Amplitude Probability Density Distribution Research Articles

Design and performance of multi-channel switched sequential amplifiers

This paper presents switched sequential amplifiers (SSAs) using reconfigurable directional couplers as power splitters and combiners. The SSA concept allows matching the efficiency characteristics to the amplitude probability density distribution of the applied modulated signal. Therefore the back-off efficiency can be increased significantly. A three-channel SSA can e.g. theoretically achieve a −10 dB back-off efficiency exceeding 50%. Design parameters and potential efficiency enhancement are discussed for two- and three-channel SSAs. After a brief introduction of the used switched couplers, the circuit concept for two- and three-channel SSAs is described. Calculations for the possible efficiency enhancement are presented. Also signal distortions by the directional couplers are outlined. The paper closes with experimental results for a two-channel SSA.

ニューラルネットの学習による健常例，迷路・中枢障害例の重心動揺の識別

The present paper investigated methods of discriminating stabilograms of healthy subjects from those of patients with labyrinthine and central disorders using a neural network (NN).Stabilometry was performed with eyes open and closed with both feet close together for 60 seconds using a stabilometer. From the stabilograms, area, locus length, deviations of the sway, Romberg ratio, power spectrum, position and velocity vectors, and amplitude probability density distribution were measured. Stabilograms were evaluated using a NN program produced by Anima corporation. Data file for learning was composed of healthy subjects and patients with various labyrinthine and central disorders. Data file for evaluation was composed of patients diagnosed with labyrinthine disorders.As a result of learning, stabilograms of healthy subjects and patients of labyrinthine and central disorders were clearly discriminated. The square error was 0.005. In evaluations using a NN weighted by learnig, the square error was 0.326.In medical examinations of patients with vertigo and equilibrium disturbances, discrimination of stabilograms is important for diagnosis of sites of lesion and classification of types and stages of disease. Learning and evaluation using a neural network are expected as a useful method for discriminating stabilograms. However, errors in evaluation (i.e. generalization error) remain high value. In the future, reducing generalization errors is a key issue.

パーキンソン病の重心動揺 測定値と因子分析について

This study investigated the characteristics of postural sway in cases of Parkinson' s disease (PK). We examined 16 patients diagnosed with PK, of whom 2 were classified as positive symptoms (PK-P), while 6 (PK-Na) and 8 (PK-Nb) were found to exhibit negative symptoms. The subjects stood on a stabilometer with their eyes open or closed with both foot closed together, and the sway of the center of gravity of the body was recorded for one minute. This paper presents 20 measurements of stabilometry in PK, comparing the mean ±2 SD classified by gender and age of healthy subjects, mean ±1 SD, and with observation of factor analysis.1) There were only a few cases demonstrating data exceeded the mean ±2 SD, considering each parameter. All cases of PK-Na and 6 of 8 PK-Nb cases exceeded the mean ±2 SD, considering every parameter.2) Four of 8 PK-Nb cases exceeded the mean ± 1 SD, for area, locus length, Romberg's coefficient, vector of velocity in the forward-backward and right-left and standard deviation of amplitude probability density distribution in X- and Y- axes considering each parameter. The proportion of patients exceeding the mean was higher in PK-Nb than in PK-Na.3) Factor 1 showed centripetal and forward-backward sway type with high factor loading as to locus length, high frequency band in X and Y, vector of velocity in the forward-backward and kurtosis of amplitude probability density distribution in Y. Factor 2 showed right-left and diffuse sway type with high factor loading as to area, vector of velocity in the right-left and standard deviation of amplitude probability density distribution in X and Y. Factor 3 showed displacement and multiple center type with high factor loading as to deviation of the center of sway in X and skewness of amplitude probability density distribution in X and Y.

パーキンソン病の重心動揺 ニューラルネットによる症状群の識別の試み

This study investigated the characteristics of postural sway in cases of Parkinson's disease (PK). We previously reported sway patterns, its measurements, and factor analysis. This paper investigates learning and evaluation by neural networks.Each subject stood on a stabilometer with their eyes open or closed, and the sway of the center of gravity was recorded for one minute. The learning and evaluation was performed using a neural network program developed by Anima corporation. Input data were 6 units (measurements values related to area and length) in analysis A and 20 units (measurements values related to area and length, power spectrum, vector of velocity, amplitude probability density distribution curve) in analysis B. Output consisted of 3 units (positive, negative a, and negative b symptoms) in both analyses. There were 16 subjects, of whom 13 were used for learning and 3 for evaluation. Learning was carried out until the number of learning trials reached 10000, or the square error margin decreased to 0.005.Results1) In analysis A, learning revealed a square error margin of 0.005 after 690 trials, while the evaluations revealed a square error margin of 0.263.2) In analysis B, learning revealed a square error margin of 0.005 after 215 trials, while the evaluations revealed a square error margin of 0.267.Three symptoms were classified clearly as results of learning in analysis A and B. The number of learning trials in analysis B was less than that in analysis A, indicating that increased input resulted in fewer learning trials. The square error margin for evaluation was not good in either analysis.

Acoustical measurement of the intuitive understanding effect in lecture education

Lecture is one of the most fundamental and traditional education methods. Especially in the initial education of freshmen in university engineering courses, its role becomes more important. A learner's understanding in lecture differs from an essential understanding mastered systematically by self-consciousness. It is defined as intuitive understanding. It becomes a motivation for the essential understanding and correlates strongly with their attitudes in lecture. Their whispering in lecture is caused by lack of attention or concentration. It is considered that their whispering correlates strongly with the intuitive understanding. This paper describes trial measurements to acquire knowledge about the state and situation of learners' intuitive understanding by measuring the hum of their whispering in crowded lectures. The hum was represented as an amplitude probability density distribution (APDD) of the time series acoustical signal recorded by a microphone and its time transition. We presumed a state of their whispering from the forms of the APDDs and a situation from the time transition of the maximum peak values of the differential distributions (DD) of the APDDs. The maximum peak values of the DDs of the APDDs are inversely proportional to the loudness of their whispering. Comparing these data with the learners' self-estimation for each lecture contents, it was confirmed that the less learners could obtain an intuitive understanding of a lecture content, the more noisy their whispering became with progression of the lecture. From these results, we confirmed that it is possible to acquire the situation of their intuitive understanding by using their whispering. One direction for estimation of lecture education was shown by the objective measurement of learners' intuitive understanding.

Estimation of the maximum instantaneous distortion

IN this synoptic, a new statistical method of estimating the maximum instantaneous inlet pressure distortion is described. By this method, the time average and root-meansquare (rms) values of the instantaneous pressure distortion index Ke, Krad, and KA2 can be obtained analytically from the measured inlet total steady-state pressure and rms values. The most probable maximum instantaneous distortion index that occurs in a given duration can also be obtained. Comparison between the estimated values and the experimental results shows that the described method can estimate accurately the maximum instantaneous distortion index with 3 s on an Intel 86/330 microcomputer. Contents In the evaluation of inlet and engine compatibility of a new aircraft, the maximum instantaneous pressure distortions of the intake are usually estimated in the earlier stages of the development to forecast whether they are greater than the allowable values of the engine. There are three well-known statistical estimating methods discussed in Ref. 1. In this paper, the time average and rms values of the instantaneous distortion index K6, Krad, and KA2 are obtained analytically from inlet total steady-state pressure and rms measurements beforehand. By assuming that the amplitude probability density distribution of the distortion index is Gaussian, the most probable probability with which the maximum instantaneous distortion value occurs in a given duration and the maximum instantaneous distortion itself are found. This method is of practical value if the distortion pattern that pertained to the maximum instantaneous distortion is not indispensable as in the preliminary design stage of the intake. The distortion index K can usually be expressed as

