Showing papers by "Brigham Young University published in 1978"

Bubbles, Drops, and Particles

Abstract: The standard κ-ϵ equations and other turbulence models are evaluated with respect to their applicability in swirling, recirculating flows. The turbulence models are formulated on the basis of two separate viewpoints. The first perspective assumes that an isotropic eddy viscosity and the modified Boussinesq hypothesis adequately describe the stress distributions, and that the source of predictive error is a consequence of the modeled terms in the κ-ϵ equations. Both stabilizing and destabilizing Richardson number corrections are incorporated to investigate this line of reasoning. A second viewpoint proposes that the eddy viscosity approach is inherently inadequate and that a redistribution of the stress magnitudes is necessary. Investigation of higher-order closure is pursued on the level of an algebraic stress closure. Various turbulence model predictions are compared with experimental data from a variety of isothermal, confined studies. Supportive swirl comparisons are also performed for a laminar flow case, as well as reacting flow cases. Parallel predictions or contributions from other sources are also consulted where appropriate. Predictive accuracy was found to be a partial function of inlet boundary conditions and numerical diffusion. Despite prediction sensitivity to inlet conditions and numerics, the data comparisons delineate the relative advantages and disadvantages of the various modifications. Possible research avenues in the area of computational modeling of strongly swirling, recirculating flows are reviewed and discussed.

Conversion of complex contour line definitions into polygonal element mosaics

Abstract: A simple algorithm is presented for processing complex contour arrangements to produce polygonal element mosaics which are suitable for line drawing and continuous tone display. The program proceeds by mapping adjacent contours onto the same unit square and, subject to ordering limitations, connecting nodes of one contour to their nearest neighbors in the other contour. While the mapping procedure provides a basis for branching decisions, highly ambiguous situations are resolved by user interaction. The program was designed to interface a contour definition of the components of a human brain. These brain data are a most complex definition and, as such, serve to illustrate both the capabilities and limitations of the procedures.

Bäcklund Transformation for the Ernst Equation of General Relativity.

Abstract: A B\"acklund transformation for the Ernst equation arising in general relativity in connection with several physical problems is derived, using the pseudopotential method of Wahlquist and Estabrook. A prolongation structure is also constructed, using a method of writing the equations in terms of differential forms, and an equation in the spirit of Lax is constructed, somewhat different from that given by Maison. Possible uses of the B\"acklund transformation to generate new solutions are mentioned.

A C4 plant from the Pliocene

Abstract: THE Kranz syndrome1,2 is a group of physiological and anatomical features occurring in certain angiosperms; the grasses in particular show increasing efficiency in CO2 assimilation. Recent research3,4 suggests an origin of the syndrome in South America and its subsequent dominance in other continents. The Kranz syndrome occurs in all plants fixing CO2 by phosphoenolpyruvate carboxylase in the mesophyll and subsequent production of Calvin–Benson cycle intermediates in the bundle sheath5. The physiological processes in C4 plants are closely related to their specialised leaf anatomy known as Kranz anatomy6 by which they are distinguished from C3 plants. It is suggested that ancestral non-Kranz C3 grasses originated during the Cretaceous period4. We report here fossil evidence indicating that C4 plants occurred at least during the late Tertiary period.

The structure of subject matter content and its instructional design implications

Abstract: This paper discusses the analysis of subject matter structure for purposes of designing instruction. The underlying assumption is that subject matter structures provide an important basis for deciding how to sequence and synthesize the “modules” of a subject matter area. Four types of fundamental structures are briefly described and illustrated: the learning hierarchy, the procedural hierarchy, the taxonomy, and the model. Then a theoretical framework is presented for classifying types of subject mater content — both “modules” and structures. Finally, some implications of these content classifications are discussed. The classification of “modules” is hypothesized to be valuable for prescribing strategies for the presentation of single “modules”, and the classification of structures is hypothesized to be valuable for prescribing strategies for selecting, sequencing, synthesizing, and summarizing related “modules”. The need to take into account more than one kind of structure in the process of instructional design is emphasized.

Insect herbivory on C3 and C4 grasses.

Abstract: This study tested the hypothesis that grasses with the C4 photosynthetic pathway are avoided as a food source by insect herbivores in natural communities. Insects were sampled from ten pairs of C3−C4 grasses and their distributions analyzed by paired comparisons tests. Results showed no statistically significant differences in herbivore utilization of C3−C4 species. However, there was a trend towards heavier utilization of C3 species when means for both plant groups were compared. In particular, Homoptera and Diptera showed heavier usage of C3 plants. Significant correlations between insect abundances and plant protein levels suggest that herbivores respond to the higher protein content of C3 grasses. δ13C values for six of the most common grasshopper species in the study area indicated that three species fed on C3 plants, two species fed on C4 plants, and one species consumed a mixture of C3 and C4 tissue.

