DYNAMICS AND CONTROL OF REACTIVE DISTILLATION PROCESS FOR MONOMER SYNTHESIS OF POLYCARBONATE PLANTS

Polycarbonate (PC) is an important engineering thermoplastic that is currently produced in large industrial scale using bisphenol A and monomers such as phosgene. Since phosgene is highly toxic, a non-phosgene approach using diphenyl carbonate (DPC) as an alternative monomer, as developed by Asahi Corporation of Japan, is a significantly more environmentally friendly alternative. Other advantages include the use of CO2 instead of CO as raw material and the elimination of major waste water production. However, for the production of DPC to be economically viable, reactive-distillation units are needed to obtain the necessary yields by shifting the reaction-equilibrium to the desired products and separating the products at the point where the equilibrium reaction occurs. In the field of chemical reaction engineering, there are many reactions that are suffering from the low equilibrium constant. The main goal of this research is to determine the optimal process needed to shift the reactions by using appropriate control strategies of the reactive distillation system. An extensive dynamic mathematical model has been developed to help us investigate different control and processing strategies of the reactive distillation units to increase the production of DPC. The high-fidelity dynamic models include extensive thermodynamic and reaction-kinetics models while incorporating the necessary mass and energy balance of the various stages of the reactive distillation units. The study presented in this document shows the possibility of producing DPC via one reactive distillation instead of the conventional two-column, with a production rate of 16.75 tons/h corresponding to start reactants materials of 74.69 tons/h of Phenol and 35.75 tons/h of Dimethyl Carbonate. This represents a threefold increase over the projected production rate given in the literature based on a two-column configuration. In addition, the purity of the DPC produced could reach levels as high as 99.5% with the effective use of controls. These studies are based on simulation done using high-fidelity dynamic models

A Strategic Vision for Combating Cyberterrorism

Cyberterrorism has become a well-known cybersecurity subject in today's digital world. The spread of cybercrimes calls for disseminating ethical values and peace between countries and individuals. Because of this phenomenon's danger to society, this study sought to lay down directives for security strategies to confront cyberterrorism. Hence, the study's main research problem revolves around highlighting the role of security authorities in addressing cyberterrorism according to the specialists in information technology (IT) centers in Saudi universities in Riyadh. Hence, a descriptive analysis method was adopted as a research methodology. We distributed questionnaires as a study tool to 150 specialists in IT centers in Saudi universities in Riyadh. The study yielded different views regarding the types and ways of cyberterrorism committed through the internet. Results showed the respondents' opinions regarding the essential types of cyberterrorism. Moreover, they emphasize the need to raise awareness in dealing with cyberterrorism by enforcing cybersecurity with the most prominent means and procedures that the authorities are responsible for. The most critical recommendations are: (1) the need to provide the employees with the technical skills to know how to deal with any potential security breach, (2) the need to provide specialized training courses in protection methods for workers, and (3) the need to develop the means of security and legal protection through developing e-government security agreements

Surface Functionalization of Graphene-based Materials

Graphene-based materials have generated tremendous interest in the past decade. Manipulating their characteristics using wet-chemistry methods holds distinctive value, as it provides a means towards scaling up, while not being limited by yield. The majority of this thesis focuses on the surface functionalization of graphene oxide (GO), which has drawn tremendous attention as a tunable precursor due to its readily chemically manipulable surface and richly functionalized basal plane. Firstly, a room-temperature based method is presented to reduce GO stepwise, with each organic moiety being removed sequentially. Characterization confirms the carbonyl group to be reduced first, while the tertiary alcohol is reduced last, as the optical gap decrease from 3.5 eV down to 1 eV. This provides greater control over GO, which is an inhomogeneous system, and is the first study to elucidate the order of removal of each functional group. In addition to organically manipulating GO, this thesis also reports a chemical methodology to inorganically functionalize GO and tune its wetting characteristics. A chemical method to covalently attach fluorine atoms in the form of tertiary alkyl fluorides is reported, and confirmed by MAS 13C NMR, as two forms of fluorinated graphene oxide (FGO) with varying C/F and C/O ratios are synthesized. Introducing C-F bonds decreases the overall surface free energy, which drastically reduces GO’s wetting behavior, especially in its highly fluorinated form. Ease of solution processing leads to development of sprayable inks that are deposited on a range of porous and non-porous surfaces to impart amphiphobicity. This is the first report that tunes the wetting characteristics of GO. Lastly as a part of a collaboration with ConocoPhillips, another class of carbon nanomaterials - carbon nanotubes (CNTs), have been inorganically functionalized to repel 30 wt% MEA, a critical solvent in CO2 recovery. In addition to improving the solution processability of CNTs, composite, homogeneous solutions are created with polysulfones and polyimides to fabricate CNT-polymer nanocomposites that display contact angles greater than 150o with 30 wt% MEA. This yields materials that are inherently supersolvophobic, instead of simply surface treating polymeric films, while the low density of fluorinated CNTs makes them a better alternative to superhydrophobic polymer materials

