bluuebunny/crossref_metadata_2025 huggingface dataset:
The energies and charge and spin distributions in the low-lying levels of singlet and triplet N2V defects in diamond from direct variational calculations of the excited states
Authors: Mackrodt William C. , Platonenko Alexander , Pascale Fabien , Dovesi Roberto
Published: January 2024

This paper reports the energies and charge and spin distributions of the low-lying excited states in singlet and triplet N2V defects in diamond from direct Δ-SCF calculations based on Gaussian orbitals within the B3LYP, PBE0, and HSE06 functionals. They assign the observed absorption at 2.463 eV, first reported by Davies et al. [Proc. R. Soc. London 351, 245 (1976)], to the excitation of a N(sp3) lone-pair electron in the singlet and triplet states, respectively, with estimates of ∼1.1 eV for that of the unpaired electrons, C(sp3). In both cases, the excited states are predicted to be highly local and strongly excitonic with 81% of the C(sp3) and 87% of the N(sp3) excited charges localized at the three C atoms nearest neighbor (nn) to the excitation sites. Also reported are the higher excited gap states of both the N lone pair and C unpaired electron. Calculated excitation energies of the bonding sp3 hybrids of the C atoms nn to the four inner atoms are close to that of the bulk, which indicates that the N2V defect is largely a local defect. The present results are in broad agreement with those reported by Udvarhelyi et al. [Phys. Rev. B 96, 155211 (2017)] from plane wave HSE06 calculations, notably for the N lone pair excitation energy, for which both predict an energy of ∼2.7 eV but with a difference of ∼0.5 eV for the excitation of the unpaired electron.
Effects of cavitation and hydraulic flip on liquid film formed by jet impinging on the wall
Authors: Wang Sheng-Ju , Guan Liang , Zhao Bin-Hong , Liu Meng-Yuan , Zhang Zi-Han , Li Wei-Feng , Lin Qing-Guo
Published: January 2024

The technology of the liquid film formed by jet impinging on the wall is widely applied in the aerospace, steel quenching, and cleaning. In this paper, the spreading and evolution of the liquid film are experimentally studied. The effects of the cavitation and hydraulic flip on the film are examined, and it is identified that they are a serious problem of the nozzle design. Results demonstrate that the jets formed by using a nozzle with 120° contraction angle and 3.5 mm outlet length sequentially produce the cavitation and hydraulic flip as the Reynolds number increases. Small contraction angle or long outlet length promotes the stability of the discharge coefficient and jet states and inhibits the occurrence of the cavitation and hydraulic flip. For the flip jet, the jet cross section is axially switched. Several patterns of the liquid film, such as the gravity flow, gravity flow with dry patch formation, rivulet flow with outward streams, and outward flow with triple rivulets, etc., are observed as the jet regime and inclination angle change. Particularly, for the film formed by the cavitation jet, the rivulets and dry patches emerge in the tail of the film; meanwhile, a lot of splashing droplets are generated. For the film generated by the flip jet, the bifurcation of the film shapes occurs. An impressive flow feature is that the two sprays are formed when the flip jet impinges on the wall, which is caused by the collision of the fluids in the secondary impingement zones.
Resistive drift wave turbulence and anomalous transport of multi-species plasma
Authors: Knyazev A. R. , Krasheninnikov S. I.
Published: January 2024

Anomalous transport of multi-species plasma is considered with the generalized Hasegawa–Wakatani model. It is shown that the transport of all plasma species is described by fractional diffusion equations with the same effective diffusion coefficient. Strongly enhanced perturbations of heavy impurity density are found in long-living plasma flow vortices.
Heat transfer characteristics of H2/air rotating detonation combustor
Authors: Qiu Yanming , Wu Yuwen , Huang Yakun , Li Qun , Weng Chunsheng
Published: January 2024

The heat release process in a rotating detonation combustor (RDC) exhibits highly transient characteristics, posing significant demands on the thermal protection and management of the rotating detonation engine (RDE). In this work, the wall heat transfer characteristics of the RDC supplied by H2/air were experimentally examined with different equivalence ratios, mass flow rates, and initial wall temperatures. High-speed photography and dynamic pressure transducers were used to determine the propagation mode of the rotating detonation wave, while the wall temperature and heat flux were monitored by thermocouples. The results showed that the wall temperature and heat flux decreased along the axial direction. A parabolic temperature variation occurs when equivalence ratio increases from 0.8 to 1.3, and the extreme value appears at Φ = 1.2. The same trend happens between heat flux and equivalence ratio. The mass flow rate increase leads to the overall increase in the temperature and heat flux, with the spatial distributions remaining unchanged. The higher initial wall temperature leads to the increase in the combustor outer wall temperature, a reduction in the spatial variation of temperature distribution, a decrease in heat flux, and a reduction in the spatial variation of heat flux. Furthermore, an empirical model was developed to estimate the heat transfer characteristics. Valid calculations show that the temporal and spatial temperature function results in lower errors of peak temperature prediction by approximately 50% and higher spatial resolution compared to a constant heat flux boundary condition. The research findings provide a theoretical foundation for the RDE thermal protection issues.
Numerical study on the hydrodynamic performance and wake dynamics of propulsive wing propulsors with different cross-flow fans
Authors: Lu Jiaxin , Lu Yang , Wang Junjie , Xu Xice , Shao Mengxue , Tang Zhengfei
Published: January 2024

