bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and properties of biobased copolyamides based on polyamide 10T and polyamide 56 through one-pot polymerization
Authors: Ai Tianhao , Zou Guangji , Feng Wutong , Ren Zhonglai , Li Fei , Wang Pingli , Lu Bo , Ji Junhui
Published: July 2021

A series of new biobased polyamide 10T-co-56 were synthesized with various comonomer compositions by a one-pot polycondensation reaction, and their structures, crystalline and melting behavior were systematically investigated.
Non-sterical stabilization of one-electron-oxidized NiSalen complex by thiophene core
Authors: Lukyanov Daniil A. , Vereshchagin Anatoliy A. , Sizov Vladimir V. , Kalnin Arseniy Y. , Novoselova Julia V. , Alekseeva Elena V. , Levin Oleg V.
Published: July 2021

A combined theoretical/experimental study of the new thiophene-based NiSalen complex with unconjugated bridging fragment. This complex demonstrates unusual stability of the oxidized form, which is not typical for this class of compounds.
Shape-tuned, surface-active and support-free silver oxygen reduction electrocatalyst enabled high performance fully non-PGM alkaline fuel cell
Authors: Anandha Ganesh P. , Prakrthi A. N. , Selva Chandrasekaran S. , Jeyakumar D.
Published: July 2021

A fully non-PGM alkaline membrane fuel cell with “highest fuel cell activity” was achieved using a hierarchically shape-tuned, small, surface-active, support-free, worm-shaped nano-structured silver oxygen reduction reaction electro-catalyst.
Terpyridine-derived perovskite single crystals with tunable structures and electronic dimensionality
Authors: Yuan Yaxuan , Xian Yeming , Long Yi , Zhang Yangyi , Rahman Naveed Ur , Zhang Yongli , Fan Jiandong , Li Wenzhe
Published: July 2021

Terpyridine-derived perovskite single crystals displaying tunable low-dimensional structures and outstanding optoelectronic performances suitable for device applications have been developed.
Fabrication of a novel core–shell–shell temperature-sensitive magnetic composite with excellent performance for papain adsorption
Authors: Chen Pengfei , Yao Shun , Zheng Dongmei , Xu Zhiyuan , Yu Jinling , Liang Tingting
Published: July 2021

A novel core–shell–shell temperature-sensitive magnetic composite was designed. The composites showed excellent performance for papain adsorption and could thermally protect papain.
Facile synthesis of carbon nitride quantum dots as a highly selective and sensitive fluorescent sensor for the tetracycline detection
Authors: Bai Ruining , Sun Heli , Jin Peng , Li Jingwei , Peng Anzhong , He Jieli
Published: July 2021

The g-C3N4QDs were synthesized by a simple solvothermal “tailoring” process from bulk g-C3N4 which have a “strong quenching” behaviour in the presence of TC. The proposed fluorescent sensor has been successfully applied to detect TC in actual samples.
Highly conductive locust bean gum bio-electrolyte for superior long-life quasi-solid-state zinc-ion batteries
Authors: Liu Binbin , Huang Yuan , Wang Jiawei , Li Zixuan , Yang Guoshen , Jin Shunyu , Iranmanesh Emad , Hiralal Pritesh , Zhou Hang
Published: July 2021

Locust bean gum was utilized to prepare a free-standing quasi-solid-state ZnSO4/MnSO4 electrolyte. Zinc-ion batteries with locust bean gum electrolyte achieved high energy density and superior lifetime.
FOXD1 expression in head and neck squamous carcinoma: a study based on TCGA, GEO and meta-analysis
Authors: Huang Junjie , Liang Bin , Wang Tianjiao
Published: July 2021

Forkhead box D1 (FOXD1) is a new member of FOX transcription factor family. FOXD1 has demonstrated multilevel roles during normal development, and several diseases’ pathogenesis. However, little is known about the role of FOXD1 in the progression of head and neck squamous cancer (HNSC). In the present study, we analyzed FOXD1 expression pattern using The Cancer Genome Atlas (TCGA) dataset, Gene Expression Omnibus (GEO) datasets, HNSC cell lines, and HNSC tissues. Then, we analyzed the correlation between FOXD1 expression and clinical characteristics, and evaluated the prognostic value of FOXD1 in HNSC. Moreover, we assessed the relationship between FOXD1 expression and tumor microenvironment (TME) and immune cell infiltration using Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) and Cell-type Identification By Estimating Relative Subsets Of known RNA Transcripts (CIBERSORT) algorithms. Finally, we predicted the FOXD1-related biological processes (BPs) and signal pathways. FOXD1 was up-regulated in HNSC tissues in TCGA datasets, validated by GEO datasets, HNSC cell lines and HNSC tissues. FOXD1 expression was significantly associated with tumor site and HPV infection. Univariate and multivariate Cox regression analyses showed that FOXD1 expression was an independent prognostic factor. Moreover, we found that the proportions of naïve B cells, plasma cells, and resting dendritic cells (DCs) were negatively correlated with FOXD1 expression, otherwise, the proportion of activated mast cells was positively correlated with FOXD1 expression using CIBERSORT algorithm. Gene Set Enrichment Analyses (GSEAs) revealed that FOXD1 was mainly involved in cancer-related signaling pathway and metabolism-related pathways. FOXD1 was a potential oncogene, and might represent an indicator for predicting overall survival (OS) of HNSC patients. Moreover, many cancer-related pathways and metabolism-related processes may be regulated by FOXD1.
Expanding the Role of Educational Audiologists After a Failed Newborn Hearing Screening: A Quality Improvement Study
Authors: Sapp Caitlin , Stirn Jonathan , O'Hollearn Tammy , Walker Elizabeth A.
Published: July 2021

