Surface Stack Research Articles

Investigation on 2D SiCf/SiC composite scribing mechanism by single- and double-grit

To validate the proposed removal mechanism of 2D SiCf/SiC composite, single- and double-grit scribing experiments were conducted on the fiber woven surface (WS) and stacking surface (SS) along the 0°, 45°, and 90°. The results indicate that transverse fibers mainly undergo shear, tensile, and bending fractures. The removal modes of normal fibers are shear and bending fractures. The longitudinal fibers are damaged by tensile (cut-in side) and bending (cut-off side) fractures, accompanied by fiber peel-off. The removal forms of the matrix include crack propagation, ductile scratch, powdery removal, and brittle peel-off. The order of scribing force is FSS0 > FWS45 > FSS90 > FWS0. The maximum and minimum scribing force occur on SS0 and WS0, respectively, due to the powdery removal of matrix and fibers + matrix peel-off. The 2nd grit scribes the matrix layer and fiber tip in a very low depth to cause powdery and ductile removal, which exhibit the different material removal mechanism with the 1st grit. The scribing damage formed by 1st grit greatly reduces the force required by the 2nd grit for the same material removal volume. The coupling effect among grits in multi-grit scribing and grinding cannot be ignored.

Exploring threshold of Al-impurities towards high-performance Al-doped Regenerated LiCoO2

Direct regeneration, as the main recycling manner, displays the short-process and high economic value, which has been devoted to considerable attentions. Limited by the existed pre-treatments, there are still some Al-impurities of spent material, resulting in the unstable electrochemical properties of regenerated material, meanwhile the excessive removal of Al-impurities brings the risk of regeneration cost. Thus, exploring the threshold reference of Al-impurities is urgent for regeneration of spent materials. Herein, through the introduction of Al2O3 with different content, spent LiCoO2 were successfully regenerated, displaying the evolution of physical-chemical properties. With suitable Al adding (0.02 wt.%), the broadening layer distance and storage space are found. As a cathode, the as-optimized sample shows a capacity of 172.7 mAh g−1 at 0.2 C, and the capacity retention was 84 % after 500 cycles at 5.0 C, even better than Al-impurity-free regenerated sample. Supported by the detailed kinetic analysis, it could be deduced that, suitable Al-introduction is beneficial for the fast insertion/extraction of ions, meanwhile too excess adding could bring about the blocking of diffusion paths and by-production surface stacking. Given this, this work is expected to shed light on the physical-chemical effect of Al-impurities, meanwhile offering the threshold reference for Al-doping content in practical regenerated industry.

X-ray photoelectron diffraction as a modern tool for determining surface stacking sequence in layered materials

We investigated the surface structure of a NbSe2 single crystal at room temperature, using angle-scanned x-ray photoelectron diffraction (XPD) combined with multiple scattering calculations. Different stacking sequences were tested (1T, 2H a , 2H c , and 3R), including possible stacking faults and a mixed 2H–3R stacking proposed earlier in the literature. We confirm the capability of XPD to distinguish different proposed structural models and, unambiguously, determine the true surface structure. Also, our findings provide reliable in-plane and interlayer distances. We observed expansions of the perpendicular distances between atomic planes within the monolayer and between monolayers of 3%–5%. These results are important as accurate experimental input for the development of theoretical methods that involve a quantitative description of van der Waals systems.

Deep Seismic Reflection Imaging of Mesozoic Kachchh Rift, NW India: Implications for Evolution

AbstractDeep crustal seismic reflection profiling is carried out for first time across various tectonic domains of seismically active Mesozoic Kachchh rift basin, formed during the breakup of Gondwanaland. The seismic data, processed using the common reflection surface stack approach, provided maiden images of the shallow and deep sub‐surface structures in the region. These images reveal a 15 km thick subhorizontal lower crustal reflection fabric and crustal‐scale domal‐type structure extending from the surface to the Moho. We interpret the earlier structure represent magmatic underplating and the latter as the Kachchh Mainland uplift. We find large variations in the thickness of sediments from 150 m to 6.5 km and crustal thickness from 45 to 35 km from north to south, with a Moho up warp of 4 km beneath the Kachchh Mainland fault. The Kachchh rift basin exhibits an unusually thick crust of 45 km, contrary to many rift basins. We interpret the syn‐rifting and the Reunion mantle plume activity, manifested as Deccan volcanics, are responsible for magmatic underplating and crustal thickening. Uplift in the region is multi‐genetic in origin. Present study illuminated new faults and nature of various other faults. Moderate to large earthquakes in the region are attributed to the regional and local stresses resulting from the plate boundary and heterogeneous crustal structure. Based on the mafic lower crust and distribution of aftershocks through the entire crust, we interpret the lower crust is brittle, contrary to most models of continental rheology.

