共查询到20条相似文献,搜索用时 31 毫秒
1.
Li Jian Zheng Kai Chang DeYuan Wei Huai Ning TiGang Fu YongJun Mao XiangQiao Yan FengPing Jian Wei Jian ShuiSheng 《中国科学E辑(英文版)》2008,51(1):58-64
An optimal refractive index profile of pure silica core optical fiber (PSCF) was designed, in combination with the characters
of the modified chemical vapor deposition (MCVD) process. Techniques of preform fabrication by a new furnace round heating
MCVD process and fiber drawing process were reviewed. Difficulties in doping fluorine in silica, widening the depressed-index
cladding and maintaining the index of fiber core were discussed. Methods used to overcome these difficulties were given at
the same time. Additionally, the optimal refractive index profiles of PSCF were presented.
Supported by the Hi-Tech Research and Development Program of China (Grant No. 2002AA312190), National Natural Science Foundation
of China (Grant No. 60477017), Program for the New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing
Natural Science Foundation (Grant No. 4052023) and the Beijing Jiaotong University Foundation (Grant No. 2006XM003) 相似文献
2.
The stochastic averaging method for quasi-integrable Hamiltonian systems with time-delayed feedback bang-bang control is first
introduced. Then, two time delay compensation methods, namely the method of changing control force amplitude (CFA) and the
method of changing control delay time (CDT), are proposed. The conditions applicable to each compensation method are discussed.
Finally, an example is worked out in detail to illustrate the application and effectiveness of the proposed methods and the
two compensation methods in combination.
Supported by the National Natural Science Foundation of China (Grant No. 10772159), the Research Fund for the Doctoral Program
of Higher Education of China (Grant No. 20060335125), Zhejiang Natural Science Foundation (Grant No. Y7080070), and Fujian
Provincial Science and Technology Project (Grant No. 2005YZ1021) 相似文献
3.
In order to detect the damage locations of complex spatial structures, a sensor region-based damage detection approach was
developed based on the damage locating vectors method. A normalized damage locating index was introduced to identify the damage
regions. An experiment on damage detection of a substructure model of the National Swimming Center ‘Water Cube’ was carried
out. Two damage patterns were involved in the experiment. The test model was excited by using hammer impacts. Acceleration
responses of the undamaged and damaged structure model were measured. Modal parameters were identified from the acceleration
responses by utilizing the eigensystem realization algorithm (ERA). By using the developed sensor region-based method, the
damage regions of the substructure model were located. The results show that the proposed method is able to effectively locate
the damage regions.
Supported by Beijing Natural Science Foundation (Grant No. 8041002), the National Natural Science Foundation of China (Grant
No. 8041002), the National Science and Technology Committee of China (Grant No. 2004BA904B02), and Beijing Science and Technology
Committee (Grant No. Z0004028040221) 相似文献
4.
FAN HuiQing & KE ShanMing State Key Laboratory of Solidification Processing School of Materials Science Engineering Northwestern Polytechnical University Xi’an China 《中国科学E辑(英文版)》2009,52(8):2180-2185
Several typical high dielectric constant materials are reviewed to study the electrical properties and relaxation mechanism.
It is found that a Lorenz-type law can be used to describe the dielectric permittivity of either the normal ferroelectrics
with or without diffuse phase transitions (DPT) or the typical ferroelectric relaxors. The ferroelectric DPT can be well described
by just one fitting process using the Lorenz-type law, while the relaxor ferroelectric transition needs two independent fitting
processes. The Lorenz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric
phase transition. Above the transition temperature, the dielectric curves of all the studied materials can be well described
by a Lorenz-type law.
Supported by the National Natural Science Foundation of China (Grant No. 50672075), New Century Excellent Talents (Grant No.
05-087), Natural Science Foundation of Northwestern Polytechnical University (Grant No. 200703), Xi’an Science & Technology
Foundation (Grant No. CXY08006) and 111 Project (Grant No. B08040) 相似文献
5.
