检索结果-南通市图书馆

On the yield functions in Lagrangian stress space of elastic-plastic materials with internal constraints

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2007年第3期23卷 297-303页

作者： Mingfu fu Liangsen chen Center for Engineering Mechanics Nanchang UniversityNanchang 330031 China

In the present paper it is shown that the elastic range in the second Piola-Kirchhoff stress space can be chosen in a hyperplane which is through the origin of Lagrangian stress space and perpendicular to the normal of the constraint manifold at the plastic configuration, if the determinate stress response of the elastic-plastic material with simple internal constraints with some condition is correctly chosen, otherwise, it is in general in a hypersurface and the normal flow rule by Ⅱ yushin＇s postulate will have an indeterminate part. The choice of deterrninate stress response is probable because of its indeterminacy. Therefore the yield function should be a function of the second Piola-Kirchhoff stress lying in the hyperplane so that it is more simple and the back stress as the geometric center of the elastic range in general is inside the elastic range. Finally some examples are concerned.

关键词： Elastic-plastic materials Constitutive relations Internal constraints

The redshift number density evolution of Mg Ⅱ absorption systems

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2013年第6期13卷 641-650页

作者： Zhi-fu chen Department of Physics and Telecommunication Engineering Baise University Center for Astrophysics Guangzhou University

We make use of the recent large sample of 17 042 Mg Ⅱ absorption systems from Quider et al. to analyze the evolution of the redshift number density. Regardless of the strength of the absorption line, we find that the evolution of the redshift number density can be clearly distinguished into three different phases. In the intermediate redshift epoch （0.6 ≤ z ≤ 1.6）, the evolution of the redshift number density is consis- tent with the non-evolution curve, however, the non-evolution curve over-predicts the values of the redshift number density in the early （z ≤ 0.6） and late （z ≥ 1.6） epochs. Based on the invariant cross-section of the absorber, the lack of evolution in the red- shift number density compared to the non-evolution curve implies the galaxy number density does not evolve during the middle epoch. The fiat evolution of the redshift number density tends to correspond to a shallow evolution in the galaxy merger rate during the late epoch, and the steep decrease of the redshift number density might be ascribed to the small mass of halos during the early epoch.

关键词： methods: statistical -- galaxies: evolution -- quasars: absorption lines

Evaluation of 3D crustal seismic velocity models in southwest China:Model performance,limitation,and prospects

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第2期67卷 604-619页

作者： Xin WANG Ling chen Qi-fu chen Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing100049China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing100029China

Southwest China is a tectonically and seismically active region,witnessing strong deformation due to the collision between the Indian and Eurasian *** the subsurface velocity structure of this region is thus important in understanding the tectonics and geodynamic processes of continental collision and in mitigating seismic *** studies have provided various 3D seismic velocity models in southwest ***,discrepancies exist among these models,and less effort has been made to quantify the reliability and accuracy of these existing velocity *** this study,we use regional 3D waveform simulation to evaluate the performance of various regional crustal 3D velocity models in reproducing observed *** particularly focus on two recent earthquake sequence in the region,the 2021 Yunnan Yangbi MS_(6.4) earthquake sequence and the 2022 Sichuan Luding MS_(6.8) earthquake *** tested 3D velocity models include the Southwest China Community Velocity model V1.0,the Unified Seismic Tomography Models for Continental China Lithosphere V2.0,the adjoint full waveform tomography model of the crustal and upper mantle beneath Eastern Tibetan Plateau,and the shallow seismic structure model beneath continental *** results show that the tested 3D velocity models generally capture well long-period(full-waveform tomography model shows a slighter better performance than the other models,especially for the body-waves,highlighting the advantages

关键词： Southwest China Seismic tomography models Shallow Structures Waveform simulation Model evaluation

Overview of deep structures under the Changbaishan volcanic area in Northeast China

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2019年第6期62卷 935-952页

作者： Qi-fu chen Yinshuang AI Yun chen Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences College of Earth and Planetary Sciences University of Chinese Academy of Sciences Institutions of Earth Science Chinese Academy of Sciences State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences

The Changbaishan volcano is an active and considerably hazardous volcano located on the border of China and North Korea. This paper summarizes a series of geophysical surveys as well as seismological and volcano-observational networks around the Changbaishan volcanic area. We characterize deep structures related to the Changbaishan volcanic area. The prominent low-velocity anomalies and low-resistance bodies associated with the magma system under the Changbaishan volcano were detected in the crust and upper mantle, and high-velocity anomalies were imaged within the mantle transition zone,suggesting that the origin of the Changbaishan volcano is related to the subducted Pacific slab. However, there exist a few major obstacles for comprehensively elucidating the deep structure of the Changbaishan volcano as well as for the preparedness for and response toward future volcanic unrest and activity. It is essential to collect data from both China and Korean Peninsula to image the deep structure beneath the Changbaishan volcanic area. A multi-disciplinary approach comprising seismological investigations, deformation information from GNSS and InSar, and gravity and magnetotelluric surveying is a reliable manner for imaging high-resolution structures and fluid movement for the spatial distribution and variation of the volcanic magma *** effective volcano-monitoring network system is considerably important to improve hazard assessments and characterize the potential future eruption of the Changbaishan volcano.

关键词： Changbaishan volcano Deep structure Geophysical observation

Vitamin D differentially regulates Salmonella-induced intestine epithelial autophagy and interleukin-1β expression

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2016年第47期22卷 10353-10363页

作者： fu-chen Huang Department of Pediatrics Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of MedicineKaohsiung 833 TaiwanChina

AIM To investigate the effects of active vitamin D3 on autophagy and interleukin(IL)-1β expression in Salmonella-infected intestinal epithelial cells(IECs).METHODS Caco-2 cells, NOD2 siR NA-, Atg16L1 siR NA- or vitamin D receptor(VDR) siR NA-transfected Caco-2 cells were pretreated with 1,25-dihydroxyvitamin D3(1,25D3), and then infected by wild-type S. typhimurium strain SL1344. The conversion of LC3-I to LC3-II was detected by Western blot analysis and LC3+ autophagosome was analyzed by immunofluorescence. Caco-2 cells or VDR si RNA-transfected cells were pretreated with 1,25D3, and then infected by SL1344. Membrane protein and total RNA were analyzed by Western blot and RT-PCR for VDR and Atg16L1 protein and m RNA expression, respectively. Atg16L1 si RNA-transfected Caco-2 cells were pretreated by 1,25D3 and then infected with SL1344. Total RNA was analyzed by RT-PCR for IL-1β mR NA *** The active form of vitamin D, 1,25D3, showed enhanced VDR-mediated Atg16L1 mR NA expression, membranous Atg16L1 protein expression leading to autophagic LC3 II proteins expression and LC3 punctae in Salmonella-infected Caco-2 cells which was counteracted by Atg16L1 and VDR si RNA, but Atg16L1 mediated suppression of IL-1β expression. Thus, active vitamin D may enhance autophagy but suppress inflammatory IL-1β expression in Salmonella-infected *** Active vitamin D might enhance autophagic clearance of Salmonella infection, while modulation of inflammatory responses prevents the host from detrimental effects of overwhelming inflammation.

关键词： Vitamin D Atg16L1 Autophagy Interleukin1β Salmonella Intestinal epithelia

Speciation and bioaccessibility of lead and cadmium in soil treated with metal-enriched Indian mustard leaves

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2011年第4期23卷 624-632页

作者： Yanshan Cui Jin fu Xiaochen chen College of Resources and Environment Graduate University of Chinese Academy of Sciences Beijing 100049 China.

Indian mustard （Brassica juncea （L.） Czern.） has shown good potential for the phytoremediation of soil contaminated with heavy metals. However, there is little information about the speciation and bioaccessibility of heavy metals in soil during the decomposition of metal-rich Indian mustard leaves. Incubation experiments （1-, 3-, and 6-month） were carried out in Beijing and Hunan soil with metal-rich Indian mustard leaves addition （1% and 3%） and the effects of mustard leaves addition on the speciation and bioaccessibility of heavy metals were studied. The results showed that the addition of mustard leaves led to significant increases in pH and DOC in the Hunan soil. Both 1% and 3% of mustard leaf amendment caused the percentage of the exchangeable （F1）, precipitated with carbonates （F2）, bound to Fe/Mn oxides （F3） and bound to organic matter （F4） fractions of Pb and Cd to increase dramatically, while the percentage of the residual fraction （F5） of Cd and Pb significantly dropped in both Beijing and Hunan soils. Mustard leaf addition caused the bioaccessibility of Pb to decrease in the gastric phase, whereas the values increased in the small intestinal phase. The Cd bioaccessibility increased with mustard leaf addition in both the gastric and small intestinal phases. In conclusion, the metal-enriched mustard leaves addition induces Pb and Cd concentrations and their mobility increasing in the Beijing and Hunan soils. Therefore, heavy metal risk in metal-enriched plant leaves should be considered in phytoremediation system in which heavy metal might be brought back to soil and changed over time.

