scholarly journals Study on Micro-Characteristics of Microbe-Induced Calcium Carbonate Solidified Loess

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1492
Author(s):  
Xiaojun Liu ◽  
Chaofan Pan ◽  
Jing Yu ◽  
Jinyue Fan
Keyword(s):  
Calcium Carbonate ◽  
Contact Area ◽  
Structural Characteristics ◽  
Point Contact ◽  
Silty Clay ◽  
Indirect Contact ◽  
Soil Particles ◽  
Pore Area ◽  
Surface Contact ◽  
Before And After

Microbial-induced carbonate precipitation (MICP) has outstanding characteristics in solidifying soil, such as good fluidity, ecological environmental protection, adjustable reaction, etc., making it have a good application prospect. As a typical silty clay, the composition of loess is fine, and the microstructure is quite different from that of sand. Previous research has found that the unconfined compressive strength of loess cured by MICP can be increased by nearly four times. In this paper, by comparing the changes of structural characteristics of undisturbed loess before and after MICP solidification, the mechanism of strength improvement of loess after MICP solidification is revealed from the microscopic level. Firstly, the microstructure of loess before and after solidification is tested by scanning electron microscope, and it is found that the skeleton particles of undisturbed loess are granular, and the soil particles coexist in direct contact and indirect contact, and the pores in soil are mainly overhead pores compared with the microstructure of solidified loess, it is found that the surface contact between aggregates increases obviously, and calcium carbonate generated by MICP is adsorbed around the point contact between aggregates, which makes the contact between soil particles change from point contact to surface contact. Then, Pores (Particles) and Cracks Analysis System (PCAS) is used to quantitatively analyze the pores of loess before and after solidification. The results show that the total pore area, the maximum total pore area and porosity of soil samples decrease, and the total number of pores decreases by 13.2% compared with that before MICP solidification, indicating that a part of calcium carbonate produced by MICP reaction accumulates in tiny pores, thus reducing the number of pores. One part is cemented between soil particles, which increases the contact area of particles. Therefore, some pores of loess solidified by MICP are filled and densified, the contact area between soil particles is increased, and the strength of loess under load is obviously improved.

scholarly journals Improving the Erosion Resistance Performance of Pisha Sandstone Weathered Soil Using MICP Technology

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1112
Author(s):  
Yanxing Wang ◽  
Chi Li ◽  
Cuiyan Wang ◽  
Yu Gao
Keyword(s):  
Calcium Carbonate ◽  
Wind Erosion ◽  
Erosion Resistance ◽  
Carbonate Content ◽  
Calcium Carbonate Precipitation ◽  
Undisturbed Soil ◽  
Soil Particles ◽  
Weathered Soil ◽  
Before And After ◽  
Internal Mechanism

In this study, we applied microbial induced calcium carbonate precipitation (MICP) technology to improve the undesirable characteristics of Pisha sandstone weathered soil that collapses easily upon environmental erosion. Through disintegration tests and wind erosion tests, the anti-water scour and anti-sand erosion performance of the weathered soil was tested before and after the improvement. Combined with an analysis of the physical properties and pore structure of the samples, this paper analyzes the internal mechanism by which MICP technology improves the poor characteristics of the soil. The results show that after improvement with the use of MICP technology, effective cementation is formed between the soil particles to form a solidified material with a strength of up to 1 MPa with a precipitated carbonate content of up to 15%, which effectively improves the water erosion resistance and wind erosion resistance. The disintegration rate of the improved soil sample was only 1.95% at the 30th minute, the remolded soil completely disintegrated, and the undisturbed soil reached 39.64%. The wind erosion resistance of the improved sample is improved, and its coefficient at a 30° erosion angle is increased roughly 20-fold on average when the wind speed is 31 m/s. The internal mechanism of the improved soil when it comes into contact with water and wind is that the induced calcium carbonate crystals fill the pores of the soil particles and adhere to and bridge between soil particles for effective cementation. When the soil expands after water invasion or the soil is destroyed after external erosion, the cementation of mineral crystals on the particles can resist the expansion force and punching force so as to improve the soil’s overall anti-erosion performance.

scholarly journals Physicochemical and structural characteristics of HEU-type zeolitic tuff treated by hydrochloric acid

2004 ◽  
Vol 69 (4) ◽  
pp. 273-282 ◽  
Author(s):  
Ana Radosavljevic-Mihajlovic ◽  
Vera Dondur ◽  
Aleksandra Dakovic ◽  
Jovan Lemic ◽  
Magdalena Tomasevic-Canovic
Keyword(s):  
Crystal Structure ◽  
Hydrochloric Acid ◽  
Bosnia And Herzegovina ◽  
Acid Treatment ◽  
Structural Characteristics ◽  
Chemical Analyses ◽  
Zeolitic Tuff ◽  
Zeolitic Tuffs ◽  
Before And After

Samples of natural HEU-type zeolites ? clinoptilolite-Ca, from the Novakovici deposit (near Prijedor, Bosnia and Herzegovina) were treated with the hydrochloric acid of various concentrations (from 10-3Mto 2M). Zeolitic tuffs before and after the acid treatment were examined using IR, XRPD, and chemical analyses. The changes in the crystal structure of acid treated samples showed a significant reduction in the crystallinity of zeolitic tuffs (60?70 %), which were effected by hydrochloric acid with concentrations of 1 M and above.

