Showing papers by "Rensselaer Polytechnic Institute published in 1993"

Upon Opening the Black Box and Finding It Empty: Social Constructivism and the Philosophy of Technology:

Abstract: What do philosophers need to know about technology? What kind of knowledge do we need to have? And how much? Perhaps it is enough simply to have lived in a society in which a wide variety of technologies are in common use. Drawing upon an everyday understanding of such matters, one can move on to develop general perspectives and theories that may enable us to answer important questions about technology in general. The problem is that one's grasp may be superficial, failing to do justice to the phenomena one wants to explain and interpret. One may seize upon a limited range of vaguely understood examples of technical applications-a dam on a river, a robot in a factory, or some other typification-and try to wring universal implications from a sample that is perhaps too small to carry the weight placed upon it. An alternative would be to focus one's attention more carefully, becoming expert in the technical knowledge of a specific field, attaining the deeper understanding of, say, a worker, engineer, or technical professional. Even that may prove limiting, however, because the experience available in one field of practice may not be useful in comprehending the origins, character, and consequences of technical practices in other domains. The sheer multiplicity of technologies in modern society poses serious difficulties for anyone who seeks an overarching grasp of human experience in a technological society. Yet another strategy might be to study particular varieties of technology in a scholarly mode, drawing upon existing histories and contemporary social studies of technological change as one's base of understanding. And one

A morphological biosensor for mammalian cells

Abstract: An electrical biosensor is described that can continuously track morphological changes of adherent cells providing quantitative data from both sparse and confluent cultures. The method is capable of detecting vertical motion of cells of the order of 1 nm, much below the resolution of an optical microscope.

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part II—Transition and Turbulent Flows

Abstract: Thermal-hydraulic design correlations are developed to predict isothermal f and Nu for in-tube, turbulent flows with twisted-tape inserts. Experimental data taken for water and ethylene glycol are analyzed, and various mechanisms attributed to twisted tapes are identified. Tube blockage and tape-induced vortex mixing are the dominant phenomena that result in increased heat transfer and pressure drop; for loose- to snug-fitting tapes, the fin effects are insignificant. The limiting case of a straight tape insert correlates with the hydraulic-diameter-based smooth tube equation

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part I—Laminar Flows

Abstract: Laminar flow correlations for f and Nu m are developed based on experimental data for water and ethylene glycol, with tape inserts of three different twist ratios. The uniform wall temperature condition is considered, which typifies practical heat exchangers in the chemical and process industry. These and other available data are analyzed to devise flow regime maps that characterize twisted-tape effects in terms of the dominant enhancement mechanisms. Depending upon flow rates and tape geometry, the enhancement in heat transfer is due to the tube partitioning and flow flockage, longer flow path, and secondary fluid circulation; fin effects are found to be negligible is snug-to loose-fitting tapes

Coping with ambiguity and unknown words through probabilistic models

Abstract: From spring 1990 through fall 1991, we performed a battery of small experiments to test the effectiveness of supplementing knowledge-based techniques with probabilistic models. This paper reports our experiments in predicting parts of speech of highly ambiguous words, predicting the intended interpretation of an utterance when more than one interpretation satisfies all known syntactic and semantic constraints, and learning caseframe informationfor verbsfrom example uses.From these experiments, we are convinced that probabilistic models based on annotated corpora can effectively reduce the ambiguity in processing text and can be used to acquire lexical informationfrom a corpus, by supplementing knowledge-based techniques.Based on the results of those experiments, we have constructed a new natural language system (PLUM) for extracting data from text, e.g., newswire text.

Biomechanics of Diarthrodial Joints: A Review of Twenty Years of Progress

Abstract: A survey of some of the advances made over the past twenty years in understanding diarthrodial joint biomechanics is presented. Topics covered in this review include: biotribology (i.e., friction, lubrication and wear of diarthrodial joints); contact area determinations; stereophotogrammetric rendering of articular surfaces; deformational field analysis using canonical problems; and finite element formulations for both infinitesimal and finite deformations of biphasic materials and precise anatomic surfaces. Suggestions are made for future research directions as well.

