In this paper we approach the challenges of partial discharges (PD) detection in high voltage cables using signal processing techniques based on time frequency methods combined with Recurrence Plot Analysis (RPA) and high order spectrum analysis (HOSA). Detection of PD poses many problems in terms of speed of calculation, selection criteria and multitude of causes which lead to the occurrence of PD. In order to overcome these drawbacks, we have developed an algorithm which uses the spectrogram to perform a fast detection of parts from the signal which are susceptible of PD activity. The second stage calculates for each zone a detection curve using the HOSA concept of bispectrum and RPA. The latter has been applied in many non-linear systems in order to characterize the process on the basis of the recurrence matrix obtained from a time series given by the system.

In this paper we approach the challenges of partial discharges (PD) detection in high voltage cables using signal processing techniques based on time frequency methods combined with Recurrence Plot Analysis (RPA) and high order spectrum analysis (HOSA). Detection of PD poses many problems in terms of speed of calculation and selection criteria, due to the nature of PD spectrum (frequency varying from a few hundreds of kilohertz up to hundreds of megahertz) and multitude of causes which lead to the occurrence of PD. These challenges take a great toll on the computing capability of today's PD detection systems. In order to overcome these drawbacks, we have developed an algorithm which uses the spectrogram to perform a fast detection of parts from the signal which are susceptible of partial discharge (PD) activity. The second stage calculates for each zone a detection curve using the HOS concept of bispectrum and RPA. The latter has been applied in many non-linear systems in order to characterize the process on the basis of the recurrence matrix obtained from a time series given by the system.

Buck switching power supplies usually use a PWM voltage control to stabilize the output voltage at the reference voltage level. If a classical PWM control technique is used, than high EMI noise peaks appear at the switching frequency and its harmonics. Spreading of the output voltage spectrum can be done, for example, by chaotification of the PWM command signal. This kind of the switching power supplies with low EMI is utilize in electronics equipments from different domains: medical, aeronautics etc. The proposed nonlinear control is based on the opto-coupler nonlinear characteristic included into nonlinear circuit of the feedback loop. The feedback nonlinear circuit assures a symmetrical nonlinear characteristic using two opto-couplers and a differential amplifier. The nonlinear characteristic is designed to minimize output voltage ripple. The nonlinear characteristic is initially modeled by a look-up table for an easy designing by changing of the characteristic parameters using trial and error method. The feasibility and effectiveness of this new and relative simple method is shown by simulation.

This paper analyzes the possibility of using a nonlinear controller to mitigate the current ripple of an inverter system powered by a Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack. Hybrid and fuel cell technologies need to be merged in Hybrid Power Sources (HPS) to assure high performance regarding the PEMFC energy efficiency and PEMFC life cycle. The nonlinear controller is designed based on inverse gain that gives a constant answer for all levels of current ripple. Its advantages will be showed in comparison with hysteretic current control technique (that was shown in part I). Finally, a fuzzy logic controller is proposed to design the nonlinear control law.

The paper presents a comprehensive approach of the fuzzy logic gates/circuits from both technological and circuit analysis point of view, using SPICE simulation, based on computing the sensitivities of current mirrors with n and p-channel MOS-FET (using units or tens microns for L and W parameters). CMOS technology has been recognized as the technology for implementing fuzzy logic gates/circuits in the current mode, which offers a high versatility for different fuzzy logic operations, low power dissipation and high integration density. The basic units of fuzzy logic gates/circuits are the current mirrors with single and/or multiple outputs, usually designed and fabricated in 5-10 microns CMOS technology.

The skin is the largest organ of the body and it protects against heat, light, injury and infection. Skin temperature is an important parameter for diagnosing diseases. Thermal analysis is non-invasive, painless, and relatively inexpensive, showing a great potential research. Since the thyroid regulates metabolic rate it is intimately connected to body temperature, more than, any modification of its function generates a specific thermal image on the neck skin. The shapes of thermal signatures are often irregular in size and shape. Euclidean geometry is not able to evaluate their shape for different thyroid diseases, and fractal geometry is used in this paper. Different thyroid diseases generate different shapes, and their complexity are evaluated by specific mathematical approaches, fractal analysis, in order to the evaluate selfsimilarity and lacunarity. Two kinds of thyroid diseases, hyperthyroidism and papillary cancer are analyzed in this paper. The results are encouraging and show the ability to continue research for thermal signature to be used in early diagnosis of thyroid diseases.

