bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective site occupancy engineering enabling Mn5+ activated highly efficient near infrared-II emission in Ba3BPO7:Mn5+
Authors: Tang Minping , Song Enhai , Zhang Qinyuan
Published: February 2024

The development of highly efficient near infrared (NIR) luminescence materials is crucial for advancing the next generation compact light sources. However, the realization of target material with emission in the NIR-II spectral region (1000–1700 nm) remains a major challenge. Herein, a NIR-II emission phosphor Ba3BPO7:Mn5+ peaking at 1176 nm with a full width of half maximum of 22 nm is demonstrated via a selective site occupancy engineering strategy. Upon 660 nm red-light excitation, high internal quantum efficiency of 50.6% and external quantum efficiency of 30.5% are obtained in this phosphor. Density functional theory calculations and structural analyses provide an understanding of stabilizing pentavalent manganese in Ba3BPO7:Mn5+. The highly efficient NIR-II emission is mainly ascribed to the relatively high distorted tetrahedral crystal field environment of Mn5+ in this system and the stable valence state. Combining this phosphor with 660 nm red-light chip, we fabricate a light emitting diode with NIR-II output power of 19.2 mW@300 mA, which shows promising applications in anti-counterfeiting, special information identification, etc. This work provides some important insights into the design of highly efficient Mn5+ based NIR-II emission and the emerging applications.
Direct observation and elemental analysis of material nanoparticles in solution using scanning electron-assisted dielectric microscopy and EDS
Authors: Ogura Toshihiko , Nakajima Hideaki , Usukawa Ryutaro , Kondo Naoki , Okazaki Toshiya
Published: February 2024

High-resolution observation and elemental analysis of various particles in solution are important in the fields of materials, analytical chemistry, and industrial applications. Analysis of slurries of raw materials is essential for the development of highly functional materials. Recently, we have developed an SEM-based scanning electron assisted dielectric microscope (SE-ADM), which can directly observe biological samples and organic materials in aqueous solutions. Here, we have developed an SE-ADM system with the addition of energy-dispersive x-ray spectrometry that enables direct observation and elemental analysis of nanoparticles in solution. Using this system, we were able to directly observe and conduct elemental analysis of ceramic slurries and to clarify the dispersion state of alumina particles in solution, the distribution of binder, and the bonding state of silica and magnesium particles. Furthermore, our system can be applied to diverse liquid samples across a broad range of scientific and industrial fields, for example, nanotubes, organic specimens, batteries, and catalytic materials.
Preferential ordering of incommensurate-length guest particles in a smectic host
Authors: Kusters Guido L. A. , Barella Martijn , van der Schoot Paul
Published: February 2024

Using density functional theory, we study the preferential ordering of rod-like guest particles immersed in a smectic host fluid. Within a model of perfectly aligned rods and assuming that the guest particles do not perturb the smectic host fluid, simple excluded-volume arguments explain that guest particles that are comparable in length to the host particles order in phase with the smectic host density layering, whereas guest particles that are considerably shorter or longer order in antiphase. The corresponding free-energy minima are separated by energetic barriers on the order of the thermal energy kBT, suggesting that guest particles undergo hopping-type diffusion between adjacent smectic layers. Upon introducing a slight orientational mismatch between the guest particles and the perfectly aligned smectic host, an additional, smaller free-energy barrier emerges for a range of intermediate guest-to-host length ratios, which splits the free-energy minimum into two. Guest particles in this range occupy positions intermediate between in-phase ordering and in-antiphase ordering. Finally, we use Kramers’ theory to identify slow, fast, and intermediate diffusive regimes for the guest particles as a function of their length. Our model is in qualitative agreement with experiment and simulation and provides an alternative, complementary explanation in terms of a free-energy landscape for the intermediate diffusive regime, which was previously hypothesized to result from temporary caging effects [M. Chiappini, E. Grelet, and M. Dijkstra, Phys. Rev. Lett. 124, 087801 (2020)]. We argue that our simple model of aligned rods captures the salient features of incommensurate-length guest particles in a smectic host if a slight orientational mismatch is introduced.
Anisotropic creep velocity of Dzyaloshinskii domain walls
Authors: Pakam Tchilabalo , Adjanoh Assiongbon Adanlété , Afenyiveh Serge Dzo Mawuefa , Vogel Jan , Pizzini Stefania , Ranno Laurent
Published: February 2024

We have measured the field-driven velocity of chiral Néel domain walls (DWs) stabilized by the Dzyaloshinskii–Moriya interaction (DMI) in a Pt/Co/Ta/Pt film with perpendicular magnetic anisotropy. A simple model based on the universal creep theory allows us to describe the anisotropic propagation of a DW along the contour of a bubble domain, driven by an out-of-plane field in the presence of a static in-plane field. This model is used to obtain the DMI constant from the measurement of the DW propagation with only one value of the in-plane field, simplifying the existing method relying on several measurements. The DMI constant extracted from the model is in good agreement with independent measurements.
Singular jets during the impingement of compound drops upon lyophilic surfaces
Authors: Zhao Yan , Li Xiangyu , Guo Jianwei
Published: February 2024

