Warped Surface Research Articles

Reducing Deflection of Thin Glass by Prestress

Enclos has identified a novel technique to substantially stiffen glass via prestress. Significant reductions in deflection of thin glass have been demonstrated numerically and on prototype mockups using this technique. The potential integration of this technology with glass such as AGC’s Falcon Glass presents opportunities for performance improvement and material optimization. This study examines prestressed glass specimens which are 0.5mm, 1.1mm, and 2.1mm thick in comparison to glass of the same thicknesses that has not been enhanced by the novel stiffening method. The technology relies on a prestress pattern generated by cold-forming a double-curved surface into a flat pane. Unlike most cold-warping that starts with a flat sheet of glass deformed to a final warped surface, this approach begins with a hot-formed glass shape that is flattened elastically to a planar lite. The process results in a pattern of membrane prestress contained within the glass. As a result of the deformation, the center region of the glass is put into tension, which is balanced by regions of compression within the glass at the perimeter, adjacent to the frame. The membrane tension region that develops increases the glass stiffness for deflections out-of-plane, in a similar manner to the way tensioning a cable generates higher stiffness to resist applied lateral loads acting on it. Numerical models and test results from Enclos and AGC are presented in this study.

Machining behaviour analysis of PBF-LB warped components with internal lattice microstructures

Metal additive Powder Bed Fusion, Laser Based (PBF-LB) manufacturing offers significant improvements in the design of complex parts of inner components areas for several sectors, from dies and moulds, to blades and aerofoils. Generating internal structures helps to move fluids, work as heat exchanges, or achieve dramatic weight relief, only possible by additive manufacturing, concretely PBF-LB. Along with these designs, sculptured surfaces and warped surfaces are also common in blades and other aerodynamic pieces. However, it is mandatory that these designs accomplish the final required mechanical properties without surface damage and non-admissible dimensional deviations. In this study, the five-axis milling of a part containing internal structures has been investigated. Two types of PBF-LB Inconel® 718 blades were manufactured, one solid and one with internal microstructures. They were finished using two types of ball-ended mills, ball and barrel-lens tooltip. The analysis of the blade with internal structures shows better machining behaviour, dynamic behaviour, and surface quality.

Flexible nanoimprint lithography enables high-throughput manufacturing of bioinspired microstructures on warped substrates for efficient III-nitride optoelectronic devices

III-nitride materials are of great importance in the development of modern optoelectronics, but they have been limited over years by low light utilization rate and high dislocation densities in heteroepitaxial films grown on foreign substrate with limited refractive index contrast and large lattice mismatches. Here, we demonstrate a paradigm of high-throughput manufacturing bioinspired microstructures on warped substrates by flexible nanoimprint lithography for promoting the light extraction capability. We design a flexible nanoimprinting mold of copolymer and a two-step etching process that enable high-efficiency fabrication of nanoimprinted compound-eye-like Al2O3 microstructure (NCAM) and nanoimprinted compound-eye-like SiO2 microstructure (NCSM) template, achieving a 6.4-fold increase in throughput and 25% savings in economic costs over stepper projection lithography. Compared to NCAM template, we find that the NCSM template can not only improve the light extraction capability, but also modulate the morphology of AlN nucleation layer and reduce the formation of misoriented GaN grains on the inclined sidewall of microstructures, which suppresses the dislocations generated during coalescence, resulting in 40% reduction in dislocation density. This study provides a low-cost, high-quality, and high-throughput solution for manufacturing microstructures on warped surfaces of III-nitride optoelectronic devices.

Transport theory and the founding of condensed matter physics

In 1966, Woon Siong Gan coined and invented the name transport theory in condensed matter physics. Today, transport theory is the backbone theory of condensed matter physics and the whole condensed matter physics can be represented by transport theory. His PhD thesis pioneered the application of statistical mechanics to ultrasound propagation in semiconductor in the presence of high magnetic fields and low temperatures with the phase transition from the spherical energy surface of metal to the warped energy surface of semiconductor. The usual treatment is using the many-body theory of quantum field theory. Phase transition is an important topic in condensed matter physics. Thus, his PhD thesis also played a role in the founding of condensed matter physics. In this paper, transport theory is applied to phase transition, an important topic in condensed matter physics. The advantages of using transport theory is its broad coverage of both particles interaction and description of the singularity characteristics of phase transition. An example for illustration is that of magnetization which has Ising model describing spins interaction and the Lee Yang theory describing the singularity behavior of the partition function at the critical point of phase transition.

The Structure of the Warped Io Plasma Torus Constrained by the Io Footprint

AbstractStandard models of force balance along Jovian field lines predict the location of the Io Plasma Torus to be the centrifugal equator of Jupiter’s magnetosphere, that is, the position along the magnetic field lines farthest away from Jupiter’s rotational axis. In many models, the centrifugal equator is assumed to lay on a plane, calculated from a (shifted) dipole magnetic field, rather than on a warped surface which incorporates Jupiter’s higher magnetic field moments. In this work, we use Hubble Space Telescope observations of the Io Main Footprint to constrain density, scale height, and lateral position of the Io Plasma Torus. Therefore, we employ the leading angle of the footprints to calculate expected travel times of Alfvén waves and carry out an inversion of the observations. For the magnetic field, we use the JRM33 magnetic field model. The inversion results show peak densities between ρ0 = 1,830 cm−3 and ρ0 = 2,032 cm−3 and scale heights between H = 0.92RJ and H = 0.97RJ consistent with current literature values. Using a warped multipole centrifugal equator instead of a planar dipole increases the quality of the fit by about 25%. We additionally develop two tests to confirm that the multipole centrifugal equator from the JRM33 model fits explains the applied data set better than the dipole centrifugal equator. The quadropole moments alter Io’s relative position to the torus, which changes the plasma density around Io by up to Δρ/ρ = 20%.

Late Quaternary Deformation of the Ambon fault, Indonesia: Preliminary Results

The Ambon fault in the northern Banda Arc has capability of generating Mw 6.9 earthquake. The Ambon fault poses a significant seismic hazard to Ambon Island because the fault is located near populous areas, the Ambon City. Recent seismicity in Ambon Island and surrounding areas indicates that this region is actively deforming. Ambon Island has experienced many damaging earthquakes since the 17th century. However, the potential seismic hazard on this island remains enigmatic due to the lack of detailed geological information, such as fault traces, slip rate, and paleoseismic history. This study reports the preliminary results of tectonic geomorphic investigations and ground-penetrating radar (GPR) surveys on the Ambon fault. Tectonic geomorphic features, such as fault scarps, warped surfaces, and sag ponds indicate the late Quaternary activity of the Ambon fault. The Ambon fault predominantly shows a normal sense of motion with a dip of ~60-70°. The Ambon fault is related to the extensional tectonics in the Banda Sea.

Active faults studies in Delhi and national capital region (NCR): Inferences from satellite data and field investigations

