Look Out—EPA Is Repowering Its Hazy Visibility Program

Of all the controversial Environmental Protection Agency air regulations making headlines in recent years, regional haze is not likely the first to come to mind.     

Elastic Moduli of Refractory Spinels

Elastic moduli of spinel phases in the system Mg(Al, Cr, Fe)₂O₁ were determined from sonic analyses of porous, polycrystalline specimens prepared by hot-pressing. A special iterative least-squares technique (ILS) and standard curve-fitting techniques were used to obtain moduli at zero porosity by extrapolation. A minimal standard error of estimate was achieved in all cases by using an exponential form for the porosity dependence and the ILS technique. Moduli were checked for self-consistency. Extrapolated moduli for MgAl₂O₁ agreed well with respective moduli calculated from single-crystal elastic constants and Birch's law. Longitudinal and shear sound velocities decreased with increasing phase density in the solid-solution systems and systematics indicate that elastic moduli of arbitrary solid solutions can be estimated to lt; ± 10% from the phase density.     

Dietary Folate in a Changing Environment: Bioavailability, Fortification, and Requirements

ABSTRACT: The US and several other countries have instituted mandatory inclusion of folic acid in many enriched cereal grain products, and certain other countries allow optional addition. Nutritional surveys in the US now indicate that folate deficiency is infrequent, and vitamin B12 status is often a primary determinant of plasma homocysteine concentration. Thus, the current situation in the US is markedly different from that of the pre-fortification era and from countries that do not allow the addition of folic acid to foods. Recent analytical studies have indicated that food composition databases may underestimate naturally occurring folate, although folate intakes calculated from database values have allowed accurate ranking of intakes among population groups in many epidemiological studies. Published analyses of cereal grain foods in the US indicate that added folic acid exceeds intended ranges. Studies comparing folate nutritional status in the US before and after fortification indicate that the fortification program has contributed about 200 micrograms of folic acid to the average person per day. This increment is twice that predicted due, in part, to a greater than anticipated intake as well as the higher bioavailability of folic acid than most naturally occurring forms of food folate. More precise information is needed regarding the actual difference in bioavailability between natural folate and added folic acid.     

Manufacturing and performance assessment of stamped,laser welded,and nitrided FeCrV stainless steel bipolar plates for proton exchange membrane fuel cells

A manufacturing and single-cell fuel cell performance study of stamped, laser welded, and gas nitrided ferritic stainless steel foils in an advanced automotive bipolar plate assembly design was performed. Two developmental foil compositions were studied: Fe–20Cr–4V and Fe–23Cr–4V wt.%. Foils 0.1 mm thick were stamped and then laser welded together to create single bipolar plate assemblies with cooling channels. The plates were then surface treated by pre-oxidation and nitridation in N₂–4H₂ based gas mixtures using either a conventional furnace or a short-cycle quartz lamp infrared heating system. Single-cell fuel cell testing was performed at 80 °C for 500 h at 0.3 A/cm² using 100% humidification and a 100%/40% humidification cycle that stresses the membrane and enhances release of the fluoride ion and promotes a more corrosive environment for the bipolar plates. Periodic high frequency resistance potential-current scans during the 500 h fuel cell test and post-test analysis of the membrane indicated no resistance increase of the plates and only trace levels of metal ion contamination.     

THE ROLE OF FEDERAL MILITARY SPENDING IN THE TIMING OF THE NEW ENGLAND EMPLOYMENT TURNAROUND

ABSTRACT This paper examines the role of military spending in the recent economic revival of New England, particularly the region's turnaround in employment growth. The long-term re structuring of New England's economy after World War II in terms of industry mix and labor costs positioned the region for a turnaround. We argue that the precipitating factor in the liming of the was the significant increase starling in the late 1970s in federal military purchases of durable goods from [lie region's high-technology manufacturing industry. New England benefited disproportionately from the military buildup because of the region's concentration in high-technology manufacturing industries producing defense-related goods. The labor-intensive nature of high-technology industry has resulted in a large portion of the money received from defense purchases going to labor and producing important regional multiplier effects in sectors other than manufacturing.     

