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Characteristics of bifurcation and buckling load of space truss in consideration of initial imperfection and load mode

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第3期14卷 206-218页

作者： Su-deok SHON seung-jae lee Kang-guk lee School of Architectural Engineering Korea University of Technology and Education1800 ChungjeolroCheonan ChungnamRepublic of Korea Research Center for Urban Affair Kyungil UniversityGyeongsan-city GyeongbukRepublic of Korea

This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss,which were sensitive to initial *** critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness *** two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence,and characteristics of the parameters as defined by the load ratio of the center node and surrounding node,as well as rise-span ratio were *** sensitivity to the imperfection of the initial shape of the two-free-nodes example,which occurs due to snapping at the critical point,resulted in bifurcation before the limit point due to the buckling mode,and the buckling load was reduced by the increase in the amount of *** two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes,and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or ***,the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified *** star dome,which was used to examine the influence among several nodes,indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was ***,global buckling is occurred with reaching bifurcation point as the value of load ratio was higher,and the buckling load level was about 50%-70% of load level at limit point.

关键词： Space truss Geometric nonlinearity Initial imperfection Snap-through Bifurcation Global buckling

Numerical evaluation of buckling behavior in space structure considering geometrical parameters with joint rigidity

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Journal of Central South University 2014年第3期21卷 1115-1124页

作者： Su-Deok Shon Kyung-Ju Hwang seung-jae lee School of Architectural Engineering Korea University of Technology and Education School of Architecture University of Seoul

The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stiffness of joint system, which is neither total pin assumption nor perfect fix condition, is very important to apply to the real single layer space one. Therefore, the purpose of this work was to investigate the buckling behavior of single layer space structure, using the development of the upgraded stiffness matrix for the joint rigidity. To derive tangential stiffness matrix, a displacement function was assumed using translational and rotational displacement at the node. The geometrical nonlinear analysis was simulated not only with perfect model but also with imperfect one. As a result, the one and two free nodal numerical models were investigated using derived stiffness matrix. It was figured out that the buckling load increases in proportion to joint rigidity with rise-span ratio. The stability of numerical model is very sensitive with the initial imperfection, responding of bifurcation in the structure.

关键词： space frame geometric nonlinearity snap-through bifurcation initial imperfection joint rigidity

Milk protein-shelled gold nanoparticles with gastrointestinally active absorption for aurotherapy to brain tumor

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Bioactive Materials 2022年第2期7卷 35-48页

作者： Hyung Shik Kim seung jae lee Dong Yun lee Department of Bioengineering College of Engineeringand BK FOUR Biopharmaceutical Innovation Leader for Education and Research GroupHanyang UniversitySeoul04763Republic of Korea Institute of Nano Science and Technology Hanyang UniversitySeoul04763Republic of Korea

Orally absorbable gold nanoparticles(AuNP)having cancer ablation therapy is strongly demanded to treat glioblastoma multiforme(GBM)for patients with its highest incidence ***,we develop a milk protein lactoferrin-conjugated AuNP for its oral absorption and targeting to the GBM through the interaction between lactoferrin(Lf)and lactoferrin receptor(LfR)that is highly expressed in the intestine,blood-brain barrier and *** stability and long circulation of AuNP,glutathione and polyethylene glycol(PEG)is introduced,which is called to *** Lf-PEG-AuNP are orally administered to orthotopic GBM-bearing mice,11-fold and 8-fold higher concentrations of AuNP are measured in bloodstreams and GBM in the brain,respectively,compared with ***,orally administered Lf-PEG-AuNP exhibit an outstanding temperature rise in GBM by irradiating laser and significantly reduce tumor ***,we suggest that the Lf-PEG-AuNP can fundamentally target GBM in the brain through oral absorption,and that its efficient photothermal therapy is possible.

关键词： intestine absorption gastrointestinal

The Impact of Ecosystem Functional Type Changes on the La Plata Basin Climate

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Advances in Atmospheric Sciences 2013年第5期30卷 1387-1405页

作者： seung-jae lee E. Hugo BERBERY Domingo ALCARAZ-SEGURA Department of Atmospheric and Oceanic Science University of Maryland College Park Department of Botany University of Granada

