Increase In Rotation Angle Research Articles

A novel lattice structure design approach based on Schwarz Primitive triply periodic minimal surfaces

In recent years, lattice structures based on triply periodic minimal surfaces have attracted the attention of researchers worldwide due to their exceptional geometrical and mechanical features. In this paper, using two distinct implicit functions for the rotation angle and the axis of rotation, the surface points of the Schwarz’ Primitive cellular lattice are moved to a new position to construct some novel lattices. Various cellular lattices are then generated by manipulating different design parameters and investigated using finite element method to evaluate porosity, surface-to-volume ratio, elastic modulus and Zener ratio. The findings indicate that although the porosity doesn’t change profoundly by applying the transformation, the surface-to-volume ratio and elastic modulus increases and decreases respectively as the maximum rotation angle increases. In addition, Zener ratio exhibits non-linear variation with the transformation, potentially increasing or decreasing by increasing the maximum rotation angle, depending on other parameters. The maximum difference between the values of surface-to-volume ratio, elastic modulus, and Zener ratio of the novel lattices and those of the original one is 16.9% (for one case it decreases by 68.7%), 68.5%, and 45.6%, respectively. These observations suggest that the proposed method might presents significant potential for facilitating the creation of innovative shell-based lattice structures.

Measurement of Postoperative Apical Vertebral Rotation Using Radiographic Images in Adolescent Idiopathic Scoliosis-Quantitative Evaluation Using Inverse Trigonometric Functions.

Conventional methods for analyzing vertebral rotation are limited to postoperative patients who underwent posterior fusion. A previous methodology calculated vertebral rotation using inverse trigonometric functions based on the length of the pedicle screw (PS). Accordingly, this study evaluates rotational deformity in patients with postoperative adolescent idiopathic scoliosis (AIS) using inverse trigonometric functions. This retrospective single-center study includes patients with AIS who underwent posterior fusion surgery. Postoperative radiography and computed tomography (CT) scans were retrospectively evaluated. The magnification ratio was calculated using the rod diameter (δ=lateral/frontal rod diameter), and the visible screw lengths were measured using radiographs. The rotation angle was calculated using the apex of the main curve and the lower instrumented vertebra (LIV) (rotation angle=tan-1 (lateral PS length/(δ×frontal PS length))) immediately following the surgery as well as two and five years postoperatively. The correlation between the direct CT measurement and postoperative rotation angle progression was investigated. The crankshaft phenomenon (CSP) and distal adding-on (DAO) were evaluated as postoperative deformities. CSP was defined as a 5° increase in rotation angle. Seventy-eight patients (age: 15.3±2.0 years, eight boys and seventy girls) were included. The rotation angle was strongly correlated with CT rotation measurements (r=0.87). The mean rotation angle at the apex and LIV did not change within five years postoperatively (mean: 0.5±3.6° and 0.4±3.4°, respectively). CSP and DAO were observed in 6.4% and 3.8% of patients, respectively. The inverse trigonometric method is useful to quantitatively evaluate the postoperative rotation angle and identify CSP.

A device for magnetic-field angle control in magneto-optical filters using a solenoid-permanent magnet pair.

Atomic bandpass filters are used in a variety of applications due to their narrow bandwidths and high transmission at specific frequencies. Predominantly, these filters are in the Faraday (Voigt) geometry, using an applied axial (transverse) magnetic field with respect to the laser propagation direction. Recently, there has been interest in filters realized with arbitrary-angle magnetic fields, which have been made by rotating permanent magnets with respect to the k-vector of the interrogating laser beam. However, the magnetic field angle achievable with this method is limited as field uniformity across the cell decreases as the rotation angle increases. In this work, we propose and demonstrate a new method of generating an arbitrary-angle magnetic field, using a solenoid to produce a small, and easily alterable, axial field, in conjunction with fixed permanent magnets to produce a large transverse field. We directly measure the fields produced by both methods, finding them to be very similar over the length of the vapor cell. We then compare the transmission profiles of filters produced using both methods, again finding excellent agreement. Finally, we demonstrate the sensitivity of the filter profile to changing magnetic field angle (solenoid current), which becomes easier to exploit with the much improved angle control and precision offered by our new design.

