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An efficient multi-resolution SPH framework for multi-phase fluid-structure interactions

Science china(Physics,Mechanics & Astronomy) 2023年第10期66卷 92-113页

作者： chi Zhang Yujie Zhu Xiangyu Hu TUM School of Engineering and Design Technical University of MunichGarching 85748Germany Huawei Technologies Munich Research Center Munich 80992Germany Xi'an Research Institute of Hi-Tech Xi'an 710025China

Applying different spatial and temporal resolutions for different sub-systems is an effective approach to increase computational efficiency for particle-based methods. However, it still has many challenges in terms of achieving an optimized computational efficiency and maintaining good numerical robustness and accuracy for the simulation of multi-phase flows involving large density ratio and interacting with rigid or flexible structures. In the present work, based on the multi-resolution smoothed particle hydrodynamics(SPH) method [Zhang et al., JCP 429, 110028(2021)], an efficient multi-resolution SPH framework for multi-phase fluid-structure interactions(FSI) is proposed. First, an efficient multi-phase model, exploiting different density reinitialization strategies instead of applying different formulations to implement mass conservation to the light and heavy phases, respectively,is developed and the same artificial speed of sound for both phases can be used. Then, the transport velocity formulation is rewritten by applying temporal local flow state dependent background pressure to eliminate the unnatural voids, unrealistic phase separation and decrease the numerical dissipation. Finally, the one-sided Riemann-based solid boundary condition is modified to handle the FSI coupling in both single-and multi-resolution scenarios in the triple point. A set of examples involving multi-phase flows with high density ratio, complex interface and multi-phase FSI are studied to demonstrate the efficiency, accuracy and robustness of the present method.

关键词： multi-resolution method smoothed particle hydrodynamics multi-phase flows multi-phase FSI

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Global collaboration of eye research--personal experience

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International Journal of Ophthalmology(English edition) 2024年第6期17卷 985-990页

作者： chi-Chao Chan Laboratory of Immunology National Eye InstituteNational Institutes of HealthBethesdaMD 20892-1858USA Zhongshan Ophthalmic Center Sun Yat-sen UniversityGuangzhou 5410060Guangdong ProvinceChina

On December 9,2023,I was privileged to be honored and participate in the *** Chao Chan Symposium on Global Collaboration of Eye Research as the Global Eye Genetic Consortium(GEGC)session,which was held in the 16th Congress of the Asia-Pacific Vitreo-Retina Society(APVRS)in Hong *** with my talk on“Global collaboration of eye research:personal experience”,other prominent international speakers provided their own perspectives on opportunities for networking,collaboration,and exchange of ideas with global leaders and experts in ophthalmic practice,research,and education.

关键词： speakers collaboration Global

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Integrative Medicine Demonstrates Advantage in COVID-19 Treatment

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chinese Journal of Integrative Medicine 2020年第11期26卷 805-805,804页

作者： Yung-chi Cheng Henry Bronson Professor of Pharmacology Yale University Chairman and Founder of Consortium for the Globalization of chinese Medicine

In December 2019,a cluster of patients in Wuhan,china with a new type of pneumonia with unknown etiology were *** origin was subsequently discovered to be an infectious disease caused by a new coronavirus,SARS-CoV-2,a... 详细信息

关键词： Medicine etiology patients

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Long-term impacts of graphene oxide and Ag nanoparticles on anammox process: Performance, microbial community and toxic mechanism

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Journal of Environmental Sciences 2019年第5期31卷 239-247页

作者： Huai Li Zifang chi Baixing Yan Key Laboratory of Wetland Ecology and Environment Northeast Institute of Geography and Agroecology Chinese Academy of Sciences Key Laboratory of Groundwater Resources and Environment Ministry of Education Jilin University

The increasing application of engineered nanoparticles(NPs) has posed an emerging challenge to constructed wetland wastewater treatment. The performance, microbial community and toxic mechanism of anammox-based unplanted subsurface-flow constructed wetlands(USFCWs) were investigated under the long-term exposure of different graphene oxides(GOs) and Ag NP concentrations. Results showed that the addition of GO could promote TN removal, manifesting as function anammox bacteria C. Anammoxoglobus having a relative high abundance, for GO did not cause significant damage to the cell integrity though there was an increase in ROS concentrations. TN removal would not be obviously affected under exposure of 1 mg/L Ag NPs, for the function gene related to cell biogenesis and repair was up-regulated; while the addition of 10 mg/L Ag NPs would have an inhibiting effect on TN removal in the USFCWs, for the disappearance of some species having anammox ability. Key enzymes of anammox process(NIR and HDH) decreased to some extent under GO and Ag NP exposure, and function gene of defense mechanisms had an increase trend in samples.

