Biological records of paleoclimate and paleoenvironment changes from Guanzhong area, Shaanxi Province during the last glacial maximum

We have collected a suite ofPaleoloxodon naumanni-Coelodonta antiquitatis fossils from a river terrace profile between Xi’an and Xianyang cities in Guanzhong Area, Shaanxi Province. A detailed examination of the fossils, together with¹⁴C determinations and pollen analyses, have enabled us to reconstruct preliminary features of climate and environment changes and their evolutionary processes, within the last glacial maximum (LGM): about 20 ka ago, the climate was basically cool and wet, and was favourable for the existence ofPaleoloxodon naumanni-Coelodonta antiquitatis fauna. This was followed by a cold, dry phase which was no longer suitable for this type of faunal suite, causing the death of a large number of mammalian assemblages. The available evidence indicates the existence of cold-dry and cool-wet climate and environment fluctuations during the LGM. The cool-wet stage within the LGM reflects a Heinrich event occurring in the high latitude areas, proving the existence of a teleconnection between polar-high latitude areas and the Loess Plateau.     

Backstepping tracking control for nonlinear time-delay systems

1. INTRODUCTION The presence of time delay has a significant effect on system performance and destroys the stability of closed-loop system[1]. Therefore, the study on time-delay systems has important practical significance. Recen- tly,considerable progress has been made in this field[1~10]. According to the dependency of the designed contr-oller depends on the time delay, the control approa-ches for time-delay systems can be classified into two categories: delay-dependent[2~3,10] and dela…     

Properties of PbLa（Zr,Sn, Ti）O3 ceramics near ferroelectric-antiferroelectric phase boundary

Shirane found in the middle of the 20th century that the solid solution PZT had a lot of fine characteristics and carried out detailed researches[1]. The critical phase transition field of antiferroelectric decreased by adding titanate. Titanate expands t…     

Research on development of in situ titanium matrix composites and in situ reaction thermodynamics of the reaction systems

The in situ synthesis method for titanium matrix composites (TMCs) has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur,interface bonding was good, and the reinforcement particle was the rmodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.     

Electrochemical behaviors of silicon wafers in silica slurry

The electrochemical behaviors of n-type silicon wafers pH value and solid content of the slurry on the corrosion of silicon in silica-based slurry were investigated, and the influences of the wafers were studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that these factors affected the corrosion behaviors of silicon wafers to different degrees and had their suitable parameters that made the maximum corrosion rate of the wafers. The corrosion potential of (100) sttrface was lower than that of(111), whereas the current density of (100) was much higher than that of(111).     

Rapid solidification of acoustically levitated Al-Cu-Si eutectic alloy under laser irradiation

Al-27%Cu-5.3%Si ternary eutectic alloy was melted using a YAG laser and then solidified while being acoustically levitated. A maximum undercooling to 195 K (0.24 TL) was achieved with a cooling rate of 76 K/s. The solidification microstructure was composed of (Al+θ+Si) ternary eutectics and (Al+θ) pseudobinary eutectics. During acoustic levitation, the (Al+θ+Si) ternary eutectics are refined and the (Al+θ) pseudobinary eutectics have morphological diversity. On the surface of the alloys, surface oscillations and acoustic streaming promote the nucleation of the three eutectic phases and expedite the cooling process. This results in the refinement of the ternary eutectic microstructure. During experiments, the reflector decreases with increasing alloy temperature, and the levitation distance always exceeds the resonant distance. Because of the acoustic radiation pressure, the melted alloy was flattened, and deformation increases with increasing sound pressure. The maximum aspect ratio achieved was 6.64, corresponding to a sound pressure of 1.8×104 Pa.     

Preparation and luminescence properties of YeO3：Er^3＋/TiO2 with high specific surface area

The three composites Y2O3 :Er3+ , Y2O3 :Er3+ /Yb 3+ andY2O3 :Er3+ /TiO2 were prepared using coprecipitation and sol-gel techniques. Their morphology, specific surface area, porosity, UV-vis. absorption spectra and fluorescence spectra were measured using SEM, TEM, surface analysis, UV-vis. absorption and photoluminescence spectrophotometry. SEM and TEM showed that samples prepared using coprecipitation were dispersed, while Y2O3 :Er3+ /TiO2 particles possessed a mesoporous surface and average diameter of ab...     

Micro-particle deposition and lobar distribution of mass flow in human upper respiratory tract model

A representative human upper respiratory tract model consisting of oropharyngeal and asymmetric tracheobronchial(TB) airways from the trachea(G0) to the main lobar bronchi(G2) was constructed. Laminar-to-turbulent airflow for typical inhalation modes as well as micro-particle transportation,wall deposition and mass flow to lobes was simulated using the CFX10.0 software from Ansys Inc. The numerical particle deposition efficiency of the oropharynx region and two generations(G1 and G2) of TB airways shows gre...     

Characteristics and realization of the second generation surface acoustic wave’s wavelet device

1.INTRODUCTIONDue to the process and characteristics of the non-stationary signals both in ti me and frequency do-mains,wavelet technology has been widely em-ployedin scientific research and engineering appli-cation fields[1~3].To date,wavelet algorithmthatneeds a larger number of mathematic operationsand complicated program is mainly realized bycomputer,whichis quite difficult and expensive toapplyit to engineeringfields and portable electron-ic systems.To solve these problems,we proposed…     

Study on RS- and GIS-based ecological capital assessment in arid areas

Ecological capital assessment is currently one of the important research contents in the interdisciplinary field of ecology, resources economics, environmental economics and ecological economics. To scientifically assess ecological capital redounds to decision-makers to consider the ecological cost in economic development, and is also necessary for sustainable economic development in arid areas. Based on the theory of landscape ecology in this paper the per unit area ecological capital values in arid areas are researched by using the Landsat TM data, CBERS satellite data, meteorological data, MODIS satellite data and other ecological data, and the RS- and GIS-based models of assessing ecological capital values in arid areas are developed. Moreover, based on the field-measured data, a case study on ecological capital assessment in the Manas River basin, Xinjiang in 2003 is carried out. The basin is divided into 4 ecological capital areas so as to quantitatively calculate the ecological capital values of the ecosystems, analyze the spatial distribution of ecological capital, and chart the maps of spatial distribution of ecological capital. The results show that the total ecological capital value of the ecosystems in the Manas River basin in 2003 was 1.49454×10^11 yuan RMB. In spatial distribution, the ecological capital decreases from the alpine zones to the plains and from the oases to the deserts, which accords with the distribution of vegetation zonality in this arid area. The assessed results can objectively reflect the ecological capital and its spatial distribution in the aridbasin, and can also provide reference for roundly carrying out the assessment of ecological capital in arid areas.