Machine learning applications on lunar meteorite minerals:From classification to mechanical properties prediction

Amid the scarcity of lunar meteorites and the imperative to preserve their scientific value,nondestructive testing methods are essential.This translates into the application of microscale rock mechanics experiments and scanning electron microscopy for surface composition analysis.This study explores the application of Machine Learning algorithms in predicting the mineralogical and mechanical properties of DHOFAR 1084,JAH 838,and NWA 11444 lunar meteorites based solely on their atomic percentage compositions.Leveraging a prior-data fitted network model,we achieved near-perfect classification scores for meteorites,mineral groups,and individual minerals.The regressor models,notably the KNeighbor model,provided an outstanding estimate of the mechanical properties—previously measured by nanoindentation tests—such as hardness,reduced Young’s modulus,and elastic recovery.Further considerations on the nature and physical properties of the minerals forming these meteorites,including porosity,crystal orientation,or shock degree,are essential for refining predictions.Our findings underscore the potential of Machine Learning in enhancing mineral identification and mechanical property estimation in lunar exploration,which pave the way for new advancements and quick assessments in extraterrestrial mineral mining,processing,and research.

Low-power SiPM readout BETA ASIC for space applications

The BETA application-specific integrated circuit(ASIC)is a fully programmable chip designed to amplify,shape and digitize the signal of up to 64 Silicon photomultiplier(SiPM)channels,with a power consumption of approximately~1 mW/channel.Owing to its dual-path gain,the BETA chip is capable of resolving single photoelectrons(phes)with a signal-to-noise ratio(SNR)>5 while simultaneously achieving a dynamic range of~4000 phes.Thus,BETA can provide a cost-effective solution for the readout of SiPMs in space missions and other applications with a maximum rate below 10 kHz.In this study,we describe the key characteristics of the BETA ASIC and present an evaluation of the performance of its 16-channel version,which is implemented using 130 nm technology.The ASIC also contains two discriminators that can provide trigger signals with a time jitter down to 400 ps FWHM for 10 phes.The linearity error of the charge gain measurement was less than 2%for a dynamic range as large as 15 bits.

Seasonal metal fluxes derived by the interaction of surface water and groundwater in an aquaculture estuary

Submarine groundwater discharge(SGD)plays a major role as a conveyor of metals to coastal waters.However,the seasonal change of metal fluxes derived through SGD is unclear.Here,we evaluated the behaviours and fluxes of trace metals(Mn,Fe,Ba,Pb,U,Cr,Zn,Cu)in an estuary under different seasonal conditions.The behaviours of trace metals revealed that SGD was the source of Mn(3.51 mmol/(m^(2)·d)),Fe(0.174 mmol/(m^(2)·d))and Ba(0.024 mmol/(m^(2)·d)),but the Cu sink(−0.55μmol/(m^(2)·d))and other metals exhibited a seasonal source‒sink conversion.The seasonal variation of dissolved organic matter and the fresh groundwater proportion in subterranean estuaries may have an important effect on metals fluxes especially for the Fe,Mn and Ba.Our result shows that the single seasonal metal fluxes estimation applied to the annual scale will cause a large deviation,up to 3.6 times for Fe,5.5 times for Mn,and 15 times for Ba.Therefore,the influence of seasonal fluctuations on SGDderived metal fluxes cannot be ignored,and our findings will be important for comprehending the metal budget and cycle in nearshore environment.

Partially Diffusive Helium-Silica Compound under High Pressure

Helium is the second most abundant element in the universe, and together with silica, they are important components of giant planets. Exploring the reactivity and state of helium and silica under high pressure is crucial for understanding of the evolution and internal structure of giant planets. Here, using first-principles calculations and crystal structure predictions, we identify four stable phases of a helium-silica compound with seven/eight-coordinated silicon atoms at pressure of 600–4000 GPa, corresponding to the interior condition of the outer planets in the solar system. The density of He Si O2 agrees with current structure models of the planets.This helium-silica compound exhibits a superionic-like helium diffusive state under the high-pressure and hightemperature conditions along the isentropes of Saturn, a metallic fluid state in Jupiter, and a solid state in the deep interiors of Uranus and Neptune. These results show that helium may affect the erosion of the rocky core in giant planets and may help to form a diluted core region, which not only highlight the reactivity of helium under high pressure but also provide evidence helpful for building more sophisticated interior models of giant planets.

