bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal scheduling of combined pumped storage-wind-photovoltaic-thermal generation system considering the characteristics of source and load
Authors: Ding Kun , Yang Changhai , Wang Zhuxiu , Zhao Chunjuan
Published: October 2023

With the rapid development of renewable energy, the integration of multiple power sources into combined power generation systems has emerged as an efficient approach for the energy utilization. Pumped storage power stations, as large-capacity flexible energy storage equipment, play a crucial role in peak load shifting, valley filling, and the promotion of new energy consumption. This study focuses on the combined pumped storage-wind-photovoltaic-thermal generation system and addresses the challenges posed by fluctuating output of wind and photovoltaic sources. First, a K-means clustering analysis technology has been introduced to identify the typical daily scene output and load fluctuation patterns in an energy base in northwest China. Based on the operation constraints of each subsystem, aiming at the optimal comprehensive benefit, minimum generalized load fluctuation, and minimum carbon emission, an operation optimization scheduling model for the pumped storage-wind-photovoltaic-thermal combined power generation system has been established. When the optimization model has a configuration scale of 3000 MW for wind power and 2800 MW for photovoltaics, the pumped storage power station in the combined power generation system can achieve full pumping for 4 h and full generation for 5 h, which plays an obvious role in peak and valley regulation. Meanwhile, the combined system minimizes operating costs and carbon emissions, resulting in a minimum fluctuation of thermal power output by 6.6%. Furthermore, different capacity configurations demonstrate a non-linear relationship between the comprehensive benefits, carbon emissions, and the scene penetration rate. When prioritizing economic stability over carbon emissions, a thermal power capacity configuration of 7200 MW leads to the lowest total operating cost for the combined system, amounting to 26.38 million ¥. Results indicate that pumped storage effectively suppresses grid power fluctuations, promotes the consumption of renewable energy sources, and enhances the stability of thermal power output.
Prediction by a hybrid machine learning model for high-mobility amorphous In2O3: Sn films fabricated by RF plasma sputtering deposition using a nitrogen-mediated amorphization method
Authors: Kamataki Kunihiro , Ohtomo Hirohi , Itagaki Naho , Lesly Chawarambawa Fadzai , Yamashita Daisuke , Okumura Takamasa , Yamashita Naoto , Koga Kazunori , Shiratani Masaharu
Published: October 2023

In this study, we developed a hybrid machine learning technique by combining appropriate classification and regression models to address challenges in producing high-mobility amorphous In2O3:Sn (a-ITO) films, which were fabricated by radio-frequency magnetron sputtering with a nitrogen-mediated amorphization method. To overcome this challenge, this hybrid model that was consisted of a support vector machine as a classification model and a gradient boosting regression tree as a regression model predicted the boundary conditions of crystallinity and experimental conditions with high mobility for a-ITO films. Based on this model, we were able to identify the boundary conditions between amorphous and crystalline crystallinity and thin film deposition conditions that resulted in a-ITO films with 27% higher mobility near the boundary than previous research results. Thus, this prediction model identified key parameters and optimal sputtering conditions necessary for producing high-mobility a-ITO films. The identification of such boundary conditions through machine learning is crucial in the exploration of thin film properties and enables the development of high-throughput experimental designs.
Modulating impurity levels in two-dimensional polar materials for photocatalytic overall water splitting
Authors: Sun Dazhong , Li Wentao , Shi Anqi , Liu Kaifei , Zhang Wenxia , Shu Huabing , Chi Fengfeng , Wang Bing , Zhang Xiuyun , Niu Xianghong
Published: October 2023

Doping to induce suitable impurity levels is an effective strategy to achieve highly efficient photocatalytic overall water splitting (POWS). However, to predict the position of impurity levels, it is not enough to only depend on the projected density of states of the substituted atom in the traditional method. Herein, taking in phosphorus-doped g-C3N5 as a sample, we find that the impurity atom can change electrostatic potential gradient and polarity and then significantly affect the spatial electron density around the substituted atom, which further adjusts the impurity level position. Based on the redox potential requirement of POWS, we not only obtain suitable impurity levels but also expand the visible light absorption range. Simultaneously, the strengthened polarity induced by doping further improves the redox ability of photogenerated carriers. Moreover, the enhanced surface dipoles obviously promote the adsorption and subsequent splitting of water molecules. Our study provides a more comprehensive view to realize accurate regulation of impurity levels in doping engineering and gives reasonable strategies for designing an excellent catalyst of POWS.
Similar electronic state effect enables excellent activity for nitrate-to-ammonia electroreduction on both high- and low-density double-atom catalysts
Authors: Lv Wenjing , Deng Jianming , Wu Donghai , He Bingling , Tang Gang , Ma Dongwei , Jia Yu , Lv Peng
Published: October 2023