In recent years, the National Capital Region (NCR) of Delhi has experienced several earthquakes ranging in magnitude from 1.0 to 6.7. According to the last 50 years of earthquake data, the majority of earthquakes in the NCR have occurred near the Mahendragarh Dehradun Fault (MDF) and the Sohna Fault (SF). The region is bounded by a number of subsurface Ridges, Faults, and Lineaments, which are also influenced by the active plate boundary of the Indian and Eurasian plates. Active fault mapping is critical for the precise identification and marking of active fault traces in the NCR area for a precise seismic hazard assessment. We used high resolution Cartosat-1 stereopair data obtained from NRSC, Hyderabad, and Anaglyph (A 3D representation of the surface) and DEM prepared with ENVI software to map the active faults. We identified 12 sites in the NCR region based on satellite data interpretation, primarily along the MDF and Sohna Fault and their extensions. The presence of tectono-geomorphic markers along the MDF and Sohna Fault, such as warped surfaces indicative of fault scarps, stream offsets, gully erosion, and sag ponds, suggests active tectonic movement along these faults, most likely in the recent geological past. We believe the MDF is a right-lateral strike-slip fault with a compressional component on the western side and an extensional component on the eastern side. It acts as a segment boundary between compressional and extensional boundaries. We also identified the right lateral Nuh-Jhirka fault (NJF), which can be the Sohna Fault’s southern extension from Nuh to Jhirka. The western limb of the Delhi Mega fold has also seen a few right-lateral strike-slip movements that have extended up to the eastern bank of the Yamuna River, where the river reflects the base-level change and tight meandering on its upward side and a straight pattern on its downward side. This fault is known as the Delhi Fault (DF). The findings are preliminary, and further research would be required to create a detailed active fault map of the Delhi-NCR region to conduct a precise Seismic Hazard Assessment (SHA) of the region.

Self-Referenced Method for Geometrical Distortion Removal in THz Time-Domain Reflection Imaging

In this article, we develop a method for removing the phase drift induced by physically distorted object in terahertz time-domain reflection imaging (THz-TDRI). The proposed approach is defined as self-referenced, as it does not rely on any numerical parameter optimization nor extra instrumental components, and it is based on the unique manipulation of time-domain imaging data. In fact, we demonstrate that the problem can be solved assuming a linear contribution of the temporal shift induced by surface curvature. We illustrate how the self-referenced method is modeled and implemented, and we report the results obtained on two objects with different characteristics: a tilted and highly reflective surface, and a warped and heterogeneous surface. The proposed method demonstrates how to successfully remove the phase alterations induced on the reflected electric field, and how to repair the heavily corrupted images in the frequency-domain.

Nonlinear antidamping spin-orbit torque originating from intraband transport on the warped surface of a topological insulator

Motivated by recent experiments observing a large antidamping spin-orbit torque (SOT) on the surface of a three-dimensional topological insulator, we investigate the origin of the current-induced SOT beyond linear-response theory. We find that a strong antidamping SOT arises from intraband transitions in non-linear response, and does not require interband transitions as is the case in linear transport mechanisms. The joint effect of warping and an in-plane magnetization generates a non-linear antidamping SOT which can exceed the intrinsic one by several orders of magnitude, depending on warping parameter and the position of Fermi energy, and exhibits a complex dependence on the azimuthal angle of the magnetization. This nonlinear SOT provides an alternative explanation of the observed giant SOT in recent experiments.

Tectonogeomorphic investigation of Kashmir Basin NW Himalaya

ABSTRACT The present study has been carried out in Kashmir Basin (KB), NW Himalaya, to determine the relative tectonic activity using morphotectonic analysis, drainage patterns, lineament analysis and geomorphological field observations. Geomorphic signatures in KB indicate that intrabasinal faults have been quite active during the Quaternary time and have played a dominant role in kinematic and structural evolution of the basin. The manifestation of this activity has been recorded by terrain morphology, uplifted river terraces, warped fluvial surfaces, strath surfaces, fault scarps, offset of Holocene sedimentary successions, braided, and offsetted drainage patterns and recent seismic activity in the region. Presence of active mountain fronts; concave, convex, and concavo-convex hypsometric curves; ambiguous stream gradient index and drainage basin asymmetry, elongated sub-basins clearly manifest tectonic influences in sculpting the basin geometry. The presence of NW-SE to NNE-SSW lineaments that generally strike parallel with the major regional tectonic structures (faults) clearly suggest intense deformation zones produced by ongoing regional tectonism. We propose that the techniques employed, the data obtained and the technical interpretations, are potentially useful and may also be extrapolated to similar tectonically active regions.

