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991.
This paper is concerned with the application of a multi-scale model of permeability evolution to the simulation of permeation tests of lead nitrate solutions in a compacted natural bentonite. In a previous work, the weathered hydraulic conductivity has been measured for different pollutant concentrations. Textural and structural evolutions induced by heavy metal sorption have also been investigated, therefore giving us information about the various pore spaces that may be encountered during the process of pollutant leaching. Such knowledge has been exploited during the construction of the numerical microstructures. First of all, pure water permeability tests have been simulated, this has allowed us to ascertain the representation of compacted clay before pollutant permeation. For both Prrenjas and Wyoming clays, permeation tests after pollutant permeation have then been simulated, using connected and non-connected macro-voids configurations. Different conclusions have been drawn based on simulation results for the two different clays investigated, which are supported by experimental evidence. 相似文献
992.
"一带一路"倡议提出与建设为中国西部地区发展带来重大机遇。甘肃是"一带一路"倡议的重要区域。本文利用DEA模型、熵权法对甘肃省14个地州市2004年、2008年、2012年和2016年四个节点时间的城市化效率、经济发展水平进行了度量。并利用耦合度模型对两者之间的耦合协调度进行了时空分析,研究结果表明,甘肃省城市化效率在2004-2016年间处于波动中提升状态,且总体效率较低,甘肃省城市化效率值(0.441)远低于全国平均值(0.740);2004-2016年甘肃省经济发展水平稳中有升,但与全国比较劣势明显,且省域内部经济发展差距显著;研究期内,甘肃省城市化效率与经济发展耦合协调度均处于波动上升状态,耦合度由中强度发展为高强度耦合,协调度由濒临失调发展为勉强协调。省内14个地区,嘉峪关、兰州、金昌和酒泉在四年间始终处于高水平耦合与协调状态,张掖、白银等余下十个地区的耦合协调度也由中低水平发展为中高水平,说明各地区城市化效率与经济发展水平的耦合协调度相对较好。 相似文献
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为了研究紫贻贝与厚壳贻贝种间杂交的核相变化,并评估其杂交优势,本实验以两种贻贝亲本为材料建立了4个交配组合,分别为:紫贻贝自交组EE(Mytilus edulis♀×M.edulis♂)、厚壳贻贝自交组CC(Mytilus coruscus♀×M.coruscus♂)、正交组EC(M.edulis♀×M.coruscus♂)和反交组CE(M.coruscus♀×M.edulis♂)。通过Hoechst 33258染色、荧光显微观察的方法,对4个交配组从受精、减数分裂到卵裂的核相变化过程进行了观察,并对孵化后幼虫到稚贝期的生长情况进行了记录。结果表明:正反交组的受精细胞学过程与自交组较为相似,但第二极体排出时间延长。对各实验组子一代早期的生长和存活研究表明:浮游阶段,杂交组幼虫生长优势不明显;附着变态后,正交组EC在壳长及壳高等生长指标的杂交优势表现明显,且正交组(EC)大于反交组(CE)。自交组的受精率、孵化率、成活率均高于杂交组。 相似文献
998.
The influence of oil-expulsion efficiency on nanopore development in highly mature shale was investigated by using anhydrous pyrolysis (425–600 °C) on solvent-extracted and non-extracted shales at a pressure of 50 MPa. Additional pyrolysis studies were conducted using non-extracted shales at pressures of 25 and 80 MPa to further characterize the impact of pressure on pore evolution at high maturity. The pore structures of the original shale and relevant artificially matured samples after pyrolysis were characterized by using low-pressure nitrogen and carbon-dioxide adsorption techniques, and gas yields during pyrolysis were measured. The results show that oil-expulsion efficiency can strongly influence gas generation and nanopore development in highly mature shales, as bitumen remained in shales with low oil expulsion efficiency significantly promotes gaseous hydrocarbon generation and nanopore (diameter < 10 nm) development. The evolution of micropores and fine mesopores at high maturity can be divided into two main stages: Stage I, corresponding to wet gas generation (EasyRo 1.2%–2.4%), and Stage II, corresponding to dry gas generation (EasyRo 2.4%–4.5%). For shales with low oil expulsion efficiency, nanopore (diameter < 10 nm) evolution increases rapidly in Stage I, whereas slowly in Stage II, and such difference between two stages may be attributed to the changes of the organic matter (OM)’s mechanical properties. Comparatively, for shales with high oil expulsion efficiency, the evolution grows slightly in Stage I, not as rapidly as shales with low efficiency, and decays in Stage II. The different pore evolution behaviors of these two types of shales are attributed to the contribution of bitumen. However, the evolution of medium–coarse mesopores and macropores (diameter >10 nm) remains flat at high maturation. In addition, high pressure can promote the development of micropores and fine mesopores in highly mature shales. 相似文献
999.
《Marine Policy》2017
Low carbon shipping research focuses on energy efficiency and mitigation measures related to operations and technology. However, reducing energy use and greenhouse gas emissions associated with a vessel’s material production receives limited attention. Material efficiency is defined as “providing material services with less material production and processing”. The current business model for ship building and breaking does not embrace fully material efficiency principles. Exploring a case study of a vessel's steel hull, this study applies a Life Cycle Assessment approach to determine the effectiveness of material efficiency to reduce CO2 emissions. When compared to Business as Usual, designing and manufacturing for 100% hull reuse provides an emissions reduction of 29% from 221,978 t CO2 to 158,285 t CO2; 50% reuse provides a 10% reduction (199,816 t CO2). From a technical and safety perspective there remain key barriers that need addressing: a vessel’s hull would require to be designed for dismantling to improve reuse; the operation and maintenance schedule must ensure the value of the steel is retained and; data must flow between key stakeholders on the quality of the steel. Despite these challenges, progressing material efficiency would require different business models that reach out and integrate the whole supply chain. There is a need for public and privately funded demonstration projects at a range of scales and markets, to provide investors the confidence that there is retained value in the steel hull when it reaches its end-of-life. 相似文献
1000.
根据南方和北方海带夏苗培育采用苗帘苗绳差异,在山东烟台国家级海带良种场海带育苗基地进行两种夏苗培育工艺的实验研究。在同一个育苗车间内,利用种海带采集游孢子并附苗,跟踪观测维尼纶苗帘和棕绳苗帘对海带育苗期间配子体发育、孢子体(幼苗)生长的影响,并比较两种不同苗帘育苗成本差异。结果显示:相同育苗条件下,维尼纶苗帘采苗后,配子体发育速度、孢子体形成速度显著优于棕绳苗帘上的配子体和孢子体;转化孢子体后,在育苗第15~31天时间内,维尼纶苗帘海带幼苗相对生长速率(RGR)显著大于棕绳苗帘幼苗(P0.05);维尼纶苗帘幼苗经55天培育,幼苗平均长度长至1.53 cm±0.13 cm,达到出库下海暂养规格,此时棕绳帘幼苗平均长度约0.47 cm±0.03cm。至70天,棕绳苗帘幼苗平均长度约1.78 cm±0.19 cm,维尼纶绳苗帘幼苗平均长度达7.87 cm±1.35cm,显著大于棕绳苗帘幼苗。采用维尼纶苗帘育苗,每1m3育苗水体育苗量约为60万株,综合育苗成本约为23元/万株,采用棕绳苗帘育苗,每1m~3育苗水体育苗量约40万株,综合育苗成本约为31元/万株。综上所述,北方采用维尼纶帘进行海带育苗在生产上具有可行性,并且可降低生产成本约25.8%。 相似文献