Orthogonal frequency division multiplexing (OFDM) is an important enabler of highspeed transmission in wired and wireless communication systems. The increasing popularity and accessibility of bandwidth-demanding indoor applications such as realtime video streaming and gaming make it imperative for indoor communication technologies to support high transmission speeds. visible light communication (VLC) is a promising technology that offers a wide and an unregulated bandwidth. The employment of OFDM techniques in VLC is the perfect combination to answer for bandwidth demanding applications. However, the implementation of OFDM in VLC requires modifications in the nature of the waveform. This paper discusses the different methods that exist in the literature to facilitate for the application of OFDM in VLC. Each scheme is briefly explained displaying its concept, pros and cons.
A simple and low-cost method for enhancing the efficiency of a-Si solar cells is reported. By coating 2.85 nm silicon nanoparticles (Si NPs) on the top of the solar cells, efficiency improvement above 6% is observed, with respect to the uncoated reference cells. The efficiency enhancement can be attributed to scattering and photo luminescent (UV absorption followed by red re-emission) properties of Si NPs. Spin coating technique was used to integrate Si NPs on the cells. Compared to uncoated solar cells, Si NPs coated solar cells show an average improvement of 5.68% and 6.4% in short circuit current (Jsc) and efficiency respectively.
Benzene, toluene, ethylbenzene and xylene (BTEX) are aromatic feed contaminants known to cause catalyst deactivation by soot formation in the catalytic section of Claus process. At high temperature, polycyclic aromatic hydrocarbons (PAH), which are known to form soot, are also formed inside Claus furnace. Both BTEX and PAH reduce Claus process efficiency and increase operational cost. In this work, we develop a detailed reaction mechanism based on the existing ones in literature, to improve the quantitative predictions of aromatics decomposition/formation in Claus furnace. This mechanism was validated successfully using different sets of experimental data from previous works and used to investigate suitable Oxygen enriched feed conditions that mitigate the impact of BTEX and PAH in Claus process. The results proved that use of oxygen enriched air in Claus process enhances destruction of BTEX and PAH, while more of carbonyl sulfide (COS) was formed.
The main objective of this work was to investigate the effect of ethanol composition in water coagulation bath on polyvinylidene fluoride (PVDF) hollow fiber membrane (HFM) structure and performance. Thermally induced phase separation method was employed to fabricate HFMs at four different ethanol compositions in water coagulation bath. It was found that the increase in ethanol composition in water coagulation bath increased the membrane pore size and porosity and mechanical strength. In contrast it reduces the hydrophobicity of the membrane and significantly reduces the LEPw. From the CO2 absorption experiments it was observed even though the membrane with high ethanol composition have high absorption flux its long stability was very poor and membranes made with ethanol wet easily. In conclusion, as addition of ethanol to the coagulation bath reduces the performance of the membrane PVDF HFM made with ethanol in water coagulation bath is not suitable for GLMC application.
The potential application of the ionic liquid 1-Butyl-3-methylimidazolium Tricyanomethanide ([bmim] [TCM]) as absorption solvent in de-aromatization of natural gas is the main focus of this research. The unique properties of ILs include their non-volatility, high thermal stability, high absorption capacity and low regeneration energy compared to conventional amine based solvents, which are the most common solvents used for the removal of various natural gas contaminants such as aromatic hydrocarbons. Solubility measurements of the hydrocarbons were performed in a jacketed liquid-liquid equilibrium cell and samples from the ionic liquid rich phase were analyzed by gas chromatography with a flame ionization detector. The ionic liquid [bmim] [TCM] was very effective for BTEX absorption because the solubility of benzene was about 99.5 mol% in this IL at room temperature and generally, benzene showed a higher solubility in the aforementioned ionic liquid than hexane at the same temperature.
Metal Organic Framework HKUST-1 and Graphene oxide composites were synthesized using solvothermal process for acid gas removal. XRD confirmed that the basic structure of MOF is preserved in the MOF/GO composite while GO is fully exfoliated. SEM revealed uniform dispersion of MOF crystallites in the MOF/GO composites. The BET of the HKUST-1 and HKUST-1/GO composite was 434 and 369 m2/g, respectively. The HKUST-1/GO composite showed enhanced H2S sorption kinetics (mg H2S adsorbed/ mg MOF*min) as compared to the parent MOF. The results indicate that the MOF/GO composites hold positive prospect for further study towards industrial gas sweetening applications.
This work is concerned with the synthesis and characterization of Multi-Walled Carbon Nanotube (MWCNT) reinforced Kevlar KM2Plus composites with various MWCNT contents (0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8 wt. %), by the wet lay-up technique. These samples were experimentally investigated for their thermo-mechanical properties using Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and tensile testing. The mechanical properties showed remarkable improvement with increasing MWCNT wt.% up to certain content.
In the past years, there has been a growing interest in the use of cheaper adsorbent materials for CO2 capture process which has been recognized as an important technology for sustainable energy generation. Fly ash is a cheap solid material that has attracted a lot of interest recently. Although its adsorption properties are limited, it can be modified through various means to achieve better performance. This work looks at amine impregnation as a method to improve fly ash performance. The impact of the amine solvents will be investigated using a micro reaction calorimeter which also provides information such as specific heat capacity and heat of desorption that will be used to evaluate the energy requirement of the fly ash based CO?2 capture process. The results obtained from this work will be used as basis to develop more effective methods for the synthesis of cheap CO2 sorbents from fly ash.
Mobile agents (MAs) are an important element in the creation of efficient distributed applications in many fields. The motivation behind interest in MAs is derived from the various advantages they offer. However, the dynamic behavior of agents and hosts in MASs is considered a serious issue. Moreover, maintaining good performance is an important feature that affects MASs and the provided services. Addressing both of these issues, we propose a new dynamic trust model for MASs. The proposed trust model provides users with the means to assess service providers and base a decision on who to interact with.
Due to their powerful generalization ability while maintaining model flexibility, ensemble Machine-Learning (ML) models have been well accepted for Intrusion Detection and Prevention Systems (IDPSs). However, such models require high computational cost to find an optimal model. The problem is further exacerbated by the new forms of large-scale data (i.e., big data). As such, not only the detective accuracy, but also the scalability and efficiency are important. In this paper, we propose a Multi- Layered Clustering Model (MLCM) based on data clustering. In addition, a novel Imbalance Ratio (IR) analyzer is designed and used to identify the prior probability at which cluster labeling does not degrade the detection capabilities of the classifier, leading to lower model's complexity. Theoretical analysis and experimental results on a real intrusion detection and prevention data as well as paired significance t-test prove that the proposed MLCM outperforms other well-known ensemble ML models in the literature.
