Decrease In Velocity Research Articles

A new Adomian decomposition technique for a thermal analysis forced non-Newtonian magnetic Reiner-Rivlin viscoelastic fluid flow

This paper presents a new semi-analytical method, called the Adomian Decomposition Method (ADM), as well as Finite Element Methods, to study forced Reiner-Rivlin non-Newtonian Magnetohydrodynamic (MHD) fluid motion confined between two disks. The innovation presented in this paper is the utilization of both analytical and numerical methods, namely ADM and FEM, to solve coupled linear differential equations, which enables the calculation and examination of parameters such as heat transfer and fluid velocity between the two disks by simplifying these equations. This model incorporates the magnetic field, and the system of partial differential equations (PDEs) acts as the governing equation in this study, which are then transformed into a set of non-linear ordinary differential equations (ODEs) using von Karman analog variables. The Adomian decomposition method can be used to solve ODEs that are related to boundary conditions. The main findings of this article suggest that as the dimensionless force parameter increases, the displacement of the fluid velocity decreases, as the particles collide with each other, the temperature gradient around the disks decreases inversely. Moreover, when the stress tensor increases, the heat transfer rate reaches its maximum value, and the transverse velocity gradient between different disks decreases.

Delamination characterization in thin asphalt pavement structure using dispersive GPR data

Detection of delamination in asphalt pavement by non-destructive ground penetrating radar (GPR) is useful for effective maintenance and repair. However, limitations of GPR survey resolution and multiple wave interferences have made thin delamination layer characterization a challenging task in conventional common offset profiling (COP) mode. In this paper, a new method is proposed for characterizing delamination layers in asphalt pavement using the GPR waveguide dispersion model in a wide-angle reflection and refraction (WARR) configuration. The approach was validated through synthetic experiments and laboratory experiments using an asphalt pavement model. The results show that the cutoff frequencies of all modes are sensitive to air-filled delamination, while water-filled delamination leads to a significant decrease in the phase velocity of GPR waves. By observing these trends, we are able to detect delamination layers with 1 cm thickness and identify delamination layers with different properties. This new method can aid in the detection and identification of delamination layers in asphalt pavement structures.

Increased Riparian Vegetation Density and Its Effect on Flow Conditions

The physical and biological structure of riparian vegetation fundamentally influences floodplain roughness, and thus the flood velocity and flood levels of a river. The study aims to provide detailed spatial data on the vegetation density of a floodplain, and to model the effect of the actual vegetation and various scenarios on flow conditions. LiDAR data were applied to evaluate the density and roughness of the submerged understory vegetation over the densely vegetated floodplain of Lower Tisza, Hungary. Then, HEC–RAS 2D modelling was applied to analyse the effect of the actual vegetation on flow conditions. Further scenarios were also created to predict the effect of (i) invasive plant control, (ii) no maintenance, and (iii) riparian vegetation restoration (meadows). According to the results, since the 19th Century, the increased vegetation density is responsible for a 17-cm flood level increase, and if the vegetation grows even denser, a further 7 cm could be expected. As the vegetation density increases, the overbank flow velocity decreases, and the crevasses and flood conveyance zones gradually lose their function. Simultaneously, the flow velocity increases in the channel (from 1 m/s to 1.4 m/s), resulting in an incision. Applying LiDAR-based 2D flow modelling makes it possible to plan sustainable riparian vegetation maintenance (e.g., forestry, invasive species clearance) from both ecology and flood control perspectives.

Evaluation of the Effect of Surface Irregularities on the Hydraulic Parameters within Unlined Dam Spillways