An important phenomenon produced during the impingement of drops upon solid surfaces is the formation of singular jet, which is often followed by the pinch-off of satellite droplets. Great efforts have been made to investigate the jetting dynamics of low-viscosity single-phase drops impact upon sufficiently lyophobic surfaces. However, whether such singular jets can be produced during the impact of compound drops and how the liquid properties and surface wettabilities affect the dynamics have remained largely unexplored. Herein, we perform comparative and systematic experiments on the impact dynamics of single-phase water and silicon oil drops, as well as water-in-oil compound drops on lyophilic substrates. We show that singular jets only occur during the impact of compound drops. The critical values in terms of the Weber number depend on both the viscosity of the silicon oil and the volume ratio of the two liquids composing the compound drops. We also show that the singular jets break up and throw out satellite droplets only when they are considerably fast and thin. Power-law correlations between the jet velocities and the jet radii, between the jet neck radius and time, and between the maximum jet height and the jetting time are obtained. A linear correlation between the radii of the jet droplets and those of the singular jets is also found and analyzed.
A low-frequency ultrathin metamaterial absorber using magnetic material
Authors: Shou Haijun , Qi Buxiong , Lv Huanchang , Feng Junlang , Mei Zhonglei
Published: February 2024

In this paper, an ultra-thin metamaterial absorber (UMA) in the S-band is designed. The overall structure adopts a three-layer design. The top layer is a magnetic material, and the middle layer of the UMA is composed of a centrally symmetrical open square ring (four edges are opened) and a circular pattern placed at the center, which is etched on the FR4 dielectric substrate by printed circuit board technology. The absorptivity of the absorber is more than 90% in 1.73–4.04 GHz under normal incidence, and the fractional bandwidth is 80.1%. The total thickness of the absorber is about 3.4 mm, corresponding to 0.02 λL at the lowest operating frequency. Moreover, it also has good polarization insensitivity and wide-angle incident characteristics. The absorption mechanism of the UMA is analyzed from the aspects of power loss density and surface current. Finally, a sample was fabricated and measured. The measured results are in good agreement with the simulation results, which verifies the effectiveness of the design method.
Determining the bulk viscosity in clay–sand mixtures: A combined investigation with slump tests and lattice Boltzmann simulations
Authors: Guo Junwei , Zhou Qi , Wong Ron Chik-Kwong
Published: February 2024

Viscosity measurements for clay slurry and sand mixtures can be challenging for standard rheometers because of the sand particles. To solve this, we suggest combining slump test experiments with numerical simulations. Slump tests are performed on clay–sand mixtures, with the sand's volume fraction varying between 0≤ϕ≤0.32. The run-out distance of the slump is tracked over time using a high-speed camera. By comparing the results of lattice Boltzmann simulations with the experimental data, we can accurately estimate the mixture's overall viscosity. Our findings reveal that fluid consistency increases significantly with ϕ, consistent with predictions made by the Maron–Pierce formula.
Comparisons between the disturbances in chemiluminescence and heat release rate from acoustically perturbed partially premixed and diffusion flames
Authors: Liang Xuanye , Wang Zixuan , Ji Liang , Yang Lijun , Li Jingxuan
Published: February 2024

Heat release rate is a critical parameter in the combustion process, yet its quantification can be challenging to obtain experimentally. In this study, an acoustical measurement system based on the Rijke tube was established to investigate the heat release rate perturbations of 25 propane/air flames under different mixing conditions. For premixed flames, perturbations in CH* and OH* chemiluminescence were consistent with the heat release rate disturbances determined using the acoustical method, thereby validating the proposed acoustical method and platform. Based on these, a comprehensive analysis was carried out on the chemiluminescence results and heat release rate perturbations of flames under different fuel–air mixing conditions, revealing the condition where the chemiluminescence method no longer reliably indicates the heat release rate. The research also investigated the chemiluminescence structure of flames under different fuel–air mixing conditions, identifying a difference in the distribution of CH* and OH* chemiluminescence at higher equivalence ratios (approaching diffusion flame conditions). In fully diffusion flames, the perturbation of OH* chemiluminescence was primarily observed near the base of the flame, while the peak perturbation of CH* chemiluminescence resides within the soot reaction zone downstream of the flame front.
Physical origin of enhanced electrical conduction in aluminum-graphene composites
Authors: Nepal K. , Ugwumadu C. , Subedi K. N. , Kappagantula K. , Drabold D. A.
Published: February 2024

