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Real-Time and Accelerated Solar Weathering of Commercial PV Modules: Preprint

Description: Presented at the 2001 NCPV Program Review Meeting: We report the observed degradation in 6 different types of PV modules as a function of total UV exposure and give a number of recommendations for future weathering tests. Since 1997, using existing ASTM standards for weathering of materials, we have been conducting a solar weathering program on a group of six different types of photovoltaic (PV) modules. The methods used include real-time outdoor, accelerated outdoor, and accelerated indoor weathering. We have employed the technique specified in these standards that quantifies exposure totals by the time integral of the ultraviolet (UV) irradiance. In this paper, we report the observed degradation in the test modules as a function of total UV exposure, and give a number of recommendations for future weathering tests that resulted from our first attempt at a formal test program.
Date: October 1, 2001
Creator: Osterwald, C. R.; Pruett, J.; Myers, D. R.; Rummel, S.; Anderberg, A.; Ottoson, L. et al.
Partner: UNT Libraries Government Documents Department
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TASK 2.5.5 NATURAL EXPOSURE TESTING IN CALIFORNIA

Description: Airborne particulate matter that settles on a roof can either reflect or absorb incoming solar radiation, dependent on the chemical content and size of the particles. These light scattering and absorption processes occur within a few microns of the surface, and can affect the solar reflectance of the roof. Wilkes et al. (2000) tested 24 different roof coatings on a low-slope test stand and observed about a 25% decrease in the solar reflectance of white-coated and aluminum-coated surfaces as the time of exposure increased; however, the decrease leveled off after 2 years. SPRI Inc. and its affiliates studied the effect of climatic exposure on the surface properties of white thermoplastic single-ply membranes and determined that membranes lose from 30 to 50% of their reflectance over 3 years (Miller et al. 2002). The CMRC and its affiliates AISI, NamZAC, MBMA, MCA and NCCA exposed unpainted and painted metal roofing on both steep- and low-slope test roofs and found that after 3 years, the painted polyvinylidene fluoride (PVDF) metal roofs lost less than 5% of their original reflectance (Miller et al. 2004). The results of the three different weathering studies are very interesting in terms of their solar reflectance after 3 years of exposure. The white thermoplastic membrane and white ceramic coating with white topcoat had original reflectance measures that were about 20 percentage points higher than the painted metal; however, after 3-years of field exposure the solar reflectance of the painted metal exceeds that of the thermoplastic membrane and equals that of the coating. The long-term loss of reflectance appears driven by the ability of the particulate matter to cling to the roof and resist being washed off by wind and or rain. Miller et al. (2002) discovered that aerosol deposition introduced biomass of complex microbial consortia onto the test roofs …
Date: March 1, 2010
Creator: Miller, William A; Cheng, Mengdawn; New, Joshua Ryan; Ronnen, Levinson; Akbari, Hashem & Berhahl, Paul
Partner: UNT Libraries Government Documents Department
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Deterioration of Airplane Fabrics

Description: The observation that airplane fabrics, after long use, lose their original strength, caused the German Experimental Institute for Aviation to carry out a series of experiments on the effect of weathering on the cloth covering of airplane wings and fuselages.
Date: February 1922
Creator: Wendt, F.
Partner: UNT Libraries Government Documents Department
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Investigation of Durability of Concrete Exposed to Natural Weathering, Report No. 5: Summary of Results 1936-1953

Description: The following report presents the results of various investigations on the study of the durability of concrete exposed to natural weathering. The report is divided into two parts: first, the natural weathering exposure stations and test procedures are analyzed, then follows the analysis of the programs of investigations.
Date: May 1954
Creator: Waterways Experiment Station (U.S.)
Partner: UNT Libraries Government Documents Department
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The Effect of Continuous Weathering on Light Metal Alloys Used in Aircraft

