Prehistoric disasters at Lajia Site, Qinghai, China

Lajia Site, located near the upper reaches of the Yellow River and the border of Qinghai Province and Gansu Province, is a large-scale site of the Qijia Culture. In 2000 and 2001, archaeologists excavated an unusual scene of prehistoric dramatic and miserable disasters. Lots of geo-logic-geographic evidences revealed that the Lajia Site was ruined by coinstantaneous disasters, mainly floods from the Yellow River and earthquakes, accompanying mountainous torrents. Study on these disasters and their driven forces could provide us not only the knowledge on the palaeoenvi-ronment of the area, but also offer us a valuable site to assess the influence of the natural disasters on human civilization development.     

FEATURES OF POINT BAR DEPOSITION IN THE JUMA RIVER, RONG CHENG, HEBEI PROVINCE, NORTHCHINA

A section is described through the point bar sediments of a meander bend on the Juma River, Rong Cheng. The point bar is characterised by lateral depositional units separated by inclined erosion surfaces. Each unit displays an upward sequence of grain- size fining and reduced trough cross-bedding scale. These units, formed by flood flows, reflect the lateralmigration of the bend and the flood regime of this semi-arid environment . The prevalence of chute deposits in the upper element of the lateral depositional units reflects the rate of outer bank erosion and bend migration, which in turn depend on bank strength and river gradient. The sedimentology of this point bar illustrates the potentiail complexity of the process of point bar construction.     

Eocrinoid echinoderms from the Lower Cambrian Guanshan Fauna in Wuding, Yunnan, China

This is a brief report of a new occurrence of eocrinoids from the Early Cambrian Wulongqing Formation in Yunnan, China. The eocrinoids from the Guanshan fauna are among the earliest known eocrinoids. Different from many other Early and Middle Cambrian eocrinoids, the Guanshan eocrinoids are char-acterized by the absence of sutural pores and epispires, the long and spiral brachioles, the extremely long stalk, and the ratio of the length of the stalk versus that of the calyx. The discovery of the eocri-noids from the Guanshan fauna not only provides new information to the investigation of the early evolution of this animal group, but also shed new light on the occurrence and migration of early eocrinoids.     

Neolithic rice paddy from the Zhaojiazhuang site, Shandong, China

To identify and study the Neolithic rice paddy in Shandong, eastern China, is not only an important issue in the development of Chinese rice agriculture, but also a key part of the study on rice spread in East Asia. Due to the limitation of archaeological materials and the research methods, there have been no discoveries about the Neolithic rice paddy in Shandong Province for a long time. Based on the identification of possible rice paddy by archaeological excavation, phytolith analysis of soil samples from this "paddy" has been systematically carried out and the results have shown a 4600—4300 years old rice paddy preserved at the Zhaojiazhuang site. This is the first examination and study of the rice paddy in North China by systematic phytolith analysis, which is very important for the Neolithic archaeological research and the study of the eastward spread of rice agricultural techniques in East Asia.     

A new Euprox from the Late Miocene of Yuanmou,Yunnan Province,China,with interpretation of its paleoenvironment

The Yuanmou Basin of Yunnan Province is a hotspot for the research of early homind evolution and its environmental background.During the implementation of the Program“Research of the Origin and Evolution of Early Man and Its Environmental Baqckground” from 1998 to 2001,a huge quantity of hominoid and mammal fossils were collected.The present report systematically describes an Euprox robustus sp.nov.identified during the recent laboratory work on the collected material.Euprox is a group of earliest cervids with true antlers.The new species is the third one of the genus discovered in China.Judged by its morphologic characteristics,the new species feed on juicy and tender leaves of dicotyledon.It implies that the vegetation of its epoch in the Yuanmou Basin is a kind of southern subtropical evergreen forest and the climate is humid and temperate with evident seasonality.The latter is mostly influenced by the monsoon and secondly by the latitude.     

