Showing papers by "University of New Hampshire published in 1990"

Neural networks for control

Abstract: Neural Networks for Control highlights key issues in learning control and identifies research directions that could lead to practical solutions for control problems in critical application domains. It addresses general issues of neural network based control and neural network learning with regard to specific problems of motion planning and control in robotics, and takes up application domains well suited to the capabilities of neural network controllers. The appendix describes seven benchmark control problems. Contributors Andrew G. Barto, Ronald J. Williams, Paul J. Werbos, Kumpati S. Narendra, L. Gordon Kraft, III, David P. Campagna, Mitsuo Kawato, Bartlett W. Met, Christopher G. Atkeson, David J. Reinkensmeyer, Derrick Nguyen, Bernard Widrow, James C. Houk, Satinder P. Singh, Charles Fisher, Judy A. Franklin, Oliver G. Selfridge, Arthur C. Sanderson, Lyle H. Ungar, Charles C. Jorgensen, C. Schley, Martin Herman, James S. Albus, Tsai-Hong Hong, Charles W. Anderson, W. Thomas Miller, III

Perceiving Affective Content in Ambiguous Visual Stimuli: A Component of Emotional Intelligence

Abstract: Emotional intelligence involves the accurate appraisal and expression of emotions in oneself and others and the regulation of emotion in a way that enhances living One aspect of emotional intelligence is the ability to recognize the consensually agreed upon emotional qualities of objects in the environment One hundred thirty-nine adults viewed 18 reproductions of faces, color swatches, and abstract designs and rated the emotional content of these visual stimuli Three scores were extracted, including consensual accuracy, amount, and range of emotion perceived These scores were compared with other aspects of emotional intelligence such as empathy and related to constructs such as alexithymia and neuroticism A general ability to perceive consensual emotional content in visual stimuli was found, and it was most strongly associated with the ability to respond empathically to others

Relative helix-forming tendencies of nonpolar amino acids

Abstract: An important issue in understanding the relationship between protein sequence and structure is the degree to which different amino acids favour the formation of particular types of secondary structure. Estimates of the 'helix-forming tendency' of amino acids have been made based on 'host-guest' experiments, in which copolymers are made of the amino acid of interest (the 'guest') and a host residue (typically hydroxypropyl- or hydroxybutyl-L-glutamine). Recently, however, short alanine-based peptides were found to form stable monomeric helices in water, contrary to the result predicted from host-guest experiments. We have now measured the helix-forming tendency of five different nonpolar amino acids (Ala, Ile, Leu, Phe, Val) by substituting each in turn for alanine in a 17-residue alanine-based peptide and determining the extent of alpha-helix formation. Our results differ from those of host-guest experiments both in the degree of variation in helix-forming tendency of different amino acids, and in the rank order of the helix-forming tendency. We conclude that the helix-forming tendency of a particular amino acid depends on the sequence context in which it occurs; and the restriction of side-chain rotamer conformations is important in determining the helix-forming tendency.

Real-time dynamic control of an industrial manipulator using a neural network-based learning controller

Abstract: A learning control technique that uses an extension of the cerebellar model articulation control network developed by J.S. Albus (1975) is discussed, and results of real-time control experiments that involved learning the dynamics of a five-axis industrial robot (General Electric P-5) during high-speed movements are presented. During each control cycle, a training scheme was used to adjust the weights in the network in order to form an approximate dynamic model of the robot in appropriate regions of the control space. Simultaneously, the network was used during each control cycle to predict the actuator drives required to follow a desired trajectory, and these drives were used as feedforward terms in parallel to a fixed-gain linear feedback controller. Trajectory tracking errors were found to converge to low values within a few training trials, and to be relatively insensitive to the choice of control system gains. The effects of network memory size and trajectory characteristics on learning system performance were investigated. >

Alternative reinforcement increases resistance to change: pavlovian or operant contingencies?

