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91.
Thomas Mueller Karsten Brueninghaus Hermann Rohling 《Wireless Personal Communications》1995,2(4):295-305
Uncoded orthogonal frequency division multiplexing (OFDM) transmission technique applied in a multipath environment has a bit error rate (BER) comparable with a narrowband radio channel because the fading of each subcarrier is frequency-nonselective. To overcome this behaviour and to reduce the BER, a combination of OFDM and CDMA has been proposed recently. In an OFDM-CDMA system the energy of each information symbol is spread over several subcarriers. Therefore a diversity gain can be obtained in a broadband fading channel.In this paper we discuss the performance of OFDM-CDMA with coherent QPSK signalling over a frequency-selective Rayleigh fading channel. Channel estimation and demodulation are integral parts that determine the performance of the system. The method for channel estimation presented in this paper is based on a two-dimensional array of pilot symbols with second-order regression in the time domain and interpolation in the frequency domain. Quantitative comparison of four different detection algorithms in frequency-selective Rayleigh fading with noisy channel state information (CSI) will be presented in this paper: conventional correlation (equal gain correlation, EGC), orthogonality restoring correlation (ORC), ORC with a threshold in order to suppress subcarriers with low signal strength (TORC), and an iterative improvement based on a maximum likelihood approach. With TORC and iterative improvement a gain of approximately 9 dB over conventional OFDM can be obtained at a BER of 10–3 in Rayleigh fading. 相似文献
92.
Patrick Ruther Stanislav Herwik Sebastian Kisban Karsten Seidl Oliver Paul 《IEEJ Transactions on Electrical and Electronic Engineering》2010,5(5):505-515
Extracellular recordings from the brain are the basis for the fundamental understanding of the complex interaction of electrical signals in neural information transfer. Going beyond wire electrodes and bundles of electrode wires such as tetrodes, multielectrode arrays based on silicon technologies are receiving growing attention, since they enable a pronounced increase in the number of recording sites per probe shaft. In this paper, recent innovations contributed by the authors to the development of probe arrays based on microelectromechanical system (MEMS) technologies within the EU‐funded research project NeuroProbes are described. The resulting structures include passive electrode arrays based on single‐shaft and four‐shaft probes comprising nine planar electrodes per shaft with lengths of up to 8 mm. Further, active probe arrays with complementary metal–oxide–semiconductor (CMOS) circuitry integrated on the probe shaft, enabling the arrangement of 188 electrodes in two columns along a 4‐mm‐long probe shaft with an electrode pitch of only 40 µm, are described. These active probes were developed for an electronic depth control. Further, the paper reports assembly technologies for combining the probe arrays with highly flexible ribbon cables. Applications of the probes in in vivo experiments are summarized. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
93.
This study examines the feasibility that peroxidation and lipolysis of 1-O-alkyl-2,3-diacyl-sn-glycerols (DAGE) found in shark liver oil and human milk fat constitutes a potential source of dietary precursors of platelet
activating factor (PAF) mimics and of gamma-hydroxybutyrate (GHB). Purified DAGE were converted into 1-O-alkyl-2-acyl-sn-glycerols by pancreatic lipase, without isomerization, and transformed into 1-O-alkyl-2-oxoacyl-sn-glycerols by mild autooxidation. The various core aldehydes without derivatization, as well as the corresponding dinitrophenylhydrazones,
were characterized by chromatographic retention time and diagnostic ions by online electrospray mass spectrometry. Core aldehydes
of oxidized shark liver oil yielded 23 molecular species of 1-O-alkyl-sn-glycerols with short-chain sn-2 oxoacyl groups, ranging from 4 to 13 carbons, some unsaturated. Autooxidation of human milk fat yielded 1-O-octadecyl-2-(9-oxo)nonanoyl-sn-glycerol, as the major core aldehyde. Because diradylglycerols with short fatty chains are absorbed in the intestine and
react with cytidine diphosphate-choline in the enterocytes, it is concluded that formation of such PAF mimics as 1-O-alkyl-2-(ω-oxo)acyl-sn-glycerophosphocholine from unsaturated dietary DAGE is a realistic possibility. Likewise, a C4 core alcohol produced by aldol-keto reduction of a C4 core aldehyde constitutes a dietary precursor of the neuromodulator and recreational drug GHB, which has not been previously
pointed out. 相似文献
94.
95.
From a top-down to a bottom-up urban discourse: (re) constructing the city in a family-inclusive way
Lia Karsten 《Journal of Housing and the Built Environment》2009,24(3):317-329
This paper focuses on urban discourses as powerful instruments intertwined with the dialectic of inclusion and exclusion.
First, three dominant contemporary urban discourses developed in the field of urban planning are scrutinized on their inclusiveness
of families and daily family life. The attractive city, the creative city and the city as an emancipation machine are examples
of urban discourses communicated top-down via reports, debates and media attention. It is argued that these three discourses
do not address families as urban citizens nor the very notion of reproduction and its daily manifestation. The exclusionary
character of contemporary urban discourses does not only result in a neglect of urban families, it also legitimates non-intervention
when it comes to family issues. This conclusion activated the search for an alternative discourse as expanded in the second
part of the paper. This alternative discourse is constructed from the bottom-up and is rooted in the day-to-day experiences
of urban families themselves. It is a refined discourse, with interrelated geographical scales including the city as a whole,
the neighbourhood, the street and the home. This is a city that integrates—as families themselves do—the different domains
of life. The city is appreciated for its qualities of proximity, the neighbourhood for its ethnically mixed children’s domains,
the street as an urban haven and the house as the place that accommodates private life for each member of the family. This
alternative discourse is called the balanced city. The empirical basis is drawn from middle-class urban families in Rotterdam, The Netherlands. 相似文献
96.
Mette Schmedes Asker Daniel Brejnrod Eli Kristin Aadland Pia Kiilerich Karsten Kristiansen Hlne Jacques Charles Lavigne Ingvild Eide Graff
yvin Eng Asle Holthe Gunnar Mellgren Jette Feveile Young Ulrik Krmer Sundekilde Bjrn Liaset Hanne Christine Bertram 《Molecular nutrition & food research》2019,63(1)
97.
Karsten Müller 《化学,工程师,技术》2019,91(4):383-392
The efficient and dense storage of hydrogen still is a challenge for research and development. Next to compression and liquefaction, there are a number of alternative approaches, which try to enhance storage density by bonding hydrogen to another substance. Physisorbing as well as chemisorbing organic and inorganic carrier systems are possible. Many of these technologies have not yet exceeded the technology readiness level of lab‐scale tests. However, some of the technologies have already reached significantly higher technological levels. The first part of this study discusses storage approaches with recovery of elemental hydrogen. 相似文献
98.
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