Description: "An investigation of the corrosion of light metal alloys used in aircraft was begun at the National Bureau of Standards in 1925 and has for its purpose causes of corrosion in aluminum-rich and magnesium-rich alloys together with the development of methods for its prevention. The results, obtained in an extensive series of laboratory and weather-exposure tests, reveal the relative durability of a number of commercially available materials and the extent to which the application of various surface coatings of oxide alone and with paint coatings afforded additional protection. The paper may be considered as a supplement to NACA report 490" (p. 395).
Date: December 2, 1938
Creator: Mutchler, Willard
Partner: UNT Libraries Government Documents Department
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Effect of Simulated Service Conditions on Plastics During Accelerated and 2-Year Weathering Tests

Description: "The effects of outdoor weathering for 2 years and of an accelerated weathering test on the weight, dimensional stability, and flexural properties of selected reinforced plastics were investigated. The results of all tests, both in this report and the previous report (NACA TN No. 1240), indicate that none of the laboratory aging tests correlated with outdoor weathering with respect to all properties and all materials" (p. 1).
Date: May 1948
Creator: Crouse, W. A.; Caudill, D. C. & Reinhart, F. W.
Partner: UNT Libraries Government Documents Department
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Chemistry of Supraglacial Ponds in thte Debris-Covered Area of Lirung Glacier in Central Nepal Himalayas

Description: This article examines elevation trends and their control by seasonality, dominant geochemical processes, and season dynamics in these supraglacial ponds at elevations ranging between 3989 and 4292 m above sea level in the debris-covered area of Lirung glacier in central Nepal Himalayas, from November 2010 to October 2011 on a bimonthly basis.
Date: August 27, 2015
Creator: Bhatt, Maya P.; Takeuchi, Nozomu & Acevedo, Miguel F.
Partner: UNT College of Engineering
open access

The Weathering of Aluminum Alloy Sheet Materials Used in Aircraft

Description: This report presents the results of an investigation of the corrosion of aluminum alloy sheet materials used in aircraft. It has for its purpose to study the causes of corrosion embrittlement in duralumin-type alloys and the development of methods for its elimination. The report contains results, obtained in an extensive series of weather-exposure tests, which reveal the extent to which the resistance of the materials to corrosion was affected by variable factors in their heat treatment and by the application of various surface protective coatings.
Date: March 23, 1934
Creator: Mutchler, Willard
Partner: UNT Libraries Government Documents Department
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Investigation of the Suitability of Prepakt Concrete for Mass and Reinforced Concrete Structures: Appendices A and B

Description: Introduction: Three matters discussed in the main report on the investigation of the suitability of Prepakt concrete for mass and reinforced concrete structures, issued in October 1951, required further study. These matters are (a) the properties of Alfesil, (b) the permeability of Prepakt concrete, and (c) the resistance of Prepakt concrete to natural weathering.
Date: August 1954
Creator: Waterways Experiment Station (U.S.)
Partner: UNT Libraries Government Documents Department
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Investigation of Performance of Concrete and Concreting Materials Exposed to Natural Weathering, Volume 1: Active Investigations

Description: Partial summary: "To assess the durability of concrete and other materials used in concrete construction when exposed to natural weathering, the Corps of Engineers maintains severe-, mild-, moderate-, and non-weathering exposure stations at various locations in the United States. Specimens from actual structures and experimental specimens in which the amounts or kinds of components are varied are exposed until they fail or until testing is completed, whichever occurs first. The specimens are inspected periodically, and tested to determine their dynamic modulus of elasticity and pulse velocity. [...] Volume 1 contains the active evaluations" (p. ix).
Date: June 1960
Creator: Waterways Experiment Station (U.S.)
Partner: UNT Libraries Government Documents Department
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Effects of Fuel-Vapor Loss on Knock-Limited Performance and Inspection Properties of Aviation Fuels

