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Noise Levels (noise + level)
Selected AbstractsThe Effect of Noise in the Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 7 2005Leslie S. Zun MD Abstract Background: It is hypothesized that high ambient noise in the emergency department (ED) adversely affects the ability of the examiner to hear heart and lung sounds. Objective: To determine the ability of various examiners to hear heart tones and lung sounds at the high end of loudness typically found in the ED setting. Methods: The study was divided into two parts. First, sound levels in the ED were measured over various times during the months of January through June 2001, using a sound level monitor. The second part of the study was the determination of the ability to hear heart and lung sounds on a young healthy volunteer using the same Littmann lightweight stethoscope at a predetermined ambient noise level of 90 dB. The results were entered into a database and analyzed using SPSS version 10 (Chicago, IL). Descriptive statistics, analysis of variance, frequencies, and correlation were calculated using this program. Results: Two hundred five sound measurements were taken in the ED during the study period in three locations at various hours. The mean noise level at the nursing station was 57.60 dB, with a minimum of 45.00 dB and a maximum of 70.00 dB. Four of the 104 test subjects (3.8%) were unable to hear the heart tones, and nine of the 104 (8.7%) were unable to hear the lung sounds. Fifty percent (27 of 54) of the test subjects reported diminished lung sounds and eight of 15 (53.3%) reported diminished heart sounds. No significant difference was found between hearing heart sounds and years of experience, age, professional position, and quality of the sound. Significant differences were found between hearing lung sounds and years of experience and professional position, but not with age, gender, and sound quality. Conclusions: This study demonstrated that most of the tested examiners have the ability to hear heart and lung sounds at the extreme of loudness found in one ED. [source] Noise-improved signal detection in cat primary visual cortex via a well-balanced stochastic resonance-like procedureEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Klaus Funke Abstract Adding noise to a weak signal can paradoxically improve signal detection, a process called ,stochastic resonance' (SR). In the visual system, noise might be introduced by the image jitter resulting from high-frequency eye movements, like eye microtremor and microsaccades. To test whether this kind of noise might be beneficial or detrimental for cortical signal detection, we performed single-unit recordings from area 17 of anaesthetized cats while jittering the visual stimulus in a frequency and amplitude range resembling the possible range of eye movements. We used weak, sub- and peri-threshold visual stimuli, on top of which we superimposed noise with variable jitter amplitude. In accordance with the typical SR effect, we found that small noise levels actually increased the signal-to-noise ratio (SNR) of previously weak cortical visual responses, while originally strong responses were little affected or even reduced. Above a certain noise level, the SNR dropped a little, but not as a result of increased background activity , as would be proposed by SR theory , but because of a lowered response to signal and noise. Therefore, it seems that the ascending visual pathway optimally utilizes signal detection improvement by a SR-like process, while at the same time preventing spurious noise-induced activity and keeping the SNR sufficiently high. [source] Estimating the number of independent components for functional magnetic resonance imaging dataHUMAN BRAIN MAPPING, Issue 11 2007Yi-Ou Li Abstract Multivariate analysis methods such as independent component analysis (ICA) have been applied to the analysis of functional magnetic resonance imaging (fMRI) data to study brain function. Because of the high dimensionality and high noise level of the fMRI data, order selection, i.e., estimation of the number of informative components, is critical to reduce over/underfitting in such methods. Dependence among fMRI data samples in the spatial and temporal domain limits the usefulness of the practical formulations of information-theoretic criteria (ITC) for order selection, since they are based on likelihood of independent and identically distributed (i.i.d.) data samples. To address this issue, we propose a subsampling scheme to obtain a set of effectively i.i.d. samples from the dependent data samples and apply the ITC formulas to the effectively i.i.d. sample set for order selection. We apply the proposed method on the simulated data and show that it significantly improves the accuracy of order selection from dependent data. We also perform order selection on fMRI data from a visuomotor task and show that the proposed method alleviates the over-estimation on the number of brain sources due to the intrinsic smoothness and the smooth preprocessing of fMRI data. We use the software package ICASSO (Himberg et al. [ 2004]: Neuroimage 22:1214,1222) to analyze the independent component (IC) estimates at different orders and show that, when ICA is performed at overestimated orders, the stability of the IC estimates decreases and the estimation of task related brain activations show degradation. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source] Neural Electrodes: Interfacing Conducting Polymer Nanotubes with the Central Nervous System: Chronic Neural Recording using Poly(3,4-ethylenedioxythiophene) Nanotubes (Adv. Mater.ADVANCED MATERIALS, Issue 37 200937/2009) Microelectrodes implanted in the brain are increasingly being used to treat neurological disorders. However, robust and reliable chronic application of neural electrodes remains a challenge. Mohammed Reza Abidian and co-workers report on p. 3764 the use of conducting polymer nanotubes as highly selective neural interfaces for chronic neural recordings at the microscale. The quality of neuronal spike recordings was significantly improved relative to comparably sized metal electrode sites, primarily through a reduced noise level amidst maintained spike amplitudes. [source] Bayesian estimation of hyperparameters for indirect Fourier transformation in small-angle scatteringJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2000Steen Hansen Bayesian analysis is applied to the problem of estimation of hyperparameters, which are necessary for indirect Fourier transformation of small-angle scattering data. The hyperparameters most frequently needed are the overall noise level of the experiment and the maximum dimension of the scatterer. Bayesian methods allow the posterior probability distribution for the hyperparameters to be determined, making it possible to calculate the distance distribution function of interest as the weighted mean of all possible solutions to the indirect transformation problem. Consequently no choice of hyperparameters has to be made. The applicability of the method is demonstrated using simulated as well as real experimental data. [source] Tikhonov regularization in standardized and general form for multivariate calibration with application towards removing unwanted spectral artifactsJOURNAL OF CHEMOMETRICS, Issue 1-2 2006Forrest Stout Abstract Tikhonov regularization (TR) is an approach to form a multivariate calibration model for y,=,Xb. It includes a regulation operator matrix L that is usually set to the identity matrix I and in this situation, TR is said to operate in standard form and is the same as ridge regression (RR). Alternatively, TR can function in general form with L,,,I where L is used to remove unwanted spectral artifacts. To simplify the computations for TR in general form, a standardization process can be used on X and y to transform the problem into TR in standard form and a RR algorithm can now be used. The calculated regression vector in standardized space must be back-transformed to the general form which can now be applied to spectra that have not been standardized. The calibration model building methods of principal component regression (PCR), partial least squares (PLS) and others can also be implemented with the standardized X and y. Regardless of the calibration method, armed with y, X and L, a regression vector is sought that can correct for irrelevant spectral variation in predicting y. In this study, L is set to various derivative operators to obtain smoothed TR, PCR and PLS regression vectors in order to generate models robust to noise and/or temperature effects. Results of this smoothing process are examined for spectral data without excessive noise or other artifacts, spectral data with additional noise added and spectral data exhibiting temperature-induced peak shifts. When the noise level is small, derivative operator smoothing was found to slightly degrade the root mean square error of validation (RMSEV) as well as the prediction variance indicator represented by the regression vector 2-norm thereby deteriorating the model harmony (bias/variance tradeoff). The effective rank (ER) (parsimony) was found to decrease with smoothing and in doing so; a harmony/parsimony tradeoff is formed. For the temperature-affected data and some of the noisy data, derivative operator smoothing decreases the RMSEV, but at a cost of greater values for . The ER was found to increase and hence, the parsimony degraded. A simulated data set from a previous study that used TR in general form was reexamined. In the present study, the standardization process is used with L set to the spectral noise structure to eliminate undesirable spectral regions (wavelength selection) and TR, PCR and PLS are evaluated. There was a significant decrease in bias at a sacrifice to variance with wavelength selection and the parsimony essentially remains the same. This paper includes discussion on the utility of using TR to remove other undesired spectral patterns resulting from chemical, environmental and/or instrumental influences. The discussion also incorporates using TR as a method for calibration transfer. Copyright © 2006 John Wiley & Sons, Ltd. [source] SERS and infrared reflection-absorption spectroscopy of NO on cold-deposited Cu,JOURNAL OF RAMAN SPECTROSCOPY, Issue 1-3 2006M. Lust Abstract Surface enhanced Raman spectroscopy (SERS) of NO on cold-deposited Cu yields only bands of the dissociation products of NO, but not the stretching bands of NO. In contrast, infrared reflection-absorption spectroscopy (IRRAS) on similarly prepared samples displays strong NO stretching bands and only a very weak band of N2O from multilayer NO. The differences can be explained neither by thermal or photo-desorption nor by photochemical effects in the laser focus. Whereas the SERS results may be explained by the action of special sites, it is still unclear why the IRRAS signal from the dissociation products of NO at the ,catalytically active sites' is below the noise level. Copyright © 2006 John Wiley & Sons, Ltd. [source] Multiple-Cell Spike Density and Neural Noise Level Analysis by Semimicroelectrode Recording for Identification of the Subthalamic Nucleus During Surgery for Parkinson's DiseaseNEUROMODULATION, Issue 1 2008Toshikazu Kano MD ABSTRACT Objective.,, For targeting the subthalamic nucleus (STN), we attempted to quantify the changes in multiple cell activities by computing the neural noise level and multiple-cell spike density (MSD). Methods.,, We analyzed the neural noise level and MSD by stepwise recording at every 0.25-mm increment during the final tracking in 90 sides of 45 patients with Parkinson's disease. The MSD was analyzed with cut-off levels ranging from 1.2- to 2.0-fold the neural noise level in the internal capsule or zona incerta in each trajectory. Results.,, The dorsal boundary of the STN was identified from an increase in the neural noise ratio in all sides. The ventral boundary was identifiable, however, from a decrease in the neural noise ratio in only 70 sides (78%). In contrast, both the dorsal and ventral boundaries were clearly identified from an increase and a decrease in the MSD, respectively, in all of the 90 sides. Conclusion.,, MSD