bluuebunny/crossref_metadata_2025 huggingface dataset:
Realization of logic operations via spin–orbit torque driven perpendicular magnetization switching in a heavy metal/ferrimagnet bilayer
Authors: Jacob Mathew Arun , Gao Yufei , Wang Junwen , Mohammadi Mojtaba , Awano Hiroyuki , Takezawa Masaaki , Asada Hironori , Fukuma Yasuhiro
Published: June 2024

Programmable and non-volatile spin-based logic devices have attracted significant interest for use in logic circuits. Realization of logic operations via spin–orbit torque (SOT) driven magnetization switching could be a crucial step in the direction of building logic-in-memory architectures. In this work, we demonstrate experimentally, the realization of four logic operations in a heavy metal/ferrimagnet bilayer structure via SOT switching. We also propose a general scheme for choosing input parameters to achieve programmable logic operations. The bulk and tunable perpendicular magnetic anisotropy and relatively lower saturation magnetization in ferrimagnets are found to make them more energy efficient in performing logic operations, as compared to conventional ferromagnets. Thus, ferrimagnets are promising candidates for use in logic-in-memory architectures, leading to the realization of user-friendly spin logic devices in the future.
Core performance predictions in projected SPARC first-campaign plasmas with nonlinear CGYRO
Authors: Rodriguez-Fernandez P. , Howard N. T. , Saltzman A. , Shoji L. , Body T. , Battaglia D. J. , Hughes J. W. , Candy J. , Staebler G. M. , Creely A. J.
Published: June 2024

This work characterizes the core transport physics of SPARC early-campaign plasmas using the PORTALS-CGYRO framework. Empirical modeling of SPARC plasmas with L-mode confinement indicates an ample window of breakeven (Q > 1) without the need of H-mode operation. Extensive modeling of multi-channel (electron energy, ion energy, and electron particle) flux-matched conditions with the nonlinear CGYRO code for turbulent transport coupled to the macroscopic plasma evolution using PORTALS reveals that the maximum fusion performance to be attained will be highly dependent on the near-edge pressure. Stiff core transport conditions are found, particularly when fusion gain approaches unity, and predicted density peaking is found to be in line with empirical databases of particle source-free H-modes. Impurity optimization is identified as a potential avenue to increase fusion performance while enabling core-edge integration. Extensive validation of the quasilinear TGLF model builds confidence in reduced-model predictions. The implications of projecting L-mode performance to high-performance and burning-plasma devices is discussed, together with the importance of predicting edge conditions.
Classification of musical intervals by spiking neural networks: Perfect student in solfége classes
Authors: Bukh A. V. , Rybalova E. V. , Shepelev I. A. , Vadivasova T. E.
Published: June 2024

We investigate a spike activity of a network of excitable FitzHugh–Nagumo neurons, which is under constant two-frequency auditory signals. The neurons are supplemented with linear frequency filters and nonlinear input signal converters. We show that it is possible to configure the network to recognize a specific frequency ratio (musical interval) by selecting the parameters of the neurons, input filters, and coupling between neurons. A set of appropriately configured subnetworks with different topologies and coupling strengths can serve as a classifier for musical intervals. We have found that the selective properties of the classifier are due to the presence of a specific topology of coupling between the neurons of the network.
Investigating three-dimensional vortex evolution in centrifugal pump under rotating stall conditions using tomographic particle image velocimetry
Authors: Tong Zheming , Shang Bingyang
Published: June 2024

A rotating stall in centrifugal pumps commonly occurs under off-design operations, which is a detrimental phenomenon leading to flow instabilities, pressure fluctuations, and reduced performance. A time-resolved non-intrusive three-dimensional (3D) flow visualization method is developed for investigating complex vortex structures in centrifugal pumps based on Omega vortex identification and tomographic particle image velocimetry (tomo-PIV). A special-made centrifugal pump prototype was developed with acrylic glass allowing for optical access. This method enables both qualitative and quantitative analysis of high spatiotemporal resolution on flow behaviors and dynamics under various stall conditions. The ultra-high sampling frequency realized over 40 time-consecutive observations per revolution under 0.2 Qd, 0.4 Qd, 0.6 Qd, and 0.8 Qd. It captures the instantaneous evolution of vortex structures that undergoes a growth–breakup transition within 7–9 ms. The rotating stall mechanism is revealed experimentally from the evolution of the vortex structure. Our analysis shows the tomo-PIV's additional velocity component aids in understanding the 3D characteristics of the stall. A substantial region of reverse flow in the z-axis direction is observed under 0.2 Qd. Vortex structures are more prone to blockage at the impeller inlet, exacerbating the stall phenomenon. As the flow rate increases, the velocity distributions across different layers exhibit a laminar characteristic with a more uniform profile. The vortex structures extend radially and migrate toward the outlet. The evolutions of the stall vortex, wake vortex, and inlet vortex share the same dominant frequency components (4.75fn and 5.25fn), but the flow rate affects the proportion of different frequency components.
Low-loss vanadium dioxide-enabled mmWave tunable reflective electromagnetic surface with complementary unit cells for wave manipulation
Authors: Ramsey J. A. , Lee S. Y. , Disharoon W. R. , West D. L. , Ghalichechian N.
Published: June 2024

