• Resources Recycling
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• v.29 no.6
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• pp.104-113
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• 2020

Bubble size in froth flotation has long been recognized as a key factor which affects the bubble residence time, the bubble surface area flux (Sb) and the carrying rate (Cr). This paper presents method of bubble size measurement, relationship between operating variables and gas dispersion properties in flotation column. Using high speed camera and image analysis system, bubble size has been directly measured as a function of operating parameters (e.g., superficial gas rate (Jg), superficial wash water rate (Jw), frother concentration) in flotation column. Relationship compared to measured and estimated bubble size was obtained within error ranges of ±15~20% and mean bubble size was 0.718mm. From this system the empirical relationship to control the bubble size and distribution has been developed under operating conditions such as Jg of 0.65~1.3cm/s, Jw of 0.13~0.52cm/s and frother concentration of 60~200ppm. Surface tension and bubble size decreased as frother concentration increased. It seemed that critical coalescence concentration (CCC) of bubbles was 200ppm so that surface tension was the lowest (49.24mN/m) at frother concentration of 200ppm. Bubble size tend to increase when superficial gas rate (Jg) decreases and superficial wash water rate Jw and frother concentration increase. Gas holdup is proportional to superficial gas rate as well as frother concentration and superficial wash water rate (at the fixed superficial gas rate).

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.57-62
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• 2011

This study investigated the effects of various inorganic anions($Cl^-$, $NO_3{^-}$, $HCO_3{^-}$) on the Methyl tert Butyl Ether(MTBE) degradation by photocatalysis using statistical method. Generally, this process in general demands the generation of hydroxyl radicals(OH radical) in solution in the presence of UV light. The generation of radicals were affected by inorganic anions in solution that inhibited the photodegradation by their trapping hydroxyl radicals. The effects of inorganic anions were mathematically described as the independent variables such as $Cl^-$, $NO_3{^-}$, and $HCO_3{^-}$, and these were designed by mixture analysis that was one of the response surface methodology(RSM). Regression analysis on ANOVA showed significant p-value(p<0.0001) and high coefficients for determination value($R^2$=99.28%, ${R^2}_{adj}$=98.91%). Contour and response surface plots showed that the effects of inorganic anions for MTBE photodegradation based on $UV/H_2O_2$ process. In the result, $Cl^-$ and $HCO_3{^-}$ inhibited the photodegradation of the MTBE by their trapping hydroxyl radicals, and the interaction by these two factors was observed.

• Journal of Korean Society of Forest Science
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• v.100 no.3
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• pp.476-482
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• 2011

As part of studies on the reduction of forest trails degradation caused by high users density, this study was carried out to investigate soil physical properties of forest trails of Gyeongnam Domain in Mt. Jiri, Southeast Korea. Since the forest were opened for leisure trailing in 2008, the average soil erosion amounts per a square meter on the forest trails were $0.0015m^3$ from Inweol to Gumgeo, $0.0018m^3$ from Dongang to Suchol, and $0.0027m^3$ from Suchol to Chungam for 3 years. But, from Chungam to Agyang, the erosion was almost not occurred because it was recently opened. The soil hardness in 5 cm depth was significantly higher than in 10 cm depth. It indicates that intensive soil compaction by users has mainly affected in 5 cm soil depth until now on. In three forest trails compacted intensively, the porosity of 0-7.5 cm soil layer was down to 1.4-1.5 times compared to that in 2008. In additions, the bulk density was up to 1.6-3.1 times compared to the controls, which were not opened to users. As a result, the degradation caused by high users density would keep occurring on the three forest trails unless any counterplans are considered for the degradation reduction. At the moment, users distribution to other forest trails and long-term sabbatical years would be the most effective counterplans to keep from users gravitation on the three forest trails.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.167-172
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• 2011

In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.25-37
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• 2020

In this study, hybridization of graphene oxide and metal was carried out by the functional groups containing oxygen and thermal treatment for reduction in order to enhance the electrical conductivity and magnetic properties of graphene materials. Graphene-metal hybrid materials were synthesized using the oxygen-containing functional groups (-OH, -COOH and so on) on the surface of graphene oxide by replacing them with metal ions via ion exchange method as well as thermal reduction. The metals used in this study were Fe, Ag, Ni, Zn, and Fe/Ag, and it was confirmed that metal particles of uniform size were well dispersed on the graphene surface through SEM, TEM, and EDS. All of the metal particles on the graphene surface had an oxide-crystalline structure. To check the electrical properties, sheet resistance of the rGO-metal hybrid sample was measured on the PET film made by the dip-coating, and the specific resistance was calculated by measuring the thickness of the specimen through SEM. As a result, the specific resistance was in the range of 2.14×10-5 and 3.5×10-3 ohm/cm.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.312-319
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• 2021

Photothermal therapy is a treatment that necrotizes selectively the abnormal cells, in particular cancer cells, which are more vulnerable to heat than normal cells, using the heat generated when irradiating light. In this study, we synthesized a reduced graphene oxide with carboxyl groups (CRGO)-gold nanorod (AuNR) nanocomposite for photothermal treatment. Graphene oxide (GO) was selectively reduced and exfoliated at high temperature to synthesize CRGO, and the length of AuNR was adjusted according to the amount of AgNO₃, to synthesize AuNR with a strong absorption peak at 880 nm, as an ideal photothermal agent. It was determined through FT-IR, thermogravimetric and fluorescence analyses that more carboxyl groups were conjugated with CRGO over RGO. In addition, CRGO exhibited excellent stability in aqueous solutions compared to RGO due to the presence of carboxylic acid. The CRGO-AuNR nanocomposites fabricated by electrostatic interaction have an average size of ~317 nm with a narrow size distribution. It was confirmed that under radiation with a near-infrared 880 nm laser which has an excellent tissue transmittance, the photothermal effect of CRGO-AuNR nanocomposites was greater than that of AuNR due to the synergistic effect of the two photothermal agents, CRGO and AuNR. Furthermore, the results of cancer cell toxicity by photothermal effect revealed that CRGO-AuNR nanocomposites showed superb cytotoxic properties. Therefore, the CRGO-AuNR nanocomposites are expected to be applied to the field of anticancer photothermal therapy based on their stable dispersibility and improved photothermal effect.

