Aerotherm charring materials ablation computer program

Ablating-surface boundary conditions involve considerations of surface thermochemistry. Several programs may be used to provide surface thermochemistry information

Aerotherm chemical equilibrium (ACE) computer program

Computer code was developed for calculating chemical quantities and qualities in equilibrium

Testing Broken U(1) Symmetry in a Two-Component Atomic Bose-Einstein Condensate

We present a scheme for determining if the quantum state of a small trapped Bose-Einstein condensate is a state with well defined number of atoms, a Fock state, or a state with a broken U(1) gauge symmetry, a coherent state. The proposal is based on the observation of Ramsey fringes. The population difference observed in a Ramsey fringe experiment will exhibit collapse and revivals due to the mean-field interactions. The collapse and revival times depend on the relative strength of the mean-field interactions for the two components and the initial quantum state of the condensate.Comment: 20 Pages RevTex, 3 Figure

Direct Observation of Mechanical Ablation

This presentation describes an experiment that solved a mysterious problem affecting the material that protects solid rocket motor cases from burning propellant gases: Why was the ablation of this material in the forward dome region of recovered flight test motors as much as 2x that observed in full-scale ground test firings? Heat transfer to the forward dome elastomeric insulation is predominantly radiation from the burning propellant. The 15- kW CO2 laser at the Wright Patterson AFB Laser Hardened Material Evaluation Laboratory (LHMEL) was used to provide uniform incident radiation from 200 to 400 W/cm2. We suspected that the rocket acceleration force (which isn’t simulated in static firing tests) was removing char layers, so we used a centrifuge to simulate these forces. Gold-plated mirrors directed the laser beam from the centrifuge centerline onto the outward-facing material specimen mounted on the rotating arm. A pyrometer and video camera were also mounted on the arm to observe the specimen response. Accelerations of 0 to 20 gs were generated by varying the centrifuge RPM, and the specimen velocity provided a rudimentary simulation of the convective environment. The highlight of this presentation is a video that very clearly shows char layers being removed by acceleration forces. At zero and very low acceleration levels, the char layer is robust. At higher acceleration, char layers sequentially grow and are then pulled off when their mass x acceleration exceeds their tensile strength x area. The removal frequency increases with acceleration and heat flux, and some materials are more susceptible than others. The pyrometer data shows a saw-tooth pattern with abrupt surface temperature decreases when char layers are removed to expose virgin material. This phenomenon was modeled using the CMA code modified to include effects of acceleration forces, pyrolysis gas porous flow forces, and char strength. Predictions were consistent with experimental data when an appropriate char strength was input, but of course this was essentially a fudge factor since its impractical to directly measure the tensile strength of an ablating char

Overview of Roughness and Blowing Effects in Flows Over Ablating Surfaces

The scope of this session includes ablation effects on surface roughness and surface roughness effects on ablation. Ablation involves blowing, and so we address blowing including combined roughness and blowing effects. The two distinct types of ablating material surface roughness are defined with examples: 1) roughness related to the material inhomogeneity, and 2) roughness induced by turbulent flow that appears to be unrelated to material inhomogeneties. Existing approaches for modeling ablative material surface roughness and blowing effects are overviewed. These range from empirical “augmentation factor” correlations to high-fidelity simulations of flow-surface interactions using modern CFD techniques. For models requiring input of roughness morphology information (e.g., effective sand grain roughness height), potential experimental and analytical sources of this information, and associated challenges, will be discussed. With regard to all modeling approaches for predicting ablative material surface roughness and its effects, experimental strategies for generating data needed for model development and validation will be emphasized

Ablative response of a silica phenolic to simulated liquid propellant rocket engine operating conditions

Ablative response of silica phenolic to simulated liquid propellant rocket engine operating condition

