bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetric flow in a double-suction centrifugal fan induced by an inclined impeller
Authors: Chen Zhiyun , He Haijiang , Yang Hui , Wei Yikun , Zhang Wei
Published: January 2024

The impeller and volute of a centrifugal fan are designed to be coaxially placed; however, the impeller might be inclined about the central axis of the volute due to installation fault, inducing asymmetric flow in the left and right halves of the fan. We performed a detailed numerical investigation on the non-uniform and asymmetric flow in a double-suction multi-blade centrifugal fan with a slightly inclined impeller using the unsteady Reynolds-averaged Navier–Stokes simulation approach. The impeller is assumed to rotate about each of the two minor axes perpendicular to the central axis to model the inclination. This work aims to quantify the influence of the impeller inclination on the aerodynamic performance of the centrifugal fan and to reveal the physics of transient flow in the two halves of the fan to demonstrate the impact of various inclination ways. Numerical results denote that a slight impeller inclination could stabilize the flow in the fan, while the flow is highly asymmetric as the inclination is enhanced, and the efficiency of the fan decreases due to the recirculation generated by the interaction of flow exiting from the impeller. An in-depth inspection shows sharply intensified pressure fluctuation at the collector, where the local clearance varies. The flow entering the collector and impeller substantially decreases in velocity, resulting in separated flow in part of the blade passages. The flow in the volute is also asymmetric since the impeller outlet is biased toward the volute wall.
Linear and angular momentum conservation in surface hopping methods
Authors: Wu Yanze , Rawlinson Jonathan , Littlejohn Robert G. , Subotnik Joseph E.
Published: January 2024

We demonstrate that, for systems with spin–orbit coupling and an odd number of electrons, the standard fewest switches surface hopping algorithm does not conserve the total linear or angular momentum. This lack of conservation arises not so much from the hopping direction (which is easily adjusted) but more generally from propagating adiabatic dynamics along surfaces that are not time reversible. We show that one solution to this problem is to run along eigenvalues of phase-space electronic Hamiltonians H(R, P) (i.e., electronic Hamiltonians that depend on both nuclear position and momentum) with an electronic–nuclear coupling Γ · P [see Eq. (25)], and we delineate the conditions that must be satisfied by the operator Γ. The present results should be extremely useful as far as developing new semiclassical approaches that can treat systems where the nuclear, electronic orbital, and electronic spin degrees of freedom altogether are all coupled together, hopefully including systems displaying the chiral-induced spin selectivity effect.
Laun's rule for predicting the first normal stress coefficient in complex fluids: A comprehensive investigation using fractional calculus
Authors: Das Mohua , Rathinaraj Joshua David John , Palade Liviu Iulian , McKinley FRS Gareth H.
Published: January 2024

Laun's rule [H. M. Laun, “Prediction of elastic strains of polymer melts in shear and elongation,” J. Rheol. 30, 459–501 (1986).] is commonly used for evaluating the rate-dependent first normal stress coefficient from the frequency dependence of the complex modulus. We investigate the mathematical conditions underlying the validity of Laun's relationship by employing the time-strain–separable Wagner constitutive formulation to develop an integral expression for the first normal stress coefficient of a complex fluid in steady shear flow. We utilize the fractional Maxwell liquid model to describe the linear relaxation dynamics compactly and accurately and incorporate material nonlinearities using a generalized damping function of Soskey–Winter form. We evaluate this integral representation of the first normal stress coefficient numerically and compare the predictions with Laun's empirical expression. For materials with a broad relaxation spectrum and sufficiently strong strain softening, Laun's relationship enables measurements of linear viscoelastic data to predict the general functional form of the first normal stress coefficient but often with a noticeable quantitative offset. Its predictive power can be enhanced by augmenting the original expression with an adjustable power-law index that is based on the linear viscoelastic characteristics of the specific material being considered. We develop an analytical expression enabling the calculation of the optimal power-law index from the frequency dependence of the viscoelastic spectrum and the strain-softening characteristics of the material. To illustrate this new framework, we analyze published data for an entangled polymer melt and for a semiflexible polymer solution; in both cases our new approach shows significantly improved prediction of the experimentally measured first normal stress coefficient.
Vibronic coupling of Rhodamine 6G molecules studied by doubly resonant sum frequency generation spectroscopy with narrowband infrared and broadband visible
Authors: Zeng Wei-Wang , Luo Ting , Xu Peng , Zhou Chuanyao , Yang Xueming , Ren Zefeng
Published: January 2024

