• Clinical and Experimental Pediatrics
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• 제54권6호
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• pp.272-275
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• 2011

A recently recognized connective tissue disorder, Loeys-Dietz syndrome (LDS) is a genetic aortic aneurysm syndrome caused by mutations in the transforming growth factor-receptor type I or II gene (TGFBR1 or TGFBR2). They have distinctive phenotypic abnormalities including widely spaced eyes (hypertelorism), bifid uvula or cleft palate, and arterial tortuosity with aortic aneurysm or dissection throughout the arterial tree. LDS is characterized by aggressive and rapid progression of aortic aneurysm. Therefore, the patients with distinct phenotype, marked aortic dilatation and aneurysm at early age should be suspected to be affected by LDS and rapid TGFBR gene analysis should be done. We report one child diagnosed as LDS due to typical phenotypes and two novel missense mutations of the TGFBR2 gene (c.1526G>T and c.1528A>T).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.885-891
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• 2003

Effects of each acoustic property on absorption characteristics of polyester fiber materials has been studied in this paper. It would be impossible for us to measure effects of each acoustic property by experimental method since we cannot make sound-absorbing materials in which only one of the properties is changed. We have adopted a numerical prediction method to carry out parameter studies for each acoustic property. And to get a general behavior of acoustic performance of the materials, the numerical simulation has been repeated to several cases of different bulk density. Finally we have obtained frequency-dependent control factors in the absorption performance which gives us design capability of acoustic absorbing materials.

• Water Engineering Research
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• 제3권3호
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• pp.177-193
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• 2002

Experiments were conducted in an initially straight laboratory alluvial channel to investigate channel meandering characteristics. The experimental observations revealed an empirical relation between three types of tortuosity ratios used for describing meandering characteristics. Furthermore, the Strauhal number was found to be higher for bed material with greater resistance to erosion than with lower resistance to erosion. The meandering characteristics were also investigated using the concept of buckling employed in solid mechanics and the concept of siphoning of fluid mechanics. The buckling of flow, attributable to the flow nonuniformity across the channel cross-section, was found to follow the same pattern as did meandering observed experimentally. The processes of expansion of meanders and cut-off can be explained using the concept of siphoning. The results of expanding meander planforms observed in four experimental tests supported the viability of these concepts.

• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.

• Investigative Magnetic Resonance Imaging
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• 제14권1호
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• pp.47-55
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• 2010

목적 : 조영증강 MR 혈관조영술을 이용하여 경동맥의 기하학(geometry)을 측정하고, 경동맥 기하학과 임상요인 사이의 상관관계를 분석하고자 하였다. 대상 및 방법 : 2007년 1월부터 6월까지 대동맥궁 상부 조영증강 MR 혈관조영술을 시행한 216명을 대상으로 하였다. 동맥경화 위험인자(나이, 고혈압, 당뇨, 고지혈증, 흡연), 성별, 체중, 신장, 체질량지수를 조사하였다. MR 혈관조영술에서는 경동맥 기시부 유형, 경동맥의 굴곡도, 내경동맥 분지각, 내경동맥 비틀림, 대동맥궁 소-유형(bovine type) 여부를 평가하였다. 경동맥 기시부 유형은 위치에 따라 3단계로 분류하였다. 기하학 요소와 임상정보간의 상관관계를 회귀분석을 이용하여 분석하였다. 결과 : 경동맥 기시부를 종속변수로 한 다항 로지스틱 회귀분석에서 나이가 많을수록 경동맥 기시부 1형의 빈도가 높았고, 체질량지수가 클수록 2형, 3형일 빈도가 높았다. 좌, 우측 경동맥의 굴곡도의 평균은 각각 $240.9{\pm}69.0^{\circ}$과 $154.4{\pm}55.0^{\circ}$였다. 다변량 회귀분석에서 고혈압 환자와 여자, 나이, 체질량지수가 클수록 경동맥의 굴곡도가 증가하였다. 내경동맥 분지각, 내경동맥 비틀림, 대동맥궁 소-유형은 통계분석에서 임상정보와 유의한 상관관계를 보이지 않았다. 결론 : 경동맥 기하학에 나이, 체질량지수, 성, 고혈압 여부가 영향을 미칠 수 있다. 이러한 정보는 대동맥궁 및 경동맥의 영상정보가 없는 경우, 경동맥 기하학 예측 및 침습적 혈관내 시술 전략 수립에 도움이 될 것이다.

• 물과 미래
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• 제14권1호
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• pp.39-49
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• 1981

하천 재해 방지 및 하천 유지의 관점에서 반드시 구명되어야 하는 하천 사행에 관한 연구는 자연 현상에 대한 관점에서 출발하여, 금세기초부터 체계적이고 과학적인 연구가 진행되어 왔다. 그 발생 원인은 정설이 확립되지 않은 가운데 복합적인 여러 요인에 의하여 사행은 생성, 발달되며, mechanism의 고찰과 함께 계량형태학적 분석으로 사행 특성이 일부 밝혀지고 있다. 본 연구에서는 유로연장 30km 이상의 67개 대상하천에서 사행특성인자인 사행파장(M$$)과 사행대(M$$) 등의 관계를 구명하여 유량과의 상관성을 분석하였다. 또한 하천의 기점에서 종점까지의 직선 거리에 대한 유로 연장의 비인 유로형상계수(L$$)를 처음으로 제안했으며, 유로 연장에 대한 만곡부연장의 비인 Tortuosity(t)와 더불어, 유로연장, 사행경사, Horton의 유역형상계수 등과 상관분석 및 복합회귀분석을 시행한 결과 L$$와 T가 하천사행의 한 척도가 됨을 밝혔다. 사행 유로부와 직유로부에서 유속과 수면경사, 하상굴곡도(degre of sinuosity)를 비교 검토한 결과, 사행 유로부가 직유로부보다 하상의 안정성이 높음을 알았다. 하천 수계별 사행파장과 사행대의 상관식은 각기 선형관계와 역함수관계로 대별되었으며, 남한강 수계의 경우에는 선형관계, 낙동강, 금강 수계의 경우에는 역함수 관계식을 제시하였다.

