Speed Operation Research Articles

Research on key technologies of railway station codification digital twin

According to the requirements of railway transportation, to ensure that locomotives can receive frequency-shifted signal information through the track within the station, the track circuits must be codified. Due to the increased speed of train operations, braking has become more challenging, increasing the possibility of running a red signal compared to the present. Therefore, it is imperative to implement pre-overlay codification technology and equipment suitable for use in speed-enhanced sections. As the pre-overlay coding method must be adopted, it requires the isolation components in the interface equipment to have "fault-safe" performance. When the isolation component fails, the current or voltage introduced into the parallel track relay must not cause malfunction. Therefore, ensuring that the current and voltage of each component in the codified track meet the requirements is crucial. This research aims to establish a circuit simulation model based on MATLAB Simulink to achieve dynamic simulation of the pre-overlay ZPW-2000 codification circuit diagram of the 25Hz phase-sensitive track circuit in the electrified section. Through this model, the electrical characteristic indicators such as current, voltage, and waveform of each component on the circuit can be observed in real-time. This helps optimize the design and maintenance of the railway signal system, improving the safety and efficiency of train operations and contributing to the establishment of a digital twin model for the entire railway system's signal system.

Influence of electric current on tribological performance of grease-lubricated steels

In the rapidly growing field of electrification of mechanical systems, such as electric vehicles (EVs), it is needed to understand how electric currents affect lubricated mechanical interfaces. In this research, we employed a ball-on-disc tribometer to analyze the friction and wear behavior under varying direct current (DC) conditions (0, 1, 2, 3 A) on the steel contact surfaces lubricated with lithium base grease. To study the influence of electrical parameters on the mechanical behaviors of the interface, the impedance of the contact was measured with an alternating current (AC). The results revealed 35 % increase in coefficient of friction and 670 % rise in wear under 3 A compared to non-electrified conditions. Furthermore, the effect of operational speeds on the pitting density and electrical impedance were analyzed. Lower impedance was measured in at low speed, which increases the likelihood of electrical discharges and subsequent wear. Consequently, as sliding speed increases from 0 to 5 cm/s, the pitting density on lubricated surfaces significantly decreases from 1.8 to 0.4 pits per square micrometer. This study laid a groundwork for future research aimed at reducing wear and extending the lifespan of lubricated mechanical systems under the influence of electrical currents.

Succinimide-Functionalized Reduced Graphene Oxide Nanosheets: A High-throughput Resistive Sensing Platform for Age-Related Macular Degeneration Biomarker Determination Using Human Tears.

Age-related macular degeneration (AMD) is a well-recognized affliction among the elderly, causing vision impairment ranging from blurred vision to complete blindness. This underscores the critical need for accurate, precise, and early detection methods. Herein, we developed a noninvasive, label-free electrical biosensor, constructed on an economical printed circuit board (PCB) substrate, designed specifically for the precise quantification of AMD biomarker: complement component III (C3). The hydrothermally reduced graphene oxide (rGO) was deposited between gold-interdigitated microelectrodes, forming a conductive channel. The fabricated C3 biosensor exhibits a low detection limit of 0.4342 ng/mL and an impressive sensitivity of 9.238 ((ΔR/R)/ng.mL-1)/cm2 with a regression coefficient of 0.9815 calibrated within the clinical C3 range of 10-30 ng/mL. This excellent performance is ascribed to the synergistic effects of 1-pyrenebutanoic acid succinimidyl ester (PBASE) linker and conducting properties of rGO as they generate large active sites for higher anti-C3 antibody immobilization, thereby enhancing sensitivity and specificity. Furthermore, the performance of this proposed C3 sensor chip was validated with enzyme-linked immunosorbent assay (ELISA) using five human tear samples exhibiting an outstanding correlation of a regression value of 0.9774. The unparalleled merits of this newly crafted C3 biosensor transcend those of preceding platforms, boasting superior accuracy and precision in quantifying C3 levels in human tears, accelerated operational speed with results attainable within a mere 15 min, cost-effectiveness, and excellent sensitivity.

