Initial Depth Research Articles

Experimental study on failure mode and failure mechanism of multi-box girder bridge under attack of tsunami

Comprehensive and intensive understanding to the failure process and failure mechanism of girder bridges is extremely crucial for anti-tsunami design of coastal bridges. The scaled down model of the multi-box girder bridge was manufactured and physical experiments were conducted in the dam-break flume to investigate the failure mode and failure mechanism. Results show that the superstructure can fail in three modes: HM (horizontal movement), HMR (horizontal movement with rotation) and HMRD (horizontal movement with rotation and dropping). And the two variables, namely the exceedance duration and the exceedance impulse, are proposed to analyze the possible failure mode and failure mechanism of the superstructure. The analysis conclusions obtained by the proposed method agree with the failure modes observed in the physical experiments. It is found that transverse horizontal movement of the superstructure always takes precedence over rotation and flow upward. With the increase of incoming tsunami bore height, the risk of failure increases; with the increase of the initial downstream water depth, the exceedance duration and exceedance impulse of horizontal force decreases firstly and then increases, the exceedance duration and exceedance impulse of vertical force and overturning moment increase.

Numerical study of water wave generation by granular-liquid mixture collapse using two-phase material point method

Debris flow sliding with high-speed and its possible interactions with a confined water body may lead to dangerous hazard. Therefore, it is important in practical applications to accurately predict the granular-liquid flows and their possible interactions with the water body. A two-phase material point method (MPM) with double-point formulation was applied in this paper to simulate the generation of the water wave by granular-liquid mixtures collapse into water. In our study, the debris flow was idealized as a granular-liquid mixture, the liquid phase was considered as a compressible viscous fluid, the granular response was modeled using the Mohr–Coulomb yield criterion and the granular-liquid interaction forces including viscous drag force and buoyancy force. Two experimental tests of dam-breaking flow and the wave generation by a dry granular column collapse were simulated, the accuracy and effectiveness of the proposed approach has been proven by comparing the numerical results with experimental data. We performed an experiment of saturated granular column collapsed into water and the test results were used to validate the proposed method, then applied the validated method to simulate the water wave generation by granular-liquid mixture collapse into water and investigate the effects of the initial degree of saturation defined as the initial depth ratio of water to granular material on the time evolution of the granular front and the amplitude of leading wave.

ПРИМЕНЕНИЕ КСЕНОГЕННОГО КОЛЛАГЕНОВОГО ГЕЛЯ И ЛАЗЕРНОГО ИЗЛУЧЕНИЯ ПРИ ПРОФИЛАКТИКЕ И ЛЕЧЕНИИ ПЕРИИМПЛАНТИТА: ПИЛОТНОЕ ИССЛЕДОВАНИЕ

Subject. The periimplantitis management and prophylaxis technique using xenogenic collagen gel and laser technique, analysis of their results.
 Aim. To evaluate the effect of periimplantitis management and prophylaxis with xenogenic collagen gel and laser technique. 
 Methodology. The study was conducted on the basis of Sechenov University from 2020 to 2022. The study included ten patients with diagnosed peri-implantitis (age range 28–45 years, median is 35 years). All patients underwent professional hygiene followed by division into 2 groups by random sampling: patients of group 1 were injected with xenogenic collagen gel in the area of the peri-implant pocket and in the soft tissues around the dental implant in the area of alveolar bone resorption, patients of group 2 were subjected to laser bactericidal treatment of peri-implant pockets. The results were evaluated by the depth of probing of the peri-implant pocket and the clinical symptoms of the disease, the presence of adverse outcomes after the application of the techniques.
 Results. During 12 months of observation, a decrease in the depth of the peri-implant pocket during probing was noted by an average of 3 mm from the initial depth in both groups (p < 0.05), an increase in the volume of soft tissues around the implants, mainly when xenogenic gel was used (p < 0.05).
 Conclusions. Xenogenic collagen gel and laser microbiocidal treatment of peri-implant pockets may be an alternative treatment for peri-implantitis after full-fledged randomized clinical multicenter trials.

