Understanding the Past and Present and Predicting the Future: Farmers’ Use of Multiple Nutrient Best Management Practices in the Upper Midwest     

Riva C. H. Denny  Sandra T. Marquart-Pyatt  Matthew Houser 《社会与自然资源》2019,32(7):807-826

Understanding what drives farmers’ voluntary adoption of nutrient and soil best management practices has important consequences for many environmental outcomes including water quality. We build on research revealing the need for simultaneous use of multiple nitrogen best management practices to achieve water quality improvement goals. Using social, economic and attitudinal variables we predict the use of multiple nitrogen best management practices at three time points: current use (2013), past use (before 2013), and likelihood of use on their largest field in the next three years. Our empirical analysis uses structural equation modeling with latent variables and 2014 farmer survey data from three Midwestern US states. Most farmers in our sample used at least one of the six best management practices. Our results reveal that farmers’ attitudes, use of information sources, and conservation program participation affect the number of nitrogen best management practices concurrently in use at multiple time points.  相似文献   

A hypoplastic macroelement formulation for single batter piles in sand          下载免费PDF全文

Zheng Li  Panagiotis Kotronis  Sandra Escoffier  Claudio Tamagnini 《国际地质力学数值与分析法杂志》2018,42(12):1346-1365

Batter piles are widely used in geotechnical engineering when substantial lateral resistance is needed or to avoid the interference with existing underground constructions. Nevertheless, there is a lack of fast numerical tools for nonlinear soil‐structure interactions problems for this type of foundation. A novel hypoplastic macroelement is proposed, able to reproduce the nonlinear response of a single batter pile in sand under monotonic and cyclic static loadings. The behavior of batter piles (15°, 30°, and 45°) is first numerically investigated using 3D finite element modeling and compared with the behavior of vertical piles. It is shown that their response mainly depends on the pile inclination and the loading direction. Then, starting from the macroelement for single vertical piles in sand by Li et al (Acta Geotechnica, 11(2):373‐390, 2016), an extension is proposed to take into account the pile inclination introducing simple analytical equations in the expression describing the failure surface. 3D finite element numerical models are adopted to validate the macroelement that is proven able to reproduce the nonlinear behavior in terms of global quantities (forces‐displacements) and to significantly reduce the necessary computational time.  相似文献   

Hydromagnetic field line resonances and modulation of particle precipitation     

L.J. Lanzerotti  T.J. Rosenberg  A. Wolfe  C.G. Maclennan 《Planetary and Space Science》1985,33(3):253-262

Hydromagnetic wave and modulated particle precipitation data are reported from conjugate areas near the particledrift shell L ～ 4. A modulation of electrons precipitating from the magnetosphere is observed in the conjugate regions when the accompanying hydromagnetic wave period is ~ 90 s and the wave polarization is linear. When the wave period changes abruptly to ~ 30 s and the polarizations at the observing stations are no longer linear, the modulation of the precipitating electrons is no longer observed. The change in hydromagnetic wave characteristics does not appear to be related to interplanetary plasma and magnetic field conditions. Rather, it is proposed to arise from a change in the wave generation mechanism from an internal magnetospheric source near the inner edge of the plasmapause (lower frequency) to an externally driven source outside the magnetosphere (higher frequency). This observation of a change in the wave characteristics (frequency and polarization) associated with modulated electron precipitation appears to be related to two previous examples wherein modulated electron precipitation was reported to be closely associated with the existence of a wave resonance region near the observing site.  相似文献   

Storylines: an alternative approach to representing uncertainty in physical aspects of climate change     

Theodore G. Shepherd  Emily Boyd  Raphael A. Calel  Sandra C. Chapman  Suraje Dessai  Ioana M. Dima-West  Hayley J. Fowler  Rachel James  Douglas Maraun  Olivia Martius  Catherine A. Senior  Adam H. Sobel  David A. Stainforth  Simon F. B. Tett  Kevin E. Trenberth  Bart J. J. M. van den Hurk  Nicholas W. Watkins  Dimitri A. Zenghelis 《Climatic change》2018,147(3-4):555-569

