• Journal of the Korean Chemical Society
• /
• v.53 no.2
• /
• pp.175-188
• /
• 2009

In this study, we developed an experimental method of the Charles' law applicable to school. Science textbooks and literatures on this principle were analyzed to extract factors utilized in organizing the experimental setup and method. A combined structure such as with a vial and a glass tube, the former of which is for deciding the total volume and the latter of which is for easy measurement of volume, was better in measurement of volume with temperature rather than a simple structure such as syringe. Use of graduated cylinder as a water bath to control the temperature showed advantage in cooling time than using other bath of larger volume such as a beaker. A liquid drop was used as a plug in the glass tube. This plug has little resistance with the glass wall when the gas volume changes. Water as a liquid drop in the glass tube had a significant effect in volume change of gas due to evaporation, especially in the beginning of the measurement. Glycerol showing negligible effect in volume change was used. This method took about one hour and produced a good linear relationship between the temperature and volume of gas with $R^2$ = 0.999 and absolute zero temperature = $-216.7\;{^{\circ}C}$. The Charles' law experiment developed in this study can be performed with appropriate adjustment of procedure considering the purpose of the curriculum of science and chemistry subject at each school level.

• Journal of Soil and Groundwater Environment
• /
• v.8 no.1
• /
• pp.17-26
• /
• 2003

The sorption experiment of cobalt was performed after the TRIGA soil was intentionally contaminated with cobalt was found that the sorption equilibrium coeficiency of soil decontamination was high when the ratio of soil mass to the volume of citric acid becomes 1:5 The TRIGA soil contaminated with 0.01 M, 0.001 M, and 0.0001 M of cobalt solution were decontaiminated with 0.01 M citric acid. The cobalt concentrtion in the wastewater were measured to be correspondingly 36.0, 14.0, 1.5 ppm. The results of wastewater recycling experiment by chemical precipitation method revealed that corresponding cobalt removal efficiency were 97% 88%. It was shown that the removal efficiency decreases as the cobalt concentration in the wastewater decreases. During the decontamination experiment, a lot of NaOH had to be added, and the volume of final solid waste reached almost 10% of that of the contaminated soil. The result of wastewater recyling experiment by ion exchange resin meted rethod revealed that to more the strong acid resins are used, the higher the cobalt removal efficiency becomes and the cobalt removal efficiency becomes and the lower the pH of recycling wastewater become. In order to obtain more than 95% removal efficiency, more than 0.625 g of strong acid resin was necessary in each of 3 experiments. There was an unexpected problem that a lot of strong acid resin waste was produced which amounts to 9.2% (volume) of the contaminated soil.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.50 no.2
• /
• pp.155-167
• /
• 2023

The aim of this study was to investigate the effects of slow maxillary expansion (SME) on the dentoalveolar, skeletal, upper airway, and maxillary sinus using cone-beam computed tomography (CBCT). Twenty-three orthodontic patients (mean age 8.93 ± 1.61 years) who were treated with maxillary expansion using banded hyrax in the Department of Pediatric Dentistry at Jeonbuk National University Dental Hospital were included. According to the expansion speed applied, they were divided into two groups: SME (12 subjects, mean age 8.92 ± 1.45 years) and rapid maxillary expansion (RME, 11 subjects, mean age 8.94 ± 1.84 years). CBCT were obtained before (T0) and after (T1) the treatment and were analyzed with InVivo5 software (Anatomage, San Jose, CA, USA). Descriptive statistics showed no significant differences between the two groups in age, sex, or skeletal maturity. There were significant increases in maxillary width at the dentoalveolar and skeletal levels for both groups. Upper airway volume revealed a significant increase of 38.59% in the SME group and 28.72% in the RME group. However, there was no significant difference between SME group and RME group in all measurements. This study suggested the efficacy of SME in growing patients. SME was effective in increasing not only dentoalveolar and skeletal measurements but also airway volume. Therefore, pediatric dentists should select an appropriate expansion method considering the physiological aspects of periodontal tissues and discomfort in growing children.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.48 no.1
• /
• pp.1-11
• /
• 2021

The purpose of this study is to investigate factors influencing the upper airway dimensions in skeletal Class II children and adolescents. In total, 67 patients were selected. Airway volume and minimal cross-sectional area were three-dimensionally assessed. Craniofacial morphology and skeletal maturity were assessed on generated two-dimensional cephalograms. The measurements were analyzed using Mann-Whitney test, one-way ANOVA, Pearson's correlation, and multiple regression analysis. Upper airway dimensions were significantly smaller in pre-peak stage group, and positively associated with age. Anterior facial height and age were the most relevant factors for airway volume. Mandibular width and age were the most relevant factors for minimal cross-sectional area. Upper airway dimensions were significantly associated with age, skeletal maturity and craniofacial morphology in all three planes.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.1
• /
• pp.83-91
• /
• 2018

