bluuebunny/crossref_metadata_2025 huggingface dataset:
Thrust enhancement of a flapping foil through interaction with a Kármán vortex street
Authors: Wang Zhuo , Du Lin , Sun Xiaofeng
Published: July 2024

How to increase the thrust without efficiency deterioration is a significant issue for an oscillating-foil propeller. This paper presents a numerical study to the phenomenon of thrust enhancement of a flapping foil through interaction with a Kármán vortex street. A circular cylinder is placed upstream the foil to generate the Kármán street. Simulations are performed at different combinations of the gap between the cylinder and the foil and the reduced frequencies. It is found that the upstream vortices are helpful to increase both the thrust and propulsive efficiency simultaneously. Under specific oscillation parameters, the synchronization between the vortices shedding and the foil's oscillation will occur, which further results in the phenomenon of thrust enhancement, with a high thrust more than twice that of the same flapping foil in the uniform oncoming flow, as well as a higher efficiency. The occurrence of thrust enhancement is sensitive to the oscillation amplitudes of the foil and the optimal pitching amplitude is found in the range of [30°,40°]. Flow analysis shows that a large relative flow angle higher than 90° is induced around the leading edge of the foil when a vortex of the cylinder approaches the foil, which prompts the generation of the leading-edge vortex and further results in an expanding wake pattern as two triplets (2 T). Besides, the phase between the Kármán street and the oscillation of the foil can be effectively adjusted by forcing the cylinder to vibrate, which can further control the generation of the thrust enhancement.
Application and evaluation of dynamic Bradshaw coefficient in shear stress transport turbulence model for hydraulic machinery
Authors: Wang Hao , Wang Fujun , Wang Chaoyue , Chen Wenhao , Tang Yuan , Hong Yiping , Shi Xiaoyan
Published: July 2024

The Bradshaw assumption, that the ratio of Reynolds shear stress to turbulence kinetic energy (TKE) is a constant roughly equal to 0.3, is introduced into eddy viscosity and TKE dissipation term of the shear stress transport turbulence model (SST). This constant is calibrated by the zero-pressure-gradient plate boundary layer test. This is not applicable to rotating separation flows in hydraulic machinery, while its dynamic effects are usually ignored. In this article, a comprehensive evaluation of the dynamic Bradshaw coefficient (DBC) in SST is conducted. First, theoretical analyses of the existing typical DBCs are carried out, and a suitable expression form driven by a single turbulence Reynolds number is adopted in view of its well-reflected dynamic effects and high robustness. According to the equation structures of SST, three dynamic strategies are proposed, including only introducing DBC into eddy viscosity (SST-M1), only introducing DBC into TKE dissipation term (SST-M2), and introducing DBC both into eddy viscosity and TKE dissipation term (SST-M1 + M2). Second, the classical case of flows around a hydrofoil is employed to evaluate the application effects of these three dynamic strategies. The results show that SST-M1 exhibits severe lift/drag oscillations at large angles of attack accompanied by the eddy viscosity fluctuations, indicating poor numerical stability and potential risk of this strategy. In contrast, both SST-M2 and SST-M1 + M2 can effectively improve the deficiencies of SST in overestimating lift and underestimating drag at large angles of attack, which is attributed to the promotion of earlier and larger flow separation. The consistency between these two strategies implies that introducing DBC into the TKE dissipation term plays a key role in enhancing the prediction of SST. Therefore, the dynamic strategy SST-M2 is recommended to extend the applicability of SST for rotating separation flows in hydraulic machinery.
Variation in Asian and Pacific Islander North American English
Authors: Cheng Andrew , Cheng Lauretta , Gonzales Wilkinson Daniel Wong , Umbal Pocholo
Published: July 2024

Within sociolinguistic research on English variation, Asian and Pacific Islander North Americans (APINAs) are
frequently described as an “understudied population” due to the relative lack of published studies that analyze these speakers or
communities. This structured literature review systematically characterizes the state of the field from a variationist
perspective. We find that while studies on APINAs have become more common in the last decade, different groups are represented
unevenly in the existing literature; for example, East Asian groups are commonly represented in the literature in contrast to
South Asian groups. Furthermore, the vast majority of variationist studies analyze phonetic and phonological variation, with a
theoretical focus on identifying participation in race-based varieties (ethnolects/raciolects) or in sound changes of the
“majority” population, rather than using the inherent diversity of APINA groups to bring attention to how race and ethnicity are
being used in Sociolinguistics.
Bourdieu’s trajectory concept as an approach to microhistorical research in translation
Authors: Ali Hisham M.
Published: July 2024

This article explores the potential of Bourdieu’s trajectory concept as an approach to microhistorical research, using the life history of Egypt’s late Minister of Culture Tharwat Okasha as a case study. The focus throughout is on Okasha’s multipositionality throughout his trajectory as a military officer and then as a military attaché in France between 1939 and 1956. Through a close reading of memoirs, translations and writings, the article investigates how he traversed different fields (the military, psychology, history and journalism) and the effect of this movement on his translation practices. In so doing, the article integrates this analysis into a sociological examination of the politics of the Free Officers, who led the 1952 coup, and argues that the relational concept of trajectory allows the reconstruction of history at the intersection between the lived experience of an individual and the network of agents engaged in the same fields.
Ionization Potential Depression Model for Warm/Hot and Dense Plasmas
Authors: Wu 武 Chensheng 晨晟 , Zhou 周 Fuyang 福阳 , Yan 颜 Jun 君 , Gao 高 Xiang 翔 , Wu 吴 Yong 勇 , Zeng 曾 Chunhua 春华 , Wang 王 Jianguo 建国
Published: July 2024

