城市化影响下北京植物多样性现状与保护对策研究

城市化是引起生物多样性降低的主要原因之一，因此，应特别注意城市区域和城市化过程中的生物多样性保护。北京近三十年来经历了最为持久的城市化过程，城市的迅速扩张，人口的快速增加和经济的蓬勃发展给北京的生态环境带了巨大的压力，也给生物多样性工作带来了巨大的挑战。为有效开展生物多样性保护工作，迫切需要开展北京生物多样性现状及保护对策的研究。北京市以前在生物多样性方面作过大量工作，但缺乏系统的整理。本文通过深入的现场调查和对已有文献资料的整理，对当前北京市维管植物多样性现状及问题作了分析，并提出相应对策，以期为北京生物多样性保护工作提供参考。主要内容如下： 1．北京市自然生态系统主要有森林生态系统、灌丛生态系统、草甸生态系统和湿地生态系统4种类型。在人类长期干扰下，各生态系统多为次生。目前森林生态系统面积逐步扩大，而草甸生态系统和湿地生态系统受人为活动破坏严重，呈现严重退化趋势。 2．整理关于北京物种新纪录的各种文献，结合野外调查，构建了北京维管植物多样性数据库。北京维管植物多样性比较丰富，已知维管植物有2276种，然而特有性不强，严格属于北京特有维管束植物仅有5种。境内共分布有25种国家重点保护植物，包括野大豆、紫椴、河北梨以及22种野生兰科植物。根据调查资料初步评估，确定40种植物在北京处于受威胁状态。 3．根据北京人口密度、城市人口比例以及建设土地比例，将北京市按城市化程度的高低划分为城区，近郊区、远郊区三个区域。物种丰富度以远郊区最高，城区次之，近郊区最低，而外来物种比例则以城区最高，远郊区最低。城区分布有北京市93%以上的外来种，是其物种丰富度较近郊区为高的原因之一。对北京市特有植物、受危植物、国家保护植物和北京市保护植物的分布的分析表明，远郊区分布有93%以上的上述植物，是北京市生物多样性的重点保护区域，而城区和近郊区也分别分布有近1/4和1/3，说明保护稀有濒危物种方面，城区和近郊区也不容忽视。 4．对北京市外来植物作了分析，认为北京有126种归化植物，其中47种为入侵植物。菊科、禾本科、大戟科和苋科在入侵植物中占优势，美洲为最大起源地，其次为欧洲。园艺苗木引种是入侵物种的主要侵入途径，导致海淀、丰台、西城、朝阳等城区分布有较多的入侵种。 5．对外来物种火炬树的地理分布格局和入侵潜力作了研究。火炬树在人为大力推广下已遍布各风景区，在公路两侧也常见分布并侵入农田，甚至出现在某些自然保护区。火炬树在贫瘠和肥沃生境下均具有较高的繁殖速度，在3年内靠克隆繁殖扩散距离已超过6米，并能行成郁闭度很高的单优群落，其物种丰富度、个体密度以及物种多样性指数均显著低于本地荆条灌丛群落。由于其强阳性生长特性，使其不能侵入森林，然而却能对灌丛生态系统构成危害，其克隆繁殖的特点也使其难以根除，在北京地区具有潜在的入侵能力，不适合继续作为绿化北京的主要树种。 6．北京市生物多样性面临的主要问题包括城区本土生物多样性低、生态系统退化、湿地萎缩、污染严重、强度的旅游开发和外来物种入侵等。本文对这些问题作了分析，提出在城区大力应用本地种构建自然群落，对退化生态系统因势利导结合人工和自然力进行恢复，规范旅游活动向生态旅游方向发展，加强公众教育，促进全社会参与生物多样性保护工作。

Detecting air pockets for architectural concrete quality assessment using visual sensing

Air pockets, one kind of concrete surface defects, are often created on formed concrete surfaces during concrete construction. Their existence undermines the desired appearance and visual uniformity of architectural concrete. Therefore, measuring the impact of air pockets on the concrete surface in the form of air pockets is vital in assessing the quality of architectural concrete. Traditionally, such measurements are mainly based on in-situ manual inspections, the results of which are subjective and heavily dependent on the inspectors’ own criteria and experience. Often, inspectors may make different assessments even when inspecting the same concrete surface. In addition, the need for experienced inspectors costs owners or general contractors more in inspection fees. To alleviate these problems, this paper presents a methodology that can measure air pockets quantitatively and automatically. In order to achieve this goal, a high contrast, scaled image of a concrete surface is acquired from a fixed distance range and then a spot filter is used to accurately detect air pockets with the help of an image pyramid. The properties of air pockets (the number, the size, and the occupation area of air pockets) are subsequently calculated. These properties are used to quantify the impact of air pockets on the architectural concrete surface. The methodology is implemented in a C++ based prototype and tested on a database of concrete surface images. Comparisons with manual tests validated its measuring accuracy. As a result, the methodology presented in this paper can increase the reliability of concrete surface quality assessment

Kernel conditional quantile estimation via reduction revisited

Quantile regression refers to the process of estimating the quantiles of a conditional distribution and has many important applications within econometrics and data mining, among other domains. In this paper, we show how to estimate these conditional quantile functions within a Bayes risk minimization framework using a Gaussian process prior. The resulting non-parametric probabilistic model is easy to implement and allows non-crossing quantile functions to be enforced. Moreover, it can directly be used in combination with tools and extensions of standard Gaussian Processes such as principled hyperparameter estimation, sparsification, and quantile regression with input-dependent noise rates. No existing approach enjoys all of these desirable properties. Experiments on benchmark datasets show that our method is competitive with state-of-the-art approaches. © 2009 IEEE.

