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1.
Lu Qiang He GuangYu Mei ShengWei Sun YingYun Ruan QianTu Wang Wei Zhang WangJun Yu XuFeng 《中国科学E辑(英文版)》2008,51(2):220-224
To meet the demand of high stability, high quality, and low losses of power systems, the advanced energy management system
(AEMS) is established and revealed in this bulletin, which has been put into trial operation in Shanghai power system for
almost half a year. The AEMS is novel from all aspects covering idea, theory, method, software, and engineering. The essence
of AEMS is exercising the hybrid automatic control theory and technology to realize multi-objective optimal closed-loop control
of power systems. Based on an “event-driven” strategy, the AEMS transforms multi-objective optimal control problems into event
identification and elimination by defining the unsatisfactory states of a power system as events. This bulletin concisely
presents the theory and main advantages of AEMS, as well as its implementation in Shanghai power system.
Supported by the National Natural Science Foundation of China (Grant Nos. 50595411, 50377018), the 973 Project (Grant No.
2004CB217903) and the Key Project of State Grid Company 相似文献
2.
YongShun Zhang Ming Yue DongMing Guo DianLong Wang HongHai Yu ShengYuan Jiang XueWen Zhang 《中国科学E辑(英文版)》2009,52(7):2079-2086
A drive and control method is put forward for a variable diameter capsule micro robot to screw forward in intestine using
magnetic coupling between an inner actuator inside the robot and the rotational magnetic field generated by a rotating outer
actuator. The structures of the outer and inner actuators are magnet cylinders with multiple magnetic poles in tegular shape
alternating with dissimilar radial magnetization. An universal mathematical model of magnetic torque at eccentric state is
established based on the equivalent magnetic charge method, and the characteristics of magnetic torque with respect to structural
parameters of actuators are theoretically studied. Experiments show that the driving method features advantages such as powerful
magnetic torque, high safety, reliability, etc. The driving ability of the variable diameter capsule micro robot is greatly
improved by its automatic radial clearance compensation. The magnetic drive system has a promising prospect of medical applications
in intestine.
Supported by the Natural Science Foundation of Liaoning Province (Grant No. 20082171) and the National Natural Science Foundation
of China (Grant Nos. 60675054,60275034,60875064) 相似文献
3.
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
4.
For quickly clearing up a fault of distribution lines, which concerned with complex structure and operating modes, a directional
comparison protection is necessary. The paper evaluated the traditional directional relay through modeling a typical distribution
system and presented a novel negative sequence directional relay and a new directional comparison protection scheme specially
designed for distribution systems. In the relay and the protection scheme, a particular negative sequence component has been
constructed to solve the problem that there is no negative sequence component in a symmetrical fault case so that they could
operate correctly in both asymmetrical fault and symmetrical fault. Extensive EMTP simulation studies proved that the protection
schemes are able to provide fast and reliable responses for all fault conditions. In particular, they are able to give correct
responses adapting to the change of system operation conditions, including the changing of system configuration, power flow
direction, and source and tapped-offload conditions.
Supported by the National Natural Science Foundation of China (Grant Nos. 50077011 and 50377019) and the National Basic Research
Program of China (“973” Project) (Grant No. 2004CB217906) 相似文献
5.
The narrow definition of the digital power system (DPS) is proposed. The architecture, features and key contents of the DPS
are presented, which include intelligent dispatching system, hybrid automatic control system and data sharing platform. The
successful construction of the DPS can greatly improve the performances of power system operating and dispatching, which mainly
reflect a fundamental increase of the ability of avoiding catastrophes resulting from blackouts of power supply, a significant
improvement of economic efficiency of power system operation, and an improvement of decision efficiency of power system developing.
The DPS describes a vision of the development of power system and the way to achieve this vision. At the same time, the paper
also proposes the principles of the design and implementation of the DPS.
Supported by the National Natural Science Foundation of China (Grant Nos. 50595411 and 50377018) and the Major State Basic
Research Development Program (973 Program) (Grant No. 2004CB217903) 相似文献
6.
