bluuebunny/crossref_metadata_2025 huggingface dataset:
Study in Gas-Phase Agglomeration Characteristics of Spiral Flow Gas-Liquid Multiphase Pump
Authors: Han Wei , Guo Xuanchen , Feng Huiming , He Chunpei , Zhang Yukun , Xie Wenqi
Published: October 2024

The spiral flow gas-liquid mixed transport pump experiences gas phase accumulation in the impeller flow passage, leading to blockage and a decrease in pumping performance. To understand the rules and mechanisms of gas phase aggregation in the spiral flow gas-liquid mixed transport pump, numerical calculations based on the Eulerian multiphase flow model and SST k – ω turbulent flow model were conducted. The effects of different gas volume fractions, speeds, and liquid phase viscosities on the pump were explored, and the external characteristics, flow characteristics, and gas phase aggregation processes in the impeller were analysed for these three variables. The results indicate that the head and efficiency of the pump gradually decrease with increasing gas volume fraction and liquid phase viscosity, while they increase with increasing speed. When the liquid phase viscosity changes from pure water to 50 times its viscosity, the gas phase aggregation at the impeller outlet decreases, resulting in reduced pressure and a smaller vortex region. The relative gas phase aggregation degree λ decreases from 0.5 to almost 0. When the gas volume fraction increases from 20% to 60%, the gas phase aggregation at the impeller outlet increases, the pressure difference between the impeller hub and the rim increases, and the vortex region expands, leading to an increase in λ by 8 times. When the speed increases from 3000 rpm to 5000 rpm, the gas phase aggregation at the impeller outlet increases, the pressure increases, and the vortex region expands, resulting in a 16-fold increase in λ.
Application of intelligent algorithms in optimal operation of pumping stations
Authors: Sun Xiaoyu , Feng Xiaoli
Published: October 2024

An optimal operation model of pumping stations is established in this paper, with the minimum energy consumption of the pumping station as the optimization objective, considering the constraints of the pumping station operating head, flowrate of the pumping station and so on. Simulated annealing is introduced into genetic algorithm, particle swarm optimization, wolf pack algorithm and grey wolf optimization to solve the model. The minimum value, average value, relative standard deviation of the objective function and infeasibility of constraint conditions are selected as the evaluation indexes of the algorithms performance. The calculation results show that simulated annealing ensures that the intelligent algorithms can find the optimal solution in the feasible solution space and avoid them falling into local optimization. The operation schemes obtained by solving the example model with the improved algorithm can reduce the energy consumption of the pumping station by 5.759%∼6.682%, which provides guidance for the operation schemes of the example pumping station. The results can be further applied in other pumping stations.
Effect of Gasket Wear Rate on Hydraulic Performance and Internal Flow of Multistage Centrifugal Pump with Floating Impellers
Authors: Bian Junjie , Gu Yandong , Wang Dongcheng
Published: October 2024

The sealing gaskets of multistage centrifugal pumps are prone to wear during operation. This study investigates the influence of gasket wear rate on hydraulic performance and internal flow field through numerical simulations. As the wear rate of the gasket increases, both the efficiency and head coefficient of the pump gradually decrease. When the gasket is completely worn out, the efficiency decreases by 5.6% and the head coefficient decreases by 9.5% compared to the unworn gasket condition. Analysis of the internal flow field reveals that the front side chamber is most significantly affected by gasket wear. As the gasket wears, the flow velocity within the front side chamber increases gradually, and the high-entropy production zone expands, thereby affecting the hydraulic performance of the pump. The findings of this study provide practical engineering insights for enhancing the operational performance of multistage centrifugal pumps.
Numerical simulation on energy characteristics of pump-turbine under pump condition
Authors: Chen Zhenyu , Li Chenhao , Luo Xingqi , Zhu Guojun
Published: October 2024

To investigate the energy characteristics of the pump turbine in pump mode, we selected the pump turbine as the research object and employed the SST k-ω turbulence model to conduct three-dimensional steady numerical simulations of the internal flow field of the pump turbine under several typical flow conditions. Our findings indicate that the unit’s energy loss is primarily concentrated in the runner and guide vane areas. In the small flow condition area, the energy loss of the draft tube basin cannot be ignored, while the energy loss in the stay guide vane and spiral casing areas is relatively small due to their low flow velocity. As the flow rate decreases, the energy loss in the draft tube, runner, and guide vane areas increases continuously. Additionally, complex flows such as vortex flow and backflow appear in the double-row cascade flow channel, which obstructs the flow channel and increases dissipation energy. In typical flow conditions, the energy loss in the draft tube, runner, and guide vane areas is a significant factor contributing to the decrease in head.
Research on Rapid Detection Method of Cavitation State of Water jet Propulsion Pump Based on Multi-source and Multi-feature of Acoustic Emission Signal and Bayesian Network
Authors: Feng Chao , Zhu Hualun , Chen Beibei , Yang Mengzi
Published: October 2024

