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 \(N=256\).

     

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...     

Measuring research performance of Iraqi universities using Scopus data

Scientometrics - This study investigates the research performance of the Iraqi public and private universities using the Scopus citation database. The investigation consists of three stages. The...     

A solar and wind driven energy system for hydrogen and urea production with CO2 capturing

A novel solar PV and wind energy based system is proposed in this study for capturing carbon dioxide as well as producing hydrogen, urea and power. Both Aspen Plus and EES software packages are employed for analyses and simulations. The present system is designed in a way that PEM electrolyzer is powered by the wind turbines for hydrogen production, which is further converted into ammonia and then synthesizes urea by capturing CO₂ and additional power is supplied to the community. The solar PV is employed to power the cryogenic air separation unit and the additional power is used for the industrial purpose. In the proposed system, ammonia does not only capture CO₂ but also synthesizes urea for fertilizer industry. The amount of electrical power produced by the system is 2.14 MW. The designed system produces 518.4 kmol/d of hydrogen and synthesizes 86.4 kmol/d of urea. Furthermore, several parametric studies are employed to investigate the system performance.     

Convergence Variability and Population Sizing in Micro-Genetic Algorithms

The issues of micro-genetic algorithm (micro-GA) convergence, population size, internal variability, and performance are examined. Procedures are developed to determine best population size when micro-GAs are used for optimization of real-world problems. Results show that the best population size cannot be determined before convergence has occurred and that convergence may occur without reaching an optimal solution. To determine the best population size, this article proposes the use of consistency of the final fitness values in addition to the fitness value at convergence. Internal variability must be considered in finding the best population size, and that best population size depends on the level of computational resources used. Smaller populations with generous computational resources performed as good as and sometimes better than larger populations. Midsized populations consistently exhibited lower variation in fitness value. For a given population size, the increase in fitness value may not be worth the added computation cost beyond a certain point. Three approaches are proposed to determine the best population size: (1) a random selection approach, (2) a detailed approach, and (3) a simplified approach. We used the detailed approach with our traffic problem and found that, with sufficient computational resources, the micro-GA performed best with population size around the square root of the string length. We tested this proposition on standard simple and deceptive problems and found it to hold true.     

Using lithium nitrate and pozzolanic glass powder in concrete as ASR suppressors

This investigation studies the influence of two different mineral admixtures, lithium nitrate (Li) and pozzolanic glass powder (PGP) on the expansion induced by alkali-silica reaction (ASR). Four numbers of concrete prisms were produced for each concrete mix to measure the expansion resulted from the ASR according to the test method of the BS 812-123:1999. Chemical analysis was performed using X-ray spectra. Test results confirmed that Li and PGP have significantly reduced the ASR expansion. Lower calcium to silica ratio (Ca/Si) was found in concrete mix contains (PGP) because of the high amorphous reactive silica and low calcium content in PGP compared to ordinary Portland cement CEM1. Similar components and minerals phases were obtained in different concrete mixes by using XRD.     

Effectiveness of the earth tube heat exchanger system coupled to a space model in achieving thermal comfort in rural areas

The aim of this work is to investigate by modelling the possibility of reducing the operational energy of a typical house without negatively affecting its embodied energy. This is done through consideration of different building materials coupled with the use of an earth to air heat exchanger (EAHE) for fresh air supply and cooling. For known indoor and outdoor conditions and for given building materials (thermal capacity and conductance), a ventilation controller determines the amount of flow rate needed to temperate the indoor air temperature to achieve thermal comfort. Different wall configurations are assumed for each of the living zone and the bedroom zone of the apartment. It is found that the use of an optimal wall configuration in each zone coupled with the EAHE results in 76.7% energy savings compared with the reference case with conventional cooling.     

HYDROCARBON LOADS FROM STREET CLEANING PRACTICES: COMPARISON WITH DRY AND WET WEATHER FLOWS IN A PARISIAN COMBINED SEWER SYSTEM

Abstract

So far, little attention has been given to the effect of the street cleaning waters (SCW) load on the sewer systems during dry-weather periods. However, the knowledge of this pollution is needed to better understand the contribution of SCW to dry weather flow (DWF) pollution within combined sewers. Therefore, hydrocarbon loads conveyed by SCW were analyzed for two different sites of the Paris agglomeration. Median n-alkane, Unresolved Complex Mixture (UCM) and Polycyclic Aromatic Hydrocarbon (PAH) concentrations have been estimated at 19, 628 and 1.4 μ g · l^{? 1}for the Marais catchment (or 4th district), and at 8, 249, and 2.1 μ g · l^{? 1}for the 13th district, respectively. The observed contamination was mainly attributed to road traffic. Moreover, a comparison between SCW and street runoff showed that street cleaning removes a higher PAH stock than street runoff. In addition, SCW hydrocarbon fluxes evaluated at 5.4, 178 and 0.4 g · d^{? 1}for n-alkanes, UCM and PAH, respectively, were compared to the hydrocarbon fluxes of the DWF pollutant load at the combined sewer outlet of the Marais catchment. Hydrocarbon loads conveyed by SCW into Paris combined sewers appeared to be a minor source of DWF pollution for n-alkane and UCM, but represented a significant source for PAHs.     

Bilateral filtering of diffusion tensor magnetic resonance images.

We extend the well-known scalar image bilateral filtering technique to diffusion tensor magnetic resonance images (DTMRI). The scalar version of bilateral image filtering is extended to perform edge-preserving smoothing of DT field data. The bilateral DT filtering is performed in the Log-Euclidean framework which guarantees valid output tensors. Smoothing is achieved by weighted averaging of neighboring tensors. Analogous to bilateral filtering of scalar images, the weights are chosen to be inversely proportional to two distance measures: The geometrical Euclidean distance between the spatial locations of tensors and the dissimilarity of tensors. We describe the noniterative DT smoothing equation in closed form and show how interpolation of DT data is treated as a special case of bilateral filtering where only spatial distance is used. We evaluate different recent DT tensor dissimilarity metrics including the Log-Euclidean, the similarity-invariant Log-Euclidean, the square root of the J-divergence, and the distance scaled mutual diffusion coefficient. We present qualitative and quantitative smoothing and interpolation results and show their effect on segmentation, for both synthetic DT field data, as well as real cardiac and brain DTMRI data.