Interest For Many Applications Research Articles

Land-Cover Change Detection using One-Class Support Vector Machine

Change detection using remote sensing has considerable potential for monitoring land-cover change. Commonly, one specific class of change is of interest in many applications. In this paper, a recently developed one-class classifier, the One-Class Support Vector Machine (OCSVM), is proposed for the change detection of one specific class by multitemporal classification. The classifier only requires samples from the change class of interest as the training data. The performance of the proposed method was evaluated in two applications by comparing with conventional post-classification comparison methods. The results demonstrated the proposed method achieved both higher overall accuracy and higher kappa coefficient than the conventional methods, and demonstrated good potential for further application. The study also indicated that with the OCVSM, the analysis can focus only on the specific class of interest and does not need to treat other classes, thus providing highly accurate change detection. The OCSVM-based change detection method, as a general and easily implemented method, can be used for applications where only the change of one specific class is of interest.

Study on rotor structure with different magnet assembly in high-speed sensorless brushless DC motors

High-speed permanent magnet (PM) brushless DC motors have gained more and more interests for many applications. The technique of detecting the electromotive force (EMF) zero-crossings is a common method in sensorless operation of PM brushless DC motors. However, the zero-crossings of the phase EMF will be obscured and the sensorless control will be malfunctioned, since the free-wheeling diode conduction can last more than 30 elec-degs under high-speed condition. Therefore it is supposed that the utilisation of third-harmonic EMF is more preferable, as it is not influenced by the free-wheeling diode conduction. Some design features for the high-speed sensorless operation are presented, primarily focusing on the rotor structure with different magnet assembly. The influence of the pole-arc to pole-pitch ratio on the third-harmonic airgap field will be analysed with both finite-element method and analytical model. Based on these analyses, another method which can improve both the third harmonic and fundamental components in the airgap field, by segmenting the parallel-magnetised PMs, is employed and studied. Motor prototypes are then designed and fabricated, and the experimental results confirm the validity of the proposed design method.

Sign consistent linear programming problems

This article studies linear programming problems in which all minors of maximal order of the coefficient matrix have the same sign. We analyse the relationship between a special structure of the non-degenerate dual feasible bases of a linear programming problem and the structure of its associated matrix. In the particular case in which the matrix has all minors of each order k with the same strict sign ϵ k , we provide a dual simplex revised method with good stability properties. In particular, this method can be applied to the totally positive linear programming problems, of great interest in many applications.

Simulation of laser-generated ultrasonic wave propagation in solid media and air with application to NDE

Ultrasonic methods are well known as powerful and reliable tool for defect detection. In the previous decades focus and interest have been directed to non-contact sensors and methods, showing many advantages over contact techniques where inspection depends on contact conditions (pressure, coupling medium, contact area). The non-contact hybrid ultrasonic method described here is of interest for many applications, requiring periodic inspection in service or after manufacturing. Despite the potential impact of laser-generated ultrasound in many areas of industry, robust tools for studying the phenomenon are lacking and thus limit the design and optimization of non-destructive testing and evaluation techniques. Here a specific numerical method is presented to efficiently and accurately solve ultrasound wave propagation problems with frequencies in the MHz range traveling in relatively large bodies and through air. This work improves a previous numerical model where propagation of the acoustic waves through air had not been considered, allowing us to simulate the presence of a non-contact transducer in reception in order to simulate numerically the complete experimental setup. It is very important to limit the amount of air to be considered in the FE analyses; otherwise the computational cost would often exceed the resources available. A way to solve the problem is to implement non-reflecting boundary conditions. A non-reflecting boundary condition allows all outgoing waves to exit the domain at the boundary where they have been imposed without reflection; thus, it is possible to model only the portion of air between the non-contact transducer and the solid under testing. Several numerical and experimental analyses were conducted on a 136 lb AREMA rail; here we study in detail two fully non-contact testing configurations for the rail head and web. The information that can be acquired is very valuable for choosing the right setup and configuration when performing non-contact hybrid ultrasonic inspection.