Numerical modelling on dispersion behavior of particulate contamination induced by a moving operator in a semiconductor cleanroom: A eulerian-eulerian method

Contamination control in cleanrooms is crucial across various industries. In semiconductor manufacturing, operator-induced contamination presents a significant challenge, as it reduces the critical dimension. In this research, one comprehensive model describing contamination behaviour induced by operator motion was proposed, considering the moving operator as both a flow pattern changer and a contaminant source, combined with the number of particles accumulated (NPA) on the process instruments. To quantitatively characterise the transient contaminant dispersion behaviour caused by the operator, a Eulerian-Eulerian-based particle number density equation, integrated with overset mesh technology was employed. Our findings reveal that contamination dispersion behaviour is governed by convection and diffusion. The NPA on the side instruments at operator moving speeds at 0.5, 1, and 1.5 m/s were 4404.33, 8241.26, and 9384.41, respectively. And those of central instruments are 28463.75, 35848.60, and 43680.74 in corresponding cases. The largest reduction in influence on both the central and side instruments was found between cases with a maximum operator speed of 0.5 and 1.5 m/s, with NPA reaching reductions of 53.08 % and 34.84 % respectively. This indicates that the moving speed significantly affects contaminant dispersion.

Analisa Kinerja Jalan terhadap Kecepatan Kendaraan di Ruas Jalan Lingkar Barat Tiga Kenali Besar Kota Jambi

This research aims to identify the main factors that influence vehicle speed. Analyzing the level of service on the West Ring Road 3 in Kenali Besar, Jambi City. Researchers use quantitative methods where data is taken by carrying out direct observations in the field. The objects aimed at by researchers are road geometric data, vehicle volume, vehicle travel time, traffic volume and vehicle speed obtained by conducting surveys and direct measurements in the field. The main factor that influences vehicle operational speed is the number of motorized vehicles and heavy vehicles that exceed road capacity. Where the average number of light vehicles at peak hours is 8,434 and heavy vehicles 1,524. With the average highest speed of motorized vehicles being 30 KM/hour and heavy vehicles 15/14 KM/hour. Level of Service on the West Ring Road Section 3 with a Degree of Saturation value from the direction of Pall 10 - Simpang Rimbo or vice versa from the direction of Simpang Rimbo - Pall 10 has a service value of C (0.45-0.74) in the stable flow zone. Drivers are limited in choosing speed

Sensorless control using single current sensor with PFC assisted SRM drive for cost-effective domestic appliances

This paper presents a sensorless control designed for low to medium speed operation of an 8/6 pole switched reluctance motor (SRM) drive, utilizing only a single current and voltage sensor while ensuring grid-side power quality. It emphasizes a cost-effective solution suitable for low-power applications in both domestic and industrial appliances, employing SRM drive technology. In this, AC input is fed to Cuk converter that suppresses grid current total harmonic distortion (THD). Using symmetrical structural properties of SRM allows for a cost-friendly sensorless control approach. Position estimation for four-phase SRM is achieved by comparing two-position reference fluxes with running flux. In case of four-phase SRM, phases A and C are conducted sequentially, enabling a single voltage and current sensor to estimate flux for both phases. This method contrasts with lookup table-based rotor position estimation, requiring only two sets of position flux data, thus reducing memory usage, controller complexity, and speeding up response. A laboratory prototype of a four-phase 8/6 SRM is used to estimate rotor position in sensorless control. Finally, test results are used to validate effectiveness of presented PFC assisted sensorless control approach.

A high-speed dynamic comparator with automatic offset calibration

A high-speed dynamic comparator with preamplifier and automatic dc offset calibration in all stages is proposed in this paper. The offset compensation is applied in two stages, following a two-part sequential loop training topology, offering significant reduction of the dc offset in each stage. The final resolution is improved with a final value less than 800 μV operating at 7.5 GHz clock speed. The dynamic comparator stage is a double-tail topology while the calibration topology is based on a current injection technique, instead of the commonly used capacitive calibration which can reduce the operating speed. Designed in a CMOS 65 nm technology node, the circuit operates with 1 V supply voltage. Results of PVT Monte Carlo post-layout simulations verify the operation of the proposed topology.