Erosional incidents have heightened the necessity of studies regarding rock mass erosion in unlined dam spillways. Enhanced comprehension of hydraulic erodibility necessitates an investigation into the geomechanical and hydraulic aspects of erosional phenomena. Controlled blasting is commonly employed to establish unlined spillways in rock masses, and this process results in irregularities along the spillway surface profile. Recent research has identified key geometric parameters of rock masses that impact erosion in unlined spillways, such as joint opening, dip and dip direction, and joint spacing. However, the effect of spillway surface irregularities on hydraulic parameters remains uncertain. Numerous studies have examined the surface roughness of rock at the millimeter scale within the domain of hydraulic engineering. Despite these efforts, a noticeable gap persists in our understanding of how surface irregularities specifically exert influence over hydraulic parameters. Currently, there is a lack of a clear equation or methodology to incorporate irregularities into hydraulic erosive parameters. The main aim of this study is to show how such irregularities affect the hydraulic parameters. This study is dedicated to emphasizing the importance of considering these irregularities. Building upon the findings obtained, the core aim of this research is to facilitate the formulation of an equation in future investigations that effectively accounts for these irregularities when calculating hydraulic erosive parameters. To assess the significance of surface irregularities in unlined spillways, computational fluid dynamics (CFD) with ANSYS-Fluent software was employed to analyze 25 configurations of spillway surface irregularities and their effects on various factors, including pressure (total, dynamic, and static pressures), shear stress, flow velocity, and energy. The findings indicated that irregularities significantly influenced the hydraulic parameters. Specifically, an increased irregularity height led to a decrease in maximum velocity, total pressure, and shear stress. Conversely, total energy loss increased, amplifying the rock mass’s vulnerability to erosion due to these irregularities.

Effect of Combustor Outlet Geometry on Operating Characteristics of Disk-Shaped Rotating Detonation Engine

A disk-shaped rotating detonation engine with H2/air mixture was tested to identify the impact of combustor outlet geometry on the engine’s operating characteristics. Three combustor outlet diameters and five outlet lengths are employed in the experiments. Results show that with the increase of combustor convergent ratio, the propagation stability of the rotating detonation wave decreases, and the propagation velocity and pressure peak decrease slightly. When the convergent ratio increases to a certain value (1.70 in this study), a “platform zone” with a lower pressure value appears before the sharp rise of the dynamic pressure curve. The propagation mode varies with the increase of mass flow rate at different convergent ratios. As the mass flow rate increases, the wave head number in the combustor increases. But the change rule of propagation mode with mass flow rate is greatly affected by convergent ratio. Increasing the convergent ratio is conducive to the formation of multi-wave modes, and the critical mass flow rate for mode transition drops sharply. When the convergent ratio increases to 1.70, the unstable asymmetric dual-wave mode is obtained. With the increase in the convergent ratio, the engine’s operating range and operating stability decrease significantly. Finally, changing the combustor outlet length has little influence on the engine’s operating characteristics and detonation-wave parameters.

Efficacy and Safety of Triptorelin 3-Month Formulation in Chinese Children with Central Precocious Puberty: A Phase3, Open-Label, Single-Arm Study.

Triptorelin is available as 1- and 3-month prolonged-release (PR) formulations; at the time of the study, only the former was approved for central precocious puberty (CPP) in China. This study assessed the efficacy and safety of the triptorelin 3-month PR formulation in Chinese children with CPP. In this 12-month, prospective, open-label, multicentre, single-arm study (NCT04736602), Chinese children (mean age [standard deviation (SD)], 7.6 ± 0.8years) with CPP received triptorelin pamoate 15mg on day1 and at months 3, 6 and 9. The primary endpoint was the proportion with luteinizing hormone (LH) suppression (stimulated peak LH ≤ 3IU/L after gonadotropin-releasing hormone [GnRH] stimulation) at month 3. Secondary endpoints included changes from baseline in hormone levels and clinical parameters, as well as safety assessments. Overall, 32 children were enrolled, including three boys. LH suppression to prepubertal levels (≤ 3IU/L) after GnRH stimulation was observed in 100%, 93.5% and 93.5% of participants at months 3, 6 and 12, respectively. Basal and peak LH and follicle-stimulating hormone levels were substantially suppressed at months 3, 6 and 12, and most participants showed sex hormone suppression. At months 6 and 12 respectively 92.9% and 89.3% of girls had stable breast development, and all boys had stable genital development. There was a decrease in mean growth velocity from baseline (8.96cm/year) to months 3, 6 and 12 (8.07, 5.24 and 6.94cm/year, respectively). The mean difference between bone and chronological age decreased from baseline (2.85years) to month 12 (2.39years). In girls, uterine length was stable or reduced at month 12; in boys, testicular volume was reduced. Triptorelin was well tolerated. The triptorelin 3-month PR formulation demonstrated similar efficacy to that previously reported in non-Chinese patients with CPP and had an acceptable safety profile. This supports triptorelin 3-month PR as a viable option for Chinese children with CPP.

