For a large organization to successfully complete a complex project, many constituent tasks must all be successfully completed. A typical such task can be completed only if several other, tailored input tasks are completed. Thus a complex project, such as designing a new product and bringing it to market, requires many collaborations among workers to succeed, both within and across business units. Some collaborations succeed, while others fail. Corporate culture---a broad notion that entails many aspects of the working environment---supports collaborations by establishing norms and reducing miscommunications or misunderstandings. However, the strength of a corporate culture is endogneous. Individual actions of workers that run counter to it undermine it and adhering to the corporate culture in a given situation can be costly to a worker. Because a strong corporate culture relies on costly, voluntary investments by many workers, we model it as an organizational public good, subject to standard free-riding problems, which become severe in large organizations. Indeed, a standard analysis would suggest that workers' incentives to make voluntary contributions to the corporate culture vanish as an organization becomes large, because their marginal impact becomes negligible while their marginal cost does not. This raises an important question: Why do workers exert voluntary effort to enhance the corporate cultures of large organizations? We propose a perspective on this question based on a network model of complex production within a large organization: The productive activity of the organization occurs via the completion of tasks, where a given worker in charge of a task relies on the completion of several types of essential subtasks, which are incorporated into the task via collaborations with other workers. We find that voluntary contributions to culture can be sustained, because an organization's equilibrium productivity is endogenously highly sensitive to individual contributions. This implies a new mechanism generating incentives for voluntary, decentralized investment in culture even as an organization becomes large and the free-rider problem becomes severe: the marginal impact of contributions becomes large enough to compensate. However, the completion of complex tasks is then necessarily fragile to small shocks that can disrupt the organization's culture, such as a merger or a change in the company's top management.

An economy can be thought of as a network in which the nodes are agents and links among them represent heterogeneous opportunities for exchange or cooperation. This paper argues that studying properties of such a network -- how dense it is, how "central" various agents are in it -- yields insights about issues such as the efficiency and fragility of an economic system, as well as its market outcomes. We develop this conceptual point in a model of a public goods economy: one in which each agent can incur a private cost to take an action -- e.g., reducing pollution -- that creates nonrival but heterogeneous benefits for others. The network we study is a directed, weighted graph in which an edge from agent i to agent j captures the marginal benefits i can provide to j, at the current action profile, as i increases his public good provision.

The video presents recent progress of the wall-climbing robot project at the City College of New York. The robots are named as City-Climbers which adopt a novel adhesive mechanism based on aerodynamic attraction to achieve good balance between strong adhesion force and high mobility. The video demonstrates that the City-Climber robots can operate on virtually any kind of smooth or rough surfaces and have the capabilities to move on the ground, climb walls, and transit between them. The modular design achieves both fast motion of each module on planar surfaces and smooth transition between the surfaces by a set of two modules. The video also displays the Fluent simulation results of the aerodynamic attraction with the aim to optimize the design. DSP-based control system is introduced which enables the robot to operate both manually and autonomously