This study presents a novel implementation of vanadium dioxide (VO2) phase change material in an electromagnetic (EM) surface with beam steering capabilities. For the first time, we present the design, fabrication, and measurement of a globally actuated, VO2-based beamforming reflective EM surface. We propose a design featuring complementary unit cells that enable beam steering with a single excitation, marking a pioneering use of low-loss VO2 in creating a complementary EM surface for the mmWave band. The unit cells incorporating VO2 exhibit low-loss characteristics, with −0.92 and −1.9 dB in the hot state and −0.49 and −0.25 dB in the cold state, respectively. We incorporate both positive and negative phase variants alongside two temperature-independent phase unit cells. The complementary design enables us to utilize two beam operating states, effectively exploiting the otherwise unused cold state. We experimentally demonstrated beamforming at ±5° and ±10° from the broadside. In the case of ±10°, the measured gains at 35 GHz in the cold and hot states were 19.4 and 20.3 dB, respectively, which aligned well with the simulated gains of 20.9 and 21.5 dB. Manipulation of the electromagnetic wave direction with a single excitation has the potential for imaging, sensing, and communication applications. The complementary unit cell design methodology can be further adapted for mmWave beamforming, absorbing, and cloaking reconfigurable EM surfaces. Furthermore, the use of VO2 can be extended up to sub-THz frequencies due to the wideband, low-loss characteristics compared with conventional reconfigurable devices, such as PIN diodes or MEMS switches.
Ethane under pressure revisited using x-ray diffraction, Raman spectroscopy, infrared absorption, and ab initio calculations up to 150 GPa
Authors: Toraille Loïc , Weck Gunnar , Geneste Grégory , Pépin Charles , Garbarino Gaston , Loubeyre Paul
Published: June 2024

Ethane (C2H6) is anticipated to be the most stable compound within the carbon–hydrogen system under the 100 GPa pressure range. Nevertheless, the properties of ethane under pressure are still poorly documented. Here, we present a comprehensive study of the structural and vibrational properties of C2H6 in a diamond anvil cell at pressures up to 150 GPa. To obtain detailed data, ethane single-crystal was grown in a helium pressure-transmitting medium. Utilizing single-crystal x-ray diffraction, the distortion mechanism between the tetragonal and monoclinic phases, occurring over the 3.2–5.2 GPa pressure range, is disclosed. Subsequently, no phase transition is observed up to 150 GPa. The accurately measured compression curve is compared to various computational approximations. The vibrational modes measured by Raman spectroscopy and infrared absorption are well identified, and their evolution is well reproduced by ab initio calculations. In particular, an unusual anticrossing phenomenon occurs near 40 GPa between a rocking and a stretching mode, likely attributable to intermolecular interactions through hydrogen bonding.
Effect of replacing titanium with zirconium on the solubility of lithium in the LixZryTi1−yS2 system
Authors: Kuznetsova Alexsandra Yu. , Suslov Evgeniy A. , Titov Alexsander N.
Published: June 2024

Solid solutions of ZryTi1−yS2 (y = 0.1, 0.2) compositions have been synthesized. The electrochemical introduction of lithium is carried out by the galvanostatic intermittent titration technique. An isothermal section of the phase diagram of the LixZryTi1−yS2 system at room temperature has been constructed. The limiting solubility of lithium in solid solutions decreases with an increasing amount of titanium substituted for zirconium. It was noted that at low lithium concentrations (x < 1), there is no change in the E(x) dependence when titanium is replaced by zirconium. This may indicate the formation of separate TiS2 and ZrS2 layers.
Steady-state triad resonance between a surface gravity wave and two hydroacoustic waves based on the homotopy analysis method
Authors: Yang X. Y. , Yang J.
Published: June 2024

Under water compressibility, resonant triads can occur within the family of acoustic-gravity waves. This work investigates steady-state triad resonance between a surface gravity wave and two hydroacoustic waves. The water-wave equations are solved as a nonlinear boundary value problem using the homotopy analysis method (HAM). Within the HAM framework, a potential singularity resulting from exact triad resonance is avoided by appropriately choosing the auxiliary linear operator. The resonant hydroacoustic wave component, along with the two primary waves (one hydroacoustic wave and one gravity wave), is considered to determine an initial guess for the velocity potential. Additionally, by selecting an optimal “convergence-control parameter,” the steady-state resonance between a surface gravity wave and two hydroacoustic waves is successfully obtained. It is found that steady-state resonant acoustic-gravity waves are ubiquitous under certain circumstances. The two primary wave components and the resonant hydroacoustic wave component take up most of the energy in the steady-state resonant acoustic-gravity wave system. The amplitude of the resonant hydroacoustic wave component is mainly determined by the primary hydroacoustic wave component, and the amplitudes of both hydroacoustic waves are approximately equal in all cases considered. In addition, when the overall amplitude of the wave system increases, both dimensionless angular frequencies decrease, indicating that the nonlinearity of the entire wave system becomes stronger with an increase in the wave system amplitude. The amplitude of the primary hydroacoustic wave has a relatively large effect on the system's nonlinearity. This work will enrich and deepen our understanding of acoustic-gravity waves.
The racial composition of road users, traffic citations, and police stops
Authors: Xu Wenfei , Smart Michael , Tilahun Nebiyou , Askari Sajad , Dennis Zachary , Li Houpu , Levinson David
Published: June 2024

