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Numerical Visualization of Air Intake Induced by Free Surface Vortex

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Journal of Thermal Science 2017年第6期26卷 540-544页

作者： Young kyu Park Mohan Kumar Dey Yoon Hwan choi Yeon Won Lee Research Institute of Industrial Science & Technology Pukyong National University Busan Korea Interdisciplinary Program of Biomedical Mechanical and Electrical Engineering Pukyong National University Busan Korea Department of Mechanical Design Engineering Pukyong National University Busan Korea

Free surface vortex control is vital in a pump sump system because the air absorbed by free surface vortex induc- es noise, vibration, and cavitation corrosion on the pumping system. In this study, the change of free surface vor- tex and air absorption in a pump intake has been investigated by the Volume of Fraction （VOF） method with steady multiphase flow model in order to represent the behavior of the free surface vortex exactly. The homoge- neous free surface model is used to apply interactions of air and water. The results show that air intake by the free surface vortex motion can be visualized using the iso-surface of air volume fraction. The vortices make an air column from the free surface to the pump intake. Also, it was found that the flee surface vortex can be controlled by installing curtain walls.

关键词： free surface vortex numerical visualization curtain wall air intake

海产养殖水体中复杂组分致光催化剂杀菌失活的机理研究

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生态环境学报 2025年第1期34卷 89-98页

作者：王艺霓蔡仪威孙彤李桂英 Wonyong choi 安太成广东工业大学环境科学与工程学院/广东工业大学环境健康与污染控制研究院/环境催化与健康风险控制重点实验室/粤港澳污染物暴露与健康联合实验室广东广州510006

光催化技术在养殖水体净化方面具有很好的应用前景。然而,海水水产养殖水体组分复杂,造成光催化剂失活的机理鲜有研究。以典型近海养殖水体为研究对象,重点探讨以腐殖酸为典型天然有机物(NOM)组分,以细菌和真菌作为主要微生物,对光催化... 详细信息

光催化技术在养殖水体净化方面具有很好的应用前景。然而,海水水产养殖水体组分复杂,造成光催化剂失活的机理鲜有研究。以典型近海养殖水体为研究对象,重点探讨以腐殖酸为典型天然有机物(NOM)组分,以细菌和真菌作为主要微生物,对光催化剂TiO_(2)纳米管杀菌失活的影响机制进行研究。发现在汕头海水养殖水体中,0-8 h细菌(k=0.23 h^(-1))和真菌(k=0.32 h^(-1))具有较高的杀菌效率,在8-24 h阶段细菌杀菌效率(k=0.03 h^(-1))开始下降,在湛江海水养殖水体中也观察到同样的趋势;在珠海海水养殖水体中,前0-8h对细菌(k=0.14h^(-1))有较高的杀灭效率,在0-6h内对真菌也具备较高的杀灭效率(k=0.24 h^(-1)),细菌和真菌分别在8 h和6 h时杀菌效率变化明显。并且3个地点的水样分别在杀菌48、48、8h后菌体数量呈现增长的现象,这可能与菌体的VBNC状态有关。同时,通过微生物多样性测定发现在海水养殖水体中假单胞菌为优势菌种;衣原体,支原体和军团菌3种细菌菌属在杀灭过程中细菌的占比减少程度最大。通过使用稳态瞬态荧光光谱仪结合PARAFAC和荧光区域积分法(FRI)得到3个不同地区水体样品的腐殖酸的降解程度均在40%以上;最后通过ATR-FTIR、SEM-EDS等实验表征,验证了在杀菌过程中,腐殖酸中间产物以及菌体破裂泄漏的生物分子附着在TiO_(2)纳米管表面并堵塞部分微孔,堵塞了催化剂表面的活性位点,致使光催化剂加速失活。对光催化技术应用于环境复杂水体处理中的失活现象和机理进行研究,可填补此领域的空白。

关键词：光催化剂失活 TiO_(2)催化剂海水养殖水体微生物灭活腐殖质

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Enhanced biometric encryption algorithm for private key protection in BioPKI system

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Journal of Central South University 2014年第11期21卷 4286-4290页

作者： Cheol-Joo Chae Kwang-nam choi Kiseok choi Jae-Soo Kim Yong Ju Shin Korea Institute of Science and Technology Information 245 DaehangnoYuseong-gu Daejeon Korea

Protection of private key is the most critical part in public key infrastructure(PKI) system since it depends on the confidentiality of private key. Thread of password detection has been known as the vulnerability in this PKI system. Recently, studies have been conducted on Bio PKI system that uses the biometric information of users in order to replace the password type of private key protection in PKI system. However, Bio PKI system also has vulnerability in that biometric information used for protection of private key cannot be reused once it is stolen or lost. So, we propose the method to protect the private key using FIDSEQi which binds sequence to biometric information. The proposed method enhances reusability of biometric information and presents higher attack complexity than the method of authentication by cross matching single biometric information.

