Journal articles on the topic 'Shaft surface topography'
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1
Pusterhofer, Michael, Florian Summer, Michael Maier, and Florian Grün. "Assessment of Shaft Surface Structures on the Tribological Behavior of Journal Bearings by Physical and Virtual Simulation." Lubricants 8, no. 1 (January 15, 2020): 8. http://dx.doi.org/10.3390/lubricants8010008.
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Optimizing the surface topography of cast iron crankshafts offers the opportunity to use this material as an alternative to steel in high-performance combustion engines. In the past, this was not possible due to the higher wear on bearing shells and the higher friction losses in relation to forged steel shafts. In order to find an optimized shaft micro topography, the friction and wear behavior of steel and cast iron shafts with different surface treatments were compared to each other, using a combined physical (experimental) and a virtual (computational) simulation approach. The experiments were carried out with a rotary tribometer using a journal bearing test configuration with the possibility to test real-life bearing shells and shaft specimens, manufactured from real-life crankshafts. In the experiments, a polished steel shaft with low bearing wear was effective. The optimization of cast iron crankshafts by a novel surface treatment showed a significant reduction of bearing wear in relation to the classical surface finishing procedures of cast iron shafts. A computational simulation approach, considering the real-life micro topography by using the Navier–Stokes equations for the calculation of micro hydrodynamics, supports the assessment of fluid friction. The virtual simulation shows, in accordance to the experimental results, only a minor influence of the investigated shaft topographies on the fluid friction. Further optimization of shaft surfaces for journal bearing systems seems possible only by the usage of patterned micro topographies.
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Kozuch, Emilia, Petros Nomikos, Ramin Rahmani, Nick Morris, and Homer Rahnejat. "Effect of Shaft Surface Roughness on the Performance of Radial Lip Seals." Lubricants 6, no. 4 (November 13, 2018): 99. http://dx.doi.org/10.3390/lubricants6040099.
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Reduction of leakage from the shaft–radial lip seal conjunction is critical in ensuring enduring performance of entire lubrication system. This paper investigates leakage from three types of shaft surfaces, finished using different manufacturing processes. The measurement of surface topography is conducted in order to determine the pertinent roughness parameters which correspond to the observed sealing performance in real practical applications. It is found that the skewness of the surface topography correlates well with the anecdotal leakage failure rate. To quantify this association, a hydrodynamic model, accounting for shaft roughness in a deterministic manner is developed. The results from the numerical analyses confirm that the lubricant mass flow rate is reduced in the case of negatively skewed surface height distributions, when compared with the positively skewed profiles.
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R.S., Suja, Mini Alikunju, Aswathy Maria Oommen, Sreekumar R, Sheena Kalyani Sukumaran, Chandra Mohan Nair Kaleeluvilayil Ragbavannair, Lincy Varghese, and Swapna Thampi. "Morphology, Topography and Clinical Significance of Primary Nutrient Foramina in Tibia." Journal of Evolution of Medical and Dental Sciences 10, no. 14 (April 5, 2021): 999–1002. http://dx.doi.org/10.14260/jemds/2021/214.
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BACKGROUND Nutrient foramina are seen in the shaft of long bones. They vary in number, size and their position on the surface of bones. It transmits the nutrient artery which is the main source of blood supply to the long bones. We intend to study the location, number, type and direction of primary nutrient foramina (PNF) on the shaft of tibia. METHODS The descriptive study was done using 120 tibiae (right-66, left-54) from Department of Anatomy, Govt. Medical College, Thiruvananthapuram. Length of each bone and distance of the nutrient foramen from the upper end of tibia was measured using osteometric board. The location of the primary nutrient foramina on the surface of tibia, the direction of the nutrient canal and the presence of secondary nutrient foramina were noted. RESULTS Single primary nutrient foramina were located on the posterior surface of 113 tibiae. 4 tibiae showed PNF and secondary nutrient foramina (SNF). No nutrient foramina were observed in 3 tibiae. CONCLUSIONS The precise knowledge and topography of PNF of tibia will help orthopaedic surgeons in minimising damage to vasculature of tibia during various surgical procedures. KEY WORDS Tibia, Nutrient Foramen, Nutrient Artery
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Jin, Cheng Zhe, and Rui Fang. "Research on Surface Topography and Roughness of Micro Parts by High Speed Turn-Milling." Materials Science Forum 800-801 (July 2014): 607–12. http://dx.doi.org/10.4028/www.scientific.net/msf.800-801.607.
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High speed turn-milling has superiority on the productivity and the quality of work pieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. In this papers adopting orthogonal experiment method cutting experiments of orthogonal turn-milling Aluminum alloy have been done. The relation between turn-milling regimes (cutter rotate speed, axial feed, feed per tooth etc.) and machined surface roughness has been ascertained. Finally, primary and secondary order of cutting regimes impacting surface roughness has more been confirmed through orthogonal experiments variance analysis, the rotate speed of cutter (cutting speed) influence greatly on surface roughness. Through 2-dimension surface topography diagram and 3-dimension surface topography of processed surface, it can be seen that high speed turn-milling processing technology can process micro miniature component of high surface quality, and features excellent development prospect and application value.
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Jin, Cheng Zhe, and Rui Fang. "Research on Surface Topography and Tool Wear in Micro-Turn-Milling of Micro-Screw." Advanced Materials Research 500 (April 2012): 377–82. http://dx.doi.org/10.4028/www.scientific.net/amr.500.377.
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Turn-milling technology can replace turning with milling to high speed machining rotationally body parts. So, micro-turn-milling has superiority on the productivity and the quality of workpieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. Micro-turn-milling can be used for the machining of micro-parts in its hardened state. In this paper, the influence of cutting parameters on surface topography and tool wear is presented in micro-turn-milling of micro-screw. The interaction effect of parameters to surface topography and tool wear is investigated. The results show that micro-turn-milling technology has its peculiar advantages in realizing high-speed cutting and ensuring machining quality.
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Engelfried, Maximilian, Matthias Baumann, and Frank Bauer. "Three-dimensional structure-based approach for the analysis of macroscopic lead structures on sealing counterfaces." International Journal of Metrology and Quality Engineering 13 (2022): 2. http://dx.doi.org/10.1051/ijmqe/2022003.
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The seal failure of an elastomer rotary shaft seal is often caused due to lead on the shaft counterface. In sealing technology, the term ‘lead’ includes all structures on sealing counterfaces that are capable of transporting fluid in axial direction through the sealing contact and thus disrupting the sealing mechanism. Lead structures are created during the manufacturing process of the shaft surface or throughout the handling. They occur in various shapes and sizes. Depending on the characteristics of the lead structures, several specialized measurement and evaluation methods exist which have to be applied in combination. However, not all types of lead can be covered with the methods known so far. State of the art are frequency-based and model-based analysis methods, which are only able to detect periodic lead structures. Aperiodic and stochastically distributed lead structures cannot be detected due to the functional principle. This article provides an approach for a structure-based evaluation of macroscopic lead structures based on optical topography measurement data. This allows to detect all known types of macroscopic lead on the shaft surface and in future to measure microscopic and macroscopic lead with a single measurement procedure.
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Labuda, Wojciech. "The Influence of Cutting Parameters on Surface Topography During Turning Marine Pump Shafts." Journal of KONES 26, no. 4 (December 1, 2019): 141–48. http://dx.doi.org/10.2478/kones-2019-0101.
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AbstractOne of the greatest problems of modern production techniques is the achievement of an appropriate quality at minimal costs and accompanied by the production efficiency increase. Therefore, while designing the production process. The technology used should have a considerable influence on the durability and reliability of machine parts to be produced. During finish treatment, the final dimensions as well as functional properties are imparted to a given element by application of proper treatment type. The engineer has a range of production techniques to choose for the proper surface layer formation. Conventional turning machines belong to the basic equipment of ships, because in sea conditions, they enable the execution of a spare part or carrying out the necessary operations in the process of their regeneration. The use of modern cutting tools makes it possible to obtain a surface with low values of surface roughness parameters. The use of new generation cutting inserts on conventional lathes can cause problems for operators. The lack of the ability to ensure proper of treatment condition and setting errors of cutting tools contribute to the damage of the cutting insert or the surface of the workpiece. The article presents the results of influence of different cutting parameters on surface topography during turning process of stainless steel. A shaft made of 304L stainless steel was used for the research. The cutting process was carried out on a universal TUM 25B x 500 centre lathes. During the turning the following machining parameters were used: cutting speed Vc [m/min], feed f [mm/rev] and depth of cut ap [mm].The turning process was conducted by a cutting tool with CCGT 09T302 UM, CCGT 09T304 UM and CCGT 09T308 UM inserts. Measurement of surface topography was carried out by T8000 profilometer.
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Wu, Quanhui, Yazhou Sun, Wanqun Chen, Qing Wang, and Guoda Chen. "Theoretical prediction and experimental verification of the unbalanced magnetic force in air bearing motor spindles." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 233, no. 12 (March 26, 2019): 2330–44. http://dx.doi.org/10.1177/0954405419838656.
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Dynamic vibrations of air bearing motor spindles have significant influence on the surface quality in ultra-precision machining. In this article, the influence of the vibration caused by the unbalanced magnetic force on the diamond turning is investigated on the basis of the theoretical and experimental method. A permanent magnet motor model (10 poles and 12 slots) is built and then simulated to gain a periodic unbalanced magnetic force. The effects of unbalanced magnetic force on the inclination of the spindle shaft is analyzed, which would affect the surface quality of the workpiece, and the surface topography of the workpiece is predicted during an unbalanced magnetic force acting on air bearing motor spindle. The theoretical analysis and experimental turning results validate that the angle between the direction of unbalanced magnetic force and the feed direction has a certain relationship with the profile of the machined surface. Also, under different turning speeds and directions, the surface topography of the machined workpiece shows a 10-cycle-per-revolution pattern, which has good agreement with the simulations of periodic unbalanced magnetic force. This research work provides a theoretical foundation for the fault diagnosis of air bearing motor spindle caused by motor rotor eccentricity and its effect on surface generation in turning.
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Nguyen Phi, Hung, and Thang Pham Duc. "Using Topographic Advantages in Formulating a Strategy to Access Ore Bodies at Ban Phuc Nikel Mine." E3S Web of Conferences 174 (2020): 01013. http://dx.doi.org/10.1051/e3sconf/202017401013.
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There are various types of underground mining that are categorized based on the kind of shafts used, the technique of extraction and the process used to get to a deposit. Development mining is composed of excavation almost entirely in (non-valuable) waste rock in order to gain access to the orebody. To start the mining, the first step is to make the path to go down. Development, the work of opening a mineral deposit for exploitation is performed. With it begins the actual mining of the deposit. Access to the deposit must be gained either by stripping the overburden, which is the soil and/or rock covering the deposit,to expose the near- surface ore for mining or by excavating openings from the surface to access more deeply buried deposits to prepare for underground mining. The type of underground mining technique used is typically based on the geology of the area, especially the amount of ground support needed to make mining safe. When using to exploit ore body by underground mining method, the textbook guide in universities of Vietnam had had 4 main strategies include: access by horizontal tunnel lines, access by incline shaft, vertical shaft and combination of above access method. In this study, we developed a solution outside of four above approaches, to take advantage of the topography, transport potential energy, and advantages when constructing sloped incline, backward from outside to inside.
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Muszyński, Zbigniew, and Marek Wyjadłowski. "Assessment of the Shear Strength of Pile-to-Soil Interfaces Based on Pile Surface Topography Using Laser Scanning." Sensors 19, no. 5 (February 27, 2019): 1012. http://dx.doi.org/10.3390/s19051012.
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This article presents in situ research on the side surface of continuous flight auger (CFA) foundation piles using a three-dimensional (3D) laser scanner (Leica ScanStation C10) in order to evaluate the morphology assessment of pile concrete surfaces in various geotechnical layers. Terrestrial laser scanning describes the 3D geometry of the construction with high spatial resolution and accuracy. A total of six areas were selected from the acquired point cloud for which a two-step approach for removing the form was applied. In the first step, the reference surface was fitted using the least squares method, and then, cylindrical projection of the surface was performed. In the second step, an operator of removal of the multi-plane form was applied. For each sample, height parameters (Sq, Ssk, Sku, Sp, Sv, Sz, Sa) and functional volume parameters (Vmp, Vmc, Vvc, Vvv) according to the standard ISO 25178-2:2012 were determined. Significant differences in the values of surface height and functional volume parameters were observed for each geotechnical layer where piles were formed. Because the piles remain embedded in the ground, in situ tests of the side surface of piles are rarely performed and taken into account in the assessment of pile bearing capacity. The study of surface topography is a crucial stage in the assessment of the shear strength at the interface between a concrete pile and the soil layer. The obtained concrete morphology assessments are applicable during the determination of the skin friction factor in the analytical or numerical estimation of pile shaft resistance. The proposed procedure of morphology evaluation may improve the fidelity of the assumed friction factor between the concrete and soil and increase the reliability of direct shear experiments.
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Zhao, Bo, C. Y. Zhao, and G. F. Gao. "Research on the Topography Features of the Densely Bonded Diamond Grinding Wheel Dressed by Elliptical Ultrasonic Vibration." Advanced Materials Research 188 (March 2011): 330–35. http://dx.doi.org/10.4028/www.scientific.net/amr.188.330.
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In this paper, on the influence of different dressing methods, such as elliptical ultrasonic vibration, on the grinding wheel bonded delta, the morphology of abrasive grains of wheel, the protrusion height and the grinding wheel topography was studied by experiment. The experiment shows that the abrasive grains of grinding wheel surface dressed by elliptical ultrasonic vibration are great in protrusion height and trench depth, and the bonded delta grain after grinding is narrow, short, and irregular with significant reduced semi-surrounded area compared with by ordinary dressing method. The abrasive grains of metal-bonded diamond grinding wheel surface dressed by elliptical ultrasonic vibration are basically intact, and due to the high-speed collision between abrasive grains, local micro-break is easy to occur on the abrasive grains to form multiple micro-cutting edges. The abrasive grains of grinding wheel surface dressed by ordinary dressing method are fractured and broken, while that of resin-bonded grinding wheel surface have a high ratio to be loose and shedding. For the metal or resin-bonded grinding wheel surface dressed by elliptical ultrasonic vibration, its material removal mechanism may primarily be the removal of bonding ductility and the fine-crushing of abrasive grains; for the metal-bonded grinding wheel surface dressed by ordinary method, its material removal mechanism may primarily be the fracture and break of abrasive grains, secondly be the fracture of bonding agent; and for the resin-bonded grinding wheel surface, its material removal mechanism may mainly be the looseness and shedding of abrasive grains caused by the fracture of bonding agent, secondly be the fracture of abrasive grains. Compared with ordinary dressing method, elliptical ultrasonic vibration dressed abrasive grains are dense at shaft and sparse in periphery, with a large quantity of static effective abrasive grains, great protrusion height and an excellent nature of contour.
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Li, Biao, Jun Sun, Shaoyu Zhu, Yangyang Fu, Xiaoyong Zhao, Hu Wang, Qin Teng, Yanping Ren, Yunqiang Li, and Guixiang Zhu. "Effect of the axial movement of misaligned journal on the performance of hydrodynamic lubrication journal bearing with rough surface." Mechanics & Industry 20, no. 4 (2019): 402. http://dx.doi.org/10.1051/meca/2019028.
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Generally, the movement of journal along the direction of bearing axis under the combined action of various factors is neglected in the lubrication study of bearing, which is quite different from the actual working condition of bearing in the shaft-bearing system. In this paper, with a comprehensive consideration of the axial movement of journal, the surface topography of journal and bearing and the misalignment of journal, a new model about the hydrodynamic lubrication of misaligned journal bearing is established based on the average Reynolds equation. Considering the effect of the axial movement of misaligned journal, the lubrication characteristics parameters of rough journal bearing is presented and mainly discussed. The results show that the axial movement of misaligned journal has a distinct effect on the bearing lubrication characteristics. The influence of the axial movement of misaligned journal on the bearing lubrication characteristics is slightly reduced when considering the surface roughness.
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Sklenak, Sebastian, Dieter Mevissen, Jens Brimmers, Christian Brecher, Bastian Lenz, and Andreas Mehner. "Methode zur Verschleißvorhersage für den feststoffgeschmierten Zwei-Scheiben-Kontakt." Tribologie und Schmierungstechnik 69, no. 4 (September 26, 2022): 50–57. http://dx.doi.org/10.24053/tus-2022-0020.
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In the design of solid-lubricated gears, knowledge of the wear behavior is essential for service life calculations. The detailed wear analysis of a MoS2:Ti TiN solid lubricant system on gear analogy test specimens shows that continuous wear of the MoS2 solid lubricant takes place on the contact surface and a specific local wear characteristic occurs in the areas with initial roughness peaks. The question arises whether the specific wear characteristic can be determined with a wear calculation. By taking into account the real topography of the test shaft and experimentally determined wear coefficients, it was shown that a qualitative relationship exists between the real wear and the calculated total frictional energy on a local level. However, the wear calculation shows that further research is needed in the future to predict locally severe wear.
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Liu, Tingfa, Haoruo Chen, Róisín M. Buckley, V. Santiago Quinteros, and Richard J. Jardine. "Characterisation of sand-steel interface shearing behaviour for the interpretation of driven pile behaviour in sands." E3S Web of Conferences 92 (2019): 13001. http://dx.doi.org/10.1051/e3sconf/20199213001.
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The installation and loading of steel piles driven in sands modifies both the piles' surface topography and the characteristics of the granular materials present adjacent to the pile shaft. Large-displacement ring shear interface tests incorporating pre-conditioning stages are capable of reproducing such physical processes in the laboratory and can generate case-specific interface design parameters. This paper summarises laboratory research that characterised the interface shearing behaviour of three natural sandy soils retrieved from field test sites (Dunkirk, France; Blessington, Ireland; Larvik, SE Norway) where extensive piling studies on micro and industrial scale driven piles have been carried out. The programme examined the influences of soil characteristics (physical properties and chemical compositions), interface type (mild steel or stainless steel) and surface roughness, and highlighted the significant effects of normal effective stress level and ageing time duration. Remarkable trends of increasing interface friction angles with elevated normal effective stress levels and prolonged ageing were observed. The results from supplementary small-displacement direct shear interface tests and triaxial tests are also reported. The experiments are interpreted with reference to earlier studies to develop an overview of interface shearing characteristics between steels and sandy soils and provide important insights into the mechanisms of axial capacity increases applying to steel piles driven in sands.
