Binary Orientation Research Articles

Template mode hierarchies for binary black hole mergers

Matched filtering is a popular data analysis framework used to search for gravitational wave signals emitted by compact object binaries. The templates used in matched filtering searches are constructed predominantly from the quadrupolar mode since this is the energetically most dominant mode. However, for highly precessing binaries or binaries with moderately large mass ratios, quadrupole templates lose sensitivity for a significant fraction of source orientations. We investigate how the inclusion of higher modes in the templates alleviates this loss of sensitivity and thus increases the prospects for detecting gravitational waves. Specifically, we use numerical relativity waveforms from the late inspiral and coalescence of binary black holes to identify mode hierarchies from which one can construct templates that cover the entire sky of binary orientations. The ordering in these hierarchies depends on the characteristics of the binary system and the mode strengths. The proposed hierarchies could assist in deciding which modes to add to template banks according to their ability to maximize sky coverage.

Parameter estimation for inspiraling eccentric compact binaries including pericenter precession

Inspiraling supermassive black hole binary systems with high orbital eccentricity are important sources for space-based gravitational wave observatories like the Laser Interferometer Space Antenna. Eccentricity adds orbital harmonics to the Fourier transform of the gravitational wave signal, and relativistic pericenter precession leads to a three-way splitting of each harmonic peak. We study the parameter estimation accuracy for such waveforms with different initial eccentricity, using the Fisher matrix method and a Monte Carlo sampling of the initial binary orientation. The eccentricity improves the parameter estimation by breaking degeneracies between different parameters. In particular, we find that the source localization precision improves significantly for higher-mass binaries due to eccentricity. The typical sky position errors are $\ensuremath{\sim}1\text{ }\text{ }\mathrm{deg}$ for a nonspinning, ${10}^{7}{M}_{\ensuremath{\bigodot}}$, equal-mass binary at redshift $z=1$, if the initial eccentricity 1 yr before merger is ${e}_{0}\ensuremath{\sim}0.6$. Pericenter precession does not affect the source localization accuracy significantly, but it does further improve the mass and eccentricity estimation accuracy systematically by a factor of 3--10 for masses between ${10}^{6}{M}_{\ensuremath{\bigodot}}$ and ${10}^{7}{M}_{\ensuremath{\bigodot}}$ for ${e}_{0}\ensuremath{\sim}0.3$.

Fragile Bits in Palmprint Recognition

Recent years have witnessed a growing interest in developing automatic palmprint recognition methods. Among them, coding-based ones, representing the texture of a palmprint using a binary code, are most prevalent and successful. We find that not all bits in a code map generated by a specific coding scheme are equally consistent. A bit is deemed fragile if its value changes across code maps created from different images of the same palmprint. In this paper, we first analyze the fragile bits phenomenon in a state-of-the-art palmprint coding scheme, namely, binary orientation co-occurrence vector (BOCV). Then, based on our analysis, we extend BOCV to E-BOCV by incorporating fragile bits information in appropriate ways. Experiments conducted on the benchmark dataset demonstrate that E-BOCV can achieve the highest verification accuracy among all the state-of-the-art palmprint verification methods evaluated. To our knowledge, this is the first work investigating the fragile bits of coding-based palmprint recognition approaches.

A LIGHTHOUSE EFFECT IN ETA CARINAE

We present a new model for the behavior of scattered time-dependent, asymmetric near-UV emission from the nearby ejecta of {\eta} Car. Using a 3-D hydrodynamical simulation of {\eta} Car's binary colliding winds, we show that the 3-D binary orientation derived by Madura et al. (2012) is capable of explaining the asymmetric near-UV variability observed in the Hubble Space Telescope Advanced Camera for Surveys/High Resolution Camera (HST ACS/HRC) F220W images of Smith et al. (2004b). Models assuming a binary orientation with i ~ 130 to 145 degrees, {\omega} ~ 230 to 315 degrees, PAz ~ 302 to 327 degrees are consistent with the observed F220W near-UV images. We find that the hot binary companion does not significantly contribute to the near-UV excess observed in the F220W images. Rather, we suggest that a bore-hole effect and the reduction of Fe II optical depths inside the wind-wind collision cavity carved in the extended photosphere of the primary star lead to the time-dependent directional illumination of circum-binary material as the companion moves about in its highly elliptical orbit.

Chaos-Based Cancelable Palmprint Authentication System

While biometrics presents obvious advantages over password and token-based security, the security concerns that biometric authentication raises need to be addressed. In this paper, we outlined cancelable palmprint binary orientation co-occurrence vector (BOCV) based on anisotropic filter(AF) using feedforward–feedback nonlinear dynamic filter (FFNDF) and then the independent matching scores is fused at the score level, which can efficiently protect the security of template and enhance the user's privacy. The cancelable system can provide large re-issuance ability and can be implemented very fast for real applications. It also has better robustness--- even in the stolen-token case, the result just reverts to the original performance without loss in performance and it can still achieve state-ofthe-art authentication accuracy, i.e., the EER is 0.07%.. Experiments on PolyU Palmprint Database confirm the effectiveness of the proposed approach.