The electronic and transport properties of aluminum-graphene composite materials were investigated using the ab initio plane wave density functional theory. The interfacial structure is reported for several configurations. In some cases, the face-centered aluminum (111) surface relaxes in a nearly ideal registry with graphene, resulting in a remarkably continuous interface structure. The Kubo–Greenwood formula and space-projected conductivity were employed to study electronic conduction in aluminum single- and double-layer graphene-aluminum composite models. The electronic density of states at the Fermi level is enhanced by the graphene for certain aluminum–graphene interfaces, thus improving electronic conductivity. In double-layer graphene composites, conductivity varies non-monotonically with temperature, showing an increase between 300 and 400 K at short aluminum-graphene distances, unlike the consistent decrease in single-layer composites.
Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era
Authors: Clark Rachel W. , Wellner Julia S. , Hillenbrand Claus-Dieter , Totten Rebecca L. , Smith James A. , Miller Lauren E. , Larter Robert D. , Hogan Kelly A. , Graham Alastair G. C. , Nitsche Frank O. , Lehrmann Asmara A. , Lepp Allison P. , Kirkham James D. , Fitzgerald Victoria T. , Garcia-Barrera Georgina , Ehrmann Werner , Wacker Lukas
Published: February 2024

Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier’s history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability.
Pervasive mimicry in flight behavior among aposematic butterflies
Authors: Page Edward , Queste Lucie M. , Rosser Neil , Salazar Patricio A. , Nadeau Nicola J. , Mallet James , Srygley Robert B. , McMillan W. Owen , Dasmahapatra Kanchon K.
Published: February 2024

Flight was a key innovation in the adaptive radiation of insects. However, it is a complex trait influenced by a large number of interacting biotic and abiotic factors, making it difficult to unravel the evolutionary drivers. We investigate flight patterns in neotropical heliconiine butterflies, well known for mimicry of their aposematic wing color patterns. We quantify the flight patterns (wing beat frequency and wing angles) of 351 individuals representing 29 heliconiine and 9 ithomiine species belonging to ten color pattern mimicry groupings. For wing beat frequency and up wing angles, we show that heliconiine species group by color pattern mimicry affiliation. Convergence of down wing angles to mimicry groupings is less pronounced, indicating that distinct components of flight are under different selection pressures and constraints. The flight characteristics of the Tiger mimicry group are particularly divergent due to convergence with distantly related ithomiine species. Predator-driven selection for mimicry also explained variation in flight among subspecies, indicating that this convergence can occur over relatively short evolutionary timescales. Our results suggest that the flight convergence is driven by aposematic signaling rather than shared habitat between comimics. We demonstrate that behavioral mimicry can occur between lineages that have separated over evolutionary timescales ranging from <0.5 to 70 My.
Variable carbon isotope fractionation of photosynthetic communities over depth in an open-ocean euphotic zone
Authors: Henderson Lillian C. , Wittmers Fabian , Carlson Craig A. , Worden Alexandra Z. , Close Hilary G.
Published: February 2024

Marine particulate organic carbon (POC) contributes to carbon export, food webs, and sediments, but uncertainties remain in its origins. Globally, variations in stable carbon isotope ratios (δ
13
C values) of POC between the upper and lower euphotic zones (LEZ) indicate either varying aspects of photosynthetic communities or degradative alteration of POC. During summertime in the subtropical north Atlantic Ocean, we find that δ
13
C values of the photosynthetic product phytol decreased by 6.3‰ and photosynthetic carbon isotope fractionation (ε
p
) increased by 5.6‰ between the surface and the LEZ—variation as large as that found in the geologic record during major carbon cycle perturbations, but here reflecting vertical variation in δ
13
C values of photosynthetic communities. We find that simultaneous variations in light intensity and phytoplankton community composition over depth may be important factors not fully accounted for in common models of photosynthetic carbon isotope fractionation. Using additional isotopic and cell count data, we estimate that photosynthetic and non-photosynthetic material (heterotrophs or detritus) contribute relatively constant proportions of POC throughout the euphotic zone but are isotopically more distinct in the LEZ. As a result, the large vertical differences in ε
p
result in significant, but smaller, differences in the δ
13
C values of total POC across the same depths (2.7‰). Vertical structuring of photosynthetic communities and export potential from the LEZ may vary across current and past ocean ecosystems; thus, LEZ photosynthesis may influence the exported and/or sedimentary δ
13
C values of both phytol and total organic carbon and affect interpretations of ε
p
over geologic time.
Spatially resolved land and grid model of carbon neutrality in China
Authors: Zhang Da , Zhu Ziheng , Chen Shi , Zhang Chongyu , Lu Xi , Zhang Xiliang , Zhang Xiaoye , Davidson Michael R.
Published: February 2024