Double-atom catalysts (DACs) for harmful nitrate (NO3−) electroreduction to valuable ammonia (eNO3RR) is attractive for both environmental remediation and energy transformation. However, the limited metal loading in most DACs largely hinders their applications in practical catalytic applications. Therefore, exploring ultrahigh-density (UHD) DACs with abundant active metal centers and excellent eNO3RR activity is highly desired under the site-distance effect. Herein, starting from the experimental M2N6 motif deposited on graphene, we firstly screened the low-density (LD) Mn2N6 and Fe2N6 DACs with high eNO3RR activity and then established an appropriate activity descriptor for the LD–DAC system. By utilizing this descriptor, the corresponding Mn2N6 and Fe2N6 UHD–DACs with dynamic, thermal, thermodynamic, and electrochemical stabilities, are identified to locate at the peak of activity volcano, exhibiting rather-low limiting potentials of −0.25 and −0.38 V, respectively. Further analysis in term of spin state and orbital interaction, confirms that the electronic state effect similar to that of LD–DACs enable the excellent eNO3RR activity to be maintained in the UHD–DACs. These findings highlight the promising application of Mn2N6 and Fe2N6 UHD–DACs in nitrate electroreduction for NH3 production and provide impetus for further experimental exploration of ultrahigh-density DACs based on their intrinsic electronic states.
The ocean carbon sinks and climate change
Authors: Sunny Eros M. , Ashok Balakrishnan , Balakrishnan Janaki , Kurths Jürgen
Published: October 2023

The oceans act as major carbon dioxide sinks, greatly influencing global climate. Knowing how these sinks evolve would advance our understanding of climate dynamics. We construct a conceptual box model for the oceans to predict the temporal and spatial evolution of CO2 of each ocean, and the time-evolution of their salinities. Surface currents, deep water flows, freshwater influx, and major fluvial contributions are considered, as also the effect of changing temperature with time. We uncover the strongest carbon uptake to be from the Southern Ocean, followed by the Atlantic. The North Atlantic evolves into the most saline ocean with time and increasing temperatures. The Amazon River is found to have significant effects on CO2 sequestration trends. An alternative flow scenario of the Amazon is investigated, giving interesting insights into the global climate in the Miocene epoch.
Many-body GW calculations with very large scale polarizable environments made affordable: A fully ab initio QM/QM approach
Authors: Amblard David , Blase Xavier , Duchemin Ivan
Published: October 2023

We present a many-body GW formalism for quantum subsystems embedded in discrete polarizable environments containing up to several hundred thousand atoms described at a fully ab initio random phase approximation level. Our approach is based on a fragment approximation in the construction of the Green’s function and independent-electron susceptibilities. Further, the environing fragments susceptibility matrices are reduced to a minimal but accurate representation preserving low order polarizability tensors through a constrained minimization scheme. This approach dramatically reduces the cost associated with inverting the Dyson equation for the screened Coulomb potential W, while preserving the description of short to long-range screening effects. The efficiency and accuracy of the present scheme is exemplified in the paradigmatic cases of fullerene bulk, surface, subsurface, and slabs with varying number of layers.
Effects of a subsonic gas flow on the wave blocking and energy of interfacial waves with a constant vorticity
Authors: Zakaria Kadry , Gamiel Yasser
Published: October 2023

Negative energy waves play a significant role in hydrodynamic instabilities of flow and are involved in all kinds of instability in flows because they can withdraw energy from the flow. Effects of subsonic gas flow and vorticity on the existence of negative energy for water waves as well as the occurrence of capillary-gravity wave blocking have been studied. The existence of blocking points and variation in group velocity for different flow parameters such as the vorticity and subsonic gas factor is studied. The results are in agreement with a previous experiment [Suastika et al., “Experimental study of wave blocking,” Coastal Eng. 1, 227 (2000)]. The present study aims to deal with the combined effect of a subsonic gas flow parallel to solid boundaries and a moving liquid layer with linear velocity profile to establish the existing condition for negative energy waves and the blocking waves, especially for waves propagating in the opposite direction of the current. As a limiting case of the present model, in the absence of aerodynamic effect, it is found that the incident and reflected interfacial waves propagate inside the stability domain; this means that the transformed wave is generated at the expense of the energy of incident wave.
Obtaining extended insight into molecular systems by probing multiple pathways in second-order nonlinear spectroscopy
Authors: Fellows Alexander P. , Balos Vasileios , John Ben , Díaz Duque Álvaro , Wolf Martin , Thämer Martin
Published: October 2023

Second-order nonlinear spectroscopy is becoming an increasingly important technique in the study of interfacial systems owing to its marked ability to study molecular structures and interactions. The properties of such a system under investigation are contained within their intrinsic second-order susceptibilities which are mapped onto the measured nonlinear signals (e.g. sum-frequency generation) through the applied experimental settings. Despite this yielding a plethora of information, many crucial aspects of molecular systems typically remain elusive, for example the depth distributions, molecular orientation and local dielectric properties of its constituent chromophores. Here, it is shown that this information is contained within the phase of the measured signal and, critically, can be extracted through measurement of multiple nonlinear pathways (both the sum-frequency and difference-frequency output signals). Furthermore, it is shown that this novel information can directly be correlated to the characteristic vibrational spectra, enabling a new type of advanced sample characterization and a profound analysis of interfacial molecular structures. The theory underlying the different contributions to the measured phase of distinct nonlinear pathways is derived, after which the presented phase disentanglement methodology is experimentally demonstrated for model systems of self-assembled monolayers on several metallic substrates. The obtained phases of the local fields are compared to the corresponding phases of the nonlinear Fresnel factors calculated through the commonly used theoretical model, the three-layer model. It is found that, despite its rather crude assumptions, the model yields remarkable similarity to the experimentally obtained values, thus providing validation of the model for many sample classes.
Possible way to achieve valley-polarized quantum anomalous Hall insulator
Authors: Guo San-Dong , Wang Guangzhao , Ang Yee Sin
Published: October 2023