For warm/hot and dense plasmas (WDPs), ionization potential depression (IPD) plays a crucial role in determining its ionization balance and understanding the resultant microscopic plasma properties. A sophisticated and unified IPD model is necessary to resolve those existing discrepancies between theoretical and experimental results. However, the applicability of those widely used IPD models nowadays is limited, especially for the nonlocal thermodynamic equilibrium (non-LTE) dense plasma produced by short-pulse laser. In this work, we propose an IPD model that considers inelastic atomic processes, in which three-body recombination and collision ionization processes are found to play a crucial role in determining the electron distribution and IPD for a WDP. This IPD model is validated by reproducing latest experimental results of Al plasmas with a wide-range condition of 70 eV–700 eV temperature and 0.2–3 times solid density, as well as a typical non-LTE system of hollow Al ions. It is demonstrated that the present IPD model has a significant temperature dependence due to the consideration of the inelastic collision processes. With a lower computational cost and wider application range of plasma conditions, the proposed model is expected to provide a promising tool to study the ionization balance and the atomic processes, as well as the related radiation and particle transports properties of the WDP.
Impact of Co2+ substitution on structure and magnetic properties of M-type strontium ferrite with different Fe/Sr ratios
Authors: Sun 孙 Yang 洋 , Liu 刘 Ruoshui 若水 , Gong 宫 Huayang 华扬 , Shen 沈 Baogen 保根
Published: July 2024

Ion substitution has significantly improved the performance of ferrite magnets, and cobalt remains a key area of research. Studies on the mechanism of Co2+ in strontium ferrite, especially SrFe2n–x
Co
x
O19–δ
(n = 6.1–5.4; x = 0.05–0.20) synthesized using the ceramic method, showed that Co2+ preferentially enters the lattice as the Fe/Sr ratio decreases. This results in a decrease in the lattice constants a and c due to oxygen vacancies and iron ion deficiency. The impact of Co substitution on morphology is minor compared to the effect of the Fe/Sr ratio. As the Fe/Sr ratio decreases and the Co content increases, the saturation magnetization decreases. The magnetic anisotropy field exhibits a nonlinear change, generally increasing with higher Fe/Sr ratios and Co content. These changes in the performance of permanent magnets are attributed to the absence of Fe3+ ions at the 12k + 2a and 2b sites and the substitution of Co2+ at the 2b site. This suggests that by adjusting the Fe/Sr ratio and appropriate Co substitution, the magnetic anisotropy field of M-type strontium ferrite can be effectively optimized.
SQI-DOANet: electroencephalogram-based deep neural network for estimating signal quality index and depth of anaesthesia
Authors: Yu Rui , Zhou Zhuhuang , Xu Meng , Gao Meng , Zhu Meitong , Wu Shuicai , Gao Xiaorong , Bin Guangyu
Published: July 2024

Objective. Monitoring the depth of anaesthesia (DOA) during surgery is of critical importance. However, during surgery electroencephalography (EEG) is usually subject to various disturbances that affect the accuracy of DOA. Therefore, accurately estimating noise in EEG and reliably assessing DOA remains an important challenge. In this paper, we proposed a signal quality index (SQI) network (SQINet) for assessing the EEG signal quality and a DOA network (DOANet) for analyzing EEG signals to precisely estimate DOA. The two networks are termed SQI-DOANet. Approach. The SQINet contained a shallow convolutional neural network to quickly determine the quality of the EEG signal. The DOANet comprised a feature extraction module for extracting features, a dual attention module for fusing multi-channel and multi-scale information, and a gated multilayer perceptron module for extracting temporal information. The performance of the SQI-DOANet model was validated by training and testing the model on the large VitalDB database, with the bispectral index (BIS) as the reference standard. Main results. The proposed DOANet yielded a Pearson correlation coefficient with the BIS score of 0.88 in the five-fold cross-validation, with a mean absolute error (MAE) of 4.81. The mean Pearson correlation coefficient of SQI-DOANet with the BIS score in the five-fold cross-validation was 0.82, with an MAE of 5.66. Significance. The SQI-DOANet model outperformed three compared methods. The proposed SQI-DOANet may be used as a new deep learning method for DOA estimation. The code of the SQI-DOANet will be made available publicly at https://github.com/YuRui8879/SQI-DOANet.
A model-based brain switch via periodic motor imagery modulation for asynchronous brain-computer interfaces
Authors: Meng Jianjun , Li Songwei , Li Guangye , Luo Ruijie , Sheng Xinjun , Zhu Xiangyang
Published: July 2024

