• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.231-236
• /
• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• Korean Journal of Remote Sensing
• /
• v.21 no.1
• /
• pp.91-98
• /
• 2005

On board satellite magnetometer measures all possible magnetic components, such as the core and crustal components from the inner Earth, and magnetospheric, ionospheric and' its coupled components from the outer Earth. Due to its dipole and non-dipole features, separation of the respective component from the measurements is most difficult unless the comprehensive knowledge of each field characteristics and the consequent modeling methods are solidly constructed. Especially, regional long wavelength magnetic signals of the crust are strongly masked by the main field and dynamic external field and hence difficult to isolate in the satellite measurements. In particular, the un-modeled effects of the strong auroral external fields and the complicated behavior of the core field near the geomagnetic poles conspire to greatly reduce the crustal magnetic signal-to-noise ratio in the polar region relative to the rest of the Earth. We can, however, use spectral correlation theory to filter the static lithospheric and core field components from the dynamic external field effects that are closely related to the geomagnetic storms affecting ionospheric current disturbances. To help isolate regional lithospheric anomalies from core field components, the correlations between CHAMP magnetic anomalies and the pseudo-magnetic effects inferred from satellite gravity-derived crustal thickness variations can also be exploited, Isolation of long wavelengths resulted from the respective source is the key to understand and improve the models of the external magnetic components as well as of the lower crustal structures. We expect to model the external field variations that might also be affected by a sudden upheaval like tsunami by using our algorithm after isolating any internal field components.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.41.1-41.1
• /
• 2019

The stability analysis of coronal magnetic structures is important for studying the initiation of solar flares and eruptions. In order to understand the flare onset process, we first reconstructed the 3D coronal magnetic structures of active region 12371 with an M6.5 flare using a nonlinear force-free field (NLFFF) model based on vector magnetic fields. The NLFFFs successfully produce the observed sigmoidal structure which is composed of two branches of sheared arcade loops. The stability analysis were examined for three representative MHD instabilities: the kink, the torus, and the double arc instabilities. Our stability analysis shows that the two branches of sheared arcade loops are quite stable against the kink and torus instabilities, but unstable against the double arc instability before the flare occurrence. Finally, we discuss a probable onset process of the M6.5 flare.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.32.6-32
• /
• 2001

This paper describes the steering control and geomagnetism cancellation for an autonomous mobile robotusing MR sensors. The magnetic-resistive (MR) sensor obtains the vector summation of the magnetic fields from embedded magnets and the Earth. The robot is controlled by the magnetic fields from embedded magnets. So, geomagnetism is the disturbance in the steering control system. In this paper, we propose a new method of the sensor arrangement in order to remove the geomagnetism and robotbody interference. The proposed method uses two MR sensors located in a level plane and the steering controller has been developed. The controller has three input variables (dBx, dBy, dBz) using the measured magnetic field difference, and an output variable (the steering angle) ...

• Resources Recycling
• /
• v.27 no.6
• /
• pp.11-22
• /
• 2018

Magnetic separators has been used in the mining and the recycling fields in general, and is still applied in wide variety of fields. It is classified into the equipments for separating coarse ferrous scrap from non-ferrous materials and the equipments for concentrating fine ferromagnetic particles below 3mm. Magnetic separation equipments for concentrating fine materials also falls into two categories of low intensity and high intensity magnetic separators. The former is used for ferromagnetic materials but also paramagnetic materials of high magnetic susceptibility, and the latter for paramagnetic materials of lower magnetic susceptibility. Both low and high intensity magnetic separators could be utilized either dry and wet. Recently, the High gradient magnetic separators(HGMS) used in the range of less than 0.7 tesla has been gradually replaced by the magnetic separator made of rare earth permanent magnets commercialized in the 1980s. In addition, the expansion of nanotechnology in terms of synthetic magnetic materials in the environmental and biological fields is expected to contribute positively to the development of magnetic separation technology.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.41.3-42
• /
• 2021

Conventional global magnetic field maps, such as daily updated synoptic maps, have been constructed by merging together a series of observations from the Earth's viewing direction taken over a 27-day solar rotation period to represent the full surface of the Sun. It has limitations to predict real-time farside magnetic fields, especially for rapid changes in magnetic fields by flux emergence or disappearance. Here, we construct accurate synchronic magnetic field maps using frontside and AI-generated farside data. To generate the farside data, we train and evaluate our deep learning model with frontside SDO observations. We use an improved version of Pix2PixHD with a new objective function and a new configuration of the model input data. We compute correlation coefficients between real magnetograms and AI-generated ones for test data sets. Then we demonstrate that our model better generate magnetic field distributions than before. We compare AI-generated farside data with those predicted by the magnetic flux transport model. Finally, we assimilate our AI-generated farside magnetograms into the flux transport model and show several successive global magnetic field data from our new methodology.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.439-441
• /
• 2003

In this study the formula of electro magnetic fields under 3-phase power lines with vertical or horizontal line-configurations were deduced and the effect of the earth was considered in the formula. Using the formula the electric field and the magnetic flux density under distribution and transmission lines constucted currently in our country were calculated and the components of each field were investigated with horizontal distance from tower and height above the earth.

• Geophysics and Geophysical Exploration
• /
• v.26 no.2
• /
• pp.77-83
• /
• 2023

In this study, the expressions of magnetic vector and magnetic gradient tensor due to an elliptical cylinder were derived. Igneous intrusions and kimberlite structures are often shaped like elliptical cylinders with axial symmetry and different radii in the strike and perpendicular directions. The expressions of magnetic fields due to this elliptical cylinder were derived from the Poisson relation, which includes the direction of magnetization in the gravity gradient tensor. The magnetic gradient tensor due to an elliptical cylinder is derived by differentiating the magnetic fields. This method involves obtaining a total of 10 triple derivative functions acquired by differentiating the gravitational potential of the elliptical cylinder three times in each axis direction. As the order of differentiation and integration can be exchanged, the magnetic gradient tensor was derived by differentiating the gravitational potential of the elliptical cylinder three times in each direction, followed by integration in the depth direction. The remaining double integration was converted to a complex line integral along the closed boundary curve of the elliptical cylinder in the complex plane. The expressions of the magnetic field and magnetic gradient tensor derived from the complex line integral in the complex plane were shown to be perfectly consistent with those of the circular cylinder derived by the Lipschitz-Hankel integral.

• Bulletin of the Korean Space Science Society
• /
• 1994.04a
• /
• pp.10-10
• /
• 1994

No Abstract. See Full-text

• Smart Structures and Systems
• /
• v.10 no.2
• /
• pp.181-192
• /
• 2012

Magnetic suspensions based on passive levitation of diamagnetic materials on permanent magnets provide attractive systems for several applications on the micro and meso scales. The magnetic properties of these kinds of suspensions dramatically reduce the global mechanical stiffness of the devices providing significant effects on their dynamic response. The goal of this paper is to investigate the static and dynamic behavior of magnetic suspensions with respect to its dependant parameters. Experimental measurements have been performed on the response of dedicated prototypes where the geometrical dimensions and magnetic field strength have been intended as variable parameters. Some benefits have been documented in the fields of energy harvesting and inertial sensing, while additional applications of magnetic suspensions are under investigation.