Doubly resonant sum frequency generation (DR-SFG) serves as a potent characteristic technique for probing the electronic spectra and vibronic coupling of molecules on surfaces. In this study, we successfully developed a novel infrared (IR)–white light (WL) DR-SFG spectroscopy based on narrowband IR and tunable broadband WL. This novel method was employed to explore the excitation spectrum and vibronic couplings of sub-monolayer Rhodamine 6G molecules. Our findings elucidate that the xanthene skeleton vibrational modes exhibit strong coupling with the S0–S1 electronic transition. Notably, we observed not only the 0–0 transition of the S0–S1 electronic continuum but also the 0–1 transition, a first time observation in the realm of DR-SFG spectroscopy. This advanced DR-SFG spectroscopy methodology facilitates a more sensitive examination of electronic spectra and the coupling between electronic transitions and vibrational modes, heralding a significant advancement in the understanding of molecular interactions on surfaces.
Wall effect on the wake characteristics of a transversely rotating sphere
Authors: Kumar Abhishek , Das S. P. , Tiwari Shaligram
Published: January 2024

In the present work, the flow over a transversely rotating sphere placed at varying separation from a plane wall at a Reynolds number Re=U∞Dν of 300 is numerically investigated using Open Source Field Operation and Manipulation, where Re is defined based on the free stream velocity (U∞) and the diameter (D) of the sphere. Three values of the non-dimensional rotational speed ω*=ωD2U∞, viz., −1, 0 and 1, have been chosen with ω being the dimensional rotation rate with anticlockwise rotation being positive. The non-dimensional separation gap G=gD between the sphere and the wall is varied from 0.25 to 3.0. Here, g is the dimensional gap between the sphere and the wall. At ω*=0 and G = 0.25, the wall completely suppresses vortex shedding from the sphere, whereas flow is found to be unsteady for other values of ω* and G. As compared to the case in the absence of the wall, the presence of the wall causes an increase in vortex shedding frequency for ω*=0 and 1 and decrease for ω*=−1. Hilbert spectrum reveals that the wake nonlinearity remains unchanged with an increase in G for ω*=0. On the other hand, it increases for ω*=−1 and decreases for ω*=1. Similar to the observation made for vortex shedding, the presence of wall increases drag force on the sphere for ω*=0 and 1 and decreases for ω*=−1. In order to reveal the spatial and temporal behavior of the coherent structures in the unsteady wake, dynamic mode decomposition (DMD) has been performed. For all the values of G, DMD mode 1 is found to be the primary vortex shedding mode.
Extensive analysis of the applicability range of the linear kinetic approaches in the case of the pressure driven gas mixture flows
Authors: Tantos C. , Teichmann T. , Sarris I. , Day C.
Published: January 2024

The study of gas mixture flows through micro- and macro-channels remains a very attractive area for theorists and experimentalists worldwide, mainly due to their great practical applicability in several aspects of science and industry. The present work includes a comparative study between the linear (McCormack model) and the nonlinear (DSMC method) kinetic theories of binary gas mixture flows through channels over a wide range of the involved parameters. The results show that the McCormack model is a reliable kinetic model for predicting the gas mixture flow behavior. Specific criteria with respect to the applicability range of the linear kinetic theory of short and long capillaries are proposed. The analysis shows that the separation phenomenon remains strong even in the case of small pressure drops. The applicability range of the linear kinetic theory for binary gas mixture flows driven by large pressure drops is obtained to be smaller compared to that of single gases but still wide enough covering a wide range of pressure ratios. Furthermore, the present work shows that the long capillary theory remains a very powerful tool for studying the gas mixture flow behavior under weak and strong nonequilibrium conditions. This work provides a kinetic database of the linear kinetic data (as supplementary material), which until today is still missing from the literature, and as it is shown throughout this work, it can be used far beyond the restrictions defined by the linear kinetic theory.
Coexistence and competition: Double attractors in hybrid mode-locked fiber lasers
Authors: Lv Chenyue , Lu Baole , Bai Jintao
Published: January 2024

The hybrid mode-locking technique has been widely used in enhancing pulse quality, but the specific mechanism of hybrid mode-locking remains unclear. In this work, we experimentally investigate three pulse formation mechanisms in saturable absorbers (SA) and nonlinear polarization evolution (NPE) passively hybrid mode-locked fiber laser, which are SA domination, NPE domination, and SA-NPE co-domination switching and clarified the existent dynamic competition and cooperation between the two mode-locking mechanisms of the hybrid mode-locked fiber laser. The method of simulating the filtered gain spectrum with customized filtering is proposed, and the switching of pulse formation mechanisms is numerically investigated using the coupled Ginzburg–Landau equations. The presence of a double attractor subsystem in a hybrid mode-locked fiber laser is proposed and demonstrated. Our results deepen the understanding of hybrid mode-locked fiber lasers and provide experimental ideas for the study of multi-attractor coexistence.
Scraper factors investigation on Al2O3 paste flow based on marine predators algorithm-bidirectional gated recurrent unit pseudo-lattice Boltzmann method for stereolithography molding
Authors: Wu Weiwei , Liu Xin , Gu Minheng , Ding Shuang , Zhang Yanjun , Wei Xinlong
Published: January 2024

