Variable Speed Research Articles

Prospective control of steering through multiple waypoints.

Some locomotor tasks involve steering at high speeds through multiple waypoints within cluttered environments. Although in principle actors could treat each individual waypoint in isolation, skillful performance would seem to require them to adapt their trajectory to the most immediate waypoint in anticipation of subsequent waypoints. To date, there have been few studies of such behavior, and the evidence that does exist is inconclusive about whether steering is affected by multiple future waypoints. The present study was designed to address the need for a clearer understanding of how humans adapt their steering movements in anticipation of future goals. Subjects performed a simulated drone flying task in a forest-like virtual environment that was presented on a monitor while their eye movements were tracked. They were instructed to steer through a series of gates while the distance at which gates first became visible (i.e., lookahead distance) was manipulated between trials. When gates became visible at least 1-1/2 segments in advance, subjects successfully flew through a high percentage of gates, rarely collided with obstacles, and maintained a consistent speed. They also approached the most immediate gate in a way that depended on the angular position of the subsequent gate. However, when the lookahead distance was less than 1-1/2 segments, subjects followed longer paths and flew at slower, more variable speeds. The findings demonstrate that the control of steering through multiple waypoints does indeed depend on information from beyond the most immediate waypoint. Discussion focuses on the possible control strategies for steering through multiple waypoints.

Rapid deceleration in the ice-flow velocity of the Shirase Glacier ice tongue and its influence on the velocity field: Observations from Sentinel-1 C-SAR

Temporal and spatial variations in the ice-flow speed of Shirase Glacier ice tongue in East Antarctica between July 2018 and December 2021 were investigated using Sentinel-1 C-band Synthetic Aperture Radar (C-SAR) imagery. We identified pronounced slowdown events in the eastern part of the outer ice tongue, 30–40 km from the grounding line in 2020 and 55 km in 2021. Comparison of ice thickness and bathymetry in areas where the deceleration events occurred suggests that the events were caused by icebergs grounding or landing on the seafloor. The absence of slowdown propagation towards the grounding line demonstrates the ice tongue offers very limited buttressing. This study contributes to a better understanding of the factors influencing glacier dynamics, particularly in the context of grounding events and their localized impacts.

Mechanistic insights into abnormal grain growth suppression in friction stir welded 7075-T651 aluminum alloys through variation in tool rotational speed

Friction stir weld joints of precipitation-hardenable aluminum alloys invariably show abnormal grain growth (AGG) during the post-weld T6 heat treatment. This study investigates the influence of tool rotational speed on AGG in FSW joints and elucidates the underlying mechanisms. Friction stir welding (FSW) of heat-treatable 7075-T651 aluminum alloy was conducted at various tool rotational speeds such as 386 rpm, 664 rpm, 931 rpm, and 1216 rpm with a constant traverse speed of 20 mm/min, followed by T6 heat treatment. Further, metallurgical characterization of FSW joints, such as optical stereotype microscopy and electron backscattered diffraction (EBSD) analysis, was employed. In addition, micro-hardness distribution and transverse tensile test of the FSW joints were studied to understand the effect of AGG on the mechanical performance of the weld joint. Results indicate that higher tool rotational speeds lead to more uniform deformation and a higher strain rate, resulting in the formation of a strong B/B̅ texture and higher geometrical necessary dislocation density (GND) within the nugget zone. The presence of this texture, coupled with a higher fraction of high-angle grain boundaries, proves less susceptible to AGG. Conversely, welds produced at lower tool rotational speed exhibit a strong C texture with relatively lower high-angle grain boundaries and GND formation, rendering them more susceptible to AGG. Microstructural analysis reveals that continuous grain growth dominates in welds developed at higher tool rotational speeds, while discontinuous grain growth prevails in those developed at lower tool rotational speeds. A weld joint with AGG leads to a lower tensile strength of 502 MPa and higher ductility of 14.1 %, and the fracture mechanism was found to change from ductile to quasi-cleavage fracture. However, no significant effect of AGG was found on micro-hardness. This study establishes the critical role of optimized tool rotational speed in controlling AGG during FSW and provides a comprehensive understanding through EBSD analysis. The finding of this study bridges the gap between controlled AGG and a detailed mechanistic comprehension, offering valuable insights for enhancing the reliability and performance of FSW joints in precipitation-hardenable aluminum alloys.

