Time Spectral Analysis Research Articles

A new approach to low-frequency QTF and its application in predicting slow drift force

In this paper, the classical free surface integral formula is examined by an analysis based on the development of the free surface forcing term in a power expansion with respect to Δω. The zero order contribution to the infinite integration which produces the corresponding load of first order Δω is formulated. Then a novel approach which can be easily implemented for predicting the low-frequency QTF is proposed. By applying higher order BEM and adaptive method in element integration, a numerical program is developed. The developed program is tested on simple geometric bodies and offshore platforms. The results from the present study agree well with the results of available exact solutions. Time domain simulation and spectral analyses of the slow drift force are performed for typical kinds of platforms. Extensive discussions and comparisons of the results based on the present method, Teng's exact method and widely used Newman's approximation are presented. The effectiveness of the proposed novel method is further demonstrated by these comparisons.

Spectral Analysis of Tropical Atmospheric Dynamical Variables Using a Linear Shallow-Water Modal Decomposition

Abstract Space–time spectral analysis has been used frequently in studying observational evidence of convectively coupled equatorial waves. Here 23 yr of brightness temperature Tb data and dynamical reanalysis data are analyzed by an appropriate projection onto the meridional basis functions of the β-plane linear shallow-water equations. Evidence of peaks in power along linear equatorial mode dispersion curves in Tb, zonal and meridional wind, divergence, and geopotential spectra are presented. Another feature of all space–time spectra considered is the redness in frequency, zonal wavenumber, and meridional mode number. It is found that spectral peaks in the dynamical variable spectra are largely consistent with linear shallow-water waves, but peaks related to barotropic waves and extratropical storm track activity are also apparent. The convectively coupled wave signals are seen to be confined to the first few meridional basis functions, suggesting a filtering method to reduce noise for these signals. This result also has implications for future modeling and theoretical work. A comparison of the results herein for two different reanalysis products shows only minor differences, adding confidence in the robustness of the results presented. This work implies that any comprehensive theory of tropical convection should explain the ubiquity of moist linear waves as well as the spectral redness with respect to all temporal and horizontal scales.

Temporal variability of the N2pc during efficient and inefficient visual search

Efficient and inefficient visual search are characterized by the difference in the time required to find the target. Efficient “popout” search time is relatively unaffected by increases in the number of search items, whereas inefficient “non-popout” search time requires more time increases in duration. Electrophysiological investigations of the neural correlates of visual search have revealed a component of the event-related potential (ERP) known as the N2pc. The N2pc is thought to reflect the orienting of attention to the target during visual search. If the N2pc is more closely associated in time with the moment of target selection than the onset of the search display, it may be predicted that the N2pc would be delayed or more temporally variable during inefficient compared to efficient visual search. In the present study, we contrasted efficient “popout” search with inefficient “non-popout” search to investigate the hypothesis that the N2pc is temporally associated with the moment of search completion, and this would be reflected as a delayed or attenuated N2pc during non-popout search compared to popout. In Experiment 1, we observed a robust N2pc during popout search, but not during non-popout search. However, sorting trials by the N2pc latency recovered the N2pc during non-popout search. In Experiment 2 we replicated this observation and demonstrated that popout and non-popout search reflected differences in the temporal variability of the N2pc latency. Further investigation using time-spectral analysis suggests that evoked posterior–contralateral theta (4–6Hz) underlies the N2pc during both popout and non-popout search.

An Efficient Time-Varying Filter for Detrending and Bandwidth Limiting the Heart Rate Variability Tachogram without Resampling: MATLAB Open-Source Code and Internet Web-Based Implementation

The heart rate variability (HRV) signal derived from the ECG is a beat-to-beat record of RR intervals and is, as a time series, irregularly sampled. It is common engineering practice to resample this record, typically at 4 Hz, onto a regular time axis for analysis in advance of time domain filtering and spectral analysis based on the DFT. However, it is recognised that resampling introduces noise and frequency bias. The present work describes the implementation of a time-varying filter using a smoothing priors approach based on a Gaussian process model, which does not require data to be regular in time. Its output is directly compatible with the Lomb-Scargle algorithm for power density estimation. A web-based demonstration is available over the Internet for exemplar data. The MATLAB (MathWorks Inc.) code can be downloaded as open source.

