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Reduced Order Modeling of Backward-Facing-Step Flow Field (후향계단 유동장 축약모델링 기법)

  • Lee, Jin-Ik;Lee, Eun-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.10
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    • pp.833-839
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    • 2012
  • In this paper, we analyze the reconstruction error in the modeling of flow field on BFS(Backward Facing Step). In order for the mathematical modelling of a density on the field, the spatial and temporal modes are extracted by POD(Proper Orthogonal Decomposition) method. After formulating the modeling error, we summarize the relationship between the energy strength and the reconstruction errors. Moreover the allowable modeling error limits in the flow control point of view are confined by analysing in the frequency domain as well as time domain of the reconstructed data.

Prediction of Turbulent Flows with Separation and Swirl Using the RNG K-$\varepsilon$ Turbulence Model (RNG k-$\varepsilon$ 난류모델을 이용한 유동박리 및 선회를 가지는 난류유동의 예측)

  • 김성구;오군섭;김용모;이창식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.119-129
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    • 1996
  • This study is concerned with the critical evaluation of predicative capability of a k-$\varepsilon$ turbulence model using the Renormalization Group(RNG) theory. The present numerical model for solution of the Navier-Stokes System is based on the modified PISO algorithms. Computations have been performed with the RNG-based K-$\varepsilon$ model for the two-dimensional flow over a backward-facing step, a confined coaxial jet, and a swirling flow in a swirl combustor. Numerical results are compared with experimental data in terms of mean flow velocities, turbulent kinetic energy, and turbulent stresses. Numerical results clearly indicate that the RNG-based K-$\varepsilon$ turbulence model shows a significant improvement over a standard K-$\varepsilon$ model in predicting the turbulent flows with flow separation and swirl.

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Numerical Study of Turbulent Swirling Isothermal and Spray-Combusting Flows (난류선회 등온 및 분무연소 유동에 대한 수치해석)

  • 김성구;안국영;김용모;이창식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.130-141
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    • 1996
  • Numerical study of a confined, swirling, isothermal and spray-combusting flows has been presented. The pressure-velocity coupling in the Eulerian gas-phase equation is handled by the improved PISO algorithm. The droplet dispersion by turbulence is introduced by a Stochastic Separated Flow(SSF) model. The k-$\varepsilon$ turbulence model and the eddy dissipation model are employed to account for turbulence-combustion interaction. The detailed comparison with experimental data has been made for the isothermal jet swirling flows and the nearly monodisperse spray-combusting flow in the swirl combustor.

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A New Linearized Equation for Modelling a Servovalve in Hydraulic Control Systems (유압 제어계에서 서보밸브 모델링을 위한 새로운 선형화 방정식의 제안)

  • Kim, Tae-Hyung;Lee, Ill-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.5
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    • pp.789-797
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    • 2003
  • In the procedure of the hydraulic control system design, a linearized approximate equation described by the first order terms of Taylor series has been widely used. Such a linearized equation is effective just near the operating point, However, pressure and flowrate in actual hydraulic systems are usually not confined near an operating point. This study suggests a new linearized flow equation for a servovalve as a modified form of the conventional linearized flow equation. Subsequently, a procedure to determine effective operating point for the new linearized equation is proposed. From the evaluations of time responses and frequency responses obtained from simulations for a hydraulic control system, the effectiveness of the new linearized equation and the procedure to determine effective operating point is confirmed.

First report of Halopeltis (Rhodophyta, Rhodymeniaceae) from the non-tropical Northern Hemisphere: H. adnata (Okamura) comb. nov. from Korea, and H. pellucida sp. nov. and H. willisii sp. nov. from the North Atlantic

  • Schneider, Craig W.;Freshwater, D. Wilson;Saunders, Gary W.
    • ALGAE
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    • v.27 no.2
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    • pp.95-108
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    • 2012
  • Using genetic sequencing (COI-5P, LSU, $rbc$L) to elucidate their phylogenetic positions and then morphological characters to distinguish each from existing species, three procumbent species, including two novel species, from warm temperate Northern Hemisphere waters are added to the recently resurrected genus $Halopeltis$ J. Agardh: $H.$ $adnata$ (Okamura) comb. nov. from Korea, $H.$ $pellucida$ sp. nov. from Bermuda and $H.$ $willisii$ sp. nov. from North Carolina, USA. Prior to these reports, the genus was confined to the Southern Hemisphere and tropical equatorial waters of the Northern Hemisphere although the latter records lack molecular confirmation. These three additional species join the six known species presently residing in $Halopeltis$.

