Monitoring Delamination of Thermal Barrier Coating During Interrupted High-Heat Flux Laser Testing Using Upconversion Luminescence Imaging

Upconversion luminescence imaging of thermal barrier coatings (TBCs) has been shown to successfully monitor TBC delamination progression during interrupted furnace cycling. However, furnace cycling does not adequately model engine conditions where TBC-coated components are subjected to significant heat fluxes that produce through-thickness temperature gradients that may alter both the rate and path of delamination progression. Therefore, new measurements are presented based on luminescence imaging of TBC-coated specimens subjected to interrupted high-heat-flux laser cycling exposures that much better simulate the thermal gradients present in engine conditions. The TBCs tested were deposited by electron-beam physical vapor deposition (EB-PVD) and were composed of 7wt% yttria-stabilized zirconia (7YSZ) with an integrated delamination sensing layer composed of 7YSZ co-doped with erbium and ytterbium (7YSZ:Er,Yb). The high-heat-flux exposures that produce the desired through-thickness thermal gradients were performed using a high power CO2 laser operating at a wavelength of 10.6 microns. Upconversion luminescence images revealed the debond progression produced by the cyclic high-heat-flux exposures and these results were compared to that observed for furnace cycling

A Sequential Stratification Method for Estimating the Effect of a Time-Dependent Experimental Treatment in Observational Studies

Survival analysis is often used to compare experimental and conventional treatments. In observational studies, the therapy may change during follow-up and such crossovers can be summarized by time-dependent covariates. Given the ever-increasing donor organ shortage, higher-risk kidneys from expanded criterion donors (ECD) are being transplanted. Transplant candidates can choose whether to accept an ECD organ (experimental therapy), or to remain on dialysis and wait for a possible non-ECD transplant later (conventional therapy). A three-group time-dependent analysis of such data involves estimating parameters corresponding to two time-dependent indicator covariates representing ECD transplant and non-ECD transplant, each compared to remaining on dialysis on the waitlist. However, the ECD hazard ratio estimated by this time-dependent analysis fails to account for the fact that patients who forego an ECD transplant are not destined to remain on dialysis forever, but could subsequently receive a non-ECD transplant. We propose a novel method of estimating the survival benefit of ECD transplantation relative to conventional therapy (waitlist with possible subsequent non-ECD transplant). Compared to the time-dependent analysis, the proposed method more accurately characterizes the data structure and yields a more direct estimate of the relative outcome with an ECD transplant.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66010/1/j.1541-0420.2006.00527.x.pd

The Slothful Claw: Osteology and Taphonomy of \u3cem\u3eNothronychus mckinleyi\u3c/em\u3e and \u3cem\u3eN. graffami\u3c/em\u3e (Dinosauria: Theropoda) and Anatomical Considerations for Derived Therizinosaurids

Nothronychus was the first definitive therizinosaurian discovered in North America and currently represents the most specialized North American therizinosaurian genus. It is known from two species, No. mckinleyi from the Moreno Hill Formation (middle Turonian) in west-central New Mexico, and No. graffami from the Tropic Shale (early Turonian) in south-central Utah. Both species are represented by partial to nearly complete skeletons that have helped elucidate evolutionary trends in Therizinosauria. In spite of the biogeographical and evolutionary importance of these two taxa, neither has received a detailed description. Here, we present comprehensive descriptions of No. mckinleyi and No. graffami, the latter of which represents the most complete therizinosaurid skeleton known to date. We amend previous preliminary descriptions of No. mckinleyi and No. graffami based on these new data and modify previous character states based on an in-depth morphological analysis. Additionally, we review the depositional history of both specimens of Nothronychus and compare their taphonomic modes. We demonstrate that the species were not only separated geographically, but also temporally. Based on ammonoid biozones, the species appear to have been separated by at least 1.5 million years and up to 3 million years. We then discuss the impacts of diagenetic deformation on morphology and reevaluate potentially diagnostic characters in light of these new data. For example, the ulna of No. mckinleyi is curved whereas the ulna of No. graffami was considered straight, a character originally separating the two species. However, here we present the difference as much more likely related to diagenetic compression in No. graffami rather than as a true biologic difference. Finally, we include copies of three-dimensional surface scans of all major bones for both taxa for reference

Temperature mapping above and below air film-cooled thermal barrier coatings using phosphor thermometry

Thermal barrier coatings (TBCs) are typically used in conjunction with air film cooling to maximize overall cooling effectiveness and reliability while minimizing sacrifices in engine performance. The effects of thermal barrier coating (TBC) thermal protection and air film cooling effectiveness have usually been studied separately; however, their contributions to combined cooling effectiveness are interdependent and are not simply additive. The combined cooling effectiveness is always less than the sum of the cooling effectiveness of stand-alone TBC protection and stand-alone air film cooling. These diminishing returns arise because adding the thermally insulating TBC between the cooling air and the surface to be cooled reduces the air film cooling effectiveness and because the air film cooling reduces the heat flux through the TBC and therefore reduces the temperature difference sustained across the TBC thickness. Due to these considerations, combined cooling effectiveness must be measured to achieve an optimum balance between TBC thermal protection and air film cooling. In this investigation, temperature mapping above and below air film-cooled TBCs was performed using luminescence lifetime imaging-based phosphor thermometry. Measurements were performed in the NASA GRC Mach 0.3 burner rig on a TBC-coated plate using a scaled-up cooling hole geometry where both the hot mainstream gas temperature and the blowing ratio were varied. Surface temperature maps were obtained from a Cr-doped GdAlO3 thermographic phosphor deposited on the surface of the electron-beam vapor-deposited yttria-stabilized zirconia (YSZ) TBC. From separate plates, temperature maps from the bottom of the TBC were obtained from a thin Er-doped YSZ layer integrated into the TBC below the overlying undoped YSZ. Procedures for temperature and cooling effectiveness mapping above and below the air film-cooled TBC surface are described. Most importantly, these measurements enable mapping the combined cooling effectiveness below the TBC, which is more important than surface cooling effectiveness when there is a barrier coating between the hot mainstream gas and the surface that needs thermal protection. Advantages of the luminescence lifetime imaging method over infrared thermography, as well as its limitations to steady-state conditions are discussed

