Surface microtopography and micromechanics of various rank coals

For a long time,coalbed gas has brought about various problems to the safety of coal mine production.In addition,the mining of gas and coalbed methane(CBM)has attracted much attention.The occurrence and migration of CBM are believed to be closely related to the micro-surface properties of coal.To further explore the characteristics of CBM occurrence and migration,in this study,the micro-surface topography,adhesion,and elastic modulus of five metamorphic coals were measured by atomic force microscopy(AFM).The results show that the microtopography of coal fluctuates around 40 nm,reaching a maximum of 66.5 nm and the roughness of the surface decreases with the increase of metamorphism.The elastic modulus of coal micro-surface varies from 95.40 to 9626.41 MPa,while the adhesion varies from 15.08 to 436.22 nN,and they both exhibit a trend of"M"shape with the increase of metamorphism.Furthermore,a high correlation exists between adhesion and microtopography fluctuation.In most cases,the adhesion is larger in the concavity area and smaller in the convexity area.The research results may provide a new method for revealing the occurrence and migration of CBM and ensure efficient and safe CBM exploitation.

Effects of microtopography on spatial point pattern of forest stands on the semi-arid Loess Plateau,China

Microtopography may affect the distribution of forests through its effect on rain redistribution and soil water distribution on the semi-arid Loess Plateau,China.In this study,we investigated the characteristics of microtopography on two shady slopes（slope A,5 hm2,uniform slope;slope B,5 hm2,microtopography slope） and surveyed the height,the diameter at breast height and the location（x,y coordinates） of all selected individual trees（Robinia pseudoacacia Linn.,Pyrus betulifolia Bunge,Populus hopeiensis Hu ＆ Chow,Armeniaca sibirica Lam.,Populus simonii Carr.and Ulmus pumila Linn.） on slope A and slope B in the watersheds of Wuqi county,Shaanxi province.Subsequently,the effects of microtopography on the spatial pattern of forest stands were analyzed using Ripley＇s K（r） function.The results showed that：（1） The maximal aggregation radiuses of the tree species on the uniform slope（slope A） were larger than 40 m,whereas those of the tree species on the microtopography slope（slope B） were smaller than 30 m.（2） On slope B,the spatial association of R.pseudoacacia with P.betulifolia,A.sibirica,P.simonii and U.pumila varied from being strongly negative to positive at microtopography scales.The spatial association of Populus hopeiensis Hu ＆ Chow with U.pumila also varied from being strongly negative to positive at microtopography scales.However,there was no spatial association between P.betulifolia and P.hopeiensis,P.betulifolia and A.sibirica,P.betulifolia and P.simonii,P.betulifolia and U.pumila,P.hopeiensis and A.sibirica,P.hopeiensis and P.simonii,A.sibirica and P.simonii,A.sibirica and U.pumila,and P.simonii and U.pumila.On slope A,the spatial association between tree species were strongly negative.The results suggest that microtopography may shape tree distribution patterns on the semi-arid Loess Plateau.

Microtopography driven plant species composition in alpine region: a fine-scale study from Southern Norway

This study explores the relationship between the species composition of lichen and vascular plant species with microtopography at fine scale. We conducted our study in Hardengervidda National Park, Norway. Specifically, we aim to test whether the species richness of different plant lifeforms peaks at middle of the microtopography gradient, and then explain the observed patterns with an aid of snow cover gradient along microtopography and snow cover. We sampled 69 species of vascular plants and lichens in 151 plots of 4 m^2 along 23 transects during summer on Tronsbu, Sandhaug and Besso. Detrended correspondence analysis(DCA) was performed to explore how microtopographical gradient was related to the variation in the species composition. One-way ANOVA was performed to test the microtopographic variability in species richness.Afterwards, generalized linear model(GLM) was used to reveal species richness patterns along the snow cover gradient. The first axis in DCA represents the complex gradient from snow free ridge to wet snowbed habitats and the second axis represents a gradient from acidic to calcareous sites. Lichen’s species richness is greater in ridge than in snowbeds, while all other life forms follow the opposite trend. Species richness for total plant species, vascular plant species and herbaceous plant species increased with increase in weighted average snow indicator value(WASI), whilst species richness for lichen species declined substantially towards the maximum WASI value. In contrast, species richness for dwarf shrub species showed a unimodal relationship with WASI. This study shows that liquid water availability provides a good potential explanation for species composition and richness in mountains, which is controlled by snow cover and prevalent wind direction.

