泥河湾古湖湖心区石片的发现

Nihewan basin is famous for its lacustrine deposits, animal fauna and occupied evidence of early humans. All of the discovered Palaeolithic sites are distributed along ancient lakeside or on the terraces of the Sangganhe river and its tributaries. However, the authors discovered a stone flake from the central part of the ancient Nihewan lake in an outcrop section on the right bank of the Sangganhe river. The location is 40°06′33″N and 114°20′15″E, near Jinerwa village, Yangyuan County, Heibei Province. The flake is basaltic and has a size of 4.5 cm×3.2 cm×1.7 cm. Its ventral surface is a fresh plane of fracture with a clear point of percussion,a bulb and a bulbar scar on it. The dorsal surface is composed of a residual part of a rounded pebble surface and a fresh plane formed along a joint. The flake is unearthed at 50.73 m under the lacustrine platform surface in perfectly laminated beds of Mid-Pleistocene. The feafures of the flake do not rule out the possibility of natural origin. But combined with the sedimentary features of the horizon where it is unearthed, the most reasonable explanation is that the flake may be the trace of ancient human activities on the frozen lake of Nihewan.     

Comparative analysis of temperature and CO2 fluxes for winter wheat in Tibetan Plain and North China Plain using the EMD method

Comparative study of spectral properties of temperature and CO₂ fluxes measured by eddy covariance method at Yucheng (36°57′N, 116°36′E, 28 m a.s.l., in the North China Plain) and at Lhasa (29°41′N, 91°20′E, 3688 m a.s.l., on the Tibetan Plateau) is described using the empirical mode decomposition (EMD) method. The main results are: (1) The intrinsic oscillation modes or intrinsic mode functions (IMFs) were extracted from data of temperature (T) and CO₂ fluxes (F) measured at Yucheng (T₁ and F₁) and Lhasa (T₂ and F₂). (2) Hilbert transform was applied to these IMF components, then the Hilbert-Huang spectra and the marginal spectra of these data were obtained. (3) Comparison of temperature and CO₂ fluxes in North China Plain and on Tibetan Plain illustrated that the characteristic frequencies corresponding to T₁, F₁, T₂ and F₂ are 0.05 Hz, 0.03 Hz, 0.014 Hz and 0.005 Hz, respectively.     

Comparative analysis of temperature and CO2 fluxes for winter wheat in Tibetan Plain and North China Plain using the EMD method

Comparative study of spectral properties of temperature and CO₂ fluxes measured by eddy covariance method at Yucheng (36°57′N, 116°36′E, 28 m a.s.l., in the North China Plain) and at Lhasa (29°41′N, 91°20′E, 3688 m a.s.l., on the Tibetan Plateau) is described using the empirical mode decomposition (EMD) method. The main results are: (1) The intrinsic oscillation modes or intrinsic mode functions (IMFs) were extracted from data of temperature (T) and CO₂ fluxes (F) measured at Yucheng (T₁ and F₁) and Lhasa (T₂ and F₂). (2) Hilbert transform was applied to these IMF components, then the Hilbert-Huang spectra and the marginal spectra of these data were obtained. (3) Comparison of temperature and CO₂ fluxes in North China Plain and on Tibetan Plain illustrated that the characteristic frequencies corresponding to T₁, F₁, T₂ and F₂ are 0.05 Hz, 0.03 Hz, 0.014 Hz and 0.005 Hz, respectively.     

Discovery of C<Subscript>4</Subscript> species at high altitude in Qinghai-Tibetan Plateau

Plant specimens are collected from the areas between latitude 27°?2′N and 40°57′N, and longitude 88°93°E and 103°24′E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m, and Pennisetum centrasiaticum, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant's tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau.     

