28 research outputs found
Anatomical description of Pisidium johnsoni EA Smith, 1882 (Bivalvia : Sphaeriidae) from Madagascar
Volume: 45Start Page: 358End Page: 36
Synthesis of controllers for electromechanical tracking systems
The article presents an algorithm for the synthesis of regulators for servomechanisms, in which the control object is linear. The algorithm is focused on electromechanical systems, the main element of which is a controlled electric drive. The synthesis algorithm is based on the use of the L–Markov moment problem. The advantage of the proposed algorithm with respect to the others is that the regulators synthesized on its basis ensure the minimization of energy for the objects control. The essence of the proposed algorithm of synthesis is that the control, according to the provisions underlying the L – moment problem, can be determined not only through the system of moment functions, but also through the moments. The latter depends both on the time interval during which the object is transferred from the initial state to the final state, but also on the state of the object itself. To solve the problem of controller design for servo systems, the following is proposed: 1. Explicitly express management through moments. 2. Perform «unfreezing» the initial and final states of the object. When «unfreezing» the initial state of the object is considered to be the current phase, and the final state is determined by the monitored signal. The time interval during which the object is transferred from one state to another is set arbitrarily in the general case. However, the longer this interval, the smaller the control rate, but, respectively, the greater the tracking error
Moitessier\u27s pea clam Pisidium moitessierianum (Bivalvia, Sphaeriidae): A cryptogenic mollusc in the Great Lakes
Pisidium moitessierianum Paladilhe, 1866, a small pea clam native to Europe, was identified for the first time from the lower Great Lakes basin based on an examination of historical collections of Pisidium performed by V. Sterki in 1894 and 1903 and new material collected during 1997 and 1998. During recent surveys, P. moitessierianum individuals were found in the St. Clair River delta, Lake St. Clair and western Lake Erie, but were not detected in the Detroit River or western Lake Ontario. Pisidium moitessierianum was collected on sand, silty sand and mud substrata from water depths ranging between 0.6 and 5.4 m. Populations occurred at an average density of 51 ind. m-2 and included juveniles and adults. All individuals were less than 2.0 mm in length. We examined the structure of the umbos and hinge, surface sculpture and shape of the shell, and the anatomy of gills, mantle and nephridia in populations from the lower Great Lakes and Ukrainian inland basins (Dnieper River and Lake Beloye). The results indicated that the Great Lakes\u27 pea clams match European specimens of P. moitessierianum in these conchological and anatomical characteristics. As with other nonindigenous sphaeriids in the Great Lakes, P. moitessierianum was likely introduced through shipping activities into the Great Lakes, possibly as early as the 1890s
SYNTHESIS OF OPTIMAL CONTROLS FOR NONLINEAR OBJECTS BY THE CRITERION OF MAXIMUM SPEED
The article presents an algorithm for synthesizing optimal program controls for nonlinear control-affine objects by the criterion of maximum speedy. The mathematical apparatus used is the linearization of Newton-Kantorovich and the apparatus of matrix operators. The structure of the algorithm includes the following steps at the first stage, the linearization of the nonlinear mathematical model of the object is performed by the Newton-Kantorovich method; at the second stage, we carry out the reduction of the synthesis problem by the criterion of minimum time in the presence of constraints on the control energy to the synthesis problem by the energy minimum criterion for finding the (optimal) minimum value of the sought time; at the third stage we perform parametrization of the mathematical model of the control object and a new quality criterion using the apparatus of matrix operators with the subsequent construction of the optimal control. The fourth final stage consists in realizing the iterative process prescribed by the Newton-Kantorovich method-there is an optimal (minimal) time value. The synthesis algorithm is illustrated by an example