analysis by semimicroelectrode recording represents a useful, practical, and apparently reliable means for identifying the boundaries of the STN. [source] Modular solvers for image restoration problems using the discrepancy principleNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 5 2002Peter Blomgren Abstract Many problems in image restoration can be formulated as either an unconstrained non-linear minimization problem, usually with a Tikhonov -like regularization, where the regularization parameter has to be determined; or as a fully constrained problem, where an estimate of the noise level, either the variance or the signal-to-noise ratio, is available. The formulations are mathematically equivalent. However, in practice, it is much easier to develop algorithms for the unconstrained problem, and not always obvious how to adapt such methods to solve the corresponding constrained problem. In this paper, we present a new method which can make use of any existing convergent method for the unconstrained problem to solve the constrained one. The new method is based on a Newton iteration applied to an extended system of non-linear equations, which couples the constraint and the regularized problem, but it does not require knowledge of the Jacobian of the irregularity functional. The existing solver is only used as a black box solver, which for a fixed regularization parameter returns an improved solution to the unconstrained minimization problem given an initial guess. The new modular solver enables us to easily solve the constrained image restoration problem; the solver automatically identifies the regularization parameter, during the iterative solution process. We present some numerical results. The results indicate that even in the worst case the constrained solver requires only about twice as much work as the unconstrained one, and in some instances the constrained solver can be even faster. Copyright © 2002 John Wiley & Sons, Ltd. [source] Effect of Noise on T-Wave Alternans Measurement in Ambulatory ECGs Using Modified Moving Average versus Spectral MethodPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2009RAJA J. SELVARAJ M.D. Background: The modified moving average (MMA) and spectral method (SM) are commonly used to measure T-wave alternans (TWA), but their accuracy has not been compared in ambulatory electrocardiograms (ECGs) where TWA signal-to-noise ratio is low. Our objective was to compare the effect of noise and signal nonstationarity on the accuracy of TWA measurement using MMA versus SM when applied to synthetic and ambulatory ECGs. Methods: Periodic and nonperiodic noise were added to noiseless synthetic ECGs. Simulated TWA (0,20 ,V) was added to synthetic ECGs and ambulatory ECG recordings. TWA was measured using SM and MMA, and the measurement error relative to added TWA was compared. An MMA ratio was used to discriminate TWA signal from noise. Signal nonstationarity was simulated by changing heart rate, TWA magnitude, and TWA phase. Results: With no added TWA, MMA falsely measured TWA in synthetic and ambulatory ECGs, while false measurement was not seen with SM. An MMA ratio > 1.2 eliminated false TWA detection. In the presence of low TWA magnitude (<10 ,V), TWA was overestimated by MMA and underestimated by SM in proportion to the noise level. In synthetic ECGs with periodic noise and 10-,V added TWA, MMA was less accurate than SM. The effects of simulated signal nonstationarity on the TWA magnitude measured with MMA versus SM were similar using a 64-beat analysis window. Conclusions: In the presence of noise, MMA falsely detects or overestimates simulated TWA in ambulatory ECG recordings. In this setting, the proposed MMA ratio improves the specificity of MMA. [source] Cohort study for the effect of chronic noise exposure on blood pressure among male workers in Busan, KoreaAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 6 2009Ji Ho Lee MD Abstract Objective It has not yet been established whether exposure to chronic noise induces an increase in blood pressure or an increase in the development of hypertension. Therefore, a cohort study was performed to identify the effects of chronic noise exposure on blood pressure. Methods Five hundred thirty male workers at a metal manufacturing factory in Busan, Korea, were enrolled in the study. They were monitored with an annual health check-ups for nine consecutive years from 1991 to 1999. The subjects were divided into four groups which were determined by noise level categories (NLCs) according to the exposure of noise intensity; NLC-I: office workers who were exposed to <60 dBA at work; NLC-II: worksite technical supporters or inspectors who were intermittently exposed to noise and were not using hearing protection devices; NLC-III: worksite workers exposed to a noise below 85 dBA (TWA) and used one type of hearing protection device, earplug or earmuff; NLC-IV: worksite workers who were exposed to a noise level of 85 dBA or higher in average and used both earplug and earmuff. Results After controlling the possible confounders, such as baseline age, smoking, alcohol intake, exercise, family history of hypertension, systolic blood pressure (SBP), or diastolic blood pressure (DBP), and changes in body mass index (BMI), we determined that the mean values for the SBP over the duration of this study were 3.8, 2.0, and 1.7 mmHg higher in groups NLC-IV, NLC-III, and NLC-II, respectively, in comparison to that of the NLC-I group. There was no significant difference in DBP among the groups. Conclusion This study suggests that chronic noise exposure increases SBP independently, among male workers. Am. J. Ind. Med. 52:509,517, 2009. © 2009 Wiley-Liss, Inc. [source] A fast radiative-transfer model for the assimilation of infrared limb radiances from MIPASTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 608 2005N. Bormann Abstract A new fast radiative-transfer model to compute emitted infrared limb radiances for the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) has been developed and validated. The model, referred to as RTMIPAS, can simulate apodized radiances