Artigos de revistas sobre o tema "Step-Like topography"
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Tenreiro, M., L. Zavala Sansón e G. J. F. van Heijst. "Interaction of dipolar vortices with a step-like topography". Physics of Fluids 18, n.º 5 (maio de 2006): 056603. http://dx.doi.org/10.1063/1.2204070.
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Alter, U., J. Härtwig e J. Kuběna. "Plane wave topography on crystals with step-like impurity distributions". Czechoslovak Journal of Physics 35, n.º 2 (fevereiro de 1985): 158–67. http://dx.doi.org/10.1007/bf01595627.
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White, Andrew J., e N. Robb McDonald. "The Motion of a Point Vortex near Large-Amplitude Topography in a Two-Layer Fluid". Journal of Physical Oceanography 34, n.º 12 (1 de dezembro de 2004): 2808–24. http://dx.doi.org/10.1175/jpo2658.1.
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Abstract This work examines the dynamics of point vortices in a two-layer fluid near large-amplitude, sharply varying topography like that which occurs in continental shelf regions. Topography takes the form of an infinitely long step change in depth, and the two-layer stratification is chosen such that the height of topography in the upper layer is a small fraction of the overall depth, enabling quasigeostrophic theory to be used in both layers. An analytic expression for the dispersion relation of free topographic waves in this system is found. Weak vortices are studied using linear theory and, if located in the lower layer, propagate mainly because of their image in the topography. Depending on their sign, they are able to produce significant topographic wave radiation in their wakes. Upper-layer vortices propagate much slower and produce relatively small amplitude topographic wave radiation. Contour dynamics results are used to investigate the nonlinear regions of parameter space. For lower-layer vortices, linear theory is a good approximation, but for upper-layer vortices complicated features evolve and linear theory is only valid for weak vortices.
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Bidlot, Jean-Raymond, e Melvin E. Stern. "Maintenance of continental boundary-layer shear through counter-gradient vorticity flux in a barotropic model". Journal of Fluid Mechanics 271 (25 de julho de 1994): 55–85. http://dx.doi.org/10.1017/s0022112094001680.
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The use of a classical eddy parametrization in the analysis of continental boundary currents leads to the diffusion of momentum and relative vorticity and fails to recognize that the relevant eddies are dominated by the conservation of potential vorticity, which in turn may produce an increase in the mean relative vorticity. To illustrate this effect, we examine a non-inflected barotropic shear flow destabilized by the cross-steam variation in the bottom topògraphy of a continental slope. The finiteamplitude evolution of the waves is analysed in a simple model with a step-like bottom topography and with a piecewise-uniform potential vorticity distribution. The increase in maximum mean vorticity is computed for various values of the Rossby number and the topographic elevation, and it is suggested that a similar effect, taking into account the isopycnal topography as well as the isobaths, could maintain the large inshore shear of the Gulf Stream. Cross-shelf transport of different water ‘types’ (i.e. potential vorticity and passive tracers) are also computed and suggested to be pertinent to the more realistic oceanic problem involving baroclinic effects. The numerical calculation employs the well-known method of contour dynamics, and the Green's function appropriate for the step-like topography is derived.
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Xiong, Qi, Xiangyi Liu, Yanxin Li, Lingran Xi e Shuang Qiu. "Analysis of the Influence of Complex Terrain around DC Transmission Grounding Electrodes on Step Voltage". Energies 17, n.º 2 (15 de janeiro de 2024): 420. http://dx.doi.org/10.3390/en17020420.
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The distribution of renewable energy sources is geographically limited. In the process of long-distance transmission, the direct current flowing from a ground electrode into the ground will cause a higher step voltage, which will bring serious security risks to the surrounding industry and life. Accurate calculation of the complex soil electrical model around the grounding electrode is crucial for site selection. Existing simulation software like CDEGS results in significant errors, particularly in complex karst topography. Therefore, constructing a finite element model that accurately reflects the characteristics of geotechnical soil near the DC grounding electrode is an essential but unresolved problem. This paper establishes a soil electrical model for karst topography and explores the impact of cave-type caverns and underground rivers on the step voltage distribution of DC grounding electrodes. These research findings can guide the site selection of DC transmission projects in karst topography.
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Sasaki, Masayuki, Kentaro Tamura, Hideki Sako, Makoto Kitabatake, Kazutoshi Kojima e Hirohumi Matsuhata. "Analysis on Generation of Localized Step-Bunchings on 4H-SiC(0001)Si Face by Synchrotron X-Ray Topography". Materials Science Forum 778-780 (fevereiro de 2014): 398–401. http://dx.doi.org/10.4028/www.scientific.net/msf.778-780.398.
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Surface roughening regions running like scratches are often observed locally after epitaxy film grown on a very flat 4H-SiC wafer surfaces. We investigated generation mechanism of such roughening surface by using X-ray topography and confocal optical microscopy. We found that lattice defects were often introduced during CMP at local regions, and those local regions cannot be recognized by optical microscopy, since very flat surface can be observed. By H2 etching which is preprocess of epitaxy film growth, those lattice defects are almost etched off, but local rough surface consists of pits and step bunching regions appear like scratches, and those local pits and surface roughening regions grew up to step bunching during epitaxy film growth.
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Scholle, Markus, Philip H. Gaskell e Florian Marner. "A Potential Field Description for Gravity-Driven Film Flow over Piece-Wise Planar Topography". Fluids 4, n.º 2 (2 de maio de 2019): 82. http://dx.doi.org/10.3390/fluids4020082.
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Models based on a potential field description and corresponding first integral formulation, embodying a reduction of the associated dynamic boundary condition at a free surface to one of a standard Dirichlet-Neumann type, are used to explore the problem of continuous gravity-driven film flow down an inclined piece-wise planar substrate in the absence of inertia. Numerical solutions of the first integral equations are compared with analytical ones from a linearised form of a reduced equation set resulting from application of the long-wave approximation. The results obtained are shown to: (i) be in very close agreement with existing, comparable experimental data and complementary numerical predictions for isolated step-like topography available in the open literature; (ii) exhibit the same qualitative behaviour for a range of Capillary numbers and step heights/depths, becoming quantitively similar when both are small. A novel outcome of the formulation adopted is identification of an analytic criteria enabling a simple classification procedure for specifying the characteristic nature of the free surface disturbance formed; leading subsequently to the generation of a related, practically relevant, characteristic parameter map in terms of the substrate inclination angle and the Capillary number of the associated flow.
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Yokoi, Toshiaki. "Numerical study on the generation of downgoing S‐waves by a vertical force acting close to a step‐like topography". GEOPHYSICS 61, n.º 1 (janeiro de 1996): 192–201. http://dx.doi.org/10.1190/1.1443939.
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I present detailed numerical experiments on a recently proposed S‐wave generation method and show the excitation characteristics of the downgoing S‐wave caused by a vertical impact acting close to a step‐like topography. The geophysicists’ group of Akita University recently studied and confirmed this phenomenon by in‐situ measurements and named it the “pit effect.” The numerical simulation is performed in 2-D space by the indirect boundary‐element method using the Green’s function for a homogeneous unbounded medium. The results show that the pit effect is a practical S‐wave generator vertical seismic profiling (VSP) and refraction surveys. The generation of a vertical downgoing S‐wave does not require any special machinery, so the pit effect can be used in many situations and especially in remote areas and difficult enviroments such as swamps and steep mountain ranges.
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Falcone, Gaetano, Gaetano Elia e Annamaria di Lernia. "Investigating the Influence of a Pre-Existing Shear Band on the Seismic Response of Ideal Step-like Slopes Subjected to Weak Motions: Preliminary Results". Geosciences 13, n.º 5 (15 de maio de 2023): 148. http://dx.doi.org/10.3390/geosciences13050148.
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The assessment of slope susceptibility to seismically-induced displacements receives wide attention in the geotechnical earthquake engineering field, but the alteration of the seismic wave inside the slope and at the ground surface due to the presence of a shear band confining a quiescent landslide body is rarely investigated. This paper describes the preliminary results of the numerical analysis of two step-like FE models, reproducing a gentle slope and steep cutting subjected to weak earthquakes, thus focusing on seismic wave amplification processes only. The results show that the higher the thickness of the weakened zone, the higher the maximum value of the amplification factors predicted at the ground surface. For gentle slopes affected by a landslide body confined by a thick shear band, the highest amplification factors are expected in the longer period range of 0.7–1.1 s, while the highest level of amplification is achieved in the intermediate period interval of 0.4–0.8 s in the case of steep slopes. In addition, the parasitic vertical component of acceleration can be considerably amplified beyond the crest and at the toe of the slope for increasing band thickness, especially in the case of steep topography, for which the effects of the shear band morphology enhance those related to the topographic profile. Finally, the fundamental frequency of the sloping deposit is not particularly affected by the presence of the shear band, while the amplitude of the amplification function at the fundamental frequency is clearly related to its thickness.
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Raffaini, Giuseppina. "Surface Chemistry, Crystal Structure, Size and Topography Role in the Albumin Adsorption Process on TiO2 Anatase Crystallographic Faces and Its 3D-Nanocrystal: A Molecular Dynamics Study". Coatings 11, n.º 4 (4 de abril de 2021): 420. http://dx.doi.org/10.3390/coatings11040420.
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TiO2 is widely used in biomaterial implants. The topography, chemical and structural properties of titania surfaces are an important aspect to study. The size of TiO2 nanoparticles synthetized by sol–gel method can influence the responses in the biological environment, and by using appropriate heat treatments different contents of different polymorphs can be formed. Protein adsorption is a crucial step for the biological responses, involving, in particular, albumin, the most abundant blood protein. In this theoretical work, using molecular mechanics and molecular dynamics methods, the adsorption process of an albumin subdomain is reported both onto specific different crystallographic faces of TiO2 anatase and also on its ideal three-dimensional nanosized crystal, using the simulation protocol proposed in my previous theoretical studies about the adsorption process on hydrophobic ordered graphene-like or hydrophilic amorphous polymeric surfaces. The different surface chemistry of anatase crystalline faces and the nanocrystal topography influence the adsorption process, in particular the interaction strength and protein fragment conformation, then its biological activity. This theoretical study can be a useful tool to better understand how the surface chemistry, crystal structure, size and topography play a key role in protein adsorption process onto anatase surface so widely used as biomaterial.