China has committed to achieve net carbon neutrality by 2060 to combat global climate change, which will require unprecedented deployment of negative emissions technologies, renewable energies (RE), and complementary infrastructure. At terawatt-scale deployment, land use limitations interact with operational and economic features of power systems. To address this, we developed a spatially resolved resource assessment and power systems planning optimization that models a full year of power system operations, sub-provincial RE siting criteria, and transmission connections. Our modeling results show that wind and solar must be expanded to 2,000 to 3,900 GW each, with one plausible pathway leading to 300 GW/yr combined annual additions in 2046 to 2060, a three-fold increase from today. Over 80% of solar and 55% of wind is constructed within 100 km of major load centers when accounting for current policies regarding land use. Large-scale low-carbon systems must balance key trade-offs in land use, RE resource quality, grid integration, and costs. Under more restrictive RE siting policies, at least 740 GW of distributed solar would become economically feasible in regions with high demand, where utility-scale deployment is limited by competition with agricultural land. Effective planning and policy formulation are necessary to achieve China’s climate goals.
Extracellular vesicle formation in
Euryarchaeota
is driven by a small GTPase
Authors: Mills Joshua , Gebhard L. Johanna , Schubotz Florence , Shevchenko Anna , Speth Daan R. , Liao Yan , Duggin Iain G. , Marchfelder Anita , Erdmann Susanne
Published: February 2024

Since their discovery, extracellular vesicles (EVs) have changed our view on how organisms interact with their extracellular world. EVs are able to traffic a diverse array of molecules across different species and even domains, facilitating numerous functions. In this study, we investigate EV production in
Euryarchaeota,
using the model organism
Haloferax volcanii
. We uncover that EVs enclose RNA, with specific transcripts preferentially enriched, including those with regulatory potential, and conclude that EVs can act as an RNA communication system between haloarchaea. We demonstrate the key role of an EV-associated small GTPase for EV formation in
H. volcanii
that is also present across other diverse evolutionary branches of Archaea. We propose the name, ArvA, for the identified family of archaeal vesiculating GTPases. Additionally, we show that two genes in the same operon with
arvA
(
arvB
and
arvC
) are also involved in EV formation. Both,
arvB
and
arvC
, are closely associated with
arvA
in the majority of other archaea encoding ArvA. Our work demonstrates that small GTPases involved in membrane deformation and vesiculation, ubiquitous in Eukaryotes, are also present in Archaea and are widely distributed across diverse archaeal phyla.
Strategy to develop broadly effective multivalent COVID-19 vaccines against emerging variants based on Ad5/35 platform
Authors: Chang Soojeong , Shin Kwang-Soo , Park Bongju , Park Seowoo , Shin Jieun , Park Hyemin , Jung In Kyung , Kim Jong Heon , Bae Seong Eun , Kim Jae-Ouk , Baek Seung Ho , Kim Green , Hong Jung Joo , Seo Hyungseok , Volz Erik , Kang Chang-Yuil
Published: February 2024

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron strain has evolved into highly divergent variants with several sub-lineages. These newly emerging variants threaten the efficacy of available COVID-19 vaccines. To mitigate the occurrence of breakthrough infections and re-infections, and more importantly, to reduce the disease burden, it is essential to develop a strategy for producing updated multivalent vaccines that can provide broad neutralization against both currently circulating and emerging variants. We developed bivalent vaccine AdCLD-CoV19-1 BA.5/BA.2.75 and trivalent vaccines AdCLD-CoV19-1 XBB/BN.1/BQ.1.1 and AdCLD-CoV19-1 XBB.1.5/BN.1/BQ.1.1 using an Ad5/35 platform-based non-replicating recombinant adenoviral vector. We compared immune responses elicited by the monovalent and multivalent vaccines in mice and macaques. We found that the BA.5/BA.2.75 bivalent and the XBB/BN.1/BQ.1.1 and XBB.1.5/BN.1/BQ.1.1 trivalent vaccines exhibited improved cross-neutralization ability compared to their respective monovalent vaccines. These data suggest that the developed multivalent vaccines enhance immunity against circulating Omicron subvariants and effectively elicit neutralizing antibodies across a broad spectrum of SARS-CoV-2 variants.
Magnetically powered microwheel thrombolysis of occlusive thrombi in zebrafish
Authors: Pontius M. Hao Hao , Ku Chia-Jui , Osmond Matthew J. , Disharoon Dante , Liu Yang , Warnock Mark , Lawrence Daniel A. , Marr David W. M. , Neeves Keith B. , Shavit Jordan A.
Published: February 2024

