• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.8-16
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• 2024

Limestone (CaCO₃, calcium carbonate), which is used as a raw material in the portland cement and steel industry, emits CO₂ through decarbonation by high temperatures in the manufacturing process. To reduce CO₂ emissions by the use of raw materials like limestone, it has been proposed to replace limestone with various industrial by-products that contain CaO but less or none of the carbonated minerals, that cause CO₂ emissions. Loss of Ignition (LOI), Thermogravimetric analysis (TG), and Infrared Spectroscopy (IR) are used to quantitative the amount of CO₂ emission by using these industrial by-products, but CO₂ emissions can be either over or underestimated depending on the characteristics of by-product materials. In this study, we estimated CO₂ contents by LOI, TG, IR and DTG(Differential Thermogravimetric analysis) of calcite(CaCO₃) and samples that contain CO₂ in the form of carbonate and whose weight increases by oxidation at high temperatures. The test results showed for CaCO₃ samples, all test methods have a sufficient level of reliability. On the other hand, for the CO₂ content of the sample whose weight increases at high temperature, LOI and TG did not properly estimate the CO₂ content of the sample, and IR tended to overestimate compared to the predicted value, but the estimated result by DTG was close to the predicted valu e. From these resu lts, in the case of samples that contain less than a few percent of CO₂ and whose weight increases during the temperature that carbonate minerals decompose, estimating the CO₂ content using DTG is a more reasonable way than LOI, TG, and IR.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.3
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• pp.277-288
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• 2017

Previous studies of health effects of $PM_{2.5}$ performed spatial monitoring campaigns to assess spatial variability of $PM_{2.5}$ across people's residences. Highly reliable portable and cost-effective samplers will be useful for such campaigns. This study aimed to investigate applicability of the Deployable Particulate Impact Sampler(DPIS), one of the compact impact samplers, to spatial monitoring campaigns of $PM_{2.5}$ in Seoul, Korea. The investigation focused on the consistency of $PM_{2.5}$ concentrations measured by DPISs compared to those by the Low-volume Cyclone sampler (LCS). LCS has operated at a fixed site in the Seoul National University Yeongeon campus, Seoul, Korea since 2003 and provided qualified $PM_{2.5}$ data. $PM_{2.5}$ sampling of DPISs was carried out at the same site from November 17, 2015 through February 3, 2016. $PM_{2.5}$ concentrations were quantified by the gravimetric method. Using a duplicated DPIS, we confirmed the reliability of DPIS by computing relative precision and mean square error-based R squared value ($R^2$). Relative precision was one minus the difference of measurements between two samplers relative to the sum. For accuracy, we compared $PM_{2.5}$ concentrations from four DPISs (DPIS_Tg, DPIS_To, DPIS_Qg, and DPIS_Qo) to those of LCS. Four samplers included two types of collection filters(Teflon, T; quartz, Q) and impaction discs(glass fiber filter, g; pre-oiled porous plastic disc, o). We assessed accuracy using accuracy value which is one minus the difference between DPIS and LCS $PM_{2.5}$ relative to LCS $PM_{2.5}$ in addition to $R^2$. DPIS showed high reliability (average precision=97.28%, $R^2=0.98$). Accuracy was generally high for all DPISs (average accuracy=83.78~88.88%, $R^2=0.89{\sim}0.93$) except for DPIS_Qg (77.35~78.35%, 0.82~0.84). Our results of high accuracy of DPIS compared to LCS suggested that DPIS will help the assessment of people's individual exposure to $PM_{2.5}$ in extensive spatial monitoring campaigns.

