• 제목/요약/키워드: magnetic absorption

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Underwater Acoustic Communication Link Analysis (수중음향통신 링크 해석)

  • Choi, Young-Chol;Byun, Sung-Hoon;Lim, Yong-Kon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.8
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    • pp.1465-1471
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    • 2007
  • The electro-magnetic wave propagates through the air in the terrestrial communications, but the acoustic wave propagates through the seawater in the underwater acoustic communication(UAC). It makes the differences between the UAC link and the well hon air communication links. In this paper, we have studied path loss, absorption and ambient noise of the ocean as a medium for UAC. We have analyzed the absorption coefficient and ambient noise level of the coastal area of South Korea and suggested a strategy for the selection of the frequency band by considering the absorption coefficient and ambient noise level. Also, we present an illustrative example of a link budget for the QPSK UAC system which has carrier frequency 25kHz, bit rate 10kbps, range 1km and BER $10^{-3}$ in the shallow water environment with an ideal AWGN assumption.

Soft x-ray Synchrotron Radiation Spectroscopy Study of Molecule-based Nano Bioparticles Containing Fe (철원소를 함유한 분자기반 생체물질 나노입자들의 연 x선 방사광 분광 연구)

  • Lee, Eun-Sook;Kim, D.H.;Hwang, Ji-Hoon;Lee, Ki-Ho;Kang, J.S.
    • Journal of the Korean Magnetics Society
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    • v.22 no.4
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    • pp.125-129
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    • 2012
  • By employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD), the electronic structures of molecule-based nano bioparticles, such as Helicobacter pylori ferritin (H. pylori ferritin), Heme, $NaM[Fe(CN)_6]{\cdot}H_2O$-type Prussian Blue (M=Co, Ni) analogue, have been investigated. The measured Fe 2p XAS spectra reveal that Fe ions are trivalent ($Fe^{3+}$) in H. pylori ferritins, while they are in the $Fe^{2+}-Fe^{3+}$ mixed-valent states in $NaM[Fe(CN)_6]{\cdot}H_2O$ Prussian Blue analogues (M=Co, Ni). According to the Fe 2p XMCD spectrum of high-state H. pylori ferritin, all the $Fe^{3+}$ ions have the same local symmetry and their magnetic moments are aligned in the same direction. It is also found that the Fe 3d orbitals in $NaM[Fe(CN)_6]{\cdot}H_2O$ have a strong covalent bonding to $(CN)^-$ ligands, but with a very weak bonding to the 2p orbitals of O ligands.

High Frequency Magnetic Characteristics of $Co_{90}Fe_{10}$ Thin Films and $Co_{90}Fe_{10}/SiO_2$ Multilayers ($Co_{90}Fe_{10}$ 박막 및 $Co_{90}Fe_{10}/SiO_2$ 다층박막의 고주파 자기특성)

  • 윤의중;진현준;박노경;문대철;김좌연
    • Journal of the Korean Magnetics Society
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    • v.8 no.5
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    • pp.300-307
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    • 1998
  • The $Co_{90}Fe_{10}$ single layer films were deposited on various substrates (glass, Si, polymide) using high vacuum RF magnetron sputtering system and nominall 1000 $\AA$ thick $Co_{90}Fe_{10}$ alloy films had a good high frequency characteristic. $M_S$ and $H_{an}$ values obtained from the B-H characteristic of the $10{\times}[100 nm \;Co_{90}Fe_{10}/100 nm\; SiO_2]$ multilayers agreed well with those obtained by calculation. Complex relative permeability $(={\{\mu}_r={\mu}_r',-j{\mu}$\mu$_r")$ at frequency f was measured from the transmission characteristics $(S_{11},\; S_{21}\;parameters)$ of the microstrip line which has a stacked structure consisting of sample magnetic films and a conductor and is connected to a network analyzer. The ${\mu}_r'-f$ characteristic was abtained from the megnetic absorption, which was analyzed from the S-parameter characteristics of the microstrip line. The ${\mu}_r'-f$ characteristic was also calculated from the ${\mu}_r"-f$-f characteristic using the Kramers-Kronig relation. The measurement results were confirmed to agree well with those obtained by calculations.culations.

