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231.
William R. Doyle 《Research in higher education》2009,50(1):52-72
The impact of increased academic intensity on transfer rates from community colleges to 4-year institutions has been estimated only from observational data, with the possibility of selection bias. This study uses matching estimators to overcome possible selection bias and estimate the causal impact of increased academic intensity on transfer rates. Using student unit record data from Tennessee for the years 1995 through 2004, I find that taking 12 or more credit hours increases the probability of transfer from between 11% and 15%.
相似文献
| William R. DoyleEmail: |
232.
The relation between types of tasks and the mathematical reasoning used by students trying to solve tasks in a national test situation is analyzed. The results show that when confronted with test tasks that share important properties with tasks in the textbook the students solved them by trying to recall facts or algorithms. Such test tasks did not require conceptual understanding. In contrast, test tasks that do not share important properties with the textbook mostly elicited creative mathematically founded reasoning. In addition, most successful solutions to such tasks were based on this type of reasoning. 相似文献
233.
Heinz-Hermann Krüger Catharina Keßler Ariane Otto Anne Schippling 《Zeitschrift für Erziehungswissenschaft》2014,17(3):221-241
Against the backdrop of the recent political discourse on elite and excellence in the German education system, this paper examines how such constructions manifest themselves in programmatic concepts of schools and in the orientations of their pupils and their peers. They are reconstructed on the basis of a qualitative research project on educational careers of young people. This paper focuses on pupils and their peers at an elite school of sports and an international school. Firstly, the state of research on those types of school as well as on educational careers of their pupils will be presented. Secondly, the theoretical reference points and the methodological design of the study will be introduced. At the core of the paper is the analysis of the education related orientations of selected cases of young people and their peers: How do they position themselves towards elite and excellence in their individual and collective orientations and how is this relevant for processes of distinction and coherence building in the groups? In the resuming part of the paper, the results will be summarised and related to the state of research and the scientific discourse on elite and excellence. 相似文献
234.
Denise Nacu Caitlin K. Martin Nichole Pinkard 《Educational technology research and development : ETR & D》2018,66(4):1029-1049
With the growing emphasis on developing 21st century skills among today’s youth, there is continued optimism about the possibilities granted by increasing access to networked technologies, particularly for encouraging youth to pursue their interests and take ownership of their learning. Yet, research demonstrates the importance of adult support in realizing the promise of achieving these outcomes. Designers of such systems are thus faced with the need to create youth-centered spaces that also provide adult facilitation of learning. This paper presents an adaptation of the traditional heuristic evaluation method which provides designers of online learning systems with a holistic view of how adult learning support is enabled across the system. We describe how the heuristic evaluation method was adapted, and through a case example analyzing one online social learning system used in a middle school context, we demonstrate how it can be used to help identify areas for improvement and promising areas for further research. We also present a framework of heuristics which reflect specific educator learning support roles that have been found to be important for youth learning, particularly for supporting 21st century skills. This work contributes a novel heuristic evaluation method that can help designers of online learning platforms attend not only the experiences of learners, but also to how educators are enabled to support their learning. 相似文献
235.
In this work, synchronization of chaotic Colpitts circuits, using adaptive controllers to combat circuit parameter mismatches and channel distortions, is studied by numerical simulations. Synchronization errors caused by different main circuit components are compared, and compensation for time-constant and time-varying circuit parameter mismatches is demonstrated. Different kinds of channel distortions, including time-constant and time-varying channel attenuation, Additive White Gaussian Noise (AWGN) are all investigated by numerical simulations and discussed. Simulation results indicated that the synchronization performance of chaotic Colpitts circuits can be greatly improved by applying adaptive controllers when parameter mismatches and channel attenuation are considered as time-constant or time-varying, but have no obvious enhancements regarding the effect on AWGN channel. 相似文献
236.
Of several formulas for calculating bursting pressure of mild steel vessel, the Faupel formula is the most famous one. In fact, Faupel formula is conservative in calculating mild steel pressure. Based on hundreds of bursting experiments on mild steel pressure vessels such as Q235(Gr.D), 20R(1020) and, after statistically analyzing data on bursting pressure, it was found that the Faupel formula had some errors in calculation. The authors derived a more approximate modified formula from the data, which proved more general after examining the data on other mild steel pressure vessels with different diameters and shell thickness. 相似文献
237.
HAO Qing-duo WANG Yan-lei ZHANG Zhi-chun OU Jin-ping 《浙江大学学报(A卷英文版)》2007,8(9):1356-1365
Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embedded in concrete. Two kinds of conventional reinforcing rebars were also studied for comparison. Each rebar was embedded in a 150 mm concrete cube,with the embedded length being four times the rebar diameter. The experimental parameters were the rebar type,rebar component,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the bond strength of GFRP rebars was about 13%～35% lower than that of steel rebars. The bond strength and bond-slip behavior of the specially machined rebars varied with the rebar type,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Using the results,design recom-mendations were made concerning optimum rib geometries of GFRP ribbed rebars with superior bond-slip characteristics,which concluded that the optimal rib spacing of ribbed rebars is the same as the rebar diameter,and that the optimal rib height is 6% of the rebar diameter. 相似文献
238.
LIU Dong WANG Fei HUANG Qun-xing YAN Jian-hua CHI Yong CEN Ke-fa 《浙江大学学报(A卷英文版)》2007,8(11):1853-1857
Radiative imaging of combustion flame in furnace of power plant plays an increasingly important role in combustion diagnosis. This paper presents a new method for calculating the radiative imaging of three-dimensional (3D) combustion flame based on Monte Carlo method and optical lens imaging. Numerical simulation case was used in this study. Radiative images were calculated and images obtained can not only present the energy distribution on the charge-coupled device (CCD) camera target plane but also reflect the energy distribution condition in the simulation furnace. Finally the relationships between volume ele- ments and energy shares were also discussed. 相似文献
239.
JIANG Zhi-chao DOI Yasuaki ZHANG Shu-you 《浙江大学学报(A卷英文版)》2007,8(9):1414-1421
Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine. 相似文献
240.
ZHANG Ji-gao 《浙江大学学报(A卷英文版)》2007,8(3):361-369
Particle pollution in air, also sometimes known as fine dust contamination, may cause electric contact failure. Recent research further proved that the fine particle is becoming a major disruption of the electronic connectors in signal transmission system. This paper specifies the connector contact in mobile phone application. To study the contact failure of mobile phone, a series of inspections and analytical research methods are introduced. Special features that cause the contact failure are summarized. Particle accumulation is the main problem; organic material such as lactates from sweat of the human body may act as adhesives to stick the separate particles together and make them adhere on the contact surface; chemical properties of dust cause serious local corrosion. The corrosion products may trap the particles and firmly attach on the contact surface; micro motion frequently occurs at the contact interface. Hard particle can be embedded into the surface, and soft particle could be squeezed and inserted into the contact; silicon compounds in dust play the most important role in forming high resistance regions that lead to failure; deposition of particles depends on the amount of materials, static electricity attracting force and gravity force applied on the particles. Current dust test can hardly reflect the serious contact failure. It is difficult to simulate the complexity of contact failure caused by particle contamination. Thus alternative ways of simulation experiment and improvement of contact reliability are proposed. 相似文献