High electron mobility transistors are made up of the GaAs semiconductor material, but the research on HEMT experts says that GaN has good characteristics than GaAs because of their good breakdown voltage, less power dissipation. It can operate at high temperature, and it is having more powerdensity and can operate at high voltage com- pared to GaAs based HEMT for that purpose. We are talking about GaN/AlGaN HEMT here -.
In this work a voltagenoisepowerspectraldensity was studied for the YBaCuO HTC superconductor. Those materials exhibit a 1/f α noise. The shape of the noise in our sample is common to many electronic systems even though the noise in those systems is found to be very smaller compared with that of superconductors. The major source of the noise in our sample is supposed to be the vortex fluctuations in the mixed state. The motion of vortex is a main cause which creates the noise in these materials, so in this research the effect of temperature is strongly observed giving start to vortex motion.
of scientiﬁc eﬀorts have focused on the proposal of statistical BPL channel models that exploit either the bottom-up approach or the top-down approach and their corresponding measurement data, simulation results, and numerical ﬁndings [28, 44–50]. In this paper, the proposed statistical hybrid model is based on the formality and validity of the deterministic hybrid model while its results are considered as the ﬁltered hybrid model results through a set of proper channel attenuation statistical distributions, which are well known in the communications research ﬁelds, such as Gaussian, Lognormal, Wald, Weibull, and Gumbel channel attenuation distributions . The results of the proposed statistical hybrid model provide capacity ranges for given injected powerspectraldensity (IPSD) limit, noise PSD level, coupling scheme, and BPL topology class where a BPL topology class consists of overhead Medium-Voltage (OV MV) and underground Medium-Voltage (UN MV) BPL topologies that come from the channel attenuation statistical distribution processing of the respective indicative BPL topologies. In fact, the exact theoretical procedure of implementing a statistical hybrid model, which comprises the reception and processing of the input data of the hybrid model, the deﬁnition of the applied channel attenuation distributions, the computation of the maximum likelihood estimators (MLEs) of the channel attenuation statistical distributions, the deﬁnition of the random number generator based on the respective channel attenuation distribution MLEs, and the computation of the capacity ranges of distribution BPL topology classes, is detailed in this paper. In the companion paper of , the numerical results concerning the statistical hybrid model are demonstrated.
AWGN is a channel model used for analyzing modulation schemes. It adds a white Gaussian noise to the signal passing through it. The channel’s amplitude frequency response is flat and phase frequency response is linear for all frequencies so that modulated signals pass through it without any amplitude loss and phase distortion of frequency components. Fading does not exist but the only distortion is introduced by the AWGN. The received signal is simplified to (Navjot Kaur and Lavish Kansal, 2013)-
ABSTRACT: PowerSpectralDensity (PSD) refers to the amount of power per unit of frequency as a function of the frequency. The PSD describes how the power (or variance) of a time series is distributed with frequency. In this research, we calculated Grms (Root-Mean-Square Acceleration) and PSD of NAJI fire pump on healthy and unhealthy situations. In addition, we calculated Grms and PSD of NAJI fire pump electromotor on healthy, misalign and looseness situations. The results showed that different situations showed different PSD vs. frequency. With calculating PSD, we could find some fault and diagnosis of pump and electromotor as soon as possible. The results of this paper have given more understanding on the dependent roles of vibration analysis and PowerSpectralDensity carve in predicting and diagnosing of the pump and the electromotor faults.
All animal procedures were in accordance with protocols approved by the Institutional Animal Care and Use Committee at the San Francisco Veterans Affairs Medical Center. Adult male Long Evans rats (n = 8, 250-400 g, ~ 8 weeks old, Charles River Laboratories) were housed in a 12 h light:12 h dark cycle with lights out at 6:00 AM and were kept under controlled temperature. One animal was excluded from the study due to significant recording drift and electrical noise in the recording, thus n = 7 animals were used for the analysis shown. Animals were initially anesthetized using a ketamine/ xylazine cocktail (85 mg/kg ketamine, and 10 mg/kg xylazine), with supplemental ketamine (at half of the induction dose) given every 40–60 min as needed to main- tain a stable anesthetic level, and also to maintain anesthesia at stage III characterized by predominantly slow oscillations. Moreover, 0.05 mg/kg of atropine was given separately to counter respiratory and cardiac depres- sion, and decrease secretion. Animals were sacrificed at the end of the recordings.
