• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.147-151
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• 2016

Graphene has a monolayer crystal structure formed with C-atoms and has been used as a base layer of HETs (hot electron transistors). Graphene HETs have exhibited the operation at THz frequencies and higher current on/off ratio than that of Graphene FETs. In this article, we report on the preliminary results of current characteristics from the HETs which are fabricated utilizing highly doped Si collector, graphene base, and 5 nm thin $Al_2O_3$ tunnel layers between the base and Ti emitter. We have observed E-B forward currents are inherited to tunneling through $Al_2O_3$ layers, but have not noticed the Schottky barrier blocking effect on B-C forward current at the base/collector interface. At the common-emitter configuration, under a constant $V_{BE}$ between 0~1.2V, $I_C$ has increased linearly with $V_{CE}$ for $V_{CE}$ < $V_{BE}$ indicating the saturation region. As the $V_{CE}$ increases further, a plateau of $I_C$ vs. $V_{CE}$ has appeared slightly at $V_{CE}{\simeq}V_{BE}$, denoting forward-active region. With further increase of $V_{CE}$, $I_C$ has kept increasing probably due to tunneling through thin Schottky barrier between B/C. Thus the current on/off ration has exhibited to be 50. To improve hot electron effects, we propose the usage of low doped Si substrate, insertion of barrier layer between B/C, or substrates with low electron affinity.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.847-854
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• 1994

An amorphous single phase and coexistent amorphous and hcp-Mg phases in Mg-Zn-Ce system were found to form in the composition ranges of 20 to 40% Zn, 0 to 10% Ce and 5 to 20% Zn, 0 to 5% Ce, respectively. A $Mg_{85}Zn_{12}Ce_{3}$ amorphous alloy containing nanoscale hcp-Mg particles was found to form either by melt spinning or by heat treatment of melt -spun ribbon. The particle size of the hcp-Mg phase can be controlled in the range of 4 to 20 nm. The mixed phase alloy prepared thus has a good bending ductility and exhibits high ultimate tensile strength($\sigma_{B}$) ranging from 670 to 930 MPa and fracture elongation($\varepsilon_{f}$) of 5.2 to 2.0%. The highest specific strength($\sigma_{B}$/density =$\sigma_{s}$)$3.6 \times 10^5N \cdot m/kg$. It should be noted that the highest values of flB, US and ？1 are considerably higher than those (690MPa,$2.5 \times 10^5N \cdot m/kg$and 2.5%) for amorphous Mg-Zn-Ce alloys. The increase of the mechanical strengths by the formation of the mixed phase structure is presumably due to a dispersion hardening of the hcp supersaturated solution which has the hardness higher than that of the amorphous phase with the same composition.

• The Journal of Korean Medicine
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• v.26 no.3 s.63
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• pp.215-227
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• 2005

Objectives : This study was carried out to investigate the effects of Pyungjintang on indomethacin-induced gastric mucosal lesions of mire. Methods : Experimental mice were classified into not-treated group (NOR group), gastro-inflammation elicitated group (CON group), misoprostol-administered group after gastro-inflammation elicitation (MA group), and Pyungjintang-administered group after gastro-inflammation elicitation (PA group). This study examined the morphological change, distribution of mast cells, mucus surface cells, neutral mucus secreting cells, acid mucus secreting cells, PNA reaction, angiogenesis (MIP-2), COX-1, Hsp70, NF-kB p50, COX-2IL-12B, ICAM-1, BrdU and apoptotic cells of gastric mucosa. Results : 1. The scars of diapedesis, dilatation of right gastric artery and the hemorrhagic erosions of gastric mucosa were reduced in the MA and PA groups. 2. Gastric perforation was observed in the gastro-inflammation elicitated group, but not in the MA and PA groups. 3. The COX-1 positive cellsl, cell proliferation of gastric mucosa, neutral mucus secreting ce31s, acid mucus secreting cells and PNA positive reaction of surface mucus cells were increased in the MA and PA groups. 4. The distribution of apoptotic cells, mast cells, MIP-2, Hsp70, NF-kB p50, COX-2, IL-l2B and ICAM-1 were decreased in the MA and PA groups. Conclusions : Pyungjintang had excellent effects on indomethacin-induced gastric mucosal lesions in mice.

