Catalyst-free growth of pyramidal zinc sulfide nanostructure arrays on single walled carbon nanotubes

Uniform and ordered pyramidal zinc sulfide (ZnS) nanostructure arrays have been fabricated on the single walled carbon nanotube (SWNT) films by chemical vapor deposition without using any metal catalyst. Each ZnS pyramid has a 100 nm-sized base, a uniform length of 600 nm, and a sharp tip of 10 nm. The control of interspatial distance between ZnS nanostructures was achieved by creation of selective growth on the SWNTs in voids with the assistance of a close-packed silica particle monolayer as a template. Furthermore, this kind of morphology control of nanostructure arrays can play an important role for potential applications, such as high efficiency of field emission because of the strong correlation between shapes and functionalities of nanostructures.     

非平稳强噪条件下的视频相位放大技术研究

针对视频信号在非平稳和强噪声情况下,视频放大技术难以提取目标信号且会将频带内噪声同时放大的缺点,提出了一种基于参数化时频分析及主成分分析的滤波方法。将相变信号降维后,对降维信号做时频分析,提取其中的非平稳信号。不仅重构的信号具有良好的时频特性,且算法运算量也大大降低。实验结果表明,此方法在非平稳强噪信号提取方面具有明显优势。     

Exposure Fusion: A Simple and Practical Alternative to High Dynamic Range Photography

We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to High dynamic range (HDR) first. Skipping the physically based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators.     

How influential is the role of oligotrophication on the integrity of fish assemblages in the littoral zone?

Food web theory predicts that one of the consequences of oligotrophication is the decline in fisheries following the establishment of nutrient-deficient conditions and low biogenic production. However, emerging evidence suggests that more complex trophic interactions, induced by plankton composition, dietary diversification, temporal and spatial heterogeneity, variations in fish age and size structure can lead to ecosystem responses that deviate from theoretical predictions; especially in the shallow littoral zone. In this study, two end-to-end modelling strategies are used to characterize potential food web structural shifts and overall ecosystem productivity in response to oligotrophication. Our modelling strategy draws upon empirical and theoretical evidence from the Bay of Quinte, a semi-enclosed embayment in northeastern Lake Ontario that has been subjected to phosphorus (P) abatement strategies in the 1970s. We first show that the role of food abundance has been a primary factor shaping fish production, but the fish community gradually responded to the reduced availability of pelagic staples of their diet by displaying greater reliance upon alternative sources, including benthic and other autochthonous (or even allochthonous) food items. Our analysis further suggests that degree of diet overlap between competing trophic guilds can significantly modulate realized biomass levels. The composition of the autotrophic community is another major confounding factor that can induce significant variations from the predicted food web productivity patterns in response to oligotrophication. Overall, our analysis suggests that the proposed reduction of the ambient total phosphorus levels may not necessarily trigger a significant decline in fish biomass in the Bay of Quinte.