Comparing the efficacy of different climate indices for prediction of labor loss, body temperatures, and thermal perception in a wide variety of warm and hot climates.

The purpose of this study was to investigate which climate/heat indices perform best in predicting heat-induced loss of physical work capacity (PWCloss). Integrating data from earlier studies, data from 982 exposures (75 conditions) exercising at a fixed cardiovascular load of 130 beats·min-1, in varying temperatures (15-50°C), humidities (20-80%), solar radiation (0-800 W·m-2), wind (0.2-3.5 m·s-1), and two clothing levels, were used to model the predictive power of ambient temperature, universal thermal climate index (UTCI), wet bulb globe temperature (WBGT), modified physiologically equivalent temperature (mPET), heat index, apparent temperature (AT), and wet bulb temperature (Twb) for the calculation of PWCloss, skin temperature (Tskin) and core-to-skin temperature gradient, and thermal perception (thermal sensation vote, TSV) in the heat. R2, RMSE, and Akaike information criterion were used indicating model performance. Indices not including wind/radiation in their calculation (Ta, heat index, AT, and Twb) struggled to provide consistent predictions across variables. For PWCloss and TSV, UTCI and WBGT had the highest predictive power. For Tskin, and core-to-skin temperature gradient, the physiological models UTCI and mPET worked best in seminude conditions, but clothed, AT, WBGT, and UTCI worked best. For all index predictions, Ta, vapor pressure, and Twb were shown to be the worst heat strain predictors. Although UTCI and WBGT had similar model performance using the full dataset, WBGT did not work appropriately in windy, hot-dry, conditions where WBGT predicted lower strain due to wind, whereas the empirical data, UTCI and mPET indicated that wind in fact increased the overall level of thermal strain. The findings of the current study highlight the advantages of using a physiological model-based index like UTCI when evaluating heat stress in dynamic thermal environments.NEW & NOTEWORTHY There is an urgent need to determine the optimal heat stress metric when forecasting the impact of heat stress on human performance, physiological stress, and perception. We analyzed a wealth of laboratory data, simulating heart rate (HR)-paced work with wide variations in air temperature, humidity, wind speed, solar radiation, and clothing. We conclude that the universal thermal climate index (UTCI) [followed by wet-bulb globe temperature (WBGT)] is the optimal heat index to reliably predict reductions in performance, and elevations in physiological and perceptual stress.

Bayesian Algorithm-Based Force Profiles Optimization of Hip-Assistive Soft Exosuits Under Variable Walking Speeds

Bayesian Algorithm-Based Force Profiles Optimization of Hip-Assistive Soft Exosuits Under Variable Walking Speeds

The randomness and determinacy of wall pressure fluctuations in incompressible flow

Wall pressure fluctuations caused by turbulent boundary layers have a significant impact on aircraft structural vibration and cabin noise. This study aims to investigate the mechanism of turbulence-induced pressure fluctuations by focusing on the randomness of wall pressure fluctuations, analyzed in both the time–frequency and spatial-wavenumber domains using measured data obtained from a phase array in a wind tunnel. Three roughness elements were designed and installed upstream of the plate to manipulate the turbulent boundary layer at a specific Mach number. The results of the investigation demonstrate that the disturbance strength induced by the roughness element influences the randomness of wall pressure fluctuations, in addition to the parameters utilized for data analysis. Generally, stronger turbulence fluctuations tend to decrease the randomness of pressure fluctuations. Moreover, wall pressure fluctuations also exhibit certain statistical principles that cannot be precisely calculated using mathematical expressions, highlighting their inherent randomness. Further investigation into randomness in the spatial-wavenumber domain revealed the hydrodynamic modes of turbulence fluctuations with varying convection velocity analyzed through wavenumber maps computed using the beamforming algorithm. These modes with variable convective speed significantly contribute to the generation of randomness in wall pressure fluctuations. Both the time–frequency domain and the spatial-wavenumber domain affect the randomness characteristics of wall pressure fluctuations. However, such effects are not easily discernible through a rudimentary analysis of the space–time correlation of turbulence fluctuations.

