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In this study, we develop a finite element model to examine the oblique soccer ball bounce. A careful simulation of the interaction between the ball membrane and air pressure in the ball makes the model more realistic than analytical models, and helps us to conduct an accurate study on the effect of different parameters on a bouncing ball. This finite element model includes a surface-based fluid cavity to model the mechanical response between the ball carcass and the internal air of the ball. An experimental set-up was devised to study the bounce of the ball in game-relevant impact conditions. Ball speed, angle, and spin were measured before and after the bounce, as well as ball deformation and the forces during the impact. The finite element model has been validated with three different sets of data, and the results demonstrate that the finite element model reported here is a valuable tool for the study of ball bounce. After validation of the model, the effect of the friction coefficient on soccer ball bounce was studied numerically. Simulation results show that increasing the friction coefficient may result in reversal of the horizontal impact force. 相似文献
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This paper introduces a new way of evaluating instructional strategies by using computers. Two basic theories, instructivism and constructivism, are discussed and critically evaluated in terms of their effectiveness in conceptual learning. Despite the current popularity of constructivism, the radical form of it is criticized in this paper. The advantages and limitations of these two approaches, especially the radical forms of constructivism, are outlined. After borrowing some ideas from other effective conceptual change models, an integrative model for conceptual learning (the Inventive Model) is introduced. Two versions of multimedia physics software are developed by the authors. The first version is based on the Inventive Model and the second version based on a radical constructivist model. The effectiveness of the Inventive Model was compared with the radical constructivist approach and conventional science instruction. Students' log files were analyzed to investigate the nature and the processes of the conceptual change. A conceptual test and a knowledge test were used to compare the groups. The quantitative results showed the superiority of the Inventive Model over the other models in conceptual learning and the superiority of conventional instruction in learning the basic knowledge. The qualitative analysis showed that only the Inventive Model lead to coherent conceptual learning. It was concluded that the process of conceptual change is gradual and continuous. Analysis of students' log files revealed no moments of dramatic change in students' conceptions. 相似文献
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Ali Rezaei 《Gender and education》2012,24(4):393-409
Official statistics from several resources in Iran indicate that female enrollment and achievement in Iranian universities has recently exceeded that of male students. Despite the fact that a religious government has been ruling the country for three decades, and despite many regulations against women, Iranian women have managed to overcome social, cultural, and political barriers. They have also been able to pass a highly competitive entry exam to enter the university at higher performance rates than male students. In this study it was proposed that this increasing enrollment and graduation rate might be attributed to their gender-based self-confidence and their self-efficacy. The results showed that female students scored higher on collective, gender-based self-confidence but their personal feeling about their gender was more negative and their general self-efficacy was not different from the self-efficacy of male students. 相似文献
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Abdolmotalleb Rezaei Ali Asadi Ahmad Rezvanfar Hajar Hassanshahi 《International Information and Library Review》2009,41(3):163-172
Information system success has been widely discussed in the past two decades. As systems and technologies are being improved and developed, discussions on their effectiveness and evaluation on their success have been continuously debated by researchers, scholars and practitioners throughout the years. Besides the major concern of IS effectiveness, factors influencing IS effectiveness are also important. One of these factors is the organizational factor. Using perceptual measures, this study aims to investigate the influence of organizational factors on MIS success. Survey questionnaires were gathered from 132 Extension Managers from Iran's Agricultural Extension Providers. Seven items were identified to influence MIS success. They are IS department structure, top management support, management style, managerial IT knowledge, goal alignment, resources allocation and IS infrastructure. The study also identified five MIS success dimensions; systems quality, information quality, perceived Ease of use, organizational impact and individual impact. The study found that the MIS success variables are significantly and highly correlated. The study also found all the organizational factors are significantly correlated to the five IS success factors investigated; the system quality, information quality, perceived ease of use, organizational impact and individual impact. Multiple regression analyses also found goal alignment as the highest predictor of IS success, followed by IS department structure, IS infrastructure and management style. 相似文献
