Armstrong axioms and Boyce-Codd-Heath Normal Form under bag semantics

The theory of functional dependencies is based on relations, i.e. sets of tuples. Over relations, the class of functional dependencies subsumes the class of keys. Commercial database systems permit the storage of bags of tuples where duplicate tuples can occur. Over bags, keys and functional dependencies interact differently from how they interact over relations.We establish finite ground axiomatizations of keys and functional dependencies over bags, and show a strong correspondence to goal and definite clauses in classical propositional logic. We define a syntactic Boyce-Codd-Heath Normal Form condition, and show that the condition characterizes schemata that will never have any redundant data value occurrences in their instances. The results close the gap between the existing set-based theory of data dependencies and database practice where bags are permitted.     

Can Variational Models for Correspondence Problems Benefit from Upwind Discretisations?

Optic flow and stereo reconstruction are important examples of correspondence problems in computer vision. Correspondence problems have been studied for almost 30 years, and energy-based methods such as variational approaches have become popular for solving this task. However, despite the long history of research in this field, only little attention has been paid to the numerical approximation of derivatives that naturally occur in variational approaches.     

Die patentierten Erfindungen von Wolfgang Gaede aus der Zeit von 1905 bis 1945

The Patented Inventions from Wolfgang Gaede from 1905 to 1945 The collection of Gaede's patents shows how successfully cooperation between science and industry could bee. Several up to now important inventions in vacuum technique have been made and this in sometimes hard and difficult circumstances. Even when Gaede has lost his chair at the university of Karlsruhe from illegal intrigues by the Nazis.     

Social psychophysiological compliance in a four-person research team

A continuous, non-invasive and objective measure of teamwork effectiveness could be very useful to the human factors design community. Social psychophysiological compliance (SPC), estimated by scoring the extent that heart rate variation was synchronous across team members, was explored as a predictor of teamwork effectiveness during 20 real planning meetings over a 6-month period. Speech activity and heart rate variability of all four (2 male, 2 female) team members were continuously monitored. Exploratory analyses tested if team member ratings of various aspects of teamwork effectiveness were predicted by SPC scored (1) over whole meetings, (2) during one team member's speech, (3) during periods in which two team members spoke in sequence or (4) over 30-s periods and averaging highest values. SPC during periods of sequential speech negatively predicted team members' ratings of Team productivity, Quality of communication, and Ability to work together. SPC shows potential as an objective, non-invasive means to monitor teamwork effectiveness but this relationship warrants further investigation and replication before use in ergonomics applications.     

Multicriteria dimensioning of hard-finishing operations regarding cross-process interdependencies

The production of high performance metal parts requires a well balanced sequence of operations and can usually technologically not be achieved in a single process. This issue leads to complex process chains on the shop floor and the requirement to split single processes into multistage processes in hard-finishing operations. In both cases, the objective for the process planning is to achieve not only a local optimum for the individual processes but rather an overall optimum for the complete sequence. In order to reach the overall optimum, the process planner needs to integrate the effects between the processes into consideration. These effects which are referred to as cross-process interdependencies lead to balanced settings of process parameters and results in a much more effective operation of the sequence. In this paper, a novel approach dealing with the integration of cross-process interdependencies in the hard-finishing process of multistage grinding is introduced. It is based on an a-priori multicriteria dimensioning procedure which allows the integration of cross-process interdependencies and is implemented in software programmed in JAVA. A multistage plunge grinding process for crankshaft journals is used for evaluation of the results predicted by a developed software prototype.     

Strain-induced internal fibrillation in looped aramid filaments

By mapping the small-angle X-ray scattering (SAXS) from a looped poly-(para-phenylene terephtalamide) (aramid, PPTA) filament using a synchrotron X-ray microbeam, we investigate the effects of axially compressive and tensile strain on internal fibrillar structures. Unique observations of oscillations in the highly anisotropic SAXS patterns indicate a regular internal structure. Upon increase of the applied compressive strain, a significant decrease in oscillation frequency is observed in the scattering pattern. With an increase in imposed tensile strain an increase in oscillation frequency in the scattering pattern is observed. One model capable of describing the intensity is a model of stacked cylinders. These cylinders could be part of the fibrillar structure present in the PPTA fibres, which consist of cylinder- to tape-like objects, the presence of which is supported by SEM images. One hypothetical physical interpretation presented here for the appearance of a regular internal structure is the occurrence of fibrillar separation in regions undergoing axially compressive strain, and the appearance of strain relief/slip planes between packs of fibrils in regions undergoing tensile strain. Compaction of these packs upon increase of tensile strain could increase the repetition distance in the structure as multiple packs combine to form a single pack.     

德国并不是加热欧洲太阳能市场的唯一国家

据iSuppli公司,虽然德国作为新增太阳能安装之王获得了光伏(PV)市场的王冠,但欧洲其它国家也在扩大自己的2010年及未来光伏计划. 实际上,欧洲其它可以替代德国成为投资热点的地区大量涌现,意大利和法国的投资回报(ROI)就非常吸引人.iSuppli公司已经看到,大多数德国太阳能投资者涌向这些国家,以拓宽投资范围.