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Lin, Chunhui, Shiyang Tang, Linrang Zhang e Ping Guo. "Focusing High-Resolution Airborne SAR with Topography Variations Using an Extended BPA Based on a Time/Frequency Rotation Principle". Remote Sensing 10, n.º 8 (13 de agosto de 2018): 1275. http://dx.doi.org/10.3390/rs10081275.
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With the increasing requirement for resolution, the negligence of topography variations causes serious phase errors, which leads to the degradation of the focusing quality of the synthetic aperture (SAR) imagery, and geometric distortion. Hence, a precise and fast algorithm is necessary for high-resolution airborne SAR. In this paper, an extended back-projection (EBP) algorithm is proposed to compensate the phase errors caused by topography variations. Three-dimensional (3D) variation will be processed in the time-domain for high-resolution airborne SAR. Firstly, the quadratic phase error (QPE) brought by topography variations is analyzed in detail for high-resolution airborne SAR. Then, the key operation, a time-frequency rotation operation, is applied to decrease the samplings in the azimuth time-domain. Just like the time-frequency rotation of the conventional two-step approach, this key operation can compress data in an azimuth time-domain and it reduces the computational burden of the conventional back-projection algorithm, which is applied lastly in the time-domain processing. The results of the simulations validate that the proposed algorithm, including frequency-domain processing and time-domain processing can obtain good focusing performance. At the same time, it has strong practicability with a small amount of computation, compared with the conventional algorithm.
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Sasaki, Masayuki, Kentaro Tamura, Hirotaka Yamaguchi, Hirofumi Matsuhata, Kazutoshi Kojima e Makoto Kitabatake. "Observation of Damaged Layers in 4H-SiC Substrates by Mirror Projection Electron Microscope". Materials Science Forum 821-823 (junho de 2015): 285–88. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.285.
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Surface defects with scratch-like appearances are often observed locally on 4H-SiC wafers after epitaxial growth. We evaluated such damaged layer which is the cause of local step bunching using Mirror Projection Microscope (MPJ). As a result, MPJ can be detected l damaged layer which could not be detected using Synchrotron X-ray topography, even if these defects are extremely flat surface, no morphology, damaged layer is used to exist on the subsurface region. Thus, MPJ can be detected dislocation loops on the subsurface region of damage, it is effective to elucidate damaged layer of polishing process, MPJ is to be one of the candidates for inspection techniques of the damaged layer at substrate surface.
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Major, R., K. Maksymow, J. Marczak, J. M. Lackner, M. Kot e B. Major. "Migration channels produced by laser ablation for substrate endothelialization". Bulletin of the Polish Academy of Sciences: Technical Sciences 60, n.º 2 (1 de outubro de 2012): 337–42. http://dx.doi.org/10.2478/v10175-012-0045-2.
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Abstract. Seeding of cells on functional, biocompatible scaffolds is a crucial step in achievement the desired engineered tissue. In the present study, a pulsed laser modification onto inorganic substrate was made to promote endothelium cells migration and spread. Presented scaffolds were fabricated on carbon and titanium based coatings. Fabricated films provided very good mechanical properties together with a chemical stability preservation. The substrate modification consisted of grid-like template fabrication of micrometer size meshes. The microstructure analysis of laser traces revealed the grain size increase in the zone of laser beam interaction, which exerts an influence on a surface topography. Endothelium cells locomotion was observed within 10 day time period. As a result it was shown that the modified area enhanced cells adhesion with a preferred static behavior. The performed research work improved our understanding on the pulsed laser ablation process and template size influence on cells spatial arrangement. It constituted an important step towards fabrication of inorganic, biocompatible scaffolds for successful substrate endothelialization.
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Unnithan, S. L. Kesav, Basudev Biswal, Wendy Sharples, Christoph Rüdiger, Katayoon Bahramian e Jiawei Hou. "Sensitivity Analysis of Modelled Flood Inundation Extents over Hawkesbury–Nepean Catchment". Geosciences 13, n.º 3 (27 de fevereiro de 2023): 67. http://dx.doi.org/10.3390/geosciences13030067.
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Rainfall runoff and topography are among the major factors controlling the accuracy of modelled riverine inundation extents. We have evaluated the sensitivity of both these variables on a novel 1-D conceptual flood inundation model employing Height Above Nearest Drainage (HAND) thresholds within sub-catchment units called Reach Contributing Area (RCA). We examined the March 2021 flood extent over the Hawkesbury–Nepean Valley (HNV) with 0.05′ gridded runoff derived from the Australian Water Resources Assessment (AWRA) modelling framework. HAND thresholds were enforced within each RCA using rating curve relationships generated by a modelled river geometry dataset obtained from Jet Propulsion Laboratory (JPL) and by modelling Manning’s roughness coefficient as a function of channel slope. We found that the step-like topographic nature of HNV significantly influences the back-water effect within the floodplain. At the same time, the improved accuracy of the GeoFabric Digital Elevation Model (DEM) outperforms SRTM DEM-derived flood output. The precision of HAND thresholds does not add significant value to the analysis. With enhanced access to river bathymetry and an ensemble point-based runoff modelling approach, we can generate an ensemble runoff-based probabilistic extent of inundation.
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XUE, M. Q., G. H. NI, A. X. PAN e J. XU. "2D/2D HETEROSTRUCTURE OF FLOWER-LIKE MoS2 NANOSPHERES ANCHORED ON g-C3N4 NANOSHEETS FOR REDUCING FRICTION AND WEAR". Chalcogenide Letters 18, n.º 2 (fevereiro de 2021): 91–102. http://dx.doi.org/10.15251/cl.2021.182.91.
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Novel 2D/2D structural nanocomposites of g-C3N4/MoS2 with high tribological properties was fabricated through a facile one-step process. The tribological properties of the as-prepared g-C3N4/MoS2 as additives in the HVI500 base oil are evaluated by an UMT-2 multi-specimen tribo-tester and the topography of worn scars was obtained using a common SEM,which indicates the minimal friction coefficient (~0.10) and wear rate (3.86×10-5 mm3 /Nm) and demonstrate the accentuating improvement in reducing-friction and anti-wear properties. The enhanced tribological performance of base oil can be ascribed to the combination of g-C3N4 and spherical-like MoS2 to share the role of synergistic lubrication. More importantly, our work provides a fresh insight into designing lubricating oil additive and extending the 2D/2D structural nanocomposites.
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Yee, Andrew L., H. C. Ong, L. M. Stewart e R. P. H. Chang. "Development of flat, smooth (100) faceted diamond thin films using microwave plasma chemical vapor deposition". Journal of Materials Research 12, n.º 7 (julho de 1997): 1796–805. http://dx.doi.org/10.1557/jmr.1997.0248.
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A novel approach has been used to develop (100) faceted diamond films with flat, smooth surfaces. A morphological study of the early stages of growth behavior of (100) homoepitaxial films versus process temperature and methane percentage was carried out using atomic force microscopy. The results showed that spiral growth features and penetration twin density were dominant for growth conditions not well suited for (100) growth. Optimized process parameters were found to proceed via a step mechanism consistent with ledge growth on (2 × 1) reconstructed (100) diamond surfaces. These optimized conditions were then applied to growth of polycrystalline diamond on pretreated silicon substrates. A unique octahedral faceted film resulted, indicating strong preference for growth in the 〈100〉 direction. Scanning electron microscopy, x-ray diffraction, and Raman spectroscopy were used to assess film morphology, internal fiber texture, and carbon phase, respectively. A second stage growth step was used to flatten the surface topography to achieve the desired (100) flat tile-like morphology. This smooth (100) surface exhibited enhanced tribological performance compared to a typical randomly textured diamond film.
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Cooperrider, Kensy, James Slotta e Rafael Núñez. "The ups and downs of space and time: topography in Yupno language, culture, and cognition". Language and Cognition 14, n.º 1 (11 de janeiro de 2022): 131–59. http://dx.doi.org/10.1017/langcog.2021.25.
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AbstractMuch prior research has investigated how humans understand time using body-based contrasts like front/back and left/right. It has recently come to light, however, that some communities instead understand time using environment-based contrasts. Here, we present the richest portrait yet of one such case: the topographic system used by the Yupno of Papua New Guinea, in which the past is construed as downhill and the future as uphill. We first survey topographic concepts in Yupno language and culture, showing how they constitute a privileged resource for communicating about space. Next, we survey time concepts in Yupno, focusing on how topographic concepts are used to construe past, present, and future. We then illustrate how this topographic understanding of time comes to life in the words, hands, and minds of Yupno speakers. Drawing on informal interviews, we offer a view of the topographic system that goes beyond a community-level summary, and offers a glimpse of its individual-level and moment-to-moment texture. Finally, we step back to account for how this topographic understanding of time is embedded within a rich cognitive ecology of linguistic, cultural, gestural, and architectural practices. We close by discussing an elusive question: Why is the future uphill?
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del Río, María S., Lluís Raventós e Valentina Garza. "Zoning of the Querétaro wine region". BIO Web of Conferences 68 (2023): 01029. http://dx.doi.org/10.1051/bioconf/20236801029.
