• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.127-137
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• 2019

Zr electrorefining is demonstrated herein using Zirlo tubes in a chloride-fluoride mixed molten salt in the presence of $AlF_3$. Cyclic voltammetry reveals a monotonic shift in the onset of metal reduction kinetics towards positive potential and an increase in intensity of the additional peaks associated with Zr-Al alloy formation with increasing $AlF_3$ concentration. Unlike the galvanostatic deposition mode, a radial plate-type Zr growth is evident at the top surface of the salt during Zr electrorefining at a constant potential of -1.2 V. The diameter of the plate-type Zr deposit gradually increases with increasing $AlF_3$ concentration. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses for the plate-type Zr deposit show that trace amount of Al is incorporated as Zr-Al alloys with different chemical compositions between the top and bottom surface of the deposit. Addition of $AlF_3$ is effective in lowering the residual salt content in the deposit and in improving the current efficiency for Zr recovery.

• Journal of Climate Change Research
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• v.3 no.4
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• pp.259-270
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• 2012

Mobile air conditioning(MAC) systems of light-duty vehicles consume the most energy among auxiliary parts. Vehicle $CO_2$ reduction policies in Korea, US EPA and EU include the strategies to reduce additional $CO_2$ by MAC operation with providing incentive for the high-efficient MAC technologies. It is under development how to estimate MAC $CO_2$ and to differentiate advanced or high-efficient MAC system in US EPA and EU. The additional energy by MAC operation would beaffected by not only driving patterns but also environmental conditions such as temperature and humidity. In this study, we estimated MAC $CO_2$ of Korean light-duty vehicles with various driving cycles and environmental conditions. Test results were corrected to reference conditions for varied temperature and humidity during tests to get the comparable data for test vehicles. The test results showed that high-efficient MAC technologies have potential to reduce MAC $CO_2$ approximately by 50%. Considering the rate of MAC $CO_2$ to vehicle $CO_2$, it is expected that the introduction of high-efficient MAC technologies would considerably reduce vehicle $CO_2$ emission in MAC operation.

• Journal of Applied Biological Chemistry
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• v.61 no.4
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• pp.397-403
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• 2018

The leaves of Spiraea prunifolia were extracted with 80% aqueous MeOH and the concentrates were partitioned into EtOAc, n-BuOH, and $H_2O$ fractions. The repeated $SiO_2$ or ODS column, and medium pressure liquid chromatographies for the n-BuOH fraction led to isolation of two phenolic glucosides. The chemical structures of these compounds were determined as isosalicin (1) and crenatin (2) based on spectroscopic analyses including Nuclear magnetic resonance and MS. Extracts were analyzed using UPLC-MS/MS providing a short analysis time within 5 min using MRM technique. The concentration of crenatin was higher as 9.53 mg/g and isosalicin was lower as 0.65 mg/g. Neuroprotective effects of these compounds against hydrogen peroxide ($H_2O_2$)-induced neurotoxicity were evaluated. The results showed that exposure to $H_2O_2$ induced morphological changes, cell death and neurotoxicity in SK-N-MC cells. However, pretreatment with crenatin resulted in inhibition of morphological change, reduction of loss of cell viability and attenuation of neuronal damage. These results suggested that neuroprotective effect of crenatin isolated from S. prunifolia can be a good candidate for the development of health beneficial foods which can ameliorate the degenerative neuronal disease caused by oxidative stress.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1383-1398
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• 2018

Sea surface wind is one of the most fundamental variables for understanding diverse marine phenomena. Although scatterometers have produced global wind field data since the early 1990's, the data has been used limitedly in oceanic applications due to it slow spatial resolution, especially at coastal regions. Synthetic Aperture Radar (SAR) is capable to produce high resolution wind field data. KOMPSAT-5 is the first Korean satellite equipped with X-band SAR instrument and is able to retrieve the sea surface wind. This study presents the validation results of sea surface wind derived from the KOMPSAT-5 backscattering coefficient data for the first time. We collected 18 KOMPSAT-5 ES mode data to produce a matchup database collocated with buoy stations. In order to calculate the accurate wind speed, we preprocessed the SAR data, including land masking, speckle noise reduction, and ship detection, and converted the in-situ wind to 10-m neutral wind as reference wind data using Liu-Katsaros-Businger (LKB) model. The sea surface winds based on XMOD2 show root-mean-square errors of about $2.41-2.74m\;s^{-1}$ depending on backscattering coefficient conversion equations. In-depth analyses on the wind speed errors derived from KOMPSAT-5 backscattering coefficient data reveal the existence of diverse potential error factors such as image quality related to range ambiguity, discrete and discontinuous distribution of incidence angle, change in marine atmospheric environment, impacts on atmospheric gravity waves, ocean wave spectrum, and internal wave.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.1
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• pp.1-13
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• 2019