Differences between More Divergent and More Rotational Types of Convectively Coupled Equatorial Waves. Part I: Space–Time Spectral Analyses

Abstract Precipitation-related differences in different types of convectively coupled equatorial waves are examined here and in a companion paper. Here the authors show spectra and cross-spectra among tropical-belt time sections of satellite-derived surface rain, infrared brightness temperature Tb, precipitable water (PW), and Japan Meteorological Agency reanalysis of divergence and PW. Cross-spectra between rain and divergence at 1000- and 200-hPa levels show significant coherence peaks oriented along the dispersion curves of Kelvin, n = 1 equatorial Rossby (ERn1), mixed Rossby–gravity (MRG), n = 0 eastward inertial gravity (EIGn0), and n = 1 and n = 2 westward inertial gravity (WIG) waves, as well as the spectral signatures of the Madden–Julian oscillation (MJO) and tropical depression (TD)-type disturbances. Middle-troposphere divergence (indicative of stratiform rain and half-depth convection involvement in the coupling) is coherent with rain for the higher-frequency and more divergent wave types (Kelvin, EIGn0, WIG) but shows little coherence with rain for more rotational disturbance types (ERn1, MRG, TD). These two broad families also exhibit different rain–PW phase lags, a result supportive of the notion that stratiform rain (which occurs in dry conditions after peak PW and rain) is more involved in the more divergent wave types.

Modeling the Association between HR Variability and Illness in Elite Swimmers

To determine whether HR variability (HRV), an indirect measure of autonomic control, is associated with upper respiratory tract and pulmonary infections, muscular affections, and all-type pathologies in elite swimmers. For this study, 7 elite international and 11 national swimmers were observed weekly for 2 yr. The indexes of cardiac autonomic regulation in supine and orthostatic position were assessed as explanatory variables by time domain (SD1, SD2) and spectral analyses (high frequency [HF] = 0.15-0.40 Hz, low frequency [LF] = 0.04-0.15 Hz, and HF/LF ratio) of HRV. Logistic mixed models described the relationship between the explanatory variables and the risk of upper respiratory tract and pulmonary infections, muscular affections, and all-type pathologies. The risk of all-type pathologies was higher for national swimmers and in winter (P < 0.01). An increase in the parasympathetic indexes (HF, SD1) in the supine position assessed 1 wk earlier was linked to a higher risk of upper respiratory tract and pulmonary infections (P < 0.05) and to a higher risk of muscular affections (increase in HF, P < 0.05). Multivariate analyses showed (1) a higher all-type pathologies risk in winter and for an increase in the total power of HRV associated with a decline SD1 in supine position, (2) a higher all-type pathologies risk in winter associated with a decline in HF assessed 1 wk earlier in orthostatic position, and (3) a higher risk of muscular affections in winter associated with a decrease SD1 and an increase LF in orthostatic position. Swimmers' health maintenance requires particular attention when autonomic balance shows a sudden increase in parasympathetic indices in the supine position assessed 1 wk earlier evolving toward sympathetic predominance in supine and orthostatic positions.

The possible association between summer monsoon rainfall in India and sunspot numbers

Studies are presented on the association between mean annual sunspot numbers (SNs) and the summer monsoon rainfall over India. Sunspots are related directly to solar magnetism, which governs the source of the solar wind. SN is correlated with the 10.7 cm solar flux, a quantity measured by remote sensing techniques. The statistical properties of the time series for SN and summer monsoon rainfall were studied and it was found that, although the SNs exhibit persistence, this is not the case for the mean annual summer monsoon rainfall. The cross-correlations were also studied. After a Box–Cox transformation, a time spectral analysis was conducted and it was found that both of the time series have an important spectrum at the fifth harmonic. A neural network model was developed on the data series averaged continuously over 5 years and this neural network could be used to establish a predictor–predictand relationship between the SNs and the mean yearly summer monsoon rainfall over India.

