Anomalous Objects Research Articles

3D inversion of gravity data by separation of sources and the method of local corrections: Kolarovo gravity high case study

We present a novel methodology for 3D gravity/magnetic data inversion. It combines two algorithms for preliminary separation of sources and an original approach to 3D inverse problem solution. The first algorithm is designed to separate sources in depth and to remove the shallow ones. It is based on subsequent upward and downward data continuation. For separation in the lateral sense, we approximate the given observed data by the field of several 3D line segments. For potential field data inversion we apply a new method of local corrections. The method is efficient and does not require trial-and-error forward modeling. It allows retrieving unknown 3D geometry of anomalous objects in terms of restricted bodies of arbitrary shape and contact surfaces. For restricted objects, we apply new integral equations of gravity and magnetic inverse problems. All steps of our methodology are demonstrated on the Kolarovo gravity anomaly in the Danube Basin of Slovakia.

Nonparametric Framework for Detecting Spectral Anomalies in Hyperspectral Images

Over the past few years, hyperspectral data exploitation aimed at detecting spectral anomalies within remotely sensed images has been of growing interest in many applications. In this letter, we are interested in an anomaly detection (AD) scheme for hyperspectral images in which spectral anomalies are defined with respect to a statistical model of the background probability density function (PDF). Among the multitude of PDF estimators discussed in statistics literature, Parzen windowing (PW) has always attracted much attention. However, its ability to estimate the PDF of global background in order to detect anomalies in hyperspectral images has not been investigated yet. Here, we propose the use of PW to provide reliable background PDF estimation. As is widely recognized, PW performance is primarily affected by the choice of the bandwidth matrix, which controls the degree of smoothing for the resulting PDF approximation. In this letter, the bandwidth selection problem is approached, resorting to an unsupervised method based on a Bayesian approach. Once the background PDF is approximated through PW, it is employed to detect anomalous objects within the scene by using the likelihood ratio test.

Finding anomalous periodic time series

Catalogs of periodic variable stars contain large numbers of periodic light-curves (photometric time series data from the astrophysics domain). Separating anomalous objects from well-known classes is an important step towards the discovery of new classes of astronomical objects. Most anomaly detection methods for time series data assume either a single continuous time series or a set of time series whose periods are aligned. Light-curve data precludes the use of these methods as the periods of any given pair of light-curves may be out of sync. One may use an existing anomaly detection method if, prior to similarity calculation, one performs the costly act of aligning two light-curves, an operation that scales poorly to massive data sets. This paper presents PCAD, an unsupervised anomaly detection method for large sets of unsynchronized periodic time-series data, that outputs a ranked list of both global and local anomalies. It calculates its anomaly score for each light-curve in relation to a set of centroids produced by a modified k-means clustering algorithm. Our method is able to scale to large data sets through the use of sampling. We validate our method on both light-curve data and other time series data sets. We demonstrate its effectiveness at finding known anomalies, and discuss the effect of sample size and number of centroids on our results. We compare our method to naive solutions and existing time series anomaly detection methods for unphased data, and show that PCAD's reported anomalies are comparable to or better than all other methods. Finally, astrophysicists on our team have verified that PCAD finds true anomalies that might be indicative of novel astrophysical phenomena.

A two-loop frequency-domain electromagnetic induction system for detection of anomalous objects

We discuss a two-loop frequency-domain electromagnetic induction sounding system which allows vertical focussing of the primary magnetic field thus reducing the disturbance from shallow subsurface. The frequency dependence of apparent resistivity estimated from the real part of the measured magnetic field turns out to be more sensitive than that found from the absolute total field. The advantage of the suggested FD EMI system has been validated by experiments.