This paper exploits the potential of Global Positioning System datasets sourced from mobile phones to estimate the racial composition of road users, leveraging data from their respective Census block group. The racial composition data encompasses approximately 46 million trips in the Chicago metropolitan region. The research focuses on the relationship between camera tickets and racial composition of drivers vs. police stops for traffic citations and the racial composition in these locations. Black drivers exhibit a higher likelihood of being ticketed by automated speed cameras and of being stopped for moving violations on roads, irrespective of the proportion of White drivers present. The research observes that this correlation attenuates as the proportion of White drivers on the road increases. The citation rate measured by cameras better matches the racial composition of road users on the links with cameras than do stops by police officers. This study therefore presents an important contribution to understanding racial disparities in moving violation stops, with implications for policy interventions and social justice reforms.
Enhancement of electron–phonon coupling due to increased magnetism and applied hydrostatic pressure in FeSe
Authors: Ouyang Xiao-Fang , Song Ze-Yi , Zhang Yu-Zhong
Published: June 2024

Inspired by the parabolic trend of the superconducting transition temperature (Tc
) of bulk FeSe under hydrostatic pressure, we investigated the effect of magnetism and hydrostatic pressure on the electron–phonon coupling (EPC) in FeSe using density-functional perturbation theory. We found that both magnetism and hydrostatic pressure enhanced EPC. The enhancement of the EPC is mainly attributed to phonon softening and deformation potential induced by magnetism, rather than Fermi surface nesting. Furthermore, we investigated the effect of spin fluctuations on superconductivity by applying the random phase approximation method. A possible application of our results to the phase diagram of FeSe under hydrostatic pressure was discussed, and we demonstrated that when EPC and spin fluctuations are both considered, a parabolic superconducting Tc
may be obtained, providing a plausible explanation for the phase of FeSe under hydrostatic pressure.
Impact of media information and reinfection in a COVID-19 dynamical model: emergence of periodic orbits through Hopf bifurcation
Authors: Devi Arpita , Gupta Praveen Kumar
Published: June 2024

In the current study, we investigate an SIRI compartmental model of COVID-19 incorporating the effect of social media and TV advertisements on the disease transmission of COVID-19 in the presence of reinfection. We have performed basic analysis on the model and studied the basic reproduction number

R

0

. The proposed model admits two disease-free equilibria and upto four endemic equilibria under certain parametric restrictions. We have performed local stability analyses via the Routh-Hurwitz criterion. Global asymptotic stability is established for the unique endemic equilibrium, when it exists, via the geometric approach. We have also scrutinized the proposed model for occurrence of the bifurcation phenomena and found that both forward and backward bifurcation transpires for a certain set of parameters. Simultaneously, the proposed model also displays saddle-node bifurcation. When

R

0

>
1

, the possibility of numerous endemic equilibria exists. These numerous equilibria exhibit oscillations through Hopf bifurcation leading to rich and complicated dynamics. The model is found to show hysteresis. Effect of levels of media and reinfection on the infected compartment is demonstrated and sensitivity analysis of influential model parameters is carried out. Data fitting is carried out to validate the proposed model by comparison of real data in India and the proposed model. Lastly, numerical simulations are executed for several examples to provide analytical and epidemiological understanding into model behaviour.
Machine learning and time-series decomposition for phase extraction and symbol classification in CV-QKD
Authors: Alsaui Abdulmohsen , Alghofaili Yousef , Venkitesh Deepa
Published: June 2024

The predictability of phase estimation and symbol classification using machine learning (ML) for experimental continuous-variable quantum key distribution (CV-QKD) is investigated. ML outperforms standard techniques, with up to 2.3% enhancement in the symbol accuracy, showcasing classical noise impact. The time-series decomposition method upper-bounds the predictable space due to shot noise. Ultimately, a 1 kbits/s secret key rate is achieved at 20 km for a 1.8 pW symbol power.
Ultrathin absorber with independently tunable dual-resonances for terahertz sensing
Authors: Verma Vikrant , Varshney Gaurav
Published: June 2024

A technique is implemented for the generation and alteration of two independently tunable resonance peaks in a graphene based ultrathin absorber structure designed for the terahertz spectrum. The proposed structure is a multi-layered stacked arrangement of two resonator layers of graphene grown over the top of two isolated dielectric (SiO2) substrate layers shielded by a gold metal reflector at the bottom. The structure exhibits very low thickness profile and can be implemented with a thickness equivalent to λ/19.6 where λ is the free space wavelength. Two patterned graphene layers contributes to two independently tunable narrowband/near-perfect absorption peaks at 9.56 THz and 10.96 THz. This polarisation insensitive absorber structure also exhibits frequency ratio tunability of higher order mode with respect to lower order mode by distinctly/separately varying the Fermi level of graphene layers. The response is stable for a wider angle of wave incidence up to 70°. Its narrowband response makes it a suitable candidate to be utilized as biosensor for refractive index sensing.
An Autonomous Navigation Method for Planetary Rover Based on Multi-modal Fusion and Multi-factor Graph Optimization
Authors: Zheng Bo , Cao Tao , Hu Tao , Qian Zhouyuan , Wang Shisun , Han Fei
Published: June 2024