Description: Report discussing the results of testing to discover the effects of fuel-vapor loss on F-3 and F-4 knock-limited performance ratings and inspection properties of two aviation fuels, 28-R and 33-R. The percentage of loss at several temperatures, ability to meet Army-Navy fuel specifications, and antiknock rating change is described.
Date: March 1946
Creator: Barnett, Henry C. & Marsh, Edred T.
Partner: UNT Libraries Government Documents Department
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Determining flow, recharge, and vadose zonedrainage in anunconfined aquifer from groundwater strontium isotope measurements, PascoBasin, WA

Description: Strontium isotope compositions (87Sr/86Sr) measured in groundwater samples from 273 wells in the Pasco Basin unconfined aquifer below the Hanford Site show large and systematic variations that provide constraints on groundwater recharge, weathering rates of the aquifer host rocks, communication between unconfined and deeper confined aquifers, and vadose zone-groundwater interaction. The impact of millions of cubic meters of wastewater discharged to the vadose zone (103-105 times higher than ambient drainage) shows up strikingly on maps of groundwater 87Sr/86Sr. Extensive access through the many groundwater monitoring wells at the site allows for an unprecedented opportunity to evaluate the strontium geochemistry of a major aquifer, hosted primarily in unconsolidated sediments, and relate it to both long term properties and recent disturbances. Groundwater 87Sr/86Sr increases systematically from 0.707 to 0.712 from west to east across the Hanford Site, in the general direction of groundwater flow, as a result of addition of Sr from the weathering of aquifer sediments and from diffuse drainage through the vadose zone. The lower 87Sr/86Sr groundwater reflects recharge waters that have acquired Sr from Columbia River Basalts. Based on a steady-state model of Sr reactive transport and drainage, there is an average natural drainage flux of 0-1.4 mm/yr near the western margin of the Hanford Site, and ambient drainage may be up to 30 mm/yr in the center of the site assuming an average bulk rock weathering rate of 10-7.5 g/g/yr.
Date: June 29, 2004
Creator: Singleton, Michael J.; Maher, Katharine; DePaulo, Donald J.; Conrad, Mark E. & Dresel, P. Evan
Partner: UNT Libraries Government Documents Department
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Caustic Waste-Soil Weathering Reactions and Their Impacts on Trace Contaminant Migration & Separation - Final Report

Description: Studies of the reactivity of radionuclides (Cs, Sr, I) in STWL with model clays and natural sediments were conducted by coupling macroscopic sorption-desorption experiments with spectroscopic and microscopic investigations over a wide range of reaction times. Three experimental systems were studied: (1) model clay minerals, (2) products of homogeneous precipitation from STWL, and (3) representative Hanford sediments, with (1) and (3) reacted with STWL from 1 h to 369 d. The clay minerals included illite, vermiculite, smectite and kaolinite, which constitute a sequence of micaceous weathering products with variable reactivity toward Cs+, Sr2+ and I-. Coarse and fine sediments collected from the Hanford formation (HC and HF, respectively) and Ringold Silt (RS) were studied in batch experiments and Warden silt loam was used in batch and column experiments. Solutions were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). Solid products (referred to here as ''secondary phases'' relative to the initial reactant minerals) were analyzed for time-dependent changes in mineralogy and modes of contaminant bonding by a variety of methods, including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) with energy dispersive spectrometry (EDS), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, and Fourier-transform infrared spectroscopy (FTIR).
Date: September 15, 2005
Creator: Tyburczy, James A. : Chorover, John & O'Day, Peggy
Partner: UNT Libraries Government Documents Department
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Weight Losses of Marble and Limestone Briquettes Exposed to Outdoor Environments in the Eastern United States : Results of Exposures, 1984-1988

