A proposed model for frequency tuned antennas used in mobile communication systems

The antenna is considered as one of the most fundamental elements in wireless communication systems, especially in mobile devices. Desirable specifications of antennas include covering wide range of operating frequencies, while maintaining high quality of system performance over the whole range of operating frequencies. Therefore, the ability of tuning the resonant frequency of the antenna without altering its physical dimensions would be highly recommended in up-and-coming designs of antennas in mobile devices. This research work proposes a model for tuning the operating frequency of the inverted F-antenna over a reasonably wide range of frequencies, via altering the electromagnetic properties of its ferrite material. In this proposed model, it will be shown that the electronic control of the permeability of the ferrite material of the antenna leads effectively to a significant shift in its resonant frequency, and hence to an overall improvement in the performance of the communication system

Exploration the extrudability of aluminum matrix composite (LM6/TIC) through modeling, simulation and experimental process

Aluminum matrix composites (LM6/TiC) is a mix of excellent properties of aluminum casting alloy (LM6), and particles of (TiC) which make it the first choice in many applications like airplane and marine industries. During this research the extrudability and mechanical specifications of this composite (LM6/TiC) are investigated before and after extrusion theoretically and experimentally. In this research; ABAQUS/CAE software has been successfully employed for Modeling and simulation the extrusion process before experiments in order to predict any error before fabrication. The experimental works includes design and fabrication the extrusion mold. The extruded parts are test by (SEM) to show the microstructure properties. Simulation results indicate the positions of stresses concentration (Mises stresses), and also the velocity of dislocation elements during extrusion. Experimental results show that, many mechanical properties are improved and enhanced after extrusion like stiffness and wear resistance. The microstructure test show that, the addition of (5%) wt. of (TiC) particulate with (T6) heat treatment (treating the solution in (525°C) and then ageing for (8) h at 180 °C) to the master alloy (LM6) will improve the strength about more than (15%) comparing with original matrix (LM6). Comparison between theoretical and practical results before and after extrusion indicates significant improvements after adding (TiC) particulates. This improvement is due to the high interference and bonding forces between the master alloy and composite particulates, which result in a fine grain size after the process. Keywords: Aluminum, Extrusion, Composite, TiC, LM6

Drill Bit Whirl Mitigation Analysis: An Under Actuated System Perspective

Abstrac

A Simulated Annealing Algorithm For Fuzzy Unit Commitment Problem

This paper presents a new algorithm based on integrating simulated annealing and fuzzy logic methods to solve the unit commitment problem. The uncertainties in the load demand and the spinning reserve constraints are formulated in a fuzzy logic frame. The simulated annealing is used to solve the combinatorial part of the unit commitment problem, while the nonlinear part of the problem is solved via a quadratic programming routine. A simple cooling schedule has been implemented to apply the simulated annealing test in the algorithm. Numerical results show the superiority of the solutions obtained compared to the classical methods and the simulated annealing method as individual

A Simulated Annealing Algorithm For Fuzzy Unit Commitment Problem

This paper presents a new algorithm based on integrating simulated annealing and fuzzy logic methods to solve the unit commitment problem. The uncertainties in the load demand and the spinning reserve constraints are formulated in a fuzzy logic frame. The simulated annealing is used to solve the combinatorial part of the unit commitment problem, while the nonlinear part of the problem is solved via a quadratic programming routine. A simple cooling schedule has been implemented to apply the simulated annealing test in the algorithm. Numerical results show the superiority of the solutions obtained compared to the classical methods and the simulated annealing method as individual

Tannakian duality for Anderson-Drinfeld motives and algebraic independence of Carlitz logarithms

We develop a theory of Tannakian Galois groups for t-motives and relate this to the theory of Frobenius semilinear difference equations. We show that the transcendence degree of the period matrix associated to a given t-motive is equal to the dimension of its Galois group. Using this result we prove that Carlitz logarithms of algebraic functions that are linearly independent over the rational function field are algebraically independent.Comment: 39 page

Structure factor of polymers interacting via a short range repulsive potential: application to hairy wormlike micelles

We use the Random Phase Approximation (RPA) to compute the structure factor, S(q), of a solution of chains interacting through a soft and short range repulsive potential V. Above a threshold polymer concentration, whose magnitude is essentially controlled by the range of the potential, S(q) exhibits a peak whose position depends on the concentration. We take advantage of the close analogy between polymers and wormlike micelles and apply our model, using a Gaussian function for V, to quantitatively analyze experimental small angle neutron scattering profiles of semi-dilute solutions of hairy wormlike micelles. These samples, which consist in surfactant self-assembled flexible cylinders decorated by amphiphilic copolymer, provide indeed an appropriate experimental model system to study the structure of sterically interacting polymer solutions

Reduction of Maternal Mortality with Highly Active Antiretroviral Therapy in a Large Cohort of HIV-Infected Pregnant Women in Malawi and Mozambique

Background: HIV infection is a major contributor to maternal mortality in resource-limited settings. The Drug Resource Enhancement Against AIDS and Malnutrition Programme has been promoting HAART use during pregnancy and postpartum for Prevention-of-mother-to-child-HIV transmission (PMTCT) irrespective of maternal CD4 cell counts since 2002. Methods: Records for all HIV+ pregnancies followed in Mozambique and Malawi from 6/2002 to 6/2010 were reviewed. The cohort was comprised by pregnancies where women were referred for PMTCT and started HAART during prenatal care (n = 8172, group 1) and pregnancies where women were referred on established HAART (n = 1978, group 2). Results: 10,150 pregnancies were followed. Median (IQR) baseline values were age 26 years (IQR:23-30), CD4 count 392 cells/mm(3) (IQR:258-563), Viral Load log(10) 3.9 (IQR:3.2-4.4), BMI 23.4 (IQR:21.5-25.7), Hemoglobin 10.0 (IQR:9.0-11.0). 101 maternal deaths (0.99%) occurred during pregnancy to 6 weeks postpartum: 87 (1.1%) in group 1 and 14 (0.7%) in group 2. Mortality was 1.3% in women with <than 350 CD4 cells/mm(3) and 0.7% in women with greater than 350 CD4s cells/mm(3) [OR = 1.9 (CL 1.3-2.9) p = 0.001]. Mortality was higher in patients with shorter antenatal HAART: 22/991 (2.2%) if less than 30 days and 79/9159 (0.9%) if 31 days or greater [OR = 2.6 (CL 1.6-4.2) p<0.001]. By multivariate analysis, shorter antenatal HAART (p, 0.001), baseline values for CD4 cell count (p = 0.012), hemoglobin (p = 0.02), and BMI (p<0.001) were associated with mortality. Four years later, survival was 92% for women with shorter antenatal HAART and 98% for women on established therapy prior to pregnancy, p = 0.001. Conclusions: Antiretrovirals for PMTCT purposes have significant impact on maternal mortality as do CD4 counts and nutritional status. In resource-limited settings, PMTCT programs should provide universal HAART to all HIV+ pregnant women given its impact in prevention of maternal death