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Understanding the unique characteristics of wine regions, especially those that are developing or expanding like Querétaro, requires a key element known as terroir. In this regard, we have conducted a survey of 69 vineyards in the state, covering a total area of 525 hectares. Additionally, we have studied the composition and texture of the soils, analysed rainfall patterns over a span of 23 years, examined the topography and watershed basins, and compared common climate indices with those of other regions in Europe and the USA, such as Winkler, Huglin, Grown Season Temperature, and Cold Indices. As a next step, we are calculating various vegetation indices, such NDVI, for multiple vineyards throughout the year 2022 to assess the adaptability and development of different grape varieties, and determine which ones thrive best in the soil and climate conditions of the region.
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Kabraji, Sheheryar Kairas, Giorgio Gaglia, Danae Argyropoulou, Yang Dai, Shu Wang, Johann Bergholz, Shannon Coy et al. "Temporal and spatial topography of cell proliferation in cancer." Journal of Clinical Oncology 39, n.º 15_suppl (20 de maio de 2021): 3122. http://dx.doi.org/10.1200/jco.2021.39.15_suppl.3122.
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3122 Background: Tumors are complex ecosystems where exogenous and endogenous cues are integrated to either stimulate or inhibit cancer cell proliferation. However, the nature of these complex cell cycle states, their spatial organization, response to perturbation, and implications for clinical outcomes, are poorly characterized in tumor tissues. Methods: We used multiplexed tissue imaging to develop a robust classifier of proliferation, the multivariate proliferation index (MPI), using 513 unique tumors across five cancer types. Next, we used dimensionality reduction analysis to assess how the patterns of cell cycle protein expression in tumors were altered in response to perturbation. Results: The MPI outperforms single markers, like Ki67, when classifying proliferative index across diverse tumor types and reveals the proliferative architecture of tumors in situ. We find that proliferative and non-proliferative cancer cells are organized across microscopic (cell-to-cell) and macroscopic (tissue-level) scales. Both domains are reshaped by therapy, and local clusters of proliferative and non-proliferative tumor cells preferentially neighbor distinct tumor-infiltrating immune cells. We further phenotyped non-proliferating cancer cells using markers of quiescent cancer cells, cancer stem cells, and dormant cancer cells. We found that these types of non-proliferating cancer cells can occupy distinct regions within the same primary tumor. In high-dimensional marker space, populations of proliferative cancer cells express canonical patterns of cell cycle protein markers, a property we refer to as “cell cycle coherence”. Untreated tumors exist in a continuum of coherence states, ranging from optimal coherence, akin to freely cycling cells in culture, to reduced coherence characterized by either cell cycle polarization or non-canonical marker expression. Coherence can be stereotypically altered by induction and abrogation of mitogen signaling in a HER2-driven model of breast cancer. Cell cycle coherence is modulated by neoadjuvant therapy in patients with localized breast cancer, and coherence is associated with disease-free survival after adjuvant therapy in patients with colorectal cancer, mesothelioma and glioblastoma. Conclusions: The MPI robustly defines proliferating and non-proliferating cells in tissues, with immediate implications for clinical practice and research. The coherence metrics capture the diversity of post-treatment cell cycle states directly in clinical samples, a fundamental step in advancing precision medicine. More broadly, replacing binary metrics with multivariate traits provides a quantitative framework to study temporal processes from fixed static images and to investigate the rich spatial biology of human cancers.
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Zieger, S., J. Vinoth e I. R. Young. "Joint Calibration of Multiplatform Altimeter Measurements of Wind Speed and Wave Height over the Past 20 Years". Journal of Atmospheric and Oceanic Technology 26, n.º 12 (1 de dezembro de 2009): 2549–64. http://dx.doi.org/10.1175/2009jtecha1303.1.
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Abstract Since 1985, for a period of more than 23 yr, seven altimeter missions have provided global coverage of significant wave height and wind speed. This study undertakes a long-term analysis of the accuracy and stability of altimeter-derived values of significant wave height and wind speed from the following satellites: European Remote Sensing-1 (ERS-1), ERS-2, Environmental Satellite (Envisat), Geosat, Geosat Follow-On (GFO), Jason-1, and the Ocean Topography Experiment (TOPEX). This study is a necessary step in developing a quality-controlled and fully calibrated and validated dataset from the combined satellites. Calibration of all altimeters is performed against National Oceanographic Data Center (NODC) buoy data over the extended period. These calibrations are validated using intercomparisons between satellite missions at crossover ground points. This analysis shows that, for a number of the satellites, small “step like” changes occur during the missions. These inconsistencies are removed by subdividing these missions and undertaking a partial calibration for each section of the mission. The analysis also highlights that care is necessary when attempting to apply relationships between radar cross section and wind speed derived for one altimeter to other platforms. Before undertaking such steps, it is first necessary to apply a platform-specific radar cross-sectional offset to the data.
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Moskal, Grzegorz, Lucjan Swadźba, Wacław Supernak, Marta Mikuśkiewicz, Adrian Mościcki, Magdalena Jabłońska, Dawid Niemiec et al. "Microstructural Characterization of Silicide Coatings on Mo and TZM Alloy". Advanced Materials Research 1036 (outubro de 2014): 164–67. http://dx.doi.org/10.4028/www.scientific.net/amr.1036.164.
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Characterization of microstructure of silicide coatings obtained during diffusion process of pack cementation type was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloys as well. The coatings were deposited in out of pack process with three different times of exposure. The temperature of deposition process was constant. In first step the phases compositions of coatings was described by XRD analysis. In each cases the MoSi2 phase was obtained on top surface of the coatings. The morphology of the coatings was very similar as well. All types of coatings were characterized by network of cracks on top surface of the coatings. There was no influence of depositions time on phases constituent and coatings topography. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases. Basic differences was related to the thickness of coatings. All coatings were good quality without deep cracks. Microstructure was a columnar-like type without pores and voids.
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Ellinger, Andreas, Christian Woerner e Raimar Scherer. "Automatic Segmentation of Bulk Material Heaps Using Color, Texture, and Topography from Aerial Data and Deep Learning-Based Computer Vision". Remote Sensing 15, n.º 1 (30 de dezembro de 2022): 211. http://dx.doi.org/10.3390/rs15010211.
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This article proposes a novel approach to segment instances of bulk material heaps in aerial data using deep learning-based computer vision and transfer learning to automate material inventory procedures in the construction-, mining-, and material-handling industry. The proposed method uses information about color, texture, and surface topography as input features for a supervised computer vision algorithm. The approach neither relies on hand-crafted assumptions on the general shape of heaps, nor does it solely rely on surface material type recognition. Therefore, the method is able to (1) segment heaps with “atypical” shapes, (2) segment heaps that stand on a surface made of the same material as the heap itself, (3) segment individual heaps of the same material type that border each other, and (4) differentiate between artificial heaps and other objects of similar shape like natural hills. To utilize well-established segmentation algorithms for raster-grid-based data structures, this study proposes a pre-processing step to remove all overhanging occlusions from a 3D surface scan and convert it into a 2.5D raster format. Preliminary results demonstrate the general feasibility of the approach. The average F1 score computed on the test set was 0.70 regarding object detection and 0.90 regarding the pixelwise segmentation.
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Colombo, Pedro, Bernard Barnier, Thierry Penduff, Jérôme Chanut, Julie Deshayes, Jean-Marc Molines, Julien Le Sommer, Polina Verezemskaya, Sergey Gulev e Anne-Marie Treguier. "Representation of the Denmark Strait overflow in a <i>z</i>-coordinate eddying configuration of the NEMO (v3.6) ocean model: resolution and parameter impacts". Geoscientific Model Development 13, n.º 7 (30 de julho de 2020): 3347–71. http://dx.doi.org/10.5194/gmd-13-3347-2020.
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Abstract. We investigate in this paper the sensitivity of the representation of the Denmark Strait overflow produced by a regional z-coordinate configuration of NEMO (version 3.6) to the horizontal and vertical grid resolutions and to various numerical and physical parameters. Three different horizontal resolutions, 1∕12, 1∕36, and 1/60∘, are respectively used with 46, 75, 150, and 300 vertical levels. In the given numerical set-up, the increase in the vertical resolution did not bring improvement at eddy-permitting resolution (1/12∘). We find a greater dilution of the overflow as the number of vertical level increases, and the worst solution is the one with 300 vertical levels. It is found that when the local slope of the grid is weaker than the slope of the topography the result is a more diluted vein. Such a grid enhances the dilution of the plume in the ambient fluid and produces its thickening. Although the greater number of levels allows for a better resolution of the ageostrophic Ekman flow in the bottom layer, the final result also depends on how the local grid slope matches the topographic slope. We also find that for a fixed number of levels, the representation of the overflow is improved when horizontal resolution is increased to 1∕36 and 1/60∘, with the most drastic improvements being obtained with 150 levels. With such a number of vertical levels, the enhanced vertical mixing associated with the step-like representation of the topography remains limited to a thin bottom layer representing a minor portion of the overflow. Two major additional players contribute to the sinking of the overflow: the breaking of the overflow into boluses of dense water which contribute to spreading the overflow waters along the Greenland shelf and within the Irminger Basin, and the resolved vertical shear that results from the resolution of the bottom Ekman boundary layer dynamics. This improves the accuracy of the calculation of the entrainment by the turbulent kinetic energy mixing scheme (as it depends on the local shear) and improves the properties of the overflow waters such that they more favourably compare with observations. At 300 vertical levels the dilution is again increased for all horizontal resolutions. The impact on the overflow representation of many other numerical parameters was tested (momentum advection scheme, lateral friction, bottom boundary layer parameterization, closure parameterization, etc.), but none had a significant impact on the overflow representation.
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Mazina, Ainur, Dinara Syzdykova, Ainur Myrzhykbayeva, Gulnur Raikhanova e Aliya Nurgaliyeva. "Impact of Green Fiscal Policy on Investment Efficiency of Renewable Energy Enterprises in Kazakhstan". International Journal of Energy Economics and Policy 12, n.º 5 (27 de setembro de 2022): 491–97. http://dx.doi.org/10.32479/ijeep.13437.
