Obtuse Edges Research Articles

Experimental study on anti-frost property and edge effect of superhydrophobic surface with millimeter-scale geometries

Frost suppression ability and edge effect are crucial for the frost formation on engineering surfaces. However, certain fundamental aspects remain ambiguous, particularly in the context of superhydrophobic surfaces featuring millimeter-scale structures.. In this study, condensation, frosting, and defrosting experiments were conducted on superhydrophobic surfaces with multiple millimeter-scale geometries. The results indicate that condensate droplets tend to grow on the top of right-angled, semi-circular protrusions, and conical structures. In the course of frost formation, superhydrophobic surfaces with millimeter-scale structures exhibit certain anti-frost properties when compared to the non-structured superhydrophobic surface. Condensation state of droplets can be maintained for a long time on the bottom area of the grooves, creating a frost-free zone. By observing the growth of frost crystals in various regions of the millimeter structure, it has been revealed that the manipulation of water vapor contact spaces can lead to the design of anti-frost surfaces with adjustable rates of frost crystal growth. Frost formation process on superhydrophobic surfaces can generate the so-called "edge effect" and is influenced by the edge structure. Frost crystals tend to form first on conical edges due to their sharp structural features. The average height of frost crystals on 90° edges, obtuse edges, and semicircular edges is significantly lower than that on conical edges, with the reductions of 31.8 %, 28.4 %, and 14.3 %, respectively. During the defrosting process, two spontaneous methods were observed to remove the frost layer: a "hand-in-hand" manner lifting off the groove and an "airfoil retraction" contraction on the protruding structures. Regardless of the structure shape, defrosting water floats on top and falls off, allowing for rapid drying of the surface and groove. This work has broadened the understanding of frost formation and defrosting on millimeter-structured superhydrophobic surfaces, and holds potential for applications in anti-frost engineering.

Reliability of automatic finish line detection for tooth preparation in dental computer-aided software.

This study aimed to investigate the accuracy of automatic tooth finish line registration compared to manual registration with regard to various finish line configurations and dental computer-aided design (CAD) software. Finish line registrations were performed on 15 digital tooth models with different finish line configurations (edge roundness radius = 0 mm, 0.2 mm, and 0.4 mm; edge angle = 30°, 60°, 90°, 120°, and 150°) using automatic and manual methods for designing virtual copings (N = 150). The discrepancies between the registered finish line extracted from the copings and the actual finish line segmented from the digitized tooth model were measured. Three-way analysis of variance (ANOVA) and post-hoc analyses with Bonferroni correction (α = 0.05) were used to analyze the results. The finish line configurations, registration methods, and CAD software interacted with the accuracy of the registered finish line (p = 0.001). The automatic finish line registration method exhibited larger error values than the manual method, especially at high finish line edge roundness and obtuse edge angles for both EXOCAD and R2CAD software (p < 0.001). The difference in dental CAD software affected the registration accuracy in the automatic method (p < 0.001), but not in the manual method (p = 0.676). Finish line registration errors may occur when the automatic registration method is applied to the indistinct edge of tooth preparation. The accuracy of the automatic finish line registration could differ according to the CAD software program.

Gomphocantharellus, a new genus of Gomphales

ABSTRACT The genus Gomphocantharellus and species Gomphocantharellus cylindrosporus are proposed as new based on morphological assessments and molecular phylogenetic evidence inferred from nucleotide sequences of mitochondrial (mt) adenosine triphosphate (ATPase) subunit 6 (atp6) and mt small subunit rDNA (mtSSU). Basidiomes of G. cylindrosporus are characterized by the peach to pinkish orange color, cantharelloid habit with a gill-like hymenophore with obtuse edges, smooth and cylindrical to allantoid basidiospores, and cylindrical to narrowly clavate flexuous pleurocystidia. The species resembles a species of Cantharellus but differs from the latter by the cylindrical basidiospores. Phylogenetic analyses confirm the placement of Gomphocantharellus as an independent lineage within the order Gomphales.