An Iterative Adaptive Vold–Kalman Filter for Nonstationary Signal Decomposition in Mechatronic Transmission Fault Diagnosis Under Variable Speed Conditions

An Iterative Adaptive Vold–Kalman Filter for Nonstationary Signal Decomposition in Mechatronic Transmission Fault Diagnosis Under Variable Speed Conditions

Analisis Pengaruh Kecepatan, Akurasi, dan Biaya Pengiriman terhadap Kepuasan Pelanggan

This research aims to research, test and assess the influence of the independent variables Speed, Accuracy and Delivery Costs on the dependent variable customer satisfaction for products from CV Konita Agro Putra. The sample for this research was 110 customers who had used products from CV Konita Agro Putra. This type of research uses a quantitative approach. Data was collected directly from respondents using research instruments in the form of questionnaires via Google Form and purposive sampling techniques. then the data results are processed using the SPSS 24 data processing application. The results of this research prove that there is a significant and positive influence of Delivery Speed on Customer Satisfaction, there is a significant and positive influence of Delivery Accuracy on Customer Satisfaction, there is a significant and positive influence of Delivery Costs on Satisfaction Customers, there is a simultaneous influence between Delivery Speed, Delivery Accuracy and Delivery Costs significantly and positively on Customer Satisfaction.

Research on grid-related performance laboratory testing for variable speed pumped storage unit

Abstract Variable speed pumped storage unit is an energy storage device with excellent operation and regulation performance. For the grid-related performance laboratory testing of the AC excitation controller of variable speed pumped storage unit integrated into the power grid, this paper studied the methods of grid-related testing of the AC excitation controller based on actual pumped storage power station data, established semi-physical hardware in the loop simulation platform based on RTDS and its function boards, and proposed the key laboratory testing items for the grid-related test. The simulation testing results verified the functions of the platform.

A Knee-Guided Evolutionary Algorithm for Multi-Objective Air Traffic Flow Management

Air traffic flow management plays a crucial role in efficient aviation. Most existing studies assume the flight speed as constant throughout the trip, leading to ineffective fixed-speed schedules. To address this issue, we propose a new problem model, which allows variable speed control to improve the flexibility and maneuverability of the management. In addition, we consider two conflicting objectives, which are minimizing the total flight delays and conflicts between flights, where the conflicts depend on the flight 4D trajectories (3D position plus time). To solve this new challenging problem, we propose a novel multi-objective evolutionary algorithm with new problem-specific individual representation and search operators. Specifically, the multi-chromosomes encoding scheme is designed to adapt to different types of operations. Then, to search the huge search space effectively, we develop a hybrid crossover operator that recombines the parents based on their flight routes. Furthermore, to balance the exploration and exploitation, we develop a new mutation strategy to utilize the heterogeneous search potential of different individuals. For exploitation, the knee individual in the Pareto front is improved by a new time shift operator for exploitation, and other non-dominated solutions are mutated by fixed-route mutation. For exploration, the dominated solutions are mutated randomly. To verify the effectiveness, we compare it with the real air traffic flow management schedules and the state-of-the-art algorithms on a range of real-world air traffic datasets. Extensive results show that the proposed algorithm can significantly outperform the baselines in generating safe and efficient 4D trajectories.

The Impact of Speed Variations on Individuals’ Emotional Journey During Post-Merger Integration

The Impact of Speed Variations on Individuals’ Emotional Journey During Post-Merger Integration

Load Capacity and Bending Strength of Double-Acting Friction Stir Welded AA6061 Hollow Panels