Purpose

Lack of timely and proximal access to diagnostic hearing evaluation using auditory brainstem response (ABR) testing hampers the effectiveness of Early Hearing Detection and Intervention (EHDI) programs in the United States. This study measured the impact of a state-based quality-improvement (QI) project that provided diagnostic ABR equipment and training to educational audiologists distributed throughout Iowa in regional special education centers.

Method

We used de-identified administrative data generated by the state EHDI program to analyze markers of access to early hearing health care for infants in a preproject condition (“Baseline”) compared to the implementation of diagnostic ABRs at the regional special education centers (“QI Project”).

Results

Our findings revealed that the QI Project was associated with improvements in timeliness of first hearing evaluation, distance traveled for first hearing evaluation, and likelihood of receiving on-guideline audiology care during the first hearing evaluation.

Conclusions

Following the onset of the QI Project, infants and their families had greater access to initial hearing evaluation after failed newborn hearing screening. This improvement could have cascading effects on timeliness of later intervention among those with confirmed permanent childhood hearing loss.
Design of planar waveguide directional couplers with arbitrary modal electric field
Authors: Boucouvalas Anthony , Angelis Kostas , Aidinis Konstantinos , Zhan Min , Wang Danshi
Published: July 2021

The purpose of this work is to present a method for designing planar waveguide couplers of arbitrary modal electric field distributions. The idea here is to create couplers with unusual electric fields, which confine in one planar waveguide. This is possible if a planar waveguide profile supporting two pre‐selected mode fields is designed. Their interference will have to transfer the optical power from one region (bottom layer) to another region (top layer) completely. The inverse transmission‐line technique and the desired electric field are applied, based on which the refractive index profile of the couplers exhibiting excellent crosstalk is reconstructed. By choosing this technique, it is feasible to design planar components in sensing applications, such as high power, temperature or pressure sensors and numerous other possibilities, using unusual electric field distributions.
The unusual widespread solar energetic particle event on 2013 August 19
Authors: Rodríguez-García L. , Gómez-Herrero R. , Zouganelis I. , Balmaceda L. , Nieves-Chinchilla T. , Dresing N. , Dumbović M. , Nitta N. V. , Carcaboso F. , dos Santos L. F. G. , Jian L. K. , Mays L. , Williams D. , Rodríguez-Pacheco J.
Published: July 2021

Context. Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey, and the L1 spacecraft, spanning a longitudinal range of 222° in the ecliptic plane, observed an energetic particle flux increase. The widespread solar energetic particle (SEP) event was associated with a coronal mass ejection (CME) that came from a region located near the far-side central meridian from Earth’s perspective. The CME erupted in two stages, and was accompanied by a late M-class flare observed as a post-eruptive arcade, persisting low-frequency (interplanetary) type II and groups of shock-accelerated type III radio bursts, all of them making this SEP event unusual.

Aims. There are two main objectives of this study, disentangling the reasons for the different intensity-time profiles observed by the spacecraft, especially at MESSENGER and STEREO-A locations, longitudinally separated by only 15°, and unravelling the single solar source related with the widespread SEP event.

Methods. The analysis of in situ data, such as particle fluxes, anisotropies and timing, and plasma and magnetic field data, is compared with the remote-sensing observations. A spheroid model is applied for the CME-driven shock reconstruction and the ENLIL model is used to characterize the heliospheric conditions, including the evolution of the magnetic connectivity to the shock.

Results. The solar source associated with the widespread SEP event is the shock driven by the CME, as the flare observed as a post-eruptive arcade is too late to explain the estimated particle onset. The different intensity-time profiles observed by STEREO-A, located at 0.97 au, and MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering beyond Mercury’s orbit. The longitudinal extent of the shock does not explain by itself the wide spread of particles in the heliosphere. The particle increase observed at L1 may be attributed to cross-field diffusion transport, and this is also the case for STEREO-B, at least until the spacecraft is eventually magnetically connected to the shock when it reaches ∼0.6 au.
X-ray intensity fluctuation spectroscopy measurements
of the charge density wave phases of NbSe3
Authors: Sutton M. , Li Y. , Brock J. D. , Thorne R. E.
Published: July 2021

An introduction to X-ray Intensity Fluctuation Spectroscopy (XIFS) is given by
describing its relationship to speckle from coherent sources. A brief description of the relationship
of XIFS measurements to the underlying equations of motion is given. Preliminary results for the
charge density wave (CDW) system NbSe3 are then presented. Static speckle patterns are shown for
the $\overrightarrow {Q}_1 = (0 .76$ 0) CDW peak showing that XIFS experiments are possible in this systom provided
time constants are long enough. For electrical currents below threshold, a static speckle pattern is
observed but for currents above threshold the speckles are smeared out showing movement of the
CDW. It is also shown that above threshold, the longitudinal correlation length decreases.
Strong sensitivity to magnetic field of the low-temperature heat
capacity of (TMTSF)2PF6
Authors: Lasjaunias J. C. , Sahling S. , Biljakovic K. , Monceau P.
Published: July 2021

