陕甘宁交界地区地壳S波Q值成像特征研究

利用陕甘宁交界地区测震台网记录到的2009—2018年4423个近震波形资料,采用衰减结构层析成像方法对该地区地壳Q_S值进行成像分析,获得了陕甘宁交界地区地壳衰减模型,分析讨论了Q_S值分布与活动断裂及强震活动等之间的关系。结果显示,陕甘宁交界地区地壳剪切波衰减横向变化显著,整体上,海原-六盘山构造带和西秦岭构造带地壳Q_S值相对偏低,鄂尔多斯盆地和陇中盆地地壳Q_S值相对较高。活动构造带和活动断裂交汇区呈现低Q_S值,结合前人研究成果,推断这与活动断裂带及交汇区地壳岩石较为破碎且富含流体有关。有历史地震记录以来,研究区6级以上地震大多分布在高、低Q_S值的过渡区,分析认为这与"硬"、"软"地壳介质交界处容易积累地震应变能有关。研究区域低Q_S值分布与低横波速度和低电阻率区的主要分布特征较为一致,但是与大地热流研究结果存在区域性差异。     

城市发展转型研究进展及展望

城市发展转型是城市经济社会发展的必然趋势。通过对城市发展转型的内涵、内容、影响因素、模式等方面的深入分析,认为目前城市发展转型研究多是注重资源型城市转型而忽视一般性区域中心城市转型,注重城市经济转型而忽视城市文化与社会转型,注重定性研究而忽视定量研究。今后应加强一般性区域中心城市转型研究,突出城市发展转型中的软环境研究,推进不同发展水平城市转型的比较研究,注重城市转型中定性与定量相结合的系统性研究。     

A WENO algorithm for radiative transfer with resonant scattering and the Wouthuysen–Field coupling

We develop a numerical solver for the integral–differential equations, which describe the radiative transfer of photon distribution in the frequency space with resonant scattering of Lyα photons by hydrogen gas in the early universe. The time-dependent solutions of this equation is crucial to the estimation of the effect of the Wouthuysen–Field (WF) coupling in relation to the 21 cm emission and absorption at the epoch of reionization. However, the time-dependent solutions of this equation have not yet been well performed. The resonant scattering leads to the photon distribution in the frequency space to be piecewise smooth containing sharp changes. The weighted essentially nonoscillatory (WENO) scheme is suitable to handle this problem, as this algorithm has been found to be highly stable and robust for solving Boltzmann equation. We test this numerical solver by (1) the analytic solutions of the evolution of the photon distribution in rest background; (2) the analytic solution in expanding background, but without resonant scattering; (3) the formation of local Boltzmann distribution around the resonant frequency with the temperature to be the same as that of atom for recoil. We find that the evolution of the photon distribution due to resonant scattering with and without recoil generally undergoes three phases. First, the profile of the photon distribution is similar to the initial one. Second, an extremely flat plateau (without recoil) or local Boltzmann distribution (with recoil) form around the resonant frequency, and the width and height of the flat plateau or local Boltzmann distribution increase with time. Finally, the distribution around the resonant frequency is saturated when the photons from the source is balanced by the redshift of the expansion. This result indicates that the onset of the W–F coupling should not be determined by the third phase, but by the time scale of the second phase. We found that the time scale of the W–F coupling is equal to about a few hundreds of the mean free flight time of photons with resonant frequency, and it basically is independent of the Sobolev parameter if this parameter is much less than 1.     