Planetary surface is a complex unstructured environment with strong light, strong shadows, weak textures and numerous obstacles. There is no GPS signal support and satellite networking support on the planetary surface. The limited computer and sensor capabilities of planetary rover have a significant gap from the ground autonomous driving configuration, which presents a great challenge to the autonomous navigation methods of planetary rover. Extreme lighting conditions will increase the camera mismatching rate, and poor texture will increase the lidar matching error, which will reduce the estimation accuracy. Moreover, camera and lidar produce great motion distortion in the rugged terrain and bumpy environment, which leads to a large increase in the cumulative error of odometer. Camera and lidar are not suitable as the main sensor of SLAM algorithm in unstructured environment because they are sensitive to the change of environment. Therefore, an autonomous navigation method for planetary rover based on multi-modal fusion and multi-factor graph optimization is presented in this paper. The IMU (Inertial Measurement Unit) odometer node is added to the lidar odometer and visual odometer thread, and the IMU is taken as the central node to build a multi-factor graph optimization model. A multi-factor graph optimization model and a strong adaptive constraint strategy with reasonable weights are constructed. The pose estimation of other sensors is used to constrain IMU bias, meanwhile historical rut tracking, obstacle contour matching and skyline feature matching are introduced. Finally, motion prediction is achieved in the IMU odometer node. Simulation results and field tests show that this method can effectively cope with the unstructured environment on planetary surface, which achieves adaptive and robust autonomous navigation of planetary rover.
Simulation of fatigue crack initiation life under compressive loading based on material meso-characteristics
Authors: Zhai Yahao
Published: June 2024

The fatigue problem under compressive loading is common in the key components of aeroengine. Most of the fatigue life prediction methods studied in the past are macroscopic phenomenological methods based on a large amount of experimental data. Due to the difficulty in carrying out the fatigue test under compressive loading, the S-N curve or Manson-Coffin formula commonly used on the fatigue life prediction of material under compressive stress were obtained through fatigue tests under conditions where the average stress was greater than or equal to zero. Although the average stress can be corrected by some formulas, whether the life estimation formulas fitted by those fatigue test data are applicable to the fatigue life analysis with average stress less than zero has not been solved in engineering. And there were few studies on the influence of compressive stress on fatigue life at home and abroad. On the basis of Tanaka-Mura fatigue crack initiation theory, a mesoscopic model suitable for fatigue characteristic analysis under compressive loading was established in this article. The model verified the feasibility in predicting the fatigue initiation life using test data of 7075-T651 aluminum alloy under the compressive fatigue load.
Research on optimal design method of dynamic stress parameters of helical gear based on orthogonal experimental design
Authors: Ke Chen , Huan Liu , Suliang Yang , Zheyuan Liu , Xindang He
Published: June 2024

Aiming at the reliability optimization design problem of two-grade helical cylindrical gear transmission system, the UG parameterized model based on expression and ADAMS dynamic simulation model under real working conditions are integrated in ISIGHT platform, and the distribution law of peak contact force on the tooth surface of helical gear pair in the transmission system at different meshing times is obtained. Considering the uncertainty of material properties, load conditions and geometric parameters, the sample set was generated according to the orthogonal experimental design method, and the Kriging approximation model was established. On this basis, the contact strength reliability of helical gear was analyzed. The mathematical model of meshing efficiency reliability optimization of helical gear pair was established and solved by Hooke-Jeeves Direct Search method. The results show that the meshing efficiency and reliability of the optimized helical gear pair are improved, and the peak value of the contact force is obviously reduced.
Random Vibration Characteristics and Vibration Suppression of an Aero-engine Inlet Rake Fabricated by Laser Powder Bed Fusion
Authors: Niu Hongwei
Published: June 2024

