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A fast and adaptive method for automatic weld defect detection in various real-time X-ray imaging systems

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China Welding 2012年第1期21卷 8-12页

作者：邵家鑫都东石涵常保华郭桂林 Key Laboratory tier Advanced materials Processing Technology MinislzT of Education Department of Mechanical Engineering Tsingbua University BeJjing 100084.mMI. ~lIm~(o)l~{n~hll〉l p(lll ~.rt

A first and effective method is proposed to detect weld deject adaptively in various Dypes of real-time X-ray images obtained in different conditions. After weld extraction and noise reduction, a proper template of median filter is used to estimate the weld background. After the weld background is subtracted from the original image, an adaptite threshold segmentation algorithm is proposed to obtain the binary image, and then the morphological close and open operation, labeling algorithm and fids＇e alarm eliminating algorithm are applied to pracess the binary image to obtain the defect, ct detection result. At last, a fast realization procedure jbr proposed method is developed. The proposed method is tested in real-time X-ray image,s obtairted in different X-ray imaging sutems. Experiment results show that the proposed method is effective to detect low contrast weld dejects with few .false alarms and is adaptive to various types of real-time X-ray imaging systems.

关键词： non-destructive testing real-time X-ray imaging weld defect automatie detection

Numerical modeling of dam-break flood through intricate city layouts including underground spaces using GPU-based SPH method

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Journal of Hydrodynamics 2013年第6期25卷 818-828页

作者：吴建松张辉杨锐 DALRYMPLE Robert A. HéRAULT Alexis Faculty of Resources and Safety Engineering China University of Mining and Technology department of Engineering Physics Tsinghua University department of Civil Engineering Johns Hopkins University Conservatoire National des Arts et Métier

This paper applies the meshfree Smoothed Particle Hydrodynamics （SPH） method with Graphical Processing Unit （GPU） parallel computing technique to investigate the highly complex 3-D dam-break flow in urban areas including underground spaces. Taking the advantage of GPUs parallel computing techniques, simulations involving more than 107 particles can be achieved. We use a virtual geometric plane boundary to handle the outermost solid wall in order to save considerable video card memory for the GPU computing. To evaluate the accuracy of the new GPU-based SPH model, qualitative and quantitative comparison to a real flooding experiment is performed and the results of a numerical model based on Shallow Water Equations （SWEs） is given with good accuracy. With the new GPU-based SPH model, the effects of the building layouts and underground spaces on the propagation of dambreak flood through an intricate city layout are examined.

关键词： dam-break flood city layouts Graphical Proceeding Unit (GPU) Smoothed Particle Hydrodynamics (SPH) method

Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications

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Chinese Physics B 2014年第3期23卷 13-31页

作者：孙圣男魏超朱赞赞侯仰龙 Subbu S Venkatraman 徐梽川 School of materials and Science Engineering Nanyang Technological University department of Chemical Engineering Worcester Polytechnic Institute department of materials Science and Engineering College of Engineering Peking University

Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite （Fe304） and maghemite （γ-Fe203）, usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles （SPIONs） and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging （MRI）, and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanopar- ticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.

关键词： Fe3O4 γ-Fe203 synthesis surface coating biomedical application

Effect of exchange-correlation functionals on the estimation of migration barriers in battery materials

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npj Computational materials 2022年第1期8卷 1533-1545页

作者： Reshma Devi Baltej Singh Pieremanuele Canepa Gopalakrishnan Sai Gautam department of materials Engineering Indian Institute of ScienceBengaluruKarnatakaIndia department of materials Science and Engineering National University of SingaporeSingaporeSingapore department of Chemical and Biomolecular Engineering National University of SingaporeSingaporeSingapore

Facile ionic mobility within host frameworks is crucial to the design of high-energy-density batteries with high-power-densities,where the migration barrier(Em)is the governing ***,we assess the accuracy and computational performance of generalized gradient approximation(GGA),the strongly constrained and appropriately normed(SCAN),and their Hubbard U corrections,GGA+U and SCAN+U,within the density functional theory-nudged elastic band framework,in the prediction of Em as benchmarked against experimental ***,we observe SCAN to be more accurate than other frameworks,on average,albeit with higher computational costs and convergence difficulties,while GGA is a feasible choice for“quick”and“qualitative”Em ***,we quantify the sensitivity of Em with adding uniform background charge and/or the climbing image approximation in solid electrolytes,and the Hubbard U correction in *** findings will improve the quality of Em predictions which will enable identifying better materials for energy storage applications.

关键词： correction Hubbard approximation

Electroluminescence from pure resonant states in hBN-based vertical tunneling junctions

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Light(Science & Applications) 2024年第8期13卷 1557-1564页

作者： Magdalena Grzeszczyk Kristina Vaklinova Kenji Watanabe Takashi Taniguchi Konstantin SNovoselov Maciej Koperski Institute for Functional Intelligent materials National University of SingaporeSingapore 117544Singapore Research Center for Functional materials National Institute for Materials ScienceTsukuba 305-0044Japan International Center for materials Nanoarchitectonics National Institute for Materials ScienceTsukuba 305-0044Japan department of materials Science and Engineering National University of SingaporeSingapore 117575Singapore

Defect centers in wide-band-gap crystals have garnered interest for their potential in applications among optoelectronic and sensor ***,defects embedded in highly insulating crystals,like diamond,silicon carbide,or aluminum oxide,have been notoriously difficult to excite electrically due to their large internal *** address this challenge,we realized a new paradigm of exciting defects in vertical tunneling junctions based on carbon centers in hexagonal boron nitride(hBN).The rational design of the devices via van der Waals technology enabled us to raise and control optical processes related to defect-to-band and intradefect *** fundamental understanding of the tunneling events was based on the transfer of the electronic wave function amplitude between resonant defect states in hBN to the metallic state in graphene,which leads to dramatic changes in the characteristics of electrons due to different band structures of constituent *** our devices,the decay of electrons via tunneling pathways competed with radiative recombination,resulting in an unprecedented degree of tuneability of carrier dynamics due to the significant sensitivity of the characteristic tunneling times on the thickness and structure of the *** enabled us to achieve a high-efficiency electrical excitation of intradefect transitions,exceeding by several orders of magnitude the efficiency of optical excitation in the sub-band-gap *** work represents a significant advancement towards a universal and scalable platform for electrically driven devices utilizing defect centers in wide-band-gap crystals with properties modulated via activation of different tunneling mechanisms at a level of device engineering.