Zircon SHRIMP U-Pb geochronology and petrogenesis of the plagiogranites from the Lagkor Lake ophiolite, Gerze, Tibet, China

Field relationship, along with petrographical, petrological, and geochemical characteristics, and zircon populations, indicates that the plagiogranites from the Lagkor Lake ophiolite in the Bangong-Nujiang suture zone (~ 20 km south of Gerze County, central Tibet, China), derived from anatexis of hydrated gabbros by ductile shearing during transport of the oceanic crust. Therefore, this kind of plagiogranite is coeval to or little later than the spreading of the oceanic crust. Zircon SHRIMP age of 166 ± 2.5 Ma for the plagiogranites indicates that an oceanic basin existed in the western part of the Bangong-Nujiang zone in the Middle Jurassic.     

Composition of sandstone and heavy minerals implies the provenance of Kuqa Depression in Jurassic, Tarim basin, China

The petrological characteristics and heavy mineral assembly of the Jurassic System in Kuqa Basin are consistent with the tectonic evolution, which is the major factor controlling the filling process of Kuqa Basin. Controlled by the source areas at the both sides of the Basin, the matrixes are dominated by sedimentary rock, high-grade metamorphic rock, acid magmatic rock, and the highest heavy mineral assemblage of zircon-garnet-magnetite in the content. According to heavy mineral indexes, the Jurassic strata can be classified into three rhythmic units of heavy mineral. The lower sequence contains abundant heavy minerals and relatively high content of detritus and its matrixes primarily came form the recycling orogen. The assemblage of “zircon-garnet-magnetite” indicates that the sedimentary area in the early evolution period of the basin is relatively near the provenance. The middle sequence is different from the lower sequence in the heavy mineral assemblage and has the different characteristics from that of source rock. The heavy mineral assemblage is “garnet-zircon” with the highest content of garnet and its main matrices are the high-grade metamorphic rock, acid magmatic rock and hydrothermal vein at the northeastern edge of the basin. The middle and upper sequences are characterized by the clast provenance, which is primarily from the recycling orogen at the northern edge of the basin and secondarily from the southern uplift. As a result of the two provenances, the strata with apparent changes of heavy mineral assemblage and index better coincides with the interfaces of the secondary strata sequences, which reflects the denudation history and the filling process of the orogen at the northern edge of the basin.     

Sponge spicules in phosphorites of the Early Cambrian Gezhongwu Formation, Zhijin, Guizhou

Phosphorites occurring at the bottom of the Cambrian system contain abundant small shelly fossils, which are the product of the first episode of life explosion in the Cambrian. It was previously reported that the small shelly fossils are dominated by hyolithids, olivooids, zhijinitids, conodontomorphs, yubelichitids, camenitids and algae, with minor amounts of sponge fossils. Large amounts of sponge spicules, diverse in form, have been found for the first time in the Gezhongwu Formation phosphorites at Shixing, Zhijin County, Guizhou Province, of which such spicules as diaxon-triactins, diaxon-tetractins, pentaxon-pentactins and hexon-hexactins account for 30%. These spicules constitute the sponge clastic phosphorites made up of sponge clastics. Meanwhile, it is also expected that the radiation and diversity of sponge animals started as early as in the earliest Early Cambrian. Habit and burying environment of sponge animal are discussed in the paper.     

Discovery of Cathaysiodendron Lee from the Early Carboniferous of Jingyuan, Gansu, western China

As one of the representative members of the Late Palaeozoic Cathaysian flora, Cathaysiodendron has been previously recorded from the Early Permian Taiyuan and Shanxi Formations in north China. The species of Cathaysiodendron presented here are from the lower member of Chouniugou Formation of Ciyao, Jingyuan, Gansu. The overlying marine beds yield fusulinids that are of Visean age in western Europe and conodonts of the Datang Stage in south China, so that the age of the bed containing Cathaysiodendron as Visean, Early Carboniferous, is well constrained. Such a record of Cathaysiodendron is significant in terms of Carboniferous phytogeography and the evolution of the Cathaysian Lepidophytes. A new species, Cathaysiodendron jingyuanense Wang & Wu sp. nov. is described and a second one mentioned.     

