The role of surface generated radicals in catalytic combustion

Experiments were conducted to better understand the role of catalytic surface reactions in determining the ignition characteristics of practical catalytic combustors. Hydrocarbon concentrations, carbon monoxide and carbon dioxide concentrations, hydroxyl radical concentrations, and gas temperature were measured at the exit of a platinum coated, stacked plate, catalytic combustor during the ignition of lean propane-air mixtures. The substrate temperature profile was also measured during the ignition transient. Ignition was initiated by suddenly turning on the fuel and the time to reach steady state was of the order of 10 minutes. The gas phase reaction, showed no pronounced effect due to the catalytic surface reactions, except the absence of a hydroxyl radical overshoot. It is found that the transient ignition measurements are valuable in understanding the steady state performance characteristics

Data base for crack growth properties of materials

A computerized data base of crack growth properties of materials was developed for use in fracture control analysis of rocket engine components and other NASA space hardware. The software system has files of basic crack growth rate data, other fracture mechanics material properties such as fracture toughness and environmental crack growth threshold values, and plotting and fitting routines for deriving material properties for use in fracture control analysis. An extensive amount of data was collected and entered, and work is continuing on compiling additional data. The data base and software codes are useful both for fracture control analysis and for evaluation or development of improved crack growth theories

Letter from B. H. Royce to John Muir, 1889 Jul 13.

Chico July 13 1889Mr John MuirWill you permit me as one of the legion of delighted readers of Picturesque California, to suggest an improvement as to the placing of vignettes and cuts. Up in a corner, down at the bottom, over one side, or entirely across the middle of the page; so the text is not torn, is what I would suggest. What can be more exasperating for instance, than for a reader to be perfectly entranced with living glowing word painting, spellbound, drawing in 013652inspiration from wonderful glaciers, basking in the sunshine reflected from eternal snows, gazing on the fantastic cloud weather that lovingly enfold a mountain crest listening to the rythm of waterfalls! Every pulse and fibre vibrating with tense enjoyment: When suddenly some men on snowshoes come crashing down through the middle of the page! Sentences are haggled in twain, left-ragged and raw, The spell is broken the visions vanish After the rude shock and we pull ourselves together, there is but one feeling dominating outraged nature, and that is the eager hope that those men will get01365 [3]their necks broken when they reach the bottom! Mountain peaks, mule deer, sage hens, burros and mountaineer, burst through the text very much as a circus girl jumps through a paper hoop. The girl looks pretty and triumphant; the hoop is ruined until covered again! Hoping that the spell your magic pen will in future weave around your readers will not be rudely broken by the printer or artist\u27s whims.I am very trulyYour indebted [illegible]B.H. Royc

Phosphatic Urinary Calculi

Many questions as to the cause, prevention and treatment of urinary calculi remain yet unanswered. However, many experiments the past several years provide a basis for a greater understanding of this problem and its control

Coupling of Transport and Chemical Processes in Catalytic Combustion

Catalytic combustors have demonstrated the ability to operate efficiently over a much wider range of fuel air ratios than are imposed by the flammability limits of conventional combustors. Extensive commercial use however needs the following: (1) the design of a catalyst with low ignition temperature and high temperature stability, (2) reducing fatigue due to thermal stresses during transient operation, and (3) the development of mathematical models that can be used as design optimization tools to isolate promising operating ranges for the numerous operating parameters. The current program of research involves the development of a two dimensional transient catalytic combustion model and the development of a new catalyst with low temperature light-off and high temperature stablity characteristics

Experimental Evaluation of Fatigue Crack Initiation from Corroded Hemispherical Notches in Aerospace Structural Materials