The coating process is an essential part of stereolithography technology to mold alumina paste, achieved using a scraper. The characteristics of the scraper (geometry and roughness) are investigated to discover the potential influence mechanism on the coating process. To complete the analysis, the bidirectional gated recurrent unit (BiGRU) optimized by the marine predator algorithm (MPA) is proposed to provide a predicted model for the rheological data instead of the traditional fitting by using the known rheological equations. Then, a pseudo-lattice Boltzmann (pseudo-LB) method is proposed to conduct the coating flow simulation without a specific rheological equation, where the predicted rheological model is applied to obtain the relaxation time for each iteration. Based on the above MPA-BiGRU pseudo-LB method, three geometries and different roughnesses are explored for the coating process. The results indicate that the rectangle geometry suits the large coating speed, and the trapezium geometry is recommended for conditions with the small coating speed. The roughness significantly affects the coating process with the rectangle geometry, and the smoother scraper generates a minor disturbance. However, it is almost ineffective in the cases with trapezium geometry.
Role of cavity in a Mach 8 axisymmetric scramjet combustor: Flame stabilization vs combustion enhancement
Authors: Ma Guangwei , Zhao Guoyan , Sun Mingbo , Tang Tao , Li Fan , Xiong Dapeng
Published: January 2024

The cavity-assisted scramjet has been proven to be the most promising propulsion system for air-breathing hypersonic vehicles. In this paper, numerical simulations of a Mach 8 axisymmetric scramjet combustor are conducted and validated to investigate the effect of the cavity. The results indicate that the combustion state undergoes significant changes as the combustion heat release increases. Detailed analysis reveals that the role of the cavity in flame stabilization and combustion enhancement also changes with combustion heat release. Under weak heat release conditions, the high-speed environment results in reduced combustion efficiency, and the primary role of the cavity is to stabilize the flame. Increasing the cavity size does not yield significant gains but could bring redundant mass. As heat release intensifies, the combustion enhancement effect of the cavity becomes more prominent. The presence of the cavity dramatically improves fuel combustion efficiency. The distribution of supersonic and subsonic combustion modes, as well as that of premixed and diffusion combustion modes, is also affected by cavity size and combustion heat release. In the engineering development of scramjets, it is suggested that the design of the cavity flameholder should involve careful consideration of combustion heat release.
Spin reorientation transition in (110)-oriented NiCo2O4 epitaxial thin films
Authors: Wang Yuqi , Wu Yang , Liu Shengkai , Xi Zhongnan , Hou Pengxiang , Han Yajie , Wu Di
Published: January 2024

Magnetic anisotropy is an important character for magnetic materials. In this work, magnetic anisotropy of (110)-oriented ferrimagnetic NiCo2O4 (NCO) thin films deposited epitaxially on MgAl2O4 substrates by pulsed laser deposition is studied and compared with (001)-oriented NCO films. While the (001)-oriented films show a perpendicular magnetic anisotropy with the out-of-plane [001] direction as the magnetic easy axis, a jump in magnetic hysteresis loop is observed for the (110)-oriented films with a field applied vertically along the out-of-plane [110] direction. This jump in hysteresis loop is associated with a spin reorientation transition, depending on the applied field and temperature. Magnetic force microscopy reveals that this spin reorientation develops as domains nucleate, grow, and coalesce. This spin reorientation transition is discussed in terms of the competition between different magnetic anisotropy in an external field.
Validation of wall boundary conditions for simulating complex fluid flows via the Boltzmann equation: Momentum transport and skin friction
Authors: Dzanic T. , Witherden F. D. , Martinelli L.
Published: January 2024

The influence and validity of wall boundary conditions for non-equilibrium fluid flows described by the Boltzmann equation remains an open problem. The substantial computational cost of directly solving the Boltzmann equation has limited the extent of numerical validation studies to simple, often two-dimensional, flow problems. Recent algorithmic advancements for the Boltzmann–Bhatnagar–Gross–Krook equation introduced by the authors [Dzanic et al., J. Comput. Phys. 486, 112146 (2023)], consisting of a highly efficient high-order spatial discretization augmented with a discretely conservative velocity model, have made it feasible to accurately simulate unsteady three-dimensional flow problems across both the rarefied and continuum regimes. This work presents a comprehensive evaluation and validation of wall boundary conditions across a variety of flow regimes, primarily for the purpose of exploring their effects on momentum transfer in the low Mach limit. Results are presented for a range of steady and unsteady wall-bounded flow problems across both the rarefied and continuum regimes, from canonical two-dimensional laminar flows to unsteady three-dimensional transitional and turbulent flows, the latter of which are the first instances of wall-bounded turbulent flows computed by directly solving the Boltzmann equation. We show that approximations of the molecular gas dynamics equations can accurately predict both non-equilibrium phenomena and complex hydrodynamic flow instabilities and show how spatial and velocity domain resolution affect the accuracy. The results indicate that an accurate approximation of particle transport (i.e., high spatial resolution) is significantly more important than particle collision (i.e., high velocity domain resolution) for predicting flow instabilities and momentum transfer consistent with that predicted by the hydrodynamic equations and that these effects can be computed accurately even with very few degrees of freedom in the velocity domain. These findings suggest that highly accurate spatial schemes (e.g., high-order schemes) are a promising approach for solving molecular gas dynamics for complex flows and that the direct solution of the Boltzmann equation can be performed at a reasonable cost when compared to hydrodynamic simulations at the same level of resolution.
A decentralized dispatch model for multiple micro energy grids system considering renewable energy uncertainties and energy interactions
Authors: Si Shengli , Sun Wei , Wang Yuwei
Published: January 2024

