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1.
首先对ISC、SCSN与CRN地震目录进行地方时转换 ,并进行序列统计 ,建立了地方时地震时间频度分布 ,然后对地震地方时序列做了频谱分析 ,以提取地震序列中的特征周期成分 .地方时统计结果显示 :( 1 )地震频度在地方时 9时和 1 9时附近最低 ,0时和 1 3时附近最高 ;( 2 )存在以 1 2h和 2 4h为主的周期 ;( 3)较大地震和小地震有不同的活动规律 .频谱分析的结果表明 ,ISC、SCSN与CRN地震地方时序列除了存在 1 2h、2 4h等特征周期对应日潮和半日潮之外 ,还存在 1 1 7a、1a与 1 7 5a等的周期 ,分别对应太阳黑子的活动周期、地球公转及接近对应月球升交点的回归年 .  相似文献   

2.
Nonfullerene acceptors are being investigated for use in polymer solar cells (PSCs), with their advantages of extending the absorption range, reducing the energy loss and therefore enhancing the power conversion efficiency (PCE). However, to further boost the PCE, mobilities of these nonfullerene acceptors should be improved. For nonfullerene acceptors, the π–π stacking distance between cofacially stacked molecules significantly affects their mobility. Here, we demonstrate a strategy to increase the mobility of heteroheptacene-based nonfullerene acceptors by reducing their π–π stacking distances via control over the bulkiness of lateral side chains. Incorporation of 2-butyloctyl substituents into the nonfullerene acceptor (M36) leads to an increased mobility with a reduced π–π stacking distance of 3.45 Å. Consequently, M36 affords an enhanced PCE of 16%, which is the highest among all acceptor-donor-acceptor-type nonfullerene acceptors to date. This strategy of control over the bulkiness of side chains on nonfullerene acceptors should aid the development of more efficient PSCs.  相似文献   

3.
应急地震学的研究进展   总被引：6，自引：0，他引：6       下载免费PDF全文
因孕震过程很难进行直接观测,人类对孕震过程及地震破裂起始过程了解尚少,地震的短临预报在短期难以取得突破。目前美、日等发达国家及地区采取的对策是,强化建筑物抗震设防、深化地震快速应急研究。应急地震学是指在地震发生后以最短的时间确定地震的位置及强度,利用现代通信的快速性,在破坏性地震波(主要是地震面波)达到之前几到几十秒的时间内采取适当的措施,避免一些人员财产损失,形成地震预警系统。应急地震学另一个重要内容则是地震灾害的快速估计,即利用国家及全球的地震波形信息,结合地震灾区的强地面震动记录,快速确定地震的起始、终止时间、地点及能量释放的具体过程,结合当地地质结构信息,从而估计各地区可能的受灾程度,为合理分配救灾资源提供第一手资料。在进一步加密我国地震台网的基础上,在东部平原大都市地区我国应可实现强震(6.5级以上)发生后20秒内快速确定震中及震级,实现地震极早期预警。同时可在几小时内确定地震能量释放过程,形成地面震动理论评估图(shakemap),按照灾情程度合理分配救灾资源,提高救灾效率。  相似文献   

4.
不同意义下的震源深度   总被引：1，自引：0，他引：1  
通过对1993年6月发生在环太平洋地震带上几个5．7级以上地震的分析，利用震中初始确定（PDE）资料及全球数字地震台网（GDSN）宽频带资料，对震源深度进行了初步讨论。  相似文献   

5.
The traditional view of a dry, volatile-poor Moon has been challenged by the identification of water and other volatiles in lunar samples, but the volatile budget delivery time(s), source(s) and temporal evolution remain poorly constrained. Here we show that hydrogen and chlorine isotopic ratios in lunar apatite changed significantly during the Late Accretion (LA, 4.1–3.8 billion years ago). During this period, deuterium/hydrogen ratios in the Moon changed from initial carbonaceous-chondrite-like values to values consistent with an influx of ordinary-chondrite-like material and pre-LA elevated δ37Cl values drop towards lower chondrite-like values. Inferred pre-LA lunar interior water contents are significantly lower than pristine values suggesting degassing, followed by an increase during the LA. These trends are consistent with dynamic models of solar-system evolution, suggesting that the Moon''s (and Earth''s) initial volatiles were replenished ∼0.5 Ga after their formation, with their final budgets reflecting a mixture of sources and delivery times.  相似文献   