Modeling and Robust Control of Twin Rotor MIMO System

Recently, unmanned aerial vehicles (UAVs) have witnessed immense popularity in various fields, ranging from surveillance, rescue, and fire fighting to other more sophisticated military and commercial applications. However, due to their highly nonlinear nature and dynamic operational environment, the control of UAVs is still a challenging task. Linear Quadratic-Gaussian Regulator (LQG), is an optimal control technique, which has been very popular for UAVs control. However, for robust performance, an accurate dynamic model of a system is required. In order, to overcome this limitation, the present work couples an integral sliding mode controller with the LQG controller to deal with the modeling inaccuracies. Experimental results of pitch control of the laboratory-based twin rotor MIMO system (TRMS), validate the performance of ISMC-LQG controller

Improving crop quality: investigations on soil selenium and zinc transfer and bioavailability

Doctor of PhilosophyDepartment of AgronomyGanga M. HettiarachchiManagement of beneficial and/or essential trace elements, such as Se and Zn, is challenging, and it is complicated by the fact that the margin of safety between the levels that will cause dietary deficiency, and those that result in toxicity, is narrow. This research focused on the ability of the plant system to pretreat wastewaters rich in potentially toxic trace elements and nutrients and enhancing phytoavailability of Zn in Zn-deficient calcareous soils. Plant systems may possess a significant capacity to remediate marginal waters through several phytoremediation processes, including uptake, accumulation, and assisting with biotransformation of inorganic and organic compounds. The aim of the first study was to determine the ability of the halophyte, salicornia europaea, to grow in wastewater or brackish waters and to remove excess trace elements, nutrients, and salts in these highly saline wastewaters. Greenhouse and growth chamber studies were conducted to examine the ability of salicornia europaea to grow and remediate marginal waters. Salicornia europaea showed the ability to remove excess trace elements (Se and B) and salts (Na), indicating salicornia europaea has the potential to be used for precleaning the highly saline wastewaters. Enhanced biomass showed that it can also produce valuable stock for biofuel and bio-based products from marginal waters. Agronomic biofortification is an effective way to increase micronutrient concentrations in grain crops. Formation of dissolved micronutrient-organic C complexations can enhance the solubility of micronutrients. The aims of the second study were to investigate the effectiveness of various Zn sources (organic and inorganic) with and without organic C-based fertilizer co-additives on biofortification of wheat with Zn in a mildly-calcareous soil and to determine distribution (stems/leaves, whole grain, bran and flour) and bioavailability of Zn in different plant parts (bran and flour). A greenhouse experiment was conducted to study wheat grown under different Zn sources. Application of Zn significantly increased grain yield, grain Zn concentration, and Zn bioavailability in white flour. Less soluble ZnO showed more promising results compared to soluble ZnSO4. Co-additives did not improve the soil Zn extractability or the Zn uptake by wheat. Understanding the interactions and speciation of Zn is very important to gain more insights into the fate of added Zn in calcareous soil and also for the efficient management of soil for optimum crop production and environmental conservation. The objectives of the third study were to investigate and understand differences in mobility, extractability, and fractionation of Zn from different sources of granular and liquid Zn, with and without co-additives, in two mildly calcareous soils. A 5-wk long incubation study allowed for spatial evaluation of Zn fate and transport in two soils. Diffusion of Zn was limited to a 0 to 7.5 mm section for all treatments with or without co-additives. The energy dispersive X-ray analysis results were in agreement and revealed that the remaining Zn-incorporated monoammonium phosphate granules, after incubation in soil, contained significant amounts of P and Zn. This study also showed that the liquid Zn sources with no P were better than the co-granulated Zn-P fertilizers

Investigating the Effect of Tube Diameter on the Performance of a Hybrid Photovoltaic–Thermal System Based on Phase Change Materials and Nanofluids