Aluminum alloy hollow panels are essential components in both civil and mechanical structures, such as building floors or large vehicle platforms. They enhance rigidity while staying lightweight and conserving material volume. In its application, this panel must be joined using welding methods. One common issue encountered in aluminum welding is the formation of porosity defects. Solid-state welding methods like Friction Stir Welding (FSW) can be a solution to address this problem. The FSW joining process on hollow panels cannot be completed in one welding operation due to their thickness. The FSW process must be performed on both surfaces, which requires a relatively long time. Therefore, FSW needs to be developed into a Double-acting FSW that utilizes two tools simultaneously. These two tools introduce two sources of heat input, pressing force, and friction-stirring, resulting in a novel response that needs further research. This study delves into the impact of welding speed variations in Double-Acting FSW on the load capacity and bending strength of AA 6061 hollow panel joints. Welding speeds of 20, 30, and 40 mm/min were tested alongside rotational speed (1500 rpm), tilt angle (2°), and shoulder diameter (24 mm). It was discovered that reducing welding speed enhances both load capacity and bending strength. Notably, specimens welded at 20 mm/min exhibited a load capacity of 15.61 kN and bending strength of 52 MPa, highlighting the potential of slower speeds for superior weld performance. Doi: 10.28991/CEJ-2024-010-08-018 Full Text: PDF

Scientific Publication Speed of Korean Medical Journals during the COVID-19 Era.

This study compared the scientific publication speeds of Korean medical journals before and during the coronavirus disease 2019 (COVID-19) era. We analyzed 2,064 papers from 43 international Korean medical journals, selecting 12 papers annually from 2019 to 2022. We assessed publication speed indicators, including the time from submission to revision and from submission to publication. Additionally, we examined variations in publication speed based on journal and paper characteristics, including whether the studies were related to COVID-19. Among the 43 journals analyzed, 39.5% disclosed the peer review duration from submission to the first decision, and 11.6% reported their acceptance rates. The average time from submission to acceptance was 127.0 days in 2019, 126.1 days in 2020, 124.6 days in 2021, and 126.4 days in 2022. For COVID-19-related studies, the average time from submission to revision was 61.4 days, compared to 105.1 days for non-COVID-19 studies; from submission to acceptance, it was 87.4 days for COVID-19-related studies and 127.1 days for non-COVID-19 studies. All indicators for COVID-19-related studies showed shorter durations than those for non-COVID-19 studies, and the proportion of studies accepted within 30 or 60 days was significantly higher for COVID-19-related studies. This study investigated the publication speed of Korean international medical journals before and during the COVID-19 pandemic. The pandemic influenced journals' review and publication processes, potentially impacting the quality of academic papers. These findings provide insights into publication speeds during the COVID-19 era, suggesting that journals should focus on maintaining the integrity of their publication and review processes.

Climatology of Diurnal Variation of Surface Wind Speed in Japan

Climatology of Diurnal Variation of Surface Wind Speed in Japan

CHARACTERIZATION OF CENTRIFUGAL CASTING METHOD FOR PULLEY MANUFACTURING USING VARIABLE ROTATIONAL SPEED

Due to advancements in the industrial sector, aluminum is progressively gaining popularity as a material of choice in the field of engineering. A pulley is a component that functions as a link or transfers power or engine rotation to the load via the V-belt belt. This study aims to determine the characterization of aluminum material made by the centrifugal casting method from used brake shoes with rotational speed variables of 0 RPM, 100 RPM, and 200 RPM. The characterization of the casting results in this study was analyzed using the Brinell hardness test and the Charpy impact test. The results of the Brinell hardness test showed that aluminum castings for making pulleys with an additional 100 RPM die rotation speed had a Brinell hardness value of 53.22 BHN. The results of the impact test with the Charpy method showed that specimens with a mold rotation speed of 100 RPM had an impact value of 0.0135 kg.m/mm2. The results of this study concluded that variations in rotational speed of 100 RPM in the casting of pulleys made of used aluminum using the centrifugal casting method can produce products that have good toughness.

Tribological Research of Resin Composites with the Fillers of Glass Powder and Micro-Bubbles.

This study investigates the tribological properties of resin composites reinforced with the fillers of glass powder and micro-bubbles. Resin composites were prepared with varying concentrations from 1% to 5% wt of fillers. Tribological tests were conducted using a block-on-ring scheme under dry friction conditions. The measurements of friction coefficient and wear values were performed under variable rotation speeds and loading conditions. The study showed that resin composites with 2-3% glass powder fillers and resin composites with 3-4% micro-bubbles exhibited optimal tribological properties. The resin glass powder modifications reduce the wear by 63% and resin micro-bubbles reduce wear by 32%. SEM analysis of the surfaces revealed surface imperfections and structural damage mechanisms, including abrasive and fatigue wear. The study concludes that specific filler concentrations improve the friction and wear resistance of resin composites, highlighting the importance of material preparation and surface quality in tribological performance. The increased wear resistance on both composites would hopefully expand the usage of additive manufactured composite, namely industrial moving components such as polymer gear, wheel, pulley, etc.

