Showing papers by "Clarkson University published in 1989"

Carbon and nitrogen dynamics along the decay continuum: Plant litter to soil organic matter

Abstract: Decay processes in an ecosystem can be thought of as a continuum beginning with the input of plant litter and leading to the formation of soil organic matter. As an example of this continuum, we review a 77-month study of the decay of red pine (Pinus resinosa Ait.) needle litter. We tracked the changes in C chemistry and the N pool in red pine (Pinus resinosa Ait.) needle litter during the 77-month period using standard chemical techniques and stable isotope analyses of C and N.

Motion planning in a plane using generalized Voronoi diagrams

Abstract: An algorithm for planning a collision-free path for a rectangle in a planar workspace populated with polygonal obstacles is presented. Heuristic techniques are used to plan the motion along a nominal path obtained from a generalized Voronoi diagram (GVD). The algorithm was demonstrated to be quite fast with execution times comparable to, or exceeding, those of the freeway method. Unlike the freeway method, the GVD technique can be successfully applied to difficult problems which arise in cluttered workspaces. The planned paths stay well away from the obstacles when possible and are somewhat shorter than the freeway paths due to parabolic arcs around corners. Furthermore, motion along the paths is smooth in the sense that rotations are performed during translation, not just at isolated points in the workspace. >

Coherent structures in multidimensions.

Abstract: We solve an initial-boundary value problem for the Davey-Stewartson equation, a multidimensional analog of the nonlinear Schr\"odinger equation. It is shown that for large time, an arbitrary initial disturbance will, in general, decompose into a number of two-dimensional coherent structures. These structures exhibit interesting novel features not found in one-dimensional solitons.

Production of phenol oxidases and peroxidases by wood-rotting fungi

Abstract: Quantitative studies of extracellular phenol oxidase and peroxidase production by eight species of wood-rotting fungi were performed. Coriolus versicolor, Phellinus igniarius and Lycoperdon sp. exh...

Temporal changes in colony cuticular hydrocarbon patterns ofSolenopsis invicta : Implications for nestmate recognition.

Abstract: Heritable cuticular hydrocarbon patterns ofSolenopsis invicta workers are consistent within colonies for a given sampling time but vary sufficiently from colony to colony to distinguish the colonies from each other. In addition, cuticular hydrocarbon patterns change within colonies over time. Nestmate recognition cues found on the individual's cuticle, can be from heritable or environmental sources, and are a subset of colony odor. The cuticular hydrocarbons can be used as a model for heritable nestmate recognition cues. We propose that because potential nestmate recognition cues, both environmental and genetic, are dynamic in nature rather than static, during its lifetime a worker must continually update its perception (template) of colony odor and nestmate recognition cues.

Numerically induced chaos in the nonlinear Schrödinger equation.

Abstract: The cubic nonlinear Schr\"odinger equation and some of its discretizations, one of which is integ- rable, are studied. Apart from the integrable version the discretizations produce chaotic solutions for intermediate levels of mesh (mode) refinement. Chaos disappears when the discretization is fine enough and convergence to a quasiperiodic solution is obtained. Details are given for finite difference calculations, although similar results are also obtained by Fourier spectral methods. Results regarding a forced nonlinear Schr\"odinger equation are briefly described.

On the conductivity of phosphoric acid electrolyte

Abstract: The specific electric conductivity and viscosity of 7.5–100 wt% aqueous phosphoric acid electrolyte have been measured in the temperature range 25–200°C. The product of conductivity and viscosity was found to decrease exponentially with increasing temperature. This suggests that the electric conduction in phosphoric acid follows the Grotthus proton switching mechanism. The measured conductivity data were correlated by the following empirical equation: $$\begin{array}{*{20}c} {k\mu = {\rm A} exp [BT]}\\ {A = 702.7X^{1.5} - 1734.2X^2 + 1446.5X^{2.5} - 350.7X^3 }\\ {B = - 0.010163 + 0.011634X - 0.08313X^2 }\\ \end{array}$$ wherek is conductivity in mho cm−1; μ is viscosity in centipoise;T is the absolute temperature in K; andX is mole fraction of phosphoric acid in the electrolyte. The standard deviation for the percentage difference between the calculated and experimental values of 188 data points was less than 7.5%.