The valley-polarized quantum anomalous Hall insulator (VQAHI), which combines valleytronics and topology in one material, provides a path toward integrating valleytronics, topological quantum effects, and spintronics. Here, we propose a way of realizing VQAHIs in tetragonal quantum anomalous Hall insulators (QAHIs) by introducing valley polarization, which can be achieved by breaking C4 rotational symmetry. We use a concrete example of a QAHI Fe2I2 monolayer, where there are equivalent valleys along the Γ-X and Γ-Y lines in momentum space, to illustrate our proposal through first-principle calculations. By applying uniaxial strain along the x direction, the rotational symmetry C4 is reduced into C2, which induces valley polarization. With uniaxial strain from a compressive one to a tensile one, valley polarization transition can be induced. Moreover, the nonzero Berry curvature around valleys can produce the anomalous valley Hall effect. With the considered strain range, the quantum anomalous Hall properties can be maintained. Therefore, a VQAHI can be realized in strained Fe2I2. Our works propose an experimentally feasible way to realize valley polarization and VQAHIs.
Underwater microsecond timescale electrical explosions of aluminum and copper foils
Authors: Asmedianov N. , Grikshtas R. , Maler D. , Liziakin G. , Krasik Ya. E.
Published: October 2023

We present results on underwater electrical explosions of thin aluminum and copper foils using a generator delivering ∼200 kA current amplitude, ∼0.9 μs rise time pulses. Time-resolved shadow imaging displays the generation of a strong planar shock wave in water in the vicinity of the exploding foil. Using time-resolved spectroscopy, aluminum oxide (AlO) absorption bands were observed in a Planckian-like spectrum, indicating that aluminum combustion starts when aluminum vaporizes. It is also shown that the strongest shock wave is obtained for the largest linear energy deposition rate to the foil.
Viscous effects on morphological and thermodynamic non-equilibrium characterizations of shock–bubble interaction
Authors: Zhang Dejia , Xu Aiguo , Gan Yanbiao , Zhang Yudong , Song Jiahui , Li Yingjun
Published: October 2023

A two-fluid discrete Boltzmann model with a flexible Prandtl number is formulated to study the shock–bubble interaction (SBI). This paper mainly focuses on the viscous effects on morphological and thermodynamic non-equilibrium (TNE) characterizations during the SBI process. Due to the rapid and brief nature of the SBI process, viscosity has a relatively limited influence on macroscopic parameters but significantly affects the TNE features of the fluid system. Morphologically, viscosity affects the configuration of the vortex pair, increases both the amplitudes of gradients of average density and average temperature of the fluid field, and reduces circulation of the bubble. As a higher viscosity fluid absorbs more energy from the shock wave, it leads to an increase in both the proportion of the high-density region and the corresponding boundary length for a fixed density threshold. The spatiotemporal features of TNE quantities are analyzed from multiple perspectives. The spatial configuration of these TNE quantities exhibits interesting symmetry, which aids in understanding the way and extent to which fluid unit deviates from the equilibrium state. Theoretically, viscosity influences these TNE quantities by affecting the transport coefficients and gradients of macroscopic quantity. Meanwhile, the viscosity increases the entropy production rate originating from the non-organized momentum flux mainly through amplifying the transport coefficient and enhances the entropy production rate contributed by the non-organized energy flux by raising the temperature gradient. These multi-perspective results collectively provide a relatively comprehensive depiction of the SBI.
Assessment of the partial saddle point approximation in field-theoretic polymer simulations
Authors: Quah Timothy , Delaney Kris T. , Fredrickson Glenn H.
Published: October 2023

Field-theoretic simulations are numerical treatments of polymer field theory models that go beyond the mean-field self-consistent field theory level and have successfully captured a range of mesoscopic phenomena. Inherent in molecularly-based field theories is a “sign problem” associated with complex-valued Hamiltonian functionals. One route to field-theoretic simulations utilizes the complex Langevin (CL) method to importance sample complex-valued field configurations to bypass the sign problem. Although CL is exact in principle, it can be difficult to stabilize in strongly fluctuating systems. An alternate approach for blends or block copolymers with two segment species is to make a “partial saddle point approximation” (PSPA) in which the stiff pressure-like field is constrained to its mean-field value, eliminating the sign problem in the remaining field theory, allowing for traditional (real) sampling methods. The consequences of the PSPA are relatively unknown, and direct comparisons between the two methods are limited. Here, we quantitatively compare thermodynamic observables, order-disorder transitions, and periodic domain sizes predicted by the two approaches for a weakly compressible model of AB diblock copolymers. Using Gaussian fluctuation analysis, we validate our simulation observations, finding that the PSPA incorrectly captures trends in fluctuation corrections to certain thermodynamic observables, microdomain spacing, and location of order-disorder transitions. For incompressible models with contact interactions, we find similar discrepancies between the predictions of CL and PSPA, but these can be minimized by regularization procedures such as Morse calibration. These findings mandate caution in applying the PSPA to broader classes of soft-matter models and systems.
Universal abundance fluctuations across microbial communities, tropical forests, and urban populations
Authors: George Ashish B. , O’Dwyer James
Published: October 2023