Effects of freeze-thaw cycling on the engineering properties of vegetation concrete

Vegetation concrete has been widely applied for the ecological restoration of bare steep slopes in short-term frozen and non-frozen soil regions in China. However, field experiments conducted in seasonally frozen soil regions have revealed decreases in the bulk density, nutrient content and vegetation coverage. This study aimed to clarify the evolution process and mechanism of the engineering properties of vegetation concrete under atmospheric freeze-thaw (F-T) test conditions. The physical, mechanical, and nutrient properties of vegetation concrete were investigated using six F-T cycles (0, 1, 2, 5, 10 and 20) and two initial soil water contents (18 and 22%). The results revealed decreases in the acoustic wave velocity and cohesive forces and an increase in the permeability coefficient of the vegetation concrete owing to F-T action. X-ray diffraction tests indicated that the decreased cohesive force was closely related to the overall decrease in the content of gelling hydration products in the vegetation concrete. Additionally, the contents of NH4+–N, PO43–P and K+ in the vegetation concrete increased, whereas that of NO3−–N decreased. The loss rates of these soluble nutrients increased, indicating that the nutrient retention capacity of the vegetation concrete had decreased. Specifically, the decreased nutrient retention capacity was mainly related to the disintegration and fragmentation of larger aggregates due to F-T action. This study provides theoretical support for future research on improving the anti-freezing capability of ecological slope protection substrates in seasonally frozen soil regions.

Developmental and neurobehavioral toxicity of 2,2′-methylenebis(6-tert-butyl-4-methylphenol) (antioxidant AO2246) during the early life stage of zebrafish

Background2,2′-Methylenebis (4-methyl-6-tert-butylphenol) (AO2246) is a synthetic phenolic antioxidant extensively used in food packaging bags and cosmetics. Recently, AO2246 was detected with unexpectedly high concentrations in plasma and breast milk samples from pregnant and lactating women. Hence, it is essential to conduct a thorough investigation to evaluate the detrimental effects of AO2246 on biota. ObjectiveTo investigate the developmental and behavioral toxicity of AO2246 in zebrafish, as well as the molecular mechanisms underlying these effects. MethodsZebrafish embryos were exposed to AO2246 at concentrations ranging from 0.05 to 10 μM for up to 6 days postfertilization (dpf). Hatching rate, survival rate, heart rate, and body length were measured. Locomotor behavioral and electrophysiologal analyses were performed. Two fluorescence-labeled transgenic zebrafish lines (endothelium-Tg and macrophage/microglia-Tg) were employed. RNA sequencing was carried out. ResultsAO2246 has a 96-hour LC50 value of 3 μM. The exposure of AO2246 resulted in a significant reduction in both hatching rate and heart rate. Analysis of locomotor behavior demonstrated that larvae exposed to AO2246 doses exceeding 2 μM exhibited a significant decrease in both total distance and mean velocity. Electrophysiological recordings demonstrated a noteworthy reduction in spike activity at a concentration of 3 μM, relative to control conditions. The administration of AO2246 at 3 μM elicited morphological reactivity and immune alteration of the midbrain microglia in the macrophage/microglia-transgenic zebrafish line, indicating a potential contribution of neurological disorders to behavioral defects. RNA sequencing analysis revealed altered gene expression profiles at high AO2246 concentrations, particularly the dysregulation of pathways associated with neuronal function. ConclusionsThe present study demonstrates that AO2246 exposure elicits developmental and neurobehavioral toxicity in zebrafish larvae. Specifically, exposure to AO2246 was found to cause disturbances in neuronal electrophysiological activity and neurological disorders, which ultimately led to the impairment of locomotor behavior in zebrafish larvae.

