Optimal Velocity Research Articles

The Evolution of Dilatant Shear Bands in High-Pressure Die Casting for Al-Si Alloys

Bands of interdendritic porosity and positive macrosegregation are commonly observed in pressure die castings, with previous studies demonstrating their close relation to dilatant shear bands in granular materials. Despite recent technological developments, the micromechanism governing dilatancy in the high-pressure die casting (HPDC) process for alloys between liquid and solid temperature regions is still not fully understood. To investigate the influence of fluid flow and the size of externally solidified crystals (ESCs) on the evolution of dilatant shear bands in HPDC, various filling velocities were trialled to produce HPDC samples of Al8SiMnMg alloys. This study demonstrates that crystal fragmentation is accompanied by a decrease in dilatational concentration, producing an indistinct shear band. Once crystal fragmentation stagnates, the enhanced deformation rate associated with a further increase in filling velocity (from 2.2 ms−1 to 4.6 ms−1) localizes dilatancy into a highly concentrated shear band. The optimal piston velocity is 3.6 ms−1, under which the average ESC size reaches the minimum, and the average yield stress and overall product of strength and elongation reach the maximum values of 144.6 MPa and 3.664 GPa%, respectively. By adopting the concept of force chain buckling in granular media, the evolution of dilatant shear bands in equiaxed solidifying alloys can be adequately explained based on further verification with DEM-type modeling in OpenFOAM. Three mechanisms for ESC-enhanced dilation are presented, elucidating previous reports relating the presence of ESCs to the subsequent shear band characteristics. By applying the physics of granular materials to equiaxed solidifying alloys, unique opportunities are presented for process optimization and microstructural modeling in HPDC.

Determining the Fish Migration Patterns Based on Fish Habitat Assessment at a River Confluence

ABSTRACTMuch effort has been devoted to predicting fish migration routes to assist target species migration, and yet, fish migration science and practice remain imperfect. This study aimed to predict the migration paths of Gymnocypris przewalskii at the river confluence in the Qinghai Lake basin. The authors proposed an approach for fish migration route prediction, which involves a hydrodynamic module, a habitat model and a fish migration module. The TELEMAC‐MASCARET system was used to simulate hydrodynamic conditions and statistical analyses were carried out. During the flood season, G. przewalskii migrates downstream, whereas during the migratory season, they migrate upstream. The results indicate that flow velocity was the most significant hydrodynamic parameter affecting fish migration behaviour. The optimal flow velocity range for the target fish species was between 0.7 and 1.7 m/s. The impact of water depth was only observed in low discharge situations. Besides, the temperature plays a vital role in determining fish migration and abundance. However, the results reveal that in the morning hours, the temperature exhibits a range of 10°C to 16°C, and in the noon, the average temperature ranges from 16°C to 19°C, with a maximum temperature reaching 23°C. These temperature variations enable fish to migrate towards the tributary offering a more favourable water temperature during route selection at a river confluence. The study concludes that future research should consider incorporating the swimming capacity of the focal fish species to provide insights into fish migration patterns.

