Effect of Scraper Geometry on Scraping HAP/ZrO2 Slurry in Digital Light Processing

Digital light processing (DLP) can be used to form HAP/ZrO2 mixed ceramic slurry. In the printing technology, the scraper geometry has an important effect on the scraping process; thus, it is necessary to conduct analysis. A modified lattice Boltzmann method (LBM) is proposed to conduct the numerical simulations according to the non-Newtonian behavior of the slurry. The Cross behavior of the slurry is viewed as a special external force; then, the traditional LBM including the true external force can be utilized effectively. The triangle, rectangle, trapezium, and rounded rectangle are the main considered section geometries of the scraper. When the flow velocity is set to 0.1 m/s, the results show that the maximum velocity occurs near the bottom surface of the scraper. In four situations, the velocity peak of the triangle case is 0.6270 m/s, which is the maximum, and much larger than the flow velocity of 0.1 m/s. The velocity peak of the rectangle case is 0.0466 m/s, which is the minimum. Although the velocity peak of the rounded rectangle case is 0.0556 m/s, the second velocity peak is 0.0465 m/s; the difference is smaller than that of the rectangle case. In addition, the streamlines figures show that the sharp corner leads to the obvious velocity change. In summary, the rounded rectangle is considered to be more suitable for scraping the HAP/ZrO2 mixed slurry.

Reconstruction of Velocity Curve in Long Stroke and High Dynamic Range Laser Interferometry

To study the law that governs the complex movements of the mechanism in the process of automatic weapon operation, the velocity tracking test technology of photon Doppler velocimetry is introduced to accurately measure velocity, displacement and acceleration, on the condition that there are long displacement and rapid velocity change. In the traditional way, out of interference signal time-frequency (TF) transformation draws TF distribution, and then by modulus maxima frequency extraction, comes to the law of velocity change. Due to the influence resulting from the change of fundamental signal as well as that of light intensity signal in the test, based on the TF distribution obtained by TF transformation, the traditional modulus maxima frequency extraction can extract frequency signals, but they show abnormal sudden changes at some moments, making the velocity discontinuous, unsmooth and unreal, which brings obvious errors to the subsequent calculation of acceleration and accurate displacement. Addressing the above-mentioned problems, this paper proposes a ridge extracting correction algorithm based on modulus maxima frequency extraction; this method, based on a large number of experiments where rodless cylinders are used to simulate the motion of a gun automatic mechanism, conducts a detailed calculation and analysis of the experimental results. A comparison of the two algorithms’ processing results, in terms of the speed, displacement and acceleration, suggests that the ridge extracting correction algorithm successfully corrects the frequency selection error, which draws a more continuous and, therefore, effective curve of the velocity change, and by so doing, the error of the displacement test (within 1.36 m displacement) is reduced from more than 3.6% to less than 0.58%, and the uncertainty dropped 97.07%. All these show that the accurate measurement of velocity, displacement and acceleration, with sudden and rapid velocity changes considered, is realized successfully.

Global Wave Velocity Change Measurement of Rock Material by Full-Waveform Correlation

Measuring accurate wave velocity change is a crucial step in damage assessment of building materials such as rock and concrete. The anisotropy caused by the generation of cracks in the damage process and the uncertainty of the damage level of these building materials make it difficult to obtain accurate wave velocity change. We propose a new method to measure the wave velocity change of anisotropic media at any damage level by full-waveform correlation. In this method, the anisotropy caused by the generation of cracks in the damage process is considered. The accuracy of the improved method is verified by numerical simulation and compared with the existing methods. Finally, the proposed method is applied to measure the wave velocity change in the damage process of rock under uniaxial compression. We monitor the failure process of rock by acoustic emission (AE) monitoring system. Compared with the AE ringing count, the result of damage evaluation obtained by the proposed method is more accurate than the other two methods in the stage of increasing rock heterogeneity. These results show that the proposed method is feasible in damage assessment of building materials such as rock and concrete.