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Years of industrialization and reliance on energies such as oil and coal have resulted in global pollution on an unprecedented scale. Carbon footprint, destruction of forests, melting away of ice caps in the North Pole, and climate change have persuaded many to adopt a more sustainable growth. In the wake of this catastrophe, “green” energy is a phenomenon that takes a step toward sustained development. Green energy consists of innovative and cost-effective ways to address the global consciousness by switching to renewable energy, water resources management, waste reduction, etc. Green Fiscal Policy aims to align prices and mobilize resources for climate change and sustainable development. Many developed and developing countries like Kazakhstan are taking the initiative towards zero carbon emission and renewable energy. The challenges of implementing the required policies include overcoming the barriers of the status quo to establish a new Geo-political and economic system in Kazakhstan. Political and economic challenges persist despite its vision for 2050 that Green Economy influences. This report focuses on Kazakhstan's natural resources, topography, and renewable energy enterprises. The Green Fiscal Policy is closely examined over Kazakhstan's current investment efficiency scenario.
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Song, Chao, Tariq Alkhalifah e Umair Bin Waheed. "A versatile framework to solve the Helmholtz equation using physics-informed neural networks". Geophysical Journal International 228, n.º 3 (23 de outubro de 2021): 1750–62. http://dx.doi.org/10.1093/gji/ggab434.
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SUMMARY Solving the wave equation to obtain wavefield solutions is an essential step in illuminating the subsurface using seismic imaging and waveform inversion methods. Here, we utilize a recently introduced machine-learning based framework called physics-informed neural networks (PINNs) to solve the frequency-domain wave equation, which is also referred to as the Helmholtz equation, for isotropic and anisotropic media. Like functions, PINNs are formed by using a fully connected neural network (NN) to provide the wavefield solution at spatial points in the domain of interest, in which the coordinates of the point form the input to the network. We train such a network by backpropagating the misfit in the wave equation for the output wavefield values and their derivatives for many points in the model space. Generally, a hyperbolic tangent activation is used with PINNs, however, we use an adaptive sinusoidal activation function to optimize the training process. Numerical results show that PINNs with adaptive sinusoidal activation functions are able to generate frequency-domain wavefield solutions that satisfy wave equations. We also show the flexibility and versatility of the proposed method for various media, including anisotropy, and for models with strong irregular topography.
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Salka, Nabeel, e John A. Grant. "Contralateral Lateral Femoral Condyle Allografts Provide an Acceptable Surface Match for Simulated Classic Osteochondritis Dissecans Lesions of the Medial Femoral Condyle". Orthopaedic Journal of Sports Medicine 6, n.º 7_suppl4 (1 de julho de 2018): 2325967118S0013. http://dx.doi.org/10.1177/2325967118s00136.
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Objectives: The purpose of this study was to determine whether contralateral lateral femoral condyle (LFC) allografts can provide an acceptable surface topography match for classic osteochondritis dessicans (OCD) lesions of the medial femoral condyle (MFC). Achievement of an acceptable donor-recipient articular surface match (1 mm deviation) has been associated with physiological joint stresses and predictably positive clinical outcomes. It was hypothesized that LFC and MFC allografts would show no differences in step-off height or surface deviation in all four quadrants of the graft. Methods: ample size calculation suggested ten groups of fresh frozen size-matched human condyles, each group consisting of a donor MFC, donor LFC, and recipient MFC. A 20 mm circular osteochondral “defect” simulating a “classic” OCD lesion was created in the recipient MFC. Its most anterior position was 1 cm posterior and 1 cm medial to the roof of the intercondylar notch. A randomly selected donor MFC or LFC plug was then harvested and transplanted using standard procedure (Fig 1A). The transplanted condyle was scanned with nano-CT, reconstructed (Fig 1B), registered to an initial scan of the recipient MFC, and processed with a custom MATLAB program to determine the surface root mean squared deviation (dRMS) between the native and donor surfaces (Fig 1C), percent area unacceptably proud (>1 mm; %Aproud) and sunken (<-1 mm; %Asunk). Scans were uploaded into DragonFly software where step-off height (hRMS), percent circumference unacceptably proud (>1 mm; %Cproud) and sunken (< -1 mm; %Csunk) were measured (Fig 1D). The process was then repeated for the other allograft plug. Two-way mixed ANOVAs with Sidak corrections for multiple comparisons (α=0.05) were used. Exempt status was obtained from the University’s IRB. Results: Both MFC and LFC plugs showed acceptable step-off heights in all four quadrants. Neither allograft type nor location within the defect had a main effect on step-off height (hRMS). In general, plugs were more unacceptably sunken than proud, though no differences in %Csunk were seen between allograft types or locations within the defect. In LFC plugs, %Cproud was significantly greater laterally (by the intercondylar notch) compared to all other locations around the plug (p<0.0001), while no differences were seen based on location in MFC plugs. The cartilage surface deviationn (dRMS), %Aproud, and %Asunk were not significantly affected by allograft type or location (Table 1). Conclusion: Previous studies demonstrated that contralateral LFCs provide acceptable surface topography matches for centrally located defects of the MFC. In evaluating the utility of LFC allografts for more laterally located lesions characteristic of OCD, it was found that, similarly, allograft type does not have an effect on surface deviation or step-off height. With comparable surface deviations, both MFC and LFC allografts can be expected to present similar stresses on the knee joint and achieve predictably positive clinical outcomes, thus improving donor availability and reducing surgical wait times for matches. LFC plugs did not differ from MFC plugs in overall %Aproud, %Asunk, %Cproud, or %Csunk suggesting that well placed LFC plugs, like MFC plugs, may result in few post-surgical complications. Higher step-off heights of LFC plugs near the intercondylar notch may contribute to higher joint stresses and may serve as an area of focus in future studies. [Figure: see text][Table: see text]
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Mandlburger, G., C. Hauer, B. Höfle, H. Habersack e N. Pfeifer. "Optimisation of LiDAR derived terrain models for river flow modelling". Hydrology and Earth System Sciences Discussions 5, n.º 6 (16 de dezembro de 2008): 3605–38. http://dx.doi.org/10.5194/hessd-5-3605-2008.
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Abstract. Airborne LiDAR (Light Detection And Ranging) combines cost efficiency, high degree of automation, high point density of typically 1–10 points per m2 and height accuracy of better than ±15 cm. For all these reasons LiDAR is particularly suitable for deriving precise Digital Terrain Models (DTM) as geometric basis for hydrodynamic-numerical (HN) simulations. The application of LiDAR for river flow modelling requires a series of preprocessing steps. Terrain points have to be filtered and merged with river bed data, e.g. from echo sounding. Then, a smooth Digital Terrain Model of the Watercourse (DTM-W) needs to be derived, preferably considering the random measurement error during surface interpolation. In a subsequent step, a hydraulic computation mesh has to be constructed. Hydraulic simulation software is often restricted to a limited number of nodes and elements, thus, data reduction and data conditioning of the high resolution LiDAR DTM-W becomes necessary. We will present a DTM thinning approach based on adaptive TIN refinement which allows a very effective compression of the point data (more than 95% in flood plains and up to 90% in steep areas) while preserving the most relevant topographic features (height tolerance ±20 cm). Traditional hydraulic mesh generators focus primarily on physical aspects of the computation grid like aspect ratio, expansion ratio and angle criterion. They often neglect the detailed shape of the topography as provided by LiDAR data. In contrast, our approach considers both the high geometric resolution of the LiDAR data and additional mesh quality parameters. It will be shown that the modelling results (flood extents, flow velocities, etc.) can vary remarkably by the availability of surface details. Thus, the inclusion of such geometric details in the hydraulic computation meshes will gain importance for river flow modelling in the future.
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Mandlburger, G., C. Hauer, B. Höfle, H. Habersack e N. Pfeifer. "Optimisation of LiDAR derived terrain models for river flow modelling". Hydrology and Earth System Sciences 13, n.º 8 (14 de agosto de 2009): 1453–66. http://dx.doi.org/10.5194/hess-13-1453-2009.
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Abstract. Airborne LiDAR (Light Detection And Ranging) combines cost efficiency, high degree of automation, high point density of typically 1–10 points per m2 and height accuracy of better than ±15 cm. For all these reasons LiDAR is particularly suitable for deriving precise Digital Terrain Models (DTM) as geometric basis for hydrodynamic-numerical (HN) simulations. The application of LiDAR for river flow modelling requires a series of preprocessing steps. Terrain points have to be filtered and merged with river bed data, e.g. from echo sounding. Then, a smooth Digital Terrain Model of the Watercourse (DTM-W) needs to be derived, preferably considering the random measurement error during surface interpolation. In a subsequent step, a hydraulic computation mesh has to be constructed. Hydraulic simulation software is often restricted to a limited number of nodes and elements, thus, data reduction and data conditioning of the high resolution LiDAR DTM-W becomes necessary. We will present a DTM thinning approach based on adaptive TIN refinement which allows a very effective compression of the point data (more than 95% in flood plains and up to 90% in steep areas) while preserving the most relevant topographic features (height tolerance ±20 cm). Traditional hydraulic mesh generators focus primarily on physical aspects of the computation grid like aspect ratio, expansion ratio and angle criterion. They often neglect the detailed shape of the topography as provided by LiDAR data. In contrast, our approach considers both the high geometric resolution of the LiDAR data and additional mesh quality parameters. It will be shown that the modelling results (flood extents, flow velocities, etc.) can vary remarkably by the availability of surface details. Thus, the inclusion of such geometric details in the hydraulic computation meshes is gaining importance in river flow modelling.