• The Journal of Pediatrics of Korean Medicine
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• v.19 no.2
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• pp.13-30
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• 2005

Objective: Danguieumja-gagambang (DGEJGB), a traditional Korean prescription, has been used as therapeutics for allergic diseases such as atopic dermatitis (AD). In this study, we compared with regulatory Effect of Atopic Allergic Reaction by Prescriptions A and by Prescriptions B. Methods : To evaluate and compare the atopic allergic effectiveness of two prescription (A, B) of DGEJGB, the author investigated a possible effect of DGEJGB on mast cell-mediated allergic reaction, cytokine secretion and mRNA expression in vivo and in vitro. Results : Mast cells are a potent source of mediators that regulate the inflammatory response in allergic reaction. In mice orally administered A, B of DGEJGB ( 0.1, 0.1 and 1.0 g/kg) for 1 h, compound 48/80-induced ear swelling was significantly reduced. Significant reduced levels (P < 0.05). of tumor necrosis factor $(TNF)-{\alpha}$ was observed in the human mast cell line (HMC-1) with DGEJGB (A). IL-6 and IL-8 secretion were significantly inhibited by DGEJGB (A, B). In addition, $TNF-{\alpha}$ and IL-8 mRNA expression were reduced by DGEJGB (A) at the dose of 0.01 mg/ml without cell toxicity. Conclusions : These results suggest that DGEJGB (A) contributes to the treatment of atopic allergic reactions rather than DGEJGB (B), and that its action may be due to inhibition of cytokine secretion and mRNA expression HMC-1.

• Journal of the Korean Society of Food Culture
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• v.37 no.6
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• pp.547-554
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• 2022

This study aimed to investigate the physicochemical characteristics and antioxidant activity of cereal bars containing various concentrations (0, 10, 20, or 30%) of apple pomace (AP). Highest vitamin B₁ and C contents were observed in 30% AP-containing bars, but vitamin B₂ and B₃ contents were highest in the control (0.347 and 3.566 mg/100 g, respectively). Cutting strength decreased significantly in an AP concentration-dependent manner. Total polyphenol and flavonoid contents in 10% AP bars were 2.949±0.157 mg of GAE/g and 1.001±0.009 mg of CE/g, respectively. Antioxidant activities were assessed by measuring free radical scavenging activities, and 10% AP bars had the highest activities, as determined by ABTS (2,2'azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (α-α-diphenyl-β-picrylhydrazyl) assays (0.412±0.008 and 0.492±0.021 mg GAE/g, respectively). These results suggested that apple pomace should be regarded a potential nutritional and antioxidant source.

• The Journal of Korean Medicine
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• v.40 no.4
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• pp.72-83
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• 2019

In this study, we investigated the antioxidant and anti-inflammatory effect of the Paulownia tomentosa extracts (PTE). The total polyphenol and flavonoid contents of PTE were 148.98±1.84 mg GAE/g extract, and 115.33±4.16 mg CE/g extract, respectively. The PTE showed that strong antioxidant activity via -diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ABTS radical scavenging activity and FRAP assay. The anti-inflammatory activity was evaluated on lipopolysaccharide (LPS)-stimulated RAW264.7 cells. PTE remarkably reduced protein expression of inducible nitric oxide (iNOS), resulting in inhibition of production of nitric oxide (NO). Additionally, pre-treatment of PTE significantly suppressed the production of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Moreover, PTE significantly attenuated LPS-induced IkappaB (IκB) degradation and suppressed nuclear factor kappa B (NF-κB) nuclear translocation in macrophages. The PTE showed high antioxidant and anti-inflammatory activity. These data suggest that PTE has pharmacological activity and may be useful for the development of anti-inflammatory agents.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.3
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• pp.287-297
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• 2019

This study was carried out to evaluate the antioxidant, anti-inflammation, and whitening effect of Hordeum vulgare L. extracts and their fractions. Total polyphenol and flavonoid contents in fractions were varied from 13.58 to 40.06 mg GAE/g and 7.67 ~ 13.67 mg CE/g, respectively. Among the three fractions(chloroform, hexane, and water), $400{\mu}g/mL$ of the chroloform fraction showed similar antioxidant activity to ascorbic acid ($30{\mu}M$) against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The chloroform and hexane fractions inhibited the NO production of RAW 264.7 cells similar to quercetin ($15{\mu}M$) and the chloroform fraction of $100{\mu}g/mL$ significantly reduced IL-6, iNOS and COX2 gene expression. Additionally, the chloroform fraction inhibited ${\beta}$-hexosaminidase degranulation, IL-4, and IL-13 gene expression in RBL-2H3 cells. All of the fractions inhibited tyrosinase activity in a concentration-dependent manner, and the hexane fraction at $50{\mu}g/mL$ and the chloroform fraction at $100{\mu}g/mL$ significantly inhibited melanin production of B16F10 cells. These results indicated that H. vulgare L. can be used as an effective cosmetic ingredient having anti-inflammation and whitening activity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.844-851
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• 2009