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a De Souza, Fatima Maria, Siddhesh Prakash Prabhu, and Jai Krishnan D. "Diaphyseal Tibial Nutrient Foramen in Goan Population - A Morphometric Study with Clinical Implications." Journal of Evidence Based Medicine and Healthcare 8, no. 13 (March 29, 2021): 801–5. http://dx.doi.org/10.18410/jebmh/2021/157.
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BACKGROUND Tibia is the weight bearing bone of the leg. Usually it has a single nutrient foramen located posteriorly near the soleal line and transmits a branch of posterior tibial artery. The nutrient artery is the principal source of supply to a long bone. We carried out this study to find out the number, size, location, position and direction of the diaphyseal nutrient foramen in dried human tibia in Goan population. METHODS The study was carried out on 66 unpaired dry human tibiae of unknown age, gender and without deformity in the Department of Anatomy, Goa Medical College, using sliding and digital Vernier callipers, 20- and 24-gauge needles. Hughes formula was used to compute foraminal index. The data was statistically analysed with SPSS software version 23. RESULTS Most of the tibia in our study had a single nutrient foramen. Majority of the nutrient foramina were medium sized and directed downwards in our study. In 81.42 % tibiae, the nutrient foramina were present in the upper 1 / 3 rd of the shaft and in 18.57 % in the middle 1 / 3 rd of the shaft of the bone. Almost all nutrient foramina in the upper 1 / 3 rd of posterior surface were situated lateral to the soleal line. We computed the mean foraminal index as 30.25 % with standard deviation of 6.14. CONCLUSIONS A proper knowledge of morphometry and topography of the nutrient foramen is of utmost importance to orthopaedic surgeons as the nutrient artery may get damaged if fracture line passes through the nutrient canal. Also, it will help the surgeon to conserve vascular supply while performing bone grafting and fracture reduction. KEYWORDS Nutrient Foramen, Morphometry, Foraminal Index, Soleal Line
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Keche, Harsha Atul, Preeti Prabhakar Thute, Darshna Gulabrao Fulmali, and Atul Shankarrao Keche. "Morphometric Study of Nutrient Foramina in Dry Human Clavicles in Central India." Journal of Evolution of Medical and Dental Sciences 10, no. 28 (July 12, 2021): 2099–103. http://dx.doi.org/10.14260/jemds/2021/429.
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BACKGROUND The clavicle or collar bone is a modified long bone. It is the first bone to ossify in the membrane. The inferior surface of shaft of clavicle presents a subclavian groove. A nutrient foramen lies at the lateral end of the groove. The nutrient artery is derived from the supraclavicular or clavicular branch of thoracoacromial artery. A bone is supplied by a nutrient artery which passes through the small tunnel called as nutrient foramina. In orthopaedic procedures to preserve the circulation, the topographical knowledge of the nutrient foramen is important. The study was undertaken to analyse nutrient foramina in adult human clavicles in relation to their number, position, direction, and distribution over bone length. METHODS Our study consisted of 67 adult dry human clavicles (31 right sides and 36 left sides). The number, topography and direction of the foramina were studied. The distance of foramina from the sternal end & total length of the clavicles were measured in millimetres by using digital Vernier calipers. The foramen index was calculated by applying the Hughes formula: FI = (DNF TL) x 100. RESULTS Nutrient foramina were present in all the clavicles. Most of the clavicles have single nutrient foramen. We observed 62 (68.13 %) foramina on the posterior surface mostly in the middle 1 / 3rd region. All the nutrient foramina were directed towards acromial end and the foramina index (FI) was 50.2. CONCLUSIONS The topographical knowledge of the nutrient foramen is important in orthopaedic procedures like nail plating, K wire fixation, reduction, internal fixation devices for the treatment of fracture, coracoclavicular ligament repair and in free vascularized bone graft to preserve the circulation. KEY WORDS Clavicle, Nutrient Foramina, Nutrient Artery, Foramina Index (FI)
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Ritz, Christian, Tino Wagner, and Andreas Stemmer. "Measurement of electrostatic tip–sample interactions by time-domain Kelvin probe force microscopy." Beilstein Journal of Nanotechnology 11 (June 15, 2020): 911–21. http://dx.doi.org/10.3762/bjnano.11.76.
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Kelvin probe force microscopy is a scanning probe technique used to quantify the local electrostatic potential of a surface. In common implementations, the bias voltage between the tip and the sample is modulated. The resulting electrostatic force or force gradient is detected via lock-in techniques and canceled by adjusting the dc component of the tip–sample bias. This allows for an electrostatic characterization and simultaneously minimizes the electrostatic influence onto the topography measurement. However, a static contribution due to the bias modulation itself remains uncompensated, which can induce topographic height errors. Here, we demonstrate an alternative approach to find the surface potential without lock-in detection. Our method operates directly on the frequency-shift signal measured in frequency-modulated atomic force microscopy and continuously estimates the electrostatic influence due to the applied voltage modulation. This results in a continuous measurement of the local surface potential, the capacitance gradient, and the frequency shift induced by surface topography. In contrast to conventional techniques, the detection of the topography-induced frequency shift enables the compensation of all electrostatic influences, including the component arising from the bias modulation. This constitutes an important improvement over conventional techniques and paves the way for more reliable and accurate measurements of electrostatics and topography.
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Fraundorf, P., and B. Armbruster. "Log-log scale roughness spectroscopy of surfaces." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 224–25. http://dx.doi.org/10.1017/s0424820100146965.
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Optical interferometry, confocal light microscopy, stereopair scanning electron microscopy, scanning tunneling microscopy, and scanning force microscopy, can produce topographic images of surfaces on size scales reaching from centimeters to Angstroms. Second moment (height variance) statistics of surface topography can be very helpful in quantifying “visually suggested” differences from one surface to the next. The two most common methods for displaying this information are the Fourier power spectrum and its direct space transform, the autocorrelation function or interferogram. Unfortunately, for a surface exhibiting lateral structure over several orders of magnitude in size, both the power spectrum and the autocorrelation function will find most of the information they contain pressed into the plot’s origin. This suggests that we plot power in units of LOG(frequency)≡-LOG(period), but rather than add this logarithmic constraint as another element of abstraction to the analysis of power spectra, we further recommend a shift in paradigm.
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Xu, F., M. Sato, M. J. Spellman, R. A. Mitchell, and J. W. Severinghaus. "Topography of cat medullary ventral surface hypoxic acidification." Journal of Applied Physiology 73, no. 6 (December 1, 1992): 2631–37. http://dx.doi.org/10.1152/jappl.1992.73.6.2631.
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The topographic relationship between previously identified medullary ventral surface respiratory chemosensitive regions and brain surface extracellular fluid (ECF) acid production during acute hypoxia was explored in anesthetized, paralyzed, and artificially ventilated cats. Glass pH electrodes (0.8-mm diam, sheathed in stainless steel tubing) were mounted in mechanical contact with surfaces of medullary surface or adjacent pyramids, pons, spinal cord, or parietal cortex. Isocapnic hypoxia of 5 min [at arterial O2 saturation (SaO2) = 48 +/- 10%] reduced pH over rostral (Mitchell) and caudal (Loeschcke) areas by 0.12 +/- 0.09 and 0.07 +/- 0.04, respectively (n = 10, P < 0.05). Change in pH (delta pH) was proportional to desaturation with slopes 100 delta pH/delta SaO2 of 0.45 (rostral) and 0.20 (caudal) (R = 0.91 and 0.88, respectively). pH drop usually began within 3 min of hypoxia, became stable between 5 and 15 min, began to rise within 2 min of reoxygenation, and returned to control within 10 min. During equally hypoxic tests, intermediate area (Schlafke), pons, and spinal cord surfaces showed no significant acid shift. Parietal cortex ECF pH dropped more slowly but steadily by 0.079 +/- 0.034 during 20 min at SaO2 = 50% after a small but significant initial alkaline shift, and acidification of cortical surface continued for > 5 min after reoxygenation. We conclude that medullary ventral chemosensitive regions produce more lactic acid during hypoxia than neighboring brain surfaces.(ABSTRACT TRUNCATED AT 250 WORDS)
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Krawczyk, Bartłomiej, Piotr Szablewski, Michał Mendak, Bartosz Gapiński, Krzysztof Smak, Stanisław Legutko, Michał Wieczorowski, and Edward Miko. "Surface Topography Description of Threads Made with Turning on Inconel 718 Shafts." Materials 16, no. 1 (December 22, 2022): 80. http://dx.doi.org/10.3390/ma16010080.
