Current state and potential of variability management practices in software-intensive SMEs: Results from a regional industrial survey

ContextMore and more, small and medium-sized enterprises (SMEs) are using software to augment the functionality of their products and offerings. Variability management of software is becoming an interesting topic for SMEs with expanding portfolios and increasingly complex product structures. While the use of software product lines to resolve high variability is well known in larger organizations, there is less known about the practices in SMEs.ObjectiveThis paper presents results from a survey of software developing SMEs. The purpose of the paper is to provide a snapshot of the current awareness and practices of variability modeling in organizations that are developing software with the constraints present in SMEs.MethodA survey with questions regarding the variability practices was distributed to software developing organizations in a region of Sweden that has many SMEs. The response rate was 13% and 25 responses are used in this analysis.ResultsWe find that, although there are SMEs that develop implicit software product lines and have relatively sophisticated variability structures for their solution space, the structures of the problem space and the product space have room for improvement.ConclusionsThe answers in the survey indicate that SMEs are in situations where they can benefit from more structured variability management, but the awareness need to be raised. Even though the problem space similarity is high, there is little reuse and traceability activities performed. The existence of SMEs with qualified variability management and product line practices indicates that small organizations are capable to apply such practices.     

“Teacher effects” in early literacy development: Evidence from a study of twins.

It is often assumed that differences in teacher characteristics are a major source of variability in children's educational achievements. We examine this assumption for early literacy achievement by calculating the correlations between pairs of twin children who either shared or did not share a teacher in kindergarten, Grade 1, and Grade 2. Teacher effects—or, more strictly, classroom effects—would show up as higher correlations for same-class than for different-class twin pairs. Same-class correlations were generally higher than different-class correlations, though not significantly so on most occasions. On the basis of the results, we estimate that the maximum variance accounted for by being assigned to the same or different classrooms is 8%. This is an upper-bound figure for a teacher effect because factors other than teachers may contribute to variation attributable to classroom assignment. We discuss the limitations of the study and draw out some of its educational implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mating Disruption of Plodia interpunctella in Small-Scale Plots: Effects of Pheromone Blend, Emission Rates, and Population Density

An indoor mating disruption experiment was performed on the stored-product pest Plodia interpunctella. The female of this species emits a four-component pheromone blend consisting of Z9,E12–14 : OAc, Z9,E12–14 : OH, Z9,E12–14 : Ald, and Z9–14 : OAc. Mating of Plodia interpunctella was disrupted up to 93% by using synthetic pheromone in small-scale plot experiments. The study was performed in 2.5 m × 2.5 m × 2.5 m polythene cubicles housed in a greenhouse, and pheromones were released by MSTRS spraying every 15~min. The disruption effect was tested at different doses 0.075, 0.75, and 3.75 mg/spray (corresponding to 5, 50, and 250 g/min), different pheromone formulas (one-component (Z9,E12–14 : OAc) and four-component), and at different population densities (10, 20, and 30 individuals, equivalent to 0.32, 0.64, and 0.96 individuals/m²). The moths were released into the cubicles and recaptured 24 hr later. The females were checked for spermatophore presence indicating successful mating. The mating was significantly suppressed in all treatments compared to the control. There was, however, no difference in mating activity between the one-component and four-component disruptants. In addition, EAG measurements were conducted with a portable device to keep track of aerial concentrations of pheromone. The results show that the one-component formula disrupts mating as efficiently as the more complete four-component blend at doses applied in this study. This fact improves the prospects for mating disruption of indoor pyralids, since many pyralid species share the major component in their pheromones, and, thus, can probably be controlled simultaneously by using this compound only.     

Timing of Male Sex Pheromone Biosynthesis in a Butterfly – Different Dynamics under Direct or Diapause Development

The life history traits and behavior of the butterfly Pieris napi are well-known, as the species is often used as a model organism for evolutionary and ecological studies. The species has two or more generations per year in the major part of its temperate distribution, and as different selection pressures affect the different generations, both behavioral and physiological seasonal polyphenisms have been shown previously. Here, we explored the dynamics of male sex pheromone production. The two generations are shown to have significantly different scent compositions early in life; the direct developers--who have shorter time for pupal development--need the first 24 hr of adult life after eclosion to synthesize the sex pheromone citral (geranial and neral 1:1)--whereas the diapausing individuals who have spent several months in the pupal stage eclose with adult scent composition. Resource allocation and biosynthesis also were studied in greater detail by feeding butterflies (13)C labeled glucose either in the larval or adult stage, and recording incorporation into geranial, neral, and other volatiles produced. Results demonstrate that the pheromone synthesized by newly eclosed adult males is based on materials ingested in the larval stage, and that adult butterflies are able to synthesize the pheromone components geranial and neral and the related alcohols also from adult intake of glucose. In summary, our study shows that time-stress changes the timing in biosynthesis of the complete pheromone between generations, and underpins the importance of understanding resource allocation and the physiological basis of life history traits.     