闽北烤烟移栽期的预报

用对比分析和相关分析相结合的方法选取预报因子,分析得出移栽日期与前期冷空气活动有关,且冷空气活动存在一定韵律关系。用逐步回归建立的预报方程效果好,且对移栽期特迟和特早有较好的预报能力。     

应用AMSU B微波资料分析0509号Matsa台风水汽场分布特征

热带气旋的形成、发展、移动以及消亡与大范围水汽输送和集中息息相关.此研究以2006年7-8月的AMSU-B的183.3±1、183.3±3、183.3±7GHz三个水汽通道亮温为主要资料源,利用三个通道所在的权重高度差异,分别建立了对流层高、中、低层水汽量与三个通道亮温的e指数统计回归关系.在此基础上,选取西北太平洋2005年09号麦莎台风,利用AMSU-B亮温通过回归关系式计算出的高、中、低层水汽量,就其水汽输送与强度变化关系进行了分析.结果表明,其一,微波水汽通道亮温能够很好地表征热带气旋环境场不同高度的水汽分布和水汽输送,尤其是对流层中层亮温的变化显示出的水汽量的变化与热带气旋强度密切相关;其二,热带气旋发展过程中,除了西南季风形成的西南水汽通道是水汽维持的重要输送带外,东南水汽通道也经常成为登陆热带气旋强度维持的主要水汽供给.     

2007年7月重庆和济南城市暴雨洪水灾害认识和思考

介绍了2007年7月发生在重庆、济南两座城市的暴雨洪水灾害发生情况及损失。从地形、气候与自然环境、城市排水系统、灾害预警和防灾应急管理五个方面对致灾原因进行了综合分析,提出了应对暴雨洪水等城市自然灾害的建议,即合理规划城市发展,提高城市排水系统和防洪标准,建立和完善科学的城市灾害应急机制与防灾体系,提高灾害预警水平,并注重增强全民的防灾意识。     

塔里木盆地中南部麻扎塔格逆冲—褶皱带变形特征及其意义

麻扎塔格地区地层、地貌及构造变形特征的研究,对于认识塔里木盆地新生代构造演化过程、塔里木—西昆仑的盆山耦合关系、新构造运动对塔里木油气资源分布的影响以及塔克拉玛干沙漠的气候、环境变化都具有重要意义。本文通过卫星照片解译、野外变形观察、剖面实测、地球物理资料解释等手段,对该地区晚新生代的构造特征进行了研究,确定了麻扎塔格构造带为典型的逆冲—褶皱带,并探讨了麻扎塔格逆冲—褶皱带的构造指向、活动时限、隆升速率及缩短速率、东西方向的延伸等问题,取得如下认识:1)麻扎塔格逆冲—褶皱带为西昆仑山前陆褶皱冲断带的前缘部位,和田河气田就是处在逆冲前锋背斜顶部,晚新生代变形作用已明显地改造了塔里木盆地南部及中部的古生代和中生代构造,并促成了和田河气田的形成;2)麻扎塔格山在中新世末(约7 Ma)和中更新世(约780 ka B.P.)经历了两次构造隆升,后一次形成了麻扎塔格逆冲—褶皱带和麻扎塔格山现今的地貌特征;3)估算出麻扎塔格逆冲—褶皱带中更新世以来的隆升速率约为0.26～0.4 mm/a,缩短速率约为0.9 mm/a;4)认为麻扎塔格逆冲—褶皱带向西应与同属西昆仑山前褶皱—冲断带前缘的喀什背斜相连,东端的突然消失可能是由于东段和田河附近存在北东—南西向的走滑断层造成。     

基于长度贝叶斯生物量估算法的北部湾带鱼资源评估

带鱼是南海西北部北部湾主要经济鱼类种群之一,估算其种群参数和评估其资源状况对北部湾渔业资源管理具有重要意义.本文利用2006-2016年北部湾带鱼(Trichiurus haumela)的生物学数据,通过长度贝叶斯生物量估算法(Length-based Bayesian Biomass Estimation Metho...     

WebGIS中间件在WebGIS开发中的优势和灵活性

以ArcGIS Server为核心技术并以ESRI公司的控件为基础的WebGIS,其开发在某种程度上受到一定限制和约束,为了摆脱这些限制和约束,开发了WebGIS中间件,并以北京数字市政地下管网系统为例进行说明.     

An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses

In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd.