• Journal of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.197-204
• /
• 1985

The dependence of polarographic parameters on pressure and temperature for the reduction of 2.0 ${\times}\;10^{-4}$M 1-(2-pyridylazo)-2-naphthol (PAN) and 5.0 ${\times}\;10^{-4}$M 4-(2-pyridylazo)-resorcinol(PAR) in buffered methanol-water mixed solution at the dropping mercury electrode, has been discussed. In this experiment the temperature is varied from 25$^{\circ}C$ to 35$^{\circ}C$ and the pressure is ranging from 1 atmosphere to 1,800 atmospheres. The reduction half-wave potentials are shifted to the more positive potentials with increase in pressure. The diffusion currents of two depolarizers become considerably larger with increase in pressure from 1 atmosphere to about 1,000 atmospheres but are getting smaller above 1,000 atmospheres. The slopes of log plot become much larger with increase in pressure, which indicates the more irreversible reduction. The reduction currents of two depolarizers are found to be diffusion controlled over all pressure ranges. The linear relationships between diffusion current and the concentration of two depolarizers are good agreement over all pressure ranges (1 atm∼1,800atm.).

• The Korean Journal of Physiology
• /
• v.29 no.1
• /
• pp.13-27
• /
• 1995

single $K^{+}$ channels of skeletal muscle from the rat and frog were into planar lipid bilayers and their properties were studied. Fusion was induced by an osmotic gradient. Of the four types of $K^{+}$ channels recorded, the two most frequently observed were a voltage and $Ca^{2+}-activated$ $K^{+}$ channel and a $K^{+}$ channel with a prominent conductance substate. The first $K^{+}$ channel was identified as the large $Ca^{2+}-activated$ $K^{+}$ (BK) channel because the open-state probability was increased with depolarization (e-fold change per $10.6{\pm}3.5$ mV, n=8) and internal $Ca^{2+}$ (half-activation at $16.7{\pm}3.8$ mV, n=8, pCa 4) and its conductance was large ($247{\pm}4.9$ pS, n=24 in 0.1 M KCI). Lifetime distributions of open- and closed-states could be fitted with single exponentials of several milliseconds. The mean open- and closed-lifetimes were linearly dependent on the intracellular $[Ca^{2+}]$ and $1/[Ca^{2+}]$, respectively. The second $K^{+}$ channel showed a conductance substate at $30{\sim}60%$ of the open state. Its current-voltage relation was linear in the range of $-80\;{\sim}\;+80\;mV$. The slope conductance of the substate and open-state were 40 and 144 pS in 0.2 M KCl, respectively. The channel was highly selective for $K^{+}$ over Cl. The open-state probability was weakly voltage-dependent (e-fold change per 35 mV. The lifetime distributions of open- and closed-states were fitted with two exponentials and the major gating occurred slowly at several hundred milliseconds. Based on the above results, we think the second type of $K^{+}$ channel is the sarcoplasmic reticulum $K^{+}$ (SRK) channel. In addition, both types of channel were also incorporated into the lipids extracted from the skeletal muscle. The channel properties recorded in the bilayers termed from synthetic and extracted lipids were qualitatively similar. Our data indicate that BK and SRK channels are rich in the skeletal muscle and their properties and regulation could be effectively studied in planar lipid bilayer.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.3
• /
• pp.275-282
• /
• 2009

Generally, the sinusoidal cavity dither is adopted to ring laser gyroscope for eliminating the lock-in which is non-linear effect at the small rotation input. Despite this method, there are some remained errors which are generated at the dither turnaround, and those errors produce random walk which is a general character of a ring laser gyroscope. As one of the numerous research results for compensating these errors, there is a special lock-in compensation method which is the method of error estimation and compensation by comparing the beat signal periods of before and after the dither turnarounds. In this paper, by ring laser gyroscope modeling and numerical analysis, we verified the theoretical validity and confirmed the effectiveness of this method in expectation of the possible beat signal measurement time resolution. As a result, we confirmed the random walk decreases from a-half to a-third by this lock-in compensation method. So, it is expected to be a remarkable method for reducing the INS alignment time.

• Journal of Korean Society of Forest Science
• /
• v.89 no.5
• /
• pp.576-584
• /
• 2000

The term 'greenways' is a fairly new one. The term greenways refer to linear corridors which set aside pieces of nature. The objective of this study was to find out the feasibility of developing greenways in Taegu. Sample of 446 trail users were asked to describe their use patterns and as well as their perceptions of the benefits and problems associated with trails through on-site interviews conducted during the months of July and August of 1999. Trail users in Taegu were predominately male(61%) and over half of the respondents used private vehicle to access to the study areas as compared to 2% of respondents used bicycle. Trail users responded that health & fitness and open space preservation were the two most important benefits, and the provision of trail access to disabled persons was ranked last. As problems at study areas, lack of interpretive information was the biggest problem followed by lack of drinking water, poor trail marking/signs and not enough information. Most(94.1%) of the trail users surveyed indicated that they would support greenways development and 96.8% of respondent would use after greenways development. Willingness to pay for developing greenways was assessed with hypothetical scenario. Average willingness to pay in the survey was 10,200 won as a tax. The development/application of greenways in Taegu would work best when establish a network of trails with environmentally sensitive manner.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.64.2-64.2
• /
• 2019

