Circular Pits Research Articles

Corrosion Behavior of Stainless Steel 316 for Carbon Anode Oxide Reduction Application

Here, the stability of stainless steel 316 (SS-316) was investigated to identify its applicability in the oxide reduction process, as a component in related equipment, to produce a complicated gas mixture composed of O2 and Cl2 under an argon (Ar) atmosphere. The effects of the mixed gas composition were investigated at flow rates of 30 mL/min O2, 20 mL/min O2 + 10 mL/min Cl2, 10 mL/min O2 + 20 mL/ min Cl2, and 30 mL/min Cl2, each at 600℃, during a constant argon flow rate of 170 mL/min. It was found that the corrosion of SS-316 by the chlorine gas was suppressed by the presence of oxygen, while the reaction proceeded linearly with the reaction time regardless of gas composition. Surface observation results revealed an uneven surface with circular pits in the samples that were fed mixed gases. Thermodynamic calculations proposed the combination of Fe and Ni chlorination reactions as an explanation for this pit formation phenomenon. An exponential increase in the corrosion rate was observed with an increase in the reaction temperature in a range of 300 ~ 600℃ under a flow of 30 mL/min Cl2 + 170 mL/min Ar.

A Massive, Late Neolithic Pit Structure associated with Durrington Walls Henge

A series of massive geophysical anomalies, located south of the Durrington Walls henge monument, were identified during fluxgate gradiometer survey undertaken by the Stonehenge Hidden Landscapes Project (SHLP). Initially interpreted as dewponds, these data have been re-evaluated, along with information on similar features revealed by archaeological contractors undertaking survey and excavation to the north of the Durrington Walls henge. Analysis of the available data identified a total of 20 comparable features, which align within a series of arcs adjacent to Durrington Walls. Further geophysical survey, supported by mechanical coring, was undertaken on several geophysical anomalies to assess their nature, and to provide dating and environmental evidence. The results of fieldwork demonstrate that some of these features, at least, were massive, circular pits with a surface diameter of 20m or more and a depth of at least 5m. Struck flint and bone were recovered from primary silts and radiocarbon dating indicates a Late Neolithic date for the lower silts of one pit. The degree of similarity across the 20 features identified suggests that they could have formed part of a circuit of large pits around Durrington Walls, and this may also have incorporated the recently discovered Larkhill causewayed enclosure. The diameter of the circuit of pits exceeds 2km and there is some evidence that an intermittent, inner post alignment may have existed within the circuit of pits. One pit may provide evidence for a recut; suggesting that some of these features could have been maintained through to the Middle Bronze Age. Together, these features represent a unique group of features related to the henge at Durrington Walls, executed at a scale not previously recorded.

Effect of novel hybrid texture tool on turning process performance in MQL machining of Inconel 718 superalloy

ABSTRACTHigher cutting zone temperatures are responsible for poor turning process performance during dry machining of Inconel 718 material. In the present work, a novel hybrid surface texture tool under minimum quantity lubrication (MQL) has been proposed to reduce the decremental effects that cause during machining of Inconel 718 material. Present work compared to the performance of three tools, namely, untextured tool (T1), texture tool having circular pit holes (T2) and hybrid texture tool combination of circular pit holes and linear grooves (T3) under MQL cooling technique. It was observed that hybrid texture tool (T3) significantly reduced the cutting zone temperature (Tm), tool flank wear (Vb) and surface roughness (Ra) to a maximum of 36%, 59% and 46%, respectively, when compared to the T1 tool whereas it was 22%, 48%, and 30% when compared to the T2 tool, respectively. The present work meets the stringent environmental regulation along with the improved machinability of Inconel 718 superalloy.

