Best-first Enumeration Based on Bounding Conflicts, and its Application to Large-scale Hybrid Estimation

With the rise of autonomous systems, there is a need for them to have high levels of robustness and safety. This robustness can be achieved through systems that are self-repairing. Underlying this is the ability to diagnose subtle failures. Likewise, online planners can generate novel responses to exceptional situations. These planners require an accurate estimate of state. Estimation methods based on hybrid discrete/continuous state models have emerged as a method of computing precise state estimates, which can be employed for either diagnosis or planning in hybrid domains. However, existing methods have difficulty scaling to systems with more than a handful of components. Discrete state estimation capabilities can scale to this level by combining best-first enumeration and conflict-directed search. Best-first methods have been developed for hybrid estimation, but the creation of conflict-directed methods has previously been elusive. While conflicts are used to learn from constraint violation, probabilistic hybrid estimation is relatively unconstrained. In this paper we present an approach to hybrid estimation that unifies best-first enumeration and conflict-directed search through the concept of "bounding" conflicts, an extension of conflicts that represent tighter bounds on the cost of regions of the search space. This paper presents a general best-first search and enumeration algorithm based on bounding conflicts (A*BC) and a hybrid estimation method based on this enumeration algorithm. Experiments show that an A*BC powered state estimator produces estimates faster than the current state of the art, particularly on large systems

Radiation resistance of Ge, Ge0.93Si0.07, GaAs and Al0.08Ga0.92 as solar cells

Solar cells made of Ge, Ge(0.93)Si(0.07) alloys, GaAs and Al(0.08)Ga(0.92)As were irradiated in two experiments with 1-meV electrons at fluences as great as 1 x 10(exp 16) cm(exp-2). Several general trends have emerged. Low-band-gap Ge and Ge(0.93)Si(0.07) cells show substantial resistance to radiation-induced damage. The two experiments showed that degradation is less for Al(0.08)Ga(0.92)As cells than for similarly irradiated GaAs cells. Compared to homojunctions, cells with graded-band-gap emitters did not show the additional resistance to damage in the second experiment that had been seen in the first. The thickness of the emitter is a key parameter to limit the degradation in GaAs devices

Wireless sensed environment for body area networks

In low power wireless body area networks it is envisaged that there will be communication between on-body devices and wireless nodes placed in the environment (sensed environment) to provide a range of applications including health monitoring. However, there remain major challenges to realise this scenario such as decisions on the optimal node location, node orientation, transmit power level, and the number of nodes to cover the area of interest (sensed environment) which if not correct can lead to poor coverage or over-provisioned, oversized networks. In this paper we experiment with a BAN device and nodes deployed in a variety of locations throughout an office environment to represent a sensed environment. Packet loss rates (PLR) were analysed to explore trade-offs between node densities and transmit power levels. We determine that the deployment location, the density, and BAN transmission power level are important factors to be considered in the scenario where a mobile BAN communicates with a sensed environment. We found that deploying the environment nodes at chest height on the surrounding wall yielded the best results in terms of coverage and node density providing an optimal link between the BAN and the sensed environment

Your Estate - What Property? What Rights?

This last article of the Your Estate series explains the two basic kinds of proprerty and outlines the types of rights of ownership in property that form the base for sound planning of an estate and other property transfers

How Estates Are Settled

This is the first of a series of articles about the procedures necessary or available in settling an estate, in transferring property before or after death and about the different purposes and needs for these procedures

If You Have a Will

Only by making a will or some other advance property transfer arrangement can a person set up his own laws of descent and make sure that his wishes for the distribution of his property will be carried out after his death

What Costs for Settlement?

Besides tax costs, what other kinds of costs are involved in settling an estate? This fifth article in the series deals with these, how to anticipate them and also with the importance of financial liquidity of an estate