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51.
This paper describes an analytical solution for turning and milling stability that includes process damping effects. Comparisons between the new analytical solution, time-domain simulation, and experiment are provided. The velocity-dependent process damping model applied in the analysis relies on a single coefficient similar to the specific cutting force approach to modeling cutting force. The process damping coefficient is identified experimentally using a flexure-based machining setup for a selected tool-workpiece pair (carbide insert-AISI 1018 steel). The effects of tool wear and cutting edge relief angle are also evaluated. It is shown that a smaller relief angle or higher wear results in increased process damping and improved stability at low spindle speeds. 相似文献
52.
Martins Amanda Weege S. Silveira Tony L. R. Remião Mariana H. Domingues William Borges Dellagostin Eduardo N. Junior Antônio Sergio Varela Corcini Carine D. Costa Patrícia G. Bianchini Adalto Somoza Gustavo M. Robaldo Ricardo B. Campos Vinicius Farias 《Environmental science and pollution research international》2021,28(46):65127-65139
Environmental Science and Pollution Research - Roundup Transorb® (RDT) is a glyphosate-based herbicide commonly used in agricultural practices worldwide. This herbicide exerts negative effects... 相似文献
53.
Tony Svejcar Chad Boyd Kirk Davies Matthew Madsen Jon Bates Roger Sheley Clayton Marlow David Bohnert Mike Borman Ricardo Mata-Gonzàlez John Buckhouse Tamzen Stringham Barry Perryman Sherman Swanson Kenneth Tate Mel George George Ruyle Bruce Roundy Chris Call Kevin Jensen Karen Launchbaugh Amanda Gearhart Lance Vermeire John Tanaka Justin Derner Gary Frasier Kris Havstad 《Environmental management》2014,53(6):1035-1038
In a previous article, Beschta et al. (Environ Manag 51(2):474–491, 2013) argue that grazing by large ungulates (both native and domestic) should be eliminated or greatly reduced on western public lands to reduce potential climate change impacts. The authors did not present a balanced synthesis of the scientific literature, and their publication is more of an opinion article. Their conclusions do not reflect the complexities associated with herbivore grazing. Because grazing is a complex ecological process, synthesis of the scientific literature can be a challenge. Legacy effects of uncontrolled grazing during the homestead era further complicate analysis of current grazing impacts. Interactions of climate change and grazing will depend on the specific situation. For example, increasing atmospheric CO2 and temperatures may increase accumulation of fine fuels (primarily grasses) and thus increase wildfire risk. Prescribed grazing by livestock is one of the few management tools available for reducing fine fuel accumulation. While there are certainly points on the landscape where herbivore impacts can be identified, there are also vast grazed areas where impacts are minimal. Broad scale reduction of domestic and wild herbivores to help native plant communities cope with climate change will be unnecessary because over the past 20–50 years land managers have actively sought to bring populations of native and domestic herbivores in balance with the potential of vegetation and soils. To cope with a changing climate, land managers will need access to all available vegetation management tools, including grazing. 相似文献
54.
Prato T 《Environmental management》2011,48(1):142-149
Wildlife managers have little or no control over climate change. However, they may be able to alleviate potential adverse
impacts of future climate change by adaptively managing wildlife for climate change. In particular, wildlife managers can
evaluate the efficacy of compensatory management actions (CMAs) in alleviating potential adverse impacts of future climate
change on wildlife species using probability-based or fuzzy decision rules. Application of probability-based decision rules
requires managers to specify certain probabilities, which is not possible when they are uncertain about the relationships
between observed and true ecological conditions for a species. Under such uncertainty, the efficacy of CMAs can be evaluated
and the best CMA selected using fuzzy decision rules. The latter are described and demonstrated using three constructed cases
that assume: (1) a single ecological indicator (e.g., population size for a species) in a single time period; (2) multiple
ecological indicators for a species in a single time period; and (3) multiple ecological conditions for a species in multiple
time periods. 相似文献
55.
