bluuebunny/crossref_metadata_2025 huggingface dataset:
Exciton energy transfer inside cavity—A benchmark study of polaritonic dynamics using the surface hopping method
Authors: De Priyam Kumar , Jain Amber
Published: August 2024

Strong coupling between the molecular system and photon inside the cavity generates polaritons, which can alter reaction rates by orders of magnitude. In this work, we benchmark the surface hopping method to simulate non-adiabatic dynamics in a cavity. The comparison is made against a numerically exact method (the hierarchical equations of motion) for a model system investigating excitonic energy transfer for a broad range of parameters. Surface hopping captures the effects of the radiation mode well, both at resonance and off-resonance. We have further investigated parameters that can increase or decrease the rate of population transfer, and we find that surface hopping in general can capture both effects well. Finally, we show that the dipole self-energy term within our parameter regime does not significantly affect the system’s dynamics.
Unsteady flow in a compound channel during flooding: Insights from a combined two-dimensional and three-dimensional numerical simulation
Authors: Liu Jiaming , Xiao Yang , Zhou Jian , Lin Qingwei , Yuan Saiyu , Zhang Taotao , Jiang Qihao , Liu Jieqing , Gualtieri Carlo
Published: August 2024

Natural channels often take the form of compound channels during flooding events. The unsteadiness of floods is crucial for flood management and river-floodplain ecosystems. However, the impact of unsteady flow on three-dimensional hydrodynamic processes within compound channels remains poorly understood. This study employed a validated two-dimensional/three-dimensional numerical model to examine how unsteady features influence key hydrodynamic indicators of compound channels, such as velocity distribution, turbulence characteristics, and discharge partitioning between the main channel and floodplain. A definitive positive correlation was found between water level fluctuation amplitudes and integrated discharge during unsteady events, as well as between mean water levels and mean discharges. The proportion of discharge conveyed by the main channel relative to the total was directly linked to the water depth ratio. The exchange at the main channel–floodplain interface exhibits a dual-layer flow pattern: surface waters spill into the floodplain, while deeper waters are siphoned into the main channel. Unsteady conditions principally modulate the intensity of these exchanges, altering hydraulic interactions and water transfer between areas. Pronounced wall shear stresses were detected at the main channel–floodplain interface due to swift channel flows and momentum exchange at the floodplain margin, with maxima adjacent to the floodplain edge correlating with peak flow velocities. Under deep conditions, cross-sectional flow across the compound channel's mixing layer was essentially two-dimensional. These findings elucidate the complex hydrodynamics inherent to unsteady overbank flows while holding implications for enhancing floodplain management and advancing the understanding of unsteady fluvial hydraulics.
Short-time asymmetric droplet coalescence dynamics on a pre-wetted fiber
Authors: Feng Leyun , Jiang Youhua , Machado Christian , Choi Wonjae , Patankar Neelesh A. , Park Kyoo-Chul
Published: August 2024

This study presents an unprecedented directional transport phenomenon during the coalescence of two droplets on a pre-wetted cylindrical fiber, where the larger droplet is pulled toward the smaller one. The magnitude of this effect often exceeds the gravitational pull, enabling coalescing droplets to climb up a vertical fiber. This occurs primarily because the viscous friction that the droplets experience is negatively correlated with the droplet size. We present a scaling relation and a mass-spring-damper model to explain the phenomenon, which shows good agreement with the experimental results. This research reveals an intriguing aspect of the coalescence dynamics of droplets on a pre-wetted fiber, offering a fresh perspective on the interfacial phenomena in droplet–fiber systems.
Dynamic characteristics of suspended particles influenced by cavitation bubble in a free field
Authors: Shen Xiaobo , Li Rennian , Han Wei , Yang Shiqi , Nan Haozhi , Bai Lu , Dong Yifan
Published: August 2024

This study investigates the dynamic characteristics of suspended particles in a free field under the influence of a single cavitation bubble. The phenomenon of suspended particles being influenced by cavitation bubbles of comparable size reflects the dynamic characteristics of particles, a common occurrence in both hydraulic machinery and biopharmaceutical fields. A high-speed camera captures the process of a single cavitation bubble interacting with suspended particles. Combined with three-dimensional numerical simulations, the motion states of suspended particles as the cavitation bubble expands and contracts are analyzed. Observations reveal that at various initial distances between suspended particles and the cavitation bubble, suspended particle motion is consistently influenced by the expansion and contraction of the same cavitation bubble during the initial four processes. The particle motion direction is parallel to the propagation direction of the radiation force produced during the expansion and collapse of the cavitation bubble, consistent with the characteristics of motion under longitudinal wave effects. The initial distance between suspended particles and the cavitation bubble dictates the ultimate displacement direction of suspended particles, with the influence of the cavitation bubble on suspended particle velocity weakening as their distance increases. Under conditions where particle size closely matches that of the bubble, the jet produced by the cavitation bubble does not significantly accelerate particles, and the influence of the jet on suspended particle motion states could be disregarded. The investigation reveals that the suspended particles are primarily influenced by the radiation force, drag force, and virtual mass force exerted by the cavitation bubble.
A robust three-dimensional numerical model for heat transfer characteristics in sintered–grooved thin flat heat pipes
Authors: Abdizadeh G. R. , Noori Sahar , Saeedi Mohammad
Published: August 2024

