An explicit method for numerical simulation of wave equations

In this paper, a method to develop a hierarchy of explicit recursion formulas for numerical simulation in an irregular grid for scalar wave equations is presented and its accuracy is illustrated via 2-D and 1-D models. Approaches to develop the stable formulas which are of 2M-order accuracy in both time and space with M being a positive integer for regular grids are discussed and illustrated by constructing the second order (M = 1) and the fourth order (M = 2) recursion formulas.     

Investigation of ionospheric TEC changes related to the 2008 Wenchuan earthquake based on statistic analysis and signal detection

Ionospheric TEC (total electron content) time series are derived from GPS measurements at 13 stations around the epicenter of the 2008 Wenchuan earthquake. Defining anomaly bounds for a sliding window by quartile and 2-standard deviation of TEC values, this paper analyzed the characteristics of ionospheric changes before and after the destructive event. The Neyman-Pearson signal detection method is employed to compute the probabilities of TEC abnormalities. Result shows that one week before the Wenchuan earthquake, ionospheric TEC over the epicenter and its vicinities displays obvious abnormal disturbances, most of which are positive anomalies. The largest TEC abnormal changes appeared on May 9, three days prior to the seismic event. Signal detection shows that the largest possibility of TEC abnormity on May 9 is 50.74%, indicating that ionospheric abnormities three days before the main shock are likely related to the preparation process of the M_S8.0 Wenchuan earthquake.     

旅游空间营造的理论与实例探析——以重庆三峡广场为例

尽管研究旅游空间已有多年历史,但从景观、建筑、游憩的角度入手并不多见.在此基础上,探讨旅游空间营造的基本理论.首先,从图底理论、联系理论、场所理论的角度构思了旅游空间营造的设想;其次,指出旅游空间营造的核心理念--场所精神,并对其影响因素作了详细的分析;第三,从物质性空间与非物质性空间出发,深入解剖重庆三峡广场旅游空间营造的具体内容;最后,对旅游空间可持续发展作出展望.     

喀斯特山区不同复种指数条件下的土壤质量变化——以普定县猫洞小流域为例

选择贵州中部喀斯特山区普定县猫洞小流域地区,通过长期受不同生产行为影响的区域（低复种旱作区、高复种旱作区、高复种复合农作区）的土壤采样分析,结果表明:喀斯特山区小流域土壤在长期不同生产行为影响下,从低复种指数旱作区、高复种指数旱作区到高复种指数复合农作区,土壤容重、粘粒含量减小,而土壤有机质、腐殖酸含量、全氮、碱解氮、速效磷、速效钾、土壤呼吸强度、脲酶、磷酸酶、蛋白酶活性含量依次增大,土壤全钾含量和过氧化氢酶活性却依次减小。聚类分析结果进一步表明:高复种复合农作区土壤保肥、保水、供肥等状况最好;而低复种旱作区土壤质量和供肥、保肥、保水等性状最差。上述结果说明,农户的不同生产行为对土壤质量有一定的影响。      

从5.12汶川地震前后分量应变仪观测到的应变异常看建设密集应变观测网络的必要性

2004年我国“数字地震观测网络工程”决定在我国布设40套YRY-4型四分量钻孔应变仪。本文介绍5·12汶川地震前后分量应变仪观测到的应变异常及根据应变异常与其它观测手段对8·30会理6.1级地震较准确的预测。据此,提出我国有必要加速应变密集台网建设。     

基于多源数据的湖北省COVID-19疫情时空扩散影响因子分析

利用武汉市人口迁出规模指数与武汉迁入到湖北各市人口比例的乘积(MSI)及市内交通强度(TI),建立时间回归模型,分析各市的COVID-19每日新增病例;利用交通可达性及各市GDP比例,建立空间回归模型,分析湖北省各市COVID-19的万人累计感染率.结果显示:1)基于人口迁徙数据与各市每日新增COVID-19病例构建的...     

大型水库分层期和混合期溶存温室气体空间变化及排放通量

水库作为温室气体的重要来源,对区域气候变化有不可忽略的影响。然而,目前对水库溶存温室气体的空间异质性及垂向特征的认知仍然欠缺。为了揭示水库分层期和混合期溶存温室气体空间特征及排放通量,也为厘清水库温室气体产生和排放的关键过程提供重要支撑。研究选择东北地区大型水库——汤河水库为对象,于2021年7—9月和10月(分别代表水库分层期和混合期)对水库不同位置(坝前、库中和库尾)开展溶存温室气体垂向分层监测。研究结果显示,水库CH₄排放通量变化范围为0.018～0.174 mmol/(m²·d),是大气CH₄的源,空间分布为库尾>库中>坝前;CO₂通量为-4.91～58.77 mmol/(m²·d),除分层期东支库尾,其余点位均表现为大气CO₂的源,空间分布为坝前>库中>库尾。时间上,分层期CH₄排放通量(0.071±0.044 mmol/(m²·d))高于混合期((0.027±0.008) mm...     

太原地震台地磁相对记录室建设中的质量控制

中国地震局在“十五”期间将太原地磁台列为地磁基本台,2007年3～8月进行相对记录室的重建工作,本文对地磁观测室建设中是如何做好质量控制的问题做了一些总结,为今后的地磁台站建设提供参考。     

Paleoproterozoic granitic gneisses of the Dinggye and LhagoiKangri areas from the higher and northern Himalaya, Tibet: Geochronology and implications

Granitic gneisses have been widely found in crystalline rocks in the Dinggye area of the Higher Himalaya (HHM) and the LhagoiKangri area of the North Himalaya (NHM), Tibet. In the HHM, the gneisses intruded in the granulite-amphibolite facies metamorphosed sedimentary rocks, known as Nyalam group. In the NHM, the gneisses intruded in the amphibolite facies metamorphosed ones, known as LhagoiKangri group. These granitic gneisses are peraluminous monzonitic granites in terms of their mineral assemblage, and are considered as being derived from metamorphosed sedimentary rocks by anatexis based on the transitional relationship of the gneisses with their migmatitized wall rocks. Zircons are similar in crystal shape and interior structure from both gneisses. Most of them are euhedral or subhedral elongated prism-shaped transparent crystals, with fine oscillatory zoning, showing the magmatic genesis. Some of them are short prism-shaped and with relict core inherited from magma source and oscillatory zoning mantle crystallized from magma. SHRIMP U-Pb dating of zicons shows that both the granitic gneisses in the HHM and NHM are Paleoproterozoic (1811.6±2.9 Ma and 1811.7±7.2 Ma, respectively). These ages are similar to those (1815 to 2120 Ma) from granitic gneiss which is widely distributed in the Lesser Himalaya (LHM). The ages of inherited zircons (>2493.9±7.0 Ma, 2095.8± 8.8 Ma, 1874±29 Ma) exhibit the possible presence of several thermal events in Paleoproterozoic. All of the ages suggest the same India basement beneath the different units in Himalaya area, and do not support the idea that the HHM and NHM are accretionary terranes in Pan-Africa orogenic event. The fact that the basement in HHM is as old as or even younger than LHM is inconsistent with the presently prevalent orogenic models such as either extrusion of low-viscosity mid-crust or orogenic channel.     

九龙江口磷的界面分配和转移

１９９２年８月航次调查结果表明，九龙江口水体中磷的迁移呈保守行为，ＴＰ和ＰＰ含量随着海水盐度的降低呈增加趋势，ＤＰ含量刚好相反；Ｓ〈１５的低盐区，盐度对磷迁移的影响比较显著。