We have observed a very large sensitivity to low magnetic field (i.e. below 0.5 Tesla) of the
low-temperature specific heat Cp of the quasi-1D compound (TMTSF)2PF6 in
its spin-density wave (SDW) ground state.
This effect is independent on the field direction compared to that
of the crystal orientation (with H || either to $\bf a$ or
$\bf b'$ axis), and hence does not seem to be related in a direct way to the electronic SDW itself.
In addition, we did not
detect any feature in Cp at the spin-flop transition (at $H=0.45$ T, || $\bf b'$ axis).
Band features and strong correlations in 1D Peierls systems
Authors: Grioni M. , Berger H. , Perfetti L. , Mitrovic S. , Reginelli A. , Hoechst H.
Published: July 2021

High-resolution angle-resolved (ARPES) photoemission in the quasi-one dimensional (1D) Peierls
systems (TaSe4)2I and K0.3MoO3 reveals spectral features with clear 1D character. Their dispersion and
polarization dependence is consistent with open Fermi surfaces and with the symmetry properties of the lattice,
However the measured spectral lineshapes are unusual in various respects, as shown also by a comparison with
the quasiparticle spectra of a `good' metal. A consistent description of the normal metallic phase and of the
low-temperature insulating phases is possible within a polaronic scenario, where the carriers are strongly
renormalized by the interaction with the lattice and the spectrum is largely incoherent. The quasiparticle
signatures are hidden at the spectral leading edge.
Charge ordering and superconductivity
in α-(BEDT-TTF)$_2M$Hg(SCN)4
Authors: Dressel M. , Drichko N. , Salameh B. , Thorns J. , Schlueter J. , Merino J.
Published: July 2021

In the optical spectra of the non-superconducting salt α-(BEDT-TTF)2KHg(SCN)4 a strong feature
appears at frequencies of about 200 cm-1 and temperatures below 200 K which indicates the opening of a pseudogap.
This is in contrast to the superconducting α-(BEDT-TTF)2NH4Hg(SCN)4 whch exhlbits metallic-like optical
properties down to 2 K. Based on exact diagonalisation calculations of the optical conductivity on an extended
Hubbard model at quarter-filling we argue that the proximity of these salts to a charge ordering transition is
responsible for the observed pseudogap. Our proposed scenario suggests that the different ground states, including
superconductivity, are a consequence of the fluctuations associated with short range charge ordering which builds up
close to the quantum phase transition.
Variational wave function for generalized Wigner lattices
in one dimension
Authors: Fratini S. , Valenzuela B. , Baeriswyl D.
Published: July 2021

We study a system of electrons on a one-dimensional lattice, interacting through the long
range Coulomb forces, by means of a variational technique which is the strong coupling analog of
the Gutzwiller approach. The problem is thus the quantum version of Hubbard's classical model
of the generalized Wigner crystal [J. Hubbard, Phys. Rev. B 17, 494 (1978)]. The magnetic
exchange energy arising from quantum fluctuations is calculated, and turns out to be smaller
than the energy scale governing charge degrees of freedom. This approach could be relevant
in insulating quasi-one-dimensional compounds where the long range Coulomb interactions are
not screened. In these compounds charge order often appears at high temperatures and coexists
with magnetic order at low temperatures.
Modification of charge density wave fluctuations
by charge perturbations
Authors: Artemenko S. N.
Published: July 2021

Spectral density of fluctuations of the CDW phase are calculated taking into account electric
field induced by phase fluctuations. The approach based upon the fluctuation-dissipation theorem (FDT)
combined with equations of linear response of the CDW conductor is used. Fluctuating electric field is
found to suppress fluctuations of the phase, while fluctuations of the electric potential are sizeable. This
suggests that transition from the CDW to the normal state (which is usually observed well below the
mean-field transition temperature) may he provoked by fluctuations of the chemical potential, rather than
by destruction of the CDW coherence between conducting chains due to phase fluctuations.
Search for narrow-band-noise modulations
of the infrared transmission of blue bronze
Authors: Rai R. C. , Bondarenko V. A. , Brill J. W.
Published: July 2021

We have searched for narrow-band-noise (NBN) modulations of the infrared transmission in blue
bronze, using tunable diode lasers. No modulations were observed, giving an upper limits for NBN changes
in the absorption coefficient of $\Delta \alpha_{NBN} < 0.3 $ / cm ($\approx \alpha/2000$).
The implication of these results on proposed CDW
properties and NBN mechanisms are discussed.
Experimental evidence of interlayer coherent tunneling in NbSe3
Authors: Latyshev Yu. I. , Bulaevskii L. N. , Kawae T. , Ayari A. , Monceau P.
Published: July 2021

Zero bias conductance peak (ZBCP) and gap features have been studied on tunneling interlayer spectra of
the micron-sized NbSe3 stacks of high quality. We show that temperature dependence and the shape of the ZBCP is
self-consistently described by Bulaevskii theory of coherent interlayer tunneling of pocket carriers.
Point-contact spectroscopy probing the NbSe3 CDW gap
in different crystallographic orientations
Authors: Sinchenko A. A. , Monceau P.
Published: July 2021

