• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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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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• v.13 no.3
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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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• v.25 no.1
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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.

• Korean Journal of Head & Neck Oncology
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• v.23 no.2
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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.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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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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• v.51 no.3
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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.

• Journal of Korea Soil Environment Society
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• v.1 no.2
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• pp.83-90
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• 1996

A diffusion process is often the main mechanism of soil gas/vapor movement in the vadose zone. The diffusion coefficients in the porous soil media are different from those in the free air phase by the reduction of available area for diffusion, tortuous diffusion path and variable cross section area along the diffusion path. To take account those effects of the diffusion process in the porous media, usually the terms of effective diffusion coefficient and tortuosity are have been used. However, as there are many differents definitions for the tortuosity, when the term of tortuosity is used, it is necessary to examine it throughly. Moreover, there are many different equations for the effective diffusion coefficient according to the investigators and the differences in the values of effective diffusion coefficients between the equations are not insignificant, the selection of the equation should be done with caution. In this paper, the different definitions of effective diffusion coefficient are examined and discussed. As well as definitions, the lots of availabe models for the diffusion coefficient in terms of porosities are compared. Also, the constrictiviy which explains the effect of cross sectional area change over the diffusion path was discussed.

• Journal of Genetic Medicine
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• v.10 no.1
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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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• v.7 no.5
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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.

• Membrane Journal
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• v.14 no.2
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• pp.132-141
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• 2004

NBR-Clay hybrid membranes were prepared by melt intercalation method with internal mixer and two roll mills. MMT was intercalated or ekfoliated by the NBR and it was confirmed by X-ray diffraction method. D-spacing of the characteristic peak from MMT plate in WAXD was moved and diminished. Gas permeability, mechanical properties and thermal properties of the NBR-Clay hybrid membranes were investigated. Gas permeability through the NBR-Clay hybrid membranes decreased due to increased tortuosity made by intercalation of clay in NBR.