Exploring the effects of turbulent field on propagation behaviors in confined hydrogen-air explosion using OpenFOAM

Explosion always happens in turbulent field, which is hard to measure in reality. This paper explores the influence of turbulent kinetic energy on the propagation behaviors of flame and pressure of stoichiometric hydrogen-air explosion in confined vessel, using large eddy simulation. The momentum equation and progressive variable equation are adapted to consider interaction of turbulence and flame. The results reveal that with initial turbulent kinetic energy increasing, its promoting effects on flame and pressure propagation weaken. For flame at low initial turbulent kinetic energy and low initial pressure, it undergoes three propagating stages: acceleration, steady propagation and deceleration. In addition, flame deceleration is caused by rapid decrease of flow velocity which falls faster with initial turbulent kinetic energy increasing. Furthermore, explosion pressure propagates faster with initial turbulent kinetic energy increasing. Sharp fluctuation of flow velocity appears in the flame zone where big pressure gradient exists.

Heat transfer characteristics in nanochannels with rough walls based on capillary flow: A molecular dynamics study

Passive micro/nanoscale cooling based on capillary flow has become a promising and widely used thermal management technology for electronic devices. In this study, nanochannels with different surface roughness are established based on the chord function, and the capillary flow and heat transfer in different nanochannels are investigated by molecular dynamics simulation. Compared with smooth walls, rough walls retard capillary flow, and the heat transfer process also affects capillary flow to some extent. The region of low potential energy is much larger near rougher walls in nanochannels. When fluid flows through a depression on a wall, the velocity decreases, resulting in an uneven flow velocity. An analysis of the temperature field, Nusselt number and heat transfer amount shows that although rougher structure causes more atoms to gather, thus improving the heat transfer rate, it reduces the total heat transfer amount due to reduced capillary flux. The microscopic mechanism of the impact of surface roughness on capillary flow and heat transfer is revealed at the atomic scale by potential energy analysis. Furthermore, increasing solid-liquid interaction hinders capillary flow, but it increases the heat transfer rate at the solid-liquid interface.

4D Seismic Inversion and Rock Physic Modeling to Monitor CO2 Injection at Carbon Capture and Storage Project in The Utsira Formation, Sleipner Field, North Sea, Norway

Carbon Capture and Storage (CCS) is used at Sleipner Field due to the implementation of a carbon emission tax off the coast of Norway. This project causes the fluid at the Utsira Formation as a reservoir to be replaced by CO2, so the elastic property of the reservoir rock will change. Because of that, the 3D seismic survey was carried out in 1994 (baseline) and re-acquisition in 2001 (monitor) to observe CO2 distribution and changes in rock properties. This study aims to monitor the distribution of CO2 as well as changes in reservoir rock's acoustic and elastic parameters. This research performed the cross-equalization, 4D Seismic Inversion model-based, and rock physics modeling process. From data processing, obtained information that CO2 spreads laterally, then moves to the northeast and does not penetrate the overburden. Also, we get the NRMS value of 0.443068 and the cross-correlation value of 0.907426. 4D Inversion results reveal a change in the reflector at the reservoir zone, as indicated by the velocity pushdown caused for a decrease in seismic velocity owing to CO2. In addition, rock physics modeling provides that changes occur in bulk modulus, Vp, Vs, density, and AI. From the process, there are differences in AI values where the Inversion results show a decrease in AI values of 2.9%, while rock physics modeling shows a 12% reduction.

Time-lapse imaging of seismic scattering property and velocity in the northeastern Japan

Investigating spatio-temporal changes in crustal structure is a key to understanding the dynamic processes in the earth's crust associated with large earthquakes and volcanic activities. The dense seismic network in the northeast part of Japan (Tohoku region) allows us to apply seismic interferometry to continuous records of ambient noise data for studying crustal changes related to the 2008 Mw 6.9 Iwate-Miyagi Nairiku earthquake and the 2011 Mw 9.0 Tohoku-oki earthquake. We track changes in both seismic scattering properties and velocities over five years and spatially localize them based on the coda wave decorrelation and travel time sensitivity kernels calculated from the solution of the radiative transfer equation. The 2008 Iwate-Miyagi Nairiku earthquake caused significant changes in both seismic scattering properties and seismic velocities in the vicinity of the epicenter subjected to dynamic or/and static stress perturbations. Changes in scattering properties associated with the 2011 Tohoku-Oki earthquake around some active volcanoes in the Tohoku region are likely related to geofluid migrations triggered by strong vibrations during the large earthquake. The decrease in seismic velocity exists mainly along the eastern coastal region and extends to the central Quaternary volcanic chains under the combined dynamic and static stress changes by the earthquake. The waveform correlation is possibly sensitive to the fluid content and might be a useful indicator of fluid migration in the crust. This is the first comprehensive demonstration and comparison of the spatio-temporal changes of seismic scattering properties and velocities at long-term and regional scales under the influence of two large earthquakes.

