• 한국자기공명학회논문지
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• 제15권1호
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• pp.40-53
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• 2011

The NMR spectra of $Li_3Rb(SO_4)_2$ crystals and their relaxation processes were investigated by using $^7Li$ and $^{87}Rb$ NMR. The relaxation rates of the $^7Li$ and $^{87}Rb$ nuclei in the crystals were found to increase with increasing temperature, and can be described by the relation $T_1^{-1}{\propto}AT^2$. The dominant relaxation mechanism for these nuclei with electric quadrupole moments is provided by the coupling of these moments to the thermal fluctuations of the local electric field gradient via Raman spin-phonon processes.

• 한국자기공명학회논문지
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• 제14권1호
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• pp.18-27
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• 2010

The NMR spectrum and spin-lattice relaxation times, $T_1$, of the $^{1}H$ nuclei in $(NH_{4})_{2}Cd_{2}(SO_{4})_{3}$ single crystals were obtained. The two minima in $T_1$ in the paraelectric phase are attributed to the reorientational motions of the $NH_{4}^{+}$ groups. The $^{1}H\;T_1$ of the $(NH_{4})_{2}Cd_{2}(SO_{4})_{3}$ crystals can be described with Bloembergen- Purcell-Pound (BPP) theory. The experimental value of $T_1$ can be expressed in terms of an isotropic correlation time ${\tau}_H$ for molecular motions by using the BPP theory, and determine the role of protons in these processes.

• 한국자기공명학회논문지
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• 제17권2호
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• pp.86-91
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• 2013

Detailed information about the structural nature of three-coordinate borons in ${\beta}-BaB_2O_4$ is obtained through $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR. The three-coordinate $BO_3$ of the two borons B(1) and B(2) in ${\beta}-BaB_2O_4$ were distinguished. The spin-lattice relaxation time in the laboratory frame $T_1$ for B(1) and B(2) slowly decreases with increasing temperature, whereas the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for B(1) and B(2), which differs from $T_1$, is nearly constant. The B(1) and B(2) of the two types were distinguished by $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR.

• 한국자기학회지
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• 제3권1호
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• pp.13-17
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• 1993

수소$(^{1}H)$와 불소$(^{19}F)$ 원자핵에 대한 펄스 핵자기공명 기법을 써서 $CuF_{2}.2H_{2}O$ 분말 시료를 연구하였다. 선모양과 스핀-격자 완화의 측정으로 공명 원자핵들은 격자내 상자성 이온들의 영향을 강하게 받음을 알 수 있었다. 또 이로부터 상자성 이온의 상관시간(correlation time)을 계산할 수 있었으며 관측된 공명선 폭과 스핀 메아리 붕괴상수로부터 스핀-스핀 상호작용의 크기와 공명원자핵들은 운동상태를 유추할 수 있었다.

• 한국자기공명학회논문지
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• 제14권2호
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• pp.76-87
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• 2010

The structural phase transition of $Cs_2MnCl_4{\cdot}2H_2O$ single crystals was investigated by determining the $^{133}Cs$ spin-lattice relaxation time $T_1$. The number of resonance lines in the $^{133}Cs$ spectrum changes from seven to one near 375 K, which means that above 375 K the Cs sites are symmetric. Further, the $T_1$ of the $^{133}Cs$ nucleus undergoes a significant change near 375 K, which coincides with the change in the splitting of the $^{133}Cs$ resonance lines. The change in $T_1$ near $T_C$ is related to the loss of $H_2O$, and means that the forms of the octahedra of water molecules surrounding $Cs^+$ are disrupted.

• 한국자기학회지
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• 제25권6호
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• pp.185-188
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• 2015

본 연구에서는 FT-NMR 분광기를 사용하여 $NaMgCl_3$ 단결정의 구성 원자인 $^{23}Na$ 원자핵에 대한 핵 자기 공명 실험을 하였다. 이로부터 $^{23}Na$ 원자핵이 모결정 내에서 입방정계 대칭성 내에 존재한다는 것을 알았고, 200 K~410 K 온도 범위에서 $^{23}Na$ 원자핵에 대한 스핀-격자 완화 시간 $T_1$을 온도 변화에 따라 계산하였다. 온도가 증가함에 따라서 $^{23}Na$ 원자핵의 $T_1$ 값이 점차적으로 감소하였다. 스핀-격자 완화율 $1/T_1$ 이 온도 T에 선형적으로 비례하였고, $^{23}Na$ 원자핵의 스핀-격자 완화 메커니즘을 $^{23}Na$ 원자핵 스핀과 단일 포논이 직접적으로 작용하는 직접과정(direct process)으로 설명하였다. 또한 $^{23}Na$ 원자핵의 활성화 에너지를 계산하여 $E_a=4.82J/mol$를 얻었다.