An experiment investigating the application of clustering procedures and similarity coefficients to the GT machine cell formation problem

Abstract: This paper reports the development of a number of similarity-based coefficients designed for applying hierarchical cluster analysis to the group technology machine cell formation problem. The paper also discusses an experimental investigation applying these and other well-known similarity coefficients in conjunction with some well-known clustering algorithms. The mixture model experimental approach is used for the investigation. A number of problems were generated via simulation, randomly ‘mixed’ to hide the original cellular structure, and the clustering techniques applied. Extensions of prior research include the development of new similarity coefficients, their comparative evaluation, and the incorporation of the concept of part ‘weighting’ into the cluster analysis, and hence, cell formation

A comparative study of performances of various base isolation systems, part I: Shear beam structures

Abstract: A comparative study of performances of different base isolators for shear beam type structures is carried out. Several leading base isolation systems, including the laminated rubber bearing with and without lead plug, the resilient-friction base isolator with and without sliding upper plate, and the EDF system are considered. Displacement and acceleration response spectra for a shear beam structure subject to the accelerograms of the N00W component of El Centro 1940 and the N90W component of Mexico City 1985 earthquakes and their magnified forms are evaluated. A series of parametric studies is carried out and advantages and disadvantages of various base isolation systems are identified. Comparisons of the results with the response spectra of a fixed-base structure show that the base isolation systems are, in general, highly effective in reducing the peak acceleration transmitted to the superstructure. Thus, the deflections and stresses generated in a base-isolated structure are significantly lower than those of a fixed-base one. Furthermore, the results of the study also show that the friction-type base isolators are less sensitive to severe variations in frequency content and amplitude of the ground acceleration.

Quasi-static typing

Abstract: We present a new approach to dynamic typing in a static framework. Our main innovation is the use of structural subtyping for dynamic types based on the idea that possible dynamic typing as a property should be inherited by objects of all types. Two properties of our system set it apart from existing systems which combine static and dynamic typing: all tagging and checking takes place via implicit coercions, and the semantics of dynamic typing is representation independent. The latter property leads to a significant increase in expressive power—for instance it allows us to define a general call-by-value fixpoint operator.The resulting system—which we call quasi-static typing—is a seamless merger of static and dynamic typing. The system divides programs into three categories: well-typed, ill-typed and ambivalent programs. Ill-typed programs contain expressions that are guaranteed to go wrong. Run-time checking is limited to doubtful function applications in ambivalent programs. Conceptually, quasi-static typing takes place in an unusual two-phase process—a first phase infers types and coercions and a second plausibility checking phase identifies ill-typed programs. The typing rules allow minimal typing judgements and plausibility checking can be characterized as simplification via a canonical set of rewrite rules. The two phase process can therefore be implemented with a one pass algorithm.

Fine Particles: Science and Technology

Abstract: Some readers may wonder about the reasons for having two issues focus on fine particles. Hopefully, this introduction and the articles to follow will offer the necessary justification.It is fully expected by everybody, professional or laie, that the properties of matter will change if its chemical composition is altered. It is less frequently recognized that many characteristics of materials can be dramatically affected by varying dimensions, yet countless examples in everyday life clearly demonstrate such phenomena. Consider water in droplet form. Driving in rain creates little problem, providing the car has working windshield wipers. In contrast fog, which consists of droplets of much smaller size, represents one of the major hazards in transportation. Obviously, the optical properties of the same matter have greatly altered with diminution. In another example, it is well known that finely dispersed carbon is an excellent adsorbent, a property used in gas masks and in many industries as a purifying agent. Large-sized lumps of such carbon would be useless in these applications.The effect of particle size on properties of materials can be readily understood from a simple consideration. The total energy of any System, (Etot), consists of two contributions, the internai energy, Ei, and the surface energy, Ei.