Cavitation prevents the conversion of internal dynamic and pressure energy in a water jet propulsion pump and causes erosion of flow passage components. Acoustic emission is a non-destructive test method for instability signals. Based on the incipient mechanism and development process of cavitation, three acoustic emission signal feature parameters (ring counting rate, energy release rate, Hurst index) are proposed to define the cavitation state utilizing the waveform pattern and signal self-similarity. The multi-source and multi-feature cavitation identification model of acoustic emission signals is established through cavitation simulation, multi-monitoring point acoustic emission signal testing, and feature parameter extraction, and a large number of probabilistic trainings are carried out using Bayesian network, resulting in a fast cavitation state identification method based on acoustic emission signals. The research results have important practical engineering application significance for the prediction of cavitation resistance, real-time dynamic monitoring of cavitation phenomenon and prevention of cavitation damage.
Researches on the Dynamics of the Cavitation Bubble Near the Rigid Wall with a Hole
Authors: Zhao Zi-Yi , Zi Dan , Yao Zhi-Feng , Sun Yu-Rong , Qiang-Zhong  , Wang Fu-Jun
Published: October 2024

When cavitation bubbles collapse near the wall, the micro-jet and shock wave causes damage to the surface of hydraulic machineries. In severe cases, this damage may lead to structural harm. This paper focuses on the cavitation bubble evolution process near the rigid wall with a hole by the experiment and numerical simulation. The space-time morphological characteristics of the bubble at distinct stages (the growth stage, the collapse stage and the rebound stage) are described for the situation of γ=0.7. The distribution of the pressure and the velocity fields at different stages are elucidate. At γ=0.7, a shock wave with a maximum value of the pressure approximately to 14MPa is emitted when the bubble collapses. Meanwhile, a micro-jet attaining a maximum velocity of about 129 m/s is created. Notably, the micro-jet induced by the collapse of a bubble near the rigid wall with a hole is away from the wall, which is different from the micro-jet caused by the collapse of a bubble near the rigid wall.
Fatigue failure analysis of bulb turbine sealing gland bolts based on vibration signal
Authors: Yin Xinyuan , Liu Zhong , Li Bajun , Liu Bo , Zeng Zuopeng , Li Le
Published: October 2024

Aiming at the issue of fatigue fracture of the sealing gland bolts, this paper takes a bulb tubular turbine with frequent breakage of sealing gland bolts as the research object, establishes a finite element model of the sealing gland, and collects the vibration signals of the sealing gland under three common working conditions through vibration tests. Based on the vibration signal data and dynamic analysis, the vibration fatigue load spectrum of the sealing gland is calculated, and then the fatigue analysis of the sealing gland bolts is carried out. The results revealed that vibration of the sealing gland in the -X direction is much more severe than that in the +X direction, and the minimum fatigue life of the sealing gland bolt group in the - X direction is much shorter than that in the +X direction. Comparing the fatigue analysis results of the ±X-direction sealing gland bolts under different working conditions, it is found that under the same test water head, the service life of the sealing gland bolts under stable operation of 15MW is longer than that of 10MW and 20MW. It is recommended to take measures to reduce the problem of excessive vibration in the -X direction of the unit.
Identification and monitoring of wall-attached vortices in open pump intake based on continuous wavelet transform
Authors: Yu Kai , Huang Xianbei , Guo Qiang , Jin Guanqi
Published: October 2024

Wall-attached vortices in pump intake commonly appear and has a negative impact on the safety and efficiency of the pumping stations. The monitoring of these vortices are crucial for safe operation of the pump intake. In this paper, SAS model were performed on a pump intake with an axial-flow pump installed in the suction pipe. Two submergences (500mm and 600mm, namely 3.33DL
and 4DL
) and three flow rates (0.8Qd
, 1.0Qd
, 1.2Qd
) were studied. The continuous wavelet transform (CWT) was applied to the pressure signals near the vortices, showed the similarity of time-frequency characteristics at different points under the same flow rate and water level condition.. It was found that the generation and development were slower for larger submergence. At low flow rate 0.8Qd, the flow angle shows larger deviation from 90°, which causes the higher CWT power. By analyzing the powers of dominant frequencies at all the monitor points, it is recommended to set the monitor points within a rectangle that is 0.77DL and 0.97 DL from the back wall and side wall respectively. The conclusions are suitable for similar intakes under similar conditions with 1.2Qd
of the pump. Also, they can be good guidance for more generalized open pump intakes.
Internal flow analysis and design optimization of a membrane oxygenator
Authors: Jian Meng , Zheng Kexin , Zhang Mingkui , Huang Jianbing , Luo Xianwu
Published: October 2024

