• Journal of Biosystems Engineering
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• 제16권1호
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• pp.37-48
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• 1991

Rice plants are subjected to various forces such as natural force of wind and mechanical force of cultivating machines. Rheological behavior of the rice stem can be expressed in terms of three variables : stress, relaxation and time. The objectives of this study are to examine stress relaxation, creep and recovery characteristics on the rice stem in case of axial and radial loading. Stress relaxation with time was studied on three levels of loading rate and on four levels of applied stress. The results were summarized as follows : 1. The hysterisis losses of the rice stem distinctly observed at the radial compression in comparison with axial compression. The hysterisis loss implied that the stem to absorbed energy without being deformed beyond the yield point. 2. Ageneralized Maxwell model consisting of three elements gave a good description of the relaxation behavior of the rice stem. Rate of loading was more significant on the observed relaxation behavior within the short relaxation time, but there were little influences of rate of loading on the relaxation time. 3. The stress relaxation intensity and the residual stress increased in magnitude as the applied stress increased, but the relaxation time was little affected by the applied stress. 4. The coefficients of the stress relaxation model showed much differences in the radial compression and the axial compression, especially the higher relaxation stress of the third element was observed in the radial compression. 5. The behaviors of rice stem in creep and recovery test also might be represented by a four element Burger's model. But the coefficients of the creep model were different from those of the recovery model. 6. The steady-state phenomena of creep appeared at the stress larger than 20 MPa in Samkang and 1.8 MPa in Whajin. 7. The elastic modulus of the stem showed the range from 40 to 60 MPa. It could be considered, as a result, the rice stems had viscoelastic properties.

• 동의신경정신과학회지
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• 제28권2호
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• pp.109-121
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• 2017

Objectives: The purpose of this study was to investigate clinical trends of Traditional Chinese Medicine (TCM) on combined treatment of acupuncture and relaxation therapy. Methods: Clinical trials based on acupuncture and relaxation therapy searched and were selected from China National Knowledge Infrastructure (CNKI). In this study we selected clinical research articles using acupuncture and relaxation therapy as intervention. Studies were assessed by Risk of Bias (RoB) tool, and Jadad scale. Results: Eleven randomized controlled trials on combined treatment of acupuncture and relaxation therapy were selected, and these studies were published in China. Most studies have targeted psychiatric disorders such as insomnia and anxiety. Manual Acupuncture (MA) was the most used acupuncture treatment, and in five studies two or more relaxation therapies were used in parallel. Although the treatment result using acupuncture and relaxation therapy was superior, heterogeneity of the control group was high and it was difficult to estimate additional effects of relaxation therapy. Conclusions: Qualitative analysis revealed that the combination of acupuncture and relaxation was more effective than control in most studies. However, quality of most studies was low. Therefore, higher quality clinical research on combined treatment of acupuncture and relaxation therapy is required.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.355-356
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• 2002

The dielectric permittance and the dielectric loss factor of several lubricating oils were measured at frequencies from 100 Hz to 1.5 MHz. The measurements were carried out under atmospheric pressure as a function of temperature and under fixed temperature as a function of pressure. Temperature and pressure dependence of dielectric relaxation time were investigated. The temperature dependence of relaxation time obeyed the Vogel-Fulcher-Tammann (VFT) law. We modified the VFT equation in order to express the dielectric relaxation time as a function of temperature and pressure. Furthermore. by taking into consideration the similarity of the temperature and pressure dependence between dielectric relaxation and mechanical relaxation. the prediction of high-pressure viscosity were conducted. The predicted results were compared with the viscosity data obtained from the falling-sphere type viscometer.

• Advances in Computational Design
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• 제2권1호
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• pp.71-87
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• 2017

This study focuses on the efficiency and applicability of dynamic relaxation methods in form-finding of membrane structures. Membrane structures have large deformations that require complex nonlinear analysis. The first step of analysis of these structures is the form-finding process including a geometrically nonlinear analysis. Several numerical methods for form-finding have been introduced such as the dynamic relaxation, force density method, particle spring systems and the updated reference strategy. In the present study, dynamic relaxation method (DRM) is investigated. The dynamic relaxation method is an iterative process that is used for the static equilibrium analysis of geometrically nonlinear problems. Five different examples are used in this paper. To achieve the grading of the different dynamic relaxation methods in form-finding of membrane structures, a performance index is introduced. The results indicate that viscous damping methods show better performance than kinetic damping in finding the shapes of membrane structures.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.317-323
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• 2017

This work presents a new strategy to model stress dependent relaxation process in large deformation. The strategy is relied on the fact that in some particular soft materials undergoing large deformation, e.g., elastomers, rubbers and soft tissues, the relaxation time depends strongly on stress levels. To simplify the viscoelastic model, we consider that the relaxation time is the function of previous elastic deviatoric stress state experienced by materials during loading. Using the General Maxwell Model (GMM), we simulate numerically conditions with the constant and the stress dependent relaxation time for uniaxial tension and compression loading. Hence, it can be shown that the proposed model herein not only can represent different relaxation time for different stress level but also maintain the capability of the GMM to model hysteresis phenomena.

