Fitting maintenance cost vs maintainability data to a standard curve

Practical maintainability design problems involve discrete points of maintenance cost vs maintainability data. It is essential that these data be fitted to any of the standard cost vs maintainability curves. The conventional least squares method is used here to achieve this task.     

Water-in-oil microemulsion as mobile phase in thin-layer chromatographic retention studies of anions

A water-in-oil (W/O) microemulsion, consisting of sodium dodecyl sulphate (SDS)/1-pentanol/water/heptane, has been used as mobile phase for the separation of inorganic anions from their binary mixtures, for example, IO ₄ ⁻ -NO ₂ ⁻ , IO ₄ ⁻ -BrO ₃ ⁻ , IO ₄ ⁻ -I⁻, MnO ₄ ⁻ -BrO ₃ ⁻ , MnO ₄ ⁻ -NO ₂ ⁻ , and MnO ₄ ⁻ -Br⁻. The weight ratio, SDS/n-pentanol was kept constant at 1/2.46 for all compositions. The retention efficiency of anions on layers of silica gel G, alumina, microcrystalline cellulose, kieselguhr G, and mixtures of kieselguhr and cellulose in 4:1 and 3:2 ratios has been examined with the W/O microemulsion system as a mobile phase. Thin layers of kieselguhr were most useful for differential migration of anions. Quantitative separation of IO ₄ ⁻ from accompanying ions, limits of identification, and dilution of few anions are reported. The effects of amines, phenols, and heavy metals on the separation efficacy of IO ₄ ⁻ also have been investigated.     

Philosophy of a new structure of software reliability modelling

A new philosophy is defined for software reliability modelling. It uses execution time concept as a centralized parameter of modelling. Basic generalized equations of software reliability modelling have been suggested which use execution time T and operational time t. The number of remaining errors in the program should be defined as a function of execution time T. An attempt has been made to unify the quantitative aspects of modelling.     

Reliability of a stand-by system with common-cause failures and scheduled maintenance

The paper investigates the reliability of a stand-by system incorporating the concepts of repair and scheduled maintenance. Further, the system experiences dual mode of failures—first, failure due to change in operating characteristics and second, failure due to common-cause. Certain important results have been derived as particular cases. In the end, a numerical example has also been discussed.     

Low density TEOS based silica aerogels using methanol solvent

Highly transparent monolithic silica aerogels based on the TEOS precursor were prepared by the two-step (acid-base) sol–gel process. The hydrolysis and condensation reactions of tetraethoxysilane (TEOS) proceeded in methanol solvent with oxalic acid and NH₄OH as the catalysts, respectively. The wet gels were supercritically dried using methanol. The aerogels were characterized by transmission electron microscopy (TEM) and measurements of optical transmission, bulk density, volume shrinkage, porosity and thermal conductivity. Monolithic silica aerogels with high optical transmission (∼93%), low density (∼0.055 g/cm³), low thermal conductivity (∼0.04 W/mK), and minimum volume shrinkage (∼10%), were obtained for the molar ratio of TEOS:MeOH:acidic H₂O:basic H₂O at 1:33:3.5:3.5 alongwith the oxalic acid and NH₄OH concentrations at 0.001 M and 1 M, respectively.     

Open source software success: Measures and analysis

Despite a growing body of research on OSS production, much remains to be learned. One important issue concerns the measures of OSS project success and its determinants. In this paper, we empirically study the determinants of OSS success as measured by the number of subscribers and developers working on an OSS project. Furthermore, we demonstrate that our model forecasts these success measures more accurately as compared to a naive model.We find that OSS projects that develop software to work on Windows/UNIX/Linux operating systems, and developed using C or its derivative languages experience larger increase in subscribers and attract more developers than projects that do not have these characteristics. OSS projects with semi-restrictive licenses have fewer subscribers and attract fewer developers. Interestingly, OSS projects that accept financial donations and are targeted at IS/IT professionals have more subscribers than others, although these characteristics do not affect the developer base. The number of subscribers and developers increases with the age of the OSS project. Finally, the impact of developers on subscribers and subscribers on developers is positive and significant.     

On computing minimal independent support and its applications to sampling and counting

Constrained sampling and counting are two fundamental problems arising in domains ranging from artificial intelligence and security, to hardware and software testing. Recent approaches to approximate solutions for these problems rely on employing SAT solvers and universal hash functions that are typically encoded as XOR constraints of length n/2 for an input formula with n variables. As the runtime performance of SAT solvers heavily depends on the length of XOR constraints, recent research effort has been focused on reduction of length of XOR constraints. Consequently, a notion of Independent Support was proposed, and it was shown that constructing XORs over independent support (if known) can lead to a significant reduction in the length of XOR constraints without losing the theoretical guarantees of sampling and counting algorithms. In this paper, we present the first algorithmic procedure (and a corresponding tool, called MIS) to determine minimal independent support for a given CNF formula by employing a reduction to group minimal unsatisfiable subsets (GMUS). By utilizing minimal independent supports computed by MIS, we provide new tighter bounds on the length of XOR constraints for constrained counting and sampling. Furthermore, the universal hash functions constructed from independent supports computed by MIS provide two to three orders of magnitude performance improvement in state-of-the-art constrained sampling and counting tools, while still retaining theoretical guarantees.