Pit Edge Research Articles

Analysing the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau

Abstract The coal mining has brought a series of ecological problems and environmental problems in permafrost regions. Taking Muli coal-mining area as an example, this article attempts to analyse the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau. This article analyses the influence of open mining on the surrounding permafrost around the open pit by using the numerical simulation. The results show that (1) based on the interrelation between coal mining and permafrost environment, these main environmental harm include the permafrost change and the natural environment change in cold regions; (2) once the surface temperature rises due to open mining, the permafrost will disappear with the increase of exploitation life. If considering the solar radiation, the climate conditions and the geological condition around the pit edge, the maximum thaw depth will be more than 2 m; (3) the protection measures are proposed to avoid the disadvantage impact on the permafrost environment caused by coal mining. It will provide a scientific basis for the resource development and environment protection in cold regions.

Prospective analysis of isolated gastrocnemius recession for Achilles tendinopathy

The article presents research on predicting landslides of different origin; also addressed an important question of spatial specification of earth surface displacement in undermining areas. Normative and methodological sources have no concrete solutions to these issues for a variety of territory conditions. For prediction of natural landslides used digital elevation models built on the basis of the airborne laser scanning data. Dangerous areas are modeled on the landslide potential and with neural network analysis. Suggested the technique of technogenic landslide prediction. Determined the influence of landslide curvature parameter (in horizontal plane) on the basis of numerical 3D simulations. Showed technological schemes of pit edge deformation observations. Described the technique of instrumental observations on the spatial determination of earth surface subsidence zone in undermining. Used laser scanning system. Dynamic visualization of the earth surface is implemented in 3ds Max.

Takedown of ankle fusions and conversion to total ankle replacements: A prospective longitudinal study

The article presents research on predicting landslides of different origin; also addressed an important question of spatial specification of earth surface displacement in undermining areas. Normative and methodological sources have no concrete solutions to these issues for a variety of territory conditions. For prediction of natural landslides used digital elevation models built on the basis of the airborne laser scanning data. Dangerous areas are modeled on the landslide potential and with neural network analysis. Suggested the technique of technogenic landslide prediction. Determined the influence of landslide curvature parameter (in horizontal plane) on the basis of numerical 3D simulations. Showed technological schemes of pit edge deformation observations. Described the technique of instrumental observations on the spatial determination of earth surface subsidence zone in undermining. Used laser scanning system. Dynamic visualization of the earth surface is implemented in 3ds Max.

Prediction of Natural and Technogenic Negative Processes Based on the Analysis of Relief and Geological Structure

The article presents research on predicting landslides of different origin; also addressed an important question of spatial specification of earth surface displacement in undermining areas. Normative and methodological sources have no concrete solutions to these issues for a variety of territory conditions. For prediction of natural landslides used digital elevation models built on the basis of the airborne laser scanning data. Dangerous areas are modeled on the landslide potential and with neural network analysis. Suggested the technique of technogenic landslide prediction. Determined the influence of landslide curvature parameter (in horizontal plane) on the basis of numerical 3D simulations. Showed technological schemes of pit edge deformation observations. Described the technique of instrumental observations on the spatial determination of earth surface subsidence zone in undermining. Used laser scanning system. Dynamic visualization of the earth surface is implemented in 3ds Max.

Cleaning Up After a Meal: The Consequences of Prey Disposal for Pit‐Building Antlion Larvae

AbstractPredators use a variety of strategies for capturing prey. Trap‐building predators can save on searching and encountering costs by investing in the construction and maintenance of traps such as webs and pits. However, what to do with partially consumed prey poses a potential problem. Antlion larvae (Myrmeleon acer) catch ants in conical pits, and dispose of partially consumed carcasses by flicking them a short distance away. We tested whether this prey‐disposal behaviour affects the effectiveness of antlion pits. We observed ant behaviour around artificially constructed pits and compared falls into pits with clean margins to those with conspecific ant carcasses or control objects around the pit edge. The presence of objects near pits affected the behaviour of live ants, and reduced the effectiveness of pits. Live ants spent the most time examining fresh ant carcasses, but the presence of any object near pits deterred pitfalls. Ants fell into pits significantly more often when pit edges were clean, suggesting that antlions could incur a prey capture cost from flicking carcasses from pits as well as from the accumulation of other debris around pit margins.