Experimental and numerical study on cavitation under elastohydrodynamic lubrication point contact

2021 ◽  
pp. 135065012110527
Author(s):  
Mingfei Ma ◽  
Wen Wang ◽  
Wenxun Jiang
Keyword(s):  
Contact Area ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Pressure Area ◽  
Cavitation Pressure ◽  
Experimental Researches ◽  
State 1

As a common phenomenon in elastohydrodynamic lubrication, cavitation has an effect on the completeness of the oil film in the contact area. Many studies have therefore been conducted on cavitation. Experimental researches on cavitation usually rely on optical interference observation, which offers a limited resolution and observation range. In this paper, an infrared thermal camera is used to observe the cavity bubbles on a ball-on-disc setup under sliding/rolling conditions. The results show that the cavity length increases with an increases of the entrainment speed and the viscosity of the lubricants. These observations are explained by a numerical model based on Elrod's algorithm. Effects of entrainment speed and lubricant viscosity on the breakup of cavitation bubbles and the cavitation states are investigated. Both the simulation and experimental results show that a negative pressure area is present behind the Hertzian contact area. The ambient pressure plays a role in maintaining cavitation state 1. The cavitation pressure is close to the vacuum pressure when the entrainment speed is low and to the ambient pressure instead when the entrainment speed is high.

scholarly journals Strontium Oxide Deposited onto a Load-Bearable and Porous Titanium Matrix as Dynamic and High-Surface-Contact-Area Catalysis for Transesterification

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 973 ◽  
Author(s):  
Han Lee ◽  
Jiunn-Der Liao ◽  
Mu Lee ◽  
Bernard Liu ◽  
Wei-En Fu ◽  
...  
Keyword(s):  
Contact Area ◽  
Porous Matrix ◽  
Porous Titanium ◽  
Transesterification Reaction ◽  
Biodiesel Production ◽  
Strontium Oxide ◽  
Chemical Structures ◽  
Surface Contact ◽  
Surface Contact Area ◽  
Highly Porous

Strontium oxide (SrO) deposited onto a porous titanium (Ti)-based scaffold (P-Ti) is a promising and novel approach for high-throughput transesterification. Notably, a highly porous and calcinated scaffold provides a load-bearable support for a continuous process, while the calcinated SrO catalyst, as it is well distributed inside the porous matrix, can extend its surface contact area with the reactant. In this work, the formation of transesterification reaction with the conversion and production of olive oil to biodiesel inside the porous matrix is particularly examined. The as-designed SrO-coated porous titanium (Ti)-based scaffold with 55% porosity was prepared via a hydrothermal procedure, followed by a dip coating method. Mechanical tests of samples were conducted by a nanoindentator, whereas the physical and chemical structures were identified by IR and Raman Spectroscopies. The results implied that SrO catalysts can be firmly deposited onto a load-bearable, highly porous matrix and play an effective role for the transesterification reaction with the oil mass. It is promising to be employed as a load-bearable support for a continuous transesterification process, such as a process for batch or continuous biodiesel production, under an efficient heating source by a focused microwave system.

A friction based approach for modeling wire bonding

2013 ◽  
Vol 2013 (1) ◽  
pp. 000208-000212 ◽  
Author(s):  
Simon Althoff ◽  
Jan Neuhaus ◽  
Tobias Hemsel ◽  
Walter Sextro
Keyword(s):  
Contact Area ◽  
Copper Wire ◽  
Point Contact ◽  
Welding Process ◽  
Friction Model ◽  
Ultrasonic Power ◽  
Physical Effects ◽  
Wedge Bonding ◽  
Work Done ◽  
Do So

A model approach for wedge/wedge bonding copper wire is presented. The connection between wire and substrate is based on a variety of physical effects, but the dominant one is the friction based welding while applying ultrasound. Consequently, a friction model was used to investigate the welding process. This model is built up universal and can be used to describe the formation of micro welds in the time variant contact area between wire and substrate. Aim of the model is to identify the interactions between touchdown, bond normal force, ultrasonic power and bonding time. To do so, the contact area is discretized into partial areas where a Point Contact Model is applied. Based on this approach it is possible to simulate micro and macro slip inside the contact area between wire and substrate. The work done by friction force is a main criterion to define occurring micro joints which influence the subsequent welding.

scholarly journals Microscopic and mechanical properties of undistributed and remoulded red clay from Guiyang, China