Objective. Brain switches provide a tangible solution to asynchronized brain-computer interface, which decodes user intention without a pre-programmed structure. However, most brain switches based on electroencephalography signals have high false positive rates (FPRs), resulting in less practicality. This research aims to improve the operating mode and usability of the brain switch. Approach. Here, we propose a novel virtual physical model-based brain switch that leverages periodic active modulation. An optimization problem of minimizing the triggering time subject to a required FPR is formulated, numerical and analytical approximate solutions are obtained based on the model. Main results. Our motor imagery (MI)-based brain switch can reach 0.8FP/h FPR with a median triggering time of 58 s. We evaluated the proposed brain switch during online device control, and their average FPRs substantially outperformed the conventional brain switches in the literature. We further improved the proposed brain switch with the Common Spatial Pattern (CSP) and optimization method. An average FPR of 0.3 FPs/h was obtained for the MI-CSP-based brain switch, and the average triggering time improved to 21.6 s. Significance. This study provides a new approach that could significantly reduce the brain switch’s FPR to less than 1 Fps/h, which was less than 10% of the FPR (decreasing by more than a magnitude of order) by other endogenous methods, and the reaction time was comparable to the state-of-the-art approaches. This represents a significant advancement over the current non-invasive asynchronous BCI and will open widespread avenues for translating BCI towards clinical applications.
Wasserstein distance in speed limit inequalities for Markov jump processes
Authors: Shiraishi Naoto
Published: July 2024

The role of the Wasserstein distance in the thermodynamic speed limit inequalities for Markov jump processes is investigated. We elucidate the nature of the Wasserstein distance in the thermodynamic speed limit inequality from three different perspectives by resolving three remaining problems. First, we derive a unified speed limit inequality for a general weighted graph, which reproduces both the conventional speed limit inequality and the trade-off relation between current and entropy production as its special case. Second, we treat the setting where the tightest bound with the Wasserstein distance has not yet been obtained and investigate why such a bound is out of reach. Third, we compare the speed limit inequalities for Markov jump processes with the L1-Wasserstein distance and for overdamped Langevin systems with the L2-Wasserstein distance, and argue that these two have different origins, despite their apparent similarity.
Unexpected Electrical Breakdown Characteristics and Protection of PPU in Space Electric Propulsion System
Authors: Sheng Beifei , Ge Siqiao , Jiang Shuo , Zhang Xuan , He Fengping , Li Kang
Published: July 2024

The application of fully electric propulsion satellites will increase the risk of low-pressure discharge in electric propulsion devices, especially ion thrusters, whose unexpected breakdown will directly affect the reliability of satellite applications. Existing on-orbit cases show that the unexpected breakdown occurred in the power processing unit (PPU) of the ion thruster during orbit change, which led to the failure of thruster. Therefore, this paper analyses the high-voltage components inside the PPU, and systematically discusses the PPU and its working environment, the control and protection technology of unexpected electrical breakdown of the electric propulsion system and its aerospace engineering. In this paper, we discuss the electric field intensity and discharge margin of components in the PPU under different conditions, and further propose a method for insulation evaluation based on partial discharge (PD) detection. The research results show that the discharge margin in the PPU is close to the lowest discharge voltage level of uniform electric field, so reasonable insulation protection measures should be taken against discharge under high voltage condition. Furthermore, we propose a feasibility analysis method based on PD insulation defect detection, which provides a basis for quantitative analysis and evaluation of component insulation design in PPU systems.
End-to-end design of multistage high-pressure axial compressor for a promising aviation gas turbine engine
Authors: Goryachkin E S , Kudryashov I A
Published: July 2024

The paper describes the results of an end-to-end design of a multistage high-pressure axial compressor for a promising aircraft engine. The design included the steps of initial design and detailed fine-tuning of the working process using three-dimensional numerical modelling. The initial design included the steps of flow path shape determination, design thermodynamic calculation, and one-dimensional gas dynamic calculation at the mid-diameter and height of the flow path. Statistical processing of parameters of known compressors was used to select parameters during the initial compressor design. The initial design was performed for several compressor configurations differing in the main design parameters: type of flow path, number of stages, speed and others. Three-dimensional modelling and comprehensive comparison of working process parameters were performed for the most promising of the obtained variants. On its basis, the most promising variant was selected, for which the subsequent refinement using three-dimensional numerical modelling was carried out. As a result of compressor design, all required parameters were achieved.
Temperature Field Analysis and Temperature Control of Vacuum Ultra High Speed Angular Contact Ball Bearings
Authors: Cui Baoli , Cheng Yongjun , Jia Pengyang , Liu Zhihui , Wang Bi , Ye Jun , Li Yangsen , Chen Weiyu , Wang Zixi
Published: July 2024

In order to investigate the temperature field distribution of bearings under vacuum and ultra-high-speed conditions and put forward a good temperature control method, this paper adopts the local method to analyse and calculate the temperature of various parts of the bearing, and establishes a simulation model of the bearing by using the finite element analysis method of ANSYS, and carries out a test on the experimental platform of the vacuum and ultra-high-speed motors, which proves that the temperature of the rollers is the highest, followed by the inner-ring raceway and the outer-ring raceway, and provides effective theoretical methods for the analysis of the temperature field of the angular contact ball bearing under the conditions of high vacuum and high speed; the temperature of the bearing as a whole is controlled by the structure of the installed water jacket.
LULAD (LUnar LAva tube Discoverer) Instrument for NASA’s Commercial Lunar Payload Services (CLPS) Program
Authors: Karmakar Riya , Shastri Bhardwaj , Choomjinda Ubol , Mukundan Arvind , Wang Hsiang-Chen
Published: July 2024