The inlet rake is generally installed in aero-engine during rig and flight test for flow field pressure and temperature measuring. There are usually complex flow channels and pipelines inside the rake to extract air flow to the sensor. The laser powder bed fusion(L-PBF) technique was applied in rake fabrication recently due to its progressive layer stacking molding procedure. However, the difference of thermoforming method between L-PBF and the traditional casting process leads to the mechanical property disparities of the material. In this work, the determinants of random vibration response of the inlet rake manufactured by L-PBF with GH4169 powder were studied individually. The stiffness and yield property of the material were investigated by the specimen tensile test, which indicates higher elasticity modulus and yield stress comparing to the ones by castling or forging process. The damping ratio of the inlet rake was obtained through stress attenuation characteristics experiment and analysis under stepwise excitation. The stress distribution and resonance margin of the inlet rake under the aero-engine random vibration spectrum were simulated by finite element modal and random vibration analysis. The results showed that the damping ratio of the L-PBF inlet rake is much smaller than engineering recommendations, and the resonance margin is insufficient. Thus, the stress level of the inlet rake was very high, especially in the blade root section, quite close to the yield limit of the material. To solve this problem, the vibration suppression methods of the inlet rake were studied from the perspective of structural design optimization and damping ratio increasing. Through the rational design of the resonance margin and addition of vibration damping structure, the vibration stress of inlet rake was significantly suppressed. As the result, the rake was installed in the inlet during the aero-engine rig test for flow field pressure and temperature measurement successfully.
Low-frequency broadband vibration isolation study of inertial amplification Meta-lattice sandwich structure
Authors: Zhang Zhilin , Li Hao , Li Bing
Published: June 2024

In the pursuit of excellent mechanical properties, the realization of lightweight structure has attracted great attention from researchers in recent years. To reduce the mass of structures while providing them with low-frequency, broadband vibration damping and multifunctional integration capabilities, this paper presents the use of a Meta-lattice sandwich structure designed using the inertial amplification mechanism. By utilizing a combination of Bloch boundary conditions and the finite element method, we calculated the band gap of the metamaterial structure through finite element software. Afterwards, we examined the impact of the internal structural dimensions and the angle of the internal core truss on the bandgap of the metamaterial structure, as well as their effects on the load-bearing performance. The results demonstrate that the implementation of the concept of inertial amplification achieves low-frequency broadband vibration damping while decreasing the overall mass of the structure, while also retaining good load-bearing performance.
Experimental and Simulation Study on Low-velocity Impact Damage of Composite Laminates under Temperature Environment
Authors: Huanhuan Liang , Hongwei Niu , Ye Wang , Xiewen Sun
Published: June 2024

The composite material casing of aero-engine operates in different temperature environments and is inevitably impacted by external objects during use. The resin matrix composite materials are sensitive to temperature, which leads to more complex damage propagation and failure modes of materials under temperature environment. The influence of temperature environment on low-velocity impact damage of composite materials needs to be studied. In this paper, the T300/QY8911 composite laminates were subjected to low-velocity impact test and simulation study under three different temperature environments of 20°C, 120°C, and 180°C. The impact damage detection was carried out by visual inspection and ultrasonic C-scan to analyze the influence of temperature on the damage of composite laminates. Finite element simulation analysis was also conducted on the gradual expansion process of impact damage of composite laminates under different temperature environments to predict the impact damage area of laminates. The results show that the main damage forms are matrix cracking and delamination and the temperature has a significant effect on the low-velocity impact damage of composite laminates. Under the same impact energy, the length of the back crack and the cracking damage of the matrix of the laminate decreases as the temperature increases; the impact damage area and the delamination damage of the laminate increases as the temperature increases.
Integrated dynamics and control of space multi-joint robotic arm
Authors: Zhang Xianliang , Wang Peiji , Guo Zhongjin , Zhao Xiaodong , Li Tongxing
Published: June 2024

This paper presents research on the integrated dynamics and control methods of a multi-joint robotic arm system installed on a spatial inertial platform. An integrated recursive dynamic model of the posture of the multi-joint robotic arm is established by using the method of dual quaternions. This model can succinctly describe the position and attitude relationships among the joints of the robotic arm. Based on this model, a sliding mode variable structure controller is designed, which can achieve convergence of position and attitude errors even in the presence of external disturbances. The designed controller is validated through simulations, the results of which demonstrate satisfactory control performance, offering reference value for practical engineering applications.
Study on the effect of high temperature on the mechanical properties of composites plates containing initial defects
Authors: Dai Yaguang , Li Guowei , Zhao Meiying , Huang Heyuan
Published: June 2024

In this study, against the background of the high temperature environment faced by hypersonic vehicles, an in-depth study is carried out to investigate the influence of temperature on the mechanical properties of reinforced wall plates of composites containing initial defects. First, the in-plane shear mechanical property data and failure morphology of two groups of specimens of T1100/5405 composites at different test temperatures (25°C, 150°C) were obtained through experimental tests. The tests show that high temperature accelerates the damage failure process of the wall plate structure, the shear capacity of the wall plate is weakened, and the ultimate load decreases by 26.06%. Secondly, a numerical model based on the CZM and the CDM of the composite is established, and the accuracy of the model is verified by combining with the test results. The work carried out in this paper has certain engineering application value for the design of composite structures for hypersonic vehicles.
Dynamic deformation reconstruction of propulsion system pipe based on inverse finite element method
Authors: Mei Mengmei , Huang He , Zheng Zhe , Wu Ziyan , Cheng Hongchuan
Published: June 2024

