54 research outputs found
The analogue of grad-div stabilization in DG methods for incompressible flows: Limiting behavior and extension to tensor-product meshes
No full textSchroeder, Philipp W./0000-0001-7644-4693WOS: 000442638700037grad-div stabilization is a classical remedy in conforming mixed finite element methods for incompressible flow problems, for mitigating velocity errors that are sometimes called poor mass conservation. Such errors arise due to the relaxation of the divergence constraint in classical mixed methods, and are excited whenever the spatial discretization has to deal with comparably large and complicated pressures. In this contribution, an analogue of grad-div stabilization for Discontinuous Galerkin methods is studied. Here, the key is the penalization of the jumps of the normal velocities over facets of the triangulation, which controls the measure-valued part of the distributional divergence of the discrete velocity solution. Our contribution is twofold: first, we characterize the limit for arbitrarily large penalization parameters, which shows that the stabilized nonconforming Discontinuous Galerkin methods remain robust and accurate in this limit; second, we extend these ideas to the case of non-simplicial meshes; here, broken grad-div stabilization must be used in addition to the normal velocity jump penalization, in order to get the desired pressure robustness effect. The analysis is performed for the Stokes equations, and more complex flows and Crouzeix-Raviart elements are considered in numerical examples that also show the relevance of the theory in practical settings. (C) 2018 Elsevier B.V. All rights reserved.German Academic Exchange Service (DAAD)Deutscher Akademischer Austausch Dienst (DAAD); program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 [57299291]; National Science FoundationNational Science Foundation (NSF) [DMS1522191]; U.S. ArmyUnited States Department of Defense [65294-MA]The authors would especially like to thank Christoph Lehrenfeld for several related fruitful discussions on stabilization and hybridization and the invaluable help he provided in using the finite element library NGSolve in the context of this work. Mine Akbas acknowledges support from the German Academic Exchange Service (DAAD) with the program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 (57299291). The third author was supported by National Science Foundation grant DMS1522191 and U.S. Army grant 65294-MA
Comparison of the resonance sonorheometry based Quantra® system with rotational thromboelastometry ROTEM® sigma in cardiac surgery – a prospective observational study
No full textBackground: Measures of the sonorheometry based Quantra® viscoelastic hemostatic analyzer (HemoSonics, LCC, Charlottesville, VA, USA) were compared with corresponding results of the ROTEM® sigma device (Instrumentation Laboratory, Bedford, MA, USA).
Methods: In thirty-eight patients scheduled for elective cardiac surgery between December 2018 and October 2019, blood samples were taken after induction of anesthesia (sample 1) and after heparin neutralization (sample 2) and measured on Quantra (QPlus® Cartridge) and ROTEM sigma (ROTEM® sigma complete + hep Cartridge). Clot times and clot stiffness values were recorded. Clot stiffness values of ROTEM amplitudes (A in mm) were converted to shear modulus (G) in hectoPascal (hPa): G (hPa) = (5 x A)/(100-A). Additionally, time-to-results was recorded. Spearman rank test correlation and Bland Altman analysis were performed.
Results: Clot stiffness parameters of the Quantra correlated strongly with corresponding measurements of the ROTEM with r = 0.93 and 0.94 for EXTEM A10 vs CS and r = 0.94 and 0.96 for FIBTEM A10 vs FCS for sample 1 and 2, respectively. Quantra clot time correlated strongly with ROTEM INTEM CT with r = 0.71 for sample 1 and r = 0.75 for sample 2. However, Bland Altman analysis showed no agreement in all compared assays of both methods. The median time to delivery of first and complete results was significantly shorter for Quantra (412 and 658 s) compared to ROTEM sigma (839 and 1290 s).
Conclusions: The Quantra showed a strong correlation with the ROTEM sigma for determining clot times and clot stiffness and the parameters assess similar aspects of clot development. However, these parameters are not directly interchangeable and implicate that separate cut-off values need to be established for users of the Quantra device. Word count: 278.
Trial registration: The study was retrospectively registered with ClinicalTrials.gov (ID: NCT04210830 ) at December 20th 2019.