Advanced Processing of 2D Marine Reflection Seismic Data Using the Common Reflection Surface (CRS) Stack Method with K-L Filter Application

Data processing using the seismic reflection method is an important stage in the exploration of natural resources and minerals. This research was conducted to determine the effective and efficient stacking and filtering methods in reconstructing the subsurface geological structure of the earth from the results of data processing using ProMAX software. The data processing method used is the conventional stack and the Common Reflection Surface (CRS) stack. Aperture values of 0 ms – 50 m and 3000 ms – 150 m in the CRS stack process produce the most optimum seismic sections. Both methods produce a different quality of seismic cross-section display. The 2D cross-section model from the conventional stack method looks noisier than the results from the CRS stack method. In addition, the reflector pattern on the cross-section of the results of the CRS stack method is clearer and visible with a relatively large amplitude compared to the results of the conventional stack method. To maximize the quality of data display, data enhancement is applied, which is the K-L filter. The eigenimages value of 0.10% on the K-L filter with a horizontal window width of 120 is used to reduce random noise. Thus, an increase in the S/N ratio will be obtained in the seismic data so that the 2D cross-sectional model of the seismic reflection method can approach the original conditions of the subsurface geological structure.

The Properties of Sodium-Hypochlorite-Activated Crumb Rubber and the Influence of Aging on the Rheological Properties of Activated Asphalt Rubber

Asphalt rubber shows good road performance. However, the compatibility and aging problems of asphalt rubber limit its application. The improvement of the solubility of crumb rubber in asphalt was investigated in this research, and the mechanism of its aging effect on the rheological properties of activated asphalt rubber was studied. First, the crumb rubber was activated by using a sodium hypochlorite (NaClO) solution, and the pore characteristics and microstructure of the activated crumb rubber were analyzed. Second, the influence of the crumb rubber’s activation characteristics on the rheological properties of the asphalt rubber before and after aging was analyzed. Finally, the aging mechanism of the activated asphalt rubber was revealed at a microscopic level. The results showed that with the increase in the activation degree, the pore characteristics of the crumb rubber decreased first and then increased. The surface stacking structure of the crumb rubber increased, and a dense gel film gradually formed. The asphalt rubber prepared by the activated crumb rubber had better rheological properties and had a more significant effect under higher stress conditions. This may have been due to the activation of the crumb-rubber surface, forming oxygen-containing functional groups, which, in turn, increased the combination of the crumb rubber and the asphalt. In addition, the activation degree and aging effect of crumb rubber can reduce the large-particle-size molecule (LMS) content of activated asphalt rubber. There is a significant correlation between LMS content and rheological properties, and LMS content can be used to predict the rheological properties of asphalt rubber.

Anisotropy and Hybrid Heterosurface-Modulated Two-Dimensional Hydrogen Bond Network of Water

We report the structure and dynamics of layered water structure near a bilayer heterosurface using classical molecular dynamics simulations and network graph theory. The heterosurfaces of our choice are technologically essential and well-studied hexagonal boron nitride (h-BN) and graphitic carbon nitride (g-C3N4). Starting with the water density distribution profile, we have studied different hydrogen bondings (HBs) associated with distance and angle distributions and correlated them with the HB count, followed by the investigations of dynamic properties. We realize the oddity while corresponding to the tetrahedral order parameter (TOP), HB donor/acceptor count, and HB lifetime. A quantitative gap is observed between the TOP and HB counts, and we perceive another structural factor playing a significant role. We observe a 2D sheetlike arrangement of hydrogen-bonded water molecules, namely, 2D-HB, in the interfacial layer instead of 3D tetrahedral arrangements. 2D-HB qualitatively acts as a key descriptor of the hydrophobicity of the interface. The probability of higher TOP among the interfacial layer water molecules is less for h-BN compared to g-C3N4. However, the per-water HBs for both the heterosurfaces remain indistinguishable, implying the existence of another significant physical factor related to HB. Hence, 2D-HB serves as a deciding factor. In the case of h-BN, water molecules in the first layer form extended 2D sheets compared to the second and bulk, which is not a scenario for g-C3N4. Following the network graph theory, we calculated the temporal evolution of the maximum number of water molecules connected in a single network. The layer 1 water molecules have slower orientational dynamics, higher HB lifetime, and consequently slower translational diffusion than layer 2 and bulk water molecules. The experimental studies suggested that the contact angle of water on h-BN can vary from 61.4 to 85.8°, higher than that of g-C3N4, depending on the surface stacking, support material, and exposure to air, which effectively makes h-BN more hydrophobic compared to g-C3N4. The interfacial water molecules have a smaller HB lifetime and a faster diffusion coefficient than g-C3N4. The HB lifetime of water molecules in bulk is less than that in the interface, irrespective of the surface. A slower reorientation lifetime, that is, 2.69 ps, for g-C3N4 interfacial water molecules is observed versus 2.20 ps for h-BN. Our results agree with the experimental observations and can help to understand the hydrophobicity of other relevant materials.

