Extreme Value Point Research Articles

The influence of the mixed alkaline earth effect on the structure and properties of (Ca, Mg)–Si–Al–O–N glasses

Alkaline earth oxynitride glasses of (Ca, Mg)–Si–Al–O–N with different CaO/(CaO + MgO) molar ratios (0, 0.25, 0.5, 0.75, and 1) were successfully prepared using the sol-gel method, and their structural compositions were characterised by Raman and FT-IR techniques. The glass dynamic properties of thermal expansion coefficient, glass transition temperature (Tg), and static properties of density, molar volume, Vickers hardness and compressive strength were systematically measured and analysed. The results showed that the static properties exhibited an overall regular change as the CaO/(CaO + MgO) ratio gradually increased, while the dynamic properties had an obvious mixed alkaline earth effect, which represented the appearance of an extreme value point in CaO/(CaO + MgO) mole ratios of 0.25 and 0.75, respectively. The typical thermal expansion coefficient and Tg of mixed alkaline earth oxynitride glasses deviated far from the linear connection between single alkaline earth oxynitride glasses. Raman spectra and infrared spectra revealed that the ratio value of the Q3/(Q2+Q4) decreased (Qn: n = no. of bridging anions joining SiO4 tetrahedra) in the mixed alkaline earth oxynitride glasses with increasing the amount of Ca, confirming that Ca decreased the crosslinking between individual tetrahedra via the transformation of Q3 species into Q2 and Q4 species.

Small Angle X-ray Scattering Test of Hami Coal Sample Nanostructure Parameters with Gas Adsorbed Under Different Pressures.

The complexity and multiscale structure of coal pores significantly influence the gas diffusion and seepage characteristics of coal. To apply small angle X-ray scattering (SAXS) to study the coal pore structure parameters within the scale of 1-100 nm in the methane adsorption process, the X-ray window was optimized and a gas adsorption chamber was designed to interface with the small angle X-ray scattering platform. The fractal dimension and porosity of Hami coal samples under different methane pressures were studied using the small angle X-ray scattering platform and adsorption chamber. The surface and nanopore fractal information of the nanopores in coal were distinguished. The variation trends of the pores and surface fractal dimension with time under the same methane pressure were compared. The results indicate that the surface dimension changes from 2.56 to 2.75, and the extremum point may indicate that the primary nanopore structure is crushed by the adsorbed gas after approximately 15 minutes. This work clarifies that the fractal dimension can characterize the changes in nanopores in the process of gas adsorption by using SAXS. According to the fractal characteristics, the adsorption of gas in coal nanopores is summarized as four steps: expansion from adsorbance, deformation, crushing and recombination. The minimum porosity is 0.95% and the extreme value point is 1.47%. This work also shows that decrease in surface energy affect the porosity changes in nano-size pores. This work is of some significance to coalbed methane permeability improvement and gas extraction.

Crack Detection in Pavement Images Based on a Self- Adaptive Niche Algorithm

ABSTRACT This study focuses on optical image pavement damage detection instead of artificial detection in pavement maintenance. Based on the characteristics of cracks and combined with the niche theory, it proposes a dynamic adaptive curve extraction algorithm. First, we construct the matrix space, map the original pavement image data to the target space, process the data in target space using the multi-trough algorithm, then connect the extreme gray value points between two adjacent scanning rows with lines, compare the average gray value of the line with the average gray value of this area, and judge the possibility of cracks according to curve extension characteristics. The method considers oil, water stain, irregular concave spot, and other kinds of image noise on the pavement surface. It has good adaptability, and experimental results show that the algorithm is effective.

Processing method of EMD endpoint effect based on SVRM extension

Aiming at the problem of endpoint effect in empirical mode decomposition (EMD), the application method of support vector regression machine (SVRM) in EMD extension data prediction is studied. Firstly, the basic principle, data extension method and parameter setting of SVRM are introduced. Secondly, several application methods of SVRM in EMD extension are studied to analyze and verify the operational efficiency and decomposition accuracy characteristics of each method respectively. Finally, the proposed extension method based on SVRM extreme value point prediction can greatly improve the operation efficiency of SVRM long time extension. The simulation signal analysis shows that the SVRM extreme point prediction extension method not only improves the accuracy and reliability of EMD decomposition, but also effectively inhibits the end-point effect phenomenon, significantly reduces the SVRM extension time, and improves the practicability of EMD method.