Tissue plasminogen activator (tPA) is the only FDA-approved treatment for ischemic stroke but carries significant risks, including major hemorrhage. Additional options are needed, especially in small vessel thrombi which account for ~25% of ischemic strokes. We have previously shown that tPA-functionalized colloidal microparticles can be assembled into microwheels (µwheels) and manipulated under the control of applied magnetic fields to enable rapid thrombolysis of fibrin gels in microfluidic models of thrombosis. Transparent zebrafish larvae have a highly conserved coagulation cascade that enables studies of hemostasis and thrombosis in the context of intact vasculature, clotting factors, and blood cells. Here, we show that tPA-functionalized µwheels can perform rapid and targeted recanalization in vivo. This effect requires both tPA and µwheels, as minimal to no recanalization is achieved with tPA alone, µwheels alone, or tPA-functionalized microparticles in the absence of a magnetic field. We evaluated tPA-functionalized µwheels in CRISPR-generated plasminogen (
plg
) heterozygous and homozygous mutants and confirmed that tPA-functionalized µwheels are dose-dependent on plasminogen for lysis. We have found that magnetically powered µwheels as a targeted tPA delivery system are dramatically more efficient at plasmin-mediated thrombolysis than systemic delivery in vivo. Further development of this system in fish and mammalian models could enable a less invasive strategy for alleviating ischemia that is safer than directed thrombectomy or systemic infusion of tPA.
Tuning Excitation Transport in a Dissipative Rydberg Ring
Authors: Han 韩 Yiwen 奕文 , Yi 易 Wei 为
Published: February 2024

We demonstrate the flexible tunability of excitation transport in Rydberg atoms, under the interplay of controlled dissipation and interaction-induced synthetic flux. Considering a minimum four-site setup, i.e., a triangular configuration with an additional output site, we study the transport of a single excitation, injected into a vertex of the triangle, through the structure. While the long-range dipole-dipole interactions between the Rydberg atoms lead to geometry-dependent Peierls phases in the hopping amplitudes of excitations, we further introduce on-site dissipation to a vertex of the triangle. As a result, both the chirality and destination of the transport can be manipulated through the flux and dissipation. In particular, we illustrate a parameter regime where our Rydberg-ring structure may serve as a switch for transporting the injected excitation through to the output site. The underlying mechanism is then analyzed by studying the chiral trajectory of the excitation and the time-dependent dissipation. The switchable excitation transport reported here offers a flexible tool for quantum control in Rydberg atoms, and holds interesting potentials for applications in quantum simulation and quantum information.
Constructing Hopf Insulator from Geometric Perspective of Hopf Invariant
Authors: Chang 常 Zhi-Wen 治文 , Hao 郝 Wei-Chang 维昌 , Bustamante Miguel , Liu 刘 Xin 鑫
Published: February 2024

We propose a method to construct Hopf insulators based on the study of topological defects from the geometric perspective of Hopf invariant I. Firstly, we prove two types of topological defects naturally inhering in the inner differential structure of the Hopf mapping. One type is the four-dimensional point defects, which lead to a topological phase transition occurring at the Dirac points. The other type is the three-dimensional merons, whose topological charges give the evaluations of I. Then, we show two ways to establish the Hopf insulator models. One approach is to modify the locations of merons, thereby the contributions of charges to I will change. The other is related to the number of defects. It is found that I will decrease if the number reduces, while increase if additional defects are added. The method developed in this study is expected to provide a new perspective for understanding the topological invariants, which opens a new door in exploring and designing novel topological materials in three dimensions.
Quantum matter and gravitation: photons in a waveguide
Authors: Atanasov Victor , Saxena Avadh
Published: February 2024

The conditions required by quantum matter to modify space-time geometry are explored within the framework of the general theory of relativity. The required characteristics for space-time modification in solid state structures, are met in either (a) massive photon Bose–Einstein condensate in a waveguide, or (b) the massive photons in superconductor’s bulk, or (c) the Bose–Einstein condensate of acoustic phonons, or (d) a metal–insulator-topological insulator heterostructure.
Adaptive tempered reversible jump algorithm for Bayesian curve fitting
Authors: Tian Zhiyao , Lee Anthony , Zhou Shunhua
Published: February 2024

Bayesian curve fitting plays an important role in inverse problems, and is often addressed using the reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. However, this algorithm can be computationally inefficient without appropriately tuned proposals. As a remedy, we present an adaptive RJMCMC algorithm for the curve fitting problems by extending the adaptive Metropolis sampler from a fixed-dimensional to a trans-dimensional case. In this presented algorithm, both the size and orientation of the proposal function can be automatically adjusted in the sampling process. Specifically, the curve fitting setting allows for the approximation of the posterior covariance of the a priori unknown function on a representative grid of points. This approximation facilitates the definition of efficient proposals. In addition, we introduce an auxiliary-tempered version of this algorithm via non-reversible parallel tempering. To evaluate the algorithms, we conduct numerical tests involving a series of controlled experiments. The results demonstrate that the adaptive algorithms exhibit significantly higher efficiency compared to the conventional ones. Even in cases where the posterior distribution is highly complex, leading to ineffective convergence in the auxiliary-tempered conventional RJMCMC, the proposed auxiliary-tempered adaptive RJMCMC performs satisfactorily. Furthermore, we present a realistic inverse example to test the algorithms. The successful application of the adaptive algorithm distinguishes it again from the conventional one that fails to converge effectively even after millions of iterations.
Towards optimal sensor placement for inverse problems in spaces of measures
Authors: Huynh Phuoc-Truong , Pieper Konstantin , Walter Daniel
Published: February 2024

