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131.
Norman D. Folmar Arthur C. Miller Donald E. Woodward 《Journal of the American Water Resources Association》2007,43(3):829-838
Abstract: Many of the hydrologic methods that are used in engineering practice today resulted from the Spring Flood of 1936, which blanketed the Northeastern portion of the United States. Because of the flood damage that was caused by this rainfall‐snowmelt event, many federal agencies including the U.S. Army Corp of Engineers and the Soil Conservation Service (SCS) implemented the hydrologic theories that were available in the literature at this time and developed hydrologic procedures for design flow estimation. Sherman had recently published his unit hydrograph theory in 1932, and later in 1938 Snyder, who had been charged by the Water Resource Council to develop a synthetic unit hydrograph, published his famous paper. The SCS unit hydrograph theory was developed by Victor Mockus in the late 1950s. Most if not all of the theories at that time reported the rainfall‐runoff process for floods as a surface phenomenon, and as such those theories all required some type of a timing parameter to estimate watershed response time. This article documents the development of the SCS lag equation. 相似文献
132.
Arthur?J.?Kehas Kathleen?A.?Theoharides John?J.?GilbertEmail author 《Marine Biology》2005,146(6):1111-1117
At Discovery Bay, Jamaica, Tripneustes ventricosus lives in beds of the turtle grass Thalassia testudinum. Especially during daylight hours, it covers its aboral surface with fragments of this plant and other objects. Normally pigmented, wild-type sea urchins covered themselves significantly less with Thalassia when sunlight was experimentally decreased to 66% or 32% ambient intensity. Consistent with this result, naturally occurring sea urchins exhibited significantly less covering at a deep (3.5 m) site than at a shallow (1 m) site, where light intensities at the bottom were 619 and 946 mol s–1 m–2, respectively. The graded covering response to light intensity suggests that covering is a defense against damaging solar radiation. Albino sea urchins covered themselves significantly more with Thalassia than wild-type sea urchins in both full and 66% sunlight. In addition, at the shallow site where they accounted for about 4% of the population, they showed significantly greater covering than wild-type urchins. The greater covering response of albino sea urchins suggests a greater susceptibility to solar radiation.Communicated by P. W. Sammarco, Chauvin 相似文献
133.
McFarland MJ Palmer GR Peters S Olivas AC Nelson TM 《Journal of the Air & Waste Management Association (1995)》2005,55(3):365-372
To effectively reduce the environmental compliance costs associated with meeting specific requirements under the Aerospace Manufacturing and Rework Facility's National Emission Standard for Hazardous Air Pollutants rule, the U.S. Environmental Protection Agency's (EPA) Data Quality Objective (DQO) process has been proposed as a suitable framework for developing a scientifically defensible surface compliance monitoring program. By estimating the variability associated with the air cap pressure of high- volume, low-pressure (HVLP) surface-coating spray equipment, the number of monitoring samples necessary for an affected facility to claim compliance with a desired statistical confidence level was established. Using data taken from the pilot test facility, the DQO process indicated that the mean of at least 21 HVLP air cap pressure samples taken over the compliance period must be < or = 10 pounds per square inch (psig) gauge for the facility to claim regulatory compliance with 99.99% statistical confidence. Fewer compliance samples could be taken, but that decision would lead to a commensurate reduction in the compliance confidence level. Implementation of the DQO-based compliance sampling plan eliminates the need for an affected facility to sample all regulated HVLP surface-coating processes while still maintaining a high level of compliance assurance. 相似文献
134.