The growth of complex populations, such as microbial communities, forests, and cities, occurs over vastly different spatial and temporal scales. Although research in different fields has developed detailed, system-specific models to understand each individual system, a unified analysis of different complex populations is lacking; such an analysis could deepen our understanding of each system and facilitate cross-pollination of tools and insights across fields. Here, we use a shared framework to analyze time-series data of the human gut microbiome, tropical forest, and urban employment. We demonstrate that a single, three-parameter model of stochastic population dynamics can reproduce the empirical distributions of population abundances and fluctuations in all three datasets. The three parameters characterizing a species measure its mean abundance, deterministic stability, and stochasticity. Our analysis reveals that, despite the vast differences in scale, all three systems occupy a similar region of parameter space when time is measured in generations. In other words, although the fluctuations observed in these systems may appear different, this difference is primarily due to the different physical timescales associated with each system. Further, we show that the distribution of temporal abundance fluctuations is described by just two parameters and derive a two-parameter functional form for abundance fluctuations to improve risk estimation and forecasting.
Physical mechanisms of red blood cell splenic filtration
Authors: Moreau Alexis , Yaya François , Lu Huijie , Surendranath Anagha , Charrier Anne , Dehapiot Benoit , Helfer Emmanuèle , Viallat Annie , Peng Zhangli
Published: October 2023

The splenic interendothelial slits fulfill the essential function of continuously filtering red blood cells (RBCs) from the bloodstream to eliminate abnormal and aged cells. To date, the process by which 8

μ

m RBCs pass through 0.3

μ

m-wide slits remains enigmatic. Does the slit caliber increase during RBC passage as sometimes suggested? Here, we elucidated the mechanisms that govern the RBC retention or passage dynamics in slits by combining multiscale modeling, live imaging, and microfluidic experiments on an original device with submicron-wide physiologically calibrated slits. We observed that healthy RBCs pass through 0.28

μ

m-wide rigid slits at 37 °C. To achieve this feat, they must meet two requirements. Geometrically, their surface area-to-volume ratio must be compatible with a shape in two tether-connected equal spheres. Mechanically, the cells with a low surface area-to-volume ratio (28% of RBCs in a 0.4

μ

m-wide slit) must locally unfold their spectrin cytoskeleton inside the slit. In contrast, activation of the mechanosensitive PIEZO1 channel is not required. The RBC transit time through the slits follows a

−

1 and

−

3 power law with in-slit pressure drop and slip width, respectively. This law is similar to that of a Newtonian fluid in a two-dimensional Poiseuille flow, showing that the dynamics of RBCs is controlled by their cytoplasmic viscosity. Altogether, our results show that filtration through submicron-wide slits is possible without further slit opening. Furthermore, our approach addresses the critical need for in vitro evaluation of splenic clearance of diseased or engineered RBCs for transfusion and drug delivery.
Ultra-wideband chiroptical response by tri-layer anisotropic plasmonic metamaterial
Authors: Hussain Shahid , Guan Xueyu , Ji Ruonan , Wang Shaowei
Published: October 2023

The use of plasmonic chiral metamaterials for the control of circular polarization has the potential to replace conventional optical equipment for polarization-related applications. The ultra-broadband chiroptic response using plasmonic constituents is delivered by elaborate three-dimensional (3D) helical structures, nevertheless, their implementation is complicated, time-consuming, and poses a significant scaling difficulty at the nano level. Ultra-broadband response from planar constituents is particularly necessary as a means to circumvent the challenges of 3D metamaterials. Here we present a planar plasmonic structure composed of tri-layer anisotropic arrays constituting nanowires and cut-wires to generate dual overlapped chiral bands. Based on this tri-layer approach, we numerically realized ultra-broadband planar plasmonic metamaterials to function in the near- and mid-infrared regions with a bandwidth range of 1.38–3.07 µm and 4.00–8.10 µm, and maximum circular dichroism performance of 0.90 and 0.92 respectively. The structures are ultracompact, misalignments tolerant, and can be extended to additional spectral regions through structural engineering. The proposed metamaterial has the potential to be used in the creation of ultra-compact, high-performance devices for a wide variety of uses, such as those in the fields of optical communication, biological diagnosis, high-contrast polarization imaging, high-accuracy polarimetric measurements, and spectroscopy.
Magnetic properties and critical behaviors of the nodal-line semimetal candidate ErIn3
Authors: Chen Y , Tang F , Yin X-Q , Han Z-D , Qian B , Zhao W , Jiang X-F , Fang Y , You L
Published: October 2023

