Scielo RSS<![CDATA[Journal of Microwaves, Optoelectronics and Electromagnetic Applications]]>
http://www.scielo.br/rss.php?pid=2179-107420130002&lang=en
vol. 12 num. 2 lang. en<![CDATA[SciELO Logo]]>http://www.scielo.br/img/en/fbpelogp.gif
http://www.scielo.br
<![CDATA[<b>Nulls and side lobe levels control in a time modulated linear antenna array by optimizing excitations and element locations using RGA</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200001&lng=en&nrm=iso&tlng=en
In this paper a novel approach based on the Real coded Genetic Algorithm (RGA) is proposed to improve nulling performance as well as suppression of Side Lobe Level (SLL) of a Time Modulated Linear Antenna Arrays (TMLA). RGA adjusts the static excitation amplitudes as well as the location of each element from the origin to place deeper nulls in the desired direction. Three design examples are presented that illustrate the use of the RGA, and the optimization goal in each example is easily achieved.<![CDATA[<b>Modal domains and selectivity in large square lasers</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200002&lng=en&nrm=iso&tlng=en
Modes in square resonators have C4v symmetry. A special set of modes in these resonators have odd parities and behave like whispering gallery modes. These quasi-whispering gallery modes have high quality factors and exhibit interesting features. In particular, higher order quasi-whispering gallery modes present nodes that seem to be grouped into smaller domains. We show that the removal of one of these domains does not significantly affect a particular mode but can lead to significant increment in the radiation losses of other modes. This mode selectivity process can eventually be used to develop quasi single-mode lasers.<![CDATA[<b>Dynamic analysis of superconductor at high temperature for antennas array</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200003&lng=en&nrm=iso&tlng=en
The analysis and new results of the resonance frequency and radiation pattern of antennas array, for glass fiber FR-4 substrate using superconductor and copper patch, are presented. The linear superconducting rectangular antennas array uses the new materials SnBaCaCuOy at temperature of 160 K with conductivity equal 1.5 x 10(5) S/m. The concise full wave Transverse Transmission Line (TTL) method is used in the analysis and to obtain some results. The HFSS is also used and new results for the reflection coefficient (S11), return loss as functions of the resonant frequency, and pattern radiation of antennas array, are presented.<![CDATA[<b>A new circular photonic crystal fiber for effective dispersion compensation over E to L wavelength bands</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200004&lng=en&nrm=iso&tlng=en
This paper presents a new circular photonic crystal fiber (C-PCF) for effective dispersion compensation covering E to L wavelength bands ranging from 1360-1625 nm. To investigate its guiding properties, finite element method (FEM) with a perfectly matched layer absorbing boundary condition is used. From our numerical simulation, it is found that the designed C-PCF simultaneously shows a large negative dispersion of about -248.65 to -1069 ps/(nm.km) over E to L wavelength bands and a relative dispersion slope (RDS) exactly equal to that of a single mode fiber (SMF) at 1.55 µm wavelength. It is also found that residual dispersion after compesating 40 km long SMF is within ±62 ps/nm which ensures application of C-PCF in high speed WDM system. Besides, dispersion slope, slope compensation ratio, effective area and confinement loss of the proposed C-PCF are also evaluated and discussed.<![CDATA[<b>A systematic sensitivity analysis of the performance of a transcutaneous energy transmitter for design purposes</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200005&lng=en&nrm=iso&tlng=en
This work studies a Transcutaneous Energy Transmitter (TET) which uses electromagnetic fields to transfer power from outside the body to an artificial organ in the body, working like a high frequency transformer with the skin being part of the magnetic coupling between the primary (external coil) and secondary (internal coil). For this reason, this project made two different kinds of analyses of the efficiency and the induced current density in a biologic tissue: first, simulations were performed using core types of distinct geometries, each with multiples sizes, ranking which type is more recommended; second, the sensitivity of the chosen core type to misalignments was evaluated for different dimensions. In addition, the sensitivity to the core permeability was also investigated for both analyses.<![CDATA[<b>Analysis and PIC simulation of a Gyrotron travelling wave tube amplifier</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200006&lng=en&nrm=iso&tlng=en