Amanda C. O’Toole Andy J. Danylchuk Tony L. Goldberg Cory D. Suski David P. Philipp Edd Brooks Steven J. Cooke 《Marine Biology》2011,158(10):2227-2237
Great barracuda (Sphyraena barracuda) were implanted with acoustic telemetry transmitters (n = 42) and monitored within a stationary acoustic receiver array (n = 53 receivers) in The Bahamas to examine residency, seasonal movements, and habitat use. Barracuda were monitored for up
to 980 days and remained within the array area ~33% (median value) of the time. Most tagged barracuda were transient and would
often disappear from the array for months at a time, particularly in the summer where they were usually last detected on receivers
located in deeper shelf habitats, and then return at other times in the year. Habitat use across the footprint of the array
differed, with most detections occurring in coastal areas and comparatively fewer in deeper mosaic or shelf habitats. Linear
home range estimates revealed that some barracuda moved >12 km within a single day and are capable of migrating >100 km to
other islands in the Bahamian Archipelago. Our results provide some of the first telemetry data for this apex marine predatory
fish and the first reliable information on the residency and localized seasonal movements of adult great barracuda in the
coastal waters of the Western Atlantic. 相似文献
56.
The concern for sustainable development which has been accentuated by the United Nations Conference on Environment and Development (UNCED), is now being reflected at national and local government levels. In particular, Agenda 21, which was endorsed at the conference, has led to the implementation of a Local Agenda 21 programme. In Britain, extensive guidance and support on the interpretation of sustainable development has been provided by the Local Government Management Board and others. This paper reviews the general response to Local Agenda 21 in Britain and describes one local authority's approach. 相似文献
57.
Albert C. F. Lam Daniel H. C. Chan Tony M. F. Tong Mary H. Y. Tang Steven Y. F. Lo Ivan F. M. Lo Stephen T. S. Lam 《黑龙江环境通报》2006,26(11):1018-1020
We present the first confirmed case by molecular analysis of a metaphyseal chondrodysplasia, McKusick type, in a 22-week fetus. Two novel compound heterozygous mutations, 64T> A and 79G > T, were found in the highly conserved regions of the RMRP gene. Twenty-two heterozygous g.1018 T> C mutations, two homozygous g.1018 T> C mutations, two heterozygous insertion mutations g.799_g.800insC and one heterozygous insertion mutation g.849_g.850insT were found among 100 normal controls. Careful radiological examination of the fetus for skeletal dysplasia allowed definitive diagnosis, proper genetic counselling and future prenatal diagnosis. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
58.
Forest Renewal British Columbia (FRBC) was created in 1994 to deliver programmes of sustainable development within the leading economic sector of the province, serving as a key element of the radical new natural resource management agenda being promoted by an interventionist provincial administration. Its funding consisted solely of the hypothecated revenues of a 'super' stumpage on timber harvesting. This paper considers the role FRBC played in helping to gain agreement to changes in provincial land use planning and forest strategy, and evaluates its effectiveness as an eco-tax recycling mechanism. 相似文献
59.
60.
The relationship between plant nutrient content and insect herbivore populations and community structure has long interested ecologists. Insect herbivores require multiple nutrients, but ecologists have focused mostly on nitrogen (an estimate of plant protein content), and more recently phosphorus (P); other nutrients have received little attention. Here we document nutrient variation in grass and forb samples from grassland habitats in central Nebraska using an elemental approach; in total we measured foliar concentrations of 12 elements (N and P, plus S, B, Ca, Mg, Na, K, Zn, Fe, Mn, and Cu). We detected significant variability among sites for N, P, Mg, Na, K, and Cu. We next used a model selection approach to explore how this nutritional variation and plant biomass correlate with grasshopper densities (collectively and at the feeding-guild level), and principal component analysis to explore nutrient correlations with grasshopper community species composition. When all grasshoppers were pooled, densities varied among sites, but only P was associated with abundance of the elements shown to vary between sites. Different responses occurred at the feeding-guild level. For grass specialists, densities were associated with N, plus P, Mg, and Na. For forb specialists, N and P were often associated with density, but associations with Na and K were also observed. Finally, mixed-feeder abundance was strongly associated with biomass, and to a lesser extent P, Mg, Na, and Cu. At the community level, B, Ca, Zn, and Cu, plus biomass, explained > 30% of species composition variation. Our results confirm the positive association of N and P with insect herbivore populations, while suggesting a potential role for Mg, Na, and K. They also demonstrate the importance of exploring effects at the feeding-guild level. We hope our data motivate ecologists to think beyond N and P when considering plant nutrient effects on insect herbivores, and make a call for studies to examine functional responses of insect herbivores to dietary manipulation of Mg, Na, and K. Finally, our results demonstrate correlations between variation in nutrients and species assemblages, but factors not linked to plant nutrient quality or biomass likely explain most of the observed variation. 相似文献