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1.
An 18-year long (1993-2011) comprehensive dataset of snow and meteorological variables from Col de Porte, France is used to analyze the variation of shortwave broadband albedo with elapsed time after snowfalls (snow aging) during each snow season. The effects of air temperature, snow surface temperature and snow depth on snow albedo are investigated. An index based on the accumulation of air temperature over several consecutive days with daily mean higher than 2.5 ℃ is proposed to divide each snow-covered period into a dry and the following wet snow season when this index reaches 18 ℃. The results indicate that snow surface albedo decreases exponentially with time in both dry and wet snow seasons. Snow albedo reduction with snow aging is small at low surface temperature and the reduction rate increases with the rise of surface temperature. However, the reduction rate is widely scattered within the observed range of temperature, implying a loose relationship between snow albedo and snow surface temperature. Snow albedo in wet snow season is generally smaller and decreases faster than in dry snow season. For Col de Porte site, snow depths to effectively mask the underlying surface are 21 and 33 cm in dry and wet snow season respectively.  相似文献   

2.
Vegetation phenology is an important indicator of climate change impacts on the seasonal dynamics of the biosphere. However, little is known about the influence of elevation on spring phenological sensitivity to temperature in an alpine ecosystem. Based on remotely sensed land surface phenology and temperature data from 2001 to 2010, this study investigated the rate of spring phenological change of the Tibetan Plateau (TP) grasslands in response to interannual temperature variations at different elevations. Results suggest that spring phenology in the TP grasslands exhibits a stronger response to changes in temperature at higher elevations than at lower ones. In particular, spring phenology advanced by 1-2 days in response to a 1 ℃ increase in May average temperature at elevations from 3,000 to 3,500 m, while the rate was up to 8-9 days/℃ at 5,000-5,500 m. Analysis using accumulated growing degree days (AGDD) from January 1 through May 31 showed the same general trend with increased elevation associated with increased sensitivity (as measured by phenological change per unit of AGDD change). Such temperature sensitivity gradients in the TP grasslands could be partly explained by the growth efficiency hypothesis which suggests that vegetation adapted to colder climates likely requires less heat energy for the onset of growing season and vice versa in warmer climates. Furthermore, accumulated growing degree days from January 1 to the greenup date were found to decrease with increasing elevations, which provided evidence to support the applicability of the growth efficiency hypothesis in an alpine grassland ecosystem.  相似文献   

3.
Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments; among these, some 25 % are free-living marine forms with a population density of (1-12) × 10^6 inds m^-2 in seabed sediment, reaching maximum values in muddy estuaries and salt marshes. A large quantity of carbon from the salt marsh plants enters the ecosystem via the detritus pathway, in which nematodes play an important role through their feeding and bioturbation activities. Vegetation influences the sedimentary environment and modifies the distribution pattern of nematode communities in coastal wetlands. Nematodes are coupled closely with bacteria/detritus in microbial food webs, stimulating bacterial growth and subsequent nutrient remineralization; they provide food sources for higher trophic levels and serve as a linkage between micro- and macro-fauna. Furthermore, nematodes have a potential to provide proxies that can be used in diagnosing environmental quality. In China, only a limited number of nematode data sets are available for the coastal wetlands across several different climatic zones. It is necessary to carry out additional investigations into the biology and ecology of nematodes in order to delineate their ecological functioning in coastal wetlands. On such a basis, the contribution made by nematodes to material cycling and the ecological functioning in coastal wetlands can be quantified. The assessment of their biological diversity should be a focus, which is fundamental in the study of wetland ecosystem dynamic mechanisms. In addition to laboratory and mesocosm experiments, mathematical models should be established to predict the responses of ecosystem to the environmental disturbance. Finally, it is necessary to improve the techniques for nematode analysis, to enhance the efficiency of data acquisition.  相似文献   