Ultrasonic reflection characteristics of FRP-to-FRP bonded joints with thick adhesive layers for bonding evaluation: Theoretical analysis

Theoretical analysis for bonding evaluation by ultrasonic reflection characteristics is carried out with respect to FRP-to-FRP (Fiber Reinforced Polymer) bonded joints with thick adhesive layers. Spectrums of reflection coefficients depending on frequencies and incident angles are obtained, which are calculated theoretically and validated by finite element simulation. Meanwhile, in order to study the effect of interface degradation on reflection characteristics, variations of interfacial stiffness for single/dual bonding interfaces are investigated. It’s found that local extreme value points in frequency spectrums intend to shift to the lower frequency side with the decrease of interfacial stiffness. However, in angular spectrums, local extreme value points will shift to the larger angle side with the decrease of interfacial stiffness. The results also show that the local minima in both spectrums are closely related to the symmetry of the bonded joints, which is connected with the thicknesses of adherend layers, material properties, and the bonding states of dual adherend-adhesive interfaces.

Mobile Terminal Video Image Fuzzy Feature Extraction Simulation Based on SURF Virtual Reality Technology

Extracting the fuzzy feature of the mobile video image can effectively improve the low illumination image quality. Traditional methods are used to construct fuzzy feature indexes of mobile terminal video images, and the detailed information of video images is divided, but the bidirectional matching of feature points is ignored, which leads to low extraction accuracy. Therefore, this paper proposes a method for extracting fuzzy features of mobile terminal video images based on SURF-based virtual reality technology. First, perform video image grayscale extraction on the input mobile terminal video image, and detect the closed area in the mobile terminal video image as the radiation invariant area of the terminal video image. Secondly, Hessian matrix is used to detect the feature points of the image, and the non-maximum suppression method and interpolation operation are used to find and locate the extreme value points. Then, the main direction of feature points was determined, and SURF description operator was used for matching to obtain initial matching point pairs. Finally, the obtained fuzzy feature one-way matching result of the video image is matched in two directions, the closest distance ratio is used to match the feature points, and the full constraint condition is used to filter out the wrong matching point pairs, thereby completing the mobile terminal video image fuzzy feature extraction. The experimental results show that the proposed algorithm is effective in feature extraction and matching, stability and speed. The misrecognition rate of the algorithm in this paper is 0.101, and the time used is only 0.41 s, which fully meets the real-time requirements.

Extreme Value Condition of Stabilizing Lead/Lag Region

This paper considers the problem of stabilizing linear time-invariant plants by a lead/lag compensator. The extreme value condition of the stablilizing lead/lag region is given. The coordinates of the local extreme value point is obtained. At the local extreme value point, the closed-loop system contains a pair of conjugate imaginary poles and a pole at the origin. If the zero gain is fixed, the stability region in the plane with respect to the proportional gain and the pole gain is determined by plotting the stability boundary locus. The effectiveness of the method presented is illustrated a numerical example.

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

During loading and unloading test, various rocks manifest different stress values of elastic-plastic transformation. This study proposes to include axial pressure increment ratio in the conventional triaxial compression test to evaluate different variables (nominal elastic modulus, nominal Poisson’s ratio, strain, and energy). The relationships among various factors including variables, the stress level of initial confining stress and axial pressures, were analyzed by analyzing the stress–strain plot record obtained from testing various rocks. The extreme value point of the deformation parameter, also known as the elastic-plastic threshold, was analyzed. In addition, the elastic-plastic thresholds were later used as unloading points during the unloading tests. Under the same confining condition, different rocks demonstrated different unloading levels. Furthermore, a linear correlation was observed between unloading levels and changing confining pressures, and the gradient is mainly related to the types of rocks. During the unloading tests of rocks, the rational unloading level is recommended to be no higher than the stress level at the elastic-plastic threshold under the corresponding confining pressure.