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yanzhao Zhang ◽  
Shaoyun Pu ◽  
Rita Yi Man Li ◽  
Jing Zhang
Keyword(s):  
Point Contact ◽  
Morphological Properties ◽  
Line Contact ◽  
Red Clay ◽  
Undisturbed Soil ◽  
Pore Area ◽  
Distribution Index ◽  
Curved Slice ◽  
Clay Aggregates ◽  
Scanning Electron

Abstract Unconsolidated-undrained (UU) tests were conducted to investigate the mechanical and morphological properties of undisturbed and remoulded red clay, with the microscopic characteristics determined by scanning electron microscopy (SEM). The microanalysis showed that the red clay aggregate was granular, curved-slice and thin layered and flower-shaped ellipsoid, with X and Y-type cracks and pores in the undisturbed red clay. Moreover, the contact modes of red clay aggregates were point contact, line contact, surface contact and mosaic contact. In addition, the main microstructure red clay was flocculation, honeycomb and pseudosphere structures. The pores in undisturbed soil were arranged in one direction, with no obvious directionality in remoulded red clay. The pore area, perimeter and maximum length of undisturbed red clay were smaller than those of remoulded red clay, with a larger probability entropy, probability distribution index and fractal dimension of pore distribution of undisturbed red clay than remoulded red clay. UU tests showed that the shear strength of undisturbed red clay was higher than that of remoulded red clay.

scholarly journals The effect of medial arch support over the plantar pressure and triceps surae muscle strength after prolonged standing

2015 ◽  
Vol 24 (3) ◽  
pp. 146-9 ◽  
Author(s):  
Hindun Saadah ◽  
Deswaty Furqonita ◽  
Angela Tulaar
Keyword(s):  
Muscle Strength ◽  
Contact Area ◽  
Plantar Pressure ◽  
Peak Pressure ◽  
Standing Position ◽  
Triceps Surae ◽  
Prolonged Standing ◽  
Triceps Surae Muscle ◽  
Before And After ◽  
Arch Support

Background: The activity with prolonged standing position is one of the causes of abnormalities in the lower leg and foot. The aim of this study is to discover the effect of medial arch support over the distribution of plantar pressure when standing and walking.Methods: This was an experimental study with pre- and post-design the strength of triceps surae muscle after prolonged standing, was also evaluated in an experimental study with pre- and post-design. Variables of plantar pressure measurement are the contact area and pressure peak were measured by using the Mat-scan tool. The measurement of the triceps surae muscle strength was done with a hand-held dynamometer, before and after using the medial arch support. Measurement was performed before and after working with prolonged standing position which took place about seven hours using the medial arch support inserted in the shoes. Data was analyzed using paired T-test.Results: There was a significant difference of peak pressure between standing (p = 0.041) and walking (p = 0.001). Whereas the contact area showed a significant decrease in the width of the contact area when standing (104.12 ± 12.42 vs 99.08 ± 10.21 p = 0.023). Whereas, the triceps surae muscle strength pre- and post-standing prolonged did not indicate a significant difference.Conclusion: There was decrease in peak pressure when standing and walking and decrease in contact area when standing on plantar after used of the medial arch support after prolonged standing.

scholarly journals Experimental Setup for Splash Erosion Monitoring—Study of Silty Loam Splash Characteristics

2019 ◽  
Vol 12 (1) ◽  
pp. 157 ◽  
Author(s):  
David Zumr ◽  
Danilo Vítor Mützenberg ◽  
Martin Neumann ◽  
Jakub Jeřábek ◽  
Tomáš Laburda ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Soil Surface ◽  
Outer Diameter ◽  
Rainfall Simulator ◽  
Soil Particles ◽  
Splash Erosion ◽  
Laboratory Setup ◽  
Before And After ◽  
Silty Loam ◽  
Raindrop Splash

An experimental laboratory setup was developed and evaluated in order to investigate detachment of soil particles by raindrop splash impact. The soil under investigation was a silty loam Cambisol, which is typical for agricultural fields in Central Europe. The setup consisted of a rainfall simulator and soil samples packed into splash cups (a plastic cylinder with a surface area of 78.5 cm2) positioned in the center of sediment collectors with an outer diameter of 45 cm. A laboratory rainfall simulator was used to simulate rainfall with a prescribed intensity and kinetic energy. Photographs of the soil’s surface before and after the experiments were taken to create digital models of relief and to calculate changes in surface roughness and the rate of soil compaction. The corresponding amount of splashed soil ranged between 10 and 1500 g m−2 h−1. We observed a linear relationship between the rainfall kinetic energy and the amount of the detached soil particles. The threshold kinetic energy necessary to initiate the detachment process was 354 J m−2 h−1. No significant relationship between rainfall kinetic energy and splashed sediment particle-size distribution was observed. The splash erosion process exhibited high variability within each repetition, suggesting a sensitivity of the process to the actual soil surface microtopography.

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