In-flight direct-strike lightning research

Tests designed to investigate the lightning-generated electromagnetic environment affecting aircraft are discussed. An F-106B aircraft specially instrumented for lightning electromagnetic measurements was used. The instrumentation system is reviewed and typical results recorded by the instrumentation during simulated-lightning ground tests performed for a safety survey are presented. Several examples of data obtained during summer flight testing are presented and future plans are discussed

The 1981 direct strike lightning data

Data waveforms obtained during the 1981 direct strike lightning tests, utilizing the NASA F-106B aircraft specially instrumented for lightning electromagnetic measurements are presented. The aircraft was operated in a thunderstorm environment to elicit strikes. Electromagnetic field data were recorded for both attached lightning and free field excitation of the aircraft

The role of labor market intermittency in explaining gender wage differentials

Using the Health and Retirement Survey and standard wage decomposition techniques, this paper finds that the difference in intermittent labor force participation between men and women accounts for 47 percent of the contribution to the wage gap of differences in observed characteristics. Not controlling for intermittent behavior results in too much importance being placed on gender differences in job characteristics.

Female labor force intermittency and current earnings: a switching regression model with unknown sample selection

Using the Health and Retirement Survey, this paper finds a 16 percent selectivity-corrected wage penalty among women who engage in intermittent labor market activity. This penalty is experienced at a low level of intermittent activity but appears not to play an important role in a woman’s decision to undertake such activity. In addition, employer preferences appear to play a larger role than human capital atrophy in the determination of the wage penalty.

Assessing the impact of education and marriage on labor market exit decisions of women

During the late 1990s, the convergence of women's labor force participation rates to men's rates came to a halt. This paper explores the degree to which the role of education and marriage in women's labor supply decisions also changed over this time period. Specifically, this paper investigates women's decisions to exit the labor market upon the birth of a child. The results indicate that changing exit behavior among married, educated women at this period in their lives was not likely the driving force behind the aggregate changes seen in labor force participation. Rather, changes in exit rates among single women, particularly those less educated, are much more consistent with the changing pattern of aggregate female labor force participation.

A Semi-Blind Source Separation Method for Differential Optical Absorption Spectroscopy of Atmospheric Gas Mixtures

Differential optical absorption spectroscopy (DOAS) is a powerful tool for detecting and quantifying trace gases in atmospheric chemistry \cite{Platt_Stutz08}. DOAS spectra consist of a linear combination of complex multi-peak multi-scale structures. Most DOAS analysis routines in use today are based on least squares techniques, for example, the approach developed in the 1970s uses polynomial fits to remove a slowly varying background, and known reference spectra to retrieve the identity and concentrations of reference gases. An open problem is to identify unknown gases in the fitting residuals for complex atmospheric mixtures. In this work, we develop a novel three step semi-blind source separation method. The first step uses a multi-resolution analysis to remove the slow-varying and fast-varying components in the DOAS spectral data matrix $X$. The second step decomposes the preprocessed data $\hat{X}$ in the first step into a linear combination of the reference spectra plus a remainder, or $\hat{X} = A\,S + R$, where columns of matrix $A$ are known reference spectra, and the matrix $S$ contains the unknown non-negative coefficients that are proportional to concentration. The second step is realized by a convex minimization problem $S = \mathrm{arg} \min \mathrm{norm}\,(\hat{X} - A\,S)$, where the norm is a hybrid $\ell_1/\ell_2$ norm (Huber estimator) that helps to maintain the non-negativity of $S$. The third step performs a blind independent component analysis of the remainder matrix $R$ to extract remnant gas components. We first illustrate the proposed method in processing a set of DOAS experimental data by a satisfactory blind extraction of an a-priori unknown trace gas (ozone) from the remainder matrix. Numerical results also show that the method can identify multiple trace gases from the residuals.Comment: submitted to Journal of Scientific Computin

Earnings on the information technology roller coaster: insight from matched employer-employee data

This paper uses matched employer-employee data for the state of Georgia to examine workers’ earnings experience through the information technology (IT) sector’s employment boom of the mid-1990s and its bust in the early 2000s. The results show that even after controlling for individual characteristics before the sector’s boom, transitioning out of the IT sector to a non-IT industry generally resulted in a large wage penalty. However, IT service workers who transitioned to a non-IT industry still fared better than those who took a non-IT employment path. For IT manufacturing workers, there is no benefit to having worked in tech, likely because of the nontransferability of manufacturing experience to other industries.

Freshman learning communities, college performance, and retention

This paper applies a standard treatment effects model to determine that participation in Freshman Learning Communities (FLCs) improves academic performance and retention. Not controlling for individual self-selection into FLC participation leads one to incorrectly conclude that the impact is the same across race and gender groups. Accurately assessing the impact of any educational program is essential in determining what resources institutions should devote to it.

The ups and downs of jobs in Georgia: what can we learn about employment dynamics from state administrative data?

This paper demonstrates how state administrative data (from Georgia) can be used to decompose net employment growth in order to track establishment births, deaths, contractions, and expansions over time. Even though net employment growth can look quite similar across industries, the composition of that employment change can look quite different. The panel nature of the data allow the authors to see that overall lack of expansion and continued contraction among large establishments were the driving forces behind the weak employment growth immediately following the 2001 recession.

The push-pull effects of the information technology boom and bust: insight from matched employer-employee data

This paper examines the inflow and outflow of workers to different industries in Georgia during the information technology (IT) boom of the 1990s and the subsequent bust. Workers in the software and computer services industry were much more likely to have been absent from the Georgia workforce prior to the boom but were no more likely than workers from other industries to have exited the workforce during the bust. Consequently, the Georgia workforce likely experienced a net gain in worker human capital as a result of being an area of concentration of IT-producing activity during the IT boom.