• 한국정보전자통신기술학회논문지
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• 제13권5호
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• pp.419-424
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• 2020

Poroelasticity theory has been widely used for detecting cancellous bone deterioration because of the safe use for humans. The tortuosity itself is an important indicator for ultrasound detection for bone diseases. The transport properties of cancellous bone are also important in bone mechanotransduction. In this paper, two important factors, the wave velocity and attenuation are examined for permeability (or tortuosity). The theoretical calculation for the relationship between the wave velocity (and attenuation) and permeability (or tortuosity) for cancellous bone is shown in this study. It is found that the wave along the solid phase (trabecular struts) is influenced not by tortuosity, but the wave along the fluid wave (bone fluid phase) is affected by tortuosity significantly. However, the attenuation is different that the attenuation of a fast wave has less influence than that of a slow wave because the slow wave is observed by the relative motion between the solid and fluid phases.

• Computers and Concrete
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• 제13권3호
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• pp.309-323
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• 2014

Based on the compositions and structures of cement-based materials, the geometrical models of the tortuosity of transport paths in hardened cement pastes, mortar and concrete, which are associated with the capillary porosity, cement hydration degree, mixture particle shape, aggregate volume fraction and water-cement ratio, are established by using a geometric approach. Numerical simulations are carried out to investigate the effects of material parameters such as water-cement ratio, volume fraction of the mixtures, shape and size of aggregates and cement hydration degree, on the tortuosity of transport paths in hardened cement pastes, mortar and concrete. Results indicate that the transport tortuosity in cement-based materials decreases with the increasing of water-cement ratio, and increases with the cement hydration degree, the volume fraction of cement and aggregate, the shape factor and diameter of aggregates, and the material parameters related to cement pastes, such as the water-cement ratio, cement hydration degree and cement volume fraction, are the primary factors that influence the transport tortuosity of cement-based materials.

• Neonatal Medicine
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• 제25권1호
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• pp.49-52
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• 2018

Arterial tortuosity syndrome (ATS) is a very rare autosomal recessive connective tissue disease characterized by generalized elongation and tortuosity of the medium- to large-sized arteries, and other systemic connective tissue manifestations. To date, this disease entity has not been reported in Korea. We report a case of ATS diagnosed in a neonate who presented with severe elongation and tortuosity of the aorta and its major branches, as well as the intracranial arteries. Additionally, the patient presented with a tortuous dilatation of the inferior vena cava, an aneurysmal dilatation of the extra-hepatic bile ducts, and an inguinal and sliding hiatal hernia. The diagnosis was confirmed using DNA sequencing analysis, and the patient demonstrated a compound heterozygosity for two novel mutations (c.738delG [p.Gln247Serfs*33] and c.362T>C [p.Ile121Thr]) in exon 2 of the SLC2A10 gene. Genetic analysis also confirmed that both parents were heterozygous carriers of the responsible mutations. Owing to such clinical manifestations, ATS is often misdiagnosed as other connective tissue diseases including Loeys-Dietz syndrome, Marfan syndrome, and Ehlers-Danlos syndrome. In patients presenting with a high index of suspicion, thorough clinical evaluation and screening for ATS including computed tomography or magnetic resonance angiography and target gene analysis are necessary for early diagnosis and management.

• 대한두경부종양학회지
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• 제23권2호
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• pp.178-180
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• 2007

Tortuosity of the internal carotid artery is not a rare condition. A 68-year-old woman presented with a 3 years' history of a pulsatile tinnitus and throat abnormal sensation. On physical examination, a soft pulsatile mass on the left posterior oropharyngeal wall was noted. By neck CT and neck MRI the tortuous internal carotd artery was visualized. Otolaryngologists should recognize this anomaly and the patient should be made aware of their condition, because it may cause a fatal or near-fatal hemorrhage during surgical procedures in the pharynx, especially tonsillectomy and adenoidectomy and drainage of peritonsillar abscess. We report a case of a left internal carotid artery tortuosity as an oropharyngeal mass.