The membrane oxygenator is an essential component in the Extracorporeal Membrane Oxygenation (ECMO) system to offer temporary support to the respiratory system. This study aims to optimize the hemodynamic performance and reduce the thrombosis risk of a membrane oxygenator prototype using computational fluid dynamics. Numerical simulations of steady laminar flow in a full-scale oxygenator prototype (model 1) and two optimized structure Models 2 and 3 at flow rates of 5∼7L/min are carried out using the porous media model. Flow-field-based hydraulic performance indicators and the thrombus risk indicator of the three models are compared extensively. Detailed internal flow analysis revealed that adverse flow states such as insufficient flow circulation in the inlet shunt cone zone, large flow separations at the top corners of heat exchangers, and intensive flow impingement at the exit elbow tube are notably improved in the optimized model 2 and 3. The improvement is more significant at high flow rates. Performance parameters quantitatively validate the effect of optimized configurations. Specifically, at a flow rate of 7L/min, the flow uniformity indexes for the original model at the shunt cone exit increase from 0.884 to 0.923 and 0.890 in the two modified models. The total pressure loss is reduced by over 14%, and maximum wall shear stress is notably reduced from 241.46Pa to 135.9Pa. Additionally, the optimized models exhibited lower thrombus risk. The optimized designs emphasize the importance of smooth transitions between cross-sections and minimizing abrupt changes in flow direction. The employment of flow-field-based parameters allows for the establishment of the relationship between geometric and performance parameters to guide effective design optimization and ensure the safe clinical operation of oxygenator prototypes.
Numerical analysis of cavitation characteristics on front surfaces of different Pelton turbine buckets
Authors: Zishi Liu , Jie Liu , Quanwei Liang , Yexiang Xiao , Yushu Zhou , Haijun Li , Zhengshu Liu , Zongqiu Hu , Qingpin Du
Published: October 2024

Cavitation may occur in the runner bucket of the Pelton turbine, which could lead to cavitation erosion on the bucket surface. In this paper, three types of bucket were selected to carry out transient multiphase flow simulation at the same operating point of a model Pelton turbine. The hydraulic performance and cavitation characteristics of different buckets were analysed. The 3 bucket models were developed for Pelton turbines operating under the middle-high and the high-water head range, respectively. Results showed that the participation of cavitation model in simulation would slightly affect the working process of the bucket. The cavitation on the front surface of three buckets all happened at the beginning stage of jet inflowing the bucket, among which bucket C had the most serious cavitation on the front surface. This work showed different cavitation characteristics among various types of bucket, and the relevant result suggested comprehensive design considering cavitation characteristics should be done on the front surface of the bucket for a specific range of water head.
Modal characteristics analysis of a variable-speed pump-turbine rotor system: a perspective of resonance
Authors: Wang Lei , Yu Shuang , Wang Zhengwei
Published: October 2024

The safety and stability of the rotor system is crucial to the pump-turbine unit. The present paper analyzed the modal characteristics of a variable-speed pump-turbine rotor system based on the rotor dynamics theory and FEM method. The results show that the bending mode of the rotor system exhibits the forms of forward whirling (FW) and backward whirling (BW). The added mass effect will reduce the natural frequency of the rotor system, and it is more obvious for the torsional mode Torsional 1. In addition, the critical speed analysis shows that both the critical speed of the dry mode and wet mode of the rotor system is greater than 700rpm, which proves the safety of the unit. The results of the analysis can be used as a reference for the optimized design of similar variable-speed pump-turbine rotor system, which is conducive to the improvement of the reliability and life of the rotor system.
Numerical simulation of unsteady cloud cavitation in an orifice nozzle by a compressible gas-vapor/liquid mixture cavitation model
Authors: Peng Guoyi , Onishi Taihei
Published: October 2024

Focused on the behaviour of unsteady cloud cavitation in a submerged orifice nozzle, this work presents a numerical investigation by using a compressible gas-vapor/liquid mixture cavitation model. The mean flow of the two-phase mixture is calculated by URANS for compressible fluid and the intensity of cavitation is evaluated by the gas volumetric void fraction considering the effect of fluid compressibility varying with phase change. Water jets issuing from a submerged orifice nozzle are investigated under different cavitation conditions. Computation results are compared with experiment data and the validity of computation is confirmed. The periodical shedding of cavitation clouds is captured reliably. Numerical simulations reveal that a leading cloud principally split by the shear flow and a subsequent cloud detached by the re-entrant jet are successively shed downstream, and they coalesce over the range of approximately x/d ≈ 2∼3. This process is repeated and the flow rate coefficient pulsates periodically under the effect of cavitation clouds.
Large Eddy Simulation of an impinging Jet for Cooling of Blades
Authors: Ou Y Q , Lai H X
Published: October 2024

The impinging jet shows extremely high performance in local blade cooling and has been widely applied. In this study, high precision Large Eddy Simulation (LES) was employed to simulate compressible fully turbulent impinging jet under specific conditions, using three subgrid-scale (SGS) models - the Smagorinsky model (SM), the Coherent-structure Smagorinsky Model (CSM), and the Selective Mixed Scale Model (SMSM). The predictive accuracy and computational efficiency of the three SGS models were evaluated. Compared with existing DNS and experimental results, the results indicate that there is no significant difference among the three models in computational efficiency. However, subgrid models have a crucial impact on heat transfer. The SMSM model, which utilizes small-scale turbulence information, can better simulate the heat transfer in the impingement region compared with the SM model and the CSM model.
Stability impact on wind turbine blades trailing edge from bonding zone modelling methods
Authors: Zhao Jing , Mao Zhongyu , Zhou Wenming , Feng Yongguo
Published: October 2024

