• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.260-266
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• 2023

In recent years, excessive emissions of carbon dioxide(CO₂) have become the cause of global climate change. Consequently, there has been significant research activity aimed at both removing and utilizing CO₂. This study assesses the potential utilization of railway tie concrete waste, generated from railway infrastructure, as a CO₂ absorption material and investigates the physicochemical properties before and after CO₂ absorption to understand the CO₂ removal mechanisms. Railway tie concrete waste primarily consists of Si(26.60 %) and contains 9.82 % of Ca. Compared to samples of Cement and Normal concrete waste, it demonstrated superior potential for use as a CO₂ absorption material, with approximately 98 % of the Ca content participating in CO₂ absorption reactions. Through Thermogravimetric Analysis(TGA) and X-ray Diffraction(XRD) analysis, it was confirmed that the carbonate reaction, where the Ca in railway tie concrete waste converts into CaCO₃ through reaction with CO₂ gas, is the primary mechanism for CO₂ removal. Furthermore, Scanning Electron Microscopy(SEM) analysis revealed the formation of numerous CaCO₃ particles with sizes less than 0.1 ㎛ after the CO₂ absorption reaction. This transformation of large internal voids in the CO₂ absorption material into mesopores resulted in an increase in the specific surface area of the material.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.3
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• pp.163-170
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• 2009

Several species of the genus Pseudo-nitzschia produce the neurotoxin domoic acid (DA) known to be responsible for amnesic shellfish poisoning. In spite of the potentially toxic effects on marine ecosystem, even the representative Pseudo-nitzschia species occurring in Korean coastal waters have not been clearly reported. Plankton samples from several outer coastal sites of Tongyeong were collected fortnightly from May to November 2008 and the presence of diatoms of the genus Pseudo-nitzschia was examined using light and scanning electron microscopy. Thirteen species were observed, including P. americana, P. brasiliana, P. caciantha, P. calliantha, P. cuspidata, P. delicatissima, P. micropora, P. multiseries, P. multistriata, P. pseudodelicatissima, P. pungens, P. subfraudulenta, and P. subpacifica. The number of Pseudo-nitzschia species observed were only four in May, which was minimum during this survey, and then gradually increased attaining maximum, twelve, in September. After September it began to decrease again and got to five in November. Of these, P. americana, P. brasiliana, P. caciantha, P. calliantha, P. micropora, and P, pseudodelicatissima are new records for the Korean coastal waters and P. calliantha, P. cuspidata, P. delicatissima, P multiseries, P. multistriata, and P. pungens have been reported as DA producers around the world, but the potential toxicity of these species was not ascertained in Tongyeong area.

• Journal of the Korea Society of Computer and Information
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• v.29 no.5
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• pp.21-29
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• 2024

Reducing the radiation dose during CT scanning can lower the risk of radiation exposure, but not only does the image resolution significantly deteriorate, but the effectiveness of diagnosis is reduced due to the generation of noise. Therefore, noise removal from CT images is a very important and essential processing process in the image restoration. Until now, there are limitations in removing only the noise by separating the noise and the original signal in the image area. In this paper, we aim to effectively remove noise from CT images using the wavelet transform-based GAN model, that is, the WT-GAN model in the frequency domain. The GAN model used here generates images with noise removed through a U-Net structured generator and a PatchGAN structured discriminator. To evaluate the performance of the WT-GAN model proposed in this paper, experiments were conducted on CT images damaged by various noises, namely Gaussian noise, Poisson noise, and speckle noise. As a result of the performance experiment, the WT-GAN model is better than the traditional filter, that is, the BM3D filter, as well as the existing deep learning models, such as DnCNN, CDAE model, and U-Net GAN model, in qualitative and quantitative measures, that is, PSNR (Peak Signal-to-Noise Ratio) and SSIM (Structural Similarity Index Measure) showed excellent results.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.633-638
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• 2011

Mn substituted La, Sr or Ba-hexaaluminate were prepared by $(NH_4)_2CO_3$ co-precipitate method and calcined at $1,200^{\circ}C$ for 5 h. Catalysts were characterized by X-ray diffraction and $N_2$ physisorption and scanning electron microscope (SEM). Compared to $SrMnAl_{11}O_{19}$ and $BaMnAl_{11}O_{19}$, $LaMnAl_{11}O_{19}$ in which La located at mirror plane showed better crystallinity and high surface area, 13 $m^2/g$. $LaMnAl_{11}O_{19}$ revealed well developed plate-like structure which is characteristic structure of hexaaluminate. The catalytic activity of methane combustion increased in the following order: $LaMnAl_{11}O_{19}$ > $SrMnAl_{11}O_{19}$ > $BaMnAl_{11}O_{19}$ and was dependent on surface area of catalysts. 60 wt% $CeO_2/LaMnAl_{11}O_{19}$ calcined at $700^{\circ}C$ showed enhanced methane activity and methane was oxidized completely at low temperature ($700^{\circ}C$). It was confirmed that addition of ceria seems to be effective for the low and middle temperature combustion of methane. But, after calcination at high temperature of $1,200^{\circ}C$, it lost the promoting effect of ceria due to increase of ceria particle size and it had a limit to applying to the high temperature catalytic combustion.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.3
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• pp.584-609
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• 1995

