Technology University of Denmark

Kongens Lyngby, Denmark

Technology University of Denmark

Kongens Lyngby, Denmark

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Korhonen J.,Technology University of Denmark | Burini N.,Technology University of Denmark | Forchhammer S.,Technology University of Denmark | Pedersen J.M.,Bang and Olufsen
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Traditionally, algorithm-based (objective) image and video quality assessment methods operate with the numerical presentation of the signal, and they do not take the characteristics of the actual output device into account. This is a reasonable approach, when quality assessment is needed for evaluating the signal quality distortion related directly to digital signal processing, such as compression. However, the physical characteristics of the display device also pose a significant impact on the overall perception. In order to facilitate image quality assessment on modern liquid crystaldisplays (LCD) using light emitting diode (LED) backlight with local dimming, we present the essential considerations and guidelines for modeling the characteristics of displays with high dynamic range (HDR) and locally adjustable backlight segments. The representation of the image generated by the model can be assessed using the traditional objective metrics, and therefore the proposed approach is useful for assessing the performance of different backlight dimming algorithms in terms of resulting quality and power consumption in a simulated environment. We have implemented the proposed model in C++ and compared the visual results produced by the model against respective images displayed on a real display with locally controlled backlight units. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Ramsay J.,University of Aarhus | Dupont S.,University of Aarhus | Johansen M.,University of Aarhus | Rishoj L.,Technology University of Denmark | And 3 more authors.
Optics Express | Year: 2013

Using femtosecond upconversion we investigate the time and wavelength structure of infrared supercontinuum generation. It is shown that radiation is scattered into higher order spatial modes (HOMs) when generating a supercontinuum using fibers that are not single-moded, such as a step-index ZBLAN fiber. As a consequence of intermodal scattering and the difference in group velocity for the modes, the supercontinuum splits up spatially and temporally. Experimental results indicate that a significant part of the radiation propagates in HOMs. Conventional simulations of super-continuum generation do not include scattering into HOMs, and including this provides an extra degree of freedom for tailoring supercontinuum sources. © 2013 Optical Society of America.

Dupont S.,University of Aarhus | Petersen C.,University of Aarhus | Thogersen J.,University of Aarhus | Agger C.,Technology University of Denmark | And 2 more authors.
Optics Express | Year: 2012

Combining the molecular specificity of the infrared spectral region with high resolution microscopy has been pursued by researchers for decades. Here we demonstrate infrared supercontinuum radiated from an optical fiber as a promising new light source for infrared microspectroscopy. The supercontinuum light source has a high brightness and spans the infrared region from 1400 nm to 4000 nm. This combination allows contact free high resolution hyper spectral infrared microscopy. The microscope is demonstrated by imaging an oil/water sample with 20 μm resolution. © 2012 Optical Society of America.

Hernandez J.C.,Technology University of Denmark | Petersen L.P.,Technology University of Denmark | Andersen M.A.E.,Technology University of Denmark | Petersen N.H.,Grundfos A S
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2014

This paper presents a guide on characterizing state-of-the-art silicon superjunction (SJ) devices in the 600V range for single phase power factor correction (PFC) applications. The characterization procedure is based on a minimally inductive double pulse tester (DPT) with a very low intrusive current measurement method, which enables reaching the switching speed limits of these devices. Due to the intrinsic low and nonlinear capacitances in vertical SJ MOSFETs, special attention needs to be paid to the gate drive design to minimize oscillations and limit the maximum at turn off. This paper investigates the latest SJ devices in order to set a reference for future research on improvement over silicon (Si) attained with the introduction of wide bandgap devices in single phase PFC applications. The obtained results show that the latest generation of SJ devices set a new benchmark for its wide bandgap competitors. © 2014 IEEE.

Cuttone A.,Technology University of Denmark | Lehmann S.,Technology University of Denmark | Larsen J.E.,Technology University of Denmark
PDM 2013 - Proceedings of the 1st ACM International Workshop on Personal Data Meets Distributed Multimedia, Co-located with ACM Multimedia 2013 | Year: 2013

We describe a personal informatics system for Android smartphones that provides personal data on mobility and social interactions through interactive visualization interfaces. The mobile app has been made available to N=136 first year university students as part of a study of social network interactions in a university campus setting. The design of the interactive visualization interfaces enabling the participants to gain insights into own behaviors is described. We report initial findings based on device logging of participant interactions with the interactive visualization app on the smartphone and from a survey on usage with response from 45 (33%) of the participants indicating that the system allowed new insights into behavioral patterns. © 2013 ACM.

