Riemann Surface Structure for a Curved Surface with Punctured Features

In this paper, a generic procedure for the development and subsequent validation of the Riemann surface structure (RSS) for a punctured curved surface lying on a Riemann surface is discussed. The proposed procedure differs from the existing methods involving triangular meshes and rectangular grids that rely on induced patches on surfaces. This procedure can be applied to non-punctured surfaces as well as to surfaces with irregularly located punctures. Further, by defining appropriate transition functions, the proposed procedure eliminates the requirement for smooth transitions across the boundaries of adjacent patches. The analytic formulations of the RSS for an ellipsoid and a sphere are elaborated using the proposed procedure. Moreover, the RSS of a sphere defined through a family of conformal unit discs is proven equivalent to that defined by an existing method based on stereographic projection. This study proves that a smooth projection between the surface and (a subset of) the complex plane , can be remapped to the original surface.

Study on Electrochemical Effects Assisted Magnetic Abrasive Finishing for Finishing Stainless Steel SUS304

In order to obtain a high accuracy with high machining efficiency for finishing hard alloy metal material, we proposed a hybrid finishing method which is electrochemical (ECM) effects assisted magnetic abrasive finishing (MAF). In this study, the electrochemical magnetic abrasive finishing (EMAF process) was divided into EMAF stage and MAF stage. The metal surface can be easily finished with the passive films formed in electrochemical reactions. Simultaneously, the passive films can be removed by frictional action between magnetic brush and workpiece surface. Thus, the essence of EMAF process is to form and remove the passive films on the workpiece surface. This study focused on investigating the finishing mechanism and finishing characteristics of EMAF process. Through a series of experimental investigations, it can be confirmed that the finishing efficiency is remarkably improved by EMAF process. The optimal experimental result of EMAF process showed that the surface roughness was reduced to less than 30 nm from the original surface roughness 178 nm at 4 min in EMAF stage, and the surface roughness was finally reduced to 20 nm at 10 min in MAF stage. Additionally, we also found the finishing ability of magnetic abrasive decreased after 4 min EMAF stage.

Computation of Implicit Representation of Volumetric Shells with Predefined Thickness

We propose and validate a method to find an implicit representation of a surface placed at a distance h from another implicit surface. With two such surfaces on either side of the original surface, a volumetric shell of predefined thickness can be obtained. The usability of the proposed method is demonstrated through providing solid models of triply periodic minimal surface (TPMS) geometries with a predefined constant and variable thickness. The method has an adjustable order of convergence. If applied to surfaces with spatially varying thickness, the convergence order is limited to second order. This accuracy is still substantially higher than the accuracy of any contemporary 3D printer that could benefit from the function as an infill volume for shells with predefined thicknesses.

Sequential dual sided SPIF using low order geometry reconstruction

Harmonic decomposition is an analytical technique that is able to express a manifold surface as the sum of a number of simple surface harmonic components. By reconstructing the initial geometry using a reduced number of components, a similar surface is obtained with a lower level of geometric detail. Because small features are filtered out and the resulting surface lies equal parts above and below the original surface, a tailored multi-step SPIF (Single Point Incremental Forming) processing strategy can be devised. This sequential SPIF strategy uses three processing passes to form a workpiece. The first step is a regular SPIF operation using a conventional toolpath strategy to form the reduced geometry. Two finishing steps are then needed, one from the same side to form the smaller features that lies deeper than the reduced geometry and one backwards pass from the other side of the sheet. To add features that need to be shallower than the reduced geometry, the part is flipped around. The used sequence of these finishing steps and the toolpath strategy used significantly influence the final part accuracy and surface quality. The advantages and disadvantages of four of these combined strategies are examined and compared to regular SPIF.

ON INVERSE OF A REGULAR SURFACE WITH RESPECT TO THE UNIT SPHERE S2 IN E3

The purpose of this paper, first, is to give a definition of the inverse surface of a given regular surface with respect to a unit sphere in E3. Second, some characteristic properties of the inverse surface are to express depending on the algebraic invariants of the original surface. In the last part of the study, we gave examples supporting our claims and plotted their graphics with the help of Maple software program.

