bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional wake transition for CO2 flow at supercritical pressure over single heated cylinder
Authors: Xie Jingzhe , Xie Gongnan
Published: September 2022

The three-dimensional wake transition for supercritical CO2 (SCO2) with Reynolds number (Re) ranging from 100 to 300 is systematically investigated by large eddy simulation. Numerical results of the constant-property fluid are validated with the classical conclusions. The secondary instabilities, i.e., mode A (spanwise scale of ∼4.5 times cylinder diameter) and mode B (approximately equal to cylinder diameter), are well captured in the wake. The results at Re = 120 show that the evolution of vortex dislocations is mainly manifested in the alternating occurrence of three stages, i.e., the two-dimensional vortex shedding stage, pure mode A stage, and dislocation stage. The stable state of pure mode A is found at Re = 140. As Re continues to increase, the wake shows a gradual transition from mode A to mode B, rather than the transition from mode A* (mode A + dislocation) to mode B. The frequency spectrum in this process is the gradual shift of a single peak from the low frequency to the high frequency. The wake cycle sequence changes from the alternation of four structures at Re = 155 to the alternation of pure and “contaminated” mode B structures at Re = 170. The critical condition of wake “resonance” is determined at Re = 175, where the final state of the wake is relatively ordered mode B structure, representing the weakest three-dimensionality in the transition regime. After that, the three-dimensionality of the wake enhances with Re, and the probability of the occurrence of disordered structures increases accordingly. The vortex shedding frequency of the pure mode follows the order: 2D > B > A > A*. The width of the frequency spectrum is mainly related to whether the wake flow state is a continuous single mode or the alternation of multiple modes. Based on the Strouhal–Reynolds number relationship, flow pattern in the wake transition process is finally discussed.
Nanomechanical and tribological properties of nickel–chromium multilayer coating on Inconel 617
Authors: Asif Ayesha , Rahman Saifur , Polycarpou Andreas A.
Published: September 2022

Multilayer coatings of Ni and Cr were deposited onto Inconel 617, and multi-scale physical properties were characterized using high temperature tribological experiments, nanoindentation, and microscratch. The effect of high temperature aging (950 °C under helium environment) on two different Ni/Cr multilayer coatings with individual layer thicknesses of 50 and 200 nm denoted by Ni/Cr(50) and Ni/Cr(200) was investigated. Nanoindentation of original coatings showed a hardness of 6 GPa that increases to 14 GPa for both samples once aged. Microscratch results support the macro-tribology results where Ni/Cr(50) (without aging) was the only delaminated coating with significant wear. Additionally, aging in both cases reduced the in situ coefficient of friction and wear. Cross-section energy dispersive spectrometry confirmed that the aged oxide layer was two to three times thicker than the original coating. An abundance of chromium oxide was found in the main body of the coatings, which led to higher hardness and better wear resistance.
Test of a multi-gigawatt, 800 ns high power microwave driver based on Marx generator and metal-oxide varistors
Authors: Yang H. , Gao J. , Zhang Z. , Xun T. , Zhang H. , Ge X.
Published: September 2022

High power microwave (HPM) sources usually require a well-defined rectangular pulse waveform, which is especially true for the case of long pulse (>100 ns), stable, and high efficiency operation. Most long pulse HPM drivers are realized with pulse forming networks. This paper presents a long pulse driver composed of a conventional Marx generator and metal-oxide varistors (MOVs), utilizing the MOV’s nonlinear V–I characteristic. This method is easy to implement, and it has an additional benefit that the voltage can be stabilized even if the load’s impedance changes slightly. A low inductance zig-zag folding structure of the MOV is designed to decrease its size and self-inductance. An LC filter is used to reduce the energy loss in the MOV. In the experiment, a 400 kV, 800 ns long pulse is achieved at a foil-less electron diode, and longer than 300 ns HPM generation is obtained.
Robust estimation of charge carrier diffusivity using transient photoluminescence microscopy
Authors: Nagaya Wong Narumi , Ha Seung Kyun , Williams Kristopher , Shcherbakov-Wu Wenbi , Swan James W. , Tisdale William A.
Published: September 2022

Transient microscopy has emerged as a powerful tool for imaging the diffusion of excitons and free charge carriers in optoelectronic materials. In many excitonic materials, extraction of diffusion coefficients can be simplified because of the linear relationship between signal intensity and local excited state population. However, in materials where transport is dominated by free charge carriers, extracting diffusivities accurately from multidimensional data is complicated by the nonlinear dependence of the measured signal on the local charge carrier density. To obtain accurate estimates of charge carrier diffusivity from transient microscopy data, statistically robust fitting algorithms coupled to efficient 3D numerical solvers that faithfully relate local carrier dynamics to raw experimental measurables are sometimes needed. Here, we provide a detailed numerical framework for modeling the spatiotemporal dynamics of free charge carriers in bulk semiconductors with significant solving speed reduction and for simulating the corresponding transient photoluminescence microscopy data. To demonstrate the utility of this approach, we apply a fitting algorithm using a Markov chain Monte Carlo sampler to experimental data on bulk CdS and methylammonium lead bromide (MAPbBr3) crystals. Parameter analyses reveal that transient photoluminescence microscopy can be used to obtain robust estimates of charge carrier diffusivities in optoelectronic materials of interest, but that other experimental approaches should be used for obtaining carrier recombination constants. Additionally, simplifications can be made to the fitting model depending on the experimental conditions and material systems studied. Our open-source simulation code and fitting algorithm are made freely available to the scientific community.
Laser-induced dynamic alignment of the HD molecule without the Born–Oppenheimer approximation
Authors: Adamowicz L. , Kvaal S. , Lasser C. , Pedersen T. B.
Published: September 2022

