Frequency domain unsteady transonic aerodynamics for flutter and limit cycle oscillation prediction

The purpose of this study was to develop new approaches for predicting transonic flutter and limit cycle oscillations (LCO) using computational methods. The TSD equation is separated into the in-phase and out-of-phase components through a nonlinear harmonic averaging method. It is then solved in the frequency domain to obtain the aerodynamic forcing function which is needed in the flutter and LCO analyses. To predict flutter, equations are developed using the concept of generalized coordinates. The flutter speed is determined by examining the frequency-domain matrix equation eigenvalues. Flutter characteristics of the AGARD I-445.6 wing are analyzed. Flutter speed and frequency are well predicted in subsonic speed, but are overestimated in supersonic flow. To predict limit cycle oscillations, the frequency-domain aerodynamic coefficients are used to obtain a nonlinear time-domain expression for the aerodynamic force. Limit cycle oscillation characteristics of the DAST ARW-2 wing are analyzed. The results show LCO for Mach numbers ranging from 0.915 to 0.940

Infinite compressibility states in the Hierarchical Reference Theory of fluids. II. Numerical evidence

Continuing our investigation into the Hierarchical Reference Theory of fluids for thermodynamic states of infinite isothermal compressibility kappa[T] we now turn to the available numerical evidence to elucidate the character of the partial differential equation: Of the three scenarios identified previously, only the assumption of the equations turning stiff when building up the divergence of kappa[T] allows for a satisfactory interpretation of the data. In addition to the asymptotic regime where the arguments of part I (cond-mat/0308467) directly apply, a similar mechanism is identified that gives rise to transient stiffness at intermediate cutoff for low enough temperature. Heuristic arguments point to a connection between the form of the Fourier transform of the perturbational part of the interaction potential and the cutoff where finite difference approximations of the differential equation cease to be applicable, and they highlight the rather special standing of the hard-core Yukawa potential as regards the severity of the computational difficulties.Comment: J. Stat. Phys., in press. Minor changes to match published versio

Effect of Process Parameter on the in-situ Intermetallic Composite Coating and Microstructural Evolution of Zn-Al2O3 in the Presence of TEA/MEA on Mild Steel

Zn-Al2O3 composite coating electrodeposits have been produced from chloride bath in the presence of Triethanolamine (TEA) and Monoethanolamine (MEA). The plating effect of TEA and MEA as addition agent on the Zn-Al2O3 alloy is investigated using SEM/EDS, x-ray diffraction (XRD) and atomic force microscope (AFM). The mechanical properties were examined through micro-hardness tester. The presence of TEA and MEA as a surface-active additive is also felt to accompany the performance of the fabricated coating. The SEM results for Zn-Al2O3 deposits in the presence of TEA/MEA indicate that surface-active additive have a strong influence on the deposit surface morphology and improved micro-hardness behavior which is assisted by the change in the deposition process parameter

Cirurgia neuroendoscópica para tratamento da hidrocefalia unilateral secundária à obstrução inflamatória do forame de Monro

OBJECTIVE: Unilateral hydrocephalus (UH) is characterized by enlargement of just one lateral ventricle. In this paper, the authors will demonstrate their experiences in the neuroendoscopic management of this uncommon type of hydrocephalus. METHOD: The authors retrospectively reviewed a serie of almost 800 neuroendoscopic procedures performed from September 1995 to July 2010 and selected seven adult patients with UH. Clinical and radiological charts were reviewed and analyzed. RESULTS: Six patients had intraventricular neurocysticercosis and one patient had congenital stenosis of the foramen of Monro. Headaches were the most common symptom. A septostomy restored cerebrospinal fluid circulation. During follow-up period (65.5 months, range 3-109) no patient has presented clinical recurrence as well as no severe complications have been observed. CONCLUSION: UH is a rare condition. A successful treatment can be accomplished through a neuroendoscopic approach avoiding the use of ventricular shunts.OBJETIVO: Hidrocefalia unilateral (HU) é caracterizada pelo alargamento de apenas um dos ventrículos laterais. Neste estudo, os autores demonstraram sua experiência no manejo deste tipo incomum de hidrocefalia. MÉTODO: Foram revisados, de uma série de quase 800 cirurgias neuroendoscópicas realizadas entre Setembro de 1995 e Julho de 2010, sete pacientes adultos com diagnóstico de HU. Dados clínicos e radiológicos foram analisados. RESULTADOS: Seis pacientes tinham neurocisticercose intraventricular e um apresentava uma estenose congênita do forame de Monro. Cefaléia foi o sintoma clínico mais comum. Uma septostomia restabeleceu o fluxo liquórico. Durante o seguimento (65,5 meses, de 3-109), nenhum paciente apresentou recorrência clínica assim como nenhuma complicação grave foi observada. CONCLUSÃO: HU é uma condição rara. O tratamento satisfatório pode ser alcançado por meio de uma abordagem neuroendoscópica evitando, desta maneira, o uso de sistemas de derivação ventricular.Federal University of São Paulo Division of Neurosurgery Department of Neurology and NeurosurgeryUNIFESP, Division of Neurosurgery Department of Neurology and NeurosurgerySciEL

Implementation of the Hierarchical Reference Theory for simple one-component fluids

