Search Results (760)

To improve the flux regulation range of the Axial–Radial Flux Hybrid Excitation Machine (ARFHEM) and the utilization rate of permanent magnets (PMs), the effects of different length–diameter ratios (LDRs) on the ARFHEM performance are studied. Firstly, the principle of the flux regulation of the ARFHEM is introduced by means of the structure and equivalent magnetic circuit method. Then, based on the principle of the bypass effect, the analytical formulas of LDRs, the number of pole-pairs, and the flux regulation ability are derived, and then the restrictive relationship between the air-gap magnetic field, LDR, and the number of pole-pairs is revealed. On this basis, the influence of an electric LDR on motor performance is studied. By comparing and analyzing the air-gap magnetic density and no-load back electromotive force (EMF) of motors with different LDRs, the variation in the magnetic flux regulation ability of motors with different LDRs is obtained and its influence mechanism is revealed. In addition, the torque regulation ability and loss of motors with different LDRs are compared and analyzed, and the influence mechanism of the LDR on torque and loss is determined. Finally, the above analysis is verified by experiments. Full article

Accurate estimation of the state of charge (SOC) of lithium batteries is critical for the safe and optimal operation of battery management systems (BMSs). Traditional SOC estimation methods are often limited by model inaccuracy and noise interference. In this study, a novel type-2 fuzzy cerebellar model neural network (Type-2 FCMNN) is proposed for accurately estimating the state of charge of lithium batteries. Based on the traditional fuzzy cerebellar model neural network (FCMNN), type-2 fuzzy rules are innovatively introduced to enhance the robustness of the model against uncertainties and noise disturbances. This enables the model to better cope with nonlinear complexity and external disturbances when dealing with SOC estimation of lithium batteries and significantly improves the accuracy of prediction. On this basis, by analyzing the working principle of lithium batteries, a battery equivalent circuit model is successfully established and simulated and tested by Simulink R2022b, which provides a theoretical basis for the selection of the size of the input parameters of the subsequent neural network. Then, this paper designs and implements the SOC estimation model based on Type-2 FCMNN and tests it in Matlab. Finally, this paper carries out simulation comparison experiments between Type-2 FCMNN and various classical neural network algorithms in Matlab R2022b including traditional FCMNN, a backpropagation neural network, radial basis function neural network, and Kalman filtering algorithm. The simulation results show that Type-2 FCMNN exhibits a significant advantage in SOC estimation accuracy, with mean absolute error and root mean square error values of only 43.1% and 36.0% of FCMNN’s, respectively, while FCMNN achieves the best results among the compared methods. Full article

The increase in the incidence of hyperglycemia and diabetes poses the challenge of finding cost-effective natural inhibitors of starch digestion enzymes. Among natural compounds, phenolics have been considered as promising candidates. The aims of this study were as follows: (a) to investigate the effectiveness of the inhibition of different winemaking byproducts towards intestinal brush border α-glucosidase and pancreatic α-amylase in vitro; (b) to calculate an efficacy index relative to the standard acarbose for the phenolic pool of winemaking byproducts, as well as for isolated phenolic compounds and for the phenolic pools of different plants studied in the literature, in order to rank winemaking byproducts with respect to the reference drug and other natural alternatives. Among winemaking byproducts, red grape skins showed the highest inhibitory activities towards both α-glucosidase and α-amylase, which were, on average, 4.9 and 2.6 µg acarbose equivalents/µg total phenolics (µg Ac eq/µg GAE), respectively. A correlation was observed between the total phenolic contents of red grape skins and their inhibitory effectiveness, which is useful for standardizing the efficacy of phenolic extracts obtained from different winemaking processes. In general, the inhibitory activity of the phenolic pool of grape skins was higher than those of isolated phenolic compounds, namely anthocyanins and monomeric and polymeric flavanols and flavonols, probably due to synergistic effects among compounds. Hence, bioactive phenolic fractions could be produced with the focus on functionality rather than purity, in line with the principles of sustainable processing. Based on the efficacy index developed to compare different phenolic compounds and phenolic-rich plants studied in the literature as starch digestion enzyme inhibitors, red grape skins proved to be cost-effective candidates. Full article

