• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.810-815
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• 2004

In this paper, we propose new parallel mechanism of a 3 dimensional biped robot whose each leg is composed of two 3-dof parallel platforms linked serially. This proposed parallel mechanism is able to move freely in the man-made environment and is applied to various fields, such as medical, welfare, and so on. And a total weight of each leg is expected to be lighter than serial linked leg. One side leg consists of a 3-dof orientation platform and 3-dof asymmetric parallel platform. The former consists of three active linear actuators and seven passive joints, and the latter of two active linear actuators, one active rotational actuator and eight passive joints. Thus, there are two kinds of parallel platforms each chain's elements and active joint's positions are different for the biped robot to move freely like a serial link without the kinematics constraints. The effectiveness and the performance of the proposed parallel mechanism and locomotion trajectory are shown in computer simulations with a 12-DOF parallel biped robot.

• 대한전자공학회논문지SD
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• 제41권8호
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• pp.9-16
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• 2004

여러 개의 IP 코아로 구성된 SoC(System-on-a-Chip)를 위해, 테스트 래퍼와 스캔 체인의 다양한 연결구성이 가능한 테스트 기술이 제안되고 있다. 본 논문에서는, 테스트 래퍼와 스캔 체인을 효과적으로 재구성하며 테스트 할 수 있는 새로운 SoC 테스트 접근 기법을 소개한다. IEEE 1149.1 및 P1500 기반의 테스트 래퍼를 위해 테스트 래퍼 제어기인 WCLM(Wrapped Core Linking Module)과, WCLM과 맞물려 코아 내부의 스캔 체인에 효과적으로 접근 가능한 TAM(Test Access Mechnism) 구조를 제안한다.

• 한국정보통신학회논문지
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• 제8권2호
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• pp.289-294
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• 2004

IPv4가 가지고 있는 문제점의 해결방안으로 차세대 인터넷 프로토콜인 IPv6가 표준화되었지만, 현실적으로 일시에 IPv6로 변환되는 것은 불가능하다. IPv4와 자연스럽게 호환되면서 점진적으로 IPv6망으로 변환될 수 있는 전이 메커니즘이 매우 중요하게 인식되고 있다. 현재 다양한 전이 메커니즘들이 개발되어진 상태이지만, 아직까지 IPv6망이 확산되지 못하고 있다. 이유는 주로 기술적인 측면에서만 연구가 되어왔고, 실제로 현재의 시스템 환경에 맞는 연구는 거의 되지 않았기 때문이다. 따라서, 본 논문에서는 이미 제안된 전이 메커니즘에 대하여 실험을 통하여 그 성능을 분석하고, 이를 통하여 현재 환경에 적용가능한 적절한 방법을 찾고자 한다.

• 생약학회지
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• 제50권1호
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• pp.18-24
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• 2019

Andrographolide, the main compound of Andrographis paniculata (A. paniculata), shows various biological properties including anti-viral, anti-inflammatory, anti-diabetic, and hepatoprotective effects. Our previous study has shown that A. paniculata extract exerts antiaging effects by activation of stemness in epidermal stem cells (EpSCs). In this study, we investigated the effect of andrographolide as a main compound of A. paniculata on EpSCs and its mechnism of action using several in vitro assays. Andrographolide increased the proliferation of EpSCs and induced cell cycle progression. Additionally, andrographolide increased VEGF production and the expression of stem cell markers integrin ${\beta}1$ and p63. Furthermore, phosphorylation levels of extracellular signal-regulated kinase 1/2 (ERK1/2), S6 ribosomal protein (S6RP) and Akt were increased by andrographolide. Taken together, these results indicate that andrographolide-induced proliferation of EpSCs is mediated by the ERK1/2, Akt-dependent pathway with increased production of VEGF and upregulated stemness through integrin ${\beta}1$ and p63.