Palmprint Recognition Based on Statistical Local Binary Orientation Code

A novel coding based method named as local binary orientation code (LBOCode) for palmprint recognition is proposed. The palmprint image is firstly convolved with a bank of Gabor filters, and then the orientation information is attained with a winner-take-all rule. Subsequently, the resulting orientation mapping array is operated by uniform local binary pattern. Accordingly, LBOCode image is achieved which contains palmprint orientation information in pixel level. Further we divide the LBOCode image into several equal-size and nonoverlapping regions, and extract the statistical code histogram from each region independently, which builds a global description of palmprint in regional level. In matching stage, the matching score between two palmprints is achieved by calculating the two spatial enhanced histograms' dissimilarity, which brings the benefit of computational simplicity. Experimental results demonstrate that the proposed method achieves more promising recognition performance compared with that of several state-of-the-art methods.

Binary Orientation Trees for Volume and Surface Reconstruction from Unoriented Point Clouds

AbstractGiven a complete unoriented point set, we propose a binary orientation tree (BOT) for volume and surface representation, which roughly splits the space into the interior and exterior regions with respect to the input point set. The BOTs are constructed by performing a traditional octree subdivision technique while the corners of each cell are associated with a tag indicating the in/out relationship with respect to the input point set. Starting from the root cell, a growing stage is performed to efficiently assign tags to the connected empty sub‐cells. The unresolved tags of the remaining cell corners are determined by examining their visibility via the hidden point removal operator. We show that the outliers accompanying the input point set can be effectively detected during the construction of the BOTs. After removing the outliers and resolving the in/out tags, the BOTs are ready to support any volume or surface representation techniques. To represent the surfaces, we also present a modified MPU implicits algorithm enabled to reconstruct surfaces from the input unoriented point clouds by taking advantage of the BOTs.

Palmprint verification using binary orientation co-occurrence vector

The development of accurate and robust palmprint verification algorithms is a critical issue in automatic palmprint authentication systems. Among various palmprint verification approaches, the orientation based coding methods, such as competitive code (CompCode), palmprint orientation code (POC) and robust line orientation code (RLOC), are state-of-the-art ones. They extract and code the locally dominant orientation as features and could match the input palmprint in real-time and with high accuracy. However, using only one dominant orientation to represent a local region may lose some valuable information because there are cross lines in the palmprint. In this paper, we propose a novel feature extraction algorithm, namely binary orientation co-occurrence vector (BOCV), to represent multiple orientations for a local region. The BOCV can better describe the local orientation features and it is more robust to image rotation. Our experimental results on the public palmprint database show that the proposed BOCV outperforms the CompCode, POC and RLOC by reducing the equal error rate (EER) significantly.

Gravitational-Wave Astronomy with Inspiral Signals of Spinning Compact-Object Binaries

Inspiral signals from binary compact objects (black holes and neutron stars) are primary targets of the ongoing searches by ground-based gravitational-wave interferometers (LIGO, Virgo, and GEO-600). We present parameter-estimation simulations for inspirals of black hole-neutron star binaries using Markov Chain Monte Carlo methods. For the first time, we both estimated the parameters of a binary inspiral source with a spinning, precessing component and determined the accuracy of the parameter estimation, for simulated observations with ground-based gravitational-wave detectors. We demonstrate that we can obtain the distance, sky position, and binary orientation at a higher accuracy than previously suggested in the literature. For an observation of an inspiral with sufficient spin and two or three detectors we find an accuracy in the determination of the sky position of the order of tens of square degrees.

A three-stage search for supermassive black-hole binaries in LISA data

Gravitational waves from the inspiral and coalescence of supermassive black-hole (SMBH) binaries with masses m1 ∼ m2 ∼ 106M⊙ are likely to be among the strongest sources for the Laser Interferometer Space Antenna (LISA). We describe a three-stage data-analysis pipeline designed to search for and measure the parameters of SMBH binaries in LISA data. The first stage uses a time–frequency track-search method to search for inspiral signals and provide a coarse estimate of the black-hole masses m1, m2 and the coalescence time of the binary tc. The second stage uses a sequence of matched-filter template banks, seeded by the first stage, to improve the measurement accuracy of the masses and coalescence time. Finally, a Markov chain Monte Carlo search is used to estimate all nine physical parameters of the binary (masses, coalescence time, distance, initial phase, sky position and orientation). Using results from the second stage substantially shortens the Markov chain burn-in time and allows us to determine the number of SMBH-binary signals in the data before starting parameter estimation. We demonstrate our analysis pipeline using simulated data from the first Mock LISA Data Challenge. We discuss our plan for improving this pipeline and the challenges that will be faced in real LISA data analysis.

