• 한국항공우주학회지
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• 제49권9호
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• pp.759-769
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• 2021

발사체 추진 시스템에서 Titanium Hydride Potassium Perchlorate (THPP)는 에너지를 인가받으면 gas를 발생시키는 pyrotechnic initiator로써 혹은 NASA Standard Initiator (NSI)의 supplement charge로써 흔히 사용되는 물질이다. 하지만 금속으로 이루어진 복합 화약이 오랫동안 보관이 되면 노화라는 문제에 직면하게 된다. 본 연구에서는 열분석 및 표면분석을 통하여 다양한 습도환경에서 노화된 THPP에 대하여 열역학적 특성의 변화를 확인하였고, 이를 바탕으로 THPP에 대한 전반적인 노화 메커니즘을 구축해내었다. 우선, THPP가 노화됨에 따라 산화제 표면의 균열빈도가 증가하고 길이가 길어졌는데, 이는 열·수분 노화가 공통적으로 산화제의 분해를 초래함을 보여준다. 이때 열 노화된 경우 Viton의 열화 현상이, 수분 노화된 경우 연료의 산화가 더욱 두드러졌다. 또한 실험을 통해 계산된 반응률에 대한 THPP의 화학반응인자의 경우 습도에 따라 크게 달라졌는데, 이는 수분이 THPP의 연소에 상당한 변화를 미쳐 결국에는 수명의 감소로 이어지게 될 것을 시사한다.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.75-84
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• 2023

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H₂WO₄ was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO₃, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO₃ was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na₂WO₄-WO₃ molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10^-10 cm²·s^-1.

• 대한환경공학회지
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• 제29권7호
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• pp.846-851
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• 2007

본 연구는 PCP를 UV, $UV/H_2O_2$, $Fe^{2+}$, $Fe^{2+}/H_2O_2$, 그리고 $UV/Fe^{2+}/H_2O_2$의 공정을 이용하여 처리할 저 각각 공정의 처리효율을 비교하여 각 반응의 결합에 의한 개선 효과와 분해 기전을 규명한 연구이다. 실험의 결과 UV 반응에 $H_2O_2$의 첨가에 따라 약 13배 정도의 유사 일차 반응 속도의 증가를 보였으며, $Fe^{2+}$ 단독 반응에 비해 180 mM과 16 mM의 $H_2O_2$의 첨가는 각각 4배와 7.25배의 반응 속도 증가를 보였다. 또한 $Fe^{2+}/H_2O_2$의 반응에 비해 UV를 조사한 반응의 경우 약 3.1배의 반응 속도의 개선을 보였다. 이러한 반응속도의 증가는 각 반응에서 생성되는 OH 라디칼의 생성과 밀접한 관계가 있었다. $Fe^{2+}/H_2O_2$ 반응에서 일어나는 슬러지 침전 반응은 UV를 조사함으로서 상당부분 제거가 가능하였다.

• 동의생리병리학회지
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• 제16권4호
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• pp.810-817
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• 2002

This study was carried out to know the effects of sopunghwalhyeoltang-gamibang(hereinafter referred to SPHHT) on the inhibition of arthritis induced by collagen on the mouse. Various experimental were performed in vivo (in DBA/1 J mice which are experimental model of arthritis induced by collagen) to analyse the immunomodulatory effects of SPHHT. The results were obtained as follows: 1. The cytotoxicity against mLFC was not measured in all concentration. 2. The arthritis index, incidence, hind paw edema, delayed-type hypersensitivity reaction, spleen weight were reduced in SPHHT treated group. 3. The expression of CD3 ε +/CD4+, CD3 ε +/CD8+ and CD19+ in peripheral blood mononuclear were reduced in SPHHT treated group. 4. The production of pro-inflammatory cytokines such as IL-6 and TNF-α were significantly reduced in SPHHT treated group. 5. The formation of new bones and synivium were stimulated in SPHHT treated group. Comparison of the results for this study showed that Sopung-hwalhyeoltang-gamibang had immunomodulatory effects. So we expect that Sopunghwalhyeoltang-gamibang should be used as a effective drugs for not only rheumatoid arthritis but also another auto-immune disease. Therefore we have to survey continuously in looking for the effective substance and mechanism in the future.

• Journal of Ginseng Research
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• 제45권1호
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• pp.75-85
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• 2021

Background: Invasive infections due to foodborne pathogens, including Salmonella enterica serovar Typhimurium, are prevalent and life-threatening. This study aimed to evaluate the effects of ginsenoside Rg3 (Rg3) on the adhesion, invasion, and intracellular survival of S. Typhimurium. Methods: The impacts of Rg3 on bacterial growth and host cell viability were determined using the time kill and the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assays, respectively. Gentamicin assay and confocal microscopic examination were undertaken to determine the effects of Rg3 on the adhesive and invasive abilities of S. Typhimurium to Caco-2 and RAW 264.7 cells. Quantitative reverse transcription polymerase chain reaction was performed to assess the expression of genes correlated with the adhesion, invasion, and virulence of S. Typhimurium. Results: Subinhibitory concentrations of Rg3 significantly reduced (p < 0.05) the adhesion, invasion, and intracellular survival of S. Typhimurium. Rg3 considerably reduced (p < 0.05) the bacterial motility as well as the release of nitrite from infected macrophages in a concentration-dependent manner. The expression of genes related to the adhesion, invasion, quorum sensing, and virulence of S. Typhimurium including cheY, hilA, OmpD, PrgK, rsgE, SdiA, and SipB was significantly reduced after Rg3 treatment. Besides, the compound downregulated rac-1 and Cdc-42 that are essential for actin remodeling and membrane ruffling, thereby facilitating Salmonella entry into host cells. This report is the first to describe the effects of Rg3 on "trigger" entry mechanism and intracellular survival S. Typhimurium. Conclusion: Rg3 could be considered as a supplement agent to prevent S. Typhimurium infection.

