最新刊期
卷 58 ， 期 1 ， 2024
- 摘要：ChatGPT has emerged as a significant advancement in natural language processing, specifically in the domain of dialogue generation, and has achieved excellent performance in many areas. This paper aims to explore its architecture, underlying technologies, and potential areas for further investigation. The paper begins by discussing the architecture and technology evolution process. Next, the focus shifts to a comprehensive analysis of the key technologies, including the prompt learning and instruction fine-tuning, chain of thought and reinforcement learning through human feedback. Furthermore, the paper addresses the limitations of ChatGPT stemming from its probabilistic generation principles, including factual errors, poor performance in specific domain, potential malicious risk, poor interpretability and real-time. Finally, the paper outlines possible research directions based on the practical challenges observed in real-world applications, including the ethical and safety factors in the training process to reduce potential risks. Additionally, integrating external expert knowledge and employing transfer learning methods are proposed to enhance ChatGPT's performance in domain-specific tasks. Moreover, improving its information understanding capabilities based on the multimodal data is also considered as a notable avenue for development. By providing an in-depth analysis of ChatGPT's framework and key technologies, this paper aims to foster a deeper understanding of the system and also presents potential research directions to inspire further investigation in the field.关键词：ChatGPT model architecture;probabilistic generative model;reinforcement learning;transfer learning510|7|0更新时间：2025-05-13
- 摘要：Flexible contact seals are vital components in refrigeration equipment, as they contribute to effective thermal and moisture insulation. Improving the performance of these seals faces technical challenges arising from the assembly state's combination of rigid and flexible multi-contact elements. To enhance their performance, a comprehensive understanding of the technical characteristics and overall development of flexible contact seals is crucial. Therefore, this research summarizes the current state of research on key issues affecting their performance improvement, including measurement and modeling techniques. The future development of seal performance improvement is anticipated. According to the research findings, the heat transfer measurement technology based on reverse heat loss lacks accuracy. However, by incorporating filtering algorithms, the noise fluctuation in heat flux signals can be effectively reduced. The current tracer gas technology fails to consider the flow and diffusion of moist air within the rigid and flexible contact interface. To address this limitation, it is suggested to employ interface microscopic detection and contact dynamics theory, to elucidate the flow pattern. Additionally, constructing a tracer source and detection circuit that are appropriately matched is recommended. Currently, the research on thermal-fluid-solid coupling modeling of flexible contact seals is lacking, leaving a significant knowledge gap. Only a heat transfer numerical model and flow average analytical equation have been developed so far. To address this gap, a coupling model can be established using iterative algorithms for numerical calculations of the temperature and deformation field, along with analytical calculation of seepage parameters. In addition to conducting fundamental research on measurement and modeling, it is crucial to overcome the bottleneck of size effect, achieve good coordination between sealing components, and apply ultra-low thermal conductivity materials and electromagnetic induction technology to improve the thermal and moisture insulation performance of seals.关键词：flexible contact seal;refrigeration equipment;heat and moisture transfer;measurement technologies;thermal-fluid-solid coupling221|4|0更新时间：2025-05-13
- 摘要：To enhance understanding of the role different cascade profiling techniques play in improving turbine cascade performance within the combined design space, a knowledge mining framework is proposed. This framework integrates data mining information through the analysis of variance-based global sensitivity analysis method and employs visualization techniques like parallel axis, histogram and scatterplot. By using this framework, knowledge mining of the non-axisymmetric endwall/blade combined parameterization design space of a low aspect ratio cascade is conducted. It reveals that the aerodynamic loss of the cascade is highly influenced by the section profiling. The reduction in loss achieved through the implementation of a non-axisymmetric endwall is comparable to that of section profiling. However, it is observed that the performance variations among different samples