The propulsive wing propulsor (PWP), which means an underwater thruster equipped with a wing, a cross-flow fan (CFF), and a deflector, is capable of generating both horizontal thrust and vertical lift, thus enhancing the maneuverability of underwater vehicles and serving as a propulsion device. The hydrodynamic performance of the PWP is significantly influenced by the blade number it possesses. An unsteady numerical method based on the Reynolds-averaged Navier–Stokes equations was developed to examine the impact mechanism of blade number on the hydrodynamic performance, load fluctuation, and wake evolution of the PWP. The results indicate that as the blade number increases, the hydrodynamic forces, power, and propulsive efficiency of the PWP gradually increase. When the blade number exceeds 26, the performance of the PWP tends to stabilize. Insufficient blades can lead to turbulence in the internal flow of the CFF, intensifying interference between blade vortices, resulting in secondary peaks and frequency-domain bifurcations in hydrodynamics. With an increasing blade number, disturbances to the blade vortices decrease, enhancing the periodicity of PWP hydrodynamic fluctuations, but there may be an increase in high-frequency noise levels. The wake modes of the PWP undergo four transitions: double vortex pair mode, single vortex pair mode, single vortex pair + single vortex mode, and vortex strip mode. Disturbed blade vortices promote the transition of vortex pair shedding modes in the PWP wake, thereby causing variations in the periodicity of PWP hydrodynamics. Excessive amplitude and frequency may lead to structural fatigue damage in the PWP.
Realizing an ultralow thermal conductivity via interfacial scattering and rational-electronic band reformation in p-type Mg3Sb2
Authors: Priyadharshini S. , Vijay V. , Kamalakannan S. , Archana J. , Navaneethan M.
Published: January 2024

Eco-friendly Magnesium antimonide (Mg3Sb2) has been extensively investigated as a promising and low-toxic thermoelectric material for intermediate (500–900 K) thermoelectric applications. Herein, p-type Zn-incorporated Mg3Sb2 was prepared by hot press technique, and its thermoelectric transport properties were investigated. The formation of Mg3−xZnxSb2 solid-solution plays a significant role in enhancing electrical conductivity of 34.59 S cm−1 due to the increased carrier concentration and reduced energy gap. Reduction in lattice thermal conductivity of 0.46 W m−1 K−1 at 753 K was obtained for Mg3−xZnxSb2 (x = 0.15) by combined scattering effect of dislocations, lattice strain, and interfaces, which is clearly seen in HR-TEM and strain analysis. These favorable conditions lead to an enhanced thermoelectric figure-of-merit (zT) of 0.25 at 753 K, which is 400% improved compared to the pure Mg3Sb2 sample.
Absolute doubly differential angular sputtering yields for 20 keV Kr+ on polycrystalline Cu
Authors: Bu Caixia , Morrissey Liam S. , Bostick Benjamin C. , Burger Matthew H. , Bowen Kyle P. , Chillrud Steven N. , Domingue Deborah L. , Dukes Catherine A. , Ebel Denton S. , Harlow George E. , Hillenbrand Pierre-Michel , Ivanov Dmitry A. , Killen Rosemary M. , Ross James M. , Schury Daniel , Tucker Orenthal J. , Urbain Xavier , Zhang Ruitian , Savin Daniel W.
Published: January 2024

We have measured the absolute doubly differential angular sputtering yield for 20 keV Kr+ impacting a polycrystalline Cu slab at an incidence angle of θi = 45° relative to the surface normal. Sputtered Cu atoms were captured using collectors mounted on a half dome above the sample, and the sputtering distribution was measured as a function of the sputtering polar, θs, and azimuthal, ϕs, angles. Absolute results of the sputtering yield were determined from the mass gain of each collector, the ion dose, and the solid angle subtended, after irradiation to a total fluence of ∼1 × 1018 ions/cm2. Our approach overcomes shortcomings of commonly used methods that only provide relative yields as a function of θs in the incidence plane (defined by the ion velocity and the surface normal). Our experimental results display an azimuthal variation that increases with increasing θs and is clearly discrepant with simulations using binary collision theory. We attribute the observed azimuthal anisotropy to ion-induced formation of micro- and nano-scale surface features that suppress the sputtering yield through shadowing and redeposition effects, neither of which are accounted for in the simulations. Our experimental results demonstrate the importance of doubly differential angular sputtering studies to probe ion sputtering processes at a fundamental level and to explore the effect of ion-beam-generated surface roughness.
Open-boundary cluster model with a parameter-free complex absorbing potential
Authors: Imamura Kosuke , Yasuike Tomokazu , Sato Hirofumi
Published: January 2024

