Building Credit-Risk Evaluation Expert Systems Using Neural Network Rule Extraction and Decision Tables.

In this paper, we evaluate and contrast four neural network rule extraction approaches for credit scoring. Experiments are carried out on three real life credit scoring data sets. Both the continuous and the discretised versions of all data sets are analysed. The rule extraction algorithms, Neurolinear, Neurorule, Trepan and Nefclass, have different characteristics with respect to their perception of the neural network and their way of representing the generated rules or knowledge. It is shown that Neurolinear, Neurorule and Trepan are able to extract very concise rule sets or trees with a high predictive accuracy when compared to classical decision tree (rule) induction algorithms like C4.5(rules). Especially Neurorule extracted easy to understand and powerful propositional ifthen rules for all discretised data sets. Hence, the Neurorule algorithm may offer a viable alternative for rule generation and knowledge discovery in the domain of credit scoring.Credit; Information systems; International; Systems;

Transforming two-dimensional guided light using nonmagnetic metamaterial waveguides

Almost a decade ago, transformation optics established a geometrical perspective to describe the interaction of light with structured matter, enhancing our understanding and control of light. However, despite their huge technological relevance in applications such as optical circuitry, optical detection, and actuation, guided electromagnetic waves along dielectric waveguides have not yet benefited from the flexibility and conceptual simplicity of transformation optics. Indeed, transformation optics inherently imposes metamaterials not only inside the waveguide's core but also in the surrounding substrate and cladding. Here we restore the two-dimensional nature of guided electromagnetic waves by introducing a thickness variation on an anisotropic dielectric core according to alternative two-dimensional equivalence relations. Our waveguides require metamaterials only inside the core with the additional advantage that the metamaterials need not be magnetic and, hence, our purely dielectric waveguides are low loss. We verify the versatility of our theory with full wave simulations of three crucial functionalities: beam bending, beam splitting, and lensing. Our method opens up the toolbox of transformation optics to a plethora of waveguide-based devices

Nonmagnetic metamaterial landscapes for guided electromagnetic waves

Transformation optics provides a geometry-based tool to create new components taking advantage of artificial metamaterials with optical properties that are not available in nature. Unfortunately, although guided electromagnetic waves are crucial for optical circuitry, transformation optics is not yet compatible with two-dimensional slab waveguides. Indeed, after determining the propagation of confined waves along the waveguide with a two-dimensional coordinate transformation, the conventional application of transformation optics results in metamaterials whose properties are insensitive to the coordinate perpendicular to the waveguide, leading to bulky, and therefore impractical, designs. In this contribution, we formulate an alternative framework that leads to feasible coordinate-based designs of two-dimensional waveguides. To this end, we characterize a guided transverse-magnetic light mode by relevant electromagnetic equations: a Helmholtz equation to account for wave propagation and a dispersion relation to impose a continuous light profile at the interface. By considering how two-dimensional conformal transformations transform these equations, we are able to materialize the coordinate-designed flows with a nonmagnetic metamaterial core of varying thickness, obtaining a two-dimensional device. We numerically demonstrate the effectiveness and versatility of our equivalence relations with three crucial functionalities, a beam bender, a beam splitter and a conformal lens, on a qualitative and quantitative level, by respectively comparing the electromagnetic fields inside and the transmission of our two-dimensional metamaterial devices to that of their three-dimensional counterparts at telecom wavelengths. As a result, we envision that one coordinate-based multifunctional waveguide component may seamlessly split and bend light beams on the landscape of an optical chip

Transforming guided waves with metamaterial waveguide cores

Metamaterials make use of subwavelength building blocks to enhance our control on the propagation of light. To determine the required material properties for a given functionality, i.e., a set of desired light flows inside a metamaterial device, metamaterial designs often rely on a geometrical design tool known as transformation optics. In recent years, applications in integrated photonics motivated several research groups to develop two-dimensional versions of transformation optics capable of routing surface waves along graphene-dielectric and metal-dielectric interfaces. Although guided electromagnetic waves are highly relevant to applications in integrated optics, no consistent transformation-optical framework has so far been developed for slab waveguides. Indeed, the conventional application of transformation optics to dielectric slab waveguides leads to bulky three-dimensional devices with metamaterial implementations both inside and outside of the waveguide's core. In this contribution, we develop a transformation-optical framework that still results in thin metamaterial waveguide devices consisting of a nonmagnetic metamaterial core of varying thickness [Phys. Rev. B 93.8, 085429 (2016)]. We numerically demonstrate the effectiveness and versatility of our equivalence relations with three crucial functionalities: a beam bender, a beam splitter and a conformal lens. Our devices perform well on a qualitative (comparison of fields) and quantitative (comparison of transmitted power) level compared to their bulky counterparts. As a result, the geometrical toolbox of transformation optics may lead to a plethora of integrated metamaterial devices to route guided waves along optical chips

