Showing papers by "University of Colorado Boulder published in 1993"
TL;DR: It is demonstrated that the differential efficiency of experimental and field tests of interactions is also attributable to the differential residual variances of such interactions once the component main effects have been partialed out.
Abstract: Although interaction effects are frequently found in experimental studies, field researchers report considerable difficulty in finding theorized moderator effects. Previous discussions of this discrepancy have considered responsible factors including differences in measurement error and use of nonlinear scales. In this article we demonstrate that the differential efficiency of experimental and field tests of interactions is also attributable to the differential residual variances of such interactions once the component main effects have been partialed out. We derive an expression for this residual variance in terms of the joint distribution of the component variables and explore how properties of the distribution affect the efficiency of tests of moderator effects. We show that tests of interactions in field studies will often have less than 20% of the efficiency of optimal experimental tests, and we discuss implications for the design of field studies.
3,123 citations
TL;DR: The Center for the Study of Earth from Space (CSES) at the University of Colorado, Boulder, has developed a prototype interactive software system called the Spectral Image Processing System (SIPS) using IDL (the Interactive Data Language) on UNIX-based workstations to develop operational techniques for quantitative analysis of imaging spectrometer data.
2,686 citations
Book•
01 Jul 1993TL;DR: In this paper, the authors introduce basic elements of elasticity theory: foundations geometric foundations, kinematic foundations, dynamic foundations, constitutive relations elastostatic problems of linear elasticity boundary value problems and extremum principles three-dimensional problems solution of singular problems.
Abstract: Part 1 Overall properties of heterogeneous solids: aggregate properties and averaging methods aggregate properties, averaging methods elastic solids with microcavities and microcracks linearly elastic solids, elastic solids with traction-free defects, elastic solids with micrcavities, elastic solids with microcracks elastic solids with micro-inclusions overall elastic modulus and compliance tensors, examples o elastic solids with elastic micro-inclusions, upper and lower bounds for overall elastic moduli, self-consistent differential and related averaging methods, Eshelby's tensor and related topics solids with periodic microstructure general properties and field equations, overall properties of solids with periodic microstructure, mirror-image decomposition of periodic fields. Part 2 Introduction to basic elements of elasticity theory: foundations geometric foundations, kinematic foundations, dynamic foundations, constitutive relations elastostatic problems of linear elasticity boundary-value problems and extremum principles three-dimensional problems solution of singular problems. Appendix: references.
2,544 citations
01 Oct 1993
TL;DR: It is shown that a proper use of an four channels is of critical importance in achieving high performance telepresence in the sense of accurate transmission of task impedances to the operator.
Abstract: Tools for quantifying teleoperation system performance and stability when communication delays are present are provided A general multivariable system architecture is utilized which includes all four-types of data transmission between master and slave: force and velocity in both directions It is shown that a proper use of an four channels is of critical importance in achieving high performance telepresence in the sense of accurate transmission of task impedances to the operator It is also shown that transparency and robust stability (passivity) are conflicting design goals in teleoperation systems The analysis is illustrated by comparing transparency and stability in two common architectures, as well as a recent passivated approach and a new transparency-optimized architecture, using simplified one-degree-of-freedom examples >
2,083 citations
TL;DR: In this article, the authors present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core, and observe large, rapid climate fluctuations throughout the last glacial period.
Abstract: RECENT results1,2 from the Greenland Ice-core Project (GRIP) Summit ice core suggest that the climate in Greenland has been remarkably stable during the Holocene, but was extremely unstable for the time period represented by the rest of the core, spanning the last two glaciations and the intervening Eemian inter-glacial. Here we present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core. We observe large, rapid climate fluctuations throughout the last glacial period, which closely match those reported for the GRIP core. However, in the bottom 10% of the cores, spanning the Eemian interglacial and the previous glacia-tion, there are significant differences between the two records. It is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores. Considerable further work will be necessary to evaluate the likelihood of this, and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores.
1,885 citations
TL;DR: In this paper, seven price-related constructs are used as independent variables, five consistent with a perception of price in negative role and two consistent with price in its positive role.
Abstract: Seven price-related constructs—five consistent with a perception of price in its “negative role” and two consistent with a perception of price in its “positive role”— are used as independent variab...
