One of the most present issues of computer wireless networks is the security. Comparing with their wired counterpart, the wireless networks not only accentuate some of the well-known security vulnerabilities but they are subject of new and specific ones. Among the existing wireless networks the ad hoc ones are the most exposed to attacks and collusions due to the absence of any centralized control. The most efficient way to ensure the communication secrecy, inclusively for ad hoc wireless networks, is the cryptography. From many reasons, following from specific operating conditions, the employment of asymmetric key techniques and Public Key Infrastructure is not a realistic choice. In the networks with a large number of nodes, as wireless sensor networks, a large number of secret keys are involved in order to ensure the communication secrecy. While dynamicity is one of the essential features of mobile wireless networks, when nodes may leave or join the network and in the absence of a centralized control entity, the management of secret keys is crucial. The paper presents the main aspects of mobile wireless networks security and focuses on the key management issue in ad-hoc wireless networks

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Abmuct-This paper presents two current-mode circuits which provide frequency multiplication for sinusoidal input signals. The circuits are based on translinear topologies that ensure high performances concerning frequency range, linearity and temperature stability, No selective circuits or signal conditioners ape required.

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Labour productivity growth is a necessary condition for social and economic progress, in general, and to overcome the economic crisis facing most of the world, in special. Applying innovative solutions, based on the ITC, is one of the straight ways for achieving that objective, both important and necessary. This paper presents a software solution applicable to industrial production based on numerically controlled machines. It involves a distributed client -server communication system, combined with MLP neural networks for the recognition of the 2D industrial objects, viewed from any angle. The information on prismatic and rotational parts to be processed by numerically controlled machine, are stored on a database server together with the corresponding processing programs. The client applications run on the numerically controlled machines and on the robots serving groups of machines. While the machines are fixed, the robots are mobile and can move from a machine to another. As a novelty of the proposed solution, in some well defined situations, the clients are allowed to change messages among them, in order to avoid the server overload. The neural networks are used to help robots to recognize the parts before and during manipulation.