Highly transparent AgGaS 2 single crystals, a compound for mid-IR laser sources, using a combined static/dynamic vacuum annealing method

Mid-IR laser sources are of great interest for many applications. One interesting way to reach such wavelengths is the frequency conversion using a nonlinear material. Thus, the crystal growth of AgGaS 2 is presented in this paper. As often reported, it must be annealed to be as transparent as possible for optical applications. Nevertheless, traditional vacuum annealings are too much long and the mechanism occurring not so well understood. Here, a new method based on a combination of a static and a dynamic vacuum annealing is proposed as well as its mechanism. Thus, highly transparent AgGaS 2 samples were obtained for further optical experiments.

Numerical simulation of gaseous fuel injection: A new methodology for multi‐dimensional modelling

AbstractThe use of natural gas (instead of liquid or solid fuels) is nowadays drawing an increasing interest in many applications (gas turbines, boilers, internal combustion engines), because of the greater attention to environmental issues. To facilitate the development of these applications, computer models are being developed to simulate gaseous injection, air entrainment and the ensuing combustion.This paper introduces a new method for modelling the injection process of gaseous fuels that aims to hold down grid requirements in order to allow the simulation also of other phenomena, like combustion or valve and piston motion, in reciprocating internal combustion engines. After a short overview of existing models, the transient jet model and the evaluation of inflow conditions are described in detail. Then a basic study of the grid effects on the jet evolution is presented. The model is updated and validated by comparing numerical results with available experimental data for two different operating conditions: a subsonic and a supersonic under‐expanded case. The model demonstrates to be fast enough to be used in a multi‐dimensional code and accurate enough to follow the real gas jet evolution. Copyright © 2009 John Wiley & Sons, Ltd.

Monte Carlo Approximations of the Quantiles of a Sample Statistic

We consider in this article the problem of numerically approximating the quantiles of a sample statistic for a given population, a problem of interest in many applications, such as bootstrap confidence intervals. The proposed Monte Carlo method can be routinely applied to handle complex problems that lack analytical results. Furthermore, the method yields estimates of the quantiles of a sample statistic of any sample size though Monte Carlo simulations for only two optimally selected sample sizes are needed. An analysis of the Monte Carlo design is performed to obtain the optimal choices of these two sample sizes and the number of simulated samples required for each sample size. Theoretical results are presented for the bias and variance of the numerical method proposed. The results developed are illustrated via simulation studies for the classical problem of estimating a bivariate linear structural relationship. It is seen that the size of the simulated samples used in the Monte Carlo method does not have to be very large and the method provides a better approximation to quantiles than those based on an asymptotic normal theory for skewed sampling distributions.

Characterisation of oxidised aluminium powder: Validation of a new anodic oxidation bench

Aluminium powder is of major interest in many applications but it presents a risk due to its high explosibility, particularly when dispersed in air. The safety is directly linked to the particles oxidation because the Minimum Ignition Energy (MIE), which is required to initiate an Al dust explosion, increases with the oxide layer thickness. This study provides a controlled method to furnish reproducible homogeneous set of powder for such safety studies. Thanks to a new experimental bench, the influence on the oxidation rate of seven treatment parameters is investigated (current density, time of treatment, acid concentration, mass of powder, particles size, stirring, neutralisation by ammonia solution). The oxide content is plotted versus the current density, the time and the acid concentration to provide reference curves for further elaboration of oxidised powder. The particles size of sieved powder is measured before and after treatment by different methods (optical and Scanning Electron Microscopes, laser measurement). A high refinement of the powder in terms of size distribution is achieved thanks to the employed sieving. The present bench and the elaborated procedure are of great interest to provide well-calibrated oxidised powder directly available for safety studies. The time must be adjusted, depending on the wanted oxide content – from 2 to 18 wt.% – and the other treatment parameters must be kept constant: acid concentration (5 wt.%), current density (1 A dm −2), treated powder (20 g). In these conditions, the ratio of the oxide layer thickness on the particles diameter is found to be constant for a given oxide content whatever the particles size.

