Horizontal And Vertical Research Articles

Research on the Relative Placement Angle of the Induction Heater and the Channel in a Four-Channel Induction-Heating Tundish.

In order to optimize the application effect of induction heating (IH) tundishes, a four-channel IH tundish is taken as the research object. Based on numerical simulation methods, the influence of different relative placement angles of induction heaters and channels on the electromagnetic field, flow field and temperature field of the tundish is investigated. We focus on comparing the magnetic flux density (B) and electromagnetic force (EMF) distribution of the channel. The results show that regardless of the relative placement angle between the heater and the channel, the distribution of B in the central circular cross-section of the channel is eccentric. When the heater rotates around channel 1 towards the bottom of the tundish, the distribution of B in the central circular cross-section of the channel changes from a horizontal eccentricity to a vertical one. Through the analysis of the B contour in the longitudinal section of the channel, the difference in effective magnetic flux density area (ΔAB) between the upper and lower parts of the channel can be obtained, thereby quantitatively analyzing the distribution of B in this section. The distribution pattern of ΔAB is consistent with the distribution pattern of the electromagnetic force in the vertical direction (FZ) of the channel centerline. The ΔAB and FZ of channel 1 gradually increase as the heater rotates downwards, while those of channel 2 reach their maximum value at a rotation angle of 60°. Compared to the conventional placement, when the heater rotation angle is 60°, the outlet flow velocities at channel 1 and channel 2 decrease by 15% and 12%, respectively. However, the outlet temperature at channel 2 increases by 1.96 K, and the molten steel flow at the outlet of channel 1 and channel 2 no longer exhibits significant downward flow. This shows that when the heater rotation angle is 60°, it has a dual advantage. On the one hand, it is helpful to reduce the erosion of the molten steel on the channel and the bottom of the discharging chamber, and on the other hand, it can more effectively exert the heating effect of the induction heater on the molten steel in the channel. This presents a new approach to enhance the application effectiveness of IH tundish.

Deteksi Tepi Sederhana Pada Citra Menggunakan Operator Sobel

implemented and evaluated the edge detection method using the Sobel Operator, which calculates the gradient of image intensity through two convoluted kernels for horizontal (Gx) and vertical directions. (Gy). The magnitudo gradient is obtained from the combination of both such directional gradients to represent the edge force on each pixel. The main steps include image pre-processing, the application of the Sobel kernel, the calculation of magnitudo gradients, and the filtering of results to extract significant edges. The results show that the Sobel Operator is effective in highlighting intensity differences that indicate the boundary of the object, although it is sensitive to noise and less accurate for fine edges. Despite its limitations, this method is simple to implement and useful as an initial step in image processing applications such as segmentation, pattern identification, and object shape analysis.

A Vertical Surface Flow Analysis of MHD Nanofluids Influenced by Radiation, Viscous Dissipation, and Joule Heating with Soret and Dufour Effects

The purpose of this study is to investigate the effects of radiation and activation energy on mass transfer nanofluids flowing across an expanding sheet in a vertical direction, as well as joule heating, viscous dissipation, Soret and Dufour, and magnetohydrodynamic (MHD) flow. The boundary layer (BL) equations for nonlinear momentum, energy, solute, and nanoparticle volume fraction are reduced by using similarity transformations. After that, the shooting technique and bvp4c are used to numerically solve the boundary layer equations. Schmidt and Eckert’s numbers, along with Soret effects on velocity, temperature, and the volume percentage of nanoparticles, cause an increase in skin friction. Fluid temperature rises significantly with Eckert number. As the Dufour and Schmidt numbers rise, so does the local Nusselt number. A greater thermophoresis parameter, enhanced skin friction, and an increased Schmidt number.

