Xin He

Bio: Xin He is an academic researcher from University of Pennsylvania. The author has contributed to research in topic(s): Planar graph & Parallel algorithm. The author has an hindex of 29, co-authored 139 publication(s) receiving 2773 citation(s). Previous affiliations of Xin He include China Aerodynamics Research and Development Center & Sun Yat-sen University.

Regular edge labeling of 4-connected plane graphs and its applications in graph drawing problems

Abstract: In this paper we extend the concept of the regular edge labeling for general plane graphs and for triconnected triangulated plane graphs to 4-connected triangulated plane graphs. We present two different linear time algorithms for constructing such a labeling. By using regular edge labeling, we present a new linear time algorithm for constructing rectangular dual of planar graphs. Our algorithm is simpler than previously known algorithms. The coordinates of the rectangular dual constructed by our algorithm are integers, while the one constructed by known algorithms are real numbers. Our second regular edge labeling algorithm is based on canonical ordering of 4-connected triangulated plane graphs. By using this technique, we present a new algorithm for constructing visibility representation of 4-connected planar graphs. Our algorithm reduces the size of the representation by a factor of 2 for such graphs.

Scalar aggregation in inconsistent databases

Abstract: We consider here scalar aggregation queries in databases that may violate a given set of functional dependencies We define consistent answers to such queries to be greatest-lowest/least-upper bounds on the value of the scalar function across all (minimal) repairs of the database We show how to compute such answers We provide a complete characterization of the computational complexity of this problem We also show how tractability can be improved in several special cases (one involves a novel application of Boyce-Codd Normal Form) and present a practical hybrid query evaluation method

Photocatalytic mechanism of TiO2–CeO2 films prepared by magnetron sputtering under UV and visible light

Abstract: TiO 2 –CeO 2 films were fabricated by rf reactive magnetron sputtering, and pure TiO 2 and CeO 2 films were also prepared for comparison The Raman spectra, TEM, XPS, UV–visible and PL spectra were used to characterize the film structure and composition It is found that the uniform TiO 2 –CeO 2 films consist of TiO 2 and CeO 2 phases connected by CeO 16 2TiO 2 phase The photocatalytic activity under UV and visible irradiation were evaluated by the degradation of methylene blue The result under UV illumination shows that the TiO 2 –CeO 2 films have better activity than pure TiO 2 films, furthermore, the TiO 2 –CeO 2 film is a kind of photocatalyst responded to the visible light The electron transferring between the TiO 2 and CeO 2 networks via Ti–O–Ce structure units plays a great role in the photocatalysis The visible light absorption by the CeO 16 2TiO 2 phase is the original cause of visible light responded photocatalysis The holes drifting from CeO 16 2TiO 2 to TiO 2 under inner electric field force can inject photoinduced holes into TiO 2 and endow the TiO 2 –CeO 2 composite films with photocatalysis

Compact Encodings of Planar Graphs via Canonical Orderings and Multiple Parentheses

Abstract: We consider the problem of coding planar graphs by binary strings. Depending on whether O(1)-time queries for adjacency and degree are supported, we present three sets of coding schemes which all take linear time for encoding and decoding. The encoding lengths are significantly shorter than the previously known results in each case.

On finding the rectangular duals of planar triangular graphs

Abstract: This paper presents a new linear-time algorithm for finding rectangular duals of planar triangular graphs. The algorithm is conceptually simpler than the previously known algorithm. The coordinates of the rectangular dual constructed by the new algorithm are integers and carry clear combinatorial meaning.

Fast approximate energy minimization via graph cuts

Abstract: In this paper we address the problem of minimizing a large class of energy functions that occur in early vision. The major restriction is that the energy function's smoothness term must only involve pairs of pixels. We propose two algorithms that use graph cuts to compute a local minimum even when very large moves are allowed. The first move we consider is an /spl alpha/-/spl beta/-swap: for a pair of labels /spl alpha/,/spl beta/, this move exchanges the labels between an arbitrary set of pixels labeled a and another arbitrary set labeled /spl beta/. Our first algorithm generates a labeling such that there is no swap move that decreases the energy. The second move we consider is an /spl alpha/-expansion: for a label a, this move assigns an arbitrary set of pixels the label /spl alpha/. Our second algorithm, which requires the smoothness term to be a metric, generates a labeling such that there is no expansion move that decreases the energy. Moreover, this solution is within a known factor of the global minimum. We experimentally demonstrate the effectiveness of our approach on image restoration, stereo and motion.

Chemical analysis of graphene oxide films after heat and chemical treatments by X-ray photoelectron and Micro-Raman spectroscopy

Abstract: Several nanometer-thick graphene oxide films deposited on silicon nitride-on silicon substrates were exposed to nine different heat treatments (three in Argon, three in Argon and Hydrogen, and three in ultra-high vacuum), and also a film was held at 70 °C while being exposed to a vapor from hydrazine monohydrate. The films were characterized with atomic force microscopy to obtain local thickness and variation in thickness over extended regions. X-ray photoelectron spectroscopy was used to measure significant reduction of the oxygen content of the films; heating in ultra-high vacuum was particularly effective. The overtone region of the Raman spectrum was used, for the first time, to provide a “fingerprint” of changing oxygen content.

A surface science perspective on TiO2 photocatalysis

Abstract: The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO2 photocatalysis has made significant contributions in the literature.

mTOR Signaling in Growth, Metabolism, and Disease

Abstract: The mechanistic target of rapamycin (mTOR) coordinates eukaryotic cell growth and metabolism with environmental inputs, including nutrients and growth factors. Extensive research over the past two decades has established a central role for mTOR in regulating many fundamental cell processes, from protein synthesis to autophagy, and deregulated mTOR signaling is implicated in the progression of cancer and diabetes, as well as the aging process. Here, we review recent advances in our understanding of mTOR function, regulation, and importance in mammalian physiology. We also highlight how the mTOR signaling network contributes to human disease and discuss the current and future prospects for therapeutically targeting mTOR in the clinic.