Average PSD Research Articles

Detection of distorted interference pulses for UWFBG array based on odd function decomposition

In this paper, we propose a distorted pulse detection method based on odd function for pulse decomposition, to solve the problem of optical path mismatch in UWFBG array. In theory, we build a mathematical model of the distortion pulse and derive the corresponding odd function. Then, we analyze the peak trajectory obtained by the difference curve by simulation, and determine the optimal interference position of the distorted pulse. Finally, we use the vibrating liquid column method to carry out underwater acoustic sensing experiments, under different conditions of optical path mismatch. The results show that, when the distance between adjacent UWFBGs is 50 m and pulse width with 100 ns, the gain of harmonic SNR and average PSD is improved from 2.3 dB and 1.8 dB to 11.2 dB and 10.0 dB respectively, under different circumstances with length difference for 1 m, 1.5 m, and 2 m respectively. So, the algorithm is more robust to length mismatch, and verifies the effectiveness of the algorithm, and has potential significance for reducing the difficulty of designing the UWFBG array interferometer.

FDD based modal identification of structures using least squares approach

In the conventional frequency domain modal identification procedures, modal parameters are attempted to be identified using power spectral density matrix decomposition. As it is well stated in the literature, the quality of estimated mode shapes significantly increases when an average PSD matrix over a selected frequency band is utilized in the identification procedure. In this context, this study aims at deriving a weighted average for the PSD matrix to increase the quality of the estimated mode shapes by using an FDD-based modal model. Then, the remaining modal parameters comprising modal frequency, damping ratio and spectral density of modal exciting force are calculated through a least squares equation. Moreover, the presented FDD based approach is also adapted to the solution of multiple setup problem. The proposed method for single and multiple setup cases is validated by making use of one numerical and two field data examples. The obtained results reveal that the presented frequency domain technique can successfully achieve high quality of modal estimates in the presence of measurement noise, and it can be easily implemented to field applications.

Stereometric analysis of Amazon rainforest Anacardium occidentale L. leaves.

AFM, profilometry and SEM measurements on both sides of the Anacardium occidentale L. leaf reveal that ultrastructure presented some singularities due to their different morphologies and roughness. The advanced stereometry and power spectrum density of both sides of the Anacardium occidentale L. leaf were carefully studied. We use three different microscopy techniques such as scanning electron microscopy, profilometry, and atomic force microscopy for a complete description of the leaf surface morphology. The morphology of the adaxial and abaxial sides revealed a surface composed of striated cuticles and stomata cells, respectively. The height parameters obtained by profilometry revealed that the abaxial side was rougher. However, both sides presented similar Gaussian height distribution and asymmetry. The advanced stereometric parameters obtained by the topographic maps of AFM revealed that the two sides have some singularities due to their different morphologies and roughness, but with similar microtextures. However, average PSD spectra showed that adaxial and abaxial sides are dominated by relatively low and high spatial frequencies, showing that the microtextures, unlike what was shown in stereometric parameters, are different. These results revealed that leaves surface morphology under different aspects and scales and the quantitative parameters confirmed the different spatial patterns displayed, which can be of great interest for the study of the biological behavior of plants from their leaves.

Automatic and Efficient Fault Detection in Rotating Machinery using Sound Signals

Vibration and acoustic emission have received great attention of the research community for condition-based maintenance in rotating machinery. Several signal processing algorithms were either developed or used efficiently to detect and classify faults in bearings and gears. These signals are recorded, using sensors like tachometer or accelerometer, connected directly or mounted very close to the system under observation. This is not a feasible option in case of complex machinery and/or temperature and humidity. Therefore, it is required to sense the signals remotely, in order to reduce installation and maintenance cost. However, its installation far away from the intended device may pollute the required signal with other unwanted signals. In an attempt to address these issues, sound signal-based fault detection and classification in rotating bearings is presented. In this research work, audible sound of machine under test is captured using a single microphone and different statistical, spectral and spectro-temporal features are extracted. The selected features are then analyzed using different machine learning techniques, such as K-nearest neighbor (KNN) classifier, support vector machine (SVM), kernel liner discriminant analysis (KLDA) and sparse discriminant analysis (SDA). Simulation results show successful classification of faults into ball fault, inner and outer race faults. Best results were achieved using the KLDA followed by SDA, KNN and SVM. As far as features are concerned, the average FFT outperformed all the other features, followed by average PSD, RMS values of PSD, PSD and STFT.