Niemann H.,Technology University of Denmark | Poulsen N.K.,Technology University of Denmark
Proceedings of the American Control Conference | Year: 2015

The aim of this paper is to present a method for estimation of parametric faults in closed-loop systems. The key technology applied in this paper is coprime factorization of both the dynamic system as well as the feedback controller. Using the Youla-Jabr-Bongiorno-Kucera (YJBK) parameterization, it is shown that a certain matrix transfer function, the fault signature matrix, is an LFT (linear fractional transformation) of the parametric faults. Further, for limit parametric faults, the fault signature matrix transfer function can be approximated with a linear matrix function of the parametric faults. © 2015 American Automatic Control Council.

Hviid C.A.,Technology University of Denmark | Svendsen S.,Technology University of Denmark
Energy and Buildings | Year: 2013

An experimental study is reported in this paper for a diffuse ceiling ventilation concept. The analyses were carried out with two different porous surfaces mounted in a suspended ceiling: perforated tiles of aluminium and of gypsum. Ventilation air was supplied above the suspended ceiling effectively creating a plenum for air distribution. The experiments were carried out in a climatic chamber and documented an air change efficiency equal to fully mixed conditions with a pressure drop of 0.5-1.5 Pa and with no evidence of thermal discomfort. The magnitude of the pressure drop was enough to sustain the pressure of the plenum and ensure uni-directional airflow through the ceiling. Consequently only reverse flow of insignificant magnitude was observed which has a positive impact on the hygiene of the plenum. Furthermore, the measurements documented that the ceiling acts as a radiant cooling surface which increases the potential and applicability of the concept. Risk of thermal discomfort was not disclosed but the study did show evidence of large fluctuating air movements which could stem from transient behaviour creating sensations of draught to the occupants. © 2012 Elsevier B.V. All rights reserved.

Hansen S.,Technology University of Denmark | Ravn O.,Technology University of Denmark
16th International Conference on Research and Education in Mechatronics, REM 2015 - Proceedings | Year: 2015

Experiences from a new course in mechatronics at Technical University of Denmark are conveyed in this paper. The course is supposed to teach students enrolled in the bachelor degree in electrical engineering some fundamental knowledge about mechanics and to teach students enrolled in the bachelor degree in mechanical engineering fundamentals about electronics. Furthermore the course uses project work as a method to keep the students actively participating and in part have them teach each other the subjects. The general course plan is presented and the reasoning behind the course structure is discussed in the paper, together with a brief look at the student's reactions in form of data from the course evaluation. © 2015 Deutsche Gesellschaft für Mechatronik.

Burini N.,Technology University of Denmark | Nadernejad E.,Technology University of Denmark | Korhonen J.,Technology University of Denmark | Forchhammer S.,Technology University of Denmark | Wu X.,McMaster University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Local backlight dimming in Liquid Crystal Displays (LCD) is a technique for reducing power consumption and simultaneously increasing contrast ratio to provide a High Dynamic Range (HDR) image reproduction. Several backlight dimming algorithms exist with focus on reducing power consumption, while other algorithms aim at enhancing contrast, with power savings as a side effect. In our earlier work, we have modeled backlight dimming as a linear programming problem, where the target is to minimize the cost function measuring the distance between ideal and actual output. In this paper, we propose a version of the abovementioned algorithm, speeding up execution by decreasing the number of input variables. This is done by using a subset of the input pixels, selected among the ones experiencing leakage or clipping distortions. The optimization problem is then solved on this subset. Sample reduction can also be beneficial in conjunction with other approaches, such as an algorithm based on gradient descent, also presented here. All the proposals have been compared against other known approaches on simulated edge- and direct-lit displays, and the results show that the optimal distortion level can be reached using a subset of pixels, with significantly reduced computational load compared to the optimal algorithm with the full image. © 2012 SPIE.

Niemann H.,Technology University of Denmark | Poulsen N.K.,Technology University of Denmark
Proceedings of the American Control Conference | Year: 2014

The focus in this paper is on active fault detection (AFD) for MIMO systems with parametric faults. The problem of design of auxiliary inputs with respect to detection of parametric faults is investigated. An analysis of the design of auxiliary inputs is given based on analytic transfer functions from auxiliary input to residual outputs. The analysis is based on a singular value decomposition of these transfer functions Based on this analysis, it is possible to design auxiliary input as well as design of the associated residual vector with respect to every single parametric fault in the system such that it is possible to detect these faults. © 2014 American Automatic Control Council.

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