Data reconstruction combining MWNI and CRS-based interpolation methods

Many seismic processes, such as migration, inversion, and quantitative interpretation, can be improved via multidimensional regularization and interpolation methods. Different algorithms based on signal processing principles have been proposed for multidimensional seismic data reconstruction. Similarly, the Common Reflection Surface (CRS) stack method, a technique based on ray-theory principles, can also be used for regularization and interpolation. CRS-based reconstruction requires determining the wavefront attributes of the CRS stacking operator directly from the data. These wavefront attributes are commonly searched through global optimization algorithms, where a coherence measure is maximized. The precision and reliability of the wavefront attributes (also called CRS attributes) depend on the optimization method used in their search and the quality of the input data. Onshore field data with missing traces and gaps due to missing shot records can introduce attribute errors and create artifacts that contaminate seismic stacks. To solve this problem, we propose applying the Minimum Weighted Norm Interpolation (MWNI) method for the reconstruction of the prestack data before estimating the CRS attributes. Then we use the wavefront attributes to CRS-based prestack data reconstruction and denoising. We validate the combination of MWNI and CRS-based interpolation methods with synthetic data and show that the CRS attributes extracted by the combined approach are very similar to the reference values. The proposed processing flow shows excellent results on an onshore vintage dataset from the Parnaíba Brazilian basin, where MWNI operates as a fold regularization. The reconstructed data obtained by combining MWNI and CRS show significant improvements compared to the reconstructed data using the two algorithms separately. Prestack time migration images show increased quality when the two methods are adopted in the processing flow.

In Situ Growth Dynamics of Uniform Bilayer Graphene with Different Twisted Angles Following Layer-by-Layer Mode.

Synthesis of large-area uniform bilayer graphene (BLG) with different twisted angles has gathered extensive interest but remains a challenge, hindered by the ubiquitous layer-plus-island growth and the uncontrollable layer rotation. Herein, using real-time surface imaging, film uniformity and stacking structures in BLG were well controlled by a two-step carbon segregation on Ni(111) films following the layer-by-layer growth mode. The aligned first graphene layers formed at 850 °C through a thermodynamics-limit process, followed by decreasing temperatures to grow the second layers, eventually enabling the extremely uniform 15°-twisted BLG at 790 °C and AB-stacked BLG at 720 °C, respectively. Essentially, the growth dynamics is perceived to determine that for the different stacking structures, nonaligned second layers are more kinetically preferable than aligned ones at relatively high temperatures, but the case reverses at low temperatures. This work conveys a fundamental dynamic understanding of the controllable integration of uniform BLG and tuning stacking structures.

Restoring the surface layer of Bi2Sr2CaCu2O8+δ single crystals by current injection

In 2010, we reported a new method to electronically tailor the hole concentration of the high-Tc superconductor Bi2Sr2CaCu2O8+δ (Bi-2212). We discovered that current injection along the c-axis of Bi-2212 provides a convenient tool to reversibly increase the carrier concentration. In this study, we have investigated the current injection effect on the surface junction of Bi-2212 by a series of current injection experiments carried out in samples of slightly overdoped and of extremely underdoped Bi-2212 crystals. The c-axis transport characteristics of bulk and surface intrinsic Josephson junctions are examined in a wide range of doping by current injection. Before injection treatment, typically, our samples demonstrate non-superconducting characteristics across their surface junctions, because standard preparation procedures cause the topmost CuO2 layers to be heavily degraded by oxygen loss. The electronic doping enables to substantially restore the hole concentration of the topmost CuO2 layers. The contact resistance is significantly reduced, and the intrinsic junction at the surface gets back its superconducting tunneling characteristic. We examine systematically the doping results of surface and bulk junction stacks and discuss the enhancement of their superconducting properties.

Moiré Modulation of Van Der Waals Potential in Twisted Hexagonal Boron Nitride.

