Block 5 module design summary

The Flat Plate Solar Array Block 5 Module design efforts of six manufacturers are summarized. Residential designs and module designs for intermediate-load applications are described. It is planned that a few prototype modules of each design will be fabricated. The modules incorporate advanced concepts, are larger than earlier ones and have high power output

The radiation resistance of cylindrical shells

Radiation resistance of cylindrical shells in ideal compressible acoustic mediu

Analytical Model of the Progression of Cracking in Fiber-Reinforced Composites.

Two analytical shear lag models have been developed for the progressive damage and final failure of epoxy matrix, fiber-reinforced composites under biaxial loading. The first is a three layer model for laminates of the type ($\pm\theta$,90n) s under general biaxial loading. It gives matrix cracking predictions for the central 90\sp\circ ply group. The second model is a five-layer model for laminates of the type (90n/0m/90p) s under biaxial loading, but it does not include in-plane shear. The five-layer model predicts matrix cracking in all ply groups. The amount of damage in terms of modulus decrease and number of matrix cracks is determined for each layer under increasing static loads. This is done by assuming that a crack occurs, calculating the energy dissipated due to the crack formation, dividing by the critical crack size, and comparing the result with the critical strain energy re!ease rate. When a layer cracks, the other layers must take additional load. Final failure occurs when the primary load carrying plies reach their ultimate strength. The models incorporate an algorithm for the effect of small, initial local delaminations on matrix cracking. The three-layer model has been verified experimentally using literature data and in-house experimental data. The five-layer model has also been experimentally verified in this work. Experimental verification was performed by statically loading uniaxial glass-epoxy tension specimens and measuring damage accumulation in terms of crack density and the decrease of Young\u27s modulus. The present study shows that the models developed can be used for initial predictions of damage and failure of epoxy matrix, fiber-reinforced composites

What should DOE do to help establish voluntary consensus standards for measuring and rating the performance of PV modules?

In response to concern expressed by the photovoltaics community over progress toward the establishment and issuance of concensus standards on photovoltaic performance measurements, a review of the status of and progress in developing these standards was conducted. It examined the roles of manufacturers, and consumers and the national laboratories funded by the U.S. Department of Energy (DOE) in supporting this effort. This was done by means of a series of discussions with knowledgeable members of the photovoltaic community. Results of these interviews are summarized and a new approach to managing support of standards activity is recommended that responds to specific problems found in the performance measurement standards area. The study concludes that there is a positive role to be played by the U.S. Department of Energy in establishing collector performance measurement standards. It recommends that DOE continue to provide direct financial support for selected committees and for research at national laboratories, and that management of the activity be restructured to increase the authority and responsibility of the consensus committees

Alternative computational approaches to inference in the multinomial probit model

This research compares several approaches to inference in the multinomial probit model, based on two Monte Carlo experiments for a seven choice model. The methods compared are the simulated maximum likelihood estimator using the GHK recursive probability simulator, the method of simulated moments estimator using the GHK recursive simulator and kernel-smoothed frequency simulators, and posterior means using a Gibbs sampling-data augmentation algorithm. Overall, the Gibbs sampling algorithm has a slight edge, with the relative performance of MSM and SML based on the GHK simulator being difficult to evaluate. The MSM estimator with the kernel-smoothed frequency simulator is clearly inferior. © 1994

Engineering sciences area and module performance and failure analysis area

Photovoltaic-array/power-conditioner interface studies are updated. An experiment conducted to evaluate different operating-point strategies, such as constant voltage and pilot cells, and to determine array energy losses when the array is operated off the maximum power points is described. Initial results over a test period of three and a half weeks showed a 2% energy loss when the array is operated at a fixed voltage. Degraded-array studies conducted at NE RES that used a range of simulated common types of degraded I-V curves are reviewed. The instrumentation installed at the JPL field-test site to obtain the irradiance data was described. Experiments using an optical filter to adjust the spectral irradiance of the large-area pulsed solar simulator (LAPSS) to AM1.5 are described. Residential-array research activity is reviewed. Voltage isolation test results are described. Experiments performed on one type of module to determine the relationship between leakage current and temperature are reviewed. An encapsulated-cell testing approach is explained. The test program, data reduction methods, and initial results of long-duration module testing are described

Occupational Risks and Pregnancy and Infant Health Outcomes in Florida Farmworkers

The agricultural industry has some of the highest incidence rates and numbers of occupational injuries and illnesses in the United States. Injuries and illnesses in agriculture result from accidents, falls, excessive heat, repetitive motion and adverse pesticide exposure. Women working in agriculture are exposed to the same hazards and risks as their male counterparts, but can face additional adverse impacts on their reproductive health. Yet, few occupational risk assessment studies have considered the reproductive health of female farmworkers. The objective of this community-based participatory research study was to conduct a retrospective, cross-sectional survey to collect information on workplace conditions and behaviors and maternal, pregnancy and infant health outcomes among a sample of female nursery and fernery farmworkers in Central Florida. Survey results showed that nursery workers were more likely to report health symptoms during their pregnancy than fernery workers. We also observed a self-reported increased risk of respiratory illness in the first year of life for infants whose mothers worked in ferneries. Our findings confirm that agricultural work presents potential reproductive hazards for women of childbearing age

Large-scale synchrony of gap dynamics and the distribution of understory tree species in maple-beech forests

Large-scale synchronous variations in community dynamics are well documented for a vast array of organisms, but are considerably less understood for forest trees. Because of temporal variations in canopy gap dynamics, forest communities—even old-growth ones—are never at equilibrium at the stand scale. This paucity of equilibrium may also be true at the regional scale. Our objectives were to determine (1) if nonequilibrium dynamics caused by temporal variations in the formation of canopy gaps are regionally synchronized, and (2) if spatiotemporal variations in canopy gap formation aVect the relative abundance of tree species in the understory. We examined these questions by analyzing variations in the suppression and release history of Acer saccharum Marsh. and Fagus grandifolia Ehrh. from 481 growth series of understory saplings taken from 34 mature stands. We observed that (1) the proportion of stems in release as a function of time exhibited a U-shaped pattern over the last 35 years, with the lowest levels occurring during 1975–1985, and that (2) the response to this in terms of species composition was that A. saccharum became more abundant at sites that had the highest proportion of stems in release during 1975–1985. We concluded that the understory dynamics, typically thought of as a stand-scale process, may be regionally synchronized