Douglas Hague

University of North Carolina at Charlotte | UNC Charlotte · School of Data Science

As the health care industry adopts artificial intelligence, machine learning, and other modeling techniques, it is seeing benefits to both patient outcomes and cost reduction; however, it needs to be cognizant of and ensure proper management of the risks, including bias. Lessons learned from other industries may provide a framework for acknowledgin...

Nanocrystalline (15 nm) yttria (3 mol%)-stabilized zirconia (3Y-TZP) was sinter-forged under conditions of varying temperature (1050–1200°C), plastic strain rate (5 × 10−5 to 2 × 10−3s−1), and green density (33–48%), using constant-crosshead-speed tests, constant-load (i.e., load-and-hold) tests, and constant-loading-rate tests. The densification a...

The present study shows that an extremely high water: alkoxide ratio during the hydrolysis of titanium isopropoxide results in a partially crystalline precipitate (5-nm anatase crystallites); however, when these crystallites are rinsed with ethanol, the precipitate becomes amorphous. The degree of crystallinity of the precipitate determines its sub...

A quantitative computer simulation of densification, pore-size evolution, and grain growth during sinter-forging has been developed and applied to the sinter-forging of nanocrystalline yttria (30 mol%)-stabilized zirconia (3Y-TZP) at 1050° and 1100°C. Densification is simulated as a superposition of stress-assisted and plastic-strain-controlled por...

Signal degradation due to polarization-mode dispersion (PMD) effects may become significant for signaling rates of 10 Gb/s, 40 Gb/s, and beyond. To assess the utility of various PMD mitigation schemes, temporal and spectral measurements of differential group delay (DGD) were made on 95 km of buried standard single-mode fiber over an 86-d period to...

Signal degradation due to polarization-mode dispersion (PMD) effects may become significant for signaling rates of 10 Gb/s, 40 Gb/s, and beyond. To assess the utility of various PMD mitigation schemes, temporal and spectral measurements of differential group delay (DGD) were made on 95 km of buried standard single-mode fiber over an 86-d period to...

Temporal and spectral measurements were made on three different 95-km fibers within a slotted-core, direct buried, standard single-mode fiber-optic cable over many days to characterize DGD variability. From this data we observed that DGD varies slowly over time but rapidly over wavelength. This data showed good agreement with a Maxwellian distribut...

The unusual bulk behavior of nanoparticle and nanograined systems often originates in surface chemistry effects. Three examples are used to illustrate this point. In the first, newly precipitated nanocrystalline titania is washed with ethanol, and the mixture of these two supposedly inert substances causes the titania to lose its anatase crystal st...

A quantitative computer simulation of densification, pore-size evolution, and grain growth during sinter-forging has been developed and applied to the sinter-forging of nanocrystalline yttria (30 mol%)-stabilized zirconia (3Y-TZP) at 1050° and 1100 °C. Densification is simulated as a superposition of stress-assisted and plastic-strain-controlled po...

Nanocrystalline (15 nm) yttria (3 mol%)-stabilized zirconia (3Y-TZP) was sinter-forged under conditions of varying temperature (1,050--1,200 C), plastic strain rate (5 {times} 10{sup {minus}5} to 2 {times} 10{sup {minus}3} s{sup {minus}1}), and green density (33--48%), using constant-crosshead-speed tests, constant-load (i.e., load-and-hold) tests,...

A model to predict the densification and microstructural development of a nanocrystalline ceramic powder compact during sinter-forging has been developed. In the model, densification is predicted by superimposing stress-assisted densification mechanisms with a plastic-strain-controlled pore closure mechanism. During densification, grain growth is m...

Nanocrystalline titania powder compacts (green bodies) were uniaxially compressed at 610 °C under initial stresses of 0, 12, and 60 MPa to determine the influence of deformation mechanism on pore shrinkage during a sinter-forging operation. It was observed that at 0 and 12 MPa, small pores shrink preferentially, as would be the case for diffusional...

Nanocrystalline titania powder was produced by the hydrolysis of titanium alkoxide. The precipitation procedure can be controlled so as to produce either crystalline (anatase) or amorphous powder. A comparison of the crystalline size in these two powders after calcination reveals the impact of the crystallization reaction. This reaction, which occu...

The microstructural development of nanocrystalline TiO2 is followed throughout second stage sintering. Porosimetry data reveal that pore growth and pore shrinkage adhere relatively well to Kingery's predictions based on a critical pore-size grain size ratio. In addition, it appears that open pores severely limit grain growth during stage II sinteri...

The production of nanocrystalline ceramics for subsequent use in superplastic forming operations requires that the ceramics be made in large quantities, with high densities, and under stringent grain growth control. To make large amounts of nanocrystalline starting powders, two popular wet chemical techniques (precipitation from salt solutions and...

Two mechanisms appear to occur during the sinter-forging of nanocrystalline titania. The first mechanism occurs at stresses below ≈ 25 MPa where the densification kinetics are shown to be independent of the stress. However, at higher stresses, the densification kinetics are greatly enhanced by a plastic flow mechanism. The nucleation rate of rutile...

Yttrium-barium-copper-oxide (123) superconducting ceramic pellets where obtained from J.P. Singh and K.C. Goretta at Argonne National Laboratory (ANL). The pellets were prepared in accordance with established methods. The pellets were then thermocompressively bonded by the methods of Meiser, et al. The resistivities of the samples were determined u...