A Genetic Analysis of Population Differences in Pheromone Production and Response Between Two Populations of the Turnip Moth,Agrotis segetum

The genetic basis of the differences in female pheromone blend ratio and male behavioral response in the turnip moth,Agrotis segetum, was examined by crossing individuals derived from Scandinavian and Zimbabwean populations. These two populations differ both in the ratio of the three major female pheromone components,Z5–10:OAc,Z7–12:OAc, andZ9–14: OAc and in the behavioral response of the males in both wind-tunnel and field-trapping assays. The female pheromone blend in this study is treated as the log ngZ5–10:OAc/ngZ7–12:OAc and log ngZ9–14:OAc/ngZ7–12:OAc for statistical analysis. The mean log ngZ5–10:OAc/ngZ7–12:OAc, is under control by a major autosomal factor or factors, but it is unclear what genetic factor or factors may control the mean log ngZ9–14:OAc/ngZ7–12:OAc. Frequency distributions of the proportions of each component show wide individual variation and also suggest control ofZ5–10:OAc andZ7–12:OAc by major autosomal factors, which forZ5–10:OAc may show partial dominance. Analysis of male behavioral response to synthetic blends in the wind tunnel yields inconclusive results, but suggests thatA. segetum may have a broad window of response that reflects the range of individual variation in female blends.     

On causal algorithms for speech enhancement

Kalman filtering is a powerful technique for the estimation of a signal observed in noise that can be used to enhance speech observed in the presence of acoustic background noise. In a speech communication system, the speech signal is typically buffered for a period of 10-40 ms and, therefore, the use of either a causal or a noncausal filter is possible. We show that the causal Kalman algorithm is in conflict with the basic properties of human perception and address the problem of improving its perceptual quality. We discuss two approaches to improve perceptual performance. The first is based on a new method that combines the causal Kalman algorithm with pre- and postfiltering to introduce perceptual shaping of the residual noise. The second is based on the conventional Kalman smoother. We show that a short lag removes the conflict resulting from the causality constraint and we quantify the minimum lag required for this purpose. The results of our objective and subjective evaluations confirm that both approaches significantly outperform the conventional causal implementation. Of the two approaches, the Kalman smoother performs better if the signal statistics are precisely known, if this is not the case the perceptually weighted Kalman filter performs better.     

Characterizing solute-lean defects in superalloys

Solute-lean defects, commonly called white spots, are frequently found in superalloys. These defects limit the service life of components made from superalloys, and alloy producers have devoted intense study to their characterization and elimination. Recent work shows that solute lean defects can be classified as “discrete,” “diffuse” and “mini,” and can be further classified into “clean” and “dirty” white spots. More than one formation mechanism for white spots is exemplified by the chemical and morphological differences between discrete, diffuse and mini white spots. White spot detection depends on the thermomechanically developed precipitation of hardening phases, coupled with specific etches that preferentially react to microstructure differences. The white spot defect is indigenous to the vacuum arc remelting process, but defect formation can be minimized by careful process control.     

Influence of polymerization conditions on microstructure of norbornene-ethylene copolymers made using metallocene catalysts and MAO

When characterized with ¹³C-NMR, it was found that norbornene-ethylene copolymers had a more complicated microstructure when dimethylsilyl bis(indenyl) zirconium dichloride was used as the catalyst compared to ethylene bis(indenyl) zirconium dichloride. One could see more block sequences but less alternating sequences. For both catalysts the highest amounts of block sequences were obtained for high norbornene concentrations, medium to high Al/Zr ratios, and low polymerization temperatures. There were also more alternating sequences for high norbornene concentrations and high polymerization temperatures. The isolated norbornene units (separated by more than one ethylene unit) were all exoconfiguration. No unsaturation was seen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1071–1076, 1997