Xiaohao Yang

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We report the structure of methylammonium lead(II) iodide perovskite in mesoporous TiO2, as used in high-performance solar cells. Pair distribution function analysis of X-ray scattering reveals a two component nanostructure: one component with medium range crystalline order (30 atom %) and another with only local structural coherence (70 atom %). The(More)
Discovery of new complex oxides that exhibit both magnetic and ferroelectric properties is of great interest for the design of functional magnetoelectrics, in which research is driven by the technologically exciting prospect of controlling charges by magnetic fields and spins by applied voltages, for sensors, 4-state logic, and spintronics. Motivated by the(More)
The atomic pair distribution function (PDF) analysis of X-ray powder diffraction data has been used to study the structure of small and ultra-small CdSe nanoparticles. A method is described that uses a wurtzite and zinc-blende mixed phase model to account for stacking faults in CdSe particles. The mixed-phase model successfully describes the structure of(More)
Luminescent semiconducting quantum dots (QDs) are central to emerging technologies that range from tissue imaging to solid-state lighting. However, existing samples are heterogeneous, which has prevented atomic-resolution determination of their structures and obscured the relationship between their atomic and electronic structures. Here we report the(More)
The key task in spoken language understanding research is the semantic tagging of sequences. Deep belief networks have recently shown great performance in word-labeling tasks while conditional random field has been a successful approach to model probabilities of sequences in a global fashion. In contrast to CRFs, DBNs are optimized based on a tag-by-tag(More)
The atomic structure of Ni-Pd nanoparticles has been studied using atomic pair distribution function (PDF) analysis of X-ray total scattering data and with transmission electron microscopy (TEM). Larger nanoparticles have PDFs corresponding to the bulk face-centered cubic packing. However, the smallest nanoparticles have PDFs that strongly resemble those(More)
An emerging theme of modern composites and devices is the coupling of nanostructural properties of materials with their targeted arrangement at the microscale. Of the imaging techniques developed that provide insight into such designer materials and devices, those based on diffraction are particularly useful. However, to date, these have been heavily(More)
Semantic slot filling is one of the most challenging problems in spoken language understanding (SLU) because of automatic speech recognition (ASR) errors. To improve the performance of slot filling, a successful approach is to use a statistical model that is trained on ASR one-best hypotheses. The state of the art models for slot filling rely on using(More)
One of the key components in spoken dialog systems is semantic slot-filling, a sequence tagging task. There are several state-of-the-art supervised approaches to model the slot-filling problem such as conditional random fields (CRF), support vector machine (SVM) and stochastic finite state transducers (SFST). A general way to improve their performance is to(More)