for all channels of the high spectral resolution MIPAS instrument in the 685,2000 cm,1 wave-number region. RTMIPAS is part of a wider effort to develop the capability to assimilate infrared limb radiances into the ECMWF model. The model uses a linear regression scheme to parametrize the effective layer optical depths, and it can simulate the effect of variable water vapour and ozone; for other gases included in the model, a fixed climatological profile is assumed. The development of the model has involved the calculation of an accurate line-by-line transmittance database, the selection of suitable predictors for the gases and the viewing geometry modelled, and the generation of regression coefficients for 43205 MIPAS channels. RTMIPAS can reproduce line-by-line radiances to an accuracy that is below the noise level of the instrument for most spectral points and tangent heights, while offering significantly more rapid radiance calculations compared with currently available radiative-transfer models. The comparison of RTMIPAS transmittances with line-by-line model equivalents indicates that the accuracy of the RTMIPAS transmittance model is comparable to that of similar regression-based radiative-transfer models for nadir-viewing geometry. Copyright © 2005 Royal Meteorological Society [source] Lack of Impact of Myocardial Ischemia on the Signal-Averaged ECG Assessment by Time-Domain AnalysisANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2002Michael A. E. Schneider M.D. Background: Late potentials represent an arrhythmogenic substrate in chronically infarcted myocardium. It is hypothesized that acute transient ischemia enhances anisotropic electrical ventricular activation and facilitates reentry mechanisms. Study aim was the prospective assessment of the impact of dipyridamole-induced myocardial ischemia on the signal-averaged ECG. Methods: Dipyridamole stress thallium-201 SPECT imaging was utilized to avoid noise contamination of the signal-averaged ECG from exercise and to document evidence and localization of myocardial ischemia or persistent perfusion defects in 68 patients with suspected coronary artery disease. Before and during dipyridamole-induced vasodilatation serial signal-averaged ECG was performed to evaluate the influence of transient ischemia on the occurrence of late potentials. Results: There was a significant difference between heart rate at rest and heart rate under dipyridamole influence in patients with inducible ischemia (70 ± 13 vs. 87 ± 13; P < 0.0001) in contrast to patients without dipyridamole-induced ischemia (74 ± 20 vs. 80 ± 16; n.s.). The number of averaged beats and achieved noise level was comparable between both groups. Thirty-three of 68 patients (49%) revealed dipyridamole-induced ischemia; however, no changes of the SAECG parameters, such as QRS, RMS, LAS at 25,250 and 40,250 Hz bandpass filtering in the leads X, Y, Z and vector magnitude, respectively, were observed as a result of ischemia. Conclusion: These results suggest that transient myocardial ischemia does not affect the signal-averaged ECG. Clinically, the signal-averaged ECG analysis seems not to be helpful in identifying patients with silent ischemia. A.N.E. 2002;7(3):191,197 [source] Classroom experiments on the effects of different noise sources and sound levels on long-term recall and recognition in childrenAPPLIED COGNITIVE PSYCHOLOGY, Issue 8 2003Staffan Hygge A total of 1358 children aged 12,14 years participated in ten noise experiments in their ordinary classrooms and were tested for recall and recognition of a text exactly one week later. Single and combined noise sources were presented for 15 min at 66 dBA Leq (equivalent noise level). Single source presentations of aircraft and road traffic noise were also presented at 55 dBA Leq. Data were analysed between subjects since the first within-subjects analysis revealed a noise after-effect or a asymmetric transfer effect. Overall, there was a strong noise effect on recall, and a smaller, but significant effect on recognition. In the single-source studies, aircraft and road traffic noise impaired recall at both noise levels. Train noise and verbal noise did not affect recognition or recall. Some of the pairwise combinations of aircraft noise with train or road traffic, with one or the other as the dominant source, interfered with recall and recognition. Item difficulty, item position and ability did not interact with the noise effect. Arousal, distraction, perceived effort, and perceived difficulty in reading and learning did not mediate the effects on recall and recognition. Copyright © 2003 John Wiley & Sons, Ltd. [source] A synoptic program for large solar telescopes: Cyclic variation of turbulent magnetic fieldsASTRONOMISCHE NACHRICHTEN, Issue 6 2010L. Kleint Abstract Upcoming large solar telescopes will offer the possibility of unprecedented high resolution observations. However, during periods of non-ideal seeing such measurements are impossible and alternative programs should be considered to best use the available observing time. We present a synoptic program, currently carried out at the Istituto Ricerche Solari Locarno (IRSOL), to monitor turbulent magnetic fields employing the differential Hanle effect in atomic and molecular lines. This program can be easily adapted for the use at large telescopes exploring new science goals, nowadays impossible to achieve with smaller telescopes. The current, interesting scientific results prove that such programs are worthwhile to be continued and expanded in the future. We calculate the approximately achievable spatial resolution at a large telescope like ATST for polarimetric measurements with a noise level below 5 × 10 -5 and a temporal resolution which is sufficient to explore variations on the granular scale. We show that it would be important to optimize the system for maximal photon throughput and to install a high-speed camera system to be able to study turbulent magnetic fields with unprecedented accuracy (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Monitoring the anomalous scattering signal and noise levels in X-ray