Variability of flow velocity induced by Dongsam Seawater Stream Floodgate installation

The Dongsam seawater stream on a reclaimed land flows by tidal forcing. The flow in generally slow, especially in the central portion of the stream because the outflow and inflow each occurs at both ends of the stream simultaneously. As a result, sediments accmulate constantly with the deteorating water quality. In this study, field observation was conducted using Aquadrifter and Aquadopp and analyzed for the analysis of the flow velocity in the stream. The computational fluid dynamics (CFD) modeling was run with and without Seawater Stream Floodgate to predict the variability of the flow. The flow velocity of the Dongsam Seawater Stream was recorded in the range of 0.01 ~ 0.13 m/s, and the tidal range was within 1.0 m. According to the simulation, the flow velocity could increase remarkably with two floodgates used to force the stream to flow unidirectionally (toward Korea Maritime & Ocean University). The flow velocity change rate at each point is recorded -97 ~ 638% at P1 (front of Malfunction Floodgate near Busan Int. Cruise Terminal), -89 ~ 659% at P2 (back of Malfunction Floodgate near Busan Int. Cruise Terminal), -100 ~ 1198% at P3 (central channel), and at P4 (toward Korea Maritime & Ocean University) was -100 to 1163%, and Case III-a showed the largest flow velocity rate increase in the central part. Therefore, if two Floodgates are installed and flowed out toward Korea Maritime & Ocean University, the flow velocity rate of the Stream can be increased.

Numerical Solution of the Time-Depending Flow of Immiscible Fluids with Fuzzy Boundary Conditions

Fluid flow modeling using fuzzy boundary conditions is one of the viable areas in biofluid mechanics, drug suspension in pharmacology, as well as in the cytology and electrohydrodynamic analysis of cerebrospinal fluid data. In this article, a fuzzy solution for the two immiscible fluid flow problems is developed, which is motivated by biomechanical flow engineering. Two immiscible fluids, namely micropolar and Newtonian fluid, are considered with fuzzy boundary conditions in the horizontal channel. The flow is considered unsteady and carried out by applying a constant pressure gradient in the X-direction of the channel. The coupled partial differential equations are modeled for fuzzy profiles of velocity and micro-rotation vectors then the numerical results are obtained by the modified cubic B - spline differential quadrature method. The evolution of membership grades for velocity and microrotation profiles has been depicted with the fuzzy boundaries at the channel wall. It is observed that Micropolar fluid has a higher velocity change than Newtonian fluid, and both profiles indicate a declining nature toward the interface.

Debris Emergence Elevations and Glacier Change

Debris-covered glaciers represent potentially significant stores of freshwater in river basins throughout High Mountain Asia (HMA). Direct glacier mass balance measurements are extremely difficult to maintain on debris-covered glaciers, and optical remote sensing techniques to evaluate annual equilibrium line altitudes (ELAs) do not work in regions with summer-accumulation type glaciers. Surface elevation and glacier velocity change have been calculated previously for debris-covered glaciers across the region, but the response of debris cover itself to climate change remains an open question. In this research we propose a new metric, i.e. the debris emergence elevation (ZDE), which can be calculated from a combination of optical and thermal imagery and digital elevation data. We quantify ZDE for 975 debris-covered glaciers in HMA over three compositing periods (1985–1999, 2000–2010, and 2013–2017) and compare ZDE against median glacier elevations, modelled ELAs, and observed rates of both mass change and glacier velocity change. Calculated values of ZDE for individual glaciers are broadly similar to both median glacier elevations and modelled ELAs, but slightly lower than both. Across the HMA region, the average value of ZDE increased by 70 +/− 126 m over the study period, or 2.7 +/− 4.1 m/yr. Increases in ZDE correspond with negative mass balance rates and decreases in glacier velocity, while glaciers and regions that show mass gains and increases in glacier velocity experienced decreases in ZDE. Regional patterns of ZDE, glacier mass balance, and glacier velocities are strongly correlated, which indicates continued overall increases in ZDEE and expansion of debris-covered areas as glaciers continue to lose mass. Our results suggest that ZDE is a useful metric to examine regional debris-covered glacier changes over decadal time scales, and could potentially be used to reconstruct relative mass and ELA changes on debris-covered glaciers using historical imagery or reconstructed debris cover extents.