Micro energy grids (MEGs) play a vital role in realizing carbon neutrality and efficient utilization of renewable energy resources. This research focuses on optimizing the synergy of MEG interconnections. Given the diverse development paths of different operating entities within the system, information barriers emerge among MEGs, creating great difficulties for the collaborative system management. In response, this paper proposes a decentralized coordinated dispatch model targeting multiple stakeholders within the system. This model accounts for energy interactions between MEGs and the inherent uncertainty associated with renewable energy sources. Specifically, stochastic optimization approach was applied to characterize the uncertainty of renewable energy output by generating stochastic scenarios. Furthermore, it incorporates the analytical target cascading (ATC) method to decouple objective functions and constraints, creating autonomous scheduling sub-models for individual MEGs. This decentralized approach ensures independent modeling and coordinated problem-solving. Simulations verify that (1) the ATC-based inter-MEG energy interaction strategy effectively achieves decentralized coordinated scheduling of multiple MEGs and (2) the decentralized coordinated scheduling solution closely approximates the global optimum while considering the interest of various system entities.
Prevalence of pathogens important to human and companion animal health in an urban unowned cat population
Authors: Michaelian Tamar , Harriott Lana , Gentle Matthew , Proboste Tatiana , Ho Ian Kei , Cobbold Rowland
Published: January 2024

Context The deleterious impacts of cat predation on wildlife have been well documented. Additionally, unowned cats may act as reservoirs of disease important to public and companion animal health and their proclivity for roaming and fighting enables effective disease transmission. Urban environments support the highest human populations and companion animal densities, increasing the potential for disease transmission from unowned cats to people and pets. However, there is little data on the prevalence of pathogens in unowned cat populations. Aims This aim of this research was to establish baseline prevalence data for priority pathogens in an urban population of unowned cats. Methods One hundred unowned cat cadavers were collected from the Brisbane City Council region, Queensland, Australia. Blood and additional organ or tissue samples were collected post-mortem. Diagnostic methods for pathogen detection included use of real-time polymerase-chain reaction, commercially available rapid enzyme-linked-immunosorbent assay, lavage and faecal flotation. Key results Pathogen carriage was found in 79% (95% CI 71, 87%) of sampled cats. In total, 62% (95% CI 52, 72%) of cats showed evidence of co-carriage of two or more pathogenic organisms. The overall prevalence found for pathogens and parasites investigated were: Toxoplasma gondii, 7% (95% CI 2, 12%); Coxiella burnetii, 0.0% (95% CI 0, 0%); feline immunodeficiency virus, 12% (95% CI 6, 18%); feline leukaemia virus, 0.0% (95% CI 0, 0%); and gastrointestinal parasites, 76.8% (95% CI 68, 85%). Conclusions This study reports contemporary prevalence data for these pathogens that have not previously been available for unowned cats of south-east Queensland. High rates of gastrointestinal parasitism observed throughout the study population prompt concerns of a general increase in pathogenic prevalence, especially in comparison with that of owned domestic cats, as per previously published literature. The presence of signs of fighting is an important risk factor for increased likelihood of infection. Implications Data produced from this study contribute to informing cat management efforts throughout urban regions. Continued and expanded investigations, considering prevalence and risk factors of pathogens important to human and companion animal health, are recommended for the south-east Queensland area and beyond.
Variation in the bird-name lexicon in Qaqet (East New Britain Province, Papua New Guinea)
Authors: Frye Henrike , Si Aung
Published: January 2024

Birds are of great cultural importance to the Qaqet-Baining people of East New Britain Province, Papua New Guinea.
In this paper, we investigate whether there are differences in people’s ability to name common birds in the local environment, and
focus primarily on the variables gender and location. We showed pictures of local birds to small groups of Qaqet speakers in two
villages—one located in an area of significant deforestation—and asked them to name them. Overall, men were able to name more
birds, as were people from the village associated with greater forest cover. Our results show that gender, environmental
degradation and shift to the local lingua franca Tok Pisin may all be responsible for the variation in Qaqet people’s
ethno-ornithological lexicon.
Sociophonetic variation in the alveolar lateral in Yami
Authors: Lai Li-Fang , Gooden Shelome
Published: January 2024

