共查询到20条相似文献,搜索用时 78 毫秒
1.
LaBao Zhang YangYin Zhong Lin Kang Jian Chen ZhengMing Ji WeiWei Xu ChunHai Cao 《科学通报(英文版)》2009,54(12):2150-2153
A superconductor single photon detector based on NbN nanowire was fabricated using electron beam lithography (EBL) and reactive ion etching (RIE) for infrared photon detection. When biased well below its critical current at 4.2 K, NbN nanowire is very sensitive to the incident photons. Typical telecommunication photons with a wavelength of 1550 nm were detected by this detector. Data analysis indicates the repeating rate of the device with 200 nm NbN nanowire may be up to 100 MHz, and the quantum efficiency is about 0,01% when biased at 0.95/c. 相似文献
2.
LIN Yi SHEN XinCheng WANG JingJing BAO Lei ZHANG ZhiLing PANG DaiWen 《科学通报(英文版)》2007,52(23):3189-3192
Based on tapping mode AFM imaging, a method was demonstrated to evaluate compression elasticity of single double-stranded DNA (dsDNA) molecules in the force region. With images under ambient conditions, Young's moduli of dsDNA in compression were calculated. Results demonstrated that Young's moduli of dsDNA can be simply deduced according to the proposed model. The method can also be used to evaluate the compression elasticity of similar soft nanomaterials. 相似文献
3.
JingBo Xu HaiYing Zhang WenXin Wang Liang Liu Ming Li XiaoJun Fu JieBin Niu TianChun Ye 《科学通报(英文版)》2008,53(22):3585-3589
GaAs-based metamorphic HEMTs (MHEMT) consist of GaAs substrates and InP-based epitaxial structure, and have the advantages of both InP HEMT's excellent performances and GaAs-based HEMT's mature processes. GaAs-based MHEMTs were applied to millimeter-wave low-noise, high-power applications and systems. The current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are important performance parameter of GaAs-based MHEMTs, and they are limited by the gate-length mainly. Electron beam lithography is one of the lithography technologies which can be used to realize the deep submicron gate-length. The 200 nm gate-length GaAs-based MHEMTs have been fabricated by electron beam lithography. In order to reduce the parasite gate capacitance and gate resistance, a trilayer resist structure was used to pattern the T-gate resist profile. Excellent DC, high frequency and power performances have been obtained. FT and frnax are 105 GHz, 70 GHz respectively. The research is very helpful to obtain higher performance GaAs-based MHEMTso 相似文献
4.
Via systematic investigation of the anodization of both patterned and unpatterned specimens, phenomena of pronounced discrepancy
with respect to pore size, pore density and pore etch-rate were evidenced. Based on the detailed analysis of scanning electron
microscope (SEM) micrographs and current-voltage curves, the competition between physical and chemical elements was found
to be crucial to understanding the observations. The results indicate that the size, density and growth-speed of pores may
act as an evident function of the initial morphology of the sample surface, despite a nearly fixed width of the space charge
region. Electric-field effect as well as current-burst-model (CBM) was employed to interpret the underlying mechanism.
Supported by the Hi-Tech Research and Development Program of China (Grant No. 2006AA04Z312) and National Basic Research Program
of China (Grant No. 2006CB300403) 相似文献
5.
Degenerate four-wave mixing measurements, using the 35 ps pulses at 532 nm, have been employed to investigate the third-order nonlinear optical parameters of two chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring (1) or the unsubstituted ring (2) and their precursor 3-amino-9-ethylcarbazole (AECz). The second-order hyperpolarizability y of the compounds 1 and 2 were found to be 42.9×10^-31 and 35.9×10^-31 esu, respectively, approximately one order of magnitude greater than AECz. The relation between the molecular structure and second-order hyperpolarizability of the compounds I and 2 was explored in detail based on the three-level model and the density functional theory (DFT) calculation. The theoretical results indicate that the spatial distribution of electron density has the profound role in the third-order nonlinear optical properties. 相似文献
6.
On the development of the GRAPES——A new generation of the national operational NWP system in China 总被引:9,自引:4,他引:5
ZHANG RenHe SHEN XueShun 《科学通报(英文版)》2008,53(22):3429-3432
Numerical weather prediction (NWP) has become one of the most important means for weather forecasts in the world. It also mirrors a nation's comprehensive strength in meteorology. In 2000, China Meteorological Administration (CMA) established the National Innovative Base for Meteorological Numerical Prediction in the Chinese Academy of Meteorological Sciences (CAMS), to work on developing a new generation of the national operational NWP system-Global/Regional Assimilation and PrEdiction System (GRAPES), to enhance meteorological services in China in the new century. In recent years, the GRAPES has witnessed a fast development. The GRAPES has been set up as an integration of the model framework, data assimilation, regional and global NWP system, which can be commonly used for both operation and research. In this paper, a brief review is made for illustrating the GRAPES system, including the advanced designs of the GRAPES, its diverse applications in multi-fields, and efficiencies of the regional and global GRAPES in operational applications based on hindcast results. 相似文献
7.
