Effects of Herbicide Management Practices on the Weed Density and Richness in 2,4-D- Resistant Cropping Systems in Indiana

Commercialization of 2,4-D-resistant soybean varieties allows for postemergence (POST) applications of 2,4-D in soybean. With the increase in POST applications of 2,4-D in soybean, shifts in weed populations may occur. A long-term field trial was conducted over seven years in a corn-soybean rotation. Weed populations were subjected to four herbicide strategies with variable levels of 2,4-D reliance. The strategies used included: 1) diversified glyphosate strategy with six herbicide sites of action (SOA); 2) 2,4-D reliant strategy with three SOA; 3) diversified 2,4-D reliant strategy with seven SOA; and 4) fully diversified strategy with eight SOA. Soil residual herbicides were utilized for both corn and soybean years, except for the 2,4-D reliant strategy which only utilized a residual herbicide during the corn years. A 52% or greater reduction in weed densities for all herbicide strategies, except the 2,4-D reliant strategy, was observed by the end of the study. However, the density of weeds tolerant to 2,4-D, such as monocots, increased after three years of selection pressure, and more than doubled after five years of selection pressure in the 2,4-D reliant strategy. Additionally, in the 2,4-D reliant strategy with three SOA, species richness was 30% higher in the soil seedbank compared to herbicides strategies with six or more SOA. In order to delay weed shifts, diversified herbicide strategies with more than three SOA that include residual herbicides should be used in corn:soybean rotational systems that utilize 2,4-D-resistant soybean.

Grazing Into the Anthropocene or Back to the Future?

This essay examines three central components of extensive livestock production—herd composition, grazing/pasture management, and rangeland tenure. In all of these areas, fenced, and open-range forms of migratory pastoralism face a number of shared problems. Set aside the presumption that either one of these systems is technically or institutionally more advanced than the other, and it turns out that each has lessons for the other. 1. For a variety of reasons, including climate change, we can look forward to a future world with less grass, which presents a challenge for livestock producers reliant on grass feeding livestock. With little delay and minimal scientific support, East African pastoralists are already adjusting to a new woody world by diversifying the species composition of their herds to include more browsers—camels and goats. There is a potential lesson here for commercial ranchers who have traded the stability of mixed herds for the profitability of keeping sheep or cattle alone. 2. Migratory rangeland systems distribute livestock very differently than fenced, rotational systems of livestock, and pasture management. Whereas, migratory herds exploit environmental heterogeneity, fenced ranching attempts to suppress it. Emerging archaeological evidence is demonstrating that pastoralists have amplified rangeland heterogeneity for millennia; ecological research shows that this heterogeneity sustains both plant and wildlife biodiversity at the landscape scale; and new approaches to ranch management are appropriating aspects of migratory herding for use on fenced ranches. A rapprochement between the environmental sciences, ranching, and open-range migratory pastoralism has occurred and merits wider policy recognition. 3. In contemporary Africa, indigenous tenure regimes that sustain open rangelands are eroding under pressure from market penetration and state encapsulation. At the same time in the American West, there are emerging novel land tenure instruments that replicate some of the most important functional characteristics of tenure arrangements in pastoral Africa. After many false starts, it appears that some aspects of American ranching do provide an appropriate model for the preservation of the open-range migratory systems that they were once supposed to supplant. “Development” policy needs to reflect upon this inversion of roles and its implications for accommodating diversity.

Application of Genetic Algorithm Elements to Modelling of Rotation Processes in Motion Transmission Including a Long Shaft

Genetic algorithms are used to parameter identification of the model of oscillatory processes in complicated motion transmission of electric drives containing long elastic shafts as systems of distributed mechanical parameters. Shaft equations are generated on the basis of a modified Hamilton–Ostrogradski principle, which serves as the foundation to analyse the lumped parameter system and distributed parameter system. They serve to compute basic functions of analytical mechanics of velocity continuum and rotational angles of shaft elements. It is demonstrated that the application of the distributed parameter method to multi-mass rotational systems, that contain long elastic elements and complicated control systems, is not always possible. The genetic algorithm is applied to determine the coefficients of approximation the system of Rotational Transmission with Elastic Shaft by equivalent differential equations. The fitness function is determined as least-square error. The obtained results confirm that application of the genetic algorithms allow one to replace the use of a complicated distributed parameter model of mechanical system by a considerably simpler model, and to eliminate sophisticated calculation procedures and identification of boundary conditions for wave motion equations of long elastic elements.