Porifera of the Middle Cambrian Wheeler Shale, from the Wheeler Amphitheater, House Range, in western Utah

Abstract: Continued collection of trilobites and the associated fauna out of the Elrathia kingii beds of the Middle Cambrian Wheeler Shale, in the Wheeler Amphitheater of the House Range in western Millard County, Utah, has yielded a varied fauna of sponges. Included and described from the collection are Choia carteri Walcott, 1920; Choia utahensis Walcott, 1920; Diagoniella cyathiformis (Dawson & Hinde, 1890) and Chancelloria eros Walcott, 1920. In addition to those forms, the new species, Diagoniella robisoni, Chancelloria pentacta and a large-spiculed Chancelloria sp., are de- scribed and figured. Diagoniella cyathiformis is reported from the Wheeler Shale for the first time. Protospongia fenestrata Hicks, listed by Walcott from the Wheeler Shale, could be a fragment of Diagoniella for orientation of the fragment is impossible to determine. Kiwetinokia utahensis Walcott, 1920 occurs as disassociated spicules in the basal part of the formation, well below the Elrathia kingii beds which include the most fossiliferous and productive part of the formation. Chancelloria pentacta is distinguished by a preponderance of spicules with five tangential rays, in addition to the buttonlike, proximal-distal rays. Diagoniella robisoni is a small thin-walled, keg-shaped to goblet-shaped, stalked sponge. It lacks pronounced marginalia and prostalia, other than the basal stalk. These species, plus Sentinelia draco Walcott, 1920 and Hintzespongia bilamina Rigby & Gutschick, 1976 comprise the known sponge fauna of the Wheeler Shale.

Scheduling Rules For The Multiple Product Single Machine System With Stochastic Demand

Abstract: The scheduling of multiple products with stochastic demand on a single machine system was modelled. Simulation of six scheduling rules under varying cost and system parameters was performed. It was shown that several of the commonly proposed rules resulted in very costly schedules. It was also shown that the best scheduling rule for a particular system depends on the number of products, distribution of demand among those products, and the proportion of capacity utilization, as well as on the relative costs for carrying inventory, setup, and shortages.

Cyclic polyether-protonated organic amine binding: significance in enzymatic and ion transport processes

Abstract: The cyclic polyether, 18-crown-6, reacts with protonated amines in methanol to form complexes whose formation constants (log K) decrease in the order NH4+, RNH3+ greater than R2NH2+ greater than R3NH+. In the case of the organic amines, this stability order is identical to the earlier observed permeability sequence for protonated organic amines in glyceryl dioleate bilayers treated with valinomycin, nonactin, or gramicidin, and in bullfrog and rabbit gallbladder membranes. The decrease in log K values in the above series is primarily a result of decreased enthalpy change (deltaH) values, the entropy change (TdeltaS) term being essentially constant for the systems studied.

The flora of Great Basin mountain ranges: diversity, sources, and dispersal ecology

Abstract: The high elevation floras of 9 mountainous "mainlands" (3 in the Sierra-Cascade system and 6 in the High Plateau-Wasatch-Teton system) and 15 isolated mountain "islands" in the Intermountain Region have been analyzed. Mainland floras support more species per unit area and show a smaller increase in diversity as area is increased than islands (never exceeding 5 percent of any flora), however; and the island floras are overwhelmingly dominated by species with no apparent modifications for long-range dispersal. Furthermore, the eastern mainland has exerted a far greater influence on the flora and the vegetation of the islands than has the western mainland, despite the fact that the former is downwind of the islands. Thus, evidence from endemics, dispersal ecology, and sources of the floras suggests that the isolated mountains have not acquired there full floras by long-range dispersal. We conlude that although the floras of this lands have many insular chaacteristics, they were less isolated in the relatively recent past than at the present. The island floras do not appear to be in equilibrium in the sense that immigrations equal extinctions.

Energy distribution in reproductive structures of amaryllis

Abstract: Energy content of tissue produced in male and female reproductive structures as well as in associated flower parts of Amaryllis was measured with an oxygen bomb calorimeter. In typical flowers, 6.6% of their total energy (2,880 cal) was in pollen, 4.9o in anther walls, 4.6% in ovules and placentae, and 12.6% in ovary walls and septa. Ovules were estimated to contain only about one-third as much energy as pollen. Mature seeds typically contained about 100 times as much energy as ovules. Total energy in mature seeds per flower was approximately equal to total energy in flower tissues. Proportional allocation of anther energy to pollen increased with anther size. The biological significance of these results is discussed.