Metallicities and Physical Conditions in Star‐forming Galaxies atz∼ 1.0–1.51

We present a study of the mass-metallicity (M-Z) relation and H II region physical conditions in a sample of 20 star-forming galaxies at 1.0 < z < 1.5 drawn from the DEEP2 Galaxy Redshift Survey. We find a correlation between stellar mass and gas-phase oxygen abundance in the sample and compare it with the one observed among UV-selected z ∼ 2 star-forming galaxies and local objects from the Sloan Digital Sky Survey (SDSS). This comparison, based on the same empirical abundance indicator, demonstrates that the zero point of the M-Z relationship evolves with redshift, in the sense that galaxies at fixed stellar mass become more metal-rich at lower redshift. Measurements of [O III]/Hβ and [N II]/Hα emission-line ratios show that, on average, objects in the DEEP2 1.0 < z < 1.5 sample are significantly offset from the excitation sequence observed in nearby H II regions and SDSS emission-line galaxies. In order to fully understand the causes of this offset, which is also observed in z ∼ 2 star-forming galaxies, we examine in detail the small fraction of SDSS galaxies that have similar diagnostic ratios to those of the DEEP2 sample. Some of these galaxies indicate evidence for AGN and/or shock activity, which may give rise to their unusual line ratios and contribute to Balmer emission lines at the level of ~20%. Others indicate no evidence for AGN or shock excitation yet are characterized by higher electron densities and temperatures, and therefore interstellar gas pressures, than typical SDSS star-forming galaxies of similar stellar mass. These anomalous objects also have higher concentrations and starformation rate surface densities, which are directly connected to higher interstellar pressure. Higher star formation rate surface densities, interstellar pressures, and H II region ionization parameters may also be common at high redshift. These effects must be taken into account when using strong-line indicators to understand the evolution of heavy elements in galaxies. When such effects are included, the inferred evolution of the M-Z relation out to z ∼ 2 is more significant than previous estimates.

Bulge and Halo Kinematics Across the Hubble Sequence

The correlation between the maximum rotational velocity of the disk (vm) and the central stellar velocity dispersion of the bulge (σ0) offers insights into the relationship between the halo and the bulge. We have assembled integrated H I line widths and central stellar velocity dispersions to study the vm-σ0 relation for 792 galaxies spanning a broad range of Hubble types. Contrary to earlier studies based on much smaller samples, we find that the vm-σ0 relation exhibits significant intrinsic scatter and that its zero point varies systematically with galaxy morphology, bulge-to-disk ratio, and light concentration, as expected from basic dynamical considerations. Nucleated but bulgeless late-type spiral galaxies depart significantly from the vm-σ0 relation. While these results render questionable any attempt to supplant the bulge with the halo as the fundamental determinant of the central black hole mass in galaxies, the observed distribution of vm/σ0, which depends on both the density profile and kinematic structure of the galaxy, offers a useful constraint on galaxy formation models. With the aid of a near-infrared Tully-Fisher relation, we identify a population of otherwise normal, luminous galaxies that have exceptionally low values of vm/σ0. We argue that a significant fraction of the H I gas in these kinematically anomalous objects is dynamically unrelaxed, having been acquired externally either through capture from tidal interactions or through cold accretion from the intergalactic medium.

Geoelectric nondestructive testing of hydraulic structures via differential induction facilities

The problem of differential induction profiling above an anomalous object is solved. It is shown that differential profiling enables monitoring of how the boundaries of the zones where water drains through the body of a dam change with time.

Multipixel anomaly detection in noisy multispectral images

Basing ourselves on a novel segmentation algorithm for multispectral images, we consider how to detect multipixel anomalous objects in image cubes where spectral information is available. In particular, we have developed several morphological filters to compensate for noise that may be present in the initial cube. We show that for different types of noise (Gaussian and speckle), a modification of our morphology technique allows us to better detect targets without an enhanced false-alarm result.

Active asteroids: mystery in the Main Belt

Classically, comets from the outer solar system (beyond the orbit of Neptune), are expected to be icy, and thus active near the Sun, while asteroids in the inner solar system (interior to the orbit of Jupiter) are expected to be relatively ice-deficient, and thus inert. Studies of anomalous objects, most recently 133P/Elst-Pizarro, challenge this classical picture, however, and suggest that either (1) subsurface ice can in fact be preserved over billions of years in small bodies in the inner solar system but still be close enough to the surface to be excavated by an impact by another body, or (2) non-gravitational dynamical evolution (primarily driven by asymmetrical outgassing) of icy bodies from the outer solar system can drive these cometary bodies onto thoroughly asteroid-like orbits, erasing all dynamical signs of their trans-Neptunian origins in the process. The question thus boils down to whether occasionally sublimating icy bodies on stable asteroid-like orbits in the inner solar system, particularly in the main asteroid belt, may in fact be native to the region or whether they must necessarily be recent arrivals.

