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.

Structural determination of bulk and surface tungsten oxides with UV-vis diffuse reflectance spectroscopy and raman spectroscopy

Abstract: Combined UV−vis diffuse reflectance spectroscopy (DRS) and Raman spectroscopy were applied to examine the electronic and molecular structures, respectively, of well-defined W(VI) bulk mixed oxide reference compounds consisting of (i) isolated WO4 or WO6 monomers, (ii) dimeric O3W−O−WO3, (iii) polymeric chain of alternating WO4/WO6 units, and (iv) WO6-coordinated W9−W18 clusters. Raman spectroscopy was employed to confirm the identity and phase purity of the different tungsten oxide structures. UV−vis DRS provided the corresponding electronic edge energy (Eg) of the ligand-to-metal charge transfer (LMCT) transitions of the W(VI) cations. A correlation between the edge energy and the number of covalent bridging W−O−W bonds around the central W(VI) cation was found with Eg linearly decreasing with increasing number of bridging W−O−W bonds. However, a direct relationship between Eg and the domain size, NW, for finite WOx clusters does not exist. Subsequently, UV−vis and Raman spectroscopy information were app...

Optimized signaling for MIMO interference systems with feedback

Abstract: The system mutual information of a multiple-input multiple-output (MIMO) system with multiple users which mutually interfere is considered. Perfect channel state information is assumed to be known to both transmitters and receivers. Asymptotic performance analysis shows that the system mutual information changes behavior as the interference becomes sufficiently strong. In particular, beamforming is the optimum signaling for all users when the interference is large. We propose several numerical approaches to decide the covariance matrices of the transmitted signals and compare their performance in terms of the system mutual information. We model the system as a noncooperative game and perform iterative water-filling to find the Nash equilibrium distributively. A centralized global approach and a distributed iterative approach based on the gradient projection method are also proposed. Numerical results show that all proposed approaches give better performance than the standard signaling, which is optimum for the case without interference. Both the global and the iterative gradient projection methods are shown to outperform the Nash equilibrium significantly.

Supply chain integration in vendor-managed inventory

Abstract: This paper develops an analytical model that explores how important supply chain parameters affect the cost savings to be realized from collaborative initiatives such as vendor-managed inventory (VMI). Results from the model show that benefits, in the form of inventory cost reductions, may be generated from integration depending upon the ratio of the order costs of the supplier to the buyer and the ratio of the carrying charges of the supplier to the buyer. Results also show that these benefits are disproportionally distributed between buyers and suppliers.