Evaluation of hybrid textured tool performance under minimum quantity lubrication while turning of AISI 304 steel

Nowadays, the surface texture of tool is an attractive machining technique due to the benefits in any chip removal machining process performance. However, surface texture design on texture tool plays a significant role in improving the turning process performance, in this context, a novel hybrid surface texture design has been proposed in the current work. The present work focused on the machinability improvement of AISI 304 material by employing the surface texture tool under minimum quantity lubrication (MQL) condition. In this work, comparative evaluation of turning performance has been carried out with a fabricated single texture tool which consists of circular pit holes pattern (T-1) and a fabricated novel hybrid texture tool combination of linear grooves and circular dimples (T-2), respectively, during machining of AISI 304 material at increasing cutting velocity condition. From the result, it was observed that the proposed hybrid texture tool (T-2) significantly reduced the cutting temperature (Tm), tool flank wear (Vb) and surface roughness (Ra) to a maximum of 26%, 31% and 34%, respectively, when compared to T-1. Further, low built-up edge (BUE) was found in T-2 tool over T-1, respectively.

Tribological properties of surface microtexture friction pairs under different lubrication conditions

In the field of journal bearings, the microtexture processing technology of the bush inner surface has become an effective way to improve the performance of journal bearing. The two-dimensional finite element model of microtexture surface with different shapes of friction pairs is established based on the Navier–Stokes (N-S) equation, and the effect of lubrication conditions on the frictional performance of friction pairs is analyzed. Four microtextures that are radial grooves, circular pits, local reticulation, and circumferential grooved microtexture are processed by laser microcarving on the surface of specimen, and three different lubricating medium conditions are set up with high-viscosity oil, low-viscosity oil, and oil–solid mixture, and the effect of lubrication condition and texture shape on the wear reduction of the microtexture friction pair is studied. Results show that the concave microtexture and the radial groove can improve effectively the friction performance of the friction pair. The microtexture can effectively store the lubricating medium and wear abrasive particles in the mixed lubrication, and avoid effectively the second wear, and its average friction coefficient of radial groove microtexture is 22%, 30% lower than that of high- and low-viscosity lubricating media, respectively. Both theory and experiment have proved that the effect of microtexture on high-viscosity lubricant is better than that of low-viscosity lubricant.

Influence of interface slip on the surface frictional force of texturing sliding bearing

Purpose The purpose of this paper is to explore the sensitive parameters affecting the friction resistance of sliding bearings under different interface slip conditions and the influence of the texture position of circular pits on the friction force of sliding bearings. Design/methodology/approach Based on the mechanical equilibrium equation and Newton's viscous fluid mechanics formula and wedge oil film model, the calculation model of sliding bearing friction resistance under interface slip state is established, and the influence of interface slip on friction resistance under different slip conditions is analyzed by means of ANSYS. Friction simulation model of circular pit textured journal bearing under different interface slip conditions. Findings The friction resistance of bearings is mainly determined by journal linear velocity, oil film slip ratio, pressure of inlet and outlet of bearings, oil film thickness and bearing capacity. When both the upper and lower surfaces of the oil film slip, the friction resistance decreases significantly, which is only 4-17 per cent of that without slip. And the friction force of the texture model of circular pit at the exit is better than that at the entrance and the middle of the pit. Originality/value Relevant research results will lay a new theoretical foundation for friction reduction and optimization design of sliding bearings.

Fabrication of the laser textured nickel surface and its tribological property under the water lubrication

Friction is one of the main causes of mechanical component failure and material waste. It is known from the friction theory that changing the roughness of the surface of the material can change the friction property of the material. Laser surface texturing is a good method for constructing a rough surface. In the experiment, the texture of the circular pits with different areal densities was constructed on the nickel surface. The coefficient of friction of the circular pit under the water-lubricated friction condition was kept at about 0.17, while the untreated metal nickel under the same conditions exceeds 0.65. The circular pit texture improves the frictional properties of the nickel surface.