Investigating the relationships between climate extremes and crop yield can help us understand how unfavourable climatic conditions affect crop production. In this study, two statistical models, multiple linear regression and random forest, were used to identify rainfall extremes indices affecting wheat yield in three different regions of the New South Wales wheat belt. The results show that the random forest model explained 41–67% of the year-to-year yield variation, whereas the multiple linear regression model explained 34–58%. In the two models, 3-month timescale standardized precipitation index of Jun.–Aug. (SPI_JJA), Sep.–Nov. (SPI_SON), and consecutive dry days (CDDs) were identified as the three most important indices which can explain yield variability for most of the wheat belt. Our results indicated that the inter-annual variability of rainfall in winter and spring was largely responsible for wheat yield variation, and pre-growing season rainfall played a secondary role. Frequent shortages of rainfall posed a greater threat to crop growth than excessive rainfall in eastern Australia. We concluded that the comparison between multiple linear regression and machine learning algorithm proposed in the present study would be useful to provide robust prediction of yields and new insights of the effects of various rainfall extremes, when suitable climate and yield datasets are available.  相似文献   

The influence of El Niño–Southern Oscillation on boreal winter rainfall over Peninsular Malaysia     

Sandra?RichardEmail authorView author&#;s OrcID profile  Kevin?J.?E.?Walsh 《Theoretical and Applied Climatology》2018,134(1-2):121-138

Multi-scale interactions between El Niño–Southern Oscillation and the Boreal Winter Monsoon contribute to rainfall variations over Malaysia. Understanding the physical mechanisms that control these spatial variations in local rainfall is crucial for improving weather and climate prediction and related risk management. Analysis using station observations and European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) reanalysis reveals a significant decrease in rainfall during El Niño (EL) and corresponding increase during La Niña particularly north of 2°N over Peninsular Malaysia (PM). It is noted that the southern tip of PM shows a small increase in rainfall during El Niño although not significant. Analysis of the diurnal cycle of rainfall and winds indicates that there are no significant changes in morning and evening rainfall over PM that could explain the north–south disparity. Thus, we suggest that the key factor which might explain the north–south rainfall disparity is the moisture flux convergence (MFC). During the December to January (DJF) period of EL years, except for the southern tip of PM, significant negative MFC causes drying as well as suppression of uplift over most areas. In addition, lower specific humidity combined with moisture flux divergence results in less moisture over PM. Thus, over the areas north of 2°N, less rainfall (less heavy rain days) with smaller diurnal rainfall amplitude explains the negative rainfall anomaly observed during DJF of EL. The same MFC argument might explain the dipolar pattern over other areas such as Borneo if further analysis is performed.  相似文献   

Elastic and visco-elastic stress triggering in the South Iceland Seismic Zone due to large earthquakes since 1706   总被引：1，自引：0，他引：1  

Sandra M. Richwalski  Frank Roth 《Tectonophysics》2008,447(1-4):127

Damaging earthquakes in the South Iceland Seismic Zone (SISZ) occur fairly regularly and often as a series of events with a few days only between individual events. Tolerably reliable information on epicentre locations and mechanisms are available for 13 M ≥ 6 events between 1706 and 2000. For these events, we computed the co- and post-seismic stress fields, hereby approximating the SISZ by a mixed elastic/visco-elastic layered half-space. The horizontal shear stress and the Coulomb stress changes were analysed to detect possible trigger mechanisms, which may aid future earthquake mitigation efforts. We tested several criteria but must conclude that the start of an earthquake series in the SISZ cannot be explained by triggering through previous events. Inside an individual series, however, one may infer triggering. Our results are in contradiction with the findings in other regions of the world. The reason might be related to the fact that the SISZ is not a mature fault zone, in which old faults are re-activated if a certain stress level threshold is passed. In addition, uncertainties in the model parameters as well as the neglect of horizontal variations in the model and of possible stress transfer due to volcanic activity further complicate the evaluation of our results and need to be taken into account in future studies.  相似文献   

CO2 emission accompanying the fracture of calcite     

J. T. Dickinson  L. C. Jensen  S. C. Langford  P. E. Rosenberg  D. L. Blanchard 《Physics and Chemistry of Minerals》1991,18(5):320-325

Time resolved mass spectroscopy of the emissions accompanying the fracture of calcite (rhombohedral CaCO₃) show that the principle volatile product, CO₂, is released in bursts milliseconds after the fracture event. Similar measurements during the abrasion of calcite and during low temperature thermal decomposition of pulverized calcite show similar CO₂ bursts. We argue that the observed bursts reflect localized decomposition of the calcite during the relaxation of reversible plastic deformation created by fracture and abrasion. This implies that mechanical, non-thermal processes play an important role in producing the observed decomposition products.  相似文献   

