We consider the classical synchronised multiple access system with a single transmission channel and a randomised transmission protocol (ALOHA). We assume in addition that there is an energy supply mechanism, and any message transmission requires a unit of energy. There are two stochastic renewal inputs to the system, of messages and of energy supply. We study conditions on these inputs for (in)stability of the system.Index Terms-random multiple access; stochastic energy supply; (in)stability; generalised Foster criterion.

We study various models for the classical synchronised multiple access system with a single transmission channel, randomised transmission protocol (ALOHA) and additional common energy supply mechanism: any message requires charging energy for transmission. There are two stochastic renewal inputs to the system, of messages and of energy supply. We study conditions on these inputs for (in)stability of the models and their energy efficiency.

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This article describes the development of a multifunctional geoinformation system RANDOM (Risk Assessment of Nature Detriment due to Oil spill Migration), realizing a multiprocessor calculation of probabilistic risk models to assess the negative impact of the oil spill on the biota of the North Caspian. The urgency of the problems associated with the development of oil fields in a very vulnerable shallow part of the Caspian Sea, where a major accident could have disastrous consequences. We describe a risk model of biota damage in the case of accidental environmental pollution. The model rests on the formalization of the notions of the accident, environmental pollution, biomass, and biota sensitivity, which depend on each other in the case of an accident. In addition, this article describes the development process from design to implementation. The system is designed on the basis of service-oriented architecture (SOA), which allows for easy, flexible integration of services, and access them via the Internet. Through the use of SOA, the system can be expanded and upgraded. In this approach, the services may be located on physically different servers. Tests have shown the benefit of using a supercomputer; it enables us to obtain a risk assessment for an adequate time. This system is designed for professionals in the field of ecology and mathematical modelling and subsoil oil fields on the continental shelf of the seas and oceans. The RANDOM system as the final result of the decision of risk assessment tasks includes a series of calculation modules based on the methods of probability theory, computational mathematics, hydrodynamics, oil chemistry, marine biology, mathematical modelling, and geoinformatics.

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