• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.485-488
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• 2007

Riverbank filtration is a kind of artificial aquifer recharge for the fresh water supply. By construction of several production wells penetrating the riverbank, surface water withdrawn from the river would pass riverbed. This extracted water is well known to be cooler than surface water in summer and warmer than surface water in winter, showing more constant water temperature. This characteristic of extracted water is applied to geothermal energy utilization. Prediction of the annual temperature variation of filtrated water is the major concern in this study. In Daesan-myeon, Changwon-si, Gyeongsangnam-do, South Korea, riverbank filtration facility has been on its operation for municipal water supply and thermal energy utilization since 2006. Appropriate hydraulic and thermal properties were estimated for flow and heat transfer modeling with given pumping rate and location. With the calibrated material properties and boundary conditions, we numerically reproduced measured head and temperature variation with acceptable error range. In the numerical simulation, the change of saturation ratio and river stage caused by rainfall was calculated and the resulting variation of thermal capacity and thermal conductivity was considered. Simulated temperature profiles can be used to assess the possible efficiency of geothermal energy utilization using riverbank filtration facility. Influence of pumping rate, pumping location on the extracted water temperature will be studied.

• Journal of Radiation Protection and Research
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• v.45 no.4
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• pp.171-177
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• 2020

Background: This study aims to determine the effective atomic number (Zeff) from dual-energy image sets obtained using a conventional computed tomography (CT) simulator. The estimated Zeff can be used for deriving the stopping power and material decomposition of CT images, thereby improving dose calculations in radiation therapy. Materials and Methods: An electron-density phantom was scanned using Philips Brilliance CT Big Bore at 80 and 140 kVp. The estimated Zeff values were compared with those obtained using the calibration phantom by applying the Rutherford, Schneider, and Joshi methods. The fitting parameters were optimized using the nonlinear least squares regression algorithm. The fitting curve and mass attenuation data were obtained from the National Institute of Standards and Technology. The fitting parameters obtained from stopping power and material decomposition of CT images, were validated by estimating the residual errors between the reference and calculated Zeff values. Next, the calculation accuracy of Zeff was evaluated by comparing the calculated values with the reference Zeff values of insert plugs. The exposure levels of patients under additional CT scanning at 80, 120, and 140 kVp were evaluated by measuring the weighted CT dose index (CTDIw). Results and Discussion: The residual errors of the fitting parameters were lower than 2%. The best and worst Zeff values were obtained using the Schneider and Joshi methods, respectively. The maximum differences between the reference and calculated values were 11.3% (for lung during inhalation), 4.7% (for adipose tissue), and 9.8% (for lung during inhalation) when applying the Rutherford, Schneider, and Joshi methods, respectively. Under dual-energy scanning (80 and 140 kVp), the patient exposure level was approximately twice that in general single-energy scanning (120 kVp). Conclusion: Zeff was calculated from two image sets scanned by conventional single-energy CT simulator. The results obtained using three different methods were compared. The Zeff calculation based on single-energy exhibited appropriate feasibility.

• Progress in Medical Physics
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• v.20 no.4
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• pp.317-323
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• 2009

The standard dosimetry systems based on an absorbed dose to water recommend to use a planeparallel chamber for the calibration of such a low-megavoltage electron beam as a nominal energy of 6 MeV. For this energy ranges of an electron beam a cylindrical chamber should not be used for the routinely regular beam calibration, but the feasibility of the temporary use of a cylindrical chamber was studied to give temporary solutions for special situations users meet. The PTW30013 chambers and the electron beam quality of $R_{50}=2.25\;g/cm^2$ were selected for this study. 10 PTW30013 chambers, a cylindrical type of chamber, were calibrated in KFDA, the secondary standards dosimetry laboratories, and given the absorbed dose-to-water calibration factors, respectively. A "temporary" $k_{Q,Q_0}$ for each chamber were calculated using the absorbed dose determined by a cross-calibrated planeparallel chamber, with the result of an average 0.9352 for 10 chambers. This value for PTW30013 chamber was used to determine an absorbed dose to water at the reference depth. The absorbed doses determined by PTW30013 chambers were in an agreement within 2% with that by ROOS chamber. In a certain situation where a cylindrical chamber be used instead of a planeparellel chamber, the value of 0.9352 might be useful to determine an absorbed dose to water in the same beam quality of electron beam as this study.