Expansion of Dreissena into offshore waters of Lake Michigan and potential impacts on fish populations

Lake Michigan was invaded by zebra mussels (Dreissena polymorpha) in the late 1980s and then followed by quagga mussels (D. bugensis) around 1997. Through 2000, both species (herein Dreissena) were largely restricted to depths less than 50 m. Herein, we provide results of an annual lake-wide bottom trawl survey in Lake Michigan that reveal the relative biomass and depth distribution of Dreissena between 1999 and 2007 (although biomass estimates from a bottom trawl are biased low). Lake-wide mean biomass density (g/m²) and mean depth of collection revealed no trend between 1999 and 2003 (mean = 0.7 g/m² and 37 m, respectively). Between 2004 and 2007, however, mean lake-wide biomass density increased from 0.8 g/m² to 7.0 g/m², because of increased density at depths between 30 and 110 m, and mean depth of collection increased from 42 to 77 m. This pattern was confirmed by a generalized additive model. Coincident with the Dreissena expansion that occurred beginning in 2004, fish biomass density (generally planktivores) declined 71% between 2003 and 2007. Current understanding of fish population dynamics, however, indicates that Dreissena expansion is not the primary explanation for the decline of fish, and we provide a species-specific account for more likely underlying factors. Nonetheless, future sampling and research may reveal a better understanding of the potential negative interactions between Dreissena and fish in Lake Michigan and elsewhere.     

Theory of a distributed feedback laser

This paper treats distributed feedback laser operation in which a classical electromagnetic field obeying Maxwell's equations interacts with an active medium according to the laws of quantum mechanics. The theory describes arbitrarily intense two-mode operation of fundamental and higher modes in both index and gain grating configurations. Spacial hole burning and finite atomic linewidth are included in the analysis and are shown to give marked changes in some laser intensity profiles.     

Automated visual inspection: A tutorial

This article introduces the topic of automated visual inspection (AVI) as a subset of machine vision. The components of a generic AVI system will be presented and current applications of AVI systems will be discussed. Specifically, the applications of automated dimension verification, bare printed circuit board inspection, stuffed printed circuit board inspection and component identification using color technology will be covered in some detail.     

Power indices and easier hard problems

The concepts of power_index, satisfiability hypothesis (SH), and structure tree are introduced and used to make sharper hypotheses about a problem's complexity than the problem isNP-complete. These concepts are used to characterize the complexities of a number of basicNP-complete problems, including both CLIQUE and PARTITION which are shown to have power-indices at most 1/2. Also, the problem 3SAT is shown to be solvable deterministically in time exponential only in thesquare root ofv+c, wherev is the number of variables andc is the number of crossovers needed to layout the formula in the plane.The research of R. E. Stearns was supported by NSF Grants DCR 83-03932 and CCR 89-03319, and that of H. B. Hunt was supported by NSF Grants DCR 86-03184 and CCR 89-03319.     

Graph partitioning using annealed neural networks

A new algorithm, mean field annealing (MFA), is applied to the graph-partitioning problem. The MFA algorithm combines characteristics of the simulated-annealing algorithm and the Hopfield neural network. MFA exhibits the rapid convergence of the neural network while preserving the solution quality afforded by simulated annealing (SA). The rate of convergence of MFA on graph bipartitioning problems is 10-100 times that of SA, with nearly equal quality of solutions. A new modification to mean-field annealing is also presented which supports partitioning graphs into three or more bins, a problem which has previously shown resistance to solution by neural networks. The temperature-behavior of MFA during graph partitioning is analyzed approximately and shown to possess a critical temperature at which most of the optimization occurs. This temperature is analogous to the gain of the neurons in a neural network and can be used to tune such networks for better performance. The value of the repulsion penalty needed to force MFA (or a neural network) to divide a graph into equal-sized pieces is also estimated.