Laser-induced molecular alignment is well understood within the framework of the Born–Oppenheimer (BO) approximation. Without the BO approximation, however, the concept of molecular structure is lost, making it hard to precisely define alignment. In this work, we demonstrate the emergence of alignment from the first-ever non-BO quantum dynamics simulations, using the HD molecule exposed to ultrashort laser pulses as a few-body test case. We extract the degree of alignment from the non-BO wave function by means of an operator expressed in terms of pseudo-proton coordinates that mimics the BO-based definition of alignment. The only essential approximation, in addition to the semiclassical electric-dipole approximation for the matter–field interaction, is the choice of time-independent explicitly correlated Gaussian basis functions. We use a variational, electric-field-dependent basis-set construction procedure, which allows us to keep the basis-set dimension low while capturing the main effects of electric polarization on the nuclear and electronic degrees of freedom. The basis-set construction procedure is validated by comparing with virtually exact grid-based simulations for two one-dimensional model systems: laser-driven electron dynamics in a soft attractive Coulomb potential and nuclear rovibrational dynamics in a Morse potential.
Experimental verification of a novel hierarchical lattice material with superior buckling strength
Authors: Bluhm Gore Lukas , Christensen Keld , Poulios Konstantinos , Sigmund Ole , Wang Fengwen
Published: September 2022

Recently, a systematic approach for the design of lattice materials with extreme buckling strength has led to optimized hierarchical lattice materials with unprecedented load carrying capacity. This is obtained at the cost of a small decrease in linear stiffness. However, the superior buckling resistance of such optimized hierarchical lattice materials has so far only been predicted numerically. In fact, concerns have been raised regarding the validity of the employed linear buckling analysis and potential risk of catastrophic failure due to the coalescence of multiple critical buckling modes. This work aims at refuting these concerns by designing and testing manufacturable novel hierarchical lattice materials with superior buckling strength. Thereby, the basis is provided for wide applications of these high-performing materials in mechanical design. A novel hierarchical material is generated for this work by combining the mentioned design procedure with a requirement on the minimum feature size to ensure manufacturability. For addressing the raised concerns, the optimized material design, together with a reference material, is realized with the help of additive manufacturing and experimentally tested in uniaxial compression. The obtained results are compared to numerical simulations considering geometrical and material nonlinearities, and an overall good agreement is found between experimental and numerical results. This confirms an increase in buckling resistance and post-buckling load carrying capacity by a factor of more than three compared to the regular reference lattice structure. Hence, the buckling superiority of this novel type of architected materials is clearly demonstrated.
A narrow-linewidth three-mirror VCSEL for atomic devices
Authors: Huang M. , Serkland D. K. , Camparo J.
Published: September 2022

We consider the use of a recently invented three-mirror vertical-cavity surface-emitting laser (VCSEL) as an optical-pumping light source for next-generation atomic devices (e.g., atomic clocks). While VCSELs are attractive given their very low size, weight, and power and intrinsic resistance to longitudinal mode hops, their relatively large linewidths give rise to efficient laser phase-noise to transmitted intensity noise conversion (PM-to-AM), which severely limits the signal-to-noise ratio in vapor-cell signals. In contrast, the three-mirror VCSEL has a linewidth more than ten times narrower than traditional VCSELs. Using a three-mirror VCSEL in a continuous-wave Cs vapor-cell atomic clock testbed, we demonstrate the utility of this laser for next-generation atomic devices in general, obtaining a short-term stability of 3.6 × 10−12/τ1/2 without any attention to PM-to-AM mitigation strategies.
Competing roughness effects on the non-stationary crossflow instability of the boundary-layer over a rotating broad cone
Authors: Al-Malki M. A. S. , Fildes M. , Hussain Z.
Published: September 2022

There are two primary aims of this paper: the first aim is to investigate the effects of the roughness types of the Miklavčič and Wang model on stationary disturbances of the boundary-layer flow over a broad rotating cone in still fluid. The second aim is to examine similar effects of surface roughness, but on non-stationary modes of crossflow instability. This study begins with the formulations of the mean-flow system based on the cone geometry. These equations are solved using a spectral numerical method based on Chebyshev polynomials and then used to formulate the linear stability system, which are computed for obtaining neutral curves of the unsteady flows. For the stationary modes, our results indicate that the inviscid instability (type I mode) is more stable, while the viscous instability (type II mode) entirely eliminates, as concentric grooves or isotropic roughness and the cone half-angle increase. In contrast, streamwise grooves have a slight stabilizing effect on the type I mode and a significant destabilizing effect on the viscous instability. Another finding indicates that decreasing the half-angle leads to a greater stabilizing effect of isotropic roughness on the type I modes. Our outcomes are also confirmed by the growth rate and the energy analysis, which shows a large reduction of the total energy balance as a result of increasing concentric grooves or isotropic roughness for the crossflow mode. For non-stationary modes, similar effects are observed in that increasing all levels of roughness stabilizes the type I branch (with concentric grooves and isotropic roughness having a much stronger effect than streamwise grooves), and although increasing concentric grooves and isotropic roughness stabilizes the type II branch, increasing streamwise grooves destabilizes this branch. For modes traveling slower than the rotation of the cone, concentric grooves generally have a stronger stabilization effect for the type I branch, whereas for modes traveling faster than the cone, isotropic grooves have a stronger stabilization effect on the type I branch for all broad half angles. Importantly, increasing concentric grooves and isotropic roughness increases the frequency at which the most dangerous modes occur, whereas increasing the streamwise grooves reduces the frequency at which the most dangerous modes occur.
Droplet impact on liquid films: Bouncing-to-merging transitions for two-liquid systems
Authors: Wu Xian , Saha Abhishek
Published: September 2022

