不同开口比人工鱼礁体水动力特性及礁体稳定性研究

为研究方型人工鱼礁体开口比的变化对其水动力特性的影响,利用Fluent软件模拟了边长为3m、开口比为0～0.6之间7种不同方型鱼礁体周围水流场,通过分析水流场变化规律得到了礁体流场效应、阻力系数随开口比的变化情况;基于Morison方程计算了礁体在波流作用下的受力及其抗滑移、抗倾覆安全系数。研究结果表明:当礁体开口比小于0.2时,背涡区范围较大,流场效应明显;随着开口比的增大,礁体产生的上升流范围及竖直向最大速度分量逐渐减小;对于方形开口礁体,阻力系数与开口比的关系式为Cd=0.875φ+1.088(R2=0.963,P<0.01);随着开口比的增大,礁体所受最大波流作用力、抗滑移及抗倾覆安全系数逐渐减小,但礁体不会发生滑移和倾覆,可为实际礁体结构的设计提供参考。     

一种新的基于Wold分解的纹理分析方法

针对纹理图像具有结构性和随机性的特点,提出一种新的统一的纹理描述方法。该方法基于Wold分解,在图像为均匀同质随机场的条件下,将纹理图像分解为结构性成份和随机性成份,用少量参数对纹理特征进行描述,为纹理图像的分割、检索、压缩提供了一个统一的纹理模型。     

吉林大安油田储层裂缝的综合评价

本文在岩芯描述和三维有限元数值模拟的基础上,对大安油田裂缝的分布特征,发育规律,分组裂缝所起作用及其对开发的影响等方面进行了综合评价。大安油田储层中发育了受沉积微相和构造控制的四组裂缝。     

二次电流场多次叠加概率成像

基于地下电流场的积分公式,离散化的二次电流场被分解为电性不连续界面上的一系列点电荷电场的代数和.单位正点电荷电场被引入作为空间扫描函数（SDS）,积累电荷出现的概率（COP）函数定义为二次电流场与SDS的互相关.为对概率成像结果进行定量分析解释,提出了规范的积累电荷出现的概率（NCOP）函数.通过应用有限元算法对2D地电模型进行二次电流场合成,实现了二次电流场的多次叠加概率成像.结果表明对均匀半空间中赋存地质异常体的电性结构,概率成像方法对地下异常体的空间位置有较好的指示作用.     

基于IGRF的地磁基准图技术

地磁导航需要获得目标区域的地磁基准图。研究了基于国际地磁参考场的地磁场要素计算和等值线绘制方法。以给定目标区域的经纬高为输入,计算高阶地磁球谐函数获取地磁矢量并计算地磁场要素,修正了因地球扁率带来的数据差异。采用具有虚节点的移动矩形网格算法来绘制地磁参数等值线,生成目标区域的地磁基准图。采用C#实现了地磁基准图软件,测试表明,获得的地磁等高线数据满足使用要求,等值线精度较高。     

EXPERIMENTAL STUDY OF TEMPERATURE EVOLUTION AND IDENTIFICATION OF INSTABILITY POSITION OF PLANAR STRIKE-SLIP FAULT DURING PROCESS OF STICK-SLIP

Stick-slip of fault in laboratory accompanies change of temperature. Temperature change is not only concerned with sliding friction, but also with the stress state of the sample. In this article, we use infra-red thermal imaging system as wide-range observation means to study the temperature variation of different stages during the deformation of sample. The rock sample for the experiment is made of granodiorite from Fangshan County with a size of 300mm×300mm×50mm. It is cut obliquely at an angle of 45°, forming a planar fault. Two-direction servo-control system was used to apply load on the sample. The load in both directions was forced to 5MPa and maintained constant (5MPa) in the X direction, then the load in the Y direction was applied by a displacement rate of 0.5μm/s, 0.1μm/s and 0.05μm/s successively. The left and below lateral of the sample were fixed, and the right and top lateral of the sample were slidable when loaded. The experiment results show not only the temperature change from increase to decrease caused by conversion of stress accumulation to relaxation before and after the peak stress, but also opposite variation of temperature increase on fault and temperature decrease in rock during instability stage. Most important of all, we have found the temperature precursor identifying the position of instability through the temperature variation with time along the fault. It shows that rate of temperature increase of instability position keeps relative high value since the stage of strongly off-linear stage, and accelerates in stage of meta-instability. After separating the effect of friction and stress, we found that temperature increase occurs in the rock near the fault instead of on the fault, which means the mechanism of temperature increase is stress accumulation. Temperature of fault at the instability position does not increase, which means the position is locked. We speculate that the position of locked area on fault with high stress accumulation near the fault may be the future instability position. It is of significance of studying temperature variation during stick-slip to the monitoring of earthquake precursors. Heat caused by friction of earthquake needs long time to transfer to the surface and could not be detected as a precursor. While the stress of surface rock near the fault would change as the stress of interior rock changes, which could cause detectable temperature variations. The research purpose of this article is to find special change positions before instability. As the temperature variations are caused by stress and slip of fault, the results are also meaningful to analysis of stress and displacement data related to earthquake precursors.     

新型闪电电场变化测量仪的研究与初步应用

闪电电场变化测量系统是目前用于闪电物理研究以及闪电定位的重要手段之一,提高测量系统的探测性能,对于推动闪电物理以及闪电定位的研究具有重要作用.根据电磁感应原理,研制出探测带宽为10 Hz～5 MHz的新型闪电电场变化测量仪.并进行了实验,标定了测量仪输出信号与电场变化信号在频域上的数值关系.利用三套测量仪系统对南京多个...     

华南春季强风暴背景流场的若干特征

本文利用常规探测资料,分析了1983年3月25日发生在珠江三角洲地区的一次强对流天气过程背景流场的几个重要特征,如高空急流的结构与变化、辐散风场及与之相联系的背景次级环流、风场垂直切变和水平切变等.     

宁夏南部地区地震活动特征

研究了宁夏南部地区（35°20＇～37°40＇N，104°30＇～106°30＇E）小震综合机制解的变化特征．发现在中强地震前，该地区小震综合机制解的P轴方位偏离平均值，向E或SE偏转，其仰角有增大的趋势，同时小震纵波（Pn和Pg）初动符号一致．6次中强地震的震源机制解表明，该地区P轴方位与主压应力方向基本一致，因此该地区发生破坏性地震的可能性不大．近几年来的地震活动图像显示，该地区的地震活动有向中卫、中宁和同心地区集中的迹象．     

基于地磁场的自主导航研究

研究了基于地磁场的自主导航,建立了以卫星轨道动力学方程为基础的系统状态方程,并详细推导了以地磁场大小和地磁场矢量为观测量时的观测方程.由于系统的非线性,传统的卡尔曼滤波无能为力,为了解决系统的非线性问题把常用来解决非线性问题的EKF引入到基于地磁场的自主导航系统中.最后用Matlab对基于地磁场的自主导航系统进行了仿真,仿真结果表明EKF有很好的收敛性和稳定性,以地磁场矢量为观测量的导航精度要远高于以地磁场大小为观测量的导航精度.