Study on dynamic change of the oasis-desert ecotone using fractal theory

2003 ◽  
Author(s):  
Tashpolat Tiyip ◽  
Jianli Ding ◽  
Jianqiang Zhan ◽  
Takamura Hiroki ◽  
Michelle M. Glantz
Keyword(s):  
Fractal Theory ◽  
Dynamic Change

scholarly journals Dynamic characteristics and fractal representations of crack propagation of rock with different fissures under multiple impact loadings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bing Sun ◽  
Shun Liu ◽  
Sheng Zeng ◽  
Shanyong Wang ◽  
Shaoping Wang
Keyword(s):  
Fractal Dimension ◽  
Crack Propagation ◽  
Crack Growth ◽  
Impact Test ◽  
Fractal Theory ◽  
Dynamic Change ◽  
Fractal Dimensions ◽  
Peak Stress ◽  
Dynamic Mechanical Properties ◽  
Gravitational Potential Energy

AbstractTo investigate the influence of the fissure morphology on the dynamic mechanical properties of the rock and the crack propagation, a drop hammer impact test device was used to conduct impact failure tests on sandstones with different fissure numbers and fissure dips, simultaneously recorded the crack growth after each impact. The box fractal dimension is used to quantitatively analyze the dynamic change in the sandstone cracks and a fractal model of crack growth over time is established based on fractal theory. The results demonstrate that under impact test conditions of the same mass and different heights, the energy absorbed by sandstone accounts for about 26.7% of the gravitational potential energy. But at the same height and different mass, the energy absorbed by the sandstone accounts for about 68.6% of the total energy. As the fissure dip increases and the number of fissures increases, the dynamic peak stress and dynamic elastic modulus of the fractured sandstone gradually decrease. The fractal dimensions of crack evolution tend to increase with time as a whole and assume as a parabolic. Except for one fissure, 60° and 90° specimens, with the extension of time, the increase rate of fractal dimension is decreasing correspondingly.

scholarly journals The Porosity Dynamic Model of the Compacted Broken Coal

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xuefeng Han ◽  
Tingxiang Chu ◽  
Minggao Yu ◽  
Jiangkun Chao ◽  
Zhihui Ma ◽  
...  
Keyword(s):  
Spontaneous Combustion ◽  
Axial Stress ◽  
Fractal Theory ◽  
Dynamic Change ◽  
Strain Curve ◽  
Fractal Model ◽  
Evolution Model ◽  
Dynamic Evolution ◽  
Permeability Evolution ◽  
Loading Test

In order to study the dynamic change law of the porosity of the compacted broken coal under different axial stress loading, based on the environment of the broken and compacted coal in the gob, aiming at the influence of the porosity on the spontaneous combustion of the coal, combined with the fractal theory, the fractal model of the porosity of the broken coal is established. A self-designed “testing device for permeability evolution and spontaneous combustion characteristics of crushed coal under pressure” is used to carry out axial loading test on selected coal samples in the gob. By comparing and analyzing the calculated results of void dynamic evolution model and experimental data, it is found that the relative error of void dynamic evolution model is between 2.8% and 6.2%, which meets the engineering needs. According to the stress-strain curve, initial accumulation state parameters, fractal dimension of initial crushing, and particle size distribution, the change of porosity under different compacted conditions can be predicted by the model, which has certain significance for identifying the change of compacted broken coal porosity and analyzing the process of coal spontaneous combustion and oxidation.

INVESTIGATION OF DYNAMIC TEXTURE AND FLOW CHARACTERISTICS OF FOAM TRANSPORT IN POROUS MEDIA BASED ON FRACTAL THEORY

Fractals ◽  
2019 ◽  
Vol 27 (01) ◽  
pp. 1940013 ◽  
Author(s):  
FEI WANG ◽  
HAIFENG LI ◽  
DONGXING DU ◽  
XU DONG
Keyword(s):  
Porous Media ◽  
Fractal Dimension ◽  
Fractal Theory ◽  
Dynamic Change ◽  
Quantitative Description ◽  
Flow Characteristics ◽  
Transport In Porous Media ◽  
Steady Stage ◽  
Profile Control ◽  
Fractal Characteristics

