Automated Cellular Modeling and Prediction on a Large Scale

We describe CHAMP (CHurn Analysis, Modeling, andPrediction), an automated system for modeling cellularsubscriber churn that is predicting which customerswill discontinue cellular phone service. We describevarious issues related to developing and deployingthis system including automating data access from aremote data warehouse, preprocessing, featureselection, model validation, and optimization toreflect business tradeoffs. Using data from GTE'sdata warehouse for cellular phone customers, CHAMP iscapable of developing churn models customized byregion for over one hundred GTE cellular phone marketstotaling over 5 million customers. Every month churnfactors are identified for each geographic region andmodels are updated to generate churn scores predictingwho is likely to churn in the short term. Learningmethods such as decision trees and genetic algorithmsare used for feature selection and a cascade neuralnetwork is used for predicting churn scores. Inaddition to producing churn scores, CHAMP alsoproduces qualitative results in the form of rules andcomparison of market trends that are disseminatedthrough a web based interface.     

A chemical mechanical polishing model incorporating both the chemical and mechanical effects

A comprehensive model for the material removal in a chemical mechanical polishing (CMP) process is presented in which both chemical and mechanical effects are taken into consideration. The chemical effects come into play through the formation of chemically modified surface layer on the wafer surface that, in turn, is removed mechanically by the plastic deformation induced by slurry particles. This model describes the influence of most, if not all, variables involved in the CMP process including slurry characteristics (solid loading, particle size and distribution, modulus), pad properties (modulus, hardness, asperity sizes and distribution) and processing conditions (down-pressure, velocity). Although more elaborate experimental verification of the model is yet to follow, this model appears to be capable of explaining many experimental observations on both oxide and metal CMP that, otherwise, could not be explained properly.     

Enhanced Mechanical Properties and Corrosion Behavior of Biodegradable Mg-Zn/HA Composite

Metallurgical and Materials Transactions A - Magnesium (Mg) and its alloys have shown potential for use in the biomedical industry due to their excellent biological performance and biodegradability...     

Particle engulfment and pushing by solidifying interfaces: Part 1. Ground experiments

Directional solidification experiments have been carried out to determine the pushing/engulfment transition for two different metal/particle systems. The systems chosen were aluminum/zirconia particles and zinc/zirconia particles. Pure metals (99.999 pct A1 and 99.95 pct Zn) and spherical particles (500 μm in diameter) were used. The particles were nonreactive with the matrices within the temperature range of interest. The experiments were conducted so as to ensure a planar solid/liquid (SL) interface during solidification. Particle location before and after processing was evaluated by X-ray transmission microscopy (XTM) for the Al/ZrO₂ samples. All samples were characterized by optical metallography after processing. A clear methodology for the experiment evaluation was developed to unambiguously interpret the occurrence of the pushing/engulfment transition (PET). It was found that the critical velocity for engulfment ranges from 1.9 to 2.4 μm/s for Al/ZrO₂ and from 1.9 to 2.9 μm/s for Zn/ZrO₂.     

Dilemmas of Representation in Post-apartheid Durban

This paper aims to provide a sketch of the ways in which ‘formal’ institutions of democratic representation worked in practice in Durban/eThekwini in the 2000-2004 period. In so doing, it assesses how the representation of eThekwini’s citizens functioned at both the ward and metropolitan levels. After outlining the formation of the new metropolitan political arena, we consider the relationships amongst political parties at Metro and Ward levels, and, in particular, explore some contextually specific forms of democratic practice which emerged through the interaction of proportional representation and ward representation over time. The election of councillors as such does not resolve a series of dilemmas concerning how to institutionalise democratic representation within a racially diverse, spatially divided, and rapidly changing metropolitan area. Electoral-representative aspects of a urban democratisation are not a straightforward ‘formal’ framework alongside which other processes of democratic discussion, mobilisation and contestation can be easily situated.

Nusselt number and friction factor correlations for solar air heater duct having artificially roughened absorber plate

An experimental investigation has been carried out for a range of system and operating parameters in order to analyse effect of artificial roughness on heat transfer and friction in solar air heater duct having protrusions as roughness geometry. An increase in heat transfer and friction loss has been observed for duct having roughened absorber plate. Experimental data have been used to develop Nusselt number and friction factor correlations as function of system and operating parameters for predicting performance of the system having investigated type of roughness geometry.     

Selective serotonin reuptake inhibitors in pregnancy and lactation

Selective serotonin reuptake inhibitors (SSRIs) have become the agents of first choice in the treatment of depression because of their safe side effect profile. This paper reviews the current literature on the use of SSRIs in pregnancy and lactation concerning their safety. There are human studies that only used fluoxetine in pregnancy, which established its safety. SSRIs are excreted in breast milk, and their long-term effects on the newborn are unknown at this time. The decision to use SSRIs in pregnancy should be made on a case by case basis with active involvement of the patient in the informed consent process during which the risks and benefits are discussed and documented.