1,525 citations
01 Jan 1993
1,228 citations
TL;DR: In this article, the authors present results from a new Greenland ice core (GISP2) showing that snow accumulation doubled rapidly from the Younger Dryas event to the subsequent Preboreal interval, possibly in one to three years.
Abstract: THE warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate, the best-known of which is the Younger Dryas event1. Despite much study of the causes of this event and the mechanisms by which it ended, many questions remain unresolved1. Oxygen isotope data from Greenland ice cores2–4 suggest that the Younger Dryas ended abruptly, over a period of about 50 years; dust concentrations2,4 in these cores show an even more rapid transition (≲20 years). This extremely short timescale places severe constraints on the mechanisms underlying the transition. But dust concentrations can reflect subtle changes in atmospheric circulation, which need not be associated with a large change in climate. Here we present results from a new Greenland ice core (GISP2) showing that snow accumulation doubled rapidly from the Younger Dryas event to the subsequent Preboreal interval, possibly in one to three years. We also find that the accumulation-rate change from the Oldest Dryas to the Bo11ing/Allerod warm period was large and abrupt. The extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the North Atlantic climate system.
1,126 citations
TL;DR: This presentation demonstrates that a well-tuned implementation of tabu search makes it possible to obtain solutions of high quality for difficult problems, yielding outcomes in some settings that have not been matched by other known techniques.
Abstract: We describe the main features of tabu search, emphasizing a perspective for guiding a user to understand basic implementation principles for solving combinatorial or nonlinear problems. We also identify recent developments and extensions that have contributed to increasing the efficiency of the method. One of the useful aspects of tabu search is the ability to adapt a rudimentary prototype implementation to encompass additional model elements, such as new types of constraints and objective functions. Similarly, the method itself can be evolved to varying levels of sophistication. We provide several examples of discrete optimization problems to illustrate the strategic concerns of tabu search, and to show how they may be exploited in various contexts. Our presentation is motivated by the emergence of an extensive literature of computational results, which demonstrates that a well-tuned implementation makes it possible to obtain solutions of high quality for difficult problems, yielding outcomes in some settings that have not been matched by other known techniques.
941 citations
TL;DR: In this paper, the authors synthesize what is known in terms of the economic and organizational consequences of downsizing, and argue that in many firms anticipated economic benefits fail to materialize, for example, lower expense ratios, higher profits, increased return-on-investment, and boosted stock prices.
Abstract: Executive Overview Downsizing, the planned elimination of positions or jobs, is a phenomenon that has affected hundreds of companies and millions of workers since the late 1980s. While there is no shortage of articles on “How To” or “How Not To” downsize, the current article attempts to synthesize what is known in terms of the economic and organizational consequences of downsizing. We argue that in many firms anticipated economic benefits fail to materialize, for example, lower expense ratios, higher profits, increased return-on-investment, and boosted stock prices. Likewise, many anticipated organizational benefits do not develop, such as lower overhead, smoother communications, greater entrepreneurship, and increases in productivity. To a large extent, this is a result of a failure to break out of the traditional approach to organization design and management—an approach founded on the principles of command, control, and compartmentalization. For long-term. sustained improvements in efficiency, reductio...
831 citations
TL;DR: C4 and CAM photosynthesis are evolutionarily derived from C3 photosynthesis, with a tendency toward ecological adaptation of C4 plants into warm, monsoonal climates and CAM plants into water-limited habitats and in an anthropogenically altered CQ2 environment, C 4 plants may lose their competitive advantage over C3 plants.
Abstract: C4 and CAM photosynthesis are evolutionarily derived from C3 photosynthesis. The morphological and biochemical modifications necessary to achieve either C4 or CAM photosynthesis are thought to have independently arisen numerous times within different higher plant taxa. It is thought that C4 photosynthesis evolved in response to the low atmospheric CO2 concentrations that arose sometime after the end of the Cretaceous. Low CO2 concentrations result in significant increases in photorespiration of C3 plants, reducing productivity; both C3-C4 intermediate and C4 plants exhibit reduced photorespiration rates. In contrast, it may be argued that CAM arose either in response to selection of increased water-use efficiency or for increased carbon gain. Globally, all three pathways are widely distributed today, with a tendency toward ecological adaptation of C4 plants into warm, monsoonal climates and CAM plants into water-limited habitats. In an anthropogenically altered CQ2 environment, C4 plants may lose their competitive advantage over C3 plants. 411
25 Oct 1993
TL;DR: In this paper, a linear mixing model and a set of hypothesized end-member spectra are used to estimate the fractional abundance patterns of the various materials occurring within the imaged area.
