Complexity of mixed shop scheduling problems: A survey

We survey recent results on the computational complexity of mixed shop scheduling problems. In a mixed shop, some jobs have fixed machine orders (as in the job shop), while the operations of the other jobs may be processed in arbitrary order (as in the open shop). The main attention is devoted to establishing the boundary between polynomially solvable and NP-hard problems. When the number of operations per job is unlimited, we focus on problems with a fixed number of jobs.

Predicting optimal process conditions for flip-chip aassembly using copper column bumped dies

Recently, research has been carried out to test a novel bumping method which omits the under bump metallurgy (UBM) forming process by bonding copper columns directly onto the Al pads of the silicon dies. This bumping method could be adopted to simplify the flip chip assembly process, increase the productivity and achieve a higher I/O count. Computer modelling methods are used to predict the shape of solder joints and response of the flip chip to thermal cyclic loading. The accumulated plastic strain energy at the comer solder joints is used as the damage indicator. Models with a range of design parameters have been compared for their reliability. The ranking of the relative importance of these parameters is given. Results from these analyses are being used by our industrial and academic partners to identify optimal design conditions.

A modelling and experimental analysis of the no-flow underfill process for flip-chip assembly

In the flip-chip assembly process, no-flow underfill materials have a particular advantage over traditional underfills as the application and curing of this type of underfill can be undertaken before and during the reflow process - adding high volume throughput. Adopting a no-flow underfill process may result in underfill entrapment between solder and fluid, voiding in the underfill, a possible delamination between underfill and surrounding surfaces. The magnitude of these phenomena may adversely affect the reliability of the assembly in terms of solder joint thermal fatigue. This paper presents both an experimental and mdeling analysis investigating the reliabity of a flip-chip component and how the magnitude of underfill entrapment may affect thermal-mechanical fatigue life.

[Book review] Piero della Francesca: A Mathematician's art by J.V. Field, Yale University Press.

Review of the book 'Piero della Francesca: A Mathematician’s Art' by J.V. Field, Yale University Press, 420 pp, £35 ISBN 0300103425.

Systematic review of worldwide variations of the prevalence of wheezing symptoms in children

Background: Considerable variation in the prevalence of childhood asthma and its symptoms (wheezing) has been observed in previous studies and there is evidence that the prevalence has been increasing over time. Methods: We have systematically reviewed the reported prevalence and time trends of wheezing symptoms among children, worldwide and within the same country over time. All studies comprising more than 1000 persons and meeting certain other quality criteria published over a 16-year period, between January 1990 and December 2005, are reported and a comparison of ISAAC (International Study of Asthma and Allergies in Childhood) and non-ISAAC studies is made, in part as a way of expanding the power to examine time trends (the older studies tend to be non-ISAAC), but also to examine possible methodological differences between ISAAC and non-ISAAC questions. Results: A wide range of current prevalence of wheeze was observed between and within countries over time. The UK had the highest recorded prevalence of 32.2% in children aged 13–14 in 1994–5 and Ethiopia had the lowest prevalence, 1.7% in children aged 10–19 in 1996. All studies in Australia and the UK were compared using multiple logistic regression. ISAAC phase I and III studies reported significantly higher prevalence of current wheeze (OR = 1.638) compared with non-ISAAC studies, after adjusting for various other factors (country, survey year, age of child, parental vs child response to the survey). Australia showed a significantly higher prevalence of current wheezing (OR = 1.343) compared with the UK, there was a significant increase in the prevalence odds ratio per survey year (2.5% per year), a significant decrease per age of child (0.7% per year), and a significantly higher response in current wheezing if the response was self-completed by the child (OR = 1.290). These factors, when explored separately for ISAAC and non-ISAAC studies, showed very different results. In ISAAC studies, or non-ISAAC studies using ISAAC questions, there was a significant decrease in current wheezing prevalence over time (2.5% per year). In non-ISAAC studies, which tend to cover an earlier period, there was a significant increase (2.6% per year) in current wheezing prevalence over time. This is very likely to be a result of prevalence of wheezing increasing from the 1970s up to the early 1990s, but decreasing since then. Conclusion: The UK has the highest recorded prevalence of wheezing and Ethiopia the lowest. Prevalence of wheezing in Australia and the UK has increased from the 1970s up to the early 1990s, but decreased since then and ISAAC studies report significantly higher prevalences than non-ISAAC studies.