关键词： BioPKI system fingerprint biometric encryption secret share

Enhanced performance of solution-processed carbon nanotube transparent electrodes in foldable perovskite solar cells through vertical separation of binders by using eco-friendly parylene substrate

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Carbon Energy 2024年第7期6卷 83-93页

作者： Unsoo Kim Jeong-Seok nam Jungjin Yoon Jiye Han Mansoo choi Il Jeon Department of Mechanical Engineering Seoul National UniversitySeoulRepublic of Korea Global Frontier Center for Multiscale Energy Systems Seoul National UniversitySeoulRepublic of Korea Frontier Energy Solution SeoulRepublic of Korea Department of Nano Engineering Department of Nano Science and TechnologySKKU Advanced Institute of Nanotechnology(SAINT)Sungkyunkwan University(SKKU)SuwonRepublic of Korea Department of Materials Science and Engineering Pennsylvania State UniversityUniversity ParkPennsylvaniaUSA

The successful utilization of an eco-friendly and biocompatible parylene-C substrate for high-performance solution-processed double-walled carbon nanotube(CNT)electrode-based perovskite solar cells(PSCs)was *** the use of a novel inversion transfer technique,vertical separation of the binders from the CNTs was induced,rendering a stronger p-doping effect and thereby a higher conductivity of the *** resulting foldable devices exhibited a power conversion efficiency of 18.11%,which is the highest reported among CNT transparent electrode-based PSCs to date,and withstood more than 10,000 folding cycles at a radius of 0.5 mm,demonstrating unprecedented mechanical ***,solar modules were fabricated using entirely laser scribing processes to assess the potential of the solution-processable nanocarbon ***,this is the only one to be processed entirely by the laser scribing process and to be biocompatible as well as eco-friendly among the previously reported nonindium tin oxide-based perovskite solar modules.

关键词： double-walled carbon nanotubes parylene substrates perovskite modules perovskite solar cells solution-processable electrodes surfactant removal

Diagnosis of Middle Ear Diseases Based on Convolutional Neural Network

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Computer Systems Science & Engineering 2023年第8期46卷 1521-1532页

作者： Yunyoung nam Seong Jun choi Jihwan Shin Jinseok Lee Department of Computer Science and Engineering Soonchunhyang UniversityAsan31538Korea Department of Otolaryngology-Head and Nech Surgery Soonchunhyang University College of MedicineCheonan HospitalCheonan31151Korea Department of Biomedical Engineering Kyung Hee UniversityYonginKorea

An otoscope is traditionally used to examine the eardrum and ear canal.A diagnosis of otitis media(OM)relies on the experience of *** an examiner lacks experience,the examination may be difficult and *** paper presents an ear disease classification method using middle ear images based on a convolutional neural network(CNN).Especially the segmentation and classification networks are used to classify an otoscopic image into six classes:normal,acute otitis media(AOM),otitis media with effusion(OME),chronic otitis media(COM),congenital cholesteatoma(CC)and traumatic perforations(TMPs).The Mask R-CNN is utilized for the segmentation network to extract the region of interest(ROI)from otoscopic *** extracted ROIs are used as guiding features for the *** classification is based on transfer learning with an ensemble of two CNN classifiers:EfficientNetB0 and *** proposed model was trained with a 5-fold cross-validation *** proposed method was evaluated and achieved a classification accuracy of 97.29%.

关键词： Otitis media convolutional neural network acute otitis media otitis media with effusion chronic otitis media congenital cholesteatoma traumatic perforation Mask R-CNN

Virtual Mold Technique in Thermal Stress Analysis during Casting Process

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Journal of Materials Science & Technology 2008年第3期24卷 359-363页

作者： Si-Young Kwak Jae-Wook Baek Jeong-Ho nam Jeong-Kil choi E-Design Center Korea Institute of Industrial Technology Department of Virtual Engineering Korea University of Science & Technology

It is important to analyse the casting product and the mold at the same time considering thermal contraction of the casting and thermal expansion of the mold. The analysis considering contact of the casting and the mold induces the precise prediction of stress distribution and the defect such as hot tearing. But it is difficult to generate FEM mesh for the interface of the casting and the mold. Moreover the mesh for the mold domain spends lots of computational time and memory for the analysis due to a number of meshes. Consequently we proposed the virtual mold technique which only uses mesh of the casting part for thermal stress analysis in casting process. The spring bar element in virtual mold technique is used to consider the contact of the casting and the mold. In general, a volume of the mold is much bigger than that of casting part, so the proposed technique decreases the number of mesh and saves the computational memory and time greatly. In this study, the proposed technique was verified by the comparison with the traditional contact technique on a specimen. And the proposed technique gave satisfactory results.