of non-axisymmetric endwall are relatively small, leading to the underestimation of its significance by the global sensitivity analysis method. Furthermore, it is found that utilizing only a bending curved blade is unlikely to yield a reduction in cascade loss. However, by combining blade bending, section profiling and non-axisymmetric endwall, it is possible to achieve a performance gain that exceeds the sum of the individual contributions(“1+1+1>3”). Within the combined design space of non-axisymmetric endwall/blade parameterization, it is observed that a cascade with low aerodynamic loss can be achieved by adjusting the section profile towards an after-loading style and incorporating a non-axisymmetric endwall with deep concave near the throat and negatively bending blade as well. In conclusion, this research has successfully elucidated the characteristics of optimized solutions within the end-wall/blade joint forming design, offering reference for the design optimization of similar low aspect ratio cascades. The above findings have effectively clarified the characteristics of the optimized solutions within the endwall/blade combined design space, offering guidance for the design optimization of similar low aspect ratio cascades.关键词：turbine cascade with low aspect ratio;non-axisymmetric endwall/blade combined design;data mining123|5|0更新时间：2025-05-13
- 摘要：Film cooling performance on a gas turbine squealer tip was numerically investigated by incorporating plasma actuation forces into the momentum equations of Reynolds-averaged Navier-Stokes equations. The objective was to analyze the impact of plasma actuation strength and actuation frequency on the film cooling effectiveness and total pressure loss in tip region. Furthermore, a plasma control strategy was proposed to improve the coolant coverage on the cavity floor of squealer tip, and the mechanism of plasma actuation on the coolant and mainstream in the tip gap was elucidated. The results showed that the downstream plasma actuation within the squealer cavity effectively counteracts the swirling effect provided by the upstream coolant to the downstream coolant. Such resistant effect is increased with increasing the actuation strength and actuation frequency. When the plasma actuation is minimal, the upstream coolant provides little swirling effect to the downstream coolant in squealer cavity, resulting in effective film cooling effect on the cavity floor near trailing edge. As the actuation strength increases, the coolant near the trailing edge is blown away from the cavity floor by the upstream coolant, but the film cooling effect on the central part of cavity floor becomes better. Compared to the no actuation case, the area-averaged film cooling effectiveness on the cavity floor of squealer tip is increased by 25.11% for actuation strength Ds=204. The actuation frequency displays a similar effect on the film cooling at squealer tip as the actuation strength. If the actuation strength is fixed at Ds=156, the area-averaged film cooling effectiveness on the cavity floor is increased by 28.71% for actuation frequency Dθ=6.25 and actuation frequency 29.27% respectively as compared to the no actuation case. Additionally, non-uniform plasma actuation on the squealer tip leads to a 39.12% increase in the area-averaged film cooling effectiveness on the cavity floor compared to the no actuation case. Notably, the total pressure loss in the rotor blade is almost unchanged with the specified plasma excitation.关键词：gas turbine;squealer tip;plasma actuation;film cooling144|13|0更新时间：2025-05-13
- 摘要：To effectively monitor the operation safety status of high-temperature turbine blades, an experimental study was conducted, focusing on a high-temperature blade using the response surface model. The aim was to investigate the impact of key working condition parameters on its cooling performance, thereby providing reliable data support. The central composite design was applied to the experimental design of the working parameters of the blade. The influence of mainstream inlet temperature, mainstream outlet pressure, pressure ratio of mainstream inlet to outlet, temperature ratio of mainstream to cooling air and flow ratio on the cooling efficiency distribution, dimensionless temperature distribution and temperature non-uniformity of the blade was experimentally studied. Subsequently, a response surface model was constructed to comprehensively assess the combined effects of the working parameters on the blade's cooling performance. The results demonstrate the high accuracy of the obtained response surface model, with root mean square errors below 0.001 and coefficient of determination exceeding 0.99. The inlet temperature and outlet pressure of the mainstream of the mainstream were found to have minimal impact on the cooling performance of the blade. However, within the range of operating parameters, when the inlet/outlet pressure ratio of the mainstream, the temperature ratio of the cooling air to the mainstream, and the flow ratio increase from 1.3 to 1.5, 0.6 to 0.7, and 3 to 8, respectively. The average cooling efficiency of the blade is increased by 9.67%, 9.39% and 30.49%, respectively. The average dimensionless temperature of the blade is increased by 2.98%, decreased by 1.34% and 3.78%, respectively. The temperature non-uniformity of the blade is decreased by 2.69% and 28.79%, increased by 50.27%, respectively.78|6|0更新时间：2025-05-13
