Beyond royal estates and monasteries: landownership in the early medieval Ardennes

Most historians who have studied the medieval Ardennes have focused exclusively on royal and monastic properties, assuming that every early reference to land in the area is either to the property of royal monasteries or to fiscal land. Actually, the evidence from the region around Bastogne (Belgium), the centre of what would later be called pagus Ardennensis, shows that as early as the seventh century ‘private’ landowners were present and active in the area. This observation leads to a new reading of the rural economy and society, the formation of monastic property and the links between local and royal power in the early medieval Ardennes.     

The democracy tradition in US foreign policy and the Obama presidency

This article proposes a three‐level analysis of the democracy tradition in American foreign policy that identifies its ideational, strategic and policy dimensions and situates Barack Obama's presidency to date within it at each level. At the heart of this approach is the understanding that the motivations and practice of the United States' democracy promotion are shaped by its ideas about national identity, political order, national interest and international relations. This is the ideational source of the democracy tradition, which, as US power has grown, has led increasingly to decision‐makers setting strategic goals that include democratization abroad as a facilitator of other US goals. Only slowly has this led to the development of specific policies to that end, though, and democracy promotion as a discrete policy field mostly developed from the 1980s onwards. Democracy promotion went through a ‘boom’ after the end of the Cold War as the United States enjoyed unparalleled power on the international stage. It is clear that Barack Obama and his administration belong firmly in the democracy tradition at the ideational, strategic and policy level, and they have given no cause to expect any major change in his second term as far as democracy promotion is concerned. It is in any case a mistake to think that changes in the democracy tradition come from particular leaders; rather, it is the changing international environment confronting US foreign policy that is more likely, in the longer term, to lead to a shift away from democracy promotion.     

NONLINEAR SHAKE TABLE IDENTIFICATION AND CONTROL FOR NEAR-FIELD EARTHQUAKE TESTING

The primary focus of a structural shake table system is the accurate reproduction of acceleration records for testing. However, many systems deliver variable and less than optimal performance, particularly when reproducing large near-field seismic events that require extreme table performance. Improved identification and control methods are developed for large hydraulic servo-actuated shake table systems that can exhibit unacceptable tracking response for large, near-field seismic testing. The research is presented in the context of a 5-tonne shake table facility at the University of Canterbury that is of typical design. The system is identified using a frequency response approach that accounts for the actual magnitudes and frequencies of motion encountered in seismic testing. The models and methods developed are experimentally verified and the impact of different feedback variables such as acceleration, velocity and displacement are examined.

The methods show that shake table control in testing large near-field seismic events is often a trade off between accurate tracking and nonlinear velocity saturation of the hydraulic valves that can result in severe acceleration spikes. Control methods are developed to improve performance and include both acceleration and displacement feedback to reduce the acceleration spikes, and record modification, where the reference signal is modified to conform to the shake table's operational parameters. Results show record modification gives exact tracking for near-field ground motions, and optimal system response for reference signals with velocity components greater then the system capabilities. Overall, the research presents a methodology for simple effective identification, modelling, diagnosis and control of structural shake table systems that can be readily generalised and applied to any similar facility.