Development of Nano-ZrO2 Reinforced Self-Flowing Low and Ultra Low Cement Refractory Castables

The main goal of this research is to develop high strength high toughness nano-ZrO2 reinforced self flow low cement (5%) and ultra low cement (3 and 1%) castables based on tabular alumina. In processing these castables, the Andreassen model was used to obtain optimum self flow properties in both, low and ultra low castables. The castables thus produced were fired at 110 and 1000, 1300 and 1500oC and the phases obtained were investigated by X-ray diffraction (XRD) including energy dispersive X-ray (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition, the other castable properties were measured such as cold crushing strength (CCS), apparent porosity (AP), bulk density (BD), water absorption (WA), weight loss (WL), zeta potential (ZP), flexural strength (MOR), fracture toughness (KIC), indentation toughness and self-leveling flowability. It was found that 5% cement castables exhibit the highest densification and strength after firing at 1500oC for 3 hours. In addition, castables with various amounts of of nano-ZrO2 and YSZ (yttria stabilized zirconia) (5%, 3%, 1%, 0.1% and 0.01%) were fired at 1300oC in order to improve the flexural strength and fracture toughness. The results indicate that the addition of nano-ZrO2 improves the flexural strength by 20% but it does not have an important effect on the KIC. Apparently, the presence of a relatively high density of pores and cracks overrides the potential benefits associated with the nano-ZrO2 and YSZ reinforcement additions

Improving coverage of rectangular confidence interval

To find a better confidence region is always of interest in statistics. One way to find better confidence regions is to uniformly improve coverage probability over the usual confidence region while maintaining the same volume. Thus, the classical spherical confidence regions for the mean vector of a multivariate normal distribution have been improved by changing the point estimator for the parameterIn 1961, James and Stein found a shrinkage estimator having total mean square error, TMSE, smaller than that of the usual estimator. In 1982, Casella and Hwang gave an analytical proof of the dominance of the confidence sphere which uses the James Stein estimator as its center over the usual confidence sphere centered at the sample mean vector. This opened up new possibilities in multiple comparisonsThis dissertation will focus on simultaneous confidence intervals for treatment means and for the differences between treatment means and the mean of a control in one-way and two-way Analysis of Variance, ANOVA, studies. We make use of Stein-type shrinkage estimators as centers to improve the simultaneous coverage of those confidence intervals. The main obstacle to an analytic study is that the rectangular confidence regions are not rotation invariant like the spherical confidence regions Therefore, we primarily use simulation to show dominance of the rectangular confidence intervals centered around a shrinkage estimator over the usual rectangular confidence regions centered about the sample means. For the one-way ANOVA model, our simulation results indicate that our confidence procedure has higher coverage probability than the usual confidence procedure if the number of means is sufficiently large. We develop a lower bound for the coverage probability of our rectangular confidence region which is a decreasing function of the shrinkage constant for the estimator used as center and use this bound to prove that the rectangular confidence intervals centered around a shrinkage estimator have coverage probability uniformly exceeding that of the usual rectangular confidence regions up to an arbitrarily small epsilon when the number of means is sufficiently large. We show that these intervals have strictly greater coverage probability when all the parameters are zero, and that the coverage probability of the two procedures converge to one another when at least one of the parameters becomes arbitrarily largeTo check the reliability of our simulations for the one-way ANOVA model, we use numerical integration to calculate the coverage probability for the rectangular confidence regions. Gaussian quadrature making use of Hermite polynomials is used to approximate the coverage probability of our rectangular confidence regions for n=2, 3, 4. The difference in results between numerical integration and simulations is negligible. However, numerical integration yields values slightly higher than the simulationsA similar approach is applied to develop improved simultaneous confidence intervals for the comparison of treatment means with the mean of a control. We again develop a lower bound for the coverage probability of our confidence procedure and prove results similar to those that we proved for the one-way ANOVA model. We also apply our approach to develop improved simultaneous confidence intervals for the cell means for a two-way ANOVA model. We again primarily use simulation to show dominance of the rectangular confidence intervals centered around an appropriate shrinkage estimator over the usual rectangular confidence regions. We again develop a lower bound for the coverage probabilities of our confidence procedure and prove the same results that we proved for the one-way mode

Inversion of Randomly Corrugated Surfaces Structure from Atom Scattering Data

The Sudden Approximation is applied to invert structural data on randomly corrugated surfaces from inert atom scattering intensities. Several expressions relating experimental observables to surface statistical features are derived. The results suggest that atom (and in particular He) scattering can be used profitably to study hitherto unexplored forms of complex surface disorder.Comment: 10 pages, no figures. Related papers available at http://neon.cchem.berkeley.edu/~dan

Time-dependent quantum study of H(2S) + FO(2?) ? OH(2?) + F(2P) reaction on the 1 3A? and 13A? states

PubMed ID: 20740560The dynamics of the H(2S) + FO(2?) ? OH( 2?) + F(2P) reaction on the adiabatic potential energy surface of the 13A? and 13A? states is investigated. The initial state selected reaction probabilities for total angular momentum J = 0 have been calculated by using the quantum mechanical real wave packet method. The integral cross sections and initial state selected reaction rate constants have been obtained from the corresponding J = 0 reaction probabilities by means of the simple J-Shifting technique. The initial state-selected reaction probabilities and reaction cross section do not manifest any sharp oscillations and the initial state selected reaction rate constants are sensitive to the temperature. © 2010 Wiley Periodicals, Inc

Quantum dynamics of H(2S)+FO(2?) ? HF( 1?+) + O(3P)reaction on the 1 3A? state

The H(2S)+FO(2?) ? HF(1? +) + O(3P) reaction on the 13A? state potential energy surface is investigated using the quantum mechanical real wave packet method. The state-to-state and state-to-all reaction probabilities for total angular momentum J = 0 have been calculated. The probabilities for J>0 have been calculated by means of the simple J-shifting method. The initial state selected integral cross-sections and rate coefficients have been calculated. The state-to-state, state-to-all reaction probabilities and the reaction cross-section do not manifest any significant oscillations and the initial state selected reaction rate constants are sensitive to the temperature. © 2011 Taylor & Francis