Eyebox expansion of a lensless near-eye display using diverging spherical wave illumination and a multiplexed holographic optical element

We expand the eyebox size of a lensless holographic near-eye-display (NED) using passive eyebox replication technique that incorporates a spatial light modulator (SLM) and a holographic optical element (HOE). In holographic NEDs, the space-bandwidth product (SBP) of the SLM determines the exit pupil dimensions and corresponding eyebox size. The base eyebox size is replicated in the horizontal direction by using the horizontal high-order diffractions of an SLM under spherical wave illumination and a multiplexed HOE combiner. When a digital blazed grating and a digital lens phase are added to the computed phase hologram sent to the SLM, two spatially separated, horizontal high-order diffraction terms with identical intensity and information can be uniformly formed without the zero-order term. When the eyebox size is expanded, the field-of-view (FOV) is not sacrificed; spherical divergence wave illumination alleviates the need for a tradeoff between FOV and eyebox size. The astigmatism introduced during HOE fabrication is counterbalanced by pre-correcting the target image using a computer-generated, holographic computation algorithm. The prototype system shows simple and effective, distortion-free eyebox expansion of a wide-angle, lensless, holographic NED.

Taking inspiration from the natural tubular sponge to enhance momentum exchange in marine environments

Coral reefs consist of various alive elements with specific biological functions. Tubular sponges, as the main coral reefs' constituents, have a marvelous mechanism. They receive nutrients by suctioning from the perforated body (Ostia) and pumping the un-digested materials through the water column from the top mouth (Osculum). This mechanism can be an inspiration for making a device to control or improve sediment/pollutant transport. In the current study, an attempt has been made to evaluate an inspired concept's effects on flow hydrodynamics. In this regard, OpenFOAM® V. 1812 (interFOAM solver) and image processing technique were deployed. The perforated finite-height cylinders (height to diameter ratio of 2.5) with various suction/pump discharges (i.e., J = 150, 300, 350, 400, 450, and 600 lit/h) were considered. The results indicated that increasing the outflow discharge (J ≥ 600 lit/h) could widen the wake by flapping the shear layer. In the vertical plane, the results showed that dipole vortices turned into quadrupole vortex. On the free surface, tip-vortices and counter-rotating vortex pairs (CRVP) generated saw-toothed vortices on two sides of the cylinder. Generating these unique vortices is proof of enhancing the momentum exchange through the water column.

Interlayer Delocalized Electrons Activate Basal Plane for Ultrahigh-Current-Density Hydrogen Evolution.

The basal plane of transition metal dichalcogenides (TMDCs) is inert for the hydrogen evolution reaction (HER) due to its low-efficiency charge transfer kinetics. We propose a strategy of filling the van der Waals (vdW) layer with delocalized electrons to enable vertical penetration of electrons from the collector to the adsorption intermediate vertically. Guided by density functional theory, we achieve this concept by incorporating Cu atoms into the interlayers of tantalum disulfide (TaS2). The delocalized electrons of d-orbitals of the interlayered Cu can constitute the charge transfer pathways in the vertical direction, thus overcoming the hopping migration through vdW gaps. The vertical conductivity of TaS2 increased by 2 orders of magnitude. The TaS2 basal plane HER activity was extracted with an on-chip microcell. Modified by the delocalized electrons, the current density increased by 20 times, reaching an ultrahigh value of 800 mA cm-2 at -0.4 V without iR compensation.

Simulation of landslide dam failure due to overtopping considering vertical soil particles distribution

Accurate prediction of potential landslide dam breaches is crucial for timely and effective emergency responses to the resulting flood. Although many models for landslide dam overtopping have been proposed in past studies, most of these models did not consider the heterogeneity of dam materials, which is important in reflecting the erodibility of soil. In this study, a new mathematical model for landslide dam breaches due to overtopping was proposed based on a constructed vertical distribution model of dam particle size. Two real-world dams, the Tangjiashan landslide dam and Baige landslide dam, were used to evaluate the performance of the proposed model. In addition, the proposed model was compared with four existing dam failure models, and sensitivity analysis was conducted on the median particle size and particle size distribution. The results demonstrate that the computational outcomes of the proposed model align more closely with the actual results, indicating that the proposed model outperforms the four existing models in accurately simulating the landslide dam failure process. It also suggests that ignoring the variation of dam material particle size along the vertical direction inside the dam body would increase the prediction relative errors of key breach outcomes.

