Concave Layer Research Articles

Sustainable development of geological resources: the Characteristics of Red Karst Landscape and Tourism Development in Tongren, Guizhou

<abstract> <p>China is rich in karst resources and famous for its karst landscape. As a part of karst, the popularity of red karst is obviously low and has received little attention; moreover, the related scientific research and tourism development are relatively immature. Therefore, this paper takes the red karst in Tongren, Guizhou as the research object, analyzes the characteristics and causes of the red karst, comprehensively evaluates its landscape value, and puts forward development strategies and protection suggestions. Through the above research, the following three research results are obtained. (1) On the basis of a field investigation and a literature review, the geographical situation, background, and landscape characteristics of the red karst landform and its surrounding areas in Tongren City were investigated in detail. It forms isolated peaks, rock walls, protruding rocks, stone pillars, and other forms. The most prominent features of the red karst landscape in Tongren City are that the color is red and white, and the shape is concave and convex in order. (2) Geochemical test and structural data collection and analyses of the collected samples were performed. The obtain concave layer rock is dolomitic limestone, and that convex lay rock is argillaceous dolomitic limestone. Because the convex layer rock sample is high in silicon element content, the convex layer rock sample is not easy to be weathered, is rich in clay mineral, and is not easy to be corrode; the convex layer rock sample gradually protrudes with the passage of time to form an uneven shape. The red karst landform is developed in either the rock stratum or tectonic zone with moderate tectonic deformation intensity. First, the formation of a single-layer honeycomb morphology requires that the rock stratum is subjected to a sufficient horizontal compressive stress at a certain burial depth. Second, it is necessary to widely exist in areas with relatively gentle rock formation occurrence; too strong of a structural deformation will make the rock formation occurrence steep, which is not conducive to the occurrence of differential dissolution between adjacent strata. (3) Through the construction of an evaluation index system, the red karst in Tongren City is evaluated, and it is concluded that the geological heritage value is high, and the development and utilization conditions are weak. The conclusion of this article is a supplement to the geological and geomorphological system characteristics of southern karst. From the perspective of world natural heritage, the study enriches the academic evidence of red karst and enables its exemplary role to be well played. From the perspective of the tourism development value, more people should be made aware of the diverse types of karst landforms, which provide experience and suggestions for the value of landforms, tourism resources, and tourism development in similar areas.</p> </abstract>

Carrier Velocity Modulation by Asymmetrical Concave Quantum Barriers to Improve the Performance of AlGaN-Based Deep Ultraviolet Light Emitting Diodes

Carrier velocity modulation by asymmetrical concave quantum barriers to improve the performance of AlGaN-based deep-ultraviolet light emitting diodes has been investigated. The concave structure is realized by inserting a low Al composition AlGaN layer in the barrier, and thus forming a concave region on energy band. The measured device performance shows a significant improvement under 0-250 mA operation current, with the maximum external quantum efficiency and light output power of 1.02% and 8.0 mW, which are more than double (2.32 and 2.35 times) of that for the conventional one, respectively. Simulation confirms that the concave quantum barriers make it possible for electrons to be scattered, which reduce the electron energy before being injected into quantum wells, and thus the capability of quantum wells to capture electrons is enhanced. Meanwhile, the vertical transport of holes within the active region is also enhanced because the asymmetrical setting of the concave layer in the quantum barriers helps holes accelerate under the polarization field, and then get more energy to overcome the barrier.

Low-Temperature Cu–Cu Direct Bonding Using Pillar–Concave Structure in Advanced 3-D Heterogeneous Integration

Low-temperature Cu–Cu bonding utilizing pillar and concave on silicon substrate with and without polymer layer is successfully implemented at 200 °C under atmospheric pressure. Finite-element method (FEM) simulations on stress and deformation generated during bonding process are also presented in order to discuss their influence on bonding result of several pillar diameters and of concave sidewall angles originating from the manufacturing process. The alteration of parameters in FEM simulations would also be investigated to enhance the bonding outcome. The parameters include the diameter of pillar, the sidewall angle of concave, the shape of the concave opening, the addition of extra polymer layer under Cu concave layer, the bonding temperature, and the pitch of the pillar–concave structure. The implementation of Cu–Cu bonding using pillar–concave structure could have a prospective effect on existing packaging methods in semiconductor industry with benefits of applicability to various sorts of substrates and low bonding temperature.

Active reinforcement of externally imposed folding in amphibians embryonic tissues

Although the folding of epithelial layers is one of the most common morphogenetic events, the underlying mechanisms of this process are still poorly understood. We aimed to determine whether an artificial bending of an embryonic cell sheet, which normally remains flat, is reinforced and stabilized by intrinsic cell transformations. We observed both reinforcement and stabilization in double explants of blastocoel roof tissue from Xenopus early gastrula embryos. The reinforcement of artificial bending occurred over the course of a few hours and was driven by the gradual apical constriction and radial elongation of previously compressed cells situated at the bending arch of the concave layer of explant. Apical constriction was associated with actomyosin contraction and endocytosis-mediated engulfing of the apical cell membranes. Cooperative apical constrictions of the concave layer of cells produced a tensile force that extended over the entire surface of the explant and correlated with apical contraction of the concave side cells. In the explants taken from the anterior regions of the embryo, this reinforcement was more stable and the bending better expressed than in those taken from suprablastoporal areas. The morphogenetic role of cell responses to the bending force is discussed.

