• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.435-442
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• 2008

Natural, synthetic, and treated diamonds were studied by NMR and EPR. It was demonstrated that natural and synthetic diamonds, treated and non-treated diamonds, high pressure high temperature (HPHT) treated and electron beam treated diamonds could be distinguished among each other based on the $^{13}C$ NMR spectra acquired for relatively short periods of 100 minutes. The $^{13}C$ NMR linewidths of gem quality synthetic diamonds were broader than 1.6 ppm due to the paramagentic effects of transition metals, generally used as catalysts, while the linewidths of gem quality natural diamonds were narrower than 0.5 ppm regardless of the methods of treatment. The linewidth (0.5 ppm) for a HPHT treated, gem quality natural diamond was as broad as more than twice of the linewidth (0.2 ppm) of an electron beam treated diamond. The $^{13}C$ NMR signal intensities of treated, gem quality natural diamonds were as strong as more than 10 times of the intensities of non-treated, gem quality natural diamonds. When correlated with the concentrations of the paramagnetic defects (electrons) obtained from the EPR spectra, the relative $^{13}C$ NMR signal intensities increased in proportion to the concentrations of the paramagnetic electrons contained in each sample but the electron beam treated diamond was an exception. This suggested that the lattice component, in addition to the paramagnetic defect component, should also be considered in determining the $^{13}C$ NMR signal intensity of the electron beam treated diamond.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.69-78
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• 2008

In this study, in order to verify the reinforcement effects of the cracked concrete tubes and culverts, static load test was conducted. After the load carrying capacity of the original concrete tubes (nominal diameter 0.8 m, 1.0 m, 1.5 m) and box culverts (inner width 2.0 m. 2.5 m) was reduced by the cracking test, the cracked concrete specimens were strengthened by installing profile with steel stiffener and high strength mortar. And then, the maximum load tests were conducted the renewal concrete tubes and box culverts. According to the method application, the load carrying capacity increased 1.66~3.50 times than it of the original tubes before applying the method. In case of the original box culverts, the load carrying capacity increased 1.66~3.10 times than the case before installing profile and high strength mortar. Also non-linear analysis was carried out by using the commercial FEM program of ABAQUS 6.6. Solid (C3D8R) elements and concrete damage plasticity option was applied to the analysis. For reflecting confined reinforcing bars in the analysis, the composite material properties were used.

• Korean Journal of Materials Research
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• v.2 no.4
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• pp.293-297
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• 1992

The magnetic properties of the amorphous Fe/sub 32/Ni/sub 36/Cr/sub 14/P/sub 12/B/sub 6/ has been studied by Mossbauer spectroscopy in the temperature range of 88-400K. The analysis of the spectrum of B8K, the magnetic hyperfine field and quadrupole splitting are found to be 140.5kOe and almost zero, which means that the magnetic hyperfine field is randomly oriented with respect to the principal axes of the electric field gradient, respectively. The values of quadrupole splitting in paramagnetic phase with Tc=280K are independent on the changes of temperature. Debye temperature is found to be about 288k from the analysis of recoilless fraction.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.30 no.4
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• pp.56-60
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• 2001

경험에 의하면 앞에서 언급한 장비의 사용, 규율, 규제된 용제의 사용, 기름 페인트 사용의 억제, 그리고 엄격한 페인트 과정을 따르는 것에 의해 잠수함내의 탄화수소 농도를 100만분의 1 또는 2 수준으로 유지할 수 있다. 예방책으로는 세심한 관찰, 선체내로 들여오는 모든 물질의 기록 그리고 규제된 물질의 사용 시간, 장소 및 양의 제어이다. 이러한 점들은 잠수함 내부를 안전하고 건강한 환경으로 설계하기 위하여 활용될 수 있는 자료들이다. 잠수함 내의 공기질은 적외선 분광 광도계, 질량 분광계, 상자성(paramagnetics), 열전도율, 광이온화 그리고 열량 검사에 의해 분석될 수 있다. 분석된 결과는 과거의 데이터와 비교되어 활성탄충의 교체등을 포함하여 유지 관리의 자료로 활용된다. 이러한 원리를 이용한 다양한 계측기가 선체 내의 대기 상태를 분석하기 위하여 사용된다. 중앙 대기 측정기, 추적 가스 분석기, 수소 탐지기, 이동형 대기 모니터, 이동형 산소 분석기, 탄광 안전 지시계, 열량 분석관, 탐지 펌프 시험기가 사용된다. 이러한 계측기는 잠수 전 또는 후에 사용된다. 계측기는 화재 발생시 영향을 받지 않은 공간 또는 냉매가 충전되는 장소에 사용된다. 오늘날 여러 종류의 특별한 잠수함이 존재한다. 정찰 업무를 통해 세계 평화를 유지하고 특별한 임무를 수행하는 것보다 덜 복잡한 목적을 지닌 잠수함도 있다. 그러나 선원들이 안전한 내부 환경 속에서 바다 속을 항해하고 계속 그 응용 범위를 확장하기 위하여 앞에서 언급한 장비들 또는 그 변형들이 사용되어야 한다.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.1-6
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• 1993

