Detecting latent mean differences between non-invariant groups using ordered categorical variables

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Though more and more applied researchers have begun to treat response options as ordered-categorical variables when conducting measurement invariance (MI) testing, little is known about the role of ordered-categorical variables when comparing latent means between groups. Therefore, this study simulated ordered-categorical data to specifically examine the detection of latent mean differences between non-invariant groups across a variety of conditions, including the number of items, population latent mean differences, etc. The purpose of this study was to investigate the relative parameter bias, power rates, and Type I error rates that may arise when ignoring various types of MI in both the configural invariance and metric invariance models. In summary, the most important contributors to relative bias of the true latent mean difference estimates were a) the number of items and the size of the factor loadings in the configural invariance model, b) the size of the factor loading and threshold differences in the metric invariance model that ignored group parameter differences, and c) the number of items in the metric invariance model that addressed the group parameter differences. Thus, in order to reduce the bias in estimating the true latent mean difference between groups, practitioners should identify and address the non-invariance and use a test instrument with more items. The dominant effect on the power to identify whether the latent mean difference was different from 0, in both the configural invariance model and the metric invariance model that ignored true group differences, was the population latent mean difference. In the metric invariance model that addressed the group differences, the most important effects were a) population latent mean differences, and b) loading and threshold differences. When the latent mean difference was at least moderate or the large threshold difference was ignored, the power rate was inflated to be above .90. Applied researchers should know that it will be easier to detect relatively large latent mean differences if both the loading and threshold differences are free to differ between groups. The dominant effect on Type I error rate in the configural invariance model was the number of items. In the metric invariance model that ignored the group parameter differences, the most important effects were a) the size of threshold differences, b) the loading and threshold differences, and c) the number of items. In the metric invariance model that addressed the group parameter differences, the most important effect on Type I error was the number of noninvariant items, which also significantly interacted with the number of items. Often, applied researchers assume their groups are equal, and may not concern themselves with detecting the true latent mean differences. Of course, true population differences cannot be known, so it is recommended that researchers should still conduct a MI analysis. It is especially important to note that in the metric invariance model that addressed group parameter differences, the Type I error rate was below .05. This result suggests that conducting MI testing will help applied researchers detect the true latent mean difference regardless of the magnitude of that difference (i.e., 0, .2 and .5 in this study).

Structural changes of lymph nodes under high calorie diet and melatonin correction

The article presents and analyzes data from an experimental study conducted on white rats in females and males of reproductive age. The purpose of the study to study the morphometric and histological changes in the parenchyma of the lymph nodes of rats under the high-calorie diet (HCD) and with the correction of melatonin. The study was performed on 80 white rats of reproductive age. Microanatomy of the structural components of lymph nodes of white rats under physiological norms was examined in 10 intact animals. Experimental animals are divided into 5 groups. Statistical processing of digital data was performed using “Excel” software and “STATISTICA 6.0” using the parametric method. Eight weeks after HCD, there was a significant decrease in the relative area of the cortical substance in the parenchyma of lymph nodes of white rats of males and females by 10.3 % and 8.3 %, respectively, and an increase in the relative area of the medullary substance by 16.1 % and 13.2 %, respectively, greater than the intact animal group parameter. Corticomedullary index (CMI) decreased by 22.9 % and 19.0 %. After six weeks of HCD and the next six weeks of standard vivarium diet and melatonin administration, the relative area of cortical substance in the parenchyma of lymph nodes of white rats in males and females was 2.0 % and 2.9 %, respectively, greater than the parameters of the intact group of animals. Accordingly, the relative area of the medullary substance is 3.1 % and 4.6 % less than the parameters of the intact group of animals. CMI in both male and male rats was 5.1 % and 7.6 %, respectively, greater than the intact animal group parameter. Under the conditions of melatonin correction, it was found that on the histological preparations of lymph nodes the vein and artery were full-blooded. Empty hemocapillaries with thickened wall are observed. In the paracortical region, the number of high endothelial capillary venules decreases. Thus, long-term administration of melatonin improves the morphometric parameters of the parenchyma of the lymph nodes of rats, restores the morphological structure of the organ.

MHD Casson Fluid Flow over a Stretching Sheet with Entropy Generation Analysis and Hall Influence

The impacts of entropy generation and Hall current on MHD Casson fluid over a stretching surface with velocity slip factor have been numerically analyzed. Numerical work for the governing equations is established by using a shooting method with a fourth-order Runge–Kutta integration scheme. The outcomes show that the entropy generation is enhanced with a magnetic parameter, Reynolds number and group parameter. Further, the reverse behavior is observed with the Hall parameter, Eckert number, Casson parameter and slip factor. Also, it is viewed that Bejan number reduces with a group parameter.

