Al-5%Fe合金的热速处理研究

研究热速处理工艺对Al-5?合金力学性能和初生Al3Fe相形貌的影响.研究结果发现,未热速处理时,初生Al3Fe相为粗大的针片状或针状;初生Al3Fe相占基体的面积百分率为40.39%;合金的抗拉强度为107 MPa.经热速处理后,小部分初生Al3Fe相长成细小的针状,大部分则长成针点状;初生Al3Fe相占基体的面积百分率达到50.77%;抗拉强度达到145 MPa,提高35.5%.研究认为,热速处理之所以能细化初生Al3Fe相是由于高温过热减小了Al与Fe之间的原子团簇,最大限度地消除了合金的遗传性和增大了形核过冷度.     

电磁搅拌与变质复合作用对Al-20Si合金初生硅相的影响

使用电磁搅拌、变质处理及其复合工艺分别成功制备了过共晶Al-20Si半固态浆料，研究了电磁搅拌和变质的复合作用对过共晶Al-20Si合金中初生Si长大和形貌的影响。研究结果表明：复合作用可以获得比单种变质处理和电磁搅拌的过共晶Al-20Si合金更加细小、更加圆整的初生Si组织。复合作用获得的初生硅比单一处理尺寸平均减小25．19％，圆整度平均提高8．40％。而且共晶Si组织也得到球化。复合作用细化组织的机理为：变质后施加旋转磁场，促进了变质剂的扩散，更多的初生Si与共晶Si组织相互打碎，深化了变质和电磁搅拌效果，细化显微组织。     

Doing a Good Job—the Effect of Primary Task Quality on Well‐Being and Job Satisfaction

This paper investigates whether employees’ assessment of their primary task quality has a significant impact on their well‐being and job satisfaction, respectively. Furthermore, the paper hypothesizes that professional values and norms affect employees’ quality expectations on their work tasks and thus their assessment of primary task quality. The paper proposes a measure for primary task quality and uses it in the analyses of responses from 1,247 preschool teachers and teaching assistants in 94 public daycare centers in Denmark. The results indicate that an important factor for employees is their experience of quality in the job they perform. Moreover, quality expectations can differ between employees performing the same task due to, for example, difference in professional training. This leads us to propose a new research direction for job design theory that addresses employees’ assessment of the quality of their primary task job performance.     

The Rise of Twitter in the Political Campaign: Searching for Intermedia Agenda‐Setting Effects in the Presidential Primary

Questions exist over the extent to which social media content may bypass, follow, or attract the attention of traditional media. This study sheds light on such dynamics by examining intermedia agenda‐setting effects among the Twitter feeds of the 2012 presidential primary candidates, Twitter feeds of the Republican and Democratic parties, and articles published in the nation's top newspapers. Daily issue frequencies within media were analyzed using time series analysis. A symbiotic relationship was found between agendas in Twitter posts and traditional news, with varying levels of intensity and differential time lags by issue. While traditional media follow candidates on certain topics, on others they are able to predict the political agenda on Twitter.     

发动机初级工况对冷却夹套隔片损伤影响分析

针对可重复使用液体火箭发动机推力室冷却夹套隔片的损伤问题,为确保发动机的工作寿命,对建立了冷却夹套隔片的夹芯梁结构模型、粘塑性模型和细化损伤模型,发动机起动过程中初级工况给冷却夹套隔片损伤发展的影响进行了仿真计算。结果表明:初级工况过高,压力等性能参数振荡明显,振幅也较大,但引起的冷却夹套隔片损伤较小;初级工况选择过低,引起的冷却夹套隔片损伤较大,且压力等性能参数振荡也比较明显,但振幅较小。通过对比分析给出了用于发动机起动的合适初级工况,采用此工况使发动机起动过程中引起的损伤较小,而且压力等性能参数的振荡也较小。     

ICT integration in the classroom: Challenging the potential of a school policy

Despite the assumption that the integration of ICT influences the entire school system, research focusing on ICT in schools is generally limited to the study of variables at class level. In contrast to these studies, the present research explores ICT integration from a school improvement approach. More particularly, it examines the local school policy with respect to ICT integration from both the principal’s perspective and perceptions of teachers. Furthermore, it studies the relationship between school policies and the actual use of ICT in the classroom. To answer the research questions, a representative sample of 53 primary school principals was interviewed. In addition, the interview data were supplemented with survey data of 574 teachers from the same 53 schools. What emerged from the analyses was that school-related policies, such as an ICT plan, ICT support and ICT training have a significant effect on class use of ICT. In addition, the findings from the interviews indicate that school policies are often underdeveloped and underutilised. The discussion section focuses on challenges to improve the potential of an ICT school policy.     

同兴垃圾发电厂DCS控制系统

重庆同兴垃圾发电厂采用的是德国马丁公司(原法国阿尔斯通公司)的逆推式炉排焚烧技术。本文叙述了焚烧技术的工艺流程、DCS控制系统的硬件构成及功能。以全厂集中操作与各工段分散控制相结合的系统运行模式,实现了垃圾焚烧发电厂整体生产过程的监控和低成本运行,提高了垃圾焚烧发电机组的自动化和管理水平。     

压电发电悬臂梁的非线性动力学建模及响应分析

以单晶悬臂梁压电发电装置为研究对象,在考虑压电材料非线性的情况下,利用广义Hamilton原理、Rayleigh-Ritz法、Euler-Bernoulli梁理论及压电元件恒定电场假设建立了悬臂梁压电发电装置的分布式机电耦合模型,通过数值计算分析谐振频率附近解的特性与系统参数及初始条件的关系,揭示了压电材料非线性、外激励参数对系统响应的影响规律,并通过实验验证了解析解的正确性.结果表明,压电材料的非线性特性会导致近似解的共振峰向左偏移,呈现软特性的非线性特征;当激励频率变化时,系统响应存在多解、跳跃等现象,主共振解的真正实现与初始条件的选取有关.     

Inventory model for seasonal demand with option to change the market

In real life, when bulk purchase becomes convenient or even mandatory, it is a common practice for distributors to explore an alternative market in order to maximize the revenue earned. In this paper, we consider an inventory model for a product having seasonal demand with two potential markets, say, primary and alternate. The distributor has a single opportunity of procurement prior to multiple demand seasons in the primary and the alternate market. Both the markets have similar demand patterns, with time lag between their demand seasons. The demand is a price and time dependent function with increasing, constant and declining phases within each demand season. The scale parameter of demand rate depends upon the market. In each market, successive seasons are separated by random time. In one replenishment cycle, the distributor has a single option to exit the primary market by transferring the inventory, with or without change in selling price. This option can be exercised at the end of any complete season at the primary market. Our investigations indicate that it will be beneficial for the distributor to shift to the alternate market even at a slightly lower selling price if demand rate in the alternate market is higher. Optimal number of seasons at the primary market before change of price or market is obtained. Optimal policy is obtained for jointly determining the order quantity and price. Concavity of the profit function is discussed. Solution procedure, numerical examples and sensitivity analysis are presented.