Nonequilibrium phase transitions and stationary state solutions of a three-dimensional random-field Ising model under a time dependent periodic external field

Nonequilibrium behavior and dynamic phase transition properties of a kinetic Ising model under the influence of periodically oscillating random-fields have been analyzed within the framework of effective field theory (EFT) based on a decoupling approximation (DA). Dynamic equation of motion has been solved for a simple cubic lattice ($q=6$) by utilizing a Glauber type stochastic process. Amplitude of the sinusoidally oscillating magnetic field is randomly distributed on the lattice sites according to bimodal and trimodal distribution functions. For a bimodal type of amplitude distribution, it is found in the high frequency regime that the dynamic phase diagrams of the system in temperature versus field amplitude plane resemble the corresponding phase diagrams of pure kinetic Ising model. Our numerical results indicate that for a bimodal distribution, both in the low and high frequency regimes, the dynamic phase diagrams always exhibit a coexistence region in which the stationary state (ferro or para) of the system is completely dependent on the initial conditions whereas for a trimodal distribution, coexistence region disappears depending on the values of system parameters.Comment: 11 pages, 11 figure

Effective field theory analysis of 3D random field Ising model on isometric lattices

Ising model with quenched random magnetic fields is examined for single Gaussian, bimodal and double Gaussian random field distributions by introducing an effective field approximation that takes into account the correlations between different spins that emerge when expanding the identities. Random field distribution shape dependencies of the phase diagrams and magnetization curves are investigated for simple cubic, body centered and face centered cubic lattices. The conditions for the occurrence of reentrant behavior and tricritical points on the system are also discussed in detail.Comment: 13 pages, 8 figure

Modeling and Experimental Investigation of Laminar Ceiling Air Distribution System for Operating Room in Merjan Teaching Hospital

Room air distribution in operating rooms is critical to successful surgical treatment. The present study investigated the effects of the location of the air supply and exhaust grills on the air movement and air parameters inside an operating room. This paper presents an experimental and numerical analysis of air distribution in the operating room. The experimental work was conducted in an operating room in Merjan Teaching Hospital in the city of Babylon. Air was supplied from one square plenum box located in the middle of the ceiling, while air was exhausted through eight grills: large exhaust grills in the four upper corners and small exhaust grills in the four lower corners. In the theoretical work, a model of the operating room was developed and two cases were analyzed using the FLUEN 6.3.26 software program. The first case included all eight exhaust grills, while the second case included only the four lower exhaust grills. The ceiling system gave good ventilation for air distribution inside the operating room. There was no clear effect of the small exhaust grills located in the upper corners of the operating room. The height of the ceiling room is an effective factor in air distribution

Enhancement in thermal and mechanical properties of bricks

A new type of porous brick is proposed. Sawdust is initially well mixed with wet clay in order to create voids inside the brick during the firing process. The voids will enhance the total performance of the brick due to the reduction of its density and thermal conductivity and a minor reduction of its compressive stress. All these properties have been measured experimentally and good performance has been obtained. Although a minor reduction in compressive stress has been observed with increased porosity, this property has still been larger than that of the common used hollow brick. Data obtained by this work lead to a new type of effective brick having a good performance with no possibility that mortar enters inside the holes which is the case with the common used hollow bricks. The mortar has a determent effect on thermal properties of the wall since it has some higher thermal conductivity and density than that of brick which increases the wall overall density and thermal conductivity of the wall

Fly ash from modern coal-fired power technologies::Chloride ingress and carbonation of concrete

Low-lime fly ashes produced from modern coal-fired power technologies (developed to enhance efficiency/lower emissions), including nitrogen oxide (NO x) reduction, co-combustion, supercritical steam and oxy-fuel combustion, and their effects on chloride ingress and carbonation of concrete are investigated in this paper. Earlier work indicates that some of these technologies influence fly ash properties, but they mainly follow typical behaviour found for the material (consistence and compressive strength) in concrete. Both accelerated and normal-type exposure tests were carried out on a range of practical water/cement ratio concretes (also enabling interpolation for comparisons at equal 28 d strength). The test fly ash concretes were evaluated against (i) those containing three reference fly ashes covering a range of fineness and (ii) corresponding studies on fly ash concretes from the 1990s. The results show that there was an influence of fly ash fineness, reflected in reactivity/porosity (measured on mortar), and aspects of chemistry on chloride ingress, but there appeared to be minor material effects on carbonation. Comparison with the 1990s data indicated similar behaviour for the materials between studies for both properties. A relationship was also identified for the product of reactive alumina and sub-10 μm contents of the modern fly ashes and chloride resistance of concrete. </p

