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Dynamic Response of Mold Oscillator Interacting with Steel Slabs

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Journal of Iron and Steel Research International 2016年第9期23卷 900-909页

作者： Yonghui park Hyunchul park Graduate School of Engineering Masterships Pohang University of Science and Technology(POSTECH)

A mathematical model to show the dynamic response of the mold oscillator was suggested. The model con- sidered a frictional interaction between the mold oscillator and slab as several connected nodes. The governing equation considered the slab as a multi-degree-of-freedom （DoF） system, and included a hysteresis model to describe elastic-plastic behavior of the slab; the mold oscillator was given two DoF by utilizing pressure and displacement experiment data. Simulations indicate that the mold and slab execute various vibrations, and that mold oscillation marks are caused by a stick-and-slip phenomenon during intervals, in which the slab contacting the mold moves downward compared to the other slab （negative strip time）. The slab shows the formation of mold oscillation marks to previous formation criterion equally when the mold velocity is faster than the casting speed about downward. The oscillation mark will grow up over 2 Hz exciting frequency with constant 4 mm stroke in simulations. Finally, the negative strip time was compared to the frictional force, hysteresis variable, and plastic force to investigate formation mechanism of the oscillation marks.

关键词： mold oscillating mechanism mathematical model direct integration method hysteresis model stick-and-slip

Effect of Sn on the Microstructure and Mechanical Properties of Mg-5AI-2Si Alloys

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Journal of Materials Science & Technology 2008年第3期24卷 296-301页

作者： Sangwon Lee Bonggyu park Yongho park Ikmin park Department of Material Science and Engineering Pusan National University 30Jangjeon-dongGeumjeong-gu

The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.

关键词： Magnesium Tin Microstructure Mechanical properties

Effects of an Urban park and Residential Area on the Atmospheric CO_2 Concentration and Flux in Seoul,Korea

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Advances in Atmospheric Sciences 2013年第2期30卷 503-514页

作者： Moon-Soo park Seung Jin JOO Chang Seok LEE Center for Atmospheric and Environmental Modeling Seoul 151 919Korea Life and Environmental Engineering Seoul Women's UniversitySeoul 139 774Korea

The CO2 concentrations and fluxes over an urban forest site （Namsan） and an urban residential region （Boramae） in Seoul, Korea, during the non-growing season （2 4 March 2011）, the growing season （10-12 June 2011）, and the late-growing season （22-24 September 2011） were analyzed. The CO2 concentrations of two sites showed nearly the same diurnal variation, with a maximum value occurring during the night and a minimum value occurring during daytime, as well as the same seasonal variation, with a maximum value during the non-growing season （early spring） and a minimum value during the growing season （summer）. The CO2 flux over the urban forest did not show any typical diurnal variation during the non-growing season, but did show diurnal variation with a small positive value during the night and a large negative value during daytime in the growing and late-growing seasons due to photosynthesis in the urban forest. The CO2 flux over the urban residential region showed a positive daily mean value for all periods, with large values during the non-growing season and small values during the growing season, and it also showed diurnal variation with two maxima at 0600-1000 LST and 1800-2400 LST, and two minima at 0300-0600 LST and 1100-1500 LST, and was strongly correlated with the use of liquefied natural gas for cooking and heating by surrounding houses.

关键词： C02 concentration C02 flux Seoul urban forest urban residential region

Kinematic Analysis of the Neck and Upper Extremities During Walking in Healthy Young Adults

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Journal of Bionic Engineering 2011年第3期8卷 305-312页

作者： Kwon Son Junghong park Seonghun park School of Mechanical Engineering Pusan National University Busan 609-735 Republic of Korea

The objective of this paper is to quantify the local stabilities of the neck and upper extremities （right/left shoulders and right/left elbows）, and investigate differences between linear and nonlinear measurements of the associated joint motions and differences in the local stability between the upper and lower extremities. This attempt involves the calculation of a nonlinear parameter, Lyapunov Exponent （LE）, and a linear parameter, Range of Motion （ROM）, during treadmill walking in conj unction with a large population of healthy subjects. Joint motions of subjects were captured using a three-dimensional motion-capture system. Then mathematical chaos theory and the Rosenstein algorithm were employed to calculate LE of joints as the extent of logarithmic divergence between the neighboring state-space trajectories of flexion-extension angles. LEs computed over twenty males and twenty females were 0.037~0.023 for the neck, 0.043＋0.021 for the right shoulder, 0.045i0.030 for the left shoulder, 0.032i0.021 for the right elbow, and 0.034~0.026 for the left elbow. Although statistically significant difference in the ROM was observed between all pairs of the neck and upper extremity joints, differences in the LE between all pairs of the joints as well as between males and females were not statistically significant. Between the upper and lower extremities, LEs of the neck, shoulder, and elbow were significantly smaller than those of the hip （-0.064） and the knee （-0,062）. These results indicate that a statistical difference in the local stability between the upper extremity joints is not significant. However, the different result between the ROM and LE gives a strong rationale for applying both linear and nonlinear tools together to the evaluation of joint movement. The LEs of the joints calculated from a large population of healthy subjects could provide normative values for the associated joints and can be used to evaluate the recovery progress of patients with joint rel

关键词： kinematic analysis Lyapunov exponent range of motion chaos theory upper extremities

Metasurface-Based Imagers Enabled Arbitrary Optical Convolution Processing

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Light(Science & Applications) 2022年第5期11卷 741-742页

作者： Minsu park Yeonsang park Department of Physics Chungnam National UniversityDaejeon 34134Korea Institute of Quantum Systems Chungnam National UniversityDaejeon 34134Korea

Using meta-imagers composed of a meta-lens and a complex-amplitude meta-modulator,all-optical convolutional processing that arbitrarily reshapes the point spread function of an optical system can now be implemented.