Pipes are necessary components of the propulsion system. The water hammer effect is easy to provoke severe vibration of the pipe, which is harmful to the safety of the propulsion system. Therefore, it is necessary to monitor the health status of the propulsion system pipe in real time. In this paper, the FSI analysis is adopted to study the water hammer pressure and pipe vibration response caused by valve closure in RPV system. The iFEM algorithm is performed to invert the dynamic deformation of the pipe in real time. Four sensor layout schemes are considered, and the influence of sensor layout on the reconstruction accuracy based on the iFEM algorithm is discussed. It is concluded that the iFEM algorithm is very promising for the dynamic deformation reconstruction of the pipe.
A Fault Diagnosis Method for Rectifier-Filter Circuit Integrating EEMD Algorithm and Transformer Network
Authors: Wang Fu , He Pan , Zhou Chengning , Yang Taibo , Niu Jiang , Liu Caixue
Published: June 2024

Rectifier-filter circuit, as a critical component of the drive circuit in instrumentation and control systems of nuclear power plants, can convert the 50 Hz AC into the smooth DC. Thus, it plays a vital role in the power control of reactors. However, the weak waveform anomalies of soft faults in the rectifier-filter circuit make fault feature extraction difficult. Therefore, in this article, an ensemble empirical modal decomposition (EEMD) algorithm is employed to decompose the signal mode components in the monitor data of the rectifier-filter circuit. The weak waveform anomalies are indirectly enhanced by the IMF and residual components. Subsequently, the Transformer network is utilized to construct the feature extractor. With the advantage of multi-head attention (MHA) mechanism in the Transformer network, the multi-directional, multi-scale, and highly sensitive long-range time-dependent features in the EEMD feature data are extracted. Then, a deep Softmax classifier is adopted to reduce the dimensionality and diagnose the soft faults of the rectifier-filter circuit. Finally, a fault simulation model of the rectifier-filter circuit is constructed and the condition monitor data are collected. The effectiveness and diagnosis accuracy of the proposed method are verified by a real case experiment and some comparative methods.
Control Moment Gyroscope Anomaly Detection Based on Sparse Autoencoder
Authors: Zheng Yuxue , Dou Haijun , Cui Hutao , Xu Minqiang
Published: June 2024

The Control Moment Gyroscope (CMG) is an important executing part of spacecraft, and its anomaly detection has a key influence on the reliability of spacecraft. With the rapid growth of the number of spacecraft and telemetry data, data-driven spacecraft anomaly detection methods have received extensive attention, and such methods may become an important means of spacecraft anomaly detection. However, at present, the spacecraft is faced with the problem of unknown anomalies and lack of abnormal data during orbit. To solve this problem, a sparse autoencoder (SAE) based CMG anomaly detection method was proposed, which takes the telemetry signal of CMG as the object and lacks the sample of anomalous telemetry signal in training data. Firstly, data sample selection and processing were carried out to normalize the data of each telemetry value. Secondly, the SAE model was constructed, and the model was trained with the training set data. Then the sample reconstruction error of the test set was calculated to complete the anomaly detection of the CMG. Finally, it was compared with the traditional artificial threshold monitoring method. The results indicated that the CMG anomaly detection method based on SAE can effectively detect the anomaly samples of the CMG telemetry data, and has better anomaly detection performance than the traditional artificial threshold monitoring method.
Research on Dynamics Characteristic of The Filling Liquid Tank
Authors: Shanglong He , Yanyang Zi , Zhenyi Chen
Published: June 2024

The dynamics characteristic of the rocket tank with liquid propellant in it, which takes the large part of a carrier rocket, make a great influence to the whole rocket. The tank of some model was investigated systematically by the PATRAN finite element software. Firstly, it established a finite element modal of the tank and calculated the modal frequency and shape of the empty or filling tank by the virtual fluid mass and acoustic-structure coupling analysis. Then, it contrasted the veracity and applicability of the two methods and investigated how the liquid depth and density and the middle clapboard’s thickness influenced the immanent frequency of tank. Further, the filled tank’s characteristic of response was researched by the coupled acoustic-structural analysis. Finally, it investigated how the liquid depth and density influenced the filling tank’s characteristic of response. The main conclusions are shown below:

1.The result of the filling tank’s modal is approaching to the test.

2.Augmenting the density of liquid reduces the modal frequency of tank and increases the pulsant pressure of liquid.

3.Raising the depth of liquid reduces the modal frequency of tank and increases the pulsant pressure of liquid.

The paper’s achievement and conclusion will help to avoid the coupling between the launch vehicle structure and propulsion system and improve the dynamic stability. It also can provide references for design of the new tank according to the result.
Application of On-Rotor Sensing in Planetary Gearbox Fault Diagnosis
Authors: Du Xinda , Feng Guojin , Shi Dawei , Zhen Dong , Gu Fengshou
Published: June 2024

Planetary gearbox is a crucial mechanical transmission component, widely used in various mechanical equipment and industrial fields. Its failure will not only cause significant economic losses, but also may bring threats to the life and health of workers. Therefore, the condition monitoring and fault diagnosis of planetary gearbox is of great significance. In this paper, a novel on-rotor sensing (ORS) technique based on a three-axis MEMS accelerometer is employed to collect vibration signals from planetary gearboxes, in which the accelerometer is mounted on the shaft near to the sun gear and rotates together with the shaft. The two orthogonal outputs of the collected vibration signals is used to construct an analytic signal and then demodulated to get the envelope spectrum, which is then used diagnose the fault in the planetary gearbox. Results show that the proposed method can effectively diagnose the sun gear crack fault, while conventional piezoelectric sensors placed on planetary gearbox casing are less capable of detecting such faults, demonstrating the superiority of ORS technology in the field of rotating machinery fault diagnosis.
Test and Analysis on High-pressure Turbine Tip Clearance Measurement of Turbofan Engine
Authors: Ren Ruidong , Tao Ye
Published: June 2024