In quantum chemical calculations of heterogeneous structures in solids, e.g., when an impurity is located on the surface, the conventional cluster model is insufficient to describe the electronic structure of substrates due to its finite size. The open-boundary cluster model (OCM) overcomes this problem by performing cluster calculations under the outgoing-wave boundary condition. In this method, a complex absorbing potential (CAP) is used to impose the boundary condition, but the CAP used in the previous studies required parameter optimization based on the complex variational principle. This study proposes and applies a parameter-free CAP to OCM calculations. This approach makes it possible to uniquely determine the band-specific CAP based on the surface Green’s function theory. Using this CAP, we conducted OCM calculations of the tight-binding model of a one-dimensional semi-infinite chain, and we found that the calculated density of states agreed with the exact one. Surface states of the Newns–Anderson–Grimley model were also computed using the CAP, and the projected density of states on the adsorbed atom was successfully reproduced.
Dynamic excitations and inertial effects of antiskyrmions in a synthetic antiferromagnet
Authors: Agorou A. , Trypiniotis T.
Published: January 2024

We study the dynamics of antiskyrmions in synthetic antiferromagnets with respect to the interlayer coupling strength by micromagnetic simulations. As the system is excited with an in-plane oscillating magnetic field, we identify four eigenmodes: two gyrotropic and two azimuthal, which we categorize based on their radial and azimuthal numbers. Surprisingly, the excitation of the first gyrotropic mode is seen to be fully suppressed in the absence of interlayer coupling in contrast to the case of skyrmions. We qualitatively show that this suppression is due to the dipolar interaction between the antiskyrmions that is competing against the external field influence. Finally, based on the generalized Thiele equation, we calculate the inertial mass of the antiskyrmions in this system and report a strong dependence on the interlayer coupling strength. Our results provide useful insights for controlling the dynamic behavior of antiskyrmions via interlayer coupling for future skyrmion-based spintronic devices.
Structural instability in LaNbO4 under compression
Authors: Garg Alka B. , Rao Rekha , Rodriguez-Hernandez Placida , Muñoz Alfonso , Errandonea Daniel
Published: January 2024

In this work, we report a high-pressure study on fergusonite-type LaNbO4. Powder x-ray diffraction and Raman spectroscopic experiments support the occurrence of a phase transition between 11 and 14 GPa. The transition takes place from a monoclinic fergusonite-type structure (space group I2/a) to another monoclinic structure (space group P21/c). The phase transition is reversible, and the high-pressure phase is isomorphic to the high-pressure phase of HoNbO4. The high-pressure phase remains stable up to 33.3 GPa, the highest pressure reached in the present measurements. Density-functional theory calculations found that in the pressure range of the studies; the high-pressure phase has a higher enthalpy than the low-pressure fergusonite phase. We propose that the high-pressure phase is metastable and it is observed because of non-hydrostatic conditions in the experiments. The pressure dependence of unit-cell parameters of the low-pressure phase and the room-temperature equation of state are reported. The pressure dependence of various Raman and IR frequencies as obtained from experiment and theory is also reported. For the fergusonite phase, we have also obtained the isothermal compressibility tensor, elastics constants, and elastic moduli.
Closed-loop plasma flow control of a turbulent cylinder wake flow using machine learning at Reynolds number of 28 000
Authors: Chen Jie , Zong Haohua , Song Huimin , Wu Yun , Liang Hua , Su Zhi
Published: January 2024

Machine learning is increasingly used for active flow control. In this experimental study, alternating-current dielectric barrier discharge plasma actuators are deployed for the closed-loop intelligent control of the flow around a cylinder at a Reynolds number of 28 000 based on the velocity feedback from two hot-wire sensors placed in the wake. Variations in the cylinder drag are monitored by a load cell, and the temporal response of the wake flow field is visualized by a high-speed particle image velocimetry system working at 1 kHz. The high-speed control law is operated using a field programmable gate array optimized by genetic programing (GP). The results show that the peak drag reduction achieved by machine learning is of similar magnitude to that of conventional steady actuation (∼15%), while the power saving ratio is 35% higher than with conventional techniques because of the reduced power consumption. Analysis of the best GP control laws shows that the intensity of plasma actuation should be kept at a medium level to maximize the power-saving ratio. When compared with the baseline uncontrolled flow, the best controlled cases constrain the meandering motion of the cylinder wake, resulting in a narrow stabilized velocity deficit zone in the time-averaged sense. According to the results of proper orthogonal decomposition and dynamic mode decomposition, Karman vortex shedding is promoted under the best GP control.
Robust valley quantum coherence in synthetic 3R-phase MoS2: A material for future valley based devices
Authors: Rajarapu Ramesh , Barman Prahalad Kanti , Biswal Bubunu , Poudyal Saroj , Yadav Renu , Deka Mrinal , Rahman Wahidur , S Anusree , Nayak Pramoda K. , Misra Abhishek
Published: January 2024

