Johnson System Research Articles

Dielectronic Recombination of Mgiiin Stellar Envelopes

The aim of the present paper is to discuss the significance, in the infrared continuum of Be stars, of the dielectronic recombination (DR) of Mg II atoms. To accomplish this, we have calculated the emissivity in the lines of Mg I atoms after the process of electron capture has taken place. In order to estimate its influence in the photospheric flux, we have considered the total energy emitted in all lines with λ1 ≤ λ ≤ λ2, where λ1 and λ2 define the wavelength ranges of the Johnson system filters. We conclude that the DR of Mg II atoms does actually contribute significantly to the infrared excess observed in Be stars.

A photometric and spectroscopic study of the brightest northern Cepheids -- I. Observations

We present simultaneous UBVuvby photometry for the 18 brightest northern Cepheids carried out between 1995 and 1997. Additionally, two fainter stars have been observed in the Johnson system only. The whole photometric data base contains about 3500 individual data points for 20 stars. The accuracy has been carefully tested with different methods. A serious systematic difference has been found between the present data set and the Stro¨mgren photometry available in the literature, which has probably been caused by the peculiar filter set used in the earlier study. As an extension to the photometry, we took high-resolution optical spectra at David Dunlap Observatory in the red spectral region (λ/Δλ≈ 40 000, in the interval of 6200 and 6600 Å including Hα). The spectroscopic programme contained 12 stars from the photometric programme, the newly discovered bright classical Cepheid CK Cam and two double-mode Cepheids (TU Cas and CO Aur). New radial velocities obtained with the cross-correlation technique are presented. We found significant velocity differences between two cross-correlated spectral regions (6188–6220 and 6405–6435 Å) as large as 0.8–1.2 km s−1, which show very characteristic phase dependence in certain Cepheids. Finally, recent period variations are briefly discussed in terms of phase jumps and duplicity.

Transforming Non-Normal Data to Normality in Statistical Process Control

Quality characteristics analyzed in statistical process control (SPC) often are required to be normally distributed. This is true in many types of control charts and acceptance sampling plans, as well as in process capability studies. If a characteristic is not normally distributed, but normal-based techniques are used, serious errors can result. One approach to solving this problem is to transform the non-normal data to normality using the Johnson system of distributions. In this paper, we use the sample quantile ratio, in conjunction with the Shapiro-Wilk test of normality, to find a suitable transformation for non-normal data. Examples of fitting non-normal SPC data are presented and discussed. The effect of the Johnson transformation on an SPC procedure involving an estimator for the population standard deviation is studied using non-normal data and Johnson-transformed data.

UBV photometry of Be stars at Hvar: 1972–1990

A summary of results of the systematic UBV photoelectric monitoring of bright northern Be stars carried out at the Hvar Observatory betwen 1972 and 1990 is presented. Altogether, 76 Be stars of all luminosity classes were observed and 13848 UBV measurements secured. Simultaneously, 9648 UBV measurements of 48 check stars (most of them of early spectral types) were obtained. A careful transformation of all observations into the standard Johnson system allowed detection and monitoring of even very mild long-term light and colour variations of these objects. Almost all early-type Be stars in the sample turned out to be variable. For several stars phase-locked light variations related to their binary nature were establihsed. Sudden brightenings, on a time scale of a days, were detected for o Cas and QR Vul.

Comparison and evaluation of five methods of estimation of the Johnson system parameters

The Johnson system of distributions was used to fit both diameter and height data collected from 226 sample plots located in the ponderosa pine (Pinusponderosa P. Laws, ex C. Laws.) and mixed-conifer forest types in New Mexico and Arizona. To estimate the Johnson system parameters, five methods (namely the four-percentile method, Knoebel–Burkhart method, mode method, maximum likelihood estimation method, and a new method developed in the study, linear regression method) were compared and evaluated. For these sample plots, the linear regression method was superior for estimating parameters of SB distributions for both diameter and height.

On weighting the studentized empirical characteristic function for testing normality

The aim in this paper is to propose a test of the composite hypothesis of ρ-variate normality. The test is based on the weighted integral of the squared modulus of the studentized empirical characteristic function. In the present weighting method, it is easy to investigate the asymptotic performance of the proposed test through its asymptotic normality. The performances of the proposed test through Monte Carlo experiments are also discussed. Especially the estimated power of the test against the Johnson system of distributions are illustrated by plots of isodynes.

