Improving measurements of SF6 for the study of atmospheric transport and emissions

Sulfur hexafluoride (SF6) is a potent greenhouse gas and useful atmospheric tracer. Measurements of SF6 on global and regional scales are necessary to estimate emissions and to verify or examine the performance of atmospheric transport models. Typical precision for common gas chromatographic methods with electron capture detection (GC-ECD) is 1–2%. We have modified a common GC-ECD method to achieve measurement precision of 0.5% or better. Global mean SF6 measurements were used to examine changes in the growth rate of SF6 and corresponding SF6 emissions. Global emissions and mixing ratios from 2000–2008 are consistent with recently published work. More recent observations show a 10% decline in SF6 emissions in 2008–2009, which seems to coincide with a decrease in world economic output. This decline was short-lived, as the global SF6 growth rate has recently increased to near its 2007–2008 maximum value of 0.30±0.03 pmol mol−1 (ppt) yr−1 (95% C.L.)

Evaluation available encapsulation materials for low-cost long-life silicon photovoltaic arrays

Experimental evaluation of selected encapsulation designs and materials based on an earlier study which have potential for use in low cost, long-life photovoltaic arrays are reported. The performance of candidate materials and encapsulated cells were evaluated principally for three types of encapsulation designs based on their potentially low materials and processing costs: (1) polymeric coatings, transparent conformal coatings over the cell with a structural-support substrate; (2) polymeric film lamination, cells laminated between two films or sheets of polymeric materials; and (3) glass-covered systems, cells adhesively bonded to a glass cover (superstrate) with a polymeric pottant and a glass or other substrate material. Several other design types, including those utilizing polymer sheet and pottant materials, were also included in the investigation

Acquisition of an Interactive Computing System for Academic Use: A Case Study

The acquisition of a large-scale computer system is a complex and important task that universities face periodically. The large capital expenditures and the always expanding need for computing services ensure an increasing importance. Virginia Tech recently made such an acquisition. This paper describes the evaluation procedures leading to the acquisition, beginning with needs assessment and concluding with system selection. The acquisition of a computing system, in this instance a system primarily for interactive instructional support of undergraduates, is a decision that is subject to a variety of influences technical, managerial, political, and personal. This paper describes the authors' attempts (as then Associate Director of the Computing Center and then Head of the Computer Science Department, respectively) to deal with these influences through the use of quantitative techniques, behavioral analysis, and common sense

Simulation Model Development: System Specification Techniques

A review of software specification techniques and specification languages is described. Special emphasis given to simulation model specification and the degree to which general software techniques are applicable in the modeling domain. The role of specification is examined in terms of existing techniques as well as abstraction permitting the identification of desirable properties unrelated to existing tools. A categorization of specification languages assists in understanding the similarities and differences among current approaches

Proceedings of the 11th Annual Meeting, Southern Soybean Disease Workers (March 27-29, 1984, Ft. Walton Beach, Florida): Economics of Soybean Disease

Contents 1984 Southern Soybean Disease Workers Officers 1984 Southern Soybean Disease Workers Program Committee 1984 Southern Soybean Disease Workers Committee Chairmen Workshop Diagnosing early season soybean disorders. D Stuckey and A Wrather General session Presidential address. HJ Walters Southern United States Soybean Disease Loss Estimate for 1983. Southern Soybean Disease Workers, Soybean Disease Loss Estimate Committee. RP Mulrooney Soybean nematodes. R Dunn presiding A New Publication on the Soybean Cyst Nematode. WF Moore Soybean Cultivars and Development of Populations of Meloidogyne incognita in Soil: A Concept of Tolerance. R Rodríguez-Kábana and DB Weaver A Comparison of Soybean Cultivars for Their Resistance to Meloidogyne incognita and M. arenaria. RA Kinloch Ethylene Dibromide and Alternative Nematicides for Soybeans. RA Dunn Involvement of Fungi in Phytonematode Pathology. G Morgan-Jones and R Rodríguez-Kábana Graduate student presentations. EC McGawley presiding Interaction Between Heterodera glycines and Glomus macrocarpus on Soybeans as Affected by Aldicarb. DP McCormack, DP Schmitt, and KR Barker Phomopsis sp. and Soybean Seedling Emergence: Influence of Soil Water Potential. M Gleason and RS Ferriss Soybean seed, seedling and soil-borne diseases. WS Gazaway presiding Report of Southern Soybean Disease Workers Seed Treatment Committee, 1983. MC McDaniel Effects of Soil Source, Soil Moisture, Seed Quality and Seed Treatment on Soybean Emergence. RE Stuckey, RS Ferriss, and MR Siegel Epidemiological and Mycofloral Relationships in Soybean Seedling Disease. JF Killebrew and KW Roy Seed Treatments for Control of Seedling Diseases and Rhizoctonia Root Rot in No-Till Soybeans. AY Chambers Soybean foliar, pod and stem diseases. JW Shriver presiding Southern Soybean Disease Workers Standardized Foliar Fungicide Test, 1983. AY Chambers and MA Newman Stem Canker in the Southeastern United States. WS Gazaway Timings of Foliar Fungicide Applications on Soybeans in Louisiana. JS Gershey, GT Berggren, and ME Pace Levels of Chlorine in Leaves and Seed Causing Leaf Scorch of Soybeans. MB Parker, TP Gaines, and GJ Gascho Incidence and Yield Loss Estimates on Stem and Foliar Diseases as Affected by Row Spacing and Overhead Irrigation. MC Hirrell and MC McDaniel Foliar Fungicides in Georgia: A Ten-Year Summary. DV Phillips New developments. E Barrett presiding The Use of Microcomputers in Soybean Disease Research. ME Pace, GT Berggren, Jr, and JS Gershey Aerial Web Blight in Mississippi in 1983. JA Fox SSDW Treasurer\u27s repor