Numerical Modeling of Debris Flows Induced by Dam-Break Using the Smoothed Particle Hydrodynamics (SPH) Method

Dam-break flows may change into debris flows if certain conditions are satisfied, such as abundant loose material and steep slope. These debris flows are typically characterized by high density and can generate strong impact forces. Due to the complexity of the materials that they are made of, it has always been very challenging to numerically simulate these phenomena and accurately reproduce experimentally debris flows’ processes. Therefore, to fill this gap, the formation-movement processes of debris flows induced by dam-break were simulated numerically, modifying the existing smoothed particle hydrodynamics (SPH) method. By comparing the shape and the velocity of dam break debris flows under different configurations, it was found that when simulating the initiation process, the number of particles in the upstream section is overestimated while the number of particles in the downstream area is underestimated. Furthermore, the formation process of dam-break debris flow was simulated by three models which consider different combinations of the viscous force, the drag force and the virtual mass force. The method taking into account all these three kinds of interface forces produced the most accurate outcome for the numerical simulation of the formation process of dam-break debris flow. Finally, it was found that under different interface force models, the particle velocity distribution did not change significantly. However, the direction of the particle force changed, which is due to the fact that the SPH model considers generalized virtual mass forces, better replicating real case scenarios. The modalities of dam failures have significant impacts on the formation and development of debris flows. Therefore, the results of this study will help authorities to select safe sites for future rehabilitation and relocation projects and can also be used as an important basis for debris flow risk management. Future research will be necessary to understand more complex scenarios to investigate mechanisms of domino dam-failures and their effects on debris flows propagation

Solid Freeform Fabrication of Artificial Human Teeth

In this paper, we describe a solid freeform fabrication procedure for human dental restoration via porcelain slurry micro-extrusion. Based on submicron-sized dental porcelain powder obtained via ball milling process, a porcelain slurry formulation has been developed. The formulation developed allows the porcelain slurry to show a pseudoplastic behavior and moderate viscosity, which permits the slurry to re-shape to form a near rectangular cross section. A well-controlled cross-section geometry of the extrudate is important for micro-extrusion to obtain uniform 2-D planes and for the addition of the sequential layers to form a 3-D object. Human teeth are restored by this method directly from CAD digital models. After sintering, shrinkage of the artificial teeth is uniform in all directions. Microstructure of the sintered teeth is identical to that made via traditional dental restoration processes.Mechanical Engineerin

Numerical Simulation of Non-Homogeneous Viscous Debris-Flows Based on the Smoothed Particle Hydrodynamics (SPH) Method

Non-homogeneous viscous debris flows are characterized by high density, impact force and destructiveness, and the complexity of the materials they are made of. This has always made these flows challenging to simulate numerically, and to reproduce experimentally debris flow processes. In this study, the formation-movement process of non-homogeneous debris flow under three different soil configurations was simulated numerically by modifying the formulation of collision, friction, and yield stresses for the existing Smoothed Particle Hydrodynamics (SPH) method. The results obtained by applying this modification to the SPH model clearly demonstrated that the configuration where fine and coarse particles are fully mixed, with no specific layering, produces more fluctuations and instability of the debris flow. The kinetic and potential energies of the fluctuating particles calculated for each scenario have been shown to be affected by the water content by focusing on small local areas. Therefore, this study provides a better understanding and new insights regarding intermittent debris flows, and explains the impact of the water content on their formation and movement processes

Pinning Cluster Synchronization in Linear Hybrid Coupled Delayed Dynamical Networks

The problem on cluster synchronization will be investigated for a class of delayed dynamical networks based on pinning control strategy. Through utilizing the combined convex technique and Kronecker product, two sufficient conditions can be derived to ensure the desired synchronization when the designed feedback controller is employed to each cluster. Moreover, the inner coupling matrices are unnecessarily restricted to be diagonal and the controller design can be converted into solving a series of linear matrix inequalities (LMIs), which greatly improve the present methods. Finally, two numerical examples are provided to demonstrate the effectiveness and reduced conservatism

Advances in the adsorption of heavy metal ions in water by UiO-66 composites

The innovative adsorbents known as the Metal-organic Framework (MOFs) had a high specific surface area, various structural types, and good chemical stability. MOFs have been produced through hydrothermal, mechanochemical, microwave-assisted, gelation, and other synthesis methods, and the solvothermal process is one of them that researchers frequently utilize. The UiO materials have a more comprehensive application potential than different subtypes of MOFs among the numerous MOFs that have been synthesized. The synthesis of MOFs and their composites, as well as the adsorption characteristics of UiO materials in the adsorption of various heavy metal ions, have all been examined and summarized in this study