• 한국초전도ㆍ저온공학회논문지
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• 제23권4호
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• pp.49-55
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• 2021

The Cable in Conduit Conductor (CICC) configurations are designed, tested and realized to make high field superconducting (SC) magnets. The evolution of CICC design makes it challenging to forecast thermo-hydraulic behavior. A common objective of thermo-hydraulic studies is to obtain the most reliable predictive correlation for friction factor in CICC geometries and to reduce the dependency on the experiment. So far, only the void fraction and Reynolds number have been considered in the predictive correlations in an explicit way. In the present paper, the CICC twisting pattern dependency, called tortuosity (τ), on the pressure drop prediction, has been assessed through a numerical simulation approach. The CICC twisting pattern with 6+1 petals (solid conductor in the present study) with different twisting pitches is mimicked in the numerical simulation for the range 100 ≤ Re ≤10000 and 1 < τ < 1.08 and a correlation for friction factor, f, has been proposed as a function of Re and τ.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.329-332
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• 2021

A markedly enlarged foramen transversarium was discovered incidentally on a cone-beam computed tomography scan of a 72-year-old male patient who was referred for dental implant placement. Further evaluation with magnetic resonance angiography revealed that the foramen enlargement was caused by a tortuosity in the course of the vertebral artery. This case report highlights the importance of recognizing significant incidental findings on diagnostic images and the potential need for additional imaging as part of the complete interpretative process.

• 한국토양환경학회지
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• 제1권2호
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• pp.83-90
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• 1996

토양내에서의 가스나 증기상의 오염물질의 이동은 여러 가지 현상에 의해서 일어나고 있으나 농도차에 의해서 일어나는 확산이 가장 중요하다. 그런데 토양내에서의 확산은 토양 입자들로 인한 확산 부피의 감소, 또 확산경로의 불규칙성, 확산 경로에 있어서 단면적의 변화 등으로 인해 대기중에서 일어나는 확산과는 다른 면을 보인다. 본 논문에서는 이러한 현상을 설명하기 위하여 흔히 사용되는 굴절계수(toruosity), 유효확산계수(effective diffusion coefficient)의 서로 다른 그러나 같은 이름으로 사용되는 많은 정의들과 다양한 수학적 모델들에 대한 비교 검토가 이루어졌다. 굴절계수나 유효확산계수를 사용할 때는 각각의 경우 정의와 각 식의 특징에 대하여 세밀한 검토와 주의가 행하여져야 한다.

• Journal of Genetic Medicine
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• 제10권1호
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• pp.47-51
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• 2013

Loeys-Dietz syndrome (LDS) is an autosomal dominant disorder caused by heterozygous mutations in the genes encoding transforming growth factor-${\beta}$ receptor type 1 or 2. It is typically characterized by a triad of hypertelorism, cleft palate or bifid uvula, and arterial tortuosity with aneurysm or dissection. Characteristic vascular abnormalities such as tortuosity, aneurysms, dissections, and stenosis are the most severe complications of LDS and can occur in the neurovascular system. We report a 5-year-old boy who presented with headaches and neurovascular abnormalities and was diagnosed with LDS with a novel mutation of the TGFBR1 gene. It is the first Korean report of neurovascular abnormalities in LDS.

• Computers and Concrete
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• 제7권5호
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• pp.421-435
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• 2010

This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test, have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

• 멤브레인
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• 제14권2호
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• pp.132-141
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• 2004

본 연구에서는 NBR과 여러 가지의 유기화물로 처리된 MMT type의 clay를 이용하여 NBR-Clay 하이브리드 막을 용융삽입법으로 제조하였다. Internal mixer를 사용하여 clay를 NBR에 분산시켰으며, 제조된 NBR-Clay 하이브리드에서 clay의 특성피크가 다소 감소하거나 이동하는 XRD 결과로부터 clay의 층간거리가 넓어지는 고분자의 clay층간삽입을 확인하였다. Clay의 종류에 따라서 제조된 NBR-Clay 하이브리드 막의 가스투과도, 기계적 물성 및 열적 성질을 측정하였다. NBR-Clay 하이브리드 막은 clay 자체의 도입과 층간거리의 확대로 기체분자의 tortuosity를 증가시켜서 가스투과도를 저하시키는 것을 확인하였다.