Abstract: Two multiple-schedule experiments with pigeons examined the effect of adding food reinforcement from an alternative source on the resistance of the reinforced response (target response) to the decremental effects of satiation and extinction. In Experiment 1, key pecks were reinforced by food in two components according to variable-interval schedules and, in some conditions, food was delivered according to variable-time schedules in one of the components. The rate of key pecking in a component was negatively related to the proportion of reinforcers from the alternative (variable-time) source. Resistance to satiation and extinction, in contrast, was positively related to the overall rate of reinforcement in the component. Experiment 2 was conceptually similar except that the alternative reinforcers were contingent on a specific concurrent response. Again, the rate of the target response varied as a function of its relative reinforcement, but its resistance to satiation and extinction varied directly with the overall rate of reinforcement in the component stimulus regardless of its relative reinforcement. Together the results of the two experiments suggest that the relative reinforcement of a response (the operant contingency) determines its rate, whereas the stimulus-reinforcement contingency (a Pavlovian contingency) determines its resistance to change.

An ice-core record of atmospheric response to anthropogenic sulphate and nitrate

Abstract: RECORDS of sulphate and nitrate concentrations in ice cores show that these concentrations have increased recently because of the long-range transport of pollution from middle latitudes1–5. But these records have been neither complete enough nor long enough to allow an assessment of their sensitivity to variations in the emissions of sulphate and nitrate precursors. We have now analysed sections from an ice core in South Greenland which have allowed us to extend its sulphate and nitrate record back from 1869 to 1767. This longer record has enabled us to determine the pre-industrial natural interannual variability of non-sea-salt sulphate and nitrate. We find that the background concentration in the remote atmosphere over South Greenland is sensitive to changes in the anthropogenic emissions of sulphate and nitrate, and responds to these variations on a timescale of the order of decades.

Complexity of K-tree structured constraint satisfaction problems

Abstract: Trees have played a key role in the study of constraint satisfaction problems because problems with tree structure can be solved efficiently. It is shown here that a family of generalized trees, k-trees, can offer increasing representational complexity for constraint satisfaction problems, while maintaining a bound on computational complexity linear in the number of variables and exponential in k. Additional results are obtained for larger classes of graphs known as partial k-trees. These methods may be helpful even when the original problem does not have k-tree or partial k-tree structure. Specific tradeoffs are suggested between representational power and computational complexity.

Morphology development of polymeric microparticles in aqueous dispersions. I. Thermodynamic considerations

Abstract: A thermodynamic analysis of polymer particle morphology highlights the role of interfacial tensions in controlling particle structure. The influence of the surfactant and the nature of the incompatible polymers is seen through their individual and collective effects upon these interfacial tensions. It has been found that by simply changing the type of surfactant used in the emulsion the particle morphology can change from core-shell to hemispherical, in agreement with thermodynamic predictions. Several apparently different morphologies (hemispherical, sandwich, multiple lobes) have been found to coexist at the same time within a single emulsion, suggesting that they may be simply different states of phase separation and not thermodynamically stable, unique morphologies. The thermodynamic analyses are independent of particle size and method of emulsion processing. Experimental evidence shows that the morphology of particles formed via in situ polymerization (as in a synthetic latex) is controlled by interfacial tensions in the same manner as those particles formed via solvent evaporation from a solution of an incompatible polymer pair (as in an artificial latex or microencapsulation).

The momentum of human behavior in a natural setting.