In the current research, a robust three-dimensional numerical model is developed for thin flat heat pipes (TFHPs) with a hybrid sintered–grooved wick structure. Numerical simulations for laminar incompressible flow in liquid wick and ideal gas incompressible flow in the vapor core are performed to predict temperature, pressure, and velocity profiles. The model utilized non-Darcy transport through a porous wick to determine liquid flow in the liquid-wick section. The mass flow rate of the fluid at the liquid–vapor interface is modeled using kinetic theory. Furthermore, the hybrid wick structure is modeled as an inhomogeneous porous medium. Additionally, this formulation enhances the stability and convergence of the numerical solution and accelerates the solving time. The developed model is validated with experimental data, showing very good agreement with axial wall temperatures, with a maximum error of about 2% in steady-state conditions. The numerical results, including system pressure, wall temperature, mass transfer at the liquid and vapor interface, and velocity magnitude streamlines, are investigated for a comprehensive understanding of the flow physics and performance of the hybrid wick. The results show that, at heat inputs of 5, 10, 20, and 30 W, the thermal efficiency of hybrid wick TFHP is 4.9%, 10.4%, 34.38%, and 23.3%, respectively, greater than that of the grooved wick. The TFHP with a hybrid wick indicates the best thermal efficiency at a heat input of 20 W, with a thermal resistance of 0.95 K/W.
Impact and spread dynamics of a viscoelastic droplet on an inclined hydrophilic surface
Authors: Zhang Haifeng , Luan Qinlei , Yuan Wenjun , Chen Fei , Meng Bo
Published: August 2024

In this work, the impact of a three-dimensional viscoelastic droplet on an inclined hydrophilic surface is investigated by means of direct numerical simulations. The volume-of-fluid method is adopted to capture the interface, and the Oldroyd-B model is used to describe the rheological behavior of the viscoelastic droplet. The effects of the Weissenberg number (Wi) and the Weber number (We) on the impacting and spreading processes are studied, including the viscoelastic droplet shape, velocity, energy transformation, and stress distribution. Our results are in good agreement with the experimental data in the literature. In particular, the elastic force markedly influences droplet deformation at intermediate Wi values, although this trend diminishes at higher or lower Wi values. With increasing We, the impacting viscoelastic droplet reaches its maximum deformation more rapidly, while the nonmonotonic peak of kinetic energy indicates that the droplet elasticity plays significant role at moderate We. Additionally, the inclination of the surface has a pronounced effect on the droplet spreading process, and the elongated viscoelastic droplet at larger inclination angle is likely to experience a stronger oscillation. According to further analyses, We exerts a modest influence on the change rates of the droplet potential energy and spreading length in the flow direction. However, a larger inclination angle reduces stress concentration and accelerates the change rates. Due to the oscillation dynamics, Wi exhibits a non-monotonic effect on the spreading process and induces a monotonous increase in potential energy of viscoelastic droplets. The above analyses provide insights into the impact mechanism of droplets on an inclined hydrophilic wall and, therefore, will guide the applications in the future.
An enhanced model based on deep operator network for very short-term forecasting of ship motion
Authors: Zhao Jinxiu , Zhao Yong
Published: August 2024

Very short-term forecasting of ship motion involves forecasting future ship movements based on learned characteristics from historical motion data. However, ship motion exhibits not only temporal features but also features in the frequency domain, which are often overlooked. This paper introduces a novel method called Fourier Transform and Multilayer Perceptron-net enhancement based on Deep Operator Network (DeepONet), abbreviated as FMD. This approach effectively captures and learns ship motion patterns in both the temporal and frequency domains. Specifically, the branch net of DeepONet learns temporal features, while the trunk net performs Fourier filtering to capture the underlying ship motion patterns. In addition, the learning effectiveness of Fourier filtering is complemented by using MPL-net to enhance the extraction of detailed features in motion data. To evaluate the prediction performance of FMD, this study explores the optimal filtering frequency of the FMD model using experimental ship model motion data. Comparative testing with the DeepONet model includes multi-step prediction, coupled data forecasting, and generalization studies. Testing results demonstrate that the proposed FMD model improves prediction accuracy from 11.78% to 33.10% under Mean Squared Error (MSE) compared to the DeepONet model. Even under sea conditions ranging from mild to intense, the FMD model maintains high accuracy, with an improvement of over 30% in accuracy compared to DeepONet at longer step lengths under MSE conditions. Testing results indicate the superiority and advancement of FMD in prediction accuracy, generalization, and versatility, showcasing significant advantages in very short-term forecasting of ship motion.
Optimal tree tensor network operators for tensor network simulations: Applications to open quantum systems
Authors: Li Weitang , Ren Jiajun , Yang Hengrui , Wang Haobin , Shuai Zhigang
Published: August 2024