The first maps of κd - the dust mass absorption coefficient - in nearby galaxies, with DustPedia

The dust mass absorption coefficient, κd is the conversion function used to infer physical dust masses from observations of dust emission. However, it is notoriously poorly constrained, and it is highly uncertain how it varies, either between or within galaxies. Here we present the results of a proof-of-concept study, using the DustPedia data for two nearby face-on spiral galaxies M 74 (NGC 628) and M 83 (NGC 5236), to create the first ever maps of κd in galaxies. We determine κd using an empirical method that exploits the fact that the dust-to-metals ratio of the interstellar medium is constrained by direct measurements of the depletion of gas-phase metals. We apply this method pixel-by-pixel within M 74 and M 83, to create maps of κd. We also demonstrate a novel method of producing metallicity maps for galaxies with irregularly sampled measurements, using the machine learning technique of Gaussian process regression. We find strong evidence for significant variation in κd. We find values of κd at 500 μm spanning the range 0.11-0.25 m^{2 kg^{-1}} in M 74, and 0.15-0.80 m^{2 kg^{-1}} in M 83. Surprisingly, we find that κd shows a distinct inverse correlation with the local density of the interstellar medium. This inverse correlation is the opposite of what is predicted by standard dust models. However, we find this relationship to be robust against a large range of changes to our method - only the adoption of unphysical or highly unusual assumptions would be able to suppress it

Insights into gas heating and cooling in the disc of NGC 891 from Herschel far-infrared spectroscopy

We present Herschel PACS and SPIRE spectroscopy of the most important far-infrared cooling lines in the nearby edge-on spiral galaxy, NGC 891: [CII] 158 $\mu$m, [NII] 122, 205 $\mu$m, [OI] 63, 145 $\mu$m, and [OIII] 88 $\mu$m. We find that the photoelectric heating efficiency of the gas, traced via the ([CII]+[OII]63)/$F_{\mathrm{TIR}}$ ratio, varies from a mean of 3.5$\times$10$^{-3}$ in the centre up to 8$\times$10$^{-3}$ at increasing radial and vertical distances in the disc. A decrease in ([CII]+[OII]63)/$F_{\mathrm{TIR}}$ but constant ([CII]+[OI]63)/$F_{\mathrm{PAH}}$ with increasing FIR colour suggests that polycyclic aromatic hydrocarbons (PAHs) may become important for gas heating in the central regions. We compare the observed flux of the FIR cooling lines and total IR emission with the predicted flux from a PDR model to determine the gas density, surface temperature and the strength of the incident far-ultraviolet (FUV) radiation field, $G_{0}$. Resolving details on physical scales of ~0.6 kpc, a pixel-by-pixel analysis reveals that the majority of the PDRs in NGC 891's disc have hydrogen densities of 1 < log ($n$/cm$^{-3}$) < 3.5 experiencing an incident FUV radiation field with strengths of 1.7 < log $G_0$ < 3. Although these values we derive for most of the disc are consistent with the gas properties found in PDRs in the spiral arms and inter-arm regions of M51, observed radial trends in $n$ and $G_0$ are shown to be sensitive to varying optical thickness in the lines, demonstrating the importance of accurately accounting for optical depth effects when interpreting observations of high inclination systems. With an empirical relationship between the MIPS 24 $\mu$m and [NII] 205 $\mu$m emission, we estimate an enhancement of the FUV radiation field strength in the far north-eastern side of the disc.Comment: Accepted for publication in A&A. 25 pages, including 17 figures and 3 tables, abstract abridged for arXi

Intelligent Financial Fraud Detection Practices: An Investigation

Financial fraud is an issue with far reaching consequences in the finance industry, government, corporate sectors, and for ordinary consumers. Increasing dependence on new technologies such as cloud and mobile computing in recent years has compounded the problem. Traditional methods of detection involve extensive use of auditing, where a trained individual manually observes reports or transactions in an attempt to discover fraudulent behaviour. This method is not only time consuming, expensive and inaccurate, but in the age of big data it is also impractical. Not surprisingly, financial institutions have turned to automated processes using statistical and computational methods. This paper presents a comprehensive investigation on financial fraud detection practices using such data mining methods, with a particular focus on computational intelligence-based techniques. Classification of the practices based on key aspects such as detection algorithm used, fraud type investigated, and success rate have been covered. Issues and challenges associated with the current practices and potential future direction of research have also been identified.Comment: Proceedings of the 10th International Conference on Security and Privacy in Communication Networks (SecureComm 2014