NASA’s latest lunar exploration program is Artemis. In-situ Resource Utilization (ISRU) will become more important as human space travel moves toward a lunar presence. CLPS helps the Artemis Program develop and use compact autonomous landers and rovers. A series of lunar micro-rovers will be launched in the coming years to collect data and conduct scientific research on the moon. Subterranean lava tubes on celestial bodies are promising habitats for human expansion beyond Earth. Due to its lack of atmosphere, the moon is vulnerable to meteoroid impacts and cosmic and solar particle radiation. These factors make surface lunar base construction difficult. Subterranean lava tubes can provide safety due to the many strata of lava basalt that form a thick roof several meters thick. This paper will discuss the design of the LUnar LAva tube Discoverer (LULAD) instrument, which aims to explore regions of interest and possibly find candidate lava tubes on the moon.
Experimental Investigation on Aerodynamic Performance of a Contra-rotor System
Authors: Xiao Jun , Shi Yongjie
Published: July 2024

The unique environment of Mars (low pressure, low density, and low temperature) causes rotorcraft to face a common situation: the low Reynolds number - high Mach number aerodynamics. The current study focuses on the aerodynamic performance of a series rotor blades under low-pressure and -density testing condition.

Firstly, the optimization of two-dimensional airfoils is carried out and its use as a basic configuration to design four sets of three-dimensional rotors. Secondly, the components of the experimental force measuring system are introduced. An experimental study of the APC 9*6E propeller in its hovering mode was undertaken as part of an effort to understand the acquisition accuracy of the force balance system. The experimental error is within 5 %, which proves that the accuracy of the force measuring platform meets the experimental requirements. Finally, rotors in single- and contra-rotating configurations are all tested. and the results are analyzed. The numerical simulations are also taken at the design conditions for the purposes of results comparison.
Design of improving volumetric efficiency of waverider based on area rule
Authors: Ma Haoyuan , Zhu Dehua , Lou Hao
Published: July 2024

In terms of waverider’s aerodynamic performance degradation due to the design of increasing volume in engineering, it’s a solution to improve the design operations referring to area rule. With theory analysis and numerical simulation, the application of supersonic area rule at hypersonic speed was studied; an improved shape modification method based on area rule was developed and validated. The research results could support the design of improving volumetric efficiency of waverider and showed as follows: Object is supposed to be slender enough to ensure supersonic area rule’s application accuracy at hypersonic speed, which indicates the challenge to apply supersonic area rule to practical hypersonic vehicle due to unsatisfactory geometrical character; referring to some scholars’ development of area rule at hypersonic speed, improved shape modification method based on transonic area rule was developed and the influence of object’s geometrical character on drag reduction at hypersonic speed was studied; Applying the improved shape modification method, the modified combination of volume body and waverider had the drag reduced by 4% and volume increased by 31%, volumetric efficiency increased by 5%.
Design and Application of Micro-vibration Test Platform for Control Moment Gyroscope of Space Station
Authors: Yicun Xie , Qiang Jiang , Yao Wu , Zhiqiang Shen , Chuang Liu , Dong Li , Kexin Liu , Xinying Li
Published: July 2024

In order to obtain the disturbance force and torque of large control moment gyroscopes used in China space station, a calculation method of the resultant force and moment at the product center of mass was studied. A disturbance force testing system for large control moment gyroscopes was designed, and structural modal testing and disturbance force and torque testing were carried out on the rigid installation and isolator installation states of the control moment gyroscopes. By analyzing the root mean square values of disturbance force and torque, as well as the isolation efficiency at the operating frequency of the control torque gyroscope, it can be concluded that the isolator has a good isolation effect.
Tanker remote vision system:review and key technologies
Authors: Zhang Chao , Fan Zhenkai , Liu Yuxuan , Shi Aobo
Published: July 2024

The Remote Vision System (RVS) employed in tanker aircraft, crucial for furnishing operators with requisite visual acuity and informational support during air-to-air refueling maneuvers, has emerged as an indispensable component in modern tanker configurations, forming the bedrock of autonomous aerial refueling capabilities. This paper offers a comprehensive overview of the deployment, constituent elements, and evolutionary trajectory of visual augmentation systems implemented in KC-46A and A-330MRTT aircraft. Furthermore, it delineates key technological imperatives essential for the advancement of tanker visual systems, encompassing high-definition imaging sensors, multi-sensor data fusion methodologies, 3D virtual precise imaging techniques, and all-weather high-precision target data perception technologies. The elucidation of these critical facets serves as a foundational resource for guiding future research and development endeavors aimed at enhancing the efficacy and reliability of tanker remote vision systems
Geometry modeling of solar UAV: considerations and guidelines for design and analysis
Authors: Layachi Hemza , Bennaceur Mohamed amine
Published: July 2024