Planetary Wave Amplitude Bimodality in the Southern Hemisphere

A preliminary study of the probability density distribution of the wavenumber 3 amplitude in midlatitudes of the Southern Hemisphere is undertaken with 4.25 years of 500 mb height data compiled by the European Centre for Medium-Range Weather Forecasts. The wavenumber 3 amplitude probability density appears to be bimodal during winter. Analogous results during the Southern Hemisphere summer reveal a unimodal wavenumber 3 amplitude probability density distribution with the single summer mode corresponding in value to the winter low amplitude mode. The physical implications of the winter bimodality are examined to gain confidence in the result. Partitioning the data based on the two modes leads to a consistent picture of the large amplitude events in physical space. Synoptically, the large amplitude mode corresponds to “amplified waves” of broad extent. It is suggested that the SH winter time-mean eddies for wavenumbers greater than one are the statistical residue of the intermittent large-amplitude events. Individual Southern Hemisphere large amplitude events exhibit grid point height departures from zonal symmetry comparable to their Northern Hemisphere counterparts. In addition, the summer mean eddy field is very similar to the winter low amplitude mode's mean eddy field. Examination of the time series of the wave 3 amplitude and phase during winter reveals that the more persistent of the individual large amplitude events exhibit relatively stationary phase lines, although different large amplitude events may have different phases. A remarkable feature of these time series is that certain of the more persistent events exhibit a sudden phase shift while the amplitude remains large with the phase being steady both before and after the shift.

Further Observational Characteristics of Bimodal Planetary Waves: Mean Structure and Transitions

Further results concerning the mean gates of the bimodal wavnumber 2 to 4 amplitude probability density distribution are presented followed by composites of transitions from one side of this distribution to the other. The data used are ECMWF analyses from the four winters from 1980/81 to 1983/84. Cross sections of the mean states associated with the two modes reveal that both modes exhibit a baroclinic vertical structure, but that the difference between the two is more nearly equivalent barotropic. The composite transitions between the low-amplitude and high-amplitude states indicate that the transition time for the onset or decay of the large amplitude waves is about 4 days. The kinetic energy and available potential energy of wavenumbers 2 to 4 increases (or decreases) by 50 percent in this same time interval during the onset (or decay) of the large amplitude state. Nonlinear interaction with intermediate-scale waves is the only apparent source for the observed kinetic energy tendency during the transition from the low amplitude to the high amplitude mode. Thus, the growth of the 1arge amplitude events does not strictly resemble that of a classical baroclinic instability. During the decay of the large amplitude waves, nonlinear interaction between the wavenumber 2 to 4 ensemble and wavenumber 1 accounts for the decline in kinetic energy, while nonlinear interaction between wavenumbers 2 to 4 and smaller-scale waves accounts for the decline in available potential energy. Examples of individual cases are presented to corroborate the composite results. Finally, a case study of the synoptic evolution of a large-amplitude event is presented to illustrate the event's life cycle.

Visual control in the upright standing position

The role of static and kinetic visual information in the regulation of the upright standing position was studied in 7 healthy subjects.The subject stood on a stabilometer with the feet close together and gazed at the visual pattern (11 vertical stripes drawn at intervals of 4 cm). The postural sway under normal illumination, stroboscopic illumination at a frequency of 10 Hz, 5 Hz, and 1.4 Hz, and in darkness was recorded for 30 seconds with an X-Y recorder and stored in the disk of a microcomputer. On the basis of the stored data, concerning the area, unit locus length, forward-backward and right-left diameters, standard deviation, skewness and kurtosis of amplitude, the probability density distribution and power spectrum were calculated by a specially designed program.1. The size of body sway under stroboscopic illumination at a frequency of 1.4 Hz was larger than in the dark. Examinations related to sway-area, for-ward-backward and right-left diameters, and standard deviation of amplitude probability density distribution showed similar results.2. Kurtosis tended to be small under stroboscopic illumination at a frequency of 1.4 Hz.3. The rate of low frequency (0.033-0.195 Hz) in the power spectra of body sway under stroboscopic illumination at a frequency of 1.4 Hz was larger than in the dark.Static visual information without kinetic visual information caused destabilization of posture regulation. Kinetic visual information plays a major role in visual control in the upright standing position, especially in the control of body sway at low frequency.