The dynamics of a liquid droplet impacting a liquid film of different compositions is critical for many industrial processes, including additive manufacturing and bio-printing. In this work we present an exposition of droplet impact on liquid films investigating the effects of mismatch in their properties on bouncing-to-merging transitions. Experiments are conducted for two sets of liquid combinations, namely, alkanes and silicon oils. The regime maps for impact outcomes (bouncing vs merging) are created from detailed experiments with various single- and two-liquid systems. The results highlight that the two-liquid systems exhibit an additional merging regime, which is not observed for single-liquid systems. Subsequently, the scaling analyses for transitional boundaries between various regimes are revisited, and new scaling laws are proposed to include the effects of asymmetry in the droplet and film properties. Finally, the experimental results are used to assess the performance of the proposed scaling laws.
Separation of binary gas mixture in a microchannel with oscillating barriers
Authors: Kosyanchuk Vasily
Published: September 2022

The time-dependent flow of a neon–argon mixture in a microchannel interrupted by a row of oscillating barriers is numerically studied using the Direct Simulation Monte Carlo method in a range of Knudsen numbers from 0.1 to 10 and in a wide range of oscillation frequencies. The emphasis of the study is on the effect of mixture separation. It is demonstrated that in addition to a mid-frequency (“resonance”) regime, as discovered in the author's previous works [Kosyanchuk et al., “Numerical simulation of novel gas separation effect in microchannel with a series of oscillating barriers,” Microfluid. Nanofluid. 21, 116 (2017) and Kosyanchuk and Pozhalostin, “Non-stationary rarefied gas flow in a plane channel with a series of oscillating barriers,” Eur. J. Mech.-B/Fluids 92, 90–99 (2022)], two other enhanced separation regimes at very low and at very high oscillation frequencies are present. It is also demonstrated that the effect in the mid-frequency regime degrades with decreasing Knudsen number and is almost absent for Kn values around 0.1. The effect in the high-frequency regime is shown to be dictated both by the high frequency of barrier oscillations and by the high speed of barrier motion, and it is shown that with decreasing Knudsen number, the impact of barriers speed becomes dominant. The effect in the low-frequency regime is present for all Knudsen numbers and significantly depends on the phases of barrier motion, which is not observed in other regimes. The separation factor in the low-frequency regime also increases with the number of barriers but only up to the level of molecular diffusion. It was also shown that in the low-frequency regime, there is a trade-off between the separation factor and the gas flow rate.
Does non-reciprocity break the Shockley–Queisser limit in single-junction solar cells?
Authors: Park Yubin , Fan Shanhui
Published: September 2022

The efficiency of single-junction solar cells is bounded by the Shockley–Queisser limit of 41%. However, standard derivation for this limit constrains the system to be reciprocal, and what non-reciprocity can bring for single-junction solar cells remains yet to be clarified. Here, we prove that even with non-reciprocity, the ultimate efficiency of single-junction solar cells is still subject to the Shockley–Queisser limit. We show that the Shockley–Queisser limit does not rely on the detailed balance, but rather is a consequence of the integrated balance between the absorption and emission processes, as required by the second law of thermodynamics.
Engineered kinases as a tool for phosphorylation of selected targets in vivo
Authors: Lepeta Katarzyna , Roubinet Chantal , Bauer Milena , Vigano M. Alessandra , Aguilar Gustavo , Kanca Oguz , Ochoa-Espinosa Amanda , Bieli Dimitri , Cabernard Clemens , Caussinus Emmanuel , Affolter Markus
Published: September 2022

Reversible protein phosphorylation by kinases controls a plethora of processes essential for the proper development and homeostasis of multicellular organisms. One main obstacle in studying the role of a defined kinase–substrate interaction is that kinases form complex signaling networks and most often phosphorylate multiple substrates involved in various cellular processes. In recent years, several new approaches have been developed to control the activity of a given kinase. However, most of them fail to regulate a single protein target, likely hiding the effect of a unique kinase–substrate interaction by pleiotropic effects. To overcome this limitation, we have created protein binder-based engineered kinases that permit a direct, robust, and tissue-specific phosphorylation of fluorescent fusion proteins in vivo. We show the detailed characterization of two engineered kinases based on Rho-associated protein kinase (ROCK) and Src. Expression of synthetic kinases in the developing fly embryo resulted in phosphorylation of their respective GFP-fusion targets, providing for the first time a means to direct the phosphorylation to a chosen and tagged target in vivo. We presume that after careful optimization, the novel approach we describe here can be adapted to other kinases and targets in various eukaryotic genetic systems to regulate specific downstream effectors.
Analytic S-Shaped Temperature Dependence of Peak Positions of the Localized-State Ensemble Luminescence and Application in the Analysis of Luminescence in Non- and Semi-Polar InGaN/GaN Quantum-Wells Micro-Array
Authors: Wang Xiaorui , Xu Shijie
Published: September 2022