Deep Learning Method for Video-Based Data to Classify Peripheral Edema Grades

Introduction Peripheral edema is a common precursor to decompensation for patients with heart failure (HF), and commonly measured with the pitting test. Video recordings of the pitting peripheral edema test can capture details of skin topography and time-evolution of tissue recovery with much greater precision than a human eye. Video-based deep learning can potentially overcome the subjectivity of the peripheral edema test and assist patients in identifying objective changes in their peripheral edema. We have previously shown that our deep learning model can accurately estimate peripheral edema grade with 98% accuracy using physical edema models. The objective of this study was to evaluate feasibility of collecting videos of peripheral edema from hospitalized patients with heart failure who have various skin colors and features for the purpose of refining the deep learning model for automated edema classification. Methods We enrolled 18 patients from February-April, 2019 from cardiac medical, surgical, and intensive care units at an urban university medical center. Patients were first screened for peripheral edema through the inpatient electronic medical record system. After meeting enrollment criteria and signing informed consent, trained personnel recorded 10 videos of the pitting test on patients with peripheral edema each day of their hospitalization using a Samsung Galaxy S9 phone. The personnel used one index finger to make a circular pit on the left and right side of three bony prominences (foot, ankle, and shin). Videos were taken freehand, under diffuse indoor light conditions and were 5 seconds to 2 minutes long, depending on the time it took for the skin/tissue to fully rebound from the pitting test. Each video was labeled independently with the edema grade by a research assistant and nurse, and downloaded from a secure endpoint (phone) to a central database for analysis. Results We collected 376 videos from 18 patients over an average of three days. Overall, the sample of participants was 16% female, 33% Black, 11% Hispanic and had grades of edema that ranged from grade 0 (12%), grade 1 (51%), grade 2 (18%), grade 3 (9%), and grade 4 (10%). The videos contained a wide variability of diverse skin tones and features to ensure that the method is robust and generalizable to a multiracial patient population (Figure 1). Discussion We established the feasibility of collecting videos of peripheral edema from hospitalized patients with HF. Deep learning holds promise for the automatic classification and objective measurement of clinical signs captured with video data.

Human and animal deposits in circular pits of the 5th millennium between the Rhine and the Danube

On account of recent developments in the absolute chronology of circular-shaped grave deposits from Bavaria, new bibliographic research and a series of discoveries in the south of the Upper Rhine Plain, we can now advance the hypothesis of an origin of this phenomenon in Central Europe, between the Czech Republic and Bavaria. These regions have yielded the earliest deposits with typologies encompassing all of the defined categories: burials in conventional or non-conventional positions, asymmetrical deposits, mixed deposits, anatomic segments, etc. The introduction of this practice in the south of the Upper Rhine Plain and in the Neckar Valley, undoubtedly under the direct influence of Munchshofen, occurs in the second third of the 5th millennium: it is illustrated in particular by mixed deposits, anatomic segments, isolated individuals in conventional or non-conventional positions, singular deposits with a warrior connotation and deposits of animals. The Michelsberg culture, attested in Lower Alsace at the end of the millennium, perpetuates this practice which undergoes a new development during the middle stage of this culture and a direct diffusion towards Upper Alsace. To the east, in Slovakia, it is possible that the group from Ludanice, affected by the phenomenon during the last centuries of the 5th millennium, played a relay role in diffusion towards early Trichterbecherkultur groups.Thus, rather than a progressive diffusion of the phenomenon from the Chassean towards Michelsberg, then towards the Danubian regions, we propose a polycentric model in which South and Central Europe evolve separately without necessarily interacting.

Deposits of bodies in circular pits in the Neolithic period (mid-fifth to the mid-fourth millennium BCE)

Among the numerous human remains found in circular pits belonging to the fourth millennium BCE cultures north of the Alps, there are many examples of bodies laid in random (or unconventional) positions. Some of these remains in irregular configurations, interred alongside an individual in a conventional flexed position, can be considered as a ‘funerary accompaniment’. Other burials, of isolated individuals or multiple individuals buried in unconventional positions, suggest the existence of burial practices outside of the otherwise strict framework of funerary rites. The focus of this article is the evidence recently arising from excavation and anthropological studies from the Upper Rhine Plain (Michelsberg and Munzingen cultures). We assume that these bodies in unconventional positions were not dumped as trash, but that they were a part of the final act of a complex ritual. It is hypothesised that these bodies, interpreted here as ritual waste, were sacrificial victims, and a number of possible explanations, including ‘peripheral accompaniment’ or victims of acts of war, are debated.

The Us of Dice Game in Teaching Vocabulary for Young Learners

Dice games is a cube (often with corners slightly rounded), Marked on each of its six faces with a different number of circular patches or Pits called pips. Based on the purpose of this research to find out whether the use of Loaded Dice Game can increase or not the students’ Vocabulary mastery at the fourth-grade students of SDIT Anak Sholeh Mataram in the school year 2016/2017. In this research, the writer used quasi-experimental research (pre-test and post-test design) with the population was 111 of 4 classes, and the sample was 58 students by using cluster sampling. The writer took two classes as samples, they are Malik class as an experimental and Khuzaifah class as a control group. To collect the data, the writer used multiple choices items with 20 numbers items. The finding of this research from the value of t-test was 5.01 higher than the value of t-table in the significance level 95% (1.67) and at the confidence level 99% (2.39). The value of t-test is higher than t-table, it means that the hypothesis alternative (Ha) is accepted. So, the writer can conclude that the use of Loaded Dice game can increase the students’ vocabulary mastery at the fourth-grade students of SDIT Anak Sholeh Mataram in the school year 2016/2017.

One hundred million years of stasis: Siphonophora hui sp. nov., the first Mesozoic sucking millipede (Diplopoda: Siphonophorida) from mid-Cretaceous Burmese amber

Fossil records of the ancient and less studied millipede order Siphonophorida are rare and only known from Oligocene-Miocene Dominican amber to date. Here, we describe a Mesozoic species of this order, Siphonophora hui sp. nov., based on two well-preserved specimens from mid-Cretaceous Burmese amber. The new species can be placed in the family Siphonophoridae by having mouthparts strongly modified into a long beak, straight antennae, the separation of tergites, pleurites and sternites, leg-like gonopods derived from 9th and 10th leg pairs, and absence of ommatidia. This discovery pushes back the fossil record of Siphonophorida by more than 60 Ma. It also demonstrates that the details of the siphonophorid body plan have remained virtually unchanged for nearly 100 million years. An enigmatic structure on the antennae of the paratype may represent either the ancestral form of the circular sensory pits, or more unlikely, the earliest occurrence of a fungus parasitic or commensal on an arthropod.

A Computational Investigation of the Group Effect of Pits on the Ultimate Strength of Steel Plates

In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxial compression. Meanwhile, we investigate different corroded patterns from a single circular pit to 25 circular pits distributed over the plate and carry out hundreds of nonlinear finite element simulations by combining the number, depth, distribution of pits with imperfections and slenderness of plate. The distribution of multiple pits causes scattering of stress concentration on the plate, then the plastic section of plate changes with wider distribution of damage simultaneously. The ultimate strength arises when un-loading zone comprised of the yielding strips and holes extends across the plate. It can be concluded that the corroded condition defined as group effect of pits manipulates the deformation state and the loading capacity of plate at the ultimate strength mode that coincides with the proportion of effective loading area and section in the process of post-buckling. To validate the effect of pits group, we perform the numerical experiments of the post-buckling of steel plates containing pits in a row with different orientation.