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Interferometric Monitoring of Gamma-Ray Bright AGNs: 4C +28.07 and Its Synchrotron Self-Absorption Spectrum

  • Myoung-Seok Nam;Sang-Sung Lee;Whee Yeon Cheong
    • Journal of The Korean Astronomical Society
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    • v.56 no.2
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    • pp.231-252
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    • 2023
  • We present the analysis results of the simultaneous multifrequency observations of the blazar 4C +28.07. The observations were conducted by the Interferometric Monitoring of Gamma-ray Bright Active Galactic Nuclei (iMOGABA) program, which is a key science program of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN). Observations of the iMOGABA program for 4C +28.07 were conducted from 16 January 2013 (MJD 56308) to 13 March 2020 (MJD 58921). We also used γ-ray data from the Fermi Large Array Telescope (Fermi-LAT) Light Curve Repository, covering the energy range from 100 MeV to 100 GeV. We divided the iMOGABA data and the Fermi-LAT data into five periods from 0 to 4, according to the prosody of the 22 GHz data and the presence or absence of the data. In order to investigate the characteristics of each period, the light curves were plotted and compared. However, a peak that formed a hill was observed earlier than the period of a strong γ-ray flare at 43-86 GHz in period 3 (MJD 57400-58100). Therefore, we assumed that the minimum total CLEANed flux density for each frequency was quiescent flux (Sq) in which the core of 4C +28.07 emitted the minimum, with the variable flux (Svar) obtained by subtracting Sq from the values of the total CLEANed flux density. We then compared the variability of the spectral indices (α) between adjacent frequencies through a spectral analysis. Most notably, α22-43 showed optically thick spectra in the absence of a strong γ-ray flare, and when the flare appeared, α22-43 became optically thinner. In order to find out the characteristics of the magnetic field in the variable region, the magnetic field strength in the synchrotron self-absorption (BSSA) and the equipartition magnetic field strength (Beq) were obtained. We found that BSSA is largely consistent with Beq within the uncertainty, implying that the SSA region in the source is not significantly deviated from the equipartition condition in the γ-ray quiescent periods.

Optical and Magnetic Properties of Copper Doped Zinc Oxide Nanofilms

  • Zhao, Shifeng;Bai, Yulong;Chen, Jieyu;Bai, Alima;Gao, Wei
    • Journal of Magnetics
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    • v.19 no.1
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    • pp.68-71
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    • 2014
  • Copper doped Zinc Oxide nanofilms were prepared using a simple and low cost wet chemical method. The microstructures, phase structure, Raman shift and optical absorption spectrum as well as magnetization were investigated for the nanofilms. Room temperature ferromagnetism has been observed for the nanofilms. Structural analyses indicated that the films possess wurtzite structure and there are no segregated clusters of impurity phase appreciating. The results show that the ferromagnetism in Copper doped Zinc Oxide nanofilms is driven either by a carrier or defect-mediated mechanism. The present work provides an evidence for the origin of ferromagnetism on Copper doped Zinc Oxide nanofilms.

Study on the production of the ceramic by the mineral-Oriental medicine and the property of the clean active water depositting on the ceramic stone (광물성 한약재 세라믹 조성 및 세라믹 침적 청정활성수 특성에 대한 연구)

  • Kim Gyeong Cheol
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.18 no.4
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    • pp.1159-1162
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    • 2004
  • We studied on the production of the ceramic by the mineral-Oriental medicine and the property of the clean active water depositting on the ceramic stone. The results are as follows: We properly mixed of maifanshi, mica, ochre, and added to a small amount cinnabar, and therefore formed the ceramic stone. By the plasticity process and the irradiating magnetic force recovered the disappeared a part of constitutent elements. The recovered effects were become higher the freshness, maintenance, deodoriztion, clean water. As well as having the ability on capture of the notoxious heavy metal on human. The ceramic powder were mixed proper dose maifanshi, mica. And the powder had ionization, absorption, adhesion by the plasticity process and magnetic force. The clean active water of depositting on the ceramic stone during 24hours were observed significant the content of micro element, dissolved oxygen, abstraction on Herbs.

Spectroscopic characterization of N,N'-bis(salicylidene)pentane-1,3-diamine nickel(II) complex

