3D Printed Torsional Mechanism Demonstrating Fundamentals of Free Vibrations

Commercially available turn-key systems are expensive and require substantial lab space making it harder to accommodate many in vibrations laboratories. This study presents a low-cost, compact and portable torsional mechanism incorporating multiple rotating disks and a long thin rod supported vertically with bearings and fixed supports at the top and bottom ends to study modeling of systems using experimental data. The mechanism consisting of a rod, disks, bearing and disk supports, and a base, is built by 3D printing using thermoplastic PETG. The long, thin rod in this mechanism serves as a torsional spring. The equivalent stiffnesses of the 2 DOF system can be changed by adjusting the vertical position of the disks with respect to the ends, thereby shortening or lengthening the effective twist length of the thin rod. The overall dimensions of the mechanism are 6 inches in height, 5 inches in width and 2 inches in depth, and the expected cost including the experimental setup is around $30 if an Arduino is used for data acquisition and $170 if equipped with National Instruments (NI) external data acquisition card (DAQ). Learning objectives of the lab course utilizing the proposed mechanism are identified. The free response data is collected for single degree of freedom system using an external data acquisition card and potentiometer and unknown parameters of the system are determined by system identification. Mechanism unknown parameters are calculated using system identification and theoretical model is compared with the experimental data.

Entropy Production and Its Application to the Coupled Nonequilibrium Processes of ATP Synthesis

Starting from the universal concept of entropy production, a large number of new results are obtained and a wealth of novel thermodynamic, kinetic, and molecular mechanistic insights are provided into the coupling of oxidation and ATP synthesis in the vital process of oxidative phosphorylation (OX PHOS). The total dissipation, Φ , in OX PHOS with succinate as respiratory substrate is quantified from measurements, and the partitioning of Φ into the elementary components of ATP synthesis, leak, slip, and other losses is evaluated for the first time. The thermodynamic efficiency, η , of the coupled process is calculated from the data on Φ and shown to agree well with linear nonequilibrium thermodynamic calculations. Equations for the P/O ratio based on total oxygen consumed and extra oxygen consumed are derived from first principles and the source of basal (state 4) mitochondrial respiration is postulated from molecular mechanistic considerations based on Nath’s two-ion theory of energy coupling within the torsional mechanism of energy transduction and ATP synthesis. The degree of coupling, q , between oxidation and ATP synthesis is determined from the experimental data and the irreversible thermodynamics analysis. The optimality of biological free energy converters is explored in considerable detail based on (i) the standard biothermodynamic approach, and (ii) a new biothermokinetic approach developed in this work, and an effective solution that is shown to arise from consideration of the molecular aspects in Nath’s theory is formulated. New experimental data in state 4 with uncouplers and redox inhibitors of OX PHOS and on respiratory control in the physiological state 3 with ADP and uncouplers are presented. These experimental observations are shown to be incompatible with Mitchell’s chemiosmotic theory. A novel scheme of coupling based on Nath’s two-ion theory of energy coupling within the torsional mechanism is proposed and shown to explain the data and also pass the test of consistency with the thermodynamics, taking us beyond the chemiosmotic theory. It is concluded that, twenty years since its first proposal, Nath’s torsional mechanism of energy transduction and ATP synthesis is now well poised to catalyze the progress of experimental and theoretical research in this interdisciplinary field.

Analytical solutions of the torsional mechanism for a new hybrid fiber-reinforced polymer–aluminum twin-trackway space truss bridge

For emergency purposes, a lightweight space truss bridge was designed. The bridge is composed of twin triangular deck-truss beams incorporating new structural forms and advanced fiber-reinforced polymer profiles. As a new structure, the structural properties of its triangular deck-truss beam have been studied in detail; however, a design-oriented study facilitating the application of the entire twin-trackway bridge under pure torsion remains to be undertaken. The objective of this article is to analytically explore the torsional mechanism of the twin-trackway bridge, which is characterized by torsional angle and torsional stiffness. To verify the derivation procedures and formulae, the pure torsion test and numerical analysis are conducted on a full-scale specimen. The results indicate that the analytical solutions compare well with the experimental and numerical results. The torsional moment is primarily resisted by the vertical bending of twin triangular deck-truss beams. The simplified analytical model can be used with sufficient accuracy for the design of the bridge.

Compilation of Pavement Interface Bond Strength Devices for Bond Strength Quantification

Flexible pavement is a multilayered structure constructed in layers. In order to ensure proper bonding such that a pavement behaved monolithically, tack coat is often applied. The developed pavement interface bond strength is therefore paramount in governing the overall performance of pavement serviceability. The present work reviews the current state of pavement interface bond strength quantification mechanisms, and the devices developed based on the mechanism. Related accessible literatures are collected and analyzed to compile the characteristics of each bond testing devices and evaluated for the capabilities and test performance. The investigation reveals 3 testing mechanisms incorporating shearing (pushing), tensile (pulling) and torsioning (twisting). However, shearing test seems to be the most popular device adopted to investigate the bond strength between two interfaces in contact, utterly due to the simplicity of the test setup. For tensile mechanism, the developed devices are generally portable and are mostly used to examine the tack coat quality. Finally, the device with torsional mechanism is not so popular as compared to the aforementioned mechanism. Nonetheless, it is developing steadily with the continuous research.