期刊文献+
共找到16,471篇文章
< 1 2 250 >
每页显示 20 50 100
Realization of -bit semiclassical quantum Fourier transform on IBM’s quantum cloud computer
1
作者 付向群 鲍皖苏 +5 位作者 黄合良 李坦 史建红 汪翔 张硕 李风光 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第2期117-122,共6页
To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z2n), which could realiz... To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z2n), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z23 on IBM’s quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the experiments.The squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N = 15 is successfully factorized by implementing Shor’s algorithm. 展开更多
关键词 QUANTUM cloud COMPUTATION QUANTUM FOURIER TRANSFORM SEMICLASSICAL QUANTUM FOURIER TRANSFORM Shor’s algorithm
ON THE VALIDITY OF THE LOCAL FOURIER ANALYSIS
2
作者 Carmen Rodrigo Francisco J.Gaspar Ludmil T.Zikatanov 《计算数学:英文版》 SCIE CSCD 2019年第3期340-348,共9页
Local Fourier analysis(LFA)is a useful tool in predicting the convergence factors of geometric multigrid methods(GMG).As is well known,on rectangular domains with periodic boundary conditions this analysis gives the e... Local Fourier analysis(LFA)is a useful tool in predicting the convergence factors of geometric multigrid methods(GMG).As is well known,on rectangular domains with periodic boundary conditions this analysis gives the exact convergence factors of such met hods.When other boundary conditions are considered,however,this analysis was judged as been heuristic,with limited capabilities in predicting multigrid convergence rates.In this work,using the Fourier method,we extend these results by proving that such analysis yields the exact convergence factors for a wider class of problems,some of which can not be handled by the traditional rigorous Fourier analysis. 展开更多
关键词 LOCAL FOURIER ANALYSIS MULTIGRID FOURIER METHOD
Rockfall seismic features analysis based on in situ tests:frequency, amplitude, and duration
3
作者 Liang FENG Veronica PAZZI +2 位作者 Emanuele INTRIERI Teresa GRACCHI Giovanni GIGLI 《山地科学学报:英文版》 SCIE CSCD 2019年第5期955-973,共19页
In the seismic event classification,determining the seismic features of rockfall is significantly important for the automatic classification of seismic events because of the huge amount of raw data recorded by seismic... In the seismic event classification,determining the seismic features of rockfall is significantly important for the automatic classification of seismic events because of the huge amount of raw data recorded by seismic stations in continuous monitoring. At the same time, the rockfall seismic features are still not completely understood.This study concentrates on the rockfall frequency content, amplitude(ground velocity), seismic waveform and duration analysis, of an artificial rockfall test at Torgiovannetto(a former quarry in Central Italy). A total of 90 blocks were released in the test, and their seismic signals and moving trajectories were recorded by four tri-axial seismic stations and four cameras, respectively. In the analysis processing,all the artificial rockfall signal traces were cut separately and the seismic features were extracted individually and automatically. In this study, the relationships between a) frequency content and impacted materials, b) frequency content and the distance between block releasing position and seismic station(source-receiver distance) were discussed. As a result, we found that the frequency content of rockfall focuses on 10-60 Hz and 80-90 Hz within a source-receiver distance of 200 m, and it is well correlated with impacted material and source-receiver distance. To evaluate the difference between earthquake and rockfall, 23 clear earthquake signals recorded in a seven month-long continuous seismic monitoring, carried out with the four seismic stations, were picked out, according to the Italian national earthquakes database(INGV). On these traces we performed the same analysis as in the artificial rockfall traces, and two parameters were defined to separate rockfall events from earthquake noise. The first one, the amplitude ratio, is related to the amplitude variation of rockfall between two stations and is greater than that of earthquakes, because of the higher attenuation occurring for rockfall events, which consists in high frequencies whereas for earthquakes it consists 展开更多
关键词 ROCKFALL SEISMIC noise ANALYSIS Fourier TRANSFORM SEISMIC events classification Time-series ANALYSIS SEISMIC monitoring
Constant envelope FrFT OFDM: spectral and energy efficiency analysis 预览