• 한국자기공명학회논문지
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• 제11권1호
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• pp.1-9
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• 2007

An unequal site exchanging system induced by restricted rotation of 9-methyl group in 1,8-dichloro-9-triptycene has been studied by spin-lattice relaxation and 2D-EXSY experiments. The exchange rate obtained from relaxation studies is very well coincident to the result of line shape analysis, and the difference of the relaxation times ($T_1$) in two different sites has an important role to analyze 2D-EXSY experimental data.

• Bulletin of the Korean Chemical Society
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• 제23권5호
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• pp.727-735
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• 2002

Proton coupled carbon-13 relaxation experiment was performed to investigate the effect of vicinal protons on spin-lattice relaxation of methylene carbon-13 in n-undecane. A BIRD type pulse sequence was employed as a way to check the validity of describing the 13CH2 moiety as an isolated AX2 spin system. The results show that the presence of vicinal protons exerts substantial influence on the relaxation of methylene carbon-13, indicating that it is not a very good approximation to treat a methylene moiety as an isolated AX2 spin system.

• Journal of Magnetics
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• 제1권1호
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• pp.37-41
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• 1996

The frequency dependence of complex permeability for various NiCuZn ferrites was investigated. The variation of complex permeability for NiCuZn ferrites can be presented as a form of a semi-circle, so called the Cole-Cole plot, and the relaxation phenomena were explained with various shapes of the plots. The relaxation time $\Upsilon$ was calculated from $f_rx$, which is a relaxation frequency at ${\mu"}_{max}$. Relations between anisotropy field $H_A$ and relaxation time $\Upsilon$, initial permeability $\mu_i$ and $H_A$ were plotted to identify the frequency dependence of complex permeability.lity.

• Bulletin of the Korean Chemical Society
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• 제8권5호
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• pp.406-408
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• 1987

It has been shown that the distribution of relaxation times, H(ln $\tau$), in semi-logarithmic time scale can easily be calculated numerically from the derivative of the relaxation function in semilogarithmic scale. In that, ln$\tau$, the abscissa, is divided into N different segments of equal size, then H is considered to be a linear function of ln $\tau$within each segment. The technique has been applied to a Williams-Watts function as well as to the relaxation function obtained by photon correlation spectroscopy from atactic polystyrene glass. It has been demonstrated that the relaxation functions can be precisely reproduced from the calculated distribution functions.

• 대한디지털의료영상학회논문지
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• 제15권2호
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• pp.63-68
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• 2013

Purpose : The relaxation times of tissue in MRI depend on strength of magnetic field, morphology of nuclear, viscosity, size of molecules and temperature. This study intended to analyze quantitatively that materials' temperatures have effects on T1 and T2 relaxation times without changing of other conditions. Materials and Methods : The equipment was used MAGNETOM SKYRA of 3.0T(SIEMENS, Erlagen, Germany), 32 channel spine coil and Gd-DTPA water concentration phantom. To find out T1 relaxation time, Inversion Recovery Spin Echo sequences were used at 50, 400, 1100, 2500 ms of TI. To find out T2 relaxation time, Multi Echo Spin Echo sequences were used at 30, 60, 90, 120, 150, 180, 210, 240, 270 ms of TE. This experiment was scanned with 5 steps from 25 to $45^{\circ}C$. next, using MRmap(Messroghli, BMC Medical Imaging, 2012) T1 and T2 relaxation times were mapped. on the Piview STAR v5.0(Infinitt, Seoul, Korea) 5 steps were measured as the same ROI, and then mean values were calculated. Correlation between the temperatures and relaxation times were analyzed by SPSS(version 17.0, Chicago, IL, USA). Results : According to increase of temperatures, T1 relaxation times were $214.39{\pm}0.25$, $236.02{\pm}0.87$, $267.47{\pm}0.48$, $299.44{\pm}0.64$, $330.19{\pm}1.72$ ms. T2 relaxation times were $180.17{\pm}0.27$, $197.17{\pm}0.44$, $217.92{\pm}0.39$, $239.89{\pm}0.53$, $257.40{\pm}1.77$ ms. With the correlation analysis, the correlation coefficients of T1 and T2 relaxation times were statistically significant at 0.998 and 0.999 (p< 0.05). Conclusion : T1 and T2 relaxation times are increased as temperature of tissue goes up. In conclusion, we suggest to recognize errors of relaxation time caused local temperature's differences, and consider external factors as well in the quantitative analysis of relaxation time or clinical tests.