Tree tensor network states (TTNS) decompose the system wavefunction to the product of low-rank tensors based on the tree topology, serving as the foundation of the multi-layer multi-configuration time-dependent Hartree method. In this work, we present an algorithm that automatically constructs the optimal and exact tree tensor network operators (TTNO) for any sum-of-product symbolic quantum operator. The construction is based on the minimum vertex cover of a bipartite graph. With the optimal TTNO, we simulate open quantum systems, such as spin relaxation dynamics in the spin-boson model and charge transport in molecular junctions. In these simulations, the environment is treated as discrete modes and its wavefunction is evolved on equal footing with the system. We employ the Cole–Davidson spectral density to model the glassy phonon environment and incorporate temperature effects via thermo-field dynamics. Our results show that the computational cost scales linearly with the number of discretized modes, demonstrating the efficiency of our approach.
A statistical study of the impact of the stream interaction regions on the heliospheric current sheet
Authors: Xu Xiaojun , Xu Jiaying
Published: August 2024

The heliospheric current sheet (HCS) serves as the boundary that separates two sectors in which the interplanetary magnetic field lines diverge in opposite directions. In this study, we conducted a statistical analysis of 216 HCS events, utilizing data from the Wind spacecraft to examine the impact of stream interaction regions (SIRs) on the HCSs. Our findings revealed that out of all the HCS events, 153 (70.8%) were succeeded by a SIR within 36 h. Conversely, 63 HCS events (29.2%) were not followed by any SIR. The occurrence of HCSs accompanied by SIRs displayed a rough anti-correlation with solar sunspots. The statistical results further indicated that the presence of a SIR exerts some influence on the preceding HCS. Specifically, the thickness of the HCS is significantly reduced by the trailing SIR, and the subsequent SIR can cause the leading HCS to stand more vertically to the ecliptic plane and more aligned with the Sun–Earth line (a smaller angle between the normal of the HCS and the Earth's dawn–dusk line in the ecliptic plane).
Salt induced slowdown of kinetics and dynamics during thermal gelation of egg-yolk
Authors: Anthuparambil Nimmi Das , Timmermann Sonja , Dargasz Michelle , Retzbach Sebastian , Senft Maximilian D. , Begam Nafisa , Ragulskaya Anastasia , Paulus Michael , Zhang Fajun , Westermeier Fabian , Sprung Michael , Schreiber Frank , Gutt Christian
Published: August 2024

We investigated the effect of the NaCl concentration (0.3–2M) on the structure and dynamics of hen egg yolk at room temperature and during thermal gelation at temperatures in the range of 66–90 °C utilizing low-dose x-ray photon correlation spectroscopy in ultra-small angle x-ray scattering geometry. With an increase in the salt concentration, we observe progressive structural and dynamic changes at room temperature, indicating the disruption of yolk components such as yolk-granules and yolk-plasma proteins. Temperature- and salt-dependent structural and dynamic investigations suggest a delay in the gel formation and aggregation of yolk low-density lipoproteins with increasing ionic strength. However, the time–temperature superposition relationship observed in all samples suggests an identical mechanism underlying protein aggregation–gelation with a temperature-dependent reaction rate. The sol–gel transition time extracted from kinetic and dynamic information follows Arrhenius’s behavior, and the activation energy (460 kJ/mol) is found to be independent of the salt concentration.
Various and orderly formations in the hydrodynamic schooling of multiple flapping swimmers
Authors: Lin Xingjian , Liu Yusheng , Wu Jie
Published: August 2024

The fluid mechanics underlying the collective motion of fish schools and bird flocks still lack full understanding. In this paper, the collective motion of multiple asynchronous flapping foils is numerically studied. It is found that various and orderly formations are achieved by multiple foils only via hydrodynamic interactions. Three distinct states have been verified according to the equilibrium distance between adjacent foils, i.e., the sparse state, the compact state, and the combined state. The “head goose effect” is found in the combined state, and the significant speed enhancement can be observed in both the compact and combined states, except when the first subgroup of the combined group is isolated. The obvious energy savings can be observed in most cases examined in the current work, no matter which state occurs. Moreover, for a given phase difference, the compact group has the highest propulsive efficiency, while the sparse group has the lowest. In addition, the fluid mechanics by which the multiple-foil system achieves speed enhancement and energy savings are analyzed. The results obtained here may shed some light on understanding the collective motion of fish schools and bird flocks.
Importance sampling for counting statistics in one-dimensional systems
Authors: Burenev Ivan N. , Majumdar Satya N. , Rosso Alberto
Published: August 2024

In this paper, we consider the problem of numerical investigation of the counting statistics for a class of one-dimensional systems. Importance sampling, the cornerstone technique usually implemented for such problems, critically hinges on selecting an appropriate biased distribution. While an exponential tilt in the observable stands as the conventional choice for various problems, its efficiency in the context of counting statistics may be significantly hindered by the genuine discreteness of the observable. To address this challenge, we propose an alternative strategy, which we call importance sampling with the local tilt. We demonstrate the efficiency of the proposed approach through the analysis of three prototypical examples: a set of independent Gaussian random variables, Dyson gas, and symmetric simple exclusion process with a steplike initial condition.
Dynamics of turbulent natural convection in a cubic cavity with centrally placed partially heated inner obstacle
Authors: Jena Sofen Kumar , Manceau Rémi
Published: August 2024

