基于单片机控制的编织袋折边折角装置设计

为提高编织袋折边折角的自动化水平和效率，更好地与编织袋缝纫工序结合起来，文章设计了基于单片机控制的编织袋折边折角装置.首先利用Pro/E 4.0设计了编织袋折边折角装置的机械结构三维模型，然后在Microsoft Office Visio中设计了该设备的气动系统，最后利用AT89C51单片机对该套设备进行设计与控制.结果表明，这套编织袋折边折角装置结构紧凑合理，成本控制在1万多元，单片机控制系统稳定有效，整个折边折角动作耗时在6 s左右，效率较高，能够真正提高编织袋折边折角自动化水平，具有很高的工程实践价值.     

On the behavioural relevance of optional and mandatory impure public goods

Impure public goods combine a private good with a public good. Often, impure public goods have a charitable or ethical dimension, giving ethically motivated consumers a convenient option to contribute to public goods through the marketplace (in addition to direct donations). Impure public goods could potentially promote ethical giving or alternatively hinder charitable behaviour. We implement an economics experiment with a between-subject design to test the behavioural relevance of impure public goods with only a token (i.e. small) contribution to a public good. Contributions to the public good are negatively affected by the presence of impure public goods with token contributions. We explore one mechanism to offset this negative impact by making the token impure public good mandatory. We observe higher average contributions and several positive impacts on charitable behaviour, which supports the claim that this mechanism can potentially offset the negative impact of impure public goods.     

How income and tax rates provoke cheating – An experimental investigation of tax morale

Anecdotal evidence suggests that tax morale diminishes with income and with levels of taxation. We designed an experiment that enables identification of causal effects. Subjects carry out a sequence of real effort tasks. The income earned varies with individual differences in effort (combined with variances related to skill or luck) and with the exogenously given length of the tasks. For each task, subjects privately roll a die, whose value determines the tax rate, which is then reported by subjects. This provides subjects with an incentive to cheat. Tax morale diminishes with higher effort, which might find ethical justification, but also with longer tasks, which would not. We implement treatments that vary the range of taxation. Contrary to widespread belief, participants’ tax morale is invariant to these treatments. Our findings are best explained by a psychological force that tempts rich people to cheat more. This force does not seem to be related to fairness ideals that are prominent in theories of distributional justice nor to absolute levels of taxation.     

The effect of conflict history on cooperation within and between groups: Evidence from a laboratory experiment

We study cooperation within and between groups in the laboratory, comparing treatments in which two groups have previously been in conflict with one another, in conflict with a different group, or not previously exposed to conflict. We model conflict using an inter-group Tullock contest, and measure its effects upon cooperation using a multi-level public good game. We find that conflict increases cooperation within groups, while decreasing cooperation between groups. Moreover, we find that an increase in the gains from cooperation only increases cooperation between groups when the two groups have not previously interacted.     

Better stuck together or free to go? Of the stability of cooperation when individuals have outside options

How do outside options affect cooperation? We examine the stability of cooperation and the reasons for exit in public projects with stochastic outcomes, imperfect monitoring and an exit option. We find that treatments with high barriers to exit generate higher welfare overall as they foster stability and prevent inefficient separation of pairs. There is excessive exit in treatments with low barriers to exit, driven in part by an overestimate of the likelihood that the peer will leave and a desire not to be left alone in the public project. We contrast long-term “strategic” and short-term “egoistic” drivers of exit and find that short-term cost-benefit considerations play a more important role in treatments with lower barriers to exit.     

Involuntary job loss and changes in personality traits

Economists consider personality traits to be stable, particularly throughout adulthood. However, evidence from psychological studies suggests that the stability assumption may not always be valid, as personality traits can respond to certain life events. Our paper analyzes whether and to what extent personality traits are malleable over a time span of eight years for a sample of working individuals. Furthermore, we specifically look at changes in personality traits after a major adverse life event: involuntary job loss. We use data from the German Socio-Economic Panel Study (SOEP) from 2004 to 2014 – a period over which individuals’ Big Five personality inventory was measured three times. Our dataset allows us to exploit detailed employment information, particularly reasons for job termination and unemployment spells. We focus solely on plant closures as a reason for job termination. Job loss due to plant closure is widely used as a relatively exogenous event to identify causal effects. Our results suggest that personality traits are indeed malleable during adulthood. Although the Big Five measures are relatively stable within the overall population of workers, we find an increase in openness, that is, the willingness to seek new experiences, for the average displaced worker. This increase, however, is fully driven by individuals with high educational attainment and by those who find a new job immediately after dismissal. The other dimensions of the Big Five personality inventory remain nearly unchanged after an involuntary job loss. Our findings hold for a number of robustness checks and are supported by the results of a falsification test using a placebo treatment.     

Development and validation of the Perceived Investment Value (PIV) scale

This study aims to develop a complementary and more comprehensive measurement to assess the nature of investment value affecting consumers’ investment behavior. Recent research suggests that consumers may desire and obtain certain outcomes from investments that have not been anticipated in mainstream finance and economics literature. These benefits might be hedonistic or altruistic, self-expressive or emotional and experiential. Yet, while an increasing amount of attention has been paid to this topic, little effort has been made to develop an appropriate measurement scale for the subjective consumer perceptions of investments. To address this gap in the literature, this study introduces the concept of Perceived Investment Value (PIV), and develops and validates a measurement scale for the concept. The ultimate 18-item PIV scale parsimoniously represents six Perceived Investment Value dimensions: Economic value—Monetary savings; Economic value—Efficiency; Functional value—Convenience; Emotional value—Emotions and Experiences; Symbolic value—Altruism; and Symbolic value—Esteem. The final measurement scale demonstrates acceptable reliability and validity. Implications related to the developed scale are discussed in terms of their potential to inform a future research agenda.     

Social Studies in the Modern Era: A Case Study of Effective Teachers' Use of Literacy and Technology

The purpose of this research project was to highlight the practices and philosophies of two effective—but different—social studies teachers who balance the demands of teaching in the modern era while honoring their own philosophies for teaching social studies. This project was ground in the theoretical framework provided by TPACK and used a case study methodology for its research design. While the pedagogical content knowledge of the participants was strong and technology was used abundantly for instructional purposes, this research raised questions regarding how teachers can most effectively use technology to enhance instruction by helping students conceptualize content knowledge and apply their learning in new ways.     

LETTING DOWN THE TEAM? SOCIAL EFFECTS OF TEAM INCENTIVES

This paper estimates social effects of incentivizing people in teams. In three field experiments featuring exogenous team formation and opportunities for repeated social interactions, we find large team effects that operate through social channels. In particular, assignment to a team treatment increases productivity by 9%–17% relative to an individual incentive treatment, even though the individual incentive yields a higher private return. Further, we find that in a choice treatment individuals overwhelmingly prefer the individual incentive to the team incentive, despite the latter being more effective. These results are most consistent with the team effects operating through guilt or social pressure as opposed to pure altruism.