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Croft’s cycle in Arabic: The negative existential cycle in a single language
No full textThe negative existential cycle has been shown to be operative in several language families. Here it is shown that it also operates within a single language. It happens that the existential fī that has been adduced as an example of a type A in the Arabic of Damascus, Syria, negated with the standard spoken Arabic verbal negator mā, does not participate in a negative cycle, but another Arabic existential particle does. Reflexes of the existential particle šay(y)/šē/šī/ši of southern peninsular Arabic dialects enter into a type A > B configuration as a univerbation between mā and the existential particle ši in reflexes of maši. It also enters that configuration in others as a univerbation between mā, the 3rd-person pronouns hū or hī, and the existential particle šī in reflexes of mahūš/mahīš. At that point, the existential particle šī loses its identity as such to be reanalyzed as a negator, with reflexes of mahūš/mahīš negating all manner of non-verbal predications except existentials. As such, negators formed of reflexes of šī skip a stage B, but they re-enter the cycle at stage B > C, when reflexes of mahūš/mahīš begin negating some verbs. The consecutive C stage is encountered only in northern Egyptian and southern Yemeni dialects. An inchoate stage C > A appears only in dialects of Lower Egypt
Ramsey numbers of partial order graphs (comparability graphs) and implications in ring theory
No full textFor a partially ordered set(A, ≤), letGA be the simple, undirected graph with vertex set A such that two vertices a ≠ ∈ b A are adjacent if either a ≤ b or b a ≤ . We call GA the partial order graph or comparability graph of A. Furthermore, we say that a graph G is a partial order graph if there exists a partially ordered set A such that G = GA. For a class of simple, undirected graphs and n, m ≥ 1, we define the Ramsey number (n m, ) with respect to to be the minimal number of vertices r such that every induced subgraph of an arbitrary graph in consisting of r vertices contains either a complete n-clique Kn or an independent set consisting of m vertices. In this paper, we determine the Ramsey number with respect to some classes of partial order graphs. Furthermore, some implications of Ramsey numbers in ring theory are discussed.American University of SharjahAustrian Science Fund (FWF
In-Vitro Degradation of Hollow Silica Reinforced Magnesium Syntactic Foams in Different Simulated Body Fluids for Biomedical Applications
No full textThis article reports the mechanical and biocorrosion behaviour of hollow silica nanosphere (SiO₂) reinforced (0.5–2 vol.%) magnesium (Mg) syntactic foams. Room temperature tensile properties’ characterization suggests that the increased addition of hollow silica nanospheres resulted in a progressive increase in tensile yield strength (TYS) and ultimate tensile strength (UTS) with Mg-2 vol.% SiO₂ exhibiting a maximum TYS of 167 MPa and a UTS of 217 MPa. The degradation behaviour of the developed Mg-SiO₂ syntactic foams in four different simulated body fluids (SBFs): artificial blood plasma solution (ABPS), phosphate-buffered saline solution (PBS), artificial saliva solution (ASS) and Hanks’ balanced saline solution (HBSS) was investigated by using potentiodynamic polarization studies. Results indicate that corrosion resistance of the Mg-SiO₂ syntactic foam decreases with increasing chloride ion concentration of the SBF. Mg-1.0 vol.% SiO₂ displayed the best corrosion response and its corrosion susceptibility pertaining to corrosion rate and polarisation curves in different SBF solutions can be ranked in the following order: ABPS > PBS > HBSS > ASS. The surface microstructure demonstrated the presence of a better passivated layer on the syntactic foams compared to pure Mg. The observed increase in corrosion resistance is correlated with intrinsic changes in microstructure due to the presence of hollow silica nanospheres. Further, the effect of corrosive environment on the degradation behaviour of Mg has been elucidated.Singapore Ministry of EducationAmerican University of Sharja
HBN Nanoparticle-Assisted Rapid Thermal Cycling for the Detection of Acanthamoeba
No full textAcanthamoeba are widely distributed in the environment and are known to cause blinding keratitis and brain infections with greater than 90% mortality rate. Currently, polymerase chain reaction (PCR) is a highly sensitive and promising technique in Acanthamoeba detection. Remarkably, the rate of heating–cooling and convective heat transfer of the PCR tube is limited by low thermal conductivity of the reagents mixture. The addition of nanoparticles to the reaction has been an interesting approach that could augment the thermal conductivity of the mixture and subsequently enhance heat transfer through the PCR tube. Here, we have developed hexagonal boron nitride (hBN) nanoparticle-based PCR assay for the rapid detection of Acanthamoeba to amplify DNA from low amoeba cell density. As low as 1 X 10¯⁴ wt % was determined as the optimum concentration of hBN nanoparticles, which increased Acanthamoeba DNA yield up to ~16%. Further, it was able to reduce PCR temperature that led to a ~2.0-fold increase in Acanthamoeba DNA yield at an improved PCR specificity at 46.2 °C low annealing temperature. hBN nanoparticles further reduced standard PCR step time by 10 min and cycles by eight; thus, enhancing Acanthamoeba detection rapidly. Enhancement of Acanthamoeba PCR DNA yield is possibly due to the high adsorption affnity of hBN nanoparticles to purine (Guanine—G) due to the higher thermal conductivity achieved in the PCR mixture due to the addition of hBN. Although further research is needed to demonstrate these findings in clinical application, we propose that the interfacial layers, Brownian motion, and percolation network contribute to the enhanced thermal conductivity effect.American University of Sharja