We have measured the differential current-voltage characteristics of normal metal-NbSe3 direct
point contacts (without insulating barrier) formed along different crystallographic orientations under applied
magnetic field with different orientations. At low temperature two energy gaps, $\Delta_{p1}$ and $\Delta_{p2}$, corresponding
to the high and the low-temperature CDW were observed simultaneously as a singulanty of the excess
resistance which is attributed to an analog of Andreev reflection, in which the incident electron reflects on
the Peierls energy gap barriers with its charge unchanged. An applied magnetic field up to 8.5 T does not lead
to a change in the density of states and in the Peierls energy gaps, suggesting that the large magnetoresistance
observed in NbSe3 might not result from the change in the CDW order parameter with magnetic field but
rather from the increase of scattering of non-condensed to CDW carriers.
On the critical current for the charge density wave transport
Authors: Sinchenko A. A. , Zybtsev S. G. , Gorlova I. G. , Latyshev Yu. I. , Pokrovskii V. Ya. , Monceau P.
Published: July 2021

We report transport measurements under very high current densities j, up to 108 A/cm2, of
quasi-one-dimensional charge-density wave (CDW) conductors NbSe3 and TaS3. Above $j_0-10^1$ A/cm2 the point contacts
NbSe3-NbSe3 show a sharp singularity, and the TaS3 nanosamples show metallic temperature dependence (positive
dR/dn. We interpret both results as an evidence for the suppression of the Peierls gap 2A and development of the
metallic state above j0. Possible scenarios of the Peierls state destruction are discussed.
Currents conversion in the submicron CDW-N-CDW structures
Authors: Zybtsev S. G. , Timofeev V. N.
Published: July 2021

Using selective area irradiation by electrons with high energies the submicron CDW-N -CDW
heterostructures were obtained on NbSe, single crystals. In sliding CDW regime an excess voltage appears on this
narrow normal region that depends neither on a sample, nor on the length of the irradiated area l and represents
threshold phase slip (PS) voltage Vps, induced on CW-N boundaries. The obtained Vps, data for lower CDW strongly
differ (5-6 times higher) from the known results for NbSe, obtained in the conventional configuration. This suggests
that CDW-N boundaries created by irradiation represent the "ideal" face contacts introducing small perturbations. At
low temperature (T<7 K) and at l<0.5 μm we observe narrow (-0.5 mV width) dynamic conductance peak at zero
bias voltage. The peak amplitude grows with decreasing temperature and length of the irradiated area.
Microscopic investigation of moving flux line structures
in superconductors using neutron diffraction and μSR
Authors: Forgan E. M. , Charalambous D. , Fort D. , Cubitt R. , Simon Ch. , Lee S. L. , Amato A.
Published: July 2021

We have used a variety of microscopic techniques to reveal the structure and motion of flux line
arrangements, while the flux lines are caused to move by a transport current. Using small-angle neutron scattering,
we are able to demonstrate direaly the alignment of the nearest-neighbour direction of flux lines while they are
moving. The results are similar but not identical to those from two-dimensional simulations. We also see the
destruction of the flux lattice by plastic flow and the bending of flux lines. We have also employed μSR, which
measures the distribution of field values within the mixed state, to obtain information about the speed and degree of
order of the motion of flux lines past the muons. Such measurements give complementary information to that
obtained by neutron techniques. The general aspects of these measurements, of interest to those working in other
areas, are the creation of order in non-equilibrium situations and the interplay of the ordering cccuning during
dissipation and the ordering caused by the crystal structure of the superconductor which is host to the flux lines.
Charge ordering in non-dimerized BEDT-TTF based organic
conductors: 13C-NMR experiments
Authors: Takahashi T. , Chiba R. , Takano Y. , Kubo Y. , Hiraki K. , Yamamoto H. , Nakamura T.
Published: July 2021

Experimental evidences of the charge ordering with the use of 13C-NMR techniques in various organic
conductors are reviewed. In the insulating states of two-dimensional BEDT-TTF salts, a-I, and 8-RbZn(SCN)4, the
formation of charge stripes perpendicular to molecular stacks are confiied. Charge disproportionation is estimated
as 0.8:0.2 in the latter and more in the former. It is also observed that charge disproportionation already develops
well above the MI transition temperature while no long-range charge order is stabilized. This seems to require a
serious reconsideration of the transport properties in the `metallic' state.
Inhomogeneities in antiferromagnetic solids
Authors: Kusmartsev F. V.
Published: July 2021

We find that in narrow hand anti-ferro-magnetic (AF) solids described by general
t-J model there may arise electronic molecules or clusters consisting of holes. These holes are
segregated around the topological defects such as loops of anti-phase domain walls. The loops
are naturally self-organized into the closed loops of triangular, square, rectangular or other
form depending on physical situations. This kind of electron molecules is spontaneously formed
in AF background and constitute a new type of elementary excitations of the AF solids. We
find that the size and shape of these e-molecules depend mostly on the AF coupling J and the
bandwidth $4t$ as well as on the inter-site Coulomb repulsion between holes.
Disordered quantum smectics
Authors: Orignac E. , Chitra R.
Published: July 2021

