Ethical Issues in Empirical Studies of Software Engineering

The popularity of empirical methods in software engineering research is on the rise. Surveys, experiments, metrics, case studies, and field studies are examples of empirical methods used to investigate both software engineering processes and products. The increased application of empirical methods has also brought about an increase in discussions about adapting these methods to the peculiarities of software engineering. In contrast, the ethical issues raised by empirical methods have received little, if any, attention in the software engineering literature. This article is intended to introduce the ethical issues raised by empirical research to the software engineering research community, and to stimulate discussion of how best to deal with these ethical issues. Through a review of the ethical codes of several fields that commonly employ humans and artifacts as research subjects, we have identified major ethical issues relevant to empirical studies of software engineering. These issues are illustrated with real empirical studies of software engineering

Low Size-Complexity Inductive Logic Programming: The East-West Challenge Considered as a Problem in Cost-Sensitive Classification

The Inductive Logic Programming community has considered proof-complexity and model-complexity, but, until recently, size-complexity has received little attention. Recently a challenge was issued "to the international computing community" to discover low size-complexity Prolog programs for classifying trains. The challenge was based on a problem first proposed by Ryszard Michalski, 20 years ago. We interpreted the challenge as a problem in cost-sensitive classification and we applied a recently developed cost-sensitive classifier to the competition. Our algorithm was relatively successful (we won a prize). This paper presents our algorithm and analyzes the results of the competition

Globular cluster systems in fossil groups: NGC6482, NGC1132 and ESO306-017

We study the globular cluster (GC) systems in three representative fossil group galaxies: the nearest (NGC6482), the prototype (NGC1132) and the most massive known to date (ESO306-017). This is the first systematic study of GC systems in fossil groups. Using data obtained with the Hubble Space Telescope Advanced Camera for Surveys in the F475W and F850LP filters, we determine the GC color and magnitude distributions, surface number density profiles, and specific frequencies. In all three systems, the GC color distribution is bimodal, the GCs are spatially more extended than the starlight, and the red population is more concentrated than the blue. The specific frequencies seem to scale with the optical luminosities of the central galaxy and span a range similar to that of the normal bright elliptical galaxies in rich environments. We also analyze the galaxy surface brightness distributions to look for deviations from the best-fit S\'ersic profiles; we find evidence of recent dynamical interaction in all three fossil group galaxies. Using X-ray data from the literature, we find that luminosity and metallicity appear to correlate with the number of GCs and their mean color, respectively. Interestingly, although NGC6482 has the lowest mass and luminosity in our sample, its GC system has the reddest mean color, and the surrounding X-ray gas has the highest metallicity.Comment: 16 pages, 13 figures. Accepted for publication in A&

The Spectral Energy Distributions of White Dwarfs in 47 Tucanae: The Distance to the Cluster

We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting the spectral energy distributions of its white dwarfs to pure hydrogen atmosphere white dwarf models. Our photometric dataset is obtained from a 121 orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 square arcmins and extend over a radial range of 5-13.7 arcmin (6.5-17.9 pc) within the globular cluster. Using a likelihood analysis, we obtain a best fitting unreddened distance modulus of (m - M)o=13.36+/-0.02+/-0.06 corresponding to a distance of 4.70+/-0.04+/-0.13 kpc, where the first error is random and the second is systematic. We also search the white dwarf photometry for infrared excess in the F160W filter, indicative of debris disks or low mass companions, and find no convincing cases within our sample.Comment: Accepted to The Astronomical Journal, 13 Figures, 2 Tables. Figures 3 and 6 are figure sets, each composed of 59 subfigures (to appear in the electronic journal). This is a Companion paper to the article ID: submit/037561

Some Global Characteristics of the Galactic Globular Cluster System

The relations between the luminosities $M_{V}$, the metallicities $[Fe/H]$, the Galactocentric radii $R$, and the central concentration indices $c$ of Galactic globular clusters are discussed. It is found that the most luminous clusters rarely have collapsed cores. The reason for this might be that the core collapse time scales for such populous clusters are greater than the age of the Galaxy. Among those clusters, for which the structure has not been modified by core collapse, there is a correlation between central concentration and integrated luminosity, in the sense that the most luminous clusters have the strongest central concentration. The outermost region of the Galaxy with $R>10$ kpc was apparently not able to form metal-rich $([Fe/H]>-1.0)$ globular clusters, whereas such clusters (of which Ter 7 is the prototype) were able to form in some nearby dwarf spheroidal galaxies. It is not yet clear how the popular hypothesis that globular clusters were initially formed with a single power law mass spectrum can be reconciled with the observation that both (1) Galactic globular clusters with $R>80$ kpc, and (2) the globulars associated with the Sagittarius dwarf, appear to have bi-modal luminosity functions.Comment: 15 pages, 1 figur