4.
The type of pinion and rack vertical shiplifts has been developed in recent a couple of years in the construction of dams. But the design methods and methodologies have rarely been discussed in literature. The Xiangjiaba shiplift is the second shiplift of this type following the Three Gorges shiplift. Being aimed at the technological rationality of the design in synthetically considering security, economy and applicability, this paper presents the research results of some vital issues relating the design of the Xiangjiaba shiplift, including the determination of design water depth of ship chamber based on fluid numeral computation and physical model test, the optimum design of general layout of main equipments and the civil structure of the Xiangjiaba shiplift, the finite element method (FEM) analysis of stress, vibration modes and the buckling of ship chamber, antiseismic research and the design of structures and mechanisms of the shiplift and the optimum design of driving mechanisms. This research provides the theoretical basis for the design of the Xiangjiaba shiplift. The design principles and research methods are valuable for the design of the same type of shiplifts.  相似文献   

5.
Pelitic granulite from the Khondalite Belt, North China Craton, is composed of garnet, sillimanite, perthite, biotite and quartz. Oriented rutile needles in gar- net are reported for the first time from the granulite. The rutile needles have been identified by optical microscopy and confirmed by in situ Raman spectroscopy, where they show the characteristic bands at 446-448 and 610 cm-1. Because of their very strong shape preferred orientation in 3-4 easily observable directions, these futile needles are interpreted to have formed by precipitation during exhu- mation and cooling following peak metamorphism. The ternary feldspar geothermometer gives a peak metamorphic temperature of ,- 980 ℃ at 10 kbar. The presence of oriented rutile needles in garnet is suggested to be a valuable indicator of ultrahigh-temperature (UHT) metamorphism in the Khondalite Belt and therefore likely in other UHT terrains.  相似文献   

6.
Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3–2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar (SHPB) were used to investigate the effect of strain rate on the compressive deformation behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate (< 1.0 s-1), the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.  相似文献   

7.
The photoluminescence(PL)dynamics of nano-silicon prepared in various environments is investigated,which involves the emission in nanostructures related to a wider band from 550 nm to 900 nm and the localized states emission at 694 nm,605 nm,604 nm and 560 nm.It is observed that the sharp PL peak on the samples prepared in nitrogen has the shape of single tip near 605 nm,but the shape of twin tips always occurs in the two sharp peaks on the samples prepared in oxygen.The threshold behavior and the optical gain are discovered in the PL emission at 694 nm,605 nm and 604 nm.The experiments demonstrate that the optimum pressure to prepare samples in oxygen for the enhancement of emission near 700 nm is about 10~100 Pa,and the optimum one in oxygen for the enhancement of emission near 600 nm is about 1/10~1 Pa,while in high vacuum(10μPa) the PL emission becomes weaker.  相似文献   

8.
孙宝凤 《科技信息》2009,(19):150-151
In the process of social linguistic communication, due to the different circumstances and conditions, people can not express certain things clearly in a direct way when they come across something painful, unpleasant, disgusted and even embarrassing. Instead, they have to use some vague, implicit, mild and euphemistic expressions, so as to achieve the purpose of expressing feelings and exchanging ideas and thoughts in an appropriate and light atmosphere. This paper tries to deal with the application of euphemisms in various fields, thereby reveal some main functions of euphemism, i.e. avoidance function, politeness function, gloss-over function and disguise function.  相似文献   

9.
A wave-tide-circulation coupled model is used to simulate upwelling off the south coast of Java, Indone- sia. The results show that the vertical velocity off East Java is stronger than other parts in this area. The strongest vertical velocity is located approximately at 80 m depth. The annual averaged values of upwelling are 2.3 × 10-6 and 1.06 × 10-5 m/s for south of West Java and south of East Java, respectively. The vertical velocity from the model shows that upwelling off West Java has seasonal variability, while it is quite steady and strong off East Java. Additional numerical experiments show that the wind is not the dominant factor for the steady upwelling off the southern part of East Java. It is then hypothesized that the Indonesian Throughflow (ITF) may be responsible for the upwelling. To test this hypothesis, two scenarios are implemented, both of which block the outflow of the ITF. Sensitive study shows that the ITF plays a key role in the formation of East Java upwelling. The effect of the ITF can account for about 55 %-65 % of the upwelling.  相似文献   

