检索结果-南通市图书馆

Flexible and Accurate Frequency estimation for Complex Sinusoid Signal by Interpolation Using DFT Samples

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of electronics 2018年第1期27卷 109-114页

作者： XIANG Jinzhi cui Wei SHeN qing School of Information and electronics Beijing Institute of Technology

A flexible and accurate frequency estimator is first proposed for frequency estimation of a complex sinusoid weighted with a rectangular window function in additive white Gaussian noise. This proposed frequency estimator can be operated in the application of an arbitrary length discrete Fourier transform where the original input data is padded with any zeroes, which makes it more flexible in practice. The proposed frequency estimator utilizes the maximum sample value and its two adjacent samples in the frequency domain to perform the fine frequency estimation with unbiased results obtained. Then a modified frequency estimator is proposed to estimate the frequency when the complex sinusoid signal is weighted with different nonrectangular window functions. Although the modified frequency estimator is nonanalytic and biased, it can still improve the estimation performance for certain applications. Simulation results demonstrate that both of the proposed frequency estimators are effective to achieve the high frequency estimation accuracy. And the root mean square errors of the proposed frequency estimators approach the Cramer-Rao bound when the signal-to-noise ratio is large enough to make the coarse frequency estimation work effectively.

关键词： Frequency estimation Complex sinusoid DFT interpolation Zero-padding

Sparse Reconstruction Method for DOA estimation Based on Dynamic Dictionary and Negative exponent Penalty

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of electronics 2018年第2期27卷 386-392页

作者： QIAN Tong cui Wei SHeN qing School of Information and electronic Beijing Institute of Technology

This paper proposes a novel sparse representation method for direction of arrival estimation based on dynamic dictionary and negative exponent penalty. The dynamic dictionary can eliminate the off-grid effect and the negative exponent penalty is capable of strengthening the sparse constraint to improve the performance. The basis is regarded as a part of the optimal target and the cross iteration is utilized to jointly update the dictionary and sparse support in this method. Based on the propositions of the penalty function, the penalty function is designed to replace of 1 norm because of its unbiasedness and stronger sparse constraint. The regularization parameter is simplified as a constant due to pre-white process, which greatly extends the application range of the proposed method. The simulation results show that the proposed method can efficiently reduce the off-grid effect and the over-complete rate of the original dictionary. Compared with the conventional sparse representation methods, it has better performance and lower computation complexity.

关键词： Direction of arrival(DOA) Sparse reconstruction Dynamic dictionary Penalty function

Genetic algorithm for pareto optimum-based route selection

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems engineering and electronics 2007年第2期18卷 360-368页

作者： cui Xunxue Li Qin Tao qing New Star Research Inst. of Applied Technology Hefei 230031 P. R. China Jiangsu Key Lab of Computer Information Processing Technology Soochow Univ. Suzhou 215006 P. R. China

A quality of service （QoS） or constraint-based routing selection needs to find a path subject to multiple constraints through a network. The problem of finding such a path is known as the multi-constrained path （MCP） problem, and has been proven to be NP-complete that cannot be exactly solved in a polynomial time. The NPC problem is converted into a multiobjective optimization problem with constraints to be solved with a genetic algorithm. Based on the Pareto optimum, a constrained routing computation method is proposed to generate a set of nondominated optimal routes with the genetic algorithm mechanism. The convergence and time complexity of the novel algorithm is analyzed. experimental results show that multiobjective evolution is highly responsive and competent for the Pareto optimum-based route selection. When this method is applied to a MPLS and metropolitan-area network, it will be capable of optimizing the transmission performance.

关键词： Route selection Multiobjective optimization Pareto optimum Multi-constrained path Genetic algorithm.

Influence of austempering process on microstructures and mechanical properties of V-containing alloyed ductile iron

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2018年第1期25卷 81-89页

作者： Jun-jun cui Li-qing Chen State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 Liaoning China College of Mechanical and Vehicle engineering ShenyangInstitute of Technology Fushun 113122 Liaoning China

The influence of austempering time and vanadium addition on microstructure and mechanical properties of the alloyed ductile iron has been investigated. The 0.30 wt% V-containing and V-free alloyed ductile irons were firstly austenitized at 850 ℃ for 1 h and then austempered in a salt bath at 300 ℃ for 2, 3 and 4 h, respectively. For the 0.3 wt% V-containing alloyed ductile iron, the transformation product （ausferrite） was finer, and a small amount of martensite and a large amount of stable austenite were obtained after austempering for 2 h, while higher hardness and compressive strength of 62.8 HRC and 3000 MPa were achieved. For the V-free alloyed ductile iron, lower hardness and compressive strength were measured to be 56.8 HRC and 2320 MPa. As the austempering time increases, the amount of stable austenite decreases in the V-containing ductile iron, typically for the start of the second stage formation （retained austenite （γτ） →α ＋ carbide）. Based on this, it is assumed that the optimal processing window （OPW） was narrowed due to the addition of 0.30 wt% V as compared to the V-free ductile iron. When the hardness of 0.30 wt% V-alloyed ductile iron was higher than 59 HRC, the highest wear resist- ance was obtained. The mechanical cutting plays a dominant role in abrasive wear process.

关键词： Alloyed ductile iron Vanadium Austempering Microstructure Property Wear resistance

WAPN:a distributed wormhole attack detection approach for wireless sensor networks

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & engineering) 2009年第2期10卷 279-289页

作者： Fan-rui KONG Chun-wen LI qing-qing DING Guang-zhao cui Bing-yi cui Department of Automation. Tsinghua University Beijing 100084. China State Key Lab of Power Systems Departmet of Electrical Engineering Tsinghua University Beijing 100084 China State Key Lab of Informational electric Apparatus in Henan Zhengzhou 450002 China Department of Phvsics Nanjing University Nanjing 210093 China

As the applications of wireless sensor networks(WSNs) diversify,providing secure communication is emerging as a critical requirement. In this paper,we investigate the detection of wormhole attack,a serious security issue for WSNs. Wormhole attack is difficult to detect and prevent,as it can work without compromising sensor nodes or breaching the encryption key. We present a wormhole attack detection approach based on the probability distribution of the neighboring-node-number,WAPN,which helps the sensor nodes to judge distributively whether a wormhole attack is taking place and whether they are in the in-fluencing area of the attack. WAPN can be easily implemented in resource-constrained WSNs without any additional requirements,such as node localization,tight synchronization,or directional antennas. WAPN uses the neighboring-node-number as the judging criterion,since a wormhole usually results in a significant increase of the neighboring-node-number due to the extra attacking link. Firstly,we model the distribution of the neighboring-node-number in the form of a Bernoulli distribution. Then the model is simplified to meet the sensor nodes' constraints in computing and memory capacity. Finally,we propose a simple method to obtain the threshold number,which is used to detect the existence of a wormhole. Simulation results show that WAPN is effective under the conditions of different network topologies and wormhole parameters.

关键词： Wireless sensor networks (WSNs) Security Wormhole detection

Liquid phase in-situ synthesis of LiF coated boron powder composite and performance study

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2020年第3期16卷 635-641页

作者： Yang Xu qing-zhong cui Cheng-wen Zhao State Key Laboratory of explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Shanxi Jiangyang Chemical Factory Shanxi 030000China

Among practical metal additives,boron(B) has a high volumetric heating value,making it a promising choice as a fuel *** B can theoretically yield a large amount of energy upon complete combustion,its combustion is retarded by the initial presence of B oxide,which coats the surfaces of B *** improve the ignition and combustion properties of B powder,LiOH and NH4F were used as precursors to synthesize uniformly LiF-coated B composites(LiF-B) in *** LiF-B mixture was also prepared for comparison using a physical method.X-ray diffraction(XRD),Fourier-transform infrared(FTIR),scanning electron microscope(SeM),and energy-dispersive X-ray spectroscopy(eDS) were used to characterize the morphologies and compositions of the *** thermal and combustion properties of the samples were characterized by thermal gravity-differential thermal gravity(TG-DTG),differential scanning calo rimetry(DSC) and closed bomb *** XRD,FTIR,SeM and eDS results demonstrated the successful preparation of the coated LiF-B *** TG-DTG and closed bomb experiment results indicated that the addition of LiF decreased the ignition temperature of B powder,and increasing its reaction *** results show that when LiF-B was added,the released heat of underwater explosive increased by 6727.2,7280.4 and 3109.6 J/g at heating rates of 5,10,and 15℃/min,***,LiF-B decreased the activation energy of secondary combustion reaction of explosive system as calculated through Kissinger’s method by 28.9%,which indicated an excellent catalytic effect for the thermal decomposition of underwater *** results reveal that LiF can improve the combustion efficiency of B powder,thereby increasing the total energy of *** mechanical sensitivity increased slightly after adding LiF-B to the underwater *** mpared to the underwater explosive with added B,the mechanical sensitivity of the explosive with added LiF-B was significantly

关键词： Boron LiF Coating Thermal decomposition properties energy efficiency

Real-time accurate Free-Form Deformation in terms of triangular Bézier surfaces

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2014年第4期29卷 455-467页

作者： cui Yuan-min FeNG Jie-qing State Key Lab of CAD&CG Zhejiang University

We implemented accurate FFD in terms of triangular Bezier surfaces as matrix multiplications in CUDA and rendered them via OpenGL. experimental results show that the proposed algorithm is more efficient than the previ... 详细信息

关键词： accurate Free-Form Deformation GPU acceleration CUDA triangular B@zier surface.

On Cauchy Problem of the Benney-Lin equation with Low Regularity Initial Data

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,english Series 2009年第12期25卷 2157-2168页

作者： Xiang qing ZHAO Shang Bin cui Department of Mathematics Zhejiang Ocean University Zhoushan 316000 P. R. China Department of Mathematics Shanghai University Shanghai 200444 P. R. China Institute of Mathematics Sun Yat-Sen University Guangzhou 510275 P. R. China

In this work we prove that the initial value problem of the Benney-Lin equation ut ＋ uxxx ＋ β（uxx ＋ u xxxx）＋ ηuxxxxx ＋ uux = 0 （x ∈ R, t ≥0 0）, where β 〉 0 and η∈R, is locally well-posed in Sobolev spaces HS（R） for s ≥ -7/5. The method we use to prove this result is the bilinear estimate method initiated by Bourgain.

关键词： Benney-Lin equation initial value problem local well-posedness

effect of Boron on Morphology of Inclusions in Tire Cord Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2012年第4期19卷 22-27页

作者： cui Huai-zhou CHeN Wei-qing State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Metallurgical Process Research Institute CentralIron and Steel Research Institute Beijing 100083 China

B2O3 was added to tire cord steel during refining in a carbon tube *** influence of boron on the deformability of oxide inclusions was studied by metallographic and scanning electron microscope（SeM） *** melting points of boron-bearing compound oxide inclusions were calculated using Factsage *** results showed that the main inclusion was a boron-bearing compound oxide and the deformation properties of the inclusions were clearly improved by adding *** the boron content was increased from 0.0046% to 0.039%,the proportion of long strip type inclusions changed slightly and the number of inclusions *** low-melting point areas of the MnO-SiO2-Al2O3 and CaO-SiO2-Al2O3 ternary system increased with the addition of ***,the area increased with the increase of B2O3 *** improvements in the deformation ability of the inclusions occurred when the B2O3 mass percent rose to 5% in the CaO-SiO2-Al2O3 inclusion system and to 10% in the MnO-SiO2-Al2O3 inclusion system

关键词： boron tire cord steel inclusions morphology