This paper examines lateral (/l/) variation in Yami, an indigenous language of Orchid Island, Taiwan. New acoustic evidence on F2–F1 distance and duration shows that palatalized laterals [lj] in Yami are characterized by greater formant distance and longer duration. These acoustic correlates are influenced by a mixed bag of social and linguistic factors, indicating the need for a coordinated assessment of these factors. Results also suggest that in general, younger, less-rooted, and Mandarin-dominant speakers have a narrower formant distance and shorter duration, indicating a less palatal-like /l/ pronunciation. The loss of [lj] among these speakers may be linked to a rapidly changing linguistic ecology, which fuels cross-linguistic transfer from Mandarin, the language of communication with outsiders. Since [lj] only occurs in Yami, younger speakers may have converged towards Mandarin and predominantly use [l]s, leading to a restructuring process in Yami phonology.
The semantics of taste in interaction
Authors: Mondada Lorenza
Published: January 2024

Tasting sessions constitute a perspicuous setting that reveals how a community of practice uses and shapes
specialized lexicons and semantics within a situated and embodied activity. The activity aims at associating words and sensations:
Participants engage with material objects (samples to taste), and utter/write down words corresponding to the way they experience
them through their senses. This association between words and sensorial qualities constitutes an endogenous semantic task. This
task can be seen as a respecification of various semantic problems, addressing within social interaction several semantic issues,
such as the embodied grounding of sensory semantics, qualia, sensory lexicons, and specialized terminological
repertoires. The paper is based on video recordings of training tasting sessions for professional cheese tasters in Italy and
Italian Switzerland. The analyses show how participants engage not only in describing sensorial features, but also in normatively
assessing the descriptors used, categorizing them as well as the features described as more or less standard. Moreover, the
descriptive task is also guided by the use of several artefacts, such as tasting sheets to fill in and official repertoires of
terminology available to read, which further socialize the participants. The analysis shows the reflexive mutual shaping of
lexicons and sensations as well as the way participants address the semantics of taste in situ.
A deep learning technique to control the non-linear dynamics of a gravitational-wave interferometer
Authors: Xiangyuan Ma Peter , Vajente Gabriele
Published: January 2024

In this work we developed a deep learning technique that successfully solves a non-linear dynamic control problem. Instead of directly tackling the control problem, we combined methods in probabilistic neural networks and a Kalman-filter-inspired model to build a non-linear state estimator for the system. We then used the estimated states to implement a trivial controller for the now fully observable system. We applied this technique to a crucial non-linear control problem that arises in the operation of the Laser Interferometer Gravitational-Wave Observatory (LIGO) system, an interferometric gravitational-wave observatory. We demonstrated in simulation that our approach can learn from data to estimate the state of the system, allowing a successful control of the interferometer’s mirror. We also developed a computationally efficient model that can run in real time at high sampling rate on a single modern CPU core, one of the key requirements for the implementation of our solution in the LIGO digital control system. We believe these techniques could be used to help tackle similar non-linear control problems in other applications.
Enhancement of perovskite spontaneous emission by phase change materials
Authors: Litvinov D A , Kushchenko O M , Sinelnik A D , Rybin M V
Published: January 2024

Controlling the spontaneous emission intensity of perovskites is one of the main unsolved problems of perovskite photonics. To date, to solve this problem, chemical methods have been used to passivate defects in the material and thereby to increase the radiation intensity. However, this method does not allow reversible control of the spontaneous emission intensity of perovskites. Here, we theoretically demonstrate the reversibly controlling the spontaneous emission of perovskites through the use of phase change materials (PCMs). We show changes in the Purcell factor by more than 50% with a change in the PCM phase in the all-visible wavelength range. We also conduct a comparative analysis of the two most popular PCMs, namely Ge–Sb–Te and SbSe. We anticipate that our theoretical results will serve as a foundation for future technological solutions for the development of tunable radiation sources.
Feasibility study to characterize the production of antineutrons in high energy pp collisions through charge exchange interactions
Authors: Lugo-Porras F , Gomez-Coral D M , Menchaca-Rocha A
Published: January 2024

Simulations to evaluate the feasibility of antineutron identification and kinematic characterization via the hadronic charge exchange (CEX) interaction

n

+

n
¯

→

p

+

p
¯

are reported. The target neutrons are those composing the silicon nuclei of which inner tracking devices present in the Large Hadron Collider experiments ALICE, ATLAS, and CMS. Simulations of pp collisions in PYTHIA were carried out at different energies to investigate

n

¯

production and energy spectra. These simulations produced a decreasing power-law

n

¯

energy spectra. Then, two types of GEANT4 simulations were performed, placing an

n

¯

point source at the ALICE primary vertex, as a working example. In the first simulation, the kinetic energy E

k
was kept at an arbitrary (1 GeV) fix value to develop an

n

¯

identification and kinematics reconstruction protocol. The second GEANT4 simulation used the resulting PYTHIA at

s

pp

=

13

TeV

n

¯

energy spectra. In both GEANT4 simulations, the occurrence of CEX interactions was identified by the unique outgoing

p

¯

. The simplified simulation allowed to estimate a 0.11% CEX-interaction identification efficiency at E

k
= 1 GeV. The p CEX-partner identification is challenging because of the presence of silicon nucleus-fragmentation protons. Momentum correlations between the

n

¯

and all possible

p

¯

p

pairs showed that p CEX-partner identification and

n

¯

kinematics reconstruction corresponds to minimal momentum-loss events. The use of inner tracking system dE/dx information is found to improve

n

¯

identification and kinematic characterization in both GEANT4 simulations. The final protocol applied to the realistic GEANT4 simulation resulted in a

n

¯

identification and kinematic reconstruction efficiency of 0.006%, based solely on

p

¯

p

pair observable. If applied to the ALICE minimum-bias RUN2 pp at

s

pp

=
13

TeV data sample, this technique is found to have the potential to identify and reconstruct the kinematics of