Radio communications is spreading more increasingly and people exposure to non-ionizing electromagnetic fields has increased due to emitting antennas. Human beings are complex electrochemical systems that communicate with the environment through electrical pluses. Electromagnetic field penetrates the human body and can alter functions of his cell, tissue and organs by modifying the biochemical processes. People have the ability to physiologically regulate their inner environment to ensure stability in response to fluctuations in the outside environment as a result of homeostasis process if the external sources are less than certain levels. The thyroid gland is one of the most exposed vital organs to electromagnetic radiation. Production of thyroid hormone is essential for metabolism, temperature regulation, and many other vital processes in the body. There are only few published papers reporting the effect of microwave radiation on thyroid. In this generic framework of the electromagnetic smog, that becomes less and less friendly, it is necessary to perform theoretical and experimental studies on the possible field levels that are currently applied to certain body parts. The aim of the present study was to assess the microwave field absorbed by human thyroid gland, and to predict local temperature increase for staff working in the vicinity of antennas transmitting high microwave power, for example on maritime ships. The temperature does not depend linear versus microwave power density. The finite element method was used to solve coupled equations governing the propagation microwave field in different environments with heat generation and propagation. In the paper are presented the necessary specific absorption rates, (SAR), as temperature increases up to 38-43 Celsius degrees for the frequency range between 1 and 4 GHz. Microwave signal power used by ships may lead to increase of 2-4 degrees Celsius.

In order to control water flow in power generation systems, obtaining precise information about the parameters of the flow is important. The construction of such systems, as well as the operating conditions, impose the use of non-intrusive techniques. The use of ultrasounds allows solving this problem in a simple and elegant manner. The technique consists in sending a signal to be affected by the flow without sensibly interacting with it, and then extracting the desired parameters of the flow from the received signal. The paper first presents how the acoustic wave is altered by the propagation in the liquid environment, and then it studies the means to analyze the received signal in order to obtain from it information about two important parameters of the flow - the temperature of the water and the flow rate. Polynomial phase modeling is used, for obtaining a good estimation of the propagation times.

In this paper, we present a novel cryptosystem based on programmable cellular automata (PCA). The cryptosystem is featured by its large key space and high speed due to cellular automata's parallel information processing property. Moreover, the encryption and decryption devices share the identical module, which preserves the merit of local connection of cellular automata in both encryption and decryption devices. So the scheme could be implemented efficiently in hardware. The design has been implemented in both: in software using C# programming language and in hardware on a XC3S400 FPGA board using VHDL. We apply such system in encryption of medical data sent over the internet and Yahoo messenger conversations.

The Digital Video Broadcasting—Satellite (DVB‐S) standard was originally conceived for TV and radio broadcasting. Later, it became possible to send IP packets using encapsulation methods such as Multi Protocol Encapsulation, MPE, or Unidirectional Lightweight Encapsulation, ULE. This paper proposes a chaos based security system for IP communications over DVB‐S with ULE encapsulation.The proposed security system satisfies all the security requirements while respecting the characteristics of satellite links, such as the importance of efficient bandwidth utilization and high latency time. It uses chaotic functions to generate the keys and to encrypt the data. The key management is realized using a multi‐layer architecture.A theoretical analysis of the system and a simulation of FTP and HTTP traffic are presented and discussed to show the cost of the security enhancement and to provide the necessary tools for security parameters setup.

The security of computer networks connected to the internet is an important, vital and hotly contested real-world issue. Once the computer networks get connected to the internet, the number of attacks, their strength and intensity grow exponentially. All the attacks then exploit breaches in the network security. In this paper some of the passive and active attacks against the computer networks are presented. The anatomy of the attack is presented showing the phases and the techniques for penetrating into the computer networks – with the purpose to stress and highlight the several dangers faced by the network manager and the utmost necessity of setting a proper corporate network security policy in place. The detection of an attack is a difficult task because the detection technology is still in its infancy and has yet to mature, also once the attack is detected, the attacker in most cases still remains unknown. After the detection of the attack, the analyst needs some time to establish the actual nature of the attack.

We notice a very strong “all IP” trend characterizing today's communication technology. There is a powerful IP backbone in place, but, in some cases, the “last mile problem” remains to be solved. One of the solutions for this problem is represented by IP communications over satellite. This paper analyses the compatibility between a recently proposed security enhancement for IP communications over satellite DVB and the multicast communications. We discuss the importance of multicast services and we show that the recently proposed security enhancement has built in multicast support, i.e. only a small upgrade in the receivers is needed to allow multicast communications.