This paper describes a methodology of the geometry analysis of a solar UAV in order to satisfy energy flight requirements by the integration of PV panels. It is shown that the surface of an UAV’s wing has a direct relation to the structural weight. Since aerospace industry relay on weight saving concepts in order to enhance the overall performance, this paper shows the importance of an optimized selection of such geometry parameters in order to satisfy both concepts.
A Frequency Swept Interferometer (FIS) Based Sensing System for Mega Satellite Constellation
Authors: Jiang Yifei , Chao Zhong , He Wanxie , Bei Wan , Wu Shufan , Mo Qiankun
Published: July 2024

As the novel research of space technologies, non-terrestrial-network (NTN) is one of the most important technologies. Mega satellite constellation is the baseline of the NTN technologies. Unfortunately, as the density of satellite deployment, the risk of collisions between satellites also increases significantly. Therefore, sensing technology is an important solution to avoid collisions within constellation. In this article, a sensing system for satellite constellation is proposed. It contains multiple subsystems working together to ensure measurement accuracy. An accurate laser measurement based on frequency swept interferometer (FIS) is the core of the sensing technologies. With a sensing distance of a few hundred meters, the specific FSI system can realize microns meterss accuracy in many experiments. Those results guarantee the well performance of the sensing system.
Numerical analysis clarifying non-equilibrated periodic flows generated by dual-scaling Taylor’s analytical solution
Authors: Gong Xuanyou , Suzuki Hiroki , Kouchi Toshinori
Published: July 2024

This study investigates the properties of a flow field derived from the multiplexed Taylor solution, focusing on its impact on established equilibrium relationships. We numerically analyse a multiplexed flow field by introducing a secondary flow with twice the period of the original Taylor solution, hypothesising that this dualisation affects the balance between transient and viscous terms. The visualisation of the flow field and the time evolution of the kinetic energy are investigated. Using second and sixth order central differences and the fractional step method with BiCGStab, we analyse three flow fields with different coefficients in a two-dimensional periodic domain. The study shows that the dualisation of the flow field disturbs the equilibrium between the unsteady and viscous terms. The time-averaged kinetic energy shows that the evolution of the dualised field approaches the kinetic energy distribution of the analytical solution, with variations depending on the coefficient of the quadratic term. The spatial distribution of the kinetic energy in fully developed fields is also compared with the analytical solution.
Can Newtonian kinetic energy and Einsteinian rest-mass energy be expressed by the binomial expansion of the Lorentz factor? And how valid is using Einstein’s E = mc2 to calculate the nuclear fission energy?
Authors: Al-Ameen Talal , Mahmud Maythem , Muhi Imad
Published: July 2024

The binomial (Taylor) expansion of the Lorentz factor has been reconsidered here in an attempt to find out whether the Newtonian kinetic energy and the Einsteinian rest-mass energy are implicitly embedded in the mathematical structure of the binomial expansion of the Lorentz factor (as Einstein postulated in his Special Theory of Relativity). Advocates of Standard Special Relativity show that it is possible to obtain these two kinds of energy by multiplying both sides of the expansion of the Lorentz factor by the moving object’s rest mass m
0 and the square of the speed of light c
2. This study shows that the apparent reconciliation between classical and relativistic physics made possible by employing the binomial expansion of the Lorentz factor

γ
=

[
1
−
(

v
2

c
2

)
]

−

1
2

, where v is the moving object’s velocity, is challengeable. Also it is unclear how Einstein’s famous rest-mass energy equation E = m
0
c
2 from Ekinetic net
= mrelativistic c
2 − m
0
c
2 can be used to calculate the amount of nuclear fission energy released?
Attempt to compensate for effects of energy conservation error on static pressure fluctuation using sub-grid scale components with the Reynolds number dependence of isotropic/anisotropic steady turbulence
Authors: Chitose Makoto , Suzuki Hiroki , Kouchi Toshinori
Published: July 2024

This study focuses on the kinetic energy conservation error and the compensation effect by adjusting a model constant. The kinetic energy conservation error is caused by the implicit time integration of the second-order Crank-Nicholson method, and we investigate how much this error affects the RMS of the static pressure fluctuation. Anisotropic and isotropic external force terms are used to generate a steady turbulent flow field, and the numerical analysis employs Large Eddy Simulation (LES) and the Smagorinsky model. Studies have shown that the influence of kinetic energy conservation errors on turbulent kinetic energy is limited, but large-scale turbulent structures are affected by errors in anisotropic turbulent fields with large Re numbers. Ta. Regarding the compensation of the RMS of the static pressure fluctuation, it was shown that the error could be reduced in both isotropic and anisotropic fields by adjusting the model constant, but there was a clear difference for the turbulent kinetic energy. This result shows that the compensation of kinetic energy conservation errors by a model constant is not perfect and that the errors can have different effects on the turbulence statistics.
Analytical Fermi energy for broadened Landau levels of 2DEG under a perpendicular strong magnetic field
Authors: Sese L J , Bercasio C J , Gammag R
Published: July 2024