Modeling mode i fracture of bitumen films

The fracture behavior of thin films of bitumen in double cantilever beam (DCB) specimens was investigated over a wide range of temperature and loading rate conditions using finite-element analysis. The model includes a phenomenological model for the mechanical behavior of bitumen, implemented into a special-purpose finite-element user material subroutine, combined with a cohesive zone model (CZM) for simulating the fracture process. The finite-element model is validated against experimental results from laboratory tests of DCB specimens by comparing measured and predicted load-line deflection histories and fracture energy release rates. Computer simulation results agreed well with experimental data of DCB joints containing bitumen films in terms of peak stress, fracture toughness, and stress-strain history response. The predicted "normalized toughness," G=2h, was found to increase in a power-law manner with effective temperaturecompensated strain rate in the ductile region as previously observed experimentally. In the brittle regime, G=2h is virtually constant. The model successfully captured the ductile and brittle failure behavior of bitumen films in opening mode (tension) for stable crack growth conditions. © 2013 American Society of Civil Engineers.

非流体介质中多环芳烃污染的微生物固定化修复技术

非流体介质中多环芳烃(PAHs)污染的修复是目前环境工作者所面临的艰巨而紧迫的任务.由于非流体介质环境的特殊性,常规修复方法难以高效地发挥作用,传统微生物修复技术采用的游离微生物也存在许多弊端.而微生物固定化能大幅度地提高参加反应的微生物浓度,避免优势菌受土著菌的恶性竞争,增强微生物的耐环境冲击性.微生物固定化技术在一定程度上克服了传统工艺的不足,因而广泛应用于流体介质(废水等)和半流体介质(泥浆等)环境污染的修复.在概述固定化微生物技术的特点和分析国内外研究进展的基础上,指出将该技术应用于非流体介质中PAHs污染的原位修复领域的可行性,并论述了需要解决的关键科学问题,提出了利用微生物固定化技术修复非流体介质中PAHs污染的未来研究课题.

维生素C“二步发酵法”第二步发酵混合菌关系的研究

维生素Ｃ“二步发酵法”第二步发酵混合菌关系的研究马成新，杨凤玫，焦鹏，薛德林，王书锦（中国科学院沈阳应用生态研究所，１１００１５）维生素Ｃ作为一种重要的医药产品，不但用于治疗多种疾病，而且已被广泛用于食品、化妆品、饲料产品中，随着维生素Ｃ应用范围的增...

Poly(aryl ether)s containing ter- and pentafluorene pendants for efficient blue light emission

Four novel thermally stable poly(aryl ether)s, e.g., P3F, P5F, P2A3F, and P2A5K containing ter- or pentafluorene units in the side chains for efficient blue light emission have been designed and synthesized. All the polymers show the optical properties identical to the corresponding monomers and are amorphous with higher glass transition temperature (T-g) than their monomeric Counterparts. The polymer light-emitting diodes (PLEDs) were fabricated with the device structure of ITO/(PEDOT:PSS)/polymer/Ca/Al. The incorporation of diphenylamine group to oligofluorene terminals significantly reduces the hole-injection energy barrier in PLEDs. The devices based on P2A3F and P2A5F show the luminous efficiencies of 1.2 and 2.0 cd/A at a brightness of 300 cd/m(2) with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.13) and (0.19, 0.20), respectively. All these indicate that the high-performance light-emitting polymers can be synthesized with the traditional condensation polymerization through careful design of polymer structures.

Synthesis, characterization and crystal structure of a new layered heterometallic coordination polymer {[(CuL) Sr-2(H2O)center dot Sr-2(H2O)(7)]center dot 2H(2)O center dot 0.5CH(3)OH}(n)

A copper-strontium heterometallic coordination polymer was synthesized and characterized by elemental analysis and IR spectra. The crystal structure was determined by single-crystal X-ray diffraction analyses. The title complex is a 2 D coordination polymer with the chemical formula [[(CuL)(2)Sr (H2O) center dot Sr-2 ((HO)-O-2)(7)]center dot 2H(2)O center dot 0.5CH(3)OH](n), where H4L = N-(2-hydroxybenzamido)-N'-(3-carboxylsalicylidene) ethylenediamine. Its structural unit is comprised of two adjacent units, which polymerized with each other to form a new layered heterometallic coordination polymer.

Studies on the room temperature conductivity of PEO-LiClO4-Al2O3 composite polymer electrolyte

A composite polymer electrolyte of Polyethylene oxide (PEO)-LiClO4 containing fine Al2O3 particles was studied by using differential scanning calorimetry, infrared spectroscopy and electrochemical impedance spectroscopy. Compared with the polymer electrolyte without Al2O3 particles, the glass transition temperature and the degree of crystallinity were decreased, and the room temperature conductivity of PEO-LiClO4-Al2O3 composite polymer electrolyte was considerably enhanced. Moreover, the equivalent circuits and the effect of dc potential on impedance spectroscopy were discussed.