Analytic Determination of the Critical Coupling for Oscillators in a Ring

We study a model of coupled oscillators with bidirectional first nearest neighbours coupling with periodic boundary conditions. We show that a stable phase-locked solution is decided by the oscillators at the borders between the major clusters, which merge to form a larger one of all oscillators at the stage of complete synchronization. We are able to locate these four oscillators as well as the size of major clusters in the vicinity of the stage of full synchronization which we show to depend only on the set of initial frequencies. Using the method presented here, we are able to obtain an analytic form of the critical coupling, at which the complete synchronization state occurs.Comment: 5 pages and 3 figure

The Performance of Portland Cement Pastes (OPC) Incorporated with Ceramic Sanitary Ware Powder Waste (CSPW) at Ambient Temperature

The physical and mechanical performance of Portland cement pastes (OPC) incorporated waste ceramic sanitary ware powder waste (CSPW) at ambient temperature has been investigated. Cement mixes were prepared by replacing the cement with CSPW at proportions of 0, 4, 8, 12, 16 and 20 wt. %. The results showed that the water of consistency and setting times (initial and final) were increased with the gradual addition of CSP, whereas the water absorption and total porosity were decreased, while the bulk density slightly was enhanced but only up to 16 wt. % CSPW. The same trend was displayed with mechanical properties, where the flexural (FS) and compressive strengths (CS) of the cement specimens were also improved and enhanced till 16 wt. %, but then all were decreased with further addition of CSPW. The experimental results indicated that the CSPW has the potential to be successfully recycled in the OPC pastes as a partial replacement merely up to 16 wt. % which had a better performance than the blank at ambient temperature. The FT-IR spectra illustrated that the amount of CSHs was increased, while that of free lime content decreased. This was confirmed by SEM microscopy. Moreover, the recovery of CSPW contributes to both reducing environmental pollution and CO2 emissions

On Dirac Zero Modes in Hyperdiamond Model

Using the SU(5) symmetry of the 4D hyperdiamond and results on the study of 4D graphene given in "Four Dimensional Graphene" (L.B Drissi, E.H Saidi, M. Bousmina, CPM-11-01, Phys. Rev. D (2011)), we engineer a class of 4D lattice QCD fermions whose Dirac operators have two zero modes. We show that generally the zero modes of the Dirac operator in hyperdiamond fermions are captured by a tensor {\Omega}_{{\mu}}^{l} with 4\times5 complex components linking the Euclidean SO(4) vector {\mu}; and the 5-dimensional representation of SU(5). The Bori\c{c}i-Creutz (BC) and the Karsten-Wilzeck (KW) models as well as their Dirac zero modes are rederived as particular realizations of {\Omega}_{{\mu}}^{l}. Other features are also given. Keywords: Lattice QCD, Bori\c{c}i-Creutz and Karsten-Wilzeck models, 4D hyperdiamond, 4D graphene, SU(5) Symmetry.Comment: LaTex, 28 pages, To appear in Phys Rev

Linearna i nelinearna optička svojstva modulirane kvantne jame

The electron energy levels and envelope wave functions in a double confinement quantum-barrier structure, are numerically calculated utilizing the transfer matrix method. Analytic forms of the linear and the nonlinear optical absorption coefficients and change in refractive indices due to intersubband optical transitions with an applied electric field are derived theoretically based on the density-matrix formalism.Za konačno duboku kvantnu jamu određeni su numerički energetski nivoi elektrona i valne funkcije primjenom metode matrice prijelaza. Nađen je analitički oblik za koeficijente linearne i nelinearne optičke apsorpcije te za promjenu indeksa loma zbog optičkih prijelaza medu podvrpcama uzrokovanih vanjskim električnim poljem. Račun je napravljen pomoću formalizma matrice gustoće

Energija vezanja donora u paraboličkoj kvantnoj jami

We solved the impurity problem in a parabolic quantum well. The binding energy of a neutral donor in GaAs-Alx Ga1!xAs parabolic quantum well is determined variationally. For a dopant at the well center, and at the edge of the well in the interface region, the changes in the binding energy of donors are calculated, for different well sizes and depths. The 2s excited state is reported.Riješili smo problem primjese u paraboličkoj kvantnoj jami. Energija vezanja neutralnog donora u GaAs-Alx Ga1−xAs paraboličkoj kvantnoj jami se rješava varijacijski. Izračunali smo energije vezanja donora ako je u sredini jame i ako je uz rub u međusloju, za različite širine i dubine jame. Izvješćujemo o uzbuđenom stanju 2s

Drag On Non-Spherical Particles In Non-Newtonian Fluids

The drag coefficient (CD ) was determined for three different non-spherical particles (cubes, rectangles and cylinders) of different sizes falling in two different non-Newtonian fluids (glycerol and polymer - paraffin oil mixture) using the terminal velocity technique. The variation of the drag coefficient with the variation of non-spherical particle size was explained. Also the relation between CD and Reo (0.25-5) is graphically compared with those previously published in the literature for discs and cylinders with infinite length. Moreover some mathematical relations, previously published in the literature, are verified for the three tested non-spherical particles

Symmetry analysis for steady boundary-layer stagnation-point flow of Rivlin–Ericksen fluid of second grade subject to suction

An analysis for the steady two-dimensional boundary-layer stagnation-point flow of Rivlin–Ericksen fluid of second grade with a uniform suction is carried out via symmetry analysis. By employing Lie-group method to the given system of nonlinear partial differential equations, the symmetries of the equations are determined. Using these symmetries, the solution of the given equations is found. The effect of the viscoelastic parameter k and the suction parameter R on the tangential and normal velocities, temperature profiles, heat transfer coefficient and the wall shear stress, have been studied. Also, the effect of the Prandtl number Pr on the temperature and the heat transfer coefficient has been studied

The critical level of vitamin D in childhood asthma

Objectives: Studies have suggested a significant link between vitamin D status and asthma. We sought to determine the cutoff level of25 hydroxy (25-OH) vitamin D that is significantly linked to asthma status in children.Methods: Our cross-sectional study comprised 90 asthmatic children, aged 2-18 years. They were evaluated clinically and classified according to asthma severity and control. Asthma control test (ACT) was performed in those aged above 4 years.Pulmonary functions were performed in cooperative children (n=59). Serum 25-OH vitamin D levels were measured by ELISA in all patients.Results: The study comprised 52 boys (57.7%) and 38 girls (42.3%) with mean age 7.03±4.36 years. Thirty-six patients (40%) had mild asthma, 37 (41%) moderate asthma and 17 (19%) had severe asthma. Forty-two patients (46.6%) had controlled asthma; 14 (15.6%) partially controlled and 34 (37.8%) had uncontrolled asthma. ACT score ranged: 11-26, with mean score: 18.9 ± 4.3 SD. Serum 25-OHvitamin D levels ranged between 2-48 ng/ml (mean± SD: 12.2 ± 9 ng/ml); levels were comparable among different grades of asthma severity (f= 1.975, p=0.145), while the uncontrolled asthma group showed the lowest levels (f=8.511, p <0.001). 25-OH vitamin D levels correlated positively with ACT score (r= 0.369, p= <0.001) but not with inhaled steroids doses or any of the pulmonary function parameters. A level of 7.5 ng/ml was associated with partial/completeuncontrol of asthma with 81 % sensitivity and 53 % specificity.Conclusion: 25-OH vitamin D levels below 7.5 ng/ml are associated with poor asthma status in children.Keywords: Asthma, allergy, children, severity, inhaled steroids, 25 hydroxy vitamin D