7.
Internal state variable models for microstructure in high temperature deformation of titanium alloys
There exists an interaction between microstructural evolution and deformation behavior in high temperature deformation of
titanium alloys. And the microstructure of titanium alloys is very sensitive to the process parameters of plastic deformation
process. In this paper, on the basis of plastic deformation mechanism of metals and alloys, a microstructural model including
dislocation density rate equation and grain growth rate equation is established with the dislocation density rate being an
internal state variable. Applying the model to the high temperature deformation process of Ti60 titanium alloy, the average
relative errors of grain sizes between the experiments and the predictions are 9.47% for sampled data, and 13.01% for non-sampled
data.
Supported by the National Natural Science Foundation of China (Grant No. 50475144), the NPU Foundation for Research (Grant
No. NPU-FFR-006), and the National Basic Research Program of China (“973”) (Grant No. G20000672) 相似文献
8.
Understanding reliability value for electricity customer is important to market-based reliability management. This paper proposes
a novel approach to evaluate the reliability for electricity customers by using indifference curve between economic compensation
for power interruption and service reliability of electricity. Indifference curve is formed by calculating different planning
schemes of network expansion for different reliability requirements of customers, which reveals the information about economic
values for different reliability levels for electricity customers, so that the reliability based on market supply demand mechanism
can be established and economic signals can be provided for reliability management and enhancement.
Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-07-0484), the National Natural Science
Foundation of China (Grant No. 50777031) and the Fok Ying-Tong Education Foundation (Grant No. 104020) 相似文献
9.
A theoretical model of the erbium-doped waveguide ring laser is established according to the theory of erbium-doped waveguide
amplifier and the transmission matrix of waveguide directional coupler. The influence of bend radius, coupling coefficient
and doped erbium ion concentration on the characteristics of waveguide ring laser is investigated. It is shown that due to
the co-action of waveguide bend loss and other relevant loss there is an optimal bend radius which can provide simultaneously
low threshold pumping power and high laser light output power. As one part of the resonator’s loss, the laser light coupling
coefficient of directional coupler has an impact on the laser property. The analysis indicates that the laser achieves the
high output power when the coupling coefficient is about 0.2. The threshold pumping power is the minimum when the doped erbium
ion concentration is 0.85×1026 m−3. Increasing the concentration of doped erbium ions will enhance the output power of laser light as long as the concentration
doesn’t introduce remarkable up-conversion effect. The results give a good theoretical basis for the design and fabrication
of erbium-doped waveguide ring laser devices.
Supported by the National Natural Science Foundation of China (Grant No. 60807015), the Specialized Research Fund for the
Doctoral Program of Higher Education (Grant No. 200801411037), the Young Teacher Cultivation Foundation of Dalian University
of Technology (Grant No. 893210) and Doctor Start-up Foundation of Dalian University of Technology (Grant No. 893322) 相似文献
10.
The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting
the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the
case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration
fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform
external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt,
the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface.
Nevertheless, the shape of the interface still remains nearly a paraboloid.
Supported by the National Basic Research Program of China (Grant No. 2006CB605205) and the National Natural Science Foundation
of China (Grant No. 10672019) 相似文献
11.
Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of
bridge wind engineering, and the structural health monitoring system (SHMS) employed in many long-span bridges provide a research
basis for the field measurement. In order to provide reliable basis for wind resistant evaluation of Runyang Suspension Bridge
(RSB), two anemometers and 85 accelerometers were installed in the SHMS of RSB. In August 2005, Typhoon Matsa crossed over
Jiangsu, the SHMS timely recorded the typhoon and structural vibration responses. In this paper by using the time-frequency
technique and statistical theory, the recorded data were analyzed to obtain the strong wind characteristics, the buffeting
response characteristics of the cable and deck, and the variation of buffeting response RMS versus wind speed. Results obtained
in this study can be employed to validate the credibility of current buffeting response analysis theory techniques, and provide
reference values for wind resistant evaluation of other long-span bridges.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA04Z416), the
Key Project of the National Natural Science Foundation of China (Grant No. 50538020) and the Outstanding Youth Fund of the
National Natural Science Foundation of China (Grant No. 50725828) 相似文献
12.
