Anomalous Structure Research Articles

Subset Multivariate Collective and Point Anomaly Detection

In the recent years, there has been a growing interest in identifying anomalous structure within multivariate data sequences. We consider the problem of detecting collective anomalies, corresponding to intervals where one, or more, of the data sequences behaves anomalously. We first develop a test for a single collective anomaly that has power to simultaneously detect anomalies that are either rare, that is affecting few data sequences, or common. We then show how to detect multiple anomalies in a way that is computationally efficient but avoids the approximations inherent in binary segmentation-like approaches. This approach is shown to consistently estimate the number and location of the collective anomalies—a property that has not previously been shown for competing methods. Our approach can be made robust to point anomalies and can allow for the anomalies to be imperfectly aligned. We show the practical usefulness of allowing for imperfect alignments through a resulting increase in power to detect regions of copy number variation. Supplemental files for this article are available online.

Innovative geophysikalische Vorauserkundungstechnologie in verkarstungsfähigen und kristallinen Gesteinen

AbstractIn rock formations prone to karstification there are only limited geological/hydrological principles that allow a safe prognosis of the existence and location of karstic and fault structures. A combination of geophysical borehole radar measurements utilizing both reflection and crosshole probe setups can be used to reliably detect anomalous structures, especially air‐filled karstic cavities and fault zones, when a sensible measuring concept for karstified or crystalline rocks is applied. Besides the determination of the anomalous structure's location it is also possible to distinguish its type of filling. Using examples from the major railway project Albaufstieg between Wendlingen‐Ulm the investigation concepts ahead of the tunnel construction are presented. The borehole radar measurements were successfully utilized during different phases of the tunnel excavation and could be integrated into the construction process without significant delays, thus contributing to a safe construction process and later operation of the tunnels. The reliability and high efficiency of these borehole radar investigation concepts places this technology of karst detection at a significant advantage over the commonly applied seismic methods, especially in karst‐prone and crystalline rocks.

INVESTIGATION OF THE CAUSES OF UNSATISFACTORY RESULTS OF ULTRASOUND CONTROL OF EXPERIMENTAL FORGES FROM AUSTENITE HIGH-ALLOY STEEL

The purpose of the work is to establish the main causes of defects by ultrasonic testing (UST) of experimental forgings made of high-alloyed austenitic steel 08Kh18N10T on the basis of comprehensive comparative studies of samples of defective and suitable forgings. Techniques. Chemical analysis of forgings was performed on a high-sensitivity spectrometer "SPECTROMAX" company "SPECTRO", Germany; studies of macro- and microstructure (liquation heterogeneity, grain boundary structure, non-metallic inclusions, excess phases, etc.) were carried by the methods: metallographic and electron microscopic with micro-X-ray spectral analysis; tests of forgings for durability against intergranular corrosion (IGC) were carried out by the methods of AMU, GOST 6032. Results. It was established that experimental forgings rejected by UZK, in contrast to suitable forgings, were characterized by: the presence of areas of liquation inhomogeneity of steel, including high content of δ-ferrite; local defects of the macrostructure in the form of flocs; areas with anomalous multi-grained microstructure with a grain size of –2 to 8 points according to GOST 5639; release of chromium carbides at the boundaries of austenitic grains; susceptibility to intergranular corrosion (ICC). All forgings contained non-metallic inclusions within the permissible limits according to GOST 1778, as well as titanium carbides. Scientific novelty. For the first time on the basis of complex researches it is proved that the main reason of unsatisfactory results of UZK of experimental forgings from high-alloyed austenitic steel, is the anomalous multigrain structure connected with the unstable temperature-deformation mode of forging of ingots. Practical significance. Recommendations for improving the structure and improving the quality characteristics of industrial forgings made of high-alloy austenitic steels in terms of industrial production have been developed.

