一种新型的复合式开关稳压电源的设计

本文给出一种实用的输出精密的复合式开关稳压电源设计方法.给出具体的设计电路和实际中应注意的一些事项.该电源具有重量轻、体积小、效率高等优点,是一种较为理想实用的精密稳压电源.     

耗散颗粒动力学模拟油水体系相行为

用耗散颗粒动力学模拟方法（Dissipative Particle Dynamics,DPD）研究了油分子量、油分子浓度、剪切及表面活性剂SDS（十二烷基硫酸钠）对油水体系相行为的影响.发现随着油分子量的增加,油水界面张力增加;随着油浓度的增加,体系由最初的水包油聚集状态逐渐演变为油水分层状态.随着剪切速率的加大,油滴被逐渐拉长,最后断裂;表面活性剂加入油水体系后,以亲水头基伸入水相、疏水尾巴伸入油相的方式分布在油水界面上.     

中药寒热相关药性和抑制脂肪酸合酶能力关系的探索

测定了药典中106味温热性中药和119味寒凉性中药对脂肪酸合酶的抑制水平,发现温热药中对该酶强抑制的频数高于寒凉药约38%. 进一步分析发现,温热药中的温里和散内寒药中强抑制药的频数大幅提高,而寒凉药中的清热泻火、明目、清虚热药中强抑制药的频数则进一步降低,差异均具有显著性. 综合以上结果提出,直接影响能量代谢系统、造成能量代谢率变化是形成中药的寒热药性的因素之一.     

WRF土地利用/覆被数据优选及其在城市热岛模拟中的应用

针对WRF模式自带土地利用数据更新不及时及精度不高的现象,本文将国内外主要土地利用数据（MODIS2012、GLC2009、GLC2000）与WRF模式耦合进行土地利用数据的优选,并将优选数据初步应用于枣庄城市热岛模拟中。结果表明：①MODIS2012数据能够较好地反映研究区域土地利用类型的空间分布特征,有较好的模拟结果;②研究区10月份热岛强度最大为0.671℃,其次是1月份和7月份分别为0.570℃和0.550℃,而4月份热岛强度较小为0.467℃;城市热岛强度日最大值出现在22~23点,最小值出现在13~14点;③由于盛行风向的影响,滕州市与枣庄市中区城市热岛中心均存在春夏季北进、秋冬季南移的现象;④枣庄地区城市热岛主要受枣庄市中区的影响,各土地利用类型对城市热岛的贡献率大小排序为：城镇建设用地>农田>林地>未利用地>草地>水体。     

Pd/CeO2催化CO氧化活性对载体CeO2形貌的依赖效应

Pd纳米颗粒的氧化还原性能对Pd/CeO₂催化氧化反应的性能至关重要,且与Pd-CeO₂的界面结构密切相关.我们发现Pd/CeO₂的低温催化CO氧化活性高度依赖于载体CeO₂的形貌和暴露晶面.利用胶体沉积法,得到Pd/CeO₂八面体和Pd/CeO₂立方块两种催化剂.结果表明暴露{111}晶面的CeO₂八面体负载Pd催化剂的催化CO氧化活性远优于暴露{100}晶面的CeO₂立方块负载Pd催化剂.DFT理论模拟计算结果表明,催化剂表面的Pd物种的氧化还原活性可能决定催化剂的可还原性和催化活性:钯从氧化态到金属态的循环更容易在CeO₂(111)上进行,而这取决于Pd与载体CeO₂之间的相互作用.我们的结果表明,催化剂表面活性Pd物种的氧化还原性能对Pd/CeO₂的催化活性至关重要,可以通过调控载体暴露的晶面实现Pd与载体CeO₂之间的相互作用,最终实现对催化剂可还原性和催化活性的可控调变.     