With commercial apps popular in EU, MaaS has been emerging around the globe as a new approach to worsening urban traffic problems. In contrast, it is still mainstay in Korea simply discussing the concept and necessities of MaaS, rather than seeking for real-world solutions for the commercialization. The purpose of this research is to analyze the demand-side i1mpacts of travel time and cost changes according to MaaS adoption, and to see its commercial feasibility in Korea. The 2010 KTDB traveler's nationwide OD data is used to estimate the level of fare discount for balancing the mode shift and fare revenue changes followed by MaaS implementation. The analysis results show that MaaS leads to the increase of public transport ridership as a result of the diminishing travel cost and time, and that the time saving works more positively for ridership increase. Also, the optimum level of fare discount is estimated 2.56% without damaging the revenue. This finding reveals that MaaS impact is superior to the other single-sided public transport inventive measures since it can affect both travel cost and time reduction at the same time.

• Structural Engineering and Mechanics
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• v.70 no.1
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• pp.67-80
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• 2019

Strengthening with near surface mounted carbon fibre reinforced polymers (NSM-CFRP) is a strengthening technique that have been used for several decades to increase the load carrying capacity of reinforced concrete members. In Iraq, many concrete buildings and bridges were subjected to a wide range of damage as a result of the last war and many other events. Accordingly, there is a progressive increase in the strengthening of concrete structures, bridges in particular, by using CFRP strengthening techniques. Near-surface mounted carbon fibre polymer has been recently proved as a powerful strengthening technique in which the CFRP strips are sufficiently protected against external environmental conditions especially the high-temperature rates in Iraq. However, this technique has not been examined yet under repeated loading conditions such as traffic loads on bridge girders. The main objective of this research was to investigate the effectiveness of NSM-CFRP strips in reinforced concrete beams under repeated loads. Different parameters such as the number of strips, groove size, and two types of bonding materials (epoxy resin and cement-based adhesive) were considered. Fifteen NSM-CFRP strengthened beams were tested under concentrated monotonic and repeated loadings. Three beams were non-strengthened as reference specimens while the remaining were strengthened with NSM-CFRP strips and divided into three groups. Each group comprises two beams tested under monotonic loads and used as control for those tested under repeated loads in the same group. The experimental results are discussed in terms of load-deflection behavior up to failure, ductility factor, cumulative energy absorption, number of cycles to failure, and the mode of failure. The test results proved that strengthening with NSM-CFRP strips increased both the flexural strength and stiffness of the tested beams. An increase in load carrying capacity was obtained in a range of (1.47 to 4.49) times that for the non-strengthened specimens. Also, the increase in total area of CFRPs showed a slight increase in flexural capacity of (1.02) times the value of the control strengthened one tested under repeated loading. Increasing the total area of CFRP strips resulted in a reduction in ductility factor reached to (0.71) while the cumulative energy absorption increased by (1.22) times the values of the strengthened reference specimens tested under repeated loading. Moreover, the replacement of epoxy resin with cement-based adhesive as a bonding material exhibited higher ductility than specimen with epoxy resin tested under monotonic and repeated loading.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.11-25
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• 2023

In this study, the design and numerical analysis method of the inclined self-supported wall using cement treated soil were studied. In the case of the inclined self-supported wall, the active earth pressure decreased due to the decrease in the coefficient, Ka according to the slope (angle) and the weight decreasing effect, thereby increasing the overall stability. The wall with the slope caused a change in failure mode from overturning to sliding on the excavation side, and the optimal slope was evaluated to be about 10°. Compared to the strength reduction method, the overall stability in numerical analysis results in conservative results in limit equilibrium analysis, so it was found that this method should be attended when designing. As a result of the parameteric study, the stability on bearing capacity and compression failure did not significantly increase above the slope of 10° when the surcharge was small (about 20kPa or less). In the case of cohesion of the backfill, The results similar to numerical analysis were found to consider cohesion. It was evaluated that stability on sliding, oveturning, shear, and tension failure increases in proportion to the thickness of the wall, but there is no significant change in the stability on the bearing capacity and compressive failure regardless of the thickness of the wall above a certain angle (about 10°).

