Four wave mixing nonlinearity effect in wavelength division multiplexing radio over fiber system

The integration of wireless and optical networks is a potential solution for the increasing capacity and mobility as well as decreasing costs in the access networks. Optical networks are fast, robust and error free, however, there are nonlinearity obstacles preventing them from being perfect media. The performance of wavelength division multiplexing (WDM) in radio over fiber (RoF) systems is found to be strongly influenced by nonlinearity characteristics in side the fiber. The effect of four wave mixing (FWM) as one of the influential factors in the WDM for RoF has been studied here using Optisystem and Matlab. From the results obtained, it is found that the FWM effects have become significant at high optical power levels and have become even more significant when the capacity of the optical transmission line is increased, which has been done by either increasing the channel bit rate, and decreasing the channel spacing, or by the combination of both process. It is found that when the channel spacing is 0.1 nm, 0.2 nm and 0.5 nm the FWM power is respectively, becomes about -59 dBm, -61 dBm and -79 dBm. This result confirms that the fiber nonlinearities play decisive role in the WDM for RoF system. The simulation results obtained here are in reasonable agreement as compared with other numerical simulation results obtained, elsewhere, using different simulation tools

Unsteady Euler and Navier-Stokes Computations Around Oscillating Delta Wing Including Dynamics

Unsteady flows around rigid or flexible delta wings with and without oscillating leading-edge flaps are considered. These unsteady flow problems are categorized under two classes of problems. In the first class, the wing motion is prescribed a priori and in the second class, the wing motion is obtained as a part of the solution. The formulation of the first class includes either the unsteady Euler or unsteady Navier-Stokes equations for the fluid dynamics and the unsteady linearized Navier-displacement (ND) equations for the grid deformation. The problem of unsteady transonic flow past a bicircular-arc airfoil undergoing prescribed thickening-thinning oscillation is studied using the CFL2D code. This code is used to solve the Navier-Stokes equations using an implicit, flux-difference splitting, finite-volume scheme. For the unsteady supersonic flows around flexible delta wings with prescribed oscillating deformation and rigid delta wings with leading-edge-flap oscillations, the conservative, unsteady Euler and thin-layer Navier-Stokes equations in a moving frame-of-reference, along with the linearized ND equations, have been used. Two main problems are solved to demonstrate the validity of the developed schemes. The first problem is that of a flexible delta wing undergoing a prescribed bending-mode oscillation. In the second problem, a rigid-delta wing with symmetric and anti-symmetric flap oscillations is considered. These applications fall under the first class of problems. For the unsteady flow applications, where the wing motion is not prescribed a priori (second class of problems), either the unsteady Euler or thin-layer Navier-Stokes equations and the rigid-body dynamics equations, in a moving frame of reference, are solved sequentially to obtain the flow behavior and the wing motion. The main application for this class of unsteady flow phenomena, is the wing-rock problem. Using the locally-conical flow assumption, three problems are solved. The first is that of a delta wing undergoing a damped rolling oscillation. The second is that of a delta wing undergoing a limit-cycle, wing-rock motion. In the third problem, suppression of the wing-rock motion is demonstrated using a tuned anti-symmetric oscillation of the leading-edge flap

Determinants of stock returns: Evidence from Egypt

This paper aims at identifying the determinants of stock returns in the Egyptian stock market. It does so by means of applying four different asset pricing models to the Egyptian stock returns: the CAPM, Fama-French three-factor model, Carhart four-factor model, and Fama-French five-factor model. The main findings of this thesis are that there is a significant size effect in the Egyptian stock returns, but there is no evidence of the presence of value or momentum effects. The results for operating profitability and investment are mixed therefore they need to be investigated further. Also, this paper provides evidence of the superiority of Fama-French five-factor model relative to the other asset pricing models tested

Performance of Hollow Bar Micropiles Under Axial and Lateral Loads in Cohesive Soils

The use of hollow core bars in micropiles has greatly increased over the past ten years. Hollow core construction, also known as “self drilled”, is becoming a popular option because it allows a faster installation processes and ground improvement at the same time. Despite the growing demand for hollow bar micropiles, little work has been devoted to evaluating the nominal bond strength between the micropile grout and the surrounding soil, especially in clayey soils. Moreover, the performance of such micropiles under different kinds of loading is still largely unknown and needs to be investigated. In this study, a research methodology encompassing two primary elements is adopted. The first element is a series of full scale field studies on hollow bar micropiles installed in cohesive soils, while the second is numerical investigations on hollow bar micropiles. To accomplish the study, four hollow core micropiles were installed using an air flushing technique employing large drilling carbide bits. Twenty-two load tests were conducted on the four hollow bar micropiles. The hollow bar micropiles were loaded in four consecutive phases, which included; five axial monotonic, five axial cyclic load tests on single micropiles, four axial monotonic tests on pairs of hollow bar micropiles, two monotonic and six cyclic lateral tests on single micropiles. The results of each set of tests were utilized to validate a numerical model. Parametric studies were conducted on the calibrated model to provide design guide lines for hollow bar micropiles under different loads. An equation is proposed to estimate the axial capacity of hollow bar micropiles in cohesive soils depending on the installation method adopted. In addition, an equation for the stiffness degradation under axial cyclic loading is proposed. It reveals that the group efficiency factor for hollow bar micropiles should be taken equal to 1, despite the spacing to diameter ratio employed. Moreover, a family of interaction factor diagrams is established to estimate the settlement of hollow bar micropiles group. Finally, the study demonstrated that hollow bar micropiles can carry moderate lateral loads with proper reinforcement configurations and pile head fixity condition

