• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.1
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• pp.86-92
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• 2019

Di-ethylhexyl phthalate (DEHP) is an environmental contaminant that is used as a plasticizer. Endometriosis is a complex disease with an unknown etiology that is believed to be associated with exposure to DEHP. The present study examined the potential toxicity of DEHP by exposing endometrial adenocarcinoma cells (Ishikawa cells) to DEHP. In the experiments, the cells were treated with stepwise DEHP concentrations (0, 0.01, 0.1, 1, and $5{\mu}M$) for different exposure times (24, 48, and 72 h). When the relationship between the resulting survival rate of the cells and initial inflammation was examined, the cell viability, expression of $TNF-{\alpha}$, an inflammatory mediator, and the expression of MMP-9, an ECM degradation protein, were increased remarkably when the cells were exposed to $5{\mu}M$ DEHP for 48 and 72 hours. These results suggest that the exposure of Ishikawa cells to certain concentrations of DEHP, estrogen mimics, may cause time-dependent toxicity that affects the cell viability and inflammation, implying a potential role in the etiology of endometriosis. Further research on the effects of endocrine disruptors on the pathogenesis of endometriosis may reveal strategies to prevent this disease.

• Korean Journal of Ecology and Environment
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• v.52 no.3
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• pp.192-201
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• 2019

While a fairly large amount of organic matter is produced daily via phytoplankton photosynthesis in Lake Paldang, South Korea, knowledge of the role of algal-derived organic matter (OM) as a refractory OM source is not adequate. To understand the contribution of algal-derived OM to the refractory pool, biodegradation experiment and $KMnO_4$ oxidation experiment were conducted for 60 days using $^{13}C$ and $^{15}N$ labeled natural phytoplankton assemblage. The assemblage was collected from Lake Paldang on May 20, 2010. The photosynthetically produced total organic carbon ($TO^{13}C$), particulate organic carbon ($PO^{13}C$), and particulate nitrogen ($P^{15}N$) remained at 26%, 20%, and 17% of the initial concentrations, respectively, in the form of non-biodegradable organic matter. In addition, 12% and 38% of $PO^{13}C$ remained after $KMnO_4$ treatment on Day 0 and 60, respectively. These results indicate that photosynthetic products could be an important source of refractory organic matter after microbial degradation. Moreover, the microbially transformed algal-derived OM could contribute to the oxidation rate of the chemical oxygen demand.

• Korean Journal of Environmental Agriculture
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• v.40 no.3
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• pp.219-230
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• 2021

BACKGROUND: Biochar is a solid material converted from agricultural biomass such as crop residues and pruning branch through pyrolysis under limited oxygen supply. Biochar consists of non-degradable carbon (C) double bonds and aromatic ring that are not readily broken down by microbial degradation in the soils. Due to the recalcitrancy of C in biochar, biochar application to the soils is of help in enhancing soil carbon sequestration in arable lands that might be a strategy of agricultural sector to mitigate climate change. METHODS AND RESULTS: Data were collected from studies on the effect of biochar application on soil C content conducted in East Asian countries including China, Japan and Korea under different experimental conditions (incubation, column, pot, and field). The magnitude of soil C storage was positively correlated (p < 0.001) with biochar application rate under field conditions, reflecting accumulation of recalcitrant black C in the biochar. However, The changes in soil C contents per C input from biochar (% per t/ha) were 6.80 in field condition, and 12.58 in laboratory condition. The magnitude of increment of soil C was lower in field than in laboratory conditions due to potential loss of C through weathering of biochar under field conditions. Biochar production condition also affected soil C increment; more C increment was found with biochar produced at a high temperature (over 450℃). CONCLUSION: This review suggests that biochar application is a potential measures of C sequestration in agricultural soils. However, as the increment of soil C biochar was affected by biochar types, further studies are necessary to find better biochar types for enhanced soil C storage.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.405-415
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• 2021

