• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1992.05a
• /
• pp.125-129
• /
• 1992

When relaxation time will be distributed, TSC observed in the experimental procedure was analysed by using a potential model having two equilibrium positions and equations of dielectric properties was derived. Calculation of distribution was made by matrix method and compared/confirmed values obtained by TSC and alternating current which have a correspondence with each other. In this measurement, distribution of activation energy and relaxation time was determined by TSC peak at around 147k/364 of which center is 10$\^$-4/ sec/10$\^$5/ sec respectively at room temperature and also obtained dielctric loss factor at the range of 10$\^$-7/-10$\^$5/Hz. It seems that low temperature peak is local dispersion and high temperature peak have a relation to dielectric transition of the material.

• Transactions on Electrical and Electronic Materials
• /
• v.15 no.2
• /
• pp.100-102
• /
• 2014

$Ag(Ta,Nb)O_3$ materials have a perovskite structure with a low loss tangent. These materials have been widely researched for their applications as high-frequency, passive components. Also, $Ag(Ta,Nb)O_3$ materials have weak frequency dispersion with high dielectric permittivity which gives them enormous potential for use in electronic components, including the filters, and embedded capacitors. Therefore, our research will discuss the structural and electrical relaxation properties of $Ag(Ta_{0.8}Nb_{0.2})O_3$ ceramics for device applications. We will investigate using X-ray diffraction to understand their structural properties and will analyze voltage dependent leakage current and timedependent relaxation behavior to understand their material properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.8
• /
• pp.658-663
• /
• 2002

Hall factor of electrons in $\Gamma$-valley is calculated as functions of temperature, impurity concentration, and nonparabolicity of conduction valleys by taking into account the current density obtained from the Boltzmann transport equation. The dependence of the Hall factor on the temperature is clearly shown in the case of the optical phonon scattering and that on the impurity concentration is obvious in the case of the ionized impurity scattering. As the nonparabolicity of the conduction band increases, the Hall factor due to the acoustic or optic phonon scattering increases, whereas that due to the ionized impurity scattering decreases. The change of the Hall factor can be analysed in terms of the dispersion of relaxation time.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.181-186
• /
• 2005

We demonstrate that the finite rate of dielectric relaxation in liquid crystals which has been ignored previously causes profound effects in the fast dielectric reorientation of the director. The phenomenon is relevant for submillisecond switching of the director when the switching rate approaches the rate of dielectric relaxation through the reorientation of the molecular dipoles. A submillisecond switching ($15-400\;{\mu}s$ for an optical retardation shift $0.3-2.2\;{\mu}m$ in $10-15\;{\mu}m$ thick cells) is demonstrated for dual frequency nematic cells with high pretilt that maximizes the dielectric torque acting on the director. We propose the theory of dielectric response in which the electric displacement depends not only on the present (as in the standard theory) but also on the past values of electric field and director. We design an experiment in which the standard "instantaneous" model and our model predict effects of opposite signs; the experimental data support the latter model.

• Journal of the Korean Magnetic Resonance Society
• /
• v.21 no.2
• /
• pp.55-62
• /
• 2017

It is now well established that RNAs exhibit fundamental roles in regulating cellular processes. Many of these RNAs do not exist in a single conformation. Rather, they undergo dynamic transitions among many different conformations to mediate critical interactions with other biomolecules such as proteins, RNAs, DNAs, or small molecules. Here, we briefly review NMR techniques that describe the dynamic behavior of RNA by determining structural, kinetic, and thermodynamic properties.

• Korean Journal of Materials Research
• /
• v.29 no.4
• /
• pp.221-227
• /
• 2019

This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated $ZrO_2$ ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated $ZrO_2$ particles are observed by FE-TEM and FT-IR. The rheological properties of VTES-coated $ZrO_2/High-temp$ composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3D-printed objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated $ZrO_2$ ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.

• Journal of Fashion Business
• /
• v.24 no.3
• /
• pp.17-29
• /
• 2020

This study aimed to produce fiber stretch sensors for smart soccer socks to prevent injuries during training. A sensor was manufactured with stretchable fabric and tested to ensure convenience during training. In order to manufacture the fiber stretch sensor, a CNT dispersion solution was applied to an e-band and elastic polyester fabric, and the performance of the sensors was evaluated by a tensile test. Performance evaluation showed that both of the tested fabrics are excellent for this purpose. Both sensors were attached to socks to create prototype wearable devices, and an experiment was conducted to determine whether a resistance change accompanying relaxation and contraction of the gastrocnemius muscle could be detected. In order to accurately evaluate performance as a sensor, the fabric was stretched 20 times at low speeds of 1 Hz and 0.5 Hz. A change in resistance due to tension was observed, with both the E-band and the stretchable poly fabric showing high sensitivity and high reproducibility. Both can be used as relaxation/contraction sensors. Smart soccer socks were made using the two materials, and an evaluation was conducted. Tensile tests were done on the smart soccer socks; the tests were done 20 times per sock, and the sensor showed a stable resistance change between 30 and 40 ohms depending on the tension of the sensor. As a result, we confirmed that smart soccer socks with stretch sensors made of E-bands can measure changes in the gastrocnemius muscle.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.11C no.3
• /
• pp.70-74
• /
• 2001

Admittance or impedance spectroscopy is one of the powerful tools to study dielectric relaxation and loss processes in organic and inorganic materials. In this study, the frequency dependent properties of an indium tin oxide/tris(8-hydroxyquinoline) aluminum($Alq_3$)/aluminum structure have been studied. The conductance of the $Alq_3$ film increases with the DC applied voltage up to 4V and decreases above 4V in the low frequency region. This indicates that the resistance of the device decreases with the applied bias due to the carrier injection enhancement, thereafter the injected carriers form the space charge and the additional injection of carriers is prevented. The Cole-Cole plot of the admittance takes a one-semicircle shape, which means that the device can be modeled as a parallel resistor-capacitor network. The resistance and capacitance were estimated as 8.62k${\Omega}$ and 2.7nF, respectively, at 3V in the low frequency region. The dielectric constant ( ${\epsilon}'$ ) of the $Alq_3$ film is independent of the frequency in the low frequency region below 100kHz, while the frequency dependency was observed at above 100kHz. The dielectric loss factor ( ${\epsilon}"$ ) of the $Alq_3$ film shows the dielectric dispersion below 100kHz and dielectric absorption in higher frequency domain. The dispersion is thought to be related to the hopping process of the carriers. The ${\epsilon}"$ is proportional to the reciprocal of the frequency. The dielectric relaxation time was extracted to about 0.318${\mu}s$ from the dielectric absorption spectrum.

• Investigative Magnetic Resonance Imaging
• /
• v.3 no.2
• /
• pp.159-166
• /
• 1999

Purpose : To evaluate the effect of rotational correlation time (${\tau}_R$) and the possible related changes of other parameters, ${\tau}_M,{\;}{\tau}_S,{\;}and{\;}(\tau}_V$ of gadolinium (Gd) chelate on T1 relaxation enhancement in two pool model. Materials and Methods : The NMRD (Nuclear Magnetic Relaxation Dispersion) profiles were simulated from 0.02 MHz to 800 MHz proton Larmor frequency for different values of rotational correlation times based on Solomon-Bloembergen equation for inner-sphere relaxation enhancement. To include both unbound pool (pool A) and bound pool (pool B), the relaxivity was divided by contribution from unbound pool and bound pool. The rotational correlation time for pool A was fixed at the value of 0.1 ns, which is a typical value for low molecular weight complexes such as Gd-DTPA in solution and ${\tau}_R$ for pool B was changed from 0.1 ns to 20 ns to allow the slower rotation by binding to macromolecule. The fractional factor of was also adjusted from 0 to 1.0 to simulate different binding ratios to macromolecule. Since the binding of Gd-chelate to macromolecule cab alter the electronic environment of Gd ion and also the degree of bulk water access to hydration site of Gd-chelate, the effects of these parameters were also included. Results : The result shows that low field profiles, ranged from 0.02 to 40 MHz, and dominated by contribution from bound pool, which is bound to macromolecule regardless of binding ratios. In addition, as more Gd-chelate bound to macromolecule, sharp increase of relaxivity at higher field occurs. The NMRD profiles for different values of ${\tau}_S$ show the enormous increase of low field profile whereas relaxivity at high field is not affected by ${\tau}_S$. On the other hand, the change in ${\tau}$V does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the maximum relaxivity value. The results shows a parabolic dependence of relaxivity on ${\tau}_M$. Conclusion : Binding of Gd-chelate to a macromolecule causes slower rotational tumbling of Gd-chelate and would result in relaxation enhancement, especially in clinical imaging field. However, binding to macromolecule can change water enchange rate (${\tau}_M$) and electronic relaxation ($T_le$) vis structural deformation of electron environment and the access of bulk water to hydration site of metal-chelate. The clinical utilities of Gd-chelate bound to macromolecule are the less dose requirement, the tissue specificity, and the better perfusion and intravascular agents.

• Korean Journal of Optics and Photonics
• /
• v.13 no.1
• /
• pp.58-64
• /
• 2002

Using Mach-Zehnder type intensity modulator, we stabilized a 10 GHz harmonically mode-locked dispersion-compensated fiber ring laser using a feedback controlling system, and we measured its stability. The laser was stabilized for more than 16 hours by controlling the cavity length to suppress the relaxation oscillation frequency component which had caused the laser output instability. The ms timing jitter and ms amplitude noise were measured to be 260-524 fsec and 4~11.5%, respectively, and BER test measurement showed a value of 10$^{-13}$ .