Flexo-Phototronic Boosted Self-Powered Ultraviolet Detection in ZnAl:Layered Double Hydroxide Nanosheets/NiO Heterostructure.

Developing self-powered and flexible optoelectronic sensors with high responsivity and speed is crucial for modern applications, motivating continuous efforts to enhance their performance. Flexo-phototronics is a less-explored but promising technique to elevate the performance of optoelectronics. Therefore, this work addresses the potential of utilizing the flexo-phototronic effect to enhance the performance of a flexible and self-powered ultraviolet photodetector (UV PD) based on ZnAl:LDH (layered double hydroxides) nanosheets (Ns)/NiO heterostructure. The vertically oriented ZnAl:LDH Ns are synthesized via a simple method involving the immersion of a sputtered 10% Al-doped ZnO thin film in deionized water at room ambient conditions. The fabricated PD exhibits an impressive response to 365 nm UV light, with high sensitivity in the order of 103. The device's photocurrent and responsivity are significantly enhanced by the flexo-phototronic effect, attributed to the flexoelectric properties of ZnAl:LDH Ns. Specifically, applying an inhomogeneous tensile strain of 2% boosted the device responsivity by 57.1% and improved its operational speed. Furthermore, a working model revealing the altered energy-band structure is demonstrated to elucidate the flexo-phototronic-induced boost in the photoresponse. The PD also demonstrated a sustainable performance under severe bending cycles, underlining the good flexibility of the device. The results presented in this study demonstrate a self-powered and flexible UV PD and provide a viable approach to augment the performance of optoelectronics through the flexo-phototronic effect.

On the operational similarities of bladed rotor vibrations with casing contacts

AbstractRotor-to-stator rubbing in rotating machinery, resulting from tight clearances, introduces complex dynamics that can potentially lead to high vibrations and machine failure. Historically, the rubbing models were addressed using cylinder-to-cylinder contacts; however, recent attention has shifted towards examining blade-tip contact in turbines, which affects the systems dynamics and efficiency. This study investigates the impact of the variations in blade number on bladed rotor systems, emphasizing on the types of motion that occur as function of the operational speed in the sub-critical range. A simplified bladed rotor model has been developed, using a Jeffcott rotor with blades represented as damped elastic pendulums. The equations of motion are derived and numerical simulations are performed to explore the system’s behaviour with varying blade numbers (3, 5, 7, and 10) in order to analyse displacements, contact forces and bifurcation diagrams as function of the rotating speed. Results reveal distinct regions: periodic motion (I and III) and chaotic motion (II and IV) appear alternatively in the bifurcation diagram, with the chaotic regions occurring at specific fractions of the natural frequency and the number of blades. The study concludes that chaotic motions are associated with larger displacements and higher contact forces, and the vibrational behaviour becomes less hazardous as the number of blades increases. In addition, the appearance of periodic and chaotic motions occur in the same regions by scaling the rotating speed with the number of blades and natural frequency of the system. From an operational perspective, this dynamic investigation offers valuable insights into the severity of blade rubbing in industrial systems. It can guide the implementation of mitigation solutions to prevent worst-case failure scenarios and help to perform adjustments to either operational or design parameters.

Suboptimal Analysis of the Differential System of the Conceptual Trailer Air Brake Valve

Motivation: To increase the efficiency of the brake valve by adding a corrective member. Background: The speed of response and smooth transition between modes of operation in the braking system are the primary research questions. Objective and research question: Will the optimal selection of the input parameters of the differentiating part of a conceptual brake valve ensure the speed of operation and enable a smooth transition from the accelerating mode to the tracking mode? Methods: The mathematical model of the differentiating part of the brake valve uses the lumped method, and the solution was obtained by numerical means. Results: Within the assumed range of variation of spring stiffness and control piston bore throughput, the distribution maps of action times and piston lift were determined, and the optimal configuration of the analyzed input parameters was obtained by a genetic algorithm. Future research: future activities will focus on the development of a system of smooth variation of the throughput of the connecting chamber of the differential part of the valve. Conclusions: The determined maps of functional parameter distributions are the basis for the selection of components of the braking system; optimization indicates the directions of modification of the valve in order to obtain an acceptable performance system.

