Substructure: Clues to the Formation of Clusters of Galaxies

We have examined the spatial distribution of substructure in clusters of galaxies using Einstein X-ray observations. Subclusters are found to have a markedly anisotropic distribution that reflects the surrounding matter distribution on supercluster scales. Our results suggest a picture in which cluster formation proceeds by mergers of subclusters along large-scale filaments. The implications of such an anisotropic formation process for the shapes, orientations and kinematics of clusters are discussed briefly.Comment: 7 pages, uuencoded compressed postscript. To appear in ApJ Letters (September 20, 1995 issue

To catch a falling robber

We consider a Cops-and-Robber game played on the subsets of an $n$-set. The robber starts at the full set; the cops start at the empty set. On each turn, the robber moves down one level by discarding an element, and each cop moves up one level by gaining an element. The question is how many cops are needed to ensure catching the robber when the robber reaches the middle level. Aaron Hill posed the problem and provided a lower bound of $2^{n/2}$ for even $n$ and $\binom{n}{\lceil n/2 \rceil}2^{-\lfloor n/2 \rfloor}$ for odd $n$. We prove an upper bound (for all $n$) that is within a factor of $O(\ln n)$ times this lower bound.Comment: Minor revision

Reinforcement Learning for UAV Attitude Control

Autopilot systems are typically composed of an "inner loop" providing stability and control, while an "outer loop" is responsible for mission-level objectives, e.g. way-point navigation. Autopilot systems for UAVs are predominately implemented using Proportional, Integral Derivative (PID) control systems, which have demonstrated exceptional performance in stable environments. However more sophisticated control is required to operate in unpredictable, and harsh environments. Intelligent flight control systems is an active area of research addressing limitations of PID control most recently through the use of reinforcement learning (RL) which has had success in other applications such as robotics. However previous work has focused primarily on using RL at the mission-level controller. In this work, we investigate the performance and accuracy of the inner control loop providing attitude control when using intelligent flight control systems trained with the state-of-the-art RL algorithms, Deep Deterministic Gradient Policy (DDGP), Trust Region Policy Optimization (TRPO) and Proximal Policy Optimization (PPO). To investigate these unknowns we first developed an open-source high-fidelity simulation environment to train a flight controller attitude control of a quadrotor through RL. We then use our environment to compare their performance to that of a PID controller to identify if using RL is appropriate in high-precision, time-critical flight control.Comment: 13 pages, 9 figure

Advancing Information Design for Architectural Image Interfaces

A Level II Digital Humanities Start-Up grant of $49,673 is requested for the design and implementation of an innovative and highly sophisticated user interface for the Brumfield Russian Architecture Photographic Collection of some 30,000 images, which has been digitized and cataloged by the University of Washington Libraries-- an enormously labor-intensive process. This work was supported by an NEH grant in 2006-2009, an earlier pilot grant from the Gladys Kriebel Delmas Foundation, and subsequent smaller awards from the Allen and Smith Foundations. This project will realize in a fully functioning interface both the possibilities inherent in the already innovative metadata structure devised for the collection under the previous grants, and the potential of the most recent techniques and strategies for managing and presenting large and complex data sets on the internet

US presidents exercise centralized control over thebureaucracy primarily through reactive oversight.

More than 2.5 million people work across the entire executive branch of the US government in hundreds of agencies and commissions. William West takes an in-depth look at how the President is able to oversee this vast bureaucracy. He writes that centralized influence over agency policy making is mostly reactive and based around the practice of regulatory review. He argues that Presidents lack the organizational capacity to monitor and influence what agencies do in more than a selective way, and that this reactive strategy allows the White House to focus its limited resources on agency initiatives that are problematic while ignoring the majority that are not