It is known that lights scattered by comets and asteroids are partially polarized. From polarimetric observations of those objects, we can investigate physical properties, such as albedos, sizes of cometary dust particles and regolith of asteroids. Since the polarization degrees of those objects highly depend on their phase angles (Sun-object-observer's angles), long-term monitoring observations are required. Moreover, comets show unforeseeable activations (i.e., outbursts) which need follow-up observations to understand the mechanism. In order to realize such monitoring and transient observations, we installed the Triple-Range Imager and POLarimeter (TRIPOL) on the 61cm telescope of Seoul National University (Hereafter, SNU) Gwanak campus. With this combination, we can obtain g', r', i' bands photopolarimetric images simultaneously with $8.0^{\prime}{\times}8.0^{\prime}$ field of view and pixel resolution of 0.94" pixel-1. Here, we make a presentation regarding the photometric and polarimetric performances of TRIPOL on the SNU 61cm telescope. In addition, we introduce initial polarimetric results of asteroid and comets with the instruments. First, we determine the limiting magnitudes (defined as magnitudes for S/N=5) of $15.17{\pm}0.06$ (g'-band), $15.68{\pm}0.01$ (r'-band), $16.24{\pm}0.03$ (I'-band), respectively, with total 240-seconds exposure (four 60-seconds exposure images, each was taken at different rotation angle for the half-wave plate). Second, we found that the instrumental polarization is negligibly small, ($-0.32{\pm}0.04%$ in the g', $-0.36{\pm}0.05%$ in the r' and $-0.21{\pm}0.04%$ in the i'-bands), while the polarization efficiencies are large enough to maximize the performance (i.e., $97.52{\pm}0.03%$ in the g', $98.83{\pm}0.02%$ in the r' and $99.15{\pm}0.02%$ in the i'-bands). With the instruments, we made observations of three Jupiter-family comets, 21P/Giacobini-Zinner, 38P/Stephan-Oterma, and 46P/Wirtanen and plan to observe one near-Earth asteroid, (433) Eros, on a trial basis. Especially for comets, we discriminate signals from dust and gas to eliminate gas contamination, which are known to change observed degree of linear polarization, using multi-band images. We confirm that the phase angle dependency of these comets are consistent with previous observations, probably because polarimetric property of Jupiter-family comets are broadly homogeneous unlike asteroids. We will also describe future observation plans using TRIPOL and SNU 61cm telescope.

• Nuclear Engineering and Technology
• /
• v.54 no.1
• /
• pp.318-325
• /
• 2022

In this study, composites containing undoped and barium-doped Bi₂WO₆:Ba²⁺were investigated for their shielding against diagnostic X-ray. At first, Bi₂WO₆ and barium-doped Bi₂WO₆ were synthesized with different weight percentages of barium oxide through a hydrothermal process. The as-synthesized nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy (RS). After that, some shields were generated with undoped and barium-doped Bi₂WO₆:Ba²⁺ nanostructure particles incorporated into polyvinyl chloride (PVC) polymer with different thicknesses and 15% weight of the nanostructure. Finally, the prepared samples were exposed to an X-ray tube at 40, 80, and 120 kV voltages, 10 mAs and, 44.5 cm SID (i.e. the distance from the X-ray beam source to the specimen). Linear and mass attenuation coefficients were also calculated for different samples. The results indicated that, among the samples, the one with 7.5 mmol barium-doped Bi₂WO₆ had the most attenuation at the voltage of 40kV, and the attenuation coefficients would increase with an increase in the amount of barium. The samples with 15 and 17.5 mmol barium-doped Bi₂WO₆ had higher attenuation than the others at 80 and 120 kV. Moreover, the half-value layer (HVL), tenth-value layer (TVL) and 0.25 mm lead equivalent thickness were calculated for all the samples. The lowest HVL value was for the sample with 7.5 mmol barium-doped Bi₂WO₆. As the result clearly show, an increment in the barium-doping content leads to a decrease in both HVL and TVL. In every three voltages, 0.25 mm lead equivalent thickness of the barium-doped composites (7.5 mmol and 15 mmol) had less than the other composites. The lowest value of 0.25 mm lead equivalent thickness was 7.5 barium-doped in 40 kV voltage and 15 mmol barium-doped in 80 kV and 120 kV voltages. These results were obtained only for 15% weight of the nanostructure.

