• Journal of Microbiology and Biotechnology
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• v.34 no.6
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• pp.1322-1327
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• 2024

The accurate and rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) holds significant clinical importance. This work presents a new method for detecting methicillin-resistant Staphylococcus aureus (S. aureus) in clinical samples. The method uses an aptamer-based colorimetric assay that combines a recognizing probe to identify the target and split DNAzyme to amplify the signal, resulting in a highly sensitive and direct analysis of methicillin-resistance. The identification of the PBP2a protein on the membrane of S. aureus in clinical samples leads to the allosterism of the recognizing probe, and thus provides a template for the proximity ligation of split DNAzyme. The proximity ligation of split DNAzyme forms an intact DNAzyme to identify the loop section in the L probe and generates a nicking site to release the loop sequence ("3" and "4" fragments). The "3" and "4" fragments forms an intact sequence to induce the catalytic hairpin assembly, exposing the G-rich section. The released the G-rich sequence of LR probe induces the formation of G-quadruplex-hemin DNAzyme as a colorimetric signal readout. The absorption intensity demonstrated a strong linear association with the logarithm of the S. aureus concentration across a wide range of 5 orders of magnitude dynamic range under the optimized experimental parameters. The limit of detection was calculated to be 23 CFU/ml and the method showed high selectivity for MRSA.

• Geomechanics and Engineering
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• v.35 no.1
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• pp.29-39
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• 2023

As the intensity of urban underground space development increases, more and more tunnels are planned and constructed, and sometimes it is inevitable to encounter situations where tunnels have to underpass the river embankments. Most previous studies involved tunnels passing river embankments perpendicularly or with large intersection angle. In this study, a project case where two EPB shield tunnels with 8.82 m diameter run parallelly underneath a river embankment was reported. The parallel length is 380 m and tunnel were mainly buried in the moderate / slightly weathered clastic rock layer. The field monitoring result was presented and discussed. Three-dimensional back-analysis were then carried out to gain a better understanding the interaction mechanisms between shield tunnel and embankment and further to predict the ultimate settlement of embankment due to twin-tunnel excavation. Parametrical studies considering effect of tunnel face pressure, tail grouting pressure and volume loss were also conducted. The measured embankment settlement after the single tunnel excavation was 4.53 mm ~ 7.43 mm. Neither new crack on the pavement or cavity under the roadbed was observed. It is found that the more degree of weathering of the rock around the tunnel, the greater the embankment settlement and wider the settlement trough. Besides, the latter tunnel excavation might cause larger deformation than the former tunnel excavation if the mobilized plastic zone overlapped. With given geometry and stratigraphic condition in this study, the safety or serviceability of the river embankment would hardly be affected since the ultimate settlement of the embankment after the twin-tunnel excavation is within the allowable limit. Reasonable tunnel face pressure and tail grouting pressure can to some extent suppress the settlement of the embankment. The recommended tunnel face pressure and tail grouting pressure are 300 kPa and 550 kPa in this study, respectively. However, the volume loss plays the crucial role in the tunnel-embankment interaction. Controlling and compensating the tunneling induced volume loss is the most effective measure for river embankment protection. Additionally, reinforcing the embankment with cement mixing pile in advance is an alternative option in case the predicted settlement exceeds allowable limit.

• Journal of Korea Water Resources Association
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• v.45 no.9
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• pp.887-900
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• 2012

Drought is a non-negligible disaster of nature and it is mainly caused by rainfall shortage for a long time though there are many definitions of drought. 'Standard Precipitation Index' (SPI) that is widely used to express the level of meteorological drought intensity has a limit of not being able to consider the hydrological changes such as rainfall and evapotranspiration caused by climate change, because it does not consider the temperature-related variables other than the precipitation. Recently, however, 'Standardized Precipitation Evapotranspiration Index' (SPEI), a drought index of new concept which is similar to SPI but can reflect the effect of temperature variability as well as the rainfall change caused by climate variation, was developed. In this study, the changes of drought occurrence in South Korea were analyzed by applying SPEI for meteorological data (1973~2011) of 60 climate observatories under Korea Meteorological Administration (KMA). As the result of application, both of SPI and SPEI showed the trend of deepening drought in spring and winter and mitigating drought in summer for the entire nation, with SPI showing greater drought intensity than SPI. Also, SPI and SPEI with 12 months of duration showed that severe droughts with low frequency of around 6 years are generally being repeated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.63-72
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• 2016

An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.

• KSBB Journal
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• v.14 no.6
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• pp.688-695
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• 1999

Biodegradation of the reactive dye, Remazol Black B was investigated in an upflow anaerobic sludge blanket(UASB) reactor. Important parameters studied include dye concentration(20-60 mg/L), glucose concentration as a co-substrate(1,000-3,000 mg/L), hydraulic retention time(3-24 hr), and influent pH(6.0-8.0). Under most conditions tested, the molecules of Black B were degraded readily and completely according to HPLC chromatograms. However, the color removal efficiency based on spectroscopic measurement was always approximately 75%. This suggests that the degradation products have some color intensity corresponding to 25% of the original dye molecules. The maximum influent dye concentration which satisfies the legal discharge limit of color intensity of 400 ADMI was 13 mg/L. and the highest removal rate at this dye concentration was 104 mg/L${\cdot}$day.

• Analytical Science and Technology
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• v.25 no.5
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• pp.265-272
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• 2012

Okamoto cavity was modified to generate high power (2.45 GHz, 2 kW) He, N2 and Ar plasmas with WR-340 waveguide. Many factors which influence to the plasma generation were optimized and investigated for the spectroscopic properties of the He plasma generated. Some of the important factors are the diameter of the inner conductor, the distance between the inner and outer conductors and the distance between the tip of the inner conductor and the torch. After optimization for the He, two torches (a commercial mini torch for ICP and a tangential flow torch made locally) were compared and showed similar results for the helium plasma gas flow of 25 L/min~30 L/min. A tall torch (extended) was used to block the air in-flow and reduced the background intensity at 340 nm region (NH band). Emission intensity was measured for determination of halogen element in the aqueous solution with power and carrier gas flow rate. Electron number density and the excitation temperature were on the order of $3.67{\times}10^{11}/cm^3$ and 4,350 K, respectively. These values are similar or a bit smaller than other microwave plasmas. It has been possible to analyze aqueous samples. The detection limit for Cl (479.45 nm) was obtained to be 116 mg/L and needs analytical optimization for the better performance.

• Journal of Radiation Industry
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• v.10 no.1
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• pp.29-35
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• 2016

Radiation generating devices must be properly shielded for their safe application. Although institutes such as US National Bureau of Standards and National Council on Radiation Protection and Measurements (NCRP) have provided guidelines for shielding X-ray tube of various purposes, industry people tend to rely on 'Half Value Layer (HVL) method' which requires relatively simple calculation compared to the case of those guidelines. The method is based on the fact that the intensity, dose, and air kerma of narrow beam incident on shielding wall decreases by about half as the beam penetrates the HVL thickness of the wall. One can adjust shielding wall thickness to satisfy outside wall dose or air kerma requirements with this calculation. However, this may not always be the case because 1) The strict definition of HVL deals with only Intensity, 2) The situation is different when the beam is not 'narrow'; the beam quality inside the wall is distorted and related changes on outside wall dose or air kerma such as buildup effect occurs. Therefore, sometimes more careful research should be done in order to verify the effect of shielding specific radiation generating device. High energy X-ray tubes which is operated at the voltage above 400 kV that are used for 'heavy' nondestructive inspection is an example. People have less experience in running and shielding such device than in the case of widely-used low energy X-ray tubes operated at the voltage below 300 kV. In this study, Air Kerma value per week, outside concrete shielding wall of various thickness surrounding 450 kVp X-ray tube were calculated using MCNP simulation with the aid of Geometry Splitting method which is a famous Variance Reduction technique. The comparison between simulated result, HVL method result, and NCRP Report 147 safety goal $0.02mGy\;wk^{-1}$ on Air Kerma for the place where the public are free to pass showed that concrete wall of thickness 80 cm is needed to achieve the safety goal. Essentially same result was obtained from the application of HVL method except that it suggest the need of additional 5 cm concrete wall thickness. Therefore, employing the result from HVL method calculation as an conservative upper limit of concrete shielding wall thickness was found to be useful; It would be easy, economic, and reasonable way to set shielding wall thickness.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.6
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• pp.853-861
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• 2018

