• The Korean Journal of Pain
• /
• 제19권2호
• /
• pp.137-141
• /
• 2006

Background: It has been known that melatonin is involved in the modulation of nociceptive transmission. However, the effect of melatonin administered spinally has not been examined. Therefore, we examined the effect of melatonin on the formalin-induced or thermal-induced nociception at the spinal level. Methods: Intrathecal catheter was inserted into the subarachnoid space of male Sprague-Dawley rats. Pain was assessed by formalin test (induced by injection of $50{\mu}l$ of a 5% formalin solution to the hindpaw) or Hot-Box test (induced by radiant heat application to the hindpaw). The effect of intrathecal melatonin was examined on flinching behavior in the formalin test or withdrawal response in Hot-Box test. Results: Intrathecal melatonin produced a limited, but dose-dependent reduction of the flinching response during phase 1 and 2 in the formalin test. In addition, melatonin delivered at evening also decreased the flinching response in both phases of the formalin test. Melatonin restrictively increased the withdrawal latency in Hot-Box test. Conclusions: These results suggest that melatonin is active against the formalin- and thermal-induced nocicpetion at the spinal level, but the effect is limited.

• Composites Research
• /
• 제25권4호
• /
• pp.117-125
• /
• 2012

필름 삽입 사출 시편의 휨은 비대칭적인 잔류응력 분포에 기인한다. 비대칭적 잔류응력과 온도 분포는 삽입된 필름 표면의 수직방향으로 지연되는 열 전달에 의해 발생한다. 사출 공정조건 최적화를 통해 필름 삽입 사출 시편의 휨을 억제할 수 없었기 때문에, 필름 삽입 사출 시편의 휨을 최소화하기 위해서 유리 섬유가 강화된 복합재료를 기판으로 사용하였다. 유리 단섬유의 분포를 마이크로 CT 장비를 이용하여 평가하였다. 복합재료로 구성된 기판을 이용한 필름 삽입 사출 시편의 배향 텐서와 휨을 계산하기 위해서는 적절한 마이크로 역학, 이방적 열팽창계수 및 닫힌 어림법 모델이 선택되어야만 한다. 여섯 종류의 마이크로 역학모델, 세 종류의 열 팽창 계수 모델 및 다섯 종류의 닫힌 어림법 모델을 고려한 후, Mori-Tanaka 모델, Rosen and Hashin 모델 및 third orthotropic 닫힌 어림법 모델을 선택하였다. 수치적으로 계산된 섬유 배향 텐서와 휨에 관한 결과들은 실험결과와 잘 일치하였고, 유리 섬유의 보강효과가 필름 삽입 사출 복합 재료 시편의 휨에 미치는 영향을 파악하였다.

• 한국자동차공학회논문집
• /
• 제14권2호
• /
• pp.114-120
• /
• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.

• Mass Spectrometry Letters
• /
• 제5권1호
• /
• pp.24-29
• /
• 2014

An advanced and reliable high performance liquid chromatography (HPLC)/ultraviolet detector (UV)/ion-trap time-of-flight (IT-TOF) mass spectrometry was developed for the simultaneous quantification of 19 marker compounds in Bang-poong-tong-sung-san (BPTS), a traditional oriental prescription. Various parameters affecting HPLC separation and IT-TOF detection were investigated, and optimized conditions were identified. The separation was achieved on a Capcell PAK C18 column ($1.5mm{\times}250mm$, $5{\mu}m$ particle size) using a gradient elution of acetonitrile and water containing 0.1% formic acid at a flow rate of 0.1 mL/min. The column temperature was maintained at $40^{\circ}C$ and the injection volume was $2{\mu}L$. IT-TOF system was equipped with an electrospray ion source (ESI) operating in positive or negative ion mode. The optimized electrospray ionization parameters were as follows: ion spray voltage, +4.5 kV (positive ion mode), or -3.5 kV (negative ion mode); drying gas ($N_2$), 1.5 L/min; heat block temperature, $200^{\circ}C$. Automatic $MS^n$ (n = 1~3) analyses were carried out to obtain structural information of analytes. Elemental compositions and their mass errors were calculated based on their accurate masses obtained from a formula predictor software. The marker compounds in BPTS were identified by comparisons between $MS^n$ spectra from standards and those from extracts. Moreover, the libraries of $MS^2$ and $MS^3$ spectra and accurate masses of parent and fragment ions for marker compounds were constructed. The developed method was successfully applied to the BPTS extracts and identified 17 out of 19 marker compounds in the BPTS extracts.

• 한국분무공학회지
• /
• 제25권1호
• /
• pp.21-26
• /
• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• ETRI Journal
• /
• 제31권6호
• /
• pp.660-666
• /
• 2009

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top-gate In-Ga-Zn-oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below $200^{\circ}C$, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as $Si_3N_4$ and $Al_2O_3$, the electrical properties are analyzed. After post-annealing at $200^{\circ}C$ for 1 hour in an $O_2$ ambient, the sub-threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative-bias stress tests on TFTs with a $Si_3N_4$ IDL, the degradation sources are closely related to unstable bond states, such as Si-based broken bonds and hydrogen-based bonds. From constant-current stress tests of $I_d$ = 3 ${\mu}A$, an IGZO-TFT with heat-treated $Si_3N_4$ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge-injection and electron-trapping behavior.

