Applying Source Parameter Imaging (SPI) to Aeromagnetic Data to Estimate Depth to Magnetic Sources in the Mamfe Sedimentary Basin

Aeromagnetic data over the Mamfe Basin have been processed. A regional magnetic gridded dataset was obtained from the Total Magnetic Intensity (TMI) data grid using a 3 × 3 convolution (Hanning) filter to remove regional trends. Major similarities in magnetic field orientation and intensities were observed at identical locations on both the regional and TMI data grids. From the regional and TMI gridded datasets, the residual dataset was generated which represents the very shallow geological features of the basin. Processing this residual data grid using the Source Parameter Imaging (SPI) for magnetic depth suggests that the estimated depths to magnetic sources in the basin range from about 271 m to 3552 m. The highest depths are located in two main locations somewhere around the central portion of the study area which correspond to the area with positive magnetic susceptibilities, as well as the areas extending outwards across the eastern boundary of the study area. Shallow magnetic depths are prominent towards the NW portion of the basin and also correspond to areas of negative magnetic susceptibilities. The basin generally exhibits a variation in depth of magnetic sources with high, average and shallow depths. The presence of intrusive igneous rocks was also observed in this basin. This characteristic is a pointer to the existence of geologic resources of interest for exploration in the basin.

Numerical and experimental study of magnetic fluid seal with large sealing gap and multiple magnetic sources

To improve the pressure capability of magnetic fluid seal with more than a 0.25 mm single edge gap,a magnetic fluid sealing structure with multiple magnetic sources which has five permanent magnets was designed.Magnetic field distributions under the pole pieces of the magnetic fluid seal with single and multiple magnetic sources were simulated by finite element method and its sealing pressure difference could be calculated according to the theoretical formula of the magnetic fluid seal.The effects of sealing gap height and magnetic source amount on the sealing capability were investigated experimentally.The theoretical and experimental results were compared,analyzed and discussed.The results demonstrated that the magnetic fluid seal with multiple magnetic sources was an effective method to improve the sealing capability for the rotary shaft with large gaps.The theoretical results agreed well with the experimental results when the height of the single edge gap was equal to 0.4 mm.However,it was found that when the height of the single edge gap was larger than 0.4 mm,the difference between the theoretical values and experimental values increased with the gap height because part of magnetic source had less or even no effect on magnetic fluid sealing capability.

Localization of the human language cortex by magnetic source imaging

Objective To localize the language cortex associated with Chinese word processing by magnetic source imaging (MSI) Methods Eight right handed and one left handed healthy native Chinese subjects were examined by magnetoencephalography (MEG) and a 1 5T magnetic resonance imaging (MRI) unit All subjects were given pure tone stimuli 50 times, 150 pairs of Chinese words (meaning related or unrelated) auditory stimuli, and pure tone stimuli subsequently 50 times Evoked response fields time locked to the pure tone and Chinese words were recorded using a whole head neuromagnetometer in real time The acquired data were averaged by the acquisition computer according to the response to the pure tone, related pairs of words and unrelated pairs of words The data obtained by MEG were superimposed on MRI, using a GE Signa 1 5T system Results MEG, showed there were two obviously higher magnetic waves named M50 and M100, which were localized in the bilateral transverse temporal gyri in all subjects The responses to the pairs of Chinese words (meaning related or unrelated) were similar in the same hemisphere of the same subjects There was a higher peak during 300-600 ms in the right hemisphere of one left handed subject, but no peak in the left hemisphere, indicating that the language dominant hemisphere was localized in the right hemisphere Superimposing the MEG data on MRI, the language area was localized in the Wernicke's areas A 300-600 ms response peak was obsarved in each hemisphere (the amplitude of the 300-600 ms response peak in each hemisphere was almost the same) in two right handed subjects, showing that the language area was localized in the 2 hemispheres in the two subjects There was one peak in each hemisphere (300-600 ms response) in 6 subjects, but the amplitude of the wave in the left hemisphere in the 6 subjects was much higher than that in the right hemisphere By choosing randomly from the later component (300-600 ms response) several time points and superimposing them on MRI, all time points were localized in the posterior part of the superior temporal gyri, which is the Wernicke's areas Conclusions Comparing with the later component of the bilateral hemispheres, the wave amplitude in the language dominant hemisphere was much higher than that in the non language dominant hemisphere The language areas could be identified by judging whether meanings of pairs of Chinese words were related or not

Algorithm study of transient response of vertical magnetic bipolar source in whole space plane layered medium

For some time, whole space feature as a theoretical problem has been a puzzle in mining transient electromagnetic method （TEM）. We have introduced a detailed method of calculating the transient response of a vertical magnetic bipolar source in a whole space plane layered medium in order to obtain whole space features. After designing a whole space plane layered medium model, equations were established based on boundary conditions in terms of electromagnetic vector potential. Expressions of electromagnetic fields were obtained by solving these equations. The expressions were computed by the Hankel transform after dispersion. The results in a frequency domain were changed into a time domain by using a multinomial cosine transform method. The expressions were correctly validated by comparing them with the analytical solution in half space. The half space and whole space results show that the whole space features are dear, suggesting that the theory of half space is not suitable for the whole space. Our algorithm supplied the technical instrument for studying the distributed features of whole space transient electromagnetic fields.