Two analytic expressions of temperature-dependent peak positions employing the localized-state ensemble (LSE) luminescence model are deduced for the cases of ΔE = E
a – E
0 > 0 and < 0, respectively, under the first-order approximation of Taylor’s expansion. Then, the deduced formulas are applied to examine the experimental variable-temperature photoluminescence data of non- and semi-polar InGaN/GaN quantum-wells (QWs) array by jointly considering the monotonic bandgap shrinking described by Pässler’s empirical formula. S-shaped temperature dependence of luminescence peaks of both non- and semi-polar QWs is well reproduced with the analytic formulas. As a result, the localization depths are found to be 31.5 and 32.2 meV, respectively, for non- and semi-polar QWs.
MICROSCOPE’s constraint on a short-range fifth force
Authors: Bergé Joel , Pernot-Borràs Martin , Uzan Jean-Philippe , Brax Philippe , Chhun Ratana , Métris Gilles , Rodrigues Manuel , Touboul Pierre
Published: September 2022

The MICROSCOPE experiment was designed to test the weak equivalence principle in space, by comparing the low-frequency dynamics of cylindrical ‘free-falling’ test masses controlled by electrostatic forces. We use data taken during technical sessions aimed at estimating the electrostatic stiffness of MICROSCOPE’s sensors to constrain a short-range Yukawa deviation from Newtonian gravity. We take advantage of the fact that in the limit of small displacements, the gravitational interaction (both Newtonian and Yukawa-like) between nested cylinders is linear, and thus simply characterised by a stiffness. By measuring the total stiffness of the forces acting on a test mass as it moves, and comparing it with the theoretical electrostatic stiffness (expected to dominate), it is a priori possible to infer constraints on the Yukawa potential parameters. However, we find that measurement uncertainties are dominated by the gold wires used to control the electric charge of the test masses, though their related stiffness is indeed smaller than the expected electrostatic stiffness. Moreover, we find a non-zero unaccounted for stiffness that depends on the instrument’s electric configuration, hinting at the presence of patch-field effects. Added to significant uncertainties on the electrostatic model, they only allow for poor constraints on the Yukawa potential. This is not surprising, as MICROSCOPE was not designed for this measurement, but this analysis is the first step to new experimental searches for non-Newtonian gravity in space.
MICROSCOPE mission: data analysis principle
Authors: Bergé Joel , Baghi Quentin , Hardy Emilie , Métris Gilles , Robert Alain , Rodrigues Manuel , Touboul Pierre , Chhun Ratana , Guidotti Pierre-Yves , Pires Sandrine , Reynaud Serge , Serron Laura , Travert Jean-Michel
Published: September 2022

After performing highly sensitive acceleration measurements during two years of drag-free flight around the Earth, MICROSCOPE provided the best constraint on the weak equivalence principle (WEP) to date. Beside being a technological challenge, this experiment required a specialised data analysis pipeline to look for a potential small signal buried in the noise, possibly plagued by instrumental defects, missing data and glitches. This paper describes the frequency-domain iterative least-square technique that we developed for MICROSCOPE. In particular, using numerical simulations, we prove that our estimator is unbiased and provides correct error bars. This paper therefore justifies the robustness of the WEP measurements given by MICROSCOPE.
MICROSCOPE mission: statistics and impact of glitches on the test of the weak equivalence principle
*
Authors: Bergé Joel , Baghi Quentin , Robert Alain , Rodrigues Manuel , Foulon Bernard , Hardy Emilie , Métris Gilles , Pires Sandrine , Touboul Pierre
Published: September 2022

MICROSCOPE’s space test of the weak equivalence principle (WEP) is based on the minute measurement of the difference of accelerations experienced by two test masses as they orbit the Earth. A detection of a violation of the WEP would appear at a well-known frequency f
EP depending on the satellite’s orbital and spinning frequencies. Consequently, the experiment was optimised to minimise systematic errors at f
EP. Glitches are short-lived events visible in the test masses’ measured acceleration, most likely originating in cracks of the satellite’s coating. In this paper, we characterise their shape and time distribution. Although intrinsically random, their time of arrival distribution is modulated by the orbital and spinning periods. They have an impact on the WEP test that must be quantified. However, the data available prevents us from unequivocally tackling this task. We show that glitches affect the test of the WEP, up to an a priori unknown level. Discarding the perturbed data is thus the best way to reduce their effect.
The MICROSCOPE space mission: the first test of the equivalence principle in a space laboratory
Authors: Touboul Pierre , Métris Gilles , Rodrigues Manuel , Bergé Joel , Chhun Ratana , Foulon Bernard , Robert Alain
Published: September 2022