Composite failure analysis of an aero-engine inter-shaft bearing inner ring

The inter-shaft bearing is a critical component in dual rotors aero-engine. Due to the complex and severe loads caused by the interactive excitation of HP and LP rotors during operation, the inter-shaft bearing is prone to damage accumulation and failure. Focusing on a typical failure of inter-shaft bearing inner ring fragmentation and cannot be spliced together completely in high thrust-weight ratio turbofan engine, this paper conducted morphological investigation, fractographic analysis, vibration signal processing, finite element numerical simulation, and fully studied the failure mechanism of this failure.The results indicated that: there exists an uncoordinated resonance speed of the HP rotor in close proximity to the operating speed. This puts the rotor in non-synchronous procession state, accompanied by the uncoordinated angular displacement of the inner and outer rings, which resulting in a lager rolling dynamic load in bearing inner ring. This further leads to high tangential impact load at the root fillet of the anti-rotation pin, causing significant stress concentration, and eventually leads to the generation of initial cracks. These cracks persist and propagate into fatigue oblique fracture over time. After oblique fracture, the modal frequencies of the inner ring become more dispersed. Under the rolling dynamic load (traveling wave load), nodal diameter vibration occurs, causing high stress vibration fatigue damage, and ultimately leading to multiple-point simultaneous fragmentation.The investigation suggests that reducing the stress levels at the root fillet of the anti-rotation pin of the inner ring is an effective approach to prevent bearing failure. This can be achieved through two methods: one is optimizing the rotor structure to decrease the rolling dynamic load on the inner ring, the other is eliminating the anti-rotation pin and appropriately reducing the tightening torque of the compression nut and the interference between the bearing inner ring and the HP turbine rear journal.

Diamond wire saw forming cutting simulation analysis of arc workpieces

Abstract The application of diamond wire saws in the field of cutting hard and brittle materials is becoming increasingly widespread, especially in the photovoltaic industry where the demand for slicing processes for monocrystalline and polycrystalline silicon is continuously growing. Among these, the craftsmanship involved in arc-shaped workpieces is particularly complex. To analyze the impact of diamond wire saw processes on arc-shaped workpieces, PFC discrete element simulation software was utilized, aiming to produce a 1/8 arc segment, and the influence of the wire saw’s linear speed on the process was analyzed. The simulation results indicate that an increase in linear speed leads to improved particle distribution and a shape more closely resembling a circular form. However, the cutting process with a diamond wire saw must be controlled at an appropriate operating speed. If the speed is too high, it may lead to the destruction of the workpiece.

An Ultrafast Multibit Memory Based on the ReS2/h-BN/Graphene Heterostructure.

The exponential growth of data in the big data era has made it imperative to improve the data storage density and calculation speed. Therefore, the development of a multibit memory with an ultrafast operational speed is of great significance. In this work, a floating-gate (FG) memory based on the ReS2/h-BN/graphene van der Waals heterostructure is reported. The device exhibits ultrafast and multilevel nonvolatile memory characteristics, notably featuring an exceptionally large memory window of 113.36 V, a substantial erasing/programming current ratio of 107, an ultrafast operational speed of 30 ns, outstanding endurance exceeding 1000 cycles, and retention performance exceeding 1100 s. Furthermore, the device exhibits both electrically and optically tunable multilevel nonvolatile memory behavior. By controlling the voltage and light pulse parameters, the device achieves an electrical memory state of 130 levels (>7 bits) and an optical memory state of 45 levels (>5 bits).