An analytical form of the Fermi energy is derived for broadened Landau levels (LLs) of the two-dimensional electron gas (2DEG) under a perpendicular strong magnetic field. A Gaussian density of states with the broadening parameter Γ is used to derive the analytical form under the assumption of asymptotically non-overlapping states between two consecutive Landau levels, i.e. Γ/ħωc
→ 0. It is shown that the smoothening of the Fermi energy around the neighborhood for fully filled Landau levels is due to the linear dependence of Γ and its factor with the inverse error function. The validity of the analytical form shows a threshold up to Γ/ħωc
∼ 0.23.
A reliable semi-analytic solution for the Caputo fractional human liver model
Authors: Ansar Abrar , Abukhaled Marwan
Published: July 2024

This article presents a dependable semi-analytic solution for the Caputo fractional human liver model, employing an enhanced classical differential transform method. Our methodology is direct and produces highly accurate results. We confirm the stability of the equilibrium solution and demonstrate the positivity and boundedness of our solution. The paper includes graphs that juxtapose analytical and numerical simulations for both integer and fractional models, comparing our findings with clinical data and the fourth-order Runge-Kutta method.
A survey on topological solitons in planar nonlinear Dirac models
Authors: Dikole R
Published: July 2024

In this text, we review tardyonic and tachyonic planar Dirac models with several cubic nonlinearities such as the Kerr, Soler and massive Thirring nonlinearities. These models have relevance in a newly discovered class of solids named topological insulators and have been shown to exhibit topological properties such as the Berry phase and Chern number. Moreover, nonlinear Dirac models have vortex solutions and edge state solitons. As understood in quantum mechanics that a Hamiltonian must yield real eigenvalues or dispersion relation, we argue that Dirac equations in the tachyonic case are valid when studied in non-vanishing backgrounds because this gets rid of the complexity in the dispersion relation.
Investigation of a MEMS resonator model with quintic nonlinearity
Authors: Abdelraouf M. E. , Kandil A. , Zahra W. K. , Elsaid A.
Published: July 2024

Micro-electromechanical system (MEMS) resonator is decidedly utilized in a diversity of areas, including time referencing, movement sensing, signal filtration, mass detecting, and further numerous applications. The aim of this article is to use the multiple scales approach to derive analytical formulas for MEMS resonator vibration response. The properties of the complicated nonlinear system at various AC and DC voltages are investigated to be extremely well captured by modeling the dynamics of the micro-beam using multiple scales technique. The resulting Jacobian matrix eigenvalues are tested to verify the stability ranges of these solutions; hence, the jump phenomenon that occurs in experimental performance is interpreted. To study the influence of resonator characteristics on the nonlinear dynamical behavior of such a beam, several response plots are presented. Finally, a numerical solution is obtained with the fourth order Rung-Kutta method to verify the studied model’s overall behavior.
A Monte Carlo study of K escape phenomena of X-ray spectra in CdTe and Gd2O2S detectors
Authors: Wang Dan , Shi Zhe , Yang Zhi
Published: July 2024

Detectors can be categorized as energy-integrated detectors (EID) and photon-counting detectors (PCD). Both of them show K x-ray escape effects, leading to potential inaccuracies in spectral data. This paper focuses on investigation of the detector’s K x-ray escape effects on spectra. Geant4-based Monte Carlo simulations were initially validated against literature results. Subsequently, the X-ray escape events and spectra in both a CdTe (PCD) and Gd2O2S (EID) were explored. X-ray spectra generated using Geant4 demonstrated close agreement with the existing literature. The spectra with typical absorption edges were observed in both detectors. This study highlights the successful application of Monte Carlo simulations for spectral measurements and emphasizes impact of K escape effects on X-ray spectra. The positions of escape events are contingent upon the element properties in the detectors, providing valuable insights into understanding K escape effects.
A Collaborative Diagnosis Method for Abnormal Discharge of SF6/N2 Mixed Gas Insulation Based on Multi-parameter Sensing
Authors: Peng Zhaoyu , Qiu Pengfeng , Long Yunfeng , Tan Xiangyu , Xu Tengbo , Fu Wencheng
Published: July 2024

At present, SF6/N2 gas mixture with 30% volume fraction has been gradually applied to gas-insulated power equipment. However, most of the existing operation and maintenance management experience comes from traditional GIS equipment. Consequently, there is an urgent need to propose a discharge fault diagnosis method suitable for SF6/N2 mixed gas insulation equipment based on the development characteristics of SF6/N2 gas discharge and the applicability of detection technology. In this study, a gas insulation experiment platform was initially established to collect pulse current, optical, and UHF signals during SF6/N2 defect discharge through the simulation of three typical insulation defects: metal spikes, surface anomalies of insulation components, and suspension potential, as well as sensor settings. Then, the phased changes of various physical characteristics with the development of discharge were analyzed. Finally, a partial discharge collaborative diagnosis model based on multivariate information perception was proposed. By comparing the recognition accuracy of SF6 and SF6/N2 databases, the differences in feature selection and pattern recognition criteria between the two were found. It has high guiding value for the establishment of differentiated operation and maintenance criteria for SF6/N2 mixed gas GIS equipment.
Research and Application of Big Data Analysis in Energy Storage of Distributed Energy System
Authors: Liu Huizhou , Ni Yanyan , Wang Ming , Chang Le
Published: July 2024