• Journal of Radiation Protection and Research
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• v.24 no.3
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• pp.155-160
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• 1999

In the natural, there exist several kinds of radioactive isotopes. From atmospheric weapon tests and then some isotopes are naturally radioactivity above all things, nuclear power plant operation and man-made radioactive isotopes concern steadily growing in the environment. During the fission process of nuclear weapon tests and nuclear power plant operation, more than 200 radioactive isotopes are generated. Among them, $^{90}Sr$ and $^{137}Cs$ has been regarded as very important isotopes due to characteristics. In this paper, a quantitative analysis method of environment low level $^{90}Sr$ is studied. Radioactivity level of the environmental $^{90}Sr$ is very low, and it emits continuous beta spectrum, and $^{90}Sr$ exists together with $^{89}Sr$, $^{90}Y$ and other radioactive isotopes. It very difficult to make the quantitative analysis of $^{90}Sr$. For the analysis of low level radioactive strontium, enrich and chemical separation of strontium from the other radioactive isotopes are needed. For the estimation of strontium recovery ratio, so called SGAT(Strontium Gravimetric Analysis Technique) was generally used among the domestic research groups, and chemical procedures were developed appropriation for the SGAT, Recently, by using ICP(Inductively Coupled atomic Plasma emission spectrophotometer), amounts of stable atoms can be measured easily and accurately to the extend of ppm or ppb. In this paper, new chemical procedures are developed to exploits the ICP technique. New developed method has simpler chemical treatment procedures and then it gives more accurate results compared with the traditional SGAT.

• Membrane Journal
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• v.19 no.4
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• pp.341-347
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• 2009

Nanohybrid based on environmentally friendly and biodegradable polymer, poly propylene carbonate (PPC) and cloisite 20B (PPC/C-20B) have been synthesized by solution blending method and their morphology, thermal and water absorption properties have been evaluated. The structure of PPC/C-20B nanohybrid was confirmed by X-ray diffraction (XRD). The thermal property of PPC and PPC/C-20B nanohybrid were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). The experimental results demonstrated that nanohybrid showed the highest thermal stability in TGA and DSC. TGA tests revealed that the thermal decomposition temperature ($T_{d50%}$) of the nanohybrid increased significantly, being $23^{\circ}C$ higher than that of pure PPC while DSC measurements indicated that the introduction of 5 mass% of clay increased the glass transition temperature from 21 to $30^{\circ}C$. Further the water absorption capacity of the PPC was significantly decreased by the incorporation of clay. Water absorption cause degradation of the coating by the moistures and affect the physical and mechanical performance. This result indicates that organic modifiers have effect on thermal and water absorption capacity of PPC and are of importance for the practical process and application of PPC.

• Korean Journal of Food Science and Technology
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• v.19 no.4
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• pp.317-323
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• 1987

This study was undertaken to examine the applicability of domestic enzymes in the quantitative determination of dietary fibers according to the official enzymatic-gravimetric method of AOAC and to apply it to 4 kinds of fruits (apple, pear, peach and persimmon) and 4 kinds of vegetables (Korean radish, lettuce, Korean cabbage and cabbage Kimchi). With domestic enzymes, an optimum condition was selected to use 1/10 units of enzyme activity and to extent the reaction time two-fold as compared with the recommended method, in the case of fruits and vegetables. On a dry matter basis, fiber contents of fruits were in the range of 9.4-28.8% total dietary fiber, 1.8-7.8% non-cellulosic polysaccharides, 3.7-5.8% cellulose and 1.3-21.3% lignin. Fiber contents of vegetables were 26.0-35.7% total dietary fiber, 11.3-14.4% non-cellulosic polysac-charides, 12.3-19.7% cellulose and 1.4-7.4% lignin. On a dry matter basis, crude fiber contents were 3.5-6.7%in fruits and 9.1-13.8% in vegetables. Therefore, crude fiber contents of fruits and vegetables accounted for only 12-50% of total dietary fibers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1071-1080
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• 2003

A national standard system was developed in order to calibrate and test the oil flowmeters for the petroleum field. A stop valve and a gyroscopic weighing scale were employed for the primary standard of the flow quantity. It is operated by the standing start and finish mode and the static weighing method. The model equation for uncertainty evaluation was based on the calibration principle of standard system. The sources of the uncertainties were quantified and combined according to the GUM(Guide to the Expression of Uncertainty in Measurement). It was found that the standard system had the relative expanded uncertainty of 0.04 % in the range of 18 - 350 ㎥/ｈ. According to the uncertainty budget, the uncertainties of the fluid density and the volume of pipeline, which were temperature dependent, contributed 92% of final uncertainty in the oil flow standard system.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.123-128
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• 2001