关键词： carbide tunneling defect

Cyclopenta-fused perylene: a new soluble, stable and functionalizable rylene building block

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Science Bulletin 2015年第14期60卷 1266-1271页

作者： Wangdong Zeng Qingbiao Qi Jishan Wu department of Chemistry National University of Singapore Institute of materials Research and Engineering

We report a facile synthesis of a [l,12-b,c,d]- cyclopenta-fused perylene 5 from the parent perylene via a formylation-oxidative esterification-nucleophilic additionfollowed-by-Friedel-Crafts alkylation strategy. Compared with the perylene, dye 5 exhibits much higher solubility, smaller energy gap, and can undergo regio-selective bromination at the peri-positions. Compared with the N- annulated perylene 8, compound 5 shows lower HOMO energy level and is more stable in air. Therefore, 5 can be regarded a new versatile building block for the development of high-order soluble and stable rylenes and various perylene-based functional materials.

关键词： Organic dye Rylene Perylene Polycyclic aromatic hydrocarbon

Optimization Strategies Toward Functional Sodium-Ion Batteries

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Energy & Environmental materials 2023年第4期6卷 332-354页

作者： Jingwei Chen Gupta Adit Lun Li Yingxin Zhang Daniel H.C.Chua Pooi See Lee School of materials Science and Engineering Ocean University of ChinaQingdao 266100China School of materials Science and Engineering Nanyang Technological UniversitySingapore City 639798Singapore department of materials Science and Engineering National University of SingaporeSingapore City 117575Singapore

Exploration of alternative energy storage systems has been more than necessary in view of the supply risks haunting lithium-ion *** various alternative electrochemical energy storage devices,sodium-ion battery outstands with advantages of cost-effectiveness and comparable energy density with lithium-ion *** to the similar electrochemical mechanism,the research and development of lithium-ion batteries have forged a solid foundation for sodium-ion battery *** in sodium-ion batteries have been witnessed in terms of superior electrochemical performance and broader application ***,the strategies adopted to optimize the battery components(cathode,anode,electrolyte,separator,binder,current collector,etc.)and the cost,safety,and commercialization issues in sodium-ion batteries are summarized and *** on these optimization strategies,assembly of functional(flexible,stretchable,self-healable,and self-chargeable)and integrated sodium-ion batteries(−actuators,−sensors,electrochromic,etc.)have been *** these achievements,challenges including energy density,scalability,trade-off between energy density and functionality,cost,*** to be addressed for sodium-ion battery *** review aims at providing an overview of the up-to-date achievements in sodium-ion batteries and serves to inspire more efforts in designing upgraded sodium-ion batteries.

关键词： energy storage integration multifunctional optimization strategies sodiumion batteries

Texture Engineering to Boost the Thermoelectric Properties

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Transactions of Tianjin University 2023年第3期29卷 189-195页

作者： Kivanc Saglik Xianyi Tan Ady Suwardi Alex Qingyu Yan department of materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore Institute of materials Science and Engineering Agency for Science Technology and Research(A*STAR)Singapore 138634Singapore department of materials Science and Engineering National University of SingaporeSingapore 117575Singapore

A round 60% of useful energy is wasted in industry, homes, or transportation. Therefore, there has been increasing attention on thermoelectric materials for their ability to harvest waste heat into useful energy. The efficiency of a thermoelectric material depends on its electrical conductivity, Seebeck coefficient, and thermal conductivity in a conflicting manner which results in efficiency optimization challenges. Single crystals and polycrystalline layered materials have comparatively better thermoelectric and mechanical properties in a certain direction. Texture engineering is a special strategy that allows the exploitation of superior material properties in a specific direction. Texturing could be achieved by various sintering and deformation methods, which yield defects improving thermoelectric and mechanical properties. The results show that for(Bi,Sb)_(2)Te_(3), Bi_(2)(Se,Te)_(3), C uSbSe_(2), and SnSe, significant enhancement in the thermoelectric figure of merit is achieved by enhancing the preferred orientation. Texture engineering provides a wide range of strategies to elevate the zT of anisotropic materials to values comparable to those of their single crystalline counterparts.

关键词： Texture engineering Thermoelectricity Hot forging Layered materials Anisotropy Defects

Novel magnetic vortex nanorings/nanodiscs: Synthesis and theranostic applications

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Chinese Physics B 2015年第12期24卷 165-174页

作者：刘晓丽杨勇吴建鹏张艺凡樊海明丁军 department of materials Science and Engineering Faculty of Engineering National University of Singapore School of Chemical Engineering Northwest University

Recent discoveries in the synthesis and applications of magnetic vortex nanorings/nanodiscs in theranostic applications are reviewed. First, the principles of nanomagnetism and magnetic vortex are introduced. Second, methods for producing magnetic vortex nanorings/nanodiscs are presented. Finally, theranostic applications of magnetic vortex nanorings/nanodiscs are addressed.

关键词： magnetic nanorings/nanodiscs vortex domain magnetic resonance imaging magnetic hyperthermia