Sensor-Less Control of Mirror Manipulator Using Shape Memory Polyimide Composite Actuator: Experimental Work.

Integrated thin film-based shape memory polyimide composites (SMPICs) are potentially attractive for efficient and compact design, thereby offering cost-effective applications. The objective of this article is to design and evaluate a mirror manipulator using an SMPIC as an actuator and a sensor with control. A sensor-less control strategy using the SMPIC (a self-sensing actuator) with a proportional derivative combined variable structure controller (PD-VSC) is proposed for position control of the mirror in both the vertical and angular directions. The mirror manipulator is able to move the mirror in the vertical and angular directions by 3.39 mm and 10.5 deg, respectively. A desired fast response is obtained as the performance under control. In addition, some benefits from the proposed control realization include good tracking, stable switching, no overshoot, no steady state oscillations, and robust disturbance rejection. These superior properties are experimentally validated to reflect practical feasibility.

Kinematic characteristics analysis of highly difficult movements "324C+1D" of the first level Wushu athletes

Background "324C+1D” movements are key techniques and winning factors in Wushu competitions. It is necessary for scientific training to analyze the kinematic characteristics of “324C+1D” by using the method of sports biomechanics. Methods In this study, 3D high-speed camera and 3D motion analysis software were used to study “324C+1D” completed by three Chinese wushu first-level athletes, and the kinematic characteristics of this movement were obtained. Results The run-up speed of completing the “324C+1D” is not high; The lift Angle of the center of gravity is close to 90°. The vertical height of the center of gravity is significantly higher than the vertical height of the center of gravity when landing, and the vertical moving distance of the center of gravity in the lifting stage is significantly less than the vertical moving distance of the center of gravity in the descending stage. The vertical height of the center of gravity at departure is significantly higher than that at landing. Conclusions In the take-off stage, increase the twisting Angle of shoulders and hips, speed up the swing arm speed and squat speed of the center of gravity in the vertical direction, and shorten the take-off time. Increase the vertical speed of the center of gravity before the patting foot and the vertical moving distance between the center of gravity lifting stage and the descending stage, extend the air time, accelerate the swing speed of the right leg, move the foot patting time forward to the rapid rising stage of the center of gravity lifting, accelerate the rotational angular speed of the shoulder shaft in the air stage and improve the strength of the leg, which is conducive to the athletes to complete the movement.

Lightweight polyimide composite foams with anisotropic hierarchical pore structure for enhanced mechanical, flame retardancy and thermal insulation purposes

In this study, lightweight polyimide foam (PIF) with anisotropic pore structure were fabricated by adopting microwave-assisted foaming technique. Afterward, lightweight PIF/PI aerogel/silica aerogel (PIF/PIA/SiA) composite foams with anisotropic hierarchical pore structures was prepared by impregnation and directional freeze-drying method. The directional growth of foam pores and ice crystals endowed PIF/PIA/SiA composite foams with anisotropic skeleton structures and hierarchical porous filling structures, leading to anisotropic mechanical and thermal insulation performances. PIF/PIA/SiA composite foams presented mechanical robustness in vertical direction and mechanical flexibility in horizontal direction due to its unique pore structure. In addition, PIF/PIA/SiA composite foams showed outstanding thermal stability and flame retardancy, suggesting a promising application in the field of high temperature fire protection. The PIF/PIA/SiA composite foams exhibited superior thermal insulation performance with thermal conductivities ranging from 0.0253 to 0.0523 W/(m·K) between 25 and 300 °C. Therefore, a facile strategy was developed to fabricate PIF-based composite foams for mechanical, flame retardancy and thermal insulation applications in high-end engineering fields.

