Study of deposition offset in plasma spray of zirconia

Numerical modeling and experimental measurements have been performed to study the effects of powder carrier gas flow rates and powder sizes on the deposition offset in a plasma spray of yttria-stablized zirconia. The mathematical model involved simultaneous solution of the continuity, momentum and energy equations of the plasma gas, the dynamics and heat transfer of powder particles in the plasma, and the coupling effects between the plasma and panicles. Experiments included measurement of particle velocities by laser strobe technique and measurement of deposition offset. Calculated plasma temperatures and velocities are greater than 13,000 K and 2,000 m/s, respectively, in the vicinity of nozzle exit. For the plasma-particle momentum transfer, the drag coefficient was computed in two ways- with corrections accounting for the strongly varying plasma properties, and without these corrections. Calculated and experimental results, in respect to deposition offset, are in agreement to within 25% when calculated without varying properties corrections, and within about 40% with corrections; agreement in respect to average particle velocities is within 20% when calculated without varying properties corrections, and within the range 30–50% with corrections.     

Aluminum Chloride (Alcl3) Promotes Selective Oxidative Deprotection of Benzylic Trimethylsilyl and Tert- Butyldimethylsilyl Ethers to the Corresponding Carbonyl Compounds with Manganese Dioxide (Mno2)

Various types of trimethylsilyl and tert-butyldimethylsilyl ethers of primary and secondary benzylic alcohols could be selectively converted to their corresponding carbonyl compounds with MnO₂ in the presence of AlCl₃ in good to excellent yields.     

d-Glucosamine as an efficient and green additive for palladium-catalyzed Heck reaction

The Heck coupling of haloarenes with various alkenes was successfully performed in the presence of 0.5 mole % Pd(OAc)₂ and 1.0 mole % d-glucosamine as an additive with K₂CO₃ as the optimal base in a mixture of H₂O/iPrOH (φ _r = 2: 1) as the reaction solvent at 80°C after 6 h. d-Glucosamine was found to be an inexpensive, air-stable, easy to available, and efficient additive in palladium-catalyzed Heck reactions of aryl iodides (67–95 % conversion) and bromides (38–72 % conversion).     

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Collision problems of random walks in two-dimensional time

The collision problems of two-parameter random walks are studied. That is, some criteria have been established in terms of the characteristic functions of two or more mutually independent random walks in order to determine if they meet infinitly often in certain restricted time sets.     

An implicit approach to predict the dynamics of granular media

The objective of this study is to present an implicit method to predict the dynamics of granular particles. In the proposed methodology, the dynamics equation of colliding particles are solved implicitly which means the positions of particles at the next time step are also used to compute the next state of the particles. This is in contrast with the explicit approach where only known i.e. past information is used to calculate the new positions. The method is tested in a simple setting where a spherical particle is in continuous movement between two boundary walls. The results show that considerably larger time steps are enabled with the implicit method compared to the explicit method. Future work will compare the overall efficiency of the implicit and explicit methods in more detail. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Real‐Time and Broadband Terahertz Wave Scattering Manipulation via Polarization‐Insensitive Conformal Graphene‐Based Coding Metasurfaces

Here, for the first time, the real‐time and broadband manipulation of terahertz (THz) waves are acquired by introducing a multifunctional graphene‐based coding metasurface (GBCM). The designed structure consists of subwavelength patterned graphene units whose operational statuses can be dynamically switched between two digital states of “0” and “1”. By engineering the spatial distribution of chemical potentials across the GBCM, various scattering patterns having single, two, four, and numerous reflection beams are elaborately achieved just within one planar structure. To compute the far‐field pattern of GBCM, an inverse discrete Fourier transform (IDFT) is established, providing a fast and efficient design method. The proposed GBCM provides a low reflection bellow ?10 dB over a broad frequency band ranging from 1 THz to 1.9 THz. In addition, the metasurface retains its low reflection behavior in a wide range of incident wave angles for both TE and TM polarizations. According to conformal invariance of graphene sheets, the stealth property of GBCM is well preserved while wrapping around a curved object. The proposed technique of real‐time scattering manipulation leads to multifunctional THz devices, opening new routes contributing to numerous applications such as imaging and stealth technology.     

A Combinatorial Model for the Teichmüller Metric

We study how the length and the twisting parameter of a curve change along a Teichmüller geodesic. We then use our results to provide a formula for the Teichmüller distance between two hyperbolic metrics on a surface, in terms of the combinatorial complexity of curves of bounded lengths in these two metrics. Received: October 2005 Revision: April 2006 Accepted: May 2006     

Fourier Series Representation of Low-Lying Eigenfunctions for a Particle on the Torus

A Fourier series method for finding the low-lying eigenfunctions and eigenvalues of the Schrödinger equation for a particle on the surface of a torus is given.     

Crystal structure of form 1, magnetic properties and polymorphism of bis (NN-di-(n-propyl)dithiocarbamato iron (III) iodide

The crystal structure of bis (NN-di(n-propyl)dithiocarbamato iron(III) iodide, Fe^III(S₂CN₆H₁₄)₂I, has been determined by the heavy-atom method and refined toR=0.055 for 3487 reflections withI(hkl)>3I(hkl). The crystals are triclinic,C¯1,Z=8,a=27.644(6),b=19.186(4),c=8.694(2) Å,=87.79(1),=88.72(1), =101.87(2)°. The I-Fe bond lengths are different in the two moleculesA andB in the asymmetric unit, having values of 2.642 Å (2.655) and 2.612 Å (2.634) respectively (libration-corrected values given in parentheses). The measured effective magnetic moment _eff3.89 BM, independent of temperature (93-353K), suggests a spinS of 3/2 with three unpaired electrons for Fe^III.