The high speeds seen in rapidly rotating pulsars after supernova explosions present a longstanding puzzle in astrophysics. Numerous theories have been suggested over the years to explain this sudden “kick” imparted to the neutron star, yet each comes with its own set of challenges and limitations. Key explanations for pulsar kicks include hydrodynamic instabilities in supernovae, anisotropic neutrino emission, asymmetries in the magnetic field, binary system disruption, and physics beyond the Standard Model. Unraveling the origins of pulsar kicks not only enhances our understanding of supernova mechanisms but also opens up possibilities for exploring new physics. In this brief review, we will introduce pulsar kicks, examine the leading hypotheses, and explore future directions for this intriguing phenomenon. Full article

Permanent magnet synchronous motors (PMSMs) are widely used in a variety of fields such as aviation, aerospace, marine, and industry due to their high angular position accuracy, energy conversion efficiency, and fast response. However, driving errors caused by the non-ideal characteristics of the driver negatively affect motor control accuracy. Compensating for the errors arising from the non-ideal characteristics of the driver demonstrates substantial practical value in enhancing control accuracy, improving dynamic performance, minimizing vibration and noise, optimizing energy efficiency, and bolstering system robustness. To address this, the mechanism behind these non-ideal characteristics is analyzed based on the principles of space vector pulse width modulation (SVPWM) and its circuit structure. Tests are then conducted to examine the actual driver characteristics and verify the analysis. Building on this, a real-time compensation method is proposed, physically matched to the driver. Using the volt–second equivalence principle, an input–output voltage model of the driver is derived, with model parameters estimated from test data. The driving error is then compensated with a voltage method based on the model. The results of simulations and experiments show that the proposed method effectively mitigates the influence of the driver’s non-ideal characteristics, improving the driving and speed control accuracies by 88.07% (reducing the voltage error from 0.7345 V to 0.0879 V for a drastic command voltage with a sinusoidal amplitude of 10 V and a frequency of 50 Hz) and 53.08% (reducing the speed error from 0.0130°/s to 0.0061°/s for a lower command speed with a sinusoidal amplitude of 20° and a frequency of 0.1 Hz), respectively, in terms of the root mean square errors. This method is cost-effective, practical, and significantly enhances the control performance of PMSMs. Full article

This article introduces a novel approach for assessing microstructure, particularly its degradation after extended operation. The authors focus on creep processes in power plant components, highlighting the importance of diagnostics in this field. This article emphasizes the value of combining traditional microstructure observation techniques with image analysis. A non-destructive method of evaluating microstructure parameters (matrix replicas) is presented, and its accuracy is evaluated against the conventional destructive method. The assessment utilizes quantitative data derived from classical stereological principles and image analysis. Parameters like mean chord length, relative surface area, mean cross-sectional area, and mean equivalent diameter are compared for replica and metallographic specimens. The results show that the replica method accurately reproduces the microstructure. In their conclusions, the authors highlight the importance of developing visual methods alongside the application of artificial intelligence while indicating the challenges in achieving this goal. Full article

The present work describes the development of a graphical environment to represent typical flight instruments on a computer screen. The instruments’ behavior is displayed according to information regarding the aircraft’s flight conditions. Some of the instruments represented in this work, such as the altimeter, the vertical speed indicator, the aircraft speed indicator, and the Mach indicator, use air pressure principles. The algorithms and routines developed for the screen display are created using the C++ programming language and compiled independently to be included as libraries to improve the software performance. The algorithms developed for this purpose also include the corresponding relationship between the physical variables, such as the speed and displacement, and the standard atmosphere to provide an equivalent value. These algorithms are successfully tested using data information to simulate three hypothetical flights, which are divided into maneuvers with the aircraft in a stopped position, running on the ground, taking off and flying away, including some changes in directions. Moreover, the routines for displaying the aircraft path with the instruments’ animation are also successfully tested by comparison. Finally, an approach analysis as a function of the step time (Δt) used for calculation of the aircraft displacement to evaluate the efficiency of the numerical method integrated in the simulator is also described. It is proved that the aircraft instrument representation is appropriate according to the input data of the analyzed flights, and an improvement in the calculation can be easily obtained, making it possible to represent any flight condition on the aircraft instruments. Full article