Keywords: Quantra; ROTEM sigma, cardiac surgery; Resonance Sonorheometry; Viscoelastic testin
Reliability Analysis of an Anchored Contiguous Pile Wall in Ankara Clay with the Random Set Finite Element Method
No full textA deep excavation application characterized by imprecise data and lack of adequate information is used to demonstrate the efficiency, applicability, and validity of the random set theory in combination with finite element method (RS-FEM). A case history of an anchored contiguous pile wall in overconsolidated fissured Ankara Clay constructed for supporting the 15 m deep basement excavation of a nursing house in Seyranbaglari district of Ankara is considered. Existing buildings around the excavation area necessitated a careful examination of the wall deformations and the reliability of the system as a whole. However, the geotechnical parameters of the soil had to be estimated combining the results of very limited in-situ and laboratory tests with those obtained through previous experience of finite element analyses under similar conditions, i.e., expert knowledge. Plane strain finite element analyses were then performed to predict the contiguous pile retaining wall behavior. The parameters in the random set finite element model were chosen according to sensitivity analyses. Most likely bounds of the wall horizontal deformations were compared with those obtained from inclinometer readings. As suggested by previous case histories, wall deformations were observed to fall within the lower third of the range predicted by RS-FE
Probabilistic Slope Stability Analyses Using Limit Equilibrium and Finite Element Methods
No full textThis paper compares the results of different probabilistic approaches and emphasizes the necessity of probabilistic analyses in slope stability studies. To do that, Limit Equilibrium Method (LEM) and Finite Element Method (FEM) are utilized and their outputs are compared in terms of probability of failure (PF), reliability index (RI), factor of safety (FS) and the failure surface. Lastly, concept of Random Finite Element Method (RFEM) is studied and effects of spatial correlation distance are investigate
Commitment-detachment and authorial presence in postgraduate academic writing: A comparative study of Turkish native speakers, Turkish speakers of English and English native speakers.
No full textThis thesis reports an exploratory and contrastive corpus study examining two phenomena in postgraduate academic writing: expressing commitment/detachment and signalling authorial presence in dissertations. More specifically, the overall purpose of the study is to investigate how postgraduate academic writers from particular contexts build their academic stance and voice by employing a range of linguistic items that could be identified as hedges, boosters and authorial references.
The corpus consists of a total of 90 discussions sections of master’s dissertations, 30 from Turkish L1 writers, 30 from Turkish writers of English and 30 from UK English L1 writers. A range of items, discourse functions and roles were determined during the pilot study via Nvivo 9. Then, the whole corpus was searched and analysed via WordSmith 5.0 based on the linguistic item list signalling certainty/doubt or authorial presence. In order to address two crucial phenomena in dissertation writing of postgraduates represented by three groups, both quantitative and qualitative approaches were adapted. Three key findings are as follows:
1. The postgraduates polarised: they either frequently qualified their level of commitment or else they seemingly intentionally withheld their commitment from what they asserted. The tone of writing adopted by the Turkish L1 writers differed markedly from that of the English L1 & L2 writers, as evidenced by their use of linguistic signalling expressions; the English L1 and L2 writers preferred to sound more detached from their knowledge claims, compared with the Turkish L1 writers. Therefore, the findings emphasise the importance of the language factor in expressing commitment-detachment across groups.
2. The authorial references included two broad categories: (1) Explicit authorial references (I and we-based pronouns); (2) Implicit authorial references (passive and element-prominent constructions speaking for the author). The Turkish L1 writers and the Turkish writers of English (from Turkish culture) appeared to construct less personal academic prose compared with the English L1 writers. This seems to reflect a broader cultural difference.
3. In terms of the authorial roles identified in relation to the accompanying verbs, the postgraduate writers tended to appear in their discourse most frequently as (1) Research Conductor, followed by (2) Discourse Creator & Participant; then (3) Opinion Holder. The rhetorical role indicating the membership of the postgraduates to a community (either academic or institutional), (4) Community-self, was the least frequent role adopted by the postgraduates in their discussion sections.
It is recommended that, in order to raise postgraduates’ awareness about the writing conventions and practices in their disciplines, they should be provided with the standards required with respect to style via modelling from previous successful dissertations completed in their field. This is suggested as particularly important for ‘novice’ writers
Suitability of Agile Methodology in Globally Distributed Software Development : A Case Study
No full textThis thesis investigates the suitability of agile methodology in distributed software development.
This is done by first identifying the challenges of distributed software development which are, by the
reviewed literature, communication and collaboration, decrease in teamness feeling, architectural
and technical challenges, and decreased visibility for the project status. Then, the thesis presents
the agile methodology with its two methods, namely Scrum and Extreme Programming (XP).
Thirdly, the benefits and the challenges of applying the agile methodology in distributed software
development are determined.
Findings from literature are tested versus a case study which was done in a globally distributed
software development team who had worked on an important project in a multinational private
software company. The data collection methods were the participant-observation done by the
author as a part of the team, author’s notes on the critical events, and also the semi-structured
interviews done with the team members from different roles and different teams.
Empirical results show that agile methodology, more specifically Scrum and XP, helps with many
aspects in distributed software development, which include increased communication and collaboration, improved visibility for the project status, and also increased the sense of trust within the
team. It is also discovered that agile methodology helps with onboarding new people to the team.