Combining renormalization group theoretical ideas with the integral equation approach to fluid structure and thermodynamics, the Hierarchical Reference Theory is known to be successful even in the vicinity of the critical point and for sub-critical temperatures. We here present a software package independent of earlier programs for the application of this theory to simple fluids composed of particles interacting via spherically symmetrical pair potentials, restricting ourselves to hard sphere reference systems. Using the hard-core Yukawa potential with z=1.8/sigma for illustration, we discuss our implementation and the results it yields, paying special attention to the core condition and emphasizing the decoupling assumption's role.Comment: RevTeX, 16 pages, 2 figures. Minor changes, published versio

On acceleration of Krylov-subspace-based Newton and Arnoldi iterations for incompressible CFD: replacing time steppers and generation of initial guess

We propose two techniques aimed at improving the convergence rate of steady state and eigenvalue solvers preconditioned by the inverse Stokes operator and realized via time-stepping. First, we suggest a generalization of the Stokes operator so that the resulting preconditioner operator depends on several parameters and whose action preserves zero divergence and boundary conditions. The parameters can be tuned for each problem to speed up the convergence of a Krylov-subspace-based linear algebra solver. This operator can be inverted by the Uzawa-like algorithm, and does not need a time-stepping. Second, we propose to generate an initial guess of steady flow, leading eigenvalue and eigenvector using orthogonal projection on a divergence-free basis satisfying all boundary conditions. The approach, including the two proposed techniques, is illustrated on the solution of the linear stability problem for laterally heated square and cubic cavities

Comparative study on lipase production using solid state and submerged fermentation systems by several fungal strains and the predicted molecular characteristics

Background: Lipases produced from microbial fermentation systems belong to the group of hydrolase enzymes and have tremendous commercial applications. The performance of solid state and submerged fermentation in producing lipase by several fungal strains was compared and the structure and functions of the lipases were predicted by molecular prediction studies. Methods: Lipase production was investigated using both solid state fermentation (SSF) and submerged liquid fermentation (SLF); with palm kernel cake as the fermentation substrate for SSF. Lipase activity, protease activity, total protein and biomass content were assayed. The predictive molecular characterization techniques were employed to determine possible structure and function of the lipases. Results: All fungal strains tested showed substantially higher lipase activity in SSF compared to SLF except for Trichoderma viride SDTC EDF 002. Aspergillus niger SDTC SRW-4 (44.43 U g-1; 176.36 mg g-1) and Aspergillus niger DSMZ 2466 (42.05 U g-1; 176.28 mg g-1) showed the highest lipase activities and total protein content. All lipases showed the presence of “lipase 3” domain with conserved dyad catalytic site of two residues (Ser-Asp) unlike several other esterase lipases with triad catalytic site (Ser-Asp/Glu-His). Predicted pI range of lipases was 4.22 to 8.28 with molecular weight ranging from 31.6 kDa to 54.1 kDa. Conclusions: Production of lipase by Aspergillus niger SDTC SRW-4 and Aspergillus niger DSMZ 2466 using palm kernel cake as substrate was substantially higher in SSF as compared to SLF. Lipases produced by these fungus were predicted to have similar properties and functionality of triacylglycerol lipases (EC 3.1.1.3)

Theoretical description of phase coexistence in model C60

We have investigated the phase diagram of the Girifalco model of C60 fullerene in the framework provided by the MHNC and the SCOZA liquid state theories, and by a Perturbation Theory (PT), for the free energy of the solid phase. We present an extended assessment of such theories as set against a recent Monte Carlo study of the same model [D. Costa et al, J. Chem. Phys. 118:304 (2003)]. We have compared the theoretical predictions with the corresponding simulation results for several thermodynamic properties. Then we have determined the phase diagram of the model, by using either the SCOZA, or the MHNC, or the PT predictions for one of the coexisting phases, and the simulation data for the other phase, in order to separately ascertain the accuracy of each theory. It turns out that the overall appearance of the phase portrait is reproduced fairly well by all theories, with remarkable accuracy as for the melting line and the solid-vapor equilibrium. The MHNC and SCOZA results for the liquid-vapor coexistence, as well as for the corresponding critical points, are quite accurate. All results are discussed in terms of the basic assumptions underlying each theory. We have selected the MHNC for the fluid and the first-order PT for the solid phase, as the most accurate tools to investigate the phase behavior of the model in terms of purely theoretical approaches. The overall results appear as a robust benchmark for further theoretical investigations on higher order C(n>60) fullerenes, as well as on other fullerene-related materials, whose description can be based on a modelization similar to that adopted in this work.Comment: RevTeX4, 15 pages, 7 figures; submitted to Phys. Rev.

Liquid-microjet photoelectron spectroscopy of the green fluorescent protein chromophore

Green fluorescent protein (GFP), the most widely used fluorescent protein for in vivo monitoring of biological processes, is known to undergo photooxidation reactions. However, the most fundamental property underpinning photooxidation, the electron detachment energy, has only been measured for the deprotonated GFP chromophore in the gas phase. Here, we use multiphoton ultraviolet photoelectron spectroscopy in a liquid-microjet and high-level quantum chemistry calculations to determine the electron detachment energy of the GFP chromophore in aqueous solution. The aqueous environment is found to raise the detachment energy by around 4 eV compared to the gas phase, similar to calculations of the chromophore in its native protein environment. In most cases, electron detachment is found to occur resonantly through electronically excited states of the chromophore, highlighting their importance in photo-induced electron transfer processes in the condensed phase. Our results suggest that the photooxidation properties of the GFP chromophore in an aqueous environment will be similar to those in the protein