Load model is one of the most important elements in power system operation and control. However, owing to its complexity,
load modeling is still an open and very difficult problem. Summarizing our work on measurement-based load modeling in China
for more than twenty years, this paper systematically introduces the mathematical theory and applications regarding the load
modeling. The flow chart and algorithms for measurement-based load modeling are presented. A composite load model structure
with 13 parameters is also proposed. Analysis results based on the trajectory sensitivity theory indicate the importance of
the load model parameters for the identification. Case studies show the accuracy of the presented measurement-based load model.
The load model thus built has been validated by field measurements all over China. Future working directions on measurement-based
load modeling are also discussed in the paper.
Recommended by Prof. LU Qiang, Member of Editorial Committee of Science in China, Series E: Technological Sciences
Supported in part by the Chinese National Key Basic Research Special Fund (Grant No. 2004CB217901), the National Science Foundation
of China (Grant No. 50595410) and by the Program for Changjiang Scholars and Innovative Research Team in University under
IRT0515 相似文献
13.
A reduced-order method for estimating the stability region of power systems with saturated controls 总被引:1,自引:0,他引:1
In a modern power system, there is often large difference in the decay speeds of transients. This could lead to numerical
problems such as heavy simulation burden and singularity when the traditional methods are used to estimate the stability region
of such a dynamic system with saturation nonlinearities. To overcome these problems, a reduced-order method, based on the
singular perturbation theory, is suggested to estimate the stability region of a singular system with saturation nonlinearities.
In the reduced-order method, a low-order linear dynamic system with saturation nonlinearities is constructed to estimate the
stability region of the primary high-order system so that the singularity is eliminated and the estimation process is simplified.
In addition, the analytical foundation of the reduction method is proven and the method is validated using a test power system
with 3 buses and 5 machines.
Recommended by Prof. LU Qiang, member of Editorial Committee of Science in China, Series E: Technological Sciences
Supported by the National Natural Science Foundation of China (Grant No. 50595411) and the New Century Outstanding Investigator
Program of the Ministry of Education (Grant No. NCET-04-0529) 相似文献
14.
According to the typical variable heat source of solar energy and the unsteady adsorption process of adsorption chiller, the
research of cyclic transient characteristics of the solar-powered adsorption cooling system is presented in this work. A mathematic
model of the whole system including the model of adsorption chiller, which reveals the transient operation process of the
solar-powered adsorption cooling system, is developed and verified by experimental data. On the basis of the simulated results,
the transient characteristics and the overall performance of the system, not only in the traditional open cycle mode but also
in closed cycle mode, are both analyzed theoretically. Furthermore, the influence of parameters matching of components configuration
and operation process on the cyclic characteristics of the system, such as the solar collector area, the water tank capacity
and the chiller startup temperature, are discussed. The research in this work may play a very important role in optimizing
the system cyclic process and improving the system adaptability especially under the condition of variable heat source.
Supported by the National Natural Science Foundation of China (Grant No. 50676060) 相似文献
15.
通过研究江苏省68个城市的地价空间分布,发现城市体系地价具有分形特征,并提出若干分形模型:以区域中心的某个城市为圆心,用半径范围内城市面积的和为自变量对地价属性进行分形维数测度;以地价特征排序后的城市面积和作为自变量对地价属性进行分形维数测度.采用软件SPSS为统计分析工具,进行分形特征分析、实证检验.结果表明:自变量为半径范围内的城市面积和的分形特征显著且有效,一定区域范围内城市地价的空间变化与分形维数服从一定的关联关系.此外,发现以地价特征排序后的城市面积和为自变量的分形维数反映不同区域城市地价的等级体系差异. 相似文献
16.
A level set method for reliability-based topology optimization of compliant mechanisms 总被引:1,自引:0,他引:1
Based on the level set model and the reliability theory, a numerical approach of reliability-based topology optimization for
compliant mechanisms with multiple inputs and outputs is presented. A multi-objective topology optimal model of compliant
mechanisms considering uncertainties of the loads, material properties, and member geometries is developed. The reliability
analysis and topology optimization are integrated in the optimal iterative process. The reliabilities of the compliant mechanisms
are evaluated by using the first order reliability method. Meanwhile, the problem of structural topology optimization is solved
by the level set method which is flexible in handling complex topological changes and concise in describing the boundary shape
of the mechanism. Numerical examples show the importance of considering the stochastic nature of the compliant mechanisms
in the topology optimization process.
Supported by the National Natural Science Foundation of China (Grant No. 50775073), the Teaching and Research Award Program
for Outstanding Young Teacher in Higher Education Institutions of the Ministry of Education of China, the Guangdong Hong Kong
Technology Cooperation Funding (Dongguan Project 20061682), the Research Project of Ministry of Education and Guangdong Province
(Grant No. 2006D90304001), and the Natural Science Foundation of Guangdong Province, China (Grant No. 05006494) 相似文献
17.
A molecular dynamics (MD) model of the fluidic electrokinetic transport in a nano-scale channel with two bulk sinks was presented,
and the process of ion transport in the nanochannel was simulated in this paper. The model consists of two water sinks at
the two ends and a pump in the middle, which is different from a single pump model in previous MD simulations. Simulation
results show that the charged surfaces of the nanochannel result in the depletion of co-ions and the enrichment of counterions
in the nanochannel. A stable current is induced because of the motion of ions when an external electric field is applied across
the nanochannel, and the current in the pump region is mainly induced by the motion of counterions. In addition, the ion number
in the pump region rapidly decreases as the external electric field is applied. In the equilibrated system, the electrically
neutral character in the pump region is destroyed and this region displays a certain electrical character, which depends on
the surface charge. The ion distribution is greatly different from the results predicted by the continuum theory, e.g. a smaller
peak value of Na+ concentration appears near the wall. The transport efficiency of counterions (coions) can be effectively increased (decreased)
by increasing the surface charge density. The simulation results demonstrate that the ion distribution in the electric double
layer (EDL) of a nanochannel cannot be exactly described by the classical Gouy-Chapman-Stern (GCS) theory model. The mechanism
of some special experimental phenomena in a nanochannel and the effect of the surface charge density on the ion-transport
efficiency were also explored to provide some theoretical insights for the design and application of nano-scale fluidic pumps.
Supported by the National Basic Research Program of China (Grant No. 2006CB300404), the National Natural Science Foundation
of China (Grant Nos. 50475077, 50676019, 50506008), the Natural Science Foundation of Jiangsu Province (Grant No. BK2006510),
and the Foundation of Education Ministry of China (Grant No. 20050286019). The author Y. Chen also acknowledges the financial
support from the Program for New Century Excellent Talents in University (NCET-04-0470). 相似文献
18.
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
19.
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
20.
Experimental investigation on operating instability of a dual compensation chamber loop heat pipe 总被引:1,自引:0,他引:1
The operating instability of a dual compensation chamber loop heat pipe (DCC-LHP) including temperature hysteresis, reverse
flow and temperature oscillation is described and explained in this paper. Test results indicate that the steady state operating
temperature under the variable conductance mode is not the same during the power cycle tests with the same heat load, and
it is lower during the power reduction cycle than that during the power increase cycle. Orientation has an effect on the heat
load range when temperature hysteresis occurs, and the effect of power variation amplitude can be ignored. Reverse flow tends
to occur in some of the startups at low heat loads, even if vapor existed in the vapor grooves initially, which is caused
by a higher pressure inside the wick due to evaporation in the evaporator core or vapor penetration into it. Temperature oscillation
tends to occur in some of the startups at low head loads or some steady-state operations at high heat loads. Especially when
the compensation chamber with the bayonet through is above the evaporator, the incidence rate of temperature oscillation is
high.
Supported by the National Natural Science Foundation of China (Grant No. 50676006) 相似文献