6996 Optimal Growth Hormone Response Despite Low Insulin-Like Growth Factor-1: Clinical Picture of an A67T IGF-1 Variant

Abstract Disclosure: E.M. Bomberg: Research Investigator; Self; Novo Nordisk. Z. Wu: Employee; Self; Quest Diagnostics. I. Motorykin: Employee; Self; Quest Diagnostics. J. Torkelson: None. N. Schmitz: None. A. Drilling: None. M.J. McPhaul: Employee; Self; Quest Diagnostics. B.S. Miller: Advisory Board Member; Self; Abbvie, Ascendis Pharma, Biomarin, Bristol-Myers Squibb, Eton Pharmaceuticals, EMD Serono, Endo Pharmaceuticals, GenSci, Novo Nordisk, Pfizer, Inc., Provention Bio, Sanofi, Tolmar. Consulting Fee; Self; Abbvie, Ascendis Pharma, Biomarin, Bristol-Myers Squibb, Eton Pharmaceuticals, EMD Serono, Endo Pharmaceuticals, GenSci, Provention Bio, Sanofi, Tolmar. Grant Recipient; Self; Alexion Pharmaceuticals, Inc., Abbvie, Aeterna Zentaris, Amicus, Foresee Pharmaceuticals, Lumos Pharma, Lysogene, Novo Nordisk, OPKO Health, Pfizer, Inc., Prevail Therapeutics, Sangamo Therapeutics. Research Investigator; Self; Alexion Pharmaceuticals, Inc., Abbvie, Aeterna Zentaris, Amicus, Foresee Pharmaceuticals, Lumos Pharma, Lysogene, Novo Nordisk, OPKO Health, Pfizer, Inc., Prevail Therapeutics, Sangamo Therapeutics. Speaker; Self; Biomarin, Novo Nordisk, Pfizer, Inc., Tolmar. Introduction: Insulin-like growth factor-1 (IGF-1) measurements are used for growth hormone (GH) deficiency screening and helpful in monitoring GH treatment effectiveness. However, IGF-1 variants have been reported with mass spectrometry (MS)-based assays, potentially limiting interpretation of reported results. Clinical Case: A 14-year-old male presented for short stature. Evaluation was non-revealing aside from low serum IGF-1 measured via liquid chromatography (LC)-MS assay (58 ng/mL; -3.8 standard deviation score [SDS]), and IGF-Binding Protein 3 (3.7 ug/mL; -1.7 SDS). Height was 148.2 cm (1st percentile, -2.08 SDS; mid-parental height 172.7 cm [31st percentile, -0.48 SDS]), pubertal exam Tanner stage 2, and bone age 2.5 years delayed. A GH stimulation test showed a peak GH of 8.1 ug/L; brain MRI was normal. GH was started at 0.29 mg/kg/wk. One month later, IGF-1 remained low (89 ng/mL; -3.2 SDS) and GH was increased to 0.36 mg/kg/wk, and over time to 0.52 mg/kg/wk due to persistently low IGF-1 (-2.9 to -2.3 SDS), despite reports of good compliance and significant catch-up growth (height increased to 19th percentile, -0.84 SDS). He reported no significant side effects during GH treatment. At 17.5 years old, he returned to clinic reporting self-discontinuing GH 1 month prior. Height was at the 27th percentile (171.5 cm, -0.59 SDS), he was fully pubertal, IGF-1 128 ng/mL (-3.1 SDS), and bone age 1.5 years delayed. Further review of IGF-1 linked reports accompanying lab values directly entered into the electronic health record (EHR; starting 2021) described the presence of a rare heterozygous IGF-1 functional variant with unknown clinical significance based on MS data. Concentration of the variant was expected to be identical to that reported for the wild type IGF-1 protein, potentially explaining the lower than expected values. Analysis of the raw LC-MS data (variant peak at m/z 1098.09, isotopic peak index [IP6], relative retention time [rRT]=0.00 min) was consistent with either an A67T or A70T IGF-1 variant. To resolve this ambiguity, the specimen was reanalyzed with an LC-tandem MS/MS fragmentation method, which identified distinguishing peaks at m/z 503.28 (y5 ion) and 305.18 (y3 ion) characteristic of A67T, a known benign variant. Conclusions: Benign IGF-1 variants should be considered in cases of unexplained low IGF-1 levels, including when these remain low despite increasing GH doses, good adherence, and optimal growth velocity. Presence of IGF-1 variants should not affect GH stimulation results (e.g., GH levels), however, may lower reported IGF-1 levels used to determine need for diagnostic testing and followed when monitoring GH response. Careful review of IGF-1 lab reports and full abstraction of these into the EHR should be performed. Knowing a variant is benign could help providers set lower wild-type IGF-1 targets when monitoring GH response to avoid unnecessarily high GH doses. Presentation: 6/3/2024