- 摘要：To improve the film cooling and heat transfer performance on the squealer tip of the first turbine stage in aero-engines, a design platform for optimization was constructed using a self-developed program, aiming at enhancing the film cooling effectiveness and minimizing heat transfer on the squealer tip. The Hooke-Jeeves searching algorithm combined with the third-order response surface model was utilized to find a proper double-rim squealer tip geometry with excellent aero-thermal performance. Additionally, a comparative analysis was conducted to assess the heat transfer and film cooling effects of the optimized double-rim squealer tip against those of the conventional squealer tip as well as four commonly used double-rim squealer tips. The study also investigated the influence of various geometrical parameters for inner-rim on the flow structures, heat transfer and film cooling effectiveness in the tip region, and involved evaluating the sensitivities of heat transfer and film cooling performance on the double-rim squealer tip to various design variables. The findings indicated that the optimized configuration of the inner rim in the double-rim squealer tip consisted of two layers, an upper and a lower layer. The selection of appropriate geometrical parameters for the inner rim resulted in a reduction of the impingement effect caused by the leakage flow, providing effective coolant coverage on the internal and external squealer cavities. In comparison to the conventional squealer tip, the optimized double-rim squealer tip showcased a 24.96% reduction in the area-averaged heat transfer coefficient and a 5.38% enhancement in the area-averaged film cooling effectiveness. The height of the lower layer in the inner rim had the most significant impact on the area-averaged heat transfer coefficient, while the starting location of the upper layer in the inner rim played a crucial role in the area-averaged film cooling effectiveness among the studied parameters. On the other hand, the height of the upper layer in the inner rim exhibited a relatively minor influence on the film cooling and heat transfer performance of the double-rim squealer tip.关键词：aero-engine;squealer tip;double rim;optimization;heat transfer;film cooling109|6|0更新时间：2025-05-13
- 摘要：To address the limited understanding of the photo-thermal coupling effects and microscopic mechanisms involved in solar-driven photothermochemical methanol steam reforming for hydrogen production, a comparative study that compares the performance of photothermochemical reactions with thermochemical reactions is conducted, with the microscopic experiments complemented. This study aims to examine the synergistic effects of light and heat in photothermochemical methanol steam reforming and elucidate the reaction pathways of light and heat involved in the microscopic conversion of the reactants. The research findings reveal that, at relatively low temperatures, light has a positive influence on enhancing hydrogen yield. Compared to thermochemical reactions that achieve the same hydrogen yield, photo-thermochemical reactions operate at lower temperatures. The reason for the experimental observation is attributed to the facilitation of water dissociation, the generation of HCOO*, and the decomposition of carbonate species facilitated by light. The importance of water in the reaction is confirmed through experiments involving varying water-to-methanol ratios. Furthermore, as the temperature increases, the promoting effect of light diminishes under a fixed light intensity, which is primarily attributed to the light's diminishing influence on the decomposition of carbonate species with increasing temperature. The study provides a clear understanding of synergistic effects of light and heat, and analyzes the corresponding microscopic mechanisms, thereby establishing a theoretical basis for understanding the photo-thermal synergistic mechanisms.关键词：photo-thermal synergistic effects;methanol steam reforming;hydrogen production;microscopic mechanisms52|6|0更新时间：2025-05-13
