Abstract
In this paper we analyse the estimates of the matrices produced by the non-biased deterministic-stochastic subspace identification algorithms (NBDSSI) proposed by Van Overschee and De Moor ( 1996). First, an alternate expression is derived for the A and C estimates. It is shown that the Chiuso and Picci result ( Chiuso and Picci 2004) stating that the A and C estimates delivered by this algorithm robust version and by the Verhaegen's MOESP (Verhaegen and Dewilde 1992a, Verhaegen and Dewilde 1992b, Verhaegen 1993, Verhaegen 1994) are equal, can be obtained from this expression. An alternative approach for the estimation of matrices B and D in subspace identification is also described. It is shown that the least squares approach for the estimation of these matrices estimation can be just expressed as an orthogonal projection of the future outputs on a lower dimension subspace in the orthogonal complement of the column space of the extended observability matrix. Since this subspace has a dimension equal to the number of outputs, a simpler and numerically more efficient ( but equally accurate) new subspace algorithm is provided.

Abstract
In this paper a hybrid algorithm to solve Irregular Strip Packing problems is presented. The metaheuristic simulated annealing is used to guide the search over the solution space while linear programming models are solved to generate neighbourhoods during the search process. These linear programming models, which are used to locally optimise the layouts, derive from the application of compaction and separation algorithms. Computational tests were run using instances that are commonly used as benchmarks in the literature. The best results published so far have been improved by this new hybrid packing algorithm.

Abstract
This paper presents a motion planning and control method with application in the field of legged robots. The general aim is to explore a set of simple underlying principles that govern balance of posture and gait of biped robots, and to develop control methodologies for such a highly unstable and non linear plants. The proposed controller reflects a hierarchical structure based on the interaction forces between the foot and ground and simple feedback rules used online. The algorithms are applied to a simulated 3-D leg model with five degrees of freedom (DOF). The simulation analyses demonstrate the capability of the control system to keep balance when the leg executes different tasks. To validate the proposed method several aspects are investigated, such as the posture robustness on the level ground when subject to external perturbations, the adaptation when standing in a moving platform and the improvements introduced by the compensation of the tangential reaction forces.

Abstract
Recently renewed interest in scalable database systems for shared nothing clusters has been supported by replication protocols based on group communication that are aimed at seamlessly extending the native consistency criteria of centralized database management systems. By using a read-one/write-all-available approach and avoiding the fine-grained synchronization associated with traditional distributed locking, one needs just a single distributed interaction step for each update transaction. Therefore the system can easily be scaled to a large number of replicas, especially, with read intensive loads typical of Web server support environments. In this paper we point out that 1-copy equivalence for causal consistency, which is subsumed by both serializability and snap-shot isolation criteria, depends on basic session guarantees that are costly to ensure in clusters, especially in a multi-tier environment. We then point out a simple solution that guarantees causal consistency in the Database State Machine protocol and evaluate its performance, thus highlighting the cost of seamlessly providing common consistency criteria of centralized databases in a clustered environment. Copyright 2006 ACM.

Abstract
In this paper it is proposed a probabilistic stead-state security assessment of an electric power system using a Monte Carlo method. This approach evaluates a probabilistic measure of the system security, instead of just a particular response to a specified contingency. Performance indices are used to assess the impact of the contingencies in the power system security. These indices allow to accurately evaluate the influence of the overloads, voltage limit violations and voltage stability problems in the power network. A probabilistic version the SECURsySTEM software package developed by the authors was applied to the IEEE 118 busbars test power system. During the simulation time, the occurrence of contingencies and the subsequent protective actions are assumed as a stochastic process. Finally, some conclusions that provide a valuable contribution to the understanding of the power system security analysis are pointed out.

Abstract
Ad-hoc networks that are connected with the infrastructure Internet are named hybrid ad-hoc networks. In 4G communications scenarios, hybrid ad-hoc networks seem to be valuable since they may increase the coverage of wireless networks with minor costs. Using them, terminals out of range of an access point or a base station, or not having adequate network interfaces, may reach the operator's infrastructure via other terminals. This paper presents a hybrid ad-hoc network solution and a testbed implementation.