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The technology of producing threads, especially in materials that are difficult to cut, is a rare subject of research and scientific publications. The requirements for the production of these elements apply not only to the geometry, but also to the quality of the surface obtained. This is particularly important in the aviation industry, where the durability of the threaded connection affects passenger safety. Due to the design of the thread, the quality of its surface is assessed visually in industrial practice. The authors of this study decided to examine the surface topography of external threads made by turning on Inconel 718 shafts in order to confirm the visual evaluation, as well as to investigate the influence of such factors as cutting speed, turning direction and type of profile. Three types of contours were cut for the research: triangular, trapezoidal symmetrical and trapezoidal asymmetrical. Turning of each was carried out twice at cutting speeds vc = 17 m/min and vc = 30 m/min. On each of the threads, the side surface of the profile made in the direction of the insert feed and the opposite surface were examined. The surface texture parameters Sa, Sq, Sp, Sv, Sz, Ssk and Sku were determined and compared. It was noticed that the thread surfaces show a tendency to irregular roughness, which was confirmed by the analysis of the Sku and Ssk coefficients. The sides of the contours made in the direction of the insert feed are characterized by a higher roughness in relation to the opposite sides, which may result from high cutting forces and difficulties with chip evacuation. With the cutting speed being considered, lower values of Sa and Sq were obtained for vc = 17 m/min, which differed from the visual assessment, proving its high subjectivity.
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Bevc, Dimitri. "Flooding the topography: Wave‐equation datuming of land data with rugged acquisition topography." GEOPHYSICS 62, no. 5 (September 1997): 1558–69. http://dx.doi.org/10.1190/1.1444258.
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Wave‐equation datuming overcomes some of the problems that seismic data recorded on rugged surface topography present in routine image processing. The main problems are that (1) standard, optimized migration and processing algorithms assume data are recorded on a flat surface, and that (2) the static correction applied routinely to compensate for topography is inaccurate for waves that do not propagate vertically. Wave‐based processes such as stacking, dip‐moveout correction, normal‐moveout correction, velocity analysis, and migration after static shift can be severely affected by the nonhyperbolic character of the reflections. To alleviate these problems, I apply wave‐equation datuming early in the processing flow to upward continue the data to a flat datum, above the highest topography. This is what I refer to as “flooding the topography.” This approach does not require detailed a priori knowledge of the near‐surface velocity, and it streamlines subsequent processing because the data are regridded onto a regularly sampled datum. Wave‐equation datuming unravels the distortions caused by rugged topography, and unlike the static shift method, it does not adversely effect subsequent wave‐based processing. The image obtained after wave‐equation datuming exhibits better reflector continuity and more accurately represents the true structural image than the image obtained after static shift.
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Hitchcock, Peter, Theodore G. Shepherd, Masakazu Taguchi, Shigeo Yoden, and Shunsuke Noguchi. "Lower-Stratospheric Radiative Damping and Polar-Night Jet Oscillation Events." Journal of the Atmospheric Sciences 70, no. 5 (April 23, 2013): 1391–408. http://dx.doi.org/10.1175/jas-d-12-0193.1.
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Abstract The effect of stratospheric radiative damping time scales on stratospheric variability and on stratosphere–troposphere coupling is investigated in a simplified global circulation model by modifying the vertical profile of radiative damping in the stratosphere while holding it fixed in the troposphere. Perpetual-January conditions are imposed, with sinusoidal topography of zonal wavenumber 1 or 2. The depth and duration of the simulated sudden stratospheric warmings closely track the lower-stratospheric radiative time scales. Simulations with the most realistic profiles of radiative damping exhibit extended time-scale recoveries analogous to polar-night jet oscillation (PJO) events, which are observed to follow sufficiently deep stratospheric warmings. These events are characterized by weak lower-stratospheric winds and enhanced stability near the tropopause, which persist for up to 3 months following the initial warming. They are obtained with both wave-1 and wave-2 topography. Planetary-scale Eliassen–Palm (EP) fluxes entering the vortex are also suppressed, which is in agreement with observed PJO events. Consistent with previous studies, the tropospheric jets shift equatorward in response to the warmings. The duration of the shift is closely correlated with the period of enhanced stability. The magnitude of the shift in these runs, however, is sensitive only to the zonal wavenumber of the topography. Although the shift is sustained primarily by synoptic-scale eddies, the net effect of the topographic form drag and the planetary-scale fluxes is not negligible; they damp the surface wind response but enhance the vertical shear. The tropospheric response may also reduce the generation of planetary waves, further extending the stratospheric dynamical time scales.
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Rudenko, Anton, Cyril Mauclair, Florence Garrelie, Razvan Stoian, and Jean-Philippe Colombier. "Self-organization of surfaces on the nanoscale by topography-mediated selection of quasi-cylindrical and plasmonic waves." Nanophotonics 8, no. 3 (January 29, 2019): 459–65. http://dx.doi.org/10.1515/nanoph-2018-0206.
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AbstractUsing coupled electromagnetic and hydrodynamic calculations, we elucidate theoretically the topographic transition from a random metallic surface to a periodic sub-wavelength grating by ultrashort laser ablation. The origin of this transition lies in the successive selection of hybrid surface waves scattered by random nanoholes. Contrary to the common belief that surface plasmon polaritons play the dominant role in the process and define the grating periodicity, we show that both quasi-cylindrical and surface plasmon waves are involved, whereas the diversity in the resulting spacings λ/2–λ (λ is the laser wavelength) is the manifestation of a broad frequency overlap of these waves, controlled by their relative phase shifts with respect to the plasmonic counterparts. The topography evolution imposes the dominant contribution to the surface sub-wavelength pattern by selecting the appropriate wave character from plasmonic modes to evanescent cylindrical waves. With the radiation dose, the grating periodicity exhibits a pronounced blue shift due to reinforced dipole–dipole coupling between the nanoholes and surface curvatures in the laser-processed area. This allows the creation of regular patterns with tunable periodicity.
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Zhang, Jiawei, Gitanjali Kolhatkar, and Andreas Ruediger. "Localized surface plasmon resonance shift and its application in scanning near-field optical microscopy." Journal of Materials Chemistry C 9, no. 22 (2021): 6960–69. http://dx.doi.org/10.1039/d1tc00877c.
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Anooshehpoor, Abdolrasool, and James N. Brune. "Foam rubber modeling of topographic and Dam interaction effects at Pacoima Dam." Bulletin of the Seismological Society of America 79, no. 5 (October 1, 1989): 1347–60. http://dx.doi.org/10.1785/bssa0790051347.
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Abstract A study of the topographic and dam interaction effects was made using a 3-D foam rubber model of the actual topography around the Pacoima Dam accelerograph which recorded over 1 g high-frequency horizontal ground accelerations during the 1971 San Fernando earthquake. Scaling of frequency from the model to the earth depends on the average value of shear-wave velocity in the upper few hundred meters. Assuming βe = 2 km/sec, for vertically incident SH waves, the spectral ratio of the ground acceleration on the ridge to the free field (flat surface) indicates an amplification of about 60 per cent around 6.5 Hz on the N76°W component. Topography has little effect upon the motion recorded on the S14°W component. Motion on the ridge is lower than the free-field motion on both horizontal components for frequencies above 9 Hz. Amplification peaks shift to higher or lower frequencies depending on the assumed shear-wave velocity in the upper few hundred meters. Results from nonvertically incident SH waves show that the topographic effect is dependent on the direction of approach of the seismic energy. The effect is either de-amplification (in part by shadowing) or amplification (relative to the case where no topography is present), depending on whether the canyon is on the ray path or not. The Fourier spectrum of the ground motion at the dam crest shows peak frequencies at about 5 Hz and 10 Hz (resonance), which correspond to the normal modes of the dam. A study of dynamic interaction between the Pacoima Dam and the ridge shows that the coupling is less than 2 per cent at about 10 Hz and less than 12 percent at about 5 Hz.
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YANG Lian-gen, 杨练根, 何浪 HE Lang, 王选择 WANG Xuan-ze, 刘文超 LIU Wen-chao, and 何涛 He Tao. "Surface topography measuring system based on wavelength switching and phase shift scanning." Optics and Precision Engineering 23, no. 9 (2015): 2466–72. http://dx.doi.org/10.3788/ope.20152309.2466.
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Ma, Jianwei, Xiangqian Jiang, and Paul Scott. "Complex ridgelets for shift invariant characterization of surface topography with line singularities." Physics Letters A 344, no. 6 (September 2005): 423–31. http://dx.doi.org/10.1016/j.physleta.2005.06.091.
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Xu, Zhijia, Qinghui Wang, and Jingrong Li. "Modeling porous structures with fractal rough topography based on triply periodic minimal surface for additive manufacturing." Rapid Prototyping Journal 23, no. 2 (March 20, 2017): 257–72. http://dx.doi.org/10.1108/rpj-09-2015-0121.
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Purpose The purpose of this paper is to develop a general mathematic approach to model the microstructures of porous structures produced by additive manufacturing (AM), which will result in fractal surface topography and higher roughness that have greater influence on the performance of porous structures. Design/methodology/approach The overall shapes of pores were modeled by triply periodic minimal surface (TPMS), and the micro-roughness details attached to the overall pore shapes were represented by Weierstrass–Mandelbrot (W-M) fractal representation, which was integrated with TPMS along its normal vectors. An index roughly reflecting the irregularity of fractal TPMS was proposed, based on which the influence of the fractal parameters on the fractal TPMS was qualitatively analyzed. Two complex samples of real porous structures were given to demonstrate the feasibility of the model. Findings The fractal surface topography should not be neglected at a micro-scale level. In addition, a decrease in the fractal dimension Ds may exponentially make the topography rougher; an increase in the height-scaling parameter G may linearly increase the roughness; and the number of the superposed ridges has no distinct influence on the topography. Furthermore, the synthesis method is general for all implicit surfaces. Practical implications The method provides an alternative way to shift the posteriori design paradigm of porous media to priori design mode through numeric simulation. Therefore, the optimization of AM process parameters, as well as the porous structure, can be potentially realized according to specific functional requirement. Originality/value The synthesis of TPMS and W-M fractal geometry was accomplished efficiently and was general for all implicit freeform surfaces, and the influence of the fractal parameters on the fractal TPMS was analyzed more systematically.
