Linköping University

About: Linköping University is a education organization based out in Linköping, Sweden. It is known for research contribution in the topics: Population & Health care. The organization has 15671 authors who have published 50013 publications receiving 1542189 citations.

Electrode Grids for ITO Free Organic Photovoltaic Devices

Abstract: Organic materials, such as conjugated polymers, have emerged as a promising alternative for the production of inexpensive and flexible photovoltaic cells. As conjugated polymers are soluble, liquid based printing techniques enable production on large scale to a price much lower than that for inorganic based solar cells. Present day state of the art conjugated polymer photovoltaic cells are comprised by blends of a semiconducting polymer and a soluble derivative of fullerene molecules. Such bulk heterojunction solar cells now show power conversion efficiencies of up to 4-6%. The quantum efficiency of thin film organic solar cells is however still limited by several processes, of which the most prominent limitations are the comparatively low mobility and the high level of charge recombination. Hence organic cells do not yet perform as well as their more expensive inorganic counterparts. In order to overcome this present drawback of conjugated polymer photovoltaics, efforts are continuously devoted to developing materials or devices with increased absorption or with better charge carrier transporting properties. The latter can be facilitated by increasing the mobility of the pure material or by introducing beneficial morphology to prevent carrier recombination. Minimizing the active layer film thickness is an alternative route to collect more of the generated free charge carriers. However, a minimum film thickness is always required for sufficient photon absorption. A further limitation for low cost large scale production has been the dependence on expensive transparent electrodes such as indium tin oxide. The development of cheaper electrodes compatible with fast processing is therefore of high importance. The primary aim of this work has been to increase the absorption in solar cells made from thin films of organic materials. Device construction, deploying new geometries, and evaluation of different methods to provide for light trapping and photon recycling have been strived for. Different routes to construct and incorporate light trapping structures that enable higher photon absorption in a thinner film are presented. By recycling the reflected photons and enhancing the optical path length within a thinner cell, the absorption rate, as well as the collection of more charge carriers, is provided for. Attempts have been performed by utilizing a range of different structures with feature sizes ranging from nanometers up to centimeters. Surface plasmons, Lambertian scatterers, micro lenses, tandem cells as well as larger folded cell structures have been evaluated. Naturally, some of these methods have turned out to be more successful than others. From this work it can nevertheless be concluded that proper light trapping, in thin films of organic materials for photovoltaic energy conversion, is a technique capable of improving the cell performance. In addition to the study of light trapping, two new alternative electrodes for polymer photovoltaic devices are suggested and evaluated.

Ethical and Methodological Issues in Interviewing Persons With Dementia

Abstract: People with dementia have previously not been active participants in research, with ethical difficulties often being cited as the reason for this. A wider inclusion of people with dementia in research raises several ethical and methodological challenges. This article adds to the emerging debate by reflecting on the ethical and methodological issues raised during an interview study involving people with dementia and their spouses. The study sought to explore the impact of living with dementia. We argue that there is support for the inclusion of people with dementia in research and that the benefits of participation usually far outweigh the risks, particularly when a ;safe context' has been created. The role of gatekeepers as potentially responsible for excluding people with dementia needs further consideration, with particular reference to the appropriateness of viewing consent as a primarily cognitive, universalistic and exclusionary event as opposed to a more particularistic, inclusive and context relevant process.

Power and Channel Allocation for Non-Orthogonal Multiple Access in 5G Systems: Tractability and Computation

Abstract: A promising multi-user access scheme, non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC), is currently under consideration for 5G systems. NOMA allows more than one user to simultaneously access the same frequency-time resource and separates multi-user signals by SIC. These render resource optimization in NOMA different from orthogonal multiple access. We provide theoretical insights and algorithmic solutions to jointly optimize power and channel allocation in NOMA. We mathematically formulate NOMA resource allocation problems, and characterize and analyze the problems’ tractability under a range of constraints and utility functions. For tractable cases, we provide polynomial-time solutions for global optimality. For intractable cases, we prove the NP-hardness and propose an algorithmic framework combining Lagrangian duality and dynamic programming to deliver near-optimal solutions. To gauge the performance of the solutions, we also provide optimality bounds on the global optimum. Numerical results demonstrate that the proposed algorithmic solution can significantly improve the system performance in both throughput and fairness over orthogonal multiple access as well as over a previous NOMA resource allocation scheme.

Trading speed for low power by choice of supply and threshold voltages

Abstract: The trading of speed for low power consumption in CMOS VLSI by using the supply voltage and the threshold voltage as variables was investigated. It is shown that it is desirable to minimize the supply voltage for minimizing the power consumption. The lower bound of the supply voltage and the possible decrease in power consumption without speed loss were investigated under different circuit constraints, and the consequences for circuit performance were calculated. Results show, for example, that power reductions of about 40 times can be obtained without speed loss by using supply voltages down to about 0.48 V. >

Continuing high early death rate in acute promyelocytic leukemia: a population-based report from the Swedish Adult Acute Leukemia Registry.

Abstract: Our knowledge about acute promyelocytic leukemia (APL) patients is mainly based on data from clinical trials, whereas population-based information is scarce. We studied APL patients diagnosed betwe ...