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61.
Huan-Xin Weng Ya-Chao Qin Xiang-Wei Sun Hailiang Dong Xiang-Hua Chen 《Estuarine, Coastal and Shelf Science》2007,73(3-4):501-509
Based on lab-culture experiments analyzing limitation and combination of iron and phosphorus on the growth of Cryptomonas sp. (Cryptophyceae), and the study of accumulation and release of Fe-bound P in sediment cores collected from the marine region of the Pearl River Estuary, China, reasons for the high frequency of phytoplankton bloom therein are discussed. Results show that the combined effect of Fe and P can obviously accelerate algal development, and the optimum culture conditions maintaining maximum growth rate are 0.05 μM Fe and 50 μM P. Cellular contents of Fe and P is consistent and the P:Fe molar ratio is 159:1. The optimum range of the P:Fe molar ratio in culture experiments for cell incubation is 500–1400. The vertical trends of total Fe and total P variations in sediments are parallel. Fe-bound P is the main species of inorganic sedimentary P. Through continuous leaching with agitation, 34–80% of exchangeable P and 4–23% of exchangeable Fe are concurrently released from the surficial sediments. This is a possible way by which nutrients are made available to phytoplankton. These factors might be responsible for a high frequency of harmful algal blooms in the Pearl River Estuary. 相似文献
62.
城市空气质量数值预报的不确定性与可预报性 总被引:1,自引:0,他引:1
主要综述了数据误差、随机误差和模式物理误差所造成的城市空气质量数值预报的不确定性,简要介绍分析预报不确定性的统计方法。并对由内在随机性和外在误差引起的可预报性问题进行了分析讨论 相似文献
63.
根据天山中段8套四分量钻孔应变仪观测资料,利用自洽方程计算应变观测的信度,用信度指标检验数据的可靠性,从而进一步用自洽方程计算实际各元件灵敏度的相对大小,并用相对标定的结果,对观测数据进行校正。结果表明:①石场、巴仑台、巴音沟、雀儿沟、榆树沟和库米什台经过校正后,数据观测信度有了明显提升,其中石场和雀儿沟台的数据信度最高;②库米什台校正前数据观测信度较高,因个别“坏点”影响,校正后,观测信度反而下降;③小泉沟和新源台数据信度较低,存在从自洽到失洽的情况,分析认为这可能与系统自身存在问题有关,也有可能是前兆异常,有待进一步研究。 相似文献
64.
Origin and Evolution of Aquitard Porewater in the Western Coastal Plain of Bohai Bay,China 总被引:2,自引:0,他引:2 下载免费PDF全文
High‐salinity paleowater from low‐permeability aquitards in coastal areas can be a major threat to groundwater resources; however, such water has rarely been studied. The chemical and isotopic compositions of porewater extracted from a 200‐m‐thick Quaternary sedimentary sequence in the western coastal plain of Bohai Bay, China, were analyzed to investigate the salinity origin and chemical evolution of porewater in aquitards. Porewater samples derived at depths shallower than 32 m are characterized by Cl‐Na type saline water (total dissolved solids [TDS], 10.9–84.3 g/L), whereas those at depths greater than 32 m comprise Cl·SO4‐Na type brackish water (TDS, 2.2–6.3 g/L). Saline porewater is interpreted as evaporated seawater prior to halite saturation, as evidenced by Cl‐Br relationships. Although substantial dilution of saline porewater with meteoric water is supported by a wider Cl? range and δ2H‐δ18O covariance, the original marine waters were not completely flushed out. The deeper brackish porewater is determined to be a mixture of fresher porewater and brine groundwater and had a component of old brine of less than 10%, as indicated by a mixing model defined using δ2H and Cl? tracers. Porewater δ2H‐δ18O relationships and negative deuterium excess ranging from ?25.9‰ to ?2.9‰ indicate the existence of an arid climate since Late Pleistocene in Tianjin Plain. The aquitard porewaters were chemically modified through water‐rock interactions due to the long residence time. 相似文献
65.
A probability-based analytical model for predicting the seismic residual deformation of bilinear single-degreeof-freedom(SDOF) systems with a kinematic/Takeda hysteretic model is proposed based on a statistical analysis of the nonlinear time history response,and the proposed model explicitly incorporates the influence of record-to-record variability.In addition,the influence of primary parameters such as the natural vibration period,relative yield force coefficient,stiffness ratio and peak groun... 相似文献
66.
67.
A large‐scale survey for offshore aggregates is carried out on the northern shelf of the East China Sea. Results show that most of them are directly exposed in the Yangtze Shoal and the linear sand ridges system at water depths 25–55 m and 60–120 m, respectively. The components of these deposits belong to fine aggregates in terms of the fineness modulus. The potential resources are as high as 147.8 × 1012 kg for the Yangtze Shoal yet only 36.68 × 1012 kg for the sand ridges area, respectively. A preliminary feasibility analysis suggests that the Yangtze Shoal is suitable for dredging under the present conditions of technology and economy. 相似文献
68.
Zeng Jingjing Qu Jiansheng Pei Huijuan Dong Liping Liao Qin Liu Yanfei Zhang Zhiqiang 《地球科学进展》2015,30(11):1210-1217
The international climate change negotiation has been carried out over 20 years. The issue of climate change has shifted from a scientific question into a complex political matter which is related to the sustainable development of mankind. Based on the overview of major processes and stages of international climate conferences, this paper analyzed the key measures that major countries have taken to address climate change, as well as the primary tasks of Paris climate conference and recent international actions. The recent international climate policy issues were also analyzed in order to provide suggestions for China’s activel participation in the development of a new round of international climate change system. 相似文献
69.
70.
超声回弹综合法检测单一构件混凝土强度推定值的保证率分析 总被引:1,自引:0,他引:1
在实际工程检测数据的基础上,利用M on te C arlo试验对单一构件混凝土强度推定值的保证率问题进行了分析。30片梁板实测数据分析结果表明:将构件各测区混凝土强度换算值的最小值作为该构件的混凝土强度推定值的保证率范围为79.0%~94.2%,小于《超声回弹综合法检测混凝土强度技术规程》(CECS 02:88)规定的95%保证率要求,因此,对结构性能鉴定而言该混凝土强度推定值是偏于不安全的,应引起试验检测人员的充分重视。 相似文献