A Novice's Process of Object-Oriented Programming

Exposing students to the process of programming is merely implied but not explicitly addressed in texts on programming which appear to deal with 'program' as a noun rather than as a verb.We present a set of principles and techniques as well as an informal but systematic process of decomposing a programming problem. Two examples are used to demonstrate the application of process and techniques.The process is a carefully down-scaled version of a full and rich software engineering process particularly suited for novices learning object-oriented programming. In using it, we hope to achieve two things: to help novice programmers learn faster and better while at the same time laying the foundation for a more thorough treatment of the aspects of software engineering

Phase separation in hydrogen-helium mixtures at Mbar pressures

The properties of hydrogen-helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures around 5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter.Comment: 6 pages, 7 figures. Published in "Proceedings of the National Academy of Sciences USA

Fra teknologiforståelse til informatik

Kommentar til Keld Nielsen og Martin Sillasen: Teknologiforstyrrelse: Hvad mener Børne- og Undervisningsministeriet, når de skriver “teknologi”? MONA 2020‑

The effectiveness of interventions targeting physical activity and/or sedentary behaviour in people with Multiple Sclerosis: a systematic review

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Analytic binary alloy volume-concentration relations and the deviation from Zen`s law

Alloys expand or contract as concentrations change, and the resulting relationship between atomic volume and alloy content is an important property of the solid. While a well-known approximation posits that the atomic volume varies linearly with concentration (Zen`s law), the actual variation is more complicated. Here we use an apparent size of the solute (solvent) atom and the elasticity to derive explicit analytical expressions for the atomic volume of binary solid alloys. Two approximations, continuum and terminal, are proposed. Deviations from Zen`s law are studied for 22 binary alloy systems

Surface currents and slope selection in crystal growth

We face the problem to determine the slope dependent current during the epitaxial growth process of a crystal surface. This current is proportional to delta=(p+) + (p-), where (p+/-) are the probabilities for an atom landing on a terrace to attach to the ascending (p+) or descending (p-) step. If the landing probability is spatially uniform, the current is proved to be proportional to the average (signed) distance traveled by an adatom before incorporation in the growing surface. The phenomenon of slope selection is determined by the vanishing of the asymmetry delta. We apply our results to the case of atoms feeling step edge barriers and downward funnelling, or step edge barriers and steering. In the general case, it is not correct to consider the slope dependent current j as a sum of separate contributions due to different mechanisms.Comment: 6 pages. The text has been strongly revised and Fig.1 has been changed. Accepted for publication in the "Comptes Rendus Physique

Hvad skal ph.d.- studerende på naturvidenskab vide om undervisning?

Vi præsenterer en teoretisk analyse af rammesætningen af et kursus i undervisning for ph.d.-studerende ved Det Naturvidenskabelige Fakultet på Aarhus Universitet (NAT-AU).Analysen anvendes som referenceramme for en præsentationaf det udviklede kursus og de studerendes evaluering af første gennemløb. Fremover er et lettere revideret kursus obligatoriskfor alle ph.d.-studerende ved NAT-AU, bl.a. begrundet i de positive erfaringer fra det beskrevne kursus.Med afsæt i den teoretiske analyse og evalueringsresultaterne diskuteres, hvordan man kan indarbejde en progressionstankegang i udvikling af universitetsunderviseres undervisningsfaglighed, der omfatter dette grundkursus og adjunktpædagogikum

Usability and Usage of Interactive Features in an Online Ebook for CS Teachers

There are too few secondary school computing teachers to meet international needs for growing secondary school computing education. Our group has created an ebook to help prepare secondary teachers to teach the programming and big data concepts in the new AP Computer Science Principles course. The ebook was designed using principles from educational psychology, specifically worked examples and cognitive load. The ebook interleaves worked examples and interactive practice activities, which we believe will lead to more efficient and effective learning than more typical approaches to learning programming. This paper reports the results from initial studies of our ebook. First, we conducted a usability study comparing three different ebook platforms. Next, we conducted a study of teacher use of the ebook. Ten teachers worked through the first eight chapters of the ebook at their own pace. Five of the ten teachers completed the first eight chapters which is a 50% completion rate. Significantly, teachers who used more of the interactive features in the ebook did better on the post-tests and reported higher confidence in their ability to teach the material than teachers who used few of the interactive features

An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker

We present an estimate of net CO2 exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO2 mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO2 called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO2 in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed –0.65 PgC/yr (1 petagram = 10^15 g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of –0.4 to –1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to –0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov