Combining steady-state with frequency and time domain data to quantitatively analyze charge transport in organic light-emitting diodes

Typically, organic light-emitting diodes (OLEDs) are characterized only in steady-state to determine and optimize their efficiency. Adding further electro-optical measurement techniques in frequency and time domain helps to analyze charge carrier and exciton dynamics and provides deeper insights into the device physics. We, therefore, first present an overview of frequently used OLED measurement techniques and analytical models. A multilayer OLED with a sky-blue thermally activated delayed fluorescent dopant material is employed in this study without loss of generality. Combining the measurements with a full device simulation allows one to determine specific material parameters such as the charge carrier mobilities of all the layers. The main part of this tutorial focuses on how to systematically fit the measured OLED characteristics with microscopic device simulations based on a charge drift-diffusion and exciton migration model in 1D. Finally, we analyze the correlation and sensitivity of the determined material parameters and use the obtained device model to understand limitations of the specific OLED device

Witnessing Entanglement of EPR States With Second-Order Interference

The separability of the continuous-variable EPR state can be tested with Hanbury-Brown and Twiss type interference. The second-order visibility of such interference can provide an experimental test of entanglement. It is shown that time-resolved interference leads to the Hong, Ou and Mandel deep, that provides a signature of quantum non-separability for pure and mixed EPR states. A Hanbury-Brown and Twiss type witness operator can be constructed to test the quantum nature of the EPR entanglement.Comment: 9 pages, 5 figure

Effective Strategies for Increasing Citation Frequency

Due to the effect of citation impact on The Higher Education (THE) world university ranking system, most of the researchers are looking for some helpful techniques to increase their citation record. This paper by reviewing the relevant articles extracts 33 different ways for increasing the citations possibilities. The results show that the article visibility has tended to receive more download and citations. This is probably the first study to collect over 30 different ways to improve the citation record. Further study is needed to explore and expand these techniques in specific fields of study in order to make the results more precisely.Available online: http://ssrn.com/abstract=234458

The design decision trail

This was a published paper presented at the International Conference on Engineering and Product Design Education on the 6th and 7th of September 2012 at the Artisis University College, Antwerp, Belgium. The Design Decision Trail is a student produced, visual narrative of a design project. It includes the signposting of key design decision points within the edited from the project. It is used to share information with student peers, tutors and potential employers. It is now being used in both undergraduate and postgraduate design study at the University of Northampton. Employers have endorsed its use at interview and offered students design employment. It is now being considered as a teaching aid in non-design subject areas within the universit

Test of the He-McKellar-Wilkens topological phase by atom interferometry. Part II: the experiment and its results

In this paper, we describe an experimental test of the He-McKellar-Wilkens (HMW) topological phase with our lithium atom interferometer. The expected value of the HMW phase shift in our experiment is small and its measurement was difficult because of stray phase shifts due to small experimental defects. We start by describing our setup and we characterize the effects of the electric and magnetic fields needed to observe the HMW effect. Then, we develop a model of our interferometer signals including all the defects we have identified. After various tests of this model, we use it to suppress the largest part of the stray phase shifts. We thus obtain a series of measurements of the HMW phase: the results are 31% larger than expected and this discrepancy is probably due to some limitations of our model

Spin squeezing, entanglement and quantum metrology with Bose-Einstein condensates

Squeezed states, a special kind of entangled states, are known as a useful resource for quantum metrology. In interferometric sensors they allow to overcome the "classical" projection noise limit stemming from the independent nature of the individual photons or atoms within the interferometer. Motivated by the potential impact on metrology as wells as by fundamental questions in the context of entanglement, a lot of theoretical and experimental effort has been made to study squeezed states. The first squeezed states useful for quantum enhanced metrology have been proposed and generated in quantum optics, where the squeezed variables are the coherences of the light field. In this tutorial we focus on spin squeezing in atomic systems. We give an introduction to its concepts and discuss its generation in Bose-Einstein condensates. We discuss in detail the experimental requirements necessary for the generation and direct detection of coherent spin squeezing. Two exemplary experiments demonstrating adiabatically prepared spin squeezing based on motional degrees of freedom and diabatically realized spin squeezing based on internal hyperfine degrees of freedom are discussed.Comment: Phd tutorial, 23 pages, 17 figure

Supporting Focus and Context Awareness in 3D Modelling Tasks Using Multi-Layered Displays

Most 3D modelling software have been developed for conventional 2D displays, and as such, lack support for true depth perception. This contributes to making polygonal 3D modelling tasks challenging, particularly when models are complex and consist of a large number of overlapping components (e.g. vertices, edges) and objects (i.e. parts). Research has shown that users of 3D modelling software often encounter a range of difficulties, which collectively can be defined as focus and context awareness problems. These include maintaining position and orientation awarenesses, as well as recognizing distance between individual components and objects in 3D spaces. In this paper, we present five visualization and interaction techniques we have developed for multi-layered displays, to better support focus and context awareness in 3D modelling tasks. The results of a user study we conducted shows that three of these five techniques improve users' 3D modelling task performance

Evaluating groupware support for software engineering students

Software engineering tasks, during both development and maintenance, typically involve teamwork using computers. Team members rarely work on isolated computers. An underlying assumption of our research is that software engineering teams will work more effectively if adequately supported by network-based groupware technology. Experience of working with groupware and evaluating groupware systems will also give software engineering students a direct appreciation of the requirements of engineering such systems. This research is investigating the provision of such network-based support for software engineering students and the impact these tools have on their groupwork. We will first describe our experiences gained through the introduction of an asynchronous virtual environment ­ SEGWorld to support groupwork during the Software Engineering Group (SEG) project undertaken by all second year undergraduates within the Department of Computer Science. Secondly we will describe our Computer Supported Cooperative Work (CSCW) module which has been introduced into the students' final year of study as a direct result of our experience with SEG, and in particular its role within Software Engineering. Within this CSCW module the students have had the opportunity to evaluate various groupware tools. This has enabled them to take a retrospective view of their experience of SEGWorld and its underlying system, BSCW, one year on. We report our findings for SEG in the form of a discussion of the hypotheses we formulated on how the SEGs would use SEGWorld, and present an initial qualitative assessment of student feedback from the CSCW module