• International Journal of Oral Biology
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• 제33권1호
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• pp.13-23
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• 2008

Taste is a critically important sense for the survival of an organism. However, structure and distribution of taste receptors were only recently investigated. Although expression of the ion channels responsible for the sense of salty taste and acidity was observed in the non-taste cells, receptors for sweet and bitter taste were only identified in taste cells. Salivary glands are involved in the sensing of taste and plays important roles in the transduction of taste. The purpose of this study is to examine whether taste receptors are present in the salivary glands and to provide clues for the investigation of the taste-salivary glands interaction. Using microarray and RT-PCR analyses, the presence of taste receptor mRNAs in the rat von Ebner gland and submandibular gland was confirmed. Type I taste receptors were preferentially expressed in von Ebner gland, whereas type II taste receptors were expressed in both von Ebner gland and submandibular gland. The tastespecific signal tranducing proteins, $G_{\alpha}gustducin$ and phospholipase C ${\beta}2$, were also detected in both salivary glands by immunohistochemistry. Finally, the activation of the calcium signal in response to bitter taste in the acinar cells was also observed. Taken together, these results suggest that taste receptors are present in the von Ebner gland and submandibular gland and that type II taste receptors are functionally active in both salivary glands.

• 대한기계학회논문집
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• 제19권4호
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• pp.968-980
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• 1995

Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites are fabricated by the direct squeeze infiltration method. From the microstructure of Al/Al$_{2}$O$_{3}$/C composites, uniform distribution of reinforcements and good bondings are found. Optimum processing conditions for preforms and squeeze castings are suggested. Mechanical properties, such as elastic modulus, elongation, 0.2% offset yield strength and ultimate tensile strength are obtained. Through the abrasive were test and wear surface analsis, wear behavior and its mechanism of AC2B aluminum and Al/Al$_{2}$O$_{3}$/C composites can be characterized under various sliding speed conditions. Tensile strenght elongation of Al/Al$_{2}$O$_{3}$/C composites are decreased with increasing the addition of carbon fiber. On the contrary, elastic modulus of Al/Al$_{2}$O$_{3}$/C composites is slightly improved compared with that of the unreinforced matrix alloy. The addition of carbon fiber to al/al$_{2}$O$_{3}$/C composites gives rise to improvement of the wear resistance. Specially, carbon chopped fibers play an important role in interfering sticking between the counter material and metal matirix composites. Al/Al$_{2}$O$_{3}$/C composites are suitable to high speed due to solid lubication of carbon. And wear model of Al/Al$_{2}$O$_{3}$/C composites is suggested by the examination of worn surfaces.

• 한국제4기학회지
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• 제18권2호통권23호
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• pp.23-31
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• 2004

Temperature variations, and carbon dioxide and methane concentrations are summarized during the past 400,000 years. Atmospheric temperature varied approximately within $10^{\circ}C$ during the past 400,000 years. Most of the time during the past 400,000 years, temperature was lower than today except 410000, 320000, 250000, and 125000 years ago. Temperature was slightly higher or at least similar to today during the time period of 410000. 320000, 250000, and 125000 years ago. The carbon dioxide concentration varied between 180 and 300 ppm, and the methane concentration varied between 40 and 700ppb. The present atmospheric concentration of carbon dioxide is 375 ppm and methane is 1750 ppb. Temperature was 5-$7^{\circ}C$ lower than today during the Last Glacial Maximum(18,000 years ago) and the Younger Dryas(10,000 years ago). Temprature was varied within $1^{\circ}C$ during the past 10,000 years. Especially Middle Holocene Climatic Optimum(6,000 years ago), Medieval Warm Period (500-1,000 years ago), and Little Ice Age(100-500 year ago) were global climatic events. In general, mechanism for the Middle Holocene Climatic Optimum, Medical Warm Period, and Little Ice Age can be explained by the solar insulation, however their exact mechnism is not well known. Carbon dioxide concentration during the past 400,000 years never reached the current value of 375 ppm. Furthermore, the current methane concentration never reached during the past 20Ma. However, current temperature value has happened several times during the past 400,000 years. The implication of this is unsolved question so far. This should be challenged in the near future.

• 한국진공학회지
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• 제6권4호
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• pp.343-347
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• 1997

전기적 고립(isolation) 효과를 알아보기 위해 $P^+$-InGaAs층에 oxygen을 이온 주입하 여 annealing 온도에 따른 compensation mechnism을 조사하였다. $500^{\circ}C$이하에서는 전도도 가 손상에 관련된 트랩들에 의해 지배되며 500~$600^{\circ}C$영역에서는 oxygen의 활성화로 acceptor를 compensate시키는 화학적 효과를 나타냈으며 특히 $600^{\circ}C$에서 type conversion(p $\longrightarrow$n-type)이 일어났다. 이는 annealing온도가 증가함에 따라 oxygen의 화학적 작용에 의해 생성된 donor로 작용하는 결함들의 증가에 기인하며, 이때 면 저항의 활성화 에너지는 24.2meV로 shallow donor로 작용하는 In interstitial과 같은 native defect들이 형성되기 때 문이라 생각된다. Type conversion이 일어난 $600^{\circ}C$ 이상의 영역에서는 이온 주입에 의해 형 성된 interstitial Be의 재활성화로 인해 n형 전도도가 감소하는 경향을 보였다.