关键词： lead cadmium speciation bioaccessibility decomposition

Improvements of corner frequency and scaling factor for stochastic finite-fault modeling

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2010年第4期9卷 503-511页

作者： Sun Xiaodan Tao Xiaxin chen fu School of Civil Engineering Harbin Institute of Technology Harbin 150090 China School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China

In this paper, three existing source spectral models for stochastic finite-fault modeling of ground motion were reviewed. These three models were used to calculate the far-field received energy at a site from a vertical fault and the mean spectral ratio over 15 stations of the Northridge earthquake, and then compared. From the comparison, a necessary measure was observed to maintain the far-field received energy independent of subfault size and avoid overestimation of the long- period spectra/level. Two improvements were made to one of the three models （i.e., the model based on dynamic comer frequency） as follows：（i） a new method to compute the subfault comer frequency was proposed, where the subfault comer frequency is determined based on a basic value calculated from the total seismic moment of the entire fault and an increment depending on the seismic moment assigned to the subfault; and （ii） the difference of the radiation energy from each suhfault was considered into the scaling factor. The improved model was also compared with the unimproved model through the far-field received energy and the mean spectral ratio. The comparison proves that the improved model allows the received energy to be more independent of subfault size than the unimproved model, and decreases the overestimation degree of the long-period spectral amplitude.

关键词： stochastic finite-fault modeling corner frequency scaling factor far-field received energy long-period spectral amplitude

Combined immersed boundary method and multiple-relaxation-time lattice Boltzmann flux solver for numerical simulations of incompressible flows

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2017年第12期38卷 1679-1696页

作者： Xiaodi WU fu chen Huaping LIU Department of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

A method combining the immersed boundary technique and a multi- relaxation-time （MRT） lattice Boltzmann flux solver （LBFS） is presented for numerical simulation of incompressible flows over circular and elliptic cylinders and NACA 0012 Airfoil. The method uses a simple Cartesian mesh to simulate flows past immersed complicated bodies. With the Chapman-Enskog expansion analysis, a transform is performed between the Navier-Stokes and lattice Boltzmann equations （LBEs）. The LBFS is used to discretize the macroscopic differential equations with a finite volume method and evaluate the interface fluxes through local reconstruction of the lattice Boltzmann solution. The immersed boundary technique is used to correct the intermediate velocity around the solid boundary to satisfy the no-slip boundary condition. Agreement of simulation results with the data found in the literature shows reliability of the proposed method in simulating laminar flows on a Cartesian mesh.

关键词： immersed boundary method lattice Boltzmann equation (LBE) multiple relaxation time incompressible flow

Gaussian fitting in gamma-ray spectral decomposition

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2010年第4期21卷 214-217页

作者： fu chen WANG Nanping Key Laboratory of Geo-detection (China University of Geosciences Beijing) Ministry of Education Beijing 100083 China

In order to extract the information of 662-keV 137Cs spectra from the overlapping peaks with 583-keV 208Tl,609-keV 214Bi,the overlapping peaks are measured by in-situ γ-ray spectrometer using a NaI(Tl) *** spectral model is optimized by the Gaussian fitting algorithm,and the optimized fitting indexes for fitting/original value are from 0.96 to *** fitting verified by experiment is feasible for γ-ray spectrum *** full energy peak of 137Cs is extracted correctly from the overlapping peaks,it is important for in-situ γ-ray spectrometer to estimate contamination of 137Cs in radiated environment and nuclear accident.

关键词：伽玛射线高斯拟合光谱分解 137Cs 拟合算法拟合指数辐射环境重叠峰