综合地球物理法在金属矿复杂地质环境勘探中的应用

传统勘探技术存在勘测效率低、精准度差等问题,很难满足现代人们的需求,为此,综合地球物理法对金属矿复杂地质环境进行勘探。针对地下地质结构展开分析,并对分层信息和矿区构造进行精细刻画,进而达到高精度的勘测准;利用航空电磁法对探测金属矿的电性或电磁差异进行快速、高效的勘测,并获取磁型参数;按照发射的电磁频率和特点,将航空电磁法分为频率域和时间域,并展开分析。该方法具有勘测效率高、精准度强的优势,能够为金属矿复杂地质环境提供详细的参考资料。     

物探在铜钼矿勘探中的应用研究

铜钼矿伴生有少量磁铁矿,利用高精度磁测圈定与矿体有关的磁异常,再利用可控源音频大地电磁法对与矿体有关的磁异常进行异常解剖,确定磁异常空间特征;在勘探铜钼矿过程中,两种物探方法的结合是最直接有效的。     

电磁法在金矿野外勘探中的应用

进行金矿野外勘察时有很多的限制因素,包括技术能力、经济实力和地质条件等,电磁法的选取及使用严重的困惑着众多的勘探工作人员。本文细致的叙述了广域电磁法、音频大地电磁法和可控源音频大地电磁法的工作机理,而且深度研究了这些电磁法的数据及处理措施,希望可以使电磁法在金矿勘探过程中得到最大水平的发挥。     

航空瞬变电磁法对地下低阻目标体的响应能力分析

航空瞬变电磁法具有速度快、效率高、勘探深度大、分辨率高、地形影响小、对良导体探测能力强等优点。在研究航空瞬变电磁异常及后期钻探验证结果的基础上,分析了航空瞬变电磁法对地下低阻目标体响应的能力,认为航空瞬变电磁法反映低阻异常的效果明显,并具有一定的深探测能力。     

小方坯结晶器电磁搅拌磁场测试与分析

对重钢小方坯结晶器电磁搅拌磁场进行了测试,分析了其磁场特性,总结了磁场随电流与频率的变化规律及磁场的空间位置分布特点.并计算出工作温度下理论最佳搅拌频率为4 Hz.分析结果对结晶器电磁搅拌工艺参数优化具有指导意义.     

CSAMT电场y方向视电阻率的定义及研究

在准静态近似条件下,利用水平电偶源在均匀半空间表面激发电磁场的计算公式,讨论了可控源音频大地电磁法(CSAMT)水平电场y分量Ey的观测范围、特点和由其定义视电阻率的应用优势;Ey与常规标量CSAMT测量的Ex、Hy幅值范围不同,采集并利用Ey数据可以扩大CSAMT野外观测扇区,减少采集成本.依据电法及电磁法勘探中视电阻率定义的基本原则,提出了Ey视电阻率的定义,说明了其具备频率测深的意义;通过几种典型层状模型(均匀半空间,两层D、G,三层H、K以及四层KH、HK型)的数值计算,对比了Ey视电阻率和Ex、Hy、Zxy Re(Zxy)等对应的波区视电阻率及Ex、Zxy等对应的全区视电阻率对地电断面电性特征的反映效果.结果表明:Ey视电阻率的求取仅需测点的坐标和一个方向的电场值,计算方便、不必迭代,并且在曲线低频端收敛于一稳定值,可以明显改善非波区的畸变效应.     

电磁搅拌对大方坯结晶器流场和液面波动的影响

针对260 mm×300 mm大方坯结晶器,采用有限元和有限体积法相结合的方法研究了电磁搅拌对结晶器流场和液面波动的影响.磁场模拟结果与现场实测数据一致.电磁搅拌使结晶器内钢液在水平截面呈旋转流动,在纵截面上形成两对回流方向相反的环流区,最大切向速度随电流和频率的增加而增大,结晶器自由液面的波动随电流和频率的增加而加剧.对于260 mm×300 mm大方坯轴承钢连铸,合理的结晶器电磁搅拌电流和频率分别是300 A和3 Hz.      

可控源音频大地电磁测深法在隐伏铁多金属矿勘查中的应用效果

可控源音频大地电磁法是勘探深部隐伏矿床的一种重要物探方法,但是其在铁多金属矿方面的试验研究较少。通过采用可控源音频大地电磁法对青海省某矿区铁多金属矿上进行试验研究,通过采用winglink软件对可控源音频大地电磁数据进行反演,反演结果在矿体位置具有较明显的低阻异常,表明可控源音频大地电磁法对浅部水平板状体有良好的勘探效果。通过反演结果,我们可进一步看出在已知矿体的下部还存在一处规模较大的低阻良导体,推测为深部隐伏铁多金属矿,表明该方法在深部隐伏铁多金属矿勘查中具有较好的应用效果。     

绿色勘查技术在矿产资源勘探中的应用分析

因为矿产资源在勘探时会对生态环境造成一定程度的破坏,所以提出了绿色勘查技术在矿产资源勘探中的应用分析。对利用频率域航空电磁测量技术进行勘探做出了详细的分析,解释了其基本原理和技术特点,阐述了该技术在实施时的实施要点,最后通过应用实例说明该技术能够在绿色勘探的同时减小成本和提高工作效率。     

绿色勘查技术在矿产资源勘探中的应用分析

因为矿产资源在勘探时会对生态环境造成一定程度的破坏,所以提出了绿色勘查技术在矿产资源勘探中的应用分析。对利用频率域航空电磁测量技术进行勘探做出了详细的分析,解释了其基本原理和技术特点,阐述了该技术在实施时的实施要点,最后通过应用实例说明该技术能够在绿色勘探的同时减小成本和提高工作效率。     

Relationship between dipole parameter estimation errors and measurement conditions in magnetoencephalography

The relationship between dipole parameter estimation errors and measurement conditions in magnetoencephalography is determined by computer simulation. The model uses a single current dipole in a spherical homogeneous medium. Dipole parameters are estimated using a moving dipole procedure. Signal-to-noise ratio (SNR) is defined as the square-root of the ratio of the average signal power to the average noise power over all measurement points. At SNR > 20, accurate estimation can be carried out independently of dipole depth and coil size. At SNR < 20, dipole depth influences estimation error. When the dipole is located near the center of the sphere, the measurement region should include both extrema of the magnetic field to minimize estimation error. However, when the dipole is not so deep, the position of the measurement region does not influence estimation error. When SNR < 4, estimation error increases as coil size increases. Coil size minimizing estimation error is determined by the ratio of environmental magnetic field noise to electrical noise. For a constant size of measurement region, increasing the number of measurement points decreases estimation error to a certain level. This error level depends on SNR. The number of measurement points required to minimize estimation error also depends on SNR.     

Seismic Response of Liquid Storage Tanks Incorporating Soil Structure Interaction

A frequency domain method is presented to compute the impulsive seismic response of circular surface mounted steel and concrete liquid storage tanks incorporating soil-structure interaction (SSI) for layered sites. The method introduces the concept of a near field region in close proximity to the mat foundation and a far field at distance. The near field is modeled as a region of nonlinear soil response with strain compatible shear stiffness and viscous material damping. The shear strain in a representative soil element is used as the basis for strain compatibility in the near field. In the far field, radiation damping using low strain soil response is used. Frequency dependent complex dynamic impedance functions are used in a model that incorporates horizontal displacement and rotation of the foundation. The focus of the paper is on the computation of the horizontal shear force and moment on the tank foundation to enable foundation design. Significant SSI effects are shown to occur for tanks sited on soft soil, especially tanks of a tall slender nature. SSI effects take the form of period elongation and energy loss by radiation damping and foundation soil damping. The effects of SSI for tanks are shown to reverse the trend of force and moment reduction under earthquake loading as is usually assumed by designers. The reasons for this important effect in tank design are given in the paper and relate to the very short period of most tanks, hence, period lengthening may result in load increase. A comparison is made with SSI effects evaluated using the code SEI/ASCE 7-02. Period elongation is found to be similar for relatively stiff soils when assessed by the code compared with the results of the dynamic analysis. For soft soils, the agreement is not as good. Code values of system damping are found to agree reasonably well with an assessment based on the dynamic analyses for the range of periods covered by the code. Energy loss by material damping and radiation damping is discussed. It is shown that energy loss may be computed using the complex dynamic impedance function associated with the viscous dashpot in the analytical model. The proportion of energy loss in the translation mode compared to that dissipated in the rotational mode is addressed as a function of the slenderness of the tank. Energy loss increases substantially with the volume of liquid being stored.     

冷却速率对高碳铬铁粉电磁性能的影响

采用矢量网络参数法在1~18 GHz频段内分别对电阻炉、空气和水浴中冷却的高碳铬铁粉的电磁性能进行研究.随着冷却速率的提高,高碳铬铁粉的相对复介电常数实部和虚部在大多数频率下均增大.空冷和水冷粉料的相对复介电常数虚部在12~18 GHz频率范围内因极化弛豫而产生较大的峰值.同一频率下相对复磁导率实部随冷却速率变化的趋势与相对复介电常数相反.水冷粉料的相对复磁导率虚部在3~5 GHz以外的频段内均大于另两组冷却粉料,且三组粉料的虚部在低频及高频条件下均具有峰值.在2.45 GHz的微波加热频率下,炉冷、空冷及水冷粉料的反射损耗分别为-2.30、-2.15和-2.07 d B.水冷粉料的介电损耗因子及磁损耗因子最大,微波场下具有最佳的升温速率与反应效果.      

Numerical Simulation of Linear Electromagnetic Stirring in Secondary Cooling Region of Slab Caster

SymbolList　　B———Magneticfluxdensity ,T ;　　B ———ConjugatedcomplexnumberofB ,T ;　　Bc———Magneticfluxdensityinboundaryproducedbycoilcurrent,T ;　　Bi———Magneticfluxdensityinboundaryproducedbyin nerinductioncurrent ,T ;　　F———Electromagneticforce ,N·m- 3;　　g———Gravitationalacceleration ,m·s- 2 ;　　I———Coilcurrent ,A ;　　j———Symbolusedcommonlyinelectricalnotation(=- 1) ;　　J———Inductioncurrentdensity ,A·m- 2 ;　　k———Turbulencekineticenergy ,m2·…     

物探新方法-多通道瞬变电磁法在金属矿勘探中的应用

多通道瞬变电磁法是一种新的电磁勘探方法,具有分辨率高和探测深度大等优点。多通道瞬变电磁法同时记录发射电流和多道接收电压,通过接收电压和发射电流的互相关可以估计大地脉冲响应的峰值时刻,从而得到一种新的视电阻率剖面,能够很好地反映地下地电结构。通过对多通道瞬变电磁法野外工作与数据处理方法进行探讨,在内蒙古巴尔陶勒盖-复兴屯银铅锌多金属矿普查区进行了多通道瞬变电磁法实际勘探。野外数据采集时,通过240 m（或480 m）接地偶极子发射电流,180道60 m接收偶极沿10.8 km的接收剖面布设采集接收电压。对采集的数据进行处理获得了多通道瞬变电磁法视电阻率剖面,该剖面与已知钻孔资料吻合很好。研究认为多通道瞬变电磁法在未来金属矿勘探中具有良好的应用前景。     

电磁场对复杂黄铜凝固组织及性能的影响

通过对水平连铸黄铜棒添加电磁场后的铸态组织、密度、力学性能的研究,分析了电磁场对复杂黄铜铸造的影响.分别进行了普通水平连铸和加电磁场水平连铸试验,研究了电磁场作用下黄铜水平连铸铸坯的凝固组织、力学性能、物理性能等的变化,为黄铜的加电磁场水平连铸生产提供合理的电磁场设计、优化铸造工艺奠定一定基础.     

Numerical Simulation of Level Magnetic Field

TheLMF (LevelMagneticField)technologybasedonstaticmagneticfieldcanbeusedtoimprovecontinuouscasting ,suchasforreducingimpactonnarrowsidesofshell ,eliminatinglargenonmetallicinclusions ,preventingmoldfluxentrappingandim provingslabcleanliness ,etc[1,2 ] .Theeffectofstaticmagneticfieldonsolutebehaviorandcrystallizationduringsolidificationwasinvestigated[3 ] .Theknowl edgeanddesignofmagneticfieldisveryimportantbaseofLMFtechnology .However ,themagneticfieldwasgenerallytakenasaone dimensionalfie…     

Study of electromagnetic separation of nometallic inclusions from aluminum melt

Several methods using the concept of electromagnetic separation of nonmetallic inclusions from an aluminum melt were analytically studied and compared in this article. The migration rate of inclusion particles for each method by exerting different types of electromagnetic field, viz. DC electric field with steady magnetic field, AC magnetic field, and AC electric field, was calculated and compared with the gravity settling velocity. Effects of various operating parameters, such as the imposing time of electromagnetic field, the radius of circular pipe, and the magnitude of electromagnetic force, on inclusion removal efficiency were analyzed and illustrated for each case. It was found that the removal efficiency increases with the increase of imposing time and decreases dramatically with the increase of pipe radius, especially for the AC electric field method. As far as the removal of small inclusions is concerned, the AC magnetic field method is the most favorable one because it has the least dependence of removal efficiency upon the particle size. However, high frequency is needed in order to get the optimum results, and the best values of a/δ are in the range of 2 to 3.     

Prediction of Near Field Plume Characteristics Using Far Field Circulation Model

3-D numerical models are being used more commonly to predict changes in coastal water quality associated with point discharges such as sewage outfalls. Because these “far field” models use grid sizes which are orders of magnitude larger than the scale of near field entrainment processes, it is of interest to compare their predictive capability with that of initial mixing models and to identify ways in which the two model types can be coupled. Comparisons between the 3-D circulation model ECOMsi and the Environmental Protection Agency's mixing model RSB suggest that the former does a reasonable job predicting plume trap height and volumetric dilution but often overpredicts plume width. Results are sensitive to source representation and parameterization of horizontal and vertical diffusion. The success results from the fact that initial dilution is governed in part by gravitational exchange flow (a large-scale phenomenon that can be resolved in a far field model) in addition to plume entrainment (which is clearly subgrid scale), as well as the self-regulating relationship between plume trap height and initial dilution. Overprediction of plume width is attributed to numerical diffusive effects. Several procedures for improving predictions by coupling near and far field models are explored, ranging from the use of the near field model to dynamically adjust far field mixing parameters, so that the far field model simulates the correct trap height, to simply using the near field model to assign source location and dimension for the far field.     

虚分量感应电磁法在金厂沟金矿床上的应用

本文从虚分量感应电磁法的基本原理入手，着重介绍了加拿大产ＥＭ３４－３型电导率仪在金厂沟金矿床上的试验及追索矿体确定矿体空间产状的过程。为今后利用虚分感电磁法寻找良导性金矿体展示了广阔前景。