The tip clearance of high-pressure turbine rotor is a key parameter for the performance and control of turbofan engine. It is of great significance to master the variation law of tip clearance for evaluating the working efficiency and performance attenuation of turbofan engine. The high-frequency dynamic analysis method based on time-frequency analysis is established. The variation law of high-pressure turbine tip clearance with engine state is obtained, and the influencing factors are analysed by simulation. The test results show that the variation law of the tip clearance of the high-pressure is consistent with the design, that is about 0∼3mm. The tip clearance of the high-pressure turbine is greatly affected by the rotor vibration. It means that we can monitor vibration of the rotor by monitoring changes in tip clearance. Real-time measurement and control adjustment should be carried out in the flight test to improve the working efficiency of the engine.
Investigation on dynamic behaviour of tin-lead welding spot of spacecraft circuit board
Authors: Zhu Jianbin , Qi Zhengpan , Yang Yanjing , Lu Dongdong , Liu Chuang , Fei Gao
Published: June 2024

Spacecraft shall be subjected to mechanical environments such as mechanical shocks during loading, unloading and transportation, and the shocks shall be transmitted to the circuit boards inside. There are plenty of tin-lead spots on the circuit board as there are a large number inside the spacecraft. The dynamic behaviour of tin-lead welding spot determines the anti-impact and anti-fatigue properties of the circuit board, and therefore, it is essential to investigate the dynamic behaviour of tin-lead welding spot based on sufficient experiments and accurate simulation. In this research work, the dynamic uniaxial tension at five different strain rates (0.1/s, 1/s, 10/s, 100/s and 1000/s) were performed, the morphology of the fracture surface was examined and the alloy ingredient was analyzed. Furthermore, the finite element models (FEM) of both the tensile sample and the circuit board were developed based on the modified Darveaux model and the cohesive zone method. According to the experiments and the simulation of the uniaxial tensile samples, it was the mass ratio of the tin to the lead that govern the micro mechanical properties, and the modified Darveaux model could precisely describe the stress-strain response of the welding spot. As a result, the calculated results of the impacting dynamical behaviour of the circuit board are reasonable and helpful. The modified Darveaux model and the developed simulation approach could also be applied to other welding structures experiencing impulsive loads. The investigation shall provide research support for the mechanical environment analysis of spacecraft and other mechanical impact.
Two-phase cooling system for electric vehicles’ battery
Authors: Cattani L , Malavasi M , Bozzoli F , Sciancalepore C
Published: June 2024

The objective of this research project is to design an innovative cooling system for effectively managing the thermal conditions of batteries in electric vehicles. Electric vehicles commonly utilize Lithium-Ion cells as their power source. Despite significant advancements in Lithium-Ion technology from an electrochemical standpoint, the thermal management of these batteries remains a formidable challenge. This is primarily due to the demanding operational conditions that Lithium-Ion cells face during battery discharge, motion, and charging. The power supply unit in electric vehicles often demands high power outputs within short durations, leading to the generation of substantial heat by the batteries. This elevated working temperature poses a risk of decreased battery performance or even malfunction. Therefore, an efficient battery thermal management system is essential to optimize the performance of the batteries. In our research project, we propose and investigate a cooling system that is directly integrated into the power supply unit. Our study introduces an innovative thermal management system that combines two-phase direct liquid cooling with pulsating heat pipes. This system provides a compelling solution by combining high thermal efficiency, passive operation, and cost-effectiveness. Within this configuration, batteries are immersed in a low-boiling dielectric fluid contained in a Plexiglas container, facilitating efficient heat exchange. Simultaneously, the pulsating heat pipe operates to manage heat spikes by promoting vapor recondensation, thereby maintaining safe operational temperatures. The proposed battery thermal management system has demonstrated remarkable efficiency, ensuring that battery temperatures remain within the recommended range even under high load conditions. A notable advantage of this cooling system is its complete passivity, eliminating the need for energy-consuming coolant circulation.
A numerical investigation on a liquid-cooled battery thermal management system: Effect of inlet temperature and flow rate
Authors: Birinci S , Albayrak M , Yazici M Y , Sarper B , Aydin O
Published: June 2024