Super-regular femtosecond laser nanolithography based on dual-interface plasmons coupling

Abstract Advances in femtosecond laser-material interaction facilitate the extension of maskless optical processing to the high efficiency and deep-subwavelength scale. Here, a hybrid plasmon lithography technique has been demonstrated by irradiating near-infrared femtosecond laser pulses onto the Si material coated with thin Cr films in a vacuum chamber, and superior nanograting structures are found to deeply penetrate through the thin Cr film into the underlying Si substrate. In stark contrast to the common ripple structures formed on the Si surface, the Cr-layer mediated Si nanograting structures not only exhibit the spatially super-regular arrangements with a deep-subwavelength period of 355 nm but also present the nonsinusoidal sharp-edged groove geometry with a large depth-to-width aspect ratio of 2.1. Theoretical analyses and calculations reveal that the anomalous structure characterizations are physically ascribed to the excitation of dual-interface coupled plasmons in the thin metal layer, which possess the squeezed spatial wavelength and the periodic columnar intensity distributions. Moreover, the further deepening of periodic nanostructures into the Si substrate is also elucidated by the simulation of electric field enhancements at the bottom of shallow grooves under irradiation of subsequent laser pulses. In combination with a wet etching process, the Si nanograting structures can be modified into the smooth and narrow-mouthed V-profiles, whose optical measurements show a near omnidirectional antireflection especially in the visible range of 565–750 nm, which is expected for the design of advanced photonic devices.

“Warm cover”: precursory strong signals for haze pollution hidden in the middle troposphere

Abstract. Eastern China (EC), located in the downstream region of the Tibetan Plateau (TP), is a large area with frequent haze pollution. In addition to air pollutant emissions, meteorological conditions are a key inducement for air pollution episodes. Based on the study of the Great Smog of London in 1952 and haze pollution in EC over recent decades, it is found that the abnormal “warm cover” (air–temperature anomalies) in the middle troposphere, as a precursory strong signal, could be connected to severe air pollution events. The convection and vertical diffusion in the atmospheric boundary layer (ABL) were suppressed by a relatively stable structure of warm cover in the middle troposphere leading to ABL height decreases, which were favorable for the accumulation of air pollutants in the ambient atmosphere. The anomalous structure of the troposphere's warm cover not only exist in heavy haze pollution on the daily scale, but also provide seasonal, interannual and interdecadal strong signals for frequently occurring regional haze pollution. It is revealed that a close relationship existed between interannual variations of the TP's heat source and the warm cover strong signal in the middle troposphere over EC. The warming TP could lead to anomalous warm cover in the middle troposphere from the plateau to the downstream EC region and even the entire East Asian region, thus causing frequent winter haze pollution in EC region.

Fast extreme-mass-ratio-inspiral waveforms: New tools for millihertz gravitational-wave data analysis

We present the FastEMRIWaveforms (FEW) package, a collection of tools to build and analyze extreme mass ratio inspiral (EMRI) waveforms. Here, we expand on the Physical Review Letter that introduced the first fast and accurate fully-relativistic EMRI waveform template model. We discuss the construction of the overall framework; constituent modules; and the general methods used to accelerate EMRI waveforms. Because the fully relativistic FEW model waveforms are for now limited to eccentric orbits in the Schwarzschild spacetime, we also introduce an improved Augmented Analytic Kludge (AAK) model that describes generic Kerr inspirals. Both waveform models can be accelerated using graphics processing unit (GPU) hardware. With the GPU-accelerated waveforms in hand, a variety of studies are performed including an analysis of EMRI mode content, template mismatch, and fully Bayesian Markov Chain Monte Carlo-based EMRI parameter estimation. We find relativistic EMRI waveform templates can be generated with fewer harmonic modes ($\sim10-100$) without biasing signal extraction. However, we show for the first time that extraction of a relativistic injection with semi-relativistic amplitudes can lead to strong bias and anomalous structure in the posterior distribution for certain regions of parameter space.