The AuCu3-type intermetallic compounds ReIn3 (Re = a rare earth ion) with type-IV magnetic space groups are predicted to show topologically nontrivial electronic states. Here, we grow ErIn3 single crystals, and study their magnetic properties and critical behaviors by means of the magnetic susceptibility, and magnetization isotherm measurements. Combining a detailed analysis of the magnetic susceptibility and isothermal magnetization, we find that this compound harbors a complicated magnetic phase diagram, and its magnetic moment arrangement appears not to simply follow the fashion as observed in the isostructural counterpart GdIn3 (it adopts a conventional type-C magnetic structure that belongs to type-IV magnetic space groups). A careful study of the magnetic properties around the antiferromagnetic (AFM)-paramagnetic transition yields the critical exponents β = 0.309 (0.297), γ = 1.117 (1.038), and δ = 4.617 (4.454), indicating that the tricritical mean field model or the three-dimensional Ising model works for ErIn3’s magnetic behaviors and the presence of a long-range AFM interaction therein. Besides, the exchange interaction distance J(r) ∼ r
−4.665 as well confirms a long-range magnetic coupling in ErIn3. Our results offer the clues that the magnetic structure varies from one member of ReIn3 family to another, and to confirm their electronic features in the AFM phases further experimental and theoretical studies are still desired.
Non-trivial topological phases in transition metal rich half-Heusler oxides
Authors: Dhori Bhautik R , Sattigeri Raghottam M , Jha Prafulla K
Published: October 2023

Topological insulators with gapless surface states and insulating bulk in non-centrosymmetric cubic systems have been extensively explored following the discovery of two-dimensional quantum spin hall effect in zincblende HgTe. In such systems the negative band inversion strength E

B
I
S

(= E

Γ
6

−

E

Γ
8

<

0) governs the robustness of the non-trivial topological states at ambient conditions. Hence, realizing large negative values of E

B
I
S

has been a guiding motivation of several investigations reported in literature. Here, we present a material design approach which can be employed to realize large negative values of E

B
I
S

in cubic materials such as half-Heusler (HH) oxides with 18 valence electron configurations. We explore 27 HH oxides of the form ABO (A = Li, K, Rb; B = Cu, Ag, Au) in α-, β-, and γ-phase (by placing transition metal atom at different Wyckoff positions) for their non-trivial topological phase. Off these three phases, we found that, the α-phase of nine HH oxides (wherein the transition metal atoms occupy 4a Wyckoff positions in the crystal structure) is the most promising with non-trivial topological phase which is governed by the mass-Darwin fully-relativistic effects enhancing E

B
I
S

. Whereas the other phases were found to be either trivial semiconductors or semimetals or metals and most of them being dynamically unstable. We focus on RbAuO in α-phase with E

B
I
S

of −1.29 eV and the effect of strain fields on the topological surface states of this compound. We conclude that the α-phase of HH oxide presented here can be synthesized experimentally for diverse room temperature applications in spintronics and nanoelectronics.
First-principles investigation of the electronics, optical, mechanical, thermodynamics and thermoelectric properties of Na based Quaternary Heusler alloys (QHAs) NaHfXGe (X = Co, Rh, Ir)
Authors: Zosiamliana R , Kima Lalrin , Mawia Zodin , Zuala Lalhriat , Abdurakhmanov G , Rai D P
Published: October 2023

In this study, we explored the electronic and thermoelectric (TE) properties of the Na-based Quaternary Heusler Alloys (QHAs) NaHfXGe (X = Co, Rh, Ir) using density functional theory (DFT). We performed the spin-polarized DFT calculations at the general gradient approximation (GGA) level and confirmed the ground state non-magnetic configuration of NaHfXGe. The mechanical and thermodynamical stabilities are analyzed and discussed to validate the stability by calculating the elastic constant and phonon dispersion curve. A thorough investigation on the electronic properties are carried out by performing the GGA, GGA+U, and GGA+SOC formalism where we report the semi-conducting characteristic of NaHfCoGe and NaHfRhGe QHAs. However, NaHfIrGe is predicted to be a non-magnetic metal. From the calculated optical properties we found that the most active optical absorption occurs within the vis–UV region with

α
>

105 cm−1, therefore the studied QHAs are proposed to be a promising optoelectronic materials. The results of the thermodynamic properties have shown that NaHfXGe follows Debye’s low-temperature specific heat law and the classical thermodynamics of the Dulong-Petit law at high temperatures. The calculated TE efficiency using GGA+SOC formalism at T = 1200 K are ZT∼1.22 and 0.57 for NaHfCoGe and NaHfRhGe, suggesting that these materials are potential TE materials to operate at high temperature.
Application of MMI-SVP theory in spindle fault feature extraction
Authors: Kang Yi , Liu Tao , Wang Zhenya , Li Dongguo
Published: October 2023

Singular value decomposition (SVD) is an effective method for estimating and separating noise in a signal. However, its performance depends on several factors, including the construction of the Hankel matrix, the number of retained reconstructed components, the length of data analysis, and even the fault feature frequency of the monitored object. This paper aims to discuss these issues and proposes an adaptive selection method of singular value pairs (SVP) based on minimum mutual information (MMI). Firstly, SVD is used to obtain singular values (SV), and the anti-angle averaging method is employed to generate a set of sub-signals for reconstruction. SV is utilized to characterize the energy of the sub-signals and determine the SVP. Subsequently, mutual information is introduced to quantitatively evaluate mutation signals and adaptively select SVP to avoid excessive or insufficient noise reduction. Additionally, the optimal dimension for the Hankel matrix decomposition is automatically determined by considering the singular value ratio and MMI index. Finally, based on prior knowledge of bearing size and fault characteristics, the minimum sample length of the Hankel matrix is determined. The effectiveness of MMI-SVP is verified through simulation analysis and real bearing fault cases.
Remaining useful life prediction based on a PCA and similarity methods
Authors: Duan Chaoqun , Shen Yilin , Guo Kanghao , Sheng Bo , Wang Yuanhang
Published: October 2023

