Synthesizing framework models for symbolic execution

Symbolic execution is a powerful program analysis technique, but it is difficult to apply to programs built using frameworks such as Swing and Android, because the framework code itself is hard to symbolically execute. The standard solution is to manually create a framework model that can be symbolically executed, but developing and maintaining a model is difficult and error-prone. In this paper, we present Pasket, a new system that takes a first step toward automatically generating Java framework models to support symbolic execution. Pasket's focus is on creating models by instantiating design patterns. Pasket takes as input class, method, and type information from the framework API, together with tutorial programs that exercise the framework. From these artifacts and Pasket's internal knowledge of design patterns, Pasket synthesizes a framework model whose behavior on the tutorial programs matches that of the original framework. We evaluated Pasket by synthesizing models for subsets of Swing and Android. Our results show that the models derived by Pasket are sufficient to allow us to use off-the-shelf symbolic execution tools to analyze Java programs that rely on frameworks.National Science Foundation (U.S.) (CCF-1139021)National Science Foundation (U.S.) (CCF-1139056)National Science Foundation (U.S.) (CCF-1161775

Quantum and frustration effects on fluctuations of the inverse compressibility in two-dimensional Coulomb glasses

We consider interacting electrons in a two-dimensional quantum Coulomb glass and investigate by means of the Hartree-Fock approximation the combined effects of the electron-electron interaction and the transverse magnetic field on fluctuations of the inverse compressibility. Preceding systematic study of the system in the absence of the magnetic field identifies the source of the fluctuations, interplay of disorder and interaction, and effects of hopping. Revealed in sufficiently clean samples with strong interactions is an unusual right-biased distribution of the inverse compressibility, which is neither of the Gaussian nor of the Wigner-Dyson type. While in most cases weak magnetic fields tend to suppress fluctuations, in relatively clean samples with weak interactions fluctuations are found to grow with the magnetic field. This is attributed to the localization properties of the electron states, which may be measured by the participation ratio and the inverse participation number. It is also observed that at the frustration where the Fermi level is degenerate, localization or modulation of electrons is enhanced, raising fluctuations. Strong frustration in general suppresses effects of the interaction on the inverse compressibility and on the configuration of electrons.Comment: 15 pages, 18 figures, To appear in Phys. Rev.

The continuum limit of quark number susceptibilities

We report the continuum limit of quark number susceptibilities in quenched QCD. Deviations from ideal gas behaviour at temperature T increase as the lattice spacing is decreased from T/4 to T/6, but a further decrease seems to have very little effect. The measured susceptibilities are 20% lower than the ideal gas values, and also 10% below the hard thermal loop (HTL) results. The off-diagonal susceptibility is several orders of magnitude smaller than the HTL results. We verify a strong correlation between the lowest screening mass and the susceptibility. We also show that the quark number susceptibilities give a reasonable account of the Wroblewski parameter, which measures the strangeness yield in a heavy-ion collision.Comment: 8 pages, 5 figure

Fluctuations of particle ratios and the abundance of hadronic resonances

In this letter we will argue that the event-by-event fluctuations of the ratio of positively over negatively charged pions provides a measurements of the number of rho and omega mesons right after hadronization. This finding can be utilized to put the hypothesis of chemical equilibration in relativistic heavy ion collisions to a test.Comment: 4 pages. No figure. Uses revtex with prl, aps, and multicol style

Using conditional kernel density estimation for wind power density forecasting

Of the various renewable energy resources, wind power is widely recognized as one of the most promising. The management of wind farms and electricity systems can benefit greatly from the availability of estimates of the probability distribution of wind power generation. However, most research has focused on point forecasting of wind power. In this paper, we develop an approach to producing density forecasts for the wind power generated at individual wind farms. Our interest is in intraday data and prediction from 1 to 72 hours ahead. We model wind power in terms of wind speed and wind direction. In this framework, there are two key uncertainties. First, there is the inherent uncertainty in wind speed and direction, and we model this using a bivariate VARMA-GARCH (vector autoregressive moving average-generalized autoregressive conditional heteroscedastic) model, with a Student t distribution, in the Cartesian space of wind speed and direction. Second, there is the stochastic nature of the relationship of wind power to wind speed (described by the power curve), and to wind direction. We model this using conditional kernel density (CKD) estimation, which enables a nonparametric modeling of the conditional density of wind power. Using Monte Carlo simulation of the VARMA-GARCH model and CKD estimation, density forecasts of wind speed and direction are converted to wind power density forecasts. Our work is novel in several respects: previous wind power studies have not modeled a stochastic power curve; to accommodate time evolution in the power curve, we incorporate a time decay factor within the CKD method; and the CKD method is conditional on a density, rather than a single value. The new approach is evaluated using datasets from four Greek wind farms