等静压和温度作用下Pb(Zr,Sn,Ti)O3陶瓷的介电性能研究

对反铁电-铁电相界附近的Nb掺杂Pb(Zr,Sn,Ti)O3陶瓷，采用2GPa等静压装置测试了其在不同等静压力下的介电温度性能，分析了各种介电异常，发现了精细的相变特性，指出随着温度升高，在较低的等静压范围内发生反铁电-铁电-顺电相变，而在较高的等静压范围内发生反铁电-顺电相变，其中，铁电相分为微弱频率弥散的弛豫型铁电相和正常铁电相两个不同的介电性能区域，最后，得到了该组分材料的温度-等静压相图。     

Research on effects of hydrostatic pressure on the dielectric property of Pb(Zn 1/3Nb2/3) O3-Ba Ti O3PbTiO3 relaxor ferroelectric ceramics

The dielectric properties of Pb(Zn1/3Nb2/3)O3BaTiO3-PbTiO3 relaxor ferroelectric ceramics near the rhombohedral and tetragonal phase boundary were investigated under hydrostatic pressure. It was found that hydrostatic pressure made their phase transition temperature Tc and the peak temperature Tm decreased, and the frequency dispersion and relaxor behavior enhanced. In these disorder systems of composite pervoskite structures, there appeared polar clusters or nanodomains. The unique physical characteristics, which made the relaxor behavior enhanced, is that the correlation length among these nanodo- mains decreases greatly with the pressure increasing.     

Effects of temperature on hydrostatic pressure-induced FE-AFE phase transition in PbLa(Zr, Sn, Ti)O3 ceramics

Hydrostatic pressure-induced ferroelectricantiferroelectric (FE-AFE) phase transition and the pressure dependence of dielectric properties in La-doped Pb(Zr,Sn, Ti)O₃ ceramics were researched; the effects of temperature on hydrostatic pressure-induced FE-AFE phase transition and dielectric properties of the samples were studied. It was found that the temperature made the FE-AFE phase transition pressure decrease, and there existed the behavior of dielectric frequency dispersion and phase transition diffusion in the dielectric-pressure spectrum. These phenomena were very useful to enrich and develop the knowledge on the diffused phase transition behavior of polycomponent relaxor ferroelectric.     

Phenomenon of multiple field-induced phase transition in PLZST antiferroelectric ceramics

The multiple field-induced phase transition in 4 at.% La modified Pb(Zr,Sn,Ti)O 3 family with temperature from -40℃ to 45℃ in reported. Two electric field-induced transitions from a metastable antiferroelectric phase to two ferroelectric phases are observed is polarization at the applied field of 4 MV/m. The critical field of phase transition between two ferroelectric phases is not larger than 2.5 MV/m, about ten to twenty percent of that ever found in PZT based ceramics. Lattice structure is shown to be orthorhombic by X-ray diffraction. Dielectric investigation reveals a relaxor-like ferroelectric behavior. Temperature-electric field phase diagram is also presented. An appreciate kind of materials is provided to investigate multiple field-induced phase transition with PZT-based ceramics.     

TGS铁电相变的时域方法研究

利用时域方法在 TGS 单晶居里点附近以±0.001℃的恒温精度研究了铁电相变的过程,观察到驰豫机构可分为晶格和电子云畸变、电畴运动、和自发极化电偶极矩的屏蔽电荷的激发三种成分.介电损耗在10~(-3)—10~3Hz 频程的峰值表明,在铁电相变过程中晶体和外界的能量交换主要来自屏蔽电荷的激发.     