The Development and Investigation of the Diffusion-Stabilizing Burner with the Niche

The article presents the results of researches of the development and field tests in bench conditions of the microdiffusion stabilizer burner device of a rectangular slot type with a niche deepening along the entire perimeter of the burner. The air passes through a rectangular slot, gaseous fuel for combustion is supplied to the recirculation zone through a system of holes in the end wall of the stabilizer. On the side of the output end of the stabilizer, there is a niche deepening. As studies have shown, the niche deepening is an additional source of stabilization and intensification of torch burning. The experimental data and calculated dependences on the stabilization of the torch in the modes of “poor” disruption are obtained. It is shown that the stable operation of the burner on the lean limit expands – the coefficient of excess air increases with an increase in the width of the stabilizer, the diameter of the gas distribution holes, the coefficient of shading of the burner and air temperature, as well as with a decrease in the speed of the air flow. The research results showed that “rich” flame failure – flame failure with a gradual increase in gas flow occurs at air excess ratios less than unity. This ensures the reliable operation of the burner at the calculated operating modes with respect to the coefficient of excess air a = 1.15 – 6.0 and the air flow speed Wp = 12.0 m/s. A dependence was obtained that determines the influence of regime and design factors on the characteristics of a rich flare failure. The sustainability of the burner operation on the rich limit increases – the coefficient of excess air decreases, with an increase in the width of the stabilizer, the shading coefficient of the burner, air temperature and a decrease in air velocity. The experimental data and calculated dependences on the length of the combustion zone in the burner device are obtained. It was established that at the calculated coefficient of excess air a = 2.0 and higher coefficients, complete combustion of fuel occurs on the length of the combustion space X = 1000 mm. The relative length of the flame decreases when the shading coefficient of the burner and the air temperature increases. Measurements of harmful nitrogen oxides showed that the maximum content of oxides is observed at the coefficient of excess air a = 1.0 and is 125 mg/m3, which is less than the limit values which allowed by regulatory documents.

Forced convective heat transfer for Stokes flow including viscous dissipation in arbitrary corrugated channels

AbstractThe forced convective heat transfer for Stokes flow, including viscous dissipation in arbitrary corrugated channels, is studied using both an asymptotic method and a numerical solution. The aim is to specify the range of shape parameters for which the validity of the asymptotic approach is ensured, particularly regarding the characteristics of heat transfer. The axial velocity, transversal velocity, pressure, and temperature, for small corrugation's slope compared with unity, are sought as an asymptotic expansion in terms of a parameter that represents the corrugation's slope. The numerical solution is obtained by using ANSYS Fluent solver. Additionally, Python scripting is integrated to automate several parts of the simulations, including the creation of the geometry and a parametric study. Three different types of corrugations are investigated including zigzag, sinusoidal, and arbitrary corrugations defined using a function given by a particular case of the Fourier series. The Nusselt number is calculated to evaluate convective heat transfer. It is found that the asymptotic and numerical solutions for small corrugation's slope, are in good agreement with negligible quantitative differences. However, as the corrugation's slope increases (approaches unity), these quantitative differences increase up to cases where a change in the behavior of the local Nusselt number is observed. The results show that the local Nusselt number decreases in the channel's region with divergent walls due to the decrease in the average velocity. In contrast, it increases in the channel's region with convergent walls due to the increase in the average velocity.

