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Residual stress of physical vapor-deposited polycrystalline multilayers

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 55-63页

作者： zhang song zhang Hui ZHENG LiLi School of Aerospace Tsinghua University Department of Engineering Physics Tsinghua University

An extended one-dimensional stress model for the deposition of multilayer films is built based on the existing stress model by considering the influence of deposition conditions. Both thermal stress and intrinsic stress are considered to constitute the final residual stress in the model. The deposition process conditions such as deposition temperature, oxygen pressure, and film growth rate are correlated to the full stress model to analyze the final residual stress distribution, and thus the deformation of the deposited multilayer system under different process conditions. Also, the model is numerically realized with in-house built code. A deposition of Ag-Cu multilayer system is simulated with the as-built extended stress model, and the final residual stresses under different deposition conditions are discussed with part of the results compared with experiment from other literature.

关键词： growth models stresses physical vapor deposition processes polycrystalline deposition metals

Berry-Esseen bounds for self-normalized sums of locally dependent random variables

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Science China Mathematics 2024年第11期67卷 2629-2652页

作者： Zhuo-song zhang Department of Statistics and Data Science Southern University of Science and TechnologyShenzhen 518055China

The Berry-Esseen bound provides an upper bound on the Kolmogorov distance between a random variable and the normal *** this paper,we establish Berry-Esseen bounds with optimal rates for self-normalized sums of locally dependent random variables,assuming only a second-moment *** proof leverages Stein's method and introduces a novel randomized concentration inequality,which may also be of independent interest for other *** main results have applied to self-normalized sums of m-dependent random variables and graph dependency models.

关键词： Berry-Esseen bounds self-normalized sums local dependence m-dependence graph dependency

Fundamental Groups of Real Toric Spaces over Simple Polytopes

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1887-1900页

作者： Zhi LU song zhang School of Mathematical Sciences Fudan UniversityShanghai 200433P.R.China

In this paper we study the cubical stuctures and fundamental groups of real toric *** give an explicit presentation of the fundamental group of the real toric space over a simple *** using this presentation,we give a ... 详细信息

关键词： Real toric space fundamental group simple polytope real Buchstaber invariant

Microstructure investigation of dynamic recrystallization in hard machining:From thermodynamic irreversibility perspective

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Frontiers of Mechanical Engineering 2021年第2期16卷 315-330页

作者： Binxun LI Xinzhi zhang song zhang Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education School of Mechanical EngineeringShandong UniversityJinan 250061China Key National Demonstration Center for Experimental Mechanical Engineering Education Shandong UniversityJinan 250061China China Unicom(Shandong)Industrial Internet Co. Ltd.Jinan 250001China

The drastically changed thermal,mechanical,and chemical energies within the machined surface layer during hard machining tend to initiate microstructural *** this paper,attention is paid to the introduction of thermodynamic potential to unravel the mechanism of microstructure ***,the thermodynamic potential-based model expressed by the Helmholtz free energy was proposed for predicting the microstructure changes of serrated chip and the machined surface ***,the proposed model was implemented into a validated finite element simulation model for cutting operation as a user-defined *** addition,the predicted irreversible thermodynamic state change in the deformation zones associated with grain size,which was reduced to less than 1 mm from the initial size of 1.5 mm on the machined surface,was provided for an in-depth *** good consistency between the simulated results and experimental data validated the efficacy of the developed *** research helps to provide further insight into the microstructure alteration during metal cutting.

关键词： thermodynamic irreversibility Helmholtz free energy microstructure evolution dynamic recrystallization hard milling

Tool wear criterion,tool life,and surface roughness during high-speed end milling Ti-6Al-4V alloy

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第8期11卷 587-595页

作者： song zhang Jian-feng LI MOE Key Laboratory of High Efficiency and Clean Mechanical Manufacture School of Mechanical Engineering Shandong University Jinan 250061 China

The objective of the present research is to investigate the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy, and also to define an optimal flank wear criterion for the cutting tool to integrate tool life and the surface roughness requirements of the finish milling process. An annealed Ti-6Al-4V alloy was selected as the workpiece material, undergoing end milling with uncoated carbide inserts. The flank wear of the insert was observed and measured with the toolmaker's microscope. To examine machined surfaces, 3D surface topography was provided by the white light interferometer, and the arithmetical mean roughness (Ra) was calculated with the WYKO Vision32 software. The flank wear increases with cutting time, and the maximal flank wear is set as the flank wear criterion. As the cutting process progresses, tool wear is the predominant factor affecting the variation of surface roughness. According to the plots for the tool wear propagation and surface roughness variation, an optimal flank wear criterion can be defined which integrates the tool life and the surface roughness requirements for the finish milling process.