Macular Pseudoholes With Lamellar Cleavage of Their Edge Remain Pseudoholes

To reappraise macular pseudohole characteristics using spectral-domain optical coherence tomography (OCT) and characteristics and postoperative outcomes of macular pseudoholes. Retrospective, observational case series. In this institutional study, 54 eyes with macular pseudohole were selected among 369 patients examined for an epiretinal membrane (ERM) by Cirrus spectral-domain OCT (Carl Zeiss Meditec) within a 2-year period. The diagnosis of macular pseudohole was based on the presence of a deep foveal pit, with verticalized edges and a macula thickened by the contraction of an ERM. All eyes underwent color fundus photography and spectral-domain OCT examination comprising a macular map, line raster scans, and en face images of the inner retinal surface. The main outcome measures were the morphologic description of the foveal profile in macular pseudoholes in relation to the pattern of the ERM contraction and the postoperative changes. In 24 eyes, the foveal pit had vertical, straight, smooth edges on the OCT scan corresponding to centripetal contraction of the ERM. Thirty other eyes exhibited some degree of stretching and cleavage of the foveal pit edge resulting from asymmetrical tangential traction of the ERM between multiple epicenters of contraction. Thirty-three patients underwent surgery, and their macular profile and visual acuity improved whatever their initial foveal profile. The OCT profile of macular pseudohole varies according to the pattern of the causal ERM contraction. Macular pseudoholes with a stretched foveal edge respond to ERM peeling as positively as other eyesand should not be confounded with macular lamellar holes.

Current Conditions of Open Mining of Mineral Fields of Kazakhstan

The paper contains the review of issues of completeness and quality of mineral mining at the opencast mines and creation of geomechanical justification of systems with internal p iling. Current mining production is characterized by the increase of share of open mining of mineral resources, the ratio of which in the world mineral mining is nearly 70%. Capacit ies of mining co mpanies keep on g rowing, production processes are being intensified; depth and periods of operation of open mines are being increased. In these cond it ions , issues of increase o f econo mic efficiency and env iron mental safety o f min ing operat ions beco me of mo re impo rtance; on e o f the most rad ical ways o f solut ion o f th is p rob lem is the maxi mu m use fo r locat ion o f ov erbu rden ro ck and p roduct ion waste fro m the waste qu arry area as a vo lu me man -caused resource. The work contains the analytical rev iew o f the current state of open mining of mineral resources of Kazakhstan, sequence of mining operations with internal piling, sequence of format ion and development of internal dump, optimal parameters of dumps (volu me, height, stratification, angles of d ips) as well as the stability of inactive pit edge before and after its loading with embankment.

Asymmetric coalescence of reactively wetting droplets

Coalescence of droplets during reactive wetting is investigated for the liquid Ga/GaAs(001) system. In situ mirror electron microscopy reveals that coalescence predominantly involves the motion of one reactive droplet relative to the other. This behaviour differs significantly from coalescence in non-reactive systems and is associated with contact line pinning at a ridge/etch pit edge which is identified using atomic force microscopy and selective etching. A simple geometrical model is presented to describe the pinning.

Estimate of the stability of stratified slopes based on the plastic theory

The study is carried out into the stability of edges of open pits with a stratified structure. The angle of the strata slope and the ultimate elastic compressive and shear strengths are assigned. The maximal allowable depth of an open pit is determined depending upon the pit edge incline. The problem is solved from the constructed equations of plasticity of a stratified material. The limiting loads under which the plastic zone come onto the pit side surfaces and cause the pit slope stability loss are calculated.

Algorithm and Search Method for the Critical Surfaces in the Vicinity of Mined-out Spaces

The principal aspects, algorithm, and search method are presented for the surface of least shear resistance on the basis of minimization of the strength functional. The coefficients allowing estimation of possible rock failure in different sections of the surface in question are proposed. As an example, the results of search of a probable failure surface in a pit edge are cited.