- 摘要：This study investigates the mechanism of concentrated light in the photothermal CO2 methanation process using a highly reactive Ni/Al2O3 catalyst with excellent photothermal conversion characteristics experimental investigations were performed under concentrated photothermal and thermal driven conditions to shed light on the reaction mechanism. Apparent activation energy tests, temperature gradient experiments and time-resolved in-situ diffuse reflectance infrared spectroscopy experiments were conducted, to gain insights into the process. The results demonstrate that the photothermal-driven process outperforms the thermal-driven process, exhibiting superior catalytic performance at the same temperature. Remarkably, a Ni/Al2O3 catalyst containing 15% mass fraction of Ni achieved an impressive CO2 conversion rate of 86.8% at 350 ℃ under the photothermal-driven condition. Notably, the photothermal-driven process required a 25 ℃ lower temperature to achieve the highest CO2 conversion rate compared to the thermal-driven process. The apparent activation energy of the photothermal-driven process was reduced by 25%, and the concentrated light-induced temperature gradient further enhanced CO2 conversion. Time-resolved in-situ diffuse reflectance infrared spectroscopy experiments showed that concentrated light improved CO2 adsorption on the catalyst surface, promoted the transformation of key intermediates, and enhanced the reaction pathway of CO* to CH4, thereby enhancing CO2 conversion at a microscopic level. This study provides valuable insights into the role of concentrated light in CO2 methanation driven by concentrated solar energy, shedding light on the underlying mechanism.关键词：concentrated solar;carbon dioxide;methanation;in-situ diffuse reflectance infrared Fourier transform spectroscopy51|7|0更新时间：2025-05-13
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Experimental Study on Flow Distribution Characteristics of Parallel Two-Phase Heat Transfer Channels
摘要：This study aims to improve heat transfer performance and operating stability in a two phase cooling system while exploring the characteristics of flow maldistribution in parallel channels. An experimental setup with two parallel channels using water as the working fluid is established to examine the impact of flow maldistribution on system performance. The main factors considered include inlet water temperature, heating flux density, and mass flow rate, and the obtained experimental data are compared with the theoretical calculation results. The results demonstrate that flow maldistribution in parallel channels leads to uneven flow distribution and significant temperature deviations. Specifically, the channel with the less flow experiences boiling first, while the unboiling channel exhibits a considerable reduction in outlet temperature. Additionally, certain factors contribute to the occurrence of flow maldistribution. Increasing the inlet temperature, increasing the heat flux density and reducing the inlet flow rate could lead to flow maldistribution, meantime, the inlet temperature, heat flux density and inlet flow rate corresponding to the occurrence and disappearance of flow maldistribution changed by 24.8 ℃, 175.6 W/m, and 19.8%, respectively, and there are lags among them; the external disturbance might accelerate the appearance of flow maldistribution, the corresponding difference of inlet temperature is about 3.2 ℃ in experiment; the header structure affects the position of the firstly boiling channel, and the channel with less flow rate in the single-phase state tends to preferentially boil. These research findings provide valuable insights for improving flow distribution uniformity in parallel channels.关键词：parallel channels;flow distribution;two phase;flow and heat transfer31|6|0更新时间：2025-05-13 - 摘要：To understand the impact of jet flow rate and jet angle on liquid film spreading shape, wall temperature, and liquid film thickness, an independent liquid film cooling experiment system based on the heated wall conditions was designed and constructed. The experiment focused on liquid film cooling with a jet angle of 25°—45° and a jet flow rate of 200—400 mL·min-1 was conducted. The results show that increasing the jet angle leads to a decrease in spreading length, while spreading width and spreading angle increase. At a certain jet angle, liquid film spreading length, width and angle both increase with the growth of jet flow rate. Notably, when the jet angle is 25°, the jet flow rate increases from 300 mL·min-1 to 400 mL·min-1, the maximum increase in the liquid film spreading length is 20.94 mm, and the increase in the jet flow rate can effectively reduce the wall temperature, when the jet angle is 35° and the jet flow rate is 300 mL·min-1, the maximum wall temperature can be reduced by 141.81 ℃ after cooling; The liquid film has a peak thickness at the impingement point on the wall, and the higher the liquid film flow rate, the higher the peak value. For instance, when the incidence angle is 25° and the flow rate is 400 mL·min-1, the maximum peak value reaches 679.32 μm. Additionally, a numerical model for liquid film cooling was established with the volume of fluid(VOF)method to calculate the evaporative heat absorption and flow spreading process of the liquid film. It is shown that when the jet flow rate is 300 mL·min-1, the maximum deviation between the simulation results of liquid film thickness and the experimental results is 7.9%, which is within the 10% error allowed for engineering applications, so as to verify the feasibility of the VOF method for the simulation of liquid film formation on jet impingement wall. The present research can provide significant reference for the liquid film cooling technology in liquid rocket engine.关键词：liquid rocket engine;liquid film cooling;thermal wall condition;volume of fluid method151|5|0更新时间：2025-05-13
