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Uncertainty analysis of flow rate measurement for multiphase flow using CFD

Acta Mechanica Sinica 2015年第5期31卷 698-707页

作者： joon-Hyung Kim Uk-Hee Jung Sung Kim joon-yong yoon Young-Seok Choi Department of Mechanical Design Engineering Hanyang University Thermal & Fluid System R&BD Group Korea Institute of Industrial Technology Energy System Engineering University of Science and Technology

The venturi meter has an advantage in its use,because it can measure flow without being much affected by the type of the measured fluid or flow ***,it has excellent versatility and is being widely applied in many *** flow of a liquid containing air is a representative example of a multiphase flow and exhibits complex flow *** particular,the greater the gas volume fraction（GVF）,the more inhomogeneous the flow *** a result,using a venturi meter to measure the rate of a flow that has a high GVF generates an *** this study,the cause of the error occurred in measuring the flow rate for the multiphase flow when using the venturi meter for analysis by *** ensure the reliability of this study,the accuracy of the multiphase flow models for numerical analysis was verified through comparison between the calculated results of numerical analysis and the experimental *** a result,the Grace model,which is a multiphase flow model established by an experiment with water and air,was confirmed to have the highest ***,the characteristics of the internal flow Held about the multiphase flow analysis result generated by applying the Grace model were analyzed to find the cause of the uncertainty occurring when measuring the flow rate of the multiphase flow using the venturi meter.A phase separation phenomenon occurred due to a density difference of water and air inside the venturi,and flow inhomogeneity happened according to the flow velocity difference of each *** was confirmed that this flow inhomogeneity increased as the GVF increased due to the uncertainty of the flow measurement.

关键词： Multiphase flow Measurement Numerical analysis Venturi meter Gas volume fraction(GVF) Uncertainty Multiphase flow model Grace model

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Performance Enhancement of a Pump Impeller Using Optimal Design Method

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Journal of Thermal Science 2017年第2期26卷 119-124页

作者： Seok-Yun Jeon Chul-Kyu Kim Sang-Moon Lee joon-yong yoon Choon-Man Jang Korea Institute of Civil Engineering and Building Technology Goyang-siGyeonggi-do10223Korea Dep.of Mechanical Engineering Hanyang UniversityAnsanGyeonggi-do15588Korea

This paper presents the performance evaluation of a regenerative pump to increase its efficiency using optimal design method. Two design parameters which define the shape of the pump impeller, are introduced and analyzed. Pump performance is evaluated by numerical simulation and design of experiments(DOE). To analyze three-dimensional flow field in the pump, general analysis code, CFX, is used in the present work. Shear stress turbulence model is employed to estimate the eddy viscosity. Experimental apparatus with an open-loop facility is set up for measuring the pump performance. Pump performance, efficiency and pressure, obtained from numerical simulation are validated by comparison with the results of experiments. Throughout the shape optimization of the pump impeller at the operating flow condition, the pump efficiency is successfully increased by 3 percent compared to the reference pump. It is noted that the pressure increase of the optimum pump is mainly caused by higher momentum force generated inside blade passage due to the optimal blade shape. Comparisons of pump internal flow on the reference and optimum pump are also investigated and discussed in detail.

关键词： Regenerative Pump Efficiency Impeller Optimal Design Computational Fluid Dynamics

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Designing a Biomimetic Ornithopter Capable of Sustained and Controlled Flight

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Journal of Bionic Engineering 2008年第1期5卷 39-47页

作者： joon Hyuk Park Kwang-joon yoon Department of Aerospace Information System and Artificial Muscle Research Center Konkuk University Seoul 143-701 Korea

We describe the design of four ornithopters ranging in wing span from 10 cm to 40 cm, and in weight from 5 g to 45 g. The controllability and power supply are two major considerations, so we compare the efficiency and characteristics between different types of subsystems such as gearbox and tail shape. Our current omithopter is radio-controlled with inbuilt visual sensing and capable of takeoff and landing. We also concentrate on its wing efficiency based on design inspired by a real insect wing and consider that aspects of insect flight such as delayed stall and wake capture are essential at such small size. Most importantly, the advance ratio, controlled either by enlarging the wing beat amplitude or raising the wing beat frequency, is the most significant factor in an ornithopter which mimics an insect.

关键词： biomimetic ornithopter flapping wing unsteady state low Reynolds number

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Topically administered bevacizumab had longer standing anti-angiogenic effect than subconjunctivally injected bevacizumab in rat corneal neovacularization

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International Journal of Ophthalmology(English edition) 2013年第5期6卷 588-591页

作者： Jae yong Kim Dong yoon Kim Eun-Soon Kim Myoung joon Kim Hungwon Tchah Department of Ophthalmology University of Ulsan College of MedicineAsan Medical Center

AIMTo compare the effect of topically administered and subconjunctivally injected bevacizumab on experimental corneal neovascularization in rats for two weeks after treatment.