Piezometric levels as possible indicator of aquifer structure: analysis of the data from Maknassy basin aquifer system (Central Tunisia)

The knowledge of piezometric data is of vast interest in many applications, such as assessing groundwater flow direction and identifying recharge zone of the aquifer. In this paper, a methodology is presented as a complementary approach to characterize multilayered aquifer system structure and functioning using piezometric data and the cartography of the hydraulic charge difference. The methodology is presented to gradually discriminate the aquifer system levels and to evaluate the spatial distribution of hydraulic heads. The hydraulic charge difference mapping permits to track spatial evolution of the impermeable levels. The methodology has been applied over the Maknassy basin aquifer system, located in central Tunisia. The obtained results, showing the multilayered aquifer structure, are validated using hydrochemical approach and piezometric data not considered in the reasoning.

Improving Zernike Moments Comparison for Optimal Similarity and Rotation Angle Retrieval

Zernike moments constitute a powerful shape descriptor in terms of robustness and description capability. However the classical way of comparing two Zernike descriptors only takes into account the magnitude of the moments and loses the phase information. The novelty of our approach is to take advantage of the phase information in the comparison process while still preserving the invariance to rotation. This new Zernike comparator provides a more accurate similarity measure together with the optimal rotation angle between the patterns, while keeping the same complexity as the classical approach. This angle information is particularly of interest for many applications, including 3D scene understanding through images. Experiments demonstrate that our comparator outperforms the classical one in terms of similarity measure. In particular the robustness of the retrieval against noise and geometric deformation is greatly improved. Moreover, the rotation angle estimation is also more accurate than state-of-the-art algorithms.

Downstream variation in bankfull width of wadeable streams across the conterminous United States

Bankfull channel width is a fundamental measure of stream size and a key parameter of interest for many applications in hydrology, fluvial geomorphology, and stream ecology. We developed downstream hydraulic geometry relationships for bankfull channel width w as a function of drainage area A, w = α A β, (DHG wA) for nine aggregate ecoregions comprising the conterminous United States using 1588 sites from the U.S. Environmental Protection Agency's National Wadeable Streams Assessment (WSA), including 1152 sites from a randomized probability survey sample. Sampled stream reaches ranged from 1 to 75 m in bankfull width and 1 to 10,000 km 2 in drainage area. The DHG wA exponent β, which expresses the rate at which bankfull stream width scales with drainage area, fell into three distinct clusters ranging from 0.22 to 0.38. Width increases more rapidly with basin area in the humid Eastern Highlands (encompassing the Northern and Southern Appalachians and the Ozark Mountains) and the Upper Midwest (Great Lakes region) than for the West (both mountainous and xeric areas), the southeastern Coastal Plain, and the Northern Plains (the Dakotas and Montana). Stream width increases least rapidly with basin area in the Temperate Plains (cornbelt) and Southern Plains (Great Prairies) in the heartland. The coefficient of determination ( r 2) was least in the noncoastal plains (0.36–0.41) and greatest in the Appalachians and Upper Midwest (0.68–0.77). DHG wA equations differed between streams with dominantly fine bed material (silt/sand) and those with dominantly coarse bed material (gravel/cobble/boulder) in six of the nine analysis regions. Where DHG wA equations varied by sediment size, fine-bedded streams were consistently narrower than coarse-bedded streams. Within the Western Mountains ecoregion, where there were sufficient sites to develop DHG wA relationships at a finer spatial scale, α and β ranged from 1.23 to 3.79 and 0.23 to 0.40, respectively, with r 2 > 0.50 for 10 of 13 subregions (range: 0.36 to 0.92). Enhanced DHG equations incorporating additional data for three landscape variables that can be derived from GIS—mean annual precipitation, elevation, and mean reach slope—significantly improved equation fit and predictive value in several regions, most notably the Western Mountains and the Temperate Plains. Channel width was also related to human disturbance. We examined the influence of human disturbance on channel width using several indices of local and basinwide disturbance. Contrary to our expectations, the data suggest that the dominant response of channel width to human disturbance in the United States is a reduction in bankfull width in streams with greater disturbance, particularly in the Western Mountains (where population density, road density, agricultural land use, and local riparian disturbance were all negatively related to channel width) and in the Appalachians and New England (where urban and agricultural land cover and riparian disturbance were all negatively associated with channel width).

