Some extensions of elementary plasticity theory

A detailed investigation is presented of yield or loading criteria, for work hardening materials, which lead to constant strain ratios under increasing stress when stress ratios are maintained constant. The experimenter is given a choice of incremental stress-strain theories with which results of simple or complicated combined loading tests may be correlated. These theories are dealt with in order of increasing complexity and, at the same time, increasing capacity to represent experimentally established phenomena.The objective is the use of the mathematically simplest theory which will provide the desired flexibility in the analysis of experimental data.Loading functions of isotropic as well as anisotropic types are examined, among them those depending explicitly on stress alone and those depending on both stress and plastic strain. In the latter cases only those functions are investigated in which plastic strain appears to the first order. The predicted results of some basic tests are examined for several loading criteria.     

‘An Outrage,Not Athletics’: Apartheid and South African–United States Rugby Relations, 1976–1990

Abstract

In the period from1976 to1990 during the international campaign against apartheid, some affiliate members of the USA Rugby Football Union, went out of their way to establish and maintain a strong relationship with the South African Rugby Football Board and its successor, the South African Rugby Board. Over the course of six reciprocal tours, they ignored the campaigns of the worldwide anti-apartheid movement and the British Commonwealth. In their dogged pursuit of a sporting relationship with a key South African cultural institution that buttressed apartheid in a sport that, at best, enjoyed minority status in the United States, they defied both their own national federation and the American Olympic Committee. By 1990 as the international campaign against apartheid became a truly worldwide affair, US–South Africa rugby relations were suspended in line with larger political developments both within and outside of the country. This essay, beyond mapping the trials and tribulations of that relationship, also foregrounds a largely hidden history in order to fill the existing gap in the official sporting histories of both the United States and South Africa.     

空间均匀低温氢气燃烧器开发（英文）

目的:设计制造低温的催化氢气燃烧器,并对其进行相关功能性测试。创新点:成功设计并制造出一个集成流量分配器的催化低温氢气燃烧器。方法:1.基于树状分叉方法,设计燃烧器的流量分配器,均匀分配气体到催化表面,并利用熔融沉积成型技术制备原型样机。2.基于测试结果,利用选择性激光熔化技术对燃烧器进行最优化设计。3.对设计的催化燃烧器的相关功能进行验证。结论:1.设计的低温催化燃烧器与传统的非催化燃烧器相比具有很多优势,尤其是实现了无焰均匀低温(约200°C)的产热;这一技术有望运用于化工领域的增材制造。2.本文不但用选择性激光熔融技术制备了最终产品,而且利用了熔融沉积成型技术进行快速的样机制备。3.催化剂多孔载体的调控和催化剂的负载方式研究有望进一步提升燃烧器的综合性能。     

Fairness constraints on profit-seeking: evidence from the German club concert industry

Unlike Kahneman et al. (Am Econ Rev 76(4):728–741, 1986) iconic snow shovel, live music is a performance good that fans attach a particular value to. Hence, an artist’s pricing decision might differ from standard rent-seeking behavior. In this paper, I propose a model that incorporates fairness concerns into the pricing decision for concert tickets. The hypotheses derived from this model are tested on data from the German club concert industry. The results are consistent with the model: Although (1) price dispersion is the dominant pricing strategy in the club concert industry and artists prefer to perform on a Friday or Saturday night, (2) artists do not set higher prices on the weekend. These results are consistent with fairness constraints, but are difficult to explain within a standard profit maximization framework. As a third result, (3) the data reveal that ticket prices are positively correlated with a city’s number of inhabitants .     

Human vs. Computer Diagnosis of Students’ Natural Selection Knowledge: Testing the Efficacy of Text Analytic Software

Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements (or Key Concepts) that comprise undergraduate students’ explanatory models of natural selection with equal fidelity as expert human scorers in a sample of >1,000 essays. We used SPSS Text Analysis 3.0 to perform our CAS and measure Kappa values (inter-rater reliability) of KC detection (i.e., computer–human rating correspondence). Our first analysis indicated that the text analysis functions (or extraction rules) developed and deployed in SPSSTA to extract individual Key Concepts (KCs) from three different items differing in several surface features (e.g., taxon, trait, type of evolutionary change) produced “substantial” (Kappa 0.61–0.80) or “almost perfect” (0.81–1.00) agreement. The second analysis explored the measurement of human–computer correspondence for KC diversity (the number of different accurate knowledge elements) in the combined sample of all 827 essays. Here we found outstanding correspondence; extraction rules generated using one prompt type are broadly applicable to other evolutionary scenarios (e.g., bacterial resistance, cheetah running speed, etc.). This result is encouraging, as it suggests that the development of new item sets may not necessitate the development of new text analysis rules. Overall, our findings suggest that CAS tools such as SPSS Text Analysis may compensate for some of the intrinsic limitations of currently used multiple-choice Concept Inventories designed to measure student knowledge of natural selection.     