6.
赵志谨 《科教文汇》2011,(36):205-206
2008年5月12日,我国四川汶川地区发生里氏8.0级地震,特大自然灾害牵动了全中国人民的心。尽管地震已经过去了,但是留给我们很多需要思考和学习的地方。作为我们一衣带水的邻国,日本素以地震多而闻名。全世界每年所发生的6级以上地震,有20%发生在日本。据不完全统计,日本全国平均每天有4次地震,6级以上地震每年也有1次。  相似文献   

7.
The Chinese lunar probe Chang''e-4 (CE-4) landed in the Von Kármán crater within the South Pole–Aitken (SPA) basin on the far-side of the Moon on 3 January 2019. Following this, the moon rover Yutu-2 separated from the CE-4 lander and started its travels and exploration on the far-side of the Moon. Before this landing, humans had remotely observed the far-side of the Moon with lunar satellites. However, it was the first time that a man-made spacecraft had landed there and actually left behind wheel prints belonging to humanity.Since China''s Lunar Exploration Project (CLEP), or Chang''e Project, started in 2004, China has accomplished the first two steps of its three-step plan of ‘Orbiting, Landing and Returning’. CE-3 and CE-4 landed successfully on the near-side and far-side of the Moon, respectively. In the near future, CE-5 will land again on the near-side of the Moon and take lunar rock and soil samples back to Earth, thus completing the three-step plan of CLEP. In April 2019, National Science Review (NSR) interviewed three key figures of CLEP: CLEP Chief Engineer Weiren Wu (), the first CLEP Chief Scientist and CLEP senior consultant Ziyuan Ouyang (), and CLEP third phase Vice-Chief Engineer, CE-4 Ground Research and Application System Director Chunlai Li (). They talked about the scientific expectations and future plans of China''s lunar and deep space exploration.  相似文献   

8.
Chang’E-4 landed in the South Pole-Aitken (SPA) basin, providing a unique chance to probe the composition of the lunar interior. Its landing site is located on ejecta strips in Von Kármán crater that possibly originate from the neighboring Finsen crater. A surface rock and the lunar regolith at 10 sites along the rover Yutu-2 track were measured by the onboard Visible and Near-Infrared Imaging Spectrometer in the first three lunar days of mission operations. In situ spectra of the regolith have peak band positions at 1 and 2 μm, similar to the spectral data of Finsen ejecta from the Moon Mineralogy Mapper, which confirms that the regolith''s composition of the landing area is mostly similar to that of Finsen ejecta. The rock spectrum shows similar band peak positions, but stronger absorptions, suggesting relatively fresh exposure. The rock may consist of 38.1 ± 5.4% low-Ca pyroxene, 13.9 ± 5.1% olivine and 48.0 ± 3.1% plagioclase, referred to as olivine-norite. The plagioclase-abundant and olivine-poor modal composition of the rock is inconsistent with the origin of the mantle, but representative of the lunar lower crust. Alternatively, the rock crystallized from the impact-derived melt pool formed by the SPA-impact event via mixing the lunar crust and mantle materials. This scenario is consistent with fast-cooling thermal conditions of a shallow melt pool, indicated by the fine to medium-sized texture (<3 mm) of the rock and the SPA-impact melting model [Icarus 2012; 220: 730–43].  相似文献   

9.
慢地震研究中的一些问题   总被引：16，自引：0，他引：16  
对慢地震研究中一些问题的研究现状进行了综述 ,包括 :慢地震的定义及特征、慢地震的识别和定位、慢地震孕育的地质构造背景和产生的物理机制、慢地震孕育和发生过程的数值模拟等 ,也涉及到长周期前兆与慢地震的关系、慢地震与应力触发、地震活动性的关系 .笔者认为 ,在中国起动慢地震研究 ,首先应解决慢地震识别、定位和震源机制问题 ,确切验证中国大陆是否存在慢地震 .为此需要加强各个地区的台网观测密度和发展宽频带地震仪、应变仪、GPS、InSAR的综合观测 ,并应加强对多种资料的综合理论分析及模拟的能力 .  相似文献   

10.
针对中强地震前是否会出现地震活动性增强现象的问题,研究了1990～2003年中国MS7.0以上地震.对于同一个地震事件,考虑了多个不同的时间和空间尺度,结果表明,中强震前的地震活动性远比用简单的应变加速释放模型来描述复杂得多.因此,将应变加速释放模型应用于地震危险性估计,仍需做更多的研究.  相似文献   

11.
西南天山地区的地震重定位与活动性分析   总被引：1，自引：0，他引：1  
利用双差地震定位方法对西南天山地区24个台站记录到的864个地震的P波绝对到时数据和相对到时数据进行了地震重新定位,并给出了522个地震的震源参数.重定位后的地震定位精度均有了显著提高.重新定位后,本研究区域内地震活动密集成东西向与北西向线性排列分布,与已知活动断裂呈更加清晰的联系.  相似文献   

