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区域可持续发展评价:进展与展望 总被引:55,自引:4,他引:55
可持续发展的评价是目前可持续发展研究的热点和前沿。当前评价可持续发展的单项指标和指标体系在指标与可持续性的关系、指标权重的选择、指标的定量化、可持续性的总体判别方法、资本替代性与替代速度、指标阈值的确定等方面具有不同的局限性 ,这也是可持续发展评价的主要难点。可持续发展的评价必然要落实到不同尺度的空间地理单元上 ,区域发展是评价的对象 ,因而可持续发展的评价必然具有显著的区域性 ,不同区域的评价指标或指标体系必然会有所不同。社会、经济与人口的发展是人类社会发展的主要目标 ,而发展的可持续性依赖于自然环境的质量 ,包括自然资源的再生或替代、生命支持系统与生物多样性的维持或改善。据此 ,论文构建了区域可持续发展评价的理论框架和发展——可持续性二维评价坐标体系 ,并提出了“自上而下”和“自下而上”的指标遴选方法。 相似文献
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In our trials, from 2007 to 2008, of mass production of seedlings of Hizikia fusiformis using synchronization techniques, problems of a dark thalli phenomenon and epiphytes contamination severely threatened the health of juvenile seedlings. In this investigation, we optimized conditions for improving the growth of juvenile seedlings. Seven string collectors were seeded with zygotes and a series of experiments were conducted including direct exposure to solar irradiance, co-culture with Ulva spp. and treatme... 相似文献
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During sexual reproduction of seaweeds, spermatozoid (sperm) discharge is triggered by chemical messengers (pheromones) released by the female gametes. The chemotactic ability of the sperm ensures fertilization success. Using unialgal male and female gametophyte material under designated standard gametogenesis testing (SGT) conditions, the potential life-span of the sperm of two seaweeds, Saccharina japonica and Undaria pinnatifida, was assessed by their ability to fertilize eggs. Results show that within 20-30 min after being discharged, sperm of both species could complete fertilization without an apparent decline in fertilization rate. Although fertilization rate 60–120 min after sperm discharge dropped significantly in both species, some sperm were viable enough to fertilize the eggs. In S. japonica, at 12°C, some sperm were able to fertilize eggs up to 12 h after discharge. In both species, egg discharge rates (EDR) in the male and female mixed positive controls were significantly higher than those of all the sperm-testing groups. Doubling the seeded male gametophytes of S. japonica in the SGT tests significantly increased the EDR, further confirming the effect of the presence of the male on the female in terms of facilitating egg discharge from oogonia. 相似文献
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The annual life cycle of the brown seaweed Undaria pinnatifi da(Harvey)Suringer comprises a macroscopic diploid sporophyte stage and a microscopic haploid gametophyte stage.In 2011,an unusual zoospore-derived monoecious gametophyte isolate(designated as line 10-5-3)of U.pinnatifi da was observed.To understand this phenomenon,a comprehensive screening of eighty-two previously identifi ed male gametophyte cultures,isolated from three randomly selected cultivars(lines 10,7,and 5)was performed.Thirty-six of the isolates developed both antheridia and oogonia on the same fi lamentous fragment in a standard gametogenesis test(SGT: 18°C,60 μmol photons/(m 2·s)).Selfi ng of the monoecious gametophyte or crossing it with a normal male gametophyte both gave rise to morphologically normal sporophytic offspring.However,crossing resulted in a much higher fertilization rate(89.7%).The hybrid and selfed sporophytic offspring were grown to maturity in fl ow tanks at an ambient temperature of 10–18°C over a period of 69 days.Active zoospores were released from both types of mature sporophylls.The majority of these developed into male gametophytes,while 15%–20% developed into the observed monoecious structures on the same fi lament.Using PCR amplifi cation it was found that all the monoecious gametophyte isolates and the sporophytic offspring resulting from the selfi ng and crossing lacked the femalelinked microsatellite sequence(a part of the locus Up-AC-2A8,GenBank accession No.AY738602.1),indicating their male nature.U.pinnatifi da is an invasive species in some regions and the implications of the above fi ndings for this species in nature are briefl y discussed. 相似文献
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神经网络技术在地面沉降区划中的应用研究 总被引:1,自引:2,他引:1
复杂的第四系沉积环境构成地面沉降的地质背景,在对比分析第四系厚度、地下水位、含水层以及软土层发育程度的基础上,尝试性地运用人工神经网络技术对苏锡常地区地面沉降易发区进行识别。除基岩出露区外全区共被划分成4类块段,这种分布与第四系条件具有很强的空间相关性,经检验具有较高的可信度。 相似文献
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一种双向测距与时间同步系统的设计与分析 总被引:1,自引:0,他引:1
在研究双向单程伪距测量原理的基础上,设计了双向测距与时间同步(DRTS)终端系统总体构架,阐述了在系统中使用的技术,并搭建了基于DSP+FPGA的双向测距与时间同步系统软硬件平台。实验结果表明,此系统的码速率为5MHz、中心频率为15MI-Iz时,测距和时间同步的分辨率可达0.15cm和5ps(@1S),采用不同频率源时测距和时间同步的精度分别为1.038m和3.46ns,采用相同频率源时分别为0.28cm和9.43ps(参考频率稳定度1×10^-10/d量级)。与国外同类产品相比具有测量精度优势,但考虑通用性,此系统的硬件仍需进一步优化,软件上需要做到码速率可调。 相似文献