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Data-driven sparse polynomial chaos expansion for models with dependent inputs

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Journal of Safety Science and Resilience 2023年第4期4卷 358-365页

作者： Zhanlin Liu Youngjun choe Industrial&Systems Engineering University of WashingtonSeattleWAUSA

Polynomial chaos expansions(PCEs)have been used in many real-world engineering applications to quantify how the uncertainty of an output is propagated from inputs by decomposing the output in terms of polynomials of the *** for models with independent inputs have been extensively explored in the ***,different approaches have been proposed for models with dependent inputs to expand the use of PCEs to more real-world *** approaches include building PCEs based on the Gram–Schmidt algorithm or transforming the dependent inputs into independent ***,the two approaches have their limitations regarding computational efficiency and additional assumptions about the input distributions,*** this paper,we propose a data-driven approach to build sparse PCEs for models with dependent inputs without any distributional *** proposed algorithm recursively constructs orthonormal polynomials using a set of monomials based on their correlations with the *** proposed algorithm on building sparse PCEs not only reduces the number of minimally required observations but also improves the numerical stability and computational *** numerical examples are implemented to validate the proposed *** source code is made publicly available for reproducibility.

关键词： Uncertainty quantification Polynomial chaos expansion Sparse polynomial chaos expansion Gram-Schmidt orthogonalization

Dominant edge direction based fast intra mode decision in the H.264/AVC encoder

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 767-777页

作者： Byeongdu LA Minyoung EOM Yoonsik choe Department of Electrical and Electronic Engineering Yonsei University

The H.264/AVC video coding standard uses an intra prediction mode with 4×4 and 16×16 blocks for luma and 8×8 blocks for chroma. This standard uses the rate distortion optimization (RDO) method to determine the best coding mode based on the compression performance and video quality. This method offers a large improvement in coding efficiency compared to other compression standards, but the computational complexity is greater due to the various intra prediction modes. This paper proposes a fast intra mode decision algorithm for real-time encoding of H.264/AVC based on the dominant edge direction (DED). The DED is extracted using pixel value summation and subtraction in the horizontal and vertical directions. By using the DED, three modes instead of nine are chosen for RDO calculation to decide on the best mode in the 4×4 luma block. For the 16×16 luma and the 8×8 chroma, only two modes are chosen instead of four. Experimental results show that the entire encoding time saving of the proposed algorithm is about 67% compared to the full intra search method with negligible loss of quality.

关键词： H 264 Intra prediction Mode decision Dominant edge direction

Nanostructure and corrosion behaviors of nanotube formed Ti-Zr alloy

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中国有色金属学会会刊：英文版 2009年第4期19卷 1005-1008页

作者： Won-Gi KIM Han-Cheol choe Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials College of DentistryChosun University

In order to investigate the nanostructures and corrosion behaviors of Ti-Zr alloys,nanotube formed Ti-Zr(10%,20%,30% and 40% in mass fraction) alloys were prepared by arc melting and the condition of controlling nanostructure was at 1 000 ℃ for 24 h in argon atmosphere;formation of nanotubes was conducted by anodizing a Ti-Zr alloy in H3PO4 electrolyte with a small amount of fluoride ions at room *** corrosion properties of specimens were examined through potentiodynamic test(potential range of -1 500-2 000 mV) in 0.9% NaCl solution by using *** of the alloys were observed by optical microscope(OM),field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD).Diameter of nanotube does not depend on Zr content,but interspace of nanotube predominantly depends on Zr content,which confirms that ZrO2 oxides play a role to increase the interspace of nanotube formed on the surface.

关键词：钛锆合金纳米结构腐蚀行为扫描电子显微镜 NaCl溶液阳极氧化光学显微镜 X射线衍射

Electrochemical behavior of Co-Cr and Ni-Cr dental cast alloys

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中国有色金属学会会刊：英文版 2009年第4期19卷 785-790页

作者： Viswanathan S. SAJI Han-Cheol choe Department of Dental Materials College of DentistryChosun University

The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.

关键词：镍铬合金合金铸造电化学行为牙科电化学腐蚀行为 X射线衍射分析 NaCl溶液钴

COVID-19 economic policy effects on consumer spending and foot traffic in the U.S.

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Journal of Safety Science and Resilience 2021年第4期2卷 230-237页

作者： Zhiqing Yang Youngjun choe Matthew Martell Department of Statistics University of WashingtonUnited States Information School University of WashingtonUnited States Department of Industrial&Systems Engineering University of WashingtonUnited States

To battle with economic challenges during the COVID-19 pandemic,the US government implemented various measures to mitigate economic *** issuance of stimulus checks to reopening businesses,consumers had to constantly alter their behavior in response to government *** anonymized card transactions and mobile device-based location tracking data,we analyze the factors that contribute to these behavior changes,focusing on stimulus check issuance and state-wide *** finding suggests that stimulus payment has a significant immediate effect of boosting spending,but it typically does not reverse a downward ***-wide reopening had a small effect on *** traffic increased gradually after stimulus check issuance,but only increased slightly after reopening,which also coincided or preceded several policy changes and confounding events(e.g.,protests)in the *** also find differences in the reaction to these policies in different regions in the *** results may be used to inform future economic recovery policies and their potential consumer response.