Implementation of a Flexible and Lightweight Depth-Based Visual Servoing Solution for Feature Detection and Tracing of Large, Spatially-Varying Manufacturing Workpieces

This work proposes a novel solution for detecting and tracing spatially varying edges of large manufacturing workpieces, using a consumer grade RGB depth camera, with only a partial view of the workpiece and without prior knowledge. The proposed system can visually detect and trace various edges, with a wide array of degrees, to an accuracy of 15 mm or less, without the need for any previous information, setup or planning. A combination of physical experiments on the setup and more complex simulated experiments were conducted. The effectiveness of the system is demonstrated via simulated and physical experiments carried out on both acute and obtuse edges, as well as typical aerospace structures, made from a variety of materials, with dimensions ranging from 400 mm to 600 mm. Simulated results show that, with artificial noise added, the solution presented can detect aerospace structures to an accuracy of 40 mm or less, depending on the amount of noise present, while physical aerospace inspired structures can be traced with a consistent accuracy of 5 mm regardless of the cardinal direction. Compared to current industrial solutions, the lack of required planning and robustness of edge detection means it should be able to complete tasks more quickly and easily than the current standard, with a lower financial and computational cost than the current techniques being used within.

Looking at handaxes from another angle: Assessing the ergonomic and functional importance of edge form in Acheulean bifaces

Edge angle is widely considered to be a morphological attribute that influences the functional performance of lithic technologies. However, the comparative performance capabilities of handaxes that vary in terms of edge angles has never been investigated under experimental conditions. Similarly, detailed accounts of Acheulean handaxe angle variation from archaeological examples have not been reported in the literature. Consequently, it has not previously been possible to assess the extent to which Palaeolithic individuals adhered to specific edge angle ranges during handaxe production or whether resultant artifactual properties may have been in response to varying rates of utility. Here, using a substantial experimental program (n=500 handaxes), we investigate the impact that edge angle variation has on the cutting efficiency of handaxes at a “whole tool” and “edge-point localized” level. We then examine edge angles in a temporally and geographically wide range of handaxes (n=643) and assess the extent to which hominins were likely altering tool production choices in response to functional pressures. Our experimental results demonstrate that, up to a certain value, higher edge angles in handaxes can actually increase functional performance. Furthermore, results indicate that edges in the proximal portion of handaxes have the greatest influence over efficiency rates. Combined with examination of archaeological specimens, these results suggest that hominins actively pursued the production of more obtuse edges in the proximal (butt) portion of handaxes in order to increase ergonomic features that facilitated greater efficiency during use. Edge angle values in the proximal portion of the archaeological handaxes were, however, consistently found to be below an efficiency threshold identified at ∼70 degrees, above which, an edge’s ability to effectively be applied to cutting tasks decreases markedly. This further suggests that the proximal edges of handaxes, at least occasionally, were required as a functional working edge.

Equivalent self-adaptive belt grinding for the real-R edge of an aero-engine precision-forged blade

Because of the special characteristics of aero-engine precision-forged blade edges such as heat-resistant and high-strength materials, the unequal distribution and small removal allowance, and easy deformation in processing, edge profile shape errors are easily caused by using conventional processing methods. These errors include chamfered, sharp, flat, and obtuse edges and cervical part shrinkage, so the real-R shape of the edge is difficult to guarantee, and the aero-engine air dynamic performance is seriously affected. The purpose of this research is to improve the dimensional precision, profile shape errors, and surface quality of the real-R edge of the precision-forged blade. With these aims, the method of equivalent self-adaptive belt grinding (ESBG) using a cubic boron nitride (CBN) belt is developed in this study. First, the grinding characteristics and process planning to the blade real-R edge are analyzed. The methodologies of equivalent belt grinding (EBG) and ESBG using a CBN belt are then illustrated, the control equation for EBG is established, and the method of force adaptive control is introduced. Finally, the ESBG method using the CBN belt is verified by experimental investigation of the aero-engine precision-forged blade and comparison with manual and EBG methods. The experimental results showed that the ESBG method using the CBN belt achieved the requirements of the aero-engine precision-forged blade real-R edge. It was verified that the method of ESBG using the CBN belt has the advantages of real-R shape dimensional precision and surface quality for the blade edge compared with the conventional method.

