chenyao07

To protect fragile paintings and calligraphy, Taiwan's National Palace Museum (NPM) has policies controlling the frequency and duration of their exposure. So, visitors might not see the works they planned to see. To address this problem, the NPM installed an interactive tabletop for viewing the works. This tabletop, the first to feature multiresolution and gigapixel photography technology, displays extremely high-quality images revealing brushwork-level detail. A user study at the NPM examined the tabletop's performance and collected visitor feedback.

The amount of distributed energy resources (DERs) has increased constantly worldwide. The power ratings of DERs have become considerably high, as required by the new grid code requirement. To follow the grid code and optimize the function of grid-connected inverters based on DERs, a phase-locked loop (PLL) is essential for detecting the grid phase angle accurately when the grid voltage is polluted by harmonics and imbalance. This paper proposes a novel low-pass notch filter PLL (LPN-PLL) control strategy to synchronize with the true phase angle of the grid instead of using a conventional synchronous reference frame PLL (SRF-PLL), which requires a $d{-}q$-axis transformation of three-phase voltage and a proportional–integral controller. The proposed LPN-PLL is an upgraded version of the PLL method using the fast Fourier transform concept (FFT-PLL) which is robust to the harmonics and imbalance of the grid voltage. The proposed PLL algorithm was compared with conventional SRF-PLL and FFT-PLL and was implemented digitally using a digital signal processor TMS320F28335. A 10-kW three-phase grid-connected inverter was set, and a verification experiment was performed, showing the high performance and robustness of the proposal under low-voltage ride-through operation.

SIAM Journal on Computing, Volume 42, Issue 4, Page 1720-1736, January 2013.
Highly connected and yet sparse graphs (such as expanders or graphs of high treewidth) are fundamental, widely applicable, and extensively studied combinatorial objects. We initiate the study of such highly connected graphs that are, in addition, geometric spanners. We define a property of spanners called robustness. Informally, when one removes a few vertices from a robust spanner, this harms only a small number of other vertices. We show that robust spanners must have a superlinear number of edges, even in one dimension. On the positive side, we give constructions, for any dimension, of robust spanners with a near-linear number of edges.

SIAM Journal on Matrix Analysis and Applications, Volume 34, Issue 3, Page 1174-1188, January 2013.
We develop a new approach for characterizing $k$-primitive matrix families. Such families generalize the notion of a primitive matrix. They have been intensively studied in the recent literature due to applications to Markov chains, linear dynamical systems, and graph theory. We prove, under some mild assumptions, that a set of $k$ nonnegative matrices is either $k$-primitive or there exists a nontrivial partition of the set of basis vectors, on which these matrices act as commuting permutations. This gives a convenient classification of $k$-primitive families and a polynomial-time algorithm to recognize them. This also extends some results of Perron--Frobenius theory to nonnegative matrix families.

SIAM Review, Volume 55, Issue 3, Page 547-566, January 2013.
This article offers an accessible but rigorous and essentially self-contained account of some of the central ideas in compressed sensing, aimed at nonspecialists and undergraduates who have had linear algebra and some probability. The basic premise is first illustrated by considering the problem of detecting a few defective items in a large set. We then build up the mathematical framework of compressed sensing to show how combining efficient sampling methods with elementary ideas from linear algebra and a bit of approximation theory, optimization, and probability allows the estimation of unknown quantities with far less sampling of data than traditional methods.