Seasonal variation of hypertrophic pyloric stenosis: a population-based study

Seasonal variation in the incidence of hypertrophic pyloric stenosis (HPS) has been long debated. The goal of this study was to determine if seasonal variation exists in the incidence of pyloric stenosis. A population-based cohort consisted of all infants in the province of Ontario, Canada with HPS from 1993 to 2000. The incidence of HPS per season was adjusted by birth rate and expressed as number of pyloromyotomies per 100,000 infants less than 12 months of age. One-way analysis of variance was used to compare HPS incidence between seasons. Further time series and spectral analysis were performed to examine for seasonal variation. There were 1,777 infants included in the population-based cohort. June was the month with the highest rate of HPS. The highest rate of pyloromyotomy occurred in the summer 14.92 and the lowest in the winter 10.73, this difference was statistically significant (p = 0.01). Spectral analysis showed that June was the month with the highest rate and February had the lowest rates p = 0.0014. Hypertrophic pyloric stenosis more commonly presents in the summer. Seasonal variation suggests a possible etiological role for environmental factors.

Exploring the electrocardiogram as a potential tool to screen for premotor Parkinson's disease

The aim of this study was to test the hypothesis that patients with REM sleep behavior disorder, many of whom will develop Parkinson's disease (PD) or a related synucleinopathy, will demonstrate decreased heart rate variability (HRV) compared with a group of age-matched controls as measured by an electrocardiogram during wakefulness. We compared HRV in 11 untreated idiopathic REM sleep behavior disorder patients (9 men and 2 women; mean age, 63.3 years; SD, 7.5 years) and 11 control subjects with idiopathic insomnia without REM sleep behavior disorder (7 men and 4 women; mean age, 59.5 years; SD, 8.7 years). Subjects with other causes of reduced HRV were excluded. HRV was determined from 5-minute presleep segments of a single channel electrocardiogram recorded during polysomnographic evaluations, using R-R intervals during wakefulness. Time domain, geometric measures, and spectral analysis of the R-R intervals were significantly different between cases and controls. A discriminant function analysis correctly classified 95.5% of subjects (overall model fit, P = 0.016). Leave-one-out cross-validation correctly classified 77.3% of subjects. HRV during wakefulness is significantly decreased in patients with idiopathic REM sleep behavior disorder compared with control subjects, suggesting abnormalities of both sympathetic and parasympathetic function. Patients with RBD may later develop motor and cognitive features of a Lewy body disorder, such as PD. Cardiac autonomic dysfunction is also impaired in PD, suggesting that impaired HRV may be an early sign of PD. HRV measured by routine electrocardiograms could be used to screen for Lewy body disorders such as PD.

Exploration of the MODIS Cloud-Top Property Products for the Investigation of Equatorial Wave Systems

Abstract The Moderate Resolution Imaging Spectroradiometer (MODIS) observations provide an unprecedented opportunity for studying cloud macrophysical (cloud-top pressure, temperature, height, and phase), microphysical (effective particle size), and optical (optical thickness) properties. Given the length of time these MODIS products have been available, it is found that the cloud products can provide a wealth of information about equatorial wave systems. In this study, more than six years of the MODIS cloud-top properties inferred from the Aqua MODIS observations are used to investigate equatorial waves. It is shown that the high-resolution daily gridded cloud-top temperature product can be used to quantitatively study convective clouds. Various modes of convectively coupled equatorial waves including Kelvin, n = 1 equatorial Rossby, mixed Rossby–gravity, n = 0 eastward inertial-gravity waves, and the Madden–Julian oscillation are identified on the basis of space–time spectral analysis. The application of spectral analysis to cirrus cloud optical thickness, retrieved from MODIS cirrus reflectance, confirms the convective signals at high altitudes. A cluster of Kelvin pulses is found to propagate eastward around the globe at a phase speed approximately 15 m s−1. The Madden–Julian oscillation propagates at a slower speed and is most prominent over the Indian–Pacific Oceans region. The consistency between the present results with those of previous studies demonstrates that the MODIS cloud-top property products are valuable for studying phenomena associated with atmospheric dynamics.