关键词： corneal neovascularization bevacizumab topical and subconjunctival administration

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Emission wavelength selection via anomalous polarized fluorescence in ZnO-C nanowires

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Nano Research 2024年第5期17卷 4489-4497页

作者： joon Kiat Kang Kim yong Lim Chorng Haur Sow Department of Physics National University of SingaporeSingapore 117542Singapore

Defect fluorescence from high aspect ratio semiconductor nanowires typically displays a weak polarization parallel to the nanowire’s long axis due to dielectric mismatch in high aspect ratio ***,anomalous 2.2 eV defect fluorescence distinctly polarized perpendicular to the nanowire is observed and measured from carbon-incorporated zinc oxide *** observations are significant because polarized defect emissions with consistent polarization on a mesoscopic scale are *** a systematic study and comparison of experimental results with density functional theory calculations,an oriented defect complex comprising carbon substituting on an oxygen site and an oxygen vacancy(CO-VO)is deduced to be responsible for the anomalous yellow fluorescence,demonstrating a method for relating atomic-scale defect geometry to mesoscopic *** anomalous emission can appear in both green-and red-fluorescing nanowires grown with different carbon concentrations,verifying the independence and uniqueness of the 2.2 eV *** allows for polarization-dependent emission wavelength selection from a single nanowire.

关键词： anomalous polarization defects fluorescence zinc oxide carbon

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Biliary drainage for obstructive jaundice caused by unresectable hepatocellular carcinoma: the endoscopic versus percutaneous approach

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Hepatobiliary & Pancreatic Diseases International 2012年第6期11卷 636-642页

作者： Jongkyoung Choi Ji Kon Ryu Sang Hyub Lee Dong-Won Ahn Jin-Hyeok Hwang yong-Tae Kim yong Bum yoon joon Koo Han Department of Internal Medicine and Liver Research Institute Seoul National University College of Medicine Seoul Korea Department of Internal Medicine National Medical Center Seoul Korea Department of Internal Medicine Seoul National University Bundang Hospital Seongnam Gyeonggi-do Korea Department of Internal Medicine Seoul National University Boramae Medical Center Seoul Korea Department of Radiology Seoul National University College of Medicine Seoul Korea

BACKGROUND: For palliative treatment of the obstructive jaundice associated with unresectable hepatocellular carcinoma (HCC), percutaneous transhepatic biliary drainage (PTBD) or endoscopic retrograde biliary drainage (ERBD) has been performed. PTBD is preferred as an initial procedure. Little is known about the better option for patients with obstructive jaundice caused by unresectable HCC. METHODS: Sixty patients who had received ERBD or PTBD for the palliative treatment of obstructive jaundice caused by unresectable HCC between January 2006 and May 2010 were included in this retrospective study. Successful drainage, drainage patency, and the overall survival of patients were evaluated. RESULTS: Univariate analysis revealed that the overall frequency of successful drainage was higher in the ERBD group (22/29, 75.9%) than in the PTBD group (15/31, 48.4%) (P=0.029); but multivariate analysis showed marginal significance (P=0.057). The duration of drainage patency was longer in the ERBD group than in the PTBD group (82 vs 37 days, respectively, P=0.020). Regardless of what procedure was performed, the median survival time of patients who had a successful drainage was much longer than that of the patients who did not have a successful drainage (143 vs 38 days, respectively, P<0.001).CONCLUSION: Besides PTBD, ERBD may be used as the initial treatment option to improve obstructive jaundice in patients with unresectable HCC if there is a longer duration of drainage patency after a successful drainage.

关键词： hepatocellular carcinoma obstructive jaundice endoscopic retrograde biliary drainage percutaneous transhepatic biliary drainage

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Byte Frequency Based Indicators for Crypto-Ransomware Detection from Empirical Analysis

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Journal of Computer Science & Technology 2022年第2期37卷 423-442页

作者： Geun yong Kim joon-Young Paik Yeongcheol Kim Eun-Sun Cho Department of Computer Science and Engineering Chungnam National UniversityDaejeon 34134South Korea School of Computer Science and Technology Tiangong UniversityTianjin 300387China

File entropy is one of the major indicators of crypto-ransomware because the encryption by ransomware increases the randomness of file ***,entropy-based ransomware detection has certain limitations;for example,when distinguishing ransomware-encrypted files from normal files with inherently high-level entropy,misclassification is very *** addition,the entropy evaluation cost for an entire file renders entropy-based detection impractical for large *** this paper,we propose two indicators based on byte frequency for use in ransomware detection;these are termed EntropySA and DistSA,and both consider the interesting characteristics of certain file subareas termed“sample areas”(SAs).For an encrypted file,both the sampled area and the whole file exhibit high-level randomness,but for a plain file,the sampled area embeds informative structures such as a file header and thus exhibits relatively low-level randomness even though the entire file exhibits high-level *** and DistSA use“byte frequency”and a variation of byte frequency,respectively,derived from sampled *** indicators cause less overhead than other entropy-based detection methods,as experimentally proven using realistic ransomware *** evaluate the effectiveness and feasibility of our indicators,we also employ three expensive but elaborate classification models(neural network,support vector machine and threshold-based approaches).Using these models,our experimental indicators yielded an average Fl-measure of 0.994 and an average detection rate of 99.46%for file encryption attacks by realistic ransomware samples.

