An object-oriented product database using ROSE

A product database for a design and manufacturing enterprise serves as a repository for the data needed to manufacture a product. This paper discusses how an object-oriented persistent object manager named ROSE, under development at Rensselaer, has been used in the Rensselaer CIM program to develop a STEP/PDES-compliant product database for its research test bed. In so doing, it provides an overview of the requirements for a product database system in an integrated design and manufacturing facility, and it discusses how the chosen system meets these requirements.     

Small-angle neutron scattering study of creep cavity nucleation and growth in sintered alumina

The early stages of creep cavitation in sintered alumina are characterized using small-angle neutron scattering (SANS). It is found that the initial cavity density is of the order of 10¹¹ cm^–3, and that the average initial pore is approximately 60 nm in radius. The incubation time for nucleating additional pores during subsequent creep is extremely short, in agreement with the theory based on the precipitation of grain-boundary diffusing vacancies. Pore density at constant stress and temperature is a linearly increasing function of time, as predicted by classical nucleation theory. However, a local stress of 10^–2 E is required to achieve the measured nucleation rate. Cavities are observed to lie primarily on two-grain junctions in linear arrays, with an average cavity radius of approximately 60 nm. It is hypothesized that the cavities nucleate at grain boundary ledges which provide the necessary local stress concentrations. Calculation of the individual cavity growth rate yields a zero or near zero value. This suggests a rapid transient growth period following nucleation which quickly decreases to a negligible growth rate.     

Three-Phase Three-Thyristor Voltage Control Scheme

This paper describes and analyzes the performance of a three-phase voltage control scheme that uses only three thyristors. This scheme produces balanced three-phase currents and voltages, the harmonic content of which are discussed along with its suitability for use as a simple control scheme for heating lighting and motor loads.     

Application of atmospheric pressure ionization time-of-flight mass spectrometry coupled with liquid chromatography for the characterization of in vitro drug metabolites

Atmospheric pressure ionization time-of-flight mass spectrometry coupled with high-performance liquid chromatography was used to characterize the in vitro metabolites of glyburide. Metabolic products formed in vitro by human microsomes were separated using a C18 column with gradient elution at a flow rate of 200 microL/min without postcolumn splitting. In-source collision-induced dissociation (CID) by automated nozzle potential switching was employed to obtain both abundant protonated molecules and characteristic fragments whose accurate masses were measured simultaneously by internal mass calibration, performed by continuous postcolumn infusion of two reference standards. The mass errors were within 9 ppm for all ions measured, whose abundance was greater than 5%, relative to the most abundant isotopic "A" ion. Exact mass differences between the parent drug and metabolite(s) were determined and these values corresponded to a unique elemental composition. The elemental compositions of all metabolite fragment ions were generated based upon the known compositional elements of the protonated molecule. The structures of metabolites and their fragment ions were proposed based on the determined elemental composition and in-source CID spectra. The elemental composition and fragmentation pathways of four cyclohexyl hydroxylation metabolites and one ethylhydroxy metabolite are discussed.     

The Measurement of Compressive Creep Deformation and Damage Mechanisms in a Single-Phase Alumina Part II Correlation of creep cavitation and grain boundary sliding

It has been theorized that stochastic grain boundary sliding (GBS) is the primary driving force for the nucleation, growth, and coalescence of cavities located on the grain boundaries of polycrystalline ceramics undergoing creep. This paper reports on the results of co-ordinated measurements of both GBS and creep cavitation during the creep of a single-phase alumina. Constant compressive stress creep experiments were performed at a temperature of 1600 °C, and stress levels of 70, 100, and 140 MPa. Small angle neutron scattering measurements (SANS) show that cavities nucleate continuously due to creep at all three stress levels, and that since negligible cavity growth was measured, creep cavitation appears to be ruled by a nucleation rather than a growth process. Also, at a constant creep temperature, the number and volume of cavities measured was observed to decrease with a decrease in the applied stress. GBS displacements reported in Part 1 of this paper [1] are related to the number of cavities nucleated per unit volume and shown to relate directly, thereby providing experimental evidence that GBS may act as the driving force for creep cavitation.     

Utilization of Reliability Measurements in Bayesian Inference: Models and Human Performance

A normative 2-stage model for incorporating reliability measurements of data-reporting sources in a Bayesian inference system is presented. An experiment required human subjects to make intuitive inferences about two hypotheses on the basis of sample data which were reported with a given reliability. When compared with the optimal model, subjects exhibited systematic errors in estimating the diagnostic impact of less than perfectly reliable data. Their responses reflected the use of specific nonoptimal heuristic strategies to process the information. A utility function was added to the normative model to illustrate how a best choice might be made from among potential data-gathering experiments whose costs increase with their reliabilities. Recommendations for using computer aids to enhance efficiency in inference systems are made     

Pedestal control in a diac-triac circuit

The diac-triac circuit discussed has a controlled pedestal with a cosine ramp, and may be used as the basis of many circuits, including a simple soft-start circuit which has very small losses.     

Further studies on the effect of aldosterone on electrical resistance of toad bladder

The fall in transepithelial electrical resistance which accompanies aldosterone stimulation of short-circuit current (Isc) in toad urinary bladder has been studied further to evaluate the possible causal role of this response in hormonal stimulation of Na+ transport. A steady-state change in tissue conductance was found to depend upon both the simultaneous stimulation of transport by the steroid and the metabolic state of the tissue. Changes in metabolic state alone did not alter resistance. A sustained increase in Na+ transport, dependent on pretreatment with aldosterone and elicited by addition of glucose, could be obtained without a sustained decrease in resistance. Amiloride, an inhibitor of Na+ uptake, produced changes in Isc that were linearly correlated with its effects on tissue conductance. On the basis of the conductance-Isc relationship with amiloride, the Isc response to aldosterone was about two-fold higher than would be predicted from its effects on conductance alone. Despite the apparent lack of a simple quantitative dependence of the change in Isc on the change in conductance when the response is fully developed, the results suggest that conductance changes may mediate the initial or early stage of the response.