Molecular dynamics study of primary damage in the near-surface region in nickel

We carried out a large-scale molecular dynamics (MD) simulation to study displacement cascades in the near-surface region in pure nickel. These MD simulations were performed both in the bulk and near-surface regions with primary knock-on atom (PKA) energies of EPKA=1,5, or 10keV and at temperatures T=300,425, or 525K. In our study, the primary knock-on atom was taken to be created by a neutron knocking off a lattice atom. Accordingly, cascades were initiated by giving a lattice atom the appropriate velocity corresponding to the PKA energy. Assuming isotropic neutron fluence, the PKA was initiated in random directions (including toward and parallel to the free surface) in both bulk and near-surface simulations. This contrasts with previous studies in which the cascades were initiated by the projectiles directed toward the free surface to mimic ion irradiation. Therefore, for every (T,EPKA), near-surface cascade simulations were performed also as a function of PKA's initiation depth. Present results provide quantitative information about defect production and clustering in the primary damage state for near-surface and bulk displacement cascades. The effect of EPKA and T on the defect production (averaged over all PKA directions) is similar for both the near-surface and bulk cascades. In both cases, the defect production increases with EPKA, but the temperature has minimal effect. However, the production and clustering of vacancies are higher for near-surface cascades. In contrast, the production and clustering of self-interstitial atoms are lower and increase monotonically with depth. The decrease in the average number of vacancies and average vacancy cluster size with increasing depth is not monotonic.

Improving the planarity and sharpness of monocularly estimated depth images using the Phong reflection model

Depth estimation based on a single RGB image (a.k.a. monocular depth estimation) is a challenging task, with applications in robotics, autonomous vehicles, and other areas. With the advance of deep learning, several monocular depth estimation approaches have emerged with remarkable results. However, it is still possible to observe deficiencies in the depth maps generated by current techniques. We present a deep neural network that takes the result produced by some existing monocular depth estimation approach and enhances it by adding the details that the depth map requires to be sharp. We train the proposed Depth Enhancer Neural Network (DENN) using a new loss function that compares the input color image of the scene to the color image produced by rendering it using the Phong reflection model. Our experiments show a clear visual improvement in the sharpness of the depth image produced by the DENN, leading to edge enhancement and regularity of planar surfaces without compromising non-planar objects. On average, the standard metrics show a 5% reduction in error when considering the quantitative results. This reduction is dependent on the initial monocular depth estimation technique used by DENN to train the model.

Collagen fiber anisotropy characterization by polarized photoacoustic imaging for just-in-time quantitative evaluation of burn severity

Just-in-time burn severity assessment plays a vital role in burn treatment and care. However, it is still difficult to quantitatively and promptly evaluate burn severity by existing medical imaging methods via initial burn depth measurement since burn wounds are usually dynamically developed. As an elastic skeleton of skin, the degree of conformational changes of collagen fibers caused by overheating can reflect the burn severity in a timelier manner. Herein, the polarized photoacoustic technique (PPAT) for just-in-time quantitative evaluation of burn severity via collagen fiber anisotropy assessment is proposed. First, phantom experiments demonstrate the ability of PPAT for deep imaging in a transport mean free path and accurately quantify changes in microstructural order by thermal damage. Then, the Pearson correlation coefficient of the PPAT in assessing burn severity is shown to be up to 0.95, validated by burn skin samples. The PPAT provides a just-in-time quantitative strategy for burn severity evaluation.

A Fast VVC Intra Prediction Based on Gradient Analysis and Multi-Feature Fusion CNN

The Joint Video Exploration Team (JVET) has created the Versatile Video Coding Standard (VVC/H.266), the most up-to-date video coding standard, offering a broad selection of coding tools. The maturity of commercial VVC codecs can significantly reduce costs and improve coding efficiency. However, the latest video coding standards have introduced binomial and trinomial tree partitioning methods, which cause the coding units (CUs) to have various shapes, increasing the complexity of coding. This article proposes a technique to simplify VVC intra prediction through the use of gradient analysis and a multi-feature fusion CNN. The gradient of CUs is computed by employing the Sobel operator, the calculation results are used for predecision-making. Further decisions can be made by CNN for coding units that cannot be judged whether they should be segmented or not. We calculate the standard deviation (SD) and the initial depth as the input features of the CNN. To implement this method, the initial depth can be determined by constructing a segmented depth prediction dictionary. For the initial segmentation depth of the coding unit, regardless of its shape, it can also be determined by consulting the dictionary. The algorithm can determine whether to split CUs of varying sizes, decreasing the complexity of the CU division process and making VVC more practical. Experimental results demonstrate that the proposed algorithm can reduce encoding time by 36.56% with a minimal increase of 1.06% Bjøntegaard delta bit rate (BD-BR) compared to the original algorithm.

