Initial thoughts on rapid prototyping techniques

This paper sets some context, raises issues, and provides our initial thinking on the characteristics of effective rapid prototyping techniques.After discussing the role rapid prototyping techniques can play in the software lifecycle, the paper looks at possible technical approaches including: heavily parameterized models, reusable software, rapid prototyping languages, prefabrication techniques for system generation, and reconfigurable test harnesses.The paper concludes that a multi-faceted approach to rapid prototyping techniques is needed if we are to address a broad range of applications successfully -- no single technical approach suffices for all potentially desirable applications

By a Thread: The New Experience of America's Middle Class

Developed in collaboration with the Institute on Assets and Social Policy at Brandeis University, By a Thread: The New Experience of America's Middle Class looks at the financial security of the middle class using the innovative Middle Class Security Index, rating household stability across five core economic factors: assets, educational achievement, housing costs, budget and healthcare. The Index provides a comprehensive portrait of how well middle-class families are faring in each of these areas, with spotlight on the strengths and vulnerabilities of today's middle class

From Middle to Shaky Ground: The Economic Decline of America's Middle Class

A middle-class standard of living requires that families have adequate financial security to meet current obligations, invest in the future, and access opportunities. The most recent findings from the Middle Class Security Index show that between 2000 and 2006--even before the most recent economic downturn--the economic well-being of middle-class families slipped noticeably.Between 2000 and 2006 an estimated 4 million middle-class families lost their financial security, bringing the total number of middle-income families on shaky ground to 23 million.These worrisome changes in the overall financial health of the middle class were driven by a decline in assets, rising housing costs, and a growing lack of health insurance

Economic (In)Security: The Experience of the African-American and Latino Middle Classes

As the next installment in the By a Thread series, Economic (In)Security uses the Middle Class Security Index to provide the first comprehensive portrait of the level of financial security enjoyed by African-American and Latino middle-class families. The findings show that, in the wake of fading economic opportunity, these two rapidly growing groups face mounting obstacles in becoming part of, and remaining securely in, America's middle class

Less Debt, More Equity: Lowering Student Debt While Closing the Black-White Wealth Gap

The dramatic increase in wealth inequality over the past several decades now forms the backdrop for many of today's most pressing public policy debates. Currently, the top 1 percent of U.S. households controls 42 percent of the nation's wealth, and nearly half of the wealth accumulated over the past 30 years has gone to the top 0.1 percent. Simultaneously, the wealth held by the bottom 90 percent of U.S. households continues to shrink, just as people of color are a growing percentage of the U.S. population. These trends have converged to produce a wealth divide that is apparent not just by class, but by race as well. The average white family owns $13 for every$1 owned by a typical Black family, and $10 for every$1 owned by the typical Latino family.This analysis uses the Racial Wealth Audit, a framework developed by the Institute on Assets and Social Policy (IASP) to assess the impact of public policy on the wealth gap between white and Black households. We use the framework to model the impact of various student debt relief policies to identify the approaches most likely to reduce inequities in wealth by race, as opposed to exacerbating existing inequities. We focus specifically on the Black-white wealth gap both because of the historic roots of inequality described above, and because student debt (in the form of borrowing rates and levels) seems to be contributing to wealth disparities between Black and white young adults, in particular

Gas mass tracers in protoplanetary disks: CO is still the best

Protoplanetary disk mass is a key parameter controlling the process of planetary system formation. CO molecular emission is often used as a tracer of gas mass in the disk. In this study we consider the ability of CO to trace the gas mass over a wide range of disk structural parameters and search for chemical species that could possibly be used as alternative mass tracers to CO. Specifically, we apply detailed astrochemical modeling to a large set of models of protoplanetary disks around low-mass stars, to select molecules with abundances correlated with the disk mass and being relatively insensitive to other disk properties. We do not consider sophisticated dust evolution models, restricting ourselves with the standard astrochemical assumption of $0.1~\mu$m dust. We find that CO is indeed the best molecular tracer for total gas mass, despite the fact that it is not the main carbon carrier, provided reasonable assumptions about CO abundance in the disk are used. Typically, chemical reprocessing lowers the abundance of CO by a factor of 3, compared to the case of photo-dissociation and freeze-out as the only ways of CO depletion. On average only 13% C-atoms reside in gas-phase CO, albeit with variations from 2 to 30%. CO$_2$, H$_2$O and H$_2$CO can potentially serve as alternative mass tracers, the latter two being only applicable if disk structural parameters are known.Comment: Accepted for publication in Ap