Description: Gravimetric changes in marble and limestone briquettes exposed to outdoor environment at five sites in the eastern United States have been monitored since 1984. An earlier report describes procedures and results obtained in 1984--1988. This report presents the results of the exposure period 1984--1988 and reviews and summarizes those of prior years. A linear relationship was found between cumulative gravimetric losses and exposure period or rain depth. These losses resulted in an average recession rate of 14 to 24 {mu}m/yr for marble and twice that for limestone. Variations in recession among the various exposure sites can be ascribed to differences in rain depth and hydrogen ion concentration. The annual recession rates obtained from gravimetry yielded rates that were for marble twice those obtained from runoff experiments, and more than three times those for limestone; this indicates that physical erosion plays an important role. Gravimetric monitoring of exposed briquettes is continuing in a planned 10-yr program.
Date: September 1991
Creator: Reimann, K. J.
Partner: UNT Libraries Government Documents Department
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Weight Losses of Marble and Limestone Briquettes Exposed to Outdoor Environment in the Eastern United States: Results of Exposure 1988-1992

Description: Monitoring continued on weight changes in marble and limestone briquettes exposed to the outdoor environment at sites in the eastern US. This report presents data for the exposure period 1988 - 1992 and summarizes results for the entire period from 1984. Since 1989, only three exposure sites have remained active, but briquettes from pre-exposed material were added at those sites. A linear relationship was found between cumulative gravimetric losses and exposure period. These losses resulted in an average recession rate of 11 to 21 micrometers/yr for marble and 21 to 45 micrometers/yr for limestone. The recession rates are site-dependent and can be described with respect to rain depth and other atmospheric conditions, as evidenced by the very low rates at the Ohio site on the movable rack, dry regime. Weight monitoring is continuing in a planned 10-year program.
Date: April 1995
Creator: Reimann, K. J.
Partner: UNT Libraries Government Documents Department
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Seasonal variations of biogeochemical matter export along the Langtang-Narayani river system in central Himalaya

Description: Article describes study in which weathering and suspended matter fluxes of the Langtang Narayani river system in central Nepal Himalaya were investigated at 16 stations for one year, based on monthly water sampling in the lower reaches and bi-monthly in higher elevation areas, to determine temporal variations of weathering fluxes along an elevation profile between 169 and 3989 m asl.
Date: July 7, 2018
Creator: Bhatt, Maya P.; Hartmann, Jens & Acevedo, Miguel F.
Partner: UNT College of Engineering
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Effects of composition and exposure on the solar reflectance of Portland cement concrete

Description: Increasing the solar reflectance (albedo) of a paved surface keeps it cooler in the sun, reducing convection of heat from pavement to air and thereby decreasing the ambient air temperature. Simulations of the influence of pavement albedo on air temperature in Los Angeles predict that increasing the albedo of 1,250 km2 of pavement by 0.25 would save cooling energy worth $15M yr-1, and reduce smog-related medical and lost-work expenses by $76M yr-1. Most sidewalks and a small fraction of roads and parking areas are paved with portland cement concrete, which can be made quite reflective through suitable choice of cement and aggregate. Variations with composition and environmental exposure of the albedos of portland cement concrete pavements were investigated through laboratory fabrication and exposure of 32 mixes of concrete. Twenty-four mixes yielded substandard, ''rough'' concretes due to high, unmet aggregate water demand. The albedos of the remaining eight ''smooth'' concrete mixes ranged from 0.41 to 0.77 (mean 0.59). Simulated weathering, soiling, and abrasion each reduced average concrete albedo (mean decreases 0.06, 0.05, and 0.19, respectively), though some samples became slightly more reflective through weathering or soiling. Simulated rain (wetting) strongly depressed the albedos of concretes (mean decrease 0.23) until their surfaces were dried. Concrete albedo grew as the cement hydration reaction progressed (mean increase 0.08), but stabilized within six weeks of casting. White-cement concretes were on average significantly more reflective than gray-cement concretes. The albedo of the most-reflective white-cement concrete was 0.18 to 0.39 higher than that of the most-reflective gray-cement concrete, depending on state of exposure. Concrete albedo generally correlated with cement albedo and sand albedo, and, after abrasion, with rock albedo. Cement albedo had a disproportionately strong influence on the reflectance of concrete. Efflorescence and surface carbonation whitened some gray-cement mixes.
Date: December 21, 2001
Creator: Levinson, Ronnen & Akbari, Hashem
Partner: UNT Libraries Government Documents Department
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Step-Stress Accelerated Degradation Testing for Solar Reflectors: Preprint