An Experimental Investigation of Turbulence Features Induced by Typical Artificial M-Shaped Unit Reefs

Artificial reefs are considered to have the function of repairing and improving the coastal habitat and increasing the fishery production, which are mainly achieved by changing the regional hydrodynamic conditions. The characteristics of flow turbulence structure are an important part of the regional hydrodynamic characteristics. Different methods are used to evaluate the performance of artificial reefs according to their shape and the purpose for which the reef was built. For this study, the M-shaped unit reefs, which are to be put into the area of Liaodong Bay, were selected as the research object and have never been fully investigated before. Experimental tests were conducted to assess the effect of these M-shaped artificial reefs on the vertical and longitudinal turbulent intensity under different hydraulic conditions and geometries, and datasets were collected by using the Particle Image Velocimetry technique implemented within the experimental facility. The distribution and variation characteristics of the turbulence intensity were analyzed, and the main results obtained can confirm that in the artificial reef area, there was an extremely clear turbulent boundary. Furthermore, the area of influence of the longitudinal turbulence was identified to be larger than that of the vertical turbulence, and the position where the maximum turbulence intensity appeared was close to where the maximum velocity was measured. Finally, results demonstrate that low turbulence conditions are typically located in front of the unit reef, the general turbulence area is located within the upwelling zone, and the more intense turbulence area is located between the two M-shaped monocases. These results are extremely important, because they provide the local authorities with specific knowledge about what could be the effect of these M-shaped reefs within the area where they will be implemented, and therefore, specific actions can be taken in consideration with the geometrical setup suggested as an optimal solution within this study

Expression of fatty acid synthesis genes and fatty acid accumulation in haematococcus pluvialis under different stressors

<p>Abstract</p> <p>Background</p> <p>Biofuel has been the focus of intensive global research over the past few years. The development of 4^thgeneration biofuel production (algae-to-biofuels) based on metabolic engineering of algae is still in its infancy, one of the main barriers is our lacking of understanding of microalgal growth, metabolism and biofuel production. Although fatty acid (FA) biosynthesis pathway genes have been all cloned and biosynthesis pathway was built up in some higher plants, the molecular mechanism for its regulation in microalgae is far away from elucidation.</p> <p>Results</p> <p>We cloned main key genes for FA biosynthesis in <it>Haematococcus pluvialis</it>, a green microalga as a potential biodiesel feedstock, and investigated the correlations between their expression alternation and FA composition and content detected by GC-MS under different stress treatments, such as nitrogen depletion, salinity, high or low temperature. Our results showed that high temperature, high salinity, and nitrogen depletion treatments played significant roles in promoting microalgal FA synthesis, while FA qualities were not changed much. Correlation analysis showed that acyl carrier protein (ACP), 3-ketoacyl-ACP-synthase (KAS), and acyl-ACP thioesterase (FATA) gene expression had significant correlations with monounsaturated FA (MUFA) synthesis and polyunsaturated FA (PUFA) synthesis.</p> <p>Conclusions</p> <p>We proposed that ACP, KAS, and FATA in <it>H. pluvialis </it>may play an important role in FA synthesis and may be rate limiting genes, which probably could be modified for the further study of metabolic engineering to improve microalgal biofuel quality and production.</p

Electrochemical Reduction of CO2 on Compositionally Variant Au-Pt Bimetallic Thin Films

The electrocatalytic reduction of CO2 on Au-Pt bimetallic catalysts with different compositions was evaluated, offering a platform for uncovering the correlation between the catalytic activity and the surface composition of bimetallic electrocatalysts. The Au-Pt alloy films were synthesized by a magnetron sputtering co-deposition technique with tunable composition. It was found that the syngas ratio (CO:H2) on the Au-Pt films is able to be tuned by systematically controlling the binary composition. This tunable catalytic selectivity is attributed to the variation of binding strength of COOH and CO intermediates, influenced by the surface electronic structure (d-band center energy) which is linked to the surface composition of the bimetallic films. Notably, a gradual shift of the d-band center away from the Fermi level was observed with increasing Au content, which correspondingly reduces the binding strength of the COOH and CO intermediates, leading to the distinct catalytic activity for the reduction of CO2 on the compositionally variant Au-Pt bimetallic films. In addition, the formation of formic acid in the bimetallic systems at reduced overpotentials and higher yield indicates that synergistic effects can facilitate reaction pathways for products that are not accessible with the individual components.</p