The trailing edge of wind turbine blade will undergo a large deformation under the action of load, resulting in a higher risk of damage and failure. The finite element analysis modeling method directly affects the simulation result, furthermore impacts the result of blade structure design. Therefore, it is necessary to find out a modeling method, which is capable to reflect the stability of bonding regions more accurately. This paper aims to discuss the influences of different finite element modeling methods on the buckling stability of blade trailing edge. The influences of shell element, tetrahedron element and hexahedron element on the blade stiffness are considered. The bonding region were simulated separately by combining shell element with bonding web, shell element with tetrahedron element and shell element with hexahedron. The influences of different bonding region modeling methods on the trailing edge buckling factor were analyzed by using the eigenvalue buckling analysis method of finite element. The simulation results provided data support for the future validation of the blade trailing edge bonding area modeling method. The results show that, the tetrahedral mesh provides a higher stiffness, followed by the hexahedral mesh, and the adhesive web form has the smallest stiffness. In order to simulate the more realistic stiffness of the adhesive area at the trailing edge of the blade, adhesive web plates can be built in the flange area of the blade root and the core material area of the trial adhesive mold; The direct bonding area can be simulated employing the hexahedron mesh; The tetrahedral mesh has high stiffness and is not suitable for modeling the adhesive area at the trailing edge. Blade simulation modeling can flexibly use different adhesive forms according to actual situations, ensuring the reliability of the simulation model.
Optimization of impeller parameters for hydrodynamic turbine based on multi-objective orthogonal test design
Authors: Wang Chengpeng , Wang Shenghui , Xiao Yexiang , Sun Xiang , Tian Xiugui , Luo Xianwu
Published: October 2024

The inherent instabilities within the structure of turbine-type energy recovery integrated machine (TT-ERIM) can compromise its smoothness and longevity, potentially leading to malfunctions. The dynamics of the dual-side impeller of TT-ERIM is research using computational fluid dynamics software CFX and manipulating the inlet flow rate. The pressure pulsation and radial force on each side under different flow conditions, and their impact on the hydraulic performance of the impeller and volute are compared and evaluated through unsteady numerical calculations. The results show that the pressure fluctuation pattern of a hydraulic turbine impeller is suboptimal at low flow rates, escalating at conditions below the rated flow. Conversely, the pressure fluctuations of the turbine impeller remain consistent and are slightly reduced with excessively high flow rates. Generating a negative pressure zone in the turbine impeller indicates an uneven overall pressure distribution. This research provides a theoretical platform for enhancing the TT-ERIM operational stability.
Design and analysis of hundred-meter wind turbine blade trailing edge based on finite element method (FEM)
Authors: Chai Hongmei , Luo Xiaojun , Li Peixin , Mao Zhongyu , Li Meizhi , Zhou Wen Ming , Feng Yongguo
Published: October 2024

The trailing edge region of composite wind turbine blades usually has a large deformation under wind load and the accidents caused by the damage of blade trailing edge accounts for a large proportion among blade accidents. With the development of large blade size, higher requirements are put forward for the stability of wind turbine blade trailing edge. Therefore, the trailing edge region is critical in the design of blade. A detailed study of the design and analysis for wind turbine blade trailing edge region was carried out in which the structure stability was regarded as the key. The influence of auxiliary spar cap and auxiliary spar web on the stiffness distribution and stability of the trailing edge were studied based on focus and finite element method (FEM). The respiratory effect of different structures due to deformation were analyzed and compared. The results showed that the structure of the auxiliary spar cap and auxiliary spar web can significantly increase stiffness, stability and decrease respiratory deformation at the trailing edge of blade compared to the traditional three webs structure. The structure of auxiliary spar and auxiliary spar web is the best design scheme for hundred-meter composite blade trailing edge.
Analysis of High and Low Temperature Performance of Titanium Zirconium Molybdenum Alloy and High Temperature Alloy Brazed Joint
Authors: Jian Yang , Jianyu Yuan , Wenwen Li , Yuchen Yang , Zihan Tu , Jintao Liu , Wenjiang Zou , Wei Mao , Yanlin Hu
Published: October 2024

Using niobium as the intermediate layer and gold nickel (Au82-Ni) filler metal, TZM alloy and high-temperature alloy GH3128 were brazed. The brazed specimens were subjected to 400 cycles of high and low temperature cycling tests at temperatures ranging from 650 °C ∼ 680 °C (high temperature) to -196 °C (low temperature) for 10 minutes seperately. Then the microstructure variation before and after the experiment were observed and the shear strength of the specimens were tested at room temperature for 50 cycles of 400 high and low temperature testing..

The results show that the microstructure of the transition zone at the brazing interface after brazing is uniform and dense, with good wettability with the substrate and no defects such as cracks. The solder and substrate undergo diffusion reactions, and the molybdenum alloy, niobium, and niobium, high-temperature alloy had each form diffusion layers, formed intermetallic compounds on the brazing surface.