Asteroid spectroscopy: Progress and perspectives

Abstract: A broad understanding of meteorite and asteroidal studies is needed for the most dynamic progress of both disciplines, in their common goal of understanding the origin and early evolution of the solar system. Asteroid compositional investigations are currently shifting from the survey mode to focused investigations of selected targets, in pursuit of specific problems. Attention is presently given the compositional nature and diversity of asteroid taxonomic classes, as addressed by the Small Main-Belt Asteroid Spectroscopic Survey.

Correlation between the Width of the Glass Transition Region and the Temperature Dependence of the Viscosity of High‐Tg Glasses

Abstract: A correlation exists between the width of the glass transition region measured using DTA or DSC during heating and the activation enthalpy ΔH η * for the shear viscosity of high-Tg inorganic glasses. This is demonstrated by the constancy of a dimensionless parameter C = (ΔH η * /R)(1/Tg − 1/Tg'), where Tg and Tg' are temperatures marking the extrapolated onset and finish of the transition region on the DTA or DSC trace. The logarithm of the shear viscosity at Tg, log η (Tg), is also approximately constant for high-Tg glasses. Using the universal values of C and log η (Tg), fairly reliable estimates of shear viscosities from the transition range through the working range can be made from the Tg and Tg' values obtained using DTA or DSC

X¯ chart with adaptive sample sizes

Abstract: Standard Shewhart control charts employ fixed sample sizes at equal sampling intervals. By varying the sample size depending on the current location of the process mean, the mean time to detect an off-target condition can be reduced. The adaptive-sample-size control chart is compared with the fixed-sample-size control chart in terms of average run length under shifts in the process mean of variable magnitude. Significant improvements have been obtained with the adaptive-sample-size charts, particularly for small shifts. These improvements are achieved without increasing the in-control average sample size beyond that of the fixed-sample-size approach. A fast initial response is suggested and advantages of the procedure over fixed-sample-size control are illustrated with two examples from discrete manufacturing processes.

Expert system verification and validation: a survey and tutorial

Abstract: Assuring the quality of an expert system is critical. A poor quality system may make costly errors resulting in considerable damage to the user or owner of the system, such as financial loss or human suffering. Hence verification and validation, methods and techniques aimed at ensuring quality, are fundamentally important. This paper surveys the issues, methods and techniques for verifying and validating expert systems. Approaches to defining the quality of a system are discussed, drawing upon work in both computing and the model building disciplines, which leads to definitions of verification and validation and the associated concepts of credibility, assessment and evaluation. An approach to verification based upon the detection of anomalies is presented, and related to the concepts of consistency, completeness, correctness and redundancy. Automated tools for expert system verification are reviewed. Considerable attention is then given to the issues in structuring the validation process, particularly the establishment of the criteria by which the system is judged, the need to maintain objectivity, and the concept of reliability. This is followed by a review of validation methods for validating both the components of a system and the system as a whole, and includes examples of some useful statistical methods. Management of the verification and validation process is then considered, and it is seen that the location of methods for verification and validation in the development life-cycle is of prime importance.

A particle-based model for simulating the draping behavior of woven cloth

Abstract: This thesis presents a model of woven cloth that is capable of reproducing the draping behavior of a variety of fabrics. Here, draping behavior means the final draped configuration of a cloth, consisting of characteristic folds, over a solid object. The model utilizes a new approach, called particle-based modeling, to simulate the mechanical properties of complex materials. In contrast to continuum techniques, particle modeling is founded on the premise that by directly modeling the microstructures of a material and computationally aggregating their interactions correct macroscopic behavior will emerge. Cloth is not a continuous material, but rather a complex mechanism. Cloth's microstructure consists of threads interlaced in a particular weave pattern. Therefore, the model treats the thread crossing as the fundamental modeling unit, which is called a "particle". It is at the level of these particles that constraints are maintained, in the form of potential energy functions, on the relationships between the threads. The constraints maintained in the particle grid embody four basic mechanical interactions occurring in cloth at the thread level. They are thread collision, thread stretching, thread bending, and trellising. An important feature of the model is that its thread-relationship constraints can be defined to simulate specific types of woven materials. This is accomplished by deriving the model's energy functions from empirical mechanical data produced from a standard set of fabric measurement equipment, the Kawabata Evaluation System. Given this capability, a woven material may be measured on the Kawabata System, and a model with the material's mechanical properties may then be defined to confidently simulate its draping behavior on a computer. The validity of the model has been verified by performing two experiments with three different kinds of woven cloth. The first experiment recreates in simulation the standard measurement procedures that are applied to cloth and produces simulated mechanical data. The second experiment performs controlled draping experiments with real cloth, then recreates those experiments with draping simulations utilizing the model. This experiment demonstrates that the model is capable of reproducing the unique large-scale draping structures present in each of the experimental samples.

Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA.

Abstract: Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. These oligomers are joined by phosphodiester bonds in which the 3',5'-linkage predominates over the 2',5'-linkage by a 2:1 ratio. Reaction of a 9:1 mixture of ImpA, A5'ppA results in the formation of oligomers with a 3:1 ratio of 3',5'- to 2',5'-linked phosphodiester bonds. A high proportion of these oligomers contain the A5'ppA grouping. A5'ppA reacts much more rapidly with ImpA than does 5'-ADP (ppA) or 5'-ATP (pppA). The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. 2',5'-Linked oligomers, up to the tetramer in length, are formed using UO2(2+)-montmorillonite. The structure analysis of individual oligomer fractions was performed by selective enzymatic and KOH hydrolytic studies followed by HPLC analysis of the reaction products. It is concluded from the composition of the oligomers that the rate of addition ImpA to a 3'-terminus containing a 2',5'-linkage is slower than the addition to a nucleoside joined by a 3',5'-linked phosphodiester bond. The potential importance of mineral catalysis of the formation of RNA and other oligomers on primitive Earth is discussed.

Gauge capability and designed experiments. part i: basic methods

Abstract: (1993). GAUGE CAPABILITY AND DESIGNED EXPERIMENTS. PART I: BASIC METHODS. Quality Engineering: Vol. 6, No. 1, pp. 115-135.

Image compression using the spatial-orientation tree

Abstract: The zero-tree method for image compression, proposed by J. Shapiro (1992), is studied. The method is presented in a more general perspective, so that its characteristics can be better understood. From this analysis, an improved method is proposed, and it is shown that the new method can increase the PSNR up to 1.3 dB over the original method. >

Non-exponential structural relaxation, anomalous light scattering and nanoscale inhomogeneities in glass-forming liquids

Abstract: Light scattering from glass-forming liquids exhibits an anomalous time dependence in the glass transition region, e.g. maxima in the scattering intensity versus temperature curves during heating. It is shown that this behavior is consistent with the presence of nanoscale inhomogeneities (density fluctuations) which relax at different rates. It is suggested that this could be the source of non-exponential structural relaxation kinetics. An expression relating the size of these regions to structural relaxation kinetic parameters has been developed and predicts sizes in excellent agreement with those determined by other methods.

Rutile solubility and mobility in supercritical aqueous fluids

Abstract: Experimental and thermodynamic data and the apparent immobility of Ti under metamorphic conditions suggest that rutile is very insoluble in aqueous fluids at upper crustal conditions. New solubility measurements at 1.0–2.93 GPa and 800–1200°C show, however, that under certain pressure and temperature conditions rutile is quite soluble in H2O. Solubilities were estimated from the measured weight loss of a single crystal equilibrated with a known mass of fluid in a piston cylinder apparatus. Measured solubilities in H2O range from 0.15 wt% (wt loss crystal/wt fluid) at 2.93 GPa and 1000°C to 1.9% at 1.0 GPa and 1100°C. Solubility increases with increasing temperature and with decreasing pressure in a manner given by the following fit to the experimental data: $$\log _{10} m_{Ti} = - 7049/T - (0.589* P)/T + 5.14$$ wherem Ti is the molality of Ti in the fluid,T is in degress Kelvin andP is in MPa. The effect of fluid composition on rutile solubility was also examined at 1.0 GPa and 1000°C for H2O-CO2, 1m NaCl, and 1m HF fluids. Kesults suggest that solubility depends on the mole fraction of H2O in the fluid but is independent of ionic strength and fluid pH. This behavior implies that Ti dissolves as the neutrally-charged hydrolysis product Ti(OH)4. The free energy of this species was calculated for each set of experimental conditions. TheP-T dependence of rutile solubility suggests that aqueous fluids derived from subducted oceanic lithosphere would dissolve rutile or other Ti-rich minerals from the deepest portion of the mantle wedge and precipitate them at higher levels. Subsequent melting of the base of the mantle wedge would form HFSE-depleted IAB.

