就医空间可达性分析的两步移动搜索法——以江苏省东海县为例   总被引：8，自引：5，他引：3  

胡瑞山  董锁成  胡浩 《地理科学进展》2012,31(12):1600-1607

精确评价医疗设施可达性的空间分异样状况是合理配置医疗资源的前提。本文在回顾国内外关于医疗空间可达性研究的基础上, 采用两步移动搜索法, 以江苏省贫困县--东海县为案例, 以行政村和医院为分析单元, 基于迪卡斯特拉算法计算出各村到医院(卫生院)的最短通行时间, 进而分析各村医疗空间可达性分异情况。采用不用服务时间阈值范围进行空间敏感性分析, 综合研判缺医地区分布特点。与传统的医卫人员和人口比值的方法相比, 两步移动搜索法能有效显示县域范围内医疗可达性的空间分异情况。采用较大的时间阈值, 医疗空间可达性分异较为平滑, 采用较小服务阈值则空间分异显著, 缺医范围也较大。东海县医疗空间可达性整体呈单核结构, 并沿主要交通线延伸, 缺医地区多分布于边缘乡镇。提高边缘乡镇的行政村的甲级卫生院等级和乡村道路等级将会改善边缘乡镇的就医可达性。  相似文献   

Experimental study of the density influence on the incipient motion and erosion modes of muds in unidirectional flows: the case of Huangmaohai Estuary   总被引：1，自引：1，他引：0  

Dong Xu  Yuchuan Bai  Chunning Ji  John Williams 《Ocean Dynamics》2015,65(2):187-201

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Effects of Buoyancy and Season on Turion Dispersal of Submerged Macrophyte Potamogeton crispus L          下载免费PDF全文

Dong Xie  Hengjie Zhou  Haiting Ji  Yushun Chen  Shuqing An 《洁净——土壤、空气、水》2015,43(3):324-329

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下扬子黄桥地区构造特征及其与油气的关系          下载免费PDF全文

沈淑鑫  李一泉  崔键  苑京文  贾东 《高校地质学报》2015,21(3):538

下扬子黄桥地区位于下扬子对冲构造带上,记录了多期构造变形,并且保存了较完整的中古生界海相地层,发育多 套烃源岩,具有良好的油气前景。文中采用三维地震工区构造精细解释及运动学正演模拟方法,分析了研究区的构造变形 特征及其变形过程,结果表明黄桥地区中上古生界和下中生界地层在自SE向NW的挤压应力作用下,以前展式发育了多个 断层相关褶皱构造。在构造前锋,断层相关褶皱反向发育,于工区中部偏北西侧形成明显的对冲构造,地层遭受强烈的褶 皱、隆升,构造总缩短率高于47.55%;之后,区域应力场转变为NW-SE向拉张,工区南东侧发育负反转断层,且自南西 向北东负反转程度逐渐变大,由上正下逆复合型转变为似正断层型;此次拉伸正断作用导致断层回滑,形成上白垩统填充 的半地堑构造,对冲构造也受到了一定的破坏。在此基础上,结合前人油气成藏的研究成果,探讨了黄桥构造变形与其油 气成藏的关系,并提出了对冲构造背斜、对冲构造下盘及南东侧的广陵构造背斜为黄桥地区的有利油气区块。研究结果对 进一步认识黄桥及下扬子区的构造变形特征和演化、以及该区的油气勘探提供一定的参考。  相似文献   

吉林省下三叠统卢家屯组LA-ICP-MS锆石U-Pb定年及其地质意义     

聂立军  于宏斌  张建泽  王聪  李栋  李阳 《吉林大学学报(地球科学版)》2015,45(2):453-470

卢家屯组按岩性组合自下而上分为影背山砾岩段、漏斗山杂色岩段、杨树河子黑色岩段,前人采集到的Palaeanodonta-Palaeomutela动物群、Pleuroneia? sp.和叶肢介等生物化石组合指示时代为二叠纪。本次对九台市影背山双顶山卢家屯组建组剖面下、中、上段进行了系统的碎屑锆石U-Pb同位素年代学研究,证实卢家屯组由下至上存在3个最小锆石年龄峰值,分别为(283.4±7.9)、(262.4±3.9)、(255.5±5.8) Ma,确定了卢家屯组的上限为晚二叠世。根据卢家屯组中碎屑锆石存在1 800 Ma和2 500 Ma左右的典型华北板块基底年龄,认为华北板块北缘与其北侧地块群最终闭合时间应为P₃-T₁。  相似文献   

秦皇岛柳江地区辉绿岩脉特征及其成因     

董福湘  曹家鑫  于红玉  闫攀攀 《吉林大学学报(地球科学版)》2015,45(3):820-831

秦皇岛柳江地区辉绿岩脉主要分布于碳酸盐岩出露区的亮甲山、石门寨、潮水峪西北、砂锅店东北、揣庄北、石岭西北、鸡冠山等地,且多以脉状,岩墙、岩床等形式产出。对柳江地区辉绿岩常量元素的分析表明:w(SiO₂)变化较大,且平均值较低;w(FeO+Fe₂O₃)平均值比基性岩类略偏高;w(Al₂O₃)、w(CaO)、w(MgO)、w(K₂O+Na₂O)的平均值均在基性岩类平均值范围内;w(TiO₂)的平均值为1.53%。微量元素富集高场强元素Ta、Nb、Zr、Hf,La/Nb>1,表明岩浆上升过程中受到地壳不同程度的混染;稀土元素球粒陨石标准化分布型图各样品基本一致,呈右倾,稀土元素总量较高,轻稀土较重稀土富集,无明显的Eu异常,反映出岩浆演化过程中分离结晶作用并不明显,样品之间的稀土分馏程度相同。分析结果与研究区辉绿岩的岩相学特征相结合,表明柳江地区辉绿岩属于钾玄岩系列,来自于板内环境。结合研究区大地构造背景,认为研究区辉绿岩脉是钾玄质系列玄武质岩浆沿早期断裂或岩层层面灌入冷凝而形成。  相似文献   

The contribution of aeolian processes to fluvial sediment yield from a desert watershed in the Ordos Plateau,China   总被引：2，自引：0，他引：2       下载免费PDF全文

Wanquan Ta  Haibin Wang  Xiaopeng Jia 《水文研究》2015,29(1):80-89

In arid zones, many active aeolian dunes terminate at ephemeral and perennial desert rivers. The desert rivers show very high rates of sediment transport that cause deleterious downstream effects on the river system and ecology. High sediment loading has been attributed to severe water erosion of sparsely covered watersheds during infrequent but heavy rainfall. Although aeolian erosion is known to lead to high rates of wind‐blown sand transport, direct confirmation of whether the aeolian processes accelerate or inhibit fluvial sediment loss is lacking. Here, we show that an aeolian‐fluvial cycling process is responsible for the high rate of suspended sediment transport in a Sudalaer ephemeral desert channel in the Ordos Plateau of China. Frequent aeolian processes, but low frequency (once every 3 years on average) flooding, occur in this region. Wind‐blown saltating grains appeared to be unable to cross the desert channel because of interruption of channel‐induced recirculating air flow, and therefore tended to settle in the channel during the windy seasons, leading to channel narrowing. During flooding, this narrowed channel was found to yield a threefold increase in suspended sediment loading and a 3.4‐fold increase in the weight percentage of the 0.08–0.2 mm sediment fraction on 18 July 2012. Loss of stored aeolian sand due to channel erosion accounted for about half of the total sediment yield in this watershed. These findings show that aeolian processes play an essential role in accelerating the sediment yield from a watershed characterized by aeolian‐fluvial interplay and also suggest that the drier the region and the greater the aeolian process, the more the aeolian process contributes to fluvial sediment yield. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

南天山巴音布鲁克花岗岩岩体成因:锆石U-Pb定年、Hf同位素及其地球化学证据     

魏强  张成立  何贤英  马中平  高晓峰  杨蓉  黄栋  李平 《地质学报》2017,91(7):1433-1453

巴音布鲁克岩体为南天山北缘出露不多的代表性早古生代花岗岩体,由二长花岗岩和钾长花岗岩构成,两类岩石均显示富集Rb、Ba、Th、K和Pb等LILE,亏损Nb、Ta、Ti等HFSE的活动陆缘弧岩浆地球化学特征。其中,二长花岗岩相对低SiO_2和K_2O,略高CaO、Fe_2O_3T和MgO,具轻重稀土中等分馏、弱负Eu异常的稀土元素分布模式。钾长花岗岩明显高SiO_2,富K_2O,低CaO和MgO,强烈亏损Sr、Ba、Eu、Ti和P,高DI指数(94.31~95.52)和高Rb/Sr比值,轻重稀土中等分馏,呈现出强负Eu异常的稀土分布模式,指示岩浆经历了较高程度演化。二长花岗岩和钾长花岗岩分别获得464.5±3.5Ma和430.2±3.2 Ma的形成年龄,对应的锆石εHf(t)分别为-8.66~-6.56和-5.33~-2.19,Hf陆壳模式年龄TDMC分别为1.58~1.69Ga和1.33~1.49Ga,明显高于其形成年龄,表明岩浆主要源自中元古代基底陆壳物质的部分熔融。结合南天山北缘和中天山南缘类似的同期花岗岩的广泛出现认为,巴音布鲁克岩体中的二长花岗岩和钾长花岗岩分别代表了南天山洋早期俯冲消减活动陆缘弧岩浆和晚期成熟岩浆演化的结果,表明其大洋俯冲消减作用一直持续到志留世仍未结束。  相似文献   