Improved impulse noise modeling for indoor narrow-band power line communication

This paper presents a novel low-complexity fully parametric frequency-dependent impulse noise model for Narrow-Band PLC in the frequency band below 500 kHz. The statistical characterization of measured noise in terms of impulse temporal waveform and the average PSD allowed to confirm the limitations of the commonly used Middleton class-A model due to its flat PSD that is not matching measurements results. To improve the impulse noise model matching with measurement results, a two-state model using impulses in the form of damped sinusoids is proposed. Comparison of the time and frequency characteristics of the proposed model with measurement show the presence of modeled pulses with shapes close to the measured noise, as well as a good matching in the average PSD. Simulation results in using the proposed model for FSK and OFDM systems design show good accuracy to the measured noise, in terms of detector outputs in 2-FSK, bit error rates and fraction of errors per sub-band in the OFDM-based transmission.

Optic nerve compression: the role of the lamina cribrosa and translaminar pressure.

To describe the morphological changes of the lamina cribrosa (LC) in patients with optic nerve compression. Cross-sectional study. Twenty eyes with optic nerve compression, affected by Graves' ophthalmopathy (GO) were compared with 18 refractive error-matched healthy eyes. The following examinations were performed: best-corrected visual acuity (BCVA), intraocular pressure, optic nerve echography, visual field, SD-OCT including the retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and LC thickness and extent. A-scan revealed significant differences in the subarachnoid space (SAS) between the affected and control groups. LC thickness and LC area were 233 µm (SD 23) and 0.41 mm2 (SD 0.19), respectively. Average GCC thickness (P=0.0005), LC thickness (P=0.001), MD (P=0.001) and PSD (P=0.001) differed significantly between the two groups; whereas LC area (P=0.2) and average RFNL (P=0.1) did not. Optic nerve compression reduces the SAS thereby altering the morphology of LC thickness and causing GCC damage.

Loss of SynDIG1 Reduces Excitatory Synapse Maturation But Not Formation In Vivo.

Modification of the strength of excitatory synaptic connections is a fundamental mechanism by which neural circuits are refined during development and learning. Synapse Differentiation Induced Gene 1 (SynDIG1) has been shown to play a key role in regulating synaptic strength in vitro. Here, we investigated the role of SynDIG1 in vivo in mice with a disruption of the SynDIG1 gene rather than use an alternate loxP-flanked conditional mutant that we find retains a partial protein product. The gene-trap insertion with a reporter cassette mutant mice shows that the SynDIG1 promoter is active during embryogenesis in the retina with some activity in the brain, and postnatally in the mouse hippocampus, cortex, hindbrain, and spinal cord. Ultrastructural analysis of the hippocampal CA1 region shows a decrease in the average PSD length of synapses and a decrease in the number of synapses with a mature phenotype. Intriguingly, the total synapse number appears to be increased in SynDIG1 mutant mice. Electrophysiological analyses show a decrease in AMPA and NMDA receptor function in SynDIG1-deficient hippocampal neurons. Glutamate stimulation of individual dendritic spines in hippocampal slices from SynDIG1-deficient mice reveals increased short-term structural plasticity. Notably, the overall levels of PSD-95 or glutamate receptors enriched in postsynaptic biochemical fractions remain unaltered; however, activity-dependent synapse development is strongly compromised upon the loss of SynDIG1, supporting its importance for excitatory synapse maturation. Together, these data are consistent with a model in which SynDIG1 regulates the maturation of excitatory synapse structure and function in the mouse hippocampus in vivo.

Distribution of the vibration effect within the stacked boxes during vehicular road transportation of tomatoes

Parameters of the Road-Vehicle-Load system influence the vibration effects generated at vehicular road transportation. Vertical vibration acceleration (PSDmax) experienced by the tomato boxes and tomatoes within the box was studied using the popular transport means in Illukkumbura area in Matale. The road quality was estimated using the International Road Roughness Index (IRI). Fully loaded Mitsubishi Canter truck at an average speed of 20 kmh-1 on a road rated at IRI between 2 to 3.5 mm/m registered increasing trend in the PSD of vibration from the front side towards the rear side of the truck in the horizontal direction. The observed average PSD values are in the approximate ratio, front : middle : rear ≈ 1 : 3: 6. Also the PSD of the vibration was found to be amplified from the bottom stack towards the topmost stack in the vertical direction. The observed average PSD values at 1st, 2nd, 3rd, and 4th stacks are in the approximate ratio, 1 : 1 : 1.5 : 2.5. PSD of vibration was studied with a fully loaded truck at different speeds on a road consisting of segments rated at varying IRI. The fully loaded truck at different speeds on a road consisting of segments rated at varying IRI registered varying PSD values of vibration. Even at lower speeds such as 25 kmh-1 the vibration acceleration produced at “poor” quality (IRI > 5 mm/m) roads was nearly 4 times higher compared to that produced at “fair” (IRI 2 to 3.5 mm/m) or “good” quality (IRI 0.9 to 2 mm/m) roads. Registered pattern of the PSD appears to be similar at the tomato boxes and at the tomatoes within the same box.

