Preparation and crystallization of chromium-based amorphous alloys

The glass formability of the Cr₇₂ (B, Si, C)₂₅Al₃ system has been investigated. Samples were prepared by rapid quenching from the melt by the melt spinning technique. Of the compositions investigated, only Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇₁ C₁₇Si₈Al₃ formed fully amorphous alloys. These showed crystallization temperatures of 997 and 990 K, respectively, among the highest reported for transition metal-metalloid amorphous alloys. The crystallization products have been found to be Cr₇C₃ and Cr₃(Si, B) for Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇C₃ and Cr₃Si for Cr₇₂C₁₇Si₈Al₃. The effects of substituting iron in place of chromium in Cr₇₂C₁₇Si₈AI₃ have been investigated. For up to 20 at% Fe the crystallization products are (Cr, Fe)₇C₃ and Cr₃Si. An alloy with 30 at% Fe crystallizes into (Cr, Fe)₇C₃ and hexagonal Cr-Si-C.     

Averaging correlation coefficients: Should Fisher's z transformation be used?

Averaging correlations leads to underestimation because the sampling distribution of the correlation coefficient is skewed. It is also known that if correlations are transformed by Fisher's z prior to averaging, the resulting average overestimates the population value of z. The behavior of these procedures for averaging correlations was investigated via Monte Carlo simulation, both in terms of bias (under- and overestimation) and precision (standard errors). It was found that average z backtransformed to r is less biased positively than average r is biased negatively. The standard error of average r was smaller than that of average z when the population correlation was small; however, the reverse was true when the population correlation exceeded .5. Regardless of sample size, back transformed average z was always less biased; therefore, the use of the z transformation is recommended when averaging correlation coefficients, particularly when sample size is small. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Data transformation, power, and skew: A rejoinder to Games.

The present authors (see record 1982-27158-001) concluded that if a transformation can be found that will minimize skew while tending to equate group variances, the use of that transformation will increase power of the F test. P. A. Games (see record 1983-20171-001) challenges this conclusion and presents what he considers to be counterexample. That counterexample is shown to be flawed; however, it aptly demonstrates the misconceptions that may arise with respect to the issue of data transformation, skew, and power. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frequency tracking in power networks in the presence of harmonics

Three new techniques for frequency measurement are proposed. The first is a modified zero-crossing method using curve fitting of voltage samples. The second method is based on polynomial fitting of the discrete Fourier transform (DFT) quasi-stationary phasor data for calculation of the rate of change of the positive sequence phase angle. The third method operates on a complex signal obtained by the standard technique of quadrature demodulation. All three methods are characterized by immunity to reasonable amounts of noise and harmonics in power systems. The performance of the proposed techniques is illustrated for several scenarios by computer simulation     

Effect of ovarian secretions on female behavioral potentiality in the rat.

Measured receptivity in female Sprague-Dawley rats ovariectomized at 5 ages, in neonatally gonadectomized females and males implanted with ovaries, and in neonatally castrated males injected with estradiol benzoate (EB) or oil. Mean receptivity, darting, and lordosis scores were higher during the 1st 4-5 mating tests in females and males having ovaries prepubertally. In amounts greater than .01 mg., EB inhibited female behavior. Even after ovariectomy, body weight was lightest in males and females having ovaries for 60 days. Progesterone and EB decreased weight gain faster in Ss gonadectomized prepubertally. Results indicated that physiological amounts of ovarian hormones, while not necessary for development of female potentiality, permanently influence it by modifying rate of utilization of estrogen circulating during adulthood. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural and electrochemical studies of (SnxCo1−x)60C40 alloys prepared by mechanical attriting

Using a vertical-axis attritor, samples of (Sn_xCo_1−x)₆₀C₄₀ for 0 ≤ x ≤ 0.7 have been prepared in increments of Δx = 0.1. The effect of Sn content on the structure and performance of the Sn-Co-C nanocomposites was examined by X-ray diffraction (XRD), ¹¹⁹Sn Mössbauer effect spectroscopy and electrochemical methods. XRD shows a diffraction pattern characteristic of a nanostructured material having amorphous CoSn grains in a carbon matrix for x = 0.5. Broad Bragg peaks of Co₃C, SnCo₃C_0.7 and CoSn₂ were observed for samples with 0 ≤ x ≤ 0.1, 0.1 ≤ x ≤ 0.4 and 0.5 < x ≤ 0.7, respectively. ¹¹⁹Sn Mössbauer effect spectroscopy shows the presence of an amorphous CoSn component in samples with 0.3 ≤ x ≤ 0.6. Samples with a large amount of the SnCo₃C_0.7 phase showed small capacity for lithium. Therefore, SnCo₃C_0.7 is best described as an inactive phase. The sample with x = 0.7 shows the highest specific capacity (about 600 mAh/g) of all samples prepared but exhibited poor capacity retention after cycle 45. Excellent charge-discharge capacity retention, reasonable specific capacity (>450 mAh/g) along with stable differential capacities were observed for samples near x = 0.5.     

Analysis of variance with ipsative measures.

Measures with more than 1 score per participant, when the total for each participant equals the same constant, are said to be ipsative. Ipsativity occurs when data are percentages, with each participant's total equal to 100%, or when data are ranks, with each participant's total equal to the sum of the ranks. When ipsative measures are analyzed with analysis of variance (ANOVA), certain sums of squares equal 0, and the average intercorrelation among measures is negative. These characteristics of ipsativity may result in violations of ANOVA assumptions, producing an inflated Type I error rate and affecting power. The purpose of this Monte Carlo study was to empirically examine the extent to which ANOVA is affected by ipsative data. Findings indicated that, with few exceptions, ANOVA worked quite well with ipsative data. Not only were Type I error rates well preserved, but power was nearly equivalent to that with nonipsative data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Skew and internal consistency.

The effects of skew on the standardized item alpha were examined with Monte Carlo techniques. Alphas computed from normal variables were compared with alphas from lognormal variables, ranks, and skewed versus normal Likert-type variables. The extent and direction of skew were varied, as was the size of the population interitem correlation (rho), the number of items, and the number of categories for Likert-type variables. Because the average interitem correlation affects alpha and skew affects the average interitem correlation, the effect of skew on the average interitem correlation also was examined. Results indicated that skew decreased the average interitem correlation and produced small decreases in alpha that were largest when skew was large, rho was small, items were skewed in opposite directions, and there were fewer items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)