High temperature localized corrosion is one of the most hazardous corrosion form producing fast and unanticipated destruction into a small section of a metal structure. Electrochemical Noise (EN) is an electrochemical technique providing rate and corrosion mechanism of corrosion in-situ process. Amplitude fluctuations intensities are associated to corrosion process that can be observed in electrochemical noise measurements (ENMs) and their shape related with the type of corrosion process. For corrosion the electrochemical noise signals (ENS) consist on a high overlapped transient therefore they need appropriated mathematical treatment. Since 1990 the wavelet analysis proposed as a mathematical tool for signal processing alternative to Fourier transform when a precise time-scale analysis is required or to study transients into a signal. For the present study the EN technique was used to monitor the corrosion of a NiAl+Cu Intermetallic HVOF protective coating of Inconel alloy 600 at 750 °C in molten salts. The Discrete Wavelet Transform (DWT) technique was used for treating noise signal from respective transients and detect highly localized pitting corrosion. The original potential and current noise were first disintegrated into a series of time by DWT at increasing scale . Then, the noise resistance was calculated as a ratio of the standard deviation of the reconstructed potential noise to the reconstructed current noise. The experimental results demonstrated that the DWT technique could improve the calculation of the classic noise resistance
the uncertainty of the CSD depends on the readout noise contribute from each sensor. Consequently, the cross correlation technique for readout noise rejection gives optimal results when the readout noise of the two detectors is comparable. When one of the two contributes much larger readout noise than the other, the cross correlation still pro- vides a good estimation of the external torque powerspectraldensity, but with a larger uncertainty than the PSD of the output of the less noisy detector, due to the noise con- tribution of the noisiest sensor. The ability of extracting from noisy measurements the external torque acting on the torsion pendulum is limited by the noisiest of the readouts. It is possible to use some strategies to reduce the uncertainty of the spectral estimator. First of all it is possible to divide the data string from which the powerspectraldensity is performed into n segments of the same length. Then, the best estimate of the cross spectraldensity is then computed as the average of the CSD obtained from each segment, obtaining a reduction of the uncertainty by a factor √ n. However, dividing the time series into shorter segments for averaging, therefore limits the minimum frequency and the frequency resolution of the obtained cross spectraldensity because they are related to the inverse of the time duration of the data segment. Because we are interested to measure the performance of our instruments in the low frequency region, by averaging to reduce the uncertainty on the estimation of the spectral densities we need to perform measurements longest possible. For our frequency region of interest, that extends below 0.1 mHz, we need data stretches of at least 10000 s. Usually we choose 25000 s long spectral windows for discarding the first three points of the spectrum known to be biased with a Blackman Harris windowing function.
Orthogonal Frequency Division Multiplexing (OFDM) has recently been introduced in optical communications because of its robustness against channel dispersion and its high spectral efficiency . It is a promising technique for long haul and high speed optical transmission systems. It is also becoming popular because it can effectively reduce inter symbol interference caused by dispersive channel also it is immune to chromatic dispersion (CD) and polarization dispersion (PMD) . The use of OFDM in optical communications mitigates transmission impairments and at the same time, provides high-data rate transmission across dispersive optical media. It is also used in wireless and wireline applications and in almost every major communication standards. Among the proposed OFDM systems, Intensity Modulation and Direct-Detection (IM/DD) technique inherently is a low cost and attractive for future cost- sensitive, short-range & high-speed transmission such as passive optical network (PON), indoor optical wireless communication and interconnections in data centre . The two most popular IM/DD OFDM systems are DC- offset OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM) . Fast Hartley transform (FHT) has been proposed as an alternative modulation/demodulation processing in IM/DD optical OFDM systems . The complexity of FHT with real input constellation is half of that of FFT with complex input constellation .Thus; FHT is perfect for IM/DD systems due to its low complexity.
The impact of δ on the array performance is very important and should be investigated where it controls both the sidelobe level and ripple width in the array gain over the coverage area (i.e., main lobe). As mentioned before, the value of δ ranges from 1 to 2, and its eﬀect on the power pattern is negligible at values greater than 2.6. To describe the eﬀect of δ on the array power pattern, we use two values of δ (1.6 and 2.6) as shown in Fig. 16 to achieve 100 km coverage diameter. At δ = 2 . 6 the smoothing eﬀect is negligible, and the weights are almost the same as the ﬂattening weights while the tapered proﬁle of ω s ( n ) at δ = 1 . 6 greatly aﬀects the performance of the array especially the sidelobe levels and reduces
A SAR image filtered using the ideal LPF is shown in figure 4. It can be observed that even though the noise present in the image is reduced, the filtered image is affected by ringing noise. Ringing produces special artifacts that appear at sharp pixel transitions in the image, e.g. edges and curves. They appear like bands or echoes on the edges of the images giving a faded repetitive look to the edges.