• 한국자기공명학회논문지
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• 제22권4호
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• pp.107-114
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• 2018

In this exploration, the nuclear magnetic resonance of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ Single Crystals using FT-NMR spectrometer is investigated. The line width of the resonance line for the $^{207}Pb$ nucleus decreases as temperature increases due to motional narrowing. The chemical shift of $^{207}Pb$ NMR spectra also increases as temperature decreases for both crystals. The spinlattice relaxation times $T_1$ of $^{39}K$ nucleus were calculated as a function of temperature (180 K~400 K). The $T_1$ of $^{207}Pb$ nucleus decreases as temperature increases. The dominant relaxation mechanism at the studied temperature range can be deduced as the Raman process, which is the coupling between lattice vibrations and the nuclear spins. This deduction is substantiated by the fact that the nuclear spin-lattice relaxation rate $1/T_1$ of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystal is proportional to $T^2$, or temperature squared. The activation energies for the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystals are $E_a=49{\pm}1meV$ and $E_a=47{\pm}2meV$, respectively.

• Journal of Biosystems Engineering
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• 제39권4호
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• pp.345-351
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• 2014

Purpose: Rapid detection of bacteria is very important in agricultural and food industries to prevent many foodborne illnesses. The objective of this study was to develop a portable nuclear magnetic resonance (NMR)-based system to detect foodborne pathogens (E. coli). This study was focused on developing a method to detect low concentrations of magnetic nanoparticles using NMR techniques. Methods: NMR relaxometry was performed to examine the NMR properties of iron nanoparticle mixtures with different concentrations by using a 1 T permanent magnet magnetic resonance imaging system. Exponential curve fitting (ECF) and inverse Laplace transform (ILT) methods were used to estimate the NMR relaxation time constants, $T_1$ and $T_2$, of guar gum solutions with different iron nanoparticle concentrations (0, $10^{-3}$, $10^{-4}$, $10^{-5}$, $10^{-6}$, and $10^{-7}M$). Results: The ECF and ILT methods did not show much difference in these values. Analysis of the NMR relaxation data showed that the ILT method is comparable to the classical ECF method and is more sensitive to the presence of iron nanoparticles. This study also showed that the spin-spin relaxation time constants acquired by a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence are more useful for determining the concentration of iron nanoparticle solutions comparwith the spin-lattice relaxation time constants acquired by an inversion recovery pulse sequence. Conclusions: We conclude that NMR relaxometry that utilizes CPMG pulse sequence and ILT analysis is more suitable for detecting foodborne pathogens bound to magnetic nanoparticles in agricultural and food products than using inversion recovery pulse sequence and ECF analysis.

• Journal of Ginseng Research
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• 제22권2호
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• pp.96-101
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• 1998

This paper describes the determination of bulk density and the discrimination of internal structure of red ginseng by nuclear magnetic resonance (NMR). The 102 red ginseng roots were tested for bulk density. The NMR properties measured by NMR parameters such as spin-lattice relaxation time ($T_1$) and spin-spin relaxation time ($T_2$) were determined using the low field proton NMR analyzer. Bulk density of red ginseng root showed a highly negative significant correlation (r=-0.8934) with the value of $T_1$, but a highly positive significant correlation (r=0.7672 and 0.5909) with the value of T21 (short T2) and T22 (long T2), respectively. Multiple regression equation, Y=-0.0069.$T_1$+0.3044.$T_{21}$-0.0156.$T_{22}$-0.6368, using the MNR parameter values of 80 red ginseng roots can effectively predict the bulk density of 22 red ginseng roots with the correlation coefficient of 0.9396 and the standard error of 0.086. The differences in the internal structure of normal and inside white part of red ginseng were easily found by the signal intensity of NMR image based on magnetic properties of proton nucleus.

• 한국광물학회지
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• 제20권2호
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• pp.97-102
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• 2007

보석질 천연 다이아몬드와 합성 다이아몬드의 $^{15}N$와 $^{13}C$에 대하여 다양한 스핀 이완 시간과 반복 시간을 적용한 NMR 실험을 수행하였다. $^{13}C$에 대해서는 보석질 천연 다이아몬드는 실험 반복 시간이 30초에서 34.1 ppm의 미약한 신호를 얻었으며 합성 다이아몬드에서는 실험 반복 간격이 0.5초에서부터 34.2 ppm의 신호를 얻었으며 실험 반복 시간이 50초에서는 더 뚜렷한 34.7 ppm의 신호를 얻을 수 있었다. 천연 및 합성 다이아몬드의 극히 낮은 함량에 기인하여 $^{15}N$는 NMR 신호가 감지되지 않았다. 천연 다이아몬드와 합성 다이아몬드의 이완 시간과 불순물의 성분 함량은 서로 밀접한 관련성이 있음을 확인하였으나 $^{13}C$의 NMR 특성의 유사성으로 신호의 강약의 차이를 제외하고는 천연 혹은 합성 여부의 구별은 가능하지 않았다.