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151.
Katharine M. Marko Edward S. Rutherford Brian J. Eadie Thomas H. Johengen Margaret B. Lansing 《Journal of Great Lakes research》2013
Drowned river mouth lakes are major features of coastal Great Lakes habitats and may influence nutrient and organic matter contributions from watersheds to near shore coastal zones. In May through October 2003, we measured loads of nutrients, surficial sediment, and seston to track the delivery of riverine-derived materials from the lower Muskegon River Watershed (MRW) into the near shore area of southeast Lake Michigan. Nutrient flux data indicated that seasonal loads of 1800 metric tons (MT) of particulate organic carbon, 3400 MT of dissolved organic carbon, and 24 MT of total phosphorus were discharged from the lower Muskegon River, with approximately 33% of TP load and 53% of the POC load intercepted within the drowned river mouth terminus, Muskegon Lake. Carbon: phosphorus molar ratios of seston in Muskegon River (C:P = 187) and Muskegon Lake (C:P = 176) were lower than in Lake Michigan (C:P = 334), indicating phosphorus limitation of phytoplankton in near shore Lake Michigan. Isotopic signatures of seston collected in Muskegon Lake were depleted in δ13C (− 30.8 ± 1.6‰) relative to the isotope signatures of seston from Lake Michigan (− 26.2 ± 1.3‰) or the mouth of the Muskegon River (− 28.1 ± 0.5‰), likely due to the presence of biogenic methane in Muskegon Lake. Seston δ15N increased on a strong east-to-west gradient within Muskegon Lake, indicating significant microbial processing of nutrients. The extent of nutrient uptake in Muskegon Lake altered the chemical and isotopic characterization of seston flowing into Lake Michigan from Muskegon River. 相似文献
152.
Abstract Emerging intrastate transboundary issues focus on use of the Mahomet aquifer, which underlies about fifteen counties and many other political entities in east-central Illinois. This sand and gravel aquifer in the lower part of the buried Mahomet Bedrock Valley ranges between four and fourteen miles wide and from about 50 to 200 feet thick. Much of the region's rural population, several large communities, and many small towns obtain water from the Mahomet aquifer, as do industrial, agricultural, and commercial users. Increased development of the Mahomet aquifer to meet growing demands for water has caused conflicts over real or perceived adverse effects. One result has been the creation of fifteen resource protection zones and twelve water authorities. For groundwater supplies, resource protection zones help municipalities protect water-supply wells from potential adverse impacts. Many resource protection zones overlap one another, however, so this situation could lead to disputes over use of the resource. The reason that several of the twelve water authorities were organized was to meet a challenge perceived from a demand to be placed on the aquifer, in other words, a potential for conflict of use. Complicating the situation is that some of the water authorities overlap the resource protection zones. This could lead to disputes not only about water use, but also over which jurisdiction has the authority to settle a dispute. The Mahomet Aquifer Consortium was recently organized by concerned people representing diverse groundwater interests at the local level, including the private sector, professional organizations, and various governmental units. The consortium brings together representatives of some groups that typically did not communicate with each other in the past. The consortium may provide a forum through which emerging transboundary issues pertaining to use of the Mahomet aquifer can be addressed. Because the consortium is a voluntary organization that relies on consensus building, the success it may achieve in resolving future conflicts over groundwater use from the Mahomet aquifer remains to be seen. 相似文献
153.
Hyunkyu Lee Pauline L. Baniqued Joshua Cosman Sean Mullen Edward McAuley Joan Severson Arthur F. Kramer 《Computers in human behavior》2012
Many studies conducted in a laboratory or university setting are limited by funding, personnel, space, and time constraints. In the present study, we introduce a method of data collection using a mobile application that circumvents these typical experiment administration issues. Using the application, we examined cross-sectional age differences in cognitive function. We obtained data from more than 15,000 participants and replicated specific patterns of age-related differences in cognition. Using a subset of these participants, we also examined the processing speed account of age-related cognitive differences, and the association of exercise and leisure activity with cognitive function across the lifespan. We discuss the relative advantages and disadvantages of data collection with a mobile application, and provide recommendations for the use of this method in research. 相似文献
154.
Linda A. Jackson Edward A. Witt Alexander Ivan Games Hiram E. Fitzgerald Alexander von Eye Yong Zhao 《Computers in human behavior》2012
This research examined relationships between children’s information technology (IT) use and their creativity. Four types of information technology were considered: computer use, Internet use, videogame playing and cell phone use. A multidimensional measure of creativity was developed based on and test of creative thinking. Participants were 491 12-year olds; 53% were female, 34% were African American and 66% were Caucasian American. Results indicated that videogame playing predicted of all measures of creativity. Regardless of gender or race, greater videogame playing was associated with greater creativity. Type of videogame (e.g., violent, interpersonal) was unrelated to videogame effects on creativity. Gender but not race differences were obtained in the amount and type of videogame playing, but not in creativity. Implications of the findings for future research to test the causal relationship between videogame playing and creativity and to identify mediator and moderator variables are discussed. 相似文献
155.
