• Title/Summary/Keyword: 쌍극자

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Development of Surface RF Coil with extremely short RF penetration depth

  • 김대흥;김은주;정은기;이삼현
    • Proceedings of the KSMRM Conference
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    • 2001.11a
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    • pp.147-147
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    • 2001
  • 목적: RF 자기장이 존재하는 공간이 좁을수록 신호 대 잡음비가 증가한다. 이것을 이용하여, 기존의 표면 코일보다 RF 자기장의 공간을 좁혀서 코일 근방에서 신호 대 잡음비를 개선할 수 있는 표면 코일을 개발한다. 대상 및 방법: 기존의 표면 코일의 RF 자기장은 쌍극자(Dipole) 자기장 형태이다. 쌍극자 모드는 자기장의 세기가 1/r$^3$로 감소한다 하지만 자기장을 사중극자(Quadrupole) 형태도 발생시키면, 1/r$^{5}$ 로 감소하게 되어, 극자(pole)로부터 먼 곳에서는 자기장의 감소가 매우 급격히 일어난다. 극자 근방에서는 쌍극자와 사중극자 자기장의 세기 차이가 거의 없다. 이런 원리들을 이용하여 표면코일의 형태를 사중극자 자기장이 발생하도록 제작하여, 코일로부터 먼 곳의 신호는 코일에 검출되지 못하게 하였다. 그러므로 신호 대 잡음비에 큰 이득을 볼 수 있다.

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A STUDY ON THE ROLL-ALONG TECHNIQUE USED IN 2D ELECTRICAL RESISTIVITY SURVEYS (2차원 전기비저항 탐사에 사용되는 ROLL-ALONG 기법에 대한 고찰)

  • WonSeokHan;JongRyeolYoon
    • Journal of the Korean Geophysical Society
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    • v.6 no.3
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    • pp.155-164
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    • 2003
  • The validity and efficiency of the roll-along technique widely used in 2-D electrical resistivity survey are analyzed in case of the dipole-dipole and the Wenner-Schlumberger arrays by numerical modelling. The shallow anomalous resistivity bodies are successfully inverted both in the dipole-dipole and in the Wenner-Schlumberger arrays because the shallow data of pseudosection are not omitted by the roll-along technique. However, the deep anomalous resistivity bodies can not be well resolved due to the skip of observed data which is more significant in the Wenner-Schlumberger array having relatively poor horizontal coverage of obtaining data. Carrying out electrical survey adopting the dipole-dipole array, the skip of data is insignificant because it is unfeasible to expand the electrodes to the maximum electrode separation coefficient($n_max$) owing to low S/N ratio. In case of the Wenner-Schlumberger array, however, because it is generally feasible to expand the electrodes $n_max$ to the owing to high S/N ratio, it is highly possible that skip of data from the roll-along technique causes significant distortion of inversion results. Therefore, adopting the Wenner-Schlumberger array having deeper median depth(Edwards, 1977) than do the dipole-dipole array on condition of the same unit electrode spacing( ($a$) ) and $n_max$, it is recommended to determine $a$ based on not $n_max$but $n_prob$free from the skip of observing data and forward electrodes with keeping overlap interval 3/4 of the survey line length in order to reduce the distortion of resistivity structure and perform resistivity survey efficiently. These results are confirmed by numerical modelling.

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Calculation of the Dipole Moments for Transition Metal Complexes by Valence Bond Method (I). Calculation of the Dipole Moments for Octahedral $[M(III)O_3S_3]$ Type Complexes [M(III) = V(III), Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) and Os(III)] (원자가 결합법에 의한 전이원소 착물에 대한 쌍극자모멘트의 계산 (제1보). 팔면체 $[M(III)O_3S_3]$ 형태 착물의 쌍극자모멘트의 계산 [M(III) = V(III), Cr(III), Mn(III), Fe(III), Co(III), Ru(III), Rh(III) 및 Os(III)])

  • Sangwoon Ahn;Jeoung Soo Ko
    • Journal of the Korean Chemical Society
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    • v.23 no.4
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    • pp.198-205
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    • 1979
  • A valence bond method of calculation of the dipole moments for octahedral $(M(III)0_3S_3)$ type complexes are developed, using $d^2sp^3 $hybrid orbitals of the central metal ions and the single basis set orbital of ligands. (M (III) =V (III), Cr (III), Mn (III), Fe (III), Co (III), Ru (III), Rh (III) and OS (III)). In this method the mixing coefficient of the valence basis sets for the central metal ion with the appropriate ligand orbitals is not required to be the same, differently from the molecular orbital method. The valence bond method is much more easier to calculate the dipole moments for octahedral complexes than the approximate molecular orbital method and the calculated results are also in the range of the experimental vaues.