Surface Warping Incorporating Machine Learning Assisted Domain Likelihood Estimation: A New Paradigm in Mine Geology Modeling and Automation

This paper illustrates an application of machine learning (ML) within a complex system that performs grade estimation. In surface mining, assay measurements taken from production drilling often provide useful information that allows initially inaccurate surfaces created using sparse exploration data to be revised and subsequently improved. Recently, a Bayesian warping technique has been proposed to reshape modeled surfaces using geochemical and spatial constraints imposed by newly acquired blasthole data. This paper focuses on incorporating machine learning into this warping framework to make the likelihood computation generalizable. The technique works by adjusting the position of vertices on the surface to maximize the integrity of modeled geological boundaries with respect to sparse geochemical observations. Its foundation is laid by a Bayesian derivation in which the geological domain likelihood given the chemistry, p(g|c), plays a similar role to p(y(c)|g). This observation allows a manually calibrated process centered around the latter to be automated since ML techniques may be used to estimate the former in a data-driven way. Machine learning performance is evaluated for gradient boosting, neural network, random forest and other classifiers in a binary and multi-class context using precision and recall rates. Once ML likelihood estimators are integrated in the surface warping framework, surface shaping performance is evaluated using unseen data by examining the categorical distribution of test samples located above and below the warped surface. Large-scale validation experiments are performed to assess the overall efficacy of ML assisted surface warping as a fully integrated component within an ore grade estimation system where the posterior mean is obtained via Gaussian Process inference with a Matern 3/2 kernel.

The effect of dilute magnetic doping of a topological insulator on the surface states

Spin-dependent electronic properties are theoretically investigated in a diluted magnetic topological insulator (DMTI) with out-of-plane magnetization using a quantum theory based on self-consistent mean-field theory, including the spin-splitting effect in the presence of warped surface states. The effects of magnetic dopant concentration, carrier density, temperature, and external magnetic field are discussed on the surface of Bi2−xFexTe3 magnetically TI-doped sample. The parameters in the carrier-mediated magnetic mechanism are in excellent qualitative agreement with the experimentally observed magnetization. The numerical results showed that (i) the Dirac cone can shift in momentum space by the considered factors, (ii) the equal-energy contours of the DMTI deform for several different Fermi energies, (iii) an energy gap induces at surface state by doping of a small number of magnetic atoms, (iv) the spin-splitting energy becomes more when exchange interaction is included, and (v) more difference between equal-energy contours of two spin carriers with increasing the ratio of dopant density to carrier density and the spin-splitting energy. The origin of the large surface state gap will be discussed below. Moreover, the fermion spin polarization (FSP) energy ratios more than 17% are obtained in the momentum space on the surface state of Bi1.96Fe0.04Te3 compound for a density ratio of nc∕ni=0.1 at a fixed temperature T=0.2TC. Also, the FSP energy ratio reduces monotonically with decreasing the band-gap opening between the upper and lower Dirac cones at the Dirac point. The numerical results may shed light on the next applications of the magnetic topological insulator and make them convenient for future spintronics and magnetoelectric devices.

Warped Translation Surfaces of Finite Type in Simply Isotropic 3-Spaces

In this paper, we classify warped translation surfaces being invariant surfaces of i-type, that is, the generating curve has formed by the intersection of the surface with the isotropic xz-plane in the three-dimensional simply isotropic space $\mathbb I^3$ under the condition $\Delta^{J}x_i=\lambda_i x_i,$ with J=I,II. Here, $\Delta^{J}$ is the Laplace operator with respect to first and second fundamental form and $\lambda_i$, $i=1,2,3$ are some real numbers. Also, as an application, we give some examples for these surfaces and also some explicit graphics of them. All graphics have been plotted with Maple14.