Arthur H. Purcell 《Resources Policy》1979,5(2):149
The impacts of materials substitution in the automobile industry were examined in a symposium at the 99th Winter Annual Meeting of the American Society of Mechanical Engineers. Papers were contributed by W.D. Compton of the Ford Motor Company, R.B. Gavert of the Office of Technology Assessment, US Congress, J.T. Herridge and R.W. Hale of Battelle Columbus Laboratories, A.H. Purcell of Technical Information Project Incorporated, and M.B. Bever of the Massachusetts Institute of Technology. Symposium on Measurements of the Impacts of Material Substitution – A Case Study in the Automobile Industry, San Francisco, 10–15 December 1978. 相似文献
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The incinerator at the T.Z. Osborne Plant in Greensboro, North Carolina burns sludge from its own waste water treatment plant and sludge pumped from the nearby North Buffalo plant. The two plants have a combined capacity of 36 million gallons per day of wastewater. Because of the age of and increasing high maintenance on the existing multiple hearth incinerator, and the need to increase treatment capacity, the Osborne plant concluded a study in 1992 evaluating its options for future municipal sewage sludge disposal. Options which were evaluated during the study included; (i) rehabilitation of the existing eight-year old multiple hearth unit; (ii) addition of a new multiple hearth; (iii) addition of a new fluid bed system; (iv) drying, composting, or land application. The chosen option, based on both economic and environmental considerations, was a new fluid bed system with a capacity of 2.55 tons per hour, approximately double that of the existing multiple hearth. Design of the new fluid bed system began in December 1994 and equipment delivery for the incineration system was begun in April 1995. Initial operation occurred in August 1996. Primary and secondary sludge, dewatered to 28% dry solids by centrifuge, is delivered by piston pumps to the twenty-foot freeboard ID incinerator. A shell and tube heat exchanger recuperates heat from the exhaust gas and preheats the combustion air to 1250°F, resulting in minimal auxiliary fuel use. The air pollution control device is a high-energy Tandem Nozzle® scrubber. Greensboro was the initial installation of this scrubber design on a fluid bed incinerator and its characteristics and performance are discussed. Ash is dewatered in an ash thickener/belt press system prior to disposal to landfill. The system includes a state of the art Programmable Logic Controller (PLC) system for computer control of the operation. The unit was commissioned in August 1996 and has been in continuous operation since that time except for a one week inspection and maintenance shutdown in February 1999. The plant operates 24 h/day, 7 days per week. The initial performance test showed the system to readily meet federal and state air emission standards. Particulate released was 0.002 grains per dry standard cubic foot, carbon monoxide was 22.5 parts per million volumetric (ppmv) and opacity was 0.4%. These results show a significant emission reduction with the fluid bed when compared to the multiple hearth. Annual tests conducted since then and continuous emission monitoring have shown the unit to be in consistent compliance. Since the fluid bed system became operational, the old multiple hearth system has been maintained on standby as a backup, but its use has not been required. Operational experience is discussed, the most interesting of which is the relatively trouble-free operation. The minor problems which occurred and their solutions are detailed. Also included is a comparison of operation and maintenance experience of the fluid bed and the multiple hearth. Current sludge disposal actual cost data are also provided including the average cost per ton of dry solids treated. The almost three years of operational experience to date has shown that the decision to install a new fluid bed system was the correct one on both an environmental and economic basis. It has provided benefits to all interested parties — the wastewater treatment plant, the regulators, the taxpayers, and the surrounding community. 相似文献
140.
Implication of two in-stream processes in the fate of nutrients discharged by sewage system into a temporary river 总被引:2,自引:0,他引:2
David A Perrin JL Rosain D Rodier C Picot B Tournoud MG 《Environmental monitoring and assessment》2011,181(1-4):491-507
The aim of this study was to better understand the fate of nutrients discharged by sewage treatment plants into an intermittent Mediterranean river, during a low-flow period. Many pollutants stored in the riverbed during the low-flow period can be transferred to the downstream environments during flood events. The study focused on two processes that affect the fate and the transport of nutrients, a physical process (retention in the riverbed sediments) and a biological process (denitrification). A spatial campaign was carried out during a low-flow period to characterize the nutrient contents of both water and sediments in the Vène River. The results showed high nutrient concentrations in the water column downstream of the treated wastewater disposal (up to 13,315 μg N/L for ammonium and 2,901 μg P/L for total phosphorus). Nutrient concentrations decreased rapidly downstream of the disposal whereas nutrient contents in the sediments increased (up to 1,898 and 784 μg/g for total phosphorus and Kjeldahl nitrogen, respectively). According to an in situ experiment using sediment boxes placed in the riverbed for 85 days, we estimated that the proportion of nutrients trapped in the sediments represents 25% (respectively 10%) of phosphorus (respectively nitrogen) loads lost from the water column. In parallel, laboratory tests indicated that denitrification occurred in the Vène River, and we estimated that denitrification likely coupled to nitrification processes during the 85 days of the experiment was significantly involved in the removal of nitrogen loads (up to 38%) from the water column and was greater than accumulation processes. 相似文献