Protective effect of ecological embankment on a building subjected to tsunami bores

The mangrove has a remarkable wave reducing effect, and it is arranged around the embankment to form an ecological embankment (eco-embankment), which complement each other's strengths. The tsunami wave simulated by the dam breaking wave is used in the flume to impact the test models. By measuring the tsunami bore height, transmission coefficient and impact pressure, and observing the flow state during the impact process, the wave elimination effect and protection effect of the eco-embankment are studied. The results show that the bore height is related to the initial water depth and the reservoir water level. The change of water level in the eco-embankment setting area (front, top, and behind of embankment) is related to the bore height, the location and the distribution density of mangroves. The transmission coefficient increases linearly with the relative water depth, but the magnitude of the increase is different for each eco-embankment model. Based on the experimental data, the equations for estimating the transmission coefficient are proposed. When tsunami waves impact buildings protected by embankments or eco-embankments, the pressure decreases and the time history of pressure appear a reflection stage compared to an unprotected building, this stage will change with the initial water depth and the distribution density of mangroves. Finally, based on the measured pressure data, the equations for estimating the dimensionless quasi-steady pressure for different models and different mangrove distribution densities are proposed as functions of relative height and Froude number, the calculated value is in good agreement with the measured value.

청수현상 추정을 위한 댐 붕괴 흐름의 유체동역학적 특성에 관한 실험적 연구

In this study, hydrodynamic characteristics of dam break flow were investigated by a series of experiments. The experiments were performed in a 2-D rectangular flume with obtaining instantaneous images of dam break flow to capture the free surface elevation, and pressure distributions on vertical wall and bottom of the flume. The initial water depth of the dam break flow was changed into 3 different heights, and the gate opening speed was changed during the experiments to study the effect of the gate speed in the dam break flow. Generation of dam break phenomena could be classified into three stages, i.e., very initial, relatively stable, and wall impact stages. The wall impact stage could be separated into 4 generation phases of wall impinge, run-up, overturning, and touchdown phases based on the deformation of the free surface. The free surface elevation were investigated with various initial water depth and compared with the analytic solutions by Ritter (1892). The pressures acting on the vertical wall and bottom were provided for the whole period of dam break flow varying the initial water depth and gate open speed. The measurement results of the dam break flow was compared with the hydrodynamic characteristics of green water phenomena, and it showed that the dam break flow could overestimate the green water loading based on the estimation suggested by Buchner (2002).

An Integrated Approach for Simulating Debris-Flow Dynamic Process Embedded with Physically Based Initiation and Entrainment Models

Recent studies have indicated that the accurate simulation of debris flows depends not only on the selection of numerical models but also on the availability of precise data on the initial source location and depth. Unfortunately, it is currently difficult to obtain quantitative data on source locations and depths during field investigations or model experiments of debris flow disasters. Therefore, in this study, we propose an integrated approach for simulating the debris-flow dynamic process that includes the physically based slope initiation source estimation and the entrainment-incorporated process simulation. We treat the potential slip surfaces’ locations and depths as random variables to search for the critical surface corresponding to the minimum stability factor by Monte Carlo simulation. Using the spatial variation interval of the soil parameters, we estimate the range of possible critical slip surfaces and the interval of the initiation source volume. Moreover, we propose a wet/dry front treatment method applied to the finite difference scheme and integrate it into our entrainment-incorporated model to improve the stability and accuracy of the numerical solution over complex topography. The effectiveness of the method is demonstrated through a case study of the 2010 Hongchun debris flow event in Yingxiu town. The result indicates that our method is effective in simulating debris flow dynamics, including slope initiation source estimation and dynamic process simulation.

