968 resultados para Constant amplitude


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We present a simplified model for a simple estimation of the eye-closure penalty for amplitude noise-degraded signals. Using a typical 40-Gbit/s return-to-zero amplitude-shift-keying transmission, we demonstrate agreement between the model predictions and the results obtained from the conventional numerical estimation method over several thousand kilometers.

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Mathematics Subject Classification: 26D10.

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Identification of humans via ECG is being increasingly studied because it can have several advantages over the traditional biometric identification techniques. However, difficulties arise because of the heartrate variability. In this study we analysed the influence of QT interval correction on the performance of an identification system based on temporal and amplitude features of ECG. In particular we tested MLP, Naive Bayes and 3-NN classifiers on the Fantasia database. Results indicate that QT correction can significantly improve the overall system performance. © 2013 IEEE.

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One of the extraordinary aspects of nonlinear wave evolution which has been observed as the spontaneous occurrence of astonishing and statistically extraordinary amplitude wave is called rogue wave. We show that the eigenvalues of the associated equation of nonlinear Schrödinger equation are almost constant in the vicinity of rogue wave and we validate that optical rogue waves are formed by the collision between quasi-solitons in anomalous dispersion fiber exhibiting weak third order dispersion.

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We experimentally characterize the distributed Raman amplification induced amplitude and phase impairments and evaluate the performance dependence of unrepeated 28 Gbaud 16QAM coherent transmissions over standard single mode fiber.

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We propose a novel scheme for multilevel (9 and more) amplitude regeneration based on nonlinear optical loop mirror and demonstrate its efficiency and cascadability on 256-symbol constellation. © 2014 OSA.

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Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communications by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370-780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation formats such as orthogonal frequency-division multiplexing. In this article we introduce a new modulation scheme into the VLC domain; multiband carrier-less amplitude and phase modulation (m-CAP) and describe in detail its performance within the context of bandlimited systems.

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2010 Mathematics Subject Classification: 37K40, 35Q15, 35Q51, 37K15.

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ACM Computing Classification System (1998): G.1.1, G.1.2.

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2000 Mathematics Subject Classification: Primary 53B35, Secondary 53C50.

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A high-dielectric constant (high-k) TiOx thin layer was fabricated on hydrogen-terminated diamond (H-diamond) surface by low temperature oxidation of a thin titanium layer in ambient air. The metallic titanium layer was deposited by sputter deposition. The dielectric constant of the resultant TiOx was calculated to be around 12. The capacitance density of the metal-oxide-semiconductor (MOS) based on the TiOx/H-diamond was as high as 0.75 µF/cm2 contributed from the high-k value and the very thin thickness of the TiOx layer. The leakage current was lower than 10-13 A at reverse biases and 10-7A at the forward bias of -2 V. The MOS field-effect transistor based on the high-k TiOx/H-diamond was demonstrated. The utilization of the high-k TiOx with a very thin thickness brought forward the features of an ideally low subthreshold swing slope of 65 mV per decade and improved drain current at low gate voltages. The advantages of the utilization high-k dielectric for diamond MOSFETs are anticipated.

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A new nonlinear electrodynamic phenomenon in layered superconducting slabs irradiated on one side by plane electromagnetic waves in the terahertz range is predicted and studied theoretically. It is shown that the surface reactance of a sample and its reflection coefficient have hysteresis behavior when the amplitude of the incident wave is changed. The analogy between the electrodynamic problem of the electromagnetic field distribution in a superconductor and the mechanical problem of particle motion in a central field is also discussed.

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I would like to thank Dr. Philip Stoddard for his patience and guidance throughout the past four years. He has not only taught me about behavior and electricity, but he has also taught me how to think scientifically. Vielka Salazar for making herself available to answer my questions and to help me with my projects. Montserrat Alfaro for providing me with support under times of frustration. Fabian A. Pal, who has often made himself available when I needed help to finish my projects, for being supportive, and for believing in me and my abilities. Most importantly, I would like to thank my parents who have shown tremendous support and patience during the past years. I would also like to thank the Honors Committee, specially Dr. Richards for taking the time to review my thesis and helping me modify it. Finally, I would like to thank the MARC program for providing me with financial assistance and the opportunity to perform this project.

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At four sites in the central equatorial Pacific Ocean the flux of extraterrestrial 3He, determined using the excess 230Th profiling method, is 8 * 10**-13 cm**3 STP/cm**2/ka. This supply rate is constant to within 30%. At these same sites, however, the burial rate of 3He, determined using chronostratigraphic accumulation rates, varies by more than a factor of 3. The lowest burial rates, which occur north of the equator at 1°N, 139°W are lower than the global average rate of supply of extraterrestrial 3He by 20% and indicate that sediment winnowing may have occurred. The highest burial rates, which are recorded at the equator and at 2°S, are higher than the rate of supply of extraterrestrial 3He by 100%, and these provide evidence for sediment focusing. By analyzing several proxies measured in core PC72 sediments spanning the past 450 kyr we demonstrate that periods of maximum burial rates of 230Th, 3He, 10Be, Ti, and barite, with a maximum peak-to-trough amplitude of a factor of 6, take place systematically during glacial time. However, the ratio of any one proxy to another is constant to within 30% over the entire length of the records. Given that each proxy represents a different source (234U decay in seawater, interplanetary dust, upper atmosphere, continental dust, or upper ocean), our preferred interpretation for the covariation is that the climate-related changes in burial rates are driven by changes in sediment focusing.

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The industrial Brazilian pig farming despite of the constant advance in the genetic improvement, nutrition, and in handling, seasonality problems occur in the production of weaned piglet, mainly due to the stations of the year that can impact directly in the profitability. These problems can be deepen due to breed and line of decent used in Brazil are all source from tempered weather countries. To the pig farmer it's difficult to determine the relations between indoor temperature of the barns, relative humidity of the air and top thermal amplitude which can provide good reproductive rates for the boars and arrays lodged in conventional barns. The lack research to production of environmental indices of easy interpretation to pigs, which are not dependent of complicated handling machines and also which are not expensive is considered as a negative factor from the producers. the objective os this experiment is evaluate the effects of the stations of the year over the reproductive performance of the boars Agroceres PIC 425, Agroceres PIC 337 and D.B. Dambred LM 6200, and of arrays Agroceres Canborough 22, Penarlan Naima e DB90 Danbred, in addition develop an environmental index with easy interpretation and use to the pig farmers of the region of Uberlândia - MG, using the maxim temperatures, rainfall monthly accumulated and of the thermal amplitude of the barn. The features rated during the stations of the years 2013 and 2014 were the volume and spermatic quality of the boars and the mainly reproductive indexes of the arrays as the total number of piglets born alive and total number of weaned piglets/ array/ parturition. The station of the year which had the worst results in the reproductive feature of the boars and arrays was the spring. Boars from different line of decent are sensitive to the effects of stress of the heat of spring causing lowest volume, concentration and problems in the spermatic morphology (p<0,05). The spring prejudice the reproductive indexes of arrays from different line of decent (p<0,05) and the pig farmers of Uberlândia are subjected to operating losses and income evasion due to the thermal stress in the reproduction that added can reach $150.000,00 annual for each 1000 arrays lodged/year.