While using an electrokinetic method to analyze the characteristics of cement solidification of radioactive wastes from decontaminated uranium soil and concrete, the compressive strength, pH, electrical conductivity, irradiation effects, and volume expansion were measured for the solidified cement specimens. The workability of cement solidified from radioactive waste was about 170-190%. After the solidified cement was irradiated, the compressive strength decreased by about 15%, but met the criteria ($34kgf{\cdot}cm^{-2}$) of KORAD (Korea Radioactive Waste Agent). According to the results of SEM-EDS for solidified cement, the aluminum phase was well combined with cement, while the calcium phase was separated from cement. The volume of solidified cement in radioactive wastes was dependent on the waste-to-cement ratio and the amount of water, and increased by about 30% under the conditions used in this study. Therefore, it was concluded that permanent disposal of electrokinetically decontaminated radioactive wastes is appropriate.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.5
• /
• pp.291-300
• /
• 1999

Surfactant flushing for enhancing the removal of BTEX from contaminated sand/clay mixtures was investigated. Eight soil columns packed with relatively undisturbed BTEX contaminated soils, were leached with water, methyl alcohol and then flushed with surfactant with or without several additives. Initial concentrations of BTEX mixture range from 278mg/kg to 1975mg/kg. Initial BTEX removal efficiency was 98% when the contaminated soil was flushed with water of 850 pore volumes. Because of tailing effect, water flushing could not remove below 8mg/kg concentrations during the experimental period. Eventually, the most effective surfactant for flushing was turned out to be 4% SOFTANOL(equation omitted)-90 with 3% ethyl alcohol and 3% SXS. In interrupted flow conditions, the removal efficiency was 99.5% with the flushed water of 95 pore volumes. The BTEX mixture removed from the soil columns during the surfactant flushing ranges from 84.5% to 99.5% of the initial amount for both water leaching(850 pore volumes) and surfactant flushing(95-165 pore volumes), respectively. Test results indicated that surfactant flushing could enhance the removal of BTEX mixture from contaminated soils and could reduce the aqueous phase BTEX mixture concentration in leachate.

• Journal of the Korean Magnetics Society
• /
• v.26 no.6
• /
• pp.196-200
• /
• 2016

In this study the mechanisms of magnetization reversal and magnetic interaction effects on activation volumes for Sr-ferrite with different particle sizes are investigated. The activation volumes of C2 sample are larger than those of C3 sample in the range of low magnetic fields. But the fields above the coercivity of sample C2, the activation volumes of both samples are decreased linearly with increasing the applied magnetic field. These phenomena can be explained by the strengths of two critical fields representing the reverse domain nucleation field and the domain wall pinning field as well as the strength of dipolar interaction.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.1
• /
• pp.49-59
• /
• 2019

In this study, the durability of conical pick cutter was compared and analyzed by pre- and post-test visual inspection, measurement of weight loss and wear volume through field test on two types of conical pick cutters applied to rotary drum cutter. In the visual inspection, it was found that only 9 inserts were lost in the slim type conical pick cutter. This result show that the thickness of the head cover surrounding a insert was important to maintain the insert during excavation. The weight loss and wear volume of the heavy type conical pick cutter were less than half that of the slim type. From these results, it can be confirmed that heavy type is more useful than slim type in hard rock. It should be noted that, when determining the wear loss of the conical pick cutter, the mutual comparison of the weight measurement and the wear volume measurement results may be different due to the unit weight of the material and the spalling caused by excavation.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.415-420
• /
• 1998

시판중인 대표적 유·무기이온교환수지를 이용하여 방사성폐액의 주 방사성핵종인 코발트와 세슘에 대하여 방사성패액에 함유되어 있는 대표적 일반이온인 나트륨이온이 이들의 이온교환에 미치는 영향을 분석하였다. 나트륨 존재 하에서 세슘이온에 대한 선택도와 수지단위 부피당 폐액 처리 부피는 무기이온교환수지인 DT 30과 Durasil 230이 가장 높으며 반면에 유기이온교환수지는 두 수치 모두 낮아서 유기이온교환수지는 저농도의 나트륨 이온을 갖는 증발기 응축수의 처리에는 적합하나 나트륨이온의 농도가 비교적 높은 폐액처리에는 적합하지 않으며, 또한 코발트 제거 면에서는 무기이온교환수지인 DT 10 보다 유기이온교환수지인 Amberlite IRN 77이 바람직하다는 결론을 얻었다.

• Journal of the Korean Ceramic Society
• /
• v.37 no.12
• /
• pp.1159-1164
• /
• 2000

페롭스카이트 구조를 갖는 E $r_{1-x}$S $r_{x}$Cr $O_{3-y}$ 계에서 x=0.0, 0.05, 0.1, 0.2인 비화학양론적 화합물 고용체를 1573 K 대기압 하에서 제조하였다. X-선 회절분석을 통하여 제조된 모든 계들이 등방정계 단일상을 형성하였고, 또한 반지름이 큰 S $r^{2+}$를 doping 시켜줌에 따라 격자상수 및 환산부피가 증가됨을 알 수 있었으며, 단위 세포의 부피는 직선성을 보이며 증가하였다. TG-DTA에 따른 열분석 결과 Sr이 치환되지 않은 계에서는 상전이가 발생하는 반면, x값이 0.05 이상인 계들은 고온영역에 이르기까지 등방정계에서 마름모정계로의 상전이가 억제되었다. 전자현미경을 통하여 치환된 Sr의 몰비에 따른 시료들이 미세구조를 관찰하였고, d.c 전도도 측정을 통하여 다결정성 시료계들이 가지는 전도도의 온도 의존성으로부터 구한 활성화 에너지는 0.17 eV였다.다.