4
作者 DIDA Mussa Ally HUAN Hao +2 位作者 TAO Ran WANG Teng URYNBASSAROVA Didar 《系统工程与电子技术:英文版》 SCIE EI CSCD 2019年第3期467-473,共7页
Constant envelope with a fractional Fourier transformorthogonal frequency division multiplexing(CE-FrFT-OFDM)is a special case of a constant envelope OFDM(CE-OFDM),both being energy efficient wireless communication te... Constant envelope with a fractional Fourier transformorthogonal frequency division multiplexing(CE-FrFT-OFDM)is a special case of a constant envelope OFDM(CE-OFDM),both being energy efficient wireless communication techniques with a 0 dB peak to average power ratio(PAPR).However,with the proper selection of fractional order,the first technique has a high bit error rate(BER)performance in the frequency-time selective channels.This paper performs further analysis of CE-FrFT-OFDM by examining its spectral efficiency(SE)and energy efficiency(EE)and compare to the famous OFDM and FrFT-OFDM techniques.Analytical and comprehensive simulations conducted show that,the CE-FrFT-OFDM has five times the EE of OFDM and FrFT-OFDM systems with a slightly less SE.Increasing CE-FrFT-OFDM’s transmission power by increasing its amplitude to 1.7 increases its SE to match that of the OFDM and FrFT-OFDM systems while slightly reducing its EE by 20%to be four times that of OFDM and FrFTOFDM systems.OFDM and FrFT-OFDM’s amplitude fluctuations cause rapid changing output back-off(OBO)power requirements and further reduce power amplifier(PA)efficiency while CE-FrFTOFDM stable operational linear range makes it a better candidate and outperforms the other techniques when their OBO exceeds 1.7.Higher EE and low BER in time-frequency selective channel are attracting features for CE-FrFT-OFDM deployment in mobile devices. 展开更多
关键词 FRACTIONAL Fourier TRANSFORM (FrFT) constant ENVELOPE SPECTRAL EFFICIENCY (SE) energy EFFICIENCY (EE) high power AMPLIFIER
在线阅读 下载PDF
Voice Recognition by Neuro-Heuristic Method
5
作者 Dawid Pofap Marcin Wozniak 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2019年第1期9-17,共9页
The amount of digital data is increasing every day.At every step of our daily lives,we deal with technologies in which our data are stored (e.g.,mobile phones and laptops),and this is one of the main reasons for the d... The amount of digital data is increasing every day.At every step of our daily lives,we deal with technologies in which our data are stored (e.g.,mobile phones and laptops),and this is one of the main reasons for the design of various types of encryption and user identity verification algorithms.These algorithms are meant not only to fulfill the desire of protecting data but also to address the possibility of granting access of specific digital data to selected individuals.This process brings with it the problem of identity verification.This paper discusses the problem of voice verification and presents a voice verification method based on artificial intelligence methods. Numerous tests are performed herein to demonstrate the effectiveness of the presented solution.The research results are shown and discussed in terms of the advantages and disadvantages of the solution. 展开更多
关键词 neural network HEURISTIC ALGORITHMS DISCRETE FOURIER TRANSFORM (DFT) image processin
A 3D Finite Radon Transform 预览
6
作者 Mustapha Boukour Abderrahim El Omri 《数学和系统科学:英文版》 2019年第2期64-69,共6页
The present work is devoted to the development of the extension of FRT (Finite Radon Transform) to the tridimensional case. One simple formulation is proposed and it is shown that it is the exact discretization of the... The present work is devoted to the development of the extension of FRT (Finite Radon Transform) to the tridimensional case. One simple formulation is proposed and it is shown that it is the exact discretization of the continuous Discrete Radon Transform. More precisely this is the case when the sampling is given on a regular grid i.e. the continuous function is filtered by the mean of the box function. Relation of this transform with the Discrete Fourier one is given and is for some help in numerical implementation. 展开更多
关键词 RADON TRANSFORM DISCRETE RADON TRANSFORM FRT DISCRETE FOURIER NUMERICAL COMPUTING
在线阅读 下载PDF
Revelation of the birth and extinction dynamics of solitons in SWNT-mode-locked fiber lasers
7
作者 Yudong Cui Xueming Liu 《光子学研究:英文版》 CSCD 2019年第4期423-430,共8页