Natural convection in a cavity with a partially heated obstacle at the center at the Rayleigh number Ra=1.46×109 is investigated using large eddy simulation (LES). The standard and dynamic Smagorinsky models, as well as the wall-adapting local eddy-viscosity model, are used for the subgrid scales, and the flow statistics are compared with recent experiments. The LES results obtained with different meshes show overall good agreement with the experiments as concerns the flow and heat transfer. Simulation with a non-ideal wall at the adiabatic side of the obstacle is also performed to explain the residual discrepancies observed in the unheated channel. Additional simulations performed with periodic conditions in the spanwise direction are very different from the full three-dimensional (3D) simulations, which demonstrate the significance of 3D effects in the cavity. In particular, periodic simulations show Tollmien–Schlichting kind waves in the transitional region, while the 3D cavity shows an early cross-flow transition to turbulence.
The current state of sustainable healthcare in Australia
Authors: Verlis Krista , Haddock Rebecca , Barratt Alexandra
Published: August 2024

Objective To provide the first document map of sustainability and decarbonisation actions across the Australian healthcare sector, as reported in publicly available documents online, and to identify gaps in actions. Methods Healthcare providers were identified across all state and territories. Structured Google searches between August and December 2022 were followed by document searches. Updates were undertaken, most recently in December 2023. Targeted documents included position statements, strategies, and reports. Key points from these documents pertaining to sustainability and/or decarbonisation were extracted and descriptively analysed. Results A total of 294 documents were included, mostly focused on power generation, transport, building design, and circular procurement/waste pathways. In contrast, relatively few plans for decarbonisation of clinical care were identified (n = 42). National and two state governments (New South Wales, Western Australia) have established healthcare sustainability and decarbonisation units, and two further states have publicly committed to doing so (Queensland, Tasmania). However, these documents generally reported separate, siloed actions. While attempts were made to make this review comprehensive, some documents may have been missed or are only available inside an organisation, and new actions will continue to emerge. Conclusion Broad sustainability plans have been developed by many healthcare providers; however, to achieve net zero, decarbonising of clinical practices is also needed, and this is where the least action is currently occurring. To decarbonise clinical care, the sector needs to come together in a more coordinated way.
Panmixia and local endemism: a revision of the Eubranchus rupium species complex with a description of new species
Authors: Grishina Darya Y. , Schepetov Dimitry M. , Antokhina Tatiana I. , Malaquias Manuel António E. , Valdés Ángel , Ekimova Irina A.
Published: August 2024

Species of the genus Eubranchus Forbes, 1838 (Mollusca: Gastropoda: Nudibranchia) are common faunistic elements of boreal benthic ecosystems, associated with hydroid communities. Recent studies have suggested that the widely distributed trans-Arctic E. rupium (Møller, 1842) constitutes a complex of at least three candidate species, but the detailed taxonomy of the complex remains unresolved. The purpose of the present paper is to conduct an integrative taxonomic study including molecular genetic methods (a phylogenetic analysis using COI, 16S rRNA and histone H3 with application of species delimitation methods) and morphological study (light and scanning electron microscopy) of E. rupium and closely related species. The specific aims of this study were to establish the species boundaries, morphological variability, and the phylogeographic structure within this group. The phylogeographic analysis included a TCS-based network analysis, an analysis of molecular variance (AMOVA), divergence time estimations, and ancestral area reconstructions. We demonstrate that specimens initially identified as E. rupium included three distinctive species: the nominal E. rupium with an amphiboreal range, the new species Eubranchus novik sp. nov. from the Sea of Japan, for which a taxonomic description is provided in this paper, and Eubranchus sp. from the northern Kuril Islands, which requires the collection and study of additional material for formal description. Our results confirm the amphiboreal distribution of E. rupium, as no geographic structure was found across Pacific, Arctic and Atlantic populations, and the results of the AMOVA analysis showed no differences between groups of samples from different geographic regions. The divergence of the ‘Eubrancus rupium species complex’ is estimated from the late Miocene or the Miocene–Pliocene boundary to the late Pliocene. It is hypothesised that the most probable ancestral region for the Eubranchus rupium species complex is the north-western Pacific, and the subsequent speciation likely occurred due to dispersal followed by allopatric speciation. ZooBank: urn:lsid:zoobank.org:pub:228E0C46-0BF7-4DDD-9C00-67B50E298D65
Ventilation does not affect close-range transmission of influenza virus in a ferret playpen setup
Authors: Rockey Nicole C. , Le Sage Valerie , Shephard Meredith , Vargas-Maldonado Nahara , Vu Michelle N. , Brown Cambria A. , Patel Krishna , French Andrea J. , Merrbach Grace A. , Walter Sydney , Ferreri Lucas M. , Holmes Katie E. , VanInsberghe David , Clack Herek L. , Prussin Aaron J. , Lowen Anice C. , Marr Linsey C. , Lakdawala Seema S.
Published: August 2024