Abstract: Adults with mental retardation in a group home received popcorn or coffee reinforcers for sorting plastic dinnerware. In Part 1 of the experiment, reinforcers were dispensed according to a variable-interval 60-s schedule for sorting dinnerware of one color and according to a variable-interval 240-s schedule for sorting dinnerware of a different color in successive components of a multiple schedule. Sorting rates were similar in baseline, but when a video program was shown concurrently, sorting of dinnerware was more resistant to distraction when correlated with a higher rate of reinforcement. In Part 2 of the experiment, popcorn or coffee reinforcers were contingent upon sorting both colors of dinnerware according to variable-interval 60-s schedules, but additional reinforcers were given independently of sorting according to a variable-time 30-s schedule during one dinnerware-color component. Baseline sorting rate was lower but resistance to distraction by the video program was greater in the component with additional variable-time reinforcers. These results demonstrate that resistance to distraction depends on the rate of reinforcers obtained in the presence of component stimuli but is independent of baseline response rates and response-reinforcer contingencies. Moreover, these results are similar to those obtained in laboratory studies with pigeons, demonstrating that the determination of resistance to change by stimulus-reinforcer relations is not confined to controlled laboratory settings or unique to the pigeon.

Compounds in the droplets of the orb spider's viscid spiral

Abstract: THE orb web of the garden spider Araneus diadematus, like those of other ecribellate orb spiders, relies on the remarkable extensibility of its sticky capture spiral to intercept and entrap prey1,2. The spiral strands consist of core fibres and an all-enveloping aqueous coat, which forms into a pattern of droplets3. The core fibres are paired and probably made of typical spider silk4,5. The aqueous solution droplets are more or less evenly spaced6 and are required to allow the special mode of extension of the fibres3,7. Knowledge of the chemical composition and general physical properties of this liquid phase is necessary to understand its function in web mechanics and prey capture8. We have now investigated the chemical composition of this aqueous solution and found the droplets to be a concentrated solution of hygroscopic substances related to neurotransmitters. We offer an explanation as to the function and origin of this solution.

Total charge and mass changing cross sections of relativistic nuclei in hydrogen, helium, and carbon targets.

Abstract: This is the first in a series of papers describing the results of a systematic study of total, elemental, and isotopic cross sections measured in hydrogen, helium, and carbon targets. These fragmentation studies are based on measurements using 42 beams of 12 separate nuclei from $^{12}\mathrm{C}$ to $^{58}\mathrm{Ni}$. This has resulted in the measurement of more than 100 secondary elemental cross sections and over 300 secondary isotopic cross sections in addition to the total charge changing and mass changing cross sections reported in this paper. These measurements have been made at energies from 300 to 1700 MeV/nucleon and include ten separate energies for $^{56}\mathrm{Fe}$, for example. The measurements have been made with the objective of interpreting the production of secondary nuclei during cosmic-ray propagation in the galaxy in order to better estimate the source elemental and isotopic composition of cosmic rays. At the same time they provide a valuable data base for nuclear physics and the understanding of peripheral interactions of energetic heavy nuclei. In the work reported in this paper \ensuremath{\sim}100 total charge changing and mass changing cross sections have been measured for various targets and energies. The mass changing cross sections we measure are found to agree with earlier cross section measurements using energetic protons incident on targets composed of heavier elements to within \ensuremath{\sim}2% in cases where a comparison can be made. The systematics of this new data set are described and a new, more accurate cross section formula is presented and discussed.

Recent increase in nitrate concentration of Antarctic snow

Abstract: POLAR ice cores provide a unique record of global climate change. In particular, their records of nitrate concentration can yield new insight into the atmospheric nitrogen cycle, but first it is necessary to understand the processes controlling the spatial distribution of nitrate at the ice-sheet surface, and to define any trends in its temporal distribution. Here we report trends in the nitrate time series deduced from low-accumulation sites such as Dome C and Vostok in Antarctica. These trends must be treated with caution because of the possibility of post-depositional alteration. But the increases in the concentration of the spring maximum in nitrate that we find in the South Pole record for the past few years deserve careful consideration, as they may be a result of denitrification of polar stratospheric clouds in the lower stratosphere and may hence be connected in some way with the Antarctic ozone 'hole'.

Individual isotopic fragmentation cross sections of relativistic nuclei in hydrogen, helium, and carbon targets

Abstract: In this paper, the third in a series of papers, we discuss isotopic fragmentation cross sections measured in hydrogen, helium, and carbon targets. Over 300 of these cross sections have been measured in 24 separate runs using 12 charges from $^{12}\mathrm{C}$ to $^{58}\mathrm{Ni}$. Most of these isotope cross sections were measured at an energy \ensuremath{\sim}600 MeV/nucleon, however, some measurements of the $^{56}\mathrm{Fe}$ fragmentation are available at an energy \ensuremath{\gtrsim}1 GeV/nucleon. We observe, comparing both these data and other data, that to first order, the mass fractions for each isotope are essentially independent of energy. This indicates that the energy dependence of the isotopic cross sections is essentially the same as for the charge changing cross sections. It is also observed that the isotopic mass fractions and the width of the mass distributions for each charge are essentially independent of the H, He, and C targets involved. These systematics greatly simplify the construction of a semiempirical formula to describe these cross sections. New isotopic cross sections are presented for a number of interesting reactions, $^{12}$C\ensuremath{\rightarrow}Be, $^{16}$O\ensuremath{\rightarrow}N, $^{27}$Al\ensuremath{\rightarrow}Na, and $^{56}\mathrm{Fe}$ into Mn and Ar among others. A large body of new data on proton and neutron stripping reactions are also presented and discussed.

Disaggregation methods to expedite product line forecasting

Abstract: This paper addresses the issue of forecasting individual items within a product line; where each line includes several independent but closely related products. The purpose of the research was to reduce the overall forecasting burden by developing and assessing schemes of disaggregating forecasts of a total product line to the related individual items. Measures were developed to determine appropriate disaggregated methodologies and to compare the forecast accuracy of individual product forecasts versus disaggregated totals. Several of the procedures used were based upon extensions of the combination of forecast research and applied to disaggregations of total forecasts of product lines. The objective was to identify situations when it was advantageous to produce disaggregated forecasts, and if advantageous, which method of disaggregation to utilize. This involved identification of the general conceptual characteristics within a set of product line data that might cause a disaggregation method to produce relatively accurate forecasts. These conceptual characteristics provided guidelines for forecasters on how to select a disaggregation method and under what conditions a particular method is applicable.

The CCR4 gene from Saccharomyces cerevisiae is required for both nonfermentative and spt-mediated gene expression.

Abstract: Mutations in the yeast CCR4 gene inhibit expression of the glucose-repressible alcohol dehydrogenase (ADH2), as well as other nonfermentative genes, and suppress increased ADH2 expression caused by the cre1 and cre2 alleles. Both the cre1 and ccr4 alleles were shown to affect ADH II enzyme activity by altering the levels of ADH2 mRNA. Mutations in either CRE1 or CRE2 bypassed the inhibition of ADH2 expression caused by delta insertions at the ADH2 promoter which displace the ADH2 activation sequences 336 bp upstream of the TATA element. These cre1 and cre2 effects were suppressible by the ccr4 allele. The cre1 and ccr4 mutations also affected ADH2 expression when all the ADH2 regulatory sequences upstream of the TATA element were deleted. The relationship of the CRE genes to the SPT genes, which when mutated are capable of bypassing the inhibition of HIS4 expression caused by a delta promoter insertion (his4-912 delta allele), was examined. Both the cre1 and cre2 mutations allowed his4-912 delta expression. ccr4 mutations were able to suppress the ability of the cre alleles to increase his4-912 delta expression. CRE2 was shown to be allelic to the SPT6 gene, and CRE1 was found to be allelic to SPT10. We suggest that the CRE genes comprise a general transcriptional control system in yeast that requires the function of the CCR4 gene.

Recruitment of marine species: Is the bandwagon rolling in the right direction?

Abstract: A highly variable rate of recruitment from pelagic larval to demersal or sessile juvenile and adult stage is characteristic of marine organisms. At present it is a major subject of attention by ecologists interested in population or community processes. Several factors conspire to ensure this variability, but in studying them it will be important to focus on the behavioral capabilities of marine larvae, and on the very small proportion of (perhaps lucky) larvae destined to be successful.

Individual charge changing fragmentation cross-sections of relativistic nuclei in hydrogen, helium, and carbon targets

Abstract: In this paper we describe individual elemental cross sections. Over 100 of these cross sections have been measured by studying the fragmentation of beams of 12 charges ranging from $^{12}\mathrm{C}$ to $^{58}\mathrm{Ni}$ in hydrogen, helium, and carbon targets. The energies of the beams ranged from \ensuremath{\sim}300 to 1700 MeV/nucleon. The relative cross sections in hydrogen, helium, and carbon targets are examined as a function of both beam charge and energy. Limits are placed on the energy region in which the concept of factorization or scaling of cross sections for different beam charges and targets applies. The approach of these elemental cross sections to the asymptotic high-energy values is examined as a function of the beam charge and the charge change. The systematics of the energy dependence of these cross sections is also described in terms of the beam charge and the charge change. Another important systematic in our data is a regular decrease in the elemental cross sections into a particular charge, ${Z}_{f}$, with increasing charge change at a constant energy. It is found that this regular behavior of the cross sections follows a simple exponential law in the charge change, ${Z}_{B}$-${Z}_{f}$. This has important implications for constructing an empirical formula to describe these cross sections, as well as having theoretical implications.

Formula for calculating partial cross-sections for nuclear reactions of nuclei with E >= 200-MeV/nucleon in hydrogen targets

Abstract: In this paper we describe a new formula for calculating the partial cross sections for the production of secondary fragments with energy \ensuremath{\gtrsim}200 MeV/nucleon in hydrogen targets. This formula and the systematics of these cross sections are based on fragmentation studies using 42 beams of 12 separate nuclei between Z=6 and 28. This has resulted in the measurement of more than 100 secondary elemental cross sections and over 300 secondary isotopic cross sections. The systematics of these cross sections allow us to write the cross section formula as a product of three essentially independent terms, one which describes the elemental cross sections, another the isotopic cross sections, and a third term describing the energy dependence. Overall, this formula, which is considerably simpler than earlier semiempirical formulations, is able to predict the cross sections in hydrogen for Z=4--28, A=7--60 nuclei above \ensuremath{\sim}200 MeV/nucleon to an accuracy \ensuremath{\sim}10% or better---a substantial improvement over earlier formulations.

Antecedent retrieval processes.

Abstract: In three experiments we examined the nature of the search for antecedents during reading. Subjects read passages that contained two possible antecedents: one appearing early in the passages and the other appearing late. The degree of elaboration was varied, with one antecedent receiving additional elaboration for half the passages and the other antecedent receiving additional elaboration for the remaining half. Reading time differences from the first two experiments demonstrated that late antecedents are reinstated more quickly than early antecedents and elaborated antecedents are reinstated more quickly than nonelaborated antecedents. Experiment 1 showed that concepts that fall in the path of an antecedent search can be activated by the search. Experiments 2 and 3 showed that this activation is restricted to concepts that are from the same general category as the target antecedent.

Stereophonic and surface sound generation for exploratory data analysis

Abstract: The analysis and interpretation of very high dimensional data require the development and use of data presentation techniques that harness human perceptual powers. The University of Lowell's Exploratory Visualization project (Exvis) aims at designing, implementing, and evaluating perceptually-based tools for data presentation using both visual and auditory domains. This paper describes several auditory data presentation techniques, including the generation of stereophonic sound with apparent depth and sound that appears to emanate from a two-dimensional area. Both approaches can produce sound with auditory texture.

Spectral peak verification and recognition using a multilayered neural network.

Abstract: The verification and recognition of peak-shaped signals in analytical data are ubiquitous scientific problems. Experimental data contain overlapping signals and noise, which make sensitive and reliable peak recognition difficult. A peak detection system based on a class of neural networks known as "multilayered perceptrons" has been created. The network was trained and evaluated with use of vapor-phase infrared spectral data. The results of varying the network architecture on system training and prediction performance along with refinement of the form of the input pattern are presented.

