Showing papers by "Rensselaer Polytechnic Institute published in 1983"

Nonlinear Oscillations, Dynamical Systems, and Bifurcations of Vector Fields

Abstract: Contents: Introduction: Differential Equations and Dynamical Systems.- An Introduction to Chaos: Four Examples.- Local Bifurcations.- Averaging and Perturbation from a Geometric Viewpoint.- Hyperbolic Sets, Sympolic Dynamics, and Strange Attractors.- Global Bifurcations.- Local Codimension Two Bifurcations of Flows.- Appendix: Suggestions for Further Reading. Postscript Added at Second Printing. Glossary. References. Index.

The Laplacian Pyramid as a Compact Image Code

Abstract: We describe a technique for image encoding in which local operators of many scales but identical shape serve as the basis functions. The representation differs from established techniques in that the code elements are localized in spatial frequency as well as in space. Pixel-to-pixel correlations are first removed by subtracting a lowpass filtered copy of the image from the image itself. The result is a net data compression since the difference, or error, image has low variance and entropy, and the low-pass filtered image may represented at reduced sample density. Further data compression is achieved by quantizing the difference image. These steps are then repeated to compress the low-pass image. Iteration of the process at appropriately expanded scales generates a pyramid data structure. The encoding process is equivalent to sampling the image with Laplacian operators of many scales. Thus, the code tends to enhance salient image features. A further advantage of the present code is that it is well suited for many image analysis tasks as well as for image compression. Fast algorithms are described for coding and decoding.

Admissibility criteria for propagating phase boundaries in a van der Waals fluid

Abstract: : This paper gives admissibility criteria for weak solutions to the partial differential equations governing isothermal motion of a van der Waals fluid. The main issue is that an admissibility criterion based on viscosity alone is too restrictive - it rules out all slowly propagating phase boundaries. Instead a criterion based on viscosity and capillarity is proposed. The viscosity-capillarity condition is studied and shown to imply that the state on one side of a phase boundary specifies both the speed of the phase boundary and the state of the other side of the phase boundary (a result which is different from classical gas dynamics).

Kinetics of zircon dissolution and zirconium diffusion in granitic melts of variable water content

Abstract: The experimental dissolution of zircon into a zircon-undersaturated felsic melt of variable water content at high pressure in the temperature range 1,020° to 1,500° C provides information related to 1) the solubility of zircon, 2) the diffusion kinetics of Zr in an obsidian melt, and 3) the rate of zircon dissolution. Zirconium concentration profiles observed by electron microprobe in the obsidian glass adjacent to a large, polished zircon face provide sufficient information to calculate model diffusion coefficients. Results of dissolution experiments conducted in the virtual absence of water (<0.2% H2O) yield an activation energy (E) for Zr transport in a melt ofM=1.3 [whereM is the cation ratio (Na+K+2Ca)/(Al·Si)] of 97.7±2.8 kcal-mol−1, and a frequency factor (D 0) of 980 −580 +1,390 cm2-sec−1. Hydrothermal experiments provide an E=47.3±1.9 kcal-mol−1 andD 0=0.030 −0.015 +0.030 cm2-sec−1. Both of these results plot close to a previously defined diffusion compensation line for cations in obsidian. The diffusivity of Zr at 1,200° C increases by a factor of 100 over the first 2% of water introduced into the melt, but subsequently rises by only a factor of five to an apparent plateau value of ∼2×10−9 cm2-sec−1 by ∼6% total water content. The remarkable contrast between the wet and dry diffusivities, which limits the rate of zircon dissolution into granitic melt, indicates that a 50 μm diameter zircon crystal would dissolve in a 3 to 6% water-bearing melt at 750° C in about 100 years, but would require in excess of 200 Ma to dissolve in an equivalent dry system. From this calculation we conclude that zircon dissolution proceeds geologically instantaneously in an undersaturated, water-bearing granite. Estimates of zircon solubility in the obsidian melt in the temperature range of 1,020° C to 1,500° C confirm and extend an existing model of zircon solubility to these higher temperatures in hydrous melts. However, this model does not well describe zircon saturation behavior in systems with less than about 2% water.