Time-Spectral Analysis Methods for Spent Fuel Assay Using Lead Slowing-Down Spectroscopy

Nondestructive techniques for measuring the mass of fissile isotopes in spent nuclear fuel is a considerable challenge in the safeguarding of nuclear fuel cycles. A nondestructive assay technology that could provide direct measurement of fissile mass, particularly for the plutonium (Pu) isotopes, and improve upon the uncertainty of today's confirmatory methods is needed. Lead slowing-down spectroscopy (LSDS) has been studied for the spent fuel application previously, but the nonlinear effects of assembly self shielding (of the interrogating neutron population) have led to discouraging assay accuracy for realistic pressurized water reactor fuels. In this paper, we describe the development of time-spectral analysis algorithms for LSDS intended to overcome these self-shielding effects. The algorithm incorporates the tabulated energy-dependent cross sections from key fissile and absorbing isotopes, but leaves their mass as free variables. Multi-parameter regression analysis is then used to directly calculate not only the mass of fissile isotopes in the fuel assembly (e.g., Pu-239, U-235, and Pu-241), but also the mass of key absorbing isotopes such as Pu-240 and U-238. Modeling-based assay results using this self-shielding relationship indicate that LSDS has the potential to directly measure fissile isotopes with less than 5% average relative error for pressurized water reactor assemblies with burnup as high as 60 GWd/MTU. Shortcomings in the initial self-shielding model and potential improvements to the formulation are described.

Further Developments in the Study of Cointegrated Variables

This article was the brainchild of Clive W.J. Granger, which is not really surprising, giventhat a great number of his jointly written published papers began with his ideas. In addition, this isone of Clive’s many papers where his main objective was to “sow seeds so that some might have achance to grow and bear fruit, while others might not,” as he used to so aptly put it. In this sense,thus, it would perhaps be much more fitting if my beloved adviser and mentor were himself able todescribe how the ideas for the paper came about, what it was like to write it, and what his mainobjectives were. Sadly, of course, that is not to be the case. It is thus my humble duty to provide afew of the insights that Clive, in one way or another, taught me, as we wrote this papertogether. Needless to say, one of the many ideas that Clive had which dramatically impacted our profession and which effectively single-handedly charted the future course that an important strand of research in theoretical and applied econometrics would take was the notion of cointegration. His work on cointegration alone, in my view, was enough to warrant the Nobel prize that he won. Of course, he did write papers in numerous other areas that are pivotal and that guided researchers into various important areas of endeavor. Some of the areas that he is the father of, in my view, are: forecast combination, nonlinear modeling in macroeconomics and finance, causal analysis and testing, nonstationarity and long-memory properties of time series, spectral analysis, seasonality, forecasting and loss functions, and empirical finance. He wrote seminal papers on these topics over a long period of time, from around 1960 until his untimely passing. It’s funny for me to think that I have shaped my research career in econometrics by simply undertaking to make contributions in each of these areas. Many econometricians seem to have also done the same, and young researchers today are still doing the same. New papers in all of these areas are constantly still being written. In some sense, Clive seems to have not only written the road map to research in econometrics and empirical time-series analysis but also mapped out the benchmarks any young econometrician should attain along the road, as they begin and develop their research careers.

