Multinuclear NMR studies of relaxor ferroelectrics

Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN).;93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the 28 possible nBn configurations, isotropic chemical shifts and quadrupole product constants have been extracted from the data. The seven configurations with only larger cations, Mg 2+ and Sc3+ (and no Nb5+) are assigned to the seven observed narrow peaks, whose deconvoluted intensities facilitate quantitative evaluation of, and differentiation between, different models of B-site (chemical) disorder. The completely random model is ruled out and the random site model is shown to be in qualitative agreement with the NMR experiments. to obtain quantitative agreement with observed NMR intensities, the random site model is slightly modified by including unlike-pair interaction energies.;To date, 45Sc studies have not been as fruitful as 93Nb NMR because the resolution is lower in the 45Sc spectra. The lower resolution of 45Sc spectra is due to a smaller span of isotropic chemical shift (40 ppm for 45Sc vs. 82 ppm for 93Nb) and to the lack of a fortuitous mechanism that simplifies the 93Nb spectra; for 93Nb the overlap of the isotropic chemical shifts of 6-Sc and 6-Nb configurations results in the alignment of all the 28 configurations along only seven quadrupole distribution axes.;Finally we present variable temperature 207Pb static, MAS, and 2D-PASS NMR studies. Strong linear correlations between isotropic and anisotropic chemical shifts show that Pb-O bonds vary from more ionic to more covalent environments. Distributions of Pb-O bond lengthes are also quantitatively described. Such distributions are used to examine two competing models of Pb displacements; the shell model and the unique direction model. Only the latter model is able to reproduce the observed Pb-O distance distribution

Application of An Improved Deviation Analysis of Double Mean Data in Student’S Teaching Evaluation Data

This paper analyzes the main problems of College Students’ evaluation of teaching, and proposes a new method to analyze and process the evaluation data.In this paper, we first use the deviation analysis of double mean data method. Through numerical examples, we find an advantage of this method that it can effectively eliminate invalid data in the teaching evaluation data, but the result has a certain deviation from the original teaching evaluation data, and can not directly reflect the specific gap between different teachers or define the maximum and minimum of the teaching evaluation score. In order to objectively reflect the effects of teachers’ classroom teaching, we make a little improvement on the basis of this method in this paper, and give each student a certain weight, so as to get a more real and effective comprehensive evaluation score of each teacher. Numerical examples are given to compare the results of the two methods, and the improved method of deviation analysis of double mean data is more reasonable and effective

The Mechanical Behavior of the Cable-in-Conduit Conductor in the ITER Project

Cable-in-conduit conductor (CICC) has wide applications, and this structure is often served to undergo heat force-electromagnetic coupled field in practical utilization, especially in the magnetic confinement fusion (e.g., Tokamak). The mechanical behavior in CICC is of relevance to understanding the mechanical response and cannot be ignored for assessing the safety of these superconducting structures. In this chapter, several mechanical models were established to analyze the mechanical behavior of the CICC in Tokamak device, and the key mechanical problems such as the equivalent mechanical parameters of the superconducting cable, the untwisting behavior in the process of insertion, the buckling behavior of the superconducting wire under the action of the thermo-electromagnetic static load, and the Tcs (current sharing temperature) degradation under the thermo-electromagnetic cyclic loads are studied. Finally, we summarize the existing problems and the future research points on the basis of the previous research results, which will help the related researchers to figure out the mechanical behavior of CICC more easily

Does Conservatism Alleviates Firms from Under-over Investments in Pakistan?

This study investigates the relationship between timely recognition of losses in financial reporting and investment efficiency, claiming that accounting conservatism improves the investment efficiency through mitigating under (over) investments of firms listed on Pakistan Stock Exchange (PSX). For this purpose, annual reports of 142 firms were selected on sample basis from six different sectors covering the period from 2006 to 2011. We find the existence of conservatism in financial reporting of Pakistani firms which was measured through Basu (1997) model, later to develop hypotheses that conservatism improves investment efficiency by alleviating firms from under and over-investments. The results found that accounting conservatism improves investment efficiency of Pakistani firms at insignificant level; however we found that conservatism restricts firms from over-investments at highly significant level. Furthermore, we find significant relation of CEO duality with investment efficiency and conservatism, which inferred that CEO duality, has influenced to improve investment efficiency in Pakistan. As a first study in context of Pakistan, it plays an important role in academic literature of accounting from developing country. Keywords: Investment efficiency, Conservatism, Corporate Governance, Pakistan

Reinforcement Calculation of Circular and Annular Cross Section

Circular and annular cross-section is one of the more common cross-section forms, such as water towers, piers, etc. But reinforcement calculation of these crosssections is dual, the nonlinearity in width change and the nonlinear stress-strain relationship of concrete and reinforcement, which brings inconvenience to the calculation. In this paper, the corresponding calculation formulas are analytically derived and practical design charts (nomograms) are obtained. Based on stress-stain curve of concrete and reinforcement, five strain distribution regions were constructed. Via strains stress can be determined and then via the stress internal force can be computed, without application of the traditional equivalent rectangular stress block in concrete compression zone. The obtained dimensionless design charts can be applied to all load cases, such as uniform tension, tension with a small and large eccentricity, pure bending, compression with a large and small eccentricity and uniform compression. The calculation by using the design charts is simple and quick

Process monitoring based on orthogonal locality preserving projection with maximum likelihood estimation

By integrating two powerful methods of density reduction and intrinsic dimensionality estimation, a new data-driven method, referred to as OLPP-MLE (orthogonal locality preserving projection-maximum likelihood estimation), is introduced for process monitoring. OLPP is utilized for dimensionality reduction, which provides better locality preserving power than locality preserving projection. Then, the MLE is adopted to estimate intrinsic dimensionality of OLPP. Within the proposed OLPP-MLE, two new static measures for fault detection TOLPP2 and SPEOLPP are defined. In order to reduce algorithm complexity and ignore data distribution, kernel density estimation is employed to compute thresholds for fault diagnosis. The effectiveness of the proposed method is demonstrated by three case studies