MMBR system has been suggested as a promising system to resolve harvesting problems induced from low settling efficiency of microalgae. And recently, a lot of research on reducing fouling at the MMBR system has investigated focused on EPS in many cases. EPS of microalgae mainly consists of polysaccharides and protein components, and is produced through photosynthesis and nitrogen-carbon metabolic pathways. Especially, P-EPS is one of major compounds which occur membrane fouling phenomenon, as its hydrophobic protein components cause floc formation and cake layer accumulation. And it is already known that almost every microalgae can metabolize P-EPS or Chl-a when nitrogen sources as a substrate is insufficient or exhausted situation. With the above backgrounds, uptake rates of P-EPS or Chl-a by Scenedesmus quadricauda according to the type of carbon source and nitrogen concentration were evaluated in order to verify correlation between carbon source vs P-EPS production, and indeed Scenedesmus quadricauda uses P-EPS or Chl-a when the amounts of nitrogen sourc es in the feed is not satisfied. As a result, it was shown that P-EPS and Chl-a production were increased proportional to nitrogen concentration under organic carbon condition. And especially, the amo unts of P-EPS and Chl-a in the cell were diminished with the nitrogen source becomes insufficient or exhausted. Because P-EPS accelerates fouling at the MMBR system, P-EPS degradation by Scenedesmus quadricauda in order to get nitrogen source may contribute to reducing fouling. About a affects of N-consumed Chl-a to the MMBR fouling, more survey is needed. On the contrary, considering the purpose of MMBR system of this study, i.e. harvesting useful high value microalgae efficiently feeding adequate industrial process wastewater, it seems like difficult to maintain satisfied metabolic activity and to harvest with high yield rate using nitrogen-poor MMBR feed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.1-8
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• 2022

The corrosion of reinforcement is the main reason for the performance degradation of concrete structures. The pre-rusted parts of rebar in concrete structures are vulnerable to the corrosion, especially if the structure is exposed to wet or chlorinated environments. In this study, effects of different curing solution on corrosion behavior of the pre-rusted rebars in the cement composites were investigated. HCl(3%) and CaCl₂(10%) solution were utilized to accelerate the pre-rust of the rebar, and each pre-rust condition rebar including reference (RE) were placed in mortar cylinder. Three kinds of samples then were cured in CaCl₂ (3%) solution and tap water respectively for 120 days. Electrochemical polarization and half-cell potential measurement were used to monitor the influence of curing water on the corrosion behavior of pre-rusted steel bar in cement composite. The surface morphology and composition of corroded steel bar were analyzed by scanning electron microscope and energy dispersive X-ray diffraction. The results show that the corrosion rates of pre-rusted samples in both curing water are higher than that of non-pre-rusted samples. The corrosion rates of RE, CaCl₂ and HCl pre-rusted samples in salt water were 8.14, 4.48, 13.81 times higher than those in tap water respectively, on the 120th day.

• Journal of Conservation Science
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• v.36 no.6
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• pp.541-548
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• 2020

There is a growing demand for natural materials to replace adhesives based on volatile organic compounds (VOCs). However, the exclusion of VOCs from the manufacturing process leads to difficulties in manufacturing, and reduction in productivity and preservability. In this paper, we report the manufacture of natural bioadhesives using the carrageenan component of seaweed. λ-carrageenan, isolated from the extracted total carrageenan, was used to prepare a highly stable adhesive for paper. The resulting composition was 52.0 ± 1.0% λ-carrageenan, 30.5 ± 0.5% Polyvinylpyrrolidone, 1.0 ± 0.05% ethylhexylglycerin, 1.5 ± 0.05% glycerin, 13.5 ± 0.5% dextrine, and 0.6 ± 0.05% food-grade antifoam emulsion. The viscosity was found to be 1.13 ± 0.07 × 105 cP (25℃), UV degradation occurred at pH6.22, drying rate was 15min, △b^* was -10.79, and △E^* ab was 8.18. The bioadhesive showed an excellent adhesion strength of 44.63 kgf/cm². Thus this adhesive showed excellent fungal resistance and good adhesive persistence, without the presence of total volatile organic compounds (TVOC), formaldehyde (HCHO), and heavy metals.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.570-575
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• 2022

