Parametric Analysis of Epoxy/Crumb Rubber Composite by Using Taguchi—GRA Hybrid Technique

Effect of parameters affecting solid particle erosion of crumb rubber epoxy composite is investigated. Five important process parameters—impact velocity, impingement angle, standoff distance, erodent size, and crumb rubber content—are taken into consideration. Erosion rate and erosion efficiency are included as the chief objectives. The Taguchi coupled gray relational analysis type statistical model is implemented to study interaction, parameters' effect on responses, and optimized parameters. ANOVA and regression model affirmed impingement angle and crumb rubber content play a significant role to minimize the erosion. Validity of the proposed model is justified with the standard probability plot and R2 value. A confirmation experiment conducted with A2B2C3D3E3 condition registers noticeable enhancement in GRG to the tune of 0.0893.

Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models

Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models.

Anti-Erosion Efficiency of Stands Installed On Degraded Land

Background: The naturally present erosion phenomenon has been active throughout the geological eras, shaping the land surface to date. Today, this phenomenon causes significant damage to the environment and human activities.In the geographical conditions of Romania, where the sloping land represents up to 67% of the national territory and supported by a complex number of natural factors, as well as the intense human interventions from the end of the 19th century and the beginning of the 20th, the vegetation and soils face serious ecological imbalances. The afforestation of degraded lands gained momentum after 1948, and the most used species were pines, especially black pine and Scots pine.Methods: In order to achieve the proposed objectives regarding the evaluation of stands in terms of anti-erosion effectiveness, were analyzed the consistency of trees, the number of trees on the surface, the weight of the seedlings, and surface runoff, from the perspective of rainfall and soil retention.Results: Analyzing the influence of rain intensity, respectively 39% in compartment 49, 38% in 73 and ground retention on surface runoff, being 28% in both compartments, it results that the two parameters directly influence surface runoff. Thus, it can be stated that indirectly surface runoff is influenced by the consistency of the stands, by the degree of proximity of the crowns, which directly influence the intensity of rain and the number of trees and the vegetation that grows under them directly influences the retention in the soil through the litter that is formed, which promotes retention.Conclusions: The results obtained suggest that indirectly surface runoff is influenced by the consistency of the tree, by the degree of proximity of the crowns, which directly influence the intensity of rain.Also, the number of trees and the vegetation that grows under them directly influences the retention in the soil through the litter that is formed, which promotes retention and by creating areas that reduce the speed of water, favoring infiltration into the soil.

ANTI-EROSION EFFICIENCY OF FALLOW LANDS DEVELOPMENT TECHNOLOGIES IN THE STEPPE ZONE

Research was conducted with the aim of developing technology for the development of fallow lands in the south of Central Siberia. The work was carried out in 2012-2015 on chestnut soil (experiment 1) and southern chernozem (experiment 2) in the Republic of Khakassia. The humus content in the 0 ... 20 cm layer of chestnut soil is 2.67%, N-NO3 is 20.1 ... 22.4 mg/kg, P2O5 and K2O (according to Machigin) are 23.5 and 328 mg/kg, respectively, in southern chernozem - respectively 4.5%, 16.6 ... 19.2, 19.3 and 720 mg/kg. The experimental designs provided for various combinations of mechanical tillage and spraying with herbicides of fallow plots, performed at different times, in the year preceding the sowing of crops. In technologies using herbicides in August, the amount of conditional stubble in spring was 60 pcs/m2 more, and erosion was 1.7 ... 2.5 times lower than in versions with flat cutting. The dumping of chestnut soil increases the yield of green mass of oats, compared with flat-cut, by 2.5 t/ha (24.5%), corn - by 4.0 t/ha (31.2%). In the southern chernozem, the technology with plowing ensured the formation of 5.7 t/ha of green mass of oats, which is 0.5 t/ha (8.8%) more than during flat cutting. In general, in the steppe zone of Central Siberia, the use of plowing in the technology for the development of fallow lands increases their productivity, while the greatest protection of the soil from erosion is provided by replacing its mechanical treatment in August with spraying with herbicides

Investigation into the Water Jet Erosion Efficiency of Hydrate-Bearing Sediments Based on the Arbitrary Lagrangian-Eulerian Method

As an innovative way to exploit marine natural gas hydrates (NGH), the solid fluidization exploitation method is to erode hydrate-bearing sediment (HBS) into fine particles by a water jet and transport the particles to an offshore platform. To investigate the water jet erosion efficiency of HBS under various work parameters, such as jet velocity, standoff distance, and nozzle diameter, the Arbitrary Lagrangian–Eulerian (ALE) method was adopted to establish numerical models based on the characteristics of HBS in the South China Sea, and orthogonal experiments were performed to optimize the work parameters. The results show that the water jet erosion efficiency of HBS increases with the increase in jet velocity and nozzle diameter, however it decreases with the increase in standoff distance. The jet velocity is the most significant factor for the erosion efficiency and there exists a threshold velocity which describes the minimum jet velocity required to erode HBS. In addition, comprehensive analysis of the results of the orthogonal experiments indicates that, when the jet velocity is 150 m·s−1, the standoff distance is 0.5 cm, and the nozzle diameter is 2.5 mm, the maximum erosion volume can be obtained, which is 6.0329 cm3. This research provides valuable theoretical support for the solid fluidization exploitation of marine NGH.

Studies on Velocity Fields Around the Cavitation Vortices Generated by the Model of a Rotating Blade

The elimination of hazards caused by cavitation phenomena is an important issue to be considered in the design of process equipment including flow machinery. These hazards are: cavitation erosion, efficiency decrease as well as vibration and noise. One of the most intensive and dangerous forms of cavitation is vortex cavitation that accompanies the operation of hydraulic machines in which components comprised of rotating blades are applied. Velocity fields around cavitation vortices generated by the model of a propeller blade were experimentally studied in a cavitation tunnel. Flow images were recorded using a high-speed camera and processed using particle image velocimetry (PIV) complemented with computer-aided techniques that had been developed for the purpose of this research. These techniques included the removal of image distortions on the basis of a calibration mask, determination of instantaneous velocity distributions and removal of air-bubble traces from flow images. Experimental studies result examples were presented in the form of velocity fields determined in the longitudinal plane as well as in three transverse planes remote from the blade. Instabilities of the cavitating vortex stream and of the local liquid-flow velocity in its surrounding were detected. The effect of the angle of attack of propeller blade on the instability of the vortex stream and the effect of the presence of the cavitating vortex kernel on the local velocities of the surrounding liquid, were determined.

Experimental Investigation on the Material Removal of the Ultrasonic Vibration Assisted Abrasive Water Jet Machining Ceramics

The ultrasonic vibration activated in the abrasive water jet nozzle is used to enhance the capability of the abrasive water jet machinery. The experiment devices of the ultrasonic vibration assisted abrasive water jet are established; they are composed of the ultrasonic vibration producing device, the abrasive supplying device, the abrasive water jet nozzle, the water jet intensifier pump, and so on. And the effect of process parameters such as the vibration amplitude, the system working pressure, the stand-off, and the abrasive diameter on the ceramics material removal is studied. The experimental result indicates that the depth and the volume removal are increased when the ultrasonic vibration is added on abrasive water jet. With the increase of vibration amplitude, the depth and the volume of material removal are also increased. The other parameters of the ultrasonic vibration assisted abrasive water jet also have an important role in the improvement of ceramic material erosion efficiency.