Detection of rice pests based on RepMob-Yolo

Abstract Aiming at the disadvantages of high labor intensity, poor real-time performance, and low efficiency of traditional methods for identifying rice pests, a rice pest identification model based on RepMob-Yolo is proposed. MobileNetV3 is used as the backbone network, and the RepMob structure is used to replace the conventional downsampling structure in MobileNetV3, the GELU is used to replace the ReLU and the last four convolutional layers of MobileNetV3, the global average pooling layer and the fully connected layer are pruned to realize the lightweight design of the model. The DANet module is embedded to realize the extraction of effective information by the model, extract the semantic information of higher key features, and improve the recognition accuracy. The FPN structure is combined with the RepMob structure for feature extraction and prediction, which improves the operation speed of the model. The experimental results show that RepMob-Yolo achieves 97.68% accuracy, 96.00% recall, 96.82% prediction rate, and 146.37 f/s frame rate in the identification of public pest datasets, which provides technical support for accurate and real-time identification of rice pests.

Energy efficient improved content addressable memory using quantum-dot cellular automata

Quantum-dot cellular automata (QCA) is an emerging technology with high integration density, low power consumption, and high operating speed. This study introduces a QCA-based modified content addressable memory (CAM) cell employing a five-input minority gate. The functionality, temperature sensitivity, and heat distribution of this modified CAM cell are comprehensively analyzed using QCADesigner E and QCA Pro simulation tools. The results reveal significant advancements over existing designs, with a remarkable 8.33% reduction in area and a substantial 63.7% decrease in energy consumption. Additionally, this modified CAM cell exhibits a notable 5% enhancement in temperature tolerance. These findings emphasize the QCA-based modified CAM cell is more efficient and thermally robust.

Simulation data-driven fault diagnosis method for metro traction motor bearings under small samples and missing fault samples

Abstract Traction motor bearings are crucial for guaranteeing the safe operation of metro vehicles. However, in the metro traction motor bearing fault diagnosis, there are usually problems of small samples and missing fault samples, leading to inaccurate results. Therefore, a novel bearing fault diagnosis method utilizing a track-vehicle-bearing coupled dynamic model and the improved deep convolutional generative adversarial network-multiscale convolutional neural network with mixed attention (IDCG-MAMCNN) model is proposed in this paper. The IDCG-MAMCNN model combines an improved deep convolutional generative adversarial network (IDCGAN) with a multi-scale convolutional neural network with mixed attention (MA-MCNN). Specifically, simulation data is first provided by the coupled dynamic model to supplement missing fault samples. Secondly, the IDCGAN, along with a training method that involves pre-training models with simulation samples and fine-tuning models with experimental samples, is introduced to generate high-quality samples and augment experimental samples under small samples. Lastly, the MA-MCNN serves as the classification model, trained with the augmented dataset comprising experimental, simulation, and generated samples. The fault diagnosis performance of the proposed method is evaluated on the experimental samples of two bearing datasets under small samples and various conditions of missing fault samples. It has been demonstrated by the experimental results that the proposed method exhibits robust fault diagnosis performance and generates high-quality samples under small samples and missing fault samples. Furthermore, the proposed method showcases its adaptability to different operation speeds.

Determining Quasi-Static Load Carrying Capacity of Composite Sandwich Rotor Blades for Copter-Type Drones

The development of light composite rotor blades with acceptable load carrying capacity is an essential issue to be dealt with in the design of relatively large copter-type drones. In this paper, a method is established to determine the quasi-static blade load carrying capacity which is vital to drone reliability. The proposed method, which provides a systematic procedure to determine blade load carrying capacity, consists of three parts, namely, a procedure to determine the distributed quasi-static blade aerodynamic load via the Blade Element Momentum (BEM) approach, a finite element-based failure analysis method to identify the actual blade failure mode, and an optimization method to determine the actual blade load carrying capacity. The experimental failure characteristics (failure mode, failure thrust, failure location) of two types of composite sandwich rotor blades with different skin lamination arrangements have been used to verify the accuracy of the theoretical results obtained using the proposed load carrying capacity determination method. The skin lamination arrangement for attaining the optimal blade-specific load carrying capacity and the blade incipient rotational speed for safe drone operation has been determined using the proposed method.

Electrical Detection of Acoustic Antiferromagnetic Resonance in Compensated Synthetic Antiferromagnets.

