• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.743-749
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• 2015

In this paper, we describe the dynamic tumble-stability analysis of a seabed-walking robot named Crabster (CR200) in forward-incident currents. CR200 is designed to be operated in tidal-current conditions, and its body shape is also designed to minimize hydrodynamic resistances considering hydrodynamics. To analyze its tumble stability, we adopt the dynamic stability margin of a ground-legged robot and modify the definition of the margin to consider tidal-current effects. To analyze its dynamic tumble stability, we use the estimated hydrodynamic forces that act on the robot in various tidal-current conditions, and analyze the dynamic tumble-stability margin of the robot using the estimated results obtained for the various tidal-current conditions. From the analyses, we confirm the improved tumble stability of the robot according to the movement of the tumble axis caused by the supporting points of the legs.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.2
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• pp.170-176
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• 2018

This study examined the antioxidative effects of Cornis fructus (CF) extract on cultured C6 glioma cells. For this purpose, cytotoxicity analysis of chromium trioxide ($CrO_3$) was performed and the protective effects of the CF extract on $CrO_3$-induced cytotoxicity was examined after the C6 glioma cells were cultured for 48 hours. The antioxidative effects, such as electron donating activity (EDA) and lactate dehydrogenase (LDH) activity were also analyzed. In this study, $CrO_3$ decreased the cell viability in a dose dependent manner. The $XTT_{50}$ value was determined to be $33{\mu}M$ after the cells were treated for 48 hours at a concentrations of $20{\sim}40{\mu}M$ $CrO_3$. The catalase (CAT) antioxidant increased significantly the cell viability that had been decreased by $CrO_3$-induced cytotoxicity. Regarding the protective effect of the CF extract, the cell viability of the CF extract was increased significantly compared to that of $CrO_3$ only. In addition, the CF extract showed antioxidative effects, such as EDA and an inhibitory effect on the LDH activity. These findings suggest that the cytotoxicity of $CrO_3$ is correlated with oxidative stress, and the CF extract effectively prevented $CrO_3$-induced cytotoxicity through the antioxidative effects. In conclusion, natural products, such as the CF extract may be a useful therapeutic agent for the prevention or treatment of toxicity induced by heavy metals via oxidative stress.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.709-716
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• 2016

Recently, the operating conditions of the various mechanical structures have become more severe and the running time has become longer as the development of plant equipment increases with the introduction of high technology. Thus, the reliability of the system and its accessories is becoming a problem. Normally, synthetic natural gas (SNG) plants use 1.25Cr-0.5Mo or 2.25Cr-1Mo heat resistant steel according to the operating conditions. In this study, a lab-scale reactor was set up using 1.25Cr-0.5Mo steel, in order to carry out corrosion tests for producing synthetic natural gas. The corrosive characteristics were investigated under 1st-methanator operating conditions and fundamental data about the durability and reliability were obtained by using the experimental test. The analysis of results obtained on the durability of the reactor under emission and injection compositions showed that the hydrogen embrittlement caused by hydrogen and the oxidation corrosion caused by H2O had the most effect on the durability of 1.25Cr-0.5Mo steel in the SNG reactor. However, the hydrogen embrittlement and oxidation corrosion occurred simultaneously under emission conditions, so that the corrosion of the material increased suddenly after a long operating time. Besides, the corrosion of the 1.25Cr-0.5Mo steel under the injection composition was faster than that under the emission composition.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.56-62
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• 2008

This paper proposes the use of decision tree classification for the measuring pattern recognition from industrial Computed Radiography(CR) images used in nondestructive evaluation(NDE) of steel-tubes. It appears that NDE problems are naturally desired to have machine learning techniques identify patterns and their classification. The attributes of decision tree are taken from NDE test procedure. Geometric features, such as radiative angle, gradient and distance, are estimated from the analysis of input image data. These factors are used to make it easy and accurate to classify an input object to one of the pre-specified classes on decision tree. This algerian is to simplify the characterization of NDE results and to facilitate the determination of features. The experimental results verify the usefulness of proposed algorithm.

• Analytical Science and Technology
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• v.13 no.1
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• pp.96-100
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• 2000

The adsorption of heavy-elements to zeolite has been investigated at various adsorptional condition for purification of waste water. Four heavy elements, Cd, Cr, Cu and Pb, were examined, because they are concerned to the major heavy-element contamination. The adsorption efficiencies are measured at the different conditions such as adsorption times and pHs. The practical adsorption was achived and reaches to maximum within 30 minute by using of 2-g zeolite for 50 mL of heavy-element solution. The overall adsorption efficiencies for Cr and Cu are high and become better at low pH. Cd and Pb have 95% of adsorption ratio and this is lower than other two elements. Cadmium shows an abnormally low adsorption at low pH.