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Zhu, Xiaochun, Zhurong Dong, Yachen Zhang, and Zhengkun Cheng. "Fatigue Life Prediction of Machined Specimens with the Consideration of Surface Roughness." Materials 14, no. 18 (September 19, 2021): 5420. http://dx.doi.org/10.3390/ma14185420.
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The fatigue strength and fatigue life of high-strength steels are greatly affected by their surface roughness. This study investigates the underlying mechanisms responsible for fatigue failure of the high-strength steel 42CrMo. Bending fatigue tests of stepped shafts with different levels of surface roughness were conducted to observe the fatigue live reduction affected by surface topography. Besides, the mechanical properties of 42CrMo and its strain–life relationship were established. Moreover, the analytical formulas to describe the stress concentration factor (SCF) and fatigue notch factor (FNF) induced by surface topography were introduced. To estimate the fatigue life of machined specimens with the consideration of surface roughness, the elastic portion of the total strain–life curve of the material was revised with the proposed analytical FNF imposed by surface topography. Comparisons between the estimated fatigue lives and experimentally obtained fatigue lives show that the effect of surface roughness on fatigue lives could be estimated effectively and conveniently by the proposed procedure.
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Sizov, Oleg, Ekaterina Ezhova, Petr Tsymbarovich, Andrey Soromotin, Nikolay Prihod'ko, Tuukka Petäjä, Sergej Zilitinkevich, Markku Kulmala, Jaana Bäck, and Kajar Köster. "Fire and vegetation dynamics in northwest Siberia during the last 60 years based on high-resolution remote sensing." Biogeosciences 18, no. 1 (January 14, 2021): 207–28. http://dx.doi.org/10.5194/bg-18-207-2021.
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Abstract. The rapidly warming Arctic undergoes transitions that can influence global carbon balance. One of the key processes is the shift towards vegetation types with higher biomass underlining a stronger carbon sink. The shift is predicted by bioclimatic models based on abiotic climatic factors, but it is not always confirmed with observations. Recent studies highlight the role of disturbances in the shift. Here we use high-resolution remote sensing to study the process of transition from tundra to forest and its connection to wildfires in the 20 000 km2 area in northwest Siberia. Overall, 40 % of the study area was burned during a 60-year period. Three-quarters of the burned areas were dry tundra. About 10 % of the study area experienced two–three fires with an interval of 15–60 years suggesting a shorter fire return interval than that reported earlier for the northern areas of central Siberia (130–350 years). Based on our results, the shift in vegetation (within the 60-year period) occurred in 40 %–85 % of the burned territories. All fire-affected territories were flat; therefore no effect of topography was detected. Oppositely, in the undisturbed areas, a transition of vegetation was observed only in 6 %–15 % of the territories, characterized by steeper topographic slopes. Our results suggest a strong role of disturbances in the tree advance in northwest Siberia.
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Kuhn, Michael, Jakob Abermann, Michael Bacher, and Marc Olefs. "The transfer of mass-balance profiles to unmeasured glaciers." Annals of Glaciology 50, no. 50 (2009): 185–90. http://dx.doi.org/10.3189/172756409787769618.
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AbstractFor estimation of the mass balance of an unmeasured glacier, its area distribution with altitude, s (h), generally is the only available quantitative information. The appropriate specific balance profile, b (h), needs to be transferred from a measured glacier, where transfer means modification and adaptation to the topographic and climatic situation of the unmeasured glacier, such as altitude, exposure to sun and wind, or temperature. This study proposes the area median elevation, M, as a parameter of prime importance for the transfer. Using as an example ten Alpine glaciers, the similarity of M and equilibrium-line altitude is quantified and the effect of aspect and surrounding topography is qualitatively suggested. The transfer of b (h) between well-measured glaciers yielded differences in the mean specific balance of 150 mm in the mean of a 10 year period, which corresponds to a change in median altitude by 30 m. Transfer of b (h) with a shift according to median glacier elevation to a basin with 27 glaciers and 23 km2 ice cover agreed to within 10% with elevation changes converted from digital elevation models of 1969 and 1997.
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Hsu, Huang-Hsiung, and Ming-Ying Lee. "Topographic Effects on the Eastward Propagation and Initiation of the Madden–Julian Oscillation." Journal of Climate 18, no. 6 (March 15, 2005): 795–809. http://dx.doi.org/10.1175/jcli-3292.1.
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Abstract This study investigates the relationship between deep convection (and heating anomaly) in the Madden–Julian oscillation (MJO) and the tropical topography. The eastward propagation of the deep heating anomalies is confined to two regions: the Indian Ocean and the western Pacific warm pool. Superimposed on the eastward propagation is a series of quasi-stationary deep heating anomalies that occur sequentially and discretely downstream in a leapfrog manner in the central Indian Ocean, the Maritime Continent, tropical South America, and tropical Africa. The deep heating anomaly, usually preceded by near-surface moisture convergence and shallow heating anomalies, tends to occur on the windward side of the tropical topography in these regions (except the central Indian Ocean) under the prevailing surface easterly anomaly of the MJO. It is suggested that the lifting and frictional effects of the tropical topography and landmass induce the near-surface moisture convergence anomaly, which in turn triggers the deep heating anomaly. Subsequently, the old heating anomaly located to the west of the tropical topography weakens and the new heating anomaly east of the topography develops because of the eastward shift in the major moisture convergence center to the east of the mountains. Therefore, the deep heating anomaly shifts eastward from one region to another. The equatorial Kelvin wave, which is forced by the tropical heating anomaly and propagates quickly across the ocean basins in the lower troposphere, plays an important role by helping to strengthen the easterly anomaly and lowering the surface pressure. This process is proposed to further our understanding of the shift in the deep convection from the Indian Ocean to the western Pacific, the reappearance of the deep convection in tropical South America, and the initiation of the MJO in the western Indian Ocean. It is suggested that the fast eastward propagation and the slow development of quasi-stationary convection together determine the quasi-periodicity of the MJO.
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Osakabe, N., J. Endo, T. Matsuda, and A. Tonomura. "Observation of surface morphology by reflection electron holography." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 536–37. http://dx.doi.org/10.1017/s0424820100154652.
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Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.
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Nowak, Kamil, Michał Jurczyszyn, Maciej Chrobak, Krzysztof Maćkosz, Andrii Naumov, Natalia Olszowska, Marcin Rosmus, et al. "Influence of Doping on the Topological Surface States of Crystalline Bi2Se3 Topological Insulators." Materials 15, no. 6 (March 11, 2022): 2083. http://dx.doi.org/10.3390/ma15062083.
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We present STM/STS, ARPES and magnetotransport studies of the surface topography and electronic structure of pristine Bi2Se3 in comparison to Bi1.96Mg0.04Se3 and Bi1.98Fe0.02Se3. The topography images reveal a large number of complex, triangle-shaped defects at the surface. The local electronic structure of both the defected and non-defected regions is examined by STS. The defect-related states shift together with the Dirac point observed in the undefected area, suggesting that the local electronic structure at the defects is influenced by doping in the same way as the electronic structure of the undefected surface. Additional information about the electronic structure of the samples is provided by ARPES, which reveals the dependence of the bulk and surface electronic bands on doping, including such parameters as the Fermi wave vector. The subtle changes of the surface electronic structure by doping are verified with magneto-transport measurements at low temperatures (200 mK) allowing the detection of Shubnikov-de Haas (SdH) quantum oscillations.
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Vidal Vázquez, E., J. G. V. Miranda, and J. Paz-Ferreiro. "A multifractal approach to characterize cumulative rainfall and tillage effects on soil surface micro-topography and to predict depression storage." Biogeosciences Discussions 7, no. 2 (March 24, 2010): 2099–141. http://dx.doi.org/10.5194/bgd-7-2099-2010.
