Mean drift forces on arrays of bodies due to incident long waves

The scattering of long water waves by an array of bodies is investigated using the method of matched asymptotic expansions. Two particular geometries are considered, these are a group of vertical cylinders extending throughout the depth and a group of floating hemispheres. From these solutions, the low-frequency limit of the ratio of the mean drift force on a group of N bodies to that on a single body is calculated. For a wide range of circumstances this drift force ratio is N2 which is in agreement with previous numerical work. Further drift force enhancement is possible for certain configurations of vertical cylinders

The added mass for two-dimensional floating structures

The diagonal terms in the added mass matrix for a two-dimensional surface-piercing structure, which satisfies a geometric condition known as the John condition, are proven to be non-negative. It is also shown that the heave coefficient, associated with a symmetric system of two such structures, is non-negative when the length of the free surface connecting the structures lies between an odd, and the next higher even, number of half-wavelengths. The sway and roll coefficients, associated with antisymmetric motion of the system, are non-negative in the complementary intervals. For a specific geometry these intervals are equivalent to frequency ranges. Negative added mass is associated with rapid variations with frequency, due to complex resonances that correspond to simple poles of the associated radiation potential in the complex frequency domain. Approximate techniques are used to show that, for systems of two structures, complex resonances are located at frequencies consistent with the intervals in which negative added mass is able to occur

Capturing the Benefits of Restoration: Local Business Utilization and Opportunities for Growth in Northwestern Montana

Restoration and maintenance of forests and watersheds is increasingly a focus of management on public lands and, in addition to traditional forest management activities, has the potential to contribute to the economic vitality of local, forest-dependent communities. However, research has shown that the extent to which local communities benefit from restoration and management activities is highly variable. This study seeks to understand whether local communities in northwestern Montana are capturing the benefits of these activities on public lands by analyzing federal contracting trends. Specifically, this study 1) characterizes the value and type of federal contracts along with the spatial distribution of businesses engaged in restoration and management activities in northwestern Montana; 2) identifies the determinants of local business utilization; and 3) analyzes the use of subcontractors and the impacts this has on the distribution of benefits. The results of this study suggest that factors including Small Business Administration set-asides can negatively affect local business utilization, while certain types of work, such as heavy equipment work, and the location of work can have a positive effect on local business utilization. Businesses awarded contracts by the Forest Service were found to be distributed across 28 states and two countries. However, subcontractors were found to be predominantly located in Montana, suggesting that the analysis of only prime contracts may obscure impacts to rural, forest-dependent communities in the study area. Opportunities to increase the share of benefits captured by forest-dependent communities could include education and training on Small Business Administration set-aside programs to improve participation, targeted outreach to tribal- and other minority-owned businesses, and restructuring of contract opportunities

Strong, Weak and Branching Bisimulation for Transition Systems and Markov Reward Chains: A Unifying Matrix Approach

We first study labeled transition systems with explicit successful termination. We establish the notions of strong, weak, and branching bisimulation in terms of boolean matrix theory, introducing thus a novel and powerful algebraic apparatus. Next we consider Markov reward chains which are standardly presented in real matrix theory. By interpreting the obtained matrix conditions for bisimulations in this setting, we automatically obtain the definitions of strong, weak, and branching bisimulation for Markov reward chains. The obtained strong and weak bisimulations are shown to coincide with some existing notions, while the obtained branching bisimulation is new, but its usefulness is questionable

Metamorphic Domain-Specific Languages: A Journey Into the Shapes of a Language

External or internal domain-specific languages (DSLs) or (fluent) APIs? Whoever you are -- a developer or a user of a DSL -- you usually have to choose your side; you should not! What about metamorphic DSLs that change their shape according to your needs? We report on our 4-years journey of providing the "right" support (in the domain of feature modeling), leading us to develop an external DSL, different shapes of an internal API, and maintain all these languages. A key insight is that there is no one-size-fits-all solution or no clear superiority of a solution compared to another. On the contrary, we found that it does make sense to continue the maintenance of an external and internal DSL. The vision that we foresee for the future of software languages is their ability to be self-adaptable to the most appropriate shape (including the corresponding integrated development environment) according to a particular usage or task. We call metamorphic DSL such a language, able to change from one shape to another shape

Wrinkling of a bilayer membrane

The buckling of elastic bodies is a common phenomenon in the mechanics of solids. Wrinkling of membranes can often be interpreted as buckling under constraints that prohibit large amplitude deformation. We present a combination of analytic calculations, experiments, and simulations to understand wrinkling patterns generated in a bilayer membrane. The model membrane is composed of a flexible spherical shell that is under tension and that is circumscribed by a stiff, essentially incompressible strip with bending modulus B. When the tension is reduced sufficiently to a value \sigma, the strip forms wrinkles with a uniform wavelength found theoretically and experimentally to be \lambda = 2\pi(B/\sigma)^{1/3}. Defects in this pattern appear for rapid changes in tension. Comparison between experiment and simulation further shows that, with larger reduction of tension, a second generation of wrinkles with longer wavelength appears only when B is sufficiently small.Comment: 9 pages, 5 color figure

Developing an international higher education partnerships between high and low-income countries: two case studies

Many people and departments in higher education institutions and hospitals across the globe have objectives that include cross-national partnership working, internationalisation, capacity-building and sharing education and research. We find such commendable ideals at a global level in the Sustainable Development Goals (SDGs) to strategic plans of individual organisations from both low and high-income countries. Using a case-study approach this paper offers insights into some of the key practical issues around global partnership working. We use two case studies of a developing partnership between two separate higher education institutions from the United Kingdom (UK) and one from Nepal. To inform and guide others interested in developing global partnerships we highlight key the reasons for, considerations about, key procedures around the development of such Nepal-UK partnerships and key challenges

A knowledge-based approach to scientific workflow composition

Scientific Workflow Systems have been developed as a means to enable scientists to carry out complex analysis operations on local and remote data sources in order to achieve their research goals. Systems typically provide a large number of components and facilities to enable such analysis to be performed and have matured to a point where they offer many complex capabilities. This complexity makes it difficult for scientists working with these systems to readily achieve their goals. In this thesis we describe the increasing burden of knowledge required of these scientists in order for them to specify the outcomes they wish to achieve within the workflow systems. We consider ways in which the challenges presented by these systems can be reduced, focusing on the following questions: How can metadata describing the resources available assist users in composing workflows? Can automated assistance be provided to guide users through the composition process? Can such an approach be implemented so as to work with the resources provided by existing Scientific Workflow Systems? We have developed a new approach to workflow composition which makes use of a number of features: an ontology for recording metadata relating to workflow components, a set of algorithms for analyzing the state of a workflow composition and providing suggestions for how to progress based on this metadata, an API to enable both the algorithms and metadata to utilise the resources provided by existing Scientific Workflow Systems, and a prototype user interface to demonstrate how our proposed approach to workflow composition can work in practice. We evaluate the system to show the approach is valid and capable of reducing some of the difficulties presented by existing systems, but that limitations exist regarding the complexity of workflows which can be composed, and also regarding the challenge of initially populating the metadata ontology