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Effect of Asynchronous Adjustments of Clamping Cylinders on Triangular Crack of Slab Castings Under Application of Soft Reduction

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Journal of Iron and Steel Research International 2013年第2期20卷 38-47页

作者： LIU Ke CHANG Yun-he HAN zhan-guang zhanG Jia-quan State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological EngineeringUniversity of Science and Technology Beijing

Soft reduction is known to be one of the best ways to improve the internal quality of slab castings such as center segregation, center porosity, centerline or triangular zone cracks, which is based on a proper adoption of the amount of reduction upon the given final solidification zone through roll gap adjustments. The synchronization of the clamping cylinders for roll gap adjustments should be very important to the application of soft reduction, including the synchronization of the clamping cylinders adjustments in the same and different segments. The synchronization of clamping cylinders adjustments is mainly affected by the adjustable accuracy of the four position-controlled clamping cylinders mounted in the upper frames of the segments according to a predetermined transformation relationship between the signals of displacement sensors and aimed roll gap, which, however, is also influenced by the installation accuracy, the precision of displacement sensors, the deformation of the segment frames and/or its bearing pedestals. Due to the actual asynchronous adjustments of the four clamping cylinders, the dynamic soft reduction operation is normally applied at non-ideal mechanical conditions. Here 7 possible situations of asynchronous adjustments of the local segments which may induce gap deviation have been presented. The roll gap deviation in the soft reduction region of a slab casting has been studied by a 3-D visco-elastic plastic FEM model, through which the additional inter-roll bulging, the related triangular cracks induced by one kind of the possible asynchronous adjustment situation and the effectiveness of soft reduction have been analyzed. A critical tolerance for the gap adjustments has been proposed for better contribution of soft reduction to the internal quality of slabs.

关键词： slab casting soft reduction clamping cylinder asynchronous adiustment

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Micro/nanosystems for controllable drug delivery to the brain

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The Innovation 2024年第1期5卷 139-157页

作者： Mingzhen tian Zhichao Ma guang-Zhong Yang Institute of Medical Robotics School of Biomedical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Drug delivery to the brain is crucial in the treatment for central nervous system *** significant progress has been made in recent years,there are still major challenges in achieving controllable drug delivery to the *** clinical needs arise from various factors,including controlled drug transport,handling large drug doses,methods for crossing biological barriers,the use of imaging guidance,and effective models for analyzing drug *** advances in micro/nanosystems have shown promise in addressing some of these *** include the utilization of microfluidic platforms to test and validate the drug delivery process in a controlled and biomimetic setting,the development of novel micro/nanocarriers for large drug loads across the blood-brain barrier,and the implementation of micro-intervention systems for delivering drugs through intraparenchymal or peripheral *** this article,we present a review of the latest developments in micro/nanosystems for controllable drug delivery to the *** also delve into the relevant diseases,biological barriers,and conventional *** addition,we discuss future prospects and the development of emerging robotic micro/nanosystems equipped with directed transportation,real-time image guidance,and closed-loop control.

关键词： equipped doses barriers

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Simulation and experiment on prediction of total rice seeds mass in vibrating tray for vacuum plate seeder

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International Journal of Agricultural and Biological Engineering 2019年第5期12卷 81-86页

作者： zhan Zhao Mingzhi Jin Chunjie tian Fang Qin Institute of Agriculture Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina

To improve the seeds pick-up precision of a vacuum plate seeder,it is important to accurately control the relative distance between suction plate and seeds layer in vibrating *** the excitation of reciprocating vibration with a time varying interference in direction angle,the seeds motion is simulated using the discrete element method(DEM).By analyzing the seeds distribution characteristics,it was found that the seeds-mass-per-unit-area(SMA)was approximately plane distributed in the ***,four square areas on the bottom of rectangular tray were divided symmetrically near the four vertices to measure the corresponding SMA respectively,and a monitoring plane model was established to predict the average SMA and total seeds mass in the *** prediction results of DEM simulation showed that the maximum and the mean relative errors were 6.75%and 2.85%.The influences of the normal vector of monitoring plane model and the standard deviation of SMA in four monitoring areas on the prediction errors were analyzed.A method for improving prediction accuracy by using linear regression correction was proposed,and the maximum and the mean relative errors could be reduced to 5.01%and 2.07%.When the tray was vibrated with the frequency of 11 Hz and the amplitude of 4 mm,experiments were carried out on the vacuum plate seeder test-rig.A Kalman filter was adopted to suppress the SMA measurement noise in four monitoring *** results indicated that the maximum and the mean relative errors were 10.2%and 3.46%with the average SMA in range of 0.9-1.5 g/cm2,*** paper can provide a basis for further study on the automatic control of suction plate motion according to the variation of seeds mass in the tray.