关键词： Anammox Ag NPs GO Microbial community Function gene Key enzymes

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Equations of state for aqueous solutions under mantle conditions

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Science china Earth Sciences 2016年第6期59卷 1095-1106页

作者： ZHANG ZhiGang ZHANG chi GENG Ming Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences

With unique physical and chemical properties, aqueous solutions in the mantle may play important roles for a number of geochemical and geodynamical processes. However, since experimental data available are very limited, people still know little about the aqueous solutions and their interactions with surrounding rocks and melts. From the perspective of thermodynamics, equation of state(EOS) is the key to push forward the modeling of aqueous solutions. Nevertheless, up to now accurate EOSs suitable for the mantle conditions are still in shortage. With discussions over several recognized EOSs, we summarize several ways to enhance the predictability of EOS: utilizing high quality data from molecular simulations, choosing functions with sound physical background, and improving the regression procedures for the empirical parameters. In the meantime, we find that the ion-bearing systems are still the focus of challenges in this area. New developments of experiments and computer simulations effectively deal with these challenges and in-depth understandings of aqueous solutions in the mantle are expected in the near future.

关键词： Aqueous solutions Mantle Equation of state Molecular dynamics First principles Fluid-rock interactions

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Automated regression test method for scientific computing libraries:Illustration with SPHinXsys

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Journal of Hydrodynamics 2024年第3期36卷 466-478页

作者： Bo Zhang chi Zhang Xiangyu Hu TUM School of Engineering and Design Technical University of MunichMunichGermany

Scientific computing libraries,whether in-house or open-source,have witnessed enormous progress in both engineering and scientific ***,it is important to ensure that modifications to the source code,prompted by bug fixing or new feature development,do not compromise the accuracy and functionality that have been already validated and *** paper introduces a method for establishing and implementing an automatic regression test environment,using the open-source multi-physics library SPHinXsys as an illustrative ***,a reference database for each benchmark test is generated from observed data across multiple *** comprehensive database encapsulates the maximum variation range of metrics for different strategies,including the time-averaged,ensemble-averaged,and dynamic time warping *** accounts for uncertainties arising from parallel computing,particle relaxation,physical instabilities,and ***,new results obtained after source code modifications undergo testing based on a curve-similarity comparison against the reference *** the source code is updated,the regression test is automatically executed for all test cases,providing a comprehensive assessment of the validity of the current *** regression test environment has been successfully implemented in all dynamic test cases within SPHinXsys,including fluid dynamics,solid mechanics,fluid-structure interaction,thermal and mass diffusion,reaction-diffusion,and their multi-physics couplings,and demonstrates robust capabilities in testing different *** is noted that while the current test environment is built and implemented for a particular scientific computing library,its underlying principles are generic and can be easily adapted for use with other libraries,achieving equal effectiveness.

关键词： Scientific computing open-source library verification and validation regression test automatic test environment curve similarity comparison smoothed particle hydrodynamics

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Modeling of environmental influence in structural health assessment for reinforced concrete buildings

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Earthquake Engineering and Engineering Vibration 2010年第2期9卷 295-306页

作者： Ka-Veng Yuen Sin-chi Kuok Department of Civil and Environmental Engineering Univeristy of Macao

One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.

关键词： Bayesian inference model selection reinforced concrete building structural health monitoring temperature and humidity effects Timoshenko beam

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Theoretical Study on the Stable Structures and Aromaticities for Pnictogen Dianionic Sb4^2-, Bi4^2-, and （SbBi）2^2- Clusters

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chinese Journal of Chemical Physics 2009年第1期22卷 75-81页

作者： Xing-bao Wang Xian-xing chi School of Physics and Electronic Information Wenzhou University Wenzhou 325027 China