• Proceedings of the Korea Technology Innovation Society Conference
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• 1998.05a
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• pp.8-8
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• 1998

한 국가의 경쟁력은 여러 가지 생산요소들의 질적·양적 우위에 의해 결정되나, 그 중에서도 특히 기술이 체화된 인적자원이 경쟁력 확보의 핵심요소임은 재론의 여지가 없다. 과거 우리나라 급성장의 주요 원동력이었던 우수하고 풍부한 인력이 이제 더 이상 우리 경쟁력의 원천이 되지 못하고 있다. 무한경쟁시대를 이끌어갈 창의력과 지도력을 갖춘 고급기술인력이 부족하고, 우수한 기술인력이 과학기술계를 회피하고 있으며, 산업현장에서 실제문제를 해결할 수 있는 실천적 전문기술과 숙련된 기능을 제대로 갖춘 인력을 배출하지 못하고 있다. 이러한 기숙인력 양성의 문제들을 해결하기 위한 방안의 하나로서 일반대학과 별도로 기술인력양성을 전문으로 하는 학위과정 설치의 필요성이 대두되었으며, 1996년 교육개혁의 일환으로 단설대학원제도와 전문학위제도가 시행되기 시작하였다. 그동안 여러 분야에서 단설대학원 설립이 추진되었으며, 일부에서 운영이 시작되고 있으나 과학기술분야에서는 극히 일부의 사례만이 있을 뿐이고 아직 본격적으로 설립운영되고 있다고 보기 어렵다. 본고는 외국 공공연구기관에서 시행되는 단설대학원의 사례들을 조사 분석함으로써 우리나라 과학기술계 출연연구기관에서의 바람직한 운영모델을 제시하고자한다. 일본의 총합연구대학원대학과 연계대학원제도, 중국 국가연구소들의 학위수여제도, 프랑스 국가연구소들의 석·박사과정, 독일 연구기관들의 박사과정 등을 소개하며, 이 들의 특징과 장단점들을 비교한다. 이어서 우리나라에서 현재 진행되고 있는 현황을 분석하고, 과학기술계 출연연구기관의 단설대학원 설립의 방향과 활성화를 위한 개선방안 등을 제시한다. 보고하였다2) 이 경우 보호피막으로서 NiO 와 $LiCrO_2$가 작용하는데, $LiCrO_2$가 용융탄산염 중에서 보다 안정한 것으로 부터, Cr의 첨가가 내식성에 기여하는 것으로 판단하였다. 다음 단계 로서 Fe/Cr재료에 용-융탄산염 중에서 안정한 산화물을 형성하는 Al의 첨가효과를 검토하였다. Al의 첨가는 더욱 내식성을 향상시키는 것이 발견되었고, 약 4wt%의 첨가로 충분한 내식성을 가지 는 것을 보고 하였다. 그러나 이러한 안정한 산화물에 의한 내식성 향상은 전기진도도의 희생을 바탕으로 한 것으로서, 다읍 단계로서 Ti산화물의 반도체적인 특성을 이용하고자 제 4의 원소로서 Ti첨가를 시도하였다. 그러나 Fe/Cr/AVTi재료가 뛰어난 내식성을 가지는 것은 관찰되었으나, 전도도 향상에는 기여하지 못하는 것이 보고되었다. 현재 MCFC는 실용화를 위한 고성능화의 하나로서 가압하에서의 운전을 시도하고 있다. 이 러한 가압하에서의 운전은 기전력의 향상 및 전극반응의 촉진 등으로 출력의 향상을 가져오나. 현재 문제로 되고 있는 Cathode극인 NiO의 용해/석출 현상을 가속화하는 결과를 초래해, 이에대 한 대책으로서 Li-K보다 NiO의 용해가 적은 Li-Na탄산염으로의 전환이 진행되고 있다. 이러한 배경으로부터 Uchida그룹에서 개발한 FeiCr/AVTi재료와 현재 분리판 재료로 사용증인 SUS 310, S SUS 316재료에 대해. 산화성 분위기의 5기압까지의 가압하에서, Li-K, Li-Na탄산염에 대하여 부 식거동을 검토한 결과, 가압하에서 내식성이 향상되는 것이

• Journal of the Korean Society of Radiology
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• v.1 no.1
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• pp.25-30
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• 2007

ROC(Receiver Operating Characteristic)curve is the method that estimate detected insignificant signal from the human's sense of sight, it has been raised excellent results. In this study, we evaluate image quality and equipment character by obtaining a chest image from CR(Computed Radiography) and DDR(Direct Digital radiography) using the human chest phantom, The parameter of exposure for obtaining chest image was 120 kVp/3.2 mAs and the SID(Source to Image Distance) was 180cm. The images were obtained by CR(AGFA MD 4.0 General plate, JAPAN) and DDR(HOLOGIC nDirect Ray, USA). Using some pieces of Aluminum and stone for expressing regions, then attached them on the heart, lung and thoracic vertebrae of the phantom. 29 persons hold radiology degrees were participated in ROC analysis. As a result of the ROC analysis, TPF(true positive fraction) and FPF(false positive fraction) of DDR and CR are 0.552 and 0.474 and 0.629 and 0.405, respectively. By using the results, the ROC curve of CR has higher image quality than DDR. According to the theory, DDR has the higher image quality than CR in chest X-ray image. But, CR has the higher image quality than DDR. quality of DDR inserted the enhance board. The results confirmed that image post-processing is important element decipherment of clinical.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.350-356
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• 2017