关键词： vacuum plate seeder rice seeds total mass prediction method vibrating tray discrete element method

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Manipulated microtopography alters plant community development in fragile farm-pastoral transition zone

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Journal of Plant Ecology 2024年第5期17卷 176-188页

作者： Minxuan Gao Yining Wang Yongning Ren Jinyan zhan tian Xie School of Environment State Key Joint Laboratory of Environmental Simulation and Pollution ControlBeijing Normal UniversityBeijing 100875China Yellow River Estuary Wetland Ecosystem Observation and Research Station Ministry of EducationDongying 257500China

The ecosystems within agro-pastoral transition zones exhibit inherent fragility and heightened susceptibility to climate variability,exacerbated by profound degradation resulting from anthropogenic *** vegetation degradation in these areas precipitates severe soil erosion,presenting formidable challenges for ecological restoration *** utilization of microtopographic structures to mitigate soil erosion and facilitate vegetation recovery stands as a prominent strategy for vegetation restoration within agro-pastoral transition *** the acknowledgment in current restoration practices that the efficacy of microtopography-based restoration is contingent upon slope,aspect and elevation,there remains a notable absence of precise observed information on this *** study,conducted in the Bashang Grassland,a typical agro-pastoral transition zone in northern China,aims to fill the information gap concerning the correspondence between microtopographic structures and restoration *** findings revealed that microtopography has a significant impact on vegetation characteristics,with outcomes varying by *** slopes displayed higher biomass and density compared with sunny slopes and *** microtopography affected community structure,it did not substantially alter species richness,highlighting the critical role of location and pit construction in successful restoration *** study provides insights for the selection,design and assessment of microtopography-based restoration in vulnerable ecosystems.

关键词： community structure microtopography-based restoration plant diversity plant restoration soil erosion

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Agro-climatic adaptation of cropping systems under climate change in Shanghai

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Frontiers of Earth Science 2015年第3期9卷 487-496页

作者： Zhuoran LIANG Tingting GU zhan tian Honglin ZHONG Yuqi LIANG Hangzhou Meteorological Service Hangzhou 310051 China Shanghai Climate Center Shanghai Meteorological Service Shanghai 200030 China Zhejiang Meteorological Service Center Hangzhou 310017 China Department of Geographical Sciences University of Maryland College Park MD 20742 USA Department of Physics and Technology Nanjing Normal University Nanjing 210023 China

Climate change affects the heat and water resources required by agriculture, thus shifting cropping rotation and intensity. Shanghai is located in the Taihu Lake basin, a transition zone for various cropping systems. In the basin, moderate climate changes can cause major shifts in cropping intensity and rotation. In the present study, we integrated observational climate data, one regional climate model, land use maps, and agricultural statistics to analyze the relationship between heat resources and multi-cropping potential in Shanghai. The results of agro-climatic assessment showed that climate change over the past 50 years has significantly enhanced regional agro- climatic resources, rendering a shift from double cropping to triple cropping possible. However, a downward trend is evident in the actual multi-cropping index, caused principally by the increasing costs of farming and limitations in the supply of labor. We argue that improving the utilization rate of the enhanced agro-climatic resources is possible by introducing new combinations of cultivars, adopting more laborsaving technologies, and providing incentives to farmers.