Getrocknete Stimmen. Menschen mit Behinderung benutzen Kassettenrekorder

Der Autor stellt drei Thesen zu der Fragestellung „Wie gehen Jugendliche und junge Erwachsene alltagstauglich mit dem Kassettenrekorder um?“ auf, die er in drei Anläufen begründet: „Es geht zunächst um Alltag und wie sich Menschen mit Benachteiligungen und Behinderung darin bewegen. In einem zweiten Anlauf [skizziert er] kurz die gegenwärtigen sonderpädagogische Fragestellungen und deren Aufmerksamkeit für das Hören und Zuhören … [Daraus] soll deutlich werden, wie man mit O-Tönen Sollbruchstellen herstellen kann, und wie sich eine solche Praxis begründen lässt.“ Indem junge Menschen mit Behinderung mit Audiorekordern ihren Alltag erkunden, kehrt sich durch die Erkundungsform Interview die bisher erlebte asymmetrische Kommunikationssituation um, weil selbst über Inhalt, Anfang und Ende einer Kommunikation bestimmt werden kann. Somit begründen Audioclips Erfahrung von Kommunikationssouveränität. (Orig./Autor)

Mobile authoring of open educational resources for authentic learning scenarios

The proliferation of smartphones in the last decade and the number of publications in the field of authoring systems for computer-assisted learning depict a scenario that needs to be explored in order to facilitate the scaffolding of learning activities across contexts. Learning resources are traditionally designed in desktop-based authoring systems where the context is mostly restricted to the learning objective, capturing relevant case characteristics, or virtual situation models. Mobile authoring tools enable learners and teachers to foster universal access to educational resources not only providing channels to share, remix or re-contextualize these, but also capturing the context in-situ and in-time. As a further matter, authoring educational resources in a mobile context is an authentic experience where authors can link learning with their own daily life activities and reflections. The contribution of this manuscript is fourfold: first, the main barriers for ubiquitous and mobile authoring of educational resources are identified; second, recent research on mobile authoring tools is reviewed, and 10 key shortcomings of current approaches are identified; third, the design of a mobile environment to author educational resources (MAT for ARLearn) is presented, and the results of an evaluation of usability and hedonic quality are presented; fourth, conclusions and a research agenda for mobile authoring are discussed.

Notes and memoranda

Callionymus maculatus. Phrynorhombus unimaculatus. Motella cimbria. Sepia elegans. Mysis longicornis. Mysidopsis angusta. Malformation of the mouth in the common sea-bream.

Biological controls on resuspension and the relationship between particle size and the Kolmogorov length scale in a shallow coastal sea

Measurements of suspended particle matter (SPM) and turbulence have been obtained over five tidal surveys during spring and summer 2010 at station L4 (5025 degrees N 04.22 degrees W, depth 50 m), in the Western English Channel. The relationship between turbulence intensity and bed stress is explored, with an in-line holographic imaging system evaluating the extent to which material is resuspended. Image analysis allows for the identification of SPM above a size threshold of 200 pm, capturing particle variability across tidal cycles and the two seasons. Dissipation of turbulent kinetic energy, which exceeds 10(-5) W kg(-1), yields maximum values of bed stress of between 0.17 and 0.20 N m(-2), frequently resulting in the resuspension of material from the bed. Resuspension is shown to promote aggregation of SPM into flocs, where the size of such particles is theoretically determined by the Kolmogorov microscale, l(k). During the spring surveys, flocs of a size larger than lk were observed, though this was not repeated during summer. It is proposed that the presence of gelatinous, biological material in spring allows flocculated particles to exceed l(k). This suggests that under specific circumstances, the limiting factor on the growth of flocculated SPM is not only turbulence, as previously thought, but the presence or absence of certain types of biological particle.