The dispersive Fourier transform(DFT) technique opens a fascinating pathway to explore ultrafast non-repetitive events and has been employed to study the build-up process of mode-locked lasers. However, the shutting p... The dispersive Fourier transform(DFT) technique opens a fascinating pathway to explore ultrafast non-repetitive events and has been employed to study the build-up process of mode-locked lasers. However, the shutting process for the mode-locked fiber laser seems to be beyond the scope of researchers, and the starting dynamics under nearzero dispersion remains unclear. Here, the complete evolution dynamics(from birth to extinction) of the conventional soliton(CS), stretched pulse(SP), and dissipative soliton(DS) are investigated by using the DFT technique.CS, SP, and DS fiber lasers mode locked by single-walled carbon nanotubes(SWNTs) are implemented via engineering the intracavity dispersion map. The relaxation oscillation can always be observed before the formation of stable pulse operation due to the inherent advantage of SWNT, but it exhibits distinct evolution dynamics in the starting and shutting processes. The shutting processes are dependent on the dispersion condition and turn-off time, which is against common sense. Some critical phenomena are also observed, including transient complex spectrum broadening and frequency-shift interaction of SPs and picosecond pulses. These results will further deepen understanding of the mode-locked fiber laser from a real-time point of view and are helpful for laser design and applications. 展开更多
关键词 dispersive Fourier transform(DFT) fascinating pathway PICOSECOND pulses
Association of Variations in the Dynamics of the Lithosphere with Sea Temperature 预览
8
作者 Nabil H.Swedan 《地质研究(英文)》 2019年第1期12-20,共9页
Variations in the dynamics of the oceanic lithosphere are important at the societal and research levels because geological activities are associated with these variations. At any given section of the lithosphere, the ... Variations in the dynamics of the oceanic lithosphere are important at the societal and research levels because geological activities are associated with these variations. At any given section of the lithosphere, the time in which its typical geophysical parameters vary is considerably smaller than section's age. The lithosphere can, therefore, be assumed to proceed from one state of dynamic equilibrium to another displaced deferentially. When these conditions are accounted for in the thermal analysis of the oceanic lithosphere, the earth's internal heat flux through the lithosphere is found to be an adiabatic invariant. Lithosphere physical parameters exhibit constant change and linearity. These findings simplify analysis of heat and work inter actions between oceanic lithosphere and continents, lithosphere dynamics, and deep mantle heat transfer. The temperature of the solid earth remains unchanged for the foreseeable future, and variations in sea temperature vary the intensity of geological activities. If sea temperature increases, the geological activities increase and vice versa. Relevant equations are derived using this thermal analysis of the lithosphere and validated based on observations and the work of others. In addition, the analysis reveals that the eleven-year solar constant cycle is capable of inducing 1.56×10^16 J yr^-1 of geological activities. 展开更多
关键词 LITHOSPHERE Dynamic EQUILIBRIUM FOURIER Equation Climate Change SEASONAL VARIATIONS Solar CONSTANT
在线阅读 免费下载
Extraction of mode shapes of beam-like structures from the dynamic response of a moving mass 预览
9
作者 Yao Zhang Longqi Wang +1 位作者 Haisheng Zhao Seng Tjhen Lie 《力学学报:英文版》 SCIE EI CAS CSCD 2019年第3期664-673,共10页
This paper proposes an approach to extract the mode shapes of beam-like structures from the dynamic response of a moving mass. When a mass passes through a beam containing several artificially installed humps, its ver... This paper proposes an approach to extract the mode shapes of beam-like structures from the dynamic response of a moving mass. When a mass passes through a beam containing several artificially installed humps, its vertical acceleration can be recorded. After applying fast Fourier transformation to the dynamic response, one can extract the mode shapes of the beam. The surface roughness was neglected compared to the humps and its adverse effect on the extraction was reduced. The passing mass performs as both “exciter” and “massage receiver”;therefore, this method requires only one single accelerometer, making it more convenient and time saving in practice. Moreover, to estimate the possible error in extracting mode shapes, a wavenumber domain filtering technique is used to reconstruct the general profiles of mode shapes. Experimental validation of this approach in laboratory scale was conducted. The experimental results show that the proposed method performs well in extracting lower order mode shapes. It should also be noted that the passing mass can not have a very high velocity (e.g. 80 mm/s), otherwise the mass may jump and separate from the beam, and the proposed method may fail to identify mode shapes. 展开更多
关键词 Mode shape Beam-like STRUCTURES MOVING mass Artificially installed humps Fast FOURIER TRANSFORMATION
在线阅读 下载PDF
THE STRUCTURE-PRESERVING METHODS FOR THE DEGASPERIS-PROCESI EQUATION
10
作者 Yuze Zhang Yushun Wang Yanhong Yang 《计算数学:英文版》 SCIE CSCD 2019年第4期475-487,共13页
This paper gives several structure-preserving schemes for the Degasperis-Procesi equation which has bi-Hamiltonian structures consisted of both complex and non-local Hamiltonian differential operators. For this sake, ... This paper gives several structure-preserving schemes for the Degasperis-Procesi equation which has bi-Hamiltonian structures consisted of both complex and non-local Hamiltonian differential operators. For this sake, few structure-preserving schemes have been proposed so far. In our work, based on one of the bi-Hamiltonian structures, a symplectic scheme and two new energy-preserving schemes are constructed. The symplecticity comes straightly from the application of the implicit midpoint method on the semi-discrete system which is proved to remain Hamiltonian, while the energy conservation is derived by the combination of the averaged vector field method of second and fourth order, respectively. Some numerical results are presented to show that the three schemes do have the advantages in numerical stability, accuracy in long time computing and ability to preserve the invariants of the DP equation. 展开更多
关键词 DEGASPERIS-PROCESI EQUATION bi-Hamiltonian STRUCTURE Structure-preserving SCHEME FOURIER PSEUDOSPECTRAL method
Comparative study of otolith and sulcus morphology for stock discrimination of yellow drum along the Chinese coast 预览
11
作者 SONG Junjie ZHAO Bo +2 位作者 LIU Jinhu CAO Liang DOU Shuozeng 《海洋湖沼学报(英文)》 SCIE CAS CSCD 2019年第4期1430-1439,共10页
Otolith morphology is widely used for fish stock identification. The sulcus, a structure on the medial side of the otolith, is an important feature in morphological analysis. This study was conducted to evaluate the f... Otolith morphology is widely used for fish stock identification. The sulcus, a structure on the medial side of the otolith, is an important feature in morphological analysis. This study was conducted to evaluate the feasibility of using sulcus morphology for stock identification and to compare its performance with commonly used otolith morphology analysis. Otoliths were collected and analyzed from three geographical groups (the Huanghe (Yellow) River estuary, HHE;the Jiaozhou Bay, JZB;and the Changjiang (Yangtze) River estuary, CJE) of yellow drum Nibea albiflora. The results show that the analysis of sulcus morphology based on shape indices (SIs), elliptic Fourier coefficients (EFc), and a combination of the two parameters identified stocks at overall classification rates of 51.0%, 72.5%, and 73.2%, respectively. These classification rates are similar to those obtained using otolith morphology analysis (57.0%, 73.8%, and 76.5% by SIs, EFc, and their combination, respectively). The findings suggest that sulcus morphology is comparable to the commonly used otolith morphology for identifying stocks of sciaenids, such as the yellow drum. For both otolith and sulcus morphology, EFc could identify the stocks more efficiently than SIs, while the combination of SIs and EFc was even better. 展开更多
关键词 OTOLITH SULCUS shape indices ELLIPTIC Fourier analysis STOCK DISCRIMINATION Nibea albiflora
在线阅读 下载PDF
Fast Fourier single-pixel imaging based on Sierra–Lite dithering algorithm
12
作者 梁振宇 程正东 +2 位作者 刘严严 于快快 胡洋頔 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第6期189-194,共6页
The single-pixel imaging(SPI) technique is able to capture two-dimensional(2 D) images without conventional array sensors by using a photodiode. As a novel scheme, Fourier single-pixel imaging(FSI) has been proven cap... The single-pixel imaging(SPI) technique is able to capture two-dimensional(2 D) images without conventional array sensors by using a photodiode. As a novel scheme, Fourier single-pixel imaging(FSI) has been proven capable of reconstructing high-quality images. Due to the fact that the Fourier basis patterns(also known as grayscale sinusoidal patterns)cannot be well displayed on the digital micromirror device(DMD), a fast FSI system is proposed to solve this problem by binarizing Fourier pattern through a dithering algorithm. However, the traditional dithering algorithm leads to low quality as the extra noise is inevitably induced in the reconstructed images. In this paper, we report a better dithering algorithm to binarize Fourier pattern, which utilizes the Sierra–Lite kernel function by a serpentine scanning method. Numerical simulation and experiment demonstrate that the proposed algorithm is able to achieve higher quality under different sampling ratios. 展开更多
关键词 single-pixel IMAGING binary FOURIER basis pattern the dithering ALGORITHM
基于Burton-Miller方程的轴对称结构声学边界元方法
13
作者 刘宝 王德石 +1 位作者 周奇郑 朱拥勇 《声学学报》 EI CSCD 北大核心 2019年第3期303-311,共9页
提出了一种求取轴对称结构任意边界条件下声辐射特性的边界元方法。采用Burton和Miller改进型公式将高阶奇异项转化为弱奇异项之和,保证声辐射参数的唯一性,且计算简单精确。将结构表面声压与振速按照旋转轴角度进行Fourier级数展开,利... 提出了一种求取轴对称结构任意边界条件下声辐射特性的边界元方法。采用Burton和Miller改进型公式将高阶奇异项转化为弱奇异项之和,保证声辐射参数的唯一性,且计算简单精确。将结构表面声压与振速按照旋转轴角度进行Fourier级数展开,利用级数的正交性建立各项待定系数的求解公式;然后转化格林函数的法向偏导为切向偏导,方便直接计算各项积分,并将面积分公式表示为沿结构边界的线积分和沿旋转角度的积分;进一步采用二次等参单元离散结构边界线,建立声压与振速的关系矩阵,从而确定结构声辐射参数。以脉动球源和横向振动球源为例计算,与解析解和传统边界元法结果作对比,说明该方法的有效精确性。 展开更多
关键词 边界元方法 轴对称结构 结构声学 FOURIER 高阶奇异项 方程 任意边界条件 Burton
Feasibility assessment of phenotyping cotton fiber maturity using infrared spectroscopy and algorithms for genotyping analyses 预览
14
作者 KIM Hee Jin LIU Yongliang +1 位作者 FANG David D. DELHOM Christopher D. 《棉花研究(英文)》 2019年第1期44-55,共12页
Background:Cotton fiber maturity is an important property that partially determines the processing and performance of cotton.Due to difficulties of obtaining fiber maturity values accurately from every plant of a gene... Background:Cotton fiber maturity is an important property that partially determines the processing and performance of cotton.Due to difficulties of obtaining fiber maturity values accurately from every plant of a genetic population,cotton geneticists often use micronaire(MIC) and/or lint percentage for classifying immature phenotypes from mature fiber phenotyp es although they are complex fiber traits.The recent development of an algorithm for determining cotton fiber maturity(MIR)from Fourier transform infrared(FT-IR)spectra explores a novel way to measure fiber maturity efficiently and accurately.However,the algorithm has not been tested with a genetic population consisting of a large number of progeny pla,nts.Results:The merits and limits of the MIC-or lint percentage-bas ed phenotyping method were demonstrated by comparing the observed phenotypes with the predicted phenotypes based on their DNA marker genotypes in a genetic population consisting of 708 F2 plants with various fiber maturity.The observed MIC-based fiber phenotypes matched to the predicted phenotypes better than the observed lint percenta ge-based fiber phenotypes.The lint percentage was obtained from each of F2 plants,whereas the MIC values were unable to be obtained from the entire population since certain F2 plants produced insufficient fiber mass for their measurements.To test the feasibiility of cotton fiber infrared maturity(MIR)as a viable phenotyping tool for genetic analyses,we me asured FT-IR spectra from the second population composed of 80 F2 plants with various fiber maturities,determined MIR values using the algorithms,and compared them with their genotypes in addition to other fiber phenotypes.The results showed that MIR values were successfully obtained from each of the F2 plants,and the observed MIR-based phenotypes fit well to the predicted phenotypes based on their DNA marker genotypes as well as the observed phenotypes based on a combination of MIC and lint percentage.Conclusions:The M,R value obtained from FT-IR spectra of c 展开更多
关键词 Attenuated total reflection Fourier transform infrared spectroscopy Cotton FIBER MATURITY CRYSTALLINITY IMMATURE FIBER (im) mutant
在线阅读 下载PDF
Analysis and Approximation of Gradient Flows Associated with a Fractional Order Gross-Pitaevskii Free Energy 预览
15
作者 Mark Ainsworth Zhiping Mao 《应用数学与计算数学学报(英文)》 2019年第1期5-19,共15页
We establish the well-posedness of the fractional PDE which arises by considering the gradient flow associated with a fractional Gross-Pitaevskii free energy functional and some basic properties of the solution.The eq... We establish the well-posedness of the fractional PDE which arises by considering the gradient flow associated with a fractional Gross-Pitaevskii free energy functional and some basic properties of the solution.The equation reduces to the Allen-Cahn or Cahn-Hilliard equations in the case where the mass tends to zero and an integer order derivative is used in the energy.We study how the presence of a non-zero mass affects the nature of the solutions compared with the Cahn-Hilliard case.In particular,we show that,analogous to the Cahn-Hilliard case,the solutions consist of regions in which the solution is a piecewise constant(whose value depends on the mass and the fractional order)separated by an interface whose width is independent of the mass and the fractional derivative.However,if the average value of the initial data exceeds some threshold(which we determine explic让ly),then the solution will tend to a single constant steady state. 展开更多
关键词 FRACTIONAL differential equation NON-LOCAL energy WELL-POSEDNESS FOURIER spectral method
在线阅读 下载PDF
Estimating rock properties using sound signal dominant frequencies during diamond core drilling operations 预览
16
作者 Ch.Vijaya Kumar Harsha Vardhan +1 位作者 Ch.S.N.Murthy N.C.Karmakar 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第4期850-859,共10页
In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimatio... In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimation of the rock properties.Nevertheless,determination of rock properties is very difficult by the conventional methods in terms of high accuracy,and thus it is expensive and timeconsuming.In this context,a new technique was developed based on the estimation of rock properties using dominant frequencies from sound pressure level generated during diamond core drilling operations.First,sound pressure level was recorded and sound signals of these sound frequencies were analyzed using fast Fourier transform (FFT).Rock drilling experiments were performed on five different types of rock samples using computer numerical control (CNC) drilling machine BMV 45 T20.Using simple linear regression analysis,mathematical equations were developed for various rock properties,i.e.uniaxial compressive strength,Brazilian tensile strength,density,and dominant frequencies of sound pressure level.The developed models can be utilized at early stage of design to predict rock properties. 展开更多
关键词 Rock properties SOUND pressure level Fast FOURIER TRANSFORM (FFT) SOUND signal Core DRILLING DOMINANT frequencies
在线阅读 下载PDF
Classification and uniformity optimization of mesh-plate DBD and its application in polypropylene modification
17
作者 辉妍 鲁娜 +4 位作者 罗朋振 商克峰 姜楠 李杰 吴彦 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第5期51-59,共9页
The classification of spatial characteristics and discharge modes of dielectric barrier discharge(DBD)are gaining increasing attention in industrial applications,especially in the field of surface treatment of materia... The classification of spatial characteristics and discharge modes of dielectric barrier discharge(DBD)are gaining increasing attention in industrial applications,especially in the field of surface treatment of materials.In this work,gray level histogram(GLH)and Fourier energy spectrum based on the digital image processing tech no logy are applied to investigate the spatial structure and discharge mode of mesh-plate DBD.The coefficient of variation(CV)is calculated to describe the uniformity of the discharge.The results show that the discharge mode of mesh-plate DBD changes from periodic discharge to filamentary discharge when the applied voltage increases from 11-15 kV.Moreover,a more regular spatial structure is obtained under lower applied voltages during the discharge process.It is also found that the apertures of mesh electrodes which are below 1 mm have smaller values of CV compared to plate electrodes,indicating more uniform discharge.Finally,polypropylene is treated by mesh-plate DBD for surface modification.The hydrophilicity is significantly improved as the water contact angle decreased by 64°,and the dyeing depth is also enhanced. 展开更多
关键词 mesh-plate DBD gray level HISTOGRAM Fourier energy spectrum CV surface MODIFICATION
Quantitative SNR analysis of QFM signals in the LPFT domain with Gaussian windows
18
作者 Yan-Na ZHANG Bing-Zhao LI +1 位作者 Navdeep GOEL Salvador GABARDA 《中国科学:信息科学(英文版)》 SCIE EI CSCD 2019年第2期127-141,共15页
The purpose of this paper is to present a quantitative SNR analysis of quadratic frequency modulated(QFM)signals.This analysis is located in the continuous-time local polynomial Fourier transform(LPFT)domain using a G... The purpose of this paper is to present a quantitative SNR analysis of quadratic frequency modulated(QFM)signals.This analysis is located in the continuous-time local polynomial Fourier transform(LPFT)domain using a Gaussian window function based on the definition of 3 dB signal-to-noise ratio(SNR).First,the maximum value of the local polynomial periodogram(LPP),and the 3 dB bandwidth in the LPFT domain for a QFM signal is derived,respectively.Then,based on these results,the 3 dB SNR of a QFM signal with Gaussian window function is given in the LPFT domain with one novel idea highlighted:the relationship among standard SNR,parameters of QFM signals and Gaussian window function is clear,and the potential application is demonstrated in the parameter estimation of a QFM signal using the LPFT.Moreover,the 3 dB SNR in the LPFT domain is compared with that in the linear canonical transform(LCT)domain.The validity of theoretical derivations is confirmed via simulation results.It is shown that,in terms of SNR,QFM signals in the LPFT domain can achieve a significantly better performance than those in the LCT domain. 展开更多
关键词 SNR ANALYSIS QUADRATIC FREQUENCY modulated signal local polynomial Fourier TRANSFORM linear CANONICAL TRANSFORM time FREQUENCY representations
Turing pattern in the fractional Gierer–Meinhardt model
19
作者 王语 张荣培 +1 位作者 王震 韩子健 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第5期57-63,共7页
It is well-known that reaction–diffusion systems are used to describe the pattern formation models.In this paper,we will investigate the pattern formation generated by the fractional reaction–diffusion systems.We fi... It is well-known that reaction–diffusion systems are used to describe the pattern formation models.In this paper,we will investigate the pattern formation generated by the fractional reaction–diffusion systems.We first explore the mathematical mechanism of the pattern by applying the linear stability analysis for the fractional Gierer–Meinhardt system.Then,an efficient high-precision numerical scheme is used in the numerical simulation.The proposed method is based on an exponential time differencing Runge–Kutta method in temporal direction and a Fourier spectral method in spatial direction.This method has the advantages of high precision,better stability,and less storage.Numerical simulations show that the system control parameters and fractional order exponent have decisive influence on the generation of patterns.Our numerical results verify our theoretical results. 展开更多
关键词 TURING PATTERNS FRACTIONAL Gierer–Meinhardt MODEL FOURIER SPECTRAL method
Scattering and reflection of SH waves around a slope on an elastic wedged space 预览
20
作者 Liu Qijian Wu Zhiyu Vincent W Lee 《地震工程与工程振动:英文版》 SCIE EI CSCD 2019年第2期255-266,共12页
The scattering and reflection of SH waves by a slope on an elastic wedged space is investigated. A series solution is obtained by using the wave function expansion method. The slope on a wedged space is divided into t... The scattering and reflection of SH waves by a slope on an elastic wedged space is investigated. A series solution is obtained by using the wave function expansion method. The slope on a wedged space is divided into two subregions by an artificial, auxiliary circular arc. The wave fields with unknown complex coefficients within each sub-region are derived. Applying Graf addition theorem, the scattered waves in the sub-regions are expressed in a global coordinate system. Fourier transform is adopted to derive a consistent form of standing waves in the inner region using the orthogonality of the cosine functions. The boundary-valued problem is solved by stress and displacement continuity along the artificial, auxiliary arc to obtain the unknown complex coefficients. Parametric studies are next performed to investigate how the topography from the slope on the wedged space will affect the scattering and diffraction, and hence the amplification and de-amplification of the SH waves. Numerical results show that the surface motions on the slope of the wedged space is influenced greatly by the topography. Amplification of the surface motions near the slope vertex is significant. The corresponding phases along the wedged space surfaces are consistent with the direction that the SH waves are propagating. 展开更多
关键词 earthquake ground motion wave SCATTERING and DIFFRACTION Graf addition THEOREM FOURIER TRANSFORM
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