Mormon perception and settlement

Abstract: The distribution of Mormon settlements in the Great Basin is the result of the environmental perception of the Mormon leaders The leaders selected the Salt Lake Valley as a destination on the basis of reports of explorers, and their perception of the region was formed before they ever saw the West The central feature of the leaders'perception was the idea that the division between the then Oregon and California territories at the 42 parallel marked a climatic divide Believing it was too cold for crops north of that boundary, Mormon leaders directed their settlement efforts southward from the Salt Lake Valley for three decades Because the regions to the south were arid and only marginal for settlement, the leaders faced a constant struggle in convincing migrants they should attempt their settlement To convince prospective settlers that they could successfully occupy the marginal sites of the Southwest, the leaders in their public statements transformed the Mormon perception of the Salt Lake V

Explosive evolution of perennial atriplex in western america

Abstract: New habitats opened up in western North America since the recession of Lake Bonneville and Lake Lahontan have admitted a host of new species of Atriplex . Every known evolutionary force is operating and at accelerated paces. Autoploidy appears to be more common than in any other reported group of plants. Natural hybridization between closely related species has provided a wealth of fertile segregants from which new adaptive types have been and are being selected. Hybrids between more distantly related species are sterile and some appear to have given rise to fertile alloploid derivatives. All evidence points to a center of origin for Atriplex in northern Mexico. The numerous species which have migrated northward into western United States and Canada were apparently able to do so because attributes acquired to make them adaptive in the hot dry deserts of Mexico were characteristics which, uniquely, also pre-adapted them for colder climates and alkaline clay soils to the north. Woody species such as Atriplex canescens and A. confertifolia hybridize rather easily with herbaceous perennial species such as A. cuneata, A. gardneri, A. corrugata, and A. obovata. Since most such hybrids are at least partly fertile and produce F 2 segregants of both woody and nonwoody types, the genetic basis for the accumulation of wood is apparently rather simple.

Electrophysiological response of honey bee labial palp contact chemoreceptors to sugars and electrolytes

Abstract: . The sensilla chaetica on segments II, III and IV of honey-bee labial palps were investigated electrophysiologically. The responses (spikes/s) correlated with the log of the concentrations of sucrose, glucose, fructose, NaCl, KCl and LiCl, but not with CaCl2 or MgCl2, which gave inconsistent responses. The firing rates were higher and thresholds lower to the sugars than to the electrolytes. The sensitivity of the segments fell in the order: III > II > IV for most of the stimulants, which elicited responses in the order: sucrose > glucose = fructose’ KCl > LiCl > NaCl. The sensilla adapted logarithmically with time. No synergism of response was noted when mixed-sugar solutions were applied, but inhibition of response was seen when glucose–sucrose, fructose–sucrose, and glucose–fructose–sucrose mixtures were applied. None of the sensilla tested responded to water.

A knowledge base for improving our methods of instruction

Abstract: This paper discusses the importance of developing the knowledge base (both scientific and technological) that is needed for improving our present‐day methods of instruction. It proposes seven steps as being necessary to develop that knowledge base: (1) definition of concepts of instruction, (2) derivation of principles of instruction, (3) validation of those principles, (4) development of theories or models, (5) testing of those theories or models, (6) development of application procedures, and (7) testing of those application procedures. Related work done by M.D. Merrill's instructional research laboratory is outlined. Attention is drawn to some important areas that need much greater expenditure of effort and resources to develop the kind of scientific and technological knowledge base that can help us to improve our methods of instruction.

Cold flow mixing rate data for pulverized coal reactors

Abstract: Mixing rates of particles and gases in confined, coaxial jets are reported for tests with conditions simulating those of pulverized coal gasification and combustion processes. Gas velocity, particle mass flux, and gas composition were measured at various radial and axial locations downstream of the primary jet exit plane. Effects of inlet velocity, density, injection angle, particle loading level, and particle size on the rates of mixing were determined. Increasing injection angle and secondary velocity significantly increased gas and particle mixing rates, while effects of other variables were much less significant. Dispersion of particles lagged that of the gas in all cases investigated.

What is the design science of instruction

Abstract: This paper is an attempt to identify what instructional science is and what instructional scientists do.First, prescriptive design sciences are distinguished from descriptive sciences in general, and instructional science is characterized as a prescriptive design science.Second, three major phases of instructional development are described (design, production, and validation), and three approaches for each phase are identified (artistic, empirical, and analytic). The design science of instruction is described as being the foundation for one of the three approaches (the analytic) to one of the three phases (design) of instructional development.Third, typical activities of people in instructional science are described. Like all design sciences, instructional science has three types of professionals: scientists, technologists, and technicians. The major activities of instructional scientists are the derivation and validation of prescriptive principles of instruction.Fourth, a four-stage theory-construction procedure is proposed as a particularly promising methodology for instructional scientists to conduct their activities of deriving and validating prescriptive principles and theories of instruction.Fifth, reference is made to recent work by one instructional science laboratory which uses this four-stage theory-construction procedure. Andfinally, the controversy over basic vs. applied research is addressed from the perspective of the previous analyses.

A Comparison of Five Statistical Methods for Analyzing Pretest-Posttest Designs

Abstract: Five methods for analyzing data arising from research involving pretests and posttests are considered. These methods include: (1) posttest analysis only; (2) analysis of raw gain scores (posttest minus pretest); (3) analysis of the data with a pretest-posttest factor included in the statistical model; (4) analysis of posttest data with pretests as a covariate, and (5) analysis of gain scores with pretests as a covariate. The characteristics of each are discussed, with a conclusion that the fifth method is superior to the others when the assumptions underlying covariance analysis are met.