XU Wei PENG JunBiao XU YunHua WANG Jian HUANG Zhe NIU QiaoLi CAO Yong 《科学通报(英文版)》2007,52(12):1612-1615
Saturated red polymer light-emitting diodes have been fabricated with a single emitting polymer blend layer of poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) and poly[9,9-dioc- tylfluorene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole] (PFO-DBT15). Saturated red emission with the Commission Internationale de l’Eclairage (CIE) coordinates of (0.67, 0.33) was obtained. The device stability was investigated. The results showed that energy transfer occurred from MEH-PPV to PFO-DBT15, and MEH-PPV improved the hole injection and transportation. 相似文献
8.
ADELMAN John 《科学通报(英文版)》2009,54(2):220-226
Protein kinase CK2 consists of two catalytic subunits (CK2α) and two regulatory subunits (CK2β). Here, we report the crystal structures of rat CK2α mutant (rCK2α-△C, 1—335) and CK2β (rCK2β). The overall topology of rCK2α-△C and rCK2β are very similar to the human enzyme, although large structural differences could be observed in the N-terminal domain of rCK2α-△C. Our reported structure of rCK2α-△C is in the close conformation state while the counterpart hCK2α is in the open conformation state, indi- cating ... 相似文献
9.
Brain computer interface (BCI) aims at creating new communication channels without depending on brain’s normal output channels
of peripheral nerves and muscles. However, natural and sophisticated interactions manner between brain and computer still
remain challenging. In this paper, we investigate how the duration of event-related desynchronization/synchronization (ERD/ERS)
caused by motor imagery (MI) can be modulated and used as an additional control parameter beyond simple binary decisions.
Furthermore, using the non-time-locked properties of sustained (de)synchronization, we have developed an asynchronous BCI
system for driving a car in 3D virtual reality environment (VRE) based on cumulative incremental control strategy. The extensive
real time experiments confirmed that our new approach is able to drive smoothly a virtual car within challenging VRE only
by the MI tasks without involving any muscular activities.
Supported by the National High-Tech Research Program of China (Grant No. 2006AA01Z125) and the National Basic Research Program
of China (Grant No. 2005CB724301) 相似文献
10.
Multiferroic BiFeO3 (BFO) nanotube arrays (∼100 nm in diameter and ∼50 μm in length) were synthesized by the sol-gel method utilizing the anodic
aluminum oxide (AAO) membrane technique. The microstructure and chemical components of the BFO nanotubes were investigated
using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS).
The BFO nanotubes exhibited polycrystalline microstructures. The novel Y-junction BFO nanotubes were simultaneously fabricated.
Supported by the National Natural Science Foundation of China (Grant No. 90306010), Program for New Century Excellent Talents
in University (Grant No. NCET-04-0653) and National Basic Research Program of China (Grant No. 2007CB616911) 相似文献
11.
Gang Wu YaLi Xie Hong Chen Min Zhong RongHua Liu BingCai Shi QiuJu Li XiangFeng Wang Tao Wu YaJun Yan JianJun Ying XianHui Chen 《科学通报(英文版)》2009,54(11):1872-1875
We synthesized the samples Ba1-xSmxFFeAs and Eu1-xSmxFFeAs with ZrCuSiAs-type structure. These samples were characterized by resistivity and susceptibility. It is found that the substitution of rare earth metal for alkaline earth metal in the two systems suppresses the anomaly in resistivity and induces superconductivity. Superconductivity at 54 K in nominal composition Ba0.5Sm0.5FFeAs and at 51 K for Eu0.5Sm0.5FFeAs is realized, indicating that the superconducting transition temperatures in the iron arsenide fluorides is the same as that in oxypnictides with the same structure. 相似文献
12.
According to the modularization and standardization of program structure in Global/Regional Assimilation and Prediction System (GRAPES), the plug-compatible and transplantable regional meso-scale and global middle-range physics software package is established. The package's component integrality is comparative with the other advanced models physics. A three-level structure of connecting GRAPES physics and dynamic frame has been constructed. The friendly interface is designed for users to plug in their own physics packages. Phenomenon of grid-point storm rainfall in numerical prediction is analyzed with the numerical tests. The scheme of air vertical velocity calculation is improved. Opti- mizing tests of physics schemes are performed with the correlative parameters adjusting. The results show that the false grid-point storm rainfall is removed by precipitation scheme improving. Then the score of precipitation forecast is enhanced. 相似文献
13.
WeiXiao Shen 《科学通报(英文版)》2009,54(11):1859-1862
We prove that a C2 unimodal interval map with critical order not greater than 2 has the decay of geometry property, by showing that all the cross-ratio estimates needed in the previous proof for the C3 case remain true. 相似文献
14.
Highly crystalline gold nanoribbons have been synthesized via a simple method by L-cysteine reduction of aqueous chloroaurate
ions at room temperature, without additional capping agent or surfactant. Based on transmission electron microscopy (TEM)
and UV-vis absorption studies for the intermediate products, the formation of gold nanoribbons is regarded as a kind of oriented
attachment growth.