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Abstract. Most of the indices currently employed for assessing soil surface micro-topography, such as random roughness (RR), are merely descriptors of its vertical component. Recently, multifractal analysis provided a new insight for describing the spatial configuration of soil surface roughness. The main objective of this study was to test the ability of multifractal parameters to assess decay of initial surface roughness induced by natural rainfall under different soil tillage systems in field conditions. In addition, we evaluated the potential of the joint use of multifractal indices plus RR to improve predictions of water storage in depressions of the soil surface (MDS). Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plough, chisel plough, disc harrow + disc level, disc plough + disc level and chisel plough + disc level were tested. In each treatment soil surface micro-topography was measured four times, with increasing amounts of natural rainfall, using a pin meter. The sampling scheme was a square grid with 25×25 mm point spacing and the plot size was 1350×1350 mm (≈1.8 m2), so that each data set consisted of 3025 individual elevation points. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental data sets. MDS was estimated from grid elevation data with a depression-filling algorithm. Multifractal analysis was performed for experimental data sets as well as for oriented and random surface conditions obtained from the former by removing slope and slope plus tillage marks, respectively. All the investigated microplots exhibited multifractal behaviour, irrespective of surface condition, but the degree of multifractality showed wide differences between them. Multifractal parameters provided valuable information for characterizing the spatial features of soil micro-topography as they were able to discriminate data sets with similar values for the vertical component of roughness. Both, rough and smooth soil surfaces, with high and low roughness values, respectively, can display similar levels of spectral complexity. Although in most of the studied cases trend removal produces increasing homogeneity in the spatial configuration of height readings, spectral complexity of individual data sets may increase or decrease, when slope or slope plus tillage tool marks are filtered. Increased cumulative rainfall had significant effects on various parameters from the generalized dimension, Dq, and singularity spectrum, f(α). Overall, micro-topography decay by rainfall produced was reflected on a shift of the singularity spectra, f(α) from the left side (q>>0) to the right side (q<<0) and also on a shift of the generalized dimension spectra from the right side (q>>0) to the left side (q<<0). The use of an exponential model of vertical roughness indices, RR, and multifractal parameters accounting for the spatial configuration such as D1, D5, and D10 improved estimation of water stored in surface depressions.
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Haack, T., S. D. Burk, and R. M. Hodur. "U.S. West Coast Surface Heat Fluxes, Wind Stress, and Wind Stress Curl from a Mesoscale Model." Monthly Weather Review 133, no. 11 (November 1, 2005): 3202–16. http://dx.doi.org/10.1175/mwr3025.1.
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Abstract Monthly averages of numerical model fields are beneficial for depicting patterns in surface forcing such as sensible and latent heat fluxes, wind stress, and wind stress curl over data-sparse ocean regions. Grid resolutions less than 10 km provide the necessary mesoscale detail to characterize the impact of a complex coastline and coastal topography. In the present study a high-resolution mesoscale model is employed to reveal patterns in low-level winds, temperature, relative humidity, sea surface temperature as well as surface fluxes, over the eastern Pacific and along the U.S. west coast. Hourly output from successive 12-h forecasts are averaged to obtain monthly mean patterns from each season of 1999. The averages yield information on interactions between the ocean and the overlying atmosphere and on the influence of coastal terrain forcing in addition to their month-to-month variability. The spring to summer transition is characterized by a dramatic shift in near-surface winds, temperature, and relative humidity as offshore regions of large upward surface fluxes diminish and an alongshore coastal flux gradient forms. Embedded within this gradient, and the imprint of strong summertime topographic forcing, are small-scale fluctuations that vary in concert with local changes in sea surface temperature. Potential feedbacks between the low-level wind, sea surface temperature, and the wind stress curl are explored in the coastal regime and offshore waters. In all seasons, offshore extensions of colder coastal waters impose a marked influence on low-level conditions by locally enhancing stability and reducing the wind speed, while buoy measurements along the coast indicate that sea surface temperatures and wind speeds tend to be negatively correlated.
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Reshef, Moshe. "Depth migration from irregular surfaces with depth extrapolation methods." GEOPHYSICS 56, no. 1 (January 1991): 119–22. http://dx.doi.org/10.1190/1.1442947.
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Nonflat surface topography introduces a numerical problem for migration algorithms that are based on depth extrapolation. Since the numerically efficient migration schemes start at a flat interface, wave‐equation datuming is required (Berryhill, 1979) prior to the migration. The computationally expensive datuming procedure is often replaced by a simple time shift for the elevation to datum correction. For nonvertically traveling energy this correction is inaccurate. Subsequent migration wrongly positions the reflectors in depth.
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Monaghan, Andrew J., Michael Barlage, Jennifer Boehnert, Cody L. Phillips, and Olga V. Wilhelmi. "Overlapping Interests: The Impact of Geographic Coordinate Assumptions on Limited-Area Atmospheric Model Simulations." Monthly Weather Review 141, no. 6 (June 1, 2013): 2120–27. http://dx.doi.org/10.1175/mwr-d-12-00351.1.
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Abstract There is growing use of limited-area models (LAMs) for high-resolution (<10 km) applications, for which consistent mapping of input terrestrial and meteorological datasets is critical for accurate simulations. The geographic coordinate systems of most input datasets are based on spheroid-shaped (i.e., elliptical) Earth models, while LAMs generally assume a perfectly sphere-shaped Earth. This distinction is often neglected during preprocessing, when input data are remapped to LAM domains, leading to geolocation discrepancies that can exceed 20 km at midlatitudes. A variety of terrestrial (topography and land use) input dataset configurations is employed to explore the impact of Earth model assumptions on a series of 1-km LAM simulations over Colorado. For the same terrestrial datasets, the ~20-km geolocation discrepancy between spheroidal-versus-spherical Earth models over the domain leads to simulated differences in near-surface and midtropospheric air temperature, humidity, and wind speed that are larger and more widespread than those due to using different topography and land use datasets altogether but not changing the Earth model. Simulated differences are caused by the shift of static fields with respect to boundary conditions, and altered Coriolis forcing and topographic gradients. The sensitivity of high-resolution LAM simulations to Earth model assumptions emphasizes the importance for users to ensure terrestrial and meteorological input data are consistently mapped during preprocessing (i.e., datasets share a common geographic coordinate system before remapping to the LAM domain). Concurrently, the modeling community should update preprocessing systems to make sure input data are correctly mapped for all global and limited-area simulation domains.
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Bejjani, R., S. Odelros, S. Öhman, and M. Collin. "Shift of wear balance acting on CVD textured coatings and relation to workpiece materials." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 235, no. 1 (May 21, 2020): 114–28. http://dx.doi.org/10.1177/1350650120926781.
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Innovative textured alumina coatings have been engineered to boost the performance of cutting tools. Different workpiece materials affect the wear inside the CVD textured alumina coating differently on the crater and flank side of the tools. How the balance in wear changes between the crater and flank side of the tool inside the alumina is not fully understood. Furthermore, any changes in steel elements in the workpiece can affect this balance differently. In this work, the wear of alumina coating has been studied after turning different workpiece materials (low alloy steel with and without Ca, ball bearing steel and stainless steel). The worn surfaces of the inserts were studied and their features related to the different materials. It was found that after machining under similar conditions, each workpiece material leaves a different signature, or worn surface, with unique features in the alumina coating layer. The transition between the sliding to the sticking region was studied in order to help understand the relation to wear when machining different workpiece materials. SEM and topography characteristics were identified on worn surfaces of the coated tools. The resulting worn volume and surface characteristics were related to different wear mechanisms acting on the rake and flank sides of the tool. This work studies the shift in balance between crater and flank wear by identifying different wear mechanisms acting inside the same alumina coating layer when machining different grades of steel. Such work can be a good resource for FEM wear modeling, where good simulation models must take into consideration the physics lying behind the wear types acting on each side of the tool.
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Vidal Vázquez, E., J. G. V. Miranda, and J. Paz-Ferreiro. "A multifractal approach to characterize cumulative rainfall and tillage effects on soil surface micro-topography and to predict depression storage." Biogeosciences 7, no. 10 (October 1, 2010): 2989–3004. http://dx.doi.org/10.5194/bg-7-2989-2010.
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Abstract. Most of the indices currently employed for assessing soil surface micro-topography, such as random roughness (RR), are merely descriptors of its vertical component. Recently, multifractal analysis provided a new insight for describing the spatial configuration of soil surface roughness. The main objective of this study was to test the ability of multifractal parameters to assess in field conditions the decay of initial surface roughness induced by natural rainfall under different soil tillage systems. In addition, we evaluated the potential of the joint use of multifractal indices plus RR to improve predictions of water storage in depressions of the soil surface (MDS). Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plough, chisel plough, disc harrow + disc level, disc plough + disc level and chisel plough + disc level were tested. In each treatment soil surface micro-topography was measured four times, with increasing amounts of natural rainfall, using a pin meter. The sampling scheme was a square grid with 25 × 25 mm point spacing and the plot size was 1350 × 1350 mm (≈1.8 m2), so that each data set consisted of 3025 individual elevation points. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental data sets. MDS was estimated from grid elevation data with a depression-filling algorithm. Multifractal analysis was performed for experimental data sets as well as for oriented and random surface conditions obtained from the former by removing slope and slope plus tillage marks, respectively. All the investigated microplots exhibited multifractal behaviour, irrespective of surface condition, but the degree of multifractality showed wide differences between them. Multifractal parameters provided valuable information for characterizing the spatial features of soil micro-topography as they were able to discriminate data sets with similar values for the vertical component of roughness. Conversely, both, rough and smooth soil surfaces, with high and low roughness values, respectively, can display similar levels of spectral complexity. Although in most of the studied cases trend removal produces increasing homogeneity in the spatial configuration of height readings, spectral complexity of individual data sets may increase or decrease, when slope or slope plus tillage tool marks are filtered. Increased cumulative rainfall had significant effects on various parameters from the generalized dimension, Dq, and singularity spectrum, f(α). Overall, micro-topography decay by rainfall was reflected on a shift of the singularity spectra, f(α) from the left side (q>>0) to the right side (q>0) to the left side (q
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Ramstein, G., and S. Joussaume. "Sensitivity experiments to sea surface temperatures, sea-ice extent and ice-sheet reconstruction, for the Last Glacial Maximum." Annals of Glaciology 21 (1995): 343–47. http://dx.doi.org/10.3189/s0260305500016049.