Collision-Free Tracking for a Mobile Robot Based on Purely Geometric Planning

A purely geometric planning method for a mobile robot in unknown environments is proposed to ensure robot collision avoidance against obstacles within the safety time interval while moving to the goal. The robot initially detects a point cloud of obstacles using a 2D LiDAR. Euclidean clustering is employed to classify the point cloud into point classes. The obstacle is then identified as a directed closed-loop rectangle for each point class. A relative orientation kd-tree is designed to store the vertices of the obstacles and to determine the obstacles to be considered in the obstacle avoidance algorithm. A velocity divider is introduced to obtain a linear convex area of possible obstacle avoidance velocities. Thus, linear planning is employed to calculate the optimal obstacle avoidance velocity for control. A virtual reference point method is proposed to solve the problem of an unreachable goal in a singular configuration. Experimental results show that the directed closed-loop rectangle and the relative orientation kd-tree facilitate the quick updating of required obstacle points with low-cost sensor equipment. The deterministic path for a given scenario can be obtained, demonstrating the reliability of geometric planning for both the obstacle avoidance velocity region and the optimal obstacle avoidance velocity. The proposed algorithm is finally validated for multiple obstacles and dynamic environments with moving obstacles.

Comprehensive Influence of Dimensionless Wave Velocity and Expansion Ratio on Energy Absorption Characteristics of Variable Wavelength Traveling Wave Turbine

Based on the traveling wave motion of fish, this paper introduces a new type of variable wavelength traveling wave turbine that significantly differs from traditional turbine designs in its mechanical structure. By developing a two-dimensional traveling wavy plate model and conducting numerical simulations, this study investigates the relationship between the dimensionless wave velocity, variable wavelength coefficient, and expansion ratio, as well as their combined effects on the energy absorption characteristics of the variable wavelength traveling wave turbine. The results reveal that energy absorption efficiency peaks at an optimal dimensionless wave velocity, which is unaffected by changes in the variable wavelength coefficient. Furthermore, the expansion ratio significantly influences both the dimensionless wave velocity and the variable wavelength coefficient, with an optimal ratio of π* = 2.5 achieving 90.42% efficiency. The energy absorption characteristics of the plate with a larger variable wavelength coefficient are found to be constrained by the expansion ratio. Additional analysis reveals that flow characteristics, such as the pressure distribution, vortex street, and velocity field surrounding the traveling wavy plate, are closely related to its energy absorption performance. These findings provide valuable insights for the design of variable wavelength traveling wave turbine.

Comparing Carotid Artery Velocities with Current ASCVD Risk Stratification: A Novel Approach to Simpler Risk Assessment.

To explore the potential of a novel approach to simplify risk assessment by comparing carotid artery velocities with current atherosclerotic cardiovascular disease (ASCVD) risk stratification method using nonlinear measurements. In this prospective study conducted at a medical center in southern Taiwan from January 1, 2020, to December 31, 2021, 1636 participants aged 40-75 years without prior ASCVD events were enrolled. Carotid flow velocity was obtained through duplex ultrasonography. ASCVD risk was categorized into two groups according to the 2022 USPSTF guidelines for primary prevention. We analyzed associations between flow indices and ASCVD risk using logistic regression and generalized additive models (GAMs). The end diastolic velocity (EDV) of common carotid artery (CCA) and the peak systolic velocity (PSV) of internal carotid artery (ICA) were inversely and nonlinearly associated with cardiovascular event risk. Multivariate logistic regression analysis with ROC curves revealed that the optimal speed for the EDV of CCA was approximately 23.75cm/s, and the optimal PSV and EDV of ICA were approximately 81.75cm/s and 26.75cm/s, respectively. The GAMs showed U-shaped relationships between elevated ASCVD risk and blood flow velocity in the carotid arteries, with inflection points of approximately 82cm/s in the PSV of ICA and near 25cm/s in the EDV of CCA. Both methods revealed similar results. The EDVs and PSVs of the CCA and ICA are associated with the development of cardiovascular events. Optimal velocity ranges were identified; however, further hemodynamic investigations are warranted.

Batch and column studies for the removal of basic red-46 dye and textile by using magnesium oxide (MgO), strontium titanium trioxide (SrTiO3), cobalt- and iron-doped lanthanum chromium trioxide (Co.Fe.LaCrO3), and cadmium sulfide (CdS)-doped graphene oxide nanocomposites.