Towards Extracting Semantically Meaningful Key Frames From Personal Video Clips: From Humans to Computers

Extracting key frames from video is of great interest in many applications, such as video summary, video organization, video compression, and prints from video. Key frame extraction is not a new problem but existing literature has focused primarily on sports or news video. In the personal or consumer video space, the biggest challenges for key frame selection are the unconstrained content and lack of any pre-imposed structures. First, in a psychovisual study, we conduct ground truth collection of key frames from video clips taken by digital cameras (as opposed to camcorders) using both first- and third-party judges. The goals of this study are to: 1) create a reference database of video clips reasonably representative of the consumer video space; 2) identify consensus key frames by which automated algorithms can be compared and judged for effectiveness, i.e., ground truth; and 3) uncover the criteria used by both first- and third-party human judges so these criteria can influence algorithm design. Next, we develop an automatic key frame extraction method dedicated to summarizing consumer video clips acquired from digital cameras. Analysis of spatio-temporal changes over time provides semantically meaningful information about the scene and the camera operator's general intents. In particular, camera and object motion are estimated and used to derive motion descriptors. A video clip is segmented into homogeneous parts based on major types of camera motion (e.g., pan, zoom, pause, steady). Dedicated rules are used to extract candidate key frames from each segment. In addition, confidence measures are computed for the candidates to enable ranking in semantic relevance. This method is scalable so that one can produce any desired number of key frames from the candidates. Finally, we demonstrate the effectiveness of our method by comparing the results with two alternative methods against the ground truth agreed by multiple judges.

Drying of High Aspect Ratio Structures: A Comparison of Drying Techniques via Electrical Stiction Analysis

Nanostructures with high aspect ratios, HAR, (ratio of height to lateral feature size) are of interest for many applications. One of the immediate advantages is the large surface area of these structures. In the field of DRAM manufacturing for example, the capacitance of cylindrical DRAM capacitors increases linearly with height. Wet etching and drying of these fragile high aspect ratio structures without lateral collapse (stiction) is a big challenge for the fabrication of DRAM capacitors. The problem with HAR structures is stiction during drying [1]. In order to reduce stiction by improvement of drying techniques, a good metric to quantify the occurrence of stiction is needed. However, currently used methods like SEM or brightfield defect inspection are extremely time-consuming.

Autoreduction of Metallic Species on the Surface of Silica Nanoparticles by Surface Functionalization

AbstractSilica nanoparticles with metallic nanoclusters are of great interest in many applications from bio imaging to optical devices. The nanometric size of metallic particles induces specific absorption properties due to surface plasmon resonance. This absorption mainly depends on the morphology of the nanoparticles. If the encapsulation of metallic nanoparticles into a silica shell is now well developed, there is a great interest on the synthesis of either silica nanoparticles covered by metallic nanoparticles or silica cores with metallic shells. Two main ways are described in the literature to bind metallic nanoparticles onto the silica nanoparticles. The first way consists on the mixing of a metallic colloidal sol with another sol containing silica nanoparticles bringing at their surface the suitable chemical functions, able to properly interact with the metal nanoparticles. The second way consists on the use of a reducing agent to reduce the metallic ions introduced successively into a suspension of silica nanoparticles. Herein is proposed an original third method based on a double surface functionalization of the silica nanoparticles. This method is actually based on an in-situ reduction of metallic ions by two chemical function (amino and thiol) previously grafted onto the surface of the silica nanoparticles. The silica nanoparticles are synthesized by a reverse micro-emulsion sol-gel process. This synthesis gives monodispersed silica nanoparticles of 40 nm diameter. The surface functionalization of the silica nanoparticles is performed by sol-gel reactions within the micro-emulsion, using two silane-coupling agents owning either a thiol function or a diamino function.The functionalized silica shell increases the chemical activity of the surface of the nanoparticles. But the capability of this functionalized surface to reduce metallic ions depends mainly on the chemical function used. Two examples are given in this study: the diamino functions, which reduce the copper ions, and the combination of the diamino and the thiol functions in a silver nitrate solutionwhich induces the growth of small silver nanoparticles (4-5 nm) on the silica nanoparticles’ surface.

Testing for Stochastic Monotonicity

We propose a test of the hypothesis of stochastic monotonicity. This hypothesis isof interest in many applications. Our test is based on the supremum of a rescaledU-statistic. We show that its asymptotic distribution is Gumbel. The proof is difficultbecause the approximating Gaussian stochastic process contains both a stationaryand a nonstationary part and so we have to extend existing results that only applyto either one or the other case.