  • Kim, Gilhoon;Won, Hoshik
    • Journal of the Korean Magnetic Resonance Society
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    • v.18 no.2
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    • pp.74-81
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    • 2014
  • The $N_2O_2$ tetradentate Schiff base ligand, N,N'-bis(salicylidene)pentane-1,3-diamine (Salpn), coupled with 1:2 concentration ratio of 1,3-diaminopentane and salicylaldehyde was used to produce a series of macrocyclic Nikel(II) complexes. In the metal complexation, it was observed that Salpn macrocyclic ligand can adopt more than a metal ion giving an unique multinuclear metal complexes including Ni(II)Salpn and $Ni(II)_3(Salpn)_2$. Characteristic IR ${\upsilon}(M-O)$ peaks for Ni(II)Salpn and $Ni(II)_3(Salpn)_2$ were observed to be $1028cm^{-1}$ and $1024cm^{-1}$, respectively. Characteristic UV-Vis absorption ${\lambda}_{max}$ peaks for $Ni(II)_3(Salpn)_2$ were observed to be 241nm and 401 nm. Structural characterization of $Ni(II)_3(Salpn)_2$ by NMR exhibits that the salicylidene ring moiety has two different resonance signals originated from the magnetically asymmetric diligand and trinuclear bis complex. Complete NMR signal assignments and characterizations elucidating structural features of $Ni(II)_3(Salpn)_2$ were described in detail.

Numerical Computation of Matching Boundary Values of Electromagnetic Wave Absorbers (전파흡수체 정합경계값의 수치계산)

  • 김왕성;김경용;배규식
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.2
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    • pp.19-26
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    • 1995
  • The design of broad-band, thin layer electromagnetic wave absorbers usually employs magnetic materials. The common absorber consists of a magnetic material layer bonded to a metal plate at the back. For such structure, a theoretical expression involving six parameters defines the allowable material shape and values of electromagnetic parameters that will produce zero reflection or more practically more than 99% absorption (20dB attenuation). The Secant Method was employed to compute the matching boundary values corresponding to 20dB attenuation. In addition, a search algorithm coupled with the Secant Method was developed to obtain allowable range of material parameters for the design of wave absorbers. These numerical methodes applicable to any six parameters effectively yielded accurate solutions in the least iterations.

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A Study on Electromagnetic Absorption Characteristics of the Anisotropic Composite Structure with Specific Thickness (특정두께를 갖는 이방성복합재 구조의 전자파 응답특성 연구)

  • 정헌달;김덕주;이윤상
    • Journal of the Korea Institute of Military Science and Technology
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    • v.1 no.1
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    • pp.114-127
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    • 1998
  • A user friendly computer code(EMCOMST; Electro-Magnetic response for COMposite STructures) was developed which provides with computations of the response characteristics such as reflectance and transmittance to the incident wave angles, frequencies, composite thicknesses, ply orientations, and types of backplate as the linearly polarized transverse electro-magnetic wave is emitted to the advanced composite structures. In this investigation were reviewed the electromagnetic characteristics of the continuous orthotropic fiber-reinforced organic matrix composites with or without ferrite fillers, which are actively applied to low-weight and high-strength aircraft structures. Also were calculated the response of the three layered compound structures which have appropriately stacked above-mentioned materials as transmitting layer, absorbing layer, reflection layer, respectively under the specific thickness constraints for mechanical strength design requirements. For the composite structures presented in this study, minimum reflectance value less than -5㏈ can be obtained in the frequency range of 4 to 12 ㎓. In addition, analysis of structures attached isotropic radar absorbing materials(RAM) is facilitated by putting the material properties in the material input card entries adequately.

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Comparison and Optimization of Parallel-Transmission RF Coil Elements for 3.0 T Body MRI (3.0 T MRI를 위한 Parallel-Transmission RF 코일 구조의 비교와 최적화)

  • Oh, Chang-Hyun;Lee, Heung-K.;Ryu, Yeun-Chul;Hyun, Jung-Ho;Choi, Hyuk-Jin
    • Proceedings of the KIEE Conference
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    • 2007.04a
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    • pp.61-63
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    • 2007
  • In high field (> 3 T) MR imaging, the magnetic field inhomogeneity in the target object increases due to the nonuniform electro-magnetic characteristics and relatively high Larmor frequency. Especially in the body imaging, the effect causes more serious problems resulting in locally high SAR(Specific Absorption Ratio). In this paper, we propose an optimized parallel-transmission RF coil element structure and show the utility of the coil by FDTD simulations to overcome the unwanted effects. Three types of TX coil elements are tested to maximize the efficiency and their driving patterns(amplitude and phase) optimized to have adequate field homogeneity, proper SAR level, and sufficient field strength. For the proposed coil element of 25 cm ${\times}$ 8 cm loop structure with 12 channels for a 3.0 T body coil, the 73% field non-uniformity without optimization was reduced to about 26% after optimization of driving patterns. The experimental as well as simulation results show the utility of the proposed parallel driving scheme is clinically useful for (ultra) high field MRI.

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