This paper introduces the current special issue focussed on the MICROSCOPE mission. This mission is the first experimental test in space of the weak equivalence principle (WEP) using man-made test-masses—as opposed to astronomical tests—with the goal to reach a precision two orders of magnitude better than ground-based experiments. Selected in 1999 by CNES as part of its MYRIADE microsatellite programme, the satellite was launched in 2016 and the mission lasted 2.5 years. This paper summarises the articles of the special issue and highlights the key technological and data analysis aspects that allowed for an unprecedented precision on the test of the WEP.
Result of the MICROSCOPE weak equivalence principle test
Authors: Touboul Pierre , Métris Gilles , Rodrigues Manuel , Bergé Joel , Robert Alain , Baghi Quentin , André Yves , Bedouet Judicael , Boulanger Damien , Bremer Stefanie , Carle Patrice , Chhun Ratana , Christophe Bruno , Cipolla Valerio , Damour Thibault , Danto Pascale , Demange Louis , Dittus Hansjoerg , Dhuicque Océane , Fayet Pierre , Foulon Bernard , Guidotti Pierre-Yves , Hagedorn Daniel , Hardy Emilie , Huynh Phuong-Anh , Kayser Patrick , Lala Stephanie , Lämmerzahl Claus , Lebat Vincent , Liorzou Françoise , List Meike , Löffler Frank , Panet Isabelle , Pernot-Borràs Martin , Perraud Laurent , Pires Sandrine , Pouilloux Benjamin , Prieur Pascal , Rebray Alexandre , Reynaud Serge , Rievers Benny , Selig Hanns , Serron Laura , Sumner Timothy , Tanguy Nicolas , Torresi Patrizia , Visser Pieter
Published: September 2022

The space mission MICROSCOPE dedicated to the test of the equivalence principle (EP) operated from April 25, 2016 until the deactivation of the satellite on October 16, 2018. In this analysis we compare the free-fall accelerations (a
A and a
B) of two test masses in terms of the Eötvös parameter

η

(

A,B

)

=
2

a

A

−

a

B

a

A

+

a

B

. No EP violation has been detected for two test masses, made from platinum and titanium alloys, in a sequence of 19 segments lasting from 13 to 198 h down to the limit of the statistical error which is smaller than 10−14 for η(Ti, Pt). Accumulating data from all segments leads to η(Ti, Pt) = [−1.5 ± 2.3 (stat) ± 1.5 (syst)] × 10−15 showing no EP violation at the level of 2.7 × 10−15 if we combine stochastic and systematic errors quadratically. This represents an improvement of almost two orders of magnitude with respect to the previous best such test performed by the Eöt-Wash group. The reliability of this limit has been verified by comparing the free falls of two test masses of the same composition (platinum) leading to a null Eötvös parameter with a statistical uncertainty of 1.1 × 10−15.
Paths from stationary to chaos in passively mode-locked fiber lasers: research progress of soliton pulsations and soliton explosions
Authors: Han Ying , Gao Bo , Hao Yabin , Ponraj Joice Sophia , Ma Chunyang , Huo Jiayu , Wu Ge , Li Yingying , Al-Amoudi Bashaer Omar , Wageh S , Al-Ghamdi Ahmed A , Liu Lie , Zhang Han
Published: September 2022

Research has shown that passively mode-locked fiber lasers produce chaotic output, which has caught the attention of physicists, chemists, and bio-scientists owing to their wide bandwidth, good random characteristics, and strong anti-interference. In passively mode-locked fiber lasers, soliton pulsations and soliton explosions with period bifurcation characteristics have been demonstrated to be effective paths to chaos as far as 20 years ago. However, due to the lack of real-time spectrum measurement techniques, the earlier research investigated their theoretical aspect. In recent years, the rise of the dispersive Fourier transform technique has activated an upsurge of experimental research. The present work first discussed the theoretical model of passively mode-locked fiber lasers, the computational analysis method of soliton dynamics, and the related theory of the dispersive Fourier transform technique. In addition, we presented and evaluated the progress of the theoretical and experimental research on soliton pulsations as well as on soliton explosions in passively mode-locked fiber lasers. Finally, we proposed the future research directions of the soliton pulsations and soliton explosions that offer great promise for scientific discoveries.
Generalization of microscopic multipoles and cross-correlated phenomena by their orderings
Authors: Kusunose Hiroaki , Hayami Satoru
Published: September 2022

The generalization of the atomic-scale multipoles is discussed. By introducing the augmented multipoles defined in the hybrid orbitals or in the site/bond-cluster, any of electronic degrees of freedom can be expressed in accordance with the crystallographic point group. These multipoles are useful to describe the cross-correlated phenomena, band-structure deformation, and generation of effective spin–orbit coupling due to antiferromagnetic ordering in a systematic and comprehensive manner. Such a symmetry-adapted multipole basis set could be a promising descriptor for materials design and informatics.
Nanoporous GaN on p-type GaN: a Mg out-diffusion compensation layer for heavily Mg-doped p-type GaN
Authors: Lee Kwang Jae , Nakazato Yusuke , Chun Jaeyi , Wen Xinyi , Meng Chuanzhe , Soman Rohith , Noshin Maliha , Chowdhury Srabanti
Published: September 2022