We study the effect of disorder on the properties of the Quantum Hall smectic state arising
in two dimciisional electron systems in high Landau levels. We use the replica trick and the Gauzsian
Variational method to treat the disorder. We find that the quantum smectics are rather different from
the usual classical smectics in that the density correlations along the direction of the stripes manifest a
Bragg-Glass type behaviour whereas those in the transverse direction are infra-red divergent. This results
in an amsotropic behaviour of all physical quantities. We calculate the dynamical conductivity
$\sigma _{xx} ({\bf q}, \omega )$
along the stripe direction and find a $\bf q$ dependent pinning peak.
Static aging
vs. dynamic rejuvenation in solid friction
Authors: Caroli C. , Baumberger T. , Bureau L.
Published: July 2021

Dry friction between macroscopic solids can be understood in terms of the elastic (static regime) versus plastic
(dynamic regime) responses to a shear stress of a set of dilute micrometric adhesive contacts.
When pinned, such a system is
the seat of two distinguishablc slow, quasi-logarithmic aging dynamics:
- a “geometric" aging process, originating from the bulk of the contacting asperities, which results in the increase of the
real area of contact.

- a structural one, taking place within the nm-thick adhesive layers, which behave as 2D confined “soft " structural
glasses.

Both mechanisms give rise to associated dynamic rejuvenation phenomena, akin to those observed in threshold fluids,
which govern the rich variety of frictional dynamics exhibited by extended systems.
Thermodynamics of disordered elastic systems in the Bragg glass
phase
Authors: Schehr G. , Giamarchi T. , Le Doussal P.
Published: July 2021

We study the thermodynamics of a pinned quantum object when the elastic description applies, e.g.
in the Bragg glass phase for a crystal with point disorder or for a single elastic line. Using the replica variational
method we compute the specific heat both in the quantum and classical limits. In the quantum regime, we show
that the specific heat behaves - at low temperature - as T3 in dimension $d = 2$ and $d = 3$.
Electronic properties of (DMTSA)BF4 at ambient pressure
Authors: Nagasawa M. , Kawabata K. , Sambongi T. , Monceau P. , Otsubo T.
Published: July 2021

Organic conductor (DMTSA)BF4 [DMTSA: 2,3dimethyl-tetra-sleno-antracene] is a compound composed
of an electron donor DMTSA and a monovalent acceptor BF$_4^-$. In the salt, the electronic system is expected to be the
Mott-Hubbard insulator. However, its conductivity at room temperature is 200~400$\Omega^{-1}$cm-1 and behaves metallic
above ∼2OOK. At ambient pressure, we found anomalies both in the DC conductivity components and in the
permittivity at ~80K, similar to those in (TMTTF)2X associated with charge ordering at ~100K. In the insulating state
under low pressure, we found that the sample shows non-linear conduction with threshold. We discuss the possible
origin of the anomalies and the apparent similarity with the non-linear electric conduction by the density wave sliding.
Model for the fractional quantum Hall effect problem
Authors: Dyakonov M. I.
Published: July 2021

A simple one-dimensional model is proposed, in which N spinless interacting fermions occupy $M>N$
degenerate states on a circle. It is argued that the energy spectrum and the wavefunctions of this system strongly
resemble the spectrum and wavefunctions of 2D electrons in the lowest Landau level (the problem of the
Fractional Quantum Hall Effect). In particular, Laughlin-type wavefunctions describe ground states at filling
factors $\nu N/M=1/(2m+1)$. Within this model the complimentary wavefunction for $\nu =l-I/(2m+1)$ is found
explicitly.
Evidence for a liquid crystal phase transition in two-dimensional
electrons in high Landau levels
Authors: Cooper K. B. , Lilly M. P. , Eisenstein J. P. , Pfeiffer L. N. , West K. W.
Published: July 2021

Transport measurements of high-mohility two-dimensional electron systems at low temperatures have
revealed a large resistance anisotropy around half-filling of excited Landau levels. These results have been
attributed to electronic stripe-phase formation with spontaneously broken orientational symmetry. Mechanisms
which are known to break the orientational symmetry include poorly-understood crystal structure effects and an
in-plane magnetic field, $B_{||}$. Here we report that a large $B_{||}$ also causes the transport anisotropy to persist up to much
higher temperatures. In this regime, we find that the anisotropic resistance scales sublinearly with $B_{||}/T$. These
observations support the proposal that the transition from anisotropic to isotropic transport reflects a liquid crystal
phase transition where local stripe order persists even in the isotropic regime.
High magnetic field NMR investigation of the spin density wave
phase of TMTSF2PF6
Authors: Clark W. G. , Zamborsky F. , Alavi B. , Vonlanthen P. , Moulton W. , Kuhns P. , Reyes A.
Published: July 2021

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T
(1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6.
Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton
relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase
transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than
$1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition
is weakly first order, so that the full critical divergence is never achieved. The measurements
also show a dependence of the transition temperature on the orientation of the magnetic field
and a quadratic dependence on its magnitude that agrees with earlier transport measurements
at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.
Macro-, meso-, and nanoscopic metallo thermo mechanics
Authors: Inoue T.
Published: July 2021