4.3
×

10

8

n

¯

's, illustrating the feasibility of the method.
The thermal history of the directed energy deposition process monitored by pyrometer and camera
Authors: Li Jiansen , Liu Tingting , Zhang Kai , Zou Zhiyong , Lu Xing , Zhu Zhiguang
Published: January 2024

In the process of directed energy deposition (DED), the local thermal history of a component can change significantly owing to its complex heat transfer characteristics. The main objective of this study is to elucidate the distribution of the thermal history of a static scroll plate by monitoring its manufacturing process through a pyrometer and camera and to provide insights into the factors affecting the variation of its thermal history from the point of view of the part shape and scanning strategy. The melt pool area and temperature were extracted using a camera and pyrometer as the thermal features under study, and the thermal features were mapped in three dimensions. This mapping strategy provides a comprehensive visualization of the distribution of thermal features in parts with equal and variable cross-section structures. In the case of an equal cross-section structure, three factors, printing time, scan vector length, and probability density, are selected to analyze the main factors affecting the distribution of thermal features. In the case of the variable cross-section structure, the effects of the layer printing time, cumulative layer printing time, and probability density on the distribution of thermal features were analyzed. By calculating the correlation between the thermal features of the monitored signals and the factors mentioned above, it was found that the factors affecting the thermal distribution of the parts vary in different structures. In equal cross-section structures, the probability density plays a pivotal role, while in variable cross-section structures, the cumulative layer printing time has the most significant influence on the thermal distribution. The above studies have provided a better understanding of the thermal processes of DED technology, paving the way for the control and optimization of DED manufacturing.
Underwater target correlation detection and location method based on normalized magnetic moment
Authors: Jin Huanghuang , Wang Hong , Zhuang Zhihong , Qian Qingwen , Wu Chengwei , Shi Yungui
Published: January 2024

For the dynamic magnetic detection platform represented by airborne magnetic anomaly detection, the magnetic field measured by the vector magnetometer is easily affected by the rapid attitude change. Therefore, traditional anti-submarine aircraft are equipped with scalar magnetometers that are less affected by changes in the carrier attitude. However, the scalar magnetometer can only measure the total magnetic field signal, and its measurement information is single. It contains a time-varying environmental magnetic field signal, including the geomagnetic field, which is difficult to effectively reject. This brings great difficulties to the single real-time location of a magnetic anomaly target. This paper proposes a target correlation detection method based on the normalized magnetic moment that can effectively solve the above problems, considering the rotational invariance of magnetic anomaly measurements for dynamic magnetic exploration platforms and the efficient detection methods required for the single real-time positioning of targets. Correlation detection based on the normalized magnetic moment characteristic function and characteristic time search based on the correlation detection are included. Simulation and experimental results verify the single-point real-time positioning ability of the improved detection method within an effective operating distance. This method has strong usability for actual magnetic anomaly detection of underwater targets.
Borehole transient electromagnetic response calculation and experimental study in coal mine tunnels
Authors: Sun Qidi , Ding Hao , Sun Yong , Yi Xiaofeng
Published: January 2024

Water damage seriously threatens the safe production of coal mines, so it is necessary to carry out advanced detection to determine the hydrogeological situation, and the preliminary survey often involves the drilling of on-site drill holes in the tunnel. The use of directional drill holes, combined with advanced geophysical prospecting technology, enables advanced water disaster detection with long distance and high precision and is independent of the tunnel environment influence. The transient electromagnetic method (TEM) is highly sensitive to low-resistivity anomalies and plays a crucial role in water damage detection. To address the size limitation of borehole detection, in this study, a small rectangular multi-turn loop borehole advanced detection method was developed (borehole TEM, BTEM) to detect low-resistivity anomalies within 10 m of the borehole in the radial direction. To satisfy the size requirements for borehole detection and the detection distance, a small rectangular multi-turn loop device with a width of 6 cm and a length of 50 cm was designed. To resolve the issue of self-inductance and mutual inductance enhancement caused by multi-turn coils, a uniform full-space low-resistivity abnormal body model was established using the Ansys Maxwell software, and we analyzed the vertical magnetic field component of the rectangular multi-turn small loop at different time points and the transient electromagnetic response of the different turns. Then, we determined the appropriate parameters for the transmitting and receiving device. The developed method was applied to several different experimental scenarios to obtain the electrical distribution of the anomalous body in front of the device, and the measured data were inverted and interpreted to obtain the apparent resistivity-depth profile. The results demonstrate that the inversion results align well with the actual situation, confirming the effectiveness of the BTEM. This research offers a potential solution for borehole advance detection and provides a solid theoretical foundation for further studies.
Lateral junctions of transition metal dichalcogenides as ballistic channels for straintronic applications
Authors: Dechamps Samuel , Nguyen Viet-Hung , Charlier Jean-Christophe
Published: January 2024

