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61.
南海南部大陆架的残留沉积   总被引:1,自引:0,他引:1  
研究了南海南部大陆架的残留沉积物的粒度、石英砂表面结构特征、生物分布等,并指出残留沉积普遍遭受改造。按其早期的形成环境差异和改造作用不同,划分出加里曼丹-巴拉望残留沉积区和亚南巴斯-纳土纳残留沉积区。  相似文献   
62.
钝段螺旋藻(Spirulina platensisGeitler)培养在低浓度NaHCO3(2~5g/dm^3)和适量生长素QS(0.5~5mg/dm^3)中,研究了生长素QS对钝顶螺旋藻生长、生物量和生化组成的影响,结果表明,在生长素QS为1mg/dm^3,NaHCO3浓度为5g/dm^3时,钝顶螺旋藻的生长最好,生物量、蛋白质及总碳水化合物的含量也与主浓度NaHCO3(8g/dm^3)培养条件下的基本相同,说明生物素QS的加入在一定程度上可降低NaHCO3的使用量,而不影响钝顶螺旋藻生长、生物量和生化组成。因而生长素QS在钝顶螺旋灌的养殖中可作为NaHCO3部分替代剂,从而达到降低养殖成本的目的。  相似文献   
63.
根据水资源对厄尔尼诺事件的响应,得出了钱塘江流域水资源的统计预报模式:(1)在春季型厄尔尼诺事件的当年和夏季型厄尔尼诺事件的次年,金华站年径流量的距平一般都大于零:(2)厄尔尼诺事件的结束时间若超过5月1日,那么次年金华站年径流量的距平一般都大于零;(3)厄尔尼诺事件的强度越大。对钱塘江流域水资源的影响也越大。这对该流域长期及超长期的水资源预报具有重要的指示作用。  相似文献   
64.
The acoustic properties of seafloor sediments are of great importance in geoacoustic modeling, detecting, and oceanic engineering. The methods based on the first arrival cycle are investigated to calculate sound speed and attenuation of sediment more precisely in in situ measurements. The comparison of different data analysis methods based on the first arrival cycle approach for in situ measurement results in the following conclusions: (1) the calculated methods can help find the effective cycles and reduce the errors in calculating sound speed and attenuation; (2) using this approach, the point judgment method-based data analysis has the same effectiveness as the cross-correlation method-based data analysis in calculating group sound speed and has the same effectiveness in calculating attenuation in the time domain as the spectrum analysis method-based data analysis has in calculating attenuation in frequency domain; and (3) measurement in water can help not only calibrate the transmitting distance but also can calculate the time delay for the sound speed and the attenuation loss in the transmitting process. Finally, theoretical calculation was used to calculate the measured results, indicating a good agreement, which supports that first arrival cycle-based calculated methods can be used to analyze the measured data and the effective density fluid model can be used to analyze more acoustic properties and invert several physical properties in this experiment.  相似文献   
65.
Numerical analysis and centrifuge modeling of shallow foundations   总被引:1,自引:0,他引:1  
The influence of non-coaxial constitutive model on predictions of dense sand behavior is investigated in this paper. The non-coaxial model with strain softening plasticity is applied into finite-element program ABAQUS, which is first used to predict the stress-strain behavior and the non-coaxial characteristic between the orientations of the principal stress and principal plastic strain rate in simple shear tests. The model is also used to predict load settlement responses and bearing capacity factors of shallow foundations. A series of centrifuge tests for shallow foundations on saturated dense sand are performed under drained conditions and the test results are compared with the corresponding numerical results. Various footing dimensions, depths of embedment, and footing shapes are considered in these tests. In view of the load settlement relationships, the stiffness of the load-displacement curves is significantly affected by the non-coaxial model compared with those predicted by the coaxial model, and a lower value of non-coaxial modulus gives a softer response. Considering the soil behavior at failure, the coaxial model predictions of bearing capacity factors are more advanced than those of centrifuge test results and the non-coaxial model results;besides, the non-coaxial model gives better predictions. The non-coaxial model predictions are closer to those of the centrifuge results when a proper non-coaxial plastic modulus is chosen.  相似文献   
66.