重心動揺検査の検討 検査条件について

In 1983, the board of the Japan Society for Equilibrium Research presented a standard of stabilometry, but some problems remain.In order to determine the test conditions, we performed the following examination with a standard stabilometer.1 . For visual target testing, the distance from the subject to the target and the illumination of the peripheral visual field were studied.2. For the standing posture, body sway in the military standing posture was compared with that in natural standing.3. For foot position, body sway while standing with both feet together was compared with that feet in the fan-shaped position and with feet apart but parallel.4. For recording time, body sway while standing for 30 seconds was compared with that while standing for 60 seconds.5. To elimilinate transitional sway after standing erect with eyes closed, the time when the recording should start was studied.The parameters for stabilometry are as follows ; unit locus lengh, forward-backward and right-left diameters, area, rejection ellipse, center of sway, standard deviation, skewness and kurtosis of amplitude probability density distribution, velocity, vector of velocity, power spectrum.1. When the visual target was placed one meter from the subject and the peripheral field of vision was lighted, the mean and standard deviation of all parameters in stabilometry were the smallest.2. Standard deviations of the unit locus length, area and velocity during military posture standing were lower than during natural standing. However, maintenance of military standing for 60 seconds was difficult. Therefore, stabilometry with natural standing was considered more suitable for clinical examinations.3. Body sway while standing with feet 10 cm apart was less than when standing with the feet close together or in the fan-shaped position. However, standing with the feet close together was suitable for detecting slight equilibrium disturbances.4. Body sway observation for 60 seconds clarified the pattern of the body sway more definitely than did observation for 30 seconds.5.Irregular sway was recorded after the subject stood erect with eyes closed for 10 seconds. To eliminate transitional sway, the recording should be started when the body movements of the standing subject are stabilized.

Stabilometry in paitents with equilibrium disturbances

Body sway in the upright standing posture of patients with equilibrium disturbances was examined by stabilometry. Routine and precision tests recommended by the Board of the Japan Society for Equilibrium Research were performed.I. Routine test resultsBody sway while standing was investigated in 88 patients by routine tests, which included forwardbackward diameter, left-right diameter, Romberg rado and pattern of sway.The 88 patients were classified into 5 groups: (1) 10 with bilateral loss of labyrinthine excitability; (2) 57 with unilateral loss of labyrinthine excitability; (3) 17 with cerebellar disturbances; (4) 3 with spinal disorders; (5) 1 with peripheral neuropathy.1. In Group 1, forward-backward diameter, leftright diameter and/or Romberg ratio of sway was increased. The sway pattern was of the diffuse type in most.2. In 29 patients in Group 2, forward-backward diameter, left-right diameter and/or Romberg ratio was increased, and left-right sway was observed.3. Sixteen patients in Group 3 had a diffuse large sway pattern.4. Group 4 patients had a large sway, forwardbackward or diffuse.IT. Precision test resultsSix patients with abnormal sway patterns that were specific for a given localization of the disease were examined by the precision test which included unit locus length, forward-backward and left-right diameter, area, ellipse, center of the sway, velocity, standard deviation, skewness and kurtosis of amplitude probability density distribution, vector of velocity and power spectrum.The diagnoses were bilateral loss of labyrinthine function of unknown origin, right sudden deafness with unilateral loss of labyrinthine excitability, arterio-venous malformation of the cerebellum, infarction of a cerebellar hemisphere, caisson disease and Charcot-Marie-Tooth disease.1. In the patient with bilateral loss of labyrinthine function, the sway of the center of gravity showed a large forward/backward sway with a regular periodicity of about 0.6 Hz.2. Body sway of the patient with sudden deaf-ness showed a large left-right sway with 0.08-0.2 Hz.3. Body sway of the patient with arterio-venous malformation showed a large and diffuse sway with a regular periodicity of about 0.7 Hz.4. Body sway of the patient with cerebellar infarction indicated a slight increase of the area and velocity of the sway.5. In caisson disease, the unit locus length, diameter and velocity of the forward-backward sway was markedly increased.6. In Charcot-Marie-Tooth disease, the area of the sway and the velocity of the forward-backward sway was increased.