Ergogenic effects of precooling with cold water immersion and ice ingestion: A meta-analysis

This review evaluated the effects of precooling via cold water immersion (CWI) and ingestion of ice slurry/slushy or crushed ice (ICE) on endurance performance measures (e.g. time-to-exhaustion and time trials) and psychophysiological parameters (core [T_core] and skin [T_skin] temperatures, whole body sweat [WBS] response, heart rate [HR], thermal sensation [TS], and perceived exertion [RPE]). Twenty-two studies were included in the meta-analysis based on the following criteria: (i) cooling was performed before exercise with ICE or CWI; (ii) exercise longer than 6?min was performed in ambient temperature ≥26°C; and (iii) crossover study design with a non-cooling passive control condition. CWI improved performance measures (weighted average effect size in Hedges’ g [95% confidence interval]?+?0.53 [0.28; 0.77]) and resulted in greater increase (ΔEX) in T_skin (+4.15 [3.1; 5.21]) during exercise, while lower peak T_core (?0.93 [?1.18; ?0.67]), WBS (?0.74 [?1.18; ?0.3]), and TS (?0.5 [?0.8; ?0.19]) were observed without concomitant changes in ΔEX-T_core (+0.19 [?0.22; 0.6]), peak T_skin (?0.67 [?1.52; 0.18]), peak HR (?0.14 [?0.38; 0.11]), and RPE (?0.14 [?0.39; 0.12]). ICE had no clear effect on performance measures (+0.2 [?0.07; 0.46]) but resulted in greater ΔEX-T_core (+1.02 [0.59; 1.45]) and ΔEX-T_skin (+0.34 [0.02; 0.67]) without concomitant changes in peak T_core (?0.1 [?0.48; 0.28]), peak T_skin (+0.1 [?0.22; 0.41]), peak HR (+0.08 [?0.19; 0.35]), WBS (?0.12 [?0.42; 0.18]), TS (?0.2 [?0.49; 0.1]), and RPE (?0.01 [?0.33; 0.31]). From both ergogenic and thermoregulatory perspectives, CWI may be more effective than ICE as a precooling treatment prior to exercise in the heat.     

In-season changes in ventricular morphology and systolic function in adolescent female athletes

Purpose: To evaluate the influence of physical maturity on the changes in ventricular morphology and function with sport training in female youth athletes.

Methods: Thirty-two female athletes (age 13–18 years) underwent height and weight measurement and 2-D echocardiographic evaluation immediately prior to, and following, a 20-week soccer season. Pre- and post-season left ventricular end-diastolic diameter (LVEDD), end-diastolic volume (LVEDV), ejection fraction (LVEF), stroke volume (LVSV), mass (LVM), and posterior wall thickness (LVPWT), right ventricular end-diastolic diameter (RVEDD), end-diastolic area (RVEDA), and fractional area change (RVFAC), and interventricular septal thickness (IVST) were compared. In-season change in each variable was compared across pre-season hours of vigorous physical activity (0–1, 2–3, >3 hours).

Results: Significant increases were identified in LVEDV (51.3?±?10.4?v 56.4?±?9.6?ml/m², p?=?0.001) and RVEDA (10.5?±?1.9?v 11.3?±?2.5?cm²/m², p?=?0.040), but not LVEDD, LVM, LVPWT, LVSV, RVEDD, RVEDA, RVFAC, or IVST (p?>?0.05 for all). In-season changes in echocardiographic variables did not differ across hours of pre-season vigorous physical activity (p?>?0.05 for all).

Conclusion: Among female adolescent soccer players, in-season training elicits changes in resting ventricular volume, but not wall thickness or systolic function. These adaptations do not appear to be influenced by pre-season physical activity level.     

Taking risks with a growth mindset: long-term influence of an elementary pre-service after school science practicum

In this study, we present the long-term influence of an after school science practicum associated with an elementary science methods course. The practicum or field experience could be considered a community-based service learning programme as it is situated both within and for the community. Study participants included eight third- and fifth-grade teachers who had participated in elementary science methods courses; four of these teachers participated in the after school teaching practicum while four participants experienced a more traditional observation-based elementary science practicum. All of these teachers were in their second or third year teaching which was 3–4 years after taking the methods course. Investigation methods included questionnaires, field observations and semi-structured, individual interviews. Teachers more regularly utilised reform-based teaching strategies and cited the after school teaching practicum as preparing them to use these strategies in their own classrooms. All teachers exhibited a growth mindset to some degree, but the after school practicum participants did demonstrate a wider use of reformed-based teaching strategies and a higher growth mindset. Elementary teachers perceive risk associated with these key aspects of instruction: (1) managing instruction and classroom management, (2) teaching science through guided inquiry, and (3) overcoming adoptions in other ‘mandated’ curriculum like math and reading.     

