861 research outputs found
OVERLAP PARAMETERS OF MOLECULAR PAIRS FROM COLLISION-INDUCED INFRARED ABSORPTION
No full textS. P. Reddy, G. Varghese, and R. D. G. Prasad, Phys. Rev. A 15, 975 (1977). S. P. Reddy and R. D. G. Prasad, J. Chem. Phys. 66, 5259 (1977).Author Institution:The collision-induced fundamental band of in the pure gas at 77, 196 and 298 K was recorded for a number of gas densities up to 60 amagat with two 2 m absorption cells. The contributions to the intensity of the band from the short-range overlap and long-range quadrupolar interactions were separated by carrying out an analysis of the absorption profiles. For the molecular pairs, the overlap parameters, and , which represent, respectively, the magnitude and range of the induced-overlap dipole moment, and , the induced dipole moment at the Lennard-Jones intermolecular diameter were determined. Finally these parameters of were compared with those of and HD - HD, determined earlier in our $laboratory.^{1,2}
VIBRONIC COUPLING THROUGH METHYL TORSIONS IN HEXAMETHYLBENZENE
No full textP. N. Prasad and R. Kopelman, Chem. Phys. Letters 21, 505 (1973). S. D. Woodruff, P. S. Prasad, and R. Kopelman, J. Chem. Phys. (1974). P. N. Prasad S. D. Woodruff, and R. Kopelman, Chem. Phys.1, 173 (1973).Author Institution: Department of Chemistry, The University of MichiganIt has been shown recently that crystal vibrations can be conveniently classified as internal, semi- (or semi-external), or external. While the nature of the vibronic coupling with internal and external has been explored extensively, the coupling with semi-internal vibrations has not received attention. We present such an investigation on hexamethy1benzene in which its coupling of the electronic states with the methyl torsional vibration has been studied. Results will be presented from fluorescence, absorption and phosphorescence studies of isotopic and chemically mixed hexamethy1benzene condensed phases at very low temperature, as well as from Raman of neat and isotopic mixed crystals. The vibronic coupling through methyl torsions will be discussed with emphasis on the relative contributions from the static and dynamic interactions in the various condensed phases
Adaptive OFDM and CDMA Algorithms for SISO and MIMO Channels
No full textThe objective of this thesis is to study adaptive modulation algorithms for Single Input Single Output (SISO) and Multiple Input Multiple Output (MIMO) channels. The adaptive modulation technique has the advantages of flexibility, providing high transmission quality and throughput; and it can lead to a smaller volume of radio and more applications. The major contribution of the author is discussed in the following paragraphs. To the best of the authorâs knowledge, the strategy and working procedures of the adaptive modulation technique have not yet been described in the literature. We propose strategies and work procedures for adaptive modulation in this dissertation. In addition, for the first time, it is proposed that the development of adaptive modulation consists of three stages, in which the adaptivity is taken to a higher level. We assert in this thesis that adaptive modulation algorithms involve two themes, i.e., channel and modulation. We analyze two types of channels: SISO and MIMO channels. We investigate the SISO channel in time, frequency, and space domains, which is efficient for designing adaptive modulation algorithms. Further, initially we propose three approaches as solutions to problems in each of the domains, i.e., adaptive techniques (time domain), OFDM (frequency domain), and MIMO technique (space domain). These three approaches are investigated in this thesis. We study the concept, structure, and characteristics of MIMO channels. The gains of three MIMO schemes and parameters influencing these gains are generalized. What is more, we introduce a new factor, the Rician K gain, to describe the MIMO gain with respect to that of SISO channels. In addition, we work out the SNR gains of these three MIMO schemes compared with SISO channels for a large SNR range, which have not been found in literature. This is indispensable for the design of adaptive modulation algorithms for MIMO channels. With regard to modulation, we list the parameters of OFDM and CDMA modulations for adaptive OFDM and adaptive CDMA algorithms to be designed. In order to obtain direct relationships between modulation parameters and throughput, we derive two throughput formulas, an OFDM formula and a CDMA formula. We show that the traditional commonly held belief that the subcarrier bandwidth influences transmission quality is true only if the channel RDS is constant. To explain this, we define a new parameter, PFR, as the product of subcarrier bandwidth and RDS. How this parameter works and by what factors it is limited are studied in this thesis. Subsequently, we propose three successful adaptive modulation algorithms, i.e., an adaptive OFDM algorithm for SISO channels, an adaptive OFDM