Despite efforts to reduce the risk of toxic chemicals, colors, and dyes being released into the environment from urban and industrial areas, there is still cause for concern. Colored water must be filtered and sterilized before it can be used for irrigation. The utilization of metal oxide and nanocomposite materials in wastewater treatment procedures appears to be a viable option for the future. Therefore, different compounds were doped with graphene oxide to identify the best material for dye removal by the adsorption process. According to recent studies, the ideal conditions for graphene oxide-doped magnesium oxide (GO/MgO) are as follows: pH 10 showed the highest adsorption capacity (qe) at 49.4mg/g; an adsorbent dosage of 0.01g/50mL showed 48.3mg/g qe; a shaking time of 30min resulted in 44.2mg/g qe; an initial dye concentration of 100mg/L yielded 53.6mg/g qe; and a temperature of 35°C gave 49.5mg/g qe. For graphene oxide-doped strontium titanate (GO/SrTiO3), the optimum conditions were as follows: pH 10 with 45.8mg/g qe; an adsorbent dose of 0.01g/50mL with 40.5mg/g qe; a shaking time of 30min with 75mg/g qe; and a temperature of 35°C with 44.7mg/g qe. Graphene oxide-doped cobalt and iron-doped lanthanum chromium titanate (GO/Co.Fe.LaCrO3) showed optimum conditions of pH 9 with 34.2mg/g qe; an adsorbent dose of 0.01g/50mL with 27.5mg/g qe; a shaking time of 45min with 33.2mg/g qe; an initial dye concentration of 100mg/L with 37.6mg/g qe; and a temperature of 35°C with 42.5mg/g qe. Graphene oxide-doped cadmium sulfide (GO/CdS) showed the following optimum conditions: pH 8 with 23.1mg/g qe; an adsorbent dose of 0.01g/50mL with 25.5mg/g qe; an initial dye concentration of 75mg/L with 28.3mg/g qe; and a temperature of 35°C with 33.5mg/g qe. The pseudo-first-order model was the best fit only for graphene oxide-doped magnesium oxide (GO/MgO) with an R2 value of 0.966, while the pseudo-second-order adsorption isotherm was the best fit for all four products, with R2 values ranging from 0.991 to 0.998. Additionally, the Langmuir adsorption isotherms provided good results for all four products, with R2 values ranging from 0.957 to 0.985. The Freundlich adsorption kinetics showed satisfactory fit only for graphene oxide-doped magnesium oxide (GO/MgO) and graphene oxide-doped cadmium sulfide (GO/CdS), with R2 values of 0.951 and 0.982, respectively. To examine the characteristics and practicality of the adsorption process, certain thermodynamic variables were calculated. The adsorption capability of the most efficient nanocomposites for the degradation of basic red-46 was significantly affected by various concentrations of heavy metal ions and electrolytes. In dye solutions containing surfactants/detergents, the adsorption efficiency of several effective photocatalysts for basic dyes was significantly reduced. A 0.5M HCl solution was found to be the most effective for desorption. In column investigations, the optimal bed height, flow velocity, and dye intake levels were determined to be 3cm, 1.8mL/min, and 70mg/L, respectively, for maximal adsorption of basic red-46. The adsorption investigation of genuine textile waste products has also been carried out to facilitate the practical deployment of this approach. The methods used in this study were cost-effective, easy to handle, and eco-friendly and involved no hazardous materials in the synthesis, making the resulting materials non-hazardous. All these methods were part of green chemistry.