Supported by the National Natural Science Foundation of China (Grant Nos. 90406023 and 90406024), National Important Basic
Research Program of China (Great Nos. 2006CB933206 and 2006CB705606) and Foundation for Top Doctoral Candidate of Southeast
University. 相似文献
15.
Gyrotrons are the most powerful terahertz sources and have potential applications in many areas. A terahertz gyrotron oscillator
with a pulsed solenoid producing up to an 8 T magnetic field has been designed, constructed and tested. In a 7.96 T magnetic
field, 3 kW output power radiations at 0.22 THz frequency have been generated.
Supported by the State Key Development Program of Basic Research of China (Grant No. 2007CB310400) and National Natural Science
Foundation of China (Grant No. 1067611) 相似文献
16.
JIN XinChun QI XueLian YANG XiaoFei LI BaoMing 《科学通报(英文版)》2007,52(18):2532-2542
It is known that consolidation of fear conditioning requires de novo protein synthesis in the amygdala. However, there is controversy about the role of protein synthesis in post-retrieval extinction of fear memory. The present study investigated the effect of protein synthesis inhibition (PSI) in the baso- lateral nucleus of amygdala (BLA) on post-retrieval extinction of auditory fear memory. Intra-BLA infu- sion of the protein synthesis inhibitor anisomycin ‘0’ h post-retrieval facilitated the extinction, but was ineffective if the memory was not retrieved. Anisomycin had no effect on the extinction when it was infused 6 h post-retrieval. The present results suggest that there exists a protein-synthesis-dependent mechanism in the BLA that retards extinction of auditory fear memory. 相似文献
17.
Arctic dipole anomaly and summer rainfall in Northeast China 总被引:10,自引:0,他引:10
A dipole structure anomaly in summer Arctic atmospheric variability is identified in this study, which is characterized by the second mode of empirical orthogonal function (EOF) analysis of summer monthly mean sea level pressure (SLP) north of 70°N, accounting for 12.94% of the variance. The dipole anomaly shows a quasi-barotropic structure with opposite anomalous centers over the Canadian Arctic and the Beaufort Sea and between the Kara Sea and the Laptev Sea. The dipole anomaly reflects alternating variations in location of the polar vortex between the western and eastern Arctic regions. The positive phase of the dipole anomaly corresponds to the center of the polar vortex over the western Arctic, leading to an increase in summer mean rainfall in Northeast China. The dipole anomaly has a predominant 6-year periodicity, and shows interdecadal variations in recent decades. 相似文献
18.
Mineral magnetic properties of surface sediments at Bei’anhe, Beijing, and its environmental significance 总被引:1,自引:0,他引:1
A multiparameter investigation of surface sediments from the Bei'anhe section (Beijing) has been conducted using environmental magnetic approaches. The studied sedimentary sequence consists of pluvial and lacustrine silts and clay of the Holocene age. Magnetite, hematite and pyrrhotite were identiffed as the dominant magnetic minerals. The mineral magnetic characteristics are considered to reflect the Holocene paleoenvironmental processes of the studied area, which are different from the mineral magnetic properties of typical polluted sections reported in the Beijing area. The low-field magnetic susceptibility and saturated isothermal remanence magnetization of the section decrease gradually with increasing depth. This indicates that the concentration of magnetic minerals in the strata decreases down the section. Values of interparametric ratios, such as ARM/SIRM, XARM/Xand SIRM/X, gradually increase with increasing depth, which indicates a down-section decreasing trend in the magnetic grain size of the sediments. Pyrrhotite occurs below the depth of 22 cm, suggesting the existence of redox interface. The magnetic variations of the Bei'anhe surface sediments might be controlled by two geological processes: reductive diagenesis and pedogenesis. Our findings may have provided a reference point for magnetic investigation of polluted surface sediments in the Beijing area. 相似文献
19.
Niobic tellurite glass doped by silver chloride nanocrystal was prepared with the melting-quenching and heat treatment method,
and the self-trapped exciton absorption band of the silver chloride nanocrystal was observed at 532 nm in the UV-visible absorption
spectrum. The glass structure characteristics were investigated by Raman spectroscopy, and the mechanism of self-trapped exciton
was analyzed by Jahn-Teller model. Its optical limiting was measured with 532 nm picosecond laser pulses, and the corresponding
nonlinear absorption coefficient was measured with open-aperture Z-scan. The experimental results showed that optical limiting
at 532 nm was attributed to free carrier absorption between the self-trapped state and the continuum band.
Supported by Shanghai Leading Academic Discipline Project (Grant No. B408), National Basic Research Program of China (Grant
Nos. 2006CB806006, 2006CB921105), Program for Changjiang Scholars and Innovative Research Team in University, Doctoral Program
of High Education (Grant No. 20050269011) and Project sponsored by Shanghai Science and Technology Committee (Grant Nos. 06DJ14008,
07dz22025, 06QH14003) 相似文献
20.
The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this
paper, a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication
may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial
function of the distance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret
messages are transmitted directly over a quantum channel.
Supported by the National Basic Research Program of China (Grant No. 2006CB921106), National Natural Science Foundation of
China (Grant No. 10325521) and Key Project of Ministry of Education of China (Grant No. 306020) 相似文献