检索结果-内蒙古大学图书馆

A selective bitplane image encryption scheme using chaotic maps

MULTIMEDIA TOOLS AND APPLICATIONS 2019年第8期78卷 10373-10400页

作者： Som, Sukalyan Mitra, Abhijit Palit, Sarbani Chaudhuri, B. B. Barrackpore Rastraguru Surendranath Coll Dept Comp Sci Kolkata W Bengal India Gargi Mem Inst Technol Kolkata 144 India Indian Stat Inst Comp Vis & Pattern Recognit Unit Kolkata W Bengal India

Partial encryption is one of the viable solutions for low power, high speed, real time secure multimedia communication. In this paper, a chaotic tent map based selective bitplane encryption technique is proposed for both gray scale and color images. After decomposing the original image into eight bitplanes, each bitplane is classified into either significant or non-significant category by defining a flexible threshold value of 0.3, deduced experimentally. Following this segregation, only the significant bitplanes are encrypted with the key stream sequences generated by a chaos-based pseudo-random binary number generator. The cipher image is then transmitted through public channel. The proposed scheme has three important contributions v.i.z. a) determination of significant bitplanes, b) encryption of only the significant bitplanes leading to reduction in computational complexity and c) elimination of the need for separate channel for transmitting the information about the significant bitplanes. It is shown that the proposed partial encryption scheme saves around 35% computation on the image database used here. Different types of attacks against this scheme are also analysed to show the robustness of this approach.

关键词： Partial image encryption auto-correlation function Bitplane Tent map Uniformity test correlation coefficient Key sensitivity Differential attack Cropping attack Replacement attack

来源：评论

学校读者我要写书评

暂无评论

A novel method of weakness imbalance fault identification and application in aero-hydraulic pump

引用

JOURNAL OF VIBROENGINEERING 2019年第1期21卷 52-65页

作者： Yu, Mingyue Cheng, Jincai Pan, Hui Zhang, Runze Lin, Zeli Shenyang Aerosp Univ Shenyang Liaoning Peoples R China Aeromeasurement & Control Technol Res Shanghai Peoples R China

A method of combining auto-correlation and Hilbert envelope analysis is proposed and used to identify weakness imbalance fault of aero-hydraulic pump, the central part of hydraulic system of aircraft. Firstly, the integral and polynomial least square fitting is applied to convert acceleration signal to velocity one;secondly, the Hilbert envelope spectrum of auto-correlation function of velocity signal is obtained and used to identify the weakness imbalance fault of aero-hydraulic pump;finally, the energy ratio of velocity signal is calculated according to Hilbert envelope spectrum for identifying imbalance fault of aero-hydraulic pump by means of easier and more visual method. Meanwhile, the comparing analysis is carried out between traditional research method and proposed new one. The result shows that the weakness imbalance fault of aero-hydraulic pump can be identified and diagnosed effectively and correctly according to the velocity signal whether Hilbert envelope spectrum or calculation energy ratio while direct acceleration signal cannot.

关键词： energy ratio casing vibration signal aero-hydraulic pump auto-correlation function velocity signal

来源：评论

学校读者我要写书评

暂无评论

New scaling procedure for quantitative determination of surface anisotropy-application to plastic deformation of AISI 316 L stainless steel

引用

SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES 2020年第1期8卷

作者： Kubisztal, Julian Kubisztal, Marian Haneczok, Grzegorz Univ Silesia Inst Mat Sci 75 Pulku Piechoty La PL-41500 Chorzow Poland

Application of the power spectral density (PSD) function and the auto-correlation (AC) function to the quantitative determination of surface anisotropy is presented and discussed in detail. A new scaling procedure of the anisotropy ratio is proposed and discussed as well. Our approach is based on the obvious fact that a random system by definition is free from any texture pattern and can be considered as a reference system. The proposed procedure was successfully tested using numerically generated surface maps with a systematic variation of the anisotropy intensity. It was shown that the elaborated method allows determining the surface anisotropy over 80% and even below 1%. Finally, the procedure was used to analyze the grain anisotropy forced by plastic deformation (up to 30%) of AISI 316 L stainless steel. It was shown that the anisotropy intensity is directly proportional to the strain determined from the tensile tests.