The purpose of this study was to evaluate the difference of the galvanic corrosion behaviour of the titanium in contact with gold alloy, silva-palladium alloy, and nickel-chromium alloy using the immersion and electrochemical method. And the effects of galvallit couples between titanium and the dental alloys were assessed for their usefulness as materials for superstructure. The immersion method was performed by measuring the amount of metal elementsreleased by Inductivey coupled plasma emission spectroscopy(ICPES) The specimen of fifteen titanium plates, the five gold alloy, five silver-palladium, five nickel-chromium plates, and twenty acrylic resin plates ware fabricated, and also the specimen of sixty titanium plugs, the thirty gold alloy, thirty silver-palladium, and nickelc-hromium plugs were made. Thereafter, each plug of gold alloy, silver-palladium, and nickel-chromium inserted into the the titanium and acrylic resin plate, and also titanium plug inserted into the acrylic resin plate. The combination specimens uf galvanic couples immersed in 70m1 artificial saliva solution, and also specimens of four type alloy(that is, titanium, gold, silver-palladium and nickel-chromium alloy) plugs were immersed solely in 70m1 artificial sativa solution. The amount of metal elements released was observed during 21 weeks in the interval of each seven week. The electrochemical method was performed using computer-controlled potentiosta(Autostat 251. Sycopel Sicentific Ltd., U.K). The wax patterns(diameter 11.0mm, thickness,in 1.5mm) of four dental casting alloys were casted by centrifugal method and embedded in self-curing acrylic resin to be about $1.0cm^2$ of exposed surface area. Embedded specimens were polished with silicone carbide paper to #2,000, and ultrasonically cleaned. The working electrode is the specimen of four dental casting alloys, the reference electrode is a saturated calmel electrode(SCE) and the ounter electrode is made of platinum plate. In the artificial saliva solution, the potential scanning was carried out starting from-700mV(SCE) TO +1,000mV(SCE) and the scan rate was 75mV/min. Each polarization curve of alloy was recorded automatically on a logrithmic graphic paper by XY recorder. From the polarization curves of each galvanic couple, corrosion potential and corrosion rates, that is, corrosion density were compared and order of corrosion tendency was determined. From the experiments, the following results were obtained : 1. In the case of immersing titanium, gold alloy, silver-palladium alloy, and nickel-chromium alloysolely in the artificial saliva solution(group 1, 2, 3, and 4), the total amount of metal elements released was that group 4 was greater about 2, 3 times than group 3, and about 7.8 times than group 2. In the case of group 1, the amount of titanium released was not found after 8 week(p<0.001). 2. In the case of galvanic couples of titanium in contact with alloy(group 5, 6), the total amount of metal elements released of group 5 and 6 was less than that of group 7, 8, 9, and 10(p<0.05). 3. In the case of galvanic couples of titanium in contact with silver-palladium alloy(group 7, 8), the total amount of metal elements released of group 7 was greater about twice than that of group 5, and that of group 8 was about 14 times than that of group 6(p<0.05). 4. In the case of galvanic couples of titanium in contact with nickel-chromium alloy(group 9, 10), the total amount of metal elements released of group 9 and 10 was greater about 1.8-3.2 times than that of group 7 and 8, and was greater about 4.3~25 times than that of group 5 and 6(p<0.05). 5. In the effect of galvanic corrosion according to the difference of the area ratio of cathode and anode, the total amount of metal elements released was that group 5 was greater about 4 times than group 6, group 8 was greater about twice than group 7, and group 10 was greater about 1.5 times than group 9(p<0.05). 6. In the effect of galvanic corrosion according to the elasped time during 21 week in the interval of each 7 week, the amount of metal elements released was decreased markedly in the case of galvanic couples of the titanium in contact with gold alloy and silver-palladium alloy but the total amount of nickel and beryllium released was not decreased markedly in the case of galvanic couples of the titanium in contact with nickel-chromium alloy(p<0.05). 7. In the case of galvanic couples of titanium in contact with gold alloy, galvanic current was lower than any other galvanic couple. 8. In the case of galvanic couples of titanium in contact with nickel-chromium alloy, galvanic current was highest among other galvanic couples.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.244-250
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• 2012

