检索结果-南通市图书馆

Starch grain analysis reveals function of grinding stone tools at Shangzhai site, Beijing

Science China Earth Sciences 2009年第8期52卷 1164-1171页

作者： YANG XiaoYan yu JinCheng lü Houyuan CUI TianXing GUO JingNing GE QuanSheng Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China Beijing Cultural Relics Institute Beijing 100009China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China School of Archaeology and Museology Peking UniversityBeijing 100871China

Prehistoric groundstone tools including slabs (metate, mo-pan) and mullers (mano, mo-bang) are often considered to be tools that were used to process cereals in ancient China. Most archaeologists believe that groundstone tools are indicators of an agrarian economy. This study employed starch grain analysis to examine a slab and a muller excavated from the Shangzhai Site (7500-7000 cal a BP), Beijing. Identifiable starch grains recovered from the stone tools were classified into 9 genera and 12 species, most of which were from acorns and foxtail millets. Remains from the oak species Q. mongolicus, Q. acuttssima, and Q. dentate were identified as well as a few starch grains from broomcorn (Panicum miliaseum) and bean (Vigna sp.). Other starch grains were from unidentifiable roots and grasses. A variety of starch grains indicates that the grinding stone tools were used to process not only cereals, but also other seeds or roots that had to be ground or husked, thus bringing into question the aforementioned cereal hypothesis. Because the numbers of starch grains from nuts and millets were so large, both gathering and cultivation might have been important economic patterns before 7000 years ago in Beijing area. Moreover, the starch remains are derived from plants that indicate that the paleoclimate of Beijing was wetter and warmer than today’s.

关键词： starch grain analysis artifact function slab and muller Shangzhai Site Beijing

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A study of hydrate plug formation in a subsea natural gas pipeline using a novel high-pressure flow loop

引用

Petroleum Science 2013年第1期10卷 97-105页

作者： li Wenqing Gong Jing lü Xiaofang Zhao Jiankui Feng Yaorong yu Da Beijing Key laboratory of Urban Oil and Gas Distribution Technology China University of Petroleum China National Oil and Gas Exploration and Development Corporation CNPC Tubular Goods Research Institute

The natural gas pipeline from Platform QKI8-1 in the southwest of Bohai Bay to the onshore processing facility is a subsea wet gas pipeline exposed to high pressure and low temperature for a long distance. Blockages in the pipeline occur occasionally. To maintain the natural gas flow in the pipeline, we proposed a method for analyzing blockages and ascribed them to the hydrate formation and agglomeration. A new high-pressure flow loop was developed to investigate hydrate plug formation and hydrate particle size, using a mixture of diesel oil, water, and natural gas as experimental fluids. The influences of pressure and initial flow rate were also studied. Experimental results indicated that when the flow rate was below 850 kg/h, gas hydrates would form and then plug the pipeline, even at a low water content （10%） of a water/oil emulsion. Furthermore, some practical suggestions were made for daily management of the subsea pipeline.

关键词： Natural gas hydrate blockage flow assurance high-pressure loop water cut flow rate

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

MICROSTRUCTURE AND MECHANICAl PROPERTIES OF AZ91D EXTRUDED TUBE

引用

Acta Metallurgica Sinica(English letters) 2006年第3期19卷 203-208页

作者： B.Y. yu C.l. Bao H.W. Song Z. liu H.P. yu School of Materials Science and Engineering Shenyang University of Technology Shenyang 110023 China

The effect of extrusion ratio on microstruetures and mechanical properties of magnesium alloy AZ91D extruded tube at 430℃ has been studied. After the evolution of microstracture and mechanical properties of AZ91D during extrusion were studied, the following parameters were obtained： tensile strength reached the climax value of 306.9MPa and elongation peak value of 10.1% at an extrusion ratio of 7.125, and with the increase of the extrusion ratio to 7.45, yield strength reached a top value of 285.795MPa with decreased tensile strength and elongation. It was concluded that mechanical properties of magnesium alloys AZ91D could be enhanced by adjusting the extrusion ratio near recrystallization.

关键词： magnesium tube microstructure tensile property

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Characteristics and composition of particulate matter from coal-fired power plants

引用

Science China(Technological Sciences) 2009年第6期52卷 1521-1526页

作者： lIU XiaoWei XU MingHou YAO Hong yu DunXi ZHANG ZhongHua lüDangZhen State Key laboratory of Coal Combustion Huazhong University of Science and TechnologyWuhan 430074China

Measurements of the characteristics of particulate matter(PM)were performed at the inlet and outlet of the electrostatic precipitators(ESP)of four boilers in two full-scale pulverized coal power *** was collected with a 13-stages low-pressure-impactor(lPI)having aerodynamic cut-off diameter ranging from 10.0 to 0.03μm for a size-segregated *** properties of PM including its con-centration,mass size distribution,emission characteristics,percent penetration of PM through ESP and elemental composition were *** experimental results indicate that,in all the cases the mass size distribution of PM10 had typical ***1 contained up to 1.15wt% of the total particle(TP)generated in the ***2.5 contained about 2wt%―7wt% of the TP and PM10 contained about 4wt%―19wt% of the *** additive limestone used for desulphurization as sorbent besides PM generated from coal combustion,there was new PM generated from *** as a func-tion of particle diameter had a clear peak in particle size ranging from 0.2 to 0.6μ*** in the submicrometer size range were much more difficult to be collected with ESP than larger ***-tributions of individual elements within PM10 were different.

