• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.857-862
• /
• 2011

3 dimensional turbine exhaust gas flow was simplified to an axisymmetrical flow and calculated with detailed chemistry models. GRI 35 species-217 reaction step model and simplified 11 species 15 reaction model was applied to the secondary reaction of the turbine exhaust gas and compared. All the model captured the secondary combustion on the base region, and the temperature was 600K higher than that without turbine exhaust gas. This means the local temperature of the base can be higher in the case of real 3 dimensional flow. The simplified model show the similar results to the GRI detailed chemistry model although the former affected the engine plume structure slightly.

• Journal of the Korean Chemical Society
• /
• v.39 no.9
• /
• pp.722-727
• /
• 1995

The electrochemical impedance spectra of polyaniline film prepared by cyclic voltammetry have been investigated in 0.1 M aqueous sulfuric acid solution. Charge transfer resistances were rather low at the oxidized states in agreement with the conductive behavior reported at these potentials. The corresponding exchange current densities were very high. Large values of capacitance associated with the polymer have been found which vary as a function of the electrode potentials. An equivalent electrical circuit has been deduced from the impedance data. It was therefore possible to obtain the parameters of the ionic mass transport within the film.

• Radiation Oncology Journal
• /
• v.24 no.3
• /
• pp.157-163
• /
• 2006

[ $\underline{Purpose}$ ]: To evaluate the role of postoperative adjuvant chemoradiotherapy in rectal cancer, we retrospectively analyzed the treatment outcome of patients with rectal cancer taken curative surgical resection and postoperative adjuvant chemoradiotherapy. $\underline{Materials\;and\;Methods}$: A total 46 patients with AJCC stage II and III carcinoma of rectum were treated with curative surgical resection and postoperative adjuvant chemoradiotherapy. T3 and T4 stage were 38 and 8 patients, respectively. N0, N1, and N2 stage were 12, 16, 18 patients, respectively. Forty patients received bolus infusions of 5-fluorouracil ($500\;mg/m^2/day$) with leucovorin ($20\;mg/m^2/day$), every 4 weeks interval for 6 cycles. Oral Uracil/Tegafur on a daily basis for $6{\sim}12$ months was given in 6 patients. Radiotherapy with 45 Gy was delivered to the surgical bed and regional pelvic lymph node area, followed by $5.4{\sim}9\;Gy$ boost to the surgical bed. The follow up period ranged from 8 to 75 months with a median 35 months. $\underline{Results}$: Treatment failure occurred in 17 patients (37%). Locoregional failure occurred in 4 patients (8.7%) and distant failure in 16 patients (34.8%). There was no local failure only. Five year actuarial overall survival (OS) was 51.5% and relapse free survival (RFS) was 58.7%. The OS and RFS were 100%, 100% in stage N0 patients, 53.7%, 47.6% in N1 patients, and 0%, 41.2% in N2 patients (p=0.012, p=0.009). The RFS was 55%, 78.5%, and 31.2% in upper, middle, and lower rectal cancer patients, respectively (p=0.006). Multivariate analysis showed that N stage (p=0.012) was significant prognostic factor for OS and that N stage (p=0.001) and location of tumor (p=0.006) were for RFS. Bowel complications requiring surgery occurred in 3 patients. $\underline{Conclusion}$: Postoperative adjuvant chemoradiotherapy was an effective modality for locoregional control of rectal cancer. But further investigations for reducing the distant failure rate are necessary because distant failure rate is still high.

• Journal of The Korean Association For Science Education
• /
• v.20 no.1
• /
• pp.166-173
• /
• 2000

Purpose of this study is to investigate on the attitude toward science of science gifted and talented(G/T) middle school students. The inventory instrument used for study was a revision of TOSRA which consisted of six domains. Subjects were 131 students who had entered into Center for Science G/T Education, Seoul National University in 1999. This center is composed of five divisions: mathematics, physics, chemistry, biology, and earth science. There was no difference between genders totally, but the attitude level of male was higher than that of female in 'career interest in science' domain. Compared among domains, while the attitude score toward leisure interest in science' was the highest, 'normality of scientist' was the lowest. Whereas the attitude level was no difference among divisions except chemistry, that of chemistry division was higher than mathematics in 'adoption of scientific attitudes' domain. Thus, it is needed to provide social and national encouragement for superior science G/T students as well as to develope special programs for them so as to achieve their dreams and to contribute to scientific development of nations.