Foam fluid has found wide applications in oilfield development, such as profile control, water plugging, gas channeling control, fracturing, and so on. As a non-Newtonian fluid, the successful application of foam is significantly influenced by its structure. The foam texture, however, is complex and irregular, and becomes even more complicated in porous media by the boundary effects. Therefore, the description of dynamic foam structure is crucial and a quantitative description method for foam fluid is worth exploring. In this paper, the fractal characteristics of foam in porous media are verified and combined with foam microdisplacement experiment, and the fractal rule of foam is found. The relationship between fractal dimension and pressure is also discussed. The results show that foam has dynamic fractal characteristics during transport in porous media and the box-counting fractal dimension ranges from 1 to 2. Furthermore, the dynamic change of foam fractal dimension during transport in porous media could be divided into three stages. In the first stage when no foam forms, the fractal dimension is about 2; in the second unsteady foam stage, the fractal dimension is reduced from 1.9 to 1.6; the last one is the steady stage and the fractal dimension is almost constant (about 1.6). Besides, the fractal dimension of foam fluid is closely related to displacement pressure. Low pressure corresponds to higher fractal dimension, and high pressure corresponds to lower fractal dimension. Pressure is negatively linearly correlated with fractal dimension. These results are expected to enrich the understanding of the foam dynamic characteristics in their advanced applications.

scholarly journals Multi-fractal characteristics of pore structure for coal during the refined upgrading degassing temperatures

2021 ◽  
Author(s):  
Jianjun Wang ◽  
Lingli Liu ◽  
Zehong Cui ◽  
Hongjun Wang ◽  
Teng Li ◽  
...  
Keyword(s):  
Low Temperature ◽  
Pore Structure ◽  
Fractal Theory ◽  
Dynamic Change ◽  
Ordos Basin ◽  
Nitrogen Adsorption ◽  
Low Rank ◽  
Low Rank Coal ◽  
Adsorption Measurement ◽  
Fractal Spectrum

AbstractThe low-temperature nitrogen adsorption measurement is commonly used to describe the pore structure of porous medium, while the role of degassing temperature in the low-temperature nitrogen adsorption measurement does not attract enough attention, various degassing temperatures may lead to the different pore structure characterization for the same coal. In this study, the low-rank coal collected from Binchang mining area, southwest of Ordos Basin was launched the low-temperature nitrogen adsorption measurement under seven various degassing temperatures (120 °C, 150 °C, 180 °C, 210 °C, 240 °C, 270 °C and 300 °C), respectively, the dynamic change of the pore structure under refined upgrading degassing temperatures are studied, and it was also quantitative evaluated with the multi-fractal theory. The results show that the pore specific surface area and pore volume decrease linearly with the increased degassing temperatures, ranges from 12.53 to 2.16 m2/g and 0.01539 to 0.00535 cm3/g, respectively. While the average pore aperture features the contrary characteristics (various from 4.9151 to 9.9159 nm), indicating the pore structure has been changed during the refined upgrading degassing temperatures. With the upgrading degassing temperatures, the sizes of hysteresis loop decrease, and the connectivity of pore structure enhanced. The multi-fractal dimension and multi-fractal spectrum could better present the partial abnormal of pore structure during the refined upgrading degassing temperatures, and the quality index, Dq spectrum, D−10–D10 and multi-fractal spectrum could describe the homogeneity and connectivity of the pores finely. The degassing temperatures of 150 °C, 180 °C and 270 °C are selected as three knee points, which can reflect the partial abnormal of the pore structure during the refined upgrading degassing temperatures. Under the lower degassing temperature (< 150 °C), the homogeneity and connectivity of the pore feature a certain increase, following that it presents stable when the degassing temperatures various from 150 to 180 °C. The homogeneity and connectivity of the pore would further enhanced until the degassing temperature reaches to 270 °C. Because of the melting of the pore when the degassing temperature exceeds 270 °C, the complexity of pore structure increased. In this study, we advise the degassing temperature for low-temperature nitrogen adsorption measurement of low-rank coal should not exceed 120 °C.