关键词： computer security cryptography machine learning ransomware

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Unilateral foveomacular retinitis resembling solar retinopathy among young soldiers in Korean army and associated multimodal imaging findings

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International Journal of Ophthalmology(English edition) 2020年第1期13卷 112-119页

作者： Chang Ki yoon Kyu Hyung Park Se joon Woo Department of Ophthalmology Seoul National University College of MedicineSeoul National University Bundang HospitalSeongnam 13620Korea Department of Ophthalmology Hallym University College of MedicineHallym University Kangnam Sacred Heart HospitalSeoul 07441Korea

AIM: To describe the clinical features and multimodal images of unilateral foveomacular retinitis in young Korean soldiers. METHODS: Ten patients having foveomacular retinitis were included. Fluorescein angiography, fundus autofluorescence(FAF), infrared reflectance(IR), and spectral-domain optical coherence tomography(SD-OCT) were ***: All patients were young males experienced insidious visual decline without exposure to bright light. Initial and final vision ranged from hand movement to 20/20(median 20/200) and 20/2000 to 20/20(median 20/500), respectively. Vision decreased in 6 patients while improved in two. Typical macular abnormality was yellow granular spots. SD-OCT showed ellipsoid zone(EZ) or interdigitation zone(IZ) disruption of fovea. The degree of EZ/IZ damage correlated with vision. Lesions were clearly visualized through IR and matched with SD-OCT ***: This is the first case series of foveomacular retinitis diagnosed with multimodal imaging. Foveomacular retinitis should be suspected in sudden unilateral visual decline especially in young soldiers. SD-OCT is the most important diagnostic modality.

关键词： foveomacular retinitis Korean multimodal imaging solar retinopathy soldiers unilateral

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Phase separations in graded-indium content InGaN/GaN multiple quantum wells and its function to high quantum efficiency

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Journal of Semiconductors 2012年第5期33卷 13-16页

作者：郭洪英孙元平 yong-Hoon Cho Eun-Kyung Suh Hai-joon Lee Rak-Jun Choi yoon-Bong Hahn Institute of Science and Technology for Opto-Electronic Information Yantai University Department of Physics Korea Advanced Institute of Science and Technology School of Semiconductor and Chemical Engineering Semiconductor Physics Research CenterChonbuk National University School of Chemical Engineering Chonbuk National University

Phase separations have been studied for graded-indium content In_xGa_（1-x）N/GaN multiple quantum wells（MQWs） with different indium contents by means of photoluminescence（PL）,cathodeluminescence（CL） and time-resolved PL（TRPL） *** the main emission peaks,all samples show another 2 peaks at the high and low energy parts of the main peaks in PL when excited at 10 *** images show a clear contrast for 3 samples,which indicates an increasing phase separation with increasing indium *** spectra at 15 K of the main emissions show an increasing delay of rising time with indium content,which means a carrier transferring from low indium content structures to high indium content structures.

关键词： carrier transfer phase separation graded-indium content multiple quantum wells

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Ion shielding functional separator using halloysite containing a negative functional moiety for stability improvement of Li–S batteries

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Journal of Energy Chemistry 2021年第9期30卷 334-340页

作者： yong Min Kwon Jihoon Kim Kuk Young Cho Sukeun yoon Division of Advanced Materials Engineering&Institute for Rare Metals Kongju National UniversityChungnam 31080Republic of Korea Department of Materials Science and Chemical Engineering Hanyang UniversityGyeonggi 15588Republic of Korea

Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to theienvironmental friendliness,low cost,and high specific energy ***,the low electrical conductivity of sulfur,shuttling of soluble intermediate polysulfides between electrodes,and low capacitretention have hampered their commercial *** address these issues,we use a halloysitemodulated(H-M)separator in a lithium–sulfur battery to mitigate the shuttling *** H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries,thereby selectively permitting Lions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode sideMoreover,the use of halloysite switches the surface of the separator from hydrophobic to hydrophilicconsequently improving the electrolyte wettability and adhesion between the separator and cathodeWhen sulfur-multi-walled carbon nanotube(S-MWCNT)composites are used as cathode active materialsa lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 an1527 m Ah g-1,***,there is a consistent capacity retention up to 100 cyclesAccordingly,our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.

关键词： Li–S batteries Halloysite Ion shielding Negative functional moiety Lithium polysulfides

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