Showing papers by "Brigham Young University published in 1986"

A variable step (VS) adaptive filter algorithm

Abstract: In recent work, a new version of an LMS algorithm has been developed which implements a variable feedback constant μ for each weight of an adaptive transversal filter. This technique has been called the VS (variable step) algorithm and is an extension of earlier ideas in stochastic approximation for varying the step size in the method of steepest descents. The method may be implemented in hardware with only modest increases in complexity ( \approx 15 percent) over the LMS Widrow-Hoff algorithm. It is shown that an upper bound for the convergence time is the classical mean-square-error time constant, and examples are given to demonstrate that for broad signal classes (both narrow-band and broad-band) the convergence time is reduced by a factor of up to 50 in noise canceller applications for the proper selection of variable step parameters. Finally, the VS algorithm is applied to an IIR filter and simulations are presented for applications of the VS FIR and IIR adaptive filters.

The Dimensions of Religiosity: A Conceptual Model with an Empirical Test

Abstract: This paper develops and tests a conceptual model of religiosity. Particular attention is given to measuring the dimensions of religiosity among Mormons, but the model is adaptable to the study of religiosity within other denominations and groups. Six dimensions are theoretically derived by a cross-classification of three general components: religious belief, commitment, and behavior; and two modes of religiosity: personal and institutional. An empirical test of the model is reported using data collected from a large sample of Mormons.

Body size, ecological dominance and Cope's rule

Abstract: We present data and analyses demonstrating that large species utilize a disproportionately large share of the resources within local ecosystems. Even though small species tend to have higher local population densities, these are not sufficient to compensate for their lower rates of energy use per individual. The relationship is very general; holding for example for birds, mammals, fish and plants. We suggest that several ecological advantages enable larger species and larger individuals within species to monopolize resources, and that the resulting selection pressures are responsible for the evolutionary trend towards increasing body size seen in many phyletic lineages. Our results contradict important studies1–4 that have concluded that species of small body size use at least as large a proportion of the resources within ecosystems as their larger relatives.

Test of a Bonding/Association Theory of Adolescent Drug Use

Abstract: A theoretical model of adolescent drug use is developed which integrates propositions derived from social control and differential association theories. The path model includes parental attachment, religious attachment, educational attachment, conventional values, and drug-using friends as precursors of drug use. For a sample of 2,626 adolescents from the southwestern United States, the model explains 34 percent of the variation in self-reported lifetime alcohol use, 27 percent in lifetime cigarette use, 42 percent in lifetime marijuana use, 26 percent in lifetime use of amphetamines and depressants, and 50 percent in overall lifetime drug use. The best single predictor of drug use is association with drug-using friends. The processes leading to involvement with drugs appear to be very similar across drug types. Adolescent drug use is widespread in America. Numerous recent authors suggest that involvement in such behavior has become a national concern, whether the substance is tobacco (Grunberg and Baum 1984; Humble et al. 1985; Lichtenstein 1982), alcohol (Barnes 1984; Pandina et al. 1984; Wechsler et al. 1984), marijuana (Hendin et al. 1981; Smith et al. 1982; Smith 1984), or other drugs (McDermott 1984; Marcos and Bahr 1985; Weidman 1983). Macdonald (1984) refers to adolescent drug use as a national disaster because of the high proportion of adolescents who use drugs and the negative consequences associated with use. By the time they are seniors in high school, over 90 percent of American adolescents have tried alcohol *Paper presented at the 1985 meeting of the Pacific Sociological Association. We acknowledge the cooperation of the schools that participated in this project, particularly the students who completed the questionnaires. We are grateful to Grant Rose and Tom Martin for computer assistance, to two anonymous referees for their suggestions, and to Norene Petersen and Brenda Johnson for clerical assistance. Address correspondence to Anastasios C. Marcos, Department of Sociology, 800 SWKT, Brigham Young University, Provo, UT 84602.

International cometary explorer encounter with giacobini-zinner: magnetic field observations.