关键词： auto-correlation function power spectral density function anisotropy ratio texture aspect ratio plastic deformation

来源：评论

学校读者我要写书评

暂无评论

Reliability analysis of stability against piping and sliding in diversion dams, considering four cutoff wall configurations

引用

COMPUTERS AND GEOTECHNICS 2018年第Jun.期98卷 217-231页

作者： Hekmatzadeh, Ali Akbar Zarei, Farshad Johari, Ali Haghighi, Ali Torabi Shiraz Univ Technol Dept Civil & Environm Engn POB 71555-313 Shiraz Iran Univ Oulu Water Resources & Environm Engn Res Grp POB 4300 FIN-90014 Oulu Finland

The stability against piping and sliding, which is subject to numerous sources of uncertainty, is of great importance in the design of diversion dams. In this study, the performance of four cutoff wall configurations, including a single wall and two walls with half the length of the single wall, was evaluated stochastically using the random finite element method. The Cholesky decomposition technique in conjunction with three types of auto-correlation function (ACF) was employed to generate numerous random fields. The results indicate that the probabilities of failure related to different cutoff wall configurations are similar, considering isotropic hydraulic conductivity. However, there are noticeable differences between the probabilities of failure of these configurations in anisotropic situations. Moreover, the use of a single cutoff wall on the upstream face of an impervious blanket provides the lowest probability of failure for piping. In addition, the exponential ACF ends up with greater exit hydraulic gradients than the second-order Markov and binary noise ACFs. In addition, the sliding stability of the ordinary and earthquake load combinations was examined stochastically using random field theory and Monte Carlo Simulation (MCS). The probability of failure appears to increase with an increase in the autocorrelation distance.

关键词： Probability of failure Diversion dam Piping Sliding stability Random finite element method auto-correlation function

来源：评论

学校读者我要写书评

暂无评论

Effects of noise correlation on the coherence of a forced van der Pol type birhythmic system

引用

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION 2018年 62卷 1-17页

作者： Yamapi, R. Yonkeu, R. Mbakob Filatrella, G. Tchawoua, C. Univ Douala Fac Sci Dept Phys Fundamental Phys Lab Box 24 157 Douala Cameroon Max Planck Inst Math Sci Inselstr 22 D-04103 Leipzig Germany Univ Yaounde I Fac Sci Dept Phys Lab Mech & Mat Box 812 Yaounde Cameroon Univ Sannio CNSIM Dept Sci & Technol Via Port Arsa 11 I-82100 Benevento Italy Univ Sannio CNSIM Salerno Unit Via Port Arsa 11 I-82100 Benevento Italy

We investigate the effects of noise correlation on the coherence of a forced van der Pol type birhythmic system. The coherence of the dynamics on the time scale of intrawell oscillations, as measured by the signal-to-noise-ratio, is shown to be maximized for an appropriate choice of the noise intensity and of the noise correlation time. Other measures, related to the autocorrelation function and applicable on the longer time scale of interwell oscillations do not exhibit such nonlinear behavior. When occurs, the coherence appears similar to noise induced stochastic resonance in ordinary bistable potential systems, while the investigated birhythmic system only posses a nonequilibrium or quasi-potential associated to the orbits. Thus, it is demonstrated that correlated noise, even if the attractors are not fix points but orbits, can give rise to stochastic resonance. (c) 2018 Elsevier B.V. All rights reserved.

关键词： correlation time Birhythmic system auto-correlation function Signal-to-noise ratio Stochastic resonance

来源：评论

学校读者我要写书评

暂无评论

Can high-frequency ECG fluctuations differentiate between healthy and myocardial infarction cases?

引用

Biomedical Engineering Advances 2021年 2卷

作者： Yiannis Contoyiannis Fotios K. Diakonos Myron Kampitakis Stelios M. Potirakis Department of Electrical and Electronics Engineering University of West Attica Ancient Olive Grove Campus 250 Thivon & P. Ralli Aigaleo Athens GR-12244 Greece Department of Physics University of Athens Athens GR-15874 Greece Network Major Installations Department Hellenic Electricity Distribution Network Operator SA 72 Athinon Ave. Palaio Faliro GR-18547 Greece

