Airborne LiDAR for DEM generation: some critical issues

Airborne LiDAR is one of the most effective and reliable means of terrain data collection. Using LiDAR data for DEM generation is becoming a standard practice in spatial related areas. However, the effective processing of the raw LiDAR data and the generation of an efficient and high-quality DEM remain big challenges. This paper reviews the recent advances of airborne LiDAR systems and the use of LiDAR data for DEM generation, with special focus on LiDAR data filters, interpolation methods, DEM resolution, and LiDAR data reduction. Separating LiDAR points into ground and non-ground is the most critical and difficult step for DEM generation from LiDAR data. Commonly used and most recently developed LiDAR filtering methods are presented. Interpolation methods and choices of suitable interpolator and DEM resolution for LiDAR DEM generation are discussed in detail. In order to reduce the data redundancy and increase the efficiency in terms of storage and manipulation, LiDAR data reduction is required in the process of DEM generation. Feature specific elements such as breaklines contribute significantly to DEM quality. Therefore, data reduction should be conducted in such a way that critical elements are kept while less important elements are removed. Given the highdensity characteristic of LiDAR data, breaklines can be directly extracted from LiDAR data. Extraction of breaklines and integration of the breaklines into DEM generation are presented

Decomposition of Integral Self-Affine Multi-Tiles

In this paper, we propose a method to decompose an integral self-affine ${\mathbb Z}^n$-tiling set $K$ into measure disjoint pieces $K_j$ satisfying $K=\displaystyle\bigcup K_j$ in such a way that the collection of sets $K_j$ forms an integral self-affine collection associated with the matrix $B$ and this with a minimum number of pieces $K_j$. When used on a given measurable $\mathbb{Z}^n$-tiling set $K\subset\mathbb{R}^n$, this decomposition terminates after finitely many steps if and only if the set $K$ is an integral self-affine multi-tile. Furthermore, we show that the minimal decomposition we provide is unique.Comment: 15pages, 5figures, added references, typo correction

The role of education in regional innovation activities and economic growth: spatial evidence from China

This study examines one of the channels through which education may contribute to economic growth, specifically, innovation. Endogenous growth theory has long suggested that human capital lead to greater innovation and, through technology innovation and diffusion, contribute to economic growth. However, there is little evidence on the role of human capital in innovation. Using the Chinese provincial data from 1997 to 2006, we show that workers’ tertiary education is significantly and positively related to provincial innovative activities measured by invention patent applications per capita. This result does not vary when spatial dependence is allowed in the estimation. Thus, we find strong and robust evidence for the prediction of endogenous growth theory regarding the effect of human capital on innovation. However, we do not find the consistently significant effect of innovation on growth. This finding may, however, relate to the growth pattern in China.Education; Human Capital; Innovation; Paten; Economic Growth; Spatial Analysis

Spectrality of Self-Similar Tiles

We call a set $K \subset {\mathbb R}^s$ with positive Lebesgue measure a {\it spectral set} if $L^2(K)$ admits an exponential orthonormal basis. It was conjectured that $K$ is a spectral set if and only if $K$ is a tile (Fuglede's conjecture). Despite the conjecture was proved to be false on ${\mathbb R}^s$, $s\geq 3$ ([T], [KM2]), it still poses challenging questions with additional assumptions. In this paper, our additional assumption is self-similarity. We study the spectral properties for the class of self-similar tiles $K$ in ${\mathbb R}$ that has a product structure on the associated digit sets. We show that any strict product-form tiles and the associated modulo product-form tiles are spectral sets. As for the converse question, we give a pilot study for the self-similar set $K$ generated by arbitrary digit sets with four elements. We investigate the zeros of its Fourier transform due to the orthogonality, and verify Fuglede's conjecture for this special case.Comment: 22page

Issues Surrounding the Drafting of China\u27s Anti-Monopoly Law

The 1997 United States v. Microsoft Anti-Monopoly lawsuit has caught the attention of not only the world in general, but also the Chinese government and the Chinese people. Considering the existing variety of monopolistic practices in Chinese businesses, many scholars are expressing their views on the necessity of anti-monopoly legislation in China