Managing a Facial Talon: A Rare Morphological Variation on Maxillary Permanent Central Incisor

Talon cusp or Eagle's Talon is a developmental anomalous structure that is thought to arise due to evagination of the coronal surface of a tooth before the commencement of calcification. The facial form of talon cusp is a rare morphological variation occurred on the facial surface of incisors that are often associated with clinical problems such as poor esthetic, soft tissue irritation, and caries susceptibility. We report a case of facial talon cusp on permanent maxillary right central incisor in a 9-year-old girl who visited our department with esthetic concern. The patient was managed with a minimally invasive approach by selective grinding followed by the application of fluoride varnish at a regular interval. Direct resin-based composite restoration performed to achieve esthetic rehabilitation, demonstrated satisfactory clinical and radiographic treatment outcomes.

Examining Conditions Supporting the Development of Anomalous Charge Structures in Supercell Thunderstorms in the Southeastern United States

AbstractHypotheses regarding favorable conditions for anomalous charging have primarily resulted from studies within the Great Plains region of the United States, where the efficiency of warm precipitation processes is thought to be fundamental. Rare observations of anomalous charge structures in the Southeastern region challenge existing conceptual models used to explain anomalous charging. As a rigorous evaluation of conditions that support anomalous charge structures, environmental characteristics and bulk kinematic and microphysical properties of two normal and two anomalous supercell thunderstorms observed in the Southeast were compared. Within the anomalous supercells, greater quantities of precipitation ice were identified at higher altitudes and colder temperatures, suggesting a greater depth of riming growth and increased vertical transport of rimed hydrometeors. Deeper anomalous supercell updrafts were larger and stronger in the upper mixed‐phase and glaciated regions. However, normal supercells were characterized by more robust low‐level updrafts, resulting in comparable warm cloud residence times that suggested warm precipitation processes were not necessarily less efficient in the anomalous supercells. Indications of enhanced mixed‐phase liquid water content in favor of anomalous charging were observed in the anomalous supercells, though contrasts in related environmental parameters were not as large as observed in other comparative studies. Anomalous supercell environments were characterized by increased instability, shallower warm cloud depth, as well as lower relative humidity in the 700–500 mb layer. Evidence of impacts from dry air in anomalous storm structures suggested that water vapor content may have affected particle‐scale charge transfer in support of anomalous charge structure development.

Characterizing Charge Structure in Central Argentina Thunderstorms During RELAMPAGO Utilizing a New Charge Layer Polarity Identification Method.

A new automated method to retrieve charge layer polarity from flashes, named Chargepol, is presented in this paper. Using data from the NASA Lightning Mapping Array (LMA) deployed during the Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign in Cordoba, Argentina, from November 2018 to April 2019, this method estimates the polarity of vertical charge distributions and their altitudes and thicknesses (or vertical depth) using the very‐high frequency (VHF) source emissions detected by LMAs. When this method is applied to LMA data for extended periods of time, it is capable of inferring a storm's bulk electrical charge structure throughout its life cycle. This method reliably predicted the polarity of charge within which lightning flashes propagated and was validated in comparison to methods that require manual assignment of polarities via visual inspection of VHF lightning sources. Examples of normal and anomalous charge structures retrieved using Chargepol for storms in Central Argentina during RELAMPAGO are presented for the first time. Application of Chargepol to five months of LMA data in Central Argentina and several locations in the United States allowed for the characterization of the charge structure in these regions and for a reliable comparison using the same methodology. About 13.3% of Cordoba thunderstorms were defined by an anomalous charge structure, slightly higher than in Oklahoma (12.5%) and West Texas (11.1%), higher than Alabama (7.3%), and considerably lower than in Colorado (82.6%). Some of the Cordoba anomalous thunderstorms presented enhanced low‐level positive charge, a feature rarely if ever observed in Colorado thunderstorms.

