中国科学院机构知识库网格系统: 检索

Acceleration of Weak Galerkin Methods for the Laplacian Eigenvalue Problem 期刊论文 OAI收割
JOURNAL OF SCIENTIFIC COMPUTING, 2019, 卷号: 79, 期号: 2, 页码: 914-934
作者: Zhai, Qilong; Xie, Hehu; Zhang, Ran; Zhang, Zhimin

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收藏 | 浏览/下载：37/0 | 提交时间：2020/01/10

Weak Galerkin finite element method Eigenvalue problem Two-grid method Two-space method Lower bound

食用蔬菜能吸收和积累微塑料 期刊论文 OAI收割
科学通报, 2019, 卷号: 64, 期号: 9, 页码: 928-934
作者: 李连祯; 周倩; 尹娜; 涂晨; 骆永明

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收藏 | 浏览/下载：142/0 | 提交时间：2020/06/17

微塑料生菜聚苯乙烯微球吸收积累健康风险 microplastics lettuce polystyrene microbeads uptake accumulation human health risk Microplastic (MP, 100 nm-5 mm) may present an attributable risk to ecosystem and human health, and its pollution has become a global environmental concern. Despite a wealth of information on the accumulation of MPs in aquatic species, there is no information on the uptake and accumulation of MPs by higher plants. Terrestrial edible plants are directly exposed to MPs when agricultural soil was applied with organic manure, sewage sludge as fertilizer or plastic mulching. In this paper, the uptake of two sizes of polystyrene (PS) microbeads (0.2 and 1.0 mum) and then their distribution and migration in an edible plant lettuce were firstly investigated based on laboratory experiments. We used fluorescent markers to track PS microbeads in plant tissues and found fluorescence to be a sensitive and reliable detection method. Sections from untreated control lettuce showed no autofluorescence. When roots were treated with fluorescently labeled PS microbeads, the microbeads could be identified by its fluorescence. Our main study investigated the uptake of 0.2 mum beads, as few luminescence signals were observed in lettuce roots for 1.0 mum beads in our experiment. We observed that 0.2 mum fluorescent microbeads were extracellularly trapped in the root cap mucilage (which is a highly hydrated polysaccharide) and a dark green tip (which was typical of lettuce roots exposed to label PS beads) was usually visible to the naked eye. Confocal images revealed that the PS luminescence signals were mainly located in the vascular system and on the cell walls of the cortex tissue of the roots, indicated that the beads passed through the intercellular space via the apoplastic transport system. Once inside the central cylinder, the 0.2 mum PS beads were transferred from the roots to the stems and leaves via the vascular system following the transpiration stream. We also observed that the PS beads adhered to one another and self-assembled systematically into grape-like and (chain) string-like clusters in the intercellular space of the root and stem vascular tissue of lettuce plant. In contrast to the root and stem, PS beads were dispersed in the leaf tissue. Here, for the first time we provide evidence of the adherence, uptake, accumulation, and translocation of submicrometer MPs within an edible plant. Our findings highlight the previously underappreciated human exposure pathway to MPs through the consumption of contaminated crops and emphasize the need for new management strategies to control the release of MPs waste products into the terrestrial environment. Ultimately, the potential impacts of low range sized MPs on food safety of crop plants and human health need to be urgently considered.

Measuring spatial accessibility to ecological recreation spaces in the Pearl River delta region: an improved two-step floating catchment area method 期刊论文 OAI收割
JOURNAL OF SPATIAL SCIENCE, 2018, 卷号: 63, 期号: 2, 页码: 279-295
作者: Wang, Fuyuan; Wang, Kaiyong

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收藏 | 浏览/下载：15/0 | 提交时间：2019/05/23

Pearl River Delta Region mega-city region ecological recreation space accessibility two-step floating catchment area method

Measuring spatial accessibility to ecological recreation spaces in the Pearl River delta region: an improved two-step floating catchment area method 期刊论文 OAI收割
JOURNAL OF SPATIAL SCIENCE, 2018, 卷号: 63, 期号: 2, 页码: 279-295
作者: Wang, Fuyuan; Wang, Kaiyong

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收藏 | 浏览/下载：29/0 | 提交时间：2019/05/23

Pearl River Delta Region mega-city region ecological recreation space accessibility two-step floating catchment area method

Measuring spatial accessibility to ecological recreation spaces in the Pearl River delta region: an improved two-step floating catchment area method 期刊论文 OAI收割
JOURNAL OF SPATIAL SCIENCE, 2018, 卷号: 63, 期号: 2, 页码: 279-295
作者: Wang, Fuyuan; Wang, Kaiyong

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收藏 | 浏览/下载：11/0 | 提交时间：2019/05/23

Pearl River Delta Region mega-city region ecological recreation space accessibility two-step floating catchment area method

A line mapping based automatic registration algorithm of infrared and visible images 会议论文 OAI收割
5th International Symposium on Photoelectronic Detection and Imaging (ISPDI) - Infrared Imaging and Applications, Beijing, June 25-27, 2013
作者: Ai R(艾锐); Shi ZL(史泽林); Xu DJ(徐德江); Zhang CS(张程硕)

收藏 | 浏览/下载：35/0 | 提交时间：2013/12/26

There exist complex gray mapping relationships among infrared and visible images because of the different imaging mechanisms. The difficulty of infrared and visible image registration is to find a reasonable similarity definition. In this paper, we develop a novel image similarity called implicit linesegment similarity(ILS) and a registration algorithm of infrared and visible images based on ILS. Essentially, the algorithm achieves image registration by aligning the corresponding line segment features in two images. First, we extract line segment features and record their coordinate positions in one of the images, and map these line segments into the second image based on the geometric transformation model. Then we iteratively maximize the degree of similarity between the line segment features and correspondence regions in the second image to obtain the model parameters. The advantage of doing this is no need directly measuring the gray similarity between the two images. We adopt a multi-resolution analysis method to calculate the model parameters from coarse to fine on Gaussian scale space. The geometric transformation parameters are finally obtained by the improved Powell algorithm. Comparative experiments demonstrate that the proposed algorithm can effectively achieve the automatic registration for infrared and visible images, and under considerable accuracy it makes a more significant improvement on computational efficiency and anti-noise ability than previously proposed algorithms.

