A min-max problem of optimal actuator placement for lifting
Summary The paper addresses the following problem: for a three-bar lifting linkage, find the locations of the two ends of the actuated link so as to minimize the maximum value of the force seen by the actuator over a specified range of arm angular positions. A simple analytical solution to this min-max problem is given, showing that the optimal locations are with the actuated link perpendicular either to the fixed link or to the lifting arm, when the arm is in a horizontal position. The method can be used to optimize the actuation of robots, doors, platforms, landing gears, etc., and allows to account for actuator length constraints. It can be extended also to Stewart's platform-type spatial manipulators.
Quality of motion and force transmission
Abstract Actual mechanism performance can differ markedly from the performance expected from a theoretically perfect model. A good quality design is one which not only theoretically solves the design problem but actually does so reliably when installed in its applications. This paper summarized work done by the author in developing merit functions which reflect motion and force transmission quality, and in combining these quality merit functions with primary design merit functions to form viable mechanisms design algorithms.
Convergence Anatomization of Aquaculture Production in Leading Fish-Producing Countries During the Period of 1997-2013
Growth and national importance of aquaculture production is empirically assessed as an important indicator of development. The present article aims to test whether the major aquaculture producing countries of the world are converging over time. The authors have applied the absolute and conditional beta convergence and sigma convergence approaches on the data of FAO for the period 1997-2013. The results show that there is an absolute beta convergence and sigma convergence among 25 major aquaculture producing countries; negative sign of coefficient of conditional beta convergence with per capita income is also noticed. It implies, the growth rates of aquaculture for developed nations are declining with rise in per capita income and backward fish-intensive countries are catching up with the giant producers like China and India. The cross-country variations are also going down which means that the countries' development gaps are getting narrowed by means of growth of aquaculture resources.