Prediction of heat release effects on a mixing layer

A fully second-order closure model for turbulent reacting flows is suggested based on Favre statistics. For diffusion flames the local thermodynamic state is related to single conserved scalar. The properties of pressure fluctuations are analyzed for turbulent flows with fluctuating density. Closure models for pressure correlations are discussed and modeled transport equations for Reynolds stresses, turbulent kinetic energy dissipation, density-velocity correlations, scalar moments and dissipation are presented and solved, together with the mean equations for momentum and mixture fraction. Solutions of these equations are compared with the experimental data for high heat release free mixing layers of fluorine and hydrogen in a nitrogen diluent

Influence of masonry infill on the seismic performance of concentrically braced frames

This paper presents an experimental and analytical study to investigate the effect of masonry infill on the seismic performance of special Concentrically Braced Frames (CBFs). Cyclic lateral load tests are conducted on three half-scale specimens including two special CBFs with and without masonry infill and a moment resisting steel frame with masonry infill for comparison purposes. Companion analyses are performed to study the influence of masonry infill on the potential rupture of gusset plates and top-seat angle connections by using detailed FE models validated with experimental results. It is shown that the presence of masonry infill could increase the lateral stiffness and load carrying capacity of the special CBF by 33% and 41%, respectively. However, the interaction between masonry infill and the frame significantly increased the strain demands and failure potential of the connections. The results of the experimental tests and analytical simulations indicate that ignoring the influence of masonry infill in the seismic design process of CBFs results in a premature fracture of the connection weld lines and a significant reduction in the deformation capacity and ductility of the frame. This can adversely influence the seismic performance of the structure under strong earthquakes. The results of this study compare well with the damage observations after the 2003 earthquake in Bam, Iran

Hydrogen patterning of Ga1-xMnxAs for planar spintronics

We demonstrate two patterning techniques based on hydrogen passivation of Ga1-xMnxAs to produce isolated ferromagnetically active regions embedded uniformly in a paramagnetic, insulating host. The first method consists of selective hydrogenation of Ga1-xMnxAs by lithographic masking. Magnetotransport measurements of Hall-bars made in this manner display the characteristic properties of the hole-mediated ferromagnetic phase, which result from good pattern isolation. Arrays of Ga1-xMnxAs dots as small as 250 nm across have been realized by this process. The second process consists of blanket hydrogenation of Ga1-xMnxAs followed by local reactivation using confined low-power pulsed-laser annealing. Conductance imaging reveals local electrical reactivation of micrometer-sized regions that accompanies the restoration of ferromagnetism. The spatial resolution achievable with this method can potentially reach <100 nm by employing near-field laser processing. The high spatial resolution attainable by hydrogenation patterning enables the development of systems with novel functionalities such as lateral spin-injection as well as the exploration of magnetization dynamics in individual and coupled structures made from this novel class of semiconductors.Comment: ICDS-24, July 2007. 8 pages with 4 figure

A Sensitive Liquid Chromatographic Method for the Analysis of Clarithromycin with Pre-Column Derivatization: Application to a Bioequivalence Study

Objective(s)A sensitive liquid chromatographic method for the analysis of clarithromycin- a macrolide antibiotic- in human serum, using pre-column derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) is described. Materials and MethodsThe method involved liquid–liquid extraction of the drug and an internal standard (amantadine) followed by pre-column derivatization of the analytes with FMOC-Cl. A mixture of 0.05 M phosphate buffer containing triethylamine (2 ml/l; pH 3.8) and methanol (17:83, v/v) was used as mobile phase and chromatographic separation was achieved on a Shimpack CLC-ODS column. The eluate was monitored by a fluorescence detector with respective excitation and emission wavelengths of 265 and 315 nm. ResultsThe analytical method was linear over the concentration range of 0.025-10 μg/ml of clarithromycin in human serum with a limit of quantification of 0.025 μg/ml. The assay is sensitive enough to measure drug levels obtained in human single dose studies.ConclusionIn the present method, sensitivity and the running time of analysis have been improved and successfully applied in a bioequivalence study of three different clarithromycin preparations in 12 healthy volunteers

Analgesic and Anti-inflammatory Activity of Teucrium chamaedrys Leaves Aqueous Extract in Male Rats