Channel avulsion and river metamorphosis: The case of the Thomson River,Victoria, Australia     

Sandra O. Brizga  Brian L. Finlayson 《地球表面变化过程与地形》1990,15(5):391-404

Channel avulsion occurred on the Thomson River in Victoria, Australia, in 1952 along a 12 km length of the valley. A comparison of the old and new channels reveals considerable differences in channel characteristics. The old channel was perched above the floodplain on an alluvial ridge such that when bankfull capacity was exceeded, floodwaters concentrated on the lowest part of the floodplain some distance away. This is where the new channel formed. It is an incised channel with larger capacity and longer meander wavelength than the old channel and is also shorter and steeper. The new channel is subject to larger floodflows and a more variable flood regime than the old course because of the differences in the channel/floodplain relationship and channel capacity. The resulting concentration of stream power along the new course is responsible for the contrast in channel characteristics and for the more rapid meander migration. This example shows that river metamorphosis can occur without major environmental changes. Measures of channel geometry such as gradient, sinuosity, and meander wavelength therefore cannot be used in palaeohydrological work to infer climatic or other environmental changes without independent supporting evidence. Differences in channel geometry can arise simply from changes in the relationship between the channel and its loodplain.  相似文献   

Simulated Effects of Quarry Dewatering Near a Municipal Well Field   总被引：4，自引：0，他引：4  

Sandra M. Eberts  E. Scott Bair 《Ground water》1990,28(1):37-47

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The Solar Oscillations Investigation - Michelson Doppler Imager     

P. H. Scherrer  R. S. Bogart  R. I. Bush  J. T. Hoeksema  A. G. Kosovichev  J. Schou  W. Rosenberg  L. Springer  T. D. Tarbell  A. Title  C. J. Wolfson  I. Zayer  The MDI Engineering Team 《Solar physics》1995,162(1-2):129-188

The Solar Oscillations Investigation (SOI) uses the Michelson Doppler Imager (MDI) instrument to probe the interior of the Sun by measuring the photospheric manifestations of solar oscillations. Characteristics of the modes reveal the static and dynamic properties of the convection zone and core. Knowledge of these properties will improve our understanding of the solar cycle and of stellar evolution. Other photospheric observations will contribute to our knowledge of the solar magnetic field and surface motions. The investigation consists of coordinated efforts by several teams pursuing specific scientific objectives.The instrument images the Sun on a 1024² CCD camera through a series of increasingly narrow spectral filters. The final elements, a pair of tunable Michelson interferometers, enable MDI to record filtergrams with a FWHM bandwidth of 94 m. Normally 20 images centered at 5 wavelengths near the Ni I 6768 spectral line are recorded each minute. MDI calculates velocity and continuum intensity from the filtergrams with a resolution of 4 over the whole disk. An extensive calibration program has verified the end-to-end performance of the instrument.To provide continuous observations of the longest-lived modes that reveal the internal structure of the Sun, a carefully-selected set of spatial averages are computed and downlinked at all times. About half the time MDI will also be able to downlink complete velocity and intensity images each minute. This high rate telemetry (HRT) coverage is available for at least a continuous 60-day interval each year and for 8 hours each day during the rest of the year. During the 8-hour HRT intervals, 10 of the exposures each minute can be programmed for other observations, such as measurements in MDI's higher resolution (1.25) field centered about 160 north of the equator; meanwhile, the continuous structure program proceeds during the other half minute. Several times each day, polarizers will be inserted to measure the line-of-sight magnetic field.MDI operations will be scheduled well in advance and will vary only during the daily 8-hour campaigns. Quick-look and summary data, including magnetograms, will be processed immediately. Most high-rate data will be delivered only by mail to the SOI Science Support Center (SSSC) at Stanford, where a processing pipeline will produce 3 Terabytes of calibrated data products each year. These data products will be analyzed using the SSSC and the distributed resources of the co-investigators. The data will be available for collaborative investigations.The MDI Engineering Team leaders include: D. Akin, B. Carvalho, R. Chevalier, D. Duncan, C. Edwards, N. Katz, M. Levay, R. Lindgren, D. Mathur, S. Morrison, T. Pope, R. Rehse, and D. Torgerson.  相似文献