10.
The Large Hadron Collider at CERN is performing direct searches for top-quark anomalous flavor-changing neutral current (FCNC) processes. However, these processes may be correlated closely with the low-energy rare B and K meson decays. In this paper, we review the anomalous top-quark coupling effects in these low-energy flavor transitions, summarize the flavor constraints and discuss their implications for direct detection of top-FCNC processes at the Large Hadron Collider.  相似文献   

11.
Terahertz(THz) frequency region, defined from0.1 to 10 THz, is an important frequency band for radio astronomy and atmospheric science. As NbN Superconductor-Insulator-Superconductor(SIS) mixers used for terahertz detection, which are studied by the Purple Mountain Observatory(PMO), Chinese Academy of Sciences(CAS), work at 8–10 K, and require condition of micro vibrations, its astronomical observation in aerospace is limited by suitable refrigeration method. 4 K high frequency pulse tube cryocooler developed by Key Laboratory of Space Energy Conversion Technologies(SECT), Technical Institute of Physics and Chemistry(TIPC), CAS, offers an opportunity for the application of SIS mixers. This article introduces the progress of the two-stage high frequency pulse tube cryocooler researched by TIPC. The cryocooler has reached a no load temperature of 4.5 K which is the lowest temperature for this kind of cryocooler reported so far. The successful coupling between the THz component and the high frequency pulse tube cryocooler lays a solid foundation for space detection in the terahertz band.  相似文献   

12.
吴艳 《科技信息》2008,(17):239-239
The development and wide spread of English language has led to the internationalization and localization of English language, during which English language is widely used in international communications by people with different mother tongues, in addition, English variations on different levels and local varieties have emerged. In consideration to the changes above, this paper aims to, firstly, examine the status of English language as an international language (EIL); secondly, explore the future of English language teaching (ELT) in China under a global context.  相似文献   

13.
Strong disturbances associated with auroral substorms originate from the ionosphere-magnetosphere owing to the effects of the solar wind, and the wind field in the ionosphere is related to such substorm activity. Here, we describe the analysis of four auroral substorm events, for which we employed an all-sky Fabry-Perot interferometer to observe the two-dimensional horizontal wind field and combined the results with data from an all-sky charge-coupled device imager, a fluxgate magnetometer installed at Yellow River Station, and the Super Dual Auroral Radar Network. The results demonstrate that, during auroral substorms, the vector wind field is related closely to variations in the ion drift and geomagnetic field. Moreover, we observed a changing wind field of approximately 300 rn/s in response to variations in the electric and magnetic fields (likely caused by ion drag) and a disturbance of about 200 m/s that we attribute to the interaction of Joule heating and ion drag.  相似文献   

14.
The responses of the East Asian summer monsoon (EASM) to large volcanic eruptions were analyzed using a millennial simulation with the FGOALS-gl climate system model. The model was driven by both natural (solar irradiance, volcanic eruptions) and anthro- pogenic (greenhouse gases, sulfate aerosols) forcing agents. The results showed cooling anomalies after large volcanic eruptions almost on a global scale. The cooling over the continental region is stronger than that over the ocean. The precipitation generally decreases in the tropical and subtropical regions in the first summer after large volcanic eruptions. Cooling with amplitudes up to -0.3 ℃ is seen over eastern China in the first summer after large volcanic eruptions. The East Asian continent is dominated by northeasterly wind anomalies and the corresponding summer rainfall exhibits a coherent reduction over the whole of eastern China. An analysis of the surface heat flux suggested the reduction in summer precipitation over eastern China can be attributed to a decrease of moisture vapor over the tropical oceans, and the weakening of the EASM may be attributed to the reduced land-sea thermal contrast after large volcanic eruptions.  相似文献   