Connector-based self-healing mechanism for components of a reliable system

This paper describes the self-healing mechanism for components in reliable systems. Each component in a self-healing system is designed as a layered architecture, structured with the healing layer and the service layer. The healing layer of a self-healing component is responsible for detection of anomalous objects in the service layer, reconfiguration of the service layer, and repair of anomalous objects detected. The service layer of a self-healing component provides functionality to other components, which consists of tasks (concurrent or active objects), connectors, and passive objects accessed by tasks. A connector supports the self-healing mechanism for self-healing components as well as encapsulates the synchronization mechanism for message communication between tasks in a component. Connectors are involved in detection of anomalous objects, reconfiguration of components, and repair of anomalous objects. This paper also specifies connectors - the message queue self-healing connector. message buffer self-healing connector, and message buffer and response self-healing connector - which provide functionalities for the self-healing mechanism.

Microscopic oxygen isotopic homogeneity/heterogeneity in the matrix of the Vigarano CV3 chondrite

Two-dimensional 18O/ 16O isotopic analysis of the Vigarano matrix was conducted by secondary ion-imaging using a novel two-dimensional ion-imager. Quantitative oxygen-isotope images (isotopographs) of the Vigarano matrix show that 16O-rich micrograins are scattered within 16O-poor matrix. This heterogeneous O-isotopic distribution indicates that matrix is composed of different O-isotopic components that formed in different locations and/or at different times. However, the O-isotopic composition of groundmass in the matrix is the same as the bulk isotopic composition of the matrix within ±5 ‰ uncertainty. The spatial resolution and isotopic precision of our technique should allow submicron-size objects (>0.2 μm) with extreme O-isotopic anomalous characteristics (δ 18O SMOW ∼250 ‰) to be detectable in isotopographs. Because the mean grain size of the matrix is ∼0.2 μm, the inability to detect such O-isotopic anomalous objects indicates that isotopically anomalous micrograins (e.g., presolar grains) are extremely rare in the Vigarano matrix and that most objects in the matrix were formed in the solar nebula or in the parent body.

A Pet Study of Visual and Semantic Knowledge About Objects

The distinctiveness of temporal lobe regions activated during the retrieval of knowledge regarding structural, colour and associative (encyclopaedic) aspects of familiar objects was investigated using PET. These three types of knowledge were contrasted using well matched tasks requiring the detection, in a series of coloured-in line drawings, of occasional anomalous objects (in the three conditions: structurally incorrect chimeras composed of parts of real objects; inappropriately coloured objects; familiar objects that do not exist in the modern world). Relative to a resting baseline condition, all semantic retrieval tasks yielded extensive bilateral activations in occipital and temporal areas, extending anteriorly on the ventral surface of the brain, plus an area in the right superior parietal lobe. In direct semantic-task comparisons focussing on the temporal lobe: (i) structural relative to associative decisions activated the right posterior middle/inferior temporal gyrus; (ii) colour decisions relative to structural judgements were associated with a region in the right superior temporal gyrus; (iii) the associative decision task selectively activated the left anterior middle/superior temporal gyrus and temporal pole relative to both object structure and colour, and also the homologous right temporal pole relative to colour only. These results indicate that each type of stored knowledge involves at least partially distinct cortical areas, and suggest that both anterior/posterior and left/right temporal regions have specialised roles.

Physical conditions in hotspots—what the new data are telling us

I review the current constraints on the nature of the hotspots of FR II radio sources, and the physical conditions that obtain in them. New Chandra observations suggest that the majority of X-ray detections of hotspots are due to inverse-Compton processes, with magnetic field strengths close to the standard equipartition/minimum-energy values. However, a few broad-line objects have X-ray emission much brighter than the expected inverse-Compton level. These may be due to synchrotron emission from a second population of electrons. I discuss the advantages and disadvantages of models for the anomalous objects involving relativistic bulk motions in the hotspots.

The refinement of PLS models by iterative weighting of predictor variables and objects

The flexibility of PLS algorithm can be used to assign suitable weights to predictors or to objects or to both predictors and objects. Weights of predictors are obtained from the regression coefficients and the standard deviation. Weights of objects are obtained from the prediction residuals. By iterative weighting, the regression models are refined and a steady state is attained, where useless predictors and anomalous objects are cancelled, and a very economical model is obtained. The predictive ability and stability of this final model are better than those of the original model with all the available predictors and objects.

