Complex Design by Simple Robots: A Collective Embodied Intelligence Approach to Construction

Nature's builders – from termites to beavers – offer a model of collective intelligence that can inspire robotic construction. Kirstin Petersen , Assistant Professor in Electrical and Computer Engineering at Cornell University, Ithaca, New York, and Radhika Nagpal , Professor in Computer Science at the Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts, describe several recent projects in this field that they have been involved in, both separately and collaboratively.     

Applicability of Shape Memory Alloy Wire for an Active, Soft Orthotic

Current treatments for gait pathologies associated with neuromuscular disorders may employ a passive, rigid brace. While these provide certain benefits, they can also cause muscle atrophy. In this study, we examined NiTi shape memory alloy (SMA) wires that were annealed into springs to develop an active, soft orthotic (ASO) for the knee. Actively controlled SMA springs may provide variable assistances depending on factors such as when, during the gait cycle, the springs are activated; ongoing muscle activity level; and needs of the wearer. Unlike a passive brace, an active orthotic may provide individualized control, assisting the muscles so that they may be used more appropriately, and possibly leading to a re-education of the neuro-motor system and eventual independence from the orthotic system. A prototype was tested on a suspended, robotic leg to simulate the swing phase of a typical gait. The total deflection generated by the orthotic depended on the knee angle and the total number of actuators triggered, with a max deflection of 35°. While SMA wires have a high energy density, they require a significant amount of power. Furthermore, the loaded SMA spring response times were much longer than the natural frequency of an average gait for the power conditions tested. While the SMA wires are not appropriate for correction of gait pathologies as currently implemented, the ability to have a soft, actuated material could be appropriate for slower timescale applications.     

Effect of beam stiffness–column reinforcement on creep and shrinkage behaviour of R.C frames

Vertical deflections and load transfer among columns of R.C frames depend on the percentage of reinforcement in columns and stiffness of beams. No systematic studies are available in the literature on the effect of these parameters. Such systematic studies are reported in this paper. The beam stiffness is expressed in terms of a non‐dimensional parameter, designated as stiffness factor, which is the ratio of shear stiffness of beams to axial stiffness of columns. It is shown that depending on stiffness factor and column reinforcement, a column may receive the load from the adjacent columns or transfer the load to the adjacent columns, or may receive the load from one of the adjacent columns and at the same time transfer the load to the other adjacent column. Further, the effect of the creep and shrinkage on column axial forces can be of design significance in the lower and middle portions of buildings. The effect becomes greater with the increase in stiffness factor and difference in percentage reinforcement of the adjacent columns. Copyright © 2007 John Wiley & Sons, Ltd.     

The complete identity of the isotherm equations of dubinin and john for determination of the volume and degree of microporosity of carbon

Complete identity of adsorption isotherms of Dubinin and John is proved by showing that the slope D of Dubinin equation is equal to slope D₀ of Dubinin type equation derived from John's isotherm and also showing that the terms involved in D and D₀ are fundamentally the same. It is shown that the degree of microporosity is proportional to n the slope of John's isotherm. B the measure of microporosity in Dubinin equation is inversely proportional to n. The advantages of John's isotherm are also given.     

Liquid-liquid equilibria for toluene-heptane-N-methyl pyrrolidone and benzene-heptane solvents

The liquid-liquid equilibria for toluene-n-heptane-N-methyl pyrrolidone containing 10 and 20% water at 298 and 313 K, and of benzene-n-heptane with N-methyl pyrrolidone-ethylene glycol and γ-butyrolactone-ethylene glycol, which is a new solvent combination, have been determined at 303 K.     

Effect of creep and shrinkage in reinforced concrete frame–shear wall system with high beam stiffness

The behaviour of frames and frame–shear wall systems with regard to creep and shrinkage with high beam stiffness has been largely unexplored until recently since no procedure has been available. For low beam stiffness the most widely used procedure available in literature for determining creep and shrinkage effects in reinforced concrete building frames and frame–shear wall systems designated herein as approximate procedure, AP has been recommended for buildings having flexible slab systems and with a limited number of storeys. Recently an accurate procedure termed Consistent Procedure (CP) has been developed which is applicable to low as well as high beam stiffness and requires no restriction on number of storeys. In this paper, using CP, studies are reported for frame–shear wall systems with high beam stiffness. The effect of introduction of shear walls on load transfer among vertical members considering creep and shrinkage is studied. It is shown that the presence of shear wall alters significantly the load transfer among vertical members. It is also shown that whereas differential vertical deflections between adjacent vertical members are small owing to high stiffness of beams, the load transfer between them can be significant. Copyright © 2003 John Wiley & Sons, Ltd.     

A recursive least error squares algorithm for power system relayingand measurement applications

A recursive algorithm suitable for microprocessor-based power system relaying and measurement applications is described. The algorithm is designed using the least error squares (LES) curve fitting technique. The mathematical background for the nonrecursive least error squares algorithm is extended to form a recursive algorithm. A method for including decaying DC and harmonic frequencies in the algorithm is described. Sample studies are presented to demonstrate the performance of the developed algorithm. The recursive LES (RLES) algorithm is shown to be computationally efficient and does not require the time constant of decaying DC and statistical information concerning the signal. It is shown that a 12-RLES algorithm can be used for implementing transformer differential protection     

Determination of mesopore surface area in presence of micropores

A modified t-method known as $\text{t}\text{J}$ method, capable of finding mesopore surface area in absence or presence of micropores in which adsorption may be pressure dependent or pressure independent is described by the application of John's adsorption isotherm equation.