The Electrocardiogram (ECG) is a standard diagnostic tool for heart's health condition, while the “gold standard” in ECG interpretation is still by observation by the cardiologist. In this article we show that the analysis of the high frequency ECG amplitude fluctuations, which are ignored during the conventional interpretation of the ECG by the cardiologist, regarded as measurement noise, can reveal any deviations from the ideal critical behavior as well as the degree of stability of the heart in stochastic stimulus. By applying the time series analysis method termed “method of critical fluctuations” (MCF) to cardiologist-annotated human ECGs – Physikalisch-Technische Bundesanstalt (PTB) Diagnostic ECG database – we show that it is possible to discriminated between ECGs from healthy and myocardial infarction subjects, as well as to quantify the degree to which they approach the “ideal” critical state or how far from criticality they are, respectively. MCF analysis 100% verifies the characterization of the ECGs belonging to the “Myocardial infarction” class by absence of critical fluctuations. Interestingly, a disagreement with the medical classification of the order of ∼10% was found for the ECGs belonging to the “Healthy controls” set. For the specific ECGs we also find no critical fluctuations, which is a strong deviation from the rest ∼90% of the ECGs belonging to the same class and present critical fluctuations. Moreover, based on a proposed reference ECG, the autocorrelation function can also be used to reveal any differentiation of the studied ECGs from the ideal critical state.

关键词： Electrocardiogram Nonlinear time series analysis Complex systems Method of critical fluctuations Criticality auto-correlation function

来源：评论

学校读者我要写书评

暂无评论

Study of structural and surface morphological properties of Tb doped ZnO nanoparticles using XRD, XPS and fractal analysis

引用

MATERIALS RESEARCH EXPRESS 2019年第11期6卷

作者： Kumar, Anil Sharma, A. Bhasker, Savita Yadav, R. P. Bhasker, H. P. Priya, P. K. Pandey, K. L. Mandal, Satish Kumar Anand, R. K. Dr Ram Manohar Lohia Avadh Univ Dept Phys & Elect Faizabad 224001 Uttar Pradesh India KJ Somaiya Coll Engn Dept Sci & Humanities Mumbai 400077 Maharashtra India Univ Allahabad Dept Phys Allahabad 211002 Uttar Pradesh India Govt PG Coll Dept Phys Saidabad 221508 India Univ Allahabad CMP Degree Coll Dept Phys Allahabad 211002 Uttar Pradesh India Univ Allahabad Ewing Christian Coll Dept Phys Allahabad 211003 Uttar Pradesh India Saha Inst Nucl Phys Surface Phys & Mat Sci Div Kolkata 700064 India

Asystematic study was performed on Tb3+ doped ZnO nanoparticles of different mole-fraction using Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and X-ray Photoemission Spectroscopy (XPS) measurements. XRD studies confirm that all the samples are in wurtzite phase. XRD analysis suggests a compressive lattice strain as doping concentration increases. The strain generated in the doped samples is found to be more as compared to pure nanoparticle samples. XPS result indicates the presence of several oxygen species adsorbed on the surface. Furthermore, the effect of incorporation of Tb3+ ions into ZnO nanoparticles was explored using fractal analysis approach to extract the quantitative surface parameters. The fractal dimension is a scale invariant technique for representation and understanding of surface morphology of nanostructures. Fractal dimension provides a clear distinction between vertical and horizontal properties of the surfaces and their correlation. This technique could be very useful in selecting the suitable substrate for various technological applications. The lateral correlation length was estimated by auto-correlation function. While, the roughness exponent and fractal dimension were calculated from height-height correlation function. Moreover, this study reveals that the complexity of surface increases with doping. Moreover, as doping increases, the surface becomes more and more zagged as compared to pure samples.

关键词： ZnO atomic force microscopy XPS fractal dimension height-height correlation function auto-correlation function

来源：评论

学校读者我要写书评

暂无评论

An Unambiguous Acquisition Algorithm Based on Unit correlation for BOC(n,n) Signal

引用

IEICE TRANSACTIONS ON COMMUNICATIONS 2017年第8期E100B卷 1507-1513页

作者： Ji, Yuan-fa Liu, Yuan Zhen, Wei-min Sun, Xi-yan Yu, Bao-guo State Key Lab Satellite Nav Syst & Equipment Tech Shijiazhuang 050000 Hebei Peoples R China Guilin Univ Elect Technol Guangxi Key Lab Precis Nav Technol & Applicat Guilin 541004 Peoples R China Key Lab Radio Wave Environm & Modeling Technol Qingdao 266000 Peoples R China Guangxi Expt Ctr Informat Sci Guilin 541004 Peoples R China

To overcome the false lock or detection missing problems caused by the multiple peaks of the auto-correlation function (ACF) of Binary Offset Carrier (BOC) modulated signal, an acquisition algorithm based on unit correlation for BOC(n,n) signal is proposed in this paper. The local BOC signal is separated into two unit signals, an odd one and an even one. Then a reconstruction of the unit correlation functions between the unit signals and the received BOC signal is performed and M sections of reconstructed correlation function are accumulated according to the non coherent method, so that this novel acquisition algorithm can not only eliminate the multiple secondary peaks, but also retain the advantage of the narrow correlation main peak. Simulation results show that the acquisition sensitivity of the proposed algorithm is increased 3 dBHz compared with the ASPeCT method, and the computation cost is only 41.46% of the ASPeCT method when M=2.