Geochemistry of late Palaeozoic granitoids of the Balkhash metallogenic belt,Kazakhstan: implications for crustal growth and tectonic evolution of the Central Asian Orogenic Belt     

Gang Liu  Shu-Wen Dong  Zheng-Le Chen  Shu-Qin Han  Yi Yang 《International Geology Review》2017,59(9):1053-1081

ABSTRACT

The Balkhash metallogenic belt (BMB) in Kazakhstan is a famous porphyry Cu–Mo metallogenic belt in the Central Asian Orogenic Belt (CAOB). The late Palaeozoic granitoids in the BMB are mainly high-K calc-alkaline and I-type granites, with shoshonite that formed during a late stage. Geochemical analyses and tectonic discrimination reveal a change in the tectonic environment from syn-collision and volcanic arcs during the Carboniferous to post-collision during the Permian. The late Palaeozoic granitoids from the Borly porphyry Cu deposit formed in a classical island-arc environment, and those from the Kounrad and Aktogai porphyry Cu deposits and the Sayak skarn Cu deposit are adakitic. The ε_Nd(t) values for the late Palaeozoic granitoids are between ?5.87 and +5.94, and the ε_Sr(t) values range from ?17.16 to +51.10. The continental crustal growth histories are different on either side of the Central Balkhash fault. On the eastern side, the ε_Nd(t) values of the granitoids from the Aktogai and Sayak deposits are very high, which are characteristic of depleted mantle and suggest that crustal growth occurred during the late Palaeozoic. On the western side, the ε_Nd(t) values of the granitoids from the Borly and Kounrad deposits are slightly low, which suggests the presence of a Neoproterozoic basement and the mixing of crust and mantle during magmatism. The granitoids have initial ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb values of 18.335–20.993, 15.521–15.732, and 38.287–40.021, respectively, which demonstrate an affinity between the late Palaeozoic magmatism in the BMB and that in the Tianshan, Altai, and Junggar orogens.  相似文献   

四川盆地及周缘五峰组-龙马溪组钾质斑脱岩特征及其地质意义   总被引：1，自引：0，他引：1       下载免费PDF全文

卢 斌 邱 振 周 杰董大忠  王红岩薛华庆 周尚文 《地质科学》2017,(1):186-202

四川盆地及周缘五峰组-龙马溪组黑色页岩地层中斑脱岩广泛分布,蕴含着丰富的地球化学信息。开展相关矿物学（XRD）、主量元素（XRF）,以及微量元素（ICP-MS）等分析,结合野外露头观察,对四川盆地及周缘五峰组-龙马溪组黑色页岩地层中斑脱岩进行了分析。研究结果表明：1）斑脱岩主要由伊利石、斜长石、石英等矿物组成;2）主量元素以SiO₂、Al₂O₃、Fe₂O₃、K₂O 为主,其中K₂O/Na₂O介于15.54～270之间;3）微量元素富集Th、U、Pb、Zr、Hf、Ta等高场强元素（HFSE）和Rb、Cs、Ba等大离子亲石元素,亏损La、Ce、Sr、Sm、Eu等元素;4）稀土元素∑REE介于19.58×10^-6～383.88×10^-6之间,平均值为105.43×10^-6,LREE/ HREE介于0.74～12.67之间,平均值为3.93,总体表现为轻稀土（LREE）富集,而重稀土（HREE）亏损,轻、重稀土元素分异明显,Eu表现出一定的负异常,而Ce未出现明显异常。综合分析认为：1）四川盆地及周缘五峰组-龙马溪组斑脱岩具有高钾低钠的特点,与钾质斑脱岩特征相符,且五峰组与龙马溪组斑脱岩特征相似,火山灰物质来源相近;2）原岩构造环境主要为岛弧环境,同时也存在板内环境,火山灰主要来源于北部秦岭地区;3）火山灰可以提高海洋表层初级生产力,为优质页岩有机质形成提供物质基础。  相似文献