Using an apparent-magnitude limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 7(SDSS DR7), we investigate the correlation between morphologies and luminosity for the Main galaxy sample. Our Main galaxy sample is divided into two classes: Main galaxies only with TARGET_GALAXY flag (bestPrimtarget = 64), and ones also with other flags. It is found that for the second class Main galaxies, the early-type proportion monotonously increases with increasing luminosity nearly in the whole luminosity region. But for the first class Main galaxies, the early-type proportion increases with increasing luminosity only within a certain luminosity region (−22.2 < M r  < −19.8). In the high luminosity region (M r  < −22.2), the early-type proportion of the first class Main galaxies even decreases dramatically with increasing luminosity. We also analyze the correlation between morphologies and luminosity of galaxies around the peak of the redshift distribution ( 0.07 ≤ z ≤ 0.08 ). In such a narrow redshift region, we still observe strong correlation between morphologies and luminosity, which shows that this correlation is fundamental.  相似文献   
67.
本研究基于非平稳序列极值理论,定量分析极端水位事件年超越概率受海平面上升的影响;以工程设计使用年限内极端水位发生概率作为控制条件,构建考虑海平面上升的极值水位计算方法;结合平均海平面的长期变化过程,推算海平面上升下的极值水位。基于全球10个验潮站历史水位观测资料,验证历史平均海平面长期变化与高、低水位耿贝尔分布位置参数变化的一致性以及构建方法的合理性。结合政府间气候变化专门委员会对海平面上升的预测,推算和对比分析不同海平面上升情景下的极值水位,并评估相应极值水位在当前极值分布中的重现期。  相似文献   
68.
罗葆荣  段长春 《天文学报》1997,38(4):386-393
本文用1970-1995年的冕洞资料,分析了冕洞的分布规律,磁场极性的演化特征和冕洞的地磁效应,以及它们与太阳黑子周期的演化关系,得到了一些有意义的结论。特别指出赤道冕洞和极区冕洞具有相反的演化规律和不同的特征。  相似文献   
69.
We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4,1.7,2.3,5.0,8.4,15.4GHz and the European VLBI Network at 6.7 GHz.The low frequency(1.4,1.7 and 2.3GHz)ob- servations reveal a weak and extended steep-spectrum component at about 30mas away at position angle-110°,which may be a remnant emission.The radio structure of OQ 208 con- sists of two mini-lobes at 5.0,6.7,8.4 and 15.4 GHz.Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region.By fitting the 8.4 GHz images from 1994 to 2005,we obtain a separation speed of 0.031±0.006 mas yr~(-1)between the two mini-lobes.This indicates a jet proper motion of 0.105±0.020 c and a kinematic age of 219±42 yr for the radio source.  相似文献   
70.
Radio frequency interference (RFI) test observations were carried out at one of the candidate Square Kilometre Array (SKA) sites in Guizhou province, following the “RFI Measurement Protocol for Candidate SKA Sites” (hereafter RFI protocol). All data (raw and calibrated) are preserved in some suitable format, such as that set by the international RFI working group of the Site Evaluation and Selection Committee (SESC). An RFI test in December 2003 was performed according to Mode 1 of the RFI Protocol, in order to identify technical difficulties which might arise during a co-ordinated RFI measurement campaign over a period of 1 year. In this paper we describe the current equipment, observational technique and data presentation. The preliminary results demonstrate that the RFI situation at Dawodang depression in Guizhou province makes it quite a promising location for the proposed SKA. Furthermore, the first session of the RFI monitoring program, which was made in May 2004, showed that a complete RFI measurement including both modes 1 and 2 of the RFI Protocol would take about 2 weeks. The possible ways to minimize some limitations of the current equipment are also discussed, which will enable us to meet the RFI protocol.  相似文献   
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