A Chronology of Ancient Earthquake Damage in the Modena Cathedral (Italy): Integrated Dating of Mortars (14C, Pollen Record) and Bricks (TL)

ABSTRACT The 15th century cross-vaults of the medieval Modena Cathedral (UNESCO site) consist of intricate patches of different masonry portions bound by three types of lime mortars and at least two types of gypsum mortars. Such anomalous structure suggests multiple repair works over time after damaging earthquakes. The absolute dating of lime mortars (14C) and bricks (TL) integrated with the pollen record of mortars allowed to clarify the construction and restoration history of the vaults and to link the repairs to the earthquake chronology for the area. The results reveal that the original construction of the vaults (1404–1454) was carried out using lime mortar binding reused Roman and medieval older bricks. Lime mortar was used also for later repairs caused by earthquakes in the 16th and 17th centuries. Gypsum mortars were then used to entirely rebuild some vaults and to repair others in the 18th and 19th centuries. The study indicates that unexpected damage could be revealed by the detailed chronology of masonry binders. These data represent fundamental steps to implement earthquake risk assessments and strengthening projects of ancient buildings.

Intraregional Comparisons of the Near‐Storm Environments of Storms Dominated by Frequent Positive Versus Negative Cloud‐to‐Ground Flashes

AbstractWe gridded 11 years of cloud‐to‐ground (CG) flashes detected by the U.S. National Lightning Detection Network during the warm season in 15 km × 15 km × 15 min grid cells to identify storms with substantial CG flash rates clearly dominated by flashes lowering one polarity of charge to the ground or the other (+CG flashes vs. −CG flashes). Previous studies in the central United States had found that the gross charge distribution of storms dominated by +CG flashes included a large upper negative charge over a large middle level positive charge, a reversal of the usual polarities. In each of seven regions spanning the contiguous United States (CONUS), we compared 17 environmental parameters of storms dominated by +CG flashes with those of storms dominated by –CG flashes. These parameters were chosen based on their expected roles in modulating supercooled liquid water content (SLWC) in the updraft because laboratory experiments have shown that SLWC affects the polarity of charge exchanged during rebounding collisions between riming graupel and small ice particles in the mixed phase region. This, in turn, would affect the vertical polarity of a storm's charge distribution and the dominant polarity of CG flashes. Our results suggest that the combination of parameters conducive to dominant +CG flash activity and, by inference, to anomalous storm charge structure varies widely from region to region, the lack of a favorable value of any particular parameter in a given region being offset by favorable values of one or more other parameters.

Capping and gate control of anomalous Hall effect and hump structure in ultra-thin SrRuO3 films

Ferromagnetism and exotic topological structures in SrRuO3 (SRO) induce sign-changing anomalous Hall effect (AHE). Recently, hump structures have been reported in the Hall resistivity of SRO thin films, especially in the ultra-thin regime. We investigate the AHE and hump structure in the Hall resistivity of SRO ultra-thin films with an SrTiO3 (STO) capping layer and ionic liquid gating. STO capping results in sign changes in the AHE and modulation of the hump structure. In particular, the hump structure in the Hall resistivity is strongly modulated and even vanishes in STO-capped 4 unit cell films. In addition, the conductivity of STO-capped SRO ultra-thin films is greatly enhanced with restored ferromagnetism. We also performed ionic liquid gating to modulate the electric field at SRO/STO interface. Drastic changes in the AHE and hump structure are observed with different gate voltages. Our study shows that the hump structure as well as the AHE can be controlled by tuning inversion symmetry and the electric field at the interface.

Mass-constrained basin basement mapping

The irregular interface model setting side by side two dense homogeneous media has found many applications in gravity-data exploration such as for petroleum and gas in sedimentary basins, groundwater resources in buried paleochannels, characterization of abandoned landfills, and variable regolith-depth mapping. Despite its simplicity and wide range of applicability, the determination of the interface position from inverting surface gravity data configures an ill-posed problem requiring specialized regularizing procedures to produce reliable results. Common approaches to obtain stable and reliable solutions require a judicious choice of regularizing functionals, each of them able to convey a desired geologic attribute that the unknown interface is expected to feature. In assuming a style that the unknown interface may have, a mathematical procedure is elected to convey such an attribute when the interface is mapped from gravity data inversion. We have developed a different approach to the interface mapping problem by imposing a common constraint that all model solutions must have, meanwhile preventing oscillations for the interface to be mapped. As a constraint that the solutions must have, we fix the volume or the cross section for 2D structures that the anomalous density structure has. This volume (or 2D cross section) is determined by applying the mass excess theorem to the measured gravity data and assuming as known the density contrast caused by the two media paired by the interface. We find that this simple formulation for the interface-mapping problem is effective in imaging a variety of basin styles without introducing specific information about the interface attributes. Our technique is applied to invert previously published gravity data in cases with good drillhole control or with a known interface.

