This paper presents an architecture and a proof of concept implementation of a security infrastructure for mobile devices in an infrastructure based pervasive environment. The security infrastructure primarily consists of two parts, the policy engine and the policy enforcement mechanism. Each mobile device within a pervasive environment is equipped with its own policy enforcement mechanism and is responsible for protecting its resources. A mobile device consults the nearest policy server, notifies its current state including its present user, network presence, other accessible devices and location information if available. Using this information the policy server queries the "Rei" engine to dynamically create a policy certificate and issues it to the requesting device. The system wide policy is described in a semantic language "Rei", a lightweight and extensible language which is able to express comprehensive policies using domain specific information. The "Rei"policy engine is able to dynamically decide what rights, prohibitions, obligations, dispensations an actor has on the domain actions. A policy certificate is created and issued to the device. The policy certificate contains a set of granted permissions and a validity period and scope within which the permissions are valid. The policy certificate can be revoked by the policy enforcer based on expiration of the validity period or a combination of timeout, loss of contact with an assigned network.

The age of technology has changed the way that surgeons are being trained. Traditional methodologies for training can include lecturing, shadowing, apprenticing, and developing skills within live clinical situations. Computerized tools which simulate surgical procedures and/or experiences can allow for "virtual" experiences to enhance the traditional training procedures that can dramatically improve upon the older methods. However, such systems do not to adapt to the training context. We describe a ubiquitous computing system that tracks low-level events in the surgical training room (e.g. student locations, lessons completed, learning tasks assigned, and performance metrics) and from these derive the training context. This can be used to create an adaptive training system.

At the Krasnoyarsk hydroelectric plant, during construction of the concrete dam, double grouting of several test-construction outlines of contrac~on-shrinkage joints was carried out [i]. To evaluate the quality of the groutLug, controlholes were drilled* (Fig. 1), cores were removed from the zone of intersection with the joints, and hydraulic tests were performed. A total of 212 m of holes was drilled. During the drilling process it was found that the actual number of intersections with joints (44) amounts to 6890 of the design number (6190 in the construction outlines). This was due to the presence, in certain zones, of heavily shattered cores which made it difficult to establish the point of intersection of the hole with the joint, or to locate the toothing on the opposite side of the joint (with respect to the design).The nature of the core rupture depends on the relation between the strengths of the cement stone filling the joint and of the adjoining concrete, and the bond along the contact surfaces of these materials. In the test outlines, 12 cores were monolithic, 26 failed along the joint, and the remaining cores were shattered. As a rule, all three types of core are ex~acted from any given outline, since the conditions governing the formation and hardening of cement stone over the area of even a single outline are dissimilar.From the results of the core inspections, three characteristic types of concrete surfaces in the joints may be established (Table 1).

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Technologies of grout sealing and strengthening of soils and concretes by synthetic resins -epoxy and polyurethane -have become widespread during the past 10-20 years in world construction practice. For example, the technology of structural restoration of concrete (SCB) by injection of epoxy resins made it possible to restore the concrete structural members of coke ovens without extinguishing them in the Netherlands. The use of polyurethane foams for soil stabilization at coal mines in Germany, Japan, and other countries, including the Commonwealth of Independent States, is displacing traditional methods of supporting mine workings. The "Podur" technology is being used successfully by the Soletanche company for repairing a number of concrete dams in European countries. Our own specialists successfully used epoxy resins for repairing structures of the Volga-Baltic canal as far back as 1967-1971. Many research and industrial institutions of our country are engaged in problems of the synthesis, study, and use of epoxy and polyurethane resins. Polyurethane foam (PUF) materials PUF-328 and PUF-329 were developed by the "Polimersintez" research and industrial association (by I. R. Metlyakova) for strengthening weakened rocks by the grouting method. The consumption of polyurethanes for strengthening mine workings at Donbas mines was at the level of 3500 tons/yr in 1985-1990 [1].Experience in the area of the synthesis and use of hydrophilic isocyanate prepolymers [2] showed that by manipulating a limited quantity of initial substances (hydrophilic polyether, isocyanates) it is possible to obtain a broad spectrum of hydrophilic urethane-isocyanate oligomers able to form polyurethane ureas with hardening by a large but not strictly controllable quantity of water. The hydrophilic polyurethane foams of the Aquisol type created by our specialists on contact and mixing with water (including with ground and seepage waters) react with it, "solidify" the water, and in so doing increase in volume (due to liberation of gas during the reaction). The degree of expansion of the chemical foam forming reaches 5-30 (100) depending on the type of PUF material, relationship with water, and certain other factors. The use of analogous American-made PUFs on the Buchanan dam [3] was extremely effective. After numerous and ineffective attempts to reduce seepage on this dam over the course of many years, an effective method of eliminating seepage by injecting solutions foaming on mixing with water was found and realized. It was established that the foamed solution has great flexibility, mobility, and seals joints and cracks well despite their periodic opening and closing in accordance with the temperature and shrinkage deformations in the dam.At present considerable experience has been gained in using PUFs on many objects in our country and abroad. An analysis of this experience indicates that it is quite effective and economical in the case of grouting in media where the pressure of the ground and seepage waters is within limits up to 0.3-0....