A Modified Quadtree Approach To Finite Element Mesh Generation

Abstract: By allowing the use of quadrants with cut corners, this modeling technique overcomes some of the drawbacks of standard quadtree encoding for finite element mesh generation.

Intelligent robotic control

Abstract: A theoretical approach is developed to deal with man-machine interactive systems requiring advanced decision making in unpredictable environments. The hierarchical method consists of a three-layer control of "increasing intelligence and decreasing precision." The lowest level consists of several controllers designed for effective control with existing hardware using an approximation theory of optimal control. The next level is that of a coordinator which utilizes new computer architectures to effectively control the overall hardware system. The highest level is the organizer which supervises the performance of the overall system. Both highest levels are computer implemented and the research involved is in developing the appropriate architecture and software to accommodate others. The lowest level, aimed for end-point control tasks, is dominated by typical hardware control methods. The coexistence of the two approaches makes the method novel. Application of intelligent control techniques to robotics and manipulative systems is considered.

Deposition of GaAs Epitaxial Layers by Organometallic CVD Temperature and Orientation Dependence

Abstract: Epitaxial layers of have been grown in an atmospheric organometallic CVD system, for a wide variety of gas phase reactant partial pressures and over a broad range of temperature (450°–1050°C). The growth rates for (100), , (110), (11l)Ga, and (11l)As substrates are reported as functions of temperature and gas composition. Three distinct temperature dependent regions of growth are identified, corresponding to a mid‐temperature mass transport limited range, a low‐temperature kinetic controlled regime, and a high‐temperature desorption limited region. The growth rate is studied as a function of the growth parameters and substrate orientation, and is related to the decomposition of the two reactants trimethylgallium and arsine. A model for the epitaxial growth of by the organometallic process is proposed, based on these findings.

Kinetics of Crystallization of ZrF4‐Ba2‐LaF3 Glass by Differential Scanning Calorimetry

Abstract: The kinetics of devitrification in ZrF4-BaF2-LaF3 (62–33–5 mol %) glass were studied by isothermal and nonisothermal methods using differential scanning calorimetry. The crystallization reaction followed the Avrami equation, x=1-exp[—(kt)], where x is the fraction crystallized after time t. The rate con stant k obeyed an Arrhenius equation, k(s−1)=6.69 × 1021 exp The value of the Avrami exponent, n, bas 3.2×0.2, indicating three-dimensional crystal growth at a constant number of nucleation sites. Values of kinetics parame ters obtained from isothermal and nonisothermal techniques were in excellent agreement. The heat of crystallization measured from isothermal peaks was computed to be 38.5×3.5 J/g.

Secondary baby talk: judgments by institutionalized elderly and their caregivers.

Abstract: Elderly care receivers and their caregivers judged vocal nonverbal messages prepared from audiotapes of caregivers interacting with their co-workers and elderly nursing home residents. This study investigated the relationship between these judgments and, respectively, the functional ability of the aged judges and the expectations of the elderly held by the caregivers. The stimulus tape judged consisted of three types of messages: caregivers' speech to care receivers in baby talk, caregivers' speech to care receivers not in baby talk, and speech to other caregivers assumed to be in normal adult speech. For the elderly judges, lower functional ability scores were found to be associated with a greater liking for baby talk speech as compared to other speech, but no relationships were found for their judgments of "soothing" or "irritating." For caregivers, expectancy was associated with their predictions of elderly residents' liking for baby talk speech and caregivers' endorsements that adult speech would not be effective for interacting with care receivers. The pattern of results suggests that variations in caregiver expectancy may operate through a common social stereotype of the elderly.

Using Simultaneous Structures to Cope With Uncertainty

Abstract: The article discusses a study pertaining the corporate use of simultaneous structures in work units to cope with uncertainty. A work unit in this context refers to a supervisor and their subordinat...

