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971.
Lanyun Zhang Christian Wagner 《International journal of human-computer interaction》2018,34(7):640-652
Previous studies have investigated the experiences and characteristics of holiday decision-making among groups of travelers. This study adds to the knowledge of group trip holiday planning through exploring influential factors (including the individual and group characteristics of travelers), and linking those with their intragroup interactions when planning a group trip. A total of 261 usable questionnaires were collected across two university campuses in the UK and China. The survey employed a retrospective approach, asking participants to recall one of their past group trip planning experiences within the previous 3 months. This study found that intragroup interactions during a group trip planning process are influenced both by tourists’ individual factors, such as age, gender, and nationality, and by group characteristics, such as group size, common interest, group type, and group travel style. This study shows that common interest is the most influential factor in terms of its positive impact on group collaboration, feeling of connectedness, strength of preparation, and flexibility and spontaneity during group trip planning process. Further, in general, Chinese groups tend to spend less time on planning their trips before departure, but focus more on the details of the itinerary. Finally, the implications for technologies that are designed to facilitate the group trip planning process, with a view to enhancing the level of group enjoyment, are discussed based on the findings in this study. 相似文献
972.
Although IS research acknowledges the importance of path dependence with the generalized response that “history matters,” this broad understanding does not substitute for a more systematic historical analysis of how paths emerge and how technological change breaks them. In this context, we draw on the theory of strategic path dependence from organization and management research to develop a more nuanced understanding of path dependence and then explore how technological change breaks these strategic paths. Based on a narrative analysis of the strategic development of incumbents in the funeral industry, we reconstruct the core components of strategic paths – strategic patterns and self-reinforcing mechanisms – and scrutinize the Internet’s role in breaking these paths. We suggest that technological change helps break strategic paths by destabilizing the very self-reinforcing mechanisms that led to their emergence and reproduction in the first place. Furthermore, by showing that breaking strategic paths involves a subsequent critical event that destabilizes the strategic pattern, we advance a process understanding of how strategic paths are broken. This paper thus provides much-needed historical analyses of IS-related phenomena, offers a more precise and systematic understanding of path dependence in IS research, and yields insights into the process of how strategic paths are broken. 相似文献
973.
974.
To improve the barrier properties of poly(ethylene terephthalate) (PET), PET/poly(ethylene 2,6‐naphthalate) (PEN) blends with different concentrations of PEN were prepared and were then processed into biaxially oriented PET/PEN films. The air permeability of bioriented films of pure PET, pure PEN, and PET/PEN blends were tested by the differential pressure method. The morphology of the blends was studied by scanning electron microscopy (SEM) observation of the impact fracture surfaces of extruded PET/PEN samples, and the morphology of the films was also investigated by SEM. The results of the study indicated that PEN could effectively improve the barrier properties of PET, and the barrier properties of the PET/PEN blends improved with increasing PEN concentration. When the PEN concentration was equal to or less than 30%, as in this study, the PET/PEN blends were phase‐separated; that is, PET formed the continuous phase, whereas PEN formed a dispersed phase of particles, and the interface was firmly integrated because of transesterification. After the PET/PEN blends were bioriented, the PET matrix contained a PEN microstructure consisting of parallel and extended, separate layers. This multilayer microstructure was characterized by microcontinuity, which resulted in improved barrier properties because air permeation was delayed as the air had to detour around the PEN layer structure. At a constant PEN concentration, the more extended the PEN layers were, the better the barrier properties were of the PET/PEN blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1309–1316, 2006 相似文献
975.
976.
Dr.-Ing Ludwig Wagner 《Electrical Engineering (Archiv fur Elektrotechnik)》1952,40(6):331-342
Übersicht Zur Klärung der Vorgänge bei Koronaentladungen in atmosphärischer Luft werden die Ströme gemessen und mit Hilfe einer besonderen Oszillographenschaltung dargestellt, die während der Entladung an einer Spitze-Platte-Funkenstrecke auftreten, deren Spitze aus halbkugelig zugefeilten Drahtenden (Kugelspitzen) bestebt. Gleichzeitig werden die Leuchterscheinungen und Veränderungen an der Spitzen-oberfläche mit einem Mikroskop beobachtet.Die mit gleicher Spannung verschiedener Polarität und Wechselspannung an verschiedenem Spitzen-material ermittelten Meßergebnisse und Beobachtungsresultate führen zusammen mit der Berechnung zu einem vollständigen Bild des Entladungsmechanismus. Danach wird der Beginn der selbständigen Entladung bei der negativen Kugelspitze durch die Elektronembefreiung beim Aufprall positiver Ionen auf die Kathode () bestimmt. Bei Spannungen, die etwas höher als die Anfangsspannung liegen, bilden sich zunächstTownsend-Lawinen, deren Umfang durch das rasch abnehmende Feld begrenzt wird. Bei Spannungen, die je nach Material etwa 50 bis 300 V über der Anfangsspannung liegen, wird an einzelnen Stellen der Kugeloberfläche, das durch die mit großer Energie aufprallenden positiven Ionen sprunghaft vergrößert. Durch die erhöhte Trägervermehrung und die rasche Anlagerung der Elektronen an Gasmoleküle wird aber die Dichte der raumladung so groß, daß der Entladungsprozeß nach 0,36·10–6 s unterbunden wird. So entstehen nur einzelne Entladeimpulse, deren Häufigkeit mit wachsender Spannung zunimmt. Das Auftreten dieser Impulse wurde bisher irrtümlich für den Beginn der selbständigen Entladung gehalten. Der Beginn der selbständigen Entladung bei der positiven Kugelspitze ist dann gegeben, wenn bei den Stoßprozessen genügend energiereiche Strahlung ausgesendet wird, so daß die für die Entladung notwendigen Nachfolgeelektronen im Raum zwischen Spitze und Platte durch Fotoionisation gebildet werden können. Die mittlere Wellenlänge der wirksamen Strahlen wird zu 60 bis 110 Å ermittelt. Zu Beginn der positiven Entladung tritt zunächst ein intermittierender Bereich auf, in dem die Entladung kurzzeitig zündet und wieder abreißt, bis dann bei höheren Spannungen die Entladung stetig brennt. In diesen intermittierenden Bereich können einzelne Lawinen mit besonders großer Trägerzahl zu einer kathodengerichteten Kanalbildung führen (Stromfaden). Entsprechend den verschiedenen Entladungsmechanismen der negativen und positiven Kugelspitzen sind auch die Leuchterscheinungen verschieden geartet.Mit 17 Textabbildungen 相似文献
977.
978.
979.
Leonardo Heidrich Jorge Luis Victória Barbosa Wagner Cambruzzi Sandro José Rigo Márcio Garcia Martins Renan Belarmino Scherer dos Santos 《Telematics and Informatics》2018,35(6):1593-1606
The amount of data generated by computer systems in Online Distance Learning (ODL) contains rich information. One example of this information we define as the Learner Learning Trail (LLT), which is the sequence of interactions between the students and the virtual environment. Another example is the Learner Learning Style (LLS), which is associated with the student behavior and choices during the learning process. This information can be used to identify learner behavior and learning style. We perceived, after the study of related literature, that the research field of learner diagnosis for ODL does not apply the conjoint use of LLT and LLS. In this article, we propose a model capable of integrating data generated from the behavior of students in ODL with cognitive aspects of them, such as their Learning Styles, by crossing LLT with LLS. We also propose the CPAD method (Collect, Preprocessing, Analysis, Diagnosis), which is implemented by collecting the raw data regarding learning activities, preprocessing the data into structured time sequences, analyzing the sequences regarding the learning styles and using this analysis to diagnose the learner behavior. We selected the dropout to investigate, once the dropout rate in ODL is a real problem in universities around the world. In addition, the dropout is a student decision which can be associated with previous students behaviors. We performed a study with 202 learners to evaluate if learning styles are capable of explaining aspects of the student behavior. The results suggest that Sequential/Global learning style dimension is more capable of explaining the dropout than the other dimensions. Also, we performed four classification experiments to verify how the dimensions of Felder-Silverman Learning Style Model influence the learner diagnosis. We perceived that the Sequential/Global dimension could provide a higher accuracy average with lower variation independently of the diagnosis technique. 相似文献
980.
Thiago Gonçalves das Neves Wagner Brandão Ramos Gilvan Wanderley de Farias Neto Romildo Pereira Brito 《Korean Journal of Chemical Engineering》2018,35(4):826-834
We developed and implemented an intelligent control system to be used in an extractive distillation column that produces anhydrous ethanol using ethylene glycol as solvent. The concept of artificial neural networks (ANN) was used to predict new setpoints after disturbances, and proved to be a fast and feasible solution. The developed control system receives data from temperature, flowrate and composition measurements of the azeotrope feed, and the ANN estimates the new set-points of the controllers to maintain 99.5 mol% of ethanol at the top and less than 0.1mol% at the bottom; feed composition was also estimated using an ANN. All ANN were trained to provide output data corresponding to an optimized operating condition. The results showed that the intelligent control system can predict a new operating condition for any disturbance in the column feed and presented superior performance when compared with the control system without ANN. 相似文献