Multi-step deformation lattice structures from the rotation of unit cell

A multi-step deformation lattice structure (MSLS) is introduced. MSLS can exhibit multiple deformation pathways under compression. It leads to multi-stress plateaus in the stress–strain relationship. The underlying mechanism is caused by the rotation of the unit cell that composes the structures. Analytical models of plateau stress is first established based on the plastic hinge dissipation principle and is validated by experiments. By studying the MSLS composed of different unit cells rotated with different angles, four stress–strain relationships are obtained. Furthermore, the Young's modulus and the yield strength of MSLS show a tendency of decreasing and then increasing with the increase of rotation angle. Moreover, the rotation angle can lead to a transition of the MSLS between bending-dominated behavior and stretching-dominated behavior. Finally, it is found that MSLS has a negative Poisson's ratio and a minimum value is −0.9, and Poisson's ratio tends to zero rapidly when strains is larger than 0.3. This work provides new insights into the use of rotating unit cell to create multi-step pathways and auxetic lattices that can be used to design engineering structures with multiple tasks and application for impact protection.

Experimental study on seismic performance and deformation damage of loose dovetail-tenon joints in ancient timber structures

A looseness is typical damage for mortise-tenon joints in ancient timber structures. The tenon of the loose dovetail-tenon joints is prone to be pulled out, leading to joint failure in the earthquake. Hence, it is necessary to investigate the seismic performance and deformation damage of loose dovetail-tenon joints. This study conducts pseudo-static and acoustic emission (AE) tests on three full-scaled dovetail-tenon joints to determine the four stress stages of each joint, including slight damage, medium damage, severe damage, and nearly failure. It examines the hysteretic and skeleton curve, stiffness and strength degradation, energy dissipation performance, and the variation raw of the amount of tenon pulled out at each stage. The deformation damage mode, damage degree, and damage evolution equation of the joint at each stage are obtained based on the AE characteristic parameters measured at each stage. The results indicate that as the rotation angle increases, each joint's stiffness and energy dissipation capacity decrease, while the joint bending moment rises and then reduces, and the amount of tenon pulled out increases. The greater the degree of looseness, the lower the bearing capacity of each joint, and the more pronounced the degradation of stiffness and strength. At each stage, the maximum decrease of initial stiffness is 85.75%, and the maximum amount of tenon pulled out is 93 mm. The failure modes of joints are mainly tenon pulled out failure, and extrusion deformation greatly influences the tenon pulled out failure. As the degree of looseness grows, joints are more prone to severe deformation damage under large rotation angles. At the slight and medium stages, the joints primarily suffer from tensile damage of material, but at the severe damage and nearly failure stage, they mainly suffer from shear damage of material. The damage value of each joint increases with the relative stress ratio, and looseness significantly impacts the damage degree of the joint.

Effect of rotation angle on surface morphology, microstructure, and mechanical properties of Inconel 718 alloy fabricated by high power laser powder bed fusion

Rotation angle of the laser scan direction between two adjacent layers is a key controlling parameter during the high-power (≥ 1 kW) laser powder bed fusion (HP-LPBF) process. This study investigates the influences of rotation angles (θ = 0°, 45°, 90°, 105°) on the surface morphology, microstructure, and mechanical properties of Inconel 718 (IN718) alloy produced by HP-LPBF. Results show that adopting low rotation angles (e.g., 0° and 45°) is prone to relatively poor surface finish and lack-of-fusion defects, whereas adopting high rotation angles (e.g., 90° and 105°) induces smaller surface roughness and better relative density. Each case reveals a noticeable edge effect but the maximal heights witness a downward trend with the increase of rotation angle. There are some minor differences in the primary dendrite arm spacing and grain morphology by varying the rotation angles. Moreover, the tensile property is slightly enhanced as the rotation angle increases. The present work suggests that high rotation angles like 90° and 105° would probably be more favorable for the 1 kW HP-LPBF process than rotation angles with relatively low values.

Soil-structure interaction of a laterally loaded hybrid foundation for offshore wind turbine

With the ramping up of the capacity of the offshore wind turbine (OWT), the water depth, and the weight of the superstructure, the need of foundation structure with higher performance but reasonable cost demands innovation from geotechnical and structural engineering. The novel hybrid foundation takes advantage of the mature monopile technology, and innovatively integrates a loading wheel-bucket component around the monopile in the upper layer of soil. The addition of the integrated hybrid component is proven to enhance the overall performance of the foundation by previous research. The soil-structure interaction (SSI) of the hybrid foundation is the key to optimize the design of the structure. In this paper, a series of finite element (FE) analysis of the hybrid foundation under monotonic load are performed. The results of the FE analysis are compared with that of the geotechnical centrifuge tests. The soil pressure distributions on the pile and the hybrid component are investigated. The variation of the soil pressure profile with the increase of rotation angle is also studied. The soil resistance on the skirt of the bucket component is illustrated in the analysis. The FE models also prevail the failure mechanism of the hybrid foundation.

Dwarf Kingfisher-Inspired Bionic Flapping Wing and Its Aerodynamic Performance at Lowest Flight Speed.

This paper aims to understand the aerodynamic performance of a bio-inspired flapping-wing model using the dwarf Kingfisher wing as the bionic reference. The paper demonstrates the numerical investigation of the Kingfisher-inspired flapping-wing followed by experimental validation to comprehend the results fully and examine the aerodynamic characteristics at a flight velocity of 4.4 m/s, with wingbeat frequencies of 11 Hz, 16 Hz, and 21 Hz, at various angles of rotation ranging from 0° to 20° for each stroke cycle. The motivation to study the performance at low speed is based on lift generation as a challenge at low speed as per quasi-steady theory. The temporal evolution of the mean force coefficients has been plotted for various angles of rotation. The results show amplification of the maximum value for the cycle average lift and drag coefficient as the rotation angle increases. The history of vertical force and the flow patterns around the wing is captured in a full cycle with asymmetric lift development in a single stroke cycle. It is observed from the results that the downstroke generates more lift force in magnitude compared to the upstroke. In addition to the rotation angle, lift asymmetry is also affected by wing–wake interaction. Experimental results reveal that there is a stable leading-edge vortex developed in the downstroke, which sheds during the upstroke. An optimum lift and thrust flapping flight can be achieved, with a lift coefficient of 3.45 at 12°. The experimental and parametric study results also reveal the importance of passive rotation in wings for aerodynamic performance and wing flexibility as an important factor for lift generation.

Tunable Faraday effect in Graphene/SiO2/Ta2O5 layered structure using a pump He-Ne laser light

Faraday rotation spectrum of a Graphene/SiO2/Ta2O5 layered structure under an external magnetic field and a pump light of a He-Ne laser with the wavelength of 632.8 nm is investigated in the THz frequency region. The results showed that, when the pump light is turned off and the magnetic field strength is increased, the maximum Faraday rotation angle frequency shifts toward the higher frequencies, as well as, the value of the maximum Faraday rotation angle increases. Furthermore, for a constant external magnetic field, by increasing the pump light power, the value of Faraday rotation increases, and the maximum Faraday rotation frequency shifts toward the lower frequencies. However, the noticeable changes in the transmission spectrum were not observed by changing the magnetic field strength and the pump light power. These results would have potential applications in designing the magneto-optical devices with tuning property of the Faraday rotation using a pump He-Ne laser.