New evidence of morphological characters and DNA barcoding ofPampus argenteus(Euphrasen,1788)

The Pampus fishes are important commercial species and widely distributed in the coastal waters of China. Due to the similarities and complexities of morphological characters used in traditional taxonomy,taxonomic confusion has arisen in Pampus concerning the nomenclature. Among the genus,perhaps none is more confusing in the taxonomic studies than Pampus argenteus. Up to date,no reports about neotype of P.argenteus can be found. In the present study,redescription of morphological characters and redefinition of DNA barcoding of P. argenteus are conducted based on sixteen specimens collected from Kuw ait( northern w aters of Kuw ait),Pakistan( Sonmiani Bay,Ormara,Pasni),Beibu Bay and Taiw an during October 2010 to September 2012. The diagnostic characters of P. argenteus: dorsal fin Ⅶ- Ⅷ-39- 43,pectoral fin 21- 29,anal fin Ⅴ- Ⅵ-35- 41,caudal fin 26- 28. First gill arch w ith 10- 12[( 2- 3) +( 8- 9) ]small and sparse gill rakers. Vertebrae 37- 38. In the occipital region,the area of the w avy branches above lateral line is developed and plume-like,w ith a little obtuse edge. Ventral w avy branches below lateral line are curvy and shorter than that above lateral line,and not reaching the base of dorsal fin. Combining all COⅠ sequences of P. argenteus from GenBank w ith those of this study,four absolute groups can be found in all specimens based on the genetic differences in amino acids and distance betw een groups. From the NJ tree,w e can find that only one sequence( FJ384702) is similar to our DNA barcoding of P. argenteus. Therefore,it is urgent to guarantee the correctness of all sequences from GenBank. Redescription of morphological characters and the right DNA barcoding of P. argenteus are given,w hich provide a guarantee for efficient and accurate study,and theoretic basis for classification of Pampus in future.

Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite–water interface

Calcite-water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different surface sites is distinct. In addition to observing the expected formation of more calcium-water interactions and hydrogen-bonds at lower-coordinated sites, we also observed subtle differences in hydrogen bonding around acute versus obtuse edges and corners. We subsequently used this information to refine the protonation constants for the calcite surface sites, according to the Charge Distribution MUltiSite Ion Complexation (CD-MUSIC) approach. The subtle differences in hydrogen bonding translate into markedly different charging behaviour versus pH, in particular for acute versus obtuse corner sites. The results show quantitatively that calcite surface reactivity is directly related to surface topography. The information obtained in this study is not only crucial for the improvement of existing macroscopic surface models of the reactivity of calcite towards contaminants, but also improves our atomic-level understanding of mineral-water interactions.

A new species of the genus Triplophysa (Nemacheilinae: Balitoridae), Triplophysa jianchuanensis sp. nov, from Yunnan, China

A new loach species, named Triplophysa jianchuanensis, has been recognized in collections from Jianchuan in Dali Prefecture, Yunnan, China. Triplophysa jianchuanensis can be distinguished from the other Triplophysa species by the following combination of characteristics: smooth skin, scaleless; lateral line complete; head long (26.7–29.8% of SL); eyes large (25.9–31.0% of dorsal head length); snout shorter than postorbital length (26.9–30.1% of HL); middle of lower lip interrupted and forming a pair of furrows; lower jaw spoon-like with obtuse edge; posterior chamber of air bladder completely degenerated; intestines short, bending in zigzag-shape behind stomach; pelvic-fin tip not reaching anus; caudal fin emarginate; branched rays of dorsal fin 7; branched rays of caudal fin 16. A key to the known species of Triplophysa from the Lancangjiang River is provided.

Visual Sensor for Automatic Weld Seam Tracking System to Submerged Arc Inner Welding of Spirally Steel Tubes

Aimed at submerged arc inner welding of spirally steel tubes,a visual sensor for automatic weld seam tracking system is developed.Visual camera is used as sensor,the image of the side obtuse edge is taken at three hundred millimeters front of welded point. Video signal is magnified,trimmed and processed into binary,the pulse waveform of obtuse edge is obtained.Based on vertical center in video signals,the deviation from direction is judged and the deviation value is estimated by computer on-slice,and the deviation signals in the form of pulse signals are transmitted to the drive ofAC servo motor,the motor will control the movement of torch sliding platform, so as to ensure the welding wire to be directed at the weld in real time.Experiment results show that the method is feasible to identify obtuse edge with visual camera;a reliable system for real-time seam tracking to submerged arc inner welding of spirally steel tubes is developed.The response cycle of this system is less than 50 ms,and the tracking precision is±0.3mm.

