Thermal optimization of a totally enclosed forced ventilated permanentmagnet traction motor using lumped parameter and partial computational fluid dynamics modeling

In this study, we present a thermal optimization method using the overall lumped parameter (LP) and partial computational fluid dynamics (CFD) modeling for a 600-kW permanent magnet traction motor developed for high-speed trains. The motor is totally enclosed forced ventilated to achieve high power density, high efficiency, and low maintenance requirements. Considering the electro-magnetic performance, bogie space, and thermal capacity, we propose a ventilation structure with zigzag plates in sector cross-section. We focus particularly on the ventilation channels and propose an overall LP model for thermal optimization, in which the full consideration of the influence of turbulent flow is given by using a partial CFD model. Given the specific critical parameters from the optimization results, we present a complete 3D CFD model of the whole motor to obtain an accurate temperature distribution and the maximum temperature rises in local points. The benefit of zigzag plates is studied extensively using both the LP and the complete CFD models and the results are verified by equivalent thermal experiments under rated operations. Experimental results indicate that the ventilation structure fulfills the normal operational demands of high-speed trains by improving thermal performance by more than 15%. Additionally, we propose an engineering method to estimate iron loss constraint with the complete CFD model to guide the control system design.     

Study on EEG power and coherence in patients with mild cognitive impairment during working memory task

To investigate the features of electroencephalography (EEG) power and coherence at rest and during a working memory task of patients with mild cognitive impairment (MCI). Thirty-five patients (17 males, 18 females; 52～71 years old) and 34 sex- and age-matched controls (17 males, 17 females; 51～63 years old) were recruited in the present study. Mini-Mental State Examination (MMSE) of 35 patients with MCI and 34 normal controls revealed that the scores of MCI patients did not differ significantly from those of normal controls (P＞0.05). Then, EEGs at rest and during working memory task with three levels of working memory load were recorded. The EEG power was computed over 10 channels: right and left frontal (F3, F4), central (C3,C4), parietal (P3, P4), temporal (TS, T6) and occipital (O1, O2); inter-hemispheric coherences were computed from five electrode pairs of F3-F4, C3-C4, P3-P4, T5-T6 and O1-O2 for delta (1.0～3.5 Hz), theta (4.0～7.5 Hz), alpha-1 (8.0～10.0 Hz), alpha-2 (10.5～13.0 Hz), beta-1 (13.5～18.0 Hz) and beta-2 (18.5～30.0 Hz) frequency bands. All values of the EEG power of MCI patients were found to be higher than those of normal controls at rest and during working memory tasks. Furthermore, the values of EEG power in the theta, alpha-1, alpha-2 and beta-1 bands of patients with MCI were significantly high (P＜0.05) in comparison with those of normal controls. Correlation analysis indicated a significant negative correlation between the EEG powers and MMSE scores. In addition, during working memory tasks, the EEG coherences in all bands were significantly higher in the MCI group in comparison with those in the control group (P＜0.05). However, there was no significant difference in EEG coherences between two groups at rest. These findings comprise evidence that MCI patients have higher EEG power at rest, and higher EEG power and coherence during working conditions. It suggests that MCI may be associated with compensatory processes at rest and during working memory tasks. Moreover, failure of normal cortical connections may be exist in MCI patients.     

Virtual and Dynamic Hierarchical Architecture: an overlay network topology for discovering grid services with high performance

This paper presents an overlay network topology called Virtual and Dynamic Hierarchical Architecture (VDHA) for discovering Grid services with high performance. Service discovery based on VDHA has scalable, autonomous, efficient, reliable and quick responsive. We propose two service discovery algorithms. Full Search Query and Discovery Protocol (FSQDP) discovers the nodes that match the request message from all N nodes, which has time complexity O(logN), space complexity O(nvg) (nvg being node numbers of each virtual group), and message-cost O(N), and Domain-Specific Query and Discovery Protocol (DSQDP) searches nodes in only specific domains with time complexity O(nvg), space complexity O(nvg), and message-cost O(nvg). In this paper, we also describe VDHA, its formal definition, and Grid Group Management Protocol.     