Rotation induced symmetry change of friction coefficient of water on graphene/h-BN heterostructures

The graphene/h-BN heterostructure provides a promising device for biomedical applications and biosensor. However, the friction characteristics of water on graphene/h-BN are still elusive. By means of molecular dynamics simulations, we investigated the friction coefficient of water on both sides of graphene/h-BN heterostructures under various rotation angle, which shows a non-monotonic but symmetrical variation with relative interlayer angle. Despite that friction coefficient of h-BN surface is larger than that of graphene, as the rotation angle increases, the friction coefficient of water on both sides of the graphene/h-BN heterostructure exhibits the same “M”-shaped curve. The center of symmetry of the curve is at the rotation angle of 30°; the friction coefficient is the largest when the rotation angle is 10° and 50°. It was found that graphene/h-BN heterostructure is a device whose friction coefficient is different on both sides and can be adjusted by twisting the relative interlayer angle. These results could be demonstrated by the van der Waals interaction and different pattern of free energy landscape. These findings provide detailed insights into the mechanism of the friction property of water at nanoscale, which would facilitate feasible applications of graphene/h-BN heterostructure in biosensor and biomedicine.

Research on mathematical modeling of the servo valve torque motor considering the variation of working air-gaps leakage flux

In the current research of the magnetic circuit model of the servo valve torque motor, the magnetic flux leaking from working air-gaps is regarded as constant. However, the working air-gaps leakage flux varies with the armature rotation angle, which affects the accuracy of the existing mathematical model of the torque motor. To solve this problem, a new mathematical model of the torque motor with two working air-gaps is built. First, different from the previous model, the variation of the working air-gaps leakage flux is considered in the magnetic circuit model. A more detailed mathematical model of the torque motor is established based on the magnetic circuit model. Second, the finite element method is used to reveal that there is a linear relationship between working air-gaps leakage flux and armature rotation angle in a certain range of rotation angles. Then, the new model is validated by numerical calculation, which indicates that the theoretical results calculated by this new model show better agreement with the simulation results compared to the previous model when the armature rotation angle increases. Further, the theoretical results of the electromagnetic torque constant and magnetic spring stiffness acquired by the new model and the previous model are compared. The comparison shows that the variation of the working air-gaps leakage flux has the greatest influence on the magnetic spring stiffness. Finally, the experiments on the torque motor are conducted to verify the accuracy of the new model. The theoretical results obtained by this new model are better consistent with the experimental results than that obtained by the previous model. This study shows that considering the variation of working air-gaps leakage flux is valuable to improve the accuracy of the magnetic circuit model of the torque motor, which provides an effective guidance for the structural optimization and performance prediction of the torque motor.

Analytical Formula to Investigate the Modulation of Sloped Targets Using LiDAR Waveform

The relationship between the properties of targets and the features of modulated waveforms is fundamental to remote sensing based on the full-waveform light detection and ranging (LiDAR). Developing a mathematical formula of modulated LiDAR waveforms is of great importance in establishing this relationship. In this study, we derive the mathematical formula of a laser echo waveform modulated by four typical targets: a rectangle, a square, a circle, and an equilateral triangle. By using these formulas, numerical calculations are performed to investigate the relationship between the properties of the targets and the features of the modulated waveform. The results show that, at a rotation angle of 80°, the modulated waveform changes from a Gaussian form to a non-Gaussian form and finally returns to a Gaussian form as the target size increases. When the target center deviates from the laser spot center and the rotation angle increases, the modulated waveform varies from Gaussian to non-Gaussian form, the value of the peak intensity decreases, and the position of the peak intensity shifts. The specific trends of these changes are successfully explained in terms of the geometric characteristics of the target and the spatial intensity distribution of the incident laser. The distinct dependencies of modulated waveforms on geometric shape, size, center position, and rotation angle indicate a convenient method for identity extraction and target recognition in remote sensing using full-waveform LiDAR. This offers exciting implications for applications, such as topological mapping, environment monitoring, and aerial target detection and recognition.

Mechanism of Corrugated Graphene Moiré Superstructures on Transition-Metal Surfaces.