The analysis of a Ka-band gyrotron Travelling Wave Tube (gyro-TWT) amplifier using a uniform cylindrical waveguide as its interaction circuit has been presented for the TE01 mode of operation a self-consistent nonlinear analysis in the large signal regime. The analysis predicts that the saturated peak output power of ~ 134 kW with a power conversion efficiency of ~ 22.7 %. The saturated gain has been calculated as ~ 41.3 dB for the amplifier driven by 72 kV, 8.2 A electron beam of a pitch factor 1.05. The critical interaction length of smooth wall uniform metal guide is found 10.7 cm for the stable amplifier operation. The form factor and the norm factor have also been estimated with the large signal non-linear code. Further, for 5% spread the amplifier develops the peak power of ~ 128 kW with an electronic efficiency of ~ 21.7 % and the gain of ~ 41.07 dB. These results are found to be good harmony when the beam wave interaction is studied with a commercial 3-D electromagnetic particle in cell (PIC) code. The behaviour of the beam all over the length of the interaction circuit has been monitored by calculating its energy, momentum, phase, etc. with the help of a commercial PIC code and which also in good agreement with analytical results with 1% deviation.<![CDATA[<b>Resonant properties, of modified triangular plasmonic nanoparticles with higher field concentration</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200007&lng=en&nrm=iso&tlng=en
In this paper, we present an analysis of the resonant response of modified triangular metallic nanoparticles with polynomial sides. The particles are illuminated by an incident plane wave and the method of moments is used to solve numerically the electromagnetic scattering problem. We investigate spectral response and near field distribution in function of the length and polynomial order of the nanoparticles. Our results show that in the analyzed wavelength range (0.5-1.8) µm these particles possess smaller number of resonances and their resonant wavelengths, near field enhancement and field confinement are higher than those of the conventional triangular particle with linear sides.<![CDATA[<b>Particle swarm optimization in WDM/OCDM networks with physical impairments</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200008&lng=en&nrm=iso&tlng=en
In this paper, optimization procedures based on particle swarm optimization (PSO) are investigated, aiming to efficiently solve the optimal resource allocation for signal-to-noise plus interference ratio (SNIR) optimization of optical code paths (OCPs) from wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) considering imperfections on physical layer. The characteristic of the PSO is attractive due their performance-complexity tradeoff and fairness regarding the optimization methods that use numerical methods, matrix inversion and other heuristics. The SNIR model considers multiple access interference (MAI) between the OCP based on 2-D codes (time/wavelength), amplifier spontaneous emission (ASE) at cascaded amplified spans, and group velocity dispersion (GVD) and polarization mode dispersion (PMD) dispersion effects. The numerical results have revealed the viability of the PSO algorithm considering solution quality and convergence. Besides, the numerical results have shown a penalty when the ASE, GVD and PMD effects are considered.<![CDATA[<b>PIC simulation study of a 35 GHz, 200 kW Gyroklystron</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200009&lng=en&nrm=iso&tlng=en
A three-dimensional PIC simulation of a 35 GHz, 200 kW two cavity gyroklystron amplifier has been performed to study the electron beam and RF wave interaction behavior using a commercial PIC code 'MAGIC'. The electromagnetic field analysis of the RF structure in the absence of the electron beam and beam-wave interaction study in the presence of the electron beam have been carried out for the performance evaluation of the device. Electromagnetic field analysis has been done using the eigenmode solver, which ensures the structure operation in the desired TE01 operating mode at 35 GHz frequency. Electron beam and RF wave interaction simulation confirm that the present gyroklystron meet the required specification in terms of output power and gain. Moreover, the particles phase space behavior along the interaction length has been also demonstrated to realize the energy transfer phenomena. An output power around 200 kW at 34.95 GHz with ~35% efficiency and a bandwidth of 0.29% have been obtained considering no spread in electrons velocity. Our simulated result matches with the experimental values within 8%.<![CDATA[<b>SAR Analysis for handheld mobile phone using DICOM based voxel model</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200010&lng=en&nrm=iso&tlng=en
In this paper, Specific Absorption Rates (SAR) inside the human head and hand have been analyzed for a handheld mobile phone operated at GSM 900 band. Both the head and hand are modeled electrically using Digital Imaging and Communication in Medicine (DICOM) formatted CT Scan voxel data considering the electrical parameters of different internal anatomical structures. Three-dimensional Finite Difference in Time Domain (FDTD) method has been used to simulate SAR induced in the head and hand. Maximum peak 1-g and 10-g SARs of 1.33 W/kg and 0.388 W/kg are found at antenna resonance frequency of 930 MHz for 0.6 W applied input power which are below the limits set by ANSI/IEEE and FCC, respectively.<![CDATA[<b>All-optical cryptography through spectral amplitude and delay encoding</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200011&lng=en&nrm=iso&tlng=en