Description: To meet the challenge to reduce the cost of electricity generated with concentrating solar power (CSP) new low-cost reflector materials are being developed including metalized polymer reflectors and must be tested and validated against appropriate failure mechanisms. We explore the application of testing methods and statistical inference techniques for quantifying estimates and improving lifetimes of concentrating solar power (CSP) reflectors associated with failure mechanisms initiated by exposure to the ultraviolet (UV) part of the solar spectrum. In general, a suite of durability and reliability tests are available for testing a variety of failure mechanisms where the results of a set are required to understand overall lifetime of a CSP reflector. We will focus on the use of the Ultra-Accelerated Weathering System (UAWS) as a testing device for assessing various degradation patterns attributable to accelerated UV exposure. Depending on number of samples, test conditions, degradation and failure patterns, test results may be used to derive insight into failure mechanisms, associated physical parameters, lifetimes and uncertainties. In the most complicated case warranting advanced planning and statistical inference, step-stress accelerated degradation (SSADT) methods may be applied.
Date: September 1, 2011
Creator: Jones, W.; Elmore, R.; Lee, J. & Kennedy, C.
Partner: UNT Libraries Government Documents Department
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Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

Description: Where Martian rocks have been exposed to liquid water, chemistry versus depth profiles could elucidate both Martian climate history and potential for life. The persistence of primary minerals in weathered profiles constrains the exposure time to liquid water: on Earth, mineral persistence times range from {approx}10 ka (olivine) to {approx}250 ka (glass) to {approx}1Ma (pyroxene) to {approx}5Ma (plagioclase). Such persistence times suggest mineral persistence minima on Mars. However, Martian solutions may have been more acidic than on Earth. Relative mineral weathering rates observed for basalt in Svalbard (Norway) and Costa Rica demonstrate that laboratory pH trends can be used to estimate exposure to liquid water both qualitatively (mineral absence or presence) and quantitatively (using reactive transport models). Qualitatively, if the Martian solution pH > {approx}2, glass should persist longer than olivine; therefore, persistence of glass may be a pH-indicator. With evidence for the pH of weathering, the reactive transport code CrunchFlow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profile. For the profile measured on the surface of Humphrey in Gusev Crater, the minimum exposure time is 22 ka. If correct, this estimate is consistent with short-term, episodic alteration accompanied by ongoing surface erosion. More of these depth profiles should be measured to illuminate the weathering history of Mars.
Date: March 15, 2008
Creator: Steefel, Carl; Hausrath, E. M.; Navarre-Sitchler, A. K.; Sak, P. B.; Steefel, C. & Brantley, S. L.
Partner: UNT Libraries Government Documents Department
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Chemical Alteration of Limestone and Marble Samples Exposed to Acid Rain and Weathering in the Eastern United States, 1984-1988

Description: In a long-term program that began in 1984, limestone and marble briquettes have been exposed to both anthropogenic acid deposition and natural weathering at four field sites in the eastern United States. Similar tests began at an Ohio site in 1986. Effects of exposure on the briquettes and other materials at the sites are evaluated periodically by several federal agencies cooperating in the National Acid Precipitation Assessment Program (NAPAP). Wet chemical analysis was used to detect sulfates, nitrates, fluorides, chlorides, and a series of metal cations in sequential layers of stone removed from the briquettes after field exposure. Results from the first four years of the program indicate that rinsing by rain keeps skyward-facing stone relatively clean of reaction products, especially sulfate, the most abundant product.
Date: June 1991
Creator: Reimann, K. J.
Partner: UNT Libraries Government Documents Department
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