This paper proposes the application of harmonic constraints to address the problems caused by abnormal voltage increases when electric railway vehicles are running. The AC line that supplies the train with power during operation is used to provide electricity of 25kV/60 Hz, but gradually the size and frequency of harmonics involved in the line are varied with the technological evolution of the railroad vehicle electrical equipment. An increase in heat losses due to the failure of the instrument transformer (PT), the main circuit device, which is a serious problem with the recent train safety operation, or to the main displacement voltage. When high frequency components are introduced through low frequency Transformers of the main circuit device, the high intensity of the components is caused by the high intensity of the core and the current flow of the parasitic core is increased, thus generating heat. To solve this problem, the recent adjustment of the sequence has applied artificial NOTCH OFF of the power converter. However, the method of receiving and controlling the OFF signal operates by interaction between the ground and the vehicle's devices, thus it is invalid in the event of failure, and an actual accident is occurring. Therefore, the harmonic currents were required to prevent possible flow of harmonics, and conducted a study to prevent accidental occurrence of train accidents and to verify feasibility of the device through the simulations of the train's experimental analysis and the simulations of the train for safe operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.352-359
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• 1997

The visual acuity of filefish Stephanolepis cirrhifer was studied through a series of experiments by observing their responses to target plates. The fish were trained to respond to the target plates made of white acrylic resin with a vertical black line 5cm long in the center. The width of the black line ranged from 0.2mm to 8.0 mm. The line width was diminished unto the fish could no longer distinguish the line at a distance of 100 cm from the target plate. This was repeated under light intensities of 400, 20, 5, 3 and 1 lx at the water surface. Fish were rewarded with bait in front of the target plate if the fish went to the target date (i.e., success).The results show that the training effect of 1lensh had a success rate of over 80% and that the reach times to the target plates were 4~5 seconds over 210 experimental tunes. The success rate was high using the thick line with strong apparent contrast, but was low at the 1 lx. The visible critical width of line became thick with decreasing light intensity, 0.24mm at 400 lx, followed by 0.30mm at 20 lx, 0.40mm at 5 lx, 0.46 mm at 3 lx and 2.87mm at 1 lx. The apparent contrast for visible critical width of line increased with decreasing light intensity, 0.01 at 400 and 20 lx, 0.02 at 5 lx, 0.03 at 3 lx and 0.09 at 1 lx. The line acuity of filefish was best 1.21 at the 400 lx, followed by 0.97 at 20 lx, 0.73 at 5 lx, 0.63 at 3 lx and sharply decreased to 0.10 at 1 lx. The visible ranges for 1mm and 6mm in width of line were about 4.2 m and 25.0 m at the 400 lx light intensity and decreased m 1/14 times and 1/12 times of the 400 lx at 1 lx, respectively.

• Journal of Powder Materials
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• v.15 no.5
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• pp.393-398
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• 2008

Trace analysis of Cd and Pb at surface modified thick film graphite electrode with Bi nanopowder has been carried out using square-wave anodic stripping voltammetry (SWASV) technique. Bi nanopowder synthesized by gas condensation (GC) method showed the size of $50{\sim}100$ nm with BET surface area, $A_{BET}=6.8m^{2}g^{-l}$. For a strong adhesion of the Bi nanopowder onto the screen printed carbon paste electrode, nafion solution was added into Bi-containing suspension. From the SWASV, it was found that the Bi nanopowder electrode exhibited a well-defined responses relating to the oxidations of Cd and Pb. The current peak intensity increased with increasing concentration of Cd and Pb. From the linear relationship between Cd/Pb concentrations and peak current, the sensitivity of the Bi nanopowder electrode was quantitatively estimated. The detection limit of the electrode was estimated to be $0.15{\mu}g/l$ and $0.07{\mu}g/l$ for Cd and Pb, respectively, on the basis of the signal-to-noise characteristics (S/N=3) of the response for the $1.0{\mu}g/l$ solution under a 10 min accumulation.