Geometric Prior-Guided Self-Supervised Learning for Multi-View Stereo

Recently, self-supervised multi-view stereo (MVS) methods, which are dependent primarily on optimizing networks using photometric consistency, have made clear progress. However, the difference in lighting between different views and reflective objects in the scene can make photometric consistency unreliable. To address this issue, a geometric prior-guided multi-view stereo (GP-MVS) for self-supervised learning is proposed, which exploits the geometric prior from the input data to obtain high-quality depth pseudo-labels. Specifically, two types of pseudo-labels for self-supervised MVS are proposed, based on the structure-from-motion (SfM) and traditional MVS methods. One converts the sparse points of SfM into sparse depth maps and combines the depth maps with spatial smoothness constraints to obtain a sparse prior loss. The other generates initial depth maps for semi-dense depth pseudo-labels using the traditional MVS, and applies a geometric consistency check to filter the wrong depth in the initial depth maps. We conducted extensive experiments on the DTU and Tanks and Temples datasets, which demonstrate that our method achieves state-of-the-art performance compared to existing unsupervised/self-supervised approaches, and even performs on par with traditional and supervised approaches.

Effect of Rotary Speed on Soil and Straw Throwing Process by Stubble-Crushing Blade for Strip Tillage Using DEM-CFD

Strip tillage is a widely used land preparation approach for effective straw management in conservation agriculture. Understanding the dynamic throwing process during the stubble-crushing operation has important implications for seedbed preparation. However, the airflow generated by the high-speed rotation of stubble-crushing blades has yet to be considered. We established a coupled DEM-CFD simulation model and explored the dynamic motion of soil particles varied with their initial depth (at 0, 20, 40, 60, 80 mm depth) and surface straw under different blade rotary speeds (270, 540, 720, and 810 rpm) based on the model. The coupled model simulation results were proved to be well correlated with the field test results by the field high-speed camera test. The simulation results showed that airflow had a significant effect on the longitudinal displacement of straw (p < 0.05). An increase in rotary speed could increase the longitudinal and lateral throwing displacement of soil particles and straw and increase the blade–soil–straw interaction, while there was no directional effect on the vertical motion. The lateral movement of soil particles decreased with increasing soil particle depth. The stubble-crushing operation allowed the exchange of deep and shallow soil layers, as well as the burial of straw. Plain, straight stubble-crushing blades with a rotary speed of 540 rpm were able to form the optimal seeding row with a width of 80.86 mm. The simulation results were useful for assessing the design solutions of high-speed rotational tools and evaluating seedbed preparation practices.

Phase-Resolved Optical Coherence Elastography: An Insight into Tissue Displacement Estimation.

Robust methods to compute tissue displacements in optical coherence elastography (OCE) data are paramount, as they play a significant role in the accuracy of tissue elastic properties estimation. In this study, the accuracy of different phase estimators was evaluated on simulated OCE data, where the displacements can be accurately set, and on real data. Displacement (∆d) estimates were computed from (i) the original interferogram data (Δφori) and two phase-invariant mathematical manipulations of the interferogram: (ii) its first-order derivative (Δφd) and (iii) its integral (Δφint). We observed a dependence of the phase difference estimation accuracy on the initial depth location of the scatterer and the magnitude of the tissue displacement. However, by combining the three phase-difference estimates (Δdav), the error in phase difference estimation could be minimized. By using Δdav, the median root-mean-square error associated with displacement prediction in simulated OCE data was reduced by 85% and 70% in data with and without noise, respectively, in relation to the traditional estimate. Furthermore, a modest improvement in the minimum detectable displacement in real OCE data was also observed, particularly in data with low signal-to-noise ratios. The feasibility of using Δdav to estimate agarose phantoms' Young's modulus is illustrated.

Long-term stability of infrabony defects treated with enamel matrix derivative alone: A retrospective two-centre cohort study.