Internet street view image fusion method using convolutional neural network

The use of image fusion technology in the area of information processing is continuing to advance in depth thanks to ongoing hardware advancements and related research. An enhanced convolutional neural network approach is developed to fuse visible and infrared images, and image pre-processing is carried out utilising an image alignment method with edge detection in order to gain more accurate and trustworthy image information. The performance of the fast wavelet decomposition, convolutional neural network, and modified convolutional neural network techniques is compared and examined using four objective assessment criteria. The experimental findings demonstrated that the picture alignment was successful with an offset error of fewer than 3 pixels in the horizontal direction and an angle error of less than 0.3∘ in both directions. The revised convolutional neural network method increased the information entropy, mean gradient, standard deviation, and edge detection information by an average of 46.13%, 39.40%, 19.91%, and 3.72%. The runtime of the modified approach was lowered by 19.42% when compared to the convolutional neural network method, which enhanced the algorithm’s performance and boosted the effectiveness of picture fusion. The image fusion accuracy reached 98.61%, indicating that the method has better fusion performance and is of practical value for improving image fusion quality.

The role of muscle function and pointe shoe characteristics in Arabesque movement among ballet dancers with non-specific low back pain

ABSTRACT This study aimed to investigate posterior chain muscle function and the influence of pointe shoes in ballet dancers with and without low back pain (LBP) in the Arabesque. Twenty-nine young professional ballet dancers (17 with LBP and 12 healthy controls) were recruited. Muscle strength and mechanical properties of the erector spinae and hamstrings were assessed. The displacement of centre of mass (COM) during Arabesque under different shoe conditions (R-class, Chacott, and own shoes) was measured with a motion capture system. The LBP group exhibited greater dynamic stiffness and decreased mechanical stress relaxation time in the lateral hamstring compared to the control group. During Arabesque, the LBP group demonstrated significantly greater anterior-posterior displacement of the COM and a larger percentage of time to achieve maximal trunk extension angle. The COM displacement in vertical and medial-lateral directions was smaller in the R-class than in their own shoes. LBP impacts muscle mechanical properties, particularly in the lateral hamstring. The compromised muscle function resulted in a longer time to spinal extension during Arabesque, signifying that reduced trunk control contributed to greater COM displacement. Hence, it is essential to emphasise that evaluating muscle properties and dynamic postural control is imperative for dancers experiencing LBP.

Characteristics and effectiveness of deep and ultradeep tight sandstone fractures: Insights from geological and geophysical data analysis

“Effective” natural fractures are those that contribute to reservoir storage and conductivity. In this paper, the effectiveness of fractures in deep and ultradeep reservoirs (gt;6 km depth) is evaluated by using geophysical image log data, core, microstructures, mechanical tests, and geological evidence of tectonic context (including current in situ stress) and sedimentary faces and diagenesis. Intraformational open mode fractures are the most common type in this tectonically active region, and their effectiveness is affected by the coupling between past tectonic activity, in situ stress, and chemical reactions such as mineral precipitation or dissolution (diagenesis). Our results show that the effectiveness of fractures is mainly related to the aperture and filling, and fractures formed by early tectonic movement are more likely to be filled by minerals, reducing their effectiveness. Near orogenic belts in strongly cemented tight diagenetic facies exhibit a greater abundance of mineral-filled fractures, while dissolution can increase the fracture aperture and produces secondary pores in host rocks and roughen fracture walls. The effective normal stress acting on the fracture surface decreases when the fracture is parallel to the maximum horizontal stress component, so the fracture has a large aperture and therefore is more effective. The laboratory measurement results reveal that the contribution of fractures to reservoir space is limited, and the reservoir space provided by fractures accounts for only 13% of all types of reservoir space, while the development of fractures increases reservoir permeability by 1-2 orders of magnitude. Fractures improve the effectiveness of reservoir by connecting the dispersed pores in the reservoir matrix. Fractures with a low angle to the maximum horizontal stress component direction have greater apertures and permeabilities, and are the main channels for fluid flow.