- 摘要：This study aims to investigate the effect of surface tension on the spreading dynamics of a droplet impacting a supercooled substrate. To accomplish this, a visualization experimental system is established. The influence of substrate supercooling on the spreading dynamics of low surface tension droplet is analyzed. In the experiment, hydrophilic silicon substrate and a smaller impact velocity are used to observe the spreading dynamics of an ethanol droplet impacting the supercooled substrate. In addition, this study compares the applicability of typical models with different maximum spreading factor and maximum spreading time to the spreading dynamic factors of an ethanol droplet impacting supercooled substrate. The results demonstrate that the spreading dynamics of an ethanol droplet impacting the supercooled hydrophilic substrate can be divided into three stages: splash, spreading, and stability. The maximum spreading time decreases with an increase in substrate supercooling. Moreover, the influence of substrate supercooling on the maximum spreading factor is non-monotonic. At low substrate supercooling, the reduction of the maximum internal spreading factor plays a dominant role. Conversely, at high substrate supercooling levels, the enhancement of Rayleigh-Taylor instability leads to an increase in the “fingering-like” protrusion of the infinite chain plays a major role. The combined effect of the two causes non-monotonic changes. The existing models have good predictive performance for the maximum spreading time, with a relative mean error of 6.05%. However, their predictive accuracy for the maximum spreading factor is poor.关键词：droplet impact;supercooled substrate;surface tension;spreading dynamics37|4|0更新时间：2025-05-13
- 摘要：This study presents a solution to address the efficiency and stability issues in geothermal energy power generation technology. A medium and deep geothermal energy coaxial tube heat exchanger energy storage and power generation system is proposed that integrates coaxial tube heat extraction technology with compressed air energy storage technology. By developing a thermodynamic model of the system, the evolution of key parameters and thermodynamic performance under typical operating conditions is analyzed, and the dynamic mechanism of geothermal recovery and extraction under different operating characteristics is examined. The results show that the operation of energy storage and generation system is divided into two phases: unstable cycle and stable cycle phase. In the unstable cycle phase, the heat extraction amount and expander output work increase with the number of cycles, while the heat compensation amount and the system efficiency exhibit the opposite trend. Once a balance is reached between heat extraction, heat compensation and geothermal consumption reach equilibrium, the system enters a stable cycle from the 8th cycle onwards. In this phase, the system parameters remain constant regardless of the number of cycles, and the output of a single cycle is measured at 47 956.7 kW·h, with a system efficiency as high as 63.5%. To increase the geothermal recovery temperature, the compressor pressure ratio and the flow rate of water for heat compensation can be adjusted. When the compressor pressure ratio is increased from 6 to 7, the geotechnical temperature at a depth of 1 300 m and a radius of 0.116 m is increased by 4.3 ℃, and flow rate of water for heat compensation is increased from 4.5 to 6 m3/h, the temperature at the same site is increased by 6.4 ℃. This study provides a promising approach to improve the efficiency and stability of geothermal energy generation.关键词：geothermal power generation;stability;geothermal recovery;thermodynamic proper49|7|0更新时间：2025-05-13