When a twist angle is applied between two layered materials (LMs), the registry of the layers and the associated change in their functional properties are spatially modulated, and a moiré superlattice arises. Several works explored the optical, electric, and electromechanical moiré-dependent properties of such twisted LMs but, to the best of our knowledge, no direct visualization and quantification of van der Waals (vdW) interlayer interactions has been presented, so far. Here, we use tapping mode atomic force microscopy phase-imaging to probe the spatial modulation of the vdW potential in twisted hexagonal boron nitride. We find a moiré superlattice in the phase channel only when noncontact (long-range) forces are probed, revealing the modulation of the vdW potential at the sample surface, following AB and BA stacking domains. The creation of scalable electrostatic domains, modulating the vdW potential at the interface with the environment by means of layer twisting, could be used for local adhesion engineering and surface functionalization by affecting the deposition of molecules or nanoparticles.

The toroidal field surfaces in the standard poloidal-toroidal representation of magnetic field

The representation of magnetic field as a sum of a toroidal field and a poloidal field has not rarely been used in astrophysics, particularly in relation to stellar and planetary magnetism. In this representation, each toroidal field line lies entirely in a surface, which is named a toroidal field surface. The poloidal field is represented by the curl of another toroidal field and it threads a stack of toroidal field surfaces. If the toroidal field surfaces are either spheres or planes, the poloidal-toroidal (PT) representation is known to have a special property that the curl of a poloidal field is again a toroidal field . We name a PT representation with this property a standard PT representation while one without the property is called a generalized PT representation. In this paper, we have addressed the question whether there are other toroidal field surfaces allowing a standard PT representation than spheres and planes. We have proved that in a three dimensional Euclidean space, there can be no standard toroidal field surfaces other than spheres and planes, which render the curl of a poloidal field to be a toroidal field.

Research progress on seismic imaging technology

High-precision seismic imaging is the core task of seismic exploration, guaranteeing the accuracy of geophysical and geological interpretation. With the development of seismic exploration, the targets become more and more complex. Imaging on complex media such as subsalt, small-scale, steeply dipping and surface topography structures brings a great challenge to imaging techniques. Therefore, the seismic imaging methods range from stacking-to migration-to inversion-based imaging, and the imaging accuracy is becoming increasingly high. This review paper includes: summarizing the development of the seismic imaging; overviewing the principles of three typical imaging methods, including common reflection surface (CRS) stack, migration-based Gaussian-beam migration (GBM) and reverse-time migration (RTM), and inversion-based least-squares reverse-time migration (LSRTM); analyzing the imaging capability of GBM, RTM and LSRTM to the special structures on three typical models and a land data set; outlooking the future perspectives of imaging methods. The main challenge of seismic imaging is to produce high-precision images for low-quality data, extremely deep reservoirs, and dual-complex structures.

Improvement of Seismic Sections and Well Logs for Joint Geophysical Interpretation

Seismic and well-logging data are useful for comparison and then integratation for a comprehensive geophysical interpretation. In the course of this work, seismic results were compared with well-logging geophysical data and profiles for more reliable evaluation of groundwater formations in the Tokaj region, north-east Hungary. The seismic results and profiles were obtained by the Common Reflection Surface (CRS) stacking technique. This is an advantageous stacking technique that is expected to greatly improve seismic profiles. In connection with this, we also examined some well-logging geophysical profiles so that we can improve later results. By comparing and examining the two types of sections together, we provide a basis for various method developments that improve the sections. Thus, the aim is to fill in the missing data, so that the well-logging and seismic sections can be examined together as accurately as possible in order to gain a more accurate picture of the subsurface formations. It is important to determine the lithology and petrophysical characteristics using well logs. The section replacement the improvement of the units is done using machine learning-based and inversion methods such as factor analysis or cluster analysis. An important outcome in the application of geophysical inversion methods is that the results of different methods can be jointly interpreted and this can significantly increase the reliability of the results. The application of these methods and their development is expected to reduce uncertainty and ambiguity and to increase the accuracy of the sections.