Determination of Seed Storage Proteins and Total Isoflavones in Wild and Cultivated Soybeans

Two soybean components namely, storage proteins and isoflavone content in a wild and three cultivated soybean genotypes were characterized and compared. The storage proteins, β-conglycinin and glycinin were separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and two major storage proteins and their subunits were characterized using mass spectrometry. The three isoflavones, aglycon and the nine conjugated forms were separated by HPLC (high performance liquid chromatography) and identified by comparison of retention time, ultraviolet and mass spectral analyses. Comparison between the number of 2D-PAGE protein spots of the storage protein subunits and HPLC area of twelve isoflavones was also evaluated. The analysis of proteins and isoflavones from the wild genotype and the three cultivated genotypes suggested possible interactions between proteins and isoflavones. The same wild genotype, which showed significant statistical differences in β-conglycinin and glycinin protein profiles also revealed considerable reduction in total isoflavones (> 55%) content.

MJO Simulation Diagnostics

Abstract The Madden–Julian oscillation (MJO) interacts with and influences a wide range of weather and climate phenomena (e.g., monsoons, ENSO, tropical storms, midlatitude weather), and represents an important, and as yet unexploited, source of predictability at the subseasonal time scale. Despite the important role of the MJO in climate and weather systems, current global circulation models (GCMs) exhibit considerable shortcomings in representing this phenomenon. These shortcomings have been documented in a number of multimodel comparison studies over the last decade. However, diagnosis of model performance has been challenging, and model progress has been difficult to track, because of the lack of a coherent and standardized set of MJO diagnostics. One of the chief objectives of the U.S. Climate Variability and Predictability (CLIVAR) MJO Working Group is the development of observation-based diagnostics for objectively evaluating global model simulations of the MJO in a consistent framework. Motivation for this activity is reviewed, and the intent and justification for a set of diagnostics is provided, along with specification for their calculation, and illustrations of their application. The diagnostics range from relatively simple analyses of variance and correlation to more sophisticated space–time spectral and empirical orthogonal function analyses. These diagnostic techniques are used to detect MJO signals, to construct composite life cycles, to identify associations of MJO activity with the mean state, and to describe interannual variability of the MJO.

The significance of amlodipine on autonomic nervous system adjustment (ANSA method): A new approach in the treatment of hypertension

Cardiovascular autonomic modulation is altered in patients with essential hypertension. To evaluate acute and long-term effects of amlodipine on cardiovascular autonomic function and haemodynamic status in patients with mild essential hypertension. Ninety patients (43 male, mean age 52.12 +/- 10.7) years with mild hypertension were tested before, 30 minutes after the first 5 mg oral dose of amlodipine and three weeks after monotherapy with amlodipine. A comprehensive study protocol was done including finger blood pressure variability (BPV) and heart rate variability (HRV) beat-to-beat analysis with impedance cardiography, ECG with software short-term HRV and nonlinear analysis, 24-hour Holter ECG monitoring with QT and HRV analysis, 24-hour blood pressure (BP) monitoring with systolic and diastolic BPV analysis, cardiovascular autonomic reflex tests, cold pressure test, mental stress test. The patients were also divided into sympathetic and parasympathetic groups, depending on predominance in short time spectral analysis of sympathovagal balance according to low frequency and high frequency values. We confirmed a significant systolic and diastolic BP reduction, and a reduction of pulse pressure during day, night and early morning hours. The reduction of supraventricular and ventricular ectopic beats during the night was also achieved with therapy, but without statistical significance. The increment of sympathetic activity in early phase of amlodipine therapy was without statistical significance and persistence of sympathetic predominance after a few weeks of therapy detected based on the results of short-term spectral HRV analysis. All time domain parameters of long-term HRV analysis were decreased and low frequency amongst spectral parameters. Amlodipne reduced baroreflex sensitivity after three weeks of therapy, but increased it immediately after the administration of the first dose. The results of the study showed that amlodipine affected autonomic modulation as a shift to sympathetic hyperactivity, but without statistical significance. In the selected group of patients with vagal predominance in sympathovagal balance, amlodipine increased sympathetic and decreases vagal activity. Therefore we conclude that amlodipine mostly exerts impact on autonomic function modulation in patients with vagal predominance in resting state.

