Václav Přenosil

Quick algorithms for real-time discrimination of neutrons and gamma rays

Several new methods for the digital discrimination of neutrons and gamma-rays in a mixed radiation field are presented. The methods introduced discriminate neutrons and gamma rays successfully in the digital domain. They are mathematically simple and exploit samples during the life time of the pulse, hence appropriate for field measurements. All these methods are applied to a set of mixed neutron and photon signals from a stilbene scintillator and their discrimination qualities are compared.

Network Monitoring Approaches: An Overview

Network monitoring and measurement have become more and more important in a modern complicated network. In the past, administrators might only monitor a few network devices or less than a hundred computers. The network bandwidth may be just 10 or 100 Mbps; however, now administrators have to deal with not only higher speed wired network (more than 10 Gbps and ATM (Asynchronous Transfer Mode) network) but also wireless networks. Network administrators are constantly striving to maintain smooth operation of their networks. Network monitoring is a set of mechanisms that allows network administrators to know instantaneous state and long-term trends of a complex computer network. This paper provides the readers with an overview of the current network monitoring approaches, their architectures, features and properties. In addition, it presents a comparison between those approaches.

A Survey on Botnet Command and Control Traffic Detection

Internet users have been attacked by widespread email viruses earlier, but now scenario has been changed. Now attackers are no more interested to just attract media attention by infecting a large number of computers on the network; in fact, their interest has been shifted to compromising and controlling the infected computers for their personal profits. This new attack trend brings the concept of botnets over the global network of computers. With the high reported infection rates, the vast range of illegal activities and powerful comebacks, botnets are one of the main threats against the cyber security. This paper provides the readers with a background on botnet life-cycle, architecture and malicious activities. It also classifies botnet detection techniques, reviews the recent research works on botnet traffic detection and finally indicates some challenges posed to future work on botnet detection.

General solutions for MTTF and steady-state availability of NMR systems

Voting redundancy is a well-known technique to improve the fault tolerance of digital systems. Calculation of reliability and availability is a necessary part of every fault tolerant system design. Conventional techniques, including block diagram method, are unsuccessful when there is dependent failure, repair, or standby operation in the system. Use of Markov models also almost fails when system is composed of many elements or is repairable. However, the alternatives to reliability and availability, i.e. mean time to failure and steady state availability, respectively, are easily measurable using Markov graphs. In this paper, novel general form solutions for calculation of mean time to failure and steady-state availability of N-modular redundancy systems are presented.

Compact hybrid real-time hyperspectral imaging system with high effective spatial, spectral, and temporal resolution

Medical endoscopes for image-guided surgery commonly use standard color image sensors, discarding any more detailed spectral information. Medical spectroscopy devices with various spectral working ranges are specialized to specific medical procedures and in general are not usable for image-guided surgery due to limitations in spatial or temporal resolution. In this paper, we present an initial demonstrator of hyperspectral endoscope, composed of two image sensors with complementing parameters. Using this hybrid approach, combining sensors with different spatial and spectral resolutions and spectral ranges, we obtain improved coverage of all the respective parameters. After digitally processing and merging the video streams, while maintaining the better features of both, we obtain an imaging system providing high effective spatial, spectral, and temporal resolution. The system is based on field programmable gate arrays. It provides real-time video output (60 Hz), which is usable for navigation during image-guided surgery. The flexible system architecture allows for an easy extension of the processing algorithms and enables minimal video signal latency. Physical dimensions and portability of the system are comparable to standard off-the-shelf medical endoscope cameras. The device can output both processed video and standard visible light video signals on one or more video outputs of the system. The resulting processed video signal obtained from the combined image sensor data greatly increases the amount of useful information available to the end user.