Nanoindents produced by nanobubbles on ultrathin polystyrene films in water

Nanobubbles are produced on hydrophobic surfaces when they are immersed in aqueoussolutions. The effect of nanobubbles on the immersed surface is of interest in manyapplications. In the study presented here, immersion of the polystyrene film inde-ionized water for several hours produces nanoindents on the film surface. Thetypical diameter of the nanoindents is around 20 nm, and the density is about2.0 × 108 mm−2. The location and formation of nanoindents show strong correlation with the size andlocation of nanobubbles. A mechanism of nanobubble-induced formation of nanoindents isproposed. The influences of film thickness and nanobubble size on the nanoindents are alsodiscussed.

Characterization of Cr(III) Compounds of O, OH, F and Cl by XPS

Cr2O3, CrCl3, α-CrF3, CrF3⋅3H20 and Cr(OH)3 were investigated by x-ray photoelectron (XPS) and x-ray excited Auger electron spectroscopy (XAES) using a latest generation XPS spectrometer. Non-conductive powders are analyzed with ultimate energy resolution. Multiplet splitting features and/or satellite emission were observed in the Cr 2p and Cr 3s spectra. Cr(III) compounds are of interest in many applications as for example in corrosion and catalysis. Chromia and chromium-III-fluoride activated by reaction with fluoroalkanes are very promising industrial catalysts. It is the aim of this selection of spectral reference data to enable deeper insight in the formation of catalytically active fluorinated chromia phases by using XPS analysis.

Permeability calculations in three-dimensional isotropic and oriented fiber networks.

Hydraulic permeabilities of fiber networks are of interest for many applications and have been studied extensively. There is little work, however, on permeability calculations in three-dimensional random networks. Computational power is now sufficient to calculate permeabilities directly by constructing artificial fiber networks and simulating flow through them. Even with today's high-performance computers, however, such an approach would be infeasible for large simulations. It is therefore necessary to develop a correlation based on fiber volume fraction, radius, and orientation, preferably by incorporating previous studies on isotropic or structured networks. In this work, the direct calculations were performed, using the finite element method, on networks with varying degrees of orientation, and combinations of results for flows parallel and perpendicular to a single fiber or an array thereof, using a volume-averaging theory, were compared to the detailed analysis. The detailed model agreed well with existing analytical solutions for square arrays of fibers up to fiber volume fractions of 46% for parallel flow and 33% for transverse flow. Permeability calculations were then performed for isotropic and oriented fiber networks within the fiber volume fraction range of 0.3%-15%. When drag coefficients for spatially periodic arrays were used, the results of the volume-averaging method agreed well with the direct finite element calculations. On the contrary, the use of drag coefficients for isolated fibers overpredicted the permeability for the volume fraction range that was employed. We concluded that a weighted combination of drag coefficients for spatially periodic arrays of fibers could be used as a good approximation for fiber networks, which further implies that the effect of the fiber volume fraction and orientation on the permeability of fiber networks are more important than the effect of local network structure.

Analysis of Basis Pursuit via Capacity Sets

Finding the sparsest solution $\alpha$ for an under-determined linear system of equations $D\alpha=s$ is of interest in many applications. This problem is known to be NP-hard. Recent work studied conditions on the support size of $\alpha$ that allow its recovery using L1-minimization, via the Basis Pursuit algorithm. These conditions are often relying on a scalar property of $D$ called the mutual-coherence. In this work we introduce an alternative set of features of an arbitrarily given $D$, called the "capacity sets". We show how those could be used to analyze the performance of the basis pursuit, leading to improved bounds and predictions of performance. Both theoretical and numerical methods are presented, all using the capacity values, and shown to lead to improved assessments of the basis pursuit success in finding the sparest solution of $D\alpha=s$.

Dynamical Systems Gradient Method for Solving Nonlinear Equations with Monotone Operators

A version of the Dynamical Systems Gradient Method for solving ill-posed nonlinear monotone operator equations is studied in this paper. A discrepancy principle is proposed and justified. A numerical experiment was carried out with the new stopping rule. Numerical experiments show that the proposed stopping rule is efficient. Equations with monotone operators are of interest in many applications.