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1.
2.
We present a two-sorted algebra, called aPeirce algebra, of relations and sets interacting with each other. In a Peirce algebra, sets can combine with each other as in a Boolean algebra, relations can combine with each other as in a relation algebra, and in addition we have both a set-forming operator on relations (the Peirce product of Boolean modules) and a relation-forming operator on sets (a cylindrification operation). Two applications of Peirce algebras are given. The first points out that Peirce algebras provide a natural algebraic framework for modelling certain programming constructs. The second shows that the so-calledterminological logics arising in knowledge representation have evolved a semantics best described as a calculus of relations interacting with sets. 相似文献
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4.
Markert Yvonne; Koditz Jens; Ulbrich-Hofmann Renate; Arnold Ulrich 《Protein engineering, design & selection : PEDS》2003,16(12):1041-1046
The virtue of the so-called proline concept andthe charge concept for stabilizing protease-susceptibleregions of a protein structure was compared on bovine pancreaticribonuclease A. Alanine 20 and serine 21, both of whichare located in a loop that is susceptible to the unspecificproteases subtilisin Carlsberg, subtilisin BPN', proteinaseK and elastase, were replaced with proline or lysine by site-directedmutagenesis. The rate constant of proteolysis was decreasedby up to three orders of magnitude for the proline mutants dependingon the site of the mutation and the protease used. In contrast,substitution by lysine increased the proteolytic resistanceby only one order of magnitude characterizing the prolineconcept as superior to the charge concept.Although the four applied proteases are considered to be unspecific,the degree of stabilization of the ribonuclease molecule variedconsiderably, indicating the impact of individual differencesin their substrate specificity on the proteolytic resistanceand degradation pathway of the target protein. Received May 12, 2003; revised October 23, 2003; accepted October 30, 2003 相似文献
5.
A key challenge faced by organizations is to provide project teams with workspaces, information, and collaboration technologies
that fosters creativity and high-performance team productivity. This requires understanding the relation between and impacts
of (1) workspace, (2) activity and content that is created, and (3) social, behavioral, and cognitive aspects of work. This
paper describes an exploratory study of everyday activities in the context of knowledge work in a shared workspace used by
a high-tech global design team that explores future products. The study formalizes key elements for productive knowledge work
as a function of tasks, context, and team. It identifies enablers, hindrances, and requirements for physical, virtual, and
social work environments. The study identified, through semi-structured interviews, surveys, and on-site shadowing, a key
workspace component that facilitates dynamic participation of all team members. This workspace component is a wall used as
a large, public, physical display surface for project content (the WALL). The WALL acts as a mediator for individual reflection-in-action
and team reflection-in-interaction. It serves as “social glue” both between individuals and between geographically distributed
subgroups. 相似文献
6.
We explore in this paper the relation between activities, communication channels and media, and common ground building in
global teams. We define re-representation as a sequence of representations of the same concept using different communication
channels and media. We identified the re-representation technique to build common ground that is used by team members during multimodal and multimedia communicative events in cross-disciplinary,
geographically distributed settings. Our hypotheses are as follows: (1) Significant sources of information behind decisions
and request for actions are embedded within the fabric of communicative events in which participants use both informal and
formal media to express their ideas. Capturing these information sources can facilitate common ground building and accelerate
the execution of action requests. (2) Re-representations of concepts, i.e., sequences of representations using diverse media
and communication channels, mediate and accelerate common ground building. (3) The use of intra- or interdisciplinary re-representations
correlates with high team performance, i.e., effective team process and high product quality. We used AEC Global Teamwork
course offered in 2008–2009 as the testbed for our study to validate our hypothesis. 相似文献
7.
Renate A. Schmidt Dmitry Tishkovsky 《Annals of Mathematics and Artificial Intelligence》2004,42(1-3):5-36
This paper investigates a family of logics for reasoning about the dynamic activities and informational attitudes of agents, namely the agents' beliefs and knowledge. The logics are based on a new formalisation and semantics of the test operator of propositional dynamic logic and a representation of actions which distinguishes abstract actions from concrete actions. The new test operator, called informational test, can be used to formalise the beliefs and knowledge of particular agents as dynamic modalities. This approach is consistent with the formalisation of the agents' beliefs and knowledge as K(D)45 and S5 modalities. Properties concerning informativeness, truthfulness and preservation of beliefs are proved for a derivative of the informational test operator. It is shown that common belief and common knowledge can be expressed in the considered logics. This means, the logics are more expressive than propositional dynamic logic with an extra modality for belief or knowledge. The logics remain decidable and belong to 2EXPTIME. Versions of the considered logics express natural additional properties of beliefs or knowledge and interaction of beliefs or knowledge with actions. It is shown that a simulation of PDL can be constructed in one of these extensions. 相似文献
8.
Rhode Heyns G. Weiss Schwaibold Steingroever Hans Müller Kanitz H. J. Steinbeck K. Felix K. Höll P. de Fremery Edward Hofmann Konrad Lang O. Windhausen Trendtel W. Leithe W. Schulze Ilse Gaede v. Noël Jesser H. Elsner Pieper W. Schreiber Rudolf Abderhalden Renate Teske Hanson I. Stahn Krzywanek Fr. Bartschat Lars Erlandsen Ad. Hanak W. Bartels Kluge E. -E. Bauke Karl Bernhard G. Steinhoff W. Hämmerle C. I. Kruisheer Brüning Reichard K. J. Demeter M. Gordienko Flössner Jahr Diemair H. Mohler 《European Food Research and Technology》1939,78(1):48-112
9.
Modified FeCrAl coatings were studied with respect to their capability to form a thin protective oxide scale in liquid lead environment. They were manufactured by low pressure plasma spraying and GESA surface melting, thereby tuning the Al content. The specimens were exposed for 900 h to liquid lead containing 10?6 and 10?8 wt.% oxygen, respectively, at various temperatures from 400 to 550 °C. Threshold values for an Al content that guarantees the formation of thin protective Al-rich oxide scales are determined, dependent on the respective chromium content, on the presence of yttrium in the modified coating, and on the exposure conditions. 相似文献
10.
Synthesis of 2,4-Bisalkyl(aryl)amino-6-cyanamino-s-triazines Reaction of 2,4-bisalkyl(aryl)amino-6-chloro-s-triazines with disodiumcyanamide to 2,4-bisalkyl(aryl)amino-6-cyanamino-s-triazines ( 3a – g ) strongly depends on the solvent used. In dimethylformamide by-products predominate. The best results are found in dimethylsulphoxide. 相似文献