Analytical investigation of tunnel deformation caused by circular foundation pit excavation

With the continuous progress of urbanization, excavation works near tunnel engineering projects are increasing. The stress relief caused by the excavation inevitably affects the deformation of a tunnel. Therefore, it is of great theoretical and practical significance to correctly evaluate the tunnel’s transverse and longitudinal deformation to ensure its safe and normal operation. Many studies have been conducted on the effect of quadrangle excavation on the deformation of adjacent subway tunnels. However, the influence of circular excavation on tunnel deformation is still not fully understood, and remains the main technical barrier toward optimal engineering design and construction. Based on Mindlin’s displacement solutions, an analytical model of tunnel deformation resulting from a circular excavation was developed, and the reliability of the solution was verified by comparison with existing centrifuge model test results and an analytical solution for a square excavation. On this basis, the influence of the basement geometry, relative position of the tunnel and basement, and soil’s Young’s modulus on tunnel deformation resulting from a circular excavation were analyzed. The results revealed that the analytical solutions proposed in this paper can better predict the maximum tunnel heave resulting from a circular excavation. Moreover, the maximum tunnel heave increased linearly as the diameter and depth of the circular basement excavation increased. However, the non-linearity decreased with the tunnel cover depth. The results obtained by this study can provide a simple calculation method to predict the maximum tunnel heave caused by a circular excavation, and can also be used to confirm the rationality of a numerical simulation.

Two new finds of turtle remains from the Danian and Selandian (Paleocene) deposits of Denmark with evidence of predation by crocodilians and sharks

Two new fragments of a turtle carapace and a turtle plastron (hypoplastron) have been recovered from glacially transported boulders of Danian and Selandian age. The hypoplastron is identified as Ctenochelys cf. stenoporus, while the carapace fragment can only be assigned to the family Cheloniidae indet. Both specimens show evidence of predation by crocodilians in the form of rows of circular pits in the bones, and one specimen has rows of elongated scrape traces interpreted as scavenging by sharks. Together with the other, rare finds from the middle Danian of the Faxe Quarry and from late Danian deposits in the Copenhagen area, these new finds add important new knowledge to the sparse fossil record of turtles in Scandinavia, as well as evidence that the genus Ctenochelys survived across the K/Pg Boundary.

MICROSTRUCTURE AND PROPERTIES OF THE Ni–B AND Ni–B–Ce ULTRASONIC-ASSISTED ELECTROLESS COATINGS

We successfully obtained Ni–B and Ni–B–Ce coatings with and without sonication on low-carbon steel (Q235) through electroless plating with the deposition time of 60[Formula: see text]min. The surface morphology and elemental composition of the coatings were evaluated by scanning electron microscopy (SEM) and inductively coupled plasma (ICP). The 11[Formula: see text][Formula: see text]m thick sonicated Ni–B–Ce (Son-Ni–B–Ce) coating is uniform with the composition of Ni 87.1%, B 6.2% and Ce 6.6%. X-ray diffraction (XRD) measurements implied a typical broaden peak around 44∘, considered as amorphous structure which was confirmed by selected area electron diffraction pattern (SAED). Atomic force microscopy (AFM) showed a typical circular pit of Ni–B–Ce coating and Son-Ni–B–Ce coating. X-ray photoelectron spectroscopy (XPS) revealed the chemical status of coating components. The mechanical and corrosion resistance properties were determined by Vickers hardness tester, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5[Formula: see text]wt. % NaCl solution. As a result, the Son-Ni–B–Ce coating revealed the optimum hardness (956[Formula: see text]HV), minimum roughness [Formula: see text] (92.38[Formula: see text]nm) and excellent corrosion resistance (3.65[Formula: see text][Formula: see text]Acm[Formula: see text] among all coatings.

Atomically-Resolved Oxidative Erosion and Ablation of Basal Plane HOPG Graphite Using Supersonic Beams of O2 with Scanning Tunneling Microscopy Visualization

The detailed mechanism and kinetics for the oxidative erosion and ablation of highly oriented pyrolytic graphite (HOPG) with molecular oxygen has been examined by monitoring the spatiotemporal evolution of the reacting interface. This has been accomplished using a new, unique gas-surface scattering instrument that combines a supersonic molecular beam with a scanning tunneling microscope (STM) in ultrahigh vacuum. Using this new instrument, we are able to tightly control the energy, angle, and flux of impinging oxygen along with the surface temperature and examine the reacted surface spanning atomic, nano, and mesocopic length-scales. We observe that different oxidation conditions produce morphologically distinct etching features: anisotropic channels, circular pits, and hexagonal pits faceted along crystallographic directions. These outcomes depend upon independent effects of oxygen energy, incident angle, and surface temperature. Reaction probability increased with beam energy and demonstrated non-Arrhen...