A graphene layer on a transition-metal (TM) surface can be either corrugated or flat, depending on the type of the substrate and its rotation angle with respect to the substrate. It was broadly observed that the degree of corrugation generally decreases with the increase of rotation angle or the decrease of Moiré pattern size. In contrast to a flat graphene on a TM surface, a corrugated graphene layer has an increased binding energy to the substrate and a concomitant elastic energy. Here, we developed a theoretical model about the competition between the binding energy increase and the elastic energy of corrugated graphene layers on TM surfaces in which all the parameters can be calculated by density functional theory (DFT) calculations. The agreement between the theoretical model and the experimental observations of graphene on various TM surfaces, for example, Ru(0001), Rh(111), Pt(111), and Ir(111), substantiated the applicability of this model for graphene on other TM surfaces. Moreover, the morphology of a graphene layer on an arbitrary TM surface can be theoretically predicted through simple DFT calculations based on the model. Our work thus provides a theoretical framework for the intelligent design of graphene/TM superstructures with the desired structure.

Statistical Properties of Small-scale Linear Magnetic Holes in the Martian Magnetosheath

Abstract The small-scale linear magnetic hole (LMH) is a magnetic dip with a size less than or on the order of ρ i (proton gyroradius), which may contribute to turbulence properties in the solar wind and other astrophysical plasmas. Based on one-month measurements of the Mars Atmosphere and Volatile EvolutioN mission, 174 small-scale LMH events in the Martian magnetosheath are used to investigate their statistical properties in this study. Our results show that small-scale linear LMHs are ubiquitous in the Martian magnetosheath, and their occurrence rate is estimated to be approximately 1.5 events per hour based on one-month observations. Compared with the ambient plasma, the averaged magnitude of the magnetic field in these holes can decrease from 6.8–3.5 nT. Nearly 66% of events have a B min/B value in the range of (0.45, 0.75). The duration of small-scale MHs is mainly less than 0.4 s. For 90% of the events, the size along the solar wind flow is less than ρ i . As the rotation angle increases, the occurrence rate of small-scale LMHs decrease. However, the B min/B, size, and duration of small-scale LMHs have no obvious dependence on their rotation angle.

Reliability Analysis of Embedded Strip Footings in Rotated Anisotropic Random Fields

This study explores the influence of rotated anisotropy of soil property on the bearing capacity of embedded strip footings using the random finite element method. An extensive parametric study was carried out considering the different scales of fluctuations, embedded depths, and rotation angles of the random fields. Results show that for various footing embedded depths considered in this study, the major scale of fluctuation has a large influence on the probability of bearing capacity failure in all cases. Furthermore, the mean bearing capacity remains almost constant regardless of the change of rotation angle, while the probability of bearing capacity failure decreases with the increase of rotation angle. The significant role of rotation angle in probabilistic analysis highlights the need to understand and consider the soil layer orientation in geotechnical foundation design to achieve safety and reliability.

Mechanical modulation of spontaneous emission of nearby nanostructured black phosphorus.

In this study, we investigate the spontaneous emission of a quantum emitter nearby black phosphorus (BP) sheet. The spontaneous emission can be modulated mechanically by rotating the BP sheet when the quantum emitter is placed parallel to the sheet. The spontaneous emission is dependent on the electron doping and rotation angle of BP with respect to the x-axis. The Purcell factor decreases with the increase in rotation angle under smaller electron doping. The Purcell factor increases with the increase in rotation angle under larger electron doping. The spontaneous emission of quantum emitter nearby two types of BP ribbon arrays tailored along armchair (type I) and zigzag (type II) directions is studied in detail. The spontaneous emission of quantum emitter parallel to type I is enhanced compared with that parallel to BP sheet. The spontaneous emission decreases remarkably for the quantum emitter parallel to type II compared with that parallel to BP sheet. The spontaneous emission can be flexibly modulated by rotating BP ribbon arrays mechanically in two types. The results obtained in this study provide a new method to actively modulate the spontaneous emission.

