Impingement Density Analysis on Heat Transfer and the Appearance of Edge Cracks in Conventional Slab Using Hydraulic Nozzles

In this work, the fluid dynamics and heat transfer of two hydraulic nozzles used in the secondary cooling of the conventional slab continuous casting machine were analyzed. Impingement density maps, the jet opening angle and heat flux associated with different operating conditions (impingement distance, pressure) were experimentally determined. The opening angle and impingement density footprint were found to vary considerably in shape and magnitude with varying operating pressure and distances. Finally, it was found that when short operating distances are used, a greater heat extraction gradient occurs in the major axis of the impingement footprint, which promotes edge-cracks in the slab in plant.

Assembly and Disassembly Mechanics of a Cylindrical Snap Fit

Snap fit is a common mechanical mechanism. It uses the physical asymmetry that is easy to assemble but difficult to disassemble to provide a simple and fast link between objects. The ingenious combination of geometric shape, bending elasticity and friction of the snap fit is the mechanism behind the easy to assemble but difficult to disassemble disassemble. Yoshida and Wada (2020) has done a groundbreaking work in the analysis of the elastic snap fit. During our study of their paper, while we really enjoyed their research, unfortunately we detected several questioning formulations. After careful checking, we found that those formulations are not typographical, therefore it is necessary to make corrections. This paper reformulates the linear elasticity of a cylindrical snap fit, obtains an exact solution and proposes an accurate relation between the opening angle and bending tangent angle. Under the first order approximation, our formulations can reduced to the results of Yoshida and Wada and hence confirms the scientific correctness of Yoshida and Wada's work. Furthermore, this paper also derives a correct vertical displacement expression, and propose a new way of disassembly by bending for the first time and formulate a scaling law by data fitting. All formulations are validated by finite element simulation and experiment. The research here is helpful to the design of elastic snap fit or adjustable mechanical mechanism and metamaterial cell.

Effect of malocclusion on jaw motor function and chewing in children: a systematic review

Objective To investigate the effects of dental/skeletal malocclusion and orthodontic treatment on four main objective parameters of chewing and jaw function (maximum occlusal bite force [MOBF], masticatory muscle electromyography [EMG], jaw kinematics, and chewing efficiency/performance) in healthy children. Materials and methods Systematic searches were conducted in MEDLINE (OVID), Embase, and the Web of Science Core Collection. Studies that examined the four parameters in healthy children with malocclusions were included. The quality of studies and overall evidence were assessed using the Joanna Briggs Institute and GRADE tools, respectively. Results The searches identified 8192 studies; 57 were finally included. The quality of included studies was high in nine studies, moderate in twenty-three studies, and low in twenty-five studies. During the primary dentition, children with malocclusions showed similar MOBF and lower chewing efficiency compared to control subjects. During mixed/permanent dentition, children with malocclusion showed lower MOBF and EMG activity and chewing efficiency compared to control subjects. The jaw kinematics of children with unilateral posterior crossbite showed a larger jaw opening angle and a higher frequency of reverse chewing cycles compared to crossbite-free children. There was a low to moderate level of evidence on the effects of orthodontic treatment in restoring normal jaw function. Conclusions Based on the limitations of the studies included, it is not entirely possible to either support or deny the influence of dental/skeletal malocclusion traits on MOBF, EMG, jaw kinematics, and masticatory performance in healthy children. Furthermore, well-designed longitudinal studies may be needed to determine whether orthodontic treatments can improve chewing function in general. Clinical relevance Comprehensive orthodontic treatment, which includes evaluation and restoration of function, may or may not mitigate the effects of malocclusion and restore normal chewing function.

Late-time Evolution and Modeling of the Off-axis Gamma-Ray Burst Candidate FIRST J141918.9+394036

We present new radio and optical data, including very-long-baseline interferometry, as well as archival data analysis, for the luminous, decades-long radio transient FIRST J141918.9+394036. The radio data reveal a synchrotron self-absorption peak around 0.3 GHz and a radius of around 1.3 mas (0.5 pc) 26 yr post-discovery, indicating a blastwave energy ∼5 × 1050 erg. The optical spectrum shows a broad [O iii]λ4959,5007 emission line that may indicate collisional excitation in the host galaxy, but its association with the transient cannot be ruled out. The properties of the host galaxy are suggestive of a massive stellar progenitor that formed at low metallicity. Based on the radio light curve, blastwave velocity, energetics, nature of the host galaxy and transient rates, we find that the properties of J1419+3940 are most consistent with long gamma-ray burst (LGRB) afterglows. Other classes of (optically discovered) stellar explosions as well as neutron star mergers are disfavored, and invoking any exotic scenario may not be necessary. It is therefore likely that J1419+3940 is an off-axis LGRB afterglow (as suggested by Law et al. and Marcote et al.), and under this premise the inverse beaming fraction is found to be f b − 1 ≃ 280 − 200 + 700 , corresponding to an average jet half-opening angle < θ j > ≃ 5 − 2 + 4 degrees (68% confidence), consistent with previous estimates. From the volumetric rate we predict that surveys with the Very Large Array, Australian Square Kilometre Array Pathfinder, and MeerKAT will find a handful of J1419+3940-like events over the coming years.

