Selecting a Cost-Effective Test Case Prioritization Technique

Regression testing is an expensive testing process used to validate modified software and detect whether new faults have been introduced into previously tested code. To reduce the cost of regression testing, software testers may prioritize their test cases so that those which are more important, by some measure, are run earlier in the regression testing process. One goal of prioritization is to increase a test suite's rate of fault detection. Previous empirical studies have shown that several prioritization techniques can significantly improve rate of fault detection, but these studies have also shown that the effectiveness of these techniques varies considerably across various attributes of the program, test suites, and modifications being considered. This variation makes it difficult for a practitioner to choose an appropriate prioritization technique for a given testing scenario. To address this problem, we analyze the fault detection rates that result from applying several different prioritization techniques to several programs and modified versions. The results of our analyses provide insights into which types of prioritization techniques are and are not appropriate under specific testing scenarios, and the conditions under which they are or are not appropriate. Our analysis approach can also be used by other researchers or practitioners to determine the prioritization techniques appropriate to other workloads.     

Profiling deployed software: assessing strategies and testing opportunities

An understanding of how software is employed in the field can yield many opportunities for quality improvements. Profiling released software can provide such an understanding. However, profiling released software is difficult due to the potentially large number of deployed sites that must be profiled, the transparency requirements at a user's site, and the remote data collection and deployment management process. Researchers have recently proposed various approaches to tap into the opportunities offered by profiling deployed systems and overcome those challenges. Initial studies have illustrated the application of these approaches and have shown their feasibility. Still, the proposed approaches, and the tradeoffs between overhead, accuracy, and potential benefits for the testing activity have been barely quantified. This paper aims to overcome those limitations. Our analysis of 1,200 user sessions on a 155 KLOC deployed system substantiates the ability of field data to support test suite improvements, assesses the efficiency of profiling techniques for released software, and the effectiveness of testing efforts that leverage profiled field data.     

Nucleation of a non-equilibrium phase in a first order phase transition

We report a newly observed phenomenon of nucleation and first order phase transition, from superfluid helium-four, in which a metastable solid phase nucleates and grows from the overpressured liquid in preference to the stable phase. We discuss these results in terms of the difference in nucleation probabilities that arise from the different interfacial free energies of the phases.     

Ultrasonic study of sintered SiC at low temperatures

We investigated the temperature dependence, at low temperaturs, of sound velocity in sintered silicon carbide samples, containing three different sintering additives, boron or beryllium oxide or aluminum nitride. It was found that samples containing AlN or B showed lnT dependence (T is the temperature) of sound velocity but the one with BeO did not. The slope of the lnT dependence, which is proportional to the density of states of two level tunneling systems (TLS), is much larger for SiC with AlN than that with B. This sequence and no lnT dependence in BeO, correlate with the solubility of these additives into SiC, suggesting that the TLS, at least in this case, are created by the additives in solid solutions in the crystals. The samples containing B were heat treated to allow grain growth as well as densification. The density of states of TLS in these samples (measured by the slope of the lnT dependence of velocity) increased as the grain size increased. This suggests that the TLS do not reside in grain boundaries and that B migrates from the grain boundaries (where it originally segregated) into the bulk, thus creating more TLS inside the grains.     

Pattern Formation in the Evaporation of Thin Liquid Films

We investigate the patterns formed by thin liquid films evaporating from clean substrates. The system in equilibrium is entirely homogeneous, yet a remarkably regular, symmetric pattern is generated by a change in an isotropic parameter: the vapor pressure. The hydrodynamic instabilities which come into play display strong nonlinearities, distinguishing them from the classical capillary instabilities described by Rayleigh.     

Laser‐Induced Direct Lithography for Patterning of Carbon with sp3 and sp2 Hybridization

A new method of laser‐induced lithography for direct writing of carbon on a glass surface is described, in which deposition occurs from a transparent precursor solution. At the glass–solution interface where the laser spot is focused, a micro‐explosion process takes place, leading to the deposition of pure carbon on the glass surface. Transmission electron microscopy (TEM) analysis shows two distinct co‐existing phases. The dominant one shows a mottled morphology with diffraction typical of cubic (sp³) diamond. The other region shows an ordered array of graphene sheets with diffraction pattern typical of sp²‐bonded carbon. The sp³ crystallites range in size from 9 to 30 Å and are scattered randomly throughout the sample. A UV Raman spectrum shows a broad band at the location of the expected diamond peak, together with a peak corresponding to the graphite region. We conclude that the patterned carbon is composed of a mixture of nanocrystalline sp³ and sp² carbon forms.     

Helium-4 solid-liquid interface mobility and ultrasonic energy absorption mechanisms

The first measurements of acoustic reflection, together with acoustic transmission at the solid-liquid interface of⁴He, are used to determine the total relative acoustic energy absorption at the interface as a function of temperature. Based on these results, a new mechanism for the temperature dependence of the kinetics of growth and interface mobility is proposed.     

Athermal processes in the plastic deformation of bcc 4He

Measurements have been made of the temperature dependence of the plastic deformation of bcc solid ⁴He. The results strongly indicate that the deformation process is athermal. Comparison is made with NMR measurements of the spin diffusion coefficient for the bcc phase of dilute solutions of ³He in ⁴He. The results are discussed in terms of possible mechanisms for the plastic deformation.This research was supported by the National Science Foundation through the Materials Research Laboratory of Brown University and Grant No. DMR75-14761.     

The effects of inclusion on the social functioning of students with learning disabilities

The purpose of this study was to provide data on the social functioning (i.e., the degree of peer acceptance, self-concept, loneliness, and social alienation) of students in second, third, and fourth grade who participated in an inclusive classroom for an entire year. The social functioning of students identified as learning disabled (LD; n = 16), low achieving (LA; n = 27), and average/high achieving (AHA; n = 21) was assessed at the beginning and end of the school year. The students with LD were less well liked and more frequently rejected than AHA students. Although students' overall self-worth did not differ by achievement group, the students with LD demonstrated significantly lower academic self-concept scores. The students with LD did not differ on ratings of loneliness, and they demonstrated increases in the number of within-class reciprocal friendships from fall to spring. Discussion focuses on the effects of inclusion on the social functioning of students with LD.     

Synthetic mimic of selective transport through the nuclear pore complex

The nuclear pore complex is a large protein channel present universally in eukaryotic cells. It generates an essential macromolecular separation between the nucleus and cytoplasm. The transport mechanism relies on recognition of molecular cargos by receptor proteins, and on specific interaction between the receptors and the pores. We present a chemical mimic of this "receptor-mediated" transport using modified nanoporous membrane filters, polyisopropylacrylamide as the carrier molecule, or receptor, and single-stranded DNA as the cargo. We show that a complex of ssDNA and polyisopropylacrylamide diffuses faster through the modified pores than does the bare ssDNA, in spite of the larger size of the complex. The mobile polymer thus acts as a soluble receptor to usher a macromolecular cargo specifically through the pores.