Welche bildungswissenschaftlichen Inhalte sind wichtig in der Lehrerbildung?

In reviews of university teacher training, the parts of the curriculum based on educational science are often criticized as missing practical relevance and being non-cumulative. At the same time, uncertainty exists regarding which educational science based content is important for teacher candidates. The objective of the Delphi study presented here was the identification of core educational science content in university training. To this aim, a survey was carried out amongst 49 experts from different subject areas and phases of teacher training in three rounds using a standardized questionnaire. In the first round, 213 topics were specified, which were then assessed by experts regarding their importance for various aspects of the teaching profession. In the second and third rounds, which had the objective of reducing the number of topics, the experts chose a limited number of topics based on their relevance for university teacher training and for the practical success of teaching itself. The results show that the original list was comprehensive and that there is a consensus among most of the experts on their respective importance for teaching training.     

Development of a spatially uniform low-temperature hydrogen combustor

Examples of the use of additive manufacturing and rapid prototyping in a range of applications are of great interest in order to emphasize their role in development and production technology. In this study, a catalytic low temperature burner for H₂ on a lab scale with an integrated flow distributor was designed, manufactured, and tested for functionality. Based on a theoretical approach, a flow distributor for the burner was designed and a prototype was built using fused deposition modeling (FDM). Based on test results, an optimized version of the burner was then designed and manufactured using selective laser melting (SLM). The functionality of the designed catalytic burner was proven. Several advantages were found in comparison to conventional non-catalytic burners. In particular, flameless uniform low temperature heat generation with temperatures of about 200 °C could be realized. This contribution highlights the potential of additive manufacturing in chemical engineering. Not only was the final product built using SLM, but also during the development process, FDM was used for rapid prototyping.     

Fostering children's acceptance of educational apps: The importance of designing enjoyable learning activities

Educational applications (apps) offer opportunities for designing learning activities children enjoy and benefit from. We redesigned a typical mobile learning activity to make it more enjoyable and useful for children. Relying on the technology acceptance model, we investigated whether and how implementing this activity in an app can increase children's intention to use. During the 27-day study, children (N = 103, 9–14 years) used the app to memorize one-sentence learning plans each day. Children used three different app-based learning activities throughout the study. In two standard activities, children reread or reassembled the words of the plan. In the redesigned activity, children represented the meaning of the plan with emojis. Children repeatedly reported on their attitude towards each activity. Subsequently, children reported perceived enjoyment and intention to use the app. Results showed children found the emoji activity most enjoyable, and enjoyment of the emoji activity contributed uniquely towards intention to use. Additionally, children's enjoyment of the app mediated their intention to use the app in the future. Overall, the study suggests that children's enjoyment of an app is crucial in predicting their subsequent intention to use, and it provides a concrete example of how emojis can be used to boost enjoyment.

Practitioner notes

What is already known about this topic

• Educational applications provide children with unrestricted access to mobile learning resources.
• Positive attitudes towards educational applications predict behavioural intention to use these applications, at least in young adults.
• There is a need for more research examining the relevance of enjoyable learning activities in fostering children's sustained usage of an educational application.

What this paper adds

• Positive attitude towards the use of emojis during learning activities uniquely contributed to children's behavioural intention to use the application.
• Perceived enjoyment predicted behavioural intention to use the application.
• Perceived enjoyment mediated the effect of attitude towards using learning activities on the behavioural intention to use the mobile educational application.

Implications for practice and/or policy

• These findings highlight the importance of enjoyment for children's' acceptance of educational applications.
• Enjoyable learning activities are necessary to ensure sustained usage of educational applications.
• The paper provides a concrete example of how emojis can be used to boost enjoyment of a typical mobile learning activity.