Shear horizontal wave propagation in periodically layeredcomposites

The transverse resonance approach to guided wave analysis is applied to shear horizontal (SH) wave propagation in periodically layered composites. It is found for SH waves that at high values of the guided wavevector β, the wave energy is trapped in the slower of the two media and propagates accordingly at the slower wavespeed. At low values of β, however, the modes demonstrate a clustering behavior, indicative of the underlying Floquet wave structure. The number of modes in a cluster is observed to correlate with the number of unit cells in the layered plate. New physical insights into the behavior of these systems are obtained by analyzing the partial waves of the guided SH modes in terms of Floquet waves. We show that the fast and slow shear waves in the periodically layered composite play an analogous role to the longitudinal and shear partial waves comprising Lamb waves in a homogeneous plate     

Thermoreversible Gelcasting: A Novel Ceramic Processing Technique

A new ceramic processing method, thermoreversible gelcasting (TRG), has been developed. The method uses a gelation process that can be reversed multiple times. Two Al₂O₃ systems have been explored with the use of a specific triblock copolymer to form a binding gel network. The mixture becomes a free-flowing liquid on heating above 60°C. However, on cooling below 60°C, the slurry instantaneously transforms to a physical gel. This process can be reversed easily (essentially with an infinite processing time window) while the solvent is present in the system, which is advantageous when trying to produce high-quality dense pieces if initial casting irregularities occur. Near-theoretically dense specimens have been produced with properties consistent with reported values of high-density Al₂O₃.     

Adhesive Contact of a Membrane with a Hemispherical Indenter: Theoretical Analysis and Model Liquid System

The axisymmetric Laplace equation is solved numerically to extract contact-angle data for a flat liquid/vapor interface contacting a submerged hemispherical solid. The liquid/vapor interface is treated as a membrane, with a membrane tension equal to the surface energy of the liquid. By measuring the vertical displacement of the membrane and the projected contact area the membrane makes with the hemisphere, the contact angle and correspondingly the driving force for motion of the contact line can be measured. We show that characteristic receding and advancing contact angles can be obtained by measuring the contact radii formed upon initial contact between the interface and hemisphere and final contact just prior to detachment of the interface, respectively. Use of the technique is illustrated with a model experiment involving the contact of an air/water interface with a poly(methyl methacrylate) surface.     

Measuring Developers: Aligning Perspectives and Other Best Practices

The paper discusses the software metrics programs. Software metrics programs might rank among the all-time touchiest subjects in software development. Done well, a measurement program can prove an effective tool for keeping on top of development effort-especially for large, distributed projects. It can help developers feel that they have a fair and objective way of communicating their progress and getting resources allocated where they're needed most. An effective metrics program must address both products and processes. Product-related metrics can be tied to customer satisfaction. They often represent objectively verifiable properties such as the number of bugs or defects found in a product. Process metrics, include measures of effort and effectiveness and can give quick feedback about the status of defect containment, productivity, and other desirable properties at many points during development. However, instituting these metrics poses different challenges that the authors discussed and developed some best practice solutions. These include design measures with multiple stakeholders, build on measures that come naturally out of existing processes, and transparency.     

An industry experiment on the effects of test-driven development on external quality and productivity

Existing empirical studies on test-driven development (TDD) report different conclusions about its effects on quality and productivity. Very few of those studies are experiments conducted with software professionals in industry. We aim to analyse the effects of TDD on the external quality of the work done and the productivity of developers in an industrial setting. We conducted an experiment with 24 professionals from three different sites of a software organization. We chose a repeated-measures design, and asked subjects to implement TDD and incremental test last development (ITLD) in two simple tasks and a realistic application close to real-life complexity. To analyse our findings, we applied a repeated-measures general linear model procedure and a linear mixed effects procedure. We did not observe a statistical difference between the quality of the work done by subjects in both treatments. We observed that the subjects are more productive when they implement TDD on a simple task compared to ITLD, but the productivity drops significantly when applying TDD to a complex brownfield task. So, the task complexity significantly obscured the effect of TDD. Further evidence is necessary to conclude whether TDD is better or worse than ITLD in terms of external quality and productivity in an industrial setting. We found that experimental factors such as selection of tasks could dominate the findings in TDD studies.     

Sediment and discharge yields within a minimally disturbed,headwater watershed in North Central Pennsylvania,USA, with an emphasis on Superstorm Sandy

We estimated discharge and suspended sediment (SS) yield in a minimally disturbed watershed in North Central Pennsylvania, USA, and compared a typical storm (September storm, 4.80 cm) to a large storm (Superstorm Sandy, 7.47 cm rainfall). Depending on branch, Sandy contributed 9.7–19.9 times more discharge and 11.5–37.4 times more SS than the September storm. During the September storm, the upper two branches accounted for 60.6% of discharge and 88.8% of SS at Lower Branch; during Sandy these percentages dropped to 36.1% for discharge and 30.1% for SS. The branch with close proximity roads had over two‐three times per area SS yield than the branch without such roads. Hysteresis loops showed typical clockwise patterns for the September storm and more complicated patterns for Sandy, reflecting the multipeak event. Estimates of SS and hysteresis in minimally disturbed watersheds provide useful information that can be compared spatially and temporally to facilitate management.     

Victor R. Basili's contributions to software quality

This article deals with Victor R. Basili's contributions to software quality. Basili's contributions cover three broad areas: research in the 1970s and early 1980s on software measurement and the Goal Question Metric (GQM) model, research in the 1980s and 1990s on these measurement ideas' maturation into a software engineering model of empirical studies, including the development of the Quality Improvement Paradigm (QIP) and the influence of the NASA Goddard Space Flight Center Software Engineering Laboratory, and research since 1990 in the Experience Factory as a model for creating learning organizations for continuous software process improvement. Some of Basili's most important contributions are in measuring software development processes and products and gifted the community with an invaluable tool: the GQM approach. The GQM approach is based on the assumption that for an organization to measure its products and processes usefully, it must first specify goals for itself and its projects.     

What Do We Know about Knowledge Management? Practical Implications for Software Engineering

There have been many claims about knowledge management's benefits in software engineering, such as decreased time and cost for development, increased quality, and better decision-making abilities. Although we can find some success stories illustrating these claims, particularly on aspects related to the systems and engineering schools, more research is necessary to explore the intersection between each school and the software engineering field. Researchers should continue to emphasize the need for a broad focus across multiple KM schools to suceed in improving KM's practical application in software engineering.     

ZnS nanocrystals decorated single-walled carbon nanotube based chemiresistive label-free DNA sensor

We fabricated ZnS nanocrystals decorated single-walled carbon nanotube (SWNT) based chemiresistive sensor for DNA. Since the charge transfer in the hybrid nanostructures is considered to be responsible for many of their unique properties, the role of ZnS nanocrystals toward its performance in DNA sensor was delineated. It was found that the free carboxyl groups surrounding the ZnS nanocrystals allowed large loading of single strand DNA (ssDNA) probe that provided an ease of hybridization with target complementary c-ssDNA resulting in large electron transfer to SWNT. Thus it provided a significant improvement in sensitivity toward c-ssDNA as compared to bare SWNT based DNA sensor.