Forecast Skill of the Madden–Julian Oscillation in Two Canadian Atmospheric Models

Abstract The output of two global atmospheric models participating in the second phase of the Canadian Historical Forecasting Project (HFP2) is utilized to assess the forecast skill of the Madden–Julian oscillation (MJO). The two models are the third generation of the general circulation model (GCM3) of the Canadian Centre for Climate Modeling and Analysis (CCCma) and the Global Environmental Multiscale (GEM) model of Recherche en Prévision Numérique (RPN). Space–time spectral analysis of the daily precipitation in near-equilibrium integrations reveals that GEM has a better representation of the convectively coupled equatorial waves including the MJO, Kelvin, equatorial Rossby (ER), and mixed Rossby–gravity (MRG) waves. An objective of this study is to examine how the MJO forecast skill is influenced by the model’s ability in representing the convectively coupled equatorial waves. The observed MJO signal is measured by a bivariate index that is obtained by projecting the combined fields of the 15°S–15°N meridionally averaged precipitation rate and the zonal winds at 850 and 200 hPa onto the two leading empirical orthogonal function (EOF) structures as derived using the same meridionally averaged variables following a similar approach used recently by Wheeler and Hendon. The forecast MJO index, on the other hand, is calculated by projecting the forecast variables onto the same two EOFs. With the HFP2 hindcast output spanning 35 yr, for the first time the MJO forecast skill of dynamical models is assessed over such a long time period with a significant and robust result. The result shows that the GEM model produces a significantly better level of forecast skill for the MJO in the first 2 weeks. The difference is larger in Northern Hemisphere winter than in summer, when the correlation skill score drops below 0.50 at a lead time of 10 days for GEM whereas it is at 6 days for GCM3. At lead times longer than about 15 days, GCM3 performs slightly better. There are some features that are common for the two models. The forecast skill is better in winter than in summer. Forecasts initialized with a large amplitude for the MJO are found to be more skillful than those with a weak MJO signal in the initial conditions. The forecast skill is dependent on the phase of the MJO at the initial conditions. Forecasts initialized with an MJO that has an active convection in tropical Africa and the Indian Ocean sector have a better level of forecast skill than those initialized with a different phase of the MJO.

Heart Rate Variability in a Progressive Heart Failure Model with Rapid Ventricular Pacing

Heart rate variability (HRV) is an indicator of autonomic nervous system functionality and a recognized predictor of cardiac death; however, the changes in HRV occurring in progressive heart failure are not fully understood. The purpose of this study was to evaluate the progressive changes of autonomic system activity in progressive heart failure by rapid ventricular pacing in an animal model. Heart failure was induced in 13 mongrel dogs (27.8 +/- 3.7 kg) by rapid ventricular pacing (230 beats/min) for 4 weeks and maintenance of pacing at a reduced rate (190 beats/min) for 2 weeks. Time domain analysis and spectral analysis of HRV were performed with the MemCalc system after 30 minutes of pacing cessation every week. Hemodynamic and echocardiographic data were obtained before and after induction of heart failure. Cardiac output decreased significantly (3.6 L/min versus 1.6 L/min, P < .001) after 6 weeks of ventricular pacing. Significantly increased were the heart rate (126 beats/min versus 138 beats/min, P < .05), left ventricular end-diastolic pressure (9.1 mm Hg versus 30.9 mm Hg, P < .001), and pulmonary capillary wedge pressure (8.0 mm Hg versus 18.7 mm Hg, P < .001). High-frequency components progressively decreased. Low-frequency components progressively decreased except at 5 weeks after the pacing. A ratio of low- to high-frequency components increased in moderate heart failure and decreased in severe heart failure. Changes in the high-frequency component and low-frequency component are important for assessing heart failure in progressive heart failure. Serial follow-up measurements of HRV might be helpful for patients with such disease.