Mote Cleaner System Particulate Emission Factors for Cotton Gins: Particle Size Distribution Characteristics

This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2006 and again in 2013, the United States (U.S.) Environmental Protection Agency (EPA) published a more stringent National Ambient Air Quality Standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created an urgent need to collect additional cotton gin emissions data to address current regulatory issues, because EPA AP-42 cotton gin PM2.5 (particulate matter with nominal diameter less than or equal to 2.5 µm) and PM10 (particulate matter with nominal diameter less than or equal to 10 µm) emission factors did not exist for mote cleaner systems. The objective of this study was to characterize particulate emissions for mote cleaner systems from cotton gins across the cotton belt based on particle size distribution analysis of total particulate samples from EPA-approved stack sampling methods. Two gins with mote cleaner systems were sampled. The exhaust from one of the mote cleaner systems was combined with the module feeder dust system. The average PSD based PM2.5, PM6, and PM10 emission factors for the mote cleaner system that was not combined with another cotton gin system were 0.0016 kg/227-kg bale (0.0036 lb/500-lb bale), 0.018 kg/bale (0.040 lb/bale), and 0.033 kg/bale (0.074 lb/bale), respectively. The PSD was characterized by an average MMD of 17.1 µm AED. The ratio of PM2.5 to total particulate was 1.53%, PM6 to total was 17.1%, and PM10 to total was 31.8%. The average PSD based PM2.5, PM6, and PM10 emission factors for the mote cleaner system that was combined with module feeder dust system were 0.00092 kg/227-kg bale (0.0020 lb/500-lb bale), 0.011 kg/bale (0.024 lb/bale), and 0.022 kg/bale (0.048 lb/bale), respectively. The PSD was characterized by an average MMD of 26.7 µm AED. The ratio of PM2.5 to total particulate was 0.85%, PM6 to total was 9.9%, and PM10 to total was 20.0%.

Comparison Of Grain Particle Size Distribution In The Single Kernel Characterisation System And During First Break Roller Milling

Flour milling has evolved into an efficient operation; however, process modelling, simulation, and optimisation can make significant improvements to the operation. A challenge of single kernel testing using an instrument such as the Perten Single Kernel Characterisation System (SKCS) is to relate the results to actual breakage achieved during roller milling. As a step toward this, wheat varieties covering a wide hardness range were broken in the SKCS and in the Satake STR-100 test roller mill (roll gaps of 0.3 - 0.8 mm; sharp-to-sharp and dull-to-dull roll dispositions) and the resulting breakage materials were studied for the two systems. The particle size distribution (psd) produced on breakage of wheat by the SKCS itself was measured using laboratory scale plansifting, and compared with the psd produced from first break milling at different roll gaps and under different roll dispositions. Under both sharp-to-sharp and dull-to-dull milling in the roller mill, the effect of increasing kernel hardness was due to the increase in the average size of the broken particles which showed that harder kernels do not break so readily. However, milling under dull-to-dull disposition at larger roll gaps showed the average psd decreased slightly with increasing kernel hardness. This unexpected result was also observed from the SKCS. Harder kernels resulted in smaller particles in the broken material which indicates a very positive crushing action within the SKCS. The psd from the SKCS was most similar to that produced from the roller mill at a roll gap of 0.8 mm under a dull-to- dull disposition.

Surface statistical characteristics and smoothing analysis of continuous phase plate

According to the random characteristics of surface distribution of continuous phase plate (CPP), the characteristics of such random surface are analyzed from a statistical point of view. Based on the continuous phase plate with Gaussian distribution, the ergodic theorem is introduced to describe the statistical characteristics of CPP, and the qualification that fulfills the ergodic theorem is proved. The CPP which fulfills the ergodic theorem is proved to have better beam smoothing properties in both spatial and frequency domain by numerical simulation. The results show that after smoothing, the focal spot of random distortion beam is well controlled. The average PSD value of distortion wavefront is decreased by 50% or more.