关键词： particulate matter coal-fired characteristic penetration

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

linking vegetation cover patterns to hydrological responses using two process-based pattern indices at the plot scale

引用

Science China Earth Sciences 2013年第11期56卷 1888-1898页

作者： lIU yu FU BoJie lü YiHe GAO GuangYao WANG Shuai ZHOU Ji State Key laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of Sciences laboratory of Digital Earth Sciences Institute of Remote Sensing and Digital EarthChinese Academy of Sciences

Vegetation cover pattern is one of the factors controlling hydrological processes. Spatially distributed models are the primary tools previously applied to document the effect of vegetation cover patterns on runoff and soil erosion. Models provide precise estimations of runoff and sediment yields for a given vegetation cover pattern. However, difficulties in parameterization and the problematic explanation of the causes of runoff and sedimentation rates variation weaken prediction capability of these models. landscape pattern analysis employing pattern indices based on runoff and soil erosion mechanism provides new tools for finding a solution. In this study, the vegetation cover pattern was linked with runoff and soil erosion by two previously de- veloped pattern indices, which were modified in this study, the Directional leakiness Index （Dl[） and Flowlength. Although they use different formats, both indices involve connectivity of sources ,areas （interpatch bare areas）. The indices were revised by bringing in the functional heterogeneity of the plant cover types and the landscape position. Using both artificial and field verified vegetation cover maps, observed runoff and sediment production on experiment plots, we tested the indices＇ efficiency and compared the indices with their antecedents. The results illustrate that the modified indices are more effective in indicating runoff at the plot/hillslope scale than their antecedents. However, sediment export levels are not provided by the modified indices. This can be attributed to multi-factor interaction on the hydrological process, the feedback mechanism between the hydrological function of cover patterns and threshold phenomena in hydrological processes.

关键词： cover pattern indices runoff soil erosion vegetation cover pattern

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Ab Initio Study on The Influence of Spin State upon Bonding and Interaction in FeCO*

引用

Chemical Research in Chinese Universities 1999年第2期15卷 71-81页

作者： XU Xin l Xin XIAN Hui CAI yu WANG Nanqin ZHANG Qianer State Key laboratory for Physical Chemistry of Solid Surface Institute of Physical ChemistryDepartment of ChemistryXiamen UniversityXiamen361005

Four FeCO states with 3d4s and 3d3d electrons spinpaired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding and interaction in *** calculation results show that the FeCO bonding and interaction are determined by a balance between the bonding stabilization and the exchange stabilization with 3d4s electron spinpairing or without *** 3d3d electron spinpairing versus unpairing has a surprised effect on the FeCO bonding properties even though the 3d orbitals are usually considered as non bonding ones.

关键词： Ab initio Carbon monoxide Iron Transitionmetal carbonyl Bonding mechanism

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Impacts of temperatures and phosphoric-acid modification to the physicochemical properties of biochar for excellent sulfadiazine adsorption

引用

Biochar 2022年第1期4卷 972-985页

作者： Xue-yu Zeng yu Wang Rong-Xin li Hai-lei Cao Ya-Feng li Jian lü Fujian Provincial Key laboratory of Soil Environmental Health and Regulation College of Resources and EnvironmentFujian Agriculture and Forestry UniversityFuzhou 350002China Anhui Pushi Ecological Environment Engineering Co. Ltd.Hefei 230000China State Key laboratory of Photocatalysis on Energy and Environment Fuzhou UniversityNo.2 Xue Yuan RoadFuzhou 350116China

The textural properties and surface chemistry of phosphoric acid-modified biochars(PABCs)prepared at different pyrolysis temperatures(500-700℃)were studied based on the results obtained from XRD,SEM,BET,FT-IR,Raman,XPS and elements *** prepared at higher temperatures tended to possess a bigger proportion of microporous *** adsorption capacity and initial rate of PABCs for sulfadiazine(SDZ)were notably improved to 139.2 mg/g and 9.66 mg/(g min)as calculated from the langmuir *** adsorption equilibrium time was only one quarter of that without *** H_(3)PO_(4) modification was advantageous to produce phosphate and break functional groups to form disordered carbon structure abundant of *** enhancement in the adsorption of SDZ was due to the confinement effect of hydrophobic cavities from the mircoporous structure and theπ-πelectron-donor-acceptor ***,PABCs exhibited stable adsorption capacities at a wide pH range(3.0-9.0)or relatively high concentrations of coexisting ions.