The results of analyzing the difference between performances of individual dosimeters on this research subjecting the PLD and TLD, which are the official personal dosimeters, through dosimetry are as follows. After scanning the integral dose using an automatic scanner, the values of two devices that went through dose adjustment process had a statistical difference in TLD and PLD measurements under each filming conditions which were 70kVp, 200mA, 0.012sec and 42kVp, 100mA, and 0.012sec (p<0.001 and p<0.001 respectively). As for the difference of measurement value between DAP and the two particles under 70kVp, 200mA, 0.012sec filming condition, TLD had a value lower than DAP average value by $44.2mGy{\cdot}cm^2$ and PLD had a value of $246.8mGy{\cdot}cm^2$ which was lower than DAP average value by $15.5mGy{\cdot}cm^2$, while under 42kVp, 100mA, 0.012sec filming condition, TLD had a value lower than DAP average value by $17.9mGy{\cdot}cm^2$ and PLD had a value of $82.6mGy{\cdot}cm^2$ which was lower than DAP average value by 7.6$mGy{\cdot}cm^2$. Also, compared to PLD, each of 10 devices measured dose value in TLD had a larger deviation between the particles, and for a reproducibility test which repeatedly measured one particle, PLD had ${\pm}1%$ which was lower than TLD's ${\pm}2%$. As such, PLD had a superior performance result in dose measurement capacities aspect compared to TLD, and therefore we could verify that PLD is more appropriate and advantageous in managing radiation-related task performing worker's personal radiation exposure management in the diagnostic radiation field.

• Journal of the Mineralogical Society of Korea
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• v.30 no.3
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• pp.93-102
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• 2017

Heavy mineral provide an important information for sediment provenance as well as a potential submarine mineral resources. We compared the heavy mineral characteristics between Southeastern Yellow Sea Mud (SEYSM) and Southwestern Cheju Island Mud (SWCIM) surface sediments. We separated heavy minerals from 28 surface sediments in each mudbelt, and then carried out stereo-microscopic, field-emission scanning electron microscopic, energy dispersive spectroscopic and electron probe microanalysis to characterize the type, abundance, mineralogical properties and distribution pattern of heavy mineral. Amphibole and epidote, which are two major heavy minerals, account for more than 70% of total heavy minerals. Zircon and sphene contents are more abundant in SEYSM, whereas apatite and rutile contents are more abundant in SWCIM. Monazite only occurs in some area of SEYSM. Sphene and monazite content decrease to the south in SEYSM. Both garnet-zircon index (GZi) and rutile-zircon index (RuZi) are low in SEYSM but high in SWCIM. Amphiboles in SEYSM primarily correspond to hornblende, however those in SWCIM represent variable composition from pargasite, tshermakite, hornblende to tremolite. Garnets in SEYSM have high Mg and low Ca, but those in SWCIM have low Mg with variable Ca. Different heavy mineral characteristics between SEYSM and SWCIM suggests that sediments in each mudbelt have different provenances. Although this study implies that SEYSM sediment may mostly come from nearby Korean western rivers such as the Keum and Han rivers, this study does not suggest any idea of the source area of SWCIM sediment. Further study is needed to interpret the provenance and transportation mechanism of mudbelt sediments through the heavy mineral research for the river sediments flowing into the Yellow Sea and much more marine sediments.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.1-26
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• 1996

This study was performed to estimate the effects of cultured bone cell inoculated on porous type hydroxyaptite for the regeneration of the artificial alveolar bone defect. In this experiment 3 beagle dogs were used, and each of them were divided into right and left mandible. Every surgical intervention were performed under the general anesthesia by using with intravenous injection of Pentobarbital sodium(30mg/Kg). To reduce the gingival bleeding during surgery, operative site was injected with Lidocaine hydrochloride(l:80,000 Epinephrine) as local anesthesia. After surgery experimental animal were feeded with soft dietl Mighty dog, Frisies Co., U.S.A.) for 1 weeks to avoid irritaion to soft tissue by food. 2 months before surgery both side of mandibular 1st premolar were extracted and bone chips from mandibular body were obtained from all animals. Bone cells were cultured from bone chips obtained from mandible with Dulbecco's Modified Essential Medium contained with 10% Fetal Bovine Serum under the conventional conditions. Porous type hydroxyapatite were immerse into the high concentrated cell suspension solution, and put 4 hours for attachin the cells on the surface of hydroxyapatite. Graft material were inserted on the artificial bone defect after 3 days of culture. Before insertion of cellinoculated graft material, scanning electronic microscopic observation were performed to confirm the attachment and spreading of cell on the hydroxyapatite surface. 3 artificial bone defects were made with bone trephine drill on the both side of mandible of the experimental animal. First defect was designed without insertion of graft material as negative control, second was filled with porous replamineform hydroxyapatite inoculated with cultured bone marrow cells as expermiental site, and third was filled with graft materials only as positive control. The size of every artificial bone defect was 3mm in diameter and 3mm in depth. After the every surgical intervention of animals, oral hygiene program were performed with 1.0% chlorhexidine digluconate. All of the animals were sacrificed at 2, 4, 6 weeks after surgery. For obtaining histological section, tissus were fixed in 10% Buffered formalin and decalcified with Planko - Rycho Solution for 72hr. Tissue embeding was performed in paraffin and cut parallel to the surface of mandibular body. Section in 8um thickness of tissue was done and stained with Hematoxylin - Eosin. All the specimens were observed under the light microscopy. The following results were obtained : 1. In the case of control site which has no graft material, less inflammatory cell infiltration and rapid new bone forming tendency were revealed compared with experimental groups. But bone surface were observed depression pattern on defect area because of soft tissue invasion into the artificial bone defect during the experimental period. 2. In the porous hydroxyapatite only group, inflammatory cell infiltration was prominet and dense connective tissue were encapsulated around grafted materials. osteoblastic activity in the early stage after surgery was low to compared with grafted with bone cells. 3. In the case of porous hydroxyapatite inoculated with bone cell, less inflammatory cell infiltration and rapid new bone formation activity was revealed than hydroxyapatite only group. Active new bone formation were observed in the early stage of control group. 4. The origin of new bone forming was revealed not from the center of defected area but from the surface of preexisting bony wall on every specimen. 5. In this experiment, osteoclastic cell was not found around grafted materials, and fibrovascular invasion into regions with no noticeable foreign body reaction. Conclusively, the cultured bone cell inoculated onto the porous hydroxyapatite may have an important role of regeneration of artificial bone defects of alveolar bone.