Parameter estimation of chaotic systems based on extreme value points

Parameter estimation and synchronisation of chaotic systems are one of the hottest topics in the field of nonlinear science. In this paper, we addressed how to utilise the obtained experimental time series to estimate multiple parameters in chaotic systems. On the basis of relations of critical points and extreme value points, as well as the least squares estimation, we deduced a novel statistical parameter estimation corollary method to evaluate the unknown parameters in chaotic systems. In order to illustrate the feasibility and effectiveness of the proposed method, three numerical simulation results are presented, where the validity of the proposed method is verified in detail. Furthermore, we also investigated the effects of time-series noise and system disturbances for the proposed method, and the results showed that the proposed method is robust to uncertainties.

A wavelet ridge extraction method employing a novel cost function in two-dimensional wavelet transform profilometry

We present a new wavelet ridge extraction method employing a novel cost function in two-dimensional wavelet transform profilometry (2-D WTP). First of all, the maximum value point is extracted from two-dimensional wavelet transform coefficient modulus, and the local extreme value points over 90% of maximum value are also obtained, they both constitute wavelet ridge candidates. Then, the gradient of rotate factor is introduced into the Abid’s cost function, and the logarithmic Logistic model is used to adjust and improve the cost function weights so as to obtain more reasonable value estimation. At last, the dynamic programming method is used to accurately find the optimal wavelet ridge, and the wrapped phase can be obtained by extracting the phase at the ridge. Its advantage is that, the fringe pattern with low signal-to-noise ratio can be demodulated accurately, and its noise immunity will be better. Meanwhile, only one fringe pattern is needed to projected to measured object, so dynamic three-dimensional (3-D) measurement in harsh environment can be realized. Computer simulation and experimental results show that, for the fringe pattern with noise pollution, the 3-D surface recovery accuracy by the proposed algorithm is increased. In addition, the demodulation phase accuracy of Morlet, Fan and Cauchy mother wavelets are compared.

On the maximal and minimal distances of flying-around satellite formation

PurposeThe purpose of this paper is to present the obtained analytic solutions of maximal and minimal inter-satellite distances for flying-around satellite formation.Design/methodology/approachThe relative motion equation is used to express the inter-satellite distance as the function of the orbital elements of two participating satellites for the flying-around satellite formation. Then by taking the derivative of the distance function with respect to the true anomaly, some possible extreme value points are obtained. According to the detailed analysis, the maximal and minimal distance solutions are found. By a reverse process, the expected initial differential orbital elements that generate the required extreme inter-satellite distances are also obtained.FindingsThe maximal and minimal distances of the flying-around formation can be analytically written as the functions of three initial orbital elements differences, i.e. the differential orbital inclination, the differential eccentricity and the differential right ascension. For the given maximal and minimal distances, there are lots of solutions of the initial differential orbital elements, which can produce the expected relative motions.Research limitations/implicationsThe solutions of the maximal and minimal inter-satellite distances are only accurate for the circular or near circular reference orbit. For the elliptic reference orbit, there is a need to develop new methods to find the analytic solutions.Practical implicationsThe results here can be applied to design the factual flying-around formation with dimension requirements in mission analysis stage.Originality/valueBy using the solutions presented in this paper, the engineers can design the expected flying-around formation with required maximal and minimal inter-satellite distances in a very easy way.

A generalized Sibuya distribution

The Sibuya distribution arises as the distribution of the waiting time for the first success in Bernoulli trials, where the probabilities of success are inversely proportional to the number of a trial. We study a generalization that is obtained as the distribution of the excess random variable N − k given N > k, where N has the Sibuya distribution. We summarize basic facts regarding this distribution and provide several new results and characterizations, shedding more light on its origin and possible applications. In particular, we emphasize the role Sibuya distribution plays in the extreme value theory and point out its invariance property with respect to random thinning operation.