Evolution of material structure, temperature and mechanical fields undergoing phase transformation are coupled each other as is termed metallo-thermo-mechanical coupling. Three kinds of approach from maro-, meso- and micro-scopic viewpoints are presented, in this paper, to determine the fields, and fundamental governing equations are briefly introduced in the framework of metallo-thermo-mechanics respectively based on the methods of finite element, phase field and molecular dynamics. Some examples of simulated results are illustrated: Quenching of gear wheel and Japanese sword as well as continuous casting by twin roll method by FEM and forging of billet and gear by FVM; cooled plate with induced stress and dendrite growth from molten state by PFM; and melting of a bar, crystallographic change in optical memory device and shape memory effect by MDM.
Modelling of grain boundary segregation kinetics that are responsible on irreversible and reversible temper embrittlement of engineering steels
Authors: Kovalev A. , Wainstein D.
Published: July 2021

There are presented the computer models of multicomponent grain boundary segregation (GBS) that are formed at quenching or tempering of engineering steels. The modelling of these processes requires different algorithms. The dynamic model of segregation at quenching is based on solution of independent diffusion and adsorption-desorption equations for various impurities in steel tied by feedback. The model of segregation under tempering considers the influence of alloying and tempering parameters on concentration and thermodynamic activity of carbon in the α-solid solution. It is based on regression analysis of experimental data on grain boundaries chemical composition obtained by Auger spectroscopy. There is established that grain boundary enrichment by harmful impurities (S and P) is possible after carbon and nitrogen segregation dissolution. The models allow to analyze the competition of elements during formation of GBS and to establish main factors responsible on development of different kinds of embrittlement in engineering steels with various alloying and content of harmful impurities.
Phase transitions and transformation-induced plasticity of steel in
the framework of continuum mechanics
Authors: Böhm M. , Schmidt A.
Published: July 2021

Distortion of steel under cooling is inevitably connected
with phase changes (PTs) and transformationinduced
plasticity (TRIP). We formulate a model describing these coupled phenomena,
in which motion,
temperature and phase fractions are considered as a "thermo-kinetical
process with phase changes". The essential
feature of the model is an appropriately generalised concept of stress-free
intermediate configuration generated by
TRIP. By means of the Clausius-Duhem inequality we restrict the set of
admissible material laws. It is shown that
the known laws for phase transitions as well as of TRIP are admissible in
this model. We do not consider classical
plasticity, although the present model can be adapted to allow for plastic
deformations. By simplification and
linearization we get a model discribing a quenching test. Numerical results
are obtained via a finite-element method.
An experimental mock-up for the study of steel behaviour at high temperature during phase transformation
Authors: Vincent Y. , Bergheau J.-M. , Leblond J.-B. , J.-F.Jullien
Published: July 2021

In most numerical simulations of welding, due to the very short times involved, viscoplastic effects are neglected. However an experimental mock-up developed at INSA has evidenced the possible importance of such effects, which must therefore be incorporated in a more refined description of the material behaviour. This paper presents such a description; an extension of Leblond’s model for transformation plasticity, accounting for the dependence of mechanical properties upon strain rate, is proposed. Finite element analyses using elastic-plastic or elastic-viscoplastic constitutive laws are compared with experiments, and it is found that incorporation of viscoplastic effects significantly improves the quality of the agreement between numerical and experimental results.
Prediction of phase distribution and chemical composition during gas carburizing of stainless steels
Authors: Turpin T. , Dulcy J. , Gantois M.
Published: July 2021

This article reports a theoretical and experimental study aiming at reducing gas carburizing experiments on stainless steels. This work was carried out to show the advantages of numerical calculations to simulate phase transformations during the gas carburizing process of high alloyed steels. The use of Thermo-Calc and Dictra software allows the metallurgist to predict the optimum thermochemical and heat treatments which are necessary to obtain an accurate carbon profile in a stainless steel. Moreover, the phase distribution and chemical composition can be followed as a function of time and/or distance to gas-solid interface.
Thermal modelling of a carbon/carbon composite material fabrication
process
Authors: Lines J.-F. , Vignoles G. L. , Goyheneche J.-M. , Puiggali J.-R.
Published: July 2021

The rapid densification process is a variant of Chemical
Vapour Infiltration. It allows to fabricate composite materials starting
from a fibrous preform lying in a boiling hydrocarbon precursor, the
cracking of which results in a solid deposit constituting the matrix of the
carbon/carbon composite. A phenomenological analysis emphasises the
significant role played by temperature in the couplings between various
physical and chemical phenomena. It is shown here that the control of the
thermal couplings makes it possible to decrease the power consumed while
guaranteeing the quality of the final material.
Modelling the Marangoni convection in laser heat treatment
Authors: Drezet J.-M. , Pellerin S. , Bezençon C. , Mokadem S.
Published: July 2021