Aircraft engine failures or damages not only incur substantial financial losses but also present risks of injuries or even fatalities. Hence, it is of utmost importance to devise an effective method to predict potential failures in advance, thereby mitigating accidents and minimizing losses. This paper proposes a novel approach that combines a principal component analysis (PCA) with similarity methods to establish a degradation trajectory database and predict the remaining useful life (RUL) of new engines by identifying similar trajectories. Firstly, the data dimensionality is reduced using a PCA to create a health indicator. The validity of the reduced data is confirmed by calculating the Spearman correlation coefficient between the health indicator and the system RUL. During the similarity comparison process, the Manhattan distance is employed for the similarity calculation, and parameter optimization is performed on the length of selected time segments and the number of chosen similar trajectories to optimize the similarity of RUL prediction model, resulting in the optimal prediction results among all engine test sets. Notably, this paper introduces the feasibility of employing the Manhattan distance in similarity method-based prediction, which is superior to the commonly used Euclidean distance calculation method found in most literature. This finding offers innovative ideas and perspectives for advancing RUL prediction methodologies. By adopting the proposed approach, the occurrence of accidents and losses associated with aircraft engine failures can be substantially reduced, leading to enhanced safety and economic benefits.
Classification of multi-type bearing fault features based on semi-supervised generative adversarial network (GAN)
Authors: Li Xiao , Zhang Feng-Liang
Published: October 2023

Fault diagnosis is a crucial technology for ensuring the reliable and efficient operation of industrial systems. With the advancement of industrial informatization and intelligence, fault diagnosis methods have the trend shifting from traditional signal processing to deep learning. However, traditional deep learning models are not suitable for industrial scenarios with limited labeled data, imbalanced categories. To address these challenges, this paper proposes a novel approach based on semi-supervised generative adversarial networks (SGANs) to systematically study the fault diagnosis of rolling bearings in the case of unlabeled samples and sparsely labeled samples. In this work, the vibration time-domain vibration signal of the bearing is firstly transformed into a spectrum signal through the fast Fourier transform. This transformed signal is then fed into the GAN model to extract multi-layer sensitive features, providing a deeper understanding of the underlying fault characteristics. Subsequently, the SGAN method utilizes unsupervised learning via spectral clustering algorithms to automatically classify fault patterns in industrial equipment. Furthermore, it enhances semi-supervised learning by incorporating limited label information through softmax functions, effectively discerning the authenticity of unlabeled data. For the effectiveness of SGAN for bearing fault diagnosis, two diverse datasets are utilized including the widely-used Case Western Reserve University dataset and data acquired from South Ural State University. Compared to alternative models, the results underscore SGAN’s robustness, achieving high recognition accuracy and clustering performance. The proposed methodology contributes to the advancement of fault diagnosis technologies by combining unsupervised and semi-supervised learning techniques.
Mechanics of AlCuNiTi alloy orthogonal micro-cutting
Authors: Nguyen Hoang-Giang , Fang Te-Hua
Published: October 2023

The mechanical behavior of AlCuNiTi alloy during orthogonal micro-cutting consists of conventional cutting and complex-dimensional vibration cutting (CDVC) are investigated using molecular dynamics. The material removal mechanism is studied in terms of phase angle, amplitude ratio, and vibration frequency. In both techniques, the stress and strain are localized in the contiguous location between the sample and the cutting tool. The sample temperature during CDVC is noticeably greater than during classical cutting, which might benefit the transition phase and make CDVC smoother. The total mean value cutting force of the CDVC decreases as the frequencies of vibration and ratios of amplitude increase; however, the mean values of force under the CDVC with different phase angles demonstrate hardly ever statistically significant change. The quantity of atoms in the chip indicates that the machined surface rate is higher under the CDVC, with a higher frequency of vibration, smaller phase angle, and amplitude ratio. Under CDVC, the chip of plastic deformation gets more pronounced and severe with a frequency of oscillation at 150 GHz, an amplitude at 1.5, and a phase angle degree of 75° due to the lowest cutting ratio.
High-pressure CO2 dissociation with nanosecond pulsed discharges
Authors: Yong Taemin , Zhong Hongtao , Pannier Erwan , Laux Christophe , Cappelli Mark A
Published: October 2023