Furthermore, limited documentation in agile methodology and virtual pair programming do not
affect the distributed teams negatively according to empirical evidence. Finally, empirical data also
shows that applying agile methodology in distributed software development has some challenges
such as the number of meetings.
Empirical results show resemblance with the reviewed literature in many parts such as increased
communication and collaboration as a benefit of distributed agile software development. However,
there are also some aspects contradicting the reviewed literature. For example, limited documentation appears as a challenge of distributed agile development in the reviewed literature, whereas
it did not seem to be a challenge in the empirical case.
Furthermore, this study can be extended by observing other empirical cases, notably failed projects,
not only in software development but also in other fields
Der Fußballtrainer im Spannungsfeld zwischen Verein und Öffentlichkeit - eine komparative Studie Deutschland : Türkei
No full textZusammenfassung: Der Fußball hat sich zu einem ein Phänomen entwickelt, das auf der ganzen Welt von den unterschiedlichsten Bevölkerungsschichten interessiert verfolgt wird. Eine Gruppe der wichtigsten zentralen Rollenträger im Zusammenspiel von Sport, Medien und Bevölkerung sind die Trainer. Besonders im professionellen Fußball bilden sie häufig das entscheidende Bindeglied zwischen Verein und der Öffentlichkeit und stehen daher nicht selten im Mittelpunkt, wo sie einem entsprechenden Druck ausgesetzt sind und sich das Aufgabenspektrum des Trainers in diesem Zuge erheblich verändert hat. Die bilaterale Expertenstudie beleuchtet anhand zweier kulturell sehr unterschiedlicher Untersuchungsräume das bisher unerforschte Spannungsfeld des Fußballtrainers zwischen Verein und Öffentlichkeit für die Länder Deutschland und Türkei und arbeitet entsprechende Gemeinsamkeiten und Unterschiede heraus. Es werden die übergeordneten Leitfragen der Untersuchung, wie das Spannungsfeld des Fußballtrainers aussieht und wie es in der Realität von den befragten Trainern wahrgenommen wird, komparativ zwischen deutschen und türkischen Profi-Fußballtrainern erörtert. Die Stellungnahmen der Trainer zu den unterschiedlichsten Themengebieten zeigen, dass das von nahezu jedem Trainer wahrgenommene Spannungsfeld zwischen Verein und Öffentlichkeit keinen länder- oder regionstypischen Gegebenheiten unterlegen ist. Die entsprechende Resonanz auf die Fragen sowie die hohe Konformität der Antworten weist ebenso daraufhin, dass allgemein eine intensive Auseinandersetzung mit dem Thema Spannungsfeld zur Reduzierung des Konfliktpotenzials beitragen soll und kann. Entsprechende Meinungen, Einschätzungen und Informationen zu Vorgehensweisen der Trainer sowie die abschließenden Ergebnisse der Untersuchung können problemlos als Grundlage für weitere empirische Untersuchungen auf diesem Gebiet herangezogen werden.
Abstract: The Football (Soccer) Coach in the Field of Tension between the Club and the Public - a Comparative German : Turkish Study -
Football has developed into a phenomenon which is observed world-wide with interest by the most varied population segments. One of the most important groups of protagonists in this interplay of sport, the media and the general public are the coaches. Especially in professional football, they tend to be the decisive link between the clubs and the public. They are frequently in the center of attention, exposed to strong pressure and to a quickly changing spectrum of tasks. This bi-national study analyzes the so far unexplored state of tension in which the coaches are caught up between the club and public opinion, in the culturally very different environments of Germany and Turkey. The author reveals the similarities and differences and discusses the key questions of the study - the existing pressures and how this reality is perceived by the interviewed professional coaches, both on the German and the Turkish side. The answers of the coaches to the very diversified set of questions show that the perceived tensions are not subject to national or regional conditions. The high conformity of the answers shows that there is a general need to discuss the topic in order to reduce its conflict potential. The opinions, assessments and informations about the conduct of the coaches, and the final results of the study may well be taken as a basis for further empirical analyses in this field
Impact of student-centered strategies on vocabulary learning in a foreign language classroom