12.
Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO2 nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li+ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO2/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO2/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g–1 at 1 C (1 C = 335 mA g–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g–1, respectively. Moreover, the formed Li2Ti2O4 nanodots facilitate reversed Li+ insertion-extraction during the cycling process. The above results indicate the best performance of TiO2-based materials as anodes for lithium-ion batteries reported in the literature.  相似文献   

13.
本文报道刺五加Eleutherococcus seticosus(Rupr．et Maxim．)Maxim的花朵酬物、访花者类别、访花 者在花序上的访花行为、访花频率及传粉效果。主要结果如下:(1)每朵雄花可提供的报偿是58 000～ 81 000粒花粉,5.5～8.0 µl／d×2～4d花蜜。每朵雌花仅可提供4.0～8.0µl／d× 2～3 d花蜜,不能提 供花粉。每朵两性花可提供19 000～54 000粒花粉和7.0～10.0 µl／d× 2～6 d花蜜。(2)花粉提供者 (雄花和两性花)提供报偿的日期是开花后1～3天,花粉接受者(雌花和两性花在柱头外翻变白时)是 开花后5～7或7～9天,这进一步证实了剌五加雄蕊先熟。另外,花粉提供者提供花蜜的时间在一天中 是8:30至15:30,其高峰是9:00～15:00;花粉接受者提供花蜜的时间在一天中是10:30至16:30,其高 峰是11:00～16:00。这种时间差异可能是刺五加影响传粉者流向(从花粉提供者到花粉接受者)的关键 因素。(3)在刺五加花朵上记录到的访花昆虫有50余种,分别隶属于膜翅目、鳞翅目、鞘翅目、双翅目和 半翅目。在不同天气、不同生境、不同性别的植株记录到的访花频率及高峰时间不同:花粉提供者的 访花高峰早于花粉接受者的;雄株上的访花频率高于雌株的;两性株接受花粉时的访花频率高于提供花 粉时的;而天气越晴朗,刺五加地块(patch)越大,则访花频率越高;每日接受光照越早,访花高峰越早。 (4)从传粉效果看,刺五加种子的形成完全依赖于传粉昆虫的活动。其中,蜂类,如熊蜂、花蜂、切叶蜂、胡蜂和蜜蜂等是最有效的传粉者,其它昆虫如粉蝶、食蚜蝇、寄蝇和鳃角金龟等对传粉也有帮助。  相似文献   

14.
Tumor lysis syndrome has been observed in patients with malignancies with high cellular burden and high cell turnover, tumor sensitive to therapy, especially after initiating medical treatment. It very rarely occurs spontaneously. The case described here is of 6 months male infant who presented with fever since 1 month and loose stools associated with blood since 15 days. The laboratory investigations showed lactate dehydrogenase (LDH) of 6,192 IU/L and serum uric acid 18.2 mg/dl along with pancytopenia. The infant presented with electrolyte abnormalities and renal failure.  相似文献   

15.
The goal of this work is to determine the role of the autoimmune cells in multiple sclerosis (MS) induction and the immunomodulatory mechanism of therapy with tyrosine kinase inhibitors (TKIs) in MS attenuation. Samples (5 × 105 cells per well) of C6 and primary rat astrocytes were stimulated with 10 ng/mL of platelet-derived growth factor (PDGFbb) as a positive control forming a mouse model of MS. PDGFbb was added to the astrocytes in the absence or presence of 0.1 and 1 μM of imatinib. Proliferation of C6 and primary rat astrocytes samples were assessed for samples staging by the addition of 1 μCi of 3H-thymidine per well. Samples of RAW 264.7 cells were stimulated for 48 h with 10 ng/mL of PDGFbb in the absence or presence of 0.1 and 1 μM of sorafenib. Tumour necrotic factor (TNF) levels in culture supernatants from RAW 264.7 cells were measured by ELISA. The histologic grade (HG) and the level of TNF of the mouse model of MS was 1/5 and 5 times respectively of those in the control one to clarify that MS induction is due to a major decrease in HG inversely proportional to the accompanied increase in TNF level perpetuating local inflammation and demyelination in MS lesion. The addition of 0.1 and 1 μM doses of imatinib increased HG of the mouse model of MS by 6 and 11 times respectively while 0.1 and 1 μM doses of sorafenib decreased TNF level to be 1/2 and 1/5 of that in the mouse model of MS respectively restoring normal rate of TNF level of normal lesion to show that HGand TNF level would be strongly inversely correlated (r = −0.99) in attenuating MS effectively by TKIs therapy but not in an inverse proportion as in MS induction.  相似文献   

