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Muhammad Khalifa 《International journal of qualitative studies in education》2013,26(2):259-282
This study examines Black student and parental perceptions of exclusionary practices of Black school principals. I ask why students and parents viewed two Black principals as contributing to abusive and exclusionary school environments that marginalized Black students. After a two-year ethnographic study, it was revealed that exclusionary behaviors toward Black students—which was viewed as “abuse” by students and parents—was a reproduction of the district's racism, and thus adds new considerations for discussions around the value of racially-like (i.e., all Black) educators and students. Parents perceived these two Black principals as dealing more harshly and rigidly with the Black students and their families; moreover, analysis of the interview data revealed that the principals rejected the cultural and social capital, and proclivities of Black students, and blamed Black students for their lower achievement and unique behaviors. I draw significant attention to the larger contexts of White supremacy and racism as I examine how Black principals negotiate their own roles, how they understand their own treatment of urban Black students, and how they are (knowing or unknowingly) reproducing oppressive practices of White supremacy on Black students in school. 相似文献
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Khalifa S. Al-Jabri 《Journal of The Franklin Institute》2011,348(7):1695-1716
This paper presents an overview of the modelling and simulation methods, which have recently been developed in the literature to simulate the behaviour of the beam-to-column joints at elevated temperature. These include curve-fit models, component-based models, finite element models, and artificial neural network models. The study concluded that the various numerical modelling methods can be used reliably to predict the behaviour of joints at elevated temperature to an acceptable degree of accuracy. 相似文献
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Hesham Khalifa Sherif A El-Safty Abdullah Reda Mohamed A Shenashen Alaa I Eid 《国家科学评论(英文版)》2020,7(5):863
We report on low-cost fabrication and high-energy density of full-cell lithium-ion battery (LIB) models. Super-hierarchical electrode architectures of Li2SiO3/TiO2@nano-carbon anode (LSO.TO@nano-C) and high-voltage olivine LiMnPO4@nano-carbon cathode (LMPO@nano-C) are designed for half- and full-system LIB-CR2032 coin cell models. On the basis of primary architecture-power-driven LIB geometrics, the structure keys including three-dimensional (3D) modeling superhierarchy, multiscale micro/nano architectures and anisotropic surface heterogeneity affect the buildup design of anode/cathode LIB electrodes. Such hierarchical electrode surface topologies enable continuous in-/out-flow rates and fast transport pathways of Li+-ions during charge/discharge cycles. The stacked layer configurations of pouch LIB-types lead to excellent charge/discharge rate, and energy density of 237.6 Wh kg−1. As the most promising LIB-configurations, the high specific energy density of hierarchical pouch battery systems may improve energy storage for long-driving range of electric vehicles. Indeed, the anisotropic alignments of hierarchical electrode architectures in the large-scale LIBs provide proof of excellent capacity storage and outstanding durability and cyclability. The full-system LIB-CR2032 coin cell models maintain high specific capacity of ∼89.8% within a long-term life period of 2000 cycles, and average Coulombic efficiency of 99.8% at 1C rate for future configuration of LIB manufacturing and commercialization challenges. 相似文献
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Mohammad Abd-Alrahman Mahmoud Abushariah Raja Noor Ainon Roziati Zainuddin Assal Ali Mustafa Alqudah Moustafa Elshafei Ahmed Othman Omran Khalifa 《Journal of The Franklin Institute》2012,349(7):2215-2242
This paper presents our work towards developing a new speech corpus for Modern Standard Arabic (MSA), which can be used for implementing and evaluating Arabic speaker-independent, large vocabulary, automatic, and continuous speech recognition systems. The speech corpus was recorded by 40 (20 male and 20 female) Arabic native speakers from 11 countries representing three major regions (Levant, Gulf, and Africa). Three development phases were conducted based on the size of training data, Gaussian mixture distributions, and tied states (senones). Based on our third development phase using 11 hours of training speech data, the acoustic model is composed of 16 Gaussian mixture distributions and the state distributions tied to 300 senones. Using three different data sets, the third development phase obtained 94.32% and 8.10% average word recognition correctness rate and average Word Error Rate (WER), respectively, for same speakers with different sentences (testing sentences). For different speakers with same sentences (training sentences), this work obtained 98.10% and 2.67% average word recognition correctness rate and average WER, respectively, whereas for different speakers with different sentences (testing sentences) this work obtained 93.73% and 8.75% average word recognition correctness rate and average WER, respectively. 相似文献