In order to ensure the reliability and high efficiency of the optimal scheduling strategy of distributed energy system, this paper combines big data technology to study the energy storage system of distributed energy system. In order to simplify the daily scheduling optimization of regional DES, the loss of energy storage device and energy conversion device is ignored in this paper, and the output power, conversion power and interworking power of specific equipment are treated linearly in the energy supply model to a certain extent, so as to better simulate the scheduling process. Moreover, this paper combines the big data algorithm to avoid the algorithm falling into local optimum by improving the group learning method. Taking the distribution system as the reference system, the electric energy demand is met by the power grid, the heat energy demand is generated by the gas boiler, and the cold energy is generated by the electric refrigeration. In addition, in different seasons, the comprehensive benefits of the energy supply model in this paper are compared and analyzed. The research results show that the method in this paper has certain effect.
1550nm-1600nm design and research of Erbium-doped fiber lasers
Authors: Wang Minghui
Published: July 2024

The fiber laser, an innovative laser type, holds immense significance in optical communication, industrial processing, and scientific research owing to its remarkable high power and efficiency combination. The 1550nm light wave, widely utilized in fiber communication, renders the research and production of fiber lasers in this range pivotal for diverse applications. Within the pages of this paper, we delve into the intricate design and meticulous investigation of an erbium-doped fiber laser operating within the 1550nm-1600nm band. Our noteworthy achievement lies in the adept attainment of laser emission at 1575 nm. This success is intricately woven into the reciprocal reflection of pump light within the resonant cavity of the fiber laser and the nuanced electronic transition process of erbium ions. This paper not only unfolds a detailed exploration of the structural nuances but also unveils the design principles, methodology, and results of MATLAB simulations employed in crafting erbium-doped fiber lasers. Exhibiting exemplary performance at the 1550nm wavelength, this laser proves promising in realms such as optical communication and medical applications, signalling a paradigm shift in the possibilities within these domains. The research presented herein introduces avant-garde concepts for designing high-performance fiber lasers, providing a rich foundation for further exploration in related fields. Through this comprehensive discourse, we aim to contribute not only to the advancement of fiber laser technology but also to the expansion of possibilities in optical communication and beyond.
Advances in stability control methods of distribution network for distributed photovoltaic systems
Authors: Zhang Jiarui
Published: July 2024

In the current global energy crisis, distributed photovoltaic power generation represents an innovative approach to integrated power generation and energy utilization, offering significant prospects for development. However, the distribution network’s stability may be impacted by the connection to the grid of distributed solar power generation, which will significantly affect consumers’ demand for electricity. Therefore, this paper explores several control methods for grid stability in distributed photovoltaic systems, including a multi-objective optimization method of three-phase load imbalance with distributed photovoltaic distribution network considering voltage over-limit risk, three-phase voltage imbalance compensation control method based on parallel inverters of photovoltaic micro-grid in dq coordinate system and distributed cooperative control method based on dynamic event-triggered robust average consensus algorithm (DET-RACA) and barrier Lyapunov function (BLF). The paper evaluates these control methods, discussing their respective advantages, limitations, and impact on grid stability. Additionally, the latest research trends in these areas are reviewed, providing valuable insights for future studies focused on enhancing distribution network stability in the context of distributed photovoltaic power generation.
Innovative approaches for minimizing leakage current in three-phase transformerless PV inverters
Authors: Wang Yikun
Published: July 2024

Three-phase transformerless photovoltaic (PV) inverters are widely used in solar systems due to their advantages, such as relatively low cost, small size, and high performance. However, they encounter leakage current problems, which can lead to issues such as harmonic damage, grid distortion, and safety risks to individuals. Effectively suppressing leakage current is a critical issue that needs to be addressed for transformerless PV inverters. The purpose of this research is to review advancements made in suppressing leakage current over the past few years in the research area of three-phase transformerless photovoltaic inverters. By summarizing recent research, this paper presents several topologies that efficiently eliminate system leakage current. Additionally, this paper analyzes optimal modulation methods for these topologies in detail. Through a comparison of these topologies, this paper offers insights for future photovoltaic system design. Furthermore, this paper suggests methods to effectively suppress leakage current, reduce total harmonic distortion (THD), and improve efficiency. Finally, this paper discusses expectations for future research and development in the photovoltaic industry.
Optimization of Observational Bionic Underwater Vehicle Based on TRIZ Theory
Authors: Zhang Hualin , Ma Haobo , Gao Yangjie , Li Zeru , Chen Yizhuo , Wang Yahui
Published: July 2024