Cooperative Governance of Successful Public Schooling: Successes,Frustrations and Challenges

In search of embodying values that underpin democracy at school level, the objectives of the article include exploring expectations generated by the constitutional dispensation (Constitution of the Republic of South Africa, 108/1996, section 41) and delineating those moulded by the South African Schools Act (84/1996, Preamble). While the latter formally signify a State-education-partnership, the intention for teachers, learners and parents to accept especially governance responsibilities towards school democracy prompted our focused three-way alliance between parent-teacher-learner parties for the purpose of this article. Our conceptual framework is informed by Permuth, Mawdsley and Silver (2015), who contend that the essentially new facet of moving towards integrating qualitative research with doing traditional legal research could expand legal reasoning and even complement it with empirical credibility. Authenticated by Adler (2015), the article therefore combines focusing on cooperative governance as an act to shape schooling in the traditional legal way (by asking what questions) with qualitative research features to inform us by also asking how and why questions. We chose a documentary design with a comparative angle; selected documentary resources; and took an exploratory approach to gain understanding and weigh the investigated documents by comparing and appraising primary and secondary sources. We also regarded whatever was embedded yet not recorded as similarly important to what was recorded and how a specific concept was extended (De Waal and Serfontein 2015). Reviewing relevant case law, we present an overview of cooperative school governance progress; a constitutional challenges-based intervention; continuous acceptance of responsibility and accountability; and successes, frustrations and challenges concerning the future pathway to successful schooling. Given the snowballing set of demands on public schools, the catch is for partners to know each other's strengths and weaknesses so that balanced contributions will cause governance towards quality education. The drastic parental governance and leadership role-change, with higher moral-social responsibility levels, calls for carefully designed conferences to guide parent-partners’ exercising the necessary discretion underpinned by critically considering the significance of serving society.     

An investigation into the complex process of facilitating effective professional learning: CPD tutors’ practices under the microscope

Background: Research evidence on what makes CPD effective is accumulating. Yet, fundamental questions about the specific features that lead to programme success. Furthermore, very little research investigates the nature and quality of CPD providers’ (tutors) practices. Taking a closer look at how CPD providers support teachers to learn is therefore an important direction for research in order to offer specific guidance on how to design and deliver future CPD programmes for maximum impact.

Purpose: The present study aimed to advance this line of inquiry by seeking to examine tutors’ perceptions and practices in the context of a short course on Inclusive Physical Education. Two research questions were addressed: (1) What were the tutors’ perceptions of effective CPD delivery? And (2) How were these interpretations evidenced in practice? The short course, delivered by 40 different tutors across the country, was part of a National CPD programme which reached and educated over 5000 school staff in England. The scale of this programme thus offered an ideal setting in which to address the research questions.

Participants and setting: A case study design was adopted where the case was identified at the level of individual courses. A cluster sampling procedure was adopted (one cluster for each of the nine geographical areas in England). Where possible, systematic sampling within the nine clusters was employed (i.e. collect evidence from the first two courses delivered in each cluster each year). A total of 27 courses, delivered by 20 tutors across eight geographical areas in England, were selected as cases and all tutors involved in their delivery were invited to participate in the study.

Data collection: To explore tutors’ perceptions of effective CPD delivery (research question 1), qualitative data were collected via an online questionnaire and individual interviews. To examine how these interpretations were evidenced in practice (research question 2), both quantitative and qualitative data were collected via systematic observations and ethnographic field notes.

Data analysis: Qualitative data were analysed using a constructivist approach to grounded theory. Quantitative data from the observations were entered into SPSS version 21 (IBM Statistics) for analysis.

Findings: Findings indicate that tutors’ perceptions and beliefs did not always materialise. Data from the observations suggest variation in the ways tutors structured, supported and facilitated professional learning. This variation was evident not only in the actual time dedicated to practical vs. theoretical activities and active vs. passive learning opportunities but also in tutors’ ability to facilitate professional learning. This finding suggests that there is a significant set of skills involved in supporting, nurturing and challenging professional learning in CPD contexts. It is therefore important to consider how tutors can be best supported to develop and implement these skills effectively.

Conclusion: The results consolidate existing understandings about the importance of (inter)active and practical learning opportunities in CPD; but also add nuance and detail on the diverse ways in which tutors engaged participants in the learning process. Findings draw our attention to the important issue of the selection and continuing education of CPD tutors.