diffraction of crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2004Zheng-Qing Fu A statistical index Ras is proposed in order to monitor the overall signal-to-noise ratio in an anomalous scattering data set. In this approach, symmetry-equivalent reflections are merged and grouped into centric and non-centric subsets. Reflections in the centric subset, which in theory should be equal, are used to estimate the noise level in the data. This approach differs from that used by most data-processing programs, in which the centric reflections are merged and averaged. By preserving the differences in centric reflections during data processing, an internal measure of the noise level can be estimated and used to analyze the quality of the anomalous signal in the data. An index Ras is defined as the ratio of the average Bijvoet difference of merged acentric reflections to merged centric reflections. Test results on a variety of data show that Ras has good correlation with the capability to determine the anomalous scattering substructure from the data. Ras can also be useful in monitoring the quality of the data in terms of the data-collection strategy, instrument settings and data-processing software used. Ras analysis has been implemented in the program 3DSCALE as part of a data-processing program suite that is under development in our laboratory. [source] Entangling Light in its Spatial Degrees of Freedom with Four-Wave Mixing in an Atomic VaporCHEMPHYSCHEM, Issue 5 2009Vincent Boyer Dr. Abstract Nonlinearities in atomic vapors allow the production of "entangled images",beams of light whose transverse light distributions exhibit localized correlations in their unavoidable quantum fluctuations (see picture). These spatially entangled beams may prove useful to reduce the noise in absorption imaging and beam positioning below the quantum noise level, as well as for quantum information applications. The entanglement properties of two beams of light can reside in subtle correlations that exist in the unavoidable quantum fluctuations of their amplitudes and phases. Recent advances in the generation of nonclassical light with four-wave mixing in an atomic vapor have permitted the production and the observation of entanglement that is localized in almost arbitrary transverse regions of a pair of beams. These multi-spatial-mode entangled beams may prove useful for an array of applications ranging from noise-free imaging and improved position sensing to quantum information processing. [source] The role of history, Epworth Sleepiness Scale Score and body mass index in identifying non-apnoeic snorersCLINICAL OTOLARYNGOLOGY, Issue 4 2000P.V.H. Lim Seventy-one adults referred with snoring over a 9-month period were assessed and their apnoeic-status determined by clinical assessment using symptoms suggestive of the obstructive sleep apnoea,hypopnoea syndrome, the Epworth Sleepiness Scale score (ESS) and body mass index (BMI). The results of clinical assessment were compared to that of overnight six-channel polysomnography where snoring noise level, pulse rate, capillary oxygen saturation, breathing effort, oronasal airflow and body position were monitored. Polysomnography detected an apnoea-hypopnoea index (AHI) of < 15 episodes/h in 61(86%) patients and an AHI of , 15 episodes/h in 10 (14%) patients. Clinical assessment alone identified 57 patients with AHI of < 15 episodes/h as ,non-apnoeic snorers' and six patients with AHI of , 15 episodes/h as ,apnoeic snorers'. The sensitivity of this method of clinical assessment in identifying the ,non-apnoeic snorers' from amongst patients referred with snoring was 93.4% and its specificity was 60% (P < 0.001). [source] Stable signal recovery from incomplete and inaccurate measurementsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 8 2006Emmanuel J. Candès Suppose we wish to recover a vector x0 , ,,, (e.g., a digital signal or image) from incomplete and contaminated observations y = A x0 + e; A is an ,, × ,, matrix with far fewer rows than columns (,, , ,,) and e is an error term. Is it possible to recover x0 accurately based on the data y? To recover x0, we consider the solution x# to the ,,1 -regularization problem where , is the size of the error term e. We show that if A obeys a uniform uncertainty principle (with unit-normed columns) and if the vector x0 is sufficiently sparse, then the solution is within the noise level As a first example, suppose that A is a Gaussian random matrix; then stable recovery occurs for almost all such A's provided that the number of nonzeros of x0 is of about the same order as the number of observations. As a second instance, suppose one observes few Fourier samples of x0; then stable recovery occurs for almost any set of ,, coefficients provided that the number of nonzeros is of the order of ,,/(log ,,)6. In the case where the error term vanishes, the recovery is of course exact, and this work actually provides novel insights into the exact recovery phenomenon discussed in earlier papers. The methodology also explains why one can also very nearly recover approximately sparse signals. © 2006 Wiley Periodicals, Inc. [source] Slit effect of common ground patterns in affecting crosstalk noise between two parallel signal traces on printed circuit boardsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2010Tsuyoshi Maeno Abstract It is well known that electromagnetic (EM) disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring harnesses from vehicle-mounted printed circuit boards (PCBs) having common ground patterns with slits. To evaluate the noise current outflows from PCBs of this kind, we previously measured noise current outflows from four types of simple three-layer PCBs having two perpendicular signal traces and different ground patterns with or without slits, and showed that slits on a ground pattern allow conducted noise currents to flow out from PCBs, while the levels for the symmetric slit ground type are smaller than in the case of two asymmetric slit ground types. In the present study, to further investigate the above finding, we fabricated six types of simple two-layer PCBs having two parallel signal traces and different ground patterns with and without slits, and measured the crosstalk noise between the traces. We found that the ground patterns with the slits perpendicular to the traces increased the crosstalk noise levels, which were 19 to 42 dB larger than those for the ground pattern with no slits, while the ground patterns with the slits parallel to the traces were able to reduce the noise levels, which were slightly smaller (by 2.5 to 4.5 dB) than in the case of the no-slit ground pattern. These results were confirmed by FDTD simulation, and were also qualitatively explained by means of an equivalent bridge circuit model that we previously proposed. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(10): 19,24, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10287 [source] HABITAT-DEPENDENT SONG DIVERGENCE IN THE LITTLE GREENBUL: AN ANALYSIS OF ENVIRONMENTAL SELECTION PRESSURES ON ACOUSTIC SIGNALSEVOLUTION, Issue 9 2002Hans Slabbekoorn Abstract., Bird song is a sexual trait important in mate choice and known to be shaped by environmental selection. Here we investigate the ecological factors shaping song variation across a rainforest gradient in central Africa. We show that the little greenbul (Andropadus virens), previously shown to vary morphologically across the gradient in fitness-related characters, also varies with respect to song characteristics. Acoustic features, including minimum and maximum frequency, and delivery rate of song notes showed significant differences between habitats. In contrast, we found dialectal variation independent of habitat in population-typical songtype sequences. This pattern is consistent with ongoing gene flow across habitats and in line with the view that song variation in the order in which songtypes are produced is not dependent on habitat characteristics in the same way physical song characteristics are. Sound transmission characteristics of the two habitats did not vary significantly, but analyses of ambient noise spectra revealed dramatic and consistent habitat-dependent differences. Matching between low ambient noise levels for low frequencies in the rainforest and lower minimal frequencies in greenbul songs in this habitat suggests that part of the song divergence may be driven by habitat-dependent ambient noise patterns. These results suggest that habitat-dependent selection may act simultaneously on traits of ecological importance and those important in prezygotic isolation, leading to an association between morphological and acoustic divergence. Such an association may promote assortative mating and may be a mechanism driving reproductive divergence across ecological gradients. [source] Array-conditioned deconvolution of multiple-component teleseismic recordingsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2010C.-W. Chen SUMMARY We investigate the applicability of an array-conditioned deconvolution technique, developed for analysing borehole seismic exploration data, to teleseismic receiver functions and data pre-processing steps for scattered wavefield imaging. This multichannel deconvolution technique constructs an approximate inverse filter to the estimated source signature by solving an overdetermined set of deconvolution equations, using an array of receivers detecting a common source. We find that this technique improves the efficiency and automation of receiver function calculation and data pre-processing workflow. We apply this technique to synthetic experiments and to teleseismic data recorded in a dense array in northern Canada. Our results show that this optimal deconvolution automatically determines and subsequently attenuates the noise from data, enhancing P -to- S converted phases in seismograms with various noise levels. In this context, the array-conditioned deconvolution presents a new, effective and automatic means for processing large amounts of array data, as it does not require any ad-hoc regularization; the regularization is achieved naturally by using the noise present in the array itself. [source] Sensitivity of electrical resistivity tomography data to electrode position errorsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2005Greg A. Oldenborger SUMMARY Limitations of imaging using electrical resistivity tomography (ERT) arise because of the difficulty of quantifying the reliability of tomographic images. A major source of uncertainty in tomographic inversion is data error. Data error due to electrode mislocations is characterized by the sensitivity of electrical potential to both source and receiver positions. This sensitivity is described by a scattering-type equation and, therefore, depends not only on source,receiver separation, but also on the location and magnitude of contrasts in electrical conductivity. At the overlapping scales of near-surface environmental and engineering geophysical surveys, for which electrodes may be close to the target and experiment dimensions may be on the same order as those of the target, errors associated with electrode mislocations can significantly contaminate the ERT data and the reconstructed electrical conductivity. For synthetic experiments, variations in the data due to electrode mislocation are comparable in magnitude to typical experimental noise levels and, in some cases, may overwhelm variations in the data due to changes in material properties. Furthermore, the statistical distribution of electrode mislocation errors can be complicated and multimodal such that bias may be introduced into the ERT data. The resulting perturbations of the reconstructed electrical conductivity field due to electrode mislocations can be significant in magnitude with complex spatial distributions that are dependent both on the model and the experiment. [source] The feasibility of electromagnetic gradiometer measurementsGEOPHYSICAL PROSPECTING, Issue 3 2001Daniel Sattel The quantities measured in transient electromagnetic (TEM) surveys are usually either magnetic field components or their time derivatives. Alternatively it might be advantageous to measure the spatial derivatives of