Ant Colony Optimization Inversion Using the L1 Norm in Advanced Tunnel Detection

During the construction of the tunnel, there may be water-bearing anomalous structures such as fault fracture zone. In order to ensure the safety of the tunnel, it is necessary to carry out advanced tunnel detection. The traditional linear inversion method is highly dependent on the initial model in the tunnel resistivity inversion, which makes the inversion results falling into the local optimal optimum rather than the global one. Therefore, an inversion method for tunnel resistivity advanced detection based on ant colony algorithm is proposed in this paper. In order to improve the accuracy of tunnel advanced detection of deep anomalous bodies, an ant colony optimization (ACO) inversion is used by integrating depth weighting into the inversion function. At the same time, in view of the high efficiency and low cost of one-dimension inversion and the advantages of L1 norm in boundary characterization, a one-dimensional ant colony algorithm is adopted in this paper. In order to evaluate the performance of the algorithm, two sets of numerical simulations were carried out. Finally, the application of the actual tunnel water-bearing anomalous structure was carried out in a real example to evaluate the application effect, and it was verified by excavation exposure.

Anomalous dislocation core structure in shock compressed bcc high-entropy alloys

Recent studies of complex concentrated alloys suggest unusual dislocation core structure and motion, thanks to a collective concentration/structural inhomogeneity. Less is known whether these effects also work in extreme conditions where the solid solution effect is overwhelmed by the large driving force. Here, we investigate the dislocation structure behind a shock-wave front in bcc high-entropy alloys (HEAs) using large-scale molecular dynamics (MD) simulations. In contrast to bcc elemental metals, we find anomalous “extended“ edge dislocation structure (6 ~ 8 Burgers vector) with high stability in shock compressed TiZrNb and NiCoFeTi HEAs. The unique dislocation structures can facilitate faster dislocation motion, thus deterring the early nucleation of deformation twins. Combined with continuum elasticity theory, we show that the “extended“ dislocation structure can be attributed to the presence of local structures with low elastic stability that are imparted by the nanoscale chemical heterogeneities in HEAs. We also show how the dislocation structures are affected by the interatomic potentials.

The anomalous electronic structure of electron-doped cuprate superconductors by considering the next higher harmonics of the superconducting gap

Based on the self-consistent mean field theory by considering the next higher harmonics of the superconducting (SC) gap, we discuss the energy and momentum dependence of the electron spectrum in electron-doped cuprate superconductors. By calculation of the electron spectral function, it is shown that the weight of the electron spectrum at the Fermi energy is strongly redistributed by the next higher harmonics of the SC gap in electron-doped cuprate superconductors, especially for the antinodal region. At the antinodal region, the weight of the electron spectrum at the Fermi surface increases with the increase of next higher harmonics term, reaches the maximum at a critical strength, then decreases when the next higher harmonics is larger. Our theoretical results show that the variation of the SC gap with the next higher harmonics can explain the anomalous behavior of the electron spectrum and different angle-resolved photoemission spectroscopy experimental results of different samples of electron-doped cuprate superconductors. Moreover, the magnitude of the SC gap can be suppressed by the next higher harmonics, which may be one of the reasons for the smaller SC gap in electron-doped cuprate superconductors. Obvious topological change happens in the SC gap at a critical strength of the next higher harmonics.

