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.

Use of Hammerstein Models in Identification of Nonlinear Systems

Abstract: The utility of the Hammerstein model, which is composed of a static nonlinear element in series with a linear dynamic part, was investigated to represent the dynamics of nonlinear chemical processes. Different methods to identify the parameters of Hammerstein models were tested. The methods were applied to the identification of simulated distillation columns and to an experimental heat exchanger process. The results show that the dynamics of such processes can be better represented by Hammerstein-type models than by linear models.

Oxidation of glycerol using supported Pt, Pd and Au catalysts

Abstract: The oxidation of aqueous solutions of glycerol is described and discussed for Pd, Pt and Au nanoparticles supported on graphite and activated carbon. The oxidation in a batch reactor at 60 °C and 1 bar pressure using air as oxidant was initially investigated. Under these conditions, supported Pd and Pt catalysts give some selectivity to glyceric acid, but the main reaction products are considered to be non-desired C1 by-products, e.g. CO2, HCHO and HCOOH. In addition, under these conditions, supported Au catalysts were totally inactive. Using an autoclave with pure oxygen at 3 bar pressure gave a significant improvement in reactivity and, for Pt and Au catalysts, the formation of C1 by-products was eliminated when NaOH was added. In particular, it was noted that, in the absence of NaOH, the Au/C catalyst was inactive. For 1 wt.% Au/graphite or activated carbon, 100% selectivity to glyceric acid at high conversion was readily achieved. The role of the base is discussed and it is proposed that the base aids the initial dehydrogenation via H-abstraction of one of the primary OH groups of glycerol and, in this way, the rate limiting step in the oxidation process is overcome.

Linking Routines to Operations Capabilities: A New Perspective

Abstract: A typical approach to studying capabilities in the operations management literature is to assess the intended or realized competitive operational performance and their contribution to business and organizational objectives. While it is crucial to identify the operational performance that helps create competitive advantage, it is equally important to understand the means for delivering the needed performance at the operational level. Drawing on the resource-based view (RBV), we argue that routines are a critical source of operations capabilities and subsequently investigate operations capabilities by means of their underlying routines. Because a common problem to studying capabilities is the ambiguous and confusing definitions, we conduct an extensive literature review to address the semantic confusion among various definitions of capabilities and delineate it from other related terms. We identify improvement and innovation as two critical plant level capabilities, each consisting of a bundle of interrelated yet distinct routines. We then empirically measure the two capabilities as second-order latent variables and estimate their effects on a set of operational performance measures. The results suggest that routines form internally consistent bundles which are significantly related to operational performance. This supports our notion of “capabilities as routine bundles” that are difficult to imitate and thus a source of competitive advantage.

A double‐hurdle model of cigarette consumption

Abstract: This paper shows the importance of the double-hurdle approach for modelling individuals' cigarette consumption, using data from the UK General Household Survey, and argues that participation and consumption should be treated as separate individual choices. The likelihood function for the full double-hurdle is derived, and it is shown how restrictions on the stochastic specification of the model and auxillary information, which identifies ex-smokers, allow it to be decomposed. The empirical results highlight the value of the sample separation information and the need to model starting and quitting as separate decisions.