Kollektionsunterstützung für SQL:1999     

Jens Lufter 《Informatik - Forschung und Entwicklung》2003,18(1):11-21

Zusammenfassung. Kollektionen wie Mengen, Listen und Felder spielen in objektorientierten Anwendungen und Datenbanken eine wichtige Rolle. Dementsprechend sollten sie zusammen mit anderen objektrelationalen Konzepten auch in die aktuelle Datenbanknorm SQL:1999 eingebracht werden. Aus Aufwands- und Zeitgründen wurden jedoch vom Normungsgremium, zu dem auch die Vertreter wichtiger Hersteller kommerzieller (objekt-)relationaler Datenbankmanagementsysteme gehören, zunächst nur Felder (Arrays) berücksichtigt; andere Kollektionsarten sollen erst später folgen. Auch in wichtigen DBMS-Produkten werden Kollektionen bislang nur unzureichend und auf heterogene Art und Weise unterstützt. Dieser Beitrag beschäftigt sich mit den Möglichkeiten einer Ergänzung von SQL:1999 um wichtige Kollektionsarten. Basierend auf dem aktuellen Stand von Norm und Produkten werden prinzipielle Fragen der Integration in SQL diskutiert und die Grundlagen einer adäquaten Unterstützung von Kollektionen erörtert. Der formale Sprachvorschlag auf Basis von SQL:1999 kann hier aus Platzgründen nicht näher vorgestellt werden, einige Beispiele sollen aber die Anwendung der neuen Modellierungsmöglichkeiten verdeutlichen. Eingegangen am 15. Februar 2002/Angenommen am 10. September 2002CR Subject Classification H.2.1, H.2.3, H.2.4, D.3.3  相似文献   

Loneliness and physical activity: A systematic review     

Fabian Pels  Jens Kleinert 《International review of sport and exercise psychology》2016,9(1):231-260

This article aims to provide an overview of the current state of research on the relationship between loneliness and physical activity (PA). A systematic literature search was conducted to identify all empirical studies assessing this relationship. A total of 37 studies stemming from 36 publications met the inclusion criteria. Study analyses comprised an individual consideration of each study and a systematic summarization of the studies. The majority of eligible studies focused on adolescent or elderly populations. Direct negative associations between PA and loneliness were found in half of the 24 cross-sectional studies. Of the seven identified longitudinal studies, one found a direct negative influence of PA on loneliness. Four longitudinal studies found evidence for a reverse influence, namely of loneliness on PA. Five intervention studies found PA to reduce loneliness. Two of the cross-sectional studies and one of the intervention studies found social support and social competence to moderate or to mediate the relationship between PA and loneliness. The findings indicate that PA can contribute to a decrease in loneliness. However, studies also indicate that any beneficial effect is dependent upon the quality of relationships present during physical activity. Additionally, loneliness itself might reduce the probability of being physically active.  相似文献   

The elitism dispositif: hierarchization,discourses of excellence and organizational change in European economics     

Jens Maesse 《Higher Education》2017,73(6):909-927

From the 1990s onwards, economics departments in Europe have changed toward a culture of “excellence.” Strong academic hierarchies and new forms of academic organization replace “institutes” and “colleges” by fully equipped “economics departments.” This article seeks to demonstrate how and why hierarchization, discourses of excellence and organizational change takes place in European economics departments. The concept of “elitism dispositif” will be developed in order to understand these changes as a discursive as well as power-related phenomenon based on rankings, on the formation of new academic classes as well as on the construction of an elite myth. An elitism dispositif is defined as a discursive power apparatus that transforms symbolic differences among researchers, constructed by rankings, into material inequalities, based on an unequal distribution of academic capital between departments and researchers. Based on an empirical study, the article will focus on a selection of economics departments in Germany and in the UK, in order to study the emergence of an “elite class” as well as the functioning of an “excellence culture” that is based on discourses of power and inequality.  相似文献   

Renal lactate elimination is maintained during moderate exercise in humans     

Volianitis S  Dawson EA  Dalsgaard M  Yoshiga C  Clemmesen J  Secher NH  Olsen N  Nielsen HB 《Journal of sports sciences》2012,30(2):149-153

Reduced hepatic lactate elimination initiates blood lactate accumulation during incremental exercise. In this study, we wished to determine whether renal lactate elimination contributes to the initiation of blood lactate accumulation. The renal arterial-to-venous (a-v) lactate difference was determined in nine men during sodium lactate infusion to enhance the evaluation (0.5 mol x L(-1) at 16 ± 1 mL x min(-1); mean ± s) both at rest and during cycling exercise (heart rate 139 ± 5 beats x min(-1)). The renal release of erythropoietin was used to detect kidney tissue ischaemia. At rest, the a-v O(2) (CaO(2)-CvO(2)) and lactate concentration differences were 0.8 ± 0.2 and 0.02 ± 0.02 mmol x L(-1), respectively. During exercise, arterial lactate and CaO(2)-CvO(2) increased to 7.1 ± 1.1 and 2.6 ± 0.8 mmol x L(-1), respectively (P < 0.05), indicating a -70% reduction of renal blood flow with no significant change in the renal venous erythropoietin concentration (0.8 ± 1.4 U x L(-1)). The a-v lactate concentration difference increased to 0.5 ± 0.8 mmol x L(-1), indicating similar lactate elimination as at rest. In conclusion, a -70% reduction in renal blood flow does not provoke critical renal ischaemia, and renal lactate elimination is maintained. Thus, kidney lactate elimination is unlikely to contribute to the initial blood lactate accumulation during progressive exercise.  相似文献   

The validity of a German version of the career exploration survey     

Jens Rowold  Kathrin Staufenbiel 《International Journal for Educational and Vocational Guidance》2010,10(1):21-34

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Control System Digital Computer Transfer Function Simulation     

Jonsson  Jens J. 《Education, IRE Transactions on》1962,5(1):15-17

The z transform of simple delay, integrator, leadlag, and differentiator networks are suggested as the basic building blocks for simulating complex control systems on a digital computer. The system parameters retain their explicit identity, thus facilitating analysis and design of the system as a function of specific parameter changes.  相似文献   

Sind die bildungswissenschaftlichen Standards für die Lehramtsausbildung in den Curricula der Hochschulen angekommen?     

Dipl.-Psych. Friederike Hohenstein  Prof. Dr. Friederike Zimmermann  Dr. Thilo Kleickmann  Prof. Dr. Olaf Köller  Prof. Dr. Jens Möller 《Zeitschrift für Erziehungswissenschaft》2014,17(3):497-507

During the Bologna reforms, the Standing Conference of the Ministers of Education and Cultural Affairs (abbr.: Standing Conference) formulated education standards for higher education teacher training programmes (KMK 2004a) in the areas of teaching, educating, diagnostics, and innovation. Currently there is very little research on the extent to which these education standards are reflected in the teacher training curriculums at universities. This contribution analyses the course regulations, module handbooks, and exam regulations for teacher training programmes at 16 universities for the inclusion of content required by the education standards. The document analysis shows that a large proportion of the education standards introduced by the Standing Conference (KMK 2004a) are not considered by the curriculums of many universities.  相似文献   

Die Organisation sportlichen Erfolges     

Dr. Jens Flatau  Eike Emrich 《Sportwissenschaft》2011,41(2):100-111

As the result of German efforts to advance elite sports being partially guided by the presumed successful example of the German Democratic Republic there has been an increase in vertically integrated sponsoring organizations to promote elite sports, particularly after reunification. Adhering to Williamson’s (1975) transaction costs economics, the theory is assessed that in producing sports success the effectiveness of hierarchical organizations depends on the specificity of production factors. Based on a comparison of former students of elite sports schools with non-elite students it could be shown that encouragement of talent in elite schools is advantageous in those types of sports that require specific sports locales or sites for practice. The results provide insight into how the productivity of elite sports schools could be enhanced.  相似文献   

How to stay becoming – living up to the code of conduct in a sports class     

Lotte Stausgaard Skrubbeltrang  Jesper Stilling Olesen  Jens Christian Nielsen 《Ethnography and Education》2016,11(3):371-387

In this article we show how a hybridisation of elite sport and school in lower-secondary education in Denmark produces a particular kind of learning subject with dual tracks for development, and we ask what kind of actions the students apply in order to stay becoming along both tracks. We apply theoretical conceptions of ‘becoming’ inspired by Brembeck and Johansson that allow us to understand how the sports students live up to the code of conduct of the sports classes. The article is based on an ethnographic study carried out in four schools located in four regions of Denmark. We argue that the hybrid obliges students to follow a narrow developmental track with an ambitious goal of performing in both sport and school, and that the hybrid is threatened when a sports student prioritises either sport or school while he/she is still enrolled in the class.  相似文献   

Legitimacy,stratification, and internationalization in global higher education: the case of the International Association of Universities     

Zapp  Mike  Jungblut  Jens  Ramirez  Francisco O. 《Tertiary Education and Management》2021,27(1):1-15

Tertiary Education and Management - The International Association of Universities (IAU) is the only inclusive global university association, its membership barriers are low, yet few universities...  相似文献