Silicon carbide UV photodiodes

Abstract: SiC photodiodes were fabricated using 6 H single-crystal wafers. These devices have excellent UV responsivity characteristics and very low dark current even at elevated temperatures. The reproducibility is excellent and the characteristics agree with theoretical calculations for different device designs. The advantages of these diodes are that they will operate at high temperatures and are responsive between 200 and 400 nm and not responsive to longer wavelengths because of the wide 3-eV bandgap. The responsivity at 270 nm is between 70% and 85%. Dark-current levels have been measured as a function of temperature that are orders of magnitude below those previously reported. Thus, these diodes can be expected to have excellent performance characteristics for detection of low light level UV even at elevated temperatures. >

Syntactic segmentation and labeling of digitized pages from technical journals

Abstract: A method for extracting alternating horizontal and vertical projection profiles are from nested sub-blocks of scanned page images of technical documents is discussed. The thresholded profile strings are parsed using the compiler utilities Lex and Yacc. The significant document components are demarcated and identified by the recursive application of block grammars. Backtracking for error recovery and branch and bound for maximum-area labeling are implemented with Unix Shell programs. Results of the segmentation and labeling process are stored in a labeled x-y tree. It is shown that families of technical documents that share the same layout conventions can be readily analyzed. Results from experiments in which more than 20 types of document entities were identified in sample pages from two journals are presented. >

Reversible image compression via multiresolution representation and predictive coding

Abstract: In this paper a new image transformation suited for reversible (lossless) image compression is presented. It uses a simple pyramid multiresolution scheme which is enhanced via predictive coding. The new transformation is similar to the subband decomposition, but it uses only integer operations. The number of bits required to represent the transformed image is kept small through careful scaling and truncations. The lossless coding compression rates are smaller than those obtained with predictive coding of equivalent complexity. It is also shown that the new transform can be effectively used, with the same coding algorithm, for both lossless and lossy compression. When used for lossy compression, its rate-distortion function is comparable to other efficient lossy compression methods.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Investigation of an evaporating extended meniscus based on the augmented Young-Laplace equation

Abstract: The microscopic details of fluid flow and heat transfer near the contact line of an evaporating extended meniscus of heptane formed between a horizontal substrate and a “washer” were studied at low heat fluxes. The film profile in the contact line region was measured using ellipsometry and microcomputer-enhanced video microscopy, which demonstrated the details of the transition between a nonevaporating superheated flat thin film and an evaporating curved film. Using the augmented Young-Laplace equation, the interfacial properties of the system were initially evaluated in situ and then used to describe the transport processes. New analytical procedures demonstrated the importance of two dimensionless parameters. Both fluid flow and evaporation depend on the intermolecular force field, which is a function of the film profile. The thickness and curvature profiles agreed with the predictions based on interfacial transport phenomena models. The heat flux distribution and the pressure field were obtained. Since there are significant resistances to heat transfer in this small system due to interfacial forces, viscous stresses, and thermal conduction, the “ideal constant heat flux” cannot be attained. The description of the pressure field gives the details of the coupling between the disjoining and capillary pressures.

Aminoalkylindole binding in rat cerebellum: selective displacement by natural and synthetic cannabinoids.

Abstract: A binding assay for WIN 55212-2, an aminoalkylindole (AAI) with antinociceptive activity in rodents, is described. [3H]WIN 55212-2 bound to rat cerebellar membranes with a Kd of 2 nM and a maximum binding of 1.2 pmol/mg of protein. Specific binding in this filtration assay was greater than 90%, saturable, reversible, stereospecific, pH sensitive and heat labile. Binding was decreased by Na+, K+, Li+ and nonhydrolyzable analogs of GTP and increased by Mg++ and Ca++. The density of specific binding sites varied throughout the central nervous system with the highest found in the cerebellum, hippocampus and striatum and the lowest in the medulla/pons and spinal cord. The binding affinities of other AAIs for the WIN 55212-2 binding site correlated with their potencies for inhibiting neuronally stimulated contractions in the isolated mouse vas deferens. Of more than 60 compounds representing recognized neurotransmitter systems, only cannabinoids effectively inhibited binding. The effect of cannabinoids on AAI binding was consistent with competitive inhibition and suggests that AAI activity may be mediated in whole or in part by interaction with cannabinoid receptors. AAIs appear to represent a structurally novel class of compounds with which to study cannabinoid receptors.