An electrothermal plasma model considering polyethylene and copper ablation based on ignition experiment

In order to study the characteristics of electrothermal plasma interaction with energetic materials, especially the ignition ability, a novel model considering polyethylene and copper ablation is developed, and an ignition experiment system is set up. The parameters of the plasma and the surface conditions of the energetic materials are measured in the testing. The results show the measured first peak pressure to be ~2.2 MPa, the second peak pressure to be ~3.9 MPa, and the visible flame velocity to be ~2000 m s−1. Circular pits of the order of microns and nanometers in size are observed on the surface of the energetic materials. Further, the parameters of the plasma, including static pressure, total pressure, density, temperature, velocity, copper concentration and PE concentration, are calculated and analyzed by the established model, under discharge currents of 9 kA. The simulation is similar to those of experimental results. A shock wave is observed in the experiment and is presented in the calculations; it plays an important role in the performance of the plasma in the nozzle region, where the parameters of the plasma variation trends are very complex. With the aim of obtaining the overall performance of the plasma, the coupling characteristics of multiple parameters must be taken into account, in accordance with the developed electrothermal plasma model.

Permineralized Calamitean Axes from the Upper Permian of Xinjiang, Northwest China and Its Paleoecological Implication

Two anatomically preserved calamitean axes are reported for the first time from the Late Permian Wutonggou Formation in the southern Bogda Mountains, Xinjiang Uygur Autonomous Region, Northwest China. Based on the anatomical features, these axes are assigned to Arthropitys. A new species Arthropitys taoshuyuanensis sp. nov. is established. A. taoshuyuanensis sp. nov. possesses a large pith and comprises large pith cavity and a narrow perimedullary zone at the nodes and diaphragms at the internodes. Carinal canals are circular and surrounded by a single layer of metaxylem tracheids. Secondary xylem is divided into interfascicular rays and fascicular wedges. Interfascicular rays are initially four to five cells wide and taper abruptly centrifugally. Fascicular wedge consists of thick-walled tracheids and thin-walled fascicular ray cells. Radial tracheid walls have uniseriate or biseriate circular pits, or scalariform pits. The absence of growth rings in the Arthropitys specimens indicates that they probably lived in the wetland area under stable annual temperature and water sufficient conditions.

Pitting Corrosion Behavior of 304 SS and 316 SS Alloys in Aqueous Chloride and Bromide Solutions

The importance of the present work falls on the pitting corrosion behavior investigation of 304 SS and 316 SS alloys in 3.5 wt% of aqueous solution bearing with chloride and bromide anion at different solutions temperature range starting from (20-50)oC due to the pitting corrosion tremendous effect on the economic, safety and materials loss due to leakage. The impact of solution temperatures on the pitting corrosion resistance at 3.5wt% (NaCl and NaBr) solutions for the 304 SS and 316 SS has been investigated utilizing the cyclic polarization techniques at the potential range -400 to1000 mV vs. SCE at 40 mV/sec scan rate followed by the surface characterization employing Scanning Electron Microscope. The results show that a significant decline in the pitting corrosion potential Ep values of both stainless steel alloys in chloride and bromide solution during temperature increase attributed to the pitting corrosion potential decreased arises from the modification of the passive film properties. The surface examination using optical microscope and scanning electron microscope prove the occurring of higher pitting density over 304 SS in chloride solution than that observed in bromide solution with a non-circular lacy cover pitfall out at the center and falls inside the pits hall in comparison to the isolated circular lacy cover pit formed on 316 SS in 3.5wt% NaBr solution at 50 oC.