid boiling expansion and over-pressure of liquefied water. Through the qualitative evaluation of the accident by Bow-tie model, the specific causes and consequences are analyzed, and the physical model is used to carry out a further quantitative analysis of the consequences, the hazard area is determined, and the countermeasures to prevent the burst accident of corrugated compensator are put forward, which is helpful to prevent the recurrence of such accidents.
GIS-based Fire Risk Assessment and Fire Station Site Selection——Taking Dujiangyan City as An Example
Authors: Xiao Hai , Zhou Yao , Zhang Hongtao
Published: December 2020

This study takes the urban area of Dujiangyan City as the research area, ten risk assessment factors are selected to conduct the fire risk assessment and analysis, including substations, building floor area ratios and miniature fire stations, and uses analytic hierarchy process, buffer analysis and overlay analysis. The minimize facilities model and maximize coverage model in location allocation model (LA model) are used to optimize fire station site selection. The research results show that there are still greater fire risks in the south and northeast of Dujiangyan City. The addition of two small and medium-sized fire stations in the north section of Yanhua road and in south section of Rainbow Avenue can basically realize to cover the areas with higher fire risks thoroughly.