Some Space–Time Spectral Analyses of Tropical Convection and Planetary-Scale Waves

Abstract Three aspects of space–time spectral analysis are explored for diagnosis of the organization of tropical convection by the Madden–Julian oscillation (MJO) and other equatorial wave modes: 1) definition of the background spectrum upon which spectral peaks are assessed, 2) alternate variance preserving display of the spectra, and 3) the space–time coherence spectrum. Here the background spectrum at each zonal wavenumber is assumed to result from a red noise process. The associated decorrelation time for the red noise process for tropical convection is found to be half as long as for zonal wind, reflecting the different physical processes controlling each field. The significance of spectral peaks associated with equatorial wave modes for outgoing longwave radiation (OLR), which is a proxy for precipitating deep convection, and zonal winds that stand out above the red background spectrum is similar to that identified using a background spectrum resulting from ad hoc smoothing of the original spectrum. A variance-preserving display of the space–time power spectrum with a logarithmic frequency axis is useful for directly detecting Kelvin waves (periods 5–15 days for eastward zonal wavenumbers 1–5) and for highlighting their distinction from the MJO. The space–time coherence of OLR and zonal wind is predominantly associated with the MJO and other equatorial waves. The space–time coherence is independent of estimating the background spectrum and is quantifiable; thus, it is suggested as a useful metric for the MJO and other equatorial waves in observations and simulations. The space–time coherence is also used to quantify the association of Kelvin waves in the stratosphere with convective variability in the troposphere and for detection of barotropic Rossby–Haurwitz waves.

The Impacts of Convective Parameterization and Moisture Triggering on AGCM-Simulated Convectively Coupled Equatorial Waves

Abstract This study examines the impacts of convective parameterization and moisture convective trigger on convectively coupled equatorial waves simulated by the Seoul National University (SNU) atmospheric general circulation model (AGCM). Three different convection schemes are used, including the simplified Arakawa–Schubert (SAS) scheme, the Kuo (1974) scheme, and the moist convective adjustment (MCA) scheme, and a moisture convective trigger with variable strength is added to each scheme. The authors also conduct a “no convection” experiment with deep convection schemes turned off. Space–time spectral analysis is used to obtain the variance and phase speed of dominant convectively coupled equatorial waves, including the Madden–Julian oscillation (MJO), Kelvin, equatorial Rossby (ER), mixed Rossby–gravity (MRG), and eastward inertio-gravity (EIG) and westward inertio-gravity (WIG) waves. The results show that both convective parameterization and the moisture convective trigger have significant impacts on AGCM-simulated, convectively coupled equatorial waves. The MCA scheme generally produces larger variances of convectively coupled equatorial waves including the MJO, more coherent eastward propagation of the MJO, and a more prominent MJO spectral peak than the Kuo and SAS schemes. Increasing the strength of the moisture trigger significantly enhances the variances and slows down the phase speeds of all wave modes except the MJO, and usually improves the eastward propagation of the MJO for the Kuo and SAS schemes, but the effect for the MCA scheme is small. The no convection experiment always produces one of the best signals of convectively coupled equatorial waves and the MJO.

High Throughput VLSI Architecture for Blackman Windowing in Real Time Spectral Analysis

This paper presents a high throughput VLSI architecture for Blackman windowing. Since most of the implementation of windowing functions for real time applications, are based on either ROM or DSP processor. Here the proposed architecture is designed using major blocks like CORDIC(CO-ordinate Rotation DIgital Computer) and Han-Carlson adder. This architecture is flexible in terms of window length. So that a single chip can be used for those applications, where variable length is required. The synthesized result of 16-bit word size architecture with commercially available 0.18µm CMOS technology using Synopsys Design Analyzer, shows that the throughput of this architecture is 400Msamples/s with core area of 21mm2 .