scholarly journals Numerical Study of the Dynamic Compaction Process considering the Phenomenon of Particle Breakage

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Xi Li ◽  
Jing Li ◽  
Xinyan Ma ◽  
Jidong Teng ◽  
Sheng Zhang
Keyword(s):  
Numerical Study ◽  
High Energy ◽  
Particle Breakage ◽  
Dynamic Compaction ◽  
Coarse Grained ◽  
Impact Stress ◽  
Logarithmic Curve ◽  
Before And After ◽  
Soil Foundation ◽  
Overlapping Method

Dynamic compaction (DC) is commonly used to strengthen the coarse grained soil foundation, where particle breakage of coarse soils is unavoidable under high-energy impacts. In this paper, a novel method of modeling DC progress was developed, which can realize particle breakage by impact stress. A particle failure criterion of critical stress is first employed. The “population balance” between particles before and after crushing is guaranteed by the overlapping method. The performance of the DC model is successfully validated against literature data. A series of DC tests were then carried out. The effect of particle breakage on key parameters of DC including crater depth and impact stress was discussed. Besides, it is observed that the relationship between breakage amount and tamping times can be expressed by a logarithmic curve. The present method will contribute to a better understanding of DC and benefit further research on the macro-micro mechanism of DC.

scholarly journals Hybrid Numerical Investigation on Soil-Hammer Interaction during Dynamic Compaction

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Jian Wang ◽  
Yinghui Cui ◽  
Qimin Li
Keyword(s):  
Interaction Process ◽  
Dynamic Compaction ◽  
Coarse Grained ◽  
Lateral Extrusion ◽  
Penetration Ability ◽  
Maximum Penetration ◽  
Soil Foundation ◽  
Physical Phenomena ◽  
The Impact ◽  
Coarse Grained Soil

To investigate the mechanism of hammer-soil interaction under the action of dynamic compaction (DC) on a coarse-grained soil foundation, based on the theory of projectile penetration, the continuous-discrete coupling method is used to simulate the hammer-soil interaction process with different hammer shapes and different particle radii. The physical phenomena and mechanical parameters presented by the hammers and soil particles are quantitatively analyzed. The results show that the penetrating ability of the hammer is proportional to its lateral extrusion shearing ability and inversely proportional to its vertical extrusion capacity. The convex-bottomed hammer has the maximum penetration and lateral extrusion capability, the flat-bottomed hammer has the smallest penetration ability and the lateral extrusion capacity, and the concave-bottomed hammer has a penetration and lateral extrusion ability between those of the convex- and flat-bottomed hammers. The impact strength and vertical disturbance of the flat-bottomed hammer are the strongest, followed by the concave-bottomed hammer and the convex-bottomed hammer. In addition, it is found that the smaller the particle size of the coarse-grained soil is, the greater the depth of the crater formed and the smaller the contact force and the influence range of vertical disturbance. These research results reveal the interaction mechanisms of different hammer types and coarse-grained soil, which is expected to provide reference and guidance for the design and construction of coarse-grained soil foundations enhanced by DC.

Formation of nanophases in a Cu–Zn alloy under high current density electropulsing

2000 ◽  
Vol 15 (10) ◽  
pp. 2065-2068 ◽  
Author(s):  
W. Zhang ◽  
M. L. Sui ◽  
K. Y. Hu ◽  
D. X. Li ◽  
X. N. Guo ◽  
...  
Keyword(s):  
Current Density ◽  
High Current Density ◽  
High Energy ◽  
Coarse Grained ◽  
High Current ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Before And After ◽  
Electropulsing Treatment ◽  
Zn Alloy

The microstructure of samples before and after a high current density electropulsing treatment was characterized by using high-resolution transmission electron microscopy. It has been found that in the coarse-grained Cu–Zn alloy subjected to the electropulsing treatment, two nanophases were formed, α–Cu(Zn) and β′–(CuZn), the average grain size of which is about 11 nm. A possible mechanism for the formation of nanophases was proposed. The experimental results indicated that electropulsing, as an instantaneous high-energy input, plays an important role in the nonequilibrium microstructural changes in materials and serves as a potential processing approach to synthesize nanostructured materials.

The Analysis of Stress Distribution of Hammer Bottom during Dynamic Compaction on Sandy Soil Foundation

2011 ◽  
Vol 250-253 ◽  
pp. 1460-1463
Author(s):  
Jian Qi Wu ◽  
Jian Hong Deng ◽  
Xiao Ping Wang
Keyword(s):  
Comparative Analysis ◽  
Stress Distribution ◽  
Sandy Soil ◽  
Field Monitoring ◽  
Dynamic Compaction ◽  
Dry Density ◽  
Test Results ◽  
Red Sandstone ◽  
Soil Foundation

Obtained stress distribution of hammer bottom according to the analysis of horizontal and vertical red sandstone fill dry density of the hammer bottom after dynamic compaction; affirmed the stress distribution situation of the hammer bottom through comparative analysis of the test results by laboratory and field monitoring.

