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Regular truss structure model equivalent to continuum structure

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International Journal of Agricultural and Biological Engineering 2015年第5期8卷 151-161页

作者： Won Choi JeongJae Lee Seongsoo yoon Department of Rural Systems Engineering College of Agriculture and Life SciencesSeoul National UniversitySeoul 151-921South Korea Department of Rural Systems Engineering Research Institute of Agriculture and Life SciencesCollege of Agriculture and Life SciencesSeoul National UniversitySeoul 151-921South Korea Department.of Agricultural and Rural Engineering College of AgricultureLife and Environments SciencesChungbuk National UniversityChungbuk 362-763South Korea

It is difficult to solve the structural problems related to agricultural engineering,due to the wide ranges of the means of related variables and complex structural *** these reasons,discrete models are required that are able to replace or simplify solid structure components used in traditional analysis ***,the objective of this study was to develop a regular truss structure model that behaves the same way as a solid *** was assumed that if a unit element consists of truss elements with each hinge at the end of the element and the size of the element is infinitesimal,the stress distribution and displacement field will be constant throughout the domain of the unit ***,the behavior of the truss element was assumed to be in a linear state in a two-dimensional *** law of energy conservation,based on the theory of elasticity,was applied to determine the equilibrium conditions between discretized and solid *** restrictive condition that we obtained revealed that applications are limited to only ideal elastic materials with a Poisson’s ratio of 1 to *** volumetric ratio of the equivalent truss to the continuum structures was 3:1,regardless of the size or number of the *** calculate the internal stress and strain of the unit element,the geometric relationships of each truss member,which has its own role against different stress directions,were *** calculated von Misses stresses were used to verify this *** concentrations,as explained based on Saint Venant’s principle,were also observed in the equivalent truss structure *** main stress paths,indicating the areas where reinforcement bars should be placed,were successfully shown without the requirement that each element be transformed in the direction of principal stress;this was done by eliminating elements with only compressive and near-zero stresses.

关键词： structural analysis regular mesh equivalent truss structure model discretized element energy method

Impression of prognosis regarding pathologic stage after preoperative chemoradiotherapy in rectal cancer

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World Journal of Gastroenterology 2015年第2期21卷 563-570页

作者： Kyungyeon Hwang In Ja Park chang Sik Yu Seok-Byung Lim Jong Lyul Lee Yong Sik yoon Chan Wook Kim Jin Cheon Kim Department of Colon and Rectal Surgery University of Ulsan College of Medicine and Asan Medical CenterSeoul 138-736South Korea

AIM: To ascertain pathologic stage as a prognostic indicator for rectal cancer patients receiving preoperative chemoradiotherapy(PCRT).METHODS: Patients with mid- and low rectal carcinoma(magnetic resonance imaging- based clinical stage Ⅱ or Ⅲ) between 2000 and 2009 and treated with curative radical resection were identified. Patients were divided into two groups: PCRT and No-PCRT. Recurrence-free survival(RFS) was examined according to pathologic stage and addition of adjuvant ***: Overall, 894 patients were identified. Of these, 500 patients received PCRT. Adjuvant chemotherapy was delivered to 81.5% of the No-PCRT and 94.8% of the PCRT patients. Adjuvant radiotherapy was given to 29.4% of the patients in the No PCRT group. The 5-year RFS for the No-PCRT group was 92.6% for StageⅠ, 83.3% for Stage Ⅱ, and 72.9% for Stage Ⅲ. The 5-year RFS for the PCRT group was 95.2% for yp Stage 0, 91.7% for yp StageⅠ, 73.9% for yp Stage Ⅱ, and 50.7% for yp Stage Ⅲ.CONCLUSION: Pathologic stage can predict prognosis in PCRT patients. Five-year RFS is significantly lower among PCRT patients than No-PCRT patients in pathologic stage Ⅱ and Ⅲ. These results should be taken into account when considering adjuvant treatment for patients treated with PCRT.