关键词： Casting process Thermal stress analysis Virtual mold

Sexual dimorphism and sex-differential migration of Little Buntings(Emberiza pusilla)at an East Asian stopover site

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Avian Research 2022年第1期13卷 87-93页

作者： Sook-Young Cho Hyun-Young nam Se-Young Park Chang-Yong choi Bird Research Center Korea National Park Research InstituteJeonnam58863Republic of Korea Division of Zoology Honam National Institute of Biological ResourcesMokpo58762Republic of Korea School of Biological Sciences College of Natural SciencesSeoul National UniversitySeoul08826Republic of Korea Department of Agriculture Forestry and BioresourcesCollege of Agriculture and Life SciencesSeoul National UniversitySeoul08826Republic of Korea

Sex differences in morphology provide key information for understanding a species'morphological adaptations in relation to the evolution of sexual *** migratory birds,morphological traits have adapted to long-distance travel,and sexual dimorphism is typically related to sex-differential migration *** Buntings(Emberiza pusilla)have one of the longest migrations and are the least dichromatic species among the Emberiza *** this study,we measured sexual size dimorphism and sexual dichromatism of Little Buntings in relation to the spring arrival dates at a stopover site in *** length was the most important predictor for identifying sex;the wings of males were longer than those of *** also had a significantly stronger chestnut color of the head feathers than females,but this color difference was more prominent in the spring than in the *** arrived earlier than females by four *** dates correlated with both size and color,but unlike other bunting species previously studied in the same area,there was no clear sex-differential trend in the relationship between arrival date and morphological *** differences in the degree of sexual dichromatism suggest that chestnut plumage coloration can be used as a social or sexual signal of males in the breeding *** correlation of size and color to early arrival regardless of sex may indicate that a preference for assortative mating exists or that a sex-differential migration strategy is not clearly defined in the early stages of northward *** findings on the sexual dimorphism of Little Buntings provide insight into the evolution of the sex-differential migration of buntings in the East Asian Flyway.

关键词： Digital photography Emberiza pusilla Little Bunting Protandrous migration Sexual dichromatism Sexual dimorphism

Uniaxially crumpled graphene as a platform for guided myotube formation

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Microsystems & Nanoengineering 2019年第1期5卷 144-153页

作者： Junghoon Kim Juyoung Leem Hong nam Kim Pilgyu Kang Jonghyun choi Md Farhadul Haque Daeshik Kang SungWoo nam Department of Mechanical Science and Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA Center for BioMicrosystems Brain Science InstituteKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Division of Bio-Medical Science and Technology KIST SchoolKorea University of Science and TechnologySeoul 02792Republic of Korea Department of Mechanical Engineering George Mason UniversityFairfaxVA 22030USA Department of Mechanical Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Materials Science and Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA

Graphene,owing to its inherent chemical inertness,biocompatibility,and mechanical flexibility,has great potential in guiding cell behaviors such as adhesion and ***,due to the two-dimensional(2D)nature of graphene,the microfabrication of graphene into micro/nanoscale patterns has been widely adopted for guiding cellular *** this study,we report crumpled graphene,i.e.,monolithically defined graphene with a nanoscale wavy surface texture,as a tissue engineering platform that can efficiently promote aligned C2C12 mouse myoblast cell *** imparted out-of-plane,nanoscale crumpled morphologies to flat graphene via compressive straininduced *** C2C12 mouse myoblast cells were seeded on the uniaxially crumpled graphene,not only were the alignment and elongation promoted at a single-cell level but also the differentiation and maturation of myotubes were enhanced compared to that on flat *** results demonstrate the utility of the crumpled graphene platform for tissue engineering and regenerative medicine for skeletal muscle tissues.

关键词： Uniaxial graphene alignment

Nanocrystalline Iron Pyrophosphate-Regulated Amorphous Phosphate Overlayer for Enhancing Solar Water Oxidation

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Nano-Micro Letters 2022年第12期14卷 387-400页

作者： Chengkai Xia Yuankai Li Minyeong Je Jaekyum Kim Sung Min Cho Chang Hyuck choi Heechae choi Tae-Hoon Kim Jung kyu Kim School of Chemical Engineering Sungkyunkwan University(SKKU)2066 Seobu-roJangan-guSuwon 16419Republic of Korea Theoretical Materials and Chemistry Group Institute of Inorganic ChemistryUniversity of CologneGreinstr.650939 CologneGermany Department of Chemistry Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Materials Science and Engineering Engineering Research CenterChonnam National UniversityGwangju 61186Republic of Korea

A rational regulation of the solar water splitting reaction pathway by adjusting the surface composition and phase structure of catalysts is a substantial approach to ameliorate the sluggish reaction kinetics and improve the energy conversion *** this study,we demonstrate a nanocrystalline iron pyrophosphate(Fe_(4)(P_(2)O_(7))_(3),FePy)-regulated hybrid overlayer with amorphous iron phosphate(FePO_(4),FePi)on the surface of metal oxide nanostructure with boosted photoelectrochemical(PEC)water *** manipulating the facile electrochemical surface treatment followed by the phosphating process,nanocrystalline FePy is localized in the FePi amorphous overlayer to form a heterogeneous hybrid *** FePy-regulated hybrid overlayer(FePy@FePi)results in significantly enhanced PEC performance with long-term *** with the homogeneous FePi amorphous overlayer,FePy@FePi can improve the charge transfer efficiency more significantly,from 60% of FePi to 79%of FePy@*** density-functional theory calculations reveal that the coexistence of FePi and FePy phases on the surface of metal oxide results in much better oxygen evolution reaction kinetics,where the FePi was found to have a typical down-hill reaction for the conversion from OH*to O_(2),while FePy has a low free energy for the formation of OH*.

关键词： Water oxidation Photoelectrochemical cell Metal pyrophosphate Electrochemical surface treatment