All-optical data encryption is a promising technology that could lead communication systems to an unprecedented degree of security. In this paper we use computer simulations to systematically investigate a new all-optical cryptography technique that is bit-rate independent and transparent to modulation formats. Encryption encompasses signal spectral slicing followed by two encoding stages that impose different attenuations and delays to each of the spectral slices. We analyze the quality of the encoded signal by evaluating its bit error rate (BER) performance. Results indicate that such BER may achieve 45 and 28%, respectively, for input non-return-to-zero on-off keying (NRZ-OOK) and differential quadrature phase-shift keying (DQPSK) signals. At the receiver side, results suggest that signals may be properly decoded after propagation distances that are compatible with those utilized in metropolitan area networks. The robustness of the technique against waveform analysis and brute force attacks is also approached.<![CDATA[<b>A design proposal for ultrawide band frequency selective surface</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200012&lng=en&nrm=iso&tlng=en
In this paper a three layer FSS is described which provides a ultrawide band (UWB) response. The layers use plain rectangular patches, and rectangular patches with one or two notches which provide multi-band responses; by cascading them an UWB response is obtained covering the band 4.05 - 14.12 GHz, for vertical polarization and the band 5.05 - 15.00 GHz, for horizontal polarization. Transmission properties of the proposed structure were simulated and measured.<![CDATA[<b>Wound rotor doubly fed induction machine with radial rotary transformer</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200013&lng=en&nrm=iso&tlng=en
This paper shows a wound rotor doubly fed induction machine in which the typical brushes and slip-rings are substituted by rotary transformers. The advantages of rotary transformer usage, the doubly fed induction machine operation and the dimensioning of a radial rotary transformer are the main aspects presented in this study. The use of analytical equations is a very interesting resource for the development of industrial software for the calculation of this kind of device. Comparison between simulated and measured results shows the good approximation of the steady-state model with the reality of this equipment.<![CDATA[<b>A CMOS UWB transmitter with Vivaldi Array for Ultra-fast Beam steering microwave radar</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200014&lng=en&nrm=iso&tlng=en
This work presents a new Ultra Wide Band (UWB) beamforming fifth-order derivative Gaussian pulse transmitter with dual small Vivaldi antennas for remote acquisition of vital signals in impulse radar applications. The system consists of a programmable delay circuit (PDC or τ), a UWB pulse generator (PG) circuit and an array of two Vivaldi planar antennas. The circuits is designed using the 0.18µm CMOS IBM process. Spice simulations show the pulse generation with 90mVpp amplitude and 300ps width. The average power consumption is 120µW per pulse, using a 2V power supply at a pulse repetition rate (PRR) of 100MHz. Full tridimensional electromagnetic simulations, using CST MWS, show the main lobe radiation with a gain of 5.5dB, and a beam steering between 20º and -17.5º for azimuthal (θ) angles at the center frequency of 7.5GHz.<![CDATA[<b>Rate-equations based model for the 2D-0D direct channel in quantum dot lasers under CW and gain-switching</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200015&lng=en&nrm=iso&tlng=en
Direct capture of carriers from the wetting layer to the most confined states is discussed in this paper. This channel for carrier scattering was recently used to fit typical P-I curves of quantum dot lasers. Here new numerical expressions for the escape times accounting for the carriers added by the direct channel are introduced and evaluated, and insights of the influence of these additional carriers on the continuous and pulsed laser emission spectrum are given.<![CDATA[<b>Uncertainty analysis of the conducted interferences in a power converter</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200016&lng=en&nrm=iso&tlng=en
A new methodology to analyze electrical systems in the time and frequency domain containing a large number of uncertain parameters is presented. The methodology is based on screening and design of experiments to build surrogate reduced models at a well specified set of frequency values. As an example, the conducted interferences of a Power Converter with uncertainties in its component values are analyzed. The model has a large number of parameters, which are described by Probability Density Functions (PDF). The output considered is a standard measurement of conducted interferences and its PDF is rapidly determined, if compared to the Monte Carlo (MC) approach.<![CDATA[<b>Measurement with quasi-isotropic antenna of CEM coming from multisource in a reverberation chamber and in a car</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200017&lng=en&nrm=iso&tlng=en