Epinephrine inhibits insulin-mediated glycogenesis but enhances glycolysis in human skeletal muscle

1991 ◽  
Vol 260 (3) ◽  
pp. E430-E435 ◽  
Author(s):  
I. Raz ◽  
A. Katz ◽  
M. K. Spencer
Keyword(s):  
Glycogen Synthase ◽  
Glucose Production ◽  
High Energy ◽  
Endogenous Glucose Production ◽  
Fat Free Mass ◽  
Glucose Disposal ◽  
High Energy Phosphates ◽  
Before And After ◽  
Glucose Tolerant ◽  
Femoris Muscle

The effect of epinephrine (E) infusion on insulin-mediated glucose metabolism in humans has been studied. Eight glucose-tolerant men were studied on two separate occasions: 1) during 120 min of euglycemic hyperinsulinemia (UH, approximately 5 mM; 40 mU.m-2.min-1); and 2) during UH while E was infused (UHE, 0.05 microgram.kg-1.min-1). Biopsies were taken from the quadriceps femoris muscle before and after each clamp. Glucose disposal, correcting for endogenous glucose production, was 36 +/- 3 and 18 +/- 2 (SE) mumol.kg fat-free mass (FFM)-1.min-1 during the last 40 min of UH and UHE, respectively (P less than 0.001). Nonoxidative glucose disposal (presumably glycogenesis) averaged 23.0 +/- 3.0 and 4.0 +/- 1.1 (P less than 0.001), whereas carbohydrate oxidation (which is proportional to glycolysis) averaged 13.1 +/- 1.4 and 15.3 +/- 1.1 mumol.kg FFM-1.min-1 (P less than 0.05) during UH and UHE, respectively. UHE resulted in significantly higher contents of UDP-glucose, hexose monophosphates, postphosphofructokinase intermediates, and glucose 1,6-bisphosphate (G-1,6-P2) in muscle (P less than 0.05-0.001), but there were no significant differences in high-energy phosphates or fructose 2,6-bisphosphate (F-2,6-P2) between treatments. Fractional activities of phosphorylase increased (P less than 0.01), and glycogen synthase decreased (P less than 0.001) during UHE. It is concluded that E inhibits insulin-mediated glycogenesis because of an inactivation of glycogen synthase and an activation of glycogenolysis. E also appears to inhibit insulin-mediated glucose utilization, at least partly, because of an increase in G-6-phosphate (which inhibits hexokinase) and enhances glycolysis by G-1,6-P2-, fructose 6-phosphate-, and F-1,6-P2-mediated activation of PFK.

Stratigraphy and palaeoenvironments of the Red Crag and Norwich Crag formations between Aldeburgh and Sizewell, Suffolk, England

1988 ◽  
Vol 322 (1210) ◽  
pp. 221-272 ◽  
Keyword(s):  
Amino Acid ◽  
High Energy ◽  
Coarse Grained ◽  
Core Material ◽  
Stage System ◽  
Pollen And Spores ◽  
Shallow Marine Sediments ◽  
Amino Acid Chronology ◽  
Tectonic Origin ◽  
Borehole Core

This study uses a variety of criteria to examine short-range correlation within the Crag deposits in order to assess the validity of longer-range correlations within the British Pleistocene stage system. To this end, six rotary cored boreholes spaced at 0.5-1.0 km intervals were drilled along a north-south-aligned traverse between Aldeburgh and Sizewell, Suffolk. These show that the thick Red/Norwich Crag sequence is confined to a deep, sharply bounded basin, which is of probable erosional rather than tectonic origin. The undisturbed borehole core material enabled an assessment of the limits of stratigraphic resolution within these dominantly high-energy, shallow marine sediments to be made. Subdivision of the sequence was done on the basis of lithostratigraphical and biostratigraphical (foraminifera, pollen and spores, dinoflagellate cysts, and molluscs) criteria; chronostratigraphical methods (palaeomagnetism and amino acid chronology) were also applied. The various subdivisions indicated by each of these disciplines were in large part consistent, demonstrating that valid stratigraphic units had been identified. Only amino acid chronology did not indicate any obvious subdivision of the sequence. Three lithostratigraphical units were recognized within the thick Crag sequence. The lowest unit (AS-Lith 1) consists of coarse shelly sands interbedded with thinly laminated muds and fine sands. The middle unit (AS-Lith 2) consists of fine- to coarse-grained shelly sands arranged in two coarsening-upwards cycles. Units AS-Lith 1 and AS-Lith 2 are correlated on a lithostratigraphical basis with the Red Crag Formation of the adjacent Aldeburgh-Orford area to the south and are named the Sizewell Member and the Thorpeness Member respectively. The uppermost unit (AS-Lith 3) comprises fine- to medium-grained, well-sorted sands; it correlates with the Chillesford Sand Member of the Norwich Crag Formation of the adjacent Aldeburgh-Orford area. The Sizewell Member of the Red Crag Formation is normally magnetized and palaeontologically distinctive. The pollen, foraminifera and dinoflagellate assemblages firmly establish it as Pre-Ludhamian in age, and probably equivalent to an interval within the Reuverian C to Praetiglian Stages of the Netherlands. The Thorpeness Member of the Red Crag Formation is less easy to place within the British Pleistocene stage system. It is reverse magnetized, at least in part, and foraminifera assemblages suggest possible correlation with the Ludhamian Stage. No identifiable pollen or dinoflagellate assemblages were obtained. The Chillesford Sand Member of the Norwich Crag Formation is largely unfossiliferous but the borehole material has yielded a single pollen spectrum that suggests correlation with the Bramertonian Stage.

