1,720,955 research outputs found
Modeling concepts for Laser-Wakefield Acceleration
No full textLaser-wakefield accelerators have strong potential as future compact sources
of high-charge relativistic electrons. However, their practical application is
currently limited by significant shot-to-shot variations, large energy spreads,
and high emittance. These fluctuations primarily arise from the high sensi tivity of the acceleration process on the properties of the driving laser. To
increase the knowledge of this interaction, I consider two complementary
methods to model laser wakefield acceleration: data-driven modeling and
Particle-In-Cell (PIC) simulations.
The data-driven method employs a neural network to model relationships
between laser properties, electron properties and secondary X-ray generation
in a laser wakefield accelerator. In experimental setups, measurement errors
are prevalent and in particular the developed model mitigates the influence
of these by employing a novel optimization criteria. Analysis of the model
reveals strong consistency with physics-based simulations and theoretical
expectations and, additionally, reveals unknown correlations between laser
driver and system output. Thus, the model shows strong potential as a
foundation for the stabilization and analysis of laser wakefield accelerators
in experimental settings.
On the other hand, for the design and study of laser-plasma interactions,
physics-based models, such as particle-in-cell (PIC) simulations are essential.
These simulations come at a significant computational cost, which can be
levitated by performing them in a Lorentz-boosted frame. However, this
approach is often limited by the Numerical Cherenkov Instability (NCI). In
this thesis, a lightweight PIC framework, π-PIC, is introduced to facilitate
easy testing and integration of new PIC algorithmic developments. Using
this framework, the influence of energy and momentum conservation on
NCI growth is examined
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Bayesian optimization of beam quality of plasma accelerated electron beams
No full textLaser-plasma acceleration is a promising novel technique for acceleration of charged
particles. A challenge with this technique is to maintain a high quality of the accelerated
particle bunch. In particular, for accelerated electrons used in Free Electron
Lasers, charge and shape of the energy spectrum are important parameters. The aim
of this project has been to evaluate and examine the use of Bayesian optimization
with respect to these parameters on the LUX laser-plasma accelerator. The focus
was to consider how the Bayesian optimization performed under noisy conditions.
An important part of Bayesian optimization algorithms is the acquisition function
which determines the next point to evaluate in the optimization iteration. In this
thesis, two acquisition functions were compared and evaluated from the performance
point of view.
In order to test and develop the algorithms, Particle-In-Cell (PIC) simulations were
used to emulate the LUX experiment. Further, for cheaper evaluation, a model of the
target surface was built from a vast amount of PIC simulated data using Gaussian
process regression. With this model, different sampling strategies for each parameter
set-point could be investigated. Noise was added to the input parameters as well,
yielding a more realistic imitation of the system. A significant improvement was seen
when the mean value of 20 input parameters and the mean value of corresponding
outputs were fed to the Bayesian optimization algorithm
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
It is time for you to make an effort : The implementation of Agenda 2030 in the sustainable operations management of the banking sector
No full textAgenda 2030 är en gemensam handlingsplan som tagits fram av Förenta Nationernas (FN) medlemsländer för att uppnå hållbar utveckling. Målsättningen är att de globala målen ska vara uppnådda till år 2030, men för att visionen ska bli verklighet krävs det att alla aktörer tar sitt hållbarhetsansvar. Därmed är det nödvändigt att företagen utvecklar nya verktyg och processer som bidrar till en hållbar utveckling. Tidigare forskning visar att implementeringen av hållbarhet i verksamhetsstyrningen är komplex, därför är det av betydelse att utveckla kunskapen kring implementeringen av Agenda 2030 hos en aktör som har ett betydande inflytande på den hållbara utvecklingen. Syftet med studien är att tydliggöra hur och varför banksektorn implementerar Agenda 2030 i verksamhetsstyrningen. Studiens teoretiska syfte är att visa hur incitamenten till CSR bidrar till en hållbar verksamhetsstyrning. Således avser studien att bidra till den kunskapsutveckling som är nödvändig kring bank-sektorns CSR-arbete för uppnåendet av de globala målen. För att uppnå syftet har studien undersökt fem olika banker i Värmland utifrån en kvalitativ forskningsansats. Med hjälp av tio semistrukturerade intervjuer har bankernas implementering av Agenda 2030 i verksamhetsstyrningen undersökts. Studien visar att incitamenten för att implementera hållbarhet och Agenda 2030 i verksamhetsstyrningen har förändrats. De mest centrala drivkrafterna för ett hållbart agerande är påtryckningar från intressenter, en fråga om överlevnad, erhållande av legitimitet liksom ett eget ansvarstagande. Vidare indikerar studien att Agenda 2030 till viss del är implementerad i banksektorns hållbara verksamhetsstyrning. De styrmedel som främst inkluderar Agenda 2030 är planering, cybernetisk styrning och administrativ styrning. Däremot används inte belönings- och bonussystem för att uppmuntra till ett hållbart agerande, utan studien visar snarare på att kulturstyrning bör användas för att påverka medarbetarnas beteende. För att hållbarhet och Agenda 2030 ska bli en del av kärnverksamheten är det därmed nödvändigt att utveckla och förändra kulturstyrningen. Studien visar att hållbar utveckling och uppnåendet av Agenda 2030 uppnås när företagens hållbarhetsarbete fortlöper och kontinuerligt förbättras.Agenda 2030 is a joint action plan developed by the member states of the United Nations (UN), in order to reach sustainable development. The ambitions are that the Sustainable Development Goals (SDGs) should be reached by 2030, but everyone needs to work together to make that happen. Therefore, companies must develop new tools and processes to contribute to sustainable development. Previous research shows that the implementation of sustainability in the operations management is complex. Hence, it is of great importance to create knowledge about the implementation of Agenda 2030 for an actor that plays a significant part of the sustainable development. The aim of this study is to clarify how and why the banking sector implements Agenda 2030 in their operations management. The theoretical aim is to show how incentives of CSR contributes to sustainable operations management. Therefore, this study contributes to developing the knowledge necessary for the banking sector, in order to reach the SDGs through their work with CSR. To fulfill the purpose, five different banks in Värmland have been investigated through a qualitative research approach. Throughout ten semi-structured interviews, the implementation of Agenda 2030 in the operations management of the banks have been investigated. The study shows that the incentives for implementing sustainability and Agenda 2030 in the operations management have changed. The most crucial incentive for sustainable actions is instigations from stakeholders, a matter of survival, obtaining legitimacy as well as the company’s own responsibility. Further, the study indicates that Agenda 2030 is partly implemented in the banking sector’s sustainable operations management. The controls that mainly include Agenda 2030 are planning, cybernetic control and administrative control. However, rewards and compensations are not used in the banking sector to encourage sustainable actions. In this regard, cultural control should be used in order to affect the behaviour of the employees. For sustainability and Agenda 2030 to be a part of the core business, is it crucial to develop and change the cultural control. This study shows that sustainable development and achievement of Agenda 2030 are completed when the sustainability of the companies continually is improved
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