Intermittent Synchronization in a Pair of Coupled Chaotic Pendula

Numerical simulations have been carried out for a pair of unidirectionally coupled identical pendula under the action of a common external ac torque. Both the master pendulum and the slave pendulum were in chaotic states. The only form of persistent locking appeared to be a computational artifact; otherwise the synchronization of slave to master was found to be intermittent

Intermittent Synchronization of Resistively Coupled Chaotic Josephson Junctions

Numerical simulations have been used to investigate the dynamics of a pair of resistively linked Josephson junctions with ac bias. For suitable choices of parameters, the chaotic states of the two junctions become intermittently synchronized. Intervals of synchronization are interleaved between bursts of desynchronized activity. The distributions of these laminar times and their dependence on the coupling strength are determined. The role of phase winding in the definition of synchronization intervals is considered

Inverting Chaos: Extracting System Parameters from Experimental Data

Given a set of experimental or numerical chaotic data and a set of model differential equations with several parameters, is it possible to determine the numerical values for these parameters using a least-squares approach, and thereby to test the model against the data? We explore this question (a) with simulated data from model equations for the Rossler, Lorenz, and pendulum attractors, and (b) with experimental data produced by a physical chaotic pendulum. For the systems considered in this paper, the least-squares approach provides values of model parameters that agree well with values obtained in other ways, even in the presence of modest amounts of added noise. For experimental data, the “fitted” and experimental attractors are found to have the same correlation dimension and the same positive Lyapunov exponent

Hydrological, Chemical, and Management Factors Affecting Nitrogen Fate and Transport with Agricultural Drainage

The issue of nitrogen (N) fate and transport, particularly nitrate-nitrogen (N03-N) leaching, and the resultant contamination of surface and groundwater resources is a continuing public concern. A recent newspaper editorial (July 1, 2001) in the Des Moines Register entitled Nitrate madness, noted that N03-N can pose human health hazards relative to methemoglobamemia, certain forms of cancer, and miscarriages, as well as cause ecological damages such as hypoxia in the Gulf of Mexico. It was also noted that in Iowa, agriculture is a major source ofN03-N loss, but that: A variety of means are available to reduce nitrates, but they need to be universally practiced to be effective

Phosphorus and Surface Water Quality

With increased concentration of livestock numbers and operations into smaller geographic areas, particularly confinement animal feeding operations (CAFOS) for cattle and swine (and also poultry), there are concerns surrounding the impacts of animal agriculture on the quality of our natural resources. Storage and land application management practices of manure generated by these operations can affect air and water quality. Manure management plans written to provide nutrients at rates necessary for crop production can sometimes result in over application of phosphorus (P) when the rate of manure application is based on the nitrogen (N) needs of the crop/rotation. This is particularly true for continuous com and for com rotated with soybeans where the N needs of the com and soybeans are both met with manure applications. This over application of P leads to surface water quality and possible P leaching concerns. These concerns, how they are affected by P fate and transport, and how management practices affect P fate and transport, are the subjects of this paper

Managing Infiltration to Avoid Water Quality Problems

Recent newspaper headlines in the Des Moines Register (e.g., October 19, 1994: Water is laced with pesticides report finds- 14 million affected and July 14, 1995: River boosted drinking water nitrate levels - farm fertilizer suspected ) illustrate some of the water quality concerns that exist for the off-site movement of pesticides and nutrients from treated fields to water resources. The major water quality concerns from pesticides relate to the possible impact on human health when found in surface and groundwater, and on the health of the aquatic ecosystem when found in surface waters. The major water quality concerns from nutrients, namely nitrate-nitrogen (NOrN), ammonium-nitrogen (NH4-N), and orthophosphate-phosphorus (P04-P), relate to the 10 mg/L (or ppm) drinking water standard for NOrN for prevention of blue baby or methemoglobinemia in infants, the level of concern of about 2 mg/L for NH4-N to prevent fish toxicity from free ammonia (NH3), and the levels of concerns in rivers of 0.050 mg/L and lakes of 0.025 mg/L for P04-P to prevent the acceleration of eutrophication

Limitations of Improved Nitrogen Management to Reduce Nitrate Leaching and Increase Use Efficiency

The primary mode of nitrogen (N) loss from tile-drained row-cropped land is generally nitrate-nitrogen (NO3-N) leaching. Although cropping, tillage, and N management practices can be altered to reduce the amount of leaching, there are limits as to how much can be done. Data are given to illustrate the potential reductions for individual practices such as rate, method, and timing of N applications. However, most effects are multiplicative and not additive; thus it is probably not realistic to hope to get overall reductions greater than 25 to 30% with in-field practices alone. If this level of reduction is insufficient to meet water quality goals, additional off-site landscape modifications may be necessary

Nitrate and herbicide leaching as affected by conservation tillage

Conservation tillage is widely promoted because it has been demonstrated to help reduce erosion. But soil conservation concerns must be balanced against the possibility that such tillage may allow greater chemical leaching (removal of fertilizers and pesticides from the root zone of the soil by downward-percolating water), thus degrading water quality

A Compton telescope for remote location and identification of radioactive material

The spare detectors from NASA Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of g radiation or the movement of material that might shield γ-ray sources. The Gamma-Ray Experimental Telescope Assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of- flight for each coincident detection and compiles histograms of total energy and incident angle as computed using the kinematics of Compton scattering. The GRETA field of view is a cone with full angle approximately 120°. The sensitive energy range is 0.3 to 2.6 MeV. Energy resolution is ~10% FWHM. The angular resolution, ~19° in the simplified configuration tested, will improve to better than 5° with well-defined enhancements to the data acquisition hardware and data analysis routines. When operated in the mode that was used in space, the instrument is capable of measuring and imaging up to 30 MeV with an angular resolution of 1.5°. The response of the instrument was mapped in the laboratory with 14 Ci 22Na source 3 m from the instrument. Later, we conducted demonstrations under two measurement scenarios. In one, the remotely located instrument observed an increase of background radiation counts at 1.4 MeV when a large amount of lead was removed from a building and a corresponding decrease when the lead was replaced. In the other scenario, the location and isotope-identifying energy spectrum of a 500 μCi137Cs source 3-5 m from the instrument with two intervening walls was determined in less than one minute. We report details of the instrument design and these measurements