Ji Xu

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Generating laterally ordered, ultradense, macroscopic arrays of nanoscopic elements will revolutionize the microelectronic and storage industries. We used faceted surfaces of commercially available sapphire wafers to guide the self-assembly of block copolymer microdomains into oriented arrays with quasi-long-range crystalline order over arbitrarily large(More)
Wireless sensor networks promise an unprecedented opportunity to monitor physical environments via inexpensive wireless embedded devices. Given the sheer amount of sensed data, efficient classification of them becomes a critical task in many sensor network applications. The large scale and the stringent energy constraints of such networks however challenge(More)
Cross-lingual voice transformation is challenging when source language (L1) and target language (L2) are very different in corresponding phonetics and prosodies. We propose a frame mapping based HMM approach to this problem. The source speaker's speech data is first warped in frequency toward the target speaker by mapping corresponding formants of selected(More)
In the bulk, block copolymers (BCPs) self assemble into ordered morphologies, having spherical, cylindrical, lamellar, or bicon-tinuous gyroid microdomains, where the molecular weight of the BCP dictates the sizes of the microdomains formed. In thin films, controlling the orientation and lateral ordering of the micro-domains has enabled the use of these(More)
Expectation Maximization (EM) is among the most popular algorithms for estimating parameters of statistical models. However, EM, which is an iterative algorithm based on the maximum likelihood principle, is generally only guaranteed to find stationary points of the likelihood objective, and these points may be far from any maximizer. This article addresses(More)