After high and low temperature cycling, cracks exist in the braze seam between molybdenum alloy and niobium alloy. The cracking mode should be thermal fatigue based on the fracture morphology and phase analysis. The reasons of interface cracking are that due to different thermal expansion coefficients, low mutual solid solubility, and the formation of a large number of different types of intermetallic compounds, Mo and Nb materials have poor brazing compatibility and lower interface strength. Under cold and hot cycling conditions, brittle intermetallic compounds are prone to form crack source areas. As the number of cycles increases, the cracks gradually expand, ultimately leading to product leakage. In addition, the shear strength of brazed joints shows a decreasing trend with the increase of high and low temperature cycles in 400 high and low temperature tests.
Analysis of vortex induced vibration on the hundred-meter wind turbine blade based on CFD and FEM
Authors: Mao Zhongyu , Zhao Jing , Zhou Wenming , Qiao Yujun , Fan Zhenya
Published: October 2024

Along the development of wind turbine blade toward large size and light weight, the length of blade running-now has come to the level of hundred-meter, while the structure of blade trends to be flexible. During the shutdown conditions, blades are affected by wake vortex from different inflow speed and angle, which often induce blade vibration. It seriously affects the safety and service life of wind turbines, even may cause blade breakage accident. This paper focused on the vortex induced vibration on the hundred-meter wind turbine blade. Based on the Computational Fluid Dynamics (CFD) transient method, the wake flow field of three relative thickness aerofoils has been simulated under different inflow speed and angle. The distribution of vorticity has been compared. Based on the Fast Fourier Transform (FFT) method, the frequency of wake vortex has been analysed from the pressure pulsation, compared with the natural frequency of this hundred-meter blade calculated by the Finite Element Method (FEM). This result may be regarded as a simulation support to avoid vortex induced vibration of hundred-meter wind turbine blade.
Remaining Useful Life Prediction of Rolling Bearings Based on Time-Frequency Enhanced Transformer Model
Authors: Lin Chunyu , Luo Hongli , Wu Zhenpeng , Zhang Liangwei
Published: October 2024

Deep learning has achieved a lot of progress in predicting Remaining Useful Life (RUL). However, contemporary deep learning frameworks face inherent limitations, including constrained receptive fields, difficulties in capturing long-term dependencies, and singularities within the feature extraction domain. In response to these challenges, we propose a novel time-frequency enhanced Transformer model for predicting the remaining lifespan of rolling bearings. In this model, we utilize causal convolution operations to capture local features in the time-frequency domain and incorporate position encoding into the input signal. The time-frequency enhanced model exhibits end-to-end characteristics, feature fusion and selection can be performed without tedious feature extraction compared to existing methods. Furthermore, we introduce a custom Weighted Smooth Mean Squared Loss function to enhance the model’s prediction accuracy and interference resilience. In experiments, we comprehensively compare various advanced RUL prediction methods, with the results highlighting the superior performance and robust interference resistance of the time-frequency enhanced Transformer model in predicting the RUL of bearings.
Cloud removal in landsat images based on spatial-spectral-temporal random forests
Authors: Tang Yijie
Published: October 2024

The Landsat-8 Operational Land Imager (OLI), together with the Landsat-9 OLI2 sensors, provides important optical data for various applications. Due to frequent cloud cover, the obtained Landsat images always contain different degrees of spatial information loss. Although great efforts have been made to remove clouds in remote sensing images in recent decades, there still exists a large challenge, that is, the land cover changes between the target cloudy and the auxiliary cloud-free images, which limits greatly the accuracy of cloud removal. To cope with this issue, a spatial-spectral-temporal random forest (SSTRF) algorithm was proposed in this paper. The SSTRF model aims at removing clouds in Landsat images with the assistance of a remote sensing image with spatially complete cover from another satellite, that is, the 8-day MODIS surface reflectance product (MOD09A1). By compositing the valid data from 8 separate days, the MOD09A1 product has a great possibility to provide cloud-free land cover change information for the cloud removal of Landsat images. Through experiments with simulated and real clouds, SSTRF was demonstrated to produce greater accuracy than two benchmark cloud removal methods and has great potential to be applied to practical use.
Parametric indoor 3D reconstruction based on binary image feature point extraction
Authors: Gao Yuan
Published: October 2024

In recent years, with the rapid advancement of laser scanning technology, indoor 3D modeling technology has significantly developed, becoming a research hotspot in the field of 3D reconstruction. Addressing the issues of high complexity in decoding point cloud surfaces in traditional indoor reconstruction, this paper proposes an indoor 3D reconstruction method based on binary image feature point extraction. The method utilizes point cloud data for semantic segmentation of the indoor environment to accurately extract the ceiling area, which is then projected onto the XOY plane and converted into a binary image, thereby transforming the 3D problem into a 2D problem. Subsequently, key feature points are identified through feature point detection technology, and systematic model construction is carried out based on the sequence of these feature points and their associated parameters. This method effectively simplifies the complexity of traditional 3D modeling, achieving accurate and parametric indoor 3D reconstruction.
Simulation and fabrication of a 20 kHz single-beam transducer
Authors: Zhang Yifan , Liu Yun
Published: October 2024

With the vigorous development of underwater acoustic technology in China, underwater acoustic transducers are constantly moving towards broadband, low-frequency, and high-power directions. How to obtain piezoelectric transducers with lower frequencies is still a research direction that scholars from various countries are striving to study.