How topography and neighbor shape the fate of trees in subtropical forest restoration:Environmental filtering and resource competition drive natural regeneration

The structure of plant communities at local scales depends on both the spatial heterogeneity of abiotic environmental factors and the biotic interactions within the community.However,although environmental filtering due to microtopographic heterogeneity and resource competition among plants caused by spatial variation in tree density and size are considered to be very important in explaining the mechanisms of community assembly,their effects on the processes of individual mortality and recruitment in natural forest regeneration,as well as their relative contributions,are still poorly understood.To address this,we established a 12-ha permanent plot in a subtropical evergreen broad-leaved forest area and measured microtopographic variables such as elevation,slope,aspect,and terrain position index(TPI)using a total station.We monitored the individual mortality and recruitment in forest natural regeneration through repeated surveys at 5-year intervals.We fitted spatial covariance models to jointly use multiple factors from three groups of variables(microtopographic effect,neighborhood density effects,neighborhood size effects)as explanatory variables to analyze their roles in driving the mortality and recruitment of all individual and 12 dominant species in forest natural regeneration at the neighborhood scale.Our results show that:(1)In the crucial early stages of secondary forest restoration,natural regeneration is influenced by a synergy of environmental filtering,due to microtopographic heterogeneity,and resource competition among plants.(2)For distinct species responses,evergreen dominant species'mortality is largely explained by neighborhood effects,while deciduous species are more affected by topographic factors.Furthermore,the adverse effects of larger conspecific trees on younger trees indicate a pattern of competitive pressure leading to mortality among regenerating trees,such pattern emphasis the influence of parent trees on natural regeneration.(3)As trees grow,their interaction with these stressors evolves,suggesting a shift in their resource acquisition strategies and response to neighborhood effects and environmental factors.Despite these changes,the relative importance of topographic factors in determining survival and recruitment success remains constant.This research highlights the importance of considering both environmental and neighborhood effects in forest management,particularly in early secondary forest restoration.

Atomic force microscopy study on the microtopography of natural organic matter and newly formed hydrous MnO_(2)

To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,the microtopography of its reductive products,the newly formed hydrous manganese dioxide and the aged hydrous manganese dioxide,was investigated.The morphology of natural organic matter(NOM)adsorbed by the newly formed hydrous manganese dioxide was also com-pared with that of NOM alone.By using the tapping mode atomic force microscopy(AFM),the observation results show that the newly formed hydrous manganese dioxide possess a perforated sheet(with a thickness of 0-1.75 nm)as well as some spherical particle structures compared with the hydrous manganese dioxide with 2 h aging time,which demonstrated that the newly formed hydrous manganese dioxide had a large surface area and adsorption capacity.When 1 mmol/L newly formed hydrous manganese dioxide was added,the micro-topography of NOM molecules shifted from a loosely dis-persed pancake shape(with adsorption height of 5-8.5 nm)to a densely dispersed and uniform spherical structure.These results provide a valid proof that it is the perfect adsorption capability of the newly formed hydrous manganese dioxide that might result in the coagulation aid effect of potassium permanganate preoxidation.

On Energy Assessment of Titanium Alloys Belt Grinding Involving Abrasive Wear Effects

Improved energy utilisation,precision,and quality are critical in the current trend of low-carbon green manufactur-ing.In this study,three abrasive belts were prepared at various wear stages and characterised quantitatively.The effects of abrasive belt wear on the specific grinding energy partition were investigated by evaluating robotic belt grinding of titanium plates.A specific grinding energy model based on subdivided tangential forces of cutting and sliding was developed for investigating specific energy and energy utilisation coefficient EUC.The surface mor-phology and Abbott–Firestone curves of the belts were introduced to analyse the experimental findings from the per-spective of the micro cutting behaviour.The specific grinding energy increased with abrasive belt wear,especially when the belt was near the end of its life.Moreover,the belt wear could lead to a predominance change of sliding and chip formation energy.The highest EUC was observed in the middle of the belt life because of its retained sharp cutting edge and uniform distribution of the grit protrusion height.This study provides guidance for balancing the energy consumption and energy utilization efficiency of belt grinding.

Effects of degradation succession of alpine wetland on soil organic carbon and total nitrogen in the Yellow River source zone,west China

Wetland is an important carbon pool,and the degradation of wetlands causes the loss of organic carbon and total nitrogen.This study aims to explore how wetland degradation succession affects soil organic carbon(SOC)and total nitrogen(TN)contents in alpine wetland.A field survey of 180 soilsampling profiles was conducted in an alpine wetland that has been classified into three degradation succession stages.The SOC and TN contents of soil layers from 0 to 200 cm depth were studied,including their distribution characteristics and the relationship between microtopography.The results showed that SOC and TN of different degradation succession gradients followed the ranked order of Non Degradation(ND)>Light Degradation(LD)>Heavy Degradation(HD).SWC was positively correlated with SOC and TN(p<0.05).As the degree of degradation succession worsened,SOC and TN became more sensitive to the SWC.Microtopography was closely related to the degree of wetland degradation succession,SWC,SOC and TN,especially in the topsoil(0-30 cm).This result showed that SWC was an important indicator of SOC/TN in alpine wetland.It is highly recommended to strengthen water injection into the wetland as a means of effective restoration to reverse alpine meadow back to marsh alpine wetland.

