Lehigh University

About: Lehigh University is a education organization based out in Bethlehem, Pennsylvania, United States. It is known for research contribution in the topics: Catalysis & Fracture mechanics. The organization has 12684 authors who have published 26550 publications receiving 770061 citations.

The relationship of learning and memory with organizational performance: The moderating role of turbulence

Abstract: Extensive research has documented how firms’ learning orientation and memory are related to organizational performance. The objective of this study is to examine the moderating role of turbulence on the relationships between firms’ learning orientation and memory and their organizational performance and innovativeness. The study also provides insight into the differential relationships of firms’ learning orientation and memory to their performance and innovativeness. Using survey data collected from 200 supply management professionals, the results suggest that the extent to which learning and memory are associated with organizational performance is contingent on the level of environmental turbulence. Specifically, under low environmental turbulence, learning orientation and organizational memory appear to be related to performance and innovativeness; however, under high environmental turbulence, only learning orientation is a useful predictor.

Seismic analysis of concentrically braced frame systems with self-centering friction damping braces

Abstract: This paper presents a special type of bracing element termed self-centering friction damping brace (SFDB) for use in seismic-resistant concentrically braced frame (CBF) systems. The SFDB is a passive energy dissipation device with its core recentering component made of stranded superelastic Nitinol wires while enhanced energy dissipation mechanism of the SFDB is achieved through friction. Compared with conventional braces for steel frame buildings, SFDB has a few desirable performance characteristics such as minimized residual drifts of the CBF system and its ability to withstand several design level earthquakes without the need for replacement. The mechanical configuration of the SFDB is first described. A comparative study of SFDB frame and buckling restrained braced (BRB) frame was carried out, which is based on nonlinear dynamic analysis of two prototype CBF buildings — a three- and a six-story steel frame. Two suites of earthquake ground motions, which represent the frequent and design basis earthquakes for Los Angeles, were considered in the nonlinear time-history analysis. The results of the nonlinear time-history and pushover analysis show that the SFDB frame can achieve a seismic response level comparable to that of the BRB frame while having significantly reduced residual drifts. The SFDB thus has a potential to establish a new type of CBF system with self-centering capability.

A microreactor for hydrogen production in micro fuel cell applications

Abstract: A silicon-chip based microreactor has been successfully fabricated and tested for carrying out the reaction of methanol reforming for microscale hydrogen production. The developed microreactor in combination with a micro fuel cell is proposed as an alternative to conventional portable sources of electricity such as batteries due to its ability to provide an uninterrupted supply of electricity as long as a supply of methanol and water can be provided. The microreformer-fuel cell combination has the advantage of not requiring the tedious recharging cycles needed by conventional rechargeable lithium-ion batteries. It also offers significantly higher energy storage densities, which translates into less frequent "recharging" through the refilling of methanol fuel. The microreactor consists of a network of catalyst-packed parallel microchannels of depths ranging from 200 to 400 /spl mu/m with a catalyst particle filter near the outlet fabricated using photolithography and deep-reactive ion etching (DRIE) on a silicon substrate. Issues related to microchannel and filter capping, on-chip heating and temperature sensing, introduction and trapping of catalyst particles in the microchannels, flow distribution, microfluidic interfacing, and thermal insulation have been addressed. Experimental runs have demonstrated a methanol to hydrogen molar conversion of at least 85% to 90% at flow rates enough to supply hydrogen to an 8- to 10-W fuel cell.

Scaling laws for the thrust production of flexible pitching panels

Abstract: We present experimental results on the role of flexibility and aspect ratio in bio-inspired aquatic propulsion. Direct thrust and power measurements are used to determine the propulsive efficiency of flexible panels undergoing a leading-edge pitching motion. We find that flexible panels can give a significant amplification of thrust production of and propulsive efficiency of when compared to rigid panels. The data highlight that the global maximum in propulsive efficiency across a range of panel flexibilities is achieved when two conditions are simultaneously satisfied: (i) the oscillation of the panel yields a Strouhal number in the optimal range ( ) predicted by Triantafyllou, Triantafyllou & Grosenbaugh (J. Fluid Struct., vol. 7, 1993, pp. 205–224); and (ii) this frequency of motion is tuned to the structural resonant frequency of the panel. In addition, new scaling laws for the thrust production and power input to the fluid are derived for the rigid and flexible panels. It is found that the dominant forces are the characteristic elastic force and the characteristic fluid force. In the flexible regime the data scale using the characteristic elastic force and in the rigid limit the data scale using the characteristic fluid force.

Interaction between a circular inclusion and an arbitrarily oriented crack

Abstract: The plane interaction problem for a circular elastic inclusion embedded in an elastic matrix which contains an arbitrarily oriented crack is considered. Using the existing solutions for the edge dislocations as Green's functions, first the general problem of a through crack in the form of an arbitrary smooth arc located in the matrix in the vicinity of the inclusion is formulated. The integral equations for the line crack are then obtained as a system of singular integral equations with simple Cauchy kernels. The singular behavior of the stresses around the crack tips is examined and the expressions for the stress-intensity factors representing the strength of the stress singularities are obtained in terms of the asymptotic values of the density functions of the integral equations. The problem is solved for various typical crack orientations and the corresponding stress-intensity factors are given.