Chemical equilibrium analysis of silicon carbide oxidation in oxygen and air

Due to their refractory nature and oxidation resistance, Ultra‐High Temperature Ceramic materials, including silicon carbide, are of interest in hypersonic aerospace applications. To analyze the thermodynamic behavior of silicon carbide during transition between passive and active oxidation states, chemical equilibrium calculations are performed. The predicted oxygen pressures for passive‐to‐active transition show improved agreement up to an order of magnitude with experimental transition data in the literature, compared with Wagner’s model. Both oxygen and air environments are examined, and a 3% difference in transition temperature is observed. Material response analysis demonstrates that a surface temperature jump occurs during thermal oxidation of silicon carbide, corresponding to passive‐to‐active transition.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149275/1/jace16272.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149275/2/jace16272_am.pd

Safety and efficacy of blood exchange transfusion for priapism complicating sickle cell disease.

BACKGROUND: Priapism is unwanted painful penile erection that affects about 36% of boys and men with sickle cell disease (SCD) most of whom have sickle cell anemia. Clinically, priapism could be stuttering, minor, or major. The first two types are mild, last \u3c 4 h, are usually treated at home, have good prognosis with normal sexual function. The major type of priapism lasts \u3e4 h, associated with severe pain, requires hospitalization; often does not respond to medical treatment and may require shunt surgery. Untreated major priapism and surgical intervention often cause impotence. In this study, we report our 15-year experience in treating adult patients with SCD and major priapism with blood exchange transfusion after being refractory to other medical therapies. METHODS: Adult male African Americans patients with SCD and major priapism were enrolled in this study and followed for 15 years. A Haemonitics V-50 machine was initially used for whole blood exchange and was later replaced with Cobe Spectra machine for RBC exchange. RESULTS: We used 239 blood exchanges requiring 1,136 RBC units. We maintained a post-exchange hemoglobin level of about 10 g/dL and hemoglobin S level \u3c 30%. None of the patients had any neurological complications such as headache, seizures, neurological deficits, or obtundation post-exchange. CONCLUSION: Together, the data indicate that blood exchange transfusion for the treatment of patients with SCD and major priapism is efficacious and safe

Calcareous nannofossil assemblage changes across the Paleocene–Eocene Thermal Maximum: Evidence from a shelf setting

Biotic response of calcareous nannoplankton to abrupt warming across the Paleocene/Eocene boundary reflects a primary response to climatically induced parameters including increased continental runoff of freshwater, global acidification of seawater, high sedimentation rates, and calcareous nannoplankton assemblage turnover. We identify ecophenotypic nannofossil species adapted to low pH conditions (Discoaster anartios, D. araneus, Rhomboaster spp.), excursion taxa adapted to the extremely warm climatic conditions (Bomolithus supremus and Coccolithus bownii), three species of the genus Toweius (T. serotinus, T. callosus, T. occultatus) adapted to warm, rather than cool, water conditions, opportunists adapted to high productivity conditions (Coronocyclus bramlettei, Neochiastozygus junctus), and species adapted to oligotropic and/or cool‐water conditions that went into refugium during the PETM (Zygrablithus bijugatus, Calcidiscus? parvicrucis and Chiasmolithus bidens). Discoaster anartios was adapted to meso- to eutrophic, rather than oligotrophic, conditions. Comparison of these data to previous work on sediments deposited on shelf settings suggests that local conditions such as high precipitation rates and possible increase in major storms such as hurricanes resulted in increased continental runoff and high sedimentation rates that affected assemblage response to the PETM

Postimpact deformation associated with the late Eocene Chesapeake Bay impact structure in southeastern Virginia

Upper Cenozoic strata covering the Chesapeake Bay impact structure in southeastern Virginia record intermittent differential movement around its buried rim. Miocene strata in a graben detected by seismic surveys on the York River exhibit variable thickness and are deformed above the crater rim. Fan-like interformational and intraformational angular unconformities within Pliocene–Pleistocene strata, which strike parallel to the crater rim and dip2°–3° away from the crater center, indicate that deformation and deposition were synchronous.Concentric, large-scale crossbedded, bioclastic sand bodies of Pliocene age within ~20 km of the buried crater rim formed on offshore shoals, presumably as subsiding listric slump blocks rotated near the crater rim