We investigate the conversion of CO2 into CO and O2 with nanosecond repetitively pulsed (NRP) discharges in a high-pressure batch reactor. Stable discharges are obtained at up to 12 bar. By-products are measured with gas chromatography. The energy efficiency is determined for a range of processing times, pulse energy, and fill pressures. It is only weakly sensitive to the plasma operating parameters, i.e the extent of CO2 conversion is almost linearly-dependent on the specific energy invested. A conversion rate as high as 14% is achieved with an energy efficiency of 23%. For long processing times, saturation in the yield and a drop in efficiency are observed, due to the increasing role of three-body recombination reactions, as described by zero-dimensional detailed kinetic modeling. The modeling reveals the presence of three-stage kinetics between NRP pulses, controlled by electron-impact CO2 dissociation, vibrational relaxation, and neutral elementary kinetics. Transport effects are shown to be important for CO2 conversion at high pressures. For fill pressures beyond 10 bar, CO2 may locally transit into supercritical states. The supercritical plasma kinetics may bypass atomic oxygen pathways and directly convert CO2 into O2. This work provides a detailed analysis of plasma-based high-pressure CO2 conversion, which is of great relevance to future large-scale sustainable carbon capture, utilization, and storage.
Stationary axial model of the Hall thruster plasma discharge: electron azimuthal inertia and far plume effects
Authors: Bello-Benítez E , Ahedo E
Published: October 2023

One-dimensional axial models of the plasma discharge of a Hall thruster provide a valuable picture of its physical behavior with a small computational effort. Therefore, they are very suitable for quick parametric analyses or as a support tool for analyzing the impact of modeling decisions. This paper extends a well-known drift-diffusion stationary, quasineutral model by adding electron azimuthal inertia (EAI), a nonzero thickness cathode layer, and the far-plume region where electrons demagnetize and cool down. The EAI dominates on the far plume and affects positively to thrust. For a small ion backstreaming current, EAI modifies much the electron velocities and density near the anode, but has no discernible effect on the electron cross-field transport. Electron axial inertia and azimuthal gyrovisosity are estimated. The thick cathode layer connects quasineutrally the near and far plumes but the coupling between these two regions is weak. The far plume region is sensitive to the decay length of the magnetic field, the downstream boundary conditions on the electron currents, and the stray electric currents.
Encryption of digital images and voices using the Arneodo-Coullet-Tresser chaotic system
Authors: Sanjaya W S Mada , Roziqin Akhmad , Temiesela Agung Wijaya , Zaman M Fauzi Badru , Wibiksana Aria Dewa , Anggraeni Dyah
Published: October 2023

In this study, we investigate the application of the Arneodo-Coullet-Tresser chaotic system in both image and voice encryption, considering the increasing importance of data security in the digital age. The analysis of the chaotic system involves exploring phase diagrams, time series, bifurcation diagrams, Lyapunov exponent analysis, and Poincaré maps to understand its dynamics. For image encryption, we evaluate the effectiveness of the system through various analyses, including histogram analysis, correlation analysis, entropy analysis, NPCR and UACI analysis, and noise attack analysis. Similarly, for voice encryption, we assess it through various analyses, including waveform plots, FFT, spectrograms, correlation coefficients, entropy analysis, and RMSE. The research findings demonstrate the suitability of the Arneodo-Coullet-Tresser chaotic system for both image and voice encryption, suggesting its potential as a data transmission masking technique. The research includes numerical simulations conducted using Python to support the proposed approach.
Hysteresis inversion-free predictive compensation control for soft pneumatic actuators based on a global Koopman modeling strategy
Authors: Peng Kerui , Chen Wangxing , Guan Shengchuang , Liu Zhaobing
Published: October 2023

Soft pneumatic actuators (SPAs) have increasing applications in soft robotic design owing to their good compliance, excellent adaptability, and high force density characteristics. However, the inherent hysteresis nonlinearity severely degrades the control performance of SPAs. To compensate for the hysteresis effect, one solution is to build an inverse mathematical model. Nevertheless, in this method, the control performance still highly depends on the accuracy of the built inverse model. At the same time, the computational burden of deriving the inverse model is overwhelming. In addition, the physical constraints of the input pressure of SPAs are hardly handled by the inversion-based method. This paper proposes an inversion-free model predictive controller (IFMPC), which is designed based on a global Koopman linear model (GKLM). In the above GKLM-IFMPC strategy, the inverse hysteresis model is not required. Instead, a global hysteresis model can be established without considering the effect of rate-dependent property. Additionally, the control law is derived in an explicit form. With the constrained quadratic programming technique, the proposed method still works well when dealing with the physical constraints of SPAs. To verify the effectiveness of the proposed method, several comparative experiments are performed on a two-dimensional (2D) SPA. The results show that the proposed hysteresis global modeling and control framework has satisfactory tracking performance over some existing strategies even with strong hysteresis nonlinearity.
4D Einstein-Gauss-Bonnet black hole in Power-Yang-Mills field: a shadow study
Authors: Zubair M. , Raza Muhammad Ali , Sarikulov Furkat , Rayimbaev Javlon
Published: October 2023