• Journal of the Korean Society of Radiology
• /
• v.16 no.7
• /
• pp.953-960
• /
• 2022

The measurement of branching ratio of ¹⁶⁷Yb radioactive isotopes from gamma-ray spectrum of ¹⁶⁹Tm(p,3n)¹⁶⁷Yb reaction were performed by using a 100-MeV proton linear accelerator of the Korea Multi-purpose Accelerator Complex (KOMAC). The ¹⁶⁷Yb isotope has a half-life of 17.5 minutes and decays to ¹⁶⁹Tm. The gamma rays generated from the ¹⁶⁷Yb isotope were measured using an HPGe detector gamma ray spectroscopy system. The energy calibration of the detector and the efficiency measurement of the detector were determined using a standard source. The gamma rays of known main energy (62.9, 106.2, 113.3, 143.5 and 176.3 keV) were measured. On the other hand, information about the intensity of the generated gamma rays is very inaccurate. Therefore, in this study, the decay strength of the main gamma rays was accurately measured. Overall, it was different from the previously known results, and in particular, it was found that the intensity of the main decay gamma ray, such as the 113.3 and 106.2 keV gamma ray, was overestimated, and it was found that the gamma ray, such as 62.9, 116.7 and 143.5 keV was underestimated. The present results are considered to be important information in the fields of nuclear fusion, astrophysics and nuclear physics in the future.

• Phonetics and Speech Sciences
• /
• v.14 no.2
• /
• pp.1-10
• /
• 2022

A wh-phrase positioned in an embedded clause can be interpreted as having a matrix scope if the sentence is produced with proper prosodic structures such as the wh-intonation. In a previous experiment, a sentence with a wh-phrase in an embedded clause was given to 40 speakers of Gyeongsang Korean. A script containing the sentence was provided to induce a matrix scope interpretation for the wh-phrase. These 40 utterances were prepared as stimuli for a perception test to verify whether the wh-phrases in the stimuli were perceived as having matrix scopes. Each utterance was played thrice to 24 subjects. The results showed that more than half of the 72 responses indicated a preference for an embedded scope rather than a matrix scope in 20 of the utterances. A multiple linear regression analysis showed that the matrix scope responses were best predicted by the magnitude of the pitch prominence in a prosodic word consisting of an embedded verb and a complementizer. The pitch prominence was calculated by subtracting the fundamental frequency (F0) at the right edge of the prosodic word from the peak F0 in the same prosodic word. The smaller the magnitude, the more matrix responses there were. These results suggest that the categorical perception of wh-scopes is based on the magnitude of pitch prominence.

• Radiation Oncology Journal
• /
• v.9 no.1
• /
• pp.131-141
• /
• 1991

A comprehensive set of dosimetric measurements has been made on the Varian Clinac 1800 15 MV photon beam. Beam quality, percentage depth dose, dose in the build up region, output, symmetry and flatness, transmission through iead (Cerrobend), tray attenuation, isodose curves for the open and wedged fields were measured using 3 dimensional water phantom dosimetry system (including film densitometer system) and polystyrene phantoms. These dosimetric measurements sufficiently characterized the beam to permit clinical use. The depth dose characteristics of photon beam is $d_{max}$ of 3.0 cm and percentage depth dose of $76.8\%$ at 10 cm,100 cm source-surface distance, field size of $10\times10\;cm^2$ for 15 MV X-ray beam. The Output factors ranged 0.927 for $4\times4\;cm^2$ field to 1,087 for $35\times35\;cm^2$ field. The build-up level of maximum dose was at 3.0 cm and surface dose was approximately $15.5\%$ for a field size $10\times10\;cm^2$ The stability of output is $within\pm1\%$ and flatness and symmetry are $within\pm3\%$. The half value thickness (HVL) of lead is 13 mm, which corresponds to an attenuation coefficient of $0.053\;mm^{-1}$. These figures compare facorably with the manufacturesr`s specifications.

• Korean Journal of Environmental Biology
• /
• v.26 no.3
• /
• pp.252-263
• /
• 2008

The purpose of this study was to determine trophic state, based on nutrients (TN, TP), transparency (SD), and chlorophyll-${\alpha}$ (Chl) and identify their empirical relations of TN-Chl, TP-Chl and Chl-SD depending on the dataset used along with dynamics of conductivity and suspended solids. Analysis of trophic states showed that more than half of 36 reservoirs were judged as eutrophic-hypertrophic conditions depending on the trophic variables. Seasonal values of TP varied by nearly 500% and showed greater in August than any other months. In contrast, TN varied within less than 90% and all monthly mean values of TN were never fall less than 1.2 mg L$^{-1}$ indicating low seasonal variations and high ambient concentrations (eutrophic-hypertrophic state). Analysis of empirical relations in the trophic variables showed that transparency had greater functional relations with Chl (R$^2$=0.31, p<0.001) than TP (R$^2$=0.15, p<0.001) and TN (R$^2$=0.20, p<0.001). Ratios of TN : TP in the ambient water indicated that most reservoirs showed a potential phosphorous limitation on the algal growth. Thus, algal biomass, based on Chl values, was more regulated by phosphorous than nitrogen. Analysis of linear regression model, based on log-transformed annual mean values, showed that only 30% in the variation of Chl was explained by TP (R$^2$=0.295, p=0.001, n=36) and 15% by TN (R$^2$=0.151, p=0.019, n=36). However, linear regression model, based on individual system, showed that Chl-TP model had strong positive relations (R$^2$=0.62, p=0.002, n=12), whereas the model had no any relations (p=0.892, n=12). Overall, our data suggested that averaging effect in the empirical model developments may influence the significance in the statistical analysis.