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291.
天宝山多金属矿床地球化学模式 总被引:2,自引:0,他引:2
天宝山铅锌矿山正处于资源枯竭状态,在该矿山附近寻找新的矿床对天宝山矿山来说是当务之急。我们对现有的区域地球化学和地质资料进行分析研究,总结出天宝山多金属矿床的水持地球化学异常特征、地球化学异常分带模式及地球化学找矿模式,在此基础上,提出了光新屯找远景区。 相似文献
292.
293.
泥沙颗粒沉降变加速运动研究 总被引:3,自引:0,他引:3
本文从泥沙沉降的力学机制出发,考虑泥沙与液体边界的粘性作用,建立了泥沙群体沉降的基本运动方程,通过求解得到了泥沙沉降瞬时速度的一般计算式。从理论上证明了一般泥沙静水沉降由零趋近终速过程时间极短的看法,同时发现对于尺度较大的固体颗粒(如抛石),其在沉降时趋近终速过程相对来说是相当长的过程。 相似文献
294.
295.
轨迹时空模式的研究,对于突发公共安全事件监测及政策制定评估具有重要意义。目前大量的研究仅分析了物理轨迹时空模式变化,尚缺乏从群体虚拟轨迹的视角,分析其与物理轨迹的关联性和差异性。因此,本研究选取美国10个大型样本城市作为研究对象,以OSM网络地图作为虚拟空间,利用地图瓦片访问频率构建群体虚拟轨迹,与物理轨迹对比分析居家令干预政策实施前后时空分布、时空衰减和空间要素偏好的变化。结果表明:(1)城市中群体虚拟轨迹访问频率具有一致的中心边缘空间结构,但新冠肺炎疫情导致城市中心吸引力明显减弱;干预政策实施后,群体虚拟轨迹不同空间要素访问频率相比疫情前平均下降67.84%,且不同空间要素同步下降,仅在部分区域中对医疗设施的访问频率增加,谷歌移动指数代表的物理轨迹平均下降48.05%,仅居住场所增长22.15%。(2)物理轨迹访问频率变化与干预政策时间一致,然而虚拟空间中群体提前一周左右已经进入居家管制的活动模式。研究成果表明群体虚拟轨迹相比物理轨迹对于干预政策响应时间更早、时空衰减更大,为突发公共安全事件监测及政策制定评估提供了新途径。 相似文献
296.
A bstract In the present study,the effect of one-generation divergent selection on the growth and survival of the bay scallop(Argopecten irradians concentricus)was examined to evaluate the effi cacy of a selection program currently being carried out in Beibu Bay in the South China Sea.A total of 146 adult scallops were randomly selected from the same cultured population of A.i.concentricus,and divided into two groups in shell length(anterior-posterior measurement): large(4.91–6.02 cm,n=74)and small(3.31–4.18 cm,n=72).At the same time,a control group was also randomly sampled(4.21–4.88 cm,n=80).Mass-spawned F 1 progenies from the three size groups were obtained and reared under identical conditions at all growth phases.The effects of two-way(or upward-downward)selection on fertilization rate,hatching rate,survival rate,daily growth in shell length and body weight were assessed in the three size groups.Results show that signifi cant differences(P0.01)were found in hatching rate,survival rate and daily growth of F 1 progenies,but not in fertilization rate(P0.05),among the three groups.The hatching rate,survival rate and daily growth of the progeny of large-sized parents were greater than those of the control group(P0.05),which in turn were larger than those of small-sized group(P0.05).Responses to selection by shell length and body weight were 0.32±0.04 cm and 2.18±0.05 g,respectively,for the upward selection,and-0.14±0.03 cm and-2.77±0.06 g,respectively,for the downward selection.The realized heritability estimates of shell length and body weight were 0.38±0.06 cm and 0.22±0.07 g for the upward selection,and 0.24±0.06 cm and 0.37±0.09 g for the downward selection,respectively.The change in growth by bidirectional selection suggests that high genetic variation may be present in the cultured bay scallop population in China. 相似文献
297.
A sediment core MD05-2902 was collected from the deep-sea basin of the Xisha Trough. The vertical distribution and diversity of bacteria in the core was investigated through ten sub-sampling with an interval of 1 m using bacterial 16 S rRNA gene as a phylogenetic bio-marker. Eighteen phylogenetic groups were identified from 16 S rRNA gene clone libraries. The dominant bacterial groups were JS1, Planctomycetes and Chloroflexi, which accounted for 30.6%, 16.6%, and 15.6% of bacterial clones in the libraries, respectively. In order to reveal the relationship between biotic and abiotic data, a nonmetric multidimensional scaling analysis was performed. The result revealed that the δ15N, δ13C, total organic carbon and total organic nitrogen possibly influenced the bacterial community structure. This study expanded our knowledge of the biogeochemical cycling in the Xisha Trough sediment. 相似文献
298.
While passing through a lock, a ship usually undergoes a steady forward motion at low speed. Owing to the size restriction of lock chamber, the shallow water and bank effects on the hydrodynamic forces acting on the ship may be remarkable, which may have an adverse effect on navigation safety. However, the complicated hydrodynamics is not yet fully understood. This paper focuses on the hydrodynamic forces acting on a ship passing through a lock. The unsteady viscous flow and hydrodynamic forces are calculated by applying an unsteady RANS code with a RNG k-ε turbulence model. User-defined function(UDF) is compiled to define the ship motion. Meanwhile, the grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Numerical study is carried out for a bulk carrier ship passing through the Pierre Vandamme Lock in Zeebrugge at the model scale. The proposed method is validated by comparing the numerical results with the data of captive model tests. By analyzing the numerical results obtained at different speeds, water depths and eccentricities, the influences of speed, water depth and eccentricity on the hydrodynamic forces are illustrated. The numerical method proposed in this paper can qualitatively predict the ship-lock hydrodynamic interaction. It can provide certain guidance on the manoeuvring and control of ships passing through a lock. 相似文献
299.
利用AFLP技术对山东沿海菲律宾蛤仔(Ruditapes philippinarum)4个野生群体(乳山、无棣、牟平、即墨)进行了遗传多样性分析。采用6对引物组合对4个群体进行扩增,共得到356个位点,乳山群体、无棣群体、牟平群体和即墨群体的多态位点比例依次为74.40%、70.50%、72.80%、74.70%,具有较高的遗传多样性水平。其中,即墨群体多态性比例最高,无棣群体多态性比例最低。聚类分析表明,各群体间的遗传距离在0.0263~0.0448之间,乳山群体和无棣群体间的遗传距离最近(0.0263),两群体首先聚在一起,随后与牟平群体和即墨群体聚在一起。 相似文献