关键词： Coffee grounds-derived biochar Pyrolysis Surface modification Sulfadiazine adsorption Micropore structure

来源：

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

The Consistency of lSE Estimators in Partial linear Regression Models under Mixing Random Errors

引用

Acta Mathematica Sinica,English Series 2024年第5期40卷 1244-1272页

作者： yun Bao YAO yu Tan lÜ Chao lU Wei WANG Xue Jun WANG School of Mathematical Sciences Anhui UniversityHefei 230601P.R.China School of Big Data and Artificial Intelligence Chizhou UniversityChizhou 247000P.R.China School of Big Data and Statistics Anhui UniversityHefei 230601P.R.China

In this paper,we consider the partial linear regression model y_(i)=x_(i)β^(*)+g(ti)+ε_(i),i=1,2,...,n,where(x_(i),ti)are known fixed design points,g(·)is an unknown function,andβ^(*)is an unknown parameter to be estimated,random errorsε_(i)are(α,β)-mix_(i)ng random *** p-th(p>1)mean consistency,strong consistency and complete consistency for least squares estimators ofβ^(*)and g(·)are investigated under some mild *** addition,a numerical simulation is carried out to study the finite sample performance of the theoretical ***,a real data analysis is provided to further verify the effect of the model.

关键词： (α,β)-mixing random variables partial linear regression model least squares estimator consistency

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Oxidized phospholipids are ligands for lRP6

引用

Bone Research 2018年第3期6卷 266-279页

作者： lei Wang yu Chai Changjun li Haiyun liu Weiping Su Xiaonan liu Bing yu Weiqi lei Bin yu Janet l.Crane Xu Cao Mei Wan Department of Orthopaedics and Traumatology Nanfang Hospital Southern Medical University Department of Orthopaedic Surgery Johns Hopkins University School of Medicine Department of Endocrinology Endocrinology Research Center The Xiangya Hospital of Central South University Department of Dermatology Johns Hopkins University School of Medicine Department of Pediatric Endocrinology Johns Hopkins University School of Medicine

low-density lipoprotein receptor–related protein 6(lRP6) is a co-receptor for Wnt signaling and can be recruited by multiple growth factors/hormones to their receptors facilitating intracellular signaling activation. The ligands that bind directly to lRP6 have not been identified. Here, we report that bioactive oxidized phospholipids(oxPls) are native ligands of lRP6, but not the closely related lRP5. oxPls are products of lipid oxidation involving in pathological conditions such as hyperlipidemia, atherosclerosis, and inflammation. We found that cell surface lRP6 in bone marrow mesenchymal stromal cells(MSCs) decreased rapidly in response to increased oxPls in marrow microenvironment. lRP6 directly bound and mediated the uptake of oxPls by MSCs. oxPl-lRP6 binding induced lRP6 endocytosis through a clathrin-mediated pathway, decreasing responses of MSCs to osteogenic factors and diminishing osteoblast differentiation ability. Thus, lRP6 functions as a receptor and molecular target of oxPls for their adverse effect on MSCs, revealing a potential mechanism underlying atherosclerosis-associated bone loss.

关键词： low-density lipoprotein receptor–related protein 6

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Spatiotemporal-Chaos-Based Cryptosystem Taking Advantage of Both Synchronous and Self-Synchronizing Schemes

引用

Chinese Physics letters 2004年第6期21卷 1016-1019页

作者： lǖHua-Ping WANGShi-Hong lIXiao-Wen TANGGuo-Ning KUANGJin-yu YEWei-Ping HUGang DepartmentofPhysics BeijingNormalUniversityBeijing100875 DepartmentofElectronics BeijingNormalUniversityBeijing100875 TheKeylaboratoryofBeamTechnologyandMaterialModificationofMinistryofEducation BeijingNormalUniversityBeijing100875

Two-dimensional one-way coupled map lattices are used for cryptography where multiple space units produce chaotic outputs in parallel. One of the outputs plays the role of driving for synchronization of the decryption system while the others perform the function of information encoding. With this separation of functions the receiver can establish a self-checking and self-correction mechanism, and enjoys the advantages of both synchronous and self-synchronizing schemes. A comparison between the present system with the system of advanced encryption standard (AES) is presented in the aspect of channel noise influence. Numerical investigations show that our system is much stronger than AES against channel noise perturbations, and thus can be better used for secure communications with large channel noise.

关键词： Statistical physics and nonlinear systems

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：