Experimental study on the effect of bottomless structure in front of a bottom outlet on a sediment flushing cone

One of the main problems in reservoirs is sedimentation which reduces the operating life of dams if a proper plan and analysis method are not in place.The techniques to manage sediment in reservoirs include several sustainable management techniques that route sediment through or around the reservoir.One of the main economical methods in arid and semi-arid regions is pressurized flushing using moderate drawdown of the water level of the reservoir to evacuate sediment deposited behind dams.In the current study,the effect of a new structure called a dendritic bottomless extended(DBE)outlet structure at three angles of 30°,45°,and 60°
on pressurized flushing efficiency was investigated.Consequently,45 experiments were designed for three discharge rates (Qo),three sediment levels(Hs),four types of structure,and a no-structure condition(reference test).The results indicated that the DBE structure with a 30°angle between the branches,a sedimentary dimensionless index of Hs/Do=4.59,and a flow dimensionless index of Qo=/√gD05=1:43(where g is the acceleration of gravity and Do is the diameter of the bottom outlet)lead to 10-fold increase in the sediment flushing cone dimensions and sediment removal efficiency compared to the results of the reference test.Finally,according to a statistical analysis of the results,a dimensionless equation for calculating the sediment flushing cone dimensions was developed for the tested sediment characteristics.     

收缩城市建设用地利用效率时空分异及影响机制——以黑龙江省伊春市为例

建设用地是城镇经济社会活动的空间载体,其利用效率是调控建设用地扩张和配置的重要基础.论文以收缩型城市——黑龙江省伊春市为例,利用DEA模型测算了1995-2015年伊春市建设用地利用效率分析其时空演变规律,并运用地理探测器模型探究伊春市建设用地利用效率空间分异的影响机制,结论如下:①1995-2015年伊春市建设用地利...     

周至井水位气压效率和相关系数在中强地震前的变化特征

计算了2002～2004年周至井水位的气压效率和相关系数,初步分析了其与地震的关系,认为在2002年甘肃玉门5.9级地震、2003年和2004年甘肃岷县5.2、5.0级地震前,该井水位的气压效率和相关系数同时出现了明显的短临前兆异常。     

地震活动性总体参量Rt在东南沿海地震带西段地震预测中的应用

分析了1974年以来东南沿海地震带西段发生的MS≥4.9级地震前地震活动性总体状态参量Rt的变化特点,同时对Rt值在东南沿海地震带西段的地震预测效能进行了检验评估。结果表明,当Rt>0.82时,表明东南沿海地震带西段地震活动状态比较正常,发生4.9级以上地震的概率较低;反之,当Rt≤0.82时,则表明东南沿海地震带西段地震活动比较活跃,发生4.9级以上地震的概率较大。     

Structure, biomass distribution and trophodynamics of the pelagic ecosystem in the Oyashio region, western subarctic Pacific

Biomass distribution and trophodynamics in the oceanic ecosystem in the Oyashio region are presented and analyzed, combining the seasonal data for plankton and micronekton collected at Site H since 1996 with data for nekton and other animals at higher trophic levels from various sources. The total biomass of biological components including bacteria, phytoplankton, microzooplankton, mesozooplankton, micronekton, fishes/squids and marine birds/mammals was 23 g C m⁻², among which the most dominant component was mesozooplankton (34% of the total), followed by phytoplankton (28%), bacteria (15%) and microzooplankton (protozoans) (14%). The remainder (9%) was largely composed of micronekton and fish/squid. Marine mammals/birds are only a small fraction (0.14%) of the total biomass. Large/medium grazing copepods (Neocalaus spp., Eucalanus bungii and Metridia spp.) accounted for 77% of the mesozooplankton biomass. Based on information about diet composition, predators were assigned broadly into mean trophic level 3–4, and carbon flow through the grazing food chain was established based on the estimated annual production/food consumption balance of each trophic level. From the food chain scheme, ecological efficiencies as high as 24% were calculated for the primary/secondary production and 21% for the secondary/tertiary production. Biomass and production of bacteria were estimated as 1/10 of the respective values for phytoplankton at Site H, but the role of the microbial food chain remains unresolved in the present analysis. As keystone species in the oceanic Oyashio region, Neocalanus spp. are suggested as a vital link between primary production and production of pelagic fishes, mammals and birds.     