The concern about the health risks that wireless technology can provide has grown globally thanks to the growing use of the devices by the population, by the finding that the public exposure to EMFs from the devices can be enhanced by the reflection of the microwave indoors. This paper will assess the distribution of electromagnetic field in a car, in order to provide a basis for future research and to estimate the actual level of exposure to which humans are submitted. There were a number of electrical measurements to determine the electromagnetic field produced by various electromagnetic sources. From the results observed, it is possible to see that, in a car, the exposure of humans to EMF is intensified by the reflection of electromagnetic waves in metallic structures. The observed values do not exceed the values recommended by the regulation, but in the face of scientific uncertainty on this issue, is motivated to continue studying the effect of the reflection of microwaves in closed environments, in order to investigate the possible impacts on health.<![CDATA[<b>Spectrally-efficient 17.6-Tb/s DWDM optical transmission system over 678 km with pre-filtering analysis</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200018&lng=en&nrm=iso&tlng=en
We present and analyze a 17.6-Tb/s DWDM optical transmission composed of 79 channels with 224-Gb/s RZ-DP-16QAM modulation format per-channel and coherent detection. A maximum reach of 678 km is obtained with an optical recirculation loop composed by 226 km of pure-silica core fibers and EDFA amplification only in a 50-GHz grid system with spectral efficiency of 4.2-b/s/Hz. Also, a 25-GHz Gaussian optical pre-filter is applied to each channel and the same reach of 678 km is obtained in a 37.5-GHz channel grid system with spectral efficiency of 5.6-b/s/Hz. These results demonstrate a 33% system capacity improvement without transmission penalties.<![CDATA[<b>Wireless microsystems for biomedical applications</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200019&lng=en&nrm=iso&tlng=en
This paper presents a review with the state-of-the-art of wireless microsystems for biomedical applications. Aspects including the radio-frequency systems, data acquisition, application specificities (especially those in the context of implantable devices), power consumption and issues associated to their integration are presented. A review of COTS (Commercial Off-The-Shelf) systems and new concepts and technologies are also presented.<![CDATA[<b>Point interpolation methods based on weakened-weak formulations</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200020&lng=en&nrm=iso&tlng=en
This paper presents a study of meshless Point Interpolation Methods based on weakened-weak forms. The mathematical formulations of the methods are presented as well as the procedures for the support nodes selection called T-schemes. The numerical results are shown for four different types of electromagnetic static problems in order to ponctuate the characteristics of the approximation generated by these new methods.<![CDATA[<b>Transmission of a 1.12 Tb/s superchannel over 452 km fiber</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200021&lng=en&nrm=iso&tlng=en
This paper describes the transmission of a non-guard interval 1.12 Tb/s 10-carrier superchannel, launched into a 226 km recirculating loop. After two round trips (452 km) a BER below the FEC limit (3.8 x 10-3) was still obtained. To evaluate the superchannel generation technique, up to 72 comb lines (OSNRmin = 12.7 dB) were generated and modulated (DP-QPSK) at 112.5 Gb/s and, in a back-to-back configuration, such an 8.06 Tb/s signal was detected by a coherent receiver with offline processing, resulting in a maximum BER of 2.4 x 10-3.<![CDATA[<b>Characterization of the radiation pattern of antennas using time-domain spherical-multipole and moment expansion</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200022&lng=en&nrm=iso&tlng=en
This paper presents results of a time-domain spherical-multipole near-to-far-field transformation together with a moment expansion applied to antenna radiation patterns. The equivalence principle is applied to the tangential fields all over the FDTD/WP-PML spatial grid and the use of the spherical-multipole expansion leads to the near-to-far-field transformation, and energy and power norms of temporal signals are used to obtain the antenna radiation patterns for transient and steady-state responses. Such approach is employed to obtain UWB antenna radiated fields and radiation patterns directly in time-domain, it being more convenient to perform an unified characterization in time and frequency domains.<![CDATA[<b>Experimental optical generation of DP-16QAM modulation format for high spectral efficiency optical transmission</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200023&lng=en&nrm=iso&tlng=en