• 한방비만학회지
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• 제22권1호
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• pp.38-46
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• 2022

Objectives: Juknyeok (JN) is natural liquor extracted from bamboo stems (Phyllostachys bambusoides) and has been used as a traditional Korean medicine for improving vascular function, blood glucose, and treating stroke. Until now, the JN's lipid-lowering effect and underlying mechanism in adipocytes are poorly understood. The aim of this study was to scrutinize the effect of a standardized commercial JN on lipid accumulation during the differentiation of 3T3-L1 preadipocytes. Methods: Lipid and triglyceride (TG) accumulation in differentiating 3T3-L1 preadipocytes were measured by Oil Red O staining and AdipoRed assay, respectively. Cell count analysis was used to ascertain 3T3-L1 cytotoxicity. Immunoblotting and Reverse transcription polymerase chain reaction analysis were used to assess protein and messenger RNA (mRNA) expression levels in 3T3-L1 cells, respectively. Results: Treatment with JN at 25 𝜇l/ml after pH calibration with 6.35 significantly reduced lipid and TG accumulation in differentiating 3T3-L1 preadipocytes without significant cytotoxicity. On mechanistic levels, JN markedly suppressed protein expression levels of CCAAT/enhancer-binding protein (C/EBP)-𝛽 and fatty acid synthase (FAS) during the differentiation of 3T3-L1 preadipocytes. However, JN did not affect the protein expression levels of C/EBP-𝛼, peroxisome proliferator-activated receptor-𝛽/𝛾, and phosphorylation levels of signal transducer and activator of transcription-3/5 in differentiating 3T3-L1 preadipocytes. JN also reduced leptin mRNA expression levels in differentiating 3T3-L1 preadipocytes. Conclusions: JN at 25 𝜇l/ml lowers lipid accumulation and TG content in differentiating 3T3-L1 cells, mediated through the reduced expression levels of C/EBP-𝛽 and FAS.

• Journal of Acupuncture Research
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• 제22권3호
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• pp.23-35
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• 2005

본 연구에서는 전침자극이 면역계의 THl/TH2 분화평형에 미치는 영향과 opioid system 과의 관계를 알아보고자 DNP-KLH의 자극을 통해 IgE 매개 알러지 반응모델을 구축하고 족삼리(足三里).에 전침자극을 가한 후 TH1/TH2 분화평형 및 opioid receptor antagonist인 naloxone에 의 한 반전여부를 확인하기 위해 total IgE, antigen-specific IgE, IFN-${\gamma}$ 및 IL-4 mRNA 발현량을 측정하여 다음과 같은 결과를 얻었다. 1. 전침자극은 DNP-KLH로 인해 과도하게 생산 된 혈청 total IgE 및 antigen-specific IgE를 감소시킴으로서 알러지 반응에 대한 유의한 억제능을 발휘하였으며, naloxone 투여로 전침 의 효과가 상쇠된 것으로 미루어 opioid system이 전침에 의한 항알러지 효과에 중요한 역할을 하는 것으로 추정된다. 2. 또한 전침자극은 DNP-KLH로 인한 TH2 cytokine의 편향상태에 대하여 TH1/TH2 평형조절능을 가진다는 것을 확인하였으며, naloxone으로 반전되지 않는 것으로 미루어 전침이 미치는 보조 T cell 분화에 대한 효과 는 opioid system에 의존하지 않는 것으로 추정된다.

• 한국재료학회지
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• 제14권8호
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• pp.595-599
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• 2004

We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.363-364
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• 2002

Although the factors that cause the failure of orthopedic implants were not clearly determined, it was reported that the shapes of wear debris affect the tribological behavior of artificial implant. Many researches were conducted to examine the wear mechanism by debris but the role of debris shape in inflammatory reaction remains unclear. To observe the debris shape by addition of reinforcement, carbon nanotubes ( CNTs ) were added to ultra high molecular weight polyethylene ( UHMWPE ) to investigate the reinforcement effect of CNTs. CNTs which have a diameter of about 10-50 nm, while their length is about 3-5 nm were produced by the catalytic decomposition of the acetylene gas using a tube furnace. Plate on disc type wear test were performed to evaluate the tribological performance of UHMWPE composites reinforced with CNTs in lubricating condition ( bovine serum ). The wear losses of CNT added UHMWPE in bovine serum were significantly reduced. Worn surface and wear debris of UHMWPE with CNTs and without CNTs were compared to investigate the reinforcement effect of CNT on tribological behavior.

• 한국재료학회지
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• 제24권11호
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• pp.578-584
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• 2014

To synthesize Sn nanoparticles (NPs) less than 30 nm in diameter, a modified polyol process was conducted at room temperature using a reducing agent, and the effects of different pH values of the initial solutions on the morphology and size of the synthesized Sn NPs were analyzed. tin(II) 2-ethylhexanoate, diethylene glycol, sodium borohydride, polyvinyl pyrrolidone (PVP), and sodium hydroxide were used as a precursor, reaction medium, reducing agent, capping agent, and pH adjusting agent, respectively. It was found by transmission electron microscopy that the morphology of the synthesized Sn NPs varied according to the pH of the initial solution. Moreover, while the size decreased to 11.32 nm with an increase up to 11.66 of the pH value, the size increased rapidly to 39.25 nm with an increase to 12.69. The pH increase up to 11.66 dominantly promoted generation of electrons and increased the amount of initial nucleation in the solution, finally inducing the reduced-size of the Sn particles. However, the additional increase of pH dominantly induced a decrease of PVP by neutralization, which resulted in acceleration of the agglomeration by collisions between particles.