• Journal of the Korean Magnetic Resonance Society
• /
• v.17 no.1
• /
• pp.24-29
• /
• 2013

The structural characteristics of 4-coordinate $BO_4$ [B(1)] and 3-coordinate $BO_3$ [B(2)] groups in $BiB_3O_6$ were studied by $^{11}B$ magic angle spinning (MAS) and single-crystal nuclear magnetic resonance (NMR) spectroscopy. The spin-lattice relaxation time in the laboratory frame, $T_1$, for $^{11}B$ decreased slowly with increasing temperature, whereas the spin-lattice relaxation times in the rotating frame, $T_{1{\rho}}$, for B(1) and B(2), which differed from $T_1$, were nearly constant. Further, $T_{1{\rho}}$ for B(1) and B(2) showed very similar trends, although the $T_{1{\rho}}$ value of B(2) was shorter than that of B(1). The 3-coordinate $BO_3$ and 4-coordinate $BO_4$ were distinguished by $^{11}B$ MAS NMR spectrum and $T_{1{\rho}}$.

• Proceedings of the KIEE Conference
• /
• 1989.07a
• /
• pp.356-358
• /
• 1989

Linear and nonlinear complex permittivities have been measured for an alternating copolymer of vinylidene cyanide(VSCN) with vinyl propionale(VPr). It is found that the third order permittivity ${\varepsilon}_3$ depends upon frequency according to a function V ${\varepsilon}_3$/ ${1+(j{\omega}{\tau}_3)^{\beta}}^3$ while the linear permittivity ${\varepsilon}_1$obeys a Debye type function ${\nabla}{\varepsilon}_1$/ {1+$(j{\omega}{\tau}_1)^{\beta}$}. Experimental results are well fitled by predicted functions except at low frequency where dc conduction dominates. The relaxation times ${\tau}_1$ and ${\tau}_3$ at same teperature are nealy equal and depend upon temperature according to WLF form. The relaxation strengths ${\nabla}{\varepsilon}_1$ and ${\nabla}{\varepsilon}_3$ have a peak at the vicinity of glass transition temperature (Tg). The strength ${\nabla}{\varepsilon}_1$ has a value of -9 order and ${\nabla}{\varepsilon}_3$ has a negative value of -25 order. The analysis of mechanism by combined knowledge about linear and nonlinear permittivities and dipole moment gives us an imformation of the electrical and thermal dipolar motions in this copolymer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.3
• /
• pp.221-228
• /
• 1998

In this study, the $\beta$-Polyvinylidene fluoride(PVDF) thin films were fabricated by physical vapor deposition method. Also, the properties of dielectric relaxation were studied to understand carrier's behavior of PVDF thin films, to be regarded as the excellent piezo and pyroelectricity. In the process of vapor deposition, the $\beta$-PVDF thin films have been fabricated under the condition of the substrate temperature at 3$0^{\circ}C$, the applied electric field at 142.8kV/cm and the pressure at 2.0${\times}10^{-5}$torr. The dielectric properties of PVDF have been studied in the frequency range 10Hz to 1MHz at temperature from 30 to $100^{\circ}C$. The relative dielectric constant of $\alpha$ and $\beta$-PVDF were 6.8 and 9.8, respectively, under a frequency of 1kHz. Such a phenomenon was caused by the decrease in intermolecular forces originated by the phase-transition from the TGTG' molecular conformation to the TT planar zig-zag conformation. And the relative dielectric constant is increased as a measuring temperature increases, because of the reduction of relaxation time caused by the decrease of intermolecular force.

• Health Policy and Management
• /
• v.26 no.4
• /
• pp.279-288
• /
• 2016

Graphic health warning on the tobacco product package is a cost-effective tobacco control policy to convey information on harmful effect of tobacco use to health, and it is known not only to motivate smokers to quit but also to deter adolescents from start smoking. In case of Korea, amendments to National Health Promotion Act requiring implementation of graphic health warning had been submitted 13 times, from 2002 to May 2015. In May 2015, the amendment had been approved by the National Assembly and it enters into force on December 23, 2016. This research analyzed the discussions from Health and Welfare Committee of the National Assembly during the implementation of the graphic health warning in order to study decision making process of legislators. Study found that there was a shift from a general opposition on implementing graphic health warning at first to a harsh conflict over relaxation of the regulation once discussing the implementation in earnest. Particularly, while the group supporting the implementation of the graphic health warning or opposing relaxation advocated the amendment with scientific and knowledge-based evidences including the World Health Organization Framework Convention on Tobacco Control, the group opposing the adoption of the amendment itself or suggesting relaxation tended to defend their position with empathy on smokers or tobacco industries.

• Journal of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.149-155
• /
• 1975

Pivalic acid, which has a globular shape and is a plastic crystal, has been examined by means of temperature-dependent with-line proton magnetic resonance spectroscopy. Results of temperature-dependent line width, second moment, and spin-lattice relaxation time studies of pivalic acid were interpreted in terms of dynamic behavior and hydrogen bonding. The dynamic behavior consists of superimposed reorientation of the methyl groups about their three-fold axes$(C_3) and of the molecule about the central C-C bond(C_3'),$ general molecular reorientation about the center of gravity, and molecular self-diffusion. Activation energies for the motional processes have been obtained from line width measurements using the modified Bloembergen, Purcell, and Pound theory and from spin-lattice relaxation time measurements. The results were compared with the Pople-Karasz theory of fusion and the agreement was found to be poor. The discrepancy was interpreted in terms of hydrogen bonding in this molecule.