Measuring a binary's orientation with LISA

We are presenting numerical results concerning LISA's ability to distinguish between different polarizational states of a gravitational wave. Therefore, we assume a binary as a source of a gravitational wave, finding its orientation which determines the polarization of the gravitational wave. By means of signal processing, we are able to give the 1σ-uncertainty for determining the orientation of the source.

Theoretical Modeling of Thermoelectricity in Bi Nanowires

AbstractBismuth as a semimetal is not a good thermoelectric material in bulk form because of the approximate cancellation between the electron and hole contributions. However, quantum confinement can be introduced by making Bi nanowires to move the lowest conduction subband edge up and the highest valence subband edge down to get a one-dimensional (1D) semiconductor at some critical wire diameter dc. A theoretical model based on the basic band structure of bulk Bi is developed to predict the dependence of these quantities on wire diameter and on the crystalline orientation of the bismuth nanowires. Numerical modeling is performed for trigonal, binary and bisectrix crystal orientations. By carefully tailoring the Bi wire diameter and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire diameters.

Binary invariants and orientations of graphs

It is well known that Julius Petersen’s famous paper on graph factorisation [9] has its origin in a problem which arose in connection with Hilbert’s proof of the Finite Basis Theorem for the invariants of binary forms [3]. Once one accepts the graph theoretic framework, the reformulation of the algebraic problem is straightforward and needs only a minimum of explanation-at least in the context of a hundred years ago-and this is precisely what Petersen provides in his paper. It is, however, unfortunate that he chose not to give any indication of the motivation for the fundamental idea of using graphs in connection with invariants, except in a very oblique way by acknowledging that Sylvester had also worked on the problem and that there had been some correspondence between them ([9, p. 1941, [13]). Indeed, Petersen’s whole approach is based on an observation made by Sylvester in 187~ignored by most invariant theorists at the time-to the effect that regular graphs contain essentially the same information as invariants of binary forms, in the sense that there is a natural map which assigns to each regular graph of order n an invariant of the binary form of order n, and that the invariants so obtained additively generate all invariants [14]. Instead of the unwieldy invariants one can therefore study the intuitively much more accessible graphs. In 1891 this was by no means self-evident, and Petersen’s silence on this point may well have contributed to the fact that his paper remained an isolated occurrence. In the present paper we shall take as our point of departure a problem which lies at the heart of the correspondence between graphs and invariants, and to which Petersen had given a certain amount of thought. The map graphs ---, invariants is many-to-one; it is therefore of interest to know which graphs lie in its ‘kernel’, i.e., give rise to the zero invariant. Petersen recognised the importance

Magnetic properties of bismuth at high fields

The magnetizationM of bismuth is calculated as a function of the magnetic fieldH atT=0 for binary, bisectrix, and trigonal orientations in the range of highH, from beyond the last de Haas-van Alphen oscillation up to 400 kG. The method of calculation is to sum the energies of the occupied energy levels and then to differentiate with respect toH; the energy levels are based on the ellipsoidal but nonparaboloidal model of the band structure. In qualitative and almost quantitative agreement with experiment, considerable departures ΔM are found from the proportionality betweenM andH which holds in the limit of lowH, and the results are presented in the form of tables and graphs of ΔM as a function ofH; the field dependence of the Fermi energy is also presented. An important contribution to the nonproportionality ΔM at highH proves to come from the electrons in the filled band and this contribution is calculated by a special method involving a cutoff parameter; the value chosen for this cutoff parameter affects only the proportional part ofM, but not ΔM.

The band structure of the group 5A alloys: magnetoreflection experiments

Infrared interband transitions in magnetic fields up to 80 kG have been observed at low temperatures in samples (binary orientation) of single crystal alloys of Sb1-xBix (x<or=0.125) using the magnetoreflection technique (Faraday configuration). As in pure Sb, two distinct interband series were observed over the alloy range. The main series, occurring at higher photon energies ( approximately 0.1-0.2 eV), showed the same lineshape and fine structure characteristics as the corresponding series in Sb. The lineshapes have been explained by a generalized orbital selection rule while the fine structure is believed to arise from spin-flipping transitions. These effects and the observed non parabolic behaviour have been quantitatively represented by a modified Lax two band model. The second, weaker series consists of two sets of transitions across the same energy gap but with different effective masses. The energy gaps associated with both interband series are found to decrease upon alloying in qualitative, but not quantitative, agreement with predicted behaviour. Existing band structure calculations fail to predict suitable sites for the interband transitions. Intraband magnetoreflection effects were also observed in the alloys. Magnetoplasma phenomena were observed in Sb and several alloy samples. The first observation of optical Shubnikov-de Haas oscillations in a dilute alloy (Sb99Bi1) are also reported.