Humans and animals in general, are usually in a thermal steady state with respect to their surroundings. The tissues heat, generated at normal or diseases states, is lost to environment though several mechanisms: radiation, conduction, convection, evaporation, etc. Skin temperature is not the same on the entire body and a thermal body signature can be got. The temperature at skin level was measured by a thermistor, conduction component and by an IR camera, radiation component. A theoretical analysis using Weinhaum and JIJI model was done. The three images are investigated in order to get a cheap method for the early cancer diagnosis.

Traditionally physical systems have been designed by engineers using complex collections of rules and principles. The design process is top-down in nature and begins with a precise specification. This contrasts very strongly with the mechanisms which have produced the extraordinary diversity and sophistication of living creatures. In this case the ‘‘designs’’ are evolved by a process of natural selection. The design starts as a set of instructions encoded in the DNA whose coding regions are first transcribed into RNA in the cell nucleus and then later translated into proteins in the cell cytoplasm. The DNA carries the instructions for building molecules using sequences of amino acids. Eventually after a number of extraordinarily complex and subtle biochemical reactions an entire living organism is created. The survivability of the organism can be seen as a process of assembling a larger system from a number of component parts and then testing the organism in the environment in which it finds itself (Miller, 2000). The main target of the evolvable hardware is to build a digital circuit using bio inspired methods like genetic algorithms. Here the potential solutions are coded like configuration vectors which command interconnection between logical cells inside the reconfigurable circuit. All configuration vectors represent the genotype and one single configuration vector is the individual with its own characteristics (like chromosome). The individuals are generated by genetic operators like crossover or mutation. One individual give one solution circuit which is tested in evaluation module. The circuit obtained from the individual consist the phenotype. The circuit behavior is compared with target functions, which we desire to implement. The result is fitness: if the circuit approximates the behavior of the target function, we have a good fitness for the individual which generate the circuit. Then each individual whit its fitness gets into selection module where the future parents in crossover and mutation are decided. Finally we have a circuit solution which implements the target function. We have an evolved synthesis of digital circuit – a method like assemble and test. This method can be useful because explore the design space beyond the limits imposed by traditional design methods. Two research directions are developed in evolvable hardware. In extrinsic evolvable hardware the individuals are obtained from software implementation on computer and phenotype consist in high level abstract circuits like SPICE object files or FPGA configuration files (.bit). The intrinsic evolution, on the other hand, supposes that entire evolution process is inside one or more chips (FPGA): the hardware implementation of evolved hardware. The challenge is to design an intrinsic evolution because can be used for applications like robots control system. But this involves implementation of the software based algorithms in hardware modules.

This paper presents the Matlab implementation of a low bit rate communication system for transmitting Mixed-Excitation Linear Predictive vocoder data, based on Matlab's ability to interact from Simulink with external programming languages (such as Java or C Dynamic Link Libraries). Even if the use of external functions in the Simulink Module has some limitations, it allows the rapid implementation of testbeads for secure voice communication between different computers (using the encryption operations provided by the Java Cryptography Architecture). The designed system was implemented and tested in a wireless communication system.

The DVB-S (Digital Video Broadcasting - Satellite) was originally developed as a TV broadcasting protocol. Later on two encapsulation protocols were developed in order to allow network level TCP/IP encapsulation: Multi Protocol Encapsulation — MPE and Unidirectional Lightweight Encapsulation — ULE. This provided a high quality internet access via satellite, which can be multiplexed even with radio and TV transmissions. In this paper, we propose a security system for the ULE based on chaotic sequences for the key management and data encryption. The key management system is based on a multilayer key model. The proposed system provides security services responding to the security requirements of IP over satellite DVB. To quantify the efficiency of the proposed system, we have done a comparative study (theoretically and by simulation) of the data overhead for different transport protocols and different sets of security parameters. Obtained results confirm the efficiency of the proposed system.