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.147-160
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• 2008

This paper presents the results of full-scale loading tests performed on 54 passive anchors and 4 group anchored footings grouted to various lengths at several sites in Korea. The test results, the failure mechanisms as well as uplift capacities of rock anchors depend mostly on rock type and quality, embedded fixed length, properties of the discontinuities, and the strength of rebar. Anchors in poor quality rocks generally fail along the grout/rock interfaces when their depths are very shallow (a fixed length of less than 1 m). However, even in such poor rocks, we can induce a more favorable mode of rock pull-up failure by increasing the fixed length of the anchors. On the other hand, anchors in good quality rocks show rock pull-up failures with high uplift resistance even when they are embedded at a shallow depth. Laboratory test results revealed that a form of progressive failure usually occurs starting near the upper surface of the grout, and then progresses downward. The ultimate tendon-grout bond strength was measured from $18{\sim}25%$ of unconfined compressive strength of grout. One of the important findings from these tests is that the measured strains along the corrosion protection sheath were so small that practically the reduction of bond strength by the presence of sheath would be negligible. Based on test results, the main parameters governing the uplift capacity of the rock anchor system were determined. By evaluation of the ultimate uplift capacity of anchor foundations in a wide range of in situ rock masses, rock classification suitable for a transmission tower foundation was developed. Finally, a very simple and economical design procedure is proposed for rock anchor foundations subjected to uplift tensile loads.

• The Journal of the Acoustical Society of Korea
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• v.25 no.2
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• pp.49-55
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• 2006

Measurement of impact sound insulation of floor, by current Korean Standard KS F 2810-2. is to be made with peak levels over 4 point in a receiving room. But it is often the case that there is inconsistency in results at various receiving points in the receiving room. Such variations obviously have effects on the repeatability and reproducibility of measured data. The result shows that there are even 10 dB deviations in 63Hz octave band frequency range and relatively less variations are occurred in other low frequency ranges. Such variations seems to be coming from modal overlaps of the receiving room. According to current rating method of floor impact sound. KS F 2863-2, that may affect on the single number latins scheme. From the result of tests in this study, there are 2dB to 6dB differences in the sin91e number with the combination of measurement points. This means that the reduction of measurement variations from the microphone positions is needed for a better credibility of measurement results.

• Structural Engineering and Mechanics
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• v.90 no.6
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• pp.611-633
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• 2024

This study intends to investigate the response of multi-cell (MC) beams to flexural loads in which the primary reinforcement is composed of both metallic and non-metallic materials. "Multi-cell" describes beam sections with multiple longitudinal voids separated by thin webs. Seven reinforced concrete MC beams measuring 300×200×1800 mm were tested under flexural loadings until failure. Two series of beams are formed, depending on the type of main reinforcement that is being used. A control RC beam with no openings and six MC beams are found in these two series. Series one and two are reinforced with metallic and non-metallic main reinforcement, respectively, in order to maintain a constant reinforcement ratio. The first crack, ultimate load, deflection, ductility index, energy absorption, strain characteristics, crack pattern, and failure mode were among the structural parameters of the beams under investigation that were documented. The primary variables that vary are the kind of reinforcing materials that are utilized, as well as the kind and quantity of mesh layers. The outcomes of this study that looked at the experimental and numerical performance of ferrocement reinforced concrete MC beams are presented in this article. Nonlinear finite element analysis (NLFEA) was performed with ANSYS-16.0 software to demonstrate the behavior of composite MC beams with holes. A parametric study is also carried out to investigate the factors, such as opening size, that can most strongly affect the mechanical behavior of the suggested model. The experimental and numerical results obtained demonstrate that the FE simulations generated an acceptable degree of experimental value estimation. It's also important to demonstrate that, when compared to the control beam, the MC beam reinforced with geogrid mesh (MCGB) decreases its strength capacity by a maximum of 73.33%. In contrast, the minimum strength reduction value of 16.71% is observed in the MC beams reinforced with carbon reinforcing bars (MCCR). The findings of the experiments on MC beams with openings demonstrate that the presence of openings has a significant impact on the behavior of the beams, as there is a decrease in both the ultimate load and maximum deflection.