银同位素地球化学综述

银(Ag)是生活中常见的贵金属元素.Ag有2个稳定同位素107Ag和109Ag.随着多接收电感耦合等离子体质谱仪(MC-ICP-MS)的应用,国内外对银同位素体系开展了一系列研究.Ag在矿床中常与Au元素共生,且Pd-Ag同位素体系可作为早期太阳系演化计时器,因此在天体化学、环境科学、矿床地球化学等领域都具有广泛应用....     

法国旅游办公室的功能及启示

法国旅游办公室在法国旅游业发展中发挥了非常重要的作用,为当地和全国旅游业创造的附加价值为举国公认。鉴手我国旅游发展中存在的一些问题,我们可以从法国旅游办公室管理体制得到对我国旅游业发展的多方面启示。主要包括：强化行业组织及行业协会的力量;优化旅游管理机构的组织架构;健全旅游市场信息网络系统,提高旅游信息利用率;建立我国的旅游服务办公室体系。     

国内外开发区土地集约利用的途径及其启示

在国家宏观政策调控的背景下、开发区空间扩展与土地稀缺性矛盾目益会进一步突出。解决这一问题的出路在于提高开发区土地集约利用的程度。本文在对国内外开发区的土地集约利用手段与控制方法进行梳理的基础上,从土体利用控制的实施主体、实施程序等几个方面对国内外的情况做了比较分析,从借鉴国外开发区土地集约利用的经验和推广总结国内开发区已有的土地集约利用的经验两个角度提出了国内开发区土地进一步的集约化利用的对策建议。     

An unsplit complex frequency-shifted perfectly matched layer for second-order acoustic wave equations

The perfectly matched layer(PML) boundary condition has been proven to be effective for attenuating reflections from model boundaries during wavefield simulation. As such, it has been widely used in time-domain finite-difference wavefield simulations. The conventional PML has poor performance for near grazing incident waves and low-frequency reflections. To overcome these limitations, a more complex frequency-shifted stretch(CSF) function is introduced, which is known as the CFSPML boundary condition and can be implemented in the time domain by a recursive convolution technique(CPML). When implementing the PML technique to second-order wave equations, all the existing methods involve adding auxiliary terms and rewriting the wave equations into new second-order partial differential equations that can be simulated by the finite-difference scheme, which may affect the efficiency of numerical simulation. In this paper, we propose a relatively simple and efficient approach to implement CPML for the second-order equation system, which solves the original wave equations numerically in the stretched coordinate. The spatial derivatives in the stretched coordinate are computed by adding a correction term to the regular derivatives. Once the first-order spatial derivatives are computed, we computed the second-order spatial derivatives in a similar way; therefore, we refer to the method as two-step CPML(TS-CPML). We apply the method to the second-order acoustic wave equation and a coupled second-order pseudo-acoustic TTI wave equation. Our simulations indicate that amplitudes of reflected waves are only about half of those computed with the traditional CPML method, suggesting that the proposed approach has computational advantages and therefore can be widely used for forwarding modeling and seismic imaging.     

钢筋混凝土框架结构抗震超强系数分析

基于我国建筑抗震规范要求设计的14栋代表不同抗震特征要求的多高层规则钢筋混凝土框架,通过静力弹塑性分析详细地评估了框架结构的体系超强能力。分析中采用与抗震规范等效静力地震作用效应分布模式相同的单调递增侧向荷载,以二维平面框架为分析对象。分析结果表明地震分区对超强系数的影响较大;有填充墙框架比无填充墙框架的超强能力明显要大;内框架的超强能力比外框架的超强能力大;超强系数随框架楼层数的增加而减小。     

珠江口咸潮入侵分析与经验模型——以磨刀门水道为例

收集了2004-2006年珠江口磨刀门水道咸潮发生时测站(1~7)逐日定时观测的的含氯度、水位与流量数据,分析了各监测站含氯度与水位的日变化与年变化,导出了咸潮演变各过程中,含氯度与径流、潮流、河口地形等的关系式,建立了珠江口地区磨刀门水道咸潮入侵的经验模型。据此,模拟了2006年1月12日的磨刀门地区的咸潮入侵态势,经过和沿途各观测点验证发现与实测数据非常吻合。以含氯度等于250mg/L(饮用水的含氯度最大值)的点作为咸潮入侵的最远点,用简化修改后的盐度模拟模型计算了磨刀门咸潮入侵最大距离,并根据2006年1月12~20日的河口含氯度与最近的上游天河站的径流量实测数据计算出相应的咸潮入侵最大距离。研究表明,在河流枯水期(珠江河口通常是12月至翌年3月),只要获得当天河口的含氯度和上游测站的径流量数据,就能利用此经验模型估算出河流各点的含氯度,作出盐度模拟图,并估算出相应的咸潮入侵最大距离。     

中国城市群紧凑度的综合测度分析

城市群紧凑度是指在城市群形成与发育过程中; 所体现出的城市(城镇)、产业、资源、 资金、交通、技术、人才等物质实体按照一定的经济技术联系在空间上的集中程度; 包括城 市群产业紧凑度、城市群空间紧凑度和城市群交通紧凑度等类型。适度的紧凑度是城市群综 合效益最大化的集中体现; 城市群紧凑度过高、过低都不利于城市群的健康发展。从产业、 空间和交通三大视角入手; 通过构建城市群紧凑度的综合测度模型; 对选取的23 个城市群紧 凑程度进行分析后认为; 中国城市群紧凑度总体不高; 且空间差异性大; 根据这种差异; 采用聚类分析法可将中国城市群综合紧凑度划分为高度紧凑、紧凑、中度紧凑、低度紧凑和不紧凑(分散) 5 个等级。城市群综合紧凑度呈现出由东向西、由南向北逐渐降低的分异态势。 城市群综合紧凑度与城市群发育程度呈现出高度的正相关性。如何科学调控城市群紧凑程度; 紧凑程度达到一种什么样的标准才是最佳选择; 这是本文研究中试图回答的问题。该研究为 我国城市群的形成与发育; 为建设资源节约型城市群、环境友好型城市群、生态型城市群和 高效型城市群提供定量的决策依据; 为推动我国城市群的适度集聚和健康发展奠定科学基础。     

1979年9月19日3B级耀斑光谱分析:金属线的不对称性和线心位移

本文研究了1979年9月19日3B级耀斑金属谱线的不对称性和线心位移.结果表明:强金属线红不对称占主要地位,少数弱金属线也有蓝不对称存在;不对称程度极大发生于线心强度极大之前;不对称性有时可由蓝变红;不管不对称程度如何,线心的位移却很小,总体上仅表现为极微弱的蓝移.文中认为,耀斑爆发时色球压缩区的向下扩展及由此引起的温度极小区上下的物质运动这个动力学过程可基本解释这些观测现象.金属线的研究是对H_α和CaIIK线光谱研究的补充.     

Variations in High-frequency Oscillations of Tropical Cyclones over the Western North Pacific

Variations in the high-frequency oscillations of tropical cyclones(TCs) over the western North Pacific(WNP) are studied in numerical model simulations. Power spectrum analysis of maximum wind speeds at 10 m(MWS_(10)) from an ensemble of15 simulated TCs shows that oscillations are significant for all TCs. The magnitudes of oscillations in MWS_(10) are similar in the WNP and South China Sea(SCS); however, the mean of the averaged significant periods in the SCS(1.93 h) is shorter than that in the open water of the WNP(2.83 h). The shorter period in the SCS is examined through an ensemble of simulations,and a case simulation as well as a sensitivity experiment in which the continent is replaced by ocean for Typhoon Hagupit(2008). The analysis of the convergence efficiency within the boundary layer suggests that the shorter periods in the SCS are possibly due to the stronger terrain effect, which intensifies convergence through greater friction. The enhanced convergence strengthens the disturbance of the gradient and thermal wind balances, and then contributes to the shorter oscillation periods in the SCS.     

Circulation Features Associated with the Record-breaking Typhoon Silence in August 2014

Climatologically, August is the month with the most tropical cyclone(TC) formation over the western North Pacific(WNP) during the typhoon season. In this study, the reason for abnormal TC activity during August is discussed—especially August 2014, when no TCs formed. The large-scale background of August 2014 is presented, with low-level large-scale easterly anomalies and anticyclonic anomalies dominating over the main TC genesis region, a weak monsoon trough system,and a strong WNP subtropical high(WPSH), leading to significantly reduced low-level convergence, upper-level divergence,and mid-level upward motion. These unfavorable large-scale conditions suppressed convection and cyclogenesis. In August2014, equatorial waves were inactive within the negative phase of the Madden–Julian Oscillation(MJO), with fewer tropical disturbances. Although the low-level vorticity and convection of those disturbances were partly promoted by the convective envelopes of equatorial waves, the integral evolution of disturbances, as well as the equatorial waves, were suppressed when propagating into the negative MJO phase. Moreover, the upper-level potential vorticity(PV) streamers associated with anticyclonic Rossby wave breaking events imported extratropical cold and dry air into the tropics. The peripheral tropospheric dryness and enhanced vertical wind shear by PV streamer intrusion combined with the negative MJO phase were responsible for the absence of TC formation over the WNP in August 2014.