准同型相界内KNN-LS-BF无铅压电陶瓷的烧结与压电性能

采用传统的陶瓷工艺制备成分处于准同型相界(MPB)内的无铅压电陶瓷0.956K0.5Na0.5NbO3-0.004BiFeO3-0.04LiSbO3(0.956KNN-0.004BF-0.04LS),研究烧结温度对陶瓷的结构与压电、介电性能和相变温度的影响.研究结果表明:所有样品均为单一的钙钛矿结构;在1100℃以下烧结的样品的相结构均呈现明显的正交相与四方相共存的特征,同时略偏向四方相区;适当的烧结温度的提高,能促进陶瓷的致密化;随着烧结温度的升高,陶瓷的压电性能先显著提高后降低,陶瓷的介电损耗先降低后提高,但对正交相与四方相转变温度(θ0-1)和居里温度(θc)的影响比较小;当烧结温度为1100℃时,陶瓷具有最好的压电与介电性能,其压电常数(d33)高达297 pC/N,机电耦合系数(kp)高达54％,居里温度为355℃,tanδ为2.6％,这表明0.956KNN-0.004BF-0.04LS无铅压电陶瓷具有广阔的应用前景.     

Research on effects of hydrostatic pressure on the dielectric property of Pb(Zn<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3−</Subscript>BaTiO<Subscript>3−</Subscript> PbTiO<Subscript>3</Subscript> relaxor ferroelectric ceramics

The dielectric properties of Pb(Zn1_1/3Nb_2/3)O₃₋ BaTiO₃₋PbTiO₃ relaxor ferroelectric ceramics near the rhombohedral and tetragonal phase boundary were investigated under hydrostatic pressure. It was found that hydrostatic pressure made their phase transition temperature T _c and the peak temperature T _m decreased, and the frequency dispersion and relaxor behavior enhanced. In these disorder systems of composite pervoskite structures, there appeared polar clusters or nanodomains. The unique physical characteristics, which made the relaxor behavior enhanced, is that the correlation length among these nanodomains decreases greatly with the pressure increasing.     

Elastic anomalies near phase transitions of lead-free （Na,Bi）TiO3 and （Ba,Zr）TiO3 ferroelectric ceramics

We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus exhibits minimal change in elastic modulus up to 90°C,while the elastic modulus of the BaZr0.07Ti0.93O3(BZT-7)shows 12.5%change at the phase transition temperature of70°C and that of the BaZr0.15Ti0.85O3(BZT-15)ceramics shows 34.6%change at the phase transition temperature of60°C.The variations of elastic modulus will affect the temperature stability of devices made by these lead-free ferroelectric ceramics.     

Electron emission from La-doped Pb（Zr,Sn,Ti）O3 antiferroelectrics by pulse electric field and the relevant physical mechanism

We investigate the characteristics of emission current waves of antiferroelectric cathode material lanthanum-doped lead zirconate stannate titanate （PLZST） triggered by pulse field, and analyze the relationship of the emission current waveforms with the extraction voltage. The close correlation between the triggering pulse polarity and emission current waveform observed evidences the relevant physical process of electron emission. We speculate that the primary emission may result from local phase transition and field emission in the vicinity of triple junctions, and the plasma formation may enhance the electron emission.     

CeO2掺杂(Bi0.94Na0.89Li0.05)0.5Ba0.06TiO3压电陶瓷的微观结构与电性能

采用传统陶瓷工艺合成了CeO2掺杂(Bi0.94Na0.89Li0.05)0.5Ba0.06TiO3 (缩写为 BNBT6-0.05L)无铅压电陶瓷.研究了CeO2掺杂量(质量百分比为0~1.0%)对BNBT6-0.05L陶瓷相结构、体密度、微观结构及压电与介电性能的影响.XRD表明,CeO2扩散进入了BNBT6-0.05L陶瓷晶格内形成了纯的钙钛矿相.SEM表明,少量的CeO2掺杂,改变了陶瓷的微观结构.介电温谱表明,随着CeO2掺杂量的增加,铁电相向反铁电相转变温度(Td)降低. 室温下,CeO2掺杂量为0.2%时,BNBT6-0.05L陶瓷样品有很好的性能:体密度为5.901 g/cm3,压电常数为142 pC/N,平面机电藕合系数为31.3%, 相对介电常数为860, 介电损耗为0.02