Embedding p-type gallium nitride (p-GaN) with controlled Mg out-diffusion in adjacent epitaxial layers is a key for designing various multi-junction structures with high precision and enabling more reliable bandgap engineering of III-nitride-based optoelectronics and electronics. Here, we report, for the first time, experimental evidence of how nanoporous GaN (NP GaN) can be introduced as a compensation layer for the Mg out-diffusion from p-GaN. NP GaN on p-GaN provides an ex-situ formed interface with oxygen and carbon impurities, compensating for Mg out-diffusion from p-GaN. To corroborate our findings, we used two-dimensional electron gas (2DEG) formed at the interface of AlGaN/GaN as the indicator to study the impact of the Mg out-diffusion from underlying layers. Electron concentration evaluated from the capacitance-voltage measurement shows that 9 × 1012 cm−2 of carriers accumulate in the AlGaN/GaN 2DEG structure grown on NP GaN, which is the almost same number of carriers as that grown with no p-GaN. In contrast, 2DEG on p-GaN without NP GaN presents 9 × 109 cm−2 of the electron concentration, implying the 2DEG structure is depleted by Mg out-diffusion. The results address the efficacy of NP GaN and its’ role in successfully embedding p-GaN in multi-junction structures for various state-of-the-art III-nitride-based devices.
Gyrokinetic study of transport suppression in JET plasmas with MeV-ions and toroidal Alfvén eigenmodes
Authors: Mazzi S , Garcia J , Zarzoso D , Kazakov Ye O , Ongena J , Dreval M , Nocente M , Štancar Ž , Szepesi G
Published: September 2022

The impact of fast ions, generated in the MeV-range through the efficient application of the three-ion scheme in JET plasmas, on the turbulence properties is presented through complex numerical simulations. The suppression of the ion-scale turbulent transport is studied by means of in-depth gyrokinetic numerical analyses. Such a suppression is demonstrated to be achieved in the presence of toroidal Alfvén eigenmodes (TAEs) destabilized by the highly energetic ions. Details on the TAE excitation are also provided with a multi-code analysis. The inherently nonlinear and multi-scale mechanism triggered by the fast ions, also involving the high-frequency modes and the large-scale zonal flows, is deeply analyzed. Such mechanism is thus demonstrated, with experimental validating studies, to be the main cause of turbulence suppression and improvement of ion thermal confinement. Additional simulations address the implications of reversed shear magnetic equilibrium on the turbulent transport.
Enhanced nonlinearity of four-wave mixing via Rydberg–Rydberg interactions
Authors: Zhang Xiao-Jun , Chang Huan , Huo Jia-Yao , Wu Jin-Hui
Published: September 2022

We investigate the four-wave mixing (FWM) nonlinearity in an ensemble of cold Rydberg atoms with each of them regarded as a double-ladder system. The interaction is studied from the view of generating a signal field in virtue of three applied lasers. Using an approach beyond mean-field theory, we solved the equations for the one-body and two-body correlators under perturbation, and show that the system possesses not only a local FWM nonlinearity, but also a much larger nonlocal nonlinearity due to the Rydberg–Rydberg interaction which can be further strengthened by increasing the atomic density. The results obtained may have promising applications in the quantum information processes involving the FWM nonlinearity, such as the generation of squeezed or entangled states.
Vector stability in quadratic metric-affine theories
Authors: Jiménez-Cano Alejandro , Maldonado Torralba Francisco José
Published: September 2022

In this work we study the stability of the four vector irreducible pieces of the torsion and the nonmetricity tensors in the general quadratic metric-affine Lagrangian in 4 dimensions. The goal will be to elucidate under which conditions the spin-1 modes associated to such vectors can propagate in a safe way, together with the graviton. This highly constrains the theory reducing the parameter space of the quadratic curvature part from 16 to 5 parameters. We also study the sub-case of Weyl-Cartan gravity, proving that the stability of the vector sector is only compatible with an Einstein-Proca theory for the Weyl vector.
Reducing mean first passage times with intermittent confining potentials: a realization of resetting processes
Authors: Mercado-Vásquez Gabriel , Boyer Denis , Majumdar Satya N
Published: September 2022

During a random search, resetting the searcher’s position from time to time to the starting point often reduces the mean completion time of the process. Although many different resetting models have been studied over the past ten years, only a few can be physically implemented. Here we study theoretically a protocol that can be realised experimentally and which exhibits unusual optimization properties. A Brownian particle is subject to an arbitrary confining potential v(x) that is switched on and off intermittently at fixed rates. Motion is constrained between an absorbing wall located at the origin and a reflective wall. When the walls are sufficiently far apart, the interplay between free diffusion during the ‘off’ phases and attraction toward the potential minimum during the ‘on’ phases give rise to rich behaviours, not observed in ideal resetting models. For potentials of the form v(x) = k|x − x
0|
n
/n, with n > 0, the switch-on and switch-off rates that minimise the mean first passage time (MFPT) to the origin undergo a continuous phase transition as the potential stiffness k is varied. When k is above a critical value k
c, potential intermittency enhances the target encounter: the minimal MFPT is lower than the Kramer time and is attained for a non-vanishing pair of switching rates. We focus on the harmonic case n = 2, extending previous results for the piecewise linear potential (n = 1) in unbounded domains. We also study the non-equilibrium stationary states emerging in this process.
An improved engineering method for bearing capacity calculation of stiffened curved composite panels
Authors: Wang Zhe , Chen Xiangming , Li Xinxiang , Zou Peng , Yang Junchao , Bi Xue
Published: September 2022