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For the Last Glacial Maximum, (LGM; 21 000 BP), simulations using atmospheric general-circulation models (AGCMs) are very sensitive to the prescribed boundary conditions. Most of the recent numerical experiments have used the CLIMAP (1981) data set for ice-sheet topography, sea-ice extent and sea surface temperatures (SSTs). To demonstrate the impact of ice-sheet reconstruction on the LGM climate, we performed two simulations: one using CLIMAP (1981) ice-sheet topography, the other using the new reconstruction provided by Peltier. We show that, although the geographical structure of the annually averaged temperature is not modified, there are important seasonal and regional impacts on the temperature distribution. In a second step, to analyze the effects of cooler SSTs and sea-ice extent, we performed a simulation using CLIMAP (1981) for the ice-sheet topography, but with present SSTs. We find that the cooling due to ice sheets for the LGM climate is one-third of the global annually averaged cooling, and dial the southward shift of the North Atlantic low in winter is not due to sea-ice extent, but is an orographic effect due to the Laurenride ice sheet. This set of sensitivity experiments allows us also to discriminate between thermal and orographic forcings and to show the impact of the ice-sheet topography and cooler SSTs on the pattern of planetary waves during the LGM climate.
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Ramstein, G., and S. Joussaume. "Sensitivity experiments to sea surface temperatures, sea-ice extent and ice-sheet reconstruction, for the Last Glacial Maximum." Annals of Glaciology 21 (1995): 343–47. http://dx.doi.org/10.1017/s0260305500016049.
Full textAbstract:
For the Last Glacial Maximum, (LGM; 21 000 BP), simulations using atmospheric general-circulation models (AGCMs) are very sensitive to the prescribed boundary conditions. Most of the recent numerical experiments have used the CLIMAP (1981) data set for ice-sheet topography, sea-ice extent and sea surface temperatures (SSTs). To demonstrate the impact of ice-sheet reconstruction on the LGM climate, we performed two simulations: one using CLIMAP (1981) ice-sheet topography, the other using the new reconstruction provided by Peltier. We show that, although the geographical structure of the annually averaged temperature is not modified, there are important seasonal and regional impacts on the temperature distribution. In a second step, to analyze the effects of cooler SSTs and sea-ice extent, we performed a simulation using CLIMAP (1981) for the ice-sheet topography, but with present SSTs. We find that the cooling due to ice sheets for the LGM climate is one-third of the global annually averaged cooling, and dial the southward shift of the North Atlantic low in winter is not due to sea-ice extent, but is an orographic effect due to the Laurenride ice sheet. This set of sensitivity experiments allows us also to discriminate between thermal and orographic forcings and to show the impact of the ice-sheet topography and cooler SSTs on the pattern of planetary waves during the LGM climate.
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Fathy, Arwa, Bernardo T. Lopes, Renato Ambrósio, Richard Wu, and Ahmed Abass. "The Efficiency of Using Mirror Imaged Topography in Fellow Eyes Analyses of Pentacam HR Data." Symmetry 13, no. 11 (November 9, 2021): 2132. http://dx.doi.org/10.3390/sym13112132.
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Purpose: To investigate the effectiveness of flipping left corneas topography and analysethem quantitively along with fellow right corneas based on the assumption that they are mirror images of each other. Methods: The study involved scanning both eyes of 177 healthy participants (aged 35.3 ± 15.8) and 75 keratoconic participants (aged 33.9 ± 17.8). Clinical tomography data were collected for both eyes using the Pentacam HR and processed by a fully automated custom-built MATLAB code. For every case, the right eye was used as a datum fixed surface while the left cornea was flipped around in the superior–inferior direction. In this position, the root-mean-squared difference (RMS) between the flipped left cornea and the right cornea was initially determined for both the anterior and posterior corneal surfaces. Next, the iterative closest point transformation algorithm was applied on the three-dimensional flipped cornea to allow the flipped left corneal anterior surface to translate and rotate, minimising the difference between it and the right corneal anterior surface. Then, the RMS differences were recalculated and compared. Results: A comparison of the dioptric powers showed a significant difference between the RMS of both the flipped left eyes and the right eyes in the healthy and the KC groups (p < 0.001). The RMS of the surfaces of the flipped left corneas and the right corneas was 0.6 ± 0.4 D among the healthy group and 4.1 ± 2.3 among the KC group. After transforming the flipped left corneas, the RMS was recorded as 0.5 ± 0.3 D and 2.4 ± 2 D among the healthy and KC groups, respectively. Conclusions: Although fellow eyes are highly related in their clinical parameters, they should be treated with care when one eye topography is flipped and processed with the other eye topography in an optic-related research analysis where translation might be needed. In KC, an asymmetric disease, it was observed that a portion of the asymmetry was due to a corneal apex shift interfering with the image acquisition. Therefore, transforming the flipped left eyes by rotation and translation results in a fairer comparison between the fellow KC corneas.
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Kong, Weiya, Bo Liu, Xiaohong Sui, Running Zhang, and Jinping Sun. "Ocean Surface Topography Altimetry by Large Baseline Cross-Interferometry from Satellite Formation." Remote Sensing 12, no. 21 (October 27, 2020): 3519. http://dx.doi.org/10.3390/rs12213519.
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Imaging Radar Altimeter (IRA) is the current development tendency for ocean surface topography (OST) altimetry, which utilizes Synthetic Aperture Radar (SAR) and interferometry to improve the spatial resolution of OST to several kilometers or even better. Meanwhile, centimetric altimetry accuracy should be guaranteed for applications such as geostrophic currents or marine gravity anomaly inversion. However, the baseline length of IRA which determines the altimetric sensitivity is confined by the satellite platform, in consideration of baseline vibration and payload capability. Therefore, the baseline length from a single satellite can extend to only tens of meters, making it difficult to achieve centimetric accuracy. Referring to the successful experience from TerraSAR-X/TanDEM-X, satellite formation can easily extend the baseline length to hundreds or thousands of meters, depending on the helix orbit. Therefore, we propose the large baseline IRA (LB-IRA) from satellite formation for OST altimetry: the carrier frequency shift (CFS) is brought in to compensate for the severe baseline decorrelation, and the helix orbit is carefully selected to prevent severe time decorrelation from along-track baseline. The numerical results indicate that the LB-IRA, whose cross-track baseline ranges between 629~1000 m and along-tack baseline ranges between 0~40 m, can achieve ~1 cm relative accuracy at 1 km resolution.
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Liu, Wei, Zhengyu Liu, and Shouwei Li. "The Driving Mechanisms on Southern Ocean Upwelling Change during the Last Deglaciation." Geosciences 11, no. 7 (June 22, 2021): 266. http://dx.doi.org/10.3390/geosciences11070266.
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We explore the change in Southern Ocean upwelling during the last deglaciation, based on proxy records and a transient climate model simulation. Our analyses suggest that, beyond a conventional mechanism of the Southern Hemisphere westerlies shift, Southern Ocean upwelling is strongly influenced by surface buoyancy forcing and the local topography. Over the Antarctic Circumpolar Current region, the zonal mean and local upwelled flows exhibited distinct evolution patterns during the last deglaciation, since they are driven by different mechanisms. The zonal mean upwelling is primarily driven by surface wind stress via zonal mean Ekman pumping, whereas local upwelling is driven by both wind and buoyancy forcing, and is tightly coupled to local topography. During the early stage of the last deglaciation, the vertical extension of the upwelled flows increased downstream of submarine ridges but decreased upstream, which led to enhanced and diminished local upwelling, downstream and upstream of the submarine ridges, respectively.
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Rott, Helmut, Stefan Scheiblauer, Jan Wuite, Lukas Krieger, Dana Floricioiu, Paola Rizzoli, Ludivine Libert, and Thomas Nagler. "Penetration of interferometric radar signals in Antarctic snow." Cryosphere 15, no. 9 (September 13, 2021): 4399–419. http://dx.doi.org/10.5194/tc-15-4399-2021.
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Abstract. Synthetic aperture radar interferometry (InSAR) is an efficient technique for mapping the surface elevation and its temporal change over glaciers and ice sheets. However, due to the penetration of the SAR signal into snow and ice, the apparent elevation in uncorrected InSAR digital elevation models (DEMs) is displaced versus the actual surface. We studied relations between interferometric radar signals and physical snow properties and tested procedures for correcting the elevation bias. The work is based on satellite and in situ data over Union Glacier in the Ellsworth Mountains, West Antarctica, including interferometric data of the TanDEM-X mission, topographic data from optical satellite sensors and field measurements on snow structure, and stratigraphy undertaken in December 2016. The study area comprises ice-free surfaces, bare ice, dry snow and firn with a variety of structural features related to local differences in wind exposure and snow accumulation. Time series of laser measurements of NASA's Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 show steady-state surface topography. For area-wide elevation reference we use the Reference Elevation Model of Antarctica (REMA). The different elevation data are vertically co-registered on a blue ice area that is not affected by radar signal penetration. Backscatter simulations with a multilayer radiative transfer model show large variations for scattering of individual snow layers, but the vertical backscatter distribution can be approximated by an exponential function representing uniform absorption and scattering properties. We obtain estimates of the elevation bias by inverting the interferometric volume correlation coefficient (coherence), applying a uniform volume model for describing the vertical loss function. Whereas the mean values of the computed elevation bias and the elevation difference between the TanDEM-X DEMs and the REMA show good agreement, a trend towards overestimation of penetration is evident for heavily wind-exposed areas with low accumulation and towards underestimation for areas with higher accumulation rates. In both cases deviations from the uniform volume structure are the main reason. In the first case the dense sequence of horizontal structures related to internal wind crust, ice layers and density stratification causes increased scattering in near-surface layers. In the second case the small grain size of the top snow layers causes a downward shift in the scattering phase centre.