Fatigue and phosphocreatine depletion during carbon dioxide-induced acidosis in rat muscle

1983 ◽  
Vol 245 (1) ◽  
pp. C15-C20 ◽  
Author(s):  
K. Sahlin ◽  
L. Edstrom ◽  
H. Sjoholm
Keyword(s):  
High Energy ◽  
Initial Value ◽  
High Co2 ◽  
Fourfold Increase ◽  
Control Value ◽  
Before And After ◽  
Phosphate Depletion ◽  
Creatine Kinase Equilibrium ◽  
Lactate And Pyruvate ◽  
Tetanic Tension

Isolated extensor digitorum longus muscles from rat were exposed to atmospheres of 30% CO2 (high-CO2 muscles) or 6.5% CO2 (control muscles) in O2 for 95 min. Muscle contraction characteristics were studied before and after the incubation. Tetanic tension decreased in high-CO2 muscles to 55% of initial value but remained unchanged in control muscles. Relaxation time was prolonged in high-CO2 muscles but not in control muscles. Intracellular pH was 6.67 +/- 0.04 (SD) in high-CO2 muscles and 7.01 +/- 0.04 in control muscles. CO2-induced acidosis had a marked influence on the intermediary energy metabolism as shown by a fourfold increase of glucose 6-phosphate, a 14% increase of ADP, and a decrease of phosphocreatine to 44% of the control value. Lactate and pyruvate contents were unchanged. The observed metabolic changes can be explained by an effect of H+ on the activity of phosphofructokinase and on the creatine kinase equilibrium. It can be concluded that H+ concentration causes muscular fatigue. It is, however, uncertain whether this is an effect of increased H+ per se or by high-energy phosphate depletion induced by acidosis.

Numerical Study to Analyze the Effects of Hot/Cold Aisle Configurations on Heat Transfer Phenomenon in a Data Center

2013 ◽  
Author(s):  
Kamran Nazir ◽  
Naveed Durrani ◽  
Imran Akhtar ◽  
M. Saif Ullah Khalid
Keyword(s):  
Heat Transfer ◽  
Data Center ◽  
Data Centers ◽  
Cooling System ◽  
Numerical Study ◽  
High Energy ◽  
Research Area ◽  
Transfer Phenomenon ◽  
Heat Transfer Phenomenon ◽  
Active Research

Due to high energy demands of data centers and the energy crisis throughout the world, efficient heat transfer in a data center is an active research area. Until now major emphasis lies upon study of air flow rate and temperature profiles for different rack configurations and tile layouts. In current work, we consider different hot aisle (HA) and cold aisle (CA) configurations to study heat transfer phenomenon inside a data center. In raised floor data centers when rows of racks are parallel to each other, in a conventional cooling system, there are equal number of hot and cold aisles for odd number of rows of racks. For even number of rows of racks, whatever configuration of hot/cold aisles is adopted, number of cold aisles is either one greater or one less than number of hot aisles i.e. two cases are possible case A: n(CA) = n(HA) + 1 and case B: n(CA) = n(HA) − 1 where n(CA), n(HA) denotes number of cold and hot aisles respectively. We perform numerical simulations for two (case1) and four (case 2) racks data center. The assumption of constant pressure below plenum reduces the problem domain to above plenum area only. In order to see which configuration provides higher heat transfer across servers, we measure heat transfer across servers on the basis of temperature differences across racks, and in order to validate them, we find mass flow rates on rack outlet. On the basis of results obtained, we conclude that for even numbered rows of rack data center, using more cold aisles than hot aisles provide higher heat transfer across servers. These results provide guidance on the design and layout of a data center.

Characterization of X-ray irradiated graphene oxide coatings using X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy

2013 ◽  
Vol 28 (2) ◽  
pp. 68-71 ◽  
Author(s):  
Thomas N. Blanton ◽  
Debasis Majumdar
Keyword(s):  
Atomic Force Microscopy ◽  
Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
High Energy ◽  
X Ray Diffraction ◽  
Carbon Phase ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After

In an effort to study an alternative approach to make graphene from graphene oxide (GO), exposure of GO to high-energy X-ray radiation has been performed. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) have been used to characterize GO before and after irradiation. Results indicate that GO exposed to high-energy radiation is converted to an amorphous carbon phase that is conductive.

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