Investigation of the transportation characteristics of marine dredged-sediment in pipelines based on experimental pipeline models

Marine dredged-sediment(DS) is often transported through pipelines, where factors such as the solid volume concentration and transport rate can significantly influence the efficiency of the process. Inadequate selection of transport rates for a given solid volume concentration can lead to substantial energy losses. The pressure loss Δ P L or pressure loss gradient Δ P L / L are critical parameters for assessing energy loss during pipeline transport. In this study, large-scale indoor experiments on DS pipeline transport were conducted to investigate the effects of the cross-sectional mean flow velocity Vavg and solid concentration ϕ on the transport characteristics of DS. The results show that at higher solid volume concentrations, Δ P L / L increases rapidly with the square of Vavg and then plateaus, followed by a linear growth phase. In addition, a linear relationship is observed between lgf and lgVavg when the flow velocity is below critical velocity (Vavg ) critical ; above (Vavg ) critical , the friction factor f stabilizes at f 0 . Formulas for calculating (Vavg ) critical , f 0 and ϕ were developed. Additionally, a method for determining the optimal transport velocity of DS at varying volume concentrations was established, enabling the identification of the most efficient flow velocity for DS pipeline transportation across different concentrations. HIGHLIGHTS Pipeline model tests were conducted on marine dredged sediments. A formula for predicting pressure loss on the basis of solid concentration was derived. The impact of the solid concentration on the Darcy friction factor was determined. A method for determining the optimal transport velocity was established.

Computational fluid dynamics (CFD) simulation modeling for the cultivation of microalgal monoculture in axenic enclosed bubble column photobioreactor (BCPBR)

Researchers are more concerned with axenic-enclosed PBRs, where there is less or no chance of contamination during the production of biochemical and highly valuable metabolites, and monocultures of microalgae are being grown more frequently. It is a closed, manufactured vessel that aids in the photosynthesis of microalgal cells using artificial light or sunlight as the energy source. In this study, the bubble column PBR (BCPBR) was selected because it possessed some advantages over other PBRs for the growth of Chlorella vulgaris. The BCPBR system prevents contact between the enclosed microalgal cells and the environment, allowing the culturing of microalgae species that are difficult to grow in open pond systems. To compare BCPBR performance quantitatively, the efficient mixing expected in BCPBR, as discussed in the literature, was applied to the CFD model. The experimental results observed during the cultivation of C. vulgaris with restaurant wastewater (RWW) in BCPBR clearly showed better mixing, high growth, and improved treatment efficiency. CFD analysis was conducted on the evolution of bubbles in the BCPBR. The Pressure-Implicit with Splitting of Operators (PISO) pressure correction method is used for velocity and pressure coupling. A geo-reconstruct approach is used to construct the interface, and a second-order upwind calculation technique is used to determine the flow parameters. Therefore, CFD simulation in this study will contribute to the following aspects: (i) the volume fraction contours and velocity contours are going to validate the experimental study as the homogenous mixing favors the growth and productivity, (ii) To study how the size of the nozzle and inlet velocity affect the turbulence generated by bubbles in a BCPBR to identify the optimal nozzle size and velocity for the required turbulence.

A Novel Size-Based Centrifugal Microfluidic Design to Enrich and Magnetically Isolate Circulating Tumor Cells from Blood Cells through Biocompatible Magnetite-Arginine Nanoparticles.

This paper presents a novel centrifugal microfluidic approach (so-called lab-on-a-CD) for magnetic circulating tumor cell (CTC) separation from the other healthy cells according to their physical and acquired chemical properties. This study enhances the efficiency of CTC isolation, crucial for cancer diagnosis, prognosis, and therapy. CTCs are cells that break away from primary tumors and travel through the bloodstream; however, isolating CTCs from blood cells is difficult due to their low numbers and diverse characteristics. The proposed microfluidic device consists of two sections: a passive section that uses inertial force and bifurcation law to sort CTCs into different streamlines based on size and shape and an active section that uses magnetic forces along with Dean drag, inertial, and centrifugal forces to capture magnetized CTCs at the downstream of the microchannel. The authors designed, simulated, fabricated, and tested the device with cultured cancer cells and human cells. We also proposed a cost-effective method to mitigate the surface roughness and smooth surfaces created by micromachines and a unique pulsatile technique for flow control to improve separation efficiency. The possibility of a device with fewer layers to improve the leaks and alignment concerns was also demonstrated. The fabricated device could quickly handle a large volume of samples and achieve a high separation efficiency (93%) of CTCs at an optimal angular velocity. The paper shows the feasibility and potential of the proposed centrifugal microfluidic approach to satisfy the pumping, cell sorting, and separating functions for CTC separation.