The application of composite materials in the primary structures of large aircraft fuselage is a development trend in recent years. As an indispensable structure in design and structure selection, accurate and efficient evaluation of its performance is of great significance to reduce the research cost. In this paper, the bearing capacity of stiffened curved composite panel is calculated through an improved engineering calculation method, and the effectiveness of the method is verified by test, which provides technical support for the rapidly design and selection of stiffened curved composite panels.
Research on process improvement and optimization design of a certain type of mine explosion-proof electric control box
Authors: Lu Zhiqi
Published: September 2022

In order to reduce the cost of electric control box and improve its beauty and universality, the design structure of a mine explosion-proof electric control box is improved in view of the disadvantages existing in the use of a certain type of mine explosion-proof electric control box; At the same time, for the problems of heavy self-reliance, high processing cost and poor heat dissipation of the existing electric control box, by changing the material, plate thickness, stiffener treatment at the appropriate position, or changing the plate structure of the box, the stress analysis is carried out under the pressure conditions, and the box with two schemes meeting the service conditions is designed and improved. At the same time, the manufacturing cost and heat dissipation of the box before and after the improvement are compared, which can be used as a reference for the design of electric control box in the future.
Grid-connected power oscillation study of hybrid storage direct-drive wind farms based on SVG
Authors: Zhang Chao , Xin shaojie , Xu Cong
Published: September 2022

This paper studies the control strategy of hybrid energy storage to suppress power fluctuation of direct-drive wind turbine based on static var generator, and proposes a grid-connected power oscillation suppression of hybrid energy storage direct-drive wind turbine based on static var generator (SVG). Method, the static var generator is mainly to solve the reactive current generated by the large and impact load and the resulting reactive power, and the SVG connected in parallel with the fan outlet busbar performs reactive power coordinated control to support the grid voltage. This control strategy control The lead-acid battery compensates for the intermediate frequency power fluctuation and the super capacitor (SC) quickly absorbs the high frequency power fluctuation, thereby smoothing the wind power and improving the power quality. sexual demands. Finally, a system simulation model is established in the Matlab/Simulink environment to verify the effectiveness of the proposed method.
Fractal Dimension Fitting of Virtual Material and Experimental Verification
Authors: Fu Yongling , Wang Zeqi , Li Wanguo
Published: September 2022

Virtual material is a dynamic model of mechanical contact surface, which is suitable for finite element simulation. This method can characterize the stiffness and damping of the contact surface well by using fractal geometry theory to describe the contour of the contact surface. Based on standard W-M function, we verify the accuracy of the fractal dimension calculated by wavelet transform, and then fit the fractal dimension of machined surfaces with different roughness. Using the fractal dimension, we calculate the virtual material parameters to establish the finite element model of the unit specimen. Finally, we carry out the experimental modal analysis to examine reproduce the virtual material method.
Study on Friction and Wear Properties of 23CrNi3Mo Carburized Steel under Water Lubrication
Authors: Wang Jialin , Han Bin , Zhu Shaohua , Sun Xinhao
Published: September 2022

In this paper the friction and wear of 23CrNi3Mo carburized steel under water lubrication were studied. The friction and wear properties of carburized steel sliding with stainless steel, GCr15, Al2O3 and ZrO2 balls were analyzed by tribometer, 3-D topography and SEM. The results show that compared with other materials, ZrO2 and carburizing steel have better tribological properties. Compared with Al2O3, the wear depth of carburized steel sliding with ZrO2 is reduced by 41% at the load of 2 N and 50% at the load of 10 N. In the load range of 2N-10N, the wear rate of carburized steel is the lowest when rubbing with ZrO2, and it gradually decreases when the load increases. Combined with SEM and Raman spectrum analysis, Oxide film was formed on the surface of carburized steel during the sliding test of ZrO2 and carburized steel. This oxide film was mainly composed of Fe3O4 and Fe2O3, which effectively reduces the friction coefficient and wear rate of 23CrNi3Mo carburized steel under water lubrication.
Comparison Study on Machined Surface Integrity and Corrosion Resistance of 2024 Aluminum Alloy
Authors: Huang Hao , Niu Jintao , Li Jiliang , Lin Qichao , Qiao Yang
Published: September 2022

2024 aluminum alloy is an engineering equipment material with broad application prospects, which can be used in space flight and shipbuilding industry. However, the lack of corrosion resistance hinders its further application. The effects of milling and further shot peening processes on the surface integrity of 2024 aluminum alloy were investigated. Electrochemical polarization measurements were performed in 3.5wt% NaCl solution to characterize the corrosion resistance of milling alone surfaces and the further shot-peening process surfaces after milling. Experimental results reveal that the surface residual stress and microhardness of the shot-peened surfaces are much higher than those of the only milling surfaces owing to the severer plastic deformation induced by further shot peening process. While the shot-peened surfaces are roughened with the higher surface roughness. Under the synergic effects of three terms mentioned above, the corrosion potential of shot-peened surfaces is much positive than that of milled ones, meaning the corrosion resistance after shot peening is better. The comparison test gives a way to enhance the corrosion behavior of 2024 aluminum alloy milled surfaces.
Calibration error study of binocular stereo camera
Authors: Wu Hao , Hao Weidong , Sun Yulu , Wang Zhihao , Huang Yiren
Published: September 2022

