Small-scale cosmic microwave background polarization anisotropies due to tangled primordial magnetic fields     

Kandaswamy Subramanian  T. R. Seshadri  John. D. Barrow 《Monthly notices of the Royal Astronomical Society》2003,344(2):L31-L35

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PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER          下载免费PDF全文

史玉光  李清泉 《Acta Meteorologica Sinica》1996,(2)

Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February.  相似文献   

High-speed outflows driven by the 30 Doradus starburst     

M. P. Redman  Z. A. Al-Mostafa  J. Meaburn  M. Bryce 《Monthly notices of the Royal Astronomical Society》2003,344(3):741-747

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加强技术创新服务地质调查——庆祝探矿工艺研究所成立30周年   总被引：1，自引：1，他引：0  

胡时友  彭文范  周良宗 《探矿工程》2008,35(7):1-4

为加强地质探矿技术力量,改变地质装备落后现状,经国务院批准,1978年8月8日成立了探矿工艺研究所。30年来,经过新老两代工艺所人的艰苦奋斗、刻苦钻研、勇于创新,在科研攻关、成果转化、基地建设和管理等方面都取得了可喜的成绩,为国家的地质科学事业做出了贡献,目前已成为一个“以勘查技术为基础,以承担地质调查任务和科研项目、提供勘查与监测技术方法和技术服务为手段,以服务国家经济建设、社会发展和地质工作为目标,以探矿工艺技术和地质灾害监测防治技术研发为主业”的地质调查科研机构。回顾了工艺所艰苦创业、改革进取的发展历程,对科技体制改革、专业结构调整、人事分配制度改革、地质调查和科研工作进行了总结,展示了丰硕的科研成果和强劲的科技实力;指出了工艺所在“十一五”期间地质调查和科研工作的重点领域和优先发展方向。  相似文献   

胶州湾营养盐的现状和变化   总被引：28，自引：3，他引：28  

沈志良 《海洋科学》1997,21(1):60-64

报道了１９９１年５月至１９９４年２月１２个航次胶州湾ＮＯ３－Ｎ，ＮＯ２－Ｎ，ＮＨ４－Ｎ，ＰＯ４－Ｐ和ＳｉＯ３－Ｓｉ的时空分布基本特征，６０年代于至９０年代的变化表明，胶州湾营养盐的浓度和分布已发生显变化。尤其从６０年代至８０年代，３０年来，胶州湾中东部水城ＰＯ４－Ｐ，ＮＯ３－Ｎ和ＮＨ４－Ｎ浓度分别增加２．２，７．３和７．１倍，ＴＯＮ浓度也增加了３．５倍，ＴＩＮ／ＰＯ４－Ｐ从１０增加至２４．２；Ｔ  相似文献   

2007年夏季江淮强降水过程中10~30d低频变化及其与对流层上层波包活动的联系          下载免费PDF全文

陈丹萍  管兆勇  侯俊  奚子惠 《大气科学学报》2016,39(2):177-188

利用NCEP/NCAR再分析和全国740站逐日降水资料,运用一点滞后相关等方法,对2007年夏季江淮流域强降水期间低频振荡的波动活动特征及其与降水低频变化的联系进行了分析。结果表明,在2007年夏季降水中,降水低频分量起着重要作用。降水的低频振荡主周期为10~30d,降水距平时间序列与10~30d低频分量具有较好的对应关系。低频扰动在对流层上层和低层都呈现波列状分布,且在降水活跃位相时,低频环流在高、低层具有斜压结构。在对流层上层,低频扰动有缓慢的东移倾向,相速度为每天2~3个经度。西风带中存在多次移动性波列向下游的传播,且在120°E以西以每天14经度的群速度向下游频散能量,表明10~30d低频波动具有明显的下游发展特征。在强降水开始5d前,低频波动与能量可起源于高纬的乌拉尔山附近,沿着西北-东南向的路径向下游传播。下游发展的低频波动为江淮流域带来了能量,为强降水的发生提供了条件。这些结果加深了人们对低频波动在江淮流域强降水过程中所起作用的认识,可为寻找江淮流域强降水过程预报线索提供科学依据。  相似文献   