Compensated synthetic antiferromagnets (SAFs) stand out as promising candidates to explore various spintronic applications, benefitting from high precession frequency and negligible stray field. High-frequency antiferromagnetic resonance in SAFs, especially the optic mode (OM), is highly desired to attain fast operation speed in antiferromagnetic spintronic devices. SAFs exhibit ferromagnetic configurations above saturation field; however in that case, the intensity of OM is theoretically zero and hard to be detected in well-established microwave resonance experiments. To expose the hidden OM, the exchange symmetry between magnetic layers must be broken, inevitably introducing remanent magnetization. Here, we experimentally demonstrate a feasible method to break the symmetry via surface acoustic waves with the maintenance of compensated SAF structure. By introducing an out-of-plane strain gradient inside the Ir-mediated SAFs, we successfully reveal the hidden OM. Remarkably, the OM intensity can be effectively modulated by controlling strain gradients in SAFs with different thicknesses, confirmed by finite-element simulations. Our findings provide a feasible scheme for detecting the concealed OM, which would trigger future discoveries in magnon-phonon coupling and hybrid quasiparticle systems.

Experimental and statistical damage analysis in milling of S2‐glass fiber/epoxy and basalt fiber/epoxy composites

AbstractS2‐glass fiber reinforced plastics (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) have emerged as crucial materials due to their exceptional mechanical properties, and milling of composite materials plays an important role in achieving desired properties. However, they have proven challenges due to relative inhomogeneity compared with metals, resulting unpredictability in quality of milling operations. The objective of this work is to investigate the effect of cutting parameters, tool geometry and tool surface materials on the surface quality of composites using burrs as a metric. S2‐GFRP and BFRP composites were produced by the vacuum infusion method. Helical and straight flute end mills were manufactured from high‐speed steel (HSS) and carbide rounds, and half of them were coated with titanium nitride using reactive magnetron sputtering technique. Taguchi L18 orthogonal array is used to determine the effect of tool material, tool angle, coating, cutting direction, spindle speed, and feed rate on the machining quality of S2‐GFRPs and BFRPs with respect to burr formations. Milling experiments were conducted under dry conditions and then the burrs were imaged to calculate the total area and length. Statistical analysis was also performed to optimize the machining parameters and tool type for ensuring the structural integrity and performance of the final composite parts. The results showed that the selection of tool material has the most significant impact on the burr area and length of the machined surface. The novel image analysis allows to analyze the extent of the burr size with a desirable operation speed for industrial applications.Highlights Aerospace grade S2‐Glass (S2‐GFRP) and basalt fiber reinforced plastics (BFRP) were manufactured. Carbide and HSS end mills were fabricated and coated with titanium nitride protective layer. FRPs were machined at various process parameters designed by Taguchi method. Distinctive image processing was firstly used to compute milling induced Burr area and length. Statistical analysis was performed to quantify the contribution of parameters and optimize milling.

Effect of conversion time on the stability of mixed-flow pump in rotating speed conversion

The rotating speed conversion strategy has a significant impact on the stability of the variable speed operation of the mixed flow pump. Taking a mixed-flow pump as the research object, this paper collects the shaft vibration, pressure pulsation, and external characteristic parameters under different conversion times based on the synchronous acquisition system, and analyzes the influence of conversion time on these parameters. Finally, based on the improved TOPSIS evaluation method, the influence of different conversion time on the stability of the mixed-flow pump is evaluated. The results indicate that the conversion time is positively correlated with the amplitude of shaft vibration and pressure pulsation in the pump during the transition of rotating speed reduction. The local rubbing of the shaft can induce the vibration component corresponding to the high harmonics frequencies such as 2 f n, 3 f n, and 4 f n. The high correlation frequency band of the impeller outlet pressure pulsation and shaft vibration is located between 64 Hz and 120 Hz. And this frequency band is not affected by the conversion time. According to the TOPSIS evaluation results, in the transition process of speed reduction, the longer the rotating speed conversion time, the worse the stability of the mixed-flow pump during the conversion process.