Multi-Scale Pseudo-Bending Raytracing for Arbitrary Complex Media

Raytracing is a fast and effective numerical simulation method of the seismic wavefield. It plays an important role in field data acquisition design, wavefield analysis, identification, and tomography. In raytracing, pseudo-bending (PB) is a fast and efficient method, but it is unsuitable for complex media with sudden velocity changes. An improved pseudo-bending raytracing method is presented in this paper, which can be applied to any complex medium. The proposed method first decomposes complex medium into multi-scale velocity components and then applies the pseudo-bending approach to the velocity components of different scales. The numerical simulation of seismic wavefield from models shows that the improved multi-scale pseudo-bending (MSPB) method can be applied to a medium with continuous velocity variation and any complex medium with abrupt velocity change.

Robust T-S Fuzzy Fault Tolerant Control for Vehicle Lateral Dynamics Stabilization with Integrated Actuator Fault and Time Delay

This paper investigates the lateral dynamics stabilization problem for autonomous electric vehicles (AEVs) through the active front steering (AFS) system. A fault-estimation-observer-based robust fuzzy fault tolerant controller is proposed to tackle actuator faults, time delay, modeling nonlinearities and external disturbances. Firstly, to establish a more accurate dynamics model, the Takagi-Sugeno fuzzy modeling strategy is utilized to handle velocity change and parameter uncertainties. Secondly, to further improve the lateral stability and driving active safety of the AEV, an integrated actuator fault model comprising efficiency loss fault and additional bias fault is proposed. Meanwhile, in order to diagnose actuator additional bias fault, a fuzzy fault estimation observer (FFEO) is designed to acquire fault information online. Thirdly, to eliminate the influence caused by integrated fault and actuator time delay, a fuzzy fault tolerant controller (FFTC) is constructed to improve the handling performance and driving active safety of the AEV. Finally, the effectiveness of the proposed control scheme is demonstrated via a full-car model based on the joint simulation of Carsim and MATLAB/Simulink.

Design of Gust Wind Tunnel With Unsteady and Shear Main-Flows

Micro air vehicles (MAVs) have been developed for many fields. The MAVs usually receive strong impact from a velocity change in time or space, and facilities for aerodynamic experiments of MAVs under a gusty environment have been required. The present study has developed a gust wind tunnel to generate unsteady and non-uniform flows. We developed a small wind tunnel with eight multi-fans and a shutter mechanism at the upstream of the test section. We controlled the outputs of the fans independently and obtained a linear shear layer with an error of 5 percent. The velocity gradient of the shear layer was from 5 to 8 s−1. The shutter mechanisms provided a longitudinal gust with the velocity change from 2 m/s to 10 m/s within 0.3 seconds.

Sensitivity of Ultrasonic Coda Wave Interferometry to Material Damage—Observations from a Virtual Concrete Lab

Ultrasonic measurements are used in civil engineering for structural health monitoring of concrete infrastructures. The late portion of the ultrasonic wavefield, the coda, is sensitive to small changes in the elastic moduli of the material. Coda Wave Interferometry (CWI) correlates these small changes in the coda with the wavefield recorded in intact, or unperturbed, concrete specimen to reveal the amount of velocity change that occurred. CWI has the potential to detect localized damages and global velocity reductions alike. In this study, the sensitivity of CWI to different types of concrete mesostructures and their damage levels is investigated numerically. Realistic numerical concrete models of concrete specimen are generated, and damage evolution is simulated using the discrete element method. In the virtual concrete lab, the simulated ultrasonic wavefield is propagated from one transducer using a realistic source signal and recorded at a second transducer. Different damage scenarios reveal a different slope in the decorrelation of waveforms with the observed reduction in velocities in the material. Finally, the impact and possible generalizations of the findings are discussed, and recommendations are given for a potential application of CWI in concrete at structural scale.