Influence of convection on microstructure

The influence was studied of convection during directional solidification on the resulting microstructure of eutectics, specifically lead/tin and manganese/bismuth. A theory was developed for the influence of convection on the microstructure of lamellar and fibrous eutectics, through the effect of convection on the concentration field in the melt in front of the growing eutectic. While the theory agrees with the experimental spin-up spin-down results, it predicts that the weak convection expected due to buoyancy will not produce a measurable change in eutectic microstructure. Thus, this theory does not explain the two fold decrease in MnBi fiber size and spacing observed when MnBi-Bi is solidified in space or on Earth with a magnetic field applied. Attention was turned to the morphology of the MnBi-Bi interface and to the generation of freezing rate fluctuations by convection. Decanting the melt during solidification of MnBi-Bi eutectic showed that the MnBi phase projects into the melt ahead of the Bi matrix. Temperature measurements in a Bi melt in the vertical Bridgman-Stockbarger configuration showed temperature variations of up to 25 C. Conclusions are drawn and discussed

Hybrid MCDM Model of ARAS -TOPSIS - GRA for Materials Selection Problem

Since traditional Multi-Criteria Decision Making (MCDM) approaches have become defunct, academics have shifted their attention to developing hybrid MCDM models, which use a combination of two or more MCDM methods to solve decision-making issues. Using Additive Ratio Assessment (ARAS), the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), and Gray Relational Analysis (GRA), the authors of this work aimed to develop unique hybrid MCDM systems. To show how well this hybrid model works, it is applied to a real-world material selection scenario including seven possible materials and seven criteria. Results from this hybrid model are compared to those from other standalone MCDM tools as well as previously published findings based on the same illustrative situation. 3rd Material is the best option, while the 2nd material is the worst option, among these seven choices which are consistent enough to imply such a conclusion. Using many MCDM strategies is recommended since no one strategy can ensure making the best decision. Because of this, the Copeland approach is used to combine the rankings from the 11 methodologies and get a consensus result. The results from the Copeland technique show that the final consensus rank of materials may be different from the rank of the hybrid model and other standalone MCDM tools. As a result, it is crucial to use a multi-pronged approach. Furthermore, the Spearman Correlation Coefficient (SCC) shows that the suggested rankings produced from the different approaches have a significant ranking association with one another

Hybrid MCDM Model of ARAS -TOPSIS - GRA for Materials Selection Problem

Since traditional Multi-Criteria Decision Making (MCDM) approaches have become defunct, academics have shifted their attention to developing hybrid MCDM models, which use a combination of two or more MCDM methods to solve decision-making issues. Using Additive Ratio Assessment (ARAS), the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), and Gray Relational Analysis (GRA), the authors of this work aimed to develop unique hybrid MCDM systems. To show how well this hybrid model works, it is applied to a real-world material selection scenario including seven possible materials and seven criteria. Results from this hybrid model are compared to those from other standalone MCDM tools as well as previously published findings based on the same illustrative situation. 3rd Material is the best option, while the 2nd material is the worst option, among these seven choices which are consistent enough to imply such a conclusion. Using many MCDM strategies is recommended since no one strategy can ensure making the best decision. Because of this, the Copeland approach is used to combine the rankings from the 11 methodologies and get a consensus result. The results from the Copeland technique show that the final consensus rank of materials may be different from the rank of the hybrid model and other standalone MCDM tools. As a result, it is crucial to use a multi-pronged approach. Furthermore, the Spearman Correlation Coefficient (SCC) shows that the suggested rankings produced from the different approaches have a significant ranking association with one another

Alpha-Skew Generalized Normal Distribution and its Applications

The main object of this paper is to introduce a new family of distributions, which is quite flexible to fit both unimodal and bimodal shapes. This new family is entitled alpha-skew generalized normal (ASGN), that skews the symmetric distributions, especially generalized normal distribution through this paper. Here, some properties of this new distribution including cumulative distribution function, survival function, hazard rate function and moments are derived. To estimate the model parameters, the maximum likelihood estimators and the asymptotic distribution of the estimators are discussed. The observed information matrix is derived. Finally, the flexibility of the new distribution, as well as its effectiveness in comparison with other distributions, are shown via an application

On The Experience Of The Arab Open University With The Standard Deviation Method

The Arab Open University (AOU) has adopted the standard deviation method (SDM) as a grading system in replacement of a fixed scale. Adopting SDM was intended to remedy a problem that has resulted from discrepancies between AOU's graduation requirements and those of its partner, UK Open University. This paper aims mainly at investigating whether SDM has served the purpose for which it was selected. A data set of the final letter grades of students enrolled in 18 licensed courses from UK-OU at Kuwait branch was used. These letter grades were analyzed in comparison with the letter grades that would have been assigned to students had the fixed grading scale been utilized. The results of the comparative analysis revealed that SDM resulted in benefiting 39.4% of all students and lowering the letter grades of 10.4% of the students. Despite its positive results, SDM has not contributed significantly to remedying the problem in question. Thus, a case for withholding the D grade while continuing with using SDM was presented