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1.
Zhi-gen Yang Wen-yao Zhu C. K. Shum Feng-chun Shu 《Chinese Astronomy and Astrophysics》2002,26(4):303-502
The vertical deformation rates (VDRs) and horizontal deformation rates (HDRs) of Shanghai VLBI station in China and Kashima and Kashima34 VLBI stations in Japan were re-analysed using the baseline length change rates from Shanghai to 13 global VLBI stations, and from Kashima to 27 stations and from Kashima34 to 12 stations, based on the NASA VLBI global solution glb1123 (Ma, 1999). The velocity vectors of the global VLBI stations were referred to the ITRF97 reference frame, and the Eulerian vectors of different models of plate motion were used for comparative solutions. The VDR of Shanghai station is estimated to be −1.91±0.56 mm/yr, and those of Kashima and Kashima34 stations, −3.72±0.74mm/yr and −8.81±0.84mm/yr, respectively. The difference between the last two was verified by further analysis. Similar estimates were also made for the Kokee, Kauai and MK_VLBA VLBI stations in mid-Pacific. 相似文献
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通过分析CTL-713C型天气雷达发射机各组成部分工作原理,得出发射机工作信号流程示意图,提出了发射机故障诊断方法和原则,对发射机几种常见的故障现象及检修方法进行了分类,并通过实例分析对发射机故障诊断方法和原则进行了检验. 相似文献
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广东大亚湾石珊瑚群落的分布及动态变化 总被引:2,自引:0,他引:2
2006年6月对位于南海北部亚热带的大亚湾和大鹏湾石珊瑚群落的分布、种类和覆盖率进行了调查,结果显示大亚湾共有石珊瑚24种,以秘密角蜂巢珊瑚(Favites abdita)为优势种,总覆盖率为20%,大鹏湾有石珊瑚21种,以精巧扁脑珊瑚(Platygyra daedalea)为优势种,总覆盖率为7.9%。大亚湾石珊瑚群落健康状况良好,但生长稀疏,群落密度低,空间结构简单,生长带窄;与1964年、1983年、1984年和1991年的调查结果相比,覆盖率从76.6%下降到20%,优势种从枝状的霜鹿角珊瑚(Acropora Pruinosa)转变成块状或皮壳状的秘密角蜂巢珊瑚,群落生态退化严重,主要原因可能是人为破坏活动对珊瑚本身以及生长环境造成的压力所致,包括过度捕捞、盗采珊瑚、沿岸施工和水体污染等,建议采取相应的保护措施。 相似文献
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Effect of Bacillus mucilaginosus on weathering of phosphorite and a preliminary analysis of bacterial proteins 总被引:3,自引:0,他引:3
The authors investigated the effect of Bacillus mucilaginosus on weathering of phosphorite. Analysis of different proteins was of significance in exploring the molecular biological mechanism in the bacterial weathering process. The concrete methods are described as follows: Mineral powder was put into liquid culture medium and B. mucilaginosus was incubated in the medium. The control (group) had no mineral powder in the medium. The treatments and controls were cultured simultaneously under the same condition. In a few days, the supernatant was filtrated, the main cations (Ca^2+, Mg^2+, Na^+, Mn^2+, Al^3+, Fe^3+, K^+) were measured by ICP-OES, and the contents of water soluble phosphorus (Pws) and silicon (Siws) were determined by colorimetry. The residual solid was weighed on the filter paper, followed by digestion with concentrated HNO3. The concentrations of the main cations and Pws, Siws in the digest liquid were measured by using the method mentioned above. After the supernatant was centrifuged, the precipitation was used to analyze the protein differences between the treatment groups and the control groups by 2-dimentional gel electrophoresis (2-DE). The experimental results showed that apatite and quartz were partially weathered, but kaolinite was dissolved completely. The population of bacteria increased when mineral powder was added in the liquid medium. Software analysis and comparison of the 2-DE pictures of bacterial proteins revealed 1134 visible protein spots in the treatment group, and 729 visible protein spots in the control group. To compare the bacterial protein expression contents of the treatment group with those of the control group, there were 496 different protein spots, including 214 protein spots which indicated that the protein contents increased, 75 protein spots were indicative of a decrease, and 207 proteins were newly synthesized. It is proposed that the increased bacterial contents may be related to some protein expression and activation after the 相似文献
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2006年冬半年我国霾天气特征分析 总被引:23,自引:1,他引:23
利用常规气象观测资料和NCEP再分析资料,对2006年10月至2007年2月我国霾天气的时空分布、环流形势特征和霾天气过程中气象要素的变化特征进行了统计和天气学分析.结果表明:2006年10月、12月、1月和2月是我国霾频发时期,11-14时发生的范围最大.霾主要发生在中阻塞、南支槽和纬向型三种不同的环流形势下.霾天气发生时的气象要素分布存在南北区域性差异,其中湿度的差别最为显著.14时华南地区相对湿度最大值为80%左右,长江中下游地区为70%,而华北地区只有60%.24小时气压减弱有利霾的发生.华北地区24小时负变温,而长江以南地区正变温时,霾更容易发生.能见度最小值的分布表明,广东、黄淮等部分地区发生霾时能见度较其他区域更小,只有2km左右.这些对于了解霾的发生规律和预报具有重要意义. 相似文献
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Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature (SST).The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation (BDC),but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase. 相似文献
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Mechanisms for the spatio-temporal development of the Tropical Pacific Meridional Mode(TPMM) are investigated using a coupled ocean-atmosphere model and observations.In both observations and the model,this meridional mode displays decadal variations and is most pronounced in spring and early summer.The model simulation suggests that once SST anomalies in the subtropical northeastern Pacific are initiated,say by northeasterly trade wind variability,perturbations evolve into a merdional dipole in 2-3 months.A... 相似文献