Effect of concentration on the pattern formation of thin concave layer colloidal suspension

We study the effect of concentration on the drying process and pattern formation of thin concave layer colloidal suspension.Camera is used to capture the drying process.It is shown that with the increase of concentration,the width of broad-ring increases,and the number of the broad-ring decreases.The drying process is divided into five stages,which contain two stages of Marangoni convections.The convection has great influence on the self-organization of colloid particles and film pattern.Pattern formation with the characteristic of thick edge and thin center is mainly caused by the first stage of convection,and multiple broad-ring pattern formation is under the influence of the second stage of convection,which accompanies pin-slip motion of contact line.

Monte Carlo simulation of polymer brushes in narrow pores

We present the model of a cylindrical pore with chains tethered by one end to its inner surface. The conformational and “quasistatic” (under low and medium shear rates) hydrodynamic properties of the system are studied. Since it was shown by other researchers that the density profile of the polymer layer is only slightly affected by flow in the region of low and medium shear rates, we do not take flow into account when calculating chain conformations. The conformational properties of the concave layer are very similar to those of the flat one. They are characterized by the layer thickness h. The hydrodynamic properties are characterized by the hydrodynamic thickness Lh. We show that Lh depends strongly on the chain surface density σ under conditions of the “mushroom” regime in contrast to h. Finally, we predict that the net permeability of the cylinder could decrease with the increasing temperature. It enables us, principally, to control the pore permeability with temperature.

Contact analysis of biphasic transversely isotropic cartilage layers and correlations with tissue failure

Failure of articular cartilage has been investigated experimentally and theoretically, but there is only partial agreement between observed failure and predicted regions of peak stresses. Since trauma and repetitive stress are implicated in the etiopathogenesis of osteoarthritis, it is important to develop cartilage models which correctly predict sites of high stresses. Cartilage is anisotropic and inhomogeneous, though it has been difficult to incorporate these complexities into engineering analyses. The objectives of this study are to demonstrate that a transversely isotropic, biphasic model of cartilage can provide agreement between predicted regions of high stresses and observed regions of cartilage failure and that with transverse isotropy cartilage stresses are more sensitive to convexity and concavity of the surfaces than with isotropy. These objectives are achieved by solving problems of diarthrodial joint contact by the finite-element method. Results demonstrate that transversely isotropic models predict peak stresses at the cartilage surface and the cartilage–bone interface, in agreement with sites of fissures following impact loading; isotropic models predict peak stresses only at the cartilage–bone interface. Also, when convex cartilage layers contacted concave layers in this study, the highest tensile stresses occur in the convex layer for transversely isotropic models; no such differences are found with isotropic models. The significance of this study is that it establishes a threshold of modeling complexity for articular cartilage that provides good agreement with experimental observations under impact loading and that surface curvatures significantly affect stress and strain within cartilage when using a biphasic transversely isotropic model.

Polymers grafted to a convex surface

We consider the equilibrium statistics of polymers grafted to the outside of a cylinder in the limit of high molecular weight for small, fixed grafting density. Under melt conditions, we find the exact self-consistent pressure profile, the chain configurations, and the free energy in closed form. These are qualitatively different from the case of concave or flat surfaces: the free chain ends are excluded from a zone near the surface, whose thickness grows from zero for a flat surface to a fraction 21. of the layer height for a strongly curved cylinder. Despite these differences, the free energy of the convex layer is very well described by the simpler law for the concave layer, analytically continued to convex curvature, for all but the most extreme curvatures. For a cylindrical layer in a marginal solvent, we reduce the conditions for equilibrium to a linear integral equation describing the exclusion zone. For spherical curvature the analogous equation has a quadratic nonlinearity: we discuss the conditions under which this equation is suitable for describing the spherical layer.

Local effects of large-scale eddies on bursting in a concave boundary layer

Concave curvature has a destabilizing effect on a turbulent boundary layer that causes the formation of large-scale inflow and outflow regions. These structures are larger and more energetic than large eddies in a flat boundary layer, particularly in terms of velocity fluctuations normal to the wall. Flow visualization has suggested that the large-scale inflows and outflows have a strong influence on turbulence structure in the near-wall region. However, near-wall profiles of Reynolds-averaged quantities in the concave boundary layer do not indicate major structural changes. In this paper, the effects of concave curvature on near-wall structure are investigated in two flow cases: (i) the natural concave boundary layer, where the large-scale eddies do not have preferred spanwise locations and the layer remains nearly two-dimensional in the means; and (ii) a case in which vortex generators are used to induce a fixed array of longitudinal roll cells, allowing measurements to be made under stationary inflow and outflow regions. Burst frequencies obtained using an extension of the uv-quadrant method confirm the visual impression that inflows suppress the bursting process, while outflows enhance it. Reynolds-averaged measurements show that turbulence intensity and the uv correlation coefficient are also suppressed under the inflows. Based on these results, a conceptual model for the effects of large-scale eddies on near-wall flow and skin friction in a concave layer is proposed.

Theory for the Excitation and Propagation of Electromagnetic Waves Guided by an Elevated Refractive Index Discontinuity in the Troposphere

We present an analysis for waves guided by a smooth concave layer in the troposphere. The modal expansion includes both ground wave and Earth detached modes. It is shown that the excitation of the Earth detached modes by a ground based source is very weak. However, there is a possibility that these modes may be excited by a nonuniformity of the layer structure.