Sustained community spread of influenza viruses relies on efficient person-to-person transmission. Current experimental transmission systems do not mimic environmental conditions (e.g., air exchange rates, flow patterns), host behaviors, or exposure durations relevant to real-world settings. Therefore, results from these traditional systems may not be representative of influenza virus transmission in humans. To address this pitfall, we developed a close-range transmission setup that implements a play-based scenario and used it to investigate the impact of ventilation rates on transmission. In this setup, four immunologically naive recipient ferrets were exposed to a donor ferret infected with a genetically barcoded 2009 H1N1 virus (H1N1pdm09) for 4 h. The ferrets interacted in a shared space that included toys, similar to a childcare setting. Transmission efficiency was assessed under low and high ventilation, with air exchange rates of ~1.3 h
−1
and 23 h
−1
, respectively. Transmission efficiencies observed in three independent replicate studies were similar between ventilation conditions. The presence of infectious virus or viral RNA on surfaces and in air throughout the exposure area was also not impacted by the ventilation rate. While high viral genetic diversity in donor ferret nasal washes was maintained during infection, recipient ferret nasal washes displayed low diversity, revealing a narrow transmission bottleneck regardless of ventilation rate. Examining the frequency and duration of ferret physical touches revealed no link between these interactions and a successful transmission event. Our findings indicate that exposures characterized by frequent, close-range interactions and the presence of fomites can overcome the benefits of increased ventilation.
Machine learning assisted optical diagnostics on a cylindrical surface dielectric barrier discharge
Authors: Stefas D , Giotis K , Invernizzi L , Höft H , Hassouni K , Prasanna S , Svarnas P , Lombardi G , Gazeli K
Published: August 2024

The present study explores combining machine learning (ML) algorithms with standard optical diagnostics (such as time-integrated emission spectroscopy and imaging) to accurately predict operating conditions and assess the emission uniformity of a cylindrical surface dielectric barrier discharge (SDBD). It is demonstrated that these optical diagnostics can provide the input data for ML which identifies peculiarities associated with the discharge emission pattern at different high voltage waveforms (AC and pulsed) and amplitudes. By employing unsupervised (principal component analysis (PCA)) and supervised (multilayer perceptron (MLP) neural networks) algorithms, the applied voltage waveform and amplitude are predicted based on correlations/differences identified within large amounts of corresponding data. PCA allowed us to effectively visualise patterns related to the voltage waveforms and amplitudes applied to the SDBD through a transformation of the spectroscopic/imaging data into principal components (PCs) and their projection to a two-dimensional PCs vector space. Furthermore, an accurate prediction of the voltage amplitude is achieved using the MLP which is trained with PCs. A particularly interesting aspect of this concept involves examining the uniformity of the emission pattern of the discharge. This was achieved by analysing spectroscopic data recorded at four different regions around the SDBD surface using the two ML algorithms. These discoveries are instrumental in enhancing plasma-induced processes. They open avenues for real-time control, monitoring, and optimization of plasma-based applications across diverse fields such as flow control for the present SDBD.
Automatic identification and classification of surface defects in small-sized optics
Authors: Zhang Fanshu , Yi Dingrong , Kong Linghua , Zheng Jishi , Yuan Tao , Chen Siling
Published: August 2024

Precision optics are widely used in lighting systems, imaging systems, and high-precision inspection equipment. The presence of surface defects in optics can seriously affect the design performance of the equipment, so the optics must be rigorously inspected to eliminate defective optics. Currently, engineering products are moving toward smaller sizes, resulting in smaller optics in them also moving towards smaller sizes. However, realizing the surface defect detection of small-sized optics is a great challenge because it requires micrometer-scale high-resolution image acquisition and automatic detection of defects on their surfaces. A machine learning-based automatic surface defect detection method is proposed for surface defects with many types and small sizes. A dark-field micro-scattering imaging system is used to acquire dark-field images. Then the image segmentation and feature analysis are performed on each image to extract the original feature data, and the original feature data are compressed by reliefF algorithm. Based on the compressed feature data, a classification model is built using a support vector machine. The detection method can classify three kinds of defects, namely, dig, scratch, and scuff mark. The accuracy of the method is up to 98%. The experimental results of this study show that the method can automatically and accurately detect a wide range of micro defects occurring in small-sized optics, thus providing valuable insights into the realization of mass production of small-sized optics. In addition, our proposed method provides some ideas for further research in the field of defect detection in small-sized optics.
Comprehensive study of an eccentric universal joint for parallel coordinate measuring machine
Authors: Bai Yang , Yu Yang , Xu Zhenbang , Han Chunyang , Hu Haifei , Wang Jianli
Published: August 2024