• Progress in Medical Physics
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• v.9 no.4
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• pp.267-276
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• 1998

Any detector inserted into a phantom should have such a geometry that it caused as small as possible perturbation of the electron fluence. Plane parallel chambers meet this requirement better than other chambers of configurations. IAEA protocol recommends the use of plane parallel chambers for this reason. However, the cylindrical chambers are widely used for convenient. The purpose of this study is to evaluate the absorbed dose due to the differences of four different dosimetry protocols such as IAEA protocol using cylindrical chamber, TG 21 protocol using cylindrical chamber, Markus protocol using plane parallel chamber, and TG 39 report for the calibration of plane parallel chamber in electron beams. Depth-ionization measurements for the electron beams of nominal energy 6, 9, 12, 15, and 18 MeV from Siemens accelerator with a 10$\times$10 cm$^2$ field size were made using a radiation field analyser with 0.125 cc ion chamber. Dosimetric measurements by IAEA and TG 21 protocol were made with a farmer type ionization chamber in solid water for each electron energy, respectively. Dosimetric measurements by Markus protocol were made with a plane parallel ionization chamber in solid water for each electron energy, respectively. The cavity-gas calibration factor for the plane parallel chamber was obtained with the use of 18 MeV electron beam as guided by TG 39 report. Dosimetric measurements by TG 39 were performed with a plane parallel ionization chamber in solid water for each electron energy, respectively. For all the energies and protocols, measurements were made along the central axis of the distance of 100 cm (SSD = 100 cm) with 10$\times$10 cm$^2$ field size at the depth of d$_{max}$ for each electron beam, respectively. In the case of 18 MeV, the discrepancy of 0.9 % between IAEA and TG 21 was found and the two protocols were agreed within 0.7 % for other energies. In the case of 18 MeV and 6 MeV, the discrepancies of $\pm$ 0.8 % between Markus and TG 39 was found, respectively and the two protocols were agreed within 0.5 % for other energies. Since the discrepancy of 1.6 % between cylindrical and plane parallel chamber was found for 18 MeV, it is suggested to get the calibration factor using other method as guided. by TG 39.9.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2008.04a
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• pp.199-205
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• 2008

In this study, a system to measure continuously the fuel concentration in a steady flow rig on the basis of Rayleigh scattering is presented. The system can be employed to measure both the temporal and the spatial distribution. Also, it is possible to calibrate the system for the measurement of accurate absolute concentration. Firstly, the system was tested at a calibration chamber for the determination of scattering cross section from propane, butane, acetylene, Freon-12 and Genetron 143a. After this, the system was adapted to a steady flow rig to measure the temporal and spatial fuel concentration. The rig is composed of cylinder head, intake manifold, injector, and transparent cylinder which can simulate internal combustion engine. To cope with the problem of Mie scattering interference, a software filter was developed, which is based on the rise time and the time constant of the photomultiplier-amplifier system. The results show that LRS can provide useful informations about concentration field and the software filter is very effective method to remove Mie interference.