Electron Beam Recorder with Nanometer-Scale Accuracy for 100 Gbit/in2 Density Mastering

An electron beam recorder (EBR) was developed for mastering optical disks with a recording density of 100 Gbit/in2 using a multilevel recording format. In this recording format, a nanometer-scale accuracy of relative pit edge position is required in both radial and tangential directions. To achieve the recording position accuracy, a rotation stage with a noncontact vacuum seal and a correction system for rotation errors were developed. In addition, an active magnetic shield system and a learning compensation for beam displacement were adopted to improve the stability of the beam position. As a result, the ability to record with high accuracy and high resolution was confirmed from experimental results. A fine pit pattern with a minimum pit length of 70 nm was formed precisely. The recording accuracy of the EBR was evaluated to be approximately 2 nm (standard deviation) in both radial and tangential directions. Furthermore, a carrier-to-noise ratio of 64 dB was also obtained by reproducing an etched silicon master with a 240 nm monotone pit pattern.

On the kinetics of xanthine adsorption at the mercury ∣ electrolyte interface

The short-term and long-term capacity–time dependence of xanthine in 0.2 M NaCl at 35 °C inside the potential region of the capacity pit was measured at the mercury ∣ electrolyte interface. The short-term capacity–time dependence can be described well theoretically by 2D instantaneous nucleation with a constant growth rate and, for potentials near the more negative pit edge, with 2D nucleation according to an exponential law with a constant growth rate. The long-term capacity–time dependence corresponding to secondary adsorption can be modelled well by 1D instantaneous nucleation with a diffusion controlled growth rate. This mechanism refers to the formation of linear surface molecular stacks. The potential dependence of the overall nucleation and growth rate constant for the short-term and long-term capacity–time dependences will be discussed on the basis of the potential dependence of the interfacial supersaturation.

Substantiation of Deep Placer Mining Technology with Pit-Edge Profile Control

Mining technology is presented, which makes it possible to obtain stable profile of the pit edge, diminish its working area by 15-25%, and reduce impoverishment of the seam by 15-20%.

High-Track-Density Optical Disc by Radial Direction Partial Response

We propose a new recording method, the radial direction partial response (RPR), with which we are able to use a narrow track pitch. This method can be used only for optical read-only-memory discs. We present experimental results of this method combined with the multilevel recording technique called “single carrier independent pit edge recording” (SCIPER). (The combined method is called SCIPER-RPR). When a track pitch of 0.45 µm and 0.28 µm/bit in linear recording density is read out by a digital versatile disc (DVD) equivalent optical pickup, we confirmed a bit error rate of 1.5×10-4.

Readout of Optical Disk Recorded by Pit Edge and Depth Modulation

We report a Read-only (ROM) disc which is recorded by pit edge and depth modulation (PEDM). The information recorded by pit edge modulation is read out through an RF signal channel, and that recorded by pit depth modulation is read out through a tangential push-pull signal channel by detecting signal polarity at the pit edge. Each signal is sliced with a single level and is combined with another signal so that a multi-value recording is realized without multiple level slicing. The information recorded and read out using tangential push-pull signal polarity can never be copied onto recordable discs. Thus, not only a larger recording density and a higher transfer rate but also secure information storage are achieved with no change of the current optical and mechanical systems.

Effect of Sample Topography on Adhesive Force in Atomic Force Spectroscopy Measurements in Air

The effect of local curvature of a sample surface on capillary and interface tension adhesion forces of the water meniscus formed between the AFM tip and sample in air is demonstrated both theoretically and experimentally. We propose an analytical solution for capillary and tension adhesive force derived from approximation of the thermodynamic equilibrium of a symmetric water meniscus formed at the tip−sample contact region. It is shown that the sample local curvature strongly affects the water meniscus geometry and the adhesion force. Compared to the force computed for a flat sample surface, the theoretical model predicts a larger/smaller adhesive force for a concave/convex local curvature. Our theoretical predictions were confirmed by experiment. Atomic force spectroscopy measurements were performed for a silicon nitride cantilever and a standard sample of platinum-covered quartz patterned with 1.5 × 1.5 μm square, 20 nm deep pits. Maps of sample surface topography and adhesive force showed a much larger force at the bottom of the pit edge, where the local curvature was concave. This was contrasted with a much smaller force observed at the top of the pit edge, where the local curvature was convex.