Electron spin-orbit splitting in InGaAs/InP quantum well studied by means of the weak antilocalization and spin-zero effects in tilted magnetic fields

The coupling between Zeeman spin splitting and Rashba spin-orbit terms has been studied experimentally in a gated InGaAs/InP quantum well structure by means of simultaneous measurements of the weak antilocalization (WAL) effect and beating in the SdH oscillations. The strength of the Zeeman splitting was regulated by tilting the magnetic field with the spin-zeros in the SdH oscillations, which are not always present, being enhanced by the tilt. In tilted fields the spin-orbit and Zeeman splittings are not additive, and a simple expression is given for the energy levels. The Rashba parameter and the electron g-factor were extracted from the position of the spin zeros in tilted fields. A good agreement is obtained for the spin-orbit coupling strength from the spin-zeros and weak antilocalization measurements.Comment: Accepted for publication in Semiconductors Science and Technolog

The Collapse of the Spin-Singlet Phase in Quantum Dots

We present experimental and theoretical results on a new regime in quantum dots in which the filling factor 2 singlet state is replaced by new spin polarized phases. We make use of spin blockade spectroscopy to identify the transition to this new regime as a function of the number of electrons. The key experimental observation is a reversal of the phase in the systematic oscillation of the amplitude of Coulomb blockade peaks as the number of electrons is increased above a critical number. It is found theoretically that correlations are crucial to the existence of the new phases.Comment: REVTeX4, 4 pages, 4 figures, to appear in PR

Dynamics of Dense Cores in the Perseus Molecular Cloud

We survey the kinematics of over one hundred and fifty candidate (and potentially star-forming) dense cores in the Perseus molecular cloud with pointed N2H+(1-0) and simultaneous C18O(2-1) observations. Our detection rate of N2H+ is 62%, rising to 84% for JCMT SCUBA-selected targets. In agreement with previous observations, we find that the dense N2H+ targets tend to display nearly thermal linewidths, particularly those which appear to be starless (using Spitzer data), indicating turbulent support on the small scales of molecular clouds is minimal. For those N2H+ targets which have an associated SCUBA dense core, we find their internal motions are more than sufficient to provide support against the gravitational force on the cores. Comparison of the N2H+ integrated intensity and SCUBA flux reveals fractional N2H+ abundances between 10^-10 and 10^-9. We demonstrate that the relative motion of the dense N2H+ gas and the surrounding C18O gas is less than the sound speed in the vast majority of cases (~90%). The point-to-point motions we observe within larger extinction regions appear to be insufficient to provide support against gravity, although we sparsely sample these regions.Comment: 49 pages, 20 figures. Accepted for publication in the Astrophysical Journa

From Frequency to Meaning: Vector Space Models of Semantics

Computers understand very little of the meaning of human language. This profoundly limits our ability to give instructions to computers, the ability of computers to explain their actions to us, and the ability of computers to analyse and process text. Vector space models (VSMs) of semantics are beginning to address these limits. This paper surveys the use of VSMs for semantic processing of text. We organize the literature on VSMs according to the structure of the matrix in a VSM. There are currently three broad classes of VSMs, based on term-document, word-context, and pair-pattern matrices, yielding three classes of applications. We survey a broad range of applications in these three categories and we take a detailed look at a specific open source project in each category. Our goal in this survey is to show the breadth of applications of VSMs for semantics, to provide a new perspective on VSMs for those who are already familiar with the area, and to provide pointers into the literature for those who are less familiar with the field

Atomistic theory of electronic and optical properties of InAs/InP self-assembled quantum dots on patterned substrates

We report on a atomistic theory of electronic structure and optical properties of a single InAs quantum dot grown on InP patterned substrate. The spatial positioning of individual dots using InP nano-templates results in a quantum dot embedded in InP pyramid. The strain distribution of a quantum dot in InP pyramid is calculated using the continuum elasticity theory. The electron and valence hole single-particle states are calculated using atomistic effective-bond-orbital model with second nearest-neighbor interactions, coupled to strain via Bir-Pikus Hamiltonian. The optical properties are determined by solving many-exciton Hamiltonian for interacting electron and hole complexes using the configuration-interaction method. The effect of positioning of quantum dots using nanotemplate on their optical spectra is determined by a comparison with dots on unpatterned substrates, and with experimental results. The possibility of tuning the quantum dot properties with varying the nano-template is explored.Comment: 9 pages, 12 figure