• Journal of the Korean Chemical Society
• /
• v.29 no.6
• /
• pp.608-614
• /
• 1985

Electrical conductivities of $ZrO_2-Sm_2O_3$ systems containing 10, 20, 30, 40, and 50 mol% of $ZrO_2$ have been measured as a function of temperature and of oxygen partial pressure at temperature from 500 to 1000${\circ}C$ and oxygen partial pressures from 1 ${\times}10^{-5}to 1{\times}10^{-1}$ atm. Plots of log conductivity vs. 1/T are found to be linear with an inflection point at around 650$^{\circ}C$ and the temperature dependence of conductivity shows two different defect structures. The conductivities are increased with increasing pressure, slowing a p-type character. The electrical conductivity dependences on $Po_2$ are found to be ${\sigma}{\propto}Po_2^{1/5.3}$ at 650∼1000$^{\circ}C$ and ${\sigma}{\propto}Po_2^{1/6}$ at 500∼650$^{\circ}C$, respectively, The defect structures are Oi" at 650-1000$^{\circ}C$ and $Vs_m$"' at 500-650$^{\circ}C$. The electron hole is main carrier type, however ionic contribution is found at low temperature portion. Ionic contributions increased with the increasing amount of $ZrO_2$ dopant. In 60mol% $ZrO_2-Sm_2O_3$ system, the conductivity is increased with decreasing oxygen pressure.

• Journal of the Korean Chemical Society
• /
• v.47 no.1
• /
• pp.67-71
• /
• 2003

The present study examined the inquiry type, process, and context of activities presented in the matter field of the 7th grade science textbook based on the 7th curriculum. It was to investigate for educational suggestions in instruction and development of science textbook. Three units of ‘three states of matter', ‘motion of molecule', ‘the state change and energy' were analyzed. The result indicated that the types, processes and skills, and context of inquiry were not balanced, and learners should be educated with complementary inquiry activities. It is proposed that the inquiry activities presented in science textbooks be examined, and the framework to evaluate inquiry activities be reflected on the standard of science textbook authorization for development of the science textbook to accord with aims and objectives of curriculum.

• Applied Chemistry for Engineering
• /
• v.32 no.2
• /
• pp.125-131
• /
• 2021

Semiconductor-based photocatalysts can only be activated with ultraviolet or visible light due to their intrinsic bandgap, and they cannot use the energy in the near-infrared region, which accounts for about 50% of solar energy. Therefore, in order to improve the performance of the semiconductor photocatalyst, it is necessary to utilize more solar energy in a broad band ranging from ultraviolet to near-infrared. Combining upconversion nanoparticles with semiconductor photocatalysts for near-infrared absorption have thus been reported. Upconversion nanoparticles can sequentially absorb multiple near-infrared photons and convert them into ultraviolet or visible to activate photocatalysts. In addition, by coupling the semiconductor photocatalyst and the upconversion nanoparticles with the plasmonic metal nanoparticles, the photocatalytic activity can be further improved. This review summarizes the recent studies on improving the photocatalytic performance with near-infrared absorption by using upconversion nanoparticles.

• Applied Chemistry for Engineering
• /
• v.33 no.1
• /
• pp.17-27
• /
• 2022

Fluorescence imaging is widely used to image cells or small animals due to its high temporal and spatial resolution. Because conventional fluorescence imaging uses visible light, the penetration depth of light within the tissue is low, phototoxicity may occur due to visible light, and the detection sensitivity is lowered due to interference by background autofluorescence. In order to overcome this limitation, long-wavelength light should be used, and fluorescence imaging using near-infrared-I (NIR-I) in the region of 700~900 nm has been developed. To further improve imaging quality, researchers are interested in using a longer wavelength light, near-infrared-II (NIR-II) ranging from 1000 to 1700 nm. In the NIR-II region, light scattering is further minimized, and the penetration depth of light in the tissue is improved up to about 10 mm, and autofluorescence of the tissue is reduced, enabling high sensitivity and resolution fluorescence imaging. In this review, among various NIR-II fluorescence imaging probes, inorganic nanoparticle-based probes with excellent photostability and easily tunable emission wavelength were described, focusing on single-walled carbon nanotubes, quantum dots, and lanthanide nanoparticles.

• Journal of the Korean Chemical Society
• /
• v.54 no.6
• /
• pp.818-828
• /
• 2010

It has already been 17 years since the first implementation of the Korean College Scholastic Ability Test (CSAT). Having been administered so many CSAT tests including practice tests, criticisms have been made against CAST tests being stuck to the same pattern and focusing mainly on knowledge-based items. To address this issue, we analyzed the chemistry items of the Japanese National Center Test for University Admissions (NCTUA) administered in January of 2009 with regard to content factors, behavioral domains, item types, and noted any peculiarities in comparison to CSAT. Also, we estimated the predicted percentage of correct answers from the perspectives of Korean candidates to arrive at implications for chemistry items of CSAT.

• Journal of the Korean Chemical Society
• /
• v.57 no.5
• /
• pp.533-539
• /
• 2013

The electrochemical corrosion and passivation of Ni rotating disk electrod in borate buffer solution was studied with potentiodynamic and electrochemical impedance spectroscopy. The mechanisms of both the active dissolution and passivation of nickel and the hydrogen evolution in reduction reaction were hypothetically established while utilizing the Tafel slope, impedance data, the rotation speed of Ni-RDE and the pH dependence of corrosion potential and current. Based on the EIS data, an equivalent circuit was suggested. In addition, carefully measured were the electrochemical parameters for specific anodic dissolution regions. It can be concluded from the data collected that the $Ni(OH)_2$ oxide film, which is primarily formed by passivation, is converted to NiO by dehydration under the influence of an electrical field.