Theoretical study of Oldroyd-b visco-elastic fluid flow through curved pipes with slip effects in polymer flow processing

The characteristics of the flow field of both viscous and viscoelastic fluids passing through a curved pipe with a Navier slip boundary condition have been investigated analytically in the present study. The Oldroyd-B constitutive equation is employed to simulate realistic transport of dilute polymeric solutions in curved channels. In order to linearize the momentum and constitutive equations, a perturbation method is used in which the ratio of radius of cross section to the radius of channel curvature is employed as the perturbation parameter. The intensity of secondary and main flows is mainly affected by the hoop stress and it is demonstrated in the present study that both the Weissenberg number (the ratio of elastic force to viscous force) and slip coefficient play major roles in determining the strengths of both flows. It is also shown that as a result of an increment in slip coefficient, the position of maximum velocity markedly migrates away from the pipe center towards the outer side of curvature. Furthermore, results corresponding to Navier slip scenarios exhibit non-uniform distributions in both the main and lateral components of velocity near the wall which can notably vary from the inner side of curvature to the outer side. The present solution is also important in polymeric flow processing systems because of experimental evidence indicating that the no-slip condition can fail for these flows, which is of relevance to chemical engineers

Application of the thermal dose concept for predicting the necrosed tissue volume during ultrasound surgery

The concept of calculated thermal dose was used to predict the size of the necrosed tissue volume during high-intensity focussed ultrasound surgery. The model presented was verified using experimental data in rabbit muscle and cat brain. The agreement is good and therefore, this model can be used to give guidelines for the sonication prior to clinical ultrasound surgery

JACPoL: A Simple but Expressive JSON-based Access Control Policy Language

Part 2: Security of DataInternational audienceAlong with the rapid development of ICT technologies, new areas like Industry 4.0, IoT and 5G have emerged and brought out the need for protecting shared resources and services under time-critical and energy-constrained scenarios with real-time policy-based access control. The process of policy evaluation under these circumstances must be executed within an unobservable delay and strictly comply with security objectives. To achieve this, the policy language needs to be very expressive but lightweight and efficient. Many existing implementations are using XML (Extensible Markup Language) to encode policies, which is verbose, inefficient to parse, and not readable by humans. On the contrary, JSON (JavaScript Object Notation) is a lightweight, text-based and language-independent data-interchange format that is simple for humans to read and write and easy for machines to parse and generate. Several attempts have emerged to convert existing XML policies and requests into JSON, however, there are very few policy specification proposals that are based on JSON with well-defined syntax and semantics. This paper investigates these challenges, and identifies a set of key requirements for a policy language to optimize the policy evaluation performance. According to these performance requirements, we introduce JACPoL, a descriptive, scalable and expressive policy language in JSON. JACPoL by design provides a flexible and fine-grained ABAC (Attribute-based Access Control), and meanwhile it can be easily tailored to express a broad range of other access control models. This paper systematically illustrates the design and implementation of JACPoL and evaluates it in comparison with other existing policy languages. The result shows that JACPoL can be as expressive as existing ones but more simple, scalable and efficient