The MX-S2X, utilizing high-frequency broadband communication technology, provides a reliable connection between land, ship, and facilities. This technology is expected to be effectively utilized as a future maritime communication infrastructure in the upcoming mixed navigational situation among autonomous and manned and/or unmanned ships. Following the physical layer design and M&S-based performance analysis of the MX-S2X system to overcome maritime multipath fading, this paper confirms the optimized and detailed design of physical layer hardware and implemented it to verify the performance. The PER(Packet Error Rate) performance was then measured by configuring a test environment to verify the implemented hardware. The results showed that the performance degradation was 0.2 dB in the AWGN environment and 1.2 dB in the Multi-path Fading on Sea Environment, thus confirming the successful implementation of the physical layer.

• Journal of Periodontal and Implant Science
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• v.53 no.4
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• pp.306-317
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• 2023

Purpose: Biphasic calcium phosphate (BCP), a widely used biomaterial for bone regeneration, contains synthetic hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), the ratio of which can be adjusted to modulate the rate of degradation. The aim of this study was to evaluate the clinical and radiographic benefits of reconstructing peri-implant bone defects with a newly developed BCP consisting of 60% β-TCP and 40% HA compared to demineralized bovine bone mineral (DBBM). Methods: This prospective, multicenter, parallel, single-blind randomized controlled trial was conducted at the periodontology departments of 3 different dental hospitals. Changes in clinical (defect width and height) and radiographic (augmented horizontal bone thickness) parameters were measured between implant surgery with guided bone regeneration (GBR) and re-entry surgery. Postoperative discomfort (severity and duration of pain and swelling) and early soft-tissue wound healing (dehiscence and inflammation) were also assessed. Data were compared between the BCP (test) and DBBM (control) groups using the independent t-test and the χ² test. Results: Of the 53 cases included, 27 were in the test group and 26 were in the control group. After a healing period of 18 weeks, the full and mean resolution of buccal dehiscence defects were 59.3% (n=16) and 71.3% in the test group and 42.3% (n=11) and 57.9% in the control group, respectively. There were no significant differences between the groups in terms of the change in mean horizontal bone augmentation (test group: -0.50±0.66 mm vs. control groups: -0.66±0.83 mm, P=0.133), postoperative discomfort, or early wound healing. No adverse or fatal complications occurred in either group. Conclusions: The GBR procedure with the newly developed BCP showed favorable clinical, radiographic, postoperative discomfort-related, and early wound healing outcomes for peri-implant dehiscence defects that were similar to those for DBBM.

• The Korea Journal of Herbology
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• v.24 no.3
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• pp.153-160
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• 2009

Objectives : The purpose of this study was to investigate the anti-inflammatory effects of extract from Trogopterorum Faeces (TF) on the RAW 264.7 cells. Methods : To prove the TF's anti-inflammatory effects, we investigated nitric oxide (NO) production and own cell viability. We examined the cytokine productions on lipopolysacchride (LPS)-induced RAW 264.7 cells and also cellular regulatory mechanisms. Results : TF does not have any cytotoxic effect. TF reduced LPS-induced NO production, interleukin (IL)-1b, IL-6, IL-10 and tumor necrosis factor-a (TNF-a) in RAW 264.7 cells. TF inhibited the activation of mitogen-activated protein kinases (MAPKs) such as p38, extracelluar signal-regulated kinase (ERK 1/2) and c-Jun NH2-terminal kinase (JNK) and also the degradation of inhibitory kappa B a (Ik-Ba) in the LPS-stimulated RAW 264.7 cells. TF reduced the serum levels of IL-1b, IL-6, TNF-a. The survival rate of LPS-induced endotoxin shock was increased by TF administration. Conclusions : TF down-regulated LPS-induced NO and cytokines production, which could provide a clinical basis for anti-inflammatory properties.