• Analytical Science and Technology
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• v.13 no.3
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• pp.304-308
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• 2000

The iodide was recovered from a simulated spent fuel to the sodium bisulfite aqueous solution. It was discussed that the trace iodide (below 1 ppm) was determined without the matrix effect of 0.1 M sodium bisulfite and 1 mM $HNO_3$ in aqueous solution by ion chromatography with UV detection. AS4A-SC (DIONEX) column and UV-absorption spectrophotometer were used. The UV-absorption spectra of sodium bisulfite, nitric acid and iodide were obtained, and then 230 nm was selected as an absorption wavelength for iodide determination. 0.1 M NaCl eluent was optimum condition. In this condition the calibration curve of iodide was obtained on the range of about 0-1,000 ppb. The linear coefficient was 0.99993 and the detection limit was 5 ppb. The relative standard deviation was 1.26%.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.9-14
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• 2009

A numerical investigation was performed based on the Reynolds-Averaged Navier-Stokes(RANS) equations for the two-dimensional unsteady flow around a vertical axis turbine(VAT) with three or four blades. VAT is one of the promising devices for tidal current energy conversion. The geometry of the turbine blade was $NACA65_3$-018 airfoil, for which CFD analysis using Fluent was carried out at several angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Then CFD simulations were carried out for the whole vertical axis turbine with a two-dimensional setup. The CFD simulation demonstrated the usefulness of the method to study the typical unsteady flows around VATs and the results showed that the optimum turbine efficiency could be achieved for carefully selected combinations of the number of blade and Tip-Speed Ratio(TSR).

• Korean Journal of Pharmacognosy
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• v.47 no.1
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• pp.79-83
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• 2016

This study developed an HPLC analysis method for the determination of isoegomaketone (IK) and perillaketone (PK) in Perilla frutescens (L.) Britton leaves. P. frutescens ethanol extract was optimized through an HPLC analysis using a C18 column ($250{\times}4.6mml$, D, $S-5{\mu}m$, 12 nm) with gradient elution of water and acetonitrile as the mobile phase at a flow rate of 1 mL/min and a UV detection wavelength of 254 nm. The results of this method showed linearity in the calibration curve at a coefficient of correlation ($R^2$) of IK 0.9995, PK 0.9998. The limits of detection (LOD) for IK and PK were $0.234{\mu}g/mL$ and $0.952{\mu}g/mL$. The limits of quantification (LOQ) for IK and PK were $0.017{\mu}g/mL$ and $0.043{\mu}g/mL$. The inter-day precision RSDs of IK and PK in the P. frutescens were 1.25 to 2.69% and 0.36 to 1.10%, respectively, and the intra-day precision RSDs of IK and PK were 0.96 to 2.51% and 0.90 to 1.93%, respectively. The accuracies of IK and PK were 96.31 to 97.92% and 101.26 to 105.14%. In conclusion, this method was applied successfully to the detection of IK and PK in P. frutescens.

• Progress in Medical Physics
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• v.32 no.4
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• pp.165-171
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• 2021

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high-density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.49-68
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• 2023

The three-dimensional failure criterion is essential for maintaining wellbore stability and sand production problem. The convenient factor for a stable wellbore is mud weight and borehole orientation, i.e., mud window design and selection of borehole trajectory. This study proposes a new three-dimensional failure criterion with linear relation of three in-situ principal stresses. The number of failure criteria executed to understand the phenomenon of rock failure under in-situ stresses is the Mohr-Coulomb criterion, Hoek-Brown criterion, Mogi-Coulomb criterion, and many more. A new failure criterion is the extended Mohr-Coulomb failure criterion with the influence of intermediate principal stress (σ₂). The influence of intermediate principal stress is considered as a weighting of (σ₂) on the mean effective stress. The triaxial compression test data for eleven rock types are taken from the literature for calibration of material constant and validation of failure prediction. The predictions on rock samples using new criteria are the best fit with the triaxial compression test data points. Here, Drucker-Prager and the Mogi-Coulomb criterion are also implemented to predict the failure for eleven different rock types. It has been observed that the Drucker-Prager criterion gave over prediction of rock failure. On the contrary, the Mogi-Coulomb criterion gave an equally good prediction of rock failure as our proposed new 3D failure criterion. Based on the yield surface of a new 3D linear criterion it gave the safest prediction for the failure of the rock. A new linear failure criterion is recommended for the unique solution as a linear relation of the principal stresses rather than the dual solution by the Mogi-Coulomb criterion.