Numerical Simulation of Tandem Using ZnS as a Buffer Layer Cu I(1-x) CaxSe2/CuGaSe2

In the global context of diversification of usable energy sources, the use of renewable energies, in particular solar photovoltaic energy, is becoming increasingly important. As such, the development of a new generation of photovoltaic cells based on the CIGS material is promising. Indeed, the efficiency of these cells has exceeded 20% in recent years. Thus, our work consists in the modeling of a tandem solar cell based on Cu(In,Ga)Se2 (CGS/CIGS). The goal is to optimize its physical and geometrical parameters in order to obtain a better photovoltaic conversion efficiency compared to other research works on tandem in the past. We used AMPS-1D software for the simulation. When we realize the tandem, the least efficient cell (CGS) imposes the current and the shape of the J-V characteristic of the tandem. We obtained a theoretical efficiency of 39.30% which is significantly higher than the efficiencies obtained in the past by other researchers with a short circuit current of 34.60 mA/cm2, an open circuit voltage of 1.74 V and a form factor of 65.20%. The simulation also showed that the high defect density in the material strongly impacts the performance of the tandem.

Theoretical and Experimental Studies of a Box-Type Solar Cooker in Unfavorable Climatic Conditions

A box-type solar cooker with an inclined surface, equipped with a concentration reflector to allow maximum energy to be collected, enabled cooking tests to be carried out in the rainy season. Different thermocouples were implanted on various places of the cooker. The temperature measurements from these sensors were taken every 10 minutes. The tests presented in this article relate to the preparation of eggs and rice. The absorber temperatures during the tests exceeded 100°C. The cooking times were between 1 h 50 min and 2 h 20 min despite the numerous cloudy periods. The cooker made it possible to reach sufficient temperatures for healthy cooking of food. The results obtained for these first tests are satisfactory and very encouraging.

氧化铝、金和氧化锌构成的类“法国梧桐树”坚果球表面上氧化锌针的生长和特性（英文）

复杂的氧化锌复合材料在光电设备方面有着很大的潜在应用。报道一种特殊"果球"的模拟生长——由Al2O3,Au和ZnO制成的天然"法国梧桐悬铃坚果"。这种"法国梧桐悬铃坚果"表面有许多小的、溅射在Al2O3表面上的金纳米粒子层。通过电沉积技术合成的ZnO针型在金纳米粒子层上可以很好的生长。单色散针(或者六角形纳米柱)的获得有着有不同的分布密度。所制备的样品在扫描电子显微镜(SEM)下观看,像组合起来的"法国梧桐悬铃坚果"。还研究了6 000℃下样品的光致发光(PL)和其他特征。尖锐的束缚激子(BE)的和纵光学声子LO-phonon的光谱线意味着ZnO微纳结构有着高品质的光学特性。

ZnO/eosin-Y混合薄膜的生长机理和形态(英文)

Thin hybrid films of ZnO/eosin-Y were prepared by electrodeposition at-0.8 and-0.9 V in aqueous and non-aqueous baths at temperatures ranging from 40 to 90 ℃ with dye concentrations of 100 and 400 μmol·L-1.The films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),energy-dispersive X-ray analysis (EDX),and absorption spectroscopy.The films prepared in a non-aqueous bath were non-porous and did not adsorb dye molecules on their surface.However,the films grown in aqueous media were porous in nature and adsorbed dye during the deposition of ZnO.Preferential growth of the film along the (002) face was observed,and the highest crystallinity was achieved when the film was deposited at 60 ℃.The maximum absorption was achieved for the films grown at 60 to 70 ℃,a deposition potential of-0.9 V,and a dye concentration of 100 μmol·L-1.

Optimizing magneto-ionic performance in structure/composition-engineered ternary nitrides

Magneto-ionics,an emerging approach to manipulate magnetism that relies on voltage-driven ion motion,holds the promise to boost energy efficiency in information technologies such as spintronic devices or future non-von Neumann computing architectures.For this purpose,stability,reversibility,endurance,and ion motion rates need to be synergistically optimized.Among various ions,nitrogen has demonstrated superior magneto-ionic performance compared to classical species such as oxygen or lithium.Here,we show that ternary Co_(1−x)Fe_(x)N compound exhibits an unprecedented nitrogen magneto-ionic response.Partial substitution of Co by Fe in binary CoN is shown to be favorable in terms of generated magnetization,cyclability and ion motion rates.Specifically,the Co_(0.3)5Fe_(0.65)N films exhibit an induced saturation magnetization of 1,500 emu/cm^(3),a magneto-ionic rate of 35.5 emu/(cm^(3)·s)and endurance exceeding 10^(3) cycles.These values significantly surpass those of other existing nitride and oxide systems.This improvement can be attributed to the larger saturation magnetization of Co_(0.35)Fe_(0.65) compared to individual Co and Fe,the nature and size of structural defects in as-grown films of different composition,and the dissimilar formation energies of Fe and Co with N in the various developed crystallographic structures.

Size effect on the microstructure, phase transformation behavior, and mechanical properties of NiTi shape memory alloys fabricated by laser powder bed fusion

In this work,NiTi samples with different thicknesses(0.15-1.00 mm)were fabricated by laser powder bed fusion(LPBF)under variable scanning speeds(500-1200 mm s^(-1)).The densification behavior,phase transformation behavior,and mechanical properties of the sample with different thicknesses are studied.The results indicate a strong size effect in the LPBF-fabricated NiTi alloy.The decrease of the sample thickness results in(i)the increase of porosity,(ii)the decrease of the number of adhered NiTi powder particles at the surface,(iii)the monotonous decrease of the martensitic transformation temperatures(MTTs),and(iv)the decrease of the shape recovery temperature.The influence of sample thickness on the melt-pool behavior,and thus the microstructure and performance of NiTi alloys are discussed.It is suggested that the melt-pool is deeper and narrower in the thin samples than in the thick samples.We conclude that,apart from the LPBF process conditions,the sample dimensions have also to be considered to fabricate NiTi structures with predictable properties.

On the possibility that PbZrO_(3) not be antiferroelectric

Lead zirconate(PbZrO_(3))is considered the prototypical antiferroelectric material with an antipolar ground state.Yet,several experimental and theoretical works hint at a partially polar behaviour in this compound,indicating that the polarization may not be completely compensated.In this work,we propose a simple ferrielectric structure for lead zirconate.First-principles calculations reveal this state to be more stable than the commonly accepted antiferroelectric phase at low temperatures,possibly up to room temperature,suggesting that PbZrO_(3)may not be antiferroelectric at ambient conditions.We discuss the implications of our discovery,how it can be reconciled with experimental observations and how the ferrielectric phase could be obtained in practice.

Intermittent chaos for ergodic light trapping in a photonic fiber plate

Extracting the light trapped in a waveguide,or the opposite effect of trapping light in a thin region and guiding it perpendicular to its incident propagation direction,is essential for optimal energetic performance in illumination,display or light harvesting devices.Here we demonstrate that the paradoxical goal of letting as much light in or out while maintaining the wave effectively trapped can be achieved with a periodic array of interpenetrated fibers forming a photonic fiber plate.Photons entering perpendicular to that plate may be trapped in an intermittent chaotic trajectory,leading to an optically ergodic system.We fabricated such a photonic fiber plate and showed that for a solar cell incorporated on one of the plate surfaces,light absorption is greatly enhanced.Confirming this,we found the unexpected result that a more chaotic photon trajectory reduces the production of photon scattering entropy.

Local characterization of the polarization state of 3D electromagnetic fields:an alternative approach

A precise knowledge of the polarization state of light is crucial in technologies that involve the generation and application of structured light fields. The implementation of efficient methods to determine and characterize polarization states is mandatory;more importantly, these structured light fields must be at any spatial location at a low expense. Here, we introduce a new characterization method that relies on a rather convenient description of electric fields without neglecting their 3D nature. This method is particularly suitable for highly focused fields,which exhibit important polarization contributions along their propagation direction in the neighborhood of the focal region;i.e., the contributions out of the planes transverse to the optical axis, conventionally used to specify the polarization state of these fields. As shown, the method allows the extraction of information about the three field components at relatively low computational and experimental costs. Furthermore, it also allows characterization of the polarization state of a field in a rather simple manner. To check the feasibility and reliability of the method, we determined both analytically and experimentally the local polarization states for a series of benchmark input fields with it, finding excellent agreement between the theory and experiment.

