Study of high-speed angular-contact ball bearings under dynamic load

Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel

Electron- and Positron-Impact Ionization of Inert Gases

Triple-differential cross sections (TDCS) are presented for the electron and positron impact ionization of inert gas atoms in a range of geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions which cannot be separately detected in an experiment with a single projectile. A comparison is presented between theory and the recent experiments of [Gavin, deLucio, and DuBois, Phys. Rev. A95, 062703 (2017)] for e± and contrasted with the results from earlier electron experiments. For the special case of xenon(5p), cross sections are presented for both electron- and positron-impact ionization in kinematics where the electron case appears well understood. The kinematics are then varied in order to focus on the possible role of distortion, exchange, and target wave-function effects

Converting InSAR- and GNSS-derived strain rate maps into earthquake hazard models for Anatolia

&amp;lt;p&amp;gt;Geodetic measurements of crustal deformation rates can provide important constraints on a region&amp;amp;#8217;s earthquake hazard that purely seismicity-based hazard models may miss. For example, geodesy might show that strain (or a deficit of seismic moment) is accumulating faster than the total rate at which known earthquakes have released it, implying that the long-term hazard may include larger earthquakes with long recurrence intervals (and/or temporal increases in seismicity rates). Conversely, the moment release rate in recent earthquakes might surpass the geodetic moment buildup rate, suggesting that the long-term-average earthquake activity and hazard may in fact may be more quiescent than might be estimated using the earthquake history alone. Such geodetic constraints, however, have traditionally been limited by poor spatial and/or temporal sampling, resulting in ambiguities about how the lithosphere accommodates strain in space and time that can bias estimates of the resulting hazard. High-resolution deformation maps address this limitation by imaging (rather than presuming and/or modelling) where and how deformation takes place. These maps are now within reach for the Alpine-Himalayan Belt &amp;amp;#8211; one of the most populous and seismically hazardous regions on Earth &amp;amp;#8211; thanks to the COMET-LiCSAR InSAR processing system, which performs large-scale automated processing and timeseries analysis of Sentinel-1 data provided by the EU&amp;amp;#8217;s Copernicus programme. We are pairing LiCSAR products with GNSS data to generate high-resolution maps of interseismic surface motion (velocity) and strain rate for the Anatolia region. Here we quantitively investigate what these strain rate distributions imply for seismic hazard in this region, using two approaches in parallel.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;First, building on previous work, we develop a fully probability-based method to pair geodesy and seismic catalogs to estimate the recurrence times of large, moderate and small earthquakes in a given region. We assume that earthquakes 1) obey a power-law magnitude-frequency distribution up to a maximum magnitude and 2) collectively release seismic moment at the same rate that we estimate it is accumulating from the strain rate maps. Iterating over various magnitude-frequency distributions and their governing parameters, and formally incorporating uncertainties in moment buildup rate and the magnitudes of recorded earthquakes, we build a probabilistic long-term-average earthquake model for Anatolia as a whole, including the most likely maximum earthquake magnitude. Second, we estimate how seismic hazard may vary from place to place within Anatolia. Using insights from dislocation models, we identify two key signatures of a locked fault in a strain rate field, allowing us to convert the newly developed strain maps to &amp;amp;#8220;effective fault maps.&amp;amp;#8221; Additionally, we explore how characteristics of earthquake magnitude-frequency distributions may scale with the rate of strain (or moment) buildup, and what these scaling relations imply for the distribution of hazard in Anatolia, using the seismic catalog to evaluate these hypotheses. We also explore the implications of our findings for seismic hazard and address how to expand these approaches to the Alpine-Himalaya Belt as a whole.&amp;lt;/p&amp;gt; </jats:p

Configuration development study of the X-24C hypersonic research airplane

Bottom line results were made of a three-phase study to determine the feasibility of designing, building, and operating, and maintaining an air-launched high performance aircraft capable of cruising at speeds up to Mach 8 for short durations. The results show that Lockalloy heat-sink structure affords the capability for a 'work-horse' vehicle which can serve as an excellent platform for this research. It was further concluded that the performance of a blended wing body configuration surpassed that of a lifting body design for typical X-24C missions. The cost of a two vehicle program, less engines, B-52 modification and contractor support after delivery, can be kept within $70M (in Jan. 1976 dollars)

Switchgrass Biomass Production in the Midwest USA: Harvest and Nitrogen Management

Information on optimal harvest periods and N fertilization rates for switchgrass (Panicum virgatum L.) grown as a biomass or bioenergy crop in the Midwest USA is limited. Our objectives were to determine optimum harvest periods and N rates for biomass production in the region. Established stands of \u27Cave-in-Rock\u27 switchgrass at Ames, IA, and Mead, NE, were fertilized 0, 60, 120, 180, 240, or 300 kg N ha-1. Harvest treatments were two- or one-cut treatments per year, with initial harvest starting in late June or early July (Harvest 1) and continuing at approximately 7-d intervals until the latter part of August (Harvest 7). A final eighth harvest was completed after a killing frost. Regrowth was harvested on previously harvested plots at that time. Soil samples were taken before fertilizer was applied in the spring of 1994 and again in the spring of 1996. Averaged over years, optimum biomass yields were obtained when switchgrass was harvested at the maturity stages R3 to R5 (panicle fully emerged from boot to postanthesis) and fertilized with 120 kg N ha-1. Biomass yields with these treatments averaged 10.5 to 11.2 Mg ha-1 at Mead and 11.6 to 12.6 Mg ha-1 at Ames. At this fertility level, the amount of N removed was approximately the same as the amount applied. At rates above this level, soil NO3-N concentrations increased

Finite type approximations of Gibbs measures on sofic subshifts

Consider a H\"older continuous potential $\phi$ defined on the full shift A^\nn, where $A$ is a finite alphabet. Let X\subset A^\nn be a specified sofic subshift. It is well-known that there is a unique Gibbs measure $\mu_\phi$ on $X$ associated to $\phi$. Besides, there is a natural nested sequence of subshifts of finite type $(X_m)$ converging to the sofic subshift $X$. To this sequence we can associate a sequence of Gibbs measures $(\mu_{\phi}^m)$. In this paper, we prove that these measures weakly converge at exponential speed to $\mu_\phi$ (in the classical distance metrizing weak topology). We also establish a strong mixing property (ensuring weak Bernoullicity) of $\mu_\phi$. Finally, we prove that the measure-theoretic entropy of $\mu_\phi^m$ converges to the one of $\mu_\phi$ exponentially fast. We indicate how to extend our results to more general subshifts and potentials. We stress that we use basic algebraic tools (contractive properties of iterated matrices) and symbolic dynamics.Comment: 18 pages, no figure

A new displacement-based approach to calculate stress intensity factors with the boundary element method

The analysis of cracked brittle mechanical components considering linear elastic fracture mechanics is usually reduced to the evaluation of stress intensity factors (SIFs). The SIF calculation can be carried out experimentally, theoretically or numerically. Each methodology has its own advantages but the use of numerical methods has be-come very popular. Several schemes for numerical SIF calculations have been developed, the J-integral method being one of the most widely used because of its energy-like formulation. Additionally, some variations of the J-integral method, such as displacement-based methods, are also becoming popular due to their simplicity. In this work, a simple displacement-based scheme is proposed to calculate SIFs, and its performance is compared with contour integrals. These schemes are all implemented with the Boundary Element Method (BEM) in order to exploit its advantages in crack growth modelling. Some simple examples are solved with the BEM and the calculated SIF values are compared against available solutions, showing good agreement between the different schemes