The body of this thesis deals with the analysis and design of circuits from a system on chip CMOS imager. The main topics are related to the analog blocks interfacing the photodiodes, processing of the analog signals and noise sources in the analog path to the A/D converter. Minimizing noise in such applications it is an important and challenging goal for designers. A good signal to noise ratio will allow a good resolution at the system level and finally a better image. As result precautions must be taken from the very beginning of the design process in order to minimize noise sources generated in the analog blocks. One of the scopes of this thesis is to identify, analyze and recommend solutions for noise reduction in integrated circuits including array of CMOS sensors. 1. ANALYSIS OF CMOS SENSORS AND ANALOG BLOCKS PROCESSING DATA FROM PIXELS 1.1. CMOS Imager Description A CMOS imager is comprised of an array of photodiodes surrounded by analog circuits for processing the signals. The sensors are usually called pixels and are placed in a matrix structure. A first stage of amplifiers, one amplifier associated to each column, amplifies the signals from pixels in a single-end configuration and outputs the signals to a second stage. The second stage of amplifiers multiplexes the column signals to one differential signal at the input of an A/D converter with a programmable gain amplifier. The first stage of amplifiers uses a double sample technique to minimize fixed pattern noise from pixels and columns. 1.2. Functional Description of the CMOS Imager There are multiple structures of a pixel. A 3T structure have been implemented due to advantages related to higher power supply rejection ratio, higher speed in reading pixel array, lower noise in pixel and reduced fixed column pattern noise. Some disadvantages are associated with this structure: reduced fill factor, large size of pixel, relatively complicated circuit to access pixel, fixed pixel pattern noise, reduced voltage range as result of presence of a source follower. The figure 1.1 below shows two similar techniques, double sampling (DS) and correlated double sampling (CDS). 12 UNIVERSITY OF PITESTI – ELECTRONICS AND COMPUTERS SCIENCE, SCIENTIFIC BULLETIN, No. 8, Vol. 1, 2008 ISSN – 1453 – 1119 Fig. 1.1. Timing Diagram for DS and CDS In applications needing image capture sometime the system works at different levels of ambient light. The level of ambient light can have a big impact on image quality in image recognition systems. As result a special circuit has been dedicated to measure the ambient light and send the signals to a processor in order to adjust the gain the analog path. A separate array of photodiodes located at the periphery of the imager and monitored by a low resolution A/D converter allows the system to control the gain [1]. 2. SWITCHED CAPACITOR AMPLIFIERS IN PIXEL DATA PROCESSING 2.1. Circuits in Switched Capacitor Amplifiers The basic circuits in switched capacitor amplifiers are represented by CMOS switches, capacitors and operational amplifiers. In a good process an error of about 0.1% is due to the capacitor mismatch. To keep the total error within this range the ON resistance of the CMOS switch charging a capacitor is given by: Ron · C ≤ T/20 (2.1) where T is the switching period. In designing switches, a few things must be considered: Ron could be decreased by increasing W/L but charge injection will increase; Ron is dependant on input voltage; some non-linear distortion should be taken into consideration; Ron is dependant on temperature (μ, Vth) and process (Cox, μ, Vth). Non-ideal characteristics of operational amplifiers such as offset, finite open loop gain, finite bandwidth, slew rate, output impedance should also be considered in design. As general rules to follow:

This paper presents a hardware implementation in a FPGA circuit of an efficient encryption algorithm based on hybrid additive programmable cellular automata (HAPCA). We present a novel approach for a high-speed encryption system prototyped using a single FPGA. The approach is based upon a one-dimensional HAPCA architecture. A regular, modular, and cascadable hardware implementation of the cellular automata encryption algorithm has been implemented, which is efficient in terms of VLSI technology. The encryption algorithm based on the theory of cellular automata was realized using simple digital circuits and memory, and we implemented it on an emulation platform based on FPGA circuit. The experimental results prove the powerful of cellular automata encryption systems. The design has been specified in VHDL targeted on a XILINX XC3S400 based FPGA and verified for functional correctness by software simulation.

In this paper, we present a new encryption algorithm based on the programmable cellular automata (PCA) theory. The cryptosystem is featured by its large key space and high speed due to cellular automatapsilas parallel information processing property. Moreover, the encryption and decryption devices share the identical modules, which give appropriate solutions for implementation of the cryptographic modules in high speed applications. So the scheme could be implemented efficiently in hardware, in reconfigurable hardware structures. The design has been implemented in both: in software using C# programming language and in hardware on a XC3S500E FPGA board using VHDL.

In this paper we present types of nonlinearities, passive intermodulation sources concerning the materials nonlinearities and we point out that the intermodulation products will appear in the form of interchannel crosstalk. We also build a nonlinear system modelling. In conclusion high order combinations of tones and adjacent-channel interference products appear in the useful frequency band. Concerning the passive nonlinear systems, these are bilateral and have a symmetric static transfer characteristic related to the origin, resulting that can exist only odd terms. ANALYZE OF THE FEED-FORWARD CONTROL FOR A PURE SINE INVERTER Nicu BIZON, Laurentiu IONESCU, Alin MAZARE, Mihai OPROESCU University of Pitesti, Targu din Vale, Nr. 1 nbizon@upit.ro