Abstract: Spectral mixture analysis, or unmixing, has proven to be a useful tool in the semi-quantitative interpretation of AVIRIS data. Using a linear mixing model and a set of hypothesized endmember spectra, unmixing seeks to estimate the fractional abundance patterns of the various materials occurring within the imaged area. However, the validity and accuracy of the unmixing rest heavily on the 'user-supplied' set of endmember spectra. Current methods for emdmember determination are the weak link in the unmixing chain.
07 Nov 1993
TL;DR: This paper presents a treatment founded in Boolean algebras and discusses algorithms and results in applications like matrix multiplication and shortest path algorithms, and outlines possible applications of ADD's to logic synthesis, formal verification, and testing of digital systems.
Abstract: In this paper we present theory and experiments on the algebraic decision diagrams (ADDs). These diagrams extend BDD's by allowing values from an arbitrary finite domain to be associated with the terminal nodes. We present a treatment founded in Boolean algebras and discuss algorithms and results in applications like matrix multiplication and shortest path algorithms. Furthermore, we outline possible applications of ADD's to logic synthesis, formal verification, and testing of digital systems.
TL;DR: A new, interdisciplinary paradigm is emerging in developmental psychology as mentioned in this paper, which includes contextual as well as individual variation and is more consonant with the complexity of adolescent behavior and development than traditional research paradigms.
Abstract: A new, interdisciplinary paradigm is emerging in developmental psychology. It includes contextual as well as individual variation and is more consonant with the complexity of adolescent behavior and development than traditional research paradigms. Social problems, such as poverty and racial discrimination, and the ways that young people negotiate adolescence successfully, are objects of research. A research program sponsored by the MacArthur Foundation, that embodies the new paradigm, is described.
TL;DR: This set of rRNAs contains representative structures from all of the major phylogenetic groupings--Archaea, (eu)Bacteria, and the nucleus, mitochondrion, and chloroplast of Eucarya.
Abstract: A collection of diverse 16S and 16S-like rRNA secondary structure diagrams are available. This set of rRNAs contains representative structures from all of the major phylogenetic groupings--Archaea, (eu)Bacteria, and the nucleus, mitochondrion, and chloroplast of Eucarya. Within this broad phylogenetic sampling are examples of the major forms of structural diversity currently known for this class of rRNAs. These structure diagrams are available online through our computer-network WWW server and anonymous ftp, as well as from the author in hardcopy format.
TL;DR: In this paper, data from the Denver Youth Survey, a longitudinal study of families, are used to examine the prevalence and demographic composition of gangs, the degree to which gang members are involved in illegal activities, and the temporal relationship between criminal offending and gang membership.
Abstract: Youth delinquent gangs have been given considerable academic and media attention during the past decade. Much of the attention has focused on the violence and drug dealing in which gang members are assumed to be involved. Recent knowledge about gangs has relied primarily on data obtained from police gang units and from observational or case studies. Very little information has been derived from surveys or interviews with a more general sample of youths. In this paper, data from the Denver Youth Survey, a longitudinal study of families, are used to examine: (1) the prevalence and demographic composition of gangs: (2) the degree to which gang members are involved in illegal activities: and (3) the temporal relationship between criminal offending and gang membership.
TL;DR: It is demonstrated that PKCγ-mutant mice can learn to carry out hippocampus-dependent tasks, although mild deficits are evident, and the modification of hippocampal synaptic plasticity correlates with the learning deficits the authors observe.
TL;DR: In this paper, the authors considered the random cascade theory for spatial rainfall and provided empirical evidence for a random cascading theory of rainfall, and the way of using data for making estimates of parameters and for making statistical inference within this theoretical framework.