Multi-method approach for high resolution 3D data based process analyses of compound rock slides

<p>The use of high resolution 3D point clouds and digital terrain models (DTM) from laserscanning or photogrammetry becomes more and more state of the art in landslide studies. Based on a multi-temporal terrestrial laserscanning (TLS) dataset of the deep-seated compound rockslide Laatsch, South Tyrol, we present a multi-method approach to characterize processes such as sliding, falling, toppling, and flows. Sliding is the predominant process of the Laatsch rockslide, accompanied by secondary processes such as rockfall, debris flows and erosion. The presented methods are applicable to all kind of 3D point clouds and not limited to TLS data. For remote sensing-based landslide analyses a distinction between two classes of surface processes is necessary: i) processes where the original surface is destroyed and no correlations between the shape and texture of the pre- and post-failure surfaces can be found (falls, rapid flows, rapid slides) and ii) processes where the surface is displaced without major surface changes (slow slides, slow flows and toppling). For processes where the original surface is destroyed, the distance between the pre- and post-failure terrain surface is measured with the aim to delineate the scarp and depositional area, and to quantify the failure volume as well as the scarp thickness. With DTMs of differences (DoD), the distance is measured along the plumb line. DoDs can be used to quickly and reliably assess the volume and extent of fall processes on flat to moderate slopes. For steep or even overhanging terrain, a 3D distance measurement approach must be used, where the distance is measured along the local surface normal. After 3D distance measurement, the volume of steep scarp areas can be calculated by first rotating, the point cloud into the horizontal plane (by making use of the average surface normal) and by interpolating the rotated 3D distance measurement values into a grid. Summing up the distances and multiplying with the cell area of the grid yields the scrap rupture volume. Remote sensing-based analyses of sliding and toppling processes are more complex compared to fall processes because the displaced surface patch must be detected in both surveys. Displacement analyses based on image correlation of ambient occlusion shaded relief images, together with DTMs of both epochs, are used to analyse the displacement of the entire rockslide area. The result is a map with displacement vectors. Disadvantages of image correlation are the coarse spatial resolution and the inability, as it is a 2.5D approach, to deal with steep slope parts. To analyse the displacement and toppling of steep rock walls a combination of the 3D distance measurement approach and an iterative closest point (ICP) based approach is applied. The 3D distance measurement values are clustered and used for a segmentation of the point cloud. In a next step, the ICP is applied on each of the resulting segments. This approach can deal with 3D displacements. The results are still sensitive towards the geometric contrast within the segments and not fully automated yet.</p>

Topsoil removal and Sphagnum spreading improve the climate balance of peat bog restoration

<p>Many peatlands in Central Europe are under unsustainable drainage-based land use with high greenhouse gas emissions counteracting the aims of the Paris Agreement. After decades of drained and intensive land use many peat bogs are in pitiful state. Rewetting can stop the carbon dioxide (CO<sub>2</sub>) source function but may result in high methane (CH<sub>4</sub>) emissions and eutrophication. Further, lack of diaspores my hamper the establishment of typical bog species. Restoration measures like topsoil removal (TSR) or spreading target vegetation propagules are known to improve restoration success in fen peatlands or after peat extraction. However, experience on restoration of bogs after previous agricultural use is scarce and the climate effects of these restoration measures including carbon losses from TSR are unknown.</p><p>We installed a field trial in a drained bog in North-West Germany to explore the effect of TSR and Sphagnum spreading on greenhouse (GHG) emissions. The trial consists of seven plots (~8 x 24 m each) representing the status quo—intensive grassland use—and six different restoration approaches. Two approaches are rewetting on the original surface with or without regular biomass harvesting. The remaining four represent TSR prior rewetting where two of the four were inoculated with <em>Sphagnum</em> spp. On all plots we measured GHG fluxes fortnightly using closed chambers to obtain two-year GHG budgets. We assessed the climate effects of the status quo and the six restoration approaches by applying a radiative forcing model to the GHG budgets and to published emission factors while incorporating the effect of TSR through different depletion scenarios of the exported topsoil carbon.</p><p>Compared to the status quo, rewetting alone reduced CO<sub>2</sub> emissions by ~75% but substantially increased CH<sub>4 </sub>emissions, which were much higher than published emission factors for a similar peatland category. After TSR, on-site CO<sub>2</sub> emissions were close to 0 or—with Sphagnum spreading—net negative while CH<sub>4</sub> emissions remained very low. Based on our GHG budgets, TSR quickly becomes less climate warming than keeping the status quo and rewetting at the original surface. In contrast, based on emission factors, rewetting at the original surface is initially the least climate warming option.<span> </span></p><p>In general, the climatic effect of TSR is likely lowest when removing only as much topsoil as necessary to implement nutrient-poor and acidic conditions thereby ensuring rapid establishment of a <em>Sphagnum</em> carpet and by conserving the removed topsoil as long as possible. Here, the climate warming effect of TSR of ~30 cm in combination with rewetting roughly corresponds to the climate warming of rewetted nutrient-rich temperate peatlands without TSR. Therefore, from a climate perspective, we can recommend a shallow TSR of up to 30 cm for peat bog restoration given that the goal is to re-establish typical bog habitats.</p>