Handover is needed in multi-hop relay systems to support mobility. The main purpose of handover is to provide the continuous connection when a MS migrates from the air-interface of one BS to another air-interface provided by another BS. Especially the handover between different systems is essential to next generation network. Vertical Handover technology in Mobile WiMAX MMR system is very useful for operators to introduce to Mobile WiMAX system in an overlaid cell environment. This technology will be applied to technology which hands MRS(Mobile Relay Station) over to different systems for system performance enhancement in Ubiquitous environment overlaid between Micro ce11(Frequency 1,FA1) and Macro cell(Frequency 2,FA2). In this paper, FA1 and FA2 are used in order to perform Vertical Handover of MRS(Mobile Relay Station) according to suggested conditions. interferences from neighboring BS or other sectors of 6 macro cells surrounding center Macro cell are analyzed and throughputs are measured according to suggested conditions.

• Journal of Chest Surgery
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• v.3 no.2
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• pp.73-90
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• 1970

Clinical perfusion data on 16 cases of cardiopulmonary bypass using Sigmamotor pump and RyggKyvsgaard Oxygenator which performed at Seoul National University Hospital during the period of Aug. 1968 to Aug. 1970 was analized. AIl cases were hemodiluted and the perfusion was carried out under the normothermic condition. The age of the patients ranged between 6 and 43 years. The b:dy weight varied between 18.3 and 54.0 kg and the body surface area between 0.78 and 1. 59$M^2$. The priming solution was consiste:I with fresh ACD blood. Hartmann solution and Mannitol. The average amount of priming was approximately 2242 ml. The average hemodilution rate was 17%. The flow rate ranged from 1.7L to 3.5L/Min/$M^2$ and averaged 2.4L/Min/$M^2$ or 78mI/Min/kg. The duration of perfusion varied from 22 to 110 min with average of 56.9 minutes. Some hemodynamic responses were observed. The arterial pressure dropped immediately after the initiation of partial perfusion and was more marked after the total perfusion foIlowed by gradual increase to the safety level. The central venous pressure reflected the reduced blood volume especially in the cases of prolonged perfusion which lasted over 60 min. In most of the cases, red blood cell count decreased and white blood ceIl count increased after the perfusion. Hemoglobin level was decreased, averaging of 12.5mg%, Hct 3.3% and platelets count of 18% postoperatively. Plasma hemoglobin increased mildly, from pre-perfusion average value of 4. 06mg% to postperfusion value of 22.5mg%. Serum potassium was 4.4mEq/L pre-operatively and was decreased to 3.7mEq/L postoperatively. Five cases showed definite hypopotassemia immediately after the operation. Sodium and chloride decreased mildly. These electrolyte changes are thought to be related with hemodilution. diuretics and reduced blood volume during and after the perfusion. Arterial blood pH value revealed minimal to moderate elevation from preperfusion average value of 7.376 to 7.461 during perfusion and then 7.365 after perfusion. The pC02 and hicarbonate showed minimal to moderately lowered values. The total CO2 was decreased. Buffer base decreased during perfusion (Av. 42.6mEq/L) and further decreased after the perfusion (Av. 40.8mEq/L). These arterial blood acid base changes suggested that the metabolic acidosis was accompanied by respiratory alkalosis during and immediately after the perfusion. Authors belived that the acidosis could more effectively be corrected with the more additional dose of bicarbonate than we used by this study. The chest tune drainage during the first 24 hours following operation was 1158 ml in average. One case (Case No. 15) showd definite bleeding tendency and it was believed that the cause might be due to the defect of heparin and protamine titration. The average urinary out put during 24 hours post-perfusion was 1291ml. One case (Case No. ]) showed definite post perfusion oliguria. As conclusion hemodilution using fresh ACD blood. Hartmann and Mannitol solution added with Bivon and high flow rate unler normothermia. was thought to amelioratc the severity of mctabolic acidosis during and after perfusion with relatively satisfactory effect on the diuresis and bleeding tendency.