This article mainly studies and manufactures a 20 kHz single-beam piezoelectric transducer, using the classic Tonpilz transducer structure. Firstly, the Tonpilz transducer is theoretically analyzed using the classical equivalent circuit method. Secondly, the transducer is analyzed using ANSYS finite element analysis software to study the influence of piezoelectric ceramics on the frequency of the transducer, and the size of the piezoelectric ceramics is optimized to determine the size of the piezoelectric ceramic structure of the transducer. The working frequency of the transducer was calculated using software, and it was determined that the working frequency was approximately 20 kHz.
Application of UAV airborne LiDAR technology in highway engineering construction
Authors: Ding Jie , Chen Li
Published: October 2024

The airborne LiDAR technology of UAVs is an efficient and high-precision spatial information acquisition technology. This paper introduces the airborne LiDAR technology of UAV in detail and studies the application of airborne LiDAR technology of UAV in highway construction based on the sixth section of the Leibokahalo-Yongshan connection line of G4216 Yibin Xinshi to Panzhihua Section. Engineering application practice shows that this technology can solve the difficult problem of obtaining basic geographic information data, and verify the rationality of the scheme and the matching degree with the field environment. In addition, compared with traditional survey technology, the technology has obvious advantages in the construction of highways in complex terrain, which helps to improve the quality of survey and design.
Improved mangrove refined extraction method based on remote sensing intelligent extraction model
Authors: Gu Xianghui , Yang Xiaotong , Shi Zhizhou , Zhang Feng , Jiao Hongbo , Zhao Binru
Published: October 2024

Mangrove ecosystems are blue carbon ecosystems with important ecological and environmental significance. Refined monitoring of mangroves is a prerequisite for their management and protection, and remote sensing technology is an indispensable tool for timely and accurate monitoring of mangroves. However, the present methods for extracting mangroves from high-resolution images suffer from problems such as inaccurate boundaries, missing targets, and low accuracy for sparse mangroves. To address these challenges, a novel mangrove extraction method is employed, integrating DeepLabV3+ with the Convolutional Block Attention Module (CBAM). A multi-spectral dataset of mangroves has been established, using a long-time series of multi-source high-resolution images covering many provinces. This comprehensive dataset is subsequently applied to both the baseline model and an improved model for comparative assessment. In comparison with the baseline network, the improved network demonstrates superior performance in mangrove segmentation, exhibiting heightened accuracy, particularly in challenging areas such as the intricate edges and sparsely vegetated regions. The improved model is applied to GF-1 satellite images in the northern Beibu Gulf, yielding segmentation accuracy exceeding 95% when validated against ground truth measurement data. Our proposed methodology significantly contributes to the efficacious management and protection of mangrove ecosystems.
Removing thick clouds in landsat 8 OLI images with cloudy time-series auxiliary data
Authors: Wang Lanxing
Published: October 2024

Thick cloud occlusion severely limits the subsequent application of optical remote-sensing images. Existing mainstream cloud removal methods often use cloud-free homologous temporal images to provide auxiliary information. However, due to the limitation of cloud occlusion and satellite revisit cycle, the time interval between the cloud-free auxiliary image and the target cloudy image is often too large, and the possible land cover changes during the period increase the uncertainty of effective information on the auxiliary images. In this case, more accurate reconstructions may be obtained by using temporally closer and partially cloud-contaminated images. In this paper, a deep network, convLSTM, is developed for cloud removal (i.e., CR-convLSTM), which makes full use of the complementary effective information on partially cloud-contaminated time-series images. Experiments based on simulated clouds indicated that CR-convLSTM can obtain more accurate predictions than the classical cloud removal method MNSPI. CR-convLSTM is an effective cloud removal method with high computational efficiency while ensuring predicting accuracy.
Spatio-temporal grid-based storage method for aerospace operation and control data
Authors: Li Shuo , Chen Jinyong , Peng Huixiang , Wang Gang , Miao Shaobo
Published: October 2024

The current aerospace operation and control data system has problems such as difficult integration organization and difficult data retrieval in terms of mission planning efficiency, which limits the development of satellite operation and control systems. This paper is oriented to the organization and management of aerospace operation and control data, according to the nature of the current big data indexing model. Based on the principle of earth dissection, we aim to design a grid that can be indexed. First of all, the Earth is dissected to form a hierarchical and uniformly distributed global geographic grid, and then the formed grid is encoded to store satellite attribute information and orbit data for mission planning. Finally, through the data retrieval experiment, the retrieval time is within 100 milliseconds under ten million pieces of data, which proves that the spatial-temporal grid model has the characteristics of efficient and fast retrieval. It can provide the basic information for satellite mission planning to further improve the efficiency of satellite mission planning and management and the efficiency and quality of satellite mission planning.
Research on Sound velocity model construction method in GNSS-A underwater positioning
Authors: Zhang Jiyong , Sun Xiaohu , Zhao Chunhui , Lei Zhichu , Xie Long , Liu Donghui
Published: October 2024