In this paper, we present a simple experimental method to generate a DP-16QAM optical signal for high spectral efficiency optical transmission. A 16QAM optical signal is generated by passing a DP-QPSK signal through a linear polarization filter in a certain angle so that a square 16QAM can be achieved. Afterwards, we use a polarization multiplexer in order to produce a dual polarization signal. This method proved to be a straightforward and stable way to generate a DP-16QAM signal. In addition, we show that it can provide the same quality in terms of BER per OSNR demonstrated elsewhere.<![CDATA[<b>A hybrid method BEM-NRM for magnetostatics problems</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200024&lng=en&nrm=iso&tlng=en
This article proposes a new method to solve non-linear magnetostatic problems applied to the modeling of electromagnetic devices. A reduced scalar potential formulation is presented and solved by a hybrid BEM-NRM. It has been implemented and tested in a software called MaGot. We will show that the computation time of this new method is very low. Thus, it could be easily and efficiently used for the pre-sizing of actuators.<![CDATA[<b>Development of computational 3D MoM algorithm for nanoplasmonics</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200025&lng=en&nrm=iso&tlng=en
In this paper, we present an algorithm for full-wave electromagnetic analysis of nanoplasmonic structures. We use the three-dimensional Method of Moments to solve the electric field integral equation. The computational algorithm is developed in the language C. As examples of application of the code, the problems of scattering from a nanosphere and a rectangular nanorod are analyzed. The calculated characteristics are the near field distribution and the spectral response of these nanoparticles. The convergence of the method for different discretization sizes is also discussed.<![CDATA[<b>A methodology for performance evaluation of LEDs based on <i>ac </i>small signal analysis</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200026&lng=en&nrm=iso&tlng=en
This paper shows fundamentals and results that support a promising methodology for evaluation in locus of a LED from its own radiating signal, and that allows monitoring of its aging by remote inference on which degradation mechanism is acting internally to the device's structure. It brings out also an alternative route for estimation of parameters of the Shockley's equation directly from small-signal ac analysis in a simple bench circuit. This last approach is shown to be effective and advantageous relatively to methods which take near a hundred points to achieve good estimations, while it uses only two points of the I-V static characteristic. Both approaches __ referred to as remote inference method (RIM) and two-points method (TPM) __ are applied together to show that external quantum efficiency (EQE) can be closely correlated to the injection process assumed to take place in that emitting device, meanwhile overvalued serial resistances due to neutral layers and ohmic contacts in electrodes affect only its electrical performance.<![CDATA[<b>Photorefractive digital holographic microscopy</b>: <b>an application in the microdevices surfaces</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200027&lng=en&nrm=iso&tlng=en
In this work, we present a Photorefractive Digital Holographic Microscopy (PRDHM) technique based on the writing-reading holographic process in photorefractive Bi12TiO20 (BTO) crystal using the numerical reconstruction of the phase and amplitude image performed by a Digital Holographic Microscopy (DHM) method. We demonstrate that a holographic reconstructed image by diffraction process in photorefractive BTO crystal can be combined with a second reference beam to form a hologram in CCD plane in a DHM setup. The experimental results in a glass slide resolution target and thin film structure was obtained, where, amplitude, phase and 3D phase images are calculated performing digital reconstruction. This technique presents potentials possibilities to obtain 3D phase image of the microdevices for dynamic holography applications.<![CDATA[<b>Hybrid distributed Raman/EDFA amplifier with hybrid automatic gain control for reconfigurable WDM optical networks</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200028&lng=en&nrm=iso&tlng=en
Nowadays, optical amplifiers designs are induced by new requirements generated by optical networks. The introduction of WDM reconfigurable networks with increasing rate from 10-40 Gb/s to 100 Gb/s and beyond, demand new optical amplifiers development with improved gain spectral flatness and noise figure for all operational range of input powers and set-point gains. In this paper, it was developed a hybrid distributed Raman/EDFA amplifier with a novel hybrid gain control (HGC) scheme based on joint actuation. The HGC was firstly developed by numerical simulation and after experimentally, in a WDM system with 100 km SSMF fiber span and full C-band load. The Results shows an improved equivalent noise figure with flattened gain spectrum for all amplifier operation range in dynamic optical networks.<![CDATA[<b>Theoretical and experimental comparison between power and degree of polarization based optical fiber current sensors</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200029&lng=en&nrm=iso&tlng=en
