A prolog based expert system for the allocation of quality assurance program resources

The worldwide proliferation of fraudulent materials has brought about the need for a new approach to the control of purchased material quality. Nuclear power, defense, aerospace and many other industries are affected by the supply of poor quality clones that presume to be original replacement parts. Safety considerations abound as these highly defective materials are used in systems that are critical to the preservation of human lives. Commonly utilized quality assurance programs have not effectively stopped the influx of fraudulent materials. These programs fail to concentrate inspection efforts on materials and inspection attributes that would effectively prevent the acceptance of fraudulent materials. herein a solution is presented to this problem in the form of an expert system application. Information commonly available in industry is formulated into a knowledge based system wherein advisories are given to the user regarding key purchased material receipt inspection strategies.     

A knowledge-based system for sensor selection

This paper presents a Knowledge-based system (KBS) developed to allow users, who may not be knowledgeable about sensors, to select sensors suitable for their specific needs. The KBS runs on a micro-computer. The selection criteria are user specified and are based on the desired measurement parameters. The system output includes all of the operational and dimensional parameters of the recommended sensor, price, and vendor information.     

Model selection for covariance structures analysis in nursing research

Covariance structures analysis is often used in nursing research to appraise statistical models reflecting complex human health processes. The model selection approach in covariance structures analysis is designed to select the "best" model from a specified set of theoretically defensible, competing alternatives, all of which are viewed as approximations. Model selection criteria explicitly incorporate both model misfit in the population and sampling error to evaluate the set of models. The result is that interpretability of model parameters and goodness-of-fit are enhanced simultaneously. Relative merits of the model selection approach are identified in light of technical concerns, parsimony, and use of scientific theory in nursing.     

Mid-infrared phase modulation via Stark effect on intersubbandtransitions in GaAs/GaAlAs quantum wells

Mid-infrared (~10 μm) electrorefractive effects of intersubband transitions in step GaAs/GaAlAs quantum wells are experimentally analyzed. A method for studying infrared electrorefraction of a two-dimensional structure via the Stark effect is used. The anomalous dispersion is measured over the entire spectral range of the transition and is found to be consistent with the Kramers-Kronig relations in the case of a Lorentzian absorption shape. A solution of Maxwell's equations in the multiquantum well structure is detailed and leads to a good agreement with experimental data. A standard interferometer and a lock-in technique allow a quasi-direct determination of phase and amplitude modulation with very good sensitivity. A theoretical approach based on a Lorentzian model and the solution of Maxwell's equations for a multiple QW (quantum well) structure agreed well with the data     

Investigation of the heel crack mechanism in Al connections for power electronics modules

In power electronic packages, one of the main limiting factors for the module reliability stems from failure of the electrical interconnection which ensures the contact between the chip and the lead frame. The aim of this work is to model, using FEM and some analytical developments, the interconnection heel crack mechanism appearing in service. The forming process impact is particularly evaluated and it is established that the initial residual stresses contribute to limit the wire/ribbon life time.     

Investigations on junction temperature estimation based on junction voltage measurements

Reliability and ageing tests on power semiconductor devices require estimation of junction temperatures in order to control thermal stresses and monitor failure criteria. For this purpose, thermo-electrical parameters, such as voltage forward drop dependence with temperature are usually carried out in low injection level. Nevertheless, it is still difficult to evaluate the limits of such exploitation. An analytical model has been developed and validated by experimental measurements in order to evaluate self-heating effects and to understand high temperature effects. This model should also allow to highlight the role of some physical parameters in the voltage–temperature dependence and to clarify such thermal calibration.     

Accelerated active ageing test on SiC JFETs power module with silver joining technology for high temperature application

This paper presents the accelerated active power cycling test (APCT) results on SiC JFETs power module dedicated to operate at high temperature. This study partly focuses on the new chip joining technology (LTJT), which permit to use SiC JFETs transistors at higher temperatures. We present the different die attachments tested with high temperature lead solder and silver sintering joining technologies. Active power cycling results for high junction temperature T_jmax = 175 °C with ΔT_j = 80 K to perform an evaluation of main damages during active test are carried out and a comparison between lead and silver chip joining technologies is presented.     

Hypocholesterolemic agents V: Inhibition of beta-hydroxy-beta-methylglutaryl coenzyme A reductase by substituted 4-biphenylylalkyl carboxylic acids and methyl esters

Eleven substituted 4-biphenylylalkyl carboxylic acids and three methyl esters were synthesized and assayed for inhibition of rat liver beta-hydroxy-beta-methylglutaryl coenzyme A reductase. Five of the acids were analogs, resulting from various isosteric replacements of the carbonyl and ether oxygens of the previously described reversible inhibitor 1-(4-biphenylyl)pentyl hydrogen succinate. No significant change in activity was noted, except upon introduction of an amide linkage where a decrease in inhibition was found. Six carboxylic acids and three methyl esters, all containing the 4-biphenylyl radical but lacking the n-butyl side chain found in 1-(4-biphenylyl)pentyl hydrogen succinate, also were inhibitors of the reductase.     

Serial measurement of arterial plasma progesterone levels throughout gestation and parturition in individual rats

Daily blood samples were taken from 6, chronically cannulated, fully conscious rats to measure plasma progesterone levels throughout gestation. Progesterone levels in individual rats fluctuated by up to 28 ng/ml per day, but tended to be consistently higher or lower than the group mean. The accuracy of predicting progesterone levels in individual rats from previous values was examined. Progesterone levels on day 7 of gestation were negatively correlated with foetal weights near term. There was little indication that high progesterone levels at any stage of gestation lead to increased foetal or placental weights. Progesterone levels on day 17 were positively correlated with the number of corpura lutea but there was little relationship between progesterone and either the number or total mass of the placentas. Serial blood samples taken from a second group of 6 rats at 2 hourly intervals showed that the time between the major fall in progesterone levels to below 12 ng/ml and the onset of parturition was relatively constant (varying by only 8 h) despite a 29 h range in the total length of gestation.