Using electron channeling contrast imaging to inform and improve the growth of high-efficiency GaAs solar cells on nanopatterned GaAs substrates

Patterned substrates provide opportunities for reducing the cost of high-efficiency III-V devices by incorporating mechanically weak layers beneficial for substrate reuse (e.g. by spalling). In this work, the functionality of electron channeling contrast imaging (ECCI) as a tool to efficiently understand and mitigate defect formation is exemplified by developing a process in which high-quality III-V material can be grown on nanopatterned GaAs substrates. Reactive ion etching used in the patterning process was found to damage the GaAs substrate surface, leading to the formation of stacking faults in the epitaxial material as observed by ECCI. Etching the patterned substrates in a 1 NH4OH: 1 H2O2: 50 DI H2O solution for 10 s prior to growth removed the substrate surface damage and stacking faults were no longer present. Growth of solar cell device structures initially produced samples with many macroscale flaws creating shunts in the devices, which complicated the assessment of material quality by device measurements. However, ECCI revealed that the epitaxial material surrounding macroscale flaws was free from any crystallographic defects such as stacking faults and threading dislocations. With this knowledge, we focused on refining the patterning process to eliminate the macroscale flaws. Solar cells were then grown on the improved nanopatterned substrates and exhibited device structures with defect densities less than 5 × 105 cm−2 and average conversion efficiency of 24.8%, nearly identical to devices grown on unpatterned epi-ready substrates (25.0%).

Moduli spaces of stable sheaves over quasi-polarized surfaces, and the relative Strange Duality morphism

The main result of the present paper is a construction of relative moduli spaces of stable sheaves over the stack of quasipolarized projective surfaces. For this, we use the theory of good moduli spaces, whose study was initiated by Alper. As a corollary, we extend the relative Strange Duality morphism to the locus of quasipolarized K3 surfaces.

Ramie fiber reinforced composites with flame retardant structure design: flammability, smoke suppression, and mechanical properties

Abstract In this work, the structure of composite was designed as Core Stack and Surface Stack, which was treated with the expandable graphite (EG) and metal oxides such as iron oxide (IO), hydroxyapatite (HA), and aluminum tri-hydroxide (ATH). The mechanical performance of composites was characterized via flexural performance and interlaminar shear strength analysis. The flame retardance and smoke suppression of composite was explored in detail by LOI, UL-94, and cone calorimeter test. The findings presented that flexural properties of composites were observed to decrease due to delamination of surface stack, whilst no significant effect on interlaminar shear strength. In comparison with control composite, the loading of metal oxide into composite Surface Stack led to the reduction of peak heat release rate, total heat release, and fire growth index effectively. Moreover, the remarkable decrease in total smoke production could be observed due to the addition of iron oxide and the flame retardant mechanism was discussed. This study was the preliminary exploration of composite with flame retardant design which could be potential solution to improve flame retardancy and smoke suppression of composite with better mechanical structure preservation.

Study on the Velocity Analysis Method of Low SNR Seismic Data

When the signal to noise ratio of seismic data is very low, velocity spectrum focusing will be poor., the velocity model obtained by conventional velocity analysis methods is not accurate enough, which results in inaccurate migration. For the low signal noise ratio (SNR) data, this paper proposes to use partial Common Reflection Surface (CRS) stack to build CRS gathers, making full use of all of the reflection information of the first Fresnel zone, and improves the signal to noise ratio of pre-stack gathers by increasing the number of folds. In consideration of the CRS parameters of the zero-offset rays emitted angle and normal wave front curvature radius are searched on zero offset profile, we use ellipse evolving stacking to improve the zero offset section quality, in order to improve the reliability of CRS parameters. After CRS gathers are obtained, we use principal component analysis (PCA) approach to do velocity analysis, which improves the noise immunity of velocity analysis. Models and actual data results demonstrate the effectiveness of this method.

Enriques surfaces with normal K3-like coverings

We analyze the structure of simply-connected Enriques surfaces in characteristic two whose K3-like coverings are normal, building on the work of Ekedahl, Hyland and Shepherd-Barron. We develop general methods to construct such surfaces and the resulting twistor lines in the moduli stack of Enriques surfaces, including the case that the K3-like covering is a normal rational surface rather then a normal K3 surface. Among other things, we show that elliptic double points indeed do occur. In this case, there is only one singularity. The main idea is to apply flops to Frobenius pullbacks of rational elliptic surfaces, to get the desired K3-like covering. Our results hinge on Lang's classification of rational elliptic surfaces, the determination of their Mordell–Weil lattices by Shioda and Oguiso, and the behavior of unstable fibers under Frobenius pullback via Ogg's formula. Along the way, we develop a general theory of Zariski singularities in arbitrary dimension, which is tightly interwoven with the theory of height-one group schemes actions and restricted Lie algebras. Furthermore, we determine under what conditions tangent sheaves are locally free, and introduce a theory of canonical coverings for arbitrary proper algebraic schemes.

Smooth covers of moduli stacks of Riemann surfaces with symmetry

We construct explicitly a finite cover of the moduli stack of compact Riemann surfaces with a given group of symmetries by a smooth quasi-projective variety.