宁阳县蒋集镇彩山小流域水土保持技术研究

该文分析研究了彩山小流域的区域坡度和土壤特性,并根据区内土壤性质划分出4个小区域,即:自然坡度在20.～25°内为V1区,15°～20°内为V2区,10°～15°内为V3区,5°～10°内为V4区,分别反映了不同的土壤等级及土壤抗冲能力.同时,也研究出了一个系统化、理论化的科学依据i=V1035B,并对所有砂石山区水土保持治理工作具有借鉴性和实用性.     

大豆蛋白废水处理中泡沫分离过程的数学模型

假设吸附过程始终处于平衡态、气泡大小均一以及每一个气泡均为正十二面体,构建了泡沫分离过程的数学模型.模拟了液池中蛋白质在气液界面上的吸附过程和泡沫层中气泡的失水过程,得出了富集比的表达式,可用于分离效果的预测.经验证,模型与实验条件下的泡沫分离过程基本符合.     

网络营销控制二三题

网络营销控制是网络管理的重要内容,开展网络市场营销活动必须有网络运转的有效控制作保证。在讨论网络营销控制特征与内容的基础上,着重分析了网络营销活动的盈利能力、营销效率和营销策略控制的方法与技术。     

京津冀地区农业生产效率的时空格局及收敛性研究

将京津冀地区146个典型县域划分为京津近郊农业区（I）、冀东北农业区（II）、冀中平原农业区（III）、太行山农业区（IV）、坝上农业区（V）五大农业区,测算了2000—2015年京津冀及五大农业区的农业生产效率,检验了京津冀及五大农业区农业生产效率的收敛性,揭示了京津冀地区农业生产效率的收敛机理。研究结果表明,京津冀地区农业生产效率变化趋势总体较为平稳,五大农业区农业生产效率由大到小依次为：V>II>IV>I>III,Malmquist指数呈显著波动趋势,技术进步对对农业生产效率提升的作用显著;在农业资源禀赋、地理区位等内源性因素与经济发展环境、技术进步与农业政策支持等外源性因素的共同作用下,京津冀地区优化重组农业生产要素,提升了农业生产效率,并通过要素流动与要素替代作用,缩小了不同农业区内部的农业生产效率差距,使不同经济发展水平的各农业区农业生产效率收敛于不同稳态水平;最后,从现代农业生产经营体系、财政转移支付机制、农业规模经营等角度提出了京津冀地区农业协同发展的具体路径。     

Performance of small-scale irrigation schemes in Lake Tana Basin of Ethiopia: technical and socio-political attributes

This study was conducted to investigate technical and socio-political attributes that lead to the underperformance of two selected irrigation schemes (Shina and Bebeks) in the Lake Tana floodplains, Ethiopia. Irrigation application efficiency (AE) at nine experimental fields showed a wide range, from 20 to 80%, but was mostly between 40 and 60%. Irrigation water-use efficiency (IWUE) varied from 1.9 to 7.2 kg m^?3 for onion and 0.9 to 1.2 kg m^?3 for maize. The lined and earthen canal conveyance losses in Bebeks were 0.037 and 0.047 l s^?1 m^?1, whereas in Shina they were 0.033 and 0.044 l s^?1 m^?1, respectively. The overall consumed ratio (OCR) of water was 0.58 for Bebeks and varied from 0.73 to 1.2 in Shina. Both schemes are performing below the standard based on technical performance indicators. Irrigation water user associations (WUAs) were not implemented, but irrigation committees (ICs), composed of local political leaders, are managing both schemes. Canal and reservoir sedimentation from erosion of upstream catchment areas during the rainy season was the major problem.