Functional derivatives of Tc for a two-band superconductor: application to MgB2

We address the question of how phonons of various frequencies contribute to the superconducting transition temperature $T_c$ of a multi-band superconductor by considering the functional derivatives of $T_c$ with respect to various intraband and interband electron-phonon coupling functions. A general scheme for computing such functional derivatives is developed. The proofs are given that the functional derivatives which are diagonal in band indices are linear in phonon energy $\Omega$ at small $\Omega$, while the functional derivatives which are off-diagonal in band indices diverge at $\Omega$ = 0 as 1/$\Omega$. The case of a two-band model for MgB$_{2}$ is treated numerically.Comment: 6 pages, 4 figure

A Comparative Analysis of Cognitive Tutoring and Constraint-Based Modeling

Numerous approaches to student modeling have been proposed since the inception of the field more than three decades ago. hat the field is lacking completely is comparative analyses of different student modeling approaches. Such analyses are sorely needed, as they can identify the most promising approaches and provide guidelines for future research. In this paper we compare Cognitive Tutoring to Constraint-Based Modeling (CBM). We present our experiences in implementing a database design tutor using both methodologies and highlight their strengths and weaknesses. We compare their characteristics and argue the differences are often more apparent than real. For specific domains, one approach may be favoured over the other, making them viable complementary methods for supporting learning

Manifestation of pseudogap in ab-plane optical characteristics

A model in which a gap forms in the renormalized electronic density of state (DOS) with missing states recovered just above the pseudogap $\Delta_{pg}$, is able to give a robust description of the striking, triangular like, peak seen in the real part of the optical self-energy of underdoped cuprates. We use this model to explore the effect of the pseudogap on the real part of the optical conductivity and on the partial sum rule associated with it. An important result is that the optical spectral weight redistributes over a much larger frequency window than it does in the DOS.Comment: 12 pages, 3 figures. Submitted to Journal of Physics: Condensed Matte

The effects of dams on longitudinal variation in river food webs

We examined the effects of two dams on longitudinal variation of riverine food webs using stable isotope and gut contents analyses along four rivers in the Hunter Valley in eastern Australia. Longitudinal 15N enrichment was observed in most invertebrate taxa and food sources but significant longitudinal variation was rare for 13C, and composition of gut contents of invertebrate taxa did not vary significantly with longitudinal position. Most invertebrates and food sources were more 15N-enriched at sites immediately downstream of the dams than expected from their upstream longitudinal position, a result not mirrored by gut contents and 13C. Enrichment of 15N downstream may be attributed to altered water quality as a result of impoundment but further research is necessary to elucidate whether physico-chemical riverine processes or trophic mechanisms are responsible. Our observations regarding the influence of dams on isotope ratios are contrary to the few existing studies, suggesting the small volumes relative to annual inflows of dams in the present study limit downstream impacts by maintaining aspects of flow variability. © 2013 © 2013 Taylor & Francis

Evaluating and improving adaptive educational systems with learning curves

Personalised environments such as adaptive educational systems can be evaluated and compared using performance curves. Such summative studies are useful for determining whether or not new modifications enhance or degrade performance. Performance curves also have the potential to be utilised in formative studies that can shape adaptive model design at a much finer level of granularity. We describe the use of learning curves for evaluating personalised educational systems and outline some of the potential pitfalls and how they may be overcome. We then describe three studies in which we demonstrate how learning curves can be used to drive changes in the user model. First, we show how using learning curves for subsets of the domain model can yield insight into the appropriateness of the model’s structure. In the second study we use this method to experiment with model granularity. Finally, we use learning curves to analyse a large volume of user data to explore the feasibility of using them as a reliable method for fine-tuning a system’s model. The results of these experiments demonstrate the successful use of performance curves in formative studies of adaptive educational systems

Implementation of triticale in nutrition of non-ruminant animals

Cognition of chemical composition and nutritive values of triticale grain as well as the effect of its application in non-ruminant animal nutrition were pointed out in this paper. There is a high level of proteins in the grain of triticale (2 to 3% more than wheat and 4% more than rye), with very beneficial amino acid composition, and is the reason for its usage in domestic animals nutrition. Nowadays, people are of the opinion that triticale is one of potential plant species with the brightest perspective in the production of food for domestic animals. Considering the increased production of triticale, some detail researching of its nutritional value is necessary due to the required evaluation of the role and significance in domestic animal nutrition based on triticale. Due to intensive plant breeding programs, there are new varieties of triticale in the market, distinctive by the higher yield and wide range of desired traits. As a result of this, triticale is becoming very attractive and is occupying larger portions of arable land. These review will show if there are some advantages of triticale compared to other cereals and how large the frame of these advantages is, as well as how it will affect the further spreading of triticale on arable land.Key words: Triticale, chemical composition, nutritive capacity, nutrition

Electronic customer relationship management assimilation in Southeastern European companies—cluster analysis

This article aims to investigate the factors influencing the electronic customer relationship management (e-CRM) assimilation in Southeastern European companies. With ICT innovation in mind, a conceptual model is developed, integrating three theories of innovative diffusion. Multivariate techniques, factor analysis, and cluster analysis are applied in order to reduce the number of variables and classify the cases. A discriminant analysis is taken in order to test the reliability of the clustering and to explore the clusters’ characteristics. The relationships between cluster categorization and life cycle phases, along with the size of the firm, are all checked against contingency coefficients. When comparing cluster categorization, the research results show that the significance of technical, organizational, and environmental factors changes depending on the phase of the e-CRM assimilation. The results additionally show that the degree of usage and diffusion of these technologies differs in small to medium enterprises compared to big enterprises. Owing to these findings, which have enabled us to provide insights into the ways in which contextual factors influence the e-CRM assimilation, theorists, and practitioners can see the necessary patterns of action

Corrosion Behavior of the As-cast and Heat-treated ZA27 Alloy

Corrosion behaviour of the as-cast and heat-treated ZA27 alloy was examined. The alloy was prepared by conventional melting and casting route and then thermally processed by applying T4 heat treatment regime (solutionizing at 370 °C for 3 hours followed by water quenching and natural aging). Corrosion rate of the as-cast and heat-treated ZA27 alloy was determined in 3.5 wt. % NaCl solution through immersion test using both weight loss method and polarization resistance measurements. It was shown that applied thermal treatment resulted in increased ductility of the heat-treated alloy and had a small beneficial effect on the corrosion resistance of ZA27 alloy

Numerical simulation of fluid flow, heat transfer and pressure drop in thermoplates

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The objective of our investigations is to numerically investigate the optimal geometry of the thermoplate with respect to heat transfer of the inside fluid that passes through the channel as a single phase. In order to achieve this, the geometrical and process parameters such as the pattern of welding spots, the distance between the sheets, and the Reynolds number have been varied. For the simulation, the commercial software StarCD was used. The numerical experiments show that the heat transfer potential of the thermoplate having a staggered arrangement of welding spots is markedly higher than the one of a common flat channel, particularly at larger Reynolds numbers. The variations of the geometrical parameters indicate the welding spot pitch in a streamwise direction to be a pivotal quantity regarding the heat transfer optimisation.cs201