The objective of this work is to quantify the reconstruction error in sparse inverse problems with measures and stochastic noise, motivated by optimal sensor placement. To be useful in this context, the error quantities must be explicit in the sensor configuration and robust with respect to the source, yet relatively easy to compute in practice, compared to a direct evaluation of the error by a large number of samples. In particular, we consider the identification of a measure consisting of an unknown linear combination of point sources from a finite number of measurements contaminated by Gaussian noise. The statistical framework for recovery relies on two main ingredients: first, a convex but non-smooth variational Tikhonov point estimator over the space of Radon measures and, second, a suitable mean-squared error based on its Hellinger–Kantorovich distance to the ground truth. To quantify the error, we employ a non-degenerate source condition as well as careful linearization arguments to derive a computable upper bound. This leads to asymptotically sharp error estimates in expectation that are explicit in the sensor configuration. Thus they can be used to estimate the expected reconstruction error for a given sensor configuration and guide the placement of sensors in sparse inverse problems.
Gap engineering effects on transport and tunneling magnetoresistance properties in phosphorene ferromagnetic/normal/ferromagnetic junction
Authors: Oubram O
Published: February 2024

Tuning the band gap is of utmost importance for the practicality of two-dimensional materials in the semiconductor industry. In this study, we investigate the ballistic transport and the tunneling magnetoresistance (TMR) properties within a modulated gap in a ferromagnetic/normal/ferromagnetic (F/N/F) phosphorene junction. The theoretical framework is established on a Dirac-like Hamiltonian, the transfer matrix method, and the Landauer–Büttiker formalism to characterize electron behavior and obtain transmittance, conductance and TMR. Our results reveal that a reduction in gap energy leads to an enhancement of conductance for both parallel and anti-parallel magnetization configurations. In contrast, a significant reduction and redshift in TMR have been observed. Notably, the application of an electrostatic field in a gapless phosphorene F/N/F junction induces a blueshift and a slight increase in TMR. Furthermore, we found that introducing an asymmetrically applied electrostatic field in this gapless junction results in a significant reduction and redshift in TMR. Additionally, intensifying the applied magnetic field leads to a substantial increase in TMR. These findings could be useful for designing and implementing practical applications that require precise control over the TMR properties of a phosphorene F/N/F junction with a modulated gap.
Electric properties of the twelve-fold vortex structure in hexagonal manganites
Authors: Lin Hongling , Yang Kunlun , Lin Lin , Yan Zhibo , Liu J-M
Published: February 2024

Hexagonal manganites, as a functional ferroelectric (FE) material, receive considerable attention due to their improper ferroelectricity and topological vortex structures. This family exhibits three low-symmetry states accompanied by distinct vortex domain structures. In addition to the FE P63
cm and anti-FE (AFE) P-3c1 states accompanied by dual six-fold vortex structures, there is another FE P3c1 state accompanied by a twelve-fold vortex structure. The responses of FE materials to external stimuli, such as external electric fields, are the core ingredients in the physics of FEs and are significant for technological applications. Under external electric fields, the responses of FE materials are determined by special FE domain structures. The electric properties of the FE P63
cm and AFE P-3c1 states are very different. However, the electric properties of the FE P3c1 state, which only stabilizes in Ga-substituted In(Mn, Ga)O3, are unclear. The present work studies the electric properties of the FE P3c1 state. The electric-field-driven transition of the FE P3c1 state is found to follow two sequences, i.e. (1) twelve-fold P3c1 → nine-fold P3c1 + P63
cm → three-fold P63
cm, and (2) twelve-fold P3c1 → six-fold P3c1 → three-fold P63
cm. The variation of average polarization with E for the FE P3c1 state with the second transition sequence manifests as an unusual triple-hysteresis loop, different from the usual single-hysteresis loop of FE materials. The results are related to the coexistence of the FE and non-FE domain walls in the FE P3c1 state. Furthermore, it is found that the FE P3c1 state at substitution concentration 0.39 exhibits the highest dielectric response. The results advance our understanding of topological vortex structures in hexagonal manganites.
An identification algorithm of lateral correction amount for the weeding components in paddy fields based on multi-sensor fusion
Authors: Wang Shanshan , Yu Shanshan , Wang Xingsong
Published: February 2024

In this paper, an identification algorithm of lateral correction amount for the weeding components in paddy fields based on multi-sensor fusion is proposed, which can accurately obtain the lateral deviation between the weeding components and the seedling rows under different soil hardness in paddy fields to avoid crushing seedlings. The proposed method first fuses the RGB images with depth images to obtain the three-dimensional point cloud of seedlings, establishes a visual calibration system to calibrate the positions of the weeding component at the limit positions in the camera coordinate system, then obtains the relative pose relationship between the camera coordinate system and the ground coordinate system based on the inertial measurement unit to solve the influence of the altitude change of the camera on the identification of the lateral correction amount, and finally calculates the lateral correction amount based on the lateral deviation model in the ground coordinate system. The experimental platforms for the visual calibration of the weeding components and the identification of the lateral correction amount were established. The experimental results showed that the mean positioning error of the weeding components was 2.766 mm, the mean identification error of the lateral correction amount did not exceed 0.22 cm, and the standard deviation of the identification error did not exceed 0.18 cm.
Discrete-coordinate crypto-Hermitian quantum system controlled by time-dependent Robin boundary conditions
Authors: Znojil Miloslav
Published: February 2024