GNSS-A technology is a submarine positioning technique used to establish ocean control networks, and its positioning results are primarily affected by errors in ocean sound velocity. To address this issue, this paper analyzes the spatial representativeness error of the weighted average sound velocity based on the GNSS-A positioning principle. It also explores the construction method of a sound velocity model in the time domain using the average sound velocity. A sinusoidal diurnal variation model for sound velocity is developed through expanded fitting. Finally, actual measured data is used to perform GNSS-A submarine positioning, verifying the effectiveness of the sound velocity model. The results show that when the horizontal distance of the sound ray is less than 1.7 times the water depth, the average sound velocity does not introduce significant systematic errors. The constructed sound velocity model aligns with local solar elevation patterns, improving the unit weight error of GNSS-A positioning results by several decimeters and controlling the mutual difference of positioning results from different tracks to the decimeter level.
Uncertainty of evaluation of spectral mismatch correction factor
Authors: Rezazadeh Y , Sperling A , Gerloff T , Krüger U , Ferrero A , Campos J , Pellegrino O , Dubard J , Ikonen E
Published: October 2024

Addressing the effect of partially correlated components of spectral irradiance data on spectral integrals poses a substantial challenge. This study employs Monte Carlo methods to conduct an uncertainty analysis of spectral integrals, with a focus on the uncertainty of the spectral mismatch correction factor. The investigation encompasses the primary types of uncertainty contributors of spectral irradiance, based on carefully calibrated FEL lamp measurements. A novel approach is introduced to estimate the impacts of partial correlations among spectral irradiance values at different wavelengths. The findings reveal that uncertainty components arising from partial correlations significantly outweigh those associated with full spectral correlation or complete lack of correlation at different wavelengths. This insight advances our understanding of uncertainty analysis of spectral integrals and underscores the importance of accounting for partial correlations in accurate measurements.
Research on the influence of different organizational structures on the electrical life of sealed relays
Authors: Chen Yangfang , Jin Yangdeng , Ma Siping , Yan Xiaofang , Li Jie , You Yibo , Wan Xinpeng
Published: October 2024

A sealed relay is a type of power relay mainly used in fields with harsh environments, low noise requirements, or high-reliability requirements. It is used in scenarios such as vehicle loads, household appliances, industrial control, and motors. At the same time, when the input meets certain specified conditions, it is a device that can generate a jump in one or more electrical output circuits, playing a role in controlling the on/off current of the connected circuit. Power relays have been widely used in various fields due to their small size, low noise, and low power consumption advantages. This article mainly studies the electrical parameters such as arc energy, arc time, welding force, and contact burning principle of silver tin oxide electrical contact materials produced by different processes, providing a reference for the development of electrical contact materials.
Preparation and properties of new green polyacrylamide hydrogels
Authors: Zhang Lulin , Zhang Taiyang , Qin Lixia , Li Xiangqing , Kang Shizhao
Published: October 2024

The pursuit of low-toxicity hydrogels represents a focal point and frontier in contemporary research endeavors. Partially hydrolyzed polyacrylamide emerges as the most prevalent polymer employed in the formulation of priority flow control gels, owing to its favorable cost-efficiency and heightened receptivity to crosslinking agents. A noteworthy discovery pertains to the utilization of a green crosslinking agent derived from TiSO4, which induces the gelation of polyacrylamide, resulting in an elevation of apparent viscosity from 1159 mPa·s to 100, 000 mPa·s. Extensive investigations into the primary factors influencing the performance of crosslinked polymer gels and their underlying principles have been conducted. The advent of such gel plugging agents holds promise in addressing challenges encountered in select reservoir scenarios, thereby furnishing reliable technical underpinnings for the efficacious stimulation of oil fields.
Preparation of nano-TiO2 spherical catalyst doped with nonmetallic elements for potential use in CO2 reduction
Authors: Yuan Yuan , Ruan Sirui , Ye Yimng , Cai Guojie , Qiu Wenfei , Liu Hongbo , Huang Zhiyong
Published: October 2024

P (St-HEA) microsphere was synthesized as template to prepare TiO2. Nano TiO2 spheres, nitrogen doped TiO2 (N-TiO2) spheres and sulfur doped TiO2 (S-TiO2) spheres were prepared by sol-gel method with the above template. The samples were characterized by XRD, SEM, and XPS. The results showed that TiO2 from sulfur and nitrogen atoms in thiourea and urea in situ doped in the crystal lattice. The TiO2 spherical catalyst doped with nonmetallic elements showed typical anatase phase at lower temperature, and spheres structure with pores and different particle size about 200 nm to 1μm. The obtained TiO2 spherical catalyst doped with nonmetallic elements may potentially use in the photo-catalysis of CO2 reduction.
Diameter controlled fabrication of ultralong silicon wires through regulating metal mass in massive metal-assisted chemical vapor deposition
Authors: Chai Haoyuan , Gu Wenxuan , Xia Xian , Yu Jia , Zhang Bingchang
Published: October 2024