To assess the long-term stability of attachment gain in infrabony defects (IBDs) 10 years after regenerative treatment with an enamel matrix derivative (EMD) alone. Two centres (Frankfurt [F] and Heidelberg [HD]) invited patients for re-examination 120 ± 12 months after regenerative therapy. Re-examination included clinical examination (periodontal probing depths (PPD), vertical clinical attachment level (CAL), plaque index (PlI), gingival index (GI), plaque control record, gingival bleeding index and periodontal risk assessment) and review of patient charts (number of supportive periodontal care [SPC] visits). Both centres included 52 patients (29 female; median baseline age: 52.0 years; lower/upper quartile: 45.0/58.8 years; eight smokers), each contributing one IBD. Nine teeth were lost. For the remaining 43 teeth, regenerative therapy showed significant CAL gain after 1 year (3.0; 2.0/4.4 mm; p < .001) and 10 years (3.0; 1.5/4.1 mm; p < .001) during which CAL remained stable (-0.5; -1.0/1.0 mm; p = 1.000) after an average SPC of 9 years. Mixed-model regression analyses revealed a positive association of CAL gain from 1 to 10 years with CAL 12 months post operation (logistic: p = .01) as well as a higher probability for CAL loss with an increasing vertical extent of a three-walled defect component (linear: p = .008). Cox proportional hazard analysis showed a positive association between PlI after 12 months and tooth loss (p = .046). Regenerative therapy of IBDs showed stable results over 9 years. CAL gain is associated with CAL after 12 months and decreasing initial defect depth in a three-walled defect morphology. Tooth loss is associated with PlI 12 months post operation. DRKS00021148 (URL: https://drks.de).

Fracture failure analysis of insulation with initial crack defect for stator end-winding in induction motor by using magnetic-structural coupling model

The insulation mechanic failure in stator end-winding of induction motor is usually an early and serious cause to weaken the residual breakdown electrical field strength and produce the short-circuit fault, especially subjecting to the combination of dynamical electromagnetic forces, mechanical stress and vibration. In this paper, the fracturebehavior of insulation layer with considering the initial crack defects and end-hoop support failures in end-windings were analyzed by using magnetic-structural coupling model and finite element method (FEM). Firstly, the distributions of magnetic flux density and electromagnetic force around the stator end region were determined by injecting three-phase alternating current. Secondly, the dynamic characteristics of deformation, stress and strain in winding insulation were respectively calculated by coupling the transient electromagnetic and structural analysis. Furthermore, the weak points of the concentrated stress and strain were located. Thirdly, the crack model mounted in winding insulation is defined and simulated by employing three-dimensional (3-D) semi-elliptical crack element. To evaluate the fracture mechanism and the degree of crack expansion quantitatively, the stress intensity factor (SIF) was introduced. Finally, the influence of crack location, direction, depth and end-hoop support failure on SIF and crack propagation were investigated. Results show that the concentrated stress at knuckle part of the coil insulation is lager quite larger than that of other parts. The SIF of transverse crack is larger than that of longitudinal cracks. The larger the initial crack depth in the stator end-winding insulation, the more serious the tendency and degree of crack fracture. Local end-hoop support failure also has an important influence on the crack propagation. Results in this study may contribute to the understanding of fracturefailure behaviors in insulation under dynamical electromagnetic vibration and provide necessary theoretical reference for fault diagnosis and prediction of stator winding in induction motors.

Joint Deep Learning and Information Propagation for Fast 3D City Modeling

In the field of geoinformation science, multiview, image-based 3D city modeling has developed rapidly, and image depth estimation is an important step in it. To address the problems of the poor adaptability of training models of existing neural network methods and the long reconstruction time of traditional geometric methods, we propose a general depth estimation method for fast 3D city modeling that combines prior knowledge and information propagation. First, the original image is downsampled and input into the neural network to predict the initial depth value. Then, depth plane fitting and joint optimization are combined with the superpixel information and the superpixel optimized depth value is upsampled to the original resolution. Finally, the depth information propagation is checked pixel-by-pixel to obtain the final depth estimate. Experiments were conducted using multiple image datasets taken from actual indoor and outdoor scenes. Our method was compared and analyzed with a variety of existing widely used methods. The experimental results show that our method maintains high reconstruction accuracy and a fast reconstruction speed, and it achieves better performance. This paper offers a framework to integrate neural networks and traditional geometric methods, which provide a new approach for obtaining geographic information and fast 3D city modeling.