these quantities. Such gradiometer measurements are expected to have lower noise levels due to the negative interference of ambient noise recorded by the two receiver coils. Error propagation models are used to compare quantitatively the noise sensitivities of conventional and gradiometer TEM data. To achieve this, eigenvalue decomposition is applied on synthetic data to derive the parameter uncertainties of layered-earth models. The results indicate that near-surface gradient measurements give a superior definition of the shallow conductivity structure, provided noise levels are 20,40 times smaller than those recorded by conventional EM instruments. For a fixed-wing towed-bird gradiometer system to be feasible, a noise reduction factor of at least 50,100 is required. One field test showed that noise reduction factors in excess of 60 are achievable with gradiometer measurements. However, other collected data indicate that the effectiveness of noise reduction can be hampered by the spatial variability of noise such as that encountered in built-up areas. Synthetic data calculated for a vertical plate model confirm the limited depth of detection of vertical gradient data but also indicate some spatial derivatives which offer better lateral resolution than conventional EM data. This high sensitivity to the near-surface conductivity structure suggests the application of EM gradiometers in areas such as environmental and archaeological mapping. [source] The Impact of Airport Noise and Proximity on Residential Property ValuesGROWTH AND CHANGE, Issue 3 2000Molly Espey The hedonic price method is used to estimate the relationship between residential property values and airport noise and proximity to the airport in the Reno-Sparks area. Empirical results suggest there is a statistically significant negative relationship between airport noise and residential property values, with the average home in areas where noise levels are 65 decibels or high selling for about $2400 less than equivalent homes in quieter areas. However, in direct contrast to the study by Tomkins et al.(1998) who found proximity to the Manchester airport to be an amenity, this study finds proximity to the Reno-Sparks airport to have a significant negative value. [source] Least-square-based radial basis collocation method for solving inverse problems of Laplace equation from noisy dataINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2010Xian-Zhong Mao Abstract The inverse problem of 2D Laplace equation involves an estimation of unknown boundary values or the locations of boundary shape from noisy observations on over-specified boundary or internal data points. The application of radial basis collocation method (RBCM), one of meshless and non-iterative numerical schemes, directly induces this inverse boundary value problem (IBVP) to a single-step solution of a system of linear algebraic equations in which the coefficients matrix is inherently ill-conditioned. In order to solve the unstable problem observed in the conventional RBCM, an effective procedure that builds an over-determined linear system and combines with least-square technique is proposed to restore the stability of the solution in this paper. The present work investigates three examples of IBVPs using over-specified boundary conditions or internal data with simulated noise and obtains stable and accurate results. It underlies that least-square-based radial basis collocation method (LS-RBCM) poses a significant advantage of good stability against large noise levels compared with the conventional RBCM. Copyright © 2010 John Wiley & Sons, Ltd. [source] Survey of quantitative feedback theory (QFT),INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2001Isaac Horowitz QFT is an engineering design theory devoted to the practical design of feedback control systems. The foundation of QFT is that feedback is needed in control only when plant (P), parameter and/or disturbance (D) uncertainties (sets ,,={P}, ,,={D}) exceed the acceptable (A) system performance uncertainty (set ,,={A}). The principal properties of QFT are as follows. (1) The amount of feedback needed is tuned to the (,,, ,,, ,,) sets. If ,, ,exceeds' (,,, ,,), feedback is not needed at all. (2) The simplest modelling is used: (a) command, disturbance and sensor noise inputs, and (b) the available sensing points and the defined outputs. No special controllability test is needed in either linear or non-linear plants. It is inherent in the design procedure. There is no observability problem because uncertainty is included. The number of independent sensors determines the number of independent loop transmissions (Li), the functions which provide the benefits of feedback. (3) The simplest mathematical tools have been found most use ful,primarily frequency response. The uncertainties are expressed as sets in the complex plane. The need for the larger ,,, ,, sets to be squeezed into the smaller ,, set results in bounds on the Li(j,) in the complex plane. In the more complex systems a key problem is the division of the ,feedback burden' among the available Li(j,). Point-by-point frequency synthesis tremendously simplifies this problem. This is also true for highly uncertain non-linear and time-varying plants which are converted into rigorously equivalent linear time invariant plant sets and/or disturbance sets with respect to the acceptable output set ,,. Fixed point theory justifies the equivalence. (4) Design trade-offs are highly transparent in the frequency domain: between design complexity and cost of feedback (primarily bandwidth), sensor noise levels, plant saturation levels, number of sensors needed, relative sizes of ,,, ,, and cost of feedback. The designer sees the trade-offs between these factors as he proceeds and can decide according to their relative importance in his particular situation. QFT design techniques with these properties have been developed step by step for: (i) highly uncertain linear time invariant (LTI) SISO single- and multiple-loop systems, MIMO single-loop matrix and multiple-loop matrix systems; and (ii) non-linear and time-varying SISO