Average optimal minimum velocity threshold: A practical variable to increase the accuracy of one-repetition maximum estimation during the free-weight back squat

ABSTRACT The prediction of one-repetition maximum (1RM) using the submaximal load–velocity relationship (LVR) is highly relevant for the field of strength and conditioning. The optimal minimum velocity threshold (MVT) was recently proposed to increase the accuracy of 1RM predictions. However, using the average optimal MVT would allow for more practical estimations. LVRs of the free-weight back squat were obtained in 53 participants, throughout 2 sessions. LVRs were obtained using the multi- and two-point methods. Estimations of 1RM were made based on the average actual MVT (1RM velocity) and the average optimal MVT. The accuracy of 1RM predictions was examined using absolute-percent error and Bland-Altman plots. Cross-validation was performed using a leave-one-out approach. The number of selected loads did not affect the slope, y-intercept, optimal MVT or the accuracy of 1RM predictions. Predictions based on the average optimal MVT displayed greater accuracy than those obtained with the average actual MVT (~6% vs. ~8% absolute-percent error, respectively). However, wide 95% limits of agreement (LoA) were found between actual and estimated 1RM using both approaches (~13%1RM). The average optimal MVT offers more accurate 1RM estimations than the average actual MVT. However, errors prove substantial, making it challenging to precisely track minor changes in 1RM.

Particle motion characteristics on the rotational flow pneumatic conveying of horizontal-vertical pipeline

In this study, a rotational flow device (rotational blade) is developed and installed in the upstream of the particle inlet with the aim of improving the efficiency and capacity of pneumatic conveying. Firstly, this study analyzed the energy-saving effect of rotational flow based on the pressure drop and power consumption. The results shown that the optimal velocity can be reduced by a maximum of 18.7 % and the power consumption coefficient can be reduced by a maximum of 9.8 %. Furthermore, the distributions of particle concentration, velocity and pulsation velocity are analyzed by using electrical capacitance tomography (ECT) and particle image velocimetry (PIV) system. It is found that the particle velocity and velocity pulsation intensity for rotational flow are higher, and they have the ability to enhance particle suspension. Then, the power spectrum of the particle pulsation velocity shown that the rotational flow exhibited higher peak value at lower frequencies, indicating the particles are not easily deposited at pipe bottom. Finally, the auto-correlation of particle pulsation velocity indicated that the particle motion is more stable and has a longer period at low particle concentrations. The skewness factor and probability density function of particle pulsation velocity indicated that the use of rotational blades makes the particle pulsation velocity to deviate from the Gaussian distribution.

Accounting for power take-off efficiency in optimal velocity tracking control of wave energy converters

There has been much research into how Wave Energy Converters (WECs) can capture energy from the waves and convert it into kinetic energy in the mechanical system (mechanical energy). However, because WECs typically generate power at high force and with low speed, the conversion of the mechanical energy into electrical energy can be inefficient. If Power Take-Off (PTO) efficiency is not accounted for in controller design then the efficiency of the WEC from wave energy to electrical energy can be poor. In this work, an adaptation of Optimal Velocity Tracking (OVT) control is presented, termed OVT-E, that accounts for PTO efficiencies in the controller formulation such that it converts more energy from the waves to electricity than traditional OVT approaches, termed OVT-M. Results show that, for an example WEC and PTO system in a simulation environment, OVT-E produces more efficient electrical energy conversion than OVT-M with lower forces through the drive-train. OVT-E is also shown to convert more electrical energy than an adaptive linear damping method. The methodology for designing OVT-E could have further applications when coupled with other controller implementations or if used alongside machine-learning for control co-design purposes.