Battery thermal management systems (BTMSs) and their stable operation are crucial for safety and efficiency of electrical vehicles. A BTMS utilized a cold plate is proposed in this paper for cooling of a cylindrical Li-ion Battery Pack (BP) arranged in 2×18 layout. The main focus of the study is on the effects of cooling fluid inlet temperature to cooling efficiency, and it is numerically investigated for 2C discharge rate at various flow rates from 0.1 to 1.0 l/min. The maximum temperature difference (ΔT

max
) inside the BP and the maximum cell temperature (Tmax
) are analyzed via ANSYS Fluent software. Based on the comprehensive analysis of all system evaluation criteria, it can be concluded that the optimum flow rate is 0.5 l/min, and the optimum inlet temperature is 20 °C.
Evaluation of the effects of various fan parameters on the cooking process in commercial cooking ovens
Authors: Timur R , Kahraman Z , Hacı M , Soyhan H S
Published: June 2024

Commercial kitchen ovens are utilized in various capacities and models within commercial enterprises, operating on either electric or gas power. Numerous parameters affect the cooking process. Particularly, for effective cooking in an oven, it’s crucial to evenly distribute airflow over the food. Correct airflow significantly impacts the cooking process. Considering the differences in processing requirements based on the characteristics and quantity of the food (such as temperature, humidity, fan speed, duration, etc.), the method of heat transfer should be primarily assessed. Non-uniform distribution of hot air during the cooking process leads to varied cooking qualities among trays within the oven. Therefore, in achieving effective cooking, factors like oven cavity, number of trays, fan geometry, fan rotation speed, direction, movement intervals, and the turbulent airflow generated by the fan in the cooking chamber need thorough examination. This study analyzed simulation data evaluating the effects of different fan geometries, fan rotation directions, and timing on heat transfer in a prototype electric commercial cooking oven using gastronomic GN-1/1 sized with 10 trays. Additionally, comparison of test and design validation data in the specially developed prototype cooking oven was conducted. Assessments were made with different fan movements (fan diameters, rotation direction, speed etc.) and a fan protection plate in front of the oven to achieve more efficient heat distribution on the food. Depending on various fan parameters, this study contributed to reducing energy consumption in the prototype commercial cooking oven.
DNS of Marangoni effects on a suspension of droplets in microgravity using the unstructured conservative level-set method
Authors: Balcázar-Arciniega N , Rigola J , Oliva A
Published: June 2024

The multi-marker unstructured conservative level-set (UCLS) method for two-phase flow with variable surface tension is used for the Direct Numerical Simulation of thermocapillary-driven motion of a bi-dispersed suspension of droplets in microgravity. The so-called Marangoni stresses induced by surface tension gradients on the interface lead to a coupling of the momentum transport equation and the thermal energy transport equation. The finite-volume method discretizes the transport equations on three-dimensional collocated unstructured meshes. The UCLS method performs interface capturing with mass conservation of the fluid phases, whereas the multiple marker approach circumvents the numerical coalescence of fluid particles. The fractional-step projection method solves the pressure-velocity coupling. Unstructured flux-limiters schemes discretize the convective term in transport equations. Numerical and physical findings are reported.
Review of “cold shock” cases in operation of loop heat pipes and related thermal instabilities
Authors: Ivanovskis L , Mishkinis D
Published: June 2024

Loop Heat Pipes (LHP) are passive two-phase heat transfer devices, driven by capillary pumps that source energy for circulation of working fluid solely from the heat source. They have a proven track record in spacecraft thermal control as well as terrestrial applications. However, LHP may experience partial or complete wick dryout and thermal instabilities at rapid power-up steps or (and) rapid condenser cooling conditions change due to a rapid inflow of subcooled liquid from the condenser into the evaporator. Such cases do not have very wide coverage in literature and are usually presented as a little nuisance in testing of a particular LHP, for which some design workaround was found. Oftentimes suggested solutions trade performance or other design merits for robustness of operation. This article aims to review such case studies where phenomena similar to the described “cold shock” affected LHP performance. The aforementioned instabilities become even more pronounced in grid-like multievaporator LHP having multiple parallel connections between capillary pumps and compensation chambers, as heat and mass transfer between those elements becomes less definite and can eventually increase the heat leak into compensation chambers. Vulnerability of LHP with distributed network of evaporators to seemingly “safe” transient regimes fosters deeper analysis of the “cold shock” phenomenon. With comprehensive definition to the problem and a list of research questions, technical measures for getting rid of it in perspective LHP designs can be foreseen.
Simplified computational model of the primary and secondary freeze-drying process of agriculture and marine foods
Authors: Piechnik E , Stebel M , Palacz M , Haida M , Bodys J , Melka B , Ciesielska A , Smolka J , Nowak A J
Published: June 2024

The food freeze-drying is a low-pressure and low-temperature dehydration process during which the following basic steps can be distinguished: (1) freezing of the food product in the chamber, (2) vacuuming of the freezing chamber, (3) ice sublimation from a frozen food product (primary drying), (4) removing the water bound in the food product (secondary drying). This paper discusses a simplified 1-D in-house computational model of the primary and secondary freeze-drying processes, i.e. stages 3 and 4. In particular, it allows for times prognosis of both, primary and secondary freeze-dryings separately. Finally, that analysis provided the basis for the proper selection of the thermal parameters in the process. Complex analysis of the drying process can also result in the reduction of energy consumption. In this project the experimental campaign together with computer simulations has been performed for various food products including meat, fruit and vegetables.