A Hybrid Conjugate Gradient Algorithm for Solving Relative Orientation of Big Rotation Angle Stereo Pair

The fast convergence without initial value dependence is the key to solving large angle relative orientation.Therefore,a hybrid conjugate gradient algorithm is proposed in this paper.The concrete process is:①stochastic hill climbing(SHC)algorithm is used to make a random disturbance to the given initial value of the relative orientation element,and the new value to guarantee the optimization direction is generated.②In local optimization,a super-linear convergent conjugate gradient method is used to replace the steepest descent method in relative orientation to improve its convergence rate.③The global convergence condition is that the calculation error is less than the prescribed limit error.The comparison experiment shows that the method proposed in this paper is independent of the initial value,and has higher accuracy and fewer iterations.

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.

Multiple rotation averaging using only the relative rotation angle

In this work,we propose multiple rotation averaging using only the relative rotation angle,which is a straightforward camera pose optimization method.We use the axis-angle representation to parameterize the rotation and use only relative rotation angles to constrain absolute rotations instead of complete relative rotations.When used with an inertial measurement unit(IMU),our method can obviate the need to estimate and maintain extrinsic parameters between the camera and IMU.This advantage makes our method immune to extrinsic parameters and flexible.We performed extensive evaluations on both synthetic data and publicly available real datasets,which showed that our method was comparable with the state-of-the-art method and achieved a significant gain in accuracy for the visual measurement when applied to the case in which the camera and IMU are tightly fixed.

Analytical evaluation and experimental validation on dynamic rocking behavior for shallow foundation considering structural response

The challenge in the practical application of rocking foundations is the estimation of its performance,particularly the rotation angle,during a strong earthquake.In this study,the dynamic rocking behavior for a shallow foundation considering structural response was evaluated through two analytical approaches:the conventional soil-foundation-structure interaction(SFSI)governing equation of a single-degree-of-freedom(SDOF)structure on a rocking shallow foundation,and the Housner rocking model(i.e.,a rocking rigid block on a rigid base).Both approaches were validated with dynamic centrifuge tests.The test models consisted of a soft soil deposit,a shallow rectangular foundation,and an SDOF structure dominated by a bending behavior.A total of 11 foundation-structure systems and six seismic waves,including recorded earthquake signals and sinusoidal waves,were utilized.The results showed that the conventional SFSI equation well predicted the maximum rotation during strong earthquakes.However,this method was less accurate regarding the rotational phase information and maximum rotation of the foundation during weak earthquakes.On the other hand,although the modified Housner′s rocking model required five parameters relevant to a soil-foundation-structure system,it overestimated the maximum rotation of the foundation when compared with the results from dynamic centrifuge tests.

Three-dimensional numerical analysis on combustion performance and flow of hybrid rocket motor with multi-segmented grain

This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical simulations.Multi-segmented grain is composed of several thin grains with two or more ports.The numerical model consists of Navier-Stokes equations with turbulence,solid fuel pyrolysis,chemical reactions,a fluid–solid coupling model and a regression rate model.The simulations adopt 90%Hydrogen Peroxide(HP)and PolyEthylene(PE)as the propellant combination.The effects of the rotation,port number,fuel grain segment number and mid-chamber length on the flow field and combustion performances are analyzed.The results indicate that the multi-segmented grain configuration can strengthen the flow field,and the regression rate and combustion efficiency are enhanced.Take the cases with two grain segments and three ports for example,the regression rate is increased by 32.4%-45.1%and the combustion efficiency increases by 6%-8.6%in different rotation angles.

Kinematics of Non-axially Positioned Vesicles through a Pore

We employ finite element method to investigate the kinematics of non-axially positioned vesicles through a pore.To complete the coupling between fluid flow and the vesicle membranes,we use the fluid structure interactions with the arbitrary Lagrangian Eulerian method.Our results demonstrate that the vesicles show different deformations in migration process,in turn an oblique ellipse-shape,slipper-shape,oval-shape.We find that the rotation angle of non-axially positioned vesicles mainly shows the trend of increase,besides the small fluctuation induced by deformation relaxation.Moreover,when the vesicles move towards the axis of the channel,the rotation angle exhibits a decrease because of the decrease of the shear force.However,rotation of axially positioned vesicles hardly occur due to symmetrical shear force.Our results further indicate that the rotation is faster nearby the pore for non-axially positioned vesicles.Our work answers the mapping between the positions of vesicles and deformed states,as well as the change of rotation angle and rotation velocity,which can provide helpful information on the utilization of vesicles in pharmaceutical,chemical,and physiological processes.

Transmission characteristics of linearly polarized light in reflection-type one-dimensional magnetophotonic crystals

The propagation properties of linearly polarized light in reflection・type one-dimensional magnetoph tonic crystals are studied by using the 4×4 transmission matrix method.The structure models of reflectiotype one-dimensional magnetophotonic crystals are designed,the magnetic field direction control characteristics of reflection spectrum and Kerr rotation angle are discussed,and the effect of applied magnetic field direction and strength on reflection spectrum and Kerr rotation angle are analyzed.The results show that the non-diagonal elements in the dielectric constant of magneto optical materials change when the angle φ between applied magnetic field and optical path changes,the reflectivity and Kerr rotation angle decrease when the angle φ increases;when the applied magnetic field strength changes,the reflectivity and Kerr rotation angle increase when the applied magnetic field strength increases;by adjusting the angleφ and strength of the applied magnetic field,the rotation angle of Kerr can be adjusted to 45°,and a more flat reflection spectrum can be obtained by designing the appropriate structure.

Damage Detection for Simply Supported Bridge with Bending Fuzzy Stiffness Consideration

The benchmark of a simply supported beam with damage and bending fuzzy stiffness consideration is established to be utilized for damage detection. The explicit expression describing the Rotational Angle Influence Lines(RAIL) of the arbitrary section in the benchmark is presented as the nonlinear relation between the moving load and the RAIL appeared, when the moving load is located on the damage area. The damage detection method is derived based on the Difference of the RAIL Curvature(DRAIL-C) prior to and following arbitrarily section damage in a simply supported beam with bending fuzzy stiffness consideration. The results demonstrate that the damage position can be located by the DRAIL-C graph and the damage extent can be calculated by the DRAIL-C curve peak. The simply supported box girder as a one-dimensional model and the simply supported truss bridge as a three-dimensional model with the bending fuzzy stiffness are simulated for the validity of the proposed method to be verified. The measuring point position and noise intensity effects are discussed in the simply supported box girder example. This paper provides a new consideration and technique for the damage detection of a simply supported bridge with bending fuzzy stiffness consideration.