关键词： multiple peaks auto-correlation function unit correlation separation and reconstruction non-coherent

来源：评论

学校读者我要写书评

暂无评论

A Simple Approach for Specifying Velocity Inflow Boundary Conditions in Simulations of Turbulent Opposed-Jet Flows

引用

FLOW TURBULENCE AND COMBUSTION 2017年第1期98卷 131-153页

作者： Tirunagari, Ranjith R. Pettit, Michael W. A. Kempf, Andreas M. Pope, Stephen B. Cornell Univ Sibley Sch Mech & Aerosp Engn Ithaca NY 14853 USA Imperial Coll London Dept Mech Engn South Kensington CampusExhibit Rd London SW7 2AZ England Univ Duisburg Essen Inst Combust & Gas Dynam IVG D-47048 Duisburg Germany Univ Duisburg Essen Ctr Computat Sci & Simulat D-47048 Duisburg Germany CD Adapco 21800 Haggerty RdSuite 300 Northville MI 48167 USA

A new methodology is developed to specify inflow boundary conditions for the velocity field at the nozzle exit planes in turbulent counterflow simulations. The turbulent counterflow configuration consists of two coaxial opposed nozzles which emit highly-turbulent streams of varying species compositions depending on the mode considered. The specification of velocity inflow boundary conditions at the nozzle exits in the counterflow configuration is non-trivial because of the unique turbulence field generated by the turbulence generating plates (TGPs) upstream of the nozzle exits. In the method presented here, a single large-eddy simulation (LES) is performed in a large domain that spans the region between the TGPs of the nozzles, and the time series of the velocity fields at the nozzle exit planes are recorded. To provide inflow boundary conditions at the nozzle exit planes for simulations under other conditions (e.g., different stream compositions, bulk velocity, TGP location), transformations are performed on the recorded time series: the mean and r.m.s. (root-mean-square) quantities of velocity, as well as the longitudinal integral length scale on the centerline, at the nozzle exits in simulations are matched to those observed in experiments, thereby matching the turbulent Reynolds number R e (t) . The method is assessed by implementing it in coupled large-eddy simulation/probability density function (LES/PDF) simulations on a small cylindrical domain between the nozzle exit planes for three different modes of the counterflow configuration: N (2) vs. N (2);N (2) vs. hot combustion products;and C H (4)/N (2) vs. O (2). The inflow method is found to be successful as the first and second moments of velocity from the LES/PDF simulations agree well with the experimental data on the centerline for all three modes. This simple yet effective inflow strategy can be applied to eliminate the computational cost required to simulate the flow field upstream of the nozzle exits.

关键词： Turbulent counterflow simulations Velocity inflow boundary conditions LES/PDF auto-correlation function Velocity statistics

来源：评论

学校读者我要写书评

暂无评论

An Universal MMSE Channel Estimator for OFDM Receiver

引用

WIRELESS PERSONAL COMMUNICATIONS 2017年第3期94卷 659-673页

作者： Wei, Hua Huang, Yao Zhang, Tianqi Li, Li Chengdu Univ Informat Technol Sichuan Higher Educ Inst Meteorol Informat & Signal Proc Key Lab Chengdu Peoples R China Chongqing Univ Posts & Telecommun CQUPT Sch Commun & Informat Engn Chongqing Peoples R China

In this paper, we re-derived the new auto-correlation function based on Jake's Model, and an universal minimum mean square error (MMSE) channel estimator are proposed based on the new auto-correlation function. Therefore, the proposed MMSE channel estimator can be adopted to various channel scenarios owing its inherent robustness. The performance of the MMSE channel estimator is investigated through a practise DVB-T standard, which shown that the MMSE channel estimator can achieve the extraordinary minimum square error performance at a low complexity.

关键词： OFDM MMSE auto-correlation function DDCE DVB-T

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：