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In different areas of engineering, mathematical models are used to describe real life phenomena and experiments are conducted to validate them. It is common that these models may contain a number of parameters that cannot be measured directly or calculated. Thus, parameter estimation is an important step in the process of modeling based on empirical data of the system.In the control system’s literature, one can find considerable amount of research in the area of system parameters identification. Most of these techniques are based on minimizing the estimation error in some statistical framework such as least square error based methods. In most cases, using these techniques, one can prove the uniform exponential stability of the state and parameter estimation error, but the convergence rate can be too low. However, when designing control systems, knowledge of unknown immeasurable (or even time varying) parameters might be crucial for the operation of the controller and thus have to be accurately estimated with a desired rate of convergence. In this paper, we demonstrate a way to provide an estimation technique with tunable convergence rate using sliding mode with linear operators such as time delay. 相似文献
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Muhammad A. Khalifa 《The Urban Review》2011,43(5):702-727
This study investigates the relationship between low teacher expectations and principal behavior. The researcher investigated
why some teachers seem to acquiesce, or make deals and ‘give in,’ to student disengagement. After a two-year ethnographic
study in an alternative school for at-risk Black students, the author found that White teachers are more likely than Black
teachers to engage in deal-making with students, whereby Black students were allowed to academically and socially disengage.
However, another finding of this research was that the school leader—armed with a vision to combat racism and advocate for
children—imposed on his staff a policy that required them to socially and academically engage these Black, at-risk students.
Implications for school leaders and teachers of at-risk, alternative school children are presented. 相似文献
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Yan Yu Jin-Xing Hao Xiao-Ying Dong Mohamed Khalifa 《International Journal of Information Management》2013
Although it is a widely held belief that social capital facilitates knowledge sharing among individuals, there is little research that has deeply investigated the impacts of social capital at different levels on an individual's knowledge sharing behavior. To address this research gap, this study combines a multilevel approach and an optimal network configuration view to investigate the multilevel effects of social capital on individuals’ knowledge sharing in knowledge intensive work teams. This study makes a distinction between the social capital at the team-level and that of social capital at the individual level to examine their cross-level and direct effects on an individual's sharing of explicit and tacit knowledge. A survey involving 343 participants in 47 knowledge-intensive teams was conducted for testing the multilevel model. The results reveal that social capital at both levels jointly influences an individual's explicit and tacit knowledge sharing. Further, when individuals possess a moderate betweenness centrality and the whole team holds a moderate network density, team members’ knowledge sharing can be maximized. These findings offer a more comprehensive and precise understanding of the multilevel impacts of social capital on team members’ knowledge sharing behavior, thus contributing to the social capital theory, as well as knowledge management research and practices. 相似文献
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Marcy P. Driscoll Nancy Gilbert Khalifa Bakhouch 《Performance Improvement Quarterly》1997,10(4):17-30
Semiotics, or the study of signs, has much to offer the field of performance technology. In this paper, we examine the process of analysis and illustrate how semiotic theory can inform the way a performance problem is approached, analyzed, and understood. We argue that a semiotic approach to analysis can reveal meanings that would otherwise remain hidden and which can provide valuable information for the design of appropriate interventions. Semiotics is not so much a new theory of performance technology as much as it provides “value added” to current Human Performance Technology processes. 相似文献
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