A family of exactly solvable quantum square wells with discrete coordinates and with certain non-stationary Hermiticity-violating Robin boundary conditions is proposed and studied. Manifest non-Hermiticity of the model in conventional Hilbert space

H

friendly

is required to coexist with the unitarity of system in another, ad hoc Hilbert space

H

physical

. Thus, quantum mechanics in its non-Hermitian interaction picture (NIP) representation is to be used. We must construct the time-dependent states (say, ψ(t)) as well as the time-dependent observables (say, Λ(t)). Their evolution in time is generated by the operators denoted, here, by the respective symbols G(t) (a Schrödinger-equation generator) and Σ(t) (a Heisenberg-equation generator, a.k.a. quantum Coriolis force). The unitarity of evolution in

H

physical

is then guaranteed by the reality of spectrum of the energy observable alias Hamiltonian H(t) = G(t) + Σ(t). The applicability of these ideas is illustrated via an N by N matrix model. At N = 2, closed formulae are presented not only for the measurable instantaneous energy spectrum but also for all of the eligible time-dependent physical inner-product metrics Θ(N=2)(t), for the related Dyson maps Ω(N=2)(t), for the Coriolis force Σ(N=2)(t) as well as, in the very ultimate step of the construction, for the truly nontrivial Schrödinger-equation generator G
(N=2)(t).
Taming assembly bias for primordial non-Gaussianity
Authors: Fondi Emanuele , Verde Licia , Villaescusa-Navarro Francisco , Baldi Marco , Coulton William R. , Jung Gabriel , Karagiannis Dionysios , Liguori Michele , Ravenni Andrea , Wandelt Benjamin D.
Published: February 2024

Primordial non-Gaussianity of the local type induces a strong scale-dependent bias on the clustering of halos in the late-time Universe. This signature is particularly promising to provide constraints on the non-Gaussianity parameter f
NL from galaxy surveys, as the bias amplitude grows with scale and becomes important on large, linear scales. However, there is a well-known degeneracy between the real prize, the f
NL parameter, and the (non-Gaussian) assembly bias i.e., the halo formation history-dependent contribution to the amplitude of the signal, which could seriously compromise the ability of large-scale structure surveys to constrain f
NL. We show how the assembly bias can be modeled and constrained, thus almost completely recovering the power of galaxy surveys to competitively constrain primordial non-Gaussianity. In particular, studying hydrodynamical simulations, we find that a proxy for the halo properties that determine assembly bias can be constructed from photometric properties of galaxies. Using a prior on the assembly bias guided by this proxy degrades the statistical errors on f
NL only mildly compared to an ideal case where the assembly bias is perfectly known. The systematic error on f
NL that the proxy induces can be safely kept under control.
Model-based measurements in the monitoring tasks of high-power plants
Authors: Borovik S Y , Kuteynikova M M , Sekisov Y N
Published: February 2024

The tasks of the measuring information obtaining about the state of the blading section and structural elements of gas turbine engines, as typical representatives of high-power plants, in the process of their experimental research and testing are considered. Such measurements are usually characterized by extreme environmental conditions, complex shapes and multidimensional movements of the monitored surfaces, strict constraints on the number and location of primary transducers, etc. As a result, the required measurement information is obtained under the influence of a large number of interfering factors, which are not always available for direct measurements and consideration in the experimental data processing. The approach based on the modeling the immeasurable components counting the current parameters of the power plant mode and environmental conditions is considered as an alternative to the direct measurements. The use of online models allows (in addition to increasing the reliability of measurements) to evaluate the unique characteristics of the monitored object (e.g., changes in shape) and, in some cases, to predict its critical state. The examples of the practical implementation of the approach in specific measurement systems designed for bench testing of gas turbine engines are also given in the article.
Assessing the uncertainty of the means for determining the positioning accuracy of the machine
Authors: Koleva S , Enchev M , Velev K
Published: February 2024

Positioning deviations such as systematic and random errors lend a substantial influence to finish machining. In this article is carried a theoretical research of the uncertainty when determining the repeatability of positioning with standard methodology, regulated in ISO 230-2. It is carried out by simulating different levels of random deviation for the position reached and the number of points on the controlled axis. The laws of distribution are established on standard assessment of positioning repeatability and the relative share of uncertainty regarding the actual (set) random positional deviation.
Iris-Based Biometric Identification Using a Combination of the Right - Left Iris Statistical Features
Authors: Dincă Lăzărescu A M , Moldovanu S , Moraru L
Published: February 2024