关键词： Tool wear Surface topography Surface roughness Optimal flank wear criterion

Seasonal Phase-Locking of Peak Events in the Eastern Indian Ocean

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Advances in Atmospheric Sciences 2007年第5期24卷 781-798页

作者： Qin zhang song YANG RS Information System Climate Prediction Center National Weather Service/National Oceanic and Atmospheric Administration Camp Springs MD 20746 USA

The sea surface temperature （SST） anomaly of the eastern Indian Ocean （EIO） exhibits cold anomalies in the boreal summer or fall during E1 Nino development years and warm anomalies in winter or spring following the E1 Nino events. There also tend to be warm anomalies in the boreal summer or fall during La Nina development years and cold anomalies in winter or spring following the La Nina events. The seasonal phase-locking of SST change in the EIO associated with E1 Nino/Southern Oscillation is linked to the variability of convection over the maritime continent, which induces an atmospheric Rossby wave over the EIO. Local air-sea interaction exerts different effects on SST anomalies, depending on the relationship between the Rossby wave and the mean flow related to the seasonal migration of the buffer zone, which shifts across the equator between summer and winter. The summer cold events start with cooling in the Timor Sea, together with increasing easterly flow along the equator. Negative SST anomalies develop near Sumatra, through the interaction between the atmospheric Rossby wave and the underneath sea surface. These SST anomalies are also contributed to by the increased upwelling of the mixed layer and the equatorward temperature advection in the boreal fall. As the buffer zone shifts across the equator towards boreal winter, the anomalous easterly flow tends to weaken the mean flow near the equator, and the EIO SST increases due to the reduction of latent heat flux from the sea surface. As a result, wintertime SST anomalies appear with a uniform and nearly basin-wide pattern beneath the easterly anomalies. These SST anomalies are also caused by the increase in solar radiation associated with the anticyclonic atmospheric Rossby wave over the EIO. Similarly, the physical processes of the summer warm events, which are followed by wintertime cold SST anomalies, can be explained by the changes in atmospheric and oceanic fields with opposite signs to those anomalies

关键词： seasonal phase locking ENSO monsoon interaction

The development and institutional characteristics of China's built heritage conservation legislation

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Built Heritage 2022年第1期6卷 4-18页

作者： song zhang College of Architecture and Urban Planning Tongji University1239 Siping RoadYangpu DistrictShanghai 200092China

The article reviews comprehensively the emergence and development of China's national legislative system for cultural heritage,with a particular focus on built *** covers the period from the late Qing Dynasty to the *** antiquity preservation legislation and policies from the late Qing Dynasty to the early Republic of China(ROC)era signify the initial emergence of the state-led legislative system for cultural heritage protection and *** Interim Regulations on the Conservation and Management of Cultural Heritage,passed in 196o,represent the state's first targeted effort to protect significant historic monuments and *** 1982 Cultural Heritage Protection Law(CHPL)established the mechanism for the conservation of Protected Cultural Heritage Sites(PCHS),while the 2008 Regulation on the Conservation of Famous Historic and Cultural Cities,Towns and Villages(RCFHCCTV)defined the principles for the conservation and management of historic ***'s current jurisdiction for the conservation of cultural heritage is underpinned by legislation such as the CHPL,the Intangible Cultural Heritage Law(ICHL),and the *** article analyses the characteristics of the current state legislative system for built heritage conservation and the challenges and constraints regarding urban *** concludes with strategic guidance for improving the legislation for China's built heritage conservation in the present era of rapid economic development and urban regeneration.

关键词： Conservation legislative history Built heritage Historic and cultural cities Chinese conservation policies

Growth Inhibition Effect of Parthenolide on Human Hepatocellular Carcinomacell Line BEL-7402

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Chemical Research in Chinese Universities 2006年第2期22卷 173-176页

作者： song Xiao-kai zhang Wen College of Biology and Chemical Engineering Tianjin Institute of Technology Tianjin 300191 P. R. China

To study the effects of parthenolide on human hepatocellular carcinoma cell line BEL-7402 and explore its possible mechanism, human hepatocellular carcinoma cell line BEL-7402 was cultured in vitro and treated with parthenolide of different concentrations. Cells without addition of parthenolide were used as control. The growth of inhibition of cells induced by various concentrations was analyzed by using the MTT assay. The morphologic changes of apoptosis was observed under an inversion microscope by Giemsa staining. The expression levels of PCNA albumen were measured by means of immunohistochemical methods. Parthenolide can inhibit the proliferation of BEL-7402 cells in vitro in adose-dependent manner. Apoptosis with nuclear chromatin condensation, fragmentation and cell shrinkage were found by means of inversion microscopy. Formation of apoptotic bodies was observed by Giemsa staining. The immunohistochemical results show that the expression of PCNA has been decreased. Parthenolide can inhibit the tumor growing of BEL-7402 cells, and induce the apoptosis of cells. The mechanisms of those functions may be via inhibiting the expression of PCNA.

关键词： Parthenolide Human hepatocellular carcinomacell line PCNA

Progress in modification of silk fibroin fiber

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Science China(Technological Sciences) 2019年第6期62卷 919-930页

作者： LIU Li zhang song HUANG JunYi School of Materials Science and Engineering Shanghai University Shanghai 200444 China Jiangsu Aiteli Textile Technology Co. Ltd. Qidong 226200 China School of Life Sciences Shanghai University Shanghai 200444 China

Silk fibroin fiber is a natural protein fiber. It is moisturizing, breathable, soft and skin-friendly. However, unmodified silk fibroin fiber is easy to be oxidized and faded. In this paper, the recent progress in modification of silk fibroin fiber is introduced,including the composite modification, feeding modification, genetic engineering modification, spinning technology and regulating the physiological environment modification. Simultaneously, the future development trend for the modification of silk fibroin fiber is also prospected.

关键词： silk fibroin fiber nano particles modification of silk fibroin fiber genetic engineering electrospinning