The calibration accuracy of the camera largely affects the accuracy of 3D measurement, so this paper researches on the calibration error of the binocular stereo camera, introduces the imaging model of the camera, conducts the experiment of calibration according to the principle of Zhang Zhengyou's calibration, and responds to the calibration accuracy by the reprojection error, the experimental results show that the calibration meets the requirements and the average error can reach 0.05pixels.
Study on output characteristics of Offset Twist-roller Frictional Transmission Mechanism
Authors: Li Baoyu , Chen Ning , Chen Yukang , Xie Xin , Fan Dapeng
Published: September 2022

According to the requirements of high resolution and compact space of a rotational-double-prism system, combined with its practical application characteristics of small load and low speed, an offset twist-roller frictional transmission mechanism is proposed. Compared with the clearance elimination gear transmission mechanism, it has the advantages of high output resolution, adjustable reduction ratio, simple structure and low cost. The influence of twist angle on the output characteristics of offset twist-roller frictional transmission mechanism is studied by experiment. The results show that the larger the twist angle, the smaller the driving torque of the driven wheel, the larger the transmission ratio of the mechanism, the larger the fluctuation range of output angular velocity and transmission ratio, and the more unstable the transmission. The transmission ratio of the mechanism in stable transmission is about 30, which is much higher than that in single-stage cylindrical gear drive. The output angular resolution of the mechanism is better than 0.005°, meeting the system requirements. Through the above analysis, it lays a foundation for the application of offset twist-roller frictional transmission mechanism in rotational double prisms system.
Design and Rig Test of Hydro-Pneumatic Spring for Heavy Off-Road Vehicles
Authors: Liang Yinggang , Zhang ZhenHua , Lin ShuFeng
Published: September 2022

In order to meet the requirements of heavy off-road vehicles for long-stroke elastic elements, a new type of double-chamber hydro-pneumatic spring was innovatively designed. According to the structure and working characteristics, the mathematical models of the spring under two working conditions are established, and its stiffness characteristics are analyzed. The force and displacement data of the spring at different frequencies were obtained by rig test. The static friction, damping and elastic force of the spring are separated. Based on the data of elastic force and displacement, the polytropic exponent of hydro-pneumatic spring under different working conditions is identified by curve fitting. The structure and theoretical model of double-chamber hydro-pneumatic spring designed in this paper provide support for the application of hydro-pneumatic spring in long-stroke off-road vehicle.
Effect of Preload on Frame Stiffness of 1600 kN Closed Double Point Mechanical Press
Authors: Wang Chao , Cui Fujun , Liu Wenlun , Wang Qiang
Published: September 2022

A 1600kN closed double point press is used for the punching process of U-shaped longitudinal beam and more than 10 independent die frames are arranged. Different holes require different punching forces, and multi-station punching will cause eccentric loads, while preload and off-centre load are important factors affecting the precision of the combined frame of closed press. In this paper, a 1600kN press combined frame is designed based on the U-shaped longitudinal beam punching process and the three dimensional model of 1600kN press frame is established by Solidworks. The finite element analysis of preload, symmetrical load and off-centre load was carried out by Ansys Workbench. The deformation of upper beam in Z direction and the relationship between eccentric load factor i and the maximum deformation difference △h can be obtained, which has important application value to improve the manufacturing accuracy of this type of press.
Research on mechanical resonance of Precise cable drive systems
Authors: Xie Xin , Zheng Jieji , Tan Ruoyu , Li Baoyu , Yu Bin , Fan Dapeng
Published: September 2022

Precise cable drive is a light, concise and efficient spatial friction flexible transmission mode, which has the characteristics of flexible layout, lightweight and miniaturization. It is a good choice for Acquiring tracking and pointing applications (ATPs). But the cable drive mechanism (CDM) is easy to cause large-scale speed oscillation in the process of performing tasks as cable compliance. This paper focused on the mechanical resonance in a practical full-closed loop positioning control system. A dynamic model with the electro-mechanical and rigid-flexible coupling characteristics is proposed, which is capable to analyze the global influence factors on speed oscillation. The parametric sensitivities have been conducted to investigate the effects of design parameters on mechanical resonance.
Bayesian inference applied to electron temperature data: computational performances and diagnostics integration
Authors: Fassina A. , Abate D. , Franz P.
Published: September 2022

Bayesian inference proves to be a robust tool for the fitting of parametric models on experimental datasets. In the case of electron kinetics, it can help the identification of non-thermal components in electron population and their relation with plasma parameters and dynamics. We present here a tool for electron distribution reconstruction based on MCMC (Monte Carlo Markov Chain) based Bayesian inference on Thomson Scattering data, discussing the computational performances of different algorithms and information metrics. Along, a possible integration between Soft X-ray spectroscopy and Thomson Scattering is presented, focusing on the parametric optimization of diagnostics spectral channels in different plasma regimes.