Discharge Coefficient of a Round-Crested Weir

A model experimental study was conducted for the discharge capability of different shapes of the crest of a weir. The flow rate and the head over the weir measured by laboratory experiments were used as two parameters for characterizing the head discharge relationship. Experiments indicated that the head discharge relationship for different radii located upstream and downstream of the crest of the weir had different features. A series of detailed experiments investigated the effects of different upstream rounding radii on the discharge capability when the downstream rounding radius was constant and the round ratio between the radius of the rounded upstream corner to the weir breath in the direction of flow was equal to 1.00. Experimental results showed that the rounded upstream corner could increase the discharge capability. The discharge capability increased as the upstream round ratio became larger and did not change when the round ratio varied from 0.10 to 0.30 and from 0.75 to 1.00 in this experiment. Based on the experimental data distribution, the empirical formula for the discharge coefficient was fitted with the round ratio as the group parameter.

Entropy analysis in moving wavy surface boundary-layer

It is a well-established fact that significant gain in the heat transfer rate can be obtained by altering that flat surface texture of the working body. The most convenient alteration, in view of mathematical handling, is the wavy one. Existing studies reveal that the convective heat transfer phenomenon is affected significantly due to the presence of a solid wavy surface. How does the phenomena of entropy generation is effected due to a wavy surface is the question investigated in this manuscript. The expressions for irreversibility distribution rate, Bejan number, and volumetric entropy generation number have been evaluated by Keller-Box method. The effect of important parameters of interest, such as wavy amplitude, Prandtl number, and group parameter on irreversibility distribution rate, Bejan number and entropy generation number, have been discussed in detail. The study reveals that entropy generation number decreases and irreversibility rate increases by increasing the amplitude of the wavy surface.

Spatial Assessment and the Most Significant Parameters for Drinking Water Quality Using Chemometric Technique: A Case Study at Malaysia Water Treatment Plants

The objectives of this study are to determine the most significant spatial variation of drinking water pollutant and to identify the most significant parameters in each group of physico- chemical parameters (PCPs), Inorganic parameters (IOPs), heavy metals and organic parameters (HMOPs) and pesticides parameters (PPs). The Discriminant Analysis (DA) and One- Way Analysis of variance (ANOVA) showed spatial variation on four station categories and the variance of four group parameter in water drinking quality while principle component analysis (PCA) was carried out to identify the most significant of each water quality parameters base on given group. DA and ANOVA successfully reduced the physico and inorganic pollutants concentration with significant value 98.63% and 96.90%. PCA revealed six most significant drinking water quality parameters for PCPs, nine significant parameters for IOPs, fourteen parameters on HMOPs and four significant of PPs with the p value less than 0.05 (p < 0.05). Therefore, this study proves that chemometric method is the alternative way to explain the characteristic of the drinking water quality and could reduce several parameters and sampling points in the future sampling strategy.

Battery group parameter selection and dynamic simulation of pure electric vehicle

The battery pack is one of the core components of pure electric vehicle, dynamic performance of the whole vehicle is closely related to the matching design of the battery, and is affected by the air resistance coefficient and the windward area of the whole vehicle. The dynamic indicators include maximum driving speed, 0-100km/h acceleration time and climbing grade, the battery parameters are designed and matched before the vehicle design, mainly analyze influence on the vehicle dynamic performance of the types of batteries, air resistance coefficient, windward area by the simulation software ADVISOR, and optimize the combination of these parameters. The results show that the dynamic performance of the vehicle reaches the initial design index and the dynamic performance of the vehicle is improved significantly.

Entropy Generation in Thermally Developing Laminar Forced Convection Through a Slit Microchannel

The issue of entropy generation in laminar forced convection of a Newtonian fluid through a slit microchannel is analytically investigated by taking the viscous dissipation effect, the slip velocity and the temperature jump at the wall into account. Flow is considered to be hydrodynamically fully developed but thermally developing. The energy equation is solved by means of integral transform. The results demonstrate that to increase Knudsen number is to decrease entropy generation, while the effect of increasing values of Brinkman number and the group parameter is to increase entropy generation. Also it is disclosed that in the thermal entrance region the average entropy generation number over the cross section of channel is an increasing function of axial coordinate.