Permission-seeking as an agentive tool for transgressive teaching: An ethnographic study of teachers organizing for curricular change

This study describes how a group of teachers in a US public school developed and used permission-seeking moves as strategic and agentic tools to change their school curriculum and challenge norms of teaching. Although the notion of asking permission is typically considered disempowering in educational contexts, this study demonstrates that certain forms of permission-seeking (and giving) can foster collaboration and teacher agency across multiple constituent groups in a school community. This 2-year ethnographic study occurred within a context of a test-driven teaching environment with shifting student racial and economic demographics. Our research offers a reconceptualized theory of permission within a teacher agency framework and new possibilities for practitioners to engage in transgressive teaching with diverse learners in hyper-standardized teaching contexts.     

Neo-institutional analysis on response patterns of pilot schools

This study examines response patterns of pilot schools in the neo-institutional perspective to make improvements on the pilot school systematic framework. In order to achieve this goal, in-depth interviews were conducted to obtain qualitative data. The results show that pilot schools either (a) actively adopt or (b) ceremonially adopt an education policy through the process of implementation and internalization. Among the sampled schools, only one school showed active adoption, and the other three schools pursued ceremonial adoption. Each school’s response varies according to the internalization level, technical core focus, institutional pressure, and reception of legitimacy. The findings of this study suggest that in order to operate the pilot school ‘as a policy school,’ the school members should truly understand the concept of the policy and actively practice the internalized value through various activities and programs. Furthermore, this study calls for a greater attention to the institutional factors and local contexts.     

Akademisches versus schulbezogenes Fachwissen – ein differenzierteres Modell des fachspezifischen Professionswissens von angehenden Mathematiklehrkräften der Sekundarstufe

Educational research has introduced different models for the professional knowledge of (pre-service) teachers. Existing studies show major differences regarding the construct of content knowledge, which is often conceptualized based on school subject knowledge and varies with respect to academic content knowledge. The latter indicates that the question of what content knowledge teachers need has yet to be resolved. This question is particularly relevant from the perspective of teacher education at universities, since pre-service teachers for secondary schools are usually taught academic content knowledge. In this article we suggest a model of the discipline-specific teacher knowledge that includes pedagogical content knowledge (PCK) alongside two constructs of content knowledge: academic content knowledge (CK) and school-related content knowledge (SRCK). Findings from two studies for the subject area mathematics confirm that the components are empirically separable and that the three-dimensional model is superior to the two-dimensional model (CK, PCK). Moreover, the new construct SRCK holds potential for the investigation of the knowledge of pre-service teachers.     

Teaching for Creativity by Science Teachers in Grades 5–10

This classroom observation study explored how science teachers (N = 22) teach for creativity in grades 5–10 in Oman. We designed an observation form with 4 main categories that targeted the instructional practices related to teaching for creativity: questioning strategy, teacher’s responses to students’ ideas, classroom activities to support creativity, and whole-lesson methods that foster creativity. An open-ended survey was also designed to explore participants’ justifications for their instructional decisions and practices. The findings indicate that the overall level of teaching for creativity was low and that participants’ performance was the highest for teacher’s responses to students’ ideas category and the lowest for classroom activities to support creativity category. We observed that a teacher-centered approach with instructional practices geared toward preparing students for examinations was dominant and that these science teachers were bound to the textbook, following cookbook-style activities. Participants believed that they did not have enough time to cover the content and teach for creativity and that they were not prepared to teach for creativity. Based on these findings, we recommend that programs be developed to prepare science teachers to teach for creativity.     

Weighing designs to detect a single counterfeit coin

In this article, we discuss at length a combinatorial problem which has been of historic interest. It has appeared as a puzzle in several different versions with varying degrees of difficulty. It can be simply stated as follows: We are given a number of coins which are otherwise identical except that there may be at most one fake coin among them which is either slightly heavier or slightly lighter than the other genuine coins. Using only a two-pan weighing balance, we must devise a weighing scheme to identify the counterfeit coin and determine whether it is heavier or lighter (or declare that all coins are normal). We construct both sequential and non-sequential (that is, simultaneously declared) weighing plans for any given number of coins containing at most one fake coin using the minimum number of weighings needed.