The Probability Density Distribution of the Speed and Horizontal and Vertical Shear of the Zonal-Mean Flow

The probability density distribution of the speed, horizontal shear and vertical shear of the zonal-mean wind are computed from a 16-winter NMC dataset in a study designed to complement an earlier study of the planetary-scale wave amplitude probability density distribution. The speed of the zonal wind is found to have a probability density distribution that is unimodal both within the zone of the largest planetary wave amplitude (45°–70°N) and when averaged over the entire midlatitudes (25°–75°N). Unimodal distributions are also found for both the north–south shear of the zonal mean wind and the vertical shear of the zonal mean flow between 300 and 850 mb. Lagged correlations between the zonal mean wind parameters and the wavenumber 2–4 amplitude are computed and found to be small at all lags. This suggests that the temporal variability of the planetary waves in the midlatitudes of the troposphere is not directly connected to the variability in the strength or shear of the zonal mean flow.

重心動揺検査の検討 コンピュータ分析における検査項目と正常域

In 1983 the board of the Japan Society for Equilibrium Research presented a standard of stabilometry including both routine and precision tests. The precision test consists of measurments and analyses conducted automatically with the use of a computer. However, the items of the precision test are not specified. The purpose of this study is to describe the items of the precision test and to determine the normal range of each item in healthy adults.The subject was requested to stand on a stabilometer with the feet close together. The sway of the body center of gravity was recorded for 60 seconds with an X-Y recorder and stored in a microcomputer with a sampling rate at 20 Hz. Each examination was performed with eyes open and eyes closed. From the stored data, unit locus length, forward-backward and right-left diameters, area, standard deviation, skewness and kurtosis of amplitude probability density distribution, velocity, center of the sway and power were calculated with a program designed for this experiment.Ninety one healthy subjects aged 15 to 82 years were examined.1 . Unit locus length, F-B and R-L diameters and sway-area were required for evaluation of the size of the sway.2. Skewness, kurtosis, and the ratio of F-B to R-L diameter were indispensable to determine the pattern of the sway.3. The center of the sway was useful for evaluation of the shift of the body center of gravity in the upright standing posture.4. Vector analysis of velocity was necessary as a parameter of the characteristics of the sway and to determine the direction of the sway.5. Power spectrum was essential to observe the amplitude in connection with the frequency of the sway.6. In subjects over 50-years of age, the values of each item increased with age. Therefore, the values obtained in subjects aged 20 to 49 are presented as a standard for stabilometry in healthy adults.

The evaluation of the response of single-valued non-linearities to several inputs

The transform method for evaluating the coefficients of the various terms in the output autocorrelation function of a non-linearity with an input consisting of a sinusoidal signal and Gaussian noise is considered. Solutions, all of which involve confluent hypergeometric functions, are given for a few analytically defined non-linear characteristics. A short table of these functions is also given to facilitate computation. A new expression for evaluating the coefficients, a double integral involving the non-linear characteristic and the moments of the sinusoidal and Gaussian input signals, is derived. A graphical method of solution applicable to any single-valued non-linearity is given, and a comparison made, with experimental and theoretical results. Extension of the technique to several uncorrelated input signals of any known amplitude probability density distribution is shown to be possible.