The successful fabrication of ultra-long silicon wires has facilitated the study and application of silicon wires. However, research on the controlled fabrication of ultralong silicon wires, such as diameter modulation, is still insufficient. Herein, tapering ultralong silicon wires are synthesized by using a massive metal-assisted chemical vapor deposition method. By altering the mass of the tin catalyst in the growth zone, the length and changing rate of the diameter can be modulated. When a 40 g catalyst is placed in the growth region, the length of obtained silicon wires is 6.6 mm, and the changing rate of diameter with length is 541 nm/mm. When the catalyst mass in the growth region is reduced to 20 g, the length of the products decreases to 4.0 mm, and the changing rate of diameter with length increases to 964 nm/mm. This work proposes a new route for the diameter-modulated fabrication of ultralong silicon wires and will promote their application across various fields.
Research on friction stir welding technology of urban rail transit car body
Authors: Yan Zhifei , Tang Liguo
Published: October 2024

In this paper, the principle and technical characteristics of friction stir welding are introduced. According to the form of the side wall of urban rail transit vehicles, a friction-stir welding joint structure with convex is proposed. In order to verify the performance of the joint, the joint tensile strength test and the static strength test of the car body are carried out. The results show that the designed friction stir welding joint has high smoothness and excellent performance, fulfilling the requirements for the standard EN12663.
Research on temperature rise performance of DC universal disconnect switch at high altitude
Authors: Wang Yunteng , Zou Hairong , Xiang Honggang , Gong Zuoyong
Published: October 2024

Low Voltage appliances are used more and more widely in high altitude areas, but the research on their temperature rise performance is still insufficient. Aiming at this problem, a high altitude temperature rise simulation model is established and verified by experiment, and the temperature rise performance is studied. Firstly, a DC universal isolation switch with a rated current of 1600A was used as the carrier to build an electro-thermal coupling calculation model of high-altitude temperature rise. Secondly, the temperature rise experiment of the isolation switch in high altitude environment was carried out to verify the effectiveness of the simulation model. Finally, the temperature fields of the DC universal isolation switch at different altitudes are simulated, and the change of convective heat transfer coefficient is calculated, and the temperature rise performance of the isolation switch at high altitudes is analyzed. With the increase of altitude, the temperature rise of the conductor is significantly higher than that of the insulation shell, and the heat dissipation capacity of the aluminum radiator decreases significantly at high altitude. The model and conclusion can provide reference for the use of low voltage electrical apparatus in high altitude environment.
Characteristic of fluoroether gum via non-linear rheological approaches
Authors: Song Ronghao , Yang Rui , Wang Chen , Su Zhengtao
Published: October 2024

Large amplitude oscillatory shear (LAOS) tests were conducted on four types of fluoroether elastomer gum, namely VPL-85540, VPL-75545, VPL-65455, and VPL-55540 in order to study their molecular weight, chain structure, and branching degree from the perspective of rubber rheology. For the setting of shear rate in varied LAOS measurements, frequency and angular velocity controlling modes were attempted and compared. Non-linear rheological parameters showed that VPL-65455 possessed significant polymeric branching characteristics. VPL-55540 possessed the lowest molecular weight, and VPL-75545 was detected with higher long-pendant monomer content in its polymer chain. Rheological properties concluded from the analysis of two shear rate controlling modes of LAOS tests exhibited great consistency, which confirmed the reliability of LAOS tests in the characterization of fluoroether gum.
Enhancing performance of Si/C composite anode in high energy density lithium-ion batteries with CMC-CPAM-SBR binder
Authors: Zheng Yuanyuan , Wang Ning , Zhang Jianhua , Zhang Xiaobao , Yang Juanyu
Published: October 2024

The utilization of polymeric binders is indispensable in the implementation of silicon/carbon anode materials in high-energy-density lithium-ion batteries (LIBs). This necessity arises from their pivotal function in upholding structural integrity. However, current water-based binders solely focus on binder adhesion, neglecting the crucial interaction with the carbon material. In this work, a composite binder (CMC-CPAM-SBR) was constructed by combining Styrene Butadiene Rubber (SBR) with cationic polyacrylamide (CPAM) network binder with self-healing carboxymethyl cellulose (CMC). This innovative binder formulation was designed to enhance the performance of Si@C/graphite composite anodes. A capacity retention rate of 92.86% was achieved after 100 cycles, which represents the improvement over the performance of electrodes utilizing the CMC-CPAM binder, which only retained a capacity of 84.53% after the same number of cycles. A full battery with a capacity of 1992.8 mAh was designed, and the battery capacity remained at 80.6% of its capacity after completing 500 cycles. This research presents an effective technique for manufacturing high-performance anode materials.
Molecular dynamics study on the effect of crystal orientation on the plasticity and fracture behavior of α-Fe crack tip
Authors: Du Pei , Wang Jing , Zhang Yan
Published: October 2024

In this paper, the molecular dynamics technique is utilized to simulate crack propagation within the localized vicinity of the crack tip, aiming to investigate the plastic deformation behavior of the α-Fe crack tip under different crystal orientations. The influences of crystal orientation on the mechanical properties of the models were obtained, and the weakest crystal orientation associated with fracture was determined. Meanwhile, the plastic deformation mechanism of the α-Fe model under different crystal orientations was obtained by analyzing the microscopic atomic evolution process of the four models.