Abstract: The vector helium magnetometer on the International Cometary Explorer observed the magnetic fields induced by the interaction of comet Giacobini-Zinner with the solar wind. A magnetic tail was penetrated about 7800 kilometers downstream from the comet and was found to be 10,000 kilometers wide. It consisted of two lobes, containing oppositely directed fields with strengths up to 60 nanoteslas, separated by a plasma sheet about 1000 kilometers thick containing a thin current sheet. The magnetotail was enclosed in an extended ionosheath characterized by intense hydromagnetic turbulence and interplanetary fields draped around the comet. A distant bow wave, which may or may not have been a bow shock, was observed at both edges of the ionoshpeath. Weak turbulence was observed well upstream of the bow wave.

MIKE: the menu interaction kontrol environment

Abstract: A User Interface Management System (UIMS) called MIKE that does not use the syntactic specifications found in most UIMSs is described. Instead, MIKE provides a default syntax that is automatically generated from the definition of the semantic commands that the interaction is to support. The default syntax is refined using an interface editor that allows modification of the presentation of the interface. It is shown how active pictures can be created by adding action expressions to the viewports of MIKE's windowing system. The implications of MIKE's command-based dialogue description are discussed in terms of extensible interfaces, device and dialogue-style independence, and system support functions.

Religion, Family, and Adolescent Drug Use:

Abstract: Using a national sample of over 17,000 high school seniors, we examined the effect of education of parents, employment status of mother, number of parents in household, religiosity, religious affiliation, gender, and race on alcohol and marijuana use. Contrary to some previous research, neither parental education nor employment status of mother was related to use of alcohol or marijuana. Adolescents who lived with both parents were less likely than adolescents in single-parent homes to use marijuana, although the differences were relatively small. Number of parents in household was not related to adolescent alcohol use. Level of religiosity had a significant association with alcohol and marijuana use among all religious denominations, although the magnitude of the relationship varied by denomination. Religious denomination, gender, and race were also related to drug use.

Comparison of three curve intersection algorithms

Abstract: This paper treats the problem of how one can best compute the points of intersection of two planar rational curves. Three different algorithms are compared: the well known Bezier subdivision algorithm, a subdivision algorithm based on interval arithmetic, and the implicitization approach. Implementation considerations are discussed, with particular focus on how to make the implicitization method robust and fast. Report is made on a test in which the algorithms solved hundreds of randomly generated problems to eight digits of accuracy. The implicitization algorithm was faster than the others by a factor of five for degree two curves; by a factor of four for cubic curves; by a factor of three for quartic curves; and the interval method was faster for quintic curves by a factor of two.

Macrocycle-Facilitated Transport of Ions in Liquid Membrane Systems

Abstract: Ion transport in various liquid membrane systems is discussed in terms of those factors which create the environment for efficient and selective transport. The following parameters which affect ion transport are discussed: membrane configuration, cation-macrocycle complex stability, macrocycle partitioning between membrane and water phases, proton ionization of acidic macrocycles, macrocycle concentration, anion type, ion concentration, membrane solvent type and receiving phase composition. A summary of existing models of ion transport is given along with possible applications to macrocycle-facilitated liquid membraneion transport.

Muon-catalysed fusion revisited

Abstract: Muons introduced into relatively cold, dense deuterium-tritium mixtures can replace the atomic electrons and form muonic molecules which participate readily in nuclear fusion reactions. Catalysis yields of ∼150 fusions per muon have been achieved, renewing interest in muon-catalysed fusion as a possible source of energy.

Factors influencing seed germination in salicornia pacifica var. utahensis

Abstract: The halophyte, Salicornia pacifica var. utahensis (Tiderstorm) Munz produces seed under high salinity conditions, and deposits its seed on saline soil. Experiments were conducted to determine the effect of salinity, temperature and growth regulators on germination. Results indicate that the seeds can germinate at very high salt concentration (5% NaCl). Germination was sensitive to the changes in temperature regimes. At higher 30-20 C, light-dark sequence, no germination occurred at 3, 4 and 5% NaCl treatments. On the other hand, 30% germination did occur at 5% NaCl treatment at a temperature regime of 15-5 C. These seeds required light for germination. Only 50% germination occurred in the non-saline control in the dark and the addition of NaCl further reduced germination. The GA3 partially alleviated the inhibitory effect of NaCl and darkness. Kinetin did not promote germination.