A test program was developed and executed to evaluate the influence of corroded hemispherical notches on the fatigue crack initiation and propagation in aluminum 7075-T7351, 4340 steel, and D6AC steel. Surface enhancements such as shot peening and laser shock peening were also incorporated as part of the test effort with the intent of improving fatigue performance. In addition to the testing, fracture mechanics and endurance limit based analysis methods were evaluated to characterize the results with the objective of challenging typical assumptions used in modeling fatigue cracks from corrosion pits. The results specifically demonstrate that the aluminum and steel alloys behave differently with respect to fatigue crack initiation from hemispherical corrosion pits. The aluminum test results were bounded by the fracture mechanics and endurance limit models while exhibiting a general insensitivity to the residual stress field generated by shot peening. The steel specimens were better characterized by the endurance limit fatigue properties and did exhibit sensitivities to residual stresses from the shot peening and laser shock peenin

An efficient pseudomedian filter for tiling microrrays

<p>Abstract</p> <p>Background</p> <p>Tiling microarrays are becoming an essential technology in the functional genomics toolbox. They have been applied to the tasks of novel transcript identification, elucidation of transcription factor binding sites, detection of methylated DNA and several other applications in several model organisms. These experiments are being conducted at increasingly finer resolutions as the microarray technology enjoys increasingly greater feature densities. The increased densities naturally lead to increased data analysis requirements. Specifically, the most widely employed algorithm for tiling array analysis involves smoothing observed signals by computing pseudomedians within sliding windows, a <it>O</it>(<it>n</it>²log<it>n</it>) calculation in each window. This poor time complexity is an issue for tiling array analysis and could prove to be a real bottleneck as tiling microarray experiments become grander in scope and finer in resolution.</p> <p>Results</p> <p>We therefore implemented Monahan's HLQEST algorithm that reduces the runtime complexity for computing the pseudomedian of <it>n </it>numbers to <it>O</it>(<it>n</it>log<it>n</it>) from <it>O</it>(<it>n</it>²log<it>n</it>). For a representative tiling microarray dataset, this modification reduced the smoothing procedure's runtime by nearly 90%. We then leveraged the fact that elements within sliding windows remain largely unchanged in overlapping windows (as one slides across genomic space) to further reduce computation by an additional 43%. This was achieved by the application of skip lists to maintaining a sorted list of values from window to window. This sorted list could be maintained with simple <it>O</it>(log <it>n</it>) inserts and deletes. We illustrate the favorable scaling properties of our algorithms with both time complexity analysis and benchmarking on synthetic datasets.</p> <p>Conclusion</p> <p>Tiling microarray analyses that rely upon a sliding window pseudomedian calculation can require many hours of computation. We have eased this requirement significantly by implementing efficient algorithms that scale well with genomic feature density. This result not only speeds the current standard analyses, but also makes possible ones where many iterations of the filter may be required, such as might be required in a bootstrap or parameter estimation setting. Source code and executables are available at <url>http://tiling.gersteinlab.org/pseudomedian/</url>.</p

Scaling Roll Call Votes with wnominate in R

This paper presents a software package designed to estimate Poole and Rosenthal W-NOMINATE scores in R. The package uses a logistic regression model to analyze political choice data, usually (though not exclusively) from a legislative setting. In contrast to other scaling methods, W-NOMINATE explicitly assumes probabilistic voting based on a spatial utility function, where the parameters of the utility function and the spatial coordinates of the legislators and the votes can all be estimated on the basis of observed voting behavior. Building on software written by Poole in Fortran, the new wnominate package in R facilitates easier data input and manipulation, generates bootstrapped standard errors, and includes a new suite of graphics functions to display the results. We demonstrate the functionality of this package by conducting a natural experiment using roll calls -- an experiment which is greatly simplified by the data manipulation capabilities of the wnominate package in R

Material Strength Effect in the Shock Compression of Alumina

The Hugoniot elastic limits (HEL) of a high-density aluminum oxide ceramic (Lucalox) and a slightly lower-density ceramic (porosity approximately 4%) were determined to be 112±13 and 83±5 kbar, respectively. Above the HEL, the shock-stress-volume Hugoniot curves for both materials are offset by 40 kbar or more above their hydrostatic-pressure-volume curves. These results indicate that shear stresses with magnitudes of about 30–40 kbar persist in aluminum oxide to shock-pressure levels of at least 300 kbar