Determination of clinical efficiency of deproteinized dialysate from blood of milk-fed calves after endoprosthetics in patients with ventral hernias

2020 ◽  
Vol 28 (3) ◽  
pp. 323-333
Author(s):  
Sergej V. Ivanov ◽  
Ilya S. Ivanov ◽  
Evgenij G. Obyedkov ◽  
Liliya P. Popova
Keyword(s):  
Abdominal Wall ◽  
Inflammatory Reaction ◽  
Inflammatory Process ◽  
Anterior Abdominal Wall ◽  
Dynamic Change ◽  
Main Group ◽  
Control Group ◽  
Surgical Department ◽  
Regeneration Stage

Aim. To study the influence of deproteinized dialysate from blood of milk-fed calves on the type of exudative discharge and dynamics of inflammatory reaction after hernia repair with plastics of the anterior abdominal wall with hernioendoprosthesis of polypropylene. Materials and Methods. The study involved 59 patients being on stationary treatment in the surgical department of Kursk Regional Clinical Hospital. Patients were hospitalized for the herniation of small or medium dimension. The patients were divided to two groups: the main (n=30) and control (n=29) groups. After endoprosthetics, the patients of the control group were given complex conservative treatment. The patients of the main group, besides standard treatment, were administered deproteinized dialysate from blood of milk-fed calves intravenously in drips 10 ml + 200 ml of 0.9% sodium chloride solution within 7 days. For cytological examination and determination of the type of cytograms, the traumatic discharge was collected and analyzed using the method of M.F. Kamaev and M.A. Palthsev. Results. Cytomorphometric examination was conducted on the third, fifth and seventh day after endoprosthetics with the aim of studying dynamic changes. Determination of cell composition and also of its changes characteristic of each studied period, was necessary for obtaining further information characterizing inflammatory process in the region of placement of the endoprosthesis. After endoprosthetics in patients who were administered hemodialysate, the inflammatory reaction was less pronounced than in patients who did not receive the preparation. This was associated with a more dynamic change of stages of the inflammatory process. In patients of the main group who received deproteinized dialysate, regenerative type of inflammation first appeared on the fifth day and made 6.9%; by the seventh day the share of patients with the regenerative type rose to 17.5%, while in the patients of the control group no regeneration stage was observed in both periods. Conclusion. Analysis of the efficiency of influence of hemodialysate on the inflammatory reaction in plastics of the anterior abdominal wall with polypropylene endoprosthesis evidences faster course of all stages of inflammation and reduction of its intensity by 10%.

EVALUATION OF DYNAMIC CHANGE OF WATER LEVEL OF THE SMALL ARAL SEA BASED ON DATA OF OPEN SOURCES

2020 ◽  
Vol 57 (2) ◽  
pp. 69-77
Author(s):  
Г. В. Айзель ◽  
А. С. Ижицкий ◽  
А. K. Курбаниязов ◽  
Ж. А. Жанабаева
Keyword(s):  
Water Level ◽  
Dynamic Change ◽  
Aral Sea

Analysing Dynamic Change in Children’s Socio-Emotional Development using the Strengths and Difficulties Questionnaire in a large UK Longitudinal Study

2020 ◽  
Author(s):  
Lydia Gabriela Speyer ◽  
Anastasia Ushakova ◽  
Hildigunnur Anna Hall ◽  
Michelle Luciano ◽  
Bonnie Auyeung ◽  
...  
Keyword(s):  
Mental Health ◽  
Conduct Problems ◽  
Dynamic Change ◽  
Emotional Problems ◽  
Strengths And Difficulties Questionnaire ◽  
Mental Health Issue ◽  
Childhood And Adolescence ◽  
Peer Problems ◽  
Mental Health Difficulties ◽  
Strengths And Difficulties

Background: Most mental health difficulties have their onset during childhood and adolescence. Many children who suffer from one mental health issue also suffer from at least one comorbid disorder. Autoregressive latent trajectory models with structured residuals (ALT-SR) and multilevel graphical vector autoregression (GVAR) are recent complementary approaches that can help provide new insights into the reciprocal relationships between multiple mental health domains and advance the understanding of the development of comorbidities.Methods: This study uses ALT-SR and multilevel GVAR models to analyse the temporal, contemporaneous and between-person relationships between emotional problems, peer problems, conduct problems, hyperactivity/inattention and prosociality as measured by the parent-reported Strengths and Difficulties Questionnaire (SDQ) in 17,478 children taking part in the UK Millennium Cohort Study at ages 3, 5, 7, 11, 14 and 17 years. Results: Results from both the ALT-SR model and the multilevel GVAR model highlight that children’s strengths and difficulties in different domains of psychosocial functioning dynamically influence each other over- and within-time. The ALT-SR model highlighted that hyperactivity/inattention plays a central role in affecting other domains over developmental time while the GVAR model highlighted comparably strong bidirectional relationships between conduct problems and prosociality as well as between emotional problems and peer problems. Both models suggest that most domains are also related to each other over shorter timescales.Conclusion: This study highlights that mental health difficulties influence one another dynamically over time. As illustrated in the domains of the SDQ, these dynamic changes can be modelled using the complementary techniques of ALT-SR or GVAR models, each offering different insights into the nature of comorbidity.

Surface properties and structure of aspen wood.

2016 ◽  
Author(s):  
И.В. Коваленко ◽  
М.А. Чубинский ◽  
Д.С. Русаков ◽  
Г.С. Варанкина
Keyword(s):  
Surface Properties ◽  
Wood Surface ◽  
Fractal Theory ◽  
Aspen Wood ◽  
Surface Finishes ◽  
Surface Irregularities ◽  
Corrosion Susceptibility ◽  
Adhesive Molecules ◽  
First Time ◽  
Flow Study

Применение древесины осины в промышленном производстве материалов и изделий ограничено из-за ее низких механических свойств, подверженности поражению коррозионно-деструктивной гнили, отсутствием должного обоснования технологии ее переработки. Невостребованная осина осложняет условия хозяйствования в лесу, ухудшает породный состав древостоев, препятствует восстановлению хвойных пород древесины. Древесина осины хуже смачивается водой по сравнению с другими породами. Изучение ее поверхностных свойств и строения на микроуровне представляет безусловный интерес для изучения взаимодействия древесины с водой, жидкими клеящими и защитно-декоративными веществами. Это сложная многопараметрическая задача, решение которой может явиться новым инструментом для обоснования наукоемких технологических процессов сушки, пропитки, склеивания и облагораживания древесины. Истинная поверхность древесины, образованная в результате обработки резанием (лущением, пилением, фрезерованием) значительно больше ее проекции на плоскости в результате разрезания микроструктурных элементов. Неровности на поверхности искажают результаты измерения поверхностных свойств, определяемых на основе угла смачивания. Учитывая то, что размеры стенок клеток меньше размеров полостей, истинная площадь поверхности древесины, в зависимости от вида разреза, может в десятки раз превышать кажущуюся. Ухудшение способности смачиваться объясняет образование на поверхности капель клея, нанесенного на шпон методом вальцевания. При горячем прессовании фанеры в первый момент времени повышается подвижность молекул клея, снижается упругость древесины, поверхность выравнивается, улучшая условия адгезионного взаимодействия связующего и древесины. Для определения истинных характеристик древесины, обоснования расхода клея, способности древесины поглощать жидкость необходимо знать размеры ее микроструктурных элементов и характер их распределения, объем поверхностных полостей. Эффективный радиус полостей древесины осины может быть описан с использованием теории фракталов. The use of aspen wood in manufacturing of materials and products is limited due to its low mechanical properties, corrosion susceptibility destructive lesion decay, its lack of proper justification processing technology. Unclaimed aspen difficult economic conditions in the forest, degrades the species composition of forest stands and prevents restoration of softwood. Wood aspen worse moistened with water compared to other breeds. The study of its structure and surface properties at the micro level is of great interest to study the interaction of wood with water, liquid adhesives and protective-decorative materials. This is the problem whose solution can be a new tool for the study of science-intensive technological processes of drying, impregnation, gluing and surface finishes. Real wood surface, formed by the machining (peeling, sawing, milling) significantly greater its projection on the plane as a result of cutting the microstructural elements. Surface irregularities distort the results of measurement of surface properties which are determined based on the contact angle. Given that the size of the cell walls is less than the size of the cavities, the true surface area of the veneer, depending on the type of incision, may be ten times the apparent. The deterioration of the ability of wetted explains the formation of droplets on the surface of adhesive deposited on the veneer by rolling. When plywood hot pressing at a first time increases mobility of adhesive molecules, decreases the modulus of elasticity of wood, surface is aligned, improving the conditions of interaction of the glue and the wood. To determine the true characteristics of the wood, glue flow study, the ability of wood to absorb liquid it is necessary to know the size of microstructural elements and their distribution, the amount of surface cavities. The effective radius of aspen wood cavities can be described using fractal theory.

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