Fuzzy Identification of The Reliability State of The Mine Detecting Ship Propulsion System

The study presents the evaluation and comparative analysis of engine shaft line performance in maritime transport ships of the same type. During its operation, a technical system performs functions for which it was designed. It goes through different states. Dynamic state changes of a rotational system can be identified by means of its vibration measurement. For this purpose, a research was carried out which involved recording vibrations of the analysed rotational systems. The recordings were used for calculating selected characteristics in the time-domain, where one of the most unique is the value of the normalized mutual correlation function. On the basis of the concentration values, the characteristics which unambiguously determine the ability state were selected for further studies. Then an identification method for rotational system non-coaxiality was proposed. The method involves using fuzzy clustering. According to this method the values of input signal characteristics were used to formulate fuzzy clusters of system ability and inability states. The method can be used for identifying the current state of the system. The study presents the results of the application of this method in engine turbine shaft lines of minesweepers, with the rotational system selected as an example. It needs to be noted that the efficiency of identifying the operating state of the system with this method is higher than with other methods described in the literature by authors who deal with this issue. The research results have a significant impact on the evaluation of mechanical properties of the studied objects and directly affect operational states of mechanical systems, including those installed in minesweepers, thus determining their reliability.

Continuous-Discrete Boundary Problems in the Concepts of the Construction of Foundry Rotary-Conveyor Lines

The problem of mathematical construction for the process of the control of the metal casting crystallization and cooling in a foundry mold is considered. The casting is surrounded by a layer of sand mixture, which is a porous dispersed medium that conducts heat, in terms of the concepts of the construction of foundry rotary-conveyor lines (RCL). The problem of developing an interval model for determining the speed of the conveyor line from the production of metal castings is studied. Herewith, continuous processes of the transport and technological movement of the processed materials, equipment, tools, energy carriers, and final production output are combined with inevitable stops of this continuity, which lead to discreteness, and a combination with a number of accompanying continuous, discrete or reciprocating processes. The adequacy of the model for the given technological parameters is justified. The mathematical description and agreement of the values of technological parameters for regulation and finding the optimal speed of the conveyor line at the interaction of its component rotational systems, as well as the mathematical models for program control and remote monitoring of technological modes in order to obtain the casting of the given quality are considered. The possibility of selecting the corrective parameters for the change of the conveyor line speed is shown. Tiek skatīta matemātiskās konstrukcijas problēma metāla liešanas kristalizācijas un dzesēšanas kontroles procesam liešanas veidnē. Lējumu ieskauj smilšu maisījuma slānis, kas ir poraini izkliedēts materiāls, kas vada siltumu. Lietojot lietuves rotācijas konveijeru līniju (RCL) koncepciju, tiek pētīta intervāla modeļa izveides problēma konveijera līnijas ātruma noteikšanai metāla lējumu ražošanai. Tajā pašā laikā nepārtraukti apstrādājamo materiālu, iekārtu, rīku, enerģijas nesēju un gala produkcijas transportēšanas un tehnoloģiskās kustības procesi tiek apvienoti ar šīs nepārtrauktības neizbēgamajiem apstāšanās gadījumiem, kas noved pie kombinācijas ar vairākiem nepārtrauktiem, diskrētiem vai pārvietošanās procesiem. Ir pierādīta modeļa piemērotība attiecīgajiem tehnoloģiskajiem parametriem. Tiek parādīta iespēja izvēlēties koriģējošos parametrus konveijera līnijas ātruma maiņai.