关键词： Preoperative Chemoradiotherapy Rectal cancer Patho

Effects of multi-dopants （Zn and Ho） in stabilizing spinel structure for cathode materials in lithium rechargeable batteries-Novel chelated sol-gel synthesis

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Particuology 2016年第1期14卷 87-95页

作者： R. Thirunakaran Taewhan Kim Won-Sub yoon CSIR-Central Electrochemical Research Institute Karaikudi 630 006 Tamil Nadu India Department of Energy Science Sungkyunkwan University Suwon 440-746 South Korea

Multi-doped spinels, namely LiMn204 and LiZnxHoyMn2 x yO4 （x=0.10-0.18; y= 0.02-0.10）, for use as cathode materials for lithium-ion rechargeable batteries were synthesized via sol-gel method, using lauric acid as the chelating agent, to obtain micron-sized particles. The physical properties of the synthesized samples were investigated using differential thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy, energy-dispersive X-ray analysis, and electrochemical methods. XRD showed that LiMn204 and LiZnxHoyMn2_x y04 have high degrees of crystallinity and good phase purities. The SEM images of LiMn204 showed an ice-cube morphology with particles of size 1 μm. Charge-discharge studies showed that undoped LiMn2 O4 delivered the discharge capacity of 124 mA h/g with coulombic efficiency of 95% during the first cycle, whereas doped spinels delivered discharge capacities of 125, 120, and 127 mA h/g in the first cycle with coulombic efficiencies of 96%, 91%, and 91%, respectively.

关键词： Holmium Zinc Lauric acid Sol-gel Spinel cathode Lithium-ion battery

Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

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npj Computational Materials 2021年第1期7卷 41-48页

作者： Wei Luo Yuma Nakamura Jinseon Park Mina yoon Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN 37831USA Department of Physics and Astronomy University of TennesseeKnoxvilleTN 37916USA

Recent experiments identified Co_(3)Sn_(2)S_(2) as the first magnetic Weyl semimetal(MWSM).Using first-principles calculation with a global optimization approach,we explore the structural stabilities and topological electronic properties of cobalt(Co)-based shandite and alloys,Co_(3)MM’X_(2)(M/M’=Ge,Sn,Pb,X=S,Se,Te),and identify stable structures with different Weyl *** a tight-binding model,for the first time,we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers,while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms,Sn,Ge,and *** Co_(3)SnPbS_(2) alloy exhibits two distinguished topological phases,depending on the relative positions of the Sn and Pb atoms:a three-dimensional quantum anomalous Hall metal,and a MWSM phase with anomalous Hall conductivity(~1290Ω^(−1) cm^(−1))that is larger than that of Co_(2)Sn_(2)S_(2).Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

关键词： stability alloy magnetic

A Steam-Plasma Igniter for Aluminum Powder Combustion

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Plasma Science and Technology 2015年第5期17卷 392-401页

作者： Sanghyup LEE Kwanyoung NOH Jihwan LIM Woongsup yoon Mechanical Engineering Department of Yonsei University

High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high- melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.

关键词： steam plasma igniter aluminum emission spectroscopy energetic metal fuels powder ignition and combustion optical

Thermo-physical Characteristics of Nickel-coated Aluminum Powder as a Function of Particle Size and Oxidant

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Chinese Journal of Mechanical Engineering 2016年第6期29卷 1244-1255页

作者： LEE Sanghyup NOH Kwanyoung LIM Jihwan yoon Woongsup Advanced Energy and Propulsion Laboratory Department of Mechanical Engineering Yonsei University Missile System Integration / propulsion Center Hanwha Corp.

Aluminum particles 15-25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size（15-25 μm, 74-105 μm, and 2.38 mm） and oxidizer（air, CO2, and argon）, the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry （TGA/DSC） enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

关键词： nickel-coated aluminum TGA/DSC aluminum ignition combustion intermetallic reaction

Recent progress in quasi-two-dimensional and quantum dot perovskite light-emitting diodes harnessing the diverse effects of ligands:A review

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Nano Research 2022年第7期15卷 6449-6465页

作者： Yurim Bae Jun Ryu Saemon yoon Dong-Won Kang School of Energy Systems Engineering Chung-Ang UniversitySeoul 06974Republic of Korea Department of Smart City Chung-Ang UniversitySeoul 06974Republic of Korea

