Showing papers by "SRI International published in 2023"

Best practices for addressing missing data through multiple imputation

Abstract: A common challenge in developmental research is the amount of incomplete and missing data that occurs from respondents failing to complete tasks or questionnaires, as well as from disengaging from the study (i.e., attrition). This missingness can lead to biases in parameter estimates and, hence, in the interpretation of findings. These biases can be addressed through statistical techniques that adjust for missing data, such as multiple imputation. Although multiple imputation is highly effective, it has not been widely adopted by developmental scientists given barriers such as lack of training or misconceptions about imputation methods. Utilizing default methods within statistical software programs like listwise deletion is common but may introduce additional bias. This manuscript is intended to provide practical guidelines for developmental researchers to follow when examining their data for missingness, making decisions about how to handle that missingness and reporting the extent of missing data biases and specific multiple imputation procedures in publications.

The Beginning of a New Paradigm: From D. Bernouilli to M. Allais

Abstract: To represent the interaction of the human being with his environment and letting him express it, therefore blending the subject with the object and completing what was missing from Quantum theory. In our polynomial the subjective factor Xo shows up in the numerator and leads to an objective valuation since of a finite degree. Study also revives an approach to elicit human preferences based on the stimuli-response procedure long forgotten. Fifty years ago a new theory, Elementary Catastrophe Theory,(E.C.T.), unfolding a unique Potential in our brain, provided the underlying dynamics needed to fulfill all the desiderata of the so-called school of Psycho-Physics (Weber-Fechner, 1860), seeking to make mathematical sense of the procedure above. The axiomatization of a self-measurement process removes any "a priori" assumptions about human motivation from the explanation of the empirical data. This 5th degree symmetric polynomial exhibits a characteristic (Negative Schwarz' Derivative) that goes a long way to resolve disputes and remove obstacles in the development of Portfolio Theory in addition to meeting the major landmark criteria in the fields of Value and Utility. Given that chaos theory has the divergence of Newton's Method as a paradigm, we have brought order to a potentially chaotic process because our algorithm ensures local and global convergence through the careful selection of initial points. The possibility of expanding the approach to the complex field is encouraged by the expression of the Schwarz derivative's invariance to the Mobius transformation.

Global Geomagnetic Perturbation Forecasting Using Deep Learning

Abstract: Geomagnetically Induced Currents (GICs) arise from spatio-temporal changes to Earth's magnetic field, which arise from the interaction of the solar wind with Earth's magnetosphere, and drive catastrophic destruction to our technologically dependent society. Hence, computational models to forecast GICs globally with large forecast horizon, high spatial resolution and temporal cadence are of increasing importance to perform prompt necessary mitigation. Since GIC data is proprietary, the time variability of the horizontal component of the magnetic field perturbation (dB/dt) is used as a proxy for GICs. In this work, we develop a fast, global dB/dt forecasting model, which forecasts 30 min into the future using only solar wind measurements as input. The model summarizes 2 hr of solar wind measurement using a Gated Recurrent Unit and generates forecasts of coefficients that are folded with a spherical harmonic basis to enable global forecasts. When deployed, our model produces results in under a second, and generates global forecasts for horizontal magnetic perturbation components at 1 min cadence. We evaluate our model across models in literature for two specific storms of 5 August 2011 and 17 March 2015, while having a self-consistent benchmark model set. Our model outperforms, or has consistent performance with state-of-the-practice high time cadence local and low time cadence global models, while also outperforming/having comparable performance with the benchmark models. Such quick inferences at high temporal cadence and arbitrary spatial resolutions may ultimately enable accurate forewarning of dB/dt for any place on Earth, resulting in precautionary measures to be taken in an informed manner.

Understanding the Coupled OH Meinel and O2 Atmospheric Band Nightglow Emissions

Abstract: Nightglow emission signatures observed from space- and ground-based instruments are commonly used as proxies for atmospheric composition, especially for the altitude region around 100 km that cannot be easily studied in situ. Monitoring the intensity and temporal evolution of such proxies by remote sensing is often the method of choice to study a plethora of phenomena in this region of the atmosphere. Thus, the quantitative details relevant to the production and deactivation of excited atomic and molecular precursors responsible for prominent nightglow emissions are required to study atmospheric composition, radiative and energy balance, wave propagation and dissipation, as well as transport dynamics. Significant gaps and uncertainties exist in the understanding of the above processes and, as our recent studies on nightglow emissions revealed, substantial revisions of the relevant atmospheric models are warranted.We will present a progress report on our efforts to advance the understanding of key mesospheric nightglow emissions by investigating the recently established coupling between the OH Meinel and the O2 Atmospheric band emissions, mediated by collisions of O atoms with vibrationally excited OH.This work is supported by the U.S. National Science Foundation (NSF) under Grants AGS-2009960 and AGS-2113888.

Opinion: Recent Developments and Future Directions in Studying the Chemistry of the Mesosphere and Lower Thermosphere

Abstract: Abstract. This Opinion article begins with a review of important advances in the science of the Mesosphere and Lower Thermosphere (MLT) region of the atmosphere that have occurred over the past two decades since the founding of Atmospheric Chemistry and Physics. The emphasis is on chemistry (although, of course, this cannot be decoupled from discussion of atmospheric physics and dynamics), and the primary focus is on work during the past 10 years. Topics that are covered include: observations (satellite, rocket and ground-based techniques); the variability and connectedness of the MLT on various length- and time-scales; airglow emissions; the cosmic dust input and meteoric metal layers; and noctilucent (or polar mesospheric) ice clouds. The paper then concludes with a discussion of important unanswered questions and likely future directions for the field over the next decade.