The Iodide Space in Rabbit Brain

In the present investigation labeled iodide was used to investigate the interrelationship between brain, blood and cerebrospinal fluid, to examine active transport across the blood-brain- and the blood-cerebrospinal fluid barriers, and to estimate the extracellular space of the brain. The iodide space in the brain and the iodide concentration in cerebrospinal fluid after intravenous administration of radioactive iodide are determined by the following mechanisms. Iodide passes into the cerebrospinal fluid but active transport in the choroid plexus moves most of the iodide back again into the plasma, keeping the concentration at a very law value. An extracellular fluid is formed at the blood-brain barrier possibly in a similar way. The iodide concentration of this fluid is unknown but is probably higher than that in the cerebrospinal fluid. Diffusion of iodide across the brain-cerebrospinal fluid barrier transports this ion from the brain into the cerebrospinal fluid which is constantly renewed "sink action". The iodide space was found to be 2.4% four to five hours after the intravenous administration of 131I, the iodide content of the cerebrospinal fluid was 1.2% of that of the TCA serum filtrate. The iodide space increased to 10.6% in preparations in which in addition to 131I unlabeled iodide (to a serum concentration of 25 to 50 mM) was administered to saturate the active transport processes in the choroid plexuses and blood-brain barrier. The iodide activity of the cerebrospinal fluid in these experiments increased to 29.3% of that in the TCA serum filtrate. In experiments in which the inhibitor of iodide transport, perchlorate (8 mM), was injected intravenously with the 131I-, the iodide space was 8.2% and the iodide concentration in the cerebrospinal fluid 26.4%. These experiments demonstrate the effect of saturation and inhibition of active transport on the iodide space. They show furthermore that the depression of the active transport did not raise the iodide concentration in the cerebrospinal fluid to the plasma concentration. The relatively low (1/3 of that in the serum TCA filtrate) iodide concentration in the cerebrospinal fluid under these circumstances was ascribed to a differential permeability of the blood-cerebrospinal fluid barrier for iodide and chloride. The sink action can be eliminated by perfusion of the ventricles with an artificial cerebrospinal fluid containing iodide. Ventriculocisternal perfusion with 131I- alone resulted in an iodide space of 7.2% after 4.5 hours. An iodide space of 10.2% was determined by a combined intravenous administration and ventricular perfusion with an artificial cerebrospinal fluid containing the same concentration of 131I as present in the plasma. When in similar experiments perchlorate was administered intravenously, the iodide space rose to 16.8%. The iodide space determined by simultaneous intravenous injection and ventricular perfusion with both labeled and unlabeled iodide, in a concentration sufficient to saturate the active transport, was 20.8%. In the latter instances the sink action is eliminated and also active transport is inhibited or saturated. It was postulated that under these conditions the iodide concentration in plasma and brain extracellular fluid are approximately the same. The use of the iodide space as a measure of the brain extracellular space was discussed.</p

DETECTING THE EXTERNAL DEFECTS OF POTATO TUBERS USING A VISIBLE LASER

ABSTRACTPotato (Solanum tuberosum, L.) is considered as a source of the national income in Egypt, since the potato crop is exported abroad because it's high quality specifications. The aim of this study is to: Find out the potential of using the optical properties as a nondestructive quality assessment for detecting surface defects of Spunta potato tubers using a low-power Helium-Neon laser. The obtained results were as following: The percentage of reflection intensity of sound tubers (7.48%) was the highest. While, the reflection percentage of superficial shatter bruise (0.83%) was the lowest. The reflection intensity percentages of He-Ne laser light from sound and defective tubers were arranged as follow: Sound (7.48%) &gt;, Internal black spot (4.33%) &gt;, Greening (2.53%) &gt;, Cuts (1.83%) &gt;, Growth cracks (1.64%) &gt;, Shrinkage (1.54%) &gt;, Deep shatter bruise (1.33%) &gt;, Rots (1.32%) &gt;, Pressure bruise (1.09%) &gt;, Skinning (1.07%) &gt;, Insect damage (0.87%) &gt;, Superficial shatter bruise (0.83%). For quality evaluation processes it was concluded that: when the percentage of reflection intensity is less than 1%, (Ref.%&lt; 1%) then the defects may be considered superficial shatter bruise or insect damage, otherwise, when the percentage of reflection intensity greater than or equal 1% and less than 2%, (1% ≤ Ref.%&lt; 2 %) then the defects may be considered skinning, pressure bruise, rots, deep shatter bruise, shrinkage, growth cracks or cuts, if the percentage is ranged between (2.5:4.5%) then the defects may be belonging to greening defect or internal black spot. The percentage of reflection greater than 7% the surface may be considered as sound tubers. It was concluded that the reflected laser light could be used as an indicator for the defective surface defects of potato tubers, so sorting and separating processes can be conducted according to the optical properties