Influence of Ru addition on microstructure and stress-rupture property of Ni-based single crystal superalloys

The effects of Ru on the microstructure and stress-rupture property were investigated in two experimental Ni-based single crystal superalloys with and without Ru addition (5.1%, mass fraction). The results indicate that the morphology of γ′ precipitates in the dendrite core and interdendritic region are intermediate and nearly spherical, respectively, in the Ru-free alloy after bei ng aged at 1100 °C for 8 h. The Re partitioning ratio increases due to Ru addition and Ru partitioned preferentially to the γ phase in both dendrite core and interdendritic region of the Ru-containing alloy, which results in more negative lattice misfit and more cuboidal γ′ precipitates. Meanwhile, the γ′ volume fraction increases while the precipitate size and γ channel width decreases due to Ru addition in both dendrite core and interdendritic region. Ru addition improves the stress-rupture life at 1100 °C/140 MPa significantly due to higher γ′ volume fraction, more negative lattice misfit and a well rafting structure as well as less γ channel width.     

Distribution Characteristics and Influencing Factors of Geological Hazards in Tibet

0IntroductionTibet is located at26°50′-36°33′Nand78°25′-99°06′Ein the southwest of China,which isbounded by Sichuan,Yunnan,Qinghai Provincesand Xinjiang Uygur Autonomous Region and coun-tries suchas Nepal,India,Bhutan,Sikki mand My-anmar[1].As main part of Qinghai-Tibet Plateau,Tibet has a special and complex geological condi-tion.Accordingtothe geotectonics,Tibet lies with-in the east of the huge Alps-Hi malayas mountainsystem.Because the Indian Plate continues divinginto no…     

Investigation on the homogenization treatment and element segregation on the microstructure of a γ/γ′-cobalt-based superalloy

The aim of the present study was to investigate the effect of element segregation on the microstructure and γ′ phase in a γ/γ′ cobalt-based superalloy. Several samples were prepared from a cast alloy and homogenized at 1300°C for different times, with a maximum of 24 h. A microstructural study of the cast alloy using wavelength-dispersive spectroscopic analysis revealed that elements such as Al, Ti, and Ni segregated mostly within interdendritic regions, whereas W atoms were segregated within dendrite cores. With an increase in homogenization time, segregation decreased and the initial dendritic structure was eliminated. Field-emission scanning electron microscopy micrographs showed that the γ′ phases in the cores and interdendritic regions of the as-cast alloy were 392 and 124 nm, respectively. The size difference of γ′ was found to be due to the different segregation behaviors of constituent elements during solidification. After homogenization, particularly after 16 h, segregation decreased; thus, the size, chemical composition, and hardness of the precipitated γ′ phase was mostly uniform throughout the samples.     

An improvement of the too cold tongue in the tropical Pacific with the development of an ocean-wave-atmosphere coupled numerical model

A common problem in the application of the coupled ocean-atmosphere general circulation models (CGCMs) without flux correction is that the simulated equatorial cold tongue in general tends to be too strong, narrow, and extending too far west. The causes are not well understood yet. One possible reason may be the simulated mixed layer depth (MLD) is too shallow in the tropical Pacific due to insufficient vertical mixing in the OGCM. It is believed that the wave-induced vertical mixing can greatly improve the simulation of the MLD and thermocline structure. In this study, the coupled ocean-atmosphere general circulation model (FGCM-0) incorporated with wave-induced mixing has been employed to simulate the tropical Pacific sea surface temperature (SST). Generally, the wave-induced mixing lowers the SST in the OGCM because the strengthened vertical mixing can bring more cold water upward. However, in the coupled model, the non-uniformity of the space distribution in SST drop generates a horizontal gradient of the sea surface air pressure, and thus yields surface wind field anomaly. The wind anomaly leads to both ocean surface circulation anomaly and downwelling anomaly, which can restrain the overly-westward extension of the cold tongue in the tropical Pacific. Compared with the model results from the original model (FGCM-0), the modeled SST is higher by more than 0.8℃, with a maximum of 1.2℃ in the western Pacific (160—180°E, 0—3°N). The eastern boundary of the isotherm of 26.0℃ also moves from 165°E to 180°E. The overly westward extension of the simulated equatorial cold tongue is suppressed with the incorporation of the wave-induced mixing in the coupled model. The simulated SST shows in general improved results with a maximum improvement of more than 1.0℃. The simulated SST improvement in the north tropical Pacific is much better than that of the south tropical Pacific.     