In this paper, the effects of land cover changes on the climate of the La Plata Basin in southern South America are investigated using the Weather and Research Forecasting （WRF） Model configured on a 30/10- km two-way interactive nested grid. To assess the regional climate changes resulting from land surface changes, the standard land cover types are replaced by time-varying Ecosystem Functional Types （EFTs）, which is a newly devised land-cover classification that characterizes the spatial and interannual variability of surface vegetation dynamics. These variations indicate that natural and anthropogenic activities have caused changes in the surface physical parameters of the basin, such as albedo and roughness length, that contributed to regional climate changes. EFTs are obtained from functional attributes of vegetation computed from properties of the Normalized Difference Vegetation Index （NDVI） to represent patches of the land surface with homogeneous energy and gas exchanges with the atmosphere. Four simulations are conducted, each experimental period ranging from September to November in two contrasting years, 1988 and 1998. The influence of an identical EFT change on the surface heat fluxes, 2-m temperature and humidity, 10-m winds, convective instabilities and large-scale moisture fluxes and precipitation are explored for 1988 （a dry year） and 1998 （a wet year）. Results show that the surface and atmospheric climate has a larger response to the same EFT changes in a dry year for 2-m temperature and 10-m wind; the response is larger in a wet year for 2-m water vapor mixing ratio, convective available potential energy, vertically integrated moisture fluxes and surface precipitation. For EFTs with high productivity and a weak seasonal cycle, the near- surface temperature during the spring of 1988 and 1998 increased by as much as I^C in the central and western portions of La Plata Basin. Additionally, for higher productivity EFTs, precipitation differences were g

关键词： EFT ecosystem function land cover La Plata Basin model simulation

Effect of Implementing Ecosystem Functional Type Data in a Mesoscale Climate Model

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Advances in Atmospheric Sciences 2013年第5期30卷 1373-1386页

作者： seung-jae lee E. Hugo BERBERY Domingo ALCARAZ-SEGURA Complex Systems Science Laboratory Department of Landscape Architecture and Rural Systems Engineering Seoul National University Department of Atmospheric and Oceanic Science University of Maryland College Park Department of Botany University of Granada

In this paper, we introduce a new concept of land-surface state representation for southern South America, which is based on ＂functional＂ attributes of vegetation, and implement a new land-cover （Ecosystem Functional Type, hereafter EFT） dataset in the Weather and Research Forecasting （WRF） model. We found that the EFT data enabled us to deal with functional attributes of vegetation and time-variant features more easily than the default land-cover data in the WRF. In order to explore the usefulness of the EFT data in simulations of surface and atmospheric variables, numerical simulations of the WRF model, using both the US Geological Survey （USGS） and the EFT data, were conducted over the La Plata Basin in South America for the austral spring of 1998 and compared with observations. Results showed that the model simulations were sensitive to the lower boundary conditions and that the use of the EFT data improved the climate simulation of 2-m temperature and precipitation, implying the need for this type of information to be included in numerical climate models.

关键词： Ecosystem Functional Type WRF land cover climate simulation

Synergistically coupling of Ni–Fe LDH arrays with hollow Co–Mo sulfide nanotriangles for highly efficient overall water splitting

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Rare Metals 2024年第2期43卷 522-532页

作者： Yun jae lee seung-Keun Park Department of Advanced Materials Engineering Chung-Ang UniversityAnseongGyeonggi-do17546Republic of Korea Department of Intelligent Energy and Industry Chung-Ang University84 Heukseok-ro Dongjak-guSeoul06974Republic of Korea Western Seoul Center Korea Basic Science Institute150 Bugahyeon-roSeodaemun-guSeoul03759Republic of Korea

Developing bifunctional catalysts that can catalyze both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is pivotal to commercializing large-scale water ***,a novel hollow nanotriangle composed of NiFe LDH-CoMoS_(x) heterojunction(H-CMSx@NiFe LDH)is proposed as a highly efficient bifunctional electrocatalyst for both OER and *** fabricate a heterojunction system,ultra-thin nickel–iron layered double hydroxide(NiFe LDH)nanosheets are uniformly electrodeposited onto a metal–organic framework-derived hollow CoMoS_(x) *** strong coupling of CoMoS_(x) and NiFe LDH catalysts forms the intimate heterojunction interfaces to facilitate interfacial charge transfer,which is favorable to enhance the bifunctional catalytic ***,the large void of CoMoS_(x) nanotriangles and interconnected ultra-thin NiFe LDH nanosheets result in good electrolyte penetration and gas ***,the as-prepared H-CMSx@NiFe LDH on nickel foam(NF)exhibits an impressive catalytic activity and durability for OER and HER activities,delivering a current density of 100 mA·cm^(−2) at the small overpotentials of 214 and 299 mV in OER and HER,***,H-CMSx@NiFe LDH/NF proves to be an effective electrode for an alkaline electrolyzer,as a voltage of only 1.99 V is enough to achieve a current density voltage of only 1.99 V is enough to achieve a current density of 400 mA·cm^(−2) with no degradation in performance over 50 h.