Design and optimization of a breast-dedicated SPECT scanner with multi-lofthole collimation

Background: the need for simultaneous high-sensitivity and high-resolution breast SPECT imaging mandates to design and optimize dedicated scanners. Therefore, this work aims to design and optimize a novel breast-dedicated SPECT system with multi-lofthole collimator. Materials and Methods: in this research, a novel breast-dedicated scanner is designed and then optimized. The scanner is equipped with a single full-ring multi-lofthole collimation long with modular NaI(Tl) detectors. The step-and-shoot data acquisition was considered with two steps. Then, an analytic optimization was conducted to balance the existing sensitivity-resolution tradeoff. To do so, several scanner geometries were investigated. The optimal configuration maximized the system sensitivity at a given system resolution. Furthermore, the scanner was also modeled within the GATE simulator. Then, detector energy resolution, septal penetration and scattering, and system sensitivity were calculated. Analytic findings were also compared with the simulated ones. Results: the results showed that high sensitivity of about 2 cps/kBq can be obtained for a diameter of lofthole 3.05 mm with a 75° opening angle. Results of GATE simulations showed clinically acceptable performance of the system offering 9% energy resolution for a point source. The septal penetration and scattering were approximately 0.5% and 0.2%, respectively, for cylindrical water phantom and tungsten as collimator material. Conclusion: the designed SPECT scanner provides promising results in terms of sensitivity and spatial resolution and therefore outperforms the traditional multi-pinhole collimation by a much higher sensitivity at a given system resolution.

The inter-individual anatomical variation of the trochlear notch as a predisposition for simple elbow dislocation

Purpose Besides the multi-layered capsule–ligamentous complex of the elbow joint the high bony congruence in the ulnohumeral joint contributes to elbow stability. Therefore, we assume that specific anatomical configurations of the trochlear notch predispose to dislocation. In case of ligamentous elbow dislocation both conservative and surgical treatment is possible without a clear treatment algorithm. Findings of constitutional bony configurations could help deciding for the best treatment option. Methods In this retrospective matched-pair analysis we compared MRI imaging from patients sustaining a primary traumatic elbow dislocation (instability group) with patients suffering from chronic lateral epicondylitis (control group), treated between 2009 and 2019. Two independent observers measured different anatomical landmarks of the trochlear notch in a multiplanar reconstructed standardized sagittal trochlear plane (SSTP). Primarily, opening angle and relative depth of the trochlear notch were determined. After adjustment to the proximal ulnar rim in the SSTP, coronoid and olecranon angle, the articular angle as well as the ratio of the tip heights of the trochlear notch were measured. Results We compared 34 patients in the instability group (age 48 ± 14 years, f/m 19/15) with 34 patients in the control group (age 47 ± 16 years, f/m 19/15). Instability group showed a significantly larger opening angle (94.1° ± 6.9° vs. 88.5° ± 6.9°, p = 0.0002), olecranon angle (60.9° ± 5.3° vs. 56.1° ± 5.1°, p < 0.0001) and articular angle (24.7° ± 6.4° vs. 22.3° ± 5.8°, p = 0.02) compared to the control group. Measuring the height from the coronoid (ch) and olecranon (oh) tip also revealed a significantly larger tip ratio (tr = ch/oh) in the instability group (2.7 ± 0.8 vs. 2.2 ± 0.5, p < 0.0001). The relative depth (61.0% ± 8.3% vs. 62.7% ± 6.0%, p = 0.21) of the trochlear notch as well as the coronoid angle (32.8° ± 4.5° vs. 31.7° ± 5.2°, p = 0.30) showed no significant difference in the instability group compared to the control group. The interrater reliability of all measurements was between 0.83 and 0.94. Conclusion MRI of patients with elbow dislocation show that there seems to be a bony anatomical predisposition. According to the results, it seems reasonable to include predisposing bony factors in the decision-making process when surgical stabilization and conservative treatment is possible. Further biomechanical studies should prove these assumptions to generate critical bony values helping surgeons with decision making. Level of evidence III.