Reaction of water with glass: influence of a transformed surface layer

Abstract: Profiles of hydrogen and glass constituents were measured by nuclear reaction techniques in a number of silicate glasses after hydration. The results were interpreted in terms of interdiffusion of alkali and hydronium ions, including the possibility of a transformed surface layer. Durable glasses such as a commercial soda-lime and caesium-alkali-lime glasses did not have a transformed layer, whereas less durable glasses, such as a soda-lime without alumina and a sodium-potassium-lime, did have a transformed surface layer. When a transformed layer is incorporated in the interdiffusion model, the diffusion coefficient of sodium calculated is the same as found in the dry glass.

Model Reference Adaptive Control of Large Structural Systems

Abstract: Attention is given to model reference adaptive control procedures that do not require explicit parameter identification for large structural systems. Even though such applications have been shown to be feasible for multivariable systems, provided there exists a feedback gain matrix that makes the resulting input/output transfer function strictly positive real, it is shown here that this constraint is overly restrictive and that only positive realness is required. Subsequent consideration of a simply supported beam reveals that if actuators and sensors are collocated, then the positive realness constraint will be satisfied and the model reference adaptive control will then indeed be suitable for velocity following when only velocity sensors are available and for both position and velocity following when velocity plus scaled position outputs are measured. For both cases, all states are guaranteed to be stable, regardless of system dimension.

Passive shock wave/boundary layer control for transonic airfoil drag reduction

Abstract: An investigation of the passive shock wave/boundary layer interaction control for reducing the drag in 12 percent thick circular arc and 14 percent thick supercritical airfoils was conducted in a 3 in. x 15.4 in. transonic wind tunnel at transonic Mach numbers. A porous surface with a cavity beneath it was positioned on the area of the airfoils, mounted on the test section bottom wall, where the shock wave occurs. The static pressure distributions over the airfoil, the wake impact pressure data for determining the profile drag, and the Schlieren photographs for porous surface airfoils are presented and compared with the results for solid surface airfoils. With the porous surface the normal shock wave for solid surface was changed to a lambda shock wave system, and the wake impact pressure data indicated an appreciable drag reduction for both airfoils with the porous surface at transonic speeds while causing little or no loss of lift. The effect of porosity and cavity size is investigated and off-design performance is discussed.

Fast algorithms for estimating local image properties

Abstract: A common task in image analysis is that of measuring image properties within local windows. Often usefulness of these property estimates is determined by characteristics of the windows themselves. Critical factors include the window size and shape, and the contribution the window makes to the cost of computation, A highly efficient procedure for computing property estimates within Gaussian-like windows is described. Estimates are obtained within windows of many sizes simultaneously.

Generic buckling curves for specially orthotropic rectangular plates

Abstract: Using a double affine transformation, the classical buckling equation for specially orthotropic plates and the corresponding virtual work theorem are presented in a particularly simple fashion. These dual representations are characterized by a single material constant, called the generalized rigidity ratio, whose range is predicted to be the closed interval from 0 to 1 (if this prediction is correct then the numerical results using a ratio greater than 1 in the specially orthotropic plate literature are incorrect); when natural boundary conditions are considered a generalized Poisson's ratio is introduced. Thus the buckling results are valid for any specially orthotropic material; hence the curves presented in the text are generic rather than specific. The solution trends are twofold; the buckling coefficients decrease with decreasing generalized rigidity ratio and, when applicable, they decrease with increasing generalized Poisson's ratio. Since the isotropic plate is one limiting case of the above analysis, it is also true that isotropic buckling coefficients decrease with increasing Poission's ratio.