Effect of zinc supplementation on growth Hormone Insulin growth factor axis in short Egyptian children with zinc deficiency

BACKGROUND: The relationship between zinc (Zn) and growth hormone-insulin growth factor (GH-IGF) system and how Zn therapy stimulates growth in children has not been clearly defined in humans. Thus, we aimed to assess GH-IGF axis in short children with Zn deficiency and to investigate the effect of Zn supplementation on these parameters. METHODS: Fifty pre-pubertal Egyptian children with short stature and Zn deficiency were compared to 50 age-, sex-, and pubertal stage- matched controls. All subjects were subjected to history, auxological assessment and measurement of serum Zn, IGF-1, insulin growth factor binding protein-3 (IGFBP-3); and basal and stimulated GH before and 3 months after Zn supplementation (50 mg/day). RESULTS: After 3 months of Zn supplementation in Zn-deficient patients, there were significant increases in height standard deviation score (SDS, P = 0.033), serum Zn (P < 0.001), IGF-1 (P < 0.01), IGF-1 standard deviation score (SDS,P < 0.01) and IGFBP-3 (P = 0.042). Zn rose in all patients but reached normal ranges in 64 %, IGF-1 levels rose in 60 % but reached normal ranges in 40 % and IGFBP-3 levels rose in 40 % but reached reference ranges in 22 %. Growth velocity (GV) SDS did not differ between cases and controls (p = 0.15) but was higher in GH-deficient patients than non-deficient ones, both having Zn deficiency (p = 0.03). CONCLUSION: Serum IGF-1 and IGFBP-3 levels were low in short children with Zn deficiency, and increased after Zn supplementation for 3 months but their levels were still lower than the normal reference ranges in most children; therefore, Zn supplementation may be necessary for longer periods

Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field

We have presented dynamic phase transition features and stationary-state behavior of a ferrimagnetic small nanoparticle system with a core-shell structure. By means of detailed Monte Carlo simulations, a complete picture of the phase diagrams and magnetization profiles have been presented and the conditions for the occurrence of a compensation point $T_{comp}$ in the system have been investigated. According to N\'{e}el nomenclature, the magnetization curves of the particle have been found to obey P-type, N-type and Q-type classification schemes under certain conditions. Much effort has been devoted to investigation of hysteretic response of the particle and we observed the existence of triple hysteresis loop behavior which originates from the existence of a weak ferromagnetic core coupling $J_{c}/J_{sh}$, as well as a strong antiferromagnetic interface exchange interaction $J_{int}/J_{sh}$. Most of the calculations have been performed for a particle in the presence of oscillating fields of very high frequencies and high amplitudes in comparison with exchange interactions which resembles a magnetic system under the influence of ultrafast switching fields. Particular attention has also been paid on the influence of the particle size on the thermal and magnetic properties, as well as magnetic features such as coercivity, remanence and compensation temperature of the particle. We have found that in the presence of ultrafast switching fields, the particle may exhibit a dynamic phase transition from paramagnetic to a dynamically ordered phase with increasing ferromagnetic shell thickness.Comment: 12 pages, 12 figure

Statistical properties of power-law random banded unitary matrices in the delocalization-localization transition regime

Power-law random banded unitary matrices (PRBUM), whose matrix elements decay in a power-law fashion, were recently proposed to model the critical statistics of the Floquet eigenstates of periodically driven quantum systems. In this work, we numerically study in detail the statistical properties of PRBUM ensembles in the delocalization-localization transition regime. In particular, implications of the delocalization-localization transition for the fractal dimension of the eigenvectors, for the distribution function of the eigenvector components, and for the nearest neighbor spacing statistics of the eigenphases are examined. On the one hand, our results further indicate that a PRBUM ensemble can serve as a unitary analog of the power-law random Hermitian matrix model for Anderson transition. On the other hand, some statistical features unseen before are found from PRBUM. For example, the dependence of the fractal dimension of the eigenvectors of PRBUM upon one ensemble parameter displays features that are quite different from that for the power-law random Hermitian matrix model. Furthermore, in the time-reversal symmetric case the nearest neighbor spacing distribution of PRBUM eigenphases is found to obey a semi-Poisson distribution for a broad range, but display an anomalous level repulsion in the absence of time-reversal symmetry.Comment: 10 pages + 13 fig

Essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs

We give sufficient conditions for essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs. Two of the main theorems of the present paper generalize recent results of Torki-Hamza.Comment: 14 pages; The present version differs from the original version as follows: the ordering of presentation has been modified in several places, more details have been provided in several places, some notations have been changed, two examples have been added, and several new references have been inserted. The final version of this preprint will appear in Integral Equations and Operator Theor