Shape of a Rotating Slinky

If a Slinky suspended in a U-shape is rotated horizontally, it will have the shape of an upside-down [Formula: see text], like [Formula: see text], due to the centrifugal force in the horizontal direction acting on each point of the Slinky. In this paper, we discuss the shape of a rotating Slinky in both theoretical and experimental aspects. The rotating Slinky has the shape described by a multi-valued function if the angular velocity of the rotation satisfies [Formula: see text]. Our theoretical results are in good agreement with experimental observations. The video of the experiments can be viewed at https://youtu.be/rpu9Ol2jdAM .

Gradient catalyst layer design towards current density homogenization in PEM water electrolyzer with serpentine flow field

The inhomogeneous current density distribution might cause irreversible damage to the membrane electrode assemblies of proton exchange membrane water electrolyzers. Herein, the impact of gradient catalyst distribution on the current density uniformity inside the electrolyzer with serpentine flow field is investigated using a three-dimensional model. The gradient catalyst distribution in parallel and vertical flow directions is considered. It is found that, at low working voltage (1.8 V), gradient catalyst loading in the vertical flow direction would enhance the current density distribution uniformity by 77.6 %, and at the same time improve the electrolyzer performance by up to 4.0 %, whereas in parallel flow direction the corresponding improvement is by 34.5 % and 4.17 %, respectively. At high working voltage of 2.4 V, due to the pronounced impact of mass transportation process, similar and limited improvement in the current density uniformity (11.47–11.87 %) and electrolyzer performance (1.3–1.45 %) is found under the gradient catalyst loading design in both flow directions. This study provides important guidance for the design of proton exchange membrane water electrolyzer using serpentine flow field.

Research on particle accelerator control network deformation prediction algorithm with machine learning

Regular measurement of particle accelerators is imperative to ensure their long-term, stable operation and to meet future construction needs. The aim of this study is to minimise unplanned downtime and to provide data analysis and predictive insights for the remeasurement of similar particle accelerators. The focus is on the three-dimensional coordinate prediction and performance evaluation of a control network for a particle accelerator. The study uses observational data from the laser tracker in the Hefei Light Source storage ring control network, gathered from 2013 to 2023. Innovative use of the linear regression model, hyperbolic model, grey prediction model, and backpropagation neural network model has been made in the alignment of particle accelerators. A comparative analysis with measured data reveals that various deformation prediction methods can achieve a prediction accuracy of 0.25 mm. We recommend using the linear regression model for predicting the plumb direction, and the grey prediction model for predicting the horizontal direction. In addition, reducing the number of backward iteration steps can further improve the prediction accuracy. This study offers guidance for the deformation prediction of particle accelerators, and provides scientific data support and a basis for decision making on their long-term, stable operation.

Temporal and spatial determination of solidification rate during pulsed laser beam welding of hot-crack susceptible aluminum alloys by means of high-speed synchrotron X-ray imaging

Pulsed laser beam welding is primarily used to join thin-walled components. The use of 6xxx group aluminum alloys is characterized by good mechanical properties but these alloys are prone to hot cracking during solidification, i.e., requirements regarding strength and tightness, as increasingly important for electromobility related applications, cannot be fulfilled. The solidification rate has been identified as dominant factor in pulsed conduction welding which can be adjusted by the pulse shape, i.e., by varying the beam power over time for a single pulse.Pulse shapes with different, linear ramp-down slopes were studied to describe the interaction between beam power and resulting solidification rate for spot welds. Based on rotationally symmetric conditions of the spot welds, the solidification rate can be measured in radial and vertical directions. The welding process of EN AW 6082 alloy was examined by in situ high-speed synchrotron X-ray imaging at the European Synchrotron Radiation Facility (ESRF) for this reason. Frame rates up to 120,000 Hz and subsequent image analysis allowed in-depth analysis of the solidification processes, their dependence on different spatial directions, and the resulting effects on hot crack formation.