Dynamic Properties of Soil in UAE from Field and Laboratory Tests
No full textA Master of Science thesis in Civil Engineering by Ahmed Mohsen Khalil entitled, “Dynamic Properties of Soil in UAE from Field and Laboratory Tests”, submitted in December 2020. Thesis advisor is Dr. Zahid Khan and thesis co-advisor is Dr. Magdi El Emam. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Dynamic properties of soil are important for the design of structures under seismic loadings. The United Arab Emirates (UAE) is experiencing significant construction development; however, there is no systematic study to characterize the regional soils for dynamic properties. Therefore, designers have to rely on correlations of dynamic properties with other static parameters. These correlations are mostly developed for other regions which may not be suitable for the UAE. This research presents the findings of a laboratory testing program involving cyclic and static triaxial (CT) tests along with bender element (BE) testing on representative samples of regional soils. The bender element tests are used to evaluate the low strain shear wave velocity (Vs), whereas the cyclic triaxial (CT) test is used to evaluate the shear modulus (G) and the damping ratio (ξ) at different strain levels and confinement pressures. Correlations of Vs with Standard Penetration Tests N (SPT-N) values are developed. Two different sample sizes are used to evaluate the effect of sample size on dynamic properties. Static triaxial tests are also performed to develop correlations between Vs and friction angle (ɸ). The results of the experimental program indicate that the degradation of dynamic properties generally agrees with previous studies however the model parameters are different. The correlation of Vs with SPT-N values follows a power model whereas the correlation between Vs and friction angle presents as a linear model. A comparison of developed correlations with previous studies validates the importance of regional specific nature of soils as most of the models in literature neither agree with each other nor with the findings of this study.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation
No full textThe thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m⁻¹·K⁻¹ to 0.250 W·m⁻¹·K⁻¹. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m⁻¹·K⁻¹ and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids
LC Impedance Source Bi-Directional Converter with Reduced Capacitor Voltages
No full textThis paper proposes an LC (Inductor and Capacitor) impedance source bi-directional DC–DC converter by redesigning after rearranging the reduced number of components of a switched boost bi-directional DC–DC converter. This new converter with a conventional modulation scheme offers several unique features, such as a) a lower number of components and b) reduced voltage stress on the capacitor compared to existing topologies. The reduction of capacitor voltage stress has the potential of improving the reliability and enhancing converter lifespan. An analysis of the proposed converter was completed with the help of a mathematical model and state-space averaging models. The converter performance under different test conditions is compared with the conventional bi-directional DC–DC converter, Z-source converter, discontinuous current quasi Z-source converter, continuous current quasi Z-source converter, improved Z-source converter, switched boost converter, current-fed switched boost converter, and quasi switched boost converter in the Matlab Simulink environment. MATLAB/Simulink results demonstrate that the proposed converter has lesser components count and reduced capacitors’ voltage stresses when compared to the topologies mentioned above. A 24 V to 18 V LC-impedance source bi-directional converter and a conventional bidirectional converter are built to investigate the feasibility and benefits of the proposed topology. Experimental results reveal that capacitor voltage stresses, in the case of proposed topology are reduced by 75.00% and 35.80% in both boost and buck modes, respectively, compared to the conventional converter circuit.American University of Sharja
Evaluation of FRP Bars under Compression and Their Performance in RC Columns