Giacobini-Zinner magnetotail: ICE magnetic field observations

Abstract: A well developed magnetotail with a diameter of about 10,000 km has been revealed 7800 km downstream of the nucleus of Comet Giacobini-Zinner by International Cometary Explorer magnetic field observations. The tail is composed of two lobes of opposite magnetic polarity that are separated by an approximately 1500 km-thick plasma sheets. The field magnitude increases by a factor of 2 between the outer portions of the lobe and the central regions, where peak fields of about 60 nT were measured. Flaring is lowest in the high field regions of the central tail and greatest in the outer portions of the lobes, where minimum variance analyses on the magnetopause crossings furnishes flare angles of 20-40 deg. The Alfven field line draping model of type I cometary tails is confirmed by these observations.

Special Education Students as Tutors: A Review and Analysis:

Abstract: Although accounts of cross-age and peer tutoring date back to the first century A.D., only recently have special educators begun to investigate its effects with handicapped students. The purpose of the present article is to synthesize the results of these investigations, emphasizing the effects of tutoring on the academic and personal/social skills of both tutors and tutees. In general, research has shown that handicapped and remedial students can be trained to tutor both peers and younger students in a variety of content areas. Results further show that academic and personal/social benefits come to special education students, as well as to those they tutor, although the data regarding academic achievement is more convincing than the data regarding changes in general self-esteem. Following the summary of results of tutoring implications for instruction are discussed, and suggestions are given for improving the quality of future tutoring research.

Family structure and delinquency: general patterns and gender differences

Abstract: In a sample of over 700 high-school sophomores, a jive-category measure of family structure is found to be not related to either frequency or seriousness of self-reported illegal behavior, except for unusually high delinquent behavior by boys from mother/stepfather homes. On the other hand, family structure does show an overall association with self-reported trouble with police, school, and juvenile court officials. Specifically, while boys (not girls) with stepfathers admit the most delinquent acts, controlling for the amount of admitted delinquency shows that officials are more likely to respond to the misbehavior of children (especially girls) from mother-only families. None of these findings are accounted for by race, social class, the quality of parent-child relationships, or the quality of school experiences.

Tutoring interventions within special education settings: A comparison of cross-age and peer tutoring†

Abstract: In two experiments, cross-age and peer tutoring interventions conducted within special education settings were compared. In Experiment 1, learning disabled (LD) and behaviorally disordered (BD) students acted as tutors of younger LD and BD students. In Experiment 2, same-age LD and BD students alternated tutor and tutee roles. In both experiments, tutors and tutees exhibited academic gains. Only in Experiment 1, however, were attitudinal gains observed. Implications for future research and practice are given.

Effects of Exposure to Classical Music on the Musical Preferences of Preschool Children

Abstract: Musical preferences of 45 preschool children (mean age 4 years, 7 months) were assessed in a short-range longitudinal study incorporating a pre- and posttest experimental design. Six classical and ...

Dating age and stage as correlates of adolescent sexual attitudes and behavior.

Abstract: Dating experiences, especially the type or stage of dating, have consistently been found to be related to premarital sexual behavior. Findings regarding the age at 1st date and sexual behavior have been less consistent. This paper examined the age at which dating began and the type of dating relationship as correlates of premarital sexual attitudes and behavior among mid-teen adolescents. The analyses were based on a sample of high school students (n=836), most of whom were between the ages of 15 and 18 when the surveys were conducted. Early dating, especially early steady dating, was related to permissive attitudes and to premarital sexual experience among both males and females. The relationship between early dating and intercourse experience was particulary strong among Mormons, a religious group which has institutionalized age 16 as the legitimate age to begin dating.

Consideration of Worst-Case Manufacturing Tolerances in Design Optimization

Abstract: The paper discusses the effect of manufacturing tolerances for the design variables on the solution to an optimization problem. Two formulations of the tolerance problem in an optimization context are presented. Linearization is employed to reduce the problems to quadratic and linear programming problems. The formulations and solutions of the two tolerance problems are illustrated with an example application.

Comet-solar wind interaction - Dynamical length scales and models

Abstract: ICE magnetometer measurements at Comet Giacobini-Zinner and model simulations of comet-solar wind interactions are analyzed. The magnetometer data reveal the existence of intense hydromagnetic turbulence, a draping of the magnetic field lines to form a magnetotail, a weak shock, and a magnetic barrier region in the magnetosphere. The global models of the comet-solar wind interaction are described. The observed data and models are compared and good correlation is displayed.

Predicting habitat quality for grassland birds using density- habitat correlations.