Phytoplasma Associated with Yellowing Disease of Washingtonia sp. in Kuwait

  • Al-Awadhi, Husain A.;Montasser, Magdy S.;Suleman, Patrice;Hanif, Asma M.
    • The Plant Pathology Journal
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    • v.17 no.6
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    • pp.329-335
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    • 2001
  • Yellowing disease of palms caused by phytoplasma is spreading in the Arabian Gulf region. Surveys were conducted to determine the occurrence of the disease. Electron and fluorescence microscopy, and polymerase chain reaction (PCR) techniques were used to detect the phytoplasma associated with the yellowing disease of ornamental palm Washingtonia sp. grown in Kuwait. An accumulation of phytoplasmal DNA was observed by fluorescence microscopy in phloem tissues of diseased palms. Electron microscopy showed that phytoplasma cells were primarily confined to the phloemsieve elements of tissue samples collected from infected mature palms in the field. The pathogen was identified on the basis of molecular analysis using universal and specific nested primers in PCR amplifications. Prokaryotic 16S rDNA gene was detected in amplified PCR products. Nested PCR resulted in DNA amplification of 1.2 kbp fragment. This is the first report of a phytoplasmal rDNA gene identified from the putative causal pathogen of yellows in ornamental palms in the Arabian Gulf region.

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Assessment and Neurophysiology of the Limb Apraxia: Review Article (사지 실행증의 평가 및 신경생리학적 고찰)

  • Choi, Jin-Ho;Park, Ji-Won;Kwon, Yong-Hyun
    • The Journal of Korean Physical Therapy
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    • v.18 no.2
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    • pp.7-16
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    • 2006
  • The purpose of this study was to review the limb apraxia. It includes the evaluation and neurophysiological aspects for limb apraxia. Limb apraxia comprised a wide spectrum of higher-order motor disorders that results from acquired brain disease affecting the performance of skilled and/or learned movements with the forelimbs and is a common sequela of left brain damage that consists of a deficit in performing gestures to verbal command or to imitation. There are two forms in limb apraxia; ideational apraxia and ideomotor apraxia. A assessment of limb apraxia typically includes pantomiming and imitation of transitive, intransitive, and meaningless gestures. Limb apraxia has been attributed to damage confined to the cerebral cortex, cortico-cortical connecting pathways, and basal ganglia.

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Probabilistic Modeling of Fiber Length Segments within a Bounded Area of Two-Dimensional Fiber Webs

  • Chun, Heui-Ju
    • Communications for Statistical Applications and Methods
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    • v.18 no.3
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    • pp.301-317
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    • 2011
  • Statistical and probabilistic behaviors of fibers forming fiber webs of all kinds are of great significance in the determination of the uniformity and physical properties of the webs commonly found in many industrial products such as filters, membranes and non-woven fabrics. However, in studying the spatial geometry of the webs the observations must be theoretically as well as experimentally confined within a specified unit area. This paper provides a general theory and framework for computer simulation for quantifying the fiber segments bounded by the unit area in consideration of the "edge effects" resulting from the truncated length segments within the boundary. The probability density function and the first and second moments of the length segments found within the counting region were derived by properly defining the seeding region and counting region.

Radiation recall dermatitis triggered by sorafenib after radiation therapy for hepatocellular carcinoma

  • Kim, Gwi Eon;Song, Hee-Sung;Ahn, Ki Jung;Kim, Young Suk
    • Radiation Oncology Journal
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    • v.35 no.3
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    • pp.289-294
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    • 2017
  • Sorafenib is widely used for unresectable and metastatic hepatocellular carcinomas. Radiation recall dermatitis (RRD) is an acute inflammatory reaction confined to previously irradiated skin that occurs after the administration of certain drugs. RRD after sorafenib treatment is rare; five cases have been reported thus far. We describe a 44-year-old man irradiated for chest wall bone metastasis from hepatocellular carcinoma. Eight days after radiotherapy completion, systemic therapy for metastatic hepatocellular carcinoma was initiated with sorafenib treatment. Eleven days after starting sorafenib, the patient complained of erythematous rash with pruritus in the chest wall, in a location consistent with the previous radiation field. Sorafenib was continued at the same dose, despite the RRD. The skin reaction subsided over the next 2 weeks without any medical intervention.

Studies on The Diseases of the Korean Native Goat-A Review (우리나라 재래염소의 질병에 관한 연구-문헌조사)

  • 이정길;이채용;곽형수
    • Journal of Veterinary Clinics
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    • v.17 no.1
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    • pp.32-44
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    • 2000
  • The Korean native goat has been extensively used in the experimental work. Compared to those experimental work employing the goat, reports on their diseases have been scarcely documented. In the present communication, authors reviewed the literatures pertaining to the diseases of the Korean native goat. Diseases of the respiratory system, the alimentary tract, the liver, the musculoskeletal system, the skin, the urogenital system, the nervous system, the eye, and the heart were reviewed. And then metabolic, toxic, and parasitic diseases were reviewed. Of those diseases reviewed, diseases of the heart and kidney, and metabolic and toxic diseases were wholly artificially-induced. Except the parasitic diseases, a considerable number of diseases of other organ systems were also artificially-induced. And the parasitic diseases reported were confined to the internal parasites. Authors feel that the known occurrence of diseases would help diagnose new disease in the goat.

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