关键词： modulator optical Optical

Complete Solution of Diophantine Pairs Induced by Some Fibonacci Formula

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Algebra Colloquium 2023年第1期30卷 121-132页

作者： Jinseo park Department of Mathematics Education Catholic Kwandong University Gangneung 25601Korea

A set[ai,a2,...,am)of positive integers is called a Diophantine m-tuple if aiaj+1 is a perfect square for all 1≤imax(a,b].In this paper,we find the condition for the reduction of third element c,and using this result,we prove the extendibility of Diophantine pair[F_(k)-1F_(k+1),F_(k-2)F_(k+2)],where Fn is the n-th Fibonacci number.

关键词： Diophantine m-tuple Fibonacci numbers Pell equation

Evaluation of non-point source pollution reduction by applying Best Management Practices using a SWAT model and QuickBird high resolution satellite imagery

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Journal of Environmental Sciences 2010年第6期22卷 826-833页

作者： MiSeon Lee GeunAe park MinJi park JongYoon park JiWan Lee SeongJoon Kim Department of Rural Engineering Konkuk University Department of Civil and Environmental System Engineering Konkuk University

This study evaluated the reduction effect of non-point source pollution by applying best management practices （BMPs） to a 1.21 km^2 small agricultural watershed using a SWAT （Soil and Water Assessment Tool） model. Two meter QuickBird land use data were prepared for the watershed. The SWAT was calibrated and validated using dally streamflow and monthly water quality （total phosphorus （TP）, total nitrogen （TN）, and suspended solids （SS）） records from 1999 to 2000 and from 2001 to 2002. The average Nash and Sutcliffe model efficiency was 0.63 for the streamflow and the coefficients of determination were 0.88, 0.72, and 0.68 for SS, TN, and TP, respectively. Four BMP scenarios viz. the application of vegetation filter strip and riparian buffer system, the regulation of Universal Soil Loss Equation P factor, and the fertilizing control amount for crops were applied and analyzed.

关键词： QuickBird land use Soil and Water Assessment Tool best management practice non-point source

Ageing Behavior of Mg-xAl-Zn with Variation of Al Content

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Journal of Materials Science & Technology 2008年第1期24卷 51-53页

作者： Byoungho Kim Jongjin Jeon Yeongdo park Yongho park Ikmin park Department of Materials Science and Engineering Pusan National University 30 Jangjeon-dongGeumjeong-guBusan 609-735Korea Department of Advanced Materials Engineering Dong-Eui University 995 EomgwangnoJin-guBusan 614-714Korea

The ageing behavior of Mg-xAl-Zn alloys with a variation of AI contents （x=3,5,7,9 and 11 wt pct） were *** solution treatment and artificial ageing were carried out at 693 and 493 K,respectively. After the solid solution treatment,β-Mg-（17）Al-（12） was resolved to theα-Mg matrix in the specimens which contained Al up to 9 wt pct and partially resolved in the specimen of 11 wt pct *** ageing,theβ- Mg-（17）Al-（12） phase was precipitated at the grain boundary in the form of discontinuous precipitation and grown into the *** volume fraction ofβ-phase was increased with the Al *** strength increased with the volume fraction of precipitatedβ-phase,which was believed to strengthen the matrix.

关键词： Ageing Mg alloy Discontinuous precipitation

Connectivity differences between adult male and female patients with attention deficit hyperactivity disorder according to resting-state functional MRI

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Neural Regeneration Research 2016年第1期11卷 119-125页

作者： Bo-yong park Hyunjin park Department of Electronic Electrical and Computer Engineering Sungkyunkwan University School of Electronic Electrical Engineering Sungkyunkwan University Center for Neuroscience Imaging Research (CNIR) Institute for Basic Science

Attention deficit hyperactivity disorder（ADHD） is a pervasive psychiatric disorder that affects both children and adults. Adult male and female patients with ADHD are differentially affected, but few studies have explored the differences. The purpose of this study was to quantify differences between adult male and female patients with ADHD based on neuroimaging and connectivity analysis. Resting-state functional magnetic resonance imaging scans were obtained and preprocessed in 82 patients. Group-wise differences between male and female patients were quantified using degree centrality for different brain regions. The medial-, middle-, and inferior-frontal gyrus, superior parietal lobule, precuneus, supramarginal gyrus, superior- and middle-temporal gyrus, middle occipital gyrus, and cuneus were identified as regions with significant group-wise differences. The identified regions were correlated with clinical scores reflecting depression and anxiety and significant correlations were found. Adult ADHD patients exhibit different levels of depression and anxiety depending on sex, and our study provides insight into how changes in brain circuitry might differentially impact male and female ADHD patients.

关键词： neural regeneration connectivity attention deficit hyperactivity disorder sex difference functional magnetic resonance imaging depression anxiety network analysis degree centrality diagnostic and statistical manual score