The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The distribution and properties of molecular cloud associations in M31

In this paper we present a catalog of Giant Molecular Clouds (GMCs) in the An- dromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy An- dromeda (HELGA) dataset. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterise the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al (2012). 326 GMCs in the mass range 104 − 107 M⊙ are identified, their cumulative mass distribution is found to be proportional to M −2.34 in agreement with earlier studies. The GMCs appear to follow the same cloud mass to LCO correlation observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit suggesting that we are observing associations of GMCs. Following Gordon et al. (2006), we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8fdg9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system

High-resolution, 3D radiative transfer modelling : V. A detailed model of the M 51 interacting pair

Context. Investigating the dust heating mechanisms in galaxies provides a deeper understanding of how the internal energy balance drives their evolution. Over the last decade radiative transfer simulations based on the Monte Carlo method have emphasised the role of the various stellar populations heating the diffuse dust. Beyond the expected heating through ongoing star formation, older stellar populations (>= 8 Gyr) and even active galactic nuclei can both contribute energy to the infrared emission of diffuse dust.Aims. In this particular study we examine how the radiation of an external heating source, such as the less massive galaxy NGC 5195 in the M 51 interacting system, could affect the heating of the diffuse dust of its parent galaxy NGC 5194, and vice versa. Our goal is to quantify the exchange of energy between the two galaxies by mapping the 3D distribution of their radiation field.Methods. We used SKIRT, a state-of-the-art 3D Monte Carlo radiative transfer code, to construct the 3D model of the radiation field of M 51, following the methodology defined in the DustPedia framework. In the interest of modelling, the assumed centre-to-centre distance separation between the two galaxies is similar to 10 kpc.Results. Our model is able to reproduce the global spectral energy distribution of the system, and it matches the resolved optical and infrared images fairly well. In total, 40.7% of the intrinsic stellar radiation of the combined system is absorbed by dust. Furthermore, we quantify the contribution of the various dust heating sources in the system, and find that the young stellar population of NGC 5194 is the predominant dust-heating agent, with a global heating fraction of 71.2%. Another 23% is provided by the older stellar population of the same galaxy, while the remaining 5.8% has its origin in NGC 5195. Locally, we find that the regions of NGC 5194 closer to NGC 5195 are significantly affected by the radiation field of the latter, with the absorbed energy fraction rising up to 38%. The contribution of NGC 5195 remains under the percentage level in the outskirts of the disc of NGC 5194. This is the first time that the heating of the diffuse dust by a companion galaxy is quantified in a nearby interacting system

DustPedia: Multiwavelength photometry and imagery of 875 nearby galaxies in 42 ultraviolet-microwave bands

Aims. The DustPedia project is capitalising on the legacy of the Herschel Space Observatory, using cutting-edge modelling techniques to study dust in the 875 DustPedia galaxies – representing the vast majority of extended galaxies within 3000 km s-1 that were observed by Herschel. This work requires a database of multiwavelength imagery and photometry that greatly exceeds the scope (in terms of wavelength coverage and number of galaxies) of any previous local-Universe survey. Methods. We constructed a database containing our own custom Herschel reductions, along with standardised archival observations from GALEX, SDSS, DSS, 2MASS, WISE, Spitzer, and Planck. Using these data, we performed consistent aperture-matched photometry, which we combined with external supplementary photometry from IRAS and Planck. Results. We present our multiwavelength imagery and photometry across 42 UV-microwave bands for the 875 DustPedia galaxies. Our aperture-matched photometry, combined with the external supplementary photometry, represents a total of 21 857 photometric measurements. A typical DustPedia galaxy has multiwavelength photometry spanning 25 bands. We also present the Comprehensive & Adaptable Aperture Photometry Routine (CAAPR), the pipeline we developed to carry out our aperture-matched photometry. CAAPR is designed to produce consistent photometry for the enormous range of galaxy and observation types in our data. In particular, CAAPR is able to determine robust cross-compatible uncertainties, thanks to a novel method for reliably extrapolating the aperture noise for observations that cover a very limited amount of background. Our rich database of imagery and photometry is being made available to the community