A Method of Identifying Electromagnetic Radiation Sources by Using Support Vector Machines

Electromagnetic Radiation Source Identification(ERSI) is a key technology that is widely used in military and radiation management and in electromagnetic interference diagnostics.The discriminative capability of machine learning methods has recently been used for facilitating ERSI.This paper presents a new approach to improve ERSI by adopting support vector machines,which are proven to be effective tools in pattern classification and regression,on the basis of the spatial distribution of electromagnetic radiation sources.Spatial information is converted from 3D cubes to 1D vectors with subscripts as inputs in order to simplify the model.The model is trained with 187 500 data sets in order to enable it to identify the types of radiation source types with an accuracy of up to 99.9%.The influence of parameters(e.g.,penalty parameter,reflection and noise from the ambient environment,and the scaling method for the input data) are discussed.The proposed method has good performance in noisy and reverberant environment.It has an identification accuracy of 82.15% when the signal-to-noise ratio is 20 dB.The proposed method has better accuracy in a noisy environment than artificial neural networks.Given that each Electromagnetic(EM) source has unique spatial characteristics,this method can be used for EM source identification and EM interference diagnostics.

Magnetic field enhanced radio frequency ion source and its application for Si-incorporation diamond-like carbon film preparation

Various ion sources are key components to prepare functional coatings,such as diamond-like carbon(DLC)films.In this article,we present our trying of surface modification on basis of Si-incorporation diamond-like carbon(Si-DLC)produced by a magnetic field enhanced radio frequency ion source,which is established to get high density plasma with the help of magnetic field.Under proper deposition process,a contact angle of 111°hydrophobic surface was achieved without any surface patterning,where nanostructure SiC grains appeared within the amorphous microstructure.The surface property was influenced by ion flow parameters as well as the resultant surface microstructure.The magnetic field enhanced radio frequency ion source developed in this paper was useful for protective film applications.

Evaluation of Structural Framework and Depth Estimates Using High Resolution Airborne Magnetic Data over Some Parts of Middle Benue Trough, Nigeria

High-resolution aeromagnetic data of parts of Middle Benue Trough, Nigeria (sheets 212, 213, 233 and 234) was interpreted by applying source Parameter Imaging (SPI) and Spectral Depth analysis with the aim of mapping out the magnetic lineaments and analysing magnetic signals coming from different sources. The results from the derivatives maps show major and minor lineaments trends in the NE-SW and NW-SE directions respectively. Results from SPI show the maximum sedimentary thickness of about -4546.7 m (-4.5467 km) around the region of Awe, Aman, Langtang south, Gassol and the north-eastern part of Donga. Minimum depth of -167.9 m (-0.1679 km) around the region of north of Shendam, north of Wase, north-eastern part of Aman, Bantaji, Donga, Ibi and Bali. The residual map was divided into twenty-five sections. Spectral Depth was run for each of these twenty-five sections, the result shows that the depth to the deep magnetic source ranges between -0.65 km and -3.35 km. The depth to the shallow magnetic sources ranges between -0.03 km and -0.44 km showing the presence of magnetic intrusive bodies within the sediments. Since the sedimentary thickness of 3.0 km and above is only sufficient for hydrocarbon maturation and accumulation, then the results from this present study show that the study area might be sufficient enough for hydrocarbon maturation and accumulation.

Mechanical Analysis and Measurements of a Multicomponent NbTi/Cu Superconducting Magnets Structure for the Fully Superconducting Electron Cyclotron Resonance Ion Source

A fully superconducting electron cyclotron resonance （ECR） ion source （SECRAL ID is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconducting solenoids （Nb-Ti/Cu） and six superconducting sextupoles （Nb-Ti/Cu）. Different from the conventional supercon- ducting ECR magnetic structure, the SEC17AL Ⅱ includes three superconducting solenoid coils＇ that are located inside the superconducting sextupoles. The SECRAL Ⅱ can significantly reduce the interaction forces between the sextupole and the solenoids, and the magnets can also be more compact in size. For this multi-component SECRAL Ⅱ generating its self field of -8 T and being often exposed to the high self field, the mechanical analysis has become the main issue to keep their stress at 〈200 MPa on coils. The analytical and experimental results in mechanics are presented in the SECRAL Ⅱ structure. To improve the accuracy and efficiency of analysis, according to the composite rule of micromechanics, the equivalent uniform windings are used to simulate the epoxy-impregnated Nb-Ti/Cu coils. In addition, using low temperature strain gauges and a wireless fast strain acquisition system, a fundamental experiment on the based on our analysis, the stresses and deformations optimized. strains developments of a sextupole is reported. Finally, for its assembly of each SECRAL Ⅱ coil will be further

Milliampere He^2+ beam generator using a compact GHz ECRIS

Multi-charged helium ion beam He2＋ is useful for helium accelerator to obtain a higher energy with lower cost and for deuterium accelerator to avoid neutron activation during machine commissioning. An attempt to generate milliampere multi-charged helium He2＋ ion beam with a 2.45 GHz electron cyclotron resonance ion source （ECRIS） was tested recently. A design using a specfic permanent magnet 2.45 GHz ECRIS （PMECRIS） source （ERCIS） is reported and the He2~ beam production ability is described. With this source, we produced a total helium beam of 40 mA at 40 kV with 180 W of net microwave power and a gas flow of less than 0.5 seem. At steady state the He2＋ beam intensity is 4.4 rnA, that being the fraction of multi-charged he- lium ion beam is at approximately 11%.