No full textPlan B Paper. 2013. Master of Science in Education- Reading--University of Wisconsin-River Falls. Teacher Education Department. [33] leaves. Includes bibliographical references (leaves [32-33]).The traditional middle school foreign language classroom typically has the teacher imparting the knowledge and vocabulary of the unit to the class. The students are unmotivated to take ownership of their learning with this methodology and are highly dependent on the teacher for the information. They do not view themselves as capable of finding and or sharing vocabulary in the secondary language. The author of this study felt that this mentality needed to shift from the "sage on the stage" to the students becoming empowered learners. The question that arises is how to achieve this. Could student centered vocabulary learning have an impact in a foreign language classroom? What are the best ways to implement the shift of power? The author facilitated this shift by utilizing student created word expert cards that emphasized the new, unfamiliar vocabulary from the next unit of study within a curriculum textbook. When students had control of one of the new words, they were then in charge of teaching each other the new vocabulary through peer tutoring as the teacher acted as a mediator. This effectively reversed the power roles. The teacher also shifted control by implementing semantic mapping activities of the vocabulary words with the students, justifying their reasoning for word placement and usage with each other; the teacher once again acted as a mediator. Data was collected through student interviews, student surveys, and end of the unit vocabulary tests. The results of the study show that students felt they were in control of their learning, took pride in both knowing a word in the target language before everyone else and sharing that knowledge with their peers. Vocabulary comprehension and maintenance improved through the use of the semantic mapping activities versus the traditional call-out review. The conclusion of the study is that student-centered vocabulary instruction improves the motivation and ownership of students. The implementation of the vocabulary learning strategies not only assisted with the retention of the second language vocabulary but it also instilled within the students a sense of pride that they could learn a foreign language and not be dependent upon the teacher
Präklinische Schmerztherapie: Übersicht und Verbesserungsmöglichkeiten
No full textZusammenfassung. Schmerzen sind ein Problem, mit dem das Rettungsdienstpersonal in der Präklinik häufig konfrontiert ist. Eine schnelle und effektive Analgesie wirkt sich positiv auf den physiologischen und psychologischen Zustand der Patientinnen und Patienten aus. Doch nach wie vor werden präklinisch bis zu 43 % der Betroffenen unzureichend analgetisch therapiert. Mehrere Studien identifizierten Faktoren, die ursächlich für diese Problematik sind. Die drei wesentlichen sind das behandelnde Personal sowie patienten- und einsatzspezifische Besonderheiten. Damit die präklinische Analgesie künftig weiter verbessert werden kann, braucht es neben strukturellen und organisatorischen Veränderungen auch die Implementierung neuer Methoden und Therapien.
=
Prehospital Pain Management: Overview and Potential Improvements Abstract. Pain is a frequent issue in the prehospital setting. Rapid and adequate analgesia has a positive effect on the physiological and psychological condition of patients. However, up to 43 % of patients still suffer insufficient analgesia. Several studies have identified some factors that contribute to this problem; these factors can be patient- and intervention-specific or dependent on the staff on duty. In order to improve prehospital analgesia in the future, structural and organizational changes as well as the implementation of new methods and therapies are essential.
Keywords: Analgésie préhospitalière; Notarztdienst; Oligoanalgesie; Prehospital analgesia; Präklinische Analgesie; Rettungsdienst; Schmerz; douleur; emergency physician; médecin urgentiste; oligoanalgesia; oligoanalgésie; pain; rescue service; service de secours
Successful use of extracorporeal life support and hemadsorption in the context of venlafaxine intoxication requiring cardiopulmonary resuscitation: a case report
No full textVenlafaxine is a serotonin and noradrenalin reuptake inhibitor prescribed as an antidepressant. Overdose clinically manifests with neurological, cardiovascular and gastrointestinal abnormalities based on, amongst others, serotonin syndrome and can be life-threatening due to cardiovascular collapse. Besides immediate decontamination via gastric lavage and inhibition of enteral absorption through active charcoal, successful hemadsorption with CytoSorb has been reported. We present the case of a 17-year-old female who required extracorporeal life support (ECLS) for cardiovascular collapse as a result of life-threatening venlafaxine intoxication. Serial serum blood concentrations of venlafaxine/desmethylvenlafaxine on admission at a tertiary hospital (approx. 24 h after ingestion) and subsequently 6 h and 18 h thereafter, as well as on days 2 and 4, were measured. CytoSorb was initiated 6 h after admission and changed three times over 72 h. The initial blood concentration of venlafaxine/desmethylvenlafaxine was 53.52 µmol/l. After 6 h, it declined to 30.7 µmol/l and CytoSorb was initiated at this point. After 12 h of hemadsorption, the blood level decreased to 9.6 µmol/l. On day 2, it was down to 7.17 µmol/l and decreased further to 3.74 µmol/l. Additional continuous renal replacement therapy using CVVHD was implemented on day 5. The combination of hemadsorption, besides traditional decontamination strategies along maximal organ supportive therapy with ECLS, resulted in the intact neurological survival of the highest venlafaxine intoxication reported in the literature to date. Hemadsorption with CytoSorb might help to reduce blood serum levels of venlafaxine. Swift clearance of toxic blood levels may support cardiovascular recovery after life-threatening intoxications
- …