Book Review Of Leap Of Faith By Danielle Steel

Leap of Faith is a novel by a famous novelist Danielle Steel. Leap of Faith debuted at the New York Times and is listed as the best-selling novel to fifty-two of Danielle Steel. This novel is about a girl from France, she is Marie-Ange Hawkins who lives in a magnificent castle name, Chateau de Marmouton. At the castle, she has childhood like everyone\u27s dream. She has the freedom, security and abundant affection of both parents and her brother. But when Marie-Ange Hawkins is eleven years old, a tragic accident that befell his parents take her happiness. She becomes an orphan and is sent to America to live with a cruel aunt of her father. Alone in a foreign land, Marie-Ange Hawkins becomes slave of agricultural land by her aunt, only her friendship with Billy and her dream to return to the castle of her childhood memories that make Marie-Ange endures. But the magic happens when Marie-Ange is 21 years old. She makes it back to the castle Chateau de Marmouton again and even get a chance to be the hostess which is the new owner of the castle, Comte Bernard de Beauchamp proposed her. But behind his proposal, Comte Bernard de Beauchamp keeps his hidden bad intentions to Marie-Ange Hawkins. In desperation and uncertainty areas around her, Marie-Ange has to find the faith and courage to take her last step to save her love ones and herself. Danielle Steel packed this book with very interesting by a simple writing style and storyline in the 1800s which is different from the usual. This book is quite interesting and deserves to be read as entertainment by teenagers and adults

Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating

Monitoring Delamination of Thermal Barrier Coatings During Interrupted High-Heat-Flux Laser Testing using Luminescence Imaging

This presentation showed progress made in extending luminescence-base delamination monitoring to TBCs exposed to high heat fluxes, which is an environment that much better simulates actual turbine engine conditions. This was done by performing upconversion luminescence imaging during interruptions in laser testing, where a high-power CO2 laser was employed to create the desired heat flux. Upconverison luminescence refers to luminescence where the emission is at a higher energy (shorter wavelength) than the excitation. Since there will be negligible background emission at higher energies than the excitation, this methods produces superb contrast. Delamination contrast is produced because both the excitation and emission wavelengths are reflected at delamination cracks so that substantially higher luminescence intensity is observed in regions containing delamination cracks. Erbium was selected as the dopant for luminescence specifically because it exhibits upconversion luminescence. The high power CO2 10.6 micron wavelength laser facility at NASA GRC was used to produce the heat flux in combination with forced air backside cooling. Testing was performed at a lower (95 W/sq cm) and higher (125 W/sq cm) heat flux as well as furnace cycling at 1163C for comparison. The lower heat flux showed the same general behavior as furnace cycling, a gradual, "spotty" increase in luminescence associated with debond progression; however, a significant difference was a pronounced incubation period followed by acceleration delamination progression. These results indicate that extrapolating behavior from furnace cycling measurements will grossly overestimate remaining life under high heat flux conditions. The higher heat flux results were not only accelerated, but much different in character. Extreme bond coat rumpling occurred, and delamination propagation extended over much larger areas before precipitating macroscopic TBC failure. This indicates that under the higher heat flux (and surface & interface temperatures), the TBC was more tolerant of damage. The main conclusions were that high heat flux conditions can not only accelerate TBC debond progression but can also grossly alter the pathway of delamination

Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability

The covering factor of high redshift damped Lyman-α\alpha systems

We have used the Very Long Baseline Array to image 18 quasars with foreground damped Lyman-$\alpha$ systems (DLAs) at 327, 610 or 1420 MHz, to measure the covering factor $f$ of each DLA at or near its redshifted HI 21cm line frequency. Including six systems from the literature, we find that none of 24 DLAs at $0.09 < z < 3.45$ has an exceptionally low covering factor, with $f \sim 0.45 - 1$ for the 14 DLAs at $z > 1.5$, $f \sim 0.41 - 1$ for the 10 systems at $z < 1$, and consistent covering factor distributions in the two sub-samples. The observed paucity of detections of HI 21cm absorption in high-$z$ DLAs thus cannot be explained by low covering factors and is instead likely to arise due to a larger fraction of warm HI in these absorbers.Comment: 6 pages, 20 figures; MNRAS (Letters), in pres

The Production of Hospitable Space: Commercial Propositions and Consumer Co-Creation in a Bar Operation

This paper examines the processes through which a commercial bar is transformed into a hospitable space. Drawing on a study of a venue patronized by lesbian, gay, bisexual and transsexual/transgender consumers, it considers how social and commercial forms of hospitality are mobilized. The paper argues that hospitable space has an ideological, normative and situational dimension. More specifically, it suggests the bar’s operation is tied to a set of ideological conceptions, which become the potential basis of association and disassociation among consumers. It examines the forces and processes that shape who participates in the production and consumption of hospitality and how. Finally, it considers the situational, emergent nature of hospitality and the discontinuous production of hospitable space. Rather than focusing exclusively on host-guest or provider-customer relations, which dominates existing work on hospitality, the paper examines how consumers’ perceptions, actions and interactions shape the production of hospitality. By doing so the paper offers an alternative approach to understanding queer spaces, bar operation as well as hospitality