• 멤브레인
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• 제15권3호
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• pp.247-254
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• 2005

키토산 필름은 농업, 식품과 제약 분야에서 응용이 가능하다. 그러나 키토산으로만 만들어진 필름은 기체투과성이 높고 기계적 물성에 약하다. 따라서 본 연구에서는 기체 투과성을 낮추고 기계적 물성을 높이기 위해 층상구조를 갖는 점토광물의 일종인 montorillonite (MMT)와 양이온 생체고분자인 키토산을 이용하여 양이온 교환과 수소결합과정을 통해 $Na^+-MMT$에 키토산을 삽입하여 키토산/Clay 나노복합재료를 제조하였다. 키토산/clay 나노 복합재료의 X-ray 회절패턴에서 $2\theta=7.5^{\circ}$에서 MMT의 basal reflection이 나타났고, $2\theta=3\~5^{\circ}$ 주위에서의 새로운 약하고 넓은 peak로서 더 낮은 각에서 MMT의 basal reflection의 이동에 의해 삽입된 나노 구조의 형성을 증명하였다. 또한 TGA thermogram를 이용하여 clay의 함유량이 증가할수록 제조된 나노복합재료의 열분해가 일어나는 범위의 질량감소가 줄어드는 것을 확인하므로서 내열성을 관찰하였다. 기계적 물성 성질을 측정하여 clay 함유량의 증가에 따른 인장 강도와 인장 모듈러스의 변화를 관찰하고, 키토산이 층상 실리케이트 내에 삽입하여 제조된 나노복합재료에서 clay의 함유량이 증가할수록 질소 투과경로의 tortuosity를 증가시켜서 기체 투과도를 감소시키는 것도 확인하였다.

• Membrane and Water Treatment
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• 제2권3호
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• pp.187-205
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• 2011

The electric transport of the mixture of hydrochloric and phosphoric acids through strong base (Neosepta ACM) and weak base (Selemion AAV) anion-exchange membranes was investigated. The instantaneous efficiency of HCl removal from the cathode solution, $CE_{Cl}$, with and without $H_3PO_4$ was determined. It was found that $CE_{Cl}$ was 0.8-0.9 if the number of moles of elementary charge passed through the system, $n_F$, did not exceed ca. 80% of the initial number of HCl moles in the cathode solution, $n_{Cl,ca,0}$. The retention efficiency of $H_3PO_4$ in that range was close to one. The transport of acid mixtures was satisfactorily described by a model based on the extended Nernst-Planck and Donnan equations for $n_F$ not exceeding $n_{Cl,ca,0}$. Among the tested model parameters, most important were: concentration of fixed charges, the porosity-tortuosity coefficient, and the partition coefficient of an undissociated form of $H_3PO_4$. For the both membranes, the obtained optimal values of fixed charge concentration, $\bar{c}_m$, were up to 40% lower than the literature values of $\bar{c}_m$ obtained from the equilibrium measurements. Regarding the $H_3PO_4$ equilibria, it was sufficient to consider $H_3PO_4$ as a monoprotic acid.

• International Journal of Aeronautical and Space Sciences
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• 제15권4호
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• pp.419-433
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• 2014

The Mars Exploration Rover Opportunity investigated plains at Meridiani Planum, where laminated sedimentary rocks are present. The Opportunity rover's Athena morphological investigation showed microstructures organized in intertwined filaments of microspherules: a texture we have also found on samples of terrestrial (biogenic) stromatolites and other microbialites. We performed a quantitative image analysis to compare images (n=45) of microbialites with the images (n=30) photographed by the rover (corresponding, approximately, to 25,000/15,000 microstructures). Contours were extracted and morphometric indexes were obtained: geometric and algorithmic complexities, entropy, tortuosity, minimum and maximum diameters. Terrestrial and Martian textures present a multifractal aspect. Mean values and confidence intervals from the Martian images overlapped perfectly with those from the terrestrial samples. The probability of this occurring by chance is $1/2^8$, less than p<0.004. Terrestrial abiogenic pseudostromatolites showed a simple fractal structure and different morphometric values from those of the terrestrial biogenic stromatolite images or Martian images with a less ordered texture (p<0.001). Our work shows the presumptive evidence of microbialites in the Martian outcroppings: i.e., the presence of unicellular life on the ancient Mars.

• Advances in nano research
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• 제8권3호
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• pp.255-264
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• 2020

Buckling and post-buckling cases are often occurred in aorta artery because it affected by higher pressure. Also, its stability has a vital importance to humans and animals. The loss of stability in arteries may lead to arterial tortuosity and kinking. In this paper, post-buckling analysis of aorta artery is investigated under axial compression loads on the basis of Euler-Bernoulli beam theory by using finite element method. It is known that post-buckling problems are geometrically nonlinear problems. In the geometrically nonlinear model, the Von Karman nonlinear kinematic relationship is employed. Two types of support conditions for the aorta artery are considered. The considered non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. The aorta artery is modeled as a cylindrical tube with different average diameters. In the numerical results, the effects of the geometry parameters of aorta artery on the post-buckling case are investigated in detail. Nonlinear deflections and critical buckling loads are obtained and discussed on the post-buckling case.