Film Superposition Characteristics With Laidback Fan-Shaped Holes Under the Influence of Internal Crossflow

Abstract In the serpentine passage of actual rotor blades, the coolant at the inlet of the film hole has an internal crossflow. The internal crossflow significantly influences the film cooling effectiveness of multi-row film holes. This paper presents a numerical investigation of the superposition characteristics of multiple rows of laidback fan-shaped holes under the influence of internal crossflow. The numerical simulations utilize the RANS method considering the effects of blowing ratio, crossflow velocity ratio, arrangement patterns, and row-to-row spacing of the internal crossflow on the superposition characteristics of film holes. The results indicate that film cooling effectiveness exhibits a distinctly asymmetric distribution under crossflow conditions. At different blowing ratios, there exists an optimal crossflow velocity ratio, at which the laterally averaged film cooling effectiveness is maximized. The crossflow-to-jet velocity ratio (VRi) is utilized to comprehensively evaluate the impact of blowing ratios and crossflow velocity ratios, and the range of high area-averaged film cooling effectiveness is accurately captured. Regarding the study of arrangement patterns and row-to-row spacings, it has been found that under identical coolant mass flowrates, the staggered arrangement is better than the inline arrangement in both laterally averaged film cooling effectiveness and cooling uniformity. Meanwhile, reducing the row-to-row spacing leads to an improvement in laterally averaged film cooling effectiveness. Finally, an assessment of the Sellers model's applicability under crossflow conditions revealed that it demonstrates good applicability in cases of staggered arrangement with lower blowing ratios.

Collision-free trajectory tracking strategy of a UUV via finite-time extended state observer-based sliding mode predictive control

This paper focuses on a trajectory tracking problem for unmanned underwater vehicles (UUVs) subject to current disturbances and static obstacles. A double-loop framework is established. The kinematic governor employs model predictive control(MPC), which takes into account the UUV’s kinematic characteristics as well as the conditions for obstacle avoidance when calculating the control command and provides an optimal velocity command input for the dynamic controller. Then, the dynamic controller is developed based on a fast finite-time extended state observer (FESO) and a fast adaptive integral terminal sliding mode controller (FAITSMC). The construction of the fast FESO integrates UUV’s dynamics model, a proportional integral velocity variable, and a fractional order term of the output observation error, which can identify model uncertainties and external disturbances in finite time. By means of adaptive uncertainty compensation, the FAITSMC enables the error between actual speed and speed reference to converge to a minimum quickly. By applying Lyapunov stability theory and the finite-time analysis technique, sufficiency criteria are established to guide and keep the UUV on a reference trajectory via an inner-outer loop control structure. Finally, simulation examples in different scenarios are presented to verify the feasibility and effectiveness of the derived theoretical results.

Field equation of thermodynamic gravity and galactic rotational curves

The rotational velocity curve (RC) of galaxy NGC 3198 is modelled in various theoretical frameworks: Thermodynamic Gravity (TG) is compared to Dark Matter (DM) and Modified Newtonian Dynamics (MOND). The nonlinear gravitational field equation of TG is solved using the baryonic mass density as the source of the gravitational field. In this paper, first, a dissipation motivated numerical method is verified with the help of exact solutions. Then, the obtained optimal velocity curve is compared to DC14 model DM and MOND EFE (Modified Newtonian Dynamics-External Field Effect aspect) parametrisations for the RC of the galaxy.

Energy consumption model of flow-through electrolyzer considering mass transfer overpotential for hydrogen production from alkaline water splitting

Flow-through electrolyzer can improve the efficiency of hydrogen production from alkaline water splitting and determining the optimal electrolyte velocity through electrode pores is crucial for reducing energy consumption. In this study, an energy consumption model of flow-through electrolyzer considering mass transfer overpotential (Emass) has been developed. The model of Emass due to gas hold-up (ϕ) in the electrolyzer accounts for the density, viscosity, surface tension, linear velocity, and current density. The model-predicted value is in good agreement with the experimental results, which indicated that the increase of velocity effectively reduces ϕ and Emass. Then, Voltage-Current curve models combining reversible voltage, activation overpotential, ohmic overpotential, and Emass are developed. Based on this, an energy consumption model, combining both consumption from electrolyzer and pumps, is established to evaluate the overall energy consumption of hydrogen production. It can be calculated the Emass at 400 mA cm−2, 6 M KOH, 353 K can be reduced from 0.363 V to 0.048 V if the circulation velocity rises from 0.001 m s−1 to 0.1 m s−1. The model predicts that total energy consumption is 4.36 kWh Nm−3 with energy consumption for pump being 0.02 kWh Nm−3 at 400 mA cm−2 and 0.063 m s−1.