• Journal of the Mineralogical Society of Korea
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• v.31 no.1
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• pp.47-55
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• 2018

Talc, hydrous magnesium phyllosilicate, is one of the most popular industrial minerals due to their chemical stability and adsorptivity. While micro-sized talc has long been used as a filler and coating, nano-sized talc recently is attracting attention as additives for improving the stability of nanocomposites. In this study, we produced the nano-sized talc powder by mechanical method using high energy ball mill and investigated the changes in particle size and crystallinity with increasing milling time up to 720 minutes. X-ray diffraction results show that the peak width of talc gradually as the milling proceeded, and after 720 minutes of pulverization, the talc showed an amorphous-like X-ray diffraction pattern. Lase diffraction particle size analysis presents that particle size of talc which was ${\sim}12{\mu}m$ decreased to ${\sim}0.45{\mu}m$ as the milling progressed, but no significant reduction of particle size was observed even after grinding for 120 minutes or more. BET specific surface area, however, steadily increases up to the milling time of 720 minutes, indicating that the particle size and morphology change steadily as the milling progressed. Scanning electron microscope and transmission electron microscope images shows that layered particles of about 100 to 300 nm was aggregated as micro-sized particles after pulverization for 720 minutes. As the grinding time increases, the particle size and morphology of talc continuously change, but the nano-sized talc particles form micro sized agglomerates. These results suggest that there is a critical size along the a, b axes in which the size of plates is reduced even though the grinding proceeds, and the reduction of plate thickness along the c axis leads the increase in specific surface area with further grinding. This study could enhance the understanding of the mechanism of the formation of nano-sized talc by mechanical grinding.

• Korean Journal of Plant Taxonomy
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• v.34 no.2
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• pp.97-118
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• 2004

A comparative anatomical and ultrastructural study was undertaken to investigare on the leaf epidermis by light microscopy (LM) and scanning electron microscopy (SEM). On the basis of results from this study, it was grasped major characters of taxa and variation range of each character on the level of species, section and subgenus respectively. The shape of leaf epidermal cell was oblong to linear, which was varied by each taxon. Epidermal cell of taxa in sects. Microscordum, Anguinum, and Rhizirideum, which had wide leaf blade, oblong instead of linear shape in others examined taxa in this study. The leaf of taxa in sect. Anguinum was hypostomatic, while the rest of taxa had amphistomatic leaf. This was also one of characters which could discriminate taxa of sect. Anguinum from others. The guard cell in investigated taxa had not so much variation in the respect of its size. The number of stomata per unit area reduced by increasing size of epidermal cell, the fewest number of stomata per unit area was found in the taxa of sect. Anguinum. The type of stomatal apparatus of observed all taxa was anomocytic. It was found to know ultrastructural variation in the epidermal cell, like as patterns of sculpture on the cell wall, and features of deposition of wax by SEM. There were no depositions of wax in the taxa of sect. Microscordum and Anguinum, but fine thread-like structures which were parallel or cross to axis was found on the surface of epidermal cell respectively. The patterns of sculpture on the cell were prominent straight in sects. Recticulato-bulbosa and Rhizirideum, discontinuous line in the sect. Oreiprason. The epicuticular wax had been deposited on the surface of its epidermal cell in all taxa except sects. Microscordum and Anguinum.