In the context of advanced nanoelectronics, two-dimensional semiconductors such as transition metal dichalcogenides (TMDs) are gaining considerable interest due to their ultimate thinness, clean surface and high carrier mobility. The engineering prospects offered by those materials are further enlarged by the recent realization of atomically sharp TMD-based lateral junctions, whose electronic properties are governed by strain effects arising from the constituents lattice mismatch. Although most theoretical studies considered only misfit strain, first-principles simulations are employed here to investigate the transport properties under external deformation of a three-terminal device constructed from a MoS2/WSe2/MoS2 junction. Large modulation of the current is reported owing to the change in band offset, illustrating the importance of strain on the p–n junction characteristics. The device operation is demonstrated for both local and global deformations, even for ultra-short channels, suggesting potential applications for ultra-thin body straintronics.
Structural, chemical, and magnetic investigation of a graphene/cobalt/platinum multilayer system on silicon carbide
Authors: Weinert P , Hochhaus J , Kesper L , Appel R , Hilgers S , Schmitz M , Schulte M , Hönig R , Kronast F , Valencia S , Kruskopf M , Chatterjee A , Berges U , Westphal C
Published: January 2024

We investigate the magnetic interlayer coupling and domain structure of ultra-thin ferromagnetic (FM) cobalt (Co) layers embedded between a graphene (G) layer and a platinum (Pt) layer on a silicon carbide (SiC) substrate (G/Co/Pt on SiC). Experimentally, a combination of x-ray photoemission electron microscopy with x-ray magnetic circular dichroism has been carried out at the Co L-edge. Furthermore, structural and chemical properties of the system have been investigated using low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS). In situ LEED patterns revealed the crystalline structure of each layer within the system. Moreover, XPS confirmed the presence of quasi-freestanding graphene, the absence of cobalt silicide, and the appearance of two silicon carbide surface components due to Pt intercalation. Thus, the Pt-layer effectively functions as a diffusion barrier. The magnetic structure of the system was unaffected by the substrate’s step structure. Furthermore, numerous vortices and anti-vortices were found in all samples, distributed all over the surfaces, indicating Dzyaloshinskii–Moriya interaction. Only regions with a locally increased Co-layer thickness showed no vortices. Moreover, unlike in similar systems, the magnetization was predominantly in-plane, so no perpendicular magnetic anisotropy was found.
Towards large scale integration of MoS2/graphene heterostructure with ALD-grown MoS2
Authors: Hyot Bérangère , Ligaud Clotilde , Yoo Tae Jin , David-Vifflantzeff Julien , Gauthier Nicolas , Cadot Stéphane , Le Van Hoan , Brunet Paul , Le Van-Jodin Lucie
Published: January 2024

In the pursuit of ultrathin and highly sensitive photodetectors, a promising approach involves leveraging the combination of light-sensitive two-dimensional (2D) semiconducting transition-metal dichalcogenides, such as MoS2 and the high electrical conductivity of graphene. Over the past decade, exfoliated 2D materials and electron-beam lithography have been used extensively to demonstrate feasibility on single devices. But for these devices to be used in the real-world systems, it is necessary to demonstrate good device performance similar to lab-based devices with repeatability of the results from device to device and a path to large scale manufacturing. To work in this way, a fabrication process of MoS2/graphene vertical heterostructures with a wafer-scale integration in a CMOS compatible foundry environment is evaluated here. Large-scale atomic layer deposition on 8 inch silicon wafers is used for the growth of MoS2 layers which are then transferred on a 4 inch graphene-based wafer. The MoS2/graphene phototransistors are fabricated collectively, achieving a minimum channel length of 10 μm. The results measured on dozen of devices demonstrate a photoresponsivity of 50 A W−1 and a remarkable sensitivity as low as 10 nW at 660 nm. These results not only compete with lab-based photodetectors made of chemical vapor deposition grown MoS2 layers transferred on graphene, but also pave the way for the large-scale integration of these emerging 2D heterostructures in optoelectronic devices and sensors.
Rational design of hollow flower-like MoS2/Mo2C heterostructures in N-doped carbon substrate for synergistically accelerating adsorption-electrocatalysis of polysulfides in lithium sulfur batteries
Authors: Liu Hui , Tian Xin , Liu Yi , Munir Hafiz Akif , Hu Weihang , Fan Xiuyi , Pang Lingyan
Published: January 2024