Unmanned aerial vehicle trajectory planning by an integrated algorithm in a complex obstacle environment

Both the artificial potential field method and direct method for the optimal control problem have shortcomings in terms of effectiveness and computational complexity for the trajectory-planning problem. This paper proposes an integrated algorithm combining the artificial potential field method and direct method for planning in a complex obstacle-rich environment. More realistic unmanned aerial vehicle dynamics equations, which are rarely applied in the traditional artificial potential field method, are considered in this paper. Furthermore, an additional control force is introduced to transcribe the artificial potential field model into an optimal control problem, and the equality/inequality constraints on the description of the shape of the obstacles are substituted by the repulsive force originating from all the obstacles. The Legendre pseudospectral method and virtual motion camouflage are both utilized to solve the modified optimal control problem for comparison purposes. The algorithm presented in this paper improves the performance of solving the trajectory-planning problem in an obstacle-rich environment. In particular, the algorithm is suitable for addressing some conditions that cannot be considered by the traditional artificial potential field method or direct method individually, such as local extreme value points and a large numbers of constraints. Two simulation examples, a single cube-shaped obstacle and a different-shaped obstacle-rich environment, are solved to demonstrate the capabilities and performance of the proposed algorithm.

Multiscale Self-coordination of Bidimensional Empirical Mode Decomposition in Image Fusion

The bidimensional empirical mode decomposition (BEMD) algorithm with high adaptability is more suitable to process multiple image fusion than traditional image fusion. However, the advantages of this algorithm are limited by the end effects problem, multiscale integration problem and number difference of intrinsic mode functions in multiple images decomposition. This study proposes the multiscale self-coordination BEMD algorithm to solve this problem. This algorithm outside extending the feather information with the support vector machine which has a high degree of generalization, then it also overcomes the BEMD end effects problem with conventional mirror extension methods of data processing, . The coordination of the extreme value point of the source image helps solve the problem of multiscale information fusion. Results show that the proposed method is better than the wavelet and NSCT method in retaining the characteristics of the source image information and the details of the mutation information inherited from the source image and in significantly improving the signal-to-noise ratio.

Heavy Tails in Foreign Exchange Markets: Evidence from Asian Countries

In recent years, Extreme Value Theory (EVT) has been proposed to deal with the heavy tailed distributions. This paper introduces L-moments and L-moment ratios based on EVT to analyze the distributional characteristics of exchange rates, and furthermore introduce the Kappa (κ) distribution to analyze the effects of globalization by understanding differences and similarities among Asian countries and developed countries before and after the crisis. We classify the behavior of exchange rates of East Asian countries and several financially developed countries into groups: the EURO zone, UK, Japan and some Asian countries. These entire groups have experienced the same or similar shocks during credit crunch in 2008; however the responses to the event for each group are different. We take extreme value point of view to analyze the effects of globalization by examining the exchange rates. For this purpose, we calculate the so called L-moments and L-moment ratios. Based on these estimates, we implement structural break test based on Kappa distribution showing the different aspects of the analyses. The most striking features are the different shape of L-moments and the coefficients of κ distribution among each group, and a closer examination of the L-moments diagram and parameters before and after the credit crunch in 2008 will reveal the different responses on the crisis and implications of the globalization. The results obtained by examining the behavior of exchange rate returns may be pertinent to economic policy making and macroeconomic forecasting. The finding that exchange rates of several Asian countries are typically more heavy-tailed than those of developed counterparts may reflect their susceptibility to more frequent and extreme external and internal shocks. The empirical results may also indicate that behavior of the distribution of extremes in Asian countries is time variant with a tendency to become fatter tailed during turbulent periods. Analysis on currency markets based on Kappa distribution shows that before financial crisis, South Korea, Taiwan and UK have relatively low second shape parameter than other countries. However, after the mortgage crisis, the parameters of all countries are close to 2. Therefore, we may say that after 2008, the distribution of all countries converge. From this we may conclude that before crisis, South Korea and Taiwan may not manage exchange rate market as others does, but after crisis, South Korea and Taiwan have sufficient power to manage exchange rate. Through the efforts to overcome global crisis, East Asian countries start to share the common feature of exchange rates with financially well developed countries around financial crisis.