No full textThe behavior of fiber-reinforced polymer (FRP) bars under compression is not fully understood yet due to the limited research in this area. However, the long-term durability, weathering resistance, and exceptional mechanical properties of FRP bars justify the need for their use in compression members. The main objectives of this study are to evaluate the mechanical properties of glass FRP (GFRP) and basalt FRP (BFRP) bars under compression and examine their performances as main longitudinal reinforcements in reinforced concrete (RC) columns. In the first part of this research, a series of static compression tests were conducted on GFRP and BFRP bars of different diameters. The second part of this research numerically investigated the behavior of FRP-RC columns under concentric and eccentric loading using the mechanical properties of the FRP bars obtained experimentally. Nonlinear finite element models were developed to simulate the compressive behavior of the concrete columns reinforced with GFRP and BFRP bars. The FE models were verified with the experimental results conducted previously. The verified FE models are then utilized to conduct a parametric analysis considering two different column geometries and cross-sections, five reinforcement ratios, two concrete compressive strengths, three types of ties materials, and several loading eccentricities to develop a set of interaction diagrams that may provide valuable data for design purposes. The results indicated that the FRP bars could have a significant contribution to the overall capacity of FRP-RC columns by up to 35% of the total force at failure, depending on the reinforcement ratio. The performance of both the GFRP- and BFRP-RC columns was almost similar in terms of capacity, deflection, and bar strength contribution.American University of Sharja
Experimental and Analytical Investigations of the Use of Groove-Epoxy Anchorage System for Shear Strengthening of RC Beams Using CFRP Laminates
No full textReinforced concrete (RC) beams strengthened in shear with carbon fiber reinforced polymer (CFRP) laminates as externally bonded reinforcement (EBR) usually fail due to debonding. This paper presents an experimental and analytical investigation on the use of groove-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams. The aim of this study is to assess the effectiveness of using groove-epoxy in enhancing the shear capacity of RC beams. Nine rectangular RC beams were strengthened with CFRP plates and sheets with groove-epoxy anchorage systems of different groove widths and tested under four point bending. It is observed that the RC beams strengthened with the groove-epoxy anchorage system showed an increase in the shear-strength over the unstrengthened control beam up to 112 and 141% for plates and sheets, respectively. Also, the increase of shear-strength contribution of the groove-epoxy system to that of CFRP without grooves ranged between 30–190% for CFRP plates and between 40–100% for CFRP sheets. Generally, the contributions of groove-epoxy on shear-strength decreased with the increase of groove width. Moreover, shear strength prediction models, based on modifications of the ACI440.2R-17 shear model, were developed by incorporating groove factors as a modifier to the FRP shear-strength contribution. The developed models predicted the experimental shear-strength of the tested RC beams with a good level of accuracy, with an average mean absolute percent error (MAPE) = 3.31% and 6.68%, normalized mean square error (NMSE) = 0.072, 0.523, and coefficient of determination R2 = 0.964, 0.691, for plates and sheets, respectively
Polyaniline Based Composite Membranes for PEM Fuel Cells: Experiments and Factorial Design
No full textA Master of Science thesis in Chemical Engineering by Ahmed Eisa entitled, “Polyaniline Based Composite Membranes for PEM Fuel Cells: Experiments and Factorial Design”, submitted in December 2020. Thesis advisor is Dr. Amani Al-Othman and thesis co-advisor is Dr. Mohammad Al-Sayah. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Higher temperature operation (higher than 100 ºC) in proton exchange membrane fuel cells (PEMFCs) is preferred and has several advantages including enhanced fuel cell kinetics, improved catalysts tolerance for contaminants and recovery of useful heat. However, high temperature operation is not permitted using the conventional Nafion membranes as they dehydrate and their proton conductivity dramatically decreases. In this thesis, novel proton conductors based on polyaniline (PANI), ionic liquids (ILs) and zirconium phosphate (ZrP) were fabricated and proposed for the higher temperature operation in PEMFCs. PANI-IL-ZrP composite membranes were synthesized using polytetrafluoroethylene (PTFE) as support. These composite membranes were evaluated for their proton conductivity. The membrane synthesis results showed a promising proton conductivity of around 0.02 S/cm for PANI/IL/ZrP composite membrane as well as high thermal stability at 180 ºC. The membranes’ performance was assessed by generating theoretical polarization curves. The results demonstrated a promising cell performance with a current density of 0.042 A/cm² at a cell potential of 0.6 V that are comparable to the methanol fuel cell. The membrane parameters that affect the performance of fuel cells at high temperature operation were also studied and optimized using factorial design (FD) modeling approach. The studied parameters were the concentrations of PANI, IL and ZrP in addition to the operating temperature and the IL type. The modelling results showed that the concentration of 1-Hexyl-3-Methylimidazolium Tricyanomethanide (HMT) IL contributes approximately to 50% of the conductivity response. The optimization of parameters performed in this thesis offer an important basis as a rational of high temperature PEMFC design.College of EngineeringDepartment of Chemical EngineeringMaster of Science in Chemical Engineering (MSChE