Low cost automated precise time measurement system

The Aerospace Guidance and Metrology Center (AGMC) has the responsibility for the dissemination of Precise Time and Time Interval (PTTI) to Air Force timing systems requiring microsecond time. In order to maintain traceability to the USNO Master Clock in Washington D.C., and accomplish efficient logging of time and frequency data on individual precision clocks, a simple automatic means of acquiring precise time has been devised. The Automatic Time Interval Measurement System (ATIMS) consists of a minicomputer (8K Memory), teletype terminal, electronic counter, Loran C receiver, time base generator and locally-manufactured relay matrix panel. During the measurement process, the computer controls the relay matrix which selects for comparison 13 atomic clocks against a reference clock and the reference versus Loran C. Through use of the system teletype, the operator is able to set the system clock (hours, minutes and seconds), examine and/or modify all clock data and constants, and set measurement intervals. This is done in a conversational manner. A logic flow diagram, system schematic, source listing and software components are included in the presentation

Prediction of rainfall intensity measurement errors using commercial microwave communication links

Commercial microwave radio links forming cellular communication networks are known to be a valuable instrument for measuring near-surface rainfall. However, operational communication links are more uncertain relatively to the dedicated installations since their geometry and frequencies are optimized for high communication performance rather than observing rainfall. Quantification of the uncertainties for measurements that are non-optimal in the first place is essential to assure usability of the data. <br><br> In this work we address modeling of instrumental impairments, i.e. signal variability due to antenna wetting, baseline attenuation uncertainty and digital quantization, as well as environmental ones, i.e. variability of drop size distribution along a link affecting accuracy of path-averaged rainfall measurement and spatial variability of rainfall in the link's neighborhood affecting the accuracy of rainfall estimation out of the link path. Expressions for root mean squared error (RMSE) for estimates of path-averaged and point rainfall have been derived. To verify the RMSE expressions quantitatively, path-averaged measurements from 21 operational communication links in 12 different locations have been compared to records of five nearby rain gauges over three rainstorm events. <br><br> The experiments show that the prediction accuracy is above 90% for temporal accumulation less than 30 min and lowers for longer accumulation intervals. Spatial variability in the vicinity of the link, baseline attenuation uncertainty and, possibly, suboptimality of wet antenna attenuation model are the major sources of link-gauge discrepancies. In addition, the dependence of the optimal coefficients of a conventional wet antenna attenuation model on spatial rainfall variability and, accordingly, link length has been shown. <br><br> The expressions for RMSE of the path-averaged rainfall estimates can be useful for integration of measurements from multiple heterogeneous links into data assimilation algorithms

Development of a daily gridded precipitation data set for the Middle East

We show an algorithm to construct a rain-gauge-based analysis of daily precipitation for the Middle East. One of the key points of our algorithm is to construct an accurate distribution of climatology. One possible advantage of this product is to validate high-resolution climate models and/or to diagnose the impact of climate changes on local hydrological resources. Many users are familiar with a monthly precipitation dataset (New et al., 1999) and a satellite-based daily precipitation dataset (Huffman et al., 2001), yet our data set, unlike theirs, clearly shows the effect of orography on daily precipitation and other extreme events, especially over the Fertile Crescent region. Currently the Middle-East precipitation analysis product is consisting of a 25-year data set for 1979–2003 based on more than 1300 stations

Employee Benefits and Labor Markets in Canada and the United States

Alpert and Woodbury present a comprehensive set of explorations into the impacts that the provision of various types of employee benefits (or lack thereof) have on labor markets. And while there are, as the editors point out, substantial differences between the employee benefits systems of Canada and the U.S., these differences showcase the impacts of specific policies related to employee benefits on labor markets.https://research.upjohn.org/up_press/1187/thumbnail.jp

Giving patients granular control of personal health information: Using an ethics ‘Points to Consider’ to inform informatics system designers

Objective: There are benefits and risks of giving patients more granular control of their personal health information in electronic health record (EHR) systems. When designing EHR systems and policies, informaticists and system developers must balance these benefits and risks. Ethical considerations should be an explicit part of this balancing. Our objective was to develop a structured ethics framework to accomplish this. Methods: We reviewed existing literature on the ethical and policy issues, developed an ethics framework called a “Points to Consider” (P2C) document, and convened a national expert panel to review and critique the P2C. Results: We developed the P2C to aid informaticists designing an advanced query tool for an electronic health record (EHR) system in Indianapolis. The P2C consists of six questions (“Points”) that frame important ethical issues, apply accepted principles of bioethics and Fair Information Practices, comment on how questions might be answered, and address implications for patient care. Discussion: The P2C is intended to clarify whatis at stake when designers try to accommodate potentially competing ethical commitments and logistical realities. The P2C was developed to guide informaticists who were designing a query tool in an existing EHR that would permit patient granular control. While consideration of ethical issues is coming to the forefront of medical informatics design and development practices, more reflection is needed to facilitate optimal collaboration between designers and ethicists. This report contributes to that discussion

Ice nucleation from aqueous NaCl droplets with and without marine diatoms

Ice formation in the atmosphere by homogeneous and heterogeneous nucleation is one of the least understood processes in cloud microphysics and climate. Here we describe our investigation of the marine environment as a potential source of atmospheric IN by experimentally observing homogeneous ice nucleation from aqueous NaCl droplets and comparing against heterogeneous ice nucleation from aqueous NaCl droplets containing intact and fragmented diatoms. Homogeneous and heterogeneous ice nucleation are studied as a function of temperature and water activity, <i>a</i><sub>w</sub>. Additional analyses are presented on the dependence of diatom surface area and aqueous volume on heterogeneous freezing temperatures, ice nucleation rates, ω<sub>het</sub>, ice nucleation rate coefficients, <i>J</i><sub>het</sub>, and differential and cumulative ice nuclei spectra, <i>k(T)</i> and <i>K(T)</i>, respectively. Homogeneous freezing temperatures and corresponding nucleation rate coefficients are in agreement with the water activity based homogeneous ice nucleation theory within experimental and predictive uncertainties. Our results confirm, as predicted by classical nucleation theory, that a stochastic interpretation can be used to describe the homogeneous ice nucleation process. Heterogeneous ice nucleation initiated by intact and fragmented diatoms can be adequately represented by a modified water activity based ice nucleation theory. A horizontal shift in water activity, Δ<i>a</i><sub>w, het</sub> = 0.2303, of the ice melting curve can describe median heterogeneous freezing temperatures. Individual freezing temperatures showed no dependence on available diatom surface area and aqueous volume. Determined at median diatom freezing temperatures for <i>a</i><sub>w</sub> from 0.8 to 0.99, ω<sub>het</sub><u>~</u>0.11<sup>+0.06</sup><sub>−0.05</sub> s<sup>−1</sup>, <i>J</i><sub>het</sub><u>~</u>1.0<sup>+1.16</sup><sub>−0.61</sub>×10<sup>4</sup> cm<sup>−2</sup> s<sup>−1</sup>, and <i>K</i><u>~</u>6.2<sup>+3.5</sup><sub>−4.1</sub> ×10<sup>4</sup> cm<sup>−2</sup>. The experimentally derived ice nucleation rates and nuclei spectra allow us to estimate ice particle production which we subsequently use for a comparison with observed ice crystal concentrations typically found in cirrus and polar marine mixed-phase clouds. Differences in application of time-dependent and time-independent analyses to predict ice particle production are discussed