• Journal of Life Science
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• v.31 no.5
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• pp.502-510
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• 2021

The objective of this study was to develop a novel ticagrelor-loaded self-nanoemulsifying drug delivery system with an enhanced solubility and dissolution rate. Numerous oils and surfactants were screened, then medium chain triglyceride (MCT) oil and the surfactants polyoxyethylene sorbitan monooleate (Tween 80) and Labrafil M1944CS were selected for the preparation of the ticagrelor-loaded self-nanoemulsifying drug delivery system. A pseudo-ternary phase diagram was constructed to detect the nanoemulsion region. Of the various formulations tested, the liquid SNEDDS, composed of MCT (oil), Tween 80 (surfactant), and Labrafil M1944CS (cosurfactant) at a weight ratio of 20/70/10 produced the smallest emulsion droplet size (around 20.56±0.70 nm). Then, particle size, polydispersity, and zeta potential were measured using drugs containing liquid SNEDDS. The selected ticagrelor-loaded liquid SNEDDS was spray-dried to convert it into a ticagrelor-loaded solid SNEDDS with a suitable inert carrier, such as silicon dioxide, calcium silicate, or magnesium aluminometasilicate. The solid SNEDDS was characterized by scanning electron microscopy, transmission electron microscopy, and in vitro dissolution studies. SEM, PXRD, and DSC results suggested that amorphous ticagrelor was present in the solid SNEDDS. Also, the solid SNEDDS significantly increased the dissolution rate of ticagrelor. In particular, the emulsion particle size and the polydispersity index of the solid SNEDDS using silicon dioxide (SS1) as a carrier was the smallest among the evaluated solid SNEDDS, and the flowability and compressibility result of the SS1 was the most suitable for the manufacturing of solid dosage forms. Therefore, solid SNEDDS using silicon dioxide (SS1) could be a potential nano-sized drug delivery system for the poorly water-soluble drug ticagrelor.

• Journal of Digital Convergence
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• v.19 no.3
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• pp.177-185
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• 2021

This paper aimed to grasp what the percentage in the types of news stories on the online broadcast is, which was conducted by analyzing the news stories of 9 broadcasting websites on the Naver newsstand. For the analysis, a total of 270 days' samples were selected, including 30 days per broadcast on 9 broadcasting websites. For a method of analysis, One-way ANOVA was used to examine the difference among broadcasting websites. The analysis was made centering with priorities given to the type of news stories by the composition of language, the type of genre as a standard of stories, and so on. As a result of analysis, all the programs in the off-line broadcast have been produced and transmitted as a video-typed story, but a half of those in on-line broadcast have been made up of the stories composed of photo and text. The online newspaper has been producing a new type of news' story using video-typed story or computer graphic while the online broadcast has actively been utilizing stories composed of photos and text, which are types of newspaper's stories. From above-mentioned results, it can be understood that the boundary among media is getting more and more indistinct on the environment of online media, showing the phenomenon that the type of broadcast's stories is becoming old-fashioned.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.502-509
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• 2020

The aim of this study was to compare the effects of a horseback riding simulator, McKenzie, and gym ball exercises on the Korean-Oswestry Disability Index (K-ODI) and muscle activation in people suffering from chronic low back pain. The study was conducted on 30 adults with a K-ODI of 5 or more and chronic low back pain. This experiment was conducted from May to June 2020. They were randomly divided into the horse-riding exercise group (HEG), McKenzie exercise group (MEG), and the gym ball exercise group (GEG). Each group performed the relevant exercises for six weeks, three times a week. The low back pain was measured with K-ODI, and muscle activation was measured with surface electromyography (SEMG). A paired t-test was conducted to verify the change before and after the experiment in the groups, and a one-way ANOVA was conducted to verify the difference between the three groups. The results of the study showed significant differences before and after the experiment. K-ODI and muscle activity improved (p>.05), and significant differences were also found between the groups (p<.05). This study concluded that horse riding and McKenzie exercises could be effective methods for the treatment of pain and to stabilize the lumbar region in patients with chronic low back pain.

• Smart Media Journal
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• v.10 no.1
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• pp.88-98
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• 2021

As blockchain technology has emerged as a security issue for IoT, technology which integrates block chain into IoT is being studied. In this paper is a research concerning token-based IoT service access control technology for data sharing, which propose a possessor focused data sharing technic by using the permissioned blockchain. To share IoT health data, a Hyperledger Fabric Network consisting of three organizations was designed to provide a way to share data by applying different access control policies centered on device owners for different services. In the proposed system, the device owner issues access control tokens with different security levels applied to the participants in the organization, and the token issue information is shared through the distributed ledger of the HFN. In IoT, it is possible to lightweight the access control processing of IoT devices by granting tokens to service requesters who request access to data. Furthmore, by sharing token issuance information among network participants using HFN, the integrity of the token is guaranteed and all network participants can trust the token. The device owners can trust that their data is being used within their authorized rights, and control the collection and use of data.