Two-dimensional layered transition metal dichalcogenides (TMDCs) offer the ideal platform to optically initialize the qubits utilizing the superposition of valley polarized photons. However, in the commonly available 2H phase TMDCs, thickness sensitive crystal inversion symmetry demands the precise control over the number of layers, which makes the study of valley physics challenging. On the other hand, 3R-polymorphic phase TMDCs are non-centrosymmetric irrespective of the number of layers and therefore retain valley degree of freedom for all the thicknesses. Here, using polarization resolved photoluminescence measurements under linearly polarized excitations, we demonstrate the coherent superposition of the valley photons (known as valley coherence) in synthetic 3R-phase MoS2 with different numbers of layers ranging from 3 layers to 11 layers. With near-resonant excitation (633 nm for AX0), the degree of linear polarization (a measure of the valley coherence) is observed up to 70% at 80 K measurement temperatures and is found to be layer thickness independent. Robust valley coherence is attributed to the high optical quality and the 3R crystal symmetry of the MoS2. Using angle resolved polarization dependent measurements, it is established that the net dipolar emission aligns with the polarization orientations of the incident laser, which signifies the valley coherence to be independent of the crystal orientation. This study paves the way toward using 3R-phase MoS2 as a key material for the development of future quantum technologies utilizing valley polarized photons.
Investigation of In2SexOy/In2Se3/Si dual-junction photodiode for self-powered broadband photodetection
Authors: Li Kuangkuang , Ling Kang , Li Wenbo , Liu Xingzhao
Published: January 2024

We report a dual-junction strategy for fabricating a high-performance In2SexOy/In2Se3/Si heterojunction photodiode by oxidizing the epitaxial In2Se3 thin films. The device exhibits a suppressed dark current (4.2 × 10−11 A) and enhanced photocurrent at zero bias, benefiting from the double built-in electric fields. Consequently, it demonstrates excellent and uniform self-powered broadband (255–1050 nm) photodetection performance with the typical responsivity of several hundred mA/W, and detectivity of over 5 × 1011 Jones. Moreover, a fast response speed with a response time of 0.20 ms is achieved. Our investigation offers a potential route to construct full-spectrum photodetectors.
Eigenstate calculation in the state-averaged (multi-layer) multi-configurational time-dependent Hartree approach
Authors: Hoppe Hannes , Manthe Uwe
Published: January 2024

A new approach for the calculation of eigenstates with the state-averaged (multi-layer) multi-configurational time-dependent Hartree (MCTDH) approach is presented. The approach is inspired by the recent work of Larsson [J. Chem. Phys. 151, 204102 (2019)]. It employs local optimization of the basis sets at each node of the multi-layer MCTDH tree and successive downward and upward sweeps to obtain a globally converged result. At the top node, the Hamiltonian represented in the basis of the single-particle functions (SPFs) of the first layer is diagonalized. Here p wavefunctions corresponding to the p lowest eigenvalues are computed by a block Lanczos approach. At all other nodes, a non-linear operator consisting of the respective mean-field Hamiltonian matrix and a projector onto the space spanned by the respective SPFs is considered. Here, the eigenstate corresponding to the lowest eigenvalue is computed using a short iterative Lanczos scheme. Two different examples are studied to illustrate the new approach: the calculation of the vibrational states of methyl and acetonitrile. The calculations for methyl employ the single-layer MCTDH approach, a general potential energy surface, and the correlation discrete variable representation. A five-layer MCTDH representation and a sum of product-type Hamiltonian are used in the acetonitrile calculations. Very fast convergence and order of magnitude reductions in the numerical effort compared to the previously used block relaxation scheme are found. Furthermore, a detailed comparison with the results of Avila and Carrington [J. Chem. Phys. 134, 054126 (2011)] for acetonitrile highlights the potential problems of convergence tests for high-dimensional systems.
Solid-liquid phase separation diffused Nd-Fe-B sintered magnets by using DyH3 nanopowder realize high-efficiency coercivity improvement and overcome thickness limit
Authors: Wu Haihui , Liu Weiqiang , Wang Zhanjia , Ji Ming , Du RuiHua , Li Yuqing , Zhang Dongtao , Yue Ming , Yi Xiaofei , Liu Youhao , Zha Shanshun
Published: January 2024

In this study, new grain boundary diffusion (GBD) technology is applied to Nd-Fe-B sintered magnets with different thicknesses utilizing DyH3 nanopowder. The weight ratio is 0.25 wt.%. For comparison, the GBD processes include solid-liquid phase separation diffusion (SepD) and solid-liquid phase simultaneous diffusion (SimD). The magnetic properties and microstructure of GBD magnets with different thicknesses are thoroughly investigated. The comprehensive magnetic properties of SepD magnets are higher than SimD magnets. When the magnets are 8 mm thick, the SepD magnet obtains a coercivity of 18.10 kOe, which is higher than the SimD magnets (17.00 kOe). It was determined that SepD can manufacture thick magnets with excellent coercivity. In SepD magnets, the Dy element diffusion distance is deeper than in SimD magnets. For SepD magnets, there are core-shell structures formed in the surface region, while there are anti-core-shell structures that are unfavorable to magnetic properties in the surface region of the SimD magnets. The enhanced coercivity and temperature stability of the SepD magnets is primarily due to the more continuous core-shell structures produced by the deeper diffusion depth of the Dy element. This study will provide more theoretical guidance for the application of SepD in magnets with different thicknesses.
Modality for estimating NMR relaxation time using perturbed angular correlation in double-photon emission nuclides
Authors: Matsumoto Wataru , Feng Boyu , Tamai Yoshiki , Ueki Taisei , Kamada Kei , Uenomachi Mizuki , Tomita Hideki , Fushimi Motofumi , Shimazoe Kenji , Takahashi Hiroyuki , Sekino Masaki
Published: January 2024