The quantum electromagnetic (EM) field is formulated in the Weyl–Wigner representation (WW), which is equivalent to the standard Hilbert space one (HS). In principle, it is possible to interpret within WW all experiments involving the EM field interacting with macroscopic bodies, the latter treated classically. In the WW formalism, the essential difference between classical electrodynamics and the quantum theory of the EM field is just the assumption that there is a random EM field-filling space, i.e., the existence of a zero-point field with a Gaussian distribution for the field amplitudes. I analyze a typical optical test of a Bell inequality. The model admits an interpretation compatible with local realism, modulo a number of assumptions assumed plausible. Full article

Variable-speed aircraft engines require the power turbine rotor to operate stably within a wide range of output speeds, posing a challenge for rotor vibration reduction design. Non-concentric squeeze film dampers (NCSFDs) have been widely used in rotor vibration reduction design due to their simple structure. However, comprehensive research on the matching and applicability of NCSFDs under varying operating speeds is lacking. Therefore, this paper investigates the influence of oil film radial clearances on the dynamic characteristics of a variable-speed rotor system with an NCSFD, examining its suitability across variable speeds. This study introduces the principle of equivalent rotor dynamics similarity design, demonstrating good consistency between simulated and real rotor dynamic characteristics, with a radial clearance of 0.10 mm being deemed optimal. The vibration response variation in the rotor at a fixed speed within the range of 0.51 n to 1.0 n does not exceed 4 μm, and the vibration acceleration variation does not exceed 0.04 g, indicating a wide, stable operating speed range. This study can be helpful for the engineering design and vibration reduction design of variable-speed rotors in aircraft engines. Full article

The present study investigates the effects of fabrication parameters such as the nozzle temperature, the flow rate, and the layer thickness on the tensile strength of copper-filled metal-composite specimens. The selected material is a polylactic acid (PLA) filament filled with 65% copper powder. Two sets of 27 specimens each were fabricated, and equivalent tensile experiments were carried out using a universal testing machine. The experiments were planned according to the full factorial design, with three printing parameters, as well as three value levels for each parameter. The analysis revealed that the temperature and the flow rate had the greatest impact on the yielded tensile strength, with their contribution percentages being 42.41% and 22.16%, respectively. In addition, a regression model was developed based on the experimental data to predict the tensile strength of the 3D-printed copper-filled metal composite within the investigated range of parameters. The model was evaluated using statistical methods, highlighting its increased accuracy. Finally, an optimization study was carried out according to the principles of the desirability function. The optimal fabrication parameters were determined to maximize the tensile strength of the specimens: temperature equal to 220 °C, flow rate equal to 110%, and layer thickness close to 0.189 mm. Full article

Cardiac rehabilitation, a multi-component intervention designed to mitigate the impact of cardiovascular disease, often underutilises low-intensity resistance exercise despite its potential benefits. This narrative review critically examines the mechanistic and clinical evidence supporting the incorporation of low-intensity resistance exercise into cardiac rehabilitation programmes. Research indicates that low-intensity resistance exercise induces hypertrophic adaptations by maximising muscle fibre activation through the size principle, effectively recruiting larger motor units as it approaches maximal effort. This activation promotes adaptation in both type I and II muscle fibres, resulting in comparable increases in myofibrillar protein synthesis and phosphorylation of key signalling proteins when compared to high-intensity resistance exercise. Low-intensity resistance exercise provides equivalent improvements in muscular strength and hypertrophy compared to high-intensity protocols while addressing barriers to participation, such as concerns about safety and logistical challenges. By facilitating engagement through a more accessible exercise modality, low-intensity resistance exercise might improve adherence rates and patient outcomes in cardiac rehabilitation. Additionally, the ability of low-intensity resistance exercise to address sarcopenia and frailty syndrome, significant determinants of cardiovascular disease progression, can enhance the recovery and overall quality of life for patients. This review establishes evidence-based recommendations for the inclusion of low-intensity resistance exercise in cardiac rehabilitation, offering a promising pathway to enhance the effectiveness of these programmes. Full article

Existing short-circuit calculation methods for distribution networks with renewable energy sources ignore the fluctuation of renewable sources and cannot reflect the impact of renewable sources and load changes on short-circuit current in real time at all times of the day and in extreme scenarios. A real-time short-circuit current calculation method is proposed to take into account the stochastic nature of distributed generators (DGs) and electricity loads. Firstly, the continuous power flow of distribution networks is calculated based on the real-time renewable energy output and electricity loads. And then, equivalent DG models with low-voltage ride through (LVRT) strategies are substituted into the iterative calculation method to obtain the short-circuit currents of all main branches in real time. The effects of different renewable energy output curves on distribution network short-circuit currents are quantitatively analyzed during the fluctuation in distributed power output, which can provide an important basis for the setting calculation of distribution network relay protection and the study of new principles of protection. Full article