Abstract P2164: Expression Of Engineered Bacterial Sodium Channel Improves Cardiomyocyte Contractility

Introduction: Our recent studies in non-human primates have demonstrated adeno-associated virus (AAV) delivery of prokaryotic sodium channel (BacNa v ) can improve the contractile function of infarcted hearts. We hypothesized that BacNa v expression increases cardiomyocyte (CM) contractile function by indirectly augmenting Ca 2+ transient amplitude via increase in sarcoplasmic reticulum (SR) Ca 2+ stores. Methods: We developed an in vitro model of ischemia-reperfusion (I/R) injury in engineered heart tissues (cardiopatches) made from human iPSC-derived CMs (hiPSC-CMs). Prior to formation, tissues were transduced with lentivirus conferring a doxycycline (Dox)-inducible expression of BacNa v . Upon I/R injury, the tissues were treated with either vehicle or Dox for 48h followed by force testing and Ca 2+ imaging. The effect of BacNa v expression on Ca 2+ handling was additionally studied using neonatal rat ventricular myocytes (NRVMs). Results: The tissue injury from I/R was evident from increases in cleaved-caspase 3 area (0.25% vs 1.53%), ROS generation (1.2 fold), LDH release (4.1 fold), and percent dead cells (0.97% vs 4.67%). Immediately following the I/R injury, tissues showed decrease in contractile force (2.78mN vs 0.74mN) and conduction velocity (20.7cm/s vs 7.9cm/s). At 72hr post-injury, BacNa v -expressing tissues exhibited significantly higher contractile force (1.67mN vs 1.32mN) and Ca 2+ transient (1.8 fold) amplitudes compared to the vehicle control. Furthermore, in uninjured NRVM monolayers, BacNa v expression resulted in higher Ca 2+ transient amplitude (1.31 fold), as well as increased SR calcium stores (1.3 fold) and slower sodium/calcium exchanger (NCX) extrusion rate (1.03s -1 vs 0.82s -1 ) in the presence of caffeine. Blocking NCX with 10M ORM-10962 eliminated the difference in Ca 2+ transient amplitude between BacNa v -expressing and control CMs. Conclusion: Our results suggest BacNa v expression augments CM contractility and Ca 2+ transient amplitude, at least in part through the suppression of Ca 2+ efflux mode of the NCX. In addition to its antiarrhythmic effects, BacNa v gene delivery may represent an effective therapeutic strategy to improve cardiac contractility in congestive heart failure.

Migration of Mechanical Perturbations Estimated by Seismic Coda Wave Interferometry During the 2018 Pre‐Eruptive Period at Kīlauea Volcano, Hawaii

AbstractWe use seismic ambient noise correlation and coda wave interferometry to estimate velocity variations at high temporal resolution, during the pre‐eruptive period and the onset of the 2018 eruption of Kīlauea volcano. A progressive velocity increase is observed from March to the end of April. It is followed by rapid decrease starting a few days before the onset of the East Rift Zone (ERZ) eruption and then by sharp velocity drop when the eruption started. The change of trend from velocity increase to decrease is progressively delayed by a few days from the summit caldera toward the ERZ. The location of the velocity perturbations shows a migration of the sources of velocity changes from the summit caldera toward the ERZ before the eruption. Using a model of pressure source, we show that the simultaneous caldera inflation and velocity increase probably result from an anisotropic distribution of fault and crack orientations. The velocity decrease could be due to damaging processes above the shallow reservoir and to plastic deformations around the caldera. We introduce a forward model of rock damage associated with the volcano‐tectonic seismicity to calculate the velocity decrease. The good agreement between the calculated and the observed velocity variations shows that a large part of the velocity decrease results from damage of the medium. The delayed onsets of velocity decrease and the source migration of velocity perturbations are probably related to progressive fault openings in the Southern and Eastern parts of the caldera and to magma transfer toward the ERZ.