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Ogura, Naotaka, Michael B. Berger, Pavan Srivas, Sunghwan Hwang, Jiaqi Li, David Joshua Cohen, Zvi Schwartz, Barbara D. Boyan e Kenneth H. Sandhage. "Tailoring of TiAl6V4 Surface Nanostructure for Enhanced In Vitro Osteoblast Response via Gas/Solid (Non-Line-of-Sight) Oxidation/Reduction Reactions". Biomimetics 7, n.º 3 (25 de agosto de 2022): 117. http://dx.doi.org/10.3390/biomimetics7030117.
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An aging global population is accelerating the need for better, longer-lasting orthopaedic and dental implants. Additive manufacturing can provide patient-specific, titanium-alloy-based implants with tailored, three-dimensional, bone-like architecture. Studies using two-dimensional substrates have demonstrated that osteoblastic differentiation of bone marrow stromal cells (MSCs) is enhanced on surfaces possessing hierarchical macro/micro/nano-scale roughness that mimics the topography of osteoclast resorption pits on the bone surface. Conventional machined implants with these surfaces exhibit successful osseointegration, but the complex architectures produced by 3D printing make consistent nanoscale surface texturing difficult to achieve, and current line-of-sight methods used to roughen titanium alloy surfaces cannot reach all internal surfaces. Here, we demonstrate a new, non-line-of-sight, gas/solid-reaction-based process capable of generating well-controlled nanotopographies on all open (gas-exposed) surfaces of titanium alloy implants. Dense 3D-printed titanium-aluminum-vanadium (TiAl6V4) substrates were used to evaluate the evolution of surface nanostructure for development of this process. Substrates were either polished to be smooth (for easier evaluation of surface nanostructure evolution) or grit-blasted and acid-etched to present a microrough biomimetic topography. An ultrathin (90 ± 16 nm) conformal, titania-based surface layer was first formed by thermal oxidation (600 °C, 6 h, air). A calciothermic reduction (CaR) reaction (700 °C, 1 h) was then used to convert the surface titania (TiO2) into thin layers of calcia (CaO, 77 ± 16 nm) and titanium (Ti, 51 ± 20 nm). Selective dissolution of the CaO layer (3 M acetic acid, 40 min) then yielded a thin nanoporous/nanorough Ti-based surface layer. The changes in surface nanostructure/chemistry after each step were confirmed by scanning and transmission electron microscopies with energy-dispersive X-ray analysis, X-ray diffraction, selected area electron diffraction, atomic force microscopy, and mass change analyses. In vitro studies indicated that human MSCs on CaR-modified microrough surfaces exhibited increased protein expression associated with osteoblast differentiation and promoted osteogenesis compared to unmodified microrough surfaces (increases of 387% in osteopontin, 210% in osteocalcin, 282% in bone morphogenic protein 2, 150% in bone morphogenic protein 4, 265% in osteoprotegerin, and 191% in vascular endothelial growth factor). This work suggests that this CaR-based technique can provide biomimetic topography on all biologically facing surfaces of complex, porous, additively manufactured TiAl6V4 implants.
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Agrawal, Animesh, Bae Hoon Lee, Scott A. Irvine, Jia An, Ramya Bhuthalingam, Vaishali Singh, Kok Yao Low, Chee Kai Chua e Subbu S. Venkatraman. "Smooth Muscle Cell Alignment and Phenotype Control by Melt Spun Polycaprolactone Fibers for Seeding of Tissue Engineered Blood Vessels". International Journal of Biomaterials 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/434876.
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A method has been developed to induce and retain a contractile phenotype for vascular smooth muscle cells, as the first step towards the development of a biomimetic blood vessel construct with minimal compliance mismatch. Melt spun PCL fibers were deposited on a mandrel to form aligned fibers of 10 μm in diameter. The fibers were bonded into aligned arrangement through dip coating in chitosan solution. This formed a surface of parallel grooves, 10 μm deep by 10 μm across, presenting a surface layer of chitosan to promote cell surface interactions. The aligned fiber surface was used to culture cells present in the vascular wall, in particular fibroblasts and smooth muscle cells. This topography induced “surface guidance” over the orientation of the cells, which adopted an elongated spindle-like morphology, whereas cells on the unpatterned control surface did not show such orientation, assuming more rhomboid shapes. The preservation of VSMC contractile phenotype on the aligned scaffold was demonstrated by the retention ofα-SMA expression after several days of culture. The effect was assessed on a prototype vascular graft prosthesis fabricated from polylactide caprolactone; VSMCs aligned longitudinally along a fiberless tube, whereas, for the aligned fiber coated tubes, the VSMCs aligned in the required circumferential orientation.
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Chunglok, Aoythip, Nantakan Muensit e Chalongrat Daengngam. "Extreme Wetting-Resistant Multiscale Nano-/Microstructured Surfaces for Viscoelastic Liquid Repellence". Journal of Nanomaterials 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/9510156.
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We demonstrate exceptional wetting-resistant surfaces capable of repelling low surface tension, non-Newtonian, and highly viscoelastic liquids. Theoretical analysis and experimental result confirm that a higher level of multiscale roughness topography composed of at least three structural length scales, ranging from nanometer to supermicron sizes, is crucial for the reduction of liquid-solid adhesion hysteresis. With Cassie-Baxter nonwetting state satisfied at all roughness length scales, the surface has been proven to effectively repel even highly adhesive liquid. Practically, this high-level hierarchical structure can be achieved through fractal-like structures of silica aggregates induced by siloxane oligomer interparticle bridges. The induced aggregation and surface functionalization of the silica particles can be performed simultaneously within a single reaction step, by utilizing trifunctional fluoroalkylsilane precursors that largely form a disordered fluoroalkylsiloxane grafting layer under the presence of sufficient native moisture preadsorbed at the silica surface. Spray-coating deposition of a particle surface layer on a precoated primer layer ensures facile processability and scalability of the fabrication method. The resulting low-surface-energy multiscale roughness exhibits outstanding liquid repellent properties, generating equivalent lotus effect for highly viscous and adhesive natural latex concentrate, with apparent contact angles greater than 160°, and very small roll-off angles of less than 3°.
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Li, Yinan, Markus Kästner e Eduard Reithmeier. "Optimization of the GPU-based data evaluation for the low coherence interferometry". tm - Technisches Messen 85, n.º 11 (27 de novembro de 2018): 680–90. http://dx.doi.org/10.1515/teme-2017-0091.
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Abstract Optical interferometers as non-contact measurement devices are very desirable for the measurement of surface roughness and topography. Compared to phase shifting interferometers (PSIs) with a limited measurement range and a scan step of maximum λ/4, the optical interferometers like low coherence interferometers (LCIs) evaluating the degree of fringe coherence allow a larger vertical measurement range. Their vertical measurement range is only limited by the scan length allowed by the linear piezo stage and the coherence length of the light source. To evaluate the obtained data for a large range, the common LCIs require much computation time. To overcome this drawback, we present an evaluation algorithm based on the Hilbert-Transform and curve fitting (Levenberg–Marquardt algorithm) using Compute Unified Device Architecture (CUDA) technology, which allows parallel and independent data evaluation on General Purpose Graphics Processing Unit (GPGPU). Firstly, the evaluation algorithm is implemented and tested on an in-house developed LCI, which is based on Michelson configurations. Furthermore, we focus on the performance optimization of the GPU-based program using the different approaches to further achieve efficient and accurate massive parallel computing. Finally, the performance comparison for evaluating measurement data using different approaches is discussed in this paper.
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Pothineni, Bhanu K., Sabrina Kollmann, Xinyang Li, Guido Grundmeier, Denise J. Erb e Adrian Keller. "Adsorption of Ferritin at Nanofaceted Al2O3 Surfaces". International Journal of Molecular Sciences 24, n.º 16 (15 de agosto de 2023): 12808. http://dx.doi.org/10.3390/ijms241612808.
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The influence of nanoscale surface topography on protein adsorption is highly important for numerous applications in medicine and technology. Herein, ferritin adsorption at flat and nanofaceted, single-crystalline Al2O3 surfaces is investigated using atomic force microscopy and X-ray photoelectron spectroscopy. The nanofaceted surfaces are generated by the thermal annealing of Al2O3 wafers at temperatures above 1000 °C, which leads to the formation of faceted saw-tooth-like surface topographies with periodicities of about 160 nm and amplitudes of about 15 nm. Ferritin adsorption at these nanofaceted surfaces is notably suppressed compared to the flat surface at a concentration of 10 mg/mL, which is attributed to lower adsorption affinities of the newly formed facets. Consequently, adsorption is restricted mostly to the pattern grooves, where the proteins can maximize their contact area with the surface. However, this effect depends on the protein concentration, with an inverse trend being observed at 30 mg/mL. Furthermore, different ferritin adsorption behavior is observed at topographically similar nanofacet patterns fabricated at different annealing temperatures and attributed to different step and kink densities. These results demonstrate that while protein adsorption at solid surfaces can be notably affected by nanofacet patterns, fine-tuning protein adsorption in this way requires the precise control of facet properties.
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Mcintyre, N. F. "The Dynamics of Ice-Sheet Outlets". Journal of Glaciology 31, n.º 108 (1985): 99–107. http://dx.doi.org/10.1017/s0022143000006328.
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AbstractA comparison of data from aircraft altimetry, Landsat imagery, and radia echo-sounding has shown characteristic surface topographies associated with sheet and stream flow. The transition between the two is abrupt and occurs at a step in the subglacial topography. This marks the onset of basal sliding and high velocities caused by subglacial water; it results in crevassed amphitheatre-like basins round the head of outlet glaciers. It is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase. This abrupt transition appears to be topographically controlled since basal temperatures are at the pressure-melting point well inland of the change in regime. The Marie Byrd Land ice streams exhibit qualitative differences from other ice-sheet outlets, however; the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland. Such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice. The repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers. Acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable. Rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion. This is concentrated towards the heads of outlet glaciers up-stream of the region where significant basal decoupling occurs. This may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls.