Orbital-enhanced warping effect in px,py-derived Rashba spin splitting of monatomic bismuth surface alloy

Spin-split Rashba bands have been exploited to efficiently control the spin degree of freedom of moving electrons, which possesses a great potential in frontier applications of designing spintronic devices and processing spin-based information. Given an intrinsic breaking of inversion symmetry and sizeable spin–orbit interaction, two-dimensional (2D) surface alloys formed by heavy metal elements exhibit a pronounced Rashba-type spin splitting of the surface states. Here, we have revealed the essential role of atomic orbital symmetry in the hexagonally warped Rashba spin-split surface state of the sqrt 3 times sqrt 3 R30^0 BiCu2 monatomic alloy by scanning tunneling spectroscopy (STS) and density functional theory (DFT). From dI/dU spectra and calculated band structures, three hole-like Rashba-split bands hybridized from distinct orbital symmetries have been identified in the unoccupied energy region. Because of the hexagonally deformed Fermi surface, quasi-particle interference (QPI) mappings have resolved scattering channels opened from interband transitions of px,py (mj = 1/2) band. In contrast to the s,pz-derived band, the hexagonal warping is predominately accompanied by substantial out-of-plane spin polarization Sz up to 24% in the dispersion of px,py (mj = 1/2) band with an in-plane orbital symmetry.

Anion ordering transition and Fermi surface electron–hole instabilities in the (TMTSF)2ClO4 and (TMTSF)2NO3 Bechgaard salts analyzed through the first-principles Lindhard response function

The first-principles electron–hole Lindhard response function has been calculated and analyzed in detail for two (TMTSF)2 X (X = ClO4 and NO3) Bechgaard salts undergoing different anion-ordering (AO) transitions. The calculation was carried out using the real triclinic low-temperature structures. The evolution of the electron–hole response with temperature for both relaxed and quenched salts is discussed. It is shown that the 2k F response of the quenched samples of both salts display a low temperature curved and tilted triangular continuum of maxima. This is not the case for the relaxed samples. (TMTSF)2ClO4 in the AO state exhibits a more quasi-1D response than in the non AO state and relaxed (TMTSF)2NO3 shows a sharp maximum. The curved triangular plateau of the quenched samples results from multiple nesting of the warped quasi-1D Fermi surface which implies the existence of a large q range of electron–hole fluctuations. This broad maxima region is around 1% of the Brillouin zone area for the X = ClO4 salt (and X = PF6) but only 0.1% for the X = NO3 salt. It is suggested that the strong reduction of associated SDW fluctuations could explain the non detection of the SDW-mediated superconductivity in (TMTSF)2NO3. The calculated maxima of the Lindhard response nicely account for the modulation wave vector experimentally determined by NMR in the SDW ground state of the two salts. The critical AO wave vector for both salts is located in regions where the Lindhard response is a minimum so that they are unrelated to any electron–hole instability. The present first-principles calculation reveals 3D effects in the Lindhard response of the two salts at low temperature which are considerably more difficult to model in analytical approaches.

Study on wetting deformation characteristics of coarse granular materials and its simulation in core‐wall rockfill dams

SummaryThe wetting deformation of coarse granular materials is often considered to be an important cause of the core wall rockfill dam cracks during impounding. By analyzing existing research results, this paper proposes a hyperbolic relationship between the wetting axial strain and wetting stress level and puts forwards a warped surface relationship among spherical stress, shear stress, and the ratio of wetting volumetric strain to wetting axial strain. To illustrate its practicability, the wetting strain model's parameter determination process is introduced and the rockfill materials wetting parameters are determined using the triaxial wetting test data. Moreover, the collapse settlement of Guanyinyan rockfill dam during first impounding is numerically simulated using the proposed method to calculate rockfill wetting deformation and verified by field measurements and monitoring data. The results show that the calculative method of wetting deformation proposed in this paper is reasonable and practical; the wetting deformation of upstream rockfill materials would cause an adverse deformation trend, which may lead to crack occurrence at the upstream slope and dam crest; and the Guanyinyan rockfill dam cracks on the top of junction mainly caused by the wetting deformation of upstream rockfill.