关键词： COVID-19 Economic impact Interrupted time series analysis

Impact of clay particle reattachment on suffusion of sand-clay mixtures

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第10期15卷 2720-2730页

作者： Jongmuk Won Yongjoon choe Yerim Yang Hangseok Choi Department of Civil and Environmental Engineering University of UlsanDaehak-ro 93Nam-guUlsan680-749South Korea School of Civil Environmental and Architectural EngineeringAnam-dong 5-gaKorea UniversitySeoul136-713South Korea

The detached clay particles directly filtrated through the sand-clay mixture lead to suffusion;however,if the detached clay particles are subjected to reattachment,the degree of suffusion may be less *** study investigates the impact of clay particle reattachment on suffusion of sand-clay mixtures through laboratory soil-column *** observed breakthrough curves(BTCs)of kaolinite,illite,and montmorillonite for 5 different column lengths(3 in,6 in,9 in,12 in,and 18 in;1 in=2.54 cm)indicated that a higher breakthrough concentration was observed as the column length(L)decreased for kaolinite and illite,whereas a reverse trend was observed for *** addition,the increase in the fraction of filtrated clay particles(Me)with an increase in L(Me=10.42%for L=3 in and Me=3.59%for L=18 in)for the sand-illite mixture indicated that the reattachment effect became more significant as the travel length of detached clay particles *** observed BTCs,retention profiles after injection,and fraction of filtrated clay presented herein suggest the need to incorporate the reattachment effect when assessing the suffusion of clay-containing soils.

关键词： Suffusion Reattachment Sandeclay mixture Ionic concentration Column length

Characterization of three-dimensional channel reservoirs using ensemble Kalman filter assisted by principal component analysis

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Petroleum Science 2020年第1期17卷 182-195页

作者： Byeongcheol Kang Hyungsik Jung Hoonyoung Jeong Jonggeun choe Department of Energy Systems Engineering Seoul National UniversitySeoul 08826South Korea

Ensemble-based analyses are useful to compare equiprobable scenarios of the reservoir ***,they require a large suite of reservoir models to cover high uncertainty in heterogeneous and complex reservoir *** stable convergence in ensemble Kalman filter(EnKF),increasing ensemble size can be one of the solutions,but it causes high computational cost in large-scale reservoir *** this paper,we propose a preprocessing of good initial model selection to reduce the ensemble size,and then,EnKF is utilized to predict production performances *** the model selection scheme,representative models are chosen by using principal component analysis(PCA)and clustering *** dimension of initial models is reduced using PCA,and the reduced models are grouped by ***,we choose and simulate representative models from the cluster groups to compare errors of production predictions with historical observation *** representative model with the minimum error is considered as the best model,and we use the ensemble members near the best model in the cluster plane for applying *** demonstrate the proposed scheme for two 3D models that EnKF provides reliable assimilation results with much reduced computation time.

关键词： Channel reservoir characterization Model selection scheme Egg model Principal component analysis(PCA) Ensemble Kalman filter(EnKF) History matching

Reactive Core-Shell Bottlebrush Copolymer as Highly Effective Additive for Epoxy Toughening

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Chinese Journal of Polymer Science 2021年第12期39卷 1626-1633页

作者： Junsoo Moon Yoon Huh Seonghwan Kim Youngson choe Joona Bang Department of Chemical and Biological Engineering Korea UniversitySeoul 02841Republic of Korea Department of Chemical Engineering Pusan National UniversityPusan 46241Republic of Korea

Herein,we designed a core-shell structured bottlebrush copolymer(BBP),which is composed of rubbery poly(butyl acrylate)(PBA)core and an epoxy miscible/reactive poly(glycidyl methacrylate)(PGMA)shell,as an epoxy tougheni ng age *** PGMA shell allows BBP to be uniformly dispersed within the epoxy matrix and to react with the epoxy groups,while the rubbery PBA block simultaneously induced nanocavitation effect,leading to improvement of mechanical properties of the epoxy *** mechanical properties were measured by the adhesion performance test,and the tensile and fracture test using universal testing *** BBP additives were added to the epoxy resin,a sign ifica nt improveme nt in the adhesion stren gth(2-fold increase)and fracture toughness(2-fold in crease in Kic and 5-fold in crease in Gic)compared to the neat epoxy was *** contrast,linear additives exhibited a decrease in adhesion strength and no improvement of fracture toughness over the neat *** a difference in mechanical performance was investigated by comparing the morphologies and fracture surfaces of the epoxy resins containing linear and BBP additives,confirming that the nanocavitation effect and void formation play a key role in strengthening the BBP-modified epoxy resins.

关键词： Bottlebrush polymer ROMP Additive Adhesion Epoxy toughening

Study on laser pre-sowing treatment of rice seeds by free-falling transport method

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Information Processing in Agriculture 2019年第4期6卷 515-521页

作者： Phyongchol Ri Sangjin choe Yongsong Jang School of Management Harbin Institute of TechnologyNangang DistrictHarbin 150001PR China Institute of Advanced Science KimIlSung UniversityDaesong DistrictPyongyang 999093Democratic People’s Republic of Korea

Recently,laser pre-sowing treatment of seed is attracting a great attention of scientific community for its positive influence to enhance germination,seedling and growth of plants,vegetables and *** this study,effect of laser pre-sowing treatment of rice seeds was given,which was implemented by free-falling transport *** has been processed in Unzon district(DPRK)in *** kinds of Korean rice seeds(namely Pyongyang-53 and Dongsung-1)were irradiated by semiconductor laser with wavelength of 650 nm,which was controlled in PWM *** group was irradiated using exposure time of 0.28 s and duty ratio of 50 *** result,a considerable improvement has been observed in germination,growth and final *** laser pre-sowing treatment of rice seed,total productivities have been increased by 7.7%and 21%for “Pyongyang-53”and “Dongsung-1”,*** show that laser pre-sowing treatment of seed can significantly enhance germination,seedling and growth,and thus can improve the productivity of *** future research,laser pre-sowing treatment by free-falling transport method should be processed for other kinds of plants,vegetables and cereal crops to find out appropriate parameters,such as mechanical structure of device,wave length and power of laser,frequency and duty cycle of PWM control signal and exposure time,etc.

关键词： Laser irradiation Pre-sowing treatment of seed Free-falling transport