Low power VLSI devices and circuits have been a subject of keen research interest in today’s era of deep submicron technologies. Suppression of the sub-threshold leakage current and control of transistor count per chip, is highly desirable to extend the battery lifetime of high- performance portable applications with long idle periods. For reducing leakage power, different power gating (PG) structures with high performance in the active mode and short wake-up time during standby mode have been proposed in literature [1-3]. During active mode, runtime leakage is also minimized using PG techniques [4, 5]. But many negative circuit level aspects of PG, such as power supply noise, large instantaneous current through sleep transistor (ST) etc. necessitate a careful understanding of its impact on the behavior of circuits. These aspects can be controlled by controlling the current through the sleep transistor during sleep to active mode transition. Previously different strategies has been developed in order to minimize this kind of noise. Some of the literatures related to this noise in the PG circuit are described next, in this section.
The rest of this paper is organized as follows. In Section 2, the system model and the spectrum sensing hypothesis are presented, in addition to an overview of the PSD and its estimation. Our proposed detectors based on the cumulative sum of the PSD are discussed in Section 3. Section 4 provides an analytic study on the statistical dis- tributions of the test statistics as well as the calculus of the false alarm and detection probabilities. In Section 5, the probability of detection over Rayleigh flat-fading channel is provided. The numerical results of our detectors will be presented in Section 6. The effects of the noise uncertainty problem on our detectors are shown in Section 7. To over- come the noise uncertainty problem, this section presents modified versions of our detectors which are indepen- dent of the noise variance. At the end, a conclusion and perspective section of our work is provided.
Dicode pulse-position modulation is a new modulation format, which has been found that offers improved sensitivity over digital PPM and multiple PPM. The powerspectraldensity of that format theory has been described with mathematic equation and graph of that have been taken. Software simulation has been programmed and hardware (coder, decoder) have been constructed for the Dicode PPM theory. Also DiPPM’s window has been development for the proper use of the software spectral analyzer. The reliability of both power spectrum density results has been described. Although, previous equation and graph of the power spectrum density of DiPPM, have been proved for its faultiness. At last found that the DiPPM format gives output signal with increased power than that of the input signal.
(ii) is fulfilled, or vice versa. In addition, in some cases (iii) is more or less violated since the methods may introduce, so- called, musical noise. The above drawbacks with the spectral subtraction methods have been known and, in the literature, several ad hoc modifications of the basic algorithms have ap- peared. However, the fundamental question how to design spectral subtraction methods that fulfill (i)–(iii) for general scenarios has remained unanswered. The reason for this is, of course, that the requirements (i)–(iii) are in conflict with each other. The correct question to be answered is what re- duction of the noise level we can expect without distortion of the speech output and annoying artifacts in the residual noise.
capacitors” in some literature but hereafter largely referred to as ultracapacitors) as an augmentation device when placed in parallel with “electrochemical” energy storage (i.e. batteries) is presented in this paper as well as a peak power assist case where ultracapacitor technology is paralleled with a primary power supply. Since ultracapacitors possess unique attributes due to their higher energy storage density (or Joules/WattHrs per mass) compared to conventional capacitors while maintaining the peak power providing capability (to some degree) typical of conventional capacitors they may provide a near term solution in applications demanding longer battery operating life and power system robustness. Such demands may be more pronounced by the onset of evolving peak power loads and “cold-crank” Auxiliary Power Unit (APU) electric-starting in demanding cold temperature environments.
Metal-air batteries have attracted a lot of attention as a possible energy storage solution for decades . Among various metal-air batteries, zinc-air battery holds the greatest promise for future energy applications , owing to its high powerdensity, safety, and economic viability and the abundant zinc reserve in earth [3-5]. The key point for development of zinc-air battery is finding high- performance oxygen reduction reaction (ORR) catalysts. Precious metals, like Pt, are usually used as ORR catalysts [6,7]. In general, Pt-based catalysts can be prepared via various routes, such as electrochemical deposition , chemical vapor deposition [9,10], and facile hydrothermal method . Since the catalyst utilization in the fuel cell is determined mainly by the contact surface area of cata- lyst with electrolyte, the reduction of the thickness of cata- lytic layer can result in an improvement of the catalyst utilization and reduction of the fuel cell cost . There- fore, pulse laser deposition (PLD) is also used popularly in the field [13-15], because the approach is a feasible way to
The main idea behind modified Welch algorithm is to compute FFT of half of the original segments and then combining the FFTs of two segments to obtain the FFT of the complete segment. Figure 2.1 shows the flow chart of modified welch algorithm. In the modified algorithm the input signal vector is divided into (L+1) non-overlapping segments of length N/2. To each segment we apply an N/2 - point FFT. We obtain an N-point FFT by merging two N/2 - point FFTs and the specified window is applied to it. Modified periodograms of each windowed segment is then calculated and is averaged to form the spectral estimate. Figure 2.2 shows the filter circuit used for windowing in frequency domain.