- 摘要：In the limited space within new vehicles, current plate-fin heat exchangers with offset-strip fins suffer from issues such as inadequate heat transfer, high flow resistance and heavy weight. To address these challenges, an optimization scheme for vehicle-mounted compact heat exchanger is proposed. The study began by conducting tests on four types of air-water plate-fin heat exchangers, each with varying parameters for the offset-strip fins. These heat exchangers were evaluated to analyze their heat transfer and flow characteristics. Based on the experimental data, a 3D numerical model of the offset-strip fin channel was developed, and this model enabled the acquisition of highly accurate heat transfer and flow correlations applicable to a broader range of structural parameters within the heat exchanger. Additionally, a weight calculation model for the heat exchanger's core was derived from its geometric structure. A multi-objective optimization process was conducted using the non-dominated sorting genetic algorithm(NSGA Ⅱ)and a comprehensive evaluation plot considering both heat transfer and flow resistance performance. Through this optimization process, the key parameters related to fin structure of the vehicle-mounted offset-strip plate-fin heat exchanger were refined, resulting in the identification of a set of fin structure parameters that exhibit high comprehensive performance. By optimization, the flow resistance coefficient was reduced by 14.3%, the comprehensive evaluation factor was increased by 10.7%, and the core weight of the heat exchanger was decreased by 18.2%, contributing to a high-efficiency and lightweight design. This paper presents an optimization scheme specifically for the vehicle offset-strip plate-fin heat exchanger, which can serve as a valuable guidance for improving the overall performance and reducing manufacturing costs of similar heat exchangers used in vehicle applications.关键词：vehicle-mounted compact heat exchanger;comprehensive performance evaluation plot;genetic algorithm;offset strip fin;comprehensive performance optimization97|6|0更新时间：2025-05-13
- 摘要：To investigate the particle settlement behavior of slush cryogenic propellants during storage process and address the supply issue caused by deposition during transportation to rocket engines, the research on sedimentation characteristics of slush cryogenic propellants in the tank was carried out. This numerical model utilizes the Euler-Euler method, considering the kinetic particle theory, to simulate cryogenic solid-liquid two-phase flow and phase change heat transfer of propellants. The study focuses on analyzing the flow field and deposition characteristics of slush cryogenic propellants such as slush nitrogen, slush oxygen, and slush hydrogen within the tank. This study examines the influence of various factors on the deposition and flow field characteristics of cryogenic fluids, including different cryogenic propellants, particle sizes ranging from 0.02 to 0.5 mm, volume fraction of solid hydrogen ranging from 10% to 50%, and heat leakage rate ranging from 50 to 200 W/m2. It is concluded that the deposition of slush cryogenic propellant is reduced when the solid particle size is smaller, the initial solid phase content is lower, and there is less heat leakage at the wall. Additionally, slush fluids with higher solid-liquid density exhibit a faster deposition rate. For a particle size of 0.5 mm, the slurry nitrogen and slurry hydrogen phase interfaces display downward migration rates of 15.62 mm/s and 12.58 mm/s, respectively, while the slush oxygen phase interface has a significant slower downward migration rate of only 0.12 mm/s. These findings shed light on the physical behaviors of slush cryogenic propellants during storage process, providing valuable insights for the efficient storage and application of slush cryogenic propellants.关键词：slush nitrogen;slush oxygen;slush hydrogen;cryogenic propellants;numerical simulation36|5|0更新时间：2025-05-13
- 摘要：This study proposes a method for predicting the installation interference of headless rivet using a multiple nonlinear regression model based on the finite element simulation data of the riveting process, with the aim to elucidate the influence of material properties on the interference during installation and to provide reliable predictions for the use of new materials. Firstly, a finite element simulation model is established based on the actual riveting process and its validity is verified through riveting experiments. Subsequently, finite element analysis and orthogonal testing techniques are employed to examine the significance of various factors, such as elastic modulus, yield strength, strengthening coefficient, and strain strength index, along with their interactions on installation interference, determining the influence of each factor on the riveting interference. Finally, the multiple nonlinear regression model is formulated using a power function, and less significant factors are eliminated. The results show that, under specific riveting process conditions, yield strength and strain strength index, as well as their interaction, are the primary factors affecting the interference. By comparing the simulated values and the predicted values of the regression model, it is observed that the two values exhibit consistent variation trends, with errors remaining below 10%, demonstrating the effectiveness of the multiple regression models in predicting riveting interference.关键词：interference;multiple nonlinear regression;headless rivet;orthogonal test26|13|0更新时间：2025-05-13