Observations of local electron states on the edges of the circular pits on hydrogen-etched graphite surface by scanning tunneling spectroscopy

Scanning tunneling microscopy (STM) and spectroscopy (STS) are used to study electronic states at the edges of the circular pits on the hydrogen-etched graphite surface. The edge surface state revealed by tunneling spectroscopy appears as the maximum of the local density of states (LDOS) in the energy range of 90–250 meV above the Fermi level. The dispersion of the energy state is explained by the band broadening in AB stacked H-terminated graphite. The magnitude of the edge state decreases with the distance from the pit edge as theoretically predicted.

Nanoconfined Electrochemical Nucleation of Crystalline Molecular Monolayers on Graphite Substrates

Real-time in situ atomic force microscopy (AFM) has been employed to examine the electrochemical nucleation of epitaxially oriented, crystalline monolayers of bis(ethylenedithiolo)tetrathiafulvalene triiodide, (ET)2I3, on the basal plane of highly oriented pyrolytic graphite electrodes decorated with circular, single-layer-deep pits created by thermal etching. The nucleation of the monolayers in the pits is inhibited compared to the contiguous terraces. The time required for pit filling scales inversely with pit diameter, with nucleation completely suppressed in pits with diameters less than 100 nm. The suppression of growth in the pits can be attributed to the surface discontinuity created by the pit edge that prevents surface diffusion of ET growth units from the surrounding terrace to the pit. Consequently, growth of nuclei in the pits is limited by the amount of ET arriving in the pit by diffusion directly from solution. Numerical simulations of aggregate growth in pits illustrate the influences of tr...

Pitting in Aluminum Thin Films: Supersaturation and Effects of Dichromate Ions

The growth of pits in 209 nm thick Al films in chloride solutions with and without dichromate ions was examined using image analysis of the growing pits to determine pit current density. In pure chloride solutions, the pit current density decreased at high potentials after reaching a maximum value, and then was almost independent of applied potential. A hysteresis in the pit current density‐potential behavior was observed during downward stepping of the potential from high values. This is a result of a combination of supersaturation of the pit electrolyte followed by salt film formation, and changes in mass transport from hydrogen bubbles that increase convection and lift the remnant passive film away from the dissolving surface. In solutions containing dichromate ions, the corrosion and repassivation potentials shifted in the noble direction, and rather large metastable pits formed at the open circuit. A large concentration of dichromate ions was needed to inhibit pit growth. In dichromate solutions, subsequent pit growth at higher potentials often initiated at the edge of the open‐circuit pits. The rate of pit growth was lower for these pits because the remnant passive film layer was not easily lifted up at these sites, and thus created a barrier for mass transport away from the dissolving pit edge.

Cantilever flexure, adhesive\\attractive and lateral force measurements on highly-oriented pyrolytic graphite by scanning force microscopy

Pre-existing defects in the surface of highly-oriented pyrolytic graphite (HOPG) can be etched out by reaction with oxygen at high temperature. The result of this treatment is a population of one-monolayer-deep etch pits on the surface. An etch pit edge, possessing different chemical terminations than the basal plane of HOPG, may display unique interactions with any nanometer-scale material entity (viz. clusters and molecules) located in its vicinity. Since probe tips used in scanning force microscopy (SFM) can possess radii of curvature as small as 5–10 nm, it might be possible to measure the chemical uniqueness of etch pit edges with the help of SFM. In this paper, we consider possible instrumental artefacts which could hinder SPM studies of topography and friction on tailored HOPG surfaces for which there is a spatial variation in chemical properties. We conclude by discussing evidence for enhanced friction (≈100%) and adhesion (≈20%) at etch pit edges.