Lithium–sulfur (Li–S) batteries have been garnered significant attention in the energy storage field due to their high theoretical specific capacity and low cost. However, Li–S batteries suffer from issues like the shuttle effect, poor conductivity, and sluggish chemical reaction kinetics, which hinder their practical development. Herein, a novel hollow flower-like architecture composed of MoS2/Mo2C heterostructures in N-doped carbon substrate (H-Mo2S/Mo2C/NC NFs), which were well designed and prepared through a calcination-vulcanization method, were used as high-efficiency catalyst to propel polysulfide redox kinetics. Ex situ electrochemical impedance spectroscopy verify that the abundant heterojunctions could facilitate electron and ion transfer, revealed the excellent interface solid–liquid–solid conversion reaction. The adsorption test of Li2S6 showed that Mo2S and Mo2C formed heterostructure generate the binding of polysulfide could be enhanced. And cyclic voltammetry test indicate boost the polysulfide redox reaction kinetics and ion transfer of H-Mo2S/Mo2C/NC/S NFs cathode. Benefiting from the state-of-the-art design, the H-Mo2S/Mo2C/NC/S NFs cathode demonstrates remarkable rate performance with a specific capacity of 1351.9 mAh g−1 at 0.2 C, when the current density was elevated to 2 C and subsequently reverted to 0.2 C, the H-Mo2S/Mo2C/NC/S NFs cathode retained a capacity of 1150.4 mAh g−1, and it maintains exceptional long cycling stability (840 mA h g−1 at 2 C after 500 cycles) a low capacity decay of 0.0073% per cycle. This work presents an effective approach to rapidly fabricating multifunctional heterostructures as an effective sulfur host in improving the polysulfide redox kinetics for lithium sulfur batteries.
A polarization-sensitive, high on/off ratio and self-powered photodetector based on Nb2CT
x
and Nd2CT
x
@MoS2
Authors: Wang Mengyuan , Chen Jiaxing , Liu Feng , Shi Wangzhou , Xie Yiqun , Yang Bingjun , Zhang Yi
Published: January 2024

MXene two-dimensional materials have been widely used in energy storage, catalysis, sensing and other fields, Nb2C as a typical two-dimensional MXene material, its exploration in the field of optoelectronics is still in its infancy, especially Nb2C-based photodetectors are still to be developed. This paper demonstrates that two-dimensional films based on few-layer Nb2C have a photoelectric response in the wavelength range from visible to near-infrared. We have found that the light response performance can be easily adjusted by controlling the thickness of the spin-coated film, and that Nb2C photodetectors show great advantages in terms of wide bandwidth, polarization response, high switching ratio, etc. By adjusting the material concentration and sample thickness, the photocurrent can reach up to 330 nA, the switching ratio can reach 410, and the responsivity can reach 8.3 × 10−4 A W−1. In the polarization characteristic test, an extinction ratio of 7.6 can be obtained. By adjusting the content of that doped MoS2 quantum dot, the dark current can reach 7.6 × 10−13 A, and the switching ratio can reach 3 × 105, which can be increased by 700 times. The above results show that the few-layer Nb2C nanosheets can be used as optoelectronic detectors in the visible to near-infrared bands, which further broadens the application prospects of two-dimensional MXene.
Radiological injuries under low energy x-rays in mice depending on dose and protocol: comparative characterization of lesion severity and impact of the in vivo bone response on retrospective dose estimations
Authors: Guillou Manon , L’Homme Bruno , Trompier François , Errabii Anass , Marcoux Tifanie , Gruel Gaëtan , Prezado Yolanda , Dos Santos Morgane
Published: January 2024

Objective. To improve our knowledge about the biological effects of over exposures involving low-energy x-rays, we developed and characterized a preclinical mouse model allowing to mimic different lesion severity degrees induced by 80 kV x-ray depending on the dose and protocol (single or repeated exposure). Approach. Mice were locally exposed (paw) to 80 kV x-rays in a single (15, 30 or 45 Gy in K
air) or repeated exposition (2 × 15 or 3 × 15 Gy in K
air) to assess different degrees of lesion severity. Six post-irradiation euthanasia time points (0, 7, 14, 21, 42, and 84 days) were determined to follow up the evolution of lesions based on the lesion score, weighing and cutaneous blood perfusion. The bone dose was estimated at the different time points by electron paramagnetic resonance (EPR) spectroscopy. Main results. The monitoring of the lesion severity allows to classify the exposure protocols according to their severity. EPR spectroscopy measurements allow to determine the bone dose on the day of irradiation which is 7 times higher than the initial dose for single protocols. However, the initial signal measured at the end of the repeated exposure was 27% lower than the signal measured for a single dose. The study of the kinetics of EPR signal showed a decrease of the EPR signal which is dependent on the exposure protocol but not on dose highlighting the impact of bone physiology on the bone dose estimation. Significance: the preclinical model developed allows to assess the impact of the dose and protocol on the lesion severity induced by low-energy x-ray. For the first time, the dynamics of free radicals have been quantified in an in vivo model, highlighting that the doses actually administered can be underestimated if samples are taken weeks or even months after exposure.