Study on the Mechanism and Control of Rock Burst of Coal Pillar under Complex Conditions

In order to explore the mechanism of coal pillar rock burst in the overlying coal body area, taking W1123 working face of Kuangou Coal Mine as the engineering background, the full mining stage of W1123 is simulated by FLAC3D. It is found that the high stress concentration area has appeared on both sides of the coal pillar when W1123 does not start mining. With the advance of the working face, the high stress concentration area forms X-shaped overlap. There is an obvious difference in the stress state between the coal pillar under the solid coal and the coal pillar under the gob in W1123. The concrete manifestation is that the vertical stress of the coal pillar below the solid coal is greater than the vertical stress of the coal pillar below the gob. The position of the obvious increase of the stress of the coal pillar in the lower part of the solid coal is ahead of the advancing position of the working face, and the position of the obvious increase of the stress of the lower coal pillar in the gob lags behind the advancing position of the working face. At the same time, in order to accurately reflect the true stress environment of coal pillars, the author conducted a physical similarity simulation experiment in the laboratory to study the local mining process of the W1123 working face, and it is found that under the condition of extremely thick and hard roof, the roof will be formed in the gob, the mechanical model of roof hinged structurer is constructed and analyzed, and the results show that the horizontal thrust of roof structure increases with the increase of rotation angle. With the development of mining activities, the self-stable state of the high stress balance in the coal pillar is easily broken by the impact energy formed by the sudden collapse of the key strata. Therefore, the rock burst of coal pillar in the overlying coal body area is the result of both static load and dynamic load. In view of the actual situation of the Kuangou Coal Mine, the treatment measures of rock burst are put forward from the point of view of the coal body and rock mass.

Characteristics of pedestrian flow based on an improved least-effort model considering body rotation

Body rotation is a common behavior in pedestrian flow dynamics. In this paper, an improved least-effort model is proposed to reproduce this behavior and other pedestrian flow characteristics. In this model, the pedestrian chooses the velocity and angle of body rotation according to the minimum energy cost. The energy cost includes the caloric expenditure in the walking, collision loss and body rotation cost. In order to validate the accuracy of the model, an experiment is conducted to investigate the bypassing/crossing and body rotation behavior quantitatively. The pedestrian can choose to walk through the exit or pass by the wall next to the exit, in order to reach the target place. When the exit is narrow, the pedestrian prefers to pass by the short wall, but cross through the exit in long-wall cases. As the exit gets narrower, the rotation angle increases. In the multi-pedestrian simulation, the pedestrian can avoid collision in the narrow corridor by body rotation. The body rotation will also enhance flow efficiency at the narrow bottleneck.

Effects of design parameters on behaviour in bottle-shaped struts

For this paper, an experimental investigation of the impact of the concentration ratio and the mats’ rotation angle on the behaviour and efficiency coefficient of the bottle-shaped struts was conducted. The behaviour of tested panels, including the load–transverse extension curve and strain redistribution, is presented and the quantitative effects of the concentration ratio and the mats’ rotation angle on the efficiency coefficient and the dispersion angle of compressive stresses of bottle-shaped struts are given. The related provisions of ACI 318-14 and BS EN 1992-1-1 are examined. The results indicate that as the concentration ratio increases, the efficiency coefficient and the dispersion angle decrease, and that as the mats’ rotation angle increases, the efficiency coefficient also increases. Some recommendations for ACI 318-14 and BS EN 1992-1-1 are finally presented.

A novel methodology for architectural wind environment study by integrating CFD simulation, multiple parametric tools and evaluation criteria

Nowadays wind environment research usually requires lots of comparisons of simulations to study influences on wind environment of building shapes and arrangements. This research aims to develop a novel methodology by integrating computational fluid dynamics (CFD) simulation, parametric tools and evaluation criteria. The integration of multiple tools can provide abundant functions and an efficient modelling-simulation-analysis solution for comparison studies. The methodology is consisted of parametric design, CFD simulation method and analysis method. It is further demonstrated in the case study of square form and scattered configuration to study the relationship between influences on winds and building variables through iterative analysis. For square form, the increase of edge length increases the influence, because more winds are obstructed by larger windward surfaces; the increase of rotation angle reduces the influence, because it is easier for winds to flow around non-vertical windward surfaces. For scattered configuration, the increase of building intervals reduces the influences on winds, because it is easier for winds to flow through larger intervals. In summary, the novel methodology provides an accurate and efficient integrated solution for wind environmental studies of contemporary buildings to explore basic laws for architects to improve their design on the early stage.