Temperature variations of one well-known UV ceti type flare star

Temperature variations of the flare star, EV Lac, at its quiet-state luminosity were computed from its colour indices,B - V, which were measured in Johnson's system, these daily temperature changes are the essential reason of the short-term behaviour appearance in the flare star which is due to the presence of active region(s) causing a temperature difference of a few hundred degrees from the photosphere. A correlation between the annual mean of temperature variations of the flare star at its quiet-state and the annual rate of some physical parameters of the flare star at its active-state was detected. This correlation can interpret the occurrence of the long-term behaviour of the flare star at its quiescent-state as found by Mavridiset al. (1982).

Photometric survey near the Main Galactic Meridian: 1. Photoelectric stellar magnitudes and colours in the UBVR system

AbstractA catalogue of photoelectric stellar magnitudes and colours in the UBVR Johnson system in 47 sky areas with galaxies near the Main Galactic Meridian is presented. The catalogue includes 1141 stars within the V magnitude interval 4m.5–15m.5. The rms errors are ±0.014, ±0.026, ±0.012, ±0.016 mag for stellar magnitudes V and colours (U – B),(B – V),(V – R), respectively. The catalogue contains accurate equatorial coordinates (α, δ)1950.0, too.

Non‐normality in Statistical Process Control Measurements

Control charts and process capability calculations remain fundamental techniques for statistical process control. However, it has long been realized that the accuracy of these calculations can be significantly affected when sampling from a non‐Gaussian population. Many quality practitioners are conscious of these problems but are not aware of the effects such problems might have on the integrity of their results. Considers non‐normality with respect to the use of traditional control charts and process capability calculations, so that users may be aware of the errors that are involved when sampling from a non‐Gaussian population. Use is made of the Johnson system of distributions as a simulation technique to investigate the effects of non‐normality of control charts and process control calculations. An alternative technique is suggested for process capability calculations which alleviates the problems of non‐normality while retaining computational efficiency.

Spectrophotometric evolution of elliptical galaxies. 1: Ultraviolet excess and color-magnitude-redshift relations

Spectrophotometric evolution of elliptical galaxies. 1: Ultraviolet excess and color-magnitude-redshift relations

Investigation of the kinematics and structure of the Galaxy in the vicinity of the North galactic pole

AbstractIn the framework of the programme of studying the meridional section of the Galaxy (MEGA) the absolute proper motions of more than 11000 stars with respect to 3000 galaxies and their stellar magnitudes in the B, V Johnson system are determined in two sky regions near the North Galactic Pole (NGP) by means of Tautenburg Schmidt plates. The limiting and completing apparent stellar magnitudes are B = 20.4 and 18.3 mag, the overall and the investigated sky areas are 16.4 and 14.6 square degrees, respectively. Distances have been determined using the stellar magnitudes, colours, proper motions and reduced proper motions. Stellar kinematics, eccentricities of Galactic orbits, spatial distribution and changes of these characteristics with Z‐distance from the Galactic plane are obtained up to 15 kpc. Four subsystems distinguished in the NGP direction, respectively with semithicknesses of 0.25, 0.38, 0.67, 1.48 kpc and density ellipsoid axial ratios of 0.09, 0.20, 0.28, 0.49 show mean velocities in the Galactic rotation direction relative to the LSR of 5.6 ± 0.6, − 11.0 ± 0.6, − 62.5 ± 1.2, − 181.6 ± 4.4 km/s, and ages of 0.1, 0.4, 0.9, 1 of the Galaxy age.

On using percentiles to fit data by a johnson distribution

The well-known Johnson system of distributions was developed by N. L. Johnson (1949). Slifker and Shapiro (1980) presented a criterion for choosing a member from the three distributional classes (SB,SL, and Sv) in the Johnson system to fit a set of data. The criterion is based on the value of a quantile ratio which depends on a specified positive z value and the parameters of the distribution. In this paper, we present some properties of the quantile ratio for various distributions and for some selected z values. Some comments are made on using the criterion for selecting a Johnson distribution to fit empirical data.