We study the problem of scheduling unit execution time jobs with release dates and precedence constraints on two identical
processors. We say that a schedule is ideal if it minimizes both maximum and total completion time simultaneously. We give
an instance of the problem where the min-max completion time is exceeded in every preemptive schedule that minimizes total
completion time for that instance, even if the precedence constraints form an intree. This proves that ideal schedules do
not exist in general when preemptions are allowed. On the other hand, we prove that, when preemptions are not allowed, then
ideal schedules do exist for general precedence constraints, and we provide an algorithm for finding ideal schedules in O(n
3) time, where n is the number of jobs. In finding such ideal schedules we resolve a conjecture of Baptiste and Timkovsky (Math. Methods Oper.
Res. 60(1):145–153, 2004) Further, our algorithm for finding min-max completion-time schedules requires only O(n
3) time, while the most efficient solution to date has required O(n
9) time. 相似文献
156.
This paper describes and analyzes the performance of a three-phase voltage control scheme that uses only three thyristors. This scheme produces balanced three-phase currents and voltages, the harmonic content of which are discussed along with its suitability for use as a simple control scheme for heating lighting and motor loads. 相似文献
157.
Double exposure holographic interferometry (DEHI) is used to determine the strain energy release rate, craze opening displacement profile, and craze stress profile ofn-heptane and methanol crazes growing from cracks in polystyrene.n-heptane crazes have strain energy release rates (SERRs) close to those of cracks and their stress profile is almost crack-like in that the tensile stress across the craze falls almost to zero. On the other hand, the SERRs of methanol crazes are only 30 to 55% the SERR of a crack depending on stress intensity factorK
I of the precrack from which they are grown. The stress profile of the methanol craze shows it to be strongly load-bearing away from the craze tip, apparently as a result of the strain hardening of the craze fibrils. The stress concentration in front of the methanol craze tip is only 40% of that in front of then-heptane craze tip. The opening displacements of the methanol craze are almost as large as those of a crack very near its tip but are much less than those of a crack at large distances behind the tip. The Dugdale model of a strip yielding zone provides a poor representation of the craze opening displacements of the growing methanol craze. Dry (static) methanol crazes have larger opening displacements in response to an incremental tensile strain at moderate prestrains than at either low or high prestrains, suggesting that the craze fibrils undergo a yielding/strain-hardening process as the strain is increased similar to that observed in polycarbonate crazes by Kopp and Kambour. Dryn-heptane crazes do not show this response but rather open linearly with increasing prestrain. The opening displacement for long (dry)n-heptane crazes is almost crack-like whereas the largest opening of a dry methanol craze is only 20% of that of a crack. Dry methanol crazes break at aK
IC that is 40% of theK
IC of precracked but uncrazed specimens. The strongest (shortest) dryn-heptane crazes fail at only 7% ofK
IC of uncrazed specimens and theK
IC of the dryn-heptane crazes decreases markedly with increasing craze length. 相似文献
158.
James Ely Richard Kouzes John Schweppe Edward Siciliano Denis Strachan Dennis Weier 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2006,560(2):373-387
Energy windowing is an algorithmic alarm method that can be applied to plastic scintillator-based radiation portal monitor (RPM) systems to improve operational sensitivity to certain threat sources while reducing the alarm rates from naturally occurring radioactive material. Various implementations of energy windowing have been tested and documented by industry and at Pacific Northwest National Laboratory, and are available in commercial RPMs built by several manufacturers. Moreover, energy windowing is being used in many deployed RPMs to reduce nuisance alarms and improve operational sensitivity during the screening of cargo. This paper describes energy windowing algorithms and demonstrates how these algorithms succeed when applied to “controlled” experimental measurements and “real world” vehicle traffic data. 相似文献
159.
160.
Farhad Shir Catherine Mavriplis Lawrence H. Bennett Edward Della Torre 《International Journal of Refrigeration》2005,28(4):1082
Results of a room temperature magnetic refrigeration test bed and an analysis using a computational model are presented. A detailed demonstration of the four sequential processes in the transient magnetocaloric regeneration process of a magnetic material is presented. The temperature profile during the transient approach to steady state operation was measured in detail. A 5 °C evolution of the difference of temperature between the hot end and the cold end of the magnetocaloric bed due to regeneration is reported. A model is developed for the heat transfer and fluid mechanics of the four sequential processes in each cycle of thermal wave propagation in the regenerative bed combined with the magnetocaloric effect. The basic equations that can be used in simulation of magnetic refrigeration systems are derived and the design parameters are discussed. 相似文献