Through the theoretical calculation of structural optimization, vibrational frequencies and atomization energies with one method of density functional theory （B3LYP） and two post- Hartree-Fock approaches （MP2, CCSD（T））, several stable isomers for new three pnictogen dianionic Sb4^2-, Bi4^2-, and （SbBi）2^2- species were determined. For two homoatomic Sb4^2- and Bi4^2- species, there are three stable isomers： square （D4h）, roof-shaped （C2v-1）, and C2v-2 structure with the square isomer being the ground state. For the heteroatomic dian- ionic （SbBi）2^2- species, there are also three stable isomers： rhombus （D2h）, roof-shaped （C1）, and C2v structures with the rhombic isomer being the ground state. The calculated NICS values show that nucleus-independent chemical shifts （NICS） values of roof-shaped isomers for Sb4^2-, Bi4^2-, and （SbBi）2^2- species are all negative, consequently indicating that these roof-shaped isomers possess aromaticities. NICS values for the planar ring isomers are all positive, suggesting that these three planar ring isomers have antiaromatic characters. The aromaticity for the two stable roof-shaped and square isomers are preliminarily explained and discussed with MO analysis.

关键词： Pnictogen cluster Ab initio Aromaticity Nucleus-independent chemical shift

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Application of Analytic Redundancy-based Fault Diagnosis of Sensors to Onboard Maintenance System

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chinese Journal of Aeronautics 2012年第2期25卷 236-242页

作者： chi Chengzhi ZHANG Weiguo LIU Xiaoxiong School of Automation Northwestern Polytechnical UniversityXi'an 710072China

Analytic redundancy-based fault diagnosis technique （ARFDT） is applied to onboard maintenance system （OMS）. The principle of the proposed ARFDT scheme is to design a redundancy configuration using ARFDT to enhance the functions of redundancy management and built in test equipment （BITE） monitor. Redundancy configuration for dual-redundancy and analytic redundancy is proposed, in which, the fault diagnosis includes detection and isolation. In order to keep the balance between rapid diagnosis and binary hypothesis, a filter together with an elapsed time limit is designed for sequential probability ratio test （SPRT） in the process of isolation. Diagnosis results would be submitted to central maintenance computer （CMC） together with BITE information. Moreover, by adopting reconstruction, the designed method not only provides analytic redundancy to help redundancy management, but also compensates the output when both of the sensors of the same type are faulty. Our scheme is applied to an aircraft’s sensors in a simulation experiment, and the results show that the proposed filter SPRT （FSPRT） saves at least 50% of isolation time than Wald SPRT （WSPRT）. Also, effectiveness, practicability and rapidity of the proposed scheme can be successfully achieved in OMS.

关键词： fault detection analytic redundancy sequential probability ratio test (SPRT) onboard maintenance system (OMS) redundancy management sensors

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Effects of polarization calibration on aerosol optical depth retrieval: An ocean case sensitivity analysis

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Science china Earth Sciences 2015年第6期58卷 939-948页

作者： LIU TianYue chi TianHe CHEN Wei Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences College of Earth Sciences University of Chinese Academy of Sciences College of Geoscience and Surveying Engineering China University of Mining and Technology

Reflectance measurements of both the visible and infrared bands of passive remote sensing sensors are widely used to retrieve aerosol optical depth(AOD) information. This is performed commonly for data obtained over both ocean and land, and these measurements allow for the off line development of a lookup table using radiative transfer models. Owing to molecular and aerosol effects, the reflected light received by the sensor is usually highly polarized. The linear polarization effect may be up to 100%, and the polarization factor of a sensor optical system will change the total intensity as well as the polarization status of the signal reaching the detector. The detector response will be different when the incident light polarization status changes, even if the total intensity remains constant. However, if the polarization calibration is neglected, it will cause obvious errors in the aerosol data retrieval. This is especially true for aerosol optical depth retrieval over an ocean. This measurement relies directly on the reflectance output of the sensor. Cases involving land surfaces are not discussed herein because the inhomogeneous properties conceal the error due to polarization. Taking the 550 and 860 nm bands as examples, the difference between the real top-of-atmosphere(TOA) reflectance and the reflectance reaching the detector is calculated using three different sensor polarization standards according to the Sea-viewing Wide Field-of-view Sensor(Sea Wi FS) and Moderate Resolution Imaging Spectroradiometer(MODIS) standards. The differences in AOD retrieval are also demonstrated using the lookup table developed previously from a vector radiative transfer code. The results reveal that under a normal situation in which the AOD is 0.15, the maximum AOD retrieval error could reach 0.04 in 550 nm but only 0.02 in 860 nm for the dust aerosol model. For the soot aerosol model, the maximum AOD retrieval error is 0.1 in 550 nm and 0.12 in 860 nm, indicating that the lack

关键词： aerosol polarization calibration radiative transfer

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