In order to endow titanium metals with bioactivity and antimicrobial properties, titanium plates were subjected to anodic
oxidation treatment in NaCl solutions in this study. The treated titanium metals could induce apatite formation in the fast
calcification solution, and osteoblasts on the treated titanium surfaces proliferated well as those on the untreated titanium
metal surfaces. The treated metals could inhibit S. aureus growth in the microbial culture experiments. It was assumed that Ti-OH groups and Ti-Cl groups formed on the treated titanium
surface were responsible for the bioactivity and antimicrobial properties of the metals. The anodic oxidation treatment was
an effective way to prepare bioactive titanium surfaces with antimicrobial properties.
Supported by the National Natural Science Foundation of China (Grant Nos. 50672062 and 30870615), Key Programs for Science
and Technology Development of Sichuan Province, China (Grant No. 2008SZ0104) and Sichuan Youth Science & Technology Foundation,
China (Grant No. 09ZQ026-033) 相似文献
6.
Risk assessment method of major unsafe hydroelectric project 总被引:4,自引:3,他引:1
Based on the characteristics of major unsafe hydroelectric projects and the data from field detection, in situ monitoring,
and regular safety inspection, the fundamental principles of operation risk assessment are proposed in this paper. Meanwhile,
a three layer hierarchical system is constructed, and an improved analytical hierarchical process combining genetic algorithm
and analytical hierarchical process is established, with corresponding program. The operation risk of some unsafe dam was
assessed with the principles, method and program presented in this paper and the major factors which would affect the operation
of the dam were pointed out.
Supported by Key Project of NNSF and Yalongjiang Hydroelectric Development Joint Research Fund (Grant No. 50539110), Science
and Technology Support Plan (Grant No. 20006BAC14B03), National Natural Science Foundation Major Project (Grant Nos. 50539010,
50539030) and National Natural Science Foundation of China (Grant No. 50579010) 相似文献
7.
A new transient stability margin is proposed based on a new expression of dynamic security region (DSR) which is developed
from the existing expression of DSR. Applications of the DSR based transient stability margin to contingency ranking and screening
are discussed. Simulations in the 10-machine 39-bus New England system are performed to show the effectiveness of the proposed
DSR based transient stability margin.
Supported by Chinese National Basic Research Program (Grant No. 2004CB217900), the National Natural Science Foundation of
China (Grant Nos. 50525721, 50595411, 50707035) and China Postdoctoral Science Foundation (Grant No. 20060400518) 相似文献
8.
By a novel controlled combustion synthesis method, a large amount of ZnO nano-whiskers with different morphologies like nanotetrapods,
long-leg nanotetrapod and multipods, were prepared without any catalysts and additives in open air at high temperature. Their
morphologies, structures and optical properties were investigated by using SEM, XRD and PL spectrum. The possible growth mechanisms
on the ZnO nano-whiskers were proposed in this paper.
Supported by the National Natural Science Foundation of China (Grant Nos. 50572010, 50742007 and 10672020), National Defense
Founds of China (Grant Nos. 51420205BQ0154 and A2220061080), “863” Project of China (Grant No. 2007AA03Z103), and the Scientific
Research Foundation of Graduate School of BIT (Grant No. AA200802) 相似文献
9.
Blast furnace slag samples with phase separation structure were prepared by re-melting and then water quenching process. By
use of XRD, DTA and SEM technologies in combination with mechanical property experiment, the structure characteristics of
samples were determined and their effects on cementitious reactivity were investigated. The results show that the samples
with phase separation have better cementitious reactivity than sample with homogenous glass and sample with crystalline phases,
which mainly contributes to its glass structure with coexistence of Ca-O rich phase and Si-O rich phase. Moreover, the amorphous
samples possess hydrability which is affected by their formation process, since phase separation extends the range of possible
Ca-rich crystalline phases.
Supported by the National Natural Science Foundation of China (Grant No. 50674062) and the Postdoctoral Science Foundation
of China (Grant No. 20070420354) 相似文献
10.