Abstract: Predictive models relating densities of 5 grassland bird species to habitat variables were developed and tested using stepwise multiple regression and principal components regression. For most species the models gave poor quantitative estimates. Because there were distinct habitat differences among the study sites used to generate and the study sites used to verify the models, some models were required to extrapolate beyond the data used to generate them and thus failed to give accurate quantitative predictions. Other models produced predictions of low precision, whereas some may not have taken into account limiting factors not related directly to the habitat variables measured. Such problems will be encountered in most model building attempts and a strategy of continual model updating may provide a way to develop empirical regression models with more reliability. The scale at which habitats are measured to develop regression models relating density to habitat features may be too coarse to account for significant variation among individual breeding pairs in a given habitat. Nesting success, fledgling weights, and properties of nestling growth curves of individual nesting attempts can be related to habitat variables and may provide more information on habitat quality than density-habitat regressions. J. WILDL. MANAGE. 50(4):556-566 Habitat quality can be defined as the suitability of an area to support a reproducing population of a given species or group of species. The evaluation of habitat quality is a prime concern in development of management plans, impact assessments, mitigation studies, and multiple use strategies. It has long been realized that habitats have many effects on populations (e.g., Leopold 1933), so many researchers have attempted to approach the assessment of habitat quality using multivariate statistical methods (James 1971; Whitmore 1975, 1977; Smith 1977; Capen 1981; Collins et al. 1982). Multivariate habitat models are data intensive and require a substantial investment of time and money to collect and analyze the necessary data (Marcot et al. 1983). Less rigorous procedures can circumvent such expenditures. A widely used method developed by the U.S. Fish and Wildlife Service (USFWS) is the Habitat Evaluation Procedure (HEP). This method attempts to develop qualitative models reflecting habitat quality using a less data-intensive approach (Flood et al. 1977, Division of Ecological Services 1980). For any given species the HEP model produces a single index, the Habitat Suitability Index (HSI), which is a quantitative index of the quality of a given habitat for the species based on qualitative information regarding habitat requirements. The performance of HEP models when tested with actual fi ld data has been poor at best (Lancia et al. 1982, Bart et al. 1984), and it has been suggested that more rigorous procedures are neces ary (Bart et al. 1984). If quantitative habitat models are to be used in asses ing habitat quality, it is necessary to evaluat their reliability. It is not unreasonable to expect that quantitative models relating habitat variables to density will be of limited generality because they depend on a specific set of data taken in a restricted set of conditions. Because quantitative models are data specific, it s important to view them as empirical statements that describe correlations rather than causal relationships (Johnson 1981). The purpose of this paper is to evaluate the reliability of the predictive statements made by multiple regression models relating densities of 5 bird species to quantitative measurements of habitat and to demonstrate the sensitivity of such models to the specific data set used to generate them. Fieldwork for this research was made possible by support from the U.S. For. Serv. Rocky Mt. For. and Range Exp. Stn., the AppletonWhittell Res. Ranch Found., and the Ariz. Coop. Wildl. Res. Unit. C. and J. Bock were very helpful in making available the facilities of the Research Ranch (RR), and S. C. Martin provided information and unpublished data regarding the Santa Rita Exp. Range (SRER). R. W. Mannan, 'Present address: Department of Zoology, Brigham Young University, Provo, UT 84602.

Fission-track dating of volcanically derived sedimentary rocks

Abstract: Depositional ages of sedimentary rocks can be determined using fission-track single grain ages on zircons from layers of volcanic ash or bentonite, even when the layers have been contaminated by older grains. This is done by compiling an age probability distribution or age spectrum for a sample from individual grain ages. An age spectrum is a simple and unambiguous way of testing for contamination and extracting useful age information. The youngest peak in the age spectrum approximates the time of deposition. In most contaminated samples, 30 or more grains should be counted to produce a reliable spectrum. However, useful, reproducible ages can be obtained by counting less than 10 grains in samples where most of the older, contaminating grains can be removed. The few older grains that remain after removing the obviously abraded ones may then be eliminated by examining the age spectrum. Although ages determined in this way are probably not precise enough for use in defining stratigraphic boundaries, they still provide a means of obtaining an isotopic age in sediments that cannot be dated by other radiometric methods. 18 references, 3 figures, 3 tables.