Light-dependent assembly of ribulose-1,5-bisphosphate carboxylase

Abstract: Ribulose-1,5-bisphosphate carboxylase [RuP2Case; 3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] is composed of eight small subunits (Mr, 14,000) and eight large subunits (Mr, 55,000). Newly synthesized large subunits are associated with two complexes having sedimentation coefficients of 7 and 29 S. Assembly of RuP2Case occurs in isolated intact chloroplasts in the light but not in the dark. When extracts of chloroplasts are treated with ATP or GTP, RuP2Case assembly is accelerated while the 29S large subunit complex is maintained. In the presence of Mg2+, ATP brings about almost complete dissociation of the 29S complex, whereas GTP and a nonhydrolyzable analog of ATP are without effect. These results indicate the existence of a complex set of reactions involving nucleotides, Mg2+, and several putative intermediates in RuP2Case assembly. It is postulated that these reactions at least partly account for the light dependence of RuP2Case assembly. In particular, ATP and GTP promote the assembly of large subunits into RuP2Case.

Nature of the active site in surface-enhanced Raman scattering

Abstract: Experiments involving competitive and cooperative adsorption of pyridine, Cl/sup -/, SCN/sup -/, and Tl, and voltage-induced resonance shifting show that the largest surface-enhanced Raman scattering intensity comes from complexes of these species adsorbed on defects which cover less than 3% of the Ag surface. The resonance is attributed to charge transfer excitation from Ag to pyridine and from SCN/sup -/ to Ag which is communicated to all vibrations of the complex.

The viscosity-capillarity criterion for shocks and phase transitions

Abstract: This paper considers admissibility criteria for non-linear conservation laws based on (i) viscosity and (ii) capillarity and viscosity. It is shown by means of specific examples that while (ii) yields results consistent with experiment for materials exhibiting phase transitions,e.g. a van der Waals fluid, (i) does not.

Absorption from the Vagina

Abstract: PIP: Methods and results are reviewed of research on the permeability of the vagina to a wide variety of compounds including steroids, prostaglandins (PGs), antimicrobials, proteins, antigens, and hormones, nonoxynol-9, methadone, and inorganic compounds. Although the literature indicates that the vagina is capable of absorbing a wide variety of organic and inorganic compounds, quantitative data on the extent of absorption are often lacking. Most steroids were readily absorbed and their bioavailability after intravaginal instillation was greater than after oral administration because of a reduced first-pass effect. Natural and synthetic PGs were absorbed; the extent of absorption ranged from 10-43% of the dose. Penicillin and sulfanilamide exhibited extremely variable absorption from the vagina. In most women neither econazole, miconazole, nor clotrimazole were effectively absorbed. In 1943 it was demonstrated that proteins could be absorbed from the vagina. Data on human absorption of nonoxynol-9 are indirect but are consistent with absorption. Methadone, povidone-iodine, and potassium permanganate have also been shown to be absorbed through the vagina. The stage of the reproductive cycle may alter the extent of vaginal absorption, but this has been clearly demonstrated for only 1 substance in the rat.

Slow compressional wave propagation in wet human and bovine cortical bone.

Abstract: Ultrasonic wave propagation in bovine plexiform and human Haversian bone was studied in the range 0.5 to 15 megahertz. A new longitudinal wave was observed which traveled more slowly than the ordinary longitudinal wave. The slow wave was associated with the dynamics of fluid motion in the pores of bone.

Input Measurement and Productivity Growth in Japanese and U.S. Manufacturing

Abstract: This paper analyzes multifactor productivity growth (based on capital, labor, energy, and materials) and labor productivity growth in the Japanese and U.S. manufacturing sectors. We find that the tests of separability required for a value-added approach fail for both the U.S. and Japan, making gross output the correct approach.Additionally, confirming Jorgenson and Nishimizu, we find that the remarkable differences in productive efficiency between Japan and the U.S. — at the two-digit industry level — are largely due to differences in the levels of capital investment and not to differences in multifactor productivity.

Morphine and acceptability of putative reinforcers.

Abstract: Rats were given the opportunity to take one of five concentrations of saccharin solutions. Intake across concentrations generated a preference-aversion curve. Morphine, 2 mg/kg, increased intake of saccharin solutions when rats were 12-hr water deprived or were not deprived. These effects with morphine are opposite to those of naloxone and strengthen the idea that there is incentive motivation.