T2 relaxation time in magnetic resonance imaging (MRI), which is determined by magnetic dipole interactions, has been employed as a parameter for tumor detection. However, owing to the lack of MRI detection sensitivity, nuclear medicine imaging is currently the basic option for tracking low concentrations of chemical probes. Previous studies utilizing cascade radionuclides have focused on the relaxation due to electric quadrupole interactions. However, magnetic dipole interactions, which are crucial in MRI, remains to be elucidated. In this study, we determined the magnetic relaxation rate by using 111In, a cascade radionuclide used in clinical single-photon emission computed tomography (SPECT) scans. As the angle between the gamma rays from the nuclei is affected by the electrical and magnetic interactions acting on the nuclei, we measured the angular correlation ratio by using eight gadolinium gallium garnet (GAGG) multi-pixel photon counter (MPPC) 8 × 8 array detectors and extracted the magnetic relaxation rate. Consequently, we obtained a rate that increased with the Fe concentration, similar to the T2 relaxation rate, although it was influenced by the inhomogeneity of the external magnetic field. This study utilized low concentrations of the liquid-state radionuclide, which is commonly used in clinical nuclear medicine imaging scans and is expected to provide much higher sensitivity and more selective detection of tumors than conventional MRI.
Low-temperature antiferromagnetism in quaternary Mn2FeSi0.5Al0.5 alloys
Authors: Zivotsky Ondrej , Gembalova Lucie , Skotnicova Katerina , Szurman Ivo , Cegan Tomas , Jurica Jan , Malina Ondrej , Cizek Jakub
Published: January 2024

In this work, the quaternary Mn2FeSi0.5Al0.5 alloys are prepared for the first time in the form of cylinder-shaped ingots by traditional induction melting technique followed by homogenization annealing at 773 K for 100 h. The microstructural and magnetic properties of as-cast and annealed Mn2FeSi0.5Al0.5 samples are analyzed in detail and compared to the Mn2FeSi and Mn2FeAl ternary alloys. The Mn2FeSi0.5Al0.5 ingots are two-phase both before and after annealing, and their diffractograms correspond to the primitive cubic β-Mn structure. Obtained lattice constant of 0.6274 nm is only slightly lower than that of Mn2FeAl alloy (0.6339 nm) and different from Mn2FeSi (0.5672 nm). The existence of both phases enriched in Si at the expense of Al and Mn was confirmed by differential thermal analysis showing two endothermic and exothermic peaks at temperatures of 1363 K and 1407 K. The magnetic properties of both quaternary samples studied in wide temperature range from 5 K to 573 K indicate paramagnetic behavior at room and elevated temperatures. The annealed system has the values of Curie temperature and effective paramagnetic moment comparable to the ternary Mn2FeAl alloy. The transition to antiferromagnetic state occurring at Néel temperatures of 34 K (as-cast sample) and 37 K (annealed sample) is caused by strong geometric frustration of β-Mn structure. The magnetic transitions observed in both samples between Néel and room temperature are discussed in terms of the existence of Griffiths phase.
Improving environmental conditions of a Room and Pillar underground quarry using numerical modelling of the ventilation system
Authors: Nematollahi Sarvestani Amir , Oreste Pierpaolo , Gennaro Sandro
Published: January 2024

Natural ventilation can play a significant role, which requires careful evaluation. It is necessary to adopt numerical calculation methods to study the ventilation circuit. This paper illustrates a numerical study of an underground gypsum quarry in Italy using the Ventsim computer program. Through this study, it was possible to determine the improvement interventions necessary to optimize the airflow that reaches the active sites of the mine, avoiding the risk of air recirculation in the deepest zones. A detailed analysis made it possible to detect how the planned interventions were also able to significantly improve the environmental conditions, considerably lowering the concentration of harmful gases emitted by diesel engines.
Smoke stratification in a mine drift with a burning mining vehicle
Authors: Hansen Rickard
Published: January 2024

A fire in a mine will pose risks to mining personnel, where the smoke spread will be one of the risks. The smoke spread will be largely determined by the stratification. This paper studies the smoke stratification in a mine with a burning vehicle, for varying surface roughness, surface material, and impact of the vehicle. Datawas provided from full-scale experiments in an underground mine. The proposed fire gas temperature correlations successfully captured the smoke stratification in the mine and the influencing turbulence. A numerical model predicted thatnon-stratified conditions can be expected at shorter distances in a mine compared with a tunnel. Longer distances to non-stratified conditions can be expected for materials with low volumetric heat capacity. A long-lasting fire will result in longer distances to non-stratified conditions. With decreasing fire gas temperatures, the heated surface may slow down the decrease or even maintain the distances to non-stratified conditions.
A new mathematical model for the optimization of block aggregation in open pit mines
Authors: Aalian Younes , Mousavi Amin , Bsiri Mohammad Hossein
Published: January 2024

The open-pit production planning is one of the most important steps of mine design which becomes a hard and challenging optimization problem in large-scale mineral deposits. A common approach in such a situation is to cluster mining blocks (smallest mining units) into larger units. In this paper, an integer non-linear programming model of the constrained block clustering is developed with the objective of minimizing grade deviations while blocks are geometrically connected within a cluster and the shape and size of individual clusters are in the pre-defined range. Then, a population-based iterated local search algorithm is presented to solve this nonlinear model and find a near-optimum solution. The proposed model and the solution approach were applied to a case study of a gold and silver deposit with 40,947 blocks. The mining blocks are grouped into 1966 clusters which then mine planner can solve production scheduling in less computational time.
Summing over non-singular paths in quantum cosmology
Authors: Matsui Hiroki
Published: January 2024