Stochastic simulation of successive waves of COVID-19 in the province of Barcelona

Analytic compartmental models are currently used in mathematical epidemiology to forecast the COVID-19 pandemic evolution and explore the impact of mitigation strategies.In general,such models treat the population as a single entity,losing the social,cultural and economical specificities.We present a network model that uses socio-demographic datasets with the highest available granularity to predict the spread of COVID-19 in the province of Barcelona.The model is flexible enough to incorporate the effect of containment policies,such as lockdowns or the use of protective masks,and can be easily adapted to future epidemics.We follow a stochastic approach that combines a compartmental model with detailed individual microdata from the population census,including social determinants and age-dependent strata,and time-dependent mobility information.We show that our model reproduces the dynamical features of the disease across two waves and demonstrates its capability to become a powerful tool for simulating epidemic events.

Field and current driven versions of Brandt method for calculating transport ac loss of superconducting cylinder and strip

As an elegant and fast numerical tool for solving time‐dependent electromagnetic field problems in hard superconductors,Brandt’s method has played an important role in understading the magnetic behavior of superconducting strips,discs,bars and cylinders in various aspect ratios.However,the application of this convenient method was mainly in magnetization processes.Traditionally,the solution of current transport problem needs to introduce a driving electric field E_(a),which requires a low efficiency iterative process and E_(a) itself was not clearly explained.In this work,three integral algorithms based on the Brandt’s method are developed to deal with current transport problems,which directly adopt the applied current as a boundary condition.Namely the current(I)‐driven version and two current‐field‐driven versions A and B.Moreover,the arbitrary applied magnetic field can also be included in the I‐driven version.The derivation with all necessary formulas for the methods are given in this work.As an example,the new methods,as well as the traditional method are used for calculating transport ac loss Q of a superconducting cylinder or strip obeying a power‐law relation of E∝J^(n)as a function of a given I(t).Derived from the Ampère law and the differential rather than the integral expression of the Faraday law,the current‐driven version can be used for more accurate and much quicker computation.Being an intermediate quantity,E_(a)(t) in the two current‐field‐driven versions is accurately calculated under the given I(t),but version B is much quicker than A.Problems relating to E_(a)(t) and Q stabilization process are discussed.

Giant multiphononic effects in a perovskite oxide

Perovskite oxides offer tremendous potential for applications in information storage and energy conversion,owing to a subtle interplay between their spin,charge,orbital and lattice degrees of freedom.Here,we further expand the possible range of perovskite oxides operation towards the fields of thermal management and thermal computing by exploiting an exceptional synergy between different ferroic orders.We propose dynamical control of the heat flow in a distinctive family of perovskite oxides obtained via the application of small electric(~10 kV/cm)and/or magnetic(~1 T)fields.Based on first-principles simulations,we predict a relative heat conductivity variation of~100%in SrMnO_(3) thin films near room temperature resulting from a phase transition that involves huge changes in both the magnetization and electric polarization.The disclosed giant multiphononic effects are fundamentally caused by anharmonic spin-phonon couplings that strongly influence the mean lifetime of phonons.

Gain through losses in nonlinear optics

Instabilities of uniform states are ubiquitous processes occurring in a variety of spatially extended nonlinear systems.These instabilities are at the heart of symmetry breaking,condensate dynamics,self-organisation,pattern formation,and noise amplification across diverse disciplines,including physics,chemistry,engineering,and biology.In nonlinear optics,modulation instabilities are generally linked to the so-called parametric amplification process,which occurs when certain phase-matching or quasi-phase-matching conditions are satisfied.In the present review article,we summarise the principle results on modulation instabilities and parametric amplification in nonlinear optics,with special emphasis on optical fibres.We then review state-of-the-art research about a peculiar class of modulation instabilities(MIs)and signal amplification processes induced by dissipation in nonlinear optical systems.Losses applied to certain parts of the spectrum counterintuitively lead to the exponential growth of the damped mode themselves,causing gain through losses.We discuss the concept of imaging of losses into gain,showing how to map a given spectral loss profile into a gain spectrum.We demonstrate with concrete examples that dissipation-induced MI,apart from being of fundamental theoretical interest,may pave the way towards the design of a new class of tuneable fibre-based optical amplifiers,optical parametric oscillators,frequency comb sources,and pulsed lasers.