algorithm for MIMO channels, and an adaptive CDMA algorithm for MIMO channels. Perfect channel estimation is assumed in our work. For the adaptive OFDM algorithms, we propose three subband settings. Remarkable throughput gains are obtained from all these adaptive modulation algorithms in simulations. We put forward the new idea of employing more than one MIMO scheme in a system and adapting these schemes using our adaptive modulation algorithms. Simulation results show that extra gains can be obtained by this method. The performance gains of our algorithms are dependent on the channel situation. The influence of channel parameters on these relative gains is investigated in this work as well. We introduce an SNR boundary matrix to set processing gains and modulation levels in our adaptive CDMA algorithm for MIMO channels.Electrical Engineering, Mathematics and Computer Scienc
Performance Analysis of a Dual-signal Receiver with Antenna Diversity Techniques in a narrowband Rayleigh and Rician fading channel
No full textDifferent types of diversity techniques are analysed to improve the performance of a Dualsignal Receiver in a narrowband fading channel. This receiver is capable of demodulating two BPSK-modulated co-channel signals of different strength. The receiver performance deteriorates heavily when the two signals are of equal strength. The diversity techniques, used to increase the performance of the Dual-Signal Receiver are 1.) antenna selection diversity based on SIR selection, 2.) majority voting, 3.) quasi-coherent combining and 4.) maximal ratio combining. For antenna selection diversity, quasi-coherent combining and maximal ratio combining the performance is analysed using a theoretical model, the results are verified by BER calculations based on simulated fading channels. Majority Voting is only analysed by BER ejaculations based on simulated channels. Results are presented in the form of cumulative BER functions. It is shown that using diversity techniques leads to large improvements of the performance of the Dual-Signal ReceiverElectrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Effect of Pulse Shaping on the Performance of DS-CDMA in a Multipath Fading Channel
No full textThis report gives first an overview of the main modulation methods and of the multipath propagation effects. A model is described to simulate BPSK, QPSK and OK-QPSK in some measured indoor channels. Several pulse shapes are analysed and their effects discussed on single-user systems and on DS-CDMA. The main performance parameter is the bit error rate for different noise levels. Finally, some conclusions on the possible increase of a DS-CDMA system capacity are exposed, based on the different interference reductions achieved by pulse shaping.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Correction to: Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst
No full textCorrection to: Bulletin of Chemical Reaction Engineering & Catalysis (2018), 13 (2): 227-235 (doi:10.9767/bcrec.13.2.1307.227-235)
An error appeared in Corresponding Author in a paper entitled “Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst” published in Bulletin of Chemical Reaction Engineering & Catalysis. The Corresponding Author is corrected to be:
* Corresponding Authors.
Tel: +919415268192. Email: [email protected] (R. Prasad)
Tel: +917505072607. Email: [email protected] (D. Yadav)
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The original article can be found online at: https://doi.org/10.9767/bcrec.13.2.1307.227-235
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Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
How to Cite: Singh, P., Yadav, D., Thakur, P., Pandey, J., Prasad, R. (2020). Correction to: Studies on H2-Assisted Liquefied Petroleum Gas Reduction of NO over Ag/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 15 (2): 603-603 (doi:10.9767/bcrec.15.2.7659.603-603)
Permalink/DOI: https://doi.org/10.9767/bcrec.15.2.7659.603-60
VIBRATIONAL CIRCULAR DICHROISM OF THE DEUTERATED ETHANOL (R)-(+)-
No full text S. Abbate, L. Laux, J. Overend, and A. Moscowitz, 35th Symposium on Molecular Spectroscopy, Columbus, Ohio, 1968, paper RG1. P. L. Prasad and L. A. Nafie, 35th Symposium on Molecular Spectroscopy, Columbus, Ohio, 1980, paper RG8.Author Institution:The inferred absorption and circular dichroism spectra of (R)-(+)- down to have been measured. The experimental rotational strengths will be compared with those calculated on the basis of the charge and localized molecular models
OFDM Air-interface design for multimedia communications
No full textElectrical Engineering, Mathematics and Computer Scienc
Space-time multiuser receivers for wideband code division multiple access
No full textElectrical Engineering, Mathematics and Computer Scienc
A narrowband multi-user receiver for mobile communication systems
No full textElectrical Engineering, Mathematics and Computer Scienc
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