Insights into the pore-forming effect of polyvinyl butyral (PVB) as the polymer template to synthesize mesoporous alumina nanofibers via electrospinning

In this work, mesoporous alumina nanofibers were synthesized using polyvinyl butyral (PVB) as polymer template via electrospinning technique. Both alumina precursor sol and precursor solution mixed well with PVB ethanol solution in temperature range of 40–80 °C to attain transparent spinning solutions. Continuous precursor nanofibers with rough and warped surface were obtained after electrospinning. Calcination of precursor nanofibers in air yielded the opening of mesopores in alumina nanofibers. Rapid escape of gaseous products and phase separation between PVB and alumina precursors were responsible for the formation of porous framework.

Surface state transport in double-gated and magnetized topological insulators with hexagonal warping effects

We explore the scattering of Dirac electrons in a double-gated topological insulator in the presence of magnetic proximity effects and warped surface states. It is found that a magnetic field can shift the Dirac cone in momentum space and deform the constant-energy contour, or opens up a band gap at the Dirac point, depending on the magnetization orientation. The double gate voltage induces quantum wells and/or quantum barriers on the surface of topological insulators, generating surface resonant tunnelling states. It is found that the hexagonal warping effect can increase the electronic transport at high energies when the constant-energy contour exhibits a snowflake shape. The energy-dependent conductances in the parallel and antiparallel magnetic configurations exhibit out-of-phase oscillations due to the quantum interference of propagating waves in the region between the two magnetized segments. Although the conductance spectrum of the double-well structure is higher than that of the double-barrier structure, the magnetoresistance ratio versus the separation distance between the two magnetized barriers exhibits pronounced oscillations due to the resonant tunnelling states. We show that the surface state transport can be controlled by the exchange field and gate voltage without breaking time reversal symmetry, suggesting that the double gated and magnetized topological insulators can be utilized to achieve a large magnetoresistance ratio with a tunable sign.

Effect of hexagonal warping of the Fermi surface on the thermoelectric properties of a topological insulator irradiated with linearly polarized radiation

We investigate the effect of the hexagonal warped anisotropic Fermi surface on the anomalous thermoelectric properties of the topological insulator surface illuminated with linearly polarized off-resonant electromagnetic radiation. Upon irradiation of the TI surface, the linearly polarized (LP) off-resonant radiation couples with the Dirac surface states. By explicitly finding the off-resonant quasistatic Hamiltonian we show that this coupling occurs only in the presence of the hexagonal warping of the Fermi surface of the topological insulator. We calculate the spin texture of the surface states, Berry curvature, Berry phase, orbital magnetic moment, and magnetization associated with the band structure, which we find strongly depends on the angle of polarization and the amplitude of radiation. For the anomalous thermoelectric effects generated by the Berry curvature, it is found that due to the hexagonal warping induced Fermi surface deformation and the radiation parameter dependent spin texture of the surface states, the transverse Hall, Ettingshausen, Nernst, and thermal conductivities show significant variation with the change in polarization angle, chemical potential, temperature, and the amplitude of radiation. As a consequence, the thermoelectric coefficient of performance ($ZT$) of the topological insulator is found to be increased in the presence of LP off-resonant irradiation compared to the absence of radiation.

Ultimate Strength of Annular Reinforced Concrete Members Under Combined Actions

Annular reinforced concrete (RC) members are commonly used in bridge structures and offshore platforms. These RC members often fail under the combined actions of axial force, bending moment, shear force and torsion load in hazards of earthquake and wind. It is very important to study the failure mechanism of annular RC members under combined actions. This study proposes a model to analyze the ultimate strength of annular RC members under combined actions using limit failure theory. A new method is established to determine the geometric parameters of the warped failure surface, and the new calculation model for the ultimate strength is obtained using the equilibrium conditions based on the geometric parameters and the stress distribution on the failure surface. The proposed model calculations are compared with a series of experimental results of annular RC members, and they correspond well with the experimental results. The proposed model is feasible for engineering application.