Miniemulsion Polymerisation Via Reversible Addition Fragmentation Chain Transfer in Pseudo‐Bulk Regime

AbstractA mathematical model of reversible addition fragmentation chain transfer (RAFT) living miniemulsion polymerisation based on pseudo‐bulk kinetics was developed and validated successfully with experimental data. In this work, in case of large particles synthesis by RAFT miniemulsion polymerisation greater than cross‐over size, the developed mathematical model in pseudo‐bulk regime reasonably matches with the experimental results and predicts the key polymer properties such as average molecular weight and MWD, average particle size and PSD. Consequently, optimal strategy of semi‐batch operation was developed using monomer and RAFT agent feed rate as process variables with specified initial conditions. magnified image

Comparison of indirect radiation dose estimates with directly measured radiation dose for patients and operators during complex endovascular procedures

A great deal of attention has been directed at the necessity and potential for deleterious outcomes as a result of radiation exposure during diagnostic evaluations and interventional procedures. We embarked on this study in an attempt to accurately determine the amount of radiation exposure given to patients undergoing complex endovascular aortic repair. These measured doses were then correlated with radiation dose estimates provided by the imaging equipment manufacturers that are typically used for documentation and analysis of radiation-induced risk. Consecutive patients undergoing endovascular thoracoabdominal aneurysm (eTAAA) repair were prospectively studied with respect to radiation dose. Indirect parameters as cumulative air kerma (CAK), kerma area product (KAP), and fluoroscopy time (FT) were recorded concurrently with direct measurements of dose (peak skin dose [PSD]) and radiation exposure patterns using radiochromatic film placed in the back of the patient during the procedure. Simultaneously, operator exposure was determined using high-sensitivity electronic dosimeters. Correlation between the indirect and direct parameters was calculated. The observed radiation exposure pattern was reproduced in phantoms with over 200 dosimeters located in mock organs, and effective dose has been calculated in an in vitro study. Scatter plots were used to evaluate the relationship between continuous variables and Pearson coefficients. eTAAA repair was performed in 54 patients over 5 months, of which 47 had the repair limited to the thoracoabdominal segment. Clinical follow-up was complete in 98% of the patients. No patients had evidence of radiation-induced skin injury. CAK exceeded 15 Gy in 3 patients (the Joint Commission on Accreditation of Healthcare Organizations [JCAHO] threshold for sentinel events); however, the direct measurements were well below 15 Gy in all patients. PSD was measured by quantifying the exposure of the radiochromatic film. PSD correlated weakly with FT but better with CAK and KAP (r = 0.55, 0.80, and 0.76, respectively). The following formula provides the best estimate of actual PSD = 0.677 + 0.257 CAK. The average effective dose was 119.68 mSv (for type II or III eTAAA) and 76.46 mSv (type IV eTAAA). The operator effective dose averaged 0.17 mSv/case and correlated best with the KAP (r = 0.82, P < .0001). FT cannot be used to estimate PSD, and CAK and KAP represent poor surrogate markers for JCAHO-defined sentinel events. Even when directly measured PSDs were used, there was a poor correlation with clinical event (no skin injuries with an average PSD >2 Gy). The effective radiation dose of an eTAAA is equivalent to two preoperative computed tomography scans. The maximal operator exposure is 50 mSv/year, thus, a single operator could perform up to 294 eTAAA procedures annually before reaching the recommended maximum operator dose.

Comparison of Glaucoma Probability Score and Moorfields Regression Analysis to Discriminate Glaucomatous and Healthy Eyes

To compare sensitivity and specificity values of glaucoma probability score (GPS) and Moorfields regression analysis (MRA) of Heidelberg retina tomograph (HRT) to discriminate between glaucomatous and healthy eyes. A total of 160 eyes of 160 individuals (80 glaucoma patients and 80 healthy subjects) were enrolled in this prospective cross-sectional study. Confocal scanning laser ophthalmoscopy was performed with HRT. Performance of GPS and MRA were evaluated by considering borderline (BL) cases as within normal limits (WNL) or as outside normal limits (ONL). For further analysis glaucoma group was divided into two subsets: initial and moderate/severe damage group. There was no difference between glaucoma patients and normal subjects in terms of gender, disc area, and pachymetry (p>0.05). The GPS was higher, average visual field MD and PSD values were worse, and patients were older in glaucoma group (p=0.001). Sensitivity and specificity values were 72.5% and 93.8% respectively for MRA and 75.0% and 88.8% for GPS when BL cases considered as WNL, and when BL cases considered as ONL these values were 83.8% and 73.8% for MRA and 88.8% and 70.0% for GPS. There was no difference between sensitivity and specificity values of GPS and MRA for either situation (p>0.05). Sensitivity of GPS (76.2%) was higher than of MRA (61.9%) in initial glaucomatous eyes (p=0.317). Diagnostic performance of GPS was similar to MRA. It was found that GPS might differentiate between glaucomatous and healthy eyes with relatively better sensitivity but worse specificity and represent considerable advantage over MRA in early glaucoma cases.