This paper presents a theoretical and experimental comparison of two techniques of optical fiber current sensors (OFCS) based on the Faraday Effect: the power and the degree of polarization (DOP) methods. The DOP method is shown to be insensitive to state of polarization (SOP) changes induced by environmental conditions. A maximum variation of 0.4% in the DOP value in the entire range of applied current from 0 to 100 A was measured. It is the first time to our knowledge that this fact was experimentally verified. Also, for the first time known it is reported that zero current response, DOP = 0.996, is in agreement with the theoretical expected value of unitary DOP. Besides, the theoretical and experimental normalized DOP is shown to have a maximum difference of 0.33% in the entire range of applied current. On the other hand, the power method OFCS is greatly affected by SOP changes. In order to be used in a practical application, its complexity must be increased by the use, for example, of polarization maintaining fibers instead of standard fibers used in the DOP method, increasing the cost of the sensor element.<![CDATA[<b>Optimal traffic Re-Grooming model for heterogeneous carrier ethernet services over WDM Optical Network</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200030&lng=en&nrm=iso&tlng=en
This paper proposes three novel integer linear programming (ILP) formulations, where the first model deals with the Grooming, Routing, Wavelength Assignment, and Carrier Ethernet Interface Allocation Problem (GRWA-I); the second to Traffic Re-Grooming Problem (TRGP) to accommodate demand changes in a GRWA-I network scenarios; and the third to Traffic Re-Grooming demands in case of failures. The traffic re-grooming problem consists basically in assigning demands change in a working network, without affect others requests. In addition, in this work, it problem is formulated for the first time using ILP model. As TRGP needs a configured network scenario as input parameter, the first model proposed accomplish this task for the first network scenario. In numerical results, it was used a 14-node network (NSFnet) and 6 traffic matrix. Moreover, the models proposed were compared with a shortest path (SP) routing method. Results show the difference for network cost between an optimal method and a heuristic design over time, as well as the importance of an initial optimal configuration for future network growth.<![CDATA[<b>A technique to package Fiber Bragg Grating Sensors for Strain and Temperature Measurements</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200031&lng=en&nrm=iso&tlng=en
This paper reports an effective method of packaging a fiber Bragg grating (FBG) for the simultaneous measurement of temperature and strain. The technique consists of embedding two fiber Bragg grating sensors inside a polymeric material with different geometrical characteristics. The mechanical and thermal characterizations of the optical transducer were performed. Then a matrix equation used measurements of the wavelength shifts from the two sensors and yielded information about the temperature and strain coefficients. The preliminary results demonstrate the feasibility of the encapsulation technique allowing measurements of temperature and strain in smart structures and harsh environments. The experimental procedure provides robustness to the sensor and the matrix equation approach has the potential to determine simultaneously the strain and temperature coefficients.<![CDATA[<b>Numerical analysis of impedance spectra of yeast suspensions</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200032&lng=en&nrm=iso&tlng=en
Analysis of impedance spectrum of electroporated biological cell suspensions allows evaluating the state of permeabilization produced by the applied electric field. In this article we used a genetic algorithm to determine parameters of a proposed model for the impedance of suspension adjusting them numerically in order to minimize the error in relation to experimental spectra of Kluyveromyces marxianus CBS 6556 yeasts suspended in distilled water. It was possible to determine the variation of conductivity of suspension avoiding the influence of electrode polarization and dielectric dispersion due to interfacial and diffusion polarization on the cell surface. It was observed that the conductivity in the range of 1 to 100 KHz increases 2.5 times with pulses of 400 KV/m.<![CDATA[<b>Simulation and manufacturing of a miniaturized exponential UWB TEM horn antenna for UWB radar applications</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200033&lng=en&nrm=iso&tlng=en