In vitro and in vivo studies of pressurization of femoral cement in total hip arthroplasty

Improvements in cementing techniques in the absence of pressurization of the cement have led to major increases in the long-term success rate of fixation of the femoral components of cemented total hip arthroplasty (THA). The strength of the cement-bone interface is strongly related to cement intrusion into the bone. The depth of cement intrusion, in turn, is correlated with the cement-intrusion pressure. Thus, adding cement pressurization to those current techniques that have already been validated may further increase the long-term durability of fixation of the femoral component of cemented THA. To assess cement pressurization in the proximal femur for THA, the authors compared in vitro the efficacy of three existing pressurization systems (the Johnson and Johnson system [New Brunswick, NJ], the Miller system [Zimmer, Warsaw, IN], and the Zimmer system [Zimmer]) in cadaver femurs using pressure transducers and evaluated their ease and optimization for clinical use. The authors then selected one (the Zimmer system) for use in studies in vivo to quantify the actual pressures achieved in the medullary canal in vivo under surgical conditions using pressure transducers placed throughout the femoral cortex. Each of the three commercially available femoral cement pressurization systems has its own advantages and disadvantages. All three systems were shown to produce average peak cement-intrusion pressures in vitro of over 21 N/cm 2 (30 psi) throughout the cement mantle including, importantly, in the proximal portion of the femur. Under laboratory conditions all three systems produced adequate pressurization for optimal cement penetration into cancellous bone. Because the repeated application of pressure is more valuable than the single thrust provided by the Johnson and Johnson cement compactor, the Miller and Zimmer systems seemed preferable. Because the Miller system does not pressurize the most proximal portion of the canal (the volume occupied by the silicone conical seal) and because the proximal portion of the cement mantle is important to longterm fixation of the femoral component, the Zimmer system was selected for the in vivo study. The cement-intrusion pressures in the proximal portion of the femurs obtained in vivo in the operating room during the 10 primary and 5 revision THAs had a mean value from all 15 patients of 19 ± 8 N/cm 2 (27 ± 11 psi). The primary cases had a significantly higher intrusion pressure (22 ± 7 N/cm 2 [32 ± 10 psi]) than the revision cases (13 ± 6 N/cm 2 [19 ± 9 psi]). In a prior study from the authors' laboratory using bovine cancellous bone, which is more dense than human cancellous bone, cement pressures of 14 N/cm 2 (20 psi) were shown to produce a cement-intrusion depth of 5 mm. An intrusion depth of 3–4 mm has been shown to be optimal for the strength of the cement-bone interface. Therefore, 10 N/cm 2 (15 psi) is likely to be adequate to achieve optimal cement-intrusion depth in humans. The results of this study show that a pressure of 10 N/cm 2 (15 psi) was obtained in 9 of 10 primary cases and 3 of 5 revision cases.

Spectrophotometry of 83 possible blue compact dwarf galaxies from the second byurakan survey

Spectrophotometric observations of 83 possible blue compact dwarf galaxies (BCDGs) and photoelectric UBVR (Johnson system) observations of 37 galaxies from this list are discussed. The observations have been made with the 6-meter telescope of Special Astrophysical Observatory of Russian Academy of Sciences. The general characteristics of BCDGs are considered. Most galaxies are shown to have very low heavy element abundance.

An Adjustment to Cepheid Distances Calculated Using Model Atmospheres

Hindsley and Bell (1989, Ap. J., 341, 1004) determined distances for 23 Cepheids using the surface brightness method. The color V – IC on the Cousins system or V – RJ on the Johnson system was used to measure visual surface brightness. Combined with the observed visual magnitudes, angular diameters were then calculated. Comparison of angular diameters with radius differences in linear units, obtained by integrating the radial velocity curve, yielded each Cepheid's distance.Hindsley and Bell calibrated the relationship between color and surface brightness using model atmospheres. The zero point of the relationship was found using observations of Vega and an appropriate model. More recently the spectral scans of Gunn and Strycker (1983, Ap. J. Suppl., 52, 121) and the Cousins filter response curves of Hindsley and Bell were used to calculate colors and these were compared to the corresponding observed colors.

Photoelectric observations of cepheids. III

Abstract 1270 UBVR observations in the Johnson system for 56 Cepheids obtained in the 1986 season are presented.

Photoelectric observations of cepheids. V

2983 UBVR observations on the Johnson system for 104 Cepheids obtained in the 1988 season are presented.

Photoelectric observations of cepheids. VII

Abstract 1017 UBVR observations on the Johnson system for 56 Cepheids obtained in the 1990 season are presented.

Photoelectric observations of cepheids. IV

353 UBVR observations in the Johnson system for 40 Cepheids obtained in the 1987 season are presented.

Photoelectric observations of cepheids. VI

Abstract 2582 UBVR observations on the Johnson system for 67 Cepheids obtained in the 1989 season are presented.