15.
A gravity network with 302 observation points has been established in the western Sichuan Foreland Basin (SFB) to explore Bouguer gravity anomalies (BGAs). Our observational results reveal that the BGAs are negative as a whole, with a maximum value of -220 mGal (10^-5m s^-2) at the northwest region of the study area. The real Moho depths beneath the SFB revealed by BGA data change smoothly from 39.5 km in the southeast to 43.7 km in the northwest of the monitoring region. However, the isostatic ones deduced from Airy isostatic model and topographical data vary approximately 39.5-42.0 km. The maximum differences of 2.7 km between the real and isostatic Moho depths are found near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes, where the crust is in the greatest isostatic imbalance of the monitoring region. Analysis of the isostatic state indicates that the deep dynamic environment near the seismic gap between these two earthquakes indicates an M ≥ 7.0 earthquake in the future. This study indicates that we can use isostasy as a potential approach to study the dynamic process of crustal material movement and to analyze regional potential seismic risks.  相似文献   

16.
Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December, 1992, totaling 653 km with the designed annual traffic volume of 1 × 10^8 t. In order to meet the demands of national economic development, the transport capacity of the line must be enhanced greatly. Depending on independent innovation, MOR, for the first time in the world,realizes the integration between GSM-R and Locotrol, the integration between 800 MHz digital radio and Locotrol, and the integration between a single set of Locotrol and SS4 locomotive. Meanwhile, CR develops equipment portfolio for heavy-haul through combining 2 high power locomotives of HXD series ( means harmony) with controllable EOT. Relying on integration and innovation, it succeeds in operating 20 kt-level combined heavy-haul train on Datong-Qinhuangdao line, which tripled the annual traffic volume of the line from 1 × 10^8 t in 2002 to 3 × 10^8 t in 2007.  相似文献   

17.
Since the 1990s, an ultramicro-particle texture in nano- or micron-sized scale has been continually found in shear planes of various rocks, and recently further progress was made in generic physical mechanisms. In this article, the characteristics of the nano-sized particle layer in rock shear planes (including widespread distribution, layering texture, non-linear genetic mechanism, and multiple functions) on an ultra micro-scale were briefly introduced and more information was obtained by analyzing cases from home and abroad. Our findings suggest that (1) there is a paragenetic relationship between the development of shear frictional- viscous and the formation of nano-sized particles, and (2) in the shear movement, partitioning, segregating, and layering in rocks are initiated by the sliding motion of the nano-sized particle layer. Moreover, the plastic rheology of rocks is essentially the movement of ultra-micro-sized particles (nano-size and micro-size), and the nano-sized particle layer in rock shear planes is characterized by some particular physical and chemical effects.  相似文献   

18.
To evaluate gambiered Guangdong silk's ecology properties, the raw materials ecology, production ecology and use ecology are analyzed; and the safety to human is tested according to GB/T18885 - 2002. Gambiered Guangdong silk is a kind of natural product. All its raw materials are reproducible and degradable natural resources, and it can decompose completely when being discarded. R is comfortable to wear, and easy to clean and dry. It is mainly manufactured by dip-dyeing in dye yam solution, and insolating under the burning sun. The production energy is solar, a kind of clean and reproducible energy. The production process is clean and environmental friendly. There is neither the utilization of synthetic dyestuff and chemical auxiliary, nor the discharge of environment pollutant, and even the dreg of dye yam is used as fuel. The safety test results show that pH value of water extract, heavy metal content (except for Pb content), color fastness and odor meet the requirements of GB/T18885 - 2002 and Okeo-tex standard 100.  相似文献   

19.
This article introduces three outstanding innovations, i.e. utilization of the steel casing for the piles to estab- lish a construction platform for Sutong Bridge' s large and deep-pile groups; 5000 ton steel cofferdam lowered as a whole and used as a protective structure against impact from ship collision; Permanent scour protection. This article also pres- ents economical and reasonable design method for large bridge foundation and explains the significance of innovation and technical integration to large and complicated project construction based on the above theory.  相似文献   

20.
The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution (SCPE) project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.  相似文献   

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