Synthesis and sintering of beryllium oxide nanoparticles

BeO nanoparticles were prepared by polyacrylamide gel route and the sintering pr operties of synthesized powder as a function of sintering temperature and time were investigated. Thermal behaviors of the polyacrylamide gel and beryllium salt we re studied by thermogravimetry analysis (TGA). The calcination temperature (690°C) of the beryllium sulfate covered in polyacrylamide xerogel was almost 150 °C lower than that obtained by traditional methods. The nanocrystallites of the BeO particles were estimated by X-ray diffraction (X RD) according to Debye–Scherrer equation. Transmission electron microscopy (TEM) investigation revealed that the average part icle size of the BeO nanoparticles prepared by calcining at 800 °C for 2 h, ranges from 15 nm to 25 nm. The sintering temperature was down to 1 600 °C, which was around 200 °C lower than conventional sintering temperature of the compact sample with co mmon powders. The densification rate was fast at the first 3 h. The thermal conductivity of the sample sintered at 1 600 °C for 6 h was 186.6 W/(m·K).     

Paleomagnetism of early Triassic Daye Formation and its tectonic implications

The new paleomagnetic data of the early Triassic Daye Formation from Hubei Province are reported. The ChRM passes consistency test and reversal test. Two magnetic components were isolated with principal component analysis (PCA). Component B is a ChRM and component A was acquired by remagnetization during Indosinian cycle. Rock magnetic study shows that the carrier is dominantly detrital magnetite. According to the data, in conjunction with recently published Triassic paleomagnetic results, mean paleopole of the Triassic Yangtze Block is calculated as 30.3°N癗, 198.4°E, α95 = 9.2° Distribution of all Triassic declinations indicates obviously local rotation in the mid-Yangtze areas, which results in consistence of the declinations with fold axes. By comparison with Triassic paleomagnetic data in the South China Block and some of geological evidence, it is inferred that the timing of the suture between the Yangtze Block and the South China Block is earlier in western part than in eastern part in the Indosinian period.     

Cretaceous synfolding remagnetization components revealing tectonic rotation of the middle Yangtze fold belt

To reveal the deformation process of the middle Yangtze fold belt, we conducted a paleomagnetic study on Middle Triassic limestones and Middle to Late Jurassic sandstones from Wanzhou, Chongqing. Stepwise thermal and alternating field demagnetization were used to isolate the multi-component re-manent magnetizations. The Jurassic samples were overprinted by recent geomagnetic field, while three magnetization components were isolated from the Middle Triassic samples. A low temperature component (LTC) was isolated at temperatures below 200℃, an intermediate temperature component (ITC) at 200―360℃ and a high temperature component (HTC) at 400―460℃. The LTC is distributed around the present-day Earth magnetic field, probably a viscous component. Stepwise unfolding indi-cates that the maximum precision parameters of ITC and HTC components are achieved at 33±8% and 50±27% (with 95% confidence) unfolding, respectively. The best-clustered ITC mean direction, Dec = 11.2°, Inc = 45.2° (α₉₅ = 4.5°, N = 34), corresponding to a paleopole at 79.3°N, 219.5°E (d_p = 3.6°, d_m = 5.7°), is consistent with the Cretaceous reference direction of the South China Block (SCB). The best-clustered HTC mean direction (taking 70% unfolding), Dec = 24.2°, Inc =49.0° (α₉₅ = 3.6°, N = 23), corresponding to a paleopole at 69.2°N, 195.5°E (d_p =3.1°, d_m = 4.8°), suggests a clockwise rotation of 12.8°±3.5°. These synfolding remagnetization components clearly reveal that a clockwise rotation happened at the middle stage of folding, thus supporting that at least part of the variation in fold axis strikes is due to orocline rotation. Combined with published data, our analysis indicates that the Wan-zhou-Xiangxi segment of the middle Yangtze fold belt experienced oroclinal bending. Furthermore, a published post-folding component isolated from the Middle Triassic Puqi Formation suggests a 27.5°±5.8° clockwise rotation, confirming that at least 50% of the observed clockwise rotations in the eastern middle Yangtze fold belt can be attributed to oroclinal bending. The remagnetization data and geological evidence observed in the middle Yangtze fold belt suggest that collision between SCB and North China Block (NCB) probably lasted till the early period of Early Cretaceous.     