Anomalous structure transition in undercooled melt regulates polymorphic selection in barium titanate crystallization

The crystallization processes of titanates are central to the fabrication of optical and electrical crystals and glasses, but their rich polymorphism is not fully understood. Here, we show when and how polymorphic selection occurs during the crystallization of barium titanate (BaTiO3, BT) using in situ high energy synchrotron X-ray diffraction and ab initio molecular dynamic simulation. An anomalous structure transition is found in molten BT during cooling across the cubic-hexagonal transition temperature, which enables nucleation selection of BT by manipulating the undercooling: a cubic phase is preferred if nucleation is triggered at large undercooling, whereas a hexagonal phase is promoted at small undercooling. We further reveal that the nucleation selection between the cubic and the hexagonal phase is regulated by the intrinsic structure property of the melt, in particular, the degree of polymerization between Ti-O polyhedra. These findings provide an innovative perspective to link the polymorphic crystallization to the non-isomorphic structure transition of the melt beyond the conventional cognition of structural heredity.

High thermoelectrical figure of merit in chiral topological superconductor junctions

Performing the non-equilibrium Green’s function method, we calculate the Seebeck coefficient (S) and the thermoelectrical figure of merit (ZT) in the quantum anomalous Hall insulator-topological superconductor-quantum anomalous Hall insulator hybrid structure with temperature gradient. It is found that a high thermoelectrical figure of merit can be achieved with the helical topological superconductor phase. The S and the ZT are mainly affected by the temperature and the device size. At a certain temperature and the right device size, the Seebeck coefficient and the figure of merit can reach very high values.

Revealing thermally driven distortion of magnon dispersion by spin Seebeck effect in Gd3Fe5O12

We report a systematic study of the temperature and field dependences of the spin Seebeck effect (SSE) in a bilayer of $\mathrm{Pt}/{\mathrm{Gd}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. An anomalous structure is observed in the magnetic field dependent measurements at temperatures between \ensuremath{\sim}60 and \ensuremath{\sim}210 K. Unlike the ordinary SSE signal originating from the bare magnons, which changes sign at \ensuremath{\sim}95 and \ensuremath{\sim}266 K, the sign of the anomalies remains unchanged with increasing temperature. Moreover, the anomalies are found to show a temperature-sensitive double-peak structure between \ensuremath{\sim}116 and \ensuremath{\sim}143 K. We attribute these anomalies to the contribution from the quasiparticles hybridized between the Gd moment dominated spin wave (\ensuremath{\alpha} mode) and the transversal acoustic phonon, known as the magnon polarons. Given that the magnon polaron induced anomalies occur at the field where the linear phonon dispersion is tangential to the magnon dispersion curve, we explain these rich phenomena by an increase of the group velocity of the \ensuremath{\alpha}-mode magnon with increasing temperature and the nonparabolic magnon dispersion of ${\mathrm{Gd}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. Our results demonstrate that the magnon polaron induced SSE is helpful for the investigation of the magnon dispersion evolution with a simple transport approach.

Unravelling the local crystallographic structure of ferromagnetic gamma '-hbox {Ga}_y hbox {Fe}_{4-y}N nanocrystals embedded in GaN

In the Fe-doped GaN phase-separated magnetic semiconductor Gadelta FeN, the presence of embedded gamma '-hbox {Ga}_y hbox {Fe}_{4-y}N nanocrystals determines the magnetic properties of the system. Here, through a combination of anomalous X-ray diffraction and diffraction anomalous fine structure, the local structure of Ga in self-assembled face-centered cubic (fcc) gamma '-hbox {Ga}_y hbox {Fe}_{4-y}N nanocrystals embedded in wurtzite GaN thin layers is investigated in order to shed light onto the correlation between fabrication parameters, local structural arrangement and overall magnetic properties of the material system. It is found, that by adjusting the growth parameters and thus, the crystallographic surroundings, the Ga atoms can be induced to incorporate into 3c positions at the faces of the fcc crystal lattice, reaching a maximum occupancy of 30%. The magnetic response of the embedded nanocrystals is ferromagnetic with Curie temperature increasing from 450 to 500 K with the Ga occupation. These results demonstrate the outstanding potential of the employed experimental protocol for unravelling the local structure of magnetic multi-phase systems, even when embedded in a matrix containing the same element under investigation.