Design and Feasibility Tests of a Gas-driven Bionic Flytrap Soft Robot

The research of bionic soft robot is a complex system engineering, including soft matrix material, soft actuator, soft sensor and bionic control system. Unlike most animals, plants cannot move in whole voluntarily. However, for the purpose of energy and nutrition, various parts of the plant body also carry out various movements, which vary from millisecond to hour on a large time scale. As a result, Plants are considered a source of inspiration for innovative engineering solutions, and a growing number of researchers are investigating the mechanisms of plant movement and biomimetic research. In this paper, the biological morphology, microstructure and movement mechanism of Venus flytrap leaf were studied and analyzed, and a bionic flytrap grassland machine with chamber design was designed and manufactured. Firstly, according to the research report on the biological morphology, microstructure and movement mechanism of Venus flytrap, the idea of chamber design was determined. Based on this observation, we reconstructed the leaf model and bionic structure of Venus flytrap by reverse modeling. Based on the principle of turgor pressure deformation, the chamber design rules of bionic Venus flytrap blade were formulated and optimized with silica gel as the bulk material. The flow channel design of Venus flytrap blade was studied and explored. Finally, the bionic Venus flytrap leaf was made by 3D printing technology and silica gel casting process, and the two bionic leaves were clamped at a certain opening Angle. The bending performance of bionic flytrap blade and the flytrap closure experiment were studied by air pressure excitation. The experimental results show that the bionic Venus flytrap blade can complete bending and closing experiments, and the bionic Venus flytrap can complete the whole capturing process within 5s. The leaf opening Angle of the bionic Venus flytrap reaches 80 degrees, which fits well with the real Venus flytrap blade and meets the design requirements and bionic goals. Apparently, this study is the first to design the chamber of the bionic flytrap leaf, formulate rules, and study the possibility of its deformation. It provides a new idea for the study of the movement and deformation of plant leaves, and expands the application of bionic robots, especially the robot solutions for plant types.

Numerical Simulation and Experiment of Hydraulic Loss of Two-Stage Flap Valves

As a type of flap valve evolved from integral flap valve, two-stage flap valve has the advantages of large opening angle, small hydraulic loss and small impact force on the flap valve seat when the flap valve is closed. In order to analyze and study the hydraulic loss characteristics of the two-stage flap valve, this paper takes a pump station as an example. Based on theoretical analysis, combined with numerical simulation and model test, the hydraulic loss of two-stage flap valve is studied, and the relationship between hydraulic loss and pump station flow is obtained. According to the test results, the hydraulic loss of two-stage flap valve increases with the increase of flow rate under the same opening angle of flap valve. Under the same flow condition, the larger the opening angle of the flap valve is, the smaller the hydraulic loss of the two-stage flap valve is. When the opening angle of the upper flap valve is greater than 46° and the opening angle of the lower flap valve is greater than 64°, the hydraulic loss is less than 70mm and tends to be stable. The influence of hydraulic loss on the performance of pump device is gradually weakened. The relationship between hydraulic loss and flow of two-stage flap valve no longer satisfies the relationship of square under the constant opening angle. Moreover, the larger the opening angle of the two-stage flap valve is, the greater the relationship between hydraulic loss and flow is. Compared with the integral flap valve, the two-stage flap valve has better structural form and hydraulic characteristics, and has little influence on the performance of the pump device, which can provide reference for the application of the two-stage flap valve in the pump station.

Parametric study of cone angle influence on bubble vortex breakdown onset in laminar conical flow at various swirl numbers

The current work studies a swirling laminar viscous pipe flow with a controllable swirl number and varying pipe divergence cone angle. Such flows are widely used in various engineering applications. When a certain level of flow swirl is reached, a phenomenon called vortex breakdown occurs, the characteristics of which depend on the intensity of swirling of the flow and the Reynolds number. However, in addition to these two parameters, an important influence is exerted by the pipe opening angle, which often does not allow generalizing the results obtained in the pipe flow with even slightly different angles. Since experimentally it is quite difficult and expensive to change the pipe angle, especially considering the water as working fluid, this issue could be solved using CFD techniques. Using the design study, 63 different combinations of S and α are considered. The effect of the pipe divergence angle on the position of the bubble vortex breakdown and its properties is demonstrated. It is shown that there is a nonlinear relationship between the position of the bubble breakdown onset and the minimum value of the axial velocity at the axis depending on the opening angle of the cone.