• Korean Journal of Food Science and Technology
• /
• v.34 no.6
• /
• pp.1062-1066
• /
• 2002

Low field NMR was employed to discriminate the geographical origin of sesame seeds from Sudan, China, and Korea. Sudan sesame seeds had the lowest contents of moisture and crude fat. Chemical components of Korean and Chinese sesame seeds were similar, whereas relaxation times $(T_1-IR,\;T_1-SR)$ measeured through spin-lattice relaxation pluse techniques using 20 MHz NMR showed significant difference (p0.05). Canonical discriminant analysis could be used to identify the habitat of sesame seeds with over 90% accuracy of NMR results. Non-destructive and fast NMR techniques can be applied to classify Korean sesame seeds from those of other origins.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.3
• /
• pp.296-306
• /
• 1992

$^{13}C$ spin-lattice relaxation times were measured for n-alkanes of moderate chain length, ranging from n-octane to n-dodecane, under the condition of proton broad-band decoupling within the temperature range of 248-318 K in order to gain some insight into basic features of segmental motions occurring in long chain ploymeric molecules. The NOE data showed that except for methyl carbon-13 dipole-dipole interactions between $^{13}C$ and directly bonded $^1H$ provide the major relaxation pathway, and we have analyzed the observed $T_1data$ on the basis of the internal rotational diffusion theory by Wallach and the conformational jump theory by London and Avitabile. The results show that the internal rotational diffusion constants about C-C bonds in the alkane backbone are all within the range of $10^9\;-10^10\;sec^{-1}$ in magnitude while the mean lifetimes for rotational isomers are all of the order of $10^{-11}\;-10^{-10}$ sec. Analysis by the L-A theory predicts that activation energies for conformational interconversion between gauche and trans form gradually increase as we move from the chain end toward the central C-C bond and they are within the range of 2-4 kcal/mol for all the compounds investigated.

• Progress in Superconductivity
• /
• v.3 no.1
• /
• pp.36-40
• /
• 2001

We have studied vortex dynamics in$ Bi_2$$Sr_2$$CaCu_2$O$_{8}$single crystals of unirradiated and irradiated samples by using 100 $\times$ $100\mu\textrm{m}^2$Hall sensor. Doses equivalent magnetic fields are 20 G, 100 G and 1 kG. In the magnetization measurement, a second magnetization peak (SMP) was observed in unirradiated, 20 G dose and 100 G dose samples in contrast to 1 kG dose sample. In the unirradiated sample, the SMP was observed in the range of 18 K ~ 35 K and the amplitude of the SMP decreased with increasing temperature. With increase of the irradiation dose, temperature region and sharpness of the SMP were reduced. In the magnetic relaxation measurement, we observed that the normalized relaxation rate S decreased with increasing the irradiation dose. Our results suggest that the vortex dynamics is not greatly affected by low-density columnar defects.s.

• Journal of the Korean Institute of Rural Architecture
• /
• v.20 no.3
• /
• pp.1-9
• /
• 2018

This research aimed to identify walking trails' purpose of its use and the factors that influence the selection. For this, a survey targeting the walking trail users was conducted in 2016 to question the research aim stated above. The mean number of walking trail usage in a month was 2.51 times and the duration of use ranged from one to ten hours, with the average of 2.5 hours. The main reason for the usage was to maintain physical health and the following was for mental relaxation, thus showing more than 90% of the people concerned with physical and mental health. Walking trails near the residences had the greatest percentage and trails that include mountains, rivers, seas and lakes were the following. Trails near historical locations or countryside showed a lower percentage. The choices showed relevance to the proximity as a standard of selection. The next highest percentage was the convenience of transportation. Additionally, people that access the trails three or more times were inclined to be influenced by the installation of exercising equipment. The aspect of facilities showed that the place for relaxation was a significant selection factor such as bathrooms for 20s to 30s and exercising equipments for people older than 50. To access the walking trails, people reach it by automobiles, public transport, walking and bicycles and out of these, automobiles had the highest percentage.

• KIEAE Journal
• /
• v.15 no.2
• /
• pp.37-43
• /
• 2015

Purpose: It is crucially important that indoor luminous conditions of built environments be carefully studied so as to promote comfort and occupants' well-being. Method: The current study therefore focuses on the lit aspect of an enclosed space considered to be a resting room ($4.5m{\times}6.32m{\times}2.5m$). Particularly, on the effect that light levels and light color temperatures have on the physiological and psychological responses of resting occupants. To do so, a questionnaire survey was carried out on 50 subjects. The independent variables for the experiment included 9 different luminous environment conditions setup using 3 different levels of illuminance (50 lx, 150 lx, 300 lx) and 3 different color temperatures (2000 K, 3800 K, 5600 K). A questionnaire was utilized in determining which conditions were preferred by occupants. Result: As it turns out, indoor luminous environment designed for relaxation purposes should display luminance levels of at least 150 lx and 3800 K of color temperature in order to provide a visually comfortable environment suitable for the occupant's relaxation while at the same time promoting the psychological and HRV well-being of resting occupants.