Eccentric universal joint (U-joint) is a crucial component extensively used in parallel coordinate measuring machines. The workspace and stiffness are significant characteristics that can directly affect the measurement performance of the mechanism. To investigate the eccentric U-joint’s workspace, a mathematical model has been developed based on the geometrical parameters. The analysis explores the correlation between workspace and geometric specifications and compares the workspace of the eccentric U-joint with that of the traditional U-joint. Furthermore, a stiffness model for the eccentric U-joint is established, and its stiffness is analyzed using the finite element method. Finally, an experiment is designed to demonstrate the validity of the proposed model. The research lays the foundation for an engineered system that designs the desired eccentric U-joint.
Sub-micro-g resolution test of accelerometers based on tilt dynamic modulation in gravity field
Authors: Pan Yuyao , Yang Jianyu , Yang Jing , Jiang Haiyi , Chen Xingfan , Li Nan , Liu Cheng , Hu Huizhu
Published: August 2024

Strategic-grade accelerometers play a pivotal role in various application fields and fundamental research. As the performance of accelerometers are improving rapidly, the requirements for test method have been raised. However, due to the influence of environmental noise, the test facility for accelerometers, especially when the resolution reaches sub-μg level, remains a challenge. To address this limitation, this study introduces a resolution test facility based on tilt modulation in gravity field, driven by piezoelectric ceramic stacks. The input acceleration ranges from 30ng to 10 μg, and the frequency is adjustable from 0.01 Hz to 20 Hz. Since the input acceleration oscillates at certain frequency, modulation & demodulation technology enables us to extract ultra weak signal out of relatively noisy background. With this facility, we test the resolution of commercial strong motion accelerograph, quartz flexure accelerometers, and homemade accelerometer based on levitated optomechanics, proving the reliability of this method. Our advancement in test method lay solid foundation for strategic-grade accelerometers, not only provides a minimal resolution test solution in the ng to μg range, but also provides a possible scheme of evaluating dynamic response characteristic with an ultra-low acceleration input in a considerable frequency range.
Enhancement of second-order vortex harmonics in epsilon-near-zero materials
Authors: Jiang Yu , Zhang Chaojin , Du Henglei , Liu Chengpu
Published: August 2024

When a spatially-inhomogeneous vortex laser field irradiating an epsilon-near-zero (ENZ) material is theoretically investigated, second-order vortex harmonics occur due to the symmetry breaking from the field spatial-inhomogeneity. Their signal intensity is sensitive to three factors: the ENZ field enhancing ratio, the ENZ material thickness, and the field inhomogeneity degree. Their competition supports a high conversion efficiency of around 10−6 for second-order harmonics from the incident fundamental laser field under an optimum thickness of ENZ materials.
Photoelectric conversion performance of Ga0.47In0.53As/Ge0.79Sn0.21 dual-junction thermophotovoltaic cell
Authors: Li Qianying , Cui Min , Yu Tianjing , Liu Xiangrui , Deng Jinxiang , Gao Hongli , Yuan Anjuan
Published: August 2024

Based on the photovoltaic characteristics of GeSn-based materials and the theory of stacked solar cells, Ga0.47In0.53As/Ge0.79Sn0.21 dual-junction thermophotovoltaic cell has been simulated and studied for the first time. According to existing experimental material parameters, the structure of the cell is optimized, and the photoelectric performance of the cell is profoundly studied. The findings indicate that the doping concentrations of the top/bottom cell are N
a(d),t/N
a(d),b = 50(7) × 1016/17(2) × 1019 cm−3, which exhibits superior photoelectric conversion performance. For reducing material consumption and achieving high performance, the thickness of the emitter (base) of the top/bottom cell can be selected as 0.8~2.0(2.0~4.0)/0~0.2(1.0~4.0) μm (T
BB = 1500 K). With radiator temperatures increasing, the conversion efficiency of the cell significantly improves, and the open circuit voltage of the cell can reach 0.70~0.91 V (1000~2000 K). The research results can guide the design and fabrication of high-efficiency and economical GeSn-based multi-junction thermophotovoltaic cells, and can also provide a new research and development direction for low-cost thermophotovoltaic cells.
Phase structure evolution and coercivity mechanism of high-Co containing permanent magnets
Authors: Huang 黄 Min 敏 , Ding 丁 Yong 勇 , Zhao 赵 Zhihe 之赫 , Wang 王 Chunguo 春国 , Zhou 周 Bo 波 , Liu 刘 Lei 雷 , Sun 孙 Yingli 颖莉 , Yan 闫 Aru 阿儒
Published: August 2024

