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Gradient information is used in volume rendering to classify and color samples along a ray. In this paper we present an analysis of the theoretically ideal gradient estimator and compare it to some commonly used gradient estimators. A new method is presented to calculate the gradient at arbitrary sample positions, using the derivative of the interpolation(More)
OLFAR, Orbiting Low Frequency Antennas for Radio Astronomy, will be a space mission to observe the universe frequencies below 30 MHz, as it was never done before with an orbiting telescope. Because of the ionospheric scintillations below 30 MHz and the opaqueness of the ionosphere below 15 MHz, a space mission is the only opportunity for this as yet(More)
  • Arjan Meijerink, Chris G H Roeloffzen, Roland Meijerink, David A I Marpaung, Mark J Bentum, Maurizio Burla +13 others
  • 2010
—A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beam-forming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical(More)
  • A Meijerink, S L Cotton, M J Bentum, W G Scanlon
  • 2009
A frequency offset modulation scheme using wideband noise carriers is considered. The main advantage of such a scheme is that it enables fast receiver synchronization without channel adaptation, while providing robustness to multipath fading and in-band interference. This is important for low-power wireless systems with bursty traffic, such as sensor(More)
For a species to develop in nature basically two things are needed: an enabling technology and a " niche ". In spacecraft design the story is the same. Both a suitable technology and a niche application need to be there before a new generation of spacecraft can be developed. In the last century two technologies have emerged which had and still have a huge(More)
—We present a novel device-free stationary person detection and ranging method, that is applicable to ultra-wide bandwidth (UWB) networks. The method utilizes a fixed UWB infrastructure and does not require a training database of template waveforms. Instead, the method capitalizes on the fact that a human presence induces small low-frequency variations that(More)
  • A G J Nijmeijer, M A Boer, C H Slump, M M Samsom, M J Bentum, G J Laanstra +3 others
  • 1993
This paper presents the design of a real-time imaging system, with incorporated the correction of lens-distorted images. It may be used in medical applications (e.g. real-time X-ray image intensifiers), industrial robot vision products or consumer electronics. The system contains two different VLSI-circuits: a transformer and an interpolator. The(More)