Self-assembly of polystyrene spheres guided by patterned n-type InP substrates has been investigated. InP surfaces were patterned using a variety of methods including wet chemical
etching, sputter coating, thermal evaporation, and photo lithography. The self-assembly of polystyrene spheres depended on
the appearance of patterns and was affected by the deposition techniques (sputter coating and thermal evaporation) of Au micro-squares.
SEM and AFM were used to characterize the surface morphologies.
Supported by the Notional Natural Science Foundation of China (Grant No. 50672089) and the Encouraging Foundation for the
Scientific Research of the Excellent Young and Middle-aged Scientists in Shandong Province of China (Grant No. 2006BS04034) 相似文献
11.
In order to seek the co-adaptability solution to conflict events in construction engineering projects, a new method referred
to as segmented hierarchical algorithm is proposed in this paper by means of comparing co-adaptability evolution process of
conflict events to the stackelberg model. By this new algorithm, local solutions to the first-order transformation of co-adaptability
for conflict events can be obtained, based upon which, a global solution to the second-order transformation of co-adaptability
for conflict events can also be decided by judging satisfaction degree of local solutions. The research results show that
this algorithm can be used not only for obtaining co-adaptability solution to conflict events efficiently, but also for other
general decision-making problems with multi-layers and multi-subsidiaries in project management field.
Supported by Soft Science Foundation of Shaanxi Province of China (Grant No. 2005KR121) and Natural Science Foundation of
Shaanxi Province of China (Grant No. 2005E214) 相似文献
12.
High performance 1.3 μm InGaAsN superluminescent diodes (SLDs) were fabricated with Schottky contact. The structure was grown by metal organic chemical vapor deposition (MOCVD). Output power of 3 mW was obtained in continuous wave (CW) mode at room temperature. The full width at half maximum (FWHM) of the emission spectrum was 30 nm. The devices operated up to 100℃. 相似文献
13.
LI Jian LIU Peng LU ShaoHua WANG Jing MAO XiangQiao WEI Huai FU YongJun ZHENG Kai NING TiGang LI TangJun & JIAN ShuiSheng 《中国科学E辑(英文版)》2009,52(5):1234-1241
A kind of erbium doped photosensitive fiber (EDPF) was proposed and fabricated, whose core was made of double layers named
photosensitive layer and erbium doped layer. The double-layer core design can overcome difficulties in fabrication of EDPF
with single core design, i.e. the conflict between the high consistency rare earth doping and high consistency germanium doping.
A sample was fabricated through the modified chemical vapor deposition method combined with solution doping technique. The
peak absorption coefficient was 48.80 dB/m at 1.53 μm, the background loss was lower than 0.1 dB/m, and the reflectivity of
the fiber Brag gratings (FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology. Moreover, a C
band tunable fiber laser was fabricated using the sample fiber, in which a uniform FBG was written directly on EDPFs as a
reflector. A single wavelength lasing with a maximum wavelength tuning range of 1555.2–1558.0 nm was achieved experimentally.
Within this tuning range, the full-width at half maximum (FWHM) of the laser output was smaller than 0.015 nm and the side
mode suppression ratio (SMSR) was better than 50 dB.
Supported by the National High Technology Research and Development Program of China (863 Project) (Grant No. 2007AA01Z258),
the National Natural Science Foundation of China (Grant No. 60771008), Program for New Century Excellent Talents in University
(Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023), and the Beijing Jiaotong University Foundation
(Grant No. 2006XM003) 相似文献
14.
Direct replication of creatural scarfskins to form biomimetic surfaces with relatively vivid morphology is a new attempt of
the bio-replicated forming technology at animal body. Taking shark skins as the replication templates, and the micro-em-bossing
and micro-molding as the material forming methods, the micro-replicating technology of the outward morphology on shark skins
was demonstrated. The preliminary analysis on replication precision indicates that the bio-replicated forming technology can
replicate the outward morphology of the shark scales with good precision, which validates the application of the bio-replicated
forming technology in the direct morphology replication of the firm creatural scarfskins.
Supported by the National Defense Fundamental Research Foundation of China (Grant No. D2120060002) and the National Natural
Science Foundation of China (Grant No. 59975007) 相似文献
15.