In this paper we provide the DeWitt propagator and its wave function in quantum cosmology using the path integral formulation of quantum gravity. The DeWitt boundary condition is introduced as a way to avoid the Big Bang singularity by positing that the wave function of the Universe vanishes near the Big Bang. However, there is currently no clear definition of the DeWitt boundary condition in the path integral formulation. To address this issue, we use the image method, which eliminates singular paths in the forbidden region of the infinite potential, and apply this method to quantum cosmology based on the Batalin–Fradkin–Vilkovisky formulation of the path integral. We investigate the validity of the image method, and in particular, find that this method is only appropriate when the potential has symmetry with respect to the boundary. We then show that the DeWitt propagator and the DeWitt wave function derived from the image method are consistent with solutions of the Wheeler–DeWitt equation for certain models of quantum cosmology.
ΛCDM-Rastall cosmology revisited: constraints from a recent Quasars datasample
Authors: Astorga-Moreno J A , Jacobo Kyra , Arteaga Salvador , García-Aspeitia Miguel A , Hernández-Almada A
Published: January 2024

In this paper we study the impact of a recent quasar datasample in the constraint of the free parameters of an extension of general relativity. As a ruler to test, we use Rastall gravity in the context of background cosmology being a simple extension to general relativity. We compare the results from quasars dataset with other known samples such as cosmic chronometers, supernovae of the Ia type, baryon acoustic oscillations, HII galaxies, and also a joint analysis. Results are consistent with the standard cosmological model emphasizing that Rastall gravity is equivalent to general relativity. According to the constraints provided from the joint sample, the age of the Universe is

τ

U

=

12.601

−
0.066

+
0.067

Gyrs and the transition to an accelerated phase occurs at

z

T

=
0.620
±
0.025

in the redshift scale, being only the phase transition consistent with the standard paradigm and having a younger Universe. With the quasars sample, the Universe age differs with that expected in ΛCDM having a result of

τ

U

=

11.958

−
0.109

+
0.139

Gyrs with a transition at

z

T

=
0.652
±
0.032

this last consistent with standard cosmology. A remarkable result is that quasars constraints has the capability to differentiate among general relativity and Rastall gravity due to the result for the parameter

λ
=
−

2.231

−
0.546

+
0.785

. Moreover, the parameter j under quasars constraints suggests that the cause of the late Universe’s acceleration is a dark energy fluid different from a cosmological constant.
General-relativistic wave–particle duality with torsion
Authors: Guedes Francisco Ribeiro Benard , Popławski Nikodem Janusz
Published: January 2024

We propose that the four-velocity of a Dirac particle is related to its relativistic wave function byui=ψˉγiψ/ψˉψ. This relativistic wave–particle duality relation is demonstrated for a free particle related to a plane wave in a flat spacetime. For a curved spacetime with torsion, the momentum four-vector of a spinor is related to a generator of translation, given by a covariant derivative. The spin angular momentum four-tensor of a spinor is related to a generator of rotation in the Lorentz group. We use the covariant conservation laws for the spin and energy–momentum tensors for a spinor field in the presence of the Einstein–Cartan torsion to show that if the wave satisfies the curved Dirac equation, then the four-velocity, four-momentum, and spin satisfy the classical Mathisson–Papapetrou equations of motion. We show that these equations reduce to the geodesic equation. Consequently, the motion of a particle guided by the four-velocity in the pilot-wave quantum mechanics coincides with the geodesic motion determined by spacetime. We also show how the duality and the operator form of the Mathisson–Papapetrou equations arise from the covariant Heisenberg equation of motion in the presence of torsion.
Optical properties and plasmons in moiré structures
Authors: Kuang Xueheng , Pantaleón Peralta Pierre A , Angel Silva-Guillén Jose , Yuan Shengjun , Guinea Francisco , Zhan Zhen
Published: January 2024

The discoveries of numerous exciting phenomena in twisted bilayer graphene (TBG) are stimulating significant investigations on moiré structures that possess a tunable moiré potential. Optical response can provide insights into the electronic structures and transport phenomena of non-twisted and twisted moiré structures. In this article, we review both experimental and theoretical studies of optical properties such as optical conductivity, dielectric function, non-linear optical response, and plasmons in moiré structures composed of graphene, hexagonal boron nitride (hBN), and/or transition metal dichalcogenides. Firstly, a comprehensive introduction to the widely employed methodology on optical properties is presented. After, moiré potential induced optical conductivity and plasmons in non-twisted structures are reviewed, such as single layer graphene-hBN, bilayer graphene-hBN and graphene-metal moiré heterostructures. Next, recent investigations of twist-angle dependent optical response and plasmons are addressed in twisted moiré structures. Additionally, we discuss how optical properties and plasmons could contribute to the understanding of the many-body effects and superconductivity observed in moiré structures.
Interference of holon strings in 2D Hubbard model
Authors: Wang Chang-Yan , Ho Tin-Lun
Published: January 2024