- 摘要：This study aims to analyze the variation in aerodynamic resistance of high-speed trains under the combined effect of train movement and unfavorable tunnel conditions. An EMU(electric multiple units)is chosen as the calculation model to investigate the aerodynamic effects using sliding grid technology and computational dynamics theory(CFD). The k-ε two-equation turbulence model is employed to simulate the aerodynamic behavior of eight different train configurations crossing and intersecting within the most unfavorable tunnel. The proposed calculation method is validated by comparing it with the measured data of the Eryan tunnel on Suiyu line. The findings reveal several important insights: ①The aerodynamic resistance experienced by the train is directly influenced by the pressure difference between the train's head and tail. Changes in this pressure difference will cause corresponding variations in resistance. ②During single-train crossings and double-train intersections at 300 km/h in the tunnel, the maximum aerodynamic resistance occurs at 3.1 s and 2.8 s after the train enters the tunnel respectively. The resistance coefficients reach 1.37 and 1.49, and the head train contributes the largest proportion of resistance, accounting for 34.67% and 36.57% respectively. ③In head-head and head-tail intersections, the resistance exerted by the tail of train is the highest, comprising 56.79% and 37.33%, respectively. Conversely, in tail-tail intersections, the head of the train experiences the most significant resistance(44.62%), while the tail's resistance ratio is close to 0. ④As the train's speed increases, the aerodynamic resistance rises rapidly. For instance, when the train speed increases from 250 km/h to 400 km/h, the average aerodynamic resistance for single-train crossings and double-train intersections increases by 132% and 150%, respectively. These research outcomes offer valuable insights for the design and engineering considerations involved in train-tunnel configurations.关键词：high-speed train;most unfavorable tunnel;aerodynamic resistance;train intersecting27|5|0更新时间：2025-05-13
- 摘要：This study presents a novel solution to address the limitations in hand rehabilitation training, namely stimulation forms, excessive size and weight, and poor stimulation effectiveness, where a multi-modal tactile stimulation device for fingertip feedback, incorporating pressure, sliding, and roughness sensations, is proposed. The approach involves analyzing the surface characteristics of the human fingertip to design a pneumatic pressure feedback device with multiple contact points. This device comprises a central chamber, fingertip chamber, and two side chambers, totaling four air chambers. Additionally, an electrode array module is designed to provide electrical stimulation for sliding and roughness feedback, and a human impedance model is established to determine electrical stimulation parameters, such as supply voltage, which is validated through simulations. Finally, flexible materials are used to separately 3D print the pneumatic pressure actuator and electrode array, resulting in an integrated tactile feedback device measuring 40 mm in length, 30 mm in width, and weighing 14.8 grams. Experimental results demonstrate that the pneumatic pressure feedback device exhibits high linearity and minimal hysteresis, providing a maximum single-chamber force feedback of 12 N. The electrical stimulation device achieves a 100% accuracy in roughness recognition, with sliding and roughness recognition rates surpassing 80%. The device designed offers precise tactile feedback for pressure, sliding, and roughness sensations simultaneously at the fingertips. Its compact and lightweight design, coupled with strong feedback capabilities, make it highly suitable for multi-modal tactile feedback devices and potential applications in the rehabilitation training of stroke patients.关键词：haptic feedback;electrical stimulation;pneumatic pressure sensing feedback;multimodality28|5|0更新时间：2025-05-13
