Sparse channel estimation and equalization for OFDM-based underwater cooperative systems with amplify-and-forward relaying

Due to copyright restrictions, the access to the full text of this article is only available via subscription.This paper is concerned with a challenging problem of channel estimation and equalization for amplifyand- forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in sparse underwater acoustic (UWA) channels. The sparseness of the channel impulse response and prior information for the non-Gaussian channel gains, modeled by an exact continuous Gaussian mixture (CGM), are exploited to improve the performance of the channel estimation algorithm. The resulting novel algorithm initially estimates the overall sparse complex-valued channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The effective time-domain non- Gaussian noise is approximated well as a Gaussian noise in the frequency-domain, where the estimation takes place. An efficient and low complexity algorithm is developed based on the combinations of the MP and the maximum a posteriori probability (MAP) based space-alternating generalized expectationmaximization technique, to improve the estimates of the channel taps and their locations in an iterative way. Computer simulations show that the UWA channel is estimated very effectively and the proposed algorithm exhibits excellent symbol error rate and channel estimation performance.TÜBİTAK ; NS

Reactions of pentachloro-2-nitrobutadiene with some aliphatic and heterocyclic thiols and a crystallographic study

In this study, S-, S,S- and S,O-substituted novel nitrodiene compounds were synthesized. Cyclization products were formed when difunctional nucleophiles were used. The stereoisomerism of a heterocyclic nitrodiene is discussed with the help of XRD studies. The structures of all compounds were characterized by spectroscopic methods (FT-IR, H-1 NMR, C-13 NMR, F-19 NMR, MS) and microanalysis

Identification of new critical points for logistics model in cumulative methane yield curves after co-digestion of apple pulp and chicken manure with sulphuric acid pretreatment and a new modelling study

WOS: 000520732400001In this study, anaerobic co-digestion of apple pulp (AP) with high carbon content and chicken manure (CM) with high nitrogen content was evaluated with regard to sulphuric acid pretreatment conditions in the concentration range of 1%-6% v/v. The best mixing ratio of CM:AP was determined as 3:1 w/w under untreated conditions for which the methane yield was 255.88 +/- 11.55 mL/g VS (volatile solid). Sulphuric acid pretreatments were applied to this mixture ratio. The highest methane yield after pretreatment was 466.01 +/- 10.85 mL/g VS in the reactor, where the sulphuric acid pretreatment concentration was 3.0% v/v. Control of acid pretreatment results were achieved by analysis of lignocellulosic degradation and increase in soluble chemical oxygen demand. The highest cellulose, hemicellulose and lignin degradation after pretreatment were 27.5% +/- 1.4%, 35.9% +/- 2.9% and 14% +/- 1.5% w/w, respectively. The cumulative methane yields (CMY) were analysed by the modified logistic model, modified Bertalanffy model (MBM), modified Gompertz model (MGM) and modified Holling model (MHM). The MBM and MGM were found to fit the experimental data better than other models. The MHM has not previously been applied to CMY. In addition to the kinetic studies, new critical points for CMYs were identified in the logistics model (lm). The importance and critical properties of these points with regard to CMY are introduced. The differences and superior properties of these critical points compared to other modelling methods are discussed

Trends in radiation protection use and radiation exposure of European endourologists: an ESUT-YAU Endourology Group prospective trial

We have carried a theoretical study of the K^- p to M B gamma reaction with M B = K^-p, bar{K}^0 n, pi^- Sigma^+, pi^+ Sigma^-, pi^0 Sigma^0, pi^0 Lambda, for K^- lab. momenta between 200 and 500 MeV/c, using a chiral unitary approach for the strong K^-p interaction with its coupled channels. The Lambda(1405) resonance, which is generated dynamically in this approach, shows up clearly in the d sigma/dM_I spectrum, providing new tests for chiral symmetry and the unitary approach, as well as information regarding the nature of the resonance. The photon detection alone, summing all channels, is shown to reproduce quite accurately the strength and shape of the Lambda(1405) resonance. Analogous reactions in nuclei can provide much information on the properties of this resonance in a nuclear medium