A novel methodology for the selection of the optimal velocity profile for planned point-to-point trajectories in 1-DoF manipulators

In this work, an approach based on velocity profile selection is developed and validated to decrease forces, acceleration, velocity, mechanical power, and energy consumption in 1 DOF Cartesian manipulators. Initially, a mathematical modeling of the kinematic and kinetic variables rising in linear, exponential, parabolic, sinusoidal, and s-curve ramp velocity profiles is proposed for different load conditions and saturation values of the velocity profiles, focusing on generic Cartesian manipulators moving a constant inertia load and not equipped with regenerative devices. Lastly, a summary table outlining the benefits and drawbacks of each velocity profile in relation to the relevant variables is given to the reader, along with a set of recommendations for selecting the best velocity profile in accordance with the load conditions and optimization goals. It was shown that, depending on the load conditions, the inappropriate choice of one type of speed profile can increase the required forces by up to 400%, the required maximum power by more than 88%, and the energy consumption by up to 77% with respect to the optimal speed profile.

Assessment of the correlation between Doppler derived dP/dt and aortic velocity-time integral during cardiac resynchronization therapy optimization.

Suboptimal response to cardiac resynchronization therapy (CRT) may be improved by optimization of device parameters using echocardiography. For this purpose, the aortic velocity-time integral (aVTI) has been used as a target metric to define optimal velocity timings for each ventricle. dP/dt is a parameter used for the assessment of myocardial contractility. In this study, we aimed to evaluate the effectiveness of Doppler-derived dP/dt in optimization by assessing the possible correlation between aVTI and dP/dt. Patients with CRT admitted for routine follow-up were included in the study. Aortic VTI and dP/dt measurements were recorded in four different standard pacing configurations during reprogramming. A total of 45 patients were included in the final analysis. No correlation was found between the aVTI and the delta dP/dt value in the two configurations where the change in dP/dt was maximum (p = 0.894). In the two configurations where the change in aVTI was maximum, there was also no correlation between the delta dP/dt and the delta aVTI (p = 0.715). When patients were dichotomized according to the median value of dP/dt, there were no differences in aVTI, NYHA classes, LVEF, and mitral regurgitation (MR) severity (p = 0.4; p = 0.5; p = 0.7; p = 0.3; respectively). The change in both dP/dt and aVTI was statistically significant when switching from RV-only to QRS width-targeted configuration (p = 0.001; p = 0.041; respectively). In conclusion, aVTI recorded at different pacing configurations did not correlate with dP/dt during interventricular optimization. However, both parameters consistently showed a positive effect of biventricular pacing on contractile synchronization and stroke volume.

An Improved Longitudinal Driving Car-Following System Considering the Safe Time Domain Strategy.

Car-following models are crucial in adaptive cruise control systems, making them essential for developing intelligent transportation systems. This study investigates the characteristics of high-speed traffic flow by analyzing the relationship between headway distance and dynamic desired distance. Building upon the optimal velocity model theory, this paper proposes a novel traffic car-following computing system in the time domain by incorporating an absolutely safe time headway strategy and a relatively safe time headway strategy to adapt to the dynamic changes in high-speed traffic flow. The interpretable physical law of motion is used to compute and analyze the car-following behavior of the vehicle. Three different types of car-following behaviors are modeled, and the calculation relationship is optimized to reduce the number of parameters required in the model's adjustment. Furthermore, we improved the calculation of dynamic expected distance in the Intelligent Driver Model (IDM) to better suit actual road traffic conditions. The improved model was then calibrated through simulations that replicated changes in traffic flow. The calibration results demonstrate significant advantages of our new model in improving average traffic flow speed and vehicle speed stability. Compared to the classic car-following model IDM, our proposed model increases road capacity by 8.9%. These findings highlight its potential for widespread application within future intelligent transportation systems. This study optimizes the theoretical framework of car-following models and provides robust technical support for enhancing efficiency within high-speed transportation systems.