Impact Response of Elasto-Plastic Granular Chains Containing an Intruder Particle

Wave propagation in homogeneous granular chains subjected to impact loads causing plastic deformations is substantially different from that in elastic chains. To design wave tailoring materials, it is essential to gain a fundamental understanding of the dynamics of heterogeneous granular chains under loads where the effects of plasticity are significant. In the first part of this work, contact laws for dissimilar elastic-perfectly plastic spherical granules are developed using finite element simulations. They are systematically normalized, with the normalizing variables determined from first principles, and a unified contact law for heterogeneous spheres is constructed and validated. In the second part, dynamic simulations are performed on granular chains placed in a split Hopkinson pressure bar (SHPB) setup. An intruder particle having different material properties is placed in an otherwise homogeneous granular chain. The position and relative material property of the intruder is shown to have a significant effect on the energy and peak transmitted force down the chain. Finally, the key nondimensional material parameter that dictates the fraction of energy transmitted in a heterogeneous granular chain is identified

Providing nursing care in care homes

In this article, Professor Jeremy Cooper describes the new procedures for the assessment and provision of nursing care and medical needs in residential care homes. </jats:p

Doing the right thing : corporate social responsibility in a global marketplace

Globalisation, mass consumer awareness and public accountability are all factors in persuading companies to adopt ethical policies. As companies become more accountable not only for their own actions but for those within their supply chain, they have to adapt to ensure success within the context of the global society they operate in. Professor Jeremy Moon (Professor of Corporate Social Responsibility at the University of Nottingham Business School and Director of the International Centre for Corporate Social Responsibility) discusses some of the challenges faced by modern companies in responding to the various pressures driving them to focus on contributing to society as well as on business performance. He also talks about the big challenges ahead for international business and what role The University of Nottingham Business School can provide in further developing its teaching and research to best prepare graduates for success in the current climate.

Handling and Manhandling Civilians in Civil Wars: Determinants of the Strategies of Warring Factions

Abstract The toll of civil conflict is largely borne by civilian populations, as warring factions target noncombatants through campaigns of violence. But significant variation exists in the extent to which warring groups abuse the civilian population: across conflicts, across groups, and within countries geographically and over time. Using a new dataset on fighting groups in Sierra Leone, this paper analyzes the determinants of the tactics, strategies, and behaviors that warring factions employ in their relationships with non-combatants. We first describe a simple logic of extraction which we use to generate hypotheses about variation in levels of abuse across fighting units. We then show that the most important determinants of civilian abuse are internal to the structure of the faction. High levels of abuse are exhibited by warring factions that are unable to police the behavior of their members because they are more ethnically fragmented, rely upon material incentives to recruit participants, have weak social capital, and lack mechanisms for punishing indiscipline. Alternative explanations that emphasize the importance of local community ties and contestation do not find strong support in the data

Perching Using a Quadrotor with Onboard Sensing

This thesis presents an implementation of autonomous indoor perching using only onboard sensors on a low-cost, custom-built quadrotor. The perching aggressive maneuver is representative of a class of control problems for aerobatics that requires an agile and robust control system for maneuvering accurately at high speeds. Such research extends the typical functionality of micro air vehicles (MAV) from low speed and stationary observation to dynamic aerobatic transitions for broader operational capabilities including confined landings and evasive maneuvering. To achieve this, three major challenges are overcome: precise and real-time positioning, sensing of the perch and path to the perch, and control methods for robust and accurate tracking at high speeds. Navigation in unstructured, global positioning system (GPS)-denied environments is achieved using a visual Simultaneous Localization and Mapping (SLAM) algorithm that relies on an onboard monocular camera. A secondary camera, capable of detecting infrared light sources, is used to locate the pathway for the maneuver and the perch, simulating sensing of the actual perch, for perching without prior knowledge of the location of the perch. The full physical system architecture is covered in detail, indicating the components and integration necessary to obtain effective aggressive control of an inexpensive quadrotor. The difficulties of attitude stabilization on noisy and lower-quality sensors are successfully addressed so that the air vehicle can be treated as a simple second-order system for the purposes of navigation and response to dynamic maneuvering commands. The system utilizes nested controllers for attitude stabilization, vision-based navigation, and perching guidance, with the navigation controller implemented using novel nonlinear saturation control within a Proportional-Integral-Derivative (PID) structure. The quadrotor is therefore able to autonomously sense the perch, reach initial high speeds for obtaining rapid deceleration from aerodynamic effects, dynamically transition to a high angle of attack post-stall configuration, and make a low-speed accurate landing on an inclined surface, using only onboard sensors