The phase structure and magnetic properties of high-Co containing permanent magnets with high thermal stability have been systematically studied in this work. It is abnormal that the coercivity of annealed samples was slightly lower than that of sintered samples, while the coercivity was usually enhanced after annealing in conventional Nd–Fe–B samples. Further analysis showed that in addition to RE2(Fe,Co)14B main phase and RE-rich grain boundary phase, there were also new Co-rich magnetic phases located in the grain boundary. During annealing, the phase structures of high-Co containing magnets were readjusted, especially the increasing Co-rich magnetic phase and emerging RE-rich particles precipitated from the main phase. Eventually, the isolated RE-rich particles would act as the pinning center of the domain wall movement in demagnetization process. It was confirmed that the coercivity of annealed high-Co containing magnets was controlled by both nucleation and pinning. Pinning mechanism can partially compensate for the weakening of magnetic isolation due to increased Co-rich magnetic phase, which explained the moderate decrease in coercivity of annealed high-Co containing magnets. The discovery of new coercivity mechanism contributed to in-depth understanding of high-Co containing magnets.
Achievable hole concentration at room temperature as a function of Mg concentration for MOCVD-grown p-GaN after sufficient annealing
Authors: Huang Siyi , Ikeda Masao , Zhang Feng , Zhang Minglong , Zhu Jianjun , Zhang Shuming , Liu Jianping
Published: August 2024

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper. Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges. Hole concentration, resistivity and mobility were characterized by room-temperature Hall measurements. The Mg doping concentration and the residual impurities such as H, C, O and Si were measured by secondary ion mass spectroscopy, confirming negligible compensations by the impurities. The hole concentration, resistivity and mobility data are presented as a function of Mg concentration, and are compared with literature data. The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density [

] (cm−3) dependent ionization energy of Mg acceptor was determined as

= 184 − 2.66 × 10−5 × [

]1/3 meV.
Review of the SiC LDMOS power device
Authors: Hu Ziwei , Yao Jiafei , Li Ang , Sun Qi , Li Man , Yang Kemeng , Zhang Jun , Chen Jing , Zhang Maolin , Guo Yufeng
Published: August 2024

Silicon carbide (SiC), as a third-generation semiconductor material, possesses exceptional material properties that significantly enhance the performance of power devices. The SiC lateral double-diffused metal–oxide–semiconductor (LDMOS) power devices have undergone continuous optimization, resulting in an increase in breakdown voltage (BV) and ultra-low specific on-resistance (R
on,sp). This paper has summarized the structural optimizations and experimental progress of SiC LDMOS power devices, including the trench-gate technology, reduced surface field (RESURF) technology, doping technology, junction termination techniques and so on. The paper is aimed at enhancing the understanding of the operational mechanisms and providing guidelines for the further development of SiC LDMOS power devices.
International Conference on AeroSpace Science and Technology (ICASST) 2023
Authors: Hernández-Gómez J. J. , Ramírez-López F. , Pablo-Sotelo A. de J. , Yáñez-Casas G. A.
Published: August 2024

1. Introduction

Welcome to the publication of the Proceedings of the International Conference on Aerospace Science and Technology (ICASST) 2023, which was hosted at the facilities of Centro de Desarrollo Aeroespacial (CDA), Instituto Politécnico Nacional (IPN), in the historical centre of Mexico City, Mexico, from November 19th to November 24th, 2023. ICASST 2023 was a scientific forum for the dissemination of basic research and/or technological development projects, which allows interaction between professionals, scholars and industrialists, promoting scientific-technological collaborations in the aerospace field and related areas. The program included presentations, round tables, courses/workshops as well as keynote lectures given by widely recognized national and international experts in their area. The Conference was held in a hybrid way, face-to-face/virtual.
Tip air injection and plasma DBD actuator as active flow control in axial compressors - Review
Authors: Toledo M , Vazquez E , León F F , Orduño R O
Published: August 2024

Nowadays, flow control is extensively studied in fluid dynamic domain, and the principal aim is to manipulate the flow path that passes over a surface to reduce losses generated by turbulent flow, generated by detachment. The Flow control involves passive or active methods, and for approximately thirty years, active flow control methods have been studied and developed in axial compressors more intensively, active flow control methods are those in which energy is added to the fluid through an external source. The flow control reduces losses generated by secondary flow effects, such as flow detachment at rotor tip, flow detachment at casing and flow detachment at stator vanes hub. The present paper provides a summary of investigation of active flow control methods tip air injection and plasma actuators.
Attitude Control for a satellite with inertial wheels based on Attractive Ellipsoids Method
Authors: Solis Cesar U. , Montelongo Carlos M.
Published: August 2024

This article presents a robust control law based on the Attractive Ellipsoids Method applied to perform attitude control of a satellite that has inertial wheels and relatively small dimensions such as microsatellites or other similar architectures. The novelty lies in the fact that under certain characterized external and parametric perturbations it is possible to track the desired angular trajectory with an optimization method to determine the computed torque. Additionally, a demonstration of this methodology is carried out with a numerical example.
Performance Simulation of Muon Detectors Based on Structural Design and Array Layout of Plastic Scintillators
Authors: Wang Zhenyu , Li Zhiyuan , Wang Lukai , Wu Kun , Lin Hongjian , Fan Haijun , Su Hengyi , Wang Zungang , Zhou Chunzhi
Published: August 2024