Cobalt Alters the Growth of a Manganese Oxide Film

The mobility of dissolved heavy metals in natural waters is partially regulated by interactions with manganese oxide films. In the current work, the effects of aqueous cobalt(II) on manganese oxide film growth are studied by atomic force microscopy. The film is grown on the (104) surface of rhodochrosite (MnCO3). In the presence of O2(aq) and at circumneutral pH, film growth begins as manganese oxide islands that expand laterally across the surface. Addition of Co2+(aq) leads to the partial or complete dissolution of the manganese oxide film. Simultaneously, there is growth of new islands having multilayer structures that are unrestrained in the z-direction. The chemical composition of these new islands appears to include both Co and Mn ions. Empirical rules governing the growth of the two types of islands can be developed for the absence and the presence of Co2+(aq). In the absence of Co2+(aq), islands grow as flat two-dimensional rhombohedral islands of nearly uniform height (2.4 +/- 0.3 nm). These islands do not cross over steps on the substrate. The growth rules change markedly in the presence of Co2+(aq). The islands grow indefinitely in the z-direction as strata structures of polydisperse thickness and rounded tops. The islands readily grow over steps. Cobalt ions, therefore, relieve the two-dimensional restriction on layer formation and allow three-dimensional growth. Moreover, the shape of the dissolution pits on the surface of MnCO3 changes from rhombohedral in the absence of cobalt to partially rounded in the presence of cobalt. The rounding occurs for the obtuse edges of the pit. Direct microscopic observations of the interactions of cobalt with manganese oxide films provide new mechanistic insights that are important in the quantitative modeling of the mobility of heavy metals in the environment.

Biological control on calcite crystallization: AFM investigation of coccolith polysaccharide function

Calcite crystals grown by organisms can be elaborate and enigmatic. One of the best examples is the tiny calcite shields known as coccoliths that are produced by unicellular algae. Coccoliths consist of interlocking single crystals of highly modified morphology, and complex organic molecules called CAPs (coccolith associated polysaccharides) are known to be intimately associated with their formation. Here, we show how a CAP can regulate crystal morphology to enhance precipitation of specific faces, a crucial aspect of the biomineralization process. Using atomic force microscopy (AFM), we investigated the interaction of CAP from the species Emiliania huxleyi with the calcite surface during dissolution, precipitation, and dynamic equilibrium. We were able to see the polysaccharide adsorbed to the surface and observe its impact on mineral behavior. These experiments demonstrate that CAP preferentially interacts with surface sites defined by acute, rather than obtuse, angles and blocks acute sites during dissolution and growth. Therefore, CAP makes the calcite face that is most stable in the pure system, {1014}, extend preferentially on the obtuse edges, promoting development of faces with lower angles to c -axis. AFM images of E. huxleyi at micrometer and atomic scales established that this is precisely the type of faces that define the morphology of the coccolith crystals. Therefore, we propose that crystal shape regulation by CAP is a fundamental aspect of coccolith biomineralization, and that preferential growth inhibition by site-specific functional groups is the mechanism causing CAP functionality.

Windmill Hill, Avebury, and Grime's Graves: Cores and Choppers

In a former paper (Proceedings, Vol. II., Pt. IV.), a description was given of some lumps and cores from Windmill Hill, Avebury, with a few comparisons from Grime's Graves, Norfolk. Among the cores, the tortoise variety, both ideal and in its modified forms, is abundantly in evidence. Fig. 27 comes under the former category, and was, perhaps, also held in the fingers for use as a chopper. The facet whence the desired flake was taken is evident enough.Fig. 28 is a thick and coarser variety, and is commoner. It, has a useful flake removed (left-hand figure), and an obtuse edge, capable of use. Allied to the last-named is the cube type, represented by Fig. 29. Sometines, as in Fig. 30, the flake was taken off the more convex face. In this instance it was one of the small leaf-shaped and sub-triangular kind so common on Windmill Hill, also produced in larger size and numerously at Avebury Down and Grime's Graves.