Halide perovskites have been extensively studied for use as light-emitting diodes(LEDs)in next-generation displays due to their beneficial characteristics,including their high color purity and wide color *** perovskites can be categorized into four representative structures:three-dimensional(3D)bulk,two-dimensional(2D),quasi-two-dimensional(quasi-2D),and quantum dot(QD).Recently,excellent advances in the performance of perovskite LEDs(PeLEDs),especially those with quasi-2D and QD architectures,have been demonstrated with the incorporation of organic chain *** can both modify the structure of PeLEDs,such as forming multi-quantum wells in quasi-2D PeLEDs and essential passivation layers in QD PeLEDs,and also enhance their optical *** appropriate use of ligands in PeLEDs can thus lead to greater luminescence,current efficiency,power efficiency,and external quantum *** this review,the principal roles of ligands in quasi-2D and QD PeLEDs are systematically ***,current limitations and future perspectives are discussed in detail.

关键词： perovskites light emitting diode ligands quasi-two-dimensional(quasi-2D) quantum dot

Friction stir butt welding of A5052-O aluminum alloy plates

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中国有色金属学会会刊：英文版 2012年第S3期22卷 619-623页

作者： Sung-Ook yoon Myoung-Soo KANG Hyun-Bin NAM Yong-Jai KWON Sung-Tae HONG Jin-Chun KIM Kwang-Hak LEE chang-Yong LIM Jong-Dock SEO School of Materials Science and Engineering University of Ulsan School of Mechanical Engineering University of Ulsan Technical Research Laboratories Shin Young Co.Ltd.

Friction stir butt welding (FSW) between A5052-O aluminum alloy plates with a thickness of 2 mm was *** rotation speeds of the welding tool were 2000 and 3000 r/min,*** traverse speed was ranged from 100 mm/min to 900 mm/*** defect-free welds with the very smooth surface morphology were successfully obtained,except for at the welding condition of 3000 r/min and 100 mm/*** onion ring structure was observed in the friction-stir-welded zone (SZ) at the condition of 2000 r/min and 100 mm/*** all the welding conditions,the grain size of the SZ was smaller than that of the base metal,and was decreased with the decrease of the tool rotation speed and with the increase of the tool traverse *** stir zone exhibited higher average hardness than the base *** decrease of the tool rotation speed and the increase of the tool traverse speed resulted in the increase in the average hardness of the *** tensile strength of the FSWed plates was similar to that of the base metal,except for at the welding condition of 3000 r/min and 100 mm/*** total elongation of the FSWed plates was lower than that of the base metal.

关键词： friction stir butter welding A5052-O aluminum alloy microstructure mechanical property

New approaches to gastric cancer staging:Beyond endoscopic ultrasound,computed tomography and positron emission tomography

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World Journal of Gastroenterology 2014年第38期20卷 13783-13790页

作者： Hyuk yoon Dong Ho Lee Department of Internal Medicine Seoul National University Bundang Hospital Department of Internal Medicine and Liver Research Institute Seoul National University College of Medicine

Currently, there is no single gold standard modality for staging of gastric cancer and several methods have been used complementarily in the each clinical situation. To make up for the shortcomings of conventional modalities such as endoscopic ultrasound, computed tomography and 18F-fluoro-2-deoxyglucose positron emission tomography, numerous attempts with new approaches have been made for gastric cancer staging. For T staging, magnifying endoscopy with narrow-band was evaluated to differentiate mucosal cancer from submucosal cancer. Single/double contrast-enhanced ultrasound and diffusion-weighted magnetic resonance imaging were also tried to improve diagnostic accuracy of gastric cancer. For intraoperative staging with sentinel node mapping, indocyanine green infrared and fluorescence imaging was introduced. In addition, to detect micrometastasis, real-time reverse transcription-polymerase chain reaction system with multiple markers was studied. Staging laparoscopy using 5-aminolevulinic acid-mediated photodynamic diagnosis and percutaneous diagnostic peritoneal lavage were also evaluated. However, most studies reporting new staging methods is preliminary and further studies for validation in clinical practice are needed. In this mini-review, we discuss new progress in gastric cancer staging. Especially, we focus on new diagnostic approach to gastric cancer staging beyond the conventional modalities and briefly review the remarkable clinical results of the studies published over the past three years.

关键词： Gastric cancer Neoplasm staging Diagnostic accuracy New methods New approaches