Spectrally-bounded continuous-wave supercontinuum generation in a fiber with two zero-dispersion wavelengths

A common issue in fiber-based supercontinuum (SC) generation under continuous-wave pumping is that the spectral width of the resulting source is related to the input power of the pump laser used. An increase of the input pump power leads to an increase of the spectral width obtained at the fiber output, and therefore, the average power spectral density (APSD) over the SC spectrum does not grow according to the input power. For some applications it would be desired to have a fixed spectral width in the SC and to increase the average PSD proportionally to the input pump power. In this paper we demonstrate experimentally that SC generation under continuous-wave (CW) pumping can be spectrally bounded by using a fiber with two zero-dispersion wavelengths (ZDWs). Beyond a certain pump power, the spectral width of the SC source remains fixed, and the APSD of the SC grows with the pump power. In our experiment we generate a reasonably flat, spectrally-bounded SC spanning from 1550 nm to 1700 nm. The spectra l width of the source is shown to be constant between 3 and 6 W of pump power. Over this range, the increase in input power is directly translated in an increase in the output APSD. The experimental results are confirmed by numerical simulations, which also highlight the sensitivity of this configuration to variations in the fiber dispersion curve. We believe that these results open the way for tailoring the spectral width of high-APSD CW SC by adjusting the fiber dispersion.

Study of the evolution of aerosol emissions from coal-fired power plants due to coagulation, condensation, and gravitational settling and health impact

This paper studies the scavenging efficiencies of aerosol emissions from coal-fired power plants under different removal mechanisms (coagulation, heterogeneous nucleation and gravitational settling) as a function of time. It also analyses the ‘health impact’ of the aerosol before and after the above dynamic mechanisms by comparing the respirable dust fractions. The well-known equations of evolution are applied to an average PSD that represents the exhaust particulate emissions from coal-fired power plants (i.e. Aboño power plant in Asturias that belongs to Hidrocantábrico Group, S.A.). From this study it is inferred that respirable dust is scavenged with the greatest difficulty and when compared with the initial volume of respirable dust, roughly 20% remains after 18 h of gravitational settling. Therefore, gravitational settling is the main removal mechanism of respirable dust compared to condensation and coagulation.

Dayside magnetic ULF power at high latitudes: A possible long‐term proxy for the solar wind velocity?

We examine the occurrence of dayside high‐latitude magnetic variations with periods between 2 and 10 min statistically using data from around 20 magnetic stations in Greenland, Scandinavia, and Canada, many of which have been in operation for a full solar cycle. We derive time series of the power spectral density (psd) in two different frequency bands: 2–4 min period and 5–10 min period. The average psd in these bands maximizes in the early morning sector between auroral and cusp latitudes. The solar cycle variation of the average psd in the two bands during the morning hours is markedly different from the solar cycle variation of regular geomagnetic activity, measured by indices such as aa and Dst. The spectral band power is generally at minimum just prior to solar maximum and has a strong maximum in the late declining phase associated with high‐speed streams from coronal holes. We Have compared the spectral band power with satellite observations of the solar wind velocity and find a high log‐linear correlation in the range 0.7–0.8. The highest correlation is found in the 2–4 min band. Contrary to this, the correlation with Bs and υBs is very weak (∼0.0–0.2), except in the 5–10 min band for the auroral stations. We find the results encouraging for the use of dayside spectral band power at high‐latitude stations as a tool for investigating past solar wind variations.

DISTRIBUTION OF SPATIAL VARIABILITY IN VIBRATION RESPONSE

Understanding the distribution of dynamic response is important in setting random vibration test levels for equipment. This paper describes how the probability distribution of a set of data could be tested. The Kolmogorov-Smirnov test statistic indicates that the third octave average PSD vibration responses on a set of components are spatially log-normal when excited by a reverberant acoustic field. Two procedures for estimating the P95/50 level are demonstrated to agree well for the component attachment sensors: one calculates the mean and standard deviation of log-transformed PSD, while the other uses a warping function with PSD mean and standard deviation calculated directly.

Periodic signals in Spanish monthly precipitation data

Forty-two monthly rainfall time series from Spain have been analyzed for the presence of cycles and regional patterns. The study was carried out by means of periodicity tests devised by Whittle, Hannan, Bartlett, Siegel, and Priestley. These tests contribute to a mixed spectrum analysis leading to the evaluation of signals versus the background of ‘coloured’ noise (autocorrelation). Also, a direct maximum entropy method (MEM) for estimating spectra was applied to the series, in particular an autoregressive (AR) power spectral density (psd) estimation, and an autoregressive moving average (ARMA) psd estimation, with parameters obtained by exact maximum likelihood estimator (MLE).