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Mcintyre, N. F. "The Dynamics of Ice-Sheet Outlets". Journal of Glaciology 31, n.º 108 (1985): 99–107. http://dx.doi.org/10.3189/s0022143000006328.
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AbstractA comparison of data from aircraft altimetry, Landsat imagery, and radia echo-sounding has shown characteristic surface topographies associated with sheet and stream flow. The transition between the two is abrupt and occurs at a step in the subglacial topography. This marks the onset of basal sliding and high velocities caused by subglacial water; it results in crevassed amphitheatre-like basins round the head of outlet glaciers. It is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase. This abrupt transition appears to be topographically controlled since basal temperatures are at the pressure-melting point well inland of the change in regime. The Marie Byrd Land ice streams exhibit qualitative differences from other ice-sheet outlets, however; the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland. Such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice. The repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers. Acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable. Rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion. This is concentrated towards the heads of outlet glaciers up-stream of the region where significant basal decoupling occurs. This may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls.
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Doser, Diane I., e Mark R. Baker. "Geophysical Reconnaissance for Siting Dryland Critical-Zone Monitoring Experiments in Southern New Mexico, USA". Journal of Environmental and Engineering Geophysics 26, n.º 4 (dezembro de 2021): 255–66. http://dx.doi.org/10.32389/jeeg21-022.
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A dryland critical-zone observatory is planned on a piedmont setting of the Jornada Experimental Range northeast of Las Cruces, New Mexico, near a ∼10-yr eddy flux covariance tower and vegetation monitoring experiment and a 2-yr old water-uptake rainfall infiltration experiment. We carried out several geophysical surveys to help select sites that minimize geologic complexity for follow up hydrologic and biogeochemical studies that will be conducted by other researchers. First, we conducted a review of regional topography, gravity, and magnetics prior to a site visit and then collected reconnaissance magnetic and electromagnetic data to aid in planning more detailed geophysical site characterization surveys. Our initial topographic analysis using 1/3 arc-second digital elevation models (DEMs) showed the proposed area had an out-of-equilibrium curvature pointing to active erosion and possible faulting. Short-wavelength step-like topographic anomalies in the DEMs were confirmed in LiDAR elevations, and are consistent with erosionally resistant soil horizons in the old alluvial fan deposits. Comparison of 2-D density and susceptibility models based on nearby (3-8 km) hydrostratigraphic studies established that the observed regional gravity and magnetic anomalies were larger than could be modeled with the 2-D structural constraints, and established the station spacing our reconnaissance surveys would require to sample shallow soil variations. Our first site visit confirmed the general fault locations and we identified three outcropping caliche horizons distinct to alluvial channel, proximal splay and distal splay deposits in a several hundred-meter traverse that are consistent with the short-wavelength topographic features. In order to plan additional seismic, radar, gravity, and electrical surveys within a region of such high potential variability, we collected magnetic field and magnetic susceptibility measurements along two profiles at 10-50 m spacing. We found anomalies consistent with two projected faults, as well as other bedrock structures, a result significantly more complex than prior regional hydrostratigraphic mapping had suggested. We also conducted a more limited 0.5 km long ground conductivity survey with 5 m spacing that traversed the rainfall infiltration experiment site and found anomalies that aligned with one of the projected faults. The results showed deep (>6 m) 50 mS/m (milliSiemens/meter) values, indicating moister soils, on the footwall side, dropping to 20 mS/m after crossing the fault, consistent with previous observations that normal faults in the Rio Grande Valley asymmetrically influence fluid flow.
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Nakano, Takayoshi, Aira Matsugaki, Takuya Ishimoto, Mitsuharu Todai, Ai Serizawa, Ryoichi Suetoshi, Yoshihiro Noyama e Wataru Fujitani. "Control of Oriented Extracellular Matrix Similar to Anisotropic Bone Microstructure". Materials Science Forum 783-786 (maio de 2014): 72–77. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.72.
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Bone microstructure is dominantly composed of anisotropic extracellular matrix (ECM) in which collagen fibers and epitaxially-oriented biological apatite (BAp) crystals are preferentially aligned depending on the bone anatomical position, resulting in exerting appropriate mechanical function. The regenerative bone in bony defects is however produced without the preferential alignment of collagen fibers and the c-axis of BAp crystals, and subsequently reproduced to recover toward intact alignment. Thus, it is necessary to produce the anisotropic bone-mimetic tissue for the quick recovery of original bone tissue and the related mechanical ability in the early stage of bone regeneration. Our group is focusing on the methodology for regulating the arrangement of bone cells, the following secretion of collagen and the self-assembled mineralization by oriented BAp crystallites. Cyclic stretching in vitro to bone cells, principal-stress loading in vivo on scaffolds, step formation by slip traces on Ti single crystal, surface modification by laser induced periodic surface structure (LIPSS), anisotropic collagen substrate with the different degree of orientation, etc. can dominate bone cell arrangement and lead to the construction of the oriented ECM similar to the bone tissue architecture. This suggests that stress/strain loading, surface topography and chemical anisotropy are useful to produce bone-like microstructure in order to promote the regeneration of anisotropic bone tissue and to understand the controlling parameters for anisotropic osteogenesis induction.
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Waegner, Martin, Mathias Schröder, Gunnar Suchaneck, Heinz Sturm, Christiane Weimann, Lukas M. Eng e Gerald Gerlach. "Domain Formation in Nano-patterned PZT Thin Films". MRS Proceedings 1454 (2012): 267–72. http://dx.doi.org/10.1557/opl.2012.1230.
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ABSTRACTIn this work, reactive magnetron-sputtered Pb(Zr,Ti)O3thin films were used to fabricate well-ordered nanodot arrays by means of nanosphere lithography (NSL). NSL is based on a two-step etch process by means of, firstly adjusting the diameter of polystyrene spheres in the self-assembled polymeric nanosphere mask using reactive ion etching, and secondly transferring the mask to the substrate by ion milling with adjusted heights. Hence, structures with different aspect ratios can be fabricated.Piezoresponse force microscopy was used as the inspection tool on both non-patterned and patterned films. Both the topography and polarization out of plane and in plane was deduced in this mode. Grains of nanodots with low aspect ratio form domain structures comparable to domains in non-patterned films. In contrast to that, nanodots with a higher aspect ratio form particular structures. The in-plane amplitude images show mostly a bisectioned domain assembly, while the out-of-plane amplitude images show in some cases more complex structures like “c”-shaped domains or multi-domains around a center domain.The patterning of the ferroelectric material was shown to affect the formation of ferroelectric domains. The initial polycrystalline, randomly-ordered films are re-oriented and show domain structures depending on nanodisc diameter and aspect ratio. This may enable tailoring of ferroelectric materials in their piezoelectric and pyroelectric properties by patterning.
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Wopelka, Thomas, Ulrike Cihak-Bayr, Claudia Lenauer, Ferenc Ditrói, Sándor Takács, Johannes Sequard-Base e Martin Jech. "Wear of different material pairings for the cylinder liner – piston ring contact". Industrial Lubrication and Tribology 70, n.º 4 (8 de maio de 2018): 687–99. http://dx.doi.org/10.1108/ilt-07-2017-0218.
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Purpose This paper aims to investigate the wear behaviour of different materials for cylinder liners and piston rings in a linear reciprocating tribometer with special focus on the wear of the cylinder liner in the boundary lubrication regime. Design/methodology/approach Conventional nitrided steel, as well as diamond-like carbon and chromium nitride-coated piston rings, were tested against cast iron, AlSi and Fe-coated AlSi cylinder liners. The experiments were carried out with samples produced from original engine parts to have the original surface topography available. Radioactive tracer isotopes were used to measure cylinder liner wear continuously, enabling separation of running-in and steady-state wear. Findings A ranking of the material pairings with respect to wear behaviour of the cylinder liner was found. Post-test inspection of the cylinder samples by scanning electron microscopy (SEM) revealed differences in the wear mechanisms for the different material combinations. The results show that the running-in and steady-state wear of the liners can be reduced by choosing the appropriate material for the piston ring. Originality/value The use of original engine parts in a closely controlled tribometer environment under realistic loading conditions, in conjunction with continuous and highly sensitive wear measurement methods and a detailed SEM analysis of the wear mechanisms, forms an intermediate step between engine testing and laboratory environment testing.
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Quissek, Max, e Thomas Lauer. "Impact of Surface Roughness on the Impingement of Urea–Water Solution Droplets". Fluids 8, n.º 5 (12 de maio de 2023): 152. http://dx.doi.org/10.3390/fluids8050152.
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The understanding of impingement processes is crucial for optimizing automotive selective catalytic reduction (SCR) systems. An accurate description of this behavior helps design exhaust systems and increases the validity of modeling approaches. A component test bench was set up, featuring a droplet chain generator for producing droplet sizes typically found in the urea–water solution sprays of SCR systems. A heatable impingement plate with an interchangeable surface enabled investigation of the influence of surface roughness. Data were acquired using a high-speed camera and image postprocessing. The droplet–wall interaction could be described using different regimes. An approach to characterizing impingement behavior based on weighted-regime superposition enabled gradual transitions between regimes, instead of step-like changes. It was observed that the surface roughness increased the droplet–solid contact area and generated thermal-induced secondary droplets at lower temperatures. A region of enhanced mechanical disintegration of the droplet was found, caused by peaks of the surface shearing off parts of the droplet. The probability of a droplet rebounding from the wall was reduced on a rough surface, due to the interference of the surface spikes with the droplet’s spreading and contracting motion. Additionally, the influence of surface topography was investigated using a shot-peened surface. Caused by this surface’s reduced root mean square slope, the aforementioned enhancement of mechanical disintegration was not observed.
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Krakow, William. "The Structure of Thin Gold Films at the Early Stage of Continuous Film Growth". Proceedings, annual meeting, Electron Microscopy Society of America 48, n.º 1 (12 de agosto de 1990): 18–19. http://dx.doi.org/10.1017/s0424820100178847.