Epitaxial Laser Metal Forming (E-LMF) consists in impinging a jet of
metallic powder onto a molten pool formed by controlled laser heating and
thereby, generating epitaxially a single crystal deposit onto the damaged
component. This new technique aims to be used for the repair and reshape
single crystal gas turbine components. Because of the very localised melting
pool, the high temperature gradients produced during the process must be
carefully controlled in order to avoid both the columnar-to-equiaxed
transition (CET) and the appearance of hot tears. To this end, heat flow
modelling is required to establish the relationship between process
parameters such as laser power, beam diameter and scanning speed, and the
local solidification conditions. When modelling the heat transfer within the
sample, it is necessary to include the liquid flow pattern generated by the
surface tension driven convection known as the Marangoni effect. Indeed, the
fluid flow in the liquid pool dictates the shape of the traces as shown by
the measurements carried out at EPF-Lausanne in re-melting experiments. A
three dimensional (3D) model is implemented in the finite element software
calcosoft$^\text{\textregistered}$ in order to model the
development of the fluid convection within the liquid pool. It is shown that
the velocities due to natural convection are of the order of 1 mm/sec
whereas Marangoni convection produces velocities of the order of 1 m/sec.
Moreover, at low scanning speeds, the liquid pool becomes larger than the
beam diameter and the development of Marangoni eddies leads to a widening
and deepening of the pool. The local solidification conditions such as the
thermal gradient and the solidification speed can be extracted at both the
solidus and liquidus temperatures to assess the risk of CET and hot
cracking.
Optimisation of the laser surface remelting process on strain criteria
Authors: Grum J. , Šturm R.
Published: July 2021

This paper shows a process of selection of optimum conditions for laser remelting of nodular cast iron. The optimisation takes into account a specified depth of the hardened layer, for which an appropriate energy input is specified while taking into account the mode of guiding the laser beam. Strain criteria are given for the optimisation of the remelting process, i.e., minimum energy input at a given depth of the hardened layer, minimum distortion of the machine part and a desired variation of residual stresses across the hardened layer. Practical tests of optimisation showed the logic of adhering to the aforementioned criteria, because we can significantly influence the quality of the product at lower costs of manufacturing.
FEM simulation of laser forming process of shipbuilding steel plate
Authors: Liwen Zhang , Qi Zhong , Jibin Pei , Guoliang Zhang , Yuanliang Xia
Published: July 2021

Laser forming has become a promising technique to form sheet metal in recent years. This new forming process can produce plastic deformation by thermal stresses resulted from the irradiation of laser beam scanning. In this paper, a 3-D thermo-mechanical FEM model was developed to simulate the laser forming process of shipbuilding steel plate. The finite-element software MSC.Marc was used to calculate the temperature field, stress field and strain field during laser forming process. The transient temperature field and the final bending angle were predicted. Then the effect of laser forming process technical parameters was studied. To evaluate the accuracy of the simulation, a laser forming experiment was performed. It is demonstrated that the finite element simulation results are in good agreement with experimental results.
Evaluation of various phase-transition models for 100Cr6 for application in commercial FEM programmes
Authors: Böhm M. , Hunkel M. , Schmidt A. , Wolff M.
Published: July 2021

The numerical simulation of all steps of the production
of a steel workpiece is nowadays a widely used
tool for understanding and optimization of such processes. The
transformation of austenite into ferritic phases is an
important feature of heat treatment of steel. Good models for the
non-isothermal phase transition are a necessary
prerequisite for various other modeling steps. We evaluate some of the
existing algorithms based on the isothermal
Johnson-Mehl-Avrami model and compare their performance in the case of
non-isothermal phase transitions with
experimental data for steel 100Cr6 with exponential and linear cooling. The
investigations presented here are part of
a special research project on distortion engineering (SFB 570 at University
of Bremen).
Stresses in glass plate joined with other materials: Modeling and
experimental validation
Authors: Startsev Y. K.
Published: July 2021

The previously developed relaxation model for annealing
of glass seals with other materials has been applied widely. It remains
unclear whether there are a specific low temperature and very long-term
iso-thermal treatments at which this simple model ceases to work correctly
and requires complication or even revision. With the aim to determine the
minimum fictive temperature at which the relaxation model of annealing of
glass seal with an elastic material is still applicable, the stresses in the
sandwich S52-2 glass-molybdenum seals are measured at different
stabilization temperatures. The experimental temperature-time dependences of
the stresses are compared with those calculated using the relaxation model
of seal annealing. The use of this relatively simple model leads to a quite
satisfactory agreement (even if not identical at all the temperatures) in
the range from the glass transition temperature to 380${}^\circ$C for stabilization
durations as long as 81 days. This treatment duration makes it possible to
reach a structural temperature of 434${}^\circ$C, which is considerably lower than
the structural temperature (525${}^\circ$C) obtained upon simple cooling of glass at
a rate of 3 K/mm.
Modelling friction stir welding with thermally coupled fluid dynamics
Authors: Schmitter D. , Zylla I. M.
Published: July 2021

The computational fluid dynamics approach for high velocity deformation processes as friction
welding [1] or friction stir welding can successfully predict certain process aspects including microstructure
development, if the thermal behaviour is included properly. We model the solid state
material flow in the thermomechanically affected zone of the friction stir process using the Navier
Stokes equations for an incompressible non Newtonian fluid field representing the ideally plastic
material movement. Viscosity is related to the ideally plastic flow stress depending on temperature
and strain rate.
Three-dimensional numerical simulation of the nitriding process
Authors: Duranton P. , Devaux J. , Larreur M. , Fortunier R. , Bergheau J.-M.
Published: July 2021