A combination between the information extracted for both right iris and left iris could increase the efficacy of the biometric recognition systems. In this paper, we propose a biometric identification method based on density of image patterns extracted from human iris images and the combination and comparison of the right iris and the left iris characteristics. The density of the patters approach for processed images can be a new biometric feature used to implement a biometric recognition system with high performance when a small feature dimension is used. In this way, we can maximize the retention of the effective biometric information. The experiments were conducted on the MMU Iris Database containing 225 images of the left eye and 225 images of the right eye. Two morphological Top-hat and Hit or Miss transforms were implemented to find out the particular pattern of pixels. They allow for the enhancement of detail in images. Then, a statistical feature extraction technique is employed to derive the density of the patterns in morphological transformed images. To assess the density of the patterns differences between the right and left iris data groups, the Pearson’s correlation coefficient (PCC) is computed. We reported very good results with a PCC of 0.6164 (strong and positive correlation) for Top-hat morphological operation whilst the Hit or Miss transform returns a PCC of 0.0127 so there is no relationship between the density of the patterns in the right and left irises.
2D multiple waves scattering for active detection of a dummy human body in a low frequency range and for various boundary conditions
Authors: Bibcu Dorin , Florescu Culea Anisia , Moldovanu Simona , Moraru Luminita
Published: February 2024

This paper investigates the results of simulations devoted to the acoustic field variation caused by different boundary conditions applied to the backscattering of the acoustic wave in both low and moderately low frequency ranges. The goal is to analyse the object behaviour and the detection ability of the 2D acoustic field approximations when the simulation data of the scattered sound field is available. The plane waves are backscattered by a dummy human body, positioned in a cabin which has a defined size. The dummy human body is created by using clusters of finite and disjointed but tangent circular cylinders. Each cylinder is a scatterer that emulates various boundary conditions i.e., the scatterers can be sound-soft (Dirichlet boundary condition) and sound-hard scatterers (Neumann boundary condition). The cylinders are filled with biological tissue (i.e., fat). The exterior scattering problem is solved using the preconditioned Krylov subspace iterative solvers (GMRES), as a computationally cheaper alternative. We use the hypothesis that the mass density of the obstacle and wave speed in the obstacle are both constant. During the simulation experiments, we neglected the interactions among scatterers. A frequency range from 100 Hz to 1000 Hz is analysed. Both the Sound Pressure Level (SPL) and Radar Cross Section (RCS) are used to analyse the numerical simulation of the sound field.
Application of the method of moments for doublet and triplet analysis in the radiation spectra
Authors: Izosimov I N
Published: February 2024

When processing spectra, it is usually sufficient to determine only the positions of the peaks and their areas. To use the method of moments for doublet peaks analysis, it is necessary to first construct (calibrate) the dependence of the second and third moments for single peaks on the energy of the corresponding radiation. After such calibration overlapping peaks can be separated. To separate peaks in doublet using the method of moments, it is necessary to solve a quadratic equation. To separate peaks in triplet it is necessary to have an appropriate calibration curves already up to the fifth moment inclusive and solve a cubic equation. Examples of the separation of overlapping peaks in the analysis of gamma-ray spectra are presented.
Numerical experiments on paleoclimate modeling
Authors: Parkhomenko V P
Published: February 2024

The influence of climatic parameters (values of CO2 concentration in the atmosphere, solar constant), the configuration of continents, as well as the distribution of the depths of the World Ocean, characteristic of the time periods under consideration, on the climate is investigated. A global climate model is used, including a model of three-dimensional thermohaline circulation of the ocean, an energy-moisture balance model of the atmosphere and a model of the sea ice evolution. Numerical experiments have been carried out to model the climate corresponding to the periods 120.4 million years ago and 200 million years ago with sharply different parameters. The first interval was characterized by high CO2 concentrations and a continent lying in meridional direction. During the second interval a super continent was located in the Northern polar region extending to the South but not reaching the South Pole. Calculations show that the average global climatic characteristics achieve to a stationary regime during about 1500-2000 years. The main global and spatial climatic characteristics for the atmosphere, ocean, and sea ice are obtained. The estimated average global atmospheric temperature falls within the limits reconstructed from observations. The features of ocean circulation for the corresponding periods are studied.
Planar Walking of a Five-Link Biped Robot over a Stepped Surface with Obstacles of Different Heights and Lengths
Authors: Kasiyanchuk Dmitry A. , Fetisov Dmitry A.
Published: February 2024

A problem of modeling biped locomotion is an actual and complex problem of modern control theory. In the present paper, we deal with a special case when a five-link biped robot with knees moves along a given stepped surface. We describe the robot motion by a hybrid system which consists of a system of ordinary differential equations at the single support phase and an algebraic relation at the double support phase. The main contribution of this paper is the construction of a periodic motion that satisfies a set of conditions inherent in human walking. The results of the paper will be useful to those who are interested in control theory applications.