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The use of a transmission electron microscope to observe surface structure of thin films has been demonstrated in recent years by diffraction contrast imaging to ∼ 10Å resolution using the forbidden reflections of [111] Au and at atomic resolution using bright-field phase contrast on both [001] and [111] oriented Au films. It has also been possible to demonstrate that beyond a minimum thickness, these films can be free standing and viewed in the microscope without significant modification due to the incident electron beam generating sputtering events at high beam currents. It is therefore now possible to obtain free standing [001] Au films which exhibit various types of surface topography. These films were obtained by varying the growth parameters with a microprocessor controller attached to a UHV deposition system. The deposition of Au was precisely controlled onto a thick Ag substrate which was initially deposited upon NaCl single crystals.Fig. 1 shows a low magnification image ∼ 40Å thick [001] Au film grown at a vacuum level of 5 × 10-9 Torr, 50° substrate temperature and a deposition rate of ∼ 1/20 ML/sec. Clearly defined atomic step regions are visible as demonstrated by the terrace-like contrast variations over extended regions i.e. a step-ledge growth regime. Regions between these terrace areas represent coalescence of individual grains which were not attached at an earlier stage of growth. These regions exhibit finer scale terraces and ledges which follow either <100> or <110> directions as evidenced by comparing their directions to stacking faults and twins occasionally observed in the field of view. Small holes are also present which have crystallographic edge facets and anomalous contrast bands also occur which represent the lack of tracking of the upper surface layer growth to steps which exist at the lower surface. Fig. 1 was obtained by diffraction contrast from the direct beam alone. It was not necessary to use the forbidden reflections here since they produced too drastic a contrast change.
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Panidi, E., K. Popova e V. Tsepelev. "GIS-BASED MAPPING OF ESTIMATED FLOOD INUNDATION AREA, GEOMETRICAL ASPECT". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W8 (22 de agosto de 2019): 307–9. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w8-307-2019.
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<p><strong>Abstract.</strong> A full processing chain for inundation modelling/mapping is implemented in different specialised software like HEC-RAS or Flood Modeller. Alternatively, inundation water level can be estimated separately, and then can be mapped in desktop (universal) Geographic Information System (GIS) software. Last approach can be demanded in a complex already-formed GIS-based mapping processing chains, when inundation area mapping appears only as a step of analysis and mapping technology. This context is usual for cadastral accounting of inundation areas. However, such a processing chain have a lack of computation tools, as currently used desktop GISs (e.g., QGIS, ArcGIS, etc.) capable originally to map only a lake-type inundation areas (certainly, in the case of regular software assembly), while along-the-river inundation should have water surface sloping along the river body.</p> <p>Addressing to the filling the gap of along-the-river inundation mapping in desktop GIS software, we have developed an approach to mapping of river-type inundation area, and implemented it in a test mode to support cadastral accounting of river flood inundation areas. The approach is based upon geometrical modelling of the water surface only, and is not concerned with consideration of hydrogeological conditions and ground water regime. Being simplified, this technique may be rough tool for the cases when hydrogeological aspect have to be respected, however it is simple for implementation and is useful when estimating topography impact only.</p>
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Broughton, Paul L. "Alignment of fluvio-tidal point bars in the middle McMurray Formation: implications for structural architecture of the Lower Cretaceous Athabasca Oil Sands Deposit, northern Alberta". Canadian Journal of Earth Sciences 53, n.º 9 (setembro de 2016): 896–930. http://dx.doi.org/10.1139/cjes-2015-0137.
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The northern Athabasca Oil Sands Deposit accumulated on sub-Cretaceous structure partially configured by multistage pre-Cretaceous salt dissolutions in Prairie Evaporite (Middle Devonian) substrate that continued concurrent with deposition of McMurray Formation (Aptian) strata. Dissolution fronts only 250 m below advanced along NW- and NE-oriented fracture–fault lineaments that coalesced into larger salt removal areas. This structural grain was transmitted to the overlying dissected Upper Devonian karst topography draped by lower McMurray braided rivers along a lattice-like channel network. The dominant NW structural grain continued during middle McMurray deposition, with fluvial-estuarine point bars aligned along subparallel tidal channels. Regional salt removal fronts concurrent with middle McMurray deposition migrated north of the Bitumount Trough, resulting in the 200 km2 central collapse. The northern Athabasca Deposit area was configured as a funnel-shaped lower estuary structure consisting of aligned Upper Devonian – lower McMurray fault block terraces that stepped down northward into the central collapse. Sinuous river channels of the upper estuary, constrained along stable substrate of the main paleovalley, flowed northward onto the unstable floor of this funnel-form lower estuary. The main paleovalley fairway branched into multiple tens of kilometres long subparallel fluvio-estuarine tidal channels aligned parallel to the NW structural grain. Sand transport fairways cascaded over the step-down terraces and permitted aggradations of overlying fluvio-tidal point bars to accumulate into giant commercially attractive sand complexes. The internal architecture of these tens of metres thick sand deposits included deposit-wide erosion surfaces resulting from cycles of collapse–subsidence, stabilized substrate and erosion, and renewed subsidence and aggradation.
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Madden, Ian, Simone Marras e Jenny Suckale. "Leveraging Google's Tensor Processing Units for tsunami-risk mitigation planning in the Pacific Northwest and beyond". Geoscientific Model Development 16, n.º 12 (27 de junho de 2023): 3479–500. http://dx.doi.org/10.5194/gmd-16-3479-2023.
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Abstract. Tsunami-risk mitigation planning has particular importance for communities like those of the Pacific Northwest, where coastlines are extremely dynamic and a seismically active subduction zone looms large. The challenge does not stop here for risk managers: mitigation options have multiplied since communities have realized the viability and benefits of nature-based solutions. To identify suitable mitigation options for their community, risk managers need the ability to rapidly evaluate several different options through fast and accessible tsunami models, but they may lack high-performance computing infrastructure. The goal of this work is to leverage Google's Tensor Processing Unit (TPU), a high-performance hardware device accessible via the Google Cloud framework, to enable the rapid evaluation of different tsunami-risk mitigation strategies available to all communities. We establish a starting point through a numerical solver of the nonlinear shallow-water equations that uses a fifth-order weighted essentially non-oscillatory method with the Lax–Friedrichs flux splitting and a total variation diminishing third-order Runge–Kutta method for time discretization. We verify numerical solutions through several analytical solutions and benchmarks, reproduce several findings about one particular tsunami-risk mitigation strategy, and model tsunami runup at Crescent City, California whose topography comes from a high-resolution digital elevation model. The direct measurements of the simulation's performance, energy usage, and ease of execution show that our code could be a first step towards a community-based, user-friendly virtual laboratory that can be run by a minimally trained user on the cloud thanks to the ease of use of the Google Cloud platform.
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Alemam, Mustafa K., Bin YONG e Abubakar Sani-Mohammed. "A Proposed Merging Methods of Digital Elevation Model Based on Artificial Neural Network and Interpolation Techniques for Improved Accuracy". Artificial Satellites 58, n.º 3 (1 de setembro de 2023): 122–70. http://dx.doi.org/10.2478/arsa-2023-0009.
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ABSTRACT The digital elevation model (DEM) is one of the most critical sources of terrain elevations, which are essential in various geoscience applications. Most of these applications need precise elevations, which are available at a high cost. Thus, sources like the Shuttle Radar Topography Mission (SRTM) DEM are frequently accessible to all users but with low accuracy. Consequently, many studies have tried to improve the accuracy of DEMs acquired from these free sources. Importantly, using the SRTM DEM is not recommended for an area that partly contains high-accuracy data. Thus, there is a need for a merging technique to produce a merged DEM of the whole area with improved accuracy. In recent years, advancements in geographic information systems (GIS) have improved data analysis by providing tools for applying merging techniques (like the minimum, maximum, last, first, mean, and blend (conventional methods)) to improve DEMs. In this article, DEM merging methods based on artificial neural network (ANN) and interpolation techniques are proposed. The methods are compared with other existing methods in commercial GIS software. The kriging, inverse distance weighted (IDW), and spline interpolation methods were considered for this investigation. The essential step for achieving the merging stage is the correction surface generation, which is used for modifying the SRTM DEM. Moreover, two cases were taken into consideration, i.e., the zeros border and the H border. The findings show that the proposed DEM merging methods (PDMMs) improved the accuracy of the SRTM DEM more than the conventional methods (CDMMs). The findings further show that the PDMMs of the H border achieved higher accuracy than the PDMMs of the zeros border, while kriging outperformed the other interpolation methods in both cases. The ANN outperformed all methods with the highest accuracy. Its improvements in the zeros and H border respectively reached 22.38% and 75.73% in elevation, 34.67% and 54.83% in the slope, and 40.28% and 52.22% in the aspect. Therefore, this approach would be cost-effective, especially in critical engineering projects.
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Daskalova, Albena, e Liliya Angelova. "Design of Surfaces with Persistent Antimicrobial Properties on Stainless Steel Developed Using Femtosecond Laser Texturing for Application in “High Traffic” Objects". Nanomaterials 13, n.º 17 (23 de agosto de 2023): 2396. http://dx.doi.org/10.3390/nano13172396.