菲律宾迪纳加特岛30^#矿权区红土型镍矿床地质特征及成矿作用探讨          下载免费PDF全文

江胜国  王志刚  曹健 《地质找矿论丛》2018,33(2):299-305

30~#矿权区位于菲律宾迪纳加特岛北部,区内发育有红土型镍矿床。本次勘查圈定4处矿(化)体,其中以Ⅰ、Ⅱ、Ⅲ矿(化)体的矿化范围较大,厚度变化系数为45%~50%(相对稳定),经济价值较高。红土型镍矿体平面上呈地毯状展布于地表,厚度受地形控制,富镍矿体分布于矿权区东部的5、6、11、12小区;剖面上从地表向深部矿体为铁质红土层、松散红土层及高岭土化蛇纹石化橄榄岩层。30~#矿权区红土镍矿矿床的形成经历了从普通矿到富矿两个阶段,红土镍矿石属于酸性矿石。  相似文献   

30—50天低频振荡和准双周振荡对持续异常的影响     

孙永罡  陈久康 《南京气象学院学报》1992,15(3):368-376

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SEDIMENT MOBILIZATION BY SURFACE EROSION IN MIDDLE MOUNTAIN CATCHMENTS OF NEPAL     

Juerg MERZ Gopal NAKARMI Pradeep M. DANGOL Madhav P. DHAKAL Bhawani S. DONGOL Rolf WEINGARTNER 《国际泥沙研究》2006,21(3):180-199

1 INTRODUCTION Soil erosion in the foothills of the Hindu Kush-Himalayas (HKH) is considered to be a hot topic in land degradation research in the region (Scherr and Yadav, 1996). The land degradation research has mainly addressed the issue of topsoil los…  相似文献   

Application of an ecosystem model for the environmental assessment of the reclamation and mitigation plans for seagrass beds in Atsumi Bay   总被引：1，自引：0，他引：1  

Akio Sohma  Yasuyuki Sekiguchi  Kisaburo Nakata 《Estuarine, Coastal and Shelf Science》2009

An ecosystem model was used to evaluate the effects of reclaiming seagrass beds and creating artificial shallows with seagrass beds to mitigate the effects of the reclamation. The applied model can simulate the pelagic and benthic ecosystems including seagrass beds and tidal flats. The objectives of this study were (a) to investigate the likelihood of cultivating and maintaining seagrass beds in artificial shallows (Part 1), and (b) to understand the effects of the reclamation of seagrass beds and the creation of artificial shallows on the water quality in the estuary (Part 2). In Part 1, first, the nutrient turnover rates due to both biochemical and physical processes in the natural seagrass beds where reclamation is proposed were analyzed. Biological processes rather than physical processes were the most significant driving forces of nutrient cycles in seagrass beds. Second, the effects of filter feeding benthic fauna (suspension feeders) in the seagrass beds were analyzed. The scenario with suspension feeders resulted in higher transparency of the water column (8.7% decrease in the light attenuation coefficient) and an increase in nutrient supply (24.9% increase in NH₄-N in the water column) contributing to the high specific growth rate of seagrass. Third, the specific growth rate of seagrass on the proposed artificial shallows was measured. The value on the artificial shallows set at a depth of datum line minus 0.8 m (D.L. − 0.8 m) was approximately the same as that of the natural seagrass beds. In Part 2, first, water quality in the estuary was compared among the scenarios with/without natural seagrass beds and artificial shallows. Then, the defined values of the water purification capability of (a) artificial shallows with/without seagrass beds, and (b) natural seagrass beds per unit area were evaluated. The reclamation of the natural seagrass beds resulted in a decrease of the removal of phytoplankton and detritus from the pelagic system (i.e. resulted in a loss in the purification rate). In contrast, the creation of artificial shallows resulted in an increase of the removal of phytoplankton and detritus from the pelagic system (i.e. resulted in a gain in the purification rate). Based on an annual average, approximately twice as much phytoplankton was removed from the artificial shallows at the depth D.L. − 0.8 m, than at the depth, D.L. − 1.5 m, and the artificial shallows with seagrass beds removed pelagic DIN and DIP at a rate 120% higher than that without seagrass beds.  相似文献