Comparison between two vegetation indices for measuring different types of forest damage in the north-eastern United States

Abstract: The relative effectiveness of the Landsat TM-derived normalized difference vegetative index (NDVI) and the short-wave IR to NIR ratio (SWIR/NIR) index was examined in measurements of different types of damage in several forest communities. The forests examined included a site with well-defined fir waves in New Hampshire, a site undergoing well-documented coniferous forest decline in Vermont, and predominantly deciduous regions in Vermont and northwestern Massachusetts seriously impacted by pear thrips. Both NDVI and SWIR/NIR images were produced for each area. Results demonstrated that the SWIR/NIR index was superior to NDVI in distinguishing between high and low conifer damage at both fir-wave and forest decline sites; high and low deciduous-forest damage sites were easily separable using either NDVI or SWIR/NIR, but the NDVI was superior in separation between medium and low deciduous damage.

A knowledge-based approach to design for manufacturability

Abstract: In the light of growing global competition, organizations are increasingly under pressure to produce products of high quality and reliability at reasonable cost. The integration of design and manufacturing activities into one common engineering effort has been recognized as a key strategy for survival and growth. Design for Manufacturability (DFM) aims at integrating product design and process design to achieve cost and quality objectives. The implementation of the DFM approach requires the collaboration of both the design and manufacturing functions within an organization. However, due to the divergent orientations of these functions, implementation of the DFM approach has been found to be neither straightforward nor easy. Of the several methodologies available, process-driven design is recognized as one of the more effective DFM approaches. The primary objective of this research is to address the major criteria for manufacturability in the DFM approach using expert systems methodology. An expert system has been developed in two modules--one for process selection and manufacturing cost estimation and the other for evaluation of design features for manufacturability on a CAD system. The expertise for primary process selection is developed for casting and forging processes. The specialized processes considered are die casting, investment casting, sand casting, precision forging, conventional die forging, and open die forging. The processes considered for secondary process selection are end milling and drilling. The cost estimation expertise is developed for the die casting process, milling and drilling operations, and manual assembly operations. A design for a hanger used in the furniture industry is used to demonstrate the process selection and cost estimation capability of the expert system. Three different solid models created in CATIA are used to demonstrate evaluation of design features for manufacturability with respect to milling and drilling operations on a CNC milling machine. The set of manufacturability criteria considered are: (1) perpendicularity of holes to drill entry and exit surfaces, (2) conformance of hole diameters to available standard tool sizes, (3) compatibility of hole depths with respect to hole diameters, (4) adjacency of holes lying on the same surface, (5) rounded inside corners instead of sharp corners in square holes, and (6) chamfered corners instead of rounded external corners. The results obtained from the application of the expert system suggest that the use of a knowledge-based approach to generate accurate cost estimates and analyze design features for manufacturability during the design phase is certainly feasible. Such systems would enhance the quality of design decisions in organizations, resulting in improved competitiveness in the market.

Changing relationships between testis size, Sertoli cell number and spermatogenesis in Sprague-Dawley rats.

Abstract: Relationships between several reproductive characteristics were investigated in 25 Sprague-Dawley rats aged 60, 150, and 240 days (n = 75). Daily sperm production correlated with body weight (r = 0.63), paired testes weight (r = 0.68), testes weight as a percentage of body weight (r = -0.50), the number of spermatids supported per Sertoli cell (r = 0.51) and the number of Sertoli cells per gram (r = 0.89) or per testis (r = 0.95) among rats pooled across age groups. In general, the number and magnitude of significant coefficients of correlation were decreased when calculated within age groups. The latter often appeared to reflect a statistical consequence of relative homogeneity among rats rather than the absence of a biological relationship. However, the total number of Sertoli cells per testis correlated with daily sperm production within age groups, and could account for 85 to 94% of the variability in sperm production at 150 and 240 days, respectively.