Investigation of the Scanning Microarc Oxidation Process

Scanning microarc oxidation (SMAO) is a coating process which is based on conventional microarc oxidation (MAO). The key difference is that deposition in SMAO is achieved by using a stainless steel nozzle to spray an electrolyte stream on the substrate surface as opposed to immersing the workpiece in an electrolyzer. In the present study, SMAO discharge characteristics, coating morphology, and properties are analyzed and compared to results obtained from MAO under similar conditions. Results show that MAO and SMAO have comparable spark and microarc lifetimes and sizes, though significant differences in incubation time and discharge distribution were evident. Results also showed that the voltage and current density for MAO and SMAO demonstrate similar behavior but have markedly different transient and steady-state values. Results obtained from coating A356 aluminum sheet show that oxide thickness and growth rate in SMAO are strongly dependent on interelectrode spacing and travel speed. Analysis of the SMAO coating morphology and structure showed that a denser and slightly harder layer was deposited in comparison to MAO and is attributed to reduced porosity and increased formation of α-Al2O3. Preliminary results indicate that SMAO represents a viable process for coating of aluminum surfaces

Impurity states in d-wave superconductors with a competing antiferromagnetic interaction

Impurity states in d-wave superconductors with a competing antiferromagnetic (AF) order are investigated by solving the Bogoliubov-de Gennes equations. The potential scattering (PS) model with moderate strength and the Anderson impurity (AI) model with on-site hybridization are employed to describe the weak impurities. In zero external field, the impurity-induced AF order is rather weak and both models are able to give rise to impurity resonant states with close energy and similar profile of the local density of states. In the mixed state, the effect of magnetic-field-induced AF order on the impurity quasiparticle excitation is also examined. We find that the response of the impurity state to the presence of a local AF order is quite different for the two impurity models when a superconducting vortex is pinned by the impurity. For the PS model, the impurity resonance is subtly dependent on the sign and strength of the scattering potential, while for the AI model in the strong hybridization regime, the low-lying resonance is pinned near the Fermi level within the small gap opened by the AF order and is insensitive to the strength of the coupling between the impurity spin and the conduction electron. Based on our numerical results, we think that the two models give rise to different behaviors of the impurity resonances for both the nickel and zinc impurities in the magnetic field and the prospective scanning tunneling microscopic observation might give a clue to the dominant mechanism of the impurity states in the high-T c cuprates.published_or_final_versio

Angle observation of laser peripheral iridoplasty for the treatment of acute angle-closure glaucoma which could not be controlled by drugs

AIM: To evaluate the effect of laser peripheral iridoplasty(LPIP)to treat acute angle-closure glaucoma(AACG)which could not controlled by drugs and with persistent ocular hypertension. <p>METHODS: Totally 67 patients(69 eyes)with AACG were performed LPIP when intraocular pressure(IOP)was still over 30mmHg after the medicine therapy for 3-6 hours. Visual acuity and intraocular pressure were under detection before laser treatment and 30 minutes, 60 minutes and 2 hours after laser treatment. We measured the anterior chamber depth, width of angle, iris thickness with ultrasound biomicroscope(UBM). Dynamic gonioscopy was used to evaluate the degree of peripheral anterior synechia(PAS).<p>RESULTS: Angle open distance(AOD)after iridoplasty was increased(<i>P</i><0.01). Trabecular-iris angle(TIA)was widen(<i>P</i><0.01)and the extents of PAS were reduced in some cases. IOP reduced at different levels in different time after laser treatment. The mean IOP before acute attack was(53.81±10.22)mmHg. The mean IOP were(33.81±9.22)mmHg,(21.93±7.19)mmHg and(15.16±3.07)mmHg at 30 minutes, 60 minutes and 2 hours after laser treatment respectively(<i>F</i>=151.79, <i>P</i><0.01). Visual acuity increased in all patients. <p>CONCLUSION: LPIP can deepen peripheral anterior chamber, increase the angle access and lower the IOP immediately. It is an important ongoing adjuvant treatment, which can reduce the patients suffering by lowering the IOP quickly, reduce the damage of visual function caused by long-term high intraocular pressure, avoid side effect of the drugs, and can improve the prognosis

Numerical prediction of combustion instability limit cycle oscillations for a combustor with a long flame

A coupled numerical approach is investigated for predicting combustion instability limit cycle characteristics when the combustor contains a long flame. The test case is the ORACLES combustor, with a turbulent premixed flame a metre long: it exhibits limit cycle oscillations at ∼ 50 Hz and normalised velocity amplitude ahead of the flame of ∼ 0.29. The approach obtains the flame response to acoustic excitation using Large Eddy Simulations (LES), and couples this with a low-order wave-based network representation for the acoustic waves within the combustor. The flame cannot be treated as acoustically compact; the spatial distribution of both its response and the subsequent effect on the acoustics must be accounted for. The long flame is uniformly segmented axially, each segment being much shorter than the flow wavelengths at play. A series of “local” flame describing functions, one for the heat release rate response within each segment to velocity forcing at a fixed reference location, are extracted from the LES. These use the Computational Fluid Dynamics toolbox, OpenFOAM, with an incompressible approximation for the flow-field and combustion modelled using the Partially Stirred Reactor model with a global onestep reaction mechanism. For coupling with the low-order acoustic network modelling, compact acoustic jump conditions are derived and applied across each flame segment, while between flame segments, wave propagation occurs. Limit cycle predictions from the proposed coupled method agree well with those predicted using the continuous 1-D linearised Euler equations, validating the flame segmentation implementation. Limit cycle predictions (frequency 51.6 Hz and amplitude 0.38) also agree well with experimental measurements, validating the low-order coupled method as a prediction tool for combustors with long flames. A sensitivity analysis shows that the predicted limit cycle amplitude decreases rapidly when acoustic losses at boundaries are accounted for, and increases if combustor heat losses downstream of the flame are accounted for. This motivates more accurate determination of combustor boundary and temperature behaviour for thermoacoustic predictions

2-Phenyl­imidazolium nitrate monohydrate

In the title hydrated mol­ecular salt, C9H9N2 +·NO3 −·H2O, the dihedral angle between the aromatic rings in the cation is 11.09 (8)°. In the crystal, the components are linked into chains propagating in [101] by N—H⋯O and O—H⋯O hydrogen bonds