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Metal-based high-touch surfaces used for diverse applications in everyday use, like handrails, playground grab handles, doorknobs, ATM touch pads, and desks, are the most common targets for pollution with a variety of microbes; there is thus a need to improve their antimicrobial properties, an issue which has become a challenge in recent years, particularly after the COVID-19 pandemic. According to the World Health Organization (WHO), drug-resistant pathogens are one of the main concerns to global health today, as they lead to longer hospital stays and increased medical costs. Generally, the development of antimicrobial surfaces is related to the utilization of chemical methods via deposition on surfaces in the forms of various types of coatings. However, the addition of chemical substances onto a surface can induce unwanted effects, since it causes surface chemistry changes and, in some cases, cannot provide long-lasting results. A novel approach of utilising ultra-short laser radiation for the treatment of metallic surfaces by inducing a variety of micro- and nanostructuration is elaborated upon in the current research, estimating the optimum relation between the wettability and roughness characteristics for the creation of antimicrobial properties for such high-touch surfaces. In the current study, AISI 304–304L stainless steel metal was used as a benchmark material. Surface texturing via laser ablation with femtosecond laser pulses is an effective method, since it enables the formation of a variety of surface patterns, along with the creation of bimodal roughness, in one-step processing. In this investigation, a precise approach toward developing hydrophobic stainless steel surfaces with tunable adherence using femtosecond laser-induced modification is described. The impact of basic femtosecond laser processing parameters, like the scanning velocity, laser energy, and wettability properties of the laser-processed stainless steel samples, are examined. It is identified that the topography and morphology of laser-induced surface structures can be efficiently changed by adapting the laser processing parameters to create structures, which facilitate the transfer of surface properties from extremely low to high surface wettability.
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Niculiţǎ, Mihai. "Automatic landslide length and width estimation based on the geometric processing of the bounding box and the geomorphometric analysis of DEMs". Natural Hazards and Earth System Sciences 16, n.º 8 (30 de agosto de 2016): 2021–30. http://dx.doi.org/10.5194/nhess-16-2021-2016.
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Abstract. The morphology of landslides is influenced by the slide/flow of the material downslope. Usually, the distance of the movement of the material is greater than the width of the displaced material (especially for flows, but also the majority of slides); the resulting landslides have a greater length than width. In some specific geomorphologic environments (monoclinic regions, with cuesta landforms type) or as is the case for some types of landslides (translational slides, bank failures, complex landslides), for the majority of landslides, the distance of the movement of the displaced material can be smaller than its width; thus the landslides have a smaller length than width. When working with landslide inventories containing both types of landslides presented above, the analysis of the length and width of the landslides computed using usual geographic information system techniques (like bounding boxes) can be flawed. To overcome this flaw, I present an algorithm which uses both the geometry of the landslide polygon minimum oriented bounding box and a digital elevation model of the landslide topography for identifying the long vs. wide landslides. I tested the proposed algorithm for a landslide inventory which covers 131.1 km2 of the Moldavian Plateau, eastern Romania. This inventory contains 1327 landslides, of which 518 were manually classified as long and 809 as wide. In a first step, the difference in elevation of the length and width of the minimum oriented bounding box is used to separate long landslides from wide landslides (long landslides having the greatest elevation difference along the length of the bounding box). In a second step, the long landslides are checked as to whether their length is greater than the length of flow downslope (estimated with a flow-routing algorithm), in which case the landslide is classified as wide. By using this approach, the area under the Receiver Operating Characteristic curve value for the classification of the long vs. wide landslides is 87.8 %. An intensive review of the misclassified cases and the challenges of the proposed algorithm is made, and discussions are included about the prospects of improving the approach with further steps, to reduce the number of misclassifications.
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Leonova, T. D., M. G. Valitov e O. V. Belous. "The South China sea continental slope morphology and its relation to the anomalous gravitational field". Geomorphology RAS, n.º 4 (8 de novembro de 2019): 67–76. http://dx.doi.org/10.31857/s0435-42812019467-76.
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The bottom topography of the studied area of the South China Sea is characterized by an uneven distribution of depths, their sharp variations and the presence of a large number of seamounts. As a result of the research conducted, bathymetric profiles, a bathymetric map and a scheme of Faye anomalies were compiled. Geomorphological zoning was conducted. Sections of bottom distinguished by morphology were identified: 1) weakly dissected slope, steep (angles up to 15) in the upper part and more gentle (57) to the bottom of the deep-water step, 2) slope eroded by fluvial processes, 3) stepped slope, 4) chains of mountains and flat-topped hills, 5) accumulative bottom of the deep-water plain. It was established that the gravitational field as a whole reflects the complex structure of the bottom, and the local forms of the underwater relief are expressed in Faye anomalies. For elevations, zones of positive anomalies of Faye are marked, and sections of canyon-like valleys were mapped by an intense negative anomaly of the gravitational field to -60 mGal. In the process of endogenous evolution of the region, the relief became more complex. The primary endogenous continental slope was almost everywhere transformed by exogenous processes. Within the shelf, the filling of the basin led to the unification of all its projections into a single raised base. A significant role in the formation of the modern relief was played by large-scale repeated sea regressions, as a result of which the formation of the sedimentary cover was interrupted by periods of its erosion with the formation of planation surfaces. The Late Pleistocene peak of the regression (1618 thousand years BP), which caused the complete drainage of the shelf areas of the region, caused the erosion of the shelf and the movement of coarse clastic material through submarine canyons and valleys.
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Shawky, Mohamed, Adel Moussa, Quazi K. Hassan e Naser El-Sheimy. "Performance Assessment of Sub-Daily and Daily Precipitation Estimates Derived from GPM and GSMaP Products over an Arid Environment". Remote Sensing 11, n.º 23 (29 de novembro de 2019): 2840. http://dx.doi.org/10.3390/rs11232840.
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Precipitation is a critical variable for comprehending various climate-related research, such as water resources management, flash flood monitoring and forecasting, climatic analyses, and hydrogeological studies, etc. Here, our objective was to evaluate the rainfall estimates obtained from Global Precipitation Mission (GPM), and Global Satellite Mapping of Precipitation (GSMaP) constellation over an arid environment like the Sultanate of Oman that is characterized by a complex topography and extremely variable rainfall patterns. Global Satellite-based Precipitation Estimates (GSPEs) can provide wide coverage and high spatial and temporal resolutions, but evaluating their accuracy is a mandatory step before involving them in different hydrological applications. In this paper, the reliability of the Integrated Multi-satellitE Retrievals for the GPM (IMERG) V04 and GSMaP V06 products were evaluated using the reference in-situ rain gauges at sub-daily (e.g., 6, 12, and 18 h) and daily time scales during the period of March 2014–December 2016. A set of continuous difference statistical indices (e.g., mean absolute difference, root mean square error, mean difference, and unconditional bias), and categorical metrics (e.g., probability of detection, critical success index, false alarm ratio, and frequency bias index) were used to evaluate recorded precipitation occurrences. The results showed that the five GSPEs could generally delineate the spatial and temporal patterns of rainfall while they might have over- and under-estimations of in-situ gauge measurements. The overall quality of the GSMaP runs was superior to the IMERG products; however, it also encountered an exaggeration in case of light rain and an underestimation for heavy rain. The effects of the gauge calibration algorithm (GCA) used in the final IMERG (IMERG-F) were investigated by comparison with early and late runs. The IMERG-F V04 product did not show a significant improvement over the early (i.e., after 4 h of rainfall observations) and late (i.e., after 12 h of rainfall observations) products. The results indicated that GCA could not reduce the missed precipitation records considerably.
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Johnson, Michael F., e Robert W. Dalrymple. "Alluvial Terracing in a Falling-stage Braidplain: the Lower Cretaceous Cadomin Formation, West-central Alberta, Canada". Journal of Sedimentary Research 89, n.º 8 (27 de agosto de 2019): 701–27. http://dx.doi.org/10.2110/jsr.2019.39.
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Abstract The Lower Cretaceous Cadomin Formation in the Western Canada Sedimentary Basin is a thin, regionally extensive, conglomeratic fluvial deposit that accumulated over many million years on the sub-Cretaceous unconformity. Based on a dataset of approximately 50 cores and 750 wireline well logs from west-central Alberta, detailed isopach mapping of the overlying deposits reveals the presence of a complex, terraced paleo-topography on the top of the Cadomin Formation, consisting of six terrace levels in the study area. These terraces flank a series of north–south valleys that feed into a larger east–west valley to the north of the study area. This larger valley is also bordered by terraces that step downward to the north. The gradients of the north–south valley thalwegs are steeper than the flanking terraces, indicating that each terrace is diachronous and was most likely formed by the headward migration of knickpoints generated by episodic incision of the trunk valley. This paleo-topography formed during a prolonged period of falling base level caused by unroofing of the adjacent orogen. Thus, the Cadomin Formation represents a falling-stage systems tract. The deposits underlying each terrace consist mainly of channel-thalweg and braid-bar deposits. Preservation of full channel-bar successions in many terraces is consistent with terrace abandonment as incision resumed following a period of mild aggradation. Terrace abandonment is also indicated by the presence of a capping layer of wind-blown silt. Pedogenic alteration of this loessite is greatest on the highest terraces and extends to considerable depths, indicating the existence of a significant hiatus at the top of the Cadomin Formation. This surface, which lies above falling-stage deposits, should be used as the sequence boundary, if the sequence boundary is thought to coincide with the time of lowest base level. This surface, although its formation was diachronous, represents a real landscape surface, unlike the composite erosion surface beneath the Cadomin Formation (i.e., the sub-Cretaceous unconformity). The alternation of incision and aggradation that generated the terraces was probably the result of allogenic fluctuations in sediment supply caused by climate cycles, as was the case for analogous Quaternary terrace staircases. Downstepping alluvial terraces are a viable mechanism for the progradation of alluvial gravels long distances from a mountain belt during periods of basin uplift, and may explain the relatively thin, but areally extensive, alluvial sandstone and conglomerate sheets that are common at major unconformities in the stratigraphic record. We suggest that signs of subtle terracing may have been overlooked in similar sheet-like alluvial deposits elsewhere, although they can be removed by erosion during shoreline transgression or by later fluvial-channel migration. In the case of the Cadomin Formation, the exceptional preservation of the terraces is likely due to a combination of the difficulty of eroding the conglomerate and indurated loessite cap, and of the low-energy nature of floodplain sedimentation in the overlying Gething Formation.