The performances of muon detectors have prominent effects on
the accuracy and application scenario of muon imaging. Previous
studies have paid more attention to the performance improvements of
muon detectors in the assembly of imaging systems and optimization
of imaging algorithms, while, the structural design and array layout
of plastic scintillators in muon detectors have received less
attention. In this work, the simulation models of plastic
scintillator, wavelength-shifting (WLS) fibers, and muon source are
constructed in the Geant4 software. On this basis, different factors
affecting light collection efficiency (LCE) have been investigated,
including muon hitting position, plastic scintillator
cross-sectional shape and size, and WLS fiber size and
position. Meanwhile, the influences of scintillator array layout,
average width, and muon energy on the position resolution
performance of the detector are investigated. The constructive
results have been listed as follows: (a) the longitudinal length of
the plastic scintillator unit, the shape and size of the WLS fiber,
and the position of the WLS fiber have a large impact on the
LCE. (b) The Right-angled triangle staggered layout is suitable for
small-sized scintillators with single-energy muon hitting, and the
Rhombus staggered layout is suitable for large-sized scintillators
with multiple-energy muon hitting. This work provides theoretical
support for the structural design and array layout of plastic
Scintillators, and it has an important significance as a guide for
the design of the subsequent muography system.
In vitro degradation of a chitosan-based osteochondral construct points to a transient effect on cellular viability
Authors: Pitrolino Katherine , Felfel Reda , Roberts George , Scotchford Colin , Grant David , Sottile Virginie
Published: August 2024

Bioresorbable chitosan scaffolds have shown potential for osteochondral repair applications. The in vivo degradation of chitosan, mediated by lysozyme and releasing glucosamine, enables progressive replacement by ingrowing tissue. Here the degradation process of a chitosan-nHA based bioresorbable scaffold was investigated for mass loss, mechanical properties and degradation products released from the scaffold when subjected to clinically relevant enzyme concentrations. The scaffold showed accelerated mass loss during the early stages of degradation but without substantial reduction in mechanical strength or structure deterioration. Although not cytotoxic, the medium in which the scaffold was degraded for over 2 weeks showed a transient decrease in mesenchymal stem cell viability, and the main degradation product (glucosamine) demonstrated a possible adverse effect on viability when added at its peak concentration. This study has implications for the design and biomedical application of chitosan scaffolds, underlining the importance of modelling degradation products to determine suitability for clinical translation.
Power & protein—closing the ‘justice gap’ for food system transformation
Authors: Baudish Isabel , Sahlin Kajsa Resare , Béné Christophe , Oosterveer Peter , Prins Heleen , Pereira Laura
Published: August 2024

The protein shift, or transition, entails a reduction in the production and consumption of animal-source foods, and an increase in plant-based foods and alternative proteins, at a global level. The shift is primarily motivated by the need to minimise the impact of the food system on social-ecological systems. We argue that rather than focusing singularly on transitioning a ‘protein gap’ in diets, redressing the ‘justice gap’ is a prerequisite for transformative change in food systems. In this context the justice gap is understood as the gap delineating those who have access to just food systems and those who do not. To substantiate our argument a justice lens is used to analyse the political–economic dimensions of such a transformation and to propose that the future of protein must engage with three core elements to be transformative—disruption, innovation and redistribution. Disruption entails challenging both the food trends that encourage the ‘meatification’ of diets, and the influence of ‘Big Meat’ in perpetuating these trends. Innovation emphasises that true novelty is found by designing justice into practices and processes, rather than by firing alternative protein silver bullets within existing food system paradigms. Redistribution stresses that food system redesign is predicated upon establishing fair shares for remaining protein budgets, using approaches anchored in contextual specificity and positionality. Through the application of a justice framework, we expose existing food system injustices related to production and consumption of protein, invite discussion on how such injustices can be addressed and reflect on implications for food system transformations. By reshaping the crux of the protein debate around the more salient concern of the justice gap, food system transformation can take shape.
A joint spatio-temporal characterization of the major meteorological droughts in Europe
Authors: Banfi Fabiola , Cammalleri Carmelo , Michele Carlo De
Published: August 2024

Drought can be considered one of the most severe and complex weather-related natural hazards. It is a relevant stressor for ecosystems, affecting vegetation, ecosystem productivity, and water and carbon cycles, with a complex web of related impacts. Despite the interlink between the spatial and temporal scales of droughts, these two aspects are often studied separately. In addition, studies generally focus on detecting the events, without trying to investigate similarities among them. In this work, we introduce a set of tools used to summarize the main properties of major droughts in Europe, with the goal of subdividing the events in groups characterized by similar properties. We used a European dataset of meteorological droughts (from 1981 to 2020) that detects events based on the Standardized Precipitation Index using an event-oriented spatio-temporal clustering algorithm. From the analysis, we identified three groups of major meteorological droughts: a first group that is comprised by warm-season events, characterized by a longer duration, a shorter early growing phase, and a longer exhaustion phase; a second group, less numerous, comprised by droughts occurring during the cold season, that tend to have a shorter duration, a longer early growing phase and a shorter exhaustion phase; and a third group comprised of droughts occurring across the two periods. This last class is characterized by a longer duration and a high variability in most of the other characteristics, suggesting that these events may be associated with a large range of driving mechanisms. The proposed procedure allows for a drought classification that can be used for better understanding the mechanisms behind spatio-temporal evolution of these events.