Runyang Suspension Bridge (RSB) with the main span of 1490 m is the longest bridge in China and the third longest one in the
world. In this bridge the rigid central buckle is employed for the first time in the mid-span of the suspension bridge in
China. For such a super-long-span bridge, the traditional finite element (FE) modeling technique and stress analysis methods
obviously cannot satisfy the needs of conducting accurate stress analysis on the central buckle. In this paper, the submodel
method is introduced and for the first time used in analyzing the stresses of the central buckle. After an accurate FE submodel
of the central buckle was specially established according to the analysis results from the whole FE model, the connection
technique between the two-scale FE models was realized and the accurate stresses of the central buckle under various vehicle
load cases were then conducted based on the submodel method. The calculation results were testified to be accurate and reliable
by the field measurements, which show the efficiency and reliability of the submodel method on analyzing the mechanical condition
of the central buckle of long-span suspension bridges. Finally, the working behavior and mechanical characteristics of the
central buckle of the RSB under vehicle loads were analyzed based on the calculation and measurement results. The results
obtained in this paper can provide theoretic references for analyzing and designing the rigid central buckle in long-span
suspension bridges in future.
Supported by the National High Technology Research and Development Program (“863” Project) (Grant No. 2006AA04Z416), the Key
Project of the National Natural Science Foundation of China (Grant No. 50538020), the National Natural Science Foundation
of China for Young Scholars (Grant No. 50608017) and the Ph.D. Programs Foundation of Ministry of Education of China (Grant
No. 200802861012) 相似文献
16.
A bistatic range-velocity-acceleration ambiguity function (BRVAAF) is proposed. The model of radar measurements of an accelerating
target involving the time delay, Doppler frequency and Doppler rate is given. The relationships between these measurements
and the parameters of the bistatic geometry, target position, velocity and acceleration are derived. Moreover, the effects
of the bistatic geometry factors on these measurements are analyzed. Besides, the two relationships of the bistatic integration
loss and the bistatic optimum integration time with these factors are built and their change trends are described respectively.
This research is helpful to analyze the influences of the bistatic geometry factors on the target detection and signal processing.
Supported by the National Natural Science Foundation of China (Grant No. 60232010), the National Natural Science Foundation
of China for Distinguished Young Scholars (Grant No. 60625104) and the Advanced Research Project (Grant Nos. 51307060504,
9140A07040806BQ01) 相似文献
17.
Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using
smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric
actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.
Supported by the Preplan of Aeroelasticity of China (Grant No. 513130303) and the National Natural Science Foundation of China
(Grant No. 10772183) 相似文献
18.
Molecular dynamics (MD) simulations were performed to do the test of sin-gle-walled carbon nanotubes (SWCNT) under tensile loading with the use of Bren-ner potential to describe the interactions of atoms in SWCNTs. The Young’s modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT’s de-formation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure be-havior. 相似文献
19.
A high etch rate GaAs via-hole process was studied in an inductively coupled plasma system using Cl2/BCl3 gas system. The effects of process parameters on the GaAs etch rate were investigated. The influences of photoresist SiO2 and Ni masks on the resultant profiles were also studied by scanning electron microscopy. A maximum etch rate of 8.9 μm/min was obtained and the etched profiles were optimized. 相似文献
20.
Typhoon disaster zoning and prevention criteria—A double layer nested multi-objective probability model and its application 总被引:1,自引:0,他引:1
For prevention and mitigation of typhoon disasters in China, in this paper a double layer nested multi-objective probability
model of typhoon disaster zoning and prevention criteria is proposed. The multivariate compound extreme value distribution
(MCEVD) is used to predict the joint probability of seven typhoon characteristics and corresponding typhoon induced disasters.
Predicted results can be used for both typhoon disaster zoning and corresponding prevention criteria along China coast.
Supported by the National Natural Science Foundation of China (Grant No. 50679076) and the Office of State Flood Control and
Drought Relief Headquarters of China (Grant No. 20060120) 相似文献