Objective(s)Current study was undertaken to investigate the analgesic and anti-inflammatory effects of the aqueous extract of Teucrium chamaedrys in mice and rats. Materials and MethodsFor evaluating of analgesic and anti-inflammatory activity, we used the carrageenan- and dextran-induced paw oedema, acetic acid-induced writhing, tail flick and formalin pain tests.ResultsThe extract of T. chamaedrys (50–200 mg/kg) and acetylsalicylic acid (100 mg/kg) produced a significant (P< 0.01) inhibition of the second phase response in the formalin pain model, while only the high dose (200 mg/kg) of the extract showed an analgesic effect in the first phase. The extract also inhibited acetic acid-induced abdominal writhes in a dose-dependent manner. The tail flick latency was dose dependently enhanced by the extract but this was significantly (P< 0.05) lower than that produced by morphine (10 mg/kg). The extract (25–250 mg/kg) administered 1 hr before carrageenan-induced paw swelling produced a dose dependent inhibition of the oedema. No effect was observed with the dextran-induced oedema model. Results of the phytochemical screening show the presence of alkaloids, flavonoids and triterpenoids in the extract.ConclusionThe data obtained also suggest that the anti-inflammatory and analgesic effects of the extract may be mediated via both peripheral and central mechanisms. The role of alkaloids, flavonoids and triterpenoids will evaluate in future studies

Agent-based distributed performance measurement system for ITSP projects

Measuring the development of an enterprise software project progress and performance is crucial to assure a project follow its path. This attention stems in parts from the frequent reports of high profile cases of mismanaged in IT projects particularly in enterprise level such as information technology strategic planning (ITSP) projects. Many project performance measurement models and frameworks have been proposed to address the problem, however, they are usually hard to manage and inefficient in practice due to the complexity, distribution and dynamism of these types of projects. A large and growing body of literature has shown the advantages of employing the agent technology in distributed, dynamic, and complex environments. Therefore, in this study the advantages of the agent technology will be applied to improve the progress and measurement process of the software project performance measurement approaches. In this paper, a multi-agent system architectural model with the focus in implementation phase of the ITSP projects is proposed to promote and facilitate the process of project performance measurement. Furthermore the prototype of the proposed solution is explained and the evaluation approach is discussed

Concepts for radically increasing the numerical convergence rate of the Euler equations

Integral equation and finite difference methods have been developed for solving transonic flow problems using linearized forms of the transonic small disturbance and Euler equations. A key element is the use of a strained coordinate system in which the shock remains fixed. Additional criteria are developed to determine the free parameters in the coordinate straining; these free parameters are functions of the shock location. An integral equation analysis showed that the shock is located by ensuring that no expansion shocks exist in the solution. The expansion shock appears as oscillations in the solution near the sonic line, and the correct shock location is determined by removing these oscillations. A second objective was to study the ability of the Euler equation to model separated flow

Slope stability analysis with applicability of lime in capillary barrier effects

Many hill slope areas in Malaysia are vulnerable to soil erosion and shallow slope failures due to tropical climate and intense and frequent rainfall events. This failure can be attributed to the surface erosion, loss of shear strength, and formation of tension cracks on the surface. Lime as a construction material has been used to improve soil properties for long time. In this study a series of laboratory tests were performed on natural soil and soil artificially mixed with 3, 5, 7 and 9% of hydrated lime, based on dry unit weight of the soil. Numerical analysis was conducted using finite element method to simulate capillary barrier effects at the interface of soil and soil-mixture due to change in permeability. The results demonstrate that, for the soil used in this study, an addition of 7% lime is considerable to improve properties of the soil surface with optimum thickness of 30 cm in capillary barrier effects. The improvement of soil at slope surface not only prevents erosion and crack formation but also limits deep infiltration of rainwater into the slope which was achieved through numerical modeling. This study can be contributed to the path of stability of surficial slope failures

Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting

We present a detailed investigation of the magnetic and magnetotransport properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion implantation and pulsed-laser melting (II-PLM). The field and temperature-dependent magnetization, magnetic anisotropy, temperature-dependent resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have all of the characteristic signatures of the strong p-d interaction of holes and Mn ions observed in the dilute hole-mediated ferromagnetic phase. The ferromagnetic and electrical transport properties of II-PLM films correspond to the peak substitutional Mn concentration meaning that the non-uniform Mn depth distribution is unimportant in determining the film properties. Good quantitative agreement is found with films grown by low temperature molecular beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition. Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from interstitial Mn_I because of the high temperature processing. At high Mn implantation doses the kinetics of solute redistribution during solidification alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs giving evidence for this being an intrinsic property of the carrier-mediated ferromagnetic phase