Optimal Design of Maxwell-Viscous Coulomb Air Damper With a Modified Fixed Point Theory

Air damper dynamic vibration absorber (DVA) is modeled using Maxwell transformed element and coulomb element. This damper serves to minimize vibration at resonant and operation of constant speed machine. Its stiffness and damping factor are transformed from Maxwell to Voigt arrangement. Meanwhile, viscous equivalent Coulomb damping is expressed by absolute relative motion. System transmissibility contours are plotted by min–max approach. Its optimal parameters are determined using this approach. Contour operation minimization is obtained from minimum system transmissibility. Moreover, exact solution of fixed points and optimal natural frequency ratio are obtained by a modified fixed point theory. Optimal design curve is derived by Coulomb damping derivative and maximum condition. Operational vibration level is minimized by 7% at the operation minimization using minimum condition. On the experimental side, test platform of the air damper is constructed using linear slide block system. Computational model of the air damper is established by its physical details and experimental data. Linear relationship is obtained between viscous and Coulomb damping angles. Modified fixed points are validated by frequency response function resonant peaks. Experimental vibration level is minimized by 5%, which being close to the minimization result. The model is validated within 5% accuracy by its optimal experimental curve.

Controlled Hydrodynamic Cavitation: A Review of Recent Advances and Perspectives for Greener Processing

The 20th century has witnessed a remarkable enhancement in the demand for varieties of consumer products, ranging from food, pharmaceutical, cosmetics, to other industries. To enhance the quality of the product and to reduce the production cost, industries are gradually inclined towards greener processing technologies. Cavitation-based technologies are gaining interest among processing technologies due to their cost effectiveness in operation, minimization of toxic solvent usage, and ability to obtain superior processed products compared to conventional methods. Also, following the recent advancements, cavitation technology with large-scale processing applicability is only denoted to the hydrodynamic cavitation (HC)-based method. This review includes a general overview of hydrodynamic cavitation-based processing technologies and a detailed discussion regarding the process effectiveness. HC has demonstrated its usefulness in food processing, extraction of valuable products, biofuel synthesis, emulsification, and waste remediation, including broad-spectrum contaminants such as pharmaceuticals, bacteria, dyes, and organic pollutants of concern. Following the requirement of a specific process, HC has been implemented either alone or in combination with other process-intensifying steps, for example, catalyst, surfactant, ultraviolet (UV), hydrogen peroxide (H2O2), and ozone (O3), for better performance. The reactor set-up of HC includes orifice, slit venturi, rotor-stator, and sonolator type constrictions that initiate and control the formation of bubbles. Moreover, the future directions have also been pointed out with careful consideration of specific drawbacks.

On Optimizing a Class of Multi-Dimensional Loops with Reduction for Parallel Execution

This paper addresses the compile-time optimization of a form of nested-loop computation that is motivated by a computational physics application. The computations involve multi-dimensional surface and volume integrals where the integrand is a product of a number of array terms. Besides the issue of optimal distribution of the arrays among the processors, there is also scope for reordering of the operations using the commutativity and associativity properties of addition and multiplication, and the application of the distributive law to significantly reduce the number of operations executed. A formalization of the operation minimization problem and proof of its NP-completeness is provided. A pruning search strategy for determination of an optimal form is developed. An analysis of the communication requirements and a polynomial-time algorithm for determination of optimal distribution of the arrays are also provided.