Shale is a common rock in oil and gas extraction, and the study of its nonlinear mechanical behavior is crucial for the development of engineering techniques such as hydraulic fracturing. This paper establishes a new coupled elastic–plastic damage model based on the second law of thermodynamics, the strain equivalence principle, the non-associated flow rule, and the Drucker–Prager yield criterion. This model is used to describe the mechanical behavior of shale before and after peak strength and has been implemented in ABAQUS via UMAT for numerical computation. The model comprehensively considers the quasi-brittle and anisotropic characteristics of shale, as well as the strength degradation caused by damage during both the elastic and plastic phases. A damage yield function has been established as a criterion for damage occurrence, and the constitutive integration algorithm has been derived using a regression mapping algorithm. Compared with experimental data from La Biche shale in Canada, the theoretical model accurately simulated the stress–strain curves and volumetric–axial strain curves of shale under confining pressures of 5 MPa, 25 MPa, and 50 MPa. When compared with experimental data from shale in Western Hubei and Eastern Chongqing, China, the model precisely fitted the stress–strain curves of shale at pressures of 30 MPa, 50 MPa, and 70 MPa, and at bedding angles of 0°, 22.5°, 45°, and 90°. This proves that the model can effectively predict the failure behavior of shale under different confining pressures and bedding angles. Additionally, a sensitivity analysis has been performed on parameters such as the plastic hardening rate b, damage evolution rate B_ω, weighting factor r, and damage softening parameter a. This research is expected to provide theoretical support for the efficient extraction technologies of shale oil and gas. Full article

A rock mass is mainly subjected to a high internal pressure load in the lined rock cavern (LRC) for compressed air energy storage (CAES). However, under the action of long-term cyclic loading and unloading, the mechanical properties of a rock mass will deteriorate, affecting the long-term stability of the cavern. The fissures in the rock mass will expand and generate new cracks, causing varying degrees of damage to the rock mass. Most of the existing studies are based on the test data of complete rock samples and the fissures in the rock mass are ignored. In this paper, the strain equivalence principle is used to couple the initial damage variable caused by the fissures and the fatigue damage variable of a rock mass to obtain the damage variable of a rock mass under cyclic stress. Then, based on the ANSYS 17.0 platform, the ANSYS Parametric Design Language (APDL) is used to program the rock mass elastic modulus evolution equation, and a calculation program of the rock mass damage model is secondarily developed. The calculation program is verified by a cyclic loading and unloading model test. It is applied to the construction project of underground LRC for CAES in Northwest China. The calculation results show that the vertical radial displacement of the rock mass is 8.39 mm after the 100th cycle, which is a little larger than the 7.53 mm after the first cycle. The plastic zone of the rock mass is enlarged by 4.71 m², about 11.49% for 100 cycles compared to the first cycle. Our calculation results can guide the design and calculation of the LRC, which is beneficial to the promotion of the CAES technology. Full article

The article focuses on devising solutions for monitoring the condition of the filter capacitors of DC-DC converters. The article introduces two novel DC-DC buck converter designs that monitor the equivalent series resistance (ESR) and the capacitance of capacitors using a parameter observer (PO) and simple variable electrical networks (VEN). For the first scheme, the PO processes in real time the voltage at the capacitor terminals during a discharge-charge cycle. For the second scheme, the filtering is performed with two or more capacitors in parallel, and the PO processes the voltage at the terminals of each capacitor during two discharge processes without interrupting the filtering operation of the converter. The paper presents the principles and theoretical support on which the two schemes of DC-DC buck converters are based, design details regarding PO and VEN, as well as experiments performed with each of the schemes. In the experimental schemes, the PO is implemented with a microcontroller, and the parameters of some aluminum electrolytic filter capacitors are calculated in a real-time manner of about $40 \mathrm{m}\mathrm{s}$. The calculation accuracy of the equivalent capacity is very good. Regarding the calculation accuracy of the ESR, it is shown that it depends on the fulfillment of certain ratios between the VEN resistances, on the one hand, as well as between them and the ESR, on the other hand. Full article