Study of optimum discrete estimators in measurement analysis

Study of statistical techniques for obtaining estimates of true data parameters uses discrete measured quantities containing random error. These techniques develop estimation procedures as an iterative algorithm for digital computation in real time

Methods for injection error analysis and their comparison Scientific report no. 13

Formulation of direct and adjoint methods of trajectory injection error in vector matrix notation and compariso

Landing dynamics study for lunar landing research vehicle

Impact dynamics and effects on lunar landing module performance and landing gea

CROP INSURANCE VALUATION UNDER ALTERNATIVE YIELD DISTRIBUTIONS

Considerable disagreement exists about the most appropriate characterization of farm-level yield distributions. Yet, the economic importance of alternate yield distribution specifications on insurance valuation, product designs and farm-level risk management has not been investigated or documented. The results of this study demonstrate that large differences in expected payments from popular crop insurance products can arise solely from the parameterization chosen to represent yields. The results suggest that the frequently unexamined yield distribution specification may lead to incorrect conclusions in important areas of insurance and risk management research such as policy rating, and assessment of expected payments from policies.Risk and Uncertainty,

ESTIMATING FARM-LEVEL YIELD DISTRIBUTIONS FOR CORN AND SOYBEANS IN ILLINOIS

Many yield modeling approaches have been developed in attempts to provide accurate characterizations of farm-level yield distributions due to the importance of yield uncertainty in crop insurance design and rating, and for managing farm-level risk. Competing existing models of crop yields accommodate varying skewness, kurtosis, and other departures from normality including features such as multiple modes. Recently, the received view of crop yield modeling has been challenged by Just and Weninger who indicate that there is insufficient evidence to reject normality given data limitations and potential methodological shortcomings in controlling for deterministic components (trend) in yields. They point out that past empirical efforts to estimate and validate specific-farm distributional characterizations have been severely hampered by data limitations. As a result, they argue in favor of normality as an appropriate parameterization of crop yields. This paper investigates alternate representations of farm-level crop yield distributions using a unique data set from the University of Illinois Endowment farms, containing same-site yield observations for a relatively long period of time, and under conditions that closely mirror actual farm conditions in Illinois. Results from alternate econometric model specifications controlling for trend effects suggest that a linear trend provides an adequate representation of crop yields at the farm level during the period covered by the estimations. Specification tests based on a linear-trend model suggest significant heteroskedasticity is present in only a few farms, and that the residuals are white noise. With these data, Jarque-Bera normality test results indicate that normality of detrended yield residuals is rejected by a far greater number of fields than would be explained due to randomness. Thus, to further clarify the issue of yield distribution characterizations, more complete goodness-of-fit measures are compared across a larger set of candidate distributions. The results indicate that the Weibull distribution consistently ranks better than the normal distribution both in fields where normality is rejected and in fields where normality is not rejected. The results highlight the fact that failing to reject normality is not the same as identifying normality as a "best" parameterization, and provide guidance for progressing toward better representations of farm-level crop yields.Productivity Analysis, Research Methods/ Statistical Methods, Teaching/Communication/Extension/Profession,

Advanced code-division multiplexers for superconducting detector arrays

Multiplexers based on the modulation of superconducting quantum interference devices are now regularly used in multi-kilopixel arrays of superconducting detectors for astrophysics, cosmology, and materials analysis. Over the next decade, much larger arrays will be needed. These larger arrays require new modulation techniques and compact multiplexer elements that fit within each pixel. We present a new in-focal-plane code-division multiplexer that provides multiplexing elements with the required scalability. This code-division multiplexer uses compact lithographic modulation elements that simultaneously multiplex both signal outputs and superconducting transition-edge sensor (TES) detector bias voltages. It eliminates the shunt resistor used to voltage bias TES detectors, greatly reduces power dissipation, allows different dc bias voltages for each TES, and makes all elements sufficiently compact to fit inside the detector pixel area. These in-focal-plane code-division multiplexers can be combined with multi-gigahertz readout based on superconducting microresonators to scale to even larger arrays.Comment: 8 pages, 3 figures, presented at the 14th International Workshop on Low Temperature Detectors, Heidelberg University, August 1-5, 2011, proceedings to be published in the Journal of Low Temperature Physic

Parent/Caregiver Lack of Knowledge: A Barrier for Youth Swimming Ability?

This study examined how a parent’s lack of knowledge of potential opportunities and barriers may restrict the child’s opportunity to learn how to swim. A survey was completed in multiple urban areas (N=524), where parents/caregivers reported their child’s swimming ability, as well as the parent’s knowledge of possible barriers to their child’s participation in swimming. ANOVA results suggested that the only significant difference between the presence of barriers groupings for child’s swimming ability were based on the availability of a pool and ease of access. For potential barriers examined, the group who lacked of barriers had a significantly lower perception of their child’s swimming ability than the group who recognized barriers (p\u3c.001 for all), suggesting that while physical barriers may play a role in a child’s likelihood of learning to swim, the most significant barrier may be the involvement and knowledge of the parent/caregiver

Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields

Time-division SQUID multiplexers are used in many applications that require exquisite control of systematic error. One potential source of systematic error is the pickup of external magnetic fields in the multiplexer. We present measurements of the field sensitivity figure of merit, effective area, for both the first stage and second stage SQUID amplifiers in three NIST SQUID multiplexer designs. These designs include a new variety with improved gradiometry that significantly reduces the effective area of both the first and second stage SQUID amplifiers.Comment: 4 pages, 7 figures. Submitted for publication in the IEEE Transactions on Applied Superconductivity, August 201