Understanding the destabilizing role for surface tension in planar shear flows in terms of wave interaction

Both surface tension and buoyancy force in stable stratification act to restore perturbed interfaces back to their initial positions. Hence, both are intuitively considered as stabilizing agents. Nevertheless, the Taylor-Caulfield instability is a counterexample in which the presence of buoyancy forces in stable stratification destabilize shear flows. An explanation for this instability lies in the fact that stable stratification supports the existence of gravity waves. When two vertically separated gravity waves propagate horizontally against the shear, they may become phase locked and amplify each other to form a resonance instability. Surface tension is similar to buoyancy but its restoring mechanism is more efficient at small wavelengths. Here, we show how a modification of the Taylor-Caulfield configuration, including two interfaces between three stably stratified immiscible fluids, supports interfacial capillary gravity whose interaction yields resonance instability. Furthermore, when the three fluids have the same density, an instability arises solely due to a pure counterpropagating capillary wave resonance. The linear stability analysis predicts a maximum growth rate of the pure capillary wave instability for an intermediate value of surface tension corresponding to We-1=5, where We denotes the Weber number. We perform direct numerical nonlinear simulation of this flow and find nonlinear destabilization when 2≤We-1≤10, in good agreement with the linear stability analysis. The instability is present also when viscosity is introduced, although it is gradually damped and eventually quenched. © 2017 American Physical Society

Identity is About us: Leadership Lessons Learned During an Accreditation Journey

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156444/2/jls21694_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156444/1/jls21694.pd

Evolution of forced shear flows in polytropic atmospheres: A comparison of forcing methods and energetics

Shear flows are ubiquitous in astrophysical objects including planetary and stellar interiors, where their dynamics can have significant impact on thermo-chemical processes. Investigating the complex dynamics of shear flows requires numerical calculations that provide a long time evolution of the system. To achieve a sufficiently long lifetime in a local numerical model the system has to be forced externally. However, at present, there exist several different forcing methods to sustain large-scale shear flows in local models. In this paper we examine and compare various methods used in the literature in order to resolve their respective applicability and limitations. These techniques are compared during the exponential growth phase of a shear flow instability, such as the Kelvin-Helmholtz (KH) instability, and some are examined during the subsequent non-linear evolution. A linear stability analysis provides reference for the growth rate of the most unstable modes in the system and a detailed analysis of the energetics provides a comprehensive understanding of the energy exchange during the system's evolution. Finally, we discuss the pros and cons of each forcing method and their relation with natural mechanisms generating shear flows

Strong Completeness for Markovian Logics

In this paper we present Hilbert-style axiomatizations for three logics for reasoning about continuous-space Markov processes (MPs): (i) a logic for MPs defined for probability distributions on measurable state spaces, (ii) a logic for MPs defined for sub-probability distributions and (iii) a logic defined for arbitrary distributions.These logics are not compact so one needs infinitary rules in order to obtain strong completeness results. We propose a new infinitary rule that replaces the so-called Countable Additivity Rule (CAR) currently used in the literature to address the problem of proving strong completeness for these and similar logics. Unlike the CAR, our rule has a countable set of instances; consequently it allows us to apply the Rasiowa-Sikorski lemma for establishing strong completeness. Our proof method is novel and it can be used for other logics as well

Not what you expected: Implementing design thinking as a leadership practice

Changing user needs have created new opportunities for libraries, requiring evolving leadership practices that support innovation and rapid change. Design thinking can provide leaders with a concrete process to move toward action. The authors – one an executive administrator at a large, multi-branch public library, the other an academic librarian who leads a small team – share how design thinking has positively influenced their leadership practices. The benefits of implementing this flexible process have included improved user experience, more creative solutions, wise investments, staff empowerment, increased transparency and trust, and employee learning and development. Both leaders experienced these benefits even though they are in different positions on their hierarchical organization charts. The authors propose that implementing design thinking as a leadership practice has a place in the evolving role of libraries and can shift organizational cultures to become more user-centered and embrace innovation. In addition to these benefits, the chapter discusses specific project examples, challenges, and tips for library leaders to successfully implement the process. Design thinking is translatable across library types and throughout private industry. Discussing design thinking as a leadership practice can benefit the profession and communities by giving leaders a common language to use when learning from and sharing with each other in conversations about innovation

Let\u27s Talk About How We Talk: Communication Agreements in the Library Workplace

Purpose: This chapter introduces a new tool, termed the Communication Agreement, for enhancing communication in the library workplace. The chapter defines the communication agreement, provides discussion questions for forming a communication agreement, provides examples of how communication agreements are beneficial to a diverse library workforce, and provides strategies to informally assess communication agreements’ effectiveness. Practical implications: Communication problems in diverse library workplaces can lead to, or exacerbate, conflict between employees. Generational, cross-cultural, gender, and other differences can lead to misunderstandings and conflict between employees. The communication agreement provides library managers with a tool to bridge differences in communication styles between employees, enable employees to engage in more effective communication, assist employees in developing better understandings and respect for colleagues of different backgrounds, and raise employees’ emotional intelligences. Originality/Value: Numerous resources and publications provide generalized approaches to communicating with others in a heterogeneous workplace or team, but the communication agreement provides a new approach for developing effective communication between people in a diverse library workplace. Limitations: The chapter lays out informal assessment strategies for the communication agreement, but formal assessment methods and metrics still need to be developed

The Rise of the Resilient Local Authority?

The term resilience is increasingly being utilised within the study of public policy to depict how individuals, communities and organisations can adapt, cope, and ‘bounce back’ when faced with external shocks such as climate change, economic recession and cuts in public expenditure. In focussing on the local dimensions of the resilience debate, this article argues that the term can provide useful insights into how the challenges facing local authorities in the UK can be reformulated and reinterpreted. The article also distinguishes between resilience as ‘recovery’ and resilience as ‘transformation’, with the latter's focus on ‘bouncing forward’ from external shocks seen as offering a more radical framework within which the opportunities for local innovation and creativity can be assessed and explained. While also acknowledging some of the weaknesses of the resilience debate, the dangers of conceptual ‘stretching’, and the extent of local vulnerabilities, the article highlights a range of examples where local authorities – and crucially, local communities – have enhanced their adaptive capacity, within existing powers and responsibilities. From this viewpoint, some of the barriers to the development of resilient local government are not insurmountable, and can be overcome by ‘digging deep’ to draw upon existing resources and capabilities, promoting a strategic approach to risk, exhibiting greater ambition and imagination, and creating space for local communities to develop their own resilience

DIAGNOSTIC AND PREVENTIVE SERVICES IN A NATIONAL INCREMENTAL DENTAL PLAN FOR CHILDREN

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65579/1/j.1752-7325.1977.tb02874.x.pd