• Economic and Environmental Geology
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• v.34 no.4
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• pp.355-373
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• 2001

Palaeomagnesim of Paleozoic Tuwibong Type Sequence in Yemi area was studied with a total of 256 core-samples collected from 23 sites. The study area (geographical coordinates: 37.l8$^{\circ}$N, l28.610E) is located between Taebaek and Yongwol belonging to the northeastern part of the Okchon Belt. Thermal cleaning was a most effective method to extract stable characteristic remanent magnetization (ChRM) direction, even though AF cleaning also worked on some specimens. Mean ChRM direction of the Cambrian Hwajol Formation was different from the present-day field direction and showed maximum clustering (max. k value) at 100% bedding-tilt correction. However, it could not pass the fold test. Ordovician Makkol and Kosong Limestones as well as Permian Sadong and Kobangsan Formations have very weak NRM, and were remagnetized into the present-day field direction. ChRM directions from the Carboniferous Hongjom Formation passed both fold and reversal tests. IRM experiments and blocking temperature spectrum indicate that both magnetite and haematite are carrier of the primary magnetization. Palaeomagnetic pole position from the Carboniferous Hongjom Formation is very similar to that of contemporary North China Block (NCB) suggesting that the study area was a part of, or located very near to, the NCB during Carboniferous.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1146-1149
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• 2014

To discriminate polarities of stator windings for 3 phase induction motors terminal tags of which are not readable, it is possible to utilize the residual magnetic flux present at their rotors as well as to use the way based on external exciting current. The induced voltages are basically decided by parameters such as the quantity of residual flux, the rotator speed by hand force and the phase properties between stator windings. To adopt induced voltages by residual flux for polarity discrimination at sites, the measured voltages by multi-testers need to be readable in magnitude enough to discriminate winding condition with reasonable phase characteristics. This study focuses on the analysis of various connection cases in the expectation that the summing voltages induced by residual flux shall show zero in case of normal connections while the sum becomes greater indication if the connection is in wrong condition. The proposed method is applied to actual motors to disclose how effective it is for polarity discrimination at sites through comparison of output signals between normal and fault connections.

• Journal of the Korean Magnetics Society
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• v.10 no.6
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• pp.291-296
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• 2000

The manufacturing method of permalloy soft magnet with the Ni contents of 46.6 and 47.2 wt% was investigated by powder injection molding technology. The magnetic properties of permalloy were greatly affected on the residual carbon and oxygen content of the sintered magnet. Solvent extraction and thermal debinding process to minimize the residual carbon content in sintered magnet were developed by controlling the debinding atmosphere. The residual carbon content depends on the debinding condition of the binder system for powder injection molding and the residual oxygen content on the sintering atmosphere. The sintered magnet produced by powder injection molding process had a 50 ppm. residual carbon, 150 ppm. residual oxygen. The coercivity and maximum relative permeability of permalloy soft magnet were 0.46 Oe and 14,600 respectively.

• Journal of the Korean Magnetics Society
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• v.15 no.6
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• pp.325-331
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• 2005

The magnetic Hut leakage (MFL) type nondestructive testing (NDT) method is widely used to detect corrosion and defects, mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Because of the strong magnetic field enough to saturate the pipe, there could be distortion of the sensing signals because of the magnetization of the pipeline itself, To detect the defects precisely, the sensing signals are need to be compensated to eliminate the distortions coming from the media hysteresis. In this paper, the magnetizations of the pipeline in MFL type NDT are analyzed by Preisach model and 3D FEM. The distortions of the sensing signals are analyzed.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.141-151
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• 2006

A blank test was done to calculatee the car itself's magnetic effect as noise and to eliminate it from the data set of total magnetic intensity(=magnetic flux density) exploration in a car-borne magnetic exploration system. To calculate the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself, we have installed the magnetometer on a fixed point and measured the magnetic intensity letting the car move around the magnetometer, and we have changed the data set into an analogous data set as if acquired in the condition that we have parked the car on the same fixed point and measured the magnetic intensity moving the magnetometer around the magnetometer. Through an inversion with the later data set as input, we have calculated the magnetic center and the magnetic moments of the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself with the two centers coincided because of some barriers of the inversion algorithm that we have used in this study. On the other hand, we have extracted the magnetic anomaly by reducing i. e. vectorially eliminating the induced magnetic intensity(= magnetization) and the remanent magnetic intensity(= magnetization) of the car itself calculated forwardly, from the magnetic exploration data set acquired by the car-borne magnetic exploration system.

• Proceedings of the Korean Magnestics Society Conference
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• 1993.11a
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• pp.52-53
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• 1993

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.6 no.2
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• pp.99-108
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• 2002

그리드 고정용 전자석은 절단금형에서 여러 조각으로 나누어진 매우 얇고 가벼운 그리드를 전자석에 흡착시켜 그리드를 부착한 장소까지 이송하는 역할을 하는 전자석이다. 설계목표는 (1)그리드 고정용 전자석이 착자, 탈자 및 이동시 전자석에 흡착된 그리드 조각의 정렬상태가 동요되지 않는 전자석의 설계, (2)금형(그리드 흡착면)에 잔류자기가 최소화되는 설계, (3)전자석이 탈자되었을 때, 잔류자기가 최소화되는 설계에 초점을 두었다. 자장분포는 유한요소법으로 계산하였고, 전자력 계산은 Maxwell stress tensor법을 사용하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.11a
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• pp.29.1-29.1
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• 2006

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.50-57
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• 2001

Magnetic inductive probe was designed and assembled for sensing the residual stress developed in the ferromagnetic thin sheet. The residual stress measurement system with this probe could resolve the residual stresses developed in the sheet in terms of principal stress orientation, and magnitude of the principal stress. It was consumed that the obtained probe output voltage from the qualified ferromagnetic Fe-42Ni lead frame sheet and quality-rejected sheet is effectively determined using the developed device. The lead frame sheet which has accumulated a high level of residual stress always showed a distinctive stress distribution and magnitude compared with those of qualified lead frame sheet. Those differences were well resolved as functions of input current or used frequency.

• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.343-349
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• 2008

We have constructed a car-borne magnetic exploration system, in which a car drags a non-magnetic cart on which a magnetometer is installed. In the total magnetic field measured as a vectorial sum in this system, are included the magnetic field generated by the car itself. This magnetic field, doing the role of a magnetic noise, should be eliminated. For this purpose, we have set up a measurement condition to get the same effect as if we have put the car in one point and thereafter measured the magnetic field around it. In this case, if there is any magnetically anomalous body in the area, we can consider all the remaining magnetic field to have been generated by the car itself, once the geomagnetic field eliminated. We tried to invert the magnetic field considered to have been generated by the car and succeeded to derive the magnetic moment and the direction of the induced and remanent magnetic field of the car respectively. Once the magnetic moment and the direction of the induced and remanent magnetic field have been calculated, the magnetic field generated by them in specific points can be directly and analytically calculated. This result can be used in the future to eliminate the magnetic field generated by the car itself doing the role of a magnetic noise during the procedure of reduction of the measured magnetic exploration data by the car-borne magnetic exploration system.