Three-dimensional transient model for arc welding process

Abstract: A direct computer simulation technique, discrete element analysis (DEA), was utilized in the development of a transient multidimensional (2-D and 3-D) mathematical model for investi-gating coupled conduction and convection heat transfer problems associated with stationary and moving arc welding processes. The mathematical formulation considers buoyancy, electro-magnetic, and surface tension driving forces in the solution of the overall heat transfer conditions in the specimen. Furthermore, the formulation of the model allows realistic consideration of the geometrical variations in the workpiece. The model treats the -weld pool surface as a truly deformable free surface, allowing for the prediction of the weld surface deformations such as the “weld crown.≓ A marked element formulation was employed to monitor the transient de-velopment of the weld pool as determined by the latent heat considerations and the calculated velocities in the weld pool. The model was utilized to simulate the heat and fluid flows in the weld pool that occur during stationary (spot) and moving (linear) gas tungsten-arc welding. Also, the present analysis considers a simple rectangular specimen and a geometrically complex specimen to demonstrate the capability of the model to simulate realistic 3-D arc welding prob-lems. The results of the present investigation clearly demonstrate the significant influence of the heat and fluid flows and the specimen geometry on the development of the weld. Comparison of the predicted and the experimentally observed fusion zone and heat-affected zone (HAZ) geometries indicate good agreement.

Estimation of Stable-Law Parameters: A Comparative Study

Abstract: The stable distribution has many desirable properties and is applicable in many areas of scientific pursuit (e.g., the study of stock-return behavior). Despite this, little is known about the properties of the various extant estimation techniques for the parameters of the stable laws. This article compares the iterative regression technique with the latest version of the fractile technique, using both simulated and actual data.

Comparison Study Of Nonlinear Filters In Image Processing Applications

Abstract: Nonlinear filters are used in many applications, including speech and image processing, owing to their ability to suppress noise and preserve signal features such as edges. This study presents a performance evaluation of non-linear filters derived from the robust point estimation theory. The first part of the work is a classification of various approaches to nonlinear filtering into three types of estimators according to the process of the filter. The second part is a computer implementation and evaluation of all of the filters discussed. Finally, a summary of experimental results is presented.

Time scale decomposition of a class of generalized stochastic Petri net models

Abstract: A time-scale decomposition (TSD) algorithm of a class of generalized stochastic Petri net (GSPN) models of systems comprising activities whose duration differ by orders of magnitude is presented. The GSPN model of a system can be decomposed into a hierarchical sequence of aggregated subnets, each of which is valid at a certain time scale. These smaller subnets are solved in isolation and their solutions are combined to get the solution of the whole system. A degradable multiprocessor system which would be intractable using conventional techniques, is analyzed using TSD. The complexity of the TSD algorithm can be orders of magnitude smaller without any significant loss in the accuracy of the result. In general, the error due to aggregation is proportional to the maximum degree of coupling between aggregates. An expression of the error due to aggregation is also given in terms of the ratio of fast and slow transitions in the GSPN model. The algorithm is easy to use and can be easily automated. >

A new mutation at the period locus of drosophila melanogaster with some novel effects on circadian rhythms

Abstract: A new period mutation has been induced and characterized in D. melanogaster. It causes flies to be apparently arrhythmic in tests of locomotor activity and thus is superficially similar to the original per01 mutant. Yet, the new "zero" allele, per04, has some novel properties and effects: Behaviorally, per04 adults often exhibit weak, long-period rhythms of locomotor activity in constant darkness; this low-frequency rhythmicity usually was not obvious in the analog behavioral records but was readily revealed by spectral analyses. These treatments of the data also extracted hidden high-frequency (ultradian) rhythms in many of the behavioral records, of the type associated with per01 and other per-nulls. The wide range of periodicities exhibited by different per04-expressing flies implies the expression of multiple oscillatory modes by this mutant. The new mutation also leads to a tendency for flies to be hyperactive during activity monitoring and is thus dissimilar to the other arrhythmic variants in the per gene but similar to the effects of a deletion of the locus. During light:dark cycling, per04 adults once more behave differently from other per0's and in fact tend to resemble wild-type flies in these conditions. The new mutation is not caused by the same nucleotide substitution that created a stop codon in the original arrhythmic per mutant and, as it turns out, per02 and per03 as well. per04 is also not a null variant at the transcriptional level; but it leads to an anomalous form of per mRNA, which is smaller than the normal 4.5 kb species encoded by this clock gene.

Current conveyors, operational amplifiers and nullors

Abstract: Nullors are used to provide a common framework for considering both current-conveyor and operational-amplifier circuits. A condition is established under which a current-conveyor circuit and an op-amp circuit can be said to be equivalent. A procedure is given for generating equivalent op-amp and current-conveyor circuits from a given op-amp (current-conveyor) circuit.

Summation of probabilistic harmonic vectors (power systems)

Abstract: A method of determining the magnitude of the sum of random harmonic vectors of arbitrary probability characteristics is presented. Utilization of summation technique, in conjunction with harmonic load flow, to evaluate net harmonic magnitudes due to distributed sources in both deterministic and stochastic networks is discussed. It is demonstrated and stochastic networks is discussed. It is demonstrated that the widely used form of probability density function of the magnitude of the sum of random vectors arises from simplification of the general expressions developed here. To assess its validity, a comparative study between the method developed and Monte Carlo simulation is carried out, showing good agreement. However, the analytical method is a lot faster and provides closed-form expressions for the probability density characteristics of the sum of random vectors. >

Diffusion-limited coagulation in the presence of particle input: Exact results in one dimension.

Abstract: We solve the diffusion-limited single-species coagulation process (A+A\ensuremath{\rightarrow}A) with random particle input in one spatial dimension. We derive the exact time-dependent concentration, the spectrum of relaxation rates, and the distribution of interparticle distances in the nonequilibrium steady state. These results imply an interesting microscopic spatial structure induced by the nonequilibrium constraints. The validity of rate-equation descriptions of the macroscopic statics and kinetics is investigated, and we compare our results to the closely related single-species annihilation process (A+A\ensuremath{\rightarrow}inert) in the presence of input.

Transition in the relaxation dynamics of a reversible diffusion-limited reaction.

Abstract: The reversible one-species diffusion-limited reaction X+X\ensuremath{\rightleftarrows}X is solved exactly in one dimension. We find that the asymptotic approach to equilibrium exhibits a sharp (second-order-type) transition depending on the initial density ${\ensuremath{\rho}}_{0}$. The exponential relaxation time becomes infinitely long as ${\ensuremath{\rho}}_{0}$\ensuremath{\rightarrow}0. .AE

Interpersonal Conflict in Collaborative Writing: What We Can Learn from Gender Studies

Abstract: Gender-studies scholars describe the ways relationships within the family in fluence the gender identity of males and females, while composition special ists study the social nature of writing. In the areas of self-disclosure, control, trust, perceptions ofgroup and ofconflict, congruence, and reward, these gen der roles affect the abilities of men and women to collaborate successfully and determine their responses to interpersonal conflict. Through classroom activi ties and journal keeping, students can learn the limits ofgender roles and have access to a full range of collaborative strategies.

Mel'nikov's function for two-dimensional mappings

Abstract: This paper calculates explicitly the Mel’nikoV function for general perturbations of two-dimensional maps possessing a saddle connection. This result may be considered as the discrete analogue of Ziglin’s calculation of the Mel’nikoV function for time-periodic perturbations of two-dimensional continuous flows.Key words. integrable planar maps, perturbations, homoclinic orbits, Mel'nikoV's function, Poisson summation formula

Forced Nonlinear Evolution Equations and the Inverse Scattering Transform

Abstract: On considere les equations de Korteweg-De Vries et de Schrodinger non lineaire avec un forcage externe de type distribution. On trouve que le coefficient de reflexion satisfait une equation non lineaire d'une forme caracteristique qui apparait aussi dans le probleme semi-infini