16.
由互补性专利形成的专利联盟能够克服“专利丛林”问题,提高纵向产业链的经济效率是对专利联盟的一般共识。这一论断是建立在古诺标价模型基础之上的。本文建立了更加符合现实的关于专利许可的两阶段讨价还价博弈模型,得出的结论是无论下游市场是完全竞争市场还是寡头垄断市场,都存在一个弱占优战略均衡。均衡时,产业链联合利润达到最大,且产出等于专利联盟进行联合许可的产出,而总许可价格比专利联盟时的许可价格更低。 这意味着由传统的古诺互补品问题而引发的“古诺效应”并不成立,互补性专利的交易并不需要通过专利联盟许可来克服专利许可交易中出现的所谓诸如“专利丛林”、“费用叠加”、“专利挟持”、“反公地悲剧”等问题。  相似文献   

17.
The circadian periodicity of plasma lipid peroxide levels and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were studied in 50 clinically, bacteriologically and radiologically proven fresh cases of pulmonary tuberculosis (age: 21–45 years) and 60 age-matched healthy volunteers with diurnal activity from 06∶00 to about 22∶00 and nocturnal rest. A marked circadian variation in plasma lipid peroxide level was recorded in healthy subjects and pulmonary tuberculosis patients with significant amplitude and acrophase around 16∶21 and 17∶12 respectively. The acrophase tended to be delayed in tuberculosis patients. Furthermore, a statistically significant circadian rhythm was found in SOD, CAT and GPx activities in normal volunteers and pulmonary tuberculopsis patients. SOD and CAT enzyme activity was noted to be maximum at 06∶00 and minimum at 00∶00 in tuberculosis patients. The circadian acrophase for GPx activity was recorded at 16∶15 in normals and around 22∶45 in patients. Moreover, the activity was found to be decreased at all sampling hours during 24-hours sleep-awake period in patients in comparison to healthy counterparts. The MESOR and circadian amplitude also decreased markedly. The decreased activity of measured antioxidant enzymes in pulmonary tuberculosis patients could probably be associated with oxidative stress and/or decreased anti-oxidant defensive mechanism in such patients.  相似文献   

18.
地震灾害给人类带来了巨大的生命和财产损失,为了尽可能地降低地震灾害损失,人类需要不断地寻找更科学的地震预测预报方法。虽然目前的地震预测预报方法的研究已经取得了很多可喜的进步,但科学进展与实现科学预报地震的目标之间还存在很大的距离。本文将对K线理论在地震趋势分析中应用的可行性进行研究,希望能够提供一种新的地震趋势分析思路。本文根据地震活动趋势分析与投资品价格走势分析的比较,提出了可以用K线理论进行地震活动趋势分析的观点,并定义了地震K线的画法,还通过对徐州周围的历史地震K线图的分析,验证了K线理论在地震趋势分析中应用的可行性。  相似文献   

19.
微弱信号检测技术的研究   总被引：1，自引：0，他引：1  
微弱信号检测就是利用近代电子学和信号处理方法从噪声中提取有用信号,其关键在于抑制噪声,恢复、增加和提取有用信号.本文将从信号处理系统信噪比的改善来简单地论述微弱信号检测的原理,重点介绍了用相关检测法和取样积分法检测微弱信号的原理、方法和应用.  相似文献   

20.
Retrieving historical fine particulate matter (PM2.5) data is key for evaluating the long-term impacts of PM2.5 on the environment, human health and climate change. Satellite-based aerosol optical depth has been used to estimate PM2.5, but estimations have largely been undermined by massive missing values, low sampling frequency and weak predictive capability. Here, using a novel feature engineering approach to incorporate spatial effects from meteorological data, we developed a robust LightGBM model that predicts PM2.5 at an unprecedented predictive capacity on hourly (R2 = 0.75), daily (R2 = 0.84), monthly (R2 = 0.88) and annual (R2 = 0.87) timescales. By taking advantage of spatial features, our model can also construct hourly gridded networks of PM2.5. This capability would be further enhanced if meteorological observations from regional stations were incorporated. Our results show that this model has great potential in reconstructing historical PM2.5 datasets and real-time gridded networks at high spatial-temporal resolutions. The resulting datasets can be assimilated into models to produce long-term re-analysis that incorporates interactions between aerosols and physical processes.  相似文献   

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