Emission of radiation in chemical reaction

(I) The object of this work was to ascertain if chemical reactions in general are accompanied by the emission of radiation representing the energy change associated with the reaction.(2) The emission spectra of the halogens have been investigated. The essential similarity in type of the spectra of chlorine, bromine and iodine has been observed and a new line emission spectrum of iodine has been found. In all three halogens a band has been observed, of the form, and in the position of the predicted electron affinity spectrum. The spectrum of iodine has been produced by slow-electron impact and has been shown to be the same as that produced by high tension oscillatory discharges.(3) It has been shown that iodine vapour is ionised by exposure to ultraviolet light of wavelength shorter than I85 μμ.(4) The emission spectra of the halogen hydrides have been examined,, They are identical with those of the corresponding halogen with the addition of the Balmer series of hydrogen. No emission has been observed which can be identified with a "reaction spectrum"(5) A number of reactions have been examined, under various conditions of temperature and pressure, for a reaction spectrum. In no case hat- > such an emission been found. The conclusion is drawn that the energy of reaction is dissipated in the elementary process in some other way than as electromagnetic radiation.(6) The consideration of physical 'results on the transference of energy between electrons and excited atoms, on the one hand, and normal atoms, leads to the conclusion that the energy made available in chemical reactions is dissipated in collision with normal molecules, a conception which appears to account or, in a general way, the prediction of heat and of light in reactions, ionisation in reactions, photo-chemical sensitisation and certain facts of chemical kinetics

Racial Impact Assessment in Land Use Planning and Zoning

Racial impact assessments are tools that attempt to predict the effects of actions to help policymakers evaluate the consequences of those actions before their implementation. This article explains the history of race and land use in the United States, the development of racial impact assessments, and the emerging trend of racial impact assessments in land use planning and zoning. The article concludes with an analysis of how racial impact assessments in land use might develop in the future

Energy absorption and bending stiffness in CFRP laminates : the effect of 45º plies

The impact characteristics of cross-ply and angle-ply composite laminates were investigated, with an instrumented impact drop tester by performing gravity assisted drop tests on [0/90]6s and [0/45/90]4s laminates. The impact energy was kept constant at 12 J for all the tests. From the dynamic responses presented here as force history, energy history and force-displacement plots, relevant characteristics such as contact time, delamination load, absorbed energy, bending stiffness, after impact deflection etc were obtained. The plots were non-smooth, disclosing the salient features of the composites. It was important to note that the [0/45/90]4s was more resistant to impact bending, but incurred more damage as exhibited by its higher contact time and absorbed energy. The laminates were sectioned through the impact point and magnified macro and micro photographs were taken to show the failure modes, which include delamination, matrix cracking etc

Predicting Whole Forest Structure, Primary Productivity, and Biomass Density From Maximum Tree Size and Resource Limitations

In the face of uncertain biological response to climate change and the many critiques concerning model complexity it is increasingly important to develop predictive mechanistic frameworks that capture the dominant features of ecological communities and their dependencies on environmental factors. This is particularly important for critical global processes such as biomass changes, carbon export, and biogenic climate feedback. Past efforts have successfully understood a broad spectrum of plant and community traits across a range of biological diversity and body size, including tree size distributions and maximum tree height, from mechanical, hydrodynamic, and resource constraints. Recently it was shown that global scaling relationships for net primary productivity are correlated with local meteorology and the overall biomass density within a forest. Along with previous efforts, this highlights the connection between widely observed allometric relationships and predictive ecology. An emerging goal of ecological theory is to gain maximum predictive power with the least number of parameters. Here we show that the explicit dependence of such critical quantities can be systematically predicted knowing just the size of the largest tree. This is supported by data showing that forests converge to our predictions as they mature. Since maximum tree size can be calculated from local meteorology this provides a general framework for predicting the generic structure of forests from local environmental parameters thereby addressing a range of critical Earth-system questions.Comment: 26 pages, 4 figures, 1 Tabl

Who Are The Christian Churches And What Do We Believe?

https://digitalcommons.acu.edu/crs_books/1488/thumbnail.jp