The finite element (FEM) approach is used in this study to model the laminar flow of an eco-friendly nanofluid (NF) within three pipes in a solar system. A solar panel and a supporting phase change material (PCM) that three pipelines flowed through made up the solar system. An organic, eco-friendly PCM was employed. Several fins were used on the pipes, and the NF temperature and panel temperature were measured at different flow rates. To model the NF flow, a two-phase mixture was used. As a direct consequence of the flow rate being raised by a factor of two, the maximum temperature of the panel dropped by 1.85 °C, and the average temperature dropped by 1.82 °C. As the flow rate increased, the temperature of the output flow dropped by up to 2 °C. At flow rates ranging from low to medium to high, the PCM melted completely in a short amount of time; however, at high flow rates, a portion of the PCM remained non-melted surrounding the pipes. An increase in the NF flow rate had a variable effect on the heat transfer (HTR) coefficient.The Deanship of Scientific Research at Najran UniversityPeer Reviewe

Machine Learning-Based Approach for Modeling the Nanofluid Flow in a Solar Thermal Panel in the Presence of Phase Change Materials

Considering the importance of environmental protection and renewable energy resources, particularly solar energy, the present study investigates the temperature control of a solar panel using a nanofluid (NFD) flow with eco-friendly nanoparticles (NPs) and a phase change material (PCM). The PCM was used under the solar panel, and the NFD flowed through pipes within the PCM. A number of straight fins (three fins) were exploited on the pipes, and the output flow temperature, heat transfer (HTR) coefficient, and melted PCM volume fraction were measured for different pipe diameters (D_Pipe) from 4 mm to 8 mm at various time points (from 0 to 100 min). Additionally, with the use of artificial intelligence and machine learning, the best conditions for obtaining the lowest panel temperature and the highest output NFD temperature at the lowest pressure drop have been determined. While the porosity approach was used to model the PCM melt front, a two-phase mixture was used to simulate NFD flow. It was discovered that the solar panel temperature and output temperature both increased considerably between t = 0 and t = 10 min before beginning to rise at varying rates, depending on the D_Pipe. The HTR coefficient increased over time, showing similar behavior to the panel temperature. The entire PCM melted within a short time for D_Pipes of 4 and 6 mm, while a large fraction of the PCM remained un-melted for a long time for a D_Pipe of 8 mm. An increase in D_Pipe, particularly from 4 to 6 mm, reduced the maximum and average panel temperatures, leading to a lower output flow temperature. Furthermore, the increased D_Pipe reduced the HTR coefficient, with the PCM remaining un-melted for a longer time under the panel.Deanship of Scientific Research at Najran UniversityPeer Reviewe

Numerical Analysis of the Effect of Nanoparticles Size and Shape on the Efficiency of a Micro Heatsink

In this paper, two novel micro heat sinks (MHSs) were designed and subjected to thermal analysis using a numerical method. The fluid used was Boehmite alumina–water nanofluid (NFs) with high volume fractions (VOFs). Studies were conducted to determine the influence of a variety of nanoparticle (NP) shapes, such as platelet brick, blade, cylinder, and Os. The heatsink (HS) was made of copper, and the NFs entered it through the middle and exited via four outlets at the side of the HS. The finite element method was used to simulate the NFs flow and heat transfer in the HSs. For this purpose, Multi Physics COMSOL software was used. The maximum and middle values of HS temperature (T-MAX and T-Mid), thermal resistance (TH-R), heat transfer coefficient (h), FOM, etc., were studied for different NP shapes, and with Reynolds numbers (Re) of 300, 1000, and 1700, and VOFs of 0, 3, and 6%. One of the important outcomes of this work was the better thermal efficiency of the HS with rectangular fins. Moreover, it was discovered that a rise in Re increased the heat transfer. In general, adding NPs with high VOFs to MHSs is not appropriate in terms of heat. The Os shape was the best NP shape, and the platelet shape was the worst NP shape for high NPVOF. When NPs were added to an MHS, the temperature of the MHS dropped by an average of 2.8 or 2.19 K, depending on the form of the pin-fins contained inside the MHS (circular or square). The addition of NPs in the MHS with circular and square pin-fins enhanced the pressure drop by 13.5% and 13.3%, respectively, when the Re = 1700.National Research Priorities funding programPeer Reviewe