• 대한구순구개열학회지
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• 제5권2호
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• pp.95-108
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• 2002

언어 발달의 조기 단계를 이해하기 위한 일환으로 crying은 언어전 발달의 기초 단계로서 여러 학문적 분야에서 많은 연구가 있어왔다. 그러나 구순구개열(CLP))환아의 경우는cry-producing/control mechnism에 variation이 많은 이유로 이 분야의 연구는 거의 없는 실정이다. 이에 본 연구에서는 다음과 같은 의문점을 가지고 CLP환아의 cry feature에 대한분석을 하였다. 첫째, 정상아와 CLP환아의 cry에 전형적인 차이가 있는가? 둘째, CLP환아의 술전, 술후 cry feature에 변화가 있는가? 셋째, cry분석이 CLP환아의 이후 speech disorder에 대한 언어전 평가로서의 가치가 있는가? 넷째, 특정 parameter가 언어전 평가에 적절한 도구로 작용할 수 있는가? 생후 15개월 이내의 CLP 환아 3명과 유사한 나이대의 정상아 8명의 cry에 대한 공기역학 및 음향음성학적 분석을 통해 CLP 환아와 정상아, CLP환아의 술전, 술후 cry특성을 비교 분석하였다. 결과는 다음과 같다. 1 공기역학적 분석 1) airflow는 CLP 환아의 경우 정상아보다 약간 높았고 술 후 약간 증가하였다. 2)폐활량을 나타내는volume에서는 정상아보다 술전 CLP환자의 경우 보상적으로 더 큰 수치를 보였고 술후 약간 증가하였다. 3)강도를 나타내는 parameter(SPL)에서는 정상아 보다 술전 CLP환자의 계측치가 약간 작았으나 술 후 증가하는 양상을 보였다. 2. 음향음성학적 분석 1)기저 주파수 분석시 정상아에 비해 술 전 CLP환자의 경우 계측치가 약간 낮았으나 술 후 증가하여 정상군의 계측치에 근접하였다. 2)강도를 나타내는energy 측정시 정상아에 비해 술 전 CLP계측치가 보상성으로 약간 큰수치를 나타내었고 술 후 약간 더 증가하였다. 3) Shimmer에서는CUI환자의 술후계측치가술전에 비해 현저히 감소하여 정상군의 수치에 근접하였다.

• 한국환경보건학회지
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• 제20권1호
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• pp.83-95
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• 1994

This study was performed to investigate the preventive effect of KDD against lead toxicity. KDD of 133, 266, 532 and 1,064 mg/kg were administered twice to the rats of Sprague-Dawley strain and then 300 mg/kg lead acetate was given to times, respectively. 1. The $\delta$-ALAD concentration in the urine showed 10.6 ~16.4 mg/kg in the control group indicated statistical significance for the experimental group II, III, IV, V (p<0.05). Also, the Coproporphyrin concentration had 0.119 ~ 0.226 $\mu$g/ml in the control group indicated statiscial significance for the experimental group V of 10 weeks (p<0.05). 2. The $\delta$-ALAD concentration in the blood showed 13.28 ~ 16.08 ALAD unit in the control group indicated statistical significance for the experimental group I (Pb 300 mg/kg) of 6 and 8 weeks, for the experimental group III, IV of 8 and 10 weeks, and for the experimental group V of 4 weeks (p<0.05). The $\delta$-ALAD concentration of experimental group I (Pb 300 mg/kg) group was inclined to decrease during the experiment period. The $\delta$-ALAD concentration of experimental group I (Pb 300 mg/kg) showed statistical significance for the experimental group II, III, IV, V of 6, 8 and 10 weeks. But, there was no statistical significance in the concentration change of hemoglobin, RBC, WBC, hematocrit, Ca, protein among the experimental groups. In conclusion, this study revealed the preventive effect of KDD against lead toxicity and its mechnism inferred to facilitate lead excretion in urinary following hinderance of lead absorption in the gastric-intestine and organs.