THREE NEW SPECIES OF THE FAMILY SALTICIDAE FROM HAINAN,CHINA

The present paper deals with three new species of the family Salticidae collected from Mount Jianfengling, Hainan, China. All types are deposited in the Institute of Zoology, Academia Sinica, Beijing. 1. Laufeia proszynskii sp. nov. (figs.1-2) Holotype, Mount Jianfengling (18°7′N, 108°8′E), rain forest, May 3,1982.     

Effect of rare earth samarium addition on the kinetics of precipitation in Al-Cu-Mn casting alloy

The mechanical properties of Al-Cu-Mn casting alloy mainly depend on the morphology, distribution, size, and number of θ′(Al₂Cu) precipitates. In this study, we have analyzed the effect of rare earth samarium (Sm) addition on the kinetics of precipitation in the Al-Cu-Mn casting alloy by using differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy. Thermal effect peaks that are attributed to the formation and the dissolution of Guinier-Preston (GP) zone and θ′ phase were identified from the DSC curves. The activation energy of θ′ formation was calculated by using both the Kissinger method and the analytical model, and the corresponding results were compared. Results suggest that the activation energy of θ′ formation in Al-Cu-Mn alloy is dramatically higher than that in Al-Cu-Mn-Sm alloy. Accordingly, it is concluded that the addition of rare earth Sm decreases the activation energy of θ′ formation and promotes the formation of θ′ precipitates.     

Coastal seafloor observatory at Xiaoqushan in the East China Sea

The seafloor observation system is becoming an important infrastructure for marine research because it is transforming oceanic research from temporal investigation to long term observation.The East China Sea coastal seafloor observatory,located between 30°31′44″N,122°15′12″E and 30°31′34″N,122°14′40″E,is constructed near the Xiaoqushan Island outside the Hangzhou Bay on the inner continental shelf of the East China Sea.The observatory is connected by a submarine optical fiber composite power cable that is more than one kilometer long and consists of a special junction box that transmits power and communication signals to different instruments.The special junction box has a variety of waterproof plugs and connects to three different instruments installed in a trawl preventer.The submarine optical fiber composite power cable is landed on the platform by The East China Sea Branch,State Oceanic Administration and the power is continuously supplied by the solar panels and solar battery on the top of the platform.The real time data are directly sent through the cable to the platform and are transmitted by CDMA wireless to the receiver at the State Key Laboratory of Marine Geology of Tongji University.Measurements at the observatory have been taken since April 20,2009 after installation and the results have been interpreted.The characteristics of the near bottom boundary are constrained by a sediment suspension model using portion of the observed data.In particular,discussion is provided on the sea surface height anomaly at Xiaoqushan Island influenced by the tsunami driven by the 2010 Earthquake in Chile.The successful establishment of the coastal seafloor observatory is the first step toward future development of seafloor observation systems in China.It not only accumulates experiences in technology and engineering,but also paves the way for performing important oceanic research using the long term continuous observation platform.     

Temporal and spatial variabilities of sea surface heights in the northeastern South China Sea

Analyses of sea surface height anomalies (SSHA) from Jan. 1993 to Dec. 2001 measured by TOPEX/Poseidon (T/P) satellite altimetry indicate that there are two energy highs of SSHA fluctuations on both sides of the Luzon Strait. The highs centered at (19.5°N, 119.5°E) and (22.0°N, 124.0°E) respectively, are separated by a low energy band in the Strait. Empirical Orthogonal Function (EOF) analysis on the "Far Field" suggests that fluctuations of these two areas are mutually independent. EOF analysis on the "Near Field" shows that SSHA oscillation in the northeastern South China Sea (SCS) is dominated by seasonal variations accompanied with significant intra-seasonal and inter-annual fluctuations. Among which, EOFI and EOF2 reflect 66.7% of the total variance. They are both seasonal but showing three months difference in phase. The basic pattern of EOFI appears to be the seasonal SSHA oscillation centered at (18.0°N, 119.0°E) northwest off Luzon Island, which shows maximums (minimums) in August/Septemb     