• 한국수소및신에너지학회논문집
• /
• 제21권3호
• /
• pp.227-240
• /
• 2010

Coal gasification is heading for a great future as one of the cleanest energy sources, which can produce not only electricity and heat, but also gaseous and liquid fuels from the synthesis. The work focuses on 300MW shell type one-stage entrained flow coal gasifier which is used in the Integrated coal Gasification Combined Cycle(IGCC) plant as a reactor. As constructing an IGCC plant is considerably complicated and expensive compared with a pulverized-coal power plant, it is important to determine optimum design factors and operating conditions using a computational fluid dynamics (CFD) model. In this study, the results of numerical calculations show that $O_2$/Coal ratio, 0.83, Steam/Coal ratio, 0.05, coal particle diameter, $100{\mu}m$, injection angle, $4^{\circ}$ (clockwise) are the most optimum in this research.

• Journal of Ginseng Research
• /
• 제41권3호
• /
• pp.233-239
• /
• 2017

Background: Nephrotoxicity is the major side effect in cisplatin chemotherapy. Previously, we reported that the ginsenosides Rk3 and Rh4 reduced cisplatin toxicity on porcine renal proximal epithelial tubular cells (LLC-PK1). Here, we aimed to evaluate the protective effect of ginsenosides Rk3 and Rh4 on kidney function and elucidate their antioxidant effect using in vitro and in vivo models of cisplatin-induced acute renal failure. Methods: An enriched mixture of ginsenosides Rk3 and Rh4 (KG-KH; 49.3% and 43.1%, respectively) was purified from sun ginseng (heat processed Panax ginseng). Cytotoxicity was induced by treatment of $20{\mu}M$ cisplatin to LLC-PK1 cells and rat model of acute renal failure was generated by single intraperitoneal injection of 5 mg/kg cisplatin. Protective effects were assessed by determining cell viability, reactive oxygen species generation, blood urea nitrogen, serum creatinine, antioxidant enzyme activity, and histopathological examination. Results: The in vitro assay demonstrated that KG-KH ($50{\mu}g/mL$) significantly increased cell viability (4.6-fold), superoxide dismutase activity (2.8-fold), and glutathione reductase activity (1.5-fold), but reduced reactive oxygen species generation (56%) compared to cisplatin control cells. KG-KH (6 mg/kg, per os) also significantly inhibited renal edema (87% kidney index) and dysfunction (71.4% blood urea nitrogen, 67.4% creatinine) compared to cisplatin control rats. Of note, KG-KH significantly recovered the kidney levels of catalase (1.2-fold) and superoxide dismutase (1.5-fold). Conclusion: Considering the oxidative injury as an early trigger of cisplatin nephrotoxicity, our findings suggest that ginsenosides Rk3 and Rh4 protect the kidney from cisplatin-induced oxidative injury and help to recover renal function by restoring intrinsic antioxidant defenses.

• 한국주조공학회지
• /
• 제27권1호
• /
• pp.31-35
• /
• 2007

본 연구에서는 Mg합금의 반응고성형 공정기술을 개발하기 위하여 여러 가지 전단속도와 냉각속도에 따른 Mg합금의 점도와 딕소트러픽 거동을 분석하였으며, 이를 전산모사연구와 비교 검토하였다. 전산모사연구에서는 미세조직과 공정변수를 고려한 반응고 슬러리의 유변학적 거동을 분석하였다. 반응고 온도영역에서의 Mg합금(AZ91D) 슬러리의 점도는 고상율에 따라 지수함수적으로 증가하였으며, 전단속도가 증가하면 감소하는 경향을 나타났다. Mg합금 슬러리의 유변학적 거동을 정확하게 분석하기 위하여 Carreau 모델을 사용하여 ANYCAST 프로그램에서 고압다이캐스팅용 금형으로의 Mg합금 반응고 슬러리의 충진거동을 모사하였다. 전산모사된 결과는 동일한 조건에서의 실제 실험결과와 잘 일치하였다.

• Nuclear Engineering and Technology
• /
• 제48권2호
• /
• pp.457-469
• /
• 2016

During the late phase of severe accidents of light water reactors, a porous debris bed is expected to develop on the bottom of the flooded reactor cavity after breakup of the melt in water. The geometrical configuration, i.e., internal and external characteristics, of the debris bed is significant for the adequate assessment of the coolability of the relocated corium. The internal structure of a debris bed was investigated experimentally using the DAVINCI (Debris bed research Apparatus for Validation of the bubble-Induced Natural Convection effect Issue) test facility. Particle sedimentation under the influence of a two-phase natural convection flow due to the decay heat in the debris bed was simulated by dropping various sizes of particles into a water vessel with air bubble injection from the bottom. Settled particles were collected and sieved to obtain the particle mass, size distribution in the radial and axial positions, and the bed porosity and permeability. The experimental results showed that the center part of the particle bed tended to have larger particles than the peripheral area. For the axial distribution, the lower layer had a higher fraction of larger particles. As the sedimentation progressed, the size distribution in the upper layers can shift to larger sizes because of the higher vapor generation rate and stronger flow intensity.