Adaptive niche quantum-inspired immune clonal algorithm

The adaptive niche quantum-inspired immune clonal algorithm (ANQICA) is proposed by combining the quantum coding, immune clone and niche mechanism together to solve the multi-modal function optimization more effectively and make the function converge to as many as possible extreme value points. The quantum coding can better explore the solution space, the niche mechanism ensures the algorithm to converge to multi-extremum and the adaptive mechanism is introduced according to the characteristics of each procedure of the algorithm to improve the effect of the algorithm. Example analysis shows that the ANQICA is better in exploration and convergence. Therefore, the ANQICA can be used to solve the problem of multi-modal function optimization effectively.

Pile Defect Intelligent Identification Based on Wavelet Analysis and Neural Networks

In view of the phenomenon of pile test results are greatly influenced by human , the paper puts forward that to combine wavelet analysis and neural network for pile testing, use the extreme value point of the wavelet analysis as the input of neural networks, depending on the output codes to determine the defect types and position. And it is believed that there is a good potential for use in future.

Modeling and Analysis of the Bounds of Periodical Satellite Relative Motion

The precise analytic bounds of periodical satellite relative motion are obtained in this paper. To explore the bounds easily, a set of algebraic relative motion equations are applied. In these newly developed equations, the tangent value of half the true anomaly is regarded as a restated independent variable. The upper and lower bounds of the coordinates in the leader local-vertical/local-horizontal frame are found by solving the partial derivatives of the coordinates with respect to the restated independent variable. These bounds are expressed as functions of the leader’s orbital elements and the orbital element differences of the follower with respect to the leader. The bounds’ variation with differential orbital elements is further analyzed, in which some interesting phenomena are discussed. The bounds of the intersatellite separation are also studied. It has been found that there are at most four extreme value points in the intersatellite separation in most cases. In some degenerate cases, there may be two or zero extreme value points for the intersatellite separation. A few of examples are also given to test the theoretical analysis. Some potential applications, like formation configuration design and optimal control, are discussed too. It shows that the bounds theory in this paper can be used effectively in many real applications.

The Theoretical Research on the Chiral Transition of Ibuprofen Molecules under Isolated Conditions

In this article, we do a research on the chiral shift process of the isolated alpha alanine molecule using the basis set of 6-31+g(d,p), which is based on density functional theory B3LYP. Furthermore, the chiral transition path reaction potential en- ergy surface of ibuprofen molecule is drawn by looking for the extreme value point structure including the transition state and intermediate. Finally, the geometry and electronic structure properties of extreme value point are also analyzed. The results show that there are two achieve reaction paths of ibuprofen from S-type to R-type. Path 1 consists of three transition states and two intermediate states. Path 2 includes four transition states and three intermediate states. On the reaction path, the greatest barrier which is from the transfer of hydrogen in chiral carbon to oxygen in carboxyl, is 73.54 Kcal/mol. The researchprovides a theoretical reference to further realize some important application value over the chiral transition reaction control of point chiral molecule.

Research on Improved BP Learning Algorithm of BP Neural Network

Aiming at the existence of the BP neural network learning algorithm in the slow learning speed, the possibility of failure is large, poor generalization ability, there are multiple issues, extreme value point and network structure are difficult to determine, in this paper, we study algorithm improvement methods. Explain the algorithm principle, on the basis of three improved methods are studied, respectively is dynamic learning rate, conjugate gradient, improved error function. Among them, the dynamic learning rate, it reaches the learning rate of the hidden layer and output layer; Conjugate gradient, this paper gives three calculating formula; Improved error function, to solve different problems are also given in three types of error function. BP learning algorithm in this paper, the research contents, make the convergence stability, convergence speed, initial value sensitivity, it has good effect, which has large significant in terms of academic and applied significance.