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Yousef Rezaei Chianeh Rashmi Manjunath Krishnananda Prabhu Donald Fernandes M. Vidyasagar Asha Kamath 《Indian journal of clinical biochemistry : IJCB》2014,29(2):238-241
Oral squamous cell carcinoma is one of the most common malignancies recognized. Biomarkers which can predict presence of cancer and its progression can help in better management of these disorders. Over production of lipid peroxidation byproducts and disturbances in antioxidant defense system have been implicated in the pathogenesis of several diseases including oral cancer. Studies have shown a correlation of butyrylcholinesterase (BChE), with tumourigenesis, cell proliferation and cell differentiation. Earlier we have observed a significant elevation in plasma BChE and protein thiols in oral cancer patients which correlated well with stages of cancer. As it was not clear whether the above markers will be altered in saliva of oral cancer patients this study was undertaken. Institutional Ethics Committee gave permission to carry out this study. Total of 55 subjects comprising healthy controls (n = 30) and biopsy proven oral cancer patients (n = 25) consented to participate in this study. Salivary samples from cases were taken before any definitive treatment. Protein thiols and BChE were estimated in salivary samples using validated assay methods. Oral cancer patients had a significant increase in pre-treatment salivary BChE levels (p ≤ 0.001) and a significant decrease (p ≤ 0.001) in salivary thiols as compared to respective values in controls. Salivary protein thiols and BChE may have a role in pathophysiology of oral cancer. Saliva can be used as a potential non-invasive screening tool in oral cancer patients. 相似文献
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This experimental project investigated the reliability and validity of rubrics in assessment of students’ written responses to a social science “writing prompt”. The participants were asked to grade one of the two samples of writing assuming it was written by a graduate student. In fact both samples were prepared by the authors. The first sample was well written in terms of sentence structure, spelling, grammar, and punctuation; however, the author did not fully answer the question. The second sample fully answered each part of the question, but included multiple errors in structure, spelling, grammar and punctuation. In the first experiment, the first sample was assessed by participants once without a rubric and once with a rubric. In the second experiment, the second sample was assessed by participants once without a rubric and once with a rubric. The results showed that raters were significantly influenced by mechanical characteristics of students’ writing rather than the content even when they used a rubric. Study results also indicated that using rubrics may not improve the reliability or validity of assessment if raters are not well trained on how to design and employ them effectively. 相似文献
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Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Qu), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (Lw/B). Apart from Qu, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands when Lw/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity. 相似文献
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The purpose of this study is to examine the impact of perceived brand orientation, intercultural friendship, and university reputation on international students’ course satisfaction and continuance behavioral intention towards the higher education in Malaysia. A total of 348 questionnaires, administered on international students, were collected to empirically test the research model using partial least squares path modeling approach, a structural equation modeling technique for the assessment of measurement and structural model. The empirical results imply that perceived brand orientation and university reputation positively influence course satisfaction and course continuance behavioral intention, while intercultural friendships influences course continuance intention but not course satisfaction. The implications and limitations of research are discussed in the following sections. 相似文献
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A study of the interaction between ropranolol and NSAIDs in protein binding by gel filtration method
Rezaei Zahra Raissi Ahmad Moshtaghi S. Ali Asghar Asadipour Ali Khabnadideh Soghra 《Indian journal of clinical biochemistry : IJCB》2006,21(1):121-125
Drug protein binding phenomena can lead to some interesting drug—drug interactions when one drug displaces another in the
binding site. Studies of protein binding are conducted by several methods including equilibrium dialysis, ultra-filtration
and chromatographic methods. Gel filtration is a simple chromatographic method in protein binding studies. Propranolol binds
to plasma proteins by 90%–95% in circulation system and other drugs with high protein binding may displace it. In this study
protein binding of propranolol has been studied using gel filtration to Bovine Serum Albumin (BSA) alone and in the presence
of Acetyl salicylic acid (ASA), Indomethacin and mefenamic acid has been studied using gel filtration method. The results
indicated that ASA decreased protein binding of propranolol by 20% to BSA and other drugs did not displace propranolol from
the binding site. Therefore, ASA may alter pharmacological effects of propranolol. 相似文献