With increasing attention to real-time body detection, active research is being conducted on human body detection based on skin color. Despite this, most existing skin detection methods utilize static skin color models and have detection rates in images, in which colors are distorted. This study proposed a method of detecting the skin region using a fuzzy classification of the gradient map, saturation, and Cb and Cr in the YCbCr space. The proposed method, first, creates a gradient map, followed by a saturation map, CbCR map, fuzzy classification, and skin region binarization in that order. The focus of this method is to rigorously detect human skin regardless of the lighting, race, age, and individual differences, using features other than color. On the other hand,the borders between these features and non-skin regions are unclear. To solve this problem, the membership functions were defined by analyzing the relationship between the gradient, saturation, and color features and generate 108 fuzzy rules. The detection accuracy of the proposed method was 86.35%, which is 2~5% better than the conventional method.

• Progress in Medical Physics
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• v.19 no.1
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• pp.63-72
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• 2008

With recent advancement of the medical imaging systems and picture archiving and communication system (PACS), installation of digital radiography has been accelerated over past few years. Moreover, Computed Radiography (CR) which was well established for the foundation of digital x-ray imaging systems at low cost was widely used for clinical applications. This study analyzes imaging characteristics for two systems with different pixel sizes through the Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE). In addition, influence of radiation dose to the imaging characteristics was also measured by quantitative assessment. A standard beam quality RQA5 based on an international electro-technical commission (IEC) standard was used to perform the x-ray imaging studies. For the results, the spatial resolution based on MTF at 10% for Agfa CR system with I.P size of $8{\times}10$ inches and $14{\times}17$ inches was measured as 3.9 cycles/mm and 2.8 cycles/mm, respectively. The spatial resolution based on MTF at 10% for Fuji CR system with I.P size of $8{\times}10$ inches and $14{\times}17$ inches was measured as 3.4 cycles/mm and 3.2 cycles/mm, respectively. There was difference in the spatial resolution for $14{\times}17$ inches, although radiation dose does not effect to the MTF. The NPS of the Agfa CR system shows similar results for different pixel size between $100{\mu}m$ for $8{\times}10$ inch I.P and $150{\mu}m$ for $14{\times}17$ inch I.P. For both systems, the results show better NPS for increased radiation dose due to increasing number of photons. DQE of the Agfa CR system for $8{\times}10$ inch I.P and $14{\times}17$ inch I.P resulted in 11% and 8.8% at 1.5 cycles/mm, respectively. Both systems show that the higher level of radiation dose would lead to the worse DQE efficiency. Measuring DQE for multiple factors of imaging characteristics plays very important role in determining efficiency of equipment and reducing radiation dose for the patients. In conclusion, the results of this study could be used as a baseline to optimize imaging systems and their imaging characteristics by measuring MTF, NPS, and DQE for different level of radiation dose.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.1
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• pp.67-74
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• 2012

Purpose: The purpose of this study to evaluate visual acuity and refractive state and measure and analyze the components of eye's optical system in children and teenagers. Methods: With subjects of 124 (230 eyes) children and teenagers who had no eye diseases, correlation between the correlation between refractive errors and component's of eye's optical system was investigated. The spherical equivalent power of cycloplegic clinical refraction or manifest clinical refraction(SE), corneal power(CP), corneal radius(CR), axial length(AL), anterior chamber depth(ACD) and axial length to corneal radius (AL/CR) ratio were measured and analysed. Results: the SE was negatively correlated with the AL(r = -0.80, p = 0.00), the ACD(r = -0.35, p = 0.00) and the CR(r = -0.11, p=0.00) and positively correlated with the CP(r = +0.11, p=0.00). The AL was positively correlated with the AL/CR ratio (r = +0.84, p = 0.00), the ACD(r = +0.47, p=0.00) and the CR(r = +0.38, p = 0.00) and negatively correlated with the CP(r = -0.38, p=0.00). The CR was negatively correlated with CP(r = -1.00, p = 0.00), the AL/CR ratio(r = -0.19, p = 0.00) and the ACD(r = -0.06, p = 0.39). The CP was positively correlated with the AL/CR ratio(r = +0.19, p = 0.00) and the ACD(r = +0.06, p = 0.39). The ACD was positively correlated with the AL/CR ratio(r = 0.53, p = 0.00). Conclusions: the highest change of refractive errors was shown that the AL/CR ratio was a very important indicator for diagnosing the refractive errors of the children and teenagers.