This paper applies the Theory of Inventive Problem Solving (TRIZ) to address challenges in observation-type biomimetic underwater robots. Traditional underwater robots impact the environment, while biomimetic robots lack flexibility and compression resistance. By using TRIZ theory, we focus on designing and optimizing biomimetic underwater observation robots. Problems with propeller-driven robots are identified, including size, adaptability, maneuverability, and environmental impact. System analysis reveals limitations in the propulsion system and shell. To overcome these challenges, a buoyancy control system and rubberized toughened plastics are proposed. Solutions are validated through optimization design, simulations, and prototype testing, improving vertical movement and pressure resistance. TRIZ theory helps identify and resolve technical contradictions, fostering innovation and providing reliable solutions for underwater observation tasks. This research contributes to the development of observation-type underwater robots and highlights TRIZ’s potential in addressing engineering problems and fostering innovation. Further research is needed to address additional aspects and practical implementation challenges.
Investigation on Transport Phenomena and Molten Pool Dynamics During Laser Melting Deposition of Ti-6Al-4V
Authors: Wu Yongjian , Zhou Jian , Wen Yan , Xie Lechun
Published: July 2024

The physical phenomena involved in laser melting deposition are extremely complex, including solid-liquid phase transition, gas-liquid interface coupling, the Marangoni effect, and others factors. A novel multiphase model is proposed to describe the evolution of gas-liquid-solid interface during the laser melting deposition process of Ti-6Al-4V. Based on the volume of fluid (VOF) method, a volume fraction gradient method is introduced to accurately track the motion of the free surfaces. The model can simulate alterations in temperature and flow fields during deposition, predict the geometric configurations of the melt pool and deposition layer, and shows minimal deviation from the experimental data, thereby providing a significant reference value.
Research and Design of Heat Pump Air Conditioning Control System Based on Intelligent Diagnosis
Authors: Qi Susu
Published: July 2024

With the scarcity of energy resources and the requirements of environmental protection, the energy efficiency and performance optimization of heat pump air-conditioning systems have become an important research field. In this study, an intelligent diagnosis system based on support vector machine (SVM) is designed and compared with the traditional system without intelligent diagnosis. The experimental group uses an intelligent diagnostic system for troubleshooting and diagnosis, and the control group uses a traditional system for the same operation. By collecting experimental data and statistical analysis, the performance of two groups of systems in terms of troubleshooting time, fault diagnosis accuracy and energy consumption is evaluated. In the experimental group, the longest time for troubleshooting was 5 minutes, the shortest time was 1 minute; the control group took a maximum of 15 minutes and a minimum of 8 minutes. The intelligent diagnosis system based on SVM shows obvious advantages in the control system of heat pump air conditioning.
On products of Δ-sets
Authors: Carvalho Rodrigo , Rodrigues Vinicius
Published: July 2024

We prove the consistency of the existence of a

Q
Q

-set whose square is not a

Δ
\Delta

-set and that if there is a

Δ
\Delta

-set, then there exists a

Δ
\Delta

-set whose all finite powers are

Δ
\Delta

-sets.
A note on purity of crystalline local systems
Authors: Moon Yong Suk
Published: July 2024

In this short note, we prove a purity result for crystalline local systems on a smooth

p
p

-adic affine formal scheme. Our method is based on the prismatic description of crystalline local systems (see Du et al. [Compos. Math. 160 (2024), pp. 1101–1166]; cf. Guo and Reinecke [Invent. Math. 236 (2024), pp. 17–164]), which is different from the approach by Tsuji [Crystalline sheaves and filtered convergent

F
F

-isocrystals on log schemes, preprint].
On the Hawking mass for CMC surfaces in positive curved 3-manifolds
Authors: Melo Luiz Ricardo
Published: July 2024

In this paper, we present two rigidity results for stable constant mean curvature surfaces immersed in

3
3

-manifolds with positive scalar curvature, assuming that the Hawking mass is zero. In the first result, we assume the surface to be approximately round, while in the second result, we consider surfaces invariant under an even symmetry.
The logarithmic Dirichlet Laplacian on Ahlfors regular spaces
Authors: Gerontogiannis Dimitris , Mesland Bram
Published: July 2024

We introduce the logarithmic analogue of the Laplace-Beltrami operator on Ahlfors regular metric-measure spaces. This operator is intrinsically defined with spectral properties analogous to those of elliptic pseudo-differential operators on Riemannian manifolds. Specifically, its heat semigroup consists of compact operators which are trace-class after some critical point in time. Moreover, its domain is a Banach module over the Dini continuous functions and every Hölder continuous function is a smooth vector. Finally, the operator is compatible, in the sense of noncommutative geometry, with the action of a large class of non-isometric homeomorphisms.
Sense-Data
Authors: Snowdon Paul F
Published: July 2024

‘Sense-data’ is a modern term for a long-standing idea, earlier expressed in the language of ‘ideas’ and ‘impressions’. On the dominant use of ‘sense-data’ it stands for an entity present in perceptual (and other) experiences which fundamentally has a mental nature and possesses certain qualitative properties which the subject apprehends. The evolution of the term (by Moore, Ayer, and others) is described and discussed. The dominant theory that the term is attached to thinks of experience as an act relating to an object, the sense-datum. It is claimed that this structure means it is misleading to call it a theory of perception at all. The major flaw in arguments for the theory is that this assumption is lacking in any justification. When followed through this act/object analysis of experience faces considerable problems. Its popularity reflects an obsession by philosophers with visual perception. If the theory is rejected there still remain many different approaches to the analysis of perception.