关键词： climate change cropping systems multicropping index double rice Cold Dew wind

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Solvent- and catalyst-free synthesis of dihydropyrimidinthiones in one-pot under focused microwave irradiation conditions

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Chinese Chemical Letters 2008年第10期19卷 1183-1185页

作者： Hong Wen zhan Jin Xian Wang Xi tian Wang Institufe of Chemistry Department of Chemistry Northwest Normal University 967 Arming Road （E.） Lanzhou 730070 China

Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicit... 详细信息

关键词： Focused microwave-assisted Catalyst- and solvent-free Synthesis Dihydropyrimidinthiones

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Effects of van Hove Singularities on Transport of Quantum Dot Systems in Kondo Regime

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Communications in Theoretical Physics 2005年第3X期44卷 563-572页

作者： HU Zhi-Ming YANG Kai-Hua tian guang-Shan School of Physics Peking University Beijing 100871 China College of Applied Sciences Beijing University of Technology Beijing 100022 China

In the present paper, we study the effect of van Hove singularities of conduction electron on the transport of a single quantum dot system in the Kondo regime. By using both the equation-of-motion and the noncrossing approximation techniques, we show that the corrections caused by these singularities are actually minor. It can be explained by observing that the singularities in the equations, which determine the electronic DOS on the dot, are integrable. Furthermore, we find that, although each line width function is divergent at van Hove singular points, the total divergence is canceled out in the final formula to calculate the current through the system. Therefore, as far as the qualitative properties of the system is concerned, these singularities can be ignored and the wide-band approximation can be safely used in calculation.

关键词： quantum dot system van Hove singularities Kondo effect

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A Construction of Cryptogroups

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Acta Mathematica Sinica,English Series 2007年第5期23卷 789-798页

作者： guang tian SONG Guo Xin LIU Jian Gang zhanG Department of Mathematics University of Science and Technology of China Hefei 230026 P. R. China Department of Mathematics Southwest University Chongqing 400715 P. R. China

In this paper, a cryptogroup is constructed by a band and a family of groups and homomorphisms satisfying some conditions.

关键词： Cryptogroup Band Group homomorphism

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Geometries for possible kinematics

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Science China(Physics,Mechanics & Astronomy) 2012年第11期55卷 1978-2003页

作者： HUANG Chaoguang tian Yu WU XiaoNing XU zhan ZHOU Bin Institute of High Energy Physics and Theoretical Physics Center for Science FacilitiesChinese Academy of SciencesBeijing 100049China Graduate University of Chinese Academy of Sciences Beijing 100049China Institute of Mathematics Academy of Mathematics and System SciencesChinese Academy of SciencesBeijing 100190China Department of Physics Tsinghua UniversityBeijing 100084China Department of Physics Beijing Normal UniversityBeijing 100875China

The physical and geometrical realizations of algebras for all possible Lorentzian and Euclidean kinematics with so(3) isotropy are presented in contraction approach and then *** geometries associated with these realizations are also obtained by the contraction *** relations among the geometries are *** geometries fall into *** exists t 1/(ν 2 t) correspondence in each *** the viewpoint of differential geometry,there are only 9 geometries,which have right signature and geometrical spatial *** are 3 relativistic geometries,3 absolute-time geometries,and 3 absolute-space geometries.

关键词： possible kinematics geometries contraction time duality

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The structural change of Cu-Sn melt

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 414-420页

作者： HOU JiXin SUN JianJun zhan ChengWei tian XueLei CHEN XiChen Key Laboratory of Liquid Structure and Heredity of Materials of Ministry of Education Shandong UniversityJinan 250061China

With the high-temperature viscometer and magnetic susceptibility measurement device designed by our group,the viscosity and the magnetic susceptibility of the Cu65Sn35 melt were measured during the cooling *** anomalous change can be found in the curves of viscosity and magnetic susceptibility at a certain *** structure of the melt was studied by the high-temperature X-ray *** anomalous change also can be found in the pair distribution function,correlation radius,and coordination number at the approximate tem-perature,which shows the microstructural change of the Cu65Sn35 *** the results,it was confirmed that the Cu6Sn5 compound occurs in the melt,which leads to the structural change of the melt.

关键词： Cu-Sn alloy melt structure

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