A ’Millipede’ scanner model - Energy consumption and performance

This short report (1) describes an energy model for the seek and read/write operations in a mass-balanced Y-scanner for parallel-probe storage by IBM [1] and (2) updates the settings of the MEMS model in DiskSim with recent published figures from this XY-scanner. To speedup system simulations, a straight forward second-order model is used without control loop. Read/write operation is modeled by quasi-static calculations. To approximate seek behavior, ’bang-bang’ control is assumed; the result is close to the actual behavior with control loop [2]. Unfortunately, no energy measurements were available to validate the model. Using the proposed energy model, we are able to study the energy consumption of a MEMS-based storage device for different application areas and file systems

CMB Lensing Power Spectrum Biases from Galaxies and Clusters using High-angular Resolution Temperature Maps

The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to ACT and SPT. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on sigma_8 and an uncertainty on the total neutrino mass of approximately 50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M_vir = 10^14 M_sun. To achieve such percent level bias, we find that only modes up to a maximum multipole of l_max ~ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.Comment: 14 pages, 14 figures, to be submitted to Ap

Basic and regional characteristics of streamflow in the Upper Colorado River Basin: interim report

CER70-71GBE-HJMSS6.December 1970.Includes bibliographical reference (pages 23-24).Prepared for: Bureau of Reclamation, Division of Atmospheric Water Resources Management, Denver, Colorado, Project Skywater.This report describes the first phase of a research project concerned with two somewhat related subjects: 1. The study of the flow regimen of the rivers in the Upper Colorado River Basin and their relation to differences in geology, geomorphology, latitude, longitude, and physiographic parameters. 2. The application of such relations to the selection of hydrologically suitable basins for precipitation management. In this report, only general results about the flow characteristics of the streams in the Upper Colorado River Basin are presented. The determination of the streamflow characteristics was obtained from monthly flow data as published by the U.S. Geological Survey and corrected for diversions and regulations. Corrected records, stored on magnetic tape, for 707 stations were used in the study. From the monthly flow data mean yearly hydrographs have been computed for all stations. These hydrographs are expressed as specific yield in units of inches, cfs/sq. mi and liters per second per km2. The hydrographs are drawn on regular (linear), semi-logarithmic and double logarithmic scales. Monthly duration curves and mean yearly graphs of monthly coefficients of variation are also presented. This report contains a brief description of the methodology for the calculations, samples of computer output, tables of the calculated values and samples of various kinds of graphs which present in a concise and appealing visual way the characteristics of each gaging station. Maps with the results for the Colorado River Basin Project Area, a Bureau of Reclamation program of precipitation management in the San Juan Mountains area of Colorado, are given. A second report to be published later will contain an interpretation of the results and the implications for precipitation management.Under contract no. 14-06-D-6597

Minimizing gravitational lensing contributions to the primordial bispectrum covariance

The next generation of ground-based cosmic microwave background (CMB) experiments aim to measure temperature and polarization fluctuations up to ℓmax≈5000 over half of the sky. Combined with Planck data on large scales, this will provide improved constraints on primordial non-Gaussianity. However, the impressive resolution of these experiments will come at a price. Besides signal confusion from galactic foregrounds, extragalactic foregrounds, and late-time gravitational effects, gravitational lensing will introduce large non-Gaussianity that can become the leading contribution to the bispectrum covariance through the connected four-point function. Here, we compute this effect analytically for the first time on the full sky for both temperature and polarization. We compare our analytical results with those obtained directly from map-based simulations of the CMB sky for several levels of instrumental noise. Of the standard shapes considered in the literature, the local shape is most affected, resulting in a 35% increase of the estimator standard deviation for an experiment such as the Simons Observatory (SO) and a 110% increase for a cosmic-variance limited experiment, including both temperature and polarization modes up to ℓmax=3800. Because of the nature of the lensing four-point function, the impact on other shapes is reduced while still non-negligible for the orthogonal shape. Two possible avenues to reduce the non-Gaussian contribution to the covariance are proposed: First by marginalizing over lensing contributions, such as the Integrated Sachs Wolfe (ISW)-lensing three-point function in temperature, and second by delensing the CMB. We show the latter method can remove almost all extra covariance, reducing the effect to below <5% for local bispectra. At the same time, delensing would remove signal biases from secondaries induced by lensing, such as ISW lensing. We aim to apply both techniques directly to the forthcoming SO data when searching for primordial non-Gaussianity