This study was performed to find out variation of carbonation progress of agricultural hydraulic concrete structures along the used years with using Thermo Gravimetric analysis/Differential Thermal Analysis(TG/DTA) and Indicator(phenolphthalein). In this study some conclusions such as follows were derived. Firstly, The result that the age of structures and the content of $Ca(OH)_{2}\;and\;CaCO_{3}$ in concrete have proportional relationships was found in the method of TG/DTA. This relational functions could be used to estimate remain lifetime of structures, obtaining the limits of the content of $CaCO_{3}$ in concrete which reinforcement corrosion could be occurred with breaking protection cover of alkalinity. Second, if the result of strength, voids, permeability characteristics could be combined with this relational function this may be able to be used as a new more accurate assessment technique for the quality of concrete than current usual methods. Third, environmental affect could be more superintendent for concrete carbonation than the age of agricultural hydration structures. Forth, It is difficult to estimate the used year of agricultural hydraulic concrete structures with the carbonation depth measured by indicator method. Finally, the accuracy of this relational function could be decided to be upgraded with continue analysis for more structures.

• Carbon letters
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• v.15 no.3
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• pp.198-202
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• 2014

Amorphous agglomerates of carbon nanospheres (CNS) with a diameter range of 10-50 nm were synthesized using the solution combustion method. High-resolution transmission electron microscopy (HRTEM) revealed a densely packed high surface area of $SP^2$-hybridized carbon; however, there were no crystalline structural components, as can be seen from the scanning electron microscopy, HRTEM, X-ray diffraction, Raman spectroscopy, and thermal gravimetric analyses. Electrochemical and thermo catalytic decomposition study results show that the material can be used as a potential electrode candidate for the fabrication of energy storage devices and also for the production of free hydrogen if such devices are used in a fluidized bed reactor loaded with the as-prepared CNS as the catalyst bed.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.943-951
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• 1990

Steady-state sublimation vapour pressures of anhydrous bismuth triiodide have been measured by the continuous gravimetric Kundsen-effusion method from 430.0 to 558.9 K and equilibrium sublimation pressures were obtained from the steady-state data. Condensation coefficients and their temperature dependence have been derived from the effusiion measurement. Condensation coefficients ranged from 0.159 to 0.048(475 to 500K), the activation enthalpy and entropy for condensation have been obtained as -93.38kTmol-1 and -212.70JK-1mol-1. The standard sublimation enthalpy changes derived by both second(modified sigma function) and third(average enthalpy method) law methods were 138.261$\pm$0.023, 138.74$\pm$0.002kJmol-1 respectively. The standard sublimation entropy change derived by modified sigma function was 191.98$\pm$0.047 JK-1mol-1. The reliable standard sublimation enthalpy change based on a correlation of ΔgcrHom(298.15K) and ΔgcrSom(298.15K), a recommended p(T) equation has been obtained for BiI3(cr) ; 1g(p/Pa)=-C/(T/K)＋5.0711g(T/K)-2.838$\times$10-3(T/K)-7.758$\times$103(K/T)2＋1.4519 where p is in Pa, T in Kelvin, ΔgcrHom(298.15K) in kJmol-1 and C=(ΔgcrHom(298.15K)-8.7358)/1.9146$\times$10-2.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1335-1343
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• 2005

The calibration technique of Time Resolved Laser Induced Incandescence was investigated both experimentally and numerically by using standard-sized carbon black particles for the instantaneous soot measurement at exhaust tail pipe in engine. The carbon black particles (19nm, 25nm, 45nm and 58nm) used in this study are similar, though not identical, to soot particle generated from flame not only in morphology but also in micro-structure. The amount of soot loading in flow was controled by a diluted gas (nitrogen) and was measured by the gravimetric method at exhaust pipe in calibrator. The successful calibrations of primary particle size and soot mass fraction were carried out at the range from 19nm to 58nm and from $0.25mg/m^3$ to $37mg/m^3$ respectively. And based on these results the numerical simulation of LII signal was tuned and the effect of an exhaust temperature variation on the decay rate of LII signal was corrected.