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Calculation of the Dipole Moments for Tetrahedral and Square Planar $[M(II)N_2S_2]$ Type Complexes [M(Ⅱ) = Ni(Ⅱ), Co(Ⅱ), Cu(Ⅱ) or Zn(Ⅱ)] (사면체 및 사각형 $[M(II)N_2S_2]$ 형태 착물의 쌍극자 모멘트의 계산 [M(II) = Ni(II), Co(II), Cu(II) 또는 Zn(II)])

  • Ahn Sangwoon
    • Journal of the Korean Chemical Society
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    • v.23 no.1
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    • pp.1-6
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    • 1979
  • The dipole moments for square planar and tetrahedral $[M(II)N_2S_2]$ type complexes are calculated, using the expansion method for spherical harmonics [M(II) = Co(II), Ni(II), Cu(II) or Zn(II)]. The calculated values of the dipole moments for these complexes are in the range of the experimental values. The possible structures for these complexes in benzene solution are discussed on the basis of the calculated dipole moments and the the magnetic properties.

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The Effects of the cis and trans Configurations of Ligands on the Calculated Dipole Moments for $[M(II)O_3N_3]$ and $[Ni(II)O_2N_4]$ Type Complexes ($[M(II)O_3N_3]$$[Ni(II)O_2N_4]$ 형태착물의 쌍극자 모멘트에 대한 리간드의 cis 및 trans 구조의 영향)

  • Sangwoon Ahn;Eu Suh Park;Chang Jin Choi
    • Journal of the Korean Chemical Society
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    • v.27 no.2
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    • pp.83-94
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    • 1983
  • The effects of cis and trans configurations of ligands for $[M(II)O_3N_3]$ and $[Ni(II) O_2N_4]$ type complexes [M(II) = Co(III), Ni(II) and Cu(II)] on the calculated dipole moments have been investigated, adpoting the eigenvectors of EHT calculation. The calculated dipole moments for cis complexes are higher than those of trans complexes. The calculated dipole moments for the octahedral trans $[Co(III)O_3N_3]$ type complex fall in the range of experimental values. However the calculated dipole moments for cis $[Ni(II) O_2N_4]$ type complexes fall in the range of the experimental values. These results predicts the trans structure for $[Co(III)O_3N_3]$ and $[Ni(II) O_2N_4]$ type complexes. Those structures are in agreement with the experimental one (Three bidentate (O-N) ligands in $[M(II)O_3N_3]$ type complexes coordinate to the metal ion and two tridentate (O-N-N) ligands in [Ni(II)O2N4] type complexes coordinate to Ni(II) ion).

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Resistivity Survey on Stylobate of Five-story Stone Pagoda in Tamni-ri, Uiseong (의성 탑리리 오층석탑 기단부 전기비저항 탐사)

  • Oh, Hyundok;Kwon, Moonhee
    • Geophysics and Geophysical Exploration
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    • v.23 no.4
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    • pp.253-260
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    • 2020
  • The five-story stone pagoda in Tamni-ri located in Uiseong County in Gyeongsangbuk-do had an unstable upper structure, and the structural deformation of the foundation stone and the stylobate was severe. In order to repair the base of the pagoda, it must be confirmed if there are support stones inside the base. Resistivity survey was performed to study the inner base stone structure during the repair work. The stylobate was exposed soil and broken stones after removing the walls and the cover of the stylobate. Modified pole-dipole array II was used for the resistivity survey, and compared with the typical pole-dipole array method. And in this study, a physical scale-down model experiment was performed to compare and analyze distortions caused by severe topographical undulations such as right-angled lines. The results show that the stylobate of Five-story Stone Pagoda in Tamni-ri Uiseong has base stones inside the reinforced filling soil and are located beneath the pillar of the body and supporting the pagoda.

Dipole Antennas and Radiation Patterns in the Three-Dimensional GPR Modeling (쌍극자 안테나를 고려한 3차원 지표레이다 탐사 모델링과 방사 패턴에 대한 고찰)

  • Choi Yun-Gyoung;Seo1 Soon-Jee;Suh Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.4 no.2
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    • pp.45-54
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    • 2001
  • A three-dimensional finite difference time-domain modeling algorithm based on staggered grid and considering transmitting and receiving antennas has been developed to simulate Ground Penetrating Radar (GPR) survey. This algorithm adopted the subcellular method to simulate the dipole antennas being used in GPR system and added resistors to reduce ringing caused by the reflections at the ends of an antenna. Comparison of the output voltages in the presence of the resistors for half-space said that the ringing and the amplitude of output voltage decreased as the number of resistors increased, and the antenna was designed based upon this result. Radiation patterns were derived to understand the distribution of electric field energy in the planes including or normal to the antenna. The electric field energy concentrated on vertical direction in the plane including antenna more than in normal plane.

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A Study of Feasibility of Dipole-dipole Electric Method to Metallic Ore-deposit Exploration in Korea (국내 금속광 탐사를 위한 쌍극자-쌍극자 전기탐사의 적용성 연구)

  • Min, Dong-Joo;Jung, Hyun-Key;Park, Sam-Gyu;Chon, Hyo-Taek;Kwak, Na-Eun
    • Geophysics and Geophysical Exploration
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    • v.11 no.3
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    • pp.250-262
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    • 2008
  • In order to assess the feasibility of the dipole-dipole electric method to the investigation of metallic ore deposit, both field data simulation and inversion are carried out for several simplified ore deposit models. Our interest is in a vein-type model, because most of the ore deposits (more than 70%) exist in a vein type in Korea. Based on the fact that the width of the vein-type ore deposits ranges from tens of centimeters to 2m, we change the width and the material property of the vein, and we use 40m-electrode spacing for our test. For the vein-type model with too small width, the low resistivity zone is not detected, even though the resistivity of the vein amounts to 1/300 of that of the surrounding rock. Considering a wide electrode interval and cell size used in the inversion, it is natural that the size of the low resistivity zone is overestimated. We also perform field data simulation and inversion for a vein-type model with surrounding hydrothermal alteration zones, which is a typical structure in an epithermal ore deposits. In the model, the material properties are assumed on the basis of resistivity values directly observed in a mine originated from an epithermal ore deposits. From this simulation, we can also note that the high resistivity value of the vein does not affect the results when the width of the vein is narrow. This indicates that our main target should be surrounding hydrothermal alteration zones rather than veins in field survey. From these results, we can summarize that when the vein is placed at the deep part and the difference of resistivity values between the vein and the surrounding rock is not large enough, we cannot detect low resistivity zone and interpret the subsurface structures incorrectly using the electric method performed at the surface. Although this work is a little simple, it can be used as references for field survey design and field data Interpretation. If we perform field data simulation and inversion for a number of models and provide some references, they will be helpful in real field survey and interpretation.

Calculation of the Dipole Moments for Simple Molecules by the Expansion Method for Spherical Harmonics (Spherical Harmonics의 전개방법에 의한 간단한 분자의 쌍극자모멘트의 계산)

  • Ahn Sang Woon;Park, Byeong Bin
    • Journal of the Korean Chemical Society
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    • v.22 no.6
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    • pp.357-364
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    • 1978
  • The dipole moments for $NH_3$, HF, CO, HCHO, HCN, PO, $PO^-\;and\;H_2O$ molecules are calculated, using the method for evaluation of the dipole moment matrix elements by the expansion method for spherical harmonics. The calculated dipole moments in this work are closer to the experimental values than those of the other work.

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Calculation of the Dipole Moments for Trigonal Bipyramidal Complexes (Trigonal Bipyramid 구조를 갖는 착물의 쌍극자모멘트의 계산)

  • Sangwoon Ahn;Ja Hong Kim;Kee Hag Lee;Gap Choul Shin
    • Journal of the Korean Chemical Society
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    • v.26 no.1
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    • pp.18-23
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    • 1982
  • A new method for calculation of the the dipole moments for trigonal bipyramidal complexes has been developed in this work. Illustrative calculations are performed on a few trigonal bipyramidal complexes with the approximate molecular orbital and the valence bond method. The calculated values of the dipole moments by the approximate molecular orbital method are very close to the experimental values. The calculated dipole moments may be used to predict the geometric structure of trigonal bipyramidal complexes.

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