Contributing authors

Contributing authors     

Exact and asymptotic BEP of cooperative DS-CDMA systems using decode and forward relaying in the presence of multipath propagation

In this paper, we derive the bit error probability (BEP) of cooperative DS-CDMA systems using decode and forward (DF) relaying. We consider a conventional DF protocol where all the relays that have correctly decoded transmit and a selective DF (S-DF) protocol where we activate only the relay that offers the best instantaneous signal to noise ratio (SNR) of the relay to destination link among the relays that have correctly decoded. The derived results are valid for any multipath intensity profile of the channel, any path delays and take into account the correlation of the multipath gains.     

Optimal packet length for wireless communications using reconfigurable intelligent surfaces

Telecommunication Systems - Reconfigurable intelligent surfaces (RIS) allow significant throughput enhancement as all reflections have the same phase at the receiver. In this paper, we suggest to...     

Hybrid RF/VLC Communications Using Reconfigurable Intelligent Surfaces

In this paper, we suggest the use of Reconfigurable Intelligent Surfaces (RIS) for hybrid Radio Frequency (RF) Visible Light Communications (VLC). The signal is transmitted from a transmitter T to a relay C using RIS. RIS is implemented as a transmitter or a reflector between T and C. The relay node C decodes the received signal and transmits it to the receiver R using a VLC link. The proposed VLC/RF communications using RIS offers 20–45 dB gain with respect to conventional RF/VLC when the number of reflectors N is varied from \(N=16\) to \(N=256\).

     

The bacterial quality of red meat and offal in Casablanca (Morocco)

The present study aimed to evaluate the bacteriological quality of beef (n = 52), lamb (n = 52) and beef offal (n = 52) marketed in Casablanca, Morocco. Meat and offal samples (n = 156), were collected randomly from butcheries, supermarkets, and slaughterhouses. Two sampling periods were considered, one during the hot season and the second one during the cold season. The samples were analyzed for the presence of the following bacteria: Escherichia coli, coagulase-positive Staphylococcus, Clostridium perfringens, Salmonella, and Listeria monocytogenes. Results indicated that counts of the aerobic plate count, and fecal coliforms were particularly high in all the samples analyzed. E. coli, coagulase-positive Staphylococcus and C. perfringens were detected in 37.8, 16, and 4.5% of the meat samples, respectively. Neither Salmonella nor L. monocytogenes were isolated from meat samples. Approximately 26.9% of beef, 34.6% of lamb and 28.8% of beef offal samples contained bacteria above the maximum limits established by the Moroccan regulatory standards for meat and meat products. Seasonality and the distribution location significantly (p < 0.05) affected bacterial populations: the hot season and butcheries appeared to be cases where the highest populations of bacteria in meat were observed. These high levels of microbiological contamination attest the poor hygienic quality of meat and offal, possibly due to uncontrolled processing, storage, and handling of these products.     

Optimal Power Allocation and Harvesting Duration for NOMA Systems in the Presence of Nakagami Channels

In this paper, we derive and optimize the total throughput of non orthogonal multiple access (NOMA) with energy harvesting. The source S harvests energy from radio frequency signal received from node A. The source uses the harvested energy to transmit data to N NOMA users classified using instantaneous or average power of channel gains. We optimize the powers allocated to NOMA users and harvesting duration to maximize the total throughput. We also derive packet waiting time and total delays for all NOMA users. We optimize powers allocated to NOMA users and harvesting duration to minimize a combination of total delays of all users. Our results are valid for Nakagami channels with arbitrary positions of users.

     

The adsorption and corrosion inhibition of 8-hydroxy-7-quinolinecarboxaldehyde derivatives on C-steel surface in hydrochloric acid

The protection influence of 8-hydroxy-7-quinolinecarboxaldehyde derivatives against C-steel corrosion was studied in 2 mol· L-1 HCl solutions at 30 ℃.Measurements were conducted under various experimental conditions using weight loss,potentiodynamic polarization,electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques.These studies have shown that 8-hydroxy-7-quinolinecarboxaldehyde derivatives are very good "green",mixed-type inhibitors.Corrosion rates obtained from both EFM and EIS methods are comparable with those recorded using Tafel extrapolation method,confirming validation of corrosion rates measured by the latter.The inhibitive action of these 8-hydroxy-7-quinolinecarboxaldehyde derivatives was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structures following Langmuir adsorption isotherm.Quantum chemical method was also employed to explore the relationship between the inhibitor molecular properties and its protection efficiency.