• 한국자기공명학회논문지
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• 제6권2호
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• pp.132-141
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• 2002

$^1H$ nuclear magnetic resonance (NMR) relaxations have been investigated in ammonium sulfate $((NH_4)_2SO_4)$ power at temperatures ranging form 102 K to 440 K. There is a bottleneck in the spin-lattice relaxation between the nuclear spin system and the hindered rotation of ammonium ions, which is certified by measuring the relaxation according to the initial condition of the spin system. For temperatures below 318 K the $^1H$ spin-lattice relaxations have double-exponential behaviors with the exponent, n, having a value 2>n>1 initially and n=l after a long time. Above 318 K not only is the relaxation exponential initially with exponent n=1, but it is a single-exponential over the entire time, resulting in one $T_1$ value. The two types of $NH_4^+$ ions have different activation energies for hindered rotation, $E_a^1=0.27{\pm}0.02eV$ and $E_a^11=0.12{\pm}0.0eV$, in the ferroelectric phase.

• 한국자기학회지
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• 제4권1호
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• pp.52-55
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• 1994

HD 기체에 대하 수소 및 중수소 원자핵 스핀-격자 완화시간 $T_{1}(H)$와 $T_{1}(D)$가 측정되었다. 실험데이타는 온도 30 K < T < 313 K 및 압력 0.67 atm < P < 1.92 atm에서 측정되어졌다. 핵자기공명 주파수는 각각 수소원자핵에 대해서 358.012 MHz였고 중수소원자핵에 대해서는 54.958 MHz였다. 측정된 $T_{1}(H)$와 $T_{1}(D)$의 비로부터 분자스핀 연산자들인 $J_{z}$와 ${3J_z}^{2}-J(J+1)$에 관련된 상관시간의 비 ${\tau}_{1}/{\tau}_{2}$의 값이 얻어졌다. J = 1 상태에서의 원자핵 스핀-격자 완화시간이 온도의 함수로서 $T^{0.25}$에 비례하는 것이 관측되었다.

• 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.

• 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.

• Food Science and Biotechnology
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• 제17권5호
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• pp.895-898
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• 2008

The mobility of water in set yogurt during fermentation was studied using nuclear magnetic resonance (NMR) relaxometry. The spin-spin relaxation was analyzed using a 2-fraction model, resulting in 2 spin-spin relaxation time constants $T_{21}$ and $T_{22}$. Both $T_{21}$ and $T_{22}$ exhibited rapid changes between 2 and 4 hr of fermentation, coinciding with the drop in pH and the rise in lactic acid bacteria count. The spin-lattice relaxation time $T_1$ increased over the fermentation period. Both $T_1$ and $T_2$ showed an increase in the mobility of water upon gel formation during fermentation. Water redistribution within the gel matrix due to casein aggregation and structure forming may be responsible for the changes in mobility.

• 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.

• 한국자기공명학회논문지
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• 제26권1호
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• pp.10-16
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• 2022

The phase transition temperatures of CsCoCl₃·2H₂O crystals are investigated via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Three endothermic peaks at temperatures of 370 K (=T_C1), 390 K (=T_C2), and 416 K (=T_C3) were observed for phase transitions from CsCoCl₃·2H₂O to CsCoCl₃·1.5H₂O, to CsCoCl₃·H₂O, and then to CsCoCl₃·0.5H₂O, respectively. In addition, the spin-lattice relaxation time T_1ρ in the rotating frame and T₁ in the laboratory frame as well as changes in chemical shifts for ¹H and ¹³³Cs near T_C1 were found to be temperature dependent. Our analyses results indicated that the changes of chemical shifts, T_1ρ, and T₁ are associated with structural phase transitions near temperature T_C1. The changes of chemical shifts, T_1ρ, and T₁ near T_C1 were associated with structural phase transitions, owing to the changes in the symmetry of the structure formed of H₂O and Cs⁺ ions. Consequently, the structural symmetry in CsCoCl₃·2H₂O crystals based on temperature is discussed by the environments of their H and Cs nuclei.

• 한국자기공명학회논문지
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• 제23권2호
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• pp.40-45
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• 2019

The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

• 한국자기학회지
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• 제5권1호
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• pp.54-57
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• 1995

넓은 범위의 $^{1}H$ 핵자기공명 자기장에서 Heisenberg 반강자성체인 $MnCl_{2}.4H_{2}O$에 대하여 상온 수소 핵자기완화를 연구하였다. $MnCl_{2}.4H_{2}O$는 상온에서 밀접한 상자성 $Mn^{++}$ 이온계이지만 희박한 상자성계에서 예상되는 특성을 보인 반면에 희박한 상자성 근사와 매우 다른 결과도 보였다. 또한 수소 원자핵들은 0.7 T의 외부자기장 부근에서 스핀-격자 완화시간의 이상거동을 보였다.

• 전자공학회논문지SC
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• 제42권2호
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• pp.33-38
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• 2005

신체 내 혈당 변화량과 $^1H$ 원자핵의 스핀-격자 완화시간의 변화량이 관련 있음과 원자핵의 스핀-격자 완화시간을 측정하는 방법으로 자기공명흡수법이 제안된 바 있다. 자기공병흡수법에 의하여 신체 내 혈당 변화량을 감지하기 위해서는 검출 영역내 고수준의 자기장의 세기와 균일도의 확보가 필수적이다. 가정에서 손쉽게 혈당의 변화량을 측정할 수 있도록, 본 논문에서는 가정용으로 적합한 크기와 무게를 가지면서 요구되는 자기장의 세기와 균일도를 확보한 무혈혈당측정기를 디자인하였다. 여러 형상과 재질을 갖는 초기 모델들을 설계, 제작하였고, 검출 영역의 자기 특성을 비교하여 최종 재질을 결정하였다. 또한, 유한요소 해석모델을 구축하고 형상 최적화를 통하여 최종 모델을 선정하였다.