Analysis of erosion rill development under rainfall events using structure-from-motion photogrammetry——a case study from Kielce(Holy Cross Mts.,Poland)

The development of erosive landforms such as rills,ditches,slits,and gullies depends on many environmental factors;thus,the rate of the development of each individual form differs.In this paper,the author presents a case study of two erosion rills located on a hiking trails(Holy Cross Mts.)resulting after 2 years of monitoring in which the process of their evolution was precisely analyzed.Once established,such landforms develop over time with variable rates and can represent multiple different stages.Moreover,the final result of the rill development hardly reminds their original form and does not allow for interpretation of the events that affected it in the recent past.Therefore,the main objective was to determine the volumetric changes of erosion rills created by the surface runoff on both sections,during two years of observation.Additional objectives included a description of the physical and meteorological parameters,important in the development process and a comparison of them to the volumetric changes of each period.Using the Structure-from-motion(Sf M)photogrammetry technique,monitoring procedures have been performed quickly offering sufficient accuracy.For direct comparison,the digital elevation model of difference(Do D)method was used,enabling the calculation of volume.The results showed that the erosion to deposition ratio was more disproportionate during storm events or periods with higher depth of rainfall.Total erosion to deposition balance for the entire monitoring period was negative and equal to 1448.84 kg or 410 Mg/ha for the first erosion rill and 1059.5 kg or 300 Mg/ha for the second rill.Both erosion rills developed differently.The first erosion rill developed by linear cut into deeper and wider form,while the other,steeper rill,evolved from plunge pools merging together into deeper and wider form.

Guided cell migration on a graded micropillar substrate

Cell migration is facilitated by the interaction of living cells and their local microenvironment.The local topography is one of the key factors regulating cell migration.Interaction between the surface topography and the cell behaviors is critical to understanding tissue development and regeneration.In this study,a dynamic mask photolithography technique has been utilized to fabricate a surface with graded micropillars.It has been demonstrated that the cells have been successfully guided to migrate from the sparse zone to the dense zone.The cell polarization angle has been characterized in both sparse zone and the dense zone.Compared to the dense zone,the cells in the sparse zone are more aligned along the direction of the micropillar spacing gradient,which enables the guided cell migration.Moreover,the effects of the micropillar spacing gradient,micropillar diameter,and micropillar height have been investigated in terms of the cell migration speed and cell spreading area.Finally,two issues significantly affecting the cell migration have been discussed:trapped cells between the micropillars and cell clusters.

Early Snowmelt Enhances the Carbon Sequestration of Hummock-Forming Sphagnum Mosses on Boreal Wetlands

Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO2 exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO2 exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.

Research on wind erosion processes and controlling factors based on wind tunnel test and 3D laser scanning technology

The study of wind erosion processes is of great importance to the prevention and control of soil wind erosion.In this study,three structurally intact soil samples were collected from the steppe of Inner Mongolia Autonomous Region,China and placed in a wind tunnel where they were subjected to six different wind speeds(10,15,17,20,25,and 30 m/s)to simulate wind erosion in the wind tunnel.After each test,the soil surfaces were scanned by a 3D laser scanner to create a high-resolution Digital Elevation Model(DEM),and the changes in wind erosion mass and microtopography were quantified.Based on this,we performed further analysis of wind erosion-controlling factors.The study results showed that the average measurement error between the 3D laser scanning method and weighing method was 6.23%for the three undisturbed soil samples.With increasing wind speed,the microtopography on the undisturbed soil surface first became smooth,and then fine stripes and pits gradually developed.In the initial stage of wind erosion processes,the ability of the soil to resist wind erosion was mainly affected by the soil hardness.In the late stage of wind erosion processes,the degree of soil erosion was mainly affected by soil organic matter and CaCO_(3)content.The results of this study are expected to provide a theoretical basis for soil wind erosion control and promote the application of 3D laser scanners in wind erosion monitoring.

Atomic Force Microscopy of Calcite Surface

Both atomic force microscope (AFM) and scanning tunneling microscope (STM) are devices for investigating material surfaces down to atomic-scale in real space. But unlike STM, AFM can be used to study not only conductors and semiconductors but also insulators. So it has a wider application range than STM. As most minerals are insulators,