and MIMO plants, and to a more limited extent for plants with distributed control inputs and sensors. QFT has also been developed for single- and multiple-loop dithered non-linear (adaptive) systems with LTI plants, and for a special class (FORE) of non-linear compensation. New techniques have been found for handling non-minimum-phase (NMP) MIMO plants, plants with both zeros and poles in the right half-plane and LTI plants with incidental hard non-linearities such as saturation. [source] Nitric oxide decreases the excitability of interstitial cells of Cajal through activation of the BK channelJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 5a 2008Yaohui Zhu Abstract Nitrergic nerves are structurally and functionally associated with ICC. To further understand mechanisms of communication, the hypothesis was investigated that NO might affect large conductance K channels. To that end, we searched for IbTX-sensitive currents in ICC obtained through explant cultures from the mouse small intestine and studied effects of the NOS inhibitor omega N-nitro-L-arginine (LNNA) and the NO donor sodium nitroprusside (SNP). IbTX-sensitive currents acquired in the whole-cell configuration through nystatin perforated patches exhibited high noise levels but relatively low amplitude, whereas currents obtained in the conventional whole-cell configuration exhibited less noise and higher amplitudes; depolarization from ,80 to + 40 mV evoked 357 ± 159 pA current in the nystatin perforated patch configuration and 1075 ± 597 pA using the conventional whole-cell configuration. Immunohistochemistry showed that ICC associated with ganglia and Auerbach's plexus nerve fibers were immunoreactive to BK antibodies. The IbTX-sensitive currents were increased by SNP and inhibited by LNNA. BK blockers suppressed spontaneous transit outward currents in ICC. After block of BK currents, or before these currents became prominent, calcium currents were activated by depolarization in the same cells. Their peak amplitude occurred at ,25 mV and the currents were increased with increasing extracellular calcium and inhibited by cobalt. The hypothesis is warranted that nitrergic innervation inhibits ICC excitability in part through activation of BK channels. In addition, NO is an intracellular regulator of ICC excitability. [source] Fast principal component analysis of large data sets based on information extractionJOURNAL OF CHEMOMETRICS, Issue 11 2002F. Vogt Abstract Principal component analysis (PCA) and principal component regression (PCR) are routinely used for calibration of measurement devices and for data evaluation. However, their use is hindered in some applications, e.g. hyperspectral imaging, by excessive data sets that imply unacceptable calculation time. This paper discusses a fast PCA achieved by a combination of data compression based on a wavelet transformation and a spectrum selection method prior to the PCA itself. The spectrum selection step can also be applied without previous data compression. The calculation speed increase is investigated based on original and compressed data sets, both simulated and measured. Two different data sets are used for assessment of the new approach. One set contains 65,536 synthetically generated spectra at four different noise levels with 256 measurement points each. Compared with the conventional PCA approach, these examples can be accelerated 20 times. Evaluation errors of the fast method were calculated and found to be comparable with those of the conventional approach. Four experimental spectra sets of similar size are also investigated. The novel method outperforms PCA in speed by factors of up to 12, depending on the data set. The principal components obtained by the novel algorithm show the same ability to model the measured spectra as the conventional time-consuming method. The acceleration factors also depend on the possible compression; in particular, if only a small compression is feasible, the acceleration lies purely with the novel spectrum selection step proposed in this paper. Copyright © 2002 John Wiley & Sons, Ltd. [source] Development and implementation of a noise reduction intervention programme: a pre- and postaudit of three hospital wardsJOURNAL OF CLINICAL NURSING, Issue 23 2009Annette Richardson Aims., By developing, implementing and delivering a noise reduction intervention programme, we aimed to attempt to reduce the high noise levels on inpatient wards. Background., Sleep is essential for human survival and sleep deprivation is detrimental to health and well being. Exposure to noise has been found to disrupt sleep in hospitalised patients which is to be expected as noise levels have been measured and reported as high. Design., A primarily nursing focused, multi-method approach, involving development of clinical guidelines, ward environment review and a staff noise awareness and education programme, was used to target mainly nursing staff plus other healthcare staff on three wards within one hospital. Methods., This practice development initiative was carried out in three key phases (1) Preaudit of ward noise levels, (2) The development, implementation and delivery of a noise reduction intervention programme, (3) Postaudit of ward noise levels. Results., Preintervention average peak decibel levels over 24 hours were found to be 96·48 dB(A) and postintervention average peak decibel levels were measured at 77·52 dB(A), representing an overall significant reduction in noise levels (p < 0·001). Conclusions., This study describes one way to reduce peak noise levels on inpatient hospital wards. Relevance to clinical practice., Sleep deprivation is detrimental to patients with acute illness, so any developments to improve patients' sleep are important. Nurses have a key role in leading, developing and implementing changes to reduce peak noise levels on inpatient wards in hospitals. This nurse-led practice development programme has demonstrated how improvements can be achieved by significantly reducing peak noise levels using simple multi-method change strategies. [source] | ||||||||||||||||||||||||||||||||||||||||