Early Results of Surface Tomography Using Automated Surface-Wave Phase-Velocity Measuring System (ASWMS) in Hawaii

The Hawaiian Islands are a prominent place to conduct seismicity research. Geologically, occurring earthquakes in this region are unique since it is caused by the presence of a hot spot rather than the common fault activity. The research was conducted using a tomography method called Surface Wave Tomography. The goals of this study are to produce tomographic images of the Hawaiian Islands and to test the accuracy of the Automated Surface-Wave Phase-Velocity Measuring System (ASWMS). ASWMS employs a cross-correlation process to calculate the phase delay between stations, then Eikonal equation to invert the slowness vector to obtain apparent phase velocities, and lastly Helmholtz equation to correct the amplitude to obtain structural phase velocities. The teleseismic data used in this study were collected from stations located throughout the Hawaiian Islands between 2004 and 2009. This study discovered a low-velocity anomaly beneath the Hawaiian Islands with a value of 3.8 – 3.9 km/s, indicating the presence of a low-velocity body. The decrease in velocity with increasing depth suggests an increase in temperature associated with the path that magma takes from the Earth’s mantle to the Earth’s crust beneath the Hawaiian Islands.

Analysis of motion characteristics of lower limb exoskeleton robot

To address the issue of motion coordination in lower limb exoskeleton rehabilitation robots, and to meet the basic characteristics of ergonomics and human kinematics, a humanoid design was adopted to design a lower limb exoskeleton rehabilitation robot. The Denavit- Hartenberg (D-H) mathematical model of the lower limb exoskeleton rehabilitation robot was established, and the motion characteristics of each joint were analyzed to obtain the D-H parameters during the motion process. The motion characteristics were analyzed from the perspectives of forward kinematics and inverse kinematics. The variation law of motion parameters during the motion process was obtained, and simulation analysis of the motion characteristics was performed. The results show that the maximum center of mass velocity is 0.45 m/s, which is reached within 0.8 seconds. After that, the velocity decreases, with a range of approximately -0.2 m/s to 0.55 m/s. It can be seen that the displacement and velocity changes of the exoskeleton robot legs are relatively stable, which meets the design requirements.

Comprehensive Simulation Research on Microprocess and Macroscopic Electromagnetic Signals of Surface Discharge in SF6

The surface discharge on the dielectric is a common type of partial discharge in GIS, but the microscopic development process of surface discharge in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> is unclear. To find out the micro-process of surface discharge and its correlation mechanism with the partial discharge detection signals of GIS, the fluid-chemical simulation model of the streamer is used to simulate the micro-process of surface discharge in SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> . Then the current signal obtained by the micro-process simulation is used as the excitation to simulate the electromagnetic signals based on the FITD method. A close connection between the microscopic discharge and the macroscopic signals is established. The results show that the electron concentration at the streamer head and the streamer velocity decrease first and then increase during the discharge, with an average velocity of about 9.84×105m/s. The discharge current reached a peak value of about 0.22A when the surface streamer reaches the cathode. In terms of waveform correlation, the absolute value of the average correlation coefficient between the electric field signals simulated in this paper and the actual measured signals is above 0.7, which is much higher than the simulated signal excited by the Gaussian source. By changing the applied voltage and comparing with the experiment results, it is found that the simulation method in this paper can reflect the change of signals under the influence of external conditions. As the applied voltage rises, the amplitude of the electric field signals increases, and the main frequency component on the frequency spectrum grows, with the main frequency value at about 1.2 GHz. The research in this paper is an effective supplement to the existing study on the microscopic mechanism of partial discharge signals.

Microconvection of MHD solarized nanofluid in the presence of double slip and surface suction

Refrigeration systems are becoming more efficient as a result of nanofluids. Cooling and heating process improvements can lead to enhanced industrial efficiency, reduced processing times, energy conservation, and improved heating and cooling processes. A study is being conducted on the effects of magnetohydrodynamics (MHD) in nanofluids by adding double slip and thermal radiation to the governing model. It is numerically simulated using bvp4c code in MATLAB. Analyzing temperature, concentration, and velocity requires the evaluation of multiple parameters. A more uniform distribution of temperatures can be achieved by increasing the Biot number, thermal radiation, and thermophoretic motion parameters. The use of suction is an effective method of controlling the rate of temperature reduction in various manufacturing processes. A product's mechanical properties and overall quality can be enhanced if one is able to control how quickly it cools during the process of melting and condensing raw materials. As a consequence of the emergence of quadratic and linear slip factors, the flow velocity decreases. A distinguishing feature of this research is the use of boundary conditions that are tailored to the geometry that is being investigated.