We consider a static black hole immersed in the Power-Yang-Mills field in four-dimensional Einstein-Gauss-Bonnet gravity and investigate the effect of various parameters on the radius of the photon sphere. The modified form of the Newman-Janis algorithm is used for obtaining a rotating black hole solution in this gravity. Further, we try to explore the influence of the Yang-Mills magnetic charge Q with power q, Gauss-Bonnet parameter α, and spin a on the horizon radius. The geodesic equations are constructed by incorporating the Hamilton-Jacobi formalism. The radial component of the geodesic equations gives the effective potential which is further used in deriving the mathematical structure for the shadows by using Bardeen's procedure for a fixed observer at infinity. The shadows are calculated and plotted in terms of two celestial coordinates for an equatorial observer. It is observed that all the parameters have a very significant effect on the shadow and related physical observables. We also obtain the constraint values for the spin, magnetic charge, and Gauss-Bonnet parameters, using the shadow size of supermassive black holes Sagittarius A* and M87* from the EHT observations for the cases of q = 0.6 and q = 0.9. It is shown that there are upper and lower bounds for the charge and spin of M87* at q = 0.6, while only the upper bounds for the charge and spin of Sagittarius A*. Finally, we investigate the energy emission rate in the Hawking radiation around the 4D Einstein-Gauss-Bonnet black hole in the Power-Yang-Mills field.
Revisiting Lorentz invariance violation from GRB 221009A
Authors: Li Hao , Ma Bo-Qiang
Published: October 2023

As a potential consequence of Lorentz invariance violation (LIV), threshold anomalies open a window to study LIV.
Recently the Large High Altitude Air Shower Observatory (LHAASO) reported that more than 5000 photons from GRB 221009A have been observed with energies above 500 GeV and up to 18 TeV.
In the literature, it is suggested that this observation
may have tension with
the standard model result because extragalactic background light (EBL) can prevent photons around 18 TeV from reaching the earth and that LIV induced threshold anomalies might be able
to explain the observation.
In this work we further study this proposal with more detailed numerical calculation for different LIV scales and redshifts of the sources.
We find that GRB 221009A is a rather unique opportunity to search LIV, and a LIV scale E
LIV ≲ E
Planck ≈ 1.22 × 1019 GeV is
feasible
to the observation of GRB 221009A on 9 October, 2022.
Databases of 2D material-substrate interfaces and 2D charged building blocks
Authors: Deng 邓 Jun 俊 , Pan 潘 Jinbo 金波 , Du 杜 Shixuan 世萱
Published: October 2023

Discovery of materials using “bottom-up” or “top-down” approach is of great interest in materials science. Layered materials consisting of two-dimensional (2D) building blocks provide a good platform to explore new materials in this respect. In van der Waals (vdW) layered materials, these building blocks are charge neutral and can be isolated from their bulk phase (top-down), but usually grow on substrate. In ionic layered materials, they are charged and usually cannot exist independently but can serve as motifs to construct new materials (bottom-up). In this paper, we introduce our recently constructed databases for 2D material-substrate interface (2DMSI), and 2D charged building blocks. For 2DMSI database, we systematically build a workflow to predict appropriate substrates and their geometries at substrates, and construct the 2DMSI database. For the 2D charged building block database, 1208 entries from bulk material database are identified. Information of crystal structure, valence state, source, dimension and so on is provided for each entry with a json format. We also show its application in designing and searching for new functional layered materials. The 2DMSI database, building block database, and designed layered materials are available in Science Data Bank at https://doi.org/10.57760/sciencedb.j00113.00188.
Inferring population dynamics in macaque cortex
Authors: Meghanath Ganga , Jimenez Bryan , Makin Joseph G
Published: October 2023

Objective. The proliferation of multi-unit cortical recordings over the last two decades, especially in macaques and during motor-control tasks, has generated interest in neural ‘population dynamics’: the time evolution of neural activity across a group of neurons working together. A good model of these dynamics should be able to infer the activity of unobserved neurons within the same population and of the observed neurons at future times. Accordingly, Pandarinath and colleagues have introduced a benchmark to evaluate models on these two (and related) criteria: four data sets, each consisting of firing rates from a population of neurons, recorded from macaque cortex during movement-related tasks. Approach. Since this is a discriminative-learning task, we hypothesize that general-purpose architectures based on recurrent neural networks (RNNs) trained with masking can outperform more ‘bespoke’ models. To capture long-distance dependencies without sacrificing the autoregressive bias of recurrent networks, we also propose a novel, hybrid architecture (‘TERN’) that augments the RNN with self-attention, as in transformer networks. Main results. Our RNNs outperform all published models on all four data sets in the benchmark. The hybrid architecture improves performance further still. Pure transformer models fail to achieve this level of performance, either in our work or that of other groups. Significance. We argue that the autoregressive bias imposed by RNNs is critical for achieving the highest levels of performance, and establish the state of the art on the neural latents benchmark. We conclude, however, by proposing that the benchmark be augmented with an alternative evaluation of latent dynamics that favors generative over discriminative models like the ones we propose in this report.
Technologies and challenges of hydrogen powered aviation
Authors: Xu Dawei
Published: October 2023

Currently, the aviation industry mainly uses kerosene as fuel, which releases a lot of carbon emissions. As the world population grows rapidly, the requirements for air transport are increasing, which promotes an environmentally friendly transformation of the aviation industry. This paper summarizes the advantages of using hydrogen as fuel and makes a comparison to other environment-friendly technologies. The history of hydrogen aircraft and several aircraft hydrogen propulsion and storage options are discussed. In addition, the challenge and future developments of hydrogen powered craft that the aviation industry is facing are also analyzed in this paper, hoping to raise people’s awareness of the use of hydrogen in aviation, and draw the future direction of the aviation industry.