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Bonevich, J., D. Capacci, R. Patti, G. Pozzi, K. Harada, H. Kasai, T. Matsuda, and A. Tonomura. "On the Influence of Specimen Thickness in TEM Images of Super-Conducting Vortices: II." Microscopy and Microanalysis 3, S2 (August 1997): 505–6. http://dx.doi.org/10.1017/s1431927600009417.
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In our previous papers on the same topic we have shown how the finite thickness of the specimen influences the magnetic field distribution associated to a single superconducting vortex. Fortunately, Clem found an approximate, but analytical, solution for this problem predicting that the field lines are bent within the specimen and fan out near the surfaces, giving an external field topography broader than the bulk one. This is shown in Figure 1 (a) which reports the projected phase maps of the magnetic field, i.e., the phase shift experienced by a coherent electron plane wave in an ideal experiment where the beam direction is parallel to the specimen surface and the apparent infinite thickness of the specimen is overlooked. The specimen thickness has been taken equal to 2 λL, the bulk London penetration depth. Figure 1 (b) shows the trends of the z-component of the magnetic field calculated up to a distance from the core of 5 λL at the film surface (lower curve), at the film center (intermediate curve) and, for reference, the bulk Clem model (upper curve).
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Pan, Yongcheng, Qingliang Zhao, Bing Guo, Bing Chen, and Jinhu Wang. "Suppression of Surface Waviness Error of Fresnel Micro-Structured Mold by Using Non-Integer Rotation Speed Ratio in Parallel Grinding Process." Micromachines 11, no. 7 (June 30, 2020): 652. http://dx.doi.org/10.3390/mi11070652.
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Fresnel micro-structured lenses are widely used in the field of modern optoelectronic technology. High-precision Fresnel micro-structured mold is the key technology to achieve its large-scale replication production. Focusing on the surface waviness error of Fresnel micro-structured mold machined by parallel grinding process, this paper conducted theoretical modeling and experiment research. Based on the grinding kinematics theory, the simulation models of the surface waviness topography and the circular waviness profiles of the ground Fresnel micro-structured mold were developed, considering the combined influence of the non-integer rotation speed ratio and other grinding parameters. A series of grinding experiments were carried out to verify the proposed simulation models. The influence of a non-integer rotation speed ratio and a wave-shift value upon the surface waviness error of the ground Fresnel micro-structured molds were analyzed. Both the simulation and experimental results proved that choosing the non-integer rotation speed ratio and a proper wave-shift value could greatly reduce the surface waviness error and improve the surface quality and uniformity.
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Li, Qiongling, Shahin Tavakol, Jessica Royer, Sara Larivière, Reinder Vos De Wael, Bo-yong Park, Casey Paquola, et al. "Atypical neural topographies underpin dysfunctional pattern separation in temporal lobe epilepsy." Brain 144, no. 8 (March 17, 2021): 2486–98. http://dx.doi.org/10.1093/brain/awab121.
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Abstract Episodic memory is the ability to remember events from our past accurately. The process of pattern separation is hypothesized to underpin this ability and is defined as the capacity to orthogonalize memory traces, to maximize the features that make them unique. Contemporary cognitive neuroscience suggests that pattern separation entails complex interactions between the hippocampus and neocortex, where specific hippocampal subregions shape neural reinstatement in the neocortex. To test this hypothesis, the current work studied both healthy controls and patients with temporal lobe epilepsy who presented with hippocampal structural anomalies. We measured neural activity in all participants using functional MRI while they retrieved memorized items or lure items, which shared features with the target. Behaviourally, patients with temporal lobe epilepsy were less able to exclude lures than controls and showed a reduction in pattern separation. To assess the hypothesized relationship between neural patterns in the hippocampus and neocortex, we identified the topographic gradients of intrinsic connectivity along neocortical and hippocampal subfield surfaces and determined the topographic profile of the neural activity accompanying pattern separation. In healthy controls, pattern separation followed a graded topography of neural activity, both along the hippocampal long axis (and peaked in anterior segments that are more heavily engaged in transmodal processing) and along the neocortical hierarchy running from unimodal to transmodal regions (peaking in transmodal default mode regions). In patients with temporal lobe epilepsy, however, this concordance between task-based functional activations and topographic gradients was markedly reduced. Furthermore, person-specific measures of concordance between task-related activity and connectivity gradients in patients and controls were related to inter-individual differences in behavioural measures of pattern separation and episodic memory, highlighting the functional relevance of the observed topographic motifs. Our work is consistent with an emerging understanding that successful discrimination between memories with similar features entails a shift in the locus of neural activity away from sensory systems, a pattern that is mirrored along the hippocampal long axis and with respect to neocortical hierarchies. More broadly, our study establishes topographic profiling using intrinsic connectivity gradients, capturing the functional underpinnings of episodic memory processes in a manner that is sensitive to their reorganization in pathology.
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Sojoodi Farimani, Foad, Matthijn de Rooij, Edsko Hekman, and Sarthak Misra. "Frictional characteristics of Fusion Deposition Modeling (FDM) manufactured surfaces." Rapid Prototyping Journal 26, no. 6 (April 29, 2020): 1095–102. http://dx.doi.org/10.1108/rpj-06-2019-0171.
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Purpose Additive manufacturing (AM) is a promising alternative to the conventional production methods (i.e., machining), providing the developers with great geometrical and topological freedom during the design and immediate prototyping customizability. However, frictional characteristics of the AM surfaces are yet to be fully explored, making the control and manufacturing of precise assembly manufactured mechanisms (i.e., robots) challenging. The purpose of this paper is to understand the tribological behavior of fused deposition modeling (FDM) manufactured surfaces and test the accuracy of existing mathematical models such as Amontons–Coulomb, Tabor–Bowden, and variations of Hertz Contact model against empirical data. Design/methodology/approach Conventional frictional models Amontons–Coulomb and Tabor–Bowden are developed for the parabolic surface topography of FDM surfaces using variations of Hertz contact models. Experiments are implemented to measure the friction between two flat FDM surfaces at different speeds, normal forces, and surface configuration, including the relative direction of printing stripes and sliding direction and the surface area. The global maximum measured force is considered as static friction, and the average of the local maxima during the stick-slip phase is assumed as kinematic friction. Spectral analysis has been used to inspect the relationship between the chaos of vertical wobbling versus sliding speed. Findings It is observed that the friction between the two FDM planes is linearly proportional to the normal force. However, in contrast to the viscous frictional model (i.e., Stribeck), the friction reduces asymptotically at higher speeds, which can be attributed to the transition from harmonic to normal chaotic vibrations. The phase shift is investigated through spectral analysis; dominant frequencies are presented at different pulling speeds, normal forces, and surface areas. It is hypothesized that higher speeds lead to smaller dwell-time, reducing creep and adhesive friction consequently. Furthermore, no monotonic relationship between surface area and friction force is observed. Research limitations/implications Due to the high number of experimental parameters, the research is implemented for a limited range of surface areas, which should be expanded in future research. Furthermore, the pulling position of the jaws is different from the sliding distance of the surfaces due to the compliance involved in the contact and the pulling cable. This issue could be alleviated using a non-contact position measurement method such as LASER or image processing. Another major issue of the experiments is the planar orientation of the pulling object with respect to the sliding direction and occasional swinging in the tangential plane. Practical implications Given the results of this study, one can predict the frictional behavior of FDM manufactured surfaces at different normal forces, sliding speeds, and surface configurations. This will help to have better predictive and model-based control algorithms for fully AM manufactured mechanisms and optimization of the assembly manufactured systems. By adjusting the clearances and printing direction, one can reduce or moderate the frictional forces to minimize stick-slip or optimize energy efficiency in FDM manufactured joints. Knowing the harmonic to chaotic phase shift at higher sliding speeds, one can apply certain speed control algorithms to sustain optimal mechanical performance. Originality/value In this study, theoretical tribological models are developed for the specific topography of the FDM manufactured surfaces. Experiments have been implemented for an extensive range of boundary conditions, including normal force, sliding speed, and contact configuration. Frictional behavior between flat square FDM surfaces is studied and measured using a Zwick tensile machine. Spectral analysis, auto-correlation, and other methods have been developed to study the oscillations during the stick-slip phase, finding local maxima (kinematic friction) and dominant periodicity of the friction force versus sliding distance. Precise static and kinematic frictional coefficients are provided for different contact configurations and sliding directions.