Effectiveness of Cutting Speed ​​of SS 316 L Material on Surface Roughness in Laser Cutting Process

Cutting metal materials using Laser Cutting can determine the quality of the cutting material. This is because laser cutting uses high speed, so it can improve the quality of the cut material. SS316 L metal is a metal used in the manufacturing industry. The choice of SS 316 L metal aims to prevent corrosion, have high strength and be easy to maintain. The aim of this research is to determine the cutting speed parameters in laser cutting using SS 316 L material. The method used is by varying the cutting speed of the laser machine with speeds of 60 mm/minute, 70 mm/minute, 80 mm/minute, 90 mm/minute, 100 mm/min. Observation of surface roughness tests with two variations vertically and horizontally. Test samples three times for each test object. The results of this research were that the lowest (smooth) surface roughness was obtained with a cutting speed variation of 100 mm/minute and the highest (coarse) at a cutting speed of 60 mm/minute for both vertical and horizontal sampling variations. So, the faster the cutting speed of the laser machine can reduce the roughness of the SS 316 L metal surface.

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.

Nonlinear vibrations of variable speed rotating graphene platelets reinforced blades subjected to combined parametric and forced excitation

It is generally acknowledged that the disturbance of rotating speed will cause parametric resonance for blades, and the presence of rotor displacement also can make the blade vibrate transversely. However, the coupled resonance mechanism of blades under the combined action of rotating speed disturbance and rotor displacement is not yet clear. To answer this question, this article investigates the nonlinear coupled resonance behavior of rotating blades in two cases: typical tuned (the frequency ratio of parametric and forced excitations equals 2:1) and frequency ratio detuned. A nonlinear vibration equation for rotating blades is established based on Euler beam theory in conjunction with geometric nonlinearity. The mixing rule and modified Halpin-Tsai model are used to calculate the effective properties of GPLRMF materials. Subsequently, using the method of varying amplitudes (MVA), an approximate analytical solution of the coupled resonance response is derived, the Jacobian matrix is used to determine the stability of non-trivial solutions, and the accuracy of the analytical results is verified with the aid of numerical solutions. Finally, the steady-state response of typical tuned and detuned coupled resonance is analyzed, and the influence mechanism of factors such as excitation amplitude, excitation phase angle and other parameters on coupled resonance is studied in detail. The results indicate that the supercritical coupled resonance curve exhibits double resonance peaks and jumps. Meanwhile, the steady-state response of coupled resonance highly depends on the excitation phase angle.

Research and Simulation Analysis of Fuzzy Intelligent Control System Algorithm for a Servo Precision Press

With the rapid development of the manufacturing industry toward intelligence and flexibility, traditional mechanical presses are unable to meet the increased stamping requirements due to the difficulties in achieving variable speed control and changing slide motion trajectories. Servo presses, driven directly by servo motors, can realize the flexible control of press movement and have become the trend in the industry for future development. The independent research and development of servo press control systems has become a popular topic and challenge in the domestic press industry. This paper proposes a new type of press transmission mechanism suitable for high-precision stamping, analyzes the working principle of its transmission mechanism, and provides a detailed analysis and discussion on the main research methods of fuzzy intelligent control for servo presses, including fuzzy model and basic control algorithms, fuzzy modeling and control of nonlinear systems, fuzzy predictive control, and stability analysis of fuzzy control systems. Based on the principle of the control scheme, a closed-loop control system block diagram and mathematical model for servo high-precision presses are established. Taking the physical prototype parameters of the STSZG1-250 as an example, the control system is dynamically simulated and verified using Simulink modules. Finally, their role and effects in intelligent control, and prospects for the development of fuzzy intelligent control, are discussed.