Abstract: The paper considers the random cascade theory for spatial rainfall Particular attention was given to the following four areas: (1) the relationship of the random cascade theory of rainfall to the simple scaling and the hierarchical cluster-point-process theories, (2) the mathematical foundations for some of the formalisms commonly applied in the develpment of statistical cascade theory, (3) the empirical evidence for a random cascade theory of rainfall, and (4) the way of using data for making estimates of parameters and for making statistical inference within this theoretical framework An analysis of space-time rainfall data is presented Cascade simulations are carried out to provide a comparison with methods of analysis that are applied to the rainfall data
19 Apr 1993
TL;DR: The Volcano project, which provides efficient, extensible tools for query and request processing, particularly for object-oriented and scientific database systems, is reviewed, and it is shown that the search engine of the Volcano optimizer generator is more extensible and powerful.
Abstract: The Volcano project, which provides efficient, extensible tools for query and request processing, particularly for object-oriented and scientific database systems, is reviewed In particular, one of its tools, the optimizer generator, is discussed The data model, logical algebra, physical algebra, and optimization rules are translated by the optimizer generator into optimizer source code It is shown that, compared with the EXODUS optimizer generator prototype, the search engine of the Volcano optimizer generator is more extensible and powerful It provides effective support for non-trivial cost models and for physical properties such as sorting order At the same time, it is much more efficient, as it combines dynamic programming with goal-directed searching and branch-and-bound pruning Compared with other rule-based optimization systems, it provides complete data model independence and more natural extensibility >
TL;DR: It is shown that, as in the traditional memoryless multiaccess channel, frequency-division multiaccess (FDMA) with optimally selected frequency bands for each user achieves the total capacity of the multiuser Gaussian multi access channel with ISI.
Abstract: The capacity region of a two-user Gaussian multiaccess channel with intersymbol interference (ISI) in which the inputs pass through respective linear systems and are superimposed before being corrupted by an additive Gaussian noise process is discussed. A geometrical method for obtaining the optimal input power spectral densities and the capacity region is presented. This method can be viewed as a nontrivial generalization of the single-user water-filling argument. It is shown that, as in the traditional memoryless multiaccess channel, frequency-division multiaccess (FDMA) with optimally selected frequency bands for each user achieves the total capacity of the multiuser Gaussian multiaccess channel with ISI. However, the capacity region of the two-user channel with memory is, in general, not a pentagon unless the channel transfer functions for both users are identical. >
TL;DR: It is shown that the SIR3 and SIR4 gene products have a sub-nuclear localization similar to the telomere-associated RAP1 protein, which is found primarily in foci at the nuclear periphery of fixed yeast spheroplasts.
TL;DR: In this article, a method for retrieving "scaled surface reflectances" assuming horizontal surfaces having Lambertian reflectances from spectral data collected by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is presented.
TL;DR: In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth.
Abstract: In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.
01 Jan 1993
TL;DR: In this paper, the authors present a conception of why and how constructivist learning environments should be used in higher education, and propose a methodology for designing constructivistic learning environments.
Abstract: In this book on designing constructivist learning environments, we offer a conception of why and how these environments should be used in higher education.
TL;DR: Quantum Langevin equations and a master equation are derived for a two-atom system in which the first atom is driven by coherent field, and the fluorescent light is used to drive a second atom.
Abstract: Quantum Langevin equations and a master equation are derived for a two-atom system in which the first atom is driven by coherent field, and the fluorescent light used to drive a second atom. We show that the light beams from both atoms are antibunched, and that they are mutually anticorrelated.
Posted Content•
TL;DR: In this paper, the authors examine the choice between exporting, licensing, and acquiring a subsidiary in this environment and analyze the cost and technology parameters that support the alternative modes of serving the foreign market, and describe the international equilibrium that jointly determines the pattern of specialization and the market mode.
Abstract: Empirical evidence indicates a close association between multinational firms and knowledge capital, a public good within the firm We model a firm which wishes to exploit its knowledge capital abroad, but whose workers learn all the knowledge necessary for production and can defect and produce the good themselves The home firm must then choose between costly exporting and the possible dissipation of its knowledge capital by producing abroad The paper examines the choice between exporting, licensing, and acquiring a subsidiary in this environment We analyze the cost and technology parameters that support the alternative modes of serving the foreign market, and we describe the international equilibrium that jointly determines the pattern of specialization and the market mode(This abstract was borrowed from another version of this item)
TL;DR: In this article, a repeated three-level nested-logit model is used to model participant and site choice for Atlantic salmon fishing in the context of a repeated 3-Level NN model.
Abstract: Participation and site choice for Atlantic salmon fishing are modeled in the context of a repeated three-level nested-logit model. Consumer's surplus measures are derived for different levels of species availability in the Penobscot River, the most important salmon river in New England. For comparison, six other travel-cost models are estimated. These include restrictive cases of the nested-logit model, a partial demand model, and two single-site demand models. Comparisons across these models indicate the importance of modeling the participation decision, including income effects, and of adopting a nested-logit structure rather than a single-level logit structure.
TL;DR: The cloned and expressed DNA fragments that encode the putative ATP- hydrolytic sites of the cytoplasmic dynein heavy chain from HeLa cells and from Dictyostelium suggest that cytopsized dyne in plays a unique and important role in the initial events of bipolar spindle formation, while any later roles that it may play are redundant.
Abstract: The formation and functioning of a mitotic spindle depends not only on the assembly/disassembly of microtubules but also on the action of motor enzymes. Cytoplasmic dynein has been localized to spindles, but whether or how it functions in mitotic processes is not yet known. We have cloned and expressed DNA fragments that encode the putative ATP-hydrolytic sites of the cytoplasmic dynein heavy chain from HeLa cells and from Dictyostelium. Monospecific antibodies have been raised to the resulting polypeptides, and these inhibit dynein motor activity in vitro. Their injection into mitotic mammalian cells blocks the formation of spindles in prophase or during recovery from nocodazole treatment at later stages of mitosis. Cells become arrested with unseparated centrosomes and form monopolar spindles. The injected antibodies have no detectable effect on chromosome attachment to a bipolar spindle or on motions during anaphase. These data suggest that cytoplasmic dynein plays a unique and important role in the initial events of bipolar spindle formation, while any later roles that it may play are redundant. Possible mechanisms of dynein's involvement in mitosis are discussed.
TL;DR: In this paper, the role of fiscal exchange, the uses of tax revenues and the decision process by which these uses are selected, in individual compliance behavior was examined and found that individuals respond positively when tax proceeds are directed toward programs they approve of and when they feel they are active in decision process.
Abstract: It is commonly believed that voluntary tax compliance is affected by the nature of the expenditures and by the manner these expenditure decisions are made. This paper reports on the results of a series of laboratory experiments designed to examine the role of fiscal exchange, the uses of tax revenues and the decision process by which these uses are selected, in individual compliance behavior. Individuals respond positively when tax proceeds are directed toward programs they approve of and when they feel they are active in the decision process.
TL;DR: In this article, a simulation of a fully developed, low-Reynolds-number turbulent flow in a square duct is presented, which employs a time-splitting method to integrate the three-dimensional, incompressible Navier-Stokes equations using spectral/high-order finite-difference discretization.
Abstract: A direct numerical simulation of a fully developed, low-Reynolds-number turbulent flow in a square duct is presented. The numerical scheme employs a time-splitting method to integrate the three-dimensional, incompressible Navier-Stokes equations using spectral/high-order finite-difference discretization on a staggered mesh ; the nonlinear terms are represented by fifth-order upwind-biased finite differences. The unsteady flow field was simulated at a Reynolds number of 600 based on the mean friction velocity and the duct width, using 96 x 101 x 101 grid points. Turbulence statistics from the fully developed turbulent field are compared with existing experimental and numerical square duct data, providing good qualitative agreement. Results from the present study furnish the details of the corner effects and near-wall effects in this complex turbulent flow field; also included is a detailed description of the terms in the Reynolds-averaged streamwise momentum and vorticity equations. Mechanisms responsible for the generation of the stress-driven secondary flow are studied by quadrant analysis and by analysing the instantaneous turbulence structures. It is demonstrated that the mean secondary flow pattern, the distorted isotachs and the anisotropic Reynolds stress distribution can be explained by the preferred location of an ejection structure near the corner and the interaction between bursts from the two intersecting walls. Corner effects are also manifested in the behaviour of the pressure-strain and velocity-pressure gradient correlations.