Communication synchronization in wireless optical link (EI CONFERENCE) 会议论文 OAI收割
2012 International Conference on Control Engineering and Communication Technology, ICCECT 2012, December 7, 2012 - December 9, 2012, Shenyang, Liaoning, China
作者: Guo J.; Guo J.; Wang H.; Wang H.; Wang H.

收藏 | 浏览/下载：30/0 | 提交时间：2013/03/25

An FPGA based transceiving synchronization method is demonstrated for Free Space Optical (FSO) communication system which is discussed separately as the transmitting protocol and the receiving protocol. During the discussion of these two parts the co-operation of them is also discussed. The transmitting protocol interfaces the outer input data with a parallel port buffers the input data encodes the input data stream serializes the parallel data and outputs the serialized data. It also has an output management unit to manage the activity of each part of the transmitting protocol. The receiving protocol filters and synchronizes the input serial data stream parallels the serial data stream decodes the input data checks received error handles transmission exception and interfaces the outer receiver with a parallel port. The entire transceiving protocol could be programmed into a single FPGA chip to improve system integrity and reduce the system cost. The presented protocol could be taken as "protocol transparent" for outer interfaces meaning that when interfacing the presented system to an outer system users don't have to consider what protocol the outer system transceiving data stream is under for example the TCP/IP protocol or anything else in the case that its I/O interface is a parallel port. Simulation and final experiment prove that the protocol presented is a working solution at a certain bit rate scale. 2012 IEEE.

The method of the system error modification of photoelectric theodolite of T type (EI CONFERENCE) 会议论文 OAI收割
2012 International Conference on Optoelectronics and Microelectronics, ICOM 2012, August 23, 2012 - August 25, 2012, Changchun, China
作者: Zhao L.; Zhang Y.

收藏 | 浏览/下载：18/0 | 提交时间：2013/03/25

The system error of photoelectric theodolite includes Visual axis error This paper ratiocinates the formula of Azimuth orientation error horizontal axis error elevation zero error and Visual axis error of Photoelectric theodolite of T type by triangle relation in space. Photoelectric theodolite of U type with main visual axis and auxiliary visual axis shoots images and inverse images of marks to obtain system error data. Error is less than 0.4 second by comparing error data of auxiliary visual axis with error data of main visual axis and the precision of two methods is identical. It has been validated that the method of error measurement of photoelectric theodolite of T type is right. 2012 IEEE. vertical axis error Azimuth orientation error elevation zero error

Study on ultra-light secondary baffle for coaxial two-mirror telescope (EI CONFERENCE) 会议论文 OAI收割
2012 9th IEEE International Conference on Mechatronics and Automation, ICMA 2012, August 5, 2012 - August 8, 2012, Chengdu, China
作者: Zhang L.

收藏 | 浏览/下载：60/0 | 提交时间：2013/03/25

The coaxial two-mirror telescope consists of two mirrors facing each other. Classical two-mirror arrangements are Gregorian and Cassegrain. These systems are usually applied to space telescopes and often have optical baffles to prevent stray light from entering the focal plane. The optical baffles consist of concentric rings suspended between the secondary and the primary mirror. The secondary baffle for a large two-mirror optical system is designed and analyzed in this paper. According to mission of a telescope the structure should have high stiffness and high reliability and light weight. Compared with invar aluminum alloy and titanium alloy carbon fiber composite is currently the best material in terms of weight-to-strength ratio. It also has advantages of high temperature tolerance and low thermal expansion. So carbon fiber composite is chosen as material to meet requirements of the coaxial telescope. In this paper optimization method based on finite element analysis (FEA) is used for design the secondary baffle. Minimum weight of the baffle is chosen as an objective function. Thicknesses of former tube and vanes are chosen as variables. Analysis results show that the designed secondary baffle has maximum diameter of 180mm total length of 120mm and weighs 142g. And its fundamental frequency reaches 651Hz. Therefore the baffle has many advantages such as ultra-light weight high stiffness and dimensional stability etc. The optimization method and the baffle design can be helpful to other coaxial telescopes such as Cassegrain Gregorian and their subdivisions. 2012 IEEE.

An accuracy requirement analysis for LED brightness and color correction system (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Transportation, Mechanical, and Electrical Engineering, TMEE 2011, December 16, 2011 - December 18, 2011, Changchun, China
作者: Wang R.

收藏 | 浏览/下载：62/0 | 提交时间：2013/03/25

Brightness and color correction system is working for the color uniform problem of LED display. The correction system can improve LED display's quality greatly. The accuracy of the LED system must consider the accuracy requirements of the color correction system. This paper analyze the accuracy requirements from two aspects. One is that the accuracy requirements should consider the chromatic tolerance for the human eyes the other one is that the accuracy requirements should be associated with the precision of measuring equipment. This paper discuss the accuracy requirement with the CIE1976LUV as a color space to meet the chromatic tolerance of the human eyes and also give an explanation on how the accuracy of the measuring equipment affect the the correction system. Then this paper give a method to ensure the accuracy requirement for the correction system of a LED display. 2011 IEEE.