This paper presents the parameterization of the structure of a miniaturized exponential UWB TEM horn antenna and its effect on the matching impedance and directivity. In addition, a microstrip balun that feeds the antenna was proposed in order to improve the balance, and the return loss for low frequencies. Both the antenna and the microstrip balun were simulated to obtain a final high performance model to be manufactured at a later time. The proposed antenna operates in a frequency range from 3.2 GHz to 7.5 GHz, meeting the standards established by the FCC and the ETSI for ultra-wideband technology. Moreover, based on these characteristics, the antenna have many UWB radar applications such as monitoring of structures (buildings, bridges, etc.), anti-collision radar, vital signs detection, and long-distance communications, as a result of its high gain around 15 dB.<![CDATA[<b>Geometry optimization for application of radio frequency signals on diamond samples</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200034&lng=en&nrm=iso&tlng=en
This work describes the design and optimization of a printed circuit board containing a rectangular half-loop coil designed to apply radio frequency signals on micrometric diamond crystals. The structure was optimized to maximize the magnetic field perpendicular to the coil at 2,87 GHz. In the optimization process we have used transmission line theory, circuit level and 3D electromagnetic simulations. The structure was implemented and measured. The adopted methodology was validated by the good agreement between theory and experiments.<![CDATA[<b>Optimal design of a set of permanent magnet generators with the same cross-section</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200035&lng=en&nrm=iso&tlng=en
The optimal design of a set of two permanent magnet generators that share the same cross section to reduce the manufacturing cost is presented using a gradient optimization algorithm. The optimization tool is used to define the optimal number of pole pairs of the set of machines and the optimal permanent magnets width respecting the geometrical and performance constraints. The design is validated using a FEM analysis tool.<![CDATA[<b>Comparing OSNR based policies for an adaptive-alternative IA-RWA algorithm applied to all-optical networks</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200036&lng=en&nrm=iso&tlng=en
We propose two policies to select the route for an adaptive-alternative routing algorithm for all-optical networks. We use the NrPSR to find the Nr routes with lower cost for a given source-destination pair according to a cost function expanded in a power series (PSR) in which the coefficients are determined by a Particle Swarm Optimizer (PSO). The selected route to attend to the call request can be chosen among the Nr found routes depending on the adopted policy. In the first proposal, named NrPSR(OSNR JE), we select the route that presents the lower OSNR that attends the Quality of Transmission requirements. In the second approach, named NrPSR(OSNR MAX), we select the route that presents the higher OSNR. In our simulations we considered some physical layer effects, such as: ASE noise generation, Optical Amplifier gain and ASE saturation and OXC crosstalk. We compared the performance of our proposed policies to others previous proposed policies for the NrPSR and other well known algorithms described in the literature. NrPSR(OSNR JE) outperformed all other routing algorithms.<![CDATA[<b>Nonlinear effects compensation in Optical Coherent PDM-QPSK Systems</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200037&lng=en&nrm=iso&tlng=en
Nonlinear effects has been appointed as the main limitation in coherent optical fiber transmission. Digital Back-Propagation algorithms and Maximum Likelihood Sequence Estimation are two of the current studied methods to cope with such impairment and extend the systems maximum reach. In this article, we analyzed both methods in a 112 Gb/s Dual Polarization Quadrature Phase Shifting Keying (DP-QPSK) optical coherent system through simulations and experimental results. In order to reduce the huge required computational complexity, a modified back-propagation algorithm is also analyzed.<![CDATA[<b>Long-term stability decay of standard and regenerated Bragg gratings tailored for high temperature operation</b>]]>
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2179-10742013000200038&lng=en&nrm=iso&tlng=en
Thermal stability of both standard and regenerated Bragg gratings written in normal and photosensitive optical fibers was accessed. An apparent spectral wavelength stabilization of common gratings with no thermal hysteresis was reached after thermal treatments. However, after a time interval of 5 months, gratings exhibited a shift in the resonance Bragg wavelength at room temperature, as well as important changes in the thermal sensitivity above 200 ºC. Regenerated gratings proved to be stable only at temperatures below the critical regeneration temperature, with significant loss of reflectivity above that critical value.