The 2D Hubbard model with large repulsion is an important problem in condensed matter physics. At half filling, its ground state is an antiferromagnet (AMF). The dope AMF below half filling is believed to capture the physics of high Tc
superconductors. And the fermion excitation of this dope AMF is theorized as splitting up into holons and spinons that carry charge and spin separately. It is believed that these exotic holons and spinons are the origins of the unusual properties of high Tc
superconductors. Despite the interests in holons and spinons, the direct observations of these excitations remain difficult in solid state experiments. Here, we show that with the rapid advances in the experimental techniques in cold atoms, the direct observation of holons is possible in quantum quench dynamic processes in cold atom settings. We show that the well-known holon-strings generated by the motion of a holon as well as their interferences can be detected by the measurements spin–spin correlations and demonstrate the presence of the Marshall phase associated with a holon string reflecting an underlying AMF background. Moreover, we show that the interferences of the holon strings make a holon propagate anisotropically, with a diffusion pattern clearly distinct from that of spinless fermions. At the same time, we show that these interferences lead to a large suppression in magnetic order in the region swept through by the strings (even to about 95% for some bond). We further demonstrate the Marshall phase of the holon-strings by comparing the dynamics of holon in the tJ model with that of the so-called

σ
t
J

-model, which is the tJ model with the Marshall phase removed. The holons in these models propagate entirely differently.
Quantitative investigation of gamma radiation in accelerator produced ISO neutron fields
Authors: Dombrowski H , Nolte R
Published: January 2024

In standard monoenergetic ISO neutron fields, the neutron yield of neutron-producing reactions was measured in combination with the prompt photon yield, including photon energies up to 10 MeV, for the purpose of comparing the two yields. Separating the photons produced by the target (direct photons) from those generated by secondary neutron reactions was achieved using the time-of-flight method. Photon and neutron ambient dose equivalent values were calculated from measured spectral energy distributions. Quasi monoenergetic neutron fields are needed to systematically test the response of measuring instruments to neutron radiation. For this reason, ISO has defined a number of reference neutron radiation fields covering a wide energy range up to 19 MeV. Because neutron detectors may also be affected by photon radiation, the photon fluence in the ISO neutron fields has to be known. This work focuses on quasi monoenergetic accelerator-produced neutron fields in the energy range of 24 keV to 19 MeV.
Absorbed dose coefficients for pediatric differentiated thyroid cancer patients undergoing radioiodine therapy
Authors: Kwon Tae-Eun , Kitahara Cari M , Lee Choonsik
Published: January 2024

The escalating incidence of differentiated thyroid cancer (DTC) in pediatric patients and the resultant growing use of radioactive iodine (RAI) reinforce the need to evaluate radiation exposure to normal tissues and radiation-induced health risks in pediatric patients undergoing RAI therapy. In the current study, we calculated absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq−1) specific for pediatric patients with localized DTC undergoing RAI therapy following total thyroidectomy for use in epidemiological studies. We first modified previously-published biokinetic models for adult thyroid cancer patients to achieve a reasonable agreement with iodine biokinetics observed in pediatric patients or design principles addressed in the International Commission on Radiological Protection (ICRP) reference age-specific biokinetic models. We then combined the biokinetic models in conjunction with S values derived from ICRP reference pediatric voxel phantoms. The absorbed dose coefficients for pediatric patients were overall greater than those for adults with a ratio (pediatric/adult) up to 11.6 and rapidly decreased with increasing age. The sensitivity analysis showed that the renal clearance rate and S values may have the greatest impact on the absorbed dose coefficients with the rank correlation coefficients ranging from −0.53 to −0.82 (negative correlations) and from 0.51 to 0.80 (positive correlations), respectively. The results of the current study may be utilized in clinical or epidemiological studies to estimate organ-specific radiation absorbed doses and radiation-associated health risks among pediatric thyroid cancer patients.
Air kerma reference field with high energy photons using a 15 MeV electron beam from a clinical linear accelerator
Authors: Ishii Junya , Shimizu Morihito , Kato Masahiro , Kurosawa Tadahiro , Watabe Hiroshi
Published: January 2024

In the medical and nuclear fields, there are environments where exposure to photons with energies above several MeV can result in problems. The National Metrology Institute of Japan has developed a high-energy photon field using a 15 MeV electron beam of a clinical linear accelerator with a copper target and an aluminium filter unit to facilitate dosimeter calibration in terms of air kerma. To determine the air kerma rate, the energy fluence distribution at a reference point was calculated, and both calculations and experiments evaluated the effective energy and spatial dose distribution. Moreover, to validate the air kerma measurement, two commercial cavity chambers were calibrated in a developed photon field. The results obtained exhibited a 4% difference compared with those in a Co-60 γ-ray reference field.
A dynamic state estimation method for integrated energy system based on radial basis kernel function
Authors: Chen Tengpeng , Luo Hongxuan , Foo Eddy Y S , Amaratunga Gehan A J
Published: January 2024