Correlation of residual stress, hardness and surface roughness with crack initiation and fatigue strength of surface treated additive manufactured AlSi10Mg: Experimental and machine learning approaches

Post-processing methods are widely used to address the issues caused by surface imperfections and bulk defects in additive manufactured materials. In our previous studies, we analysed the effects of different peening-based treatments of shot peening (SP), severe vibratory peening (SVP) and laser shock peening (LSP) on fatigue performance of V-notched laser powder bed fusion AlSi1Mg samples. Herein, the fracture surfaces of failed samples were further analyzed and obtained experimental data were further elaborated by machine learning (ML)-based approach to identify the correlation between residual stress, hardness and surface roughness (all affected by the applied post-treatments) with the depth of crack initiation site and fatigue life of the post-treated samples. ML-based model was developed via a six layer deep neural network (DNN) as well as using stacked auto-encoder (SAE) for pre-training of the used data set. Taking the advantages of SAE, the accuracies of more than 0.96 were obtained for the predicted results. Correlations were obtained by performing parametric analyses and the importance of each input factor was assessed through sensitivity analyses. The obtained results revealed that by enhancing surface hardening and inducing higher compressive residual stresses as well as more efficient surface roughness reduction, deeper crack initiation site and superior fatigue life can be obtained. In addition, it was found that the depth of sub-surface crack initiation had direct relation with fatigue life improvement in the samples.

Research on damage effect of penetration and explosion integration based on volume filling method

It is difficult to distinguish the damage effects of penetration and explosion loads in the test of projectile penetration and explosion integration. At present, there is no mature method to simulate the whole process of projectile penetration and dynamic explosion integration. To solve this problem, a numerical simulation method of projectile penetration and explosion integration based on the volume filling method is proposed, the explosive material is generated by volume filling in the background grid (ALE), and given the same initial velocity as the cartridge case. The fluid-structure coupling algorithm is set to restrict the cooperative deformation and movement of the cartridge case and the explosive, the static or dynamic explosion occurred after the cartridge case and the explosive penetrate the target medium synchronously. The empirical formula is used to verify the model of the inert projectile penetration process, and the numerical simulation of the whole process of penetration and dynamic explosion integration and penetration and static explosion integration is completed. The change rule of the medium internal pressure field, surface crater, and crater depth are given, and the damage effects of penetration and explosion loads in the process of penetration and explosion integration are quantitatively analyzed. The results show that: when the penetration and dynamic explosion integration, the non-dissipated penetration wave field in the target medium will be superimposed with the explosion shock wave field, and the pressure peak is higher than that of the single explosion wave field of charge static explosion after penetration, but it is not obvious; When the penetration and dynamic explosion integration, the dynamic explosive effect of the explosive makes the explosion shock wave field in the medium present an irregular spherical distribution, which has an influence that can not be ignored. When the target velocity is fixed, the later the initiation time is, the smaller the surface crater is and the greater the crater depth is; In the case of fixed initiation depth, the greater the target velocity, the smaller the surface crater, and the greater the crater depth.

Development of an analytical model to predict the churning power losses of an orthogonal face gear

As one of the basic energy dissipations for one orthogonal face gear running partially submerged in an oil bath, there is no open literature concerned on the churning power losses of the face gear. This paper proposed a series of formulas to predict the churning losses for one orthogonal face gear running partially submerged in an oil bath. The analytical model of churning drag forces is based on fluid mechanics and boundary layer theory which enables quantitatively calculating the influences of the rotating speed, fluid attributes, and gear geometric construction with the minimum effort. Then, an ad hoc test bench was set up to carry out the specific splash lubrication tests for single face gear at different rotating speeds and initial immersion depth. Finally, considering both the churning and windage effects, a physical-based model adopting the real-time immersion depth instead of the static immersion depth is developed to calculate the total load-independent losses of a splash lubricated face gear. From this, the theoretical results are compared well with sets of directly measured experimental findings. Meanwhile, the model is also exploited to quantitate the contributions of each part in the total load-independent losses for one face gear under splash lubrication condition.

Insights from the first winter weather observations near Mount Everest's summit

Insights from the first winter weather observations near Mount Everest's summit