不同相构型改性718型合金的高温稳定性评价

Inconel 718 is a Ni–Fe-based superalloy widely used in aerospace engines because of its excellent mechanical properties. However, the inferior stability of the γ″ phase limits the application of Inconel 718, which coarsens rapidly at temperatures greater than 650°C. Further improving the temperature tolerance of Inconel 718 requires optimization of the phase configuration via modification of the alloy’s chemical composition. Given the aforementioned objective, this work was conducted to study the precipitation behavior and thermal stability of the strengthening phases with various structures in modified Inconel 718 alloys by tailoring the Al/Ti ratio. With increasing Al/Ti ratio, three particle configurations were formed: γ′/γ″ composite, isolated γ′, and γ′/γ″/γ′ composite particles. The results of aging tests demonstrate that the isolated γ′ and the γ′/γ″/γ′ composite structure exhibited better thermal stability at temperature as high as 800°C. The isolated γ′ exhibited a reduced coarsening rate compared with the γ′/γ″/γ′ composite particles because the isolated γ′ phase was rich in Al, Ti, and Nb. However, the γ′/γ″ composite particles coarsened and decomposed rapidly during aging at temperatures greater than 700°C because of the lower stability resulting from the larger number of γ″ particles. The obtained results provide necessary data for the compositional optimization of novel 718-type alloys.     

Evaluation on elevated-temperature stability of modified 718-type alloys with varied phase configurations

Inconel 718 is a Ni–Fe-based superalloy widely used in aerospace engines because of its excellent mechanical properties. However,the inferior stability of the γ″ phase limits the application of Inconel 718, which coarsens rapidly at temperatures greater than 650°C. Further improving the temperature tolerance of Inconel 718 requires optimization of the phase configuration via modification of the alloy's chemical composition. Given the aforementioned objective, this work was conducted to study the precipitation behavior and thermal stability of the strengthening phases with various structures in modified Inconel 718 alloys by tailoring the Al/Ti ratio. With increasing Al/Ti ratio, three particle configurations were formed: γ′/γ″ composite, isolated γ′, and γ′/γ″/γ′ composite particles. The results of aging tests demonstrate that the isolated γ′ and the γ′/γ″/γ′ composite structure exhibited better thermal stability at temperature as high as 800°C. The isolated γ′ exhibited a reduced coarsening rate compared with the γ′/γ″/γ′ composite particles because the isolated γ′ phase was rich in Al, Ti, and Nb. However, the γ′/γ″composite particles coarsened and decomposed rapidly during aging at temperatures greater than 700°C because of the lower stability resulting from the larger number of γ″ particles. The obtained results provide necessary data for the compositional optimization of novel 718-type alloys.     

Numerical and experimental study on coke size distribution in bell-type charging in the CDQ shaft

The mechanism of coke size segregation in the radial direction of pre-chamber in coke dry quenching (CDQ) shaft was investigated by experiment and numerical analysis. The experimental apparatus was a cold three-dimensional semicircle model for bell-type charging, which was used to study the influences of different kinds of bells and different stock line levels on the radial distribution of coke size in the radial direction of a pre-chamber. A mathematical model was used, which is capable of estimating the radial average size distribution as well as the radial deposit distribution of each particle size for multiple size coke with a few fixed parameters. The calculated results agree well with the experimental data, which proves the reliability of both experimental study and numerical analysis.     

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO<Subscript>2</Subscript>

This work investigated the flow-accelerated corrosion (FAC) behavior of 13Cr in a wet CO₂-containing environment at different flowing gas velocities and impinging angles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet system. Surface morphology determination, electrochemical measurements, and hydromechanics numerical analysis were carried out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13Cr stainless steel. High-flow-rate gas destroyed the passive film and decreased the pitting potential, resulting in more serious corrosion. The corrosion degree with various impact angles showed the following order: 90° > 60° > 45°. The shear force and the electrolyte from the flowing gas were concluded to be the determinant factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.