关键词： Overall water splitting Metal-organic framework Molybdenum sulfide Layered double hydroxide Heterojunction

Development of a Powder Extruder System for Dual-pore Tissue-engineering Scaffold Fabrication

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Journal of Bionic Engineering 2019年第4期16卷 686-695页

作者： Nae-Un Kang Myoung Wha Hong Young Yul Kim Young-Sam Cho seung-jae lee Department of Mechanical Design Engineering College of EngineeringWonkwang University460 Iksandae-roIks an Jeonbuk570-749Republic of Korea Department of Orthopedics Daejeon StMary's HospitalCatholic University of Korea64Daeheung-i Jung-guDaejeon301-723Republic of Korea

In this study,we developed a powder extruder system that can extrude and deposit powder mixtures to overcome the reported limitations of conventional dualpore scaffold manufacturing *** evaluate the extrusion and deposition capability of the powder extruder system,3D tissue-engineering scaffolds with dual-pore characteristics were fabricated with a PCL/PEO/NaCl(polycaprolactone/polyethylene oxide/sodium chloride)powder *** addition,to evaluate the fabricated scaffolds,their compressive modulus,morphology,and in-vitro cell activity were ***,it was confirmed that the proposed powder extruder system can fabricate dual-pore scaffolds with well-interconnected pores as well as arbitrary 3D shapes shown by the fabrication of a 3D femur-shape scaffold similar to the femur *** results of the cell proliferation and Cell Counting Kit-8(CCK-8)assays,DNA content analysis and viability assays confirm that the dual-pore scaffold fabricated by the powder extruder system improves cell attachment,proliferation,and viability.

关键词： dual-pore scaffold powder extruder system polycaprolactone 3D tissue-engineering scaffold

Novel N-doped multichannel carbon nanofiber architecture with porous CoS nanoprisms for high-performance potassium-ion batteries

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Rare Metals 2024年第3期43卷 971-983页

作者： jae Bong Lim seung-Keun Park Department of Advanced Materials Engineering Chung-Ang UniversityGyeonggi-do17546Republic of Korea Department of Intelligence Energy and Industry Chung-Ang UniversitySeoul06974Republic of Korea Western Seoul Center Korea Basic Science InstituteSeoul03759Republic of Korea

Potassium-ion batteries(PIBs)have gained significant attention as an alternative to lithium-ion batteries(LIBs)due to the abundance of potassium(K)and low ***,the difficulty in finding appropriate electrode materials that can efficiently store the larger K ions has hindered their practical ***,we report a novel anode material,N-doped multichannel carbon nanofibers embedded with porous CoS nanoprisms(CSP@NMCNF),for high-performance *** CSP@NMCNF was synthesized using a two-step strategy comprising of the electrospinning of Co acetate hydroxide nanoprism/binary polymer blend and a subsequent heat *** porous CoS nanoprisms with an anisotropic morphology were well aligned along the length axis of the N-doped multichannel carbon nanofibers,thus ensuring their structural stability during the repeated charge-discharge *** addition,numerous pores facilitated the transport of electrons and ***,the CSP@NMCNF anode exhibited excellent electrochemical performance,delivering a high specific capacity of 368 mAh·g^(-1)at 0.5 A·g^(-1)after 200 cycles and excellent rate capability(232 mAh·g^(-1)at 2.0 A·g^(-1)).

关键词： K-ion batteries Cobalt sulfide Multichannel structured composite Electrospinning Nanoprism Porous structure

Tetradentate Pt(Ⅱ)complex as a singlet exciton sensitizing host for highly efficient green fluorescent organic light-emitting diodes

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Science China Materials 2024年第8期67卷 2618-2627页

作者： Unhyeok Jo seung Chan Kim Chan Hee Ryu Kang Mun lee jae-Min Kim Jun Yeob lee School of Chemical Engineering Sungkyunkwan University2066Seobu-roJangan-guSuwon-siGyeonggi-do 16419Republic of Korea Department of Chemistry Institute for Molecular Science and Fusion TechnologyKangwon National UniversityChuncheonGangwon 24341Republic of Korea Department of Advanced Materials Engineering Chung-Ang University4726Seodong-daeroDaedeok-myeonAnseong-siGyeonggi-do 17546Republic of Korea SKKU Advanced Institute of Nano Technology Sungkyunkwan University2066Seobu-roJangan-guSuwonGyeonggi 16419Republic of Korea SKKU Institute of Energy Science and Technology Sungkyunkwan University2066Seobu-roJangan-guSuwonGyeonggi 16419Republic of Korea

Efficient green fluorescent organic light-emitting diodes were designed with a phosphorescent metal complex as a singlet exciton sensitizing host(SESH)for achieving high efficiency and low efficiency roll-off through exciton and polaron *** Pt(Ⅱ)complex(Pt-Trz)possessing a tetradentate ligand with a bulky blocking group not only suppresses the severe formation of excimer or dimer itself but also transfers radiative excitons to fluorescent dopant *** SESH assisted fluorescence(SESHF)device with Pt-Trz as the host exhibits the maximum external quantum efficiency of 13.3%and a lower efficiency roll-off compared with exciplex host device which is a general approach for harvesting triplet *** exciton dynamics modeling unravels that the SESHF device effectively utilizes triplet excitons in the host by intersystem crossing and resonance energy transfer from the triplet state of the host to the singlet state of the terminal *** quenching rates of the SESHF device are reduced by 11 times for triplet-triplet annihilation and 1.8 times for tripletpolaron annihilation compared with the exciplex device,which demonstrates that Pt-Trz could be a platform to be used as an efficient host for fluorophores.

关键词： singlet annihilation polaron