- 摘要：Addressing the challenge of low classification accuracy in ipsilateral hand movements, this paper presents a novel method named source-Lasso-CNN(SLC). The approach involves analyzing electroencephalogram(EEG)signals before movement onset in the gamma band(30—100 Hz)that are associated with four specific hand movements(tip pinch, multiple tip pinch, hand close and hand open)using spatial source localization. Region of interest(ROI)was selected using group Lasso, and then the selected signals were input into convolutional neural network(CNN)for multi-class hand movement pattern recognition. The specific steps are as follows. Firstly, EEG and EMG signals were simultaneously collected from 13 subjects during the execution of the four hand movements, followed by preprocessing. Next, a head model was established using a boundary element model based on magnetic resonance image, and the inverse problem of EEG imaging was solved by using the minimum norm estimation method. The EEG sequences in the source space were divided into 79 regions based on Brodmann area. Three time-domain features were extracted from each brain region and a group Lasso algorithm was employed to select the ROI. Finally, the selected ROI and its corresponding source space sequences were input into the CNN for classification. The results show that the LASSO-CNN method, utilizing high frequency(γ band)source space signals, achieves a superior classification accuracy of(82.23+12.71)%, which is better than that in δ(1—3 Hz), θ(4—7 Hz), α(8—13 Hz), β(14—30 Hz)and full frequency band(1—100 Hz). Furthermore, the results also show a significant improvement in accuracy compared to other advanced algorithms, highlighting its effectiveness in recognizing identical hand motion pattern.关键词：source space;Lasso;convolutional neural network;high frequency electroencephalogram signal;hand movement intent recognition37|5|0更新时间：2025-05-13
- 摘要：To solve the problem of high-efficiency optimization of highway self-consistent energy system(SCES)by utilizing an improved simulated annealing genetic algorithm(SA-GA)with a comprehensive consideration on the economic and environmental targets based on an energy-efficient optimization strategy for SCES. Firstly, an objective function is established to consider the energy efficiency from economic and environmental perspectives, taking into account the characteristics of each power unit within the SCES in the highway service area. Secondly, constraints corresponding to different types of systems are established based on the classification of SCES in highway service areas. The simulated annealing algorithm is incorporated into the solution of the objective function to avoid the defect that the genetic algorithm tends to fall into the local optimum. The improved SA-GA algorithm incorporates a cooling function, allowing for the accurate identification of the global optimal solution. By leveraging the generation and load data of the SCES in the highway service area in Xinjiang, China, along with considering the influence of new energy vehicle charging stations in addition to the load from traditional service areas. Finally, the test results show that the evaluation of various test functions demonstrates that the SA-GA algorithm significantly improves both solution speed and stability. The SA-GA algorithm is employed to compute energy efficiency optimization results for typical days in summer and winter, to obtain an effective operation strategy for the service area. Simulation results demonstrate that the proposed SA-GA algorithm improves optimization accuracy by 20.33% in comparison to the genetic algorithm.关键词：integration of energy and transportation;self-consistent energy system;high energy efficiency;charging station;simulated annealing algorithm;genetic algorithm58|6|0更新时间：2025-05-13
- 摘要：To address missing unstable eigenvalues in small signal stability analysis of power systems, a multi-spectral transform method for calculating the unstable eigenvalues of large-scale systems is proposed. Firstly, this method utilizes the proposed multi-spectral transform technique to map all unstable eigenvalues into dominant eigenvalues. Subsequently, the Krylov-Schur method is employed to ensure convergence and obtain all dominant eigenvalues. Finally, the inverse transformation allows for the retrieval of the corresponding unstable eigenvalues. Furthermore, this method establishes the intrinsic relationship between various transforms, including the exponential transform, shift-and-invert transform, and Cayley transform. Compared with the shift-and-invert transform and Cayley transform, the multi-spectral transform exhibits superior spectral performance akin to the exponential transform, facilitating eigenvalue convergence. At the same time, it avoids calculating the multiplication of exponential matrix and vector caused by the exponential transform, thereby having higher computational efficiency and accuracy. Experimental results obtained from the Xingo6u and Xingo3012 system of the Brazilian interconnected power grid demonstrate the effectiveness of this method. Notably, it ensures that unstable eigenvalues are not overlooked, enhances calculation accuracy by about 3 orders of magnitude, and reduces the calculation time by more than 90% compared to the exponential transform method.关键词：small signal stability;Krylov-Schur method;spectral transform;large-scale systems58|7|0更新时间：2025-05-13
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