R134a／R23自然复叠制冷系统的仿真和优化研究

针对使用R134a／R23混合制冷剂的自然复叠制冷系统．编制了基于NISTREFPROP的仿真程序。利用仿真和实验对系统各种优化措施的效果进行了分析和验证。两者都表明：分凝措施有利于降低系统蒸发温度、提高COP;而回热可以略微降低系统蒸发温度,但使系统COP降低、压缩机排气温度升高。     

复叠式相变蓄热热泵热水器的研究

为使热泵热水器在满足制热性的基础上兼顾经济性,提出了复叠式结构和蓄热器耦合的新型热泵热水器,探讨了它的性能,着重分析了经济性。结果表明该热水器的能效比高,工作温差大,适用区域广,在实行峰谷电价时经济性好,因而具有较高的应用价值。     

The transfer of content knowledge in a cascade model of professional development

A cascade model of professional development presents a particular risk that ‘knowledge’ promoted in a programme will be diluted or distorted as it passes from originators of the programme to local trainers and then to the target teachers. Careful monitoring of trainers’ and teachers’ knowledge as it is transferred through the system is therefore imperative. This paper focuses on the transfer of content knowledge through an in-service teacher professional development programme and offers an innovative methodology for investigating knowledge transfer, i.e. through insights gained during a mentoring process. The findings suggest that this methodology facilitated assessment of knowledge transfer because it involved the identification of knowledge in practice. The focus on knowledge in practice appeared to avoid a deficit model of trainers’/teachers’ knowledge and revealed that content knowledge was generally being successfully transferred throughout the system. A detailed analysis of different aspects of content knowledge transfer suggested various foci for additional training.     

锦屏二级水电站深埋隧洞渗控研究

用降雨入渗渗流有限单元法对锦屏二级水电站深埋隧洞最大埋深断面渗流场的水头分布进行了数值模拟。结合工程的现拟渗控措施经多种计算方案的求解，较详细地综合分析了各计算方案的渗控情况与特点，并获得了该断面隧洞支护上的外水压力及最优的渗控方案。     

串级控制系统的研究与设计一例

在各种复杂控制系统中,串级控制系统占有较大比重。以离子膜电解槽为例,介绍了串级控制系统的形成,分析了串级控制系统的工作过程、结构及特点。根据串级控制系统的特点,说明了当对象的滞后和时间常数很大,干扰作用强而频繁,负荷变化大,使用串级控制系统是合适的。尤其是当主要干扰来自控制阀方面时,选择控制介质的流量或压力作为副变量来构成串级控制系统是很适宜的。     

电网连锁跳闸事件中的关键节点研究

对电网连锁跳闸事件中的关键节点进行研究,提出一种分析关键节点的算法。结合连锁跳闸事件中继电保护的动作行为,给出一种连续型的用以衡量连锁跳闸严重度的表达形式及评价参量,并根据直流潮流法,利用支路电流和节点注入功率之间关系,进一步明确连锁跳闸严重度评价参量与节点注入功率之间的关系,以及连锁跳闸严重度评价参量对节点注入功率的灵敏度,在此基础上,形成了一套完整的算法,用以分析可引发连锁跳闸的初始故障,被初始故障波及的连锁跳闸支路,并最终用以分析对连锁跳闸支路起关键作用的节点。最后,在IEEE39节点系统上通过算例对该算法的有效性和合理性进行进一步说明。     

基于反应釜的串级控制系统抗积分饱和研究

在精密化工实验室环境中,温度控制要求精度高、鲁棒性好,采用串级控制系统实现温度控制,但在实验中出现的积分饱和现象会导致整个温度控制系统不稳定。针对这一问题,目前最常用的方法是依据特定条件切除积分作用或采用增量型或速度型算法,但都达不到预期效果。提出一种抗积分饱和方法,在一定条件下重新计算积分值,使积分累积量达到一个合适的值。该方法相比传统的抗积分饱和办法能减小超调量,缩短震荡周期且更早进入稳定状态,具有更好的鲁棒性。     

Learner orientation through professional development of teachers? Empirical results from cascade training in Anglophone Cameroon

This paper examines the effects of a professional development programme on the attitudes towards the teaching and learning of teachers in the Anglophone part of Cameroon. The development programme combines a multiplier system with school-based in-service training. The research compares the effects that the training had on the attitudes of three groups of teachers in a control group design: (1) teachers participating in the in-service training, subdivided into (1a) teachers trained as multipliers and (1b) teachers trained by the multipliers, and (2) teachers who did not participate in the training. The study featured a quantitative control group design (n = 292) and is intended to contribute to the discussion on the sustainable effects of in-service teacher training in low-income countries. The data collection was conducted in 13 secondary schools in Cameroon. The results suggest that the programme had effects on the teachers’ attitudes and classroom practices.     

考虑连锁跳闸的电网安全裕度研究

针对电网的连锁跳闸现象,对考虑连锁跳闸的电网安全裕度问题进行研究。首先根据连锁跳闸事件中继电保护的动作行为以及连锁跳闸的一般表现,通过分析论证,分别给出利用支路电气参数表示的安全裕度指标,以及利用系统总负荷表示的安全裕度指标,在此基础上,给出求取安全裕度的算法及一种用于定量分析安全裕度的方法;最后通过IEEE39节点系统和IEEE14节点系统上的算例演示进一步验证该方法的合理性和有效性。     

全球环境变化使植物体对增强UV-B辐射信号的感受和传导

据国际上的最新研究成果 ,论述了在全球环境变化引起的UV -B辐射过程中 ,植物对UV -B信号的感受和传导机理 ,其中包括细胞中UV -B信号受体 ,各种信号分子 (诸如活性氧、水杨酸、茉莉酸、乙烯和一氧化氮等 )的级联放大传递以及对于基因表达活性的影响 ,提出了UV -B胁迫信号传递的信号分子级联模型 ,从而为有效防护环境变化引起的UV -B辐射增强对于植物体的伤害提供理论依据