This paper presents a three-dimensional numerical simulation of a nitriding process applied to an industrial component. The aim of the simulation is to predict the residual stresses and distortions due to volume changes induced by chromium nitride (CrN) and carbides (M23C6 et M4C3) formation. The simulation is performed in two steps. The diffusion of nitrogen and the precipitation of chrome nitride and carbides are first simulated. Then stresses and strains are calculated, assuming an elastic behaviour of the component, and using a volume expansion due to the precipitate concentration. The proposed approach is applied on a gear tooth. Small holes and details were neglected. For symmetry reasons, only half a tooth is taken into account. As the main phenomena take place through the first millimetre from the outer surface, a special attention was paid on meshing. The mesh used for the diffusion and precipitation analysis is composed of 1 130 000 nodes and 1 110 000 elements. For the mechanical analysis, a coarser mesh including only 165 000 nodes and 290 000 elements was used.
Simulation of microstructure evolution during recrystallization using a high resolution three dimensional cellular automaton
Authors: Mukhopadhyay P. , Loeck M. , Gottstein G.
Published: July 2021

A more refined 3D cellular Automata (CA) algorithm has been developed which has increased the resolution of the space and reduced the computation time and can take care of the complexity of recrystallization process through physically based solutions. This model includes recovery, condition for nucleation and orientation dependent variable nuclei growth as a process of primary static recrystallization. Incorporation of microchemistry effects makes this model suitable for simulating recrystallization behaviour in terms of texture, kinetics and microstructure of different alloys. The model is flexible to couple up with other simulation programs on a common database.
CESAM—Coded excitation scanning acoustic microscope
Authors: Meriläinen Antti , Hyvönen Jere , Salmi Ari , Hæggström Edward
Published: July 2021

Scanning acoustic microscopy (SAM) finds use across many disciplines, e.g., biology, industrial quality control, and materials science, thanks to its unique ability to quantify mechanical sample properties combined with its high resolution. However, such imaging is often slow, especially if averaging is necessary. We present a Coded Excitation Scanning Acoustic Microscope (CESAM) that employs coded signals and show that it produces images of higher signal-to-noise ratios (SNRs) than the classical SAM in a comparable measurement time. The CESAM employs coded signals instead of the short bursts used in traditional SAMs, and we employ both linear and non-linear frequency modulation. Our results show that compared to the SAM approach, this modulation increases the SNR by 16.3 dB (from 39.9 to 56.2 dB) and reduces the echo duration by 26.7% when we employ a linear chirp to the transducer with a nominal bandwidth of 130–370 MHz. Driving the transducer with a broader bandwidth signal using non-linear chirps (100–450 MHz), we obtained a SNR increase of 10.3 dB and a reduced echo duration of 70.5%. The shorter echo duration increases z-resolution, whereas the lateral resolution remains limited by the wavelength. Finally, we show that by using these coded signals, one can obtain enhanced image quality relative to the standard actuation of the same measurement time. Our results have potential to invigorate the field of acoustic microscopy, especially with samples where the enhanced SNR and/or contrast-to-noise ratio is crucial for image quality.
2D measurements of plasma electron density using coherence imaging with a pixelated phase mask
Authors: Allcock J. S. , Silburn S. A. , Sharples R. M. , Harrison J. R. , Conway N. J. , Vernimmen J. W. M.
Published: July 2021

In this paper, the pixelated phase mask (PPM) method of interferometry is applied to coherence imaging (CI)—a passive, narrowband spectral imaging technique for diagnosing the edge and divertor regions of fusion plasma experiments. Compared to previous CI designs that use a linear phase mask, the PPM method allows for a higher possible spatial resolution. The PPM method is also observed to give a higher instrument contrast (analogous to a more narrow spectrometer instrument function). A single-delay PPM instrument is introduced as well as a multi-delay system that uses a combination of both pixelated and linear phase masks to encode the coherence of the observed radiation at four different interferometer delays simultaneously. The new methods are demonstrated with measurements of electron density ne, via Stark broadening of the Hγ emission line at 434.0 nm, made on the Magnum-PSI linear plasma experiment. A comparison of the Abel-inverted multi-delay CI measurements with Thomson scattering shows agreement across the 3 × 1019 < ne < 1 × 1021 m−3 range. For the single-delay CI results, agreement is found for ne > 1 × 1020 m−3 only. Accurate and independent interpretation of single-delay CI data at lower ne was not possible due to Doppler broadening and continuum emission.
Temperature insensitive type II quasi-phasematched spontaneous parametric downconversion
Authors: Pan Xin-Yi , Kurtsiefer Christian , Ling Alexander , Grieve James A.
Published: July 2021

The temperature dependence of the refractive indices of potassium titanyl phosphate (KTP) is shown to enable quasi-phasematched type II spontaneous parametric downconversion (SPDC) with low temperature sensitivity. Calculations show the effect to be maximized for emission of photons at around 1165 nm, as well as producing similar plateaus for wavelengths throughout the telecommunications bands. We experimentally demonstrate the effect, observing temperature-insensitive degenerate emission between 20 °C and 100 °C at 1327 nm, within the telecommunications O band. This result has practical implications for the development of entangled photon sources for resource-constrained environments, and we demonstrate a simple polarization entangled source as a proof of concept.