Investigation of the optimum surface roughness of AISI 5120 steel by using a running-in attractor

To investigate the influence of surface roughnesses on the dynamic characteristics of AISI 5120 steel in sliding friction process, a suite of running-in experiments are performed on a pin-on-disk tribometer. The running-in attractor is used to analyze the high-dimensional features of a friction system under different surface roughnesses. The experimental results show that the roughnesses of different original surfaces evolve to the same value in stable wear stage. The pin-on-disk friction system has a chaotic nature and exists a running-in attractor. The original surface of a disk of Ra=0.953 µm is the most conducive to shorten the running-in duration, reduce the friction coefficient value, and improve the stability of the friction system. This roughness value is termed as the optimum surface roughness. It is an ideal working surface for the friction pair in the running-in design.

THE RESEARCH OF THE FORTIFICATIONS OF LYTOVEZH HILL-FORT IN VOLYN REGION

Currently, the complex of the hill-fort by the meandering bend of the Bug River channel is divided into two parts: the western one where the castle is located, and the eastern one where the city is obviously placed. During the exploration the rampart of the eastern part of the fortified complex was cut by the trench. The body of rampart is stand on the ancient original surface which looked like a humus substance. It consisted of three consecutive fillings. The first is gray soil up to 0.2 m thick, the second is white sand up to 0.8 m thick, and the third, most high (up to 1.4 m) is the yellow sand that covered the previous one from inside of the rampart. The yellow sand was cut through by well visible pit at the bottom of which the bones, probably human skulls have been found. These filings contained several fragments of pots of the fourteenth and fifteenth centuries. From inside the rampart was covered by the powerful cultural layer that contained various finds from the fourteenth to the twentieth centuries. The original layer of humus sand was well visible under the body of rampart and worse under the cultural layer. In the original surface the materials of the 12th—13th and 15th—16th centuries were found. Particularly the hinged lock of the 15th—16th centuries found in the original layer of humus is noteworthy. The majority of partially explored objects were located on the inside of the rampart. Latest of them, the object 1 of the 19th century, was occurred in the cultural layer and the rest, objects 2—6, were found while cleaning the virgin soil at the bottom of the trench. Moreover, large objects 3—4 were located outside the rampart, under the powerful cultural layer, and small objects 5—6 — under the body of the rampart. Thus, the explored site in the area of the future rampart was virtually uninhabited in the Old Rus period and was poorly used during the 14th—15th centuries. It is ascertained that the fortifications of Lytovezh hill-fort consisted of the rampart up to 2.1 m high of artificial origin built in the late medieval period, most probably in the 16th—17th centuries.

PTFE Modification to Enhance Boiling Performance of Porous Surface

Boiling heat transfer is one of the most effective methods to meet the challenge of heat dissipation of high heat flux devices. A wetting hybrid surface has been shown to have better performance than the hydrophilic or hydrophobic surface. This kind of wetting hybrid modification is always carried out on a plain or flat surface. In this paper, polytetrafluoroethylene (PTFE) powders were coated on a superhydrophilic microcopper dendrite fin surface to build a wetting hybrid surface. The pool-boiling experimental results showed that after applying the coating, the wall superheat dramatically decreased to 8 K, which is 9 K lower than that on the original surface at 250 W·cm−2, and has a better performance than a silicon pin-fin-based wetting hybrid surface.