The Spatial Development Characteristics of High-Pressure Methane Jet Impinging on Methane Lean-Burn Premixed Flame

This work investigated the effect of high-pressure (10 MPa) methane gas jet impinging on the methane lean-burn premixed flame (equivalent ratio of 0.7) based on a three-dimensional numerical simulation by CONVERGE software. The results show that laminar premixed flame is accelerated to develop into a stable turbulent flame under the action of the methane jet, the whole process of flame front development is divided into three stages: laminar (Reynolds number maintains stable, 1–1.3 ms), transition (Reynolds number shows an increasing trend, 1.4–8 ms), and turbulent (Reynolds number tends to stabilize at a high value, 1.9–3 ms). The effect of high-pressure jet on flame development along jet direction (Z axis) is greater than that on vertical direction (Y axis). During turbulence stage, the momentum and kinetic energy of Z axis are 2.7 and 6.3 times greater than that of Y axis, respectively. The high-pressure methane jet causes a change in heat distribution, resulting in local flameout. The rate of change in the local flameout area is greater than that in the flame area, causing a temperature drop in Z axis. This temperature drop increases with the increase in equivalence ratio and with the decrease in distance between cross-section position and ignition center.

Muscle synergies for multidirectional isometric force generation during maintenance of upright standing posture

Muscle synergies are defined as coordinated recruitment of groups of muscles with specific activation balances and time profiles aimed at generating task-specific motor commands. While muscle synergies in postural control have been investigated primarily in reactive balance conditions, the neuromechanical contribution of muscle synergies during voluntary control of upright standing is still unclear. In this study, muscle synergies were investigated during the generation of isometric force at the trunk during the maintenance of standing posture. Participants were asked to maintain the steady-state upright standing posture while pulling forces of different magnitudes were applied at the level at the waist in eight horizontal directions. Muscle synergies were extracted by nonnegative matrix factorization from sixteen lower limb and trunk muscles. An average of 5-6 muscle synergies were sufficient to account for a wide variety of EMG waveforms associated with changes in the magnitude and direction of pulling forces. A cluster analysis partitioned the muscle synergies of the participants into a large group of clusters according to their similarity, indicating the use of a subjective combination of muscles to generate a multidirectional force vector in standing. Furthermore, we found a participant-specific distribution in the values of cosine directional tuning parameters of synergy amplitude coefficients, suggesting the existence of individual neuromechanical strategies to stabilize the whole-body posture. Our findings provide a starting point for the development of novel diagnostic tools to assess muscle coordination in postural control and lay the foundation for potential applications of muscle synergies in rehabilitation.

Laser Doppler velocimetry and particle image velocimetry measurements in a wind tunnel model of the jack rabbit II special sonic anemometer study

A 1:50 scale model of the Jack Rabbit II (JR-II) Mock Urban Environment (MUE) was constructed in the wind tunnel of the University of Arkansas. Laser Doppler Velocimetry (LDV) measurements show agreement between the approach wind characteristics in the tunnel model and field test. LDV velocity measurements within the MUE wind tunnel model also agree with the anemometry results obtained in JRII Special Sonic Anemometer Study (JRII-S) conducted in 2016.After demonstrating that the wind tunnel models the JRII-S field test with LDV measurements, Particle Image Velocimetry (PIV) experiments were conducted to provide velocity measurements that could not be obtained in the field tests. Velocity measurements in a horizontal plane parallel to the ground were made to compare to computational fluid dynamics (CFD) simulations of the JRII-S field tests found in the literature. PIV measurements taken in the wind tunnel model pointed out concerns with those simulations.