Electronic and magnetic proper tis of the rare-earth transition metal compound, $LaCo_{13}$, are investigated by performing self-consistent local density functional LMTO (linearized muffin-tin orbital) band structure calculations for both paramagnetic and ferromagnetic phases of $LaCo_{13}$. The calculated magnetic moments for the two types of Co atoms, Co I and Co II, are 1.34 and $1.65{\mu}_{B}$, respectively. The average magnetic moment of Co atoms in the ferromagnetic phase of $LaCo_{13}$ is estimated to be $1.60{\mu}_{B}$, which is in fairly good agreement with the experimental values, $1.56~1.68{\mu}_{B}$.

• Composites Research
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• v.13 no.6
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• pp.9-22
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• 2000

The Rayleigh-Ritz procedure based on energy method is used to present analytically the natural frequencies and the critical buckling loads for four types of loading conditions: (1) uniaxial, (2) biaxial, (3) positive shear and (4) negative shear, of the rectangular, composite plates unidirectionally stiffened with box beam type stiffeners. In analysis the discrete stiffener theory is adopted to present the effect of stiffeners in the plate structure. The convergence study is presented to demonstrate the accuracy of the results. Contour plots of the vibrated and buckled mode shapes are shown for some examples. The effect of various parameters such as numbers, position, aspect ratio of stiffener and layer angle, aspect ratio of plate are focused.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.07a
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• pp.202-208
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• 2002

진공냉각장치의 효율적인 설계를 위하여 파일럿 규모의 진공냉각장치에서 진공압력에 따른 작물별 냉각특성과 운전조작에 따른 냉각특성을 구명하는 요인실험을 실시한 결과 가. 배추와 같이 조밀하게 결구되어 있는 작물은 프레시 포인트로부터 습구온도와 품온에 따라 진공압을 조절함으로서 표면과 심부의 온도편차를 줄일 수 있고 버섯, 상추와 같이 개체가 작은 작물은 진공압력에 따른 온도편차가 거의 나타나지 않았다. 나. 포장방법에 따른 냉각 특성에서는 무개공 및 개공율 5% 골판지상자, PE 상자, 6mm 통기공이 있는 필름 포장에서의 냉각속도는 유사한 경향을 나타냈으나 0.8mm의 통기공을 가지고있는 필름 포장에서는 냉각속도가 현저히 낮게 나타나 필름 포장을 했을 경우 최소 개공율의 구명이 필요한 것으로 나타났다. 다. 예냉전 농산물 표면에 가수를 했을 경우 배추와 같은 결구성 농산물은 감모율 저하에는 효과적이었으나 무가수에 비해 냉각균일도와 냉각속도가 낮게 나타났으며 버섯에서는 감모율 저하 및 냉각속도 향상에 효과가 있는 것으로 나타났다.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.395-402
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• 1995

The intravoxel spin phases in magnetic resonance imaging (MRI) usually vary due to susceptibility differences of materials to be imaged. The phase variation in the voxel results in a reduction of the signal intensity. This signal intensity reduction is known as the susceptibility effect in MRI and has been studied extensively. In this paper, a new spectral decomposition technique Is proposed and the signal change due to the susceptibility effect can be analyzed. A pulse sequence for the spectral decomposition of the susceptibility was developed and applied to susceptibility imaging of venous blood possessing paramagnetic properties. The computer simulations and their corresponding experimental results obtained using both a phantom and human volunteers are reported. Key words : susceptibility effect in MRI : spectral decomposition of susceptibility effect.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.628-631
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• 1994

We have studied the paramagnetic $CuF_2$ using the techniques of pulsed nuclear magnetic resonance (NMR). The powder sample revealed two well-separated lines from the distinct $^{19}F$ sites at room temperature. One of the lines showed little frequency shift. However, the other showed a large frequency shift, suggesting electron transfers. Furthermore, the two sites have very short spin-lattice relaxation times $(T_1).$ The frequency-shifted site has the shorter $T_1$ than the unshifted one, reflecting the difference of the electron environments of the two sites.

• The Journal of Natural Sciences
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• v.7
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• pp.19-25
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• 1995

In this study, the Mossbauer effect of the $NiAl_0.8Fe_1.2O_4$ was investigated in the temperature range of 77K-1000K. The spectra were composed of two component, one is sixtet and the other doublet, at low temperature. From the temperature dependence of Mossbauer spectum, it is appeared that the magnetic properties of $NiAl_0.8Fe_1.2O_4$ varies from ferrimagnetism to paramagnetism as the increasing tempereture. And the magnetic relaxation patterns of the $NiAl_0.8Fe_1.2O_4$ were shown superparamagnetic effect.