For state estimation (SE) of dynamic electro-thermal gas coupled systems, measurements usually assume that the measurement noise obeys a Gaussian distribution. The extended Kalman filter and the unscented Kalman filter (UKF) are some of the widely used estimation methods in SE. However, the measurement noise does not always follow Gaussian distribution in practice. When the measurement noise is non-Gaussian, the performance of these methods may not be satisfactory. In this paper, we propose an unscented Kalman filtering method based on minimizing radial basis kernel function criterion (MRBFC-UKF), which explores the optimal values of the shape parameters of the kernel function instead of using the widely used Gaussian and exponential kernel functions. Simulations are run dynamically in an integrated energy system which comprises an IEEE 14-bus, a 20-node natural gas network and a 32-node local thermal network. The results show that the proposed MRBFC-UKF method has good robustness and accuracy, and can effectively cope with the presence of unexpected bad data inputs.
Three-phase series arc fault detection based on two-dimensional attention PoolFormer
Authors: Yu Qiongfang , Zhang Yuhai , Zhao Liang , Wu Qiong
Published: January 2024

Series arc faults are a major causation of electrical fires. The complexity of load types in low-voltage distribution systems makes arc faults detection more challenging for three-phase circuits with inverters. To solve this problem, this paper proposes a detection method based on two-dimensional attention PoolFormer. Firstly, a low-voltage three-phase series arc faults data acquisition platform is built to collect the required data. The collected current signals are encoded as pictures through image mapping and projected into a more discriminative space, while increasing the magnitude of the dataset. Subsequently, the two-dimensional attention PoolFormer algorithm model is constructed to fully exploit the feature information between different fault categories. This model has multi-scale parallel convolution to extract features of input samples and perform information fusion. Considering also the ability to seize the location characteristics of fault information well, the two-dimensional attention is designed to be added inside the algorithm, to grasp the precise location information to enhance the performance of the algorithm. Finally, the dataset is fed into the two-dimensional attention PoolFormer model for training and testing. The results show that the accuracy of the method proposed in this paper can achieve 99.36%.
Light-emitting diodes with Ge(Si) nanoislands embedded in photonic crystals
Authors: Shmagin V B , Yablonskiy A N , Stepikhova M V , Yurasov D V , Mikhaylov A N , Tetelbaum D I , Rodyakina E E , Morozova E E , Shengurov D V , Kraev S A , Yunin P A , Belov A I , Novikov A V
Published: January 2024

Room temperature lateral p+–i–n+ light-emitting diodes (LEDs) with photonic crystals embedded in the i-region were fabricated on structures with Ge(Si) self-assembled islands and their optical properties were investigated. The use of preliminary amorphization and solid phase epitaxy of the implanted p+ and n+ contact regions made it possible to reduce the impurity activation temperature from 800 °С–1100 °С to 600 °С, which corresponds to the growth temperature of Ge(Si) islands. This resulted in a significant reduction of the detrimental effect of the high-temperature annealing used for diode formation on the intensity and spectral position of the luminescence signal from the islands. It was shown that significant enhancement (more than an order of magnitude) of room temperature electroluminescence of Ge(Si) islands in the spectral range of 1.3–1.55 μm can be achieved due to their interaction with different modes of the photonic crystals. The measured radiation power of the obtained diodes in the spectral range of 1.3–1.55 μm exceeds 50 pW at a pump current of 8 mA, which is an order of magnitude higher than the previously achieved values for micro-LEDs with Ge(Si) nanoislands. The obtained results open up new possibilities for the realization of silicon-based light emitting devices operating at telecommunication wavelengths.
Analyzer-free hard x-ray interferometry
Authors: Bertilson M , von Hofsten O , Maltz J S , Taphorn K , Herzen J , Danielsson M
Published: January 2024

Objective. To enable practical interferometry-based phase contrast CT using standard incoherent x-ray sources, we propose an imaging system where the analyzer grating is replaced by a high-resolution detector. Since there is no need to perform multiple exposures (with the analyzer grating at different positions) at each scan angle, this scheme is compatible with continuous-rotation CT apparatus, and has the potential to reduce patient radiation dose and patient motion artifacts. Approach. Grating-based x-ray interferometry is a well-studied technique for imaging soft tissues and highly scattering objects embedded in such tissues. In addition to the traditional x-ray absorption-based image, this technique allows reconstruction of the object phase and small-angle scattering information. When using conventional incoherent, polychromatic, hard x-ray tubes as sources, three gratings are usually employed. To sufficiently resolve the pattern generated in these interferometers with contemporary x-ray detectors, an analyzer grating is used, and consequently multiple images need to be acquired for each view angle. This adds complexity to the imaging system, slows image acquisition and thus increases sensitivity to patient motion, and is not dose efficient. By simulating image formation based on wave propagation, and proposing a novel phase retrieval algorithm based on a virtual grating, we assess the potential of a analyzer-grating-free system to overcome these limitations. Main results. We demonstrate that the removal of the analyzer-grating can produce equal image contrast-to-noise ratio at reduced dose (by a factor of 5), without prolonging scan duration. Significance. By demonstrating that an analyzer-free CT system, in conjuction with an efficient phase retrieval algorithm, can overcome the prohibitive dose and workflow penalties associated grating-stepping, an alternative path towards realizing clinical inteferometric CT appears possible.