Rotation and Activity in Mid‐M to L Field Dwarfs

We analyze rotation velocities and chromospheric (H?) activity, derived from high-resolution spectra, in a large sample of mid-M to L field dwarfs. The projected rotation velocity is found to increase from mid-M to L. This is consistent with a lengthening of spin-down timescale with later type, although in the L types the trend may also be a function of the observational bias toward younger objects. From M4 to M8.5 a saturation-type rotation-activity relation is seen, similar to that in earlier types, when activity is measured through either FH? or LH?/Lbol. However, we find that activity saturates at a significantly higher velocity (~10 km s-1) in the M5.5-M8.5 dwarfs than in the M4-M5 ones (4 km s-1). This may result from a change in the dynamo behavior with later type (see also below). We note that the saturation level in H? emission appears to vary somewhat less with spectral type (from M4 to M8.5) when activity is measured through LH?/Lbol instead of FH?. In M9 and later dwarfs, we observe a drastic drop in activity and a sharp break in the rotation-activity connection: H? emission levels in these dwarfs are much lower than in earlier types, and often undetectable, in spite of very rapid rotation. This may be caused by the very high resistivities in the predominantly neutral atmospheres of these dwarfs, which would damp the magnetic energy available for supporting a chromosphere. It is also possible that the rapid formation of dust in these cool atmospheres exacerbates this effect, as charged particles are soaked up by (more massive) dust grains. Finally, we note that spectral type determination from low-resolution spectra may be affected by gravity effects: cooler, lower gravity objects may mimic hotter, higher gravity ones. Therefore, it is possible that the few unsaturated fast rotators from M5.5 to M8.5 (whose presence leads us to ascribe a higher saturation velocity to these spectral types, as noted above) may actually be very low mass objects, with lower Teff (and gravity) than their spectral types suggest. If so, their behavior (low activity, fast rotation) would be compatible with that of the cool M9 and later dwarfs (and no change in dynamo behavior would have to be postulated in the M5.5-M8.5 dwarfs). This interpretation is supported by a preliminary analysis of the high-resolution spectra of these anomolous objects. It is also bolstered by the fact that a saturation-type Rossby number-activity relation is seen in the M5.5-M8.5 dwarfs when these anomalous objects are removed from the sample, while the relationship is much weaker when they are included.

Classification and properties of UV extinction curves

The catalog of Savage et al. ([CITE]) reporting colour excesses of 1415 stars from ANS photometry offers the opportunity to deeply investigate the characteristics of UV extinction curves which differ from the standard extinction of the diffuse interstellar medium. To this aim we have selected a sample of 252 curves, which have been compared with the relations derived by Cardelli et al. ([CITE]; CCM in the following) for a variety of R V values in the range 2.4-5 and have been classified as normal if they fit at least one of the CCM curves or anomalous otherwise. We find that normal curves with small R V are just as numerous as those with large R V . The anomalous objects are arranged into two groups according to the strength of the bump at $0.217 \mu$. For a given value of c 2 this increases along the sequence: type A anomalous, normals and type B anomalous, suggesting that this sequence should correspond to an increase of the amount of small grains along the sightline. Considerations concerning the environmental characteristics indicate that the anomalous behaviour is not necessarily tied to the existence of dense gas clouds along the line of sight.

Real-time sonomammography based on the intersecting canonical body approximation of the diffracted wave field

The inverse problem of the identification of an anomalous object (e.g. cyst or tumor) in a female breast immersed in water is solved by the matching of theoretical fields (for trial objects), employing an approximate field ansatz. to the scattered ultrasonic wave field measured on a surface fully enclosing the object.

Representative noise-free complete-link classification with application to protein structures

In various applications, including many problems of knowledge discovery in databases, and particularly in the field of computational molecular biology, a compact and representative description of a vast object space is desired. In this paper, a constructive mathematical model corresponding the intuitive requirements of representativity is developed. Representativity is divided into two aspects: typicality and comprehensiveness. A new sieving method is presented where a special kind of noise is detected and eliminated by removing anomalous objects from the initial complete linkage partition. The comprehensiveness endangered by sieving is then regained by applying a special completion procedure. Theoretical results ensure that the resulting partition is representative, consisting of solid and separable classes. The conceptual model was further tested by applying the method to protein amino acid sequences of the Brookhaven Protein Data Bank. The recognized biochemical substance of the outcome confirm the representativity of the resulting classification.

センサ配置に制約を伴うときのシールド工法における塊状異常物体検知のための観測系の最適化

センサ配置に制約を伴うときのシールド工法における塊状異常物体検知のための観測系の最適化

シールド工法における傾斜面異常物体検知のための音響センサの最適配置および最適観測方策

シールド工法における傾斜面異常物体検知のための音響センサの最適配置および最適観測方策