Resonances and fluctuations of strange particle in 200 GeV Au-Au collisions

We perform an analysis of preliminary data on strange particles yields and fluctuations within the Statistical hadronization model. We begin by describing the theoretical disagreements between different statistical models currently on the market. We then show how the simultaneous analysis of yields and fluctuations can be used to differentiate between the different models, and determine if one of them can be connected to underlying physics. We perform a study on a RHIC 200 GeV data sample that includes stable particles, resonances, and the event-by-event fluctuation of the $K/\pi$ ratio. We show that the equilibrium statistical model can not describe the fluctuation, unless an unrealistically small volume is assumed. Such small volume then makes it impossible to describe the total particle multiplicity. The non-equilibrium model,on the other hand, describes both the $K/\pi$ fluctuation and yields acceptably due to the extra boost to the $\pi$ fluctuation provided by the high pion chemical potential. $\Lambda(1520)$ and $K^*$ abundance is described within error bars, but the $\Sigma^*$ is under-predicted to $\sim$ 1.5 standard deviations. We suggest further measurements that have the potential to test the non-equilibrium model, as well as gauge the effect of re-interactions between hadronization and freeze-out.Comment: References added, equations corrected. As accepted for publication by Journal of Physics

Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: comparison of different models

Differential spectra of coherent photon bremsstrahlung in relativistic heavy ion collisions are calculated within various schematic models of the projectile-target stopping. Two versions of the degradation length model, based on a phenomenological deceleration law, are considered. The simple shock wave model is studied analytically. The predictions of these models agree in the soft photon limit, where the spectrum is determined only by the final velocity distribution of charged particles. The results of these models in the case of central Au+Au collisions at various bombarding energies are compared with the predictions of the microscopic transport model UrQMD. It is shown that at the AGS energy the coherent photon bremsstrahlung exceeds the photon yield from $\pi^0$-decays at photon energies \omega\loo 50 MeV.Comment: 23 pages RevTeX, 9 eps Figure

Variable stars in the Open Cluster M11 (NGC 6705)

V-band time-series CCD photometric observations of the intermediate-age open cluster M11 were performed to search for variable stars. Using these time-series data, we carefully examined light variations of all stars in the observing field. A total of 82 variable stars were discovered, of which 39 stars had been detected recently by Hargis et al. (2005). On the basis of observational properties such as variable period, light curve shape, and position on a color-magnitude diagram, we classified their variable types as 11 delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries, and 16 eclipsing binaries with long period. Cluster membership for each variable star was deduced from the previous proper motion results (McNamara et al. 1977) and position on the color-magnitude diagram. Many pulsating stars and eclipsing binaries in the region of M11 are probable members of the cluster.Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PAS

Anatomical changes in the East Asian midface skeleton with aging

Background: Understanding the aging process of the midface skeleton is considered crucial for correct facial rejuvenation. However, the canine fossa, an important morphological feature of the midface skeleton, has not yet been observed in connection with aging, despite the fact that it is the most main part of the maxillary bone. Here, the authors focus on the depression of the canine fossa to evaluate the Asian midface skeleton. Materials and methods: Computed tomography (CT) scans of the facial skeleton of 114 Koreans (59 males and 55 females) were reconstructed to three-dimensional (3D) images using a 3D analysis software programme. The study subjects included 27 young males, 32 old males, 28 young females and 27 old females. The angular measurements of three bony regions were measured for each 3D model: the canine fossa angle (assessing depth of the canine fossa), the maxillary angle (assessing orientation of the lateral maxilla) and the piriform angle (assessing orientation of the medial maxilla). Results: The canine fossa angle showed a statistically significant decrease with aging in both sexes, indicating the canine fossa actually becomes more concave with age. In contrast, the maxillary and piriform angle showed statistically insignificant changes with aging in female subjects. Conclusions: These results suggest that the canine fossa may be one of the effective markers to evaluate the anatomical changes to the facial skeleton with midface aging. (